Greinar - HR

Varanleg URI fyrir þennan undirflokkhttps://hdl.handle.net/20.500.11815/83

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Niðurstöður 1 - 20 af 249

Plotkin's call-by-value λ-calculus as a modal calculus
(Elsevier BV, 2022-06) Espírito Santo, José; Pinto, Luís; Uustalu, Tarmo; Department of Computer Science (RU); Tölvunarfræðideild (HR); School of Technology (RU); Tæknisvið (HR)
In the authors' previous analysis of the calling paradigms call-by-name and call-by-value through Girard's and Gödel's embeddings into the S4 modal logic, an asymmetry remains: the two paradigms are unified by the call-by-box paradigm of the modal target, but only for call-by-name can one say that the paradigm exists, up to isomorphism, inside the modal target. In this paper, we show that, by pushing further the modal analysis, a symmetric situation is revealed, in that ordinary and Plotkin's λ-calculi are shown to truly co-exist inside a simple modal calculus.
Simulation of short pulse photoemission in a microdiode with implications for optimal beam brightness
(Institute of Electrical and Electronics Engineers (IEEE), 2024) Árnason, Hákon Örn; Torfason, Kristinn; Manolescu, Andrei; Valfells, Ágúst; Department of Engineering; Verkfræðideild; School of Technology; Tæknisvið
Molecular dynamics simulations, with full Coulomb interaction, are used to model short-pulse photoemission from a finite area in a microdiode. We demonstrate three emission regimes, source-limited emission, space-charge-limited emission for short pulses, and space-charge-limited emission for the steady state. We show that beam brightness is at a maximum during the transition from the source-limited emission regime to the space-charge-limited emission regime for short pulses. From our simulations, it is apparent that the emitter spot size is an important factor when estimating the critical charge density for short-pulse electron emission and that simple capacitive models may considerably underestimate the total charge emitted.
Germanium coated silicon nanowires as human respiratory sensing device
(IEEE, 2022-10-12) Aghabalaei Fakhri, Elham; Sultan, Muhammad Taha; Manolescu, Andrei; Ingvarsson, Snorri; Svavarsson, Halldor; Department of Engineering (RU); Verkfræðideild (HR); School of Technology (RU); Tæknisvið (HR); Science Institute (UI); Raunvísindastofnun (HÍ)
We report on germanium coated silicon nanowires structures synthesized with metal assisted chemical etching and qualify their functionality as human respiratory sensor. The sensors were made from p-type single-crystalline (100) silicon wafers using a silver catalyzed top-down etching, afterwards coated by 50 nm germanium thin layer using a magnetron sputtering. The germanium post-treatment was performed by rapid thermal annealing at 450 and 700◦C. The sensors were characterized by X-ray diffraction diffractogram and scanning electron microscopy. It is demonstrated that the sensors are highly sensitive as human breath detectors, with rapid response and frequency detectability. They are also shown to be a good candidate for human respiratory disease diagnoses.
Piezoresistance characterization of silicon nanowires in uniaxial and isostatic pressure variation
(MDPI AG, 2022-08-23) Aghabalaei Fakhri, Elham; Plugaru, Rodica; Sultan, Muhammad Taha; Kristinsson, Thorsteinn; Árnason, Hákon Örn; Plugaru, Neculai; Manolescu, Andrei; Ingvarsson, Snorri; Svavarsson, Halldor; Department of Engineering (RU); Verkfræðideild (HR); School of Technology (RU); Tæknisvið (HR); Science Institute (UI); Raunvísindastofnun (HÍ)
Silicon nanowires (SiNWs) are known to exhibit a large piezoresistance (PZR) effect, making them suitable for various sensing applications. Here, we report the results of a PZR investigation on randomly distributed and interconnected vertical silicon nanowire arrays as a pressure sensor. The samples were produced from p-type (100) Si wafers using a silver catalyzed top-down etching process. The piezoresistance response of these SiNW arrays was analyzed by measuring their I-V characteristics under applied uniaxial as well as isostatic pressure. The interconnected SiNWs exhibit increased mechanical stability in comparison with separated or periodic nanowires. The repeatability of the fabrication process and statistical distribution of measurements were also tested on several samples from different batches. A sensing resolution down to roughly 1 mbar pressure was observed with uniaxial force application, and more than two orders of magnitude resistance variation were determined for isostatic pressure below atmospheric pressure.
