Mastication and Rate of Set-Up. Part II

1945 ◽  
Vol 18 (2) ◽  
pp. 441-447
Author(s):  
S. Buchan
Keyword(s):  
Marked Effect ◽  
Mixing Process ◽  
Mechanical Working ◽  
Number Of Factors ◽  
Rubber Particles ◽  
Subsequent Behavior ◽  
Set Up ◽  
Effective Development ◽  
Catalytic Effects

Abstract In the earlier communication it was shown that the length of time of milling of a mixed rubber exerted a marked effect on the rate at which it commenced to scorch. The longer the time of milling, the slower was found to be its rate of set-up. It is intended in this paper to give a brief account of some experiments which were undertaken with a view to deciding which factor or factors in the process of mastication are responsible for this retardation of the initial stages of vulcanization. During the milling of rubber only a limited number of factors can be considered as having any effect on its subsequent behavior as far as its rate of set-up is concerned. These are, decomposition of the accelerating components due to heat and pressure, softening of the rubber due to mechanical working, disaggregation or other causes, breakdown of the ultimate rubber particles, depolymerization, or, finally progressive oxidation of the rubber throughout the milling and mixing process. The possibility of decomposition of the accelerator during milling was examined by adding the accelerator to one batch at the beginning of the mixing process, adding it to another at the end and comparing the results of the rates of set-up on the two rubbers. Softening of the rubber without resorting to mechanical means was carried out by adding various softeners to the rubber while in solution and dispersing these by gentle stirring. It is of interest to note that the addition of softeners to the mixing without simultaneous mechanical working resulted in only a slight lowering of the plasticity reading (Y value), which seems to indicate that, for the effective development of softening action, mechanical working or the catalytic effects induced during mechanical working are essential.

Nanoparticle Precipitation in a T-Mixer: Coupling Experimental and Numerical Investigations of the Fluid Dynamics With the Solid Formation Processes

2006 ◽  
Author(s):  
Johannes Gradl ◽  
Florian Schwertfirm ◽  
Hans-Christoph Schwarzer ◽  
Hans-Joachim Schmid ◽  
Michael Manhart ◽  
...  
Keyword(s):  
Flow Field ◽  
Fluid Dynamic ◽  
Concentration Field ◽  
Population Balance ◽  
Mixing Process ◽  
Image Velocimetry ◽  
Modeling Material ◽  
Field Information ◽  
Set Up ◽  
3D Information

Mixing and consequently fluid dynamic is a key parameter to tailor the particle size distribution (PSD) in nanoparticle precipitation. Due to fast and intensive mixing a static T-mixer configuration is capable for synthesizing continuously nanoparticles. The flow and concentration field of the applied mixer is investigated experimentally at different flow rates by Particle Image Velocimetry (PIV) and Laser Induced Fluorescence (LIF). Due to the PIV measurements the flow field in the mixer was characterized qualitatively and the mixing process itself is quantified by the subsequent LIF-measurements. A special feature of the LIF set up is to detect structures in the flow field, which are smaller than the Batchelor length. Thereby a detailed insight into the mixing process in a static T-Mixer is given. In this study a CFD-based approach using Direct Numerical Simulation (DNS) in combination with the solid formation kinetics solving population balance equations (PBE) is applied, using barium sulfate as modeling material. A Lagrangian Particle Tracking strategy is used to couple the flow field information with a micro mixing model and with the classical theory of nucleation. We found that the DNS-PBE approach including macro and micro mixing, combined with the population balance is capable of predicting the full PSD in nanoparticle precipitation for different operating parameters. Additionally to the resulting PSD, this approach delivers a 3D-information about all running subprocesses in the mixer, i.e. supersaturation built-up or nucleation, which is visualized for different process variables.

scholarly journals Effects of Malaise trap spacing on species richness and composition of terrestrial arthropod bulk samples

2020 ◽  
Author(s):  
D Steinke ◽  
TWA Braukmann ◽  
L Manerus ◽  
A Woodhouse ◽  
V Elbrecht
Keyword(s):  
Species Richness ◽  
Field Experiments ◽  
Collection Efficiency ◽  
Malaise Trap ◽  
Number Of Factors ◽  
Large Numbers ◽  
Set Up ◽  
Taxonomic Groups ◽  
A Site ◽  
Malaise Traps

