Double Contact Research Articles

A permanent insulator system for hydrometallurgy with a significant increase in electric efficiency and without short circuit

A permanent insulator system for hydrometallurgy has been developed with a significant increase in electric efficiency and without short circuits. The system consists of a double electric contact point for each cathode and anode and a new design of the insulating and contact system of the electrodes. The combination of these technologies provides a more uniform electric density inside each cathode and anode, in each cell, and also for the whole electric circuit in the cellhouse. Keeping a consistent maximum performance necessitates using parts with extreme durability against chemical attacks and short circuits. Hence, a comprehensive research into chemical stoichiometry and the behaviour of different molecules resulted in the development of an outstanding chemical resistance level to sulfuric acid and extremely high temperatures throughout the entire hydrometallurgical process. Field observations show that this formulation has been able to resist up to 19 years of continuous operation without maintenance. The goal of these developments combined with a new contact system was to reduce any type of short circuit by 70 to 80%, which in turn increases the electric current effectiveness by 8 to 10%. As a result, higher contact efficiencies have doubled the lifetime of the cathode and anode with this system. Consequently, the overall electric efficiency in a refinery cellhouse can be improved by 10-12%. Observations from real-world applications over the past decades have proven the efficiency of the earlier versions of this new concept. The system was found to be applicable to any type of contact system and has been used in various hydrometallurgical processes with great success. With the increasing price of energy and CO2 production, it has become more important to operate ecologically and efficiently to maximize profitability and this permanent insulator system can address many challenges which lead to a more efficient and cost-effective process.

Efeitos de um programa baseado em hang power clean na habilidade de salto de uma equipe profissional feminina de handebol

Coaches use olympic exercise training to improve the power generation of athletes, as it has a high potential to increase the ratio of force development, and thus, sports performance. The aim of this study was to describe the effects of an intervention using the hang power clean in elite female handball players. Fifteen players from the same team participated, who competed in the Spanish first division (DHF guerreras Iberdrola) during the 2021-2022 season (age: 25.2 ±2.4 years, weight: 70.4 ±7.9 kg, height: 171.2 ±5.3 cm). The players were evaluated both at the beginning and at the end of the 6-week intervention, in two types of vertical jump: Abalakov and Double contact jump. The results showed significant improvements from pre- to post-test in all the variables analyzed, with the exception of those related to starting speed. This information seems to indicate that a short training program in which hang power clean work is emphasized could increase the vertical jump capacity of professional handball players, as well as improve their muscular stiffness. The results found can be extrapolated to other female athletes in which the force management requirements are similar.

Theoretical derivation and analysis of strength calculation formulas of internal gear pair with double contact points

To describing the strength conditions of tooth surfaces of internal gear pair with double contact points (IGPDCP) accurately, theoretical calculation method of the strength of tooth surfaces is proposed in this paper. Theoretical derivation and analysis of strength calculation formulas of the IGPDCP drive are carried out. For contact strength analysis, based on Hertz point contact theory, general calculation idea of contact strength is provided. The main curvature of the active contact line on tooth surfaces of the pinion and internal gear are derived, respectively. Furtherly, according to theoretical calculation and derivation, the formula for calculating the contact strength of the IGPDCP drive is obtained. Orthogonal test method is used to derive the calculation formula of bending strength of the IGPDCP drive, considering test factors include the modulus, tooth number of gear, transmission ratio, helix angle, contact angle, pressure angle, and torque. Nonlinear regression equations of bending stress of the pinion and internal gear are derived, respectively. The discussion of results of contact and bending strength between formula calculation and finite element analysis are present. The conclusions show that the proposed formulas can satisfy theoretical analysis and engineering application.

Rolling pairs with shifting contact geometry: Design, development, and validation

This work introduces two innovative rolling pair concepts to minimize slippage and reduce mass in cam-roller systems of large-scale hydraulic drivetrains: The variable contact length and the Shifting Contact Geometry concepts. Both aim to improve traction in the low contact force phase in cyclically loaded rolling contacts. The shifting contact geometry concept was validated using three custom rolling contacts: a line contact, a double elliptical contact, and a combination of both (i.e., shifting contact geometry). The tests were conducted under synchronized cyclic loading to mimic the conditions in a hydraulic drivetrain. Furthermore, a model from previous work was implemented to make predictions and compare them against the experimental results. During preliminary tests, the double elliptical contact displayed superior tractive behavior than the line contact under the same load thanks to higher contact pressures. Under synchronized cyclic loading, the line contact displayed high sensitivity to applied resisting torques at low contact forces, leading to high slide-to-roll ratios and traction force peaks. In contrast, the rolling pair with shifting contact geometry exhibited minimum slippage even under high resisting torques, resulting in substantially lower (and in most cases negligible) slide-to-roll ratio and traction force peaks. The simulations also captured this behavior, proving the validity of the model for predicting and comparing the rolling-sliding dynamics of these two different rolling pairs. This study demonstrates that rolling pairs with shifting contact geometry can not only improve the tribological performance of cam-roller contacts in large-scale hydraulic drivetrains but also yield a more favorable dynamic behavior.

