Measurements of the effective mass transfer areas for the gas–liquid rotating packed bed

Rotating packed bed(RPB) is one of the most effective gas–liquid mass transfer enhancement reactors, its effective specific mass transfer area(ae) is critical to understand the mass transfer process. By using the NaOH–CO_(2) chemical absorption method, the aevalues of three RPB reactors with different rotor sizes were measured under different operation conditions. The results showed that the high gravity factor and liquid flow rate were major affecting factors, while the gas flow rate exhibited minor influence.The radius of packing is the dominant equipment factor to affect aevalue. The results indicated that the contact area depends on the dispersion of the liquid phase, thus the centrifugal force of rotating packed bed greatly influenced the aevalue. Moreover, the measured ae/ap(effective specific mass transfer area/specific surface area of packing) values were fitted with dimensionless correlation formulas. The unified correlation formula with dimensionless bed size parameter can well predict the experimental data and the prediction errors were within 15%.

Proposal of Landscape Space Transfer Index and Changes of Landscape Area Based on Transfer Matrix——With Yutian County in Xinjiang as a Study Case

The most significant changes of landscape in a certain period are landscape area changes and spatial changes of landscape patches.Based on transfer matrix and total amount change of landscape area,landscape space transfer index and landscape area change index were established,and then applied to analyze plain oasis and desert in Yutian County,Xinjiang Uyghur Nationality Autonomous Region,the results showed that landscape space transfer in this region was drastic,but total landscape area changed only slightly,thus space transfer index was much higher than area change index,which indicated that landscapes in arid area were given with particular spatial undulant features and sensitivity,while man-made landscapes(artificial oasis) are stable and expanding to some extent.With landscape space transfer index as the comprehensive indicator,space transfer intensity of landscape within a certain period can be demonstrated,which is favorable for the comparison of landscape change intensity among different types and within different periods,in addition,some macroscopic change features of landscapes can also be reflected by comprehensively analyzing landscape space transfer index and landscape area change index.

Minimizing investment cost for multi-period heat exchanger network retrofit by matching heat transfer areas with different strategies

Multi-period heat exchanger network(HEN) retrofit is usually performed by targeting and matching heat transfer areas. In this paper, based on the reverse order matching method we proposed previously, three strategies of matching heat transfer areas are proposed to minimize the investment cost for the retrofit of HEN in multiperiod, in which replacement of heat exchangers, addition of heat exchangers and addition of heat transfer areas are performed. We demonstrate the procedures through three scenarios, including maximum number of substituted heat exchangers after retrofit, minimum additional heat transfer areas in the retrofitted HEN, and minimum investment cost for retrofit. The strategies are extended to a single period HEN retrofit problem. The results of multi-period and single period HEN retro fit problems indicate the effectiveness of the strategies. Moreover, these results are better than those reported in literature. The strategies are simple and easy to implement,which are of great benefit to large-scale HEN retrofit in practice.

Empirical Analysis of Factors Influencing Surplus Labor Transfer in Poverty-stricken Areas: A Case Study of Yimatu Town in Fuxin City

From the microscopic point of view,taking the surplus labor transfer in the Yimatu Town area as study object,we conduct survey of characteristics and transfer of rural surplus labor in Yimatu Town,through questionnaires and field interviews.Then we analyze the main factors influencing surplus labor transfer in rural areas from the personal characteristics of labor forces and family factor of labor forces.The results show that gender,age,educational level,farmland management days and other factors pertaining to the labor forces all affect the transfer of surplus labor, but the size and extent of the impact vary.In accordance with various influencing factors,we put forward recommendations for promoting the effective transfer of surplus labor in rural areas as follows:first,paying equal attention to macroscopic factors and microscopic factors influencing the transfer of surplus labor;second,focusing on the factors concerning the rural households and individual farmers,to find out the factors influencing the rational transfer;third,shifting the employment concept of surplus labor in rural areas;fourth,speeding up the construction of small towns and developing the secondary and tertiary industries.

