Axial Direction Research Articles

Design and implementation of a novel wideband dual‐polarised transmitarray antenna based on tightly coupled cross dipole cells

AbstractA novel broadband dual‐polarised transmitarray antenna (TA) utilising tightly coupled cross dipole cells is proposed in this work. The transmitarray cell using the tightly coupling wideband principle comprises two radiation patches designed as two orthogonal planar dipoles with four interdigital capacitors, two meandered parallel plate transmission lines, and a ground. Each cell has a square shape and a dimension of approximately 0.28 where is the wavelength at central frequency 5.5 GHz. The transmitarray cell can achieve 475° phase shift at central frequency and transmission magnitude better than −2.5 dB within the working band. To verify the feasibility of this design, a tightly coupled dual‐polarised transmitarray antenna (TCDPTA) is modelled and manufactured. The transmitarray aperture size is approximately 4.1 4.1 . The simulation and measurement illustrate that the TCDPTA has stable and distortion‐free main beams whose side lobe levels are generally below −10 dB in the band of 3.0–8.0 GHz. The measured gain at central frequency is 16.2 dBi and peak gain is 19 dBi at 7.5 GHz. The working bandwidth is 90.9% and 3 dB gain bandwidth is 66.7%. The measured cross‐polarisation levels are below −15 dB at axial direction. This TA has potential applications for high‐date‐rate communication and high‐revolution radar imaging systems at C‐band.

Near-Field Mixing in a Coaxial Dual Swirled Injector

AbstractImproving mixing between two coaxial swirled jets is a subject of interest for the development of next generations of fuel injectors. This is particularly crucial for hydrogen injectors, where the separate introduction of fuel and oxidizer is preferred to mitigate the risk of flashback. Raman scattering is used to measure the mean compositions and to examine how mixing between fuel and air streams evolves along the axial direction in the near-field of the injector outlet. The parameters kept constant include the swirl level $$S_e = 0.67$$ S e = 0.67 in the annular channel, the injector dimensions, and the composition of the oxidizer stream, which is air. Experiments are carried out in cold flow conditions for different compositions of the central stream, including hydrogen and methane but also helium and argon. Three dimensionless mixing parameters are identified, the velocity ratio $$u_e/u_i$$ u e / u i between the external stream and internal stream, the density ratio $$\rho _e/\rho _i$$ ρ e / ρ i between the two fluids, and the inner swirl level $$S_i$$ S i in the central channel. Adding swirl to the central jet significantly enhances mixing between the two streams very close to the injector outlet. Mixing also increases with higher velocity ratios $$u_e/u_i$$ u e / u i , independently of the inner swirl. Additionally, higher density ratios $$\rho _e/\rho _i$$ ρ e / ρ i enhance mixing between the two streams only in the case without swirl conferred to the central flow. A model is proposed for coaxial swirled jets, yielding a dimensionless mixing progress parameter that only depends on the velocity ratio $$u_e/u_i$$ u e / u i and geometrical features of the swirling flow that can be determined by examining the structure of the velocity field. Comparing the model with experiments, it is shown to perform effectively across the entire range of velocity ratios $$0.6 \le u_e/u_i \le 3.8$$ 0.6 ≤ u e / u i ≤ 3.8 , density ratios $$0.7 \le \rho _e/\rho _i \le 14.4$$ 0.7 ≤ ρ e / ρ i ≤ 14.4 , and inner swirl levels $$0.0 \le S_i \le 0.9$$ 0.0 ≤ S i ≤ 0.9 . This law may be used to facilitate the design of coaxial swirled injectors.

High coupling efficiency with large axial direction coupling adjustment range in water-jet guided laser

In the traditional water-jet guided laser (WJGL) processing system, convex lens is used to focus Gaussian laser beam, where the waist and divergence angle are constrained. The focal depth is small, and there are problems such as divergence angle and aberration, which results in the difficult coupling adjustment because the adjustment range of laser coupling to water-jet fiber is limited to the Rayleigh range. In this study, non-diffraction laser (NDL) is generated by an axicon, which has the characteristics of small central spot and large non-diffraction range (NDR). The axial random coupling is realized in the NDR, and the problem of axial coupling between the focused laser and the water-jet generated by nozzle micro-hole is solved. Besides, this paper presents a novel technique to generate NDL by the combination of concave axicon (CCA) and convex axicon (CVA), which solves the small cone angle of the single CVA and the non-modulation defect of the corresponding optical and mechanical structure, and extends the starting point of the NDR to improve the coupling utilization rate of the NDR and the flexibility of the system. The focusing and coupling transmission characteristics of convex lens and axicons mode in WJGL are compared and analyzed. The generated NDL in the NDR at the axial reference coordinate point position of 50 mm and 70 mm is successfully coupled into the water-jet fiber. After the coupling transmission of 20 mm, the coupling efficiency, the morphology of the transmitted spot and the peak power density were basically the same, and the coupling efficiency of the central spot was about 81 %. However, the output spot peak power density and coupling efficiency decrease sharply when the axial coupling deviation exceeds 5 mm adopting convex lens. In contrast, the NDL can achieve a random coupling with high axial coupling tolerance in NDR. The research provides a solution for efficient adjustment and transmission of laser coupling into water-jet in highly stable WJGL.

