On the Radial Distribution of White Dwarfs in the Globular Cluster NGC 6397

Available online at Journal of Hazardous Materials155(2008)369–377Preparation of nano-iron oxide red pigment powdersby use of cyanided tailingsLi Dengxin∗,Gao Guolong,Meng Fanling,Ji ChongCollege of Environmental Science and Engineering,Donghua University,2999North Renmin Road,Songjiang District,Shanghai201620,ChinaReceived8August2007;received in revised form20November2007;accepted20November2007Available online23November2007AbstractOn one hand,cyanided tailings are one kind of pollutants.On the other hand,they contain a lot of valuable elements.So utilization of themcan bring social and environmental benefits.In this paper,cyanided tailings were used to prepare nano-iron oxide red pigment powders by anammonia process with urea as precipitant.Atfirst,cyanided tailings were oxidized by nitric acid.Then,the oxidizing mixture was separated intosolid and liquid parts.The liquid mixture was reduced by scrap iron and the impurity of it was removed by use of NH3·H2O.Then,the seed crystal of␥-FeOOH was obtained,when the pure liquid reacted with ammonia liquid at the selected experimental conditions.At last,nano-ironoxide red pigment powders were prepared.The structure,morphology and size distribution of seed crystal and iron oxide red were characterizedsystematically by means of X-ray diffraction(XRD),transmission electron microscope(TEM)and laser particle size analyzer(LPSA).The resultsrevealed that typical iron oxide nanoparticles were␣-Fe2O3with particle size of50–70nm.Furthermore,the factors that affected the hue andquality of the seed crystal and iron oxide red pigment were also discussed.©2007Elsevier B.V.All rights reserved.Keywords:Nano-iron oxide red;Pigment;Cyanided tailings;Nitric acid;Recycle1.IntroductionIron oxide red is technologically important materials and has superior character in non-toxicity,chemical stability,durability and low costs[1].It is widely applied as components in vari-ous industrial products,e.g.,pigments in the building industry, inorganic dyes,ceramics,pigments and adsorbents in the paper industry,lacquers or plastics[2–4].There are many methods reported for the preparation of iron oxide red,e.g.dry methods and wet methods.Wet meth-ods include nitric acid oxidation,sulphuric acid oxidation,and ammonia process,et al.[5].Ammonia process uses ferrous sulfate as material instead of sheet iron.So the process has advan-tages in saving metal resources and protecting the environment. On one hand,cyanided tailings are one kind of pollutants.On the other hand,they contain a lot of valuable elements.So utilization of them can bring social and environmental benefits[6].How-∗Corresponding author.Tel.:+862167792541;fax:+862167792522.E-mail addresses:lidengxin@,clidx@(L.Dengxin).ever,there is not much research on the iron oxide red preparation by cyanided tailings.In the present study,an attempt has been made to pre-pare nano-iron red oxide pigment by cyanided tailings via an ammonia process with urea as the precipitant.The factors that influenced characters of seed crystal and iron oxide red were discussed.The result shows that nano-iron oxide red could be prepared with cyanided tailings under suitable conditions. The quality of the product can meet thefirst rank criterion of GB1863-89(China Industrial Standard).2.Experimental2.1.Materials and reagentsAll reagents used in this study were of analytical grade and locally procured.The cyanided tailings used in the experiment were obtained from Penglai Gold Smelting Plant in Shandong Province,China.Table1shows its chemical composition.0304-3894/$–see front matter©2007Elsevier B.V.All rights reserved. doi:10.1016/j.jhazmat.2007.11.070370L.Dengxin et al./Journal of Hazardous Materials155(2008)369–377Table1Chemical analysis of the cyanided tailingsElement ContentAu(g/t) 3.6Ag(g/t)25.0Cu(%)0.21Pb(%)0.42Zn(%)0.64S(%)41.22As(%)0.42Si(%) 3.73Al(%) 1.24Fe(%)38.072.2.Nitric acid oxidation of cyanided tailingsThe schematic diagram of facility for the cyanided tail-ings pretreatment is shown in Fig.1.This experimental facility mainly consists of afluidized bed,a catalyst regeneration set-ting and oxidized solution comprehensive utilization unit.The fluidized bed is a quartz cylinder with100mm i.d.and2500mm high.In the bottom of thefluidized bed,there is a gas distributor. Before starting an experiment,thefluidized bed wasfluidized by oxygen and preheated to the desired operation temperature.The superficial velocity can be kept at the desired value.Cyanided tailings was mixed with certain amount of hot water and stirred for about10min.Then,the sludge was sprayed into hotfluidized bed reactor.Oxygen or air in NO x regeneration setting mixed, was injected into thefluidized bed via the gas distributor,and reacted with the sludge.The oxidized tailings were discharged out in the precipitation section outlet,and were separated into solid and liquid parts in cyclone centrifugal separator.Then,partial liquid mixed with the new sludge and reflowed intofluidized bed reactor,while the catalyst entered into regeneration setting for recycling.The remainder was used to prepare nano-iron oxide red and oxidized tailings were used to leach valuable metals.Table2Experimental parameters of seed crystal preparation for different casesNo.V olume(mL)pH Amount ofair(m3/h)Temperature(◦C)Fe2+(g/L)13009–100.120 23000.11520 33009–101520 43009–100.11553009–100.115202.3.Purification of oxidized liquidScrap iron was added to the above oxidized solution before filtration.After scrap iron reacted completely with the oxidized liquid,the reduced mixture wasfiltered.Ammonia(NH3·H2O) was added dropwise to thefiltrate until pH reached4–5to purify ferrous sulfate in order to remove As,Pb,Si,Al,et al.The obtained pure solution was used to prepare seed crystal and the filter residues could be used to leach valuable metals.2.4.Preparation of seed crystalTwenty-five percent NH3·H2O solution was added dropwise to the purified solution until the pH of reaction system reached a certain degree.Then,air was bubbled into the mixture for a certain time at preset temperature.The resulting red orange solid product was then used as the seed crystal for the preparation of hematite.The reaction processes are as follows:2NH4OH+FeSO4→Fe(OH)2↓+(NH4)2SO4(1) 4Fe(OH)2+O2→4␥-FeOOH↓+2H2O(2) Table2shows the experimental parameters of seed crystal preparation for different cases.The effect of addition order of dispersant on the quality of seed crystal was discussed.Tartaric acid with1%amountof Fig.1.Schematic pretreatment process of cyanided tailings:(1)air compressor;(2)buffer;(3)valve;(4)gasflow meter;(5)differential gage;(6)catalyst regeneration setting;(7)air compressor;(8)three-phasefluidized bed;(9)pressure probe;(10)hydraulic cyclone;(11)tailings;(12)stirred tank reactor;(13)cyanided tailings;(14)liquidflow meter;(15)oxidized solution comprehensive utilization unit;(16)strainer.L.Dengxin et al./Journal of Hazardous Materials155(2008)369–377371ferrous sulfate was chosen as the dispersant.With other exper-imental conditionsfixed as listed in Table2(case5),three