Contact Plates Research Articles

A frictionless contact problem for a flexible circular plate and an incompressible non-homogeneous elastic halfspace

In this paper we apply an energy method to examine the axisymmetric contact problem for a flexible circular plate in smooth contact an incompressible elastic halfspace, where the linear elastic shear modulus varies exponentially with depth. The approach adopted approximates the deflected shape of the plate by a power series expansion which satisfies the kinematics of deformation of the plate and the Kirchhoff boundary condition at the edge of the plate. The coefficients in the series are evaluated by making use of the principle of minimum potential energy. Results are obtained for the maximum deflection, the relative deflection and the maximum flexural moment in the circular plate. The results derived from the proposed procedure are compared with equivalent results derived from a computational procedure.

Complex local Moho topography in the Western Carpathians: Indication of the ALCAPA and the European Plate contact

Seismic data from deep refraction and wide-angle reflection profiles intersecting the Western Carpathians show distinct upper-mantle Pn phases with anomalous apparent velocities identified in the first and later arrivals. Their systematic analysis indicates that such phases are present in numerous seismic sections both for in-line and off-line shots. They are observed in data from profiles intersecting the Carpathians in the west at the contact with the Bohemian Massif; similar feature was also found in data at the northern edge of the Carpathians at the contact with the North European Platform. Modelling of these anomalous Pn phases shows that they originate due to local structural anomalies of the Moho discontinuity detected in several places along the Western Carpathian arc. Such anomalies are located in close lateral proximity of the Pieniny Klippen Belt representing the contact between the stable European Plate in the north and the ALCAPA (Alpine–Carpathian–Pannonian) microplate in the south. Thus, the complex local Moho topography modelled from the Pn phases suggests tectonic relation to the formation of the Carpathian orogen. The result is supported by correlation with the large-scale Carpathian conductivity anomaly modelled in the Carpathians at a mid-crustal level. Relative lateral position of these two structures together with the Pieniny Klippen Belt at the surface delineates a zone affected by deformations at various depths along the whole Western Carpathian arc.

Automatic design algorithms for securing the ground contact stability of mobile cranes

Abstract Background Mobile cranes overturn due to excessive lifting, heavy wind, or when appropriate ground contact pressure is not secured. Such accidents can be prevented by reviewing the force conveyed from the outrigger to the ground upon lifting, as well as the soil bearing force. The stability review of mobile crane overturn is classified into the following stages: reviewing lifting conditions, mobile crane selection and reviewing ground contact stability. However, a precise review of ground contact stability requires expertise and is extremely time-consuming. Thus, this study develops automatic design algorithms for securing the ground stability of mobile cranes for easy and quick stability reviews. Methods The stability review method and the algorithm models are created in connection with the proposed conceptual process. The algorithms proposed in this study conduct simulations for all possible candidate cases, save the results in a database, review practical alternatives, and select the solution that minimizes cost. To verify the effectiveness of the automatic design model, a case project was selected and the algorithm was applied assuming several conditions. Results Developed algorithms can select candidate cranes according to lifting conditions and design plates through simulations easily and quickly, and design components required for ground contact plate design are collected to build the database that allows easier and quicker stability review. Conclusion The algorithms proposed in this study conduct simulations for all possible candidate cases, save the results in a database, review practical alternatives, and select the solution that minimizes cost. Developed processes are useful for analyzing correlations of mobile crane performance, ground contact and soil bearing force reinforcement designs and so forth, and for systematically selecting optimal mobile cranes.

