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In the process of impact-rebound, rockfalls with an initial rotational speed (RS) often undergo a violent transformation between rotational energy and translational energy, which may affect the coefficient of restitution (COR). However, owing to the complexity of experimental simulations and the influence mechanism, this issue is often neglected during research. Therefore, in this study, four representative blocks (ellipsoid, cylinder, cone with a spherical base, and disc) were selected, and impact tests of each block rotating around different axes with various RSs were conducted using a specially developed device. Based on the impact dynamics theory, the RS has no significant effect on the tangential COR (R t), while it may exhibit a positive correlation with the R t when the size of the block size is large enough. When the block rotates around the X-axis (approximately normal impact), there is no obvious relationship between the RS and the normal COR (R n). Conversely, when the block rotates around the Y-axis (often non-normal impact), the RS influences the R n , but it is difficult to determine in what manner and to what extent. Thus, to clarify the influence mechanism of RS on the R n for non-normal impacts, a comprehensive variable, the impact posture coefficient (IPC), which comprehensively considers the RS, block shape, and impact posture, was introduced, and the impact-rebound characteristics of the blocks were classified and discussed. Under the condition of bouncing after only one impact, the IPC and R n values exhibited a positive linear correlation when the block mass centre (C) is behind the contact point (CP), whereas the opposite behaviour was observed when the C is in front of the CP. Meanwhile, under the condition of bouncing after two impacts, the R n and IPC values had a positive linear correlation. These findings explain the influence mechanism of RS on the COR and provide a new idea for the accurate prediction of the impact-rebound processes of rotating irregular rockfalls. • Effect of rotational speed (RS) on coefficient of tangential restitution is not significant only for small size block. • For non-normal impact, RS does affect coefficient of normal restitution (R n) but it's hard to directly affect Rn alone. • Introducing impact posture coefficient to quantify the effect of RS on R n for non-normal impact. • Study on block's impact- rebound characteristics by classified discussion method. • Clarify the influence mechanism of RS on coefficient of restitution. [ABSTRACT FROM AUTHOR]

Welding parameters like welding speed, rotation speed, plunge depth, shoulder diameter etc., influence the weld zone properties, microstructure of friction stir welds, and forming behavior of welded sheets in a synergistic fashion. The main aims of the present work are to (1) analyze the effect of welding speed, rotation speed, plunge depth, and shoulder diameter on the formation of internal defects during friction stir welding (FSW), (2) study the effect on axial force and torque during welding, (c) optimize the welding parameters for producing internal defect-free welds, and (d) propose and validate a simple criterion to identify defect-free weld formation. The base material used for FSW throughout the work is Al 6061T6 having a thickness value of 2.1 mm. Only butt welding of sheets is aimed in the present work. It is observed from the present analysis that higher welding speed, higher rotation speed, and higher plunge depth are preferred for producing a weld without internal defects. All the shoulder diameters used for FSW in the present work produced defect-free welds. The axial force and torque are not constant and a large variation is seen with respect to FSW parameters that produced defective welds. In the case of defect-free weld formation, the axial force and torque are relatively constant. A simple criterion, (∂ τ/∂ p) > (∂ τ/∂ p) and (∂F/∂ p) > (∂F/∂ p), is proposed with this observation for identifying the onset of defect-free weld formation. Here F is axial force, τ is torque, and p is welding speed or tool rotation speed or plunge depth. The same criterion is validated with respect to Al 5 xxx base material. Even in this case, the axial force and torque remained constant while producing defect-free welds. [ABSTRACT FROM AUTHOR]

Abstract: In recent years, the boost towards the reduction of electrical loads for air conditioning and the decentralization of energy conversion devices are determining an increasing interest in small scale trigeneration systems fueled by natural gas (“gas cooling”), able to shift energy demand in summer from electricity to gas, at the same time allowing the exploitation of natural gas surplus during the warm season. A technology that meets these requirements is represented by desiccant-based dehumidification systems, in which thermal energy for regeneration can be provided by a small scale cogenerator; the main component of these systems is the desiccant wheel, whose performances, in terms of humidity reduction and process air outlet temperature, depend on several operational parameters. The rotational speed of the desiccant wheel is widely recognized as a crucial parameter: if the wheel rotates too fast, the desiccant material does not have enough time to remove the moisture, while if the wheel rotates too slowly, saturation could occur. As a result, there must exist an optimal rotational speed, depending on the operating conditions, that guarantees the best dehumidification performance. Rotational velocity of the desiccant wheel influences the process air temperature exiting the desiccant wheel too; therefore it should be chosen in order to contemporary obtain a high dehumidification performance and an enough low outlet temperature, to reduce the cooling load on the cooling device, in particular if a conventional vapor compression chiller is used, as often occurs in high humidity climates. In this paper, experimental tests on a silica gel desiccant wheel, in order to highlight the effect of rotational speed on its performance, are shown. The adsorbent material is regenerated by thermal energy up to 65°C. The experimental results were used to calculate some of the most representative performance parameters for the wheel, that are the dehumidification effectiveness, the dehumidification coefficient of performance (DCOP) and the sensible energy ratio (SER). Finally, the influence of process air inlet temperature and humidity, regeneration temperature and the ratio between the regeneration and process air flow rates on the optimal rotational velocity is discussed. It was found that, for the analyzed desiccant wheel, the velocity that optimizes the dehumidification performances varies in the range 5–10 revolutions per hour, depending on operating conditions, while SER monotonically increases with rotational velocity. [Copyright &y& Elsevier]

Abstract: A connection disk rotating at constant speed under temperature rise and transmitted torque at the inner and outer clamped edges is modeled using a nonlinear elastic–plastic stress–strain relation, and the elastic–plastic effective stress in Von Mises yield criterion is obtained efficiently by the finite difference method with a closed-form initial predicted value. Effects of rotational speed, edge temperature rises, transmitted torque and their couplings on the elastic–plastic stresses of the connection disk are studied. It is seen that the effective stress increases generally with the edge temperature rises, and the outer edge temperature rise increases the maximum effective stress more remarkably than the inner edge one; the maximum elastic–plastic effective stress occurs at either the inner edge or outer edge. [Copyright &y& Elsevier]

