• Steel and Composite Structures
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• 제18권1호
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• pp.187-212
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• 2015

In this paper, various four variable refined plate theories are presented to analyze vibration of temperature-dependent functionally graded (FG) plates. By dividing the transverse displacement into bending and shear parts, the number of unknowns and governing equations for the present model is reduced, significantly facilitating engineering analysis. These theories account for parabolic, sinusoidal, hyperbolic, and exponential distributions of the transverse shear strains and satisfy the zero traction boundary conditions on the surfaces of the plate without using shear correction factors. Power law material properties and linear steady-state thermal loads are assumed to be graded along the thickness. Uniform, linear, nonlinear and sinusoidal thermal conditions are imposed at the upper and lower surface for simply supported FG plates. Equations of motion are derived from Hamilton's principle. Analytical solutions for the free vibration analysis are obtained based on Fourier series that satisfy the boundary conditions (Navier's method). Non-dimensional results are compared for temperature-dependent and temperature-independent FG plates and validated with known results in the literature. Numerical investigation is conducted to show the effect of material composition, plate geometry, and temperature fields on the vibration characteristics. It can be concluded that the present theories are not only accurate but also simple in predicting the free vibration responses of temperature-dependent FG plates.

• 한국정보시스템학회지:정보시스템연구
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• 제22권1호
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• pp.65-87
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• 2013

The development and expansion of communication technology in the field of information technology (IT) have changed the method and culture of communication, mediating communication among people. In particular, since social network service (SNS) has the attributes of information delivery and processing, it has a more powerful dissipating effect and influence than other existing communication methods. The role of users in SNS is important because it has the communication structure of producer-consumer, which consists of sharing, connection and participation of users. In this line, the purpose of this study is to investigate the intention for continued use of SNS by user ability. In order to explain the motivation and behavior for continued use of SNS by users, this study employed the motivation theory and post-adaptation model. The study applied 'media literacy' to the characteristics of SNS media and environment and expanded it into the concept of 'SNS literacy' to identify the moderating effect by user ability. Referred to as 'user's ability that is required to use SNS,' the SNS literacy was verified for its moderating effect with the three sub-dimensions: 'technical accessing ability,' 'understanding ability' and 'creative ability.' The major findings of this study are as follows. First, the perceived usefulness and playfulness were found to have a significant effect on the intention for continued use of SNS, showing the same result with previous studies on technology acceptance. In other words, usefulness and playfulness are variables with an explanatory power in the SNS environment as well. Second, the conceptualization of SNS literacy with accessing ability, understanding ability and creative ability was found to be valid. Third, it was verified that there was a significant difference in the SNS literacy between perceived usefulness and continued use, indicating that users with higher ability respond sensitively to usefulness and affect continued behavior. The moderating effect of SNS literacy was also verified in the relationship between perceived playfulness and intention for continued use. The results above confirm the difference in post-adaptation behavior of individuals, and are expected to provide several implications.

• 한국건설관리학회논문집
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• 제15권1호
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• pp.70-77
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• 2014

건설프로젝트의 성공적인 수행을 위해 의사소통, 협력, 정보공유 등을 포함한 구성원들 간의 협업은 반드시 필요하다. 그러나 프로젝트 조직 내의 협업과정이 성과에 미치는 영향에 대한 분석적인 시도는 부족하였다. 본 연구는 게임이론 기반의 에이전트기반 시뮬레이션을 활용하여 프로젝트 조직 내 협업과정을 보다 명시적으로 이해하는 방법을 제시하였다. 시뮬레이션의 결과로 구성원수준에서의 관계형성과 조직수준에서의 네트워크 발전양상을 관찰할 수 있었다. 본 연구는 프로젝트조직 내의 협업과정 분석방법 개발을 위한 기초연구이며, 향후 연구를 통해 조직 내 업무수행 프로세스, 생산작업 프로세스, 관리 프로세스 등의 부분과 결합하여 프로젝트 성과를 예측하는 방법으로 발전될 수 있을 것이다.

