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Effect Analysis of Tillage Depth on Rotavator Shaft Load Using the Discrete Element Method (이산요소법을 활용한 경심이 로타리 작업기의 경운날 축 부하에 미치는 영향 분석)

  • Bo Min Bae;Dae Wi Jung;Dong Hyung Ryu;Jang Hyeon An;Se O Choi;Yeon Soo Kim;Sang Dae Lee;Seung Je Cho
    • Journal of Drive and Control
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    • v.20 no.4
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    • pp.115-122
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    • 2023
  • This study utilized a discrete element method (DEM) simulation, as one of the virtual field trials, to predict the impact of tillage depth on the rotary blade shaft during rotavator tilling. The virtual field for the simulation was generated according to soil properties observed in an actual field. Following the generation of particles for the virtual field, a sequence of calibration steps followed to align the mechanical properties more closely with those of real soil. Calibration was conducted with a focus on bulk density and shear torque, resulting in calibration errors of just 0.02% for bulk density and 0.52% for shear torque. The prediction of the load on a rotary tiller's blade shaft involved a three-pronged approach, considering shaft torque, draft force, and vertical force. In terms of shaft torque, the values exhibited significant increases of 42.34% and 36.91% for every 5-centimeter increment in tillage depth. Similarly, the vertical force saw substantial growth by 40.41% and 36.08% for every 5-centimeter increment. In contrast, the variation in draft force based on tillage depth was comparatively lower at 18.49% and 0.96%, indicating that the effect of tillage depth on draft force was less pronounced than its impact on shaft torque and vertical force. From a perspective of agricultural machinery research, this study provides valuable insights into the DEM soil modeling process, accounting for changes in soil properties with varying tillage depths. These findings are expected to be instrumental in future agricultural machinery design studies.

Orally Administered Korean Herbal Medicine Medications of Randomized Controlled Trials Published in the Journal of Korean Medicine and Related Journals: A Narrative Analysis using CONSORT-CHM 2017 (CONSORT-CHM 2017 지침에 근거한 대한한의학회지 및 회원학회지에 투고된 경구투여 한약 중재를 활용한 무작위 배정 비교 임상 연구(RCT)의 양적, 질적 평가 연구)

  • Se-hun Moon;Jung-ho Jo;Seung-kwan Choi;Yun-hee Han;Hyeon-jun Woo;Byeong-hyeon Jeon;Won-bae Ha;Jung-han Lee
    • The Journal of Internal Korean Medicine
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    • v.44 no.6
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    • pp.1212-1242
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    • 2023
  • Objectives: This study aims to explore the current usage status of orally administered Korean herbal medicine in randomized controlled trials (RCTs) published in the Journal of Korean Medicine and member journals using the CONSORT-Chinese Herbal Medicine Formulas 2017 (CONSORT-CHM 2017) checklist. Methods: We searched the OASIS, RISS, and KMBASE archives as well as the websites of the Journal of Korean Medicine and 45 member journals to identify RCTs that used herbal interventions. Two independent researchers searched and categorized the RCTs and performed a quantitative evaluation by journal, study design, and target disease, as well as qualitative evaluation of the literature using CONSORT-CHM 2017. Results: After the search, 66 articles were selected. The quantitative evaluation resulted in 13 articles (19.6%) that were published in the Journal of Korean Medicine and 12 articles (18.1%) in the Journal of Internal Korean Medicine. In terms of study design, 62 articles (93.9%) were parallel, 4 articles (6%) were crossover, and 2-arm parallel study designs were the most common in 45 articles (68.2%). In terms of the study participants, physiological characteristics and mechanisms in healthy individuals were the most common in 21 studies (31.8%) and obesity in 9 studies (13.6%). In terms of assessing completeness in the CONSORT-CHM 2017 items, 29 articles were rated high, 31 were rated moderate, and 6 were rated low. Items 4a, 6a, and 7a had low reporting rates (≤ 30%), while items 2a, 2b, and 12a were completely reported in all studies. Conclusion: Future RCTs using orally administered Korean herbal medicine need to be reported completely, and the CONSORT-CHM 2017 checklist can be a helpful tool for this purpose.

