• Smart Structures and Systems
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• v.19 no.5
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• pp.487-497
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• 2017

Semi-active devices use the building's own motion to produce resistive forces and are thus strictly dissipative and require little power. Devices that independently control the binary open/closed valve state can enable novel device hysteresis loops that were not previously possible. However, some device hysteresis loops cannot be obtained without active analog valve control allowing slower, controlled release of stored energy, and is presents an ongoing limitation in obtaining the full range of possibilities offered by these devices. This in silico study develops a proportional-derivative feedback control law using a validated nonlinear device model to track an ideal diamond-shaped force-displacement response profile using active analog valve control. It is validated by comparison to the ideal shape for both sinusoidal and random seismic input motions. Structural application specific spectral analysis compares the performance for the non-linear, actively controlled case to those obtained with an ideal, linear model to validate that the potential performance will be retained when considering realistic nonlinear behaviour and the designed valve control approach. Results show tracking of the device force-displacement loop to within 3-5% of the desired ideal curve. Valve delay, rather than control law design, is the primary limiting factor, and analysis indicates a ratio of valve delay to structural period must be 1/10 or smaller to ensure adequate tracking, relating valve performance to structural period and overall device performance under control. Overall, the results show that active analog feedback control of energy release in these devices can significantly increase the range of resetable, valve-controlled semi-active device performance and hysteresis loops, in turn increasing their performance envelop and application space.

• Journal of Electrical Engineering and Technology
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• v.7 no.4
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• pp.596-600
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• 2012

ZnO-$SnO_2$ films were deposited by rf magnetron sputtering using a ZnO-$SnO_2$ (2:1 molar ratio) target. The target was made from a mixture of ZnO and $SnO_2$ powders calcined at $800^{\circ}C$. The working pressure was 1 mTorr, and the rf power was 120 W. The ratio of oxygen to argon ($O_2$:Ar) was varied from 0% to 10%, and the substrate temperature was varied from $27^{\circ}C$ to $300^{\circ}C$. The crystallographic properties and the surface morphologies of the films were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force spectroscopy (AFM). The ZnO-$SnO_2$ films deposited in $O_2$:Ar = 10% exhibited resistivity higher than $10^6{\Omega}cm$ and transmittance of more than 80% in the visible range.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.1 s.190
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• pp.118-125
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• 2007

In this study, we analyzed the plantar shear stress and normal pressure in lateral heel diabetic foot patients during walking by using in-shoe local shear stress and plantar pressure measurement systems. The shear force transducer based on the magnetic-resistive principle, was a rigid 3-layer circular disc. Shear transducers were mounted on the locations of four metatarsal heads and heel in the insole. Twelve normal subjects and three diabetic foot patients with diabetic neuropathy in the lateral heel participated in this study. The center of pressure in lateral heel diabetic foot patients moved more medially and directed toward the first, medial to the second metatarsal heads, and the hallux during late stance, making pressure at the medial heel and the second metatarsal head significantly larger than in the normal. Shear stress at the heel changed significantly in early stance and the magnitude of shear stresses in each metatarsal head also changed. Further studies would be very helpful to design foot orthoses in patients with diabetic neuropathy or other diseases.

• The Journal of Korea Robotics Society
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• v.8 no.3
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• pp.143-149
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• 2013

This paper presents a new miniature haptic display to convey ample haptic information to a user of a handheld interface. There are buttons on interfaces or general electronic devices, but existing buttons provide haptic feedback of only one passive pattern to a user. Because humans perceive tactile and kinesthetic information simultaneously when they handle objects the proposed actuator provides both sensations at once. It is able to generate various levels of kinesthetic sensations when pressing a button under diverse situations. Also, vibrotactile feedback can be delivered for exciting haptic effects with numerous patterns. Its performance was evaluated in accordance with the resistive force by changing the intensity of the input current. Experiments show that the proposed actuator has the ability to provide numerous haptic sensations for more realistic and complex haptic experiences.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.229.1-229.1
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• 2014

Tactile sensors have widely been researched in the areas of electronics, robotic system and medical tools for extending to the form of bio inspired devices that generate feeling of touch mimicking those of humans. Recent efforts in adapting the tactile sensor have included the use of novel materials with both scalability and high sensitivity [1]. Graphene, a 2-D allotrope of carbon, is a prospective candidate for sensor technology, having strong mechanical properties [2] and flexibility, including recovery from mechanical stress. In addition, its truly 2-D nature allows the formation of continuous films that are intrinsically useful for realizing sensing functions. However, very few investigations have been carrier out to investigate sensing characteristics as a device form with the graphene subjected to strain/stress and pressure effects. In this study, we present a sensor of vertical forces based on single-layer graphene, with a working range that corresponds to the pressure of a gentle touch that can be perceived by humans. In spite of the low gauge factor that arises from the intrinsic electromechanical character of single-layer graphene, we achieve a resistance variation of about 30% in response to an applied vertical pressure of 5 kPa by introducing a pressure-amplifying structure in the sensor. In addition, we demonstrate a method to enhance the sensitivity of the sensor by applying resistive single-layer graphene.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.185-189
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• 2005