Joint Observation of a Series of Magnetic Holes by Tianwen-1 and MAVEN on Mars

Magnetic holes (MHs) are transient magnetic structures responsible for energy conversion in space plasma. Using single-spacecraft measurements from Mars Atmosphere and Volatile EvolutioN (MAVEN), the existence of MHs on Mars has been confirmed. However, due to the limitations of single-spacecraft observations, significant uncertainty also arises on the identification of the spatial scale and 3D geometry of MHs. In this study, we report a series of MHs successively detected by Tianwen-1 near the high-latitude magnetopause and by the MAVEN spacecraft near the subsolar magnetopause. The large separation between Tianwen-1 and MAVEN (∼4 R M) suggests these MHs are macroscale structures extending along the axial direction. Additionally, we observe whistler waves generated by electron perpendicular anisotropy in one of the macroscale MHs. This study is the first joint observation of Martian MHs, shedding light on the research of transient magnetic structures on Mars.

A New Method for Compression Testing of Reinforced Polymers

Compressive testing of specimens taken from relatively thin composite plates is difficult, especially due to the occurrence of buckling. To prevent buckling, the central portion of the specimens used for the compression test has smaller dimensions, and the specimens can be guided along their entire length. For these reasons, optical methods, such as digital image correlation (DIC), cannot be used for the compression test and strain rosettes cannot be glued onto the samples to determine Poisson’s ratio. In this study, compression tests of a glass fiber-reinforced polymer (GFRP) were conducted using both the ASTM D695 (Boeing version) and a newly proposed method. The new method involves using special specimens that allow T-type rosettes to be bonded to determine Poisson’s ratio, whose value of 0.14 was thus determined. SEM images of the failure surfaces were presented and interpreted. A finite element analysis (FEA) of the specimens tested in compression is also presented. The first analyzed case considers the homogeneous and orthotropic composite, loaded with a uniformly distributed force. The normal stress in the central section of the specimen, determined with FEA, has an error of 6.52% compared to that determined experimentally. Additionally, the strain in the center of the strain gauge, determined with FEA, has an error of 4.76% compared to the measured one. In the second case studied with FEA, the sample is loaded with a quasi-concentrated force, which can move in the direction of the symmetry axes of the cross-section, to study the effect of the eccentricity of the compression force on the state of stress. It was shown that the eccentricity of the force has a great influence: the stress distribution in the section of the specimen becomes strongly non-uniform. For a force eccentricity of 0.4 mm in the direction of the OX axis, the minimum stress decreases by 53.7%, and the maximum stress increases by 55.4%. In order to analyze the influence of some manufacturing defects, two other cases were analyzed by FEA, in which it was assumed that the thicknesses of the outer resin layers were modified, making them asymmetrical. For this final FEA, the specimen was considered to be composed of laminates. These results demonstrate the special attention that must be paid to the centric application of force in compression testing.

Self-assembled sub-picoliter liquid periodic structures in a hollow optical fiber

In an experimental exploration, we successfully implemented a self-assembling methodology to construct a periodic liquid-air structure inside a hollow optical fiber (HOF). This fiber comprises a central air hole, a germanosilica ring core, and a silica cladding. A periodic structure of liquid droplets and air was obtained by the application of a microscopic heat source (MHS) traversing along the axial direction of the liquid-filled HOF. In the course of this study, we discerned three distinct zones within the structure. The first zone, referred to as Zone 1, demonstrated near-constant periodicity. The second zone, Zone 2, exhibited adaptable properties with regard to its periodicity, allowing it to be flexibly controlled. In the third zone, Zone 3, we noticed a chaotic response to external parameters, including temperature and the speed at which MHS was traversed. To regulate the liquid-air periodic structures, two different types of MHSs were utilized - a micro hydro-oxygen torch and a metal ring heater, each mounted on a translation stage. The study provides a detailed account of the parameters employed in utilizing these MHSs. Additionally, the optical properties of these liquid-air periodic structures were meticulously analyzed to explore the potential for developing new optofluidic applications.

