• 방송공학회논문지
• /
• 제14권6호
• /
• pp.733-741
• /
• 2009

디지털 통신 시스템에서는 대역폭과 전력을 효율적으로 사용하면서 신뢰성 높은 데이터 전송을 요구한다. 본 논문에서는 다중 반송파 방식을 사용하는 시스템에서 반송파의 직교성을 이용하여 다차원 성상도를 구현하고 전력 소비가 큰 성상 포인트의 위치를 재배치하여 평균 소비 전력을 감소시킬 수 있는 기술을 제안한다. 기존의 2차원 QAM 변조 방식을 N개의 부반송파를 사용하여 다차원 QAM 형태로 단순하게 변환하면 2 N차원 큐브 형태의 성상 포인트가 구성되는데, 전력 소비가 많은 최외각 성상 포인트들을 효율적으로 재배치하면 전력 소비를 최소화할 수 있는 2 N차원 구 형태의 성상도를 구성할 수 있다. 이와 같은 방식으로 16-QAM부터 2,048-QAM까지의 2차원 성상도를 다차원으로 변환하여 구성하고 전산모의실험을 통해 얻을 수 있는 평균 소비 전력 이득 값을 비교 분석하였다. 차원을 높일수록 재배치 성상 포인트들이 증가하므로 평균 소비 전력 이득 값이 커지는 것을 알 수 있다. 하지만 차원 증가에 따른 이득의 증가비율은 로그 형태를 가지고 있기 때문에 QAM의 성상 포인트 개수에 따라 일정한 이득값에 수렴하게 되고 수렴 값을 바탕으로 적정 다차원 성상도를 유도할 수 있다. 본 논문에서 제안한 방법으로 데이터를 전송하는 것은 하드웨어 복잡도 증가가 거의 없이 소비 전력의 효율성을 높이는데 효과적이다.

• 대한안전경영과학회지
• /
• 제22권3호
• /
• pp.1-8
• /
• 2020

The desulfurizers facility is cylindrical shape. To operate properly it needs nozzles cleaned, get rid of lime adhesion and sludge, repair the wear and corrosion of facility regularly. For this purpose, workers shall access the ceiling or vertical wall at high place. Ordinary scaffoldings such as steel pipe scaffolding or system scaffolding have been using so that workers can access them. With these ordinary scaffoldings, openings around cylindrical wall are inevitable which make workers can expose always to the risk of falling. The purpose of this study is to develop customized scaffolding to minimize the openings to prevent workers form falling during maintenance it. It consists of a hexagonal central tower and six trapezoidal outer towers. And the bracing among the towers have connected each other for self-standing and for maintaining the structure of towers. Span decks, the circumference footstools, steps, etc. are laid on each floor. The safety is reviewed by structural analysis and performance test. With this study, openings each floor of this scaffold are removed. The gap between the cylindrical wall and the edge of the work stage is approximately 100 mm. Therefore, we expect that workers can work safely and efficiently.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제14권2호
• /
• pp.562-576
• /
• 2020

The power allocation optimization problem is investigated for improving the physical-layer security in two-way relaying networks, where a full-duplex relay based half-jamming protocol (HJP-FDR) is considered. Specially, by introducing a power splitter factor, HJP-FDR divides the relay's power into two parts: one for forwarding the sources' signals, the other for jamming. An optimization problem for power split factor is first developed, which is proved to be concave and closed-form solution is achieved. Moreover, we formulate a power allocation problem to determine the sources' power subject to the total power constraint. Applying the achieved closed-form solutions to the above-mentioned problems, a two-stage strategy is proposed to implement the overall power allocation. Simulation results highlight the effectiveness of our proposed algorithm and indicate the necessity of optimal power allocation.

• ETRI Journal
• /
• 제32권2호
• /
• pp.327-329
• /
• 2010

A fully integrated small form-factor HBT power amplifier (PA) was developed for UMTS Tx applications. For practical use, the PA was implemented with a well configured bottom dimension, and a CMOS control IC was added to enable/disable the HBT PA. By using helix-on-pad integrated passive device output matching, a chip-stacking technique in the assembly of the CMOS IC, and embedding of the bulky inductive lines in a multilayer substrate, the module size was greatly reduced to 2 mm ${\times}$ 2.2 mm. A stage-bypass technique was used to enhance the efficiency of the PA. The PA showed a low idle current of about 20 mA and a PAE of about15% at an output power of 16 dBm, while showing good linearity over the entire operating power range.

