Microwave plasma synthesis of TiN and ZrN nanopowders

This work demonstrates that TiN and ZrN nanopowders can be prepared by microwave plasma synthesis method. The effects of flow rate of plasma forming gas, flow rate of carrier gas and feeding rate of precursor raw material to the average particle size were studied. The TiN and ZrN nanopowders were characterized by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD).     

Effects of ternary additions on the thermoelastic martensitic transformation of NiAl

Nickel-rich β-NiAl alloys, which are potential materials for high-temperature shape-memory alloys, show a thermoelastic martensitic transformation, which produces their shape memory effect. However, the transformation to Ni₅Al₃ phase during heating of NiAl martensite can interrupt the reversible martensitic transformation; consequently, the shape memory effect in NiAl martensite might not appear after heating. The phase transformation process in binary Ni-(34 to 37)Al martensite was investigated by differential thermal analysis (DTA) method, and we found that the condition of reversible martensitic transformation was not the β → Ni₅Al₃ transformation, but rather the M → Ni₅Al₃ transformation occurring at 250 °C to 300 °C. Therefore, the transformation temperature of M → Ni₅Al₃ determined the highest operating temperature for the shape memory effect. For verifying the critical temperature, the phase transformation process was investigated for eight ternary Ni-33Al-X alloys (X=Cu, Co, Fe, Mn, Cr, Ti, Si, and Nb). Only Ti, Si, and Nb additions were found to be effective in dropping the M _s temperature, and they facilitated the shape memory effect in Ni-33Al-X alloys. In particular, the addition of Si and Nb raised the transformation temperature of M → Ni₅Al₃, a potentially beneficial effect for shape memory at higher temperatures. This article is based on a presentation made in the symposium entitled “Fundamentals of Structural Intermetallics,” presented at the 2002 TMS Annual Meeting, February 21–27, 2002, in Seattle, Washington, under the auspices of the ASM and TMS Joint Committee on Mechanical Behavior of Materials.     

Abstract Implementation of Algebraic Specifications in a Temporal Logic Language

A formal technique for incorporating two specification paradigms is presented,in which an algebraic specification is implemented by a set of abstract procedures specified in pre and post-condition style.The link between the two level specifications is provided via a translation from terms of algebraic specifications into temporal logic formulae representing abstract programs.In terms of translation,a criterion for an abstract implementation satisfying its specification is given,which allows one to check the consistency between the two levels of specifications.The abstract implementations can be refined into executable code by refining each abstract procedure in it.It is proved that the satisfication relation between a specification and its implementations is preserved by such refinement steps.     

A compact LTCC branch-line coupler UsingModified-T equivalent-circuit modelfor transmission line

In this letter, a compact branch-line coupler is proposed by making good use of the three-dimensional layout capability of the low-temperature co-fired ceramic (LTCC) substrate. This branch-line coupler is accomplished by using lumped-inductors and lumped-capacitors to realize the modified-T equivalent-circuit model for the transmission line so that the circuit size may drastically be reduced. Specifically, a very compact LTCC branch-line coupler with a size of 0.079/spl lambda//spl times/0.0717/spl lambda/ is implemented and carefully examined, where /spl lambda/ is the wavelength of the multilayer structure at the operating frequency f/sub 0/.     

Robust Space Time Receiver for CDMA-based Antenna Arrays

In this paper, we propose a new robust code division multiple access (CDMA) receiver of which weight vector is obtained by projecting the effective spatio-temporal signature waveform onto the signal subspace of the data covariance matrix. We verified our proposed algorithm by the field measured data obtained with a custom-built wideband CDMA test-bed. It will be shown that the proposed algorithm is robust to the signal mismatch.     

降低精炼钢中氢氧含量的探索

主要介绍通过优化炼钢生产工艺,使产品满足新的技术要求:S≤0.010％,P≤0.015％.[H]≤0.0002％,[O]≤0.0045％,[N]≤0.0055％。     

鱼雷罐喷粉预处理过程水模研究

在鱼罐喷粉预处理水模实验数据的基础上，进一步利用线性回归确定各工艺操作参数对喷吹基本参数（均混时间、粉剂穿透比和粉剂停留时间）的影响，得出各传输动力学基本参数的函数关系式。     

ARTIFICIAL INTELLIGENCE CONTROL OF FOOD FREEZER USING ROTATING DISK AIR DISTRIBUTOR FOR UNIFORM FREEZING

A rotating disk air distribution (RDAD) system consisting of a rotating disk with an air supply hole was fabricated to solve the nonuniform freezing problem of a freezer that supplies air through a duct at a fixed location. The RDAD system was installed in a freezer to supply freezing air in various directions by controlling the position of the air supply hole. An equation estimating air velocity in the freezer was developed based on heat balance between a brass block thermocouple (BBT) probe and ambient air stream. The equation was applied to the analysis of airflow patterns developed through the RDAD and the fixed duct system. For control of the RDAD system, a fuzzy matrix was constructed with the measured nodal temperature at 3D locations in the freezer and used to search for the optimum direction of air supply. Uniform cooling was accomplished with the RDAD system using fuzzy and expert algorithms leading to temperature deviation σ=0.666, compared with 0.289 of the fixed air supply system. Cooling rate of model food (BBT) was 1.75 times faster than that of the fixed system.     

Synthesis and characterization of poly(siloxane-urethane)s

A series of polyurethane block copolymers based on hydroxy-terminated polydimethylsiloxane and poly(propylene glycol) soft segments of molecular weights 1818 and 2000, respectively, were synthesized. The hard segments consisted of 4,4′-diphenylnethane diisocyanate and 1,4-butanediol as the chain extender. Samples with different molar ratios were prepared. We tried to synthesize polydimethylsiloxane-based polyurethanes (PDMS-PU) containing a hard block as major fraction and a soft block as minor fraction for preparing toughened rigid systems. After a study of the pure polydimethylsiloxane-based polyurethane and poly(propylene glycol)-based polyurethane (PPG-PU), (mixed polyol)-based block copolymers and blends of PDMS-PU and PPG-PU were synthesized, and characterized by means of differential scanning calorimetry, tensile testing and scanning electron microscopy. In (mixed polyol)-based copolymers and lower hard-segment content blends, macro-phase separation occurred, but blends with higher hard-segment contents showed significant reduction in amounts of phase separation.     

Evaluation of the efficacy of sequential intravenous-oral administration of pefloxacin in community-acquired lower respiratory tract infections in patients with underlying conditions

We studied the efficacy of sequential intravenous-oral pefloxacin therapy in community-acquired lower respiratory tract infection in 24 patients with one or more underlying conditions. Twenty-eight patients were enrolled into the study but only 24 patients were evaluated. There were 16 males and 8 females with a mean age of 66.9 +/- 11.2 years (mean +/- SD, range 46 to 87 years). The underlying conditions present were bronchiectasis, chronic obstructive lung disease and diabetes mellitus. Patients who were older than 70 years but without any underlying condition were also enrolled. All received 4 days of intravenous pefloxacin 400 mg twice a day followed by oral pefloxacin 400 mg twice a day for another 10 days. Assessment of success was based on clinical, microbiological and radiological improvement. Pefloxacin produced 79.2% clinical cure rate. Another 8.3% showed improvement. Pefloxacin was well tolerated. There were few adverse effects and none of the patients required a change of antibiotic. Pefloxacin was an effective and well tolerated treatment for respiratory tract infection and had the advantage of broad in-vitro antibacterial activity, twice daily dosing and sequential availability in an intravenous and oral formulation.