Effect Of Cavity Configuration Research Articles

High-resolution spectral analysis of long single-frequency pulses generated by a self-sweeping Yb-doped fiber laser

Continuous wave self-sweeping operation is demonstrated in a classical ring cavity configuration of Yb-doped fiber laser with a saturable absorber, which is usually used to obtain single-frequency lasing. Using heterodyne-based high-resolution spectral analysis we demonstrate that the laser generates a series of long (up to 1 ms) rectangular pulses consisting of single frequency radiation (the linewidth <0.7 MHz). At the same time, the lasing frequency changes between pulses regularly in a stepwise manner by one intermode beating frequency within a self-sweeping range of 100 pm. The effect of cavity configuration on pulse parameters (duration and chirp) is investigated. We also demonstrate that saturable absorbing mirrors design can be used to control the self-sweeping direction and value of the frequency jump.

LES study on the effect of cavity configuration on combustion characteristics of a scramjet combustor with air-throttling

Three-dimensional Large Eddy Simulation (LES) is performed to numerically investigate the implication of air throttling on the combustion performance of ethylene fueled dual-cavity scramjet combustor. The augmentation of combustion performance with the conjunction of throttling and dual cavity being established, the effects of L/D ratio and interspacing distance between the cavities is discussed. Our results indicate that combustion efficiency is enhanced owing to the pre-combustion shock train generated because of the introduction of air throttling for different configurations of cavity. Further, the combination of air-throttling with dual cavity improves combustion performance in comparison with dual cavity without air throttling. Also, dual cavity with L/D = 7 and spacing S = 12 mm displays intense and larger recirculation zones in comparison with other configurations being considered. It is found that for dual cavity with L/D = 7 and S = 12 mm, shorter mixing length and higher penetration height is attained.

Numerical analysis of supersonic flows over an aft-ramped open-mode cavity

The characteristics of supersonic cavity flows were investigated using large eddy simulation together with the acoustic analogy method. A fifth-order hybrid compact-weighted essentially non-oscillatory scheme was applied to calculate the convective flux, and a sixth-order compact scheme was used for the viscous flux. Farassat's Formula 1A was used to solve the Ffowcs William–Hawkings equations to obtain the far-field acoustic pressure fluctuations. The effects of cavity configuration and flow Mach number on the pressure waves generated by the interaction of shear vortices and cavity were compared. The ramped rear-step of the cavity can increase the more-organized level of flow coherent structures, and decrease the static pressure distribution on the cavity bottom-wall. The attenuation of the interactions between the shear layer vortex and the aft-ramped wall of the cavity can reduce the feedback of pressure waves upstream. The energy of the main frequency significantly decreases for the far-field acoustics in the upstream flow over the ramped rear-step cavity. Thus, the effectiveness of noise reduction by the rear-ramp is considerable for the area upstream of the cavity for the present conditions, but it is not the case opposite to and downstream of the cavity. The present conclusions are valuable for evaluating the performance of noise suppression by cavities embedded in supersonic inflows in engineering applications.

Effect of Cavity Configuration (C Factor) on the Marginal Adaptation of Low-Shrinking Composite: A Comparative Ex Vivo Study

Aim. To investigate the effect of C factor on marginal adaptation of low-shrinking composite (Silorane).The null hypothesis was that the marginal adaptation of “Silorane” is not affected by the cavity configuration. Materials and Methods. A Silorane based and a methacrylate based composites, with their corresponding self-etch adhesive systems “Filtek Silorane/Silorane Adhesive Bond System and Filtek Z250/Prompt L-Pop” respectively were used. Standardized cavities were prepared on the buccal surfaces of 100 maxillary premolars. Teeth were grouped into 5 groups (n = 20), for the 5 C factors. Restored teeth were subjected to thermocycling. Microleakage testing was done and linear dye penetration was assessed using a stereomicroscope. Statistical analysis was done using the Student's t-test. Results. For the methacrylate based systems' overall leakage score was significantly higher than the Silorane-based one (P = 0.034). For the methacrylate-based, leakage was found in all tested teeth groups except group 1 (C factor 1/5). For the Silorane, One-way ANOVA revealed a statistically significant increase in dye penetration in the 5th group (P = 0.010). Conclusions. The null hypothesis was rejected. The Silorane-based resin although it resulted in a statistically significant good marginal adaptation, it showed tendency toward a high leakage score with C-factor of 5.

