排序方式: 共有64条查询结果,搜索用时 62 毫秒
31.
Muhammad Zakir B.D.S MSc PhD Taina Laiho Sari Granroth Edwin Kukk Chun Hung Chu James Kit-Hon Tsoi Jukka Pekka Matinlinna 《Surface and interface analysis : SIA》2022,54(7):747-758
This laboratory study aimed to compare, contrast, and evaluate the effect of a novel dual surface modification method on the adhesion strength of resin composite cement to titanium. C.p.-2 grade titanium samples were silica-coated, etched with HNO3(69vol %) or a blend of HCl (35vol %) and H3PO4 (85vol %), for 1 h at 80°C. Surface roughness was measured by surface roughness profilometry, topographic analysis by scanning electron microscopy (SEM), atomic force microscopy (AFM), and surface analyses by energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS). Silanization of all specimens was carried out after SEM, EDX, and AFM analysis, before enclosed mold microshear bond strength testing (EM-μSBS). Adhesion strengths were measured after artificial ageing: 1 day, 1 week, 4 weeks, and 8 weeks by EM-μSBS testing and failure mode analysis by optical microscopy. Polished titanium was used as a control. The highest surface roughness was observed in titanium samples treated with silica-coating + HCl-H3PO4 etching. The elemental composition confirmed the presence of Ti, O, C, with Si and Al in samples treated with silica-coating. A gradual decrease in EM-μSBS values was observed in all titanium samples with adhesive and cohesive failure modes. The novel dual surface modification method applied in this study suggests that silica-coating + HCl-H3PO4etching strongly affects titanium surface topography and roughness. The presence of Si on silica-coated surface modified titanium before silanization with an experimental silane has a positive effect on the EM-μSBS of titanium samples treated with silica-coating only or silica-coating + HNO3 etching. 相似文献
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Shelly Sheats Harkness PhD 《School science and mathematics》2013,113(7):319-320
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Bernard Rousseau MA Shigeru Hirano MD Roger W. Chan PhD Nathan V. Welham MSLT Susan L. Thibeault PhD Charles N. Ford MD Diane M. Bless PhD 《Journal of voice》2004,18(1):116-124
The purpose of the current study was to assess the histologic and rheologic properties of the scarred vocal fold lamina propria during a chronic phase of wound repair in a rabbit model. Eighteen rabbit larynges were scarred using a procedure that involved stripping the vocal fold lamina propria down to the thyroarytenoid muscle, using 3-mm microforceps. The approximate dimension of injury to the vocal fold was 3 x 1.5 x 0.5 mm [length x width x depth]. At 6 months postoperatively, histologic analysis of the scarred and control lamina propria in eight of these rabbits was completed for collagen, procollagen, elastin, and hyaluronic acid. Compared with control samples, scarred tissue samples revealed fragmented and disorganized elastin fibers. Additionally, collagen was significantly increased, organized, and formed thick bundles in the scarred vocal fold lamina propria. Measurements of the viscoelastic shear properties of the scarred and control lamina propria in the remaining 10 rabbits revealed increased elastic shear modulus (G') in 8 of 10 scarred samples and increased dynamic viscosity (eta') in 9 of 10 scarred samples. Although rheologic differences were not statistically significant, they revealed that on average, scarred samples were stiffer and more viscous than the normal controls. Histologic data are interpreted as indicating that by 6 months postinjury, the scarred rabbit vocal fold has reached a mature phase of wound repair, characterized by an increased, organized, and thick bundle collagen matrix. Rheologic data are interpreted as providing support for the potential role of increased, thick bundle collagen, and a disorganized elastin network on shear stiffness and dynamic viscosity in the chronic vocal fold scar. Based on these results, a 6-month postoperative time frame is proposed for future studies of chronic vocal fold scarring using the rabbit animal model. 相似文献
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Keith M. Roessig PhD Joseph C. Foster Jr. PhD Scott G. Bardenhagen PhD 《Experimental Mechanics》2002,42(3):329-337
Cure cast plastic bonded explosives (PBXs) consist of relatively hard particles in a soft binder. Under compressive loading,
the explosive cyrstals come into contact that causes high stress concentrations. The lines along which the crystals are loaded
are called stress chains. Damage done to these particle beds during compressive loading can lead to reaction. The photoelastic
effect of PMMA is exploited to examine the stress state within a two-dimensional particle bed. Stress chain development within
the bed is recorded and is shown to increase the stress state within some particles while leaving others unloaded. These concentrations
form early in the loading process, leading to fracture along the stress bridges and generating likely reaction initiation
sites. Through material point method simulations, contact friction is shown to have a large effect on the stress distribution
within the particle bed. 相似文献
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E. Motchenkova PhD Candidate P. M. Kort 《Journal of Optimization Theory and Applications》2006,128(2):431-451
The main feature of the penalty schemes described in current sentencing guidelines is that the fine is based on the accumulated
gains from cartel activities or price-fixing activities for the firm. The regulations suggest modeling the penalty as an increasing
function of the accumulated illegal gains from price fixing to the firm, so that the history of the violation is taken into
account. We incorporate these features of the penalty scheme into an optimal control model of a profit-maximizing firm under
antitrust enforcement. To determine the effect of taking into account the history of the violation, we compare the outcome
of this model with a model where the penalty is fixed. The analysis of the latter model implies that complete deterrence can
be achieved only at the cost of shutting down the firm. The proportional scheme improves upon the fixed penalty, since it
can ensure complete deterrence in the long run, even when penalties are moderate. Phase-diagram analysis shows that, the higher
the probability and severity of punishment, the sooner cartel formation is blocked. Further, a sensitivity analysis is provided
to show which strategies are most successful in reducing the degree of price fixing. It turns out that, when the penalties
are already high, the antitrust policy aiming at a further increase in the severity of punishment is less efficient than the
policy that increases the probability of punishment.
The authors thank Eric van Damme, Thomas Fent, and an anonymous referee for stimulating discussions and valuable comments. 相似文献
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We suggested some modifications to the controlled random search (CRS) algorithm for global optimization. We introduce new trial point generation schemes in CRS, in particular, point generation schemes using linear interpolation and mutation. Central to our modifications is the probabilistic adaptation of point generation schemes within the CRS algorithm.A numerical study is carried out using a set of 50 test problems many of which are inspired by practical applications. Numerical experiments indicate that the resulting algorithms are considerably better than the previous versions. Thus, they offer a reasonable alternative to many currently available stochastic algorithms, especially for problems requiring direct search type methods. 相似文献
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We describe a simple means of assessing the condition of the superficial lamina propria during endoscopy, which we use in our practice as an adjunct to careful stroboscopic examination. An intake of breath against partially adducted vocal folds serves to draw the mucosa inferomedially into the glottis, which reveals areas of diminished mobility, the relationship of mucosal lesions to deeper tissues of the vocal folds, and subtle submucosal lesions. This is possible because of the unique geometry of the glottis that renders the vector forces of airflow different at inspiration and expiration. Because the integrity of the superficial lamina propria is essential to healthy phonation, we have found the inspiratory maneuver useful across a wide variety of mucosal pathologic conditions. 相似文献