• 전력전자학회:학술대회논문집
• /
• 전력전자학회 2006년도 전력전자학술대회 논문집
• /
• pp.169-171
• /
• 2006

Nowadays, inverter welding is risen in spot welding, because can secure productivity. This study made changed output wave form of inverter welding equipment by several forms and measured electric current that pass to the second of transformer for welding. Purpose of study is finding electric current of most suitable form. Also, studied applies PID control in electric current control of inverter resistance weld device and heightens electric current precision.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제22권4호
• /
• pp.289-294
• /
• 2018

In this work, a recently developed semi-analytic technique, so called the residual power series method, is generalized to process higher-dimensional linear and nonlinear partial differential equations. The solutions obtained takes a form of an infinite power series which can, in turn, be expressed in a closed exact form. The results reveal that the proposed generalization is very effective, convenient and simple. This is achieved by handling the (m+1)-dimensional Burgers equation.

• 수산해양기술연구
• /
• 제39권4호
• /
• pp.298-304
• /
• 2003

In this paper a free-form hull design program and performance prediction program for planing boat is introduced. This program enables the designer to do complex geometric hull shape design on a personal computer and accurately to predict power requirements for a given loading and velocity. For a free form design, Bezier curve model is adopted as a basic representation tool of curves and surfaces, and this program has versatile functions to do fairing jobs with a convenient graphical user interface. After creating a hull form the geometric data is provided in a manner compatible with a variety of analysis tools including 'Motion Analysis(by Zarnick)' for prediction of motion characteristics in regular waves, 'Running Attitude (by Savitsky)' for prediction of the running attitude and required power.

• 동력기계공학회지
• /
• 제4권4호
• /
• pp.108-115
• /
• 2000

The continuous chip in turning operation deteriorates the precision of workpiece and can cause a hazardous condition to operator. Thus the chip form control becomes a very important task for reliable turning process. Using the difference of energy radiated from the chip, the chip form is identified using the neural network of supervised data. The feed mechanism is adjusted in order to break continuous chip according to the result of the chip form recognition and shows a good approach for precision turning operation.

• Nuclear Engineering and Technology
• /
• 제55권7호
• /
• pp.2687-2696
• /
• 2023

The fuel operating ranges of fusion tokamak-based power plants are estimated using the improved engineering breakeven equation. The Lawson criterion equations are derived in the form of a triple product with a focus on engineering breakeven and the subbreakeven operating range. The relationship of fuel parameters to the power plant net efficiency is outlined. Analysis shows that the operating ranges of the suitable fuel parameters form a closed area, the size of which affects the net efficiency of the power plant. The obtained fuel operating ranges confirm the well-known fact that DT fuel is currently the only fusion fuel useable in tokamak-based fusion power plants. It is also shown that the energy utilization of pB fuel is possible in the subbreakeven operating range but is conditioned by the very high efficiency of the power plant equipment. For the utilization of DD, DHe3, and pB fuels, the required magnetic fields are indicatively estimated.

• 한국실내디자인학회논문집
• /
• 제14호
• /
• pp.10-18
• /
• 1998

This study aims to make clear visual quality of organic form and structural order that is immanent in nature about a form as formative principles of architectural space design the significanced of this study is to prove the application possibility in to functional form architectural space design. All organic forms in nature has a unique shape and pattern in structure to be self-controled and good in order. Such an order in nature comes from regular construction and ratio principles which has aesthetical order by mathmetics. The specialty of beauty in nature can be revealed not only visual form but also the ratio balance and rhythm of structural principles. As we examine the aesthetic source embodied some object can be developed in to basic principles. Furthermore through this study we can find out that the form construction theory in nature forms share the quality attribute with geometrical form to be shown in architectural space design. Natural forms are ultimate visual expression of power that effects on the architectural space design. The rule of power in nature as nature formal characteristics have a direct influence and can be also applied to architectural construction. Therefore I expect that this study will be linked and continued to another structural view.