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Tribology International Vol.31,No.10,pp.597–599,1998©1999Elsevier Science Ltd.All rights reservedPrinted in Great Britain 0301–679X/98/$19.00ϩ0.00PII:S0301–679X(98)00080–2Tribology science,technology and education in ArmeniaA.K.Pogosian*State of the art in the field of tribology in Armenia is discussed.The main problem in research,education and technology transfer to industry are considered.©1999Elsevier Science Ltd.All rights reserved.Keywords :tribology,Armenia,technology transfer,industryAs far back as the 1950s in Armenia,investigations in the field of providing wear resistance and durability of cutting tools were set up.Considerable impulse of work development in the field of tribology was the necessity to create new wear resistant high-friction and low-friction materials,friction nodes and types of lubricants for machines for various purposes.Self-lubricating materials on polymer and cermet bases were made.Tribological problems are actual in machine-tool industry,agricultural machine building industry,automotive industry,instrument engineering,electrical machine industry,composite tribomaterial science,material cutting etc.In the direction of creating optimal friction nodes,forecasting their wear resistance and introduction into production a lot of work is carried out,first of all,at the Yerevan Polytechnic Institute (now State Engineering University of Armenia).One of the most prosperous directions of tribological studies is the calculation and design of machine parts and friction nodes on the basis of composite polymer materials instead of conventional metal parts.Scientific principles of creating of new polymer-based self-lubricating composites,calculating methods on the selection of materials and estimation of wear resistance of friction nodes,as well as physical simulation of friction and wear processes on the small-sized labora-tory samples and forecasting of serviceability of friction nodes according to the results of accelerated tests,are worked out 1,2.The set of worked out methods of calculation and many years of study in these fields,as well as the results of their application to the study of friction interactions of polymer-based self-lubricating composite materials (PSCM),present themselves as a prosperous scientific direction in the solution of theState Engineering University of Armenia,105Terian Street,Yerevan 375009,Armenia*Tel:ϩ3742-589884;fax:ϩ3742-151068;e-mail:pogosian@seua.amReceived 12February 1998;accepted 14March 1998Tribology International Volume 31Number 101998597problems of creating PSCM and new constructions of friction nodes on their basis in the Republic of Armen-ia.The basic principles of selection of the fillers and polymer matrices for PSCM on the bases of general positive interactions and limiting factors of the fillers properties,as well as optimal combinations of compo-nents of filled systems (compositions),proceeding from the purpose of machine parts and friction nodes pro-duced by PSCM are worked out 1.In the basis of composite design,the principle of a self-lubricating mechanism by using the properties of friction transfer (FT)film is given posite polymer materials are able to form on the friction surfaces the film of FT of some nature,having the properties of lubricant film.Analysis of the conditions of friction film formation and evalution of its influence on the friction interaction processes,make it possible to consider that (together with the abrasion and corrosion),the transfer of material modifies the friction surface of counterbody and,consequently,various types of wear may take place with the intensivity that is characteristic for them.A general phenomenon was discovered:in spite of the fact that the friction surface temperature reaches values that are higher than the polymer melting point,inten-sive wear begins only after destruction (failure)of the FT film 4.At the present stage of Tribology development there is no fundamental physical explaination for the FT process.None of the current theories can adequately take account of this phenomenon,which is explained by difficulties of observation and description of mech-ano-chemical and physico-mechanical phenomena tak-ing place on the real area of contact.An adhesion-energetic model 5has been used to evaluate the transfer film thickness and its effectiveness.In accordance with this concept,in the spots of discrete contact of the rubbing bodies,there develop heat sources because of transformation of the mechanical energy.As a result,the contact surface of the polymer softens under theTribology science,technology and education in Armenia:A.K.Pogosianaction of friction heating and so-called scuffing bridges form,after which mechanical fracture arises in the places of least resistance,i.e.,in the section of the weaker polymer material,and transfer to the metal surface takes place.Analytic relations have been derived for determination of the FT film thickness,and the conditions of its effectiveness have been deter-mined.Such calculations significantly extend the possi-bilities of the analytic method for evaluating transfer film lubricity in the friction of polymer-based materials.The most perspective scientific direction for Armenia is the creation of PSCM with local mineral materials as a filler 6.The bulk supply of numerous mineral materials available in the Republic (tufa,basalt,traver-tine,bentonite et al.),may and must be more effectively used along with the other fillers (graphite,fluoroplastic,coke,molybdenum disulfide et al.).Essential results are obtained in the development of wasteless techno-logies for machine parts production,using non-expens-ive raw materials including fillers with special chemical or heat treating.Eventually,a new class of self-lubri-cated materials for bearings and tooth gears has been developed,called SIPAN.These are characterized by a high wear resistivity (wear intensity 2.2ϫ10−9),a constant and low friction coefficient (0.09–0.12)and a high-precision technology of machine parts production (9–10quality accuracy).The tribological and physico-mechanical comparative tests reveal that the developed materials surpass the widely used materials of the same type (SAM-6,SFD-DM,SFD-BS)in their wear resistivity,load-carrying capacity,accuracy of machine parts production tech-nology and strength.The main exploitation conditions of SIPAN composite materials are as follows:sliding velocity 2.0mps,specific loading 6.0MPa and work temperature 90°C (in the condition of nonlubricated friction).Based on the results of a study of the friction transfer phenomena,the mechanisms of self-lubrication and wear in the conditions of ‘dry’friction are revealed,and proposals are elaborated for the evalu-ation of metalopolymer friction pairs durability (wear-resistance).The optimization of the composition of developed materials via the method of full-factor experiments is puter programs are written for the expert computation of PSCM-made machine parts (e.g.,sliding bearings)in various exploitation modes.Technological packages are developed for the production of SIPAN composite materials and machine parts pressing castings as well.One of the most urgent problems of Armenian econ-omy is the creation and utilization of lubricants based on local materials and industrial waste,as well as restoration of used oils,taking into account the market demands for wasteless technologies,environmental pro-tection and urgent needs of the Republic.New composite lubricants have been developed based on wastes of the oleic acid industry and I-40A type industrial oil.The mechanisms of their impact upon the steel surfaces of friction nodes have been revealed.It has been proved that the newly developed composite lubricants in their physicochemical properties are not worse than those of I-40A type industrial oil,while their tribological characteristics are more advantageous:598Tribology International Volume 31Number 101998the friction coefficient and the wear index are lower for 60p.c.and 10p.c.correspondingly,the grip wear loading is higher for 47p.c.This gives an opportunity to make use of these newly developed composite lubri-cants in the heavy-loaded nodes with boundary lubri-cated friction,replacing the I-40A lubricants that is mainly used at present.In order to increase the efficiency of exploitation of the lubricants,new addi-tives with high antiwear and antiscoring properties have been proposed.The antiwear and antiscoring action mechanisms are revealed for various classes of hal-ogen-,sulphur-and phosphorus-containing additives (monocyclic ketones,bi-and tri-cyclic esters,halogen-and sulphur-containing olefins and esters of phosphoric acid).For all the classes of these composites a general regularity is revealed:the optimal choice of the addition leads to both high antiwear and antigear efficiency.As a result of a large number of experiments,two characteristics of the wear and seizure processes are introduced 7.One characteristic,the wear intensity coef-ficient,is represented as a factor of the exponent in the empirical dependence of wear rate on the length of the friction path.The second value is the relative load of seizure,i.e.,the attitude of the seizure loading to the load at which the given test is carried out,and at which the wear rate is measured.These two values are connected in a generalized dependence,invariant to the load,sliding velocity,system rigidity and lubri-cation medium properties.These observations are of essential interest for the theory and practice of tribology,since a unique corre-lation between antiwear and antisoring properties of lubricants has been demonstrated,opening up the possi-bility of predicting the antiscoring properties of lubri-cants based on the results of comparatively simple wear tests.In recent years in Armenia,significant development has obtained the theory of providing motion stability at friction (stick-slip process).Complex methods of reducing friction oscillations in the guide-ways of machine tools,robots and other machines are worked out 8.For the first time,the task of motion stability conformable to the sliding guide-ways is solved,in general view on the basis of space model of oscillation process of friction nodes of slider-guider type,con-firmably to the machine tools 9.Calculation algorithms of friction oscillations on the computer,permitting an evaluation of the influence of geometrical,physico-mechanical,constructive and tribological parameters on the friction auto-ossillation,have been plex methods of increasing of vibrostability of moving by the guides slip nodes,subject to factors of external action is suggested.The obtained data could be used both for the estimation of accuracy of existing,and for the optimization of,friction nodes of newly designed machines and machine tools.In the direction of providing motion stability at friction,wear resistant composite materials NASPAN for the