太赫兹真空电子器件的研究现状及其发展评述

太赫兹真空电子器件具有输出功率高、可在常温下工作等优点,它在军用、民用领域有着广泛的应用前景。本文介绍了国内外各种太赫兹真空电子器件研究的技术水平及应用现状,并对其今后发展趋势作了相应的评述。     

通道式辐射检测系统的设计

为了能够快速、有效地检测区分出人工放射源与天然放射源,使用大面积塑料闪烁体设计了一套车辆通道式辐射检测系统。在系统的设计过程中,解决了复杂的环境本底补偿、如何大幅降低误报警率,以及使用标准的137Cs放射源标定仪器确定甄别域的问题。实验的结果表明,该系统能够快速而准确地识别并区分出人工放射源和天然放射源,不但有效地克服了现有的人工放射源检测方法的缺陷,而且准确性也得到了较大提高。     

斗提式散粮卸船机提升装置振动特性研究

斗提式散粮卸船机是一种新型的散粮卸船机,提升装置由斗提机和螺旋喂料器组成。考虑到卸船用斗提机的悬臂工作状态,与传统斗提机的安装方式不同,同时会受风浪等因素的影响,针对提升装置的弯曲振动进行理论研究。计算得出提升段横截面对于形心轴的惯性矩和悬臂梁的等效弯曲刚度。建立提升装置竖直悬臂梁模型,利用微元法建立提升段弯曲振动的动力学方程,通过对端部质量块的力学分析,确定弯曲振动的边界条件,得出弯曲振动的频率方程。利用MATLAB求解频率方程,得出提升装置弯曲振动的前四阶固有频率。使用ANSYS对提升装置进行模态仿真,得到前四阶固有频率和振型。从理论结果和仿真结果的对比来看,前四阶频率的误差值都在5%以下,理论结果具有可靠性。研究为斗提式提升装置的固有频率计算提供了新的方法思路,研究结果为斗提式散粮卸船机的进一步研究提供依据。     

Studying the indoor air quality in three non-residential environments of different use: A museum,a printery industry and an office

The aim of the present study was to identify the main sources contributing to the air pollution of three indoor environments of different use: a museum, a printery industry and an office. For that purpose, particulate matter (TSP, PM₁₀, PM_2.5), inorganic pollutants (NO_x, SO₂, O₃) and organic compounds (BTX, formaldehyde) were monitored. Factors such as the kind of the activities occurred indoors, the emissions from the existing equipment, the number of occupants, the ventilation pattern and the outdoor background substantially varied among the three sites.     

黔西南卡林型金矿床成矿物质来源研究

我国卡林型金矿床主要分布在黔西南地区.本文试图通过成矿物质来源研究,即通过成矿元素、含矿流体及矿化剂来源研究揭示矿床成因.研究结果表明:Au、As来自地层岩石及岩浆岩;含矿流体及矿化剂则主要来自深部,卡林型金矿床的形成与深部地质过程有关.     

长寿命废密封放射源整备装置冷实验验证

开发长寿命废密封放射源整备装置,使整备后废放射源满足长期贮存要求是废放射源管理的重要组成部分。研制并建立了废241Am-Be中子源的整备装置,开展了废放射源整备冷实验,实验结果表明,该整备装置满足长寿命废密封放射源整备要求。     

Advance in food-derived phospholipids: Sources,molecular species and structure as well as their biological activities

