• International Journal of Aeronautical and Space Sciences
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• 제15권3호
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• pp.241-257
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• 2014

The modern development in design of airships and aerostats has led to unconventional configurations quite different from the classical ellipsoidal and spherical ones. This new class of air-vehicles presents a mass-to-volume ratio that can be considered very similar to the density of the fluid displaced by the vehicle itself, and as a consequence, modeling and simulation should consider the added masses in the equations of motion. The concept of added masses deals with the inertia added to a system, since an accelerating or decelerating body moving into a fluid displaces a volume of the neighboring fluid. The aim of this paper is to provide designers with the added masses matrix for more than twenty Lighter Than Air vehicles with unconventional shapes. Starting from a CAD model of a given shape, by applying a panel-like method, its external surface is properly meshed, using triangular elements. The methodology has been validated by comparing results obtained with data available in literature for a known benchmark shape, and the inaccuracies of predictions agree with the typical precision required in conceptual design. For each configuration, a CAD model and a related added masses matrix are provided, with the purpose of assisting the practitioner in the design and flight simulation of modern airships and scientific balloons.

• 복식
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• 제64권6호
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• pp.161-175
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• 2014

This paper investigates the differences between characteristics of street fashions due to regional and cultural differences in southern and northern region of China. Beijing and Shenzhen were chosen as representative cities for the two areas. Empirical research and literature study were performed for this study. Empirical studies were performed by using a total of 708 images of dresses, which were collected through direct imaging. Through discussion with experts, the collected data were classified into five categories; Modern trendy, Romantic, Easy casual, Ethnic, and Classical/Traditional. The data was analyzed by using cross tabulation and frequency analysis. Content analysis for each category was also conducted. As a consequence of this study, a significant difference between Beijing and Shenzhen were observed. As a city, which puts emphasis on practicality and modernity, Beijing showed a higher frequency of modern and trendy style than the other city. On the other hand, Shenzhen showed a higher frequency of romantic style and was distinguished as a city of femininity and decorative preference of fashion style. This study intends to contribute to the academic community of Chinese fashion and to help Korean clothing companies to be launched in Chinese market in the future.

• 한국소음진동공학회논문집
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• 제22권9호
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• pp.817-824
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• 2012

정밀 시스템에 전달되는 진동은 시스템의 성능 저하 및 오작동을 초래할 수 있기 때문에 저감되어야 한다. 진동을 저감시키는 가장 일반적인 방법은 진동이 전달되는 경로에 수동 진동 절연 장치를 도입함으로 전달되는 진동을 절연시키는 방법이다. 탄성소자와 점성 감쇠기로 구성된 일반적인 수동 진동 절연 장치는 공진에서의 전달률을 낮추기 위해서 고주파수 대역에서 진동 절연 성능을 희생해야 하는 단점을 지니고 있다. 이 논문에서는 공진에서 낮은 전달률과 고주파수 대역에서 높은 진동 절연 성능을 동시에 가진 수동 진동 절연 장치들의 특성을 비교 분석하였다.

• Smart Structures and Systems
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• 제19권3호
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• pp.243-257
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• 2017

In this paper, free vibration of functionally graded (FG) size-dependent nanobeams is studied within the framework of nonlocal Timoshenko beam model. It is assumed that material properties of the FG nanobeam, vary continuously through the thickness according to a power-law form. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The non-classical governing differential equations of motion are derived through Hamilton's principle and they are solved utilizing both Navier-based analytical method and an efficient and semi-analytical technique called differential transformation method (DTM). Various types of boundary conditions such as simply-supported, clamped-clamped, clamped-simply and clamped-free are assumed for edge supports. The good agreement between the presented DTM and analytical results of this article and those available in the literature validated the presented approach. It is demonstrated that the DTM has high precision and computational efficiency in the vibration analysis of FG nanobeams. The obtained results show the significance of the material graduation, nonlocal effect, slenderness ratio and boundary conditions on the vibration characteristics of FG nanobeams.

• 건축역사연구
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• 제17권4호
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• pp.83-95
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• 2008

This study was firstly to reflect upon the background of the generation and the urban spatial value and significance of the medieval plaza. The main aim of this study was to extract the spatial determinants which give the great influence on the formation of the medieval plaza and in addition the endogenous rules and aesthetical grounds regarding the respective elements. Especially they could be applied to the design guideline. They are dimension(volume and scale), shape, elevation as the morphological elements and enclosure, proportion, grade difference, spatial sequence and plaza group as the spatial determinants and visual sequence, visual or spatial boundary, approaching axis and perspective effect as the aesthetic and visual elements and function(use), human behaviour as the social-behavioral elements and otherwise, for instance, plaza furniture, ground decoration and vegetation. This study was intended to analyze each elements based on the classical historical literatures and to suggest the planning conditions for composing the ideal plaza referring to the cases and literature review on the medieval plaza and finally is expected to contribute to the plaza design methodology.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.232-237
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• 2012

