Pair Of Contact Research Articles

Contact pressure distribution of Multi-cone friction pair considering capsizing moment and stress singularity at the interface end

Contact characteristics of friction pair play a crucial role in the torque transmission capacity and temperature rise prediction of automotive clutches. In this study, a Multi-cone friction pair used in wet clutches has been proposed. Each pair of conical contact is considered as the contact between a finite stiffness punch and an elastic half-plane, and 2D finite element (FE) models are developed to calculate the contact load assignments. Considering the capsizing moment and stress singularity at the end of the contact interface, an analytic model is established to obtain the contact pressure distribution on each conical contact interface based on the results of contact load assignments. Finally, the numerical examples are given, and the influences of axial load, mating material characteristics, friction coefficient, and cone angle on contact pressure distribution have been discussed in detail, which supplies the guidance of parameters design for Multi-cone friction pair.

Detection and Prediction of a Pair of Unmanned Aircraft Contact

In the current world of increasing density of unmanned aerial vehicle operations in the airspace, there is an enhanced emphasis on their safety due to the potential for mid-air collision, either with another aircraft or with each other. At the same time, unmanned aerial vehicles are also being used in the context of introducing smart technologies into maintenance processes, where there is also a need to prevent a potentially possible conflict when two drones come close together. The paper introduces a mathematical model for tactical prediction of a conflict between a pair of drones. The tactical prediction of drone conflict is intended to alert the drone operator to an immediate potentially dangerous situation. The mathematical simulation in this paper extrapolates the 3D trajectory in the direction of the relative velocity vector of the convergence over the advance time. If the extrapolated trajectory has at least one point in common with the conflict space of the other drone, the conflict is signalled to the drone operator. This model can then be used in practice to simulate flight operations in shared airspace or to develop the currently required rules in selected situations.

Tribological Influences of CuO Into 3Y-TZP Ceramic Composite in Conformal Contact

The aim of the study was to investigate the friction and wear phenomena of 3 mol % yttria-stabilized tetragonal zirconia polycrystals (3Y-TZP) ceramics with the inclusion of copper oxide (CuO) in large area conformal contact geometry. The pin-on-disk tribometer was used to conduct the dry sliding test using CuO/3Y-TZP as pin and alumina as counter surface. The coefficient of friction (μ) for CuO-added 3Y-TZP was decreased by ∼38% compared to pure 3Y-TZP due to formation of protective tribo film to the substrate. In addition, the experiments also showed that the specific wear rate (k) was reduced by ∼54% with the inclusion of CuO in to 3Y-TZP matrix. The different phases of the zirconia, copper, and yttria as well as the phase transformation before and after sliding test were identified by X-ray diffraction (XRD) analysis. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDS) analysis revealed the existence of CuO in the patchy layers in the worn-out surface of the tested CuO/3Y-TZP sample leading to lower coefficient of friction and improve the wear resistance against alumina counterface in conformal contact geometry. Severe wear mechanism was the dominating factor due to the local plastic deformation of the large number of asperities since the pair of contact was conformal.

GenomeDISCO: a concordance score for chromosome conformation capture experiments using random walks on contact map graphs.

The three-dimensional organization of chromatin plays a critical role in gene regulation and disease. High-throughput chromosome conformation capture experiments such as Hi-C are used to obtain genome-wide maps of three-dimensional chromatin contacts. However, robust estimation of data quality and systematic comparison of these contact maps is challenging due to the multi-scale, hierarchical structure of chromatin contacts and the resulting properties of experimental noise in the data. Measuring concordance of contact maps is important for assessing reproducibility of replicate experiments and for modeling variation between different cellular contexts. We introduce a concordance measure called DIfferences between Smoothed COntact maps (GenomeDISCO) for assessing the similarity of a pair of contact maps obtained from chromosome conformation capture experiments. The key idea is to smooth contact maps using random walks on the contact map graph, before estimating concordance. We use simulated datasets to benchmark GenomeDISCO's sensitivity to different types of noise that affect chromatin contact maps. When applied to a large collection of Hi-C datasets, GenomeDISCO accurately distinguishes biological replicates from samples obtained from different cell types. GenomeDISCO also generalizes to other chromosome conformation capture assays, such as HiChIP. Software implementing GenomeDISCO is available at https://github.com/kundajelab/genomedisco. Supplementary data are available at Bioinformatics online.

Anode Spot Formation Threshold Current Dependent on Dynamic Solid Angle in Vacuum Subjected to Axial Magnetic Fields

