Cylindrical Aluminum Research Articles

Effect of Acidic Beverages on Color Stability and Microhardness of Various Esthetic Restorative Materials: A Comparative Study.

Aim:The aim of this study was to assess the effect of acidic beverages on color stability and microhardness of various esthetic restorative materials.Materials and Methods:A total of 60 samples were included in the present study. Group I: Microhybrid composite resin, Group II: Nanoceramic, Group III: ORMOCER (Organically Modified Ceramics). 10 mm internal diameter and 5 mm depth of cylindrical aluminum mold of were utilized to prepare the samples. All the esthetic restorative samples were submerged for 10 min in 25 ml of acidic drink (Coca-Cola) each day up to 15 days. Vickers diamond intender was used to measure the microhardness of each sample. These values were calculated with baseline, 7th, and 15th days for final microhardness values.Results:The mean surface microhardness of 63.20 ± 0.46 was shown by Group III which was slightly more than that in Group II (60.08 ± 0.34) and Group I (58.10 ± 1.76). Analysis of covariance did not show any statistically significant difference between the groups. The samples in Group I showed the highest reduction in surface microhardness value after immersion into acidic drink, followed by Group II and Group III on 7th day and 15th day. A statistically significant difference (P < 0.001) was found on the 7th day.Conclusion:The present study concludes that the Organically Modified Ceramics esthetic restorative material showed the finest behavior after being dipped in the acidic drink followed next by Nanoceramic and Microhybrid composite resin.

Temperature field characteristics of cylindrical aluminum alloy reticulated roof system under localized fire

Aluminum alloy shells are increasingly used in public buildings as a supporting structure for roofing enclosure construction in large spaces. In performance-based fire protection design, an empirical design criterion of 150 °C and relevant empirical formulas are used; however, the safety margin and prediction effect are not verified through full-scale experiments, and therefore, the effect of the roof system on the near-roof temperature field in practical engineering is yet to be investigated. In this study, a simulated fire experiment was conducted using a cylindrical aluminum alloy reticulated roof system model. The heat release rate of this restricted fuel fire source during the stable burning stage reached 8.1 MW. Fire Dynamics Simulator (FDS) was used to reproduce experimental results, and the numerical model of the shell member was simplified; further, existing empirical formulas of scholars such as Li were compared. The results indicated that although 150 °C is a large safety margin, it may limit architectural function. The simplified shell model provides an effect-equivalent approach for building thin-walled members in FDS. The shell is the main factor that delays the time required for the near-roof space to reach thermal equilibrium. The existing empirical formulas cannot be used for the studied roof system directly, and they may be improved through coefficient adjustment and other such methods.

Fabrication and evaluation of complicated microstructures on cylindrical surface.

Various items of roll molds are popularly used to fabricate different kinds of optical films for optoelectronic information and other new and high-tech fields, while the fabrication and evaluation of optical microstructures on a cylindrical roller surface is more difficult than ecumenically manufactured products. In this study, the machinability of microstructures on the roll based on a fast tool servo (FTS) system is investigated. First, the flexible hinge holder for a FTS is designed and its structural parameters are optimized with finite-element analysis and fatigue reliability theory. The tool radius compensation algorithm for complicated microstructures is then deduced based on the surface fitting and bilinear interpolation algorithm of discrete data. Meanwhile, the evaluation index and method are proposed by the medium section method. Finally, a machining test of aspheric arrays on a cylindrical aluminum surface is carried out, and the high quality of the microstructure indicates that the proposed method is able to be used to fabricate optical microstructures.

