外文翻譯--zigbee檢測(cè)探頭在冷藏蔬菜運(yùn)輸現(xiàn)實(shí)條件下的測(cè)試

1、<p><b>　　中文4250字</b></p><p><b>　?。?lt;/b></p><p>　　二 〇 一 年 月</p><p><b>　　Abstract</b></p><p>　　Quality control and monitoring

2、of perishable goods during transportation and delivery services is an increasing concern for producers, suppliers, transport decision makers and consumers. The major challenge is to ensure a continuous ?cold chain? from

3、producer to consumer in order to guaranty prime condition of goods. In this framework, the suitability of ZigBee protocol for monitoring refrigerated transportation has been proposed by several authors. However, up to da

4、te there was not any experime</p><p>　　1. Introduction</p><p>　　Perishable food products such as vegetables, fruit, meat or fish require refrigerated transportation. For all these products, Temp

5、erature (T) is the most important factor for extending shelf life, being essential to ensure that temperatures along the cold chain are adequate. However, local temperature deviations can be present in almost any transpo

6、rt situation. Reports from the literature indicate gradients of 5 °C or more, when deviations of only a few degrees can lead to spoiled goods and thou</p><p>　　Transport is often done by refrigerated ro

7、ad vehicles and containers equipped with embedded cooling systems. In such environments, temperatures rise very quickly if a reefer unit fails. Commercial systems are presently available for monitoring containers and tru

8、cks, but they do not give complete information about the cargo, because they typically measure only temperature and at just one point.</p><p>　　Apart from temperature, water loss is one of the main causes of

9、 deterioration that reduces the marketability of perishable food products. Transpiration is the loss of moisture from living tissues. Most weight loss of stored fruit is caused by this process. Relative humidity (RH), T

10、of the product, T of the surrounding atmosphere, and air velocity all affect the amount of water lost in food commodities. Free water or condensation is also a problem as it encourages microbial infection and growth, <

11、;/p><p>　　Parties involved need better quality assurance methods to satisfy customer demands and to create a competitive point of difference. Successful transport in food logistics calls for automated and effic

12、ient monitoring and control of shipments. The challenge is to ensure a continuous ?cold chain? from producer to consumer in order to guaranty prime condition of goods .</p><p>　　The use of wireless sensors i

13、n refrigerated vehicles was proposed by Qingshan et al. as a new way of monitoring. Specialized WSN (Wireless Sensor Network) monitoring devices promise to revolutionize the shipping and handling of a wide range of peris

14、hable products giving suppliers and distributors continuous and accurate readings throughout the distribution process. In this framework, ZigBee was developed as a very promising WSN protocol due to its low energy consum

15、ption and advanced network capa</p><p>　　The main objective of this project is to explore the potential of wireless ZigBee/IEEE 802.15.4 motes for their application in commercial refrigerated shipments by ro

16、ad. A secondary objective was to improve the knowledge about the conditions that affect the perishable food products during transportation, through the study of relevant parameters like temperature, relative humidity, li

17、ght, shocking and psychrometric properties.</p><p>　　2. Materials and Methods</p><p>　　2.1. ZigBee Motes</p><p>　　Four ZigBee/IEEE 802.15.4 motes (transmitters) and one base station

18、 (receiver) were used. All of them were manufactured by Crossbow. The motes consist of a microcontroller board (Micaz) together with an independent transducer board (MTS400) attached by means of a 52 pin connector. The M

19、icaz mote hosts an Atmel ATMEGA103/128L CPU running the Tiny Operating System (TinyOS) that enables it to execute programs developed using the nesC language. The Micaz has a radio device Chipcon CC2420 2.4 GHz 250</p&

20、gt;<p>　　The transducer board hosts a variety of sensors: T and RH (Sensirion SHT11), T and barometric pressure (Intersema MS5534B), light intensity (TAOS TSL2550D) and a two-axis accelerometer (ADXL202JE). A lapt

21、op computer is used as the receiver, and communicates with the nodes through a Micaz mounted on the MIB520 ZigBee/USB gateway board.</p><p>　　Each Sensirion SHT11 is individually calibrated in a precision hu

