基于软交换体系下的VolP技术的研究与设计

VoIP如何与下一代网络融合是目前比较热门的讨论话题,由于目前基于网关一网守（G、nGK）的VoIP网络中网关功能过于集中,设备过于复杂以及容量受限的问题,本文将借助软交换的业务／控制与传送／接入分离的思想,将网关分离使网关只负责媒体的传输,呼叫控制功能由软交换设备来完成,不仅解决了容量问题,而且易于维护和管理。     

Computational simulation of microstructure evolution during solidification of ductile cast iron

Abstract

This paper presents a thermomicrostructural model for the simulation of the solidification process of an eutectic ductile cast iron. The thermal balance is written at a macroscopic level and takes into account both the structural component being cast and its mould. Models of nucleation and growth represent the evolution of the microstructure, and the microsegregation of silicon is also considered. The resulting formulation is solved using a finite element discretisation of the macrodomain, in which the evolution of the microstructure is taken into account at the Gauss integration points. The numerical results are presented in terms of cooling curves and are compared with available experimental values. Furthermore, the sensitivity of the response with respect to changes in the cooling rate and nucleation parameters are investigated. The agreement between experimental and computational values is acceptable in both quantitative and qualitative aspects. Ways to improve the computational model are suggested.     

太阳能电动车电源控制系统的研究

分析了太阳能电动车现状，设计了一种太阳能电动车电源电路，同时，利用SG3525芯片设计了蓄电池boost电路，满足了电动车的负载需求。该系统具有效率高、响应快、稳定性好等优点，很好地满足了太阳能电动车供电需求。     

基于随机几何的毫米波自回传网络中断性能分析

为精确分析具有线性视距(LOS)传输特性的5G 毫米波自回传网络(mW-SBN)中阻塞问题的中断性能,提出了基于随机几何和随机形状理论的毫米波自回传网络中断分析方法。推导了毫米波宏基站(MBS)和微小区(SC)之间距离的统计特性,以及mW-SBN 回传链路中断概率的闭型表达式,得出了mW-SBN 网络参数与回传链路中断概率的关系式。仿真和计算结果表明:mW-SBN 回传链路中断概率主要受MBS 与SC 之间距离及表征阻塞物大小和形状的参数等系统参数影响,仿真结果也印证了得出的理论分析。     

Development and validation of a confined space rescue training prototype based on an immersive virtual reality serious game

Due to the inherently hazardous nature of the confined space environment and a lack of effective rescue training on on-site personnel attempting the rescue of fellow workers in a confined space, accidents or even multiple fatalities may happen. For this reason, improving the skill set of rescuers is of vital importance. Immersive virtual reality serious games (IVR SG) have been shown to be effective and are now widely used in safety training. However, there is little research on its application in confined space rescue training. To bridge this gap, we have developed a confined space rescue training system (called Rescue Success) based on IVR SG, and then tested its effectiveness in a real environment. We carried out a single-blind, randomized comparative experiment to study and compare the learning effectiveness of using IVR SG compared to an E-lecture in terms of behavioral skills, knowledge acquisition, self-efficacy, and simulation-induced sickness. Our results show that both training methods significantly improve the participant’s rescue behavioral skills, knowledge, and self-efficacy. Overall, IVR SG performed better than an E-lecture in all aspects except simulation-induced sickness, where there is no difference between the two methods.     

Probabilistic safety analyses developments resurgence in Bulgaria—Kozloduy nuclear power plant example

This paper presents some of the main technical features and insights of the Kozloduy nuclear power plant (NPP) units 5 and 6 probabilistic safety analysis (PSA) level 1. Probabilistic analyses and their applications in Bulgaria were given further impetus in recent years. More than 17 years after the first PSA study in Bulgaria in 1992 today probabilistic analyses receive increasing attention and application than ever before. The Bulgarian regulatory body (BNRA) is also interested in expanding their capability of reviewing and using PSA in plant safety assessments. In November 2008 within the framework of the program financed by European Union (PHARE), a project for assisting the BNRA in establishing the regulatory requirements on the base of PSA was completed. One of the objectives of this project was performance of the independent review of Kozloduy NPP units 5 and 6 PSA. This review was a new impulse for the authors to present in more details of Kozloduy NPP probabilistic assessment studies in the present paper.     

