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Determination of Arsenic in Palm Kernel Expeller using Microwave Digestion and Graphite Furnace Atomic Absorption Spectrometry Method Abdul Niefaizal Abdul Hammid, Ainie Kuntom, RazaIi Ismail, and Norazilah Pardi 1Malaysian Palm Oil Board, Persiaran Institusi, Bandar Baru Bangi, 43000,

Kajang Selangor, Malaysia. niefaizal@https://www.wendangku.net/doc/558658797.html,.my

Abstrak – A study on the method to determine arsenic in palm kernel expeller was

carried out. Microwave digestion technique is widely applied in the analytical

chemistry field. In comparison to conventional sample digestion method, the

microwave technique is simple, reduced contamination, usage of safe reagent and

matrix completely digested. A graphite furnace atomic absorption spectrometry

method was used for the total determination of arsenic in palm kernel expeller.

Arsenic was extracted from palm kernel expeller in a closed vessel digestion system

with nitric acid and hydrogen peroxide. The results showed that the optimal ashing

and atomizing temperatures were 800°C and 2400°C respectively. The limit of

detection was estimated to be 0.001 ppm. The mean recoveries of arsenic for

repeatability and reproducibility for 1, 2 and 4 ppm were in the range between 79 –

90%. Ten samples of palm kernel expeller from mills were analyzed to contain 0.18

to 3.05 ppm of arsenic. Therefore, is proposed that this method be used to detect

arsenic in palm kernel expeller

Key Words –Microwave digestion, graphite furnace atomic absorption

spectrometry, palm kernel expeller, arsenic, mills.

1 Introduction

Arsenic has been considered as an essential trace element for normal growth and development of animals (Lasky et al, 2004). However, arsenic is more often regarded as a hazardous element rather than as essential element widely encountered in the environment and organisms (Cullen and Reimer, 1989). Arsenic is extensively distributed in the environment because of its presence naturally as well as from industrial production. Natural arsenic concentration in plants hardly exceeds 1 mg/kg (Porter and Peterson, 1975). This level increases to several folds when plants are coerced to grow in arsenic treated soils, but arsenic is primarily retained in the roots. Studies showed that vegetable grown in arsenic-spiked soils exhibited 7.1 and 5.0 mg/kg in the roots and shoots respectively Jones and Hatch, 1945). In tomato and bean plants, arsenic is primarily concentrated in the roots, and a small quantity is translocated to the pods (Cobb et al., 2000). A similar pattern is observed in Tamarik (Tamarix parviflora) and Eucalyptus (Eucalyptus camaldulensis) where the roots accumulate more arsenic compared to the shoots (Tossell et al., 2000).

In Malaysia the level of arsenic in oil palm is not well established. Contamination of arsenic may come from the use of herbicides such a monosodium methyl arsenate (MSMA), disodium methyl arsenate (DSMA) and cacodylic acid (dimethylarsenic acid) in oil palm plantations. However these compounds are not in used anymore. Numerous methods are available for extracting arsenic from various matrices and analyzing total arsenic (Hudson-Edwards et al., 2004). The most common

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methods for extracting total arsenic from soils and sediments involved wet ashing of sample using one or a combination of acids such as sulphuric acid, nitric acid, hydrochloric acid, boric acid, hydrogen fluoride and hydrogen peroxide. Ashing digestion can be carried out using hotplate or microwave oven (Mucci et al., 2003).

During the past few decades, microwave digestion method has become widely used since they are more reproducible, more accurate and less time consuming than conventional digestion on hot plates in open crucibles and lost of analyte is minimum (Kingston and Jassie, 1988). Arsenic can be determined using the following methods: colorimetry, hydride generation system in combination with atomic absorption spectrometer (Slemer et al., 1976) and atomic fluorescence spectrometry (Chen et al., 2001). Graphite furnace atomic absorption spectrophotometer (GFAAS) is another analytical instrument used for trace element analysis. It has been widely used to determine lead in food (Chen et al., 1999), biological samples (Dabeka and McKenzie, 1992) and environmental samples (Cabrera et al., 1994).

