Experimental study and modelling of the residence time distribution in a scraped surface heat exchanger during sorbet freezing

Scraped surface heat exchangers (SSHEs) are widely used for crystallization applications in several food processes (i.e. crystallization of margarine, tempering of chocolate, freezing of ice cream and sorbet). The final quality of these food products is highly related to crystal size distribution and apparent viscosity, both of which are determined by the operating conditions of the process. During the freezing of sorbet, the increase in the ice volume fraction leads to an increase in the apparent viscosity of the product. This effect modifies the fluid flow behavior, the residence time distribution (RTD) and the temperature profile inside the equipment. This work aimed at studying the influence of the operating conditions on the RTD and the axial temperature profile of the product in a SSHE, so as to characterize the product flow behavior. RTD experiments were carried out in a continuous laboratory pilot-scale SSHE by means of a colorimetric method. Experiments showed that high product flow rates led to a narrowing of the RTD and thus to less axial dispersion, due to the enhancement of the radial mixing with the decrease in the apparent viscosity of the product. Spreading of the RTD was obtained for lower refrigerant fluid temperatures, due to a higher radial temperature gradient between the wall and the center of the exchanger, leading to a higher gradient of the apparent viscosity. This effect increased the difference in axial flow velocities and thus the axial dispersion. These results can be useful for the optimization and modelling of crystallization processes in SSHEs.     

基于TR-069的光接入网远程管理

将光接入网底层的OAM管理功能和应用层的TR-069管理体系相结合,对针对ONU的光接入网远程管理架构作出研究,然后分析了该管理架构下的自动配置、远程下载、故障管理、本地设备管理等功能的相关实现.通过部署TR-069的远程管理系统,可以很大程度上减少用户的配置/管理工作,提高设备的易用性和可管理性,便于光接入网的快速部署和业务的迅速开展.     

gSOAP在基于TR069协议的网络视频监控系统中的应用

TR069（CPE广域网管理协议）提供了对下一代网络中的家庭网络设备进行管理配置的通用框架和协议,其协议栈中包括RPCMethods,SOAP,HTTP,SSL／TLS,TCP／IP等标准协议。当自动配置服务器（ACS）和网络终端设备（CPE）建立连接时,它们之间传输的是封装SOAP的HTTP数据包。在基于TR069协议的网络视频监控系统中,通过编写WSDL文档,使用gSOAP技术,生成C／C＋＋的RPC代码、XML数据绑定,不需要了解SOAP协议的具体细节,完成HTTP在SOAP上的封装,同时节约了大量时间来进行其它方面的开发。文章最后对以后更进一步的研究也作了简单的介绍。     

基于MMS的即时报警系统设计

基于MMS的即时报警系统,以AVR单片机为核心控制电路,采用了包括GPRS技术、语音处理电路、图片抓拍电路、人体热红外感应电路和DTMF译码电路等电路。系统通过人体热红外感应来触发微控制器启动图像处理模块抓拍图片,并通过手机模块以MMS形式发送到用户手机上。同时,用户也可以主动发送指令给报警系统以获取当前图片。此系统可以及时抓拍犯罪人的相貌,为公安机关抓获罪犯提供最直接的证据,有助于及时抓捕罪犯,实现家居安防及时报警功能。     

基于TR069协议的CPE安全认证机制

TR069(CPE广域网管理协议)提供了对下一代网络中的家庭网络设备进行管理配置的通用框架和协议,其协议栈中包括SOAP,HTTP,SSL/TLS,TCP/IP等标准协议.当自动配置服务器(ACS)和网络终端设备(CPE)建立连接时,可以选择使用SSL/TLS层增强通信的安全性.本文设计并实现了使用Open SSL开发包对ACS与CPE的相互认证过程进行加密,包括生成自签证认证证书的方法,以及证书验证过程.最后,通过实验验证了其有效性,并抓包分析了关键帧.     

Morphological, nanomechanical and cellular structural characterization of human hair and conditioner distribution using torsional resonance mode with an atomic force microscope

Characterization of the cellular structure and chemical and physical properties of hair are essential to develop better cosmetic products and advance the biological and cosmetic sciences. Although the morphology of the fine cellular structure of human hair has traditionally been investigated using scanning electron microscopy and transmission electron microscopy, atomic force microscopy can be used for characterization in ambient conditions without requiring specific sample preparations and surface treatment. In this study, the tapping and torsional resonance modes in an atomic force microscope are compared for measurements of stiffness and viscoelastic properties. The materials were mapped using amplitude and phase angle imaging. The torsional resonance mode showed advantages in resolving the in-plane (lateral) heterogeneity of materials. This mode was used for investigating and characterizing the fine cellular structure of human hair. Various cellular structures (such as the cortex and the cuticle) of human hair and fine sublamellar structures of the cuticle, such as the A-layer, the exocuticle, the endocuticle and the cell membrane complex were easily identified. The distribution and thickness of conditioner on the treated hair surface affects the tribological properties of hair. The thickness of the conditioner was estimated using force distance measurements with an atomic force microscope.     

Corrosion Protection of Mild Steel with Polyaniline–Thiokol Rubber Composite Coatings

The anti-corrosion performance of polyaniline-thiokol rubber (PANI/TR) composite coating applied to mild steel samples in artificial brine and hydrochloric acid environments is for the first time evaluated in this paper. The PANI/TR composite -coatings on mild steel were electropolymerized in a nonaqueous solution. EDS, XPS and SEM were concurrently used to characterize the structure, as well as composition of the coating and show that the structure is favorable to the corrosion protection. Both potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) demonstrated that the PANI/TR coating outperforms PANI coating both in the adhesion to the substrate and its corrosion protection, making the free corrosion potential by about 100mV more positive. As a result, the mild steel corrosion was greatly impeded by applying PANI/TR composite conductive polymer coating.     

D2D跨小区通信中人工噪声辅助时间反演的安全优化传输方案

针对终端直通（D2D）用户间通信在跨小区环境下被窃听的问题,提出了人工噪声辅助时间反演（TR）的反窃听安全传输方案。首先,在跨小区信道模型下对小区间干扰进行消除;其次,通过基站发送人工噪声辅助TR技术对窃听用户窃取信息能力进行恶化;最后,为了满足蜂窝用户服务质量的需求和系统遍历保密速率最大化,采用凸优化的功率控制分配方案最大化D2D用户发射功率。仿真实验分析说明,与人工噪声方案相比,该方法在信噪比（SNR）一样的情况下提高了0.8 b·s^-1·Hz^-1的可达保密速率,并且随着邻近小区分布数量的增加,所提方案对可达保密速率的提升效果明显。     

基于开源硬件的TR组件原位检测设备设计

基于相控阵雷达TR组件原位快速检测的需求,介绍了一种能快速实现的外场原位检测设备研制方法。通过分析被测对象的工作原理和输入输出接口,介绍了检测设备的测试功能,给出了如何利用开源模块来实现专用测试设备的设计方案、系统框图和软件流程图。实际测试表明：该检测设备能够满足TR组件的原位检测要求,具有便携、故障定位准确、开发周期短等优点。