Energy decay estimates for an axially travelling string damped at one end

We study the small vibrations of an axially travelling string with a dashpoint damping at one end. The string is modelled by a wave equation in a time-dependent interval with two endpoints moving at a constant speed $v$. For the undamped case, we obtain a conserved functional equivalent to the energy of the solution. We derive precise upper and lower estimates for the exponential decay of the energy with explicit constants. These estimates do not seem to be reported in the literature even for the non-travelling case $v=0$.Comment: 14 Pages, 2 Figure

Boundary stabilization of a vibrating string with variable length

We study small vibrations of a string with time-dependent length $\ell(t)$ and boundary damping. The vibrations are described by a 1-d wave equation in an interval with one moving endpoint at a speed $\ell'(t)$ slower than the speed of propagation of the wave c=1. With no damping, the energy of the solution decays if the interval is expanding and increases if the interval is shrinking. The energy decays faster when the interval is expanding and a constant damping is applied at the moving end. However, to ensure the energy decay in a shrinking interval, the damping factor $\eta$ must be close enough to the optimal value $\eta=1$, corresponding to the transparent condition. In all cases, we establish lower and upper estimates for the energy with explicit constants.Comment: 14 pages, 3 figure

Numerical Modelling of Heat Dissipation for the Pin-On-Disc Type Tribometer

This article presents numerical tests of heat distribution for the Pin-On-Disc type frictional contact. The tests were conducted for the friction pair brass CuZn39Pb2 (pin) - cast iron GJL250 (disc). The heat distribution was tested both experimentally and numerically. Experimental tests were carried out on a conventional CA 6140 lathe properly adapted for these tests. The simulations used the method of elementary balances (MEB) based on an explicit calculation algorithm. The studies were carried out with a normal force of 5N and three cutting speeds of 0.24, 0.35, and 0.48 m/s respectively. The measurements were made after the process had lasted 0, 5, 10, 15, 20, 25, and 30 minutes. As a result of the research, the average and maximum temperature of the measurement point located directly behind the pin-disc contact field was determined. On the basis of the conducted analyses, the imperfection of the applied calculation method was indicated as the probable cause of discrepancies in experimental and simulation results and the acceptance for calculations of constant and time-varying thermo-physical properties of friction pair materials. In addition, the studies proved that a change in the calculation time step has little effect on the average and maximum temperature of the measurement point

Thermodynamic-based Solvent Selection for the Separation of Lignin- derived Molecules

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Accuracy of Mean Platelet Volume (MPV) and Red Cell Distribution Width (RDW) for the Diagnosis of Acute Appendicitis: Evaluation of Possible New Biomarkers

Introduction: Acute appendicitis is the most common cause of the abdominal pain in surgery. Despite its significant prevalence, the diagnosis is associated with many problems in some cases, which leads to false appendectomy. Objective: The aim of this study was to determine the validity of diagnostic tests of mean platelet volume (MPV) and red cell distribution width (RDW), as a new possible tool in the diagnosis of acute appendicitis. Methods: In this study, all patients who referred to the emergency department of Besat Hospital, Hamadan, Iran, in 2015, with abdominal pain and first impression of acute appendicitis, undergone appendectomy, were evaluated. The diagnostic markers of pre-operative and post-operative pathology and the validity of MPV and RDW were determined in diagnosis of acute appendicitis. Results: Laboratory and clinical data from 438 patients, presenting the signs and symptoms of acute appendicitis with the mean age of 26.51±13.9 years, were examined (55.6% men). The sensitivity, specificity, positive and negative predictive value of MPV in the diagnosis of acute appendicitis were 59.77, 98.66, 99.5 and 34.26 percent, and for the RDW were 57.79, 56.00, 86.07 and 21.98 percent, respectively. The area under the receiver operating characteristic (ROC) curve for RDW and MPV was 0.61and 0.90, respectively. The mean of MPV in patients with normal pathologic outcome was 9.52±1.60 and in patients with acute appendicitis was 7.51±1.22. There was a significant difference between the mean MPV in both groups (p<0.001). The mean of RDW in patients with normal pathology were 13.42±1.97 and 13.05±1.09, in patients with acute appendicitis. There was a significant difference between the mean RDW of the two groups (p=0.009). Conclusion: MPV and RDW indexes have the potential to be used by the surgeons in diagnosis of acute and perforated appendicitis, especially in adults, in order to reduce unnecessary appendectomy, but MPV is more valid in screening acute appendicitis, compared to the RDW

