Optimal Design Strategy Research Articles

Early myocardial surgical revascularization after ST-segment elevation myocardial infarction in multivessel coronary disease: bridge therapy is the solution?

Many ST-segment elevation myocardial infarction (STEMI) patients have a multivessel disease that initially require percutaneous coronary intervention (PCI) of the culprit vessel but subsequently may require coronary artery bypass graft (CABG) of nonculprit vessels. Evidence supports staged revascularization, but the identification of optimal strategies (percutaneous or surgical), the timing and the management of antiplatelet therapy after recent PCI with stenting are matters of great controversies. In our retrospective registry, we have enrolled 21 patients presenting with STEMI and multivessel disease, who underwent PCI of the culprit vessel only and then CABG of nonculprit vessels. Demographic, clinical, echocardiographic, angiographic findings, preoperative score, surgical data and postoperative complications were collected. At 21.6 ± 15.6 months follow-up death, reinfarction and/or cardiovascular and noncardiovascular events were recorded. Patients were 62 ± 9 years old and had in the most cases a good ejection fraction. At angiography, the culprit lesion was right coronary artery in 16 patients (76%). Angiographic characteristics excluded a staged PCI (SYNTAX score = 31.6 ± 7.4) and European System for Cardiac Operative Risk Evaluation II resulted low (1.46 ± 1.01). Following the indication to cardiac surgery after Heart Team discussion, the withdrawal of oral P2Y12 inhibitor was planned and tirofiban intravenous was started. Off-pump CABG was performed after 7.2 ± 3.2 days. No death, reinfarction and/or cardiovascular and noncardiovascular events occurred at follow-up. We can conclude that a careful preoperative selection is mandatory for a good postoperative course and long-term survival and that early-staged CABG can, however, be performed using bridge therapy, also after STEMI.

Research on Gliding Aerodynamic Effect of Deformable Membrane Wing for a Robotic Flying Squirrel

Inspired by creatures with membrane to obtain ultra-high gliding ability, this paper presents a robotic flying squirrel (a novel gliding robot) characterized as membrane wing and active membrane deformation. For deep understanding of membrane wing and gliding mechanism from a robotic system perspective, a simplified blocking aerodynamic model of the deformable membrane wing and CFD simulation are finished. In addition, a physical prototype is developed and wind tunnel experiments are carried out. The results show that the proposed membrane wing is able to support the gliding action of the robot. Meanwhile, factors including geometry characteristics, material property and wind speed are considered in the experiments to investigate the aerodynamic effects of the deformable membrane wing deeply. As a typical characteristic of robotic flying squirrel, deformation modes of the membrane wing not only affect the gliding ability, but also directly determine the effects of the posture adjustment. Moreover, different deformation modes of membrane wing are illustrated to explore the possible effects of active membrane deformation on the gliding performance. The results indicate that the deformation modes have a significant impact on posture adjustment, which reinforces the rationality of flying squirrel’s gliding strategy and provides valuable information on prototype optimal design and control strategy in the actual gliding process.

Omnidirectional Aerial Vehicles With Unidirectional Thrusters: Theory, Optimal Design, and Control

This paper presents a theoretical study on omni-directional aerial vehicles with body-frame fixed unidirectional thrusters. Omniplus multi-rotor designs are defined as the ones that allow to exert a total wrench in any direction using positive-only lift force and drag moment (i.e., positive rotational speed) for each rotor blade. Algebraic conditions for a design to be omniplus are derived, a simple necessary condition being the fact that at least seven propellers have to be used. An energy optimal design strategy is then defined as the one minimizing the maximum norm of the input set needed to span a certain wrench ellipsoid for the adopted input allocation strategy. Two corresponding major design criteria are then introduced: firstly, a minimum allocation-matrix condition number aims at an equal sharing of the effort needed to generate wrenches in any direction; secondly, imposing a balanced design guarantees an equal sharing of the extra effort needed to keep the input in the non-negative orthant. We propose a numerical algorithm to solve such optimal design problem and a control algorithm to control any omnidirectional platform. The work is concluded with informative simulation results in non-ideal conditions.