• 공학교육연구
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• 제7권4호
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• pp.32-37
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• 2004

공학인으로 갖추어야 할 능력 중에서 문제를 인식하고, 이를 공식화 한 후 창의적이며 체계적으로 해결해 나갈 수 있는 능력을 길러주기 위한 방법으로 설계교육을 체계적으로 해 가는 것이 효과적이다. 이를 위하여 본 대학에서는 1학년에서 창의력을 길러주며, 효과적인 설계 추진 과정을 길러주기 위한 공학설계입문을 개설하여 운영하고 있다. 또한 나머지 학년에서도 실험과 설계가 융합된 과목, 이론과 설계가 융합된 과목을 개설하여 각종 설계문제를 해결하도록 교육하고 있다. 본 논문에서는 2학년의 교과목 중 기존의 실험실습 과목을 실험과 설계가 융합된 새로운 개념의 과목으로 개편하여 지난 2년간 운영해온 실적을 분석하여 공학인증에서 요구하는 학습성과 중 팀원으로써의 역할 수행능력이 증가함을 보여준다. 뿐만 아니라, 교과운영 내용을 비교적 상세히 소개하여 공학인증에서 요구하는 설계교육을 효율적으로 운영하는 예시를 보여주며, 주요한 학습성과를 달성하는 한 방법을 제시한다.

• 산업경영시스템학회지
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• 제4권5호
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• pp.15-26
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• 1981

While one characteristic of modern enterprises is that their forms are mostly stock company type profit organization the other characteristic is that such modern enterprises have mostly been managing under separation between capital and management. The term "Separation of ownership and Management" means that a company is controlled and managed not by its financier or investor but by the professional manager equipped with scientific management skill and knowledge. Nowadays, separation between capital and management could be adopted by advent of professional managers, and the enterprises are managed not exclusively by the interested group of stockholders but by the professional managers Professional managers can manage their enterprises in such a way as to guarantee to achieve sociality and public interests required in the modern enterprises. The purpose of this study is to formalize management ideology of enterprises in Daegu Area by means of comparative study on the degree of separation of ownership and management among enterprises in the United States, Japan and Daegu Area, thus to advise enterprising men of management idea-logy formalized. Findings from the comparative study are as follows 1. There are differences in staffing and financing between enterprises of the United States and those of Japan and Daegu Area. 2. Degree of Separation of ownership and management in Japan and Daegu Area is much less than that of the United States, and 3. The degree of separation of ownership and management is higher in open enterprises in Daegu Area. Accordingly. enterprises in Daegu Area should adopt up-to-data management theory and techniques in order to be developed themselves, and furthermore, to contribute to both the nation and the local community in economic development. In modern industrial society, the scale enterprise organization is growing very rapidly and the managerial circumstances are very much complicate and variable , thus the demand for the competent managers equipped with management knowledge and ability are high. The necessity of systematic and efficient managerial training is social demand needed urgently in modern industrial society. Therefore, it is necessary for the enterprising men in Daegu Area to establish cooperation system between university and industry in which they can participate voluntarily.luntarily.

• 한국환경복원기술학회지
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• 제6권3호
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• pp.17-28
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• 2003

The objective of this study is to review and verify whether the functions and effect of roadside trees generally known in theory are actually realized in urban roads and how well they are performed if the function and effect are really realized. The study was conducted with a focus on air purification effect of roadside trees. The m헤r study result is as follows. First, calculation of air purification effect of roadside trees showed that it is minimal. However, 7.4 units of broad-leaved trees is necessary in order to purify $SO_2$ discharged by one passenger car and 1,803.3 trees to purify $NO_2$. Second, regarding pollutant absorption capacity, air pollutant absorption capacity increased as the number of rows planted gets higher (i.e., 2-row plantation absorbs pollutant better than I-row plantation). In particular, "2-row plantation + lower-level shrub + buffer green belt" was as eight times high as "I-row plantation" in absorption capacity. Third, out of 30 roads with over 8 lanes in 15 cities, only 33.3% or a total of ten roads in seven cities had a median strip. Out of these ten roads, nine roads were planted in a double-layer consisting forest trees, shrubs, ground plants (grass). Analysis showed that out of six tree species planted along these roads, about a half of them were weak to air pollution. Also, based on the outcome of this study, charging a "plantation due" when people purchase a new car, improving layout of roadside trees, and reinforcing plantation of air purification tree species when selecting tree species for roadside trees were proposed.

• 한국IT서비스학회지
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• 제11권2호
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• pp.19-47
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• 2012

Contemporary smartphone competition is generally described as the battle between Apple's proprietary platform and Google's open platform. However, this competition is not limited within smartphone adoption itself. User's pre-adoption of one mobile platform via smartphone can be connected to the post-adoption of the same mobile platform based on the other smart devices (e.g. smart pad). In this study, we investigate whether user's preference to a certain platform is persistent over mobile ecology, from the pre-adoption of one smart device to the post-adoption of following devices. For this investigation, we adopt the dual-model as the ground theory, where post-adoption of IT product is explained by both dedication and constraint factors. The empirical testing first evidences that dual model works well as our research model for identifying the reasons of post-adoption. Next, we group our data into two parts in order to compare the switching behavior of iPhone users and Android phone users. iPhone users show much lower switching rate to Android based smart pads, while Android phone users show higher churn rate to iPad (49.3% : 96.3%). Especially, satisfaction showed much stronger effect than switching cost on the continuing intention of existing platform, when the analysis is given to the iPhone user's group. From this result, we can conjecture the relatively stronger loyalty of iPhone users. More managerial implications on the mobile platform strategy are driven.

