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排序方式: 共有1476条查询结果,搜索用时 31 毫秒
51.
Young‐Sam Cho Seyoung Im 《International journal for numerical methods in engineering》2006,65(4):494-516
Two‐dimensional variable‐node elements compatible with quadratic interpolation are developed using the moving least‐square (MLS) approximation. The mapping from the parental domain to the physical element domain is implicitly obtained from MLS approximation, with the shape functions and their derivatives calculated and saved only at the numerical integration points. It is shown that the present MLS‐based variable‐node elements meet the patch test if a sufficiently large number of integration points are employed for numerical integration. The cantilever problem with non‐matching meshes is chosen to check the feasibility of the present MLS‐based variable‐node elements, and the result is compared with that from the lower‐order case compatible with linear interpolation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
52.
Wook Hyun Kwon Jin Won Kang Young Sam Lee Young Soo Moon 《Journal of Process Control》2003,13(6):1080
In this paper, a simple receding horizon (or model predictive) control for state delayed systems is presented and its solution is given in a closed form by a reduction method. While the control for a time-delay system is usually complex, the proposed controller is simple to construct and therefore can be simply implemented in real applications. To check the closed-loop stability of the proposed controller, a sufficient condition is provided by linear matrix inequalities. In addition, a numerical algorithm is presented for computing the eigenvalues of systems with distributed time delays, which can be used as a necessary and sufficient condition to check closed-loop stability. It is shown by simulation that this simple control can be a stabilizing control for time-delay systems. 相似文献
53.
Modular Reconfigurable Robots in Space Applications 总被引:6,自引:0,他引:6
Mark Yim Kimon Roufas David Duff Ying Zhang Craig Eldershaw Sam Homans 《Autonomous Robots》2003,14(2-3):225-237
Robots used for tasks in space have strict requirements. Modular reconfigurable robots have a variety of attributes that are well suited to these conditions, including: serving as many different tools at once (saving weight), packing into compressed forms (saving space) and having high levels of redundancy (increasing robustness). In addition, self-reconfigurable systems can self-repair and adapt to changing or unanticipated conditions. This paper will describe such a self-reconfigurable modular robot: PolyBot. PolyBot has significant potential in the space manipulation and surface mobility class of applications for space. 相似文献
54.
55.
One-Dimensional Numerical Model for Nonuniform Sediment Transport under Unsteady Flows in Channel Networks 总被引:1,自引:0,他引:1
In this study, the proposed one-dimensional model simulates the nonequilibrium transport of nonuniform total load under unsteady flow conditions in dendritic channel networks with hydraulic structures. The equations of sediment transport, bed changes, and bed-material sorting are solved in a coupling procedure with a direct solution technique, while still decoupled from the flow model. This coupled model for sediment calculation is more stable and less likely to produce negative values for bed-material gradation than the traditional fully decoupled model. The sediment transport capacity is calculated by one of four formulas, which have taken into consideration the hiding and exposure mechanism of nonuniform sediment transport. The fluvial erosion at bank toes and the mass failure of banks are simulated to complement the modeling of bed morphological changes in channels. The tests in several cases show that the present model is capable of predicting sediment transport, bed changes, and bed-material sorting in various situations, with reasonable accuracy and reliability. 相似文献
56.
Ok Sam Kim 《Journal of Mechanical Science and Technology》1998,12(6):1126-1134
Single crystal silicon (SCS) is used in a variety of microsensor applications in which stresses and other mechanical effects
may dominate device performance. One of major problems associated with the manufacturing processes of the microaccelerometer
based on the tunneling current concept is temperature gradient and thermal stressess. This paper deals with finite element
analyses of residual stresses causing popping up, which are induced in micromachining processes of a microaccelerometer. The
authors model temperature-dependent mechanical properties during focused ion beam (FIB) cutting and Pt deposition processes.
The maximum thermal strain of 0.0012 occurred at the readout gap of the microaccelerometer during the Pt deposition process.
