Injection Molding of Rubber

1978 ◽  
Vol 51 (5) ◽  
pp. 1023-1043 ◽  
Author(s):  
M. A. Wheelans
Keyword(s):  
Injection Molding ◽  
Mold Temperature ◽  
Flow Lines ◽  
Wide Range ◽  
Cure Time ◽  
Degree Of Anisotropy ◽  
The Mean ◽  
Mold Flow ◽  
Optimum Modulus ◽  
Maximum Minimum

Abstract The outline of a strategy for the injection molding of a safe mix is described. Safe accelerators, safe curing systems, and mixes are suggested with machine conditions which should yield short curing times for a wide range of products. Comparisons have been made of the vulcanizate properties of injection and compression moldings prepared from the same mix in the same mold and press at the same temperature. Results have shown that, although anisotropy is more pronounced in injection moldings, the mean of values for modulus along and at 90° to radial mold flow lines of an optimum modulus cure are the same (within experimental error) as the mean of values for modulus along and at 90° to mill flow lines in a compression molding also cured to its optimum modulus. Injection moldings are similar to compression moldings in volume swelling and hardness but they have marginally higher rebound resilience and marginally lower compression set. The effect of an increase in mold temperature is to give a valuable reduction in cure time, but it also causes a reduction in modulus and modulus dependent vulcanizate properties. Optimum values for maximum-minimum Monsanto Rheometer torque, relaxed modulus, and 300% modulus are reduced to 77– 79% of their optimum values at 160°C when cured at 200°C, but this reduction can be compensated for by adding higher levels of accelerator or accelerator and sulphur. Although a certain degree of anisotropy may have to be tolerated, the analysis of vulcanizate properties has provided a means of understanding and correcting an injection molding mix which fails to pass a specification. It gives confidence that NR can be cured at relatively high temperatures such as 180–190°C, which make injection molding profitable.

Injection Molding with Natural Rubber

1971 ◽  
Vol 44 (3) ◽  
pp. 620-641 ◽  
Author(s):  
M. A. Wheelans
Keyword(s):  
Injection Molding ◽  
Natural Rubber ◽  
Injection Pressure ◽  
Orifice Diameter ◽  
Thin Sections ◽  
Wide Range ◽  
Filling Time ◽  
Cure Time ◽  
Injection Molded ◽  
Injection Temperature

Abstract Injection moldings with natural rubber compounds having sections varying between 0.16 and 10 cm thick have been prepared. Almost any natural rubber compound can be satisfactorily injection molded. Cure time, and hence cycle time, is highly dependent on injection temperature and the art of injection molding is to inject at the highest possible temperature consistent with freedom from scorch. The injection temperature of natural rubber depends on the injection molding machine variables such as screw speed, screw back pressure and barrel temperature. Injection and mold filling time are dependent on injection pressure and nozzle orifice diameter. Rubber compounding variables influence injection molding behavior. A curing system with a relatively long, safe Mooney scorch time permits a reduction in the cure time of rubber by allowing a high injection temperature. Conventional curing systems are suitable for a wide range of injection moldings but “Efficient Vulcanization ” systems have special advantages in curing thin sections adjacent to thick ones because of their superior reversion resistance. The effects of compound viscosity are described. Extenders are shown to reduce injection temperatures and thus increase cure times. Black and white fillers are examined in their effect on injection temperature, injection time and cure time. Injection molded vulcanizates are similar in mechanical properties and oven aging resistance to vulcanizates prepared by conventional press methods.

