• Structural Engineering and Mechanics
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• v.17 no.3_4
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• pp.303-329
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• 2004

Magnetostrictive materials are routinely employed as actuator and sensor elements in a wide variety of noise and vibration control problems. In infrastructural applications, other technologies such as hydraulic actuation, piezoelectric materials and more recently, magnetorheological fluids, are being favored for actuation and sensing purposes. These technologies have reached a degree of technical maturity and in some cases, cost effectiveness, which justify their broad use in infrastructural applications. Advanced civil structures present new challenges in the areas of condition monitoring and repair, reliability, and high-authority actuation which motivate the need to explore new methods and materials recently developed in the areas of materials science and transducer design. This paper provides an overview of a class of materials that because of the large force, displacement, and energy conversion effciency that it can provide is being considered in a growing number of quasistatic and dynamic applications. Since magnetostriction involves a bidirectional energy exchange between magnetic and elastic states, magnetostrictive materials provide mechanisms both for actuation and sensing. This paper provides an overview of materials, methods and applications with the goal to inspire novel solutions based on magnetostrictive materials for the design and control of advanced infrastructural systems.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.215-218
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• 2001

Finite element models are constructed using the commercial code ANSYS for two most representative types of ultrasonic transducers, cMUTs and piezoelectric transducers. Calculation result shows the origin and level of cross talk between array elements in each transducer type For reduction of the cross talk level, the effects of various structural variations are Investigated for each transducer type. The results say that proper design of the coupling isolation structures between the transducing elements can significantly reduce the cross talk in ultrasonic transducers.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.9
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• pp.841-848
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• 2010

Previous experimental results show that the magnetostrictive transducer has the peculiar characteristic with relation to their reversible magnetization and its practical usage will be hindered by this phenomena. In this paper, the idea of anhysteretization is adopted in order to solve this problem. The experimental results reveal that the anhysteretization can get rid of the extraordinary phenomena which are occurred by the change of biasing magnetic field. The effects of two important parameters, which are the amplitude and the decaying time of this process, on the anhysteretization are investigated experimentally. Finally the best operating condition is proposed in order to maximize the sensitivity under the anhysteretization.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.242-247
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• 2009

The ability of time reversal techniques to focus ultrasonic beams on the source location is important in many aspects of ultrasonic nondestructive evaluation. In this paper, we investigate the time reversal beam focusing of ultrasonic array sensors on a defect in layered media. Numerical modeling is performed using the commercially available software which employs a time domain finite difference method. Two different time reversal approaches are considered - the through transmission and the pulse-echo. Linear array sensors composed of N elements of line sources are used for signal reception/excitation, time reversal, and reemission in time reversal processes associated with the scattering source of a side-drilled hole located in the second layer of two layer structure. The simulation results demonstrate the time reversal focusing even with multiple reflections from the interface of layered structure. We examine the focusing resolution that is related to the propagation distance, the size of array sensor and the wavelength.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.11
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• pp.1128-1133
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• 2008

Cellulose based electroactive paper(EAPap) has been developed as a new smart material due to its advantages of piezoelectricity, large displacement, low power consumption, low cost and flexibility. EAPap can be used for a surface acoustic wave (SAW) device using the piezoelectric property of EAPap, resulting in the cost effective and flexible SAW device. In this paper, inter digit transducer(IDT) structure using lift-off technique with a finger gap of 10mm was used for micro fabrication of the cellulose EAPap SAW devices. The performance of IDT patterned SAW device was characterized by a Network Analyzer. The feasibility of cellulose EAPap as a potential acoustic device was presented and explained.

