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关键词： 工程支配网络   结构洞理论   k-shell算法   项目排序  

摘要： 复杂工程包含的项目众多,对项目的重要性进行综合排序,是工程实际决策亟须解决的问题。然而,现有方法忽略了项目之间的联系且分析视角单一,导致排序结果区分度不高。为此,基于复杂工程支配网络,提出结构洞理论视角下的综合项目排序方法。首先,引入结构洞理论,构建项目影响广泛性的度量模型。其次,利用k-shell算法对项目中心度进行重要性评价及层级划分,构建项目的全局重要度评价模型。在此基础上,融合结构洞理论与k-shell算法,提出项目重要性综合排序方法。最后,将该方法应用于算例网络和实际工程,并与其他方法进行了对比分析。结果显示,提出的项目排序方法具有更高的区分度,能够适应项目评价的多维度要求,为复杂工程的决策提供了参考。

关键词： 高职   护理专业   学生   手机成瘾  

摘要： 目的探讨综合干预方案对大学生手机成瘾的影响。方法于2024年4月选取自愿参与研究的84名高职护生为研究对象并随机分组。对照组不接受任何干预,实验组接受以抗战题材纪实文学阅读为主的综合干预,比较两组手机成瘾及焦虑、抑郁、压力情况。结果干预后实验组护生手机成瘾指数量表总分及失控性、逃避性维度得分,焦虑、压力量表得分与对照组相比差异有统计学意义(P<0.05)。结论综合干预方案能改善高职护生手机成瘾情况,有利于高职护生身心健康发展。

关键词： 良性前列腺增生   前列舒通胶囊   经尿道前列腺等离子体双极电切术   尿动力学  

摘要： 目的观察前列舒通胶囊对良性前列腺增生(BPH)患者经尿道前列腺等离子体双极电切术(TUPKP)术后国际前列腺症状评分(IPSS)及尿动力学指标的影响。方法选择2021年6月—2023年1月丰城市人民医院收治的BPH患者80例,采用随机数字表法分为观察组和对照组各40例。2组均接受TUPKP治疗,对照组术后采用盐酸坦索罗辛缓释胶囊治疗,观察组在对照组基础上加用前列舒通胶囊治疗,2组均治疗1个月。比较2组术前、术后1个月IPSS评分、尿动力学指标、血清炎性因子及生活质量。结果术后1个月,2组IPSS评分较术前降低,且观察组低于对照组(P<0.01);2组膀胱顺应性、逼尿肌压、最大尿流率及血清白介素-10水平较术前升高,尿残余量及血清白介素-8水平较术前降低,且观察组变化幅度大于对照组(P<0.01);2组健康调查量表36中生理职能、躯体疼痛、生理功能、总体健康、活力、社会功能、精神健康、情感职能评分较术前升高,且观察组高于对照组(P<0.01)。结论前列舒通胶囊可缓解BPH患者TUPKP术后临床症状,改善尿动力学指标,降低机体炎性反应程度,提高患者生活质量。

关键词： 混凝土   废弃塑料   粗骨料   抗压强度   耐久性能  

摘要： 研究了聚对苯二甲酸乙二醇酯类塑料(PET)的掺量(0、10%、20%、30%、40%、50%)对C30混凝土抗压强度、抗硫酸盐侵蚀、抗水渗透性能、耐高温性能和抗碳化性能的影响。结果表明:随着PET掺量由10%增至50%,混凝土试件的7、28、56 d抗压强度均降低,硫酸盐侵蚀7、28、56 d后的质量损失率基本降低,7 d、28 d抗压强度耐蚀系数基本降低,56 d抗压强度耐蚀系数基本增大,平均、最大渗水高度均增大,高温残余抗压强度基本降低,平均、最大碳化深度基本降低。尽管PET的掺入降低了混凝土的力学和耐久性能,但在10%~30%掺量下,试件的28 d抗压强度仍满足C30设计强度等级要求。

