Sequential Simplex Algorithm Research Articles

Optimization of the Powder Injection Molding Process Parameters Using the Sequential Simplex Algorithm and Sensitivity Analysis

In this work, the minimization of warpage was investigated using the “moldflow” software and sequential simplex algorithm based on feedstock properties. Also, the sensitivity analysis was implemented to determine the degree of impact of each parameter on the warpage. This study is divided into two portions: experimental analysis and numerical analysis. First, for the experimental study, four kinds of feedstock with different alumina powder loadings were prepared to investigate the rheological properties. This investigation showed that the feedstock with 60 vol. % alumina powder was the optimum feedstock for the injection molding. Also, the results indicated that the viscosity of feedstock decreases by increasing both the shear rate and temperature. Next, the thermal conductivity of this feedstock was measured at different temperatures and it was found that the change of temperature can greatly influence the thermal conductivity of feedstock. In the numerical study, the injection molding parameters were divided into three categories. Based on the feedstock properties obtained form the first portion, and in order to minimize the warpage, the values of these parameters were sequentially acquired by moldflow and used in the sequential simplex algorithm for gradual convergence to the optimum level. To show the accuracy of numerical results, several samples were injection molded using the injection molding conditions for each vertex; results showed a close correlation between the values obtained by the numerical simulation and by the actual case. After determining the optimum parameter values, the sensitivity analysis was performed to identify the level of influence of each parameter on warpage. The obtained results showed that the most effective parameters on warpage are the mold temperature, packing pressure, and the holding time. Generally, it is demonstrated that the experimental and numerical analysis, performed via the moldflow software and sequential simplex algorithm, together with the sensitivity analysis can be useful in achieving success in the powder injection molding (PIM) technique.

Population-Based Metaheuristic Approximation For Dosimetric Optimization in CyberKnife Radiation Therapy Treatment Planning

Population-Based Metaheuristic Approximation For Dosimetric Optimization in CyberKnife Radiation Therapy Treatment Planning

Development of a chaotic nonlinear tuned mass damper for optimal vibration response

In this article an efficient method is developed for optimal design of a nonlinear tuned mass damper (N-TMD) system. Using several horizontal linear springs coming into action sequentially, system nonlinearity can be achieved with ease as a novel method. Friction force between tuned mass and the structure is variably produced by a vertical linear spring that follows a specified controlling curved path allowing reduction of the desired tuned mass. Chaotic behavior of the introduced tuned mass is investigated in terms of the existing parameters in the system. Lyapunov characteristic exponents are determined to demonstrate the chaotic behavior of the system. It is confirmed by comparison that the proposed scheme is able to retrofit structures in a superior way than some other devices such as multiple tuned mass damper systems. The optimization procedure is performed by sequential Simplex algorithm, while Newmark’s beta method for step by step integration is used to find the dynamic response of the structure.

Simplex-Based Calibration of Traffic Microsimulation Models with Intelligent Transportation Systems Data

In recent years, microsimulation has become increasingly important in transportation system modeling. A potential issue is whether these models adequately represent reality and whether enough data exist with which to calibrate these models. There has been rapid deployment of intelligent transportation system (ITS) technologies in most urban areas of North America in the last 10 years. While ITSs are developed primarily for real-time traffic operations, the data are typically archived and available for traffic microsimulation calibration. A methodology, based on the sequential simplex algorithm, that uses ITS data to calibrate microsimulation models is presented. The test bed is a 23-km section of Interstate 10 in Houston, Texas. Two microsimulation models, CORSIM and TRANSIMS, were calibrated for two different demand matrices and three periods (morning peak, evening peak, and off-peak). It was found for the morning peak that the simplex algorithm had better results then either the default values or a simple, manual calibration. As the level of congestion decreased, the effectiveness of the simplex approach also decreased, as compared with standard techniques.

Simplex optimization of ion-pair reversed-phase high performance liquid chromatographic analysis of some heavy metals

The sequential simplex algorithm was used to optimize the ion-pair reversed phase high performance liquid chromatographic (IP-RPHPLC) analysis of 4-(2-pyridylazo)resorcinol (PAR) chelates of Co(II), Ni(II) and Cr(III). A chromatographic response function (CRF) which included the number of peaks, the resolution between adjacent peaks, a specified analysis time, and the individual retention times relative to a minimum retention time, was calculated to evaluate the quality of the individual chromatograms. The optimum conditions for the three experimental parameters were 28.6% acetonitrile in the mobile phase, 3.0 mmol l −1 concentration of acetate buffer at pH 6.0, and 5.2 mmol l −1 tetrabutylammonium bromide (TBABr). Optimum conditions were achieved in only 19 experiments. The order of elution was Co(II)PAR, Cr(III)PAR and Ni(II)PAR, respectively, with an analysis time of 15 min.