Management of asymptomatic to mild COVID-19 patients with Cheongpebaedok-tang on the telemedical basis: A retrospective observational case series

  • Sung-Woo Kang;Kwan-Il Kim;Mideok Song;Jinhwan Roh;Namhun Cho;Heung Ko;Sung-Se Son;Minjeong Jeong;Jun-Yong Choi;Ojin Kwon;Seojung Ha;Hee-Jae Jung;Beom-Joon Lee
    • The Journal of Korean Medicine
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    • v.44 no.4
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    • pp.41-58
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    • 2023
  • Objectives: This retrospective observational study aimed to investigate the efficacy and safety of Cheongpebaedok-tang, a traditional Korean herbal medicine, provided via telemedicine to patients with asymptomatic to mild COVID-19 in Korea. Methods: From February to April 2020, a retrospective analysis investigated COVID-19 patients treated via Korean telemedicine. The study involved asymptomatic to mild cases receiving Cheongpebaedok-tang more than three times, along with continuous Korean medicine care in convalescence. Diagnoses and treatment adhered to the telemedicine guidelines of the Association of Korean Medicine, with varied Cheongpebaedok-tang prescriptions based on symptom severity. Symptom evaluation involved a detailed assessment using a 15-item tool at initial and final sessions. Results: The study included 27 patients, with a mean age of 48.7 ± 2.3 years (mean ± standard error). Patients began self-administering oral Cheongpebaedok-tang for an average of 19.4 ± 1.8 days after the date of COVID-19 diagnosis confirmation and continued the medication for 15.8 ± 1.2 days. The reported side effects of the Cheongpebaedok-tang included palpitations (11.1%), insomnia (7.4%), dizziness (3.7%), and diarrhea (3.7%). All side effects disappeared after adjusting the prescription according to standard treatment guidelines. The occurrence of all COVID-19-related adverse symptoms, except fatigue and myalgia, decreased. Fatigue was the most common chronic symptom persisting after 6 months (51.9%), followed by ocular symptoms (37.0%) and sore throat (22.2%). Conclusions: This study implies Cheongpebaedok-tang may offer a potentially safe, symptom-alleviating approach for managing mild COVID-19 cases via telemedicine, although further comprehensive research is warranted.

Evaluation of the combination of Bone Scan Image and Pelvic X-ray Image (뼈 검사 영상과 골반 X선 영상의 결합 유용성 평가)

  • Lee, Choong Woon;You, Yeon Wook;Kim, Yong Keun;Weon, Woo Jae
    • The Korean Journal of Nuclear Medicine Technology
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    • v.22 no.1
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    • pp.23-27
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    • 2018
  • Purpose The introduction of bone scan has been reported as a useful tool in the diagnosis, treatment, and treatment response of skeletal disease. The purpose of this study is to improve the anatomical information and tolerance of the bone by combining bone scan and pelvic X-ray without additional radiation exposure. Materials and Methods From November 2015 to August 2016, 236 patients(64 men and 172 women, average age $50.96{\pm}15.39years$) take Bone scan and Pelvis AP(Anteroposterior) X-ray scan at the National Cancer Center. The scan equipment was a gamma camera, Symbia Ecam (SIEMENS, Germany), and a digital x-ray, DRS-800 (Listem, Korea). Osirix version 3.8.1 (Osirix, USA) and Stata/SE version 14.0 (StataCorp, USA) were used for image combination and analysis. The patient was intravenously injected with $^{99m}Tc-DPD$ (740 MBq), and the scan was performed 2 to 4 hours later. Gamma camera image acquisition were Matrix size $256{\times}1024$, Zoom 1.00, and scan speed 17 cm/min. The digital X-ray was made with a collimator size of $14^{{\prime}{\prime}}{\times}17^{{\prime}{\prime}}$, 77 kVp (60 to 97 kVp) and an average of 30 mAs (20 to 48). ASIS and pubic symphysis Select virtual points then Combine three virtual points and pelvic contour lines. The acquired images were evaluated by three radiologists who worked for more than 5 years in the nuclear medicine department. Results Of the total 236 patients, 216 (91.53%) were matched. The median and range (min~max) of the age were 67 (46~81) years old in the unmatched group and 52 (22~87) years old in the matched group, The Wilcoxon rank-sum test was performed to determine whether age was different between the two groups. As a result, the age difference between the two groups was statistically significant at p < 0.0001. Of the 64 men, 60 (93.75%) were match and of the 172 women, 156 (93.75%) were match. There was no statistically significant difference according to gender(p = 0.4542). Of the 54 patients without pelvic lesions, 54 (100.00%) were match, and 162 (89.01%) of 182 patients with pelvic lesions were match. There was a statistically significant difference according to the presence of pelvic lesions. Conclusion There are many variables in the combination of bone scan and pelvic X-ray imaging, and the patient's age and pelvic lesion may have some effect on the image combination. This study is expected to be useful for the diagnosis of pelvic osteosarcoma of children without radiation exposure. It is expected that this combination of images will help to develop the nuclear medicine image.

