• Journal of Korea Technology Innovation Society
• /
• v.18 no.4
• /
• pp.539-560
• /
• 2015

Korea has enacted the Performance Evaluation law on the R&D Programs since 2006. This study categorizes program size, program history, sustainability, self-evaluation result as antecedents, and analyze the relationship between the antecedents and Meta-evaluation result, the change rate of appropriations. The result shows that program size, program history, self-evaluation result have significant effect to the Meta-evaluation result. And Meta-evaluation result has significant effect to the change rate of appropriations. This study has implication that the performance evaluation system shows significant effect to the appropriations.

• Advances in nano research
• /
• v.4 no.2
• /
• pp.85-111
• /
• 2016

In this paper, the classical and non-classical boundary conditions effect on free vibration characteristics of functionally graded (FG) size-dependent nanobeams are investigated by presenting a semi analytical differential transform method (DTM) for the first time. Three kinds of mathematical models, namely; power law (P-FGM), sigmoid (S-FGM) and Mori-Tanaka (MT-FGM) distribution are considered to describe the material properties in the thickness direction. The nonlocal Eringen theory takes into account the effect of small size, which enables the present model to become effective in the analysis and design of nanosensors and nanoactuators. Governing equations are derived through Hamilton's principle and they are solved applying semi analytical differential transform method. The good agreement between the results of this article and those available in literature validated the presented approach. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as small scale effects, spring constant factors, various material compositions and mode number on the normalized natural frequencies of the FG nanobeams in detail. It is explicitly shown that the vibration of FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

• Geomechanics and Engineering
• /
• v.18 no.1
• /
• pp.49-58
• /
• 2019

The effect of microstructure on the permeability of two saturated marine clays was studied through a series of falling head permeability tests and mercury intrusion porosimetry (MIP) tests. The key findings from this experimental study include the following results: (1) The permeability of undisturbed specimens is larger than that of reconstituted specimens at the same void ratio due to different soil fabrics, i.e., the pore size distributions (PSDs), even though they have the similar variation law in the permeability versus void ratio. (2) Different permeabilities of undisturbed and reconstituted specimens at the same void ratio are mainly caused by the difference in void ratio of macro-pores based on the MIP test results. (3) A high relevant relation between $C_k$ ($C_k$ is the permeability change index) and $e*_{10}$, can be found by normalizing the measured data both on undisturbed or reconstituted specimens. Hence, the reference void ratio $e*_{10}$, can be used as a reasonable parameter to identify the effect of soil fabric on the permeability of saturated soft clays.

• Advances in aircraft and spacecraft science
• /
• v.10 no.1
• /
• pp.51-65
• /
• 2023

In this paper, the effect of deepness on in-plane free vibration behavior of a curved functionally graded (FG) nanobeam based on nonlocal elasticity theory has been investigated. Differential equations and boundary conditions have been developed based on Hamilton's principle. In order to figure out the size effect, nonlocal theory has been adopted. Properties of material vary in radial direction. By using Navier solution technique, the amount of natural frequencies has been obtained. Also, to take into account the deepness effect on vibrations, thickness to radius ratio has been considered. Differences percentage between results of cases in which deepness effect is included and excluded are obtained and influences of power-law exponent, nonlocal parameter and arc angle on these differences percentage are studied. Results show that arc angle and power law exponent parameters have the most influences on the amount of the differences percentage due to deepness effect. It has been observed that the inclusion of geometrical deep term and material distribution results in an increase in sensitivity of dimensionless natural frequency about variation of aforementioned parameters and a change in variation range of natural frequency. Finally, several numerical results of deep and shallow curved functionally graded nanobeams with different geometry dimensions are presented, which may serve as benchmark solutions for the future research in this field.

• 유체기계공업학회:학술대회논문집
• /
• 2004.12a
• /
• pp.583-589
• /
• 2004

One of noticeable features in the cross flow fan is that a working fluid passes through impeller blade twice without distinction between the inlet and exit angles. Also, it does produce higher circumferential velocity than other types of blade at the same flow rate in accordance with the application of the forward curved shape. However, a design theory for the cross-flow fan has not yet been formed owing to an eccentric vortex, which is the remarkable characteristics, occurred in a cross-flow fan. Furthermore, the eccentric vortex, which is difficult to control of the size and position, is the important cause of performance decrease. In this study, experiments are carried out to estimate the similarity of the cross-flow fan with various scales and rotational velocity changes. Pressure coefficients to flow coefficients with various scales of the cross-flow fan are plotted to research the application of the general similarity law of the turbomachinery in the cross-flow fan with Archimedes spital, which is the important factor haying an effect on it.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2017.11a
• /
• pp.54-55
• /
• 2017