A Comparison of Physiological Demand between Self-Propelled and Motorized Treadmill Exercise

2018 ◽  
Vol 7 (4) ◽  
pp. 13-21
Author(s):  
Todd Backes ◽  
Charlene Takacs
Keyword(s):  
Respiratory Exchange Ratio ◽  
Treadmill Exercise ◽  
Cardiopulmonary Exercise Testing ◽  
Mean Value ◽  
The Self ◽  
Mixing Chamber ◽  
Wide Range ◽  
The Subject ◽  
The Mean ◽  
Computer Controlled

There are a wide range of options for individuals to choose from in order to engage in aerobic exercise; from outdoor running to computer controlled and self-propelled treadmills. Recently, self-propelled treadmills have increased in popularity and provide an alternative to a motorized treadmill. Twenty subjects (10 men, 10 women) ranging in age from 19-23 with a mean of 20.4 ± 0.8 SD were participants in this study. The subjects visited the laboratory on three occasions. The purpose of the first visit was to familiarize the subject with the self-propelled treadmill (Woodway Curve 3.0). The second visit, subjects were instructed to run on the self-propelled treadmill for 3km at a self-determined pace. Speed data were collected directly from the self-propelled treadmill. The third visit used speed data collected during the self-propelled treadmill run to create an identically paced 3km run for the subjects to perform on a motorized treadmill (COSMED T150). During both the second and third visit, oxygen consumption (VO2) and respiratory exchange ratio (R) data were collected with COSMED’s Quark cardiopulmonary exercise testing (CPET) metabolic mixing chamber system. The VO2 mean value for the self-propelled treadmill (44.90 ± 1.65 SE ml/kg/min) was significantly greater than the motorized treadmill (34.38 ± 1.39 SE ml/kg/min). The mean R value for the self-propelled treadmill (0.91 ± 0.01 SE) was significantly greater than the motorized treadmill (0.86 ± 0.01 SE). Our study demonstrated that a 3km run on a self-propelled treadmill does elicit a greater physiological response than a 3km run at on a standard motorized treadmill. Self-propelled treadmills provide a mode of exercise that offers increased training loads and should be considered as an alternative to motorized treadmills.

The way of value of Correlation of genomic DNA microsatellite loci and live weight of Chukchi reindeer

2020 ◽  
pp. 27-32
Author(s):  
V. Dodokhov ◽  
N. Pavlova ◽  
T. Rumyantseva ◽  
L. Kalashnikova
Keyword(s):  
Microsatellite Markers ◽  
Agricultural Production ◽  
Live Weight ◽  
Biodiversity Loss ◽  
Tribal Community ◽  
High Germination ◽  
Wide Range ◽  
The Mean ◽  
High Level ◽  
Dna Microsatellite

The article presents the genetic characteristic of the Chukchi reindeer breed. The object of the study was of the Chukchi reindeer. In recent years, the number of reindeer of the Chukchi breed has declined sharply. Reduced reindeer numbers could lead to biodiversity loss. The Chukchi breed of deer has good meat qualities, has high germination viability and is adapted in adverse tundra conditions of Yakutia. Herding of the Chukchi breed of deer in Yakutia are engaged only in the Nizhnekolymsky district. There are four generic communities and the largest of which is the agricultural production cooperative of nomadic tribal community «Turvaurgin», which was chosen to assess the genetic processes of breed using microsatellite markers: Rt6, BMS1788, Rt 30, Rt1, Rt9, FCB193, Rt7, BMS745, C 143, Rt24, OheQ, C217, C32, NVHRT16, T40, C276. It was found that microsatellite markers have a wide range of alleles and generally have a high informative value for identifying of genetic differences between animals and groups of animal. The number of identified alleles is one of the indicators of the genetic diversity of the population. The total number of detected alleles was 127. The Chukchi breed of deer is characterized by a high level of heterozygosity, and the random crossing system prevails over inbreeding in the population. On average, there were 7.9 alleles (Na) per locus, and the mean number of effective alleles (Ne) was 4.1. The index of fixation averaged 0.001. The polymorphism index (PIC) ranged from 0.217 to 0.946, with an average of 0.695.