Thrust initiation and its control on tectonic wedge geometry: An insight from physical and numerical models

We performed a series of sandbox experiments to investigate the initiation of thrust ramping in tectonic wedges on a mechanically continuous basal decollement. The experiments show that the decollement slope (β) is the key factor in controlling the location of thrust initiation with respect to the backstop (i.e. tectonic suture line). For β = 0, the ramping begins right at the backstop, followed by sequential thrusting in the frontal direction, leading to a typical mono-vergent wedge. In contrast, the ramp initiates away from the backstop as β > 0. Under this boundary condition an event of sequential back thrusting takes place prior to the onset of frontal thrust progression. These two-coupled processes eventually give rise to a bi-vergent geometry of the thrust wedge. Using the Drucker-Prager failure criterion in finite element (FE) models, we show the location of stress intensification to render a mechanical basis for the thrust initiation away from the backstop if β > 0. Our physical and FE model results explain why the Main Central Thrust (MCT) is located far away from the Indo-Tibetan plate contact (ITSZ) in the Himalayan fold-and-thrust belts.

Micro-scale CFD study about the influence of operative parameters on physical mass transfer within structured packing elements

In this work a VOF-based 3D numerical model is developed to study the influence of several operative parameters on the gas absorption into falling liquid films. The parameters studied are liquid phase viscosity, gas phase pressure and inlet configuration, liquid–solid contact angle and plate texture. This study aims to optimize the post-combustion CO2 capture process within structured packed columns. Liquid phase viscosity is modified via MEA (i.e. monoethanolamine) concentration. The results show that an increase in liquid viscosity reduces the diffusivity of oxygen within the liquid film thus hindering the efficiency of the process. Higher pressure carries an absorption improvement that can be attractive to be applied in industry. The simulations show that enhanced oxygen absorption rates can be achieved depending on the velocity of the gas phase and the flow configuration (i.e. co- and counter-current). Also, the importance of wetting liquid–solid contact angles (i.e. less than 90°) is highlighted. Poor liquid–solid adhesion has similar effects as surface tension in terms of diminishing the spreading of the liquid phase over the metallic plate. Finally the influence of a certain geometrical pattern in the metallic surface is also assessed.

What is the best method? Recovery of methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase-producing Escherichia coli from inanimate hospital surfaces.

Environmental sampling in hospitals, when required, needs to be reliable. We evaluated different methods of sampling methicillin-resistant Staphylococcus aureus and extended-spectrum β-lactamase-producing Escherichia coli on 5 materials of the hospital setting. Petrifilms and contact plates were superior to swabs for all of the surfaces studied.

Heat Dissipation Capacity of Heat Sink Assembly with/without Vortex Generators

In this research, numerical simulation is adopted to study the cooling characteristic of a bracket-type heat sink assembly. Analysis on thermal/fluid fields are used to justify the physical mechanisms inducing the excessive heat dissipation and temperature rise. In order to enhance the cooling capacity of the heat sink assembly, two types of vortex generator, flow-up and flow-down were used to create the turbulent flow for increasing the contact opportunitybetween fluid and plate fin.Also, thermal resistance is used to evaluate the cooling capacity of the heat sink assembly in this work. As a result, the numerical simulations show thatapparent reductions on source temperature (from 348.0K to 346.2K) and thermal resistance (from 0.266 K/W to 0.253 K/W) are observed for a 150W power input. Besides, significant improvement on the heat concentrated phenomenon anduniform temperature distribution were acquired after installing the vortex generators.Furthermore,a larger longitudinal flow was generated when the flow-up type vortex generator was mounted; therefore the temperature distribution is more uniform than that of the flow-downtype. Clearly, the cooling capacity of heat sink assemblyis enhanced since the fluid is guided to the heat concentrated area when theflow-down vortex generators are adopted.

Stress and displacement fields in the outer wedge induced by megathrust earthquakes