정밀 시스템에 전달되는 진동은 시스템의 성능 저하 및 오작동을 초래할 수 있기 때문에 저감되어야 한다. 진동을 저감시키는 가장 일반적인 방법은 진동이 전달되는 경로에 수동 진동절연 장치를 도입함으로 전달되는 진동을 절연시키는 방법이다. 탄성소자와 점성 감쇠기로 구성된 일반적인 수동 진동 절연 장치는 공진에서의 전달율을 낮추기 위해서 고주파수 대역에서 진동 절연 성능을 희생해야 하는 단점을 지니고 있다. 본 논문에서는 공진에서 낮은 전달율과 고주파수 대역에서 높은 진동 절연 성능을 동시에 가진 수동 진동 절연 장치들의 특성을 비교 분석하였다.

• 한국지반환경공학회 논문집
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• 제4권2호
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• pp.93-104
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• 2003

Porous media consist of physically and chemically different materials and have an extremely complicated behavior due to the different material properties of each of its constituents. In addition, the internal structure of porous materials has generally a complex geometry that makes the description of its mechanical behavior quite complex. Thus, classical continuum mechanics cannot explain the behavior of materials with pore spaces, such as concrete, soils and organic materials in waste landfill. For these reasons, porous media theory has been developed in the nineteenth century. Biot had the greatest influence on the development of porous media theory. Biot's work has been referred by many authors in the literature. Development of numerous fundamental equations in porous media theory were made possible due to Biot's work. His contributions made the greatest influence on porous media theory. Therefore, it is highly advantageous to review Biot's publications. This work presents a review of Biot's work. It shows how porous media theory has been developing so far and provides a chance to discuss the contribution of his work to the modern porous media theory.

• Steel and Composite Structures
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• 제16권6호
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• pp.577-593
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• 2014

An exact dynamic stiffness method is introduced for investigating the free vibration characteristics of the steel-concrete composite beams consisting of a reinforced concrete slab and a steel beam which are connected by using the stud connectors. The elementary beam theory is used to define the dynamic behaviors of the two beams and the relative transverse deformation of the connectors is included in the formulation. The dynamic stiffness matrix is formulated from the exact analytical solutions of the governing differential equations of the composite beams in undamped free vibration. The application of the derived dynamic stiffness matrix is illustrated to predict the natural frequencies and mode shapes of the steel-concrete composite beams with seven boundary conditions. The present results are compared to the available solutions in the literature whenever possible.

• Structural Engineering and Mechanics
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• 제63권2호
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• pp.161-169
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• 2017

In this paper, using consistent couple stress theory and Hamilton's principle, the free vibration analysis of Euler-Bernoulli nano-beams made of bi-directional functionally graded materials (BDFGMs) with small scale effects are investigated. To the best of the researchers' knowledge, in the literature, there is no study carried out into consistent couple-stress theory for free vibration analysis of BDFGM nanostructures with arbitrary functions. In addition, in order to obtain small scale effects, the consistent couple-stress theory is also applied. These models can degenerate into the classical models if the material length scale parameter is taken to be zero. In this theory, the couple-tensor is skew-symmetric by adopting the skew-symmetric part of the rotation gradients as the curvature tensor. The material properties except Poisson's ratio are assumed to be graded in both axial and thickness directions, which it can vary according to an arbitrary function. The governing equations are obtained using the concept of Hamilton principle. Generalized differential quadrature method (GDQM) is used to solve the governing equations for various boundary conditions to obtain the natural frequencies of BDFG nano-beam. At the end, some numerical results are presented to study the effects of material length scale parameter, and inhomogeneity constant on natural frequency.

• 한국실내디자인학회논문집
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• 제22권5호
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• pp.179-187
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• 2013

The purpose of this study was to explain the uniqueness of tropical space style by identifying it in Southeast Asia. For this purpose, literature review was examined from 26 specialized tropical space style books and categorized. Its results are expected to be used as reference materials in designing spaces related to Southeast Asia and for constructors planning to run their business in Southeast Asia or Korea. The results of categorization are as follows; 'Tropical Traditional', 'Tropical Colonial' and 'Tropical Modern'. First, in case of Tropical Traditional Style, the traditional styles are adopted in roof and some of traditional styles are adopted in walls, windows and doors. Second, in case of Tropical Colonial Style, Renaissance or neo-classical styles are adopted in most of columns, archs, windows and doors. The traditional styles are also blended. Third, in case of Tropical Modern Style, straight line designs are adopted dominantly. However, decorative objects of traditional style are used to catch eyes. In summary, traditional style are imbedded more or less in all of tropical style and particularly, decorative objects of traditional style are key elements representing tropical space.