22、midity chamber. The calibration coefficients are used internally during measurements to calibrate the signals from the sensors. The accuracies for T and RH are ±0.5 °C (at 25 °C) and ±3.5% respectivel

23、y.</p><p>　　The Intersema MS5534B is a SMD-hybrid device that includes a piezoresistive pressure sensor and an ADC-Interface IC. It provides a 16 bit data word from a pressure and T (?40 to +125°C) depe

24、ndent voltage. Additionally the module contains six readable coefficients for a highly accurate software calibration of the sensor.</p><p>　　The TSL2550 is a digital-output light sensor with a two-wire, SMBu

25、s serial interface. It combines two photodiodes and an analog-to digital converter (ADC) on a single CMOS integrated circuit to provide light measurements over a 12-bit dynamic range. The ADXL202E measures accelerations

26、with a full-scale range of ±2 g. The ADXL202E can measure both dynamic acceleration (e.g., vibration) and static acceleration (e.g., gravity).</p><p>　　2.2. Experimental Set Up</p><p>　　The

27、 experiment was conducted in a refrigerated truck traveling during 23 h 41 m 21 s from Murcia (Spain) to Avignon (France), a distance of 1,051 km. The truck transported approx.14,000 kg of lettuce var. Little Gem in 28 p

28、allets of 1,000 × 1,200 mm . The lettuce was packed in cardboard boxes with openings for air circulation.</p><p>　　The length of the semi-trailer was 15 m with a Carrier Vector 1800 refrigeration unit m

29、ounted to the front of the semi-trailer. For this shipment the set point was 0 °C.</p><p>　　The truck was outfitted with the wireless system, covering different heights and lengths from the cooling equi

30、pment, which was at the front of the semi-trailer. Four motes were mounted with the cargo (see Figure 1): mote 1 was at the bottom of the pallets in the front side of the semi-trailer, mote 2 was in the middle of the sem

31、i-trailer, mote 3 was in the rear at the top of the pallet, and mote 4 was located as shown in Figure 1, about a third of the distance between the front and the rear of t</p><p>　　2.3. Data Analysis</p>

32、;<p>　　A specialized MATLAB program has been developed for assessing the percentage of lost packets (%) in transmission, by means of computing the number of multiple sending failures for a given sample rate (SR).

33、A multiple failure of m messages occurs whenever the elapsed time between two messages lies between 1.5 × m × SR and 2.5 × m × SR. For example, with a sample rate of 11 s, a single failure (m = 1) occ

34、urs whenever the time period between consecutives packets is longer than 16.5 s (1.5 × 1 × 11)</p><p>　　The standard error (SE) associated to the ratio of lost packets is computed based on a binomi

35、al distribution as expressed in Equation 1, where n is the total number of packets sent, and p is the ratio of lost packets in the experiment.</p><p>　　2.4. Analysis of Variance</p><p>　　Factori

36、al Analysis of Variance (ANOVA) was performed in order to evaluate the effect of the type of sensor in the registered measurements, including T (by means of Sensirion and Intersema), RH, barometric pressure, light intens

37、ity and acceleration module. ANOVA allows partitioning of the observed variance into components due to different explanatory variables. The STATISTICA software (StatSoft, Inc.) was used for this purpose [14]. The Fishers

38、?s F ratio compares the variance within sample groups</p><p>　　2.5. Psychrometric Data</p><p>　　Psychrometry studies the thermodynamic properties of moist air and the use of these properties to

39、analyze conditions and processes involving moist air. Psychrometric charts show a graphical representation of the relationship between T, RH and water vapor pressure in moist air. They can be used for the detection of wa

40、ter loss and condensation over the product.</p><p>　　In our study, the ASAE standard D271.2 was used for computing the psychrometric properties of air. Equations 2–5 and Table 1 enable the calculation of all

41、 psychrometric data of air whenever two independent psychrometric properties of an air-water vapour mixture are known in addition to the atmospheric pressure:where Ps stands for saturation vapor pressure (Pa), T is the t

