• Proceedings of the Korea Society of Information Technology Applications Conference
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• 2005.11a
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• pp.85-90
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• 2005

The advance of mobile and telematics technologies has produced vehicles with various convenient services for drivers. Specifically lots of researches and several technologies have been developed to provide services of a remote vehicle diagnosis and control. The existing and representative product for a vehicle control is a RCS (remote control system), but it has a problem of short control distance and fragile security. In this paper, a telematics terminal embedded with CDMA and GPS is designed, which can be connected to the Internet. It allows a driver with a cellular phone to remotely diagnosis and control a vehicle via wireless network and SMS.

• Proceedings of the Korea Information Processing Society Conference
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• 2005.11a
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• pp.1327-1330
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• 2005

모바일 기술과 텔레매틱스 기술의 발전으로 차량에 대한 다양한 서비스가 제공되어 지고 있으며, 관련 분야에 많은 연구와 다양한 방법들이 제시되고 있다. 기존의 차량 진단 및 제어 시스템은 리모컨등을 이용하여 서비스를 제공하고 있으나 수신거리 제한, 보안 취약성 등의 문제점 등을 내포하고 있다. 본 논문에서는 CDMA 모뎀과 GPS를 내장한 텔레매틱스 단말기를 설계하여 원격지에서 사용자의 휴대전화를 통해 무선 인터넷 서비스(WAP)와 SMS를 이용하여 차량의 상태를 확인하고 제어 할 수 있는 방법을 제안한다.

• Journal of the Semiconductor & Display Technology
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• v.3 no.4
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• pp.19-27
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• 2004

The characteristic evaluation of A/D converter is to measure the linearity of the converter. The evaluation of the linearity is to measure the DNL, INL, gain error and offset error in the various test parameters of A/D converter. Generally, DNL and INL are to be measured by the Histogram Test Algorithm in the DSP-based ATE environment. And gain error and offset error are to be measured by the calculation equation of the measuring algorithm. It is to propose the new Concurrent Histogram Test Algorithm for the test of the housekeeping A/D converter used in the CDMA cellular phone. Using the proposed method, it is to measure the DNL, INL, gain error and offset error concurrently and to show the measured results.

• The Journal of the Acoustical Society of Korea
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• v.17 no.8
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• pp.12-18
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• 1998

본 논문에서는 개선된 elliptic 저역통과 함수를 제시하고, CMOS DDA 소자 및 DDA 응용회로를 이용하여 CDMA 무선 휴대폰용 아날로그 DDA 저역통과 필터를 설계하 였다. 개선된 elliptic 저역통과 필터 함수는 통과대역과 저지대역에서 점진적 감소 파상 특 성을 갖고, 우수 또는 기수 차수 모두에 대해서 ω=0에서는 통과대역의 최대값, ω=∞에서 는 영이 된다. 또한 극점-Q 값이 감소함에 따라 주파수 및 시간영역의 특성 등이 기존의 함수와 비교하여 향상되었다. 아날로그 능동 저역통과 필터는 수동 복종단 제자형 회로망의 저감도 특성이 유지되는 개구리 도약법으로 모의하고, 적분기등을 외부 소자와의 정합이 필 요 없는 DDA를 이용하여 설계하였다. 설계된 DDA 회로의 단위 이득 주파수는 1.32GHz이 고 이를 이용하여 DDA 저역통과 필터를 설계하여 HSPICE로 시뮬레이션한 결과 필터의 차단 주파수는 630KHz로 설계명세조건과 일치하였다.

• Journal of Biomedical Engineering Research
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• v.29 no.6
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• pp.443-450
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• 2008

The purpose of this study is to measure both ECG and BCG(Ballistocariograph) signal of a subject on moving or resting wheelchair and detect the heart rate and respiratory rate and transmit an event message to remote server on emergent situation. To acquire ECG and BCG data, amplifier circuits were composed to be suitable for their characteristics. The output signals were converted to digital data and stored in bio-signal archiving media(SD card). CDMA module was used to transmit the event data on ECG electrode detachment and the received data was monitored by the developed C# application program. 5 volunteers participated in the experiment to evaluate the validity of the developed device. When the event occurs in each subject, 48 Kbyte data, stored for 32 seconds from that point, was transmitted to remote server through CDMA cellular phone network correctly. The received data of ECG, BCG, and 3-axial acceleration could be archived in server and the heart rate and respiratory rate could be measured and analyzed. The developed device in this study could acquire the ECG and BCG data of subjects on wheelchair simultaneously and measure their heart rate and respiratory rate. In addition, event data was verified to be transmitted to remote server without any errors.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.9
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• pp.1941-1948
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• 1997

In this paper, the power efficient linear upconversion mixer which is a functional circuit in transmit path of intermediate frequency(IF) part of Code Division Multiple (CDMA) cellular phone was explained. In generally, the low CMOS devices limits the implementation of upconversion mixer especially for lower loads. Using replica transconductor, the linear range is extended up to the limit. Thiscircuit was imprlemented using $0.8{\mu}\textrm{m}$ N-well CMOS technology with 2-poly/2-metal. The active area of chip is $0.53mm{\times}0.92mm$. The power consumption is 30mW with 3.3V suply voltage. The 1dB conpression characteristics is -27.3dB with $25{\Omega}$. load and being applied by 2-tone input signal. The mixer operates properly above 200MHz.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.493-495
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• 2003

