Effect Of Linear Velocity Research Articles

Effect of Linear Velocity on Magneto-mechanical Properties of Ni-Mn-Ga-Based Melt-Spun Ribbons

The study brings original data on the effect of linear velocity during melt-spinning process on magneto-mechanical properties of Heusler Ni-Mn-Ga-based melt-spun ribbons. The research revealed that different linear velocity of the copper wheel had a significant impact on the ribbon's geometry resulting in distinct changes in magneto-mechanical properties. X-ray diffraction measurements were used to examine the phase composition, confirming the presence of L21 austenite phase. To assess the mechanical properties of the Ni-Mn-Ga-based melt-spun ribbons, cyclic bending experiments were conducted at a strain rate of 0.1 mm/s. Additionally, experiments involving magnetic field-induced bending were carried out in an external magnetic field ranging from 0 to 0.28 T. Finally, it was observed that there was a proportional relationship between the linear velocity of the copper wheel and magnetic field-induced ribbons deflection. Conversely, the dependence between linear velocity and mechanical bending load was found to be inversely proportional. Electron backscattered diffraction measurements revealed that melt-spun ribbons produced at high linear velocity of 18.5 m/s exhibited fine-grained microstructure in contrast to low linear velocity of 3 m/s. Based on these results it seems feasible to optimize the functional properties of the studied ribbons by varying the linear velocity of the melt-spinning process.

Mixing performance of cohesive particles in a double barrel with differential velocity based on DEM

The double barrel with differential velocity (DBDV) was proposed to improve the mixture quality. However, the mixing mechanism of cohesive particles in the DBDV is unclear. So, the mixing performance of cohesive particles in the DBDV was studied. The cohesive force between particles was simulated using a viscous contact model. The effects of linear velocity, inclination and cohesive force on the mixing performance were studied. The mixing process of particles was analyzed through mixing uniformity, mixing time, velocity, and contact forces. The results show that excessive cohesion cannot promote the dispersion of particles in the mixture, affecting production efficiency. The motion intensity of particles in the differential region is stronger than that in the non-differential region. The differential zone is suitable for particle motion with high cohesion. This study reveals the detailed mixing behavior of cohesive particles in DBDV, which provides operational guidance for the actual road material mixing process.

Improved magnetorheological finishing process with arc magnet for borosilicate glass

ABSTRACT In the process of magnetorheological polishing of planar optical elements, in order to solve the problem of uneven material removal rate and improve the polishing efficiency of planar optical elements. The finite element simulation was used to optimize the shape of the permanent magnet, and an arc permanent magnet was designed with a radius of curvature of 55 mm. The magnetic flux density of the arc permanent magnet has a Gaussian distribution, which effectively attenuates the effect of linear velocity on polishing. The arc permanent magnet is beneficial to achieve a more uniform material removal and better processing quality. The experiments are conducted on the borosilicate glass using the recent arc permanent magnet and existing planar permanent magnet. The experimental results show that the arc permanent magnets can reduce the average surface roughness value from 286 nm to 16 nm and the standard deviation of surface roughness to 0.92 under the same processing parameters. Therefore, the analysis of the borosilicate glass surface verifies that the designed arc permanent magnets can effectively improve surface accuracy and surface topography .

Cr(VI) Femoval from Ground Waters by Ferrous Iron Redox-Assisted Coagulation in a Continuous Treatment Unit Comprising a Plug Flow Pipe Reactor and Downflow Sand Filtration

Chromium(VI) (Cr(VI)) is the main chromium species found in groundwater and is considered as a highly toxic and carcinogenic element to humans. In the present study, removal of Cr(VI) by coagulation with ferrous iron is studied in a continuous flow treatment unit comprising pipe flocculation reactors followed by a sand filter. The studied parameters, regarding their effect on the removal of hexavalent chromium, were the ferrous iron dose, the effect of linear velocity, and the effect of the starting Cr(VI) concentration. The experiments have shown that the Cr(VI) removal achieved was very efficient and residual Cr(VI) and total Cr concentration in the treated water was lower than 10 μg/L, provided that the required dose of ferrous iron is provided. In particular, the study demonstrated that the removal of hexavalent chromium, from initial concentration of 50 μg/L and 100 μg/L, was more than 90% with ferrous doses of 1 mg/L and 2 mg/L respectively, applying linear velocity of 8 m/h, at an initial pH value of 7.3. Iron concentration in treated water was very low, far below 200 μg/L, which is the limit for iron in drinking water. This unit comprises a simple treatment option, for applications at the household level, with minimum maintenance requirements capable of removing Cr(VI) to concentrations below 10 μg/L, which might be the future limit for chromium in drinking water.