42、emperature (K), Pv is the vapor pressure (Pa), H the absolute humidity (g/kg dry air), Patm is atmospheric pressure (Pa) and A</p><p>　　Results and Discussion</p><p>　　3.1. Reliability of Transm

43、ission</p><p>　　Signal propagation through the lettuce lead to absorption of radio signals, resulting in great attenuations in RF signal strength and link quality at the receiver. During the experiment, only

44、 motes 3 and 4 were able to transmit to the coordinator. No signals were received from mote number 1, at the bottom of the first pallet, and number 2, in the middle of the pallet. Mote 3 was closer to the coordinator tha

45、n mote 4, but mote 3 was surrounded by lettuce which blocks the RF signal. However betwee</p><p>　　Similar ratios were reported by several authors who performed experiments with WSN under real conditions, li

46、ke for example in monitoring vineyards. Also, Baggio and Haneveld, after one year of experimentation in a potato field using motes operating at the band of 868/916MHz, reported that 98% of data packets were lost. However

47、, during the second year the total amount of data gathered was 51%, which represents a clear improvement. Ipema et al. monitored cows with Crossbow motes, and found that th</p><p>　　Radio propagation can be

48、influenced by two main factors: the properties of propagation media and the heterogeneous properties of devices. In a commercial shipment, if the motes are embedded within the cargo, a significant portion of the Fresnel

49、zone is obstructed. This is a big challenge in our application. Changing the motes? location, for example the one at the bottom of the pallets (mote 1, at the front of the semitrailer) or the one in the middle of the com

50、partment (mote 2), might have yield</p><p>　　Sample rates configured in the motes were very short in order to get the maximum amount of data about the ambient conditions. In practice, a reduction in the samp

51、ling frequency of recording and transmission should be configured in order to extend battery life. According to Thiemjarus and Yang this also provides opportunities for data reduction at the mote level. It is expected th

52、at future wireless sensor motes will have on-board features to analyze recorded data and detect certain deviations. Th</p><p>　　One important feature in the motes came from the miniaturized sensors mounted o

53、n the motes that allow, in a small space (2.5 × 5 × 5 cm), to provide data not just about temperature, but also RH, acceleration and light, according to the proposal of Wang and Li. Those variables were also me

54、asured and analyzed.</p><p>　　3.2. Transport Conditions</p><p>　　For the analysis of T conditions, the average value of the two sensors mounted in each mote is considered. The set-point of the t

55、ransport trailer?s cooling system was 0 °C, but the average temperature registered during the shipment was 5.33 °C, with a maximum of 8.52 °C and a minimum of ?3.0 °C. On average, 98% of the time the

56、temperature was outside of the industry recommended range (set-point ± 0.5 °C).</p><p>　　Figure 2 shows the temperature fluctuations registered during the shipment, where four different markers are

57、 used corresponding to two T sensors per mote. There are large differences between the temperatures recorded with each sensor on the same mote even thought individual calibration curves were used. The SHT11 measures cons

58、istently higher temperatures than the Intersema. This behaviour could be due to the closer location of the SHT11 to the microcontroller, causing sensor self-heating effects</p><p>　　In other studies, like fo

59、r example Tanner and Amos, it was observed that the cargo was within the industry recommended T interval for approximately 58% of the shipment duration. Rodriguez-Bermejo et al. compared two different cooling modes in a

60、20? reefer container. For modulated cooling the percentage of time within the recommendation ranged between 44% and 52% of the shipment duration, whereas for off/on control cooling it ranged between 9.6% and 0%. In those

61、 experiments, lower percentages of </p><p>　　The analysis of variance of the T data shows that the variability in temperature depended both in the type of sensor and on the mote used. The interaction between

62、 these two factors also has an impact on the T measurements. The critical value of F at 95% probability level is much lower than the observed values of F, which means that the null hypothesis is false. The mote is the fa

63、ctor that has most influence on the variability of the measurements (highest Fishers?s F); this fact seems to be due t</p><p>　　The node is a very significant factor in the measurements registered. In the ca