The objective of this paper is to experimentally determine a relationship between an anode spot formation threshold current $I_{\rm th}$ and a dynamic solid angle in drawn vacuum arcs subjected to axial magnetic fields (AMFs). Experiments are performed in a demountable vacuum chamber, in which a Helmholtz coil is installed coaxially with a pair of butt type contacts. Dynamic solid angle $\Omega$ is related to arcing process, which is subtended by the anode from the cathode center or by a ratio of the anode diameter $D$ to the contact separation length $l$ as arc extinguishes $(D/l)$ in a drawn vacuum arc. Although a traditional definition of solid angle $(D/g)$ is related to a fixed full contact gap $g$ , no arcing process is considered. In the experiments, butt type contacts are used with contact material CuCr25 (25% Cr), and the contact diameters $D$ are 12, 25, 40, 60, and 80 mm. The contact separation length $l$ as arc extinguished is controlled in a range of 12–24 mm determined by an opening velocity with an arcing time fixed at 10 ms. A dc AMF is applied to the pair of contact with the flux density $B_{\rm AMF}$ adjusted from 0 to 122 mT. Arc current in the tests is at a range of 0–30 kA rms at 50 Hz. The results show that anode spot formation threshold current $I_{\rm th}$ is linearly dependent on the dynamic solid angle $D/l$ adjusted either by $D$ or $l$ , respectively. And the threshold current $I_{\rm th}$ is also linearly dependent on the AMF flux density $B_{\rm AMF}$ applied. Contact diameter $D$ shows more significant influence on the threshold current $I_{\rm th}$ than the contact separation length $l$ as arc extinguished. In a given contact diameter $D$ and contact separation length $l$ as arc extinguished, there is a critical peak arc voltage value, at which an anode spot first formed, regardless of arc current $I_{\rm arc}$ and AMF flux density $B_{\rm AMF}$ applied.

Evaluation of Micro Plasma Formed in the Narrow Gap in Electrolyte Solution

Microplasma was formed in a gap hole made in a quartz plate immersed in various kinds of electrolyte solutions at different concentrations. High-voltage AC was applied to the solution by using a pair of contact- or non-contact electrodes at both sides of the gap hole to ignite microplasma generation. Spectra of the light emitted from the microplasma showed elemental emission lines of the species contained in the solution, and their intensities depended on not only their concentration but also plasma conditions such as plasma temperature. A non-equilibrium plasma state was confirmed from estimated temperature of electrons and OH• radicals in the order of thousand and 10 thousand Kelvins. Deformation of the gap hole was observed depending on the polarization condition and species, probably due to high-temperature plasma and also dielectric loss in the gap hole.

Prediction of load sharing based HCR spur gear stresses and critical loading points using artificial neural networks

The prediction of the load shared by a pair of teeth, maximum contact and fillet stresses and the respective location of the critical loading point becomes rather a difficult task in High Contact Ratio HCR gears as the contact ratio exceeds two. As this prediction greatly depends on the gear parameters like pressure angle, addendum factor and teeth number, an attempt has been made to work on this area highlighting these aspects using Finite Element FE Multi Pair Contact Model MPCM. The minimum value of contact ratio under consideration is 2.1. However, the maximum is chosen as 2.9. A new methodology based on Artificial Neural Networks ANNs is proposed for the prediction of Load-Sharing Ratio LSR, maximum fillet and contact stresses and the respective critical loading points. The data set generated from the MPCM has been used to train the networks and, furthermore, its effectiveness is proved by a different data set of HCR gear pairs determined for the randomly selected parameters.

Contact handle decompositions

We review Giroux's contact handles and contact handle attachments in dimension three and show that a bypass attachment consists of a pair of contact 1 and 2-handles. As an application we describe explicit contact handle decompositions of infinitely many pairwise non-isotopic overtwisted 3-spheres. We also give an alternative proof of the fact that every compact contact 3-manifold (closed or with convex boundary) admits a contact handle decomposition, which is a result originally due to Giroux.

Polygonal Wear of Work Rolls in a Hot Leveler of Steel Making Machine (4th Report, Experimental Verification of a Countermeasure by Using Dynamic Absorbers)

In this paper, a countermeasure of pattern formation phenomena by using dynamic absorbers is investigated experimentally. An experimental equipment of a single degree-of-freedom pattern formation system with a pair of contact rotating rolls and a dynamic absorber are made. The experimental results are compared with the analytical results using approximated characteristic roots. According to the results of the experiments without a dynamic absorber, it is confirmed that the relation among the natural frequency of the system, the polygonal number and the rotating speed agree with the analytical results qualitatively. According to the results of the experiments using a damped dynamic absorber, the delaying effect of pattern formation is confirmed. Also, a good quantitative agreement between the experimental and analytical results is confirmed. According to the results of the experiments using an undamped dynamic absorber, it is confirmed that damping of a dynamic absorber is necessary to delay pattern formation phenomena.

Polygonal Wear of Work Rolls in a Hot Leveler of Steel Making Machine (4th Report, Experimental Verification of a Countermeasure by Using Dynamic Absorbers)

In this paper, a countermeasure of pattern formation phenomena by using dynamic absorbers is investigated experimentally. An experimental equipment of a single degree-of-freedom pattern formation system with a pair of contact rotating rolls and a dynamic absorber are made. The experimental results are compared with the analytical results using approximated characteristic roots. According to the results of the experiments without a dynamic absorber, it is confirmed that the relation among the natural frequency of the system, the polygonal number and the rotating speed agree with the analytical results qualitatively. According to the results of the experiments using a damped dynamic absorber, the delaying effect of pattern formation is confirmed. Also, a good quantitative agreement between the experimental and analytical results is confirmed. According to the results of the experiments using an undamped dynamic absorber, it is confirmed that damping of a dynamic absorber is necessary to delay pattern formation phenomena.

