Laboratory Evaluation of Color Change and Surface Roughness of White Spot Lesions Treated with Resin Infiltration and Fluoride Therapy

Background and Objective: Two non-invasive treatment methods for treating white spot lesions (WSLs) include resin infiltration and fluoride therapy. Contradictions have been raised regarding the color change and surface roughness of the lesions based on these methods. Therefore, this study was conducted to investigate the color change and surface roughness of white spot lesions after treatment with resin infiltration and fluoride therapy. Methods: In this laboratory study, 40 buccal and lingual sections were prepared from 20 extracted healthy premolar teeth. 10 samples were considered as the control group, and in the other 30 samples, decayed lesions were created artificially. White spot lesions were randomly prepared in three groups without treatment, 0.05% sodium fluoride solution and resin infiltration (n=10). Then, the rate of color change and surface roughness of the samples after being placed in black tea and also after brushing were measured and compared using spectrophotometer and profilometer. Findings: The surface roughness of samples in resin infiltration, intact enamel and fluoride groups were 163.46±64.67, 259.6±43.12 and 293.92±41.36 micrometers, respectively (p<0.001). Before placing in tea and after brushing, no significant difference was observed in the color of the samples, but after staining, the color change in WSL (9.14±5.85), fluoride (17.40±4.13) and resin infiltration (12.13±4.88) groups was significant (p=0.004); the fluoride group showed significantly more color change compared to the WSL group (p=0.003), but the difference between the other groups was not significant. Conclusion: The results of this study show that if the resin infiltration method is used in the treatment of white spot lesions, less surface roughness and color change is observed compared to fluoride therapy

Basic effects of pulp refining on fiber properties- a review

The requirement for high quality pulps which are widely used in paper industries has increased the demand for pulp refining (beating) process. Pulp refining is a promising approach to improve the pulp quality by changing the fiber characteristics. The diversity of research on the effect of refining on fiber properties which is due to the different pulp sources, pulp consistency and refining equipment has interested us to provide a review on the studies over the last decade. In this article, the influence of pulp refining on structural properties i.e., fibrillations, fine formation, fiber length, fiber curl, crystallinity and distribution of surface chemical compositions is reviewed. The effect of pulp refining on electrokinetic properties of fiber e. g., surface and total charges of pulps is discussed. In addition, an overview of different refining theories, refiners as well as some tests for assessing the pulp refining is presented. (C) 2014 Elsevier Ltd. All rights reserved

Experimental investigation of thermo-physical properties, convective heat transfer and pressure drop of functionalized graphene nanoplatelets aqueous nanofluid in a square heated pipe

In the present study, a facile method is used for preparation of functionalized graphene nanoplatelets (f-GNP) nanofluids. The effective thermal conductivity, density, viscosity, specific heat capacity, overall heat transfer coefficient and friction factor for fully developed turbulent flow of f-GNP/water nanofluids flowing through a square pipe at a constant heat flux were studied. f-GNP uniform nanocomposite was produced from a simple acid treatment reaction procedure. The surface characterization was performed by various techniques such as XRD, FESEM, FTIR and Raman. The f-GNP nanofluids were prepared by dispersing the functionalized nanoparticles in base fluid (water) without the assistance of a surfactant. As made nanofluids were stable for a long time and no sedimentation was observed. The experimental data for f-GNP nanofluids have shown significant enhancement in thermal conductivity and overall heat transfer coefficient in comparison to the corresponding water data. The percentage of enhancement is a function of weight concentration of nanoparticles and temperature. Highest improvement of overall heat transfer coefficient is 19.68% with 9.22% raise in friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to those data from the base fluid

Heat transfer enhancement of turbulent nanofluid flow over various types of internally corrugated channels

A numerical study is carried out to investigate the effects of different geometrical parameters and various nanofluids on the thermal performance of rib-grooved channels under uniform heat flux. The continuity, momentum and energy equations are solved by using the finite volume method (FVM). Three different rib-groove shapes are studied (rectangular, semi-circular and trapezoidal). Four different types of nanoparticles, Al2O3, CuO, SiO2 and ZnO with different volume fractions in the range of 1% to 4% and different nanoparticle diameters in the range of 20nm to 60nm, are dispersed in the base fluids such as water, glycerin and ethylene glycol. The Reynolds number varies from 5000 to 25,000. To optimize the shape of rib-groove channels different rib-groove heights from 0.1Dh (4mm) to 0.2Dh (8mm) and rib-groove pitch from 5e (20mm) to 7e (56mm) are examined. Simulation results reveal that the semi-circular rib-groove with height of 0.2Dh (8mm) and pitch equals to 6e (48mm) has the highest Nusselt number. The nanofluid containing SiO2 has the highest Nusselt number compared with other types. The Nusselt number rises as volume fraction increases, and it declines as the nanoparticle diameter increases. The glycerin-SiO2 nanofluid has the best heat transfer compared to other base fluids. It is also observed that in the case of using nanofluid by changing parameters such as nanoparticle diameter, volume fraction and base fluids the skin friction factor has no significant change

Investigation of micro- and nanosized particle erosion in a 90° pipe bend using a two-phase discrete phase model

