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71.
In the conventional sliding mode control, the relative degree of the chosen sliding surface is usually one. This paper addresses a general class of sliding surface whose relative degree is no longer restricted to one. We show that when the relative degree is more than two, it is inevitable that there will exist a limit cycle for the nonlinear sign function. And for the case of relative degree two the system possesses poor phase margin. However, these disadvantages can be remedied remarkably by smoothing out the control nonlinearity in a suitable boundary layer with a saturation function that ensures asymptotic stability of the overall system 相似文献
72.
WJ Cho EK Kim MJ Park SU Choi CO Lee SH Cheon BG Choi BH Chung 《Canadian Metallurgical Quarterly》1998,6(12):2449-2458
In this study a series of 3-arylisoquinoline derivatives were synthesized and cytotoxicity against human melanoma tumor cell evaluated, and a three dimensional quantitative structure-activity relationship was investigated using the comparative molecular field analysis (CoMFA). The results suggested that the electrostatic, steric and hydrophobic factors of 3-arylisoquinolines were strongly correlated with the antitumor activity. Considerable predictive ability (cross-validated r2 as high as 0.721) was obtained through CoMFA. 相似文献
73.
Hong-Chich Chou Chung-Ping Chung 《Parallel and Distributed Systems, IEEE Transactions on》1995,6(3):303-313
Performance in superscalar processing strongly depends on the compiler's ability to generate codes that can be executed by hardware in an optimal or near optimal order. Generating optimal code is an NP-complete problem. However, there is a need for highly optimized code, such as in superscalar or real-time systems. In this paper, an instruction scheduling scheme for optimizing a program trace is proposed. Optimized code can be arrived at without much redundant work, if some important features in code are well explored and utilized in scheduling. To formalize the task, two abstract models, one for a superscalar processor and the other for a program trace, are given. These two models reflect most of the characteristics of the scheduling problem. The interrelations between instructions and partial schedules are thoroughly studied, and dominance and equivalence relations on them are defined. These relations are then used to reduce the solution space and eventually help to produce optimal schedules. The results of experiments that show the promise of the proposed scheme are also presented 相似文献
74.
75.
N-acetyltransferase (NAT) activity was determined by incubation of purified Enterobacter aerogenes enzyme with 2-aminofluorene (2-AF) as the substrate, followed by high pressure liquid chromatography assays. The NAT activity from E. aerogenes was 0.58 +/- 0.08 nmol/min/mg protein for 2-AF. The values of apparent K(m) and Vmax were 0.72 +/- 0.14 mM and 2.45 +/- 0.29 nmol/min/mg protein, respectively, for 2-AF. The optimal pH value for the enzyme activity was 7.5 for the 2-AF tested. The optimal temperature for enzyme activity was 37 degrees C for the 2-AF substrate. The molecular weight of NAT from E. aerogenes was 44.9 kD. Among a series of divalent cations and salts, Zn2+, Ca2+, and Fe2+ were demonstrated to be the most potent protease inhibitors, and only ethylenediaminetetraacetic acid significantly protected the NAT. Iodoacetamide, in contrast to other agents, markedly inhibited NAT. 相似文献
76.
Won-Ho Chung 《Personal and Ubiquitous Computing》2012,16(6):687-696
Mobile surveillance service is regarded as one of the Internet applications to which much attention is recently given. However, the time and cost problem resulting from using heterogeneous platforms and proprietary protocols must be a burden to developing such systems and expanding their services. In this paper, we present a framework of mobile surveillance service for smartphone users. It includes the design and implementation of a video server and a mobile client called smartphone watch. A component-based architecture is employed for the server and client for easy extension and adaptation. We also employ the well-known standard web protocol HTTP to provide higher compatibility and portability than using a proprietary one. Three different video transmission modes are provided for efficient usage of limited bandwidth resource. We demonstrate our approach via real experiments on a commercial smartphone. 相似文献
77.
Many video service sites headed by YouTube know what content requires copyright protection. However, they lack a copyright
protection system that automatically distinguishes whether uploaded videos contain legal or illegal content. Existing protection
techniques use content-based retrieval methods that compare the features of video. However, if the video encoding has changed
in resolution, bit-rate or codec, these techniques do not perform well. Thus, this paper proposes a novel video matching algorithm
even if the type of encoding has changed. We also suggest an intelligent copyright protection system using the proposed algorithm.