Assuming that vibration and noise amplitude depend on coating thickness, here were performed important tests about wear of the Xylan 1052 coating. Applying variable contact stress by different load pressures on a disk coated, and keeping the rotational speed constant, a wear evolutions diagram has resulted. Also, a diagram with the wear evolutions of Xylan 1052 coating has been achieved by using the same load pressure and varying the rotational speed. This information offers significant knowledge about Xylan 1052-film wearing, reflecting an appreciation of the running-in period and the coating thickness. Further on, the proper working time is accomplished, as well as the minimum coating thickness whereas the covering becomes irrelevant to use. [ABSTRACT FROM AUTHOR]

A new method based on rotating biological contactor (RBC) was employed for solving the problems of long hydraulic retention times (HRT) low specific surface area and organic loading rates (OLR) in conventional RBCs. The system showed its particular adsorption ability of microorganisms in the biofilm-attaching period. Microbes on the first cage were observed in comparison with the second one. Packing biodisc also had a good shock load tolerance. It was observed that the system performance improved at higher HRTs, while at the increased level of input OLR, the removal performance worsened slightly. The positive role of rotational speed in the treatment of municipal wastewater was more pronounced in the range of 10-12 rpm. Chemical oxygen demand (COD) removal rate achieved 94% under the optimal operating conditions, which were HRT of 1.5 h, rotational speed of 9.9 rpm. The modified RBC system is highly beneficial to engineering application for better system performance and lower energy consumption. [ABSTRACT FROM AUTHOR]

Impeller submergence governs the performance of mixing tanks employed in oxygen transfer operation. Present work experimentally investigates the effect of impeller submergence depths on oxygen transfer and corresponding power consumption. It has been found that at higher range of impeller submergence, mixing tanks consume less power and gives higher values of oxygen transfer coefficient. Optimal range of submergence depth is 0.7 to 0.9 times the impeller diameter. Copyright ©2011 BCREC UNDIP. All rights reserved. [ABSTRACT FROM AUTHOR]

In this study, rolled plates of AA 2198 T3 aluminium alloy are friction-stir welded in butt configuration varying two fundamental process parameters: rotational and welding speeds. Two sets of empirical models based on regression analysis are developed. The first one predicts the stationary values of the in-plane and downwards forging welding forces in dependence of the process parameters under investigation. The second one predicts the mechanical strength, in particular yield and tensile strength, of the friction-stir welded joints as function of the same parameters. For the development of the empirical models, two 3 full factorial designs are used: one having the stationary values of the welding forces and the other having the yield and tensile strength as observed responses, respectively. Statistical tools such as analysis of variance, F tests, Mallows' C, coefficient of determination etc. are used to build and to validate the developed models. By using the desirability function approach, the optimum process parameters to simultaneously obtain maximum possible yield and tensile strength are found within the investigated range. The developed models can be effectively used to predict the stationary forces and the mechanical proprieties of the joints at 95% confidence level. [ABSTRACT FROM AUTHOR]

Abstract: The present work investigates the effect of varying the combustion chamber geometry and engine rotational speed on the gas flow and temperature field, using a new quasi-dimensional engine simulation model in conjunction with an in-house developed computational fluid dynamics (CFD) code served to validate the predicted in-cylinder flow field and gas temperature distribution calculated by the quasi-dimensional model, for three alternative piston bowl geometries and three rotational speeds. This CFD code can simulate three-dimensional curvilinear domains using the finite volume method in a collocated grid; it solves the generalized transport equation for the conservation of mass, momentum and energy, and incorporates the standard k–ε turbulence model with some slight modifications to introduce the compressibility of a fluid in generalized coordinates. On the other hand, the quasi-dimensional model solves the general transport equation for the conservation of mass and energy by a finite volume method throughout the entire in-cylinder volume, while for the estimation of the flow field a new simplified three dimensional air motion model is used. To compare these two models the in-cylinder spatial and temporal temperature distribution, the mean cylinder pressure diagram, as well as the mean in-cylinder radial and axial velocity are examined, for the three piston bowl geometries and the three speeds, for a high speed direct injection (HSDI) diesel engine operating under motoring conditions. From the comparison of calculated results, it becomes apparent that the two models predict similar in-cylinder temperature distributions and mean air velocity fields at each crank angle, for all cases examined. Thus, it is shown that the quasi-dimensional model with the proposed simplified air motion model is capable of capturing the physical effect of combustion chamber geometry and speed on the in-cylinder velocity and temperature field, while needing significantly lower computing time compared to the more detailed and accurate CFD model. On the other hand, the CFD model is more suitable when detailed simulation of the in-cylinder geometry is required and the way the corresponding transport phenomena are affected. [Copyright &y& Elsevier]

This research focused on polish characteristic of polymer based waveguides. The aim of the research was to show how polishing parameters affect the cut length of the end surface of SU-8 polymer on silicon and to detemine the best parameters for polishing SU-8 polymer. Then, four samples were used for characterizing the polishing of polymer. Each sample was polished with the same rotation and sandpaper size but with different rotational speed. The experiment result shows that the best rotational speed for polishing polymer SU-8 sample on silicon is 200 rpm. [ABSTRACT FROM AUTHOR]

The residence time distribution (RTD) of a model particulate–fluid mixture (potato in starch solution) in the ohmic heater in a continuous sterilization process was measured using a radio frequency identification (RFID) methodology. The effect of solid concentration and the rotational speed of the agitators on the RTD were studied. The velocity of the fastest particle was 1.62 times the mean product velocity. In general, particle velocity was found to be greater than the product bulk average velocity. Mean particle residence time (MPRT) increased with an increase in the rotational speed of the agitators ( P < 0.05), and no particular trend was observed between the MPRT and the solid concentration. The distribution curves E (θ) were skewed to the right suggesting slow moving zones in the system. [ABSTRACT FROM AUTHOR]

