604 research outputs found
Large-eddy simulation of vortex interaction in pitching-fixed tandem airfoils
Get PDFIn this study, the interaction of vortices generated from an oscillating airfoil with a hindfoil placed downstream of the oscillating forefoil at low-Reynolds-number flow was investigated numerically. The forefoil entered a deep dynamic stall induced by large-amplitude pitching oscillation. The dynamic stall process is characterized by unsteady separation and the formation of a strong clockwise vortex. A wall-resolved large-eddy simulation approach was applied to compute the flowfield. The numerical measurements were performed for an incompressible flow at a Reynolds number of Re = 30 000 based on chord length with a pitching reduced frequency of K = 0.5, and amplitude of A = 14.1 degrees over Selig-Donovan 7003 airfoils. A single-airfoil case was validated against numerical and experimental measurements. In the present study, we investigated the flowfield and aerodynamic coefficients resulting from the deep dynamic stall of the pitching forefoil and the vortex interaction in tandem-airfoil configuration related to micro-air vehicle applications by employing large-eddy simulation approach. Large-eddy simulation was also compared to two-dimensional unsteady Reynolds-averaged Navier-Stokes simulation to determine the accuracy and validity of the low-fidelity approach in prediction of deep dynamic stall and vortex interaction at low-Reynolds-number flow
Termination of Linear Loops over the Integers (Track B: Automata, Logic, Semantics, and Theory of Programming)
Get PDFWe consider the problem of deciding termination of single-path while loops with integer variables, affine updates, and affine guard conditions. The question is whether such a loop terminates on all integer initial values. This problem is known to be decidable for the subclass of loops whose update matrices are diagonalisable, but the general case has remained open since being conjectured decidable by Tiwari in 2004. In this paper we show decidability of determining termination for arbitrary update matrices, confirming Tiwari’s conjecture. For the class of loops considered in this paper, the question of deciding termination on a specific initial value is a longstanding open problem in number theory. The key to our decision procedure is in showing how to circumvent the difficulties inherent in deciding termination on a fixed initial value
Formulating a New Pharmaceutical Drug; Acetaminophen Tablet Containing N-acetyl Cysteine, To Alleviate the Severity of Liver Damage in Rats: Phase I, Animal Study
Get PDFBackground and Aim: Acetaminophen (APAP) is a commonly used analgesic and also the leading cause of medication-induced liver damage. On the other hand, N-acetylcysteine (NAC) is a medication widely used to treat APAP overdose. Despite this interest, a few studies have investigated the co-administration effects of these medications. Therefore, this study aimed to evaluate the effects of NAC and APAP on renal and liver functions in rats when they use concurrently.
Methods: Male Wistar rats were orally treated with a single dose of APAP (700 mg/kg) alone or in combination of NAC at the three different doses (200, 500, and 700 mg/kg). After 24 hours, the blood and liver samples were collected for biochemical and histopathological evaluations.
Results: Liver damage was well established in the 700 mg/kg APAP-treated rats, as evidenced by elevated the plasma levels of aspartate transaminase (AST) and alanine transaminase (ALT). In addition, the plasma level of blood urea nitrogen (BUN) was significantly increased in the APPA group compared to the control group. Moreover, histological examinations revealed that liver degeneration was evident in APAP-treated animals. NAC only at the highest dose (700 mg/kg) could inhibit ALT elevation, but had no effect on AST and BUN levels. Interestingly, co-administration of NAC (700 mg/kg) with APAP (700 mg/kg) could slightly shift liver histological alterations from the irreversible stage (fibrosis) toward reversible lesions such as necrosis and hemorrhage.
Conclusion: The study findings indicate that co-administration of NAC and APAP can reduce the severity of APAP-induced liver damage in rats.
*Corresponding Author: Mehran Hosseini; Email: [email protected];
ORCID: https://orcid.org/0000-0002-6793-2035
Please cite this article as: Mehrpour O, Dastjerdi M, Nakhaee S, Amirabadizadeh A, Bijari B, Roomi H, Hosseini M. Formulating a New Pharmaceutical Drug; Acetaminophen Tablet Containing N-acetyl Cysteine, To Alleviate the Severity of Liver Damage in Rats: Phase I, Animal Study. Arch Med Lab Sci. 2021;7:1-8 (e14). https://doi.org/10.22037/amls.v7.3552
Effective Divergence Analysis for Linear Recurrence Sequences
Get PDFWe study the growth behaviour of rational linear recurrence sequences. We show that for low-order sequences, divergence is decidable in polynomial time. We also exhibit a polynomial-time algorithm which takes as input a divergent rational linear recurrence sequence and computes effective fine-grained lower bounds on the growth rate of the sequence
Bibliometric Review of Mehran University of Engineering & Technology Research Journal: 2011-2018
No full textAim: The aim of this study is to evaluate the bibliometric indicators of articles published in Mehran University of Engineering & Technology Research Journal (MUETRJ) during the period of 2011-18.
