• Journal of the Society of Naval Architects of Korea
• /
• v.41 no.2
• /
• pp.33-46
• /
• 2004

The cavitating noise of underwater propeller is considered numerically in this study. The main purpose of this research is to analyze these noise sources from marine propeller. The approach for investigation is a potential based panel method coupled with acoustic analogy. To predict propeller sheet cavitation noise, the blade surface cavity is considered as a single valued pulsating volume of vapor attached to the blade surface. The time dependent cavity volume data are used for noise prediction. Furthermore, we analyze hydrofoil cavitation bubble behavior and noise using Eulerian/Lagrangian approach. Through this study, we can analyze dominant noise source of marine propeller and provide a basis for proper noise control strategies.

• Journal of Korea Water Resources Association
• /
• v.30 no.1
• /
• pp.63-73
• /
• 1997

Finite element model is established for the simulation of groundwater flow due to water curtain around underground oil storage Choleski decomposition method. The symmetric global conductance matrix is solved by vector storage Choleski decomposition method. The model is verified through comparison with the results of electric analogy. For the application of this model to real site, the finite element meshes are constructed according to representative vertical cross and longitudinal sections. In cross-sectional analysis, potential and flow distributions are compared based on the cavern pressure and horizontal water curtain. For longitudinal section, effects between nearly located caverns with or without vertical water curtain are analyzed. These results prove that the established model can be used as a tool for flow analysis around underground caverns.

• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2003.10a
• /
• pp.95-98
• /
• 2003

In woven or knitted preforms for composites, the yams are often twisted for avoiding damage due to the contact with the textile machine elements. When the preforms of twisted yams are used in carbon/carbon composites, the thermal conductivity of the composites varies depending upon the degree of the yarn twist. This paper presents a thermal conductivity model of spun yarn composites. The thermal-electrical analogy and the averaging technique have been adopted in this analysis. The model prediction has been correlated with experimental results in order to confirm the model predictability. Parametric study has also been conducted to examine the effect of the yam twist on the thermal conductivity of spun yarn composites.

• Journal of Korean Home Economics Education Association
• /
• v.23 no.3
• /
• pp.37-51
• /
• 2011

The contents of 'Nutrition and Diet for Adolescents' in the 12 technology and home economics middle school 1st grade textbooks are analyzed based on the elaboration theory. The elaboration theory is the lecture strategy with 7 essential elements, proposed by Reigeluth. The elaboration strategies shown in 'Nutrition of Adolescents' and 'Diet for Adolescents' are all the same in 12 books, the conceptual elaboration, and the process elaboration, respectively. On the other hand, the elaboration strategies shown in 'Diet and Dietary Habit for Adolescents Nutrition Issues' and 'Proper Eating Habit and Nutrition Issues' are different depend upon the textbooks, all 3 conceptual, theoretical, and process elaborations strategies are shown. The element of pro study is presented by study objective, opening the thinking, and looking back. The summarizer is presented in all 11 but 1 textbooks by various activities and data. On the other hand, the element of analogy has the lowest implementation rate, only 3 among the 12 textbooks implement the analogy. The cognitive-strategy activator and learner control are shown in all 12 textbooks, mostly by data. Implementation of more activities and more analogies might be helpful to the students' participation and understanding the contents of 'Nutrition and Diet for Adolescents'.

• Journal of Korean Home Economics Education Association
• /
• v.26 no.3
• /
• pp.35-52
• /
• 2014

This study analyzed the 12 different technology home economics textbooks I, II for middle school students and the content systems of the textbooks by 7 instructional strategies in Reigeluth's elaboration theory. The units analyzed were 'Clothing and self-expression' and 'Eco-friendly clothing life and recycling by reform'. The purpose of this study was to provide basic information for the development of textbooks and teaching materials by analyzing current textbooks. Researchers analyzed the textbooks individually using pre-developed analysis frame using Reigeluth's elaboration theory. The results of the study were as follows. The conceptual elaboration process was used in the unit of 'Clothing and self-expression' of all the textbooks used in this study, and procedural elaboration process was mostly used in the unit of 'Eco-friendly clothing life and recycling by reform'. The strategies of advance learning ability were presented mostly in the forms of 'Learning Objective', 'Thought Opening', 'Key terms' in either unit and sub unit. The strategies of summarizer were presented as 'Unit Summary', 'Cleanup' and 'Assessment'. The strategies of synthesizer were used in all the textbooks as the 'Exploration' to increase the students interest through the promotion of the learning content in a variety of activities and projects. The cognitive activator strategies were shown in all of the textbooks using mostly 'Figure,' and others such as 'Table,' 'Diagram', and 'Explanation of Terms'. The strategies of learner control were used to guide the supplement and deepen the learning by various forms. However the analogy strategies were hardly used in units of textbooks analyzed in this study. As a result, the technology home economics textbooks I, II for middle school students applied the Reigeluth's elaboration theory, except the analogy strategies. It is recommended to utilize th analogy strategies and various activities to enhance the students' understanding and participation.