Effect of linear velocity on sliding wear behavior of TiCN based cermets

The objective of the present study is to understand the effect of binder phase (Ni, Co) and carbides XC (where X = W/Mo/Ta) on the friction and wear of Ti(C,N) cermets. Sliding tests were done on these samples at linear velocity: 0.08 m/s, 0.16 m/s and 0.26m/s against SiC balls of 6.35 mm diameter under unlubricated conditions. It is evident from our experimental results that high frictional conditions prevailed when tests were conducted with 0.26 m/s linear velocity. A higher coefficient of friction (COF) varied from 0.47 to 0.50 with 0.26 m/s linear velocity, whereas lower coefficient of friction from 0.18 to 0.27 was found with 0.08 m/s linear velocity. The volumetric wear loss varied from 2.6 X 10-3 mm3 to 4.2 X 10-2 mm3. The cermets containing TaC showed lower wear volume when compared against those containing WC and Mo2C. The wear behavior of the cermets was related to their mechanical and microstructural characteristics. The modes of failure of cermets under investigated sliding conditions were mainly abrasion, grain pull out and adhesion.

Determination of reaction areas for the sulfur conversion during low-metamorphosed coal oxidative desulphurization

Taken into account the global trends of metallurgy, in order to save energy, new technologies in blast furnaces are actively developed in Ukraine, namely, substitution of natural gas for pulverized coal (PC). However, use of this technique is complicated by inconsistencies of characteristics of a large part of domestic coal with requirements that apply to PC raw materials, primarily because of the high sulfur content in it.To solve this problem, it is proposed to use the method of coal oxidative desulphurization that consists in selective conversion of pyritic sulfur by vapor-air mixture. However, the content of sulfur in coal is not the only requirement, so the task of research is determination of process parameters that will enable to minimize the destruction and burning of organic carbon that occurs during its oxidative desulphurization.Series of experiments on detailed determination of patterns for high-sulfur low-metamorphosed coal oxidative desulphurization to produce raw materials for PC are began in this article. The effect of linear velocity of the oxidant and the grain size of raw materials on the process is determined and the values of these factors when oxidative desulphurization isn't limited to diffusion velocity of the oxidant to the coal grain surface are established. The dependence of the process stages from parameters of fluidized bed and mass transfer criteria of the reagent is shown.

HAMR Noise Mechanism Study With Spin-Stand Testing

In this paper, we present a spin-stand testing study of heat-assisted magnetic recording (HAMR). Motivated by the understanding of the major recording noise mechanisms predicted by previous modeling, experiments were made to investigate the recording field/write current dependence of signal-to-noise ratio. The two significant noise mechanisms in HAMR, incomplete switching and erase-after-write, have been observed in the experiments and shown to be similar to the previous modeling results. Previous simulations indicate that system performance strongly correlates with recording time window (RTW). Therefore, head/media relative velocity was varied to change the RTW, and the effects of linear velocity are also compared. Further analysis has been applied to cases with different writer and media components. These results help understand the field/media requirements to optimize the HAMR recording system performance.

Flow Synthesis of Biocompatible Fe3O4 Nanoparticles: Insight into the Effects of Residence Time, Fluid Velocity, and Tube Reactor Dimension on Particle Size Distribution

PEGylated Fe3O4 nanoparticles were prepared through flow synthesis upon the pyrolysis of ferric acetylacetonate (Fe(acac)(3)) in anisole at 250 degrees C under pressure of 33 bar, in the presence of a,?-dicarboxyl-terminated polyethylene glycol (HOOC-PEG-COOH) and oleylamine. In combination with theoretical analysis, the effects of linear velocity, residence time, and reactor dimension on particle size distribution were systematically investigated. In addition, the impact of Ostwald ripening on particle size distribution was also revealed. In particular, the impacts of monomer concentration distributions along both axial and radial directions of the tube reactor on the particle size distribution were carefully investigated. Under optimized conditions, PEGylated Fe3O4 nanoparticles with the relative standard deviation of particle size down to 10.6% were thus obtained. The resulting 4.6 nm particles exhibited excellent colloidal stability and high longitudinal relaxivity (r(1)) up to 11.1 mM(-1) center dot s(-1), which manifested the reliability of flow synthesis in preparing PEGylated Fe3O4 nanoparticles as contrast agents for magnetic resonance imaging applications.