최근의 휴대 전화는 단순한 음성 통신 기기 역할 뿐만 아니라 데이터 통신 기기로도 쓰이고 있으며, CDMA-2000 망 보급으로 인하여 데이터 통신 대역폭이 멀티미디어 데이터를 처리 할 수 있을 만큼 증대 되었다. 하지만 휴대 전화는 하드웨어 성능이 음성 통신 기기로 최적화 되어 있고 휴대성을 높이기 위해 저전력의 저 성능 프로세서를 탑재 하였기 때문에 소프트웨어 방식의 비디오/오디오 재생이 매우 힘들다. 특히. 널리 사용되는 비디오/오디오 표준(MPEG-x, H.26x, 등등)은 압축 최우선의 방식으로써 계산량이 매우 크기 때문에 휴대 전화에서 하드웨어 도움 없이 소프트웨어로만 재생하기에는 적합하지 않다. 본 논문에서는 이러한 문제를 해결하기 위해 먼저 일반 목적의 널리 사용되는 코덱의 문제점과 휴대전화의 하드웨어 자원에 관해 알아 보고, 연산량을 효과적으로 조절할 수 있는 웨이블릿 함수를 이용하여 휴대 전화 시스템에 적합한 비디오/오디오 코덱을 제안한다. 또한 비디오 디코딩에 필요한 연산을 측정하고 실제 휴대 전화에 적용하여 그 성능을 확인 한다.

• Biomedical Science Letters
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• v.12 no.1
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• pp.9-16
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• 2006

We investigated the effects of 835-MHz electromagnetic field (EMF), one of the most popular communication frequency band in Korean code-division multiple-access (CDMA) mobile phone system, on cellular signal transduction. For this, we examined the change of intracellular calcium $([Ca^{2+}]_i)$, reactive oxygen species (ROS) and F-actin polymerization after exposure to 835-MHz EMF followed by the treatment of agonists in Rat-2 fibroblast cells. Culture cells were pretreated with serum-tree medium and concomitantly exposed to 835-MHz at specific absorption rate (SAR) of 4.0 W/kg for 24 hr in a specialized designed apparatus based on Transverse Electro Magnetics (TEM) wave theory. Intracellular $Ca^{2+}$ responses to lysophosphatidic acid (LPA) and epidermal growth factor (EGF) in Rat-2 fibroblast after exposure to 835-MHz EMF were shown to be similar pattern as observed in normal cultured cells. However, the LPA-induced calcium spiking was slightly delayed to 7 sec and sustained thereafter to a little higher ground level under 835-MHz EMF radiation compared to unexposed cells. ROS production level by LPA in the exposed cells was not different from that in control. Furthermore, LPA induced the production of stress fibers with no significant difference in the exposed and unexposed cells. These results suggest that mobile phone radiation (835-MHz, SAR 4.0 W/kg) may not be directly related to signal transduction in Rat-2 fibroblasts except the slight effect of calcium spiking in LPA-induced cells but remain to be further elucidated for possible indirect intervention.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2004.11a
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• pp.53-55
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• 2004

In emergency cases, such as the severe trauma involving the fracture of skull, spine, or cervical bone, from auto accident or a fall, and/or pneumothorax which can not be diagnosed exactly by the eye examination, it is necessary the radiological examination during transferring to the hospital for emergency care. The aim of this study was to design and evaluate the prototype of mobile medical image communication system based on CDMA 1X EVDO. The system consists of a laptop computer used as a transmit DICOM client, linked with cellular phone which support to the CDMA 1X EVDO communication service, and a receiving DICOM server installed in the hospital. The DR images were stored with DICOM format in the storage of transmit client. Those images were compressed into JPEG2000 format and transmitted from transmit client to the receiving server. All of those images were progressively transmitted to the receiving server and displayed on the server monitor. To evaluate the image quality, PSNR of compressed image was measured. Also, several field tests had been performed using commercial CDMA2000 1X-EVDO reverse link with the TCP/IP data segments. The test had been taken under several velocity of vehicle in seoul areas.

• Journal of Sensor Science and Technology
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• v.22 no.1
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• pp.54-64
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• 2013

In this study, we developed a falling recognition system to transmit SMS data through CDMA communication using a three axises acceleration sensor and a two axises gyro sensor. 5 healthy men were selected into a control group, and the fall recognition system using the three axises acceleration sensor and the two axises gyro sensor was devised to conduct an experiment. The system was attached to the upper of their sternum. According to the experiment protocol, the experiment was carried out 3 times repeatedly divided into 3 specific protocols: falling during gait, falling in stopped state, and falling in everyday life. Data obtained in the falling recognition system and LabVIEW 8.5 were used to decide if falling corresponds to that regulated in an analysis program applying an algorithm proposed in this study. In addition, results from falling recognition were transmitted to designated cellular phone in a SMS (Shot Message Service) form. These research results show that an erroneous detection rate of falling reached 19% in applying an acceleration signal only; 6% in applying an angular velocity; and 2% in applying a proposed algorithm. Such finding suggests that an erroneous detection rate of falling is improved when the proposed algorithm is applied incorporated with acceleration and angular velocity. In this study therefore, we proposed that a falling recognition system implemented in this study can make a contribution to the recognition of falling of the aged or the disabled.