AbstractThe Malaise trap has gained popularity for assessing diverse terrestrial arthropod communities because it collects large samples with modest effort. A number of factors that influence collection efficiency, placement being one of them. For instance, when designing larger biotic surveys using arrays of Malaise traps we need to know the optimal distance between individual traps that maximises observable species richness and community composition. We examined the influence of spacing between Malaise traps by metabarcoding samples from two field experiments at a site in Waterloo, Ontario, Canada. For one experiment, we used two trap pairs deployed at weekly increasing distance (3m increments from 3 to 27 m). The second experiment involved a total of 10 traps set up in a row at 3m distance intervals for three consecutive weeks.Results show that community similarity of samples decreases over distance between traps. The amount of species shared between trap pairs shows drops considerably at about 15m trap-to-trap distance. This change can be observed across all major taxonomic groups and for two different habitat types (grassland and forest). Large numbers of OTUs found only once within samples cause rather large dissimilarity between distance pairs even at close proximity. This could be caused by a large number of transient species from adjacent habitat which arrive at the trap through passive transport, as well as capture of rare taxa, which end up in different traps by chance.

Efficiency of Scrap Rubber Particles on Strength of Cementitious Materials

2011 ◽  
Vol 374-377 ◽  
pp. 1374-1379 ◽  
Author(s):  
Guang Cheng Long ◽  
Zhe Li ◽  
You Jun Xie
Keyword(s):  
Loss Rate ◽  
Rubber Particle ◽  
Hydrophobic Effect ◽  
Research Programme ◽  
Strength Loss ◽  
Cementitious Materials ◽  
Mortar Sample ◽  
Deformation Effect ◽  
Rubber Particles ◽  
Set Up

An extensive research programme was set up to investigate the efficiency of scrap rubber particles on strength of cementitious materials. The index of strength loss rate of paste and mortar sample caused by increasing 1% volume rubber particles was proposed to analyze the efficiency of rubber particles in cementitious materials. And the corresponding mechanism was also discussed in this paper. Results indicate that in the investigated area, the loss rate in compressive strength both for paste and mortar almost ranges from 2% to 5% caused by increasing 1% rubber particles depending on the total volume of rubber particle added into sample. However, the loss rate in flexural strength of mortar by increasing 1% volume rubber particles is obviously different from that. Three roles of scrap rubber particles played in cementitious materials, named as deformation effect, equivalent-pore effect and hydrophobic effect, are responsible for the efficiency of scrap rubber particles on strength of cementitious material. The efficiency of rubber particles on strength of paste and mortar differs from each other due to the different microstructure between paste and mortar.

A FINITE ELEMENT STRESS ANALYSIS OF THE INTERFACE STRESS GENERATED DURING THE PUSH-OUT TEST

2002 ◽  
Vol 02 (02) ◽  
pp. 197-210 ◽  
Author(s):  
K. R. WILLIAMS ◽  
R. A. DRAUGHN
Keyword(s):  
Finite Element ◽  
Bonding Agent ◽  
Hard Tissue ◽  
Bonding Agents ◽  
Dental Restorations ◽  
Number Of Factors ◽  
Similar Chemical ◽  
Uppermost Layer ◽  
Set Up ◽  
Push Out

Within the dental sphere it is advantageous to be able to bond the restoration to dentine in order to avoid clinical problems such as marginal leakage with subsequent caries. Dentine bonding agents are normally employed to create an effective interface between the restoration and hard tissue with the formation of chemical links. The measurement of the bond strength between dental restorations or implants and surrounding hard tissue is generally achieved through the use of an experimental push-out test. However, these bond strengths have been found to be quite variable between laboratories even when similar chemical bonding agents have been used. This variability may be due to a number of factors including experimental differences such as, material moduli effects, specimen loading and changes in the thickness and properties of the interdiffusional zone (IDZ) that forms following polymerization of the bonding agent. In this work, these variables have been explored using the finite element method initially through a 2-D description of the geometrical set up and subsequently a 3-D discretization. The results indicate that the loading and specimen support during testing have a significant effect on the measured push-out values. Furthermore the effects of a gradually changing modulus in the uppermost rings of the IDZ can have a significant influence on the support bearing property of the bonding agent. These changes in modulus of the IDZ may be the result of fluoride leaching to bring about increases in properties and modulus. A mixed moduli IDZ where the uppermost layer is approximately double the value of the remaining material can lead to increases in push-out values of 10% or more.

