GaN증폭기의 본드 와이어 용융단선 현상분석과과도전류를 고려한 전류용량 선정에 대한 연구

유우성,석연수,황규혁,김기준 한국전기전자학회 2022 전기전자학회논문지 Vol.26 No.4

This paper analyzes the occurrence and cause of bond wires fusing used in the manufacture of pulsed highpower amplifiers. Recently GaN HEMT has been spotlight in the fields of electronic warfare, radar, base stationand satellite communication. In order to produce the maximum output power, which is the main performance ofthe high-power amplifier, optimal impedance matching is required. And the material, diameter and number ofbond wires must be determined in consideration of not only the rated current but also the heat generated by thetransient current. In particular, it was confirmed that compound semiconductor with a wide energy band gap suchas GaN trigger fusing of the bond wire due to an increase in thermal resistance when the design efficiency is lowor the heat dissipation is insufficient. This data has been simulated for exothermic conditions, and it is expectedto be used as a reference for applications using GaN devices as verified through IR microscope. 본 논문은 최근 전자전, 레이더, 기지국 및 위성통신분야에서 각광받고 있는 GaN HEMT(Gallium Nitride High ElectronMobility Transistor) die를 이용한 고출력증폭기의 제작에 사용되는 본드 와이어의 용융단선 현상과 원인을 분석하였다. 고출력증폭기의 주요 성능인 최대 출력전력을 얻기 위해서는 최적의 임피던스 정합이 필요하고 정격전류뿐만 아니라 과도전류에 대한 발열을 고려하여 본드 와이어 소재에 부합하는 직경과 가닥수가 정해져야 한다. 특히, GaN과 같이 에너지 밴드 갭이 넓은 화합물반도체는 설계효율이 낮거나 방열이 부족하면 열 저항 증가로 인해 본드 와이어의 용융단선을 촉발하는 현상을 확인하였다. 본 자료는 발열조건에 대한 모의시험을 수행하고, IR현미경 측정을 통한 검증으로 GaN소자를 이용한 응용분야에 참고자료로 활용이 기대된다.

Clinical Significance of Hyperlactatemia and Acidosis in Patients with Suspected Generalized Convulsion

유우성,이성우,박종수,문성우,최성혁,홍윤식 대한응급의학회 2012 대한응급의학회지 Vol.23 No.6

Purpose: To determine the clinical usefulness of lactic acidosis in an evaluation of patients with suspected generalized convulsion. Methods: This was retrospective cohort study. The correlation between the lactate level and the time to blood gas analysis (ABGA) was analyzed in patients who had a final diagnosis of seizure to exclude the time effect on the spontaneous clearance of lactate. The patient’s data in the true seizure group and false seizure group was then compared. The receiver operating characteristics (ROC) curve of lactate,pH and base deficit for diagnosing true seizure was drawn. The sensitivity and specificity of the presence of hyperlactatemia or acidosis for a diagnosis of seizure and predicting epileptiform discharge at electroencephalography (EEG) was analyzed. Results: Of the 173 patients suspected of having generalized convulsion, 136 patients were diagnosed with a true seizure on hospital discharge and patients whose ABGA was performed within 60 minutes after seizure showed a significantly higher arterial lactate level, lower arterial pH and base deficit than the patients whose ABGA was performed after 60 minutes of seizure onset. 62 patients whose ABGA was performed 60 minutes after symptom onset were excluded. Finally, of 111 patients, 89 patients with true seizure showed a significantly higher arterial lactate level, lower arterial pH and base deficit than the 22patients with false seizure. The ROC curve of lactate, pH and base deficit showed a significant area under the curve for diagnosing true seizure. The presence of hyperlactatemia or acidosis showed high sensitivity for diagnosing true seizure and expecting epileptiform EEG when they were measured with 60 minutes after symptom onset. Conclusion: In patients with suspected generalized convulsion,upon presentation to the ED within 60 min of symptom onset, the presence of hyperlactatemia or acidosis increased the likelihood of a true seizure and might be an objective indicator for further evaluations of seizure. On the other hand, normal lactate levels and no acidosis could not exclude a true seizure.

