Simulation Of Random Set Covering Problems With Known Optimal Solutions And Explicitly Induced Correlations Amoong Coefficients

The objective of this research is to devise a procedure to generate random Set Covering Problem (SCP) instances with known optimal solutions and correlated coefficients. The procedure presented in this work can generate a virtually unlimited number of SCP instances with known optimal solutions and realistic characteristics, thereby facilitating testing of the performance of SCP heuristics and algorithms. A four-phase procedure based on the Karush-Kuhn-Tucker (KKT) conditions is proposed to generate SCP instances with known optimal solutions and correlated coefficients. Given randomly generated values for the objective function coefficients and the sum of the binary constraint coefficients for each variable and a randomly selected optimal solution, the procedure: (1) calculates the range for the number of possible constraints, (2) generates constraint coefficients for the variables with value one in the optimal solution, (3) assigns values to the dual variables, and (4) generates constraint coefficients for variables with value 0 in the optimal solution so that the KKT conditions are satisfied. A computational demonstration of the procedure is provided. A total of 525 SCP instances are simulated under seven correlation levels and three levels for the number of constraints. Each of these instances is solved using three simple heuristic procedures. The performance of the heuristics on the SCP instances generated is summarized and analyzed. The performance of the heuristics generally worsens as the expected correlation between the coefficients increases and as the number of constraints increases. The results provide strong evidence of the benefits of the procedure for generating SCP instances with correlated coefficients, and in particular SCP instances with known optimal solutions

Laparoscopic Cholecystectomy in Chronic Calculus Cholecystitis

Introduction: Laparoscopic cholecystectomy has clearly become the choice over open cholecystectomy in the treatment of hepatobiliary disease since its introduction by Mouret in 1987. This study evaluates a series of patients with chronic calculus cholecystitis who were treated with laparoscopic and open cholecystectomy and assesses the outcomes of both techniques. Objective: To evaluate the efficacy of laparoscopic vs open cholecystectomy in chronic calculus cholecystitis and establish the out-comes of this treatment modality at Lumbini Medical College and Teaching Hospital. Methods: This was a retrospective analysis over a one-year period (January 1, 2012 to December 31, 2012), per-formed by single surgeon at Lumbini Medical College and Teaching Hospital located midwest of Nepal. 166 patients underwent surgical treatment for chronic calculus cholecystitis. Patients included were only chronic calculus cholecystitis proven histopathologocally and the rest were excluded. Data was collected which included patients demographics, medical history, presentation, complications, conversion rates from laparoscopic. cholecystectomy to open cholecystectomy, operative and postoperative time. Results: Patients treated with laparoscopic cholecystectomy for chronic calculus cholecystitis had shorter operating times and length of stay compared to patients treated with open cholecystectomy for chronic calculus cholecystitis. Conversion rates were 3.54% in chronic calculus cholecystitis during the study period. Complications were also lower in patients who underwent laparoscopic cholecystectomy versus open cholecystectomy for cholelithiasis. Conclusions: Laparoscopic cholecystectomy appears to be a reliable, safe, and cost-effective treatment modality for chronic calculus cholecystitis

Experience of Laparoscopic Cholecystectomy at Lumbini Medical College Teaching Hospital

  Introduction: The difficult gallbladder is the most common difficult laparoscopy being performed by generalsurgeons all over the world and the potential one that places the patient at significant risk. The present study aimed to study all the cases of laparoscopic cholecystectomy conducted in current setup at Lumbini Medical College and Teaching Hospital, to compare the results with the published literature and also analyze the complications and ways to decrease the incidence of conversion to open procedure.   Methods: Five hundred twenty five patients age 10-90 years, male:female ratio of 1:3.86 with body weight 45-65 kilogram, who had undergone laparoscopic cholecystectomy for symptomatic cholelithiasis without choledocholithiasis from April 2011 to April 2013 were studied.   Results: All the laparoscopic cholecystectomy (LC) were without major complications. Only nineteen out of five hundred twentyfive (3.6%) required conversion to open cholecystectomy (OC). Reasons for conversion included: dense omental or visceral adhesions; two (0.38%), unclear anatomy; 16 (3.04%), common bile duct injury; one (0.19%). There were 20 cases of shrunken gallbladder suspicious of malignancy but didn’t required conversion.   Conclusion: Laparoscopic cholecystectomy is the preferred method in our setup even in difficult cases

EVALUATION OF IMMUNOMODULATORY ACTIVITY OF PETROLEUM ETHER EXTRACT OF SEEDS OF PITHECELLOBIUM DULCE IN WISTAR RATS

Objective: The present study was planned to assess the immunomodulatory action of petroleum ether extracts of seeds of Pithecellobium dulce (PEPD) in experimental models of immunity.Methods: Metronidazole, pyrogallol and ethanol models were used for suppression of the immune system in Wistar rats. Humoral immunity was analyzed by haemmagglutination assay, whereas, cellular immunity was carried out by paw edema and carbon clearance assay. PEPD (400 mg/kg, p. o.) was selected by acute toxicity study. Levamisole (50 mg/kg, p. o.) was used as standard.Results: Metronidazole, pyrogallol and ethanol significantly decreased the humoral and cellular immunity, whereas, PEPD and levamisole significantly increased the circulating antibody titer in the indirect haemagglunation test. PEPD and levamisole also produced significant increases in paw edema and increase in the phagocytic index in the carbon clearance assay. Animals treated with metronidazole, pyrogallol and ethanol decreased in peripheral blood RBCs and monocytes whereas, PEPD and levamisole treated groups significantly increased in peripheral blood RBCs and monocytes.Conclusion: Our data showed that PEPD possesses potential for augmenting immune activity by cellular and humoral mediated mechanisms and also significantly restores the biochemical and histopathological parameters. The present study concluded that PEPD may have therapeutic and prophylactic value as immunostimulants.Â