Revisiting the configuration of small satellites structures in the framework of 3D Additive Manufacturing

In this paper the AM-induced evolution of the design process for small satellites is investigated, leading to the identification of optimal design strategies and the definition of a new MAIT concept. A review of the open literature is presented and some introductory concepts are exposed to highlight the effect of the introduction of AM technologies in the development of new satellites systems. In particular, an innovative structural configuration for the CubeSat class of satellites is proposed, with the ultimate goal of minimizing system complexity via parts reduction and the integration of subsystems through an innovative assembly configuration, as an example to be considered for larger satellites.

Ballistic performance of UHMWPE fabrics/EAMS hybrid panel

The ballistic protection for body armor usually requires both of high strength and high energy mitigation. In this work, we introduce and evaluate a new kind of body armor, i.e. a hybrid panel of ultra-high molecular weight polyethylene (UHMWPE) fabrics and soft energy absorption materials and structures (EAMS), by combing the advantages of bullet-proof and energy absorption of the respective material structures. A combined experimental and numerical study is conducted to evaluate the ballistic performance of the UHMWPE fabrics/EAMS hybrid panel. The resulting back-face signature (BFS) values of the hybrid panel are reduced by 6–17%, compared to the pure UHMWPE fabrics panel with the same areal density. If the EAMS is simply superimposed onto the UHMWPE fabrics, the reduction of BFS can be 50% or more with respect to the pure UHMWPE one. The effects of the geometrical factors of EAMS and mass ratio of UHMWPE fabrics to EAMS on the BFS values are studied using comprehensive finite element method (FEM) analyses. The strategies for optimal design of the UHMWPE fabrics/EAMS composite armor are proposed. The results presented herein shed useful insights for the design for high performance and energy mitigating body armors.

Developing Automatic Form and Design System Using Integrated Grey Relational Analysis and Affective Engineering

In the modern highly competitive marketplace and global market environment, product quality improvements that abridge development time and reduce the production costs are effective methods for promoting the business competitiveness of a product in shorter lifecycles. Since the design process is the best time to control such parameters, systematically designing the processes to develop a product that more closely fits the demand requirements for the market is a key factor for developing a successful product. In this paper, a combined affective engineering method and grey relational analysis are used to develop a product design process. First, design image scale technology is used to acquire the best the design criteria factors, and then affective engineering methods are used to set the relationships between customer needs and production factors. Finally, grey relational analysis is used to select the optimal design strategy. Using this systematic design method, a higher quality product can be expanded upon in a shorter lead-time for improving business competition.

Multidisciplinary Optimization Design for the Section Layout of Umbilicals Based on Intelligent Algorithm

Umbilicals, which link top floaters and subsea devices, provide control functions through electrical cables and hydraulic remote transmission. These cables are considered the “lifeline” of subsea production systems for offshore oil and gas exploitation. Umbilicals should undertake self-weight and periodic loading during operation because of the severe conditions of the ocean environment. Heat is released to the umbilical body during power transmission in electric cables, which influences the mechanical properties and optical transmission in the cable. However, several sectional arrangements can be applied to a number of umbilical components. Thus, sectional layout design with multiple components should be treated as a multidisciplinary optimization problem. From the mechanical point of view, the umbilical structure should be designed with compact and symmetric layout to obtain an even probability of resistance to loads and reduce structural stress, thereby improving fatigue performance. In terms of thermal effect, these electric cables should be arranged to dissipate heat easily and avoid influence on functional and structural components. This study quantifies compactness, symmetry, and temperature distribution by introducing corresponding indices. A multidisciplinary optimization framework is then established. Particle swarm optimization (PSO) intelligent algorithm is adopted to perform optimization and obtain the optimal solution, which is superior to the initial design. The optimization design strategy is proven effective and efficient by a case study, which provides a reference for umbilical design.