The High-rise building has a problem the ventilation performance of natural ventilator by stack effect that it occurs by pressure difference. For that reason the study about natural smoke ventilator of High-rise building consistently needs. Therefore on this study does analysis of difference with abroad through investigate of Natrual smoke ventilator's law, it conducts of natural smoke ventilator's research on the actual condition. As a result on this study, in the case of abroad that it states more specific standards than domestic. Also the result of a field study, it shows that the natural smoke ventilator is installed same size and the number regardless of building's pressure difference.

• Smart Structures and Systems
• /
• v.17 no.5
• /
• pp.837-857
• /
• 2016

In the present study, for first time the size dependent vibration behavior of a rotating functionally graded (FG) Timoshenko nanobeam based on Eringen's nonlocal theory is investigated. It is assumed that the physical and mechanical properties of the FG nanobeam are varying along the thickness based on a power law equation. The governing equations are determined using Hamilton's principle and the generalized differential quadrature method (GDQM) is used to obtain the results for cantilever boundary conditions. The accuracy and validity of the results are shown through several numerical examples. In order to display the influence of size effect on first three natural frequencies due to change of some important nanobeam parameters such as material length scale, angular velocity and gradient index of FG material, several diagrams and tables are presented. The results of this article can be used in designing and optimizing elastic and rotary type nano-electro-mechanical systems (NEMS) like nano-motors and nano-robots including rotating parts.

• Advances in aircraft and spacecraft science
• /
• v.7 no.2
• /
• pp.169-186
• /
• 2020

Based upon differential quadrature method (DQM) and nonlocal strain gradient theory (NSGT), mechanical-hygro-thermal vibrational analyzes of shear deformable porous functionally graded (FG) nanoplate on visco-elastic medium has been performed. The presented formulation incorporates two scale factors for examining vibrational behaviors of nano-dimension plates more accurately. The material properties for FG plate are porosity-dependent and defined employing a modified power-law form. It is supposed that the nano-size plate is exposed to hygro-thermal and variable compressive mechanical loadings. The governing equations achieved by Hamilton's principle are solved implementing DQM. Presented results indicate the prominence of moisture/temperature variation, damping factor, material gradient index, nonlocal coefficient, strain gradient coefficient and porosities on vibrational frequencies of FG nano-size plate.

• Wind and Structures
• /
• v.27 no.6
• /
• pp.431-438
• /
• 2018

This paper presents a free vibration analysis of size-dependent functionally graded (FG) nanobeams with all surface effects considerations on the basis of modified couple stress theory. The material properties of FG nanobeam are assumed to vary according to power law distribution. Based on the Euler-Bernoulli beam theory, the modeled nanobeam and its equations of motion are derived using Hamilton's principle. An analytical method is used to discretize the model and the equation of motion. The model is validated by comparing the benchmark results with the obtained results. Results show that the vibration behavior of a nanobeam is significantly influenced by surface density, surface tension and surface elasticity. Also, it is shown that by increasing the beam size, influence of surface effect reduces to zero, and the natural frequency tends to its classical value.

• East Asian Economic Review
• /
• v.21 no.4
• /
• pp.385-432
• /
• 2017

This paper investigates how firm age, size and ownership are related with job creation and destruction, and how these patterns differ across transition and non-transition economies. The analysis finds that age is inversely related with gross job creation and net job creation in the two samples. This finding is consistent with the theory of the learning effect. The relationship between age and job destruction is indifferent in non-transition economies. On the contrary, old firms in transition economies destroy more jobs than young ones. The paper further establishes an inverse relationship between size and gross job creation in the two groups. However, there is divergence between the two samples; small firms in non-transition economies also exhibit a higher gross job destruction rate. Consequently large firms have a higher net job creation rate. In transition economies, small and large firms exhibit similar rates of job destruction. But small firms retain a higher net job creation rate. A more intriguing finding is that state owned firms do not underperform domestic private ones. This means these countries may be using soft budget constraint which allows state owned firms to overstaff. Finally, crowding out of SMEs by foreign owned firms is not evident in transition economies.