In this study, we examine a competitive Nicholson blowflies model with time-varying coefficients and continuous time delays. In the case of coincidence degree theory, constructing appropriate ...Lyapunov functionals and using several inequalities, several conditions on the extinction, periodic solution, permanence, and global attractiveness of the system are derived. Finally, three examples with numerical simulations are presented to validate the practicability and feasibility of the obtained theoretical results.
The air-gap flux linkage of a dual-stator-winding squirrel-cage induction machine comprises of four fundamental flux components due to the currents flowing in the two stator windings with P 1 and P 2 ...pole numbers and the currents that they induce in the squirrel cage. In view of the dissimilar pole numbers of the stator windings and frequencies of the supply voltages, the air-gap flux linkage waveform is complex, particularly when the stator and rotor teeth are saturated. This paper explores this complexity using analytic computer simulation, finite-element analysis, and some experimental results. Furthermore, a fundamental component circuit model of the machine is set forth, which, with the use of a specially defined reference frame transformation, permits an accurate simulation of the transient and dynamic characteristics. Computer simulation results are validated by some experimental results obtained from a 2-hp machine.
This paper investigates the use of a dual stator winding squirrel-cage induction machine for generating dc power using series- or parallel-connected ac-dc pulse width modulation rectifiers. The ...operating principles and constraints when generating under minimum total copper-loss condition are explored using the machine steady-state model considering magnetizing flux saturation effects. Regulation of the dc voltage using concepts of the nonlinear input-output linearization method including the design of the controllers is set forth and confirmed to be effective by computer simulation results. Some experimental waveforms of the generator under load are also included in this paper
•This study examines the relationship between tax and supply chain finance.•Tax have dramatic effects on multinational firms’ financial decisions.•Questions of how firms can apply this knowledge are ...considered.
Tax and capital play critical roles in the business of multinational firms. This study investigates the optimal financing strategy between bank credit financing and trade credit financing when a multinational firm invests in a capital-constrained retailer located in a low-tax jurisdiction. We find that tax differences and varying dividend rates have significant effects on a multinational firm's decisions. In a basic model, we show a tax-related dividends rate that is less than one but can eliminate double marginalization in bank credit. In trade credit, we find that the optimal wholesale price changes with tax and dividend rate. When both bank and trade credits are viable, we find that the differences in dividends rates and tax rates are two critical factors in determining the optimal strategy, and we investigate the joint effect of these rates on the optimal financing strategy. When examining the impact of tax asymmetry on both retailers’ and multinational firms’ decisions, under bank credit, multinational firms will reduce the wholesale price to induce higher orders, but they will never offer trade credit. When both bank and trade credits are viable alternatives, the optimal financing strategy is bank credit when tax asymmetry exists. Lastly, the production cost threshold value that separates the unique financing equilibrium is lower due to the impact of taxes. Our findings can offer financing insights to both multinational firms and capital-constrained divisions.
Product family design (PFD) is a popular method for increasing product variety to satisfy the needs of diversified markets. With the increasing concern for environmental friendliness in society, more ...and more companies develop launching remanufactured products and include them in their product families. Therefore, PFD should be considered in a broad decision space where configuration of product variants and remanufacturing are considered simultaneously. However, this issue was not addressed properly in previous research. In this paper, a methodology for joint decision of product configuration and remanufacturing is proposed in which a bi-objective mixed integer programming model is formulated to determine the configurations of both new and remanufactured products for minimising product cost, maximising total market share, and satisfying reliability requirements. Then, Non-dominated Sorting Genetic Algorithm II (NSGAII) is adopted to solve the optimization problem. Computational experiments were conducted and their results show that NSGAII is convergent to the model well. A case study is presented to illustrate the applicability and effectiveness of the proposed methodology.
•The study compares the cost-plus and resale-price transfer pricing strategies.•These strategies are introduced into a tax-efficient supply chain model considering tax asymmetry.
Many multinational ...companies now relocate their procurement departments to low-tax jurisdictions to benefit from low tax rates via transfer pricing. This study examines which transfer pricing strategy should be adopted: the cost-plus or the resale-price method. This study considers a two-echelon supply chain consisting of one overseas procurement center and one or several divisions that order components from the procurement center. Strategically, corporate management can choose between an operating structure with a buy–sell model or a “commissionaire” model for the procurement center. Corporate management should design a transfer pricing method to optimize the supply chain's total after-tax profits under each structure. We then examine the tax benefits the procurement center can bring and the coordination issues involved in each structure. We find that some of the optimal decisions exhibit interesting non-monotone behavior. For instance, the results do not conclusively determine which system is better. We derive and analyze the threshold values of the bargaining performance parameters that describe the main trade-offs involved in selecting an operating structure. To clarify the structure of the problem and illustrate our findings, the study also conducts numerical experiments.
