• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.3
• /
• pp.470-477
• /
• 2001

Constant ΔK fatigue crack growth tests were performed by applying an intermediate multiple overload for S45C steel. The purpose of the present study is to investigate effects of specimen thickness at various baseline stress intensity factor range levels (ΔK(sub)b), overload application position (a/W) and overload application frequency (OL(sub)HZ) on fatigue crack growth retardation behavior. The principal results are summarized as follows. The amount of retardation for a given ΔK(sub)b level is increased with increasing the baseline stress intensity factor range level for all specimen thickness. The normalized minimum crack growth rate is increased with increasing the specimen thickness, except for ΔK=45MPa√m. The retardation cycle is decreased with increasing a/W and increased with OL(sub)HZ.

• Structural Engineering and Mechanics
• /
• v.74 no.5
• /
• pp.611-633
• /
• 2020

In this paper, a comprehensive review of nanostructures that exhibit piezoelectric behavior on all mechanical, buckling, vibrational, thermal and electrical properties is presented. It is firstly explained vast application of materials with their piezoelectric property and also introduction of other properties. Initially, more application of material which have piezoelectric property is introduced. Zinc oxide (ZnO), boron nitride (BN) and gallium nitride (GaN) respectively, are more application of piezoelectric materials. The nonlocal elasticity theory and piezoelectric constitutive relations are demonstrated to evaluate problems and analyses. Three different approaches consisting of atomistic modeling, continuum modeling and nano-scale continuum modeling in the investigation atomistic simulation of piezoelectric nanostructures are explained. Focusing on piezoelectric behavior, investigation of analyses is performed on fields of surface and small scale effects, buckling, vibration and wave propagation. Different investigations are available in literature focusing on the synthesis, applications and mechanical behaviors of piezoelectric nanostructures. In the study of vibration behavior, researches are studied on fields of linear and nonlinear, longitudinal and transverse, free and forced vibrations. This paper is intended to provide an introduction of the development of the piezoelectric nanostructures. The key issue is a very good understanding of mechanical and electrical behaviors and characteristics of piezoelectric structures to employ in electromechanical systems.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.27 no.2
• /
• pp.361-371
• /
• 2017

The increase in user data stored in the device implies the increase in threats of users' sensitive data. Currently, smartphone authentication mechanisms such as Pattern Lock, fingerprint recognition are widely used. Although, there exist disadvantages of inconvenience use and dependence that users need to depend on their own memory. User behavior based authentication mechanism have advantages of high convenience by offering continuous authentication when using the mobile device. However, these mechanisms show limitations on low accuracy of authentication and there are researches to improve the accuracy. This paper proposes improved authentication mechanism that uses user's smartphone application usage pattern which has not considered on earlier studies. Also, we analyze performance of proposed mechanism with collected datasets from actual use of smartphone applications.

• Korean Journal of Materials Research
• /
• v.31 no.1
• /
• pp.43-53
• /
• 2021

Dynamic behavior of piezoelectric ZnO nanowires is investigated using finite element analyses (FEA) on FE models constructed based on previous experimental observations in which nanowires having aspect ratios of 1:2. 1:31, and 1:57 are obtained during a hydrothermal process. Modal analyses predict that nanowires will vibrate in lateral bending, uniaxial elongation/contraction, and twisting (torsion), respectively, for the three ratios. The natural frequency for each vibration mode varies depending on the aspect ratio, while the frequencies are in a range of 7.233 MHz to 3.393 GHz. Subsequent transient response analysis predicts that the nanowires will behave quasi-statically within the load frequency range below 10 MHz, implying that the ZnO nanowires have application potentials as structural members of electromechanical systems including nano piezoelectric generators and piezoelectric dynamic strain sensors. When an electric pulse signal is simulated, it is predicted that the nanowires will deform in accordance with the electric signal. Once the electric signal is removed, the nanowires exhibit a specific resonance-like vibration, with the frequency synchronized to the signal frequency. These predictions indicate that the nanowires have additional application potential as piezoelectric actuators and resonators.

• The Journal of Asian Finance, Economics and Business
• /
• v.7 no.10
• /
• pp.897-907
• /
• 2020

The development of information technology and the demands of society on an application in an operating system, as well as increasing the specifications and sophistication of smartphones, require banks to make changes to their mobile banking applications. The transformation of the mobile banking application into a digital banking application conducted by banks has made users re-evaluate based on their preferences. This study presents the behavior of users of digital banking applications in Yogyakarta, Indonesia. The hypothesis model is based on Technology Acceptance Model (TAM) with additional factors of the social image, perceived risk and perceived trust adopted from Muñoz-Leiva et al. (2017). The methodology in this study includes data collection through questionnaires distributed online and data analysis using the Structural Equation Model. The results of this study illustrate that the perceived trust and perceived risk have a more dominant part in influencing user attitude and user intention to use digital banking. Meanwhile, social image, perceived ease-of-use and perceived usefulness are not significant in influencing user attitude and user intention to use digital banking. The implication of this research helps to determine the right communication and strategy so that more users with more benefits can utilize this digital banking application.