This can serve to automatically prevent the uploading of illegal content. The proposed method has represented the accuracy
of 97% with searching algorithm in video-matching experiments and 98.62% with automation algorithm in copyright-protection
experiments. Therefore, this system could form a core technology that identifies illegal content and automatically excludes
access to illegal content by many video service sites. 相似文献
78.
Dinesh Kalyanasundaram Shinnosuke Inoue Jong-Hoon Kim Hyun-Boo Lee Zenko Kawabata Woon-Hong Yeo Gerard A. Cangelosi Kieseok Oh Dayong Gao Kyong-Hoon Lee Jae-Hyun Chung 《Microfluidics and nanofluidics》2012,13(2):217-225
Simple, high-yield concentration of DNA is important for high-throughput genetic analysis and disease diagnosis. Glass-based microfilters are popular but the process requires centrifugation steps with cumbersome chemical processes. As an alternative, a concentration method using an electric field has been explored previously, but with limited efficiency. In this paper, electric field-induced concentration and capture of DNA are studied by using high-aspect-ratio microtips coated with a gold layer. The microtips are immersed longitudinally into a solution of 100???L containing ??-phage DNA. After DNA concentration using an electric field, the microtips are withdrawn from the solution. Under AC- and biased AC fields, DNA is concentrated by electrophoresis (EP), dielectrophoresis (DEP), and electroosmotic flow (EOF). To reduce capillary effects in the withdrawal process, the microtips are coated with positively charged poly-l-lysine (PLL). The pattern of captured DNA is analyzed by fluorescence microscopy. DEP attracts DNA molecules at the edges of microtips, where the highest gradient of electric field exists. EP attracts DNA onto the surface of microtips following the vectors of an electric field. EOF generates vortexes that deliver DNA onto microtips. Using this method, 85% of DNA is captured on the PLL-coated microtips after three sequential captures. The concentration mechanism can potentially facilitate rapid and simple preparation of DNA for downstream analysis. 相似文献
79.
Predictive simulation of human walking transitions using an optimization formulation 总被引:1,自引:1,他引:0
Yujiang Xiang Jasbir S. Arora Hyun-Joon Chung Hyun-Jung Kwon Salam Rahmatalla Rajankumar Bhatt Karim Abdel-Malek 《Structural and Multidisciplinary Optimization》2012,45(5):759-772
A general optimization formulation for transition walking prediction using 3D skeletal model is presented. The formulation
is based on a previously presented one-step walking formulation (Xiang et al., Int J Numer Methods Eng 79:667–695, 2009b). Two basic transitions are studied: walk-to-stand and slow-to-fast walk. The slow-to-fast transition is used to connect
slow walk to fast walk by using a step-to-step transition formulation. In addition, the speed effects on the walk-to-stand
motion are investigated. The joint torques and ground reaction forces (GRF) are recovered and analyzed from the simulation.
For slow-to-fast walk transition, the predicted ground reaction forces in step transition is even larger than that of the
fast walk. The model shows good correlation with the experimental data for the lower extremities except for the standing ankle
profile. The optimal solution of transition simulation is obtained in a few minutes by using predictive dynamics method. 相似文献
80.
The effect of work-hardening changes, of the type that follow a rapid change of strain state or strain rate, on formability
has been investigated using finite element modeling (FEM). A standard sheet tensile test was chosen as an arbitrary forming
operation and a rigid-viscoplastic FEM program was employed for analysis. In each case, a transitional region of true strains
between 0.1 and 0.2 was modeled. Transients involving lowered work-hardening rates (negative value of An) promoted increased
strain localization and premature failure while transients with increased work-hardening rates enhanced formability. Total
engineering elongations (50 mm gage length) varied between 20 pct and 46 pct, illustrating the importance of the transient
far beyond the transient region. The controlling factor is the effective work-hardening rate in the transient region rather
than the change in strength coefficient or flow stressper se. A direct stress offset of the flow curve {
} also affects strain localization through a change in effective work-hardening rate. 相似文献