Effect of an Internal Heat Exchanger on the Performances of a Double Evaporator Ejector Refrigeration Cycle

A theoretical investigation is presented about a double evaporator ejector refrigeration cycle(DEERC).Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger(IHX).The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure.Moreover,the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor.To assess accurately the influence of the IHX on the DEERC performance,a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors.The model also accounts for the friction effect in the ejector mixing section.The equations of this model are solved using an Engineering Equation Solver(EES)for different fluids.These are:R134a as baseline fluid and other environment friendly refrigerants used for comparison,namely,R1234yf,R1234ze,R600,R600a,R290,R717 and R1270.The simulation results show that the DEERC with an IHX can achieve COP(the coefficient of performance)improvements from 5.2 until 10%.

The role of NBS1 in DNA double strand break repair, telomere stability, and cell cycle checkpoint control

真核细胞的房间的染色体在由环境代理人和内长的新陈代谢的副产品的连续袭击下面。在 DNA 导致的损坏通常导致细胞的事件的串联， DNA 损坏反应。DNA 损坏反应的失败能由减少 DNA 修理的效率和忠实导致恶意的开发。NBS1 蛋白质是在对 DNA 损坏和 chromosomal 正直的维护的细胞的反应起一个关键作用的 MRE11/RAD50/NBS1 建筑群(MRN ) 的一个部件。在 NBS1 基因的变化为 Nijmegen 破裂症候群(NBS ) 负责，给予增加的倾向到恶意的开发的世袭混乱。从病人们在 DNA 双海滨裂缝的修理指向缺乏的 NBS 孤立的房间的 phenotypic 特征。这里，我们在 DNA 损坏反应考察 NBS1 的角色的当前的知识。强调在 DNA 双海滨修理，察觉到并且发信号的 DNA 损坏的调整，房间周期检查点控制和 telomere 稳定性的维护被放在 NBS1 的角色上。

基于DDR-CycleGAN的红外图像数据增强

提出了一种基于双鉴别器相对循环一致性生成对抗网络(DDR-CycleGAN)的红外图像数据生成方法。针对双鉴别器监督机制易出现的过度优化造成的性能下降问题,该方法在双鉴别器循环一致性生成对抗网络(DD-CycleGAN)中加入了相对概率的思想,采用鉴别器鉴别图像的相对真实概率替代绝对真实概率,使得生成图片更加接近真实图片。本文方法采用FLIR数据集进行训练和测试,实验结果表明本文方法相比DD-CycleGAN在可见光图像生成红外图像的图像质量上,峰值信噪比提高了3.91%,FID(Frechet Inception Distance score)降低了3.81%。

Th–U cycle performance analysis based on molten chloride salt and molten fluoride salt fast reactors

The recent development of molten salt fast reactors has generated a renewed interest in them. As compared to traditional solid fuel fast neutron systems, it has many unique advantages, e.g., lower fissile inventory,no initial criticality reserve, waste reduction, and a simplified fuel cycle. It has been recognized as an ideal reactor for achieving a closed Th–U cycle. Based on the carrier salt, molten salt fast reactors could be divided into either a molten chloride salt fast reactor(MCFR) or a molten fluoride salt fast reactor(MFFR);to compare their Th–U cycle performance, the neutronic parameters in a breeding and burning(B&B) transition scenario were studied based on similar core geometry and power. The results demonstrated that the required reprocessing rate for an MCFR to achieve self-breeding was lower than that of an MFFR.Moreover, the breeding capability of an MCFR was better than that of an MFFR;at a reprocessing rate of 40 L/day,using LEU and Pu as start-up fissile materials, the doubling time(DT) of an MFFR and MCFR were 88.0 years and 48.0 years, and 16.5 years and 16.2 years, respectively.Besides, an MCFR has lower radio-toxicity due to lower buildup of fission products(FPs) and transuranium(TRU),while an MFFR has a larger, delayed neutron fraction with smaller changes during the entire operation.