In bed and downstream hot gas desulphurization during solid fuel gasification: A review

Syngas produced by gasification process of biomass fuels is an environmental friendly alternative to conventional petrochemical fuels for the production of electricity, hydrogen, synthetic transportation biofuels and other chemicals. However, the advanced utilization of syngas is significantly limited due to the contaminants which can seriously deactivate the catalysts used for downstream reaction such as steam reforming methane, Fischer-Tropsch synthesis and corrosion of downstream equipments such as a gas turbine. Among the contaminants, sulphur compounds produced in the gasification process, which are mainly H₂S with small amounts of COS, CS₂ and thiophenes depending on process conditions, must be removed. For biomass feedstock advances are required in the cleanup technologies and processes to upgrade the raw product gas with minimal impact on the overall process efficiency. Hot gas desulphurization (HGD) can improve the overall thermal efficiency due to the elimination of fuel gas cooling and associated heat exchangers. With this aim, the present review paper highlights currently developed methods used for desulphurization of hot gas produced from gasification process of solid fuels. The methods presented here are for both in situ and downstream sulphur capture. Also, the attention is paid to the regeneration of the used materials. In situ sulphur capture is mainly done by using calcium-based sorbents such as limestone and dolomite, whereas downstream sulphur capture is mainly focused on the use of regenerable single, mixed, and supported metal oxides. A comparison is indicated at the end to show the sulphur loading of various materials.     

QoS metrics modeling and analysis for neighborhood area network in smart grid applications

Recently, planning and designing of smart‐grid (SG) neighborhood area network (NAN) communication architecture has drawn wide attention of researchers. In order to establish an SG NAN scheme satisfying the requirement, a quality of service (QoS) metric is a critical demand. However, there are few studies on the implementation of an efficient QoS metric model. In this paper, we propose an innovative QoS metric model for SG NAN design. By exploring the natural characteristics of SG messages in many applications, we choose the reliability and latency of a message as the most important criteria and implement the QoS curve for evaluating the performance of any candidate communication scheme. In addition, we present the evaluation model for QoS metrics of multiple SG services in NAN. Compared to other existing QoS methods, our model is easy to use and helps to reduce the time and cost in the planning and designing of a NAN for SG. Simulation and analysis results indicate good agreement with our proposed QoS model. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Fuel properties of Brassica juncea oil methyl esters blended with ultra-low sulfur diesel fuel

Brassica juncea is a drought-tolerant member of the Brassicaceae plant family with high oil content and a short growing season that is tolerant of low quality soils. It was investigated as a feedstock for production of biodiesel along with evaluation of subsequent fuel properties, both neat and in blends with petroleum diesel fuel. These results were compared against relevant fuel standards such as ASTM D6751, EN 14214, ASTM D975, EN 590, and ASTM D7467. Crude B. juncea oil was extracted from unconditioned seeds utilizing a continuous tubular radial expeller. The oil was then chemically refined via degumming, neutralization and bleaching to render it amenable to direct homogeneous sodium methoxide-catalyzed transesterification. The principal fatty acid detected in B. juncea oil was erucic acid (44.1%). The resulting biodiesel yielded fuel properties compliant with the biodiesel standards with the exception of oxidative stability and kinematic viscosity in the case of EN 14214. Addition of tert-butylhydroquinone and blending with soybean oil-derived biodiesel ameliorated these deficiencies. The fuel properties of B5 and B20 blends of B. juncea oil methyl esters (BJME) in ultra-low sulfur (<15 ppm S) diesel (ULSD) fuel were within the ranges specified in the petrodiesel standards ASTM D975, EN 590 and ASTM D7467 with the exception of derived cetane number in the case of EN 590. This deficiency was attributed to the inherently low cetane number of the certification-grade ULSD, as it did not contain performance-enhancing additives. In summary, this study reports new fuel property data for BJME along with properties of B5 and B20 blends in ULSD. Such results will be useful for the development of B. juncea as an alternative source of biodiesel fuel.     

Thermoresponsive poly(oligo ethylene glycol acrylates)

Thermoresponsive polymers have been the subject of numerous publications and research topics in the last few decades mostly driven by their easily controllable temperature stimulus and high potential for in vitro and in vivo applications. P(NIPAAm) is the most studied amongst these polymers, but recently other types of polymers are increasingly being investigated for their thermoresponsive behavior. In particular, polymers bearing a short oligo ethylene glycol (OEG) side chain have been shown to combine the biocompatibility of polyethylene glycol (PEG) with a versatile and controllable LCST behavior. These polymers can be synthesized via controlled radical polymerization techniques from various monomers consisting of an OEG chain and a polymerizable group like a (meth)acrylate, styrene or acrylamide. OEG acrylates offer significant advantages over, e.g., OEG methacrylates as the lower hydrophilicity of the backbone facilitates thermoresponsive behavior with smaller, more defined side chains. Furthermore, PEG acrylates can be polymerized using all major controlled radical polymerization techniques, unlike OEG methacrylates. This review will focus on OEG acrylate based (co)polymers and will provide a comprehensive overview of their reported thermoresponsive properties. The combination and comparison of this data will not only highlight the potential of these monomers, but will also serve as a starting point for future studies.