One important objective of component-based software engineering is the minimization of the development cost of software products. Thus, the costs of software component implementation and ...verification, which may involve substantial expenses while under development, should be reduced. In addition, the costs for these processes should not be considered individually, but in an integrated manner, to further reduce development cost. In the current paper, an integrated decision model is proposed to assist decision-makers in selecting reuse scenarios for components used for implementation and in simultaneously determining the optimal number of test cases for verification. An objective of the model is the minimization of development cost, while satisfying the required system and reliability requirements. The Lagrange relaxation decomposition (LRD) method with heuristics was developed to solve integrated decision problems. Based on LRD, the nonlinear model is condensed into a 0–1 knapsack problem for the subproblem on reuse scenario selection and an integer knapsack problem for the subproblem on the determination of the optimal number of tests. Combined with the Lagrange multiplier-determined heuristic, the proposed algorithm can determine the global optimum solution. Simulations of varying sizes for problems and sensitivity analyses were conducted, and the results indicate that LRD is more effective than previous methods in determining global optimal solutions for the integrated decision problem.
► An integrated decision model is proposed to select components reuse scenarios and determine the optimal number of test cases. ► An Objective of the model is to minimize development cost and satisfy the required system and reliability requirements. ► Lagrange relaxation decomposition (LRD) method with heuristics was developed to solve the integrated decision problem. ► Combined with the Lagrange multiplier-determined heuristic, the proposed algorithm can determine global optimum solution.
This paper presents a control methodology for the dc voltage regulation of an induction generator/ac-dc boost rectifier system, in which the copper loss of the generator is minimized. With the aid of ...an input-output linearization technique, which linearizes and decouples the model equations in the synchronous reference frame, a rotor-flux-vector-control-type high performance is achieved. Steady-state analysis provides some insights into the operability regime of the generator. The effectiveness of the control scheme under different load conditions as well as varying rotor speeds has been demonstrated by computer simulations. Some experimental results have been included
Leukocyte esterase test (LET) detection is a simple and inexpensive test performed by urinalysis. This study investigated the predictive value of LET for
(CT) and
(NG) infection among men attending ...HIV and sexually transmitted infection (HIV/STI) clinics in Guangdong Province, China. A total of 5,509 urine samples were collected from HIV and sexually transmitted infection clinics in Guangdong Province between 2017 and 2019. Specimens from 5,464 males were tested by both LET and nucleic acid amplification test (NAAT). Of 5,464 males, 497 (9.1%) tested positive for CT or NG by NAAT, with respective prevalence rates of 6.4% (95% confidence interval 95% CI: 5.8-7.1%) and 3.8% (95% CI: 3.3-4.3%), including 1.2% (95% CI: 0.9-1.4%) co-infected. Compared to the HIV-negative individuals, individuals living with HIV tend to have a higher prevalence of CT, NG and co-infection with CT and NG. The LET sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for CT were 46.4% (95% CI: 41.2-51.7%), 92.0% (95% CI: 91.2-92.7%), 28.4% (95% CI: 24.8-32.1%), and 96.1% (95% CI: 95.6-96.7%), respectively. The LET sensitivity, specificity, PPV, and NPV for NG were 68.4% (95% CI: 62.1-74.7%), 91.8% (95% CI: 91.1-92.6%), 25.0% (95% CI: 21.4-28.5%), and 98.7% (95% CI: 98.3-99%), respectively. Compared to the HIV-negative individuals, higher sensitivity and specificity were observed for HIV-positive individuals, but there was no statistical difference. The incremental cost-effectiveness ratio (ICER) using economic costs per additional person CT positive and NG positive was -$238.74 and -$145.60 compared with LET positive, respectively. LET is a cost-effective test and will be valuable for predicting CT and NG infection, which is highly prevalent in low- and middle-income countries.
One of the core problems in software product family (SPF) is the coordination of product building and core asset development, specifically the integration of production strategy decision and core ...asset scenario selection. In the current paper, a model of Cost Optimization under Functional And Quality (CoFAQ) goal satisfaction constraints is developed. It provides a systematic mechanism for management to analyze all possible products and evaluate various reuse alternatives at the organizational level. The CoFAQ model facilitates decision-makers to optimize the SPF development process by determining which products are involved in the SPF (i.e. production strategy) and which reuse scenario for each module should be selected to implement the SPF toward minimum total developing cost under the constraints of satisfying functional and quality goals. A two-phase algorithm with heuristic (TPA) is developed to solve the model efficiently. Based on the TPA, the CoFAQ is reduced to a weighted set-covering problem for production strategy decision and a knapsack problem for the reuse scenario selection. An application of the model in mail server domain development is presented to illustrate how it has been used in practice.
► A model of Cost Optimization under Functional And Quality (CoFAQ) goal is developed. ► Integrated decision problem of production strategy and reuse scenario is formulated. ► We developed a six-layer hierarchical scheme to support core asset development. ► An application of the model in mail server domain development is presented.
