• 물과 미래
• /
• 제9권1호
• /
• pp.70-80
• /
• 1976

The efficient breakwater design requires a knowledge of the behaviour of the waves passing the breakwater. Wave Diffraction is an important factor and phenomeon in this behaviour. The diffraction ocean waves entering a gap in a breakwater normal to the incident wave direction in water of uniform depth has been investigated, applying a solution previously given in the author's paper, based on the theory of light diffraction by Sommerfeld. The wave profiles and heights on both the leeward side of the breakwater and the gap side have been studied and summarized in the form of diagrams with diffraction coefficients in range of x/L, y/L 0∼100, b/L=0.5∼12, with some extension of the diagrams made previously. The results of the theoretical approaches have not been experimentally verified. The theory ad computation methods with computer program in Fortran IV developed in this study make an efficient use for estimating the diffraction about a breakwater gap.

• 전자공학회지
• /
• 제38권1호
• /
• pp.56-67
• /
• 2011

As a result of quickly growing data, a digital transmission system is required to deal with the challenge of acquiring signals at a very high sampling rate, Fortunately, the CS (Compressed Sensing or Compressive Sensing) theory, a new concept based on theoretical results of signal reconstruction, can be employed to exploit the sparsity of the received signals. Then, they can be adequately reconstructed from a set of their random projections, leading to dramatic reduction in the sampling rate and in the use of ADC (Analog-to-Digital Converter) resources. The goal of this article is provide an overview of the basic CS theory and to survey some important compressed sensing applications in wireless communications.

• International Journal of Contents
• /
• 제13권2호
• /
• pp.29-34
• /
• 2017

Cloud computing is becoming an effective and efficient way of computing resources and computing service integration. Through centralized management of resources and services, cloud computing delivers hosted services over the internet, such that access to shared hardware, software, applications, information, and all resources is elastically provided to the consumer on-demand. The main enabling technology for cloud computing is virtualization. Virtualization software creates a temporarily simulated or extended version of computing and network resources. The objectives of virtualization are as follows: first, to fully utilize the shared resources by applying partitioning and time-sharing; second, to centralize resource management; third, to enhance cloud data center agility and provide the required scalability and elasticity for on-demand capabilities; fourth, to improve testing and running software diagnostics on different operating platforms; and fifth, to improve the portability of applications and workload migration capabilities. One of the key features of cloud computing is elasticity. It enables users to create and remove virtual computing resources dynamically according to the changing demand, but it is not easy to make a decision regarding the right amount of resources. Indeed, proper provisioning of the resources to applications is an important issue in IaaS cloud computing. Most web applications encounter large and fluctuating task requests. In predictable situations, the resources can be provisioned in advance through capacity planning techniques. But in case of unplanned and spike requests, it would be desirable to automatically scale the resources, called auto-scaling, which adjusts the resources allocated to applications based on its need at any given time. This would free the user from the burden of deciding how many resources are necessary each time. In this work, we propose an analytical and efficient VM-level scaling scheme by modeling each VM in a data center as an M/M/1 processor sharing queue. Our proposed VM-level scaling scheme is validated via a numerical experiment.

• 부모자녀건강학회지
• /
• 제15권1호
• /
• pp.39-49
• /
• 2012

Purpose: This study examined grandmothers' experience of child care with grandchildren to understand how it affects their stage of life based on the methodology of grounded theory. Methods: This study used grounded theory, a method of qualitative study, as the theoretical foundation. The subjects of this study were 10 grandmothers who have reared their grandchildren for at least 6 months and volunteered to participate in the study after listening to an explanation. Resources were collected through in-depth interviews and the interviews were recorded and dictated. Results: The core category of participants in this study was "solidifying the family relationship". There were five steps in the process of "solidifying the family relationship". The first step of process was "affection motion" of rearing to help their daughters. The second step was "conflict" due to physical constraint and burden of child care. The third step was "acceptance" based on compensation and support and the fourth step was "development" in search of their ego. The last step was "integration" of family relationship. Conclusion: This study provided basic data for appropriate nursing intervention to grandmother to care for their grandchildren according to the five steps of grandmother's child care experience process.

• 한국수자원학회논문집
• /
• 제34권6호
• /
• pp.587-596
• /
• 2001

본 연구는 우수를 생활용수로 활용하고 있는 도서지역의 재래적인 우수이용방법을 개선하고 안정적으로 생활용수를 공급할 수 있는 우수이용 시스템을 개발하는데 연구의 목적이 있다. 이를 위하여 연구의 대상지역으로는 제주도 지역을 선정하고 실제 강우 및 생활용수의 관계를 run이론을 이용하여 규명하고 그 결과는 우수이용 시스템의 집수면적과 탱크크기를 설계하는 기법을 제시하였다. 실제에 적용해 본 결과, 설계된 우수이용 시스템이 제주도지역에서 안정적으로 운영이 되는 것으로 나타났으며, 이는 제주도뿐만 아니라 다른 도서지역에서도 본 시스템의 적용이 가능한 것으로 판단되었다. 따라서 본 시스템을 도서 지역의 지붕개량사업과 연계시켜 시행할 때, 도서지역의 주거환경개선과 용수확보를 병행할 수 있는 효과가 기대된다.

