Waffle-Iron 도파관 여파기 설계

고지환(Ji Whan Ko),조영기(Young Ki Cho) 한국전자파학회 2007 한국전자파학회논문지 Vol.18 No.11

본 논문에서는 waffle-iron 도파관 여파기의 실용적인 설계 방법을 기술하였다. 설계 과정은 두 단계로 이루어 진다. 첫 단계로는 waffle-iron 구조의 단일 window에 대해 EM S/W tool를 이용하여 S-파라미터를 구하고, ABCD파라미터로 변환하여 K-인버터를 계산하고, 두 번째 단계는 분포 정수 원형 여파기와 일치되게 window의 크기를 최적화 한다. 설계 방법을 검증하기 위해 위성통신용 Ka 대역 여파기를 설계하고 제작하였다. 측정 결과는 계산 결과와 비교하여 양호하게 일치하였다. Simple practical design method is proposed for the waffle-iron waveguide filter. The design procedure comprises two steps. The first step is to calculate the K-inverter based on the transformed ABCD parameter from the S parameter for the single window of waffle-iron structure by use of EM S/W tool. The second step is to optimize the size of the windows such that the calculated K inverters may be in accord with the distributed constant prototype filter. In order to validate the design method, a waffle-iron filter for satellite communications over the Ka band is designed and fabricated. The measured results are in good agreement with the calculated ones.

개방된 리지 도파관을 이용한 이중 선형 편파 방사 소자 설계

고지환(Ji-Whan Ko),전종훈(Jong-Hoon Chun),조영기(Young-Ki Cho) 한국전자파학회 2008 한국전자파학회논문지 Vol.19 No.11

이중 편파 특성을 갖는 위상 배열 안테나에 사용될 수 있는 도파관형 방사 소자의 설계 방법을 제시하였다. 소형화를 위하여 리지 형태의 도파관을 사용하였고, 이중 편파를 위해서는 도파관 내에 인쇄된 다이폴 구조의 마이크로스트립 형태를 부가적으로 추가하는 형태를 취하였다. 설계 방법의 타당성 검증을 위하여 1×4 배열안테나를 제작하여 반사 손실, 인접 채널간 동일 편파 상호 간섭 및 복사 패턴을 측정하여 이론치와 비교하여 잘 일치함을 확인하였다. 본 논문에서 제시한 구조는 이중 편파 특성을 갖는 위상 배열 안테나의 단위 소자로서 유용한 구조로 사용될 수 있을 것으로 생각된다. A design approach for a radiation element of dual polarization, which can be implemented in the waveguide structure, is proposed. For minimization of the radiating element, the ridged waveguide type is used and for dual polarization, the microstrip type of printed dipole structure is additionally installed inside the waveguide. In order to validate the design approach, 1×4 array antenna is fabricated and its performances such as return loss, co-polarization coupling between adjacent channels, and radiation patterns are investigated. Theory and experiment are observed to be in good agreement. The radiating structure is thought to be a useful one in an application to the phased array antenna system, in particular, requiring dual polarization characteristics.

A case of hemolytic uremic syndrome preceded by intussusception

Ko, Eun-Young,Kim, Joo-Young,Lee, Hye-Jin,Lee, Hyun-Seung,Han, Ji-Whan,Kim, Young-Hoon,Kim, Jin-Tack,Cheong, Hae-Il,Jang, Pil-Sang The Korean Pediatric Society 2011 Clinical and Experimental Pediatrics (CEP) Vol.54 No.4

Hemolytic-uremic syndrome (HUS) is the most common cause of acute renal failure in young children. It is classically characterized by the triad of microangiopathic hemolytic anemia, thrombocytopenia, and uremia. Further, not only is intussusception one of the differential diagnoses of HUS but it may also become a complication during disease progression. We report a case of HUS. preceded by intussusception in a previously healthy 17-month-old boy. The patient presented at the emergency department with bloody stools that developed the day after reduction of intussusception. HUS was diagnosed 4 days after the reduction of intussusception. The patient was provided only supportive care and his laboratory test findings were normal at discharge.