Energy Dispatch of Decentralized Hybrid Power System

The continuous geometric growth in energy demand coupled with high operation cost of power systems have made renewable energy sources (RES) more attractive. This paper presents an optimal design and energy management strategy of photovoltaic-diesel-battery (PDB) decentralized hybrid power system (DHPS) that minimizes operating costs and provides reliable power supply. The nonlinear objective cost function is formulated for the economic dispatch problem taking into consideration various operating constraints. The diesel generator (DG) minimum operation efficiency is expanded and solved using Newton-Quasi method. The DG is constrained to operate between the proposed minimum and rated efficiency during its operation in order to achieve desired load factor. Mixed integer nonlinear programming (MINLP) technique is explored to optimize the utilization of RES to reliable supply. A combined dispatch strategy which minimizes daily fuel consumption cost by the maximization of RES using a set of prioritized rules was developed and compared with the MINLP technique. The performance of the proposed combined strategy is validated by simulating the following operating scenarios: single household and community daily load profiles. The results show the effectiveness of the proposed combined dispatch algorithm as it reduces DG fuel consumption cost and improves supply reliability. Consequently, the effectiveness of these strategies encourages the integration of DHPS in remote and isolated communities

Low Probability of Intercept-Based Optimal OFDM Waveform Design Strategy for an Integrated Radar and Communications System

The integration of radar and communications systems can provide great advantages, such as enhanced efficiency, structure simplification, less occupied hardware resources, and interference mitigation, compared with traditional individual radar and communications applications. Extensive studies have presented achieving improved system performance, whereas the problem of low probability of intercept (LPI)-based waveform design for the integrated system is seldom discussed in the literature. In this paper, an LPI-based optimal orthogonal frequency multiplexing modulation (OFDM) waveform design strategy is developed for an integrated radar and communications system (IRCS). The dedicated transmitter in this system transmits integrated OFDM waveform for simultaneously target parameter estimation and downlink communications. The basis of the underlying strategy is to employ the optimization technique to design the integrated OFDM waveform of IRCS in order to minimize the total radiated power, while satisfying the specified requirements of target parameter estimation and data information rate. We analytically show that the resulting optimization problem is convex and can be solved by formulating the Karush–Kuhn–Tuckers optimality conditions. Numerical simulation results demonstrate that our proposed strategy can solve the waveform design problem in the IRCS with low complexity, and the LPI performance of the IRCS can efficiently be enhanced by utilizing the proposed integrated OFDM waveform design strategy.

Modeling Energy Migration for Upconversion Materials

One of the key issues in upconversion materials is the design of an appropriate complex nanoarchitecture to control energy migration. We propose here a numerical tool based on a Monte Carlo approach capable of modeling the energy migration in particles with diameters of up to a few tens of nanometers. To validate the approach, the obtained results are compared with a wide range of published experimental data. The proposed simulation allows us to guide the optimal design strategies to develop upconverting nanoparticles for light-harvesting applications.

Optimal Design Strategy for Improved Operation of IPM BLDC Motors With Low-Resolution Hall Sensors

This study proposes an interior permanent magnet (IPM) brushless dc (BLDC) motor design strategy that utilizes BLDC control based on Hall sensor signals. The magnetic flux of IPM motors varies according to the rotor position and abnormal Hall sensor problems are related to magnetic flux. To find the cause of the abnormality in the Hall sensors, an analysis of the magnetic flux density at the Hall sensor position by finite element analysis is conducted. In addition, an IPM model with a notch structure is proposed to solve abnormal Hall sensor problems and its magnetic equivalent circuit (MEC) model is derived. Based on the MEC model, an optimal rotor design method is proposed and the final model is derived. However, the Hall sensor signal achieved from the optimal rotor is not perfect. To improve the accuracy of the BLDC motor control, a rotor position estimation method is proposed. Finally, experiments are performed to evaluate the performance of the proposed IPM-type BLDC motor and the Hall sensor compensation method.

Rational design strategy for optimization of clamping pressure to minimize contact resistance between electrode and current collector while preserving porosity of electrodes in water electrolyzers

AbstractThe compressive clamping pressure at the interface of gas‐diffusion‐layer (GDL) and current collector decreases the contact resistance between them though it reduces the porosity and surface roughness of electrocatalysts, which would in turn decrease the efficiency of an electrolyzer. We explore these issues of trade‐off between porosity versus contact resistance and provide a design heuristic for optimum clamping pressure. The present work provides an estimate of the optimal value of clamping pressure for an alkaline water electrolyzer having membrane electrode assembly (MEA), taking account of the variation in porosity of catalyst layers and contact resistance obtained via half‐cell studies performed at different pressures. Towards this, we define the performance‐index (Φ) which is the ratio of Faradaic current density and resistances resulting from contact‐interfaces in electrolyzers and we suggest that the maxima in Φ corresponds to optimum clamping pressure.