The main objective of this study was to test the effectiveness of microwave system for the digestion of palm kernel expeller and subsequently analyzing using graphite furnace atomic absorption spectrophotometer.

2 Materials and Methods

2.1 Reagents

All reagents were of analytical grade unless otherwise stated. Double-distilled water (Milli Q Millipore 18.2 mΩ-cm resistivity) was used for dilution. Nitric acid (65% w/v) and hydrogen peroxide (30% w/v) were of suprapure quality (E.Merck, Darmstadt). All the plastic and glassware were cleaned by soaking in diluted nitric acid-distilled water (1+9) and were rinsed with distilled water prior to use.

2.2 Arsenic Standard Solution

A standard stock solution of arsenic (1000 ppm) was purchased from BDH Laboratory Supplies.

2.3 Working Standard Solution

Working standard solution of 100 ppm and 1 ppm were prepared by diluting the standard solution with appropriate volumes of Milli Q water. Working standard for 100 ppb was prepared by adding 1 mL of

1 ppm and

2 mL of nitric acid.

2.4 Sample

About 0.5 g palm kernel expeller was spiked with 500 μL, 1 mL and 2 mL of 1 ppm working standard solution to produce 1 ppm, 2 ppm and 4 ppm respectively.

2.5 Preparation of Standard Curve

A working standard solution of 25 ppb, 50 ppb, 75 ppb and 100 ppb were prepared by diluting the 1 ppm working standard solution with appropriate volumes of Milli Q water.

642 Insan Akademika Publications

2.6 Analytical Procedure

Microwave digestion procedure was applied for palm kernel expeller sample. About 0.5 g of palm kernel expeller was weighed. Then 6 mL of nitric acid (65% w/v) and 2 mL hydrogen peroxide (30% w/v) suprapure quality were added. A blank digest was carried out in the same way. The digestion conditions for the microwave system were shown in Table 1. After treatment, the contents were cooled down, then the resultant residue was dissolved in 25 mL Milli Q water for arsenic determination by graphite furnace atomic absorption spectrophotometer.

2.7 Apparatus

Zeeman graphite furnace atomic absorption spectrophotometer AAnalyst 600 with standard transverse heated graphite atomizer (THGA) B3000641 and arsenic electrode less discharge lamp (As-EDL) were made by Perkin Elmer (Germany). Argon was used as the pure/inert gas. The instrument operating parameters are summarized in Table 2 and Table 3. For sample digestion, a Milestone Ethos MOD with Terminal 1024 closed vessel microwave digestion system with pressure and temperature controller was used.

2.8 Analysis of Arsenic in Commercial Palm Kernel Expeller

Ten different palm kernel expeller samples were collected from 10 different mills in Malaysia. The samples were preserved in covered polyethylene bags, tagged properly and kept in room temperature until analysis.

2.9 Statistic Analysis

The data obtained from the analysis were calculated using computer programme Microsoft Excel for Windows.

Table 1: Microwave oven heating program for the decomposition of palm kernel expeller

Step Time (Minute) Temperature 1 (?C) Temperature 2 (?C) Microwave Power

(Watt)

1 15 min 500 180 100

2 15 min 500 180 100

3 15 min 1000 200 120

4 10 min 1000 200 120

5 20 min 0 50 30

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Table 2: Instrument parameters for the determination of arsenic in palm kernel expeller using graphite

furnace atomic absorption spectrophotometer

Parameter

Setting

Wavelength (nm) 193.7

Slit width (nm)

0.7

Signal measurement

Peak area

Lamp

Electrode less discharge

Lamp current (mA)

380

Purge gas Argon Sample volume 20 μL Modifier volume

5 μL

Table 3: Temperature program for the determination of arsenic in palm kernel expeller by graphite

furnace atomic absorption spectrophotometer

Temperature (?C)

Ramp Time

Hold Time

Interna (ml/ l Flow Gas Type min)

Read

120 1 30 12 5 Argon

800 10 30 25 0 Argon

2400 0 5 5 0 Argon +

2500

2

3

25 0

Argon

* Temperature injects: 70 ?C .

