Single Optimal Design Research Articles

Study on the Design Parameters of Landscape Elements of Urban Tunnel Body Segments in China Based on Biomass Perception

To provide a comprehensive analysis of how an intricate landscape environment comprising various landscape elements influences driving safety and comfort. Beginning with the individual design of the tunnel body section, which includes the roof, sidewalls, road surface, and sidewalk facade markings, this paper references the driver’s biomass index to identify design alterations that satisfy basic safety requirements through simulated driving experiments. Subsequently, employing orthogonal experimental design and semi-supervised clustering algorithms, we ascertain the optimal combination of the four main landscape elements of the tunnel body section that align with both safety and comfort objectives. The experimental findings demonstrate that a safe and comfortable landscape design for urban tunnel sections does not entail a single optimal design; rather, any landscape design conforming to the criterion of “patterned landscapes are set on the side walls and roofs of the tunnel instead of the surface of the road” is the optimal design.

A design for life: Predicting cognitive performance from lifestyle choices.

Maintaining cognitive capacity through adulthood has been the target of many recent studies that have examined the influence of lifestyle choices such as exercise, diet, and sleeping habits. Many of these studies have focused on a single factor (e.g., diet) and its effect on cognitive abilities; however, humans make numerous lifestyle choices every single day, many of which interact and influence each other. Here, we investigated whether combinations of lifestyle choices can predict better or worse cognitive performance in the general population, and whether optimal combinations of choices existed depending on the cognitive domain. Specifically, we examined 20 self-reported lifestyle choices, such as playing video games, drinking alcohol, and amount of exercise taken, in a sample of almost 10,000 participants. All participants also completed 12 cognitive tests that have been shown to generate three composite cognitive domain scores pertaining to short-term memory, verbal abilities, and reasoning. Using recursive feature elimination and random forest regression, we were able to explain 9% of the variance in short-term memory scores, 8% of the variance in reasoning scores, and 7% of the variance in verbal ability scores. While the regression model provided predictive power in all three domains, these levels indicate that even when considering a large number of lifestyle choices, there remains a considerable degree of variability in predicting short-term memory, reasoning and verbal abilities. Thus, while some modifiable lifestyle factors may have an impact on cognitive capacity, there likely exists no single optimal design for life.

Exploit the study of the scenarios for the control of the response of single-degree-of-freedom systems with bumpers

In earthquake-prone areas, seismic isolation systems are designed to preserve structural safety and prevent occupants’ injury and properties’ damage. However, seismically isolated structures can be subject to large displacements relative to the ground under earthquakes, which lead to define two problems, the first problem concerns to excessive displacements, whereas the second problem relates to excessive accelerations that occur when the displacements are limited by an obstacle with high relative stiffness. An arrangement that favors the solution of these problems is an appropriate interposition between the isolated structure and the obstacle of the shock absorbers or bumpers. The aim of this paper is to investigate, via numerical parametric analyses, the possibility to exploit the occurrence of impact in a two-sided vibro-impact isolated single-degree-of-freedom (SDOF) system under harmonic base excitation with beneficial effects. Through the analysis of the response scenarios which can occur varying the obstacles’ parameters, that is the width of the gap and the mechanical (stiffness and damping) properties, the target is to reduce both the maximum value of the displacement and of the acceleration of the mass, compared to the free flight condition, without possibly reducing the vibration isolation frequency range. This research path leads to the definition of vibro-impacting control systems and to the free and constrained single and multi-objective optimal design of the control system consisting of the integrated assembly of the isolation system, bumpers and gaps. The main results obtained consist in having (i) found a unique optimality condition, (ii) calculated the dissipated energy and given an energetic interpretation to the optimality condition (iii) built maps, that allow to advance behavior predictions, provide indications on the design and allow to make evaluations of the performance of the vibro-impacting system as a function of the stiffness and damping parameters and of the width of the gap. The stiffness ratio and the damping ratio, which define the mechanical properties of the bumpers, are such that the dimensionless relaxation time is about 1, (iv) finally the results are compared to multi-objective optimal design. Ultimately, the advantages of this new isolation system are: (1) provide a physical limit switch to the isolation system in order to limit the maximum displacement of the mass; (2) reduce the effects of amplification dynamics in the resonance zone; (3) reduce the static displacement, all without possibly modifying the dynamic response in the isolation zone.

