Solenoid Assembly with Beam Focusing and Radiation Shielding Functions for the 9/6 MeV Dual Energy Linac

Sungsu Cha,Yujong Kim,Jinsik Ju,Youngwoo Joo,Byeong-No Lee,Soo Min Lee,Jae Hyun Kim,Pikad Buaphad,Byung Cheol Lee,Hyungki Cha,Jang Ho Ha,Hyung Dal Park,Ki Beak Song,Seung Hyun Lee,Heesoo Kim 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.69 No.6

The Korea Atomic Energy Research Institute (KAERI) has been developing a Container Inspection System (CIS) by using a dual-energy (9/6 MeV) S-band (= 2856 MHz) electron linear accelerator. The key components of the CIS are the electron linear accelerator (including an electron gun, an accelerating structure, an RF power source, cooling chillers, vacuum pumps, magnet power supplies, and two solenoid magnets with beam focusing and shielding functions), a tungsten target for X-ray generation, an X-ray collimator, a detector array, and a container moving system. Generally, in accelerators, beam focusing is mainly done by solenoids operating in the region of a few MeV to keep the shape of transverse beam symmetrically round so as to reduce the loss of electrons, which increases the beam current and the beam power. In addition, a specially-designed component is needed to protect against the radiation due to the lost electrons. In this paper, we describe the design, fabrication, and optimization of two specially- designed solenoids with focusing and radiation shielding functions for a dual-energy S-band electron linear accelerator for a CIS.

Solution-processable method for producing high-quality reduced graphene oxide displaying ‘self-catalytic healing’

Lee, Geonhee,Jung, Du Won,Lee, Wonki,Nah, Sanghee,Ji, Seulgi,Hwang, Jun Yeon,Lee, Sun Sook,Park, Sungsu,Chae, Soo Sang,Lee, Jeong-O Elsevier 2019 Carbon Vol.141 No.-

<P><B>Abstract</B></P> <P>Reduced graphene oxide (rGO) has potential as a mass-producible and cost-effective substitute for graphene, but displays poor crystal quality due to various types of structural defects. Though many attempts have been reported to improve the quality of rGO, most of them require sophisticated equipment or severe conditions such as toxic chemicals, high temperature, and electron beam or plasma treatment in ultra-high vacuum (UHV) conditions. Here, we report a mild and simple solution-based healing method for obtaining high-quality rGO, with this method involving the use of a simple camera flash light treatment and the nontoxic chemicals <SMALL>L</SMALL>-ascorbic acid and ethanol. Exposing a GO solution containing <SMALL>L</SMALL>-ascorbic acid and ethanol to the flash light irradiation for a short amount of time (<10 min) resulted in the formation of rGO displaying high quality both with respect to its chemical composition and its crystallinity. To elucidate the mechanism of the flash-light-induced healing of rGO, we acquired and analyzed the transient absorption spectrum for the healing reaction by using femtosecond pump-probe spectroscopy; this analysis revealed the photo-catalytic activity of GO by itself to repair chemical and topological defects, and we hence named this process ‘self-catalytic healing’.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Development of a Dual-pulse RF Driver for an S-band (= 2856 MHz) RF Electron Linear Accelerator

Sungsu Cha,김유종,Byeong-No Lee,Byung Cheol Lee,Hyungki Cha,Jang Ho Ha,박형달,Seung Hyun Lee,Hui Su Kim,Pikad Buaphad 한국물리학회 2016 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.68 No.8

The radiation equipment research division of Korea Atomic Energy Research Institute has developed a Container Inspection System (CIS) using a Radio Frequency (RF) electron linear accelerator for port security. The primary purpose of the CIS is to detect nuclear materials and explosives, as well country-specific prohibited substances, e.g., smuggled. The CIS consists of a 9/6 MeV dualenergy electron linear accelerator for distinguishing between organic and inorganic materials. The accelerator consists of an electron gun, an RF accelerating structure, an RF driver, a modulator, electromagnets, a cooling system, a X-ray generating target, X-ray collimator, a detector, and a container moving system. The RF driver is an important part of the configuration because it is the RF power source: it supplies the RF power to the accelerating structure. A unique aspect of the RF driver is that it generates dual RF power to generate dual energy (9/6 MeV). The advantage of this RF driver is that it can allow the pulse width to vary and can be used to obtain a wide range of energy output, and pulse repetition rates up to 300 Hz. For this reason, 140 W (5 MW − 9 MeV) and 37 W (3.4 MW − 6 MeV) power outputs are available independently. A high power test for 20 minutes demonstrate that stable dual output powers can be generated. Moreover, the dual power can be applied to the accelerator which has stable accelerator operation. In this paper, the design, fabrication and high power test of the RF driver for the RF electron linear accelerator (linac) are presented.

