工程车用空调器的设计及主要生产工艺

本特种工程车用空调器采用蒸气压缩制冷原理,即利用液态制冷剂吸热汽化产生制冷效应,利用车上的发动机作为驱动源,通过皮带传动带动压缩机工作,使制冷剂在系统内产生循环,通过换热器与空气进行热交换,从而实现车室的降温要求。制冷剂采用新型环保制冷剂R134 a,整机结构紧凑、性能可靠、换热效率高。     

采用半导体激光器自身pn结特性测温的 半导体激光器恒温控制

温度对半导体激光器的发射波长有很大的影响,而很多应用都要求半导体激光器的发射波长是稳定的。针对使用测温元件作为温度传感器进行半导体激光器恒温控制中存在的温度误差,提出了以半导体激光器自身pn结作为温度检测元件进行半导体激光器恒温控制的方法,设计了半导体制冷器的驱动电路。该方法利用pn结的温度敏感特性,首先通过实际测量标定pn结的温度与其两端压降的对应关系,然后通过测量压降得出相应的实际温度。实验结果表明,采用该方法消除了使用温度传感器进行半导体激光器恒温控制中温度梯度造成的恒温误差,提高了测量速度,显著减小了超调量,消除了静差和波动。     

Ejection dynamics of semiflexible polymers out of a nanochannel

Using theoretical analysis and three-dimensional Langevin dynamics simulations, we investigate the influence of chain rigidity on the ejection dynamics of polymers from a nanochannel. We find that there exist two distinct dynamical regimes divided by a critical chain length for both flexible and semiflexible chains. At the short chain regime, semiflexible chains eject faster than flexible chains of the same chain length due to the longer occupying length. In contrast, at the long chain regime, semiflexible chains eject slower than flexible ones as the effective entropic driving force decreases. Based on these results, we propose that the nanochannels could be used to separate flexible and semiflexible chains effectively.     

Magnetic hysteresis and refrigeration capacity of Ni-Mn-Ga alloys near Martensitic transformation

This paper studies the magnetic hysteresis and refrigeration capacity of Ni-Mn-Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni-Mn-Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni-Mn-Ga alloys or the alloys doped with other elements. Because of the existence of the magnetic hysteresis, the relation between the magnetic entropy change and refrigeration capacity is not simply linear. For practical consideration, magnetocaloric effect of Ni-Mn-Ga alloys should be investigated both on cooling and heating processes.     

量子简并性对气体斯特林制冷循环性能的影响

基于理想量子气体的状态方程，分析了量子气体斯特林制冷循环中的回热特征，推导出循环的制冷系数一般表达式.获得了在强简并和弱简并条件下循环的制冷系数，对全面理解气体斯特林制冷机的性能有所帮助. 关键词： 量子简并性 斯特林制冷循环     

Lanthanide‐Based Layer‐Type Two‐Dimensional Coordination Polymers Featuring Slow Magnetic Relaxation,Magnetocaloric Effect and Proton Conductivity

Three lanthanide‐based two‐dimensional (2D) coordination polymers (CPs), [Ln(L)(H₂O)₂]_n, {H₃L=(HO)₂P(O)CH₂CO₂H; Ln=Dy³⁺ (CP 1 ), Er³⁺ (CP 2 )} and [{Gd₂(L)₂(H₂O)₃}^.H₂O]_n, (CP 3 ) were hydrothermally synthesized using phosphonoacetic acid as a linker. Structural features revealed that the dinuclear Ln³⁺ nodes were present in the 2D sheet of CP 1 and CP 2 while in the case of CP 3 , nodes were further connected to each other forming a chain‐type arrangement throughout the network. The magnetic studies show field‐induced slow magnetic relaxation property in CP 1 and CP 2 with U_eff values of 72 K (relaxation time, τ₀=3.05×10^?7 s) and 38.42 K (relaxation time, τ₀=4.60×10^?8 s) respectively. Ab‐initio calculations suggest that the g tensor of Kramers doublet of the lanthanide ion (Dy³⁺ and Er³⁺) is strongly axial in nature which reflects in the slow magnetic relaxation behavior of both CPs. CP 3 exhibits a significant magnetocaloric effect with ?ΔS_m=49.29 J kg^?1 K^?1, one of the highest value among the reported 2D CPs. Moreover, impedance analysis of all the CPs show high proton conductivity with values of 1.13×10^?6 S cm^?1, 2.73×10^?3 S cm^?1 and 2, 6.27×10^?6 S cm^?1 for CPs 1 – 3 , respectively, at high temperature (>75 °C) and maximum 95 % relative humidity (RH).     

