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71.
Dieter Gorenflo Untung Chandra Stephan Kotthoff Andrea Luke 《International Journal of Refrigeration》2004,27(5):492-502
The correct prediction of the heat transfer performance of the boiling liquid within the evaporator of a refrigeration unit is one of the essential features for the successful operation of the whole unit. A theoretically consistent calculation method for the heat transfer coefficient α in nucleate boiling, which should be based on the physical phenomena connected with vapour bubbles growing, departing and sliding on the wall and with the interactions of bubbles and of neighbouring nucleation sites within the microstructure of the heating surface, does not yet exist, despite the increasing number of papers on the subject in the recent past. Instead, the predictive methods for α available at present are empirical or semiempirical, especially for heat transfer conditions relevant in practice. Many of these correlations have been established in the form of power laws in which the relative influences of the main groups of variables on α are treated by separate factors. One of these may stand for the influence of the thermophysical properties of the boiling liquid or these properties will be included in several of the factors.New experimental results are presented for pool boiling heat transfer from a single horizontal copper tube (8 mm OD) to HFC-refrigerants (R32, 125, 134a, 143a, 152a, 227ea) and hydrocarbons (propane, i-butane). The results are compared to experimental data from the literature, and methods are discussed, how to incorporate the data in semiempirical correlations to describe the influence of the thermophysical properties of the fluids on the heat transfer performance. 相似文献
72.
In the absence of reliable live animal tests for the presence of BSE in cattle, a number of measures have been applied to exclude specified risk materials (SRM) from the human food chain. However, concerns remain that current practices in the stunning and slaughter of cattle may disseminate central nervous system (CNS) tissue to meat and meat contact surfaces. The objective of this study was to establish the particular risks of CNS tissue dissemination associated with captive bolt stunning and carcass splitting. The study applied enzyme linked immunosorbent assays (ELISAs) in the detection and quantification of two CNS proteins, syntaxin 1b and GFAP. The study observed extensive dispersal of both CNS proteins onto equipment, beef hide and personnel. These results demonstrate that despite the rigorous application of current SRM control policies, normal slaughter practices continue to present significant opportunities for CNS material including BSE prion present in the CNS of any sub-clinically infected cattle to contaminate meat entering the human food chain. 相似文献
73.
Luke S 《Evolutionary computation》2003,11(1):67-106
The evolutionary computation community has shown increasing interest in arbitrary-length representations, particularly in the field of genetic programming. A serious stumbling block to the scalability of such representations has been bloat: uncontrolled genome growth during an evolutionary run. Bloat appears across the evolutionary computation spectrum, but genetic programming has given it by far the most attention. Most genetic programming models explain this phenomenon as a result of the growth of introns, areas in an individual which serve no functional purpose. This paper presents evidence which directly contradicts intron theories as applied to tree-based genetic programming. The paper then uses data drawn from this evidence to propose a new model of genome growth. In this model, bloat in genetic programming is a function of the mean depth of the modification (crossover or mutation) point. Points far from the root are correspondingly less likely to hurt the child's survivability in the next generation. The modification point is in turn strongly correlated to average parent tree size and to removed subtree size, both of which are directly linked to the size of the resulting child. 相似文献
74.
Taylor Steven; Zvolensky Michael J.; Cox Brian J.; Deacon Brett; Heimberg Richard G.; Ledley Deborah Roth; Abramowitz Jonathan S.; Holaway Robert M.; Sandin Bonifacio; Stewart Sherry H.; Coles Meredith; Eng Winnie; Daly Erin S.; Arrindell Willem A.; Bouvard Martine; Cardenas Samuel Jurado 《Canadian Metallurgical Quarterly》2007,19(2):176
Accumulating evidence suggests that anxiety sensitivity (fear of arousal-related sensations) plays an important role in many clinical conditions, particularly anxiety disorders. Research has increasingly focused on how the basic dimensions of anxiety sensitivity are related to various forms of psychopathology. Such work has been hampered because the original measure--the Anxiety Sensitivity Index (ASI)--was not designed to be multidimensional. Subsequently developed multidimensional measures have unstable factor structures or measure only a subset of the most widely replicated factors. Therefore, the authors developed, via factor analysis of responses from U.S. and Canadian nonclinical participants (n = 2,361), an 18-item measure, the ASI-3, which assesses the 3 factors best replicated in previous research: Physical, Cognitive, and Social Concerns. Factorial validity of the ASI-3 was supported by confirmatory factor analyses of 6 replication samples, including nonclinical samples from the United States and Canada, France, Mexico, the Netherlands, and Spain (n = 4,494) and a clinical sample from the United States and Canada (n = 390). The ASI-3 displayed generally good performance on other indices of reliability and validity, along with evidence of improved psychometric properties over the original ASI. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
75.
