This paper presents an open-source framework based on unstructured meshes for three-dimensional large-scale parallel topology optimization using PETSc and Eigen, which is easy to use and expand. The framework supports both eight-node hexahedral and four-node tetrahedral meshes and solves the compliance and stress topology optimization problem. The method of moving asymptotes (MMA) is chosen as the optimization solver. The validity of the framework is demonstrated by a classical cantilever beam problem and two more examples of wheel rim and rotator illustrate the expansibility of the framework.

This paper proposes a swarm intelligence based structural topology optimization method on cooling channels. This method employs the swarm intelligence concept to simulate thermal conduction phenomena in solid domain and heat exchange phenomena between fluid and solid domain. Research indicates that for cooling structures with chain-type channels, this method achieves optimization of intervals between channels; for cooling structures exhibiting grid-based channels, this method allows for optimized distribution of flow in different channels. The method was implemented on NetLogo, and the feasibility and accuracy of the simulation model were verified by commercial numerical software. This study show a prominent cost-effectiveness and new approach for topology optimization of internal cooling channels.

Turbine rotors often operate under harsh conditions, such as high rotational speeds and large temperature gradients, that requires them to withstand complex thermal and centrifugal loads. This demands careful design of their internal and external structural configuration to balance the performance and the cost. Using volume as the optimization objective with compliance and stress as the constraints, this paper presents a thermomechanical coupling topology optimization approach for the design of disk-shaft rotating structure. The influences of factors such as the rotational speed, thermal conditions, and central hole on the optimization results are analyzed. The results show that for a disk-shaft rotating body with a central hole, a "waist-like" structure that is characterized by root fusion of thick webs and large holes resists centrifugal loads well. When thermal loads are considered, the optimized configuration becomes more complex, and a "finger-like" structure with a main stem and multiple branches offers an enhanced load-bearing performance. For a disk-shaft rotating body without the central hole, a "palm-like" structure with thick branches exhibits high load-bearing capacity. Additionally, at high rotational speeds, the disk-shaft rotating body without a central hole experiences a lower overall stress than the disk-shaft rotating body with a central hole of the same radial size. For disk-shaft rotating bodies, although the thermal stress constitutes a relatively small proportion of the total stress, it still significantly affects the optimized configurations.

Cotton-moxibustion, also referred to as "thin cotton moxibustion," is a form of direct moxibustion that utilizes heat to eliminate excess heat and dispel stagnant fire, providing therapeutic benefits. It is primarily employed in the treatment of skin conditions, particularly in alleviating symptoms such as itching and pain, and promoting the healing of skin lesions. The procedure is straightforward and well-accepted by patients. This paper reviews recent literature on the application of cotton-moxibustion in treating skin diseases, aiming to standardize its practice and broaden its clinical use. Furthermore, it underscores the importance of preserving traditional principles while fostering innovation to better understand the mechanisms underlying cotton-moxibustion therapy.

Excessive exercise is an etiological factor of intervertebral disc degeneration (IVDD). Engineered extracellular vesicles (EVs) exhibit excellent therapeutic potential for disease-modifying treatments. Herein, we fabricate an exercise self-powered triboelectric-responsive microneedle (MN) assay with the sustainable release of optogenetically engineered EVs for IVDD repair. Mechanically, exercise promotes cytosolic DNA sensing-mediated inflammatory activation in senescent nucleus pulposus (NP) cells (the master cell population for IVD homeostasis maintenance), which accelerates IVDD. TREX1 serves as a crucial nuclease, and disassembly of TRAM1-TREX1 complex disrupts the subcellular localization of TREX1, triggering TREX1-dependent genomic DNA damage during NP cell senescence. Optogenetically engineered EVs deliver TRAM1 protein into senescent NP cells, which effectively reconstructs the elimination function of TREX1. Triboelectric nanogenerator (TENG) harvests mechanical energy and triggers the controllable release of engineered EVs. Notably, an optogenetically engineered EV-based targeting treatment strategy is used for the treatment of IVDD, showing promising clinical potential for the treatment of degeneration-associated disorders.

