• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.11
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• pp.1640-1649
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• 2001

The present study investigates the effects of various rib arrangements on heat/mass transfer in the cooling passage of gas turbine blades. A complex flow structure occurs in the cooling passage with rib turbulators which promote heat transfer on the wall. It is important to increase not only the heat transfer rates but also the uniformity of heat transfer in the cooling passage. A numerical computation is performed using a commercial code to calculate the flow structures and experiments are conducted to measure heat/mass transfer coefficients using a naphthalene sublimation technique. A square channel (50 mm $\times$ 50 mm) with rectangular ribs (4 mm $\times$ 5 mm) is used fur the stationary duct test. The experiments focus on the effects of rib arrangements and gap positions in the discrete ribs on the heat/mass transfer on the duct wall. The rib angle of attack is 60°and the rib-to-rib pitch is 32 mm, that is 8 times of the rib height. With the inclined rib angle of attack (60°), the parallel rib arrangements make a pair of counter rotating secondary flows in the cross section, but the cross rib arrangements make a single large secondary flow including a small secondary vortex. These secondary flow patterns affect significantly the heat/mass transfer on the ribbed wall. The heat/mass transfer in the parallel arrangements is 1.5 ∼2 times higher than that in the cross arrangements. However, the shifted rib arrangements change little the heat/mass transfer from the inline rib arrangements. The gap position in the discrete rib affects significantly the heat/mass transfer because a strong flow acceleration occurs locally through the gap.

• The Journal of the Korea Contents Association
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• v.11 no.3
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• pp.9-17
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• 2011

Recently, with the advent of stereoscopic 3D TV, the activation of 3D stereoscopic content is expected. Research on 3D auto stereoscopic display has been carried out to relieve discomfort of 3D stereoscopic display. In this research, it is necessary to generate the elemental image from a lens array. As the number of lens in a lens array is increased, it takes a lot of time to generate the elemental image, and it will take more time for a large volume data. In order to improve the problem, in this paper, we propose a method to generate the elemental image by using OpenCL based on CUDA. We perform our proposed method on PC environment with one of Tesla C1060, Geforce 9800GT and Quadro FX 3800 graphics cards. Experimental results show that the proposed method can obtain almost 20 times better performance than recent research result[11].

• Plant Biotechnology Reports
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• v.4 no.1
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• pp.85-94
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• 2010

In vitro shoot regeneration of gladiolus in three different culture systems, viz., semi-solid agar (AS), membrane raft (MR), and duroplast foam liquid (DF) cultures was evaluated following the kinetics of shoot multiplication and hyperhydricity at optimized growth regulator combinations. Compared to the AS system, matrixsupported liquid cultures enhanced shoot multiplication. The peak of shoot multiplication rate was attained at 18 days of incubation in the MR and DF systems, whereas the maximum rate in the AS system was attained at 21 days. An early decline in acceleration trend was observed in liquid cultures than the AS culture. The hyperhydric status of the regenerated shoots in the different culture systems was assessed in terms of stomatal attributes and antioxidative status. Stomatal behavior appeared to be normal in the AS and MR systems. However, structural anomaly of stomata such as large, round shaped guard cells with damage in bordering regions of stomatal pores was pronounced in the DF system along with a relatively higher $K^+$ ion concentration than in the AS and MR systems. Antioxidative status of regenerated shoots was comparable in the AS and MR systems, while a higher incidence of oxidative damages of lipid membrane as evidenced from malondialdehyde and ascorbate content was observed in the DF system. Higher oxidative stress in the DF system was also apparent by elevated activities of superoxide dismutase, ascorbate peroxidase, and catalase. Among the three culture systems, liquid culture with MR resulted in maximum shoot multiplication with little or no symptoms of hyperhydricity. Shoots in the DF system were more prone to hyperhydricity than those in the AS and MR systems. The use of matrix support such as membrane raft as an interface between liquid medium and propagating tissue could be an effective means for rapid and efficient mass propagation with little or no symptoms of hyperhydricity.

• Journal of the Korean Geotechnical Society
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• v.28 no.4
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• pp.115-124
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• 2012

The responses of stone column-improved ground under seismic loading are investigated using a series of 1g shaking table tests. These tests show similar results to those of one dimensional numerical models for stone column-improved ground based on Baez's assumption on the soil and stone-column interaction. The experimental and numerical results show that the stone column can prevent large shear deformations incurred due to cyclic softening in clayey deposits, but they also show that the surface acceleration in the improved clayey deposits may amplify more than that in unimproved clayey deposits when subjected to short periodic seismic motions.

