엔트로피 제어 비정질 형성 합금 시스템에서 비정질 형성능 및 기계적 특성 변화 고찰

학위논문(석사)--서울대학교 대학원 :공과대학 재료공학부,2019. 8. 박은수.Herein, we systematically investigated the effect of configuration entropy (CE) on the glass-forming ability (GFA) and the mechanical response in a series of equiatomic binary Cu50Zr50 to denary (CuNiBeCoFe)50(ZrTiHfTaNb)50 metallic glasses (MGs) with similar atomic size difference and heat of mixing through alloy design involving careful selection of elements chemically and topologically similar to Cu and Zr and subsequent substitution of pre-constituent elements. Interestingly, the senary (CuNiBe)50(ZrTiHf)50 MG with relatively medium CE value of 1.79R exhibited the maximum GFA among the investigated MGs, implying that the CE is not the dominant factor for GFA. The mechanical response analysis was comprehensively performed using nanoindentation test including deformation dynamics of shear avalanche through statistical analysis of pop-in behavior and the analysis result was compared to the atomic-level structure data obtained by high energy X-ray scattering experiment. The overall trend of the nanohardness and the Youngs modulus (E) was shown to outwardly increase which is dominantly due to the increased 3 atom-connection of polyhedra as well as lower fragility. However, the severe local structural irregularity and compositional complexity in MG with higher CE facilitate the chaotic deformation behavior that results in the unanticipated local softening of amorphous phase and ultimately modulate the response towards ductile deformation. Consequently, it can be concluded that the CE could be one of the crucial factors in designing an MG to alter its characteristics towards achieving desirable properties such as optimized GFA and enhanced ductility.본 연구에서는 구성 엔트로피가 비정질 형성능 및 기계적 거동에 미치는 영향을 알아보기 위해 이성분계 Cu50Zr50 부터 십성분계 (CuNiBeCoFe)50(ZrTiHfTaNb)50에 이르기 까지 다양한 금속원소들이 등가원소비로 이루어진 비정질 합금 시리즈의 기계적, 구조적 특성에 대해 분석하였다. 첨가 원소들간 원자 반경 차이, 혼합열 등의 특성이 비슷해 구성 엔트로피 효과를 확인하기 적합한 등가원소비 비정질 합금 시스템을 제조하기 위해 Cu 및 Zr과 화학적, 구조적 특성이 유사한 금속들을 선별하여 등가원소비로 첨가한 뒤 비정질 합금을 제조하였다. 특이하게도 비교적으로 중간 구성 엔트로피를 값을 (1.79R) 갖는 육성분계 (CuNiBe)50(ZrTiHf)50 비정질 합금이 가장 높은 비정질 형성능을 보이며 구성 엔트로피가 비정질 형성능의 우성인자가 아닌 것을 알 수 있었다. 구성원소 개수에 따른 구성 엔트로피 변화가 기계적 거동에 미치는 영향을 확인하기 위해 나노압입 시험을 통한 pop-in 거동의 통계적 분석을 통해 수행하였으며, 이를 이해하기 위해 고 에너지 X-선 산란 실험 (high energy X-ray scattering) 에 의해 얻어진 원자 단위 구조 데이터와 비교 하여 논하였다. 그 결과, 원자 클러스터 간 결합 패턴의 비율이 면결합 (3 atom-connection)으로 증가 및 fragility는 감소할수록 합금의 경도 및 탄성계수 변화는 전반적으로 증가함을 확인할 수 있었다. 또한 원소 첨가에 따른 구성 엔트로피 증가는 국부적으로 구조적 불규칙성 및 조성적 복잡성을 유발 하여 chaotic 변형 거동을 촉진시켜 국부적 softening 현상이 나타나게 하였으며 궁극적으로 연성 변형에 대한 반응을 조절 시킬 수 있었다. 결과적으로, 구성 엔트로피는 최적의 비정질 형성능 및 향상된 연성과 같은 우수한 특성을 달성하기 위해 비정질 합금 설계에 중요한 요소임을 알 수 있었다.Chapter 1. Introduction 1 1.1. Metallic glass 1 1.1.1. Definition and characteristics 1 1.1.2. Glass-forming ability parameter 4 1.1.3. Fragility 9 1.1.4. Deformation mechanism 11 1.1.5. Shear avalanche in metallic glass 13 1.2. High entropy alloy 16 1.2.1. Definition and characteristics 16 1.2.2. Four core effects of HEA 19 1.3. High entropy metallic glass 22 1.3.1. Properties and the current understanding 23 1.4. Thesis objective and research strategy 27 Chapter 2. Experimental procedure 29 2.1. Sample preparation 29 2.1.1. Fabrication of metallic glass ribbon 29 2.2. Structural analysis 30 2.2.1. X-ray diffraction 30 2.2.2. Transmission electron microscopy 30 2.2.3. High energy X-ray scattering 30 2.3. Thermal analysis 34 2.3.1. Differential scanning calorimetry 34 2.4. Mechanical testing 35 2.4.1. Nanoindentation test 35 Chapter 3. Results 37 3.1. Alloy design 37 3.2. Structural analysis 42 3.2.1. X-ray diffraction analysis 42 3.2.2. Transmission electron microscopy analysis 42 3.2.3. High energy X-ray scattering analysis 46 3.3. Glass-forming ability evaluation 48 3.4. Fragility evaluation 53 3.5. Nanoindentation test 55 Chapter 4. Discussion 60 4.1. Influence of configuration entropy on the atomic-level structure 60 4.2. Anomalous modulus variation in high entropy metallic glass 65 4.3. Anomalous deformation dynamics of high entropy metallic glass 70 Chapter 5. Conclusion 78Maste

