Types Of Contact Surfaces Research Articles

Comparative Study on Numerical Calculation of Modal Characteristics of Pump-Turbine Shaft System

Because a pump-turbine mainly undertakes the role of energy conversion and pumped storage in the field of hydropower engineering, the complex transition process and frequent conversion between different working conditions lead to the increase in the stress and strain of core components such as the unit shaft system, and even cause resonance phenomena. Based on ANSYS finite element numerical calculation software, this paper adopts the acoustic fluid–structure coupling method to study the influence of the shaft of the pump-turbine on the dynamic characteristics of the runner. At the same time, the paper analyses the influence of different contact modes between the runner and the shaft on the modal characteristics of the shaft system. The numerical simulation results have shown that the runner is affected by the added mass of the water. The natural frequency reduction rate of each order of wet modal is ranged from 19% to 64%. The main shaft has a greater influence on the simplification of the shaft system calculation method. The type of contact surface between the main shaft and the runner has a smaller influence on the modal characteristics and the natural frequency of the shaft system. The research in this paper contributes an evaluation of the dynamic characteristics of the runner of a hydraulic turbine unit, which is of great significance for the optimization of the analysis algorithm of the runner structure for large pumped storage units.

Joule Heating in Single-Molecule Point Contacts Studied by Tip-Enhanced Raman Spectroscopy.

Heating and cooling in current-carrying molecular junctions is a crucial issue in molecular electronics. The microscopic mechanism involves complex factors such as energy inputs, molecular properties, electrode materials, and molecule-electrode coupling. To gain an in-depth understanding, it is a desired experiment to assess vibrational population that represents the energy distribution stored within the molecule. Here, we demonstrate the direct observation of vibrational heating in a single C60 molecule by means of tip-enhanced Raman spectroscopy (TERS). The heating of respective vibrational modes is monitored by anti-Stokes Raman scattering in the TERS spectra. The precise control of the gap distance in the single-molecule junction allows us to reveal a qualitatively different heating mechanism in distinct electron transport regimes, namely, the tunneling and single-molecule point contact (SMPC) regimes. Strong Joule heating via inelastic electron-vibration scattering occurs in the SMPC regime, whereas optical heating is predominant in the tunneling regime. The strong Joule heating at the SMPC also leads to a pronounced red shift of the Raman peak position and line width broadening. Furthermore, by examining the SMPC with several types of contact surfaces, we show that the heating efficiency is related to the current density at the SMPC and the vibrational dissipation channels into the electrode.

Formation and Transfer of Multi-Species Biofilms Containing E. coli O103:H2 on Food Contact Surfaces to Beef.

Interactions of Shiga toxin–producing E. coli (STEC; O103:H2) with lactic acid bacteria (LAB) or spoilage bacteria (SP) multispecies biofilms on polyurethane (TPU) and stainless-steel (SS) were assessed at 10 and 25°C under wet and dry conditions after 6, 30, and 60 days of storage. One LAB T1: Carnobacterium piscicola + Lactobacillus bulgaricus, and two SP T2: Comamonas koreensis + Raoultella terrigena; T3: Pseudomonas aeruginosa + C. koreensis were assessed for their ability to form multispecies biofilms with O103:H2. O103:H2 single-species biofilms served as a control positive (T4). Coupons were stored dry (20–50% relative humidity; RH) or moist (60–90% RH) for up to 60 days, at which point O103:H2 transfer to beef and survival was evaluated. At 25°C, T3 decreased beef contamination with O103:H2 by 2.54 log10 CFU/g (P < 0.001). Overall, at 25°C contamination of beef with O103:H2 decreased (P < 0.001) from 3.17 log10 CFU/g on Day 6 to 0.62 log10 CFU/g on Day 60. With 60 days dry biofilms on TPU, an antagonistic interaction was observed among O103:H2 and multispecies biofilm T1 and T3. E. coli O103:H2 was not recovered from T1 and T3 after 60 days but it was recovered (33%) from T2 and T4 dry biofilms. At 10°C, contamination of beef with O103:H2 decreased (P < 0.001) from 1.38 log10 CFU/g after 6 days to 0.47 log10 CFU/g after 60 days. At 10°C, recovery of O103:H2 from 60 days dry biofilms could only be detected after enrichment and was always higher for T2 than T4 biofilms. Regardless of temperature, the transfer of O103:H2 to beef from the biofilm on TPU was greater (P < 0.001) than SS. Moist biofilms also resulted in greater (P < 0.001) cell transfer to beef than dry biofilms at 10 and 25°C. Development of SP or LAB multispecies biofilms with O103:H2 can either increase or diminish the likelihood of beef contamination. Environmental conditions such as humidity, contact surface type, as well as biofilm aging all can influence the risk of beef being contaminated by STEC within multi-species biofilms attached to food contact surfaces.

