• Journal of The Korean Astronomical Society
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• v.37 no.4
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• pp.249-255
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• 2004

Here we present a linear stability analysis and an MHD 2D model for the Parker-Jeans instability in the Galactic gaseous disk. The magnetic field is assumed parallel to a Galactic spiral arm, and the gaseous disk is modelled as a multi-component, magnetized, and isothermal gas layer. The model employs the observed vertical stratifications for the gas density and the gravitational acceleration in the Solar neighborhood, and the self-gravity of the gas is also included. By solving Poisson's equation for the gas density stratification, we determine the vertical acceleration due to self-gravity as a function of z. Subtracting it from the observed gravitational acceleration, we separate the total acceleration into self and external gravities. The linear stability analysis provides the corresponding dispersion relations. The time and length scales of the fastest growing mode of the Parker-Jeans instability are about 40 Myr and 3.3 kpc, respectively. In order to confirm the linear stability analysis, we have performed two-dimensional MHD simulations. These show that the Parker-Jeans instability under the self and external gravities evolves into a quasi-equilibrium state, creating condensations on the northern and southern sides of the plane, in an alternate manner.

• Korean Journal of Culture and Social Issue
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• v.28 no.3
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• pp.373-392
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• 2022

The present study aimed to emprically verify the materialistic pursuits process of undergraduates by applying the escape theory of materialism(Donnelly et al., 2016). Among the six steps of Donnelly's model, the first step is percieving that the fall short of high standards of life, as measured by external contingencies of self-worth. The second step is blaming the self for falling short of standards, as measured by self-discrepancy. The third step of high aversive self-awareness is measured by low stability of self-esteem. A total of 465(203 male and 262 female) college students participated in the online survey and the model was tested using structural equation model. We found that the relationship of external contingencies of self-worth and materialism was mediated by self-discrepancy and there was a sequential mediation effect of self-discrepancy and the stability of self-esteem. The direct effect of external contingencies of self-worth on materialism was also significant. This study is meaningful in that it used the escape theory to emprically verify the materialistic pursuit process of Korean undergraduates living in a meritocratic society.

• Advances in concrete construction
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• v.7 no.2
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• pp.97-105
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• 2019

In this paper, the workability and static stability were evaluated using a proposed test method. Workability and static stability represent a key property of self-compacting concrete (SCC) in fresh state. A number of standardized test methods were developed to assess these properties. However, no accelerated test method reliably predicts both workability and static stability of SCC. In the present work, a modified K-slump test method was developed to evaluate workability and static stability of SCC. In order to take implicit mixture variations of SCC constituents that can affect fresh SCC properties, a central composite design was adopted to highlight the effect of gravel to sand ratio (G/S), gravel 3/8 to gravel 8/15 ratio (G1/G2), water to cement ratio (W/C), marble powder to cement ratio (MP/C) and superplasticizer content (SP) on workability measured with slump and flow time (T50) tests and static stability measured with sieve stability test (Pi), segregation test index (SSI), Penetration test (Pd) and the proposed K-slump test (Km). The obtained results show that G/S ratio close to 1 and G1/G2 ratio close to 60% can be considered as optimal values to achieve a good workability while ensuring a sufficient static stability of SCC. Acceptable relationships were obtained between Slump flow, Pi, Pd and Km. Results show that the proposed K-slump test allow to assess both workability and static stability of fresh SCC mixtures.

• Journal of Integrative Natural Science
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• v.3 no.2
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• pp.96-102
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• 2010

It is still controversial where the improved stability of n-octadecyltriethoxysilane self-assembled monolayer (OTE SAM) on plasma-pretreated mica surface exactly originates from. To date, it has been well known that the extensive cross-polymerization between silane headgroups is a crucial factor for the outstanding mechanical strength of the monolayer. However, this study directly observed that the stability comes not only from the cross-links but also, far more importantly, from the direct chemical bonds between silane headgroups and mica surface. To observe this phenomenon, n-octadecyltrichlorosilane monolayers were self-assembled on both untreated and plasma treated mica surfaces, and their adhesion properties at various stress conditions and force profiles in pure water were investigated and compared through the use of the surface forces apparatus technique. It revealed that, in pure water, there is a substantial difference of stability between untreated and plasma treated cases and the plasma treated surface is mechanically much more stable. In particular, the protrusion behavior of the monolayer during contact repetition experiment was always observed in the untreated case, but never in the plasma treated case. It directly demonstrates that the extensive chemical bonds indeed exist between silane head-groups and plasma treated mica surface and dramatically improve the mechanical stability of the OTE monolayer-coated mica substrate.