무선 센서 네트워크의 클러스터 라우팅에서 위치기반 부하 균등화 기법

유우성(Woo Sung Yoo),강상혁(Sang Hyuk Kang) 한국통신학회 2016 韓國通信學會論文誌 Vol.41 No.8

주파수합성기의 인밴드 스퓨리어스 회피기법

김승우,유우성 대한전기학회 2011 정보 및 제어 심포지엄 논문집 Vol.2011 No.10

Research on In-band Spurious Evasion Techniques of Hybrid Frequency Synthesizer

김승우,유우성 한국전기전자학회 2015 전기전자학회논문지 Vol.19 No.2

The study aims to a design hybrid frequency synthesizer in spectrum analyzer and to propose new techniques designed for evasion of in-band spurious. The study focuses on calculating the exact location of multiple phase locked loop of hybrid frequency synthesizer and spurious of direct digital synthesizer to evade in-band spurious outside of frequency range that the user wants to see and thereby simulating technique to improve input related spurious of spectrum analyzer for algorithm. The proposed technique is designed to calculate spurious evasion algorithm in central processing system when in-band spurious arises, and to move output frequency of DDS(direct digital synthesizer) into the place where no in-band spurious exists thereby improving performance of frequency synthesizer. The study used simulation and result representation to prove the effectiveness of the proposed technique.

기면 상태의 의식 저하로 응급의료센터에 내원한 비외상 환자들에서 뇌졸중이 아닌 원인 질환 감별을 위한 혈중 C-reactive protein, delta neutrophil index, lactic acid 및 ammonia 측정의 유용성

강현구,정루비,김영식,이규현,유우성,윤영탁,김학중 대한응급의학회 2022 대한응급의학회지 Vol.33 No.4

Objective: A drowsy mentality is a common chief complaint at emergency departments (EDs), but it is difficult to evaluate the reason for drowsy mentality. Serum biomarkers are an alternative way to discover the reason for drowsy mentalities. This study examined the values of four biomarkers for a differential diagnosis of ED patients with drowsy mentality: Creactive protein (CRP), delta neutrophil index (DNI), lactic acid and ammonia. Methods: Adult patients who presented to the ED from April 2018 to March 2019 were reviewed retrospectively. Among the 369 patients with a drowsy mentality, 122 patients with acute trauma, dementia, epilepsy, seizure, alcohol abuse, syncope, psychological problems, and anaphylaxis were excluded. The four biomarkers of each patient were then measured. The clinical records were reviewed to analyze the usefulness of the four biomarkers as a differential diagnosis tool for ED patients. Results: Of the 247 included patients, 64 were diagnosed with a stroke, and 183 were not. CRP, DNI, lactic acid and ammonia were analyzed statistically, and the elevation of each biomarker level was related to a diagnosis of non-stroke disease. Conclusion: Elevations of CRP, DNI, lactic acid and ammonia suggest non-stroke disease in patients with drowsy mentality in ED. There might be metabolic causes other than stroke in ED patients with a drowsy mentality when the CRP, DNI, lactic acid and ammonia levels are highly elevated. A future study will be needed to confirm this.

응급실에서 현장검사로 시행한 β-hCG 검사의 유용성

김정윤,윤영훈,최성혁,김덕환,유우성,문성우,이성우,홍윤식 대한응급의학회 2011 大韓應急醫學會誌 Vol.22 No.5

Purpose: The rapid and accurate diagnosis of pregnancy is important in the emergency department (ED) before evaluation of radiologic tests and medication decisions. Our primary objective was to assess the agreement between whole blood pregnancy tests done in the emergency department and those done in laboratory [serum human chorionic gonadotropin (β-hCG) and urine β-hCG]. The secondary objective was to compare turnaround times for tests done in the ED and those done in the laboratory. Methods: This prospective study enrolled females of childbearing age needing a pregnancy test who visited an ED. Using whole blood, urine and serum from each patient, testing was done in the ED (whole blood - Hubi Quan pro-point of care test, POCT) and in the laboratory using a urine hCG kit (iIexscreen) and in serum (ADVIA centaur). The data included time of each test, β-hCG result, and urine pregnancy test result. Results: There was a high level of agreement between the POCT using whole blood and the serum β-hCG as indicated by a kappa value of 0.921(95% confidence interval). The POCT performed in the ED was significantly faster in time to report than tests performed in the laboratory, with mean differences of 20.21±2.0 minutes and 36.14±20.86minutes. The sensitivity and specificity of POCT was 98.18% and 93.75%, respectively. Conclusion: In ED, the POCT test can perform pregnancy test as accurately as in the laboratory, and can provide results on which to base care much faster than waiting for the laboratory results. POCT may expedite the ED management of patients who require pregnancy tests. Especially, this POCT uses whole blood instead of the urine, since the latter was inconvenient for the test.