O2 플라즈마, 자외선 조사, Biased-H2O 어닐링을 통한 저온 용액공정을 이용한 산화물 박막트랜지스터의 특성 향상에 대한 연구

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 한민구.Zinc tin oxide (ZTO)나 indium gallium zinc oxide (IGZO)를 이용한 용액공정형 산화물 박막 트랜지스터는 고이동도, 빛 투명성, 플렉서블 적합성, 물질의 광범위함, 분자 구성비에 의한 전기적 특성 조절 용이성 등의 장점 때문에 실리콘 기반의 박막 트랜지스터와 유기물 박막 트랜지스터를 대체하며 능동 매트릭스형 디스플레이의 구동 소자로서 상당한 주목을 받고 있다. 용액공정형 산화물 박막 트랜지스터는 능동 매트릭스형 액정표시장치와 능동 매트릭스형 유기발광다이오드 디스플레이 백플레인으로서 많은 문제점을 가지고 있는 실리콘 기반의 박막 트랜지스터와 유기물 박막 트랜지스터와 비교하여 우수한 특성을 보여주고 있다. 더욱이, 용액공정형 산화물 박막 트랜지스터는 우수한 균일성과 고처리량 덕분에 대면적 공정에 적합하다. ZnO 기반의 산화물 반도체 중에서, Sn 물질을 이용한 ZTO 박막 트랜지스터는 Sn이 널리 사용되고 있는 In 보다 상당히 저가의 물질이기 때문에 저가 공정을 확립하는데 유망한 소자이다. 추가적인 가격 절감과 플렉서블 디스플레이로의 응용성 확장을 위해서 용액공정형 ZTO 박막 트랜지스터는 저렴하고 플렉서블한 기판에 제작되어야 한다. 플렉서블한 기판은 고온에서 쉽게 손상되기 때문에 플렉서블한 기판에 용액공정형 ZTO 박막 트랜지스터가 제작되기 위해서는 저온 공정이 요구된다. 그러나, 저온에서 제작된 용액공정형 ZTO 박막 트랜지스터는 낮은 on-currnet, 높은 문턱 접압, 낮은 이동도 등의 열등한 특성을 가지므로, 우수한 특성의 용액공정형 ZTO 박막 트랜지스터를 제작하기 위해서는 500도 이상의 고온 공정이 필요하다. 저온에서 제작된 용액공정형 산화물 박막 트랜지스터의 소자 특성을 향상시키기 위해서는, 용액공정형 산화물 박막 트랜지스터에 대한 어닐링 온도의 영향성과 더불어 저온 공정에서 제작되더라도 우수한 소자 특성을 가지도록 하는 연구가 요구된다. 기존에 용액공정형 산화물 박막 트랜지스터에 대한 어닐링 온도의 영향상을 분석하려는 시도가 있었지만, 용액공정형 산화물 박막 트랜지스터에 대한 어닐링 온도 영향성의 전기적, 화학적 메커니즘은 거의 연구되지 않았다. 이 논문의 목적은 용액공정을 이용하여 다양한 어닐링 온도에서 산화물 박막 트랜지스터를 제작하여 문턱 전압, 포화 이동도, 신뢰성 등의 용액공정형 산화물 박막 트랜지스터의 전기적 특성에 대한 어닐링 온도의 영향성을 분석하고, 제안된 O2 플라즈마, 자외선 조사, Biased-H2O 어닐링 등의 방법을 통하여 능동 매트릭스형 디스플레이를 위한 저온 용액공정 산화물 박막 트랜지스터의 전기적 특성을 향상시키는 것이다.Solution-processed oxide thin film transistors (TFTs) with zinc-tin-oxide (ZTO) and indium-gallium-zinc-oxide (IGZO) have attracted considerable attention for the driving elements of active matrix display, instead of Si-based TFTs and organic TFTs, because of high mobility, visible light transparency, flexibility, wide range of materials, and controllability of electrical properties by atomic composition. Solution-processed oxide TFTs show superior performance for active matrix liquid crystal display (AMLCD) and active matrix organic light emitting diode (AMOLED) display backplanes, compared with solution-processed Si and organic TFTs which have a number of issues. Furthermore, solution-processed oxide TFTs are compatible with large area due to good uniformity and high throughput, so that could be a method for achieving low cost fabrication contrary to vacuum processes. Among various ZnO-based oxide semiconductors, ZTO TFTs employing tin (Sn) material maybe promising candidates for achieving low cost processes because Sn is a quite low cost material compared with widely used indium (In). Solution-processed ZTO TFTs need to be fabricated on inexpensive and flexible substrates such as glass and plastic for additional cost reduction and application extension to a flexible display. For solution-processed ZTO TFTs fabrication with these flexible substrates, low temperature processes are necessary because these substrates are easily damaged at high annealing temperatures. At low annealing temperature, however, solution-processed ZTO TFTs have poor performance such as low on-current, high threshold voltage and low mobility, so a rather high annealing temperature exceeding 500 °C is required in solution-processed ZTO TFTs. To improve the device characteristics of solution-processed oxide TFTs even at low annealing temperature on an active layer, a study of the effects of annealing temperature on the electrical characteristics of solution-processed oxide TFTs and the efforts to achieve high device characteristics of solution-processed oxide TFTs even at low annealing temperature on active layer are desired. There were some efforts to investigate the effects of annealing temperature on solution-processed oxide TFTs, but the electrical and chemical mechanisms of annealing temperature on solution-processed oxide TFTs have been scarcely studied. The purpose of this thesis is to fabricate oxide TFTs employing solution-process for an oxide semiconductor active layer with various annealing temperatures to investigate the effects of annealing temperature on the electrical characteristics of solution-processed oxide TFTs such as threshold voltage, saturation mobility, and