• BMB Reports
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• 제56권11호
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• pp.575-583
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• 2023

Mitochondria, fundamental cellular organelles that govern energy metabolism, hold a pivotal role in cellular vitality. While consuming dioxygen to produce adenosine triphosphate (ATP), the electron transfer process within mitochondria can engender the formation of reactive oxygen species that exert dual roles in endothelial homeostatic signaling and oxidative stress. In the context of the intricate electron transfer process, several metal ions that include copper, iron, zinc, and manganese serve as crucial cofactors in mitochondrial metalloenzymes to mediate the synthesis of ATP and antioxidant defense. In this mini review, we provide a comprehensive understanding of the coordination chemistry of mitochondrial cuproenzymes. In detail, cytochrome c oxidase (CcO) reduces dioxygen to water coupled with proton pumping to generate an electrochemical gradient, while superoxide dismutase 1 (SOD1) functions in detoxifying superoxide into hydrogen peroxide. With an emphasis on the catalytic reactions of the copper metalloenzymes and insights into their ligand environment, we also outline the metalation process of these enzymes throughout the copper trafficking system. The impairment of copper homeostasis can trigger mitochondrial dysfunction, and potentially lead to the development of copper-related disorders. We describe the current knowledge regarding copper-mediated toxicity mechanisms, thereby shedding light on prospective therapeutic strategies for pathologies intertwined with copper dyshomeostasis.

• 동력기계공학회지
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• 제19권2호
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• pp.49-56
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• 2015

As an alternative fuel that can be used in SI engine, LPG is one of clean fuels with larger H/C ratio compared to gasoline, low $CO_2$ emission, and small amount of pollutants such as sulfur compounds. When LPG is used in spark ignition engine, volumetric efficiency of the engine can be improved and pumping loss can be reduced by performing direct injection into the combustion chamber instead of port fuel injection. LPG-DI engine allows for lean combustion and stratified combustion under low load. In case of stratified combustion, air fuel ratio can be greatly increased compared to theoretic mixture ratio combustion. Improved thermal efficiency of the engine and reduced pumping loss can be expected from stratified combustion. Accordingly in this study, an experimental apparatus for visualization was designed and manufactured to study the combustion process of LPG after injection and ignition, intended to examine ignition probability and combustion characteristics of spark ignition direct injection(SIDI) LPG fuel. Ambient pressure, ambient temperature and fuel injection pressure were found as important variables that affect ignition probability and flame propagation characteristics of LPG-air mixture. Also, it was verified that the injected LPG fuel can be directly ignited by spark plug under appropriate ambient conditions.

• 한국유체기계학회 논문집
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• 제17권6호
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• pp.29-37
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• 2014

Non-Newtonian fluid mechanics takes charge of an important role in the oil industries. Especially in the oil well drilling process, the drilling fluid such as mud keeps the drill bit cool and clean during drilling, with suspending drill cuttings and lubricating a drill bit. The purpose of this study is to examine the effect of fluid mud rheological properties to predict different characteristics of non-Newtonian fluid in the mud mixing tank on offshore drilling platforms. In this paper, ANSYS fluent package was used for the simulation to solve the hydrodynamic force and to evaluate mud mixing time. Prediction of the power consumption and the pumping effectiveness has been presented with different operating fluid models as Newtonian and non-Newtonian fluid. The comparison between Newtonain mud model and non-Newtonian mud model is confirmed by the CFD simulation method of drilling mud mixing tank. The results present useful information for the design of the drilling mud mixing tanks and provide some guidance on the use of CFD tool for such non-Newtonian fluid flow.

