Numerical investigation on the cluster effect of an array of axial flow fans for air-cooled condensers in a power plant

The aerodynamic behavior of tens of axial flow fans incorporated with air-cooled condensers in a power plant is different from that of an individual fan.Investigation of the aerodynamic characteristics of axial flow fan array benefits its design optimization and running regulation.Based on a representative 2600 MW direct-dry cooling power plant,the flow rate of each fan and the overall flow rate of the fan array are obtained in the absence of ambient wind and at various wind speeds and directions,using CFD simulation.The cluster factor of each fan and the average cluster factor of the fan array are calculated and analyzed.Results show that the cluster factors are different from each other and that the cluster effect with ambient wind is significantly different from the cluster effect with no wind.The fan at the periphery of the array or upwind of the ambient wind generally has a small cluster factor.The average cluster factor of the array decreases with the increasing wind speeds and also varies widely with wind direction.The cluster effect of the axial flow fan array can be applied to optimize the design and operation of air-cooled condensers in a power plant.

Oxidation Effects on the Electronic Properties of Hydrogenated Silicon Clusters

The geometric and electronic properties of some hydrogenated silicon clusters in the presence of oxygen on the surface have been investigated.The density functional theory with generalized gradient approximation functional was applied in our calculations.By calculating the total energy,the double bond Si=O is shown to be more stable than the bridge bond Si-O-Si for large size oxidized clusters.The results of Mulliken population analysis indicate that a so-called passivation effect is enhanced by oxidization effects.From the energy band structures and density of states,we find that some localized states are induced by the p-orbital of O atom mainly and reduce the energy gaps substantially.

Employment Effect of the Resource-abundant Industrial Cluster in Southwestern Region of Guangxi Zhuang Autonomous Region of China——A Case of Chongzuo City

Taking Chongzuo City of Guangxi Zhuang Autonomous Region as an example, the employment effect of the resource-abundant industrial cluster in southwestern Guangxi Province is analyzed according to the data from the Chongzuo Statistical Yearbook , Guangxi Statistical Yearbook from 2003 to 2008 and the data from the relevant sections of Chongzuo City, and the four employment effects of industrial cluster--the spatial expansion effect of employment chain, optimizing effect of employment structure, the multiplier effect of employment absorption and the effect of improving the quality of labors and the degree of the intensity of employment and location quotient of employment. Results show that the employment absorption of sugar industry in Chongzuo City is stable and upward slightly, and it shows strong employment effect; the sugar industry in Chongzuo is not only competitive, but also has a great share of market in employment, so it owns strong absorption of employment. The countermeasures for improving the employment level of resource-abundant and industrial cluster in southwest of Guangxi Province are put forward, including elongating industrial chain and widening employment space; strengthening various kinds of formal and informal training to improve the employment capability of laborers; laying stress on industrial structure and optimizing the employment structure; strengthening the construction of the industrial economic zone towards ASEAN(Association of Southeast Asian Nations), and fully displaying the regional advantages of the offshore border.

Synthesis, Structural Characterization and Magnetocaloric Effect of a Butterfly [CoⅡ2GdⅢ2] Cluster

2-（2,3-Dihydroxpropyliminomethyl）6-methoxyphenol（H3L）, trimethylacetic acid（Hpiv）, Gd（NO3）3·6 H2O and Co（NO3）2·6 H2O were reacted in Me OH to obtain a heterometallic tetranuclear cluster [Gd2Co2（L）2（μ3-OH）2（piv）6]·2 Hpiv·2 CH3OH（1）. X-ray crystallographic analysis reveals that compound 1 was found to be a butterfly heterometallic tetranuclear cluster. The crystal(C64H108Co2Gd2N2O28, Mr = 1785.88) belongs to the triclinic crystal system, space group P1 with a =11.9798（6）, b = 12.0877（5）, c = 15.0367（7） ?, α = 67.320（4）°, β = 81.583（4）°, γ = 75.201（4）°, V =1939.62（18） ?3, Z = 1, T = 293.15 K, R = 0.048 and w R = 0.144 for 16299 observed reflections with I > 2σ（I）. In magnetization study, heterometallic 1 exhibits magnetocaloric effect（MCE） of 14.75 J·kg-1·K-1 at 2 K for ΔH = 5 T, while it does not show non-linear response of the ac-susceptibilities.

