• Electronics and Telecommunications Trends
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• v.22 no.1 s.103
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• pp.114-118
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• 2007

국내외적으로 지능형 차량 및 텔레매틱스/ITS 연구 개발을 통해서 차량에 IT 기술 접목을 위한 노력을 가속화하고 있다. 우리나라의 경우 산업자원부가 미래 10대 전략품목으로 자동차 부분에서 지능형 차량을 선정하였으며, 정보통신부는 u-IT839의 핵심서비스로 텔레매틱스/ITS 서비스를 추진하고 있다. EU는 i2010 Flagship에서 intelligentcar initiative 프로젝트를 통해 지능형 차량 및 보안을 위한 전략 수립과 세부과제를 수행하고 있다. 또한, IEEE 802.11p/P1609(WAVE)와 ISO TC204/WG16CALM에서는 차량 통신 보안 및 서비스에 대해서 고려하고 있다. 현재 지능형 차량과 관련하여서는 다양한 사업 모델이 제시되고 있으며, 자동차 업계의 BM과 이동통신 업계의 AM이 동반 성장하고 있다. 본 기고문은 지능형 차량 및 텔레매틱스/ITS와 관련한 보안 기술 동향을 살펴본다.

• Journal of Clinical Nutrition
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• v.10 no.2
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• pp.51-55
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• 2018

Purpose: This study was conducted to assess how extreme obesity affects 30-day mortality in this patient group. Methods: A total of 802 patients who underwent emergency gastrointestinal surgery from January 2007 to December 2017 were retrospectively reviewed. Patients were divided into three groups according to their body mass index (BMI): group 1, normal weight (BMI: $18.5{\sim}22.9kg/m^2$); group 2, overweight (BMI: $23.0{\sim}29.9kg/m^2$ ); and group 3, obesity ($BMI{\geq}30kg/m^2$). Patients with a BMI under 18.5 were excluded from the analysis. Chi-squared test, Fisher's exact test, Kaplan-Meier survival analysis, and the log-rank test were used to assess and compare 30-day mortality rates between groups. Results: The mortality rates of group 1, group 2, and group 3 were 11.3%, 9.0%, and 26.9%, respectively (P<0.017). The mortality rate did not differ significantly between group 1 and 2 (11.3% vs. 9.0%; P=0.341), but group 1 and 2 showed better survival rates than group 3 (11.3% vs. 26.9%; P=0.028, 9.0% vs. 26.9%; P=0.011). Kaplan-Meier survival analysis revealed that group 3 had higher mortality than the other two groups (P=0.001). Conclusion: Obesity ($BMI{\geq}30kg/m^2$) was one of the risk factors influencing critically ill patients who underwent emergency surgery.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.5
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• pp.337-343
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• 2013

In this paper, IEEE 802.11 based WLAN(5.2/5.8GHz) wideband Weathercock-shaped microstrip patch antenna was designed and manufactured. The antenna has a size of $17.4{\times}17.4mm^2$ and utilized FR-4 board. The size was minimized for mobility, and Weathercock-shaped U-slot and short-pin was inserted to satisfy adequate bandwidth and double bandwidth resonance characteristics. In addition, the antenna incorporated single both-sided patch, and simulation design optimized the Weathercock-shaped, position of the U-slot and the short-pin, and the length of the patch for the measurement. The manufactured antenna achieved a bandwidth of 695MHz from 5.2~5.8GHz zone(Return loss<-10dB). Achieved a beam width of $81.13^{\circ}$ and $85.43^{\circ}$ for 3-dB beam width of H plane and E p;ane radiation pattern, there was 3.17~4.85dBi gain.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.2 no.4
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• pp.42-51
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• 2003