different feeding orders were taken as follows:one method was that the dispersant was added into seed mixture after the end of preparation reaction for the seed crystal;another method was that the dispersant was added into seed mixture before adjust-ing pH of the mixture for preparation seed crystal,and the last one was that the dispersant was added into seed mixture after adjusting pH.2.5.Preparation of hematite(α-Fe2O3)The above pure ferrous sulfide solution was heated by water bath up to a certain temperature.Urea,the seed crystal and fer-rous sulfate were added to the mixture and the pH of the mixture was adjusted to3–4.Then,the air was bubbled into the mix-ture.After ageing at known temperature for a defined period of time,sodium dodecyl benzene sulfonate(SDBS)with1% amount of ferrous sulfate was added and stirred for1h.The resulting precipitate wasfiltered off and washed with distilled water and allowed to dry at room temperature.The obtained product was characterized by X-ray powder diffraction(XRD) and transmission electron microscope(TEM).The main reactions are as follows:H2NCONH2+H2O→CO2↑+2NH3(3) NH3+H2O→NH4OH(4) 4FeSO4+O2+6H2O→4␥-FeOOH↓+4H2SO4(5) H2SO4+2NH4OH→(NH4)2SO4+2H2O(6) 2␥-FeOOH→2␣-Fe2O3↓+H2O(7) On the other hand,the effects of experimental factors includ-ing temperature,pH,velocity of airflow,concentration of ferrous sulfate and SDBS on the iron oxide red and the optimum molar ratio of urea and ferrous sulfate were also investigated.Table3 shows the experimental parameters of iron oxide red preparation for different cases.2.6.Analysis method2.6.1.Titration of iron ionChemical analysis of the liquids was performed to estimate the ferrous and ferric iron content by a titration method accord-ing to GB1863-89(China Industrial Standard).The results were the mean values of the two experiments using the same sample.2.6.2.Transmission electron microscope(TEM)The size and morphology of iron oxide nanoparticles were observed by TEM(JEM-1230,JEOL,Japan).The sample for TEM analysis was obtained by placing a drop of dispersant onto a carbon coated copper grid without any staining,and drying it in air at room temperature.2.6.3.X-ray diffraction(XRD)The X-ray diffraction(XRD)analyses were performed using a Cu K␣(1.5418A)source(40KV,40mA)from Siemens D-501,with a graphite secondary monochromator and a scin-tillation counter detector.The powered sample was placed on a flat plastic plate,which was rotated at30rpm.The scans were performed at25◦C in steps of0.04◦C,with a recording time of2s for each step.Where accurate2θvalues were required,Si was added as an internal2θstandard.ser particle size analyzer(LPSA)Laser particle size analyzer(LS13320)was used to analyze the size distribution of the obtained particles.2.7.Calculation of ferrous ion conversion rateC r=W1−W2W1(8) where C r is the conversion rate of ferrous ion;W1is weight of original ferrous ion;W2is weight of unreacted ferrous ion in the reaction system.3.Result and discussion3.1.Nitric acid oxidation of cyanided tailingsIn order tofind the optimum oxidation conditions in the course of pretreatment of cyanided tailings,three important fac-tors were selected including initial temperature of oxidization, initial concentration of nitric acid and mass ratio of nitric acid and cyanided tailings(MRNACT)and orthogonal experiment as shown in Table4was conducted.From Table4,it is obvious that the optimum factors of oxidation of cyanided tailings are as follows:reaction temperature is80◦C;initial concentration of nitric acid is30%;MRNACT is3:1.Under these conditions,oxi-dation rate is90.06%and pyrite in tailings has been oxygenated efficiently.Oxidation sludge can be delivered to leaching gold.3.2.Purification of oxidized liquidIn order tofind the optimum purification conditions,three important factors were selected including reaction temperature,Table3Experimental parameters of iron oxide red preparation for different casesNo.V olume(mL)pH Amount of air(m3/h)Temperature(◦C)[H2NCONH2]/[Fe2+] 13003–40.14 3.5:123000.1480–85 3.5:133003–480–85 3.5:1372L.Dengxin et al./Journal of Hazardous Materials155(2008)369–377Table4Orthogonal experiment of cyanided tailings oxidized by nitric acidNo.FactorReaction temperature Initial concentration of nitric acid Feed proportion of nitric acid and cyanided tailings 120101220202320303450102550203650301780103880201980302K16063.729.2K266.376.376.8K376.290.890.6reaction time and M Fe:M Fe3+(M Fe3+expresses ferric ion’s mass of oxidizationfiltrate)and orthogonal experiment as shown in Table5was conducted.From Table5,it can be found that the optimum purification conditions of oxidized liquid are as fol-lows:reaction temperature is40◦C;reaction time is60min; M Fe:M Fe3+is1:1.Under the optimum conditions,conversion ratio of ferric ion is100%;rate of displacement of copper is 91.2%;rate of displacement of silver is96.9%;arsenic and lead have been removed and pure ferrous sulfate solution can be obtained.3.3.Preparation of seed crystal3.3.1.Effect of temperature on the quality of seed crystalTo study the effect of temperature,a series of experiments were performed with the temperature ranging from15to45◦C. Other experimental parameters are listed in Table2(case1). Because temperature can promote the oxidizing reaction of fer-rous sulfate,C r tends to be high with the rise of temperature as shown in Fig.2(a).When ferrous sulfate is oxidized at45◦C,C r is97%,while C r is only93%when ferrous sulfate is oxidized at15◦C.Table5Orthogonal experiment of purification of reaction mixtureNo.FactorReaction temperature Reaction time M Fe:M Fe3+ 120300.2 220600.6 32090 1.0 440300.6 54060 1.0 640900.2 76030 1.0 860600.2 960900.6K1949622K29910080K39810096The crystallinity of the crystals produced,both in terms of foreign metal impurities and crystal phase,is an important fea-ture which results in different chroma and hue of the pigment. The different phases of iron oxide have different hues.Table6 shows the color change of seed crystal prepared at different tem-peratures.It is obvious that the temperature has an obvious effect on the chroma of seed crystal.The color of the seed crystal grows darker with reaction temperature increasing.At lower tempera-ture,the color of the seed crystal is bright red brown,while the color of the seed crystal changes into black at45◦C.The latter seed crystal can not grow into red iron oxide particles because it is not an iron oxide red seed crystal proved by its XRD pattern as shown in Fig.3.Fig.3shows the XRD patterns of the seed crystal prepared at different temperatures.It is observed that XRD patterns have obvious diffraction peaks,indicating that they have the highly crystalline character of the iron oxide.The XRD patterns shows Table6Color of seed crystal prepared on different conditionsFactors Color Temperature(◦C)15Turkey red brown 25Red brown35Dark red brown 45BlackpH8–9Jacinth9–10Red brown10–11Deeper red brown >11Dark brownAir(m3/h)0.04Black0.1Turkey red brown0.14Red brown0.2Dark red brown FeSO4(g/L)10Red brown20Red brown30Dark red brown 40BlackL.Dengxin et al./Journal of Hazardous Materials155(2008)369–377373Fig.2.Effect of different conditions on the conversation rate of Fe2+.