Experimental Investigation on Convective Heat Transfer Characteristics in Ribbed Channel

The heat transfer and pressure loss characteristics on a square channel with two opposite surfaces roughened by high blockage ratio ribs are measured by systematic experiments.Reynolds numbers studied in the channel range from 1 400 to 8 000.The ratios of rib height to hydraulic diameter (e/D) are 0.2and 0.33,respectively.The ratio of rib spacing to height (P/e) ranges from 5to 15.The rib orientations in the opposite surfaces are symmetrical and staggered arrangements.The results show that the heat transfer coefficients are increased with the increase of rib height and Reynolds number,though at the cost of higher pressure losses.When the rib spacing to height ratio is 10,it keeps the highest heat transfer coefficient in three kinds of rib spacing to height ratios 5,10 and 15.The heat transfer coefficient of symmetrical arrangement ribs is higher than that of the staggered arrangement ribs,but the pressure loss of the symmetrical arrangement ribs is larger than that of the staggered arrangement ribs.

Theoretical and Experimental Investigation of Flexural Vibration Transfer Properties of High-Pressure Periodic Pipe

According to the theory of phononic crystals, the hydraulic pipeline is designed to be a periodic structure composed of steel pipes and hoses to suppress the vibration of the hydraulic system with band gaps. We present theoretical and experimental investigations into the flexural vibration transfer properties of a high-pressure periodic pipe with the force on the inner pipe wall by oii pressure taken into consideration. The results show that the vibration attenuation of periodic pipe decreases along with the elevation of working pressure for the hydraulic system, and the band gaps in low frequency ranges move towards high frequency ranges. The periodic pipe has good vibration attenuation performance in the frequency range below 1000 Hz and the vibration of the hydraulic system is effectively suppressed. A11 the results are validated by experiment. The experimental results show a good agreement with the numerical calculations, thus the flexural vibration transfer properties of the high- pressure periodic pipe can be precisely calculated by taking the fluid structure interaction between the pipe and oil into consideration. This study provides an effective way for the vibration control of the hydraulic system.

Numerical Investigation on Flow and Heat Transfer Performance of Supercritical Carbon Dioxide Based on Variable Turbulent Prandtlnumber Model

Flow and heat transfer characteristic of supercritical carbon dioxide(SCO_(2))are numerically investigated in the horizontal and vertical tubes.TWL turbulent Prandtl number model could well describe the behavior of SCO_(2) affected by the buoyancy.Under the cooling condition,the heat transfer performance of SCO_(2) along the upward direction is best and that along the downward direction is worst when bulk fluid temperatures are below the pseudocritical temperature.Reducing the ratio of heat flux to mass flux could decrease the difference of convective heat transfer coefficient in three flow directions.Under the heating condition,heat transfer deterioration only occurs in vertical upward and horizontal flow directions.Heat transfer deterioration of SCO_(2) could be delayed by increasing the mass flux and the deterioration degree is weakened in the second half of tube along the vertical upward flow direction.Compared with the straight tube,the corrugated tube shows better comprehensive thermal performance.

Industrially Experimental Investigations and Development of the Curve-ROD Baffle Heat Exchanger

The conventional heat exchanger with segmental baffles is prone to bring forth fluid-induced vibration of heat transfer tubes and increase the pressure drop of shell-side greatly at higher fluid flow velocity. In order to avoid the above defects, the ROD-baffle heat exchanger has been developed. However, its collocation of heat transfer tubes is conventionally in square, which leads to fewer heat transfer area per unit volume. Based on the ROD-baffle heat exchanger, a new type curve-ROD baffle has been developed, and an industrial investigation of the curve-ROD baffle heat exchanger with normal triangular collocation has been carried into execution. In this paper, two equations using the Reynolds number were acquired to predict the heat transfer coefficients of the shell-side and tube-side. The experimental results show that the shell-side heat transfer and pressure drop characteristics of the curve-ROD baffle heat exchanger are superior to those of the segmental baffle one.