• 한국수자원학회논문집
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• 제42권6호
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• pp.433-443
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• 2009

토양수분에 관한 관심이 급증하면서 토양수분의 시공간적 특성을 이해하고자 하는 연구가 최근 꾸준히 일어나고 있다. 토양수분의 보다 나은 이해를 위해, 본 연구에서는 이에 대한 동역학을 추계학적 기법을 이용하여 기후변화에 따른 영향평가에 대한 적용을 염두에 둔 추계학적 토양수분모형을 제시하고자 하였다. 보다 현실적인 적용을 위하여 손실항을 세 가지로 구분하여 고려하였고 강우의 추계학적인 특성 역시 고려하였다. 모의 결과 본 연구에서 유도한 토양수분 모형으로 관측 자료를 적절하게 재현 할 수 있으며 토양수분이 계절별로 강수의 패턴에 따라 일정한 순환의 형태를 가짐을 재현하였다. 또한 CGCM3.1 자료를 이용한 미래 토양수분 상태 예측으로, 토양수분의 변동성이 현재보다 커질 것으로 예측되었다.

• 한국정보과학회논문지:시스템및이론
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• 제27권1호
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• pp.34-43
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• 2000

중복 데이타는 분산 시스템에서 결함을 포용하는 방법 중 하나로 여러 복사본들의 일관성을 유지하기 위하여 복제 제어 프로토콜(replica control protocol)을 필요로 한다. 복제 제어 프로토콜 중 정 족수 동의 기법(quorum consensus method)은 정족수 이상의 동의를 얻어서 데이타에 접근하는 방법이다. 그런데 사이트나 통신 링크의 실패로 인하여 정족수 이상의 동의를 얻을 수 없으면 데이타 접근이 불가능하게 되므로 부족한 정족수를 고스트(ghost)로 대치하는 방법이 필요하다. 고스트는 메타 데이타(meta data)에 상태 정보만을 저장한 프로세스이기 때문에 생성과 관리의 비용을 줄이려면 메타 데이타를 간략화 시키는 것이 중요하다. 따라서 본 논문에서는 동료 집합을 이용하여 메타 데이타를 구성하는 방법을 제안한다. 제안된 방법은 2N+logN 비트만으로 메타 데이타를 구성할 수 있게 하고 동료 집합만을 이용하는 프로토콜이나 동적 선형 보우팅 프로토콜보다 향상된 가용성을 나타낸다. 제안된 방법의 가용성은 마코브 모델(Markov model)을 이용하여 측정하고 그 결과를 다른 프로토콜들과 비교 분석한다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2013년도 제44회 동계 정기학술대회 초록집
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• pp.159-159
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• 2013

Atomically thin graphene is the ideal model system for studying nanoscale friction due to its intrinsic two-dimensional anisotropy. Furthermore, modulating its tribological properties could be an important milestone for graphene-based micro and nano-mechanical devices. Here, we report that the tribological properties can be easily altered via simple chemical modifications of the graphene surface. Friction force microscopy measurements show that hydrogenated, fluorinated, and oxidized graphenes exhibit, 2-, 6-, and 7-fold enhanced nanoscale friction on their surfaces, respectively, compared to pristine graphene. The measured nanoscale friction should be associated with the adhesive and elastic properties of the chemically modified graphenes. Density functional theory calculations suggest that, while the adhesive properties of chemically modified graphenes are marginally reduced down to ~30%, the out-of-plane elastic properties are drastically increased up to 800%. Based on these findings, we propose that nanoscale friction on graphene surfaces is characteristically different from that on conventional solid surfaces; stiffer graphene exhibits higher friction, whereas a stiffer three-dimensional solid generally exhibits lower friction. The unusual friction mechanics of graphene is attributed to the intrinsic mechanical anisotropy of graphene, which is inherently stiff in plane, but remarkably flexible out of plane. The out-of-plane flexibility can be modulated up to an order of magnitude by chemical treatmentof the graphene surface. The correlation between the measured nanoscale friction and the calculated out-of-plane flexibility suggests that the frictional energy in graphene is mainly dissipated through the out-of-plane vibrations, or the flexural phonons of graphene.