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  • 2005-2009  (11)
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Year
  • 1
    Electronic Resource
    Electronic Resource
    CARDIOVASCULAR ALTERATIONS BY CHRONIC INTERMITTENT HYPOXIA: IMPORTANCE OF CAROTID BODY CHEMOREFLEXES (2005)
    Oxford, UK : Blackwell Science, Ltd
    Clinical and experimental pharmacology and physiology 32 (2005), S. 0 
    Details
    ISSN: 1440-1681
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 1. Humans experiencing intermittent hypoxia (IH) owing to recurrent apnoea syndromes exhibit serious cardiovascular morbidity, including high blood pressure, increased sympathetic nerve activity, cardiac arrhythmia and myocardial infarction. Although apnoeas are accompanied by a simultaneous decrease in arterial O2 (hypoxia) and an increase in CO2 (hypercapnia), studies on experimental animals suggest that hypoxia, rather than hypercapnia, is the primary stimulus for developing hypertension and enhanced sympathetic nerve activity. Enhanced hypoxic-sensing ability of the carotid bodies and the ensuing reflex activation of the sympathetic nervous system have been suggested to play a critical role in cardiorespiratory alterations resulting from recurrent apnoeas.2. The purpose of the present review is to highlight recent studies demonstrating the effects of IH on carotid body sensory activity and its consequences on sympathetic activation in a rodent model of chronic IH. Adult rats exposed to chronic IH (15 s of 5% O2 followed by 5 min of 21% O2, nine episodes per h, 8 h/day for 10 days) exhibited selective enhancement of carotid body sensory response to hypoxia. In addition, chronic IH induced a novel form of sensory plasticity in the carotid body, manifested as sensory long-term facilitation (LTF). Functional changes in the carotid body occurred in the absence of morphological changes in the chemoreceptor tissue.3. Acute hypoxia increased expiratory modulated splanchnic nerve activity (SNA) and acute IH-induced LTF in SNA. Hypoxia-induced SNA activation was prevented by bilateral sectioning of the sinus nerves. Rats exposed to chronic IH exhibited enhanced hypoxia-induced sympathetic activation and augmented LTF of the SNA. Bilateral sectioning of the sinus nerves abolished these responses, suggesting chronic IH-induced alterations in carotid body sensitivity contribute to LTF in SNA and the subsequent cardiovascular alterations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1440-1681.2005.04209.x
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  • 2
    Electronic Resource
    Electronic Resource
    Solid Shell Element and its Application in Roll Forming Simulation (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 340-341 (June 2007), p. 347-352 
    Details
    ISSN: 1013-9826
    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: Solid shell element models which possess only translational degrees of freedom and areapplicable to thin structure analyses has drawn much attention in recent years and presented goodprospect in sheet metal forming. In this study, a solid shell element model is introduced into thedynamic explicit elastic-plastic finite element method. The plane stress constitutive relation isassumed to relieve the thickness locking and the selected reduced integration method is used toovercome volumetric locking. The assumed natural strain method is adopted to resolve shearlocking and trapezoidal locking problem. Two benchmark examples and a stage of roll formingprocess are calculated, and the calculating results are compared with those by solid element model,which demonstrates the effectiveness of the element
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.340-341.347.pdf
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  • 3
    Electronic Resource
    Electronic Resource
    Numerical Simulation of Warm Deep Drawing of AZ31 Magnesium Alloy Sheet with Variable Blank Holder Force (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 340-341 (June 2007), p. 639-644 
    Details
    ISSN: 1013-9826
    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: Blank holder force (BHF) plays an important role in sheet metal forming. Previousstudies demonstrated that variable blank holder forces can improve the cold formability ofsteel blank, but the research on the application of variable blank holder force in warm formingof magnesium sheet forming has not been well investigated. In this study, the mechanicalproperty of AZ31 magnesium alloy sheet is measured through some uniaxial tensile tests. Inorder to obtain the variational rule of the BHF, a mathematical model of BHF is deducedbased on the energy theory. The variational rule of the BHF over the punch stroke is analyzed.Finally, three profiles of the BHF curve are designed, and the numerical simulation of warmdeep drawing process of magnesium alloy sheet is also performed. A suitable variable blankholder force scheme is obtained through comparison among three results of simulation. Thesimulation indicates that the limiting drawing ratio of AZ31 magnesium alloy sheet can beimproved from 3.0 to 3.5 with the suitable blank holder force varied by an inverted V curve
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/54/transtech_doi~10.4028%252Fwww.scientific.net%252FKEM.340-341.639.pdf
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  • 4
    Electronic Resource
    Electronic Resource
    A resetting signal between Drosophila pacemakers synchronizes morning and evening activity (2005)
    [s.l.] : Nature Publishing Group
    Nature 438 (2005), S. 238-242 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The biochemical machinery that underlies circadian rhythms is conserved among animal species and drives self-sustained molecular oscillations and functions, even within individual asynchronous tissue-culture cells. Yet the rhythm-generating neural centres of higher eukaryotes are usually ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/nature04192
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Constitutive Model Development and the Numerical Study on the Drawability of AZ31 Sheet (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 488-489 (July 2005), p. 645-648 
    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: To examine the formability of a magnesium-based alloy AZ31 sheet, a temperature and strain rate related constitutive model for AZ31 sheet was developed based on tensile experiments. The relative parameters were obtained by fitting the equation to the experimental data. The comparison between the fitted and the experimental data proved the effectiveness of the model. Based on this model, the deep drawing process has been simulated with the finite element method and the limit drawing ratio (LDR) of AZ31 sheet was numerically studied. The study result was helpful to theapplication of the stamping technology for the magnesium alloy sheet