Mass transfer area in a multi-stage high-speed disperser with split packing

In this study, the mean droplet diameter in the cavity zone and the total mass transfer area of a multi-stage highspeed disperser(HSD) reactor with different packing combinations were measured and evaluated. The effects of rotational speed and packing radius, as well as the packing ring radius and numbers, on the mean droplet diameter and the total mass transfer area were evaluated. A model was established to calculate the mass transfer area in the cavity zone in the HSD reactor, and it was found that the packings contribute 61%–82% of the total mass transfer area. A correlation for predicting the mass transfer area in the packing zone was regressed by the dimensionless analysis method. An enhancement factor based on the mass transfer area in the packing zone was proposed to evaluate the effect of packing combination on mass transfer area. Two optimum packing combinations were proposed in consideration of the mean droplet diameter and the enhancement factor.

The Research of Heat Transfer Area for 55/19 Steam Generator

A calculation method of heat transfer area for vertical natural circulated steam generator was introduced. According to the design requirements of steam generator 55/19 of CPR1000, its heat transfer area was calculated based on this method. The results show that the accuracy of partitional and overall calculation method is almost the same, but the result is different when using different calculation models. And the results are compared with the foreign companies for 55/19 steam generator.

Radioactivity Levels and Soil-to-Plant Transfer Factor of Natural Radionuclides from Protectorate Area in Aswan, Egypt

The aim of this study is to determine the transfer factor soil-to-plant and to assess the concentration level of natural and artificial radionuclide (238U, 226Ra, 228Ra, 232Th, 40K and 137Cs) in samples from Saluga and Ghazal Protectorate area in Aswan, Egypt, by using High Pure Germanium detector (HPGe) Environmental Radioactivity Measurements Labrotary in faculty of science Qena. Reported values for natural radionuclides ranged from 8.81 ± 0.64 to 28.88 ± 2.10, from 6.98 ± 0.51 to 26.01 ± 1.89, from 12.29 ± 0.89 to 33.32 ± 2.43, from 12.53 ± 0.91 to 32.81 ± 2.39 and from 383.90 ± 27.95 to 711.98 ± 51.83 Bq.kg-1 for 238U, 226Ra, 228Ra, 232Th and 40K, respectively. 137Cs activity concentration was found to be in the range from 0.36 ± 0.03 to 9.73 ± 0.71 Bq.kg-1 and was calculated through transfer factor TF reported in this article.

新加坡特殊经济区域创新实践及对中国科技成果转移转化示范区建设的启示

新加坡特殊经济区域通过政府主导、市场运作、产学研协同的模式,为新兴产业发展提供了良好的环境和动力。借助“制度-结构-行为-绩效”(Institution-Structure-Conduct-Performance,ISCP)范式从政府前期开发和市场机构后续运营的制度机制层面,创新主体、设施和环境引导建设的结构导向层面,资金投入、人力资源引培、土地梯次开发弹性利用和打造创新社区的行为措施层面,以及区域新兴产业发展壮大的绩效层面,对新加坡特殊经济区域创新实践进行了研究。以此框架分析了中国科技成果转移转化示范区存在的问题,得出围绕产业发展,引入空间再造和激活创新要素角度,涉及创新的制度和机制、主体和结构、环境和人才等方面的启示。

机坪管制移交区域划设影响因素研究

论文针对机坪管制移交工作中责任边界划设问题,构建机坪管制移交区域划设影响因素体系,将灰数系统理论融入DEMATEL-AISM模型中,利用中心度与熵权法改进模型主观赋权问题,构建Grey-DEMATEL-AISM模型,探寻因素间耦合关系,划分因素层级结构,并根据成都双流国际机场机坪管制移交情况进行实例验证。结果表明:机坪管制移交区域划设影响因素共15个,其结构体系可划分为5个层次,机坪管制员负荷与空管塔台管制员负荷为原因度最小的结果因素,位于上层直观层;塔台位置、跑滑构型等12项因素位于中间过渡层;场面流量是原因度最大的原因因素,位于底层根源层。

