THE TAOS PROJECT: RESULTS FROM SEVEN YEARS OF SURVEY DATA

Zhang, Z.-W.,Lehner, M. J.,Wang, J.-H.,Wen, C.-Y.,Wang, S.-Y.,King, S.-K.,Granados, Á,. P.,Alcock, C.,Axelrod, T.,Bianco, F. B.,Byun, Y.-I.,Chen, W. P.,Coehlo, N. K.,Cook, K. H.,de Pater, I.,Kim American Institute of Physics 2013 The Astronomical journal Vol.146 No.1

<P>The Taiwanese-American Occultation Survey (TAOS) aims to detect serendipitous occultations of stars by small (~1 km diameter) objects in the Kuiper Belt and beyond. Such events are very rare (<10<SUP>–3</SUP> events per star per year) and short in duration (~200 ms), so many stars must be monitored at a high readout cadence. TAOS monitors typically ~500 stars simultaneously at a 5 Hz readout cadence with four telescopes located at Lulin Observatory in central Taiwan. In this paper, we report the results of the search for small Kuiper Belt objects (KBOs) in seven years of data. No occultation events were found, resulting in a 95% c.l. upper limit on the slope of the faint end of the KBO size distribution of q = 3.34-3.82, depending on the surface density at the break in the size distribution at a diameter of about 90 km.</P>

Zn-INDUCED DENSITY-CONTROLLED GROWTH OF β-SiC NANOTUBES WITH TUNABLE FIELD EMISSION AND HYDROPHOBIC PROPERTIES

G. Z. YANG,H. CUI,C. X. WANG 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.5

Density-controlled single-crystalline β-SiC nanotubes were successfully synthesized on a large scale by adding Zn into the system via direct thermal evaporation of C60 onto silicon wafers at 1290°C. Interestingly, no Zn elements can be detected in the final products. However, the addition of Zn power is important because without Zn, density-controlled SiC nanotubes cannot be observed in our experiment. On the basis of the results, a possible growth mechanism was proposed to illustrate the role that Zn played in the growth process. The field emission and hydrophobic performances show strong dependence on the densities of as-synthesized β-SiC nanotubes. The density-controlled β-SiC nanotubes with tunable field emission and hydrophobic properties may have potential in the future of nanotechnology.

Fabrication of p-Type Nitrogen-Doped MgZnO by Depressing N-Related Donors

B. Yao,Z. P. Wei,Y. F. Li,D. Z. Shen,Y. M. Lu,Z. Z. Zhang,B. H. Li,C. J. Zheng,X. H. Wang,J. Y. Zhang,D. X. Zhao,X. W. Fan,Z. K. Tang 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.5

Wurtzite nitrogen-doped MgZnO (MgZnO:N) films were grown on c-plane sapphire by using plasma-assisted molecular beam epitaxy with radical NO as the oxygen source and nitrogen dopant. P-type conduction of MgZnO:N was obtained by decreasing the donor defects ((N2)O, VO, etc.) through annealing, revealing a hole concentration of 6.1 × 1017 cm−3 and a mobility of 6.42 cm2/Vs. Furthermore, as-grown p-type films with a hole concentration of 1 × 1017 cm−3 and a mobility of 3 cm2/Vs were obtained by decreasing the (N2)O double donor defect through control of the plasma conditions. ZnMgO:N/ZnO p-n junctions were obtained by using these p-type films. ode-like, rectifying I-V characteristics with a threshold voltage of about 5 V and a different reverse leakage current were observed at room temperature.

Electronic properties of graphene on the C-decorated Si(111) surface:An ab initio study

J. Liu,C.Y. He,W. Wang,N. Jiao,C.X. Zhang,L.Z. Sun 한국물리학회 2013 Current Applied Physics Vol.13 No.7

First principles calculations based on the density functional theory are performed to study electronic structures of graphene adsorbed on clean or C-decorated Si(111) surface. Two types of surface reconstructions,2 x 2 and ffiffiffi 3p x 3p , are considered to be decorated by carbon atoms with different concentrations. We find that graphene adsorbed on ideal clean Si(111) surface tends to induce a 2 x 1reconstruction, and its electronic dispersion characteristics are preserved. Moreover, the decoration of carbon atoms on the Si(111) surface can effectively passivate the Si dangling bonds on the surface. Such decoration effects make the carbon deco