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/10/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.488-489.645.pdf
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  • 6
    Electronic Resource
    Electronic Resource
    Thermo-Mechanical Coupled Simulation of Warm Stamping of AZ31 Magnesium Alloy Sheet (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 546-549 (May 2007), p. 281-284 
    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: Uniaxial tensile test of a cross rolled magnesium alloy sheet was conducted under differenttemperatures and strain rates. The mechanical propriety of AZ31 magnesium alloy sheet wasanalyzed according to the true strain-stress curves. Then the non-thermal drawing process, duringwhich the temperature of die, blankholder and blank is 200℃ while the punch is kept at roomtemperature, was simulated by the thermo-mechanical coupled finite element method. Thedeformation behavior and the temperature change in the drawing process was investigated. Due to theheat conduction, there was non-uniform distribution of temperature along flange area, force transferarea and deformation area. Therefore the resistance of the force transfer area is enhanced and thewarm formability of magnesium alloy sheet can be further improved. The thermo-mechanicalcoupled simulation provides a good guide for the development of non-isothermal drawingtechniques
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.546-549.281.pdf
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  • 7
    Electronic Resource
    Electronic Resource
    Numerical Study on the Low Pressure Die Casting of AZ91D Wheel Hub (2005)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 488-489 (July 2005), p. 393-396 
    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: Most magnesium alloy components available for automobile are made through die casting. In this paper, PAM-CASTTM, commercial die casting simulation software based on the finite difference method, is employed to simulate the low-pressure die casting process of magnesium wheel hub. The temperature field and velocity field during filling and solidification stages are analyzed; the evolution of temperature distribution and liquid fraction was numerically studied. Then, the potentialdefects including the gas entrapments in the middle of the spokes, shrinkages between the rim and the spokes are predicted. The cooling performance of mould during casting is also investigated. Via analyzing the shrinkage defects generated under various cooling conditions, the cooling system set in the side mould is found to be more effective for enhancing the cooling capacity at the rim/spoke junction areas. With this cooling system, the hot spots at the junctions are obviously reduced andproduct quality is improved
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/10/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.488-489.393.pdf
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  • 8
    Electronic Resource
    Electronic Resource
    Experimental Research on Warm Deep Drawing of Magnesium Alloy Sheet by Variable Blank Holder Force Control (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 546-549 (May 2007), p. 285-288 
    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: A process of warm deep drawing of magnesium alloy with variable blank holder force hasbeen presented in this study. A hydraulic press that can realize adjustable blank holder forces wasdeveloped and its working principle and control system introduced. A warm deep drawing mould wasfixed and warm deep drawing experiments are conducted on the hydraulic press. Different variationschemes of the blank holder force with the stroke of the punch was tested, and compared withexperiment results. The experimental results show that adopting the variable blank holder forcetechnique can remarkably improve the forming performance and decrease the reduction ratio ofthickness from 15.21% to 12.35%. It is further demonstrated that the suitable blank holder forcevariation scheme is an inverted V curve with the punch stroke
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.546-549.285.pdf
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  • 9
    Electronic Resource
    Electronic Resource
    Numerical Analysis of Nano- or Micro-Crystalline Materials during ECAP by Dislocation Evolution Method (2007)
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 546-549 (May 2007), p. 687-690 
    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: By the severe plastic deformation, the equal channel angular pressing method (ECAP) hasbeen used for producing metal materials with the ultra-fine grain size and specific mechanicalproperties, in particular high yield strength. Analytical approaches have also been studied by fewresearchers. However, none of the previous analyses have taken into account the strain hardening ofthe material by considering the microstructure evolution. In this paper, the deformation behavior andthe strain harden of aluminum during equal channel angular pressing was calculated on the basis of adislocation evolution model. Then simulated stress, strain and strain distribution and strain hardeningwere analyzed. The strain is seen to rapidly increase when the material passes the shear area. Thismakes a maximum value of stress. And for the congregation of dislocation density, the maximal valueof strain increase with the process continuing
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.546-549.687.pdf
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  • 10
    Electronic Resource
    Electronic Resource
    Precipitation Photografting of Functional Monomer LiAA on Polypropylene Film Surface (2006)
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 11-12 (Feb. 2006), p. 359-362 
    Details
    ISSN: 1662-8985
    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: Lithium acrylate (LiAA) was applied as a functional monomer to modify the surfaceproperties of polypropylene films via photografting polymerization in a precipitation reactionsystem. Two-step photografting polymerization technique was adopted with benzophenone (BP) asthe photoinitiator and methanol as the solvent. ATR-FITR spectra proved the occurrence of graftingpolymerization of LiAA on the substrate. Gravimetric analysis was performed to investigate theinfluences of some important factors on the photografting polymerization of LiAA. SEM wasutilized to investigate the topography of the grafted film. The experimental results indicated thatelongation of the irradiation time could increase the grafting yield (Yg) and Yg performed amaximum at a certain concentration of LiAA. SEM images showed that regular particles evenlydispersed on the surface of the grafted film
    Type of Medium: Electronic Resource
    URL: http://www.tib-hannover.de/fulltexts/2011/0528/01/39/transtech_doi~10.4028%252Fwww.scientific.net%252FAMR.11-12.359.pdf
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