The effect of linear velocity and flux on performance of ceramic graded permeability membranes when processing skim milk at 50°C

Raw milk (about 500kg) was cold (4°C) separated and then the skim milk was pasteurized at 72°C and a holding time of 16s. The milk was cooled to 4°C and stored at ≤4°C until processing. The skim milk was microfiltered using a pilot-scale ceramic graded permeability (GP) microfilter system equipped with 0.1-µm nominal pore diameter ceramic Membralox membranes. First, about 155kg of pasteurized skim milk was flushed through the system to push the water out of the system. Then, additional pasteurized skim milk (about 320kg) was microfiltered (stage 1) in a continuous feed-and-bleed 3× process using the same membranes. The retentate from stage 1 was diluted with pasteurized reverse osmosis water in a 1:2 ratio and microfiltered (stage 2) with a GP system. This was repeated 3 times, with total of 3 stages in the process (stage 1 = microfiltration; stages 2 and 3 = diafiltration). The results from first 3 stages of the experiment were compared with previous data when processing skim milk at 50°C using ceramic uniform transmembrane pressure (UTP) membranes. Microfiltration of skim milk using ceramic UTP and GP membranes resulted in similar final retentate in terms of serum proteins (SP) removed. The SP removal rate (expressed by kilogram of SP removed per meter-squared of membrane area) was higher for GP membranes for each stage compared with UTP membranes. A higher passage of SP and SP removal rate for GP than UTP membranes was achieved by using a higher cross-flow velocity when processing skim milk. Increasing flux in subsequent stages did not affect membrane permeability and fouling. We operated under conditions that produced partial membrane fouling, due to using a flux that was less than limiting flux but higher than critical flux. Because the critical flux is a function of the cross-flow velocity, the difference in critical flux between UTP and GP membranes resulted only from operating under different cross-flow velocities (6.6 vs 7.12 for UTP and GP membranes, respectively). Conditions that allow microfiltration operation at higher flux will reduce the membrane surface area required to process the same amount of milk in the same length of time. Less membrane surface area reduces investment costs and uses less energy, water, and chemicals to clean the microfiltration system.

Direct contact membrane distillation (DCMD): Experimental study on the commercial PTFE membrane and modeling

Membrane distillation (MD) is an alternative technology for the separation of mixtures through porous hydrophobic membranes. A commercially available PTFE (polytetrafluoroethylene) membrane was used in direct contact membrane distillation (DCMD) to investigate the effect of module dimensions on performance. Membrane properties, such as liquid entry pressure (LEP), contact angle (CA), pore diameter, effective porosity and pore size distribution, were characterized and used in analysis. A two dimensional (2D) model containing mass, energy, and momentum balance was developed for predicting permeate flux production. Different flow modes including co-current and counter-current flow mode were studied. The effect of linear velocity on permeation flux for both wide and short, and long and narrow module designs was investigated. The mass transfer coefficients for each condition were calculated for comparison of the module designs. The effects of operating parameters such as flow mode, temperature difference, and NaCl concentration were also considered. The simulated results were validated by comparing with experimental results. Good agreement was found between the numerical simulation and the experiments.

REMOVAL OF ARSENATES FROM CONTAMINATED WATER BY COAGULATION–DIRECT FILTRATION

The present study has been directed towards the removal of arsenic, applying a modification of conventional coagulation/flocculation process. The modifications refer to the introduction of “pipe flocculation” process in the first stage of the technique, whereas the second step has been performed by direct filtration with sand filters, instead of separation by sedimentation. Alum or ferric chloride was the coagulant agent used, enhanced in certain cases by the presence of cationic or anionic polyelectrolytes (organic polymers). The efficiency of coagulant/polymer addition was investigated, using different ratios and for different initial As(V) concentrations. The effect of linear velocity during sand filtration was also examined. In general, both the coagulants were found to be efficient regarding arsenic removal and in both cases the use of coagulant aids increased the overall efficiency of the method—reaching in some cases arsenic removals up to 99%.

Comparison of empirical peak capacities for high-efficiency capillary chromatographic techniques.

Experimental peak capacities for capillary gas chromatography (GC), capillary liquid chromatography (CLC), and capillary electrochromatography (CEC) were compared. To obtain a meaningful comparison, the following constraints were applied. First, the same sample (mixture of alkylbenzenes) was used as a test mixture for all three techniques; second, the same packing material and column diameter were used in CLC and CEC; and third, isothermal conditions were used in GC, while isocratic conditions were used both in CLC and in CEC. Comparison of peak capacities for the same total column efficiency (approximately 36000 plates) showed that the peak capacity of GC is greater than those of the liquid-phase separation techniques. Comparison of CEC and CLC for constant retention factor was also carried out. For this condition, the results depend on the particle size used; for 3-microm porous particles, CEC had a peak capacity larger than CLC due to higher efficiency from the flow profile generated by electroosmotic flow. However, when 1.5-microm nonporous particles were used, the peak capacities were approximately the same for both techniques. The effect of linear velocity on peak capacity was also studied for all three techniques. Practical conditions aimed at increasing peak capacities of liquid-phase separation techniques are discussed.

