Polytechnic University of Bucharest
Recent publications
The goal of this study is to create new variations of the well-known Hermite-Hadamard inequality (-inequality) for preinvex interval-valued functions (preinvex-s). We develop several additional inequalities for the class of functions whose product is preinvex-s. The findings described here would be generalizations of those found in previous studies. Finally, we obtain the Hermite-Hadamard-Fejér inequality with the support of preinvex interval-valued functions. Some new and classical special cases are also obtained. Moreover, some nontrivial examples are given to check the validity of our main results.
Due to its inherent properties and wide availability, cellulose acetate is an extremely competitive candidate for the production of polymeric membranes. However, for best results in particular applications, membrane modification is required in order to minimize unwanted interactions and introduce novel characteristics to the pristine polymer. In this study, the surface of commercial cellulose acetate membranes was functionalized with 4'-aminobenzo-15-crown-5 ether, using a covalent bonding approach. The main goal was the improvement of the membranes biomineralization ability, thus making them prospective materials for bone regeneration applications. The proposed reaction mechanism was confirmed by XPS and NMR analysis while the presence of the functionalization agents in the membranes structure was showed by ATR FT-IR and Raman spectra. The effects of the functionalization process on the morphology, thermal and mechanical properties of the membranes were studied by SEM, TGA and tensile tests. The obtained results revealed that the cellulose acetate membranes were successfully functionalized with crown ether and provided a good understanding of the interactions that took place between the polymer and the functionalization agents. Moreover, promising results were obtained during the Taguchi biomineralization studies. SEM images, EDX mapping and XRD spectra indicating that the CA-AB15C5 membranes have a superior Ca2+ ions retention ability, this causing an accentuated calcium phosphate deposition on the modified polymeric fibers, compared to the neat CA membrane.
Polymer nanocomposites, which are characterized by a high dielectric permittivity, are intensively studied for microelectronic devices and energy storage applications. Poly(vinylidene fluoride) (PVDF) has a higher dielectric permittivity among polymers, is flexible, lightweight and easy to be processed. One route to enhance its mechanical and dielectric properties is the addition of inorganic nanofillers. Therefore, PVDF was melt compounded with nanosilica in various proportions, from 5 to 30 wt%. For enhancing the stored and released electric energy densities, polyaniline (PANI) was obtained in situ on the surface of nanosilica in both acid and basic media; further the nanosilica particles coated with PANI were incorporated in PVDF by melt compounding to improve the dielectric properties by adding new interfaces. The addition of nanosilica in PVDF led to a strong increase in its storage modulus without reducing its good thermal stability. Moreover, an important increase in PVDF permittivity was determined by increasing content of nanosilica in nanocomposites. PANI coating influenced both thermal and mechanical properties and led to nanocomposites with more stable dielectric permittivity and lower dielectric loss than neat PVDF at frequencies between tens Hz and tens kHz, which is very important for energy storage applications.
Background: Acne has a high impact on patients being a chronic, common, and visible skin condition. Knowledge regarding treatment improves outcomes. The Cardiff Acne Disability Index (CADI) is commonly used in clinical practice for quality-of-life assessment. It has been validated in many languages, however, not in Romanian. Aims: To validate the Romanian adaptation of the CADI and educational materials for acne patients. Patients and method: A 12-week prospective cross-sectional Web-based study, including 3rd- to 5th-year medical students attending our university was conducted. We obtained permission from the CADI copyright owner and performed the steps of the standardized translation process. The Romanian CADI adaptation was delivered online in a test-retest setup, during which participants were offered acne educational materials and completed a knowledge evaluation questionnaire. Results: A total of 95 complete answers were analyzed. The Romanian CADI adaptation showed good internal consistency, with Cronbach's α = 0.807 in the first application and Cronbach's α = 0.839 in the second. High test-retest reliability was observed, with interclass correlation coefficient ICC = 0.987 and Spearman's rank correlation coefficient rs = 0.970 for the overall CADI scores between the two administrations. The mean baseline score in the knowledge evaluation questionnaire was 15.52 points (±1.556), with a statistically significant improvement after exposure to the educational material (Z = -7.207, p < 0.001). This material was considered useful or very useful by 78(82.8%) participants. Conclusion: Romanian acne patients can benefit from CADI, a reliable and disease-specific tool for quality-of-life evaluation, together with validated, guideline-aligned educational material in their language.
