• Water for future
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• v.9 no.1
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• pp.70-80
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• 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.

• The Magazine of the IEIE
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• v.38 no.1
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• pp.56-67
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• 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
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• v.13 no.2
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• pp.29-34
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• 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.

• Korean Parent-Child Health Journal
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• v.15 no.1
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• pp.39-49
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• 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.

• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.587-596
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• 2001

The purpose of this study is to improve inefficient use of rainwater in island area where it uses rainwater to supply the domestic water and to propose rainwater utilizing system that is most appropriate to the characteristics of precipitation in Korea. To accomplish these purposes, Cheju island was chosen as a study area and the design for the roof area and tank size of rainwater utilizing system was based on the result of the relationship between the actual precipitation and domestic water data which was used in the analysis by run theory to use run theory. Since the result of the analysis indicated that the designed rainwater catchment system was operated stably in Cheju island, the same result is expected in other island too. Therefore, if this system is executed together with the roof rehabilitation work of island area, it will bring positive effects on broth the improvement of residental environment and the security of domestic water.

• Journal of Korea Water Resources Association
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• v.30 no.1
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• pp.3-13
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• 1997

Modifications of Prandtl's mixing length theory were used to obtain a power velocity distribution in which the coefficient and exponent are variable over a range from 1/4 to 1/7. A simple suspended-sediment concentration distribution was developed which can be associated with this modified velocity distribution. Using nominal values of ${\beta}$=1.0, $\kappa$=0.4 and visual accumulation tube values of fall velocity, the comparison between theory and field measurements by the USGS on the Rio Grande is fair. Doubling the value of the exponent results in a good comparison. Further research is needed to be able to better choose ${\beta}$, $\kappa$, and fall velocity values, but such research will not be able to account for the effects of large-scale turbulence and secondary flows. In a pragmatic sense, a special set of fairly detailed measurements can establish coefficients and exponents for any gaging site.

• Wind and Structures
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• v.26 no.6
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• pp.355-367
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• 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.

• Journal of the Korean Operations Research and Management Science Society
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• v.39 no.2
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• pp.141-154
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• 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
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• v.55 no.2
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• pp.205-219
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• 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.

• Journal of Navigation and Port Research
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• v.46 no.2
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• pp.134-144
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• 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.