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1、 第12頁(yè) 翻譯部分 英文原文 An Analysis of Dual Shuttle Automated Storage/Retrieval Systems An Analysis of Dual Shuttle Automated Storage/Retrieval Systems Adhinarayan Keserla Brett A. Peters Abstract: This paper addresses the throughput improvement possi

2、ble with the use of a dual shuttle automated storage and retrieval system. With the use of such a system, travel between time in a dual command cycle is virtually eliminated resulting in a large throughput improvement. The dual shuttle system is then extended to perform an equivalent of two dual com

3、mands in one cycle in a quadruple command mode (QC). A heuristic that sequences retrievals to minimize travel time in QC mode is developed. Monte Carlo simulation results are provided for evaluating the heuristics performance and show that it performs well, achieving large throughput improvements co

4、mpared with that of the dual command cycle operating under the nearest neighbor retrieval sequencing heuristic. Key words: Automated Storage/Retrieval Systems Design; Automated Storage/Retrieval Systems Operation; Material Handling Systems; Performance Modeling and Analysis Introduction: A

5、utomated storage/retrieval systems (AS/RS) are widely used in warehousing and manufacturing applications. A typical unit load AS/RS consists of storage racks, S/R machines, link conveyors, and input/output (I/O) stations. An important system performance measure is the throughput capacity of the syst

6、em. The throughput capacity for a single aisle is the inverse of the mean transaction time, which is the expected amount of time required for the S/R machine to store and/or retrieve a unit load. The service time for a transaction includes both S/R machine travel time and pickup/deposit time. This t

7、ime typically depends on the configuration of the storage rack and the S/R machine specifications. Han et al. [2] improved the throughput capacity of the AS/RS through sequencing retrievals. Intelligently sequencing the retrievals can reduce unproductive travel between times when the S/R machine i

8、s traveling empty and thereby increase the throughput. They develop an expression for the maximum possible improvement in throughput if travel between is eliminated for an AS/RS that is throughput bound and operates in dual command mode. In essence, this means that if the S/R machine travels in a si

9、ngle command path but performs both storage and a retrieval operation, the above throughput improvement could be obtained. In this paper, we analyze an alternative design of the S/R machine that has two shuttles instead of one as in a regular AS/RS. The new design eliminates the travel between the

10、storage and retrieval points and performs both storage and retrieval at the point of retrieval, thereby achieving the maximum throughput increase calculated by Han et al. [3]. The dual shuttle AS/RS is a new design aimed at improving S/R machine performance. Most studies on AS/RS systems have been

11、 based on a single shuttle design. In our analysis of the dual shuttle AS/RS performance, we build upon these previous research results. 1 Alternative S/R Machine Design A typical unit-load AS/RS has an S/R machine operating in each aisle of the system. The S/R machine has a mast which is support

12、ed at the floor and the ceiling and travels horizontally within the aisle. Connected to this mast is a shuttle mechanism that carries the unit load and moves vertically up and down the mast. The shuttle mechanism also transfers loads in and out of storage locations in the rack. Figure 1 provides an

13、illustration of the single shuttle S/R machine. Figure 1. Single Shuttle S/R Machine Design A typical single shuttle AS/RS can perform a single command cycle or a dual command cycle. A single command cycle consists of either storage or retrieval. For storage, the time consists of the time to pic

14、kup the load at the I/O point, travel to the storage point, deposit the load at that point, and return to the I/O point. The time for retrieval is developed similarly. A dual command cycle involves both storage and retrieval in the same cycle. The cycle time involves the time to pickup the load at

15、 the I/O point, travel to the storage location, place the load in the rack, travel empty to the retrieval location, retrieve a load, return to the I/O point, and deposit the load at the I/O point. If we critically analyze the dual command cycle of the S/R machine (shown by the solid line in Figure

16、 2), a potential open location for a future storage is created when a retrieval is performed. Furthermore, if both a retrieval and a storage are performed at the same point, the travel between time (TB) is eliminated, and the travel time will be equal to the single command travel time. With the exis

17、ting AS/RS design, this mode of operation is not possible; therefore, an alternative to the S/R machine, a dual shuttle R/S machine, is proposed. Figure 2. Dual Command Travel Paths of S/R and R/S Machines 2 R/S Machine Operations Consider an S/R machine with two shuttle mechanisms instead of o

