3,057 research outputs found
Photodoping of doped metal oxide nanocrystals for energy storage electrodes
No full textIn an era where global warming presents significant challenges, advancing materials science is crucial to meet the collective goals of emissions reduction and the transitioning to clean energy. This PhD thesis delves into the exploration of novel heterostructures comprising Indium Tin Oxide nanocrystals (ITO NCs) and diverse NCs or chemicals, for cutting-edge light-driven optoelectronic nanodevices and energy storage systems. This research integrates the processes of energy harvesting, conversion, and storage into a singular hybrid nanomaterial. The use of Doped Metal Oxide (MO) NCs is gaining increasing attention in the realm of nano-supercapacitors, thanks to their capacity to hold additional charges within their electronic structure, achieving high values of specific capacitance. These materials are able to store charges upon illumination with light (photocharging or photodoping), via the absorption of photons and generation of photocharges. During my research, I first studied the charge accumulation process in a solution-based process, moving then to realizing MO NCs films, to work with an electrochemically functional device.
The scalability of colloidal synthesis for ITO NCs was demonstrated, highlighting the consistency of material properties such as size control, optical features, and crystalline phase across different batch sizes. The transition from small-scale to larger batches was achieved with increased efficiency and minimized mechanical losses, maintaining the quality of the nanoparticles. The material obtained was then employed to test ITO NCs charge accumulation ability both in solutions and in solid state (i.e. thin films). At first, solution-dispersed ITO NCs were tested to explore the potential combination with various redox couples (e.g., TEMPO, crystal violet, and ferrocene) to act as reversible hole scavengers and enhance photodoping in ITO NCs. The findings demonstrated that ferrocene effectively increases charge density in doped metal oxide nanoparticles. ITO NCs were then employed to fabricate thin films, underscoring the critical role of fabrication protocols in achieving optimal film properties such as uniformity and thickness. Photodoping was investigated in thin films, revealing the ability of ITO NCs to undergo photo-charging even when in solid-state dispersion, preparing their use for the final application of the work. Finally, the prepared thin films were employed as photo-electrodes in a photo-electrochemical system. The research highlighted the promising role of ITO NCs/visible light-sensitizer thin films as photo-electrodes in supercapacitor applications, with capacitances reaching up to the order of 1 mF/cm2. The use of a visible light sensitizer illustrated its compatibility with ITO NCs, enhancing the system's capacitance under UV and green light. Overall, the thesis presented a work on the scalable synthesis, photodoping capabilities, thin film fabrication, and photo-electrochemical applications of ITO NCs. The potential applications in energy conversion, storage, and photo-electrocatalysis position these findings at the forefront of sustainable energy research, opening doors to new innovations in solar energy technologies
An assessment of the impact of possible CAP reform scenarios on Romanian agriculture
No full textUsing a simplified model, with key-variable the prices of two different possible scenarios of CAP reform after 2013 (moderate and radical), this paper present a comparison between the price effects of implementation of each reform scenario at 2015 horizon on Romanian agriculture. This short analysis shows that, under the presented hypotheses, the net welfare effect, due to the price changes, for the selected products, is positive in both reform scenarios, yet greater in the case of the radical reform. Integrated in the large context of Romanian development, it seems that the influence of CAP reform upon agriculture and rural areas will be most likely a gradual one: an interpenetration between the two scenarios is foreseeable, starting with the moderate reform that will dominate the period around 2013, the reform measures acquiring a more radical character afterwards.CAP reform, Romania, welfare effects, Agricultural and Food Policy,
Light-driven reversible charge transfers from ITO nanocrystals
