Improved contact angle measurement in multiphase lattice Boltzmann

Contact angle is an essential parameter to characterize substrate wettability.The measurement of contact angle in experiment and simulation is a complex and time-consuming task.In this paper,an improved method of measuring contact angle in multiphase lattice Boltzmann simulations is proposed,which can accurately obtain the real-time contact angle at a low temperature and larger density ratio.The three-phase contact point is determined by an extrapolation,and its position is not affected by the local deformation of flow field in the three-phase contact region.A series of simulations confirms that the present method has high accuracy and gird-independence.The contact angle keeps an excellent linear relationship with the chemical potential of the surface,so that it is very convenient to specify the wettability of a surface.The real-time contact angle measurement enables us to obtain the dynamic contact angle hysteresis on chemically heterogeneous surface,while the mechanical analyses can be effectively implemented at the moving contact line.

An angular blinking jamming method based on electronically controlled corner reflectors

Passive jamming is believed to have very good potential in countermeasure community.In this paper,a passive angular blinking jamming method based on electronically controlled corner reflectors is proposed.The amplitude of the incident wave can be modulated by switching the corner reflector between the penetration state and the reflection state,and the ensemble of multiple corner reflectors with towing rope can result in complex angle decoying effects.Dependency of the decoying effect on corner reflectors’radar cross section and positions are analyzed and simulated.Results show that the angle measured by a monopulse radar can be significantly interfered by this method while the automatic tracking is employed.

A Combined Antenna Array Deployment with High Positioning Accuracy and Low Angular Measurement Error

In this paper,an antenna array composed of circular array and orthogonal linear array is proposed by using the design of long and short baseline“orthogonal linear array”and the circular array ambiguity resolution design of multi-group baseline clustering.The effectiveness of the antenna array in this paper is verified by sufficient simulation and experiment.After the system deviation correction work,it is found that in the L/S/C/X frequency bands,the ambiguity resolution probability is high,and the phase difference system error between each channel is basically the same.The angle measurement error is less than 0.5°,and the positioning error is less than 2.5 km.Notably,as the center frequency increases,calibration consistency improves,and the calibration frequency points become applicable over a wider frequency range.At a center frequency of 11.5 GHz,the calibration frequency point bandwidth extends to 1200 MHz.This combined antenna array deployment holds significant promise for a wide range of applications in contemporary wireless communication systems.

Novel Method for Spatial Angle Measurement Based on Rotating Planar Laser Beams

Spatial angle measurement, especially the measurement of horizontal and vertical angle, is a basic method used for industrial large-scale coordinate measurement. As main equipments in use, both theodolites and laser trackers can provide very high accuracy for spatial angle measurement. However, their industrial applications are limited by low level of automation and poor parallelism. For the purpose of improving measurement efficiency, a lot of studies have been conducted and several alternative methods have been proposed. Unfortunately, all these means are either low precision or too expensive. In this paper, a novel method of spatial angle measurement based on two rotating planar laser beams is proposed and demonstrated. Photoelectric receivers placed on measured points are used to receive the rotating planner laser signals transmitted by laser transmitters. The scanning time intervals of laser planes were measured, and then measured point＇s horizontal/vertical angles can be calculated. Laser plane＇s angle parameters are utilized to establish the abstract geometric model of transmitter. Calculating formulas of receiver＇s horizontal/vertical angles have been derived. Measurement equations＇ solvability conditions and judgment method of imaginary solutions are also presented after analyzing. Proposed method for spatial angle measurement is experimentally verified through a platform consisting of one laser transmitter and one optical receiver. The transmitters used in new method are only responsible for providing rotating light plane signals carrying angle information. Receivers automatically measure scanning time of laser planes and upload data to the workstation to calculate horizontal angle and vertical angle. Simultaneous measurement of multiple receivers can be realized since there is no human intervention in measurement process .Spatial angle measurement result indicates that the repeatable accuracy of new method is better than 10＂. Proposed method can improve measurement＇s automation degree and speed while ensuring measurement accuracy.

