Numerical synthesis of filtering antennas

Dizertační práce je zaměřena na kompletní metodiku návrhu tří a čtyř prvkových flíčkových anténních řad, které neobsahují žádné filtrující části a přesto se chovají jako filtrující antény (filtény). Návrhová metodika kombinuje přístup pro návrh filtrů s přístupem pro anténní řady a zahrnuje tvarování frekvenčních odezev činitele odrazu a normovaného realizovaného zisku. Směr hlavního laloku přes pracovní pásmo je kontrolován také. S cílem kontrolovat tvary uvedených charakteristik, nové gi koeficienty jsou představeny pro návrh filtrujících anténních řad. Návrhová metodika byla ověřena na tří a čtyř prvkové filtrující anténní řadě přes frekvenční pásmo od 4,8 GHz do 6,8 GHz, pro šířku pásma celé struktury od 7 % do 14 % a pro požadovanou úroveň činitele odrazu od –10 dB do –20 dB. Celá metodika byla podpořena výrobou a měřením šesti testovacích vzorků filtrujících anténních řad s rozdílnými konfiguracemi. Ve všech případech se simulované a naměřené výsledky dobře shodují.The dissertation thesis is focused on a complete design methodology of a three and four-element patch antenna arrays which are without any filtering parts and yet behave like a filtering antenna (filtenna). This design combines filter and antenna approaches and includes shaping the frequency response of the reflection coefficient and the modelling of the frequency response of the normalized realized gain. The frequency response of the main lobe direction is controlled as well. In order to control the shape of these responses, a set of gi coefficients for designing the filtering antenna array are obtained. The design methodology was verified on the three-element and four-element filtennas over the frequency range from 4.8 GHz to 6.8 GHz; for fractional bandwidth from 7 % to 14 % and for level of the reflection coefficient from –10 dB to –20 dB. The whole design methodology was supported by manufacturing and measuring six test cases of the filtering antenna array with different configurations. Simulated and measured results show a good agreement in all cases.

Tunable ARC frequency filter

Tato bakalářská práce se zabývá problematikou laditelných ARC kmitočtových filtrů. Úvodní kapitola se obecně zaměřuje na základní pojmy z oblasti kmitočtových filtrů, jako je matematické vyjádření přenosové funkce, typy selektivních filtrů, toleranční pole apod. V další části jsou popsány samotné ARC filtry vyšších řádů a jejich kaskádní řazení, zejména ARC pásmová zádrž a možnosti její realizace. Dále je uvedena konkrétní realizace ARC filtru typu pásmová zádrž s návrhy součástek pro přelaďování frekvence v kmitočtovém pásmu od 10 kHz do 100 kHz a s nastavovaným činitelem jakosti. V neposlední řadě tato práce obsahuje návrhy desek plošných spojů (DPS) analogové části ARC kmitočtového filtru a digitální části pro přelaďování kmitočtu F0 a nastavování činitele jakosti Q za pomoci digitálních potenciometrů. Mimo jiné je zde nastíněn vývojový diagram programu pro digitální řízení.This bachelor thesis deals with ARC frequency tunable filters. The introductory chapter generally focuses on the basic terms of the frequency filters, such as the mathematical expression of the transfer function, types of selective filters, tolerant field, etc. The next section describes the actual higher-order ARC filters and cascade sequencing, especially ARC band reject and possibilities of its implementation. Following is a concrete realization of the ARC filter to band reject with suggestions for tuning the frequency components in the frequency range 10 kHz to 100 kHz and retuning quality factor. Finally, this work contains the printed circuit board (PCB) design of the ARC frequency analog and digital filter section for tuning F0 frequency and quality factor Q setting using digital potentiometers. Furthermore, it also outlines the flowchart of the program for digital control.

Planar fractal filter on defected ground substrate

Tato diplomová práce se zabývá problematikou planárních filtrů kombinujících fraktální motivy a porušenou zemní plochu. Práci lze rozdělit na tři hlavní části. První část se zaměřuje na obecné poznatky z oblasti fraktálních motivů, jako jsou např. tvorba Minkowského ostrova a Kochovy smyčky. Dále je popsán princip činnosti struktur s porušenou zemní plochou a stručně jsou představeny filtry kombinující fraktální motivy a porušenou zemní plochu. Vlastnosti zkoumaných struktur jsou následně ověřeny pomocí programů CST Microwave Studio a Ansoft HFSS. V druhé části práce jsou porovnávány odlišně porušené zemní plochy pod 50 přenosovým vedením a jsou vytvořeny konvenční ekvivalenty k ověřovaným filtrům. Filtry jsou simulovány a porovnány. Poslední část obsahuje přepočet ověřovaných filtrů na substrát Arlon 25N, simulaci, výrobu, měření a konfrontaci s konvečním filtrem na substrátu s porušenou zemní plochou.The diploma thesis is focused on the design of planar filters combining fractal layouts and defected ground substrates. The diploma thesis can be divided into three main parts. First, basic knowledge about fractals is presented (creation of Minkowski Island and Koch loop, e.g.). Then, the principle of defected ground structure is described, and a combination of fractal motives with a defected ground structure is briefly introduced. Properties of investigated structures are verified by CST Microwave Studio and Ansoft HFSS. Second, different defected ground structures under the 50 transmission line are designed, and conventional equivalent filters are created. Filters are simulated and compared. In final, the investigated filters are recalculated for the substrate Arlon 25N, simulated, manufactured, measured and confronted with a conventional filter on the defected ground substrate.