Notch Pathway Targets Proangiogenic Regulator Sox17 to Restrict Angiogenesis

Lee, Seung-Hun,Lee, Sungsu,Yang, Hanseul,Song, Sukhyun,Kim, Kangsan,Saunders, Thomas L.,Yoon, Jeong K.,Koh, Gou Young,Kim, Injune American Heart Association, Inc. 2014 Circulation research Vol.115 No.2

<P><B><U>Rationale</U>:</B></P><P>The Notch pathway stabilizes sprouting angiogenesis by favoring stalk cells over tip cells at the vascular front. Because tip and stalk cells have different properties in morphology and function, their transcriptional regulation remains to be distinguished. Transcription factor Sox17 is specifically expressed in endothelial cells, but its expression and role at the vascular front remain largely unknown.</P><P><B><U>Objective</U>:</B></P><P>To specify the role of Sox17 and its relationship with the Notch pathway in sprouting angiogenesis.</P><P><B><U>Methods and Results</U>:</B></P><P>Endothelial-specific <I>Sox17</I> deletion reduces sprouting angiogenesis in mouse embryonic and postnatal vascular development, whereas <I>Sox17</I> overexpression increases it. Sox17 promotes endothelial migration by destabilizing endothelial junctions and rearranging cytoskeletal structure and upregulates expression of several genes preferentially expressed in tip cells. Interestingly, Sox17 expression is suppressed in stalk cells in which Notch signaling is relatively high. Notch activation by overexpressing Notch intracellular domain reduces Sox17 expression both in primary endothelial cells and in retinal angiogenesis, whereas Notch inhibition by delta-like ligand 4 (Dll4) blockade increases it. The Notch pathway regulates Sox17 expression mainly at the post-transcriptional level. Furthermore, endothelial <I>Sox17</I> ablation rescues vascular network from excessive tip cell formation and hyperbranching under Notch inhibition in developmental and tumor angiogenesis.</P><P><B><U>Conclusions</U>:</B></P><P>Our findings demonstrate that the Notch pathway restricts sprouting angiogenesis by reducing the expression of proangiogenic regulator Sox17.</P>

Mold exposure affects the development of atopic dermatitis in infants with skin barrier dysfunction

Lee, Eun,Lee, So-Yeon,Yoon, Ji-Sun,Jung, Sungsu,Hong, Soo-Jong Elsevier 2018 Annals of allergy, asthma, & immunology Vol.121 No.3

Clinical phenotypes of bronchial hyperresponsiveness in school-aged children

Lee, Eun,Kim, Young-Ho,Cho, Hyun-Ju,Yoon, Jisun,Jung, Sungsu,Yang, Song-I,Kim, Hyung Young,Kwon, Ji-Won,Seo, Ju-Hee,Kim, Hyo-Bin,Lee, So Yeon,Hong, Soo-Jong Elsevier 2018 Annals of allergy, asthma, & immunology Vol.121 No.4

<P><B>Abstract</B></P> <P><B>Background</B></P> <P>Bronchial hyperresponsiveness (BHR), one of the key features of asthma, has a diverse natural course in school-aged children, but studies on BHR phenotypes are lacking.</P> <P><B>Objective</B></P> <P>To classify BHR phenotypes according to onset age and persistence in children and investigate the characteristics and factors associated with each phenotype in a longitudinal study.</P> <P><B>Methods</B></P> <P>This study analyzed 1,305 elementary school children from the Children's Health and Environmental Research (CHEER) study, a 4-year, prospective, follow-up study with 2-year intervals starting at a mean age of 7 years. Total serum IgE levels and blood eosinophil counts were measured, and allergy workup, including methacholine challenge tests with the International Study of Asthma and Allergies in Childhood questionnaire, was performed at each survey.</P> <P><B>Results</B></P> <P>The 4 BHR phenotypes were classified as non-BHR (n = 942 [72.2%]), early-onset transient BHR (n = 201 [15.4%]), late-onset BHR (n = 87 [6.7%]), and early-onset persistent BHR (n = 75 [5.7%]). Early-onset persistent BHR is characterized by an increased eosinophil count, total serum IgE level, sensitization rate, decreased lung function, and increased risk of newly diagnosed asthma during follow-up (adjusted odds ratio, 3.89; 95% confidence interval, 1.70-8.88). The 2 early-onset phenotypes were associated with peripheral airway dysfunction. The late-onset BHR phenotype was related to increased risks of allergic rhinitis symptoms at baseline and later sensitization against inhalant allergens.</P> <P><B>Conclusion</B></P> <P>The early-onset persistent BHR phenotype in school-aged children is associated with high atopic burden and increased risk of newly diagnosed asthma, whereas the late-onset BHR phenotype related with later sensitization and allergic rhinitis symptoms. Diverse BHR phenotypes in children have specific characteristics that require targeted follow-ups.</P>

