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61.
The outstanding performances of the Al2O3 cutting tools in terms of potential cutting speed can lead to substantial economies in the machining of metallic materials.Nevertheless, their widespread use is limited by some drawbacks such as the tendency to edge chipping and to the propagation of microcracks, which can lead to premature failures.These shortcomings are due to the intrinsic low toughness of the ceramic material, which is in turn related to its characteristics non-metallic bonds.A well-recognised method of increasing the toughness of brittle materials is the introduction of surface compressive stresses, which can be obtained through a suitable lamination geometry of the tools as consequence of the different coefficients of thermal expansion (CTE) of the constituent layers.The performances of an alumina/zirconia laminated cutting tool used for machining steel have been investigated and compared to those of a non-laminated commercial alumina/zirconia cutting tool. The different wear mechanisms are explained on the basis of the different microstructures and chemical compositions. We have shown that residual compressive stresses, measured by Piezo-Spectroscopy, are effective in avoiding the microchipping on the flank zone but cannot avoid larger fractures caused by the residual porosity. 相似文献
62.
The modeling of a reaction unit in which the absorption of a gas is associated with a liquid-phase catalytic reaction is a difficult problem in which both chemical and fluodynamic factors are involved. Many excellent reviews in which the chemical details of the liquid-phase catalytic processes and the engineering implications of the gas-liquid reactions are separately discussed are available. 相似文献
63.
Robert R. Stromberg Elio Passaglia Daniel J. Tutas 《Journal of research of the National Institute of Standards and Technology》1963,(5):431-440
The adsorption of polystyrene from cyclohexane below the theta temperature onto chrome ferrotype plate was studied by means of ellipsometry (polarization spectrometry). In this technique changes in the state of polarization of polarized light are measured upon reflection from a film-covered surface. The measurements were carried out in situ and permitted determination of the thickness and refractive index of the swollen polymer film at the solidsolution interface. A concentration range of 0.18 to 9.7 mg/ml was studied for polymer with a molecular weight of 76,000. The thickness of the adsorbed film increased with increasing solution concentration, reaching a plateau for most of the concentration range studied. The average thickness at this plateau was approximately 210 Å. The adsorbed film was highly swollen, consisting of about 12 g/100 ml of polymer for most of the concentration range. The amount adsorbed was determined to be approximately 2.25×10−4 mg/cm2 at the plateau. Comparison of the radius of gyration of polystyrene in solvent is made to the results obtained. 相似文献
64.
Minati L Aquino D Rampoldi S Papa S Grisoli M Bruzzone MG Maccagnano E 《Magma (New York, N.Y.)》2007,20(5-6):241-253
Object
Clinical diffusion imaging is based on two assumptions of limited validity: that the radial projections of the diffusion propagator
are Gaussian, and that a single directional diffusivity maximum exists in each voxel. The former can be removed using the
biexponential and diffusional kurtosis models, the latter using generalised diffusion-tensor imaging. This study provides
normative data for these three models.
Materials and methods
Eighteen healthy subjects were imaged. Maps of the biexponential parameters D
fast, D
slow and f
slow, of D and K from the diffusional kurtosis model, and of diffusivity D′ were obtained. Maps of generalised anisotropy (GA) and scaled entropy(SE) were also generated, for second and fourth rank
tensors. Normative values were obtained for 26 regions.
Results
In grey versus white matter, D
slow and D′ were higher and D
fast, f
slow and K were lower. With respect to maps of D′, anatomical contrast was stronger in maps of D
slow and K. Elevating tensor rank increased SE, generally more significantly than GA, in: anterior limb of internal capsule, corpus
callosum, deep frontal and subcortical white matter, along superior longitudinal fasciculus and cingulum.
Conclusion
The values reported herein can be used for reference in future studies and in clinical settings. 相似文献
65.
Implementing a 1GHz Four-Issue Out-of-Order Execution Microprocessor in a Standard Cell ASIC Methodology 总被引:3,自引:0,他引:3 下载免费PDF全文
This paper introduces the microarchitecture and physical implementation of the Godson-2E processor, which is a four-issue superscalar RISC processor that supports the 64-bit MIPS instruction set. The adoption of the aggressive out-of-order execution and memory hierarchy techniques help Godson-2E to achieve high performance. The Godson-2E processor has been physically designed in a 7-metal 90nm CMOS process using the cell-based methodology with some bitsliced manual placement and a number of crafted cells and macros. The processor can be run at 1GHz and achieves a SPEC CPU2000 rate higher than 500. 相似文献
66.
67.
An agent message is an attempted action upon the information state of the receiver that, if successful, would cause the receiver
to move to a new information state. A model of normative communication can define when messages are not merely unsuccessful
but instead are illegal or impossible actions upon the receiver’s internal state. The model uses the preconditions of the
other core message types, coupled with a model of task interdependencies, agent roles, and belief-desire-intention elements,
to define the preconditions for sending a canonical not-understood error message. By defining the space of messages that are legal actions on an agent’s internal state, a normative communication
model also defines a set of ‘reasons’ that can accompany the error message. A not-understood error message signals a mismatch between agent interaction models and the accompanying reason opens the possibility for agents
to realign their respective models. The paper discusses the matters arising from this possibility. This approach assumes that
normative communication behavior reflects normative domain behavior. It also assumes that each agent accesses the normative
model, in contrast with more centralized frameworks for defining normative interaction among agents and identifying interaction
errors. 相似文献
68.
69.
70.
Uxía Regueiro Maite Lpez-Lpez Rubn Varela-Fernndez Toms Sobrino Elio Diez-Feijoo Isabel Lema 《International journal of molecular sciences》2022,23(20)
Keratoconus (KC) is a corneal disorder whose etiology shares a close relationship with Lactoferrin (LTF) dysregulation and Toll-like Receptors 2 (TLR2) overexpression. This study shows how these two important biomarkers are clinically and molecularly interrelated, increasing knowledge about KC pathophysiology, and opening the door to future therapies. In this prospective clinical study, serum and tear LTF concentrations were quantified in 90 KC patients and 60 controls. A correlation analysis with multiple blood and tear immunoinflammatory mediators, and KC-associated tomographic parameters, was performed. An in vitro study using HEK-BlueTMhTLR2 cell cultures was also conducted to determine the expression and functionality of TLR2 under the influence of LTF treatment. As a result, a LTF decreased was observed in KC patients compared to controls (p < 0.0001), evidencing the strong correlation with TLR2 overexpression at systemic and ocular surface level, with inflammatory mediator upregulation and with KC severity. In stimulated cell cultures, TLR2 expression was decreased using 2 mg/mL of LTF. The levels of secreted embryonic alkaline phosphatase (SEAP) and interleukin-8 (IL-8) were also reduced in supernatants after LTF treatment. As conclusions, the dysregulation of LTF and TLR2 in the ocular surface of KC patients contributes to KC severity by maintaining a detrimental chronic immune–inflammatory state. The immunomodulatory properties of LTF on TLR2 expression suggest its potential as a therapeutic approach for KC. 相似文献