• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2012.10a
• /
• pp.44-46
• /
• 2012

Leading companies has led to the victimization being leaked to accept personal information by the cyber attack. Also planned hacking cases on purpose such as acquiring monetary gain or social distracting is constantly increasing. In this paper, we identify examples of the project step-by-step leading IT services companies to perform security activities. Real-world projects step-by-step through security measures that can be applied are presented.

• Transactions of Materials Processing
• /
• v.16 no.4 s.94
• /
• pp.239-243
• /
• 2007

Superplastic forming/diffusion bonding(SPF/DB) has been widely used in the automotive and aerospace industry since it has great advantages to produce very light and strong components. Finite element method(FEM) is used to model the SPF/DB process of 3-sheet sandwich panel to predict the pressure-time curve and to analyze the process parameters. In order to eliminate defects of the part, a new pressurization scheme is proposed. Contrary to the conventional one-step pressurization, which causes the folding at the DB joint, two-step pressurization can eliminate the folding. Effect of pressurization cycle was investigated by using FE analysis and proper pressurization cycle is proposed.

• Fire Science and Engineering
• /
• v.32 no.1
• /
• pp.7-15
• /
• 2018

The prediction performance of combustion models in the Fire Dynamics Simulator (FDS) were evaluated by comparing with experiment for compartment propane gas fires. The mixture fraction model in the FDS v5.5.3 and Eddy Dissipation Concept (EDC) model in the FDS v6.6.3 were adopted in the simulations. Four chemical reaction mechanisms, such as 1-step Mixing Controlled, 2-step Mixing Controlled, 3-step Mixing Controlled and 3-step Mixed (Mixing Controlled + finite chemical reactions) reactions, were implemented in the EDC model. The simulation results with each combustion model showed similar level for the temperature inside the compartment. The prediction performance of FDS with each combustion model showed significant differences for the CO concentration while no distinguished differences were identified for the $O_2$ and $CO_2$ concentrations. The EDC 3-step Mixing Controlled largely over-predicted the CO concentration obtained by experiment and the mixture fraction model under-predicted the experiment slightly. The EDC 3-step Mixed showed the best prediction performance for the CO concentration and the EDC 2-step Mixing Controlled also predicted the CO concentration reasonably. The EDC 1-step Mixing Controlled significantly under-predict the experimental CO concentration when the previously suggested CO yield was adopted. The FDS simulation with the EDC 1-step Mixing Controlled showed difficulties in predicting the $CO_2$ concentration when the CO yield was modified to predict the CO concentration reasonably.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.26 no.3
• /
• pp.89-94
• /
• 2016

In this study, the crystalline property of a-plane GaN epitaxial layer grown on r-plane sapphire by a HVPE method has been investigated according to the V/III ratio and the growth time of multi-step growth. Furthermore, these results were compared with the previous result obtained from the single-step growth of a-plane GaN on r-plane sapphire substrate. In the multi-step growth for a-plane GaN epitaxial layer on r-plane sapphire, the FWHM values of rocking curve in GaN epitaxial layer were decreased as the HCl source flow rate and the growth time were increased. The void formed in epitaxial layer was continuously decreased as the growth time in first step and second step using a higher HCl flow rate was increased. As a result, the GaN layer obtained with the longest growth time on the first step and second step exhibited the lowest FWHM values of 584 arcsec and the smallest dependence of azimuth angle.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.53 no.3
• /
• pp.175-181
• /
• 2004

The protection against transient instability and consequent out-of-step condition is a major concern for the utility industry. Unstable system may cause serious damage to system elements such as generators and transmission lines. Therefore, out-of-step detection is essential to operate a system safely. The detection of out-of-step is generally based upon the rate of movement of the apparent impedance. However such relay monitors only the apparent impedance which may not be sufficient to correctly detect all forms of out-of-step and cannot cope with out-of-step for a more complex type of instability such as very fast power swing. This paper presents the out-of-step detection algorithm using voltage frequency deviation. The digital filters based on discrete Fourier transforms (DFT) to calculate the frequency of a sinusoid voltage are used, and the generator angle is estimated using the deviation of the calculated frequency component of the voltage. The proposed out-of-step algorithm is based on the assessment of a transient stability using equal area criterion. The proposed out-of-step algorithm is verified and tested by using EMTP MODELS.

