Low Temperature Flexing Apparatus

1943 ◽  
Vol 16 (3) ◽  
pp. 692-694
Author(s):  
S. M. Martin
Keyword(s):  
Low Temperature ◽  
Technical Committee ◽  
Careful Consideration ◽  
Short Description ◽  
The Past ◽  
Synthetic Rubber ◽  
Low Temperature Flexibility ◽  
Freeze Test ◽  
Modified Test

Abstract For the past ten months, Sub-Committee V of SAE-ASTM Technical Committee A on Automotive Rubber has been working on the standardization of synthetic rubber specifications. Insofar as possible, methods of tests have followed ASTM procedures. ASTM has no recommended procedure for measuring the low temperature flexibility of synthetic rubber. This committee, after careful consideration, has recommended the use of a modification of the Thiokol Corporation's freeze test. This method of testing for low temperature flexibility has been incorporated into a number of recent Aeronautical Material Standards Specifications covering synthetic rubber. The modified test uses the same apparatus as that used in the Thiokol Corporation's Laboratory, or slight modifications of this. Because of the interest in this apparatus, a short description of it is here given.

Low-Temperature Behavior of Butadiene-Styrene Copolymers. Effect of Compounding Variables

1950 ◽  
Vol 23 (4) ◽  
pp. 760-769
Author(s):  
R. D. Juve ◽  
J. W. Marsh
Keyword(s):  
Low Temperature ◽  
Natural Rubber ◽  
Compression Set ◽  
Similar Work ◽  
Styrene Copolymers ◽  
Synthetic Rubber ◽  
Low Temperature Flexibility ◽  
Extended Exposure ◽  
Butadiene Styrene ◽  
Elastic Characteristics

Abstract Synthetic rubbers and natural rubber increase in stiffness at low temperatures and tend to lose their elastic characteristics. This stiffening and hardening phenomenon occurs in varying degrees with various elastomers. Natural rubber and certain synthetic rubbers crystallize during extended exposure at low temperature, whereas other synthetic rubbers such as GR-S remain amorphous. In a general review of the low temperature properties of synthetic rubber, Liska has shown that decreased styrene in butadiene-styrene copolymers improves the flexibility at low temperature. The low temperature flexibility of vulcanized articles made from any particular rubber or synthetic rubber is influenced by the compounding ingredients admixed with the elastomer. This paper shows the results of some studies of the effect of these compounding ingredients on the low temperature serviceability of butadiene-styrene copolymers. Somewhat similar work on the effect of a large number of plasticizers in GR-S has been conducted at the Rubber Laboratory, Mare Island Naval Shipyard, with particular emphasis on compression set at low temperature.

The Cold-Compression sets of Natural and Synthetic Vulcanizates

1946 ◽  
Vol 19 (1) ◽  
pp. 151-162 ◽  
Author(s):  
Ross E. Morris ◽  
Joseph W. Hollister ◽  
Paul A. Mallard
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
Leading Edge ◽  
Testing Procedure ◽  
Present Problem ◽  
Cold Compression ◽  
The Past ◽  
Compression Set ◽  
Synthetic Rubber ◽  
Rubber Compounds

Abstract The behavior of certain large synthetic rubber gaskets on naval vessels during the past winter points to the necessity for a cold compression-set test in the specifications for these gaskets. It has been found, for example, that Neoprene gaskets on large valves, which perform satisfactorily at temperatures of 60° F and above, are not usable at temperatures of 40° F and below. They take a cold compression-set, while the valves are closed, so that when the valves are opened and then again closed, the leading edge or surface of the valve does not seat properly. This cold compression-set is not permanent; when the gaskets which exhibit cold compression-set are removed to a warm atmosphere (about 80° F), they slowly regain their original shape. A survey of the literature dealing with the effects of low temperatures on rubber compounds yielded no information on cold compression set. The set test proposed by Morris, James, and Evans in connection with their low temperature stiffness test is not directly applicable to the present problem because it is conducted in tension. Therefore to investigate cold compression-set, it was necessary to devise a new testing procedure.