Surface bonding of additive manufactured parts from multi-colored PLA materials

Producing Multi-Material parts via Rapid Prototyping can be an excellent solution for many applications, but also a challenging design task. Material Extrusion is suitable to use multiple materials simultaneously to generate a single component. In this article, the mechanical properties were examined of this kind of PLA component from tensile tests. To determine the adhesion relationship between two parts of the same sample made of PLA material of different colors, several test samples have been prepared with different types of contact surfaces. It has been taken into consideration and analyzed the horizontal-vertical adhesion and the contour lines of a Fused Deposition Modeling (FDM) additive process. In this article, the mechanical properties of the parts made from two different colored PLA in the same components manufactured with FDM technology were investigated, particularly the interfacial adhesion. This is a crucial step to understanding the behaviour of the Multi-Material parts.

Effect of contact surface type on the slip resistance in bolted connections

The use of slip-critical bolted connections is strongly emphasized for steel structures located in seismic zones by building codes. Obviously, the type of contact surface has a significant effect on the slip resistance of such connections. The purpose of this research is to experimentally and numerically evaluate the effect of the type of plate contact surface on the frictional resistance of these structural components. To this end, some samples of bolted connections with different contact situations were selected and tested. The surfaces selected for this purpose include sandblasted, painted (with different thicknesses), and grooved (triangular and square shapes with two different groove's heights). Subsequently, in order to perform numerical analyses, the force-displacement relationship of the connections are simulated by constructing some Finite Element (F.E.) models for each case. The obtained data from numerical simulations were verified by the experiments, indicating an acceptable match. Overall, the results of this study showed that the square-grooved sample had the highest frictional resistance; while, the painted specimen exhibited the least frictional resistance. The frictional resistance of grooved samples with regard to sandblasted, ordinary, and painted are significantly higher. These values imply that with grooving the steel surface, in practice, the strength of such connections can be effectively improved.

Estimating Fingertip Forces, Torques, and Local Curvatures from Fingernail Images

SUMMARYThe study of dexterous manipulation has provided important insights into human sensorimotor control as well as inspiration for manipulation strategies in robotic hands. Previous work focused on experimental environment with restrictions. Here, we describe a method using the deformation and color distribution of the fingernail and its surrounding skin to estimate the fingertip forces, torques, and contact surface curvatures for various objects, including the shape and material of the contact surfaces and the weight of the objects. The proposed method circumvents limitations associated with sensorized objects, gloves, or fixed contact surface type. In addition, compared with previous single finger estimation in an experimental environment, we extend the approach to multiple finger force estimation, which can be used for applications such as human grasping analysis. Four algorithms are used, c.q., Gaussian process, convolutional neural networks, neural networks with fast dropout, and recurrent neural networks with fast dropout, to model a mapping from images to the corresponding labels. The results further show that the proposed method has high accuracy to predict force, torque, and contact surface.

Biodynamics of supine humans and interaction with transport systems during vibration and shocks

This work investigates the effect of the contact surfaces on the biomechanical response of supine humans during whole-body vibration and shocks. Twelve participants were exposed to three-dimensional random vibration and shocks and were tested with two types of contact surfaces: (i) litter only, and (ii) litter with spinal board. The two configurations were tested with and without body straps to secure the supine human. The addition of the spinal board reduced the involuntary motion of the supine humans in most directions. There were significant reductions in the relative vertical accelerations at the neck and torso areas, especially during shocks ( p &lt; 0.01). The inclusion of body straps with the spinal board was more effective in reducing the relative motion in most directions when shocks were presented. This study shows that the ergonomic design of the human transport system and the underlying contacting surfaces should be studied during dynamic transport environments.

