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1.
Holger Claussen 《International Journal of Wireless Information Networks》2008,15(3-4):137-147
In this paper, the feasibility of user-deployed femtocells in the same frequency band as an existing macrocell network is investigated. Key requirements for co-channel operation of femtocells such as auto-configuration and public access are discussed. Methods for femtocell power auto-configuration that ensure a constant cell radius in the downlink, and a low pre-definable interference impact on co-channel macrocells in the uplink are proposed. The theoretical performance of randomly deployed femtocells in such a hierarchical cell structure and the resulting impact on existing co-channel macrocells is analysed for a cellular UMTS network using system level simulations. 相似文献
2.
Eutectic compositions of Al2O3 and ZrO2 have been melted and rapidly solidified by shock-wave quenching, flame-pressure atomization and high-pressure water atomization. Quenching rates > 104 K/s resulted in amorphous particles which, on annealing, crystallized at 1310°C. Microcrystalline particles with tetragonal ZrO2 distributed in an ?-Al2O3 matrix formed at lower quenching rates. ?-Al2O3 transformed into α-Al2O3 on annealing at 953°C. 相似文献
3.
Reaction-bonded Al2 O3 (RBAO) ceramics were fabricated starting from mechanically alloyed Al2 O3 /Al, Al2 O3 / Al/ZrO2 , and Al2 O3 /Al/ZrO2 /Zr mixtures. Isopressed compacts were heat-treated in air up to 1550°C. Reaction-bonding mechanisms, kinetics, and the influence of ZrO2 and Zr additions are investigated. Independent of additive, oxidation of Al proceeds both as solid/gas and liquid/gas reaction, and the reaction kinetics follow a parabolic rate law. The reaction rate depends strongly on the particle size of Al. The activation energy of the reaction depends essentially on green density. Below the melting temperature of Al, in samples containing 45 vol% Al and 55 vol% Al2 O3 , it is 112 and 152 kJ/mol at ∼64% and ∼74% TD, respectively, while above the melting temperature, it lies in the range ∼ 26–33 kJ/mol. Zr additions reduce the activation energy to some extent. Samples with only ZrO2 additions exhibit nearly the same activation energies as ZrO2 -free samples, though ZrO2 has a very positive effect on the microstructural development in RBAO ceramics. Microstructure evolution and some strength data of RBAO bodies are also reported. 相似文献
4.
Synthesis of Novel Niobium Aluminide-Based Composites 总被引:5,自引:0,他引:5
Daniel E. Garcia Silvia Schicker Jorn Bruhn Rolf Janssen Nils Claussen 《Journal of the American Ceramic Society》1997,80(9):2248-2252
A reactive sintering process has been used to produce almost fully dense composites with interpenetrating networks of NbAl3 and Al2 O3 . The process involves the reaction synthesis of niobium aluminides and Al2 O3 from compacts of intensively milled aluminum and Nb2 O5 powder mixtures. During carefully controlled heating under an inert atmosphere, the oxide reduction by aluminum to form niobium aluminides and Al2 O3 proceeds at temperatures below the melting point of aluminum. At temperatures of >1000°C, the reaction-formed niobium aluminides and Al2 O3 sinter. The present paper discusses processing parameters, such as attrition milling, the heating cycle, and the metal:ceramic ratio in the starting mixture, that control microstructure development and mechanical properties. 相似文献
5.
Matthew L. Breeze Elisa Leyva‐Guerrero Grant R. Yeaman Yelena Dudin Ryan Akel Phil Brune Fred Claussen Cecil Dharmasri Jenny Golbach Rong Guo Carl Maxwell Laura Privalle Hilary Rogers Kai Liu Guomin Shan Michele Yarnall Denise Thiede Nancy Gillikin 《Journal of the American Oil Chemists' Society》2015,92(8):1085-1092
Soybean agglutinin (SBA) protein, also known as soybean lectin, is regarded as an anti‐nutrient due to its negative effect on the ability of monogastric animals to gain weight following consumption of raw soybean seed. Historically, SBA has been measured using a time‐consuming and cumbersome hemagglutination procedure. The objective of our research was to obtain a validated methodology that is precise and accurate in the measurement of SBA while allowing minimally equipped laboratories to effectively conduct the analysis, thus our focus was on evaluating an existing commercially available ELISA, an enzyme‐linked‐lectin‐assay (ELLA), and a hybrid ELISA/ELLA. A new ELLA technique that can detect and quantify lectins was chosen and modified specifically for the quantitation of SBA in soybean seed. The proposed ELLA methodology is similar to a standard sandwich ELISA, and uses polyacrylamide‐linked N‐acetylgalactosamine (Gal–NAc–PAA) for a capture phase and the biotinylated version (Gal–NAc–PAA–Biotin) for detection. Based upon the validation data, the ELLA method can precisely and accurately determine soybean lectin levels in soybean seed. The validated ELLA method was used to quantify SBA in nine commercial soybean varieties introduced between 1972 and 2008 and demonstrated that the natural variability of SBA is subject to the effects of genotype and environment. 相似文献
6.
