• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.51-54
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• 2005

Shape memory alloys (SMAs) find many applications in smart composite structural systems as the active components. Their ability to provide a high force and large displacement makes them an excellent candidate for an actuator for controlling the shape of smart structures. In this paper, using a macroscopic model that captures the thermo-mechanical behaviors and the two-way shape memory effect (TWSME) of SMAs smart morphing polymeric composite shell structures like shape-changeable UAV wings is demonstrated and analyzed numerically and experimentally when subjected to various kinds of pressure loads. The controllable shapes of the morphing shells to that thin SMA strip actuator are attached are investigated depending on various phase transformation temperatures. SMA strips start to transform from the martensitic into the austenitic state upon actuation through resistive heating, simultaneously recover the prestrain, and thus cause the shell structures to deform three dimensionally. The behaviors of composite shells attached with SMA strip actuators are analyzed using the finite element methods and 3-D constitutive equations of SMAs. Several morphing composite shell structures are fabricated and their experimental shape changes depending on temperatures are compared to the numerical results. That two results show good correlations indicates the finite element analysis and 3-D constitutive equations are accurate enough to utilize them for the design of smart composite shell structures for various applications.

• Journal of The Korean Society of Integrative Medicine
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• v.12 no.1
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• pp.83-96
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• 2024

Purpose : This study was conducted to determine the effects of a brain spinning program on cognitive function, body composition, health related fitness and physical self-efficacy of children and adolescents. Methods : This study, 34 children and adolescents were selected and divided into two groups : the exercise group (n=16), which received a brain spinning program and the control group (n=16), which did not receive any exercise program. The program was conducted for 30 minutes three times a week for 4 weeks, and the cognitive function, body composition, health related fitness and physical self-efficacy were measured both before and after the program. Results : The exercise group, which received a brain spinning program showed a significant increase in short-term memory (p<.05) and working memory (p<.01), and muscle mass increased significantly only in the exercise group (p<.05). In addition, left grip strength increased in the exercise group (p<.01), and the maximum oxygen intake decreased significantly only in the control group (p<.05), and Sit-forward bend increased significantly only in the exercise group (p<.01). Physical self-efficacy significantly increased only in the exercise group (p<.05). Conclusion : In summary, short-term memory, cognitive efficiency, working memory, muscle mass, left grip strength, maximum oxygen intake, and left forward bending in children and adolescents significantly increased after the 4-week brain spinning program. However, the control group that was not provided with the 4-week brain spinning program showed a significant increase in body weight and a significant decrease in maximum oxygen intake. In conclusion, the 4-week brain spinning program has positive effects on short-term memory, cognitive function, muscle mass, muscle strength, cardiorespiratory endurance, flexibility, and physical self-efficacy.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.15 no.5
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• pp.14-20
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• 2006

In recent year, as the robot technology is developed, the researches on the artificial muscle actuator that enables robot to move dexterously like biological organ become active. Actuators are key technologies underpinning robotics. Breakthroughs in actuator technology, particular in terms of power-to-weight ratio, or energy-density, will have significant impacts upon the design and control of robotic system. In this paper, a new approach to design and control of shape memory alloy(SMA) actuator is presented to drive the robot hand. SMA wire is divided into many segments and their thermal states of the SMA are controlled individually in a binary manner. This control manner will reduce the hysteresis that the SMA material has and it becomes the fundamental technology to develop the anthropomorphic robot hand. In this paper, the mechanism In the digital step motor of the shape memory alloy that is driven by the segmented binary control, which is a new control technique, is studied. This SMA digital step actuator applies for the robot hand and the driving mechanism of the robot hand is investigated.

• School Mathematics
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• v.9 no.4
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• pp.507-521
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• 2007

The purpose of this study was to investigate the effects of memory retention of mathematical concepts in multiplication in the inquiry-based pantomime instructions. Three months later after the pre-test, a comparison was made between traditional class (TC) and class with the inquiry-based pantomime (IP) approach in terms of students retention of mathematical understandings. Results of the study indicated that the If instructions promoted effective long-term retention of knowledge. We concluded that instructional strategies that promoted active engagement in learning using life examples and drawings produced effective long-term retention of knowledge.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.05a
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• pp.129-131
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• 2011

An 6.4-Gb/s/channel 4-PAM transceiver is designed for a high speed memory application. The asymmetric 4-PAM signaling scheme is proposed to increase the voltage and time margins, and reduces the reference noise effect in a receiver by 33%. To reduce ISI in a channel, 1-tap pre-emphasis of a transmitter is used. The proposed asymmetric 4-PAM transceiver was implemented by using 0.13um 1-poly 6-metal CMOS process with 1.2V supply. The active area and power consumption of 1-charmel transceiver including a PLL are $0.294um^2$ and 6mW, respectively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1577-1580
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• 2003

In the recent years, as the research and the development of micro and precision machinery become active, the interest of micro actuators using SMA(Shape Memory Alloy) has been increased. The dynamic characteristic analysis of SMA is necessary for actuator application and many common researches report the material characteristics of SMA sufficiently. However, the research on dynamic characteristics is very deficient. In this paper, the helical spring are fabricated with NiTi SMA wire of high resistivity. The force, response speed, temperature, and displacement are measured by digital force gauge, infrared thermometer, and laser displacement sensor so that the dynamic characteristics of this SMA is analyzed. Also, bidirectional actuator was fabricated and experimented for its performance.

