毕业设计外文资料翻译
题目POLISHING OF CERAMIC TILES
抛光瓷砖
学院材料科学与工程
专业复合材料与工程
班级复材0802
学生
学号20080103114
指导教师
二〇一二年三月二十八日
MATERIALS AND MANUFACTURING PROCESSES, 17(3), 401–413 (2002) POLISHING OF CERAMIC TILES
C. Y. Wang,* X. Wei, and H. Yuan
Institute of Manufacturing Technology, Guangdong University ofTechnology,
Guangzhou 510090, P.R. China
ABSTRACT
Grinding and polishing are important steps in the production of decorative vitreous ceramic tiles. Different combinations of finishing wheels and polishing wheels are tested to optimize their selection. The results show that the surface glossiness depends not only on the surface quality before machining, but also on the characteristics of the ceramic tiles as well as the performance of grinding and polishing wheels. The performance of the polishing wheel is the key for a good final surface quality. The surface glossiness after finishing must be above 208 in order to get higher polishing quality because finishing will limit the maximum surface glossiness by polishing. The optimized combination of grinding and polishing wheels for all the steps will achieve shorter machining times and better surface quality. No obvious relationships are found between the hardness of ceramic tiles and surface quality or the wear of grinding wheels; therefore, the hardness of the ceramic tile cannot be used for evaluating its machinability.
Key Words: Ceramic tiles; Grinding wheel; Polishing wheel
INTRODUCTION
Ceramic tiles are the common decoration material for floors and walls of hotel, office, and family buildings. Nowadays, polished vitreous ceramic tiles are more popular as decoration material than general vitreous ceramic tiles as they can *Corresponding author. E-mail: cywang@https://www.doczj.com/doc/898042225.html,
401
Copyright q 2002 by Marcel Dekker, Inc. https://www.doczj.com/doc/898042225.html, have a beautiful gloss on different colors. Grinding and polishing of ceramic tiles play an important role in the surface quality, cost, and productivity of ceramic tiles manufactured for decoration. The grinding and polishing of ceramic tiles are carried out in one pass through polishing production line with many different grinding wheels or by multi passes on a polishing machine, where different grinding wheels are used.
Most factories utilize the grinding methods similar to those used for stone machining although the machining of stone is different from that of ceramic tiles. Vitreous ceramic tiles are thin, usually 5–8mm in thickness, and are a sintered material,which possess high hardness, wear resistance, and brittleness. In general, the sintering process causes surface deformation in the tiles. In themachining process, the ceramic tiles are unfixed and put on tables. These characteristics will cause easy breakage and lower surface quality if grinding wheel or grinding parameters are unsuitable. To meet the needs of ceramic tiles machining, the machinery, grinding parameters (pressure, feed speed, etc.), and grinding wheels (type and mesh size of abrasive, bond, structure of grinding wheel, etc.) must be optimized. Previous works have been reported in the field of grinding ceramic and stone[1 –4]. Only a few reports have mentioned ceramic tile machining[5 –8], where the grinding mechanism of ceramic tiles by scratching and grinding was studied. It was pointed out that the grinding mechanism of ceramic tiles is similar to that of other brittle materials. For vitreous ceramic tiles, removing the plastic deformation grooves, craters (pores), and cracks are of major concern, which depends on the micro-structure of the ceramic tile, the choice of grinding wheel and processing parameters, etc. The residual cracks generated during sintering and rough grinding processes, as well as thermal impact cracks caused by the transformation of quartz crystalline phases are the main reasons of tile breakage during processing. Surface roughness Ra and glossiness are different measurements of the surface quality. It is suggested that the surface roughness can be used to control the surface quality of rough grinding and semi-finish grinding processes, and the surface glossiness to assess the quality of finishing and polishing processes. The characteristics of the
grinding wheels, abrasive mesh size for the different machining steps, machining time, pressure, feed, and removing traces of grinding wheels will affect the processing of ceramic tiles[9].
In this paper, based on the study of grinding mechanisms of ceramic tiles, the manufacturing of grinding wheels is discussed. The actions and optimization of grinding and polishing wheels for each step are studied in particular for manualpolishing machines.
GRINDING AND POLISHING WHEELS FOR CERAMIC TILE
MACHINING
T he mac hi ni ng of cer ami c t i l e s i s a vol ume-pr oduc t i on pr oc e s s t ha t uses significant numbers of grinding wheels. The grinding and polishing wheels for
ceramic tile machining are different from those for metals or structural ceramics. In this part, some results about grinding and polishing wheels are introduced for better understanding of the processing of ceramic tiles.
Grinding and Polishing Wheels
Ceramic tiles machining in a manual-polishing machine can be divided into four steps—each using different grinding wheels. Grinding wheels are marked as 2#, 3#, and 4# grinding wheels, and 0# polishing wheel; in practice, 2# and 3# grinding wheels are used for flattening uneven surfaces. Basic requirements of rough grinding wheels are long life, high removal rate, and lower price. For 2# and 3# gr inding wheel s, Si C a brasi ve s wi th me s h #180 (#320)a r e bonde d by m a g n e s i u m o x yc h l o r i d e c e m e n t(M O C)t o g e t h e r w i t h s o m e p o r o u s f i l l s, waterproof additive, etc. The MOC is used as a bond because of its low price, simple manufacturing process, and proper performance.
T he 4# grinding wheel will refine the surface to show the brightness of ceramic tile. The GC#600 abrasives and some special polishingmaterials, etc., are bonded by MOC. In order to increase the performance such as elasticity, etc., of the grinding wheel, the bakelite is always added. The 4# grinding wheels must be able to rapidly eliminate all cutting grooves and increase the surface glossiness of the ceramic tiles. The 0# polishing wheel is used for obtaining final surface glossiness, which
is made of fine Al2O3 abrasives and fill. It is bonded by unsaturated resin. The polishing wheels must be able to increase surface glossiness quickly and make the glossy ceramic tile surface permanent.