AN EFFECTIVE ORGANO-BIMETALLIC Rh-Co CLUSTER CATALYST FOR HYDROFORMYLATION

s: RhCo3(CO) 12/Sio2 aller decarbonylated is regenerable under CO, and catalyzes ethylene hydrofornlylation with high activity and stability.

STRUCTURE EFFECTS OF SILICON AND CARBON BY CLUSTER MASS SPECTRA

Microclusters from different structures of silicon and carbon are studied by SIMS under UHV conditions in the mass range below M=200. The sputtered mass spectra of ions Sin+, Cn+ and Cn were obtained from the 10 keV O2+ primary beam bombardment. Comparisons of each spectrum in each group have shown the strong structure effects on the cluster patterns. A brief discussion on the results has been given.

Electronic Structure Effect on Model Cluster for L1_2 Structure of Al_3Ti Intermetallic Compound with an Addition of Alloying Elements Fe, Ni and Cu

By use of self-consistent field Xα scattered-wave (SCF-Xα-SW) method, the electronic structure was calculated for four models of Ti4Al14X (X=Al, Fe, Ni and Cu) clusters. The Ti4Al14X cluster was developed based on L12 Al3Ti-base intermetallic compound. The results are presented using the density of states (DOS) and one-electron properties, such as relative binding tendency between the atom and the model cluster, and hybrid bonding tendency between the alloying element and the host atoms. By comparing the four models of Ti4Al14X cluster, the effect of the Fe, Ni or Cu atom on the physical properties of Al3Ti-based L12 intermetallic compounds is analyzed. The results indicate that the addition of the Fe, Ni or Cu atom intensifies the relative binding tendency between Ti atom and Ti4Al14X cluster. It was found that the Fermi level (EF) lies in a maximum in the DOS for Ti4Al14Al cluster; on the contrary, the EF comes near a minimum tn the DOS for Ti4Al14X (X=Fe, Ni and Cu) cluster. Thus the L12 crystal structure for binary Al3Ti alloy is unstable, and the addition of the Fe, Ni or Cu atom to Al3Ti is benefical to stabilize L12 crystal structure. The calculation also shows that the Fe, Ni or Cu atom strengthens the hybrid bonding tendency between the central atom and the host atoms for Ti4Al14X cluster and thereby may lead to the constriction of the lattice of Al3Ti-base intermetallic compounds.

Vicinage Effects for a Nitrogen Molecular Cluster in Plasmas

The vicinage effects are studied for a fast nitrogen diatomic molecular cluster in a high-density plasma target.A variety of plasma parameters are discussed with regard to stopping power ratio,molecular axis deflection and Coulomb explosion.Emphasis is placed on the vicinage effects on Coulomb explosion and stopping power for a nitrogen cluster in plasmas.The results indicate that vicinage effects influence the correlation between ions in the cluster,and the Coulomb explosion will proceed faster with higher projectile speed,lower plasma density and higher plasma temperature.Comparing hydrogen and nitrogen molecular ions for Coulomb explosion and deflection angle under the same set of parameters,one can find that the nitrogen ion has faster Coulomb explosion and stronger deflection of molecular axis due to the contribution of charge.In the initial stage of the Coulomb explosion the stopping power ratio has a higher value due to enhanced vicinage effects while in the later stage the stopping power ratio approaches one,indicating that the vicinage effects disappear and the ions in the cluster simply behave as independent atomic ions in the plasma.

Method for Evaluating the Influence of Obstruction of Sea Breeze by Clusters of High-Rise Buildings on the Urban Heat Island Effect