• Journal of Sensor Science and Technology
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• v.19 no.5
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• pp.361-368
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• 2010

ACROSS device, which is composed of an implantable microphone, a signal processor, and a vibrating transducer, is a fullyimplantable middle ear hearing device(F-IMEHD) for the recovery of patients with hearing loss. And since a microphone is implanted under skin and tissue at the temporal bones, the amplitude of the sound wave is attenuated by absorption and scattering. And the vibrating transducer attached to the ossicular chain caused also the different displacement from characteristic of the stapes. For the gain control of auditory signals, most of implantable hearing devices with the digital audio signal processor still apply to fitting rules of conventional hearing aid without regard to the effect of the implanted microphone and the vibrating transducer. So it should be taken into account the effect of the implantable microphone and the vibrating transducer to use the conventional audio fitting rule. The aim of this study was to measure gain characteristics caused by the implanted microphone and the vibrating transducer attached to the ossicle chains for the gain compensation of ACROSS device. Differential floating mass transducers (DFMT) of ACROSS device were clipped on four cadaver temporal bones. And after placing the DFMT on them, displacements of the ossicle chain with the DFMT operated by 1 $mA_{peak}$ current was measured using laser Doppler vibrometer. And the sensitivity of microphones under the sampled pig skin and the skin of 3 rat back were measured by stimulus of pure tones in frequency from 0.1 to 8.9 kHz. And we confirmed that the microphone implanted under skin showed poorer frequency response in the acoustic high-frequency band than it in the low- to mid- frequency band, and the resonant frequency of the stapes vibration was changed by attaching the DFMT on the incus, the displacement of the DFMT driven with 1 $mA_{rms}$ was higher by the amount of about 20 dB than that of cadaver's stapes driven by the sound presssure of 94 dB SPL in resonance frequency range.

• Journal of Biomedical Engineering Research
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• v.29 no.6
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• pp.457-465
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• 2008

HL7(Health Level 7) is a standard for exchanging medical and healthcare data among different medical information systems. As the ubiquitous era is coming, in addition to text and imaging information, a new type of data, i.e., streaming sensor data appear. Since the HL7 is not covering the interfaces among the devices that produces sensor data, it is expected that sooner or later the HL7 needs to include the biomedical sensors and sensor networks. The IEEE 1451 is a family of standards that deals with the sensors, transducers including sensors and actuators, and various wired or wireless sensor networks. In this paper, we consider the possibility of interoperability between the IEEE 1451 and HL7. After we propose a format of messages in HL7 to include the IEEE 1451 TEDS, we present some preliminary results that show the possibility of integrating the two standards.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.1 s.343
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• pp.33-40
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• 2006

This paper presents a novel surface acoustic wave (SAW)-based pressure sensor, which is composed of single phase unidirectional transducer (SPUDT), three reflectors, and a deep etched substrate for bonding underneath the diaphragm. Using the coupling of modes (COM) theory, the SAW device was simulated, and the optimized design parameters were extracted. Finite Element Methods (FEM) was utilized to calculate the bending and stress/strain distribution on the diaphragm under a given pressure. Using extracted optimal design parameters, a 440 MHz reflective delay line on 41o YX LiNbO3 was developed. High S/N ratio, shan reflection peaks, and small spurious peaks were observed. The measured S11 results showed a good agreement with simulated results obtained from coupling-of-modes (COM) modeling and Finite Element Method (FEM) analysis.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.3
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• pp.48-55
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• 1982

In the present the strain gauge type torque transducers consist of solid shaft as sensor, slip ring, brush and bridge circuit as detecting circuit. So in the case of measuring the low-capacity torque, the error caused by technical mistake in mounting stain gauge on the small sensor and especially by contact resistance between slip ring and brush takes place more than the large sensor. Therefore in this study constant voltage in order to have no effect of contact resistance is supplied to the hollow shaft and Schrobron Bridge Circuit. Through the experiment good results were obtained as follows; linearity, hysterisis and zero drift as static characteristics is within 1% F.S respectively. Also when loading, zero drift is about 2% F.S.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.94-100
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• 2000

This paper presents a methodology for In-Process monitoring of tool wear by using ultrasonic sensor in turning operation. An integrated single ultrasonic transducer operation at a frequency of 10MHz is placed in contact with the insert tip. The change in amount of the reflected energy from the nose and flank of the tool can be related to the level of tool wear and the mechanical integrity of the tool. As the results, the tool wear monitoring system based on the ultrasonic pulse-echo method was proposed, it is useful to determine a tool life and tool change time.