Research has been conducted on acoustic metamaterials that control the transmission characteristics of reflected and refracted waves using phase delay by resonators. Using one-dimensional theory, the phase delay equations for the 1/4 wavelength and Helmholtz resonator are presented. These one-dimensional analysis results are compared with the results predicted by three-dimensional FEM. The advantages and disadvantages of 1/4 wavelength and Helmholtz resonator were confirmed in implementing phase delay. An acoustic metamaterial with a refraction angle of 30° was manufactured using multiple tubes and then the sound pressure distribution was measured. A relatively large sound pressure was measured at the target position of 30°, which was compared with the 3D FEM analysis results. Simulations confirmed that a phase delay range closer to 2π was more effective in refraction, but varying the number of resonators was found to have minimal impact on which additional research is needed for generalization.

우리나라는 근래에 들어 도시화가 급격하게 진행되고 도시 인구 밀집현상으로 인해 빗물이 땅속으로 스며들 지 못하는 불투수면이 확대되고 하전부지 및 산림습지의 감소가 급속히 진행되고 있다. 그로 인하여 저류 및 침 투수가 감소하게 되고 기후변화로 인한 기온 상승으로 물 순환의 균형이 파괴되어 도시지역의 열섬화 및 지하 수 고갈에 따른 하천의 건천화에 따른 문제점을 해결하기 위해 새로운 빗물관리가 필요하게 되었다. 따라서 본 연구는 빗물관리 방식의 사회적 환경 변환에 적합한 저류 기능과 투수기능, 지반침하에 따른 블록의 내구성 및 안전성 문제를 해결하기 위한 목적적으로 블록의 디자인 시 강도를 저해하지 않으면서 블록의 자중을 감소시키고, 저류 공간을 불록부피의 20%정도까지 빗물 저류 할 수 있고, 투수성이(투수 계수 ≥3㎜/sec) 향상된 블록을 설계하여 상부에서 침투된 빗물이 쉽게 하부로 전달될 수 있도록 하부기 층의 입도(open grade) 및 기층의 깊이를 달리하여 지역의 상황에 적합하도록 시험하였으며 또한 현장의 시공성 향상을 위해 매트 개념을 도입하여 현장 적용성 평가를 수행하였다.

The established supply chain format has been radically changing from a three-month production to a shortened lead-time in the fashion industry. The faster pace of fashion trends, changing consumer lifestyle, and consequent demands for newness have been mainly attributed to the rapid development of high-tech information systems and mass communication. In particular, global fast-fashion leaders have become more successful by producing not as was initially planned and forecasted, but with an agility subject to customer responses. Latest customer trends are captured quickly, and production and distribution is steered to meet the response. In order to further maximize benefits and efficiency in a sustainable manner, the fast-fashion industry is seeking a production optimization model under which product attributes are defined in a short period of time, and an optimal quantity of products by style is produced. This paper aims to provide an optimal production quantity which subsequently requires an optimal parts procurement from the perspective of the supplier. This is obtained in order to minimize the cost function by identifying cost factors through an economic analysis technique. In this study, we propose a model for optimal production and its parts procurement to maximize target sales and profits by taking inventory and pricing into account.

  Automobile manufacturing companies should provide the products and service that can satisfy consumers who usually want various kinds of automobiles. This paper studied the relations among several demographic characteristics(gender, age, occupation, inco

선진국일수록 서비스 산업의 비중이 큰 것은 주지의 사실이다 선진국 진입을 위해 진력하는 한국의 입장애서 신 진국 서비스 산업의 연구 및 정보는 긴요하다 이 연구는 세계 400 대 최량 기업들 중 서비스 기업들의 다양한 경영 업적들이 서비스 산업의 여러 분야와 그 하부 부문에서 어떻게 나타나고 있는지를 기술통계, 분산분석, 던칸 검정 등을 활용해 분석하였다 이로써 서비스 산업 분야에 대한 진입, 투자, 벤치마킹 등에 관해 활용할 수 있는 유의 한 결과들을

In today's mass production/consumption society, there are many important constituents people need to have/do for their happy life. Very few people think that among those components enjoying pro-sports in their life is essential, and Many business companie