This study aims to propose a method for quantitatively evaluating the influence which the obstruction of sea breezes by clusters of high-rise buildings has on the urban heat island effect using a weather simulation model and Geographic Information Systems (GIS). Specifically, a method of evaluating the influence of the obstruction of sea breeze by high-rise buildings on the urban heat island effect was proposed. In the method, two scenarios that imagine urban forms which differ with regard to whether or not they contain high-rise buildings are created and weather simulation is conducted, and the results of the simulations are comparatively analyzed focusing on temperature and wind speed. Evaluation was conducted in two stages, and Shiodome of Minato City in the Tokyo Metropolis was selected as the region for evaluation. In two stages of evaluation, a rise in temperature of approximately 0.3 K and a reduction in wind speed of approximately 1 m/s were observed in a region approximately five to ten kilometers square downwind of high-rise buildings in the period 6 PM to 9 PM, and a higher temperature caused by the obstruction of sea breeze by high-rise buildings was identified. The fact that such a higher temperature was confirmed in the time period from 6 PM onwards, in which the temperature decreases, reveals that obstruction of sea breeze by high-rise buildings dulls the decrease in temperature which occurs from evening onwards, and influences nighttime urban heat island formation.

集束化干预措施在防控新兵训练伤发生中的效果分析

目的 分析集束化干预措施对训练伤防控的效果。方法 以2022年2566名新兵为研究对象,分为试验组1384人,对照组1182人。对照组新兵采用常规训练法,试验组新兵在此基础上采用集束化干预措施。比较干预前后两组新兵体质量指数(body mass index,BMI)、左室射血分数(left ventricular ejection fraction,LVEF)、用力肺活量(forced vital capacity,FVC)、骨密度、训练伤发生率、结业考试成绩的差异。结果 干预后,试验组新兵异常指标BMI、LVEF、FVC、骨密度的异常情况较干预前明显改善(P<0.05);对照组新兵异常指标BMI、LVEF、FVC、骨密度第二次体检情况较第一次体检差异无统计学意义(P>0.05)。第二次心理测评试验组新兵阳性人员比例明显低于对照组(P<0.05)。两组新兵结业考试成绩进行比较,试验组新兵3公里、03式自动步枪精度射击、战术基础动作、双杠杠端臂屈伸优秀比例,03式自动步枪精度射击、战术基础动作合格比例均高于对照组(P均<0.05)。试验组新兵训练伤的发生率低于对照组(P<0.001)。结论 基于集束化措施构建的训练伤干预体系,能够有效防控新兵训练伤的发生。

考虑速度聚束效应的SAR海浪成像仿真方法

针对合成孔径雷达(SAR)海浪成像仿真技术对于速度聚束效应的考虑不充分,仿真数据无法准确反映实际SAR数据的问题,建立一种充分考虑速度聚束效应的SAR海浪成像仿真方法并进行了实验验证。计算了SAR图像强度的概率密度分布的仿真结果与理论结果之间的均方误差(MSE),在风速分别为5、10和15 m/s时,考虑速度聚束效应前、后比对结果的MSE分别为0.1012、0.1576、0.0556与0.0179、0.0314、0.0088。仿真结果表明,所提SAR海浪成像仿真方法有效提高了仿真数据的准确性,对SAR海浪成像的应用具有一定实用价值。

基于混合粒子群算法的波浪能发电集群优化方法

对波浪能发电集群的优化控制有助于波浪能的有效利用,为此文章提出了基于混合粒子群算法的波浪能发电集群优化方法。以直驱式发电装置为研究对象,探讨其构成发电集群短期尺度下稳定状态的数学模型,由简至繁依次考虑波浪动态压力、装置间辐射影响和遮挡效应,以便更准确地模拟一定密集度的波浪能发电装置部署下的实际效果。以集群功率最大化为优化目标,根据装置运动和海域能量约束,提出混合粒子群算法求解集群的最优参数,在传统算法基础上设定自适应惯性权重并加入交叉和变异操作,以应对复杂集群方程解空间的多峰性问题。算例结果验证了所述集群优化方法的有效性,求解质量良好;同时表明波浪能发电集群规模越大,装置之间的辐射影响越复杂,遮挡效应越明显。