Allergen‐induced cytokine phenotypes in mice: role of CD4+ and CD8+ T cell populations

CD4+ T cells expressing type 2 cytokines have been implicated in the pathogenesis of asthma to high-molecular-weight allergens. Topical exposure of BALB/c strain mice to low-molecular-weight chemical contact and respiratory allergens stimulates type 1 and type 2 cytokine secretion phenotypes, respectively. To examine the relative frequencies of cytokine-positive CD4+ and CD8+ T cells and their contributions to these cytokine secretion profiles. Methods Draining auricular lymph nodes were isolated 13 days after initiation of topical exposure of female BALB/c strain mice to chemical allergen, or to vehicle alone. The frequency of intracellular cytokine (IL-4 and IFN-gamma)-positive CD4+ and CD8+ lymphocytes was enumerated by flow cytometry. The relative contribution of CD4+ and CD8+ cells to cytokine secretion profiles was assessed by negative selection. Exposure to allergen resulted in an increased frequency of both IFN-gamma+ CD4+ and CD8+ lymphocytes, although there were no marked differences between trimellitic anhydride (TMA)- and 2,4-dinitrochlorobenzene (DNCB)-activated lymph node cells. Treatment with TMA induced approximately five times as many IL-4+ CD4+ cells as did exposure to DNCB. This pattern of cytokine staining was also observed for a further pair of contact and respiratory allergens; respectively, formalin and fluorescein isothiocyanate. These data demonstrate that the divergent immune responses induced in mice by different classes of chemical allergen are independent of changes in the frequency of IFN-gamma+ cells, but are associated with differential frequencies of IL-4-expressing CD4+ T cells.

Thermodynamic properties of binary mixtures of tetrachloromethane+ n-alcohol by application of the Dispersive Quasi Chemical Model

Data available from the literature on the excess Gibbs energy G E, activity coefficients at infinite dilution γ i ∞, excess enthalpy H E and vapor–liquid equilibria were analysed on the basis of DISQUAC model by taking in account the dispersive interaction parameters for CCℓ 4 with non-polar groups (alkyl-CH 3; –CH 2–) and dispersive quasichemical (two contributions by pair of contact) interaction parameters for polar group (hydroxyl-OH) and non-polar groups (CCℓ 4 or alkyl). The prediction concerning the change in H E and G E with temperature, composition and n-alcohol chain length and vapor–liquid equilibria are in good agreement with known experimental data. The regular change of the coefficients C sh, ℓ( m) ( s=a (alkyl) or d (CCℓ 4) and h=hydroxyl; ℓ=1, 2) with the n-alcohol chain length may help to predict the missing quantities with better accuracy. A comparison between the DISQUAC prediction with results of two models based on the associated solution theory is presented and discussed. Some systematic discrepancies between theory and experiment are found, in particular for H 2 E∞ and γ 2 ∞.

Spontaneous sleep and induced arousal: A depth-electroencephalographic study

Although arousal effects from electric stimulation have been found in animals, reports of similar responses in humans have been uncommon. During depth electroencephalography in a 16-year-old boy for evaluation of intractable temporal lobe seizures, electric stimulation of a pair of contact leads located within the dorsal and medial portions of the thalamus but not within specific sensory nuclei produced unequivocal behavioral and electrographic arousals from spontaneous sleep. Low-voltage stimuli were effective during non-REM and REM sleep. These findings verify the presence of a thalamic arousal system in the human.

BASIC STUDIES ON SCORING OF SPUR GEARS : 2ND REPORT, EXPERIMENTAL RESULTS USING POWER CIRCULATING GEAR TEST RIG

The authors previously cleared from the experimental results which are derived from the four-ball test and the roller test that the condition or scoring could be anticipated by the surface temperature rise, and discussed how the thermal conductivity in the surface layer of material affects the surface temperature rise. In this report, the effects of the following factors on scoring are discussed ; the material and the hardness of gear, the viscosity of lubricant and the surface roughness of gear tooth. The results for scoring test are summarized as follows ; on both the normalized gears and the hardened gears, the progress of wear is especially remarkable in the zone of single pair of contact and the tendency of the increase of wear depth on the tooth surface well coincides with that of the weight loss due to wear. When the scoring failure of the hardened gear is compared with that of the normalized gear, the scar of the hardened gear tooth looks like a number of the micro fragments of the welding material gathered, and the size of the wear particles of the hardened gear is smaller than that of the normalized gear. As the thermal conductivity fall, the scoring limit decreases. Though the effect of the hardness on the scoring limit is larger than that of the thermal conductivity, the influence of the hardness of gear is inseparable from the scoring limit because the thermal conductivity and the hardness interact each other. Lastly, as the viscosity of lubricant grows higher, the scoring limit increases. In the lubricating condition of 140-Turbine oil, the index values of the flash surface temperature in AGMA Standard which were calculated by the measurement value of the surface roughness after running in, are within 161172°C on the carburized gear which consists of SCM22H material, and the mean value of the flash temperature is about 168°C.