This paper addresses erosion prediction in 3-D, 90° elbow for two-phase (solid and liquid) turbulent flow with low volume fraction of copper. For a range of particle sizes from 10 nm to 100 microns and particle volume fractions from 0.00 to 0.04, the simulations were performed for the velocity range of 5-20 m/s. The 3-D governing differential equations were discretized using finite volume method. The influences of size and concentration of micro- and nanoparticles, shear forces, and turbulence on erosion behavior of fluid flow were studied. The model predictions are compared with the earlier studies and a good agreement is found. The results indicate that the erosion rate is directly dependent on particles' size and volume fraction as well as flow velocity. It has been observed that the maximum pressure has direct relationship with the particle volume fraction and velocity but has a reverse relationship with the particle diameter. It also has been noted that there is a threshold velocity as well as a threshold particle size, beyond which significant erosion effects kick in. The average friction factor is independent of the particle size and volume fraction at a given fluid velocity but increases with the increase of inlet velocities

Convective heat transfer enhancement with graphene nanoplatelet/platinum hybrid nanofluid

The work here looked into heat transfer performance in addition to friction loss of graphene nanoplatelet (GNP) - Platinum (Pt) hybrid nanofluids. The experiments were performed with non-changing limit parameters of heat-flux. Nanofluid movement was turbulent at a weight percentage ranging between 0.02 and 0.1%, with the Reynold number from 5000 to 17,500. The experimental findings revealed that compared with the base liquid, all nanofluid samples had higher heat transfer abilities. Nusselt number elevation and the increment of the heat transfer coefficient were found to be dependent on Reynold number, and the weight concentration of the nanocomposite. The greatest value recorded for Nusselt number was 28.48%, accompanied by a 1.109-fold penalty. There was a rise in friction factor with regards to the highest load of nanocomposite (0.1 wt%), with the Reynolds number of 17,500

Recent advances in cellulose nanofibers preparation through energy-efficient approaches: A review

Cellulose nanofibers (CNFs) and their applications have recently gained significant attention due to the attractive and unique combination of their properties including excellent mechanical properties, surface chemistry, biocompatibility, and most importantly, their abundance from sustainable and renewable resources. Although there are some commercial production plants, mostly in developed countries, the optimum CNF production is still restricted due to the expensive initial investment, high mechanical energy demand, and high relevant production cost. This paper discusses the development of the current trend and most applied methods to introduce energy-efficient approaches for the preparation of CNFs. The production of cost-effective CNFs represents a critical step for introducing bio-based materials to industrial markets and provides a platform for the development of novel high value applications. The key factor remains within the process and feedstock optimization of the production conditions to achieve high yields and quality with consistent production aimed at cost effective CNFs from different feedstock.</jats:p

Experimental investigation on the use of reduced graphene oxide and its hybrid complexes in improving closed conduit turbulent forced convective heat transfer

The present research highlighted on the use of Reduced Graphene Oxide (RGO) and its hybrid complexes in an effort to improve the convective heat transfer performance in closed conduit configuration. The RGO was synthesized via the reduction process of chemically exfoliated Graphene Oxide (GO) using Tannic Acid (TA) as reductant. Different amount of pristine carbon sources (i.e. Multiwall Carbon Nanotube (MWCNT), Carbon Nanofiber (CNF) and Graphene nanoPlatelets (GnP)) was allowed to interact with RGO to form a hybrid complexes aiming to explore the capability of the mixtures to promote heat transfer process. It was discovered that the trend of results appeared to coincide to the previous documented findings on heat transfer enhancement related to the addition of graphene based materials. Further, the enhancement of heat transfer coefficient was beyond the increase in thermal conductivity alone which suggested prominent contribution from both the particle and turbulent induced flow characteristics. The enhancement was more pronounced at the entrance of the heating section as well as at high Reynolds number (Re), paving opportunities for further investigation to gain in-depth understanding on the mechanisms involved. As high as 144% enhancement in Nu was recorded near the conduit entrance and about 63% at the downstream section. Studies on hydrodynamic parameters indicated negligible increase in pressure loss as well as friction factor for RGO and its hybrid mixtures, indicating the potential use of RGO as favorable additives in addressing the persistent limitation of conventional heat transfer liquid within the perspective of convective heat transport system

Graphene nanoplatelets–silver hybrid nanofluids for enhanced heat transfer

In the present experimental work, a new synthesis method is introduced for decoration of silver on the functionalized graphene nanoplatelets (GNP-Ag) and preparation of nanofluids is reported. The thermo-physical properties, heat transfer performance and friction factor for fully developed turbulent flow of GNP-Ag/water nanofluids flowing through a circular tube at a constant heat flux were investigated. GNP-Ag uniform nanocomposite was produced from a simple chemical reaction procedure, which includes acid treatment for functionalization of GNP. The surface characterization was performed by various techniques such as XRD, FESEM, TEM and Raman. The GNP-Ag nanofluids were prepared by dispersing the nanocomposite in distilled water without the assistance of a surfactant and/or ultrasonication. The prepared nanofluids were found to be stable and no sedimentation was observed for a long time. The experimental data for GNP-Ag nanofluids were shown improvements of effective thermal conductivity and heat transfer efficiency in comparison with the corresponding to the base-fluid. The amount of enhancement was a function of temperature and weight concentration of nanoparticles. Maximum enhancement of Nusselt number was 32.7% with a penalty of 1.08 times increase in the friction factor for the weight concentration of 0.1% at a Reynolds number of 17,500 compared to distilled water. Improved empirical correlations were proposed based on the experimental data for evaluation of Nusselt number and friction factor