空降作战装备保障及力量建设若干问题研究

空降作战是信息化条件下联合作战的重要作战样式之一,搞好装备保障是夺取空降作战胜利的重要环节。分析了空降作战装备保障的主要特点;研究了装备保障力量的编组和运用的若干问题;对装备保障力量建设进行了探讨。     

疲劳可靠性二维统计Miner准则

首先建立了等幅疲劳中值Sa-Sm-(?)c曲面方程和变幅加载下疲劳可靠性二维统计Miner准则。其次,重点分析了国外船舶与海洋工程领域广泛采用的疲劳可靠性Wirsching模型,发现其在理论上存在不自洽性,并基于二维统计Miner准则建立了改进的Wirsching模型。最后,给出了一个具体应用实例。表明本文建立的二维统计Miner准则具有较好的工程实用价值。     

Biological Evaluation and X‐ray Co‐crystal Structures of Cyclohexylpyrrolidine Ligands for Trypanothione Reductase,an Enzyme from the Redox Metabolism of Trypanosoma

The tropical diseases human African trypanosomiasis, Chagas disease, and the various forms of leishmaniasis are caused by parasites of the family of trypanosomatids. These protozoa possess a unique redox metabolism based on trypanothione and trypanothione reductase (TR), making TR a promising drug target. We report the optimization of properties and potency of cyclohexylpyrrolidine inhibitors of TR by structure‐based design. The best inhibitors were freely soluble and showed competitive inhibition constants (K_i) against Trypanosoma (T.) brucei TR and T. cruzi TR and in vitro activities (half‐maximal inhibitory concentration, IC₅₀) against these parasites in the low micromolar range, with high selectivity against human glutathione reductase. X‐ray co‐crystal structures confirmed the binding of the ligands to the hydrophobic wall of the “mepacrine binding site” with the new, solubility‐providing vectors oriented toward the surface of the large active site.     

The Reliable Facility Location Problem Under Random Disruptions

The classical location models implicitly assume that the facilities, once built, will always operate as planned. However, some of the facilities may become unavailable from time to time due to disruptions caused by natural disasters, key-supplier bankruptcy, terrorist attacks, or labor strikes. Therefore, supply chain disruptions have gained considerable attention by researchers and practitioners in the past few decades. The catastrophic accidents highlighted the urgent need for effective solutions to manage supply chain disruptions in spite of their low probability of occurrence. Therefore, it is critical to take account of disruptions when designing supply chain networks so that they perform well as a whole even after a disruption. Taking into account the random disruption risk, this paper proposes a mixed integer programming model for the reliable facility location problem. This model try to minimize the sum of initial facility construction costs and expected transportation costs in both the regular and the failure scenarios, and present a Lagrange relaxation algorithm to solve it. This paper also analyzes the algorithm’s solving performance by a numerical experiment.     

Fabrication and properties of Cf/ZrC‐SiC‐based composites by an improved reactive melt infiltration

C_f/ZrC‐SiC composites with a density of 2.52 g/cm³ and a porosity of 1.68% were fabricated via reactive melt infiltration (RMI) of Si into nano‐porous C_f/ZrC‐C preforms. The nano‐porous C_f/ZrC‐C preforms were prepared through a colloid process, with a ZrC “protective coating” formed surrounding the carbon fibers. Consequently, highly dense C_f/ZrC‐SiC composites without evident fiber/interphase degradation were obtained. Moreover, abundant needle‐shaped ZrSi₂ grains were formed in the composites. Benefiting from this unique microstructure, flexural strength, and elastic modulus of the composites are as high as 380 MPa and 61 GPa, respectively, which are much higher than C_f/ZrC‐SiC composites prepared by conventional RMI.     

Dynamic stress of impeller blade of shaft extension tubular pump device based on bidirectional fluid-structure interaction

Current research on the stability of tubular pumps is mainly concerned with the transient hydrodynamic characteristics. However, the structural response under the influence of fluid-structure interaction hasn’t been taken fully into consideration. The instability of the structure can cause vibration and cracks, which may threaten the safety of the unit. We used bidirectional fluid-structure interaction to comprehensively analyze the dynamic stress characteristics of the impeller blades of the shaft extension tubular pump device. Furthermore, dynamic stress of impeller blade of shaft extension tubular pump device was solved under different lift conditions of 0° blade angle. Based on Reynolds-average N-S equation and SST k-ω turbulence model, numerical simulation was carried out for three-dimensional unsteady incompressible turbulent flow field of the pump device whole flow passage. Meanwhile, the finite element method was used to calculate dynamic characteristics of the blade structure. The blade dynamic stress distribution was obtained on the basis of fourth strength theory. The research results indicate that the maximum blade dynamic stress appears at the joint between root of inlet side of the blade suction surface and the axis. Considering the influence of gravity, the fluctuation of the blade dynamic stress increases initially and decreases afterwards within a rotation period. In the meantime, the dynamic stress in the middle part of inlet edge presents larger relative fluctuation amplitude. Finally, a prediction method for dynamic stress distribution of tubular pump considering fluid-structure interaction and gravity effect was proposed. This method can be used in the design stage of tubular pump to predict dynamic stress distribution of the structure under different operating conditions, improve the reliability of pump impeller and analyze the impeller fatigue life.     

