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Optical Absorption of Sol-Gel Derived ZnO/TiO_(2) Nanocomposite Films

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Chinese Physics Letters 2001年第11期18卷 1520-1522页

作者： YUAN Zhi-Hao TANG Cheng-Chun FAN Shou-Shan Department of Chemistry Tsinghua UniversityBeijing 100084 Department of Physics Tsinghua UniversityBeijing 100084

ZnO/TiO_(2) nanocomposite films on quartz substrates were prepared by the sol-gel method, and the corresponding optical absorption properties were investigated. In the ultraviolet region, it was found that the position of fundamental absorption edge partially depends on the composition of the ZnO/TiO_(2 ) films, and shifts toward a shorter wavelength with the increasing content of ZnO in the films. Moreover, a blueshift of the absorption edge resulted from a quantum size effect and the quantum confinement effect was observed in the ZnO/TiO_(2) system.

关键词： composite absorption effect

A Remote Quantum Adding Machine

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Chinese Physics Letters 2002年第11期19卷 1579-1580页

作者：张圣醒龙桂鲁等 DepartmentofPhysics TsinghuaUniversityBeijing100084 KeyLaboratoryforQuantumInformationandMeasurements MinistryofEducationBeijing100084 CenterforAtomicandMolecularNanosciences T

We design a scheme to perform additions of N remote addends. This adder is useful for some quantum information processing purposes, such as statistics and multi-party quantum game. The quantum remote adder is construc... 详细信息

关键词： Adders

On a New Class of Self-Referencing, 1/τ Atomic Clocks

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Chinese Physics Letters 2014年第8期31卷 24-26页

作者：王力军 DepartmentofPhysics TsinghuaUniversityBeijing100084 JointInstituteforMeasurementScience(JMI) TsinghuaUniversityBeijing100084 DepartmentofPrecisionInstrument TsinghuaUniversityBeijing100084 NationalInstituteofMetrologyofChina Beijing100013

The merit of a modern atomic clock is measured by its phase stability. A clock＇s absolute time-keeping uncertainty typically worsens over its operating time τ as Δτα√τ, with an Allan deviation of sy σy（τ）=Δτ/τατ^-1/2. Here we analyze a new class of self-referencing clocks, whose phase is locked to itself after a certain time delay. We show that the Allan deviation of such clocks decreases as 1/τ over a long and controllable operating time. This class of clocks can maintain synchronization over a prolonged period with only a fixed, almost non-increasing, absolute uncertainty, forming an ideal time-piece.

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Fabrication of Pentacene Thin-Film Transistors with Patterned Polyimide Photoresist as Gate Dielectrics and Research of Their Degradation

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Chinese Physics Letters 2004年第11期21卷 2278-2280页

作者：梁琰董桂芳胡远川胡雁王立铎邱勇 KeyLabofOrganicOptoelectronics&MolecularEngineeringofMinistryofEducation TsinghuaUniversityBeijing100084 DepartmentofChemistry TsinghuaUniversityBeijing100084

Pentacene organic thin-film transistors using commercial photoresist as gate dielectrics were fabricated. The photoresist was spin-coated and directly patterned by photolithography. As a result, the fabrication processes were greatly reduced. With the characteristics of the transistors measured, the degradation of the transistors was investigated. In the search for the factors causing degradation, a transistor using poly(methyl methacrylate) as the gate dielectric was also fabricated. It is regarded that the degradation is caused by the changes at the interface between photoresist and pentacene film.

关键词： Gate dielectrics

Gas phase tricholoethylene removal at low concentration using activated carbon fiber

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Journal of Environmental Sciences 2004年第1期16卷 53-55页

作者： LIUJun HUANGZheng-hong WANGZhan-sheng KANGFei-yu DepartmentofEnvironmentScienceandEngineering TsinghuaUniversityBeijing100084China DepartmentofMaterialScienceandEngineering TsinghuaUniversityBeijing100084China

The breakthrough adsorption behaviors of gas phase trichloroethylene in a packed bed of activated carbon fibers(ACF) were investigated. The specific surface area of the ACF was 600 m 2/g, 1400 m 2/g and 1600 m 2/g, respectively, and the concentration of trichloroethylene ranged from 270 mg/m 3 to 2700 mg/m 3. Results showed that the capacity of adsorption increased with increasing specific surface area, the relationship between the logarithms of 10% breakthrough time and concentration was approximately linear over the experimental range, the breakthrough time decreased with increasing temperature and humidity. The breakthrough curves at different inlet concentration or different temperature can be predicted by several simple theoretical models with good agreements.

关键词： trichloroethylene activated carbon fiber adsorption breakthrough curve

Processes of depositing platinum on carbon nanotubes and their effect on performance of proton exchange membrane fuel cell

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Journal of University of Science and Technology Beijing 2004年第4期11卷 349-353页

作者： YanhuiLi JunDing JunfengChen ZongqiangMao CailuXu DehaiWu DepartmentofMechanicalEngineering TsinghuaUniversityBeijing100084China InstituteofNuclearEnergyTechnology TsinghuaUniversityBeijing100084China

The ultrafine platinum nanoparticles deposited on the surfaces of carbonnanotubes (Pt/CNTs) were prepared by a chemical precipitation method and used as the catalyst ofproton exchange membrane fuel cell. The depositing process parameters such as the solution pH value,Pt content and treatment temperature were analyzed. The experimental results show that the optimumprocess parameters to prepare Pt/CNTs are the solution pH value of 7.0, the theoretical Pt contentof 25 percent (mass fraction) and the heating temperature of 500 deg C, under the conditions thebest performance of the proton exchange membrane fuel cell can be obtained and its voltage can reach580 mV at a current density of 500 mA/cm^2.

