• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.47-50
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• 1990

종래에는 공조덕트의 소음 감소를 위하여 주로 흡음재료를 사용하여 왔다. 그러나 이러한 흡음재료를 이용한 소음감소대책은 500HZ 이상의 고주파 영 역에서는 효과가 있으나 500HZ 이하의 저주파 영역에서는 효과가 적다. 이 러한 500HZ이하의 저주파 소음은 각종 구조물의 진동을 야기시켜 정밀작업 이 요구되는 작업환경을 파괴하고, 심지어는 구조물에 손상을 입힐수도 있 다. 또한 이러한 저주파 소음에 노출된 사람의 심리를 불안하게 하여 일의 효율을 떨어뜨릴 뿐만 아니라 청력장애를 일으키기도 한다. 또한 청정환경이 요구되는 곳에서의 소음감소를 위하여 흡음재료를 사용할 경우 흡음재료로 부터 떨어져 나오는 미세분에 의해 청정환경의 보존이 어려워진다. 이러한 흡음재료를 이용한 수동소음제어 대책의 단점을 해결하기 위하여 소음을 그 소음과 동일한 진폭을 갖으며 위상차가 180도인 인위적인 음파로 상쇠시키 는 능동소음제어대책의 개발이 요구되어 왔다. 본 논문은 덕트 또는 이와 유 사한 음향환경내에서의 적응필터기법(adaptive filtering technique)을 이용한 능동소음제어방법의 개발, 실제구현 및 성능평가에 관한 것으로서, 특히 다 수의 에러 마이크로폰과 다수의 소음제어용 스피커를 사용하여 제어계통의 가관측성(Observability)및 가제어성(Controllability)을 향상시켜 평면파로 전 달되는 소음의 감소를 증대시킬수 있을 뿐만 아니라 고차모드(Higher-order mode)로 전달되는 소음의 제어도 가능케하는 능동소음제어 방법에 관하여 논하였다.

• The Journal of the Korea Contents Association
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• v.13 no.10
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• pp.37-45
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• 2013

In recent years, the demands of multimedia data in wireless sensor networks have been significantly increased for the high-quality environment monitoring applications that utilize sensor nodes. However, since the amount of multimedia data is very large, the network lifetime is significantly reduced due to excessive energy consumption on particular nodes. To overcome this problem, in this paper, we propose a high efficiency data compression scheme in wireless multimedia sensor networks. The proposed scheme reduces the packet size by a multiple compression technique that consists of primary compression that deletes the lower priority bits considering characteristics of multimedia data and secondary compression based on Chinese Remainder Theorem. To show the superiority of our scheme, we compare it with the existing compression scheme. Our experimental results show that our proposed scheme reduces the amount of transmitted data by about 55% and increases network lifetime by about 16% over the existing scheme on average.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.18-26
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• 2009

Recently, from an environmental conservative point of view, the need of high-efficiency lighting system, using LED(Light Emitting Diode) light sources have been increased. However, applied LED light sources without regard to its color and pattern provide visual discomfort to occupant. The objective of this study is not only to evaluate the performance of task work under different correlated color temperature condition, but also furnish the preliminary data as concerning its purpose and user of inner space. For the purpose of this study, two types of LED light sources and a fluorescent light source were selected. Thirty undergraduate students served as the participants. Two different task work sheets were conducted to evaluate the accuracy and duration of time. Results from subjective performance, task work of error modification showed that LED light sources were 2.5[%] higher in accuracy with 17.1[%] lower duration than a fluorescent light source. In the case of reading task work, It is presented 20.6[%] decrease with the LED light sources comparison with a fluorescent light source.

• Plant Journal
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• v.17 no.2
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• pp.48-53
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• 2021

In the case of a 900 MW combined cycle power plant, most of the load on the site is a rotating device and is operated at a low power factor, and the power factor decrease increases the reactive power, which causes the efficiency of the device to be consumed and unnecessary unnecessary power consumption. This study intends to present the results by installing and operating a reactive power compensation device that absorbs and removes reactive power, which is a solution to this problem, on a 6.9 kV on-board bus. As a result of application of this system, first, it was confirmed that the power factor of the rotating machine was improved to 0.22 and the load power in the house was reduced by 1.4%, and the thermal efficiency of the generator was increased by 0.1% and the power generation power by 810 kW. Next, it was confirmed that the cost of construction and operation can be reduced in the future due to economic feasibility, with a decrease of 200 million won/year in electricity loss compared to 1.5 billion won in investment, an increase of 1 billion won/year in sales, and a one-year capital recovery period.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.7C
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• pp.627-636
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• 2012

Recently, XML is used to describe details of service and contents for various fields such as IPTV and digital broadcast services because of it's high readability and extensibility. TV-Anytime's schema and delivery protocol have been especially adopted as basic standards for them, and extended to include their own private functions. However, XML describes documents using text-based method, and this causes to create big documents rather than traditional methods. Therefore, many encoding algorithms have been proposed to reduce XML documents like EXI, BiM, GZIP and fast-info set etc. Although these algorithms shows efficient compression effects for XML documents, but they can't avoid fragmentation degradation during encapsulation steep. This paper proposes an efficient encapsulation scheme of TV-Anytime to avoid fragmentation degradation of encoding effect using common string tables.

