Migration and Blooming of Waxes to the Surface of Rubber Vulcanizates

1981 ◽  
Vol 54 (2) ◽  
pp. 255-265 ◽  
Author(s):  
S. H. Nah ◽  
A. G. Thomas
Keyword(s):  
Melting Point ◽  
Ambient Temperature ◽  
Driving Force ◽  
Volume Fraction ◽  
Adequate Explanation ◽  
Practical Applications ◽  
Elastic Stresses ◽  
Factors Influencing ◽  
Set Up

Abstract The model proposed in this paper appears to give an adequate explanation for the magnitude of the blooming rates observed. The driving force is due to elastic stresses set up around the precipitated wax particles and thus the blooming rate is influenced quite strongly by the modulus of the rubber. On the basis of this mechanism it would be expected that unvulcanized rubber would show little blooming, and this is in accord with general observations on such materials. The solubility of the wax is an important parameter and, because of its sensitivity to temperature, the ambient temperature and the melting point of the wax will be important factors influencing the blooming in practical applications. The precipitation of the wax has been assumed to occur at imperfections in the material. The source of these is not yet clear, although impurities could clearly be important. The values that have to be assumed for the volume fraction of these seeding sites, about 10−3, is not unreasonable in general magnitude for impurity concentrations.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

scholarly journals Educator perspectives on factors influencing children’s school-based physical activity

2018 ◽  
Vol 34 (5) ◽  
pp. 931-940 ◽  
Author(s):  
Matthew S Domville ◽  
Paula M Watson ◽  
Dave J Richardson ◽  
Lee E F Graves
Keyword(s):  
Physical Activity ◽  
Driving Force ◽  
Barriers And Facilitators ◽  
Organizational Level ◽  
Ecological Approach ◽  
Institutional Barriers ◽  
Intrapersonal Factors ◽  
School Based ◽  
Factors Influencing ◽  
Interpersonal Level

Summary Formative research is an important first step in the design and development of children’s school-based physical activity (PA) interventions. Exploration of educator [headteacher and physical education (PE)-co-ordinator] perceptions toward the promotion of school-based PA, including PE delivery has however been limited. This study took a socio-ecological approach to explore the barriers and facilitators of children’s school-based PA from the perspective of school educators. Interviews were conducted with headteachers (n = 4), PE-co-ordinators (n = 4) and a deputy headteacher (n = 1) and data thematically analysed using Nvivo software (version 10). Findings suggested that, at an organizational level headteachers were the predominant driving force in the promotion of PA opportunities, yet institutional barriers including low priority for PA and PE were perceived to negate delivery. At an interpersonal level, strategies to increase the delivery of school-based PA were developed, however poor teacher-coach relationships and significant others reduced PA promotion opportunities. Child PA was further negated through intrapersonal factors, including lack of PE-specific teacher training and varying teacher interest in PA and sport. To increase primary school children’s school-based PA, barriers and facilitators at the organizational, interpersonal and intrapersonal level must be considered and targeted and researchers and schools should work in partnership to develop future interventions.

scholarly journals Reliability Analysis and Motion Simulation of Steel Coil Upender Clamp

2011 ◽  
Vol 2-3 ◽  
pp. 924-927
Author(s):  
An Yuan Jiao ◽  
Feng Hui Wang
Keyword(s):  
Reliability Analysis ◽  
Driving Force ◽  
Motion Simulation ◽  
Steel Coil ◽  
Turnover Process ◽  
Set Up ◽  
Clamping Device

A kind of new steel coil upender clamping device was designed. The model was set up by use of SolidWorks and the reliability analysis and motion simulation was further performed in ADAMS. Because of risk at steel coil upender, once the accident appears, it gently slowed-up production and damaged the device, and it could cause people’s dying vitally, it is especially important to assure the longtime work and safety of device which we studied on. The results showed that the efficiency of turnover process of the device was high and the system could save driving force. These also provided some theory bases for the design of the device.

Design Model and Prediction Model on Preparation of Functionally Graded Material by Co-Sedimentation

2005 ◽  
Vol 492-493 ◽  
pp. 471-476 ◽  
Author(s):  
Zhi Guang Zhou ◽  
Lian Meng Zhang ◽  
Qiang Shen ◽  
Dao Ren Gong
Keyword(s):  
Prediction Model ◽  
Volume Fraction ◽  
Functionally Graded ◽  
Design Model ◽  
Design Experiment ◽  
Mathematical Relationship ◽  
Graded Material ◽  
Powder Properties ◽  
Set Up ◽  
The Relationship

