• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.1
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• pp.1-9
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• 2015

To satisfy stricter $NO_X$ emission regulations for light- and heavy-duty diesel vehicles, a control algorithm needs to be developed based on a selective catalytic reaction (SCR) dynamics model for chemical reactions. This paper presents the development and validation of a SCR dynamics model through test rig experiments and MATLAB simulations. A nonlinear state space model is proposed based on the mass conservation law of chemical reactions in the SCR dynamics model. Experiments were performed on a test rig to evaluate the effects of the $NO_X$ and $NH_3$ concentrations, gas temperature, and space velocity on the $NO_X$ conversion efficiency for the urea-SCR system. The parameter values of the proposed SCR model were identified using the experimental datasets. Finally, a control-oriented model for an SCR system was developed and validated from the experimental data in a MATLAB simulation. The results of this study should contribute toward developing a closed-loop control strategy for $NO_X$ and $NH_3$ slip reduction in the urea-SCR system for an actual engine test bench.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.193-198
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• 2015

Ceria supported on various commercial $TiO_2$ catalysts were prepared by wet-impregnation method. We confirmed that the correlation between physicochemical properties of $TiO_2$ supports and SCR activities. Physicochemical properties of the various $TiO_2$ were evaluated using X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area, X-ray photoelectron spectroscopy (XPS), and pH analysis. Ce/Ti catalyst exhibited different SCR activities with respect to physicochemical properties of $TiO_2$. An excellent activity was obtained as the surface area of $TiO_2$ increased. In the case of CeOx surface density, the excellent activity in a range of $2.5{\sim}14.5CeOx/nm^2$ was achieved and the activity tended to decrease above $14.5CeOx/nm^2$. The O/Ti mole ratio of $TiO_2$ in the range of 1.32 to 1.79 showed an excellent SCR activity. It was also confirmed that the pH of the $TiO_2$ has no effects on the SCR activity. In order to achieve excellent SCR activities, ceria oxide should be supported on $TiO_2$ possessing a high specific surface area and certain O/Ti mole ratio. In addition, the catalyst with the low CeOx surface density resulted from the high dispersed ceria oxide should be prepared.

• Journal of Power System Engineering
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• v.19 no.6
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• pp.68-74
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• 2015

NOx emission has been controlled because it is a major cause of the acid rain and effects considerably on formation and destruction of ozone. A SCR system on diesel engine is necessary to clear TierIII, because IMO(International Maritime Organization) plans on tightening regulations to TierIII at $1^{st}$ January 2016. In this study, flow analysis was accomplished with ANSYS Fluent program so that the SCR system would be retrofitted in training ship KAYA and the temperature distributions of exhaust gas in SCR sytem were investigated after it was installed. As a result, it was confirmed that pressure and velocity distributions in SCR system were depended on pipe line shapes, then it was designed as the pressure was lower. The temperature differential between 1 and 3 point was $15^{\circ}C$ because of evaporative latent heat of urea and the temperature of 4 point after catalyst was increased by $5^{\circ}C$ than 3 point because of exothermic reaction.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.88-89
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• 2016

선택적 환원 촉매(SCR : Selective Catalytic Reduction) 시스템은 대기오염을 예방하기 위한 배기가스 처리장치 중 하나이다. 본 연구에서는 전산유체역학(CFD : Computational Fluid Dynamics)를 사용하여 SCR 시스템 의 효율향상을 위하여 ANSYS-CFX package를 이용하여 점성 유동 해석을 수행하였다. SCR 시스템의 점성 유동 흐름의 전산 유체 역학을 이용하여 시뮬레이션하기 위하여 Navier-Stokes 방정식을 지배방정식으로 사용하였다. CATIA V5를 사용하여 SCR 시스템의 형상을 3D 모델링을 하였고, 암모니아와 배기가스의 혼합 비율을 확인하기 위해 요소수 분사 노즐의 위치를 변경하였다. 요소수 분사 노즐은 배기관의 입구로부터 1/3, 1/2, 2/3에 위치한다. 또한, 분사 노즐의 위치가 배기관 입구의 1/3에 위치할 때 노즐의 분사구수에 따른 효율을 확인하기 위하여 분사구수를 4Hole, 6Hole, 8Hole일 경우를 확인하여 비교하였다. 시뮬레이션의 결과로는 배기관 입구에 가까울수록, 분사구수가 많을수록 효율이 좋아짐을 확인하였다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.34 no.6
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• pp.904-909
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• 2005

