A Study of Polymers. II. Dynamic Method of Studying Elastic Materials

1940 ◽  
Vol 13 (4) ◽  
pp. 898-904 ◽  
Author(s):  
Yu S. Lazurkin
Keyword(s):  
Elastic Deformation ◽  
Dynamic Tests ◽  
Elastic Materials ◽  
General Picture ◽  
High Frequencies ◽  
Dynamic Conditions ◽  
Automobile Tire ◽  
General Law ◽  
Long Time ◽  
Time Required

Abstract Most articles made from elastic substances are intended for service under dynamic conditions. Static methods of investigation are clearly insufficient for determining the behavior of elastic substances under dynamic conditions and therefore there has for a long time been a need for dynamic tests. In recent years several dynamic tests have been developed, and a number of investigations of elastic properties under dynamic conditions have been published. The works of Frumkin, Roelig, Kosten, Naunton and Waring and other investigators have established a series of relations in the behavior of elastic substances under dynamic conditions. However, the limited intervals of frequency and temperature in these experiments gave relations of peculiar character and even led to contradictions. Thus Naunton and Waring showed that, under dynamic conditions (at high frequencies), automobile tire casings act as solid hoops and, according to Roelig and Kosten, the relation between modulus and frequency, though still existing, is of relatively little importance. The development of a concept of the mechanism of highly elastic deformation, and in particular the disclosure of relaxation made it possible for Kornfel'd and Poznyak and Mikhai˘lov and Kirilina to demonstrate experimentally the existence of a more general law relating the phenomena. However, in their experiments, the frequency in both cases changed within narrow limits, and consequently these investigations too do not give a general picture of the behavior of elastic materials in relation to the frequency of deformation and temperature. The idea of highly elastic deformation, as well as that of relaxation, comes down to the fact that the magnitudes of the deformations observed depend on the relation between the time of action of the force and the time required for regrouping of the particles in the substance during the deformation.

Elastic deformation and the laws of friction

1957 ◽  
Vol 243 (1233) ◽  
pp. 190-205 ◽  
Keyword(s):  
Surface Topography ◽  
Elastic Deformation ◽  
Frictional Force ◽  
Metal Surfaces ◽  
Applied Load ◽  
Elastic Contact ◽  
Elastic Materials ◽  
General Law ◽  
Highly Elastic Materials

This paper examines whether the hypothesis of elastic deformation of surface protuberances is consistent with Amontons’s law, that the friction is proportional to the applied load. For a single elastic contact, the area of contact A is known to be proportional to the ⅔ power of the load W . Since the frictional force is generally assumed to be proportional to A , it has been thought that in elastic deformation Amontons’s law would not be obeyed. However, conforming surfaces usually touch at many points, and it is shown that in these circumstances A and W become nearly proportional. Experiments are described which show that the general law is that the friction is proportional to the true area of contact; whether or not Amontons’s law is obeyed depends upon the surface topography. For highly elastic materials such as Perspex, Amontons’s law is obeyed when contact is made at many points, and other relations between A and W are observed when the contacts are few. Experiments with lubricated brass specimens show that the same conclusions apply to carefully prepared or well run-in metal surfaces running in conditions where the damage is small.

Effect of Vial shaking on Loading Time of Epirubicin into Drug-Eluting Bead

2015 ◽  
Vol 5 (3) ◽  
Author(s):  
Kenji Ikeda ◽  
Yusuke Kawamura ◽  
Masahiro Kobayashi ◽  
Taito Fukushima ◽  
Yushi Sorin ◽  
...  
Keyword(s):  
Antitumor Agent ◽  
Loading Rates ◽  
Vortex Mixer ◽  
Long Time ◽  
Group A ◽  
Drug Eluting ◽  
Large Hepatocellular Carcinoma ◽  
Group B ◽  
Time Required ◽  
Short Time

