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Electric impedance properties of biological tissue closely relate with their tissue structure. A few published investigations have shown that electric impedance has a rapid detection capability to meat quality. To explore the impedance detection ability for frozen-thawed meat, electric impedance magnitude and phase properties of unfrozen and frozen-thawed chicken breasts subjected to different thawing times were studied. The maximum freezing-thawing circle was three times. Sixteen different frequencies from 50 Hz to 200 kHz and quality parameters like thawing loss, cooking loss, pH value, and TBARS (Thiobarbituric acid reactive substances) of 20 samples of each group were investigated. The impedance of the samples was measured by an LCR electronic bridge at the voltage of 3 V. Copper needle electrodes with a length up to 15 mm and a distance of 15 mm between two electrodes were used. The temperature of the meat was kept within 0-4? during the measurement. The location of each test was the same and measurement time was 1-2 sec at every frequency. The experimental results showed that changes in the tissue structure caused by freezing and thawing could be reflected by the impedance magnitude and phase. The impedance magnitude of both fresh and frozen-thawed meat would decrease as the frequencies increased and the impedance magnitude of fresh meat was significantly higher (P<0.01) than frozen-thawed meat in the low-frequency range, while the opposite trend was found in the high-frequency range. Those changing trends of impedance are indicators for capacitance characteristics of cell remembrance. Biological tissues are composed of cells that are surrounded by extracellular liquid. The main current flows through the extracellular fluid and the cells are bypassed when low-frequency current is applied to the tissue. The cell membrane acts as an insulator at low frequencies. With the current frequency increases, a part of the current will flow through intracellular fluid through the cell membrane. So, low-frequency impedance of biological tissue is larger than high-frequency impedance. The impedance phase angle of both fresh and frozen-thawed meat would increase as the frequencies increase. Compared with frozen-thawed meat, fresh meat had a higher (P<0.05) impedance phase angle in the low-frequency range but a lower (P<0.05) value in the high-frequency range. So, the significant difference (P<0.05) of high-frequency phase angle and low-frequency impedance magnitude between fresh and frozen-thawed meat would be an ideal index to distinguish those two kinds of meat. After freezing-thawing cycles, low-frequency impedance magnitude would decrease significantly (P<0.05), but the difference between two and three times freezing-thawing cycle was not significant (P>0.05). High-frequency phase angle would increase (P<0.05) which is different with normal frozen processing groups, especially at levels higher than 50 kHz. This impedance phase property of meat with more than one freezing-thawing cycle gives a clear distinction between them and meat with one freezing-thawing cycle. These changes of impedance properties demonstrate that freezing-thawing cycles have a remarkable influence on the structure of cell membrane and lead to a decline of cell membrane capacitance. From the quality aspect, the increasing of freezing-thawing cycles lead to inevitable decline in meat quality. More thawing loss, cooking loss and higher TBARS value are found after freezing-thawing cycles. The precise calculation of the quality by impedance measurement could not be obtained for no accordant significant correlation (P>0.05) was found between impedance properties and quality parameters in different groups. Radial Basis Function (RBF) Neural Networks that are built up based on impedance magnitude and phase angle of specific frequencies from 50 Hz to 200 kHz (Total 12 frequencies) could give a solution to estimate the freezing-thawing cycles of meat without complex mathematics modeling, and the prediction accuracy satisfies the requirement. Accuracy of the testing samples of fresh chicken meat was up to 100 percent, one time freezing-thawing cycle samples also had a high degree of distinction from two and three times. These results reflect that electrical impedance measurement is a simple innocuous tool for frozen meat characterization. For improving the measurement accuracy, a dadatabase with a big enough data volume needs to be built in future work. [ABSTRACT FROM AUTHOR]

In this paper, the solar hot water and pure water co-production system was built and the mathematical model of energy conversion and transmission was established based on the system's operation, which aimed to improve the thermal performance and water productivity of the system experimentally and theoretically. The double evacuated tube solar collector was integrated into the desalination stills to ensure the continuity production of distillate. The evaporation-condensation tank and the heat storage water tank were designed and built with a φ58 mm×1.8 m×24 double evacuated heat pipe, a hot water tank capacity of 109.2 L, an evaporation area of 0.6235 m2, a condensation water tank capacity of 124.8 L, a condensation area of 0.7092 m2, and a heat storage water tank of 200 L. The governing energy balance equations were solved analytically with Matlab software and compared with the experimental results. The results indicated that water productivity and performance coefficient increased first and then decreased with the increase of temperature at a certain temperature range (50-70°C). It was found that the productivity of water and the coefficient of performance increased to a maximum at 60°C. The constant temperature (60°C) heat storage had a significant advantage in terms of superior performance as compared to quantitative heat storage at 60°C. The increments of the distilled water productivity, the total coefficient of performance, and the gained output ratio were 950 mL, 0.102 and 0.056 respectively. Furthermore, the system performance was conducted without heat storage. The distilled water productivity, the overall system coefficient of performance, and the gained output ratio were 5 978.4 mL, 1.2498 and 0.468, respectively. The decrease of the coefficient of performance and the gained output ratio were 0.1979 and 0.219, compared with constant temperature heat storage at 60°C. Finally, the water quality of the distilled water was also tested It was found that each parameter test result of water quality reached the standard of drinking water, including the sensory index, chemical index, bacteriological index, and toxicology index. The pH of distilled water was increased from 6.98 to 7.6, and its weakly alkaline properties excellently accorded with human body physiological needs. The chromaticity of the distilled water was reduced from 12 to 4.2, and chloride content and fluoride content were reduced from 360.3 to 2.5 mg/L and from 1.38 to 0.08 mg/L, respectively. The total hardness and total soluble solids were reduced from 275.62 to 4 mg/L and from 639.6 to 12 mg/L, oxygen consumption was decreased from 2.8 to 0.54 mg/L, the iron and manganese content had been reduced from 0.29 to 0.2 mg/L and from 0.16 to 0.04 mg/L as well, and total coliforms and toxicity index in water were not detected. The percent of pass of the system was obtained as 100%. The proposed method could be used to provide living hot water and drinking water for brackish water areas, coastal areas, and overseas islands, and has very good social and economic value. [ABSTRACT FROM AUTHOR]

