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Characteristics of complicated AISI316L automobile components manufactured by powder/metallurgy
L. Zhong Liang,L. Jin Hui,S. Yu Sheng,Y. Chun Ze 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.7
Indirect Selective Laser Sintering/ Isostatic Pressing (SLS/IP), with Cold Isostatic Pressing (CIPing) and Hot Isostatic Pressing (HIPing) IPs, is adopted for the manufacture of complicated automobile components. The preparation of PA12-coated AISI316L powder and airproof plastic canning during CIPing are also investigated. The influence of technology parameters on the performances of AISI316L specimens during SLS/IP is likewise analyzed. Results show that PA12-coated AISI316L powders are successfully prepared through the dissolution and precipitation process, and that it is better to fabricate airproof canning for complicated components with natural latex. After sintering AISI316L specimens from 1300℃ to 1340℃ (CIPed at more than 300 MPa ahead), their relative densities increased, approaching 92%. Subsequently, their relative densities are improved by HIPing, whose optimal pressure and temperature parameters are between 90 MPa and 20 MPa, and 1150℃ and 1250℃, respectively. The optimal tensile performances are close to those of annealed AISI316L compact materials.
Synthesis of Co3O4 nanowire arrays supported on Ni foam for removal of volatile organic compounds.
Hui, K N,Yin, Cui-Lei,Hui, K S,Lee, J Y,Li, M,Lee, S K,Tsui, K L,Chao, C Y H,Kwong, C W American Scientific Publishers 2012 Journal of Nanoscience and Nanotechnology Vol.12 No.4
<P>Crystalline Co3O4 nanowire arrays freely supported on Ni foam are successfully synthesized using a template-free method. The effects of reaction time, concentration of reactants, and temperature on the morphology of the nanowires are studied. The results indicate that uniform Co3O4 nanowires could be synthesized at 90 degrees C, and a transformation of the samples' morphology from nanoparticles to nanowires to microrods is observed by controlling the concentration of the reactants. The well-ordered nanowires synthesized under the selected reaction conditions are composed of spinel Co3O4 with diameters of 500-580 nm and lengths of 6-8 microm. These nanowires show good catalytic activity for the ozone catalytic oxidation of toluene.</P>
Hui, K.S.,Hui, K.N.,Yin, C.L.,Hong, X. North-Holland 2013 Materials letters Vol.97 No.-
Spinel cobalt oxide (Co<SUB>3</SUB>O<SUB>4</SUB>) nanowires grown on Ni foam are successfully synthesized using a novel microwave-assisted template-free method. The effect of reaction temperature, concentration of reactants, and reaction time on the morphology and crystalline structures of the prepared nanowires is studied. The present work has demonstrated that uniform Co<SUB>3</SUB>O<SUB>4</SUB> nanowires with diameters of 500-580nm and lengths of 6-8μm can be synthesized under proper reaction condition. Moreover, the proposed microwave-assisted template-free method can significantly reduce reaction time, increase reaction efficiency, and provide better control over the geometry of the nanostructures.
SEARCHES FOR MILLISECOND PULSAR CANDIDATES AMONG THE UNIDENTIFIED<i>FERMI</i>OBJECTS
Hui, C. Y.,Park, S. M.,Hu, C. P.,Lin, L. C. C.,Li, K. L.,Kong, A. K. H.,Tam, P. H. T.,Takata, J.,Cheng, K. S.,Jin, Ruolan,Yen, T.-C.,Kim, Chunglee IOP Publishing 2015 The Astrophysical journal Vol.809 No.1
<P>Here we report the results of searching millisecond pulsar (MSP) candidates from the Fermi LAT second source catalog (2FGL). Seven unassociated gamma-ray sources in this catalog are identified as promising MSP candidates based on their gamma-ray properties. Through the X-ray analysis, we have detected possible X-ray counterparts, localized to an arcsecond accuracy. We have systematically estimated their X-ray fluxes and compared them with the corresponding gamma-ray fluxes. The X-ray to gamma-ray flux ratios for 2FGL J1653.6-0159 and 2FGL J1946.4-5402 are comparable with the typical value for pulsars. For 2FGL J1625.2-0020, 2FGL J1653.6-0159, and 2FGL J1946.4-5402, their candidate X-ray counterparts are bright enough to perform a detailed spectral and temporal analysis to discriminate their thermal/non-thermal nature and search for the periodic signal. We have also searched for possible optical/IR counterparts at the X-ray positions. For the optical/IR source coincident with the brightest X-ray object associated with 2FGL J1120.0-2204, its spectral energy distribution is comparable with a late-type star. Evidence for the variability has also been found by examining its optical light curve. All the aforementioned 2FGL sources resemble a pulsar in one or more aspects, making them promising targets for follow-up investigations.</P>
