• Journal of the Korean Society for Nondestructive Testing
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• v.33 no.2
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• pp.193-197
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• 2013

In this study, ultrasonic nonlinear characteristics in the heat-treated aluminum alloy have been evaluated. The nonlinearity of ultrasonic wave has been measured as the acoustic nonlinear parameter ${\beta}$, depending upon the amplitude ratio of the second-order harmonic and the fundamental frequency component of ultrasonic wave propagating through the materials. The parameter ${\beta}$ measurement has been carried out with the reflected signals from the back-wall of specimens at the same plane using the contact-type transducers. The heat-treatment, aging, has been achieved at $300^{\circ}C$ for various durations in the range of 1 to 50 hours. The tensile strength and elongation are obtained by the tensile test and then compared with the parameter ${\beta}$. There is a peak of the acoustic nonlinear parameter ${\beta}$ on 5 hours aging and the ${\beta}$ decreases thereafter, exhibiting closed relations with tensile strength and elongation. Also, the heat-treatment time showing peak in the parameter ${\beta}$ was identical to that showing severe change in the ${\sigma}-{\varepsilon}$ curve. These results suggest that the acoustic nonlinear parameter ${\beta}$ can be used for monitoring the strength variations with aging of aluminum alloys.

• Korean Security Journal
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• no.19
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• pp.139-163
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• 2009

The purpose of this study is to build up the expert system with more subdivided qualifications and improved qualities with the development of the security industry. And also it is to analyze a survey measuring how satisfied they are with curriculum, teaching faculty, educational administration, facilities among 439 private guards completing a course in Korea private guard educational institution and registered in the National Police Agency in Seoul, Gyeonggi, Chungcheong, Gyeongsang, Jeolla province. For this, SPSS(Statistical Packages for Social Science) 15.0 Version was adapted to analyze and other analysis methods used for this study are like these: frequency, reliability analysis, regressive analysis, moderated multiple regression, post hoc test for categorizing the performance changes, looking into the characteristics, examining closely job performance, intention to quit one's job, and inquiring into the influence how satisfaction measurement at education training satisfaction makes on carrying out one's job. Firstly, The Effect Satisfaction at The Program has on Performing One's Duty With respect to job performance, curriculum, educational administration, teaching abilities have positive influences on it. On the other hand, with respect to quitting one's job, curriculum just makes positive effects on leaving one's work statistically. It indicates that systematic and effective curriculum, administration, teaching faculty or contents with high quality rather than just education facilities would make the task performance excellent and satisfaction at the program well in regards to making effects on the task performance. Secondly, The Effect Satisfaction at The Program has on Performing One's Duty with Social Supports Despite being the fact that statistically any strong correlation between curriculum and social supports, one between education facilities and social supports, one between teaching abilities and social supports, and one between educational administration and social supports do not have influences on carrying out job performance, it turns out that satisfaction at the program and social supports make positive effects on performing one's task. In conclusion, the entire social system and support need to be improved and some institutions appropriate for satisfaction at the program should be established as soon as possible.

• Journal of The Korean Astronomical Society
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• v.50 no.6
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• pp.167-178
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• 2017

We present a study of the inexplicit connection between radio jet activity and ${\gamma}$-ray emission of BL Lacertae (BL Lac; 2200+420). We analyze the long-term millimeter activity of BL Lac via interferometric observations with the Korean VLBI Network (KVN) obtained at 22, 43, 86, and 129 GHz simultaneously over three years (from January 2013 to March 2016); during this time, two ${\gamma}$-ray outbursts (in November 2013 and March 2015) can be seen in ${\gamma}$-ray light curves obtained from Fermi observations. The KVN radio core is optically thick at least up to 86 GHz; there is indication that it might be optically thin at higher frequencies. To first order, the radio light curves decay exponentially over the time span covered by our observations, with decay timescales of $411{\pm}85$ days, $352{\pm}79$ days, $310{\pm}57$ days, and $283{\pm}55$ days at 22, 43, 86, and 129 GHz, respectively. Assuming synchrotron cooling, a cooling time of around one year is consistent with magnetic field strengths $B{\sim}2{\mu}T$ and electron Lorentz factors ${\gamma}$ ~ 10 000. Taking into account that our formal measurement errors include intrinsic variability and thus over-estimate the statistical uncertainties, we find that the decay timescale ${\tau}$ scales with frequency ${\nu}$ like ${\tau}{\propto}{\nu}^{-0.2}$. This relation is much shallower than the one expected from opacity effects (core shift), but in agreement with the (sub-)mm radio core being a standing recollimation shock. We do not find convincing radio flux counterparts to the ${\gamma}$-ray outbursts. The spectral evolution is consistent with the 'generalized shock model' of Valtaoja et al. (1992). A temporary increase in the core opacity and the emergence of a knot around the time of the second ${\gamma}$-ray event indicate that this ${\gamma}$-ray outburst might be an 'orphan' flare powered by the 'ring of fire' mechanism.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.6 no.3
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• pp.493-506
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• 1999