Manufacturing of Magnesium Oxychloride Cement Grinding Wheels
After the abrasives, the fills and the bond MOC are mixed and poured into the models for grinding wheels, where the chemical reaction of MOC will solidify the shape of the grinding wheels. The reaction will stop after 30 days but the hardness of grinding wheel is essentially constant after 15 days. During the initial 15-day period, the grinding wheels must be maintained at a suitable humidity and temperature.
For MOC grinding wheels, the structure of grinding wheel, the quality of abrasives, and the composition of fill will affe ct their grinding ability. All the factors related to the chemical reaction of MOC, such as the mole ratio of MgO/MgCl2, the specific gravity of MgCl2, the temperature and humidity to care the cement will also affect the performance of the MOC grinding wheels.
Mole Ratio of MgO/MgCl2
When MOC is used as the bond for the grinding wheels, hydration reaction takes place between active MgO and MgCl2, which generates a hard XMg e OH T2·Y e MgCl2T·ZH2O phase. Through proper control of the mole ratio of MgO/MgCl2, a reaction product with stable performance is formed. The bond is composed of 5Mg e OH T2·e MgCl2T·8H2O and 3Mg e OH T2·e MgCl2T·8H2O: As the former is more stable, optimization of the mole ratio of MgO/MgCl2 to produce more 5Mg e OH T2·e MgCl2T·8H2O is required. In general, the ideal range for the mole ratio of MgO/MgCl2 is 4–6. When the contents of the active MgO and MgCl2 are known, the quantified MgO and MgCl2 can be calculated.
Active MgO
The content of active MgO must be controlled carefully so that hydration reaction can be successfully completed with more 5Mg e OH T2·e MgCl2T·8H2O: If the content of active MgO is too high, the hydration reaction time will be too short with a large reaction heat, which increases too quickly. The concentrations of the thermal stress can cause generation of cracks in the grinding wheel. On the
contrary, if the content of active MgO is too low, the reaction does not go to completion and the strength of the grinding wheel is decreased.
Fills and Additives
The fills and additives play an important role in grinding wheels. Some porous fills must be added to 2# and 3# grinding wheels in order to improve the capacity to contain the grinding chips, and hold sufficient cutting grit. Waterproof additives such as sulfates can ensure the strength of grinding wheels in processing under water condition. Some fills are very effective in increasing the surface quality of ceramic tile, but the principle is not clear.
Manufacturing of Polishing Wheels
Fine Al2O3 and some soft polishing materials, such as Fe2O3, Cr2O3, etc., are mixed together with fills. Unsaturated resin is used to bond these powders, where a chemical reaction takes place between the resin and the hardener by means of an activator. The performance of polishing wheels depends on the properties of resin and the composition of the polishing wheel. In order to contain the fine chips, which are generated by micro-cutting, some cheap soluble salt can be fed into the coolant. On the surface of the polishing wheel, the salt will leave uniform pores, which not only increase the capacity to contain chips and self-sharpening of the polishing wheel, but also improves the contact situation between polishing wheel and ceramic tiles.
Experimental Procedure
Tests were carried out in a special manual grinding machine for ceramic
tiles. Two grinding wheels were fixed in the grinding disc that was equipped to the grinding machine. The diameter of grinding disc was 255 mm. The rotating speed of the grinding disc was 580 rpm. The grinding and polishing wheels are isosceles trapezoid with surface area 31.5 cm2 (the upper edge: 2 cm, base edge: 5 cm, height: 9 cm). The pressure was adjusted by means of the load on the handle for different grinding procedures. A zigzag path was used as the moving trace for the grinding disc. To maintain flatness and edge of the ceramic tiles, at least one third of the tile must be under the grinding disc. During the grinding process, sufficient water was poured to both cool and wash the grinding wheels and the tiles. Four kinds of vitreous ceramic tiles were examined, as shown in Table 1.
Two different sizes of ceramic A, A400 (size: 400 ￡400 ￡5mm3T and A500
(size: 500 ￡500 ￡5mm3T were tested to understand the effect of the tile size. For
ceramic tile B or C, the size was 500 ￡500 ￡5mm3: The phase composition of the
tiles was determined by x-ray diffraction technique. Surface reflection glossiness and surface roughness of the ceramic tiles and the wear of grinding wheels were measured.
The grinding and polishing wheels were made in-house. The 2# grinding
wheels with abrasives of mesh #150 and 3# grinding wheels with mesh #320 were used during rough grinding. Using the ceramic tiles with different surface toughness ground by the 2# grinding wheel for 180 sec, the action of the 3# grinding wheels were tested. The ceramic tile was marked as A500-1 (or B500-1, C500-1, A400-1) with higher initial surface toughness or A500-2 (or B500-2, C500-2, A400-2) with lower initial surface toughness.
Two kinds of finishing wheels, 4#A and 4#B were made with the same structure, abrasivity, and process, but different composition of fills and additives. Only in 4#B, a few Al2O3, barium sulfate, and magnesium stearate were added for higher surface glossiness. The composition of the polishing wheels 0#A and 0#B were different as well. In 0#B, a few white alundum (average diameter 1mm), barium sulfate, and chrome oxide were used as polishing additives, specially. After ground by 4#A (or 4#B) grinding wheel, the ceramic tiles were polished with 0#A (or 0#B). The processing combinations with 4# grinding wheels and 0#
RESULTS AND DISCUSSIONS
Effects of 2# and 3# Grinding Wheels
Surface Quality
In rough grinding with a 2# grinding wheel, the surface roughness for all the tiles asymptotically decreases as the grinding time increases, see Fig. 1. The initial asymptote point of this curve represents the optimized rough grinding time, as continued grinding essentially has no effect on the surface roughness. In these tests, the surface roughness curves decrease with grinding
time and become smooth at ,120 sec. The final surface quality for different kinds of ceramic tiles is slightly different. In terms of the initial size of the tile, the surface roughness of ceramic tile A400 e ￡400 ￡5mm3T is lower than that of A500 e500 ￡500 ￡5mm3T: The surface roughness of
c e r a m i c t i l e B500r a p i
d l y d r o p s a s t h
e g r i n d i n g t i m e i n c r e a s e s.