Lab-scale experiments using a synthetic wastewater were carried out to assess the influence of disk rotational speed on oxygen transfer rate in a RBC unit in the presence of biomass. The overall oxygen transfer coefficient (K L a) was computed. Five different disk rotational speeds were tested, in the typical RBC operating range (3–10RPM). The soluble organic substrate was monitored through TOC analysis. Influent hydraulic organic loadings were in the range of 5.4–35.2gTOC/m2 d. The set of kinetic coefficients calculated fitting the experimental data by the selected model resulted in good agreement with the value reported in literature. A correlation for K L a as a function of disk rotational speed and disk diameter was obtained. Accordingly, a new expression of the enhancement factor of oxygen transfer was found, and compared to literature data. [Copyright &y& Elsevier]

Abstract: This paper deals with the non-repetitive run-out (NRRO) of an angular contact ball bearing for machine tools. First, a measuring system for the rotational accuracy of the bearing was developed. Then, the following results were obtained using the developed measuring system. [(1)] The NRRO of ball cage rotation increased with rotational speed. [(2)] The influence of form errors in the inner and outer rings on NRRO was small. [(3)] The influences of form errors in the balls of the bearing and the diameter difference of balls on NRRO were significant. [Copyright &y& Elsevier]

In order to predict the high-speed error motion of the porous journal air bearing, a new dynamic accuracy model is established based on the simplified nonlinear air film force considering the rotational speed. Then the effect of the speed on the accuracy is discussed by the same averaging coefficient of quasi-static condition for various shaft and bush roundness errors. It finds that the speed only affects the amplitude of the error motion but doesn't affect its frequency information. As the speed increases, the averaging coefficient increases, while its frequency information is kept the same. The accuracy decreases with the increase of the speed. The model provides a low-cost way to predict the high-speed error motion by the low-speed error motion. ● A new dynamic accuracy model of the porous journal air bearing is built based on the simplified nonlinear air film force. ● The effect of the speed on the error motion is studied by the same averaging coefficient of quasi-static condition. ● The speed only affects the amplitude of the error motion but doesn't affect its frequency information. ● As the speed increases, the value of the averaging coefficient increases, while its frequency information is kept the same. ● It provides a low-cost way to predict the high-speed error motion by the low-speed error motion. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of abrasive waterjet turning (AWJT). The purpose of the article was to investigate significant parameters of the turning process and to evaluate their impact on the turning product. The influence of the traverse speed, the rotational speed, and the relative position of the jet to the specimen (lateral jet shift) were investigated. Based on the previous research done in this field, the multi-pass tangential turning method was selected. Rotational speed does not seem to have a significant impact on the AWJ turning process. However, the relative position of the jet is a key parameter for improving the efficiency of the process. Increasing the lateral jet shift causes the volume of the material removed to increase until the optimal impact angle is reached. These findings need to be extended in order to adjust AWJT. Without these improvements, a comparison of jet to traditional technologies is inappropriate. [ABSTRACT FROM AUTHOR]

• Effects of varying rotational speed and inertia were investigated. • Highest hardness in the weld zone (WZ) due to predominant martensite formation. • Temperature in the WZ and TMAZ reached A c 3 and in-between Ac 1 -Ac 3 respectively. • Microstructure suggested combined mode of shear and compression deformation. The effects of varying rotational speed and inertia on the mechanical properties and microstructural evolution in 8630M low-alloy steel during inertia friction welding (IFW) were investigated. The results show that increasing rotational speed and decreasing inertia magnitude detrimentally affect the weld's mechanical properties. Microstructural observations suggest that the temperature in the weld zone (WZ) and thermo-mechanically affected zone (TMAZ) reached A c 3 and in-between Ac 1 -Ac 3 , whereas that of the HAZ stayed below Ac 1. Microstructure of the weld was dominated by simple shear texture rotated under the influence of the compression at early stages of IFW, implying that the deformation was a combination of shear and compression. [ABSTRACT FROM AUTHOR]

Abstract: The joining of ceramic–metal can be done using different techniques such as brazing, diffusion bonding, and friction welding. However, the mechanism of ceramic–metal joining has still not been fully understood. In this study, an alumina rod was bonded to a mild steel rod via the friction welding technique by using an Al 1100 sheet as an interlayer. The diameters of the rods were both 10mm, respectively. A friction pressure of 20MPa and a forging pressure of 40MPa were used. Rotational speed was maintained at 900rpm and friction times from 2 to 20s were applied. The joining strength was determined through a four point bending test. The maximum bending strength, 240MPa was obtained when the friction time of 20s was used. Under optical microscope and scanning electron microscope observation, the bonding aluminum interface was clearly obtained. Mechanical interlocking and close contact between the alumina–aluminum and aluminum–mild steel were observed at magnifications of 3000×. The strength of alumina–steel bonding is much dependent on the wettability of the alumina surface by the partially molten aluminum interlayer and the existence of mechanical interlocking between the interlayer and mild steel. [Copyright &y& Elsevier]

Abstract: Wind tunnel tests were conducted to assess the aerodynamic performance of single-, two- and three-stage Savonius rotor systems. Both semicircular and twisted blades have been used in either case. A family of rotor systems has been manufactured with identical stage aspect ratio keeping the identical projected area of each rotor. Experiments were carried out to optimize the different parameters like number of stages, number of blades (two and three) and geometry of the blade (semicircular and twisted). A further attempt was made to investigate the performance of two-stage rotor system by inserting valves on the concave side of blade. [Copyright &y& Elsevier]

Abstract: Friction stir welding (FSW) is a solid state welding process for joining aluminum alloys and has been employed in aerospace, rail, automotive and marine industries for joining aluminium, magnesium, zinc and copper alloys. In FSW, the base metal properties such as yield strength, ductility and hardness control the plastic flow of the material under the action of rotating non-consumable tool. The FSW process parameters such as tool rotational speed, welding speed, axial force, etc. play a major role in deciding the weld quality. In this investigation, an attempt has been made to establish relationship between the base material properties and FSW process parameters. FSW joints have been made using five different grades of aluminium alloys (AA1050, AA6061, AA2024, AA7039 and AA7075) using different combinations of process parameters. Macrostructural analysis has been done to check the weld quality (defective or defect free). Empirical relationships have been established between base metal properties and tool rotational speed and welding speed, respectively. The developed empirical relationships can be effectively used to predict the FSW process parameters to fabricate defect free welds. [Copyright &y& Elsevier]