Camera calibration using the dual double-contact property of circles

To mitigate the influence of the relative positional relationship between circles on camera calibration, this study explores the double contact of dual circles with dual circular points. We demonstrate that one of the generalized eigenvectors of two dual circles corresponds to the line passing through their respective centers. Moreover, we establish a methodology to identify this line from the three generalized eigenvectors and show that, regardless of the positional arrangement of the three co-planar circles, the image of the circular points can be constructed by calculating the image of this line. Consequently, the applicability of circles as calibration templates is expanded, enabling the development of a novel optimization technique for fitting circular images with enhanced calibration precision.

Study on the Coupling Relationship between Wear and Dynamics in Planetary Gear Systems

The occurrence of wear is hard to avoid in gear systems because of their transmission principle. Wear will lead to a deviation of the system’s performance from the design objectives or even failure. In this paper, a dynamic wear prediction model considering the friction and wear of all meshing gears is proposed for planetary gear systems. The differences between different wear prediction methods are compared. The interactions among the wear, the dynamic response, and the uniform load performance of the planetary gears are investigated. The results show that considering friction and wear on all tooth surfaces can significantly reduce errors in the simulation. Wear mainly affects meshing stiffness in the double tooth contact region. The degree of fluctuation of stiffness and meshing force increases significantly with wear. The load-sharing factor in the dedendum and addendum regions decreases. Accordingly, the position of maximum wear on the tooth surface moves slowly towards the pitch line. Early wear improves the dynamic performance of the system. As the wear deteriorates, the higher harmonics of the meshing frequency increase significantly. The uniform load performance of planet gears exhibits the same trend of dynamic response as the others during the wear process.

Double system contact: The experiences of children-looked-after in the youth justice system

ObjectivesTo understand the needs and vulnerabilities of this cohort, and identify where there are opportunities for timely and appropriate support from a range of statutory and non-statutory organisations as they navigate the youth justice system.
 MethodsThis feasibility study linked external youth justice data from two Welsh local authorities with education, health, social services and family court data held in SAIL Databank. Once combined, it was possible to gain further insights into the nature and extent of contact with other state agencies, and to test for statistically significant differences in the profile of this cohort relative to their peers; in index risk scores across 12 domains and in the trajectory of the probability of further offending behaviour. The latter was considered via a series of hierarchical binary logistical regression models conducted under a Bayesian framework.
 ResultsThose with double system contact typically had higher index risk scores than their peers, with the greatest differences being in relation to the Family and Personal Relationships, Living Arrangements, and Emotional and Mental Health domains. In terms of vulnerabilities, the higher rates of additional learning needs were striking, with this potentially contributing to higher levels of non-compliance and more serious consequences. Notably rates of further offending are found to be higher amongst those who are care experienced and/or have additional learning needs, with care experienced children being twice as likely to commit further offences than their peers; more than 2.5 times more likely to breach; twice as likely to return to court and were more than 5 times more likely to spend time in custody.
 ConclusionFindings, reinforce the need for a more tailored, child first approach in youth justice with other agencies also needing to recognise the impact of prior trauma and adapt their practice in order to appropriately respond to the additional vulnerabilities amongst this cohort.

Formation mechanism of the double contact bands on the wheel and rail treads of a metro system

The contact band on the wheel and rail is an intuitive representation of the wheel–rail contact relationship that affects the dynamic performance of rail vehicles. In this paper, a vehicle dynamics model and the Archard wear model are established in an integrated way using the actual parameters of a metro train. The mechanism of formation of double contact bands on the wheel and rail in a metro line in China is studied by analysing the geometric combination based on the measured data. The influence of double contact bands on the dynamic performance of the metro vehicle is investigated. To suppress the formation of double contact bands, an optimisation method for asymmetric rail profiles in small radius curves is proposed based on the Kriging Surrogate Model (KSM) and the Particle Swarm Optimisation (PSO) algorithm. Through numerical simulations, it is proved that the optimised rail profiles can improve the curving performance and effectively reduce wheel wear. The methodology proposed in this paper can provide useful information on the mitigation of severe double contact bands on wheel and rail.