Expression of Angiogenic Molecules in Cochlear Vasculature

Lee, Sungsu,Cho, Hyong-Ho SAGE Publications 2014 Otolaryngology-head and neck surgery Vol.151 No.1

<P><B>Objectives:</B></P><P>(1) Three-dimensionally (3D) visualize the cochlear vessels and blood-labyrinth barrier. (2) Analyze the expression of angiogenic molecules in cochlear vessels.</P><P><B>Methods:</B></P><P>Postnatal day 5 and 8-week old mice were used. After obtaining the cochlea, bony shell was removed. Whole mount immunostaining was done with endothelial cell marker PECAM-1 and VE-cadherin. NG2 and demins were used for pericyte marker. aSMA was used as vascular smooth muscle cell and S100 was used as fibrocyte marker. 3D reconstruction was done to visualize the blood-labyrinth barrier components. VEGFR2, VEGFR3, Sox17, angiopoietin-2, Dll4 were used for angiogenic markers. Claudin-5 was used to visualize the tight junction.</P><P><B>Results:</B></P><P>We could visualize the cochlear vasculature in overall, from precapillar arteriole, stria vascularis, and postcapillary venule. The relationship between components of blood-labyrinth barrier also could be visualized from basal turn to apical turn of the cochlea. Cochlear vessels well expressed VEGFR3, VEGFR2, Sox17 in the endothelial cell showing that cochlea is in active state, not static. Claudin-5 was robustly expressed suggesting its important role in blood-labyrinth barrier. aSMA was well expressed demonstrating its need for vessel contraction.</P><P><B>Conclusions:</B></P><P>A vessel is not merely a conduit for blood flow. It is newly made and is also regressed. It permits or limits many molecules on crossing over to the tissue. The cochlear vessel is an active vessel. We suggest that visualizing the cochlear vessel and checking the expression of angiogenic molecules could help understand the pathophysiology in hearing loss models.</P>

Numerical study of wake structure behind a square cylinder at high Reynolds number

Lee, Sungsu Techno-Press 1998 Wind and Structures, An International Journal (WAS Vol.1 No.2

In this paper, the wake structures behind a square cylinder at the Reynolds number of 22,000 are simulated using the large eddy simulation, and the main features of the wake structure associated with unsteady vortex-shedding are investigated. The Smagorinsky model is used for parametrization of the subgrid scales. The finite element method with isoparametric linear elements is employed in the computations. Unsteady computations are performed using the explicit method with streamline upwind scheme for the advection term. The time integration incorporates a subcycling strategy. No-slip condition is enforced on the wall surface. A comparative study between two-and three-dimensional computations puts a stress on the three-dimensional effects in turbulent flow simulations. Simulated three-dimensional wake structures are compared with numerical and experimental results reported by other researchers. The results include time-averaged, phase-averaged flow fields and numerically visualized vortex-shedding pattern using streaklines. The results show that dynamics of the vortex-shedding phenomenon are numerically well reproduced using the present method of finite element implementation of large eddy simulation.