Performance evaluation of an arched plate solar air heater with porous aluminum wire mesh cylindrical fins

Solar air heater is used to heat air for space heating and drying process, but its low heat transfers between absorber plate and air account for its low thermal performance. Various surface geometries and fin modifications in a solar air heater have improved its thermal performance. The fabrication and performance evaluation of a solar air heater with an arched wavy absorber plate having porous aluminum wire mesh cylindrical fins attached have been investigated. The arched absorber plate design resulted in an increase in the air turbulence and vortex generation, which leads to the breaking of laminar sub-layer near the surface of the absorber plate and improved the heat transfer. In addition, cylindrical porous wire mesh aluminum fins resulted in an increase in the fin porosity which reduces the pressure drop and improved the thermal performance of the solar air heater. Comparative analysis has been carried for different arrangements at three different fluid flow velocities. The arched wavy absorber plate with fins resulted in better thermal performance with a temperature difference in the range of 55–70 °C approx. compared to the other arrangements at a fluid flow velocity of 5 m/s.

Determination of Cocoa Powder Particle Size Distribution by Using the Buoyancy Weighing-Bar Method

This study aims to examine the determination of the particle size distribution of cocoa powder by using the Buoyancy Weighing-Bar Method (BWM) with ethanol as a liquid medium. Laser diffraction and settling balance method are used as a comparison method in this study. The weighing bar used in BWM consists of cylindrical aluminium with a size of 10 cm x 210 cm. The measurement process is operated at ambient temperature and the measurement is carried out for 180 minutes. The results obtained indicate that the particle size distribution of cocoa powder can be measured by using BWM, and the results obtained are proportional to the measurement results by using the settling balance method, while laser diffraction is not suitable for measuring cocoa powder particle size distribution due to the shape of the cocoa powder that is not a sphere.

Pulsed-power-driven cylindrical aluminium liner implosions with a high aspect ratio at an 8 MA facility

First experimental investigations of foil aluminium liner implosions with a high aspect ratio of ∼ 103 at an 8 MA pulsed-power facility in China, motivated by possible application for magneto-inertial fusion, will be reported. Key diagnostics including UV cameras, micro-magnetic probes and x-ray pinhole imaging systems were fielded. Quasi-monochromatic UV images and optical streak data showed localized plasma formation at breakdown positions, suggesting that vacuum gaps in contact play a crucial role in long-time and non-uniform initiation. In liner ablation, quasi-periodic striation patterns were directly observed in UV self-emission images and were found to be azimuthally correlated with Rayleigh–Taylor instabilities. An m ≠ 0 azimuthal helical mode was obtained for the unmagnetized liner, which could be attributed to the large surface roughness that may act as an inherently and randomly seeded instability. Precursor plasma formation was confirmed by the observed x-ray emission on-axis at −70 ns by the end-on x-ray framing camera. Further quantitative current measurements taken by micro magnetic probes suggested that the current division due to precursor plasma was approximately 20% of the load current at −66 ns. Side-on imaging diagnostics indicated an evident liner implosion, however with a relatively low convergence ratio of ∼ 3.2 at stagnation. For the observed emission rings with much faster velocity in end-on x-ray images, possible mechanisms were discussed.

Interfacial geometry and its effect on the estimation of binary gas diffusivities in an isothermal Stefan column

The Stefan column was developed in the 19th Century to estimate binary gas diffusivities, DAB’s, and this goal has been achieved by many research groups. In the classical device, volatile liquid A is placed at the bottom and overlaid with stagnant gas B. A slow gas B sweep is provided at the top to remove the diffused gas A. However, column “end effects” have been largely ignored or neglected during data analysis. The present study addressed the effect of interfacial curvature on diffusivity determination. Curvature affects the interfacial transport area and the diffusion path length of gas A. Cylindrical aluminum punches with flat or curved tips were used to imprint solid naphthalene surfaces. The naphthalene-containing tubes were subjected to standard Stefan column sublimation-diffusion experiments at ∼60 °C and atmospheric pressure. With the mass loss from each tube obtained gravimetrically and the punch/tube dimensions, the experimental diffusivities, DAB,exp, were determined using the solution to a one-dimensional mass transport model for gas A. Tubes with flat interfaces had the smallest DAB,exp errors relative to the literature, while the curved surfaces (spherical and elliptical) had the largest when assumed to be flat in the calculations. When curvature was accounted for mathematically, the DAB,exp errors changed sign and magnitude depending on the actual punch shape and system dimensions. This is the first study to show that neglect of interfacial curvature can lead to significant errors in DAB,exp obtained using the isothermal Stefan column method. Therefore, curvature corrections should be considered whenever accurate DAB,exp’s are sought.