Using the METHONTOLOGY Approach to a Graduation Screen Ontology Development: An Experiential Investigation of the METHONTOLOGY Framework

  • Park, Jin-Soo;Sung, Ki-Moon;Moon, Se-Won
    • Asia pacific journal of information systems
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    • v.20 no.2
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    • pp.125-155
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    • 2010
  • Ontologies have been adopted in various business and scientific communities as a key component of the Semantic Web. Despite the increasing importance of ontologies, ontology developers still perceive construction tasks as a challenge. A clearly defined and well-structured methodology can reduce the time required to develop an ontology and increase the probability of success of a project. However, no reliable knowledge-engineering methodology for ontology development currently exists; every methodology has been tailored toward the development of a particular ontology. In this study, we developed a Graduation Screen Ontology (GSO). The graduation screen domain was chosen for the several reasons. First, the graduation screen process is a complicated task requiring a complex reasoning process. Second, GSO may be reused for other universities because the graduation screen process is similar for most universities. Finally, GSO can be built within a given period because the size of the selected domain is reasonable. No standard ontology development methodology exists; thus, one of the existing ontology development methodologies had to be chosen. The most important considerations for selecting the ontology development methodology of GSO included whether it can be applied to a new domain; whether it covers a broader set of development tasks; and whether it gives sufficient explanation of each development task. We evaluated various ontology development methodologies based on the evaluation framework proposed by G$\acute{o}$mez-P$\acute{e}$rez et al. We concluded that METHONTOLOGY was the most applicable to the building of GSO for this study. METHONTOLOGY was derived from the experience of developing Chemical Ontology at the Polytechnic University of Madrid by Fern$\acute{a}$ndez-L$\acute{o}$pez et al. and is regarded as the most mature ontology development methodology. METHONTOLOGY describes a very detailed approach for building an ontology under a centralized development environment at the conceptual level. This methodology consists of three broad processes, with each process containing specific sub-processes: management (scheduling, control, and quality assurance); development (specification, conceptualization, formalization, implementation, and maintenance); and support process (knowledge acquisition, evaluation, documentation, configuration management, and integration). An ontology development language and ontology development tool for GSO construction also had to be selected. We adopted OWL-DL as the ontology development language. OWL was selected because of its computational quality of consistency in checking and classification, which is crucial in developing coherent and useful ontological models for very complex domains. In addition, Protege-OWL was chosen for an ontology development tool because it is supported by METHONTOLOGY and is widely used because of its platform-independent characteristics. Based on the GSO development experience of the researchers, some issues relating to the METHONTOLOGY, OWL-DL, and Prot$\acute{e}$g$\acute{e}$-OWL were identified. We focused on presenting drawbacks of METHONTOLOGY and discussing how each weakness could be addressed. First, METHONTOLOGY insists that domain experts who do not have ontology construction experience can easily build ontologies. However, it is still difficult for these domain experts to develop a sophisticated ontology, especially if they have insufficient background knowledge related to the ontology. Second, METHONTOLOGY does not include a development stage called the "feasibility study." This pre-development stage helps developers ensure not only that a planned ontology is necessary and sufficiently valuable to begin an ontology building project, but also to determine whether the project will be successful. Third, METHONTOLOGY excludes an explanation on the use and integration of existing ontologies. If an additional stage for considering reuse is introduced, developers might share benefits of reuse. Fourth, METHONTOLOGY fails to address the importance of collaboration. This methodology needs to explain the allocation of specific tasks to different developer groups, and how to combine these tasks once specific given jobs are completed. Fifth, METHONTOLOGY fails to suggest the methods and techniques applied in the conceptualization stage sufficiently. Introducing methods of concept extraction from multiple informal sources or methods of identifying relations may enhance the quality of ontologies. Sixth, METHONTOLOGY does not provide an evaluation process to confirm whether WebODE perfectly transforms a conceptual ontology into a formal ontology. It also does not guarantee whether the outcomes of the conceptualization stage are completely reflected in the implementation stage. Seventh, METHONTOLOGY needs to add criteria for user evaluation of the actual use of the constructed ontology under user environments. Eighth, although METHONTOLOGY allows continual knowledge acquisition while working on the ontology development process, consistent updates can be difficult for developers. Ninth, METHONTOLOGY demands that developers complete various documents during the conceptualization stage; thus, it can be considered a heavy methodology. Adopting an agile methodology will result in reinforcing active communication among developers and reducing the burden of documentation completion. Finally, this study concludes with contributions and practical implications. No previous research has addressed issues related to METHONTOLOGY from empirical experiences; this study is an initial attempt. In addition, several lessons learned from the development experience are discussed. This study also affords some insights for ontology methodology researchers who want to design a more advanced ontology development methodology.