• Structural Engineering and Mechanics
• /
• v.77 no.5
• /
• pp.691-703
• /
• 2021

Reinforced concrete (RC) beams can be subjected to a complex combination of shear forces (V), torsional moments (T), flexural moments (M) and axial loads (N). This paper proposes a unified approach for the analysis of these elements. An existing model for the analysis of orthogonally reinforced concrete membrane elements subjected to in-plane shear and normal stresses is generalized to apply to the case of beams subjected to the complex loading. The combination of V and T can be critical. Torsion is modelled using the hollow-tube analogy. A direct equation for the calculation of the thickness of the equivalent hollow tube is proposed, and the shear stresses caused by V and T are combined using a simple approach. The development and the evaluation of the model are described. The calculations of the model are compared to experimental data from 350 beams subjected to various combinations of stress-resultants and to the calculations of the ACI and the CSA codes. The proposed model provides the most favorable results. It is also shown that it can accurately model the interaction between V and T. The proposed model provides a unified treatment of shear in beams subjected to complex stress-resultants and in thin membrane elements subjected to in-plane stresses.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2001.10a
• /
• pp.177-186
• /
• 2001

Based upon the previous experiences and typical oases of typhoon evasion fur ships as well as tile achievement in scientific research in this detrain, we developed the Intelligent Typhoon Evasion System for Ships. It consists of five subsystems, including electronic charts, ship movement management, typhoon information query and automatic plotting, real-time calculation of ship-typhoon situation, intelligent typhoon evasion decision making. With the synthetical application of analogy theory, synoptic chart, satellite cloud picture analysis, typhoon digital forecast and other relevant technologies, we leave established the typhoon evasion data bases. model bases and knowledge bases, which make it possible to automatically track the ships and typhoon paths. The system can realize ship-typhoon situation analysis, risk levee assessment, typhoon paths correction and course synoptic forecast, and intelligent typhoon evasion decision making.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2013.04a
• /
• pp.311-318
• /
• 2013

The paper describes the prediction method for the unsteady flow field and the aeroacoustic noise of an small axial fan. The prediction method is comprised of various CFD conditions and acoustic analogy by using Ffowcs Williams-Hawkings equation. The diameter of tested axial fan is 170 mm and number of blade is 5. Virtual anechoic room which has same size with real one was used for CFD. URANS and LES models were used. For mesh dependence study, a different mesh type was tested and optimized mesh was selected. Calculation conditions were also studied such as time step and turbulence model for accurate noise analysis. In this paper, we got optimum analysis conditions and computational results. The unsteady pressure fluctuation at given 4 points were compared between the measured data and computational results. Also, the predicted acoustic spectrum at 3 given microphone points were compared with measured ones.

• Journal of Korean Elementary Science Education
• /
• v.30 no.3
• /
• pp.315-329
• /
• 2011

The purpose of this study is to examine the characteristics and the relationships of PCK components of elementary school teacher in the chapter of electric circuit unit. The subjects of this study were two teachers serving as main teachers in the 5th grade and data were collected through qualitative research methods such as questionnaires for teachers, classroom observations and teacher interviews. The collected data were transcribed and then analyzed. Results of analysis showed that teacher A thought that science was a class to explore and study the principles of nature phenomena and scientific knowledge by themselves In addition, teacher A helped students to understand the content by using strategies of analogy. The teacher B conveyed the contents of text without any reconstruction. But teacher B understood the standards of curriculum, and didn't want to teach students over the standards. Based on the analysis, we could conclude that PCK is formed on the basis of knowledge and belief about curriculum and knowledge and belief about learners.

• Journal of Mechanical Science and Technology
• /
• v.16 no.4
• /
• pp.532-548
• /
• 2002

A hybrid model consisting of a modified TAB (Taylor Analogy Breakup) model and DVM (Discrete Vortex Method) is proposed for numerical analysis of the evaporating spray phenomena in diesel engines. The simulation process of the hybrid model is divided into three steps. First, the droplet breakup of injected fuel is analyzed by using the modified TAB model. Second, spray evaporation is calculated based on the theory of Siebers'liquid length. The liquid length analysis of injected fuel is used to integrate the modified TAB model and DVM. Lastly, both ambient gas flow and inner vortex flow of injected fuel are analyzed by using DVM. An experiment with an evaporative free spray at the early stage of its injection was conducted under in-cylinder like conditions to examine an accuracy of the present hybrid model. The calculated results of the gas jet flow by DVM agree well with the experimental results. The calculated and experimental results all confirm that the ambient gas flow dominates the downstream diesel spray flow.