硝酸甲胺反应过程的安全性研究

用反应量热仪(RC1e)对硝酸溶液与一甲胺溶液在反应过程中的热安定性进行初步研究,分别测试不同反应温度、加料速度和初始硝酸浓度下反应的放热情况。实验结果表明:该中和过程反应迅速,在室温就能进行;与反应温度、加料速度相比,起始硝酸浓度对反应安全性影响最大,且硝酸浓度越高,反应的速度和反应的完全程度也越高。实验还表明:RC1e是研究反应过程中热安定性情况的有效工具,能通过反应过程的热量变化体现反应速率,所得结果对硝酸甲胺的工业化生产具有重要的参考价值。     

高速电机驱动的空气循环制冷技术研究

空气循环制冷技术是一种常用的制冷技术 ,广泛应用在地面设备空调通风和飞机环境控制系统等诸多领域 ,保障人员的舒适和设备的安全。高速电机驱动的空气循环制冷技术是高速电机驱动技术与空气循环制冷技术结合产生的新型技术构想 ,采用该技术的空气循环系统具有结构简单、节约能源等优点。通过介绍该技术方案的工作原理 ,分析了高速电机驱动技术在空气循环制冷系统中应用的可能性及其实现手段。研究表明 ,高速电机驱动技术将为空气循环制冷技术的发展带来较大的影响     

抚顺石化公司硫磺回收装置的扩建和改造

抚顺石化分公司石油三厂原有硫磺回收装置的处理能力已经不能满足生产的需要,2002年对硫磺回收装置进行了扩建和改造。该装置采用了一段高温转化、二级催化转化的克劳斯工艺,采用揝SR敾乖?吸收工艺处理尾气。扩能改造后,新增的尾气处理能力与硫磺回收能力相配套,排放的废气符合国家现行的环保标准。该装置工艺路线合理、可靠,硫回收率高。     

特大型双曲线自然通风冷却塔噪声治理

本文以上海吴泾电厂八期1#、2#机组所用特大型双曲线自然通风冷却塔为例,介绍其噪声特性、控制措施及治理效果。     

延边地区公路沿线边坡失稳试验分析

延边地区公路沿线分布着大量软岩，其岩性具有强膨胀性，致使这一地区公路边坡出现了多处滑坡现象。为了合理地处理这一工程地质问题，需要认真研究该种软岩的膨胀特性。选取滑坡体软岩为研究对象，定量分析了其自由膨胀率、无荷膨胀率和有荷膨胀率，并具体测定了其膨胀力，探讨了其膨胀率和膨胀力的变化规律，揭示了研究区软岩的膨胀特性，为公路建设中软岩边坡加固参数的选取提供了科学的依据。     

A Parallel Study of SAR Levels in Head Tissues for Three Antennas Used in Cellular Telephones: Monopole, Helix and Patch

Summary This paper is a comparative study of several antennas commonly used in cellular telephones. These include a monopole, a helix-monopole and a patch antenna. Each one of these structures is modeled and numerically tested using finite-difference time-domain simulation and human models based on magnetic-resonance images, which allow for inclusion of details of the human body in the simulation. The testing procedure involves antenna simulation in the proximity of the human head. The behavior of each antenna is evaluated for variable distances from the head geometry (0, 1, 2, 4, 8 and 16 mm). Continuous waveform, representative of the sources used in mobile telephones, (250 mW, 1.8 GHz) is used as the form of the antenna excitation. The simulation outputs used as measures for this comparative study include transmitting and receiving antenna characteristics and the specific absorption rate (SAR). The SAR levels for the head tissues are calculated for and with accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP). The computed SAR levels within each of the considered tissues vary for the three antennas under investigation and are within the determined health safety standards. Results suggest that the patch antenna may be the structure of choice when considering safety standards, as its radiation yields the lowest local SAR in the head tissues.     

Effects of organic matter on Leymus chinensis germination,growth, and urease activity and available nitrogen in coastal saline soil

ABSTRACT

The present study was carried out to investigate the effect of three organic matters (stalk powder, microbial fertilizer, and manure) on Leymus chinensis germination, growth, and urease activity and available nitrogen (N) in coastal saline soil. The study was conducted in a completely randomized design with eight treatments: J₀V₀Y₀, J₁V₀Y₀, J₀V₁Y₀, J₀V₀Y₁, J₁V₁Y₀, J₁V₀Y₁, J₀V₁Y₁, J₁V₁Y₁. The notations were based on the quantities of each agent added to 1 kg of coastal saline soil: J₀ – no straw powder, J₁ – 0.2 kg straw powder, Y₀ – no manure, Y₁ – 0.3 kg manure, V₀ – no microbial fertilizer, V₁ – 0.2 L microbial fertilizer, each in quantic repeat. L. chinensis was sown as 50 seeds per pot. Results indicated that addition of organic agents exerted a significantly enhanced germination, increase in fresh weight and elevated soil urease activity. Soil available N levels were significantly positively correlated with soil urease activity and fresh weight, but not with germination rate. It is noteworthy that the halophyte L. chinensis showed improved characteristics when grown in coastal saline soil with addition of organic amendments.     

