A bi-level decision model for customer churn analysis

This paper develops a bi-level decision model and a solution approach to optimizing service features for a company to reduce its customer churn rate. First, a bi-level decision model, together with its modeling approach, are developed to describe the gaming relationship between decision makers in a company (service provider) and its customers. Then, a practical solution approach to reaching solutions for the bi-level-modeled customer churn problem is developed. Finally, experiments and case studies are conducted to illustrate the bi-level decision model and the solution approach. © 2013 Wiley Periodicals, Inc

Prevalence of Helicobacter pylori in symptomatic patients and detection of clarithromycin resistance using melting curve analysis

AbstractBackground:Clarithromycin is often a component of combination therapies for Helicobacter pylori eradication; however, increases in resistance rates have decreased the success of the treatment.Objective:This study was designed to determine the prevalence of H pylori infection in symptomatic patients and to detect clarithromycin resistance rates using melting curve analysis.Methods:Patients scheduled for upper endoscopy at the Endoscopy Unit of the Department of Gastroenterology, Duzce University, Medical Faculty Hospital, Konuralp/Duzce, Turkey, were assessed for enrollment in the study. Two pairs of gastric biopsy specimens (antrum and corpus) were obtained from each study patient. Histopathologic examination, rapid urease test, culture, and polymerase chain reaction (PCR) of the specimens were used to identify H pylori infection. Clarithromycin resistance was detected using melting curve analysis.Results:Seventy-five patients (41 women, 34 men; mean [SD]age, 42.6 [14.5] years [range, 17–70 years]) were included in the study. Using histopathology and rapid urease test, H pylori was detected in 40 (53.3%) of the 75 specimens. H pylori was detected using PCR in 40 (53.3%) specimens and by culture in 10 (13.3%) specimens. The specificity and sensitivity of PCR and culture were interpreted by comparing them with the results of histopathologic examination and urease tests. The specificity and sensitivity of PCR were 68.6% and 72.5%, respectively, and the specificity and sensitivity of culture were 97.1% and 22.5%, respectively. Of the 40 isolates, 21 (52.5%) were susceptible to clarithromycin, 12 (30.0%) were resistant, and a mixed susceptibility pattern was detected in 7 (17.5%) specimens. H pylori isolates from 19 (79.2%) of the 24 patients who had formerly used clarithromycin showed clarithromycin resistance.Conclusions:The prevalence of H pylori infection was 53.3% for the symptomatic patients in this study, and 47.5% of the isolates showed clarithromycin resistance using melting curve analysis. The PCR-based system used in this study was accurate for the detection of H pylori infection as well as clarithromycin susceptibility testing directly in biopsy specimens

New Synthesis Models for the Coplanar Waveguide with a Finite Width Ground Plane

In this study, new synthesis models for the coplanar waveguide with a finite width ground plane were obtained by genetic programming. Genetic programming is a powerful evolutionary algorithm technique for engineering problems. Genetic programming has a very important advantage with respect to the other artificial neural techniques such as determining a mathematical model by using the relationships between the variables. To show the validity of proposed synthesis models for the coplanar waveguide with a finite width ground plane, obtained results are compared with the results of quasi-static analysis results and very good agreements between them were observed. To determine the synthesis models developed by genetic programming, 9712 data sets belong to coplanar waveguides having different electrical parameters and different geometrical dimensions are used. The average percentage error of the synthesis models was determined to be 1.48%

Very simple synthesis formulas for microcoplanar striplines

Accurate and very simple synthesis formulas for the microcoplanar strip (MCS) lines are presented. They are very useful for microwave engineers to easily and accurately compute the physical dimension of MCS lines. The coefficients in the synthesis formulas are determined with the use of artificial bee colony algorithm. The results of the synthesis formulas are compared with the results of respective quasi-static analysis, other synthesis formulas, and experimental works available in the literature to show the validation of synthesis formulas presented in this article. The average percentage error is calculated 3.07% for 864 MCS line samples having different electrical parameters and physical dimensions. (C) 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:615619, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.2737

VERY SIMPLE AND ACCURATE COMPUTER-AIDED-DESIGN (CAD) MODELS DEVELOPED BY GENETIC PROGRAMMING FOR THE QUASI-STATIC ANALYSIS OF UNSHIELDED SUSPENDED AND INVERTED MICROSTRIP LINES

Very simple computer-aided-design models are introduced to determine the characteristic parameters such as effective permittivities and characteristic impedances of unshielded suspended and inverted microstrip lines. Computer-aided-design models are determined with the use of the genetic programming. The results of computer-aided-design models are compared with the results of quasi-static analysis, experimental works available in the literature and a commercial electromagnetic simulator. The comparison results clearly show that computer-aided-design models proposed in this work are in very good agreement with the simulation, theoretical and experimental results for the suspended and inverted microstrip lines. The design parameter ranges in this work are 2 <= epsilon(r2) <= 20, 0.5 <= w/b <= 10, 0.1 <= a/ b <= 1.5, and the respective characteristic impedances of unshielded suspended and inverted microstrip lines are 28 Omega <= Z(0) <= 185 Omega, and 24 Omega <= Z(0) <= 159 Omega, respectively. It is observed that the accuracies of computer-aided-design models proposed in this paper are good enough for the most practical cases

Closed-form design equations for asymmetric coplanar strip line with an infinitely wide strip

This article presents very simple closed-form design equations to calculate the geometrical dimensions of asymmetric coplanar strip line with an infinitely wide strip (CPSIWS). The coefficients of the design equations are determined by artificial bee colony algorithm (ABCA) that is a powerful optimization technique. The results of the proposed design equations are compared with the results of other design equations, experimental works previously published in the literature, quasi-static analysis in the literature, and IE3D software. Accuracy of the characteristic impedances calculated by the design equation results proposed in this work is found to be better than 0.53% with respect to the desired characteristic impedances for 1,960 asymmetric CPSIWS samples

Design and Implementation of a Control System to Mitigate Osteonecrosis in Orthopedic Bone Drilling Procedures

The drilling process in orthopedic surgery can sometimes lead to an undesired increase in temperature, which can cause serious damage to bones and soft tissues. This overheating is typically identified as a temperature above 47 °C, known as the critical limit, and can result in the condition known as osteonecrosis. This study aims to develop a new control system, using a proportional-integral-derivative (PID) controller, to prevent overheating and the resulting osteonecrosis. The bone temperature is constantly measured using a thermocouple and, when it reaches the critical temperature of 47 °C, the cooling device is activated by the PID-controlled system. This new control system makes the drill machine with cooling device more user-friendly and allows surgeons to set a desired temperature level manually