Methodology: The data of publications published in MUETAJ was downloaded from website of e-journal and analyzed various bibliometric attributes during July 2017 to 15th January 2018. The pattern of authorship, gender-wise distribution of first author, page-length of articles and institutional affiliation of the first author of publications were calculated and analyzed. Microsoft Office Excel spreadsheet was prepared for data analysis.
Results: Total 582 articles published in 32 issues of 8 volumes during the projected period with average of 18.1% articles per issue and 72.75 articles per year. Total 1777 authors contributed with an average of 3 authors per article in MUETRJ. A gender-wise distribution showed that number of male authors were much higher (n=1551; 87.2%) as compare to females authors (n=226; 12.7%). A majority of articles were written by multi-authored (n=570; 97.3%) as opposite to single author (n=12; 2%). Most the articles (n=140; 24%) have 10 pages length followed by 8 pages length (n=136; 23.7%). It was observed that Mehran University of Engineering & Technology presented itself as major contributor with 258 articles (44.3%).
Conclusion: The participation of 96 national and international institutes related to engineering and technological sciences in publishing research papers shows their confidence in MUETRJ
Pathogen simulation using soil and water tool (SWAT) model and bacteroides source tracking technique
No full textThe Upper Salem River Watershed (USRW), located in southern New Jersey, is listed as impaired for pathogens by The New Jersey Department of Environmental Protection (NJDEP) (NJDEP 2011). A 2003 Total Maximum Daily Load (TMDL) for the watershed recommended the use of pathogen source tracking to identify pathogen sources and develop a quantitative model to simulate pathogen pollution in the watershed (NJDEP 2003). This research comprises three parts: a) Fecal coliform and E. coli simulation using the Soil and Water Assessment Tool (SWAT) model in the USRW; this is the first study to conduct sensitivity analysis, calibration and validation of the SWAT model for two widely used pathogen indicators for multiple sampling stations in one watershed. The results of the sensitivity analysis indicate that pathogen input is the most sensitive parameter in the simulation of both indicators. Fecal coliform and E. coli simulation at five of six sampling stations generally showed good calibration and validation based on Nash-Sutcliffe efficiency values (0.04 to 0.71). b) Investigation of temperature effects on the persistence of bovine-Bacteroides; the primary goal of this part of the research was to identify the decay rate of bovine- Bacteroides in stream water at 4°C, 20°C and 30°C. The decay constant of bovine-Bacteroides was calculated between 0.01 h-1 in the mesocosm incubated at 4°C to 0.05 h-1 in the mesocosm at 30°C. Comparison of this study with other similar studies indicates that as temperature increased, a greater discrepancy in compared constant values was observed. c) Pathogen source tracking was done using a multiple linear regression analysis in the USRW. The primary goals of this research phase were to use a bovine-Bactreroides source tracking technique to investigate if bovine feces are a contributing pathogen source to the river system and to identify the spatial distribution of bovine pathogen discharge to the USRW. The results of the simulated model showed agreement with the potential bovine distribution sources (i.e., animal feeding facilities). A probability of occurrence map of bovine derived pathogens was also developed to spatially identify which sub-watersheds have greater likelihood of pathogen contributions from bovine sources.Ph. D.Includes bibliographical referencesby Mehran Niaz
Valsalva maneuver and strain-related ECG changes
No full textBackground: During the four steps of the Valsalva maneuver (VM), opposite changes can be observed in some physiologic parameters. Manifestations of the VM in the electrocardiogram (ECG) have been studied in detail, but there have been few reports comparing VM- related biochemical and hemodynamic changes with a focus on the strain phase of the VM.
Objectives: We studied strain-related ECG changes during the VM.
Patients and Methods: This self-control descriptive study was conducted in 20 healthy male college students aged 20.12 ± 2.23 years. They were well trained to perform the standard VM: maintenance of a 15-second expiratory pressure at 40 mmHg with open glottis. An ECG was continuously recorded in the supine position at (a) rest (before the VM) and at (b) the start and (c) end of strain maintenance in the second phase of the VM. The averages of four successive beats were computed for each set of (a), (b), and (c). Means ± standard errors of the mean were used for comparison.
Results: Following the VM, the RR and PR intervals, corrected QT interval (QTc), P wave duration and amplitude, T wave amplitude, and the ratio of T/R amplitudes showed significant changes. The QRS duration and R wave amplitude did not show significant changes.
