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Second Problem (second + problem)
Selected AbstractsLocating a Surveillance Infrastructure in and Near Ports or on Other Planar Surfaces to Monitor FlowsCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 2 2010Pitu B. Mirchandani This article addresses the problem of locating surveillance radars to cover a given target surface that may have barriers through which radar signals cannot penetrate. The area of coverage of a radar is assumed to be a disc, or a partial disc when there are barriers, with a known radius. The article shows that the corresponding location problems relate to two well studied problems: the set-covering model and the maximal covering problem. In the first problem, the minimum number of radars is to be located to completely cover the target area; in the second problem a given number M of radars are to be located to cover the target area as much as possible. Based on a discrete representation of the target area, a Lagrangian heuristic and a two-stage procedure with a conquer-and-divide scaling are developed to solve the above two models. The computational experiences reported demonstrate that the developed method solves well the radar location problems formulated here. [source] Bacteria of asymptomatic periradicular endodontic lesions identified by DNA-DNA hybridizationDENTAL TRAUMATOLOGY, Issue 5 2000J. J. Gatti Abstract , Possible inclusion of contaminant bacteria during surgery has been problematic in studies of periradicular lesions of endodontic origin. Therefore, in this study, two different surgical techniques were compared. A second problem is that some difficult to cultivate species may not be detected using bacteriological methods. Molecular techniques may resolve this problem. DNA-DNA hybridization technology has the additional advantage that DNA is not amplified. The purpose of this investigation was to determine if bacteria from periradicular endodontic lesions could be identified using DNA-DNA hybridization. A full thickness intrasulcular mucoperiosteal (IS) flap (n=20) or a submarginal (SM) flap (n=16) was reflected in patients with asymptomatic apical periodontitis. DNA was extracted and incubated with 40 digoxigenin-labeled whole genomic probes. Bacterial DNA was detected in all 36 lesions. Seven probes were negative for all lesions. In patients with sinus tract communication, in teeth lacking intact full coverage crowns, and in patients with a history of trauma, 4,13 probes provided positive signals. Seven probes were positive in lesions obtained by the IS, but not the SM technique. Two probes were in samples obtained with the SM technique, but not the IS. Only Bacteroides forsythus and Actinomyces naeslundii genospecies 2 were present in large numbers using either the IS or the SM technique. The SM flap technique, in combination with DNA-DNA hybridization, appeared to provide excellent data pertaining to periradicular bacteria. These results supported other studies that provide evidence of a bacterial presence and persistence in periradicular lesions. [source] Treatment of Neumann boundaries in the complex variable boundary element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2004Kozo Sato Abstract For potential flow, the complex variable boundary element method (CVBEM) is formulated in terms of the velocity potential , and the stream function ,. In actual flow problems, , and ,,/,n are given along Dirichlet and Neumann boundaries, respectively. In the CVBEM, the Neumann-type condition ,,/,n is not directly handled, and, instead, , is used to define Neumann boundaries. Owing to this discrepancy, numerical difficulties are raised along Neumann boundaries. The current study addresses two such difficulties: (1) multiple Neumann boundaries and (2) branch cuts across Neumann boundaries. The first problem is due to the fact that , along multiple boundaries cannot be specified a priori, and the second problem is due to the discontinuous jump inherent in , for sink/source singularities. To overcome these difficulties, a new formulation of the CVBEM to solve for the unknown , values and a proper way of branch-cut placement are proposed, and these techniques are verified against example problems. Copyright © 2004 John Wiley & Sons, Ltd. [source] A smooth switching adaptive controller for linearizable systems with improved transient performanceINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 9 2006Jeng Tze Huang Abstract The certainty equivalent control has achieved asymptotic tracking stability of linearizable systems in the presence of parametric uncertainty. However, two major drawbacks remain to be tackled, namely, the risk of running into singularity for the calculated control input and the poor transient behaviour arising frequently in a general adaptive system. For the first problem, a high gain control is activated