Group IV nanocrystals (NCs), in particular from the Si–Ge system, are of high interest for Si photonics applications. Ge-rich SiGe NCs embedded in nanocrystallized HfO2 were obtained by magnetron ...sputtering deposition followed by rapid thermal annealing at 600 °C for nanostructuring. The complex characterization of morphology and crystalline structure by X-ray diffraction, μ-Raman spectroscopy, and cross-section transmission electron microscopy evidenced the formation of Ge-rich SiGe NCs (3–7 nm diameter) in a matrix of nanocrystallized HfO2. For avoiding the fast diffusion of Ge, the layer containing SiGe NCs was cladded by very thin top and bottom pure HfO2 layers. Nanocrystallized HfO2 with tetragonal/orthorhombic structure was revealed beside the monoclinic phase in both buffer HfO2 and SiGe NCs–HfO2 layers. In the top part, the film is mainly crystallized in the monoclinic phase. High efficiency of the photocurrent was obtained in a broad spectral range of curves of 600–2000 nm at low temperatures. The high-quality SiGe NC/HfO2 matrix interface together with the strain induced in SiGe NCs by nanocrystallization of both HfO2 matrix and SiGe nanoparticles explain the unexpectedly extended photoelectric sensitivity in short-wave infrared up to about 2000 nm that is more than the sensitivity limit for Ge, in spite of the increase of bandgap by well-known quantum confinement effect in SiGe NCs.
► Modified potato starch was synthesized by alkylation. ► The chemical structural characteristics were investigated by NMR and FTIR. ► The ether modified starches present a higher aqueous solubility. ...► The alkyl succinic anhydrides starches present high capacity to desorb benzoapyrene.
For the development of renewable bioproducts able to solubilize organic persistent pollutant such as benzoapyrene (BaP), modified potato starch was synthesized by alkylation. The addition of alkyl chains was performed with three different alkylation agents: epoxyalkane, alkenyl succinic anhydride and 1,4-butane sultone. Twelve alkylated starches were obtained with different molar substitutions (MS) and various alkyl chain lengths (to three carbons up to sixteen). The chemical structural characteristics were investigated by methods of 1H NMR and FTIR. In comparison with the native starch, the ether modified starches showed in general an enhancement of their aqueous solubility whereas the ester modified starches stimulated the BaP aqueous solubilization. Indeed, the compounds P6 and P12, which increased 40-fold the BaP aqueous concentration, present high surfactant properties.
Phosphate and tellurite glasses can be used in optics, optoelectronics, magneto-optics, and nuclear and medical fields. Two series of phosphate-tellurite glasses, (50-x)ZnO-10Al2O3-40P2O5-xTeO2 and ...(40-x)Li2O-10Al2O3-5TiO2-45P2O5-xTeO2 (x = 5, 10), were synthesized by a non-conventional wet-route, and the mechanical properties as key performance measures for their application in optoelectronics were investigated. X-ray Diffraction (XRD) measurements revealed the vitreous nature of the investigated materials. Instrumented indentation tests allowed the calculation of hardness (H) and Young’s modulus (E) using the Oliver and Pharr model. The influence of increasing the TeO2 content, as well as the substitution of ZnO by Li2O-TiO2, on the variation of hardness, Young’s modulus, penetration depth (PD), and fracture toughness (FT) was evaluated in both series. As a general trend, there is a decrease in the hardness and Young’s modulus with increasing penetration depth. The addition of Li2O and TiO2 instead of ZnO leads to improved hardness and elastic modulus values. Regarding the H/E ratio, it was found that the samples with lower TeO2 content should be significantly more crack-resistant compared to the higher TeO2 content samples. The H3/E2 ratio, being lower than 0.01, revealed a poor resistance of these glasses to plastic deformation. At the same time, a decrease of the fracture toughness with increasing TeO2 content was noticed for each glass series. Based on dilatometry measurements, the thermal expansion coefficient as well as the characteristic temperatures of the glasses were measured. Field Emission Scanning Electron Microscopy-Energy Dispersive X-ray analysis (FESEM-EDX) revealed a uniform distribution of the elements in the bulk samples. The mechanical properties of these vitreous materials are important in relation to their application as magneto-optical Faraday rotators in laser cavities.