application on the surface of the guide-ways,promoting a decrease in the scale of vibro-displacements of supports of metal cutting machine tools 3or more times,are created.Based on both model and real tests of car disk brakes,the dynamics of the breaking process,as well as theTribology science,technology and education in Armenia:A.K.Pogosianaction of vibration loading on the wear and friction properties of brake materials (asbo-polymers and asbes-tos-free)are investigated.The problem of creation of the asbestos-free friction (brake)composite materials with mineral fillers of local origin,is of greatest importance and crucial for environmental protection in order to replace the asbes-tos which is harmful for human health.Regretfully at present this is the main (up to 80p.c.)component of the vehicles’brake pads (friction clutches)material in the Republic of Armenia,as well as in the former Soviet Union countries 10.A new class of asbestos-free composite friction materials—BASTENIT—is created along with its varieties.A series of local mineral materials have been investigated as asbestos substitutes,and basalt-and glass-fibers along with tufa powder turned out to be most effective ones.A technology for BASTENIT class composite materials production is developed,aiming to use to the fullest extent,the existing technological process for the present full-scale production of asbo-polymerous materials without any additional investments and equipment.The materials obtained have passed through rational cycles of labora-tory,bench and road tests.The experimental evaluation of tribological characteristics and operational indicators proved their adequacy for main technical requirements:high friction coefficient and provision of stable oper-ational (brake)regimes as well as serviceability of the friction pair,especially at high temperatures (400–600°C).A classification of the materials obtained is carried out in accordance to the operational character-istic properties of the vehicles.Complex methods for high-temperature wear and vibration resistance evaluation and constructions of brake pads are worked out based on investigations of thermal,tribologic and oscillatory processes in brake devices 11,12.The second environmental-protection advantage of BASTENIT from the viewpoint of squeak background decrease,has been revealed by means of the characterization of the squeak (shaking)oscil-lations spectrum.Tribological studies are actual in other fields of Armen-ian machine building.Prosperous are the developments of antifriction composite materials by the methods of powder metallurgy 13,e.g.,on the basis of copper pow-der,doped sulphite and phosphorous.In the study of wear process of cutting instruments and tools in the treatment of various materials (including natural stone,with which the Republic is extremely rich)and alloys,a number of investigations are devoted 14.For the increase of capacity of work on restoring worn parts,Tribology International Volume 31Number 101998599the special design and technical bureau with consider-able economical efficiency is organized.Tribology education in Armenia is mostly carried out at the State Engineering University within the whole scale of the educational system:in BE,ME and PhD programms 15.Obviously the school and new generation of the specialists in the field of tribology in Armenia have already formed.In the development of Tribology in the Republic,a significant role is played by,(organized in 1974)the Armenian Tribology Commit-tee (ATC).More than 20years of professional activities and experience within the field of tribology science,technology and education,whether pure or applied,whole country (Republican)conferences,seminars,competitions,lectures and consultations etc.,and also sufficient fame and authority of the ATC,assure in the ability of the ATC to look after all disciplines comprising tribology in Armenia.The Armenian Tri-bology Committee became a member of the Inter-national Tribology Council (ITC)in 1997.References1.Pogosian,A.K.,Friction and Wear of Filled Polymer Materials .Moscow,1977,139p.2.Pogosian,A.K.,Wear ,1973,26,175–186.3.Briscoe,B.J.,Pogosian,A.K.and Tabor,D.,Wear ,1974,27,19–34.4.Pogosian,A.K.,Tribology in the USA and the Former Soviet Union:Studies and Applications .Allerton Press Inc.,New York,1994.pp.271–283.5.Pogosian,A.K.,Friction and Wear ,1984,5(2),204–211.6.Pogosian,A.K.,Karapetian,A.N.and Oganesian,K.V.,Wear of Materials ,1989,2,521–528.7.Pogosian,A.K.,Arustamian,Y.S.and Gevorkian,G.R.,Wear ,1993,167,85–86.8.Sysoev,P.V.,Bliznetc,M.M.and Pogosian,A.K.,Antifriction Epoxside Composites in Machine Tool Building .Minsk,1990,231p.9.Pogosian,A.K.,Demirchian,A.Z.and Gagian,G.S.,EURO-TRIB .Helsinki,1989.10.Pogosian,A.K.,Sysoev,P.V.,Meliksetian,N.G.and Lamb-arian,N.A.,Polymer-Based Friction Composites .Minsk,1992,218p.11.Pogosian,A.K.and Lambarian,N.A.,J.of Lubric.Tech ,1979,101(4),481–485.12.Pogosian,A.K.and Makarian,V.K.,Friction and Wear ,1993,14(3),539–543.13.Manoukian,N.V.(ed),Composite Materials and Their Treat-ment .Yerevan,1985.14.Kasian,M.V.(ed),The Quality of Machine Parts Surface .Yerevan,1985.15.Pogosian,A.K.,Principles of Tribology (Textbook).Yerevan–Athens,1994–95,296pp.。
Correlation between Microstructure andConductance in NTC Thermistors Produced from Oxide PowdersG.D.C.Csete de Gyo rgyfalva,*A.N.Nolte and I.M.ReaneyDepartment of Engineering Materials,Sir Robert Had®eld Building,University of She eld,She eld,S13JD,UKAbstractA detailed study of spinel-structured Ni 1Àx Mn 2+x O 4formed by a mixed oxide route has shown that when x %0a high proportion of NiO is residual in the sin-tered ceramic.Wickham (Wickham,D.G.,Solid phase equilibria in the system NiO±Mn 2O 3±O 2.J.Inorg.Chem.,1964,26,1369±1377)demonstrated that the spinel phase decomposes in air above 900 C.Sintering in this system is usually per-formed around 1200 C.Decomposition of the spi-nel phase is therefore inevitable.The e ect of decomposition on the microstructure and electrical properties of Ni 1Àx Mn 2+x O 4based ceramics is discussed.#1999Elsevier Science Limited.All rights reservedKeywords :microstructure,electrical conductivity,spinels,thermistors.1IntroductionNegative temperature coe cient (NTC)thermistors are found in an ever increasing number of electrical and electronic products.Ni 1Àx Mn 2+x O 4,where x denotes the deviation from the stoichiometric 1:1NiO:Mn 2O 3ratio,o ers a range of properties that are suitable for most temperature sensing applications.When x =0,(nickel manganite,NiMn 2O 4),the solid solution has an inverse cubic spinel structure,based on a 2Â2Â2array of face centred cubic (fcc)oxygen subunits.When x =1,Mn 3O 4is present which is a tetragonally distorted spinel.The properties routinely used to characterise NTC thermistors are resistance,R 1and R 2,at 25 C (T 1)and 85 (T 2)and a B value (with units of tem-perature in Kelvin)which is a measure of the sensi-tivity of the device over a given temperature range:BT 1T 2T 2ÀT 1ln R 1R 2IThe exact mode of conduction in nickel manga-nite is poorly understood,but several modelsinvoke the small polaron theory.1,2Small polaron conduction is sometimes referred to as a `hopping'mechanism,as it involves the transfer of polarisa-tion from one cation to another.In the nickel manganite system,it has been postulated that the mixed valence,Mn 4+,Mn 3+cations present on the octahedral sites give rise to these small polaron pathways.1The octahedral cations in the spinel structure lie in chains along some <110>direc-tions.These vectors represent the smallest inter-cationic distances within the unit cell.Another important parameter when considering applications for Ni 1Àx Mn 2+x O 4ceramics is their thermal stability or aging characteristics (changes in conductance over long periods,i.e.lifetime of the component).Reports indicate that better ther-mal stability is found in tetragonal ceramics rather than cubic materials though the conductivity of the latter is 10to 100times higher.2,3This could be explained by a reduction in the concentration of Mn 4+compared to Mn 2+and Mn 3+or possibly by the presence of planar defects such as ferroelas-tic domain walls.4Ni 1Àx Mn 2+x O 4ceramics have been prepared by the carbonate and oxalate methods,in addi-tion to the more conventional mixed oxide route.5Irrespective of the preparation route,sintering (typically around 1200 C)is always carried out above the decomposition temperature in air for the system ($900 C)as discussed by Wickham.5Con-sequently,ceramics ®red using conventional pro-cessing will contain multiple phases,e.g.NiO fromJournal of the European Ceramic Society 19(1999)857±860#1999Elsevier Science LimitedPrinted in Great Britain.All rights reservedP I I :S 0955-2219(98)00331-80955-2219/99/$-see front matter857*To whom correspondence should be addressed.Fax:+44-(0)114-222-5943;e-mail:mtp96gdc@she the decomposed spinel and Mn-rich regions,3,6,7in accordance with the equation:xiwn III2y43x xiy 3Àx3xi II 3À3x a 3Àxwn II 2x a 3Àx wn III2O4 x6O2PIt is the intention of this paper to demonstrate how the degree of decomposition from single phase in¯uences conductivity and,in particular,aging. X-ray di raction and transmission electron micro-scopy will be used to monitor the degree of decomposition and accelerated aging tests(470 C) will be performed.2Experimental ProcedureThe NiO and Mn2O3powders in a1:1Mn2O3:NiO molar ratio were weighed out using an electronic balance( 0.01g)and transferred to a poly-propylene vessel with a charge of ZrO2milling media(the weight of ZrO2varied with the weight of the batch being processed).The batch was mil-led for6h to reduce particle size distribution to a mean of6"m and a maximum of12"m then drawn through a suction®lter.The resulting slurry was dried in a70 C oven overnight.The dried powder was calcined in a mullite crucible at900 C for16h and subjected to a further6h milling under the above conditions.One one cm diameter pellets were pressed from the powders and sintered at 1250 C,achieving densities better than95%. Microstructural and structural characterisation were carried out using transmission electron microscopy(TEM)and X-ray di raction(XRD), respectively.XRD was performed on solid cera-mics and loose powders using a Phillips PW1050 di ractometer with a Cu K source.A0.02 step size was used at a scan rate of0.5 minÀ1.TEM samples were prepared by grinding the ceramic to a thickness of20"m and ion beam milling to per-foration.Images were obtained using JEOL200CX and3010TEMs:the latter was equipped with a LINK energy dispersive X-ray detector. Accelerated aging tests were carried out using a non-induction wound furnace held at470 C.Tem-perature¯ux was monitored in the furnace using a thermocouple mounted immediately adjacent to the test piece.Platinum wires leading to a high precision HP4284A LCR meter were used to make contact to the electroded surface of the cera-mic.Changes in the resistance of the leads and contacts