R&D Status of High-current Accelerators at IFP

J. J. Deng,J. S. Shi,W. P. Xie,L. W. Zhang,K. Z. Zhang,S. P. Feng,J. Li,M. Wang,Y. He,L. S. Xia,Z. Y. Dai,H. T. Li,L. Wen,S. F. Chen,X. Li,Q. G. Lai,M. H. Xia,Y. C. Guan,S. Y. Song,L. Chen 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.61

High-current accelerators have many important applications in Z-pinches, high-power microwaves, and free electron lasers, imploding liners and radiography and so on. Research activities on Zpinches, imploding liners, radiography at the Institute of Fluid Physics (IFP) are introduced. Several main high-current accelerators developed and being developed at IFP are described, such as the Linear Induction Accelerator X-Ray Facility Upgrade (LIAXFU, 12 MeV, 2.5 kA, 90 ns), the Dragon-I linear induction accelerator (20 MeV, 2.5 kA, 60 ns), and the Primary Test Stand for Z-pinch (PTS, 10 MA, 120 ns). The design of Dragon-II linear induction accelerator (20 MeV, 2.5 kA, 3 × 60 ns) to be built will be presented briefly.

The high thermal stability induced by a synergistic effect of ZrC nanoparticles and Re solution in W matrix in hot rolled tungsten alloy

Zhang T.,Du W.Y.,Zhan C.Y.,Wang M.M.,Deng H.W.,Xie Z.M.,Li H. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8

The synergistic effect of ZrC nanoparticle pining and Re solution in W matrix on the thermal stability of tungsten was studied by investigating the evolution of the microstructure, hardness and tensile properties after annealing in a temperature range of 1000e1700 C. The results of metallography, electron backscatter diffraction pattern and Vickers micro-hardness indicate that the rolled W-1wt%Re-0.5 wt% ZrC alloy has a higher recrystallization temperature (1600 Ce1700 C) than that of the rolled pure W (1200 C), W-0.5 wt%ZrC (1300 C), W-0.5 wt%HfC (1400e1500 C) and WeK-3wt%Re alloy fabricated by the same technology. The molecular dynamics simulation results indicated that solution Re atoms in W matrix can slow down the self-diffusion of W atoms and form dragging effect to delay the growth of W grain, moreover, the diffusion coefficient decrease with increasing Re content. In addition, the ZrC nanoparticles can pin the grain boundaries and dislocations effectively, preventing the recrystallization. Therefore, synergistic effect of solid solution Re element and dispersed ZrC nanoparticles significantly increase recrystallization temperature

Fabricating Ultrathin Plate-Like WC Grains in WC–8Co Hardmetals by Increasing Discharge Intensity During Plasma-Assisted Ball Milling

M. Q. Zeng,J. L. Tu,M. Zhu,W. Wang,J. W. Liu,Z. C. Lu 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9

The effects of plasma discharge intensity on the microstructure evolution of ball-milled tungsten (W)–carbon (C)–cobalt (Co)mixtures and the formation mechanism of ultrathin plate-like tungsten carbide (WC) grains prepared by ball milling with andwithout plasma discharge were investigated. It was found that increasing the plasma discharge intensity during ball millingobviously promoted the formation of a thin flake-like W phase because of the electroplasticity effect and simultaneouslylowered the carburization temperature between W and C. A combination of high hardness and transverse rupture strength of92.9 HRA and 3659 MPa, respectively, was obtained for the WC–8Co alloy fabricated by plasma milling at a gas pressure of5 × 103 Pa with a dielectric barrier discharge layer thickness of 3 mm. These properties were mainly attributed to the markedlylowered activation energy of the WC phase and generation of highly oriented ultrathin plate-like WC grains by plasma milling. The combination of the flake-like structure of the plasma-milled W aggregate and high specific interfacial area and shortdiffusion distance of W/C were readily inherited by the ultrathin plate-like WC grains in the sintered WC–Co hardmetals.