3 Results and Discussion

3.1

Matrix Modification

Matrix modification is an essential step in the determination of easily volatile elements by graphite furnace atomic absorption spectrophotometer. The most common matrix modifiers used in arsenic determinations are palladium, palladium-magnesium nitrate and nickel nitrate.

Palladium-magnesium nitrate was selected as a modifier since memory effects were observed when

the nickel modifier was used (Bozsai et al., 1990). An interelement compound was formed between arsenic and palladium, which has a higher heat of vaporization than pure arsenic. Therefore, a higher ashing temperature can be used and the effects of interference are diminished. Magnesium nitrate behaves as an ashing aid during the thermal pretreatment step in graphite furnace determinations. Spectral interferences caused by aluminum and phosphate are possible at the primary resonance line (193.7 nm) of arsenic. It should be possible to almost eliminate these interferences with the Zeeman background correction technique (Bettinelli et al., 1989; Welz et al., 1988; Riley, 1982).

Characteristic mass for arsenic is quite high, and therefore a rather large absolute mass of arsenic should be injected into a graphite tube in order to obtain a reasonable sensitivity. This means that a

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higher sample volume should be used or that a preconcentration step is necessary. However, with a larger sample volume, a longer sample drying phase is needed, and there is also a maximum sample volume that can be dispensed onto a platform.

Therefore, a sample volume of 20 mL was selected for routine use. With very low arsenic concentrations, two or more sample dispensing-drying steps can be used in order to increase the absolute amount of arsenic in the graphite furnace. One should remember that this will also increase the amount of matrix introduced into the furnace. About 5 mL of modifier solution was injected onto a sample. Larger volumes of modifier had produced wider and flatter absorption signals, therefore 5 mL of modifier was determined to be the optimal volume in arsenic determinations.

3.2

Method Performance

Evaluation of quality parameters such as the linearity, recovery percentage (repeatability, and reproducibility) and limits of detection are essential to assess the method performance (Zanella et al., 2000). Calibration curve was obtained by analyzing three times each, four different solutions of known concentrations of analyte included between 25 and 100 ppb. The curve equation y = bx + m calculated with linear regression method to determine samples concentration was utilized.

The calibration curve data for standard arsenic is shown in Table 4 . The equation of the curve and the R2 value (0.999) shows the good linearity of the analytical method and the method is feasible to be used. Values of coefficients of variation are less than 5% for all concentration (25 ppb, 50 ppb, 75 ppb, and 100 ppb) and to be considered acceptable.

Table 4: Parameters values obtained from the calibration curve

Concentration of Arsenic

Standard (ppb)

Average Value

(ppb)

Mean of Areas

Standard Deviation Coefficient of Variation (%)

25

26.14 0.0412 0.0003 0.71

50

51.25 0.0807 0.0020 2.44

75

73.96 0.1165 0.0036 3.09

100

99.83

0.1573

0.0012

0.74

y = 0.0016x R2 = 0.9994

Concentration (ppb)

International Journal of Basic and Applied Science V ol. 01, No. 03, Jan 2013, pp. 641-649 Millersmtih, et. al.

Fig.1: Calibration curve for the determination of arsenic by means of the

graphite furnace atomic absorption spectrophotometer technique

The limit of quantification (LOQ) was stated as a concentration below which the method could not operate with an acceptable level of precision and trueness. The limit of detection (LOD) was the lowest concentration of arsenic in palm kernel expeller samples that was detectable but not necessarily quantified, distinguished from zero (signal/noise >3). These limits were established based on the mean recovery and relative standard deviation results obtained for the replicates of spiked samples. Limit of detection was found to be 0.001 ppm, limit of quantification was 0.006 ppm.

