Grain size and grain depth restrict oxygen movement in leaky hermetic containers and contribute to protective effect

Postharvest insect pests threaten the nutritional and financial security of smallholder farmers in the developing world. Hermetic storage, a technology that protects grain against insects by blocking their supply of oxygen, alleviates the problem of insect-caused losses. PICS (Purdue Improved Crop Storage) bags represent one hermetic technology that improves food availability and incomes of farmers. The polyethylene liners of PICS bags are sometime damaged during use, acquiring small holes or tears. Observations in the laboratory and field suggest that insect development remains localized around the point where the bag is damaged. We hypothesized that the grain within a hermetic container that has minimal localized damage (such as an insect hole), helps retard leakage of oxygen into the bag and contributes to limiting insect damage and to the overall protective effect. To test this hypothesis, we filled 4 cm dia. by 10 cm long PVC pipes with Callosobruchus maculatus (F.) infested cowpeas and sealed them with caps having a single, insect-sized hole in its center. A vertical tube positioned above the cowpea-filled PVC pipe was filled with one of three different grains (sesame, sorghum, and maize) to different depths (0, 5, 15, 30, 50 cm). Seed size and grain barrier depth significantly reduced the level of bruchid damage to the stored cowpea in the PVC container. Smaller sized grains used for the barriers retarded insect development more effectively than larger sized grains, while deeper grain depth was more effective than shallower barriers. The grain held in a hermetic container contributes in a small, but significant, way to the effectiveness of the containers.     

Field effectiveness of improved hermetic storage technologies on maize grain quality in Central Mexico

Maize is the main crop cultivated by small scale farmers (SSF) in Mexico, and its production represents an important goal for local food security. However, SSF very often face severe post-harvest losses in maize, mainly because of insect pests and the lack of suitable storage technology. This study was conducted to compare the field effectiveness in terms of maize quality under on-field conditions of SSF of two improved hermetic storage technologies with the traditional storage. The field experiment was performed on-farm in the highlands of Central Mexico. Maize grains were stored in three storage devices: hermetic plastic bag (sBag), hermetic plastic silo (Bioxilo), or traditional polypropylene sacks. The study considered the quantitative evaluation of storage, physical, nutritional, and industrial qualities of maize after 4, 8 and 12 months of storage. Environmental conditions of storage such as oxygen levels, temperature and humidity were monitored. After 1 year of field storage, compared with traditional sacks, sBag and Bioxilo showed a significant lower losses in storage due to insects. When controlled infested maize by artificial insect infestation methods was used, the improved technologies were also effective in reducing grain losses. Furthermore, both sBag and Bioxilo prevented grain quality detriment in terms of physical, nutritional and industrial (for tortilla and seed) properties (p < 0.01). Additionally, compared with traditional storage, sBag and Bioxilo showed efficient control of the hermetic conditions in terms of oxygen, temperature and humidity, but no significant differences were detected between the two improved technologies. In summary, under on-farm conditions, the successful preservation of maize grain quality was achieved by the improved sBag and Bioxilo in the highlands of Mexico. In the future, positive effects of this storage system will need to be validated under tropical conditions.     

Predicting soybean losses using carbon dioxide monitoring during storage in silo bags

The rapid increase of the overall grain production of Argentina resulted with a storage capacity deficit in permanent structures of 40–50 million tons, and this context favored the rapid adoption of the silo bag technology. Silo bag allows differing grain selling from harvest time, taking advantage of the seasonal price changes and, hence, improving farmers’ income. However, storing grain in silo bag could be risky if inadequate planning, handling or monitoring is implemented. Thus, the objective of this article was to develop a prediction model for soybean losses in silo bag storage based on monitoring CO₂ concentration and other sensible variables. During 2013, an experiment was conducted in 13 soybean silo bags placed at farms and grain elevators in Balcarce area, South East of Buenos Aires province, Argentina, since May to December. Grain samples were collected and grain quality was evaluated. Storage variables, such as moisture content and interstitial atmosphere gas composition were also recorded, and at the end of storage, physical grain losses were quantified for each silo bag (kg of spoiled grain not commercialized). The results showed that there was not generalized quality loss in any silo bag, but localized losses were observed. These losses occurred due to water entrance in the silo bag through openings which resulted in spoiled grain from 140 to 4320 kg, representing from 0.07% to 2.16% in a 200 ton silo bag. Next, a correlation to predict grain losses was developed, which considered grain moisture and a predictor related to the CO₂ concentration at the silo bag closing end as independent variables. This correlation explained 73% of the grain losses variability, allowed to model different levels of losses, and was consistent with biological concepts.     