Shockwave generation by electrical explosion of cylindrical wire arrays in hydrogen peroxide/water solutions

We report the results of experiments investigating the implosion of a shock generated by the electrical explosion of a cylindrical aluminum wire array immersed in a &amp;gt;80% hydrogen peroxide/water solution. This solution was chosen as an additional energy source to the supplied electrical energy to generate the imploding flow with higher velocity. The experiments were conducted using a generator with the stored energy of ∼4.8 kJ, delivering to the array a ≤280 kA current rising during ∼1 μs. The backlighted images of the imploding shocks were recorded using a streak camera. Using different diameter wires, the explosion of arrays, characterized by critically damped and under-damped discharges, was studied. The experiments revealed that an array explosion in a 92% H2O2/H2O solution results in the second strong shock generated after the peak of the deposited electrical power, a solid indication of H2O2 detonation. This second shock converges ∼40% faster than the first strong shock generated by the wire explosion. One-dimensional hydrodynamic simulations of the shock convergence in H2O2/H2O solutions support this proposition.

Hardness Improvement of Aluminum Reinforced with Carbon Nanotubes through Forging and Friction Surfacing Process

This research deals with the improvement of hardness property on the composite material made from aluminum matrix reinforced with carbon nanotubes (Al-CNTs). There were two experiments conducted to enhance hardness property; forging and friction surfacing process. An axial mechanical force forged the Al-CNTs composite up to 40% of height of a cylindrical aluminum. A thermo-mechanical force was also applied in producing Al-CNTs coating by the friction surfacing process using Al-CNTs composite rod. Then, the hardness property obtained from these two processes was investigated. Results of the experiments showed that the hardness of Al-CNTs after the forging process improved 40–50% due to high amount of dislocation during forging which avoids deformation. This was indicating that 1 wt% CNTs does not decrease the hardenability of aluminum alloys. Meanwhile, the hardness Al-CNTs coating was not altered too much by the process of friction surfacing. This is becaused that the homogenous dispersion of the CNTs have occurred during the stir casting process.

A novel method to determine the mixed mode (I/III) dynamic fracture initiation toughness of materials

A novel hybrid experimental-numerical approach is proposed to determine the mixed-mode (I/III) dynamic fracture initiation toughness of engineering materials. To demonstrate the methodology, cylindrical aluminum alloy specimens with V-notch spiral cracks on the surface at spiral inclined angles of $${\beta _{sp}=0}^{\circ }, {11.25}^{\circ }, {22.5}^{\circ }, {33.75}^{\circ }$$ and $${45}^{\circ }$$ are subjected to dynamic torsion load using a torsional Hopkinson bar apparatus. The torque applied at the onset of fracture is measured through strain gages attached to the incident and transmitter bars. Stereo digital image correlation (StereoDIC) is performed to measure the full field deformation and crack mouth opening displacement (CMOD) as a function of loading time. Results are used to estimate the crack initiation time. The dynamic stress intensity factors are extracted numerically based on the dynamic interaction integral method using ABAQUS. The mode-I $$ {(K}_{Id})$$, mode-III $$(K_{IIId})$$, and mixed-Mode ($$K_{(I/III)d})$$ dynamic initiation toughness data as a function of spiral angles are presented and discussed.