Seismic Response Characteristics of a Utility Tunnel Crossing a River Considering Hydrodynamic Pressure Effects

As a long lifeline system of buried structures, the utility tunnel (UT) is vulnerable to earthquake invasion. For utility tunnels with inverted siphon arrangements crossing rivers, the seismic response is more complex due to the basin effect of acceleration in the topography and the influence of fluctuating hydrodynamic pressure, but there is currently a gap in targeted seismic response analyses and references. Based on a UT project in Haikou, this paper studied seismic responses of a cast-in-place UT considering the coupled model of water–soil–tunnel structure on ABAQUS software. Herein, the dynamic fluctuation of hydrodynamic pressure is simulated using an acoustic–solid interaction model. A viscoelastic artificial boundary was used to simulate the soil boundary effect, and seismic loads were equivalent to nodal forces. Considering seismic invading direction and varying water elevation, this paper investigates the dynamic response characteristics and damage mechanisms of river-crossing utility tunnels. This study shows that the basin effect causes the soil acceleration around the UT to show variability in different sections, and the amplification factor of the peak acceleration at the central location is almost doubled. The damage and dynamic water pressure of the UT are intensified under bidirectional seismic excitation, and the damage location is concentrated at the junction of the horizontal section and the vertical section. Bending moments and axial forces are the main mechanical behaviors along the axial direction. Changes in river levels have a certain positive effect on the UT peak MISES, DAMAGEC, and SDEG, and it exhibits a certain degree of energy dissipation and seismic damping effect. For the aseismic design of cross-river cast-in-place utility tunnels, bidirectional seismic calculations should be performed, and the influence of river hydrodynamic pressure should not be neglected.

Exploring unsteady radiative nanofluid dynamics: Thomson–Troian wall slip effects on a stretching rotating disk

AbstractFluid flow over rotating disk possesses many potential application in many engineering, biological, electrical, and chemical. Along with nanoparticles flow become more enriched in terms of chemical and physical properties. This study investigates the laminar, unsteady, incompressible flow of a water‐based nanofluid above a rotating, stretchable disk. The nanofluid consists of three distinct nanoparticles (magnetite), (copper), and (silver), under the influence of radiation. The behavior of the nanofluid is modeled using the Tiwari and Das model with generalized slip on the disk surface. The new facet of study is to examines the effects of different parameters including stretching, slip, radiation, skin friction, and Nusselt numbers on the flow dynamics. The fluid motion is driven by the rotation and stretching of the disk. Through appropriate similarity transformations, the governing partial differential equations for the flow and thermal transport processes are transformed into a set of coupled ordinary differential equations. These equations are then numerically solved using bvp4c method in MATLAB. The results indicate that velocities in both the radial and axial directions increase with rising stretching parameters, due which skin friction coefficient mount by . And, Nusselt number of fluid surge by increasing volume fraction of , , nanoparticles respectively. Additionally, the temperature increases with increment in the radiation parameter . An increase in the slip parameter's value results in a reduction in both radial and axial velocities.

MPFEM investigation on densification and mechanical structures during ferrous powder compaction

Metal powder compaction is a crucial process in powder metallurgy, significantly affecting the final properties of compacts. However, the quantitative characteristics of multi-scale mechanical structures and the microscopic densification behavior, taking into account the influence of friction conditions, remain unclear. This study utilises a two-dimensional multi-particle finite element method to analyse the ferrous powder compaction. The evolution of powder densification, powder deformation and multi-scale mechanical behaviour under different friction coefficient conditions are analyzed quantitatively and qualitatively. Results reveal that powder densification occurs in distinct stages, with lower friction coefficients promoting greater powder densification, as observed from relative density and coordination number. Additionally, as the axial strain increases, plastic strain gradually rises whilst roundness decreases. Higher friction coefficients are associated with higher equivalent plastic strain but lower powder roundness. The Von Mises stress exhibits different stages of increase with the increment of axial strain. Powders with lower friction coefficients exhibit lower levels of Von Mises stress. As axial strain increases, the number, length, strength and direction coefficient of force chains undergo different evolution processes. Force chains exhibit longer length, fewer numbers, lower strength and lower direction coefficients at lower friction coefficients.

