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X-band Linac for a 6MeV dual-head radiation therapy gantry
Lee, Seung Hyun,Shin, Seung-Wook,Lee, Jongchul,Kim, Hui-Su,Lee, Byeong-No,Lee, Byung-Chul,Park, Hyung-dal,Song, Ki-back,Song, Ho-seung,Mun, Sangchul,Ha, Donghyup,Chai, Jong-Seo Elsevier 2017 Nuclear Instruments & Methods in Physics Research. Vol.852 No.-
<P><B>Abstract</B></P> <P>We developed a design for a 6MeV X-band linear accelerator for radiation therapy in a dual-head gantry layout. The dual-head gantry has two linacs that can be operated independently. Each X-band linac accelerates electron bunches using high-power RF and generates X-rays for radiation therapy. It requires a versatile RF system and pulse sequence to accomplish various radiation therapy procedures.</P> <P>The RF system consists of 9.3GHz, 2MW X-band magnetron and associated RF transmission components. A test linac was assembled and operated to characterize its RF performance without beam. This paper presents these results along with a description of the gantry linacs and their operational requirements.</P>
Graphene transfer in vacuum yielding a high quality graphene
Lee, Sangchul,Lee, Sang Kyung,Kang, Chang Goo,Cho, Chunhum,Lee, Young Gon,Jung, Ukjin,Lee, Byoung Hun Elsevier 2015 Carbon Vol.93 No.-
<P><B>Abstract</B></P> <P>The importance of proper graphene transfer process cannot be emphasized more because it is so closely related to the performance and stability of graphene devices. In this work, a new transfer method utilizing a voluntary bonding of a graphene film to a target substrate in vacuum is demonstrated. The problems originated from water and air molecules which prevent a robust bonding and degrade the electrical characteristics could be drastically alleviated. As a result, graphene field-effect transistors showed nearly symmetric <I>I</I> <SUB>d</SUB>–<I>V</I> <SUB>g</SUB> characteristics with a minimal hysteresis and drastically improved device stability in air for more than a month could be obtained.</P>
Hakmin Lee,Dong Hwan Lee,Younsoo Chung,Ngoc Ha Nguyen,Jong Jin Oh,Sangchul Lee,Sang Eun Lee,Sung Kyu Hong,Seok-Soo Byun 대한비뇨기종양학회 2017 대한비뇨기종양학회지 Vol.15 No.3
Purpose: We tried to investigate the clinical impact of Ki-67 (MIB-1) expression on the oncological and survival outcomes in patients with bladder cancer (BCa) after the radical cystectomy. Materials and Methods: We retrospectively analyzed the data of 230 patients who were treated by radical cystectomy for BCa. Multivariate Cox-proportional hazards models and logistic regression tests were performed to evaluate the prognostic value of each variable. Results: The patients with positive Ki-67 expression showed significant worse clinical characteristics and pathologic outcomes than negative Ki-67 group. Furthermore, the patients with Ki-67 expression showed significant worse recurrence (p=0.018) and cancer-specific mortality free survival (p=0.019) than negative Ki-67 group. The overall survival was also revealed to be inferior in Ki-67 positive group than Ki-67 negative group but the statistical significance was marginal (p=0.062). Subsequent multivariate Cox analyses showed that Ki-67 was independent predictor for disease recurrence after surgery (hazard ratio, 3.142; 95% CI, 1.287–7.671; p=0.012). Conclusions: In our study, high Ki-67 expression was significantly related with worse clinical outcomes after radical cystectomy in the patients with BCa. Further prospective and basic researches are needed to validate the true prognostic value of Ki-67.
Effects of infections with five sexually transmitted pathogens on sperm quality
Kim, Sung Jae,Paik, Doo-Jin,Lee, Joong Shik,Lee, Hyo Serk,Seo, Ju Tae,Jeong, Mi Seon,Lee, Jae-Ho,Park, Dong Wook,Han, Sangchul,Lee, Yoo Kyung,Lee, Ki Heon,Lee, In Ho,So, Kyeong A,Kim, Seon Ah,Kim, Jur The Korean Society for Reproductive Medicine 2017 Clinical and Experimental Reproductive Medicine Vol.44 No.4
Objective: This study investigated the prevalence of infections with human papillomavirus, Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma hominis, and Mycoplasma genitalium in the semen of Korean infertile couples and their associations with sperm quality. Methods: Semen specimens were collected from 400 men who underwent a fertility evaluation. Infection with above five pathogens was assessed in each specimen. Sperm quality was compared in the pathogen-infected group and the non-infected group. Results: The infection rates of human papillomavirus, C. trachomatis, U. urealyticum, M. hominis, and M. genitalium in the study subjects were 1.57%, 0.79%, 16.80%, 4.46%, and 1.31%, respectively. The rate of morphological normality in the U. urealyticum-infected group was significantly lower than in those not infected with U. urealyticum. In a subgroup analysis of normozoospermic samples, the semen volume and the total sperm count in the pathogen-infected group were significantly lower than in the non-infected group. Conclusion: Our results suggest that infection with U. urealyticum alone and any of the five sexually transmitted infections are likely to affect sperm morphology and semen volume, respectively.
