• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.8
• /
• pp.31-37
• /
• 2016

Ranging is divided into a synchronous scheme and an asynchronous scheme according to the presence of global synchronization between nodes. In general, the asynchronous ranging is preferred over synchronous ranging because it does not require an expensive high-precision oscillator for the global synchronization. On the other hand, in a conventional asynchronous ranging scheme, the packets, which are generated by all nodes in a positioning system of a large-scale infrastructure and need to be sent for localization by reference nodes, are considerable, which cause an increase in network traffic as the number of nodes increases. The traffic congestion lowers the throughput of the network leading to a considerable loss of energy. To solve this problem, this paper proposes a ranging scheme, in which virtual transmission slots randomly and discretely selected by a plurality of nodes are used to reduce the overheads needed in synchronizing the nodes, and the ranging is performed asynchronously based on the virtual transmission slots, thereby decreasing the network traffic. In addition, a performance test proved that the proposed ranging scheme was stronger than the TWR and SDS-TWR on an error range, even though the intensity of traffic was very low.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.18 no.5
• /
• pp.477-483
• /
• 1985

This paper describes seasonal changes of total length, hepatosomatic index (HSI), fatness, egg-diameter composition, and fecundity of the longchin goby Chasmichthys dolichognathus(HILGENDORF). The specimens used were captured in the tide pool of Tongbaekseom, Pusan, Korea from February 1983 to January 1984. The age of longchin goby, tested by size frequency, was believed to be usually one year which grows to 8.0 cm in total length. The annual variations of HSI reached the maximum in the early spring when the gonad was actively growing and decreased during the spawning season from April to July. The coefficients of fatness were represented low values for the spawning periods. Frequency distribution of the egg diameter of mature ovary has three modes: one is the evident mode of the ripe eggs group, and the other two are modes of maturing and immature eggs groups. And an individual is considered as spawns one in the spawning season. Relationships between the fish size in total length (TL cm) and the number of ovarian eggs(F), the fish weight (BW g) and the number of ovarian eggs are indicated by the exponential equation respectively : F=42.585 $TL^{1.608}$, F= 524.589 $BW^{0.475}$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.126-126
• /
• 2000

다이아몬드상 카본(DLC) 필름은 경도가 높고, 마찰계수가 낮다는 장점을 가지고 있기 때문에 내마모성 코팅이나 윤활성코팅에 응용을 위한 연구가 활발히 진행중이다. 하지만 마찰계수가 주변환경에 매우 큰 영향을 받는다는 단점이 있다. 이러한 단점은 DLC필름의 응용에 대한 저해 요인이 되며, 이 점을 보완하기 위해서 DLC 필름에 Si을 첨가하는 연구들이 진행되고 있다. 본 실험에서는 r.f-PACVD 법을 이용하여 Si이 첨가된 DLC 필름의 주위 환경 변화에 따른 마찰특성의 변화를 연구하였다. 사용한 반응 가스는 벤젠(C6H)과 희석된 Silane(SiH4 : H2 = 10 : 90)이며, 희석된 Silane과 벤젠의 첨가비율을 조절하여 필름내 Si의 함량을 조절하였고, 증착시 바이아스의 전압은 -400V로 하였다. 마찰테스트는 Ball-on-Disk type의 조건에서 대기, 건조공기, 진공의 세가지 분위기에서 마찰테스트를 실행하였다. 실험결과 마찰계수는 건조공기, 대기, 진공의 순으로 증가하였고, 필름내에 포함되어 있는 Si의 양이 증가할수록 마찰계수는 낮고 안정한 값을 나타내었다. Tribochemiacal 분석과, ball과 track의 전자현미경 사진 분석 결과, 진공에 비해서 건조공기와 대기중에서 마찰계수가 낮은 것은 DLC 필름내에 마모 track 중심부에 Si-C-O 계의 화합물이 형성되어, 이 화합물이 마찰계면에 존재하여 마찰계수를 낮추었음을 확인하였다. 그리고 대기중에서 실험한 경우, 습기의 존재로 인해 마모입자가 볼의 표면에서 엉김으로써 건조공기의 상태에서 보다 높은 마찰저항을 갖게 됨으로 인하여 마찰계수가 높아짐을 알 수 있었다.a)는 as-deposit 상태이며, 그림 1(b)는 45$0^{\circ}C$, 60min 열처리한 plan-view TEM 사진이다.dical의 영향을 조사하였으며 oxygen radical의 rf power에 따른 변화는 OES(Optical emission spectroscopy)를 사용하였다. 너무 적은 oxygen ion beam flux나 oxygen radical은 film의 전도도 및 투과도를 저하시켰고 반면 너무 과도한 flux의 증가 시는 전도도는 감소하였고 투과도는 증가하는 경향을 보였다. 기판에 도달하는 oxygen ion flux는 faraday cup을 이용하여 측정하였으며 증착된 ITO film은 XPS, UV-spectrometer, 4-point probe를 이용하여 분석하였다. 때문으로 생각되어진다. 또한, 성장 온도가 낮아짐에 따라 AlGaN의 성장을 저해하기 때문으로 판단된다. 성장 온도 변화에 따라 성장된 V의 구조적 특성 및 표면 거칠기 변화를 관찰하여 AlGaN의 성장 거동을 논의하겠다.034, 0.005 정도로 다시 감소하였다. 박막의 유전율은 약 35 정도의 값을 나타내었으며 X-선 회절 data로부터 분석한 박막의 변형은 증온도에 따라 7.2%에서 0.04%로 감소하였고 이 이경향은 유전손실은 감소경향과 일치하였다.는 현저하게 향상되었다. 그 원인은 SB power의 인가에 의해 활성화된 precursor 분자들이 큰 에너지를 가지고 기판에 유입되어 치밀한 박막이 형성되었기 때문으로 사료된다.을수 있었다.보았다.다.다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품