as a function of temperature were taken into account by performing a closed circuit run.Typically,temperature varied within a 0.2 C range over10h.3Results and DiscussionWickham,5in his study of the Ni1Àx Mn2+x O4solid solution,demonstrated that above900 C decom-position occurs resulting in the formation of NiO and a Mn-rich spinel phase.The higher the tem-perature above the onset of the decomposition reaction,the more rapid the rate.In order to study the decomposition reaction in more detail and its potential e ect on electrical properties,single phase ceramics(within the sensitivity of conventional XRD)were fabricated,as demonstrated in Fig.1. Figure2shows a series of XRD traces from single phase samples heat treated at1000,1100and 1200 C for1h.The evolution of peaks corres-ponding to NiO can be observed in accordance with the predictions of Wickham.6The relative intensities of the NiO peaks(marked)increase with increasing temperature.Figure3is a bright®eld(BF)TEM image showing a typical region of spinel grains in single phase material.The grain boundaries and interiors are free from second phase.Inset in Fig.3is a <110>zone axis di raction pattern(ZADP)from one of the spinel grains in the image.Figure4isaFig.1.XRD trace of single phase ceramic.Note absence ofNiOpeaks.Fig.2.XRD spectra of samples held at1000,1100,1200 c for1h.NiO peaks are marked.858G.D.C.Csete de GyoÈrgyfalva et al.BFTEM image obtained from a sample decom-posed for9h at1250 C.Inset is a<110>ZADP pattern from the imaged region.The fundamental re¯ections can be indexed according to a<110> zone axis from rock salt structured NiO.The weak re¯ections at half integer positions arise from regions of spinel phase,observed as dark contrast. Rock salt(NiO)and spinel structured compounds invariably exhibit a cube//cube orientation rela-tionship.Oxides with the rock salt structure are based around single fcc oxygen subunits whereas spinel structured compounds have a2Â2Â2fcc oxygen sublattice.In order to study the aging characteristics of the ceramics as a function of decomposition,con-ductance measurements were performed over10h at470 C 0.2 C.Figure5shows the change in conductance normalised to the initial value,against time at470 C for(A)single phase spinel and(B) `partially'decomposed spinel(heat treated for9h at1250 C).The single phase sample showed a negligible drift in resistivity over the test period, whereas the`partially'decomposed sample exhib-ited a steady decline in conductance.Di erences in the absolute starting values can be attributed to small variations in the dimensions of the samples. Figures6and7are XRD traces showing the samples before and after the accelerated aging experiments.Figure6,which corresponds to Fig.5(A)(decomposed),shows a reduction intheFig.4.BFTEM image of spinel regions in a NiO matrix.Insetis a<110>ZADP from the NiO.Faint re¯ections are presentat half integer positions arising from the dark regions ofspinel.Fig.5.Graph showing normalised conductance versus time at470 C for(A)single phase and(B)decomposed(9h at1250 C)material.Fig.6.XRD spectra of single phase sample(A)before and(B)after acceleratedaging.Fig.7.XRD spectra of decomposed sample(A)before and(B)after acceleratedaging.Fig.3.BFTEM image of spinel grains in single phase mate-rial.Inset is a<110>zone axis di raction pattern(ZADP)from a spinel grain.NTC thermistors produced from oxide powders859intensity of the NiO peaks(A)before and(B)after the experiment.However,Fig.7,which corre-sponds to Fig.5(B)(single phase),shows traces that are identical(A)before and(B)after.It is thought that the accelerated aging at470 C leads to NiO being re-absorbed into the ceramic during the lifetime of the experiment.It is proposed that the decomposition reaction occurs homogeneously throughout the ceramic,and the NiO is intimately mixed with the spinel phase,as evidenced by Fig.4. The reverse process may therefore occur relatively quickly because of the short di usion distances involved(of the order of nm according to Fig.4). However,it should be noted that aging at room temperature may be related to di erent phenomena than suggested by these accelerated tests.4Conclusions.The reaction between NiO and Mn2O3pro-ceeds forwards slowly at temperatures less than900 C,but will reverse as temperature increases above this value..The rate of decomposition increases with increasing temperature resulting in amicrostructure of intimately mixed NiO and Mn-rich spinel..Initial investigations indicate that a single phase ceramic gives rise to substantial improvements in thermal stability under accelerated aging.References1.Brabers,V.A.M.and Terhell,J.,Electrical conductivityand cation valencies in nickel manganite.Phys.Stat.Sol.(a),1982,69,325±332.2.Dorris,S.E.and Mason,T.O.,Electrical properties andcation valences in Mn3O4.J.Am.Ceram.Soc.,1988, 71(5),379±385.3.Rousset,A.,Larange,A.,Brieu,M.,Couderc,J.andLegros,R.,In¯uence de la microstructure sur la stabilite electrique des thermistance.C.T.N Journ.de Phys.III, 1992,4,833±845.4.Macklen,E.D.,Electric conductivity and cation distribu-tion in nickel manganite.J.Phys.Chem.Solids,1986, 47(11),1073±1079.5.Wickham,D.G.,Solid phase equilibria in the systemNiO±Mn2O3±O2.J.Inorg.Chem.,1964,26,1369±1377.6.Feltz,A.,Topfer,J.and Schirrmeister,F.,Conductivitydata and preparation routes for NiMn2O4thermistor ceramics.J.Eur.Ceram.Soc.,1992,9,187±191.7.Jung,J.,Topfer,J.,Murbe,J.and Feltz,A.,Micro-structure and phase development in NiMn2O4spinel ceramics during isothermal sintering.J.Europ.Ceram.Soc.,1990,6,351±359.860G.D.C.Csete de GyoÈrgyfalva et al.。
新人教版高中英语必修（1-3）课文英汉对照（Word精校版）必修一Welcome Unit 欢迎单元Reading and ThinkingFIRST IMPRESSION 第一印象Han Jing's World7:00a.m.So this is it-senior high school at last. I'm not outgoing so I’m a little anxious right now. I want to make a good first impression. Will I make any friends? What if no one talks to me? 韩静的世界早上7:00这就是了一一终于到了高中学校!我性格并不外向，所以现在感觉有点焦虑。
我想给别人留下良好的第一印象。
我会交到朋友吗?要是没人跟我说话怎么办呢?12:30p.mI just had my first maths class at senior high school! The class was difficult, but the teacher was kind and friendly. He even told us a funny story and everyone laughed so much! I found most of my classmates and teachers friendly and helpful.中午12:30我刚刚上完高中的第一节数学课!这课(内容)很难，但老师却很友善。
他还给我们讲了笑话,惹得每个人都哈哈大笑!我觉得我的大多数同学和老师都很友好，而且乐于助人。
5:32p.mThis afternoon, we had our chemistry class in the science lab. The lab is new and the lesson was great, but the guy next to me tried to talk to me the whole time. I couldn’t concentrate on the experiment. I really wanted to tell him to please be quiet and leave me alone.下午5:32今天下午，我们在科学实验室上化学课。
RESEARCH NOTEMICROBIAL DEGRADATION OF EDTA IN ANINDUSTRIAL WASTEWATER TREATMENT PLANTU.KALUZA,P.KLINGELHO FER and K.TAEGER*BASF Aktiengesellschaft,Speciality Chemicals,67056Ludwigshafen,Germany(First received May1997;accepted in revised form January1998)AbstractÐFor the®rst time it is shown that EDTA is ultimately biodegraded under practical industrial wastewater treatment conditions,involving a Finnish plant dedicated to treat the e uent from a paper mill.Monitoring measurements on the in¯uent and the treated e uent showed an EDTA elimination of about80%.The mean EDTA concentration in the in¯uent was23.8mg lÀ1and in the corresponding e uent5.8mg lÀ1.The biodegradability of EDTA was veri®ed in the laboratory with activated sludge from the treatment ing a combined CO2/DOC method the total mineralization of EDTA was indicated by>80%CO2formation and r99%DOC removal.#1998Elsevier Science Ltd.All rights reservedKey wordsÐEDTA,biodegradability,CO2/DOC-combination test,industrial wastewater treatment plant,chlorine-free bleachingINTRODUCTIONIn the pulp and paper industry totally chlorine-free bleaching(TCF)is increasingly being adopted.This process employs hydrogen peroxide(H2O2)instead of chlorine compounds.The disadvantage is the rapidly catalyzed decomposition of the bleach by the manganese and iron ions contained in wood. Therefore hydrogen peroxide is stabilized by adding metal chelating agents such as EDTA.But it is commonly known that EDTA is poorly degradable in natural compartments despite the fact that there are several investigations showing the biodegrad-ability with mixed cultures under de®ned laboratory conditions(Klu ner et al.,1994;Henneken et al., 1995).The advantages of the TCF process would be even greater if EDTA could also be broken down biologically in wastewater treatment plants.MATERIAL AND METHODSOperating data of the treatment plantHydraulic loading rate:ca.10000m3dÀ1pH of in¯uent:5.3±5.8;pH of e uent:7.6±7.9Sludge retention time:9dTemperature:35±408C over the whole yearMean hydraulic retention time:about1dIn¯uent load:BOD:10t dÀ1;COD:20t dÀ1Urea was added as a source of nitrogen in order to avoid bacterial growth from being curtailed by a lack of nitrogen.700kg of sludge was generated per tonne of BOD.Sampling and analysisFifty separate samples of in¯uent and treated e uent were taken daily over a period of two weeks.The daily samples taken for determining EDTA were un®ltered and preserved with1%formaldehyde.The samples taken for determining the heavy metal content were stabilized with 0.5%HNO3.EDTA was determined in the form of its iron(III) complex by HPLC on RP18phase(Randt et al.,1993) with an UV detector at320nm(detection limit 0.5mg lÀ1).The heavy metal content was determined by means of ICP-AES(inductive coupled plasma-atomic emission spec-trometry).The sample was oxidized with perchloric acid and dissolved in hydrochloric acid and water(detection limit=1mg lÀ1).Biodegradability tests in the laboratory Biodegradability tests were performed with the activated sludge from the above industrial wastewater treatment plant using a combined CO2/DOC method that allows the simultaneously determination of the formation of CO2and of the DOC removal(dissolved organic carbon)(updated ISO9439,1998,Strotmann et al.,1995).The activated sludge was incubated at358C with a concentration of 150mg lÀ1dry solids.The incubation vessels were kept in the dark to exclude any photochemical degradation pro-cesses.Blank controls were proved to show real biological EDTA degradation.Wat.Res.Vol.32,No.9,pp.2843±2845,1998#1998Elsevier Science Ltd.All rights reservedPrinted in Great Britain0043-1354/98$19.00+0.00PII:S0043-1354(98)00048-7*Author to whom all correspondence should be addressed.