Recovery test for repeatability and reproducibility were performed by spiking several concentrations

of arsenic standard to palm kernel expeller, which was then analyzed using the established method. Recoveries for repeatability from palm kernel expeller at 1, 2, and 4 ppm were found to be 80.40 ±

4.55%, 90.59 ±4.74%, and 8

5.15 ±5.06%, respectively . Recoveries for reproducibility from palm kernel expeller at 1, 2, and 4 ppm were found to be 79.20 ± 3.18%, 89.10 ± 3.11%, and 80.35 ±

6.25%, respectively .

All recoveries were greater than 80% with coefficient of variation less than 10% and to be considered acceptable. The results obtained show that the established method is capable of yielding a satisfactory recovery.

4 Conclusion

The microwave digestion method studied is suitable for the decomposition of palm kernel expeller, since good recoveries for arsenic were obtained. Digesting palm kernel expeller with microwave digester has the advantages of time-saving and more complete digestion. In addition, the graphite furnace atomic absorption spectrometry has high sensitivity and it only takes few minutes for the time taken to complete an analysis of an individual sample. The method described herein coupled microwave digester and graphite furnace atomic absorption spectrometry, which demonstrated features

of a rapid, safe and accurate analysis of arsenic in palm kernel expeller. The arsenic contents in palm

kernel expeller from mills analyzed by the present study were minimum all below the maximal permissible standard of 4 ppm for animal feed.

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中等分辨率制备分离的 快速色谱技术 W. Clark Still,* Michael K a h n , and Abhijit Mitra Departm(7nt o/ Chemistry, Columbia Uniuersity,1Veu York, Neu; York 10027 ReceiLied January 26, 1978 我们希望找到一种简单的吸附色谱技术用于有机化合物的常规净化。这种技术是适于传统的有机物大规模制备分离，该技术需使用长柱色谱法。尽管这种技术得到的效果非常好，但是其需要消耗大量的时间，并且由于频带拖尾经常出现低复原率。当分离的样本剂量大于1或者2g时，这些问题显得更加突出。近年来，几种制备系统已经进行了改进，能将分离时间减少到1-3h，并允许各成分的分辨率ΔR f≥（使用薄层色谱分析进行分析）。在这些方法中，在我们的实验室中，媒介压力色谱法1和短柱色谱法2是最成功的。最近，我们发现一种可以将分离速度大幅度提升的技术，可用于反应产物的常规提纯，我们将这种技术称为急骤色谱法。虽然这种技术的分辨率只是中等（ΔR f≥），而且构建这个系统花费非常低，并且能在10-15min内分离重量在的样本。4 急骤色谱法是以空气压力驱动的混合介质压力以及短柱色谱法为基础，专门针对快速分离，介质压力以及短柱色谱已经进行了优化。优化实验是在一组标准条件5下进行的，优化实验使用苯甲醇作为样本，放在一个20mm*5in.的硅胶柱60内，使用Tracor 970紫外检测器监测圆柱的输出。分辨率通过持续时间（r）和峰宽（w,w/2）的比率进行测定的（Figure 1），结果如图2-4所示，图2-4分别放映分辨率随着硅胶颗粒大小、洗脱液流速和样本大小的变化。

论文外文文献翻译3000字左右

南京航空航天大学金城学院 毕业设计（论文）外文文献翻译 系部经济系 专业国际经济与贸易 学生姓名陈雅琼学号2011051115 指导教师邓晶职称副教授 2015年5月

