Nonlinear vibration of crowned gear pairs considering the effect of Hertzian contact stiffness

This study aims to analyze the influence of lead crowning modification of teeth on the vibration behavior of a spur gear pair. Two dynamic rotational models including an uncrowned and crowned gear are examined. Hertzian mesh stiffness is computed using tooth contact analysis in quasi-static state along a complete mesh cycle of teeth mesh. The dynamic orbits of the system are observed using some useful attractors which expand our understanding about the influence of crown modification on the vibration behavior of the gear pair. Nonlinear impact damper consists of non-integer compliance exponents identify energy dissipation of the system beneath the surface layer. By augmenting tooth crown modification, the surface penetration increases and consequently normal pressure of the contact area becomes noticeable. Finally, the results show modification prevents gear pair to experience period doubling bifurcation as the numerical results proved. Using this new method in dynamic analysis of contact, broaden the new horizon in analyzing of the surface of bodies in contact

A Review of Optimization Models and Techniques for Maintenance Decision Support Systems in Small and Medium Industries

There are not many sufficient studies made on the application of artificial intelligence techniques to access troubleshooting activities as it always taken into consideration in a verbal sense and yet is not dealt with mathematically. The proposed study extended Choy, John, Thomas & Yan [1] models using either semi-parametric or non-parametric approaches of reliability analysis to examine the relationship between repair time and various risk factors of interest. Then the models will be embedded to neural networks to provide better estimation of repairing parameters. The proposed models can be used by maintenance managers as a benchmarking to develope quality service to enhance competitiveness among service providers in corrective maintenance field. Also the models can be deployed farther to develop a computerized decision support syste

A comparative study of chromosome morphology among some accessions of Aegilops crassa

In this study karyotype and chromosome characteristics of the nine accessions of Aegilops crassa species obtained from gene bank of Seed and Plant Improvement Research Institute (SPII) of Iran and one accession collected by authors were inspected. Aceto-iron-hematoxilin staining method was used to stain chromosomes. For each accession, chromosome characteristics including long and short arms, chromosome lengths, arm ratio index and relative chromosome lengths were measured using micro measure 3.3 software. Results revealed that all of the studied accessions were tetraploid (2n = 4x = 28) and consisted of 13 pairs of metacentric and one pair of submetacentric chromosomes, of which two pairs were satellite chromosomes. Karyotype formula for these accessions were 13 m + 1 sm. Arm ratio index value of chromosomes ranged from 1.11 in chromosome number 6 to 1.77 in chromosome number 12. The B chromosomes were not seen in any of the accessions. Karyological characteristics of these accessions were similar to each other. However, some differences were observed between the accessions in some chromosome characteristics

Molecular survey of aminoglycoside-resistant Acinetobacter baumannii isolated from tertiary hospitals in Qazvin, Iran

Aminoglycoside-modifying enzymes (AMEs) and 16S rRNA methylases (16S RMTase) are two main resistance mechanisms against aminoglycosides. This study aimed to evaluate the frequency of AMEs and 16S rRNA methylase genes among aminoglycoside nonsusceptible Acinetobacter baumannii isolates and to assess their clonal relationship using repetitive extragenic palindromic-PCR (rep-PCR). In this cross-sectional study, a total of 192 A. baumannii isolates were collected from the patients hospitalized in Qazvin, Iran (January 2016 to January 2018). Identification of isolates was performed by standard laboratory methods and API 20E strips. Antimicrobial susceptibility was determined by Kirby–Bauer method followed by examination of the genes encoding the AMEs and 16S RMTase by PCR and sequencing methods. The clonal relationship of isolates was carried out by rep-PCR. In total, 98.4% of isolates were nonsusceptible to aminoglycosides, 98.4%, 97.9% and 83.9% of isolates were found to be non-susceptible against gentamicin, tobramycin and amikacin, respectively. The frequencies of aph(30 )-VI, aac(60 )-Ib, aac(3)-II, aph(30 )-Ia and armA genes were 59.3%, 39.2%, 39.2%, 31.7% and 69.8%, respectively, either alone or in combination. Rep-PCR results showed that the aminoglycoside non-susceptible isolates belonged to three distinct clones: A (79.4%), B (17.5%) and C (3.2%). The findings of this study showed a high frequency for AMEs with the emergence of armA genes among the aminoglycoside non-susceptible A. baumannii isolates. Rational administration of aminoglycosides as well as using an appropriate infection control policy may reduce the presence of resistance to antibiotics in medical centres