基于层次聚类分场景的光伏汇聚趋势量化方法

持续功率曲线能反映长时间波动特性规律,通过研究已建设光伏集群持续功率曲线,建立预测模型揭示不同规模集群的汇聚演化规律,最终得到待建光伏集群的持续功率曲线。首先,利用层次聚类算法确定光伏集群汇聚规模的分层顺序,得到装机容量逐层递增的光伏集群,并提出汇聚效应指标验证顺序的有效性;其次,为了更好地判断和预测光伏持续功率曲线的变化趋势,对持续功率曲线进行出力场景划分;最后,为避免单一模型预测偏差,在各出力场景下,通过改进的信息熵组合预测模型掌握汇聚过程中规模演变规律,完成规划待建设集群持续功率曲线的预测。利用河北某地区实测数据仿真结果表明:验证聚类方法得到的集群分层顺序更能体现汇聚效应,并有效提高预测精度;出力场景划分准确刻画集群持续功率曲线汇聚趋势;通过模型对比表明分场景下改进信息熵组合预测模型更能精确完成待建光伏集群持续功率特性的量化分析。

基于深圳市多起校园聚集性疫情的2剂次水痘疫苗保护效果分析

目的 评估校园水痘聚集性疫情现场2剂次水痘疫苗免疫程序的保护作用,为水痘的防控提供参考。方法 以2020-2022年深圳市盐田区报告水痘聚集性疫情的学校为调查现场,按照回顾性队列研究的方法分析水痘疫苗接种情况与水痘发病的关系。对不同规模的疫情进行异质性检验,计算2剂次水痘疫苗相对保护效果(relative vaccine effectiveness, rVE)的合并效应量。结果 共纳入校园水痘聚集性疫情12起,其中中学1起,小学9起,幼儿园2起,疫情规模为4~19例/起。水痘病例共124例,水痘罹患率为8.60%,其中突破病例占58.87%。1剂次水痘疫苗接种率为52.08%,2剂次接种率为30.31%,1剂次突破感染率(8.66%)高于2剂次(1.83%),差异有统计学意义(χ^(2)=22.309,P<0.001)。异质性检验结果显示,不同校园疫情的水痘疫苗保护效果无异质性(χ^(2)=2.403,P=0.998;I2=0.007%)。采用固定效应模型,以接种1剂次水痘疫苗为参照组,接种2剂次疫苗rVE的合并效应量73.75%(95%CI:50.30%~86.13%)。亚组分析,2剂次水痘疫苗接种0~<3年、3~<6年和≥6年的rVE呈下降趋势,分别为81.48%、71.62%和67.13%。结论 接种2剂次水痘疫苗的保护效果优于1剂次,可有效降低校园水痘聚集性疫情中学生感染水痘的风险。

甘肃省科技宣传动态实践与服务路径研究

科技宣传是推进科技创新、提升科学普及、支撑实施科技自立自强的重要“软要素”。文章以甘肃省科技宣传在科技创新事业中的动态实践与服务路径为研究内容,基于部分中央驻甘肃媒体、甘肃高校、科研院所等实地调研为主体,分析甘肃省科技宣传基本情况和运行机制,对比宣传矩阵优势及短板,梳理问题并提出解决思路,为进一步完善甘肃省科技宣传布局和融媒体平台体系建设,实施“强科技”行动提供舆论保障和发展参考。

聚组训练研究前沿:结构类型、训练效应与作用机理

聚组训练作为抗阻训练的一种新型组织方式,已引起理论与实践界深入关注,但有关聚组训练的结构类型、理论基础、与传统抗阻训练的效果差异及其作用机理等都有待开展深入细致的研究。现有研究表明:聚组训练主要包括组内间歇结构、重复间休息式结构、组间休息重分配结构、休息暂停结构和等比休息结构5种;不论是在急性还是长期训练效应上,与传统抗阻训练相比,其在爆发力、肌肉力量、肌肉耐力和动作速度保持等方面的积极效应相对明显;其效应机理主要与聚组训练结构方式所导致的能量消耗与恢复过程变化、神经—肌肉疲劳与恢复效果改变,练习过程中动作机械性能的改善以及主观疲劳感明显下降等有直接关系。