Engineered Elastomer Substrates for Guided Assembly of Complex 3D Mesostructures by Spatially Nonuniform Compressive Buckling

Approaches capable of creating 3D mesostructures in advanced materials (device‐grade semiconductors, electroactive polymers, etc.) are of increasing interest in modern materials research. A versatile set of approaches exploits transformation of planar precursors into 3D architectures through the action of compressive forces associated with release of prestrain in a supporting elastomer substrate. Although a diverse set of 3D structures can be realized in nearly any class of material in this way, all previously reported demonstrations lack the ability to vary the degree of compression imparted to different regions of the 2D precursor, thus constraining the diversity of 3D geometries. This paper presents a set of ideas in materials and mechanics in which elastomeric substrates with engineered distributions of thickness yield desired strain distributions for targeted control over resultant 3D mesostructures geometries. This approach is compatible with a broad range of advanced functional materials from device‐grade semiconductors to commercially available thin films, over length scales from tens of micrometers to several millimeters. A wide range of 3D structures can be produced in this way, some of which have direct relevance to applications in tunable optics and stretchable electronics.     

Capillary‐Bridge Mediated Assembly of Conjugated Polymer Arrays toward Organic Photodetectors

Large‐scale patterning of high‐quality organic semiconductors is crucial for the fabrication of optoelectronic devices with high efficiency and low cost. Yet, owing to the uncontrollable dewetting dynamics of organic liquid in conventional solution patterning techniques, large defect density of organic architectures is inevitable, which is detrimental to the device performance. To address this challenge, herein a capillary‐bridge‐mediated assembly technique is developed for regulating the dewetting process, yielding large‐scale 1D microstructure ordered arrays. The 1D arrays organic photodetectors exhibit a high optoelectronic performance of light on/off ratio exceeding 100, responsivity of 3.24 A W^?1, detectivity of 3.20 × 10¹¹ Jones and fast response speed, showing a great improvement compared with spin‐coated membrane devices. In addition, the significant enhancement of the device photodetection under the electronic field modulation is investigated by applying a back‐gate voltage and explained with the photocurrent predominating in the OFF state and the neglected thermocurrent and tunneling current promoting in the ON state of the phototransistor devices. The research offers a new insight for the facile fabrication of large‐scale integrated photodetectors and other organic devices based on patterned conjugated polymers.     

Carbon Sequestration Within Silica Bodies Extracted from Kelp Cultured in the East China Sea

To re-evaluate ecological effects of kelp culture in marginal seas, the silica body content in kelp cultured in the East China Sea and the carbon content in the silica body extracted from kelp were measured. The silica body content in kelp cultured in the sea ranged from 0.20 to 0.60 % and the carbon content in the silica body extracted from kelp was 0.27 ± 0.06 %. The carbon sequestration rate in silica bodies extracted from kelp cultured in the East China Sea was 2.47 ± 0.40 t.a^?1 from 2000 to 2011. In the East China Sea, the production of the silica body of kelp in the kelp culture zone was 6.56 ± 1.06 g.m^?2.a^?1. The carbon sequestration rate in the silica body of cultured kelp in the East China Sea was 0.02 ± 0.00 g.m^?2.a^?1, which accounted for 1.43 % of CO₂ flux from air to sea. The carbon fixed in the silica body extracted from kelp might be one part of the missing carbon sink. Considering carbon content in silica bodies extracted from kelp cultured in the East China Sea, carbon sequestration of kelp culture in the marginal sea should be re-evaluated and some missing carbon sinks caused by anthropogenic factors might be reduced.     

Hybridity in the housing sector: examining impacts on social and private rented sector tenants in Scotland

Abstract

Housing Associations in many countries exhibit increasing levels of ‘hybridity’, as reductions in state financing for social housing, exacerbated by austerity policies since the 2008 crash, have instigated ‘enterprising’ approaches to maintaining income. Alongside this, hybrid organisations have emerged in the Private Rented Sector (PRS), responding to sectoral growth and consequent increases in vulnerable households entering private renting. These developing hybridities have been considered at a strategic level, but there has been little exploration of the impacts on tenants. This article examines two organisations, operating across the social and private rented sectors, to elucidate potential implications for tenants. The research suggests that different forms of hybridity can affect tenant outcomes and, moreover, that examining such impacts is important in understanding hybridity itself. Furthermore, the study suggests that emerging forms of hybridity, particularly in the PRS, may be blurring the boundaries between housing sectors, with implications for policy and research.