Novi rezultati u projektiranju i mjerenju antena za osobne pokretne komunikacije

Mobile communications are taking more and more importance in everyday life, creating the need for smaller and lighter mobile terminals. Unlike the electronic circuits, the size of an antenna is not technology related, but imposed by the wavelength of a given application. This makes antenna miniaturization to an art of compromise between size and radiation performances. In this presentations we will first state the limitations of antenna miniaturization, by reminding of the well known laws linking gain, bandwidth and antenna size. Then some well known ways to reduce antennas sizes will be reviewed and illustrated on a practical example designed and realized in our laboratory. Finally, we will deal with the non trivial problem of small antenna measurement: the problems encountered when measuring small antenna will be presented and some clues on how to proceed correctly will be given.Pokretne komunikacije postaju sve važnije u svakodnevnom životu, a time se povećava potreba za što manjim i lakšim pokretnim komunikacijskim uređajima. Za razliku od elektroničkih sklopova, veličina antene nije određena stupnjem tehnološkog razvoja već je zadana frekvencijskim područjem koje se koristi za određenu primjenu. Zato je minijaturizacija antena umjetnost kompromisa između malih izmjera i dobrih osobina zračenja. U ovom su radu ograničenja minijaturizacije antena prikazana kroz povezanost dobitaka, širine pojasa i izmjera antene. Zatim su opisani neki uobičajeni postupci za smanjivanje izmjera antena. Njihova je primjena prikazana na praktičnoj izvedbi koja je projektirana i izrađena u našem laboratoriju. Konačno se razmatraju problemi pri mjerenjima malih antena: izneseni su problemi koji su uočeni pri mjerenju malih antena kao i naputci za njihovo prevladavanje

Fast approximate Barnes interpolation: illustrated by Python-Numba implementation fast-barnes-py v1.0

Barnes interpolation is a method that is widely used in geospatial sciences like meteorology to remodel data values recorded at irregularly distributed points into a representative analytical field. When implemented naively, the effort to calculate Barnes interpolation depends on the product of the number of sample points N and the number of grid points W×H, resulting in a computational complexity of O(N⋅W⋅H). In the era of highly resolved grids and overwhelming numbers of sample points, which originate, e.g., from the Internet of Things or crowd-sourced data, this computation can be quite demanding, even on high-performance machines. This paper presents new approaches of how very good approximations of Barnes interpolation can be implemented using fast algorithms that have a computational complexity of O(N+W⋅H). Two use cases in particular are considered, namely (1) where the used grid is embedded in the Euclidean plane and (2) where the grid is located on the unit sphere.</p

Why did Swiss citizens vote to ban tobacco advertising?

In February 2022, Swiss citizens agreed to modify the Swiss Constitution to ban tobacco advertising reaching children and adolescents. This case study analyses the arguments used by both opponents and supporters of the constitutional amendment. Opponents argued that the proposed regulation went too far, threatened the economy, restricted personal freedom, was superfluous as the current law already protected youth and that it opened the door to marketing bans of other harmful products. Proponents focused on youth protection and invoked the burden of smoking on public health and the fact that advertising bans are an effective evidence-based measure. A comparison with previous campaigns to ban tobacco advertising that had failed suggests factors accounting for the positive vote in 2022. These include the strategic framing of youth protection, the separation of tobacco from other issues (such as alcohol advertising), the deteriorating image of the tobacco industry and the ability of the proponents to mobilise a broad coalition of health and youth organisations, with improved funding and communication. The lessons may be instructive for other campaigns seeking to regulate commercial determinants of health

Towards a Precise Parton Luminosity Determination at the CERN LHC

A new approach to determine the LHC luminosity is investigated. Instead of employing the proton-proton luminosity measurement, we suggest to measure directly the parton-parton luminosity. It is shown that the electron and muon pseudorapidity distributions, originating from the decay of W+, W- and Z0 bosons produced at 14 TeV pp collisions (LHC), constrain the x distributions of sea and valence quarks and antiquarks in the range from about 3 x 10**-4 to about 10**-1 at a Q**2 of about 10**4 GeV**2. Furthermore, it is demonstrated that, once the quark and antiquark structure functions are constrained from the W+,W- and Z0 production dynamics, other quark-antiquark related scattering processes at the LHC like q-qbar --> W+W- can be predicted accurately. Thus, the lepton pseudorapidity distributions provide the key to a precise parton luminosity monitor at the LHC, with accuracies of about +-1% compared to the so far considered goal of +-5%.Comment: plain tex, 14 pages, 5 figure

Soft and Flexible Antennas on Permittivity Adjustable PDMS Substrates

This work presents novel techniques for producing substrates for flexible antennas. The technique we propose is based on the use of an already existing and widely used substrate material Polydimethylsiloxane (PDMS), where the dielectric properties of the substrate are adjusted by loading the PDMS with low or high permittivity inclusions. The low adhesion characteristics of PDMS are overcome by immersing the conducting parts of the antenna inside the substrate, at the same time sealing the antenna against the influence of dust, or water. A patch antenna prototype is realized and characterized. The built antenna is soft and flexible and it shows good radiation characteristics in terms of input matching and total gain. Measurements are in a good compliance with the simulation results

Influence of the Barrier Shape on Resonant Activation

The escape of a Brownian particle over a dichotomously fluctuating barrier is investigated for various shapes of the barrier. The problem of resonant activation is revisited with the attention on the effect of the barrier shape on optimal value of the mean escape time in the system. The characteristic features of resonant behavior are analyzed for barriers switching either between different heights, or "on" and "off" positions. PACS number(s): 05.10-a, 02.50.-r, 82.20.-wj.Comment: 7 pages, 8 figures, RevTex4. Manuscript has been revised and enhanced. Pictures have been made more clear and some of them have been cancelled. Additional references have been added. The paper has been submitted to Phys. Rev.