Analysis of Thermomechanical Stresses of a Photovoltaic Panel Using a Passive System of Cooling

In this paper, the gradient temperature and the thermomechanical stresses of a photovoltaic panel has been studied with and without heatsink. For this purpose, a three-dimensional analysis was carried out. Accordingly, a heat transfer analysis was developed. The numerical results show a cooling close to 26.7% with the proposed triangle fins compared with the rectangular fins studied before by another author, and the temperature distribution was determined. With this information, the stress analysis was carried out in order to find the effect on the panel due to the thermomechanical stresses. The aluminium frame was restricted to move freely. The resulting stresses field established the magnitude of the alternative stresses, resulting in a 6.7% drop compared with a reference panel. The guidelines of IEC 61215 have to be take into account. Due to the results obtained, the use of this kind of system in desert conditions is desirable because of its high operational temperature and due to the increase in heat transfer by the fins.

Precision management of pollination services to blueberry crops

While the cultivated area of pollinator-dependent crops is increasing, pollinator availability is decreasing, leading to problems in many agroecosystems. For this reason, pollinator-dependent crop growers often rent beehives to support their pollination requirements to sustain fruit productivity. However, the efficiency of those pollination systems has not been extensively studied. Here, we compared the effect of “precision” pollination (i.e., application of pesticides coordinated with growers, audit of hives, dietary supplementation and individual distribution of hives) with conventional practices (i.e., pesticides applications without coordination with growers and no audit of hives, low maintenance of hives and hives distributed in large groups) on the mean level of pollination and fruit production and quality in blueberry crops. In nine blueberry fields, we measured bee visitation rate to flowers, fruit set, fruit firmness and fruit weight. On average, precision-pollinated plots had 70% more bee visits to flowers and produced 13% more fruits that were 12% heavier and 12% firmer than those obtained through conventional practices. These results showed that pollination efficiency could be improved if key management related to bee strength, distribution and health care are taken into account. Due to these results, we encourage growers and beekeepers to include precision pollination practices to both increase the productivity of blueberry fields and the wellbeing of honey bees within agroecosystems.

Financial depth in the context of the relationship with economic growth

The generalization of quantitative and qualitative scientific approaches to the essence of financial depth enables to define it as a resulting characteristic that demonstrates the saturation of the economy with financial resources, that allows assessing the ability of the financial system to effectively mobilize and redistribute financial resources to achieve sustainable economic development. The retrospective analysis of empirical hypotheses linking the financial depth of the economy and economic growth suggests that while some scholars focus on the importance of financial depth in economic development, others emphasize the effects of financial crises caused by rapid financial deepening, in particular credit expansion. The focus of contemporary research is on the nonlinearity of the relationship between financial depth and long-term economic growth and on defining the limit of financial development, exceeding which inhibits economic growth or negatively impacts it. Among the positives of financial deepening is the expansion of access to financial resources (increase in the volume and diversification of financial instruments), reduction of income inequality and smoothing of consumption, diversification of production risks. Among the risks of financial deepening is the deterioration of the current account due to excessive lending, unproductive investment, growth in employment in non-productive sectors, limitation of the use of fiscal policy as an instrument of countercyclical policy. It is noted that formation of the financial depth of the economy depends on the characteristics of financial resources and as well in structural, macroeconomic, political and institutional factors of economic development. While the world tends to increase the ratio of financial assets, broad money, domestic credit provided by financial institutions, the capitalization of listed companies to GDP, in Ukraine since 2014 there has been a significant decrease in these indicators, which is not typical in comparison with countries with the same level of income and demonstrates the low level of financial depth of the domestic economy.

Application of the steаm аssisted grаvity drаinаge (SAGD) method in the heavy oil fields