Anatomy of sour gas sweetening simulation software HYSYS with various amines

In recent decades, due to its importance for the simulation of sweetening units are taken into consideration . Natural gas often contains impurities such as carbon dioxide and hydrogen sulfide items within the gas, acid gas or sour gas is highly toxic and that they in turn can lead to corrosion of pipes and devices Hence, it must be purified before use of natural gas, ie the impurities such as carbon dioxide and hydrogen sulfide and other acid gas components can be separated and so sweet The removal of acid gases in the oil, gas & petrochemical is a very important These gases are usually by some physical or chemical solvent absorption towers, can be absorbed Alkanolan aqueous amines such as DGA and MDEA, DEA, MEA solvents commonly used in the process are important items within the natural gas sweetening In this paper, H2S and CO2 solubility in the solvent mole-time DEA, MDEA and also combinations of temperature and pressure is measured absorption tower refinery. And the absorption tower refinery using HYSYS software accurately simulated and the results for selected vehicle with real data are compared with each other and the . Keywords:Simulation, sweetening unit, sour gas, amine, software Hysys

Population Fluctuation and Diurnal Time Budgeting of WhiteHeaded Duck (Oxyura Leucocephala) During Winter at Garaet Hadj Tahar (Skikda, North East Algerian)

This study was focused on the ecology and behavior of the White-headed Duck (Oxyura leucocephala) at Garaet Hadj Tahar (Guerbes-Sanhadja, North East of Algeria). Sampling was carried out during two wintering seasons (2017-2018 and 2018-2019). High number of this duck was recorded in 2018/19 (350 individuals). We observed two Oxyura population, the first sedentary, and the second, hosted the Garaet during the wintering season. Diurnal time budget was dominated by the comfort activities the sleeping with a rate of 39.13%. Following by swimming (37.76%), feeding (17.59%) grooming (4.58%), courtship ritual (0.56%) and flying (0.38%). The feeding of white-headed duck is done exclusively by diving. Beside, this waterbird associated between Feeding by diving and grooming in order to minimized energy. The accessory activities such as: courtship ritual, flying were done by this duck at the end of wintering. This results confirm that Garaet Hadj Tahar is considered as wintering site for this threatened species. Biological Conservation plan (BCP) must be applied at level of this wetland in order to manage bioressources and threatened waterbirds

The Asymmetric Effect of Sukuk on Government Budget: Dealing with Deficit in Malaysia

Islamic economists sought to find transactions that fit and conform to the principles of Islamic religion, where Islamic bonds were one of the most critical products compatible with Islam. This study aims to shed light on the impact of Sukuk as one of the alternatives available for funding expenditures and deficit in Malaysia. This research using a non-linear autoregressive distributed lag model (NARDL) during the period 1990-2016. After identifying the asymmetric effect and the dynamic multiplier of Sukuk on government budget balance during the fluctuations of the exchange rate of the Ringgit, we have found that Islamic bonds are a very useful tool in financing deficit making Malaysia a pioneering experience in the field of Islamic engineerin

Rorty versus Habermas, A Pragmatic Turn toward Truth and its Applicability in Organizing Justification Relations

The argument between Habermas and Rorty is directed toward organizing justification relations based on the Truth. Both of them suggest a pragmatic turn to avoid Truth deadlocks of the epistemological approach. Their difference of opinion is formed from the fact that Rorty takes the pragmatic turn to the extent that eliminates the concept of Truth, but Habermas considers a Kantian meaning for Truth, according to which Truth is merely a regulative and transcendental idea that assuming its existence is necessary for the possibility of organizing justification relations of actors. Rorty, on the other hand, believes that Truth even in its regulative and transcendental sense, does not offer any useful meaning. Because nothing can be targeted and achieved unless it is recognizable how to gain it or how to get an approach to it. The criterion that Rorty offers to organize justification relations is not a Truth in the future, but a narrative of the experiences we have had. It seems that Rorty is successful in rejecting Habermas' criticisms against the possibility of eliminating the concept of Truth in organizing justification relations; in the sense that his thought is more compatible with a pragmatic turn. But Rorty's alternative for Truth also implies that no specific goal virtually is conceivable for the human being. The worthiness of narratives in organizing the relations of actors is recognizable only in the realm of experience. According to him, we should only hope to follow a better path than the previous one. This ambiguity in Rorty's thought is perhaps the most important challenge in accepting his views