The purpose of the study is to evaluate the effectiveness and competence level of trainees of Cardiopulmonary resuscitation training targeted for nursing students. 70 nursing students of Y nursing college are recruited as subjects from Dec. 1st, 1998 through Dec. 8th. 1998. For the pre-test. demographic data related to CPR and knowledge of CPR were evaluated. For the post-test, the next week of pre-test, three difference groups of subjects were tested their knowledge of CPR. CPR training was designed by two components which were 90 mins lecture and demonstration by one professor and individual practice using two educational models with two professors. As the tool of measurement estimating pre or post knowledge of CPR. questionnaires were developed based on self-diagnosis questionnaires of American Heart Association(AHA). The questionnaires were multiple choices (50 questions) and open end questions regarding CPR process. Each multiple choices questions valued 2 points (Score varied min. 0 point to max 100 points.). Collected data were computerized and analyzed by SPSS-WIN. Frequency and percentage of each questions analyzed. The differences of the knowledge and competency level of subjects between pre and post test was analyses by paired t-test. The followings are research outcome. 1. In the pre-test, 95% of subjects answered that they already knew what CPR was. but only 82% described correctly what CPR was. 49% learned CPR before, and 80s5 of them learned at high school. 2. 37 questions scores increases, and 10 questions scores decreased. 3 questions didnt change their score. After getting training, ratio of 80% correct score significantly increased 4 times. 3. In post-test. knowledge level of trainees increased compared to that of pre-test. (t=-15.075, p=.000) 4. Competence level also increased (t=-14.86, p=.00). In result, after getting CPR training, most CPR knowledge increased except open the air tract, toddler CPR, and alternative behavior when the air tract is blocked. CPR training needs to extend the educational scope not only CPR lecture but also psychomotor skill practice. CPR trainees are in need of appropriate feedback as well as enough opportunities of skill practice.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.6 no.3
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• pp.507-521
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• 1999

Yu-Dong-Kong exercise is to produce heat from rubbing hands and is composed of 10 different types of exercise using warmed hands. The objective of this research is to evaluate the effect of Yu-Dong-Kong exercise on physical function and emotional state in elderly. The design of research is Nonequivalent Control Group Pretest-Posttest Design. The independent variable is Yu-Dong-Kong exercise, and the dependent variables are physical function and emotional state. Subjects are 18 elderly in the experimental group and 16 elderly in control group. All of them are above 60 year old and live in 1-city, Kyonggi-do. The exercise period was 4 weeks and data were collected from April to August in 1998. The exercise frequency was once a day. The exercise duration was from 10 to 20 minutes. The measurement tools are modified 1) Cornell Medical Index-Health questionnaire and 2) Geriatric Depression Scale. Collected data were analyzed by t-test and paired t-test based on the purposes of research using SPSS-Window package. The results are summarized as follows : 1. There was no difference in pre-exercise physical function between two groups (t=-.95, p=.35). 2. The hypothesis that 'physical function in the experimental group will be improved compared to the control group' was not supported by t-test(t=-.925, p=.362). However. the physical function in the experimental group showed much improvement than that in the control group. 3. The hypothesis that 'emotional state in the experimental group will be improved compared to the control group' was not supported by t-test(t=-1.715, p=.096). However, the emotional state in the experimental group showed much improvement than that in the control group. 4. The hypothesis that 'physical function will be improved in the post-exercise compared to pre-exercise' was not supported by paired t-test(t=.302, p=.766) However, a slight improvement in the physical function was found. For the further study, it is recommended to reevaluate the effect of Yu-Dong-Kong exercise through large number of subjects and long-term study. Also, a separate study with different type of subjects is recommended. In addition, continuation and compliance this strategy for exercise should be developed.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.3
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• pp.96-101
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• 2015

This paper describes a design and implementation of the NFC bridge chip which performs interface between kinds of devices and mobile phones including NFC controller through NFC communication. The NFC bridge chip consists of the digital part and the analog part which are based on NFC Forum standard. Therefore the chip treats RF signals and then transforms the signal to digital data, so it can interface kinds of devices with the digital data. Especially the chip is able to detect RF signals and then wake up the host processor of a device. The wakeup function dramatically decreases the power consumption of the device. The carrier frequency is 13.56MHz, and the data rate is up to 424kbps. The chip has been fabricated with SMIC 180nm mixed-mode technology. Additionally an NFC bridge chip application to the blood glucose measurement system is described for an application example.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.194-201
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• 2012