Three-element filtering antenna array designed by the equivalent circuit approach

©2016 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.This paper introduces a design methodology of a third-order three-element patch array that has no filtering parts and yet behaves like a filtering antenna (filtenna). The design approach includes shaping the frequency response of the reflection coefficient and modeling the frequency response of the normalized realized gain. In order to control the shape of these two responses, gi coefficients of an equivalent low-pass prototype filter are derived for designing the third-order filtering antenna array. The design methodology was verified over the frequency band from 4.8 to 6.8 GHz for levels of the reflection coefficient from -10 to -20 dB and for fractional bandwidths from 7% to 14%. The whole design methodology was supported by manufacturing and measuring three third-order filtering antenna arrays designed with different configurations. The simulated and measured results show good agreement in all cases.Peer ReviewedPostprint (author's final draft

To err is human, to correct is public health: a systematic review examining poor quality testing and misdiagnosis of HIV status.

INTRODUCTION: In accordance with global testing and treatment targets, many countries are seeking ways to reach the "90-90-90" goals, starting with diagnosing 90% of all people with HIV. Quality HIV testing services are needed to enable people with HIV to be diagnosed and linked to treatment as early as possible. It is essential that opportunities to reach people with undiagnosed HIV are not missed, diagnoses are correct and HIV-negative individuals are not inadvertently initiated on life-long treatment. We conducted this systematic review to assess the magnitude of misdiagnosis and to describe poor HIV testing practices using rapid diagnostic tests. METHODS: We systematically searched peer-reviewed articles, abstracts and grey literature published from 1 January 1990 to 19 April 2017. Studies were included if they used at least two rapid diagnostic tests and reported on HIV misdiagnosis, factors related to potential misdiagnosis or described quality issues and errors related to HIV testing. RESULTS: Sixty-four studies were included in this review. A small proportion of false positive (median 3.1%, interquartile range (IQR): 0.4-5.2%) and false negative (median: 0.4%, IQR: 0-3.9%) diagnoses were identified. Suboptimal testing strategies were the most common factor in studies reporting misdiagnoses, particularly false positive diagnoses due to using a "tiebreaker" test to resolve discrepant test results. A substantial proportion of false negative diagnoses were related to retesting among people on antiretroviral therapy. Conclusions HIV testing errors and poor practices, particularly those resulting in false positive or false negative diagnoses, do occur but are preventable. Efforts to accelerate HIV diagnosis and linkage to treatment should be complemented by efforts to improve the quality of HIV testing services and strengthen the quality management systems, particularly the use of validated testing algorithms and strategies, retesting people diagnosed with HIV before initiating treatment and providing clear messages to people with HIV on treatment on the risk of a "false negative" test result

Risk factors for Coronavirus disease 2019 (Covid-19) death in a population cohort study from the Western Cape province, South Africa

Risk factors for coronavirus disease 2019 (COVID-19) death in sub-Saharan Africa and the effects of human immunodeficiency virus (HIV) and tuberculosis on COVID-19 outcomes are unknown. We conducted a population cohort study using linked data from adults attending public-sector health facilities in the Western Cape, South Africa. We used Cox proportional hazards models, adjusted for age, sex, location, and comorbidities, to examine the associations between HIV, tuberculosis, and COVID-19 death from 1 March to 9 June 2020 among (1) public-sector “active patients” (≥1 visit in the 3 years before March 2020); (2) laboratory-diagnosed COVID-19 cases; and (3) hospitalized COVID-19 cases. We calculated the standardized mortality ratio (SMR) for COVID-19, comparing adults living with and without HIV using modeled population estimates.Among 3 460 932 patients (16% living with HIV), 22 308 were diagnosed with COVID-19, of whom 625 died. COVID19 death was associated with male sex, increasing age, diabetes, hypertension, and chronic kidney disease. HIV was associated with COVID-19 mortality (adjusted hazard ratio [aHR], 2.14; 95% confidence interval [CI], 1.70–2.70), with similar risks across strata of viral loads and immunosuppression. Current and previous diagnoses of tuberculosis were associated with COVID-19 death (aHR, 2.70 [95% CI, 1.81–4.04] and 1.51 [95% CI, 1.18–1.93], respectively). The SMR for COVID-19 death associated with HIV was 2.39 (95% CI, 1.96–2.86); population attributable fraction 8.5% (95% CI, 6.1–11.1)

Independent and combined effects of improved water, sanitation, and hygiene, and improved complementary feeding, on child stunting and anaemia in rural Zimbabwe: a cluster-randomised trial.