reliability, and to improve the electrical characteristics of low temperature solution-processed oxide TFTs for low cost, stable, and flexible active matrix display backplane. The effects of annealing temperature on the bonding structure of ZTO active layer in solution-processed ZTO TFTs were investigated and the chemical formation equation of the ZTO active layer with regard to the annealing temperature was established. To improve the electrical characteristics of low temperature solution-processed oxide TFTs according to the investigation of effects of annealing temperature in regard of the chemical formation of ZTO active layer, O2 plasma treatment, UV radiation treatment, and the biased-H2O annealing were proposed to achieve high device characteristics of solution-processed oxide TFTs even at low annealing temperature. Moreover, the effects on electrical and chemical characteristics of solution-processed oxide TFTs with proposed methods were investigated in detail. These proposed methods to improve the electrical characteristics of low temperature solution-processed oxide TFTs would be suitable for the low cost, stable, and flexible active matrix display backplane.Abstract i Contents iv List of Tables vii List of Figures ix Chapter 1 Introduction 1 1.1 Recent flat panel display technology 2 1.2 Device parameter extraction 12 1.3 Dissertation organization 14 Chapter 2 Review of solution-processed oxide TFTs 16 2.1 Overview of oxide TFTs 17 2.2 Advantages of solution-process 25 2.3 Solution-processed oxide TFTs 30 Chapter 3 Optimization of the fabrication process of solution-processed oxide TFTs 36 3.1 Overview 37 3.2 Structure of solution-processed oxide TFTs 38 3.3 Stirring time on solution-processed oxide TFTs 47 3.4 Active layer thickness on solution-processed oxide TFTs 56 3.5 Effects of passivation on solution-processed oxide TFTs 60 3.6 Electrical characteristics of solution-processed oxide TFTs 63 3.6.1 Transfer characteristics 63 3.6.2 Reliability characteristics 68 Chapter 4 Effects of Annealing Temperature on Solution-processed oxide TFTs 75 4.1 Motivation 76 4.2 Fabrication of solution-processed ZTO TFTs with various annealing temperature 78 4.3 Electrical characteristics with the increase in annealing temperature 80 4.4 Dechlorination on threshold voltage with the increase in annealing temperature 83 4.5 Dechlorination and crystallization on saturation mobility with the increase in annealing temperature 89 4.6 Reliability characteristics with the increase in annealing temperature 93 4.7 Chemical formation equations with the increase in annealing temperature 95 4.8 Conclusion 99 Chapter 5 Improvement of low temperature solution-processed oxide TFTs 100 5.1 Improvement of low temperature solution-processed oxide TFTs employing O2 plasma treatment 101 5.1.1 Motivation 101 5.1.2 Fabrication of solution-processed ZTO TFTs employing O2 plasma treatment 104 5.1.3 Electrical characteristics with O2 plasma treatment 108 5.1.4 Preferential dissociation of Cl on threshold voltage by O2 plasma treatment 111 5.1.5 Increase of electron concentration on saturation mobility by O2 plasma treatment 116 5.1.6 Reliability characteristics with O2 plasma treatment 119 5.1.7 Conclusion 122 5.2 Improvement of low temperature solution-processed oxide TFTs employing Ultra-Violet radiation treatment 123 5.2.1 Motivation 123 5.2.2 Fabrication of solution-processed ZTO TFTs employing UV radiation treatment 126 5.2.3 Electrical characteristics with UV radiation treatment 130 5.2.4 Effects of UV radiation treatment on oxide active layer semiconductors 133 5.2.5 Generation of hydroxide(-OH) bonding by UV radiation treatment on oxide active layer semiconductors 137 5.2.6 Conclusion 141 5.3 Improvement of low temperature solution-processed oxide TFTs employing biaed-H2O annealing 142 5.3.1 Motivation 142 5.3.2 Effects of various annealing condition 145 5.3.3 Effects of H2O wet annealing according to the annealing temperature 148 5.3.4 Proposed biased-H2O annealing to improve low temperature solution-processed oxide TFTs 154 5.3.5 Conclusion 161 Chapter 6 Summary 162 Bibliography 171 초 록 191Docto