18、ne. This new S/R machine could now carry two loads simultaneously. Each shuttle mechanism could operate independently of the other, so that individual loads can still be stored and retrieved. An illustration of the dual shuttle S/R machine is shown in Figure 3. This new S/R machine would operate as

19、described below. Figure 3. Dual Shuttle S/R Machine Design The S/R machine picks up the item to be stored from the I/O point, loads it into the first shuttle, and moves to the retrieval location. After reaching the retrieval location, the second shuttle is positioned to pickup the item to be ret

20、rieved. After retrieval, the S/R machine positions the first shuttle and deposits the load. The S/R machine then returns to the I/O point. The operation can easily be seen as a single command operation plus a small travel time for repositioning the S/R machine between the retrieval and storage (as w

21、ell as the additional pickup and deposit time associated with the second load). Therefore, the S/R machine now operates as an R/S machine performing a retrieval first then a storage in a dual command cycle. Since the R/S machine has two shuttles, the position of the shuttles has a role in the oper

22、ation of the system. With two shuttles, the R/S machine is able to perform a dual command cycle at one location in the rack. This operation is accomplished by first retrieving the load onto the empty shuttle, transferring the second shuttle into position, and storing the load into the empty location

23、 in the rack. However, the choice of shuttle configuration does not impact the analysis in this paper. To perform these operations, the R/S machine must move the second shuttle into position after the first shuttle has completed the retrieval. Due to the small distance involved, the R/S machine wi

24、ll use a slower creep speed for positioning, but this travel time is generally small. Furthermore, an amount of creep time is usually included in the pickup and deposit time to account for this required positioning. A second design characteristic is that additional clearance beyond the first and las

25、t row and column of the rack must be provided for overtravel of the R/S machine to accommodate both shuttle mechanisms. 3 Throughput Improvement To estimate the throughput improvement by the dual shuttle system over existing designs, we use the expressions for single command and dual command cycl

26、e times developed by Bozer and White [1] and the tabulated values for the nearest neighbor heuristic from Han et al. [4]. In developing the expressions, the authors in [1] and [4] made several assumptions. The same assumptions hold for the new design and include the following. 1 The rack is consid

27、ered to be a continuous rectangular pick face where the I/O point is located at the lower left-hand corner of the rack. 2 The rack length and height, as well as the S/R machine velocity in the horizontal and vertical directions, are known. 3 The S/R machine travels simultaneously in the horizont

28、al and vertical directions. In calculating the travel time, constant velocities are used for horizontal and vertical travel. Acceleration and deceleration effects are implicitly accounted for in either a reduced top speed or an increased pickup and deposit time. A creep speed is used for repositioni

29、ng the dual shuttle. 4 Pickup and deposit times associated with load handling are assumed constant and, therefore, these could be easily added into the cycle time expressions. 5 The S/R machine operates either on a single or dual command basis, i.e., multiple stops in the aisle are not allowed.

30、(This assumption is later relaxed for the new R/S machine to perform a quadruple command cycle.) 6 For the nearest neighbor heuristic, a block of n retrievals is available for sequencing and there are m initial open locations in the rack face. 4 Dual Shuttle S/R Systems The new design of the S

31、/R machine has two shuttles and therefore could be operated as a dual shuttle system: carrying two loads and depositing them, retrieving two loads, and returning to the I/O point to deliver them as shown in Figure 4. The above operation can be performed by storing and retrieving the loads at four di

32、fferent locations. Therefore, the travel time would consist of the time for a single command travel plus three travel between times. To more efficiently perform the 4 operations, a retrieval and storage performed at one location is interspersed with a dual command operation. This mode of operation,

33、termed the quadruple command (QC) cycle, eliminates one travel between and is more efficient than the previous mode mentioned above (see Figure 5). The QC cycle can be performed with storages at randomized locations and retrievals processed in a first-come-first-served (FCFS) manner. However, by int

34、elligently sequencing the retrieval list, the travel time in performing the four operations can be significantly reduced. This type of analysis was used by Han et al. [4] to improve the throughput of a single load AS/RS. In our paper, we build on the results of their analysis. The notation and the a

