자성유체를 이용한 마이크로 믹서에 대한 실험적 연구

최재현(Jai Hyun Choi),이준식(Joon Sik Lee) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5

A new design of micromixer is developed that uses the concept of the chaotic mixing and the actuation by the ferrofluid. The micromixer has two parallel sub-channels that intersect the main channel. The flows in the sub-channels are used to perturb the main channel flow. The sub-channel flow is actuated by the ferrofluid, which is externally controlled by permanent magnets. To study the performance of the mixer, the red fluorescent dye is supplied to the base fluid in one of the inlets of T-shaped channel. The fluids from two inlet channels are to be mixed actively at the junction downstream. The mixing phenomena is visualized by ICCD (Intensified CCD) camera and analyzed by studying the intensity. The mixing is effectively achieved up to the maximum velocity of 1.81 ㎜/s at which time the perturbation frequency of 8.4 ㎐ is applied. This study suggests that the ferrofluid micromixer has good characteristics such as rapid mixing capability, low manufacturing cost, and simple fabrication procedure.

Factors Affecting the Intention to Use of Smartphone Banking Service: Focusing on Trust and Technology Acceptance Model

Choi, Jai Hyun(최재현),Lee, Seung In(이승인),Oh, Seung Won(오승원),Kim, Jeong Won(김정원) 한국서비스경영학회 2015 서비스경영학회지 Vol.16 No.2

This study aims to understand characteristics of consumers using smartphone services by examining factors affecting the intention to use of smartphone banking service targeting consumers using smartphones and to consider the mechanism of consumer behavior related with the use of smartphone banking service. To achieve these, this study investigates factors affecting the intention to use of smartphone banking service focusing on TAM and a trust model which explains the degree of consumers’ information and technology acceptance and which have drawn a constant attention of academic and professionals as the representative model of business management and information since 1990. Summaries of this research are as follows. First, perceived security, self-efficacy, diversity of service offering have a significant effect on trust. Second, the higher the trust is, the higher the perceived ease of use, perceived usefulness, and intention to use. Lastly, the higher the perceived ease of use, the higher the perceived usefulness and intention to use. And the higher perceived usefulness, the higher the intention to use. This study suggests marketing strategies to boost the use of smartphone banking service.

식도정맥류의 내시경적 경화요법 효과

최재현(Jai Hyun Choi),현진해(Jin Hai Hyun) 대한소화기학회 1996 대한소화기학회지 Vol.28 No.5

N/A Background/Aims: The clinical value of the endoscopic injection sclerotherapy(EIS) as the treatment of bleeding from esophageal varices has been accepted since early 1980s. Recently, total eradication of esophageal varices by EIS has been proposed to be the most effective method in the treatment of variceal bleeding. But the precise method of the EIS for total eradication is not yet well established. This study was performed in order to find out the effective extent of mucosal destruction of the lower esophagus for the prophylaxis of the recurrence of esophageal varices. Methods: 249 patients with esophageal varices due to portal hypertension treated by the EIS were reviewed retrospectively. The effect of the EIS was analysed according to the Child-Pughs grade, selection of the timing of initial EIS(selection) and intervals between tbe EIS and degree of mucosal destruction of the lower esophagus by Kaplan-Meier analysis with Statistical Analysis System Software. Results: Among Child-Pughs grade A, B and C group, the group A showed the highest cumulative nonrecurrence rate(p=0.001), but tbere was no significant difference in the effect of the EIS according to the selection(p=0.78) and the intervals between the EIS(p=0.69). Among the group of complete destruction of short segment(below 3cm, group I ), complete mucosal destruction of long segment(above 3cm, group II), incomplete destruction(group III) and embolization(group IV), group II showed the highest cumulative nonrecurrence rate regardless of the selection, the intervals between the EIS and the Child-Pughs classification(p=0.0001). The common complications of the EIS were esophageal stricture(35.7%) and hematoma(13.3%). The severity of the stricture was not corre1ated with the nunber and the interval beween the volume of the sclerosant and extent of the mucosal destruction of lower esophagus. Conclusions: This study indicates that total mucosal destruction of at least 3cm of lower esophagus from esophagogastric junction by intravariceal and submucosal injection was the rnost effective method of the EIS for the prophylaxis of the recurrence of the esophageal varices, regardless of the selection the intervals between the EIS and the Child-Pughs grade. (Korean J Gastroenterol 1996; 28:648 - 660)