Luke M. Geever César M. Mínguez Declan M. Devine Michael J. D. Nugent James E. Kennedy John G. Lyons Austin Hanley Sinead Devery Paul T. Tomkins Clement L. Higginbotham 《Journal of Materials Science》2007,42(12):4136-4148
In this contribution thermosensitive polymer matrices based on N-isopropylacrylamide have been developed. The hydrogels were prepared by photopolymerisation of N-isopropylacrylamide and 1-vinyl-2-pyrrolidinone in appropriate amounts of distilled water. The monomers were cured using
a UV-light sensitive initiator called 1-hydroxycyclohexylphenylketone. These copolymers were crosslinked using ethylene glycol
dimethacrylate and poly(ethylene glycol) dimethacrylate with molecular weights 600 and 1,000, at 0.1 wt% of the total monomer
content. The chemical structure of the xerogels was characterised by means of Fourier transform infrared spectroscopy (FTIR)
and the transition temperature of the hydrogels was determined using modulated differential scanning calorimetry (MDSC). By
altering the feed ratio, hydrogels were synthesised to have lower critical solution temperatures (LCST) around 37 °C. This
ability to shift the phase transition temperature of the gels provides excellent flexibility in tailoring transitions for
specific uses. The samples synthesised with PEG1000DMA crosslinking agents absorbed over 18 times their weight in water, while
maintaining good gel integrity thus falling marginally short of being characterised as superabsorbent. Each of the samples
showed similar deswelling behaviour at 37 °C. Rheological studies showed that increasing the molecular weight of the crosslinking
agent caused an increase in hydrogel strength. 相似文献
76.
A 1-Mb/s 916.5-MHz on-off keying (OOK) transceiver for short-range wireless sensor networks has been designed in a 0.18-mum CMOS process. The receiver has an envelope detection based architecture with a highly scalable RF front-end. Untuned RF circuits are leveraged and optimized in the receiver to achieve superior energy efficiency compared to tuned RF circuits. The receiver power consumption scales from 0.5 mW to 2.6 mW, with an associated sensitivity of -37 dBm to -65 dBm at a BER of 10 -3. The transmitter consumes 3.8 mW to 9.1 mW with output power from -11.4 dBm to -2.2 dBm. The receiver achieves a startup time of 2.5 mus, allowing for efficient duty cycling 相似文献
77.
Luke B. L. Pace P. E. 《IEEE transactions on information theory / Professional Technical Group on Information Theory》2007,53(5):1759-1766
The robust symmetrical number system (RSNS) is a modular system formed using Nges2 integer sequences and ensures that two successive RSNS vectors (paired terms from all N sequences) differ by only one integer. This integer Gray-code property reduces the possibility of encoding errors and makes the RSNS useful in applications such as folding analog-to-digital converters (ADCs), direction finding antenna architectures, and photonic processors. This paper determines the length of combined sequences that contain no vector ambiguities. This length or longest run of distinct vectors we call the RSNS dynamic range (Mcirc). The position of Mcirc which is the starting point in the sequence is also derived. Computing Mcirc and the position of Mcirc allows the integer Gray-code properties of the RSNS to be used in practical applications. We first extend our two-sequence results to develop a closed-form expression for Mcirc for a three-sequence RSNS with moduli of the form 2r-1,2r,2r+1. We then extend the results to solving the N-sequence RSNS ambiguity locations in general 相似文献
78.
Brett Jack Fontana Raymond P. Walsh Peter J. Thouret Wolfgang E. Gerber Max Kaufman Rudolph Thorington Luke 《Industry Applications, IEEE Transactions on》1981,(2):210-216
The design considerations for filaments in energy conserving incandescent lamps are described. Such lamps require compact high emissivity filaments to absorb infrared radiation reflected from heat mirrored focusing envelopes. The relationships between the electrical parameters in the radiation returning environment and in the clear surroundings are developed. Efficiency experiments with filaments of various geometries under conditions of radiation return were performed. A highly compact coiled coil filament seems most promising for development. A calculation is presented of the filament emissivity as a function of spacing of the windings in a coil. Measurements of the emissivity as a function of the pitch of a coiled coil filament agree with the calculation. 相似文献
79.
Chandrakasan A. P. Daly D. C. Finchelstein D. F. Kwong J. Ramadass Y. K. Sinangil M. E. Sze V. Verma N. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》2010,98(2):191-214
80.
The origins of the sampling theorem 总被引:1,自引:0,他引:1
The publications of Claude E. Shannon brought the sampling theorem to the broad attention of communication engineers. This article demonstrates how practicians, theoreticians, and mathematicians discovered the implications of the sampling theorem almost independent of one another 相似文献