Search results for "frequency"
showing 10 items of 2158 documents
Small fish in big ponds : Connections of green finance assets to commodity and sectoral stock markets
2022
We analyze return and volatility connectedness of the rising green asset and the well-established US industry stock and commodity markets from September 2010 to July 2021. We find that the time-varying return and volatility connectedness have exhibited serious crisis jumps. Some individual assets of both the green and commodity markets are in connection to the US sectoral stock market returns, and the volatility connections are even more common than the return connections. Furthermore, some financial and economic uncertainty indicators manifest positive impacts from the volatility of some `big pond markets for e.g. commodities, whereas some others affect the connectedness negatively. Additi…
Multisensorā pieeja bieži sastopamo vārdu atpazīšanas prasmju attīstībai angļu valodā no 5 līdz 6 gadu veciem bērniem
2017
Lasīšana ir viena no būtiskākajām prasmēm, ko skolēni apgūst sākumskolā. Daudziem skolēniem bieži sastopamie vārdi angļu valodā sagādā grūtības, jo tie nepakļaujas zināmajām lasīšanas stratēģijām. Turklāt bieži sastopamie vārdi parādās lielos daudzumos lasīšanas tekstos. Diploma darba autore ir novērojusi, ka ir bērni no 5 līdz 6 gadu vecumam, kuriem grūtības sagādā bieži sastopamus vārdus atpazīšana, tādēļ nav augsts lasīšanas ātrums un izpratne par tekstu. Kā pētījumu metodi autore ir izvēlējusies gadījuma pētījumu, lai izpētītu, kā multisensorā pieeja var palīdzēt 5 līdz 6 gadu veciem skolēniem atpazīt bieži sastopamos vārdus. Pētījums tika veikts 2016.gadā no 17.oktobra līdz 9.decembrim…
Rotational effects on the oscillation frequencies of newly born proto-neutron stars
2003
In this paper we study the effects of rotation on the frequencies of the quasi-normal modes of a proto-neutron star (PNS) born in a gravitational collapse during the first minute of life. Our analysis starts a few tenths of seconds after the PNS formation, when the stellar evolution can be described by a sequence of equilibrium configurations. We use the evolutionary models developed by Pons et al. (1999; 2001) that describe how a non rotating star cools down and contracts while neutrino diffusion and thermalization processes dominate the stellar dynamics. For assigned values of the evolution time, we set the star into slow rotation and integrate the equations of stellar perturbations in th…
Optimal Resource Allocation in Multi-Hop Networks: Contention vs. Scheduling
2014
CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) is actually the most used method in ad-hoc networks for transmitting on a contending medium, even if it shows poor performance in presence of hidden nodes. To increase performance, we propose an algorithm that combines CSMA and TDMA (Time Division Multiple Access) approaches. The adopted solution consists of grouping contending nodes in non-interfering subsets and granting a different numbers of time slots to different groups, while using the CSMA to manage medium access among nodes belonging to the same subset. An optimization procedure to assign the time slots to each subset of nodes and to find an equilibrium between contention …
Experimental Observation of a Large Low-Frequency Band Gap in a Polymer Waveguide
2018
The quest for large and low-frequency band gaps is one of the principal objectives pursued in a number of engineering applications, ranging from noise absorption to vibration control, and to seismic wave abatement. For this purpose, a plethora of complex architectures (including multiphase materials) and multiphysics approaches have been proposed in the past, often involving difficulties in their practical realization. To address the issue of proposing a material design that enables large band gaps using a simple configuration, in this study we propose an easy-to-manufacture design able to open large, low-frequency complete Lamb band gaps exploiting a suitable arrangement of masses and stif…
Multi-Chip RFID Antenna Integrating Shape-Memory Alloys for Detection of Thermal Thresholds
2011
Low-cost wireless measurement of objects' temperature is one of the greatest expectation of radiofrequency identification technology for the so many applications in cold supply-chain control and safety assessment in general. In this context, the paper proposes a dual-chip UHF tag embedding shape memory alloys (SMA) able to transform the variation of the tagged item's temperature into a permanent change of antenna radiation features. This event-driven antenna is hence able to selectively activate the embedded microchips according to the temperature above or below a given threshold. A general design methodology for the resulting two-ports tag antenna is here introduced and then applied to pro…
Development of vocal performance in 5th grade children - A longitudinal study of choral class singing
2009
The primary aim of the study was to assess the effects of choral class singing on vocal performance in primary school children. In particular, changes of the singing voice in terms of voice range profiles (VRP) and dysphonia severity index (DSI) were measured over the period of one school year. A further aim was to compare the effects of choral singing and regular music curriculum. A total of 50 5th-graders were assigned to two groups. Tuition of the choral singing group (n = 32) entailed a focus on singing in class as well as weekly 30-minute-sessions of special vocal training in small groups. Children in the regular music tuition group (n = 18), which also included singing, were given ext…
A Telemetry, Tracking, and Command Antennas System for Small-Satellite Applications
2019
Circularly polarized (CP) antennas are used in space applications for telemetry tracking and command (TT&
On the use of composite indicators for mobile communications network management in smart sustainable cities
2020
Beyond 5G networks will be fundamental towards enabling sustainable mobile communication networks. One of the most challenging scenarios will be met in ultra-dense networks that are deployed in densely populated areas. In this particular case, mobile network operators should benefit from new assessment metrics and data science tools to ensure an effective management of their networks. In fact, incorporating architectures allowing a cognitive network management framework could simplify processes and enhance the network&rsquo
A Channel-Aware Adaptive Modem for Underwater Acoustic Communications
2021
Acoustic underwater channels are very challenging, because of limited bandwidth, long propagation delays, extended multipath, severe attenuation, rapid time variation and large Doppler shifts. A plethora of underwater communication techniques have been developed for dealing with such a complexity, mostly tailoring specific applications scenarios which can not be considered as one-size-fits-all solutions. Indeed, the design of environment-specific solutions is especially critical for modulations with high spectral efficiency, which are very sensitive to channel characteristics. In this paper, we design and implement a software-defined modem able to dynamically estimate the acoustic channel c…