Arc Structure Research Articles

A Novel Phase Measuring Deflectometry Method Using a Curved Screen

Phase measuring deflectometry (PMD) is widely used to measure the surface of specular objects. The planar screen used in traditional PMD systems have the drawbacks of a small field of view of measurement and a large virtual image depth range. This problem can be effectively solved by using the curved screen. As the arc structure of the curved screen is different to the planar structure required in Zhang’s method, the existing methods mainly rely on the stereo vision of two cameras to obtain the screen position. This paper presents a novel PMD based on a curved screen and single camera. A method of calibrating a curved screen by constructing a virtual planar screen is presented. The method only needs one camera to calibrate the curved screen directly with high accuracy. In addition, the change from planar screen to curved screen makes the traditional phase-gradient-height relation invalid. Based on the comprehensive analysis of space optical path models, a novel phase-gradient-height relation is presented. The relation is a general formula. It can be used for any curved screen, including the planar screen. Simulation and quantitative comparison experiments verify the accuracy and reliability of the proposed calibration method. The measurement results of concave mirror show that the proposed method has higher accuracy and a larger field of view in measuring specular objects than traditional methods.

Chromium arc plasma characterization, structure and properties of CrN coatings prepared by vacuum arc evaporation

Plasma is one of the most important factors affecting the structure and properties of coatings deposited by vacuum arc evaporation, while its specific characteristics are rarely analyzed. In this study, the effects of working pressure and arc current on plasma characteristics, microstructure and intrinsic properties of CrN coatings deposited by vacuum arc evaporation were investigated. The plasma characteristics were characterized by optical emission spectroscopy, and the electron density and plasma temperature were calculated. It was found that the calculated plasma temperatures were in the range of 7000 K–9000 K under the assumption of local thermodynamic equilibrium conditions. The arc burning condition of 4.0Pa/90A corresponds to the highest plasma density and the highest temperature. The interaction between plasma and macro-particles affects the structure and intrinsic properties of the coating. When working pressure and arc current are at a low level, the number of macro-particles is small, and the coating properties match well with the change of plasma state. When working pressure and arc current are too high, the number and size of macro-particles increase explosively, which increases the influence on the structure and properties, thus weakening the influence of the plasma state on the coating. It can provide guidance for preparation of CrN coatings with high properties by vacuum arc evaporation.

Online measurement of droplet size by actively exciting droplet oscillation in GMAW and GMAW-AM

Metal transfer plays a significant role in determining the process stability and deposition quality in GMAW and GMAW-AM. Predetermined parameters for controlling metal transfer may fail because of changes in applications or external disturbances. To obtain droplets of target sizes as expected and personalize control parameters for every single droplet, a low-cost method is proposed for the online measurement of the size of the droplet before being detached. The natural frequencies of droplets of different sizes are experimentally measured. The free oscillation of the droplet is actively excited first, during which the voltage falls as the droplet moves upward and rises as the droplet moves downward, with almost the same frequency as that of the droplet. By performing a frequency domain analysis of the voltage, the droplet size is able to be determined online from the oscillation frequency. This technique contributes to the feedback control of the transfer of every single droplet. The fluctuation of the voltage during the droplet oscillation is believed related to the variation of arc structure, the underlying mechanism still needs further study.

Influence of nanoparticle and channel arc structure on comprehensive performance of nanofluids in curved tiered microchannel heat sinks

AbstractIn order to improve the heat dissipation of the electrical components, a curved tiered microchannel heat sink (TMCHS) was proposed and optimized and applied to cool the electrical components together with nanofluids. Influence of channel radian (φ = 0°, 75°, 135°, 180°), arc number (n = 0, 2, 3, 4), and nanoparticle concentration (w = 0.0%, 0.1%, 0.3%, 0.5%) on flow and heat transfer characteristics of nanofluids in curved TMCHS was numerically investigated. Comprehensive evaluation coefficient comprehensive evaluation factor (PEC) was used to evaluate the thermo‐hydraulic performance of TMCHS and nanofluids. Results indicated that the greater the radian and arc number, the better the thermal performance of TMCHS. The overall performance of TMCHS is the best when the radian is 180° and the arc number is 4. Results in this paper provide important technical guidance for the application of curved tiered microchannel heat sinks and nanofluids to the field of thermal management of electronic components.