• Proceedings of the Korean Vacuum Society Conference
• /
• 2000.02a
• /
• pp.148-148
• /
• 2000

지금까지 반도체 표면에 대한 연구는 주로 (1000, (111) 표면 등 낮은 밀러 지표를 가진 표면에 대해 이루어져 왔다. 이에 반해 밀러 지표가 높은 Si 면은 불안정하고, 가열하면 다른 표면, 즉 지표가 낮은 면으로 재배열하는 경향이 있는 것으로 알려져 있는데 아직 이들 높은 밀러 지표를 가진 표면에 대한 연구는 미미한 상태이다. 그러나, Si(113)면은 밀러 지표가 높으면서도 안정하기 때문에 Si(113)의 구조를 정확하게 알 수 있다면 밀러 지표가 낮은 Si 표면이 안정한 이유를 이해할 수 있을 것이다. 따라서 본 연구에서는 TOF-CAICISS 장치(Time of Flight - CoAxial Impact Collision Ion Scattering Spectroscopy) 장비와 RHEED(Reflection High Energy Electron Diffrction)를 이용하여 Si(113) 표면의 구조와 Si(113) 표면의 온도에 따른 구조 변화를 관찰하였다. TOF-CAICISS 실험결과를 보면 (3$\times$2)에서 (3$\times$1)으로 상변환하면서 Si(113) 표면에 오각형을 이루는 dimer 원자들과 adatom 원자들간의 높이차가 작아짐을 알 수 있다. RHEED 실험결과와 전산 모사 결과로부터 상온에서 Si(113)(3$\times$2) 구조를 가지다가 45$0^{\circ}C$~50$0^{\circ}C$에서 Si(113) (3$\times$1) 구조로 상변환한다는 것을 알 수 있다. 그러나, 아직 상전이 메카니즘은 명확하게 밝혀지지 않았다. 실험결과를 전산 모사와 비교함으로써 Si(113) 표면에 [33]방향으로 이온빔을 입사시켰을 경우 dabrowski 모델과 Ranke AI 모델이 적합하지 않다는 것을 알 수 있다./TEX>, shower head의 온도는 $65^{\circ}C$로 설정하였다. 증착된 Cu 박막은 SEM, XRD, AFM를 통해 제작된 박막의 특성을 비교.분석하였다. 초기 plasma 처리를 한 경우에는 그림 1에서와 같이 현저히 증가한 초기 구리 입자들이 관측되었으며, 이는 도상 표면에 활성화된 catalytic site의 증가에 기인한다고 보여진다. 이러한 특성은 Cu films의 성장률을 향상시키고, 또한 voids를 줄여 전기적 성질 및 surface morphology를 향상시키는 것으로 나타났다. 결과 필름의 잔류 응력과 biaxial elastic modulus는 필름의 두께가 감소함에 따라 감소하는 경향을 나타냈으며, 같은 두께의 필름인 경우, 식각 깊이에 따른 biaxial elastic modulus 의 변화를 통해 최적의 식각 깊이를 알 수 있었다.도의 값을 나타내었으며 X-선 회절 data로부터 분석한 박막의 변형은 증온도에 따라 7.2%에서 0.04%로 감소하였고 이 이경향은 유전손실은 감소경향과 일치하였다.는 현저하게 향상되었다. 그 원인은 SB power의 인가에 의해 활성화된 precursor 분자들이 큰 에너지를 가지고 기판에 유입되어 치밀한 박막이 형성되었기 때문으로 사료된다.을수 있었다.보았다.다.다양한 기능을 가진 신소재 제조에 있다. 또한 경제적인 측면에서도 고부가 가치의 제품 개발에 따른 새로운 수요 창출과 수익률 향상, 기존의 기능성 안료를 나노(nano)화하여 나노 입자를 제조, 기존의 기능성 안료에 대한 비용 절감 효과등을 유도 할 수 있다. 역시 기술적인 측면에서도 특수소재 개발에 있어 최적의 나노 입자 제어기술 개발 및 나노입자를 기능성 소재로 사용하여 새로운 제품의 제조와 고압 기상 분사기술의 최적화에 의한 기능성 나노 입자 제조 기술을 확립하고 2차 오염 발생원인 유기계 항균제를 무기계 항균제로 대체할 수 있다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.12
• /
• pp.1537-1542
• /
• 2011