关键词： 扎根理论   持续观看意愿   感知有用性   《观察者网》   媒介接触  

摘要： 自2016年《观察者网》入驻B站以来,逐渐获得了B站青年学生的喜爱与关注,根据“火烧云”数据,18—24岁的青年学生是其最主要的粉丝群体。在此情况下,研究影响青年学生持续选择B站《观察者网》的因素是有益的。本次研究使用扎根理论,利用Nvivo软件对15名受访者形成的原始数据文本进行概念化、范畴化,得出了影响青年学生持续选择B站《观察者网》的3种因素,即讲解员特质、感知有用性、视频特质,通过梳理故事线,最终得出了“接触—讲解员特质—媒介特质—感知有用性—意愿”的模型。

关键词： Bending strength  

摘要： The use of steel fibers and recycled rubber aggregate to prepare concrete can achieve the utilization of solid waste resources and ensure its good mechanical properties. In this paper, the flexural performance evolution of steel fiber reinforced rubber concrete (SFRRC) under the extreme conditions of ultra-low temperature (up to −196℃) was investigated, and seven groups of beam specimens with different ratios of steel fiber reinforced rubber concrete were designed to carry out four-point bending tests after low-temperature deep-cooling treatment to analyze the effect of ultra-low temperature on the flexural properties of SFRRC. It is demonstrated that with the increase of steel fiber and rubber volume admixture, the flexural strength of SFRRC is significantly increased at room temperature. As the temperature decreases, the bending and tensile strength of SFRRC is significantly improved, and when the temperature decreases to −196℃, its bending strength can be improved by 151.6%. Meanwhile the SFRRC toughness decreases in the ultra-low temperature environments. The research results provide support for the optimal design of SFRRC and its application in ultra-low temperature engineering. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Microhardness  

摘要： Objective Austenitic stainless steel is widely utilized in modern manufacturing due to its excellent corrosion resistance and ease of processing. However, it exhibits relatively low deformation resistance and poor hardness as well as wear resistance. Inconel 718, an alloy with superior mechanical properties and excellent corrosion resistance, is employed in laser directional energy deposition (LDED) to enable additive manufacturing of dissimilar metals. To improve the connection process and quality of the two materials as well as expand the application of LDED for joining Inconel 718 alloy with 304 stainless steel, it is essential to investigate the influence of the laser deposition thermal cycle on the microstructure evolution of Inconel 718/304 connectors. This study also seeks to clarify the changes in mechanical properties resulting from the microstructure evolution. Methods 304 stainless steel was selected as the substrate, and Inconel 718 alloy powder (particle size: 53‒150 μm) was used as the cladding deposition material. The laser heat source was generated using an IPG-YLS-6000 fiber laser (maximum power: 6 kW, wavelength: 1070 nm, spot diameter: 3 mm), with a volume fraction of 99.99% argon as the shielding gas. A reciprocating layer-by-layer deposition process model was constructed using the KUKA industrial robot KRL programming system. The thermal cycle temperature of the deposited parts was dynamically monitored using an infrared pyrometer. Specimens were prepared via wire cutting, and their microstructure, composition, microhardness, and tensile property were analyzed using a scanning electron microscope, X-ray diffractometer, microhardness tester, and universal testing machine to explore the effects of thermal cycling temperature on the mechanical properties of the components. Results and Discussions Inconel 718/304 connectors were successfully fabricated using LDED technology, and their microstructure and mechanical properties were analyzed. The resul