The present paper describes the sand slurry erosive wear behaviour of the flame sprayed stellite (Co–Cr–W–Ni–C) coating. The wear behaviour was evaluated with the help of a slurry pot tester by using two sand slurry concentrations (20 and 40% sand particles) at different rotational speeds (600–1000 rev min-1). It was observed that the weight loss of the coating material and rotational speed relationship is governed by the concentration of sand particles in slurry. Slurry erosive wear of the coating showed that in case of 20% silica sand slurry, weight loss increases with increase in rotational speed from 600 to 1000 rev min-1 while in case of 40% silica sand slurry weight loss first increases with increase in rotational speed from 600 to 800 rev min-1 followed by marginal decrease in weight loss with further increase in rotational speed from 800 to 1000 rev min-1. Improvement in wear resistance of mild steel due to development of the thermal sprayed coating was calculated as wear ratio which is a ratio of weight loss of mild steel and that of coating. Wear ratio was found in range of 4·2–7·5 under different test conditions. The microstructure study showed polyhedral shaped Cr dominated carbide particles in eutectic matrix. The average microhardness of the coating was 680 HV. Wear behaviour of coating has been discussed in light of microstructure and microhardness of coating. Scanning electron microscopy study of wear surface showed that loss of material from the coating takes place by indentation, crater formation and lip formation and its fracture. [ABSTRACT FROM AUTHOR]

Abstract: AA2219 aluminium alloy has gathered wide acceptance in the fabrication of light weight structures requiring a high strength-to-weight ratio. Compared to the many fusion welding processes that are routinely used for joining structural aluminium alloys, friction stir welding (FSW) process is an emerging solid state joining process in which the material that is being welded does not melt and recast. The welding parameters and tool pin profile play a major role in deciding the weld quality. In this investigation an attempt has been made to understand the influences of rotational speed and pin profile of the tool on friction stir processed (FSP) zone formation in AA2219 aluminium alloy. Five different tool pin profiles (straight cylindrical, tapered cylindrical, threaded cylindrical, triangular and square) have been used to fabricate the joints at three different tool rotational speeds. The formation of FSP zone has been analysed macroscopically. Tensile properties of the joints have been evaluated and correlated with the FSP zone formation. From this investigation it is found that the square tool pin profile produces mechanically sound and metallurgically defect free welds compared to other tool pin profiles. [Copyright &y& Elsevier]

Abstract: Biological treatment using attached growth in a three-stage lab-scale rotating biological contactor (RBC) was implemented for wastewater from food cannery industries. The wastewater contained high level of organic compounds due to fish and fruit cleaning, cooking and filling processes. Nutrients available in the wastewater enhanced the growth of microorganisms and allowed the biological treatment to be effective. The RBC consisted of 54 parallel discs rotating in a reservoir and was arranged in three stages, i.e. 18 discs oriented in each stage. Effect of major operating and physical variables such as hydraulic retention time (HRT), disc submergence and disc rotational speed were examined in COD removal. For duration of 5 days, 96.4% BOD removal was achieved in batch experiment. BOD constant rate (k) and ultimate BOD were determined respectively, 0.8198day−1 and 6349mg/l by Thomas graphical method. COD removal efficiency was increased from 85.3 to 97.4% while the HRT was increased from 24 to 48h. The COD removal efficiency increased from 74.9 to 87.5% as the disc submergence was increased from 31 to 36%. At submergence level of 23.7%, removal efficiency was increased due to activation of second and third compartments. When the rotational speed was increased from 3 to 11rpm, the COD removal efficiency was also increased from 62.7 to 93.7%, respectively. The stage COD removal efficiency was gradually decreased with an increase number of stage and about 88% of organic compounds were removed in the first stage of aerobic RBC, indicating that the single stage reactor may be sufficient in practical application. [Copyright &y& Elsevier]

Abstract: In this study, standard AISI 304L austenitic stainless steel and AISI 4340 steel couple were welded by friction welding process using five different rotational speeds. The joining performances of AISI 304L/AISI 4340 friction-welded joints were studied and the influences of rotational speed on the microstructure and mechanical properties of the welded joints were also estimated. The microstructural properties of heat affected zone (HAZ) were examined by scanning electron microscopy (SEM). The microhardness across the interface perpendicular to the interface was measured and the strength of the joints was determined with tensile tests. The experimental results indicate that the tensile strength of friction-welded 304L/4340 components were markedly affected by joining rotational speed selected. [Copyright &y& Elsevier]

Abstract: This paper reports the study of super-gravity effects on electroless copper coating on nickel substrate. The plating rates were obtained versus varying super-gravity accelerations and two super-gravity directions by thickness measurement of Cu coating. Composition and morphology of the coating were measured by XRD and SEM analysis. The use of super-gravity field during electroless copper plating can increase the plating rate and enlarge the size of Cu crystal grain. Coating surface vertical to super-gravity can obtain better coating than in position whose surface parallel to super-gravity. [Copyright &y& Elsevier]