• Smart Structures and Systems
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• v.18 no.4
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• pp.663-682
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• 2016

Continuum manipulators as a kind of mechanical arms are useful tools in special robotic applications. In medical applications, like colonoscopy, a maneuverable thin and flexible manipulator is required. This research is focused on developing a basic module for such an application using shape memory alloys (SMA). In the structure of the module three wires of SMA are uniformly distributed and attached to the circumference of a flexible tube. By activating wires, individually or together, different rotation regimes are provided. SMA model is used based on Brinson work. The SMA model is combined to model of flexible tube to provide a composite model of the module. Simulating the model in Matlab provided a platform to be used to develop controller. Complex and nonlinear behavior of SMA make the control problem hard especially when a few SMA actuators are active simultaneously. In this paper, position control of the two degree of freedom module is under focus. An experimental control strategy is developed to regulate a desired position in the module. The simulation results present a reasonable performance of the controller. Moreover, the results are verified through experiments and show that the continuum module of this paper would be used in real modular manipulators.

• Cross-Cultural Studies
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• v.29
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• pp.201-232
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• 2012

In the world history in the rein of totalitarianism cultural project of government had been activated, and consequently of it official culture had been organized. But at the same time on the other side of it people('narod'), who didn't have cultural means for active expression of own opinion on the reality, had expressed world-view and judgement informally in everyday language. In the literature of autocracy, subjected to censorship, had been expressed and fixed mythically idealized image of sovereign and his works. But in the folklore the image of ruler had been created by liberal fantasy of people. This article examined russian literature and folklore texts of 18 century, when russian people suffered from rapid and dramatic changes, caused by Peter I. Although russian literature of 18 century had gone over to the new literary regime, it still accepted political mechanism as dominant of age, and consequently in the literary texts of this century Peter I was represented as ideal person and great monarch. But various images in folklore texts show that people's opinion on ruler and his activities couldn't be controlled. In other worlds, diverse images of Peter I in folklore texts reflect clear and plain historical consciousness of people. This analysis reveals not only difference between mechanism of idealization of government and historical consciousness of people, but also meaning of cultural memory as indicator of historical reality.

• Smart Structures and Systems
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• v.24 no.3
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• pp.361-377
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• 2019

The stiffness of shape memory alloy (SMA) spring while in actuation is represented by an empirical model that is derived from the logistic differential equation. This model correlates the stiffness to the alloy temperature and the functionality of SMA spring as active variable stiffness actuator (VSA) is analyzed based on factors that are the input conditions (activation current, duty cycle and excitation frequency) and operating conditions (pre-stress and mechanical connection). The model parameters are estimated by adopting the nonlinear least square method, henceforth, the model is validated experimentally. The average correlation factor of 0.95 between the model response and experimental results validates the proposed model. In furtherance, the justification is augmented from the comparison with existing stiffness models (logistic curve model and polynomial model). The important distinction from several observations regarding the comparison of the model prediction with the experimental states that it is more superior, flexible and adaptable than the existing. The nature of stiffness variation in the SMA spring is assessed also from the Dynamic Mechanical Thermal Analysis (DMTA), which as well proves the proposal. This model advances the ability to use SMA integrated mechanism for enhanced variable stiffness actuation. The investigation proves that the stiffness of SMA spring may be altered under controlled conditions.

• Journal of the Korean Vacuum Society
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• v.22 no.3
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• pp.131-137
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• 2013

The thin insulator films for organic memory device were made by the plasma polymerization method using the styrene monomer which was not the wet process but the dry process. For the formation of stable plasma, we make an effort for controlling the monomer with bubbler and circulator system. The thickness of plasma polymerized styrene insulator layer was 430 nm, the thickness of the Au memory layer was 7 nm thickness of plasma polymerized styrene tunneling layer was 30, 60 nm, the thickness of pentacene active layer was 40 nm, the thickness of source and drain electrodes were 50 nm. The I-V characteristics of fabricated memory device got the hysteresis voltage of 45 V at 40/-40 V double sweep measuring conditions. If it compared with the results of previous paper which was the organic memory with the plasma polymerized MMA insulation thin film, this result was greater than 18 V, the improving ratio is 60%. From the paper, styrene indicated a good charge trapping characteristics better than MMA. In the future, we expect to make the organic memory device with plasma polymerized styrene as the memory thin film.