64、se of RH, pressure, light and acceleration, the node location has great influence in data variability . However, node location has more impact on the measured RH than on the other variables.</p><p>　　Inside

65、the semi-trailer RH ranged from 55 to 95% (see Figure 3). The optimal RH for lettuce is 95%. Humidity was always higher at mote 4 (at the top middle of the semi-trailer; average RH 74.9%) than at mote 3 (located at the r

66、ear; average RH 62.1%).</p><p><b>　　摘要</b></p><p>　　生產(chǎn)商、供應(yīng)商、運(yùn)輸決策者和消費(fèi)者越來(lái)越關(guān)心易腐貨物在運(yùn)輸和交付服務(wù)中對(duì)質(zhì)量的掌握和把控。最大的挑戰(zhàn)是確保從生產(chǎn)商到消費(fèi)者持續(xù)的“冷鏈”以保證貨物。在這個(gè)框架內(nèi)，幾位作者提出用于監(jiān)測(cè)冷藏運(yùn)輸ZigBee協(xié)議的適用性。然而，到目前為止沒有任何真實(shí)條件下進(jìn)行的實(shí)驗(yàn)

67、工作。因此，我們實(shí)驗(yàn)的主要目的是測(cè)試基于ZigBee / IEEE 802.15.4協(xié)議的無(wú)線傳感器在實(shí)際裝運(yùn)中的應(yīng)用。本次實(shí)驗(yàn)是一輛穿過(guò)兩個(gè)國(guó)家（法國(guó)和西班牙）的冷藏車的一個(gè)1051公里的旅程。本文闡述了這種類型的傳感器的巨大潛力，提供信息的幾個(gè)參數(shù)，如溫度，相對(duì)濕度，門洞口停車等。焓濕圖也被開發(fā)，提高對(duì)產(chǎn)品在運(yùn)輸和冷凝水損失知識(shí)的了解。</p><p>　　關(guān)鍵詞：ZigBee；無(wú)線傳感；冷鏈物流；食品<

68、;/p><p><b>　　1 介紹</b></p><p>　　蔬菜，水果，肉類或魚這些易腐蝕食品需要冷藏運(yùn)輸。對(duì)于這些產(chǎn)品延長(zhǎng)保質(zhì)期，以確保冷鏈保持足夠長(zhǎng)的溫度（T）是必不可少的。然而，局部溫度偏差會(huì)出現(xiàn)在大部分的運(yùn)輸情況中。從文獻(xiàn)報(bào)告顯示梯度為5°C以上時(shí)，只要溫度存在幾度的偏差，就可能會(huì)導(dǎo)致商品的腐蝕和數(shù)千歐元的賠償。最近的一項(xiàng)研究表明，從供應(yīng)商到配送中

69、心的車次冷藏運(yùn)輸?shù)臏囟葧?huì)上升30％以，而從配送中心到門店的則上升15％。Roy et al分析了，在日本供應(yīng)新鮮的西紅柿在運(yùn)輸和分配時(shí)會(huì)給產(chǎn)品帶來(lái)5％虧損，對(duì)遠(yuǎn)洋運(yùn)輸?shù)臏囟茸兓策M(jìn)行了研究。結(jié)果表明，整個(gè)容器的寬度隨著時(shí)間而逐漸上升，并超過(guò)標(biāo)準(zhǔn)時(shí)間的30％，所以存在顯著的溫度變化。在這些實(shí)驗(yàn)中，在一個(gè)容器里安裝了數(shù)百個(gè)監(jiān)測(cè)有線傳感器的裝置，這樣的系統(tǒng)架構(gòu)是不可能實(shí)現(xiàn)的。</p><p>　　在冷藏公路車輛和集裝箱

