Analysis of Characteristic and Causes of a Strong Cooling Process in China in the Early Winter of 2020/2021

The characteristics and causes of a drop in temperature during a cold wave process in the early winter of 2020/2021 were analyzed.The results show that the air temperature at 700-600 hPa over China was firstly and mostly influenced by the cold wave process,and then the cold air gradually extended to the lower layer,causing the most severe cooling in North China and its nearby areas.During the cold wave,the longitude of the upper-level jet over the Chinese mainland was larger;the Ural blocking high and the East Asian trough were stronger,so that the geopotential height gradient between the two was also significantly larger;the meridional air flow was abnormally strong,which was conducive to the southward transport of cold air from the middle and high latitudes.Results of the diagnostic analysis further show that the outbreak of the cold wave and the negative temperature tendency anomaly in the key area were mainly caused by the meridional temperature horizontal advection anomaly,while the temperature rise accompanied by abnormal air subsidence compensated for the abnormal decrease in temperature,which was conducive to the gradual rise of temperature in the key area.

Three-dimensional analysis of the modified sloping cooling/shearing process

A self-designed setup of modified sloping cooling/shearing process was made to prepare the semisolid Al-3wt%Mg alloy. A three-dimensional simulation model was established for the analysis of preparing the semisolid Al-3wt%Mg alloy. Through simulation and experiment, it is shown that the sloping angle of the plate greatly affects temperature and velocity distributions, and the temperature and velocity of the alloy at the exit of the sloping plate increase with the increase of the sloping angle. The alloy temperature decreases linearly from the pouring mouth to the exit. The alloy temperature at the exit increases obviously with the increase of pouring temperature. To prepare the semisolid Al-3wt%Mg alloy with good quality, the sloping angle θ=45° is reasonable, and the pouring temperature is suggested to be designed above 650-660℃ but under 700℃.

Controlled Rolling and Cooling Process for Low Carbon Cold Forging Steel

Effect of controlled rolling and cooling process on the mechanical properties of low carbon cold forging steel was investigated for different processing parameters of a laboratory hot rolling mill. The results show that the specimens with fast cooling after hot rolling exhibit very good mechanical properties, and the improvement of the mechanical properties can be attributed mainly to the ferrite-grain refinement. The mechanical properties increase with decreasing final cooling temperature within the range from 670 ℃ to 570 ℃ due to the finer interlamellar spacing of pearlite colony. The specimen with fast cooling after low temperature rolling shows the highest values of the mechanical properties. The effect of the ferrite grain size on the mechanical properties was greater than that of pearlite morphology in the present study. The mechanical properties of specimens by controlled rolling and cooling process without thermal treatment were greatly superior to that of the same specimens by the conventional rolling, and their tensile strength reached 490 MPa grade even in the case of low temperature rolling without controlled rolling. It might be expected to realize the substitution medium-carbon by low-carbon for 490 MPa grade cold forging steel with controlled rolling and cooling process.

Effects of Chemical Composition and Cooling Process on Structures and Properties of Direct-Quenched Steels

The microstructures and mechanical properties of a series of direct-quenched steels containing,in weight percent,from 0.05 to 0.20 carbon,0.20 to 0.40 silicon,1.10 to 1.70 manganese and at least one microalloying element of vanadium,niobium,titanium and boron have been investigated.After controlled rolling,these steels were cooled in spray water to 400,300 and 200℃,respectively and then cooled in still air.Comparison of the Charpy V-notch impact toughness of direct-quenched steels without subsequent tempering was made with that of direct-quenched steels tempered at 600℃.It is found that an attractive combination of strength and toughness is achived by means of direct-quenching.There exists two types of microstructures in accordance with carbon equivalent.Lath martensitic microstructure is obtained for C>0.4%,granular bainitic microstructures for C.< 0.35%and mixtures of martensite and bainite for C,.in the range of 0.35— 0.40%.The effect of interrupted quenching temperature on microstructure is not significant for low C.steel,but interrupted quenching temperature has a strong effect on microstructure for high C,.steel.