Three-dimensional computer holography with phase space tailoring

Computer holography is a prominent technique for reconstructing customized three-dimensional (3D) diffraction fields. However, the quality of optical reconstruction remains a fundamental challenge in 3D computer holography, especially for the 3D diffraction fields with physically continuous and extensive depth range. Here, we propose a 3D computer-generated hologram (CGH) optimization framework with phase space tailoring. Based on phase space analysis of the space and frequency properties in both lateral and axial directions, the intensity of the 3D diffraction field is adequately sampled across a large depth range. This sampling ensures the reconstructed intensity distribution to be comprehensively constrained with physical consistency. A physics-informed loss function is constructed based on the phase space tailoring to optimize the CGH with suppression of vortex stagnation. Numerical and optical experiments demonstrate the proposed method significantly enhances the 3D optical reconstructions with suppressed speckle noise across a continuous and extensive depth range.

La-Fe-Si magnetocaloric composite with anisotropic microstructure prepared by hot pressing

In this study, we have proposed an anisotropic microstructure in La-Fe-Si magnetocaloric composites for thermal management. This is vital to the rapid heat exchange and high working efficiency in magnetic refrigerator system. We demonstrate the anisotropic microstructure in composites can be fabricated via powder metallurgy in this work. By adjusting the particle size of the 1:13 phase, the introduced reinforcing phase with rheological property can effectively deform and anisotropic microstructure can be obviously observed. This can be attributed to the tailored stress distribution in cubic-anvil-type pressure apparatus. The element diffusion between the two phases was also discussed in this paper, taking into account the influence of particle size. Such anisotropic microstructure causes some other anisotropic physical properties in the composite, such as mechanical strength. The compressive measurements along the axial direction exhibit superior mechanical properties (~ 3.5% for strain and ~ 350 MPa for strength) compared to those along the radial direction. Attributed to the stress buffer-effect provided by the introduced ductile phase, magnetocaloric effect (magnetic entropy change ~ 7.8 J/kg K) can be maintained in the La-Fe-Si composite.

Elucidating the effect of strain path-dependent crystallographic texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy

This research provides insight into the effect of strain path-dependent texture evolution on the electrochemical behavior of nanostructured AA2024 aluminum alloy in a phosphate buffer solution (pH = 8.3). To achieve this, AA2024 alloy sheets were processed using two methods: accumulative roll bonding (ARB) and cross accumulative roll bonding (CARB), i.e., rotating the sheets 90° around the normal direction (ND) axis between each cycle. The ARB-processed AA2024 alloy exhibited a pancake-shaped structure and included texture components of Copper {112}<111>, Brass {011}<211>, P {110}<221>, and S {123}<634>. Meanwhile, the CARB-processed AA2024 alloy had extremely fine and equiaxed nano-grains (< 100 nm) and texture components of S {123}<634>, Brass {011}<211>, Goss {011}<100>, Rotated Cube {001}<110>, and P {110}<221> after eight cycles. Electrochemical studies demonstrated an increase in corrosion current density due to high imposed strains in the ARB route, which in effect made the conditions of passive layer formation more difficult and lowered the corrosion resistance. Additionally, achieving a more uniform distribution of extremely fine grains and {011} orientation textures such as Brass {011}<211>, Goss {011}<100>, and P {110}<221> texture components in the CARB route, provided ideal conditions for forming oxide passive films with superior protection properties compared to ARB. These unique findings can contribute to the broader application of crystallographic-orientation-dependent electrochemical behavior of alloys in the field of corrosion management.

A comprehensive study on a tapered Paul trap: from design to potential applications

Abstract We present a tapered Paul trap whose radio frequency electrodes are inclined to the symmetric axis of the endcap electrodes, resulting in a funnel-shaped trapping potential. With this configuration, a charged particle confined in this trap has its radial degrees of freedom coupled to that of the axial direction. The same design was successfully used to experimentally realize a single-atom heat engine, and with this setup amplification of zeptonewton forces was implemented. In this paper, we show the design, implementation, and characterization of such an ion trap in detail. This system offers a high level of control over the ion’s motion. Its novel features promise applications in the field of quantum thermodynamics, quantum sensing, and quantum information.

Advanced ultrasound diagnosis of extrahepatic bile duct lesions.