A review of research on directional off-road path planning algorithms

Military orienteering can cultivate the skills of map reading, map use and military charting, and has gradually become a regular military training subject. A good track design plan is the basis for the smooth running of the competition. The current research on cross-country courses is mainly focused on single-track optimization, and there is very little research on multi-track planning, and design. However, in specific events, there are often multiple tracks running at the same time, and there are many restrictions, single track optimization design solutions are often not applicable. In this paper, we review multiple path planning algorithms and summarize the problems of these algorithms. On this basis, the advantages and disadvantages of static and dynamic path planning algorithms are analyzed, and future research trends and methods of path planning algorithms in orienteering are proposed.

Investigation of the applicability of fatty acid-based deep eutectic solvent based air assisted liquid liquid microextraction for the rapid determination and extraction of butylparaben in cosmetic products

In this research paper, fatty acid-based deep eutectic solvents (FA-DESs) were prepared and investigated for the extraction of butylparaben (BP) from cosmetic products by air assisted liquid liquid microextraction (AA-DLLME). The amounts of BP were determined by UV/Vis spectrophotometry. By combining single factor optimization and Box-Behnken design based multivariate approach, key extraction parameters affecting the FA-DES AA-LLME procedure were systematically optimized. Under the optimized conditions, wide working range (5–800 μg L−1) was obtained with a good r2:0.9972 and high enrichment factor (205). For three replications run of 10 μg L−1 (low), 300 μg L−1 (medium) and 600 μg L−1 (high) of BP, the percent extraction recovery and relative standard deviation were in the range of 92 ± 4%-98 ± 2% and 1.8–2.6%, respectively. The limit of detection and the limit of quantification were 1.5 μg L−1 and 5 μg L−1, respectively. The study of the matrix effect showed that the proposed method has high selectivity for measuring BP in the selected samples. Therefore, it has great potential in sample pre-treatment and quantification of trace BP in cosmetic products.

Efficient biosynthesis of exopolysaccharide in Candida glabrata by a fed-batch culture.

Polysaccharides are important natural biomacromolecules. In particular, microbial exopolysaccharides have received much attention. They are produced by a variety of microorganisms, and they are widely used in the food, pharmaceutical, and chemical industries. The Candida glabrata mutant 4-C10, which has the capacity to produce exopolysaccharide, was previously obtained by random mutagenesis. In this study we aimed to further enhance exopolysaccharide production by systemic fermentation optimization. By single factor optimization and orthogonal design optimization in shaking flasks, an optimal fermentation medium composition was obtained. By optimizing agitation speed, aeration rate, and fed-batch fermentation mode, 118.6 g L−1 of exopolysaccharide was obtained by a constant rate feeding fermentation mode, with a glucose yield of 0.62 g g−1 and a productivity of 1.24 g L−1 h−1. Scaling up the established fermentation mode to a 15-L fermenter led to an exopolysaccharide yield of 113.8 g L−1, with a glucose yield of 0.60 g g−1 and a productivity of 1.29 g L−1 h−1.

A Course Level Analysis of Academic Performance on Adult Learners


 
 
 Thanks, in part, to the rapid development and widespread adoption of the Internet and other online technologies, academic institutions are increasingly using analytics to enhance learning and teaching. Through the use of data mining techniques, this study examines some of the determinants at a course level that affect the academic performance of adult learners (which we will refer to as students in this paper) in the Singapore University of Social Sciences (SUSS). Formerly known as SIM University, SUSS is an institution that caters mainly to the learning needs of working adults although it offers a number of full-time undergraduate degree programmes to fresh school leavers. The data analysis found that students taking introductory blended courses performed better than those who took face-to-face courses of the same level. Furthermore, students of similar age taking level-2 courses outperformed students taking similar courses where the age difference was more significant. The findings indicate that no single optimal course design will lead to improved academic performance across all courses. Instead, educators should be ready to consider the nature, level, discipline and coursework component of each course to cater to the various students’ needs.
 