AbstractWe model plate boundary slip at the outer (oceanward) segment of the megathrust wedge as slip at the base of a two‐dimensional elastic wedge, subject to gravity force, with a sloping seafloor at the top, and drag at the bottom from a rigid plate in frictional contact. The stress and displacement fields in the wedge are given analytically as functions of basal frictional coefficient μe. Unlike either conventional dislocation models (constant slip) or crack models (constant stress drop), our wedge model (constant μe drop) does not show a stress singularity at the updip toe of the plate boundary. The slip increases, but the stress drop decreases updip along the fault toward the trench axis. There is a minimum stress difference state in the wedge when μe is varied. By referring to this state (μe = μec), the stress state is separated into a horizontally tensile regime (μe < μec) and a horizontally compressional regime (μe > μec). Slip associated with a μe drop in the range μe ≤ μec occurs toward increasing horizontal tension and shear energy. Such earthquakes include tsunami earthquakes occurring in the outer segment and the 2011 great Tohoku‐Oki earthquake, which involved both the outer and inner segments, with much larger slip in the outer segment. These earthquakes are characterized by an almost complete drop of basal stress, which brings the wedge into the maximum tensile state, leading to the rare occurrence of thrust aftershocks at the base of the wedge and frequent occurrence of normal fault aftershocks within the wedge.

Biomechanical effects of plate area and locking screw on medial open tibial osteotomy

Medial open high tibial osteotomy (HTO) has been used to treat osteoarthritis of the medial compartment of the knee. However, weaker plate strength, unstable plate/screw junction and improper surgery technique are highly related to the HTO outcomes. Two π-shape plates were designed and eight variations (two supporting area × four locking stiffness) were compared by finite-element method. The computed tomography-based tibia was reconstructed and both wedge micromotion and implant stresses were chosen as the comparison indices. The construct was subjected to surgical and physiological loads. The medial-posterior region is the most loaded region and the load through the posterior leg is about four times that through the anterior leg. This indicates that the two-leg design can form a force-couple mechanism to effectively reduce the implant stresses. The use of locking screws significantly decrease the screw and hole stresses. However, the extending plate reduces the stresses of screws and holes above the wedge but makes the distal screws and holes much stressed. Wedge micromotion is affected by extending plate rather than locking screw. Three factors contribute to effective stabilisation of unstable HTO wedge: (1) intimate tibia–plate contact at medial-posterior regions, (2) sufficient rigidity at plate-screw junctions and (3) effective moment-balancing design at distal tibia–plate interfaces.

Comparison of methods for detection of four common nosocomial pathogens on hospital textiles

AbstractIntroduction: Although the most common vehicle for transmission of health-care acquired infections is the personto- person transmission route, the role of environment should not be ignored and hospital linen may contribute to the spreading of nosocomial infections. The contact plate method and swabbing are common methods for sampling microorganisms on textiles; however, results are available after two days as they are based on incubation followed by phenotype identification. An important alternative is using quick wash-off methods followed by PCR detection, which shortens the identification process from two days to a few hours.Methods:The following test microorganisms at different concentrations were inoculated onto textile swatches and dried overnight: Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and Clostridium difficile. RODAC plate sampling as well as a non-destructive wash-off method for capturing microorganisms from the textiles using a Morapex device were used. The elution suspension from the Morapex device was used for two methods. In the first method, classical incubation on selective media followed by phenotypic identification was used and in the second method DNA was extracted from the elution suspension followed by amplification and agarose gel electrophoresis to visualize amplified products.Conclusions:All chosen bacteria were found using all methods. However, the most sensitive proved to be detection using PCR amplification as we detected the sample with initial concentration of 102 cfu/mL inoculated onto the textile surface before drying. The final detectable recovered bacterial concentration on textiles was up to 10 cfu/mL.

Experimental research of heat transfer conditions influence on the distillate fuels ignition characteristics