• Journal of the Ergonomics Society of Korea
• /
• v.33 no.3
• /
• pp.175-189
• /
• 2014

Objective: The goal of this research is to develop new user behavior model using user motion analysis with microscopic perspective for attracting user's participation in interactive space. Background: The interactive space is 'human's place', which is made up of complex elements of digital virtual space and traditional analog and physical environment based on human-computer interaction system. Human behavior has changed in it at the same time. If the user couldn't make participation in interaction, the purpose of the system is not met, which reduces its effect. Therefore, we need to focus on interactive space that is potential future direction from a new point of view. Method: For this research, we would discuss and study fields of interactive space; (1) finding definition of interactive space and studying background of theory about it. (2) providing base of user behavior model with study of user's context that is to be user information and motion. (3) examining user motion, classify basic motion type and making user participation behavior model in phases. Results: Through this process, user's basic twenty motions which are systematized are taken as a standard for analysis of interaction process and participation in interactive space. Then, 'NK-$I^5$ (I Five)' model is developed for user participation types in interactive space. There are five phases of user participation behavior: Imperception, Interest, Involvement, Immersion, and Influence. In this analysis, three indicators which are time, motion types, and user relationship are found to be related to participation. Conclusion: The capabilities and limitation of this research is discussed to attract user participation. This paper focuses especially on contribution of design to lead user's participation in interactive system and expectation to help adapt to user centered design of various interactive space with new aspect of user behavior research. Application: The results of the 'NK-$I^5$ (I Five)' model might help to realize successful interactive space based on user centered design.

• Journal of Digital Convergence
• /
• v.17 no.1
• /
• pp.457-465
• /
• 2019

This study was designed to develop a positive behavior support model for children in child care institutions. For this purpose, a demand survey for PBS was conducted with 55 child care institution staff members. 76% of the respondents responded that PBS is needed to prevent problem behavior and can be a good alternative for personality education, and approximately 70% responded that they are willing to implement PBS. The specifications of the model are suggested as follows. First, the preparation step would consist of establishing a support team, educating staff members about PBS, selecting expected behaviors, assessing the current baseline behavior, and setting up a universal PBS environment. The application step would consist of instructing social skills, implementing reinforcement, personal goal-setting and assessing behavior, educating trouble-making students, and monitoring. Finally, at the outcome assessment period, measuring the change in target behavior from the pre-intervention to the post-intervention stage, change in social skills and academic achievement, and social validity is suggested. It is expected that application of this model to children in child care institution will decrease problem behaviors of students, enhance desirable behaviors, and boost the staff members' efficacy.

• Journal of Korean Academy of Nursing
• /
• v.25 no.2
• /
• pp.341-350
• /
• 1995

A quasi-experimental study was conducted to examine the effect of ice pack application to post cardiac surgery toddlers before C-tube removal. Twenty toddlers aged 13 months to 24 months, who were admitted to the hospital for open heart surgery during the period from July, 1993 to October, 1993 were randomly assigned to the experimental or control group. An ice pack was applied to the C-tube insertion site for 8 minutes before C-tube removal for the experimental group. The children were videotaped during the procedure to assess pain behavior and crying time. The score on the Modified Behavioral Pain Scale(MBPS), crying time, and vital signs were measured to determine the effect of ice pack application. The data were analyzed using Mann-Whitney U test, Paired t-test, and Pearson correlation coefficient. The result of the study are as follows : 1. There was a significant difference between the experimental group and the control group in pain behavior (U=17.0, p=.01). 2. There was no significant difference between the two groups in crying time. 3. There was a significant difference between the two groups in heart rate (U=24.5, p=.05). 4. There was a significant difference between the two groups in systolic blood pressure (U=24.0, p=.05) 5. There was a significant difference between the two groups in diastolic blood pressure (U=23.0, p=.04). 6. There was no significant difference between the two groups in respiration rate. 7. Pain behavior was significantly correlated with heart rate, systolic blood pressure, and crying time (r=.50, .54 and .59, p<.05). The result showed that the ice pack application was effective to reduce pain related to C-tube removal for the toddlers. From the study, it is recommended that the effectiveness of the cold ap-plication to children undergoing different painful procedures be examined to determine the most effective length of cold application to reduce pain in children.

• Journal of KIISE:Computer Systems and Theory
• /
• v.30 no.9
• /
• pp.461-476
• /
• 2003

Due to the implementation ease and alleviation of memory bottleneck effect, NUMA architecture has dominated in the multiprocessor systems for the past several years. However, because the NUMA system distributes memory in each node, frequent remote memory access is a key factor of performance degradation. Therefore, efficient design of RAC(Remote Access Cache) in NUMA system is critical for performance improvement. In this paper, we suggest Multi-Grain RAC which can adaptively control the RAC line size, with respect to each application behavior Then we simulate NUMA system with multi-grain RAC using MINT, event-driven memory hierarchy simulator. and analyze the performance results. At first, with profile-based determination method, we verify the optimal RAC line size for each application and, then, we compare and analyze the performance differences among NUMA systems with normal RAC, with optimal line size RAC, and with multi-grain RAC. The simulation shows that the worst case can be always avoided and results are very close to optimal case with any combination of application and RAC format.

• Journal of Information Technology Services
• /
• v.11 no.3
• /
• pp.269-285
• /
• 2012

The spontaneous interoperation is an important characteristic of ubiquitous applications and is closely related with mobility. The mobile components in ubiquitous environments are liable to appear in and disappear from one physical space to another. Because this characteristic certainly influences the structure and behavior of applications, they should adapt themselves to the changed environments by configuring their structure and behaviors. Consequently, developers are faced with the above challenging issue when they design and implement ubiquitous applications. The role concept is an efficient tool to model participant entities, their relationship, and collaboration, so role-based model are appropriate to describe a structure and behavior of software system. But, little attention has been given to reflect characteristics of ubiquitous applications. To tackle the problem, this study considers a ubiquitous application as a software organization which consists of software components and proposes an enhanced role-based application model for supporting spontaneous interoperation.