纳米孔道单分子电化学测量的低噪音控温系统研究

纳米孔道检测技术是一种利用单个分子测量界面实现在单分子水平上测量DNA、RNA、蛋白、多肽等生物分子的高灵敏的单分子检测技术. 由于单个分子与纳米孔道的相互作用受热力学控制,亟需精准控制纳米孔道单分子分析的实验温度. 因此,本文研制了一种低噪音控温系统用于具有皮安级电流分辨的纳米孔道单分子实验,以实现精确调控测量时的环境温度. 该系统利用半导体制冷片的热电效应对检测池环境加热/制冷,通过对高精度热敏电阻进行电磁屏蔽以实现在温度反馈的同时避免噪音的引入. 利用比例-积分-微分算法进行控制,达到高精度快速控温的要求. 该系统控温精度为±1 °C,无额外噪音引入至超灵敏纳米孔道单分子测量,获得了25 °C到5 °C下Poly(dA)5与单个气单胞菌溶素（Aerolysin）分子界面间作用产生信号的差异,应用于研究单分子与纳米孔道相互作用的热力学行为.     

编程计算法研究两级压缩低温热泵性能

为了优化热泵系统效率,主要采用编程计算,对以R32、R290以及R410A为工质的两级压缩热泵系统进行性能研究,对比了系统的蒸发温度、冷凝温度、中间温度和混合温度等对COP_h的影响。研究发现不完全冷却系统COP_h比完全冷却系统更高,在不同工况下存在不同的最佳中间温度,使得COP_h有最大值,R290和R410A的混合温度变化对系统COP_h影响较大。     

Comparative thermodynamic analysis of a hybrid refrigeration system for promotion of cleaner technologies

This article presents a comparative thermodynamic analysis based on numerical methods for a hybrid refrigeration system suitable to operate as vapour absorption system (VA), vapour compression–absorption system (VCA) and vapour compression system (VC). The working fluid employed for the first two systems is ammonia–water and it is pure ammonia in case of the third system. The system is being powered by waste energy and conventional energy depending on the mode of operation. The effect on performance parameters like COP and exergy efficiency during all modes of operation has been evaluated by keeping the uniform parametric conditions like condenser temperature (40 °C) and evaporator temperature (5 °C) for all the modes of operation. The effect of ambient temperature on the exergy loss in each component of the different modes of operation have also been evaluated and discussed. The results obtained indicate that COP and exergy efficiency for VCA mode initially increases and then decreases whereas for VA and VC mode the COP and exergy efficiency decreases with condenser temperature. The analysis also reveals that with the variation in evaporator temperature the COP and exergy efficiency for VC mode increases whilst for VA and VCA mode the COP shows a slight increase whereas exergy efficiency decreases. The variation of exergy efficiency and exergy loss in different components with condenser and evaporator temperature shows that exergy efficiency is found to be the highest in VC mode whereas the lowest in VCA mode for both the temperature variations. The variation of compressor work and exergy loss in compressors with evaporator and condenser temperature shows that compressor work and exergy loss is lesser for VCA mode when compared to VC mode.     

Temperature response of a number of plastic dosimeters for radiation processing

Various plastic dosemeters are employed for dosimetry control of radiation processing within gamma and electron irradiation facilities.

The temperature response of a dosimeter is important when the dose to such a dosimeter is accumulated under varying irradiation temperatures. Such measurements would be significant for proper assessment of the dose for better process control, as well as, performance evaluation of dosimetry systems.

In this work we have developed a high current peltier junction temperature controller system for our Gammacell-220. This system has been designed to regulate the operating temperature of the irradiation chamber in the range of 0 to 80 C this system has been applied to measure the temperature response of the red perspex, a local clear PMMA, Gammex, Gammachrome, and Gafchromic dosimeters. The curves of relative performance or variation of the induced optical densities of the above dosemeters versus the irradiation temperature at fixed dose values are obtained.     

空间展布体系中由化学反应-扩散-热传导耦合导致的温度场对称破缺

分析了由于化学反应-扩散-热传导耦合而导致的非等温非均匀体系中温度场对称破缺.研究结果表明,在一定的边界条件下,甚至是单组分化学反应-扩散-热传导体系,温度场的这种自组织进程也不可避免.作为温度场结构的一个范例,进一步从解析解及计算机模拟两个方面研究了小展布非等温的Lindeman模型;结果表明,温度场出现时空自组织的阈值不仅与本征参数有关,而且与体系的边界条件及外控约束相关,揭示出了诱发或避免这种温度场时空自组织之途径.     