iContractBot: A chatbot for smart contracts’ specification and code generation
(IEEE, 2021-06) Qasse, Ilham; Mishra, Shailesh; Hamdaqa, Mohammad; Department of Computer Science (RU); Tölvunarfræðideild (HR); School of Technology (RU); Tæknisvið (HR)
Recently, Blockchain technology adoption has expanded to many application areas due to the evolution of smart contracts. However, developing smart contracts is non-trivial and challenging due to the lack of tools and expertise in this field. A promising solution to overcome this issue is to use Model-Driven Engineering (MDE), however, using models still involves a learning curve and might not be suitable for non-technical users. To tackle this challenge, chatbot or conversational interfaces can be used to assess the non-technical users to specify a smart contract in gradual and interactive manner. In this paper, we propose iContractBot, a chatbot for modeling and developing smart contracts. Moreover, we investigate how to integrate iContractBot with iContractML, a domainspecific modeling language for developing smart contracts, and instantiate intention models from the chatbot. The iContractBot framework provides a domain-specific language (DSL) based on the user intention and performs model-to-text transformation to generate the smart contract code. A smart contract use case is presented to demonstrate how iContractBot can be utilized for creating models and generating the deployment artifacts for smart contracts based on a simple conversation
popSTR2 enables clinical and population-scale genotyping of microsatellites
(Oxford University Press (OUP), 2019-12-05) Kristmundsdottir, Snædis; Eggertsson, Hannes P; Arnadottir, Gudny A; Halldórsson, Bjarni; Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
Summary: popSTR2 is an update and augmentation of our previous work ‘popSTR: a population-based microsatellite genotyper’. To make genotyping sensitive to inter-sample differences, we supply a kernel to estimate sample-specific slippage rates. For clinical sequencing purposes, a panel of known pathogenic repeat expansions is provided along with a script that scans and flags for manual inspection markers indicative of a pathogenic expansion. Like its predecessor, popSTR2 allows for joint genotyping of samples at a population scale. We now provide a binning method that makes the microsatellite genotypes more amenable to analysis within standard association pipelines and can increase association power. Availability and implementation: https://github.com/DecodeGenetics/popSTR. Contact: snaedisk@decode.is or bjarni.halldorsson@decode.is Supplementary information: Supplementary data are available at Bioinformatics online.
Disputed dams: Mapping the divergent stakeholder perspectives, expectations, and concerns over hydropower development in Iceland and SwitzerlandDisputed dams: Mapping the divergent stakeholder perspectives, expectations, and concerns over hydropower development in Iceland and Switzerland
(Elsevier, 2021-02) Voegeli, Guillaume; Finger, David C.; Verkfræðideild (HR); Department of Engineering (RU); School of Technology (RU); Tæknisvið (HR)
The evaluation of the stakeholders’ perception of new hydropower projects is essential for assessing public acceptance, ensuring local involvement, and identifying feasible and desirable changes towards sustainable development. This study uses the concept of causal diagrams (CD) to identify the individual perspectives of stakeholders of two new hydropower projects, one in Switzerland (Val d’Ambra project) and one in Iceland (Hvammvirkjun project). For this purpose, semi-structured interviews with relevant stakeholders were conducted, which were then categorized into 5 interest groups. Using the software Atlas.ti, we identified and sequenced the perceived causality of impact pathways of the two projects. The results are exposed in two series of 10 topical causal networks, and two aggregated diagrams. For each case, CDs expose the complexity of multi-sequenced causalities between elements of a very heterogeneous nature, as expected and reported by stakeholders. This approach enables the identification of inter- and intra-group conflicting perspectives, and perceived uncertainties, concerning both subjectives matters along with much more tangible and predictable aspects. Our method enables the identification of areas where further research or better transfer of information between stakeholders is required. It also exposes how hydropower impacts can differ in time and space, when in one case study, intracommunity tensions and conflicts were identified at the earliest project stage, along with psychological distress of some local residents. Based on the presented CD, we conclude that this method can facilitate communication and problem-solving in complex social-environmental situations amid multiple stakeholder categories, which heterogeneity should not be underestimated.