The origin of the Perseus-arm gap revealed with VLBI astrometry

AbstractThe Perseus arm has a gap in Galactic longitudes (l) between 50° and 80° where the arm has little star formation activity. To understand the gap, we conducted VERA (VLBI Exploration of Radio Astrometry) astrometry and analyzed archival H <SC>I</SC> data. We report on parallax and proper motion results from four star-forming regions, of which G050.28–00.39 and G070.33+01.59 are associated with the gap. Perseus-arm sources G049.41+00.32 and G050.28–00.39 lag relative to a Galactic rotation by 77 ± 17 km s-1 and 31 ± 10 km s-1, respectively. The noncircular motion of G049.41+00.32 cannot be explained by the gravitational potential of the arm. We discovered rectangular holes with integrated brightness temperatures less than 30 K arcdeg in l vs. VLSR of the H <SC>I</SC> data. Also, we found extended H <SC>I</SC> emission on one side of the Galactic plane when integrating the H <SC>I</SC> data over the velocity range covering the hole. G049.41+00.32 and G050.28–00.39 are moving toward the emission. The Galactic H <SC>I</SC> disk at the same velocity range showed an arc structure, indicating that the disk was pushed from the lower side of the disk. All the observational results might be explained by a cloud collision with the Galactic disk.

Flow force research and structure improvement of cartridge valve core based on CFD method

The hydraulic force has a great negative effect on the cartridge poppet valve system. Based on the law of momentum, the calculation formula of flow force of outflow poppet valve is modified, and a new valve core structure is designed. The compensation effect of the improved main valve core structure on the hydraulic force is discussed; secondly, CFD simulation is carried out to obtain the influence rules of these parameters on hydrodynamic forces. According to the analysis, the influence of main valve core arc structure on hydrodynamic force compensation under different opening degrees is also studied; then the optimal parameters of the arc structure are obtained through analysis. AMEsim system simulation model and test-bed are built to verify the hydrodynamic formula and simulation results. The experimental results verify that the new valve core structure has a good hydrodynamic compensation effect.

Cryo-EM structures of perforin-2 in isolation and assembled on a membrane suggest a mechanism for pore formation.

Perforin-2 (PFN2, MPEG1) is a key pore-forming protein in mammalian innate immunity restricting intracellular bacteria proliferation. It forms a membrane-bound pre-pore complex that converts to a pore-forming structure upon acidification; but its mechanism of conformational transition has been debated. Here we used cryo-electron microscopy, tomography and subtomogram averaging to determine structures of PFN2 in pre-pore and pore conformations in isolation and bound to liposomes. In isolation and upon acidification, the pre-assembled complete pre-pore rings convert to pores in both flat ring and twisted conformations. On membranes, insitu assembled PFN2 pre-pores display various degrees of completeness; whereas PFN2 pores are mainly incomplete arc structures that follow the same subunit packing arrangements as found in isolation. Both assemblies on membranes use their P2 β-hairpin for binding to the lipid membrane surface. Overall, these structural snapshots suggest a molecular mechanism for PFN2 pre-pore to pore transition on a targeted membrane, potentially using the twisted pore as an intermediate or alternative state to the flat conformation, with the capacity to cause bilayer distortion during membrane insertion.

Structure and function of the reflex arc

Structure and function of the reflex arc

Arc-shaped flutter-driven wind speed sensor based on triboelectric nanogenerator for unmanned aerial vehicle

At present, it is significant for unmanned aerial vehicle (UAV) to sense the external information in the interference environment. Therefore, an arc-shaped flutter-driven wind speed sensor based on triboelectric nanogenerator (AW-TENG) for UAV is proposed in this work. The arc structure of AW-TENG, which adopts contact separation mode through air vibration, is designed according to the working principle and simulation. Then the three influencing factors of plate spacing, radian and radian direction are carried out to determine its optimal structure. The performance of the optimal structure is verified: the voltage frequency that AW-TENG can reach in the wind speed range of 6–20 m/s is 50–200 Hz, the sensitivity is 9.88 Hz/(m s−1) and the goodness of fit R2 = 0.998. Meanwhile, the voltage range that AW-TENG can reach is about 30–55 V, the generated current range is about 8–28 μA. Finally, the application experiment of the wireless wind speed transmission of the UAV with AW-TENG is carried out. The experiment proves that TENG has the ability to apply the wind speed sensor for UAV, and provides experimental support for the wind speed monitoring of the overall structural unit of UAV in the future.

