• Journal of the Korean Chemical Society
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• v.55 no.5
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• pp.812-818
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• 2011

[ $V_{0.9}Sb_{0.1}O_x$ ]systems, bulk and deposited on different supports (five types of ${\gamma}$-aluminas, ${\alpha}$-alumina, silica-alumina, silica gel, magnesium oxide), have been tested in the oxidative dehydrogenation (ODH) of iso-butane. This statement is derived from the data obtained by a set of characterisation techniques(specific surface area measurements, X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectroscopy, in situ differential scanning calorimetry and in situ diffuse reflectance-absorption infrared Fourier transform spectroscopy).

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.719-724
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• 2017

We consider an elastic isotropic plate reinforced by stringers and weakened by a periodic system of rectilinear slots of variable width. The variable width of the slots is comparable with elastic deformations. We study the case when the slots faces get in contact at some area. Determination of parameters characterizing the partial closure of variable width slots is reduced to the solution of a singular integral equation. The action of the stringers is replaced with unknown equivalent concentrated forces at the points of their connection with the plate. The contact stresses and contact zone sizes are found from the solution of the singular integral equation.

• Geomechanics and Engineering
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• v.24 no.3
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• pp.227-235
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• 2021

A criterion and a method for solving a problem on the prevention of mine working fracture under the action of tectonic and gravitational forces are offered. Based on minimal criterion, theoretical analysis of the definition of the optimal shape of working in the rock mass weakened by arbitrarily located rectilinear cracks was carried out. A closed system of algebraic equations allowing to minimize the stress state and stress intensity factors depending on mechanical and geometrical characteristics of the rock, is constructed. The relation between the shape of the working and the stress intensity factors and also location and sizes of the cracks is obtained. The found optimal shape of working increases load-bearing capacity of the rock.

• Korean Journal of Mathematics
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• v.31 no.1
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• pp.109-120
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• 2023

The Berezin symbol à of an operator A on the reproducing kernel Hilbert space 𝓗 (Ω) over some set Ω with the reproducing kernel k_λ is defined by $${\tilde{A}}(\lambda)=\,\;{\lambda}{\in}{\Omega}$$. The Berezin number of an operator A is defined by $$ber(A):=\sup_{{\lambda}{\in}{\Omega}}{\mid}{\tilde{A}}({\lambda}){\mid}$$. We study some problems of operator theory by using this bounded function Ã, including estimates for Berezin numbers of some operators, including truncated Toeplitz operators. We also prove an operator analog of some Young inequality and use it in proving of some inequalities for Berezin number of operators including the inequality ber (AB) ≤ ber (A) ber (B), for some operators A and B on 𝓗 (Ω). Moreover, we give in terms of the Berezin number a necessary condition for hyponormality of some operators.

• Journal of Navigation and Port Research
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• v.41 no.3
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• pp.155-164
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• 2017

While many countries are implementing various policies regarding the logistics network in Eurasia, China has presented "the Belt and Road" Initiative, a development strategy that focuses on connectivity and close cooperation between China and Eurasia. With more than 60 countries participating in the project, China is expected to have a major influence on logistical infrastructure development in Eurasia. This study analyzed the railway stations network using social network analysis (SNA) methodology. We collected data from major railway lines in Eurasia (TAR, TEN-T, TRACECA, GMS) and established a network of 994 railway stations in 65 countries. This study presented the general characteristics of major railway stations from the perspective of SNA and compared the Chinese network with Eurasian networks. To review the railway networks in China and Eurasia, the top 30 stations were selected based on degree centrality and betweenness centrality. Top "degree centrality" stations included Bangkok (Thailand), Tbilisi (Georgia), Baku (Azerbaijan), Kunming (China), and Bucharest (Romania). Top "betweenness centrality" stations were Baku and Alyat (Azerbaijan), Baoji and Turpan (China), Qarshi (Uzbekistan), and Kas (Turkey). In China, Kunming, Nanning, and Gejiu stations have higher degree centrality while betweenness centrality was higher in Baoji, Kunming, and Lanzhou stations. "The Belt and Road" project advocated by China envisions expansion of transportation infrastructure connections throughout Eurasia, but more emphasis is likely to be placed on connectivity that benefits China. In this regard, studies on key bases of international logistics need to consider relative significance within the Chinese network.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.1
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• pp.283-290
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• 2015

