Jet-dominated quiescent state in black hole X-ray binaries: the cases of A0620--00 and XTE J1118+480

The radiative mechanism of the black hole X-ray transients (BHXTs) in their quiescent states (defined as the 2-10 keV X-ray luminosity $\le 10^{34}{\rm \,erg\,s^{-1}}$) remains unclear. In this work, we investigate the quasi-simultaneous quiescent state spectrum (including radio, infrared, optical, ultraviolet and X-ray) of two BHXTs, A0620--00 and XTE J1118+480. We find that, these two sources can be well described by a coupled accretion -- jet model. More specifically, most of the emission (radio up-to infrared, and the X-ray waveband) comes from the collimated relativistic jet. Emission from hot accretion flow is totally insignificant, and it can only be observed in mid-infrared (the synchrotron peak). Emission from the outer cold disc is only evident in UV band. These results are consistent with our previous investigation on the quiescent state of V404 Cyg, and confirm that the quiescent state is jet-dominated.Comment: 11 pages, 1 figure, accepted for publication in Research in Astronomy and Astrophysic

Pervasive computing at tableside : a wireless web-based ordering system

Purpose &ndash; The purpose of this paper is to introduce a wireless web-based ordering system called iMenu in the restaurant industry. Design/methodology/approach &ndash; By using wireless devices such as personal digital assistants and WebPads, this system realizes the paradigm of pervasive computing at tableside. Detailed system requirements, design, implementation and evaluation of iMenu are presented.Findings &ndash; The evaluation of iMenu shows it explicitly increases productivity of restaurant staff. It also has other desirable features such as integration, interoperation and scalability. Compared to traditional restaurant ordering process, by using this system customers get faster and better services, restaurant staff cooperate more efficiently with less working mistakes, and enterprise owners thus receive more business profits. Originality/value &ndash; While many researchers have explored using wireless web-based information systems in different industries, this paper presents a system that employs wireless multi-tiered web-based architecture to build pervasive computing systems. Instead of discussing theoretical issues on pervasive computing, we focus on practical issues of developing a real system, such as choosing of web-based architecture, design of input methods in small screens, and response time in wireless web-based systems.<br /

The roughness measurement of the super-smooth surface of hard disks

Technologies for manufacturing hard disks are driven by the demand to increase magnetic storage capacity. However, the rate of increasing storage capacity is being slowed by the inability to produce ever closer flying heights between the sliders and disk surfaces. One of important requirements for flying height is to control the surface of substrates of hard disks to a super-smooth level to allow the sliders to ‘fly’ faster and more closely to the disk surfaces. Currently, there are no any assessment standards for super-smooth surfaces. In this paper, the authors attempt to build a measurement and characterisation protocol for the evaluation of hard disk surfaces using a white-light optical instrument CCI (Coherence Correlation Interferometer). The key advantage of this instrument is its exceptionally high vertical resolution which is an order of magnitude better than comparable systems. System factors and measurement factors both influence the experimental results with CCI, this paper focuses on analysing the latter including sampling intervals, the number of measurements, measurement area filter cut-off wavelength etc. Based on the experimental results, an optimised group of parameters for measurement and characterisation are recommended. The authors have successfully measured and compared the surface roughness of six hard disks derived from differing Chemical Mechanical Polishing (CMP) ‘abrasives’. It has been found that: (1) the roughness values of the six hard disks surfaces have all reached a sub-nanometre level; (2) there is little difference in the influences of different CMP regimes on the topography of the hard disk surfaces