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Low-temperature wafer-scale growth of MoS<sub>2</sub>-graphene heterostructures
Kim, Hyeong-U,Kim, Mansu,Jin, Yinhua,Hyeon, Yuhwan,Kim, Ki Seok,An, Byeong-Seon,Yang, Cheol-Woong,Kanade, Vinit,Moon, Ji-Yun,Yeom, Geun Yong,Whang, Dongmok,Lee, Jae-Hyun,Kim, Taesung Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.470 No.-
<P><B>Abstract</B></P> <P>In this study, we successfully demonstrate the fabrication of a MoS<SUB>2</SUB>-graphene heterostructure (MGH) on a 4 inch wafer at 300 °C by depositing a thin Mo film seed layer on graphene followed by sulfurization using H<SUB>2</SUB>S plasma. By utilizing Raman spectroscopy and high-resolution transmission electron microscopy, we have confirmed that 5–6 MoS<SUB>2</SUB> layers with a large density of sulfur vacancies are grown uniformly on the entire substrate. The chemical composition of MoS<SUB>2</SUB> on graphene was evaluated by X-ray photoelectron spectroscopy, which confirmed the atomic ratio of Mo to S to be 1:1.78, which is much lower than the stoichiometric value of 2 from standard MoS<SUB>2</SUB>. To exploit the properties of the nanocrystalline and defective MGH film obtained in our process, we have utilized it as a catalyst for hydrodesulfurization and as an electrocatalyst for the hydrogen evolution reaction. Compared to MoS<SUB>2</SUB> grown on an amorphous SiO<SUB>2</SUB> substrate, the MGH has smaller onset potential and Tafel slope, indicating its enhanced catalytic performance. Our practical growth approach can be applied to other two-dimensional crystals, which are potentially used in a wide range of applications such as electronic devices and catalysis.</P> <P><B>Highlight</B></P> <P> <UL> <LI> Practical growth for 2D MoS<SUB>2</SUB>-graphene heterostructure (MGH) was introduced. </LI> <LI> Low-temperature sulfurization of Mo thin film was realized by H<SUB>2</SUB>S plasma. </LI> <LI> As-grown MoS<SUB>2</SUB> film on graphene naturally contains large number of active sites. </LI> <LI> The MGH was shown enhanced electrocatalytic performance. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
PSTN과 PSDN을 연결한 데이터 통신망의 회선할당에 관한 연구
김병무,이영호,김영휘,김유환,박석지,김주성 한국경영과학회 1998 한국경영과학회 학술대회논문집 Vol.- No.1
In this paper, we seek to find an optimal allocation of link capacity in a data communication network. The architecture of the data communication network considered in the study is an online-service network based on public switched telephone network(PSTN) and packet switched data network(PSDN). In designing the architecture of the network, we need to deal with various measures of quality of service(QoS). Two important service measures are the call blocking probability in PSTN and the data transfer delay time in PSDN. Considering the tradeoff between the call blocking probability and the data transfer delay time in the network, we have developed the optimal link capacity allocation model that minimizes the total link cost, while guarantees the call blocking probability and the data transfer delay time within an acceptable level of QoS. This problem can be formulated as a non-linear integer programming model. We have solved the problem with tabu search and simulated annealing methods. In addition, we have analyzed the sensitivity of the model and provided the insight of the model along with computational results.
A case report of incidentally detected ovarian malignancy during pregnancy
( Yuhwan Kim ),( Tae-kyu Jang ),( Hyewon Chung ),( So-jin Shin ),( Sang-hoon Kwon ),( Soon-do Cha ),( Chi-heum Cho ) 대한산부인과학회 2016 대한산부인과학회 학술대회 Vol.102 No.-
Ovarian malignancies are the most common of all gynecologic cancers in older women. And these disease is the leading cause of death in all women from genital tract cancers. The types of malignancy are also markedly different in pregnant women compared with those in older women. In pregnant women, these are, in decreasing order of frequency, germ cell & sex cord-stromal tumors, low malignant potential tumors, and last, epithelial tumors. The treatment of these women is depend on how advanced the cancer is, as well as how far along they are in pregnancy. It is controversial, giving the treatment to these women, depends on their gestational age and cancer staging. Its goal is to save the life of the mother and to bring the baby as close to term as possible, so chemotherapy and radiotherapy are to be denied in 1st trimester. Surgery can be waited until after they give birth, but if the intense pain or a risk of serious complications are present, it will be necessary. Depending on the uterine size, some of these components, especially lymphadenectomy, may not be technically feasible. In this paper, we report a case of incidentally detected ovarian malignancy during pregnancy, was detected on 1st trimester, and she is waiting for fetal pulmonary maturation.
Hyeon, Yuhwan,Jung, Su-Ho,Jang, Wonseok,Kim, Mansu,Kim, Byung-Sung,Lee, Jae-Hyun,Nandanapalli, Koteeswara Reddy,Jung, Namgee,Whang, Dongmok American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.5
<P>In MoS<SUB>2</SUB>-carbon composite catalysts for hydrogen evolution reaction (HER), the carbon materials generally act as supports to enhance the catalytic activity of MoS<SUB>2</SUB> nanosheets. The carbon support provides a large surface area for increasing the MoS<SUB>2</SUB> edge site density, and its physical structure can affect the electron transport rate in the composite catalysts. However, despite the importance of the carbon materials, direct observation of the effects of the physical properties of the carbon supports on the HER activity of MoS<SUB>2</SUB>-carbon composite catalysts has been hardly reported. In this work, we conduct an experimental model study to find the fundamental and important understanding of the correlation between the structural characteristics of carbon supports and the HER performance of MoS<SUB>2</SUB>-carbon composite catalysts using surface-modified graphitic carbon shell (GCS)-encapsulated SiO<SUB>2</SUB> nanowires (GCS@SiO<SUB>2</SUB> NWs) as support materials for MoS<SUB>2</SUB> nanosheets. The surface defect density and the electrical resistance of GCS@SiO<SUB>2</SUB> NWs are systematically modulated by control of H<SUB>2</SUB> gas flow rates during the carbon shell growth on the SiO<SUB>2</SUB> NWs. From in-depth characterization of the model catalysts, it is confirmed that the intrinsic catalytic activity of MoS<SUB>2</SUB>-carbon composites for the HER is improved linearly with the conductance of the carbon supports regardless of the MoS<SUB>2</SUB> edge site density. However, in the HER polarization curve, the apparent current density increases in proportion to the product of the number of MoS<SUB>2</SUB> edge sites and the conductance of GCS@SiO<SUB>2</SUB> NWs.</P> [FIG OMISSION]</BR>