• Fisheries and Aquatic Sciences
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• v.2 no.1
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• pp.52-57
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• 1999

Air-drived rotating biological contactor (RBC) system, which is effective method in filtering performance, was tested for the nitrification capacity in a recirculating system. At ammonia concentrations between 0.029 and 0.528 mg/l, the effect of ammonia loading rate on ammonia removal rate at three different hydraulic loading rates could be defined by the following first­order regression models: Hydraulic loading rate of $14.8 m^3/m^3/day:\;y=39.2\times+3.4 (r^2=0.9137)$, Hydraulic loading rate of $26.5 m^3/m^3/day: y=53.3\times+4.0 (r^2=0.8686)$, Hydraulic loading rate of $37.3 m^3/m^3/day: y=58.4\times+4.2 (r^2=0.7755)$, where, $\times$ is ammonia loading rate (mg/l), y is ammonia removal rate $(g/m^3/day)$, The equations showed the optimal ammonia removal rate at the hydraulic loading rate of $26.5m^3/m^3/day$. Below the ammonia concentration of 2.72 mg/l, first-order regression models between ammonia loading rate and ammonia removal rate at three different rates of speed are defined as follows: Rotational speed of $0.75 rpm: y=28.5\times+4.7 (r^2=0.9143)$, Rotational speed of $1.0 rpm: y=33.6\times+8.4 (r^2=0.9534)$, Rotational speed of $2.0 rpm: y=28.9\times+3.6 (r^2=0.9488)$, where, x is ammonia loading rate (mg/l), y is ammonia removal rate $(g/m^3day)$. The equations show the ammonia removal rate at the rotational speed of 1.0 rpm is significantly higher than that at the rotational speed of either 0.75 rpm or 2.0 rpm (P<0.05).

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.7A
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• pp.967-977
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• 2000

In this paper, we apply a mixed $H_2/H_{\infty}$ control to a generalized plant of inverted pendulum system represented by an LFR(Linear Fractional Representation). First, in order to obtain the generalized plant, the linear model of the inverted pendulum represented by an LFR(Linear fractional Representation) is derived. In LFR, we consider system uncertainties as three nonlinear components and a pendulum mass uncertainty. Augmenting the LFR model by adding weighting functions, we get a generalized plant. And then, we design a mixed $H_2/H_{\infty}$ controller for the generalized plant. In order to design the mixed $H_2/H_{\infty}$ controller, we use the LMI technique. To evaluate control performances and robust stability of the mixed $H_2/H_{\infty}$ controller designed, we compare it with the $H_{\infty}$ controller through the simulation and experiment. In the result, with the fewer feedback information, the mixed $H_2/H_{\infty}$ controller shows the better control performances and robust stability than the $H_{\infty}$ controller in the sense of pendulum angle.

• Advances in robotics research
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• v.2 no.2
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• pp.113-127
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• 2018

Robotics and automation are rapidly growing in the industries replacing human labor. The idea of robots replacing humans is positively influencing the business thereby increasing its scope of research. This paper discusses the development of an experimental platform controlled by a robotic arm through Robot Operating System (ROS). ROS is an open source platform over an existing operating system providing various types of robots with advanced capabilities from an operating system to low-level control. We aim in this work to control a 7-DOF manipulator arm (Robai Cyton Gamma 300) equipped with an external vision camera system through ROS and demonstrate the task of balancing a ball on a plate-type end effector. In order to perform feedback control of the balancing task, the ball is designed to be tracked using a camera (Sony PlayStation Eye) through a tracking algorithm written in C++ using OpenCV libraries. The joint actuators of the robot are servo motors (Dynamixel) and these motors are directly controlled through a low-level control algorithm. To simplify the control, the system is modeled such that the plate has two-axis linearized motion. The developed system along with the proposed approaches could be used for more complicated tasks requiring more number of joint control as well as for a testbed for students to learn ROS with control theories in robotics.

• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.187-198
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• 1995

This paper develops practical and reallstic reliabllity models and methods for the evaluation of system rehability and system rellabllity based ratlng of R.C box glrder bridge superstructures. The precise prediction of reberved carrying capacity of bridge as d system is extremely difficult especially when the brldges are highly redundant and slgnlficantly deter 1or;itcd or dainagetl. Thls papel proposes a nt2w approach for the evaluation of reseived system c,drrying capaaty of br~dges in terms ot equ~vdleiit system strength, which may b~ ddcflned as a brtdge system strength correipcmdlng tu the system rehability of the bridge. This cm be ticrAvcd from an Inverse process bami or1 the con~ept of FOSM(F1rst Order Second Moment) form of system reliabihty index. The sf rength llmt state models for K C box girder br~dges suggested In the paper dre based on the basi~ bending and shear strength And thc system reliatxllty pro,~lerri of box gritier super structure 1s formuldted as parallel serles models obtalncd f ~ o m thc FMA(Fdilure blode Rp proath) based on major failure mc>clmusrns or c~itlcal fdure ,>tatcs of each nuder .WOSM(Ad-vanced First Order Second Moment) and IST(1mportance Sampling Technique) simulation algorithm are used for the reliability analysis of the proposed models.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.6
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• pp.89-96
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• 2001

