• International Journal of Naval Architecture and Ocean Engineering
• /
• v.7 no.4
• /
• pp.750-769
• /
• 2015

The geometry of engineering systems affects their performances. For this reason, the shape of engineering systems needs to be optimized in the initial design stage. However, engineering system design problems consist of multi-objective optimization and the performance analysis using commercial code or numerical analysis is generally time-consuming. To solve these problems, many engineers perform the optimization using the approximation model (response surface). The Response Surface Method (RSM) is generally used to predict the system performance in engineering research field, but RSM presents some prediction errors for highly nonlinear systems. The major objective of this research is to establish an optimal design method for multi-objective problems and confirm its applicability. The proposed process is composed of three parts: definition of geometry, generation of response surface, and optimization process. To reduce the time for performance analysis and minimize the prediction errors, the approximation model is generated using the Backpropagation Artificial Neural Network (BPANN) which is considered as Neuro-Response Surface Method (NRSM). The optimization is done for the generated response surface by non-dominated sorting genetic algorithm-II (NSGA-II). Through case studies of marine system and ship structure (substructure of floating offshore wind turbine considering hydrodynamics performances and bulk carrier bottom stiffened panels considering structure performance), we have confirmed the applicability of the proposed method for multi-objective side constraint optimization problems.

• Journal of Korea Multimedia Society
• /
• v.5 no.4
• /
• pp.405-414
• /
• 2002

In this paper, we propose a new objective speech quality measure using noise masking threshold for speech quality assessment of mobile telephone network environments, and verify the effectiveness of the proposed method through the experiments. For such a purpose, well known objective speech quality measures such as BSD and PSQM are first evaluated for digital mobile telephone network environments. However, these conventional methods does not have good performance under mobile networks environments compared to literary results. To be mote effective objective speech quality measure under mobile telephone environments, the proposed method employs human psychoacoustic masking effect. The DMOS, instead of MOS, is used as a subjective speech quality measure for performance evaluation. The performance comparison are carried out with speech data collected from digital mobile telephone environments. As results, the proposed measure have and average 4% higher performance, in terms of correlation, than existing objective speech quality measures such as BSD and PSQM.

• Steel and Composite Structures
• /
• v.47 no.2
• /
• pp.147-165
• /
• 2023

The paper contrasts conventional seismic design with a design that incorporates buckling-restrained bracing in three-dimensional reinforced concrete buildings (BRBs). The suboptimal structures may be found using the multi-objective chimp optimization algorithm (MEN-ChOA). Given the constraints and dimensions, ChOA suffers from a slow convergence rate and tends to become stuck in local minima. Therefore, the ChOA is improved by niching and evolutionary operators to overcome the aforementioned problems. In addition, a new technique is presented to compute seismic and dead loads that include all of a structure's parts in an algorithm for three-dimensional frame design rather than only using structural elements. The performance of the constructed multi-objective model is evaluated using 12 standard multi-objective benchmarks proposed in IEEE congress on evolutionary computation. Second, MEN-ChOA is employed in constructing several reinforced concrete structures by the Mexico City building code. The variety of Pareto optimum fronts of these criteria enables a thorough performance examination of the MEN-ChOA. The results also reveal that BRB frames with comparable structural performance to conventional moment-resistant reinforced concrete framed buildings are more cost-effective when reinforced concrete building height rises. Structural performance and building cost may improve by using a nature-inspired strategy based on MEN-ChOA in structural design work.

• Journal of Information Technology Services
• /
• v.6 no.1
• /
• pp.65-81
• /
• 2007

Recently, the affiliates of the Ministry of Information and Communication have been conducting a performance evaluation study on IT policy projects, based on the performance evaluation model of the U.S. Office of Management and Budgets, with regard to investment in computerization. The performance evaluation model for the policy project could provide the objective information required for the planning, development, and operation of the policy project. However, the performance of the most policy project is likely to be evaluated using the subjective evaluation criteria of evaluators. Therefore, this case study evaluates the relative efficiency using DEA (Data Envelopment Analysis) in order to improve the performance evaluation method of the digital pioneer' project implemented by the Korea IT Industry Promotion Agency. The improvement value of inefficient Decision Making Units (DMUs) was measured by a static efficiency analysis. The measured value will suggest a objective viewpoint of the performance between DMUs to evaluators. In doing so, it will show an appropriate direction for the policy project to be evaluated successfully.

• The Journal of Korea Robotics Society
• /
• v.17 no.2
• /
• pp.164-171
• /
• 2022

Recently, interest of a dual arm robot which can replace humans is increasing in order to improve the working environment and solve the labor shortage. Various studies related with design and analysis of dual-arm robots have been conducted because dual arm robots can have various kinematic configurations according to the objective task. It is necessary to evaluate the work performance according to various kinematic structures of the dual arm robot to maximize its effectiveness. In the paper, the performance analysis is studied according to the shoulder configuration and the wrist configuration of the dual-arm robot by using main performance indices such as manipulability, condition number, and minimum singular value by assigning proper weight values to each objective motion. Performance analysis for the robotic assembly process is effectively carried out for each representative dual arm robot configuration.