In this paper, by using some generalized convexity and differentiability (of Fréchet-type) hypotheses of the involved functionals, we establish several connections amongst the solutions of some new (weak) vector-controlled variational-type inequalities and (weak, proper) efficient solutions associated with certain multiobjective controlled variational problems. Also, the notion of invex set with respect to some given functions has an important role for proving the main results derived in the paper. The illustrative application, given in the end of the paper, provides the physical motivation of the problem under study.
A thorough understanding of biological species and emerging nanomaterials requires, among other efforts, their in-depth characterization through optical techniques capable of nano-resolution. Nanoscopy techniques based on tip-enhanced optical effects have gained tremendous interest over the past years, given their potential to obtain optical information with resolutions limited only by the size of a sharp probe interacting with focused light, irrespective of the illumination wavelength. Although their popularity and number of applications is rising, tip-enhanced nanoscopy (TEN) techniques still largely rely on probes that are not specifically developed for such applications, but for atomic force microscopy. This limits their potential in many regards, e.g., in terms of signal-to-noise ratio, attainable image quality, or extent of applications. We take the first steps toward next-generation TEN by demonstrating the fabrication and modeling of specialized TEN probes with known optical properties. The proposed framework is highly flexible and can be easily adjusted to be used with diverse TEN techniques, building on various concepts and phenomena, significantly augmenting their function. Probes with known optical properties could potentially enable faster and more accurate imaging via different routes, such as direct signal enhancement or facile, and ultra-fast, optical signal modulation. We consider that the reported development can pave the way for a vast number of novel TEN imaging protocols and applications, given the many advantages that it offers.
The development and analytical applications of electrochemical sensors based on antimony tin oxide (ATO)–Prussian blue (PB) screen-printed electrode (SPE) and PEDOT-PB modified glassy carbon electrode are presented. The ATO-PB electrode was successfully applied in the electrochemical detection of K⁺ ions. The detection and quantification limits value of 1.1 mM and of 3.7 mM, respectively, have been obtained. A high sensitivity of 0.035 A M⁻¹ cm⁻² has been also obtained. In addition, a sensing material based on poly(3,4-ethylenedioxythiophene) (PEDOT) and PB has been developed by a sinusoidal voltage electrochemical procedure and tested toward the potassium ion detection. The PEDOT-PB sensing material displayed the characteristic redox wave of the PB component and good analytical performance toward potassium ion detection. These results demonstrate the utility of the novel electrode materials in the development of electrochemical sensors for electroinactive analytes.
The scope of this study consists of setting up of an integrated cost-effective sampling & laboratory analyses procedure which delineates sampling, sub-sampling and analytical uncertainties in case of fine-grained extractive waste deposits. This procedure is designed to support the decision makers towards fine-grained waste deposits upcycling and land reclamation. This procedure consists of a balanced replicated sampling design (BRSD) coupled with a three split levels ANOVA data processing. The paper provides the readership with the mathematical backgrounds of the three split level ANOVA analysis (3L-ANOVA) and an Excel algorithm for its implementation. Also, the paper presents an example of implementation of the developed methods in the case of a Romanian iron ore tailings (IOT) old pond. The findings of the paper consist of: a) argues, based on OM, SEM-EDS, XRFS and XRD observations, that classical TOS is ineffective for fine-grained waste deposits; b) BRSD in conjunction with 3L-ANOVA analysis is the only approach fit for reliable characterization of the fine-grained stockpiles; c) sampling uncertainty is the critical factor of the uncertainty budget of the analyte concentration; d) Lilliefors approach is adequate for the hypothesis testing where or not the measurand is normal distributed; e) The outcomes of the BRDSD&3L-ANOVA investigations carried on Teliuc tailings, estimated at circa 5.5* 106 m3, consist mainly of mineral quantification at lot level i.e. quartz ∼54% (±7%), hematite ∼15% (±3%), calcite ∼11% (±3%), MgO 3% (±1%), Al2O3 9% (±2%). The concentrations of some CRMs like Ti, V, Ba, Y, W were found at ACE limits and their associated relative expanded uncertainties overpass 50%. Thus, the expanded uncertainties clearly depict the reliability of acquired data for the decision makers regarding waste valorization. f) The IOT into Teliuc can be upcycled as minerals for cement and ceramic industries as well as for geopolymer manufacture. Also, IOT can be downcycles as filler in road construction and mine closure. Finally, the Teliuc yard can be rehabilitated with zero-waste left behind. The data exactness provided by this procedure can be increased to any desirable level through increasing the number of collected items, but the cost of sampling and analyses increases proportionally. In such circumstances, the posted approach can be tailored at the stakeholder request as to safely underpin the decision to turn finegrained by-products into valuable secondary resources, facilitating a greater circularity of the mining industry.