에 감염된 십이지장궤양 환자에서 HLA - DQB1 의 역할

전훈재(Hoon Jai Chun),이상우(Sang Woo Lee),현진해(Jin Hai Hyun),이성준(Sung Joon Lee),진윤태(Yoon Tae Jeen),이홍식(Hong Sik Lee),송치욱(Chi Wook Song),엄순호(Soon Ho Um),최재현(Jai Hyun Choi),김창덕(Chang Duck Kim),류호상(Ho Sang Ryu 대한소화기학회 2002 대한소화기학회지 Vol.39 No.4

Background/Aims: Helicobacter pylori (H. pylori) infection is associated with gastroduodenal ulcer and gastric cancer only in a small proportion of infected subjects. Both virulence factors of H. pylori strains and host immune responses have been suggested to play an important role in the development of such lesions. HLA has been considered as an important host factor in many diseases. The aim of this study was to examine the HLA-DQ loci among duodenal ulcer patients with H. pylori infection as potential host genetic factors related to the development of duodenal ulcer. Methods: Thirty-two duodenal ulcer patients and 74 controls who had endoscopic chronic gastritis were studied. HLA-DQA1 and HLA-DQB1 genotypes were determined by polymerase chain reaction using sequence specific oligonucleotide probes (PCR-SSOP) with peripheral bloods obtained from the patients and controls. Results: HLA-DQA1 distribution pattern of the patients showed no significant difference from that of the controls. However, the frequency of HLA DQB1*04 was quite lower in the patients than in the controls (p=0.02). Conclusions: The HLA-DQA1 does not seem to contribute to the disease susceptibility, whereas HLA DQB1*04 may contribute to the protection from duodenal ulcer in H. pylori infected subjects. (Korean J Gastroenterol 2002;39:254-259)

젊은 환자에서 이중풍선소장내시경으로 진단한 소장암 1예

최윤지 ( Yoon Ji Choi ),정성우 ( Sung Woo Jung ),엄준원 ( Jun Won Um ),이응석 ( Eung Seok Lee ),구자설 ( Ja Seol Koo ),임형준 ( Hyung Joon Yim ),이상우 ( Sang Woo Lee ),최재현 ( Jai Hyun Choi ) 대한소화기학회 2011 대한소화기학회지 Vol.58 No.4

A 17-year old female presented with a chief complaint of melena and epigastric pain. She had a family history of colon cancer, her mother having been diagnosed with hereditary nonpolyposis colorectal carcinoma (HNPCC). After close examination including double-balloon enteroscopy, the patient was diagnosed with small bowel carcinoma, in spite of her young age. Here we report this rare case of small bowel carcinoma in a young patient with a family history of HNPCC. (Korean J Gastroenterol 2011;58:217-220)

궤양성 대장염에 합병된 직장의 국소성 거대 가성용종증

정록선 ( Rok Son Choung ),최재현 ( Jai Hyun Choi ),장윤정 ( Yun Jung Chang ),김민정 ( Min Jung Kim ),김용식 ( Yong Sik Kim ),진윤태 ( Yoon Tae Jeen ),이홍식 ( Hong Sik Lee ),전훈재 ( Hoon Jai Chun ),이상우 ( Sang Woo Lee ),김창덕 대한장연구학회 2003 Intestinal Research Vol.1 No.1

Localized giant pseudopolyposis is an interesting but unuusal manifestation of both ulcerative colitis and Crohn``s disease. It is not regarded as being premalignant, but it may mimic villous adenoma or adenocarcinoma by radiographic and endoscopic picture. and also, it may precipitate obstrucrion by stricture formation or give rise to major hemorrhage. We report a case of localized giant pseudopolyposis of the rectum complicating ulcerative colitis with reviews of other cases in the literatue. (Intestinal Research 2003;1:55-58)