35、ssumptions mentioned in section 2.2. still hold, except that multiple stops of the S/R machine are now allowed. 5 Conclusions This paper performs an analysis of dual shuttle automated storage and retrieval systems. Several contributions have been made including the following. 1 Throughput impro

36、vements in the range of 40-45% can be obtained using the quadruple command cycle relative to dual command cycles with a single shuttle system. 2 With the dual shuttle design, travel between is virtually eliminated for a dual command cycle. The dual shuttle system shows promise for situations re

37、quiring high throughput. The main disadvantage with the new design is the extra cost of the S/R machine. An economic evaluation is needed to determine if it is appropriate for a particular situation. However, based on throughput performance, the dual shuttle design appears promising. The concept o

38、f dual shuttle systems can also be extended to other material handling systems. Furthermore, research is needed to consider other storage strategies, such as class based storage policies, to examine their impact on throughput in conjunction with the dual shuttle design. This paper provides a framewo

39、rk for analyzing dual shuttle AS/RS, and it provides a foundation for other material handling research related to this concept. 中文譯文 關(guān)于自動(dòng)化立體倉(cāng)庫(kù)使用雙貨叉的探討 Adhinarayan Keserla 布雷特 A. 彼得 摘 要: 本文主要探討的是可以提高生產(chǎn)效率的雙貨叉立體倉(cāng)庫(kù)系統(tǒng)。通過(guò)使用該系統(tǒng)，可以縮短堆垛機(jī)在一個(gè)雙任務(wù)流程中的運(yùn)行時(shí)間，從而大大提高了倉(cāng)庫(kù)的工作效率。雙貨叉?zhèn)}庫(kù)系統(tǒng)相當(dāng)于一個(gè)四任務(wù)指令模塊（quadru

40、ple command mode簡(jiǎn)稱QC）中的雙指令任務(wù)書流程。一個(gè)很有建設(shè)性的思想被提出來(lái)，即通過(guò)堆垛機(jī)按某一順序運(yùn)行可以縮短在一個(gè)（QC）中的運(yùn)行時(shí)間，蒙地卡羅對(duì)此進(jìn)行了模擬對(duì)比實(shí)驗(yàn)，實(shí)驗(yàn)結(jié)果證明確實(shí)提高了堆垛機(jī)的搬運(yùn)效率，這就說(shuō)明了這種方案的可行性。 關(guān)鍵詞:自動(dòng)化立體倉(cāng)庫(kù)； 自動(dòng)化立體倉(cāng)庫(kù)的控制；功能模擬和分析 1 緒論 自動(dòng)化立體倉(cāng)庫(kù)被廣泛地應(yīng)用于倉(cāng)儲(chǔ)和制造設(shè)備當(dāng)中。典型的單位貨物裝卸立體倉(cāng)庫(kù)由儲(chǔ)藏架，堆垛機(jī)，自動(dòng)運(yùn)輸小車，和入庫(kù)/出庫(kù)臺(tái)組成。衡量一個(gè)立體倉(cāng)庫(kù)系統(tǒng)的優(yōu)劣的主要標(biāo)準(zhǔn)是倉(cāng)庫(kù)系統(tǒng)的工作效率。立體倉(cāng)庫(kù)的工作效率與堆垛機(jī)運(yùn)行一個(gè)工作流程所需的時(shí)間成反比，這個(gè)工作流

41、程時(shí)間包括堆垛機(jī)裝卸貨物的時(shí)間，顯然堆垛機(jī)裝卸貨物的時(shí)間在一定程度上取決于堆垛機(jī)和貨架的具體結(jié)構(gòu)和規(guī)格。 Han 通過(guò)立體倉(cāng)庫(kù)返回站點(diǎn)的排列提高了立體倉(cāng)庫(kù)的工作能力，合理的排列返回站點(diǎn)堆垛機(jī)能減少不必要的行程，從而縮短了時(shí)間，提高了效率。這樣他們就提出了一種最大限度提高效率理論，即如果堆垛機(jī)在雙指令模塊流程中可以縮短運(yùn)行時(shí)間那么這將最大程度的提高立體倉(cāng)庫(kù)的工作效率。也就是說(shuō)，如果堆垛機(jī)運(yùn)行的是單命令路線，卻能完成存貨和返回的動(dòng)作，則工作效率的提高也就實(shí)現(xiàn)了。 在論文中，我們分析了一種可供選擇的堆垛機(jī)設(shè)計(jì)方法，這種設(shè)計(jì)出來(lái)的堆垛機(jī)與一般的堆垛機(jī)不同，在原來(lái)的基礎(chǔ)增加了一個(gè)貨叉，這種新穎設(shè)計(jì)

