Concepts and Methods to Assess the Dynamic Thermal Rating of Underground Power Cables

With the increase in the electrical load and the progressive introduction of power generation from intermittent renewable energy sources, the power line operating conditions are approaching the thermal limits. The definition of thermal limits variable in time has been addressed under the concept of dynamic thermal rating (DTR), with which it is possible to provide a more detailed assessment of the line rating and exploit the electrical system more flexibly. Most of the literature on DTR has addressed overhead lines exposed to different weather conditions. The interest in the dynamic thermal rating of power cables is increasing, considering the evolution of computational methods and advanced systems for cable monitoring. This paper contains an overview of the concepts and methods referring to dynamic cable rating (DCR). Starting from the analytical formulations developed many years ago for determining the power cable rating in steady-state conditions, also reported in International Standards, this paper considers the improvements of these formulations proposed during the years. These improvements are leading to include more specific details in the models used for DCR analysis and the computational methods used to assess the power cable’s thermal conditions buried in soil. This paper is focused on highlighting the path from the initial theories and models to the latest literature contributions. Attention is paid to thermal modelling with different levels of detail, applications of 2D and 3D solvers and simplified models, and their validation based on experimental measurements. A salient point of the overview is considering the DCR impact on reliability aspects, risk estimation, real-time calculations, forecasting, and planning with different time horizons

Productivity differences between southern and northern slopes of Southern Carpathians (Romania) for Norway spruce, silver fir, birch and black alder

Forest vegetation across Southern Carpathians is distributed in altitudinal layers. The aim of this study was to highlight the productivity differences between the Southern and Northern slopes of the Southern Carpathians for Norway spruce, silver fir, birch and black alder. Data from 45 forest management plans (46.329 stands from the Southern slopes and 32.787 stands from the Northern slopes) were used. For each stand, the mean diameter, mean height, age, standing volume, current volume increment and production class were assessed. Elementary statistical methods were used to identify the factors influencing productivity. Significant differences between the Southern and Northern slopes were recorded for silver fir. The volume and the current volume increment were higher on the Northern slopes. In the case of birch and black alder, the same two parameters recorded higher values on the Southern slopes. As regards Norway spruce, insignificant differences were recorded between the two slopes. The correlation between structure type and stand volume was positive and statistically significant in the case of Norway spruce, silver fir and birch, but it was negative in the case of alder. Analysing the correlation between stand volume and the main stand characteristics also revealed a statistically significant positive correlation between age and stand volume for all analysed species. The results of this study are especially interested for the forest managers and forest owners whose aim is to obtain a higher productivity for the studied species

Oscillatory behavior of hollow grid cathode discharges

Multiple complex space-charge structures in unmagnetized low-temperature plasmas arise from ionization phenomena near additional negatively or positively biased electrodes or due to local constraints. Because of their usually spherical form, such structures are called fireballs. If they appear inside hollow grids, they are called inverted fireballs or plasma bubbles. The temporal evolution of such structures is often accompanied by strong plasma instabilities. The dynamics of complex space-charge structures have been investigated by using single spherical grid cathode with an orifice. Langmuir probe and optical emission spectroscopy were used to diagnose the structures. Measurements delivered the axial profiles of the plasma potential, electron temperature and density, and the densities of excited atoms and ions, that confirmed the formation of a fireball in the region near the orifice (also evidenced by visual observation). Inside the grid, a plasma bubble has developed, with a high ion density inside due to the hollow cathode effect. Information on the nonlinear dynamics of the complex space charge structures was obtained from the analysis of the oscillations of the discharge current

9. The Critical Role of Art Education in Community Building as Viewed by Art Teachers. A Qualitative Study

The present study aims to describe the ways in which art education impacts community life through art products. The sample consists of 32 teachers/creators in various fields of work such as fine arts, composition, literature, musical interpretation, choreography and acting. Categorical content analysis is used for data analysis. The highest-ranking emerging theme is related to the means of educational intervention in the community through art. Artistic education leads to empowerment and emancipation by provoking people to think differently while the exposure to artistic creations has a therapeutic effect and contributes to identifying new ways of action. Artists in the role of teachers feel a responsibility both for the educational process and also for the emotional message that their creative product transmits to the audience

