교육통합관리시스템에서 HD급 컨텐츠 전송을 위한 무선 랜 AP 최적화

김문철(Mun-Cheol Kim),이병수(Byung-Soo Lee) 한국정보기술학회 2015 한국정보기술학회논문지 Vol.13 No.6

In this paper, we examine optimization of AP(Access Point) for education integrated management systems operation via WLAN(Wireless Local Area Network) in the educational grounds following digital book application policy. Recently, educational grounds are running first society, science classes by the digital book as policy. However, existing learning management system, because it can only do SD(Standard Definition) contents transmission, comes about data delay when transmitting HD(High Definition) contents. Also, it has a problem coming about RF(Radio Frequency) interference between the installed AP for the classes and other AP as the personal AP or the unauthorized AP not to business use are largely installed around educational grounds. In this paper, to eliminate these problems, the transfer rate of WLAN device according to the density of WLANs that is related with variable distance between AP was analyzed. The experiment result showed that if a number of APs are six, the transfer rate was measured as 386.6. Above result showed that the number of AP and its transfer speed are not proportional and because rather interference increases as density increases, it causes a decrease in the total transmission rate.

MPEG-A 멀티미디어 응용 포맷 기술 소개

임정연,김문철,Im, Jeong-Yeon,Kim, Mun-Cheol 대한전자공학회 2007 전자공학회지 Vol.34 No.8

Ar/Ar-$H_2$ 플라즈마에 의한 Nb금속제조와 Nb금속의 수소용해

정용석,홍진석,김문철,백홍구,Jeong, Yong-Seok,Hong, Jin-Seok,Kim, Mun-Cheol,Baek, Hong-Gu 한국재료학회 1993 한국재료학회지 Vol.3 No.6

Ar/Ar-$H_{2}$ 플라즈마법으로 고순도 Nb금속을 환원 정련하였다. 또한, Ar-(20%)$H_{2}$플라즈마에서의 용융Nb금속과 수소간의 반응을 해석하였다. Ar플라즈마 환원에서는 $C/Nb_{2}O_{5}$=5.00의 비에서 99.5wt%의 금속 Nb을 얻었으며, 니오븀 산화물의 열분해에 의한 O/Sub 2/의 손실은 발생하지 않았다. Ar-(20%)$H_{2}$ 플라즈마에서는 $C/Nb_{2}O_{5}$=4.80의 비에서 99.8wt%의 금속 Nb을 제조하였다. 주된 탈산반응은 H, $H_{2}$와의 반응이었으며,$NbO_{x}$의 증발에 의한 탈산은 발생하지 않았으나, "splash"효과에 의해 Nb의 질량손실이 발생함을 관찰하였다. 탈산반응은 1차 반응속도론에 따랐으며, 탈산의 반응속도 상수(k')는 $7.8 \times 10_{-7}$(m/sec)였다. Ar-(20%)$H_{2}$ 플라즈마법에서 Nb금속 내의 수소 용해도는 60ppm으로 분자상태 수소의 용해도인 40ppm 보다 높았으며, 포화되는 시간은 60초 이내였다. 이를 다시 Ar 플라즈마로 처리함으로써 수소 함량을 10ppm 이하로 감소시킬 수 있었다.소시킬 수 있었다. The Ar/Ar- $H_{2}$ plasma method Lvas applied to reduce and refine high purity Nb metal. Inaddition, the reaction between molten Nb metal and hydrogen were also analyzed in the Ar-(20%)$H_{2}$plasma. The metallic Nb of 99.5wt% was obtained at the ratio of $C/Nb_{2}O_{5}$=5.00 in the Ar plasma reductionand the $O_2$ loss from the thermal decomposition of niobium oxides did not take place. In the Ar-(20%)Hi plasma the metallic Nb of 99.8wt% was produced at the ratio of $C/Nb_{2}O_{5}$=4.80. It was observedthat a major reaction of the deoxidation was the reaction with H, Hi, and a deoxidation by the evaporationof $NbO_x$ did not occur but a mass loss of Nb did by a "splash" effect. The deoxidation reaction rateobeyed the 1st order reaction kinetics and the reaction rate constant(k') of deoxidation was $7.8 \times 10_{-7}$(m/sec).The solubility of hydrogen in Nb metal was 60ppm and it was larger than the solubility of molecularstate hydrogen by 40ppm in the Ar-(20%)$H_{2}$ plasma method. A saturation was within 60sec anda hydrogen content was reduced below lOppm by a Ar plasma re-treatment.by a Ar plasma re-treatment.

