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South China has a climate characteristic of high temperature and high humidity, and the temperature and relative humidity inside a Venlo greenhouse are higher than those in the atmosphere. This paper studied the effect of ventilation conditions on the spatial and temporal distribution of temperature and relative humidity in a Venlo greenhouse. Two ventilation conditions, with and without a fan-pad system, were studied. A GA + BP neural network was applied to predict the temperature and relative humidity in fan-pad ventilation in the greenhouse. The results show that the temperature in the Venlo greenhouse ranged from 15.8 °C to 48.5 °C, and the relative humidity ranged from 24.9% to 100% during the tomato-planting cycle. The percentage of days when the temperature exceeded 35 °C was 67.3%, and the percentage of days when the average relative humidity exceeded 70% was 83.7%. The maximum temperature differences between the three heights under NV (Natural Ventilation) and FPV (Fan-pad Ventilation) conditions were 3.4 °C and 4.5 °C, respectively. The maximum relative humidity differences between the three heights under NV and FPV conditions were 8.4% and 21.7%, respectively. The maximum temperature difference in the longitudinal section under the FPV conditions was 3.2 °C, while the relative humidity was 11.4%. The cooling efficiency of the fan-pad system ranged from 16.6% to 70.2%. The non-uniform coefficients of the temperature under the FPV conditions were higher than those under the NV conditions, while the nonuniform coefficients of the relative humidity were the highest during the day. The R2, MAE, MAPE and RMSE of the temperature-testing model were 0.91, 0.94, 0.11, and 1.33, respectively, while those of relative humidity model were 0.93, 2.83, 0.10, and 3.86, respectively. The results provide a reference for the design and management of Venlo greenhouses in South China. [ABSTRACT FROM AUTHOR]

Significant intensification in livestock farming has become prevalent to meet the increasing meat production demand, resulting in a higher density of pigs in relatively small areas in a commercial swine building. The subsequent challenges of maintaining the quality of both routine management and environmental comfort of pigs to minimize the loss of both pigs' health and welfare can be attained by implementing autonomous monitoring and intelligent management decisions based on precision livestock farming (PLF). A three-layer wireless sensor network (WSN) based on ZigBee technology has been devised to monitor four environmental parameters in real-time, namely: temperature, relative humidity, concentrations of carbon dioxide and ammonia in a commercial gestating sow house. The overall packet loss rate of the WSN system which reported 16,371 records from its 41 indoor slave nodes in a 10-min interval for three consecutive days was 4%. The carbon dioxide sensors had an average outlier rate of 6.5% after a series of preprocessing procedures. The spatial and temporal characteristics showed that the carbon dioxide level exceeded the limit of 2700 mg/m3 twice during both 07:00–08:00 and 14:00–15:00. Besides, the overall NH3 concentration in the swine building was maintained in a relatively low-level range with a maximum of less than 8 mg/m3. In sum, the real-time monitoring and timely intervention of microclimate in this commercial gestating sow house can be achieved by deploying this WSN system, thereby making it possible to provide an intelligent decision on precise management of livestock automatically. [ABSTRACT FROM AUTHOR]

The autonomous navigation of unmanned vehicles in GPS denied environments is an incredibly challenging task. Because cameras are low in price, obtain rich information, and passively sense the environment, vision based simultaneous localization and mapping (VSLAM) has great potential to solve this problem. In this paper, we propose a novel VSLAM framework based on a stereo camera. The proposed approach combines the direct and indirect method for the real-time localization of an autonomous forklift in a non-structured warehouse. Our proposed hybrid method uses photometric errors to perform image alignment for data association and pose estimation, extracts features from keyframes, and matches them to acquire the updated pose. By combining the efficiency of the direct method and the high accuracy of the indirect method, the approach achieves higher speed with comparable accuracy to a state-of-the-art method. Furthermore, the two step dynamic threshold feature extraction method significantly reduces the operating time. In addition, a motion model of the forklift is proposed to provide a more reasonable initial pose for direct image alignment based on photometric errors. The proposed algorithm is experimentally tested on a dataset constructed from a large scale warehouse with dynamic lighting and long corridors, and the results show that it can still successfully perform with high accuracy. Additionally, our method can operate in real time using limited computing resources. [ABSTRACT FROM AUTHOR]