• Design & Manufacturing
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• v.10 no.1
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• pp.41-45
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• 2016

Electrical equipment in factories, buildings, etc. with the development of the industry has become a large capacity. By the development, electric load also become diversified and there is also highly functional requirements being electrical equipment. Particularly in the small and medium-sized circuit breakers, tend to preferentially consider the economy stands out and improvements in safety, ease of mounting and connection through the modularity of the basic dimensions compact and cost to block expansion of the scope of the development of capacity, etc. The product having a competitive has been strongly required. In order to implement the circuit breakers of breaking capacity and compact at the same time taking into account the economic development of this technology applied to the current-limiting mechanism is essential budget or the current limiting mechanism is currently available mechanisms applicable to small and medium-sized frame (frame) can not do it. In this paper, at the same time satisfying the economic efficiency, by minimizing the load force of the moving contactor (moving contactor) to be applied to small and medium frame other hand to secure the economical efficiency without using high speed contact parting acceleration of the moving contactor conventional current-limiting mechanism, and to develop a current-limiting mechanism that can be satisfied with the same or higher performance to meet the needs of the market.

• Journal of Biosystems Engineering
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• v.16 no.3
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• pp.228-238
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• 1991

Cam plays very important roles due to continuous requirement for the high-speed and automation of the machinery. A large number of studies of cam curve were carried out by many researchers, and CNC milling and machining center for manufacturing cam have been widely used recently. The purpose of this study was to develop a CAD/CAM system for cam using QuickBasic language in 16-bit PC for application of cam design and manufacturing. Results obtained were as follows : 1. It was possible to input data by entering cam angle and its corresponding R, from 0 to 360 deg. of cam angle. The tediousness at entering data was minimized because of the same data format for both cylindrical cam and disc cam, and free format used for data file. 2. It was possible to design cam by choosing only the number of cam curve because of developing the CAD/CAM program with dimensionless method of cam curves including widely used 19 kinds. After selecting the number of the cam curve, the CAD/CAM system automatically shows the characteristics of cam motion enough to help a designer to decide : displacement, velocity, acceleration and jerk. 3. It was possible to execute, in an efficient way, both the cam profile synthesis and the generation of NC program for CNC machining center by using the input data. 4. This NC program generated by the CAD/CAM system developed here, was evaluated as positive in relation with actual manufacturing experiments and thought to be useful in its application without any modification. It can be said that this CAD/CAM system could be used by the beginners to design and manufacture the cam automatically as the system consists of very simple dialogue methods. In addition, self-developed QuickBasic would be would used as a basic tool for further stuides in this area of research, together with application.

• Journal of Biosystems Engineering
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• v.39 no.1
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• pp.21-33
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• 2014

Background: Significant technological development and changes happened in the tractor industries. Contrariwise, the test procedures of the major standard development organizations (SDO's) remained unchanged or with a little modification over the years, demanding new tractor test standards or improvement of existing ones for tractor performance, safety, and comfort. Purpose: This study focuses on reviewing the research trends regarding performance, safety and comfort evaluation of agricultural tractors. Based on this review, few recommendations were proposed to revise or improve the current test standards. Review: Tractor power take-off power test using the DC electric dynamometer reduced human error in the testing process and increased the accuracy of the test results. GPS signals were used to determine acceleration and converted into torque. High capacity double extended octagonal ring dynamometer has been designed to measure drawbar forces. Numerical optimization methodology has been used to design three-point hitch. Numerous technologies, driving strategies, and transmission characteristics are being considered for reducing emissions of gaseous and particulate pollutants. Engine emission control technology standards need to be revised to meet the exhaust regulations for agricultural tractors. Finite Element Analysis (FEA) program has been used to design Roll-Over Protective Structures (ROPS). Program and methodology has been presented for testing tractor brake systems. Whole-body vibration emission levels have been found to be very dependent upon the nature of field operation performed, and the test track techniques required development/adaptation to improve their suitability during standardized assessment. Emphasizes should be given to improve visibility and thermal environment inside the cab for tractor operator. Tractors need to be evaluated under electromagnetic compatibility test conditions due to large growing of electronic devices. Research trends reviewed in this paper can be considered for possible revision or improvement of tractor performance, safety, and comfort test standards.