70、運(yùn)輸中會(huì)配備嵌入式冷卻系統(tǒng)，在這樣的環(huán)境中，如果冷藏系統(tǒng)發(fā)生故障會(huì)導(dǎo)致溫度上升的速度非?？?。商業(yè)系統(tǒng)主要應(yīng)用于檢測(cè)集裝箱和卡車中，由于它們僅僅測(cè)量一個(gè)點(diǎn)的溫度，所以他們給不出貨物的完整信息。</p><p>　　除了溫度的影響，水分的流失也是導(dǎo)致食物易腐爛的主要原因之一。蒸騰作用使水分子大量的流失，這個(gè)過(guò)程被稱為水果減肥。相對(duì)濕度、大氣周圍的溫度和空氣的流速都會(huì)影響食品水分的流失。通過(guò)冷凝方式減少水分的流失，這樣

71、不僅促進(jìn)了微生物的生長(zhǎng)，同時(shí)也減少了材料的包裝。</p><p>　　參與各方需要嚴(yán)格的保證產(chǎn)品質(zhì)量，以滿足客戶的需求。成功的運(yùn)輸需要食品在運(yùn)輸過(guò)程中具有有效的監(jiān)測(cè)和控制出貨量的能力。其挑戰(zhàn)是從生產(chǎn)者到消費(fèi)者保持持續(xù)的冷鏈狀態(tài)，從而保證貨物的質(zhì)量。</p><p>　　青山等人提出在冷藏車使用無(wú)線傳感器這種新的監(jiān)控方式。專業(yè)WSN監(jiān)控設(shè)備改變了易腐蝕產(chǎn)品，給供應(yīng)商和分銷商在整個(gè)分銷過(guò)程中提

72、供了連續(xù)且又準(zhǔn)確讀數(shù)范圍的運(yùn)輸和裝載能力。由于ZigBee技術(shù)其能耗低和先進(jìn)的網(wǎng)絡(luò)功能的特點(diǎn)，已成為現(xiàn)在非常有前途的無(wú)線傳感器網(wǎng)絡(luò)協(xié)議。其冷鏈監(jiān)測(cè)能力雖然有效，但沒有進(jìn)行的實(shí)驗(yàn)，出于這個(gè)原因，我們工作的目的是探索這項(xiàng)技術(shù)的優(yōu)勢(shì)。</p><p>　　這個(gè)項(xiàng)目的主要目的發(fā)掘ZigBee / IEEE 802.15.4無(wú)線技術(shù)，為他們?cè)谏虡I(yè)冷藏運(yùn)輸公路上的應(yīng)用。第二個(gè)目標(biāo)是改善其條件，通過(guò)學(xué)習(xí)相關(guān)的參數(shù)，如溫度，相對(duì)

73、濕度，光照等性能，了解易腐食品在運(yùn)輸過(guò)程中的知識(shí)。</p><p><b>　　2 材料和方式</b></p><p>　　2.1 ZigBee技術(shù)</p><p>　　應(yīng)用四個(gè)ZigBee / IEEE 802.15.4微塵（發(fā)射器）和一個(gè)基站（接收器）。微塵由一個(gè)微控制器板（Micaz）和一個(gè)具有52針連接器獨(dú)立連接的傳感器板（MTS40

74、0）組成。 Micaz微塵主板是愛特梅爾ATMEGA103/128L CPU處理器，使執(zhí)行程序使用的是TinyOS微型操作系統(tǒng)開發(fā)的nesC語(yǔ)言。 Micaz是Chipcon公司的IEEE 802.15.4無(wú)線電設(shè)備具有CC2420 2.4 GHz和250 Kbps其電源由兩節(jié)AA鋰電池構(gòu)成。</p><p>　　傳感器主板承載了各種傳感器：溫度和相對(duì)濕度（SHT11 Sensirion的），T和氣壓（MS553

75、4B INTERSEMA）的，光強(qiáng)度（TAOS TSL2550D）的兩軸加速度計(jì)（ADXL202JE）。一臺(tái)筆記本電腦被用作接收器，MIB520的ZigBee / USB網(wǎng)關(guān)板安裝在Micaz上并與各個(gè)節(jié)點(diǎn)進(jìn)行通信。</p><p>　　每個(gè)經(jīng)過(guò)SENSIRION SHT11單獨(dú)校準(zhǔn)精確的濕度室。在測(cè)量過(guò)程中，在內(nèi)部使用校準(zhǔn)系數(shù)來(lái)校準(zhǔn)來(lái)自傳感器的信號(hào)。溫度和相對(duì)濕度的精度為±0.5°C（25&