This paper presents the power management strategies for a compound hybrid excavator. The compound hybrid excavator has been replaced the hydraulic swing motor to the electric swing motor. This excavator requires a proper control algorithm to regulate the energy flow between the mechanical coupling and the electric devices. The controller should improve fuel economy and maintain the super capacitor voltage within a proper range. A thermostat controller and ECMS controller are designed such that these objectives can be achieved. The thermostat controller regulates the power of the engine-assist motor on the basis of the super capacitor voltage, and the ECMS controller determines it using the real-time fuel minimization strategy based on the concept of equivalent fuel. Simulation results showed that by using the hybrid excavator, the fuel economy becomes about 20% higher than that obtained using the conventional excavator and that the ECMS controller outperforms the thermostat controller.

• Applied Chemistry for Engineering
• /
• v.8 no.6
• /
• pp.960-966
• /
• 1997

The effects of epoxy resins and content of catalyst on the cure characteristics were studied by FT-IR, DSC and dynamic viscometer for the thermal properties and rheological properties of the catalytic (N-Benzylpyrazinium hexafluoroantimonate, BPH) epoxy thermosetting system. Compared with DSC results of DEGBF containing 0.5wt% BPH, the DSC thermograms of DGEBA containing 0.5wt% BPH indicated that the reaction was faster than that of DGEBF/BPH and the conversion rate of DGEBA/BPH was high in the initial stage of the reaction. As the concentration of BPH increases, the reaction and conversion rates show similar value in both the cases. The influence of hydroxyl group of epoxy resin on gel point defined from the crossover point of storage modulus (G') and loss modulus (G") could be explained by the formation of 3-dimensional network in the initial stage owing to the curing reaction between epoxides and hydroxyl groups of epoxy resin. This was consistent with the gel point obtained from DSC, FT-IR and moduli crossover. The activation energy (Et) obtained from the crossover point (G'/G"=1) are $31-39kJ.mol^{-1}$ for various BPH compositions in case of two epoxy systems.