• 대한전자공학회논문지SD
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• 제46권12호
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• pp.80-86
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• 2009

전하펌프의 성능은 공급전압에 의해 크게 영향을 받는다. 본 논문에서는 표준 twin-well CMOS 로직 공정으로 제작 가능하며, 낮은 공급전압에서도 높은 효율을 갖는 새로운 전하펌프 회로를 제안하고 검증하였다. 제안한 전하펌프는 이중의 전하 전달 경로와 간단한 2-phase 클락을 사용한다. 한 주기의 펌핑 사이클 동안 각 펌핑 단에서 입력전압을 2배로 승압하며, 상보적으로 연결된 PMOS 트랜지스터를 전달 스위치로 사용하여 트랜지스터의 문턱전압에 의한 전압강하 없이 승압된 전압을 다음 승압 단으로 전달한다. 시뮬레이션과 측정을 통해 제안한 전하펌프를 검증하였으며, 동일한 공정조건에서 제작 가능한 기존 전하펌프들 보다 높은 출력전압과 큰 전류 구동능력 그리고 더 높은 전력효율을 가진다는 것을 확인하였다.

• 한국세라믹학회지
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• 제37권2호
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• pp.111-116
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• 2000

700nm red emission(3F3longrightarrow3H6) in Tm3+ ion with 800 nm(3H6longrightarrow3H4) excitation via upconversion process has been reported only in host materials which have low phonon energies such as halide crystals. However, we observed 700nm and 480nm(1G4longrightarrow3H6) upconverted emission with 800nm excitation in several oxide glasses which has never reported. With spectroscopic analyses and lifetime measurements of each nergy level of Tm3+ ion doped in various oxide glasses, following mechanisms are suggested. For red upconversion, upconversion mechanism changed with Tm3+ concentration. While direct excitation up to 3F3 level via anti-Stokes excitation was dominated at low concentration, two-step excitation via 3H6longrightarrow3H4 and 3F4longrightarrow3F3 transitions was dominated at high concentration. For blue upconversion, two step excitation mechanism up to 1G4 level was suggested as follows : electrons are exciated up to 3H5 with direct excitation with pumping light up to 3H4 followed by multiphonon relaxation, and then additional reabsorption of pumping light excites electrons up to 1G4.

• 대한전자공학회논문지SD
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• 제45권5호
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• pp.50-57
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• 2008

본 논문에서는 CMOS image sensor(CIS)에서 사용될 수 있는 고 효율 charge pump를 제안하였다. 제안된 charge pump는 CIS의 동작 특성을 활용하여 switching loss 및 reversion loss를 최소화하여 고 효율 동작을 실현하였다. 즉, CIS 픽셀 동작 구간에 따라 local clock driver, 펌핑 커패시터, 그리고 charge 전달 switch의 크기를 역동적으로 조절함으로써 switching loss 를 최소화하였다. 또한, schmitt trigger를 채용한 tri-state local clock driver를 이용하여 non-overlapping 구간이 충분히 확보된 local clock을 공급할 수 있게 함으로써 reversion loss를 최소화하였다. 0.13-um CMOS 공정을 이용한 시뮬레이션 비교 결과, 제안된 charge pump는 구동 전류가 없는 조건에서 기존 구조에 비해 최대 49.1% 전력 소모를 개선하였으며, 구동 전류가 최대인 조건에서는 19.0% 전력 소모를 개선할 수 있었음을 확인하였다.

• 한국자동차공학회논문집
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• 제22권2호
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• pp.166-174
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• 2014

Fuel injection pressure has steadily increased in diesel engines for the purpose of improving fuel efficiency and cleaning exhaust gas, but it has now reached a point, where the cost for higher pressure does not warrant additional gains. Common rail systems on modern diesel engines have fuel pumps that are mechanically driven by crankshaft. The pumps actually house two pumping module inside: a low pressure pump component and a high pressure pump component. Part of the fuel compressed by the low pressure component returns to the tank in the process of maintaining the pressure in the common rail. Since the returning fuel represents pumping loss, fuel economy improves if the returned fuel can be eliminated by using a properly controled electrical fuel pump. As the first step in developing an electrical fuel pump the fuel supply system on a 6 liter diesel engine was modeled with AMESim to analyze the workload and the fuel feed rate of the injection pump, and the results served as basis for selecting a suitable servo motor and a reducer to drive the pump. A motor controller was built using a DSP and a program which controls the common rail pressure using a proportional control method based on the target fuel pressure information from the engine ECU. A test rig to evaluate performance of the fuel pump is implemented and used to show that the newly developed electrically driven fuel pump can satisfy the fuel flow demand of the engine under various operating conditions when the rotational speed of the pump is adequately controlled.