Rectal Temperature Maintenance Using a Heat Exchanger of Cardioplegic System in Cardiopulmonary Bypass Model for Rats (쥐 심폐바이패스 모델에서 심정지액 주입용 열교환기를 이용한 직장체온 유지)

  • Choi Se-Hoon;Kim Hwa-Ryong;Paik In-Hyuck;Moon Hyun-Jong;Kim Won-Gon
    • Journal of Chest Surgery
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    • v.39 no.7 s.264
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    • pp.505-510
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    • 2006
  • Background: Small animal cardiopulmonary bypass (CPB) model would be a valuable tool for investigating path-ophysiological and therapeutic strategies on bypass. The main advantages of a small animal model include the reduced cost and time, and the fact that it does not require a full scale operating environment. However the rat CPB models have a number of technical limitations. Effective maintenance and control of core temperature by a heat exchanger is among them. The purpose of this study is to confirm the effect of rectal temperature maintenance using a heat exchanger of cardioplegia system in cardiopulmonary bypass model for rats. Material and Method: The miniature circuit consisted of a reservoir, heat exchanger, membrane oxygenator, roller pump, and static priming volume was 40 cc, Ten male Sprague-Dawley rats (mean weight 530 gram) were divided into two groups, and heat exchanger (HE) group was subjected to CPB with HE from a cardioplegia system, and control group was subjected to CPB with warm water circulating around the reservoir. Partial CPB was conducted at a flow rate of 40 mg/kg/min for 20 min after venous cannulation (via the internal juglar vein) and arterial cannulation (via the femoral artery). Rectal temperature were measured after anesthetic induction, a ter cannulation, 5, 10, 15, 20 min after CPB. Arterial blood gas with hematocrit was also analysed, 5 and 15 min after CPB. Result: Rectal temperature change differed between the two groups (p<0.01). The temperatures of HE group were well maintained during CPB, whereas control group was under progressive hypothermia, Rectal temperature 20 min after CPB was $36.16{\pm}0.32^{\circ}C$ in the HE group and $34.22{\pm}0.36^{\circ}C$ in the control group. Conclusion: We confirmed the effect of rectal temperature maintenance using a heat exchanger of cardioplegia system in cardiopulmonary bypass model for rats. This model would be a valuable tool for further use in hypothermic CPB experiment in rats.

Characterizing Strategy of Emotional sympathetic Robots in Animation and Movie - Focused on Appearance and Behavior tendency Analysis - (애니메이션 및 영화에 등장하는 정서교감형 로봇의 캐릭터라이징 전략 - 외형과 행동 경향성 분석을 중심으로 -)

