• Journal of Communications and Networks
• /
• 제9권2호
• /
• pp.112-117
• /
• 2007

In this paper, we focus on the total transmission power minimization problem for downlink beamforming multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems while ensuring each user's QoS requirement. Although the linear integer programming (LIP) solution we formulate provides the performance upper bound of the margin adaptive (MA) optimization problem, it is hard to be implemented in practice due to its high computational complexity. By regarding each user's equivalent channel gain as approximate independent values and using iterative descent method, we present a heuristic MA resource allocation algorithm. Simulation results show that the proposed algorithm efficiently converges to the local optimum, which is very close to the performance of the optimal LIP solution. Compared with existing space division multiple access (SDMA) OFDM systems with or without adaptive resource allocation, the proposed algorithm achieves significant performance improvement by exploiting the frequency diversity and multi-user diversity in downlink multiple-input single-output (MISO) OFDM systems.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1999년도 하계학술대회 논문집 G
• /
• pp.3319-3321
• /
• 1999

Pt-RTD and Micro Heater was fabricated by using MgO as medium layer in order to improve adhesion of Pt thin-films to $SiO_2$ layer, MgO layer improved adhesion of Pt thin-films to $SiO_2$ layer without any chemical reactions to Pt thin-films under high annealing temperatures, In the analysis of properties of Pt-RTD, TCR value had 3927 $ppm/^{\circ}C$ and liner in the temperature range of $25-400^{\circ}C$. The temperature of Pt micro-heater had up to $400^{\circ}C$ with 1.5watts of the heating power. In investigating output characteristics of flow sensors output voltages increased as gas flow rate and its conductivity increased due to increase of heat-loss from sensor to external. Output voltage was 82 mV at $N_2$ flow rate of 2000sccm, heating power of 1.2W.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 C
• /
• pp.2138-2139
• /
• 2005

We demonstrate a simple CO2 laser by controlling firing angle of a TRIAC switch in ac power line. The power supply for our laser system switches the voltage of the AC power line (60Hz) directly. The power supply does not need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. In order to control the laser output power, the pulse repetition rate is adjusted up to 60Hz and the firing angle of TRIAC gate is varied from 45 to 135. A ZCS(Zero Crossing Switch) circuit and a PIC one-chip microprocessor are used to control the gate signal of the TRIAC precisely. The maximum laser output of 40W is obtained at a total pressure of 18Torr, a pulse repetition rate of 60Hz, and a TRAIC gate firing angle of 90.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2006년도 춘계학술대회
• /
• pp.192-194
• /
• 2006

To elucidate possible challenges for outdoor practical use of dye-sensitized solar cells(DSC), compared with conventional Si solar cells. DSC modules still need the larger area than conventional Si solar modules to attain the same rated output because of lower photoelectron-chemical conversion efficiency. However, using batteries backup systems, the measured data shows that DSCs gathered over 12% more electricity than Si solar cells of the same rated output power in same outdoor condition. Moreover, battery charging time of DSC is about 1 hour faster than same rate of Si solar module. In this paper, 12 single DSC cells prepared for 4 serialized DSC cells was connected in 3 row parallel which have same output power rate of Si solar module. This DSC module was practiced generating characteristic experiment over outdoor daylight condition and applied with PV battery charger by using DC-DC converter. The main advantages of DSC module battery charger as compared with conventional Si solar module one are shorter charge time and lower cost.