Thus, it is easier to remove surface material from the hardest of the
three kinds of the ceramic tiles (Table 1). However, as the final surface roughness of ceramic tile A500 is the same as that of ceramic tile C500, the hardness of theceramic tile does not have a direct relationship with the final surface quality.
In the 3# grinding wheel step, all craters and cracks on the surface of ceramic tiles caused by the 2# grinding wheel must be removed. If residual cracks and craters exist, it will be impossible to get a high surface quality in the next step. The surface roughness obtained by the 2# grinding wheel will
also affect the surface
Figure 1. Surface roughness of several ceramic tiles as a function of grinding time for 2# grinding
wheel.
quality of next grinding step by the 3# grinding wheel. In Fig. 2, the actions of the 3# grinding wheels are given using the ceramic tiles with different initial R a, which were ground by the 2# grinding wheel for 180 sec. The curves of surface vs. grinding time rapidly decrease in 60 sec. Asymptotic behavior essentially becomes constant after 60 sec. In general, the larger the initial surface roughness, the worse the final surface roughness. For example, for ceramic tile B500-1, the initial R a was 1.53mm, the finial R a was 0.59mm after being ground by the 3# grinding wheel. When the initial R a was 2.06mm for ceramic tile B500-2, the finial R a was 0.67mm. In Ref. [8], we studied the relations between abrasive mesh size and evaluation indices of surface quality, such as surface roughness and surface glossiness. In rough grinding, the ground surface of ceramic tile shows fracture craters. These craters scatter the light, so that the surface glossiness values are almost constant at a low level. It is difficult to improve the surface glossiness after these steps. Figure 3 shows the slow increase in surface glossiness with time by means of the 3# grinding wheel. It can be seen that the glossiness of ceramic tile B500-1 is the highest. The surface glossiness of ceramic tile A400-1 is better than that of A500-1 because the effective grinding times per unit area for former is longer than for latter. These trends are similar to those for surface r o u g h n e s s i n
Fig. 2.
Wear of Grinding Wheels
The wear of grinding wheels is one of the factors controlling the machining cost. As shown in Fig.
4, the wear of grinding wheels is proportional to grinding
Figure 2. Surface roughness of several ceramic tiles as a function of grinding time for 3# grinding
wheel.
Figure 3. Surface glossiness of several ceramic tiles as a function of grinding time by 3# grinding
wheel.
time for both the grinding wheels and the three types of ceramic tiles. The wear rate of the 3# grinding wheel is larger than the 2# grinding wheel. It implies that the wear resistance of the 3# grinding wheel is not as good as 2# for constant grinding time of 180 sec. When the slope of the
curve is smaller, life of the
grinding wheels will be longer. Comparison of the ceramic tiles hardness (Table 1) with the wear resistance behavior in Fig. 4 does not reveal a strong dependency. Therefore, the hardness of the ceramic tile cannot be used to distinguish the machinability. The difference of
Figure 4. Wear of grinding wheels of several ceramic tiles as a function of grinding time for 2# and
3# grinding wheels.
initial surface roughness of ceramic tile will affect the wear of grinding wheel. In Fig. 4, the wear of the 3# grinding wheel for ceramic tile B500-1 is smaller than that for ceramic tile B500-2. The initial surface roughness of the latter is higher than that of the former so that additional grinding time is required to remove the deeper residual craters on the surface. Improvement of the initial surface roughness can be the principal method for obtaining better grinding quality and grinding wheel life during rough grinding.
Effects of 4# Grinding Wheels and 0# Polishing Wheels
Surface Quality
The combination and the performance of 4# grinding and 0# polishing
wheels show different results for each ceramic tile. The grinding quality vs. grinding (polishing) time curves are presented in Fig. 5, where all the ceramic tiles were previously ground by 2# and 3# grinding wheels to the same surface quality.
The surface glossiness is used to assess surface quality because the surface roughness is nearly constant as finishing or polishing time increases[8]. In this test, the ceramic tile A400 were fast ground by 4#A and 4#B grinding wheels [Fig. 5(a)]. The surface glossiness increased rapidly during the initial 90 sec and then slowly increased. The surface glossiness by grinding wheel 4#B is higher than by 4#A. Afterwards, polishing was done by four different combinations of finishing wheel and polishing wheel. By means of polishing wheels 0#A and 0#B, we processed the surface finished by 4#A grinding wheel (described as 4#A–0#A and 4#A–0#B in Fig. 5), and the surface
f i n i s h e d b y4#B
g r i n d i n g w
h e e l (described as 4#B–0#A and 4#B–0#B in Fig. 5). The curves of surface glossiness vs. polishing time
show parabolic behavior. After 60 sec of polishing, the surface glossiness reaches to ,508, then slowly increases. The polishing wheel 0#B gives a better surface quality than 0#A.
In Fig. 5(a), the maximum surface glossiness of ceramic tile A400 is about ,75 by 4#B–0#B.
The relation between initial surface glossiness and the final surface quality is not strong. The effect of pre-polishing surface glossiness can be observed by 0#B polishing wheel as polishing ceramic
tile A500 [Fig. 5(b)]. The maximum surface glossiness that can be achieved is 748 in 240 sec by
4#A–0#B or 4#B–0#B. This value is lower than that of ceramic tile A400 [Fig. 5(a)].