Economic policy,tourism trade and productive diversification （Excerpt） Iza Lejárraga,Peter Walkenhorst The broad lesson that can be inferred from the analysis is that promoting tourism linkages with the productive capabilities of a host country is a multi-faceted approach influenced by a variety of country conditions.Among these,fixed or semi-fixed factors of production,such as land,labor,or capital,seem to have a relatively minor influence.Within the domain of natural endowments,only agricultural capital emerged as significant.This is a result that corresponds to expectations,given that foods and beverages are the primary source of demand in the tourism economy.Hence,investments in agricultural technology may foment linkages with the tourism market.It is also worth mentioning that for significant backward linkages to emerge with local agriculture,a larger scale of tourism may be important. According to the regression results,a strong tourism–agriculture nexus will not necessarily develop at a small scale of tourism demand. It appears that variables related to the entrepreneurial capital of the host economy are of notable explanatory significance.The human development index(HDI), which is used to measure a country's general level of development,is significantly and positively associated with tourism linkages.One plausible explanation for this is that international tourists,who often originate in high-income countries,may feel more comfortable and thus be inclined to consume more in a host country that has a life-style to which they can relate easily.Moreover,it is important to remember that the HDI also captures the relative achievements of countries in the level of health and education of the population.Therefore,a higher HDI reflects a healthier and more educated workforce,and thus,the quality of local entrepreneurship.Related to this point,it is important to underscore that the level of participation of women in the host economy also has a significantly positive effect on linkages.In sum, enhancing local entrepreneurial capital may expand the linkages between tourism and other sectors of the host country.

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外文文献及翻译 题目：利用固定化过氧化氢酶 回收纺织品漂染的废水 专业食品科学与工程 学生姓名梁金龙 班级B食品072 学号0710308119 指导教师郑清

利用固定化过氧化氢酶回收纺织品漂染的废水 Silgia A. Costa1, Tzanko Tzanov1, Filipa Carneiro1, Georg M. Gübitz2 &Artur Cavaco-Paulo1,? 1纺织工程系, 米尼奥大学, 4810吉马尔, 葡萄牙 2环境生物技术系, 格拉茨技术大学, 8010格拉茨, 奥地利 ?作者联系方式(Fax: +351 253 510293; E-mail: artur@det.uminho.pt) 关键词：过氧化氢酶的固定化，酶稳定，过氧化氢，纺织印染 摘要 过氧化氢酶固定在氧化铝载体上并用戊二醛交联，在再循环塔反应器和CSTR反应器中研究贮存稳定性，温度和pH值对酶的活性。固定化酶的在的活性维持在44％，pH值11（30?C），对照组是活性为90％，pH值7（80?C），过氧化氢酶固定化的半衰期时间被提高到2小时（pH12，60?C）。用过氧化氢漂白织物后，洗涤过程中的残留水被固定化酶处理，可以用于再次印染时，记录实验数据。 1 序言 由于新的法规的出台，从生态经济的角度来看（Dickinson1984年），对于纺织行业中存在的成本和剩余水域的污染问题，必须给予更多的关注。过氧化氢是一种漂白剂，广泛应用于工业纺织工艺（Spiro & Griffith1997年）。在去除H2O2时，会消耗大量的水和能源（Weck 1991, St?hr & Petry 1995），以避免对氧气敏感的染料（Jensen 2000）产生后续问题。过氧化氢酶可用于降低过氧化氢的含量（Vasudevan & Thakur 1994, Emerson et al. 1996），从而减少水分消耗或方便回收印染洗涤液。过氧化氢酶的使用主要问题出在漂白时温度和清洗液碱度过高。以前，我们试图通过筛选新的嗜热嗜碱的微生物（Paar et al. 2001）或使用不同的酶稳定剂（Costa et al. 2001）来解决此问题。但是染料与蛋白质之间的潜在相互作用（Tzanov et al. 2001a, b）表明，可溶性过氧化氢酶的使用是不恰当的。固定化过氧化氢酶的使用还有一种选择(Costa et al. 2001, Amar et al. 2000)。在这项研究中，我们对氧化铝进行共价固定并使用戊二醛作为交联剂，这种方法在商业中得到验证。本项研究的目的就是探讨过氧化氢酶的固定化动力学，及其稳定性和工艺条件，这将使我们能够应用此系统，以处理可能被用于清洗染色的反复使用的酒。 2 材料和方法 2.1 酶 Terminox（EC1.11.1.6），50L以上，由AQUITEX- Maia提供，葡萄牙产。 2.2 过氧化氢酶的固定化 取Al2O3颗粒或薄片（Aldrich），直径分别为3和7毫米，在45摄氏度下，先经浓度4%的γ-氨丙基三乙氧基硅烷(Sigma)烷基化，再放入丙酮中浸泡24小时。用蒸馏水洗涤硅烷化载体后，放入浓度为2％戊二醛水溶液中室温下浸泡2小时（Aldrich），重复清洗一次并在60?C下干燥1小时。取五克的烷基化载体，室温24?C下浸泡在25毫升粗酶制剂中（Costa et al. 2001）。得出，每克Al2O3

