• 대한화학회지
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• 제14권4호
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• pp.327-332
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• 1970

A simple and convenient device for deflection-type direct reading the variations in electrolytic conductance is described and applied to the analysis of sulfur by combustion-$H_2O_2$ oxidation method. The apparatus consisted of a high resistance-ratio bridge in which the other adjacent arms are the differential cells. By adopting unusually high a-c voltage source for the bridge excitation, the a-c method for unbalanced bridge is established, decreased sensitivity owing to reduced bridge factor, 0.01, is overcome and also the absolute sensitivity and linearity are greatly improved. Over 50% variations in impedance of the balanced cell, within 1% deviation from the linearity can be attained with a volt (rms)order of output which was detected directly with VTVM without further amplification. Analysis of the bridge shows that these useful features are natural result of the constant current character of the high source impedance generator and the performance of the device agreed with the theoretical predictions. A standard procedure for the rapid analysis of sulfur using the bridge is also given, the analytical accuracy was approximately 1%. A determination takes not more than 5 minutes.

• 한국태양에너지학회 논문집
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• 제35권2호
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• pp.43-52
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• 2015

The performance of a photovoltaic array is affected by temperature, solar insolation, partial shading effect, and array configuration. Maximum power point tracking(MPPT) techniques are employed in photovoltaic systems to make full utilization of the PV array output power which depends on solar irradiation and ambient temperature. As much as MPPT is important in photovoltaic systems, many MPPT techniques have been developed. In this paper, several major existing MPPT methods are comparatively analyzed and novel hybrid MPPT algorithm is proposed. The proposed hybrid MPPT algorithm is developed in combination with traditional MPPT methods to complement each other for improving performance and mitigating partial shading effects. The proposed algorithm is implemented and validated using MATLAB/Simulink simulation tool.

• 신재생에너지
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• 제8권3호
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• pp.14-22
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• 2012

Performance of photovoltaic (PV) generator systems relies on its operating conditions. Maximum power extracted from PV generators depends strongly on solar irradiation, load impedance, and ambient temperature. A most maximum power point tracking (MPPT) algorithm is based on a perturb and observe method and an incremental conductance method. It is well known the latter is better in terms of dynamics and tracking characteristics under condition of rapidly changing solar irradiation. However, in case of digital implementation, the latter has some error for determining a maximum power point. This paper presents a PID based MPPT algorithm for such PV systems. We use neural network technique for determining PID parameters by online learning approach. And we construct a boost converter to regulate the output voltage from PV generator system. Computer simulation is carried out to evaluate the proposed MPPT method and we accomplish comparative study with a perturb and observe based MPPT method to prove its superiority.

• 한국태양에너지학회 논문집
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• 제39권2호
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• pp.1-9
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• 2019

In order to increase the power generation efficiency of the photovoltaic system, a new algorithm that can follow the maximum power point of the photovoltaic power generation system having nonlinear output characteristics is proposed. Conventional maximum power point tracking (MPPT) algorithms such as Perturbation and Observation (P&O) and InCond (Increment and Conductance) schemes can not find the global maximum power point at a plurality of pole points in the unmatched state of unbalanced PV modules. However, even if the global maximum power point is found at a plurality of pole points, the global maximum power that can not be the real maximum power by the photovoltaic generation system. In order to solve this problem, a few PV companies propose installing several small PV inverters instead of if big one. However, since this will require additional costs, we herein propose a Multi-MPPT system using individual 3-point MPPT to track true MPPT at a plurality of pole points in the unmatched state of unbalanced PV modules.