• Journal of the Optical Society of Korea
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• 제1권1호
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• pp.5-9
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• 1997

Energy transfer direction in $Er^{3+}-Tm^{3+}$-codoped fluorozirconate glasses has been studied. For $Er^{3+}-Tm^{3+}$-codoped glasses, the dependence of the green emission intensity on the pump power (Pex) of 800 nm has ranged from (Pex)$^2$ to (Pex)$^3$. From this multistep absorption, a 1.48 $\mu m$ emission from the $^3F_4{\rightarrow}^3H_4$ transition on Tm$^{3+}$ ion has been found to transfer into $^4I_{13/2}$, $^4I_{9/2}$ and $^4S_{3/2}$ on $Er^{3+}$ ion. In case of the 1.06 $\mu m$ pumping, the emissin ratio of $^3H_4$ level in $Tm^{3+}$ to $^4I_{13/2}$ in $Er^{3+}$ showed that the amount of the energy transfer from $Tm^{3+}$ into $Er^{3+}$ increased with the increasing concentration of $Tm^{3+}$ ion. Our two kinds of pumping scheme suggest that the direction of dominant energy transfer between $Er^{3+}$ and $Tm^{3+}$ should be dependent on whether the $^3F_4$ level resonates in $Tm^{3+}$ the level or not.

• 정보보호학회논문지
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• 제24권3호
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• pp.453-460
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• 2014

오류주입공격(Fault Injection Attack)은 하드웨어적 또는 소프트웨어적으로 구현된 암호칩에 인위적으로 오류를 주입 또는 발생시켜 암호 알고리즘 동작/수행을 방해함으로써 칩에 내장된 정보를 찾아내는 공격으로, 이 중 레이저를 이용한 오류주입공격은 특히 성공적인 것으로 입증된 바 있다. 본 논문에서는 기존의 플래쉬 펌프 방식의 레이저와 광섬유 레이저 모델을 병렬 결합한 이중모드 레이저 방식으로 개선된 레이저 프루빙 시스템을 제안하였다. 제안된 방법은 에너지 출력은 높으나 주파수 반복률이 낮아 오류주입공격 실험에 적합하지 않은 기존의 플래쉬 펌프 방식 레이저를 레이저 절단용으로 활용하고, 추가로 별도의 오류주입을 위한 고주파 반복률을 갖는 레이저를 단순 병렬 결합시키는 방법이다. 오류주입을 위해 결합된 제 2의 신규 레이저는 반도체 레이저와 광섬유 레이저를 선택하여 두 가지 시스템을 설계하였으며, 이에 따른 장 단점을 비교분석하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1268-1270
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• 1993

In this study, the characteristics of Si-$SiO_2$ interface and its degradation in short channel SONOSFET nonvolatile memory devices, fabricated by 1Mbit CMOS process($1.2{\mu}m$ design rule), with $65{\AA}$ blocking oxide layer, $205{\AA}$ nitride layer, and $30{\AA}$ tunneling oxide layer on the silicon wafer were investigated using the charge pumping method. For investigating the Si-$SiO_2$ interface characteristics before and after write/erase cycling, charge pumping current characteristics with frequencies, write/erase cycles, as a parameters, were measured. As a result, average Si-$SiO_2$ interface trap density and mean value of capture cross section were determined to be $1.203{\times}10^{11}cm^{-2}eV^{-1}\;and\;2.091{\times}10^{16}cm^2$ before write/erase cycling, respectively. After cycling, when the write/erase cycles are $10^4$, average $Si-SiO_2$ interface trap density was $1.901{\times}10^{11}cm^{-2}eV^{-1}$. Incresing write/erase cycles beyond about $10^4$, Si-$SiO_2$ interface characteristics with write/erase cycles was increased logarithmically.