42、的堆垛機(jī)擁有兩個(gè)貨叉，它在運(yùn)作中可以縮短在貨架到返回點(diǎn)之間的運(yùn)行時(shí)間。這種設(shè)計(jì)方案符合 Han 所說(shuō)的最大效率理論。 雙貨叉堆垛機(jī)主要是針對(duì)如何提高堆垛機(jī)的工作能力這一問(wèn)題所設(shè)計(jì)的一種新穎堆垛機(jī)。目前，立體倉(cāng)庫(kù)系統(tǒng)的研究是以單貨叉堆垛機(jī)為主要對(duì)象。在本文關(guān)于雙貨叉堆垛機(jī)功能的分析也是建立有前人研究的基礎(chǔ)上的。 2 可供選擇的堆垛機(jī)設(shè)計(jì) 一個(gè)基本的單一裝載立體倉(cāng)庫(kù)系統(tǒng)中，每一個(gè)貨架巷道內(nèi)都有一臺(tái)可供操作的堆垛機(jī)，每臺(tái)堆垛機(jī)有一根立柱被固定在天花板和地面之間，這根立柱可以在巷道內(nèi)的水平位置移動(dòng)。與立柱相連的是一個(gè)貨叉機(jī)構(gòu)，它可以載著貨物沿著立柱上下移動(dòng)，貨叉也可以作相對(duì)于貨格的水平取貨和存貨

43、運(yùn)動(dòng)。 一個(gè)基本的單貨叉堆垛機(jī)立體倉(cāng)庫(kù)系統(tǒng)能夠完成一個(gè)單指令作業(yè)流程也能完成一個(gè)雙指令作業(yè)流程。一個(gè)單指令作業(yè)流程由存貨和取貨組成，對(duì)于一個(gè)存貨過(guò)程所需時(shí)間包括堆垛機(jī)在入庫(kù)處裝載貨物，行駛到目標(biāo)貨格，卸下貨物，然后回到倉(cāng)庫(kù)入口處這一連串動(dòng)作總共所需的時(shí)間。同樣可以分析取貨過(guò)程所需時(shí)間。 一個(gè)雙指令流程就是在同一個(gè)工作流程中完成存貨和取貨的操作。這個(gè)過(guò)程時(shí)間包括從入口處裝貨，運(yùn)行到存貨貨格位置，把貨放在貨架上，空運(yùn)行到取貨貨格位置，從貨架上取下貨物，回到倉(cāng)庫(kù)入口處，并卸下貨物這一過(guò)程總共需要的時(shí)間。 如果我們對(duì)堆垛機(jī)的雙指令工作流程路線稍加分析就會(huì)發(fā)現(xiàn)，當(dāng)在完成一個(gè)取貨運(yùn)作時(shí)，就暗示著可以

44、進(jìn)行下一個(gè)存貨運(yùn)作，而且，如果在同一地方可以進(jìn)行存貨和取貨運(yùn)作，那么運(yùn)行時(shí)間將被縮短，這個(gè)運(yùn)行時(shí)間相當(dāng)于運(yùn)行一個(gè)單指令流程所需的時(shí)間。就目前已存在的立體倉(cāng)庫(kù)設(shè)計(jì)，要實(shí)現(xiàn)這種操作是不可能的，因此，另外一種雙貨叉式的堆垛機(jī)就應(yīng)運(yùn)而生了。 3 堆垛機(jī)的運(yùn)作 設(shè)想一臺(tái)安裝了兩個(gè)貨叉的堆垛機(jī),這種新穎的堆垛機(jī)可以同時(shí)裝載兩件貨物,為了兩件貨物分別能存庫(kù)和出庫(kù),所以堆垛機(jī)的兩個(gè)貨叉機(jī)構(gòu)能夠相互獨(dú)立運(yùn)行,具體結(jié)構(gòu)如圖3所示,這種堆垛機(jī)的工作過(guò)程將在下文詳細(xì)介紹。 堆垛機(jī)從倉(cāng)庫(kù)入口處將要被儲(chǔ)存的貨物裝載到第一個(gè)貨叉平臺(tái)上，然后向取貨的位置移動(dòng).到達(dá)要取貨的位置之后，第二個(gè)貨叉臺(tái)伸貨格內(nèi)取貨，當(dāng)取貨的動(dòng)作

