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

The genomes of eukaryotic cells are under continuous assault by environmental agents and endogenous metabolic byproducts. Damage induced in DNA usually leads to a cascade of cellular events, the DNA damage response. Failure of the DNA damage response can lead to development of malignancy by reducing the efficiency and fidelity of DNA repair. The NBS1 protein is a component of the MRE11/RAD50/NBS 1 complex （MRN） that plays a critical role in the cellular response to DNA damage and the maintenance of chromosomal integrity. Mutations in the NBS1 gene are responsible for Nijmegen breakage syndrome （NBS）, a hereditary disorder that imparts an increased predisposition to development of malignancy. The phenotypic characteristics of cells isolated from NBS patients point to a deficiency in the repair of DNA double strand breaks. Here, we review the current knowledge of the role of NBS1 in the DNA damage response. Emphasis is placed on the role of NBS1 in the DNA double strand repair, modulation of the DNA damage sensing and signaling, cell cycle checkpoint control and maintenance oftelomere stability.

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%。

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 RESULTS： The PDT of primary culture of hepatocardnoma cells was 91.0±6.6 h, PE was 12.0±1.4%, SF2 was 0.41±0.05%. The PDT of their inadiated progeny was 124.8±5.8 h, PE was 5.0±0.7%, SF2 was 0.65±0.09%. The pdmary cultured human hepatocarcinoma cells showed significant S reduction and G^2 arrest 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.

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.

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.

基于双循环的气井产量劈分方法及应用

产量劈分系数是多层合采气藏动态预测的基础,建立产量劈分系数动态跟踪计算方法具有重要意义.基于产量劈分的物理意义,明确了产量劈分系数的求解关键参数为泄气半径,但泄气半径在实际应用中通常未知.结合产能方程和物质平衡方程,建立了闭环的产量劈分系数计算模型,计算模型包含泄气半径、平均地层压力和产量劈分系数等三个未知参数,为求解计算模型提出了双循环计算法,内循环求解泄气半径,外循环求解产量劈分系数,内循环和外循环均存在唯一解,循环规则包括正向递归和反向递归,内循环与外循环的循环规则始终相反,通过设定循环步长和误差上限,建立了双循环的计算流程,外循环包含内循环,内循环收敛时外循环才能进行,外循环决定了内循环能否收敛.数值模拟验证显示,产量劈分系数在不同产层、不同阶段、不同时间表现出不同的变化规律,双循环计算法不仅机理正确且精度很高.产气剖面对比显示,双循环计算法在现场应用中亦具有可靠的精度.双循环计算法属于三元方程组的求解方法,实现了产量劈分系数、泄气半径和平均地层压力的同时计算.

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。

在自由贸易试验区发展跨境科技贸易的实证分析:以海南为例

发展跨境科技贸易可以最大限度地匹配科技创新资源,带动经济社会真正转到依靠科技创新的发展轨道上来。随着科技水平的快速提升,中国发展跨境科技贸易的基础与条件日趋成熟。而享有零关税、低税率优惠政策以及在人员资金信息数据来往等方面具有更多优势的自由贸易试验区将是发展跨境科技贸易的前沿。海南自贸港背靠国家科技力量和新型科技创新举国体制的战略与政策支持,较早试行发展跨境科技贸易,为自由贸易试验区乃至全国发展跨境科技贸易提供了宝贵经验。未来,全国的自由贸易试验区都应充分发挥自贸区最高水平开放政策激励的价值和作用,主动布局积极融入并引导国际科技创新大循环,将自身建设成为国家科技创新双循环的重要交汇点。

“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。

“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。

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。

中国营商环境的测度、时空演变特征与优化路径研究

随着全球经济一体化和区域经济协同发展的不断加深,营商环境的优化已成为推动地区经济增长和提高区域竞争力的重要因素。基于“双循环”格局和中国式现代化的理论内涵,从市场化、法治化、国际化三个层面构建了中国营商环境评价指标体系,根据逐层纵横向拉开档次法对2005-2022年中国30个省份的营商环境进行测度,并通过Kernel核密度估计与协调度模型分析其时空演变特征与优化路径。研究发现,中国各地区营商环境的演变规律存在多元性,综合发展水平持续提升。东部地区营商环境的内部综合差异存在扩大趋势;西部地区营商环境的地区差异逐渐缩小;中部地区和东北地区营商环境的内部差异经历了多轮先增大后缩小的波浪式进程。此外,通过协调性分析发现,不同地区营商环境的短板具有异质性。整体来看,各地区营商环境的国际化水平与市场化水平、法治化水平之间的协调度普遍偏低;分地区看,中部地区的国际化与法治化平均协调度处于较低水平,且改善进展相对迟缓;东北地区和西部地区在市场化与国际化平均协调度上存在的短板是制约其整体协调度提高的主要障碍。基于上述研究结论,提出各地区应根据发展实际,关注自身营商环境的短板,找准制约营商环境发展的堵点,重视并加强营商环境的建设,以推进中国省域营商环境的整体优化与提升,助力加速构建“双循环”格局。

“双一流”建设高校高层次人才全周期评价模式构建

人才评价是人才发展的基础性制度,是人才队伍建设的“指挥棒”。相较于一般性人才评价,高层次人才评价更具复杂性和特殊性。加快建立“双一流”建设高校高层次人才评价体系,对科教兴国战略、人才强国战略、创新驱动发展战略的深入实施有重要意义。“双一流”建设高校高层次人才全周期评价模式尊重高层次人才特点、成长发展规律和人力资源管理规律,强调全方位、全过程评价人才。运用这种评价模式可以更好地实现评价的引导、激发、诊察、预测和调控功能。针对“双一流”建设高校高层次人才评价中存在的现实困境,从评价理念、甄选人才、使用人才、激励人才、培育人才、评价监控和改进等方面建立起“双一流”建设高校高层次人才全周期评价模式的分析框架,坚持评价导向要回应“国家战略”,评价理念要回归“以人为本”,评价内容要回答“任务牵引”,评价频度要对应“成长周期”,构建包括甄选层、使用层、激励层和培育层在内的“四个坚持”的“双一流”建设高校高层次人才全周期评价模式。实践中建议用科学灵活的评价方法甄选高层次人才,用个性化任务作为评价内容使人才更好发挥作用,用多样式手段激发人才发展动力,用全周期的支持服务全方位培育人才,以探索建立针对“双一流”建设高校高层次人才发展工作更加完善的评价体系。

国内国际双循环联动与高技术产业出口韧性

选取2008—2022年中国238个地级及以上城市面板数据,实证检验国内国际双循环联动对高技术产业出口韧性的影响及其内在机制。研究发现,国内国际双循环联动能够显著提升高技术产业出口韧性。机制检验表明,国内国际双循环联动可通过提升技术创新水平的途径,间接增强高技术产业出口韧性。异质性分析显示,国内国际双循环联动对Ⅰ型及以上大城市的高技术产业出口韧性促进效应更显著。鉴于此,应增强国内国际两种资源联动效应、着力提升高技术企业关键技术创新能力,以期提升高技术产业出口韧性、加速贸易强国建设进程。