Influence of Contact Surface Type on the Mechanical Damages of Apples Under Impact Loads

This paper presents an analysis of mechanical damage carried out on ‘Golden Delicious’ apple variety, which was subjected to impact loads during free drop against various rigid plates. For this purpose, an analysis of the contact pressure based on determined contours and surface pressure distributions at the contact point between the fruit dropped from various heights against fixed hard plates was performed. The impact test was conducted by means of Tekscan® system supported by computer verifying analysis. To obtain impact loads as well as their courses, the surface pressures and the bruise volumes were determined. Furthermore, use of ultra-thin pressure sensors allowed for determination of the characteristic shape of contact area and the impact of fruit onto rigid plate. The results showed that the impact of fruit against rigid surface (concrete, wood) generates high values of maximum surface pressure and the bruise volume, observed at dropping from 10 mm. A decrease in hardness of the test material (polyethylene foam) with decreasing maximum surface pressure approximately twice was noticed. The polyethylene foam is one of the best materials which protect fruit from mechanical damage, confirmed by the relation of bruise surface to contact surface, which did not exceed 35% during the impact at 150 mm. The results of proposed studies can contribute to developing of harvest, handling, and transport processes, aiming at reduction in losses among fruit growers and production costs, i.e., by improvement of transport method.

Computed tomography features of gastric cancer invasion to the pancreas and significance in the assessment of resectability of primary lesions

Computed tomography features of gastric cancer invasion to the pancreas and significance in the assessment of resectability of primary lesions

A comparative study of thermodynamic properties of binary mixtures containing perfluoroalkanes

Literature data on molar excess enthalpies and molar excess Gibbs energies, liquid-liquid equilibria, activity coefficients at infinite dilution and partial molar enthalpies at infinite dilution of binary mixtures of n-perfluoroalkanes (C5−C8)+n-alkanes (C5−C8) and of n-perfluorohexane-linear monoethers of general formula, CH3(CH2)m-O-(CH2)n-CH3 (m,n=1–4), are treated in the framework of DISQUAC, an extended quasichemical group contribution theory. The systems are characterized by two or three types of contact surfaces: aliphatic (CH3, CH2, CH and C groups), fluorine (F group) and oxygen (O group). Using a limited number of adjusted contact interchange energies parameters, structure dependent, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The model may serve to predict missing data.

A comparative study of thermodynamic properties of binary mixtures containing dimethylsulfoxide

A flow microcalorimeter has been used to determine excess enthanlpies (H E) at 298.15 K for binary mixtures of dimethylsulfoxide (1)+alkylbenzenes (benzene, methylbenzene, ethylbenzene, n-propylbenzene and sec-propylbenzene, n-butylbenzene, sec-butylbenzene and tert-butylbenzene) or tetrachloromethane, trichloromethane, tetrachloroethane, dichloromethane and monochloroalkanes (1-chloropropane, 1-chlorobutane, 1-chloropentane, 1-chlorohexane) (2). These data with the data available in the literature on the molar excess enthalpies (H E), molar excess Gibbs energies (G E), activity coefficients at infinite dilution, γ i ∞ , liquid-vapour equilibria (LVE) and liquid-liquid equilibria (LLE) for dimethylsulfoxide (DMSO)+n-alkanes, cyclohexane, benzene or alkylbenzenes (mono-, dialkyl-and trialkyl-) or tetrachloromethane, trichloromethane, dichloromethane and monochloroalkanes are treated in the framework of DISQUAC, an extended quasi-chemical group contribution theory. The systems are characterized by three types of contact surfaces: sulfoxide (S=O group), aliphatic (CH3, CH2, CH groups), cycloaliphatic (c-CH2 group), aromatic (C6H6, C6H5 groups) and chlorine (C1 group). Using a set of adjusted contact interchange energies parameters, structure dependent, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The model may serve to predict missing data.

Insights into the Role of Electrostatic Forces on the Behavior of Dry Pharmaceutical Particulate Systems

Under different charging conditions, particles can be either attracted or repulsed by each other, causing powder agglomeration or segregation. Such behavior can be detrimental in many processes aimed at achieving particulate mixture homogeneity. Consequently, the effects of electrostatic charges on mixing kinetics must be well understood to insure a high level of process control, product quality, and reproducibility. In Part 1, an electrostatic charger is used to evaluate the ability of the studied particles to develop and retain an induced charge at the surface for a fixed period of time. Part 2 assesses the natural electrostatic charge developed by powders sliding across a stainless steel, plastic, or Tyvek chute. In Part 3, 2 binary systems were formed according to an experimental design under different charging conditions, and their behavior was quantified by measuring the degree of agglomeration attained. This work has shown that each raw material develops a different charge according to its physico-chemical properties and the type of contact surface. Electrostatic charges influence the creation of agglomerates under certain conditions. The presence of electrostatic charges must be accounted for in any effort to maximize mixing efficiency.