• International Journal of Aeronautical and Space Sciences
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• v.11 no.1
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• pp.10-18
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• 2010

The purpose of this paper deals with direct multiple-shooting method (DMS) to resolve helicopter maneuver problems of helicopters. The maneuver problem is transformed into nonlinear problems and solved DMS technique. The DMS method is easy in handling constraints and it has large convergence radius compared to other strategies. When parameterized with piecewise constant controls, the problems become most effectively tractable because the search direction is easily estimated by solving the structured Karush-Kuhn-Tucker (KKT) system. However, generally the computation of function, gradients and Hessian matrices has considerably time-consuming for complex system such as helicopter. This study focused on the approximation of the KKT system using the matrix exponential and its integrals. The propose method is validated by solving optimal control problems for the linear system where the KKT system is exactly expressed with the matrix exponential and its integrals. The trajectory tracking problem of various maneuvers like bob up, sidestep near hovering flight speed and hurdle hop, slalom, transient turn, acceleration and deceleration are analyzed to investigate the effects of algorithmic details. The results show the matrix exponential approach to compute gradients and the Hessian matrix is most efficient among the implemented methods when combined with the mixed time integration method for the system dynamics. The analyses with the proposed method show good convergence and capability of tracking the prescribed trajectory. Therefore, it can be used to solve critical areas of helicopter flight dynamic problems.

• Earthquakes and Structures
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• v.8 no.6
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• pp.1363-1386
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• 2015

The October 23 2011 Van Earthquake is studied from an earthquake engineering point of view. Strong ground motion processing was performed to investigate features of the earthquake source, forward directivity effects during the rupture process as well as local site effects. Strong motion characteristics were investigated in terms of peak ground motion and spectral acceleration values. Directiviy effects were discussed in detail via elastic response spectra and wide band spectograms to see the high frequency energy distributions. Source parameters and slip distribution results of the earthquake which had been proposed by different researchers were summarized. Influence of the source parameters on structural response were shown by comparing elastic response spectra of Muradiye synthetic records which were performed by broadband strong motion simulations of the earthquake. It has been emphasized that characteristics of the earthquake rupture dynamics and their effects on structural design might be investigated from a multidisciplinary point of view. Seismotectonic calculations (e.g., slip pattern, rupture velocity) may be extended relating different engineering parameters (e.g., interstorey drifts, spectral accelerations) across different disciplines while using code based seismic design approaches. Current state of the art building codes still far from fully reflecting earthquake source related parameters into design rules. Some of those deficiencies and recent efforts to overcome these problems were also mentioned. Next generation ground motion prediction equations (GMPEs) may be incorporated with certain site categories for site effects. Likewise in the 2011 Van Earthquake, Reverse/Oblique earthquakes indicate that GMPEs need to be feasible to a wider range of magnitudes and distances in engineering practice. Due to the reverse faulting with large slip and dip angles, vertical displacements along with directivity and fault normal effects might significantly affect the engineering structures. Main reason of excessive damage in the town of Erciş can be attributed to these factors. Such effects should be considered in advance through the establishment of vertical design spectra and effects might be incorporated in the available GMPEs.

• Nuclear Engineering and Technology
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• v.47 no.1
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• pp.26-32
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• 2015

During the course of a severe accident in a light water nuclear reactor, large amounts of hydrogen can be generated and released into the containment during reactor core degradation. Additional burnable gases [hydrogen ($H_2$) and carbon monoxide (CO)] may be released into the containment in the corium/concrete interaction. This could subsequently raise a combustion hazard. As the Fukushima accidents revealed, hydrogen combustion can cause high pressure spikes that could challenge the reactor buildings and lead to failure of the surrounding buildings. To prevent the gas explosion hazard, most mitigation strategies adopted by European countries are based on the implementation of passive autocatalytic recombiners (PARs). Studies of representative accident sequences indicate that, despite the installation of PARs, it is difficult to prevent at all times and locations, the formation of a combustible mixture that potentially leads to local flame acceleration. Complementary research and development (R&D) projects were recently launched to understand better the phenomena associated with the combustion hazard and to address the issues highlighted after the Fukushima Daiichi events such as explosion hazard in the venting system and the potential flammable mixture migration into spaces beyond the primary containment. The expected results will be used to improve the modeling tools and methodology for hydrogen risk assessment and severe accident management guidelines. The present paper aims to present the methodology adopted by Institut de Radioprotection et de $S{\hat{u}}ret{\acute{e}}$ $Nucl{\acute{e}}aire$ to assess hydrogen risk in nuclear power plants, in particular French nuclear power plants, the open issues, and the ongoing R&D programs related to hydrogen distribution, mitigation, and combustion.