Experimental Investigation of Transient Heat Transferin the Once-Through Boiler Water Separator

The transient heat transfer between working fluid and inner wall of 600 MW supercritical pressureboiler's water separator model during start-up was experimentally explored. The test conditions forwater steam two-phase were as follows: pressure P = 3 ~ 11 MPa, mass now M = 0.2 ~ 0.35 kg/s,and mass quality x = O.2 ~ 0.8; for subcooled water P = 3 ~ 11 MPa, M = 0.2 ~ 0.35 kg/s, andsubcooled degree △θ = 10℃. By using an accurate and tractable inverse heat conduction solution,the correlations of single phase and twouphase transient heat transfer coefficients were obtained. Theexperimental results demonstrated the heat transfer enhanced for subcooled water and water steammixture compared with fully developed turbulent flow in tube. The increasing heat transfer effect maybe attributed to the deformation or destruction f the boundary layer.

化学新药研发企业对临床试验用药品委托制备的研发质量管理实践

临床试验用药品是化学新药研究与试验发展(以下简称研发)过程中里程碑式的产品,其制备的质量直接影响到临床受试者的用药安全性和临床试验结果的有效性。为确保临床试验用药品在委托制备过程中安全、有效且质量可控,本文阐明了化学新药药学研究在不同阶段下的研究重点,深入分析了工作中对临床试验用药品委托制备的质量管理所遇到的问题,探索出以“技术转出资料管理”“委托合同”“质量协议”三位一体,协同对临床试验用药品委托制备研发质量管理的模式,以期为新药研发企业的研发质量管理提供借鉴与思考。

Research on Personal Credit Risk Assessment Model Based on Instance-Based Transfer Learning

Personal credit risk assessment is an important part of the development of financial enterprises. Big data credit investigation is an inevitable trend of personal credit risk assessment, but some data are missing and the amount of data is small, so it is difficult to train. At the same time, for different financial platforms, we need to use different models to train according to the characteristics of the current samples, which is time-consuming. In view of these two problems, this paper uses the idea of transfer learning to build a transferable personal credit risk model based on Instance-based Transfer Learning (Instance-based TL). The model balances the weight of the samples in the source domain, and migrates the existing large dataset samples to the target domain of small samples, and finds out the commonness between them. At the same time, we have done a lot of experiments on the selection of base learners, including traditional machine learning algorithms and ensemble learning algorithms, such as decision tree, logistic regression, xgboost and so on. The datasets are from P2P platform and bank, the results show that the AUC value of Instance-based TL is 24% higher than that of the traditional machine learning model, which fully proves that the model in this paper has good application value. The model’s evaluation uses AUC, prediction, recall, F1. These criteria prove that this model has good application value from many aspects. At present, we are trying to apply this model to more fields to improve the robustness and applicability of the model;on the other hand, we are trying to do more in-depth research on domain adaptation to enrich the model.

体外受精⁃胚胎移植女性非理性生育认知的潜在剖面分析

目的:了解体外受精⁃胚胎移植(IVF⁃ET)女性非理性生育认知的分类特征,分析不同类别体外受精⁃胚胎移植女性非理性生育认知的特征差异。方法:采用便利抽样法,选取2022年10月—2023年1月于杭州市某三级甲等医院生殖内分泌科就诊的449例体外受精⁃胚胎移植女性作为调查对象。采用一般资料调查表、非理性生育认知问卷进行调查。结果:体外受精⁃胚胎移植女性非理性生育认知特征可分为低非理性生育认知组(24.3%)、中非理性生育认知组(54.8%)、高非理性生育认知组(20.9%)3个潜在类别。多元Logistic回归分析结果显示,家庭收入、文化程度、不孕时间是体外受精⁃胚胎移植女性非理性生育认知的影响因素。结论:体外受精⁃胚胎移植女性非理性生育认知存在明显的分类特征,临床工作者应结合病人特征,给予针对性的心理和信息支持,以降低病人的非理性生育认知水平。