Role of a Carbon-Fluorine-Containing Additive in the Formation of the Structure, Defect Substructure, and Fracture Surface of an Electric Arc Sprayed Coating

Role of a Carbon-Fluorine-Containing Additive in the Formation of the Structure, Defect Substructure, and Fracture Surface of an Electric Arc Sprayed Coating

Remote sensing techniques in the study of structural and geotectonic features of Iturup Island (the Kuril Islands)

The article presents structural and geotectonic features of Iturup Island, the largest island in the Greater Kuril Ridge, a unique natural site, which can be considered as a geological reference. The structural and geotectonic analysis carried out on the basis of a comprehensive study of the new Earth remote sensing data, maps of anomalous geophysical geophysical fields, and other geological and geophysical materials using modern modelling methods made it possible for the first time to identify or clarify the location of previously discovered discontinuous faults, typify them and determine the kinematics, as well as to establish a more reliable spatial relationship of the identified structures with magmatism with the stages of the geological development of the region. The constructed diagram of the density distribution of the zones with increased tectonic fracturing shows a significant correlation between the distribution of minerals and weakened areas of the Earth's crust and can be used as an alternative method for predicting minerals in the study region, especially in remote and hard-to-reach areas. The presented approach can be extended to the other islands of the Greater Kuril Ridge, thereby bringing research geologists closer to obtaining the answers to questions about the features of the geotectonic structure and evolution of the island arc. The use of customized software products significantly speeds up the process of interpreting a large array of geological and geophysical data.

On the Prediction of Macrosegregation in Vacuum Arc Remelted Ingots

The chemical homogeneity and metallurgical structure of vacuum arc remelted (VAR) zirconium ingots are directly responsible for product quality. It is therefore important to understand the relationship between these properties and the operating conditions. An in-depth analysis of the modelling of solidification phenomena during the VAR was carried out. Such model, solves a coupled set of transient equations for heat, momentum, solute transport and turbulence in an axisymmetric geometry. The remelting and cooling of a cylindrical ingot are calculated for time-dependent operating parameters. The solidification mechanisms implemented in the model can be applied to multi-component industrial alloys such as Zircaloy-4, which provides information on the macrosegregation phenomena studied in this paper. The model results were validated, based on the remelting of a specially designed chemically homogeneous Zircaloy-4 electrode. The results illustrate the importance of thermal and solute convection, the importance of the permeability of the partially solid material and the weak influence of nuclei density and solute diffusion in the solid phase on the prediction of macrosegregation in Zircaloy-4 ingots.

High-affinity anti-Arc nanobodies provide tools for structural and functional studies.

Activity-regulated cytoskeleton-associated protein (Arc) is a multidomain protein of retroviral origin with a vital role in the regulation of synaptic plasticity and memory formation in mammals. However, the mechanistic and structural basis of Arc function is poorly understood. Arc has an N-terminal domain (NTD) involved in membrane binding and a C-terminal domain (CTD) that binds postsynaptic protein ligands. In addition, the NTD and CTD both function in Arc oligomerisation, including assembly of retrovirus-like capsids involved in intercellular signalling. To obtain new tools for studies on Arc structure and function, we produced and characterised six high-affinity anti-Arc nanobodies (Nb). The CTD of rat and human Arc were both crystallised in ternary complexes with two Nbs. One Nb bound deep into the stargazin-binding pocket of Arc CTD and suggested competitive binding with Arc ligand peptides. The crystallisation of the human Arc CTD in two different conformations, accompanied by SAXS data and molecular dynamics simulations, paints a dynamic picture of the mammalian Arc CTD. The collapsed conformation closely resembles Drosophila Arc in capsids, suggesting that we have trapped a capsid-like conformation of the human Arc CTD. Our data obtained with the help of anti-Arc Nbs suggest that structural dynamics of the CTD and dimerisation of the NTD may promote the formation of capsids. Taken together, the recombinant high-affinity anti-Arc Nbs are versatile tools that can be further developed for studying mammalian Arc structure and function, as well as mechanisms of Arc capsid formation, both in vitro and in vivo. For example, the Nbs could serve as a genetically encoded tools for inhibition of endogenous Arc interactions in the study of neuronal function and plasticity.