Estimating Influence of Crystallizing Latent Heat on Cooling-Crystallizing Process of a Granitic Melt and Its Geological Implications

Based on the theory of thermal conductivity, in this paper we derived a formula to estimate the prolongation period （AtL） of cooling-crystallization process of a granitic melt caused by latent heat of crystallization as follows：△tL=QL×△tcol/（TM-TC）×CP where TM is initial temperature of the granite melt, Tc crystallization temperature of the granite melt, Cp specific heat, △tcol cooling period of a granite melt from its initial temperature （TM） to its crystallization temperature （Tc）, QL latent heat of the granite melt. The cooling period of the melt for the Fanshan granodiorite from its initial temperature （900℃） to crystallization temperature （600℃） could be estimated -210,000 years if latent heat was not considered. Calculation for the Fanshan melt using the above formula yields a AtL value of -190,000 years, which implies that the actual cooling period within the temperature range of 900°-600℃ should be 400,000 years. This demonstrates that the latent heat produced from crystallization of the granitic melt is a key factor influencing the cooling-crystallization process of a granitic melt, prolongating the period of crystallization and resulting in the large emplacement-crystallization time difference （ECTD） in granite batholith.

Mathematical model for cooling process and its self-learning applied in hot rolling mill

Control precision of coiling temperature is one of the key factors affecting the profile shape and surface quality during the cooling process of hot rolled steel strip.For this reason,the core of temperature control precision is to establish an effective cooling mathematical model with self-learning function.Starting from this point,a cooling mathematical model with nonlinear structural characteristics is established in this paper for the cooling process of hot rolled steel strip.By the analysis of self-learning ability,key parameters of the mathematical model could be constantly corrected so as to improve temperature control precision and adaptive capability of the model.The site actual application results proved the stable performance and high control precision of the proposed mathematical model,which would lay a solid foundation to improve the steel product qualities.

Application of Microstructure Engineering in Steel Coil Cooling Process

The coil cooling and its role in a hot strip mill were reviewed. A mathematical model was developed to describe and analyze the thermal history and its impact on precipitation phenomena during coil cooling for plain carbon, HSLA-V and HSLA-Nb steels. The predicted result of the thermal model was compared with that measured from industrial coil. The effect of cooling condition and coil dimension on the thermal history and final mechanical properties of the steel strip was examined. The coiling temperature and cooling rate have crucial influence on the precipitation strengthening.

Ground state cooling of an optomechanical resonator with double quantum interference processes

We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possible to cool a resonator to its ground state in the strong cavity-atom coupling regime.Moreover,with the assistance of one additional energy level,our scheme takes a larger cooling rate to realize the ground state cooling.In addition,this scheme is a feasible candidate for experimental applications.

Non-Equilibrium Grain-Boundary Segregation of Phosphorus And the Effective Time in Step Cooling Process

The non-equilibrium grain-boundary segregation of phosphorus in step cooling process in an industrial steel, 12CrlMoV, is studied based on the effective-time-method and compared with that in isothermal holding process. The non-equilibrium grain-boundary segregation concentration of phosphorus was measured with Auger Electron Spectroscopy (AES) and calculated based on the kinetic equations of non-equilibrium grain-boundary segregation. Results show that the calculated result is in good accordance with the experimental observation.

Self-Learning and Its Application to Laminar Cooling Model of Hot Rolled Strip

The mathematical model for online controlling hot rolled steel cooling on run-out table （ROT for abbreviation） was analyzed, and water cooling is found to be the main cooling mode for hot rolled steel. The calculation of the drop in strip temperature by both water cooling and air cooling is summed up to obtain the change of heat transfer coefficient. It is found that the learning coefficient of heat transfer coefficient is the kernel coefficient of coiler temperature control （CTC） model tuning. To decrease the deviation between the calculated steel temperature and the measured one at coiler entrance, a laminar cooling control self-learning strategy is used. Using the data acquired in the field, the results of the self-learning model used in the field were analyzed. The analyzed results show that the self-learning function is effective.

Maxi mumprinciple for the optimal control of an ablation-transpiration cooling system with free final time and phase constraints

This paper is concerned with an optimal control problem of an abhtion-transpiration cooling control system with Stefan-Signorini boundary condition. As the continuation of the authors＇previous paper, the Dubovits Rii-Milyutin fimctional approach is again adopted in investigation of the Pontryagin＇ s maximun principle of the system. The necessary optimality condition is presented for the problem with free final horizon and phase constraints.

Comparative Study of Cooling under Shades of Some Forestry Tree Species with Respect to Ambient Temperatures