76、#176;C）和±3.5％。</p><p>　　INTERSEMA MS5534B是SMD的一個(gè)特殊裝置，其包括一個(gè)電阻壓力傳感器和一個(gè)ADC，IC接口。它提供了一個(gè)16位數(shù)據(jù)字。此外，該模塊包含了一個(gè)六位可讀系數(shù)的高度精確的軟件傳感器。</p><p>　　TSL2550是一個(gè)具有兩線SMBus串行接口的數(shù)字輸出光傳感器。它結(jié)合了兩個(gè)光電二極管和一個(gè)模擬到數(shù)字轉(zhuǎn)換器（ADC）

77、，在一個(gè)單一的CMOS集成電路中提供一個(gè)12位的動(dòng)態(tài)范圍的光測(cè)量。ADXL202E可以測(cè)量動(dòng)態(tài)加速度（如振動(dòng)）和靜態(tài)加速度（如重力）其測(cè)量加速度的滿程范圍為±2克。</p><p><b>　　2.2實(shí)驗(yàn)裝置</b></p><p>　　實(shí)驗(yàn)進(jìn)行23小時(shí)41分鐘21秒冷藏卡車行駛從穆爾西亞（西班牙）到阿維尼（法國(guó)）1,051公里的距離?？ㄜ囘\(yùn)送約14，000

78、公斤生菜VAR。 28托盤1,000×1,200毫米的小寶石。生菜用開口的紙板箱包裝以便空氣流通。</p><p>　　拖車的長(zhǎng)度為15米，載有其1800的制冷單元，其被安裝到拖車的前部。對(duì)于這批貨物把溫度集中控制到0℃。</p><p>　　在拖車中配備了無(wú)線系統(tǒng)，在拖車的前部配備了冷卻設(shè)備，具有不同的高度和長(zhǎng)度。四微塵搭載貨物（參見圖1）：1指的半拖車的前側(cè)且的底部，2在半拖

79、車的中間，3是在后方的托板上，4在半拖車頂部大約占拖車的前部和后部之間三分之一的距離。1，2和3里面的箱子里裝有生菜。該程序安裝在一個(gè)固定的采樣率（7.2）傳感器中，每次傳輸被稱為一個(gè)“數(shù)據(jù)包”。 Micaz的RF功率可以設(shè)置從-24 dBm至0 dBm。在實(shí)驗(yàn)過(guò)程中，RF功率被設(shè)置到最大，為0dBm（1mW的約數(shù)）。</p><p>　　圖1 實(shí)驗(yàn)裝置 側(cè)面圖和俯視圖</p><p>&

80、lt;b>　　2.4方差分析</b></p><p>　　方差分析（ANOVA）時(shí)，以評(píng)估不同的傳感器的的測(cè)量，包括T（由裝置Sensirion的INTERSEMA的），相對(duì)濕度，氣壓，光強(qiáng)度和加速模塊的效果。方差分析允許所觀察劃分成組件。 STATISTICA軟件（StatSoft推出，公司）被用于此項(xiàng)研究。漁民“F比比較樣本組內(nèi)變異（”內(nèi)在差異“）組（因素）之間的差異。我們知道哪些因素具有更

81、大的影響力對(duì)此進(jìn)行統(tǒng)計(jì)。</p><p><b>　　2.5濕度分析</b></p><p>　　濕度測(cè)定法研究了濕空氣的熱力學(xué)性質(zhì)，這些性質(zhì)的使用的分析條件和過(guò)程涉及的潮濕的空氣。焓濕圖顯示之間的關(guān)系的圖形表示，相對(duì)濕度和水蒸汽壓在潮濕的空氣中。它們可用于在產(chǎn)品水分的損失和凝結(jié)的檢測(cè)。</p><p><b>　　第三章 結(jié)果與討論