The objective of this study was to establish and to mathematically describe the phenol degrading properties of a new Acinetobacter towneri CFII-87 strain, isolated from a bioreactor treating landfill leachate. For this purpose, the biokinetic parameters of phenol biodegradation at various initial phenol concentrations of the A. towneri CFII-87 strain have been experimentally measured, and four different mathematical inhibition models (Haldane, Yano, Aiba and Edwards models) have been used to simulate the substrate-inhibited phenol degradation process. The results of the batch biodegradation experiments show that the new A. towneri CFII-87 strain grows on and metabolizes phenol up to 1000 mg/L concentration, manifests significant substrate inhibition and lag time only at concentrations above 800 mg/L phenol, and has a maximum growth rate at 300 mg/L initial phenol concentration. The comparison of the model predictions with the experimental phenol and biomass data revealed that the Haldane, Aiba and Edwards models can be used with success to describe the phenol biodegradation process by A. towneri CFII-87, while the Yano model, especially at higher initial phenol concentrations, fails to describe the process. The best performing inhibition model was the Edwards model, presenting correlation coefficients of R2 > 0.98 and modelling efficiency of ME > 0.94 for the prediction of biomass and phenol concentrations on the validation datasets. The calculated biokinetic model parameters place this new strain among the bacteria with the highest tolerance towards phenol. The results suggest that the A. towneri CFII-87 strain can potentially be used in the treatment of phenolic wastewaters.
The incidence of isolated iliac artery aneurysms is approximately 2% and common iliac artery pseudoaneurysms are even rarer. A pseudoaneurysm is a localized hemorrhage as opposed to an actual aneurysm, which affects the entire vascular wall. They are typically asymptomatic and only detectable accidentally while looking for other causes. If large and symptomatic, they typically exhibit pressure symptoms as a result of the compression of the structures around them. Common symptoms include generalized stomach pain, urological problems, gastrointestinal bleeding, and neurological symptoms such as leg paralysis or sciatica-like back pain. Rarely, they may exhibit hemodynamic instability together with an aneurysm rupture, which has a high fatality rate. Due to the unique presentation, the diagnosis is typically rarely made and there is little experience with treating it. We report two cases of common iliac artery pseudoaneurysm found in two patients who had no notable medical history and who we chose to repair through the endovascular technique in the first case, an approach that has gained more ground for vascular repair worldwide, making it the current go-to method, and for the second case we chose a more traditional approach, through open surgery.
Bacterial cellulose (BC) is a biopolymer whose properties have been intensively studied, especially for biomedical applications. Since BC has no antimicrobial activity, it is necessary to use bioactive substances for developing wound healing applications. Another drawback of BC is the loss if its water retention capacity after dehydration. In order to overcome these problems, carboxymethyl cellulose (CMC) and turmeric extract (TE) were selected for the preparation of BC composites. Citric acid (CA) was used as the crosslinking agent. These composites were tested as potential antimicrobial wound dressing materials. TE-loaded BC–CMC composites were characterized in terms of their morphology, crystallinity, and thermal behavior. Swelling tests and curcumin-release kinetic analysis were also performed. All the composites tested had high swelling degrees, which is an advantage for the exudate adsorption from chronic wounds. The antibacterial potential of such composites was tested against Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Candida albicans (C. albicans). The in vitro cytotoxicity toward L929 fibroblast cells was studied as well. The obtained results allow us to recommend these composites as good candidates for wound dressing applications.