Trees create microclimate under their crowns in comparison to the outside ambient atmospheric temperature. Sun is the pivotal source of radiant energy reaching the earth atmosphere of which heat is more important than light. The radiant energy reaches the ground without any barricade whereas the tree crown impedes it in reaching the earth’s surface. During the day, when insolation impinges on tree crown, a portion of it is reflected back to the space, other portion is absorbed by the canopy increasing the temperature of leaves and the remaining part reaches the ground penetrating through the crown. Thus, a significant coolness is experienced under the shade of trees in comparison to open sunshine, with qualitative variations. The cooling produced by trees under their shades varies with species to species due to variation in several anatomical, structural and physiological attributes of the species. Climate is changing more rapidly prominently due to human activities especially indiscriminate felling of trees and it is feared that it will create problems on availability of energy, water and food security. Economic value takes over ecological benefits in selection of species in plantation programmes and this might have been due to the lack of scientific data about varying effectiveness of ecological services bestowed by different species. In the present study, an endeavor has been made to understand as to how a tree is integrated to the effects on atmosphere and responses to changing conditions with respect to differential cooling produced by five selected forestry tree species belonging to different categories. Analysis of data has come out with gradation of the sample species in respect to their cooling effect in the atmosphere in terms of yearly, quarterly, monthly and diurnal basis.

Imaging protein crystal growth behaviour in batch cooling crystallisation

The temporal and spatial growth behaviour of protein crystals, subject to different cooling strategies in protein crystallisation was investigated. Although the impact of temperature and cooling rate on crystal growth of small molecules was well documented, much less has been reported on their impact on the crystallisation of proteins. In this paper, an experimental set-up is configured to carry out such a study which involves an automatic temperature controlled hot-stage crystalliser fitted with a real-time imaging system. Linbro parallel crystallisation experiments(24-well plate) were also conducted to find the suitable initial conditions to be used in the hot-stage crystallisation experiments, including the initial concentration of HEW lysozyme solutions, precipitate concentration and pH value. It was observed that fast cooling rates at the early stage led to precipitates while slow cooling rates produced crystal nuclei, and very slow cooling rates, much smaller than for small molecules are critical to the growth of the nuclei and the crystals to a desired shape. The interesting results provide valuable insight as well as experimental proof of the feasibility and effectiveness of cooling as a means for achieving controlled protein crystallisation, compared with the evaporation approach which was widely used to grow single large crystals for X-ray diffraction study. Since cooling rate control can be easily achieved and has good repeatability, it suggests that large-scale production of protein crystals can be effectively achieved by manipulating cooling rates.

车用燃料电池散热性能实验研究

质子交换膜燃料电池(PEMFC)作为能效转换率高、清洁可靠的发电装置,在交通、储能、航天及军事等领域有着广泛应用。为了解决质子交换膜燃料电池散热密度高、发热量大、散热效率低等突出问题,本文针对散热量为15 kW的质子交换膜燃料电池,设计并搭建了一套具有四种不同流程换热器的车用燃料电池散热系统实验台。分别使用两相冷却工质HFE-7100和乙二醇水溶液作为冷却工质,探究了在35℃的高温环境中,两种工质在不同流程换热器和不同工质流量下的散热性能和系统能效比(Energy Efficiency Rating, EER)。结果表明,在相同的流程下,采用HFE-7100两相散热方式相对于采用乙二醇水溶液液冷散热方式散热量提升率在81.2%~98.8%之间,系统EER提升率在68.2%~88.6%之间。且在4种不同流程下,3流程的系统散热效果和节能效果最佳,两相工质HFE-7100散热量和系统EER分别达到14.4 kW和20.5 kW/kW,液冷工质乙二醇水溶液散热量和系统EER分别达到7.7 kW和12.1 kW/kW。冷却工质流量为4 L/min时,系统节能效果较好,其两相和液冷散热系统EER分别能达到20.9 kW/kW和10.5 kW/kW。

高液压射台前板球墨铸铁件铸造工艺设计

射台前板是注塑机中的关键部件之一,其油缸孔部位加工精度高且有承压要求。本文介绍了高液压球墨铸铁射台前板铸件的工艺难点,设计了分型方案、浇注系统及冷却系统,并借助软件模拟分析了缩孔与缩松缺陷,确定了型芯方案。通过合理选择铸件的化学成分,严格控制球化、孕育及浇注过程,铸件本体渗透检验(PT)达到EN1371标准的质量等级I级,附铸试块铸件的力学性能和金相组织均符合客户标准。