Failure of Healthcare Provision for Attention-Deficit/Hyperactivity Disorder in the United Kingdom: A Consensus Statement
(Frontiers Media SA, 2021-03-19) Young, Susan; Asherson, Philip; Lloyd, Tony; Absoud, Michael; Arif, Muhammad; Colley, William Andrew; Cortese, Samuele; Cubbin, Sally; Doyle, Nancy; Morua, Susan Dunn; Ferreira-Lay, Philip; Gudjonsson, Gisli; Ivens, Valerie; Jarvis, Christine; Lewis, Alexandra; Mason, Peter; Newlove-Delgado, Tamsin; Pitts, Mark; Read, Helen; van Rensburg, Kobus; Zoritch, Bozhena; Skirrow, Caroline; Department of Psychology (RU); Sálfræðideild (HR); School of Social Sciences (RU); Samfélagssvið (HR)
Background: Despite evidence-based national guidelines for ADHD in the United Kingdom (UK), ADHD is under-identified, under-diagnosed, and under-treated. Many seeking help for ADHD face prejudice, long waiting lists, and patchy or unavailable services, and are turning to service-user support groups and/or private healthcare for help. Methods: A group of UK experts representing clinical and healthcare providers from public and private healthcare, academia, ADHD patient groups, educational, and occupational specialists, met to discuss shortfalls in ADHD service provision in the UK. Discussions explored causes of under-diagnosis, examined biases operating across referral, diagnosis and treatment, together with recommendations for resolving these matters. Young et al. Failure of ADHD Healthcare Provision Results: Cultural and structural barriers operate at all levels of the healthcare system, resulting in a de-prioritization of ADHD. Services for ADHD are insufficient in many regions, and problems with service provision have intensified as a result of the response to the COVID-19 pandemic. Research has established a range of adverse outcomes of untreated ADHD, and associated long-term personal, social, health and economic costs are high. The consensus group called for training of professionals who come into contact with people with ADHD, increased funding, commissioning and monitoring to improve service provision, and streamlined communication between health services to support better outcomes for people with ADHD. Conclusions: Evidence-based national clinical guidelines for ADHD are not being met. People with ADHD should have access to healthcare free from discrimination, and in line with their legal rights. UK Governments and clinical and regulatory bodies must act urgently on this important public health issue.
Space–charge limited current in nanodiodes: Ballistic, collisional, and dynamical effects
(AIP Publishing, 2021-03-14) Zhang, Peng; ANG, YEE SIN; Garner, Allen; Valfells, Agust; Luginsland, John; ANG, LAY KEE; Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
This Perspective reviews the fundamental physics of space–charge interactions that are important in various media: vacuum gap, air gap, liquids, and solids including quantum materials. It outlines the critical and recent developments since a previous review paper on diode physics [Zhang et al. Appl. Phys. Rev. 4, 011304 (2017)] with particular emphasis on various theoretical aspects of the space–charge limited current (SCLC) model: physics at the nano-scale, time-dependent, and transient behaviors; higher-dimensional models; and transitions between electron emission mechanisms and material properties. While many studies focus on steady-state SCLC, the increasing importance of fast-rise time electric pulses, high frequency microwave and terahertz sources, and ultrafast lasers has motivated theoretical investigations in time-dependent SCLC. We particularly focus on recent studies in discrete particle effects, temporal phenomena, time-dependent photoemission to SCLC, and AC beam loading. Due to the reduction in the physical size and complicated geometries, we report recent studies in multi-dimensional SCLC, including finite particle effects, protrusive SCLC, novel techniques for exotic geometries, and fractional models. Due to the importance of using SCLC models in determining the mobility of organic materials, this paper shows the transition of the SCLC model between classical bulk solids and recent two-dimensional (2D) Dirac materials. Next, we describe some selected applications of SCLC in nanodiodes, including nanoscale vacuum-channel transistors, microplasma transistors, thermionic energy converters, and multipactor. Finally, we conclude by highlighting future directions in theoretical modeling and applications of SCLC.