[Tel:+49-621-6058015;Fax:049-621-6058043].2843RESULTSEDTA removal in an industrial wastewater treatment plantEDTA concentration Ðexpressed as H 4EDTA Ðwas measured in the in¯uent and the e uent of the wastewater treatment plant.The results indicate that about 80%of the EDTA was removed (Table 1).The results in Table 1are reproducible because an earlier investigation indicated a removal degree of 87%at average EDTA in¯uent and e uent con-centrations of 43.5mg l À1and 5.5mg l À1.Biodegradability of EDTA in a laboratory test The evidence of high EDTA removal degrees in the described industrial treatment plant prompted us to con®rm the removal of EDTA was due to a biological mineralization process.Therefore exper-iments were performed according to the combined CO 2/DOC method (Strotmann et al.,1995).This method allows a clear distinction between biodegra-dation and physical removal.According to the elev-ated temperature in the wastewater treatment plant the standard procedure (Strotmann et al.,1995)was performed at 358C.The result shows >80%CO 2-formation and r 99%DOC removal,obviously due to the biodegradation of EDTA (Fig.1).EDTA test concentration:20mg l À1DOC.The biodegradability of EDTA is shown during an incu-bation time of 28d at a temperature of 358C.Concentration and removal of heavy metalsIn wastewater EDTA is usually present in form of its metal complexes.The biodegradability of EDTA depends on the stability of the existing and/or newly formed metal complexes (Henneken et al.,1996).For this reason it is important to determine the metal concentrations in the in¯uent and e uent (Table 2).As a result it could be shown that out of eighteen heavy metals only iron and manganese were present in concentrations above the detection limit and that a stoichiometric excess of the sum of these ions over EDTA was given.All metals were removed below the detection limit during the wastewater treatment.DISCUSSIONThere are several investigations showing the bio-degradability of EDTA with mixed cultures under de®ned laboratory conditions (Lau et al.,1990;Gschwind,1992;Klu ner et al.,1994;Henneken et al.,1995,1996).Now it has been shown for the ®rst time that EDTA is about 80%biodegradable in an industrial wastewater treatment plant under techni-cal operating conditions.Evidence of the biodegra-dation was con®rmed by formation of >80%CO 2and r 99%DOC removal in the combined CO 2/DOC test.Table 1.EDTA removal in an industrial wastewater treatment plant In¯uent concentrationE uent concentrationH 4EDTAmg lÀ1mmol l À1mg l À1mmol l À1Removal degree Mean23.80.0814 5.80.0276%Standard deviation 2.3 2.07Maximum 28.00.0969.00.03168%Minimum18.00.0623.00.0183%Fig.1.Biodegradability of EDTA in the combined CO 2/DOC test.Research Note2844In wastewater EDTA is usually present in form of its metal complexes.The biodegradability of EDTA depends on the stability of the metal com-plexes(Henneken et al.,1996).The total concen-tration of iron and manganese ions in the in¯uent was in stoichiometric excess against EDTA.It can be assumed that EDTA is discharged in the form of its iron and manganese complexes.This obviously has no detrimental e ects on the biodegradation of EDTA nor on the removal of heavy metals,as is shown by the decrease of the Fe and Mn concen-trations in the e uent.In laboratory experiments and by de®ned mi-crobial cultures(Henneken et al.,1996)iron com-plexes and other relatively stable complexes of EDTA are more di cult to break down than mag-nesium or calcium complexes.If Ca and Mg ions exist in a stoichiometric excess,the composition of the metal complexes is slowly displaced in favor of the more degradable Ca and Mg complexes(Xue et al.,1995;Henneken et al.,1996).This process can be accelerated by increasing the pHÐas occurs between in¯uent and e uent of the treatment plant Ðreducing the stability of Fe±EDTA and increas-ing the stability of other metal complexes(BASF, 1988).The phenomenon to improve biodegradation by increasing the pH is shown by(Van Ginkel et al.,1997).However,there is also evidence that the pure iron±EDTA complex is biodegradable(Lau et al.,1990).Furthermore it is known that the iron±EDTA complex is unstable when exposed to sunlight and it is easily broken down directly by photolysis(BUA-Sto bericht,1996).This is an e ective way to elim-inate EDTA,especially in receiving waters that con-tain little suspended solids(Kari et al.,1995).The results presented are a major improvement on those that have been obtained with specially selected cultures under de®ned laboratory con-ditions(Lau et al.,1990;Gschwind,1992; Henneken et al.,1996).They illustrate very clearly that EDTA does not necessarily have to be persist-ent under conditions like wastewater treatment plants.REFERENCESBASF,Brochure Chelating Agents±Trilon11988.BUA-Sto bericht Ethylendiamintetraessigsa ure/Tetrana-triumethylendiamintetraacetat(H4EDTA/Na4EDTA); BUA-Report ethylenediaminetetraacetic acid/tetrasodiu-methylenediaminetetraacetate(H4EDTA/Na4EDTA), 168,S.Hirzel,Wissenschaftliche Verlagsgesellschaft, Stuttgart1996,ISBN3-7776-0699-5.Gschwind N.(1992)Biologischer Abbau von EDTA in einem Modellabwasser:Biological degradation of EDTA in a model waste water.Wasser Abwasser133, 546±549.Henneken L.,No rtemann B.and Hempel D.C.(1995) In¯uence of physiological conditions on EDTA degra-dation.Appl.Microbiol.Biotechnol.44,190±197. Henneken L.,Bru ggenthies A.,No rtemann B.and Hempel D.C.(1996)Teilstrombehandlung EDTA-halti-ger Abwa sser mittels Bio®lm-Wirbelbettreaktoren,treat-ment of partial stream containing EDTA with a moving-bed bio®lm reactor.Chemie-Ing.Tech.68,310±314.ISO9439,Water quality±Evaluation in an aqueous med-ium of the ultimate aerobic biodegradability of organic compounds±Method by analysis of released carbon diox-ide,updated ISO/DIS9439annex D,published1998. Kari F.G.,Hilger S.and Canonica S.(1995) Determination of the reaction quantum yield for the photochemical degradation of Fe(III)±EDTA: Implications for the environmental fate of EDTA in sur-face waters.Environ.Sci.Technol.29,1008±1017.Klu ner T.,Henneken L.,Gehle M.,Bru ggenthies A., No rtemann B.and Hempel D.C.(1994)Katabolismus von Ethylendiamintetraacetat(EDTA),Catabolism of ethylenediaminetetraacetate(EDTA).BIOforum17, 284±288.Lau J.J.,Steele D.B.,Coogan L.A.and Breitfeller J. M.(1990)Degradation of the ferric chelate of EDTA by a pure culture of an Agrobacterium sp..Appl. Environ.Microbiol.56,3346±3353.Randt C.,Wittlinger R.and Merz W.(1993)Analysis of nitrilotriacetic acid(NTA),ethylenediaminetetra-acetic acid(EDTA)and diethylenetriaminepentaacetic acid (DTPA)in water,particularly waste water.Fresenius J. Anal.Chem.346,728±731.Strotmann U.J.,Schwarz H.and Pagga U.(1995)The combined CO2/DOC test±a new method to determine the biodegradability of organic compounds. Chemosphere30,525±538.Van Ginkel C.G.,Vandenbroucke K.L.and Stroo C.A.(1997)Biological removal of EDTA in conventional activated sludge plants operated under alkaline con-ditions.Bioresource Technology59,151±155.Xue H.,Sigg L.and Kari F.G.(1995)Speciation of EDTA in natural waters:Exchange kinetics of Fe±EDTA in river water.Environ.Sci.Technol.29,59±68.Table2.Concentrations of metal ions in the industrial treatment plantIn¯uent concentration E uent concentrationMetal ions mg lÀ1mmol lÀ1mg lÀ1mmol lÀ1 Calcium ca.300ca.7.5ca.300ca.7.5 Magnesium ca.10ca.0.4ca.10ca.0.4 Manganese30.055<1<0.018Iron20.036<1<0.018S manganese and iron0.091<0.036Research Note2845。
Texts from Oxford English Book 91．Protecting the innocent innocent..............................................................................................................................................................22．An extract from Further Adventures of Sherlock Holmes Holmes’’......................33．COMPUTERS COMPUTERS (4)44．The History of the Internet Internet (5)55．The night of the horse horse..................................................................................................................................................................66．Qian Xuesen:Father of China's Aerospace Aerospace..............................................................................................77．FISHING WITH BIRDS BIRDS (8)88．Some Facts About Tea Tea (9)99．Memory Memory (10)1010．How to Improve Your Memory Memory (11)1111．Comic Strips Strips........................................................................................................................................................................................1212．The Fox and the Crow Crow (13)1313．THE GREEN CONSUMER CONSUMER......................................................................................................................................1414．Pollution Pollution (15)1515．Educational visits visits........................................................................................................................................................................1616．Education in Great Britain Britain..........................................................................................................................................1717．A SUCCESS STORY STORY (18)1818．Beniamin Franklin Franklin....................................................................................................................................................................1919．Tom Sawyer Paints The Fence Fence (20)2020．An extract from The Adventures of Tom Sawyer Sawyer....................................................................2221．Family Lives Lives........................................................................................................................................................................................2322．The importance of family family (24)249AProtecting the innocentPansy wanted to write an article on detectives for the schoolBewspapen To get infor?nation, she interviewed Detective Ken.This is part of the interview.PANSY You say that you like working as a detective.Why?KEN Let me tell you about a recent case that I dealt with,Pansy.Mr Li is a very rich man who lives alone and enjoys collecting things.He purchased a vase for two million yuan.Heshowed it to only two people his friends Jill and Jenny.Then he locked it in the safe at hishouse.That night,someone stole it.Li reported the theft,and I went to his house to lookfor clues.PANSY Did you find any?KEN Yes,a black pearl earring near the open safe and,outside the open window of the room,I saw a lot of mud on the wet ground.Inside the room,the carpet was spotlessly clean. PANSY So what did you do next?KEN I interviewed Jill and Jenny.They both denied stealing the vase.But I noticed that Jill was wearing a black pearl necklace--but no earrings.PANSY So Jill was the thief?.KEN I didn't know.I needed proof.A good detective never jumps to conclusions.I showed Jill the earring,and she admitted it was hers.She said someone had stolen it from her house amonth before.I checked her story.It was true.PANSY So Jill was no longer a suspect.But what about your other clue--the mud outside and the spotless carpet inside?KEN That told me that probably no thief broke into Li's house.So I questioned Li and,in the end,he admitted stealing his own vase.He had bought insurance for it.The insurancecompany would pay him two million yuan if the vase was stolen.PANSY And who stole Jill's earring?KEN Li did that as well.He tried to make sure that Jill would go to jail instead of him. PANSY So now Li is behind bars.KEN Yes,and Jill is free.My job is to protect the innocent as well