Obrazovne strategije u razvoju kritičkoga razmišljanja: pristup utemeljene teorije

The present qualitative approach investigated teachers’ attitudes towards critical thinking teaching and educational teaching strategies related to students’ development of critical thinking. Thirty in-service Romanian teachers with at least 5 years of experience, with a teaching range from the 8th grade to the 12th grade, participated in this study. To examine the teaching strategies adopted to develop critical thinking, the Grounded Theory methodology was used, and data were collected through semi-directive interviews. The study was carried out between September 2020 and February 2021. Following data analysis, a theoretical explanation of the process emerged describing: the prerequisites of critical thinking development, the critical thinking development phenomenon, the intervening barriers, the educational strategies employed by teachers, and the consequences of educational strategies. Two important findings highlight the educational strategies employed by teachers: the use of traditional teaching methods to the detriment of critical thinking teaching methods, and in a positive light, teachers\u27 focus on students’ self-development. In conclusion, very effective teachers understood how individual characteristics influence critical thinking development in the classroom learning environment. The results also outline the moral dimension of critical thinking, which becomes, in addition to a decision-making process, a process of assuming and understanding the consequences of individual actions.---SažetakPrikazanim kvalitativnim pristupom istraživali su se stavovi učitelja o poučavanju kritičkoga razmišljanja i obrazovne strategije poučavanja povezane s razvojem kritičkoga razmišljanja kod učenika. U ovom istraživanju sudjelovalo je trideset rumunjskih učitelja (od 8. do 12. razreda) s najmanje 5 godina iskustva rada u školi. Za istraživanje strategija učenja usvojenih za razvoj kritičkog razmišljanja korištena je metodologija utemeljene teorije, a podatci su prikupljeni polustrukturiranim intervjuima. Istraživanje je provedeno od rujna 2020. do veljače 2021. Nakon analize podataka pojavilo se teorijsko objašnjenje procesa koje opisuje: preduvjete za razvoj kritičkoga razmišljanja, fenomen razvoja kritičkoga razmišljanja, moguće prepreke, obrazovne strategije kojima se koriste učitelji i moguće posljedice obrazovnih strategija. Obrazovne strategije kojima se koriste učitelji dovele su do isticanja dvaju važnih otkrića: korištenja tradicionalnih nastavnih metoda na štetu metoda poučavanja kritičkoga razmišljanja i, nešto pozitivnije gledano, usredotočenosti učitelja na samorazvoj učenika. Zaključno, najučinkovitiji su učitelji shvatili kako individualne osobine utječu na razvoj kritičkoga razmišljanja u razrednom okruženju. Rezultati također ocrtavaju moralnu dimenziju kritičkoga mišljenja, koje, osim procesa odlučivanja, postaje i procesom prihvaćanja i razumijevanja posljedica pojedinačnih radnji. Prikazanim kvalitativnim pristupom istraživali su se stavovi učitelja o poučavanju kritičkoga razmišljanja i obrazovne strategije poučavanja povezane s razvojem kritičkoga razmišljanja kod učenika. U ovom istraživanju sudjelovalo je trideset rumunjskih učitelja (od 8. do 12. razreda) s najmanje 5 godina iskustva rada u školi. Za istraživanje strategija učenja usvojenih za razvoj kritičkog razmišljanja korištena je metodologija utemeljene teorije, a podatci su prikupljeni polustrukturiranim intervjuima. Istraživanje je provedeno od rujna 2020. do veljače 2021. Nakon analize podataka pojavilo se teorijsko objašnjenje procesa koje opisuje: preduvjete za razvoj kritičkoga razmišljanja, fenomen razvoja kritičkoga razmišljanja, moguće prepreke, obrazovne strategije kojima se koriste učitelji i moguće posljedice obrazovnih strategija. Obrazovne strategije kojima se koriste učitelji dovele su do isticanja dvaju važnih otkrića: korištenja tradicionalnih nastavnih metoda na štetu metoda poučavanja kritičkoga razmišljanja i, nešto pozitivnije gledano, usredotočenosti učitelja na samorazvoj učenika. Zaključno, najučinkovitiji su učitelji shvatili kako individualne osobine utječu na razvoj kritičkoga razmišljanja u razrednom okruženju. Rezultati također ocrtavaju moralnu dimenziju kritičkoga mišljenja, koje, osim procesa odlučivanja, postaje i procesom prihvaćanja i razumijevanja posljedica pojedinačnih radnji.