The final surface glossiness by 4#A grinding wheel is highly different from that by 4#B grinding wheel for ceramic tile B500, as shown in Fig. 5(c), but the final polishing roughness is the same when 0#A polishing wheel is used. The better performance of 0#B polishing wheel is shown because the surface glossiness can
increase from 17 to 228 in 30 sec. The maximum surface glossiness is 658 by 4#B–0#B. The
curves of polishing time vs. surface glossiness in Fig. 5(d) present the same results as polishing of ceramic tile B500 [Fig. 5(c)]. With 0#A polishing
Figure 5. Surface glossiness for ceramic tiles (a) A400, (b) A500, (c) B500, and (d) C500 as a
function of grinding (polishing) time for 4# grinding wheels and 0# polishing wheels.
wheel, the action of pre-polishing surface glossiness is significant. The best value of surface glossiness in 240 sec is 708 by 4#B–0#B as polishing ceramic tile C500. The results discussed earlier describe that the surface glossiness by 0# polishing wheel will depend not only on the pre-polishing surface glossiness formed by 4# grinding wheel, but also on the characteristics of the ceramic tiles and the performance of 0# polishing wheel. The differences of initial surface glossiness and final surface glossiness are larger for 4#A and 4#B. If the prepolishing surface
roughness is lower, the final surface glossiness will be higher.
Figure 5. Continued.
The polishing time taken to achieve the maximum surface glossiness will be also shorter. The initial surface quality will limit the maximum value of polishing surface glossiness that can be obtained. To reach a final surface glossiness of above 608, the minimum pre-polishing surface glossiness must be above 208.
The performance of the polishing wheel is the key to good surface quality. The polishing ability of the polishing wheels depends on the properties of the ceramic tiles as well. Even if the same grinding and polishing wheels are used, on all four ceramic tiles, the maximum surface glossiness values of ceramic tiles are different. The ceramic tile A500 shows the best surface glossiness, and ceramic
tile B500 shows the worst, although it is easier to roughly grind ceramic tile B500. The peak value
of the surface glossiness is also limited by the properties of
Wear of Grinding and Polishing Wheels
The life of 4# grinding wheels and 0# polishing wheels (Fig. 6) are longer than those of the rough grinding wheels (Fig. 4). For finer grinding (Fig. 6), it is impossible to distinguish the relation between grinding wheels and ceramic tiles. Polishing wheels have longer life because they produce more plastic deformation than removal.
SUMMARY OF RESULTS
(1) The performance of grinding and polishing wheels will affect its life and the surface quality of ceramic tiles.
(2) In ceramic tile machining, the surface quality gained in the previous step will limit the final surface quality in the next step. The surface glossiness of pre-polishing must be higher than 208 in
order to get the highest polishing quality. The optimization of the combination of grinding wheels and polishing wheels for all the steps will shorten machining time and improve surface quality. Optimization must be determined for each ceramics tiles.
Figure 6. Wear of grinding wheels 4# and polishing wheels 0# for several ceramic tiles as a
function of grinding time.
(3) The effect of hardness of ceramic tiles is not direct, thus the hardness of ceramic tiles cannot be used for evaluating the machinability of
ACKNOWLEDGMENT
The authors thank Nature Science Foundation of Guangdong Province and Science Foundation of Guangdong High Education for their financial support.
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Inventory management Inventory Control On the so-called "inventory control", many people will interpret it as a "storage management", which is actually a big distortion. The traditional narrow view, mainly for warehouse inventory control of materials for inventory, data processing, storage, distribution, etc., through the implementation of anti-corrosion, temperature and humidity control means, to make the custody of the physical inventory to maintain optimum purposes. This is just a form of inventory control, or can be defined as the physical inventory control. How, then, from a broad perspective to understand inventory control? Inventory control should be related to the company's financial and operational objectives, in particular operating cash flow by optimizing the entire demand and supply chain management processes (DSCM), a reasonable set of ERP control strategy, and supported by appropriate information processing tools, tools to achieved in ensuring the timely delivery of the premise, as far as possible to reduce inventory levels, reducing inventory and obsolescence, the risk of