(a)Effect of temperature on the conversation rate of Fe2+(volume:300mL;pH9–10;velocity of airflow:0.1m3/h;concentration of ferrous sulfate:20g/L);(b)effect of velocity of airflow on the conversation rate of Fe2+(volume:300mL;pH,9–10; T:15◦C;concentration of ferrous sulfate,20g/L);(c)Effect of concentration of ferrous sulfate on the conversation rate of Fe2+(volume,300mL;pH:9–10; velocity of airflow,0.1m3/h).that the peaks of the seed crystal prepared at15◦C are broader than those of the seed crystal prepared at45◦C.According to the formula of Sreeram[7],with other conditionsfixed,the width of diffraction peak is inversely proportional to the size of the particle.So it can be concluded that the grain size of seed crys-tal prepared at low temperature is greatly less than that of seed crystal prepared at high temperature.While the XRD pattern of the seed crystal prepared at15◦C matches well with the stan-dard␥-FeOOH reflections,the XRD pattern of the seed crystal prepared at45◦C can be assigned to the Fe3O4phase.It isobvi-Fig.3.XRD patterns of the seed crystal at different temperatures(a:15◦C;b: 45◦C).ous that crystal seed changes from␥-FeOOH to Fe3O4with the rise of reaction temperature.Therefore,the optimum reaction temperature is15◦C.3.3.2.Effect of pH on the quality of seed crystalTo study the effect of pH,the sample was subjected to dif-ferent pH of8–9,9–10,10–11.Other parameters are listed in Table2(case2).The results presented in Table6indicate that the color of seed crystal grows darker with the increase of pH and pH of9–10is favored for achieving a monodisperse character.Fig.4shows the XRD pattern of the seed crystal prepared at pH of8–9.The XRD pattern has obvious diffraction peaks, indicating that it has highly crystal structure.It matches well with the standard␦-FeOOH reflections.In the process of preparing iron oxide red,the seed crystal prepared at pH of8–9grows into iron oxide yellow,while the seed crystal prepared at pH of 9–10grows into iron oxide red.This implies the optimumpH Fig.4.XRD pattern of seed crystal prepared at pH of8–9.374L.Dengxin et al./Journal of Hazardous Materials155(2008)369–377Fig.5.XRD pattern of seed crystal prepared at different velocities of airflow (a)0.1m3/h;(b)0.04m3/h.is9–10in the process of preparing seed crystal.Either higher or lower pH can have drastic influence on the preparation of red iron oxide.3.3.3.Effect of velocity of airflow on the quality of seed crystalTo study the effect of velocity of airflow,a series of experi-ments were performed at different velocities of airflow ranging from0.04to0.2m3/h.Other parameters are listed in Table2 (case3).The effect of velocity of airflow on C r is given in Fig.2(b). As can be seen from Fig.2(b),C r increases with the increase of velocity of airflow.At the velocity of0.04m3/h,C r is only 88.4%,While C r is high up to97.3%at the velocity of0.20m3/h. This indicates that airflow can promote the reaction.When the airflow velocity is higher,dissolved oxygen increases and more Fe2+converts into seed crystal.Table6shows color of seed crystal prepared at different velocities of airflow.The color of seed crystal changes grad-ually from black to red brown with the increase of velocity of airflow,but the color of seed crystal changes from bright red brown to dark red brown at excessive velocity of air.Fig.5shows the XRD patterns of the seed crystal prepared at different velocities of airflow.The XRD patterns have obvi-ous diffraction maximum,indicating that they had highly crystal structure.The former XRD pattern matches well with the stan-dard␥-FeOOH reflections,while the latter can be assigned to the Fe3O4phase.According to the analysis of phase,the seed crystal of iron oxide black will form when the velocity of airflow is small.The main possibility is:the velocity of Fe(OH)2being oxidized into Fe2O3is low with little amount of air,and Fe(OH)2 maybe reacts with the formed Fe2O3into nucleus of Fe3O4crys-tallization prior to its oxidization into Fe2O3.At excessively high velocity of airflow,formed seed crystal is still␥-FeOOH.But Fig.6.XRD pattern of the seed crystal prepared at high concentration of ferrous sulfate.its color is dark,mainly because many formed crystal nucleus rubbed mutually at great velocity of air and their ability of reflect-ing light decreases.Therefore,the optimum velocity of airflow is0.1m3/h.3.3.4.Effect of concentration of ferrous sulfate on thequality of seed crystalTo study the effect of concentration of ferrous sulfate,a series of experiments were performed with the concentration ranging from10to40g/L.Other parameters are listed in Table2(case 4).Fig.2(c)shows the influence of concentration of ferrous sul-fate on C r.C r decreases with the rise of concentration of ferrous sulfate.When the concentration of ferrous sulfate is10g/L,C r is high up to98.5%.While for a40g/L ferrous sulfate concen-tration,C r is only90.2%.Table6shows the color of seed crystal prepared at differ-ent concentrations of ferrous sulfate.The color of seed crystal changes from red brown to black with the concentration of fer-rous sulfate increasing.Fig.6shows the XRD pattern of the seed crystal prepared at high concentration of ferrous sulfate.The XRD pattern has obvious diffraction maximum,indicating that it has highly crys-tal structure.It matches well with the standard Fe3O4reflections. It demonstrates that the phase of seed crystal changes with the concentration of ferrous sulfate increasing and the seed crystal cannot be used to prepare iron oxide red pigment.Ferrous sul-fate with low concentration can be used to prepare seed crystal, but when the concentration of ferrous sulfate is excessively low, the producing velocity of crystal nucleus is less than its growing velocity and the obtained grain size is big,so it can influence the characteristic of iron oxide red pigment.Therefore,the optimal concentration of ferrous sulfate in the process of seed crystal preparation is20g/L.3.3.5.Effect of addition order of dispersant on the qualityof seed crystalThe sedimentation time by the three addition orders of dis-persant separately were measured as shown in Fig.7.Fig.7 indicates when tartaric acid(dispersion)is added after adjustingL.Dengxin et al./Journal of Hazardous Materials155(2008)369–377375Fig.7.Effect of addition order of dispersion on the sedimentation time of sus-pension:(A)added after complete reaction;(B)added before adjusting pH;(C) added after adjusting pH.pH,the sedimentation time of seed crystal is the longest and the third addition method is the best to prepare seed crystal.The dispersion has a drastic effect on the size distribution of iron oxide nanoparticles in this work as shown in Fig.8.It can be found that dispersion can disperse the crystal nucleus,avoid its agglomerating and make it more regular.3.4.Preparation of iron oxide red3.4.1.Effect of temperature on the character of iron oxideTo study the effect of temperature on the character of iron oxide red,a series of experiments were performed with the tem-perature ranging from60to95◦C.Other parameters are