A sensitive EPR dosimetry system based on sulfamic acid

There is a need for a sensitive dosimeter using electron paramagnetic resonance spectroscopy (EPR) for use in medical applications, since with this method non-destructive read-out and dose archival could be achieved. Sulfamic acid as a possible detector substance was investigated before and after irradiation, its EPR spectra were recorded and analyzed, some dosimetric characteristics were studied: microwave power saturation behavior, the effect of modulation amplitude on peak-to-peak signal intensity and the line width. Energy-dependence parameters were compared to soft tissue and alanine, and the response to ionizing radiation was studied, also the decay behavior along 133 days after irradiation is presented. It is found that sulfamic acid possesses high-sensitivity and reasonable signal stability which may make it useful as a sensitive dosimeter for medical applications.     

Annihilation characteristics of positrons in free-standing thin metal and polymer films

Annihilation characteristics of positrons and positronium (Ps) in thin metal and polymer films were studied. Monoenergetic positrons were implanted into free-standing thin W and Au films and the annihilation γ-rays of positron-electron pairs were measured as a function of the incident energy of positrons. At the front-side surfaces of the films, an emission of Ps into vacuum and a resultant self-annihilation of ortho-Ps (o-Ps) were observed. At the backside surfaces, the Ps emission was found to be enhanced by an increase in the numbers of epithermal positrons and/or secondary electrons introduced by the impact of energetic positrons. For thin polymer films (polyester and polystyrene), the emission rate of o-Ps from the backside surfaces was higher than that from the metal films, which was attributed to the out-diffusion of o-Ps formed in the films. Those results suggested that the emission rate of Ps into vacuum was sensitive to the Ps formation process in the bulk and at the surface.     

移动流媒体业务质量评估及监测方案探讨

文章针对在移动流媒体业务运维中存在的各种难点,深入分析网络现状和业务特性,提出了基于用户体验的质量评价体系,探讨了全程全网的数据采集和分析方案,设计了自动化的业务监测评估工具,为实现对端到端3G数据业务的智能管控和优化做出了有益尝试。     

Signaling Performance Trials and Evaluation Results on a GPRS Platform

Generic Packet Radio Service (GPRS) enhances data transfers up to occasional transmission of large amounts of user data. Signaling procedures are specified for the provision of connection oriented services and the establishment of data channels between mobile subscribers. The time-overhead introduced with the performance of end-to-end signaling operations is a crucial performance factor that determines the provided Quality of Service (QoS). A significant time-overhead associated with the high rate establishment and release of many short-lived data channels, required during hand-over or for Internet access, would result in network performance degradation.Nevertheless, despite its main significance, there is a lack of papers in the Internet community that either investigate the issue of GPRS signaling performance or present GPRS trials and measurements. This lack becomes even more obvious and gets more importance from the moment that the deployment of GPRS, at least in the first phase, revealed significant performance delays in the connection setup times.To this respect, this paper presents the experiments conducted at a GPRS testing platform focusing on the performance assessment of signaling functionality. The trials focus on the performance evaluation of the GPRS signaling operations related to the establishment and release of user data channels through the Gn and Gi interfaces. Timing results that quantify the overall delay under diverse conditions of signaling load, rate and subscribers are presented.     

Experimental investigation of the performance of industrial evaporator coils operating under frosting conditions

This paper describes a field experimental investigation of the effects of frost formation on the performance of a low-temperature large-scale evaporator coil used in industrial refrigeration systems. A series of experiments were conducted to determine the in situ coil cooling capacity of the evaporator over time as frost builds on its surfaces. Field-measured quantities include inlet and outlet air temperatures, inlet and outlet air relative humidity, and air volume flow rate. These measurements provide a baseline set of experimental data that can be used to validate numerical models of industrial evaporators operating under frosting conditions.     