devaluation. In this sense, the physical inventory control to achieve financial goals is just a means to control the entire inventory or just a necessary part; from the perspective of organizational functions, physical inventory control, warehouse management is mainly the responsibility of The broad inventory control is the demand and supply chain management, and the whole company's responsibility. Why until now many people's understanding of inventory control, limited physical inventory control? The following two reasons can not be ignored: First, our enterprises do not attach importance to inventory control. Especially those who benefit relatively good business, as long as there is money on the few people to consider the problem of inventory turnover. Inventory control is simply interpreted as warehouse management, unless the time to spend money, it may have been to see the inventory problem, and see the results are often very simple procurement to buy more, or did not do warehouse departments . Second, ERP misleading. Invoicing software is simple audacity to call it ERP, companies on their so-called ERP can reduce the number of inventory, inventory control, seems to rely on their small software can get. Even as SAP, BAAN ERP world, the field of
转型衰退时期的土木工程研究 Sergios Lambropoulosa[1], John-Paris Pantouvakisb, Marina Marinellic 摘要 最近的全球经济和金融危机导致许多国家的经济陷入衰退，特别是在欧盟的周边。这些国家目前面临的民用建筑基础设施的公共投资和私人投资显著收缩，导致在民事特别是在民用建筑方向的失业。因此，在所有国家在经济衰退的专业发展对于土木工程应届毕业生来说是努力和资历的不相称的研究，因为他们很少有机会在实践中积累经验和知识，这些逐渐成为过时的经验和知识。在这种情况下，对于技术性大学在国家经济衰退的计划和实施的土木工程研究大纲的一个实质性的改革势在必行。目的是使毕业生拓宽他们的专业活动的范围，提高他们的就业能力。 在本文中，提出了土木工程研究课程的不断扩大，特别是在发展的光毕业生的潜在的项目，计划和投资组合管理。在这个方向上，一个全面的文献回顾，包括ASCE体为第二十一世纪，IPMA的能力的基础知识，建议在其他：显著增加所提供的模块和项目管理在战略管理中添加新的模块，领导行为，配送管理，组织和环境等；提供足够的专业训练五年的大学的研究；并由专业机构促进应届大学生认证。建议通过改革教学大纲为土木工程研究目前由国家技术提供了例证雅典大学。 1引言 土木工程研究（CES）蓬勃发展，是在第二次世界大战后。土木工程师的出现最初是由重建被摧毁的巨大需求所致，目的是更多和更好的社会追求。但是很快，这种演变一个长期的趋势，因为政府为了努力实现经济发展，采取了全世界的凯恩斯主义的理论，即公共基础设施投资作为动力。首先积极的结果导致公民为了更好的生活条件（住房，旅游等）和增加私人投资基础设施而创造机会。这些现象再国家的发展中尤为为明显。虽然前景并不明朗（例如，世界石油危机在70年代），在80年代领先的国家采用新自由主义经济的方法（如里根经济政策），这是最近的金融危机及金融危机造成的后果（即收缩的基础设施投资，在技术部门的高失业率），消除发展前途无限的误区。 技术教育的大学所认可的大量研究土木工程部。旧学校拓展专业并且新的学校建成，并招收许多学生。由于高的职业声望，薪酬，吸引高质量的学校的学生。在工程量的增加和科学技术的发展，导致到极强的专业性，无论是在研究还是工作当中。结构工程师，液压工程师，交通工程师等，都属于土木工程。试图在不同的国家采用专业性的权利，不同的解决方案，，从一个统一的大学学历和广泛的专业化的一般职业许可证。这个问题在许多其他行业成为关键。国际专业协会的专家和机构所确定的国家性检查机构，经过考试后，他们证明不仅是行业的新来者，而且专家通过时间来确定进展情况。尽管在很多情况下，这些证书虽然没有国家接受，他们赞赏和公认的世界。 在试图改革大学研究（不仅在土木工程）更接近市场需求的过程中，欧盟确定了1999博洛尼亚宣言，它引入了一个二能级系统。第一级度（例如，一个三年的学士）是进入
Statistical hypothesis testing Adriana Albu，Loredana Ungureanu Politehnica University Timisoara,adrianaa@aut.utt.ro Politehnica University Timisoara,loredanau@aut.utt.ro Abstract In this article,we present a Bayesian statistical hypothesis testing inspection, testing theory and the process Mentioned hypothesis testing in the real world and the importance of, and successful test of the Notes. Key words Bayesian hypothesis testing; Bayesian inference;Test of significance Introduction A statistical hypothesis test is a method of making decisions using data, whether from a controlled experiment or an observational study (not controlled). In statistics, a result is called statistically significant if it is unlikely to have occurred by chance alone, according to a pre-determined threshold probability, the significance level. The phrase "test of significance" was coined by Ronald Fisher: "Critical tests of this kind may be called tests of significance, and when such tests are available we may discover whether a second sample is or is not significantly different from the first."[1] Hypothesis testing is sometimes called confirmatory data analysis, in contrast to exploratory data analysis. In frequency probability,these decisions are almost always made using null-hypothesis tests. These are tests that answer the question Assuming that the null hypothesis is true, what is the probability of observing a value for the test statistic that is at [] least as extreme as the value that was actually observed?) 2 More formally, they represent answers to the question, posed before undertaking an experiment,of what outcomes of the experiment would lead to rejection of the null hypothesis for a pre-specified probability of an incorrect rejection. One use of hypothesis testing is deciding whether experimental results contain enough information to cast doubt on conventional wisdom. Statistical hypothesis testing is a key technique of frequentist statistical inference. The Bayesian approach to hypothesis testing is to base rejection of the hypothesis on the posterior probability.[3][4]Other approaches to reaching a decision based on data are available via decision theory and optimal decisions. The critical region of a hypothesis test is the set of all outcomes which cause the null hypothesis to be rejected in favor of the alternative hypothesis. The critical region is usually denoted by the letter C. One-sample tests are appropriate when a sample is being compared to the population from a hypothesis. The population characteristics are known from theory or are calculated from the population.