Specific Immunotherapy in Atopic Dermatitis

Allergen specific immunotherapy (SIT) using house dust mite (HDM) extracts has been performed mainly with patients of asthma and allergic rhinitis. In the meanwhile, there has been a long debate on the efficacy of SIT in atopic dermatitis (AD) with only a few double-blind placebo-controlled trials. However, several randomized controlled trials of SIT in AD revealed significant improvement of clinical symptoms and also, positive result was shown by a following meta-analysis study of these trials. In order to predict and evaluate the treatment outcome, finding a biomarker that can predict treatment responses and treatment end-points is critical but it is very challenging at the same time due to the complexity of causes and mechanisms of AD. Other considerations including standardization of the easiest and safest treatment protocol and optimizing the treatment preparations should be studied as well. This review summarizes the basics of SIT in AD including the brief mechanisms, treatment methods and schedules, and also highlights the clinical efficacy of SIT in AD along with mild, controllable adverse reactions. Immunologic effects and studies of various biomarkers are also introduced and finally, future considerations with upcoming studies on SIT were discussed.ope

Comparison of Postoperative Pain and Adverse Effects between Variable-Rate Feedback Infusion and Conventional Fixed-Rate Basal Infusion Modes of Patient-Controlled Epidural Analgesia following Open Gastrectomy: A Randomized Controlled Trial

