• 한국기계가공학회지
• /
• 제16권3호
• /
• pp.1-8
• /
• 2017

Tool path generation is a part of process planning in 3D printing. This is done before actual printing by a computer rather than an AM machine. The mesh geometry of the 3D model is sliced layer-by-layer along the Z-axis and tool paths are generated from the sliced layers. Each 2-dimensional layer can have two types of printing paths: (i) shell and (ii) infill. Shell paths are made of offset loops. During shell generation, twists can be produced in offset loops which will cause twisted tool paths. As a twisted tool path cannot be printed, it is necessary to remove these twists during process planning. In this research, An algorithm is presented to remove twists from the offset loops. To do so the path segments are traversed to identify twisted points. Outer offset loops are represented in the counter-clockwise segment order and clockwise rotation for the inner offset loop to decide which twisted loop should be removed. After testing practical 3D models, the proposed algorithm is verified to use in tool path generation for 3D printing.

• 신재생에너지
• /
• 제5권1호
• /
• pp.32-39
• /
• 2009

Availability of reliable and affordable energy supply is a prerequisite for economic growth. Renewables are the third largest contributor to global electricity production after coal and natural gas and account for a share of 18%. Power generating capacity from renewables has increased to around 900GW by the year 2007. Today biodiesel fuels have been in commercial use in many countries and recently the world-wide biodiesel market has experienced considerable growth, which is partly due to various tax concession programs and other financial incentives. In Korea, biodiesel has already been used for transportation fuel, but not used for power generation fuel yet Korean government has a strategy for renewable energy propagation, especially the goal of power generation amount by renewable energy is 3% of total power production by 2012. This paper focuses on the feasibility study for adaptability and strategy of using biodiesel as power generation fuel. The study also has the plan to replace the fuel of thermal power plant, gas turbine and distributed power system. As the increase of biodiesel fuel, I look forward to environment-friendly power generation and the strategy of Renewable Portfolio Standards(RPS).

• 한국교육논총
• /
• 제38권3호
• /
• pp.189-210
• /
• 2018

본고는 천원 오천석의 민주주의 교육에 대한 현대적 의미를 제고한다. 특히 그의 후기 저서에 강조된 민족주의에 대한 논의 또한 요구되는 바이나 본고에서는 천원의 민주주의 교육이념 나타난 자유 개념을 분석하는 것으로 한정짓도록 한다. 이를 위하여 오늘날의 시대적 담론을 비판적으로 분석한 한병철의 논의를 바탕으로 천원의 민주주의의 의미와 평가를 논하고 그의 사상에 내재된 교육철학적 한계를 비판적으로 고찰한다. 이를 바탕으로 천원이 궁극적으로 지향하였던 도의적 민주주의 사상을 제고하여 오늘날 픽미세대에게 요구되는 자유 개념을 고찰하도록 한다.

• 한국지열·수열에너지학회논문집
• /
• 제12권3호
• /
• pp.9-16
• /
• 2016

This study had the purpose on feasibility judgment through performance forecast of wind power generation system using the cross flow vertical type wind power turbine for the situation of domestic small size wind power technology development. Wind power generation system uses the principle of venturi tube that gathers the wind through the first guide vane, and second guide vein changes the angle of the wind simultaneously by playing the role of venturi tube. After this, wind got out from the second guide vane spins the wind power turbine and has the meaning of judging on the aspect of numerical interpretation the feasibility for the small size wind power generation through wind power generation system that comes out from the back.

• 패션비즈니스
• /
• 제12권2호
• /
• pp.28-41
• /
• 2008

Fashion style in movies delivers their image the atmosphere and becomes the means for containing the personality, spiritual world and inner thinking the characters in the movies and including its plot. When the American new cinema emerged in late 1960's and early 1970's in the American movie history, the new left wing which wants to overturn adult generation and the hippie culture which wants to escape from an existing system also emerged. Therefore, this study analyzed the fashion style in the movie 'Easy Rider (1969)', i.e. the representative new American movie which showed the isolation from adult generation and negative realities of the American society. From the movie, we can understand the young generation after the Vietnam war, i.e. baby boom generation, pursued the hippie culture as their young culture. With their strong self-consciousness, they formed their own lifestyle and values which are different from those of adult generation, and we can understand clothes were used as a tool to express their value system.