82、</b></p><p>　　3.1 傳輸?shù)目煽啃?lt;/p><p>　　通過(guò)接收生菜信號(hào)的無(wú)線電信號(hào)，發(fā)現(xiàn)在射頻信號(hào)強(qiáng)度和接收機(jī)的鏈路質(zhì)量有很大的衰減。在實(shí)驗(yàn)過(guò)程中，只有3號(hào)和4號(hào)傳感器能夠傳遞給協(xié)調(diào)器。在盤的底部遙控接收的1號(hào)和在托盤中間的2號(hào)沒有信號(hào)。傳感器3比4更靠近協(xié)調(diào)器，但傳感器3的射頻信號(hào)被生菜塊包圍。然而傳感器4和協(xié)調(diào)器有自由傳輸空間。因此丟失的數(shù)據(jù)包的最大比值在

83、100%和誤差在4.5%±0.1%。</p><p>　　類似的比率是由幾位作者進(jìn)行真實(shí)條件下的無(wú)線傳感器網(wǎng)絡(luò)實(shí)驗(yàn)報(bào)告中出現(xiàn)的，例如在監(jiān)測(cè)葡萄園。就像Baggio和Haneveld的實(shí)驗(yàn)，在一年內(nèi)將在868 / 916MHZ波段操作的傳感器在土豆田里使用，依報(bào)告顯示數(shù)據(jù)包丟失了98%。然而，在第二年的總采集數(shù)據(jù)量為51%，這是一個(gè)明顯的改進(jìn)。Ipema等也是如此。監(jiān)測(cè)奶牛中傳感器，并發(fā)現(xiàn)基站直接得到小于

84、溫度測(cè)量，存儲(chǔ)在緩沖區(qū)50%粒。Nadimi等也是這樣。誰(shuí)還監(jiān)測(cè)奶牛這種類型的傳感器，顯示關(guān)于無(wú)線傳感器數(shù)據(jù)從奶牛在牧場(chǎng)甚至到接收機(jī)的距離25%的數(shù)據(jù)包丟失率即網(wǎng)關(guān)小于12.5米的距離。</p><p>　　無(wú)線電波的傳播可以通過(guò)兩個(gè)主要因素的影響：傳播媒體的特性和設(shè)備的異構(gòu)特性。在一個(gè)商業(yè)裝運(yùn)，如果微粒嵌入在貨物，菲涅耳帶的很大一部分被阻塞。這是在我國(guó)應(yīng)用的一大挑戰(zhàn)。改變微塵?位置，例如在托盤底部的一個(gè)（節(jié)點(diǎn)1

85、，在半掛車前）或一個(gè)在車廂的中部（節(jié)點(diǎn)2），可能會(huì)產(chǎn)生更好的數(shù)據(jù)接收速率，但會(huì)導(dǎo)致的損失的空間信息在地板上或在中等身高。傳感器應(yīng)盡量接近成品運(yùn)輸；否則，將不提供精確的信息。因此，一個(gè)解決方案，如果同樣的塵埃被使用，可能包括中間體微塵，允許對(duì)等通信的基站。另一個(gè)解決方案是使用頻率較低；然而這是不可能使用ZigBee ZigBee，因?yàn)橛糜谌蛭ㄒ坏膹V播頻率是2.4 GHz的一個(gè)。其他的ISM（工業(yè)，科學(xué)和醫(yī)療）頻段（868兆赫和915兆赫

86、）不同，從美國(guó)到歐洲。其他選項(xiàng)包括發(fā)展更多的射頻功率，可以實(shí)現(xiàn)更長(zhǎng)的無(wú)線電范圍內(nèi)的塵埃。傳輸也可以通過(guò)優(yōu)化天線的方向改進(jìn)，形狀和結(jié)構(gòu)。安裝在MicaZ標(biāo)準(zhǔn)天線是一個(gè)3厘米長(zhǎng)的1／2波長(zhǎng)的偶極子天線。通訊可以采用陶瓷共線天線或使用的增強(qiáng)簡(jiǎn)單的反射屏補(bǔ)充主天線，它可以提供一個(gè)9dB的改進(jìn)。鏈路的不對(duì)稱性和不規(guī)則的無(wú)線電范圍可以由天線位置引起的。在實(shí)際環(huán)境</p><p>　　采樣率配置在塵埃非常短，為了獲得對(duì)環(huán)境條件

