• Smart Structures and Systems
• /
• v.29 no.5
• /
• pp.705-714
• /
• 2022

In this paper, the effect of magnetic field on the vibration behavior of a Magnetorheological elastomer (MRE) sandwich MEMS actuated by electrostatic actuation with conductive skins are examined within the multiple scales (MMS) perturbation method. Magnetorheological smart materials have been widely used in vibration control of various systems due to their mechanical properties change under the influence of different magnetic fields. To investigate the vibrational behavior of the movable electrode, the Euler-Bernoulli beam theory, as well as Hamilton's principle is used to derive the equations and the related boundary conditions governing the dynamic behavior of the system are applied. The results of this study show that by placing the Magnetorheological elastomer core in the movable electrode and applying different magnetic fields on it, its natural vibrational frequency can be affected so that by increasing the applied magnetic field, the system's natural frequency increases. Also, the effect of various factors such as the electric potential difference between two electrodes, changes in the thickness of the core and the skins, electrode length, the distance between two electrodes and also change in vibration modes of the system on natural frequencies have been investigated.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.66 no.1
• /
• pp.15-24
• /
• 2024

Unlike artificially created homogeneous materials, the process of calculating the elastic modulus of natural soil involves the possibility of errors. Because the stress-strain behavior of soil is nonlinear, the secant modulus of elasticity is often used based on 1/2 of the stress at failure. Since soil has the property of changing its elastic modulus depending on the confining pressure, numerical analysis models that analyze its behavior inevitably include complex elements. The hyperbolic model, which relatively accurately simulates the behavior immediately after loading in soft ground, assumes that the stress-strain curve of the consolidated undrained triaxial test is hyperbolic and requires the slope of the tangent line at the starting point. However, the slope of the initial tangent in the stress-strain curve obtained from an actual triaxial test is difficult to have regularity according to changes in confining pressure. Additionally, due to the characteristics of a hyperbola, even small changes in related factors cause large changes in the hyperbola. Therefore, there is a lot of randomness in the process of calculating model parameters from the triaxial test results, which causes large differences in the results. Therefore, the method of calculating the initial elastic modulus by the consolidation test presented in this study is also used to verify the method by the triaxial test. It can be applied. However, since this study was applied to only one sample showing typical consolidation characteristics, it is necessary to check samples with various physical properties in the future.

• Journal of the Korean Society of Fashion and Beauty
• /
• v.5 no.2 s.13
• /
• pp.56-67
• /
• 2007

This study is surveyed for understanding attitude toward make-up and purchasing behavior of cosmetics of preteen generation, elementary school students among 10 to 12 using a method of questionnaire. It helps concerned traders comprehend purchasing characteristics of preteen and map out a strategy for marketing of preteen. And it used research material being able to understand socio-psychological characteristics and attitude toward make-up and purchasing behavior of cosmetics of preteen generation. For the survey, a method of questionnaire was used. The questionnaire consisted of 4 questions for socio-psychological characteristics, 5 for appearance, 8 for attitude toward make-up and 6 for cosmetic purchase behavior and 3 for demographic factors. 458 girl students among 4, 5 and 6th graders at elementary schools in Seoul were selected on a random basis. Data was analyzed using frequency, percentage, average, standard deviation. F-test, Duncanis post test and crosstab analysis were also applied. 1. The level of interest of pre-teen generations was found normal. 2. The most popular destinations for buying cosmetics were dedicated cosmetics shops and department stores. 3. Satisfaction and interest of appearance and make-up. 4. Attitude toward make-up and behavior of purchase cosmetics as grades.

• Journal of Korean Academy of Fundamentals of Nursing
• /
• v.9 no.3
• /
• pp.484-500
• /
• 2002

Purpose: The purposes of this study were to better understand types of health behavior in middle aged women in the Korean agricultural society, understand their nursing needs, and eventually present guidelines to develop proper nursing interventions. Method: Participants for this study were 16 middle aged women from farming communities, who lived in C county and were independent and without chronic ailments. In collection and analysis of data Strauss & Cortin's (1997) research processes and methods were used. The period of data collection was between April 2001 and February 2002. Result: The results of the study showed that the core category was the family-oriented process of $yangsaeng^{1)}$, and four types of health behaviors were observed; $momboyang^{2)}$ maintenance of health through daily life, managing mental health, and managing illness. Each type was perceived to differ from the other in the terms of health behavior priority which was largely affected by the cultural surrounding, for example, degree of attention to children's education and tendency to a traditional role for women. Conclusion: In conclusion, nurses need to understand various types of health behavior in middle aged women. The findings from this study can be applied to the development of Korean nursing interventions that are based on health behavior among middle aged women in the Korean agricultural society. These interventions can then. be based upon understanding of Korean culture rather than drawn only from Western concepts of health behavior.

• Human Ecology Research
• /
• v.53 no.6
• /
• pp.641-654
• /
• 2015

This study identifies and tracks changes gender differences in adolescent users' problematic online behavior. This study used Korea Youth Panel Survey (KYPS), which has tracked respondents over 7 years, with self-control theory and social learning theory applied as a theoretical framework. The model included individual-level variables such as self-control and respondent's experience of problematic behavior (offline), as well as socialization variables such as the number close friends who engaged in problematic offline behavior, parent-child relationships, and parental monitoring. Dependent variables included problematic online behavior, unauthorized ID use (ID theft) and cyberbullying (cursing/insulting someone in a chat room or on a bulletin board). Control variables consisted of academic performance, time spent on a computer, monthly household income, and father's educational attainment. Random and fixed effects models were performed by gender. Results supported self-control theory even for the within-level analysis (fixed effects models) regardless of gender, while social learning theory was partially supported. Only peer effects were found significant (except for unauthorized ID use) among girls. Year dummy variables showed significant negative associations; however, academic performance and time spent using computers were significant in some models. Father's educational attainment and monthly household income were found insignificant, even in the random effects models. We also discuss implications and suggestions for future research and policy makers.

