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1.
We present a new algorithm,
called MCS-M,
for computing minimal triangulations of graphs.
Lex-BFS, a seminal algorithm for recognizing chordal graphs,
was the genesis for two other classical algorithms:
LEX M and MCS.
LEX M extends the fundamental concept used in Lex-BFS,
resulting in an algorithm that not only recognizes chordality,
but also computes a minimal triangulation of an arbitrary graph.
MCS simplifies the fundamental concept used in Lex-BFS,
resulting in a simpler algorithm for recognizing chordal graphs.
The new algorithm MCS-M combines
the extension of LEX M with the simplification of MCS,
achieving all the results of LEX M in the same time complexity. 相似文献
2.
Orthostatic hypotension and related neurologic symptoms are frequently encountered in clinical practice. The maintenance of appropriate blood pressure and heart rate responses upon assuming the upright posture are dependent upon: 1. intact mechanical (venous valves) mechanisms, 2. functioning arterial and cardiopulmonary baroreceptors, 3. normal peripheral neural pathways, 4. normal central neural integration, and 5. appropriate neurohormonal secretion. Dysfunction at one or more of these loci may facilitate the occurrence of orthostatic hypotension and syncope. In general, the mechanisms of orthostatic hypotension may be divided into three categories. In the first category, processes interfere with normal compensatory responses to upright posture. Examples of this mechanism include age related autonomic changes, diabetic neuropathy and central nervous system disease such as Shy-Drager syndrome. The second principal mechanism involves overwhelming otherwise normal reflexes by an intense orthostatic stimulus. An obvious example of this mechanism is syncope related to hemorrhage. A final category of orthostatic hypotension relates to interference with reflex responses by drugs that may limit vasoconstriction, heart rate or cardiac output adjustments or exaggerate venous pooling. These are commonly used medications such as vasodilators, beta-adrenergic blockers and nitrates. The treatment of orthostatic hypotension revolves around the recognition of underlying causes or contributing factors amenable to correction or avoidance. Other helpful treatment options include nocturnal head-up tilting and mineralocorticoids, both of which help to expand blood volume. Many other therapeutic agents have been tried in small and selected patient populations, often with disappointing results. While many of the drugs available (phenylephrine, ephedrine, tyramine, dihydroergotamine) can improve upright blood pressure, side effects are common, and supine hypertension is problematic in many patients. Interventions of this type should be carefully initiated in a monitored setting. The carotid sinus is an important component of a neural control system responsible for heart rate and blood pressure homeostasis. Excessive heart rate and blood pressure responses to distortion of the carotid sinus are the basis for the carotid sinus syndrome (CSS). Patients with CSS tend to be elderly males and local pathology in the neck is frequently involved. Atherosclerotic coronary artery disease and hypertension are important clinical correlates. Two major categories of carotid sinus hypersensitivity (CSH) are recognized: cardioinhibitory and vasodepressor. Cardioinhibitory CSH is the most common, and in its purest form consists of sinus bradycardia or arrest, asystole or AV block during carotid sinus massage. This vagally-mediated response is eliminated by atropine. Cardiac pacing is nearly universally successful in preventing severe symptoms.(ABSTRACT TRUNCATED AT 400 WORDS) 相似文献
3.
Eddy current measurements of electrical conductivity and magnetic permeability of porous metals 总被引:1,自引:0,他引:1
This paper presents a method, which simultaneously estimates the electrical conductivity and magnetic permeability of porous metals. Porous Cu and Fe manufactured by the lost carbonate sintering process have been tested. An air-cored solenoid coil was designed for the measurements of rod-shaped samples when inserted coaxially with the coil. It was theoretically found that the phase-frequency response of the normalised eddy current signal of the coil is virtually independent of the radius, electrical conductivity and magnetic permeability of the test samples. For non-magnetic, conductive porous Cu, the electrical conductivity was measured with a calibration curve of the coil relating the impedance change and the electrical conductivity of the sample. For magnetic porous Fe, the imaginary part of the signal at the lowest frequencies can be used to estimate the permeability. The measured conductivity values of the porous Cu are shown in the paper in comparison with that of bulk materials with known conductivity. The measured permeability values of the porous Fe are given and the sample-length effect on the measurements is also discussed. 相似文献
4.
The experience of the Mississippi State University (MSU) Libraries illustrates the challenges presented by moving from consortial to local chat, as well as an evaluation of the advantages of chat reference in an academic setting. Countering the consortial, instant-messaging model prevalent in virtual reference today, the MSU Libraries have found chat offers advantages in an academic community. Moving to a local setting, it was possible for the MSU Libraries to maintain quality control over chat transactions while building relationships with faculty and students across campus. 相似文献
5.
Alireza Pourshahid Daniel Amyot Liam Peyton Sepideh Ghanavati Pengfei Chen Michael Weiss Alan J. Forster 《Electronic Commerce Research》2009,9(4):269-316
A number of recent initiatives in both academia and industry have sought to achieve improvements in e-businesses through the
utilization of Business Process Management (BPM) methodologies and tools. However there are still some inadequacies that need
to be addressed when it comes to achieving alignment between business goals and business processes. The User Requirements
Notation (URN), recently standardized by ITU-T, has some unique features and capabilities beyond what is available in other
notations that can help address alignment issues. In this paper, a URN-based framework and its supporting toolset are introduced
which provide business process monitoring and performance management capabilities integrated across the BPM lifecycle. The
framework extends the URN notation with Key Performance Indicators (KPIs) and other concepts to measure and align processes
and goals. An example process for controlling access to a healthcare data warehouse is used to illustrate and evaluate the
framework. Early results indicate the feasibility of the approach. 相似文献
6.