87、的最大數(shù)據(jù)量。在實(shí)踐中，在記錄和傳輸?shù)牟蓸宇l率減少的配置應(yīng)以延長(zhǎng)電池壽命。根據(jù)Thiemjarus這也提供了在塵埃層數(shù)據(jù)的減排機(jī)會(huì)。預(yù)計(jì)未來(lái)無(wú)線傳感器微塵會(huì)上的特征來(lái)分析記錄的數(shù)據(jù)和檢測(cè)到一定的偏差。一個(gè)偏差水平?jīng)Q定的記錄或傳輸頻率。</p><p>　　在Motes的一個(gè)重要特征是從小型化的傳感器安裝在微塵，允許，在一個(gè)小空間（2.5×5×5厘米），提供的數(shù)據(jù)不只是溫度，而且RH，加速和光，

88、根據(jù)王、李[ 30 ]的建議。進(jìn)行測(cè)量和分析這些變量。</p><p><b>　　3.2 運(yùn)輸條件</b></p><p>　　對(duì)條件的分析，對(duì)兩個(gè)傳感器安裝在每個(gè)節(jié)點(diǎn)的平均值是。對(duì)運(yùn)輸拖車?冷卻系統(tǒng)的設(shè)定點(diǎn)為0°C，但在裝運(yùn)注冊(cè)的平均溫度是5.33°C，最多的有8.52°C和最小的?3°C.平均溫度的，是業(yè)內(nèi)外的時(shí)間98%推

89、薦的范圍（設(shè)定點(diǎn)±0.5°C）。</p><p>　　圖2顯示了在裝運(yùn)中注冊(cè)的溫度波動(dòng)，在四個(gè)不同的標(biāo)記是用對(duì)應(yīng)于每?jī)蓚€(gè)傳感器微塵。有記錄的每個(gè)傳感器在相同的塵埃溫度之間的大的差異，甚至認(rèn)為是個(gè)人的校準(zhǔn)曲線。SHT11措施比intersema始終保持較高的溫度。這種行為可能是由于該SHT11的接近的位置控制器，使傳感器的自加熱效應(yīng)。</p><p>　　在其他的研究中，

90、例如Tanner和阿摩司，發(fā)現(xiàn)貨物在行業(yè)推薦的大約58%的出貨時(shí)間 T間期。羅德里格茲貝爾梅霍等。比較了兩種不同的冷卻方式在20?冷藏集裝箱。調(diào)制在推薦的冷卻時(shí)間的百分比范圍的裝運(yùn)時(shí)間44%和52%之間，而打開/關(guān)閉的控制冷卻，在9.6%和0%之間。在這些實(shí)驗(yàn)中，較低的百分比的時(shí)間間隔內(nèi)的行業(yè)推薦發(fā)現(xiàn)高T設(shè)定點(diǎn)。</p><p>　　對(duì)數(shù)據(jù)的方差分析表明，在溫度的變化取決于在傳感器的類型和使用的微粒。這兩個(gè)因素之

91、間的相互作用還對(duì)T測(cè)量的影響。在95%的概率水平下的臨界值比F觀測(cè)值低得多，這意味著零假設(shè)是錯(cuò)誤的。這本書已在測(cè)量的變異最影響因素（最高的漁民?S F）；這一事實(shí)似乎是由于節(jié)點(diǎn)的位置。4是在較低的溫度測(cè)量更接近冷卻設(shè)備，結(jié)果。</p><p>　　節(jié)點(diǎn)注冊(cè)測(cè)量的一個(gè)重要因素。在RH，壓力的情況下，光和加速度，節(jié)點(diǎn)的位置在數(shù)據(jù)變異性很大的影響。然而，節(jié)點(diǎn)位置對(duì)測(cè)量相對(duì)濕度的影響較其他變量。</p>&