• Journal of Integrative Natural Science
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• v.3 no.2
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• pp.89-95
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• 2010

It is still controversial where the improved stability of n-octadecyltriethoxysilane self-assembled monolayer (OTE SAM) on plasma-pretreated mica surface exactly originates from. To date, it has been well known that the extensive cross-polymerization between silane head-groups is a crucial factor for the outstanding mechanical strength of the monolayer. However, this study clearly showed that the stability comes not only from the cross-links but also, far more importantly, from the direct chemical bonds between silane headgroups and mica surface. To examine this phenomenon, n-octadecyltrichlorosilane monolayers were self-assembled on both untreated and plasma treated mica surfaces, and their adhesion properties at various physical conditions (relative humidity, high stress, and contact repetition) were investigated and compared through the use of the surface forces apparatus technique. It revealed that, in highly humid conditions (>90%RH), there is a substantial difference of stability between untreated and plasma treated cases and the plasma treated surface is mechanically much more stable. It obviously proves that the extensive chemical bonds indeed exist between silane head-groups and plasma treated mica surface and dramatically improve the mechanical stability of the OTE monolayer-coated mica substrate.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.231-238
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• 2010

Combustion stability rating tests under condition low pressure of a 75-$ton_f$ liquid rocket engine(LRE) thrust chamber were carried out. Mixing head with decreased number of injectors than that of the other but with the same mass flow rate to the combustion chamber showed self-oscillation instability in chamber pressure of 30 bar. The other combustion chamber with increased number of injectors showed that high frequency combustion stability was maintained under condition of same pressure, but self-oscillation instability was generated in chamber pressure of 20 bar which can be considered as stability boundary region of this mixing head.

• The Korean Journal of Emergency Medical Services
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• v.25 no.1
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• pp.49-56
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• 2021

Purpose: This experimental study aimed to solve the problem of discomfort and stably fix the bandage. A new self-adhesive bandage was manufactured to reduce the inconveniences associated with the plaster bandage. We compared the associated stability between the plaster bandage and the new self-adhesive bandage. Methods: The traditional elastic bandage (traditional EB; i.e., plaster bandage) and modified elastic bandage (modified EB; i.e., new self-adhesive bandage) were applied to 30 people each. We measured the time of preparation and attachment for traditional TB and attachment for modified TB. A 4kg cattle bell was fixed to each bandage to compare their respective stability levels. Results: The speed for the traditional EB was 28.93(±9.28)sec (mean 25.56s) and 6.13(±1.81)sec for the modified EB (mean 5.95sec). The stability values were 1.49(±.77)min for the traditional EB (mean 1.31min) and 26.22(±9.04)min for modified EB (mean 1.31min). The differences in speed and stability were statistically significant. Conclusion: Compared to the traditional EB, applying the modified EB could solve the attachment inconvenience and provide stable maintenance.

• Journal of Institute of Control, Robotics and Systems
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• v.5 no.2
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• pp.189-199
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• 1999

This paper presents an optimization algorithm for a stable Self Dynamic Neural Network(SDNN) using genetic algorithm. Optimized SDNN is applied to a problem of controlling nonlinear dynamical systems. SDNN is dynamic mapping and is better suited for dynamical systems than static forward neural network. The real-time implementation is very important, and thus the neuro controller also needs to be designed such that it converges with a relatively small number of training cycles. SDW has considerably fewer weights than DNN. Since there is no interlink among the hidden layer. The object of proposed algorithm is that the number of self dynamic neuron node and the gradient of activation functions are simultaneously optimized by genetic algorithms. To guarantee convergence, an analytic method based on the Lyapunov function is used to find a stable learning for the SDNN. The ability and effectiveness of identifying and controlling a nonlinear dynamic system using the proposed optimized SDNN considering stability is demonstrated by case studies.

• Korean Journal of Human Ecology
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• v.12 no.3
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• pp.275-286
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• 2003

The purposes of this study were to identify the relationship between children's personality traits and self-esteem, and to find out if there were any differences in the relationship patterns in terms of children's sex. The questionnaire were collected from 984 subjects in 5th grade of elementary schools located in cities of Seoul, Suwon, Daejeon, and Daegu. Results showed that personality factors such as stability, sociability, responsibility, and superiority had stronger correlations with self-esteem factors whereas masculinity, activity level, and reflectivity did so to a less degree. Children's personality factors such as superiority, sociability and responsibility were better predictors of their self-esteem factors such as scholastic competence, social acceptance and general self-worth. Girls showed higher level of stability, sociability, responsibility and superiority, however there was no sex difference in the self-esteem such as scholastic competence, social acceptance and general self-worth. Children's behavioral conduct were mainly explained by masculinity, activity level, and responsibility. Responsibility turned out to be the strongest predictor of behavioral conduct among boys, while the activity level did among girls.

• Journal of the Korean Home Economics Association
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• v.44 no.12
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• pp.53-64
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• 2006

The purpose of this study was to investigate the variables on employees' retirement expectations divided into imposed frustration, new beginning, transition to rest, and continuing. Independent variables were individual(gender, age, occupation, income, education, and health condition), psychological(self-esteem, locus of control, attitude of leisure, and attitude of family), and job-related variables(job attitude, job satisfaction, and job stability). In order to achieve this purpose, a survey was conducted with 515 employees from Daegu and Kyungpook. Retirement expectations were measured with questionnaire based on several studies. The data analyzed by frequency, percentage, mean, factor analysis, Cronbach's $\alpha$, correlation, and multiple regression. The major findings were as follows. First, imposed frustration was affected by income, self-esteem, locus of control, job satisfaction, job attitude, and job stability. Second, new beginning was affected by self-esteem, locus of control, attitude toward leisure and family, and job stability. Individual variables were not statistically significant predictors of new beginning. Third, transition to rest was affected by locus of control, attitude toward family, job satisfaction, job attitude, and job stability. Individual variables were not statistically significant predictors of transition to rest. Finally, continuing was affected by age, education, job satisfaction. Psychological variables were not statistically significant predictors of continuing.