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  • 1
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    A thermal model for analysis of hermetic reciprocating compressors under the on-off cycling operating condition (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-08-11
    Description: The on-off cycling operating condition of compressors is very common in low capacity refrigeration systems, being characterized by alternate periods in which the compressor is either operating (on) or idle (off). Thermal interactions between the compressor components affect its performance during the operating period and establish the initial condition for the compressor start up from idle condition. This paper presents a numerical model to predict the temperature field of hermetic reciprocating compressors under on-off cycling conditions. The model adopts a lumped formulation for control volumes formed in the fluid solution domain and the finite volume method to solve heat conduction in the solid components. Some required heat transfer coefficients were experimentally adjusted. Predictions for temperature were compared to measurements and good agreement was observed, especially for the thermal transient during the period in which the compressor is off.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 2
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    Thermal modelling and analysis of an oil-free linear compressor (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-08-11
    Description: Gas superheating in the suction system may significantly reduce the volumetric and isentropic efficiencies of small reciprocating compressors adopted for household refrigeration. This paper reports a thermal modelling approach developed to predict superheating in an oil- free linear compressor. A simulation code based on the finite volume method was adopted to solve heat conduction in the solid components and gas flow inside the compressor shell. In order to reduce the computational cost, the compression cycle inside the cylinder was modelled with a transient lumped formulation, but in a coupled manner with the remainder of the solution domain. Comparisons between numerical and experimental results of temperature showed discrepancies in some solid components and in the gas path along the discharge system. However, the model was able to predict suction gas superheating in good agreement with measurements. A sensitivity analysis of the temperature distribution with respect to two d...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics (IOP)
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  • 3
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    A thermal network model for induction motors of hermetic reciprocating compressors (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-08-11
    Description: This paper describes a simulation model for small reciprocating compressors with emphasis on the electrical motor modelling. Heat transfer is solved through algebraic equations derived from lumped thermal energy balances applied to the compressor components. Thermal conductances between the motor components are characterized via a thermal network model. The single-phase induction motor is modelled via an equivalent circuit, allowing predictions for the motor performance and distributed losses. The predicted temperature distribution is used to evaluate the stator and rotor windings resistances. The thermal and electric models are solved in a coupled manner with a model for the compression cycle. Predictions of temperature distribution, motor efficiency, as well as isentropic and volumetric efficiencies, are compared with experimental data at different operating conditions. The model is then applied to analyse the motor temperature as a function of input voltage and stator wire dia...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 4
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    A parametric optimization procedure for the suction system of reciprocating compressors (2015)
    Institute of Physics (IOP)
    Details
    Publication Date: 2015-08-11
    Description: The design of the suction system of compressors is of fundamental importance for efficiency and reliability. This paper reports a method developed to optimize the suction system of a reciprocating compressor, by using the genetic algorithm NSGA-II. The isentropic and volumetric efficiencies are used as objective functions, while the bending fatigue stress is used as a constraint to meet valve reliability. A simulation model of the compression cycle was coupled to the optimization procedure, with correlations for flow and force effective areas in terms of geometric parameters of the suction valve. Valve dynamics was numerically solved via the finite element method. The proposed optimization procedure was applied to a reciprocating compressor adopted for household refrigeration, identifying suction system geometries more efficient than the original design.
