• Journal of the Korean Institute of Landscape Architecture
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• v.43 no.6
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• pp.16-24
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• 2015

This study quantified storage and annual uptake of carbon for riparian greenspaces established in watersheds of four major rivers in South Korea and explored desirable strategies to improve carbon reduction effects of riparian greenspaces. Greenspace structure and planting technique in the 40 study sites sampled were represented by single-layered planting of small trees in low density, with stem diameter at breast height of $6.9{\pm}0.2cm$ and planting density of $10.4{\pm}0.8trees/100m^2$ on average. Storage and annual uptake of carbon per unit area by planted trees averaged $8.2{\pm}0.5t/ha$ and $1.7{\pm}0.1t/ha/yr$, respectively, increasing as planting density got higher. Mean organic matter and carbon storage in soils were $1.4{\pm}0.1%$ and $26.4{\pm}1.5t/ha$, respectively. Planted trees and soils per ha stored the amount of carbon emitted from gasoline consumption of about 61 kL, and the trees per ha annually offset carbon emissions from gasoline use of about 3 kL. These carbon reduction effects are associated with tree growth over five years to fewer than 10 years after planting, and predicted to become much greater as the planted trees grow. This study simulated changes in annual carbon uptake by tree growth over future 30 years for typical planting models selected as different from the planting technique in the study sites. The simulation revealed that cumulative annual carbon uptake for a multilayered and grouped ecological planting model with both larger tree size and higher planting density was approximately 1.9 times greater 10 years after planting and 1.5 times greater 30 years after than that in the study sites. Strategies to improve carbon reduction effects of riparian greenspaces suggest multilayered and grouped planting mixed with relatively large trees, middle/high density planting of native species mixed with fast-growing trees, and securing the soil environment favorable for normal growth of planting tree species. The research findings are expected to be useful as practical guidelines to improve the role of a carbon uptake source, in addition to water quality conservation and wildlife inhabitation, in implementing riparian greenspace projects under the beginning stage.

• Land and Housing Review
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• v.4 no.1
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• pp.33-42
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• 2013

This study which are recognized that the lack of empirical research about the efficiency of the elements of environmentally friendly housing development planned presented housing design elements and policies to revitalize for the reduction of greenhouse gas emissions by analyzing the effectiveness of reduction of greenhouse gas output. In addition, it used various models of DEA which are accepted until now effective technique to evaluate the performance of the organization. In conclusion, there are effective 5 regionals which are Seoul, Incheon, Ulsan, South Chungcheong Province, South Gyeongsang Province. other regionals was analyzed to be inefficient. The conclusion from this study are as follows: First, in case of 11 regionals which are analyzed to be inefficient, they have to difference plan elements to make up. So each region should establish strategy to complement vulnerability. Second, not only internal architectural factors but institutional, and external environmental factors also affect the reduction of greenhouse gas emissions. And weighted scores also were moderately high. But levels of weighted scores still less than the ratio of Good quality housing. So it can be determined that evaluation of individual architecture still considered important. It need to pay more attention to the operating system and the external environmental factors.

• Journal of Korea Water Resources Association
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• v.55 no.8
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• pp.613-621
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• 2022

Due to the global climate change, the rainfall volume and frequency on the Korean Peninsula are predicted to increase at the end of the 21st century. In addition, impervious surface areas have increased due to rapid urbanization which has caused the urban water cycle to deteriorate. Green Infrastructure (GI) researches have been conducted to improve the water cycle soundness; the efficiency of this technique has been verified through various studies. However, there are still no suitable GI design guidelines for this aspect. Therefore, the rainfall scenarios are set up for each percentile (60, 70, 80, 90) based on the volume and frequency analysis using 10-year rainfall data (Busan Meteorological Station). After determining the GI areas for each scenario, the runoff reduction characteristics are analyzed based on Storm Water Management Model (SWMM) 10-year rainfall-runoff-simulations. The total runoff reduction efficiency for each GI areas are computed to have a range of 13.1~52.1%. As a results of the quantitative analysis, the design rainfall for GI is classified into the 80~85 percentile in the study site.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.3
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• pp.181-192
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• 2022

Active vibration control system(AVCS) for helicopter enables to control the vibration generated from the main rotor and has the superb vibration reduction performance with low weight compared passive vibration reduction device. In this paper, FxLMS algorithm-based vibration control software of the light civil helicopter tansmits the control command calculated using the signals of the tachometer and accelerometers to the circular force generator(CFG) is developed and verified. According to the RTCA DO-178C/DO-331, the vibration control software is developed through the model based design technique, and real-time operation performance is evaluated in PILS(processor in-the loop simulation) and HILS(hardware in-the loop simulation) environments. In particular, the reliability of the software is improved through the LDRA-based verification coverage in the PIL environments. In order to AVCS to light civil helicopter(LCH), the dynamic response characteristic model is obtained through the ground/flight tests. AVCS configuration which exhibits the optimal performance is determined using system optimization analysis and flight test and obtain STC certification.