• 한국경제지리학회지
• /
• 제20권1호
• /
• pp.1-15
• /
• 2017

본 연구는 2005-2013년간 울산지역의 성장을 견인하고 있는 3대 주력산업(석유화학산업, 조선산업, 자동차산업)이 어떠한 요인에 의해 성장하였는지를 투입산출 구조분해분석법을 통해 실증적으로 분석한 것이다. 이를 위해 한국은행에서 공표한 지역산업연관표를 이용하여 3대 주력산업의 구조변화를 살펴보고, 각 산업의 요인별 성장기여율을 최종수요, 수출수요, 최종재수입대체, 중간재수입대체, 기술변화 등으로 구분하여 분석하였다. 울산의 3대 주력산업 중 석유화학산업과 자동차산업의 총산출과 총수요 증가율은 2005-2010년에 비해 2010-2013년에 증가하였지만, 조선산업의 총산출과 총수요 증가율은 둔화된 것으로 나타났다. 3대 주력산업의 총산출 증가에 대한 요인별 성장기여율 분석한 결과, 수출수요가 가장 큰 영향을 미치는 것으로 나타났다. 산업별로 살펴보면, 석유화학산업은 수출수요 성장기여율이 2005-2010년에 209.23%, 2010-2013년에 113.78%로 가장 큰 비중을 차지하였다. 자동차산업은 수출수요 성장기여율이 2005-2010년에 258.72%, 2010-2013년에 72.69%의 비중을 차지하였고, 기술변화 성장기여율은 2005-2010년에 -115.36%에서 2010-2013년에 16.91%로 크게 증가하였다. 반면 조선산업은 2005-2010년에 수출수요 성장기여율이 94.47%로 가장 큰 비중을 차지하였으나 2010-2013년에는 -255.32%로 크게 감소하였고, 최종수요 성장기여율도 2005-2010년에 1.75%에서 2010-2013년에 -502.65%로 급감하였으나, 최종재수입대체와 기술변화 성장기여율은 280.68%와 492.21%로 크게 증가하였다. 울산의 3대 주력산업의 성장요인 분석은 관련 산업정책을 재정리하고 수립하는데 기초자료로서 역할을 할 것으로 기대한다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1998년도 하계학술대회 논문집 G
• /
• pp.2480-2482
• /
• 1998

In this paper, the implementation of dual rate ADPCM using G.723 16Kbps and 40Kbps speech codec algorithm is handled. For small signals, the low rate 16Kbps coding algorithm shows the same SNR as the high rate 40Kbps coding algorithm, while the low rate 16Kbps coding algorithm shows the lower SNR than the high rate 40Kbps coding algorithm for large signal. To obtain the good trade-off between the data rate and synthesized speech quality, we applied low rate 16Kbps for the small signal and high rate 40Kbps for the large signal. Various threshold values determining the rate are tested for good trade off data rate and speech quality. Also the low pass filter effect of speech input and output devices is simulated at several cut-off frequencies. To simulation result shows the good speech quality at a low rate comparing with 16Kbps & 40Kbps.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2004년도 학술대회지
• /
• pp.663-666
• /
• 2004

In this paper, a modified-SOYA (soft output viterbi algorithm) of turbo codes is proposed for quantized channel receiver filter outputs. We derive optimum branch values for the Viterbi algorithm. Here we assume that received filter outputs are quantized and the channel is additive white Gaussian noise. The optimum non-uniform quantizer is used to quantize channel receiver filter outputs. To compare the BER (bit error rate) performance we perform simulations for the modified SOYA algorithm and the general SOYA

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집; 한국과학기술대학, 충남; 16-17 Oct. 1987
• /
• pp.522-527
• /
• 1987

This paper describes the hardware of analog-to-digital converter to process the rate output of analog servo loop for the gyro rebalance of INS. The analog-to-digital converter is designed by voltage-to-frequency method which is generally used in INS, and this scheme fits well into the strapdown INS that requires the wide dynamic range and linearity. The output of the designed voltage to frequency converter is tested by computer through the counter and all the factors which affect the performance are considered.

• 한국통신학회논문지
• /
• 제9권1호
• /
• pp.45-48
• /
• 1984

A serious degradation of blocking of the detection performance in a cell aeraging-logarithmic detector/constant false alarm rate(CA-LOG/CFAR) is known to be caused by the presence of a large interfering noise in the set of sample mean. A technique consisting of the logarithmic circuit and inverter has been proposed to alleviate this problem, by modifying the conventional CA-LOG/CFAR receiver. The detection performance of the proposed technique is linearly improbed over the normal output level and the blocking characteristics of the CA-LOG/CFAR can be changed to finite output level.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
• /
• pp.761-767
• /
• 2001

In this paper, filtering techniques to reduce the adverse effects of motor leads on high-frequency PWM inverter fed AC motor drives will be examined. The filter was designed to keep the motor terminal from the cable surge impedance to reduce overvoltage reflections, ringing, and the dv/dt, di/dt. Therefore, filtering techniques are investigated to reduce the motor terminal overvoltage, ringing, and EMI noise in inverter fed ac motor drive systems. The output filter is used to limit the rate of the inverter output voltage and reduce EMI(common mode noise) to the motor. The performance of the output filter is evaluated through simulations (PSIM) and experiment on PWM inverter-fed ac motor drive(3phase, 3hp(2.2kw), input voltage 220/380V, induction motor). An experimental PWM drive system reduction of conducted EMI was implemented on an available TMS320C31 microprocessor control board. Finally, experimental results showed that the inverter output filter reduces more CM noise than the LPF(low pass filter) and reduce overvoltage and ringing at the motor terminal.