The stress produced during the heating process of FIB cut was also found to be about 33–36 MPa and cooling process the maximum
equivalent stress of about 34MPa still at the right corner of readout gap. The calculated maximum displacement occurred at
the readout gap was 0.14 μm. This is still smaller than the popping up of about 2 μm observed in the experiment. The reason for this popping up phenomenon in munufacturing processes of microaccelerometer may
be the bending of the whole wafer or it may come from the way the underetch occurs. Different SOI material and a new geometry
of the accelerometer are under investigation. We want to seek after the real cause of this pop up phenomenon and diminish
this by changing munufacturing processes of microaccelerometer. 相似文献
57.
Detecting pattern-based outliers 总被引:6,自引:0,他引:6
Outlier detection targets those exceptional data that deviate from the general pattern. Besides high density clustering, there is another pattern called low density regularity. Thus, there are two types of outliers w.r.t. them. We propose two techniques: one to identify the two patterns and the other to detect the corresponding outliers. 相似文献
58.
Alejandra Chaparro Víctor Beltrn Daniel Betancur Ye-Han Sam Haniyeh Moaven Ali Tarjomani Nikolaos Donos Vanessa Sousa 《International journal of molecular sciences》2022,23(17)
Background: The aim of this feasibility study was to investigate the concentration level of CCL-20/MIP-3α, BAFF/BLyS, IL-23, RANKL, and Osteoprotegerin in the Peri-Implant Crevicular Fluid (PICF), from patients diagnosed with peri-implant mucositis and peri-implantitis, and to compare them with PICF from patients with healthy implants. Methods: Participants with at least one dental implant with healthy peri-implant tissues, peri-implant mucositis, or peri-implantitis were included. PICF was collected using paper strips from healthy and diseased peri-implant sites (n = 19). Biomarker levels were analyzed using a custom Multiplex ELISA Assay Kit. Results: In comparison to peri-implant health, the peri-implant mucositis group showed an increased concentration of CCL-20 MIP-3α, BAFF/BLyS, IL-23, RANKL, and Osteoprotegerin. The peri-implantitis group had the lowest median concentration of Osteoprotegerin (1963 ng/mL); this group had a similar concentration of RANKL (640.84 ng/mL) when compared to the peri-implant health group. BAFF/BLyS (17.06 ng/mL) showed the highest concentration in the peri-implantitis group. Conclusions: This feasibility study suggests that IL-23 and RANKL may help to elucidate the pathogenesis during the conversion from peri-implant health to peri-implantitis. Further research is required in BAFF/BLyS for the early diagnosis of peri-implantitis. 相似文献
59.
In an attempt to develop a more conceptually oriented system of psychiatric classification, the statistical relationships occurring among various symptomatic reactions were studied in 604 patients. The deviant reactions were organized into symptom clusters, and a test of their stability was made in another group of Ss. The 3 symptom clusters which emerged were "avoidance of others… self-indulgence and turning against others… [and] self-deprivation and turning against the self." (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
60.
Sam Schellens Cynthia Lenaerts María del Rocío Prez Baca Dorien Cools Paulien Peeters Elisabeth Marchal Jozef Vanden Broeck 《International journal of molecular sciences》2022,23(16)
Ecdysteroids are widely investigated for their role during the molting cascade in insects; however, they are also involved in the development of the female reproductive system. Ecdysteroids are synthesized from cholesterol, which is further converted via a series of enzymatic steps into the main molting hormone, 20-hydoxyecdysone. Most of these biosynthetic conversion steps involve the activity of cytochrome P450 (CYP) hydroxylases, which are encoded by the Halloween genes. Three of these genes, spook (spo), phantom (phm) and shade (shd), were previously characterized in the desert locust, Schistocerca gregaria. Based on recent sequencing data, we have now identified the sequences of disembodied (dib) and shadow (sad), for which we also analyzed spatiotemporal expression profiles using qRT-PCR. Furthermore, we investigated the possible role(s) of five different Halloween genes in the oogenesis process by means of RNA interference mediated knockdown experiments. Our results showed that depleting the expression of SchgrSpo, SchgrSad and SchgrShd had a significant impact on oocyte development, oviposition and hatching of the eggs. Moreover, the shape of the growing oocytes, as well as the deposited eggs, was very drastically altered by the experimental treatments. Consequently, it can be proposed that these three enzymes play an important role in oogenesis. 相似文献