listed in Table3(case1).As shown in Table7,the color of the resulting products gives the following shade as the temperature increases:yellow,jacinth, Turkey red and mauve.This is mainly because there is␥-FeOOH Table7Color of iron oxide red prepared on different conditionsFactor Color Temperature(◦C)60–65Yellow70–75Jacinth80–85Turkey red 90–95Mauve pH2–3Yellow3–4Turkey red 4–5Mauve5–6Dark red Air(m3/h)0.08Dark red0.14Turkey red0.20Yellow dehydration process and it has close correlation with tempera-ture.Dehydration process speeds up with the rise of temperature. The obtained seed crystal is red with light yellow,because it contains partial water of crystallization under70–75◦C.Dehy-dration is very prompt and the obtained seed crystal is bright under higher temperature.If the reaction temperature maintains excessively high,the velocity of␥-FeOOH dehydration speeds up and the oxidization period shortens.So the color of resulting products is red with purple.Therefore,the optimum temperature in the process of preparation of iron oxide red is80–85◦C.3.4.2.Effect of pH on the character of iron oxideTo study the effect of pH on the character of iron oxide red, a series of experiments were performed at different pH of2–3, 3–4,4–5,and5–6.Other parameters are listed in Table3(case 2).It was observed that the color of the resulting products grows from yellow to red with pH increasing.At pH of2–3,theresult-Fig.8.TEM of seed crystal:(a)added dispersion;(b)no added dispersion.376L.Dengxin et al./Journal of Hazardous Materials 155(2008)369–377Fig.9.TEM of iron oxide red (a)added SDBS;(b)no added SDBS.ing product is iron oxide yellow,while,at pH of 3–4,the resulting product is bright iron oxide red.When pH >4,the color of the obtained iron oxide red is little darker.Therefore,the optimum pH is 3–4.3.4.3.Effect of velocity of air flow on the character of iron oxide redTo study the effect of velocity of air flow,a series of exper-iments were performed at different velocity of air flow ranging from 0.08to 0.20m 3/h.Other parameters are listed in Table 3(case 3).Table 7shows the color of the resulting product pre-pared at different velocities of air flow.The color of the resulting product grows from deeper to shallow as the velocity of air flow increases.When the velocity of air flow is 0.2m 3/h,the result-ing product is not iron oxide red but iron oxide yellow.This is mainly because there is close relationship between the oxidiza-tion velocity of ferrous sulfate and amount of air.At low velocity of air flow,ferrous sulfate is oxidized slowly and urea reacts with it to be Fe(OH)2.So the color of iron oxide red is influenced and becomes deeper.At high velocity of air flow,ferrous sulfate is oxidized excessively fast and the formed FeOOH has not enough time to dehydrate.So the resulting product is not iron oxide red but iron oxide yellow.Therefore,the velocity of air flow must have a proper scope.According to the experiments,the optimal velocity of air flow is 0.14m 3/h.3.4.4.Optimum molar ratio of urea and ferrous sulfateThe dosage of ferrous sulfate can be decided from hue change of iron oxide red and the fact that the particle size of crystal nucleus is several nanometers to dozens of nanometers as shown in the process of seed crystal preparation.Table 8shows solution actuality at different molar ratios of urea and ferrous sulfate (MRUFS).Under different MRUFS,the pH of the mixture for preparing iron oxide red is different.The reason is that the OH −from the urea hydrolysis can neutralize with H +by the ferric ion hydrolysis.When MRUFS is 3.5:1,the pH of the mixture for preparing iron oxide red is 3–4and the color of the mixture become red.Under these conditions,Table 8Solution actuality at different molar ratios of urea and ferrous sulfate MRUFS Solution actuality1:1pH is about 2;the color of solution grows yellow 2:1pH is 2–3;the color of solution grows yellow3.5:1pH is 3–4;the color of solution grows from red brown to red 5:1pH increases gradually;the color of solution grows blackthe color of the resulting product (iron oxide red)is Turkey red.Thus the optimum MRUFS is 3.5:1.3.4.5.Effect of SDBS on the size distribution of iron oxide redFig.9shows the effect of SDBS on the size distribution of iron oxide red.As shown in Fig.9,SDBS plays an important role in size distribution of iron oxide particles red.Fig.9(a)is more monodisperse and regular than Fig.9(b).3.5.Nano-iron oxide red productCharacteristics of iron oxide red product prepared under the above optimum conditions (namely phase,sizes and main con-tent)were determined by XRD,LPSA,and Titration.TheresultsFig.10.XRD pattern of iron oxide red product.L.Dengxin et al./Journal of Hazardous Materials155(2008)369–377377Fig.11.Size distribution of iron oxide red product.show that the content of Fe2O3is92.76%.Fig.10shows the XRD pattern of iron oxide red product.It indicates the highly crystalline character of the iron oxide red and matches well with the standard␣-Fe2O3(hematite)reflections.Fig.11shows the size distribution of iron oxide red product.It was observed that the size of the product is mainly between40and100nm.This is in accordance with the nano-iron oxide red standard.4.ConclusionsThe experimental results show it is feasible that cyanided tail-ings were used to prepare red iron oxide pigment via a ammonia process with urea as the precipitant.Atfirst,cyanided tailings were pretreated.It was found that,under the optimum conditions,arsenic and lead have been removed and pure ferrous sulfate can be gained.The preparation of seed crystal by the above ferrous sulfate was experimentally investigated.It is obvious that the rate of conversation of ferrous sulfate changes with oxidizing condi-tions according to the result.The rate of conversation of ferrous sulfate increases with the rise of temperature,velocity of airflow, but decreases with the rise of concentration of ferrous sulfate. On the other hand,seed crystal for preparation of␣-Fe2O3must be␥-FeOOH.,otherwise␣-Fe2O3can not be obtained.An ammonia process with urea as the precipitant is success-fully used to prepare nano-iron oxide red pigment.The optimum technological parameters are shown below:reaction tempera-ture is80–85◦C;pH is3–4;velocity of airflow is0.14m3/h;the molar ratio of urea to ferrous sulfate is3.5:1;dispersion is added just after adjusting pH.SDBS plays an important role in size distribution of iron oxide red particles and it made regular iron oxide red particles come into being.Under above conditions,we can obtain bright,regular seed crystal and lay a good foundation for preparing excellent nano-iron oxide red pigments.Maybe, this method could be applied into other tailings to prepare pigments.AcknowledgementsThe authors are thankful to the Major project of Educational Ministry(No.107124),Key Laboratory of Science&Technol-ogy of Eco-Textile(Donghua University/Jiangnan University), Ministry of Education,China(ECO-KF-2007-10)and National High Technology Research and Development Program of China (863Program,No.2006AA06Z132)forfinancial support of this study.References[1]M.A.Legodi,D.de waal,The preparation of magnetite,goethite,hematiteand maghemite of pigment quality from mill scale iron waste,Dyes Pigments 74(2007)161–168.[2]N.Guskos,G.J.Papadopoulos,V.Likodimos,et al.,Photoacoustic,EPR andelectrical conductivity investigations of three synthetic mineral pigments: hematite,goethite and magnetite,Mater.Res.Bull.37(6)(2002)1051–1061.[3]P.A.Riveros,J.E.Dutrizac,The precipitation of hematite from ferric chloridemedia,Hydrometallurgy46(1/2)(1997)85–104.[4]G.Montes-Hernandez,J.Pironon,F.Villieras,Synthesis of a red ironoxide/montmorillonite pigment in a CO2-rich brine solution,J.Colloid Interface Sci.(303)(2006)472–476.[5]C.Q.Cai,Discussion on real seed during synthesis of ammonium-based ironoxide red,Pant Coat.Ind.36(2)(2006)15–18.[6]G.Jun-feng,L.Xiaobo,Utilization of cyanided tailings from gold ore dress-ing plant,Min.Eng.4(2005)38–39.[7]K.J.Sreeram,R.Indumathy,A.Rajaram,et al.,Template synthesis of highlycrystalline and monodisperse iron oxide pigments of nanosize,Mater.Res.Bull.(41)(2006)1875–1881.。