The maturity of seeds at harvest determines their intrinsic quality characteristics such as longevity and vigor, and these characteristics are dominant factors for seed quality evaluation in the seed industry. However, little information is available on how to identify and further classify the maturation stage of seeds in a way that is nondestructive, precise, rapid, and inexpensive, while also exactly meeting the need for the uniform control of seed performance in the seed industry to improve crop yield. This study demonstrated a nondestructive method for detecting seed maturity by using the single-kernel near-infrared spectroscopy (SK-NIRS) technique. The results showed that five classes of cucumber seeds with different maturation levels can be distinguished successfully. A tree-structured hierarchical classification strategy consisting of one soft independent modeling of class analogy (SIMCA) model and three partial least squares discriminant analysis (PLS-DA) models were proposed ending up with 99.69% of the overall classification accuracy and 0.9961 of Cohen's kappa in the test set, and its predictive performance was superior to both SIMCA and PLS-DA for direct multiclass classification. SK-NIRS in combination with a multiclass hierarchical classification strategy was proved to be both intuitive and efficient in classifying cucumber seeds according to maturation levels. [ABSTRACT FROM AUTHOR]

Maintaining the humidity in the environment is very important for guaranteeing the qualities and prolonging the shelf-life of fresh products. In order to obtain the distribution characteristics of humidity field when the pipeline humidifying device was working, a transport container for fresh-keeping transportation with a pipeline humidifying device based on differential pressure principle was investigated. In this study, navel orange was used as the test material. A three-dimensional numerical turbulent model of 1/4 ratio of the container was established. The structure of this model was built in PRO/E, and the mesh was generated in ICEMCFD by unstructured mesh method; the maximum size of the cell was 0.05 m and the minimum size was 0.005 m. The humidity distribution in the container with pipeline humidifying device was simulated by adopting Porous Medium Model, Species Transport Model, SIMPLE algorithm and Enhanced Wall Treatment Function method to solve the model in FLUENT. After that, the humidifying rate and the cloud charts of humidity distributions on the longitudinal and cross sections in the container and on the surface of products were obtained. With pipeline humidifying device, the relative humidity in the container could be increased from 75% to 90% in 246 s. The distribution of humidity field in container was uniform and the difference of relative humidity was less than 2%, and the difference of relative humidity on goods surface was no more than 3%. A test in a real container with 75 kg navel oranges was done to verify the accuracy of the model. Experimental validation showed that the test results were in good agreement with the simulation results. The difference between the simulated value and experimental value was less than 1.2%, which proved that such model could be used to study the effects of pipe diameter, number of holes, air velocity of air duct on humidity distribution on products surface. Some comparison and analysis were done for the results, and some conclusions could be drawn. It showed that humidifying rate increased as the velocity of air duct and the diameter of pipe increased; and when the relative humidity at the monitoring point was 90%, the humidifying time was 258, 246, 242 and 236 s, respectively as the velocities of air duct were 2, 4, 6 and 8 m/s , while 255, 252, 246 and 242 s respectively as the diameters of pipe were 12.5, 19.0, 25.4 and 38.1 mm. The effect of the number of holes on the humidifying rate was not significant. The maximum difference of humidity on products surface decreased as the velocity of air duct increased, and the differences were 3.09%, 2.45%, 2.05% and 2.01%, respectively. But it decreased first then increased as the number of holes increased (2, 4, 6 and 8), and the differences were 2.53%, 2.18%, 2.31% and 2.45%, respectively. And it increased first then decreased as the diameter of pipe increased, with the differences being 2.38%, 2.57%, 2.45% and 2.02%, respectively. The results from this study have a certain reference value for the optimization of humidifying device for fresh-keeping transportation containers. [ABSTRACT FROM AUTHOR]