Cell cycle and radiosensitivity of progeny of irradiated primary cultured human hepatocarcinoma cells

AIM: To evaluate the change of growth characteristics and radiosensitivity of irradiated primary cultured human hepatocarcinoma cells.METHODS: All tumor tissue samples were obtained from 39 hepatocarcinoma patients with a mean age of 49.6 years (range 22-76 years). We divided the samples into irradiated group and non-irradiated group and measured their plating efficiency (PE), population doubling time (PDT), radiosensitivity index SF2 and cell cycle.RESULTS: The PDT of primary culture of hepatocarcinoma cells was 91.0±6.6 h, PE was 12.0±1.4%, SF2 was 0.41±0.05%.The PDT of their irradiated progeny was 124.8±5.8 h, PE was5.0±0.7%, SF2 was 0.65±0.09%. The primary cultured human hepatocarcinoma cells showed significant S redutiion and G2arrest in a dose-dependent manner. The progeny of irradiated primary cultured hepatocarcinoma cells grew more slowly and its radiosensitivity increased.CONCLUSION: The progeny of irradiated primary cultured human hepatocarcinoma cells grows more slowly and its radiosensitivity increases.

Double reversible transformations under various treatment states

The double reversible transformations at low temperature in CuZnAlMnNi shape memory alloy were investigated by differential scanning calorimetry. It is found that the transformations occur not only in the as quenched sample, but also in the as trained, as aged and as thermal cycled samples, and various treatments give rise to different influences on the transformation temperatures of the two transformations. Though the temperature interval between the two transformation peaks increases after training, aging and thermal cycling, the initial temperature of the M → A transformation is just the final temperature of the X → M transformation, namely, the X → M transformation is immediately followed by the M → A transformation upon heating.

Finite Element Simulation of Thermal Field in Double Wire Welding

In this paper, the thermal field of double wire welding is simulated by using ANSYS software. Simulation results were shown that the total heat input (E) is the most significant parameters to change the value of t8/5;By the mean of rationally controlling the proportion of the front arc heat input (E1) in the total heat input (E) and appropriately selecting double wire spacing (L), It is effective means to get the double wire welding thermal cycle. By the way of simulation, it is possible to manage the thermal input in the double welding wires and to control the temperature field and cooling rate that are fundamental for the final joint quality, it is great importance guidance to optimize the double wire welding process parameters.

Microstructures and hardness of flat-overhead weld of the high strength steel thick plate using double-sided arc welding

High strength steel thick plate is widely used in shipbuilding, pressure vessels, etc. , the balance between weld quality and welding efficiency is becoming a research focus. In this paper, double-sided double arc fiat-overhead welding experiments for high strength steel thick plate were conducted. Microstructures of weld have been observed through optical microscope （OM） and scanning electron microscope （SEM）. Transformation of microstructures under thermal cycles of multi peaks was analyzed. Macro and micro hardness were also tested. The results show that the heat-affected zone （HAZ） near the fusion line experiences thermal cycles up to three times. The microstructures there are the most complex, including coarse lath martensite in original coarse-grained zone, and net-like structure along grain boundaries in critical reheat coarse-grained zone. After several times of tempering for bucking welding, the features of acicula and lath are weakened. Its microstructure approaches to the microstructure of base metal which is tempering sorbite. The hardness test shows that the maximum hardness occurs at critical reheat coarse-grained zone, the hardness of reticulation structure at grain boundary can be up to 450 HV.

基于占空比波表的三相四线整流器控制

三相脉宽调制(PWM)整流器应用广泛。针对三相四线(TPFW)PWM整流器,提出了一种基于占空比波表的电压电流双闭环控制策略。该控制策略电压外环采用波表系数步进调节控制,电流内环采用离散比例积分微分(PID)控制叠加电容电压步进调节均衡控制。该方法能够提高系统功率因数,同时也能抑制整流器输出直流侧电压波动以及实现电容电压均衡。最后在硬件平台上进行实验验证,实验结果表明该控制策略具有抑制输出电压纹波、功率因数高、系统稳定性好等优点。与传统方法相比,该控制方法控制简单,易于工程实践.

