• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2005년도 학술대회 논문집
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• pp.415-420
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• 2005

This paper presents the two lossless auxiliary inductors-assisted voltage source type half bridge (single ended push pull: SEPP) series resonant high frequency inverter for induction heated king roller in copy and printing machines. The simple high-frequency inverter treated here can completely achieve stable zero current soft switching (ZCS) commutation for wide its output power regulation ranges and load variations under its constant high frequency pulse density modulation (PDM) scheme. Its transient and steady state operating principle is originally described and discussed for a constant high-frequency PDM control strategy under a stable ZCS operation commutation, together with its output effective power regulation characteristics-based on the high frequency PDM strategy. The experimental operating performances of this voltage source SEPP ZCS-PDM series resonant high frequency inverter using IGBTs are illustrated as compared with computer simulation results and experimental ones. Its power losses analysis and actual efficiency are evaluated and discussed on the basis of simulation and experimental results. The feasible effectiveness of this high frequency inverter appliance implemented here is proved from the practical point of view.

• Applied Biological Chemistry
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• 제37권5호
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• pp.414-420
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• 1994

망간 산화물 birnessite, pyrolusite, hausmannite의 표면에서 일어나는 3가 크롬의 산화현상을 조사하였다. 이들은 zero point of charge, 표면적, 그리고 결정도 등에서 차이가 많은데, 크롬 산화현상은 모두 1차 반응이었으며 반응용액의 pH 및 최초 3가 크롬농도가 반응에 큰 영향을 미쳤다. 일반적으로 hausmannite에 의한 산화가 가장 빨랐으며 pyrolusite에 의한 산화는 상대적으로 매우 느렸다. 용액 pH와 최초 3가 크롬농도의 상호 작용이 전체 반응속도를 조절하는 것 같으며 pH가 높고 3가 크롬농도가 높을 경우 망간산화물 표면에 3가 크롬 침전되거나 complex를 형성할 수 있을 것이다. Birnessite와 hausmannite에서는 $pH\;3.0{\sim}5.0$ 범위에서 pH가 낮을수록 산화력이 높았으나 pyrolusite의 경우에는 pH가 높을수록 산화력이 증가하였다. 반응속도는 온도에 또한 민감했다. pH 3.0에서의 산화반응의 activation energies는 일반적으로 diffusion에 필요한 activation energy보다 크게 나타났으나 반응속도를 결정하는 단계가 무엇인지는 확실하지 않다.

• Journal of Mechanical Science and Technology
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• 제20권5호
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• pp.602-611
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• 2006

This paper proposes a locomotion pattern and a control method for biped robots with curved soles. First, since the contact point of a supporting leg may arbitrarily move back and forth on the ground, we derived the desired trajectory from a model called the Moving. Inverted Pendulum Model (MIPM) where the Zero Moment Point (ZMP) exists at the supporting point and can be moved intentionally. Secondly, a biped robot with curved soles is an under-actuated system since the supporting point contacting with a point on the ground has no actuator during the single supporting phase. Therefore, this paper proposes a computed-torque control for this under-actuated system using decoupled dynamic equations. A series of computer simulations with a 7-DOF biped robot with curved soles shows that the proposed walking pattern and control method are effective and allow the biped robot to walk fast and stably, and move more like human beings. Also, it is shown that the curved sole shape has superior energy consumption compared to flat soles, and greater efficiency in ascending and descending the stairs.

• 한국정보통신학회논문지
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• 제19권10호
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• pp.2403-2408
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• 2015

DCT (Discrete Cosine Transform)는 최적인 KLT (Karhunen Loeve Transform)에 근접한 에너지 압축 성능을 가지고 있기 때문에 정지 및 동영상 신호의 압축에 널리 사용되고 있다. 최근에 DCT에 기반한 무곱셈 변환이 제안되고 있다. 이 변환들의 계수는 0 또는 2의 지수승으로 표현되기 때문에 덧셈만으로 변환을 수행할 수 있으며 따라서 고속 구현이 가능하다. 또한 에너지 압축 성능도 DCT에 근접하므로 실시간 응용에 적합하다. 본 논문에서는 적은 횟수의 덧셈만으로 계산이 이루어지며 에너지 압축 성능도 높은 8-포인트 근사 DCT를 제안한다. 제안된 변환의 계수는 기본적으로 DCT 계수를 따르지만 0이 아닌 계수의 갯수를 억제하며 동시에 변환의 직교성을 극대화하도록 선택하였다. 기존의 근사 DCT들과 계산량을 비교하였고, 다수의 실험 영상에 대해 압축 성능을 측정한 결과로부터 제안된 변환이 적은 횟수의 덧셈만으로 가장 우수한 압축 성능을 보임을 알 수 있다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.774-777
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• 2005

In this paper, a constant frequency phase shifting PWM controlled voltage source full bridge-type series load resonant high-frequency inverter using the IGBT power modules is presented for innovative consumer electromagnetic induction heating applications such as a hot water producer, steamer and super heated steamer. The full bridge arm side link passive quasi-resonant capacitor snubbers in parallel with the each power semiconductor device and high frequency AC load side linked active edge inductive snubber-assisted series load resonant tank soft switching inverter with a constant frequency phase shifted PWM control scheme is discussed and evaluated on the basis of the simulation and experimental results. It is proved from a practical point of view that the series load resonant and edge resonant hybrid high-frequency soft switching PWM inverter topology, what is called class DE type. including the variable-power variable-frequency(VPVF) regulation function can expand zero voltage soft switching commutation range even under low output power setting ranges, which is more suitable and acceptable for induction heated dual packs fluid heater developed newly for consumer power utilizations. Furthermore, even in the lower output power regulation mode of this high-frequency load resonant tank high frequency inverter circuit it is verified that this inverter can achieve ZVS with the aid of the single auxiliary inductor snubber.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권9호
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• pp.3172-3193
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• 2022