基于Getis-Ord Gi*方法的中山市粮食及其制品食品安全空间分析

目的研究中山市粮食及粮食制品的抽检结果和空间分布规律。方法应用Getis-Ord Gi*空间热点分析对中山市食品药品监督管理局公开发布的2015年1月1日至2018年11月9日粮食及粮食制品监督抽检数据进行分析。结果此期间中山市食品药品监督部门共完成1313批次"粮食及粮食制品"的监督抽检,合格率为97.94%,合格率最高的是生产环节(100%),其次为餐饮环节(98.79%),流通环节(97.39%)。空间热点分析结果显示存在以东北部镇区为核心的合格率"冷点区域"(Low)。结论中山市粮食及粮食制品抽检样本总体合格率较高,不合格批次较少,生产环节抽检样品全部合格,仅少部分小麦粉存在少量脱氧雪腐镰刀菌烯醇超标等问题,反映出中山市粮食及粮食制品食品安全总体形势较好,监管工作效果显著。     

Real-time fibre optic radiation dosimeters for nuclear environment monitoring around thermonuclear reactors

The ability of fibre optic sensors to operate in hazardous nuclear environments and their intrinsic immunity to electro-magnetic interference make fibre optic sensing a very promising technology for the future ITER thermonuclear fusion reactor. In this paper, we evaluate fibre optic sensing technology for monitoring radiation dose in the vicinity of ITER during its operation and during the maintenance periods.First, the performance of an OSL dosimeter interrogated remotely using radiation tolerant optical fibres is evaluated both for real-time and integrating measurements for doses exceeding 100 Gy. We demonstrate its satisfactory operation in a mixed gamma neutron field. Second, we discuss the successful calibration of a new scintillating fibre optic radiation probe based on CsI(TI) crystals for operation in the dose-rate range 0.3-3000 mGy/h. The CsI(TI) crystal scintillator is mounted at the end of a 10-m long multimode fibre transceiver link to allow for remote deployment. The probes can detect and measure gamma dose rates ranging from 1 to 1000 mGy/h. Finally, we investigate the possible use of commercially available PMMA plastic optical fibres as on-line dosimeters up to 34 kGy. The dose measurement is derived from the radiation-induced attenuation in the optical fibre itself. A novel interrogation scheme based on a ratiometric technique is proposed for real-time dosimetry.     

通过分配IP地址构建GPRS防火墙

GPRS通用分组无线业务是一种全新的业务,是移动通信和数据通信结合的产物。GPRS使用户能够在端到端分组传送模式下发送和接收数据,GPRS业务具有建链时间短,数据速率高,费用低等特点,同时在无线资源利用率上也有一定的提高。主要介绍GPRS中的Gn、Gi、Gp接口、IP地址的划分原则以及利用IP地址的划分设置防火墙。     

RADIUS协议在GPRS网络监测中的研究与实现

介绍了RADIUS协议在GPRS网络Gi接口监测的基本概念和功能,说明RADIUS协议监测模块消息结构,并以此为基础研究RADIUS协议的解码、重点探讨CDR合成及统计技术、并以RADIUS认证、计费过程为例,详细阐述合成及原理与方法,通过数据采集测试验证了相关理论的有效可行性。     

Study of substrate topographical effects on epithelial cell behavior using etched alpha-particle tracks on PADC films

Micrometer-size pits on the surface of a polymer (polyallyldiglycol carbonate or PADC) substrate created by alpha-particle irradiation and subsequent chemical etching were used to study the topographical effects alone on cell behavior. Vinculin, the cell adhesion and membrane protrusion protein, was used as an indicator of cytoskeletonal reorganization on the substrate and localization of vinculin was used to demonstrate the presence of focal adhesions. In our experiments, vinculin expressed in epithelial HeLa cells cultured on PADC films with track-etch pits, but not in cells cultured on the raw or chemically etched blank films. In other words, vinculin expression was induced by the topography of track-etch pits, while etching of the substrate alone (without alpha-particle irradiation) did not cause up-regulation of vinculin protein expression. HeLa cells cultured on PADC films with track-etch pits also showed changes in cell proliferation, cell area and cell circularity, and were largely contained by the pits. In other words, the cell membrane edges tended to be in contact with the pits. By comparing the correlation between the positions of HeLa cells and the pits, and that between the positions of cells and computer-simulated pits, the tendency for membrane edges of HeLa cells to be in contact with the pits was recognized. This could be explained by inhibition of membrane protrusion at the pits. In conclusion, substrate track-etch pits were an important determinant of epithelial cell behaviors.