Perceptions and Attitudes of Correctional Staff Toward ADHD—A Challenging Disorder in Everyday Prison Life
(Frontiers Media SA, 2021-01-28) Buadze, Anna; Friedl, Nadine; Schleifer, Roman; Young, Susan; Schneeberger, Andres; Liebrenz, Michael; Sálfræðideild (HR); Department of Psychology (RU); Samfélagssvið (HR); School of Social Sciences (RU)
Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder that is associated with risk-taking behaviors, poor self-control, and interpersonal difficulties. Affected individuals have an increased probability of involvement with the criminal justice system, contributing to a higher rate of arrest, and imprisonment compared with the general population; they are also inadequately treated once sentenced. Because prison staff play a central role in the identification of inmates with mental disorders, they could well be key to improving provision of care. There is however little knowledge of the conceptions, perceptions, and attitudes of prison staff toward ADHD. Such information could help to identify starting points for awareness training and further implementation of specific ADHD treatment. To bridge this gap, we undertook a study based on a qualitatively-driven mixed methods design, combining qualitative data collection in the form of narrative interviews with 19 prison staff from a Swiss correctional facility with quantitative data collection in the form of a survey that included the Attitudes toward Prisoners scale. The interviews were analyzed with QSR NVIVO 11 and a qualitative content analysis approach was used to evaluate findings. Prison staff were generally aware of ADHD and its symptomology, believing it to a be "real," but "fashionable" disorder and favoring hereditary-genetic or biological explanatory models for its development. They viewed inmates with ADHD rather negatively, as complicating correctional efforts, and perceived them as sticking out, as tying up more resources and as frequently being involved in confrontations. Our findings suggest that difficulties in pragmatic aspects of communication and language comprehension may be perceived "as not listening or following instructions," creating additional tensions. Consequently, inmates with ADHD are more often exposed to disciplinary sanctions, such as solitary confinement-an intervention deemed "necessary" by staff. Therefore, staff training on ADHD might need to cover evidence on adverse effects. Non-pharmacological interventions for treatment were preferred and considered to be highly efficacious. Skepticism toward pharmacological treatment prevailed, even when benefits from stimulant medication were described. Interestingly, this skepticism was not the result of negative experiences with the misuse and diversion of stimulants. Acceptance of multimodal treatment among prison staff may require customized strategies.
EM-Driven Multi-Objective Optimization of a Generic Monopole Antenna by Means of a Nested Trust-Region Algorithm
(MDPI AG, 2021-04-27) Bekasiewicz, Adrian; Koziel, Slawomir; Plotka, Piotr; Zwolski, Krzysztof; Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
Antenna structures for modern applications are characterized by complex and unintuitive topologies that are difficult to develop when conventional, experience-driven techniques are of use.In this work, a method for the automatic generation of antenna geometries in a multi-objective set up has been proposed. The approach involves optimization of a generic spline-based radiator with an adjustable number of parameters using a nested, trust region-based algorithm. The latter iteratively increases the dimensionality of the radiator in order to gradually improve its performance. The method has been used to generate a set of nine antenna designs, representing a trade-off between minimization of reflection within 3.1 GHz to 10.6 GHz and a reduction of size. The properties of the optimized designs vary along the Pareto set from−10 dB to−20 dB and from 230 mm2to 757 mm2for the first and second objectives, respectively. The presented design approach has been validated against a genuine, population-based optimization routine. Furthermore, the smallest Pareto-optimal design has been compared to the antennas from the literature.
Compact 4 × 4 butler matrix with non‐standard phase differences for IoT applications
(Institution of Engineering and Technology (IET), 2021-05) Bekasiewicz, Adrian; Koziel, Slawomir; Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
Butler matrices represent a popular class of feeding networks for antenna arrays. Large dimensions and the lack of flexibility in terms of achievable output phase difference make conventional Butler structures of limited use for modern communication devices. In this work, a com-pact planar 4×4 matrix with non-standard relative phase shifts of –30,150, –120, and 60° has been proposed. The structure is designed to operate at the centre frequency of 2.45 GHz. Small dimensions of 31.3×22.9 mm make it useful for Internet of Things applications. The structure operates from 2.35 to 2.55 GHz, which covers the industrial, scientific and medical bandwidth. At the centre frequency, the measured amplitude and phase imbalance are 1.65 dB and±4.3°, respectively. The proposed circuit has been compared to the state-of-the-art structures from the literature.
