Environmental monitoring of low-ppb ammonia concentrations based on single-wall carbon nanotube chemiresistor gas sensors: Detection limits, response dynamics, and moisture effects

EUROSENSORS 2014, the XXVIII edition of the conference series.Under a Creative Commons license.We present single-wall carbon nanotube (SWCNT) chemiresistor gas sensor (CGS) operating at room temperature, displaying an enhanced sensitivity to NH3. Ammonia concentrations in the full range of the average [NH3] in a urban environment have been measured, and a detection limit of 3 ppb is demonstrated, which is well below the sensitivities so far reported for non- functionalized SWCNTs operating at room temperature. Different materials were tested as substrates, including cheap plastic flexible substrates. In addition to a careful preparation of the SWCNT layers, the low-ppb limit is also attained by revealing and properly tracking a fast dynamics during the desorption process. On the basis of these results a model of the CGS response vs time is proposed. When functionalized with indium-tin oxide nanoparticles, a sensitivity increase is detected, along with a remarkable selectivity towards moisture.Peer Reviewe

Numerical investigation of skin-stringer separation in post-buckled thermoplastic composite structures

LAUREA MAGISTRALECon la crescente richiesta di strutture aeronautiche sempre più leggere ed efficienti, la progettazione di componenti capaci di operare in regime di post-buckling senza comprometterne l’integrità strutturale sta assumendo un ruolo sempre più centrale. I compositi termoplastici si stanno affermando come una soluzione promettente per sfruttare in sicurezza tale regime, offrendo al contempo significative riduzioni di peso e costi di produzione. Tuttavia, la loro applicazione è attualmente limitata alle strutture secondarie, a causa della conoscenza ancora insufficiente dei complessi meccanismi di danneggiamento che li caratterizzano. Il presente lavoro si propone di sviluppare modelli agli elementi finiti a supporto dell’analisi della separazione tra skin e stringer in pannelli irrigiditi realizzati in composito termoplastico. L’impiego di elementi coesivi, generalmente adottati per i compositi termoindurenti, viene qui investigato per valutarne l’applicabilità ai materiali termoplastici. I risultati preliminari ottenuti su provini DCB (Double Cantilever Beam) mostrano che una legge coesiva bilineare non è in grado di prevedere accuratamente né il carico massimo né le prime fasi di propagazione del danno, restituendo una risposta eccessivamente fragile e non rappresentativa dell'aumento progressivo della reistenza a frattura tipicamente osservato nei termoplastici. Questo fenomeno, noto come effetto R-curve, è implementato nei modelli numerici mediante la sovrapposizione di due leggi coesive bilineari, con risultati che mostrano un miglior accordo con i dati sperimentali, sia nella fase di innesco che in quella di propagazione. Una volta validata su provini DCB, la metodologia viene estesa a configurazioni più complesse, come provini single-stringer sottoposti a prove Seven-Point Bending (7PB) e Four-Point Twisting (4PT), appositamente progettate per riprodurre in modo realistico le modalità di deformazione più critiche in regime di post-buckling. I risultati mettono in evidenza l’influenza delle diverse leggi coesive sulla risposta globale della struttura. In particolare, nella configurazione 7PB, una legge bilineare basata sui valori di propagazione può risultare adeguata a rappresentare la separazione tra skin e stringer, mentre nel caso 4PT l’introduzione dell’effetto R-curve in modo I comporta un sensibile incremento del carico di rottura previsto.With the increasing demand for lighter and more efficient aircraft structures, designing components to operate in the post-buckling regime without compromising structural integrity is becoming increasingly relevant. Thermoplastic composites have emerged as a promising solution to safely exploit this regime, offering further reductions in both weight and manufacturing costs. Nevertheless, due to insufficient knowledge of their complex failure mechanisms, implementation is still limited to secondary structures. This thesis aims to develop finite element models to support the investigation of skin–stringer separation in post-buckled thermoplastic composite stiffened panels. The cohesive zone modelling approach, typically used for thermoset composites, is here investigated for its applicability to thermoplastic materials. Preliminary double-cantilever beam (DCB) results reveal that a bilinear traction–separation law fails to accurately predict the peak load and the early stages of delamination propagation, resulting in a brittle-like response that does not reflect the progressive toughening behavior typical of thermoplastics. This phenomenon, commonly referred to as the R-curve effect, is incorporated into the finite element models through the superposition of two bilinear traction–separation laws. The resulting trilinear formulation improves correlation with experimental data in terms of both initiation and propagation, proving more suitable for modeling delamination in thermoplastics. The methodology is then extended to more complex configurations, such as single-stringer specimens subjected to Seven-Point Bending (7PB) and Four-Point Twisting (4PT), specifically designed to realistically reproduce the most critical post-buckling deformation modes. The results are analyzed in detail, focusing on load–displacement responses, delamination patterns, failure initiation, and mixed-mode conditions during damage propagation, highlighting the influence of different cohesive laws on the overall structural response. In the 7PB configuration, a bilinear law based on propagation values appears sufficient to reproduce the global separation behavior. In contrast, in the 4PT case, including an R-curve in Mode I results in significantly higher predicted failure loads