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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

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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.

计算机网络-外文文献-外文翻译-英文文献-新技术的计算机网络

New technique of the computer network Abstract The 21 century is an ages of the information economy, being the computer network technique of representative techniques this ages, will be at very fast speed develop soon in continuously creatively, and will go deep into the people's work, life and study. Therefore, control this technique and then seem to be more to deliver the importance. Now I mainly introduce the new technique of a few networks in actuality live of application. keywords Internet Network System Digital Certificates Grid Storage 1. Foreword Internet turns 36, still a work in progress Thirty-six years after computer scientists at UCLA linked two bulky computers using a 15-foot gray cable, testing a new way for exchanging data over networks, what would ultimately become the Internet remains a work in progress. University researchers are experimenting with ways to increase its capacity and speed. Programmers are trying to imbue Web pages with intelligence. And work is underway to re-engineer the network to reduce Spam (junk mail) and security troubles. All the while threats loom: Critics warn that commercial, legal and political pressures could hinder the types of innovations that made the Internet what it is today. Stephen Crocker and Vinton Cerf were among the graduate students who joined UCLA professor Len Klein rock in an engineering lab on Sept. 2, 1969, as bits of meaningless test data flowed silently between the two computers. By January, three other "nodes" joined the fledgling network.

英文文献及中文翻译

毕业设计说明书 英文文献及中文翻译 学院：专 2011年6月 电子与计算机科学技术软件工程

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外文文献及翻译

文献翻译 原文 Combining JSP and Servlets The technology of JSP and Servlet is the most important technology which use Java technology to exploit request of server, and it is also the standard which exploit business application .Java developers prefer to use it for a variety of reasons, one of which is already familiar with the Java language for the development of this technology are easy to learn Java to the other is "a preparation, run everywhere" to bring the concept of Web applications, To achieve a "one-prepared everywhere realized." And more importantly, if followed some of the principles of good design, it can be said of separating and content to create high-quality, reusable, easy to maintain and modify the application. For example, if the document in HTML embedded Java code too much (script), will lead the developed application is extremely complex, difficult to read, it is not easy reuse, but also for future maintenance and modification will also cause difficulties. In fact, CSDN the JSP / Servlet forum, can often see some questions, the code is very long, can logic is not very clear, a large number of HTML and Java code mixed together. This is the random development of the defects. Early dynamic pages mainly CGI (Common Gateway Interface, public Gateway Interface) technology, you can use different languages of the CGI programs, such as VB, C / C + + or Delphi, and so on. Though the technology of CGI is developed and powerful, because of difficulties in programming, and low efficiency, modify complex shortcomings, it is gradually being replaced by the trend. Of all the new technology, JSP / Servlet with more efficient and easy to program, more powerful, more secure and has a good portability, they have been many people believe that the future is the most dynamic site of the future development of technology. Similar to CGI, Servlet support request / response model. When a customer submit a request to the server, the server presented the request Servlet, Servlet responsible for handling requests and generate a response, and then gave the server, and then from the server sent to