as find the guilty.That's whyI like working as a detective.An extract from Further Adventures of Sherlock HolmesHolmes’’The death of Ronald Adair in the spring of1894was one of the most interesting cases l ever worked on.I thought about it quite a lot,but could find no possible explanation.Adair was the son of a famous general who was abroad at the time.The young man's friends were from good families,and he seemed to have no enemies.On the day of his death he had played a game of cards at the Bagatelle Club with some friends.On the evening of30March,Adair returned from the Bagatelle at exactly ten o'clock.His mother was out,visiting relatives.The servant said Adair went upstairs to his room,where she had lit a fire.She had opened the window because some smoke from the fire had blown into the room.Just before midnight,Adair's mother returned and went to say goodnight to her son.The door was locked and there was no answer,so it was forced open.Adair was found lying near the table.A bullet from a small gun had entered his head,but the police could find no weapon.Some coins were on the table,and a note with names of friends at the Bagatelle.This appeared to be a list of all the money he had lost and won playing cards.There were no marks on the outside wall.Since it was impossible to aim a small gun from a distance,the murderer must have been in the room.Nobody had heard any noise.In addition to all this,nothing had been stolen from the room.COMPUTERSTony plans to write an article about computers.This is some of the information he has collected.Hidden helpersNot so many years ago,you hardly ever saw computers.Now they are everywhere.There may also be tiny,hidden computers in your home that you are unaware of.There may be one inside your TV set,telephone or washing machine.So maybe you depend on computers more than you realize.What kind of jobs can a computer do?It is common knowledge that computers are super calculators.They can calculate very fast and rarely give wrong answers.They can also type,print and draw things like diagrams and graphs. They can teach you and play games with you.More importantly,they can operate railways(like the underground)and fly aeroplanes and spaceships.For these reasons,we often call them electronic brains.Is a computer cleverer than I am?The answer to this question is,for the time being,'No'.Your brain can understand the meaning of things better and create new ideas.However,one day computers may be able to do most things that a human brain can do and do them better.They may be better than doctors,judges and teachers at doing their jobs.If this is true,it raises interesting questions.What will happen to us if computers can do our jobs?How will we spend our lives?Will we have nothing to do?Computers may change our lives. But will they make them better?How do we give a computer instructions?We give a computer instructions by putting a program into it.The program is written by a human being,and it is essential that the human does not make a mistake.If we want a computer to do diCferent jobs,we have to give it different programs.CD-ROMsMany of today's computers have CD-ROM drives.A CD-ROM can hold over300,000pages of writing,and can also contain pictures and sound.Thus,for example,you can use your computer to read about a famous person in history such as John F Kennedy,and you can see a photograph or video of him,and even listen to him speaking.Some people think that CD-ROMs will soon be more popular than books.The History of the InternetA research team at the United States Pentagon first developed the concept of linking computers together in the l960s.They wanted to have a system that would enable universities,research departments and the military to share resources with each puters at this time were as large as refrigerators and could not be transported easily.Another problem was that they were often complicated and not compatible with each other. The research team had to overcome these difficulties to create a network that could share computing power.Gradually,more and more scholars came online.Years later,businessmen began using the lntemet,too.The number of people using it is increasing all the time and it is becoming more widely available across the world.In fact,somewhere in every continent in the world,it is possible to use the lnternet.There is a wide range of services available on the lnternet.This means that there are many different ways to communicate.The most popular way is undoubtedly electronic mail--more commonly called'e-mail'.The second most popular is browsing on the World Wide Web(WWW). Briefly,the WWW is a very big series of connected pages containing various forms of multimedia. The third most popular way is real time text based communication between users such as IRC--lnternet Relay Chat.The night of the horseA newspaper ran a short story competition on famous talesfromhistory.This isastory one of the students sent in.The soldier came down the stairs--two at a time.'Captain,they've gone,'he cried.'They've disappeared--all of them.The plain is'But the captain of the guards was no longer listening.He was going up the stairs--three at a time.Seconds later,the captain stood on the high wall of the city of Troy.He looked down at the empty plain and,beyond it,at the empty sea.'They've gone and we've won,'he said.'The Greeks have tried for ten years to capture our city.Now they've sailed away.And they've taken everything with them.''Not everything,sir,'the soldier said.'They've left their horse.'Outside the main gates of the city stood a huge horse made of wood.'Ah,yes,'the captain said,'that wooden horse.It's so big that they couldn't take it with them. Well,it's ours now.Get some help and pull it into the city.That won't be difficult.It's on wheels.' 'But why is it on wheels,the soldier asked.'I think that maybe the Greeks want us to.'The captain interrupted him.'You're a soldier,'he said.'You don't have to think.You have to obey orders,and I'm giving you one now.Move that horse.'And so the Trojans dragged it into the city with ropes.That night,in the main square of the city,all the citizens of Troy celebrated.They sang and danced around the horse,and made jokes about their enemies,the stupid Greeks.Then the Trojans made sure all the gates of the city were securely locked,and they all went to sleep,including the gate guards.By midnight,the square was empty,except for the giant horse.The six Greek soldiers waited for another hour,to be sure.Then,very quietly,they opened the secret door in the side of the horse and climbed out.No guards stopped them as they opened the main gates.Outside stood the Greek army.It had returned in the darkness when the citizens celebrated inside.Now the army entered the city.The Greeks seized the captain and dragged him away.For ten years,they could not capture the city by fighting.In one night,they succeeded in capturing it by a trick.Qian Xuesen:Father of China's Aerospace Oian Xuesen is a pioneer in the development of China's aerospace science and technology.He is called'Father of China's aerospace'and'King of Rockets'.Qian was born in Shanghai on11December,1911.In1934,he graduated from the Mechanical Engineering Department of Shanghai Jiaotong University.He then went to study in the USA,with the help of public funds.In1939,he was awarded a doctorate in Aerospace and Mathematics from an American university.After this,he spent many years teaching and doing research work at universities in the USA.Qian returned to China in1955.After Qian left the USA,an American writer wrote an article describina the importance of Qian's theories,and the rising strength of China's national defence. Four months after Qian's return to China,he submitted a report to the State Council about using China's aerospace industry for national defence.Based on his proposal,the State Council and the Central Military Commission set up the Committee of the Aerospace Industry.This was an important body for missile and aerospace science study,and Qian was elected a member of the committee.Oian was very committed to his work on the use of rockets for national defence,and was later appointed the first President of the Missile Research Institute.He participated in the development and production of different types of missiles and the first earth-orbited satellite in China.As well as science,he is also interested in medicine,philosophy and music,and is good at these things,too.On his90th birthday,many leading scientists had a huge conference to honour his contribution to aerospace development.FISHING WITH BIRDSWang Damin sits on the side of the fiver cooking a meal,with a large bird on his head.The bird is a cormorant,and Damin is a fisherman.He is over65now but still works every day.He is thin and of average height,but he is very fit.Although he is an elderly man,he is strong enough to control his raft in the river where he lives and works with his ormorants.Cormorants are large,black birds,about a metre long.They are good at catching fish because they can swim well under water.Their large feet are used to push them quickly through the water. They can dive down25metres and stay under water for up to two minutes.Damin does not require nets or a fishing rod to catch fish.That is done for him by his twelve cormorants.A fishing trip often begins in the late afternoon.Damin sets off on his bamboo raft with his birds.When he reaches the fight place,he stops.A piece of grass is tied around the neck of each bird,so that it cannot swallow the fish.Then Damin pushes the birds into the water,and jumps up and down and bangs the water with his pole.The fish are frightened by this.At night,a light is hung from the front of the raft.This enables the fisherman to see better and also attracts the fish.The cormorants swim down and catch the fish,and bring them back to the raft.The fish are then removed from the birds'mouths by the fisherman and thrown into a big ter,some of the fish are sold,and the rest are divided between Damin's family and the cormorants.Cormorant fishing is a traditional Chinese skill,probably more than a thousand years old. Damin enjoys his work and he is teaching his grandson everything he knows.However,few young people are interested in doing this type of work in the modem world.In fifty years,perhaps there will be no more cormorant fishermen in the world.Some Facts About Te Tea aTea is the most popular drink in the world besides plain water.There are thousands of different types of tea available.All tea comes from the Camellia Sinensis bush--also known as the Tea Plant. The leaves and buds of this plant are picked several times a year,usually by hand.After picking,the tea is processed into black tea,oolong tea,green tea or white tea.Black tea was invented in China in the Ming Dynasty as a way to keep tea fresh when it was being transported long distances.As tea has to travel a long distance to reach places such as Britain, Canada and