This paper presents the performance of a multi-stage biodrum system applied to domestic wastewater treatment. The organic stabilization and nitrogen removal efficiency in the system was investigated at different hydraulic retention times (HRT) of 12, 6 and 3 hours. The rotational speed of the biodrum was examined at 2,4 and 8 rpm. Average organic removal efficiencies in the system at different HRTs of 12, 6 and 3 hours were 96.3, 94.4 and 90.9%. Simultaneously, average nitrogen removal efficiencies were 91.5, 90.6 and 81.0%. The effect of rotational speed on nitrogen removal efficiencies in the system was clearly observed at a low HRT of 3 hours. The experimental results suggested that optimum HRT in the system was 6 hours. Moreover, they revealed that nitrogen removal efficiencies in the reactors operated at different rotational speed were in the same degree when considering the effluent nitrogen concentration. However, the reactors operated at lower rotational speed needed to employ higher numbers of biodrums (4 stages) than the others with higher rotational speed (3 and 2 stages at 4 and 8 rpm.) in order to achieve similar effluent qualities. At a rotational speed of 2 rpm, maximum nitrogen removal rate was found to be 0.2 kg/m³/d. [ABSTRACT FROM AUTHOR]

A new passive and wireless magneto-optical rotational velocity sensor is described. It is based on measuring the intensity oscillations of linearly polarized light transmitted through an orthoferrite plate and an analyzer. The plate is subjected to the action of the magnetic field of a disc whose angular velocity has to be measured. Thanks to the high velocity and smooth reproducible character of the domain wall motion in the orthoferrite plate, one can continuously measure angular velocities in a very wide range—from ultralow to the MHz range. [Copyright &y& Elsevier]

Experimental studies on the effects of scaling on the performance of centrifugal blood pumps were conducted in a closed-loop test rig. For the prototype, eight different impellers of the same outer diameter of 25 mm were tested at 1,500, 2,000, and 2,500 revolutions per minute (rpm) using blood analog as fluid medium. This corresponds to Reynolds numbers (Re) of 25,900, 34,500, and 43,200, respectively. The results indicated that the nondimensional pump characteristic is a function of Re. This is understandable since the typical operating Re for centrifugal blood pumps is less than 100,000. Thus, the effects of scaling cannot be ignored for centrifugal blood pumps. Experiments on a 5× scaled-up model have also indicated that the scaled-up model is more efficient than the prototype model. Our results showed that in the range of Re tested, the nondimensional head versus flow curve is a function of Re to the power of approximately 0.25. It is observed that the nondimensional head versus flow is a function of diameter ratio to the power of 0.2. [ABSTRACT FROM AUTHOR]

Abstract Aim The purpose of this study was to evaluate the influence of rotational speed, torque, and operator experience on the incidence of locking, deformation, and separation of instruments when using a specific Ni–Ti rotary instrumentation technique in extracted human teeth. Methodology Greater Taper Ni–Ti rotary instruments (GT) were used in a crown-down technique. In one group (rotational speed evaluation) of canals (n = 300) speeds of 150, 250 and 350 r.p.m. (subgroups 1, 2 and 3) were used. Each one of the subgroups included 100 canals. In a second group (evaluation of torque) (n = 300) torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group (evaluation of operator proficiency) (n = 300) three operators with varying experience (subgroups 7, 8 and 9) were also compared. Each subgroup included the use of 10 sets of GT rotary instruments and 100 canals of extracted human molars. Each set of instruments was used in up to 10 canals and sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of locked, deformed, and separated instruments was recorded for each group. Statistical analysis was carried out with pairwise comparisons using Fisher’s exact tests for each of the failure type. Results When the influence of rotational speed was evaluated, instrument deformation and separation did not occur in subgroups 1 (150 r.p.m.), 2 (250 r.p.m.), and 3 (350 r.p.m.). Instrument locking occurred in subgroup 3 only. Statistical analysis demonstrated a significant difference between the 150 and 350 r.p.m. groups and between the 250 and 350 r.p.m. groups with respect to instrument locking. In torque evaluation, neither separation, deformation nor locking occurred during the use of the instruments, at 150 r.p.m., and at the different torque values. When the operators were compared, although two instruments were separated in canals prepared by the least experienced operator, Fisher’s exact tests did not... [ABSTRACT FROM AUTHOR]

Abstract Aim The purpose of this study was to evaluate the influence of rotational speed, torque, and operator experience with a specific Ni–Ti rotary instrumentation technique on the incidence of locking, deformation and separation of instruments. Methodology ProFile Ni–Ti rotary instruments (PRI) sizes 40–15 with a 6% taper were used in a crown-down technique. In one group of canals (n = 300) speeds of 150, 250 and 350 rpm (subgroups 1, 2 and 3) were used. Each one of the subgroups included 100 canals. In a second group (n = 300) torque was set at 20, 30 and 55 Ncm (subgroups 4, 5 and 6). In the third group (n = 300) three operators with varying experience (subgroups 7, 8 and 9) were also compared. Each subgroup included the use of 10 sets of PRI and 100 canals of extracted human molars. Each set of PRI was used in up to 10 canals and then sterilized before each case. NaOCl 2.5% was used as an irrigant. The number of locked, deformed, and separated instruments for the different groups, and within each part of the study was analysed statistically for significance with chi-squared tests. Results In group 1 only one instrument was deformed in the 150-rpm group and no instruments separated or locked. In the 250-rpm group instrument separation did not occur, however, a high incidence of locking, deformation and separation was noted in the 350-rpm group. In general, instrument sizes 30–15 locked, deformed and separated. Chi-squared statistics showed a significant difference between the 150 and 350 rpm groups but no difference between the 150 and 250 rpm groups with regard to instrument separation. Overall, there was a trend toward a higher incidence of instrument deformation and separation in smaller instruments. Locking and separation occurred during the final passage of the instruments, in the last (tenth) canal in each subgroup. In the second group, neither separation nor deformation and locking occurred during the use of the ProFile... [ABSTRACT FROM AUTHOR]