Vacuum quality evaluation for uncooled micro bolometer thermal imager sensors

This paper presents an innovative and effective method of measuring the internal vacuum quality of un-cooled micro bolometer thermal imager sensors where the bolometer sensor elements themselves are used for vacuum measurement. A feasible thermal calculation model using an extended Fourier’s Law is presented which is integrated in thermal FEM simulations. Experimental results correlating with FEM simulations prove the feasibility of this method. A measuring range to pressures as low as 5 × 10⁻³ mbar was achieved that fully covers the needed range where the internal package pressure is leading to performance losses of the IRFPA. The vacuum quality evaluation method supported by a developed temperature compensation method is showing a high repetitive accuracy with a remaining mean failure of 0.2%. Without the need to integrate additional pressure sensors this method reduces costs and chip area and it is fast and highly accurate. Therefore, it can be used for stationary test systems as well as in mobile infrared camera systems.     

Storage of red chili pepper under hermetically sealed or vacuum conditions for preservation of its quality and prevention of mycotoxin occurrence

The effect of storage under hermetically sealed or vacuum storage methods, compared with the traditional method, on important quality indices for Turkish red chili peppers (RCPs) was evaluated at a semi-commercial scale in a warehouse. One tonne lots of flaked and mechanically dried RCP of maximum moisture content 10 ± 1% were stored for six months under a low absolute pressure of 80-100 mm Hg, under sealed, airtight conditions, or under traditional storage conditions (bags stacked in barns; as a control). Basic quality parameters related to microbiological counts, amount of aflatoxins (B₁ and total), pungency properties, colour levels, organoleptic characters and moisture contents were determined before and after 6 months of storage. The experiments indicated that the best quality RCPs were obtained by vacuum storage with quite low losses in quality indicators (capsaicin, colour and aflatoxin). Hermetic storage conditions resulted in major losses of colour, while microbial growth and aflatoxin occurrence were inhibited, and the pungency of RCP was protected. The results supported the feasibility of commercial application of airtight and vacuum storage technologies for long-term storage of RCP. The sealed flexible vacuum-hermetic storage technology introduces substantial advantages over traditional storage methods in the preservation of quality characteristics such as colour, pungency, and aflatoxin of RCP for longer storage periods.     

用低温圆片键合实现传感器和微电子机械系统器件的集成和封装

集成化是传感器和微电子机械系统(MEMS)的发展方向,即将传感功能、逻辑电路和驱动功能集成在一块单芯片上。未来的系统芯片将能通过集成的传感器和逻辑电路收集并分析外界数据,将这些数据传输到中央处理器并产生必要的动作或反应。讨论了这种系统集成芯片对于封装和集成的要求,并提出一种能够满足这种要求的低温键合技术。同时这种低温键合技术还具有气密性封装、保留透明窗口等优点。     

On-farm comparison of different postharvest storage technologies in a maize farming system of Tanzania Central Corridor

Seven methods for storing maize were tested and compared with traditional storage of maize in polypropylene bags. Twenty farmers managed the experiment under their prevailing conditions for 30 weeks. Stored grain was assessed for damage every six weeks. The dominant storage insect pests identified were the Maize weevil (Sitophilus zeamais) and the Red flour beetle (Tribolium castaneum). The moisture content of grain in hermetic conditions increased from 12.5 ± 0.2% at the start of storage to a range of 13.0 ± 0.2–13.5 ± 0.2% at 30 weeks. There was no significant difference (F = 87.09; P < 0.0001) regarding insect control and grain damage between hermetic storage and fumigation with insecticides. However, the insecticide treatment of polypropylene yarn (ZeroFly^®) did not control the insect populations for the experimental period under farmers' management. Grain damage was significantly lower in hermetic storage and fumigated grain than ZeroFly^® and polypropylene bags without fumigation. No significant difference in grain damage was found between airtight treatment alone and when combined with the use of insecticides. During storage, S. zeamais was predominant and could be of more economic importance than T. castaneum as far as maize damage is concerned. At 30 weeks, the germination rate of grain stored with insecticides or in hermetic storage (68.5 ± 3.6% to 81.4 ± 4.0%) had not significantly reduced from the rate before storage (F = 15.55; P < 0.0001) except in ZeroFly^®, also in polypropylene bags without treatment. Even though such bags did not control storage pests, farmers still liked this cheap technology. Hermetic storage techniques can be recommended to farmers without the use of insecticides provided they are inexpensive, and the proper application of technologies is ensured.     