LOW TEMPERATURE THERMOELECTRIC PROPERTIES AND AGING PHENOMENA OF NANOSTRUCTURED p-TYPE Bi2-XSbXTe3 (x = 1.46, 1.48, 1.52 AND 1.55)

2013 ◽  
Vol 06 (05) ◽  
pp. 1340008 ◽  
Author(s):  
DALE HITCHCOCK ◽  
YEN-LIANG LIU ◽  
YUFEI LIU ◽  
TERRY M. TRITT ◽  
JIAN HE ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Low Temperature ◽  
Thermoelectric Properties ◽  
Optimal Composition ◽  
Ambient Conditions ◽  
Bulk Materials ◽  
The Past ◽  
Aging Phenomena ◽  
P Type ◽  
Cold Pressed

Over the past decade the widely used p-type ( Bi 2-x Sb x) Te 3 bulk thermoelectric materials have been subject to various nanostructuring processes for higher thermoelectric performance. However, these nanostructuring processing were conducted on compositions optimized for bulk materials (x ~ 1.52–1.55). This leads to the question of whether the optimal composition for bulk materials is the same for their nanoscale counterparts. In this work we hydrothermally grew Bi 2-x Sb x Te 3 nanopowders (nominally, x = 1.46, 1.48, 1.52 and 1.55) and measured their thermoelectric properties on cold-pressed vacuum-sintered pellets (74–78% of the theoretical density) below 300 K. The measurements were conducted 18 months apart to probe the aging phenomena, with the samples stored in ambient conditions. We have found that (i) the peak of thermopower shifts to lower temperatures upon nanostructuring but it shifts back to higher temperatures upon aging; (ii) the electrical conductivity degrades by a factor of 1.5–2.3 upon aging while the temperature dependence is largely retained; and (iii) the ZT of freshly made samples is sensitive to the x value, a maximum ZT ~ 1.25(~ 0.62) at ~ 270 K (~ 255 K) was attained in the freshly made sample x = 1.55(x = 1.46), respectively; while the ZT of aged samples is significantly lowered by a factor of 2–4 but lesser x-dependent. These observations have been discussed in the context of charge buildup and compensation at grain boundaries.

scholarly journals Spatio-temporal variations of the major meteorological disasters and its response to climate change in Henan Province during the past two millennia

PeerJ ◽  
2021 ◽  
Vol 9 ◽  
pp. e12365
Author(s):  
Xiang Li ◽  
Hui Lu ◽  
Zhaokang Zhang ◽  
Wei Xing
Keyword(s):  
Low Temperature ◽  
Correlation Analysis ◽  
Natural Disasters ◽  
Temporal Variations ◽  
Henan Province ◽  
Historical Documents ◽  
The Past ◽  
Meteorological Disaster ◽  
Spatio Temporal ◽  
Meteorological Disasters

In China, historical documents have recorded large quantities of information related to natural disasters, and these disasters have had long-lasting effects on economic and social activities. Understanding the occurrence of the natural disasters and their spatio-temporal variation characters is crucial for sustainable of our society. Therefore, based on the collection and collation of historical documents, and adopting mathematical statistics, Kriging interpolation, correlation analysis and other methods, we systematically explored the meteorological disasters in Henan Province during the past two millennia in analyzing their spatio-temporal distribution characters and driving forces. The results demonstrate that there were five major types of meteorological disasters in Henan Province, including drought, flood, hails, low temperature and frost and insect pests, which presented obvious spatio-temporal variations and have occurred frequently during the past two millennia. According to the historical documents, the major meteorological disasters occurred 1,929 times in Henan from 221 BCE to 2000 CE. On the whole, the disaster frequency show that the occurrence cycle of the meteorological disasters has obvious changes, which mainly occurred in the middle and late stages during the past two millennia, especially after 1300 CE. Furthermore, we also find that the variation of meteorological disaster events is consistent with the variation of temperature in eastern China and the frequency of meteorological disaster increases in the cold period, but decreases in the warm period. In addition, there are obvious differences in the spatial distribution of the major meteorological disaster, which were mainly distributed in the northwest and southern part region of the Henan Province before 1911 CE. While after 1911 CE, the northern and southeastern parts were the meteorological disaster-prone areas in this region during this period. Spatial correlation analysis of each meteorological disaster before and after 1911 CE points out the droughts disaster frequency-occurring district has transferred in different periods, while the hail and low temperature and frost disasters just have a smaller transferred during these two periods. Conversely, the frequency-occurring districts of floods and insect pest disasters have no obviously transferred in different periods. These results can provide an important scientific basis for governmental decision makers and local people to prevent and mitigate meteorological disaster in the future.

scholarly journals Discuss the abnormal exothermic phenomenon “ cold fusion “

2021 ◽  
Vol 261 ◽  
pp. 04020
Author(s):  
Yang Liu ◽  
DongJie Liu ◽  
JiaXing Zhao ◽  
Xin Lu
Keyword(s):  
Low Temperature ◽  
Heat Release ◽  
Isotope Effect ◽  
Heat Generation ◽  
Cold Fusion ◽  
Solution Model ◽  
Calculation Formula ◽  
Research Results ◽  
The Past ◽  
Charging Rate