Evaluation of sampling methods for sulfur speciation in volcanic gases
Lee, Sangchul,Ohba, Takeshi,Yun, Sung Hyo,Yang, Kyounghee,Jeong, Hoon Young Elsevier 2016 Chemical geology Vol.438 No.-
<P><B>Abstract</B></P> <P>Determination of H<SUB>2</SUB>S and SO<SUB>2</SUB> in fumarolic gases is necessary to predict volcanic activities. This study evaluated three gas sampling methods (CdS precipitation, Ag<SUB>2</SUB>S precipitation, and I<SUB>2</SUB> oxidation) using artificial fumarolic gases with known compositions. H<SUB>2</SUB>S was initially fixed as CdS(s) or Ag<SUB>2</SUB>S(s) in the sulfide precipitations and S(0) in the I<SUB>2</SUB> oxidation. On the other hand, SO<SUB>2</SUB> was collected as dissolved species (SO<SUB>3</SUB> <SUP>2−</SUP> and SO<SUB>4</SUB> <SUP>2−</SUP>). The Ag<SUB>2</SUB>S precipitation, which did not allow HCl determination in fumarolic gases by forming AgCl(s), significantly underestimated H<SUB>2</SUB>S and SO<SUB>2</SUB> due to the entrained loss of analytes as a result of water vaporization during H<SUB>2</SUB>O<SUB>2</SUB> treatment. The I<SUB>2</SUB> oxidation, which required duplicate sampling for complete analysis of H<SUB>2</SUB>S and SO<SUB>2</SUB>, tended to overestimate SO<SUB>2</SUB> probably due to difficulties in separating S(0) particles from solutions. The CdS precipitation produced more satisfactory H<SUB>2</SUB>S and SO<SUB>2</SUB> recoveries than the other methods. Additionally, the effect of delayed sample treatment was assessed by comparing H<SUB>2</SUB>S-to-SO<SUB>2</SUB> molar ratios resulting from immediate and one-week-delayed treatments after gas collection. The delayed treatment significantly lowered the ratios in the CdS precipitation likely due to the susceptibility of CdS(s) to oxidation. In the meanwhile, such an effect was minimal in I<SUB>2</SUB> oxidation. Similar results were also observed in the field evaluation of fumarolic gases at Mt. Hakone. Along with detailed sampling and treatment procedures, the causes for unsatisfactory H<SUB>2</SUB>S and SO<SUB>2</SUB> recoveries were discussed in the context of the underlying reaction schemes as well as potential experimental artifacts. Thus, this study helps to select and further modify appropriate gas sampling methods to meet specific needs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Sampling methods were evaluated for determination of fumarolic sulfur species. </LI> <LI> Fixation of H<SUB>2</SUB>S as Ag<SUB>2</SUB>S(s), unsuitable for HCl detection, underrates H<SUB>2</SUB>S and SO<SUB>2</SUB>. </LI> <LI> Fixation of H<SUB>2</SUB>S as S(0) overestimates SO<SUB>2</SUB>, but this phase is stable against O<SUB>2</SUB>. </LI> <LI> Fixation of H<SUB>2</SUB>S as CdS(s) gives agreeable results, but CdS(s) is readily oxidized. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A Systematic Approach for Dynamic Analysis of Vehicles with Dual Clutch Transmission
Sangchul Lee 한국자동차공학회 2014 한국자동차공학회 부문종합 학술대회 Vol.2014 No.5
In this study a dynamic model of a vehicle with 7-speed Dual Clutch Transmission (DCT) has been developed for the analysis of shift quality and dynamic behavior of the vehicle during shift events. Sub-system models for engine, torque converter, automatic transmission, drivetrain, transmission control unit and vehicle are developed and integrated with signal information interface. The sub-systems included in the model were carefully selected to improve the accuracy of the model by comparing the simulation results with the test data. The systematic modeling approach based on matrix operation proposed in the study enables calibrating and fine-tuning the transmission control unit for shift quality in a virtual vehicle environment. The presented model was validated with the vehicle test data and the comparison shows very good agreement. This paper presents generalized modeling methodology for DCT including launch shift. The model developed in the study provides a valuable analytical tool for the calibration and tuning of the transmission control unit by allowing quantitative analysis on the dynamic behavior and the performance metrics of an automatic transmission.
A review on volcanic gas compositions related to volcanic activities and non-volcanological effects
Sangchul Lee,Namhee Kang,Minji Park,황진연,윤성효,정훈영 한국지질과학협의회 2018 Geosciences Journal Vol.22 No.1
Volcanic gases have been monitored to predict eruptions since their compositions are strongly affected by volcanic activities. Here, volcanic gas geochemistry is reviewed with the main focus placed on the potential use of volcanic gases as eruption precursors. First, volcanic activities are differentiated into four eruptive cycles: eruptive, post-eruptive, inter-eruptive, and pre-eruptive periods. Second, we discuss geochemical factors affecting volcanic gas compositions: magma origin and degassing, hydrothermal interactions, and meteorological variability. Third, volcanic gas data in previous studies are revisited to address the practical aspects in utilizing volcanic gas compositions to predict eruptions. As a magma is depressurized due to its uprising, volcanic gases become progressively exsolved. Generally, the fluxes of volcanic gases (e.g., CO2, SO2, H2S, etc.) increase considerably close to eruptions. Also, CO2/SO2, SO2/HCl, and SO2/HF ratios in volcanic gases tend to decrease at the imminence of eruptions. Nonetheless, such trends may not be encountered due to both kinetically limited degassing and secondary effects including hydrothermal interactions and meteorological variability. Due to the site specificity of the aforementioned effects, a comprehensive understanding of volcanic gas chemistry requires the knowledge of magma vents and reservoirs as well as hydrothermal systems below volcanoes. Accordingly, the integrated use of volcanic gas data with geophysical and geomorphological information can warrant a better prediction of eruptions.