Mobile applications have rapidly grown over the past few decades to offer futuristic applications, such as autonomous vehicles, smart farming, and smart city. Such applications require ubiquitous, real-time, and secure communications to deliver services quickly. Toward this aim, sixth-generation (6G) wireless technology offers superior performance with high reliability, enhanced transmission rate, and low latency. However, managing the resources of the aforementioned applications is highly complex in the precarious network. An adversary can perform various network-related attacks (i.e., data injection or modification) to jeopardize the regular operation of the smart applications. Therefore, incorporating blockchain technology in the smart application can be a prominent solution to tackle security, reliability, and data-sharing privacy concerns. Motivated by the same, we presented a case study on public safety applications that utilizes the essential characteristics of artificial intelligence (AI), blockchain, and a 6G network to handle data integrity attacks on the crime data. The case study is assessed using various performance parameters by considering blockchain scalability, packet drop ratio, and training accuracy. Lastly, we explored different research challenges of adopting blockchain in the 6G wireless network.
These days, companies including Higher Education Institutions can no longer afford not to be innovative. They have to react with 4.0 concepts to secure their own existence. A future university graduate must easily cope with the requirements and skills of Industry 4.0, such as agile mindset, curiosity, reflection (in/on action), innovation, creativity, leadership, technology knowledge Artificial Intelligence (AI) methods, and AI-supported decision making. How exactly can Higher Education benefit from these approaches? This paper presents the paradigm shift in Engineering Education 4.0, considering high levels of volatility, uncertainty, complexity, and ambiguity (VUCA). Therefore, the paper proposes a future-ready Curriculum 4.0 for Industry 4.0 and a new mindset from content to context, from delivery to co-creation, and from training to business impact.
Suggested only a few years ago, green central banking has received a new impetus with the central bank interventions implemented in the wake of the COVID-19 pandemic. Several central banks, with the European Central Bank (ECB) and the Bank of England (BoE) being prominent examples, have stepped up their public communication on this issue in an effort to explain and justify their planned or ongoing policy actions. Carefully recorded and easy to find, these public communication messages are a rich source of insight into the process of monetary policy formation. In this article, we analyze the messages from two central banks, with the primary objective of identifying the narratives they use (if any) and describing the key features of these narratives, thus shedding new light on an ongoing process of policy change. A secondary objective of the article is to contribute to the growing literature related to the use of narratives in public policy by studying narratives in monetary policy through qualitative means, an approach that, to date, has received relatively little attention from scholars. To this end, we discuss two expectations related to the use of policy narratives derived from the literature. Thus, we hope to show how the two central banks devise and deploy narratives to help implement an unprecedented turnaround in monetary policy.
Energy efficiency plays an important role in energy systems all over the world, representing the most available and cheapest source of energy. Progress in energy efficiency translates into reduced consumption, reduced dependency on external suppliers of fossil fuels, mitigation of climate change, and improvement of quality of life. Given its tremendous importance for energy systems and national economies, this paper aims to offer salient insights on the performance of the countries of the European Union (EU-27) towards an energy-efficient future, bearing in mind the quantitative milestones of sustainable development goal 7 (SDG7) of the Agenda for Sustainable Development of the United Nations. The current research offers a new perspective and delivers a comprehensive, robust, and succinct model which provides insights on the performance of EU-27 member states based on appropriate quantitative key performance indicators related to energy efficiency. The results show that about 19% of EU-27 member states are in a leading position, while about 41% of EU-27 member states have modest performance, and about 14% are still lagging. The findings of this paper may open discussions to find better ways to valorise energy efficiency, and may offer support for legislators and other stakeholders in energy systems. Moreover, by benchmarking different types of national practices, the countries which are still struggling to use energy-efficiency measures may find suitable ways to accelerate transition to a more energy-efficient future.