WBAN 환경에서 채널 추정 기반의 공용 채널 간섭 제거 기술

김정곤(Jeong Gon Kim),정두희(Doo Hee Jeong),김문철(Mun Cheol Kim),최준성(Jun Sung Choi),최성연(Sung Yun Choi) 한국방송·미디어공학회 2012 한국방송공학회 학술발표대회 논문집 Vol.2012 No.7

본 논문은 2.4㎓ 대역을 사용하는 WBAN(Wireless Body Area Network)환경에서 동일 채널을 사용하는 경우에 발생하는 간섭을 제거하기 위해 MMSE(Minimum Mean Square Error), OC(Optimal Combining), ML(Maximum Likelihood)을 비교 분석하였으며, IEEE 802.15.6에서 정의된 시나리오 및 채널 모델에 대해서 분석하였다. 모의실험 결과 ML 알고리즘이 가장 우수한 성능을 나타내는 것을 알 수 있었다. 하지만 ML과 OC의 경우 원하는 신호의 채널 정보뿐만 아니라 간섭채널의 정보를 알아야 하기 때문에 채널을 추정하기 위한 훈련 심볼의 자리를 수신노드에서 알고 있어야 하므로 WBAN환경에 적용하는데 어려움이 있다. 따라서 복잡도와 성능사이에 적당한 trade-off를 만족하는 간섭 제거 알고리즘을 연구해야 할 것이다.

경막외강 내로의 우발적인 Ephedrine 주입(증례보고)

조현석 ( Hyun Seok Cho ),김만조 ( Man Jo Kim ),김문철 ( Mun Cheol Kim ),이동준 ( Dong Jun Lee ) 대한마취과학회 2008 Korean Journal of Anesthesiology Vol.55 No.1

Propofol-remifentanil 마취와 Sevoflurane-remifentanil 마취 시 중심체온 변화의 차이

임의재 ( Ui Jae Im ),이동준 ( Dong Jun Lee ),김문철 ( Mun Cheol Kim ),이정석 ( Jeong Seok Lee ),이상준 ( Sang Jun Lee ) 대한마취과학회 2009 Korean Journal of Anesthesiology Vol.57 No.6

Background: Hypothermia following the induction of anesthesia is caused by core to peripheral redistribution of body heat. It has been reported that propofol causes more severe hypothermia than sevoflurane by inhibiting thermoregulatory vasoconstriction during surgical procedures. Therefore, we evaluated the induction and maintenance of anesthesia with intravenous propofol to determine if it causes more core hypothermia than inhaled sevoflurane. Methods: Forty-five patients who underwent hysterectomy were divided into two groups randomly, a propofol-remifentanil (PR) anesthesia group and a sevoflurane-remifentanil (SR) anesthesia group. Each group was subjected to anesthetic induction with either 1.5 mg/kg propofol or inhalation of 5% sevoflurane, respectively. Anesthesia in the former group was maintained with propofol while it was maintained with sevoflurane in the latter group. Specifically, 6-10 mg/kg/hr propofol, 3 L/min medical air, 2 L/min O2, and 0.25 mg/kg/hr remifentanil were used in the PR group for maintenance, while 1.5 vol% sevoflurane, 3 L/min medical air, 2 L/min O2 and 0.25 mg/kg/hr remifentanil were used for maintenance in the SR group. We measured the core temperature 8 times, prior to induction and 10, 20, 30, 45, 60, 75 and 90 minutes after induction. Results: Core temperatures decreased in both the PR and SR group during surgical operation, but there was no significant difference between the two groups. Conclusions: Anesthesia induced and maintained by propofol did not cause a greater degree of hypothermia than sevoflurane. (Korean J Anesthesiol 2009; 57: 704∼8)

임산부에서 부신절제술 후 잔여 선종인한 일차성 고알도스테론증

박선욱 ( Sun Wook Park ),고행일 ( Haeng Il Koh ),노지현 ( Ji Hyun Noh ),김문철 ( Mun Cheol Kim ),이혜경 ( Hye Kyung Lee ),박상현 ( Sang Hyun Park ),나현희 ( Hyun Hee Na ) 대한신장학회 2010 Kidney Research and Clinical Practice Vol.29 No.3

Primary aldosteronism is present in approximately 1 percent of hypertensive patients, and is rarely associated with pregnancy. We report a case of unilateral aldosterone producing adenoma in a pregnant woman. A 29-year-old woman was referred to with hypertension and proteinuria at 14 weeks` gestation. She had known that she had unilateral aldosterone producing adenoma for 18 months and refused medical or surgical treatment. She was prescribed antihypertensive medication and preformed laparoscopic adrenalectomy in left adrenal gland at 22 weeks` gestation. After adrenalectomy, her blood pressure was normal. At 29 weeks` gestation, she complained headache, and her blood pressure was 200/100 mmHg with pitting edema. We thought preeclampsia and performed cesarean section. After the baby was delivered, she had uncontrolled hypertension, hypokalemia with persistent proteinuria. We checked plasma renin activitity, aldoterone and abdminopelvic computed tomography. We found remnant left adrenal adenoma and perfomed laparoscopic operation. After reoperation, her blood pressure was normal and no proteinuria.

