Rapid AC Electrokinetic Micromixer with Electrically Conductive Sidewalls

We report a quasi T-channel electrokinetics-based micromixer with electrically conductive sidewalls, where the electric field is in the transverse direction of the flow and parallel to the conductivity gradient at the interface between two fluids to be mixed. Mixing results are first compared with another widely studied micromixer configuration, where electrodes are located at the inlet and outlet of the channel with electric field parallel to bulk flow direction but orthogonal to the conductivity gradient at the interface between the two fluids to be mixed. Faster mixing is achieved in the micromixer with conductive sidewalls. Effects of Re numbers, applied AC voltage and frequency, and conductivity ratio of the two fluids to be mixed on mixing results were investigated. The results reveal that the mixing length becomes shorter with low Re number and mixing with increased voltage and decreased frequency. Higher conductivity ratio leads to stronger mixing result. It was also found that, under low conductivity ratio, compared with the case where electrodes are located at the end of the channel, the conductive sidewalls can generate fast mixing at much lower voltage, higher frequency, and lower conductivity ratio. The study of this micromixer could broaden our understanding of electrokinetic phenomena and provide new tools for sample preparation in applications such as organ-on-a-chip where fast mixing is required.

Effect of antiblock and slip additives on the properties of tubular quenched polypropylene film

In the present investigation, silica and talc were used as antiblock additives with slip additive to investigate their effects on tubular quenched polypropylene (TQPP) film properties. Polypropylene (PP) powder was compounded with additives in twin-screw extruder and subsequently processed through TQPP machine to prepare the films. Tear and tensile properties [in machine direction (MD) and transverse direction (TD)] and surface properties of the produced TQPP films were investigated in terms of optics and coefficient of friction (CoF). The effect of conditioning time on CoF was also studied. Addition of slip agent alone to PP did not show any significant change in tear strength, CoF and tensile properties, whereas CoF reduced drastically by adding both slip and antiblock agents in combination. Reduction in CoF values were found to be more pronounced in the presence of silica-based antiblock compared to talc-based antiblock. Film surface morphology was further examined by field-emission scanning electron microscopy. The tear strength and the gloss of TQPP film decreased slightly in presence of only antiblock agents, but the tensile strength was found to increase. It was also found that tensile properties of TQPP films were superior in silica-based formulation, whereas tear strength was better in talc-based formulation in MD and TD.

Flow-Induced Vibrations of a Rotated Square Tube Array Subjected to Single-Phase Cross-Flow

This paper investigates the flow-induced vibration (FIV) and possibility of fluidelastic instability occurrence in a rotated square geometry tube array through a series of experimental tests. All experiments presented here were conducted in water cross-flow. The array pitch spacing ratio of approximately P/D=1.64 is somewhat larger than that commonly found in typical steam generators. The stability of a single flexible tube as well as multiple flexible tubes were investigated. The tubes were free to vibrate purely in the streamwise direction or the transverse direction relative to the upstream flow. A single flexible tube, in the otherwise rigid tube array, was found to undergo large amplitude vibrations (up to 40 % D) in the transverse direction. Tube vibration frequency analysis indicated the presence of two frequency components related to vorticity shedding in the array. This potential vorticity-induced-vibrations (VIV) and potential coupling between VIV and FEI are discussed in the paper. Test results for streamwise flow-induced vibrations are also presented. Results in water flow show a possible effect related to flow periodicity at low velocity. At significantly high flow velocities, the tubes are found to fully restabilize. This restabilization after VIV locking has not been previously reported as an unlocking result. The present results suggest that the flow-induced vibration of tubes in a rotated square array configuration is significantly more complex than in other geometries, particularly for the streamwise vibration case.