Construction of microgrooves on the surface of alumina ceramic insulator to enhance its flashover strength

The fabrication method of grooves on the surface of alumina and their influence on the surface flashover characteristics of the alumina insulator were studied in this paper. To prepare grooves with a regular surface structure, the UV laser was applied to carve grooves on the surface of alumina ceramic, and dilute hydrochloric acid was used to corrode and remove the residual materials produced in the laser carving process. By adjusting the laser parameters, periodic grooves were prepared on the surface of a cylindrical alumina insulator with a groove depth of 60 µm and a groove width of approximately 50 µm on the laser spinning carving platform. Then, alumina insulators with different periods were prepared, and their vacuum surface flashover voltages were tested on a short pulsed high-voltage test platform. The test results indicated that the flashover voltages of the alumina insulators with laser carved periodic grooves were increased over 200%, and the improvement did not change much with the groove periods. A further study of the groove parameters showed that several grooves fabricated on the cathode end of the insulators were able to improve the flashover voltage of the alumina insulator to the voltage-withstand level of the fully grooved insulators.

Design of Log Periodic Dipole Array Antenna Ranging from 30 to 150 MHz

This paper describes construction of 16 element frequency independent and high bandwidth Log Periodic Dipole Array antenna which works within the frequency range of 30 to 150 MHz. The antenna of gain 8 dBi is designed by calculating the parameters from Matlab. Matlab program is used to calculate the parameters like length of elements, separation between elements, theoretical impedance, standing wave ratio, etc. Thus, the designed antenna was fabricated. The antenna element is a cylindrical aluminum pipe of diameter 9mm and the boom used is rectangular antenna pipe of dimension 1”X1”. Fabrication also includes other materials like M-seal, zip tie, etc for physical stability of the antenna. Log Periodic Dipole Array antenna design described in this paper is fed with 75 ohm coaxial cable to 1:1 balun. Balun is also used for impedance matching between the antenna and coaxial cable. Antenna analyzer is used to measure Standing Wave Ratio and Impedance which are found to be 1.623 and 71.5625 ohm respectively. The antenna can be a receiver or a transmitter type for operating with the signals within Very High Frequency band.

Effects of slope and flow depth on the roughness coefficient of lodged vegetation

Various vegetations are often grown on floodplains, and it has a significant influence on the movement of water flow and the protection of river slopes. In the experiments performed in this study, a cylindrical aluminum column with a diameter of 4 mm was selected to simulate natural vegetation and 7 classes of slopes (i = 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%, where i is the percentage of slope) and four categories of lodging angles (θ = 20°, 40°, 60°, and 80°) were assigned. The experimental results show that when i > 0%, the curves of Manning’s roughness coefficient (n) and flow depth (h) converge, and the degree of convergence gradually increases with the slope. In addition, Manning's roughness coefficient increases with the increase in slope at shallow flow depths, and decreases with the increase in slope at deeper flow depths. Exploration of the relationship between slope and vegetation roughness not only provides a theoretical support for flood control, but also has practical significance for river ecological environment management.

Efficient numerical evaluation of transmission loss in homogenized acoustic metamaterials for aeronautical application

This work wants to investigate the soundproofing level of passive acoustic metamaterials made of Melamine Foam and cylindrical Aluminum inclusions. Latest research shows promising acoustical possibilities on controlling certain frequencies, varying their geometry or material configuration. Typically, acoustic metamaterials are plates with inclusions that resonate in low frequencies and block basses. Investigation is carried to use them for the improvement of aircraft cabin quietness. An homogenization method is adopted to study the metamaterial: this is modelled as viscoelastic material with inclusions, using a frequency-dependent approach, and the effective properties of the homogenized metamaterial are derived using a micromechanics-based method that allow us to prescribe the simplest mesh for periodical geometries (in this case, cylindrical) by reducing drastically the computation time. MSC Actran is used for vibro-acoustic simulations, in particular for the evaluation of Sound Transmission Loss in metamaterial panels with different volume fractions and in a sandwich panel with metamaterial core. This last has been compared with a classical sandwich panel used in aeronautics and it has been demonstrated that metamaterial gets higher transmission loss over all the frequency range.