45、完成之后，堆垛機(jī)控制第一個(gè)貨叉臺(tái)卸貨。堆垛機(jī)然后再回到入口處。這整個(gè)操作流程就像是一個(gè)單指令運(yùn)作再加上一小段重新定位運(yùn)行過(guò)程（即堆垛機(jī)第二個(gè)貨叉平臺(tái)裝載和卸載過(guò)程），這樣一來(lái)，其運(yùn)作就像一臺(tái)堆垛機(jī)完成先完成取貨然后再存貨的一個(gè)雙任務(wù)命令。 因?yàn)檫@種堆垛機(jī)有兩個(gè)貨叉平臺(tái)，所以兩個(gè)貨叉的定位控制將是系統(tǒng)的一個(gè)很重要的功能。堆垛機(jī)用兩個(gè)貨叉可以在某個(gè)貨架的同一位置完成一個(gè)存、取雙任務(wù)指令，先在空貨駐臺(tái)上取下要出庫(kù)的貨物，再移動(dòng)第二貨叉到指定位置把貨物放在空貨格內(nèi)。然而，貨叉平臺(tái)結(jié)構(gòu)的選擇與本文的討論內(nèi)容無(wú)關(guān)。 為了實(shí)現(xiàn)上述操作，堆垛機(jī)的第二個(gè)貨叉必須在第一個(gè)貨叉完成取貨動(dòng)作之后才能進(jìn)行定位操作。

46、由于貨叉的定位移動(dòng)量是較小的，堆垛機(jī)采用的是低速爬行方式來(lái)實(shí)現(xiàn)貨叉微小的定位移動(dòng)量，在這個(gè)過(guò)程中所耗費(fèi)的時(shí)間與堆垛機(jī)在裝貨卸貨耗費(fèi)的時(shí)間相比一般是微乎其微的。倉(cāng)庫(kù)設(shè)計(jì)的另外一個(gè)特點(diǎn)是第一排貨格和最后一排貨格的兩端要留有位置余量，以便在堆垛機(jī)超程時(shí)給兩個(gè)貨叉平臺(tái)留有運(yùn)動(dòng)余地。 4 工作效率提高 為了估算正在設(shè)計(jì)的雙貨叉系統(tǒng)工作量的提高，我們引用Bozer 和 White[1]提出的有關(guān)單任務(wù)和雙任務(wù)指令所需時(shí)間理論和Han et al.提出的最近有意義想法價(jià)值理論，這些理論家都作了種種設(shè)想，他們?cè)O(shè)想的共同部分就是我們要引用的內(nèi)容，下面就是這些理論的內(nèi)容。 1．倉(cāng)庫(kù)的貨架被考慮成為連續(xù)矩形

47、框架，貨物出/入處被設(shè)置在貨格的左下角位置。 2．貨架的長(zhǎng)度和寬度以及堆垛機(jī)水平和垂直運(yùn)行的速度應(yīng)該明確。 3．堆垛機(jī)貨叉臺(tái)能同時(shí)在水平和垂直兩個(gè)方向運(yùn)動(dòng)，在計(jì)算運(yùn)行時(shí)間方面作如下處理，貨叉在水平和垂直方向時(shí)進(jìn)行勻速運(yùn)動(dòng)，加速和減速緩沖極限速度，爬行速度用來(lái)定位兩個(gè)貨叉臺(tái)。 4．假設(shè)與物流過(guò)程相關(guān)的裝載貨物和卸載貨物所用的時(shí)間為常量，因此，可以把它簡(jiǎn)單的加到運(yùn)行時(shí)間中去。 5．堆垛機(jī)只能以單指令要求和雙指令要求為基礎(chǔ)，例如，不允許堆垛機(jī)在巷道內(nèi)多次啟停。（這個(gè)分假設(shè)后來(lái)應(yīng)用于新設(shè)計(jì)的堆垛機(jī)完成四重作業(yè)流程。 6．為了符合最短鄰近的啟發(fā)思想， 取貨數(shù)n可用來(lái)排列，且在貨格內(nèi)有m個(gè)開(kāi)放的