Non-contact angle measurement based on parallel multiplex laser feedback interferometry

We present a novel precise angle measurement scheme based on parallel multiplex laser feedback interferometry （PLFI）, which outputs two parallel laser beams and thus their displacement difference reflects the angle variation of the target. Due to its ultrahigh sensitivity to the feedback light, PLFI realizes the direct non-contact measurement of non- cooperative targets. Experimental results show that PLFI has an accuracy of 8＂ within a range of 1400＂. The yaw of a guide is also measured and the experimental results agree with those of the dual-frequency laser interferometer Agilent 5529A.

External-cavity birefringence feedback effects of microchip Nd:YAG laser and its application in angle measurement

External-cavity birefringence feedback effects of the microchip Nd：YAG laser are presented. When a birefringence element is placed in the external feedback cavity of the laser, two orthogonally polarized laser beams with a phase difference are output. The phase difference is twice as large as the phase retardation in the external cavity along the two orthogonal directions. The variable extra-cavity birefringence, caused by rotation of the external-cavity birefringenee element, results in tunable phase difference between the two orthogonally polarized beams. This means that the roll angle information has been translated to phase difference of two output laser beams. A theoretical analysis based on the Fabry-Perot cavity equivalent model and refractive index ellipsoid is presented, which is in good agreement with the experimental results. This phenomenon has potential applications for roll angle measurement.

STUDY ON MONOPULSE ANGLE MEASUREMENT METHOD BASED ON VIRTUAL POLARIZATION MATCHING

A monopulse angle measurement method for polarization array radar is studied in this paper.The receiving signal model is established and then a monopulse angle measurement method based on virtual polarization matching is proposed.To analyze the estimation performance,the Cramer-Rao Lower Bound(CRLB)of angle estimation is derived.Both theoretical analysis and simulation show that:firstly,the proposed method is superior to the traditional angle measurement methods based on the single polarization.Secondly,the performance of the new method is unrelated to the echo polarization.Thirdly,angle estimation of this method is asymptotically optimal.The results show that this method has great potential to be used in polarization array radar.

Biosorption of Cu^(2+) and Zn^(2+) by raw and autoclaved Rocella phycopsis

The behavior of Cu2＋ and Zn2＋ biosorption onto raw and modified Roccella phycopsis from aqueous solutions was studied. Modification process was applied by autoclavation at 121°C for 30 min. The effcts of pH, initial metal concentration and biosorbent dosage were investigated. The maximum Cu2＋ biosorption was achieved at pH 5.0 and the maximum biosorption capacities of 31.5 and 37.8 mg/g were recorded for raw and modified biosorbent, respectively. In the case of Zn2＋ biosorption, maximum biosorption capacities were obtained at pH 4.0 as 29.1 and 35.3 mg/g for raw and modified biosorbent, respectively. Biosorption of Zn2＋ and Cu2＋ on all form of R. phycopsis increased much quickly with increasing initial metal concentrations from 10 to 100 mg/L. After modification process, probable changes in the surface polarity of raw and modified R. phycopsis were investigated by contact angle measurements. As expected, R. phycopsis has a polar surface and shows a highest contact angle with water, while after autoclavation water contact angle of R. phycopsis was significantly decreased from 47.5° to 34.4°.

Polarization-space joint mainlobe jamming countermeasure technique based on divided dimensions

In order to solve the problem that the traditional space jamming countermeasure cannot deal with the mainlobe self-protecting jammings,a polarization-space joint mainlobe jamming countermeasure technique based on divided dimensions is proposed.Specifically,the digital beam of each row and column is firstly formed by using dual polarization digital receiving in multi-channel.Then,the polarization-space joint cancellation in both azimuth and elevation dimensions is carried out based on the polarization-space joint difference between the target echo and the jamming,as well as the divided dimension feature of the row and column beams.Finally,the sum and difference beams of the full array in the elevation or azimuth dimension are formed by the beams after jamming cancelling,and the monopulse angle measurement is further employed to obtain target angles.The effectiveness of the proposed technique is verified by simulations,indicating that the self-protecting jamming and multiple mainlobe following jammings can be both cancelled simultaneously with the angle measurement unchanged.