喀斯特地区土地流转如何促进农户增收?——基于8省3678户的经验证据

充分发挥喀斯特地区土地流转的农户增收效应是推进山地农业高质量发展的有效渠道。基于中国喀斯特地区8个省区市3 678户农户微观调研数据,采用有序Logit模型、倾向得分匹配法、KHB方法等,考察土地流转对农户收入的影响和作用机制。结果表明:(1)土地流转显著提升了喀斯特地区农户家庭总收入水平,土地流转户收入水平较未参与流转户约高出12.86%;(2)相比于土地转入户,土地转出对农户收入增长的影响更为显著;(3)外出务工和家庭创业在土地转出影响农户收入关系中起中介作用,解释比例分别为17.18%和4.63%;农业机械化在耕地较为平整的转入户对收入的影响中起中介作用,解释比例为16.93%;(4)土地流转对种植经济作物、耕地较为平整、灌溉条件较好的农户家庭总收入影响显著为正。为此,建议进一步健全喀斯特地区土地流转机制,促进非农产业发展,加强丘陵山区农业机械化和农田水利设施建设,发展喀斯特地区特色高效农业,鼓励更多农户积极参与土地流转。

Cu对铝/钢CMT熔钎焊接头界面区组织的影响研究

采用冷金属过渡方法,以AlSi5焊丝为填充金属,在5052铝合金和镀锌钢板之间添加铜箔片进行搭接熔钎焊,使用扫描电子显微镜结合能谱分析和拉伸试验机对接头的界面区组织与性能进行研究。结果表明,未加入铜箔时,界面区组织主要由FeAl_(3)金属间化合物组成;铜箔的加入使得界面区组织中新生成了CuAl_(2)金属间化合物,同时改善了Zn在界面区的分布。Zn固溶于Al中,一定程度上抑制了Fe-Al金属间化合物产生。加入铜箔后的试样断裂位置发生改变,接头的承载能力与未加入铜箔的相近。

劳动力转移对粮食生产韧性的影响研究--基于中国粮食主产区的实证

粮食安全是“国之大者”,随着农业劳动力大量转移,粮食生产韧性是否受到影响及受到的影响有多大,已成为新时期的重要议题。基于中国粮食主产区2010-2022年省域面板数据,通过构建主产区粮食生产韧性的综合指标体系,首先使用熵权与变异系数综合赋权法对其进行测度,其次选用固定效应模型实证检验农业劳动力转移对粮食生产韧性影响的内在逻辑。研究发现:农业劳动力转移有助于主产区粮食生产韧性的提升,且对粮食生产韧性的促进效应在较长时间序列上均稳健成立。具体而言,农业劳动力转移每增加1%,主产区粮食生产韧性水平将会平均增加1.712 0%。研究还发现,北方和南方主产区农业劳动力转移影响粮食生产韧性水平存在明显异质性,北方主产区的提升作用更为显著。因此,进一步引导农业劳动力非农转移推动区域粮食生产韧性水平提升,是新时期保障我国粮食安全的有效途径。

广交会展馆四期扩建工程展厅转换层结构选型及设计若干问题分析

广交会展馆四期扩建工程项目包含展厅及其他功能建筑单体。其中,展厅设缝分为四个分区结构单体,各单体结构平面尺寸均为207m×90m,地上2层、地下1层,主体结构采用钢筋混凝土框架结构,屋盖采用带预应力的倒三角形立体桁架。展厅与地铁28号线隧道、市政隧道(双塔路隧道、会展西路隧道)相互交叉重叠。综合分析地铁线隧道、双塔路隧道多重避让条件、与展厅相对位置关系以及展厅上部使用荷载大等因素,提出交叉重叠区域共建展厅转换层及双塔路隧道结构方案,共建区横跨地铁线隧道以转换展厅上部框架柱。通过对转换层不同结构类型、不同梁截面形式进行比较,以确定最优选型方案,并对整体结构及关键节点进行分析。提出隧道施工盖挖逆作法,针对传统中间桩柱节点存在的弊端,提出利于现场施工、质量保障的改进方案。