Interspecies and seasonal variations in macroalgae from the Nordic region: Chemical composition and impacts on rumen fermentation and microbiome assembly

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A Family Of Composite Discrete Bivariate Distributions With Uniform Marginals For Simulating Realistic And Challenging Optimization-Problem Instances

We consider a family of composite bivariate distributions, or probability mass functions (pmfs), with uniform marginals for simulating optimization-problem instances. For every possible population correlation, except the extreme values, there are an infinite number of valid joint distributions in this family. We quantify the entropy for all member distributions, including the special cases under independence and both extreme correlations. Greater variety is expected across optimization-problem instances simulated based on a high-entropy pmf. We present a closed-form solution to the problem of finding the joint pmf that maximizes entropy for a specified population correlation, and we show that this entropy-maximizing pmf belongs to our family of pmfs. We introduce the entropy range as a secondary indicator of the variety of instances that may be generated for a particular correlation. Finally, we discuss how to systematically control entropy and correlation to simulate a set of synthetic problem instances that includes challenging examples and examples with realistic characteristics

Simulating Realistic Set Covering Problems With Known Optimal Solutions

This paper outlines a methodology to generate random Set Covering Problem (SCP) instances with known optimal solutions and correlated coefficients. Positive correlation between the objective function coefficients and the column sums of the SCP constraint matrix is known to affect the performance of SCP solution methods. Generating large SCP instances with known optimal solutions and realistic coefficient correlation provides a plethora of test problems with controllable problem characteristics, including correlation, and an ample opportunity to test the performance of SCP heuristics and algorithms without having to solve the problems to optimality. We describe the procedure for generating SCP instances and present the results of a computational demonstration conducted on SCP instances generated by our procedure. This computational demonstration shows that the heuristics\u27 relative errors increase as the correlation increases, that the likelihood of finding a non-optimal solution also increases with the level of correlation, and that the quality of the solutions found is affected by the number of constraints. © 2011 Elsevier Ltd. All rights reserved

Simulation Of Random Set Covering Problems With Known Optimal Solutions And Correlated Coefficients

This paper outlines a methodology to generate random Set Covering Problem (SCP) instances with known optimal solutions and correlated coefficients. It has been established that positive correlation between the objective function coefficients and the column sums of the SCP constraint matrix affects the performance of SCP solution methods. Generating large SCP instances with known optimal solutions and realistic coefficient correlation not only provides an ample opportunity to test the performance of heuristics but also provides a plethora of test problems with controllable problem characteristics, such as correlation. We describe the procedure for generating SCP instances and finally show the results for a pilot study conducted on SCP instances generated by our procedure

Modeling Consumer Sensitivity For Product Design And Perceived Usability

The primary objective of this research paper is to investigate the relationship between the perceived qualities of home appliances with respect to various design features. Consumers may define their fondness of the particular system or model over other model(s) by using different sensibility words such as robust, sleek, luxurious, reliable, sturdy, comfortable etc. It is the objective of this study to determine the principal sensibility word(s) consumers use to define their perceived feelings about the particular model and investigate if these words are related to the design elements of the system and if such relationship exits, then the objective is to determine the optimal design criteria(s) so as to attain the maximum possible perceived quality of the system for which the consumer may have upon interacting with other comparable systems. This research is based on statistical regression and correlation analysis with multiple linear objective programming (MLOP) for thirteen selected sensibility words and twelve product models with respect to forty nine design elements (37 unique design elements broken down to 49 independent variables). Results provided significance using statistical modeling arrived at fuzzy set logic and MLOP. © 2013 Springer-Verlag Berlin Heidelberg

Application Of Evolving Self-Organizing Maps For Analysis Of Human Adverse Events In The Context Of Complex Socioeconomic Infrastructure Interactions

The main objective of this study was to investigate complex human socioeconomic infrastructure interactions and information on past human adverse events (AE) in an active war theater in order to predict future AE in a given geographical region. Human AE were defined as those security-related events that threatened human lives. Human socioeconomic infrastructure development data were derived by integrating three different datasets from different sources based on the United States Agency for International Development database. Using empirical data obtained from the country of Afghanistan from 2002 to 2010, we applied evolving self-organizing maps (ESOM) to forecast future patterns of such AE. Records from 2003-2009 were used as training data, while records from year 2010 were used to test the efficacy of ESOM in predicting AE. The socioeconomic data, dates, and geographical location information was used as input for the trained model. ESOM algorithm with supervised learning was effective in understanding future patterns of AE in a war region. The results also showed the possibility of predicting future AE based on the incomplete information pertaining to the geographical location, recent history of AE in the specific region of the country, and relevant socioeconomic infrastructure development data. The differences in applying the classical self-organizing maps and ESOM approaches for modeling of complex human socioeconomic infrastructure interactions were also discussed