48、位置。 5 雙貨叉堆垛機(jī)系統(tǒng) 新設(shè)計(jì)的堆垛機(jī)有兩個(gè)貨叉臺(tái),因此可以對(duì)其進(jìn)行雙貨叉系統(tǒng)的操作:同時(shí)搬運(yùn)兩件貨物并分別把它們放置在指定的位置,在不同位置取兩件貨物并回到出入口,如圖4所示.上述工作流程能通過(guò)在四個(gè)不同的位置存、取操作來(lái)實(shí)現(xiàn)。因此，運(yùn)行時(shí)間將由一個(gè)單指令任務(wù)時(shí)間再加上三個(gè)運(yùn)行時(shí)間。為了更有效的完成上述四個(gè)操作，在完成一個(gè)雙指令任務(wù)操作中就包含完成了在一個(gè)位置存、取操作。這種被稱為四指令任務(wù)流程的模擬操作系統(tǒng)能減少運(yùn)行時(shí)間，因而比此前的所提的模擬系統(tǒng)要更能提高效率。四重指令任務(wù)流程能在倉(cāng)庫(kù)的任意一位置完成存儲(chǔ)操作，而取貨程序是按照先到先服務(wù)的原則處理。即使如此，合理的按排取貨的順

49、序也能顯著的減少四種操作中的運(yùn)行時(shí)間，Han 曾經(jīng)這樣分析以提高單貨臺(tái)立體倉(cāng)庫(kù)系統(tǒng)的工作效率。本文的分析也是以他們的研究為基礎(chǔ)的。 6 結(jié)論 本文對(duì)自動(dòng)化立體倉(cāng)庫(kù)中的一種雙貨架堆垛機(jī)進(jìn)行了較為詳細(xì)的分析，應(yīng)用這種倉(cāng)儲(chǔ)系統(tǒng)所帶來(lái)的好處表現(xiàn)在以下兩個(gè)方面： 1．四種操作運(yùn)行中與單一貨叉的堆垛機(jī)相比，雙貨叉堆垛機(jī)可以提高工作效率的范圍是40%到45%。 2．一個(gè)雙任務(wù)操作中，雙貨叉的設(shè)計(jì)顯著縮短了運(yùn)行時(shí)間。 雙貨叉系統(tǒng)使提高倉(cāng)庫(kù)的工作效率成為可能。這種設(shè)計(jì)主要的缺點(diǎn)是要增加堆垛機(jī)的額外成本。在決定是否適合于某一特定情況時(shí)，對(duì)其經(jīng)濟(jì)估算通常是必要的。盡管如此，基于立體倉(cāng)庫(kù)工作效率的考慮，雙設(shè)

50、計(jì)貨叉臺(tái)堆垛機(jī)系統(tǒng)還是大有前景的。 雙貨架系統(tǒng)的概念也可延伸到其它物流系統(tǒng)中去。因此，在這項(xiàng)工作時(shí)有必要對(duì)其它倉(cāng)庫(kù)系統(tǒng)（比如基本的倉(cāng)儲(chǔ)系統(tǒng)）進(jìn)行戰(zhàn)略考慮，相比之下以便于發(fā)現(xiàn)它們?cè)谔岣吖ぷ餍史矫娴牟蛔氵@處，本文還提供了一種雙貨叉自動(dòng)化立體倉(cāng)庫(kù)的分析框架并為其它與之相關(guān)的一些研究提供了基礎(chǔ)。 試題【】 　　1.試題的概念 　　用于考試的題目，要求按照標(biāo)準(zhǔn)回答。 　　它是命題者按照一定的考核目的編寫出來(lái)的。 　　2.試題的應(yīng)用領(lǐng)域 　　如今試題涉及各個(gè)領(lǐng)域，它是考核某種技能水平的標(biāo)準(zhǔn)。 　　比如，在各行業(yè)的招聘中，有招聘的試題?？梢哉f(shuō)，只要有考核要求，就會(huì)有試題。 　　試題用的最多的應(yīng)該