Sibylle Gruber Joy Kreeft Peyton Bertram C. Bruce 《Computer Supported Cooperative Work (CSCW)》1994,3(3-4):247-269
Research in computer-supported writing has traditionally compared electronic communication with oral, face-to-face communication to identify the benefits and weaknesses of each, as if they entailed dichotomous choices. In this article, we challenge that view and argue instead that any form of communication and its educational usefulness is shaped by the situation in which it is used, the backgrounds and goals of the participants, the institutional and technological setup, and the intended purpose of the medium. Three modes of communication in one graduate course are examined — oral discussion, synchronous written discussion on a local area network, and asynchronous written postings on an email list set up for the class. It was found that patterns of participation, topic introduction, and topic development differed across the three communication modes, but that the three were interwoven with each other and embedded within the larger classroom context and forms of knowledge creation in the class. Thus, rather than examining different communication media separately, researchers interested in understanding computer-supported collaborative writing need to look at how different media are used to create a meta-medium, which is established by the discourse community involved. 相似文献
7.
A three-dimensional inverse finite-element method applied to experimental eddy-current imaging data 总被引:1,自引:0,他引:1
Soleimani M. Lionheart W.R.B. Peyton A.J. Xiandong Ma Higson S.R. 《IEEE transactions on magnetics》2006,42(5):1560-1567
Eddy-current techniques can be used to create electrical conductivity mapping of an object. The eddy-current imaging system in this paper is a magnetic induction tomography (MIT) system. MIT images the electrical conductivity of the target based on impedance measurements from pairs of excitation and detection coils. The inverse problem here is ill-posed and nonlinear. Current state-of-the-art image reconstruction methods in MIT are generally based on linear algorithms. In this paper, a regularized Gauss-Newton scheme has been implemented based on an edge finite-element forward solver and an efficient formula for the Jacobian matrix. Applications of Tikhonov and total variation regularization have been studied. Results are presented from experimental data collected from a newly developed MIT system. The paper also presents further progress in using an MIT system for molten metal flow visualization in continuous casting by applying the proposed algorithm in a real experiment in a continuous casting pilot plant of Corus RD&T, Teesside Technology Centre. 相似文献
8.
Sema Sevinç Şengör Petros Gikas James G Moberly Brent M Peyton Timothy R Ginn 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(3):374-380
BACKGROUND: Microbial behavior in batch reactors may be different from that in continuous flow reactors, which is expected to affect microbial response to heavy metal exposure. Four parallel continuous flow reactors and batch growth tests were used to investigate the single and joint toxicity of Zn and Cu to Artrobacter sp. JM018. RESULTS: The results indicated that Cu is more toxic than Zn under all conditions. In the batch reactors, all Zn concentrations showed a stimulatory effect on microbial growth. However in the continuous system, 125 µmol L?1 Zn exposure produced inhibition. In the case of mixed Zn and Cu exposures in the batch system, the presence of Zn reduced the severity of Cu inhibition, with a net impact of reduced growth in all cases, whereas in the continuous system microbial growth and substrate utilization rates sharply decreased and ceased. CONCLUSION: The results clearly showed that growth in batch reactors underestimated significantly the heavy metal inhibition, compared with the continuous system. Therefore, the results of batch reactor tests should not be used directly when heavy metal inhibition is to be interpreted for continuous flow systems. Copyright © 2011 Society of Chemical Industry 相似文献
9.
10.
Mahbub Alam Md. Akram Hossain David R. Yonge Brent M. Peyton James N. Petersen 《Canadian Metallurgical Quarterly》2006,132(3):358-366
Hexavalent chromium (Cr(VI)) contamination of soil and groundwater is a major environmental concern for some industrial sites and most of the U.S. Department of Energy sites. Cr(VI) is toxic and fairly mobile in groundwater. Bioreduction of Cr(VI) to less toxic and less mobile Cr(III) is considered to be a feasible option. Among the Cr(VI) reducing bacteria, Shewanella oneidensis MR-1 (MR-1) has been shown to be effective in metal reduction under anaerobic conditions. Data on bioreduction of Cr(VI) by MR-1 in a flow-through soil column that better approximates the subsurface condition are not available. The objective of this research project was to study the bioreduction of Cr(VI) by MR-1 in a continuous-flow quartz sand column system. MR-1 was found to be very effective in reducing Cr(VI) to Cr(III) for concentrations ranging from 0.055 mM (2.85?mg/L) to 0.006 mM (0.31?mg/L). The amount of Cr(VI) reduced prior to its breakthrough was found to be inversely proportional to its concentration in the feed due to increased inhibition of microbial activity and a residual reduction of 20–45% of Cr(VI) was observed even after its breakthrough. 相似文献