冻融雁行裂隙花岗岩单轴压缩宏细观疲劳特性试验研究

对于季冻区的岩体工程,岩石经常受到冻融和周期荷载扰动引起的耦合疲劳损伤。为了研究冻融裂隙花岗岩的疲劳开裂扩展情况,量化裂纹的损伤程度和分类类型,对冻融40次后的双裂隙花岗岩进行了3种应力振幅下的周期荷载试验。采用实时声发射和高速摄影监测技术来揭示裂纹演化,并进一步对不同的裂纹开裂类型进行分类,以帮助理解动态压裂规律,利用核磁共振测试分析裂隙花岗岩细观孔隙特征及其宏观力学特性的关系。结果表明:随着周期荷载振幅应力比的增加,双裂隙花岗岩在周期荷载“沉寂期”内的声发射计数增加;周期荷载阶段双裂隙花岗岩产生的剪切裂纹占比大于单调加载阶段,高振幅作用下岩石容易形成剪切破坏裂纹;双裂隙花岗岩声发射的最大幅值变小即大尺度破裂减少,周期荷载下岩样预制裂隙外尖端产生的向端面扩展裂纹的角度越大;双裂隙花岗岩的疲劳寿命减小,内部微裂隙扩展发育减缓,能够储存的含H流体也越少,最终表现为核磁共振T2谱面积变化率减小。

“双循环”视域下我国跨境电商支付问题研究

近年来,受疫情的影响全球经济的压力加大,面对如此严峻的外部环境,我国顺势提出了“独立自主、高水平开放”的国内国际双循环战略。在此背景下,跨境电商行业飞速发展,成为我国经济发展中一股新的力量,为我国经济的复苏提供了新的动力。跨境支付作为跨境电商的一个重要环节,与跨境电商的健康发展息息相关。由于我国跨境电商支付不健全,存在诸多的问题,制约着跨境电商的发展前景。只有完善和解决跨境电商支付出现的问题才能为跨境电商提供不断的发展动力。本文主要分析了我国跨境电商的支付现状以及在支付方式中存在的问题和风险,并对这些问题提出自己的解决措施和建议。

热循环条件下BGA叠层焊点可靠性研究及参数优化

构建叠层焊点最优结构参数,提高BGA叠层焊点热循环条件下的可靠性具有重要的意义。建立有限元模型,分析叠层焊点在热循环条件下应力应变,运用田口正交法和曲面响应法,将焊点的高度、直径、间距、阵列作为实验设计的变量,关键焊点最大等效塑性应变作为优化目标。结果表明:焊点阵列对优化目标的影响权重最大,优化后的BGA叠层焊点结构参数如下,田口正交法:单层焊点高度为0.38 mm,焊点间距为0.55 mm,焊点直径为0.44 mm,焊点阵列为8×8;曲面响应法:单层焊点高度为0.387 mm,焊点间距为0.573 mm,焊点直径为0.446 mm,焊点阵列为8×8。对优化前后的寿命进行预测,优化后的叠层焊点寿命约是优化前的3.75倍。

中国农业经济国内国际双循环:实证测度与国际比较

文章立足国际投入产出表,构建基于供需两侧的农业经济国内国际双循环测度指标和基于全球价值链的农业贸易增加值国内国际双循环分解方法,并利用2007-2019年的ADB-MRIO数据,对中国农业经济国内国际双循环进行实证测度与国际比较。研究表明:考察期内中国农业经济供给侧国内循环的占比呈下降趋势,而需求侧国内循环的占比呈上升趋势;综合农业经济国内国际双循环测度及农业贸易增加值分解来看,中国农业经济国内循环依赖程度在90%左右;从国际比较角度来看,2019年中国依赖于国内循环的农业贸易增加值占比在全球62个主要经济体中处于第5位,若单纯基于国内国际双循环的新增经济流量看,在数量上农业经济国内循环的主体地位基本确立。

人结直肠癌细胞周期各时相中双微体存在形式及复制分离时期的分析

目的探究双微体(Double minute chromosomes,DMs)在肿瘤细胞周期各时相内的主要存在形式,明确DMs的复制、分离时相。方法通过无血清饥饿法阻滞人结直肠癌细胞COLO 320DM周期进展后,取花萼海绵体诱癌素A(Calyculin-A)诱导间期细胞以染色质超前凝集制备核型样本。用秋水仙素处理COLO 320DM细胞以获取有丝分裂(M)期细胞进行核型分析。在普通光学显微镜下观察并拍摄DNA合成前期(G1期)、DNA合成后期(G2期)、M中期、M后期和M末期核型,并统计DMs数量。结果DMs在G1期、M后期和M末期时相细胞中主要以单体形式存在;在G2期和M中期时相细胞中主要以双体形式存在。结论单体型DMs在S期发生复制后由单体转变为双体,双体型DMs在M后期完成分离并由双体转变为单体。