Challenging the representations of cancer pain: Experiences of a multidisciplinary pain management group in a palliative care unit

2005 ◽  
Vol 3 (1) ◽  
pp. 43-49 ◽  
Author(s):  
ELIZABETH CHAPMAN ◽  
DAVID HUGHES ◽  
ANNETTE LANDY ◽  
JUDITH WHALE ◽  
MARGARET SAUNDERS
Keyword(s):  
Palliative Care ◽  
Pain Management ◽  
Palliative Care Unit ◽  
Important Distinction ◽  
Extensive Experience ◽  
Management Group ◽  
Number Of Factors ◽  
Pain Experiences ◽  
Set Up ◽  
Multidisciplinary Pain Management

Objective:This article describes how a Multidisciplinary Pain Management Group was set up in a palliative care unit, and outlines the ways that the group works with different patients. We place these comments in the context of the wider representations of pain.Methods:Our observations of patients seen by the multidisciplinary team.Results:We tentatively propose that where the patient's pain has certain characteristics it may require a different approach. Patients who are older, with a lengthy treatment history, may require a different input than younger patients, who may have a number of factors that further complicate their experience of pain. We use our extensive experience with mesothelioma patients to draw a further important distinction between this patient group and other patients.Significance of research:Our observations suggest the need to allow sufficient time for intensive psychological work to be done with mesothelioma patients in order for pharmacological interventions to be effective.

Plasticization of Natural and Synthetic Rubbers. II. GR-S

1949 ◽  
Vol 22 (2) ◽  
pp. 518-534 ◽  
Author(s):  
G. H. Piper ◽  
J. R. Scott
Keyword(s):  
Natural Rubber ◽  
Plastic Flow ◽  
Elastic Recovery ◽  
Mechanical Action ◽  
Shear Stresses ◽  
Mechanical Working ◽  
Chain Molecules ◽  
Peptizing Agent ◽  
Set Up ◽  
Internal Mixer

Abstract Continuing the work described in Part I, experiments have been made to determine the separate effects of heat, oxidation, mechanical working on rolls or in an internal mixer, peptizing agents (used in hot milling), and absorption of softener on the softness, elastic recovery, and plastic flow relation (between applied force and rate of flow) of GR-S. Heat alone, without oxygen or mechanical action, does not soften GR-S, but makes it harder and more elastic, presumably by inducing cross-linking of the chain molecules; GR-S thus differs fundamentally from natural rubber, which can be softened by heat. Absorption of softener (mineral oil) softens GR-S and reduces its recovery, but these effects are too small to form a practicable plasticizing method. Either oxidation or mechanical working softens GR-S considerably, reduces its elastic recovery, and brings its plastic flow relation nearer to that of well masticated natural rubber, i.e., approaching ordinary viscous or Newtonian flow (flow rate proportional to stress). Peptizing agents such as benzaldehyde phenylhydrazone or iron naphthenate promote the effect of hot milling, presumably by accelerating oxidation, which is shown to occur during hot, but not appreciably in cold, milling. Of the methods tried, those which plasticize GR-S most quickly are (1) hot milling with a peptizing agent, and (2) oxidation at 125° C and 15 lb. per sq. in. oxygen pressure ; if the latter is continued too long, however, hardening sets in. The results show that GR-S, like natural rubber, can be plasticized by mechanical breakage of the chain molecules by the shear stresses set up during mastication, as well as by oxidation, which presumably causes breakage of the molecules at the double bonds. Mechanical and oxidative treatments, however, do not give the same properties ; mechanical breakdown in the cold gives a product completely soluble in benzene, whereas oxidation does not, and is less effective in reducing recovery, and there may be other differences not yet revealed. In view of these differences and the fact that heat has effects opposite to oxidation or mechanical working, it follows that the various possible ways of plasticizing GR-S, since they involve heat, oxidation, and mechanical action in different combinations and degrees, give plasticized batches with very different properties, even if the length of the treatments is so adjusted as to give, say, the same Williams or Mooney plasticity reading. These differences are fully discussed in the present paper; the main conclusions are:

The Effect of Heat on Raw Rubber in the Presence and Absence of Air

1928 ◽  
Vol 1 (2) ◽  
pp. 299-306
Author(s):  
J. D. Fry ◽  
B. D. Porritt
Keyword(s):  
Mechanical Treatment ◽  
Cold Water ◽  
Solution Viscosity ◽  
Apparent Difference ◽  
Normal Process ◽  
Mechanical Working ◽  
Rubber Particles ◽  
Presence And Absence ◽  
Physical Changes