Math hydrogen catalytic recombiner: Engineering model for dynamic full-scale calculations

To protect a hermetic enclosure and the equipment and systems of a reactor installation housed in it from damage caused by the ignition (explosion) of hydrogen, most nuclear power plants with pressurized water reactors are provided with a hydrogen concentration monitoring system and an emergency hydrogen removal system. These systems prevent the formation of explosive mixtures in the accident localization zone by maintaining the concentration volume of hydrogen in the mixture below the safety limits, which ensures the preservation of the density and strength of the hermetic enclosure and the operability of other localizing safety systems. A key component of an emergency hydrogen removal system is a passive autocatalytic hydrogen recombiner that operates on the principle of the catalytic recombination of hydrogen and oxygen.There is an urgent need for a full-scale dynamic calculation of the development of emergency conditions in a nuclear power plant containment accompanied by a large release of hydrogen. In efforts to achieve this, we constructed, and justified, a simple engineering thermohydraulic model of hydrogen removal in the operation of a passive autocatalytic recombiner based on the available experimental data.This paper presents the application results of the model as a part of contour industry codes RELAP, TRACE and CORSAR, intended, among other things, for carrying out multifactor and full-scale calculations of the dynamics of emergency processes with the release of hydrogen into nuclear power plant premises. This model allows us to substantiate the dynamics of local concentrations of gas components of a mixture in a confined space; the temperature of the mixture, the catalyst and the walls of the box; and the pressure when hydrogen or steam is supplied to the box.We have analysed various rates of hydrogen supply to a closed box to numerically substantiate the time at which the concentration reaches the maximum level. Furthermore, we have calculated the performance for several entrance concentrations of hydrogen, and obtained a satisfactory agreement between the dynamics of the concentrations, the temperatures of the catalyst and gas, and the productivity of the passive autocatalytic hydrogen recombiner. These calculations are based on the results of comparisons between calculated and available experimental data.     

Maintaining dryness during storage contributes to higher maize seed quality

Smallholder farmers in Pakistan store their seeds and grains in porous polypropylene (woven) and jute bags or in bulk. Seed stored in these containers is susceptible to fluctuating seasonal relative humidity and temperature, which promote mold and insect growth. The present study assessed the performance of Purdue Improved Crop Storage (PICS) bags for maize seed storage during a two-month period. Seed moisture content increased in polypropylene bags while it remained constant in PICS bags. No change in germination was observed in maize seeds stored in PICS bags while in polypropylene bags it was reduced in half when compared to the initial germination. Seed stored in polypropylene bags had higher insect damage with a weight loss of 35% while in PICS bags the infestation was minimal with a weight loss of about 3%. Higher aflatoxin contamination levels were observed in seeds stored in polypropylene than PICS bags. PICS bags are effective at preserving the dryness of maize seed in storage during high relative humidity conditions, which leads to maintenance of seed quality.     

Low Temperature Wafer Level Hermetic Package with Benzo-cyclo-butene Material

The wafer level hermetic package method was studied experimentally in low temperature for optoelectronic devices with benzo-cyclo-butene(BCB) material. The results show that the bonding temperature is below 250℃, the helium hermetic capability of both silicon-BCB-silicon and silicon-BCB-glass package are better than 6×10~ -4 Pa·cm~3/s. The shear strength is enough for package. The hermeticity is still good after the 15 cycles' thermal shock test. The relationship between the leakage rate and the distance from the hole to the device border were also discussed with a seepage model.