• The Journal of the Acoustical Society of Korea
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• v.8 no.1
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• pp.75-80
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• 1989

A Mach-Zehnder interferometer using single mode optical fiber was constructed which operates in homodyne detection scheme. Its response to air-borne soun pressure was examined experimentally. A signal stabilizer was developed for maintaining optical fiber interferometer in quadrature condition using a cylindrical piezoelectric stretcher. This maintains the optical fiber sensor at a maximum sensitivity in the presence of the phase drift caused by temperature fluctuation and other types of environmental disturbances.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.387-391
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• 2004

[ $(Bi_{1/2}Na_{1/2})TiO_3$ ](BNT) is considered to be an excellent candidate for the key material of lead-free piezoelectric ceramic due to properties of strong ferroelectricity with a relatively large remanent polarization $Pr=38{\mu}C/cm^2$, and a large coercive field, Ec=73KV/cm. In this study, electrical properties of pressure sensor using a $0.96Bi_{0.5}(Na_{0.84}K_{0.16})_{0.5}TiO_3+0.04SrTiO_3+0.2wt%La_2O_3$ ceramics are investigated. Resonant frequency of pressure sensor was decreased with increasing pressure. However, its anti-resonant frequency was increased with increasing pressure.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.2
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• pp.69-74
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• 2015

Recently, energy harvesting technology is increasing due to the fossil fuel shortages. Energy harvesting is generating electrical energy from wasted energies as sunlight, wind, waves, pressure, and vibration etc. Energy harvesting is one of the alternatives of fossil fuel. One of the energy harvesting technologies, the piezoelectric energy harvesting has been actively studied. Piezoelectric generating uses a positive piezoelectric effect which produces electrical energy when mechanical vibration is applied to the piezoelectric device. Piezoelectric energy harvesting has an advantage in that it is relatively not affected by weather, area and place. Also, stable and sustainable energy generation is possible. However, the output power is relatively low, so in this paper, newly designed honeycomb shaped piezoelectric energy harvesting device for increasing a generating efficiency. The output characteristics of the piezoelectric harvesting device were analyzed according to the change of parameters by using the finite element method analysis program. One model which has high output voltage was selected and a prototype of the honeycomb shaped piezoelectric harvesting device was fabricated. Experimental results from the fabricated device were compared to the analyzed results. After the AC-DC converting, the power of one honeycomb shaped piezoelectric energy harvesting device was measured 2.3[mW] at road resistance 5.1[$K{\Omega}$]. And output power was increased the number of harvesting device when piezoelectric energy harvesting device were connected in series and parallel.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.13-13
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• 2010

Piezoelectric sensors are extensively used to measure force because of their high sensitivity and low cost. however, the development of device with reduced size but with improved sensitivity is highly important. Low-temperature co-fired ceramic (LTCC) is one of promising materials for this application than a silicon substrate because it has very good electrical and mechanical properties as well as possibility of making various three dimensional (3D) structures. In this work, piezoelectric pressure sensors based on hybrid LTCC technology were presented. The LTCC diaphragms with thickness of $400\;{\mu}m$ were fabricated by laminating 12 green tapes which consist of alumina and glass particle in an organic binder. The piezoelectric sensing layer consists of PZT thin film deposited by RF magnetron sputtering method on between top and bottom Au electrodes. The PZT films deposited on LTCC diaphragms were successfully grown and were analyzed by using X-ray diffraction method (XRD) and field emission scanning electron microscope (FESEM).

• Journal of Sensor Science and Technology
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• v.19 no.2
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• pp.149-154
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• 2010

Top of the alumina body which is made according to plan has been printed using a screen printer equipment in order to print an electrode pattern. The electrode is connected with the quartz crystal oscillator of the piezoelectricity method which has a piezoelectric characteristic. The pressure contact department has been experimented using three type of the teflon. The teflon is good for pressure delivery vector but it is bad restitution. So we devised the structure which inserts the metal in the teflon. Bottom of the module is connected with the signal processing department which is planned in advance and then has investigated to characteristic. Therefore we have got the best output-voltage and frequency characteristic follows in the pressure.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1441-1446
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• 2017