Build an Assessment Rubric of Student Creativity in Higher Education

[EN] Attention to student creativity has triggered a number of educational transformations in higher education. However, widespread measures of creativity in higher education are primary based on norm-referenced assessment, which provide minimal information of student performance against the learning development in creativity. In reponse to the lack of effective measures and criteria to link assessment with instruction in creativity education, this article discusses the process of building an assessment rubric of creativity based on the standards-referenced model. It is intended to help teachers and students better understand the learning objectives related to creativity, as well as to monitor and guide the development of student creativity. Xu, W.; Tognolini, J. (2022). Build an Assessment Rubric of Student Creativity in Higher Education. En 8th International Conference on Higher Education Advances (HEAd'22). Editorial Universitat Politècnica de València. 135-142. https://doi.org/10.4995/HEAd22.2022.1469513514

TRACKING THE INTERFACE STATES DYNAMICS AT CARBON-BASED NANOSTRUCTURES ON METAL BY NON-LINEAR PHOTOEMISSION SPECTROSCOPY

After single-layer graphene isolation in 2004, the scientific community has concentrated its efforts in the investigation of single-atom thin materials, due to their unique electronic properties, not shown by their bulk counterpart. Among this promising class of materials, two-dimensional carbon-based nanostructures have encountered a growing interest in nanotechnology, due to the huge variety of potential applications in which they are involved, from optoelectronics and photonics to energy generation, storage and solar cells. For the industrial realization of these devices a comprehensive understanding of the interaction between 2D carbon nanostructures and metallic substrates is necessary. An excellent tool to accomplish this aim is represented by the study of the electronic properties and dynamics of the states localized at the carbon nanostructures/metal interfacial region, being extremely sensitive to any modification at the surface. The investigation of these unoccupied electronic states has been accomplished applying femtosecond, high intensity laser pulses in the near-UV ranges to photoemission techniques

Signaling by EphrinB1 and Eph Kinases in Platelets Promotes Rap1 Activation, Platelet Adhesion, and Aggregation via Effector Pathways that Do Not Require Phosphorylation of EphrinB1

We have previously shown that platelets express 2 receptor tyrosine kinases, EphA4 and EphB1, and the Eph kinase ligand, ephrinB1m and proposed that transcellular Eph/ephrin interactions made possible by the onset of platelet aggregation promote the further growth and stability of the hemostatic plug. The present study examines how this might occur. The results show that clustering of either ephrinB1 or EphA4 causes platelets to adhere to immobilized firinogen via αIIbβ3. Adhesion occurs more slowly than with adenosine diphosphate (ADP) abd requires phosphatidylinositol 3 (PI3)—kinase and protein kinase C activity but not ephrinB1 phosphorylation. By itself, Eph and ephrin signaling is insufficient to cause aggregation or the binding of soluble fibrinogen, but it can potentiate aggregation initiated by a Ca++ ionophore or by agonists for thrombin and thromboxane receptors. It also enhances Rap1 activation without requiring ADP secretion, ephrinB1 phosphorylation, or the activation of PI3-kinase and Src. From this we conclude that (1) Eph/ephrin signaling enhances the ability of platelet agonists to cause aggregation provided that those agonists can increase cytosolic Ca++; (2) this is accomplished in part by activating Rap1; and (3) these effects require not phosphotyrosine-based interactions with the ephrinB1 cytoplasmic domain

Breaking HWQCS: a code-based signature scheme from high weight QC-LDPC codes

We analyse HWQCS, a code based signature scheme presented at ICISC 2023, which uses quasi-cyclic low density parity check codes (QC-LDPC). The scheme introduces high Hamming weight errors and signs each message using a fresh ephemeral secret key rather than using only one secret key, so to avoid known attacks on QC-LDPC signature schemes. In this paper, we show that the signatures of HWQCS leak substantial information concerning the ephemeral keys and formally describe this behaviour. Furthermore, we show that for each security level, we can exploit the leakage to efficiently reconstruct partial secret data from very few signatures, and finally mount a universal forgery attack

Information Set Decoding for Ring-Linear Code

Information set decoding (ISD) algorithms currently offer the most powerful tool to solve the two archetypal problems of coding theory, namely the Codeword Finding Problem and the Syndrome Decoding Problem. Traditionally, ISD have primarily been studied for linear codes over finite fields, equipped with the Hamming metric. However, recently, other possibilities have also been explored. These algorithms have been adapted to different ambient spaces and metrics, such as the rank metric or the Lee metric over $\mathbb Z_m$. In this paper, we show that it is possible to leverage the ring structure to construct more efficient decoding algorithms than those obtained by simply adapting ISD. In particular, we describe a framework that can be applied to any additive metric including Hamming and Lee, and that can be adapted to the case of the rank metric, providing algorithms to solve the two aforementioned problems, along with their average computational costs

A Post-Quantum Digital Signature Scheme from QC-LDPC Codes

We propose a novel post-quantum code-based digital signature algorithm whose security is based on the difficulty of decoding Quasi-Cyclic codes in systematic form, and whose trapdoor relies on the knowledge of a hidden Quasi-Cyclic Low-Density-Parity-Check (QC-LDPC) code. The utilization of Quasi-Cyclic (QC) codes allows us to balance between security and key size, while the LDPC property lighten the encoding complexity, thus the signing algorithm complexity, significantly