Background. The management of a recurrent inguinal hernia varies depending on multiple factors. In the case of recurrent inguinal hernias after open anterior repair, the laparoscopic approach is ...recommended. TEP and TAPP procedures are considered to have similar results. The purpose of the study is to evaluate on our sample if there are differences between primary inguinal hernia cases and recurrent hernia after laparoscopic TAPP and TEP procedures. Materials and Methods. We retrospectively reviewed the medical records of 300 patients who underwent laparoscopic inguinal hernia repairs at our hospital from March 2013 to March 2023. Results. Of the 300 patients, 39 of them (13%) had recurrent hernias after open anterior procedures. The mean age of patients with recurrent hernias was 56.82 years, compared to 50.47 years in those with primary hernias. In 27 cases we used the TAPP approach (69%), while in the remaining 12 cases the TEP approach (31%). Operative time for recurrent hernias was 72.69 minutes as opposed to 58.49 minutes for primary hernias. The percentage of peritoneal tears was higher for recurrent hernias (38%) than for primary hernias (18%). Conclusions. Surgery for inguinal hernia recurrence, is often more complex and time-consuming than for a primary hernia. However, postoperative results are favorable, with a low complication rate. Out of the two minimally invasive approach options, TAPP is our choice, especially due to the increased incidence of peritoneal tears. Keywords: inguinal hernia, laparoscopic inguinal hernia repair, TAPP, TEP, recurrent inguinal hernia
Mohr-Coulomb (M-C) criterion is widely used for isotropic brittle materials, although it has some disadvantages which limit its wider application. One important disadvantage of this theory is that it ...ignores the effect of the intermediate principal stress, although it has an important influence on materials behaviour. Therefore, Mohr-Coulomb theory is actually used only for materials in biaxial state of stress. In this paper, a modified form of Mohr's criterion has been suggested, in order to overcome this limitation. The modified criterion takes into account the influence of intermediate principal stress in the case of materials under triaxial loading conditions. On the basis of two new hypotheses, a real triaxial state of stress is replaced by a virtual biaxial state of stress. The above mentioned stress states are considered to be equivalent for a material when the failure is imminent in both cases. Both Mohr's theory and the concept of equivalence of stress states are combined in order to obtain the virtual biaxial state of stress, which is determined using all three principal stresses. The modified Mohr's theory can be used only for triaxial state of stress. For biaxial and uniaxial state of stress it is reduced to the classical one. The proposed hypotheses have an important advantage because does not require additional material coefficients. The calculated values using the virtual biaxial state of stress and the linear M-C criterion are in good agreement with experimental data for grey cast iron. The article also presents a compact statistical analysis for both stresses and errors, in order to objectively assess the effectiveness of the formulated hypotheses.
•The modified Mohr's theory, for triaxial state of stress, is based on some new hypotheses.•It takes into account the influence of intermediate principal stress.•It does not use additional material constants.•The new criterion matches better the existing experimental data.•A statistical analyse is proposed to compare the effectiveness of different criteria.
Considering the Getica project, and the feasibility study prepared in 2011 in order to capture and storage CO2 from the Turceni Power Plant and in view of the temporary cessation of this project, we ...propose a study on the storage of CO2 in disused and closed mining areas, from the Jiu Valley, with impact on the environment and on exploitation and monitoring for long-term more than 1000 years and also alignment with similar projects in other countries, Europeans or not. Mainly, the majority of long-term capture and storage projects are carried out in deepwater aquifers, such as aquifers under the North Sea and the Barents Sea, or specially storage projects created in dissolutted salt mines, such as those in the Santos Basin in the Atlantic Ocean in Brazil, as well as others, like the pilot projects in India, with storage in volcanic rocks, etc. Storage projects in large-capacity coal mines such as those in Romania, Serbia or Bulgaria, to discuss common issues with neighboring countries, can create an exchange of knowledge with those countries on long and very long-term storage of CO2 in coal mines, with an obvious gain in greening the atmosphere and in the health of the environment.
