End Effect on the Twin—Wire Depth Probe

The end effect on the output voltage of a twin-wire depth probe was investigated both theoretically and ex-perimentally.It was found that the contribution of the end of the probe to the output voltage depends uponthe distance between the boundary and the end of the probe and the geometrical configuration of the probe.By mounting a piece of plate to the end of the electrodes,the end effect can be reduced.However,the size ofthe plate required to eliminate completely this effect is much larger than that usually mounted on commerciallyavailable probes.Comparison between theoretical and experimental results was made.Reasonable agreementwas obtained.     

储油罐内壁铁锈硫化及氧化反应

储罐内壁铁锈在低温有水的条件下与储罐中的硫化氢气体反应生成硫铁化物．硫铁化物的氧化放热是引起含硫油品储罐着火的主要原因．采用X-射线衍射仪鉴定铁锈成份,对铁锈主要成分室温下进行硫化及硫化产物的氧化实验,绘制硫化及硫化产物氧化反应温度-时间曲线,并鉴定分析硫化产物及硫化产物的氧化产物,研究对含硫储罐自燃的作用．结果表明,铁锈主要成分为Fe2O3和Fe3O4,室温硫化产物均为FeS,但FeS形状与其来源有关．形状、致密性不同,致使氧化自燃性不同．Fe2O3硫化产物比Fe3O4硫化产物的氧化自燃性高,对引发储罐自燃的危险性大．     

A novel high power density permanent magnet variable-speed motor

A novel polyphase, multipole, permanent magnet (PM) motor which possesses high power density, high efficiency and excellent controllability, yet can be produced by conventional fabrication techniques, is proposed. The basic operating principles, design features, performance analysis and control system are described. The experimental results for a 5 kW, 1500 RPM prototype PM motor and its comparison with other types of motors such as switched reluctance motors and induction motors are given. This motor also has superior dynamic performance     

Experimental investigation on the effect of natural gas composition on performance of autothermal reforming

This paper presents experimental study on catalytic autothermal reforming (ATR) of natural gas (NG) for hydrogen (_H2${\mathrm{H}}_2$) production over sulfide nickel catalyst supported on gamma alumina. The experiments are conducted on a cylindrical reactor of 30 mm in diameter and 200 mm in length with “simulated” NG of different composition under thermal-neutral conditions and fed with different molar air to fuel ratio (A/F$A/F$) and molar water to fuel ratio (W/F)$(W/F)$. The results showed that reforming performance is significantly dependent on A/F$A/F$, W/F$W/F$ and concentration of _C2+${\mathrm{C}}_{2+}$ hydrocarbons in inlet fuel. Fuels containing higher _C2+${\mathrm{C}}_{2+}$ hydrocarbons concentration have optimum performance in terms of more _H2${\mathrm{H}}_2$ at higher A/F$A/F$ and W/F$W/F$ but lower conversion efficiency. Good performance for ATR of fuel containing 15%–20% _C2H6${\mathrm{C}}_2{\mathrm{H}}_6$ can be achieved at A/F=5–7$A/F=5–7$ and W/F=4–6$W/F=4–6$, much higher than that for optimum performance of ATR of methane (A/F=3,W/F=2–2.5$A/F=3,W/F=2–2.5$). _CO2${\mathrm{CO}}_2$ in the inlet fuel does not have significant effect on the reversed water–gas shift reaction. Its effect on reforming performance is mainly due to the dilution of inlet fuel and products.     

Fine‐Grained FSMD Power Gating Considering Power Overhead

As a fine‐grained power gating method for achieving greater power savings, our approach takes advantage of the finite state machine with a datapath (FSMD) characteristic which shows sequential idleness among subcircuits. In an FSMD‐based power gating, while only an active subcircuit is expected to be turned on, more subcircuits should be activated due to the power overhead. To reduce the number of missed opportunities for power savings, we deactivated some of the turned‐on subcircuits by slowing the FSMD down and predicting its behavior. Our microprocessor experiments showed that the power savings are close to the upper bound.     