The Wombat A Large and Burrowing Marsupial The wombat is a large and burrowing marsupial that is native to Australia. It is a unique animal that has captured the hearts of many people around the world. The wombat is known for its sturdy build, powerful legs, and sharp claws, which it uses to dig extensive burrow systems in the ground. In this essay, we will explore the wombat from different perspectives, including its physical characteristics, behavior, habitat, and conservation status.The physical characteristics of the wombat are what make it such a fascinating animal. It is a sturdy animal that can weigh up to 80 pounds and reach a length of up to 3 feet. Its body is covered in thick fur that protects it from the harsh Australian climate. Wombats have short, powerful legs that are designed for digging and moving through rough terrain. Their front paws have sharp claws that they use to dig burrows and for defense against predators. Wombats also have strong jaws and teeth that allow them to chew tough vegetation.The behavior of the wombat is also unique. Wombats are mostly solitary animals that are active at night. They spend most of their time in their burrows, which they dig using their powerful claws. Wombats have a complex social structure that is based on a hierarchy of dominance. Dominant males have larger territories and access to more resources than subordinate males. Wombats are herbivores that feed on a variety of vegetation, including grasses, roots, and bark.The habitat of the wombat is mainly in Australia, where it is found in a variety of habitats, including forests, grasslands, and scrublands. Wombats are most commonly found in the southeastern part of Australia, where the climate is suitable for their survival. They are also found on some of the offshore islands of Australia. The wombat's burrow system is an important part of its habitat, providing shelter from predators and the harsh Australian climate.The conservation status of the wombat is of concern, with two of the three species listed as vulnerable or endangered. The Northern hairy-nosed wombat is one of the rarestmammals in the world, with only around 200 individuals remaining in the wild. Habitat loss, disease, and predation by introduced predators are the main threats to the survival of the wombat. Conservation efforts are underway to protect the wombat and its habitat, including the establishment of protected areas and efforts to control introduced predators.In conclusion, the wombat is a unique and fascinating animal that has captured the hearts of many people around the world. Its physical characteristics, behavior, habitat, and conservation status are all important aspects of understanding this remarkable creature. As we continue to learn more about the wombat, we can work to protect it and ensure that it continues to thrive in its natural habitat.。

氢原子光谱谱线条数The number of spectral lines in the hydrogen atom is a fascinating topic in the field of atomic physics. It has been the subject of extensive research and has played a crucial role in the development of quantum mechanics. The hydrogen atom is the simplest atomic system, consisting of a single electron orbiting a single proton in the nucleus. Despite its simplicity, the hydrogen atom exhibits a rich spectrum with a large number of spectral lines. In this essay, we will explore the reasons behind the abundance of spectral lines in hydrogen, considering various perspectives such as energy levels, electron transitions, and the mathematical framework of quantum mechanics.One of the key factors contributing to the large number of spectral lines in hydrogen is the discrete energy levels available to the electron. According to Bohr's model of the hydrogen atom, the electron can only occupy certain energy levels, which are quantized. These energy levels are determined by the principal quantum number, n, which cantake on integer values starting from 1. The energy of each level is given by the formula E = -13.6/n^2 electron volts. As the electron transitions between different energy levels, it emits or absorbs photons with specific energies corresponding to the energy difference between the initial and final levels. This leads to the appearance of distinct spectral lines in the hydrogen spectrum.Another factor that contributes to the abundance of spectral lines in hydrogen is the possibility of various electron transitions between energy levels. When anelectron undergoes a transition from a higher energy levelto a lower one, it emits a photon with a specific energy. The wavelength of the emitted photon determines the colorof the spectral line observed. The number of possible transitions increases with the number of energy levels, resulting in a larger number of spectral lines in the hydrogen spectrum. This is why hydrogen, with itsrelatively simple energy level structure, exhibits a larger number of spectral lines compared to more complex atoms.The mathematical framework of quantum mechanicsprovides a deeper understanding of the hydrogen atom's spectral lines. In quantum mechanics, the behavior of particles is described by wave functions, which are solutions to the Schrödinger equation. The wave function of the hydrogen atom can be expressed as a product of radial and angular parts, which depend on the quantum numbers associated with the energy levels and orbital angular momentum. The radial part determines the probability distribution of finding the electron at a particular distance from the nucleus, while the angular part determines the shape of the electron's orbital. The combination of different quantum numbers leads to the formation of distinct wave functions, each associated with a specific energy level and spectral line.The concept of degeneracy also plays a role in the abundance of spectral lines in hydrogen. Degeneracy refers to the phenomenon where different states have the same energy. In the case of hydrogen, energy levels with the same principal quantum number, n, but different orbital angular momentum quantum numbers, l, have the same energy. This results in multiple states with the same energy, eachcorresponding to a different orbital shape. The existence of degenerate states increases the number of possible electron transitions and, consequently, the number of spectral lines observed in the hydrogen spectrum.In conclusion, the large number of spectral lines in the hydrogen atom can be attributed to several factors. The discrete energy levels available to the electron, the possibility of various electron transitions between these levels, the mathematical framework of quantum mechanics, and the concept of degeneracy all contribute to the abundance of spectral lines. The study of hydrogen's spectral lines has not only provided valuable insights into the behavior of atoms but has also served as a foundation for the development of quantum mechanics. The richness of the hydrogen spectrum continues to inspire scientists and deepen our understanding of the fundamental nature of matter.。