Carbon dioxide (CO2) is one of the important raw materials for photosynthesis of crops in greenhouse, which can increase the harvest of the crops. In order to analyze the performance of CO2 fertilizer enrichment, this paper took indoor environment of greenhouse as the research object, and by means of unstructured mesh generation method, a two-dimensional turbulence computational model of greenhouse was built by ICEM CFD (the integrated computer engineering and manufacturing code for computational fluid dynamics) technique. After building 7532 triangle/quadrangle meshes, the skewness of mesh model was less than 0.75. To solve two-dimensional computational model of greenhouse, the CFD software FLUENT and the SIMPLE algorithm were used. Meanwhile, the porous model, the DO (discrete ordinates) model and the k-ε model were adopted. Governing equations of finite volume method were employed, including mass, momentum and energy conservation equations. In computational model, CO2 enriching inlet was set with the condition of mass flow inlet while outlet was set with the condition of pressure outlet through pre-calculation. And crop area was defined as porous material with the porosity of 0.8. Adopting steady-state solver to operate, environmental parameters such as indoor temperature, nitrogen (N2) concentration, oxygen (O2) concentration and CO2 concentration should be initialized when flow field of greenhouse was stable. Then transient solver was needed to numerical simulation when acceleration of gravity was 9.8 m/s2 and step size was 0.01 s. By such methods, the effects of CO2 jetting height, enriching flow speed and other factors on CO2 enrichment property were computed while the change of CO2 concentration and distribution regularities were studied. After the simulations, some results were obtained. CO2 enrichment process had little effect on temperature of crop area, and both temperature distribution and air velocity distribution of crop area were uniform. As CO2 enrichment process lasted only for 5 min and solar radiation affected indoor environment of the greenhouse rarely, the temperature difference in the crop area was less than 0.5°C. On the other hand, cooler air was more likely to deposit to the bottom of the greenhouse and hotter air exhausted from wet curtain because of density difference of air flow. With the influence of buoyancy lift and newly added flow, air velocity of bottom side was higher. And the biggest velocity of air flow appeared in the area between jetting nozzle and bottom side of the greenhouse. Molar mass of CO2 is greater than O2 and N2. And as a result of deposition effect of CO2, the bottom of the greenhouse had a higher CO2 concentration while CO2 concentration in upper part was less, which helped the photosynthesis of crops. Moreover, CO2 flowed to the exit of the greenhouse via bottom side. In crop area, CO2 concentration was higher when closing to entrance. Although there was nearly no different in first 30 s, CO2 jetting height had a certain effect on CO2 enrichment time. CO2 concentration could be decreased when CO2 jetting height was located at a high level. When jetting height was higher, spreading range of CO2 was larger, CO2 deposited in crop area was less and CO2 concentration was lower. However, CO2 concentration of crop area would be increased too fast when jetting height was too low. With the increase of CO2 enrichment flow, CO2 concentration increased and CO2 enrichment time decreased. CO2 enrichment flow had a certain effect on CO2 enrichment time in crop area. Thus, transforming enrichment flow or time could control CO2 concentration of the greenhouse which benefited photosynthesis of crops. A test was made to verify the accuracy of the numerical model. The simulation values and test values of CO2 concentration at the same moment were in good agreement, and the biggest difference between them was less than 5%, which demonstrated that such models were correct. Result of this paper reveals the CO2 enrichment rules and the characteristics of flow field in greenhouse, which has a certain reference for the design and optimization of CO2 enriching equipments in greenhouse. [ABSTRACT FROM AUTHOR]