Patient-controlled epidural analgesia is widely used to control postoperative pain following major intra-abdominal surgeries. However, determining the optimal infusion dose that can produce effective analgesia while reducing side effects remains a task to be solved. Postoperative pain and adverse effects between variable-rate feedback infusion (VFIM group, n = 36) and conventional fixed-rate basal infusion (CFIM group, n = 36) of fentanyl/ropivacaine-based patient-controlled epidural analgesia were evaluated. In the CFIM group, the basal infusion rate was fixed (5 mL/h), whereas, in the VFIM group, the basal infusion rate was increased by 0.5 mL/h each time a bolus dose was administered and decreased by 0.3 mL/h when a bolus dose was not administered for 2 h. Patients in the VFIM group experienced significantly less pain at one to six hours after surgery than those in the CFIM group. Further, the number of patients who suffered from postoperative nausea was significantly lower in the VFIM group than in the CFIM group until six hours after surgery. The variable-rate feedback infusion mode of patient-controlled epidural analgesia may provide better analgesia accompanied with significantly less nausea in the early postoperative period than the conventional fixed-rate basal infusion mode following open gastrectomy.ope

Characteristics of Atopic Dermatitis in a Post-childhood Atopic March Group

BACKGROUND: Little knowledge is available on the characteristic differences between patients with atopic dermatitis (AD) with and without atopic march after childhood. OBJECTIVE: To observe and compare the phenotypes of patients with AD in regards to atopic march tendency at a single point. METHODS: We enrolled patients with AD aged between 10 and 30 years. The patients were divided into the atopic march and non-atopic march groups on the basis of an investigator-designed survey questionnaire, and their serum-specific immunoglobulin E (IgE) levels or results of the skin prick test were compared. RESULTS: In a total of 182 patients enrolled in the study, 93 patients with atopic march and 89 patients with non-atopic march were observed. When their serum-specific IgE levels or results of the skin prick test were compared between the two groups, there was no significant difference, except for a in the atopic march group. Analysis of AD severity, family history of allergic diseases, and total IgE levels between the two groups showed no statistically significant differences. CONCLUSION: Our findings suggest that although no apparent phenotype characteristics could differentiate the presence of atopic march, the history of the patient's allergic diseases should be revalidated, and clinicians should watch out for future developments of atopic march when a patient shows a high-class sensitization rate to dust mite.ope

The efficacy of elastomeric patient-control module when connected to a balloon pump for postoperative epidural analgesia: A randomized, noninferiority trial

When considering the principles of a pain control strategy by patients, reliable administration of additional bolus doses is important for providing the adequate analgesia and improving patient satisfaction. We compared the efficacy of elastomeric patient-control module (PCM) with conventional PCM providing epidural analgesia postoperatively.A noninferiority comparison was used. Eighty-six patients scheduled for open upper abdominal surgery were randomized to use either an elastomeric or conventional PCM connected to balloon pump. After successful epidural catheter insertion at T6-8 level, fentanyl (15-20 μg/kg) in 0.3% ropivacaine 100 mL was administered at basal rate 2 mL/h with bolus 2 mL and lock-out time 15 minutes. The primary outcome was the verbal numerical rating score for pain.The 95% confidence intervals for differences in pain scores during the first 48 hours postoperatively were <1, indicating noninferiority of the elastomeric PCM. The duration of pump reservoir exhaustion was shorter for the elastomeric PCM (mean [SD], 33 hours [8 hours] vs 40 hours [8 hours], P = 0.0003). There were no differences in the frequency of PCM use, additional analgesics, or adverse events between groups.The elastomeric PCM was as effective as conventional PCM with and exhibited a similar safety profile.ope

Efficacy of Single-Dose Dexmedetomidine Combined with Low-Dose Remifentanil Infusion for Cough Suppression Compared to High-Dose Remifentanil Infusion: A Randomized, Controlled, Non-Inferiority Trial

Background: Combination of dexmedetomidine and opioid may be an alternative to high-dose opioid in attenuating cough during emergence from anesthesia, while also reducing the adverse effects of high-dose opioid. We tested the hypothesis that a single-dose of dexmedetomidine combined with low-dose remifentanil infusion during emergence would not be inferior to high-dose remifentanil infusion alone in attenuating cough after thyroidectomy. Methods: One hundred sixty-nine patients undergoing thyroidectomy were enrolled and randomized in a 1:1 ratio into group DR or group R. Each patient received an infusion of dexmedetomidine (0.5 μg/kg) and low-dose remifentanil infusion of effect-site concentration (Ce) at 1 ng/mL or normal saline and high-dose remifentanil infusion of Ce at 2 ng/mL for 10 min at the end of surgery. Remifentanil was maintained until tracheal extubation. Primary endpoint was the severity of coughing, which was assessed for non-inferiority using a four-point scale at the time of extubation. For comparison of coughing incidence during emergence, coughing grade was also measured at three times: before extubation, at extubation, and after extubation. Time to awakening, hemodynamic and respiratory profile, pain, and postoperative nausea and vomiting were also evaluated for superiority. Results: The 95% confidence intervals for differences in cough grade during tracheal extubation were <0.9, indicating non-inferiority of the single dose of dexmedetomidine combined with low-dose remifentanil infusion. The incidence of coughing was similar in the two groups. Hemodynamic changes during tracheal extubation were attenuated, but emergence from anesthesia was delayed, in group DR. Use of rescue antiemetic was similar in both groups, but the incidence of vomiting was less in group DR. Conclusion: A single-dose of dexmedetomidine (0.5 μg/kg) combined with low-dose remifentanil infusion at 1 ng/mL of Ce during emergence from sevoflurane-remifentanil anesthesia was not inferior to high-dose remifentanil infusion alone at 2 ng/mL of Ce with regard to suppressing cough.ope

