• 한국멀티미디어학회논문지
• /
• 제19권7호
• /
• pp.1166-1178
• /
• 2016

In Internet of Things (IoT) environments, billions of interconnected devices and multimedia sensors generate a huge amount of multimedia traffic. Since the environment are in general deployed as a server-centric architecture wireless sensor networks could be bottlenecks between IoT gateways and IoT devices. The bottleneck causes high power consumption of the device and triggers very heavy network overload by transmission of sensing data. The deterioration could decrease the quality of multimedia streaming service due to delay, loss, and waste of device power. Thus, in this paper, we propose a context-based adaptive multimedia streaming scheme to support enhanced QoS and low power consumption in IoT environments. The goal of the scheme is to increase quality score per voltage of the streaming service, given an adaptation algorithm with context that are classified network and hardware such as throughput, RTT, and CPU usage. From the both context, the quality score per voltage is used in the comparison of a only network context-based adaptive multimedia streaming scheme, a fixed multimedia streaming and our scheme. As a result, we achieves a high improvement that means the quality score per voltage is increased up to about 4, especially in case of resolution change.

• 조명전기설비학회논문지
• /
• 제30권2호
• /
• pp.65-70
• /
• 2016

Power interruption is a phenomenon that no voltage is displayed over a short time or long time. Most devices will not operate normally when the supply voltage is low or does not exist. However, the device can also be operated with a different power which is ensured by a separate power generation. Recently, power interruption has been reduced gradually by the improvement of electricity quality, its duration also has been very short. Induction motors are widely used for the pumping in the water and sewage facilities and power plant applications. The pump is used as a machine for moving the fluid in the high place from a low location. So pump equipment always have a potential energy. If a momentary interruption occurs, the potential energy of the pump is reversed as that of water turbine and motor is operated as generator. This study is an analysis for the voltage variation, current, torque and power flow by the generating operation of the induction motor before and after the change of momentary interruption.

• Journal of Electrical Engineering and Technology
• /
• 제3권4호
• /
• pp.520-527
• /
• 2008

This work focuses on the evaluation of active power filter which is controlled by fuzzy logic and neural network based controller for harmonic mitigation and power factor enhancement. The APF consists of a variable DC voltage source and a DC/AC inverter. The task of an APF is to make the line current waveform as close as possible to a sinusoid in phase with the line voltage by injecting the compensation current. The compensation current is estimated using adaptive neural network. Using the estimated current, the proposed APF is controlled using neural network and fuzzy logic. Computer simulations of the proposed APF are performed using MATLAB. The results show that the proposed techniques for the evaluation of APF can reduce the total harmonic distortion less than 3% and improve the power factor of the system to almost unity.

• 한국표면공학회지
• /
• 제29권6호
• /
• pp.739-744
• /
• 1996

Lanthanide diphthalocyanines have interesting properties on electrochemical and chemical redox reactions. It is however, difficult to use because of thier short device life. Plasma-polymerization attends to improvement thier device life. Yb-diphthalocyanine ($YbPc_2$) polymer film was deposited in a parallel plate electrodes-type RF plasma reactor. $YbPc_2$ was sublimed into the argon plasma, and polymer film was obtained on a substrate. Radio frequency was constant of 13.56MHz. Pressure of argon gas, sublimation rate of $YbPc_2$ and RF power were variable parameters depending on film quality. Surface of polymer films include a lot of sub-micron order lumps. It was indicated that size of lumps depends on polymerization degree controled by parameters. Size of lumps and polymerization degree are increased with RF power. However, by the high RF power over 40W, polymerization degree is decreased with RF power and surface of film is rough. In condition of RF power is high, polymerization will compete with etching of film. We obtained good films for electrochromic display with RF power of 20W, argon gas pressure of 8.0 Pa and sublimationrate of $1.2 \times 10$ mol/min, and good films for gas sensor with RF power of 30W, argon gas pressure of 10.6Pa and sublimation rate of $1.2 \times 10$ mol/min.