非等温单分子化学反应体系中温度场的时空对称破缺及温度波

从线性稳定性分析和计算机数值模拟两个方面研究了小尺度空间展布、伴有扩散和热传导的Lindemann单分子化学反应体系的温度场时空对称破缺. 研究结果表明, 在一定参数值和固定边界条件下, 反应体系经由时间-空间对称破缺分支能够产生温度波.     

Three-phase behavior in a mixed nonionic surfactant system

The effect of monodisperse solubilities of each surfactant in an excess oil phase on the three-phase behavior was investigated in a water/octaethyleneglycol dodecyl ether (R₁₂EO₈)/tetraethyleneglycol dodecyl ether (R₁₂EO₄)/heptane system. The mid temperature of the three-phase region is defined as the HLB temperature. The HLB temperature is largely skewed to higher temperature in a dilute region due to the difference in the distribution of each surfactant between excess oil and microemulsion (surfactant) phases forming the three-phase body. Taking account of the monodisperse solubilities, the equation for the HLB temperature was obtained on the basis of geometrical calculation of a particular three-phase triangle. The equation well describes the three-phase behavior for a mixed surfactant system in a space of compositions and temperature.In the mixed surfactant system, the monodisperse solubility of R₁₂EO₈ in oil phase forming a three-phase body is monotonously increased with the rise in temperature, whereas that of R₁₂EO₄ is first increased and then is decreased. Consequently, the sum of both solubilities does not change greatly in a wide range of temperature.     

Aerosol-OT在水和聚乙二醇-200混合溶液中有序结构转变及影响因素研究

通过电导、流变学方法等研究了温度和表面活性剂浓度对双(2-乙基己基)磺基琥珀酸钠(AOT)、水和聚乙二醇-200(PEG-200)体系有序结构形成和转变的影响。结果发现,在室温下高浓度AOT溶液中出现凝胶结构。当AOT的浓度为400mmol/kg以上时,随着温度的升高,观察到体系从透明粘稠到稍浑浊再到透明低粘度的过程,结合AOT的双链结构并通过流变实验验证了网络结构的形成,推测该体系在微观上经历了从凝胶到囊泡再到胶束的转变过程。当AOT的浓度为200~400 mmol/kg时,随着温度的升高,出现了凝胶和胶束混合体系到胶束体系的转变过程。     

在线高效液相色谱-毛细管气相色谱联用方法的建立

建立了一种以保留间隙柱技术和阀切换以及定量管样品转移为接口并具有早期溶剂蒸气出口的在线液相色谱与毛细管气相色谱联用方法。考察了主要实验条件,如溶剂蒸发温度、载气压力等对联机系统性能的影响,并用萘和联苯对该系统的线性范围进行了测定。利用联机系统对一种轻柴油样品进行了分析。     

High current power supply for electrothermal atomic absorption spectrometry

A new power supply for electrothermal atomization — atomic absorption spectrometry (ETA-AAS) with associated equipment for temperature control is presented. The system is composed of two high current commercial batteries and a MOSFET switch which controls the temperature of the atomizer by switching the current in an on-off way through a feedback loop connected to a personal computer and suitably programmed peripherals. The delivered power can be changed from 0 to 100% in 1% steps which gives the possibility of roughly controlling both the temperature at low power when the temperature sensor is not working and the heating rate. With this system, curves for which the simultaneous presence of all atoms injected in the atomizer is claimed, have been extended to Pb, Ag, Tl and Zn. With a more conventional power supply previously used, such a claim could be made only for Cd and Hg.     

On the temperature behaviour of an adsorption system described by a Frumkin-type isotherm

A theory is developed describing stepwise coverae changes with temperature in a system of adsorbed species interacting on the surface. The temperature patterns of coverage is shown to be significantly more interesting and variegated than the concentration pattern. The existence of double transitions in the system is predicted and the conditions for their realization are analyzed.     

Nonexponential relaxation and fragility in a model system and in supercooled liquids

Among the outstanding problems in the theory of supercooled liquids are the reasons for the rapid increase in their viscosity and relaxation times as the temperature is lowered towards the glass transition temperature Tg, the nonexponential time dependence of the relaxation, and the possible connection between these two properties. The ferromagnetic Potts model on a square latice is a simple system that is found to exhibit these properties. Our calculations show that in this system the connection between them is associated with the dependence on temperature and time of the average environment of the sites. Some of the consequences of this for understanding the behavior of supercooled liquids are discussed.     