集束化护理在体外膜肺氧合联合俯卧位通气治疗患者中应用效果观察

目的:观察体外膜肺氧合(ECMO)联合俯卧位通气患者开展集束化护理的临床效果。方法:2021年3月—2023年3月,选取商丘市第一人民医院重症医学科接收的ECMO与俯卧位通气联合治疗患者82例,采用随机数字表法将其分为对照组(n=41)和研究组(n=41)。对照组:给予患者常规护理;研究组:在常规护理基础上给予患者集束化护理。观察两组患者生理指标及不良事件发生情况。结果:护理后,研究组患者脉搏血氧饱和度水平较对照组高,而呼气末二氧化碳分压、动脉血pH值则较对照组低,差异有统计学意义(P<0.05);研究组不良事件发生率较对照组低,差异有统计学意义(P<0.05)。结论:对ECMO联合俯卧位通气治疗患者开展集束化护理,可促进患者生理指标改善,减少不良事件的发生。

长三角城市群FDI、技术创新与先进制造业集群发展

FDI和技术创新是长三角城市群先进制造业集群发展的重要影响因素。文章基于2010—2021年长三角城市群26个城市面板数据,分析FDI对先进制造业集群发展的直接作用机制以及技术创新在FDI与先进制造业集群发展之间的中介作用机制,并运用面板回归模型和中介效应模型检验理论假设。研究结果表明:长三角城市群FDI对先进制造业集群发展具有显著的正向作用,其作用机制主要表现为促进集群网络化、产业链优化和劳动力流动;技术创新在FDI与先进制造业集群发展之间具有显著的中介作用。根据研究结论提出长三角城市群促进FDI高质量发展、提高先进制造业集群的科技创新能力、加强FDI与技术创新的协同效应等政策建议。

基于用电数据的潍坊市工业污染源冬奥会管控效果评估

利用潍坊市安装用电监控的工业企业在冬奥会前和会中的生产用电数据及部分企业大气污染物排放在线监测数据,分析企业生产用电量和排放量的变化特征及潜在的相关性,评估管控措施落实状况及减排效果。结果表明:管控期间,潍坊市工业企业用电量相比管控前平均下降57.96%;完全停产类企业用电量下降75%以上,大气污染物(SO_(2)、NO_(x)、烟粉尘)排放量下降100%;限产类企业用电量降幅呈现随管控措施加严而增大的趋势;延迟复产类企业延迟复产率为47.83%~96.00%,用电量下降50.76%。根据管控期间各行业企业的用电量变化状况,判定各企业基本落实了减排要求。可见,企业用电数据在一定情况下,可以替代或辅助工业企业排放数据,反映企业管控措施落实状况及减排效果。

腹腔镜胆囊切除效费比聚类分析及其人工智能机器学习预测模型构建

目的探讨腹腔镜胆囊切除手术的效费比,并通过聚类分析及人工智能机器学习方法构建预测模型。方法回顾性分析中山市人民医院腹腔镜胆囊切除术206例患者的临床资料。将患者住院总费用、总住院时间、住院至手术时间、术后住院时间、术前止痛药物应用次数、术后止痛药物应用次数等维度作为效费比指标进行聚类分析分类指标,分为三类,效费比优、中、差;以CT炎症情况、CT病灶情况、CT病灶部位、病理诊断、CA19-9、AFP、术前血糖、ALB、AST、ALT、PLT、HBG、RBC、WBC、CT距手术时间、伤口疼痛程度、手术时间、术前血压、CT病灶大小、住院至手术时间、术前禁食时间等指标作为变量,进行多分类logistic回归分析及机器学习进行预测模型构建,包括逻辑回归、线性支持向量机、支持向量机、决策树、随机森林、K近邻等分类器进行模型拟合。结果多分类logistic回归分析显示模型拟合卡方值为156.986,P<0.001,似然比ALB、WBC、CT距手术时间、住院至手术时间、高血压、肾脏疾病、手术人员差异有统计学意义,P值分别为0.001、0.019、0.029、<0.001、0.005、0.027、<0.001,模型拟合分类总符合率为74.8%(即准确率为0.748)。多层感知机模型K折验证评分0.461,预测评分0.802;逻辑回归模型K折验证评分0.437,预测评分0.726;支持向量机模型K折验证评分0.529,预测评分0.755;决策树模型K折验证评分0.462,预测评分0.585;随机森林模型K折验证评分0.529,预测评分0.726;K近邻模型K折验证评分0.388,预测评分0.623。结论分析腹腔镜胆囊切除手术效费比中,机器学习建模可有效预测效费比指标,可用于术前评估,按效费比优化医疗资源分配。