毕业论文5000字英文文献翻译

英文翻译 英语原文： . Introducing Classes The only remaining feature we need to understand before solving our bookstore problem is how to write a data structure to represent our transaction data. In C++ we define our own data structure by defining a class. The class mechanism is one of the most important features in C++. In fact, a primary focus of the design of C++ is to make it possible to define class types that behave as naturally as the built-in types themselves. The library types that we've seen already, such as istream and ostream, are all defined as classesthat is,they are not strictly speaking part of the language. Complete understanding of the class mechanism requires mastering a lot of information. Fortunately, it is possible to use a class that someone else has written without knowing how to define a class ourselves. In this section, we'll describe a simple class that we canuse in solving our bookstore problem. We'll implement this class in the subsequent chapters as we learn more about types,expressions, statements, and functionsall of which are used in defining classes. To use a class we need to know three things: What is its name? Where is it defined? What operations does it support? For our bookstore problem, we'll assume that the class is named Sales_item and that it is defined in a header named Sales_item.h. The Sales_item Class The purpose of the Sales_item class is to store an ISBN and keep track of the number of copies sold, the revenue, and average sales price for that book. How these data are stored or computed is not our concern. To use a class, we need not know anything about how it is implemented. Instead, what we need to know is what operations the class provides. As we've seen, when we use library facilities such as IO, we must include the associated headers. Similarly, for our own classes, we must make the definitions associated with the class available to the compiler. We do so in much the same way. Typically, we put the class definition into a file. Any program that wants to use our class must include that file. Conventionally, class types are stored in a file with a name that, like the name of a program source file, has two parts: a file name and a file suffix. Usually the file name is the same as the class defined in the header. The suffix usually is .h, but some programmers use .H, .hpp, or .hxx. Compilers usually aren't picky about header file names, but IDEs sometimes are. We'll assume that our class is defined in a file named Sales_item.h. Operations on Sales_item Objects

变电站_外文翻译_外文文献_英文文献_变电站的综合概述

英文翻译 A comprehensive overview of substations Along with the economic development and the modern industry developments of quick rising, the design of the power supply system become more and more completely and system. Because the quickly increase electricity of factories, it also increases seriously to the dependable index of the economic condition, power supply in quantity. Therefore they need the higher and more perfect request to the power supply. Whether Design reasonable, not only affect directly the base investment and circulate the expenses with have the metal depletion in colour metal, but also will reflect the dependable in power supply and the safe in many facts. In a word, it is close with the economic performance and the safety of the people. The substation is an importance part of the electric power system, it is consisted of the electric appliances equipments and the Transmission and the Distribution. It obtains the electric power from the electric power system, through its function of transformation and assign, transport and safety. Then transport the power to every place with safe, dependable, and economical. As an important part of power’s transport and control, the transformer substation must change the mode of the traditional design and control, then can adapt to the modern electric power system, the development of modern industry and the of trend of the society life. Electric power industry is one of the foundations of national industry and national economic development to industry, it is a coal, oil, natural gas, hydropower, nuclear power, wind power and other energy conversion into electrical energy of the secondary energy industry, it for the other departments of the national economy fast and stable development of the provision of adequate power, and its level of development is a reflection of the country's economic development an important indicator of the level. As the power in the industry and the importance of the national economy, electricity transmission and distribution of electric energy used in these areas is an indispensable component.。Therefore, power transmission and distribution is critical. Substation is to enable superior power plant power plants or power after adjustments to the lower load of books is an important part of power transmission. Operation of its functions, the capacity of a direct impact on the size of the lower load power, thereby affecting the industrial production and power consumption.Substation system if a link failure, the system will protect the part of action. May result in power outages and so on, to the production and living a great disadvantage. Therefore, the substation in the electric power system for the protection of electricity reliability,