In order to obtain desirable crop yields, grain seeds need to be sown at the optimal seed amount per hectare with uniform distribution in the field. In previous grain sowing processes, the seeding rates are controlled by the rotational speed of the flute roller which significantly effects the uniform distribution of the seeds due to disturbances, such as the reduction of the seeds' mass in the hopper and the change of working length of the flute roller. In order to overcome the above problem, we developed an adaptive roller speed control system based on the seed flow rate sensor. The developed system can monitor and feedback actual seeding rates. In addition, based on the monitoring value of the real-time seeding rates, an adaptive roller speed control method (ARSCM), which contains an algorithm for calculating the seeding rate with a compensation, was proposed. Besides, the seeding performance of the ARSCM and that of the conventional roller speed control method (CRSCM) were compared. The results of constant-velocity experiments demonstrated that the accuracy (SA) and the coefficient of variation (SCV) of the seeding rates controlled by the ARSCM were 94.12% and 6.77%, respectively. As for the CRSCM, the SA and SCV were 89.00% and 8.95%, respectively. Under variable-velocity conditions, the SA and SCV of the proposed system were 91.58% and 11.08%, respectively, while those of the CRSCM were 88.48% and 13.08%, respectively. Based on the above results, this study concluded that the ARSCM is able to replace the CRSCM in practical sowing processes for the optimal and uniform seed distribution in the field. [ABSTRACT FROM AUTHOR]

The regulation of different parameters is necessary to achieve the optimal multiplication of measles virus: incubation temperature, multiplicity of virus infection, rotational speed of the bottle and the stability of the cell culture. The aim of this trial was to standardize these parameters for the measles vaccine strain Leningrad 1 6, using primary Japanese quail embryo fibroblast cell culture. The results showed that keeping the virus in a long-term preserved cell culture (18 days), incubated at 35 °C, with a viral infection multiplicity between 1:10 and 1:100 and a roller speed of 0.2 rpm during the first 24 hours, and 0,5 rpm until the end of the process, during measles antigen production we could obtain high viral yields, with an infective titer of 104,5 - 105,1. [ABSTRACT FROM AUTHOR]

Nowadays, to extend the application of clean energy sources, the utility of small power plants has been expanded and one of them is the potential utilization of water distribution networks (WDNs). By replacing pressure reducing valve (PRV) with a soft pressure regulating system (SPRS) the available hydraulic energy could be employed for generating electricity. A pump as turbine (PAT), considering its economic advantages and proper mechanical function, is a valuable option to be used in WDN. Since the use of PAT requires a precise understanding of how it operates under various hydraulic conditions, the lack of sufficient information in this area can be an obstacle to the expansion of PAT plants. In this paper, the results of a variable speed centrifugal pump installed in a WDN that has the task of regulating pressure and producing power were analyzed with the focus on the effects of speed variation on characteristic parameters. The findings showed that by incorporating a speed parameter in PAT descriptive relations, the prediction's accuracy of the head, power and efficiency curves, respectively can be improved by 3.7%, 12.2% and 34.4%, compared to the nearest model. Provided correction relations help to improve estimations of PAT's energy performance in the network. • Experimental investigation on variable speed pump as turbine is proposed. • Best efficiency point and entire curve prediction models are evaluated. • Rotational speed variation effect on pump as turbine characteristics is analyzed. • TAHA equations can increase the operating curves prediction accuracy up to 34%. • New models are provided to improve the prediction of pump as turbine performance. [ABSTRACT FROM AUTHOR]

The present study introduces a new mechanism of distillation via changing the conventional solar still to modified solar still with rotational discs. The authors aimed to decrease the saline water thickness as much as possible and increase the evaporative surface area of the basin water and the exposure surface area for solar radiation. As a result, two shapes of rotating discs were installed to be investigated inside the solar still; flat and corrugated discs with and without wick material. The performance of the modified solar still with rotating discs has been studied under different rotational speeds for the discs (0.02, 0.05, 0.1, 0.5, 1.0, 2.0, 3.0, and 4.0 rpm). Results revealed that the freshwater distillate of the discs' distiller was greater than that of the conventional (reference) distiller. Besides, the optimum performance of modified solar still was obtained at 0.05 rpm and 0.1 rpm when integrating the flat and corrugated discs with and without wick, respectively. Moreover, the freshwater distillate of the corrugated discs' solar still with wick was improved by 124% over the reference distiller. The maximum thermal efficiency was 54.5% and 50% for the corrugated and flat discs' solar stills with wick, respectively at 0.05 rpm. • Two rotating discs (flat and corrugated) were installed inside the basin still. • Four arrangements of discs were studied; flat and corrugated with and without wick. • Different speeds (0.02, 0.05, 0.1, 0.5, 1.0, 2.0, 3.0, and 4.0 rpm) were studied. • The best distillate was obtained at 0.05 and 0.1 rpm with and without wick. • The distillate of corrugated discs' distiller with wick was improved by 124%. [ABSTRACT FROM AUTHOR]

• The amplitude of out-put signal reflects the torque and frequency reflects the rotational speed. • It solves the problem of power supply and signal output of sensitive elements on the shaft. • This sensing method cleverly uses the non-contact principle of capacitance. Torque and rotational speed are important parameters to characterize the power of rotating parts for mechanical systems, so a rotational shaft's torque and rotational speed sensing method and real-time signal processing are key technologies for mechanized equipment, such as vehicles, ships, etc. Hence an advanced torque and speed sensing technology and a data processing technology are very important for improving the performance of mechanical equipment. However, the power transmission device's rotational shaft has a compact structure and narrow space, so it is difficult to install a signal transmission and power supply device of a sensor on the rotational shaft. To solve these difficult problems, this paper proposes a rotational shaft torque and rotational speed measurement method coupling resistance and capacitance. This method uses two resistance strain gauges and a capacitive grating, and the capacitive grating transmits signals in a non-contact coupling manner. The sensor on the rotational shaft needs no power supply and the signals are transmitted to a measurement circuit from a stationary sleeve, so this method essentially solves the difficult problems in signal transmission and power supply. Simulation and measurement experiments show that the resistance strain gauges obtain information and the capacitive grating sensor transfers information. The method coupling resistance and capacitance for realizing information sensing is feasible, which is suitable for measuring the torque and rotational speed of the rotational shaft of mechanical equipment in spite of the compact structure and narrow space. [ABSTRACT FROM AUTHOR]