国家重点生态功能区转移支付与基本公共服务供给——来自中国县域的证据

国家重点生态功能区转移支付对提高基本公共服务供给至关重要。文章基于2000—2021年中国县域面板数据,采用双重差分法评估国家重点生态功能区转移支付对基本公共服务供给的影响及作用机制。结果表明:国家重点生态功能区转移支付能有效提升县域基本公共服务供给水平,且政策实施时间越久,促进效应越强;机制分析发现,产业结构升级和技术创新能显著提升县域基本公共服务供给水平,而财政自给率和经济集聚水平起负向调节作用;异质性分析表明,国家重点生态功能区转移支付对县域基本公共服务供给的影响在中国西部和高人口规模的样本中更为显著,且该政策具有促进邻近县域基本公共服务供给的空间溢出效应。

文化整体性视角下北岳的移祀及两山的景观关联性探究

北岳,作为中国古代北方疆域的地理坐标,文化地位显赫且移祀历史独特。为研究北岳的历史演变历程,通过历史文献收集、舆图考证及实地调研的研究方法,考证了自五代至清,古北岳岳庙下移、浑源北岳说萌芽、古今北岳封祀并存等驱动北岳移祀的转折性事件。研究发现,在文化整体性视角下,北岳的移祀受到疆域格局扩张、王朝地理推动、军事信仰转移等制度文化影响,亦受到北岳恒山地区农业经济发展的影响,以及精神文化层面社会情绪的助力。北岳的移祀受到官方和民众的共同推动,体现了北岳在宏观人文构想下地理空间与国家秩序空间中定位的演变,催生了具有关联性特征的自然人文景观。文化整体性视角下,北岳作为一个文化符号,不仅整合了移祀前后两山具有历时性特征的风景表征,更因移祀所映射的北岳文化推动着风景名胜的保护与传承。

1985-2020年中国“两屏三带”生态屏障区土地利用时空动态演化特征

[目的]探索“两屏三带”生态屏障区土地利用时空动态演化特征,揭示其分异规律,为研究区土地资源整合和筑牢国家生态安全屏障提供依据。[方法]基于“两屏三带”生态屏障区1985—2020年内8期土地利用数据,采用单一土地利用动态度、综合土地利用动态度及转移矩阵等方法,从土地利用结构、动态度和空间转移3个方面全面分析了土地利用变化的时空动态演化特征及分异规律。[结果](1)1985—2020年“两屏三带”生态屏障区除北方防沙带草地面积增加20618.03 km^(2)外,其他四大屏障区均有所减少,其中东北森林带草地面积减少最多,为18031.03 km^(2);五大生态屏障区建设用地面积均有所增加,北方防沙带增加面积最多,为7280.79 km^(2);东北森林带生态用地显著减少、非生态用地显著增加,这与生态屏障区的发展要求相违背。(2)1985—2020年“两屏三带”生态屏障区中南方丘陵山地带土地利用类型变化速率最高(平均综合动态度为24.27%),变化速率差异最大(综合动态度极差为31.23%);除东北森林带综合土地利用动态度下降外,其他屏障区均呈上升状态。(3)1985—2020年“两屏三带”生态屏障区土地利用转化程度都有所增强,其中增强较为显著的为川滇—黄土高原屏障和北方防沙带,分别上升3.89%,3.82%。各屏障区主要转化地类为耕地和草地,未利用地在北方防沙带和青藏高原生态屏障转化中也占有较大比例。[结论]1985—2020年“两屏三带”生态屏障区土地利用呈不均衡演化特征,应因地制宜进行土地利用规划与管理,进一步筑牢国家生态安全屏障。