1、Which of the following is a type of white blood cell primarily involved in the immune response against viral infections?A. ErythrocytesB. PlateletsC. LymphocytesD. Neutrophils(答案：C)2、The process by which a drug is absorbed, distributed, metabolized, and excreted within the body is known as:A. PharmacodynamicsB. PharmacokineticsC. BioavailabilityD. Drug tolerance(答案：B)3、Which organ is responsible for filtering blood and removing waste products to form urine?A. LiverB. KidneyC. LungD. Heart(答案：B)4、The study of the structure and function of cells is called:A. HistologyB. CytologyC. AnatomyD. Physiology(答案：B)5、Which of the following hormones is released by the pancreas and plays a crucial role in regulating blood sugar levels?A. InsulinB. ThyroxineC. AdrenalineD. Glucagon (Note: correct term is Glucagon-like peptide-1, but for simplicity, 'Glucagon' is used here)(答案：A)6、The medical term used to describe the inflammation of a joint is:A. ArthritisB. CarditisC. NephritisD. Dermatitis(答案：A)7、Which of the following imaging techniques uses high-frequency sound waves to produce images of internal body structures?A. X-rayB. CT scanC. UltrasoundD. MRI(答案：C)8、The process of converting food into energy that the body can use is known as:A. DigestionB. MetabolismC. AbsorptionD. Assimilation(答案：B)9、Which vitamin is essential for maintaining healthy bones and teeth, and is primarily obtained from sunlight exposure?A. Vitamin AB. Vitamin CC. Vitamin DD. Vitamin K(答案：C)10、The branch of medicine that deals with the prevention, diagnosis, and treatment of diseases of the heart and blood vessels is called:A. NeurologyB. CardiologyC. DermatologyD. Gastroenterology(答案：B)。

分子动力学模拟计算距离Molecular dynamics simulation is a computational technique used to study the behavior and interactions of atoms and molecules over time. It provides valuableinsights into the physical and chemical properties of materials at the atomic level. One of the fundamental quantities that can be calculated using molecular dynamics simulations is the distance between atoms or molecules.The calculation of distances in molecular dynamics simulations is crucial for understanding various phenomena, such as bond lengths, intermolecular interactions, and diffusion rates. By accurately measuring the distances between atoms, scientists can gain a deeper understanding of the structural and dynamical properties of the system under investigation.To calculate distances in molecular dynamics simulations, several methods can be employed. One common approach is to use the Cartesian coordinates of the atomsor molecules. The distance between two atoms can be calculated using the Euclidean distance formula, which takes into account the differences in their x, y, and z coordinates. This method is straightforward and widely used in molecular dynamics simulations.Another approach to calculating distances in molecular dynamics simulations is the use of periodic boundary conditions. In simulations, it is common to represent a small portion of a larger system by applying periodic boundary conditions, which mimic the presence of aninfinite number of identical copies of the system. When calculating distances between atoms, the periodic boundary conditions ensure that the shortest distance between two atoms is considered, taking into account the periodicity of the system.In addition to these basic methods, more advanced techniques can be employed to calculate distances in molecular dynamics simulations. For example, the radial distribution function (RDF) can be used to analyze the distribution of distances between pairs of atoms in asystem. The RDF provides information about the probability of finding two atoms at a given distance from each other, which is useful for understanding the structure and organization of the system.Furthermore, the calculation of distances in molecular dynamics simulations can be extended to study the dynamics of molecules and their interactions. For instance, the calculation of hydrogen bond distances between molecules can provide insights into the strength and stability of these interactions. By analyzing the changes in distances over time, scientists can investigate the formation and breaking of hydrogen bonds, which play a crucial role in many biological and chemical processes.In conclusion, the calculation of distances in molecular dynamics simulations is a fundamental aspect of studying the behavior and interactions of atoms and molecules. By accurately measuring distances between atoms, scientists can gain valuable insights into the structural and dynamical properties of the system under investigation. Various methods, such as Cartesian coordinates, periodicboundary conditions, and advanced techniques like RDF analysis, can be employed to calculate distances in molecular dynamics simulations. These calculations provide a deeper understanding of the physical and chemical properties of materials at the atomic level, contributing to advancements in fields ranging from materials science to drug discovery.。

steam cleaning 蒸汽清洁法horizontal rib 横筋vertical rib 竖筋nipple 内接头ell 90 union 90°弯头HGC steel 热镀锌碳钢temperature measurer 测温元件Lacquer putty 腻子certificate of competency 合格证书tapered shim 斜垫铁advanced PVC 改性PVCFire Retardant: 阻燃性Barcol hardness 巴氏硬度Bending strength 弯曲强度Degree of cure 固化度Tensile stress 抗拉强度Anti-impaction tough stress 抗冲击韧性Resin content树脂含量Filling resistance 填料阻力PRIMARY DESIGN CONDITION 主要设计条件Concrete structure with FRP casing counter flow 钢混结构逆流式RESISTANCE CALCULATION 阻力计算Air velocity in drenching section 淋水段风速Drenching density 淋水密度Rated capacity 额定功率Hot Galvanized C.S 热镀锌碳钢Relative humidity相对湿度Wet bulb temp. 湿球温度Reduction ratio 减速比Output coefficient 驱动输出系数segment 段gel coat 胶衣，凝胶涂层plan view 平面图embedded part 预埋件bolt pitch circle 螺栓圆周距driveabrasive blast cleaning 喷砂清理prior 优先的; 在前的; 较早的spring loaded 受载弹簧coupling flange 连接法兰gluing adhering 粘结剂universal protractor 万能角度尺Trowel 批灰刀spirit bubble 水平泡centration 对中axial centration 轴对中benchmark 基准gradienter 水平仪concrete corel plan RC bracket plan 砼牛腿平面图comments on the contracts 签署意见elevation标高floor height层高no comments 没意见butterfly bolt 碟形螺栓双叶螺栓proper alignment 同轴度levelness 水平度dial test indicator 百分表weld joint 焊缝焊接头Introduction 简介.