不同冷藏条件下大黄鱼质构和风味变化的研究

为探讨贮藏温度和储藏时间对大黄鱼质构和风味变化的影响, 运用电子鼻和顶空固相微萃取气质谱联用法(HS-SPME-GC-MS)分析在4, -20, -80℃的3种条件下, 储藏不同时间(1, 3, 5, 7, 30, 60, 90d)时大黄鱼肉的挥发性风味变化, 并应用质构仪测定大黄鱼肌肉质构特征参数. 结果发现, 4℃条件下贮藏3~7d, 其质构参数值明显相对于-20℃条件偏大(主要为硬度、韧性、回复性和黏着性差异显著); -20℃和-80℃条件下储藏30~90d, -80℃条件下贮藏大黄鱼肉质构特性优于-20℃条件; 而且, 随着贮藏温度降低, 大黄鱼挥发性物质种类减少. 在-20℃和-80℃条件下, 大黄鱼挥发性成分相对较少, 且各成分占总峰面积的相对含量变化不明显, 主要挥发性物质为烃类和醛类; 在4℃条件下贮藏的鱼肉, 其挥发性组分复杂且相对含量变化明显. 结果表明, 低温冻藏能有效保留大黄鱼肉质构特性和风味.     

从物理化学的角度看室内返潮和除湿

从物理化学的角度分析了日常生活中的返潮现象,以风冷冷冻除湿机、空调、转轮除湿机为例,解析了室内除湿中蕴含的物理化学原理。引导学生利用物理化学的眼光看待生活,有利于学生分析生活现象的本质,提高逻辑分析能力,克服学习物理化学畏难情绪的同时增加学习兴趣。     

非晶态Gd45Ni30Al15Co10合金的制备与磁热性能

具有优良磁热性能的材料是磁制冷技术应用的关键.本文设计制备出了一种非晶态四元Gd₄₅Ni₃₀Al₁₅Co₁₀合金条带,系统地研究了该合金的磁热性能. Co的引入增加了合金的非晶态热稳定性,扩大了过冷液相区宽度. Gd₄₅Ni₃₀Al₁₅Co₁₀非晶态合金条带的居里温度和有效磁矩分别为80 K和7.21μB,在10 K温度下饱和磁化强度达到173 A·m~2·kg^-1,矫顽力为0.8 kA·m^-1,具有优异的软磁性能.在5 T的外加磁场下, Gd₄₅Ni₃₀Al₁₅Co₁₀非晶态合金的磁熵变峰值和相对制冷能力分别高达10.2 J·kg^-1·K^-1和918 J·kg^-1.该合金具有典型的二级磁相变特征,可以在较宽的温度范围...     

四能级量子制冷循环

本文提出以两个qubit量子纠缠系统为工质的四能级制冷循环模型, 基于量子热力学第一定律和热纠缠概念, 分析了在循环中系统与外界交换的热量、输入功、制冷系数等热力学参数与量子纠缠之间的关系, 结果表明: 制冷系数等高线图是环状曲线, 随纠缠比r增加而非单调变化; 当相互作用常数J比较小时, 量子制冷机运行区间在c₁>c₂, 当增加J值时, 制冷机运行区间在c₁>c₂和 c₁<c₂两个区域; 最大制冷系数ε_max随J值增大而增加.