Anti-allergic effects of a nonameric peptide isolated from the intestine gastrointestinal digests of abalone (Haliotis discus hannai) in activated HMC-1 human mast cells

KO, SEOK-CHUN,LEE, DAE-SUNG,PARK, WON SUN,YOO, JONG SU,YIM, MI-JIN,QIAN, ZHONG-JI,LEE, CHANG-MIN,OH, JUNGHWAN,JUNG, WON-KYO,CHOI, IL-WHAN Spandidos Publications 2016 INTERNATIONAL JOURNAL OF MOLECULAR MEDICINE Vol.37 No.1

<P>The aim of the present study was to examine whether the intestine gastrointestinal (GI) digests of abalone [Halioti s discus hannai (H. discus hannai)] modulate inflammatory responses and to elucidate the mechanisms involved. The GI digests of the abalone intestines were fractionated into fractions I (>10 kDa), 11 (5-10 kDa) and III (<5 kDa). Of the abalone intestine GI digests (AIGIDs), fraction III inhibited the passive cutaneous anaphylaxis (PCA) reaction in mice. Subsequently, a bioactive peptide [abalone intestine GI digest peptide (AIGIDP)] isolated from fraction III was determined to be 1175.2 Da, and the amino acid sequence was found to be PFNQGTFAS. We noted that the purified nonameric peptide (AIGIDP) attenuated the phorbol-12-myristate 13-acetate plus calcium ionophore A23187 (PMACI)-induced histamine release and the production of pro-inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta and IL-6 in human mast cells (HMC-1 cells). In addition, we also noted that AIGIDP inhibited the PMACI-induced activation of nuclear factor-kappa B (NF-kappa B) by suppressing I kappa B alpha phosphorylation and that it suppressed the production of cytokines by decreasing the phosphorylation of JNK. The findings of our study indicate that AIGIDP exerts a modulatory, anti-allergic effect on mast cell-mediated inflammatory diseases.</P>

Long-Term Clinical Outcomes of Iliac Artery Endovascular Therapy in the Korean Vascular Intervention Society Endovascular Therapy in Lower Limb Artery Diseases (K-VIS ELLA) Registry

Ji Woong Roh,Sanghoon Shin,Young-Guk Ko,Nak-Hoon Son,Chul-Min Ahn,Pil-Ki Min,Jae-Hwan Lee,Chang-Hwan Yoon,Cheol Woong Yu,Seung Whan Lee,Sang-Rok Lee,Seung Hyuk Choi,In-Ho Chae,Donghoon Choi 대한심장학회 2022 Korean Circulation Journal Vol.52 No.7

Background and Objectives: Limited data are available regarding long-term clinical outcomes of iliac artery endovascular therapy (EVT) in real-world practice. This study investigated long-term outcomes according to Trans-Atlantic Inter-Society Consensus (TASC) classifications. Methods: We analyzed data from 1,705 limbs of 1,364 patients from the retrospective cohort of the multicenter Korean Vascular Intervention Society Endovascular Therapy in Lower Limb Artery Disease registry. The primary endpoint was target lesion revascularization (TLR)-free survival. Results: TASC A, B, C, and D lesions were present in 19.4%, 26.2%, 28.7%, and 25.7% of the treated limbs, respectively. The technical success rate was 96.2% and did not differ between TASC lesion types. Complications occurred in 6.8% of cases and more occurred in TASC D (11.8%). Iliac artery EVT showed a 5-year TLR-free survival of 89.2%. The TASC D group had the lowest TLR-free rate of 79.3%. TASC D (hazard ratio [HR], 1.75; 95% confidence interval [CI], 1.12–2.73; p=0.014), plain old balloon angioplasty (HR, 4.25; 95% CI, 2.03–8.88; p<0.001), current smoker (HR, 1.89; 95% CI, 1.26–2.83; p=0.002), previous bypass surgery (HR, 3.04; 95% CI, 1.28–7.19; p=0.011), combined femoropopliteal treatment (HR, 4.89; 95% CI, 3.19–7.50; p<0.001), combined below the knee treatment (HR, 2.20; 95% CI, 1.25–3.89; p=0.007), and complications (HR, 1.86; 95% CI, 1.07–3.24; p=0.028) were predictors for TLR. Conclusions: Iliac artery EVT achieved excellent technical success and 5-year TLR-free survival. TASC D showed a favorable but lower 5-year TLR-free survival rate and higher complication rate compared with other TASC groups.