Celiac Disease in Kosovar Albanian Children: Evaluation of Clinical Features and Diagnosis

2020 ◽  
Vol 16 (3) ◽  
pp. 241-247
Author(s):  
Atifete Ramosaj-Morina ◽  
Alije Keka-Sylaj ◽  
Arbana Baloku Zejnullahu ◽  
Lidvana Spahiu ◽  
Virgjina Hasbahta ◽  
...  
Keyword(s):  
Celiac Disease ◽  
Disease Onset ◽  
Clinical Manifestations ◽  
Gastrointestinal Symptoms ◽  
Dominant Mode ◽  
Primary School Children ◽  
Cross Sectional ◽  
Classical Form ◽  
Wide Range ◽  
The Mean

Background: Celiac disease is an immune-mediated disorder characterized by variable clinical manifestations, specific antibodies, HLA-DQ2/DQ8 haplotypes, and enteropathy. Objectives: The aim of this study was to present the clinical spectrum and patterns of celiac disease in Kosovar Albanian children. Methods: A cross-sectional retrospective study was performed with Albanian children aged 0-18 years, treated for celiac disease in the Pediatric Clinic, University Clinical Center of Kosovo from 2005 to 2016. Results: During the study period, 63 children were treated for celiac disease. The mean age at diagnosis was 5.5 years (SD ± 3.31). The mean age at celiac disease onset was 3.3 years (SD ± 2.02), while the mean delay from the first symptoms indicative of celiac disease to diagnosis was 2.2 years (SD ± 2.09). More than 70% of the patients were diagnosed in the first 7 years of life, mainly presented with gastrointestinal symptoms, while primary school children and adolescents mostly showed atypical symptoms (p<0.001). The classical form of celiac disease occurred in 78% of the cases. Sixty (95%) patients carried HLA-DQ2.5, DQ2.2 and/or HLA-DQ8 heterodimers, and only three of them tested negative. Conclusions: Kosovo, as the majority of developing countries, is still facing the classical form of celiac disease as the dominant mode of presentation; as a result, most children with other forms of the celiac disease remain undiagnosed. : Physicians should be aware of the wide range of clinical presentations and utilize low testing thresholds in order to prevent potential long-term problems associated with untreated celiac disease.

scholarly journals Planetary Nebulae in M31: Abundances, and comparison with bright Planetary Nebulae in the LMC

1997 ◽  
Vol 180 ◽  
pp. 475-476
Author(s):  
M. G. Richer ◽  
G. Stasińska ◽  
M. L. McCall
Keyword(s):  
Planetary Nebula ◽  
Luminosity Function ◽  
Large Population ◽  
Wavelength Region ◽  
Planetary Nebulae ◽  
Surprising Result ◽  
Population Synthesis ◽  
Abundance Distribution ◽  
Wide Range ◽  
The Mean

We have obtained spectra of 28 planetary nebulae in the bulge of M31 using the MOS spectrograph at the Canada-France-Hawaii Telescope. Typically, we observed the [O II] λ3727 to He I λ5876 wavelength region at a resolution of approximately 1.6 å/pixel. For 19 of the 21 planetary nebulae whose [OIII]λ5007 luminosities are within 1 mag of the peak of the planetary nebula luminosity function, our oxygen abundances are based upon a measured [OIII]λ4363 intensity, so they are based upon a measured electron temperature. The oxygen abundances cover a wide range, 7.85 dex < 12 + log(O/H) < 9.09 dex, but the mean abundance is surprisingly low, 12 + log(O/H)–8.64 ± 0.32 dex, i.e., roughly half the solar value (Anders & Grevesse 1989). The distribution of oxygen abundances is shown in Figure 1, where the ordinate indicates the number of planetary nebulae with abundances within ±0.1 dex of any point on the x-axis. The dashed line indicates the mean abundance, and the dotted lines indicate the ±1 σ points. The shape of this abundance distribution seems to indicate that the bulge of M31 does not contain a large population of bright, oxygen-rich planetary nebulae. This is a surprising result, for various population synthesis studies (e.g., Bica et al. 1990) have found a mean stellar metallicity approximately 0.2 dex above solar. This 0.5 dex discrepancy leads one to question whether the mean stellar metallicity is as high as the population synthesis results indicate or if such metal-rich stars produce bright planetary nebulae at all. This could be a clue concerning the mechanism responsible for the variation in the number of bright planetary nebulae observed per unit luminosity in different galaxies (e.g., Hui et al. 1993).