in place of the certainty equivalent control until the risk is bypassed. Among others, it requires less control effort by taking advantages of the bounds for the input vector field. Moreover, the switching mechanism is smooth and hence avoids possible chattering behaviour. Next, to solve the second problem, a new type of update algorithm guaranteeing the exponential stability of the overall closed-loop system, on a weaker persistent excitation (PE) condition, is proposed. In particular, it requires no filtering of the regressor and hence is easier to implement. Simulation results demonstrating the validity of the proposed design are given in the final. Copyright © 2006 John Wiley & Sons, Ltd. [source] Joint power, subcarrier and subframe allocation in Multihop relay networksINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 7 2009Tolga Girici Abstract In this paper we study the problem of subframe, subchannel and power allocation in OFDMA-based multihop relay networks. The system consists of a base station (BS), a number of relay stations (RS) and mobile stations (MS). We consider frame by frame scheduling, where the frame is divided into two subframes such as BS-RS and RS-MS subframes. We study two different problems, satisfying link rate requirements with minimum-weighted total power and maximizing proportional fairness. For the first problem, we find the optimal solution and also propose a less complex subframe and bandwidth allocation scheme with good performance. For the second problem, we propose an algorithm that outperforms an existing scheme with less feedback. Copyright © 2009 John Wiley & Sons, Ltd. [source] Comonotonic Approximations for Optimal Portfolio Selection ProblemsJOURNAL OF RISK AND INSURANCE, Issue 2 2005J. Dhaene We investigate multiperiod portfolio selection problems in a Black and Scholes type market where a basket of 1 riskfree and m risky securities are traded continuously. We look for the optimal allocation of wealth within the class of "constant mix" portfolios. First, we consider the portfolio selection problem of a decision maker who invests money at predetermined points in time in order to obtain a target capital at the end of the time period under consideration. A second problem concerns a decision maker who invests some amount of money (the initial wealth or provision) in order to be able to fullfil a series of future consumptions or payment obligations. Several optimality criteria and their interpretation within Yaari's dual theory of choice under risk are presented. For both selection problems, we propose accurate approximations based on the concept of comonotonicity, as studied in Dhaene et al. (2002 a,b). Our analytical approach avoids simulation, and hence reduces the computing effort drastically. [source] Revisiting Hrdli,ka and Boas: Asymmetries of Race and Anti-Imperialism in Interwar AnthropologyAMERICAN ANTHROPOLOGIST, Issue 1 2010Robert Oppenheim ABSTRACT, Physical anthropologist Ale, Hrdli,ka is often remembered as an institutional and political opponent of Franz Boas and as an advocate of racial typology against which the Boasian antiracialist position in American anthropology developed. I argue that Hrdli,ka nonetheless also has more subtle lessons to offer about the political limits of Boasian antiracism. Examining Hrdli,ka's engagement with the politics of Europe and East Asia from the 1920s to the 1940s, particularly with the intellectual grounding of Japanese imperialism, I suggest that he was perhaps uniquely cognizant of a "second problem of race in the world",the racist assimilationism of the Japanese empire,vis-à-vis the Boasian grasp of race, rooted in a response to U.S. and Nazi racisms, as a category of invidious difference. Moreover, I contend that the lacuna that Hrdli,ka helps us identify has continued to haunt the discipline at certain key moments of Boasian critique of other ideological forces. [source] Maximizing residual flow under an arc destructionNETWORKS: AN INTERNATIONAL JOURNAL, Issue 4 2001Y. P. Aneja Abstract In this paper, we consider two problems related to single-commodity flows on a directed network. In the first problem, for a given s , t flow, if an arc is destroyed, all the flow that is passing through that arc is destroyed. What is left flowing from s to t is the residual flow. The objective is to determine a flow pattern such that the residual flow is maximized. We provide a strongly polynomial algorithm for this problem, called the maximum residual flow problem, and consider various extensions of this basic model. In the second problem, known as the "most vital arc" problem, the objective is to remove an arc so that the maximal flow on the residual network is as small as possible. Results are also derived which help implement an efficient scheme for solving this problem. © 2001 John Wiley & Sons, Inc. [source] | ||||||||||