The experimental studies results of diesel fuel ignition regularities by hot single metal particles and fuel droplets on a heated metal plate surface are presented. The ignition delay time dependences on the initial heat source temperature were determined. The results are a basis for the development of typical liquid fuels ignition models in terms of heat and mass transfer processes in a small neighborhood. Liquid fuels are widely used in road transport and under certain conditions (storage, transport, congestion) are sources of increased danger. They can cause a fire during thermal exposure of high intensity. Heat sources can be different, as well as the conditions of exposure (1-3). To date, mathematical models and solving methods for the ignition of solid (4, 5) and liquid (2, 3) fuels are worked out. Experimental conditions and the ignition characteristics of solid monolithic (9) and dispersed (7) fuels with a local heating source are established. Ignition regularities for films and drops of distillate fuels are studied much worse. The purpose of this work is an experimental study of diesel fuel ignition conditions and characteristics. Two of the most important options for practice are considered: a single fuel film heated up to high temperatures and particle droplets on the heated metal plate surface. Film fuel ignition process research was conducted on the plant (9), the concept of which is shown in Fig. 1, and drop method (1) (the experimental scheme is shown in Fig. 2). In all experiments a video registration of the investigated processes was conducted. The time moments of heat source (particle or plate) contact with a liquid (film or drop, respectively) and the ignition delay time were registered. As the heat sources the steel particles (diameter of dp = 6 · 10 −3 m and a height of hp = 3 · 10 −3 ÷7 · 10 −3 m) and the steel plate (size 5 · 10 −2 × 5 · 10 −2 m and a height hw = 5 · 10 −3 m) were used. Particles fall from a small height (0.01m) onto the fuel film surface. A possible change in its temperature is due to heat sink in the air. It is established that during the fall of the particles temperature is reduced by not more than 5K, which is about ±0.5% depending on the absolute value of the initial particle temperature. Experiments at constant heat source temperature T0 is repeated at least 7 times under identical conditions. Random error in ign determining is no more than ±10% in the experiments with the particle heat source and up to ±16% in the experiments with hot plate. The dependences of the diesel fuel ignition delay times from the initial heat source temperature obtained from the experiments results are shown in Fig. 3. Measurements have shown that the temperature of the massive plate during the experiment remained virtually unchanged (droplet sizes This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Discontinuous Galerkin finite element method for plate contact problem with frictional boundary conditions

- In this paper, we deal with the discontinuous Galerkin finite element method for the plate contact problem with the frictional boundary conditions. The weak formulation is the variational inequality problem of the second kind. In virtue of the special discrete variational formulation, the error estimate in the broken H 2 norm is derived between the discontinuous approximation solution and the exact solution.

Determine the effectiveness of mass-exchange column apparatus plates given the uneven distribution of the phases

The development of technical solutions for the modernization of mass transfer trays of columns of energy companies is impossible without determining the effectiveness of the separation of the mixture at various constructive and regime parameters. Determination of the effectiveness of the separation on contact devices is one of the important problems in the theory and practice of mass-transfer processes. Among the numerous research and industrial practice it is known that increasing the size of the apparatus (plates ) flow pattern changes significantly , there is a large number of dead zones backmixing increases, decreases the driving force of the process, it causes a decrease in the efficiency of mass transfer . This phenomenon is called "scale effect". The article considers the uneven distribution of gas (steam) input phase and liquid phase on the canvas contact device. To take account of these irregularities phase distribution on the contact device algorithm of calculation of efficiency of plates in Merfri. Given the dependence of mass transfer coefficients in the gas phase and efficiency plates in Merfri from the gradient at different speeds gas in the column for standard sieve and valve plates. The authors developed the new highly efficient contact device - structured gas-liquid contact plate (SGC) vari-free section of the hole, which is due to their distinctive properties allows to reduce the effect of inequality of distribution of phases on a plate. Compares the standard sieve plates, standard valve plates and new plates SGC. The calculation and variants of modernization heat and mass transfer devices dehydration of hydrocarbon (natural) gas (absorber and desorber) on the proposed algorithm. Chosen the most energy-efficient ways to modernization of vehicles.