Effect of Cavity Configuration on Bonding of Self-etch Adhesive Systems to Cavity Floor Dentin : Examination of Bonding Reliability

Effect of Cavity Configuration on Bonding of Self-etch Adhesive Systems to Cavity Floor Dentin : Examination of Bonding Reliability

Effect of cavity configuration and aging on the bonding effectiveness of six adhesives to dentin

Objectives: The purpose of this study was to determine the effect polymerization contraction stress may have on bond durability. Methods: Bonding effectiveness was assessed by micro-tensile bond strength testing (μTBS) and electron microscopy. The μTBS to flat dentin surfaces and in standardized cavities was determined (this after 1 day as well as 1 year water storage). Six adhesives representing all current classes were applied: two etch-and-rinse (OptiBond FL, Kerr; Scotchbond 1, 3M ESPE), two self-etch (Clearfil SE Bond, Kuraray; Adper Prompt, 3M ESPE) and two glass-ionomer (Fuji Bond LC, GC; Reactmer, Shofu) adhesives. Results: The conventional 3-step etch-and-rinse adhesive OptiBond FL bonded most effectively to dentin, and appeared insensitive to polymerization shrinkage stress and water degradation. The 2-step self-etch adhesive Clearfil SE Bond most closely approached this superior bonding effectiveness and only slightly lost bond strength after 1-year water exposure. The 2-step etch-and-rinse adhesive Scotchbond 1 and the ‘strong’ 1-step self-etch adhesive Adper Prompt appeared very sensitive to cavity configuration and water-aging effects. The 2-step resin-modified glass-ionomer adhesive Fuji Bond LC only suffered from shrinkage stress, but not from 1-year water-exposure. Remarkable also is the apparent repairability of the ‘mild’ 1-step glass-ionomer adhesive Reactmer when stored for 1 year in water, in spite of the very low 1-day μTBS. Significance: Simplified bonding procedures do not necessarily imply improved bonding performance, especially in the long term.

The effect of cavity configuration on the mechanical properties of resin composites

이 연구의 목적은 와동의 형태가 굴곡강도와 탄성계수 등 복합레진의 물리적 성질에 미치는 영향을 평가하는 것이다. 복합레진은 Clearfil AP-X(Kuraray, Japan)와 Esthet-X(Dentsply, USA)가 이용되었으며, 상아질 접착제는 Clearfil SE Bond(Kuraray, Japan)와 Prime & Bond NT(Dentsply, USA)를 사용하였다. 대조군의 시편은 split steel mold(25mm×2mm×2mm) 내에 상기 2종류의 복합레진을 충전하여 2개의 대조군 시편을 제작하였으며, 2.4 및 3.4의 C-factor를 부여하기 위한 유리 모형와동을 제작하고, 와동 내에 상기 2종류의 복합레진을 충전하기 전 유리와동의 내면은 sandblasting 처리하고 각각의 복합레진과 동일회사 제품의 상기 상아질 접착제로 처리한 후, 복합 레진을 각각 충전하여 4개의 실험군을 제작하였다. 제작된 실험군 시편은 저속 diamond saw로 충전된 복합레진 부위 의 중심부를 통과하도록 절단하여 레진기둥(25mm×2mm×2mm)이 되도록 제작하였다. 제작된 시편을 37°C의 증류 수에 24시간 동안 보관 후, 만능시험기(EZ Test, Shimadzu, Japan)를 이용하여 분당 1mm의 crosshead speed로 3 점 굴곡강도를 측정하였다. 또 Linometer(R&B, Korea)를 이용하여 복합레진의 중합수축량을 측정하였으며, 굴곡강 도측정 후 시편의 파단면은 주사전자현미경(S-2300, Hitachi, Japan)을 이용하여 관찰하였다. 실험결과의 통계분석 은 95% 수준의 one-way ANOVA/Tukey’s test를 이용하여 결과를 얻었다. 실험에 이용된 2종류 복합레진의 굴곡강 도와 탄성계수는 C-factor의 증가에 따라 감소하였으며, 파단면 또한 C-factor의 증가에 따라 더 불규칙해지는 양상을 나타내었다. 본 실험의 결과 hybrid형 복합레진이 micro-hybrid형 복합레진에 비해 C-factor의 영향을 더 많이 받는 것으로 나타 났으며, 와동의 C-factor 증가가 굴곡강도나 탄성계수와 같은 복합레진의 물리적 성질을 저하시킨다는 것을 의미하였 다.