• The Korean Journal of Physiology and Pharmacology
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• 제17권6호
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• pp.499-503
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• 2013

This study tested the hypothesis that effects of the menstrual cycle on resting blood pressure carry over to dynamic exercise. Eleven healthy females were studied during the early (EP; low estrogen, low progesterone) and late follicular (LP; high estrogen, low progesterone) menstrual phases. Stroke volume (SV), heart rate (HR), cardiac output (CO), systolic blood pressure (SBP), diastolic blood pressure (DBP), and total vascular conductance (TVC) were assessed at rest and in response to mild and moderate cycling exercise during EP and LP. During EP, compared to LP, baseline SBP ($111{\pm}1$ vs. $103{\pm}2$ mmHg), DBP ($71{\pm}2$ vs. $65{\pm}2$ mmHg) and mean arterial pressure (MAP) ($84{\pm}2$ vs. $78{\pm}1$ mmHg) were higher and TVC ($47.0{\pm}1.5$ vs. $54.9{\pm}4.2$ ml/min/mmHg) was lower (p<0.05). During exercise, absolute values of SBP (Mild: $142{\pm}4$ vs. $127{\pm}5$ mmHg; Moderate: $157{\pm}4$ vs. $144{\pm}5$ mmHg) and MAP (Mild: $100{\pm}3$ vs. $91{\pm}3$ mmHg; Moderate: $110{\pm}3$ vs. $101{\pm}3$ mmHg) were also higher, while TVC was lower (Mild: $90.9{\pm}5.1$ vs. $105.4{\pm}5.2$ ml/min/mmHg; Moderate: $105.4{\pm}5.3$ vs. $123.9{\pm}8.1$ ml/min/mmHg) during EP (p<0.05). However, exercise-induced increases in SBP, MAP and TVC at both work intensities were similar between the two menstrual phases, even though norepinephrine concentrations were higher during LP. Results indicate that blood pressure during dynamic exercise fluctuates during the menstrual cycle. It is higher during EP than LP and appears to be due to additive effects of simultaneous increases in baseline blood pressure and reductions in baseline TVC.

• 한국산학기술학회논문지
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• 제10권12호
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• pp.3626-3631
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• 2009

본 논문에서는 아날로그 회로에 사용되는 NMOSFET에 대한 Hot-Carrier 열화특성을 조사하였다. 여러 값을 갖는 게이트 전압으로 스트레스를 인가한 후, 소자의 파라미터 열화를 포화 영역에서 측정하였다. 스트레스 게이트 전압의 범위에 따라 계면 상태(interface state) 뿐 아니라 전자와 정공의 포획이 드레인 근처 게이트 산화막에서 확인되었다. 그리고 특히 낮은 게이트 전압의 포화영역에서는 정공의 포획이 많이 발생하였다. 이러한 전하들의 포획은 전달 컨덕턴스 ($g_m$) 및 출력 컨덕턴스 ($g_{ds}$)의 열화의 원인이 된다. 아날로그 동작 범위의 소자에서 파라미터 열화는 소자의 채널 길이에 매우 민감하게 반응한다. 채널길이가 짧을수록 정공 포획이 채널 전도도에 미치는 영향이 증가하게 되어 열화가 증가되었다. 이와 같이 아날로그 동작 조건 및 아날로그 소자의 구조에 따라 $g_m$ 및 $g_{ds}$의 변화가 발생하므로 원하는 전압 이득($A_V=g_m/g_{ds}$)을 얻기 위해서는 회로 설계시 이러한 요소들에 대한 고려가 필요하다.

• 태양에너지
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• 제17권1호
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• pp.59-66
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• 1997

개방전압과 단락전류와 같은 태양전지 출력변수들은 접합깊이, 도핑농도, 금속접합 및 태양전지구조에 의한 변수들이다. 태양전지 설계의 중요한 요소로서 인이 도핑된 에미터와 금속사이의 금속접합은 일함수 차이가 작아 낮은 직렬저항을 가져야 한다. PESC 태양전지는 금속 접합장벽 전극으로 티타늄을 사용한다. 새로운 접합장벽 전극물질로 티타늄과 일함수가 비슷하지만 전기전도도가 우수한 크롬은 금속 접합장벽 전극으로 유망한 금속이다. 티타늄은 일함수 차가 작지만, 접합장벽으로 크롬은 태양전지 제조시 티타늄보다 우수한 전기적 특성들을 갖는다. 본 논문에서는 실리콘 태양전지의 접합장벽 금속전극의 특성을 비교 분석하였다.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1997년도 한국감성과학회 연차학술대회논문집
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• pp.75-79
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• 1997