영상검사에서 진단이 되지 않는 소아 충수돌기염의 수술적 치료를 고려할 수 있는 예측인자 연구

최승주,김영식,정루비,이규현,유우성,윤영탁,곽경훈,정수용 대한응급의학회 2023 대한응급의학회지 Vol.34 No.6

Objective: This study examined the predictive factors to decide the surgical treatment for clinically suspected pediatric acute appendicitis with equivocal imaging findings. Methods: This study was conducted retrospectively on children who visited local emergency medical centers and outpatients from January 2018 to February 2021. The electronic medical records were reviewed from 811 pediatric patients younger than 16 years of age with the chief complaint of abdominal pain and who underwent an imaging test for the clinical suspicion of appendicitis. Ninety-two patients who showed ambiguous findings on imaging tests but were still suspected of having appendicitis were analyzed. Recursive partitioning analysis and multivariable logistic regression were used to identify the variables associated with appendicitis. Results: Of the 92 enrolled patients, 23 patients were confirmed to have appendicitis, and 69 did not. Patients with the clinical suspicion who had an elevated white blood cell (WBC) count, polymorphonuclear leukocyte differential count (PMN), absolute neutrophil count (ANC), and leukocytosis were more likely to have appendicitis. The PMN (odds ratio=1.175; 95% confidence interval, 1.092-1.265) and ANC (odds ratio=1.00050; 95% confidence interval, 1.00025- 1.00075) remained significant after multivariable logistic analysis. Conclusion: Elevated PMN and ANC are clinical predictors of pediatric appendicitis when the imaging findings are nondiagnostic, and the clinical suspicion is continuous.

응급의료센터에서 진단된 급성 단순 방광염 환자의 항생제 내성률 및 적절한 항생제에 대한 고찰

정수용,김영식,정루비,이규현,유우성,윤영탁,최승주 대한응급의학회 2022 대한응급의학회지 Vol.33 No.5

Objective: This study analyzed the urine cultures of emergency department patients diagnosed with acute uncomplicated cystitis and determined the antimicrobial resistance and appropriate treatment for our region. Methods: Results of urine analysis and urine culture of acute uncomplicated cystitis patients diagnosed in our emergency department between January 2019 and December 2020 were examined and analyzed. Results: In our study, 256 out of 340 urine culture samples (75.3%) were positive for cystitis. The most common microorganism was reported to be Escherichia coli (93.0%). The resistance rates of E. coli to the following antimicrobial agents were as follows: amikacin (0.0%), ampicillin (63.5%), amoxicillin/clavulanate (15.6%), aztreonam (7.1%), ceftazidime (3.4%), cefotaxime (16.4%), cefoxitin (5.5%), cefazolin (19.9%), ciprofloxacin (29.4%), cefepime (1.7%), ertapenem (0.0%), gentamicin (18.1%), piperacillin/tazobactam (2.1%), trimethoprim/sulfamethoxazole (36.1%), and tigecycline (0.4%). The prevalence of extended-spectrum beta-lactamase producing E. coli strains was 17.8%. Conclusion: To determine the proper empirical antimicrobial treatment for acute uncomplicated cystitis, it is essential to examine the antimicrobial resistance. For our region, fosfomycin, nitrofurantoin, and 2nd and 3rd generation cephalosporin should be considered the first-line empirical treatment for acute uncomplicated cystitis.

Delta neutrophil index가 응급센터를 통하여 중환자실로 입원한 환자들의 원내 사망률을 예측할 수 있는가?

윤영탁,김영식,하영록,신태용,정루비,이규현,유우성,김동훈 대한응급의학회 2020 大韓應急醫學會誌 Vol.31 No.2

Objective: A retrospective study was performed to evaluate the usefulness of the delta neutrophil index as a prognostic factor for mortality in intensive care unit patients admitted via the emergency department. Methods: Patients, who presented to the emergency department and were admitted to the intensive care unit from January 2018 to August 2018, were reviewed retrospectively. The clinical features, inflammatory marker levels, such as C-reactive protein, lactate, simplified acute physiology score 3, length of stay, and in-hospital mortality were obtained from the medical records. Patients, who visited the emergency department because of trauma or suicidal attempts, arrived after out-hospital cardiac arrest, or were diagnosed with cerebrovascular disease, were excluded. Results: Of the 310 patients included, 65 died during their admission, and 245 patients were discharged after treatment. The receiver operating characteristic curve showed that the delta neutrophil index (area under curve [AUC], 0.72), Creactive protein (AUC, 0.70), lactate (AUC, 0.64), and simplified acute physiology score 3 (AUC, 0.79) indicated a low predictive power for in-hospital mortality. Whole patients were divided into four subgroups (infectious diseases, cardiovascular diseases, gastrointestinal bleeding diseases, and others). The receiver operating curve of delta neutrophil index revealed infectious diseases (AUC, 0.65), in cardiovascular diseases (AUC, 0.70), and gastrointestinal bleeding diseases (AUC, 0.79). Conclusion: The role of the delta neutrophil index for predicting the prognosis of in-hospital mortality showed equally low predictive power for critically ill patients with the C-reactive protein and lactate.