갈색세포종의 마취관리 3예 보고

김경태,이승홍,김환덕,허철회,김문철,조강희 인제대학교 1998 仁濟醫學 Vol.19 No.1

갈색세포종은 부신수질이나 paravertebral sympathetic chain을 따라 분포하는 chromaffin세포에서 발생하는 내분비질환이다. 악성인경우는 약5% 미만으로 작지만 Catecholamine의 과분비를 특징으로 다양한 임상증상이 나타나 마취유도, 기관내삽관, 체위변동, 종양조작시에 심혈관계의 혈역학적 변화로 심각한 합병증을 초래할 수 있다. 저자들은 갈색세포증 마취관리 3예를 문헌적 고찰과 함께 보고한다. Three patients underwent anesthesia for pheochromocytoma resection involving adrenal gland and extra-adrenal space. All three cases were diagnosed as pheochromocytoma by abdominal computed tomography, urinary VMA level and I-MIBG scan. Anesthesia was managed with glycopyrrolate and midazolam for premedication, pentothal sodium for induction, isoflurane-nitrous oxide-oxygen for maintensive, vecuronium for muscle relaxation, and nitroprusside for controlling severe hypertensive episode. We experienced marked fluctuation in blood pressure removal the surgical manipulation of the pheochromocytoma. Severe hypotension followed removal of tumor, which was correccted by vasoconstrictor(phenylephrine), rapid blood transfusion and infusion of crystalloids. Postanesthetic recovery course was uneventful and the patients discharged in good healthy condition.

Chronic constrictive uremic pericarditis in a long-term hemodialysis patient : a case report

Kim, Hyun-Tae,Park, Kyung-Jun,Tsung, Pei-Chuan,Na, Hyun-Hee,Kim, Young-In,Kim, Mun-Cheol,Koh, Haeng-lI 인제대학교 2009 仁濟醫學 Vol.30 No.-

요독성 심낭염은 만성 선부전 환자에서 나타날 수 있는 합병증으로 투석치료의 도입이후 발생률이 감소하고 있으나 말기 산부전 환자의 투석시작 전후로 혈역학적 문제가 발생할 수 있는 심각한 합병증 중 하나이며 드물게 오랜 기간 투석 치료를 받은 환자에서도 발생할 수 있다. 요독성 심낭염이 진행되어 심낭삼출이 발생할 경우 기저 질환에 대한 치료와 요독의 효과적인 제거를 위한 고효율의 투석을 시행하지만 혈역학적으로 불안정 할 경우 심낭천자 및 심막절제술의 침습적인 치료가 필요하다. 저자들은 오랜 기간 동안 혈액투석을 시행받은 환자에서 발생한 만성 요독성 교착성 심낭염을 경험하여 이를 보고하려고 한다. 63세 남자 환자가 혈액 투석 중에 발생한 저혈압과 호흡 곤란으로 내원하였다. 2달 전 부터 투석 중 흉부 압박감이 있었고, 1 주 일 전부터는 투석 중 저혈압이 발생하고 호흡곤란이 동반되었다고 한다. 고혈압에 의한 말기신부전으로 9년 전부터 혈액 투석을 받고 있었다. 흉부 방사선 단순촬영에서 섬비대가 있었고, 심장 초음파와 흉부 컴퓨터 단층 촬영에서 교착성 심낭염을 발견하였다. 이후 섬막절제술을 시행하였고, 병리학적 소견으로 보아 만성 요독성 교착성 심낭염을 진단할 수 있었다. 환자는 수술 후 혈압은 정상이었고, 투석 중에도 저혈압은 발생하지 않았다. 현재 외래에서 추적관찰 중이다.

소하악증 환자의 기관내 삽관 곤란을 판별 할 수 있는 해부학적 인자에 관한 연구

김경태,조강희,이승홍,허철희,김문철 대한마취과학회 1998 Korean Journal of Anesthesiology Vol.35 No.1

Background: Micrognathia is the prime, constant bony finding that signals trouble for access to the airway. Anatomical factors of difficult tracheal intubation in micrognathia have been evaluated. Method : Forty one patients with micrognathia were divided into 3 groups based on modified Mallampati classification. Lateral cephalometric view taken preoperatively was used to measure 13 anatomical factors. Kruskal-Wallis test and discriminant analysis were used to select the most predictable factors for distinguishing between the difficult and easy groups. Results : The most discriminating factors are mandibulo-hyoid distance(V12), atlanto-occipital distance(V10) and mentum-hyoid distance(V11). The discriminant analysis using above 3 factors gives the following discriminant functions(Y1= 0.7924(V12) - 0.2154(V10) - 0.3531(V11) (discriminant function 1), Y2= -0.2177(V12) + 0.8221(V10) -0.6304(V11) (discriminent fuction 2)) and the discriminating power of difficult intubation is 72.9%. Conclusions : Modified Mallampati classification and lateral cephalometric assessment of 3 anatomical factors can predict the difficult intubation. (Korean J Anesthesiol 1998; 35: 40∼49)