Numerical investigation on cooling performance of PCM/cooling plate hybrid system for power battery with variable discharging conditions

To solve the cooling problems of power battery with variable discharging conditions, a hybrid thermal management system combined with phase change materials (PCM) and cooling plate is designed. Moreover, the ANSYS FLUENT is adopted to simulate the three-dimensional model. As a result, the effects of water flow direction and variable discharging conditions are discussed on the maximum temperature and maximum temperature difference inside the battery as well as the liquid fraction of PCM. The numerical results indicate that the maximum temperature is governed by the physical parameters of PCM, whereas the water flow direction in the cooling plate plays a dominant role on the maximum temperature difference. Moreover, the flow direction scheme of case 5 is benefit to reduce the maximum temperature and temperature difference simultaneously. Although the cooling performance of hybrid thermal management system can be deteriorated by increasing the pulse duration and heat flux, the melting of PCM dramatically suppresses the increase in maximum temperature and temperature difference. Considering the limited quality of PCM, enhancing the thermal conductivity of PCM and employing cooling scheme with staggered flow direction are recommendable ways to extend the applicability of the hybrid thermal management system for power battery with complex discharging conditions.

     

The effect of temperature on single-column ion-chromatography of metal ions

Temperature is shown to be a valuable parameter for optimizing single-column ion-chromatographic separations of metal ions. With a perchloric acid eluent, retention times of bivalent metal ions decrease with an increase in system temperature, but with doubly protonated amines as eluents the retention times increase with an increase in temperature. Consequently, increasing the system temperature improves separations of bivalent metal ions when p-phenylenediamine dilhydrochloride is used as the eluent. Both conductivity detection and post-column reaction followed by spectrophotometric detection are suitable detection methods at above-ambient temperatures.     

Influence of temperature on the liquid-to-liquid extraction of 1-propanol from aqueous solutions containing nitromethane

Equilibrium data for the water+1-propanol+nitromethane ternary system from room temperature (318.2 K) up to 373.2 K are reported, in order to determine the extractive properties of nitromethane for the separation of 1-propanol from aqueous solutions. The effect of temperature on liquid–liquid phase equilibrium was also studied, and its consequences are discussed. On the other hand, tie-line data were satisfactorily correlated by the Othmer and Tobias method. The experimental data are compared with values calculated by the NRTL and UNIQUAC equations for the ternary mixture, and the predictions obtained by the UNIFAC method are also included. While the water+nitromethane system has a binary upper critical solution temperature of 384 K, no ternary upper critical solution temperature was observed. It is concluded that nitromethane is appropriate for the extraction process since all distribution coefficients and selectivities have sufficiently high values for the range of temperature studied. On the other hand, the small influence of temperature on the extractive properties for this ternary system, shows that it is not necessary to use higher temperatures for the extraction process.     

Some non conventional devices with temperature control design and application

The development of a temperature control system based on semiconductor thermobatteries has been used in a set of devices for studying the martensitic transformation. The devices range from a simple stage for an optical microscope to a more elaborated system as a differential scanning calorimeter [1]. Here the attention is placed in this last system. The general problems of the temperature scanning calorimetry are reviewed from the signal theory point of view and the solutions applied to our system discussed. Some measurements are shown as an example of its application.     

Ontology of temperature in nonequilibrium systems

The laws of thermodynamics provide a clear concept of the temperature for an equilibrium system in the continuum limit. Meanwhile, the equipartition theorem allows one to make a connection between the ensemble average of the kinetic energy and the uniform temperature. When a system or its environment is far from equilibrium, however, such an association does not necessarily apply. In small systems, the regression hypothesis may not even apply. Herein, it is shown that in small nonequilibrium systems, the regression hypothesis still holds, though with a generalized definition of the temperature. The latter must now be defined for each such manifestation.     

Recyclable self-assembly-supported catalytic system for orthoalkylation

[reaction: see text] A new recyclable supported catalyst system for orthoalkylation was devised using a self-assembly consisting of the barbiturate and 2,4,6-triaminopyrimidine H-bonding motifs. At high temperature, the system is completely homogeneous so as to give an efficient catalytic activity, while it is heterogenized at room temperature to form an insoluble solid phase for the easy recovery of the catalyst after the reaction.     

温度补偿法解决二元气液平衡系统相图绘制实验中的分馏效应

通过改装二元气液平衡系统相图绘制实验的装置,同时测定了环己烷-乙醇气液系统建立平衡时的沸点和露点温度,绘制并对比未保温、保温和温度补偿条件下的环己烷-乙醇气液相图。研究发现,由于分馏效应的存在,未保温和简易保温情况下,测得的溶液的沸点与露点两者温度均存在较大的差异,利用沸点温度绘制的气相线存在严重失真;对系统进行了温度补偿后根据沸点和露点温度绘制的两条气相线能吻合较好,即气相分馏效应得到了解决。