Powell's Optimization Method Research Articles

A novel ensemble approach with deep transfer learning for accurate identification of foodborne bacteria from hyperspectral microscopy

The detection of foodborne bacteria is critical in ensuring both consumer safety and food safety. If these pathogens are not properly identified, it can lead to dangerous cross-contamination. One of the most common methods for classifying bacteria is through the examination of Hyperspectral microscope imaging (HMI). A widely used technique for measuring microbial growth is microscopic cell counting. HMI is a laborious and expensive process, producing voluminous data and needing specialized equipment, which might not be widely available. Machine learning (ML) methods are now frequently utilized to automatically interpret data from hyperspectral microscopy. The objective of our study is to devise a technique that employs deep transfer learning to address the challenge of limited data and utilizes four base classifiers - InceptionResNetV2, MobileNet, ResNet101V2, and Xception - to create an ensemble-based classification model for distinguishing live and dead bacterial cells of six pathogenic strains. In order to determine the optimal weights for the base classifiers, a Powell's optimization method was utilized in conjunction with a weighted average ensemble (WAVE) technique. We carried out an extensive experimental study to verify the efficiency of our proposed ensemble model on live and dead cell images of six different foodborne bacteria. In order to gain a better understanding of the regions, we performed a Grad-CAM analysis to explain the predictions made by our model. Through a series of experiments, our proposed framework has proven its capacity to effectively and precisely detect numerous bacterial pathogens. Specifically, it achieved a perfect identification rate of 100 % for Escherichia coli (EC), Listeria innocua (LI), and Salmonella Enteritidis (SE), while achieving rates of 96.30 % for Salmonella Typhimurium (ST), 87.13 % for Staphylococcus aureus (SA), and 94.12 % for Salmonella Heidelberg (SH). As a result, it can be considered as an effective tool for the identification of foodborne pathogens, due to its high level of efficiency.

Heat Transfer Performance Optimization of Rectangular Channel with Truncated-root Ribs

Cooling designs inside the gas turbine blades of aircraft engines are aimed to solve a problem that has existed since the very beginning of the aerospace industry. Since the working environment of turbine blades is extremely harsh when the temperature can rise to 2000K, which is considered a huge challenge for any materials. Therefore, cooling designs such as rib turbulators have always been researched and optimized for better heat transfer enhancement in the cooling mechanism of turbine blades. In this study, a geometric optimization of the rib turbulators inside a rectangular channel was performed with the aim to maximize heat transfer performance. This study investigated the effect of four rib configurations on the heat transfer efficiency of the channel, which include square, truncated-root, convergent truncated-root, and divergent truncated-root rib. Thereby, a module of coupling Python and OpenFOAM was developed to automatically perform the optimization of truncated-root rib design at Reynolds number of 37,000 with design variables are the upstream and downstream height with Powell optimization method. The aim is to figure out the point where the maximum heat transfer performance of the channel is achieved. The study presented in a specific, productive, and accurate way the factors that directly and indirectly affect the heat transfer performance of the channel, thereby giving the optimal results that the channel has the highest heat transfer performance of the presented designs. The results show that the highest heat transfer performance of the optimized design is 12.45% higher than the standard square ribs case.

Dehydrogenation kinetic model of heavy paraffins

Based on the dehydrogenation mechanism of heavy paraffins under industrial conditions, the intrinsic reaction kinetic model and catalyst deactivation model were established considering the influence of side reactions with different carbon‐number heavy paraffins. Based on the experimental data of dehydrogenation reactions with different carbon‐number paraffins in an axial continuous‐flow isothermal fixed‐bed microreactor, Powell optimization method was used to estimate the model parameters. The results show that there is a liner relationship between the activation energies and pre‐exponential factors of homologous reactions and carbon number of paraffins. A correlation model about the deactivation rate constants under different conditions was established. The validation of kinetic model showed that the model could be used to predict detailed product distribution with different feedstocks under different reaction conditions. © 2017 American Institute of Chemical Engineers AIChE J, 2017

A Broadband Chip-Level Power-Bus Model Feasible for Power Integrity Chip-Package Codesign in High-Speed Memory Circuits

Based on two-port measurements, a distributed compact model and an extraction method for the power bus of a high-speed memory chip are proposed. The 1-D model is constructed according to the relative locations of the power and ground pads on the chip. The power bus around each power or ground pad is modeled by a section of resistor-inductor-capacitor (RLC) T-model, and the complete distributed model is formed by cascading all the T-model sections. The T-model at each section can be extracted through the measured two-port Z-parameters by using the Powell's optimization method. Because the model is extracted from measured data, detailed (or proprietary) chip-layout information is not necessary. Another advantage is this compact model keeps the broadband accuracy by the distribution concept and is easy to link with the package model for the power integrity codesign.

