基于NaI（TI）探测器的车载水质放射性探测系统可行性

为了研制基于NaI（TI）探测器的车载水质放射性探测系统，优化探测系统结构，节约成本，利用蒙特卡罗方法模拟计算程序Geant4对不同体积的水箱探测器全能峰探测效率和全能峰计数进行模拟计算。效率刻度后，实验测量得到的全能峰探测效率和全能峰计数与蒙特卡罗模拟计算结果特征相同。将国防科工局一级站制备的比活度为180 Bq/L ¹³⁷Cs标准溶液放置在车载检测系统中进行实验，分析探测器的性能参数，如检测时间、探测限、比活度和相对误差之间的关系。结果表明，系统的探测性能满足课题要求。在核事故发生时，车载水质放射性探测系统可以迅速到达指定检测区域，并进行快速定量检测，可为管理部门迅速做出应对措施提供帮助。     

Nisin as a Food Preservative: Part 1: Physicochemical Properties,Antimicrobial Activity,and Main Uses

Nisin is a natural preservative for many food products. This bacteriocin is mainly used in dairy and meat products. Nisin inhibits pathogenic food borne bacteria such as Listeria monocytogenes and many other Gram-positive food spoilage microorganisms. Nisin can be used alone or in combination with other preservatives or also with several physical treatments. This paper reviews physicochemical and biological properties of nisin, the main factors affecting its antimicrobial effectiveness, and its food applications as an additive directly incorporated into food matrices.     

Significant improvement for the functional properties of konjac glucomannan based on phase separation

Konjac glucomannan (KGM) serves as a stabiliser due to its high molecular weight and viscosity. However, these properties limit its addition in food products, especially in drinks. The main aim of this study was to improve the functional properties of KGM by a green and effective method, that is phase separation. It was found that increasing temperature accelerated phase separation of KGM/gum arabic mixture. KGM‐rich phase was characterised and its physical properties were investigated by different methods. Crystal property showed no significant changes after phase separation. Nevertheless, rheological properties indicated that the viscosities of samples after phase separation (FKGM) decreased dramatically. Their emulsifying capacities also improved. Moreover, the differences in molecular rearrangement at the oil–water interface were also studied by using interfacial rheology. These results suggested that FKGM with low viscosity had better interfacial properties, and thus may have potential applications as food ingredients.     

Investigation on the pinch point position in heat exchangers

The pinch point is important for analyzing heat transfer in thermodynamic cycles.With the aim to reveal the importance of determining the accurate pinch point,the research on the pinch point position is carried out by theoretical method.The results show that the pinch point position depends on the parameters of the heat transfer fluids and the major fluid properties.In most cases,the pinch point locates at the bubble point for the evaporator and the dew point for the condenser.However,the pinch point shifts to the supercooled liquid state in the near critical conditions for the evaporator.Similarly,it shifts to the superheated vapor state with the condensing temperature approaching the critical temperature for the condenser.It even can shift to the working fluid entrance of the evaporator or the supercritical heater when the heat source fluid temperature is very high compared with the absorbing heat temperature.A wrong position for the pinch point may generate serious mistake.In brief,the pinch point should be founded by the iterative method in all conditions rather than taking for granted.     

Improvement of nanoparticle filtration efficiency through synthesis of SiC whisker on graphite felt by the VS CVD mechanism

This study examines the synthesis of SiC whisker on graphite felt through the non-catalytic VS CVD (Vapor Solid Chemical Vaporized Deposition) mechanism in order to investigate its potential as a filter to replace the conventional DPF (Diesel Particulate Filer). Since the CVD process is conducted mostly in high temperature exceeding 1000 °C, many restrictions exist in selecting the substrate. Graphite felt is a filter form of non-woven fabric. The graphite felt was selected as a suitable substrate material for this study based on the VS CVD mechanism due to its relatively low cost, high heat resistance, and high flexibility. The appropriate SiC whisker structure of the nanoscale was grown on the graphite felt that exhibited the fore-mentioned characteristics. This enhanced the filtration performance of the bare graphite felt filter more than two times without compromising the gas permeability. Additionally, thermal oxidation resistance was elevated by at least 200 °C more than the bare graphite felt, thereby indicating the transfer of a part of the desirable chemical properties of the SiC.     

