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  • 1
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: To enhance the comprehension on the internal rule of microstructure evolvement andquality-controlled relativity, the microstructure during the induction reheating of billets and diecasting of parts was systematically investigated. According to general structure observation and aidedanalysis of some computer simulations, the quantitative relationships between microscopicmorphology (including solid fraction and grain shape) and formation state was minutely discussed.The experimental results showed that liquid and solid phase in semi-solid slurry had different fillingtendency, fluid velocity of liquid phase in the area of high filling speed was relative quick and easy toflow into far area and corner. Solid particles far from gate possessed fine and round grain. Moreover,the structure configuration of original billets markedly affected forming process; billets with fine andround grain were required for the die-castings of complex shape and thin thickness. In the case of thebig change in shape and thickness of die-castings, the design of gating system and the control ofplunger speed should be so properly carried out as to avoid unequal distribution of solid and liquidphase in die-casting part as soon as possible
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 359-360 (Nov. 2007), p. 63-67 
    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: The bond in a grinding wheel cements the abrasive grains together, Among other factors,the bond plays a predominant part in the grinding wheel performances and on the quality ofgrinding results. This paper presents a literature review on organic bond grinding wheels. Itdiscusses the characteristic of the bond and the grinding performances of the two mainly types oforganic bond [1] grinding wheels: the resin bond grinding wheel and the soft-elastic grinding wheel.This paper provide a conclusion of the studying state of organic grinding wheel, which newstudying can draw lesson from
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  • 3
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Key engineering materials Vol. 334-335 (Mar. 2007), p. 525-528 
    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: Feasibility study of partially replacement of cement and ground sand by ground steel slag (GSS)and ground granulated blast furnace slag (GGBFS) in producing prestressed high strength concretepile (PHC) was conducted. The results showed that under normal curing(20oC, 95% RH)and thesteam curing condition (80oC), GSS possessed less reactivity than GGBFS. However, underautoclave curing condition (180 ℃, 1.0MPa), the reactivity of GSS can be effectively activated. Theautoclaving strength of the concrete made from 20% GSS with Blaine 550m2/kg, 55% cement and25% ground sand could reach 89.0 MPa which is not only higher than that of GGBFS (82.8MPa),but also higher than that of traditional PHC concrete (83.9Mpa, 70% cement and 30% ground sand).It’s feasible to produce PHC concrete by GSS with high fineness and optimized dosage
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Advanced materials research Vol. 53-54 (July 2008), p. 173-178 
    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: This work aims to obtain fine surface of silicon wafer during precision and ultra precisionmachining, and presents a new method called semibonded abrasive machining. A semibondedabrasive grinding plate is used in the semibonded abrasive machining. Abrasive particle of 1000#Green SiC and bond named SSB are adopted in the manufacture of the plate. Four plates withdifferent concentration of bond which are 1.5%, 2.5%, 3.5%, 4.5% respectively are made. The paperstudies the effect of concentration of bond, the control parameters which include the lapping time, theload, and the rotating velocity of the plate on the surface roughness. Experimental results indicateeach plate with different concentration of bond can obtain fine surface roughness. When the load orthe rotating velocity increases, there is little effect on the surface roughness, but the materialremoval rate increases correspondingly. The initial roughness of the silicon wafer surface lappingby the plate could be improved from Ra 0.2μm to Ra 0.02μm in 9 min
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  • 5
    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: The semibonded abrasive machining technique is expected to get high surface integrity andprocessing efficiency attributed to the „trap‟ effect which can reduce or even eliminate the surfacedamage induced by the larger particles. The goal of the work is to validate the „trap‟ effect by theexperiments of semibonded and loose abrasive machining under the conditions of adding and notadding the larger particles. Free surface damage monocrystal silicon wafers after polishing areadopted as workpieces, and 1000# SiC as abrasive particles while 180# SiC as the larger particles.The cast iron plate is used as grinding plate in the loose abrasive machining and different bondconcentration semibonded abrasive grinding plate SSB-1 and SSB-2 are used as grinding plates insemibonded abrasive machining. The roughness Rv and SEM photos of workpieces surface aretested to evaluate the extent of „trap‟ effect. The result shows that the semibonded abrasive grindingplate has the „trap‟ effect. The shore hardness value of the semibonded abrasive grinding plate canbe used to be one parameter to evaluate the degree of the ‟trap‟ effect of the semibonded abrasivegrinding plate
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 488-489 (July 2005), p. 465-472 