Lightweight and provably secure user authentication with anonymity for the global mobility network

Seamless roaming in the global mobility network (GLOMONET) is highly desirable for mobile users, although their proper authentication is challenging. This is because not only are wireless networks susceptible to attacks, but also mobile terminals have limited computational power. Recently, some authentication schemes with anonymity for the GLOMONET have been proposed. This paper shows some security weaknesses in those schemes. Furthermore, a lightweight and provably secure user authentication scheme with anonymity for the GLOMONET is proposed. It uses only symmetric cryptographic and hash operation primitives for secure authentication. Besides, it takes only four message exchanges among the user, foreign agent and home agent. We also demonstrate that this protocol enjoys important security attributes including prevention of various attacks, single registration, user anonymity, user friendly, no password/verifier table, and use of one‐time session key between mobile user and foreign agent. The security properties of the proposed protocol are formally validated by a model checking tool called AVISPA. Furthermore, as one of the new features in our protocol, it can defend smart card security breaches. Copyright © 2010 John Wiley & Sons, Ltd.     

Physicochemically Stable Polymer‐Coupled Oxide Dielectrics for Multipurpose Organic Electronic Applications

A chemically coupled polymer layer is introduced onto inorganic oxide dielectrics from a dilute chlorosilane‐terminated polystyrene (PS) solution. As a result of this surface modification, hydrophilic‐oxide dielectrics gain hydrophobic, physicochemically stable properties. On such PS‐coupled SiO₂ or AlO_x dielectrics, various vacuum‐ and solution‐processable organic semiconductors can develop highly ordered crystalline structures that provide higher field‐effect mobilities (μ_FETs) than other surface‐modified systems, and negligible hysteresis in organic field‐effect transistors (OFETs). In particular, the use of PS‐coupled AlO_x nanodielectrics enables a solution‐processable triethylsilylethynyl anthradithiophene OFET to operate with μ_FET ～ 1.26 cm² V^?1 s^?1 at a gate voltage below –1 V. In addition, a complementary metal‐oxide semiconductor‐like organic inverter with a high voltage gain of approximately 32 was successfully fabricated on a PS‐coupled SiO₂ dielectric.     

Double-Layer Data Embedding Scheme Based on Three-Pixel Differences

Steganography is a technique to hide the secret data into digital media without getting any unexpected notices. The traditional steganographic method, namely least significant bit (LSB) replacement, is a simple but insecure scheme. To overcome the traditional drawbacks, this paper proposes a steganographic scheme, which is called double-layer hiding method. The experimental results confirm that the proposed scheme achieves better hiding capacity with high ability of resisting security analysis.     

A Versatile Iterative Framework for the Reconstruction of Bandlimited Signals from Their Nonuniform Samples

In this paper, we study a versatile iterative framework for the reconstruction of uniform samples from nonuniform samples of bandlimited signals. Assuming the input signal is slightly oversampled, we first show that its uniform and nonuniform samples in the frequency band of interest can be expressed as a system of linear equations using fractional delay digital filters. Then we develop an iterative framework, which enables the development and convergence analysis of efficient iterative reconstruction algorithms. In particular, we study the Richardson iteration in detail to illustrate how the reconstruction problem can be solved iteratively, and show that the iterative method can be efficiently implemented using Farrow-based variable digital filters with few general-purpose multipliers. Under the proposed framework, we also present a completed and systematic convergence analysis to determine the convergence conditions. Simulation results show that the iterative method converges more rapidly and closer to the true solution (i.e. the uniform samples) than conventional iterative methods using truncation of sinc series.     

Effect of Composition on Thermoelectric Properties in PbTe-Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> Composites

The solidification of alloys in the Bi₂Te₃-PbTe pseudobinary system at off- and near-eutectic compositions was investigated for their microstructure and thermoelectric properties. Dendritic and lamellar structures were clearly observed due to the phase separation and the existence of a metastable ternary phase. In this system, three phases with different compositions were observed: binary Bi₂Te₃, PbTe, and metastable PbBi₂Te₄. The Seebeck coefficient, electrical resistivity, and thermal conductivity of ternary alloys as well as binary compounds were measured. The phonon thermal conductivities of Pb-Bi-Te alloys were lower than those in binary PbTe and Bi₂Te₃, which could have resulted from the increased interfacial area between phases due to the existence of the metastable ternary phase and the resultant phase separation.