Cognitive radio-simultaneous wireless information and power transfer (CR-SWIPT) has attracted much interest since it can improve both the spectrum and energy efficiency of wireless networks. This paper focuses on the resource sharing between a point-to-point primary system (PRS) and a multiuser multi-antenna cellular cognitive radio system (CRS) containing a large number of cognitive users (CUs). The resource sharing optimization problem is formulated by jointly scheduling CUs and adjusting the transmit power at the cognitive base station (CBS). The effect of accessing CUs' spatial channel correlation on the possible transmit power of the CBS is investigated. Accordingly, we provide a low-complexity suboptimal approach termed the semi-correlated semi-orthogonal user selection (SC-SOUS) algorithm to enhance the spectrum efficiency. In the proposed algorithm, CUs that are highly correlated to the information decoding primary receiver (IPR) and mutually near orthogonal are selected for simultaneous transmission to reduce the interference to the IPR and increase the sum rate of the CRS. We further develop a spatial correlation-based resource sharing (SC-RS) strategy to improve energy sharing performance. CUs nearly orthogonal to the energy harvesting primary receiver (EPR) are chosen as candidates for user selection. Therefore, the EPR can harvest more energy from the CBS so that the energy utilization of the network can improve. Besides, zero-forcing precoding and power control are adopted to eliminate interference within the CRS and meet the transmit power constraints. Simulation results and analysis show that, compared with the existing CU selection methods, the proposed low-complex strategy can enhance both the achievable sum rate of the CRS and the energy sharing capability of the network.

• 한국세라믹학회지
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• 제27권1호
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• pp.109-117
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• 1990

Magnetite for Water-based ferrofluid was synthesized by air oxidation of aqueous suspension in the pH range 7-12 at $65^{\circ}C$. The optimum condition of magneite formation was delineated by examining various physicochemcial properties such as Fe2+ content, phase characteristics, MHC and $\sigma$max. The point of zero charge of iron oxide powders obtained at various pH conditions were correlated with the oxidation state of Fe in the iron oxide. The magnetite powder prepared at pH 9 ws dispersed using sodium oleate and sodium dodecylbenzenesulfonate (SDBS) as dispersants, and the dispersion characteristics of the magnetite ferrofluid were examined by means of the fraction of solid dispersed, zeta potential data and FT-IR spectrum. A simple calculation on the potential energy of two interacting magnetite particles showed that the dispersion stability was directly correlated with height of the potential energy barrier or the shape of zeta potential.

• 대한수학회지
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• 제54권5호
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• pp.1573-1594
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• 2017

This paper deals with the existence and energy estimates of solutions for a class of degenerate nonlocal problems involving sub-linear nonlinearities, while the nonlinear part of the problem admits some hypotheses on the behavior at origin or perturbation property. In particular, for a precise localization of the parameter, the existence of a non-zero solution is established requiring the sublinearity of nonlinear part at origin and infinity. We also consider the existence of solutions for our problem under algebraic conditions with the classical Ambrosetti-Rabinowitz. In what follows, by combining two algebraic conditions on the nonlinear term which guarantees the existence of two solutions as well as applying the mountain pass theorem given by Pucci and Serrin, we establish the existence of the third solution for our problem. Moreover, concrete examples of applications are provided.

• 대한화학회지
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• 제53권1호
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• pp.7-16
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• 2009

Bz-$H_2O$와 [Bz-$H_2O]^+$의 가능한 구조(N-1, N-2, C-1, C-2, 그리고 TS)에 대하여 여러 이론 수준에 서 분자구조를 최적화 하였으며, 조화 진동주파수를 계산하여 IR 스펙트럼을 예측하였다. 분자 구조의 최적화에서 가장 높은 이론 수준은 B3LYP/cc-pVQZ이며, 보다 정확한 결합에너지를 구하기 위하여 MP2 수준에서 한 점(single point) 에너지 계산을 하였다. 또한 영점 진동에너지(zero-point vibrational energy) 보정을 하여 실험값과 비교하였다. 결합에너지는 N-1 구조에 대하여 MP2/cc-pVQZ//B3LYP/cc-pVQZ 이론 수준에서 $D_e$ 값이 3.92 kcal/mol, 그리고 $D_0$ 값은 3.11 kcal/mol로 계산되었으며, 같은 이론 수준에서 [Bz-$H_2O]^+$의 C-1 구조에 대해서 $D_e$ 값은 9.06 kcal/mol 그리고 $D_0$ 값은 7.82 kcal/mol로 계산되어 실험값 과 비교적 잘 일치하는 것으로 나타났다.

• 한국태양에너지학회 논문집
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• 제26권2호
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• pp.69-77
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• 2006

Photovoltaic is an attractive technology to remote power applications, because of its reliability, low maintenance, and zero fuel requirements. In this paper represents residential PV system based on BESS(battery energy storage system) for managing the electric power, a pattern of daily operation considering the load characteristics of the house, the generation characteristics of PV power, and utility power leveling. For apply to control algorithm, we consider the load on monthly power consumption trend and daily usage pattern. As for the control of the proposed system, to increase the conversion efficiency of the PV power, bidirectional converter is used for MPPT and SPWM inverter. An experimental system is implemented, and some experimental results are provided to demonstrate the effectiveness of the proposed system.