Evaluation of freezing pre-treatments for the lyophilisation of apple

Abstract The effect of freezing rate on the quality of dried Jonagold and Idared (Malus domestica Borkh.) was studied. Apple slices underwent various pre-treatments, i.e. freezing in household freezer (freezing speed/rate: 0,5◦C/min), contact plate freezing (2◦C/min) and vacuumfreezing (3◦C/min). The quality of the freeze-dried product was then evaluated in terms of water activity (aw), hardness, color and rehydration. The texture and color experiments were carried out with texture analyser and colorimeter. The aw of apple slices was measured by aw apparatus. It was found that drying time was influenced by freezing rate. The freezing in household freezer (slow freezing rate) significantly reduces the duration of the freeze-drying process and consequently the process costs. The slow freezing rate allows the growth of large ice crystals at the beginning of the freeze-drying process; this fact should consequently lead to larger pores and injured cell walls and thus to shorter freeze-drying time. Quality of the freezing in household freezer product was assessed as higher than the quality of the other freezing pre-treated material. Slow freezing rate resulted softer texture and higher rehydration capacity than that of other pre-treated samples. In all cases, slow freezing speed lead to lower final moisture content, total color difference and water activity. Freeze-dried samples prepared with higher freezing rates (3◦C/min) were the most white in color because small pores, originated by sublimation of small ice crystals formed by fast freezing.

ASSESSMENT OF FREEZING PRE-TREATMENTS FOR THE FREEZE DRIED OF APPLE SLICES

Abstract The effect of freezing rate on the quality of dried Jonagold and Idared was studied. Apple slices underwent various pre-treatments, i.e. freezing in household freezer (freezing rate: 0,5 °C/min), contact plate freezing (2 °C/min) and vacuum-freezing (3 °C/min). The quality of the freeze dried product was then evaluated in terms of water activity, hardness, color and rehydration. The freezing in household freezer (slow freezing rate) significantly reduces the duration of the freeze drying process and consequently the process costs. The slow freezing rate allows the growth of large ice crystals at the beginning of the freeze-drying process, this fact should consequently lead to larger pores and injured cell walls and thus to shorter freeze drying time. Quality of the freezing in household freezer product was assessed as higher than the quality of the other freezing pre-treated material. Slow freezing rate resulted softer texture and higher rehydration capacity, than that of other pre-treated samples. In all cases, slow freezing lead to lower final moisture content, total color difference and water activity.

Validation of dipslides as a tool for environmental sampling in a real-life hospital setting

Environmental sampling in hospitals is becoming increasingly important because of the rise in nosocomial infections. In order to monitor and track these infections and optimize cleaning and disinfection, we need to be able to locate the fomites with the highest amount of microorganisms, but the optimal method for this is not clear. The aim of this study was to evaluate which of four different dipslides or a standard TSA contact plate were best at recovering human bacteria from the environment. We tested four different dipslides with selective and non-selective agars versus a standard TSA contact plate in order to find the best sampling media. Two hundred sites in a children's medical ward in Copenhagen University hospital were sampled in autumn 2012. There was no difference in total bacteria count between the TSA contact plate and the dipslides. Faecal indicator bacteria recovery was the same for the dipslides and the TSA contact plate. Dipslides may be equally well suited for environmental sampling and hygiene assessment as TSA contact plates. Dipslides have some advantages, such as better sample security, easier sampling in confined spaces and longer shelf life that may speak in favour of choosing these for bacteria environmental sampling in hospitals, depending on the task.

Ultrasound assisted nickel plating and silicide contact formation for vertical multi-junction solar cells

Vertical multijunction (VMJ) silicon solar cells (SC) are considered the most preferred among all known single-crystal ones for using in various photovoltaic systems under conditions of highly concentrated sunlight. The techniques of ultrasound assisted nickel plating (USNiP) of mirror polished silicon wafers and their subsequent vacuum annealing for VMJ SC ohmic contacts creating were tested by X-ray diffractometry, scanning electron microscopy and dark current–voltage characteristics. The feasibility of utilizing nickel electroplating in the sulfamate electrolyte for the NiSi ohmic contact made on the mirror polished silicon wafers with n+–p junctions on both sides have been experimentally confirmed. Ultrasound assistance of the nickel plating insured the enhancement of NiSi adhesion and improving the quality of the ohmic contacts.