“双循环”视域下制造业供需动态平衡实现路径研究

梳理了“双循环”视域下我国制造业实现供需动态平衡的理论内涵,分析了“双循环”视域下我国制造业供需动态平衡面临的困境。作为应对,我国需要从供给侧及需求侧入手,推进制造业供需均衡。

基于钠冷快堆的超临界二氧化碳双透平发电系统

超临界二氧化碳布雷顿循环发电系统具有效率高、对管道腐蚀速率低、可降低电力成本等优点,被认为是钠冷快堆的理想动力转换系统。但也有不足之处,其系统正常运行时的压力较高,导致中间热交换器两侧压差大,极大地降低了安全性,限制了实际应用,因此本研究在原有系统的基础上进行改进,建立双透平发电循环,目的是在保持高循环效率的同时降低换热器冷流体侧工作压力。本研究对比了相同热功率下不同循环应用双透平发电系统的变化,并对影响效率的具体因素进行了敏感性分析。结果表明,再压缩循环最适配于钠冷快堆双透平发电系统,循环效率最高可达42.99%,其对主压缩机入口参数敏感度最高,其次是分流比和透平入口参数,而对透平分配比的敏感度最低。

双循环视域下高等教育发展格局优化探讨

随着当前高等教育的规模持续扩大,必须注重贯彻和落实全面深化改革的各方面要求,结合现代经济社会发展的实际情况,着重培养高素质综合应用型人才。对此,高等院校需要结合当前的结构布局做出必要的调整措施,针对目前的教育结构及资源供给和配置方式,充分结合高等教育发展的趋势和特征采取转型发展的措施。目前社会各界正在深入探究双循环对高等教育的影响,在双循环的背景下,准确把握新发展格局的内涵和意义,推动高等教育步入新的发展阶段。

双循环格局下新能源汽车供应链发展对策研究

双循环发展格局下,市场对于新能源汽车的国内供应链和产业链的高效稳定运行提出了更高要求。基于此,通过分析新能源汽车供应链网络结构模型及其特点,围绕新能源汽车产业供应链遇到的困难和瓶颈,对增强其供应链自主可控能力的对策建议进行探索。

新发展格局下中国式现代金融体系的构建

新发展格局的根本保障是中国共产党的领导,关键在于经济循环畅通无阻,最本质特征是实现高水平自立自强,强大动力是深化改革和扩大开放,内在要求是统筹安全与发展。现代金融体系是畅通国内大循环的重要基础,是提升国际循环质量和水平的核心动力,也是联通国内国际双循环的关键平台。构建高效服务新发展格局的中国式现代金融体系,一是要以中央银行为核心,完善金融基础设施体系;二是要强化常态化跨周期金融支持,构建现代化应急金融体系;三是要以多层次资本市场为导向,完善现代金融市场体系;四是要践行“人民至上”的价值理念,建立以人民为中心的普惠金融体系;五是要运用金融科技赋能,完善金融服务创新体系;六是要提升金融“三化”水平,增加现代金融体系发展“韧性”;七是要围绕总体国家安全观,构建全方位的金融安全战略体系。

基于建构性反馈的双循环对分课堂教学模式研究

随着教育数字化转型的推进,混合学习因能够结合线上线下教学优势、提供更灵活多样的学习体验、适应数字化转型的需求而受到高校课堂的青睐。然而,对于人数较多的通识课程或专业必修课程,大班式在线教学中容易出现师生和生生互动缺乏、学生社会存在感低、学习效果不佳等问题。为此,本研究提出了基于建构性反馈的双循环对分课堂教学模式,核心理念是在泛在学习环境与信息化工具的支撑下,以学习支架为引导,完成两轮相互迭代的循环:学生主体建构循环与师生生成性建构循环,最终指向以建构性反馈为基础的“教、学、评”一致性设计。针对该模式,本研究对华南地区某大学全校性公共必修课“现代教育技术”的165位本科二年级学生开展了为期16周的教学实验,结果表明,该教学模式对提高学生的社会存在感、学习动机和学习成绩具有积极的作用,可为教育数字化转型背景下开展混合学习提供参考。