From the process of sedimentation the mathematical relationship between deposition volume and powder properties as well as sedimentation parameters was deduced in this paper. The relationship was expressed by using indirect method. Based on the formula, design model and prediction model were set up. The models can be used to design powder properties and predict the volume fraction of FGM. Programs to solve the models were developed in numerical methods. As examples, TiC-Ni system FGM were designed and predicted. The prediction results fit well with the design. Experiment of Mo-Ti system FGM was used to validate the prediction model.

scholarly journals An experimental evaluation of the solute transport volume in biodegraded municipal solid waste

1999 ◽  
Vol 3 (3) ◽  
pp. 429-438 ◽  
Author(s):  
H. Rosqvist ◽  
D. Bendz
Keyword(s):  
Solute Transport ◽  
Solid Waste ◽  
Volume Fraction ◽  
Tracer Tests ◽  
Travel Times ◽  
Volume Fractions ◽  
Rapid Flow ◽  
Set Up ◽  
Log Normal ◽  
Transport Volume

Abstract. A large undisturbed sample (3.5 m3) of 22-year-old, biodegraded solid waste set up to estimate the volume fraction participating in the transport of solutes through the waste material. Altogether, five tracer tests were performed under ponding and sprinkling conditions, and under steady-state and transient conditions. The experimental break through curves (BTCs), which indicated a non-equilibrium transport of the solute by early peaks and long right-hand tails, were used to parameterize log-normal solute travel time probability density functions. The expected solute travel times (i.e. the median solute travel times) were assessed and the corresponding fraction of the experimental volumes active in the transport of solutes was estimated. The solute transport volume fractions defined by the median solute travel times were estimated to vary between 5 and 10% of the total experimental volume. Further, the magnitudes of the solute transport volume fractions defined by the modal (peak) solute travel times were estimated to vary between 1 and 2% of the total experimental volume. In addition, possible boundary effects in terms of rapid flow along the wall of the experimental column were investigated.

Cotton-Epoxy Composites: Development and Mechanical Characterization

2011 ◽  
Vol 471-472 ◽  
pp. 291-296 ◽  
Author(s):  
Piyush P. Gohil ◽  
A.A. Shaikh
Keyword(s):  
Natural Fiber ◽  
Volume Fraction ◽  
Fiber Composite ◽  
Natural Fibers ◽  
High Strength ◽  
Data Availability ◽  
Sem Images ◽  
Feasible Range ◽  
Set Up ◽  
Natural Fiber Composite

Composites are becoming essential part of today’s material because they offer advantages such as low weight, corrosion resistance, high fatigue strength; faster assembly etc. composites are generating curiosity and interest all over the worlds. The attempts can be found in literature for composite materials high strength fiber and also natural fiber like jute, flax and sisal natural fibers provides data but there is need of experimental data availability for unidirectional natural fiber composite with seldom natural fiber like cotton, palm leaf etc., it can provide a feasible range of alternative materials to suitable conventional material. It was decided to carry out the systematic experimental study for the effect of volume fraction of reinforcement on longitudinal strength as well as Modulus of Elasticity (MOE) using developed mould-punch set up and testing aids. The testing is carried out as per ASTM D3039/3039M-08. The comparative assessment of obtained experimental results with literature is also carried out, which forms an important constituent of present work. It is also observed through SEM images and theoretical investigations that interface/interphase plays and important role in natural fiber composite.

scholarly journals Factors Influencing and Contributing to Perceived Safety of Passengers during Driverless Shuttle Rides

2021 ◽  
Vol 1 (3) ◽  
pp. 657-671
Author(s):  
Claudia Luger-Bazinger ◽  
Cornelia Zankl ◽  
Karin Klieber ◽  
Veronika Hornung-Prähauser ◽  
Karl Rehrl
Keyword(s):  
Autonomous Driving ◽  
Future Research ◽  
Natural Setting ◽  
Mixed Traffic ◽  
Control Room ◽  
Driving Style ◽  
Perceived Safety ◽  
Factors Influencing ◽  
Traffic Environment ◽  
Set Up

This study investigates the perceived safety of passengers while being on board of a driverless shuttle without a steward present. The aim of the study is to draw conclusions on factors that influence and contribute to perceived safety of passengers in driverless shuttles. For this, four different test rides were conducted, representing aspects that might challenge passengers’ perceived safety once driverless shuttles become part of public transport: passengers had to ride the shuttle on their own (without a steward present), had to interact with another passenger, and had to react to two different unexpected technical difficulties. Passengers were then asked what had influenced their perceived safety and what would contribute to it. Results show that perceived safety of passengers was high across all different test rides. The most important factors influencing the perceived safety of passengers were the shuttle’s driving style and passengers’ trust in the technology. The driving style was increasingly less important as the passengers gained experience with the driverless shuttle. Readily available contact with someone in a control room would significantly contribute to an increase in perceived safety while riding a driverless shuttle. For researchers, as well as technicians in the field of autonomous driving, our findings could inform the design and set-up of driverless shuttles in order to increase perceived safety; for example, how to signal passengers that there is always the possibility of contact to someone in a control room. Reacting to these concerns and challenges will further help to foster acceptance of AVs in society. Future research should explore our findings in an even more natural setting, e.g., a controlled mixed traffic environment.

