• International Journal of Fluid Machinery and Systems
• /
• v.2 no.2
• /
• pp.179-188
• /
• 2009

Recent development of high speed computers and use of optimization techniques have given a big momentum of turbomachinery design replacing expensive experimental cost as well as trial and error approaches. The surrogate based optimization techniques being used for aerodynamic turbomachinery designs coupled with Reynolds-averaged Navier-Stokes equations analysis involve single- and multi-objective optimization methods. The objectives commonly tried to improve were adiabatic efficiency, pressure ratio, weight etc. Presently coupling the fluid flow and structural analysis is being tried to find better design in terms of weight, flutter and vibration, and turbine life. The present article reviews the surrogate based optimization techniques used recently in turbomachinery shape optimizations.

• ETRI Journal
• /
• v.30 no.4
• /
• pp.535-545
• /
• 2008

This paper introduces a systematic top-down and bottom-up design methodology to assist the designer in the implementation of continuous-time (CT) cascade sigma-delta (${\Sigma}{\Delta}$) modulators. The salient features of this methodology are (a) flexible behavioral modeling for optimum accuracy-efficiency trade-offs at different stages of the top-down synthesis process, (b) direct synthesis in the continuous-time domain for minimum circuit complexity and sensitivity, (c) mixed knowledge-based and optimization-based architectural exploration and specification transmission for enhanced circuit performance, and (d) use of Pareto-optimal fronts of building blocks to reduce re-design iterations. The applicability of this methodology will be illustrated via the design of a 12-bit 20 MHz CT ${\Sigma}{\Delta}$ modulator in a 1.2 V 130 nm CMOS technology.

• Journal of Sensor Science and Technology
• /
• v.33 no.3
• /
• pp.134-138
• /
• 2024

In this study, we propose a ternary D flip-flop using tristate ternary inverters for an energy-efficient ternary circuit design of sequential logic. The tristate ternary inverter is designed by adding the functionality of the transmission gate to a standard ternary inverter without an additional transistor. The proposed flip-flop uses 18.18% fewer transistors than conventional flip-flops do. To verify the advancement of the proposed circuit, we conducted an HSPICE simulation with CMOS 28 nm technology and 0.9 V supply voltage. The simulation results demonstrate that the proposed flip-flop is better than the conventional flip-flop in terms of energy efficiency. The power consumption and worst delay are improved by 11.34% and 28.22%, respectively. The power-delay product improved by 36.35%. The above simulation results show that the proposed design can expand the Pareto frontier of a ternary flip-flop in terms of energy consumption. We expect that the proposed ternary flip-flop will contribute to the development of energy-efficient sensor systems, such as ternary successive approximation register analog-to-digital converters.

• Membrane and Water Treatment
• /
• v.10 no.1
• /
• pp.75-82
• /
• 2019

In a highly urbanized area, land availability is limited for the installation of space consuming stormwater systems for best management practices (BMPs), leading to the consideration of underground stormwater treatment devices connected to the stormwater pipe system. The configuration of a stormwater pipe network determines the hydrological and pollutant transport characteristics of the stormwater discharged through the pipe network, and thus should be an important design consideration for effective management of stormwater quantity and quality. This article presents a multi-objective optimization approach for designing a stormwater pipe network with on-line stormwater treatment devices to achieve an optimal trade-off between the total installation cost and the annual removal efficiency of total suspended solids (TSS). The Non-dominated Sorted Genetic Algorithm-II (NSGA-II) was adapted to solve the multi-objective optimization problem. The study site used to demonstrate the developed approach was a commercial area that has an existing pipe network with eight outfalls into an adjacent stream in Yongin City, South Korea. The stormwater management model (SWMM) was calibrated based on the data obtained from a subcatchment within the study area and was further used to simulate the flow rates and TSS discharge rates through a given pipe network for the entire study area. In the simulation, an underground stormwater treatment device was assumed to be installed at each outfall and sized proportional to the average flow rate at the outfall. The total installation cost for the pipes and underground devices was estimated based on empirical formulas using the flow rates and TSS discharge rates simulated by the SWMM. In the demonstration example, the installation cost could be reduced by up to 9% while the annual TSS removal efficiency could be increased by 4% compared to the original pipe network configuration. The annual TSS removal efficiency was relatively insensitive to the total installation cost in the Pareto-optimal solutions of the pipe network design. The results suggested that the installation cost of the pipes and stormwater treatment devices can be substantially reduced without significantly compromising the pollutant removal efficiency when the pipe network is optimally designed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.7
• /
• pp.1621-1630
• /
• 2009

There is a lot of recent research to provide services of dynamic distributed contents in P2P-based distributed environment. Distributed services of contents objects, however, have problems in QoS and dynamic management of segments. This paper proposed a new segment management method for the service of P2P-based distributed contents. The proposed method manages groups by the SGM(Segment Group Manager). The SGM manages streaming efficiently by the grouping of segments to be served in P2P environment. The segments in the same group cooperate for improved QoS using the management structure based on the distance and relationship. The distance-based management structure is for the improvement of retrieval efficiency while the relationship-based management structure is for the improvement of service ratio. The simulation results of the proposed method showed improvements in average transmission efficiency and average service rate. The improvement is 8% - 30% in average transmission efficiency and 10% - 30% in average service rate.