Complexation of chitosan and gelatin: From soluble complexes to colloidal gel

The formation of soluble and insoluble complexes between chitosan (CH) and gelatin type B (GB) was investigated as a function of pH (3.0–6.5), sodium chloride (NaCl) concentration (0–100 mM), and storage time (up to 40 days). The turbidity of the CH/GB complexes achieved a maximum value at pH 5.5 and increased with time. The increase of ionic strength first intensified the complex formation but then decreased it at higher salt content. After phase separation, the main component of the separated dense phase was water, from 95.5 to 97.8 wt%, depending on NaCl concentration. With increasing storage time, the insoluble phase changed from a liquid-like system to a thermoreversible colloidal gel, as supported by confocal laser scanning microscopy as well as rheological data. The formation of this colloidal gel is explained in terms of electrostatic complexation and hydrogen bonding.     

High-precision frequency estimation of real sinusoids with reduced computational complexity using a model-based matched-spectrum approach

Frequency-estimation algorithms devised for complex sinusoids, including the maximum-likelihood (ML) approach, when operating on real sinusoidal signals, suffer from spectral interference due to the superposition of the aliasing components at negative and positive frequencies. This paper introduces a frequency estimation ML-like algorithm, based on a spectral-matching approach, that avoids such superposition effect by incorporating it in the signal/spectrum model. As a result, the proposed method is able to generate a more precise frequency estimate in comparison to previous approaches at a comparable computational cost, as endorsed by provided computational analyses and simulation results.     

Application of the phase extension method in virus crystallography

The procedure for phase extension (PX) involves gradually extending the initial phases from low resolution (e.g. ～8?Å) to the high-resolution limit of a diffraction data set. Structural redundancy present in the viral capsids that display icosahedral symmetry results in a high degree of non-crystallographic symmetry (NCS), which in turn translates into higher phasing power and is critical for improving and extending phases to higher resolution. Greater completeness of the diffraction data and determination of a molecular replacement solution, which entails accurately identifying the virus particle orientation(s) and position(s), are important for the smooth progression of the PX procedure. In addition, proper definition of a molecular mask (envelope) around the NCS-asymmetric unit has been found to be important for the success of density modification procedures, such as density averaging and solvent flattening. Regardless of the degree of NCS, the PX method appears to work well in all space groups, provided an accurate molecular mask is used along with reasonable initial phases. However, in the cases with space group P1, in addition to requiring a molecular mask, starting the PX at a higher resolution (e.g. 6?Å) overcame the previously reported problems due to Babinet phases and phase flipping errors.     

A Study of the Commercial Frequency Component and Doubled Component on the dc Side of Three‐Phase Rectifiers and Their Influence on Electric Railways

This paper discusses nontheoretical harmonics on the dc‐side of a 12‐pulse rectifier in dc railway systems. These harmonics are the commercial frequency component and the doubled component. The causes of these harmonics are (a) diode forward voltage drop difference, (b) transformer secondary inductance difference, (c) voltage harmonics at the ac‐side of the rectifier, and (d) effects of the voltage induced by adjacent high‐voltage power transmission lines. We evaluated cases (a), (b), and (c), as case (d) has been previously studied 4 . The results of the evaluation were as follows: · The effects of both the transformer secondary inductance difference and the voltage harmonics inside the electric power system are not negligible in some cases in the discussion of the EMC problem among railway equipments. · If there are several traction circuits in parallel, each of which consists of an input filter, an inverter, and several traction motors, the harmonic reduction effect of the filters weakens significantly.