• Journal of Mechanical Science and Technology
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• v.16 no.6
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• pp.839-850
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• 2002

A performance simulation program for the turboprop engine (PT6A-62), which is the power plant of the first Korean indigenous basic trainer KT-1, was developed for performance prediction, development of an EHMS (Engine Health Monitoring System) and the flight simulator. Characteristics of components including compressors, turbines, power turbines and the constant speed propeller were required for the steady state and transient performance analysis with on and off design point analysis. In most cases, these were substituted for what scaled from similar engine components'characteristics with the scaling law. The developed program was evaluated with the performance data provided by the engine manufacturer and with analysis results of GASTURB program, which is well known for the performance simulation of gas turbines. Performance parameters such as mass flow rate, compressor pressure ratio, fuel flow rate, specific fuel consumption and turbine inlet temperature were discussed to evaluate validity of the developed program at various cases. The first case was the sea level static standard condition and other cases were considered with various altitudes, flight velocities and part loads with the range between idle and 105% rotational speed of the gas generator. In the transient analysis, the Continuity of Mass Flow Method was utilized under the condition that mass stored between components is ignored and the flow compatibility is satisfied, and the Modified Euler Method was used for integration of the surplus torque. The transient performance analysis for various fuel schedules was performed. When the fuel step increase was considered, the overshoot of the turbine inlet temperature occurred. However, in case of ramp increase of the fuel longer than step increase of the fuel, the overshoot of the turbine inlet temperature was effectively reduced.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.298-307
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• 1997

TDS(Thermal Desorption Spectroscopy)system, for diagnosis of CRT manufacturing process, was designed and constructed. Outgassings and thermal desorptions from the part or materials of CRT can be measured and analysed with this system at various temperatures. The system is consisted of 3 parts, vacuum chamber and pumping system with variable conductance, sample heating stages & their controller, and outgassing measurement devices, like as ion gauge or quadrupole mass spectrometer. The ultimate pressure of the system was under $1{\times}10^{-7}$ Pa. With the variable conductance system, the effective pumping speed of the chamber could be controlled from sub l/s to 100 l/s. The effective pumping speed values were determined by dynamic flow measurement principle. The temperatures and ramp rate of sample were controlled by tungsten heater and PID controller up to 600℃ within ±1℃ difference to setting value. Ion gauge & QMS were calibrated for quantitative measurements. Some examples of TDS measurement data and application on the CRT process analysis were shown.

• Journal of the Korean Vacuum Society
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• v.6 no.4
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• pp.308-313
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• 1997

TDS (Thermal Lkso~ption Spectroscopy)system, for diagnosis of CRT manufacturing process, was designed and constructed. Outgassings and themla1 desorptions from the part or materials of CRT can be measured and analysed with this system at various temperatures. The system is consisted of 3 pirrts. vacuum chamher and pumping system with variable conductance, sample heating stages & their controller, and outgassing measurement devices, like as ion gauge or quadrupole mass spectrometer. The ultimate pressure of the system was under $1\times10^{-7}$ Pa. With the variable conductance system, the effective pumping speed of the chamber could he controlled from sub 11s to 100 11s. The effective pumping speed values were determined by dynamic flow measurement principle. The temperatures and ramp rate of sample were controlled by tungsten heater and PID controller up to $600^{\circ}C$ within t $\pm 1^{\circ}C$$difference to setting value. Ion gauge & QMS were calibrated for quantitative measurements. Some examples of TDS measurement data ;ind application on the CRT process analysis were shown.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.397-419
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• 2012

The pressurizing support tunneling method has been developed that overcomes shortcomings of conventional trenchless methods and applied to the field. The main concept of the new method is the pressurization system which, by means of pressurization bag between outer flange of steel ribs and excavated perimeter, applies higher pressure than the pressure relaxed by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through 3D numerical analyses. The new method was applied to the construction of a 10.7 m wide, 7.9 m high and 85 m long ramp tunnel that passes under ${\bigcirc}{\bigcirc}$ Expressway. By applying the new method, the tunnel construction was successfully completed in 13.5 months which decreases construction time to 35% compared to conventional methods, and ground displacement was almost negligible.