In this paper, we are going to analyze on relation of an output spectrum along phase distortion of power amplifier in wireless LAN system, and then considered an ACPR characteristic of power amplifier and consideration of an OFDM method for this. Also, we did implementation for OFDM modulation and transmission section of an IEEE 802.11a standard to have transmission speed of the maximum 54Mbps in order to know an OFDM modulation method and relation of non-linear characteristic of power amplifier. The non-linear characteristic of power amplifier did modeling with AM-to-AM and AM-to-PM, and we analyzed an output spectrum characteristic along phase distortion composed input signal supply for power amplifier. When output spectrum analysis results phase distortion increased, and an AM-to-PM characteristic of power amplifier in 5 degrees, the output spectrum was satisfied with a demand spectrum in P1 dB, but 10-20 degrees were able to confirm what cannot be satisfied with a demand spectrum in phase distortion. Also, an output spectrum of power amplifier by frequency re-growth generated by a non-linear characteristic of power amplifier did not satisfied in P1dE. therefore, a back-off value was requested according to an AM-to-PM distortion degree, and smaller back-off value were able to know what demand became in case of modulation section that used OFDM.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.221-224
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• 2005

This paper discribes the nonlinear distortion of a pHEMT power amplifier. In the paper, we have used some commercially available power amplifiers for analyzing the relationship between the $IMD_3$ and ACPR for wireless LAN. And the $IMD_3$ results using two-tone test have been compared with ACPR to satisfy the requited 802.11g standard ACPR value. Measurement result shows that $IMD_3$ of 20MHz tone-spacing need to be more than 18.45dBc for power amplifiers. The WCDMA signal is fed into the power amplifier, for analyzing relationship between the asymmetrical $IMD_3$ and ACLR. With measurement result, the asymmetrical $IMD_3$ characteristic has increased with the increase of two-tone spacing. $IMD_3$ measurement result with maximum 20MHz of the two-tone spacing, shows that the difference between $IMD_3(lower)$ and $IMD_3(upper)$ is about 7dB. And the measured ACLR shows 5dB difference at -4MHz and +4MHz offset from center frequency.

• Journal of the Korea Institute of Military Science and Technology
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• v.2 no.2
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• pp.117-130
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• 1999

In this paper, the performance of data communication function of military radio equipment P-999K is analyzed based on the standard CSMA/CA protocol which is DFWMAC standard protocol done by IEEE802.11 work group. Basic three standard protocols, i.e. Basic CSMA/CA, Stop & Wait ARQ and 4-Way Handshake CSMA/CA protocols are analyzed and compared with each other under the hidden terminal environment. The computer simulation is also done by using SIMSCRIPT II.5 which is popular software tool for an independent processing. The results show that p-persistent(with p=0.3) CSMA scheme is superior to non-persistent CSMA scheme with non-hidden terminal condition, but the performances of both schemes are almost same with hidden terminal situation. And the results of computer simulations are also showed that Basic CSMA/CA protocol is superior to the other protocols when the ratio of hidden terminals is below 10 % of total user population, however, with the above 20% hidden terminals environment and the higher offered traffic conditions the 4-Way Handshake CSMA/CA protocol shows the most superior performance.

• Journal of Korean Academy of Nursing
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• v.26 no.2
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• pp.467-482
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• 1996