Abstract During the process of milling or masticating rubber, three agents, namely, mechanical working, heat, and the constituents of the air, are evidently present which may be individually or collectively responsible for the resulting physical changes. The generally accepted explanation of the effects produced is that the mechanical treatment breaks down some form of structure existing in the raw rubber or rubber particles and consequently it is customary to describe material as “overworked” when milling has been carried too far, and to reserve the terms “burnt” and “scorched” for cases in which the heat generated in the process has caused premature vulcanization. The correctness of the assumption that milling is essentially a mechanical operation at first sight seemed to be supported by an experiment made by one of the authors in which the treatment was carried out under a stream of cold water when it was found that the solution viscosity of the material diminished in much the same way as in the normal process, the only apparent difference in the final product being the almost complete absence of the adhesiveness characteristic of milled rubber. Further consideration, however, suggested that though the conditions under which the test was made undoubtedly minimized contact with air and the development of heat, the possibility that oxygen might still play a part was not entirely excluded, while the fact that the bulk of the rubber was kept cold did not necessarily preclude local rises in temperature taking place in the material when passing between the rolls.

scholarly journals Achieving the Effectiveness of Regional Development in the Context of Modern socialand-economic Reality

2021 ◽  
Vol 295 ◽  
pp. 01022
Author(s):  
Irina Novikova ◽  
Lydia Kovalenko ◽  
Andrey Kulik
Keyword(s):  
Regional Development ◽  
Gradual Increase ◽  
National Wealth ◽  
Number Of Factors ◽  
The Social ◽  
Economic Transformations ◽  
Economic Reality ◽  
The Stability ◽  
Effective Development ◽  
Relative Differences

The social-and-economic transformations performed at the present stage of state development necessitate the formation and effective development of methods, mechanisms and tools for regional development. A key role in this development is occupied by an orientation towards the priorities of the implemented state social-and-economic policy. Based on the application of the method of relative differences, an order of ranking regions pursuant to the criterion of the current and strategic efficiency of the development of territories is proposed. The formation of a system of indicators that makes it possible to most correctly consider the largest number of factors characterizing the state of the regional economy will make it possible to maximize the potential of the territories, create conditions for achieving a socially oriented nature of transformations of the economic system while maintaining the stability of economic growth, and a gradual increase in the volume of national wealth. Assessing regional development based on the method of studying the competitive potential of territories seems to be effective, since it implies the possibility of improving the efficiency of managerial influence in this direction

An Experimental Study on Engineering Properties of Rubber Particles-Improved Fly Ash Soil

2011 ◽  
Vol 71-78 ◽  
pp. 3401-3406 ◽  
Author(s):  
Chang Yu Li ◽  
Han Bing Liu ◽  
Hai Bin Wei
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Fly Ash ◽  
Cold Resistance ◽  
Engineering Properties ◽  
Frost Heave ◽  
Technical Parameters ◽  
Rubber Particles ◽  
Set Up ◽  
Insulation Performance

In this paper, by studying the engineering properties of rubber particles-improved fly ash soil, the authors provide technical parameters for setting up cold-resistance layer in the seasonal frozen zone. In the experiment, rubber particles are mixed into the fly ash soil by mass of 0%, 1%, 2%, 3%, 5% and 7% and unconfined compressive strength testing, frost heave test, insulation test and thermal conductivity test. By analyzing the test results, the authors drew the conclusion that fly ash soil improved by rubber particles has a high compressive strength, a small amount of frost heave, good insulation performance, small thermal conductivity coefficient.Therefore, improved fly ash soil with rubber particles is one of the preferred materials to set up the cold resistance layer in seasonal frost zone.

How patients describe bulimia or binge eating

1982 ◽  
Vol 12 (3) ◽  
pp. 625-635 ◽  
Author(s):  
Suzanne F. Abraham ◽  
P. J. V. Beumont
Keyword(s):  
Binge Eating ◽  
Number Of Factors ◽  
Set Up

SYNOPSISThirty-two patients who complained of episodes of ravenous overeating which they felt unable to control (bulimia) were asked to describe their behaviour and symptoms. There was considerable variation both between and within individuals, but a number of factors were defined which appeared to be common to all with the complaint. It is difficult to set up strict criteria for the recognition of bulimia, and those that have recently been proposed are criticized in the light of our present findings.

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