• Journal of KIISE:Software and Applications
• /
• v.34 no.3
• /
• pp.226-234
• /
• 2007

In this paper, we develop a speech recognition system using a throat microphone. The use of this kind of microphone minimizes the impact of environmental noise. However, because of the absence of high frequencies and the partially loss of formant frequencies, previous systems developed with those devices have shown a lower recognition rate than systems which use standard microphone signals. This problem has led to researchers using throat microphone signals as supplementary data sources supporting standard microphone signals. In this paper, we present a high performance ASR system which we developed using only a throat microphone by taking advantage of Korean Phonological Feature Theory and a detailed throat signal analysis. Analyzing the spectrum and the result of FFT of the throat microphone signal, we find that the conventional MFCC feature vector that uses a critical pass filter does not characterize the throat microphone signals well. We also describe the conditions of the feature extraction algorithm which make it best suited for throat microphone signal analysis. The conditions involve (1) a sensitive band-pass filter and (2) use of feature vector which is suitable for voice/non-voice classification. We experimentally show that the ZCPA algorithm designed to meet these conditions improves the recognizer's performance by approximately 16%. And we find that an additional noise-canceling algorithm such as RAST A results in 2% more performance improvement.

• Applied Chemistry for Engineering
• /
• v.31 no.5
• /
• pp.575-580
• /
• 2020

In this study, we simulated an amine regeneration process with heat-stable salts removal unit. We derived the optimal operating conditions considering the flow rate of waste, the removal rate of heat-stable salts, and the loss rate of MDEA (methyl diethanolamine). In the amine regeneration process that absorbs and removes acid gas, heat-stable salt impairs the absorption efficiency of process equipment and amine solution. An ion exchange resin method is to remove heat-stable salts through neutralization by using a strong base solution such as NaOH. The acid gas removal process was established using the Radfrac model, and the equilibrium constant of the reaction was calculated using Gibbs free energy. The removed amine solution is separated and flows to the heat-stable salts remover which is modeled by using the Rstoic model with neutralization reaction. Actual operation data and simulation results were compared and verified, and also a case study was conducted by adjusting the inflow mass of removal unit followed by suggesting optimal conditions.

• KSBB Journal
• /
• v.24 no.3
• /
• pp.246-252
• /
• 2009

Rice cells were transformed to express human cytotoxic T-lymphocyte antigen 4-immunoglobulin (hCTLA4Ig) using RAmy3D promoter. hCTLA4Ig was produced and secreted into culture media inducibly when sugar was depleted. The obstacles of this system are the cell death and release of proteases by sugar starvation. These problems resulted in the losses of stability and productivity of hCTLA4Ig. Therefore, the effects of proline as an inhibitor of cell death were investigated. When 4 mM proline was added in sugar-free media, the cell death and release of proteases were reduced. As a consequence, the production of hCTLA4Ig was enhanced. In addition, the effects of protein stabilizers such as gelling agents were studied. It was found that the application of 0.01 g/L gelatin led to an increase in hCTLA4Ig production. This increase might be originated from the stabilization of hCTLA4Ig. In conclusion, the production of hCTLA4Ig could be enhanced by the additions of proline and gelatin in transgenic rice cell cultures.

• Journal of Radiation Protection and Research
• /
• v.30 no.2
• /
• pp.69-75
• /
• 2005

Gas avalanche microdetectors, such as micro-strip gas chamber (MSGC), micro-gap chamber (MGC), micro-dot chamber (MDOT), etc., are operated under high voltage to induce large electron avalanche signal around micro-size anodes. Therefore, the anodes are highly exposed to electrical damage, for example, sparking because of the interaction between high electric field strength and charge multiplication around the anodes. Gas electron multiplier (GEM) is a charge preamplifying device in which charge multiplication can be confined, so that it makes that the charge multiplication region can be separate from the readout micro-anodes in 9as avalanche microdetectors possible. Primary electron collection efficiency is an important measure for the GEM performance. We have defined that the primary electron collection efficiency is the fractional number of electron trajectories reaching to the collection plane from the drift plane through the GEM holes. The electron trajectories were estimated based on 3-dimensional (3D) finite element method (FEM). In this paper, we present the primary electron collection efficiency with respect to various GEM operation parameters. This simulation work will be very useful for the better design of the GEM.