This study was carried out to measure the degree of organizational commitment, job involvement, and role stress of clinical nurses, and to identify the relationships among personal characteristics, role stress, organizational commitment and job involvement in clinical nurses. The subjects were consisted of 412 nurses who were working at three General Hospitals in Chonbuk. The data were collected by self-reporting questionnaire from Sept. 20 to Sept. 31, 1995. The instruments used in this study were Organizational Commitment Scale developed by Mowday et al. and Job Involvement Scale developed by Kanungo. The role stress was measured by the scale developed by Rizzo( : role conflict, role ambiguity) and Beehr( : role overload). T-test, one-way ANOVA, Scheffe test and pearson's correlation coefficient were used for data ana1isis. Major findings were as follows : 1. Mean scores for organizational commitment were 3.008, job involvement 3.074, and role stress 2. 815( :role conflict 2.802, role ambiguity 2.253, role overload 3.294) on a 5 point scale. 2. All of personal characteristics were significantly related to the level of organizational commitment : age（r＝.481, p＝.000）, clinical experience（r＝ .479, p＝.000）, educational level（t＝4.11, p＝ .000）, position（F＝30.867, p＝.000）, marital status（t＝-5.63, p＝.000） and hospital agency （F＝21.374, p＝.000）. 3. All of personal characteristics were significantly related to the level of job involvement : age（r＝ .381, p＝.000）, clinical experience（r＝.393, p＝ .000）, educational level（t＝3.72, p＝.000）, position（F=18.004, p＝.000）, marital status（t＝-4. 91, p＝.000） and hospital agency（F=39.441, p＝ .000）. 4. There was a negative relationship between role stress and organizational commitment（r＝-.519, p＝.000）. 5. There was a negative relationship between role stress and job involvement（r＝-.256, p＝.000）. 6. There was a positive relationship between organizational commitment and job involvement （r＝.591, p＝.000）.

• Journal of Chest Surgery
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• v.39 no.6 s.263
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• pp.475-478
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• 2006

Background: The simultaneous bilateral spontaneous pneumothorax is a rare clinical event. Contrary to the unilateral pneumothorax, the patients with simultaneous bilateral spontaneous pneumothorax sometimes complains of severe respiratory distress, cyanosis and chest pain without tention pneumothorax. It is often dangerous; therefore, the chest drain should be inserted immediately. Material and Method: Between March 1994 and February 2004, 802 patients were treated in our department for spontaneous pneumothorax. Among these, the simultaneous bilateral spontaneous pneumothorax developed in 14 patients (1.7%). Result: Out of fourteen patients, two females and twelve males presented with simultaneous bilateral spontaneous pneumothorax. The patient age ranged between 0 and 79 years with mean age of 31.2 years. In eleven patients, this was the first episode of pneumothorax. One patient had combined hemopneumothorax and two patients had combined pyopneurnothorax. Six patients had smoking history (42.8%, average 17.3 p-y). Five patients had pulmonary tuberculosis history and among these, two patients had active pulmonary tuberculosis. Three patients were died due to meconium-aspiration pneumonia (1 patient) and ARDS (Acute Respiratory Distress Syndrome) with pneumonia (2 patients). We treated these patients with nasal oxygen inhalation, chest drain insertion, thoracotomy, VATS (Video-Assisted Thoracoscopic Surgery) and chemical pleurodesis. Conclusion: The simultaneous bilateral spontaneous pneumothorax developed in 14 patients (1.7%) among 802 patients. Prompt insertion of chest drain is needed for a relief of severe symptoms, and to reduce the risk of recurrence, early thoracotomy or VATS should be performed rather than chest drain insertion only.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.1-12
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• 1997

The performance of Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol adopted as a draft standard of IEEE 802.11 wireless LAN, is analyzed by using mathematical method based on renewal theory. We introdude three kinds of CSMA/CA protocols basic, stop-and-wait and 4-Way handshake CSMA/CA with their mathematical analysis. First, a network of finite population is considered and then expand to infinite population. We model the CSMA/CA protocol as a hybrid protocol of 1-persistent CSMA and p-persistent CSMA protocol, and verify analaytical results by computer simulation. We have found that 4-Way Handshake CAMA/CA shows better performance than those of other two types of CSMA/CA in case of high traffic load.

• Journal of information and communication convergence engineering
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• v.8 no.6
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• pp.635-639
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• 2010

A multi-resonance antenna for wireless communications is reported. By using double inverted-L strips, the antenna demonstrated compact size (15 mm ${\times}$ 14 mm) including the ground, multi-band operation for IEEE 802.11 a/b/g/p applications, and wide bandwidth of 1.7 GHz at 5 GHz band. Good radiation features of omni-directional patterns and 1.98 and 2.29 dBi peak antenna gains for the lower and upper bands, respectively, have been achieved.