本科毕业设计 外文文献及译文 文献、资料题目：Designing Against Fire Of Building 文献、资料来源：国道数据库 文献、资料发表（出版）日期：2008.3.25 院（部）：土木工程学院 专业：土木工程 班级：土木辅修091 姓名：武建伟 学号：2008121008 指导教师：周学军、李相云 翻译日期： 20012.6.1
外文文献: Designing Against Fire Of Buliding John Lynch ABSTRACT: This paper considers the design of buildings for fire safety. It is found that fire and the associ- ated effects on buildings is significantly different to other forms of loading such as gravity live loads, wind and earthquakes and their respective effects on the building structure. Fire events are derived from the human activities within buildings or from the malfunction of mechanical and electrical equipment provided within buildings to achieve a serviceable environment. It is therefore possible to directly influence the rate of fire starts within buildings by changing human behaviour, improved maintenance and improved design of mechanical and electrical systems. Furthermore, should a fire develops, it is possible to directly influence the resulting fire severity by the incorporation of fire safety systems such as sprinklers and to provide measures within the building to enable safer egress from the building. The ability to influence the rate of fire starts and the resulting fire severity is unique to the consideration of fire within buildings since other loads such as wind and earthquakes are directly a function of nature. The possible approaches for designing a building for fire safety are presented using an example of a multi-storey building constructed over a railway line. The design of both the transfer structure supporting the building over the railway and the levels above the transfer structure are considered in the context of current regulatory requirements. The principles and assumptions associ- ated with various approaches are discussed. 1 INTRODUCTION Other papers presented in this series consider the design of buildings for gravity loads, wind and earthquakes.The design of buildings against such load effects is to a large extent covered by engineering based standards referenced by the building regulations. This is not the case, to nearly the same extent, in the
吉林化工学院理学院 毕业论文外文翻译English Title（Times New Roman ，三号） 学生学号：08810219 学生姓名：袁庚文 专业班级：信息与计算科学0802 指导教师：赵瑛 职称副教授 起止日期：2012.2.27～2012.3.14 吉林化工学院 Jilin Institute of Chemical Technology
1 外文翻译的基本内容 应选择与本课题密切相关的外文文献（学术期刊网上的），译成中文，与原文装订在一起并独立成册。在毕业答辩前，同论文一起上交。译文字数不应少于3000个汉字。 2 书写规范 2.1 外文翻译的正文格式 正文版心设置为：上边距：3.5厘米，下边距：2.5厘米，左边距：3.5厘米，右边距：2厘米，页眉：2.5厘米，页脚：2厘米。 中文部分正文选用模板中的样式所定义的“正文”，每段落首行缩进2字；或者手动设置成每段落首行缩进2字，字体：宋体，字号：小四，行距：多倍行距1.3，间距：前段、后段均为0行。 这部分工作模板中已经自动设置为缺省值。 2.2标题格式 特别注意：各级标题的具体形式可参照外文原文确定。 1．第一级标题（如：第1章绪论）选用模板中的样式所定义的“标题1”，居左；或者手动设置成字体：黑体，居左，字号：三号，1.5倍行距，段后11磅，段前为11磅。 2．第二级标题（如：1.2 摘要与关键词）选用模板中的样式所定义的“标题2”，居左；或者手动设置成字体：黑体，居左，字号：四号，1.5倍行距，段后为0，段前0.5行。 3．第三级标题（如：1.2.1 摘要）选用模板中的样式所定义的“标题3”，居左；或者手动设置成字体：黑体，居左，字号：小四，1.5倍行距，段后为0，段前0.5行。 标题和后面文字之间空一格（半角）。 3 图表及公式等的格式说明 图表、公式、参考文献等的格式详见《吉林化工学院本科学生毕业设计说明书（论文）撰写规范及标准模版》中相关的说明。
农村社会养老保险的现状、问题与对策研究社会保障对国家安定和经济发展具有重要作用，“城乡二元经济”现象日益凸现，农村社会保障问题客观上成为社会保障体系中极为重要的部分。建立和完善农村社会保障制度关系到农村乃至整个社会的经济发展，并且对我国和谐社会的构建至关重要。我国农村社会保障制度尚不完善，因此有必要加强对农村独立社会保障制度的构建，尤其对农村养老制度的改革，建立健全我国社会保障体系。从户籍制度上看，我国居民养老问题可分为城市居民养老和农村居民养老两部分。对于城市居民我国政府已有比较充足的政策与资金投人，使他们在物质和精神方面都能得到较好地照顾，基本实现了社会化养老。而农村居民的养老问题却日益突出，成为摆在我国政府面前的一个紧迫而又棘手的问题。 一、我国农村社会养老保险的现状 关于农村养老，许多地区还没有建立农村社会养老体系，已建立的地区也存在很多缺陷，运行中出现了很多问题，所以完善农村社会养老保险体系的必要性与紧迫性日益体现出来。 （一）人口老龄化加快 随着城市化步伐的加快和农村劳动力的输出，越来越多的农村青壮年人口进入城市，年龄结构出现“两头大，中间小”的局面。中国农村进入老龄社会的步伐日渐加快。第五次人口普查显示：中国65岁以上的人中农村为5938万，占老龄总人口的67.4%.在这种严峻的现实面前，农村社会养老保险的徘徊显得极其不协调。 （二）农村社会养老保险覆盖面太小 中国拥有世界上数量最多的老年人口，且大多在农村。据统计，未纳入社会保障的农村人口还很多，截止2000年底，全国7400多万农村居民参加了保险，占全部农村居民的11.18%，占成年农村居民的11.59%.另外，据国家统计局统计，我国进城务工者已从改革开放之初的不到200万人增加到2003年的1.14亿人。而基本方案中没有体现出对留在农村的农民和进城务工的农民给予区别对待。进城务工的农民既没被纳入到农村养老保险体系中，也没被纳入到城市养老保险体系中，处于法律保护的空白地带。所以很有必要考虑这个特殊群体的养老保险问题。
项目成本控制 一、引言 项目是企业形象的窗口和效益的源泉。随着市场竞争日趋激烈，工程质量、文明施工要求不断提高，材料价格波动起伏，以及其他种种不确定因素的影响，使得项目运作处于较为严峻的环境之中。由此可见项目的成本控制是贯穿在工程建设自招投标阶段直到竣工验收的全过程，它是企业全面成本管理的重要环节，必须在组织和控制措施上给于高度的重视，以期达到提高企业经济效益的目的。 二、概述 工程施工项目成本控制，指在项目成本在成本发生和形成过程中，对生产经营所消耗的人力资源、物资资源和费用开支，进行指导、监督、调节和限制，及时预防、发现和纠正偏差从而把各项费用控制在计划成本的预定目标之内，以达到保证企业生产经营效益的目的。 三、施工企业成本控制原则 施工企业的成本控制是以施工项目成本控制为中心，施工项目成本控制原则是企业成本管理的基础和核心，施工企业项目经理部在对项目施工过程进行成本控制时，必须遵循以下基本原则。 3.1 成本最低化原则。施工项目成本控制的根本目的，在于通过成本管理的各种手段，促进不断降低施工项目成本，以达到可能实现最低的目标成本的要求。在实行成本最低化原则时，应注意降低成本的可能性和合理的成本最低化。一方面挖掘各种降低成本的能力，使可能性变为现实；另一方面要从实际出发，制定通过主观努力可能达到合理的最低成本水平。 3.2 全面成本控制原则。全面成本管理是全企业、全员和全过程的管理，亦称“三全”管理。项目成本的全员控制有一个系统的实质性内容，包括各部门、各单位的责任网络和班组经济核算等等，应防止成本控制人人有责，人人不管。项目成本的全过程控制要求成本控制工作要随着项目施工进展的各个阶段连续 进行，既不能疏漏，又不能时紧时松，应使施工项目成本自始至终置于有效的控制之下。 3.3 动态控制原则。施工项目是一次性的，成本控制应强调项目的中间控制，即动态控制。因为施工准备阶段的成本控制只是根据施工组织设计的具体内容确