Chloride Diffusion by Build Orientation of Cementitious Material-Based Binder Jetting 3D Printing Mortar

Binder jetting 3D printing (BJ3DP) is used to create geometrical and topology-optimized building structures via architectural geometric design owing to its high degree of freedom in geometry implementation. However, building structures require high mechanical and durability performance. Because of the recent trend of using 3D printing concrete as a structural component in reinforcing bars, its durability with respect to chloride penetration needs to be reviewed. Therefore, in this study, the compressive strength and durability of the chloride diffusion of cement-based 3D-printed output were evaluated. In addition, to confirm the performance difference based on the build orientation, the compressive strength and chloride diffusion were evaluated with respect to the build direction and transverse direction. The experimental results show that the compressive strength was approximately 22.1–26.5% lower in the transverse direction than in the build direction and that the chloride diffusion coefficient was approximately 186.1–407.1% higher in the transverse direction. Consequently, when a structure that requires long-term durability is produced using BJ3DP, it is necessary to examine the design and manufacturing methods in relation to the build orientation in advance.

Study on plowing of cotton soil using two-tier plow

The purpose of the study is to substantiate the parameters of a two-tier plow for plowing soil from under cotton. The basic principles and methods of classical mechanics, mathematical analysis and statistics were used in this study. The effects of the cotton field relief on the tillage and traction resistance of a two-tier plow were studied theoretically and experimentally. Analytical expressions are obtained for determining the uniformity of the course, the load of the bodies and the center of resistance of the plow, depending on its main parameters and the roughness of the relief of the cotton field. It is established that serial two-tier plows, due to the discrepancy between their width of the gripper and the width of the row spacing, do not meet the requirements of agricultural technology: the plowing depth is not stable, the coefficient of variation of the plowing depth reaches 16% for a trailed plow, and for a mounted plow - 25.8%; the transverse direction of the plough the bottom of the furrow turns out to be stepped; the value of the traction resistance changes at each pass of the plow. To improve the quality of plowing fields from under cotton, a new plowing method has been developed, carried out by a two-tier plow, the width of which is a multiple of the width of the row spacing of cotton. The width of the plow bodies is equal to half the width of the row spacing.

Evaluation and Analysis of Tractor Driver’s Seat Vibrations without Implements and with Implements during Tillage Process

In day to day operations tractor has to move with tillage implements and without tillage implements. In this work emphasis has been given to compare the effect of vibrations on driver’s seat of tractor while working with implements during tillage and while working without implements. The experiment was conducted in the fields of Punjab (India). During the experiment, first time the tractor was made to move without implements and second time tractor was moving with chisel plough (tillage implement). Both times real time vibration data of driver’s seat was collected with three-axis accelerometer and it was observed that when tractor was moving without implements the vibration amplitude was highest in vertical direction Z as compared to transverse direction Y and horizontal direction X. But when the tractor was moving in the fields with tillage implement (chisel plough) the vibration amplitude was high in transverse direction Y relative to horizontal direction X and vertical direction Z.

Broadband unidirectional scattering in the transverse direction and angular radiation realized by using a silicon hollow nanodisk under a radially polarized beam

In recent years, directional scattering has been one of the most active research hotspots in the field of nanophotonics. Herein, we study the directional scattering properties of a silicon hollow nanodisk illuminated by a tightly focused radially polarized beam. The induced strong longitudinal total electric dipole interferes with transverse magnetic dipole to achieve a highly-efficient transverse unidirectional scattering when the silicon hollow nanodisk is located at a specific position in the focal plane. Moreover, the manipulated unidirectional scattering in the transverse direction can be realized in the broad wavelength range from 581 nm to 656 nm. In addition, the unidirectional angular radiation towards all directions can be realized by adjusting the position of the silicon hollow nanodisk. Our research results are helpful for the design of nanophotonic devices that can manipulate the angular radiation direction, and have potential applications in sensing, optical communications, solar cells and other fields.

Water vapour permeability of wood – remarks on cup method procedure and measured data of spruce wood

Although the water vapour permeability of wood has been determined many times, there can be found a wide spread of values even related to only one wood specie and its single anatomical direction. This spread can possibly be attributed to the measurement method itself, since the cup method often shows high inter-laboratory error. However, even if the measurement and evaluation processes are well performed and under control, there were found several factors that can still highly affect the resulting value – up to ca. 70 %. These factors are neither mentioned in standards, nor were found in other sources. This paper theoretically describes those factors and their possible impact to the final value of water vapour permeability. Paper also presents one particular measurement scheme and obtained data from four cup tests performed on spruce wood in transverse direction.