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排序方式： 共有621条查询结果，搜索用时 15 毫秒
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A minimization method for material characterization of laminated composite plates using static test results is presented. Mechanical responses such as strains and displacements are measured from the static tests of the laminated composite plates. The finite element method is used to analyse the deformation of the laminated composite plates. An error function is established to measure the differences between the experimental and theoretical mechanical responses of the laminated composite plates. The identification of the material elastic constants of the laminated composite plates is formulated as a constrained minimization problem in which the elastic constants are determined by making the error function a global minimum. A number of examples are given to illustrate the feasibility and applications of the proposed method. 相似文献
615.
The static failure strength of a frangible laminated composite canister cover subjected to uniform external pressure is studied via both theoretical and experimental approaches. The frangible canister cover, which is fabricated with four plate-like laminated composite parts, which is designed in such a way that it will fail in a predetermined pattern when subjected to an impulsive internal pressure and its external failure pressure is much higher than its internal failure pressure. The stress distribution in the canister cover is determined using the finite element method and the failure of the cover identified on the basis of an appropriate failure criterion. A number of laminated composite canister covers were fabricated and subjected to static external pressure testing. The failure modes of the frangible covers are studied and the experimental results are used to verify the theoretical predictions. Close agreements between the experimental and theoretical results have been observed. The present study shows that the design of frangible covers with external failure pressure much higher than the internal failure pressure can be achieved. 相似文献
616.
Lei Zhou Kam Tim Tse Gang Hu Zijian Guo 《The Structural Design of Tall and Special Buildings》2023,32(16):e2050
This study investigates the aerodynamic performance of three square-section buildings with different aspect ratio (AR = 1:1, 1:4, and 1:6) exposed to twisted wind profile (TWP) by pressure measurement test. The effect of AR on the correlation of wind loads specifically for TWP is systematically revealed from both time–frequency domain and local–global perspective. Results show that compared with its counterparts in conventional wind profile (CWP), the effect of AR on aerodynamic load under TWP becomes significantly different and more prominent, which can be categorized into two types of patterns. For pattern low-rise building, TWP is more resembling the condition of CWP with certain attack angle. For pattern high-rise building, TWP results in stronger momentum exchange along building height but suppresses fluctuating feature associated with Karman vortex. As a result, under TWP, mean base moments of all buildings are enhanced except for longitudinal component of case AR = 1:4 and 1:6; while the fluctuating base moment for three AR cases is all reduced, which indicates that dynamic pattern of wake flow is suppressed. Moreover, the discrepancy of local wind load between case CWP and TWP concentrates on the lower-middle location for high-rise building but distributed evenly along all low-rise building height. Additionally, it is found that the effect of AR on aerodynamic correlation exhibits different mechanisms and patterns when building is under the impact of CWP or TWP. 相似文献
617.
Kam Sang Kwok Qi Huang Massimo Mastrangeli David H. Gracias 《Advanced Materials Interfaces》2020,7(5)
Self‐folding broadly refers to the assembly of 3D structures by bending, curving, and folding without the need for manual or mechanized intervention. Self‐folding is scientifically interesting because self‐folded structures, from plant leaves to gut villi to cerebral gyri, abound in nature. From an engineering perspective, self‐folding of sub‐millimeter‐sized structures addresses major hurdles in nano‐ and micro‐manufacturing. This review focuses on self‐folding using surface tension or capillary forces derived from the minimization of liquid interfacial area. Due to favorable downscaling with length, at small scales capillary forces become extremely large relative to forces that scale with volume, such as gravity or inertia, and to forces that scale with area, such as elasticity. The major demonstrated classes of capillary force assisted self‐folding are discussed. These classes include the use of rigid or soft and micro‐ or nano‐patterned precursors that are assembled using a variety of liquids such as water, molten polymers, and liquid metals. The authors outline the underlying physics and highlight important design considerations that maximize rigidity, strength, and yield of the assembled structures. They also discuss applications of capillary self‐folding structures in engineering and medicine. Finally, the authors conclude by summarizing standing challenges and describing future trends. 相似文献
618.
Jason Kam David Thomas Sandra Pierre Chris Ashman Jon P. McCalmont Sarah J. Purdy 《Food and Energy Security》2020,9(3)
Anaerobic digestion (AD) currently relies heavily on crop feedstocks to maintain a constant output. A major annual crop used is Zea mays (maize), but this practice presents significant concerns because high energy inputs and food‐growing land are required for cultivation. The autumn harvest date of maize exposes soils over winter resulting in erosion and runoff into waterways. Miscanthus is physiologically and morphologically similar to maize. It is also of interest for biogas generation. As a perennial grass, Miscanthus requires far less input and can be grown on land that is unsuitable for food crops. It is typically harvested in late winter to early spring. Maize produces higher biogas yields than the most commonly grown commercial variety of Miscanthus (Mxg), because it has a higher nonstructural carbohydrate (NSC) concentration that facilitates the AD process. We aimed to investigate whether a new Miscanthus hybrid (“GNT‐14”) that was bred from a high carbohydrate accumulating parental type can improve biogas yield from Mxg. Comparisons were made on biogas yields at two time points, October and January; the NSC, cellulose, and lignin concentrations were quantified; and the contribution of the NSC to biogas yield was determined by comparing intact and washed samples. The NSC concentrations of GNT‐14 were fivefold higher than Mxg in January, and a 28% increase in methane was observed. While Mxg showed a reduction in methane yields (L/kg) from biomass harvested in January compared to October, GNT‐14 showed no such decline. Although the potential methane yields of GNT‐14 were only 70% that of maize, the energy input (GJ ha‐1) required for cultivation was 26% of maize. Our results demonstrated that GNT‐14 could be harvested later than maize for biogas generation, offering soil protection over winter. We encourage Miscanthus breeding efforts to focus on NSC concentration as well as yield. 相似文献
619.
A remotely operated underwater vehicle (ROV) is a tethered underwater mobile device that can conduct a bathymetric survey cost-efficiently. Assessment of the utility of ROV-based bathymetric surveys in flood inundation mapping remains limited. This study aims to examine the utility of ROV-based bathymetric surveys in high-resolution flood inundation mapping for a hypothetical case study of the Lake Tuscaloosa Dam breach in the state of Alabama, USA. This study conducted the sensitivity test of flood inundation mapping to the river channel depth (ROV-based vs. digital elevation model [DEM]-based) and initial flow condition (e.g., wet vs. dry), via six different simulations of the parallelized diffusion hydrodynamic model (pDHM). This study found that the ROV-based pDHM runs had higher maximum water depths over the flood-inundated areas, ranging from +73% to +166% of the simulated depths of the DEM-based pDHM runs. However, the impact of initial streamflow condition on the maximum depths was limited. This study also found that the pDHM runs with a dry initial flow condition delayed the time to reach the maximum depth after the dam breach by 2 h relative to the pDHM runs with a wet initial streamflow condition. This study suggests that ROV-based bathymetry surveys improve flood inundation mapping by emphasizing the influence of river channel depth, initial streamflow conditions, and bathymetry, thereby bolstering community resilience to a potential human-made hazard such as dam failure. 相似文献
620.
概述了微波无线能量传输系统的研究现状及其基本原理,从可提高波束能量的一些特殊口径场以及先进的天线技术角度,分别按Whisper波束、超增益天线、平顶波束、聚焦天线技术、非衍射天线进行介绍。最后对微波能量传输系统中发射技术的未来发展趋势进行了展望。 相似文献