Experimental and Numerical Investigation of Mechanical and Thermal Effects in TiNi SMA during Transformation-Induced Creep Phenomena

(1) The paper presents experimental and numerical results of the TiNi shape memory alloy (SMA) subjected to a modified program of force-controlled tensile loading. The time-dependent development of transformation strain under the constant-force conditions was investigated to describe transformation-induced creep phenomena. (2) Mechanical characteristics of the TiNi SMA were derived using a testing machine, whereas the SMA temperature changes accompanying its deformation were obtained in a contactless manner with an infrared camera. A 3D coupled thermo-mechanical numerical analysis, realized in a partitioned approach, was applied to describe the SMA mechanical and thermal responses. (3) The stress and related temperature changes demonstrated how the transformation-induced creep process started and evolved at various stages of the SMA loading. The proposed model reproduced the stress, strain and temperature changes obtained during the experiment well; the latent heat production is in correlation with the amount of the martensitic volume fraction. (4) It was demonstrated how the transformation-induced creep process occurring in the SMA under such conditions was involved in thermo-mechanical couplings and the related temperature changes

Paul Preston. The Last Stalinist: The Life of Santiago Carrillo. London: HarperCollins, 2014.

У овом приказу књиге Пола Престона о Сантјагу Кариљу, пре свега, пренео сам Престонове истраживачке резултате и закључке о личности Сантјага Кариља. Уз то, анализирао сам његову методологију и исцрпни рад на историјским изворима, и поставио питање исправности Престоновог фокусирања на амбициозност као искључиву карактеристику политичке каријере Сантјага Кариља

Artificial neural network data analysis for classification of soils based on their radionuclide content

The artificial neural network (ANN) data analysis method was used to recognize and classify soils of an unknown geographic origin. A total of 103 soil samples were differentiated into classes according to the regions in Serbia and Montenegro from which they were collected. Their radionuclide (Ra-226, U-238, U-235, K-40, Cs-134, Cs-137, Th-232, and Be-7) activities detected by gamma-ray spectrometry were then used as inputs to ANN. Five different training algorithms with different numbers of samples in training sets were tested and compared in order to find the one with the minimum root mean square error (RMSE). The best predictive power for the classification of soils from the fifteen regions was achieved using a network with seven hidden layer nodes and 2500 training epochs using the online back-propagation randomized training algorithm. With the optimized ANN, most soil samples not included in the ANN training data set were correctly classified at an average rate of 92%

Energy performance of an exhibition hall in a life cycle perspective: embodied energy, operational energy and retrofit strategies

Nowadays, the focus on the building energy consumption in the use phase prevails over an interest concerning the energy impacts linked to all the other phases of the construction process. However, reducing operational energy could lead to shifting the impacts from one stage to another. Thus, combining the study of strategies improving energy efficiency in the use phase with a life cycle approach is crucial. Exhibition halls are peculiar buildings from the geometry, construction and use points of view, rarely addressed in energy and life cycle energy analysis studies. Therefore, in this paper, a representative hall of the Milan Trade Fair is taken as a case study. A building energy simulation model is firstly calibrated in order to derive the operational energy for climatisation. The operational energy appears artificially low due to the short use period during the year. When compared with the calculated embodied energy of the envelope and structure, it is found that 57 years would be needed to balance energy spent in the construction and in the use phase. Further, some retrofit interventions are proposed and analyzed. Insulation interventions are not attractive from the economic payback time point of view. However, when the embodied energy of the retrofit interventions is compared with the energy savings in the use phase, interesting energy payback times are obtained. Therefore, this study puts in evidence on the importance of adopting a life cycle perspective, especially for buildings with low-intensity use. Eventually, the critical issues of the life cycle energy analysis are deeply discussed

Content of the potentially harmful elements in soil around the major coal-fired power plant in Serbia: relation to soil characteristics, evaluation of spatial distribution and source apportionment

The concentrations and spatial distribution of nine potentially harmful elements (PHEs), namely Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, and their relation to soil properties were investigated in thirty soil profiles (0-50 cm depth) sampled around the largest Serbian coal-fired power plant (CFPP) "Nikola Tesla A." Soil properties were determined following standard procedures, and total contents of PHEs were analyzed by atomic absorption spectrometer. Concentrations of Cd, Co, Fe, Mn, Pb and Zn were the highest in soil profiles sampled 1 km away from the CFPP, concentrations of Ni and Cu gradually increased up to 4 km, and the highest Cr concentrations were measured in samples taken 6 km away from the CFPP. The highest concentration of PHEs analyzed, except Mn, corresponded with predominant wind directions. Depth did not show significant impact on distribution of any PHEs investigated. Among soil properties, the total organic carbon showed the closest relationship with the PHEs. Data were processed by a principal component analysis which enabled distinguishing anthropogenic from natural influences on soil properties and PHE contents. Although the impact of CFPP operations is obvious, assets of principal component analysis did not allow clear distinction of CFPP's contribution from parent material in enrichment of PHE contents in the soil in the study area

Identifying and categorizing risks of new product development in a small technology-driven company

New product development (NPD), as a locus of the innovative potential of organizations, plays an essential role in small technology-driven company survival. To address the research gap and fulfill the companies’ needs, this survey aims to post and verify a new, simple and not time-consuming methodology for risk identification and categorization of industrial products development. To check the hypothesis that NPD project technical, cost and schedule sets of risks could be categorized as both threats and opportunities, an experiment was conducted in a small Serbian enterprise that has developed 52 innovative solid state based lighting products for outdoor lighting infrastructure. There were 69 identified risks (51 threats and 18 opportunities) that through 76 factors influence new products’ technical characteristics, schedule and cost. Explorative factor analysis was applied to reduce and compress the data and 26 composite factors were obtained as valid predictors of the NPD project results. Regarding the technical characteristics risks, the threats can be grouped into four factors consisting of six risk types, while opportunities can be grouped into two factors consisting of four risk categories. The risks influencing the schedule disturbance that act as threats are grouped into eight factors consisting of ten risk types, while those that could be used in opportunities are grouped in four factors with eight risks identified. The risks influencing the costs that threaten the project are recognized as five factors described by seven risks, while those that act as opportunities are grouped into three factors described by five variables in total