    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: Among the conventional and alleged bulk deformation processes in metalworking, equal channel angular extrusion (ECAE) is an innovative and attractive method to refine grain structures effectively. Grain refining by this process on magnesium alloy AZ31 was studied and compared to published data. An interesting and unique question is proposed and studied - that is, how dominant is the accumulated strain as obtained through multiple angular extrusion passes. Tensile tests were performed at room and high temperatures, and processed AZ31 was examined with optical andtransmission electron microscopy as well as x-ray diffraction
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  • 7
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 505-507 (Jan. 2006), p. 1027-1032 
    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: Nano-imprint lithography (NIL) is one of the most promising technologies for the massproduction of nano-meter patterns. A commercial hydraulic press and a pair of hot plates were used as the NIL system reported so far. It is, however, large and heavy. In this paper, therefore, a new moving-coil actuator is proposed and is intended to be used as the driving power for a compact NIL system. Compared to the commercial hydraulic NIL system, two advantages of the new NIL systemusing the moving-coil actuator are the ease of precise control as well as the compact dimensions. Thus, it is suitable for the fabrication and replication of small-sized nano-meter patterns. To develop such a new moving-coil actuator, the electromagnetic finite element method (FEM) is utilized. In addition, a simple but effective state-space model is also established to describe the dynamic behavior of the moving-coil actuator. Finally, a series of simulations and experiments arecarried out and the results show that the positioning accuracy of the developed moving-coil actuator is 1µm
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  • 8
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The morphology of semi-solid alloy is one of the key influence factors on the rheologicalbehavior of slurry during die filling and the mechanical properties of formed parts. However, it isdifficult to study such effect due to hard controlling of morphology in semi-solid state. In this paper,a self-developed Searle-type viscometer was used to determine the rheological behavior of A356aluminum alloy in different morphology, which was refined with the salts mixture of K2TiF6 andKBF4. The results indicated that the flow behavior of refined A356 alloy in the semi-solid statepossesses obviously thixotropic behavior under isothermal shearing condition with less time toreach steady state and lower steady apparent viscosity as compared to that of the A356 alloy. Duringcontinuous cooling at a constant shearing rate, the apparent viscosity of refined A356 slurry in thesame solid fraction decreased with the content of Ti. It is shown from quantitative image analysisthat the primary α-Al grain in the refined alloy evolves from dendrites to rosettes or sphericitys, andthen tends to be rounder and finer in higher Ti content. The mechanism of the influence ofmorphology on rheological behavior was also discussed in this paper
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  • 9
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: To aid the optimizing design of filling system, computer simulation technique is introducedto predict injection-forming process and to protect defects during trial manufacture of automotiveparts by using semi-solid die cast process. By comparing formed appearance of parts in experimentsand that in simulations, and observing the relationship between internal defects inspected by X-rayand flow field obtained in simulation, it is indicated that there are quite good agreements betweensimulation and experiment, right predictions for cast defects resulting from filling process can bemade and improving direction is proposed. The realization of numerical visualization for fillingprocess of high speed during semi-solid die cast process will play an important role in optimizingtechnology plan and process
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  • 10
    ISSN: 1573-4943
    Keywords: Succinate-ubiquinone reductase ; essential thiol group ; irreversible inhibition ; chemical modification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetic theory of the substrate reaction during modification of enzyme activity previously described by Tsou [Tsou (1988),Adv. Enzymol. Relat. Areas Mol. Biol. 61, 381–436] has been applied to a study of the kinetics of the course of inactivation of the mitochondrial succinate-ubiquinone reductase by 5,5′-dithiobis-(2-nitro-benzoic acid) (DTNB). The results show that the inactivation of this enzyme by DTNB is a conformation-change-type inhibition which involves a conformational change of the enzyme before inactivation. The microscopic rate constants were determined for the reaction of the inactivator with the enzyme. The presence of the substrate provides marked protection of this enzyme against inactivation by DTNB. The modification reaction of the enzyme using DTNB was shown to follow a triphasic course by following the absorption at 412 nm. Among these reactive thiol groups, the fast-reaction thiol group is essential for the enzyme activity. The results suggest that the essential thiol group is situated at the succinate-binding site of the mitochondrial succinate-ubiquinone reductase.
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