Solid-phase microextraction method for gas chromatography with mass spectrometric and pulsed flame photometric detection: studies of organoarsenical speciation

The development, optimization, and application of a novel method for arsenic speciation based on capillary gas–liquid chromatography with simultaneous quadrupole ion-trap mass spectrometric (MS) detection and pulsed flame photometric detection (PFPD) is described. The method couples the sensitive arsenic-selectivity of PFPD with the structure elucidation capability of molecular MS detection for the determination of trace levels of unknown organoarsenicals in complex matrices. The conditions that affect the PFPD response in the presence of interfering species were optimized using the sequential Simplex algorithm for three key factors: gate delay (18.3 ms), gate width (9.1 ms), and combustion gas composition (16.6 ml/min H 2). Complete discrimination in the PFPD of the arsenic signal from interfering S-, C-, and OH-emitting species that are problematic in existing methods was achieved. Additionally, a revised interpretation of our previously reported mechanism [J. Chromatogr. A 807 (1998) 253] for the dithiol derivatization and subsequent GC–MS determination of dimethylarsinic acid is presented.

Nonisothermal kinetics — comparison of two methods of data treatment

A kinetic study of the acid-catalyzed hydrolysis of p-nitrophenyl acetate was carried out by subjecting the reaction mixture to a linear increase in temperature. Two commonly used methods of data treatment were compared to determine the precision and limitations of each. In the first method, the concentration data were transformed by a function dependent on reaction order. The resulting function was fitted to a power series with time. The derivative of this equation provided a rate constant at each temperature. A subsequent Arrhenius plot gave an estimation of the pseudo first-order rate constant at 25°C. After a correction was made for the rate of uncatalyzed hydrolysis, the second-order rate constant for acid-catalyzed reaction was determined. The values of E (activation energy) and Z (pre-exponential factor) determined by this method were dependent on the number of terms used in the polynomial fit (see Table 1). In a second data treatment, the temperature values were fitted to a polynomial with respect to time. Using initial estimates of E and Z, predicted concentrations were evaluated by numerical integration of the rate expression. A sequential simplex algorithm (Deming and Parker, 1978) located values for E and Z that satisfied the least-squares criterion. The integration method generated approximations of E, Z, and the second-order rate constant, k H, which to 3 significant figures did not vary with the number of polynomial terms. The latter method did, however, require an extensive amount of computer time, depending on the initial estimates used in the algorithm. Both techniques yielded similar rate parameter estimates which agreed favorably with literature values (Tucker and Owen, 1982; Eriksen and Stelmach, 1965; Connors, 1963; Bruice and Schmir, 1957).

Using a microprocessor in high performance liquid chromatography

The background and use of a microprocessor-controlled liquid chromatograph to carry out the automatic optimization of high performance liquid chromatography (HPLC) separations is discussed. The procedure is based upon the use of the modified sequential simplex algorithm to select the optimum composition of a three component mobile phase. The way in which the simplex algorithm is incorporated into a program and the hardware used is described. The use of this approach provides the chromatographer with the ability to optimize HPLC separations without requiring either extensive theoretical knowledge or a great expenditure of time and effort.

Unattended optimisation of reversed-phase high-performance liquid chromatographic separations using the modified simplex algorithm

It is shown that the modified sequential simplex algorithm can be used as the basis for the unattended optimisation of reversed-phase liquid chromatographic separations. A chromatographic response function is computed to evaluate individual chromatograms with respect to resolution and analysis time. This function is used automatically by a microprocessor-controlled chromatograph to optimise experimental parameters. The use of the procedure is illustrated by the automated optimisation of two and three component mobile phases and the optimisation of a gradient elution profile.

Simplex Optimization of Reaction Yields

The sequential simplex algorithm, an efficient optimization strategy, rapidly improved reaction yield as a function of time and temperature in the synthesis of pi-C(5)H(5)Mo(CO)(2)CSN(CH(3))(2). The work demonstrates the feasibility and efficiency of the simplex design and suggests its application and usefulness in other syntheses.