Harvesting Energy from the Natural Vibration of Human Walking

The triboelectric nanogenerator (TENG), a unique technology for harvesting ambient mechanical energy based on the triboelectric effect, has been proven to be a cost-effective, simple, and robust approach for self-powered systems. However, a general challenge is that the output current is usually low. Here, we demonstrated a rationally designed TENG with integrated rhombic gridding, which greatly improved the total current output owing to the structurally multiplied unit cells connected in parallel. With the hybridization of both the contact-separation mode and sliding electrification mode among nanowire arrays and nanopores fabricated onto the surfaces of two contact plates, the newly designed TENG produces an open-circuit voltage up to 428 V, and a short-circuit current of 1.395 mA with the peak power density of 30.7 W/m(2). Relying on the TENG, a self-powered backpack was developed with a vibration-to-electric energy conversion efficiency up to 10.62(±1.19) %. And it was also demonstrated as a direct power source for instantaneously lighting 40 commercial light-emitting diodes by harvesting the vibration energy from natural human walking. The newly designed TENG can be a mobile power source for field engineers, explorers, and disaster-relief workers.

Comparison of Different Fungal Agar for the Environmental Monitoring of Pharmaceutical-Grade Cleanrooms

In relation to a growth in reported incidents of fungal contamination of pharmaceutical products, there has been a developing interest by U.S. and U.K. regulators concerning the risk of fungi. This paper describes a study undertaken to examine the suitability of different commercially available mycological agars for the environmental monitoring of pharmaceutical-grade cleanrooms. Five agars were evaluated in relation to the detection of both numbers and different species of fungi (yeasts and moulds). The objective was to determine if one mycological medium is more suitable than another. Data was collected using different sampling techniques (settle plates, active air samples, and contact plates) from different locations within representative cleanrooms. Samples were taken over a 3 month time period. The study results indicated that fungi are not distributed evenly across cleanrooms and that that the prevalence of fungi partly relates to the room design and operation. In relation to the different agar types, the study indicated that Sabouraud dextrose agar was the most effective at detecting the widest number of different types of isolates, and that Sabouraud dextrose agar and malt extract agar were the most efficient in terms of the numbers of recovered isolates. Other media, notably potato dextrose agar, was relatively less effective. There has been an increased regulatory concern about the presence of fungi in cleanrooms. Some environmental monitoring regimes are not especially orientated towards the examination of fungi, and it may be that special agars are required. Given the choice of different agars available, this paper outlines a case study where different fungal agars were evaluated. The study showed that Sabouraud dextrose agar was the optimal agar.

Subduction and deformation of the continental lithosphere in response to plate and crust-mantle coupling

Physical analogue experiments are used to investigate the effect of plate and intra-lithospheric coupling on the efficiency of continental lithosphere subduction and the style of collision. Key parameters investigated in this study are: the degree of plate coupling, regulated by the viscosity ratio of the decoupling zone and the surrounding crust and/or mantle lithosphere; and the depth of decoupling. The experimental results show that subduction of the slab is deepest in cases with strong decoupling at the plate interface and at the level of the lower crust of the downgoing plate, with upper-plate deformation restricted to the area close to the plate contact. In these cases, the strongly asymmetric orogenic wedge is widest, consists of a series of imbricated upper-crustal slices derived from the lower plate, and lacks a retro-wedge. In contrast, a reduced strength contrast across the plate interface, at the depth of either the lithospheric mantle or the ductile crust, leads to a combination of subduction and thickening of the mantle lithosphere in both the upper and the lower plates. The degree of plate coupling determines the efficiency of subduction of continental lithosphere under conditions of collision of neutrally buoyant lithospheres, whereas the vertical position of decoupling horizons within the subducting plate controls the amount of subducted lower crust. Transfer of strain to the upper plate depends critically on (1) the degree of plate coupling, with stronger coupling leading to more deformation, and (2) the presence of decoupling horizons within the upper plate, which act as strain guides to propagate deformation into the upper plate. The experimental results explain the geometry and the sequence of deformation in subduction dominated orogens, such as the Carpathians or the Dinarides, and provide a mechanical basis for the transfer of strain to the upper plate.