The design of a thermal cavity receiver and the arrangement of the fluid flow layout within it are critical in the construction of solar parabolic dish collectors, involving the prediction of the thermal–fluid physical field of the receiver and optimization design. However, the thermal–fluid analysis coupled with a heat loss model of the receiver is a non-linear and computationally intensive solving process that incurs high computational costs in the optimization procedure. To address this, we implement a net-based thermal–fluid model that incorporates heat loss analysis to describe the receiver’s flow and heat transfer processes, reducing computational costs. The physical field results of the net-based thermal–fluid model are compared with those of the numerical simulation, enabling us to verify the accuracy of the established thermal–fluid model. Additionally, based on the developed thermal–fluid model, a topology optimization method that employs a genetic algorithm (GA) is developed to design the cavity receiver and its built-in net-based flow channels. Using the established optimization method, single-objective and multi-objective optimization experiments are conducted under inhomogeneous heat flux conditions, with objectives including maximizing temperature uniformity and thermal efficiency, as well as minimizing the pressure drop. The results reveal varying topological characteristics for different optimization objectives. In comparison with the reference design (spiral channel) under the same conditions, the multi-objective optimization results exhibit superior comprehensive performance.

This study aims to propose a hybrid optimization method for cooling channels based on the improved net‐based thermal‐fluid model. The channel topology was optimized through the genetic algorithm (GA), whereas the channel diameter and node position were optimized using the moving asymptote method (MMA). The linear combination of the average temperature and pressure drop was defined as the objective function. Three‐dimensional computational fluid dynamics (CFD) simulations were performed to verify the physical fields of the optimized results. The optimized results indicated that, as the weighting factor (w) for the average temperature increased, the flow distribution was more reasonable and uniform, effectively decreasing the average temperature at the cost of higher pressure drops. In comparison with the optimization entirely based on GA, the hybrid optimization could yield a similar and efficient cooling performance with lower time‐consuming. Moreover, the optimized results obtained under the suitable objective could achieve the better thermal performance at a lower pressure drop in comparison with the conventional serpentine‐shaped channel layout. Finally, the hybrid optimization method used in this article was compared with the conventional density approach, and the former could obtain the clear and complex channel distribution with greatly reduced computational time.

The reasonable arrangement of the fluid flow layout for heat exchange in the thermal cavity receiver of the parabolic dish collector (PDC) is important and the layout of the heat transfer fluid (HTF) is optimized in this article. A thermal-fluid model based on the tube network (hereinafter referred to as “net-based thermal-fluid model”) is adopted to describe the flow and heat transfer process in the receiver. A comparative numerical example is carried out, and the physical field results predicted by the net-based thermal-fluid model under a uniform heat flux are compared with those of the computational fluid dynamics (CFD) simulation to verify the accuracy of the model. Moreover, the former has lower computational cost, which only takes about 1.46 seconds to obtain the physics field. In the optimization example, the inhomogeneous heat flux distribution is applied to the inner surface of the receiver, and the temperature uniformity of the solid region (the standard deviation) is taken as the optimization objective. The genetic algorithm (GA) is used as an optimization algorithm. The optimization results show that the optimized HTF layout improves the temperature uniformity of the heated solid region.

为实现更加先进的拓扑优化算法,研究采用反应扩散方程的水平集结构拓扑优化方法,通过理论推导给出算法中的参数选择建议.该方法允许在拓扑优化过程中生成新的孔洞,初始结构无须包含孔洞,不需要重新初始化步骤,从而可提高算法的收敛性.针对传统拓扑优化中主要采用体积约束、以柔度最小为目标和体积保留率设定存在一定主观性的问题,探究不同体积保留率下的结构应力水平的变化规律,结果显示可以依据结构最大应力水平与体积保留率的变化规律确定最优体积保留率.

汽轮机是火电及核电普遍采用的原动机,在汽轮机运行过程中叶片经常受到固体颗粒物的冲击和冲蚀,严重时可能会影响到汽轮机的安全和经济运行.核电多级汽轮机内颗粒在冲蚀时具有复杂的多次反弹现象,通过数值模拟方法对低压多级汽轮机中固体颗粒物在湿蒸汽环境下的运动、反弹及蒸汽湿度对冲蚀的影响进行了研究,结果表明,颗粒在动静叶之间的反弹所造成的冲蚀现象不可忽视,且主要发生在第一级叶片;速度及粒径越大的颗粒惯性力较大,造成的最大冲蚀量数值虽小但冲蚀区域更大,叶片受到的冲蚀趋于均匀.

文章从新文科建设背景出发,调研国内8所双一流高校档案学专业的本科人才培养方案和教学实践,发现样本高校在本科人才培养的目标定位、课程体系、师资队伍、实践教学平台和评价方式等方面面临创新诉求,进而提出应定位复合型培养目标、优化培养内容、组建复合型师资队伍结构、搭建内外融通的实践教学平台和建立综合评价体系等策略.