• 한국안전학회지
• /
• 제14권2호
• /
• pp.70-76
• /
• 1999

In this paper, a mixed-integer programming approach is presented for adjusting the voltage profiles in a power system. The advent of large-scaled system makes the reactive power and voltage problem-an attempt to achieve an overall improvement of system security, service quality and economy-more complex and seriously, Although the problem is originally a nonlinear optimization problem, it can be formulated as a mixed integer linear programming(MILP) problem without deteriorating of solution accuracy to a certain extent. The MILP code is developed by the branch and bound process search for the optimal solution. The variable for modeling transformer tap positions is handled as discrete one, and other variables continuous ones. Numerical data resulting from case study using a modified IEEE 30 bus system with outaged line show that the MILP can produce more reductions of magnitude in the operating cost. The convergence characteristics of the results are also presented and discussed.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
• /
• pp.266-269
• /
• 2003

A sterilizer equipment by using electrical energy has merits that no process of chemical and no second environmental pollution. Also, the power conversion circuit for sterilizer equipment has merits that are reducing switching loss for soft switching topology by using zero current and zero voltage switching, and miniaturizing size of equipment. Thus, it is expected that the cost of sterilization process, when quality of the device is measured by power consumption, will be reduced. Therefore, the purpose of this research is to solve the sterilization problems of existing powder with plasma sterilization device, to find more economical and effective way, and to suggest more improved sterilizer.

• ETRI Journal
• /
• 제38권2호
• /
• pp.366-375
• /
• 2016

This paper describes an algorithm to suppress composite noise in a two-microphone speech enhancement system for robust hands-free speech communication. The proposed algorithm has four stages. The first stage estimates the power spectral density of the residual stationary noise, which is based on the detection of nonstationary signal-dominant time-frequency bins (TFBs) at the generalized sidelobe canceller output. Second, speech-dominant TFBs are identified among the previously detected nonstationary signal-dominant TFBs, and power spectral densities of speech and residual nonstationary noise are estimated. In the final stage, the bin-wise output signal-to-noise ratio is obtained with these power estimates and a Wiener post-filter is constructed to attenuate the residual noise. Compared to the conventional beamforming and post-filter algorithms, the proposed speech enhancement algorithm shows significant performance improvement in terms of perceptual evaluation of speech quality.

• 조명전기설비학회논문지
• /
• 제24권10호
• /
• pp.143-148
• /
• 2010

Recently, the KEPCO is constructing the PQMS(Power Quality Monitoring System) each of the distribution line and will establish the voltage sag standard based on the long time measurement data of PQMS. The voltage sag prospect is difficult for the power system manager, however, the voltage sag forecasted is very important because the damage effect of the voltage sag is very broad. This paper describes the prospect formula of the voltage sag magnitude in the PCC(Point Common Coupling) by the starting current when the high capacity equipment is connected with the distribution line. To achieve this, this paper has proposed the sag prospect formula revision of KEPCO for the reliability improvement and the proposed formula has been applied the voltage sag real case to inspect the calculation procedure and reliability.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 B
• /
• pp.1047-1049
• /
• 2005

Hydraulic power plant is operated for peak load and frequently start-stop because of no continuous operation. So the fault can happen due to field voltage swing in the middle of starting or reactive power swing on the line. On this research, we want to analyze that this status influence on line and generator. we hope this research can contribute to the power quality improvement.

• 한국건축시공학회지
• /
• 제8권1호
• /
• pp.49-56
• /
• 2008

According to the recent trends which are the diversity of customer requests and the multi-function of buildings, A construction company's business has converted from the producer-oriented approach to the consumer-oriented approach. Therefore, each construction company is continuously trying to improve the quality level as a way of corresponding to customer needs in these changing situations. The quality is one of the main management targets which judge the success of a project along with the schedule, the cost and the safety. As construction companies execute the quality management which they aimed at, it should be completed within the optimum schedule and the limit of the budget. Accordingly, the importance of the construction site management to complete a project is continuously increasing. The construction site management is the systematic method to perform the project goals such as the quality improvement, the cost saving and the safety management, which organically operate one another, by procuring the manpower, the material and the machine in the right time. Specially, as the construction industry has based on the construction site, the establish of systematic construction site management, which can effectively correspond sudden changes of the construction business environment, is essential to maximize the construction productivity. On top of that, the necessity of the quality management method is increasing to accommodate customer needs more spontaneously in the construction site. These endeavors could guarantee their competitive power.