Bio-based composites were developed from the epoxy derivatives of Lallemantia iberica oil and kraft lignin (ELALO and EpLnK), using UV radiation as a low energy consumption tool for the oxiranes reaction. To avoid the filler sedimentation or its inhomogeneous distribution in the oil matrix, different structure-directing agents (SDA) were employed: 1,3:2,4-dibenzylidene-D-sorbitol (DBS), 12-hydroxystearic acid (HSA) and sorbitan monostearate (Span 60). The SDA and EpLnK effect upon the ELALO-based formulations, their curing reaction and the performance of the resulting materials were investigated. Fourier-transform Infrared Spectrometry (FTIR) indicates different modes of molecular arrangement through H bonds for the initial ELALO-SDA or ELALO-SDA-EpLnK systems, also confirming the epoxy group’s reaction through the cationic mechanism for the final composites. Gel fraction measurements validate the significant conversion of the epoxides for those materials containing SDAs or 1% EpLnK; an increased EpLnK amount (5%), with or without SDA addition, conduced to an inefficient polymerization process, with the UV radiation being partially absorbed by the filler. Thermo-gravimetric and dynamic-mechanical analyses (TGA and DMA) revealed good properties for the ELALO-based materials. By loading 1% EpLnK, the thermal stability was improved to with 10 °C (for Td3%) and the addition of each SDA differently influenced the Tg values but also gave differences in the glassy and rubbery states when the storage moduli were interrogated, depending on their chemical structures. Water affinity and morphological studies were also carried out.
There has been a surge in interest in developing protective textiles and clothes to protect wearers from risks such as chemical, biological, heat, UV, pollution, and other environmental factors. Traditional protective textiles have strong water resistance but lack breathability and have a limited capacity to remove water vapor and moisture. Electrospun fibers and membranes have shown enormous promise in developing protective materials and garments. Textiles made up of electrospun fibers and membranes can provide thermal comfort and protection against a wide range of environmental threats. Because of their multifunctional properties, such as semi-conductivity, ultraviolet absorption, optical transparency, and photoluminescence, their low toxicity, biodegradability, low cost, and versatility in achieving diverse shapes, ZnO-based nanomaterials are a subject of increasing interest in the current review. The growing uses of electrospinning in the development of breathable and protective textiles are highlighted in this review.
Epidermoid cysts are most often benign cystic lesions, with uterine cervical localisation being very unusual. We present the case of a 52-year-old female patient diagnosed with an epidermoid cyst at the level of the uterine cervix. A bioptic and haemostatic uterine curettage was performed, followed by total hysterectomy with bilateral adnexectomy. The histopathologic analysis and immunohistochemical essay of the resection specimens confirmed the cervical epidermoid cyst. The presence of high-risk HPV (human papillomavirus) was only seen in the cervical mucosa. The exact etiopathogenesis is unknown, but postpartum cell implantation of reminiscent embryonic tissue can be involved in the development of these lesions.
The development of a porous free zone of the silicon cemented layer represents a scientific and technical challenge. The limitation of the effects of the Kirkendall–Frenkel phenomena requires the right control of the thermochemical processing parameters (temperature, time, and chemical) and thorough knowledge of the related interaction with the specific elements of the metallic matrix of the thermochemically processed product. Through the experimental programming method, the individual and cumulated effects of the thermochemical processing parameters on (Fe-Armco) high-purity iron cemented by silicon in ferrosilicon (FeSi75C) powdered solid media have been quantified. It was concluded that ferrosilicon with silicon concentrations higher than 60% (FeSi75C) represents a redoubtable active component, especially in a temperature range higher than 1100 °C. In the layer cemented with silicon, the presence of nitrogen was also observed, as a direct consequence of the composition of the medium used for cementation. The presence of this element is the predominant result of the manifestation of the ionic phenomenon of adsorption. The correlations between these parameters and the dimension of the porous free zone of the silicon cemented layer in the vicinity of the thermochemically processed surface have been determined.
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7,400 members
Tache Irina Andra
  • Department of Automatic Control and System Engineering
Ion I. Bucur
  • Department of Computers
Maria Joita
  • Department of Mathematics
Ioan Plotog
  • Department of Electronics Technology and Reliability
Florin Ciuprina
  • Faculty of Electrical Engineering
313, Splaiul Independentei, 060042, Bucharest, Romania
Head of institution
Rector Mihnea Costoiu