股权投资是创业企业获取外部关键资源的重要途径,但是已有研究主要集中在成熟企业,对创业企业股权投资行为的研究相对滞后.由于创业企业小而新的属性,已有基于成熟企业的研究结果难以系统回答创业企业如何通过股权投资实现快速成长.整合已有研究观点,基于资源依赖理论,探讨股权投资与创业企业成长绩效之间的关系,进一步探究企业年龄和研发投入在股权投资与创业企业成长绩效之间的关系中发挥的调节作用.以2013年至2017年新三板软件和信息行业185家挂牌企业为样本,采用Stata 14.0和层次回归分析方法,实证检验股权投资、企业年龄和研发投入与创业企业成长绩效之间的关系.研究结果表明,①由于股权投资能够帮助创业企业与被投资企业建立情感和利益双重纽带,及时获取外部关键资源和信息,发挥先发优势,从而对创业企业成长绩效具有显著的促进作用;②企业年龄负向调节股权投资与创业企业成长绩效之间的关系,即股权投资对创业企业成长绩效的促进作用随着企业成长趋于弱化;③研发投入负向调节股权投资与创业企业成长绩效之间的关系,并且这种负向调节效应随着创业企业成长而增大.在稳健性检验中,上述结果仍然成立.研究发现创业企业通过股权投资获取外部关键资源促进成长具有明显的阶段特征,增进了对于股权投资对企业成长绩效的作用机制及其动态特征的认知,拓展了创业情景下的资源依赖理论.在企业实践中,创业企业在成立初期需要有意识地与外部优质企业或资源达成股权合作,创造先发优势并发挥内外部资源的协同效应,同时在股权合作过程中协调与内部研发投入的关系,逐渐降低对投资对象的依赖,尽量避免同时进行过高的投资.

某大型空冷汽轮发电机转子采用导线双向进风的冷却方式,为研究其端部、轴径向转子槽内冷却空气流量分布及其内、外流场在旋转情况下的特征,本文建立了包括端部弧段和轴径向段转子槽内外流域及与之对应的气隙在内的半轴段1/2圆三维物理模型.依据计算流体动力学原理,采用有限体积法,对计算域内的三维流场进行了数值模拟.结果 表明:转子旋转会影响转子槽内、外的流场特性,并对R区(迎风区)和L区(背风区)导线内流量分布、导线内外流场压力分布及速度分布具有不同程度的影响;在轴径向进风口处的压力范围为(22.10±12) kPa;在端部进风口处压力范围为(22.25±15) kPa;轴径向槽楔出风口处的最高速度为228.2m/s.

Excellent multifunctional polymeric nanocomposite cannot be achieved without good dispersion and well protection of nanofillers, for which a highly efficient, cost-effective and environmental benign nanofiller treatment approach is demanded. Herein, we report that soy protein isolate (SPI), an extracted protein from soybean, is applied as a highly performed bio-surfactant to treat carbon nanotubes (CNTs), resulting in nanocomposite with tremendously improved dispersion, electrical and mechanical properties. TEM, UV-vis and dynamic light scattering (DLS) and real-time optical microscopic characterizations show that, compared with a conventional surfactant, sodium dodecylsulfate (SDS), SPI more effectively and efficiently functionalize CNTs with less agglomerates and more stable particle size distribution. The electrical conductivity of the SPI-CNTs/epoxy increased by 6 orders of magnitude at 0.5 wt% vs pure epoxy, which is 4 orders higher than the pristine CNTs/epoxy and even 1 order higher than that of the SDS treated counterpart. The tensile modulus, strength and fracture toughness of the SPI-CNTs/epoxy increased by 27%, 24% and 32% at 1.0 wt% loading of CNTs, respectively, which is 20%, 26% and 18% higher than the pristine CNTs/epoxy and 10%, 23% and 21% higher than the SDS-CNTs/epoxy. The in-situ tensile test accompanied by digital image correlation technique (DIC) shows that cracks are effectively arrested by the SPI-CNTs while SDS-CNTs cannot. These results establish a solid foundation for the application of SPI in the polymeric nanocomposite fields. (C) 2020 Elsevier Ltd. All rights reserved.