旧路路面技术状况调查与检测实践分析

文中以厦门某旧水泥混凝土路面提升改造项目为研究对象,调查分析各项技术参数,系统地介绍了旧水泥混凝土路面技术状况调查与评定方法,为道路改扩建及提升改造提供了准确、定量的数据资料。

膜下滴灌农田盐分运移情况调查与分析

为详细分析新疆次生盐渍化棉田膜下滴灌盐分的运移规律,从不同生育期、垂直方向、水平方向、土壤质地四个角度对膜下滴灌盐分的运移进行了分析比对,初步得出：随着生育期的推后,各土层含盐量都有不同程度的加大;垂直方向盐分的积累在0-60 cm土层逐渐增加,60-100 cm土层盐分积累受膜下滴灌影响较小;水平方向背行中央土层处盐分积累最多,滴头处盐分积累最少;对于不同土壤质地,壤土中的盐分分布较粘土中的呈更规律的变化;分析认为定期大水漫灌洗盐、做好春复水工作是土壤脱盐的必要手段。研究将为新疆棉田土壤次生盐渍化防治提供理论依据。

斜截半椭圆柱面涡流发生器强化换热和压降特性的试验研究

在矩形通道内布置一对斜截半椭圆柱面涡流发生器(高宽比h/b=1/2),通过改变斜边倾角α、来流攻角β、前沿间距S、布置方式以及顺列、错列两排涡流发生器研究不同工况下的换热和压降特性。试验雷诺数范围为Re=700～26800。结果表明,在试验条件下α=12°时的换热效果要好于α=20°,Re=1300时两者的最高局部对流换热系数分别比平直通道高19.7%和10.7%,Re=26800时分别为23.2%和18.33%。斜截半椭圆柱面涡流发生器(α=12°)的最优攻角为β=60o,最优前沿间距为S=20mm。当Re=26800,β=60°,S=20mm时的最高局部对流换热系数约比平直通道高23.2%,压力损失约比平直通道高33.7%。雷诺数较小时,由于回流滞止区的影响,布置两排涡流发生器后,换热效果反而弱于单排。随着雷诺数增大到4000,双排涡流发生器的换热效果要明显优于单排,Re=26800时,最高局部对流换热系数约比单排涡流发生器高14.4%,比平直通道高33.4%。通过试验得出斜截半椭圆柱面涡流发生器在β=60°,α=12°时的涡旋作用距离大约在250～300mm。

相间内插两种转子换热管的换热及阻力特性

对相间内插螺旋开槽转子与低流阻转子不同数目比(Y)转子的圆管进行了换热及阻力特性的实验研究,结果表明,相间内插两种转子后明显对换热效果产生影响,换热效果和阻力特性与两种转子数目比Y有关。阻力系数(f)随着Y值的增大而增加,在所有相间排列方案中,螺旋开槽转子与低流阻转子的数目比Y=2时,换热效果最好,平均努赛尔数(Nu)和阻力系数(f)均比单一螺旋开槽转子高,努赛尔数(Nu)较螺旋开槽转子提高4%左右。

地源热泵地埋管换热器传热研究(1)：综述

综述了地源热泵地埋管换热器传热问题分析解、数值解的研究情况,分析了埋管之间的热干扰、管井回填材料、土壤含水量以及埋管内循环流体流量对地源热泵运行特性的影响,总结了当前研究的不足,指出了下一步研究的方向。

分离式热管蒸发段传热特性试验研究

通过对分离式热管水平及小倾角 ( 0°～ 5°)蒸发段传热特性的大比例尺模型的试验研究 ,获得了其壁温特性及换热规律 ,探讨了热流密度、工作温度、倾角及充液率等因素对传热特性的影响 .结果表明 ,与蒸发段垂直布置的分离式热管相比 ,水平及小倾角热管的换热系数较小 .特别是当热流密度大于 2 0kW /m2 时 ,蒸发管上下管壁温差增大 ,沿管长方向上管壁温度的波动较大 ,使上壁的换热系数降低 ,局部烧干热负荷过早出现 ,使热管的工作范围减小 .此外 ,还得出了水平蒸发管平均换热系数的无量纲准则关系式 .