  • Ryu, Beom-Yeol;Yang, Se-Hyeok
    • Cartoon and Animation Studies
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    • s.48
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    • pp.85-116
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    • 2017
  • The purpose of this study is to analyze conditions that robots depicted in cinematographic works like animations or movies sympathize with and form an attachment with the nuclear person and organize characterizing strategies for emotional sympathetic robots. Along with the development of technology, the areas of artificial intelligence and robots are no longer considered to belong to science fiction but as realistic issues. Therefore, this author assumes that the expressive characteristics of emotional sympathetic robots created by cinematographic works should be used as meaningful factors in expressively embodying human-friendly service robots to be distributed widely afterwards, that is, in establishing the features of characters. To lay the grounds for it, this research has begun. As the subjects of analysis, this researcher has chosen robot characters whose emotional intimacy with the main person is clearly observed among those found in movies and animations produced after the 1920 when robot's contemporary concept was declared. Also, to understand robots' appearance and behavioral tendency, this study (1) has classified robots' external impressions into five types (human-like, cartoon, tool-like, artificial bring, pet or creature) and (2) has classified behavioral tendencies considered to be the outer embodiment of personality by using DiSC, the tool to diagnose behavioral patterns. Meanwhile, it has been observed that robots equipped with high emotional intimacy are all strongly independent about their duties and indicate great emotional acceptance. Therefore, 'influence' and 'Steadiness' types show great emotional acceptance, the influencing type tends to be highly independent, and the 'Conscientiousness' type tends to indicate less emotional acceptance and independency in general. Yet, according to the analysis on external impressions, appearance factors hardly have any significant relationship with emotional sympathy. It implies that regarding the conditions of robots equipped with great emotional sympathy, emotional sympathy grounded on communication exerts more crucial effects than first impression similarly to the process of forming interpersonal relationship in reality. Lastly, to study the characters of robots, it is absolutely needed to have consilient competence embracing different areas widely. This author also has felt that only with design factors or personality factors, it is hard to estimate robot characters and also analyze a vast amount of information demanded in sympathy with humans entirely. However, this researcher will end this thesis as the foundation for it expecting that the general artistic value of animations can be used preciously afterwards in developing robots that have to be studied interdisciplinarily.

A Study on the Cause Analysis and Countermeasures of the Traditional Market for Fires in the TRIZ Method (TRIZ 기법에 의한 재래시장 화재의 원인분석과 대책에 관한 연구)

  • Seo, Yong-Goo;Min, Se-Hong
    • Fire Science and Engineering
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    • v.31 no.4
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    • pp.95-102
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    • 2017
  • The fires in the traditional markets often occur recently with the most of them expanded into great fires so that the damage is very serious. The status of traditional markets handling the distribution for ordinary people is greatly shrunk with the aggressive marketing of the local large companies and the foreign large distribution companies after the overall opening of the local distribution market. Most of the traditional markets have the history and tradition from decades to centuries and have grown steadily with the joys and sorrows of ordinary people and the development of the local economy. The fire developing to the large fire has the characteristics of the problem that the fire possibility is high since all products can be flammable due to the deterioration of facilities, the arbitrary modification of equipment, and the crowding of the goods for sale. Furthermore, most of the stores are petty with their small sizes so that the passage is narrow affecting the passage of pedestrians. Accordingly, the traditional markets are vulnerable to fire due to the initial unplanned structural problem so that the large scale fire damage occurs. The study is concerned with systematically classifying and analyzing the result by applying the TRIZ tool to the fire risk factors to extract the fundamental problem with the fire of the traditional market and make the active response. The study was done for preventing the fire on the basis of it and the expansion to the large fire in case of fire to prepare the specific measure to minimize the fire damage. On the basis of the fire expansion risk factor of the derived traditional market, the study presented the passive measures such as the improvement of the fire resisting capacity, the fire safety island, etc. and the active and institutional measures such as the obligation of the fire breaking news facilities, the application of the extra-high pressure pump system, the divided use of the electric line, etc.

GPU Based Feature Profile Simulation for Deep Contact Hole Etching in Fluorocarbon Plasma