THE NEW TYPE BROAD BEAM ION SOURCES AND APPLICATIONS

You, D.W.,Feng, Y.C.,Wang, Y.,Kuang, Y.Z. The Korean Vacuum Society 1995 Applied Science and Convergence Technology Vol.4 No.s2

The broad beam ion sources of hot filament plasma type have widely used for modifications of materials and thin films, and the new type intensive current broad beam metal ion source including reactive gaseous ion beams is needed for preparing the hard coating films such as DLC, $\beta-C_3N_4$ Carbides, Nitrides, Borides etc. Now a electorn beam evaporation(EBE) broad beam metal ion source has been developed for this purpose in our lab. CN film has been formed by the EBE ion source. Study of the CN film shows that it has high hardness(HK=5800kgf/$\textrm {mm}^2$)and good adhesion. This method can widely changes the ratio of C/N atom's concentrations from 0.14 to 0.6 and has high coating rate. The low energy pocket ion source which was specially designed for surface texturing of medical silicon rubber was also developed. It has high efficiency and large uniform working zone. Both nature texturing and mesh masked texturing of silicon rubbers were performed. The biocompatibility was tested by culture of monocytes, and the results showed improved biocompatibility for the treated silicon rubbers. In addition, the TiB2 film synthesized by IBED is being studied recently in our lab. In this paper, the results which include the hardness, thickness of the films and the AES, XRD analysis as well as the tests of the oxidation of high temperature and erosion will be presented.

Crack-tip constraint analysis of SENB specimen under creep condition

G. C. Jiao,W. Z. Wang,S. J. Tan,C. Yu,Y. Z. Liu 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.2

A higher-order asymptotic C(t)-A2(t)-M approach was used to investigate the crack-tip stress of single edge notched bend (SENB)specimen in a power-law creeping material under plane strain conditions. Comprehensive calculations were made of SENB specimenwith a/W = 0.59 by using higher-order asymptotic C(t)-A2(t)-M approach, higher-order asymptotic C(t)-A2(t) approach and finite elementanalysis; the latter two methods were used to check the constraint significance and the calculation accuracy of C(t)-A2(t)-M approach,respectively. The results show that the stress components qq s obtained from the higher-order asymptotic C(t)-A2(t)-M solution agreedwell with that of finite element analysis, however, which gradually deviated from the results of C(t)-A2(t) approach as the distance faraway from the crack tip for small-scale creep stage.

Changes of Plasma Metabolites, Hormones, and mRNA Expression of Liver PEPCK-C in Spontaneously Ketotic Dairy Cows

Xia, C.,Wang, Z.,Liu, G.W.,Zhang, H.Y.,Zhang, C.,Xu, C. Asian Australasian Association of Animal Productio 2010 Animal Bioscience Vol.23 No.1

The objective of this study was to understand changes of plasma metabolites, hormones, and mRNA level of cytoplasmic phosphoenolpyruvate carboxykinase (PEPCK-C) in liver in spontaneous clinical ketosis; 10 clinically ketotic cows and 10 healthy cows were chosen from the same dairy farm. Eleven blood parameters and liver fat content were measured in all cows, and mRNA levels of PEPCK-C in liver were measured by semi-quantitative reverse transcription (RT) polymerase chain reaction (PCR). In ketotic cows, concentration of plasma glucose decreased (p<0.01), concentration of plasma nonesterified fatty acids (NEFA) and $\beta$-hydroxybutyric acid (BHBA) increased (p<0.01), liver fat content (18.8% wet weight) and activity of plasma aspartate aminotransferase (AST) increased (p<0.01), but concentration of plasma total bilirubin (TBIL), $\gamma$-glutamyl transpeptidase ($\gamma$-GT), and cholinesterase (CHE) increased (p>0.05). In addition, concentration of plasma insulin decreased (p<0.05), concentration of plasma glucagons decreased (p>0.05), and mRNA level of PEPCK-C in liver increased (p<0.05). It is concluded that the adaptative changes of metabolites, hormones, and mRNA level of PEPCK-C in ketotic cows were in favor of the enhancement of gluconeogenesis, the decrease of fat mobilization and the relief of ketosis, but these were still inadequate to relieve ketosis.