• Journal of the Korean Institute of Telematics and Electronics T
• /
• v.36T no.1
• /
• pp.86-92
• /
• 1999

This paper proposed a small type ofen-loop antenna model for the moisture sensor, and its operating characteristics were analyzed numerically using the moment methods. The numerical analysis results through the moment methods showed that this antenna was able to match the input impedance to 50$\Omega$ by changing parameters of the antenna in the frequency range from 300MHz to 500MHz. The gain of antenna was obtained about 2.5dBd. This antenna proposed in this paper showed not only the radiation pattern characteristics of the uniform distribution toward the axial direction above the antenna, but also the narrowband resonant characteristics. Thus we can propose that the antenna be more suitable for the moisture sensor.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.32 no.6
• /
• pp.661-668
• /
• 2012

Wireless sensor network is one of prospective methods for railway monitoring due to the long-term operation and low-maintenance performances. How to supply power to the wireless sensor nodes has drawn much attention recently. In railway monitoring, the idea of converting ambient vibration energy from vibration of railway track induced by passing trains to electric energy has made it a potential way for powering the wireless sensor nodes. In this paper, a bimorph cantilever piezoelectric energy harvester was designed based on a single degree-of-freedom model. Experimental test was also performed to validate the design. The first natural frequency of the bimorph piezoelectric energy harvester was decreased from 117.1 Hz to 65.2 Hz by adding 4 gram tip mass to the free end of the 8.6 gram energy harvester. In addition, the power generation of the piezoelectric energy harvester with 4 gram tip mass at resonant frequency was increased from 0.14 mW to 0.74 mW from $2.06m/s^2$ base excitation compared to stand-alone piezoelectric energy harvester without tip mass.

• Journal of Navigation and Port Research
• /
• v.28 no.6
• /
• pp.573-578
• /
• 2004

The most important effects on algae multiplication are coming from maintaining the growth environment such as necessary nutrients and proper temperature, but it is difficult to adjust for every species individually. In this study, therefore, the environment is obtained using the local water where target organisms live, and their growth is promoted by raising the water temperature. A sensor to count the organism population is developed here. Because the early stage of a sudden increase of the algae population is detected using the sensor, it is available to predict the sudden increase of algae, a source of red tide.

• Journal of KSNVE
• /
• v.5 no.3
• /
• pp.313-325
• /
• 1995

Two active/passive vibration dampers were designed to control a cantilever beam first mode of vibration. The active element was a piezoelectric polymer, polyvinlidene fluoride (PVDF). The passive damping was provided by the application of a viscoelastic layer on the surface of the steel beam. Two substantially different damper configurations were designed and tested. One damper consisted of a piezoelectric actuator bonded to one face of the beam, with a viscoelastic layer applied to the other surface of the beam. The second one was composed of a layer viscoeastic layer with one surface bonded to the beam, and with other being constrained by nine piezoelectric actuators connected in parallel. A control law based on the sign of the angular velocity of the cantilever beam was implemented to control the beam first mode of vibration. The piezoelectric sensor output was digitally differentiated to obtain the transverse linear velocity, and its sign was used in the control algorith. Two dampers provided the system a damping increase of a factor of four for the first damper and three for the second damper. Both dampers were found to work well at low levels of vibration, suggesting that they can be used effectively to prevent resonant vibrations in flexible structure from initiating and building up.

• Journal of the Optical Society of Korea
• /
• v.18 no.4
• /
• pp.301-306
• /
• 2014

A porous silicon microcavity (PSMC) sensor has been made for vapors of solvent solutions, and a method has been developed in order to obtain simultaneous determination of two volatile substances with different concentrations. In our work, the temperature of the solution and the velocity of the air stream flowing through the solution have been used to control the response of the sensor for ethanol and acetone solutions. We study the dependence of the cavity-resonant wavelength shift on solvent concentration, velocity of the airflow and solution temperature. The wavelength shift depends linearly on concentration and increases with solution temperature and velocity of the airflow. The dependence of the wavelength shift on the solution temperature in the measurement contains properties of the temperature dependence of the solvent vapor pressure, which characterizes each solvent. As a result, the dependence of the wavelength shift on the solution temperature discriminates between solutions of ethanol and acetone with different concentrations. This suggests a possibility for the simultaneous determination of the volatile substances and their concentrations.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.24 no.6
• /
• pp.463-467
• /
• 2011

In this study, thickness shear mode piezoelectric devices for AE sensor with excellent displacement and sensitivity characteristics were simulated using ATILA FEM program, and then fabricated. Displacement and electro mechanical coupling factors of the piezoelectric devices were investigated. The simulation results showed that excellent displacement and electromechanical coupling factor was obtained when the ratio of Length/Thickness was 1. The piezoelectric device of L/T= 1 exhibited the optimum values of fr= 150 kHz, displacement= $6.23{\times}10^{-8}$[m], $k_{15}$= 0.598. The results show that the thickness shear mode piezoelectric device is a promising candidate for the application of AE sensor piezoelectric device.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.1
• /
• pp.107-111
• /
• 2013

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM applications. As a result, comparing to the past result, the maximum prediction error of resonant frequency was within 3 percent and peak dither rate was within 5 percent. It was found that the theoretical equations can be feasible for the mechanical performance of dither.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.6
• /
• pp.1949-1954
• /
• 2010

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region(dead band) due to the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference, and an angular increment is not detected. This problem can be overcome by mechanically dithering the gyroscope. This paper presents the design method of mechanical dither by the theoretical considerations and the verification of the theoretical equations through FEM(Finite Element Method) applications. As a result, the maximum prediction error of resonant frequency and peak dither rate was under 5 percent. The theoretical equations for the mechanical performances of dither can be said to be feasible.

• 한국가시화정보학회:학술대회논문집
• /
• 2002.04a
• /
• pp.1-7
• /
• 2002

This papers describes the preparation and experimental results of a micro mass detection devices based on cantilever and a diffuser-type micro pump using screen printing thick-film technologies and Si micro-machining. PZT-PCW thick films were prepared by new hybrid method based on the screen printing. By applying these PZT-PCW piezoelectric thick films on actuator, a cantilever for mass detection sensor and a micropump for microfluidic element are successfully fabricated. Resonant frequency and displacement of PZT-PCW thick film actuator in air and in liquid are measured by laser vibrometer system as a function of actuator size. The resonant frequency of PZT-PCW thick film actuator in liquid decreases order of 1/2-1/4 due to damping effect. The sensitivity of cantilever is characterized by Au deposition method which has the mass loading effect such as adsorption of protein. The Sensitivity of PZT-0.12PCW thick film cantilever is proportional to detecting area.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.7 no.3
• /
• pp.151-160
• /
• 2007

We report the label-free biomolecules detection based on nanomechanical micro cantilevers operated in dynamic mode for detection of two marker proteins (myoglobin and creatin kinase-MB (CK-MB)) of acute myocardical infarctions. When the specific binding between the antigen and its antibody occurred on the fuctionalized microcantilever surface, mechanical response (i.e. resonant frequency) of microcantilevers was changed in lower frequency range. We performed the label-free biomolecules detection of myoglobin and CK-MB antigen in the low concentration (clinical threshold concentration range) as much as 1 ng/ml from measuring the dynamic response change of micro cantilevers caused by the intermolecular force. Moreover, we estimate the surface stress on the dynamic microcantilevers generated by specific antibody-antigen binding. It is suggested that our dynamic microcantilevers may enable one to use the sensitive label-free biomolecules detection for application to the disease diagnosis system based on mechanical immuno-sensor.