CFD analysis of flow field and hydrodynamic compensation of poppet valve

The steady-state hydrodynamic force of cartridge valve poppet valve core reduces the stability of cartridge valve. A circular arc structure is added to the main valve core of the poppet valve to compensate the steady-state flow force. Referring to the structure and parameters of the actual cartridge poppet valve, the three-dimensional geometric model of the flow channel in the valve is established with UG software. CFD method is used to calculate and analyze the flow state of fluid in the poppet valve under the working state of the valve core, and the influence of the arc size and position of the valve core on the steady-state hydrodynamic compensation of the main valve core is studied. The results show that the circular arc structure can realize the hydrodynamic compensation of the valve core and increase the stability of the valve core. When the opening amount is small, properly increasing the height h of the circular arc structure can increase the static hydrodynamic compensation of the valve core; Keep the circular arc structure size L less than 1mm, and the static hydrodynamic compensation effect of the valve core is better.

Modeling the arc and ring structures in the HD 143006 disk

Rings and asymmetries in protoplanetary disks are considered as signposts of ongoing planet formation. In this work, we conduct three-dimensional radiative transfer simulations to model the intriguing disk around HD 143006 that has three dust rings and a bright arc. A complex geometric configuration, with a misaligned inner disk, is assumed to account for the asymmetric structures. The two-dimensional surface density is constructed by iteratively fitting the ALMA data. We find that the dust temperature displays a notable discontinuity at the boundary of the misalignment. The ring masses range from 0.6 to 16Mearth that are systematically lower than those inferred in the younger HL Tau disk. The arc occupies nearly 20% of the total dust mass. Such a high mass fraction of dust grains concentrated in a local region is consistent with the mechanism of dust trapping into vortices. Assuming a gas-to-dust mass ratio of 30 that is constant throughout the disk, the dense and cold arc is close to the threshold of being gravitationally unstable, with the Toomre parameter Q~1.3. Nevertheless, our estimate of Q relies on the assumption for the unknown gas-to-dust mass ratio. Adopting a lower gas-to-dust mass ratio would increase the inferred Q value. Follow-up high resolution observations of dust and gas lines are needed to clarify the origin of the substructures.

Universal emotional arc structure in advertisements and their favorability

PurposeThis study aims to propose a novel way to explore the narrative structure of advertisements, a nascent area of research, through the protagonist’s emotional arc progression.Design/methodology/approachThe multi-methods approach is used. In Study 1, the authors explore the basic universal emotional arcs through the analysis of narrative advertisements from six key economies. In Studies 2 and 3, the authors experimentally test hypotheses concerning the narrative structure and viewers’ attitudes toward the narrative using representative samples (317 and 193 ads, respectively).FindingsThe authors identify five broad emotional arcs of the protagonist in audiovisual advertisements. Different emotional arcs are found to induce different attitudes in the audience. Narratives ending in a positive mode and the narrative arcs with higher emotional shifts are more favorably evaluated by the audience.Research limitations/implicationsThe present study is limited to textual stimuli tested in a US population and does not consider protagonist characteristic portrayal.Practical implicationsUnderstanding consumer preferences for different emotional arcs can help practitioners to develop more clutter-breaking and relevant advertisements.Originality/valueTo the best of the authors’ knowledge, this study is the first to explore the narrative structure theory in the context of advertisements using a positivist approach.