von Mises hypothesis revised Barsanescu, Paul Doru; Comanici, Ana Maria
Acta mechanica,
02/2017, Letnik:
228, Številka:
2
Journal Article
Recenzirano
The most popular isotropic yield conditions, verified for many ductile metals, were proposed by
Tresca
in 1864 (maximum shearing stresses theory) and
von Mises
in 1913. The
von Mises
yield theory ...(von Mises in Mathematisch-physikalische Klasse 582–592,
1913
), also known as maximum distortion energy criterion, finds considerable experimental support, especially for very ductile materials and plane stress (Banabic et al. in Int. J. Mater. Form. 3:165–189,
2010
). For this reason, and for its simplicity, it is common in design. During 100 years, this theory has been developed and improved systematically by
Hosford, Christensen, Tsai-Hill,
etc. The modified
von Mises
hypothesis combines the theories of maximum strain energy and maximum distortion energy, and it involves the Poisson ratio. It ensures a smooth transition from the
von Mises
to the
Beltrami
criterion. The results obtained by this new yield hypothesis are compared with those obtained both by the classic
von Mises
criterion and by experiments on different metallic materials. A quite good concordance is observed between these results.
In order to perform an efficient Fenton reaction of benzoapyrene (BaP) in the presence of starch as a reaction matrix, a computer modeling study conducted on amylopectin as a component of potato ...starch allows to identify three more stable sites, among six, available for BaP and iron complexation. For the purpose of enabling the formation of such a stable complex, starch was irreversibly modified by hydroxypropylation for favoring the accessibility of BaP to available complexation sites. The results show that such an irreversible modification significantly consequently increased starch solubilization in cold water. Hydroxypropyl starch derivative obtained in the optimized synthesis conditions (molar substitution of 0.73) increased significantly the BaP solubility and consequently influenced its degradation (38%) by Fenton oxidation. We might hypothesize that starch depolymerisation occurring through a radical chain mechanism during the Fenton reaction allows the formation of carbon centred radicals, permitting therefore an oxidation attack of BaP.
Considering the Getica project, and the feasibility study prepared in 2011 in order to capture and storage CO
2
from the Turceni Power Plant and in view of the temporary cessation of this project, we ...propose a study on the storage of CO
2
in disused and closed mining areas, from the Jiu Valley, with impact on the environment and on exploitation and monitoring for long-term more than 1000 years and also alignment with similar projects in other countries, Europeans or not. Mainly, the majority of long-term capture and storage projects are carried out in deepwater aquifers, such as aquifers under the North Sea and the Barents Sea, or specially storage projects created in dissolutted salt mines, such as those in the Santos Basin in the Atlantic Ocean in Brazil, as well as others, like the pilot projects in India, with storage in volcanic rocks, etc. Storage projects in large-capacity coal mines such as those in Romania, Serbia or Bulgaria, to discuss common issues with neighboring countries, can create an exchange of knowledge with those countries on long and very long-term storage of CO
2
in coal mines, with an obvious gain in greening the atmosphere and in the health of the environment.
The main objective of this paper is to highlight the importance of core competences as an important catalyst to enable a sustainable transition of business models to Industry 5.0. According to our ...research based on a scientific methodology, we illustrated that Industry 4.0 might greatly affect the labor market by introducing ITC, AI, IR and AR that will change many jobs in most areas of activity. One alternative solution to diminish these negative effects is to accommodate and prepare the shift to a more human-centric approach. In order to better implement this alternative solution and to generate mid- to long-run positive effects (from an economic, social and environmental perspective), we consider it is imperative that human resources be prepared to understand and to use new technologies. We have focused our research context on European countries. We found that only a part of the European Union Member Countries benefit from the use of human resources with advanced digital skills. Under these circumstances, we consider that only some countries will be able to face the challenges generated by the transition to Industry 5.0, while others, the emergent countries, such as Romania, will have to intensify the complex process of designing competitive and coherent strategies and implement a more efficient and effective mix of policies. This will help to better capitalize the potential sustainable competitive advantage of industries 4.0 and 5.0.
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