The research on cold fusion phenomenon has been in the past 30 years. Based on the research results of the predecessors, this article comprehensively describes the research results of the predecessors on the cold fusion phenomenon, and discusses it theoretically and experimentally. From the perspective of thermodynamics, this paper proposes to charge the palladium wire with hydrogen at low temperature to increase the frequency of abnormal heat generation, and gives a calculation formula for the hydrogen charging rate of the palladium wire. At the same time, a theoretical solution model for the isotope effect on the abnormal heat release phenomenon is proposed.

scholarly journals Diagnosis of a Rare Case of Acromegaly Secondary to Pituitary Macroadenoma Debuting as Sudden DKA

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A581-A582
Author(s):  
Ivan Augusto Rivera Nazario ◽  
Kyomara Hernandez Moya ◽  
Arnaldo Nieves Ortiz ◽  
Jose Ayala Rivera ◽  
Arnaldo Rojas Figueroa ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Growth Hormone ◽  
Pituitary Adenomas ◽  
Rare Case ◽  
Clinical Presentation ◽  
De Novo ◽  
Signs And Symptoms ◽  
Careful Consideration ◽  
Clinical Syndrome ◽  
The Past

Abstract Acromegaly is an uncommon clinical syndrome that results from excessive secretion of growth hormone with an annual incidence of 6 to 8 cases per 1 million of individuals with a mean age of diagnosis between 40-45 years. Pituitary adenomas can be the principal reason for an overgrowth of the anterior pituitary somatotroph cells, and account for approximately one-third of all hormone-secreting pituitary adenomas with a prevalence of about 38-69 cases per 1 million and an incidence of 3-4 cases per 1 million individuals. The onset of acromegaly is insidious, and its progression is usually very slow. At the moment of diagnosis, approximately 75% of patients have presence of macro adenomas, but most cases are diagnosed after several laboratory workups and incidental brain imaging. A characteristic clinical presentation of pituitary adenomas could be secondary to mass effect. Metabolic presentation such as diabetes is one of the most common related conditions preceding the diagnosis of acromegaly. Clinical presentation with abrupt onset of DKA could be a determining factor on disease progression due to higher GH levels correlating with an increased prevalence of insulin resistance. We present a rare case of a 28y/o female G5P3A2 without previous PMHx who presented to ER with abdominal pain, general malaise, slurred speech, headache and gait difficulty of 3 days of evolution. Upon initial evaluation at ER patient was found with hyperglycemia of 317mg/dL, low central bicarbonate, high anion gap and positive serum ketones suggestive of DKA de novo. Based on neurological complaints, head CT performed showed an incidental parasellar/suprasellar/temporal hyperdense mass measuring 2.5cm x 2.6cm with optic chiasm compression features. Upon further specific questioning patient referred amenorrhea for the past 3 years, bitemporal hemianopsia, galactorrhea and marked facial feature changes, frontal bossing, weight gain, and acanthosis nigricans, for the past year. Pituitary adenoma workup revealed low prolactin levels (1.38), markedly increased growth hormone (501) and IGF-1 (893) suggesting diagnosis of acromegaly, most likely secondary to a functioning macroadenoma. Patient initially treated with Cabergoline, uncontrolled diabetes was managed and was referred to Neurosurgery service for further evaluation and tumor removal. Based on current literature, the incidence of acromegaly cases is low, more specifically when presenting with new onset diabetic ketoacidosis, insulin resistance and secondary to functioning macroadenomas. Medical awareness should be promoted to assess for careful consideration of signs and symptoms, workup, management and treatment to assess and minimize further health complications and physical burdens acromegaly and pituitary adenomas could pose for affected individuals.

Incorporating Students' Digital Identities in Analog Spaces

2017 ◽  
pp. 257-268
Author(s):  
William J. Fassbender
Keyword(s):  
Academic Work ◽  
Careful Consideration ◽  
The Past ◽  
Classroom Conversations ◽  
Technology Educators ◽  
Digital Identities ◽  
Out Of School ◽  
Online Identities

Multiliteracies has gained significant favor in the past two decades due to the increased popularity of technology. Educators are not only finding new and exciting ways to make content relatable to students by including their digital lives in the classroom, but now the digital experience of teens is the topic of classroom conversations. The inclusion of students' online identities has certain advantages, as many students may find the bridge between academic work and their out-of-school lives advantageous to their learning. However, educators need to give careful consideration of how to safely include students' digital identities into the classroom, as these online lives are often carefully crafted for their networking platforms and are not necessarily intended for analog, classroom spaces. Throughout this article, the author explores the ways in which teachers incorporate teens' online identities and troubles the notion that teachers can safely include these identities without co-opting their out-of-school online practices.

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