Measurement of Mathematical Constant π and Physical Quantity Pi

Instead of calculating the number π in this article special attention is paid to the method of measuring it. It has been found that there is a direct and indirect measurement of that number. To perform such a measurement, a selection was made of some mathematical and physical quantities which within themselves contain a number π. One such quantity is a straight angle Pi, which may be expressed as Pi = π rad. By measuring the angle, using the direct method, we determine the number π as π = arccos(-1). To implement an indirect measurement of the number π, a system consisting of a container with liquid and equating it with the measuring pot has been conceived. The accuracy of measurement by this method depends on the precision performance of these elements of the system.

Feasible Resolution of Angular Displacement Measurement by an Optical Angle Sensor Based on Laser Autocollimation

The feasible resolution of angular displacement measurement by an optical angle sensor based on laser autocollimation is investigated.Improving the sensor sensitivity while maintaining the noise level of the sensor signal as low as possible is necessary to achieve high-resolution angular displacement measurement.In this paper,the contribution of each component,such as a photodiode,a trans-impedance amplifer,and an analog-to-digital converter in the optical angle sensor,to the noise level of the sensor signal is frst estimated on the basis of theoretical equations.The feasible sensitivity of the optical angle sensor is also estimated in numerical calculations.The sensitivity of a photodiode element at the edge of its photosensitive area is evaluated in experiments to realize the estimation of the angle sensor sensitivity.Experimental results are applied to the numerical calculations.The infuences of the measurement laser beam diameter,the spot diameter of the focused laser beam on the photosensitive area,and the focal length of the collimator objective of the optical angle sensor are also consid-ered in the numerical calculations.Finally,a prototype optical setup is developed.Experiments are performed to demonstrate that a compact optical angle sensor based on laser autocollimation with a collimator objective having a focal length shorter than 100 mm can achieve a resolution beyond 0.001 arc-second with a bandwidth of 1 kHz.This resolution is better than those achieved by commercial autocollimators employing an image sensor or a position-sensitive detector.The industrial contribution of this paper lies in the detailed breakdown of noise components in the readout signal of an angle sensor in a practical condition and the systematic estimation of its feasible resolution as well as its sensitivity.

Angle Measurement Based on Second Harmonic Generation Using Artificial Neural Network

This article proposed an angle measurement method based on second harmonic generation(SHG)using an artifcial neural network(ANN).The method comprises three sequential parts:SHG spectrum collection,data preprocessing,and neural network training.First,the referenced angles and SHG spectrums are collected by the autocollimator and SHG-based angle sensor,respectively,for training.The mapping is learned by the trained ANN after completing the training process,which solves the inverse problem of obtaining the angle from the SHG spectrum.Then,the feasibility of the proposed method is verifed in multiple-peak Maker fringe and single-peak phase-matching areas,with an overall angle measurement range exceeding 20,000 arcseconds.The predicted angles by ANN are compared with the autocollimator to evaluate the measure-ment performance in all the angular ranges.Particularly,a sub-arcsecond level of accuracy and resolution is achieved in the phase-matching area.

A technique of reconstructing field for measuring sound reflection coefficients at arbitrary angles of incidence

An improved reconstructing field method for measuring sound reflection coefficient of a large impedance surface at arbitrary incident angles is proposed in this paper. In order to get the reflection coefficient by the Spatial Transformation of Sound Fields (STSF), the complex pressure on two parallel planes near by the material surface or the reflection surface must be measured. By the acoustic intensity measurement, the phases of complex pressure on two parallel planes are given. The results of the numerical simulations are shown that the error due to the finite size of the measurement area, and it may be reduced by using a dipole sound source.

An improved method of angle measurement with a position sensitive detector

An improved method of angle measurement is proposed based on a parallel plate interferometer. A position detection system is incorporated into a parallel plate interferometer in order to realize large deflection angle measurement. A reflecting mirror is introduced for increasing the measurement resolution. In experiments, a deflection angle of a measured target was measured within ～3° with high accuracy. And as a phase modulating interferometer, it was used to measure a small angular displacement with a repeatability of 5.5 × 10^-8 rad.

Simultaneous measurement of vibration amplitude and rotation angle based on a single-channel laser self-mixing interferometer

Based on a single-channel laser self-mixing interferometcr, we present a new silnultaneous measurement of the vibration amplitude and tile rotation angle of objects that both affect the power spectrum containing two peaks of the interferometer signals. The fitted results indicate that the curve of the peak frequency versus the vibration amplitude follows a linear distribution, and the curve of the difference of the two-peak power values versus the angle follows a Gaussian distribution. A vibration amplitude with an error less than 3.0% and a rotation angle with an error less than 11.7% are calculated from the fitted results.