Near-infrared fluorescent sorbitol probe for tumor diagnosis <i>in vivo</i>

Lee, Sungsu,Lim, Wonbong,Jo, Danbi,Jung, Jin Seok,Kim, Subin,Jo, Gayoung,Min, Jung-Joon,Choi, Eun Young,Hyun, Hoon THE KOREAN SOCIETY OF INDUSTRIAL AND ENGINEERING 2018 JOURNAL OF INDUSTRIAL AND ENGINEERING CHEMISTRY -S Vol.64 No.-

<P><B>Abstract</B></P> <P>This study evaluated the near-infrared (NIR) fluorescent probe Sorbitol-ZW800-1 as tracer for targeted tumor imaging of multiple cancer types. Preliminarily, Sorbitol-ZW800-1 conjugate was validated <I>in vivo</I> on breast (MCF-7) cancer cell lines. Subsequently, the tracer was tested in xenograft mouse models with malignant breast (MDA-MB-231), lung (NCI-H460), and colorectal (HT-29) tumors, respectively. Importantly, the Sorbitol-ZW800-1 conjugate showed highly selective tumor uptake in various tumor mice models. Moreover, biodistribution for 24h exhibited the significant fluorescence signals in tumors and kidneys. Therefore, sorbitol is a promising candidate as a potential cancer targeting agent for the accurate detection of cancer cells.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nitrate Reduction without Ammonium Release using Fe-loaded Zeolite

Lee Seunghak,Lee Kwanghun,Lee Sungsu,Park Junboum Korean Society of Soil and Groundwater Environment 2005 지하수토양환경 Vol.10 No.1

영가 철을 이용한 질산성 질소 환원에 대한 연구는 지금까지 활발히 진행되어 왔지만, 이 반응에서 생성된 암모늄 부산물에 대한 적절한 처리과정은 아직 보고되지 않았다. 하지만, 암모늄은 먹는 물 수질기준에 의해 지하수 오염물로 분류되고 있어 (허용치 0.5 mg-N/L), 질산성 질소로 오염된 지하수 정화에 영가 철을 단독으로 사용하는 것에는 한계가 있다. 따라서, 본 연구의 목적은 질산성 질소를 환원함과 동시에 이 과정에서 발생하는 암모늄을 제거할 수 있는 반응물질을 개발하는데 있다. 본 연구에 사용한 Fe-loaded zeolite는, 제올라이트와 Fe(II) 용액을 교반시켜 제올라이트 구조 안으로 Fe(II)를 흡착유도하고, 이를 sodium borohydride로 환원하는 과정을 통해 제작되었다. Fe-loaded zeolite 제작에 사용된 Fe(II) 용액의 농도를 실험을 통해 산정하고, 이를 통해 Fe-loaded zeolite를 제작한 후, Fe-loaded zeolite의 질산성 질소 제거 성능을 확인하기 위해 두 가지 pH조건에서 회분식 실험을 수행하였다. 80시간의 반응을 통해 Fe-loaded zeolite는 초기 pH가 3.3인 경우 약 $60\%$의 질산성 질소를, pH가 6인 경우는 약 $40\%$의 질산성 질소를 제거하였고, 암모늄 부산물은 전혀 검출되지 않았다. 영가 철의 경우, 각 초기 pH조건에서 Fe-loaded zeolite보다 뛰어난 질산성 질소 제거성능을 보였지만, 반응 후 상당량의 암모늄 부산물을 생성하였다. 질산성 질소와 암모늄을 포함한 질소(-N)제거 효능의 관점에서 Fe-loaded zeolite의 경우 pH 3.3과 6의 경우에서 각각 $60\%$와 $40\%$의 제거효율을 보인 반면, 영가 철의 제거효율은 무시할만한 수준으로 나타났다. Nitrate reduction with zero valent iron $(Fe^0)$ has been extensively studied, but the proper treatment for ammonium byproduct has not been reported yet. In groundwater, however, ammonium is regarded as contaminant species, and particularly, its acceptable level is regulated to 0.5 mg-N/L. for drinking water. This study is focused on developing new material to reduce nitrate and properly remove ammonium by-products. A new material, Fe-loaded zeolite, is derived from zeolite modified by Fe(II) chloride followed by reduction with sodium borohydride. Batch experiments were performed without buffer at two different pH to evaluate the removal efficiency of Fe-loaded zeolite. After 80 hr reaction time, Fe loaded zeolite showed about $60\%$ nitrate removal at initial pH of 3.3 and $40\%$ at pH of 6 with no ammonium release. Although iron filing showed higher removal efficiency than Fe-loaded zeolite at each pH, it released a considerable amount of ammonium stoichiometrically equivalent to that of reduced nitrate. In terms of nitrogen species including $NO_3-N$ and $NH_4^+-N$, Fe-loaded zeolite removed about $60\%\;and\;40\%$ of nitrogen in residual solution at initial pH of 3.3 and 6, respectively, while the removal efficiency of iron filing was negligible.