云南冬季强降温过程冷空气路径及大气环流差异

基于云南125个测站日平均气温数据,判定了1961—2020年云南冬季95次强降温过程的4种冷空气路径,对比分析了不同路径冷空气对云南降温的影响及大气环流差异.结果表明,东北路径冷空气对云南降温幅度影响最剧烈、影响空间范围最广;偏东路径出现频率最高,偏东路径和偏北路径在降温幅度和影响范围上较为接近;东南路径降温幅度和影响范围最弱,出现频率最低.超前强降温日2 d时,东北路径欧亚大陆500 hPa位势高度场上正高度距平异常区域强度和面积、700 hPa反气旋距平环流强度和西伯利亚高压均为最强,东南路径最弱,偏东路径和偏北路径介于前二者之间.东北路径500 hPa上东亚槽横槽转竖特征最明显,偏东路径和偏北路径东亚槽槽底南压加深,但转竖特征不及东北路径明显;东南路径东亚槽底部较宽广;东北路径副高呈块状面积最小,其它3种路径副高则呈带状,偏东路径副高面积最大.700 hPa上东北路径和偏东路径在日本附近有较强海平面气压负距平发展,朝鲜半岛气旋距平环流较强,其西侧较强的偏北气流引导冷空气进入云南;东南路径和偏北路径在朝鲜半岛气旋距平环流及其西侧的偏北气流较弱.在200 hPa纬向风距平场上,东北路径急流轴附近正负距平区强度最强,偏东路径沿急流轴距平分布为西正东负;东南路径正负距平区强度最弱,负距平区主要分布在急流轴北侧,偏北路径负距平区分布在急流轴南北两侧.

圆弧抽芯注塑模具优化设计

基于圆弧抽芯注塑模具,根据塑件结构及材料性能特点,对浇口的位置及结构进行了优化设计,通过CAE模拟分析得到位于填充末端、最大壁厚处的塑件最大变形量为0.739 mm,变形量在设计允许范围内。以油缸作为驱动动力源,通过齿条驱动齿轮、内齿轮旋转,实现抽芯动作;将内齿轮设计为异形非标齿轮,减少了所占空间,实现了1模2腔布局。为解决圆弧型芯冷却水路难以加工的问题,设计的加工工序为先按照直型芯进行粗加工,钻孔加工型芯冷却水路,然后,将型芯加热弯曲为所需形状,并进行调质处理,最后对型芯进行精加工使其满足设计要求,达到了随形冷却效果。传动机构关键参数采用理论计算与CAE模拟分析相结合的法验证,测试结果表明,计算校核效率提高了约4倍。

铝型材冷却初拉伸控制

针对铝型材加工过程中的拉伸夹具及冷却时间度量问题,设计适用于不同型号的拉伸夹具,确定了不同加工参数下的最佳冷却时间。通过优化拉伸夹具的设计和冷却时间的控制,能够提高铝型材的加工质量和生产效率。实验结果表明,该方法能够有效地改善铝型材的性能和形状,具有较高的应用价值。

低浓度含氧煤层气净化控制系统设计

低浓度含氧煤层气直接含氧液化精馏制液化天然气(LNG),在充分利用低浓度煤层气的同时又避免了煤矿瓦斯气直接排放造成的大气污染。首先,分析了含氧煤层气制LNG工艺中净化工段的工艺流程,结合工艺要求设计了可靠的控制系统。然后,根据低浓度含氧煤层气净化控制的工艺要求和系统规模,构建了分布式控制系统(DCS)的总体架构。在此基础上进行了硬件系统功能的选型及配置,以及对DCS软件的组态设计。最后,实现了DCS在工程实例中的一体化应用。该系统的应用提高了生产效率和产品质量,为工艺流程的稳定运行提供了安全保障。

膜调控的头孢呋辛钠溶析-冷却耦合结晶成核介稳区测定及分析

溶析-冷却耦合结晶可以提高结晶产率的同时,降低溶析剂的消耗量,是一种高效的耦合分离过程。传统的溶析结晶传质的界面往往受到宏观混合规模的限制,传质调控通常为亚毫米级,容易爆发成核,导致结晶产品的纯度差、平均粒度小、晶体粒度分布宽,因而需要更精确的调节策略。本文提出了一种新型的膜辅助溶析-冷却耦合结晶的方法,应用于头孢呋辛钠的结晶过程研究。其中,聚四氟乙烯(PTFE)中空纤维膜作为精确添加溶析剂和高效混合的界面,实现过饱和度的均匀分布。为了对比膜辅助溶析-冷却耦合结晶和传统耦合结晶方式的调控效果,对膜辅助溶析-冷却耦合结晶过程进行更为精确的调控,分别测量了传统和膜辅助条件下溶析-冷却耦合结晶的头孢呋辛钠-水-乙醇体系的介稳区宽度,计算了成核动力学参数。使用响应面方法和理论模型分析了冷却速率、溶析剂添加速率和溶析剂组分对介稳区宽度的影响,并比较了传统结晶和膜辅助结晶的介稳区特征。结果表明,膜辅助溶析-冷却耦合结晶的成核级数和成核速率常数(n=2.07,kn=158.15)均小于常规耦合结晶(n=2.45,kn=493.22),成核动力学方面更加温和,可调控性更强。