51、還是在教育中，在高考中，有高考試題；在中考中有中考試題；教學(xué)中老師想考核學(xué)生，也是用試題考核。 　　3.網(wǎng)絡(luò)的試題資源 　　隨著網(wǎng)絡(luò)的發(fā)展，試題不再僅僅是寫在紙上了，網(wǎng)上也有豐富的試題資源，有很對(duì)網(wǎng)站都提供了豐富的試題資源，不過(guò)最精良的資源往往是收費(fèi)的。 　　但是通常在日常中，使用者往往更喜歡于找免費(fèi)的試題資源網(wǎng)站。 　　常用的免費(fèi)試題資源下載可以去教育網(wǎng)址站“千教網(wǎng)”上邊查找，上邊把免費(fèi)和收費(fèi)的網(wǎng)站分開(kāi)了，涵蓋了幼兒，小學(xué)，初中，高中，自考，成考，公務(wù)員，留學(xué)等方面的資源網(wǎng)址。 解考試緊張的食物 　　牛奶 　　鈣是天然的神經(jīng)系統(tǒng)穩(wěn)定劑。研究證明，人在受到某種壓力時(shí)，通過(guò)小便排出體外的鈣

52、會(huì)增加。因此，考生要注意選擇含鈣高的牛奶、酸奶等食物，可穩(wěn)定情緒。 　　香蕉 　　含有一種特殊物質(zhì)，能幫助人腦產(chǎn)生5-羥色胺，促使人的心情變得安定、舒暢。香蕉中富含的鉀能使神經(jīng)肌肉興奮性維持常態(tài)，使血壓處于正常狀態(tài)。香蕉中含有的鎂具有消除疲勞、緩解緊張的功效。 　　柑橘 　　多吃富含維生素C的食物也具有平衡心理壓力的效果。維生素C的主要來(lái)源為新鮮的蔬菜和水果，其中柑橘類水果及番茄是維生素C的最佳來(lái)源。 　　小米粥 　　富含人體所需的氨基酸及其他優(yōu)質(zhì)蛋白質(zhì)、各種礦物質(zhì)、胡蘿卜素等。常喝小米粥可調(diào)節(jié)人體內(nèi)分泌，松弛神經(jīng)。 　　紅茶 　　有降低機(jī)體應(yīng)激激素分泌水平的功效，每天飲用紅茶，有利于舒緩神經(jīng)

53、。 編輯本段常見(jiàn)的考試 　　1.升學(xué)考試：中國(guó)選拔優(yōu)秀人才，向來(lái)以考試為準(zhǔn)，在升學(xué)過(guò)程中考試就是必不可少的一部分。常見(jiàn)的升學(xué)考試有小升初、中考、高考等，其中高考也是最重要的考試之一。 　　2.職位/資格考試：同樣在選拔優(yōu)秀員工或工作人員上，也有很多非常重要的考試。常見(jiàn)的有公務(wù)員考試、招警考試等等。 　　3.語(yǔ)言考試：改革開(kāi)放，中國(guó)的留學(xué)和移民現(xiàn)象也越來(lái)越熱，其中也出現(xiàn)一些相應(yīng)的考試，留學(xué)和技術(shù)移民必須通過(guò)一定的語(yǔ)言測(cè)試，如去英美國(guó)家必考的雅思等等 編輯本段科舉考試歷史 概述 　　中國(guó)古代的科舉考試 　　科舉考試是隋唐到清代的封建王朝分科考選文武官吏及后備人員的制度。唐朝文科的科目很多，每年都舉行。明清兩代文科只設(shè)進(jìn)士一科，考八股文。武科考騎射、舉重等武藝。武則天時(shí)設(shè)立武舉,即是武狀元. 　　童生試：也叫“童試”，應(yīng)試者不分年齡大小都稱童生，合格（學(xué)習(xí)成績(jī)優(yōu)秀的一二等學(xué)生）后取得生員（秀才、相公）資格，這樣才能參加科舉考試。 　　鄉(xiāng)試： 明清兩代每三年在各省省城舉行的一次考試，由秀才參加，考取的叫舉人，取得參加中央一級(jí)的會(huì)試的資格。第一名叫解元。