Background: Although DC Bead has been useful in treatment of multiple and large hepatocellular carcinoma, loading time of doxorubicin into the DC Bead takes a long time of 30-120 minutes. Epirubicin is also used as an antitumor agent together with DC Bead, but its loading efficiency was not sufficiently elucidated. Methods: To shorten loading time of epirubicin into DC Bead (100-300µm, 300-500µm, 500-700µm), we examined the following three methods after mixing the drug: (a) let stand in room temperature, (b) agitated for 30 seconds with Vortex mixer, and (c) sonicated for 30 seconds with ultrasonic cleaner. After loading of epirubicin by each method, supernatant concentration for epirubicin was assayed at 5, 10, 30, 60, and 120 minutes. Results: Epirubicin loading rates for small bead (100-300µm) at 5 minutes were 82.9 % in group a, 93.8% in group b, and 79.9 % in group c. Similarly, medium bead (300-500µm), 40.1% in group a, 65.7% in group b and 45.5% in group c, respectively. In large-sized bead (500-700µm), loaded rates of epirubicin were 38.8% in group a, 59.0% in group b and 48.0% in group c. Agitation of mixture of epirubicin and DC Bead with Vortex mixer significantly shortened the loading time, but sonication did not affect the time required. Microscopic examination did not lead to any morphological change of microspheres in all the methods. Conclusions: Short time of agitation with Vortex mixer reduced the necessary time for loading of epirubicin in every standard of DC Bead.

Long Time Coming: Prospects for Democracy in Iraq

2009 ◽  
Vol 33 (4) ◽  
pp. 115-148 ◽  
Author(s):  
Bruce E. Moon
Keyword(s):  
Nineteenth Century ◽  
The Other ◽  
Democratic Transitions ◽  
Quarter Century ◽  
The Past ◽  
Political Experience ◽  
Long Time ◽  
Time Required ◽  
Established Democracies

Prospects for democracy in Iraq should be assessed in light of the historical precedents of nations with comparable political experiences. Saddam Hussein's Iraq was an unusually extreme autocracy, which lasted an unusually long time. Since the end of the nineteenth century, only thirty nations have experienced an autocracy as extreme as Iraq's for a period exceeding two decades. The subsequent political experience of those nations offers a pessimistic forecast for Iraq and similar nations. Only seven of the thirty are now democratic, and only two of them have become established democracies; the democratic experiments in the other five are still in progress. Among the seven, the average time required to transit the path from extreme autocracy to coherent, albeit precarious, democracy has been fifty years, and only two have managed this transition in fewer than twenty-five years. Even this sober assessment is probably too optimistic, because Iraq lacks the structural conditions that theory and evidence indicate have been necessary for successful democratic transitions in the past. Thus, the odds of Iraq achieving democracy in the next quarter century are close to zero, at best about two in thirty, but probably far less.

Time- and age-dependent effects of serotonin on gasping and autoresuscitation in neonatal mice

2013 ◽  
Vol 114 (12) ◽  
pp. 1668-1676 ◽  
Author(s):  
Jianping Chen ◽  
Jennifer Magnusson ◽  
Gerard Karsenty ◽  
Kevin J. Cummings
Keyword(s):  
Heart Rate ◽  
Tryptophan Hydroxylase ◽  
Single Injection ◽  
Heart Rate Recovery ◽  
Wild Type ◽  
Tryptophan Hydroxylase 2 ◽  
Age Dependent ◽  
Long Time ◽  
Time Required

The role of brain stem serotonin (5-hydroxytryptamine, 5-HT) in autoresuscitation in neonatal life is unclear. We hypothesized that a specific loss of 5-HT would compromise gasping and autoresuscitation mainly in the second postnatal week and that acute restoration of 5-HT would reverse the defects. We exposed postnatal day (P)4–5, P8–9, and P11–12 tryptophan-hydroxylase-2 knockout ( TPH2−/−) and wild-type littermates (WT) to 10 episodes of anoxia (97% N2, 3% CO2), measuring survival, gasp latency, gasp frequency ( fB), and the time required to restore eupnea and heart rate. We also tested P8–9 TPH2−/− mice after restoring 5-HT with a single injection of 5-hydroxytryptophan (5-HTP) 1–2 h before testing or with multiple injections beginning 24 h before testing. At P4–5 and P8–9, but not at P11–12, gasp latency and the recovery of eupnea were delayed ∼2- to 3-fold in TPH2−/− pups compared with WT ( P < 0.001). At all ages, TPH2−/− pups displayed reduced gasp fB (∼20–30%; P < 0.001) and delayed heart rate recovery (∼60%; P = 0.002) compared with WT littermates. TPH2−/− survival was reduced compared with WT ( P < 0.001), especially at P8–9 and P11–12 ( P = 0.004). Whereas 1–2 h of 5-HTP treatment improved the gasp latency and fB of P8–9 TPH2−/− pups, improved cardiorespiratory recovery and survival required 24 h of treatment. Our data suggest that 5-HT operates over a long time span (∼24 h) to improve survival during episodic severe hypoxia. Early in development (P4–9), 5-HT is critical for both respiratory and cardiovascular components of autoresuscitation; later (P11–12), it is critical mainly for cardiovascular components. Nevertheless, the effect of 5-HT deficiency on survival is most striking from P8 to P12.