scholarly journals Study on External Gas-Assisted Mold Temperature Control with the Assistance of a Flow Focusing Device in the Injection Molding Process

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 965 ◽  
Author(s):  
Nguyen Truong Giang ◽  
Pham Son Minh ◽  
Tran Anh Son ◽  
Tran Minh The Uyen ◽  
Thanh-Hai Nguyen ◽  
...  
Keyword(s):  
Injection Molding ◽  
Temperature Control ◽  
Mold Temperature ◽  
Injection Molding Process ◽  
Melt Flow ◽  
Flow Focusing ◽  
Molding Process ◽  
Heating Efficiency ◽  
Flow Length ◽  
Insert Plate

In the injection molding field, the flow of plastic material is one of the most important issues, especially regarding the ability of melted plastic to fill the thin walls of products. To improve the melt flow length, a high mold temperature was applied with pre-heating of the cavity surface. In this paper, we present our research on the injection molding process with pre-heating by external gas-assisted mold temperature control. After this, we observed an improvement in the melt flow length into thin-walled products due to the high mold temperature during the filling step. In addition, to develop the heating efficiency, a flow focusing device (FFD) was applied and verified. The simulations and experiments were carried out within an air temperature of 400 °C and heating time of 20 s to investigate a flow focusing device to assist with external gas-assisted mold temperature control (Ex-GMTC), with the application of various FFD types for the temperature distribution of the insert plate. The heating process was applied for a simple insert model with dimensions of 50 mm × 50 mm × 2 mm, in order to verify the influence of the FFD geometry on the heating result. After that, Ex-GMTC with the assistance of FFD was carried out for a mold-reading process, and the FFD influence was estimated by the mold heating result and the improvement of the melt flow length using acrylonitrile butadiene styrene (ABS). The results show that the air sprue gap (h) significantly affects the temperature of the insert and an air sprue gap of 3 mm gives the best heating rate, with the highest temperature being 321.2 °C. Likewise, the actual results show that the height of the flow focusing device (V) also influences the temperature of the insert plate and that a 5 mm high FFD gives the best results with a maximum temperature of 332.3 °C. Moreover, the heating efficiency when using FFD is always higher than without FFD. After examining the effect of FFD, its application was considered, in order to improve the melt flow length in injection molding, which increased from 38.6 to 170 mm, while the balance of the melt filling was also clearly improved.

Assessing the Ergonomic Benefits of a New Adjustable Forklift Backrest

2020 ◽  
Vol 64 (1) ◽  
pp. 976-980
Author(s):  
Pranav Madhav Kuber ◽  
Ehsan Rashedi
Keyword(s):  
Comparative Study ◽  
Motion Capture ◽  
Center Of Pressure ◽  
Body Movement ◽  
Pressure Change ◽  
Motion Capture System ◽  
Design Features ◽  
Wide Range ◽  
Body Sizes ◽  
The Mean

A new forklift backrest has been developed by incorporating adjustability concepts into the design to facilitate comfort to a wide range of users. We have conducted a comparative study between the new and original backrests to assess the effectiveness of design features. Using the phenomenon of restlessness, discomfort of the user was associated with the amount of body movement, where we have used a motion- capture system and a force platform to quantify the individuals’ movement for a wide range of body sizes. Meanwhile, subjective comfort and design feedback were collected using a questionnaire. Our results showed a reduction in the mean torso movement and the maximum center of pressure change of location by 300 and 6 mm, respectively, for the new design. Taking advantage of adjustability feature, the new backrest design exhibited enhanced comfort for longer durations and reduced magnitude of discomfort for a wide range of participants’ body sizes.