Low-Cost Unattended Design of Miniaturized 4 × 4 Butler Matrices with Nonstandard Phase Differences
(MDPI AG, 2021-01-27) Bekasiewicz, Adrian; Koziel, Slawomir; Engineering Optimization & Modeling Center (EOMC) (RU); Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
Design of Butler matrices dedicated to Internet of Things and 5th generation (5G) mobile systems-where small size and high performance are of primary concern-is a challenging task that often exceeds capabilities of conventional techniques. Lack of appropriate, unified design approaches is a serious bottleneck for the development of Butler structures for contemporary applications. In this work, a low-cost bottom-up procedure for rigorous and unattended design of miniaturized 4 x 4 Butler matrices is proposed. The presented approach exploits numerical algorithms (governed by a set of suitable objective functions) to control synthesis, implementation, optimization, and fine-tuning of the structure and its individual building blocks. The framework is demonstrated using two miniaturized matrices with nonstandard output-port phase differences. Numerical results indicate that the computational cost of the design process using the presented framework is over 80% lower compared to the conventional approach. The footprints of optimized matrices are only 696 and 767 mm(2), respectively. Small size and operation frequency of around 2.6 GHz make the circuits of potential use for mobile devices dedicated to work within a sub-6 GHz 5G spectrum. Both structures have been benchmarked against the state-of-the-art designs from the literature in terms of performance and size. Measurements of the fabricated Butler matrix prototype are also provided.
Enumeration of Permutation Classes and Weighted Labelled Independent Sets
(DIiscrete Mathematics Theoretical Computer Science, 2021-03) Nadeau, Émile; Úlfarsson, Henning Arnór; Tölvunarfræðideild (HR); Department of Computer Science (RU); Tæknisvið (HR); School of Technology (RU)
In this paper, we study the staircase encoding of permutations, which maps a permutation to a staircase grid with cellsfilled with permutations. We consider many cases, where restricted to a permutation class, the staircase encoding be-comes a bijection to its image. We describe the image of thoserestrictions using independent sets of graphs weightedwith permutations. We derive the generating function for the independent sets and then for their weighted coun-terparts. The bijections we establish provide the enumeration of permutation classes. We use our results to uncoversome unbalanced Wilf-equivalences of permutation classesand outline how to do random sampling in the permutationclasses. In particular, we cover the classes Av (2314,3124), Av (2413,3142), Av(2413,3124), Av(2413,2134) and Av (2314,2143), as well as many subclasses.
Electrodeposition of aluminium-titanium alloys from molten fluoride-oxide electrolytes
(Elsevier BV, 2021-02) Awayssa, Omar; Saevarsdottir, Gudrun; Meirbekova, Rauan; Haarberg, Geir Martin; Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
This study reports the direct production of an aluminium-titanium alloy during aluminium electrolysis in fluoride-based melts. Experiments were conducted in a laboratory cell dedicated to current efficiency mea-surements. The temperature was varied from 960 to 980 ◦C at a cathodic current density (CCD) of 0.9 A/cm2 and a cryolite ratio (CR) of 2.2. The titanium content was up to 1.0 wt%. Titanium was added in the form of a TiO2 precursor. Bath samples were collected regularly and analyzed with ICP-MS to observe the decay of titanium during electrolysis. The current efficiency for electrodeposition of Al–Ti alloys was estimated to be at least around 90%. The surface of the solidified metal deposits was mostly flat, but some deposits were partially deformed.
Electrochemical production of Al–Mn alloys during the electrodeposition of aluminium in a laboratory cell
(Elsevier BV, 2021-04) Awayssa, Omar; Haarberg, Geir Martin; Meirbekova, Rauan; Saevarsdottir, Gudrun Arnbjorg; Verkfræðideild (HR); Department of Engineering (RU); Tæknisvið (HR); School of Technology (RU)
This study reports the direct production of an aluminium–manganese alloy during aluminium electrolysis in fluoride-based melts. Experiments were conducted in a laboratory cell dedicated for current efficiency measurements. The temperature was varied from 965–980 °C at a cathodic current density (CCD) of 0.9 A/cm2 and a cryolite ratio (CR) of 2.2. The manganese content was up to 3.0 wt%. Manganese was added in the form of Mn2O3. Bath samples were collected regularly and analyzed with ICP-MS to observe the decay of manganese during electrolysis. It was possible to produce Al-Mn alloys of up to 21 wt. % Mn. Current efficiency for the electrodeposition of Al–Mn alloy was estimated to be in the range of 93%. Current efficiencies with respect to aluminium were estimated. The solidified surfaces of the metal deposits were mostly flat, but some were deformed.