We reported here nano-scale electrical phase-change recording in amorphous $Ge_2Sb_2Te_5$ media using an atomic force microscope (AFM) having conducting probes. In recording process, a pulse voltage is applied to the conductive probe that touches the media surface to change locally the electrical resistivity of a film. However, in contact operation, tip/media wear and contamination could major obstacles, which degraded SNR, reproducibility, and lifetime. In order to overcome tip/media wear and contamination in contact mode operation, we adopted the W incorporated diamond-like carbon (W-DLC) films as a protective layer. Optimized mutilayer media were prepared by a hybrid deposition system of PECVD and RF magnetron sputtering. When suitable electrical pulses were applied to media through the conducting probe, it was observed that data bits as small as 25 nm in diameter have been written and read with good reproducibility, which corresponds to a data density of $1 Tbit/inch^2$. We concluded that stable electrical phase-change recording was possible mainly due to W-DLC layer, which played a role not only capping layer but also resistive layer.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.9
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• pp.53-61
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• 2013

This paper propose a improved operating characteristics of the 5-phase 5kW within developed the surface permanent mount synchronous generator (SPMSG) in order to make a study of a polyphase ac motors keeping hold of more advantages. The developed manufacturing motor was necessary to do improvement of voltage regulation, efficiency, operating characteristics, and so on at the rated load. There are remake a redesigned and distributed stator winding connection without changing the frames of stator and rotor core in previous established generator by a repeat tests. There are shown a amplitude and waveform of the generated electromotive force, FFT analysis of harmonics within output voltages, and reviewing a experiment results in load of resistive and 5-phase induction motor by variable generator output frequency.

• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.175-179
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• 2022

Magnetic arc extinguishing technology is effective as an extinguishing device for low-voltage direct current (DC) circuit breakers with a resistive load of ≤4 kW. The separation distance between the magnet and the electrical contact must be shortened to increase the magnetic arc extinguishing force. However, if the magnet is installed too close to the electrical contact points, the magnet is exposed to high temperatures due to the arc current generated when the load current is cut off and the magnetism is lost. To solve this problem, the effective magnetic flux density at the electrical contact can be maintained high by placing the arc extinguishing magnet in a tandem structure with the electrical contact point between them, and the proper separation distance between the contact points and the magnet can be maintained. In addition, an electric arc extinguishing technology that emits arc energy using a series circuit of diode and resistor is used to suppress the continuous arc voltage generated by the inductive load. For the proposed circuit breaker, the breaking characteristics are analyzed through the breaking test for the DC load of the 760 V level, the load power of 4 kW, and the time constant of 5 ms, and an appropriate arc extinguishing design guideline is proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.10-18
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• 2012

Most of studies on existing strengthening methods were mainly on increase of stiffness and strength of shear strengthening to rectangular beam. As concrete of beam and slab is poured simultaneously on the characteristics of construction in reinforced concrete beam-slab structure, adjacent slab uniformed after hardening has T-shaped beam cross section which makes the flange of beam, enhances the stiffness of the beam and widens the area supporting compressive strength, but available data of flexural behavior of T-shaped beam are lacking. In this research the T-shaped beams would be made, then the reinforced effects and structural properties can be estimated according to the kinds of reinforced materials and reinforced position. The conclusions are shown as below. To sum up the experimental results, The specimen which was reinforce by CB embedded inside of concrete indicated excellent resistive behavior, internal force and stiffness when it was destroyed. The steel plate reinforced specimen of stiffness and internal force were increase but it expressed lower reinforce effects because of lowering anchored force between concrete. Fiber sheet strengthening showed superior effects but the interfacial delamination was found due to the lack of anchored force in destruction. So the measure is needed now.

• Journal of the Korean Electrochemical Society
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• v.7 no.3
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• pp.148-154
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• 2004

Ammonium ion selective electrodes have been prepared using nonactin as an ionophore and poly(vinyl chloride) (PVC) or polyurethane(PU) as a polymer matrix with or without a plasticizer, bis(2-ethylhexyl) adipate, and their performances have been evaluated. The reults indicate that PU-based electrodes can be designed to perform better although PVC-based electrodes generally show better performances. In efforts to explain the obervation, we also carried out atomic force microscopy as well as impedance studies, and the results suggests that islands of ion-ophores are formed in the PVC membranes through which ion transfers appear to be more facile than through the PU membranes. The PU membranes appear to have ionophores better dispersed throughout the film and are more resistive to ion mobilities in comparison to PVC films.