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排序方式： 共有153条查询结果，搜索用时 15 毫秒
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Min Min Won Suk Lee Thomas F. Burks Jonathan D. Jordan Arnold W. Schumann John K. Schueller Huikai Xie 《Computers and Electronics in Agriculture》2008,63(2):215-226
The orange (Citrus sinensis) is one of the most important agricultural crops in Florida. Heavy reliance on agricultural chemicals and low fertilizer use efficiencies in citrus production have raised environmental and economic concerns. In this study, a nitrogen sensor was developed to predict nitrogen concentrations in orange leaves. Four design criteria were chosen to maximize the sensing efficiency and reliability. They were: (1) coverage of the spectral N sensing range, (2) no moving parts, (3) single leaf detection, and (4) diffuse reflectance measurement. Based on chlorophyll and protein spectral absorption bands, the sensor's wavelength ranges were chosen to be 620–950 nm and 1400–2500 nm. A reflectance housing was designed to block environmental noise and to ensure single leaf measurement. A halogen light source, two detector arrays, two linear variable filters, and data acquisition cards with 16-bit analog-to-digital converters were used to collect data. The designed N sensor had a spectral resolution less than 30 nm. Test results showed that the nitrogen sensor had good linearity (r > 0.99) and stability. With averaged signal-to-noise ratio (SNR) of 299, the system was able to predict N content with a root mean square difference (RMSD) of l.69 g kg−1 for the validation data set. Using the N sensor, unknown leaf samples could be classified into low, medium and high N levels with 70% accuracy. 相似文献
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A.H. Ipema D. Goense P.H. Hogewerf H.W.J. Houwers H. van Roest 《Computers and Electronics in Agriculture》2008,64(1):49
A bolus containing a mote (temperature sensor, processor and radio) was placed in the rumen of a fistulated cow to monitor body temperature. Rumen temperature was measured every minute and stored in the internal buffer of the mote. The measured temperature was also transmitted to a base station by the mote every minute. A relay mote mounted on the cows’ left front leg assisted transmission of the information from rumen to the base station. Cow behaviour affected the success rate of data transmission. The base station received more than 50% of the transmitted data when the cow was standing. Success rate was lower than 40% when the cow was lying down. Rumen temperature varied diurnally with night-time temperatures higher than day-time temperatures. Drinking events resulted in distinct decreases of the rumen temperature. It is concluded that for the application of internal sensor motes wireless communication through the body and living environment of the animal works but improvements are possible. Research should also focus on the interpretation of sensor data on mote level for optimizing data recording frequency and transmission of data to dairy management practice. 相似文献
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The study was conducted to evaluate HydraProbe (HyP), Campbell Time Domain Reflectometry (TDR) and Watermarks (WM) moisture sensors for their ability to estimate water content based on calibrated neutron probe (NP) measurements. The three sensors were in-situ tested under natural weather conditions over a 3-yr period in a sandy loam and clay loam soils planted to grass. The HyP, TDR and WM sensors were evaluated for their ability to estimate soil moisture contents by comparing their outputs with those of NP measurements. Results showed that HyP, TDR and WM provided different estimates of soil moisture contents in both soils. Nevertheless, our work suggests that soil moisture sensors including those used in this study can be made suitable for irrigation scheduling without in-situ calibrations by simply setting the upper and lower irrigation trigger limits for each sensor and each soil type. The upper trigger point occurs directly after irrigation event (near field capacity) and the lower trigger point is based on about 50% depletion of available water in the crop rootzone and is occurs prior to irrigation refill. This approach can significantly help irrigators to achieve their irrigation scheduling and productivity goals without consuming any time onsite or soil specific calibrations. 相似文献
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[目的]为客观评价龙井茶的劣变提供依据。[方法]选择了几种典型具有代表性的包装材料进行了茶叶贮藏试验,采用多元线性回归研究了主要生化成分（含水量、茶多酚、氨基酸、水溶性浸出物、抗坏血酸和咖啡碱）与感官品质的相关性。[结果]抗坏血酸的氧化程度与龙井茶的感官品质劣变程度关系最为密切,达到了极显著相关性（0.997,P〈0.01）,并且两者存在显著的线性关系：即y（感官品质）=70.255＋93.776x（抗坏血酸含量）。[结论]可以由抗坏血酸的含量表征龙井茶品质劣变程度,相比带有主观因素的感官评价更精确。 相似文献
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乔木茎体水分传感器探针结构实验 总被引：1，自引：0，他引：1
基于驻波率测量原理的乔木茎体水分传感器,其测量装置由信号源、同轴传输线及双针平行不锈钢探针组成.乔木茎体的介电特性决定了同轴传输线两端电压差值(即传感器的输出电压)的大小,通过测量传感器的输出电压,可达到测量乔木茎体体积含水率的目的.通过两个实验来确定传感器的探针结构:模拟实验中研究了在不同有机试剂中探针长度对传感器输出电压的影响,实验中选取了不同的有机试剂来模拟不同体积含水率的乔木茎体.根据模拟实验数据,得出了传感器输出电压与探针长度的单调变化关系,选取了传感器的探针结构参数;对侧柏乔木茎体样本进行了干燥实验,得出传感器的输出电压与样本的体积含水率之间有较好的线性关系. 相似文献
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介绍了一种混合动力摩托车制动能量回收控制系统。利用车辆的轮毂驱动电机在制动时产生阻(制动)力矩,将车辆的动能转换为电能并向蓄电池充电,控制器根据制动要求调节制动力矩(充电电流),在满足制动安全的前提下实现能量的回收。在混合动力摩托车上的试验表明,能量回收获得较为显著的效果,能量回收率最高可达25.1%,该技术能广泛应用于电动车和混合动力摩托车。 相似文献