A genetic variant in proline and serine rich coiled-coil 1 gene is associated with the risk of cardiovascular disease

Background: Cardiovascular disease is one of the most common causes of morbidity and mortality worldwide. The Proline and Serine Rich Coiled-Coil 1 gene in 1p13.3 locus has been reported to be associated with low density lipoprotein cholesterol (LDL-C) and coronary artery disease (CAD). The objective of this study was to investigate the association between the rs599839 polymorphism of the Proline and Serine Rich Coiled-Coil 1 (PSRC1) gene with CVD outcomes in a population sample recruited as part of the Mashhad-Stroke and Heart-Atherosclerotic-Disorders (MASHAD) cohort. Methods: Five hundred and nine individuals who had an average follow-up period of 10 years were enrolled as part of the MASHAD cohort. DNA was extracted and genotyped using the TaqMan-real-time-PCR based method. Results: The study found individuals with GA/GG genotypes were at a higher risk of CVDs (OR= 4.7; 95% CI, 2.5-8.7; p< 0.001) in comparison to those with AA genotype; however, the result was not significant for GG genotype data. Conclusions: The results suggest that the GA/GG genotypes of the PSRC1gene locus were at increased risk of CVD in a representative population-based cohort, demonstrating further functional analysis to discover the value of emerging marker as a risk stratification biomarker to recognize high risk cases

Neural network in corner detection of vertex chain code series

This paper presents a Neural Network Classifier to be implemented in corner detection of chain code series. The classifier directly uses chain code which is derived using Freeman chain code as training, testing and validation set. The steps of developing Neural Network Classifier are included in this paper. Comparison results between Neural Network Classifier corner detection and other computational corner detection are presented to show the reliability of the proposed classifier. This paper ends with the discussions on the implementation of proposed neural network in corner detection of chain code series. Experimental results have shown that the proposed network has good robustness and detection performance. This makes this method a great choice for machine vision

Nonlinear vibration of crowned gear pairs considering the effect of Hertzian contact stiffness

This study aims to analyze the influence of lead crowning modification of teeth on the vibration behavior of a spur gear pair. Two dynamic rotational models including an uncrowned and crowned gear are examined. Hertzian mesh stiffness is computed using tooth contact analysis in quasi-static state along a complete mesh cycle of teeth mesh. The dynamic orbits of the system are observed using some useful attractors which expand our understanding about the influence of crown modification on the vibration behavior of the gear pair. Nonlinear impact damper consists of non-integer compliance exponents identify energy dissipation of the system beneath the surface layer. By augmenting tooth crown modification, the surface penetration increases and consequently normal pressure of the contact area becomes noticeable. Finally, the results show modification prevents gear pair to experience period doubling bifurcation as the numerical results proved. Using this new method in dynamic analysis of contact, broaden the new horizon in analyzing of the surface of bodies in contact

An integrated approach for prioritizing the barriers to airport service quality in an intuitionistic-fuzzy environment

Airports today, despite the complexity of their service environment and multicultural nature, are expected to provide high-quality services to satisfy their passengers. This way they will be able to gain competitive advantages. Hence, improving the quality of airport services has become increasingly significant. In this paper, the main components of the airport services quality with the greatest impact on the customer satisfaction have been derived based on previous articles as well as interviews with experts in this field and travelers. Subsequently, the comments of passengers were received by distributing questionnaires. Eventually, using failure mode and effects analysis (FMEA) approach along with entropy and VIKOR techniques, the risk factors were evaluated and ranked in an intuitionistic triangular fuzzy environment. The findings of this research can be addressed to the airport management team to review and reform their services and facilities. Yazd international airport was considered as a case study of this paper