Australia,it is not surprising that Westerners drink mostly black tea.However,the majority of the world drinks green tea.Herbal tea is prepared in the same way as regular tea but is not really tea.This is because it contains herbs,fruits,spices,etc but no leaves from the Tea Plant.To truly be tea,the leaves must come from this plant.All tea naturally contains caffeine,which comes from the tea leaves. Antioxidants are the properties found in some foods that reduce your risk of getting cancer and heart disease.All regular tea has a lot of antioxidants.Decaffeinated tea is regular tea(usually green or black)that has been processed to remove the caffeine.In recent years,organic tea has become popular,too.This is tea that comes from plants that have been grown without the use of any chemicals.People believe that it tastes better and is healthier,but sometimes it costs more than non-organic tea.This is because the size of the crops is often smaller.MemoryJoyce wanted to have a feature about memory.She and her editors all agreed to write short articles on this topic.ARTHURI read in a book that we have a short-term memory and a long-term memory.When people get older,their short-term memory becomes worse,but we can still remember things that happened a long time ago.My Grandad told me a joke about memory.He said,'When you get old,three things start to go wrong.First,you start to lose your memory.And I can't remember what the other things are!' JOICEMemory is essential for life.I saw a programme on television about a man who had had an accident and injured his brain.Afterwards,he could not remember anything for longer than a few minutes.His wife visited him in hospital every day,but he forgot her visits a few minutes after she left. He was often angry with her because he thought that she never visited him.It was very sad. PANNCYOne basic way of improving your memory is to use the link method.If you want to memorize something,you must make a picture in your mind.If the picture is silly,strange and colourful,you will remember it better.For example,I am trying to remember the word'smiles'.An easy way to do this is to imagine there is a'mile'between the first letter and the last letter.This makes it the longest word in the world!TONNYIn the Guinness Book of Records,we Can find some amazing stories about memory.For example,Gou Yanling from Harbin in China has memorized more than15,000telephone numbers. And Dominic O'Brien from Britain remembered the correct order of2,808playing cards,after seeing them just once.MILLIEMemory is connected with our feelings.For example,if someone says'This is a spider,'and then puts a large spider on your hand,you will probably remember the word'spider'!When something dramatic happens,we usually remember it well,and we also remember where we were and what we were doing.For example,98%of older people in the USA can remember where they were when they heard about the death of President John F Kennedy in1963.How to Improve Your MemoryThere are many things you can do to improve your memory.Among them are various memorizing methods as well as taking special care of your health.It is important that you regularly stimulate your brain to make your memory more efficient. You can do this by doing activities that you do not normally do and by changing your daily habits. Learning a new skill helps your brain to develop.When trying to memorize something,you should focus your attention and concentrate on the most important things about it.Do not allow other thoughts to enter your mind because this will lower your chances of making accurate memories.An excellent way to help memory is to link information with pictures.These are referred to as mnemonic techniques.Try to see the images in your mind.Taking notes,being organized and keeping a diary will also be useful tools.Healthy food and plenty of vitamins are essential for your memory to work properly.Drinking a lot of water also helps maintain your memory.You must allow your brain to have enough sleep and rest.When you are asleep,your brain stores memory.Not enough sleep can,therefore,cause problems with storing information.In addition,being tired will stop you from being able to concentrate well.Caffeine in tea and coffee are very good at preventing sleepiness and helping concentration,but they can also cause problems with memory.In order to concentrate well,you must be relaxed.Generally keeping fit and regular health checks are both important as well--not just for improving your memory.Comic StripsCreating a comic stripRule l Think of a________that is________or________.Make the story move Something________must happen in________each picture.Rule2Give the characters strong________which will be easy to understand just by________ looking at the________Drawing the stripRule l For variety,leave some flames without________Rule2For interest,vary the________of some frames.Rule3Explain changes of scene or time by using a line of________Rule4Use sound________to add excitement.Creating a comic stripThe first thing to do when creating a comic strip is to think of a plot.It needs to be funny or dramatic with an exciting finish.It should be full of action to keep the reader interested.The story needs to move fast,and something new must happen in each picture.The characters need strong personalities which will come across in the pictures.You can tell what the Characters above are like just from looking at them.Drawing the stripHere you can see how the script(you can,only see the first part)was made intoa finished comic strip.It was drawn using a dip pen with a special nib.Some frames can be left without borders to add variety.The story is mainly told in the pictures,but there are bubbles for speech and thoughts.Scenery can make the strip come to life．Frame sizes are varied to make the strip more interesting.Sound effects add excitement to the pictures.A line of text at the top can explain changes of scene or time.The Fox and the CrowEarly one morning,a crow was sitting in a tall tree.She was holding a big piece of meat in her mouth.She thought it would be a nice breakfast for her baby.An old fox was looking for some food.He saw the crow with the meat.He really wanted to eat the meat himself.He thought very hard about how he could take it from the crow.The fox made a plan.He could not climb the tree so he would have to make the crow drop the meat.He spoke to the crow very politely,and asked how she was and how her baby was.The fox then told the crow that she had a beautiful voice and that he would like to hear her sing. The crow was happy and thought that the fox was very kind.So she decided to sing a song for him. She opened her mouth and the fox's plan worked.The meat fell down into his mouth.9BTHE GREEN CONSUMERThis book says that our world is in danger.It is vital that we do something to save the earth. First of all,what are the threats to our environment?The Greenhouse EffectThe writers ask us to imagine the earth inside a kind of greenhouse with the atmosphere around it acting like the glass,letting sunlight in while keeping much of the warmth from getting out.The atmosphere is essential to all living things.Without it,the earth would be as cold and lifeless as the surface of the moon.'The trouble is that our atmosphere is changing because we are polluting it with chemicals--in the form of gases--and it is keeping in too much heat!'These gases,mainly carbon dioxide(CO2),are produced by burning fuels such as petrol.The Greenhouse Effect may cause the level of the sea to rise and drown cities and even whole countries. Damage to the ozone layerThe writers tell us that'ozone is a gas which occurs20-50km above the ground.It forms an essential protective layer around the earth.Without it,the sun would burn us up.'We are making holes in the ozone layer mainly by using chemicals called CFCs.We use these in fridges and spray cans,and to make plastic items such as fast food boxes.Destruction of the rain forestsThe burning and cutting down of trees is making the Greenhouse Effect worse because trees take in C02.It also causes erosion of the soil and flooding,as well as destroying the people and animals who make the forests their home.Bad habitsMany of our habits cause pollution,especially our habit of using things once and then throwing them away.This creates massive mountains of rubbish.We do not know what to do with the rubbish and it pollutes our land and sea.For example,seven billion drink cans are thrown away in Britain each year.That is enough to reach from the earth to the moon.How can we save the earth?The book's idea is that we should become green consumers.That is,we should only buy and use things that do not damage the environment.And we should buy only from companies that do not damage the environment either.PollutionPollution means contaminating the Earth's environment with materials that harm people's health and lower their quality of life.Pollution can also harm animals and plants.There are many different forms of pollution.The three major groups are air pollution,land pollution and water pollution.Air pollution comes from many different sources--not all of them are man-made.For example, dust storms in deserts and the smoke from forest fires are natural sources of air pollution.In urban areas,dirty air is more noticeable because of the fumes from traffic and the waste from factories. Air pollution can affect humans by causing sore eyes and respiratory problems,especially in children and the elderly.Land pollution is caused by the deposit of solid waste(e.g.,cans,bottles,plastic,etc.)that cannot be broken down quickly or at nd pollution can affect the lives of animals and plants, and it makes the environment look very bad.Recycling and reusing materials can help reduce the amount of land pollution.Other methods include landfill--using the rubbish to make new land--and burning the rubbish,but these two methods can pollute the water and air.Water pollution results when substances that are released into lakes,rivers,oceans,etc.stay in the water or build up at the bottom.This form of pollution may also begin in the air if the air is polluted and causes acid rain.When it rains,the rain will then pollute the water in lakes,rivers, oceans,etc.Soil erosion is one example of natural water pollution and can cause problems if the soil blocks the flow of water and leads to flooding.Pollution from human sources includes chemicals,pesticides,waste from factories and human sewage.Educational visitsJoyce wanted to have some articles in the school newspaper about educational visits to other countries.She asked some older students to write these articles.A wonderful year in New Zealand Tammy LuoIf I went to New Zealand,would I be able to understand people?This was the question which first worried me when the American Field Service programme accepted me.I stayed with a New Zealand family in Auckland for one year.At first,I found that communicating was quite