The thermal decomposition of RDX at temperatures below the melting point. V. The evolution of occluded volatile matter prior to the decomposition, and the influence of past history of the sample on the rate of decomposition

1972 ◽  
Vol 25 (11) ◽  
pp. 2337 ◽  
Author(s):  
JJ Batten
Keyword(s):  
Thermal Decomposition ◽  
Reaction Time ◽  
Melting Point ◽  
Ambient Temperature ◽  
Ultraviolet Light ◽  
Past History ◽  
Volatile Matter ◽  
Post Irradiation ◽  
Mechanism Of Decomposition ◽  
History Of

It is fist demonstrated that the occluded solvents and gases which are often present in RDX are expelled prior to zero reaction time of thermal decomposition. Thus they do not seriously interfere with the use of pressure increase as a measure of the extent of thermal decomposition. The rate of thermal decomposition of sublimed RDX at 195�C is then compared with the rate after the following treatments, (i) preliminary grinding of the crystals, (ii) preparation of the crystals by different techniques, (iii) mixing RDX with various solid additives, (iv) interruption of the reaction by cooling, and (v) pre-irradiation with ultraviolet light. The results indicated that treatments (i), (ii), and (iv) had little effect on the rate, whereas (iii) and (v) could markedly influence the rate. Their effects are discussed in terms of the mechanism of decomposition. The results also indicated that there was a post-irradiation reaction of RDX at ambient temperature.

Effect of Centrifugal Force Effect on Magneto-Rheological Fluid Clutches

2002 ◽  
Author(s):  
Vijay A. Neelakantan ◽  
Gregory N. Washington
Keyword(s):  
Magnetic Fields ◽  
Design Methodology ◽  
Volume Fraction ◽  
The Other ◽  
Particle Orientation ◽  
Centrifugal Forces ◽  
Mr Fluid ◽  
Set Up ◽  
Magneto Rheological ◽  
Very High

The property of magnetorheological fluids to change their yield stress depending on applied magnetic fields can be employed to develop many controllable devices one of them being MR fluid based clutches. One major problem however with MR fluid based clutches is that at high rotational speeds, the iron/ferrous particles in the MR fluid centrifuge due to very high centrifugal forces. Thus the particles move outward as the speed increases thereby making the fluid non-homogeneous. Many times however the initial analysis assumes fluid homogeneity, which is really not the case. In this paper this problem is addressed by assuming various volume fraction profiles describing the fluid particle orientation. Two cases, one with a linear profile and the other with an exponential profile are discussed. Expressions for the torque transmitted are derived at for both disc shaped and cylindrical shaped clutches. In addition, the use of a MR sponge based clutch that may indeed reduce the effect of centrifugal forces significantly is described. The design methodology and configuration for the sponge clutch are also discussed. An experimental set up used to test the clutch is also described.

Non-equilibrium natural convection in a differentially-heated nanofluid cavity partially filled with a porous medium

2019 ◽  
Vol 29 (8) ◽  
pp. 2524-2544 ◽  
Author(s):  
Mikhail A. Sheremet ◽  
Ioan Pop ◽  
A. Cihat Baytas
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Natural Convection ◽  
Volume Fraction ◽  
Good Control ◽  
Solid Matrix ◽  
Content Type ◽  
Practical Applications ◽  
Nanofluid Viscosity ◽  
Non Equilibrium

Purpose This study aims to numerically analyze natural convection of alumina-water nanofluid in a differentially-heated square cavity partially filled with a heat-generating porous medium. A single-phase nanofluid model with experimental correlations for the nanofluid viscosity and thermal conductivity has been considered for the description of the nanoparticles transport effect in the present study. Local thermal non-equilibrium approach for the porous layer with the Brinkman-extended Darcy model has been used. Design/methodology/approach Dimensionless governing equations formulated using stream function, vorticity and temperature have been solved by the finite difference method. The effects of the Rayleigh number, Ostrogradsky number, Nield number and nanoparticles volume fraction on nanofluid flow, heat and mass transfer have been analyzed. Findings It has been revealed that the dimensionless heat transfer coefficient at the fluid/solid matrix interface can be a very good control parameter for the convective flow and heat transfer intensity. The present results are original and new for the study of non-equilibrium natural convection in a differentially-heated nanofluid cavity partially filled with a porous medium. Originality/value The results of this paper are new and original with many practical applications of nanofluids in the modern industry.

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