In Situ Study of Layer-by-Layer Polyelectrolyte Deposition in Nanopores of Anodic Aluminum Oxide by Reflectometric Interference Spectroscopy

The modification of cylindrical anodic aluminum oxide (AAO) nanopores by alternating layer-by-layer (LBL) deposition of poly(sodium-4-styrene sulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) was studied in situ by reflectometric interference spectroscopy (RIfS). In particular, the kinetics of polyelectrolyte deposition inside the pores with a diameter of 37 ± 3 nm and a length of 3.7 ± 0.3 μm were unraveled, and potential differences in the LBL multilayer growth compared to flat silicon substrates as well as the effect of different ionic strengths and different types of ions were investigated. RIfS measures the effective optical thicknesses, which is-for a constant pore length-proportional to the effective refractive index of the AAO sample, from which, in turn, the deposited mass of the polymer or the corresponding layer thickness can be estimated. Compared to the multilayer growth by the LBL deposition on the flat aminosilane-primed silicon wafers, which was assessed by spectroscopic ellipsometry, the thickness increment per deposited bilayer, as well as the dependence of this increment on the ionic strength (0.01-0.15) and the counterion type (Na+ vs Ca2+) inside the aminosilane-primed nanopores, was for the first bilayers to within the experimental error identical. For thicker multilayers, the pore diameter became smaller, which led to reduced thickness increments and eventually virtually completely filled the pores. The observed kinetics is consistent with the mass-transport-limited adsorption of the polyelectrolyte to the charged surface according to a Langmuir isotherm with a negligible desorption rate. In addition to fundamental insights into the buildup of polyelectrolyte multilayers inside the AAO nanopores, our results highlight the sensitivity of RIfS and its use as an analytical tool for probing processes inside the nanopores and for the development of biosensors.

Metal Artifact Reduction Method Based on Noncoplanar Scanning in CBCT Imaging

This study proposed a metal artifact reduction (MAR) method based on noncoplanar scanning for cone beam computed tomography (CBCT) imaging. Cylindrical aluminum and stainless steel bars were inserted into a phantom for cross-sectional and sagittal CBCT scanning. The metal bars were removed from scanning to obtain real CBCT images without metal artifacts. Corrected CBCT images were acquired after the artifact reduction of cross-sectional and sagittal images. Real CBCT images were used as the criteria, and the computed tomography value deviations of the original cross-sectional, sagittal, linear interpolation MAR (LIMAR), normalized MAR (NMAR), beam hardening correction (BHC) and proposed method were calculated. Most metal artifacts in the original image are removed in the corrected image, and thus, image quality is remarkably improved. The root mean square deviations of the original cross-sectional, sagittal, LIMAR, NMAR,BHC and proposed method are 122, 116, 90, 103, 92 and 85 HU, respectively, whereas their mean absolute deviations are 71, 73, 57, 55, 58 and 51 HU, respectively. The CT value deviation of the proposed method is the minimum. Conclusion: The proposed MAR method based on noncoplanar scanning can effectively reduce metal artifacts and improve CBCT image quality.

Electromagnetic and Thermal Analysis of Cylindrical Aluminum Billet Heated by 1MW HTS DC Induction Heater

In order to improve the efficiency of the conventional AC induction heater, an HTS DC induction heating technology has been proposed. A 1MW HTS DC induction heater has been developed, and the efficiency of the HTS DC induction heater can be more than 80% due to the HTS DC magnet with no AC loss. The electromagnetic and thermal analysis of the HTS DC induction heater is necessary for further optimization of the 1MW HTS DC induction heater. A 3D finite element simulation model for the coupling analysis of electromagnetic and thermal has been built based on the actual 1MW HTS DC induction heater and optimized for accelerating the computing speed by using permanent magnet instead of the HTS magnet. The heating process of the cylindrical aluminum billet has also been simulated and compared with the experimental results. The results show that the simulation results can be in line with the experimental results. What is more, the optimized simulation model can be used to further optimize the device parameters for different workpiece temperature distributions, or design and evaluate the new HTS DC induction heater in the future.