Metronomic treatment of temozolomide inhibits tumor cell growth through reduction of angiogenesis and augmentation of apoptosis in orthotopic models of gliomas.

Kim, Ji Tae,Kim, Jong-Soo,Ko, Kwang Won,Kong, Doo-Sik,Kang, Chang-Mo,Kim, Mi Hyun,Son, Myung Jin,Song, Hyun Seok,Shin, Hyung-Jin,Lee, Dong-Sup,Eoh, Whan,Nam, Do-Hyun National Hellenic Research Foundation 2006 ONCOLOGY REPORTS Vol.16 No.1

<P>Glioblastoma is a highly angiogenic tumor with a dismal prognosis. Temozolomide (TMZ), a methylating agent is one of the most effective chemotherapeutic agents against glioblastoma. To overcome the problem that most of these tumors become resistant to chemotherapeutic regimens within a year, we investigated the antitumor efficacy of metronomic administration of low-dose TMZ in in vitro cell proliferation/cytotoxicity assay and in vivo rat and nude mouse orthotopic glioma model. By in vitro assay, we elucidated that C6/LacZ rat glioma cells were more resistant to metronomic treatment of TMZ than U-87MG human glioblastoma cells and bEnd.3 mouse brain endothelial cells. Compared with the conventional chemotherapeutic regimen of TMZ, we found that frequent administration of TMZ at a low dose (metronomic treatment) markedly inhibited angiogenesis as well as tumor growth in a TMZ-resistant C6/LacZ rat glioma model. In addition, metronomic treatment of TMZ significantly augmented apoptosis of tumor cells in this model. For the TMZ-sensitive U-87MG cells, even with a very low dose of TMZ, which is not effective to reduce tumor mass, the metronomic treatment of TMZ reduced the microvessel density, i.e. angiogenesis, in a nude mouse orthotopic model. In conclusion, for both models, the metronomic treatment of TMZ decreased angiogenesis. Especially, in TMZ-resistant glioma cells, this regimen increased apoptosis of tumor cells and decreased tumor growth. The metronomic treatment of TMZ in orthotopic glioma models demonstrated a successful antiangiogenic effect which can overcome the chemoresistance in conventional TMZ chemotherapy.</P>

무한한 플랜지가 장착된 개방형 직사각형 도파관 구조에 대한 산란 행렬 해석

고지환,조영기,Ko, Ji-Whan,Cho, Young-Ki 한국정보통신학회 2008 한국정보통신학회논문지 Vol.12 No.3

In this paper, scattering matrix for the open ended rectangular waveguide with infinite flange is derived. To validate the scattering matrix approach, load admittance $Y_{L,10}$ obtained from the present scattering matrix method is compared with the results of the previous work. The convergence for scattering matrix solution versus TE and TM mode numbers is investigated. Also far field power pattern radiated from the aperture of the waveguide is given. 본 논문에서는 무한한 도체 플랜지가 장착된 개방형 직사각형 도파관의 구조에 대한 산란 행렬을 구하였다. 산란 행렬의 정확도를 검증하기 위해서 산란 행렬로부터 부하 어드미던스 $Y_{L,10}$를 계산하여 기존의 논문 결과와 비교하고, TE와 TM모드 수에 증가에 따른 산란 행렬의 수렴도를 조사하여 본 논문에서 제시한 산란 행렬 방법의 타당성을 확인하였다. 그리고 도파관의 개구면을 통하여 자유공간으로 방사되는 패턴을 제시하였다.