Optimal signal design strategy with improper Gaussian signaling in the Z-interference channel

We propose a thoroughly optimal signal design strategy to achieve the Pareto boundary (boundary of the achievable rate region) with improper Gaussian signaling (IGS) on the Z-interference channel (Z-IC) under the assumption that the interference is treated as additive Gaussian noise. Specifically, we show that the Pareto boundary has two different schemes determined by the two paths manifesting the characteristic of improperly transmitted signals. In each scheme, we derive several concise closed-form expressions to calculate each user’s optimally transmitted power, covariance, and pseudo-covariance of improperly transmitted signals. The effectiveness of the proposed optimal signal design strategy is supported by simulations, and the results clearly show the superiority of IGS. The proposed optimal signal design strategy also provides a simple way to achieve the required rate region, with which we also derive a closed-form solution to quickly find the circularity coefficient that maximizes the sum rate. Finally, we provide an in-depth discussion of the structure of the Pareto boundary, characterized by the channel coefficient, the degree of impropriety measured by the covariance, and the pseudo-covariance of signals transmitted by two users.

Robust dynamic optimization in heterogeneous multiscale catalytic flow reactors using polynomial chaos expansion

This paper explores the application of optimal design and operational strategies under uncertainty to a transient multiscale catalytic flow reactor system. The catalytic reactor is modeled using a spatially-dependent multiscale model that comprises lattice-based kinetic Monte Carlo (kMC) models coupled with continuum partial differential equations (PDEs) to account for the fine-scale and the macroscale reactor behaviour, respectively. This work compares two uncertainty propagation techniques, power series expansion (PSE) and polynomial chaos expansion (PCE), to assess their performance in multiscale process systems. The analysis reveals that PCE provides accurate results at minimal computational cost for the multiscale catalytic reactor model under the conditions considered in this work. PCE is subsequently used to perform robust dynamic optimization studies on the catalytic reactor system under uncertainty. The first study determines the optimal temperature trajectories that maximize the reactor’s performance under uncertainty. The second study aims to identify the optimal design and operating policies that allow the reactor, under uncertainty in the multiscale model parameters, to meet targeted performance specifications within a level of confidence. Both studies illustrate the benefits of performing dynamic optimization studies to improve performance for multiscale process systems under uncertainty.

Optimization-based approach for design and integration of carbon dioxide separation processes using membrane technology

The purpose of this paper is to examine carbon dioxide (CO2) separation process using membrane technologies. In achieving this goal, we develop an optimization model to design and integrate the CO2 separation using multi-stage membrane technologies by maximizing the total profit calculated with the total capital and operating costs, and the expected revenue from the CH4 selling. Using the proposed model, we are able to determine the optimal design and operation strategies of the individual membrane and compressor to meet the design specification (i.e., purity and recovery rate) in the scenarios of different CO2 market prices.

An Optimization design Approach of Football Stadium Canopy Forms Based On Field Wind Environment Simulation

After the issue of General Plan of Chinese Football Reform in 2015, the development and construction of football stadium in China was put on an important agenda. Field wind environment will make a serious impact on players’ performance and game result，while canopy form plays great effect on field wind environment. The primary intention of this research is to reveal the relationship between field wind environment and canopy forms based on CFD simulation of wind environment, then construct an optimization design approach of football stadium canopy form . STAR-CCM + 9.04.009 is set as simulation platform in this paper. As for the current developing status of football game in China, a 30,000-capacity medium-sized football stadium model is proposed for research object. And then CFD simulation is carried out on the canopy section profiles and the canopy connection permeability, different external wind speed such as 5 m/s, 10 m/s, 15m/s, flows into the model from east side in all the cases. Furthermore, the wind field distribution uniformity and wind speed variation stability are taken as the evaluation criterion. In this way,the impact mechanism which different canopy forms play on the field wind environment in football stadium is attempted to characterize from the experimental results. Finally the proposal of the football stadium optimal design strategies are put forward.