The paper investigates the in-plane vibration property of static and rotating tires with the proposed tire model. The tire model is based on the linear ring model, and a mathematical approach is proposed to handle the tire contact problem. With this improvement, the tire model allows for directly calculating the eigenmodes of a loaded tire by solving its eigenvalue problem. A group of simulations is carried out using this improved ring model. For a static (not rotating) tire, the eigenfrequency and corresponding mode shape are investigated under both unloaded and loaded conditions. For a rotating tire, the effect of rotational speed on the eigenfrequencies of unloaded and loaded tires are modeled, and the results are observed using co-rotating and non-rotating reference frames. The main original contribution of this work is an evaluation of the quantitative relationship between unloaded and loaded conditions using modal assurance criterion (MAC) or improved modal assurance criterion (IMAC) analyses on both static and rotating tires. For a static tire, the eigenmodes can be classified into rigid ring modes and flexible ring modes, according to their mode shape and MAC evaluation results. For a rotating tire, the eigenfrequency and mode shape could vary with increasing rotational speed and behave differently in non-rotating and co-rotating reference frames. In a non-rotating frame, the IMAC value percentages for a loaded tire vary with increasing rotational speed, especially in the frequency veering ranges. In a co-rotating frame, the IMAC value variations for loaded modes are weaker than those seen in a non-rotating frame. [ABSTRACT FROM AUTHOR]

Impeller submergence governs the performance of mixing tanks employed in chemical and biochemical operations. Present work experimentally investigates the effect of impeller submergence depths on power consumption when arrowhead impeller has been used in the process. Arrowhead impeller performs better than the conventional Rushton impeller. It has been found that at higher range of impeller submergence, mixing processes consume less power. Optimal range of submergence depth is 0.8 to 0.9 times the impeller diameter. [ABSTRACT FROM AUTHOR]

Abstract: The dissipation rate of turbulent kinetic energy (ε) is a key parameter for mixing in surface aerators. In particular, determination ε across the impeller stream, where the most intensive mixing takes place, is essential to ascertain that an appropriate degree of mixing is achieved. Present work by using commercial software VisiMix® calculates the energy dissipation rate in geometrically similar unbaffled surface aeration systems in order to scale-up the oxygen transfer process. It is found that in geometrically similar system, oxygen transfer rate is uniquely correlated with dissipation rate of energy. Simulation or scale-up equation governing oxygen transfer rate and dissipation rate of energy has been developed in the present work. [Copyright &y& Elsevier]

• The viscosity of CRMA were test using different rotors under different conditions. • The viscosity test principle and variation law were analyzed using rheological principles. • The influence of rotors and speeds on CRMA viscosity and torque were discussed. • The relation between torque and viscosity was established. • The viscosity test Conditions of CRMA are recommended. Brookfield's rotational viscosity has been widely applied for characterizing the rheological behavior of crumb-rubber-modified asphalt (CRMA). However, the test conditions greatly influence the viscosity results of CRMA. Effectively choosing the rotor and rotational speed for CRMA remains unclear. The rotors with different specifications were selected to test 180 °C viscosity of CRMA with different rubber contents under different rotational speeds. Meanwhile, the viscosity corresponding to 50% was obtained by interpolation, and the test principles and variation law of asphalt viscosity were analyzed by applying rheological principles. This investigation analyzed the influence of rotors and speeds on CRMA viscosity and torque during viscosity testing and established the relation between torque and viscosity. Results show that rotor model and test speed significantly affect CRMA viscosity and that of the base asphalt is not affected. Torque and speed has a power- and quadratic-function relation with CRMA viscosity, respectively, whereas there is a linear relation between torque and speed. The rotor and speed recommendations for 180 ℃-viscosity of CRMA with different test accuracy requirements are given, ensuring the effectiveness and comparability of the CRMA viscosity test results. [ABSTRACT FROM AUTHOR]

• The generation mechanism and influence law of pressure pulsation is analyzed. • A new DEZ-based speed measurement method for hermetic compressor is proposed. • The maximum error of the method is smaller than ±1 rpm at 2 s sampling time. The rotational speed is an important parameter of hermetic compressor, which has a great significance on refrigeration capacity, power consumption, and coefficient of performance. However, the change of load condition causes the moving parts of compressor and the refrigerant to operate unsteadily, which leads to large deviation when the traditional speed measurement method is used. To solve this issue, this work proposes a Detrending-Extracting-Zoming (DEZ) method to measure the rotational speed of hermetic reciprocating compressor. A three-dimensional fluid structure interaction (FSI) model is set up to reveal the influence law of pressure pulsation at different operating speeds. On this basis, it can be found that the trend component and harmonic components of pressure pulsation affect the calculation of rotational frequency. Based on the above mechanism, the DEZ first eliminates the trend component of pressure pulsation, then extracts the feature component, and finally calculates the exact rotational frequency by spectrum zooming. The results of simulation and experiment show that the proposed measurement method is reliable under different load conditions, and the maximum error is smaller than ±1 rpm at 2 s sampling time. The key scientific contribution of this paper is providing a rotational frequency calculation method for unstable pressure signal, which can offer universal references to the operating state detection in hermetic reciprocating machines, such as fuel engines and air compressors. [ABSTRACT FROM AUTHOR]

Rotating machinery such as fans feature a variety of sound generating mechanisms. In addition to stationary sound sources and sources moving synchronously to the measured object, sources rotating at different speeds can occur. This paper presents a method for detecting different rotational speeds of multiple dominant sources present in one data set. It is based on modal decomposition and processing of data measured with a circular microphone array. The method is applied to data sets with simulated point sources as well as measurement data of an axial fan with forward-skewed blades at two different operating points. [ABSTRACT FROM AUTHOR]