Assessment of pedestrian comfort and safety of footbridges in dynamic conditions: case study of a landmark arch footbridge

BUILDER ◽  
2021 ◽  
Vol 286 (5) ◽  
pp. 78-82
Author(s):  
Paweł Hawryszków
Keyword(s):  
Dynamic Tests ◽  
Dynamic Conditions ◽  
Large Group ◽  
Fast Running ◽  
Live Loads ◽  
Structural Solutions

The objective of this paper is to present results of dynamic tests of an arch span of the footbridge in Wronki near Poznań in Poland and clearly summarize them. The investigated footbridge, with asymmetrical arch and the main span 90.0 m long, is an example of original architecture and interesting structural solutions. The research campaign included normal live loads and vandal actions to the footbridge. Normal live loads tests examined the influence of various kinds of the pedestrian activity on the footbridge’s behaviour as: walking, jogging or fast running. The pedestrian comfort was assessed in this type of schemes. Vandal type of excitation consisted of synchronized walking or running and rhythmical half-crouching. The main aim of the vandal live loads was to check structure’s safety and behaviour in the extreme dynamic conditions. The research was carried out in a large group of pedestrians – under a crowd of 40 volunteers.

Rapid Measurement of Nutation NQR Spectra in Powders Using an RF Pulse Train

1996 ◽  
Vol 51 (5-6) ◽  
pp. 363-367 ◽  
Author(s):  
Nicolai Sinyavsky ◽  
Michał Ostafin ◽  
Mariusz Maćkowiak
Keyword(s):  
Asymmetry Parameter ◽  
Pulse Train ◽  
Pulse Action ◽  
Rf Pulses ◽  
Time Saving ◽  
Long Time ◽  
The Asymmetry ◽  
Rf Pulse ◽  
Time Required

Abstract The method of two-dimensional nutation NQR spectroscopy, introduced by Harbison in 1989, has been successfully used for determining of the asymmetry parameter of the EFG tensor for spin-3/2 nuclei in both powdered and monocrystal samples in the absence of an external magnetic field. The inconvenience inherent in the method, however, is the long time required, because data acquisition must be repeated for various RF pulse lengths. We discuss a method to reduce the time of the nutation experiment by using a sequence of identical short RF pulses of length r w and distance τ. It is shown that for an NQR frequency ω0 , frequency offset Δω, and pulse parameters satisfying the relation ω0τ + Δωtw = 2πk (k = 1, 2, 3,..., n) a synchronism of pulse action takes place and the nutation interferogram can be measured "stroboscopically" between the pulses. The maximum time saving factor that can be obtained as compared to the conventional nutation experiment is of the order of the number of pulses used in a pulse train. The method has been successfully applied for determination of the asymmetry parameter for one of the two 3 5 Cl sites in polycrystalline 2,4,6-trichloro-1,3,5-triazine (cyanuric chloride).

scholarly journals Non-Performing Loans for Italian Companies: When Time Matters. An Empirical Research on Estimating Probability to Default and Loss Given Default

2020 ◽  
Vol 8 (4) ◽  
pp. 68
Author(s):  
Giuseppe Orlando ◽  
Roberta Pelosi
Keyword(s):  
Risk Taking ◽  
Economic Losses ◽  
Probability Of Default ◽  
Legal Environment ◽  
Loss Given Default ◽  
Recovery System ◽  
Main Driver ◽  
Long Time ◽  
The Subject ◽  
Time Required

Within bank activities, which is normally defined as the joint exercise of savings collection and credit supply, risk-taking is natural, as in many human activities. Among risks related to credit intermediation, credit risk assumes particular importance. It is most simply defined as the potential that a bank borrower or counterparty fails to fulfil correctly at maturity the pecuniary obligations assumed as principal and interest. Whenever this happens, a loan is non-performing. Among the main risk components, the Probability of Default (PD) and the Loss Given Default (LGD) have been the subject of greater interest for research. In this paper, logit model is used to predict both components. Financial ratios are used to estimate the PD. Time of recovery and presence of collateral are used as covariates of the LGD. Here, we confirm that the main driver of economic losses is the bureaucratically encumbered recovery system and the related legal environment. The long time required by Italian bureaucratic procedures, simply put, seems to lower dramatically the chance of recovery from defaulting counterparties.