Conclusions: The VM caused time and voltage changes in some ECG waves during the strain phase. Alterations in heart or lung volume, electrode-related alterations, and autonomic tone may cause these changes
ASO Author Reflections: Transdiaphragmatic Approach for Simultaneous Resection of Colorectal Liver and Lung Metastases
No full textSimultaneous resection of colorectal cancer, liver and lung metastase
Yapısal kusurlar, stres ve sıcaklığın dairesel MEMS dönü-ölçerlere etkilerinin analitik ve deneysel olarak çalışılması
No full textCataloged from PDF version of article.Includes bibliographical references (leaves 140-149).Inspired by the outstanding performance of the hemispherical resonator gyroscopes (HRG), MEMS gyroscopes with circularly symmetric structures are a promising candidate for the next generation of high-performance, cost-effective gyroscopes. However, scaling down to MEMS poses certain performance-limiting challenges: increased sensitivity to inevitable fabrication imperfections and environmental variations, chiefly stress and temperature, that perturb the gyroscope’s ideal modal space and result in quadrature/in-phase errors and, more importantly, long-term drift. Understanding these limiting factors is imperative for harnessing the full potential of circular MEMS gyroscopes. This thesis approaches this objective through an analytical modeling viewpoint. Here, “analytical” is meant to connote an approach based on the physics underlying the gyroscopes’ operation as described by the variational principles of solid mechanics. For the experimental evaluations, we use our fabricated double-ring vibrating ring gyroscope (VRG) (3.2 mm-diameter, 57-59 kHz) and 10-ring disk resonator gyroscope (DRG) (3.4 mm-diameter, 41 kHz). We start by calculating the mode shapes of the entire structure of multi-ring gyroscopes in the presence of structural imperfections and elastic anisotropy. By deriving the gyroscope’s nonideal drive-sense transfer function matrix, we provide rigorous definitions for the quadrature and in-phase outputs, highlighting the role of angular gain, frequency split, mode shape rotations, and quadrature leakage into the in-phase due to the sense mode’s phase error. Next, we present a model for the effects of mechanical stresses leading to the concept of stress stiffness, an additional stiffness induced by such stresses through geometric nonlinearity. We carry out an eigenvalue perturbation analysis to obtain the frequency shifts, mode shape rotations, and quadrature/in-phase errors generated by the stress stiffness. Taking advantage of the circular geometry, we have equipped our ring gyroscopes with 16 capacitive stress sensors located 45◦-apart (eight inside and eight outside the main ring), which pick up the local stress at the substrate level. We present an interpolation scheme to reconstruct the substrate’s stress field using the outputs of the stress sensors, providing us with the mechanical stresses responsible for the stress stiffness in the silicon layer. We validate the model based on PCB bending tests. We finally set out a modeling framework for temperature effects in ring gyroscopes. Our temperature experiments gave temperature coefficient of frequencies (TCFs), such as -10 ppm/◦C and -14 ppm/◦C, that are considerably different than the TCF value ~-30 ppm/◦C expected from the ~-60 ppm/◦C temperature dependency of Young’s modulus of silicon. The model revolves around the engendered stiffness and opposing interaction of two fundamental mechanisms of temperature effects: changes in material properties and thermal stresses. The model demonstrates remarkable efficacy in accurately predicting the TCF and sheds light on residual stresses’ role in forming frequency-temperature hysteresis loops. Considering the great potential of integrating stress with temperature for the long-term performance improvement of MEMS gyroscopes, the results of this thesis serve as a building block toward physics-informed drift compensation algorithms.Mehran Hosseini-Pishroba
You Need to Pay Better Attention: Rethinking the Mathematics of Attention Mechanism
Get PDFScaled Dot Product Attention (SDPA) is the backbone of many modern
deep-learning models. It is so versatile that it has been used in natural
language, vision, and multi-modal domains with very little change compared to
its original formulation. This paper discusses why the current formulation is
inefficient by delving into the mathematical details of the attention
mechanism. We propose three improvements to mitigate these inefficiencies,
thereby, introducing three enhanced attention mechanisms: Optimised, Efficient,
and Super Attention. Optimised and Efficient Attention have one and two matrix
multiplications fewer per head, respectively, and 25% and 50% fewer parameters,
respectively, than standard SDPA, but perform similarly to standard SDPA in
both vision and natural language tasks. They can be used in all applications
where SDPA is used while offering smaller model sizes and faster training and
inference without noticeable loss in performance. Super Attention introduces a
new linear transformation on the values, transforming them from the left. It
outperforms standard SPDA on vision and natural language tasks by up to 17%
while having one fewer matrix multiplication per head and 25% fewer parameters
than standard SDPA. Consequently, it is also faster than standard SDPA. Super
Attention is ideal in applications where the attention layer's context length
is fixed, such as Vision Transformers. In addition to providing mathematical
reasoning, we evaluate the presented attention mechanisms on several datasets
including MNIST, CIFAR100, ImageNet, IMDB Movie Reviews, and Amazon Reviews
datasets, as well as combined Europarl and Anki English-Spanish datasets for
neural machine translation
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