Purpose: The aims of this case-control study were to assess the correlation between some food habits in the last two decades and gastric cancer in East Azerbaijan of Iran. Materials and Methods: In this hospital based case control study, 616 patients (212 gastric cancer patients, 404 cancer free patients) were recruited. Food habits of patients over the past two decades were assessed with a structured questionnaire. We used conditional logistic regression analysis for estimating crude and adjusted odds ratios (OR) and their respective 95% confidence intervals (95%CI). Results: In this study, over-eating, consumption of high fat milk and yogurt and especial types of cheese increased the risk of gastric cancer (All<0.05). Consumption of such especial cheeses such as Koze and Khiki increased the risk of gastric cancer by 12.6 fold (95% CI:1.99-79.36) and 7.36 fold (95% CI:1.33-40.54), respectively. In addition, high fat food, moldy food, and pickled vegetables consumption as well as reuse of cooking oil for frying were significantly associated with gastric cancer risk. Furthermore, intake of Ghorme (deep fried meat) was positively correlated with gastric cancer risk (OR:1.31;95%CI: 0.91-1.87). Conclusions: It can be confirmed that particular food habits which have been very common in East-Azerbaijan in the last two past decades increase risk of gastric cancer. According to our results and taking into account the long latency period of gastric cancer it can be concluded that nutrition education for a healthy diet should be performed from early childhood. However, further well designed cohort studies are needed to achieve more clear results.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.7
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• pp.3451-3454
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• 2012

Background: Esophageal cancer in Iran is the sixth most common cancer and is particularly important in east Azerbaijan. The aim of this study was to calculate survival rates and define prognostic factors in esophageal cancer patients. Methods: In this study, all patients with esophageal cancer registered in the Radiation Therapy Center, during March 2006 to March 2011, were analyzed and followed up for vital status. Data were analyzed using the Kaplan-Meier method and the Cox proportional hazard models. Results: Out of 532 patients, survival information was available for 460, including 205 (44/ 5%) females and 255 (55/4%) males. The mean age was $65.8{\pm}12.2$, ranging from 29 to 90 years at the time of diagnosis. 1-, 3- and 5-year survival rates after diagnosis were 55%, 18% and 12%, respectively, with a median survival time of $13.2{\pm}.7$ (CI 95% =11.8-14.6) months. In the univariate analysis, age (P=0/001), education (P=0/001), smoking status (P= 0/001), surgery (P= 0/001), tumor differentiation (P= 0/003) and tumor stage (P= 0/001) were significant prognostic factors. Tumor morphology, sex, place of residence, tumor histology and tumor location did not show any significant effects on the survival rate. In multivariate analysis, age (P = 0/003), smoking (P= 0/01) and tumor stage (P= 0/001) were significant independent predictors of survival. Conclusion: In summary, prognosis of esophageal cancer in North West of Iran is poor. Therefore, reduction in exposure to risk factors and early detection should be emphasized to improve survival.

• Structural Engineering and Mechanics
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• v.62 no.1
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• pp.113-123
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• 2017

The bi-material elastic system consisting of the circular hollow cylinder and the infinite elastic medium surrounding this cylinder is considered and it is assumed that on the inner free face of the cylinder a point-located axisymmetric time harmonic force, with respect to the cylinder's axis and which is uniformly distributed in the circumferential direction, acts. The shear-spring type imperfect contact conditions on the interface between the constituents are satisfied. The mathematical formulation of the problem is made within the scope of the exact equations of linear elastodynamics. The focus is on the frequency-response of the interface normal and shear stresses and the influence of the problem parameters, such as the ratio of modulus of elasticity, the ratio of the cylinder thickness to the cylinder radius, and the shear-spring type parameter which characterizes the degree of the contact imperfectness, on these responses. Corresponding numerical results are presented and discussed. In particular, it is established that the character of the influence of the contact imperfection on the frequency response of the interface stresses depends on the values of the vibration frequency of the external forces.

• Coupled systems mechanics
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• v.7 no.5
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• pp.525-554
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• 2018

The paper deals with the study of the dynamics of the oscillating moving ring load acting in the interior of the hollow circular cylinder surrounded by an elastic medium. The axisymmetric loading case is considered and the study is made by employing the exact equations and relations of linear elastodynamics. The focus is on the influence of the oscillation of the moving load and the problem parameters such as the cylinder's thickness/radius ratio on the critical velocities. At the same time, the dependence between the interface stresses and load moving velocity under various frequencies of this load, as well as the frequency response of the mentioned stresses under various load velocity are investigated. In particular, it is established that oscillation of the moving load can cause the values of the critical velocity to decrease significantly and at the same time the oscillation of the moving load can lead to parametric resonance. It is also established that the critical velocity decreases with decreasing of the cylinder's thickness/radiusratio.

• Steel and Composite Structures
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• v.17 no.4
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• pp.453-470
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• 2014

This article is the result of an investigation on the influence of a Pasternak elastic foundation on the stability of exponentially graded (EG) cylindrical shells under hydrostatic pressure, based on the first-order shear deformation theory (FOSDT) considering the shear stresses. The shear stresses shape function is distributed parabolic manner through the shell thickness. The governing equations of EG orthotropic cylindrical shells resting on the Pasternak elastic foundation on the basis of FOSDT are derived in the framework of Donnell-type shell theory. The novelty of present work is to achieve closed-form solutions for critical hydrostatic pressures of EG orthotropic cylindrical shells resting on Pasternak elastic foundation based on FOSDT. The expressions for critical hydrostatic pressures of EG orthotropic cylindrical shells with and without an elastic foundation based on CST are obtained, in special cases. Finally, the effects of Pasternak foundation, shear stresses, orthotropy and heterogeneity on critical hydrostatic pressures, based on FOSDT are investigated.