说明Thaw pipe化冰管process measurement 工艺检测radial 径向axial 轴向cement mortar 水泥砂浆measure 测量量检测seamlessly 准确无误的Water Treatment System 水处理系统assembly installation 安装Wrap angle 包角elbowPartition wallboard 隔墙板Lightning rod round steel避雷环圆钢backstop 逆止器creepage distance 爬电距离electrical clearance 电气间隙ground bolt 地脚螺栓explosion-proof screw thread 防爆螺纹external diameter 外径armour 铠装nipple 内接头螺纹接头rubber hose nipple胶管接头wire entrance 进线口prograde direction: 正转方向reversal 反转方向Atmosphere tanks farm 常压罐区Pressure Tanks farm 压力罐区Pumping unit 汞设备抽油机Cylinder 汽缸Analyser Viscosity Measurement 粘度测验Hardness Barcol 巴氏硬度Flange 法兰Force and moment 压力和力矩gland 格兰头hub 轮毂Fan monitor风机监控装置Blaze detect 火焰检测器Two speed Motor 双速电机Drift eliminator system 收水系统Drift eliminator sheet 收水器片Water distribution system 配水系统Nozzle 喷溅装置喷头parent equipment. 设备母体Instrument cable 仪表电缆Delivery on site cost 运输费Unloading including the dismantling & installation on site cost 卸载及安装费Commissioning and training cost 试车及培训费fabricate 建造编造Bidder’s quotation for capital spare parts 大型备件的报价Request for Quotation number报价询求表编号:Bidder’s reference number 投标人编号:bid 投标packing list 装箱单Bidder (Company’s Description) 投标人(公司名):Normative 通设yoke plate中环内外搭接板lightning rod避雷针=arrester ring=lightning arrester fastner 避雷固定件administrative 行政的管理的settlement 协议export packing 出口包装purchase order 订购单disregard 不顾漠视receive 收到接到接纳nonetheless虽然如此但是in case 假使in case of 万一anti-rust 防锈anti-corrosion 防腐蚀preservation 保存储藏sealing of opening 管口密封preparation准备安排筹备detailed specification 详细说明provide 提供供应，规定written notice 书面通知oxygen index 氧指数special handing特殊装卸要求sensibility 敏感性center of gravity 重心render 报答归还给予呈递提供notification 通知通知单disposal 清除布置free of charge 免费facilities 能力设备carry out 执行抬出去贯彻进行完成crane 起重机forklift-trucks 铲车operational personnel 操作人员compressed air 压缩空气appropriate 适当的control cabinet 控制柜issuance 发布发行climatic conditions 气候条件courier service 快递服务peculiarity 特性古怪怪癖withstand 承受经受withstand buffe经过抛光处理by rail由铁路=by railwayif necessary 如必要的话variable 可变因素变数intermediate 中级中间storage on site 储藏位置readiness 准备就绪demand 要求需要所需之物动名词furnish 陈设布置提供technical specifications 技术规格durable 持久的耐用的experience 经验体验经历appropriate 适当的恰当的immediately 立即直接马上直接地measures 测量量出估量Water distribution pipe 配水管stairway 楼梯vent pip e 排气管Boundary 600 to the axis 工程交接处距离轴线600米ISSUED FOR IMPLEMENTATION 执行日期Abbreviation 缩写词Project designation (AAA) Valid identifiers 有法律效力的标志Facilities Identifier – BBB 设备标志符Originate 起源于来自创造创始开创Discipline 训练处罚Steel stairs钢梯Inlet connection pipe 进水管接口管Document Type 文件种类Flat steel扁钢Weld pipe 焊管Top plank顶层铺板Hood 盖帽sub-beam次梁上卡套Up guard stapleSlope support斜支撑Top boundary beam顶层边梁Big washer 大垫块Adjuster block 顶块Fastener 扣件Barb bolt 直地脚螺栓Rubber gasket 橡胶垫Square Nozzle pipe 方形喷头接管Square Nozzle nut 方形喷头并帽Pipe support 护管垫Metal strip 不锈钢带Binding clasp 不锈钢扣Base 底座Walkway support 走道支撑Pressing elbow 角件Rotundity plug 圆形赛块Gridiron Walkway 走道格栅Synthetic Resin 合成树脂Lightning arrester 避雷环Shaft hole plate 轴孔压板Motor shield stack 电机消音罩Combined parts 组合件Drift eliminator flake 收水器片Under lay 顶丝垫片不锈钢扣stainless steel buckle铁砂Iron sand 水磨砂water mill sandHood 盖帽Hoop 抱固Vent-pipe 放空管Malfunction sensor 风机监控仪French chalk 滑石粉Hexagon bolt 螺栓nut 螺母Steel expansile bolt 钢膨胀螺栓Connecting motor protector 消音罩固定According to the dimensions displayed below 按下表表示As below 如下Coupling flange 连接法兰Scheduled delivery date 合同规定交货期internal force 内力sprayer 喷头collecting tank / basin 集水池juncture 接点hexagon nut 螺母self drilling Screw 钻尾自钻螺栓reinforced加强型horsepower 功率stanchion 玻璃钢立柱Examing ladder 爬梯检修走道Handrail 扶手Kneerail 横栏AdhesionWps 焊接工艺规范pqr 工艺检验报告Respectively adv. 各自地, 各个地, 分别地adj.各自的, 分别的Auxiliary 辅助的, 补充的; 备用的Pallet 扁平工具,棘爪,货盘data sheet for increasing safety type of 3 phase low voltage induction motor 增安型三相异步电动机技术数据表grey cast iron 灰铸铁interlocked earthing 连锁接地Drift eliminator bracing 无串杆收水器架Oil pointer 油标Ball valve 球阀Inner tie-in 内接头Elbow 弯头Rivet 铆钉Monitoring 监视器anchor bolt 地脚螺栓washer 垫片Hoop 抱固Fiberglass fabric 玻纤布Shutter 百叶板百叶窗Wrap angle 包角French chalk 滑石粉Nameplate 铭牌Safeguard support 保护罩支架Transmission shaft and oil pipe 传动轴及油管Monitor 监控仪Tie rod 横拉杆Walkway platform 走道平台Stop block 限位装置Hardener固化剂Walkway grill 走道格栅Accelerant促进剂Corbel 牛腿Jack block顶块Drive shaft 传动轴Inspection plan 检验计划test manner 试验方法column cushion cap 柱承台galvanization 镀锌as-built drawings 竣工图pull beam 拉梁Lap jointed sheeting 搭接板Self-plugging rivet 抽新铆钉Ball valve 球阀Reduced tee 异径三通管pocking mark 麻点foundation pits 基坑control room philosophy 控制室原则/rulefield rack room philosophy 现场机柜室原则performance test 性能测试生产性能测定操作测验double check 仔细检查double check system 重复检验制;双重监视系统ultimate loading capacity 极限承载力bilateral agreement 双边协定party 当事人一方党派comply with 遵循遵从pressure retaining materials 持压材料consumables 消耗型材料pumps and compressors 泵和压缩机 4 pipework 管道工程reinforced concrete 钢筋混凝土pump, 汞，axes 轴线magnify 放大side elevation 侧面图varible section 变截面valve,阀，vessel 船，舰，容器，tank 油箱，罐，槽= basin 水池control panel,控制面板Instrument仪表gauge glasses 水位玻璃管viewing ports显示台machinery parts, 机械零件workstations, 操作台=work benches，操纵台contractor承包商supplier供应商Engineering Directors工程总监corrosion 腐蚀nitrogen 氮overpressure 超压力reinstatement，复原operations 运行,maintenance维护temporary laydown area 临时堆放区hoists,起重机cranes,吊车fork-lifts铲车lifting equipment起重设备,walkways 走道platform 平台appendix 附录lubrication and seal buffer systems 润滑和密封衬垫装置displays 显示设备labels 标签signs 标志orientation 方向cable trays, 电缆槽drip trays 滴水槽acoustics, 噪音welfare facilities 防护设施Dimension 尺寸Stature 身高Eye Height 双眼高度Shoulder Height 肩部高度Elbow Height 肘部高度Shoulder Breadth 肩部宽度Chest Depth 胸部厚度Upper Limb Length 上肢长度Vertical Grip Reach 垂直握固距离Forward Grip Reach 水平握固距离Blue 兰色Black on yellow 黄底黑字Yellow on black黑底黄字Red on white白底红字during construction period 施工期间Piling 打桩Pilling rig 各种打桩机等Silencers 消声器shock-absorbing seats / pads 减震座、减震垫Optimize 优化abbreviation and defination 简写和定义Gasification 煤气化装置Process Effluent System 工艺废水系统chemical storage area 化学用品储存处facility 设备设施能力power generation 发电emergency 应急，紧急情况vendor 供货商卖方Spare part description and part number 备件描述和编号commonality 通用Integrated Project Management Team 一体化项目管理组integrated 综合型Observe 观察研究in case of 万一in case 假使免得以防up to date 至今到目前为止，最新式的，现代化的transit country 通过国destination country 目的国minimum requirement 最低要求rough treatment 粗加工，rough 粗糙的不平的粗鲁的粗暴的粗野的剧烈的粗制的粗略的刺耳的necessitate 使~~成为必须rugged 崎岖不平的robust 强壮的健全的construction 建造建设建筑业建筑物解释意思结构句法关系sand 沙子沙滩用砂纸磨光moisture 水分防潮corresponding height of stacking适当高度的堆垛adj 相当的对应的符合的一致的furthermore 而且此外multiple transhipment 多次转运multiple 多种多样的倍数fork lift 叉形起重机hand barrow 担架，双轮手推车lift truck 起重机车in principle 原则上基本上static 不变化的静止的静态的静电的vertical 垂直的竖的strain 拉紧尽量利用尽全力过滤mention v. 提到说起n. 提及说起desiccant n. 干燥剂adj.使干燥的去湿的explicitly 明白地明确地opening 洞缺口开幕开张空缺缺额adj.首次的开始的metal 金属gasket 垫圈衬垫n. =washerwooden 木制的木头的僵硬的呆笨的crates n.板条箱，柳条箱装货箱v.把~~~装入箱中strapping 皮带材料橡皮膏case 容器，包装，手提箱crate 装货箱skids 滑动垫木skid 滑道saddle车座saddles 耐火土托座runners 滑行装置merchandise 商品货物accommodated to 改变~~~以适应clearance 空隙净空许可批准cylindrical vessels 圆筒形容器bevel 斜边和斜面ropes 栏索unobjectionable 不会招致反对的不惹人厌恶的provided 如果假如才precondition 前提先决条件slip 滑滑到sliding bottom滑动底座heavy lift 重件strong square timber skidssturdy 强壮的package unnecessaryvarnish 光泽面prim 循规蹈矩的整洁的clear tanks vessel in case of 万一cushion 垫子坐垫scrub 擦洗对~~不予考虑取消摩擦lashes accessible from fill out 装满充实填写（表格等）鼓起长胖containerization 货柜运输货柜装货stuffing n 填充物填料食品中的馅opening 缺口tank 油箱corresponding adj 对应的相应的符合的一致的observe 遵守遵循看到注意到评论讲loss 丢失n.