Moxibustion is utilized not only to cure disease but also to increase immunity. However, it may lead to undesired effects including severe pains(blisters and burns) because of the difficulty of controlling heat intensity. To overcome these problems we developed the RF heat stimulation system which can control stimulus. Also, we developed the RF stimulation protocol for effective heat transfer in subcutaneous tissue of rabbit. RF stimulator consists of a medical RF capacitive heating device, isolation probe, isolation plate, negative pressure control part and temperature measurement part. For the designed stimulus protocol, we measured the temperature distribution on epidermis and in subcutaneous(5mm, 10mm) area of rabbit during moxibustion. A stimulation protocol was designed by controlling the ON/OFF duty ratio, repeating number, and energy of applied pulse to get the temperature distribution similar with that by moxibustion. In results, the correlation coefficients between temperature distribution by moxibustion and that of stimulator were 95% and 91% from 5mm and 10mm thick respectively. However, temperature distribution on epidermis by stimulator was remarkably lower than that of the moxibustion. Finally, the RF stimulation system showed that it can not only transfer effectively heat similar with moxibustion to the subcutaneous area, but also the influence by unwanted side effects can be minimized.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.10
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• pp.45-52
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• 2008

We investigated the design of an RF-powered, wireless temperature sensor tag chip using $0.18-{\mu}m$ CMOS technology. The transponder generates its own power supply from small incident RF signal using Schottky diodes in voltage multiplier. Ambient temperature is measured using a new low-power temperature-to-voltage converter, and an 8-bit single-slope ADC converts the measured voltage to digital data. ASK demodulator and digital control are combined to identify unique transponder (ID) sent by base station for multi-transponder applications. The measurement of the temperature sensor tag chip showed a resolution of $0.64^{\circ}C/LSB$ in the range from $20^{\circ}C$ to $100^{\circ}C$, which is suitable for environmental temperature monitoring. The chip size is $1.1{\times}0.34mm^2$, and operates at clock frequency of 100 kHz while consuming $64{\mu}W$ power. The temperature sensor required a -11 dBm RF input power, supported a conversion rate of 12.5 k-samples/sec, and a maximum error of $0.5^{\circ}C$.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.9
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• pp.68-73
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• 2013

In this paper, we proposed a readout circuit of pulse waveform and rate for a U-health system to monitor health condition. For long-time operation without replacing or charging a battery, either pulse waveform or pulse rate is selected as the output data of the proposed readout circuit according to health condition of a user. The proposed readout circuit consists of a simple digital logic discriminator and a dual-mode ADC which operates in the ADC mode or in the count mode. Firstly, the readout circuit counts pulse rate for 4 seconds in the count mode using the dual-mode ADC. Health condition is examined after the counted pulse rate is accumulated for 1 minute in the discriminator. If the pulse rate is out of the preset normal range, the dual-mode ADC operates in the ADC mode where pulse waveform is converted into 10-bit digital data with the sampling frequency of 1 kHz. These data are stored in a buffer and transmitted by 620 kbps to an external monitor through a RF transmitter. The data transmission period of the RF transmitter depends on the operation mode. It is generally 1 minute in the normal situation or 1 ms in the emergency situation. The proposed readout circuit was designed with $0.11{\mu}m$ process technology. The chip area is $460{\times}800{\mu}m^2$. According to measurement, the power consumption is $161.8{\mu}W$ in the count mode and $507.3{\mu}W$ in the ADC mode with the operating voltage of 1 V.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.1
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• pp.23-32
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• 2008

In the VHF range, active antennas are widely used for wideband applications due to their small size. Active antenna consists of antenna elements and amplifiers, which are directly connected to each other. Gain and noise-figure characteristics are very important for good sensitivity performance, because it is located at the front end of a receiving system. In this study, we developed an active dipole antenna with 5:1 bandwidth(100${\sim}$500 MHz), which consists of a dipole antenna and a P-HEMT amplifier. To obtain required performances, the antenna and the amplifier should be designed simultaneously. In order for that, we introduced an equivalent port concept to model the 1-port dipole antenna as an equivalent 2-port system. Using the proposed equivalent port, the performance of the active dipole antenna was simulated by the ADS. In order to measure the gain and noise-figure characteristics of the antenna, we utilized the same concept of the two-port equivalent impedance model. The measurement results for typical gain, NF and VSWR in the required frequency band were 8dBi, 9dB and 1.7:1, respectively. The radiation patterns at the principal planes were same as the typical radiation pattern of a dipole antenna. By comparing the simulation results with measured ones, it is confirmed that the proposed methods works well.