In order to improve bandwidth efficiency and PAPr performance,a new hidden pilot scheme using a precoder is proposed for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFdM) systems....
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In order to improve bandwidth efficiency and PAPr performance,a new hidden pilot scheme using a precoder is proposed for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFdM) systems. Based on the hidden pilot scheme,it is possible to estimate the channel andreduce the PAPr without bandwidth consumption. We show that the inevitable unknown data interference of the hidden pilot,which degrades the performance of channel estimation,can be successively reduced by the precoderdesign for each antenna with the aid of an iterative scheme. Computer simulations are presented where the proposed scheme is compared with conventional methods using channel estimation,BEr,bandwidth efficiency and PAPr performance.
The transport characteristics of cylindrical gate-all-around twin silicon nanowire field-effect transistors with radius of 5 nm have been investigated. Mobility was estimated by extracting of source/drain resistance.
The transport characteristics of cylindrical gate-all-around twin silicon nanowire field-effect transistors with radius of 5 nm have been investigated. Mobility was estimated by extracting of source/drain resistance.
The radio on Fiber (rOF) technique has great potential in wireless communication systems. In this paper, we report on a fundamental examination of microwave wireless access systems based on radio on Fiber. First, we d...
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The radio on Fiber (rOF) technique has great potential in wireless communication systems. In this paper, we report on a fundamental examination of microwave wireless access systems based on radio on Fiber. First, we designed and constructed examination systems by applying dual band (2.4 and 5 GHz) multiservice transmission systems and confirmed that there was sufficient performance through a transmission experiment. Then, application of FP-Ld (Fabry Perot Laserdiode) was considered in order to reduce the system cost, and for the most part degradation of the transmission characteristics was not observed when FP-Ld was used. Finally, a BIdI (bidirectional) module which integrated Ld and Pd within one package was made to furtherreduce costs. By measuring the transmission performance, applying the BIdI module to rOF systems was shown to be effective. (C) 2007 Wiley Periodicals, Inc.
We report measurements of the spin susceptibility and the electron effective mass for two-dimensional electrons confined at the interfaces of MgxZn1−xO/ZnO single heterostructures (x=0.05, 0.08, and 0.11), grown by mo...
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We report measurements of the spin susceptibility and the electron effective mass for two-dimensional electrons confined at the interfaces of MgxZn1−xO/ZnO single heterostructures (x=0.05, 0.08, and 0.11), grown by molecular-beam epitaxy on (0001) ZnO substrates. By tuning the built-in polarization through control of the barrier composition, the electron density was systematically varied in the range of 5.6×1011–1.6×1012 cm−2, corresponding to a range of 3.1≤rs≤5.2, where rs is the average electron spacing measured in units of the effective Bohrradius. We used the coincidence technique, where crossings of the spin-split Landau levels occur at critical tilt angles of magnetic field, to evaluate the spin susceptibility. In addition, we determined the effective mass from the temperature dependence of the Shubnikov–de Haas oscillations measured at the coincidence conditions. The susceptibility and the effective mass both gradually increase with decreasing electron density, reflecting the role of electron-electron interaction.
Laser-excited photoemission spectroscopy is used to show that the doped carriers in metallic or superconducting diamond couple strongly to the lattice via high-energy (∼150 meV) optical phonons, with direct observat...
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Laser-excited photoemission spectroscopy is used to show that the doped carriers in metallic or superconducting diamond couple strongly to the lattice via high-energy (∼150 meV) optical phonons, with direct observations of localized Franck-Condon multiphonon sidebands appearing as Fermi-edge replicas. It exhibits a temperature-dependent spectral weight transfer from higher to lower energy sidebands and zero-phonon Fermi-edge states. The quantified coupling strength shows a systematic increase on lowering temperature, implicating its relation to the normal state transport and superconductivity.
In order to avoid the accuracy deterioration or tool damage caused by milling chatter, it is necessary to have an efficient andreliable diagnosis system that can on-line predict/detect the occur-rence of chatter. The...
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In order to avoid the accuracy deterioration or tool damage caused by milling chatter, it is necessary to have an efficient andreliable diagnosis system that can on-line predict/detect the occur-rence of chatter. The diagnosis/predicting system proposed is to on-line process and analysis the vi-bration signals of the milling machine measured by accelerometers. According to the analysis results, the system will be able to detect/predict the occurrence of the chatter. The diagnosis algorithm is, first, collecting both the normal signals and chatter signals from milling processes, and then, converting the signals through wavelet transform and fast Fourier transform （FFT）. Since the converted chatter sig-nals exhibit different characteristics from the normal signals, through defining the characteristic val-ues, such as root-mean-square value, max value, andratio of peak value to root-mean-square value, etc, a diagnosis reference library that contains the distribution of these characteristic values is built fordiagnosis. When a diagnosis is executing, the characteristic value of the measured signals is con-trasted with the diagnosis reference. The approach index which shows the possibility of occurrence of milling chatter will, then, be calculated through the diagnosis system. Cutting experiments are con-ducted to verify the proposeddiagnosis system. The results show the success of early chatterdetecting for the system.
The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope ...
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The microstructure of AISI 304 austenlte stainless steel fabricated by the thin strip casting process were investigated using optical microscope, scanning electron microscope （SEM）, transmission electron microscope （TEM）, and X-ray diffraction （Xrd）. The microstructures of the casting strips show a duplex structure consisting of delta ferrite and austenite. The volume fraction of the delta ferrite is about 9.74vo1% at the center and 6.77vo1% at the surface of the casting thin strip, in vermicular and hand shapes. On account of rapid cooling and solidification in the continuous casting process, many kinds of inclusions and precipitates have been found. Most of the inclusions and precipitates are spherical complex compounds consisting of oxides, such as, SiO2, MnO, Al2O3, Cr2O3, and FeO or their multiplicity oxides of ***2O3, ***2, and ***2. Many defects including dislocations and stacking faults have also formedduring the rapid cooling and solidification process, which is helpful to improve the mechanical properties of the casting strips.
With the support of government policy and emerging information and communication technologies (ICT), the need for assistance in performing government purchasing tasks has led to the rapiddevelopment of electronic pro...
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ISBN:
(纸本)9787811146585
With the support of government policy and emerging information and communication technologies (ICT), the need for assistance in performing government purchasing tasks has led to the rapiddevelopment of electronic procurement. Governmental electronic procurement system is a portal site providing information on public procurement and an application service provider of public procurement. This paper presents a case study describing the governmental electronic procurement systems of Liaoning Golden Tax Program;the purpose of this paper is to empirically explore the perceived benefits and the obstacles to adopting governmental electronic procurement system.
The present work focused on the determination of the interracial heat transfer coefficient (IHTC) between metal anddie during the high pressure die casting (HPdC) *** were carried out on an aluminum alloy,AdC12Z,usin...
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The present work focused on the determination of the interracial heat transfer coefficient (IHTC) between metal anddie during the high pressure die casting (HPdC) *** were carried out on an aluminum alloy,AdC12Z,using'step shape'casting-so-called because of its *** IHTC was successfully determined by solving one of the inverse heat problems using the nonlinear estimation method fkrst used by *** calculation results indicated that the IHTC immediately increased after liquid metal was brought into the cavity by the plunger anddecreased as the solidification process of the liquid metal *** liquid metal eventually solidified completely,a condition when the IHTC tended to be *** thickness played an important role in affecting the IHTC between the metal anddie not only in terms of its value but also in terms of its change ***,under the test conditions,different change tendencies of the metal solid fraction were found between castings with different thicknesses and the die.
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