卧式套管潜热蓄热单元偏心与肋片结构优化模拟

利用偏心布置增强相变蓄热单元内部自然对流是提高相变蓄热系统性能的新思路,为了更深入地研究偏心布置对相变蓄热系统性能的影响,基于焓-孔隙率法建立了卧式套管相变蓄热单元的三维数学模型,并利用Fluent软件对环形空间相变材料熔化过程进行数值模拟,通过对熔化过程流场、液相率及温度云图的分析,将熔化过程划分为三个阶段:导热主导的初始阶段,随后是自然对流和导热的混合作用的阶段,以及导热再次占主导地位的最终阶段,并将相变材料环形空间划分为两个区域,据此提出新的评价参数“偏心面积比”。结果表明:硬脂酸作为相变材料时较佳的偏心面积比位于16∶1附近,熔化时间相对于同心布置缩短了45.8%,但同时会使蓄热单元㶲效率略有降低,并且预测对于其他材料,预期的最佳偏心面积比与使用材料的自然对流强度和导热能力之间的比值有直接相关。利用偏心结构与肋片结合的方法进一步强化传热,比较了螺旋肋、十字肋和X形肋三种肋片,发现X形肋具有较佳性能,与相应偏心无肋结构相比熔化时间缩短了36.7%,比螺旋肋和十字肋结构分别缩短了20.3%和7.1%。

湍流图像退化中的模糊与畸变

基于光线传播以及相位叠加原理,构建了湍流图像退化模型,获得了湍流下目标对应的点扩散函数,并通过调制传递函数面积以及等晕角验证了仿真模型。同时,通过平均相关系数定义了像方近似不变区域,像方近似不变区域有助于对点扩散函数变化程度的理解。通过光线在湍流中的传播过程,猜测图像退化的模糊与畸变的程度和湍流的分布有关。为验证以上猜测,设置了两种极端情况下的湍流分布情形进行仿真实验,并通过调制传递函数面积以及像方近似不变区域对仿真结果进行分析。结果表明在同等湍流强度情况下,靠近镜头端的湍流会对图像造成更多的模糊效应,靠近物体端的湍流会对图像造成更多的畸变效应。基于此,解释了在湍流图像退化模型中采用先畸变后模糊是更为合理的操作,并建议湍流复原算法应根据退化结果中的模糊与畸变的程度采取相应的复原措施。

入侵植物薇甘菊在贵州的潜在适生区及其变化趋势

【目的】薇甘菊是一种危害性极大的外来入侵植物,2016—2022年间,多次在贵州省发现其入侵种群。预测薇甘菊在贵州的潜在适生区及其变化规律,可对贵州薇甘菊防控体系建设提供依据。【方法】在全球筛选薇甘菊分布点1001个,结合22个环境因子数据,采用最大熵模型(MaxEnt)预测当前及未来气候条件下薇甘菊在贵州的潜在分布情况,并进行主导因子分析。【结果】当前气候条件下,薇甘菊在贵州的高适生区面积为1.51万km 2,占全省面积的8.60%,主要位于黔西南州和黔南州;在未来气候条件下,薇甘菊在贵州的适生区呈扩增状态,适生区分布中心坐标(26.43°N,107.00°E)由黔南州向贵阳市转移;影响薇甘菊适生范围的主导因子是年平均温度、昼夜温差平均值、温度季节性变化、最冷月份最低温、年降水量和最热季平均降水量。【结论】薇甘菊在贵州的适生区范围广,温度和降水是主要影响因素。在未来气候条件下,薇甘菊在贵州的适生区呈扩增状态,整体向北迁移扩散的趋势明显。

基于迁移学习的高速公路交织区车辆轨迹预测

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