To produce functional food ingredient from the soybean curd residue (SCR), alkaline fermentation was performed with SCR from cold processed (D-SCR) or hot processed (P-SCR) tofu. The solid- state fermentation was performed by Bacillus firmus NA-1 at $42^{\circ}C$. The fermentation of heat-treated D- SCR resulted in higher production of peptides and fibrinolytic enzyme compared with D-SCR without heating. The P-SCR showed higher production of peptides, fibrinolytic enzyme, indicating alkaline pH after fermentation for 18 hr. When the moisture content of P-SCR was reduced to $60\%$, the production of peptides and fibrinolytic enzyme were enhanced. The P-SCR fortified with $10\%$ MFS (micronized full-fat soy flour) showed higher fibrinolytic enzyme activity and consistency index by fermentation of Bacillus firmus NA-1 Furthermore, the P- SCR fortified with $20\%$ MFS indicated relatively higher peptide content, fibrinolytic enzyme activity and enhanced flavor. By increasing the addition of MFS, the peptide content of fermented P-SCR was increased significantly, but fibrinolytic enzyme was slightly decreased.

• Korean Journal of Clinical Laboratory Science
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• v.36 no.2
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• pp.222-232
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• 2004

The sample collection room(SCR) will have much more influence than all the other departments for the improvement of hospital image, if anyone coming to the SCR in the hospital goes back with the perfect complacency and because most clients who have much stresses and fatigues pay a final visit to the SCR via receipt-diagnosis- acceptance process. SCR has improved its image for the purpose of gratifying clients, in order for clients to visit the hospital again, the quality improvement(QI) team in the Diagnosis Inspection Medical Department has come to a conclusion as follows. The degree of client gratification before improvement marks 65.9 point, but the degree after improvement was 74.2 point. Therefore, satisfaction has increased by 8.3 points. The degree of client gratification in groups before improvement marks (1) service parts-89.2 points (2) facilities and environments-49.1 point (3) toilet facilities-46.3 point. But its gratification after improvement marks (1) 92.5 point (2) 60.1 point (3) 61.0 point. Therefore the degree of satisfaction has increased by (1) 3.3 point, (2) 11.0 point, (3) 14.7 point. The progress of facility improvement plans and the exclusion of improvement on the facility contents in the hospital have made facilities and environments of SCR and toilet facilities to be poorly improved. Although service parts have a good mark, and the facilities and environments are not scoring well, the whole degree clients' gratification of SCR couldn't be helped by the low grade. Therefore the bottom line for the clients' gratification of SCR in the future is to ameliorate the facilities and environments. SCR will take the clients' gratification survey every year and if any items get low marks, that is, below 90 point throughout the survey, SCR will immediately starts the improvement work for the clients' gratification with operating the programs of controlling quality continually, and SCR should induce the operation of services, participating in the kind campaign drive for clients. So SCR will adopt the incentive system for the best staff members who perform these kinds of services.