China is a country that produces and consumes large amounts of fruits and vegetables. During fresh-keeping transportation, energy consumption rises with the increase of traffic volume of fruits and vegetables. The fresh-keeping transportation container with controlled atmosphere by liquid nitrogen injection is an advanced and efficient equipment for transporting fruits and vegetables. However, there is little research on the energy consumption regulations of this kind of fresh-keeping transportation container so this article puts forward a research method. Fresh-keeping transportation with controlled atmosphere by liquid nitrogen injection for fruits and vegetables keeps the temperature, relative humidity, and oxygen volume fraction of the transportation container in a state of relative balance, which could meet the demand for fruit and vegetable fresh-keeping. However, due to the influence of heat transferring towards the container, cold consuming of electrical appliances, cold consuming of fruits and vegetables, heat transferring by door opening, aperture heat leaking, container pre-cooling, and solar radiation in transportation, the equilibrium states of fresh-keeping environment in the container is broken. In addition, heat and mass transferring between the inside and outside of the container has begun. At this time, the fresh-keeping equipments started to keep the equilibrium states of fresh-keeping environment, and then energy consumption was generated. The fresh-keeping equipments of controlled atmosphere fresh-keeping transportation container by liquid nitrogen injection consist of refrigeration, humidification, and controlled atmosphere system, and the energy consumption generated from these three equipments. Finally, the energy consumption model was established based on the analysis of the heat and mass transfer and energy consumption in refrigerating, humidifying, and injecting. After the energy consumption model was set up, the verification experiment was carried out using litchi as testing material and was based on fresh-keeping transportation platform with controlled atmosphere by liquid nitrogen injection for fruits and vegetables. The fresh-keeping transportation platform can adjust the temperature, relative humidity, and oxygen volume fraction in the container automatically and intelligently through refrigeration, humidification, and controlled atmosphere system, creating a suitable fresh-keeping environment for the litchi. Results indicated that the energy consumption was mainly composed of the controlled atmosphere energy, refrigerating energy consumption, and humidifying energy. The theoretical energy consumption obtained through the energy consumption model was basically consistent to the experimental energy consumption with the average relative error of 11.86%±4.29%. The theoretical liquid nitrogen consumption value was basically consistent to the experimental liquid nitrogen consumption mass with the average relative error of 11.60%±3.51%. The total refrigerating capacity from the controlled atmosphere process was associated with the controlled atmosphere volume of the container. What's more, by consuming less energy, the controlled atmosphere could produce a large total refrigerating capacity that accounted for about 22% of the total theoretical refrigerating capacity in the experimental verification. This research provides a reference for optimizing the equipments of controlled atmosphere transportation by liquid nitrogen injection and saving energy of fruits and vegetables during fresh-keeping transportation. [ABSTRACT FROM AUTHOR]

Litchi is special fruit in China. It is important and difficult to keep fresh for litchi during transportation after harvest because it matures in hot seasons and will deteriorate rapidly while stored and transported in normal atmospheric temperature. Foam box with ice, refrigeration, and controlled atmosphere are three main fresh-keeping transportation modes for litchi at present. In order to obtain the effects of different fresh-keeping transportation modes on the quality of litchi fruit, the experiments of these three fresh-keeping transportation modes for "Feizixiao" litchi were carried out based on fresh-keeping transportation platform for fruits and vegetables. The developed fresh-keeping transportation platform can adjust temperature, relative humidity and oxygen volume fraction automatically and intelligently according to initial parameters setting and real time feedback from container to create a suitable fresh-keeping environment for litchi. The main processing of the three experiments is conducted as follows. For the experiment of ice-added transportation in foam box, litchi was packaged with polyethylene bags and then put into foam boxes with appropriate crushed ice (mass proportion of ice to fruit was about 0.30) to maintain low temperature. While for the refrigerated transportation experiment, litchi was packaged with perforated polyethylene bags (aperture ratio was 5%) and then put into plastic baskets, keeping the container environment temperature of 3-5°C and relative humidity of 90%-95%. The package type of the controlled atmosphere transportation experiment was the same as that of the refrigerated transportation experiment and the two experiments were at the same temperature and relative humidity in container, but the oxygen volume fraction should be set to 3%-5%. On this basis, the foam boxes or plastic baskets with packaged litchi were fixed on the vibration device workbench located in the container of fresh-keeping transportation platform, and set the vibration acceleration of 0.25 g (gravitational acceleration) corresponding to the vibration level of 70-80 km/h running on highway. The main fresh-keeping quality parameters of litchi were tested per 24 hours, mainly including mass loss rate, good fruit rate, browning index, total soluble solide content, titrable acidity, firmness of pulp, relative conductivity of pericarp and shelf life quality. Results indicated that the effects of three fresh-keeping transportation modes on the quality of litchi within 1 day of transportation time had no significant difference (p>0.05). However, the refrigerated transportation and controlled atmosphere transportation could effectively delay the quality decline of litchi along with the extension of the transportation time. The controlled atmosphere transportation could significantly delay the decline of pulp firmness, total soluble solids content, pericarp relative conductivity and shelf life quality (p<0.05) after 4 days of transportation compared with the other two transportation modes. It could be concluded that the three transportation modes were all suitable for the litchi quality keeping within 1 day of transportation period; and the refrigerated or controlled atmosphere transportation would be better for the litchi transportation lasting for 2-4 days; however, the controlled atmosphere transportation mode would be the most appropriate selection for the litchi transportation for more than 4 days. The research can provide a reference for the selection of fresh-keeping transportation mode for litchi fruit. [ABSTRACT FROM AUTHOR]