 

Genetic Optimisation of a Free-Stream Water Wheel Using 2D Computational Fluid Dynamics Simulations Points towards Design with Fully Immersed Blades

A large-scale two-dimensional computational fluid dynamics study is conducted in order to maximise the power output and smoothness of power delivery of a free-stream water wheel, a low-impact hydropower device. Based on models and methods developed in previous research, the study uses a genetic algorithm to optimise the geometry of a wheel with a given radius and depth, maximising two objective functions simultaneously. After convergence and suitable post-processing, a single optimal design is identified, featuring eight shortened blades that become fully immersed at the nadir point. The design results in a 71% reduction in blade material and a 113% increase in the work ratio while improving the hydraulic power by 8% compared to the previous best design. These characteristics are applied retroactively to a broad family of designs, resulting in significant improvements in performance. Analysis of the resulting designs indicates that when either the hydraulic power coefficient, rotor power coefficient, or work ratio is considered, free-stream water wheels with fully immersed blades, whose power mechanisms are shown to rely on lift, as well as drag, outperform all other designs studied so far.

Recycled Aggregate Pervious Concrete: Analysis of Influence of Water-Cement Ratio and Fly Ash under Single Action and Optimal Design of Mix Proportion

Pervious concrete is recommended, which is of great benefit to the ecological environment and human living environment. In this paper, the influences of five water-cement ratios and four fly ash contents to replace the cement by mass with a water-cement ratio of 0.30 on the properties of Recycled Aggregate Pervious Concrete (RAPC) were studied. Following this, based on the Grey relational-Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) optimization method, the strength, permeability, abrasion loss rate, and material costs of RAPC were adopted as evaluation indices to establish a mix proportion optimization model. The results show that the increase of water-cement ratio and fly ash replacement level of RAPC leads to decreased compressive strength while an increase in the permeability and abrasion loss rate. According to test results based on the optimal model 0.30 was identified as the best mix proportion. In addition, ecological-economic analysis of RAPC raw materials was carried out by comparing different natural aggregates. The results of EE (embodied energy) and ECO2e (embodied CO2 emission) pointed out that the combination of recycled aggregate and fly ash leads to significant ecological and economic benefits.

Fuzzy optimization-based Water Distribution Network design using Self-Adaptive Cuckoo Search Algorithm

Abstract Water Distribution Network(s) (WDN) design is gaining prominence in the urban planning context. Several factors that play a significant role in design are uncertainty in data, non-linear relation of head loss & discharge, combinatorial nature of the problem, and high computational requirements. In addition, many conflicting objectives are possible and required for effective WDN design, such as cost, resilience, and leakage. Most of the research work published has used multiobjective evolutionary optimization in solving such complex WDN. However, the challenge of such population-based evolutionary approaches is that they provide multiple trade-off Pareto optimal solutions to the decision-maker who will have to choose another set of techniques to arrive at a single optimal solution. The present study employs a fuzzy optimization approach that would provide a single optimal WDN design for Hanoi and Pamapur, India. Maximization of network resilience (NR) and minimization of network cost (NC) are employed in a multiobjective context. Later, minimization of network leakages (NL) is also incorporated, leading to three objective problems. Hyperbolic membership function (HMF), exponential membership function (EMF), and non-linear membership function (NMF) are employed in Self-Adaptive Cuckoo Search Algorithm-based fuzzy optimization. HMF is found suitable to determine the best possible WDN design for chosen case studies based on the highest degree of satisfaction.