Ultrasound (US) has high specificity and sensitivity, and it should be performed first for patients with suspicion of biliary tract cancer. However, the complicated anatomy in addition to the gas images makes it difficult to delineate the entire extrahepatic bile duct (EHBD). The keys to depiction of EHBD are the "J" shape manipulation in the left lateral decubitus position and the use of magnified images with high-frequency transducers. Furthermore, indirect findings such as gallbladder (GB) distension, BD dilatation, and debris echo in the GB and BD are also important for detecting occult lesions, particularly in the ampullary region of Vater. For the differential diagnosis of BD wall thickening, the spreading pattern in the long and short axial directions should be assessed first. Then, the characteristics of the innermost hyperechoic layer (IHL) and outermost hyperechoic layer (OHL) should be evaluated. Asymmetrical wall thickening, absence of IHL, and presence of irregularity or discontinuity in OHL are characteristic patterns of cholangiocarcinoma (CCA). Because CCA is the most common BD polypoid lesion, it is important to diagnose tumor extension and depth invasion in addition to differential diagnosis. Nodular-type CCA is usually hypoechoic and more likely to invade vertically. In contrast, papillary-type CCA is often hyperechoic and extends laterally. Contrast‑enhanced US may be useful for evaluating these findings. However, if the possibility of CCA cannot be ruled out or a definitive diagnosis is needed, a transpapillary biopsy or endoscopic US-guided tissue acquisition should be considered.

Investigation of Upper Critical Magnetic Field in 1111‐Type High‐Temperature Iron‐Based Superconductor SmFeAsO1−xFx

ABSTRACTIn this research work, we used a two‐band model to study the theoretical analysis of the upper critical magnetic field of a high‐temperature iron‐based superconductor . The graphs of the high‐temperature iron‐based superconductor's upper critical magnetic field (((T) and ) and angular dependence of the field () versus temperature were effectively plotted. The phase diagrams of the temperature‐dependent upper critical magnetic fields versus temperature were suppressed at the transitional temperature and decreased with rising temperature for both directions of the symmetry axis. Additionally, we plotted the phase diagrams and derived the Ginzburg–Landau (GL) parameters (( and ). At the superconducting critical temperature of the superconducting material, these GL parameters diverge at the transitional temperature. Furthermore, a phase diagram of GL characteristic parameter temperature dependence was plotted. By doping fluorine atoms into the parent compound Sm‐1111, the transitional temperature of this superconductor material increased, reaching a value of 54 K and above. Finally, our theoretical conclusion is consistent with the previous experimental results.

Neutronics Analysis on High-Temperature Gas-Cooled Pebble Bed Reactors by Coupling Monte Carlo Method and Discrete Element Method

The High-Temperature Gas-Cooled Pebble Bed Reactor (HTG-PBR) is notable in the advanced reactor realm for its online refueling capabilities and inherent safety features. However, the multiphysics coupling nature of HTG-PBR, involving neutronic analysis, pebble flow movement, and thermo-fluid dynamics, creates significant challenges for its development, optimization, and safety analysis. This study focuses on the high-fidelity neutronic modelling and analysis of HTG-PBR with an emphasis on achieving an equilibrium state of the reactor for long-term operations. Computational approaches are developed to perform high-fidelity neutronics analysis by coupling the superior modelling capacities of the Monte Carlo Method (MCM) and Discrete Element Method (DEM). The MCM-based code OpenMC and the DEM-based code LIGGGHTS are employed to simulate the neutron transport and pebble movement phenomena in the reactor, respectively. To improve the computational efficiency to expedite the equilibrium core search process, the reactor core is discretized by grouping pebbles in axial and radial directions with the incorporation of the pebble position information from DEM simulations. The OpenMC model is modified to integrate fuel circulation and fresh fuel loading. All of these measures ultimately contribute to a successful generation of an equilibrium core for HTG-PBR. For demonstration, X-energy’s Xe-100 reactor—a 165 MW thermal power HTG-PBR—is used as the model reactor in this study. Starting with a reactor core loaded with all fresh pebbles, the equilibrium core search process indicates the continuous loading of fresh fuel is required to sustain the reactor operation after 1000 days of fuel depletion with depleted fuel circulation. Additionally, the model predicts 213 fresh pebbles are needed to add to the top layer of the reactor to ensure the keff does not reduce below the assumed reactivity limit of 1.01.

Bio-Inspired Thermal Conductive Fibers by Boron Nitride Nanosheet/Boron Nitride Hybrid.

With the innovation of modern electronics, heat dissipation in the devices faces several problems. In our work, boron nitride (BN) with good thermal conductivity (TC) was successfully fabricated by constructing the BN along the axial direction and the surface-grafted BN hybrid composite fibers via the wet-spinning and hot-pressing method. The unique inter-outer and inter-interconnected hybrid structure of composite fibers exhibited 176.47% thermal conductivity enhancement (TCE), which exhibits good TC, mechanical resistance, and chemical resistance. In addition, depending on the special structure of the composite fibers, it provides a new strategy for fabricating thermal interface materials in the electronic device.