• The Journal of Asian Finance, Economics and Business
• /
• v.8 no.4
• /
• pp.809-817
• /
• 2021

The worldwide spread of the COVID-19 pandemic has had a severe impact on the global economy. The COVID-19 pandemic has spread with alarming speed and. The economic damage is already evident and represents the largest economic shock the world has experienced in decades. This study analyzes the factors that influence behavior and its impact on start-up performance, through technology capabilities, technology development, organizational structure characteristics, and leadership technology. The mixed-method was used in this research to be applied to start-up companies in Jabodetabek with a population of 522 start-ups. Then the sample was selected through purposive sampling technique to obtain a sample of 187 start-ups. Primary data was collected through a questionnaire, then statistical analysis was carried out using Partial Least Square. There are ten variables used in the model as measured by the questionnaire. The results showed that the four factors (agility, entrepreneurship capability, business transformation, and opportunity) significantly influence start-up behavior. The results showed that the start-up behavior significantly influenced technology capabilities, technology development, organizational structure characteristics, and leadership technology. This study also found that start-up behavior had the greatest influence on organizational structure characteristics, partially affect start-up performance, but leadership technology does not have a significant effect on start-up performance.

• Journal of Korea Society of Digital Industry and Information Management
• /
• v.12 no.1
• /
• pp.119-129
• /
• 2016

Rapid changes to the paradigm of smart media have created a communication environment through merging with various media such as IoT technology, which is internet of things. Among them, user' need for a start home, which is one of people living conditions, has been growing and values of the communication environment in a living space using a smart mirror have been growing. However, studies on figuring out behavior and analyzing needs of family members who actually use the living space are insufficient. This study is to draw the service system of the home smart mirror by analysis of behavior and needs of users of the living space. For a research method for analysis of behavior of family members, I wrote two kinds of user's experience maps, which are frequency of use of a quantitative space of a living space and space's important value scales by persona study and depth interview. Through this, applied spaces of the home smart mirror (living room, bathroom, powder room, dress room, porch, kitchen, room) and the types of user needs (type of providing information, entertainment type, control type, service type) have been drawn and statistical analysis methodology has been utilized for a research of user preferences in regard to correlation between living spaces and types of user needs based on a survey. As a result of analysis of ages and gender, types of user needs by space have been drawn and the service system of the home smart mirror has been drawn. It would be utilized as a basic material for various contents development and design using the smart mirror in the future.

• Tunnel and Underground Space
• /
• v.8 no.4
• /
• pp.321-331
• /
• 1998

A reliable analysis of tunnelling is needed to accomplish technically sound design and safe and economical construction. For the reliable analysis, a series of procedures of construction which include excavation and support stages must be considered. In this study, rock-support response behavior is studied and simulated in 2-D and 3-D finite element methods. Through the analysis of rock-support response behavior, the effects of the properties of shotcrete on the load distribution ratio can be quantified. The load distribution ratios for different rock types, different unsupported spans and various lateral earth pressure coefficients can be determined from the results of the 3-D finite element analysis. This load distribution ratios can be applied to a practical tunnel design through understanding of the trend of those various factors affecting the rock-support interaction.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.18 no.4
• /
• pp.44-50
• /
• 2010

Structural vibration is a significant problem in many multi-part or multi-component assemblies. In aircraft industry, structures are composed of various fasteners, such as bolts, snap, hinge, weld or other fastener or connector (collectively "fasteners"). Due to these, prediction and design involving dynamic characteristics is quite complicated. However, the current state of the art does not provide an analytical tool to effectively predict structure's dynamic characteristics, because consideration of structural uncertainties (i.e. material properties, geometric tolerance, dimensional tolerance, environment and so on) is difficult and very small fasteners in the structure cause a huge amount of analysis time to predict dynamic characteristics using the FEM (finite element method). In this study, to resolve the current state of the art, a new approach is proposed using the FEM and probabilistic analysis. Firstly, equivalent elements are developed using simple element (e.g. bar, beam, mass) to replace fasteners' finite element model. Developed equivalent elements enable to explain static behavior and dynamic behavior of the structure. Secondly, probabilistic analysis is applied to evaluate the PDF (probability density function) of dynamic characteristics due to tolerance, material properties and so on. MCS (Monte-Carlo simulation) is employed for this. Proposed methodology offers efficiency of dynamic analysis and reality of the field as well. Simple plates joined by fasteners are taken as an example to illustrate the proposed method.

• Coupled systems mechanics
• /
• v.9 no.5
• /
• pp.433-454
• /
• 2020

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures. The structural integrity of platform components under the maximum and minimum operating loads of environmental conditions is required for risk assessment and inspection plan development. In-place analyses have been executed to check that the structural member with all appurtenances robustness and capability to support the applied loads in either storm condition or operating condition. A nonlinear finite element analysis is adopted for the platform structure above the seabed and the pile-soil interaction to estimate the in-place behavior of a typical fixed offshore platform. The analysis includes interpretation of dynamic design parameters based on the available site-specific data, together with foundation design recommendations for in-place loading conditions. The SACS software is utilized to calculate the natural frequencies of the model and to obtain the response of platform joints according to in-place analysis then the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have important effects on the results of the in-place analysis behavior. The result shows that the in-place analysis is quite crucial for safe design and operation of offshore platform and assessment for existing offshore structures.