Surrogate-Assisted Design of Checkerboard Metasurface for Broadband Radar Cross-Section Reduction
(Institute of Electrical and Electronics Engineers (IEEE), 2021) Abdullah, Muhammad; Koziel, Slawomir; Engineering Optimization & Modeling Center (EOMC) (RU); Verkfræðideild (HR); Department of Engineering (RU); ; ; Tæknisvið (HR); School of Technology (RU)
Multiple-input multiple-output (MIMO) antennas are considered to be the key components of fifth generation (5G) mobile communications. One of the challenges pertinent to the design of highly integrated MIMO structures is to minimize the mutual coupling among the antenna elements. The latter arises from two sources, the coupling in the free space and the coupling currents propagating on a ground plane. In this paper, an array of H-shaped parasitic patches is proposed as a decoupling structure for compact MIMO antennas to reduce propagation of the coupling currents on a shared ground plane. The proposed decoupling structure is generic, and it can be applied to different antenna configurations as demonstrated in the work. Furthermore, it is employed to develop a new high-performance compact dual-band MIMO structure featuring acceptable level of element coupling at both operating frequencies. The design is validated both numerically and experimentally. The mutual coupling levels are less than -17 dB and -20 dB, with the total efficiency of 89% and 90%, and the realized gain of 6.6 dB and 7 dB at the two resonant frequencies of 5 GHz and 6 GHz, respectively. Topological complexity of the compact MIMO systems featuring elaborated decoupling structures, a large number of geometry parameters, as well as the necessity of handling multiple performance figures, constitute the major challenges of antenna design, in particular, its re-design for various specifications. To alleviate these difficulties, the paper also provides a procedure for rapid geometry scaling of the dual-band MIMO antennas. Our approach is based on inverse surrogate modeling methods, and results in numerically-derived expressions that enable a precise control over the operating antenna bands within broad ranges thereof (from 4 GHz to 8 GHz for the lower band, and from 1.1 to 1.3 ratio of the upper to lower operating frequency). The aforementioned procedure is accompanied by an optimization-based design refinement scheme. A practical utility of the procedure is corroborated using multiple verification case studies as well as physical measurements of the antenna designed for the exemplary set of performance specifications.
A Novel Versatile Decoupling Structure and Expedited Inverse-Model-Based Re-Design Procedure for Compact Single-and Dual-Band MIMO Antennas
(Institute of Electrical and Electronics Engineers (IEEE), 2021) Abdullah, Muhammad; Koziel, Slawomir; Engineering Optimization & Modeling Center (EOMC) (RU); Tæknisvið (HR); School of Technology (RU)
Multiple-input multiple-output (MIMO) antennas are considered to be the key components of fifth generation (5G) mobile communications. One of the challenges pertinent to the design of highly integrated MIMO structures is to minimize the mutual coupling among the antenna elements. The latter arises from two sources, the coupling in the free space and the coupling currents propagating on a ground plane. In this paper, an array of H-shaped parasitic patches is proposed as a decoupling structure for compact MIMO antennas to reduce propagation of the coupling currents on a shared ground plane. The proposed decoupling structure is generic, and it can be applied to different antenna configurations as demonstrated in the work. Furthermore, it is employed to develop a new high-performance compact dual-band MIMO structure featuring acceptable level of element coupling at both operating frequencies. The design is validated both numerically and experimentally. The mutual coupling levels are less than -17 dB and -20 dB, with the total efficiency of 89% and 90%, and the realized gain of 6.6 dB and 7 dB at the two resonant frequencies of 5 GHz and 6 GHz, respectively. Topological complexity of the compact MIMO systems featuring elaborated decoupling structures, a large number of geometry parameters, as well as the necessity of handling multiple performance figures, constitute the major challenges of antenna design, in particular, its re-design for various specifications. To alleviate these difficulties, the paper also provides a procedure for rapid geometry scaling of the dual-band MIMO antennas. Our approach is based on inverse surrogate modeling methods, and results in numerically-derived expressions that enable a precise control over the operating antenna bands within broad ranges thereof (from 4 GHz to 8 GHz for the lower band, and from 1.1 to 1.3 ratio of the upper to lower operating frequency). The aforementioned procedure is accompanied by an optimization-based design refinement scheme. A practical utility of the procedure is corroborated using multiple verification case studies as well as physical measurements of the antenna designed for the exemplary set of performance specifications.