关键词： Titanium dioxide  

摘要： The multi-walled carbon nanotubes (MWCNTs) and anatase nano-titanium dioxide (NT) are excellent fillers for the preparation of self-sensing cement-based materials. Moreover, compared with ordinary Portland cement, sulfoaluminate cement has the advantages of low carbon, corrosion resistance and rapid strength development, and the cement-based material can obtain more stable self-sensing performance when used as a matrix. Therefore, this paper prepared sulfoaluminate cement mortar specimens using NT and MWCNTs in either single-addition or double-addition form. Then, the effects of different conductive fillers on the mechanical properties, electrical properties and self-sensing properties of the sulfoaluminate cementitious composites were studied at 3 d curing, and the mechanisms were analyzed by SEM-EDS. The results show that the early mechanical properties of sulphoaluminate cementitious composites were significantly improved by adding NT. Compared to the control group, the compressive strength, flexural strength, splitting tensile strength, and compressive toughness of the cementitious composites with NT increased by 28.36%, 10.67%, 47.76%, and 9.53%, respectively. The single-addition of MWCNTs has the most significant effect on improving the conductivity. Compared with the control group, the direct current (DC) resistivity and alternating current (AC) resistivity at a frequency of 100 kHz decreased by 46.91% and 63.87%, respectively. The double-addition of MWCNTs-NT has the most significant effect on improving the self-sensing properties of the sulfoaluminate cementitious composites. Compared with the control group, the maximum fractional change in resistivity, stress and strain sensitivity of the sulfoaluminate cementitious composites with MWCNTs-NT under monotonic compression load and splitting tensile load increased by 235%, 211%, 313%, and 44%, 65%, 648%, respectively. SEM-EDS showed that in terms of compactness, the mortar with NT> control group> mortar with M

关键词： Foundry sand  

摘要： To investigate the influence of different sizes of ettringite on the early strength performance of foundry sand, various sizes of ettringite (AFt-0, AFt-1, and AFt-2) were first prepared using different dispersants. The prepared series of AFt were characterized by FTIR, XRD, and SEM. Comparative analyses were conducted on the mechanical properties, microscopic morphology, hydration heat of cement, and setting time of foundry sand using different analytical methods to assess the effects of various sizes of ettringite on the foundry sand. The results show that adding dispersants could control the size of ettringite and improve its suspension stability in solution. The addition of ettringite of different sizes could enhance the early compressive strength of foundry sand, with a greater increase observed as the size of ettringite decreases. Specifically, incorporating AFt-2 into the foundry sand increases the compressive strength by 225% compared to the blank sample at the same age, approaching the compressive strength of the blank sample at 1 d. Microscopic structural analysis of the foundry sand also reveals that with decreasing ettringite size, the early formation of ettringite in the foundry sand increases, which facilitates the formation of an early skeleton system in the foundry sand. Hydration heat analysis further indicates that as the size of ettringite decreases, the rate of cement hydration accelerates, leading to a shorter cement setting time. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.

关键词： Hydrogen storage  

摘要： Type IV hydrogen storage vessels have become one of the most promising vehicle energy storage equipment, while during the rapid filling process and service life, the hydrogen storage vessel suffers the significant temperature rise effects or environmental temperature change. To improve the safety and reliability of type IV hydrogen storage vessels, it is of great significance to investigate the burst failure behavior under such operating conditions. In this work, the steady-state heat transfer model, micromechanics model, and thermal-mechanical coupling model were established based on the micromechanics of failure theory. And a multiscale burst failure analytical method was developed to study the influence of temperature at the range of 25℃ to 85℃ on burst failure behavior. The results show that, fiber damage is the main cause of the burst failure of the type IV hydrogen storage vessel, and the predicted burst pressure and failure location agree with the experimental result well. As the temperature rises, thermal compressive stress generated by non-uniform temperature distribution and thermal expansion, partially offsets the tensile stress generated by the pressure, and slows down the development of the constituent damage. And the strength of the composite winding layer decreases, leading to a decrease in the burst pressure of the vessel. When the temperature of the outer or inner wall surface rises from room temperature to 85℃, the pressure of the initial fiber damage decreases by 27.5% and 12.1%, and the burst pressure decreases by 12.5% and 4.6%, respectively. © 2025 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.