BACKGROUND: Child stunting reduces survival and impairs neurodevelopment. We tested the independent and combined effects of improved water, sanitation, and hygiene (WASH), and improved infant and young child feeding (IYCF) on stunting and anaemia in in Zimbabwe. METHODS: We did a cluster-randomised, community-based, 2 × 2 factorial trial in two rural districts in Zimbabwe. Clusters were defined as the catchment area of between one and four village health workers employed by the Zimbabwe Ministry of Health and Child Care. Women were eligible for inclusion if they permanently lived in clusters and were confirmed pregnant. Clusters were randomly assigned (1:1:1:1) to standard of care (52 clusters), IYCF (20 g of a small-quantity lipid-based nutrient supplement per day from age 6 to 18 months plus complementary feeding counselling; 53 clusters), WASH (construction of a ventilated improved pit latrine, provision of two handwashing stations, liquid soap, chlorine, and play space plus hygiene counselling; 53 clusters), or IYCF plus WASH (53 clusters). A constrained randomisation technique was used to achieve balance across the groups for 14 variables related to geography, demography, water access, and community-level sanitation coverage. Masking of participants and fieldworkers was not possible. The primary outcomes were infant length-for-age Z score and haemoglobin concentrations at 18 months of age among children born to mothers who were HIV negative during pregnancy. These outcomes were analysed in the intention-to-treat population. We estimated the effects of the interventions by comparing the two IYCF groups with the two non-IYCF groups and the two WASH groups with the two non-WASH groups, except for outcomes that had an important statistical interaction between the interventions. This trial is registered with ClinicalTrials.gov, number NCT01824940. FINDINGS: Between Nov 22, 2012, and March 27, 2015, 5280 pregnant women were enrolled from 211 clusters. 3686 children born to HIV-negative mothers were assessed at age 18 months (884 in the standard of care group from 52 clusters, 893 in the IYCF group from 53 clusters, 918 in the WASH group from 53 clusters, and 991 in the IYCF plus WASH group from 51 clusters). In the IYCF intervention groups, the mean length-for-age Z score was 0·16 (95% CI 0·08-0·23) higher and the mean haemoglobin concentration was 2·03 g/L (1·28-2·79) higher than those in the non-IYCF intervention groups. The IYCF intervention reduced the number of stunted children from 620 (35%) of 1792 to 514 (27%) of 1879, and the number of children with anaemia from 245 (13·9%) of 1759 to 193 (10·5%) of 1845. The WASH intervention had no effect on either primary outcome. Neither intervention reduced the prevalence of diarrhoea at 12 or 18 months. No trial-related serious adverse events, and only three trial-related adverse events, were reported. INTERPRETATION: Household-level elementary WASH interventions implemented in rural areas in low-income countries are unlikely to reduce stunting or anaemia and might not reduce diarrhoea. Implementation of these WASH interventions in combination with IYCF interventions is unlikely to reduce stunting or anaemia more than implementation of IYCF alone. FUNDING: Bill & Melinda Gates Foundation, UK Department for International Development, Wellcome Trust, Swiss Development Cooperation, UNICEF, and US National Institutes of Health.The SHINE trial is funded by the Bill & Melinda Gates Foundation (OPP1021542 and OPP113707); UK Department for International Development; Wellcome Trust, UK (093768/Z/10/Z, 108065/Z/15/Z and 203905/Z/16/Z); Swiss Agency for Development and Cooperation; US National Institutes of Health (2R01HD060338-06); and UNICEF (PCA-2017-0002)

Modification of antimycobacterial active sulphonamides

The importance of the searching for novel antimycobacterial active agents is continually increasing with growing mycobacterial resistance to currently used drugs. However, the resistance-related problems are also associated with other bacteria and fungi. The systematic modification of compounds with a known antimicrobial activity represents one of the possible approaches to overcome this problem. Sulphonamide derivatives may be considered to be such a kind of compounds. That is why we synthesized various sulphathiazole derivatives. Amides were obtained by the reaction of sulphathiazole with appropriate acyl chlorides, substituted ureas from corresponding isocyanates. These ureas were cyclized via oxalyl chloride to form substituted 2,4,5-trioxoimidazolidines. Among derivatives evaluated for their antimycobacterial action, 4-(3- phenethylureido)-N-(thiazol-2-yl)benzenesulphonamide showed the highest activity. Its minimum inhibitory concentrations (MIC) against Mycobacterium tuberculosis My 331/88 (4 µmol/l) were superior to those obtained for sulphathiazole. In the case of nontuberculous mycobacteria (M. avium My 330/88, M. kansasii My 235/88 and M. kansasii My 6509/96), their activities were comparable (≥ 2 µmol/l). Amides showed also a significant antimycobacterial activity, especially against M...

Fraktálová dimenze lomové plochy tvárného porušení

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta metalurgie a materiálového inženýrství. Katedra (636) materiálového inženýrstv