丧失遗失损耗亏损损失theft n. 偷窃盗窃之物minimize vt. 把~~~减至最低数量对~~~作最低估计极力贬值~~的价值（重要性）wood-wool 西刨花木丝h ay 干草straw n. 稻草麦秆吸管毫无意义的东西brochure 小册子presence n, 出席到场存在仪表仪态solid wood 紧密材square 正方形广场平方adj. 正方形的成直角的平方的vt. 使成方形，与~~~一致结账贿赂timber 木材木料树木simplex winding 单绕组duplex winding 双绕组two-speed motor 双速电机valid adj 正当的有充分根据的符合逻辑的有效的有法律效力的guid line 指导路线方针German n.德国人德语adj 德国人的德语的Bundesverband paletteExecute 执行实行plywood 胶合板合板夹板Cutting class 采伐级defective wood 缺陷材fillet 棱条branchy vi.（树)出枝, 开叉分支; 分岔分出来, 发展出来逸出正轨vt. 使分枝, 分割用枝、叶、花等图案装饰(织物),thickness 厚(度), 粗层prone 易于~~~的，很有可能~~的俯卧的corrosion 腐蚀受腐蚀measuring instruments 测量仪表测量仪器armatures 支架电枢转子衔铁welding electrode 电极welding rodfoil 箔，金属薄片陪衬衬托，挫败使受挫折desiccant 干燥剂cushion 垫子brittle 易碎的instance 例子实例具体情况lined with 布满给~~~加casing 包装外套pointing outwardshifting slide gear 滑移齿轮longitudinal runner 纵梁encircle 包围环绕flat iron bar 扁钢条scrub vt&vi 用力擦洗vt 对…不予考虑; 取消n.擦洗prime coat 打底层attachment n. 附属物附件projecting parts 突出部分adequate adj 充分的足够的适当的胜任的lashing 大量rail wagon 运钢轨车compatible 可并存的相容的协调的diameter 直径non-skid 防滑的thread 线细线线索思路vt 将针线等穿过~~~将影片装入放映机rod n. 杆棒dry film 干膜adhesion 黏附粘合支持用户Clamp collar 夹圈卡套Degree parallels 斜垫铁Flat parallels 平垫铁SS buckle 不锈钢扣measuring instrument 测量仪表, 测量仪器wind temperature meter 风温表substrate 底面基底酶作用物培养基magnetic probe 探磁针calibrate 校准使标准化使合标准gauge n. 厚度直径测量仪表规格尺度vt. 计量度量估计判断elcometer 膜厚测定仪adhesive bitumen primer 冷底子油cold insulation 隔冷绝热保冷storage tank 储油罐acrylic polyurethane coating 丙烯酸聚氨酯漆epoxy polyamide paint 环氧聚酰胺漆specified 精确确定;规定的;额定mist coat 流平罩光涂层;湿罩光tie coat 粘结层induced draft 进气通风;诱导通风forced draft 强迫通风induced draft engine 抽风通风机variable speed motor 变速电动机diffuser n. 散步者扩散体dangerous goods classification 危险货物类别circumstance 环境条件情况境遇经济状况carbon fiber 碳化纤维,碳素纤维gauge glass 水位玻璃管level indicator 液面指示器presser switch 压力开关compensator 补偿者motor coupling 电机联轴节as far as necessarystowage 堆装物probe n. 探头探索调查探针探测器Vt./vi 探索用探针（或探测器等）调查，探测explosive adj. 爆炸的爆发的极易引起争论的n.爆炸物炸药gases n.气体煤气汽油毒气空谈吹牛有趣的事vt 使~~~吸入毒气vi空谈吹牛flammable adj 易燃的可燃的drift losses 飘移损失with limitationplates 板材plane arrangement drawing 平面布置图cubic 立方体的立方形的adjoing vt、vi 邻近，毗连cylindrical 圆柱的caution 警告durable 持久的, 耐用的经穿的，耐磨的in the event of 万一倘若evaporation loss 蒸发损失pumping head 抽水扬程axial flow fan 轴流式风机；轴流式风扇handrail 栏杆扶手mounting base 安装基座;安装机座combination 联合体组合物合作结合组合密码组合字码组合排列结合；联合；合并service engineer 维护工程师output choke 输出扼流圈transducer 传感器,变频器;变换器competent adj 有能力的能胜任的control circuit 控制电路regarding （表示论及)关于; 至于; 就…而论在…方面cable clamp 索卡gland plate 填料压盖板rail clamp 轨夹incoming line 输入线busbar connection 母线联结breaker 断电器, 开关器, 断路器; 自动保险电门; (汽车)护胎带power cable 电力电缆VVVF 可变压可变频系统JB 接线盒Junction boxhose box 消防软管箱hydrant 给水栓, 消防龙头hoisting beam for repairs 检修起重梁mandatory 命令的; 强制的; 义务的法律（或规则）规定的；强制的，必须遵守的lathe 车床drilling machine column 钻床立柱stirrer喜欢制造事端的人; (尤指)好播弄是非者搅拌物，搅拌器（非正式)挑拨者，惹是生非者line filter 线路滤波器gas cylinder 毒气筒;集气筒;高压气筒rail tanker 铁路油槽车road tanker 油槽车graphic panel 图解式面板,图表板,图示控制盘,有线路图的配电板,测量系统图示板axial direction 轴向cross section area 切面面积support point 支持点flame resistivity 阻焰性,耐火性sheet metal 金属片valveless filter无阀滤池strainer screen过滤器滤网。

2s上轨道概率密度径向分布The radial distribution of probability density on the 2s orbital can be described by the equation:P(r) = (2/Z^3)*(r/a)^2 * exp(-2r/a)Where P(r) is the probability density at a given distance r from the nucleus, Z is the atomic number, and a is the Bohr radius.该问题介绍了2s轨道上的概率密度径向分布。

可以使用以下公式描述这一分布：P(r) = (2/Z^3)*(r/a)^2 * exp(-2r/a)其中，P(r) 表示离原子核距离为 r 处的概率密度，Z 是原子序数，a 是玻尔半径。

In this equation, the term (r/a)^2 represents the square of the ratio of the distance from the nucleus to the Bohr radius. The exponential factor exp(-2r/a) describes how theprobability density decreases as you move away from the nucleus.在这个公式中，(r/a)^2 这一项表示与原子核到玻尔半径之间距离比值的平方。

指数因子 exp(-2r/a) 描述了随着远离原子核概率密度如何减小。

It is important to note that the probability density describes how likely it is to find an electron in a particular region around the nucleus. The higher the probability density, the greater chance there is of finding an electron at that distance from the nucleus.需要注意的是，概率密度描述了在原子核周围特定区域内找到电子的可能性有多大。

分子动力学模拟计算氢键作用英文回答：Molecular dynamics simulation is a powerful tool for studying the behavior of molecules and their interactions. When it comes to studying hydrogen bonding, molecular dynamics simulations can provide valuable insights into the dynamics and stability of these interactions.In a molecular dynamics simulation, the behavior of molecules is modeled over time based on the laws of physics. This allows us to observe how hydrogen bonds form, break, and fluctuate between different molecules. By analyzing the trajectories of the molecules, we can gain a better understanding of the strength and dynamics of hydrogen bonding.One common approach to studying hydrogen bonding in molecular dynamics simulations is to use force fields that explicitly account for the electrostatic and van der Waalsinteractions involved in hydrogen bonding. These force fields allow us to calculate the energy associated with hydrogen bonding and track its changes over the course of the simulation.Furthermore, by analyzing the radial distribution functions of hydrogen bonds, we can determine the average distance and coordination number of hydrogen bonds in the system. This provides valuable information about the structure and dynamics of hydrogen bonding networks.In addition to studying the behavior of hydrogen bonds in bulk systems, molecular dynamics simulations can also be used to investigate the role of hydrogen bonding inspecific chemical reactions or biological processes. For example, simulations can help elucidate the impact of hydrogen bonding on the stability of protein structures or the mechanism of enzymatic reactions.Overall, molecular dynamics simulations offer a powerful means of investigating the behavior of hydrogen bonds at the molecular level, providing valuable insightsthat can complement experimental studies.中文回答：分子动力学模拟是研究分子及其相互作用行为的强大工具。

离心泵叶轮内二维PIV非定常流动测量杨华;汤方平;刘超;周济人;徐浩然【摘要】采用二维PIV对离心泵蜗舌附近旋转叶轮内的流场进行了测量,获得了5个不同相位的二维相对速度场.结果显示:在流量Q/Qbep=0.52时,叶轮内压力面存在逆时针方向的回流,叶片在靠近蜗舌时,吸力面存在顺时针方向的回流.在流量Q/Qbep=1.0时,叶轮出口存在射流/尾迹现象.研究表明:小流量工况下,蜗舌对叶轮内的相对速度场有显著影响,而在最优工况下影响较弱.%The flow fields in a rotating impeller, near the volute tongue of a centrifugal pump, were measured by the 2-D PIV technique. At the flow rate of Q/Qbep = 0. 52, a counter clockwise recirculation flow existed on the blade pressure-side, when the blade was close to the volute tongue, a clockwise recirculation flow occurred on the blade suction-side. At the flow rate of Q/Qbep = 1. 0, a jet/wake flow existed at the exit of the impeller. The results show that the effects of the volute tongue on the relative velocity distribution are more significant at the low flow rate condition than at the best efficiency point.【期刊名称】《农业机械学报》【年(卷),期】2011(042)007【总页数】5页(P56-60)【关键词】离心泵;叶轮;PIV测量;非定常【作者】杨华;汤方平;刘超;周济人;徐浩然【作者单位】扬州大学能源与动力工程学院,扬州225127;扬州大学能源与动力工程学院,扬州225127;扬州大学水利科学与工程学院,扬州225009;扬州大学水利科学与工程学院,扬州225009;扬州大学水利科学与工程学院,扬州225009【正文语种】中文【中图分类】TH311引言离心泵叶轮内的流场具有典型的非定常性。