关键词： carbon nanotubes platinum deposition proton exchange membrane fuel cell

Electrical Performance of Electron Irradiated SiGe HBT and Si BJT

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Journal of Materials Science & Technology 2004年第6期20卷 706-708页

作者： WentaoHUANG JilinWANG ZhinongLIU PeiyiCHEN PeihsinTSIEN XiangtiMENG InstituteofMicroelectronics TsinghuaUniversityBeijing100084China InstituteofNuclearEnergyTechnology TsinghuaUniversityBeijing100084China

The change of electrical performances of 1 MeV electron irradiated silicon-germanium (SiGe) heterojunction bipolar transistor (HBT) and Si bipolar junction transistor (BJT) was studied. After electron irradiation, both the collector current IC and the base current IB changed a little, and the current gain β decreased a little for SiGe HBT. The higher the electron irradiation fluence was, the lower the IC decreased. For conventional Si BJT, IC and IB increased as well as /? decreased much larger than SiGe HBT under the same fluence. The contribution of IB was more important to the degradation of β for both SiGe HBT and Si BJT. It was shown that SiGe HBT had a larger anti-radiation threshold and better anti-radiation performance than Si BJT. The mechanism of electrical performance changes induced by irradiation was preliminarily discussed.

关键词： Electron irradiation SiGe HBT Si BJT Electrical performance

Effect of lanthanum ion implantation on oxidation behavior of zircaloy

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Journal of University of Science and Technology Beijing 2004年第3期11卷 260-262页

作者： XiaoyangLiu XindeBai DepartmentofEngineeringPhysics TsinghuaUniversityBeijing100084China DepartmentofMaterialsScienceandEngineering TsinghuaUniversityBeijing100084China

In order to investigate the effect of lanthanum ion implantation on theoxidation behavior of zircaloy at 500℃, Zircaloy specimens were implanted by lanthanum ions with adose range from 5xl0^(16) to 2xl0^(17) ions/cm^2 at room temperature, and then oxidized at 500℃ for100 min. The valence of the oxides in the scale was analyzed by X-ray Photoelectron Spectroscopy(XPS). The phase structures of the oxides in the scale were examined by Glancing Angle X-rayDiffraction (GAXRD). With the increase of implanted lanthanum ions dose, the phase structures in theoxide scale are transformed from monoclinic zirconia to hexagonal one and then to monoclinic oneagain. The measurement of weight gain showed that a similar change from the decreased gain toincreased one again is achieved in the oxidation behavior of lanthanum ion implanted zircaloycompared with that of as-received zircaloy.

关键词： zircaloy air oxidation lanthanum ion implantation hexagonal zirconia monoclinic zirconia phase transformation

Design and Efficient Hardware Implementation Schemes for Non-Quasi-Cyclic LDPC Codes

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Tsinghua Science and Technology 2017年第1期22卷 92-103页

作者： Baihong Lin Yukui Pei Liuguo Yin Jianhua Lu Department of Electronic Engineering Tsinghua UniversityBeijing 100084 China School of Aerospace Tsinghua UniversityBeijing 100084

The design of a high-speed decoder using traditional partly parallel architecture for Non-Quasi-Cyclic（NQC） Low-Density Parity-Check（LDPC） codes is a challenging problem due to its high memory-block cost and low hardware utilization efficiency. In this paper, we present efficient hardware implementation schemes for NQCLDPC codes. First, we propose an implementation-oriented construction scheme for NQC-LDPC codes to avoid memory-access conflict in the partly parallel decoder. Then, we propose a Modified Overlapped Message-Passing（MOMP） algorithm for the hardware implementation of NQC-LDPC codes. This algorithm doubles the hardware utilization efficiency and supports a higher degree of parallelism than that used in the Overlapped Message Passing（OMP） technique proposed in previous works. We also present single-core and multi-core decoder architectures in the proposed MOMP algorithm to reduce memory cost and improve circuit efficiency. Moreover, we introduce a technique called the cycle bus to further reduce the number of block RAMs in multi-core decoders. Using numerical examples, we show that, for a rate-2/3, length-15360 NQC-LDPC code with 8.43-d B coding gain for Binary PhaseShift Keying（BPSK） in an Additive White Gaussian Noise（AWGN） channel, the decoder with the proposed scheme achieves a 23.8%–52.6% reduction in logic utilization per Mbps and a 29.0%–90.0% reduction in message-memory bits per Mbps.

关键词： Non-Quasi-Cyclic(NQC) Low-Density Parity-Check(LDPC) codes decoder design Modified Overlapped Message Passing(MOMP) algorithm hardware utilization efficiency