In recent, the studies on the systems have been progressing that count the number of people passing through passageway or count people who exist in specific space. The existing people counting systems count the number of people using ultrared sensors, ultrasonic sensors or camera sensors, which can be installed only on pillar or around wall. Though ultrared sensors and ultrasonic sensors is low cost, they are inadequate to detect incoming/outgoing when several pedestrians pass through passageway concurrently. In this paper, we designed a sensor mat using piezoelectric sensors to complement the above-mentioned disadvantage. Also, we implemented the system that detects direction of progress and counts the number of people. The sensor mat detects direction of progress using pressure given on sensors and timing information and counts the number of people when pedestrians pass through on a sensor mat.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.2 s.257
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• pp.202-207
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• 2007

In order to understand the phenomena of combustion instability, an experimental study was conducted at the moderate pressure and ambient temperature conditions. The flame behavior and the pressure fluctuations were measured in a dump combustor. Various types of combustion modes occurred in accordance with the equivalence ratio and the fuel supplying conditions. The fluctuation of pressure, heat release and equivalence ratio were measured by piezoelectric pressure sensor, high speed Intensified Charge Coupled Device (HICCD) camera and gas chromatography respectively. Two representative modes were self-excited pressure oscillations at the resonance of combustion chamber (200Hz) and instabilities related to the modulated fuel flow rate through the fuel holes (10Hz). It is found that, especially in an unchoked fuel flow condition, the modulation of the fuel flow rate affects the characteristics of flame behavior and pressure fluctuations in a lean premixed flame.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.204-204
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• 2010

A development of device with reduced size and improved sensitivity is highly impotant Pb(Zr,Ti)$O_3$ thin films are widely used both to make actuator and sensor due to their high sensitivity and low cost. In this study, the feasibility of a piezoelectric presssure sensors based on hybrid low-temperaute co-fired ceramic (LTCC) technology were presented. The LTCC diaphragms with thickness of $400\;{\mu}m$ were fabricated by laminating 4 green tapes which consist of alumina and glass particle in an organic binder. PZT thin films were successfully prepared on between top and bottom Au electrode with LTCC substrates using RF magnetron sputtering. In addition, The frequency response characteristics of the sensor under varing pressure has been analysed. by Network Analyser (HP-8722D). A frequency shift range has been obseved from 1.7GHz to 1.8GHz with a good linearity for applied pressure from 0 psi up to 25 psi.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.451-464
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• 2022

The high-level nuclear waste repository is a deep geological disposal system exposed to complex environmental conditions such as high temperature, radiation, and ground-water due to handling spent nuclear fuel. Continuous exposure can lead to cracking and deterioration of the structure over time. On the other hand, the high-level nuclear waste repository requires an ultra-long life expectancy. Thus long-term structural health monitoring is essential. Various sensors such as an accelerometer, earth pressure gauge, and displacement meter can be used to monitor the health of a structure, and a piezoelectric sensor is generally used. Therefore, it is necessary to develop a highly durable sensor based on the durability assessment of the piezoelectric sensor. This study designed an accelerated life test for durability assessment and life prediction of the piezoelectric sensor. Based on the literature review, the number of accelerated stress levels for a single stress factor, and the number of samples for each level were selected. The failure mode and mechanism of the piezoelectric sensor that can occur in the environmental conditions of the high-level waste repository were analyzed. In addition, two methods were proposed to investigate the maximum harsh condition for the temperature stress factor. The reliable operating limit of the piezoelectric sensor was derived, and a reasonable accelerated stress level was set for the accelerated life test. The suggested methods contain economical and practical ideas and can be widely used in designing accelerated life tests of piezoelectric sensors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.350-351
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• 2006

Thick film mechanical sensors can be categorized into four main areas piezoresistive, piezoelectric, capacitive and mechanic tube. In this areas, the thick film strain gage is the earliest example of a primary sensing element based on the substrates. The latest thick film sensor is used various pastes that have been specifically developed for pressure sensor application. Some elastic materials exhibit a change in bulk resistivity when they are subjected to displacement by an applied pressure. This property is referred to as piezoresistivity and is a major factor influencing the sensitivity of a piezoresistive strain gage. The effect of thick film resistors was first noticed in the early 1970, as described by Holmes in his paper in 1973.