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Go to Editorial ManagerFlocculation process is used to agglomerate colloids to form large and heavy flocs. It is accomplished using mechanical or hydraulic slow mixing. The hydraulic mixing is usually achieved using baffles. The aim of this study is to conduct experimental work to study the effect of baffles shape and configuration on baffled flocculator performance. The work includes 304 experiments conducted in a pilot plant of baffled flocculator. Two arrangements of three baffle shapes (blind baffles, baffles of rectangular slot and baffles of circular slots) were adopted. During each experiment, water turbidity and temperature, influent flow rate and head loss were measured. The main outcomes of this study are; (1) for all baffle types and arrangements, flocculation efficiency (FE) increases with the increase of velocity gradient (G) till it reaches a maximum value, then, it decreases and the G value which produces the maximum FE varies with detention time (t), (2) within the applied range of Gt values (10231-25304), the correlation between FE and Gt is weak to moderate positive and varied according to baffles type and arrangement, (3) within the applied range of initial water turbidity (IWT) values (18.1-196) NTU, the correlation between FE and IWT is weak positive to good positive represented by logarithmic relationship, and (4) within the implemented baffle types, the blind baffles type gives the highest FE values for all the baffles number as compared with the other baffle types. Also, the most frequent head loss coefficient values were obtained.
This study presents three-dimensional numerical simulations of single-phase laminar flow and forced convection heat transfer of water in a five-layer microchannel heat sink with two channel configurations: radial arrangement and parallel divergence channels. The thermal performance and pressure drop characteristics were evaluated under identical operating conditions, including a constant mass flow rate of 3.925 × 10⁻⁴ kg/s and a uniform heat flux of 90 W/cm². The results indicated that the radial microchannel configuration significantly enhanced both hydrodynamic and thermal performance compared with the parallel divergence design. Specifically, the pressure drop was reduced by approximately 32.5%, the overall performance index increased by about 1.5, and improved temperature uniformity across the heat sink was achieved. These findings demonstrate the superiority of the radial microchannel arrangement for high-heat-flux thermal management applications.
The theoretical study of synchronization of two coupled single mode semiconductor lasers is achieved. The transmitter is laser subject to optoelectronic feedback that operates in a chaotic regime. The receiver can also operate in a chaotic regime similar to the transmitter. The effects of parameter mismatch on the synchronization of two lasers with optoelectronic feedback are determined, with mismatch in delay time, with mismatch in feedback strength, and with coupling strength between two systems. The synchronization is sensitive to mismatch in the delay time for the transmitter and receiver feedback loops. An open - loop receiver configuration does not have the problem of delay time mismatch and shows the highest synchronization. The synchronization phenomena that appear in the two-coupled semiconductor lasers can be used in communications systems. Finally, an encoding and decoding of message on the chaotic carrier is demonstrated.
Continuously Variable Transmission (CVT) combines the efficiency of manual transmissions with the driving comfort of automatic transmissions while providing an infinite range of gear ratios, improved fuel economy, and enhanced acceleration performance. This study presents a comparative evaluation of CVT performance against manual and automatic transmissions in a parallel hybrid electric vehicle (HEV), focusing on fuel consumption and exhaust emissions. A baseline HEV model equipped with a CVT gearbox was selected from ADVISOR simulation software and subsequently modified by replacing the CVT with manual and automatic transmissions for comparison. Exhaust emissions, including catalytic converter pollutant reactions, were recorded for all configurations. Performance assessments were conducted using several global standard driving cycles to simulate real driving conditions. Results indicated that the CVT configuration achieved superior fuel economy and a significant reduction in exhaust emissions compared with manual and automatic transmissions. This improvement is attributed to the CVT’s effective control of speed ratio and overall transmission efficiency. The findings support the suitability of CVT gearboxes for urban hybrid vehicle applications due to their low fuel consumption and high efficiency in speed ratio control.
Adhesives have been around for millennia. Nevertheless, this technique for joining has only seen significant development within the past 70 years. Professional technical engineering applications primarily use adhesives derived from synthetic polymers, a development that dates back to the mid-1940s. Its characteristics facilitate their strong adhesion to most substrates, as well as their ability to transfer substantial loads. This paper presents an extensive assessment of the current knowledge in the field of adhesives and related technologies, with a focus on adhesion theories and their parameters, as well as designing, joint configuration, geometric aspects, and failure modes. The paper also explores the interplay between research and development efforts, industrial standards, and regulatory aspects, with the goal of fostering collaboration between academia and industry. Over the past years, the development of new materials, methods, and models has resolved many of the shortcomings. Nonetheless, it is still possible to evaluate and estimate the optimal combination of aspects that will give the greatest efficiency and performance for adhesive bond joints (ABJs).