difficult.But my hosts were very patient,and they helped me to learn fast As part of the programme,AFS students try to tell people about their own culture,I took many photos and postcards of China with me,as well as some simple Chinese books.I gave a talk about China to some classes in school,and I even did some simple Chinese cooking.It was a wonderful year.I learned about a new culture,and I became more confident.Visiting the poor in Thailand EdwinSuLast year I went to Thailand for ten days,The trip was funded by World Vision,which helps poor people throughout the world.I went with another student and two reporters.The aim of the trip was to see the problems for ourselves.We were deeply affected by what we saw.There is a big gap between the lives of the rich and the poor.In some areas we saw families living in rubbish dumps.However,the Thai Government is working hard to improve the situation.The trip was actually quite hard work,but it was a very valuable experience for me.It has shown me how fortunate most of us are here in China.Scholarship to Japan Sylvia WangThis summer,I was fortunate to win a Japan Airlines scholarship.This enabled me to visit Japan for six weeks.For five weeks,all the foreign students lived in a hotel and attended Japanese language classes.We also had classes on Japanese culture,including flower-arranging and the art of tea-making.We went on sightseeing tours and visited a television station.After the first five weeks,we visited Kyoto,the old capital of Japan,and Yokohama.We stayed with friendly families in these cities.I thought that,if I went abroad,I would make many new friends.This turned out to be true.I met and talked to students from Korea,Brazil and Australia,as well as many Japanese.I left Japan three months ago and since then,I have kept in touch with my new friends by writing letters.。
The Art of Estimation*SAID SHAKERINDepartment of Mechanical Engineering,University of the Pacific,Stockton,CA 95211,USA.E-mail:sshakerin@The ability to perform estimation is an asset,for example,when dealing with problems with limited or unavailable data.Engineering students,in general,are inadequately prepared to perform rough estimation.A possible reason for this shortcoming is that the emphasis in engineering curricula is on detailed analysis and not enough attention is given to developing students'estimation skills.This paper outlines the importance of estimation and lists attributes that are necessary to carry out reasonable estimation.Furthermore,it provides a list of activities and exercises,appropriate for use in the lower division courses,to engage students in estimation scenarios and to launch them on a path to developing this skill.INTRODUCTIONESTIMATION IS an integral activity of our daily livesÐfrom determining how much cash to take along for an upcoming vacation to purchasing enough paint to add some color to our homes.Considering the latter,if our estimate is way off,we either end up with a lot of extra paint or need to make another trip to the paint shop to purchase more.Being able to estimate properly the various quantities that one encounters is a useful skill.People use experience and common sense and read labels and instructions to perform these estimations,which usually require simple arithmetic.Engineers also make use of estimation in their practice to determine answers to ill-defined problems or when a detailed solution is not required.Estimation particularly plays an impor-tant role in the preliminary stages of the design process,when decisions have to be made based on incomplete or unavailable details/data,and selec-tions must be made from a multitude of options.Furthermore,estimation is used to check the validity of answers based on back of the envelope type calculations.Engineering estimation (E 2)covers a large domain between guessing (instantly done and costing nothing)and detailed analysis (time consuming and expensive).Successful E 2is performed based on knowledge of dimensions and units,basic laws of physics and modeling,the ability to relate and compare,and common sense.Like many other attributes,an engineer's ability to estimate is enhanced and strengthened by experience and gaining professional judgment.CURRENT SITUATIONIn the late 1990s,a comprehensive study was undertaken at MIT to ascertain mechanical engin-eering students'ability to perform simple engin-eering estimations.The estimation questions posed to students in the survey related to energy in a small battery,drag on a bicyclist,and power output of a small motor.(The study also included students from five other top-ranked mechanical engineering programs,as well as practicing mechanical engineers for comparison purposes.)The study culminated in a Ph.D.dissertation by Linder [1]and resulted in a number of publications (e.g.[2,3]).The reader is encouraged to consult these references as they document details of the survey and findings with profound implications in engineering education.Two important conclusions of the study are quoted below.`Students were found to have considerable difficulty making estimates for common engineering quantities,such as force and energy.'`Students were also found to have difficulty applying basic engineering concepts in rough estimation situa-tions even at the senior level.'After reading the MIT study,the author became curious about how well University of the Pacific (Pacific)engineering students would perform E 2.He conducted a survey,borrowed from the MIT study,in the engineering Mentor III course in Spring 2003.Students in the two sections of this course were graduating seniors from all engineer-ing majors.(At Pacific,the engineering degree is a five-year program including one year of co-op.Thus,there are two years at the senior level.)Each question used in the estimation survey was given as an impromptu,five-minute in-class activ-ity.There were two questions in the survey,but only one is reported here as the other resulted in the same findings.Students were told not to write their names on their responses and that the activity had no effect on their grades in the course.The question was to estimate the energy content of a fresh 9-volt battery.Fifty-eight students participated and their numerical answers,which cover many orders of magnitude,are plotted in *Accepted 25July 2005.273Int.J.Engng Ed.Vol.22,No.2,pp.273±278,20060949-149X/91$3.00+0.00Printed in Great Britain.#2006TEMPUS Publications.Fig.1.This,in addition to other results,as organ-ized and tabulated in Appendix 1,corroborated the MIT findings that engineering students in general are not adequately prepared for even simple estimation problems and that they have problems with dimensions and units.WHAT TO DOTo help alleviate the present situation,the author advocates a systematical approach to expose students to estimation scenarios.Students should be encouraged to practice estimation and be made aware of its importance through short exercises with everyday objects and experiences.The more we ask students to estimate,the better they are prepared to use this skill in follow-up courses and eventually in their careers.Estimation exercises should be included in all courses,and especially the lower division courses,where the engineering foundations are established.Examples of such courses are Introduction to Engineering and Statics,where dimensions,units,and basic engineering concepts are discussed and learned.Several estimation activities appropriate at the freshman level are presented below to illustrate examples of what can be done.These activities could be done in class or assigned as homework.Activity No.1Ask students to make a list of familiar objects to serve as easy-to-remember estimation standards for various quantities.For example,a credit card is approximately 3.5inches long;a burning match converts chemical energy to about 3Btus of ther-mal energy;a hair dryer requires about 1kW of electrical power and so on.Of course,body parts such as feet and cubit (distance from elbow to fingertips)can be used for length standards.This activity can be performed by groups and then tallied on the board for the entire class to benefit.With such a list of objects in their memory,students will have a better grasp of units and how big,or small,they are.As students advance through their engineering programs,they can refine and add to their list of estimation standards.A fascinating source for visual comparisons among various quantities of distance,area,weight,density,energy,temperature,etc.is a book titled Comparisons [4],published in 1980.Activity No.2Take a piece of lumber,such as a length of 2by 4,to the class and ask students to estimate its length,width,and thickness.Point out the difference between the nominal and exact size in the lumber industry.Considering the lecture room,ask students to estimate the number of cans of paint needed to paint the walls,i.e.estimate the surface area.Point out the standard ceiling height in a typical older residential building (room's ceiling height %8ft in the USA).Activity No.3Ask students to estimate the weight of body extremities such as an arm or leg.This can be done,for example,by looking at a photograph with super-imposed gridlines to estimate the percentage of the body of each body part.With two views (front and side),fairly good estimates can be made.Simple experiments with bathroom scales can be performed to confirm the estimate.This kind of information is useful to designers of rehabilitative devices.Activity No.4Ask students to estimate the drag on a bicyclist traveling at 20mph.This was also one of the estimation questions that were used in the MIT study.There are several methods by which drag can be estimated as documented in Linder's disser-tation [1].A related article about drag on cars appeared in Scientific American [5].Activity No.5Ask students to estimate their own physical power.(Two excellent books that present and discuss different quantities (size,energy,etc.)in biological organisms are On Size and Life [6]and Exploring Biomechanics [7].)One simple way to do this is by climbing a flight of stairs.By estimating the person's weight (W ),the stair height (H ),and the time it took to climb (t ),the change in potential energy (PE =W ÂH ),and then power (P =PE/t )can be determined.This power is roughly 0.3hp for an average adult,but note that it would be difficult to sustain it for a long time.