This paper presents a decision making technique of reasonable $O_2$quantity needed to resolve organic matter via microbe in wastewater treatment. Decision making system of inferring reasonable $O_2$quantity consists of three parts. The first part is to compute reasonable $O_2$quantity with given process data. The second part is to find output features of processed wastewater using process model when $O_2$quantity is changed to a value inferred from decision making system. The third part is to show the results of decision making system. In order to verify performance of proposed decision making system computer simulation was done with process data gathered during 40 days. Simulation result shows that $O_2$quantity can be reduced over 10% under the condition of satisfying the specifications for processed wastewater.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.1022-1028
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• 2024

A neutronics study of a supercritical CO₂-cooled fast reactor core for nuclear propulsion has been performed in this work. The thermal power of the reactor core is 30 MWth and a ceramic UO₂ fuel can be used to achieve a 20-year lifetime without refueling. In order to make a compact core with inherent safety features, the drum-type reactivity control system and folding-type shutdown system are adopted. In addition, we suggest a cold shutdown system using gadolinium as a spectral shift absorber (SSA) against flooding. Although there is a penalty of U-235 enrichment for the core embedded with the cold shutdown system, it effectively mitigates the increment of reactivity at the flooding of seawater. In this study, the neutronics analyses have been performed by using the continuous energy Monte Carlo Serpent 2 code with the evaluated nuclear data file ENDF/B-VII.1 Library. The supercritical CO₂-cooled fast reactor core is characterized in view of important safety parameters such as the reactivity worth of reactivity control systems, fuel temperature coefficient (FTC), coolant temperature coefficient (CTC), and coolant temperature-density coefficient (CTDC). We can say that the suggested core has inherent safety features and enough flexibility for load-following operation.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.155-162
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• 1995

Solid oxide electrolytes of the MCe1-xGdxO3-x/2 (M: Ba, Mg. x=0.0-0.20) system were prepared using powders synthesized by the "liquid mix" method and calcined from the cross-linked polyacrylic polymer. The specimens were analyzed using XRD and SEM with EDX, and the sintering behavior of the electrolytes and their electrical conductivity were also studied. Although Mg-cerate is relatively inferior to Ba-cerate in the sinterability and chemical homogenity(EDX analysis data), both the Ba- and the Mg-cerate electrolytes at 80$0^{\circ}C$ show their maximum conductivities at x=0.10 and their values are in the same order of magnitude, i.e., 3.5$\pm$0.17.10-2(ohm.cm)-1.ohm.cm)-1.

• Journal of the Korean Institute of Intelligent Systems
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• v.14 no.5
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• pp.557-562
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• 2004

This paper deals with a robust mixed ${H_2}/{H_{\infty}}$ filter design problem for a nonlinear dynamic system modeled as a T-S fuzzy system. Integral quadratic constraints are used to describe various kinds of uncertainties of the plant. A sufficient condition for solvability is given in terms of linear matrix inequality problem which can be efficiently solved using a convex optimization technique. In order to demonstrate the Proposed method, a numerical design example is provided.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.5
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• pp.356-366
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• 2000

In this paper, a nonlinear $H_2/H_\infty/LTR$ control for the flexible inverted pendulum of a parallel type with Coulomb friction is presented. The dynamic equation for this system is derived by the Hamilton's principle and assumed-mode method. This hard nonlinear system can be modeled by a the quasi-linear state space model using the REF method. It is shown that the $H_2/H_\infty$ control can be applied to the nonlinear controller design of the system having Coulomb frictions if the proper LTR conditions are satisfied. In order to present the usefulness of the suggested control method, the nonlinear $H_2/H_\infty/LTR$ controller is designed to control the Position of the end point of the flexible inverted pendulum that has Coulomb frictions present in actuator parts. The results are given via computer simulations.

• Journal of Korean Society for Atmospheric Environment
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• v.6 no.1
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• pp.51-56
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• 1990

This Study shows the effect of the district heating on the $SO_2$ concentration reduction. In order to analyze the effect of the district heating, three alternatives were set up as follows; Alternative I represented present central heating system, and Alternative II and Alternative III represented district heating system of which the scale were different from. The concludions of this study are as follows; In case of the Alternative II and III, annual average $SO_2$ concentration are reduced by 9.0% and 14.6% respectively, and winter season $SO_2$ concentrations are reduced by 12.2% and 15.8% respectively, at the highest points. The average reduction rates of $SO_2$ concentration in the district heating area are about the same as the reduction rates at the highest points. Also, it was found that using the district heating system, the ground level $SO_2$ concentrations could be reduced within the area of 5 to 10 km radius.