某大型空冷汽轮发电机转子采用导线双侧进风的冷却方式.为了研究轴径向绕组导线数量、中空导线的通流面积差异、导线位置(径向与周向)对导线内流量、进出口温度、进出口温度差、平均温度的影响,建立了包括端部弧段和轴径向段转子槽内外流域及与之对应的气隙在内的半轴段1/2圆三维物理模型.依据计算流体动力学原理,采用有限体积法,对计算域内的三维热流场进行了数值模拟.结果 表明:位于绕组L1、圆周R12的导线具有的最大流量为0.018 9 m3/s;温度最高导线位于绕组T5、圆周R2处,达129.10℃,在电机正常工作范围内;通过方差分析发现径向、周向位置分布对导线平均温度不均性的影响差异较小,而导线通流面积对其的影响较大.

In order to obtain the relationship between fractal dimension and energy dissipation of rock-like materials under initial stress state, a variable cross-section split Hopkinson pressure bar (SHPB) test system with active confining pressure loading device was used to carry out impact compression and splitting tests on cemented sand specimens. The impact test results show that (1) the prediction value on the fragmentation degree of cemented sand specimens by using the fractal model is basically consistent with the screening results of actual test, which verifies the applicability of the fractal calculation model given in this study; (2) the more the fracture energy dissipated in the crushing process of cemented sand specimens, the more serious the fragmentation degree is, and accordingly the larger the fractal dimension is, that is, the fracture energy is positively correlated with the fractal dimension; (3) there is an exponential relationship between the fractal dimension and energy dissipation of cemented sand specimens under initial stress, which is so different from that under no initial stress. The experimental results in this study can be used to modify the fractal damage model for rock blasting considering the initial stress.

分析了对汽轮机末级叶片表面温度进行红外测量的各种影响因素.通过实验的方式,研究在汽轮机真空仓环境和模拟湿蒸汽环境下红外测量的可行性及影响测量精度的因素.真空仓实验表明:宽波段红外测温能较准确地获得叶片表面温度在鼓风效应中的变化过程;湿蒸汽环境下的宽波段红外测温实验表明,膜状液态水对测温结果有显著影响,3层液膜后透过的辐射能量只剩原来的3％左右,液滴态基本无影响.

Herein, a net-based topology optimization approach for cooling channels is presented, which helps to make a balance between power dissipation, thermal stress and temperature limitation in forced internal cooling problems with approximate but fast and low-cost calculations. The topology optimization procedure consists of a discrete based flow and heat coupling analysis, the flow analysis by the improved pipe-net calculation, as well as the genetic algorithm (GA). The channel sizes are used as optimization variables in the GA to achieve optimization in terms of the size and topology structure of the cooling region. Numerical simulation is carried out to validate the proposed model's applicability in topology optimization for cooling channels. A comparative study illustrates that different optimization objectives lead to varying topology features and this approach can obtain a complicated and fine optimization result within a relatively short time. Moreover, the optimization results can significantly reduce the maximum temperature and temperature distribution nonuniformity of the heating surface with a lower pressure drop.

In this study, carbon black (CB) and carbon (coal-tar pitch-based spherical activated carbon (SAC)) were used to successfully fabricate composite-type SAC (CB/coal-tar-pitch-SAC), and its surface was coated with TiO2 to produce the composite material TiO2/CB/coal-tar-pitch-SAC. CB helps in decreasing the pore size of CB/coal-tar-pitch-SAC and increasing its specific surface area and total pore volume, which can be verified by the Brunauer-Emmett-Teller (BET) method. Practically, TiO2/CB/coal-tar-pitch-SAC can sterilize the bacteria present in the water. This study intensively verifies the high reusing sterilization capacity of TiO2/CB/coal-tar-pitch-SAC. The results indicate that TiO2/CB/coal-tar-pitch-SAC can effectively improve the water environment.

As a kind of lightweight virtualization technology, container has not only been widely used in resource management and DevOps of cloud computing platform and data center in recent years, but also gradually applied to some new fields such as edge computing and Internet of things. Container has shown a good development trend and application prospect.So, operating system virtualization as a core technology of container has received widespread attention in both industry and academia.Operating system virtualization allows multiple applications to run in a set of isolated runtime environment by sharing the same host operating system kernel.It has the advantages of fast startup, convenient deployment, low resource consumption, high running efficiency.However, there are also deficiencies such as weak isolation.And the deficiency has become a research hotspot in the field of virtualization.In this survey, we first introduce the technical architecture of operating system virtualization and compare it with traditional virtualization technology to summarize its characteristics.Then we analyze the current research status of operating system virtualization from container instance layer, container management layer and kernel resource layer.Finally, the paper lays out several challenges and research prospects of operating system virtualization.