CT-MRI automatic surface-based registration schemes combining global and local optimization techniques

Medical image registration is commonly required in order to combine the complementary information provided by different medical imaging modalities. In this paper, a new automatic registration scheme is proposed to register 3-D CT-MR head images and is currently tested on a clinical environment. The proposed scheme, after the preprocessing and the outer surface extraction of the data, is based on the use the rigid transformation method, in conjunction with a combination of global and local optimization techniques. Analytically, the paper exploits the optimization efficiency of three widely used optimization techniques, in obtaining the parameters of the rigid transformation model: the Downhill Simplex Method, the Genetic Algorithms and the Simulated Annealing. These optimization techniques are further combined by the sequential application of the Powell optimization method in order to refine the registration and increase its accuracy. A comparative study involving these optimization techniques in conjunction with the rigid transformation, and two other methods, the ICP and the manual methods, is also presented, for a sufficient number of clinical CT-MR brain images. Finally, quantitative and qualitative results are also presented to validate the performance of these automatic surface-based registration schemes, in terms of consistency and accuracy. Throughout of this study, the automatic registration scheme comprising of the rigid transformation in conjunction with the Simulated Annealing method sequentially combined with the Powell method has been performed superior regarding all the other compared registration schemes.

Clinical treatment planning optimization by powell's method for gamma unit treatment system

Purpose : This article presents a new optimization method for stereotactic radiosurgery treatment planning for gamma unit treatment system. Methods and Materials : The gamma unit has been utilized in stereotactic radiosurgery for about 30 years, but the usual procedure or a physician-physicist team to design a treatment plan is a trial-and-error approach. Isodose curves are viewed on two-dimensional computed tomography (CT) or magnetic resonance (MR) image planes, which is not only time consuming but also seldom achieves the optimal treatment plan, especially when the isocenter weights are regarded. We developed a treatment-planning system on a computer workstation in which Powell's optimization method is realized. The optimization process starts with the initial parameters (the number of isocenters as well as corresponding 3D isocenters' coordinates, collimator sizes, and weight factors) roughly determined by the physician-physicist team. The objective function can be changed to consider protection of sensitive tissues. Results : We use the plan parameters given by a well-trained physician-physicist team, or ones that the author give roughly as the initial parameters for the optimization procedure. Dosimetric results of optimization show a better high dose-volume conformation to the target volume compared to the doctor's plan. Conclusion : This method converges quickly and is not sensitive to the initial parameters. It achieves an excellent conformation of the estimated isodose curves with the contours of the target volume. If the initial parameters are varied, there will be a little difference in parameters' configuration, but the dosimetric results proved almost to be the same.

Constants for an elastic–plastic cap model for limestone

AbstractTriaxial fracture tests with overburden pressures ranging from 0.69 to 136 MPa were performed to determine the material parameters involved in a cap model for limestone. Three material parameters A, B and C, were evaluated through Powell's optimization method and the remaining parameters through simulation‐curve fitting procedure. The resulting cap model was tested against separate triaxial fracture and hydrostatic compression tests. Modification of the original hardening function, as proposed by DiMaggio and Sandler, provided an improved fit for the experimental data.

Some Guidelines for Constructing ExactD-Optimal Designs on Convex Design Spaces

Some problems unique to the construction of N-point D-optimal designs on convex design spaces are considered. Multiple-point augmentation and exchange algorithms are shown to be more costly and less efficient than the analogous single-point procedures. Moreover, some recommendations for improving single-point methods are given. Finally, empirical evidence is found that supports the Galil and Kiefer option for constructing initial designs and Powell's optimization method for design augmentation.

Asymptotic solutions to the convection-dispersion equation and Powell's optimization method for evaluating groundwater velocity and dispersion coefficients from observed data of single dilution tests

Groundwater velocity and hydrodynamic dispersion coefficients can be determined simultaneously from observed data of solute concentration at the center of a single borehole. Two types of asymptotic analytical solutions to the convection-dispersion equation were proved to be applicable to analyse single borehole dilution tests. In order to calculate the groundwater velocity, and the longitudinal and transverse dispersion coefficients as three unknown variables in the asymptotic solutions, Powell's optimization method was applied to several cases together with the optimization method of Fletcher and Powell. The results of the application of these two optimization methods to several assumed sets and one actual experimental set of tracer concentrations showed that Powell's method based upon a conjugate direction procedure without calculating derivatives is more reliable, more flexible and much faster in converging to the true values than the method of Fletcher-Powell, which is based on a conjugate gradient procedure utilizing both criterion functions and their first derivatives. Furthermore, when Powell's optimization method was applied together with the proposed asymptotic solution to single borehole dilution data measured in field, the obtained values of the groundwater velocity, and the longitudinal and transverse dispersion coefficients were quite reasonable.