No full textThe combination of semiconductors and redox active molecules for light-driven energy storage systems has emerged as a powerful solution for the exploitation of solar batteries. On account of this, transparent conductive oxide (TCO) nanocrystals (NCs) demonstrated to be interesting materials, thanks to the photo-induced charge accumulation enabling light harvesting and storage. The charge transfer process after light absorption, at the base of the proper use of these semiconductors, is a key step, often resulting in non-reversible transformations of the chemicals involved. However, if considering the photocharging through TCO NCs not only as a charge provider for the system but potentially as part of the storage role, the reversible transformation of the redox compound represents a crucial aspect. In this paper, we explore the possible interaction of indium tin oxide (ITO) NCs and typical redox mediators commonly employed in catalytic applications with a twofold scope of enhancing or supporting the light-induced charge accumulation on the metal oxide NC side and controlling the reversibility of the whole process. The work presented focuses on the effect of the redox properties on the doped metal oxide response, both from the stability point of view and the photodoping performance, by monitoring the changes in the optical behavior of ITO/redox hybrid systems upon ultraviolet illumination
Rich, Sturmian, and trapezoidal words
No full textIn this paper we explore various interconnections between rich words, Sturmian words, and trapezoidal words. Rich words, first introduced by the second and third authors together with J. Justin and S. Widmer, constitute a new class of finite and infinite words characterized by having the maximal number of palindromic factors. Every finite Sturmian word is rich, but not conversely. Trapezoidal words were first introduced by the first author in studying the behavior of the subword complexity of finite Sturmian words. Unfortunately this property does not characterize finite Sturmian words. In this note we show that the only trapezoidal palindromes are Sturmian. More generally we show that Sturmian palindromes can be characterized either in terms of their subword complexity (the trapezoidal property) or in terms of their palindromic complexity. We also obtain a similar characterization of rich palindromes in terms of a relation between palindromic complexity and subword complexity
Bismuth telluride iodide monolayer flakes with nonlinear optical response obtained via gold-assisted mechanical exfoliation
No full textBismuth telluride iodide (BiTeI) is a layered material known as Rashba semiconductor, which is promising for several applications such as spintronics, nonlinear optics, and energy-related devices. Due to its layered structure and low cleavage energy, BiTeI is particularly suitable for producing two-dimensional (2D) BiTeI crystals, allowing for the development of devices at the nanoscale. However, traditional methods of mechanically exfoliating BiTeI have encountered significant challenges. To address this, we used the so-called gold-assisted mechanical exfoliation to successfully obtain 2D BiTeI flakes. Through extensive characterization employing a range of techniques including Raman spectroscopy and second-harmonic generation (SHG) measurements, we examine the morphological, structural, and chemical properties of the gold-assisted mechanically exfoliated BiTeI flakes. We confirm their crystalline nature while also providing information about strain and defects present within the flakes. Moreover, SHG measurements revealed a significant nonlinear optical response, and the non-centrosymmetric structure observed in these flakes can be attributed to quantum confinement effects and the absence of phase-matching requirements typically found in bulk nonlinear crystals
Characterization Results for the Poset Based Representation of Topological Relations - I: Introduction and Models
No full text@article{DBLP:journals/informaticaSI/ForlizziN99,
author = {Luca Forlizzi and
Enrico Nardelli},
title = {Characterization Results for the Poset Based Representation
of Topological Relations - I: Introduction and Models.},
journal = {Informatica (Slovenia)},
volume = {23},
number = {2},
year = {1999},
bibsource = {DBLP, http://dblp.uni-trier.de}
Characterization Results for the Poset Based Representation of Topological Relations - II: Intersection and Union
No full text@article{DBLP:journals/informaticaSI/ForlizziN00,
author = {Luca Forlizzi and
Enrico Nardelli},
title = {Characterization Results for the Poset Based Representation
of Topological Relations - II: Intersection and Union.},
journal = {Informatica (Slovenia)},
volume = {24},
number = {1},
year = {2000},
bibsource = {DBLP, http://dblp.uni-trier.de}
System-on-chip Computing and Interconnection Architectures for Telecommunications and Signal Processing
No full textThis dissertation proposes novel architectures and design techniques targeting SoC building blocks for telecommunications and signal processing applications.