scholarly journals Correlation and Power Distribution of Intercore Crosstalk Field Components of Polarization-Coupled Weakly Coupled Single-Mode Multicore Fibres

Photonics ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 191
Author(s):  
José A. P. Morgado ◽  
Adolfo V. T. Cartaxo
Keyword(s):  
Power Distribution ◽  
Communication Systems ◽  
Single Mode ◽  
Coupled Mode ◽  
Weakly Coupled ◽  
Wide Range ◽  
Optical Communication Systems ◽  
The Mean ◽  
Distribution Of Power ◽  
Linear Propagation

The correlation and power distribution of intercore crosstalk (ICXT) field components of weakly coupled multicore fibers (WC-MCFs) are important properties that determine the statistics of the ICXT and ultimately impact the performance of WC-MCF optical communication systems. Using intensive numerical simulation of the coupled mode equations describing ICXT of a single-mode WC-MCF with intracore birefringence and linear propagation, we assess the mean, correlation, and power distribution of the four ICXT field components of unmodulated polarization-coupled homogeneous and quasi-homogeneous WC-MCFs with a single interfering core in a wide range of birefringence conditions and power distribution among the field components at the interfering core input. It is shown that, for homogeneous and quasi-homogeneous WC-MCFs, zero mean uncorrelated ICXT field components with similar power levels are observed for birefringence correlation length and birefringence beat length in the ranges of 0.5m,10m and 0.1m,10m, respectively, regardless of the distribution of power between the four field components at the interfering core input.

SET-VALUED PERFORMANCE APPROXIMATIONS FOR THE QUEUE GIVEN PARTIAL INFORMATION

2020 ◽  
pp. 1-23
Author(s):  
Yan Chen ◽  
Ward Whitt
Keyword(s):  
Steady State ◽  
Decay Rate ◽  
Waiting Time ◽  
Partial Information ◽  
Upper And Lower Bounds ◽  
Interarrival Time ◽  
Limited Information ◽  
Wide Range ◽  
The Mean ◽  
Third Moment

In order to understand queueing performance given only partial information about the model, we propose determining intervals of likely values of performance measures given that limited information. We illustrate this approach for the mean steady-state waiting time in the $GI/GI/K$ queue. We start by specifying the first two moments of the interarrival-time and service-time distributions, and then consider additional information about these underlying distributions, in particular, a third moment and a Laplace transform value. As a theoretical basis, we apply extremal models yielding tight upper and lower bounds on the asymptotic decay rate of the steady-state waiting-time tail probability. We illustrate by constructing the theoretically justified intervals of values for the decay rate and the associated heuristically determined interval of values for the mean waiting times. Without extra information, the extremal models involve two-point distributions, which yield a wide range for the mean. Adding constraints on the third moment and a transform value produces three-point extremal distributions, which significantly reduce the range, producing practical levels of accuracy.

scholarly journals Temporal Variations of the Turbulence Profiles at the Sayan Solar Observatory Site

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 499 ◽  
Author(s):  
Artem Shikhovtsev ◽  
Pavel Kovadlo ◽  
Vladimir Lukin
Keyword(s):  
Atmospheric Turbulence ◽  
Temporal Variability ◽  
Low Frequency ◽  
Temporal Variations ◽  
Solar Observatory ◽  
Vertical Profiles ◽  
Spatial And Temporal Scales ◽  
Atmospheric Disturbances ◽  
Wide Range ◽  
The Mean

The paper focuses on the development of the method to estimate the mean characteristics of the atmospheric turbulence. Using an approach based on the shape of the energy spectrum of atmospheric turbulence over a wide range of spatial and temporal scales, the vertical profiles of optical turbulence are calculated. The temporal variability of the vertical profiles of turbulence under different low-frequency atmospheric disturbances is considered.

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