Since the numbers and capacities of dairy cattle farms are increasing with every passing day, computer aided studies for the management of these farms become more important and are widely used in daily life. In this study, we assessed the potential of Xtion as a point cloud data acquisition system for the body measurements of Holstein cows in the context of dairy cow conformation. For this purpose, we selected Xtion for point cloud data acquisition and chose a dairy cow model and a dairy cow as the experimental subjects. In an indoor environment, three dimensional laser scanners with high precision were employed to get point cloud data of the cow model as comparison data, and Xtion was used for acquiring point cloud data at different distances away from the cow model as test data. After aligning the comparison data and test data by using commercial point cloud processing software, statistical errors between comparison data and test data including positive maximum distance, negative maximum distance, positive average distance, negative average distance, standard deviation, and RMS error were calculated by the professional point cloud software in order to quantitatively analyze the precision and density of point cloud data from Xtion at different distances. The test results indicate that the errors almost increased linearly with increasing of the distance between Xtion and subject. The average errors were less than ±5mm on the condition that the distance from Xtion to the subject were between 0.6m and 1.2m. The average errors were less than ±10mm on the condition that the distance between Xtion and the subject were between 1.2m and 1.8m. Maximum errors were always less than ±20mm. The density of point clouds decreased exponentially with increasing of the distance from Xtion to the subject to such an extent that body measurements were impossible to get on account of missing the mark points on the body. These results imply that the appropriate distance between Xtion and a cow is between 0.6m and 1.2m. Under the dairy cow breeding environment, body measurements including chest width, thurl width, rear leg side view, front nipple length, rear udder width, and rear udder height of cows were first determined manually, by direct measurement. Then we used Xtion to acquire point cloud data at a distance of less than 1.2 meters from the cow. Visualization of the point cloud data and interactive measurement of the cow body based on point cloud data from Xtion were performed by Meshlab so as to qualitatively analyze the sunlight and surface materials’ influence on the quality of point cloud data acquired from Xtion under dairy farm conditions. The results indicate that Xtion failed to give normal operation under the sunlight due to the presence of the IR rays in the sunlight. Point cloud acquisition from Xtion may have some small holes due to the material and appearance of a live cow body. The relative errors of comparing the body measurements obtained by Meshlab with the manual measurements were less than 10%, which indicates that Xtion is appropriate for body measurements of Holstein cows. [ABSTRACT FROM AUTHOR]

In order to improve the thermal performance of a fixed linear mirror solar concentrator, its working principle was introduced in this paper. The equation of incidence angle and illuminate area had been obtained by vector analysis. At the same time, the 3D model of a cylindrical cavity glass-metal vacuum tube absorber and a fixed linear mirror solar concentrator were established. The Monte Carlo ray tracing method was applied to investigate the concentrating characteristics of the concentrator. The flux distribution on the receiver was simulated and drawn with TracePro software, as a ray trace analysis at different transverse angles determined optical efficiencies, optical loss, and flux distribution of the absorber. The results showed that the overall ray's acceptance of 74.08%-98%and optical efficiency of 56.97%-73.65% were obtained from the transverse angles of 0° to 40°with the mirror reflectance of 0.92 and the receiver absorbance of 0.9. In addition, the thermal performance of the trapezoidal cavity absorber and the cylindrical cavity absorber were studied experimentally at the different transverse angles and output temperatures. The cylindrical cavity glass-metal vacuum tube absorber had a significant advantage in terms of superior thermal performance as compared to the trapezoidal cavity absorber. The thermal efficiency of the cylindrical cavity glass-metal vacuum tube absorber was higher than the trapezoidal cavity absorber by 2%-3% at the low environment temperature and irradiation under the same condition. The thermal efficiency of the cylindrical cavity glass-metal vacuum tube absorber decreased from 46.93% to 39.98% as the output temperature increased from 76.7°C to 99.6°C. [ABSTRACT FROM AUTHOR]