• The Korean Journal of Physiology and Pharmacology
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• v.9 no.2
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• pp.95-101
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• 2005

In the heart, $Na^{+}-Ca^{2+}$ exchange (NCX) is the major $Ca^{2+}$ extrusion mechanism. NCX has been considered as a relaxation mechanism, as it reduces global $[Ca^{2+}]_i$ raised during activation. However, if NCX locates in the close proximity to the ryanodine receptor, then NCX would curtail $Ca^{2+}$ before its diffusion to global $Ca^{2+}_i$ This will result in a global $[Ca^{2+}]_i$ decrease especially during its ascending phase rather than descending phase. Therefore, NCX would decrease the myocardial contractility rather than inducing relaxation in the heart. This possibility was examined in this study by comparing NCX-induced extrusion of $Ca^{2+}$ after its release from SR in the presence and absence of global $Ca^{2+}_i$ transient in the isolated single rat ventricular myocytes by using patch-clamp technique in a whole-cell configuration. Global $Ca^{2+}_i$ transient was controlled by an internal dialysis with different concentrations of BAPTA added in the pipette. During stimulation with a ramp pulse from +100 mV to -100 mV for 200 ms, global $Ca^{2+}_i$ transient was suppressed only mildly, and completely at 1 mmol/L, and 10 mmol/L BAPTA, respectively. In these situations, ryanodine-sensitive inward NCX current was compared using $100{\mu}mol/L$ ryanodine, $Na^+$ depletion, 5 mmol/L $NaCl_2$ and $1{\mu}mol/L$ nifedipine. Surprisingly, the result showed that the ryanodine-sensitive inward NCX current was well preserved after 10 mmol/L BAPTA to 91 % of that obtained after 1 mmol/L BAPTA. From this result, it is concluded that most of the NCX-induced $Ca^{2+}$ extrusion occurs before the $Ca^{2+}$ diffuses to global $Ca^{2+})i$ in the rat ventricular myocyte.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.98-107
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• 2000

This paper compares the performance of feedback consolidation algorithms with or without a fast overload indication function which has been recently proposed in the ATM Forum for multicast ABR (Available Bit Rate) services in ATM networks. We use the performance criteria such as the ACR (Allowed Cell Rate) of a source, queue length at a switch, link utilization, fairness, and BRM (Backward Resource Management) cell overhead. Simulation results show that performance of the feedback consolidation algorithms with a fast overload indication function can be improved sign.ificantly than that of algorithms without this function in terms of ramp-down delay, particularly in initial start-up period or under a severe overload situation. The fast overload indication function can be combined with any feedback consolidation algorithm, whereas its performance is highly dependent on an underlying basic feedback consolidation algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.832-835
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• 2001

We report the structural and electrical properties of hafnium oxide (HfO$_2$) films with tungsten silicide (WSi$_2$) metal gate. In this study, HfO$_2$thin films were fabricated by oxidation of sputtered Hf metal films on Si, and WSi$_2$was deposited directly on HfO$_2$by LPCVD. The hysteresis windows in C-V curves of the WSi$_2$HfO$_2$/Si MOS capacitors were negligible (<20 mV), and had no dependence on frequency from 10 kHz to 1 MHz and bias ramp rate from 10 mV to 1 V. In addition, leakage current was very low in the range of 10$^{-9}$ ~10$^{-10}$ A to ~ 1 V, which was due to the formation of interfacial hafnium silicate layer between HfO$_2$and Si. After PMA (post metallization annealing) of the WSi$_2$/HfO$_2$/Si MOS capacitors at 500 $^{\circ}C$ EOT (equivalent oxide thickness) was reduced from 26 to 22 $\AA$ and the leakage current was reduced by approximately one order as compared to that measured before annealing. These results indicate that the effect of fluorine diffusion is negligible and annealing minimizes the etching damage.

• Nuclear Engineering and Technology
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• v.19 no.4
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• pp.233-241
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• 1987

Difficulties are encountered when the behavior of complex systems (i.e., fuel failure probability) that have unreliable deterministic models is predicted. For more realistic prediction of the behavior of complex systems with limited observational data, the present study was undertaken to devise an approach of combining predictions from the deterministic model and actual observational data. Predictions by this method of combining are inferred to be of higher reliability than separate predictions made by either model taken independently. A systematic method of hierarchical pattern discovery based on the method developed in the SPEAR was used for systematic search of weighting factors and pattern boundaries for the present method. A sample calculation was performed for prediction of CANDU fuel failures that had occurred due to power ramp during refuelling process. It was demonstrated by this sample calculation that there exists a region of feature space in which fuel failure probability from the PROFIT model nearly agree with that from observational data.