원편파 변환 주파수 선택 반사기 설계

고지환,조영기,Ko, Ji-Whan,Cho, Young-Ki 대한전자공학회 2001 電子工學會論文誌-TC (Telecommunications) Vol.38 No.1

편파기 특성을 갖는 새로운 주파수 선택반사기의 새로운 주기적 배열 구조를 제시하였다. 배열 구조는 평면 유전체 슬랩의 양면에 도체 다이폴을 주기적으로 배열하고 윗면의 다이폴과 아래면의 다이폴은 서로 대략 $90^{\circ}$ 정도로 직교되며 유전체 두께는 유전율을 고려한 주파수 파장의 1/8정도이다. 산란 해석으로는 파수 영역 이미턴스방법과 모멘트 방법이 사용되었다. 제시한 새로운 주파수 선택반사기의 편파 변환 기능을 확인하기 위해 설계/제작하여 반사 손실과 투과 손실을 측정하였다. 측정 결과는 이론치와 매우 일치되었으며 반사시 선형 편파인 입사파가 원형 편파로 변환됨을 확인하였다. The new periodic array structure or frequency selective surface with polarizers characteristic is proposed. The present structure is constructed with two sheets or FSS material, spaced about one-eight wavelength apart, the dipole element orientations of the two sheets being almost perpendicular to each other. The methods of the spectral domain immittance and MoM are used to analyze electromagnetic scattering from this periodic array structure. To confirm the validity of the polrizer's functions or the new periodic array structure, frequency selective surfaces are fabricated, calculated values for the frequency response of the reflection and transmission loss are compared with measured values. Good correspondence has been observed between them. Good axial ratio has been also observed to be achieved in the proposed structure.

Evaluation of 13-week repeated oral dose toxicity of <i>Areca catechu</i> in F344/N rats

Kim, Hyun-Ji,Ko, Je-Won,Cha, Seung-Beom,Heo, Hyun-Suk,Seo, Jong-Hun,Cha, Mi-Jin,Bae, Jin-Sook,Lee, Hyun-Kul,Song, Si-Whan,Kim, Jong-Choon Elsevier 2018 Food and chemical toxicology Vol.114 No.-

<P><B>Abstract</B></P> <P>This study investigated the potential toxicity of the Areca catechu water extract after 13-week repeated oral administration at 0, 166.7, 500, and 1500 mg/kg/day in rats. During the study period, clinical signs, mortality, body weight, food consumption, water consumption, urinalysis, estrous cycle, sperm count and motility, ophthalmoscopy, hematology, serum biochemistry, gross pathology, organ weights, and histopathology were examined. At 1500 mg/kg/day, both sexes exhibited an increase in the incidence of abnormal clinical signs, which included, decreased body weight gain and food consumption, and increased urine bilirubin, ketone bodies, specific gravity, and protein and kidney weight. An increase in liver weight and estrous cycle alterations was observed in females. Serum biochemical and histopathological investigations revealed an increase in the levels of serum aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase, and the incidence of hepatic necrosis in females. At 500 mg/kg/day, an increase in the incidence of abnormal clinical signs including diarrhea and soiled perineal region, was observed in both sexes. No treatmentrelated effects were observed at 166.7 mg/kg/day. Under the present experimental conditions, the target organs were determined to be the liver, kidney, and female reproductive system in rats. The no-observedeffect level was considered to be 166.7 mg/kg/day in rats.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Subchronic toxicity of <I>Areca catechu</I> water extract was investigated in rats. </LI> <LI> The target organs of the extract were determined to be the liver, kidney, and female reproductive system. </LI> <LI> The no-observed-effect level of the extract was considered to be 166.7 mg/kg/day in rats. </LI> </UL> </P>

Molecular Mechanism of Apicidin-Induced Down-regulation of DNA Methyltransferase 1 Expression

HAN Jeung Whan,YOU Jueng Soo,LEE Eunkyung,KANG Gil Myoung,KO Dae Hwan,JEON Ye Ji,KIM Nam Wook,CHOI Wahn Soo 대한약학회 2006 大韓藥學會 總會 및 學術大會 Vol.2006 No.2