Multiple-Access Bosonic Communications

The maximum rates for reliably transmitting classical information over Bosonic multiple-access channels (MACs) are derived when the transmitters are restricted to coherent-state encodings. Inner and outer bounds for the ultimate capacity region of the Bosonic MAC are also presented. It is shown that the sum-rate upper bound is achievable with a coherent-state encoding and that the entire region is asymptotically achievable in the limit of large mean input photon numbers.Comment: 11 pages, 5 figures, corrected two figures, accepted for publication in Phys. Rev.

Hospital Treatment Rates and Spill-Over Effects: Does Ownership Matter?

This paper studies the effect of hospital ownership on treatment rates allowing for spatial correlation among hospitals. Competition among hospitals and knowledge spillovers generate significant externalities which we try to capture using the spatial Durbin model. Using a panel of 2342 hospitals in the 48 continental states observed over the period 2005 to 2008, we find significant spatial correlation of medical service treatment rates among hospitals. The paper also shows mixed results on the effect of hospital ownership on treatment rates that depends upon the market structure where the hospital is located and which varies by treatment type

A New Layer Casting System for Ceramic Laser Rapid Prototyping Apparatus

In the existing Ceramic Laser Fusion system, slurry is fed on the high temperature surface of the green part; therefore, a part of water infiltrates into the green block and vaporizes before the process of layer casting. As a result, the slurry viscosity rises gradually; the quality of the layer surface is not uniform, and the green part density is uneven. The aim of present study is to develop a new layer casting system which can solve the problems mentioned above to obtain a green part with uniform surface quality and density, and to shorten the time-taken of part fabrication. The first part of the paper illustrates the major requirements and parameters of a slurry distributor; the second part describes the integration of the slurry feeding device and layer casting system. The integrated system can feed slurry and cast thin layer simultaneously; consequently, the drawbacks of the existing system can be eliminated and the time-taken of the layer casting can be shortened. A variable-frequency drive (inverter) is used to control the motor speed. The relation between the frequency and the slurry delivery can be included in the process control program to adjust the quantity in accordance with the layer thickness; hence, the waste of the slurry can be reduced.Mechanical Engineerin

The Characteristics and Applications of Ceramic Laser Fusion and Ceramic Laser Sintering

The aim of present study is to investigate the possible application of the ceramic parts which are fabricated with the process of Ceramic Laser Fusion or Ceramic Laser Sintering. The experimental results reveal: (1) CLF can lead to a reduction in the porosity of the ceramic part but also can induce micro-cracks. Therefore, this process cannot produce a part with the required strength by a post-process of infiltration; (2) CLS is capable of fabricating a ceramic part with high porosity. By adjusting the slurry formulation and varying the scanning energy, the open porosity can be over 90vol% of the total porosity. After a post-process of infiltration, the density can be increased to 95%; therefore, CLS can apply to produce a part with high strength. Because the high open porosity leads to a good permeability, the process of CLS is suitable for the fabrication of ceramic shell mold.Mechanical Engineerin

Prospect of Making Ceramic Shell Mold by Ceramic Laser Fusion

Manufacturing prototypical castings by conventional investment casting not only takes several weeks, but also is prohibitively expensive. Z Corporation in USA, EOS GmbH and IPT in Germany employ the techniques of 3DP and SLS respectively to make directly ceramic shell molds for metal castings. Although those techniques dramatically reduce time expenditure and production cost, each layer cannot be thinner than 50 µm because of using powder to pave layers. The dimensional accuracy and roughness of the castings still cannot meet the specification of precision casting. Therefore, in this paper the ceramic laser fusion (CLF) was used to pave layers. Each layer can be thinner than 25 µm, so that the step effect can be diminished and the workpiece surface can be smoother; drying time will be shortened dramatically. Moreover, the inherent solid-state support formed by green portion has the capability of preventing upward and downward deformation of the scanned cross sections. In order to make shell mold which meets the roughness requirement (Rq=3.048µm) of the precision casting, following issues have to be further studied: (1) design a proper ceramic shell mold structure, (2) design a paving chamber for paving a complete green layer which can be easily collapsed, (3) cut down drying time, (4) optimize laser scanning process parameters with the smallest distortion, (5) eliminate sunken area, (6) reduce layer thickness to less than13µm, (7) control power to guarantee the energy uniformly absorbed by workpiece, and (8) develop a method which can directly clean green portion in cavity from gate.Mechanical Engineerin

Definition, analysis and development of an optical data distribution network for integrated avionics and control systems. Part 2: Component development and system integration

Fiber optic transmission is emerging as an attractive concept in data distribution onboard civil aircraft. Development of an Optical Data Distribution Network for Integrated Avionics and Control Systems for commercial aircraft will provide a data distribution network that gives freedom from EMI-RFI and ground loop problems, eliminates crosstalk and short circuits, provides protection and immunity from lightning induced transients and give a large bandwidth data transmission capability. In addition there is a potential for significantly reducing the weight and increasing the reliability over conventional data distribution networks. Wavelength Division Multiplexing (WDM) is a candidate method for data communication between the various avionic subsystems. With WDM all systems could conceptually communicate with each other without time sharing and requiring complicated coding schemes for each computer and subsystem to recognize a message. However, the state of the art of optical technology limits the application of fiber optics in advanced integrated avionics and control systems. Therefore, it is necessary to address the architecture for a fiber optics data distribution system for integrated avionics and control systems as well as develop prototype components and systems

Classical Extended Conformal Algebras Associated with Constrained KP Hierarchy

We examine the conformal property of the second Hamiltonian structure of constrained KP hierarchy derived by Oevel and Strampp. We find that it naturallygives a family of nonlocal extended conformal algebras. We give two examples of such algebras and find that they are similar to Bilal's V algebra. By taking a gauge transformation one can map the constrained KP hierarchy to Kuperschmidt's nonstandard Lax hierarchy. We consider the second Hamiltonian structure in this representation. We show that after mapping the Lax operator to a pure differential operator the second structure becomes the sum of the second and the third Gelfand-Dickey brackets defined by this differential operator. We show that this Hamiltonian structure defines the W-U(1)-Kac-Moody algebra by working out its conformally covariant form.Comment: NHCU-HEP-94-28, 19 pages (Plain TeX