• KSBB Journal
• /
• v.15 no.6
• /
• pp.635-643
• /
• 2000

To compare the antioxidative activities of fish skin and bovine skin gelatin hydrolysate, gelatin hydrolysates from Alaska pollack and bovine skin were prepared by various enzymatic hydrolysis methods (1st step, Alcalase; 2nd step, pronase E; 3rd step, collagenase) using a continuous three-step membrane reactor. The molecular weight distributions of the 1st, 2nd and 3rd step hydrolysates were 7∼10 kDa, 2∼5 kDa and 0.7∼0.9 kDa, respectively. The antioxidative activity of fish skin gelatin hydrolysate was stronger than that of bovine skin gelatin hydrolysate, and in particular, both of 2nd step hydrolysates showed more antioxidative activity than hydrolysates of any other step. The optimum antioxidative activity concentration of the 2nd step hydeolysates of fish and boving skin were 1% (w/w) in a linoleic acid water-alcohol emulsion. In cultured cells exposed to t-butyl hydroperoxide (t-BHP), the 2nd step hydrolysate of fish skin gelatin delayed cell death most. These results suggest that the antioxidative activity of fish skin gelatin hydrolysate is higher than that of bovine skin gelatin hydrolysate because of their different amino acid contents.

• Journal of Korean Society of Water and Wastewater
• /
• v.25 no.5
• /
• pp.691-697
• /
• 2011

In this study, by using the Water footprint technique, the water consumption by washing machines, which holds higher ranks in using water than any other electric appliances, was analyzed during their life cycle. The life cycle is defined as raw materials production step, manufacturing step, and using step. In raw materials production step, Input materials were researched by using LCI DB(Life Cycle Inventory Database) and the water consumption was calculated with consideration of approximately 65% Input materials which were based weight. In manufacturing step, the water consumption was calculated by the amount of energy used in assembly factories and components subcontractors and emission factor of energy. In using step, referring to guidelines on carbon footprint labeling, the life cycle is applied as 5 years for a washing machine and 218 cycles for annual bounds of usage. The water and power consumption for operating was calculated by referring to posted materials on the manufacture's websites. The water consumption by nation unit was calculated with the result of water consumption by a unit of washing machine. As a result, it shows that water consumption per life cycle s 110,105 kg/unit. The water consumption of each step is 90,495 kg/unit for using, 18,603 kg for raw materials production and 1,006 kg/unit for manufacturing, which apparently shows that the using step consume the most water resource. The water consumption by nation unit is 371,269,584tons in total based on 2006, 83,385,649 tons in both steps of raw material production and manufacturing, and 287,883,935 tons in using step.

• Journal of Korean Port Research
• /
• v.14 no.1
• /
• pp.77-86
• /
• 2000

The planning process of complex projects in oceanic architectural engineering is characterized by the cooperation of many involved specialists and by a high degree of information exchange. In order to improve the quality of the structural design of oceanic buildings, information of different involved partners in the planning process has to be integrated. This paper aims to introduce a concept of the integrated structural design for the floating-type oceanic building using STEP(Standard for the Exchange of Product Model Data). STEP(ISO 10303) is an international standard for the computer-interpretable representation and exchange of product data and it provides a consistent data exchange format and application interfaces between different application systems. In this paper, the structural design process and information of oceanic buildings is analyzed and product models are preposed fir the exchange of the structural design information between superstructure and floating structure. The entities for calculating wind loads, metacenter and restoring forces are represented by Express. As a case study a floating hotel is applicated to describe the STEP physical file.

• Korean Journal of Computational Design and Engineering
• /
• v.13 no.2
• /
• pp.109-120
• /
• 2008

ISO 10303-112 is an integrated application resource of ISO 10303, commonly known as STEP, and specifies the procedural_sketch schema. The ISO 10303-112 provides general resources for the representation of modeling commands for the exchange of procedurally represented 2D CAD models. Procedural models have the advantage of being easy to edit, simply by changing values of parameters of their constructional operations. Such models are said to embody design intent, in the sense that modifications to them conform to the method of creation used by their original creator, and they also comply with any constraints implied by the particular constructional operations used. This paper introduces the development and standardization process of the ISO 10303-112, and describes the concept of procedural 2D CAD modeling, the way to represent the procedural 2D CAD models in STEP and the harmonization with other STEP resources.

• 연구논문집
• /
• s.31
• /
• pp.65-75
• /
• 2001

A dynamic model of pump having one step gearbox and two step gearbox is developed by the lumped parameter method. The model accounts for shafts, ball bearings and journal bearings flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Excitation forces of pump having one step gearbox and two step gearbox are considered as the mass unbalance of the rotors and gear transmission error which comes from the modified tooth surface. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors and the transmitted errors of the gearing are considered, shows that there are no critical speeds at the operating speeds. One step and two step gearboxes are manufactured and are estimated for vibration/noise, lubrication and performance.