Problem gambling and suicidality in England: secondary analysis of a representative cross-sectional survey
(Elsevier BV, 2020-07) Wardle, H.; John, A.; Dymond, Simon; McManus, S.; Sálfræðideild (HR); Department of Psychology (RU); Samfélagssvið (HR); School of Social Sciences (RU)
Objectives: Problem gamblers in treatment are known to be at high risk for suicidality, but few studies have examined if this is evident in community samples. Evidence is mixed on the extent to which an association between problem gambling and suicidality may be explained by psychiatric comorbidity. We tested whether they are associated after adjustment for co-occurring mental disorders and other factors. Study design: Secondary analysis of the Adult Psychiatric Morbidity Survey 2007, a cross-sectional national probability sample survey of 7403 adults living in households in England. Methods: Rates of suicidality in problem gamblers and the rest of the population were compared. A series of logistic regression models assessed the impact of adjustment on the relationship between problem gambling and suicidality. Results: Past year suicidality was reported in 19.2% of problem gamblers, compared with 4.4% in the rest of the population. Their unadjusted odds ratios (OR) of suicidality were 5.3 times higher. Odds attenuated but remained significant when depression and anxiety disorders, substance dependences, attentiondeficit/hyperactivity disorder, and other factors were accounted for (adjusted OR = 2.9, 95% confidence interval = 1. 1, 8.1 P = 0.023). Conclusions: Problem gamblers are a high-risk group for suicidality. This should be recognised in individual suicide prevention plans and local and national suicide prevention strategies. While some of this relationship is explained by other factors, a significant and substantial association between problem gambling and suicidality remains.
Börn sem eru sein til máls: Áhrif þjálfunar á orðaforða barns á þriðja ári
(Menntavísindastofnun, Menntavísindasvið, Háskóli Íslands, 2019-09-13) Eydal, Marta; Einarsdóttir, Jóhanna T.; Karlsson, Þorlákur; Úlfsdóttir, Þóra Sæunn; Sálfræðideild (HR); Department of Psychology (RU); Menntavísindasvið (HÍ); School of education (UI); Samfélagssvið (HR); School of Social Sciences (RU)
Tilgangur rannsóknarinnar var að skoða áhrif þjálfunar á orðaforða barns á þriðja ári, sem seint var til máls. Einn þátttakandi var í rannsókninni. Við upphaf rannsóknarinnar var hann 30 mánaða, notaði rúmlega 160 orð og var ekki farinn að tengja saman orð í setningar. Þátttakandinn var valinn af hentugleika. Þjálfunin var byggð á fyrirlögn fyrir fram ákveðinna markorða sem þjálfuð voru bæði á fjölbreyttan hátt og með ákefð. Einnig voru valin samanburðarorð sem ekki voru þjálfuð. Þjálfunin fór fram tvisvar í viku í leikskóla barnsins og voru þjálfunartímar 14 talsins. Niðurstöður leiddu í ljós að almennur orðaforði barnsins, sem mældur var með staðlaða málþroskaprófinu Orðaskil, jókst yfir þjálfunartímabilið umfram það sem vænta mátti vegna almenns þroska. Mælingar sýndu að barnið notaði markorðin meira en samanburðarorðin, bæði heima og í þjálfunartímum, og að notkun á orðunum jókst eftir því sem leið á þjálfunina. Sú aukning sem varð á orðaforða barnsins hélst mánuði eftir að íhlutun lauk. Mikilvægt er að bera kennsl á seinkun í málþroska eins snemma og kostur er. Þegar búið er að bera kennsl á barn sem seint er til máls þarf í framhaldi að veita því viðeigandi örvun eða íhlutun, en þessi rannsókn bendir til að slík þjálfun geti haft góð áhrif. Sambærileg rannsókn hefur ekki verið gerð áður á Íslandi.

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