Effects of cavity configuration on bond strength and microleakage of composite restoration

Effects of cavity configuration on bond strength and microleakage of composite restoration

Effects of dentin depth and cavity configuration on bond strength.

During polymerization of resin composites, shrinkage stresses compete with resin-dentin bonds in a manner that can cause failure of the bond, depending upon the configuration of the cavity, its depth, and the restorative technique. The hypothesis tested in this study was that the effect of cavity configuration (C) and remaining dentin thickness (RDT) influence resin bond strength to the dentin of Class I cavity floors. The occlusal enamel was ground to expose a flat superficial dentin surface as a control (superficial dentin, C-factor = 1) in human extracted third molars. Cavities 3 mm long x 4 mm wide were prepared to a depth 2 mm below the ground dentin surfaces (deep dentin within cavity floor, C-factor = 3). To assess the relationship between C-factor and RDT, we removed the walls of cavities, making a deep flat surface for bonding (deep dentin, C-factor = 1). The teeth were restored with either Clearfil Liner Bond II (LB II), One-Step (OS), or Super-Bond D Liner (DL), followed by Clearfil Photo Posterior resin composite. After 24 hrs' storage in water, the teeth were sectioned vertically into 3 or 4 slabs (0.7 mm thick) and trimmed for the micro-tensile bond test so that we could determine the strength of the resin bonds to the pulpal floor. All groups gave high bond strengths to superficial dentin, but OS and DL gave significantly lower bond strengths to flat deep dentin when the C-factor was 1. When the C-factor was increased to 3 by the creation of a three-dimensional cavity preparation, the bond strengths of all materials fell (range, 21 to 35%), but the difference was significant (p < 0.05) only with DL. SEM observations of failure patterns showed that specimens with high bond strengths tended to exhibit cohesive failures within the hybrid layer, while specimens exhibiting low bond strengths showed failures at the top of the hybrid layer. Some adhesives do not bond well to deep dentin, making them more susceptible to polymerization shrinkage stress that develops in cavities with high C-factors.

Control of Combustion in a Closed Chamber by a Hydrogen Flame Jet Ignition. Effect of Hydrogen-Oxygen Flame Jet.

Jet ignition method by hydrogen oxygen flame is proposed to control the combustion of lean mixtures. Hydrogen oxygen flame jet is supplied from the cavity whose volume is less than one percent of main chamber volume through a nozzle. The burning velocity of the cavity gas is very fast and the combustion duration can be drastically shortened. The pressure oscillation often takes place. The heat flux at the wall of main chamber becomes bigger than the case of hydrogen air mixture. Combustion processes for various conditions are investigated. The effects of cavity configuration on pressure and heat flux histories are shown. The bigger the cavity volume becomes, the larger the pressure oscillation and the value of heat flux become.

A numerical study of laminar heat transfer at bottom surface of a cavity submerged in separated flow region of duct

For the two cavity models whose upward and downward wall heights are different from each other, laminar heat transfer is studied numerically in a finite difference method. The effects of cavity configuration, free-stream velocity and buoyancy force on flow and temperature fields as well as heat transfer at the bottom surface are discussed. The flow pattern of DOF (Downward-Facing cavity)-model is more intricated than that of UPF (Upward-Facing cavity)-model, depending on the aspect ratio of cavity or main flow velocity. The mean Nusselt numberNu m at the bottom surface of both cavity models tends generally to increase with increasing ReHorGr w/Re H 2 . However, in the flow region ofRe H & 500 for DOF-cavity, theNu m for 0.4 ≦ D2/D1 ≦ 0.6 is somewhat lower than that obtained from the other cavities and does not always increase with increasingRe H.