Использование способов начертательной геометрии для графического исследования параметров режущей части спирального сверла

The article presents examples of practical application of descriptive geometry methods for solving engineering problems of determining and studying the parameters of the cutting part of a spiral drill. The necessity of graphical constructions is noted, which is due to the fact that it is impossible to measure the rear angle by a direct measurement method using a universal measuring instrument due to the complex geometric shape of the measuring object. The analysis of the geometric shape of the working part of the spiral drill, which includes the main rear conical surface of the drill tooth, the front screw surface of the drill groove, the cylindrical surface of the tooth back, the main and transverse cutting edges are presented. Using the double contact theorem, a projection of the tooth profile of a spiral drill is constructed on a plane parallel to the drill axis with a given profile projection on a plane perpendicular to the drill axis. The tooth profile is determined by the lines of intersection of the conical surface with the cylindrical surface and with the helical surface of the drill groove. The shape of the drill groove is considered to be set. Projections of the transverse cutting edge of the drill are constructed as lines of intersection of two conical surfaces with intersecting axes. The problem is solved using a bundle of auxiliary planes. The tendency of an increase in the angle of inclination of the transverse cutting edge to the drill axis with a decrease in the distance between the intersecting axes of conical surfaces is shown. Graphically, at an arbitrary point of the drill blade, the value of one of the main geometric parameters of the drill - the rear angle is determined. It is shown that the closer the point of the blade is to the center of the drill, the greater the value of the rear angle. The constructions are made in the 2D Compass-Graph design system. The paper used alternative methods for solving geometric problems, which, unlike traditional ones, provide a simpler and more visual graphical solution.

Dynamic characterization of 3D printed bolted joints

The paper deals with the effect of different parameters on the frictional energy dissipated by 3D-printed bolted joints of different configurations. A test rig is developed using the accelerometers and shaker to perform this task. The shaker provides the force that induces a relative displacement between plates. The induced relative displacement is measured using the accelerometer. The bolted plate samples are 3D printed with polylactic acid (PLA) fibre using fused deposition modelling (FDM) and joined together using a metal bolt. The four different configurations of bolted joints are developed. A single bolt flat contact, a double bolt flat contact (90°orientation), a single bolt slanted contact (1°angle on both surfaces), and a single bolt flat and curved contact. The effect of bolt preload, excitation frequency, and excitation amplitude on the experimental frictional energy dissipation of the bolted joint is studied. The energy dissipation increases with the increase in excitation amplitude and the bolt preload. However, with increasing excitation frequency, the energy dissipation decreases. The type of contact between bolted plates also seems to affect the frictional energy dissipation.

Optimization design and analysis of internal gear transmission with double contact points

Internal gear transmission with double contact points is consist of the pinion having circular-arc tooth profile and the internal gear having parabola tooth profile. To further improve load capacity and reduce total volume of internal gear drive with double contact points, a multi-objective and multi-parameter optimization mathematical model is established based on genetic algorithm. Through the comparison analysis, contact stress of tooth surfaces after optimization design is reduced by 21.9% and the volume of gear after optimization design is reduced by 3.93%. Furthermore, contact characteristics of tooth surfaces are discussed considering the parameters optimization of contact angles and pressure angles. Based on Hertz contact theory, theoretical calculations of contact stresses under different contact angles and pressure angles are provided. And finite element method is used to analyze the contact conditions of tooth surfaces to verify theoretical calculation results. Research results show that contact angle of the internal gear pair with double contact points should less than 12.5° and pressure angle of the internal gear pair with double contact points should be 20°–30°.

SÍNDROME DE BURNOUT EM PROFESSORES: um olhar para literatura com ênfase na necessidade de intervenção

Work considered as a source of survival is also linked to the formation of identity and the individual is related not only to pleasure but also to illness. The wear and tear related to working conditions can generate stress that is prolonged, originating the Burnout Syndrome in professionals. The teaching professional is one of the categories that is most exposed to the occurrence of this syndrome and this fact can harm both the professional and the school community they serve. Faced with this reality, the present study sought to briefly describe aspects of the relationship between health and work; discuss the risk factors associated with stress in the teaching profession; reporting on the Burnout Syndrome in teachers began its consequences and the need for actions aimed at the prevention and treatment of those affected. It is characterized as a narrative review of the literature that used the Google Scholar platform as a database, the search being carried out using the following words: “burnout” and “teachers”. Works in the Portuguese language were used preferably in the period from 2002 to 2022, counting for the composition of the corpus of this review a total of 56 works that include articles, books, TCCs, dissertations and theses. The study showed that work according to its organization and demands can have consequences for both physical and mental health. In the second case, one of the conditions that has been highlighted is Burnout. In the specific case of teachers, the profession is considered a complex task with many demands, often double shifts and direct contact not only with students but also with parents and other social actors in the school, which can lead to physical and mental exhaustion. , behavioral changes in the relationship with colleagues, low appreciation of their profession and consequently brought numerous consequences preventing the well-being of teachers. The investigated literature indicated some paths that can help to change this situation and alert to the urgency of rethinking working conditions through urgent actions to be adopted.