  • Im, Yeon-Ho;Chang, Won-Seok;Choi, Kwang-Sung;Yu, Dong-Hun;Cho, Deog-Gyun;Yook, Yeong-Geun;Chun, Poo-Reum;Lee, Se-A;Kim, Jin-Tae;Kwon, Deuk-Chul;Yoon, Jung-Sik;Kim3, Dae-Woong;You, Shin-Jae
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.08a
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    • pp.80-81
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    • 2012
  • Recently, one of the critical issues in the etching processes of the nanoscale devices is to achieve ultra-high aspect ratio contact (UHARC) profile without anomalous behaviors such as sidewall bowing, and twisting profile. To achieve this goal, the fluorocarbon plasmas with major advantage of the sidewall passivation have been used commonly with numerous additives to obtain the ideal etch profiles. However, they still suffer from formidable challenges such as tight limits of sidewall bowing and controlling the randomly distorted features in nanoscale etching profile. Furthermore, the absence of the available plasma simulation tools has made it difficult to develop revolutionary technologies to overcome these process limitations, including novel plasma chemistries, and plasma sources. As an effort to address these issues, we performed a fluorocarbon surface kinetic modeling based on the experimental plasma diagnostic data for silicon dioxide etching process under inductively coupled C4F6/Ar/O2 plasmas. For this work, the SiO2 etch rates were investigated with bulk plasma diagnostics tools such as Langmuir probe, cutoff probe and Quadruple Mass Spectrometer (QMS). The surface chemistries of the etched samples were measured by X-ray Photoelectron Spectrometer. To measure plasma parameters, the self-cleaned RF Langmuir probe was used for polymer deposition environment on the probe tip and double-checked by the cutoff probe which was known to be a precise plasma diagnostic tool for the electron density measurement. In addition, neutral and ion fluxes from bulk plasma were monitored with appearance methods using QMS signal. Based on these experimental data, we proposed a phenomenological, and realistic two-layer surface reaction model of SiO2 etch process under the overlying polymer passivation layer, considering material balance of deposition and etching through steady-state fluorocarbon layer. The predicted surface reaction modeling results showed good agreement with the experimental data. With the above studies of plasma surface reaction, we have developed a 3D topography simulator using the multi-layer level set algorithm and new memory saving technique, which is suitable in 3D UHARC etch simulation. Ballistic transports of neutral and ion species inside feature profile was considered by deterministic and Monte Carlo methods, respectively. In case of ultra-high aspect ratio contact hole etching, it is already well-known that the huge computational burden is required for realistic consideration of these ballistic transports. To address this issue, the related computational codes were efficiently parallelized for GPU (Graphic Processing Unit) computing, so that the total computation time could be improved more than few hundred times compared to the serial version. Finally, the 3D topography simulator was integrated with ballistic transport module and etch reaction model. Realistic etch-profile simulations with consideration of the sidewall polymer passivation layer were demonstrated.

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Retrospective Analysis for Complications of the Central Venous Catheter in Patients with Cancer at a Single Center in Korea (우리나라 일개 병원 암 환자에서 중심정맥관 합병증에 관한 후향적 조사)

  • Kim, Eun-Jung;Kim, Hyun-Jung;Kim, Han-Jo;Kim, Kyoung-Ha;Kim, Se-Hyung;Lee, Sang-Cheol;Bae, Sang-Byung;Kim, Chan-Kyu;Lee, Nam-Su;Lee, Kyu-Taek;Park, Sung-Kyu;Won, Jong-Ho;Park, Hee-Sook;Hong, Dae-Sik
    • Journal of Hospice and Palliative Care
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    • v.13 no.1
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    • pp.24-31
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    • 2010
  • Purpose: A central venous catheterization (CVC) is frequently used for delivering anti-cancer chemotherapeutic agents, blood products, parenteral nutrition, and other intravenous therapy in patients with cancer. Major complications of CVC use are thrombosis, infection, and mechanical complications. The aim of this study was to evaluate the frequency of CVC complications and related factors. Methods: The records of cancer patients who received a CVC at our university hospital from March 2001 to October 2006 were retrospectively investigated. Chi square test was used to determine whether there was a related factor for thrombosis or infection, and Kaplan-Meier analysis for univariate analysis, or Cox-regression analysis for multivariate analysis was used for catheter life span. Results: Three hundred and ten CVCs (235 nontunneled, 75 tunneled) were inserted in 310 patients (157 males, 153 females). Among them, 104 had hematologic cancers and 206 had solid cancers. The mean age of the patients was 52 years (range, 19~82 years). CVC complications occurred in 60 cases (19%). CVC-related thrombosis occurred frequently in patients with infection (P=0.003), whereas diagnosis, catheter type, transfusion, and TPN history did not affect infection or thrombosis. The mean duration of the catheter was 102 days (range, 2~1,330 days), and the duration was prolonged in patients with tunneled catheters (P=0.000), or without transfusion through CVC (P=0.030). Conclusion: The major complications for long-term use of a CVC were infectionand thrombosis. Tunneled catheter was effective tool for long term use, especially in cases without transfusion through CVC. The studies on the prevention or treatment ofthrombosis and infection are, therefore, warranted by using CVC for an extended period of time.