A comparative study of thermodynamic properties of binary mixtures containing alkynes

Literature data on molar excess enthalpies ( H E) and molar excess Gibbs energies ( G E) of linear alkynes+ n-alkanes, cycloalkanes, benzene or tetrachloromethane are treated in the framework of DISQUAC, an extended quasichemical group-contribution theory. The systems are characterized by three types of contact surfaces: acetylenic (CC group), aliphatic (CH 3 or CH 2 groups), cycloaliphatic (c-CH 2 group), aromatic (C 6H 6 group) and chlorine (CCl 4 group). Using a limited number of adjusted contact interchange energies parameters, the model provides a fairly consistent description of the thermodynamic properties as a function of concentration. The model may serve to predict missing data.

Disquac Characterization of the Carbonyl-Chlorine Interactions in Binary Mixtures of Linear Ketone with Chloroalkane

Both the published and our new data on vapour-liquid equilibrium, excess Gibbs energy GE and excess enthalpy HE for the linear ketone-chloroalkane binary mixtures are interpreted in terms of the DISQUAC group contribution model. The components are characterized by three types of contact surfaces: chlorine (Cl), carbonyl (C=O) and alkyl (CH3, CH2, CH, C). The Cl/alkyl and C=O/alkyl contact parameters are known from the literature. The parameters for C=O/Cl are re-evaluated here using extensive data on linear ketone-chloroalkane mixtures. It was found that the best description of ketone mixtures with 1-chloroalkane, trichloromethane, 1,1,1-trichloroethane, tetrachloromethane and 1,1,2,2-tetrachloroethane is obtained using a dispersive contribution of the C=O/Cl contact only. On the other hand the quasichemical term cannot be neglected for the ketone-α,ω-dichloroalkane systems. The newly evaluated interaction parameters for DISQUAC model enable good prediction of phase equilibrium and thermodynamic properties GE and HE as well as the temperature dependence of GE.

Excess Enthalpies of 1-Bromobutane + Oxaalkanes at 298.15 K. Comparison with Disquac Predictions

Excess enthalpies, HE, at 298.15 K and atmospheric pressure are reported for binary liquid mixtures of 1-bromobutane + oxaalkane of the general formula CH3−(CH2)s-1−O−(CH2)t-1−CH3. The experimental results are interpreted in terms of the DISQUAC group contribution model. The systems are characterized by three types of contact surfaces: oxygen (O), bromo (Br), and alkane. The interchange energy parameters of the alkane/O and alkane/Br contacts were determined independently from the study of n-alkane + oxaalkane and n-alkane + bromo systems. The interaction parameters of the O/Br contacts are reported in this work. The quasichemical and the dispersive parameters depend on the environment of the O group. The model provides a fairly consistent description of the experimental data.

Thermodynamic properties of n-alkylbenzene+ n-alkane or cyclohexane mixtures. Comparison with disquac predictions

The molar excess enthalpies ( H E), at 298.15 K, of some mixtures of alkylbenzenes with n-heptane or cyclohexane were measured using a flow calorimeter. These data, along with the literature data on molar excess enthalpies ( H E), molar excess Gibbs energies ( G E), molar excess heat capacity ( C E p) and activity coefficients at infinite dilution ( γ ∞ i ) of mixtures in n-alkanes or cyclohexane of mono-alkylbenzenes of general formula, C 6H 5–(CH 2) n−1 CH 3, isomeric dimethylbenzenes (xylenes) and isomeric trimethylbenzenes were treated within the framework of DISQUAC, an extended group contribution model, in the simplified `dispersive' version. The systems were characterized by three types of contact surfaces: phenyl (C 6H 5 group), alkane (CH 3 or CH 2 groups) and cyclohexane ( c-CH 2 group). The interchange energy parameters of the alkane/cyclohexane contacts were determined previously, the interaction parameters of the alkane/phenyl and cyclohexane/phenyl contacts are reported in this study. The dispersive parameters depend on the environment of the phenyl group and the number of alkyl groups adjacent to the phenyl group. The model provides a fairly consistent description of the experimental data as a function of concentration.