Impact of anatomical reverse remodelling in the design of optimal quadripolar pacing leads: A computational study

Lead position is an important factor in determining response to Cardiac Resynchronization Therapy (CRT) in dyssynchronous heart failure (HF) patients. Multipoint pacing (MPP) enables pacing from multiple electrodes within the same lead, improving the potential outcome for patients.Virtual quadripolar lead designs were evaluated by simulating pacing from all combinations of 1 and 2 electrodes along the lead in each virtual patient from cohorts of HF (n = 24) and simulated reverse remodelled (RR, n = 20) patients. Electrical synchrony was assessed by the time 90% of the ventricular myocardium is activated (AT090). Optimal 1 and 2 electrode pacing configurations for AT090 were combined to identify the 4-electrode lead design that maximised benefits across all patients.LV pacing in the HF cohort in all possible single and double electrode locations reduced AT090 by 14.48 ± 5.01 ms (11.92 ± 3.51%). The major determinant of reduction in activation time was patient anatomy. Pacing with a single optimal lead design reduced AT090 more in the HF cohort than the RR cohort (12.68 ± 3.29% vs 10.81 ± 2.34%).Pacing with a single combined HF and RR population-optimised lead design achieves electrical resynchronization with near equivalence to personalised lead designs both in HF and RR anatomies. These findings suggest that although lead configurations have to be tailored to each patient, a single optimal lead design is sufficient to obtain near-optimal results across most patients. This study shows the potential of virtual clinical trials as tools to compare existing and explore new lead designs.

Kinematic synergy analysis of crouch cerebral palsy gait reveals a reduced locomotor strategy based on movement primitives

This paper proposes an analytical method to design thermoelectric heat pumps (THPs), in order to meet a given thermal power demand with a maximum coefficient of performance (COP). The method returns the optimal thermoelectric element (TE) design (leg length, leg section and number of legs) and optimal electric current, assuming that the hot and cold operating temperatures, the thermal power demand and the material properties are known. The optimal operating conditions are derived analytically from steady-state analytical models in the literature. Analytical development leads to defining an equivalent Seebeck coefficient when the Thomson effect is taken into account. Given that the optimal variables are closely related, many designs can meet the two performance criteria: (i) meeting thermal demand and (ii) maximizing the COP. To define a single optimal design, two additional manufacturing criteria are also considered: (iii) minimizing the material volume and (iv) minimizing the number of electrical junctions. This approach leads to the following recommendations:- identify the maximum THP area acceptable, depending on the application targeted, in order to decrease the thermal flux density and thus increase THP performance;- minimize the leg length in order to reduce the material volume and thus the THP cost;- maximize the leg section (leading to work with the maximal electric current achievable) in order to reduce the number of junctions, thus facilitating the manufacturing process.Finally, the optimal number of legs and electrical current can be calculated via simple ratios.

Multi-objective Reliability Optimization Design of Planetary Transmission Cutter Mechanism

Traditional planetary cutter mechanism design needs repeated trial and verification to determine a design scheme that meets the given conditions, and the scheme is generally not the best; The conventional single objective optimization design usually only aims at a certain requirement to achieve a certain optimal performance, neglecting the optimal comprehensive performance of the product. In order to solve the above problems, the reliability theory and optimization design technology are applied, and the compact structure, transmission efficiency, transmission stability and bearing capacity of the planetary cutter mechanism are comprehensively considered. Taking the minimum volume, maximum efficiency and maximum coincidence degree of the mechanism as the objective function, a multi-objective optimization design mathematical model different from the existing models is established by using the safety factor method and other constraints, Matlab software is used for optimization calculation. The results show that compared with the conventional design, the volume of the multi-objective optimization design is reduced by 79.97% and the coincidence degree is increased by 2.64% under the premise of almost constant transmission efficiency; Compared with the conventional single objective optimization design, although the single index is not optimal, the indexes are more balanced and the optimization effect is obvious.