• ETRI Journal
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• v.37 no.1
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• pp.97-106
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• 2015

In this paper, MOS-triggered silicon-controlled rectifier (SCR)-based electrostatic discharge (ESD) protection circuits for mobile application in 3.3 V I/O and SCR-based ESD protection circuits with floating N+/P+ diffusion regions for inverter and light-emitting diode driver applications in 20 V power clamps were designed. The breakdown voltage is induced by a grounded-gate NMOS (ggNMOS) in the MOS-triggered SCR-based ESD protection circuit for 3.3 V I/O. This lowers the breakdown voltage of the SCR by providing a trigger current to the P-well of the SCR. However, the operation resistance is increased compared to SCR, because additional diffusion regions increase the overall resistance of the protection circuit. To overcome this problem, the number of ggNMOS fingers was increased. The ESD protection circuit for the power clamp application at 20 V had a breakdown voltage of 23 V; the product of a high holding voltage by the N+/P+ floating diffusion region. The trigger voltage was improved by the partial insertion of a P-body to narrow the gap between the trigger and holding voltages. The ESD protection circuits for low- and high-voltage applications were designed using $0.18{\mu}m$ Bipolar-CMOS-DMOS technology, with $100{\mu}m$ width. Electrical characteristics and robustness are analyzed by a transmission line pulse measurement and an ESD pulse generator (ESS-6008).

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.1
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• pp.95-105
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• 2012

The selective catalytic reduction (SCR) system is a highly-effective aftertreatment device for NOx reduction of diesel engines. Generally, the ammonia ($NH_3$) was generated from reaction mechanism of SCR in the SCR system using the liquid urea as the reluctant. Therefore, the precise urea dosing control is a very important key for NOx and $NH_3$ slip reduction in the SCR system. This paper investigated NOx and $NH_3$ emission characteristics of urea-SCR dosing system based on model-based control algorithm in order to reduce NOx. In the map-based control algorithm, target amount of urea solution was determined by mass flow rate of exhaust gas obtained from engine rpm, torque and $O_2$ for feed-back control NOx concentration should be measured by NOx sensor. Moreover, this algorithm can not estimate $NH_3$ absorbed on the catalyst. Hence, the urea injection can be too rich or too lean. In this study, the model-based control algorithm was developed and evaluated on the numerical model describing physical and chemical phenomena in SCR system. One channel thermo-fluid model coupled with finely tuned chemical reaction model was applied to this control algorithm. The vehicle test was carried out by using map-based and model-based control algorithms in the NEDC mode in order to evaluate the performance of the model based control algorithm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.12
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• pp.6575-6580
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• 2013

Various modified SCR catalysts were prepared and tested to improve the strength of catalysts for use under severe conditions. The SCR catalysts were modified with a binder and dispersion agent, and tested at the fixed bed reactor. FT-IR and $H_2$-TPR were used to analyze the degree of hydrogen use and ammonia adsorption by the modified catalysts. In the case of the SCR catalysts coated with 2.3g of the binder, 4.7g of ethanol, and 0.1g of dispersion agent, the strength of catalyst was increased by approximately 12%. On the other hand, despite the enhancement of strength, the activities of the SCR catalysts were decreased by 2-10%. When the mixed solution composed of binder, dispersion agent and $SiO_2$ solution was precipitated on the catalyst, the $NO_x$ conversion of the catalyst was decreased slightly. The Bronsted acid site and Lewis acid site worked as the activators for the SCR reaction, and were decreased by $SiO_2$.

• Journal of IKEEE
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• v.18 no.1
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• pp.25-30
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• 2014

In this paper, SCR(Silicon Controlled Rectifier)-based ESD(Electrostatic Discharge) protection circuit for power clamp is proposed. In order to improve latch-up immunity caused by low holding voltage of the conventional SCR, it is modified by inserting n+ floating region and n-well, and extending p+ cathode region in the p-well. The resulting ESD capability of our proposed ESD protection circuit reveals a high latch-up immunity due to the high holding voltage. It is verified that electrical characteristics of proposed ESD protection circuit by Synopsys TCAD simulation tool. According to the simulation results, the holding voltage is increased from 4.61 V to 8.75 V while trigger voltage is increased form 27.3 V to 32.71 V, respectively. Compared with the conventional SCR, the proposed ESD protection circuit has the high holding voltage with the same triggering voltage characteristic.