Effects of lateral critical current nonuniformity on stresses in dry-wound high-field REBCO coils

Abstract The distribution of critical current density (jc) in REBCO coated conductors affects the magnetization behaviors and subsequently screening-current-induced stresses, particularly for solenoid magnets in high fields. This paper studies numerically the correlation between lateral jc profile across conductor width and stress distribution in pancake coils. The modeling framework considers bending, winding, thermal contraction, and magnetic forces including coupled electromagnetic-mechanical behaviors, i.e., the deviation of the perpendicular field away from axial direction due to tilting deformation. The lateral nonuniformity is introduced using trapezoidal functions, emulating typical jc profiles originated in pristine tapes and those caused by slitting. First, parametric studies are carried out on the small test coils previously reported in the 'Little Big Coils' (LBC) paper. It is shown that while slitting edge defects have a moderate impact on peak strains, imperfections in the pristine tape with a larger shoulder width can accelerate the penetration process, shifting peak force to the structurally resilient middle section. Similar behaviors are found in the LBC3 case study, suggesting that lateral jc nonuniformity may have contributed to the observed degradation states in pancakes with different slit-edge orientations. Furthermore, the manipulation of lateral jc profile is proposed as a strategy to manage stresses in high field solenoids. This is demonstrated in the design study of a hypothetical REBCO insert. By adjusting the lateral jc distribution and the overall scaling factor, magnet designs with a reasonable current margin and moderate peak strain can be found. The multi-width concept is then applied to allow for a higher operating current and a larger margin for the end pancakes. Albeit being a generic case, this study highlights the sensitivity of peak stresses in high-field magnets to jc distribution. This feature may be taken into account to fine-tune magnet designs and adjust coil assemblies for better overall performance. It also emphasizes the need for careful characterization and effective control of lateral jc distributions in REBCO coated conductors.

Calibration of TEROS 10 and TEROS 12 electromagnetic soil moisture sensors

AbstractThe TEROS 10 and TEROS 12 are widely used capacitance‐based sensors for measuring volumetric water content (), but few systematic studies of the measurement volume and accuracy of these sensors have been published. The objectives of this study were to (1) calibrate and validate these sensors in mineral soils, (2) determine the sensing volume of each sensor, and (3) evaluate the temperature sensitivity of the sensors. Both sensors were calibrated in the laboratory using columns of packed soil at multiple moisture levels from air‐dry to near saturation. Sensors were validated using additional laboratory and field measurements. The sensing volume was determined by quantifying the response of raw sensor outputs while increasing the level of oven‐dry sand, moist sand (0.100 cm3 cm−3), or water around the sensor in the radial and axial directions. Temperature sensitivity was tested in controlled conditions over a range of temperatures from 2°C to 40°C using encapsulated sensors in packed soil columns at constant . Linear calibration models resulted in mean absolute error ≤0.030 cm3 cm−3 for both sensors during laboratory and field validations. In moist sand, the sensing volume contributing 95% of the maximum sensor response was 439 cm3 for the TEROS 10 and 423 cm3 for the TEROS 12. Both sensors exhibited changes in of ≤0.02 cm3 cm−3 when subjected to a temperature change from 2°C to 40°C. For the soils considered here, both sensors demonstrated accuracy that is likely sufficient for a variety of agricultural and hydrological applications.

A study of the coupled dynamics of asymmetric absorbing clusters in a photophoretic trap

Abstract We report a study on the dynamics of absorbing asymmetric carbon clusters trapped by a loosely focused Gaussian beam using photophoretic force. At high laser powers, all the trapped clusters display rotation coupled with oscillation along the axial direction, with a majority spinning about a body fixed axis, while the rest display dual spin as well as orbital motion about a fixed point in space. The spinning and orbiting frequency is inversely proportional to the amplitude of the axial oscillation - with one growing at the expense of the other. Further, the frequencies of these rotations are not proportional to the laser power, but to the trap stiffnesses inferred from the corresponding natural frequencies. The clusters also stop rotating below a certain laser power, and execute random thermal fluctuations. Our work suggests that the dynamics of clusters trapped with photophoretic force are largely dependent on the cluster size and morphology, which could, in principle, be tuned to obtain various motional responses, and help in the design of rotating micromachines in air.