Reference values of neutrophil-lymphocyte ratio, lymphocyte-monocyte ratio, platelet-lymphocyte ratio, and mean platelet volume in healthy adults in South Korea

There is a growing interest in research aimed at better understanding the disease status or predicting the prognosis of patients with simple blood tests associated with systemic inflammation. The neutrophil-lymphocyte ratio (NLR), lymphocyte-monocyte ratio (LMR), platelet-lymphocyte ratio (PLR), and mean platelet volume (MPV) can be used as factors to determine the prognosis of patients in various clinical situations. However, reference values for these attributes based on large, healthy populations have yet to be determined.From January 2014 to December 2016, data from routine blood analyses were collected from healthy patients in the checkup center of a tertiary hospital in Seoul, South Korea. Retrospective data review was then performed on an electronic medical record system. Data were treated anonymously as only age, sex, body mass index, medical history including cancer diagnosis, medications, and smoking status were considered. After the initial screen, we had a collection of 12,160 samples from patients without any medical history, including cancer treatment. This patient pool consisted of 6268 (51.5%, median age 47 years) and 5892 (48.5%, median age 46 years) male and female patients, respectively. The mean NLR across all ages was 1.65 (0.79), and the values for men and women were 1.63 (0.76) and 1.66 (0.82), respectively. The mean LMR, PLR, and MPV were 5.31 (1.68), 132.40 (43.68), and 10.02 (0.79), respectively. This study provides preliminary reference data on LMR, PLR, and MPV from different age and sex groups in South Korea. The results suggest that different cutoff values should be applied to the various patient populations.ope

Incidence and Risk Factors of Postoperative Nausea and Vomiting in Patients with Fentanyl-Based Intravenous Patient-Controlled Analgesia and Single Antiemetic Prophylaxis

PURPOSE: We evaluated the incidence and risk factors of postoperative nausea and vomiting (PONV) in patients with fentanyl-based intravenous patient-controlled analgesia (IV-PCA) and single antiemetic prophylaxis of 5-hydroxytryptamine type 3 (5 HT₃)-receptor antagonist after the general anesthesia. MATERIALS AND METHODS: In this retrospective study, incidence and risk factors for PONV were evaluated with fentanyl IV-PCA during postoperative 48 hours after various surgeries. RESULTS: Four hundred-forty patients (23%) of 1878 had showed PONV. PCA was discontinued temporarily in 268 patients (14%), mostly due to PONV (88% of 268 patients). In multivariate analysis, female, non-smoker, history of motion sickness or PONV, long duration of anesthesia (>180 min), use of desflurane and intraoperative remifentanil infusion were independent risk factors for PONV. If one, two, three, four, five, or six of these risk factors were present, the incidences of PONV were 18%, 19%, 22%, 31%, 42%, or 50%. Laparoscopic surgery and higher dose of fentanyl were not risk factors for PONV. CONCLUSION: Despite antiemetic prophylaxis with 5 HT₃-receptor antagonist, 23% of patients with fentanyl-based IV-PCA after general anesthesia showed PONV. Long duration of anesthesia and use of desflurane were identified as risk factors, in addition to risk factors of Apfel's score (female, non-smoker, history of motion sickness or PONV). Also, intraoperative remifentanil infusion was risk factor independent of postoperative opioid use. As the incidence of PONV was up to 50% according to the number of risk factors, risk-adapted, multimodal or combination therapy should be applied.ope