7.
Shaun P. Gaus Martin P. Harmer Helen M. Chan Hugo S. Caram Nils Claussen 《Journal of the American Ceramic Society》2000,83(7):1599-1605
The general reaction behavior of the 3A process under the thermal explosion mode of synthesis has been investigated via a continuum model. The continuum model uses mass and energy balances to predict temperature difference ( T s,avg − T f ) curves, as well as profile curves of the reactant conversions and sample temperature. In particular, the effect of the dimensionless parameters associated with the rate of local heat generation (β, the thermicity factor), the activation energy (γ, the Arrhenius number), the rate of heat redistribution (α, the modified thermal diffusivity), the rate of heat transfer by convection (Bi, the Biot number or convective heat transfer parameter), and the rate of heat transfer by radiation (Ω, the radiative heat transfer parameter) were investigated. Conditions to control the reaction process, which should produce high-density final products, were determined. It was found that the overall maximum temperature may be reduced for high γ, low β, high α, and high Bi and Ω. In terms of processing conditions, this may be obtained by reducing the initial reactant concentrations, optimizing the particle size, using small sample sizes and high compaction pressure, and increasing the heat loss by using a high thermal conductivity inert gas. 相似文献
8.
Schraml C Schwenzer NF Martirosian P Claussen CD Schick F 《Magma (New York, N.Y.)》2011,24(4):201-209
Object
Examination of blood perfusion in the masseter muscle in the course of repetitive isometric contraction by arterial spin-labeling (ASL) MR imaging and additional T2 relaxation time measurements during and after masseter muscle activation. 相似文献9.
K Junker W Werner C Mueller W Ebert J Schubert U Claussen 《Canadian Metallurgical Quarterly》1999,14(2):309-313
In order to determine the value of fluorescence in situ hybridization (FISH) in the diagnosis and follow-up of bladder cancer interphase cytogenetics was performed on cells from urine and bladder washings. 50 ml of urine or bladder washings were collected. FISH was carried out using centromere probes for chromosomes 7, 8, 9 and 12 according to standard protocols. In each case 100 cell nuclei were analysed. Fifty-four samples from urine and 67 samples from bladder washing were analysed by FISH in comparison with results obtained by conventional cytology. Sensitivity of detection of tumor cells by FISH was 68.5% in urine and 63% in bladder washings regardless of tumor stage and grade. Sensitivity obtained by conventional cytology was 50% in urine and 77.3% in bladder washings. FISH on cells from urine samples is an effective complement to the standard urine cytology. Using centromere probes this approach is characterized by high specificity and sensitivity in tumors with T-category higher than pTa and grade higher than G1. 相似文献
10.
S. Neumaier H. H. Gutbrod T. Hubbeling B. W. Kolb M. L. Purschke M. Ippolitov V. Manko G. Mgebrishvili A. Nijanin Y. Sibiryak A. Tsvetkov A. Vinogradov C. Barlag C. Blume E. -M. Bohne D. Bucher A. Claussen T. Peitzmann G. Schepers H. Schlagheck 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》1995,360(3):593-597
We describe a new high voltage power supply, developed for the leadglass calorimeter of the WA98 experiment at CERN. The high voltage is produced for each of the 10 080 photomultiplier tubes of the detector individually, by the same number of active bases with on-board Greinacher voltage multipliers. The full VME-based HV controller system, which addresses each base via bus cables once per second, is miniaturized and fits into a single VME crate. The main advantages of this approach are the low heat dissipation, the considerably reduced amount of cabling and cost, as well as the high stability and low noise of the system. 相似文献