• 한국초등과학교육학회지:초등과학교육
• /
• 제25권2호
• /
• pp.159-166
• /
• 2006

Changes in the brain activities following pre-service elementary teachers' learning hypothesis-generation were investigated using the analysis of EEG relative power and EEG coherence. In this study, the experimental group (n=16) were trained using learning methods for hypothesis-generation and the control group(n=16) were trained using learning methods for hypothesis-reception over the course of 8 weeks. EEG was measured before and following the learning process for both groups. Decreased theta ($4{\sim}7.9Hz$)/alpha 1 ($8{\sim}9.9Hz$) power and increased alpha 2 ($10{\sim}l2.9Hz$)/beta ($13{\sim}29.9Hz$)/gamma ($30{\sim}50Hz$) power were showed in the experimental group. Additionally, many changes in brian activities were observed for theta, beta and gamma coherence in the experimental group. In particular, fronto-parietal coherence increased in the experimental group. These differences in brain activities between the two groups suggest that the learning for subjects' hypothesis generation presumably leads to interesting changes in some types of brain activities in pre-service elementary teachers.

• 대한치과보철학회지
• /
• 제19권1호
• /
• pp.55-60
• /
• 1981

Some physical properties of Ni-Cr based alloy for porcelain veneering were compared after repeated casting without the addition of any new alloy. The specimen were cast in a centrifugal caster with an oxygen-propane torch at optimum temperature. The obtained results were as follows: 1. The yield strength and hardness of the second generation were no significant differences compared with first generation but the yield strength and hardness of the third generation slightly decrased. 2. The ultimate tensile strength and elongation appeared to decrease slightly in second, third generations. 3. The tensile fractured facets of the first generation specimen were normal in all specimen, but in the second generation there were six tensile specimen out of ten, in the third there were four tensile specimen out of ten.

• 한국통신학회논문지
• /
• 제22권9호
• /
• pp.1854-1866
• /
• 1997

본 논문에서는 기존의 UIO순열을 이용하는 방법을 개선하여 비결정적 유한상태기계에서 시험 경우를 생성하는 방법에 대해서 소개하였으며, 시험 경우의 자동생성을 위해서 필수적인 사항인 적합성 관계의 형식적인 정의를 새롭게 정의하였다. 또한 프로토콜의 비결정적인 성질 때문에 시험기는 한 입력을 가했을 때 어떤 출력을 낼지 미리 시험기의 입장에서 알 수 없으므로 적응력있는 시험을 위해서 트리형태의 시험 경우를 생성하는 방법을 소개하였고 시험 경우를 입력과 출력을 분리해서 고려함으로써 시험 경우 기술 언어인 TTCN으로의 변환을 쉽게 하였다.

• 한국가시화정보학회지
• /
• 제21권1호
• /
• pp.94-102
• /
• 2023

Three design parameters were considered in this study: outlet nozzle angle (30°, 60°, 80°), neck length (1 mm, 3 mm), and flow rate (0.5, 0.6, 0.7, 0.8 lpm). A neck diameter of 0.5 mm induced cavitation flow at a venture nozzle. A secondary transparent chamber was connected after ejection to increase bubble duration and shape visibility. The bubble size was estimated using a Gaussian kernel function to identify bubbles in the acquired images. Data on bubble size were used to obtain Sauter's mean diameter and probability density function to obtain specific bubble state conditions. The degree of bubble generation according to the bubble size was compared for each design variable. The bubble diameter increased as the flow rate increased. The frequency of bubble generation was highest around 20 ㎛. With the same neck length, the smaller the CV number, the larger the average bubble diameter. It is possible to increase the generation frequency of smaller bubbles by the cavitation method by changing the magnification angle and length of the neck. However, if the flow rate is too large, the average bubble diameter tends to increase, so an appropriate flow rate should be selected.

• 전기학회논문지
• /
• 제66권4호
• /
• pp.605-612
• /
• 2017

One of the biggest environmental issues that our world has been facing is climate change. In order to cope with such environmental issues, the world is putting a great deal of effort into energy conservation. The building sector, in particular, consumes 36% of the energy consumed worldwide and emits considerable amount of greenhouse gases. Therefore, introduction of renewable energies in the building sector is highly recommended. Renewable energy sources that can be utilized in the building sector include sunlight, solar heat, geothermal heat, fuel cells and wind power. The wind power generation system which converts wind energy into electrical energy has advantages in that wind is an unlimited and pollution-free resource. It is suitable to be connected to existing buildings because many years of operational experience and the enhanced stability of the system have made it possible to downsize the electrical generator. In case of existing buildings, it is necessary to consider the live loads of the buildings to connect the wind power generation system. This paper, through the connection of the wind power generation with existing buildings, promotes reduction of greenhouse gas emissions and energy independence by reducing energy consumption in the building sector. In order to connect the wind power generation system with an exciting building, the live load of the building and the area of the rooftop should be considered. The installable model is selected by comparing the live load of the building and the load of the wind power generation system. The maximum number of the wind turbines that can be installed is obtained by considering the separation distance between the wind turbines within the area of the rooftop. Installations are divided into single installations and multiple installations of two different types of wind turbines. After determining the maximum installable number, the optimal model that can achieve the maximum annual power generation will be selected by comparing the respective total annual amount of the power generation of different models.