• The Journal of the Korea Contents Association
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• v.12 no.5
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• pp.10-21
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• 2012

The role of GPU has evolved from graphics-specific processing to general-purpose processing with the development of unified shader core architecture. Especially, execution methods for general-purpose parallel applications using GPU have been researched intensively, since the parallel hardware architecture can be utilized efficiently when the parallel applications are executed. However, current GPU architecture has limitations in executing general-purpose parallel applications, since the GPU is not specialized for general-purpose computing yet. To improve the GPU performance when general-purpose parallel applications are executed, the GPU architecture should be evolved. In this work, we analyze the GPU performance according to the architecture varying the number of cores and clock frequency. Our simulation results show that the GPU performance improves by up to 125.8% and 16.2% as the number of cores increases and the clock frequency increases, respectively. However, note that the improvement of the GPU performance is saturated even though the number of cores increases and the clock frequency increases continuously, since the data cannot be provided to the GPU due to the limit of memory bandwidth. Consequently, to accomplish high performance effectiveness on GPU, computational resources must be more suitably considered.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2002.11a
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• pp.229-234
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• 2002

OFDM(Orthogonal Frequency Division Multiplexing) 전송방식은 SCM(Single Carrier Modulation)에 비해 우수한 여러 가지 장점들을 가지며, 방송시스템들 중 Eureka 147 DAB(Digital Audio Broadcasting) 시스템에 가장 먼저 채택되었다. 그러나 OFDM 신호의 높은 PAPR(Peak-to-Average Power Ratio) 특성은 D/A, A/D 변환기의 복잡도를 높이고, 고출력 증폭기의 효율성을 감소시키는 원인이 된다. 이를 개선하기 위한 방법 중에, SDT(Signal Distortion Technique)는 전송시스템의 규격 및 수신기의 변경 없이도 적용 가능하다는 장점을 갖는다. 본 논문에서는 SDT에 속하는 companding 기법을 Eureka 147 DAB 시스템에 적용하여 PAPR 개선정도에 따른 시스템의 요구 $E_2/N_0$ 및 out-of-band의 PSD 열화 정도를 분석하였으며, 이를 clipping 기법의 성능과 비교하였다. 모의실험 결과, $\mu$값이 2인 경우, companding 기법이 PAPR, $E_2/N_0$, out-of-band의 PSD 특성 모두에서 clipping 기법에 비해 우수한 성능을 나타냈다. 또한 $\mu$ 값을 고정시킨 경우, 정규화 값이 증가할수록 신호왜곡 정도가 줄어들어 $E_2/N_0$, out-of-band의 PSD 성능개선 정도는 증가하지만, 이와는 반대로 PAPR 값은 개선 정도가 줄어들었다.

• Journal of the Korean Applied Science and Technology
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• v.36 no.4
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• pp.1427-1433
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• 2019

In this paper, Gas engine was tested for the energy of synthesis gas. As excess air ratio increase 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6 in 1800 rpm and synthesis gas, thermal efficiency generally decrease and power generation was 34 kWm at λ 1.4. And excess air ratio increase 1, 1.1, 1.2, 1.3, 1.4 in power generation 34 kWm, thermal efficiency generally increase 34.2%, 36.9%, 37.2%, 37.4%, 38.1%. Total efficiency through power generation consumes 38.7 kg/h of fuel at 30 kWe load and recovers 57.3% of waste heat by recovering 57.3 kW of waste heat through 32.1% power generation efficiency and heat recovery from cooling water and exhaust gas. The total efficiency was 85.8%.

• Journal of the Korean Electrochemical Society
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• v.17 no.2
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• pp.94-102
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• 2014

Cation exchange membrane (Nafion) was modified to reduce the vanadium ion permeation through the membrane and to increase the vanadium redox flow battery (VRB) system performance by coating the graphene oxide (GO) which has nano-plate like morphology. Modified membrane properties were studied by measuring the ion exchange capacity (I.E.C), water uptake and proton conductivity. The thickness of the coated layer on the surface of the Nafion membrane was observed as $0.93{\mu}m$ by SEM. Proton conductivity and vanadium ion permeability of the modified membrane were decreased to 27% and 25% compared to that of the commercial Nafion membrane respectively. VRB single cell performance test was performed to compare the system performance of the VRB applied with commercial Nafion membrane and modified membrane. VRB system applied with modified membrane showed higher coulombic efficiency and energy efficiency than the VRB system applied with the commercial Nafion membrane due to the reduction of the vanadium ion permeation. From these result, we could suggest that the membrane modification by coating the GO on the surface of the Nafion membrane could be one of the promising strategies to reduce the vanadium ion permeation and to increase the VRB system performance effectively.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.6
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• pp.238-242
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• 2016

The effect of the alkali, alkali earth metal elements on selective catalytic reduction(SCR) catalyst deactivation behavior were investigated in terms of microstructure, surface area, pore volume and De-NOx test. Poisoned SCR catalyst were manufactured by injection of $K_2CO_3$, $Na_2CO_3$, $Ca(CH_3COO)_2{\cdot}H_2O$, $C_4H_6MgO_4{\cdot}4H_2O$, $H_3PO_4$ solutions in the new SCR catalyst at $350^{\circ}C$ for 6 hours. New and poisoned catalysts surface were similar. But specific surface area, pore volume decrease from Na, Mg, K, Ca, P compared to new SCR catalyst. Especially, Na poisoned catalyst surface area and pore size extremely decreased by $10.20m^2/g$, $0.061cm^2/g$. De-NOx test results of new and poisoned catalysts at $150{\sim}450^{\circ}C$ indicated that alkali metal (K, Na) poisoned SCR catalysts have the lowest De-NOx efficiency, alkali earth metal poisoned SCR catalysts (Ca, Mg) De-NOx efficiency are higher than alkali metal poisoned SCR catalysts. P poisoned SCR catalyst De-NOx efficiency is similar new SCR catalyst. It were considered that physical deactivation of SCR catalyst was affected by SCR catalyst surface area and pore volume change.