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 5
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    Translational blockade imposed by cytokine-derived UA-rich sequences (1989)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1989-08-25
    Description: The messenger RNAs specifying certain proteins involved in the inflammatory response and certain oncoproteins contain a conserved UA-rich sequence in the 3' untranslated region. This sequence, which is composed of several interspersed repeats of the octanucleotide UUAUUUAU, has been shown to destabilize mRNA in some eukaryotes. However, this effect is not seen when mRNAs are transferred to Xenopus oocytes, which made it possible to separate stability from translational regulation. For interferon, granulocyte-macrophage colony-stimulating factor, and c-fos RNAs, the UA-rich sequence was observed to preclude mRNA translation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kruys, V -- Marinx, O -- Shaw, G -- Deschamps, J -- Huez, G -- New York, N.Y. -- Science. 1989 Aug 25;245(4920):852-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Departement de Biologie Moleculaire, Universite Libre de Bruxelles, Belgium.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/2672333" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Base Sequence ; Colony-Stimulating Factors/*genetics ; Granulocyte-Macrophage Colony-Stimulating Factor ; Growth Substances/*genetics ; Interferon Type I/*genetics ; Molecular Sequence Data ; *Protein Biosynthesis ; *Proto-Oncogenes ; RNA, Messenger/metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Developmental biology. Hox genes in the limb: a play in two acts (2004)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2004-06-12
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Deschamps, Jacqueline -- New York, N.Y. -- Science. 2004 Jun 11;304(5677):1610-1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Hubrecht Laboratory, Uppsalalaan 8, 3584CT Utrecht, Netherlands. jacqueli@niob.knaw.nl〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15192209" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Basic Helix-Loop-Helix Transcription Factors ; *Body Patterning ; DNA-Binding Proteins/genetics/metabolism ; *Gene Expression Regulation, Developmental ; *Genes, Homeobox ; Hedgehog Proteins ; Kruppel-Like Transcription Factors ; Limb Buds/*embryology/metabolism ; Mice ; Morphogenesis ; *Nerve Tissue Proteins ; Trans-Activators/genetics/metabolism ; Transcription Factors/genetics/metabolism ; Zebrafish Proteins
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    Numerical analysis of gas leakage in the piston-cylinder clearance of reciprocating compressors considering compressibility effects (2017)
    Institute of Physics (IOP)
    Details
    Publication Date: 2017-09-06
    Description: Leakage is a major source of inefficiency in low-capacity reciprocating compressors. Not only does it lower the mass flow rate provided by the compressor, reducing its volumetric efficiency, but also gives rise to outflux of energy that decreases the isentropic efficiency. Leakage in the piston-cylinder clearance of reciprocating compressors is driven by the piston motion and pressure difference between the compression chamber and the shell internal environment. In compressors adopted for domestic refrigeration, such a clearance is usually filled by a mixture of refrigerant and lubricating oil. Besides its lubricating function, the oil also acts as sealing element for the piston-cylinder clearance, and hence leakage is expected to be more detrimental to oil-free compressors. This paper presents a model based on the Reynolds equation for compressible fluid flow to predict leakage in oil-free reciprocating compressors. The model is solved throughout the compression cycle so as to ...
    Print ISSN: 1757-8981
    Electronic ISSN: 1757-899X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
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    Identification of a transcriptional enhancer element upstream from the proto-oncogene fos (1985)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1985-12-06
    Description: Sequences upstream from the proto-oncogene fos were shown to be essential for its transcription. Transient expression of the chloramphenicol acetyl-transferase (CAT) gene linked to upstream sequences of the fos gene including its promoter reveals that sequences located 64 to 404 base pairs 5' to the fos cap site contain a typical transcriptional enhancer. Moreover, these enhancer sequences, which are strikingly conserved between mouse and human fos genes, coincide with a deoxyribonuclease I-hypersensitive site in the chromatin. The expression of the fos-CAT fusion genes was stimulated only two to three times by the fos inducer 12-0-tetradecanoyl phorbol-13-acetate. The fos enhancer does not appear to be tissue-specific.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Deschamps, J -- Meijlink, F -- Verma, I M -- New York, N.Y. -- Science. 1985 Dec 6;230(4730):1174-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/3865371" target="_blank"〉PubMed〈/a〉
    Keywords: Acetyltransferases/genetics ; Animals ; Chloramphenicol O-Acetyltransferase ; Chromatin/metabolism ; DNA, Recombinant ; Deoxyribonuclease I/metabolism ; *Enhancer Elements, Genetic ; *Genes, Regulator ; Humans ; Mice ; *Proto-Oncogenes ; *Transcription, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
    Electronic Resource
    Electronic Resource
    Phase Equilibria and Solidification of Mg-Rich Al-Mg-Si Alloys (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 508 (Mar. 2006), p. 621-628 
    Details
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The solidification and solid-state phase equilibria of four Al-Mg-Si alloys containing 30- 70%Mg and 0.5-3.5%Si, selected on the basis of an isothermal section of the Al-Mg-Si system calculated at 300 °C, have been investigated. Solidification paths of Mg-rich Al-Mg-Si alloys finish on ternary eutectics and the temperatures of two of these eutectic reactions, i.e. L↔(Al)+β+ Mg2Si and L↔(Mg)+γ+ Mg2Si, have been determined to be at ~ 448 °C and ~ 436 °C respectively by DTA. The characteristic temperatures recorded on the DTA curves are analysed and a linearrelationship is found between the peak temperature and the square root of the scanning rate
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/12/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.508.621.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Characterization of the murine Hox-2.3 promoter: involvement of the transcription factor USF (MLTF)
    Amsterdam : Elsevier
    Mechanisms of Development 33 (1991), S. 179-190 
    Details
    ISSN: 0925-4773
    Keywords: Promoter ; Transcription ; USF/MLTF
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0925-4773(91)90026-3
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