Towards desensitization of gas turbine performance to tip Clearance: Design optimization and engine analysis

Increased scrutiny on aviation’s environmental footprint has precipitated a dramatic increase in gas turbine technology development, with a focus on engine performance improvements and the reduction of noise and emissions. In a somewhat limited approach, these studies are often performed at the component level and at a single engine operating condition. In order to achieve future fuel consumption, noise, and emissions targets, it will be essential for designers to optimize the overall propulsive system across the entire trajectory. Accurate engine models will be needed to quantify the overall system performance and select the optimal components and the aircraft mission, highlighting the interconnection between optimization and engine modeling.In this paper, an engine modeling approach is described that provides a framework for analysis of the impact of component changes on the overall system for an entire trajectory. The engine model is built using a modeling environment developed by NASA called Toolbox for the Modeling and Analysis of Thermodynamic Systems (T-MATS). The modeling environment allows for transient updates to the boundary conditions, similar to what an engine would experience during operation.The emphasis on trajectory-driven design led to the development of a new blade tip optimization approach that improved turbine efficiency across a range of tip clearances rather than at a single clearance. The robust blade tip design approach used a multi-objective optimization with a differential evolution strategy and Computational Fluid Dynamics software to solve Reynolds-Averaged Navier-Stokes equations at three tip clearances. The optimization objectives were to increase the average and decrease the standard deviations of the stage efficiency for the three clearances. This approach demonstrated efficiency improvements as large as 0.50% with variations of standard deviations near zero. The robust blade tip optimization approach is discussed in detail, as well as a brief description of the physical mechanisms responsible for the performance improvement.Finally, in a demonstration of capability and applicability, turbine-specific updates are made to the baseline engine model. The updates include heat transfer and structural modules that are used to predict the turbine blade running tip clearance, which changes during the trajectory from 1.1% to 1.6% of span. Brief discussions of each module are included as well as a description of the turbine performance assessment. The impact of the blade tip clearance on the turbine efficiency across the trajectory is reported for three blade tip geometries: a baseline squealer design, a single point optimization design, and the robust blade tip optimization design. The results demonstrate the importance of trajectory-influenced design at both the component and engine level.

Stochastic approaches to generating diverse and competitive structural designs in topology optimization

Topology optimization techniques have been widely used in structural design. Conventional optimization techniques usually are aimed at achieving the globally optimal solution which maximizes the structural performance. In practical applications, however, designers usually desire to have multiple design options, as the single optimal design often limits their artistic intuitions and sometimes violates the functional requirements of building structures. Here we propose three stochastic approaches to generating diverse and competitive designs. These approaches include (1) penalizing elemental sensitivities, (2) changing initial designs, and (3) integrating the genetic algorithm into the bi-directional evolutionary structural optimization (BESO) technique. Numerical results demonstrate that the proposed approaches are capable of producing a series of random designs, which possess not only high structural performance, but also distinctly different topologies. These approaches can be easily implemented in different topology optimization techniques. This work is of significant practical importance in architectural engineering where multiple design options of high structural performance are required.

Investigation of 3D manifold architecture heat sinks in air-cooled condensers

Power plants account for a high rate of freshwater utilization in the United States. Use of air-cooled condensers (ACC) can significantly reduce or completely eliminate freshwater withdrawals for steam-electric plants but suffer from low heat transfer of single-phase air flow. In the current study, we experimentally and computationally investigate the thermal-hydraulic performance of the air-side of a traditional ACC heat sink (EVAPCO fins) and conduct an extensive comparative CFD study of a novel 3D manifolding architecture heat sink design. A parametric investigation was performed on the 3D manifold heat sinks with fin height ranging from 7.3 to 15.3 mm, three fin densities with fin pitch ranging from 1 to 3 mm, and fin angles between 0° and 45°. It is concluded that there is not a single optimal design over the range of flow rates/heat flux, and the heat sink performances are a strong function of the target operating heat flux. Overall, various manifold designs were able to offer improved COP over EVAPCO fins that covered a large range of the operating heat fluxes. Manifold designs also require less fin array material, making them a good alternative for EVAPCO ACC systems if it is desired to increase the heat flux by 3 times for the existing EVAPCO units.