3种类型波节管的强化传热模拟分析

针对外凸波节管、内凹波节管以及波纹相间波节管，用k－ε模型对此3种类型波节管的流动和传热特性进行了数值研究，比较了3种波节管在不同舶数下的流动和传热综合性能（PEC）：在Re=2300～11000时，外凸波节管最优，波纹相间波节管次之，内凹波节管最差．对波节管的换热机理和阻力机理进行了分析，得出波节管强化换热和压力损失的原因在于管内压力的强烈波动，特别在波节段末尾处的强烈负压区是压降损失过大的主要因素．另外，用热势容概念分析了波节管的性能，得到了进出口热势容差△E随Re数的变化曲线．

竖直圆管中超临界压力CO_2对流换热实验研究

本文对超临界压力CO2在竖直加热圆管内的对流换热进行了实验研究,比较了不同流向、不同热流密度等对流动和换热的影响。实验结果表明,管内径为2mm时,在低进口Re条件下,由于浮升力影响导致层流向湍流提前转变, 对流换热增强;与向上流动相比,向下流动更易由层流转变为湍流;向下流动的换热要强于向上流动,表明浮升力对换热有很大影响。对于管内径为0．27 mm的微细圆管,当进口Re高于104时,浮升力的影响可以忽略,对流换热系数的变化完全由物性的变化尤其是cp的变化导致。

能量地下蓄存及其传热效能分析

储能技术是实现能源可再生化和高效利用的一种有效途径,提高其综合利用率和实现能源的实时补充。着重论述地下蓄能技术发展状况和面临的研究问题,并通过实验和模拟计算,对蓄能的传热作用进行了分析和探讨,指出蓄能改变地下蓄能体的能位,并表现为蓄能体温度和分布的变化,这种变化随时间而改变。建议进一步开展完善地下蓄能理论研究,推动中国地下蓄能技术的发展。

熔化极气体保护焊熔滴过渡研究

研究熔化极气体保护焊(MIG/MAG)熔滴过渡的实验手段主要有示波法和高速摄影法2种,高速摄影法直接有效,已被研究工作者广泛采用。静力平衡理论(SFB)和缩颈不稳定理论(PIT)是分析熔滴过渡的两大理论,能够合理解释熔滴过渡中的一些物理现象。采用熔滴过渡信息对焊接过程进行实时控制是熔滴过渡研究的实际应用。

新型双层壁隔热屏气膜板内壁面换热特性数值研究

为了研究加入二次倾斜冲击后双层壁隔热屏内通道的流动特征和换热分布，通过数值模拟研究了不同冲击距离和不同中间孔直径下，冲击雷诺数在2500~7500，气膜板内壁面的换热系数分布特征。结果显示：冲击距离越短，高换热区域面积越大，平均换热系数越高；冲击距离对气膜孔所在环腔内的二次冲击和旋流之间的相互作用影响较大；中间孔直径越小，平均换热系数越高，气膜孔所在的环腔内二次冲击范围越小，漩涡冲击范围越大。

基于农户调查的江汉平原地区农村土地流转意愿研究及影响因素分析

农户是参与农地流转的主体之一,实现土地合理流转必须以尊重农民意愿为前提。以江汉平原为研究区,运用Logistic二元回归模型对研究区278户农户土地流转意愿的影响因素进行分析,得出以下结论:(1)研究区农户的土地流转意愿较低,流出土地的农户比例为17.99%,流入土地的农户比例为25.17%;(2)影响农户土地流出意愿的主要因素是农地收入功能、外出务工劳动比例和耕地面积,农地收入功能越高,外出务工人数越少,耕地面积越多,农户的土地流出意愿越强;(3)影响农户土地流入意愿的主要因素是户主文化水平、农地政策了解程度、是否具备耕种能力、农地收入功能、耕地质量和村集体经济状况,户主文化水平越高,对农地政策越了解,耕种能力越强,农地收入越高,农户的农地流入意愿越强,而耕地质量越高,村集体经济状况越好,农户的农地流入意愿越弱。