The present study was designed to investigate whether there is a consistint changes in the signals from the central and autonomic nervous systim due to olfactory stimulation. The olfactory stimuli were 0.6% orange and 2.5% valeric acid and the stimuli through the olfactory stimulator soth controlled consistint flow, controlled concentration, and saturated with vapour to prevent drying the nasal mucosa. A room air blunk served as the control stimulus, EEG was recorede from 4channels according to the international 10-20 systim. Additionally, ECG, EOG, heart rate, skin conductance and resputation were recorded comtinuously. The fast Fourier transform analysis of EEG waves was analysed with the power spectra. Averaged power spectra were computed for the following frequency bands ; delta(0-4.5Hz), theta (4.5-7Hz), alphal(7-9.5Hz), alpha2 (9.5-12.5Hz) and beta(12.5-30Hz). Withthe results of the subjective sensibility test for the ordor, the orange was related to pleasant and familiar and the valeric acid was realted to snpleasant and bothersome. There is the difference between orange and valeric acid in alphal at PG2-A2 channel. While the unpleasant stimuli seem to be increased in alphal, alpha2 and beta waves at all channels. Also, the heart rate, galvaric skin resistance seem to be decreased by pleasant stimuli and thd unpleasant stimuli shdwed the opposite. In respiration, respiration rate had been declinig tendency, and input/output ampoitued and duration showed an upward trend by olfactory stimulation with orange, while opposite by valeric acid. In conclusion, the consistent EEG changes and the autonomic responses suggests the possibilities of the subjective signal of human sensibility.

• 생명과학회지
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• 제22권4호
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• pp.532-537
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• 2012

흡연자의 단시간의 흡연 중단이 안정 시 및 저강도(40% of $VO_2max$), 중강도(60% of $VO_2max$)에서의 일회성 유산소성 운동 중에 나타내는 심혈관 반응의 차이를 알아보는데 있다. 따라서 성인 남성 흡연자를 대상으로 흡연 직후, 흡연 중단 24시간과 흡연 중단 48시간 경과 후의 안정 시, 저강도, 중강도의 강도별 사이클 에르고미터를 통한 일회성 유산소 운동 시 심혈관계 반응을 검토하였다. 이에 따른 결과 흡연 직후, 흡연 중단 24시간과 흡연 중단 48시간 경과 후의 안정 시, 저강도, 중강도의 수준의 운동 강도별 사이클 에르고미터를 통한 일회성 유산소 운동 시 SBP, DBP, MAP, HR에서 유의한 감소가 나타났다($p$<0.05). 또한, 안정 시와 중강도에서는 CO의 유의한 감소가 나타났다($p$<0.05). 이상의 결과로부터 단시간의 흡연 중단은 교감신경의 항진상태를 완화시키고, 부교감신경계의 활성화로 인해 HR을 감소시킴으로써 안정 시와 동일 강도 유산소운동 시의 과도한 심혈관 반응을 완화키는 것으로 사료된다. 이를 통해 흡연자에게 있어 단기간의 흡연 금지만으로도 운동 중에 심혈관계 반응의 위험을 감소시킬 수 있다는 가능성을 나타냈다.

• 대한전자공학회논문지SD
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• 제44권12호
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• pp.1-6
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• 2007

본 논문에서 기존에 사용하고 있는 metamorphic high electron transistor (MHEMT)의 채널에 InP를 추가하여 제작 하였다. InP는 In0.53Ga0.47As와 비교하여 낮은 충돌 이온화 계수를 가지고 있다. 그런 특성을 MHEMT의 문제점 중의 하나인 낮은 항복전압의 개선에 이용하였다. 우리는 기존의 MHEMT와 InP 합성 채널 MHEMT의 항복 특성과 주파수 특성을 비교 하였다. 본 논문에서 InP 합성 채널 MHEMT의 on-state와 off-state 항복전압이 각각 2.4와 5.7 V가 측정 되었고 또한 cut-off 주파수와 maximum oscillation 주파수는 각각 160 GHz와 230 GHz가 측정 되었다. 위의 결과는 InP 합성 채널 MHEMT가 밀리미터파 대역의 전력용 소자에 이용되는데 큰 장점을 갖는 소자임을 알 수 있다.