Lorenz Type Behaviors in the Dynamics of Laser Produced Plasma

An innovative theoretical model is developed on the backbone of a classical Lorenz system. A mathematical representation of a differential Lorenz system is transposed into a fractal space and reduced to an integral form. In such a conjecture, the Lorenz variables will operate simultaneously on two manifolds, generating two transformation groups, one corresponding to the space coordinates transformation and another one to the scale resolution transformation. Since these groups are isomorphs various types isometries become functional. The Lorenz system was further adapted to describe the dynamics of ejected particles as a result of laser matter interaction in a fractal paradigm. The simulations were focused on the dynamics of charged particles, and showcase the presence of current oscillations, a heterogenous velocity distribution and multi-structuring at different interaction scales. The theoretical predictions were compared with the experimental data acquired with noninvasive diagnostic techniques. The experimental data confirm the multi-structure scenario and the oscillatory behavior predicted by the mathematical model

Radial Growth Behavior of Pines on Romanian Degraded Lands

More than a third of Romania’s surface has low-productive soils, at the same time exposed to risks of climatic phenomena and generating high economic loss. Afforestation with pine has been the most common solution for the recovery of sheet erosion. Many of the pines grown on such land have run down. This paper presents the results of the first dendroecological investigation of degraded lands in Romania, 80 years after the first ecological reconstruction. In this way, the effects of reconstruction were assessed, supporting the adoption of future solutions for the improvement and efficiency of recovered ecosystems. Reconstructed radial growth was set against rainfall, air temperature, and management history. A total of 330 black pine and Scots pine trees (Pinus sylvestris L. and Pinus nigra Arn.) of different ages and social positions from 11 stands of different densities were cored for retrospective tree-ring analysis. Scots pine has made better use of these sites, with a better growth rate than black pine especially in plantations with lower survival and on dominant trees. The dynamics of radial growth distinguish the two pine species, with Scots pine showing an accentuated juvenile growth spurt and bigger growth range. The growth decline is predominantly a maturation effect that begins when the tree is around 40 years old and seems to be irreversible. After this age, weak or moderated removal is not enough to revive growth. The contribution of climate (air temperature and rainfall) to the last radial increments in decline is 3–57% and is higher than in the previous decades. On moderately degraded land by farming and grazing, the mixture of Scots pine and black pine, rather than monocultures, proved to be a sustainable solution. Dendrochronological surveying of restored ecosystems allows development of management strategies, which becomes critically important in the circumstances of climate warming

Investigations of Laser Produced Plasmas Generated by Laser Ablation on Geomaterials. Experimental and Theoretical Aspects

Several surface investigation techniques, such as X-ray diffraction (XRD), EDX, and optical microscopy, were employed in order to describe the mineral contents in several geomaterials. Space and time resolved optical emission spectroscopy was implemented to analyze the plasma generated by the laser–geomaterial interaction. The values of the plasma parameters (velocity and temperature) were discussed with respect to the nature of the minerals composing the geomaterials and the morphological structure of the samples. Correlations were found between the excitation temperatures of the atomic and ionic species of the plasmas and the presence of calcite in the samples. A mathematical model was built to describe the dynamics in ablation plasma using various mathematical operational procedures: multi structuring of the ablation plasma by means of the fractal analysis and synchronizations of the ablation plasma entities through SL (2R) type group invariance and in a particular case, through self-modulation in the form of Stoler type transformations. Since Stoler type transformations are implied in general, in the charge creation and annihilation processes, then the SL (2R) type group invariance become fundamental in the description of ablation plasma dynamics

The association between chronic pancreatitis and the iNOS-2087A>G polymorphism

Introduction. Chronic pancreatitis is morphologically characterized by ductal dysplasia, breeding grounds for the proliferation of the ductal cells, the degenerative changes in pancreatic acinar cells and fibrosis, and it is defined on the basis of the clinical, morphological and functional criteria