Capillary Biosensor for Glutamate

We have developed and characterized a novel glutamate biosensor which allows biological transduction of glutamate signal during transport of analyte from the sampling site to the detector. This biosensor exploits the high surface-to-volume ratio found in small-diameter fused silica capillaries. Glutamate dehydrogenase (GDH) was attached to the inner surface of a 75 μm i.d. capillary using biotin-avidin chemistry. In the presence of excess nicotinamide adenine dinucleotide (NAD(+)), GDH converts glutamate to α-ketoglutarate while simultaneously reducing NAD(+) to NADH. Detection of NADH was accomplished using laser-induced fluorescence. Perfusion with 30 μM glutamate in the presence of 3 mM NAD(+) resulted in a strong increase in fluorescence, with a response time of 450 ms. This effect was abolished upon exclusion of NAD(+) from the buffer. The limit of detection is 3 μM (S/N = 3), with a linear working range from 3 to 300 μM. Efficiency of the GDH-modified capillary ranged between 20% and 92% and was positively correlated with concentration of glutamate. The effect of linear velocity was also examined and was shown to be indirectly related to efficiency, with maximum response observed at 4.5 cm/min. In summary, we have demonstrated the successful attachment of glutamate dehydrogenase to the inner wall of a small-diameter fused silica capillary while retaining enzymatic activity. The resulting biosensor exhibits characteristics amenable for in vivo applications. Future efforts will be directed toward the incorporation of this biosensor into current technologies, such as capillary electrophoresis and microdialysis.

Substantial effect of linear velocity of combustion flame on oriented growth of diamond

Abstract Diamond coatings were deposited on diamond-polished molybdenum substrates using combustion flame CVD. The total (acetylene plus oxygen) flow rate was between 75 and 310 1 h−1, the acetylene-to-oxygen flow rate ratio was between 1.03 and 1.22 and the substrate temperature was from 620 to 900 °C. A strong dependence of preferred orientation and crystalline order of the coatings, as determined by X-ray diffraction, on the total flow rate is obvious in spite of the wide range of other experimental conditions used for preparation of the samples. A strong (110) preferred orientation observed at low flow rates rapidly decreases and changes to (111) preferred orientation at the highest flow rates. The preferred orientation is apparently restricted to the direction of the coating growth. The change in preferred orientation, which reflects a change in the relative growth rates in the 〈110〉 and 〈111〉 crystal directions, is related to a change in surface morphology: instead of the {111} faces appearing at low flow rates, cubo-octahedral or cubic morphology was observed at high flow rates. The crystalline size values L111 and L220, taken as a measure of crystalline order, behave differently: L111 steadily increases with increasing flow rate, while L220 remains virtually unchanged.

The frictional behavior of thin film magnetic disks

The frictional behavior of carbon-overcoated disks is studied under constant speed drag testing conditions. The effects of linear velocity, environmental conditions, and surface contamination on the friction at the head/disk interface are investigated. The results suggest that the friction build-up as a function of repeated passes may be related to changes in the carbon-hydrogen bonds in the carbon overcoat. During sliding in air, oxygen or water vapor may affect the C-H bonds, which may in turn be responsible for the observed friction increase. This phenomenon is influenced by the temperature at the interface of sliding, the environmental conditions, and the surface cleanliness of the disk. >

Supercritical Fluid Extraction as a Sample Introduction Method for Chromatography

This paper reviews some of the theoretical considerations surrounding the use of supercritical fluid extraction (SFE) as the means of introducing samples into chromatographic systems. Specifically, we discuss the effects of various instrument features and methods on the chromatography: The effects of linear velocity, cell volume, solute trapping, density, and the use of modifiers are discussed. The data indicate that SFE can be fine-tuned into a selective sample preparation/injection method for chromatography. In addition, results obtained by coupling the SFE to both gas chromatography (GC) and supercritical fluid chromatography (SFC) are presented. Samples include environmental, pharmaceutical, and industrial applications.

Sample loading and efficiency in adsorption, partition and bonded-phase high-speed liquid chromatography

With the advent of liquid chromatography columns of extremely high efficiency the effect of sample load on the height equivalent to a theoretical plate (HETP) of the column can be more clearly studied. Previously, the inefficiency of the columns masked the peak broadening due to sample load and deterioration of performance from this cause was only seen to occur at loadings of the order of 100 μg/g of adsorbent. It has now been found that the HETP is a linear function of sample load above about 1 μg/g for microparticulate silica adsorbents which have been slurry packed to give columns with minimum HETP values of between 0.02 and 0.05 mm. The degree of dependence has been found to be a function of both the capacity ratio of the solute and the surface area of the adsorbent. The effect of linear velocity and particle size will be indicated and the relevance of this to the design of preparative liquid chromatography columns will be discussed. Addition of both physically and chemically bonded stationary phases to silica adsorbents is common place in high-speed liquid chromatography and the effect of these changes on the capacity of the columns is an important consideration which will also be outlined.