• Journal of Surface Science and Engineering
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• v.36 no.6
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• pp.475-479
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• 2003

In this study, to investigate the effects of 2-step shot peening at the surface of spring steel, tests are conducted on spring steel and shot peened specimens. Various tests are accomplished to evaluate mechanical properties influenced by shot peening process, and fatigue tests are also performed to evaluate the improvement of fatigue strength. And then the residual stresses are examined. The mechanical properties of material did not change so much by shot peening. However, the fatigue strength of notched specimen remarkably increased. In the case of 1-step shot peening, fatigue strength increased by about 20％ than unpeened specimen. Especially, in the case of 2-step shot peening, fatigue strength increased by about 40％, because the residual compressive stress at surface was higher than that of 1-step shot peened specimen. The fatigue strength and life are closely related to the value and position of maximum compressive residual stress by shot peening.

• Fire Science and Engineering
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• v.32 no.4
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• pp.110-121
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• 2018

The present article is concerned with a study on the daily training protocol for field crews wearing chemical protection clothing for firefighting and the analysis of activity. To improve coping ability of & secure safety for firefighting crews initially incorporated in the fields of chemical accident & chemical terror, 10 steps in total of daily training protocol have been designed. The designed protocol is largely composed of the extensive activity protocol for daily adaptation of firefighting chemical protection clothing (steps 1, 2, 6, 7 & 9), the precision operation protocol utilizing hands (steps 3, 4 & 5), and the protocol requiring strong physical burdens (steps 8 & 10). According to the measurement results for activity as a result of the protocol, the average maximum heart rate upon wearing the firefighting chemical protection clothing was shown to increase by step 1 20.32%, step 2 18.69%, step 3 25.23%, step 4 34.77%, step 5 27.44%, step 6 30.24%, step 7 25.33%, step 8 22.25%, step 9 22.80% and step 10 20.85% compared with the time of not wearing them. The average maximum breathing rate was shown to increase by step 3 1.92%, step 4 4.11%, step 5 1.24%, step 6 3.95%, step 7 0.93%, step 8 10.23%, step 9 3.36% and step 10 15.10%, except for steps 1 & 2.

• Journal of the Korea Computer Graphics Society
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• v.2 no.2
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• pp.69-74
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• 1996

With the emergence of integrated global market and increased competition, many companies are interested in sharing the product model data. One of the solutions is to share the product model data over the computer network or the internet using a standard format. CAD/CAM, STEP, and internet technologies make it possible to share the product model data. This paper presents methods to visualize 3D STEP geometry data on the internet. To create an internet-based STEP model visualizer, the programming language Java and 3D scene description language VRML have been experimented. The STEP geometry data can be displayed either by Java applets of by a VRML browser. These visualization technologies are applied to a PDM development. Engineers who have a low cost web browser can share the expensive design information even at a remote site.

• Korean Journal of Computational Design and Engineering
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• v.4 no.4
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• pp.295-311
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• 1999

An increasing attention is paid to STEP-NC, the next generation CNC controller interfacing STEP-compatible data. In this paper, we first propose an Architecture for the STEP-NC (called FBCC: Feature Baled CNC Controller) accepting feature code compatible with STEP-data, and executing NC motion feature by feature while monitoring the execution status. The main thrust of the paper has been to develop an automatic on-line tool path generation and modification scheme for milling operation. The tool path it generated iota each feature by decomposing into a finite number of primitive features. The key function in the new scheme is haw to accommodate unexpected execution results. In our scheme, the too1 path plinker is designed to have a tracing capability iota the tool path execution so that a new path can be generated from the point where the operation is stopped. An illustrative example is included to show the capability of the developed algorithm.

• Journal of the Society of Naval Architects of Korea
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• v.34 no.4
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• pp.119-126
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• 1997

In this parer, a protocol system is developed, which automates the sequential procedure that transforms the information of compartment generated by SIKOB, the calculation program of ship design, to the STEP format which is used as the input data of next level of ship design. The schemata representing hull form and compartment are constructed. The STEP physical files are made by instancing these schemata using the results of SIKOB. They are transmitted to the CAD system and then worked on the CAD system. It means that they could be used as the data of next level of ship design.

• Progress in Superconductivity
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• v.3 no.1
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• pp.60-64
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• 2001

We have studied properties of step-edge Junction prepared with crystal orientation of sapphire substrate. The Step on sapphire substrates fabricated by conventional photolithography method and Ar ion milling method. $CeO_2$ buffer layer and in-situ YBCO thin film were deposited on the stepped sapphire substrates by a pulsed laser deposition method with the predetermined optimized condition. The step angle was centre fled low angle of about $25^{\circ}$. The YBCO film thickness was varied to obtain various thickness ratios of the film to the step height in a range from 0.7 to 1.2. I-V curves of junction were showed RSJ-behavior, double junction structure, and hysteresis due to the crystal orientation of substrate.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.903-906
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• 1997

When large capacity generation stations that consist of several large units tend to pull out of step from main power system, stabilizing control scheme as emergency control for preventing loss of synchronism of the whole stations with the remaining system is devided into two steps that the first step is to perform on-line prediction for out-of-step and the next step is on-line calculation of the amount of generation shedding for the rest of generators to be in step when out of step is expected. This paper presents on-line prediction scheme for out-of-step based on P-$\delta$ curve estimation using real-time measurement and on-line calculation of generation shedding. The proposed stabilizing scheme was applied to case study of real power system and the results obtained by the method compare well with the results by simulation.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.3
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• pp.190-196
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• 1999

Continuation power flow has been developed to remove the ill-condition problem caused by singularity of power flow Jacobian at and near at steady-state voltage instability point in conventional power flow. Continuation power flow consists of predictor and corrector. In prddictor, the direction vector at the resent solution is caluculated and the initial guess of next solution is determined at the distance of step length. The selection of step length is a very important part, since computational speed and convergence performance are both greatly affected by the choice of the step length. This paper presents the practical step length selection algorithm using the reactive power generation sensitivith. In numulation, the proposed algorithm is compared with step length selection algorithm using TVI(tangent vector index).

• Transactions of Materials Processing
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• v.12 no.5
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• pp.449-456
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• 2003

Multi-step induction heating process was applied to the powder compact melting technique as a new heating process to achieve pinpoint accuracy, faster cycle time, repeatability, non-contact and energy-efficient heat in a minimal amount of time. The objective of this study is the establishment of the input data diagram of multi step induction heating process for automation of the fabrication process of 6061 Al foams with desired density. At first, proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of specimen. By using this coil, foaming experiments were performed to investigate the multi-step induction heating conditions such as capacity, temperature and time conditions of each heating and holding step. On the basis of the obtained multi-step induction heating conditions, relationship between final heating temperature and fraction of porosity was investigated.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.6
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• pp.101-107
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• 2020

In this paper, step-curing, which includes the change of curing temperature on the curing process, was applied to reduce curing day of HTPB/AP based propellant. This study targets the improvement of productivity of HTPB/AP based solid rocket motor. Comparison of mechanical properties of propellant resulted in the change of normal curing condition (60℃, 5 days) to step-curing condition (60℃, 1 day / 65℃, 3 days). Post-cure test was conducted to determine the impact on the shelf life of the solid rocket motor. The aging characteristics of propellants were analyzed by measuring mechanical properties and thermal expansion factor. To step-cured propellant, accelerated aging test was performed for 12 weeks, followed by tensile test. Sm(bar) and Em(%) were higher than 8 bar and 40% each, showing excellent mechanical properties.