DISCOVERY OF X-RAY PULSATION FROM THE GEMINGA-LIKE PULSAR PSR J2021+4026
Lin, L. C. C.,Hui, C. Y.,Hu, C. P.,Wu, J. H. K.,Huang, R. H. H.,Trepl, L.,Takata, J.,Seo, K. A.,Wang, Y.,Chou, Y.,Cheng, K. S. IOP Publishing 2013 ASTROPHYSICAL JOURNAL LETTERS - Vol.770 No.1
<P>We report the discovery of an X-ray periodicity of similar to 265.3 ms from a deep XMM-Newton observation of the radio-quiet gamma-ray pulsar, PSR J2021+4026, located at the edge of the supernova remnant G78.2+2.1 (gamma-Cygni). The detected frequency is consistent with the gamma-ray pulsation determined by the observation of the Fermi Gamma-ray Space Telescope at the same epoch. The X-ray pulse profile resembles the modulation of a hot spot on the surface of the neutron star. The phase-averaged spectral analysis also suggests that the majority of the observed X-rays have thermal origins. This is the third member in the class of radio-quiet pulsars with significant pulsations detected from both X-ray and gamma-ray regimes.</P>
DISCOVERY OF AN X-RAY-EMITTING CONTACT BINARY SYSTEM 2MASS J11201034−2201340
Hu, Chin-Ping,Yang, Ting-Chang,Chou, Yi,Liu, L.,Qian, S.-B.,Hui, C. Y.,Kong, Albert K. H.,Lin, L. C. C.,Tam, P. H. T.,Li, K. L.,Ngeow, Chow-Choong,Chen, W. P.,Ip, Wing-Huen American Astronomical Society 2016 The Astronomical journal Vol.151 No.6
<P>We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034-2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of 7-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the 7-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of P = 0.28876208 (56) days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of (0.7 - 1.5) x 10(30) erg s(-1), which is in the expected range of an X-ray emitting contact binary.</P>
<i>XMM-NEWTON</i>OBSERVATION OF PSR B2224+65 AND ITS JET
Hui, C. Y.,Huang, R. H. H.,Trepl, L.,Tetzlaff, N.,Takata, J.,Wu, E. M. H.,Cheng, K. S. IOP Publishing 2012 The Astrophysical journal Vol.747 No.1
<P>We have investigated the pulsar PSR B2224+65 and its X-ray jet with XMM-Newton. Apart from the long X-ray jet which is almost perpendicular to the direction of proper motion, a putative extended feature at the pulsar position, which is oriented in the opposite direction to the proper motion, is also suggested by this deep X-ray imaging. Non-detection of any coherent X-ray pulsation disfavors the magnetospheric origin of the X-rays observed from the position of PSR B2224+65 and hence suggests that the interpretation of pulsar wind nebula is more viable. We have also probed the origin of PSR B2224+65 and identified a runaway star, which possibly originated from the Cygnus OB9 association, as a candidate for the former binary companion of the neutron star's progenitor.</P>
Flutter analysis of Stonecutters Bridge
Hui, Michael C.H.,Ding, Q.S.,Xu, Y.L. Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.2
Stonecutters Bridge of Hong Kong is a cable-stayed bridge with two single-column pylons each 298 m high and an aerodynamic twin deck. The total length of the bridge is 1596 m with a main span of 1018 m. The top 118 m of the tower will comprise structural steel and concrete composite while the bottom part will be of reinforced concrete. The bridge deck at the central span will be of steel whilst the side spans will be of concrete. Stonecutters Bridge has adopted a twin-girder deck design with a wide clear separation of 14.3 m between the two longitudinal girders. Although a number of studies have been conducted to investigate the aerodynamic performance of twin-girder deck, the actual real life application of this type of deck is extremely limited. This therefore triggered the need for conducting the present studies, the main objective of which is to investigate the performance of Stonecutters Bridge against flutter at its in-service stage as well as during construction. Based on the flutter derivatives obtained from the 1:80 scale rigid section model experiment, flutter analysis was carried out using 3-D finite element based single parameter searching method developed by the second author of this paper. A total of 6 finite element models of the bridge covering the in-service stage as well as 5 construction stages were established. The dynamic characteristics of the bridge associated with these stages were computed and applied in the analyses. Apart from the critical wind speeds for the onset of flutter, the dominant modes of vibration participating in the flutter vibration were also identified. The results indicate that the bridge will be stable against flutter at its in-service stage as well as during construction at wind speeds much higher than the verification wind speed of 95 m/s (1-minute mean).