BackgroundPhospholipids derived from different food sources have been extensively studied and widely used in different industrial areas, including food, animal feed, medicine, and pharmaceuticals. In recent years, the utilization of phospholipids, particularly bioactive ones, has gained attention, owing to their enrichment of n-3 polyunsaturated fatty acids.Scope and approachThis article presents a detailed and up-to-date review on the sources, molecular species, and structures of food-derived phospholipids. Moreover, this review highlights the structure–activity relationship of phospholipids and provides mechanistic insights into their biological activities.Key findings and conclusionsFood-derived phospholipids have been isolated and characterized from various sources, including plant, animal, and aquatic sources. These phospholipids possess considerable differentiation in their molecular species and structure, owing to variations in the properties of the polar headgroup, the length of the fatty alkyl chain, and the degree of unsaturation. In particular, the molecular species of aquatic-source phospholipids show a substantial amount of n-3 polyunsaturated fatty acids, particularly EPA and DHA. The diversity in molecular species and structures results in different biological activities. Polar headgroups such as choline and amino groups, as well as n-3 polyunsaturated fatty acids in phospholipids, are crucial to our food system and health, especially regarding antioxidant activity, memory, improving immunity, and preventing cardiovascular disease.     

基于BP神经网络的辐射源安全评估研究

基于人工神经网络及BP网络原理,建立了辐射源安全评估体系的数学模型。通过MATLAB仿真软件对模型进行训练,逐步改善影响辐射源安全评估的各因素权值,使网络样本的实际输出与期望输出误差和均方差达到最小。经仿真计算,BP网络评估方法具有较好的评价辨识精度。     

Effective renewable energy activities in Bangladesh

Bangladesh is endowed with plentiful supply of renewable sources of energy. Out of the various renewable sources, solar and biomass and to a limited extend, wind and hydro-power are effectively used. This paper, discusses the effective applications of these resources. Bangladesh receives an average daily solar radiation of 4–6.5 kWh/m². Solar photovoltaic (PV) are gaining acceptance for providing electricity to households and small business enterprises in grid remote rural areas. Under the ‘Rural Electrification and Renewable Energy Development (RERED) Programme’ a total of 64,000 SHSs will be installed by 2007. So far, a total of 37,000 SHSs with a capacity of about 2.5 MWp have been installed in the country.The next effective source of renewable energy is biomass. Under this category improved stoves, bio-gas plant and bio-mass briquitting are note worthy. The Institute of Fuel Research and Development (IFRD) has developed a number of improved stoves. These stoves save 50–70% fuel as compared to the traditional ones. So far, more than 100,000 stoves have been installed in the users kitchens. The potential of biogas technology is immense. According to an official estimates there is a cattle population of 24 million and poultry population of 75 million. This can produce about 3 billion m³ biogas. The Local Government Engineering Department (LGED) and IFRD are working to install the biogas plants in the rural areas. So far, a total of 19,596 biogas plants have been installed. Khulna University of Engineering and Technology (KUET) has successfully under took a research and development work on biomass briquitting technology with a grant from SIDA. By now, this technology has transferred to private entrepreneurs. Currently, about 60 small private enterprises are producing briquettes from rice husk and saw dust.Because the country is flat, hydropower is not abundant. At present, 230 MW is harnessed from the Kaptai dam. Besides, in the southeastern hilly regions a few micro-hydro sites have been identified. Very recently, one 10 kW micro-hydro plant has been installed by LGED at Bamerchara in Chittagong.Wind energy potential is not encouraging except in the coastal areas of Bangladesh. A few wind turbines have been installed as demonstration units. A project is going on for wind mapping of the country by LGED     

Reinforcement learning based energy management systems and hydrogen refuelling stations for fuel cell electric vehicles: An overview

This paper examines the current state of the art of hydrogen refuelling stations-based production and storage systems for fuel cell hybrid electric vehicles (FCHEV). Nowadays, the emissions are increasing rapidly due to the usage of fossil fuels and the demand for hydrogen refuelling stations (HRS) is emerging to replace the conventional vehicles with FCHEVs. Hence, the availability of HRS and its economic aspects are discussed. In addition, a comprehensive study is presented on the energy storage systems such as batteries, supercapacitors and fuel cells which play a major role in the FCHEVs. An energy management system (EMS) is essential to meet the load requirement with effective utilisation of power sources with various optimizing techniques. A detailed comparative analysis is presented on the merits of Reinforcement learning (RL) for the FCHEVs. The significant challenges are discussed in depth with potential solutions for future work.