(For compar-ison,the pumping power of a human heart is about 0.002hp.)Of course,unit conversion plays an important role here;e.g.,to convert from lb f .ft/s or N.m/s to hp.Bryan Allen,an avid bicyclist in top condition,sustained about 0.4hp for near 3hours as he pedaled and piloted the human-powered Gossamer Albatross in June 1979to cross the English Channel.Point out the difference between burst and sustained amounts of power.Point out the different units of power usedÐhp for prime movers,kW for appliances,MW for power plants,etc.Also,point out the differencebetweenFig.1.Answers to estimation problem.Only those answers given in joules or equivalent are shown (31out of 58students).S.Shakerin274kW and kW.h as some,even senior students,have difficulty with this.Activity No.6Ask students to estimate home energy costs and compare these with their monthly statements from the utility company.Important lessons about kW.h, Btu,therm,cost,etc.can be shared via this exercise. Also,students will get a sense of the relative magnitudes of power requirements of various appli-ances.Utility companies might have useful informa-tion on this subject(e.g.,see ).Activity No.7Almost everybody has used9-V batteries in consumer products such as toys,smoke alarms, audio devices,etc.Yet,most people,includingsome engineering students,are clueless about the amount of energy stored in such a battery.The idea behind this activity is to conduct a simple experi-ment to allow students to measure this energy.ExperimentÐHave different groups use fresh bat-teries with different brand names for comparison. Connect a9-V battery to a light bulb(or other suitable loads such as a microprocessor cooling fan).Using an inexpensive multimeter,measure and record the battery voltage(V)and the bulb's resistance(R)every hour until the bulb is very dim. (Instrumenting the circuit with two multimeters to measure voltage across the bulb and current going through the bulb will yield more accurate results but the above procedure is quite adequate for our purpose.)Using Ohm's law,students should be able to determine the power(P V2/R)at each measure-ment instant,and then calculate the energy during the entire period(E ÆP.Át).After finishing the experiment,students will have been exposed to a simple circuit and use of a multimeter,Ohm's law, units of energy and power,and perhaps learned some safety lessons.Additionally,they will hope-fully remember the amount of energy stored in a 9-V battery for future reference.It is interesting to compare the cost of this energy with the PG&E (power company in California)residential rate, which is about12cents per kW.h or0.003cents per kJ.A9-V battery contains about10kJ and costs$3,which results in30cents per kJ.A battery is indeed a very expensive,but convenient,source of electrical energy!Activity No.8Ask students to estimate the power of a commercial jetliner.Students need some basic data to properly respond,and such data for both commercial and military aircrafts can be found at .For example,specifications for the Boeing747±400ER,the largest in the700series jetliners in production,are:W max 910,000lb f, V cruise 567mph at35,000ft,engine thrust 63,300lb f.Therefore,for this aircraft,the power to takeoff and reach the cruising altitude in about 10minutes is roughly70MW.In comparison,the power of a Boeing717,the smallest in production, turns out to be about8MW.It is interesting to note that the length of a717is roughly one half that of a747as seen in Fig.2,resulting in a volume (read weight)ratio of about one eighth,which is roughly the same as the power ratio.This exercise will allow students to appreciate the enormous power exhibited in jetliners and get a sense for how big a MW is.It is also educational to estimate the energy content of a jetliner due to its fuel.At 130Â106J/gal,a gallon of jet fuel is roughly equivalent to40,000burning matches or50lb of TNT.With tens of thousands of gallons of fuel onboard,a jetliner becomes a deadly weaponÐthe destructive force that brought down the Towers in the WTC tragedy on September11[8].An excel-lent source containing estimates related to various aspects of flying is a book by Henk Tennekes[9].Activity No.9As a follow-up exercise,ask students to report on output power of different kinds of motors such as a humming bird,human heart,small DC hobby motor,car engine,power plant,rocket,etc.Power is an important quantity in all branches of engin-eering and,with this kind of exercise,students will be better able to grasp the relative magnitudes of power among somewhat familiar objects.Figure3 represents a graphical example of the outcome of this activity,which clearly depicts order of magni-tudes among familiar objects and living systems. Appendix2provides the information used to estimate the quantities shown in Fig.3.Activity No.10Assign Fermi type problems either during lectures or as homework problems.Enrico Fermi, the famous nuclear physicist of the mid-twentieth century,used to surprise his physics students by asking them questions such as:`How many piano tuners are in Chicago?'These kinds of questions require students to use very simple arithmetic and relations to find answers to seemingly impossible problems,and to gain some insight.To seethe Fig.2.Accurate scaled models of the Boeing717and747.The Art of Estimation275answer to this and some dozen other such ques-tions,refer to the NASA web site [10].Two examples of Fermi type problems that the author has assigned to students are given below.1.Estimate the amount of paper needed to print the university newspaper on an annual basis.Determine the answer in terms of boxes of standard letter size paper.2.Estimate the number of books in the university library.Estimate their weight.Overall,students should be given ample opportu-nities to develop E 2ability by systematically going through basic dimensions and units and working up on physical lawsÐapplying their knowledge to common things and experiences.The above activ-ities,as well as others available in other references (e.g.[11,12]),will help students in this endeavor.As implicitly indicated earlier,there is much more to E 2than units and dimensions.However,units and dimensions and simple relationships (e.g.P E/t )form the foundation.Once students are equipped with this,they are on the road to making estimations in more complex problems and situations.Work done at the University of the PacificIn collaboration with colleagues,the author has integrated some of the above activities in the Introduction to Engineering course,which is a required course for all engineering students.Speci-fically,one formal lecture was delivered on estima-tion,followed by a homework set of six problems and mini-projects,similar to the set described in this paper.One laboratory session was also dedicated to the height estimation,followed by crude measurement,of a tall building on campus.Students actively participated in these exercises.We are hoping to continue to strengthen our coverage of estimation throughout the curricula with the goal of equipping our students with this important skill.CONCLUSIONSBased on recent survey results,it appears that engineering students are not adequately prepared to make reasonable estimations of engineering quantities.Current engineering education practice places too much emphasis on detailed analysis.For students to learn to estimate,they have to practice by doing it.Ten activities were suggested to help students in developing their estimation skills.Much more needs to be done in rectifying the current deficiency in students'ability to estimate.Acknowledgements ÐI am grateful for the encouragement I have received from Professors Rahim Khoie and Camilla Saviz in developing my ideas about estimation.Professor Ed Pejack suggested the experiment in Activity No.7.An earlier version of this paper was presented at the 2005ASEE Annual Con-ference and Exposition in Portland,Oregon,USA.REFERENCES1.B.Linder,Understanding estimation and its relation to engineering education,1999,Ph.D.Dissertation,MIT.2.B.Linder and W.C.Flowers,Students response to impromptu estimation questions,Proceedings of the 1996ASME Design Engineering Technical Conferences and Computers in Engineering Conference ,Irvine,California,1996.Fig.3.Ten orders of magnitude among power outputs of familiar biological and engineering systems.S.Shakerin2763.B.Linder and W.C.Flowers,Integrating engineering science and design:A definition and discussion,International Journal of Engineering Education ,17(4,5)2001,pp.436±439.4.The Diagram Group,Comparisons ,St.Martin's Press,New York,NY,1980.5.M.Ross and J.DeCicco,Measuring the energy drain on your car,Scientific American ,December 1994,pp.112±115.6.T.A.McMahon and J.T.Bonner,On Size and Life ,Scientific American Books,New York,NY,1983.7.R.M.Alexander,Exploring Biomechanics:Animal Locomotion ,Scientific American Library,New York,NY,1992.8.T.J.Mackin,Engineering analysis of tragedy at WTC,/content/files/collapse.asp9.H.Tennekes,The Simple Science of FlightÐFrom Insects to Jumbo Jets ,MIT Press,Cambridge,MA,1997.10.J.Kolecki,Estimation problems,/WWW/K-12/Numbers/Math/Mathematical_Thinking/index.htm11.C.E.Swartz,Back of the Envelope Physics ,Johns Hopkins University Press,Baltimore,MD,2003.12.M.M.Hofle and K.W.Bosworth,Math,engineering,and science:Applications for grades 4±8,Proceedings of the ASEE Annual Conference ,Portland,OR,2005.APPENDIX 1Estimation surveyÐPacific's Engineering Mentor III ClassesÐMarch2003The Art of Estimation277APPENDIX 2Information used to obtain estimated quantities shown in Fig.3a.Hovering large humming bird:James Lighthill,a brilliant fluid dynamics expert,estimated the poweroutput for hovering hummingbirds to be about 13W per kg of body mass based on momentum theory.A large humming bird is about 20g.b.Human heart:Pumps about 5liters of blood per minute (1/min)at about 100mm of mercury (mmHg)in pressure rise.Proper conversion factors have to be considered to perform calculation to obtain power.c.Hobby DC motor:Consult a hobby electronics catalog,for example,.Look at theDC motors and find out their power rating;e.g.,one is listed at 12V and drawing 0.75Amps.d.Light bulb:This is obvious!e.Hair dryer:Look at the name plate of a typical household hair dryer.f.3-phase motor:Consult equipment catalog,for example,.Look at medium-size3-phase motors and find out their power.g.Car engine power:Drive your car from start to a certain speed and time ing simple relations (a =ÁV/Át,F =m .a,P =F .V),determined the power,neglecting drag,etc.Or,perform calculation based on typical values:car mass =2,000lb m (%1,000kg),reaching 60mph (%30m/s)in about 10seconds.h.Electrical power for 1000homes:If your household uses 1kW of electric power all the time,yourmonthly (720hours)electric bill will show 720kW.h.i.Jet airliner power:This was shown in Activity No.8.j.Nuclear power plant output:Consult text books on thermodynamics or electric power generation orvisit PG&E web site (they might have info on their nuclear power plants).Said Shakerin is Professor of Mechanical Engineering at the University of the Pacific,where he has been since he was awarded his Ph.D.from Colorado State University in 1986.Prior to that,he was educated at Arya-Mehr (now Sharif)University of Technology in Iran,Portland State and Oregon State Universities in the USA.He is a registered professional engineer in California,and served as department chairman from 1995to 1998,but stepped down due to medical reason.S.Shakerin278。