• Journal of the Korean Chemical Society
• /
• v.58 no.2
• /
• pp.198-204
• /
• 2014

In this present study, bagasse based pulp and paper industry wastewater was treated under different operating conditions such as initial pH (6-8), temperature ($25-35^{\circ}C$) and contact time (3-7 days) by using Bacillus subtilis. Response surface methodology (RSM) coupled with Box-Behnken response surface design (BBD) was employed to investigate the effect of process variables on the responses such as turbidity, biological oxygen demand (BOD) and chemical oxygen demand (COD) removal. The experimental data were analyzed by Pareto analysis of variance (ANOVA) and the second order polynomial models were developed. Interactive effects of the process variables on the responses were studied using plotting 3D response surface contour graph and the optimum process conditions were found to be: initial pH of 7, temperature of $30^{\circ}C$ and contact time of 5 days. Under these conditions, removal efficiencies of turbidity, BOD and COD were found to be 85%, 93% and 80% respectively which are close agreement with real experiments. These results indicate that the treatment of bagasse based pulp and paper industry wastewater using Bacillus subtilis is an effective and novel technique.

• Journal of the Korea Society of Computer and Information
• /
• v.9 no.3
• /
• pp.211-218
• /
• 2004

It was amazing that efficiency of bureaucratic system, when Marx Weber presented theory of bureaucracy. Now, Government and Bureaucratic organization are confronted with a forked road of change. The purpose of this paper is not so much to force choices among the alternative visions of governance but rather to make the choices available to governments more evident. Any choice of paradigms for government and administration is unlikely to be Pareto optimal, but we should be clear about what we receive and what we sacrifice when we make these judgements about governance. Today, government and public bureaucracy must be changed. There are needed an innovation of government and public bureaucracy. It must be changed concepts from government to governance. Governance is a national management.

• The KSFM Journal of Fluid Machinery
• /
• v.7 no.2 s.23
• /
• pp.7-13
• /
• 2004

In an attempt to solve multiobjective optimization problems, weighted sum method is most widely used for the advantage that a designer can consider the relative significance of each object functions by weight values but it can be highly sensitive to weight vector and occasionally yield a deviated optimum from the relative weighting values designer designated because the multiobjective function has the form of simple sum of the product of the weighting values and the object functions in traditional approach. To search the design solution agree well to the designer's weighting values, we proposed new multiobjective function which was the functional of each normalized objective functions and considered to find the design solution comparing the distance between the characteristic line and the ideal optimum. In this study, proposed multiobjective function was applied to design high efficiency and low noise axial flow fan and the result shows this approach is effective for the case that the quality of the design can be highly affected by the designer's subjectiveness represented as weighting values in multiobjective design optimization process.

• International Journal of Automotive Technology
• /
• v.8 no.3
• /
• pp.337-342
• /
• 2007

A multi-objective optimization technique was implemented to obtain optimal topologies of the inner reinforcement for a vehicle's hood simultaneously considering the static stiffness of bending and torsion and natural frequency. In addition, a smoothing scheme was used to suppress the checkerboard patterns in the ESO method. Two models with different curvature were chosen in order to investigate the effect of curvature on the static stiffness and natural frequency of the inner reinforcement. A scale factor was employed to properly reflect the effect of each objective function. From several combinations of weighting factors, a Pareto-optimal topology solution was obtained. As the weighting factor for the elastic strain efficiency went from 1 to 0, the optimal topologies transmitted from the optimal topology of a static stiffness problem to that of a natural frequency problem. It was also found that the higher curvature model had a larger static stiffness and natural frequency than the lower curvature model. From the results, it is concluded that the ESO method with a smoothing scheme was effectively applied to topology optimization of the inner reinforcement of a vehicle's hood.

• Advances in environmental research
• /
• v.1 no.4
• /
• pp.237-255
• /
• 2012

We review the research literature on relationship between environmental regulation and industrial development in three aspects of environmental regulation and investment, environmental regulation and efficiency, environmental regulation and trade. Indeed, the linkage between environmental regulation and material consumption of industrial system is absent. Environmental regulation is measured as the expenditure share for industrial pollutants abatement, and effluent charge intensity. Using panel-level data from 31 provinces, municipalities and autonomous regions in China, we build correlation models between material consumption and environmental regulation, results show that: (1) there are significant quadratic function relationship between material consumption and environmental regulation. And there is the fact that inflection point exists. (2) On basis of inflection points, we make two remarkable reflections. Firstly, the inflection points are the most important scale to judge reasonability and performance of regulations. Secondly, a Pareto improvement may occur when the regulations achieve a certain target. (3) Both intensities of industrial pollutants abatement expenditure and effluent charge have not yet achieved the expected target in most regions of mainland China at present. And most of regions of material consumption decreasing are distributed in western China. Main reasons lie in the impacts of industrial features as well as the regulations.