Applying monoid duality to a double contact process

In this paper we use duality techniques to study a coupling of the well-known contact process (CP) and the annihilating branching process. As the latter can be seen as a cancellative version of the contact process, we rebrand it as the cancellative contact process (cCP). Our process of interest will consist of two components, the first being a CP and the second being a cCP. We call this process the double contact process (2CP) and prove that it has (depending on the model parameters) at most one invariant law under which ones are present in both processes. In particular, we can choose the model parameters in such a way that CP and cCP are monotonely coupled. In this case also the above mentioned invariant law will have the property that, under it, ones (modeling “infected individuals”) can only be present in the cCP at sites where there are also ones in the CP. Along the way we extend the dualities for Markov processes discovered in our paper “Commutative monoid duality” to processes on infinite state spaces so that they, in particular, can be used for interacting particle systems.

Mathematical model and deviation analysis of machining cutters for internal gears with double contact points

An internal meshing gear pair that includes double contact points is proposed by the authors. For further performance evaluation and engineering application, special machining cutters for generating tooth surfaces are studied in this paper. General formulas and mathematical models of tooth surfaces of the hobbing cutter for the pinion are derived based on the actual tooth profile. Solid models of the three-dimensional hobbing cutter are established and calculation formulas of deviation conditions between the ideal tooth surface and the generated tooth surface are deduced. Deviation analysis considering the parameters of helical angle and pitch circle radius is discussed. Numerical simulations of the hobbing process are also carried out. While for the internal gear, tooth profile of skiving cutter is designed and forming formulas of tooth surfaces of the skiving cutter are derived. Solid models of the three-dimensional cutter are established, and the deviation calculation method of tooth surfaces is also provided. The research results lay the essential theoretical foundations and engineering analysis for practical applications of the new internal gears.

Influence of tooth asymmetry and mating gear material on the tooth deflection characteristics of polymer gears

Transmission error (TE) in polymer gears is significantly affected by the elastic deflection of meshing teeth. The present work describes the deflection characteristics of the asymmetric Nylon 66 spur gears under similar and dissimilar engagements. The load sharing and deflection behavior were estimated numerically using a linear viscoelastic material model. Experimental determination of mesh deflection was carried out through static load tests. The peak mesh deflection in a cycle for the 20°/34° configuration was found to be 8% and 12% smaller as compared to 34°/20° and 20°/20° configurations, respectively. The peak tooth deflection was found to be highest for the 34°/20° configuration and lowest for the 20°/34° configuration, with the deviation between their peak deflections being 15% in metal-polymer pairs and 17% in polymer-polymer pairs. In the 34°/20° configuration, the higher drive side pressure angle increased the single tooth contact period, causing greater peak-to-valley amplitude in a cycle. The negligible tooth compliance of steel gear caused unsymmetrical load sharing in the double tooth contact zones of metal-polymer engagements. The greater compliance of driver gear in polymer-polymer engagements increased the mesh deflections of 20°/20° and 20°/34° configurations by 45% and that of 34°/20° configuration by 37%. Also, gear pairs with similar material stiffness balanced the load sharing in the addendum and dedendum double tooth contact zones. The large tooth deflection extended the contact duration of all configurations for both the similar as well as for the dissimilar engagements, respectively. This was signified by the contact path extension at the peripheries of the mesh cycle.

A novel helix contact model for predicting hysteretic behavior of unbonded flexible pipes

This paper presents novel equivalent layered contact numerical and analytical models to predict the bending hysteretic behavior of unbonded flexible pipes. A double helix contact beam model, instead of surface-to-surface contact algorithm, is proposed to simulate normal contact and tangential friction behavior between tensile armor tendons and supporting layers. The spatial beam distance is evaluated based on Hertz contact theory. The proposed model is validated through comparison with bending moment-curvature relations obtained from experimental data, a full layered finite element model, and existing analytical models considering or not shear interactions. The shear stiffness is determined by accounting steel armor layers as boundary conditions. The initial contact pressure is introduced into analytical models by accounting residual stress in cylindrical layers and residual strain in helical layers. The bending stresses and relative slip displacements of tensile armor tendons are cross validated between the proposed model and available data. The results show that the proposed model could give consistent bending hysteretic consequences, while shorten simulation time due to significantly reduction of total elements. Sensitivity studies including definition of helix contact beams, equivalent material properties of inner core layer and tangential stick stiffness between layers are performed to validate feasibility of the proposed model.