This study investigates the vibration behavior of cantilever beams with bolted joints of different lap types (single lap and double lap) under free and forced vibration conditions. The effects of various parameters, including beam configuration, bolt preload, harmonic force magnitude, and force application position, on natural frequency, mode shape, and vibration amplitude are analyzed. Experimental work involved material selection, chemical composition testing, tension tests, beam preparation, and free and forced vibration tests with pre-torque ranging from 6 to 60 N·m and rotational speeds between 300 and 900 RPM. Numerical simulations were performed using the general-purpose finite element software ANSYS 16.1. Results indicate that the natural frequencies of single-lap bolted beams (1 or 2 bolts) are approximately equal to those of intact beams, while double-lap bolted beams exhibit slightly lower natural frequencies than intact beams with the same profile. Increasing bolt preload stabilizes the natural frequency for all beam configurations. For forced vibrations, the amplitude is strongly influenced by the magnitude and position of the applied harmonic force. Validation with experimental results shows good agreement, with a maximum error of approximately 5%.
In this paper, a universal testing machine and an impact testing apparatus have been upgraded by using a high- accuracy data acquisition and control system interfaced to a personal computer with proper sensors and actuators. The purpose of upgrade is to increase the accuracy of the measurements and to perform advanced material testing procedures that are not possible with the old configuration. The modernization process not only permits the accurate data acquisition and convenient operation but also the ability to study the effect of strain rate on the tensile properties of materials. Also, an experimental study of the response of CFRP (Carbon Fiber Reinforced Plastic) material to low and intermediate strain rates has been carried out.
A two-dimensional finite element method for analysis and determination of second mode stress intensity factor (KII) of several crack configurations in plates under uniaxial compression is presented in this study. Various cases including diagonal crack (i.e. corner crack, central crack as well as at different locations on the diagonal) and central kinked crack are investigated with different crack's length, orientation and location. The influence of the contact between two crack surfaces is taken into account by applying contact element procedure with desired friction coefficient. The stress intensity factor is calculated by a crack surface displacement extrapolation technique. From the obtained results of the analysis it is found that, the corner cracked plates more dangerous than the other cracked plates, since it has the highest stress intensity factor. Also, the length and orientation of the kinked crack have significant effects on the stress intensity factor. The results of this investigation is illustrated graphically, exposing some novel knowledge about the stress intensity factor and its dependence on crack configuration.
This study investigates the shear strength behavior of two-layer reinforced concrete beams consisting of two different types of concrete. One of the layers made of lightweight concrete (LWC) and the other was normal weight concrete (NWC). A total of 16 shear deficient reinforced concrete beams were fabricated and cast with NWC, LWC, and two-layer beam of both material with different configuration. All the beams were tested under four-point loading after 28 days. The variables of the experimental program include the ratio of thickness of the lightweight concrete layer to the overall depth of beam ( h LW / h ), and concrete compressive strength. Experimental results which include load-deflection response curves along with failure modes for NWC, LWC and two-layer beams. The results showed that all beams failed in a similar mode, due to diagonal tension shear crack. Based on the experimental results it can be also concluded that the shear load is governed by compressive strength of lower layer of the concrete when the shear span to overall depth ( a / h ) of the beams is 2.75 or more. While for the a / h 2.375 and 2.00 the two-layer beam has a significant reduction in the shear capacity compared to the NWC beams and increasing compared to LWC beam. The ratio of experimental shear stress divided by the root square of concrete compressive strength (vexp √f c ' ) , which demonstrates the diagonally cracked concrete's ability to transfer strain and shear was maintained for all configurations greater than 0.17, which is the minimal value recommended by ACI318-19.
The weight function prescribing the sensitivity of the electromagnetic flowmeter (EM}') to the changes in the velocity profiles must be as much as possible uniformly distributed through the measuring volume. The most commonly used criterion of the weight function distribution is a statistical quantity ( e criterion) which deals with only the axial component of the weight vector. In the present work, attempt 10 introduces a more revealing and accurate criterion to the EMF performance was studied. The curl of the weight function vector over the measuring volume has been considered and formulated (and termed as e ) in such a mathematical expression that takes Into account the contributions of the three components of the weight vector regardless of the geometry of the cross-sectional area of the flow. In addition, a numerical solution of a previously defined criterion (ey) is presented here for the first time in order to compare the validity of the newly introduced criterion. The results showed that the present new criterion e is closely harmonious with the previously defined criteria 8 and Si.. in the conventional flow cases. The results and the configuration of the formula of the present criterion, which is independent of the flow cross-sectional led us to conclude that is more reliable and applicable than other existing criteria.