Recently, the prospects for the development of the oil industry have been associated with the development of deposits of heavy oils and natural bitumen. It is economically feasible and possible to extract high-viscosity oil (HVO) and natural bitumen (NB) only thanks to the development and application of effective technologies for their development. Unconventional oil production requires an unconventional exclusive approach, one of them is the steam — gravity method of oil production. The creation of SAGD models involves solving problems of heat and mass transfer in wells and a productive reservoir to optimize the production mode. To calculate the parameters of heat transfer, reliable information is required about the complex of thermal properties (thermal conductivity, thermal conductivity, volumetric heat capacity) of rocks of the productive formation, the underlying and overlapping layers of the mountain massif. Currently, when conducting research and constructing geological and technological models for predicting development indicators, the degree of influence of variations in the thermophysical properties of reservoir rocks on the efficiency of the SAGD process is not taken into account. Due to the absence until recent years of the possibility of obtaining reliable representative data on the thermal properties of rocks of a particular deposit, averaged values based on single measurements or on reference data that do not take into account the features of the object being developed and do not contain a detailed geological description of the studied rocks are usually used. In this regard, it was necessary to conduct a study of the influence of real spatial variations of the thermophysical properties of rocks, studied in detail for one of the deposits with the help of a new highly efficient hardware and methodological measuring base, on the development indicators by the SAGD method. In this article, the authors considered the effectiveness of using horizontal wells with cyclic steam exposure at the Yareg field.

Modyfikacja znormalizowanej metody prowadzenia prób ciśnieniowych celem jej wykorzystania do badania szczelności gazociągów z poliamidu PA 12

Before being put into operation, gas pipelines are subjected to leakage and strength pressure testing. In the case of plastic gas pipelines, a combined leakage and strength test is performed at a pressure of 1.5 ´ MOP. In Poland, in accordance with the applicable regulations, the plastic material from which gas pipelines can now be built is polyethylene. In other countries gas pipelines are also built of another material, which is PA12 polyamide. Piping systems made of this material are used to transmit gas at a pressure of 1.6 MPa. Both polyethylene and polyamide gas pipelines, after loading them with internal pressure, will undergo deformation with time, which is called the material creep phenomenon. As a result, in pressure leakage tests of gas pipelines made of thermoplastics, such as polyethylene and polyamide, it is necessary to take this phenomenon into account. Due to the different properties of polyethylene and polyamide, the amount of deformation per unit time will be different, and therefore the test procedures that are used for polyethylene gas pipelines cannot be directly used for testing polyamide gas pipelines. An example of such a procedure is the one described in point A.27 of PN-EN 805: 2002. It is mainly used for leakage testing of polyethylene water pipelines and its application for leakage testing of PA12 polyamide gas pipelines with a MOP of 1.6 MPa requires changes in the test conditions. The article presents the concept of modifying the parameters of the hydrostatic method, taking into account the different properties of PA12 pipes compared to polyethylene pipes. Particular attention was paid to the higher value of Young's modulus and the related ring stiffness of PA12 polyamide pipes compared to polyethylene pipes. In order to obtain the appropriate deformation of the pipe resulting from the material creep, the time of holding the sample under pressure was experimentally extended before starting the actual test. After establishing the required test conditions for the sealed system, tests with simulated leaks were carried out. The obtained results of tests on airtight samples and with simulated leakage confirmed the possibility of using the modified method to test the tightness of PA 12 polyamide gas pipelines with a MOP of 1.6 MPa.

Double mode model of size-dependent chaotic vibrations of nanoplates based on the nonlocal elasticity theory

In this paper vibrations of the isotropic micro/nanoplates subjected to transverse and in-plane excitation are investigated. The governing equations of the problem are based on the von Kármán plate theory and Kirchhoff–Love hypothesis. The small-size effect is taken into account due to the nonlocal elasticity theory. The formulation of the problem is mixed and employs the Airy stress function. The two-mode approximation of the deflection and application of the Bubnov–Galerkin method reduces the governing system of equations to the system of ordinary differential equations. Varying the load parameters and the nonlocal parameter, the bifurcation analysis is performed. The bifurcations diagrams, the maximum Lyapunov exponents, phase portraits as well as Poincare maps are constructed based on the numerical simulations. It is shown that for some excitation conditions the chaotic motion may occur in the system. Also, the small-scale effects on the character of vibrating regimes are illustrated and discussed.

Remodeling of the Posterior Cerebral Artery P1-Segment after Pipeline Flow Diverter Treatment of Posterior Communicating Artery Aneurysms