A comprehensive survey on the methods of angle of attack measurement and estimation in UAVs

Angle of Attack(AOA) is a crucial parameter which directly affects the aerodynamic forces of an aircraft.The measurement of AOA is required to ensure a safe flight within its designed flight envelop.This paper intends to summarise a comprehensive survey on the measurement techniques and estimation methods for AOA, specifically in Unmanned Aerial Vehicle(UAV) applications.In the case of UAVs, weight constraint plays a major role as far as sensor suites are concerned.This results in selecting a suitable estimation method to extract AOA using the available data from the autopilot.The most feasible and widely employed AOA measurement technique is by using the Multi-Hole Probes(MHPs).The MHP measures the AOA regarding the pressure variations between the ports.Due to the importance of MHP in AOA measurement, the calibration methods for the MHP are also included in this paper.This paper discusses the AOA measurement using virtual AOA sensors, their importance and the operation.

Entanglement-free determination of pretilt angles of twisted nematic liquid-crystal cells by phase measurement

Because of low cost, fast response time, and high light transmittance, thin-film-transistor （TFT） driven twisted nematic （TN） liquid-crystal displays （LCDs） have been widely used in calculators, computer screens, and cell phones. The pretilt angle of the TN medium within the TFT-TN panel affects not only its response times and view- ing angles but also the light-leakage positions of fringed- field-induced disclination lines within pixels of theTFT-TN panel.

EXPERIMENTAL RESEARCH ON A SUPERCAVITATING SLENDER BODY OF REVOLUTION WITH VENTILATION

The behavior of supercavitating and cavitatlng flow around a conical body of revolution with and without ventilation at several angles of attack was studied experimentally. The hydrodynamic forces for a range of cavitation number were measured. Comparisons of the appearance and the hydrodynamic forces in condition of cavity with and without ventilation were made over the same range of the cavitation number, and a well agreement was obtained. The changes of the drag were especially studied. The experimental results showed that the drag of the model decreased with the presence of supercavity under the ventilation condition.

In-vitro biomineralization and biocompatibility of friction stir additively manufactured AZ31B magnesium alloy-hydroxyapatite composites

The present study aims to evaluate effect of hydroxyapatite(HA,Ca10(PO4)6OH2),a ceramic similar to natural bone,into AZ31B Mg alloy matrix on biomineralization and biocompatibility.The novel friction stir processing additive manufacturing route was employed to fabricate Mg-HA composites.Various HA contents(5,10,20 wt%)were incorporated into Mg matrix.Microstructural observation and chemical composition analysis revealed that refined Mg grains and dispersion of HA particles at micro/nanoscales were achieved in Mg-HA composites after the friction stir processing.The biomineralization evaluation were carried out using immersion experiments in simulated body fluid followed by mineral morphology observation and chemical composition analysis.The wettability measurements were conducted to correlate the biomineralization behavior.The results showed improvement in wettability and bone-like Ca/P ratio in apatite deposit on the composites compared to as-received Mg.In addition,the increase of blood compatibility,cell viability and spreading were found in the higher HA content composites,indicating the improved biocompatibility.Therefore,friction stir processed Mg-20 wt%HA composite exhibited the highest wettability and better cell adhesion among other composites due to the effect of increased HA content within Mg matrix.

Femtosecond laser induced periodic large-scale surface structures on metals

The periodic ripple structures on wolfram and titanium surfaces are induced experimentally by linear polarized femtosecond laser pulses at small incident angles. The structural features show a material difference in the s- and p-polarized laser irradiation. The interspace between the ripples increases significantly for p-polarized laser irradiation when it exceeds a threshold angle, and the ripples＇ periodicities are larger than the wavelength of the incident p-polarized femtosecond laser; however, no significant change in the period of the ripples is observed with increasing incident angle for s-polarized laser irradiation. To explain these phenomena we propose a resonant absorption mechanism, by which the experimental observations can be interpreted.