• International Journal of Automotive Technology
• /
• v.6 no.2
• /
• pp.141-148
• /
• 2005

In order to reduce the time and costs of improving the performance of vehicle suspensions, the techniques for optimizing damping and air spring characteristic were proposed. A full vehicle model for a bus is constructed with a car body, front and rear suspension linkages, air springs, dampers, tires, and a steering system. An air spring and a damper are modeled with nonlinear characteristics using experimental data and a curve fitting technique. The objective function for ride quality is WRMS (Weighted RMS) of the power spectral density of the vertical acceleration at the driver's seat, middle seat and rear seat. The objective function for handling performance is the RMS (Root Mean Squares) of the roll angle, roll rate, yaw rate, and lateral acceleration at the center of gravity of a body during a lane change. The design variables are determined by damping coefficients, damping exponents and curve fitting parameters of air spring characteristic curves. The Taguchi method is used in order to investigate sensitivity of design variables. Since ride and handling performances are mutually conflicting characteristics, the validity of the developed optimum design procedure is demonstrated by comparing the trends of ride and handling performance indices with respect to the ratio of weighting factors. The global criterion method is proposed to obtain the solution of multi-objective optimization problem.

• The Journal of the Korea Contents Association
• /
• v.11 no.8
• /
• pp.68-76
• /
• 2011

Due to the high interests of image quality by consumers, the concerned market becomes more heated. Recent digital camera development tendency shows to perform the higher image quality to meet consumers demand of quality satisfaction. However it is hard to confirm that development of objective image quality performance means positive subjective image quality preference. And also, we cannot find out the previous researches concerned on correlation between objective and subjective image quality comparison. Therefore, it is necessary to analyze the consumers preferred images based on objective image quality performance. Throughout this paper, we analyze statistical correlation between the objective and subjective image quality assessment methods by using ISO standards. In these results, we try to find attributes that enhance image quality. We suggest not only to analyze and reflect on customers' preferences, but also to pursue the high quality image performance practically. We expect the results of this paper to positively influence product development.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.3
• /
• pp.296-303
• /
• 2020

This study examined the factors affecting the emergency nursing performance of nursing students during a simulation. The variables related to the simulation were the objective and subjective emergency nursing performance, critical thinking, program outcome, simulation satisfaction, simulation confidence, and simulation immersion. The participants were 92 senior students who provided informed consent with an explanation about attending the study. The general characteristics and simulation-related data were obtained from the students before and after the simulation. An assessor evaluated the objective emergency nursing performance during the simulation and program outcome through a report reviewed after the simulation. Data analysis was performed using the number, percentage, mean, standard deviation, X²-test, one-way ANOVA, Pearson correlation, and progressive regression through the SPSS/WIN 22.0 program. Emergency nursing performance by the assessor was negatively associated with the satisfaction of clinical practice (r=-.31, p=.005) and positively related to the subjective clinical performance (r=.23, p=.036). The affecting rate was just 12%, which was low for explaining the objective emergency nursing performance during the simulation. Further studies will be needed to explore other factors affecting the emergency nursing performance.

• Transactions of the Society of Information Storage Systems
• /
• v.1 no.2
• /
• pp.121-126
• /
• 2005

Recently, an optical disc system has been proposed using blue laser diode, high NA objective lens and groove only disc structure. A new method is needed to readout CD and DVD in this Blu-Ray Disc Recorder. In order to readout CD and DVD in Blu-Ray Disc Recorder, we adopted dual-lenses actuator in consideration of optical utilization efficiency, optical performance and insurance of sufficient W.D(working distance). This dual-lenses actuator has two objectives in radial direction, one is for CD/DVD and the other is for BD. We had to solve the induced problems of collision between disc and lens, DC tilt increase, AC tilt increase, 2nd resonance deterioration and AC sensitivity drop caused by disposing two lenses in an actuator. Also we developed high response twin- objective actuator with radial tilt function to apply high-speed BD Recorder or BD Player. Consequently we presented that two kinds of dual-lenses actuators for BD Recorder have been possessed good performance in 3 axis directions. And we measured eye patterns of CD, DVD and BD by using one BD optical pick-up with dual-lenses actuator.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.13 no.10
• /
• pp.5013-5034
• /
• 2019

In the Peer-to-Peer (P2P) streaming systems, peers randomly form a network overlay to share video resources with a data scheduling scheme. A data scheduling scheme can have a great impact on system performance, which should achieve two optimal objectives at the same time ideally. The two optimization objectives are to improve the perceived video quality and maximize the network throughput, respectively. Maximizing network throughput means improving the utilization of peer's upload bandwidth. However, maximizing network throughput will result in a reduction in the perceived video quality, and vice versa. Therefore, to achieve the above two objects simultaneously, we proposed a new data scheduling scheme based on multi-objective particle swarm optimization data scheduling scheme, called MOPSO-DS scheme. To design the MOPSO-DS scheme, we first formulated the data scheduling optimization problem as a multi-objective optimization problem. Then, a multi-objective particle swarm optimization algorithm is proposed by encoding the neighbors of peers as the position vector of the particles. Through extensive simulations, we demonstrated the MOPSO-DS scheme could improve the system performance effectively.