장결핵의 진단을 위한 대장내시경 생검과 장외결핵의 유용성

정록선 ( Rok Son Choung ),최재현 ( Jai Hyun Choi ) 대한소화기학회 2004 대한소화기학회지 Vol.44 No.5

대장 근위부 진행성 선종 예측을 위한 원위부 용종의 임상적 의의: 전향적 다기관 대장 용종 연구

금보라 ( Bora Keum ),진윤태 ( Yoon Tae Jeen ),최재현 ( Jai Hyun Choi ),정성애 ( Sung Ae Jung ),김현수 ( Hyun Soo Kim ),김영호 ( Young Ho Kim ),김원호 ( Won Ho Kim ),김태일 ( Tae Il Kim ),김효종 ( Hyo Jong Kim ),양석균 ( Suk Kyun Y 대한장연구학회 2005 Intestinal Research Vol.3 No.2

목적: 대장암 선별 검사로 사용되는 S상결장경이 근위부 대장에 있는 진행성 병변의 상당부분을 간과할 수 있다는 것이 밝혀지면서 선별 검사로서 대장내시경의 사용과 대장 원위부 용종의 임상적 의미에 대한 연구들이 있었다. 본 연구는 국내에서 대장 근위부 진행성 선종을 예측하는 데 원위부 용종의 임상적 의미와 위험 인자를 알아보고자 하였다. 대상 및 방법: 전향적 다기관 대장 용종 연구에서 50세 이상 무증상 환자에서 대장 내시경을 시행하며 용종 절제를 시행받은 826명을 대상으로 용종의 크기, 모양, 조직형, 위치 등의 성상을 기록하였다. 비장 굴곡을 경계로 근위부와 원위부를 나누었고 용종의 성상에 따라 분류한 후 원위부 소견에 따른 근위부 소견, 근위부 진행성 선종에 대한 원위부 용종의 민감도, 양성 예측률과 위험 인자를 분석하였다. 결과: 근위부에 진행성 선종 환자는 98명이었고 이들에서 원위부 대장 용종이 없었던 경우가 45명(45.9%)이었다. 원위부 용종의 크기에 따라 5 mm 미만이었을 때 근위부 진행성 선종이 있었던 경우가 1.9%, 5-10 mm인 경우 26.4%, 10 mm 이상인 경우 71.7%였다(p<0.01). 크기와 함께 조직형을 고려하여 분석하였을 때에도 역시 원위부 용종이 진행성 선종일수록 근위부에도 진행성 선종이 증가하였다(p<0.01). 용종 크기로 근위부 진행성 선종에 대한 민감도를 구하였을 때 10 mm 이상, 5 mm 이상일 때 각각 38.7%, 53.2%였고 조직형을 합한 진행성 선종에서는 38.8%였으며 양성 예측률은 10 mm 이상, 5-9 mm일 때 각각 13.3%, 4.1%였고 진행성 선종은 14.4%였다. 근위부 진행성 선종을 예측하는 위험인자로 남자(OD 3.9, 95%CI 1.61-9.48), 원위부 용종 10 mm 이상(OD 7.8, 95%CI 1.04-58.95), 원위부 진행성 선종(OD5.4 95%CI 1.61-17.9)이 통계적으로 유의한 위험 인자였다. 결론: 원위부 용종 소견이 대장 내시경을 통한 선별 검사 시에도 근위부 병변 예측에 도움이 될 것으로 생각하나 원위부 병변없는 근위부 진행성 선종 환자를 반드시 고려해서 주의 깊게 검사해야 할 것으로 생각한다. Backgroud/Aims: Proximal lesion without distal finding is weak point in colon cancer screening. Clinical significance of distal finding for advanced proximal neoplasia (APN) is uncertain. Aims of this study were to assess distal finding for prediction of APN. Methods: Asymptomatic 826 adults (age≥50) were collected in KASID prospective study, who underwent colonoscopy and polypectomy. Polyps located distal to splenic flexure were defined as distal polyps. Age, gender, size, appearance, histology of distal polyps were analyzed as risk factor of APN (adenoma≥10 mm or villous histology or high grade dysplasia or invasive cancer). Sensitivity and positive predictive value of distal polyp on APN were assessed. Results: APN were found in 98 patients and 45 (45.9%) patients of them were not associated with any distal findings. Risk factors of APN were male, size of distal polyp and advanced distal polyp. Sensitivity of distal polyp size≥10 mm on APN was 38.8% and advanced distal polyp also 38.8%. Positive predictive value of distal polyp size≥10 mm and advanced distal polyp were 13.3%, 14.4% respectively. Conclusions: Although distal colon findings were helpful to predict APN in asymptomatic 50 years of age or order patients screening, more careful examination is required considering APN without distal polyps. (Intestinal Research 2005;3:121-126)