• Journal of the Korean Society for Advanced Composite Structures
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• v.1 no.2
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• pp.51-58
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• 2010

This work examines the identification of stiffness reduction in damaged reinforced concrete bridges under moving loads, and carries out the performance assessment after repairing using advanced composite materials. In particular, the change of stiffness in each element before and after repairing, based on the Microgenetic algorithm as an advanced inverse analysis, is described and discussed by using a modified bivariate Gaussian distribution function. The proposed method in the study is more feasible than the conventional element-based method from computation efficiency point of view. The validity of the technique is numerically verified using a set of dynamic data obtained from a simulation of the actual bridge modeled with a three-dimensional solid element. The numerical examples show that the proposed technique is a feasible and practical method which can inspect the complex distribution of deteriorated stiffness although there is a difference between actual bridge and numerical model as well as uncertain noise occurred in the measured data.

• Journal of Korean Society on Water Environment
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• v.25 no.1
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• pp.58-68
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• 2009

Low impact development (LID) technique is relatively new concept to reduce surface runoff and pollutant loading from land cover by attempting to match predevelopment condition with various integrated management practices (IMPs). In this study, computational model for designing and evaluating LID, named LIDMOD, was developed based on SCS-CN method and applied at Andong bus terminal to evaluate LID applicapability and design retention/detention area for volume or peak flow control. LIDMOD simulated with 21 years simulation period that yearly surface runoff by post-development without LID was significantly higher than that with LID showing about 2.8 times and LID could reduce efficiently yearly surface runoff with 75% reduction of increased runoff by conventional post development. LIDMOD designed detention area for volume/peak flow control with 20.2% of total area by hybrid design. LID can also efficiently reduce pollutant load from land cover. Pollutant loads from post-development without LID was much higher than those from pre-development with showing 37 times for BOD, 2 times for TN, and 9 times for TP. Pollutant loads from post-development with LID represented about 57% of those without LID. Increasing groundwater recharge reducing cooling and heating fee, creating green refuge at building area can be considered as additional benefits of LID. At the point of reducing runoff and pollutant load, LID might be important technique for Korean TMDL and LIDMOD can be useful tool to calculate unit load for the case of LID application.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.2
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• pp.244-250
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• 2015

We propose a simulation technique to estimate the reduction effect of the pressure/flow pulsation by analysis of the pulsation variables and notch shape of the valve plate of a swash-plate-type variable piston pump. First, using SimulationX$^{(R)}$, we perform a theoretical kinematic analysis according to the variable swash-plate angle and rotational velocity in order to design a single-piston pump. In designing the notch shape of the valve plate of the swash-plate-type variable piston pump as one of the pulsation variables, we investigate the effect of the pulsation by comparing two notch types (circular type and V type). Then, we extend our analysis to a nine-piston pump model. This paper not only confirms the effect of the pressure/flow pulsation according to pulsation variables but can also be applied to the development of a SimulationX$^{(R)}$-based simulation technique for notch-shape optimization for a swash-plate-type variable piston pump.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.55-65
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• 1998

In industrial fields, RTP(rapid thermal processing) system is widely used for improving the oxidation and the annealing in semiconductor manufacturing process. The main control factors are temperature control of wafer and uniformity in the wafer. In this paper, we propose an $H^{\infty}$ controller design of RTP system satisfying robust stability and performance using weighted mixed sensitivity miniimization and loop shaping technique. And we need reduction technique because of the difficulty of implementation with the obtained high order controller for original model and reduced models, namely, Hankel, square-root balanced, and Schur balanced methods. An example is proposed to show the validity of the proposed method.

• Korean Chemical Engineering Research
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• v.58 no.2
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• pp.190-196
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• 2020

The step to obtain a process dynamic model through process experiments is very important because it needs times and expenditures. Step response method is one of the standard methods to have long been used for understanding process dynamics, obtaining dynamical models and designing control systems. For the step response, it is usually required to measure process output for a step input change in the open-loop manner. Its disadvantage criticized is the long open-loop operation. For this, a method based on the time-optimal control technique to minimize the test time for obtaining the step response has been recently presented. However, the method requires iterative computations for the minimization of test times. Here, a method where iterative computations are not required is proposed. Simulation results are presented to show that test times to obtain step responses are reduced considerably and an autotuning method based on the proposed method is compared with the relay feedback autotuning method accepted widely for the autotuning of controllers.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.4
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• pp.661-674
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• 2002

The objective of this study is to develop efficient numerical method to enable solution of optimal control problems of Navier-Stokes flows and to apply these technique to the problem of viscous drag minimization on a bluff body by controlling boundary velocities on the surface of the body. In addition to the industrial importance of the drag reduction problem, it serves as a model for other more complex flow optimization settings, and allows us to study, modify, and improve the behavior of the optimal control methods proposed here. The control is affected by the suction or injection of fluid on portions of the boundary, and the objective function represents the rate at which energy is dissipated in the fluid. This study shows how reduced Hessian successive quadratic programming method, which avoid converging the flow equations at each iteration, can be tailored to these problems.