Introduction: Flow diverters such as the pipeline embolization device (PED) cause hemodynamic changes of the treated vessel segment. In posterior communicating artery (PcomA), aneurysms’ unique anatomic consideration have to be taken in account due to the connection between the anterior and posterior circulation. We hypothesize that in conjunction with PcomA remodeling, there will also be remodeling of the ipsilateral P1 segment of the posterior cerebral artery (PCA) after PED treatment for PcomA aneurysms. Methods: We retrospectively collected radiological as well as clinical data of PcomA aneurysm patients treated with PED including PcomA and P1 vessel diameters before and after treatment as well as patient and aneurysm characteristics. Results: Overall, 14 PcomA aneurysm patients were included for analysis and PED treatment was performed without complications in all patients. In 10 out of 14 patients (71%), a decrease in PcomA diameter was observed and there was a significant mean decrease of 0.78 mm in PcomA diameter on angiographic last follow-up (LFU) (p = 0.003). In the same patient population (10 out of 14 patients), there was meanwhile a significant mean increase of 0.43 mm in the ipsilateral P1 segment diameter observed (p = 0.015). These vessel remodeling effects were in direct correlation with aneurysm occlusion since all of these patients showed aneurysm occlusion at LFU while 29% showed only partial occlusion without vessel remodeling effects. A decrease in PcomA diameter was directly associated with aneurysm occlusion (p = 0.042). There were no neurologic complications on LFU. Conclusion: In the treatment of PcomA aneurysms with PED, the P1 segment of the PCA increases in diameter while the PcomA diameter decreases. Our results suggest that this remodeling effect is associated with aneurysm occlusion and decrease of PcomA is hemodynamically compensated for by an increase in the ipsilateral P1 diameter.

Modeling the Chemical Composition of Ferritic Stainless Steels with the Use of Artificial Neural Networks

The aim of this paper is an attempt to answer the question of whether, on the basis of the values of the mechanical properties of ferritic stainless steels, it is possible to predict the chemical concentration of carbon and nine of the other most common alloying elements in these steels. The author believes that the relationships between the properties are more complicated and depend on a greater number of factors, such as heat and mechanical treatment conditions, but in this paper, they were not taken into account due to the uniform treatment of the tested steels. The modeling results proved to be very promising and indicate that for some elements, this is possible with high accuracy. Artificial neural networks with radial basis functions (RBF), multilayer perceptron with one and two hidden layers (MLP) and generalized regression neural networks (GRNN) were used for modeling. In order to minimize the manufacturing cost of products, developed artificial neural networks can be used in industry. They may also simplify the selection of materials if the engineer has to correctly select chemical components and appropriate plastic and/or heat treatments of stainless steel with the necessary mechanical properties.

Understanding Online Voluntary Self-Exclusion in Gambling: An Empirical Study Using Account-Based Behavioral Tracking Data

Online gambling has continued to grow alongside new ways to analyze data using behavioral tracking as a way to enhance consumer protection. A number of studies have analyzed consumers that have used voluntary self-exclusion (VSE) as a proxy measure for problem gambling. However, some scholars have argued that this is a poor proxy for problem gambling. Therefore, the present study examined this issue by analyzing customers (from the gambling operator Unibet) that have engaged in VSE. The participants comprised of costumers that chose to use the six-month VSE option (n = 7732), and customers that chose to close their Unibet account due to a specific self-reported gambling addiction (n = 141). Almost one-fifth of the customers that used six-month VSE only had gambling activity for less than 24 h (19.15%). Moreover, half of the customers had less than seven days of account registration prior to six-month VSE (50.39%). Customers who use VSE are too different to be treated as a homogenous group and therefore VSE is not a reliable proxy measure for problem gambling. The findings of this research are beneficial for operators, researchers, and policymakers because it provides insight into gambling behavior by analyzing real player behavior using tracking technologies, which is objective and unbiased.

Parental Beliefs about Childhood and Adolescence from a Longitudinal Perspective

Research into family context as a socializing agent points to the need to take parental beliefs into account due to the role they play in both parenting strategies and, ultimately, in the psychosocial adjustment of children and adolescents. The present study aims to explore possible relationships between parental beliefs about childhood and adolescence from a longitudinal and qualitative perspective. The beliefs held by parents of teenagers about adolescence are compared with those they hold about childhood at that same moment, and the evolution of these ideas is charted over the course of 16 years as their children grow. A total of 102 parents participated in the longitudinal study. They completed two types of semi-structured interviews: one of them throughout the entire study period and the other once their children became teenagers. The results reveal an association between the type of beliefs parents hold about childhood and their perception of adolescence, and they indicate that these ideas change over time as more adjusted and modern beliefs about child development correlate with a more positive perception of adolescence. These results are interpreted from the perspective of their influence on beliefs about parenting styles, reflecting what is reported in the recent literature regarding the most successful styles for fostering children’s and adolescents’ psychosocial adjustment.