Experimental study of a PCM storage system integrated with a thermal solar collector

Recently, phase change materials (PCM) have become widely used in thermal storage systems for both industrial and domestic applications. These materials have good thermal properties, like thermal capacity and phase change temperature, however low thermal conductivity and high viscosity limits their heat transfer coefficient. This paper experimentally investigates the execution of a water-PCM storage system integrated with a flat plate solar collector. Paraffin wax is used as the PCM material and is packed in small cylindrical aluminum containers and accommodated in a hot water tank. In this study, an experimental test facility was designed and built and experiments were carried out in the City of Kerbala in Iraq. The study includes two different heat source types, namely a flat-plate solar collector and an electrical heater element. Experimental results show that the proposed configuration with the PCM material can produce hot water with up to 9.5 °C higher than that of the basic warm water storage system. In the case of the flat plate solar collector, the water remained hot, at about 28.5 °C more than the surrounding temperature during the solar system tests. This study highlights the potential of using PCM materials in heat storage systems and thermal solar energy.

Investigation of effects on heat transfer and flow characteristics of Cr-Ni alloy and aluminum pins placed in AISI 304 tube

In this study, the effects of cylindrical aluminum and Cr-Ni alloy pins placed in different arrangements on the inner wall of the pipe in the turbulent flow, the effects of heat transfer and flow characteristics on different Reynolds numbers have been experimentally investigated. The experiments were carried out under forced flow and constant heat flow conditions. Air is preferred as the fluid and the fluid velocity is adjusted between Reynolds number of 10000 and 50000. It has been observed that the Nusselt values obtained over the number of Reynolds number for the 5 different test tubes are arranged in a line from large to small, sequential row aluminum pin, sequential row Cr-Ni alloy pin, diagonal row aluminum pin, diagonal row Cr-Ni alloy pin, plain tube. There are also CFD analysis for each material, arrangements and pins geometry sets. On the other hand, it was determined that friction coefficient is directly proportional to the increase of heat transfer coefficient. As a result, it is observed that experimental results are compatible with both literature and numerical study.

Evaluation of the Impact of Acidic Drink on the Microhardness of Different Esthetic Restorative Materials: An In Vitro Study

The aim of this study was to assess the impact of acidic drink on the microhardness of different esthetic restorative materials. Sixty samples (20 samples of each group) were prepared. group I: nanohybrid ormocer-based composite, group II: glasiosite compomer, and group III: nanoceramic composite. A cylindrical aluminum mold of 5 mm depth and 10 mm internal diameter was used to prepare the samples. All the esthetic restorative samples were submerged in 25 mL of acidic drink (Coca-Cola) for 10 minutes each day up to 15 days. The microhardness of each sample was measured using a Vickers diamond intender. These values were matched with baseline, 7th day, and 15th day for final microhardness values. The mean surface microhardness of 61.13 ± 0.82 was shown by group I, which was slightly more than that in group II (59.65 ± 1.16) and group III (59.22 ± 1.30). Analysis of covariance did not show any statistically significant difference between the groups. The samples in group III showed the highest reduction in surface microhardness value after immersion into acidic drink, followed by group II and group I on 7th day and 15th day. A statistically significant difference (p < 0.001) was found on 7th day. The present study concludes that the esthetic restorative material-nanohybrid ormocer-based composite-showed the finest behavior both before and after being dipped in the acidic drink followed next by glasiosite compomer and nanoceramic composite. The various esthetic restorative materials with different physical characteristics and colors are marketed in numerous ways. Nevertheless, all dental restorative materials show surface degradation under acidic conditions over a period of time. So, it helps to know the surface microhardness changes of various esthetic restorative materials upon repeated exposure to acidic beverages.