• 한국수자원학회논문집
• /
• 제30권1호
• /
• pp.3-13
• /
• 1997

멱 유속 분포를 구하기 위해 개정 Prandtl 혼합 거리 이론이 이용되었으며, 여기에서 사용된 지수값의 범위는 1/4~1/7이었다. 이 개정된 유속분포를 이용하여 간단한 부유사 농도 분포식을 개발하였다. 미국 지질조사국이 리오그란데강에서 실측한 자료와 명목값인 $\beta$=1.0, $textsc{k}$=0.4, 그리고 가시관에 의해 얻어진 침강속도를 이용한 개정 농도식 계산결과와 실측지와의 비교는 양호한 편이었으며, 지수에 임의로 두배를 해주었을 경우에는 좋은 결과를 보였다. 적당한 $\beta$, $textsc{k}$, 그리고 침강속도를 선택하기 위해 더 많은 연구가 필요하지만 이러한 연구가 대규모 난류와 이차류 영향에 대한 설명을 할 수는 없을 것이다. 하지만 실용적인 측면에서 보면 어느 관측지점에 대한 매우 자세하고 특별하게 측정된 자료는 그 지점에 맞는 지수나 계수를 찾아낼 수도 있다.

• Wind and Structures
• /
• 제26권6호
• /
• pp.355-367
• /
• 2018

This paper studies the aerodynamic stability of a tensioned, geometrically nonlinear orthotropic membrane structure with hyperbolic paraboloid in sag direction. Considering flow separation, the wind field around membrane structure is simulated as the superposition of a uniform flow and a continuous vortex layer. By the potential flow theory in fluid mechanics and the thin airfoil theory in aerodynamics, aerodynamic pressure acting on membrane surface can be determined. And based on the large amplitude theory of membrane and D'Alembert's principle, interaction governing equations of wind-structure are established. Then, under the circumstance of single-mode response, the Bubnov-Galerkin approximate method is applied to transform the complicated interaction governing equations into a system of second-order nonlinear differential equation with constant coefficients. Through judging the frequency characteristic of the system characteristic equation, the critical velocity of divergence instability is determined. Different parameter analysis shows that the orthotropy, geometrical nonlinearity and scantling of structure is significant for preventing destructive aerodynamic instability in membrane structures. Compared to the model without considering flow separation, it's basically consistent about the divergence instability regularities in the flow separation model.

• 한국경영과학회지
• /
• 제39권2호
• /
• pp.141-154
• /
• 2014

It is widely confirmed that online retailers can obtain crucial resources and greater growth potential by depending on the external web portal sites as it is explained in resource dependence theory. Nevertheless, recent studies show that the effect of dependence may not always be beneficial for firms and stress the importance of finding relevant contingent factors. In this study, we identify and suggest that firms' age and niche width strategy, whether generalist or specialist, are contributing factors on moderating the positive relationship between resource dependence and firm growth. To test our hypotheses based on the theory, we have collected monthly web traffic data of online retailers and portals from March 2000 and July 2008. The empirical results lend support to our theory of the firm age having a negative interaction effect on web traffic dependence. Moreover, results verified that positive effect of depending on the portals may become greater if the online retailer is a specialist in terms of niche width.

• Human Ecology Research
• /
• 제55권2호
• /
• pp.205-219
• /
• 2017

This study redefines 'consumer privacy attitude and behavior discrepancy' that occurs in the transaction environment that exists between consumer and provider as 'consumer privacy paradox.' In this study, qualitative research was conducted based on grounded theory. This study explored how consumers react to a privacy paradox as well as looked into how to adapt to the negative and positive results that can be generated by the privacy paradox. 'Consumer privacy paradox' is the same as the existing privacy paradox in that consumers can utilize the resources of personal information to consume and benefit from the market environment. However, it differs from previous studies in that it examines the privacy paradox in terms of consumer influence and consumer experience. The results of the study are as follows. First, a paradigm model of the consumer privacy paradox was derived. Second, consumers used three types of strategies to rationalize themselves or maintain indifference or relief to cope with the consumer privacy paradox. Third, the possibility of damage and the responsibility for privacy protection were the mediators of the consumer privacy paradox. Fourth, the 'result' generated by the consumer privacy paradox showed four types of: non-response, satisfaction, commitment to change, and negative emotional experience. Fifth, there is a difference in strategies to respond to the consumer privacy paradox according to consumer types.

• 한국항해항만학회지
• /
• 제46권2호
• /
• pp.134-144
• /
• 2022

The development and operation of autonomous ships are spotlighted as a next-generation technology that will provide newbenefits for the maritime business during the fourth industrial revolution. To expand the adoption of autonomous ships, the much more interest of the nation and the industries will have to be changed to actual adoption in shipping companies. For this, it is judged that research to identify the factors impacting the adoption intention of autonomous ships should be preceded. However, most studies on autonomous ships have focused on developing the technology, revising the law, establishing policies, and managing human resources, with few studies on influencing factors in the adoption of autonomous ships. A model, to identify the factors that impact the intention to the adoption of autonomous ships, based on the theory of diffusion of innovation and the TOE framework was developed. The suggested model was verified through empirical analysis targeting the shipping companies and the marine industries in Korea. As the result of this study, it was found that top management support, financial slack, and competitive intensity significantly impacted the intention to adopt autonomous ships. Additionally, it was revealed that the overall awareness of autonomous ships among Korean shipping companies is poor.