Theoretical Study on a Cable-Bracing Inerter System for Seismic Mitigation

In this paper, cables are proposed to connect the inerter and main frame for translation-to-rotation conversion, i.e., the cable-bracing inerter system (CBIS), with a magnified mass and enhanced damping effect. This novel configuration has the benefits of deformation relaxation at the connecting joints, easy installation, and an adaptive layout for nonconsecutive-story deployment. Dynamic motion equations were established for a single degree-of-freedom (SDOF) model equipped with a CBIS. The influence of dimensionless parameters, such as inertance-mass ratio, stiffness ratio and additional damping ratio on vibration mitigation were studied in terms of displacement response and force output. A single objective and multiple objective optimal design method were developed for a CBIS-equipped structure based on a performance-oriented design framework. Finally, the mitigation effect was illustrated and verified by a numerical simulation in a time-domain. The results showed that a CBIS is an effective structural response mitigation device used to mitigate the response of structural systems under earthquake excitation. Using the proposed optimization method, CBIS parameters can be effectively designed to satisfy the target vibration control level.

A power‐performance tunable logic with adjustable threshold pseudo‐dynamic building blocks and CMOS compatibility

SummaryThe continued downscaling of CMOS technology has resulted in very high performance devices, but power dissipation is a limiting factor on this way. Power and performance of a device are dependent on process, temperature, and workload variation that makes it impossible to find a single power optimal design. As a result, adaptive power and performance adjustment techniques emerged as attractive methods to improve the effective power efficiency of a device in modern design approaches. Focusing on this issue, in this paper, a novel logic family is proposed that enables tuning the transistor's effective threshold voltage after fabrication for higher speed or lower power. This method along with dynamic voltage scaling allows simultaneous optimization of static and dynamic power based on the workload requirement. The externally static topology of the proposed logic makes it possible to replace static circuits without requiring significant changes in the system. Experimental results obtained using 90‐nm CMOS standard technology show that the proposed logic improves the average power‐delay product by about 40% for the attempted benchmarks.

SPREAD – Exploring the decision space in energy systems synthesis

A method is presented to systematically analyze the decision space in the synthesis of energy supply systems. Commonly, synthesis problems are solved by mathematical optimization yielding a single optimal design. However, optimization is based on a model which never represents reality to perfection. Thus, the designer will be forced to revise parts of the optimal solution. We therefore support the design process by automatically identifying important features of good solutions. For this purpose, we analyze near-optimal solutions. To explore the decision space, we minimize and maximize both the number and the capacity of units while keeping the costs within a specified range. From this analysis, we derive insight into correlations between decisions. To support the decision maker, we represent the range of good design decisions and their correlations in the flowsheet of the energy system. The method is illustrated for the synthesis of an energy system in the pharmaceutical industry.

Designing Human Immunodeficiency Virus Counselling and Testing Services to Maximize Uptake Among High School Learners in South Africa: What Matters?

Increasing human immunodeficiency virus (HIV) testing in South Africa is vital for the HIV response. Targeting young people is important as they become sexually active and because HIV risk rapidly increases as youth enter their 20s. This study aims to increase the understanding of high school learners' preferences regarding the characteristics of HIV testing service delivery models and to inform policy makers and implementers regarding potential barriers to and facilitators of HIV testing. An attitudinal survey was used to examine HIV testing preferences among 248 high school learners in KwaZulu-Natal. Statistical tests were used to identify the most favored characteristics of testing service delivery models and examine key differences in preferences based on demographic characteristics and testing history. Most learners were found to prefer testing offered at a clinic on a Saturday (43%), using a finger prick test (59%), conducted by a doctor (61%) who also provides individual counselling (60%). Shorter testing times were preferred, as well as a monetary incentive to cover any associated expenses. Time, location, the type of test, and who conducts the test were most important. However, stratified analysis suggests that preferences diverge, particularly around gender, grade, but also sexual history and previous testing experience. Human immunodeficiency virus testing services can be improved in line with preferences, but there is no single optimal design that caters to the preferences of all learners. It is unlikely that a "one-size-fits-all" approach will be effective to reach HIV testing targets. A range of options may be required to maximize coverage.