Catalysis at the Rim: A Mechanism for Low Temperature CO Oxidation over Pt3Sn

Metal alloying is commonly used as a design strategy for catalyst optimization. The mechanistic understanding of this class of systems is, however, obscured by reaction induced segregation phenomena. Herein the case of CO oxidation over Pt3Sn is investigated using Density Functional Theory calculations combined with ab initio thermodynamics and first-principles based micro-kinetic modeling. It is found that Pt3Sn under typical operating conditions segregates into SnOX and an Sn deficient metal phase. The segregation is driven both by the stability of the metal oxide and the strong bonding of CO to Pt. The catalytic consequences of a metal supported SnO2 phase are explored by comparing CO oxidation at an SnOX/Pt interface with oxidation over Pt and Pt/Pt3Sn skin models. The reaction is found to proceed with lower barriers at the interface as compared to the metal-only systems. The co-catalytic role of the SnOX rim is manifested in high low temperature activity. The present work highlights effects of reacti...

Optimal designs of the synthetic t chart with estimated process mean

The synthetic t chart, which integrates a t chart and a conforming run length chart, is robust against changes in the process standard deviation. Traditionally, the synthetic t chart is studied by assuming that the in-control process mean is known. Practically, this is not always the case. The process mean is rarely known and it has to be estimated from a Phase-I dataset. Therefore, this paper presents the Markov chain approach for studying the run-length properties of the synthetic t chart with estimated process mean for both zero- and steady-state cases. The impact of the mean estimation on the synthetic t chart is evaluated and compared with its known-process-mean counterpart and the synthetic X¯ chart. For optimum implementation, this paper develops two optimal design strategies for the synthetic t chart with estimated process mean, by minimizing (i) the average run length (ARL) and (ii) the expected ARL, for deterministic and unknown shift sizes, respectively. By taking the number of Phase-I samples and sample sizes adopted in practice into consideration, tables listing the new optimal charting parameters of the proposed chart are provided in this paper. Comparative studies show that there are some potential benefits, especially the desirable robustness property, of the synthetic t chart with estimated process mean over the synthetic X¯, Shewhart X¯ and t charts with estimated process parameters or mean. The application of the synthetic t chart with estimated process mean is illustrated with real industrial data gathered from a silicon epitaxy process.

Thermal energy and economic analysis of a PCM-enhanced household envelope considering different climate zones in Morocco

ABSTRACTThis study investigates the thermal energy potentials and economic feasibility of an air-conditioned family household-integrated phase change material (PCM) considering different climate zones in Morocco. A simulation-based optimisation was carried out in order to define the optimal design of a PCM-enhanced household envelope for thermal energy effectiveness and cost-effectiveness of predefined candidate solutions. The optimisation methodology is based on coupling Energyplus® as a dynamic simulation tool and GenOpt® as an optimisation tool. Considering the obtained optimum design strategies, a thermal energy and economic analysis are carried out to investigate PCMs’ integration feasibility in the Moroccan constructions. The results show that the PCM-integrated household envelope allows minimising the cooling/heating thermal energy demand vs. a reference household without PCM. While for the cost-effectiveness optimisation, it has been deduced that the economic feasibility is stilling insufficient under the actual PCM market conditions. The optimal design parameters results are also analysed.

Performance Analysis and Design Strategy for a Second-Order, Fixed-Gain, Position-Velocity-Measured (α-β-η-θ) Tracking Filter

We present a strategy for designing an α - β - η - θ filter, a fixed-gain moving-object tracking filter using position and velocity measurements. First, performance indices and stability conditions for the filter are analytically derived. Then, an optimal gain design strategy using these results is proposed and its relationship to the position-velocity-measured (PVM) Kalman filter is shown. Numerical analyses demonstrate the effectiveness of the proposed strategy, as well as a performance improvement over the traditional position-only-measured α - β filter. Moreover, we apply an α - β - η - θ filter designed using this strategy to ultra-wideband Doppler radar tracking in numerical simulations. We verify that the proposed strategy can easily design the gains for an α - β - η - θ filter based on the performance of the ultra-wideband Doppler radar and a rough approximation of the target’s acceleration. Moreover, its effectiveness in predicting the steady state performance in designing the position-velocity-measured Kalman filter is also demonstrated.