CT 및 EUS 상 원격전이 소견이 없는 진행위암에서 복강경 검사의 유용성

허병원(Byung Won Hur),전훈재(Hoon Jai Chun),진윤태(Yoon Tae Jeen),강창돈(Chang Don Kang),이정환(Jung Whang Lee),이홍식(Hong Sik Lee),송치욱(Chi Wook Song),엄순호(Soon Ho Um),이상우(Sang Woo Lee),최재현](Jai Hyun Choi),김창덕(Chang Du 대한내과학회 2001 대한내과학회지 Vol.61 No.2

N/A Background : The proper staging of advanced gastric cancer has crucial role in determining resectability and operative method, to prevent unnecessary operation and to predict the prognosis and survival rate. Although marked improvements have been made in computed tomography (CT) technology and endoscopic ultrasonography (EUS) in recent years, reassessment of the laparoscopy for gastric cancer is required as a preoperative staging tool. Therefore, we determined the usefulness of laparoscopy for staging of advanced gastric cancer without distant metastasis in CT and EUS. Methods : Staging laparoscopy was performed in 48 patients with advanced gastric cancer staged T3 or T4 by CT and EUS. Laparoscopy was carried out with the patients under local anesthesia, and included visual inspection of abdomen, and biopsies for suspicious metastatic lesions. Laparoscopic results were compared with the postoperative pathologic findings. Results : Laparoscopy was performed successfully in 48 patients. Laparoscopy disclosed unrecognized distant metastases in 7 patients (14.6%) judged to be eligible for potentially curative resection by CT and EUS. Preoperative laparoscopy showed an accuracy of 74% for serosal infiltration. Conclusion : Our results suggest that laparoscopy is an effective means of evaluating resectability of advanced gastric cancer staged T3 or T4 and can provide valuable help in planning surgical approach.(Korean J Med 61:127-132, 2001)

정상인의 대장내압검사 소견

강동훈(Dong Hoon Kang),송치욱(Chi Wook song),최재현(Jai Hyun Choi),현진해(Jin Hae Hyun) 대한소화기학회 1997 대한소화기학회지 Vol.29 No.5

N/A Background/Aims: The physiological mechanisms of the whole colon has not yet been established because the only available data comes chiefly from distal colonic segments, therefore the rnotor response of the whole colon to a rneal is still not fully understood. The purpose of this study is to evaluate the motor function of the whole colon and to investigate the proximal and distal colonic motor response to a meal in healthy subjects. Methods: Thirty one healthy volunteers were studied with a colonoscopically positioned multilumen manometric catheter and a low compliance infusion system. Recordings were obtained for 4 hours during fasting and for 4 hours after a standard mixed meal(810 Calory). Results: During fasting, motility was quite low and no significant differences between the proximal and the distal colon were observed. After a meal, motor activities increased in each segment significantly throughout the subsequent recording periods. Ascending and transverse colon had at first a sudden maxirnal increase and then a decrease. Whereas, the distal segments had a slower and more sustained increase in its activity. In 21 of 31 subjects, there were 48 isolated high propagated contractions(HAPCs) in each segments of the whole colon for 8 hours. The mean amplitude was recorded as being 127.3+26.7 mmHg, and the rnean duration was found to be 17.6>2.9 seconds, and the rnean velocity was 0.7+0.1 cm/sec. The peristaltic contractions were often felt as an urge to defecate or proceded defecation and this could represent the manometric equivalent of the mass movement in the colon. Conclusions: Manometric measurement of the whole colon is a useful diagnostic method to directly evaluate the colonic motor function and may be used to study the pathophysiology of colonic motor funtion of patients with colonic motility disorders. (Korean J Gastroenterol 1997; 29:610-619)