• The distribution law of the pressure parameters in the passages of the pressure stable region was obtained in this paper. • The influence of wave rotor rotational speed on the wave system with fixed design of pressure ports was studied and analyzed. • The influence of wave rotor rotational speed on the flow losses in the passages was studied by experiments and simulations. • The experiments were conducted with the optimal rotational speed proving the excellent performance of GWE in some cases. Gas wave ejector (GWE) is an efficient injection and supercharging device. The rotational speed of wave rotor is an important parameter affecting the equipment performance. The influence of rotational speed on device performance was intensively studied by experiments and numerical simulations. The results suggest that there is an optimal speed to optimize the equipment performance with fixed pressure ports. Redundant compression waves are generated destroying the ideal wave system when the speed deviates from the optimal value. And the performance reduction induced by these redundant waves is different since the pressure, initial pressure ratio and reversed pressure ratio in the passages of stable pressure region are different in different working conditions. In addition, increasing rotational speed to a certain extent can reduce various types of loss in the passages. However, the viscous dissipation increases sharply if the speed is high enough. The propagation speed of shock wave increases with the increase of rotational speed, which should be taken for granted when designing the geometries of pressure ports. In the experimental conditions, the highest isentropic efficiency and ejection rate GWE can reach about 60% and 80% respectively in the experiments of this paper. [ABSTRACT FROM AUTHOR]

In industrial production processes, rotational speed is a key parameter for equipment condition monitoring and fault diagnosis. To achieve rotational speed measurement of rotational equipment under a condition of high temperature and heavy dust, this article proposes a digital approach using an electrostatic sensor. The proposed method utilizes a strip of a predetermined material stuck on the rotational shaft which will accumulate a charge because of the relative motion with the air. Then an electrostatic sensor mounted near the strip is employed to obtain the fluctuating signal related to the rotation of the charged strip. Via a signal conversion circuit, a square wave, the frequency of which equals that of the rotation shaft can be obtained. Having the square wave, the M/T method and T method are adopted to work out the rotational speed. Experiments were conducted on a laboratory-scale test rig to compare the proposed method with the auto-correlation method. The largest relative errors of the auto-correlation method with the sampling rate of 2 ksps, 5 ksps are 3.2% and 1.3%, respectively. The relative errors using digital approaches are both within ±4‰. The linearity of the digital approach combined with the M/T method or T method is also superior to that of the auto-correlation method. The performance of the standard deviations and response speed was also compared and analyzed to show the priority of the digital approach. [ABSTRACT FROM AUTHOR]

The effect of rotation of the stagnation surface on the nanoparticle deposition in the flame stabilizing on a rotating surface (FSRS) configuration was numerically assessed using CFD method. The deposition properties including particle trajectories, deposition time, temperature and surrounding O2 concentration between the flame and stagnation surface were examined. The results revealed that although flame position is insensitive to the surface rotation, the temperature and velocity fields are remarkably affected, and the deposition properties become asymmetric along the burner centerline when the surface rotates at a fast speed (rotational speed ω ≥ 300 rpm). Particles moving on the windward side have similar deposition properties when the surface rotates slowly, but the off-center particles on the leeward side have remarkable longer deposition time, lower deposition temperature, and lower surrounding O2 concentration, and they even never deposit on the surface when the surface rotates at a high speed. The rotation effect of the stagnation surface can be quantitatively described by an analogous Karlovitz number (Ka'), which is defined as the ratio of characteristic residence time of moving surface to the aerodynamics time induced by flame stretch. For high quality semiconducting metal oxide (SMO) films, it is suggested that Ka' ≥ 1 should be kept. [ABSTRACT FROM AUTHOR]

Aiming at a high‐speed‐impeller mechanical seal structure that plays a significant role in the oxidant turbopump of cryogenic rocket systems, the computational fluid dynamic approach is introduced to analyze its working performance, including the phase distribution in the flow channel, the cooling effect of the frictional element, and the sealing function as well as the power consumptions of the impellers. The established periodic 3D model, which could simultaneously account for the turbulent flow, coupled heat transfer, cavitation, and evaporation, as well as the change of thermophysical properties, was successfully verified by the experimental data. The results show that the sealing ability of a totally liquid‐filled impeller would increase with increasing rotational speed, blade size, and density of the working fluid. After the rotational speed increasing over a certain value (14,000 r/min in this case), a dynamically steady gas–liquid interface would be maintained at the Impeller II's blades, which indicates the completely effective sealing of liquid. Meanwhile, the friction surface could be effectively cooled by this two‐stage leakage cooling scheme, and its maximum temperature could be stably controlled at the rated speed. Based on the good sealing performance and effective cooling, this high‐speed‐impeller seal structure was proved to be feasible and available for cryogenic rocket systems. [ABSTRACT FROM AUTHOR]

Abstract Martín B, Zelada G, Varela P, Bahillo JG, Magán F, Ahn S, Rodríguez C. Factors influencing the fracture of nickel-titanium rotary instruments. International Endodontic Journal , 36 , 262–266, 2003. Aim To evaluate the effect of rotational speed and the angle and radius of curvature of root canals on the fracture of two types of nickel-titanium rotary instruments: K3® and ProTaper® . Methodology A total of 240 root canals of extracted human maxillary and mandibular molars were divided into two groups of 120, according to the angle of the canal curvature (group A: <30°, group B: >30°). Each group was then divided into two subgroups of 60 canals in order to perform instrumentation using K3® and ProTaper® rotary instruments at three different rotational speeds: 150, 250 and 350 r.p.m. (20 canals at each rotational speed). Each instrument was used a maximum of 20 times and at one rotational speed only. The angle and radius of canal curvature were measured in the only group in which fractures actually took place (group B). Results There were a total of 22 instrument fractures; all of these occurred in canals with curves >30°. In a multivariate analysis, it was demonstrated that the files used at a rotational speed of 350 r.p.m. were more likely to fracture than those used at 250 r.p.m. (OR: 1113.88; 95% CI: 2.36–526420.05) and than those used at 150 r.p.m. (OR: 13531.33; 95% CI: 5.37–34120254.00). A decrease in the angle of curvature of the canal also significantly reduced the likelihood of fracture (OR: 0.2083; 95% CI: 0.068–0.6502). These relationships remained significant after being adjusted for the potential interactions between the remaining variables. No significant differences were found between the files or the radii of the canals. Conclusions Instrument fracture was associated with rotational speed and the angle of curvature of the canal. [ABSTRACT FROM AUTHOR]