소형 수문 권양기용 피니언의 강도설계

This paper presents an approach for the strength design of the pin jack-type gear system, that is, roller rack pinion (RRP) system, typically employed in small to mid-sized sluice gate devices. First, the load distribution of the pinion in the section of double tooth contact (DTC) was presented by the introduction of the load sharing factor considering the gear precision. Notably, the higher the gear precision, the lower was the contact force, contact stress, and tooth root bending stress (TRBS) in the section of DTC. Meanwhile, as the mounting distance (MD) increased, the pressure angle and geometry factor for the TRBS increased, and the tooth equivalent curvature decreased. Consequently, the change in contact force according to the increase of the MD was insignificant. However, the contact stress and TRBS significantly decreased, and the fatigue lifetime of the pinion increased.

기어 정밀도를 고려한 CRP 시스템 랙의 굽힘 강도설계

본 논문에서는 기존 랙-피니언의 인벌류트 피니언 치를 롤러로 대체한 CRP(cam rack pinion) 시스템 랙의 기어 정밀도(gear accuracy grade)를 고려하지 않았을 때와 고려하였을 때의 이뿌리 굽힘응력(TRBS: tooth root bending stress) 거동을 비교 고찰하였다. 하중전담구간(STC: single tooth contact)에서의 TRBS 거동은 기어 정밀도와 무관하게 거의 일치하였으나 STC 최고위치인 HPSTC(highest point of STC)를 지난 이후의 하중분담구간(DTC: double tooth contact)에서의 TRBS는 기어 정밀도에 따라 상당한 차이를 보였다. 또 설계제원 중 롤러 피니언 모듈이 증가하면 압력각의 감소로 최대 접촉력은 약간 감소하나 형상계수(bending strength geometry factor)의 감소로 인해 TRBS가 증가함을 확인하였다.

Rapid and inexpensive nylon-66-filter solid-phase extraction followed by gas chromatography tandem mass spectrometry for analyzing perfluorinated carboxylic acids in milk

In this study, a new rapid and inexpensive filter solid-phase extraction method (FSPE) was developed for the extraction and separation of five perfluorinated carboxylic acids (PFCAs) (namely, perfluorooctanoic acid, perfluorononanoic acid, perfluorodecanoic acid, perfluoroundecanoic acid, and perfluorododecanic acid) from milk samples. Commercial nylon 66 syringe filters were used as adsorbents without additional modification. The proposed method could achieve the fast adsorption of analytes by benefitting from the advantages of using the nylon 66 filter membrane on PFCAs with multiple adsorption interactions, namely, hydrophobic interactions and hydrogen bonds. The FSPE was designed to achieve the rapid isolation of analytes based on the rapid solid-liquid separation while using the solid-phase extraction disk. PFCAs residues in milk were extracted by first flowing the samples through a nylon 66 syringe filter from top to bottom. Double contact desorption with methanol was then accomplished by pulling and pushing the syringe, followed by derivatization with acetyl chloride-methanol. Finally, the extracted PFCAs residues were monitored using gas chromatography-tandem mass spectrometry (GC-MS/MS) quantification. Under optimal conditions, the established method presented good linearity (correlation coefficient ≥ 0.9996), precision (relative standard deviation ≤ 13%), accuracy (81–105%), sensitivity (limits of quantification: 4–18 ng kg−1) and extraction performance (10 min).

Structural design and magnetic field analysis on magnetic fluid lubricated bearings

A structural model of a bearing is proposed based on a general standard bearing structure and magneto-fluidic lubrication, and the magnetic field of the bearing lubrication gap is analyzed under the action of an applied magnetic source. Results show that the magnetic field can form a magnetic circuit in the bearing structure, and a significant magnetic flux density is formed in the contact area of the rolling element of the bearing. The magnetic induction intensity in the contact area of the rolling element of the thrust bearing can provide magnetic fluid lubrication, and the magnetic induction intensity in the contact area of the rolling element of the point contact bearing is greater than that of the linear bearing. The magnetic inductance of the rolling elements in the rolling element contact area of a double row point contact bearing is greater than that of a single ring. The double permanent magnet ring structure has a more advantageous magnetic field effect than a single ring, and the magnetic inductance in the rolling element contact area of both rows of a double row point contact bearing is relatively the same.