Discounting in the presence of scarce ecosystem services

The discount rate for cost-benefit analysis has to take account of future scarcity of ecosystem services in consumption and production. Previous literature focuses on the first aspect and shows the importance of the relative price effect, for given growth rates of consumption and ecosystem services. This paper focuses on intermediate ecosystem services in production and shows that for limited substitutability and a low growth rate of these ecosystem services, the growth rate of consumption, and thus the discount rate, declines towards a low value. Using a Ramsey growth model, the paper distinguishes three cases. If ecosystem services can be easily substituted, the discount rate converges to the usual value in the long term. Secondly, if ecosystem services can be easily substituted in production but not in consumption, the relative price effect is important. Finally, and most interestingly, if ecosystem services cannot be easily substituted in production, the discount rate declines towards a low value and the relative price effect is less important. Another part of the previous literature has shown that a declining discount rate is the result of introducing several forms of uncertainty, but this paper reaches that conclusion from an endogenous effect on the growth rate of the economy.     

Co-treatment of fruit and vegetable waste in sludge digesters. An analysis of the relationship among bio-methane generation,process stability and digestate phytotoxicity

The co-digestion of a variable amount of fruit and vegetable waste in a waste mixed sludge digester was investigated using a pilot scale apparatus. The organic loading rate (OLR) was increased from 1.46 kg VS/m³ day to 2.8 kg VS/m³ day. The hydraulic retention time was reduced from 14 days to about 10 days. Specific bio-methane production increased from about 90 NL/kg VS to the maximum value of about 430 NL/kg VS when OLR was increased from 1.46 kg VS/m³ day to 2.1 kg VS/m³ day. A higher OLR caused an excessive reduction in the hydraulic retention time, enhancing microorganism wash out. Process stability evaluated by the total volatile fatty acids concentration (mg/l) to the alkalinity buffer capacity (eq. mg/l CaCO₃) ratio (i.e. FOS/TAC) criterion was <0.1 indicating high stability for OLR <2.46 kg VS/m³ day. For higher OLR, FOS/TAC increased rapidly. Residual phytotoxicty of the digestate evaluated by the germination index (GI) (%) was quite constant for OLR < 2.46 kg VS/m³ day, which is lower than the 60% limit, indicating an acceptable toxicity level for crops. For OLR > 2.46 kg VS/m³ day, GI decreased rapidly. This corresponding trend between FOS/TAC and GI was further investigated by the definition of the GI ratio (GIR) parameter. Comparison between GIR and FOS/TAC suggests that GI could be a suitable criterion for evaluating process stability.     

Development of heat transfer and evaporation model of LNG covered by Hi-Ex foam

Natural gas is a kind of clean, efficient green energy source, which is used widely. Liquefied natural gas (LNG) is produced by cooling natural gas to −161 °C, at which it becomes the liquid. Once LNG was released, fire or explosion would happen when ignition source existed nearby. The high expansion foam (Hi-Ex foam) is believed to quickly blanket on the top of LNG spillage pool and warm the LNG vapor to lower the vapor cloud density at the ground level and raising vapor buoyancy. To identify the physical structure after it contacted with LN₂ and to develop heat transfer model, the small-scale field test with liquid nitrogen (LN₂) was designed. In experiment, three layers including frozen ice layer, frozen Hi-Ex layer and soft layer of Hi-Ex foam were observed at the steady state. By characterizing physical structure of the foam, formulas for calculating the surface of single foam bubble and counting foam film thickness were deduced. The micro heat transfer and evaporation model between cryogenic liquid and Hi-Ex foam was established. Indicating the physical structure of the frozen ice layer, there were a certain number of icicles below it. The heat transfer and evaporation mathematical model between the frozen ice layer and LNG was derived. Combining models above with the heat transfer between LNG, ground and cofferdam, the heat transfer and evaporation mathematical model of LNG covered by Hi-Ex foam was developed eventually. Finally, LN₂ evaporation rate calculated by this model was compared with the measured evaporation rate. The calculated results are 1.2–2.1 times of experimental results, which were acceptable in engineering and proved the model was reliable.