软件专业毕业论文外文文献中英文翻译 Object landscapes and lifetimes Tech nically, OOP is just about abstract data typing, in herita nee, and polymorphism, but other issues can be at least as importa nt. The rema in der of this sect ion will cover these issues. One of the most importa nt factors is the way objects are created and destroyed. Where is the data for an object and how is the lifetime of the object con trolled? There are differe nt philosophies at work here. C++ takes the approach that con trol of efficie ncy is the most importa nt issue, so it gives the programmer a choice. For maximum run-time speed, the storage and lifetime can be determined while the program is being written, by placing the objects on the stack (these are sometimes called automatic or scoped variables) or in the static storage area. This places a priority on the speed of storage allocatio n and release, and con trol of these can be very valuable in some situati ons. However, you sacrifice flexibility because you must know the exact qua ntity, lifetime, and type of objects while you're writing the program. If you are trying to solve a more general problem such as computer-aided desig n, warehouse man ageme nt, or air-traffic con trol, this is too restrictive. The sec ond approach is to create objects dyn amically in a pool of memory called the heap. In this approach, you don't know un til run-time how many objects you n eed, what their lifetime is, or what their exact type is. Those are determined at the spur of the moment while the program is runnin g. If you n eed a new object, you simply make it on the heap at the point that you n eed it. Because the storage is man aged dyn amically, at run-time, the amount of time required to allocate storage on the heap is sig ni fica ntly Ion ger tha n the time to create storage on the stack. (Creat ing storage on the stack is ofte n a si ngle assembly in structio n to move the stack poin ter dow n, and ano ther to move it back up.) The dyn amic approach makes the gen erally logical assumpti on that objects tend to be complicated, so the extra overhead of finding storage and releas ing that storage will not have an importa nt impact on the creati on of an object .In additi on, the greater flexibility is esse ntial to solve the gen eral program ming problem. Java uses the sec ond approach, exclusive". Every time you want to create an object, you use the new keyword to build a dyn amic in sta nee of that object. There's ano ther issue, however, and that's the lifetime of an object. With Ian guages that allow objects to be created on the stack, the compiler determines how long the object lasts and can automatically destroy it. However, if you create it on the heap the compiler has no kno wledge of its lifetime. In a Ianguage like C++, you must determine programmatically when to destroy the
专业资料 学院： 专业：土木工程 姓名： 学号： 外文出处：Structural Systems to resist (用外文写) Lateral loads 附件：1.外文资料翻译译文；2.外文原文。
附件1：外文资料翻译译文 抗侧向荷载的结构体系 常用的结构体系 若已测出荷载量达数千万磅重，那么在高层建筑设计中就没有多少可以进行极其复杂的构思余地了。确实，较好的高层建筑普遍具有构思简单、表现明晰的特点。 这并不是说没有进行宏观构思的余地。实际上，正是因为有了这种宏观的构思，新奇的高层建筑体系才得以发展，可能更重要的是：几年以前才出现的一些新概念在今天的技术中已经变得平常了。 如果忽略一些与建筑材料密切相关的概念不谈，高层建筑里最为常用的结构体系便可分为如下几类： 1.抗弯矩框架。 2.支撑框架，包括偏心支撑框架。 3.剪力墙，包括钢板剪力墙。 4.筒中框架。 5.筒中筒结构。 6.核心交互结构。 7. 框格体系或束筒体系。 特别是由于最近趋向于更复杂的建筑形式，同时也需要增加刚度以抵抗几力和地震力，大多数高层建筑都具有由框架、支撑构架、剪力墙和相关体系相结合而构成的体系。而且，就较高的建筑物而言，大多数都是由交互式构件组成三维陈列。 将这些构件结合起来的方法正是高层建筑设计方法的本质。其结合方式需要在考虑环境、功能和费用后再发展，以便提供促使建筑发展达到新高度的有效结构。这并
不是说富于想象力的结构设计就能够创造出伟大建筑。正相反，有许多例优美的建筑仅得到结构工程师适当的支持就被创造出来了，然而，如果没有天赋甚厚的建筑师的创造力的指导，那么，得以发展的就只能是好的结构，并非是伟大的建筑。无论如何，要想创造出高层建筑真正非凡的设计，两者都需要最好的。 虽然在文献中通常可以见到有关这七种体系的全面性讨论，但是在这里还值得进一步讨论。设计方法的本质贯穿于整个讨论。设计方法的本质贯穿于整个讨论中。 抗弯矩框架 抗弯矩框架也许是低，中高度的建筑中常用的体系，它具有线性水平构件和垂直构件在接头处基本刚接之特点。这种框架用作独立的体系，或者和其他体系结合起来使用，以便提供所需要水平荷载抵抗力。对于较高的高层建筑，可能会发现该本系不宜作为独立体系，这是因为在侧向力的作用下难以调动足够的刚度。 我们可以利用STRESS，STRUDL 或者其他大量合适的计算机程序进行结构分析。所谓的门架法分析或悬臂法分析在当今的技术中无一席之地，由于柱梁节点固有柔性，并且由于初步设计应该力求突出体系的弱点，所以在初析中使用框架的中心距尺寸设计是司空惯的。当然，在设计的后期阶段，实际地评价结点的变形很有必要。 支撑框架 支撑框架实际上刚度比抗弯矩框架强，在高层建筑中也得到更广泛的应用。这种体系以其结点处铰接或则接的线性水平构件、垂直构件和斜撑构件而具特色，它通常与其他体系共同用于较高的建筑，并且作为一种独立的体系用在低、中高度的建筑中。
毕业论文（设计）外文翻译 题目：中国上市公司偏好股权融资：非制度性因素 系部名称：经济管理系专业班级:会计082班 学生姓名：任民学号： 200880444228 指导教师：冯银波教师职称:讲师 年月日
译文： 中国上市公司偏好股权融资：非制度性因素 国际商业管理杂志 2009.10 摘要：本文把重点集中于中国上市公司的融资活动，运用西方融资理论，从非制度性因素方面，如融资成本、企业资产类型和质量、盈利能力、行业因素、股权结构因素、财务管理水平和社会文化，分析了中国上市公司倾向于股权融资的原因，并得出结论，股权融资偏好是上市公司根据中国融资环境的一种合理的选择。最后，针对公司的股权融资偏好提出了一些简明的建议。 关键词：股权融资，非制度性因素，融资成本 一、前言 中国上市公司偏好于股权融资，根据中国证券报的数据显示，1997年上市公司在资本市场的融资金额为95.87亿美元，其中股票融资的比例是72.5％，，在1998年和1999年比例分别为72.6％和72.3％，另一方面，债券融资的比例分别是17.8％，24.9％和25.1％。在这三年，股票融资的比例，在比中国发达的资本市场中却在下跌。以美国为例，当美国企业需要的资金在资本市场上，于股权融资相比他们宁愿选择债券融资。统计数据显示，从1970年到1985年，美日企业债券融资占了境外融资的91.7％，比股权融资高很多。阎达五等发现，大约中国3/4的上市公司偏好于股权融资。许多研究的学者认为，上市公司按以下顺序进行外部融资：第一个是股票基金，第二个是可转换债券，三是短期债务，最后一个是长期负债。许多研究人员通常分析我国上市公司偏好股权是由于我们国家的经济改革所带来的制度性因素。他们认为，上市公司的融资活动违背了西方古典融资理论只是因为那些制度性原因。例如，优序融资理论认为，当企业需要资金时，他们首先应该转向内部资金（折旧和留存收益），然后再进行债权融资，最后的选择是股票融资。在这篇文章中，笔者认为，这是因为具体的金融环境激活了企业的这种偏好，并结合了非制度性因素和西方金融理论，尝试解释股权融资偏好的原因。