Pingo collapse and paleoclimatic reconstruction

1988 ◽  
Vol 25 (4) ◽  
pp. 495-511 ◽  
Author(s):  
J. Ross Mackay
Keyword(s):  
Soviet Union ◽  
Field Studies ◽  
Normal Faults ◽  
Paleoclimatic Reconstruction ◽  
Air Temperatures ◽  
The Soviet Union ◽  
Long Time ◽  
Western Arctic ◽  
Arctic Coast ◽  
Time Required

Long-term field studies of contemporary pingo growth, collapse, and rampart formation along the western Arctic coast of Canada provide criteria that may be helpful in the identification of pingo ramparts in nonpermafrost environments. Such criteria include the volume of the ramparts, which should approximate that of the enclosed depressions from which the rampart materials were derived; peripheral deposits associated with mass wasting, streamflow, and debris flow; casts of dilation crack ice trending across the ramparts; and high-angle peripheral normal faults. The conventional method of correlating the present mean annual air temperature with the present pingo distribution to establish warm-side limiting temperatures for paleoclimatic reconstruction is unsound, because most pingos in North America and the Soviet Union commenced growth hundreds to thousands of years ago under mean annual air temperatures that may have differed greatly from those of the present. Some other factors to be considered in paleoclimatic reconstruction are the thermal offset; site availability; the differing requirements for the growth of large pingos as compared with small pingos; and the long time required for pingos to grow to full size.

Study on the Cement-Improved Loess under the Vibratory Load by Dynamic Tests

2013 ◽  
Vol 838-841 ◽  
pp. 1302-1308 ◽  
Author(s):  
Jia Ding Wang ◽  
Shu Jun Peng ◽  
Wan Li Xie
Keyword(s):  
Elastic Modulus ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Dynamic Deformation ◽  
Damping Ratio ◽  
Test Method ◽  
Dynamic Elastic Modulus ◽  
Dynamic Tests ◽  
Long Time ◽  
Orthogonal Test Method

In this paper based on the foundation construction of Datong Xian high-speed railway, a large number of test samples have been taken. The order and contribution rate of every experiment factor like cement commingle ratio, depths, water dipping conditions, compacting factor and vibration frequency on the dynamic characteristics of cement-improved loess such as dynamic elastic modulus, dynamic deformation, damping ratio by dynamic triaxial test, which orthogonal test method has been applied to. The dynamic load was calculated according to the train vibration attenuation rule of different depth. The dynamic characteristics of cement-improved loess such as dynamic deformation, dynamic elastic modulus, damping ratio were got form the dynamic tests of long time and large number of cycles. The results showed that with the increase of cement ratio, the dynamic characteristics of cement-improved loess are more better, there is no optimal ratio of cement.

scholarly journals Penerapan Algoritma Genetika Untuk Optimasi Penjadwalan pada MTS Negeri 1 Pangkalpinang

2020 ◽  
Vol 9 (3) ◽  
pp. 435-441
Author(s):  
Delpiah Wahyuningsih ◽  
Ellya Helmud
Keyword(s):  
Genetic Algorithm ◽  
Genetic Algorithms ◽  
Important Thing ◽  
Long Time ◽  
Time Required ◽  
Short Time

Scheduling is a very important thing to do at school. The schedule, which is still being carried out manually at MTS Negeri 1 Pangkalpinang, requires time to manage teacher slots, classes, subjects, and times where in MTS teacher hours have been determined by the department of religion so that it takes quite a long time to process the formation of the schedule. This study aims to utilize genetic algorithms in optimizing scheduling in a short time. The genetic algorithm is an algorithm that is effective in dealing with scheduling. The results of data testing were carried out with 15, 20, 25 and 30 subjects. Testing with 15 subjects took 19.56 seconds to form a schedule and there were no conflicting schedules, while with 20 data subjects the time to process the schedule formation took 42.15 seconds, 25 data with 94.07 seconds and 30 data with time 471.60. The average time required to process the data is 156.845 seconds.

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