Hardware implementation of Low-Density Parity-Check decoders is approached at both the algorithmic and the architecture level. Low-Density Parity-Check codes are a promising coding scheme for future communication standards due to their outstanding error correction performance.
This work proposes a methodology for analyzing effects of finite precision arithmetic on error correction performance and hardware complexity. The methodology is throughout employed for co-designing the decoder. First, a low-complexity check node based on the P-output decoding principle is designed and characterized on a CMOS standard-cells library. Results demonstrate implementation loss below 0.2 dB down to BER of 10^{-8} and a saving in complexity up to 59% with respect to other works in recent literature. High-throughput and low-latency issues are addressed with modified single-phase decoding schedules. A new "memory-aware" schedule is proposed requiring down to 20% of memory with respect to the traditional two-phase flooding decoding. Additionally, throughput is doubled and logic complexity reduced of 12%. These advantages are traded-off with error correction performance, thus making the solution attractive only for long codes, as those adopted in the DVB-S2 standard. The "layered decoding" principle is extended to those codes not specifically conceived for this technique. Proposed architectures exhibit complexity savings in the order of 40% for both area and power consumption figures, while implementation loss is smaller than 0.05 dB.
Most modern communication standards employ Orthogonal Frequency Division Multiplexing as part of their physical layer. The core of OFDM is the Fast Fourier Transform and its inverse in charge of symbols (de)modulation. Requirements on throughput and energy efficiency call for FFT hardware implementation, while ubiquity of FFT suggests the design of parametric, re-configurable and re-usable IP hardware macrocells. In this context, this thesis describes an FFT/IFFT core compiler particularly suited for implementation of OFDM communication systems. The tool employs an accuracy-driven configuration engine which automatically profiles the internal arithmetic and generates a core with minimum operands bit-width and thus minimum circuit complexity. The engine performs a closed-loop optimization over three different internal arithmetic models (fixed-point, block floating-point and convergent block floating-point) using the numerical accuracy budget given by the user as a reference point. The flexibility and re-usability of the proposed macrocell are illustrated through several case studies which encompass all current state-of-the-art OFDM communications standards (WLAN, WMAN, xDSL, DVB-T/H, DAB and UWB). Implementations results are presented for two deep sub-micron standard-cells libraries (65 and 90 nm) and commercially available FPGA devices. Compared with other FFT core compilers, the proposed environment produces macrocells with lower circuit complexity and same system level performance (throughput, transform size and numerical accuracy).
The final part of this dissertation focuses on the Network-on-Chip design paradigm whose goal is building scalable communication infrastructures connecting hundreds of core. A low-complexity link architecture for mesochronous on-chip communication is discussed. The link enables skew constraint looseness in the clock tree synthesis, frequency speed-up, power consumption reduction and faster back-end turnarounds. The proposed architecture reaches a maximum clock frequency of 1 GHz on 65 nm low-leakage CMOS standard-cells library. In a complex test case with a full-blown NoC infrastructure, the link overhead is only 3% of chip area and 0.5% of leakage power consumption.
Finally, a new methodology, named metacoding, is proposed. Metacoding generates correct-by-construction technology independent RTL codebases for NoC building blocks. The RTL coding phase is abstracted and modeled with an Object Oriented framework, integrated within a commercial tool for IP packaging (Synopsys CoreTools suite). Compared with traditional coding styles based on pre-processor directives, metacoding produces 65% smaller codebases and reduces the configurations to verify up to three orders of magnitude
A General Formulation to Describe Empirical Rainfall Thresholds for Landslides
No full textAbstractIn this paper, a brief description of the Generalized FLaIR Model (GFM, De Luca and Versace, 2016) is provided, that is able to reproduce all the empirical thresholds proposed in literature, aimed to forecast landslides triggered by rainfall. In particular, this paper focuses on Antecedent Precipitation (AP) schemes. The paper demonstrates that these are particular solutions of the GFM and will exemplify this using AP schemes for NE Italy1, Seattle2 and Nicaragua - El Salvador3
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