Arc‐Shaped Triboelectric Nanogenerator for Wind Energy Harvesting

The insufficient contact between triboelectric surfaces has been a key problem faced by wind driven triboelectric nanogenerator (TENG) devices. We have designed and fabricated an arc‐shaped‐TENG (AS‐TENG) based on the single‐side fixed working mode. AS‐TENG includes two arc structures with a fluorinated ethylene propylene (FEP) film and a stainless steel layer. Due to the inherent stiffness of the stainless steel layer and the arc structure design, the bent stainless steel can fully contact the FEP films attached to the arc structure, enhancing the effects of triboelectrification and electrostatic induction. The influence of the arc center angle, angle between the two arc structures, thickness of stainless steel layer on the electrical output have been systematically studied. The open‐circuit voltage and the output power obtained with the best structure design were 330 V and 2 mW, respectively. Moreover, an integrated device consisting of five AS‐TENG units was fabricated. When the wind speed was 20 ms−1, the integrated device can provide a short circuit current of about 55 μA. Due to the characteristics of simple fabrication, small size and easy integration, the AS‐TENG exhibited great potential in wind energy harvesting.

Microstructural evolution of Al0.25CoCrFeNiCu and Al0.45CoCrFeNiSi0.45 high-entropy alloys during laser cladding

Additive manufacturing of high-entropy alloys has recently attracted considerable scientific interest owing to their exceptional mechanical properties and corrosion resistance. In this work, Al0.25CoCrFeNiCu and Al0.45CoCrFeNiSi0.45 high-entropy alloys coatings are deposited on stainless steel using laser cladding. The prealloyed high-entropy alloys fabricated by arc melting followed by crushing were used as a precursor for laser cladding, which significantly decreased the optimum laser power to 1400–1600 W and hence minimized the thermal effect on the substrate. Laser cladding preserved the dendritic structure of arc melted alloys, while highly refined the dendritic microstructure. Some extent of substrate dilution effect was also observed in the cladding layers.

Distribution Law of In Situ Stress and Its Engineering Application in Gateroad Maintenance: A Case Study

In this study, the stress relief method of hollow inclusion and mathematical-statistical analysis are used to study the in situ stress distribution law of the Guotun coal mine, and the optimization strategy of roadway support is put forward. The test site is located in the city of Heze, Shandong Province, China. The main conclusions included the following: (1) among the three large-scale tectonic movements experienced by the Guotun coal mine, the middle Yanshan period has the strongest impact on it. According to the geological evolution process, it is preliminarily inferred that the maximum principal stress direction of the Guotun coal mine is northwest by west to southeast by east (NWW∼SEE). (2) Compared with the surrounding mines, the average value of the maximum principal stress in the Guotun coal mine is slightly higher, and there is a significant difference in the direction of in situ stress. The arc structure within the mine is the main reason for the deflection of the stress direction. (3) The lateral pressure coefficients KH, Kh, and Kav show a nonlinear distribution with increased depth, and the three coefficients have a decreasing trend. The value of the stress gradient in the Guotun coal mine is greater when it is compared with the surrounding mines. (4) Field tests show that the new strategy proposed in this study is effective, which provides a good reference for engineering practice under similar geological conditions.

Influence of oxygen content on structure, thermal stability, oxidation resistance, and corrosion resistance of arc evaporated (Cr, Al)N coatings

(CrxAl1-x)(OyN1-y)ε coatings with different oxygen fractions were prepared by cathodic arc evaporation through variation of injected oxygen flux, and elaborated concerning structure, mechanical properties, thermal stability, oxidation resistance, and electrochemical properties. A moderate addition of O into (Cr, Al)N coatings generates a (Cr, Al)(O, N) solid solution with a face-centered cubic structure, whereas an additional corundum-structured (Cr, Al)2O3 solid solution is formed with superfluous oxygen introduced. The addition of O effectively improves the thermal stability by retarding the formation of w-AlN as well as the dissociation of the CrN bond, allowing the oxynitride coatings to maintain higher hardness after annealing. Notably, a small fraction of O-addition (e.g. 8 or 21 at.% in non-metal sublattice) enhances significantly the resistance against oxidation to above 1100 °C by facilitating the formation of a protective Al-rich oxide scale. Further incorporation of O gives rise to a development of oxide scale with unity elemental distribution and hence results in inferior oxidation resistance. Nevertheless, the O-rich oxynitride coatings provide better protection against electrochemical corrosion while the N-rich coatings exhibit higher corrosion current as well as lower polarization resistance compared to the CrAlN coating.