Linear alkyl–alkanoates+cyclohexane mixtures. Excess enthalpies measurements and DISQUAC analysis of thermodynamic properties

The molar excess enthalpies ( H E), at 298.15 K and atmospheric pressure, of fourteen mixtures of alkyl–alkanoates with cyclohexane have been measured using a flow calorimeter LKB. These data along with the literature data on molar excess enthalpies, H E, and molar excess Gibbs energies, G E, of mixtures in cyclohexane of alkyl–alkanoates of general formula, H(CH 2) u –COO–(CH 2) v−1 CH 3 are treated in the framework of DISQUAC, an extended group contribution model. The systems are characterized by three types of contact surfaces: carboxylate (COO group), aliphatic (CH 3 or CH 2 groups) and cyclohexane (c-CH 2, group). The three types of surface, a, c, k generate three pairs of contacts (ac), (ak) and (ck). The interchange energies parameters of the aliphatic/cyclohexane and aliphatic/carboxylate contacts were determined previously, the interaction parameters of the cyclohexane/carboxylate contacts are reported in this work. The interchange energy parameters depend on the environment of the carboxylate group, the number of alkyl groups adjacent to the COO group. The dispersive parameters increase or remain constant whereas the quasi-chemical parameters decrease with the n-alkyl chain of the alkyl–alkanoate. The model provides a fairly consistent description of the experimental data as a function of concentration.

Steric and inductive effects in binary mixtures of alkanones with benzene or tetrachloromethane. Comparison with DISQUAC predictions

Literature data on molar excess enthalpies ( H E), molar excess Gibbs energies ( G E) and activity coefficients at infinite dilution ( γ i ∞) of linear alkanones+benzene or tetrachloromethane are treated in the framework of DISQUAC, an extended group contribution model. The systems are characterized by three types of contact surfaces: carbonyl (CO group), alkane (CH 3 or CH 2 groups) and solvent (benzene, C 6H 6, or tetrachloromethane, CCl 4, groups). The interchange energies parameters of the alkane/CO and alkane/solvent contacts were determined previously, the interaction parameters of the CO/solvent contacts are reported in this work. The quasi-chemical and dispersive parameters depend on the environment of the CO group. The model provides a fairly consistent description of the experimental data as a function of concentration. The solutions of alkanones in benzene or tetrachloromethane exhibit the features of polar solute+polarizable solvent mixtures, namely, the deviations from ideality are much less positive than in alkanes and may even be negative.

Calorimetric study of nitrile-chloro group interactions. Comparison with DISQUAC predictions

Excess enthalpies, H E, at 298.15 K and atmospheric pressure are reported for binary liquid mixtures of alkanenitrile + 1-chloroalkane. These experimental results, along with literature data on excess Gibbs energies, G E, are interpreted in terms of the DISQUAC group contribution model. The systems are characterized by three types of contact surfaces: nitrile (CN), chloro (Cl) and alkane. The interchange energy parameters of the alkane/CN and alkane/Cl contacts were determined independently from the study of n-alkane + nitrile and n-alkane + chloroalkane systems. The interaction parameters of the CN Cl contacts are reported in this work. The quasi-chemical parameters are constant. The dispersive parameters depend on the environment of the CN and Cl groups. The model provides a fairly consistent description of the experimental data.

Linear alkanoates + aromatic hydrocarbon binary mixtures: new excess enthalpy measurements and DISQUAC analysis of thermodynamic properties

Excess enthalpies at 298.15 K and atmospheric pressure are reported for 8 binary liquid mixtures of n-alkanoates (propyl methanoate, butyl methanoate, ethyl ethanoate, propyl ethanoate, butyl ethanoate, methyl propanoate, ethyl propanoate, propyl propanoate) + toluene. These experimental results along with literature data on vapour-liquid equilibrium (VLE), excess molar Gibbs energies (Ge), excess molar enthalpies (He), activity coefficients at infinite dilution (γi∞) and excess molar heat capacities (Cpe) of n-alkanoates + benzene, or + toluene are examined on the basis of the DISQUAC group contribution model. The components in the mixtures are characterized by three types of contact surfaces: carboxylate (COO group), aliphatic (CH3 or CH2 groups) and aromatic (C6H6 or C6H5 groups, in benzene or in toluene, respectively). Interaction parameters for aliphaticaromatic and aliphaticCOO contacts have been estimated previously. In this work, we have determined the missing heat capacity interaction parameters of the aliphaticCOO contact and all the interaction parameters of the aromaticCOO contact. The aromaticCOO contact is best described by entirely dispersive parameters. The Gibbs energy and enthalpy parameters decrease, whereas the heat capacity parameters increase, with the n-alkyl chain of the n-alkanoate.