Advantages of Managed Code Microsoft intermediate language shares with Java byte code the idea that it is a low-level language witha simple syntax , which can be very quickly translated intonative machine code. Having this well-defined universal syntax for code has significant advantages. Platform independence First, it means that the same file containing byte code instructions can be placed on any platform; atruntime the final stage of compilation can then be easily accomplished so that the code will run on thatparticular platform. In other words, by compiling to IL we obtain platform independence for .NET, inmuch the same way as compiling to Java byte code gives Java platform independence. Performance improvement IL is actually a bit more ambitious than Java bytecode. IL is always Just-In-Time compiled (known as JIT), whereas Java byte code was ofteninterpreted. One of the disadvantages of Java was that, on execution, the process of translating from Javabyte code to native executable resulted in a loss of performance. Instead of compiling the entire application in one go (which could lead to a slow start-up time), the JITcompiler simply compiles each portion of code as it is called (just-in-time). When code has been compiled.once, the resultant native executable is stored until the application exits, so that it does not need to berecompiled the next time that portion of code is run. Microsoft argues that this process is more efficientthan compiling the entire application code at the start, because of the likelihood that large portions of anyapplication code will not actually be executed in any given run. Using the JIT compiler, such code willnever be compiled.
PA VEMENT PROBLEMS CAUSED BY COLLAPSIBLE SUBGRADES By Sandra L. Houston,1 Associate Member, ASCE (Reviewed by the Highway Division) ABSTRACT: Problem subgrade materials consisting of collapsible soils are com- mon in arid environments, which have climatic conditions and depositional and weathering processes favorable to their formation. Included herein is a discussion of predictive techniques that use commonly available laboratory equipment and testing methods for obtaining reliable estimates of the volume change for these problem soils. A method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented. Relatively simple methods of evaluating potential volume change, based on results of familiar laboratory tests, are used. INTRODUCTION When a soil is given free access to water, it may decrease in volume, increase in volume, or do nothing. A soil that increases in volume is called a swelling or expansive soil, and a soil that decreases in volume is called a collapsible soil. The amount of volume change that occurs depends on the soil type and structure, the initial soil density, the imposed stress state, and the degree and extent of wetting. Subgrade materials comprised of soils that change volume upon wetting have caused distress to highways since the be- ginning of the professional practice and have cost many millions of dollars in roadway repairs. The prediction of the volume changes that may occur in the field is the first step in making an economic decision for dealing with these problem subgrade materials. Each project will have different design considerations, economic con- straints, and risk factors that will have to be taken into account. However, with a reliable method for making volume change predictions, the best design relative to the subgrade soils becomes a matter of economic comparison, and a much more rational design approach may be made. For example, typical techniques for dealing with expansive clays include: (1) In situ treatments with substances such as lime, cement, or fly-ash; (2) seepage barriers and/ or drainage systems; or (3) a computing of the serviceability loss and a mod- ification of the design to "accept" the anticipated expansion. In order to make the most economical decision, the amount of volume change (especially non- uniform volume change) must be accurately estimated, and the degree of road roughness evaluated from these data. Similarly, alternative design techniques are available for any roadway problem. The emphasis here will be placed on presenting economical and simple methods for: (1) Determining whether the subgrade materials are collapsible; and (2) estimating the amount of volume change that is likely to occur in the 'Asst. Prof., Ctr. for Advanced Res. in Transp., Arizona State Univ., Tempe, AZ 85287. Note. Discussion open until April 1, 1989. To extend the closing date one month,