• Food Industry
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• s.180
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• pp.10-26
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• 2004

제과$\cdot$제빵분야는 대표적인 내수업종이고 보수적 업종성격이 강하다고 볼 수 있다. 연간 성장률이 $30\~40\%$대의 고성장을 구가하던 과거의 좋은 시기도 있었다. 현재 우리가 처한 $\$1$만 소득에서 $\$2$만 소득으로 가는 길목에서 이 분야는 기호식품으로 완전히 변해 있다고 볼 수 있다. 저성장 내지 마이너스 성장도 올 수 있는 시대에 이미 진입했다고 볼 수 있다. 소비자의 기호를 적극적으로 반영치 못한 제품은 시장에서 생존이 어려운 시대를 이미 맞고 있고, 이러한 현상은 차후 더 심하고 세차게 진행되어 질 것이다. 엄밀히 말해 기존의 제품운영계획 그대로 진행하면 그런 기업은 퇴보하게 되어있다고 생각된다. 또 다른 말로 표현하면 이제는 제과$\cdot$제빵 산업은 과감한 변신이 없다면 이미 사양산업화 되어지고 있다고도 볼 수 있다. 과감한 변신은 무엇일까? 소비자 욕구를 정확히 파악하고 이에 부응한 제품운영계획을 충실하게 세워 시행하는 것이다. 세부적으로는, (1) 제품내용물에 좋은 기능성을 도입시키는 것이다. 소위 건강에 좋다는 각종 원료성분들을 사용한 제품을 개발하여서 생산, 판매하는 전략이다. (2) 제품의 포장의 질을 좋게 하고 고급화 시킬 필요가 있다고 본다. BT를 응용한 첨단 포장기술 도입실행이 필요하다. 소비자에게 좋은 이미지를 줄 수 있고, 포장본래의 기능 제품보호가 완벽해야 하고 사용하기에 편리하여야 한다는 것이다. (3) 외국 제품들과의 경쟁은 필수적이다. 가공식품 분야는 이제 거의 $100\%$ 시장이 개방된 상태를 맞고 있다. 외국의 고기능성 내지 고급화제품들과의 경쟁은 피할수 없는 현실을 맞고 있다. 외국시장의 정보를 면밀히 분석하고 이에 대한 대응전략은 물론 더 나아가서 외국제품을 능가 할 경쟁력있는 제품개발이 필요하다고 판단된다. R&D 분야에 투자를 필연적으로 늘여야만 한다. 국내 식품사들의 Ramp;D 투자금액이 구미선진국이 1/10이하 수준에 머물고 있는 것이 오늘날 우리들의 실정이기 때문이다. 일본 등과 FTA 협정쳬결 논의가 국가적과제로 추진되고 있는 현재의 상황에서 이에 대한 우리업계의 대응전략을 지금부터 착수하여야 할 때라고 판단된다. 기본부터 철저히 우리의 장점을 살린 실질적 대응책 마련에 많은 지혜를 발휘할 때 우리 식품산업이 대내외적으로 경쟁력을 가질수 있다고 예상된다. 이러한 상황을 미루어 볼때에 고부가가치 제품을 창출 할 수 있는 여러가지 방안을 기업과 학계 그리고 정부가 종합적으로 강구하여야 할 때인 것이다. 필자는 이에 관한 몇 가지 방안들을 제안하였다.

• Journal of the Korean Society of Propulsion Engineers
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• v.12 no.2
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• pp.24-32
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• 2008

A non-reacting experimental study on a normal injection into a Mach 1.92 crossflow which flows over various geometries(flat plate, small cavity, large cavity) was carried out to investigate the effect of the momentum flux ratio(J). The aft ramp of the cavity advances the increase of the penetration height and the strong two-dimensional shock from recompression region mainly affects the shock structure and mixing layer at the downstream flow. As flow runs downward, the transverse penetration height increases with increasing J(J = 0.9, 1.7, 3.4). However, above some critical ratio, jet penetration height growth with increasing J is not appeared in flow-field. Large scale cavity has a good mixing efficiency but it increases the drag loss in the combustor.