Interpolated Coarse Models for Microwave Design Optimization With Space Mapping

The efficiency of space-mapping optimization depends on the quality of the underlying coarse model, which should be sufficiently close to the fine model and cheap to evaluate. In practice, available coarse models are often cheap, but inaccurate (e.g., a circuit equivalent of the microwave structure) or accurate, but too expensive (e.g., a coarse-mesh model). In either case, the space-mapping optimization process exhibits substantial computational overhead due to the excessive fine model evaluations necessary to find a good solution if the coarse model is inaccurate, or due to the cost of the parameter extraction and surrogate optimization sub-problems if the coarse model is too expensive. In this paper, we use an interpolation technique, which allows us to create coarse models that are both accurate and cheap. This overcomes the accuracy/cost dilemma described above, permitting significant reduction of the space-mapping optimization time. Examples verify the performance of our approach.     

Response correction techniques for surrogate‐based design optimization of microwave structures

Simulation‐based optimization has become an important design tool in microwave engineering. However, using electromagnetic (EM) solvers in the design process is a challenging task, primarily due to a high‐computational cost of an accurate EM simulation. In this article, we present a review of EM‐based design optimization techniques exploiting response‐corrected physically based low‐fidelity models. The surrogate models created through such a correction can be used to yield a reasonable approximation of the optimal design of the computationally expensive structure under consideration (high‐fidelity model). Several approaches using this idea are reviewed including output space mapping, manifold mapping, adaptive response correction, and shape‐preserving response prediction. A common feature of these methods is that they are easy to implement and computationally efficient. Application examples are provided. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

Electroreduction of laccase covalently bound to organothiol monolayers on gold electrodes

Cerrena unicolor laccase was immobilized on the gold electrode by covalent bonding to self-assembled monolayers of mercaptoundecanoic or mercaptopropionic acids. STM images of immobilized laccase proved high population of the laccase molecules on the monolayer modified electrode. The SERS experiments in concert with resonance Raman effect confirmed that the structure at the “blue” copper site of the immobilized protein remained intact. The accessibility of individual copper sites for electron exchange with the gold electrode surface was investigated by voltammetry. The electrode behavior of laccase is different in the presence and absence of oxygen, showing that the immobilized enzyme is reactive towards oxygen. Addition of two common mediators improved the electrical connectivity of the enzyme with the electrode, increased the catalytic efficiency of immobilized laccase and switched the onset of catalytic current to the potentials of the mediator. Immobilization of laccase on well-organized mercaptoundecanoic acid separates efficiently the enzyme from the electrode and does not allow easy access of mediators to the surface. Attachment of the enzyme at smaller distance from the electrode by means of significantly shorter spacer molecule—mercaptopropionic acid improved the efficiency of catalytic reduction of oxygen on the monolayer modified electrode.     

Precise control of reflection response in bandwidth‐enhanced planar antennas

In this work, the issues of bandwidth enhancement of planar antennas and the relevance of precise and automated response control through numerical optimization have been investigated. Using an example of a planar antenna with parasitic radiator we illustrate possible effects of even minor modifications of the antenna geometry (here, applied to the ground plane) on its reflection performance. In particular, a proper handling of geometry parameters may lead to considerable broadening of the antenna bandwidth. For the sake of computational efficiency, the adjustment of geometry parameters is carried out using surrogate‐based optimization methods exploiting coarse‐discretization EM simulations as the underlying low‐fidelity antenna model. Additionally, suitably defined penalty function allows us to precisely control the maximum in‐band reflection so that sufficient margin to accommodate possible manufacturing tolerances can be achieved. The optimized designs of the two antenna structures considered in this work exhibit over 1.75 GHz (>31%) and 2.15 GHz (>38%) bandwidth, respectively, for the center frequency of 5.6 GHz. Simulation results are validated using measurements of the fabricated prototypes. Comparison with state‐of‐the‐art designs is also provided. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:653–659, 2016.     

Path Loss Modelling for Location Service Applications

The aim of this paper is the path loss modelling for the radiolocation services in radio communication networks, particularly in cellular networks. The main results of the measurements obtained in the physical layer of the UMTS are introduced. A new method for the utilization of the multipath propagation phenomenon to improve the estimation of the distance between the MS （mobile station） and the BS （base station） is outlined. This method significantly increases the quality of location services in systems which use a radio interface with DS （direct sequence） CDMA （code division multiple access）.     

Comments on “Aliasing Properties of Circular MISRs”

The analysis of aliasing probability presented in a recent article, Aliasing Properties of Circular MISRs [1], is based on an error model that cannot adequately represent real circuits. We show why conclusions presented in [1] should not be used in practice, substantiating our claim with experimental results.This work was supported in part by grants from the Natural Sciences and Engineering Research Council of Canada and in part by the British Columbia Advanced Systems Institute     

Expedited simulation‐driven design optimization of UWB antennas by means of response features

In this work, a method for fast design optimization of broadband antennas is considered. The approach is based on a feature‐based optimization (FBO) concept where reflection characteristics of the structure at hand are formulated in terms of suitably defined feature points. Redefinition of the design problem allows for reducing the design optimization cost, because the dependence of feature point coordinates on antenna dimensions is less nonlinear than for the original frequency characteristics (here, S‐parameters). This results in faster convergence of the optimization algorithm. The cost of the design process is further reduced using variable‐fidelity electromagnetic (EM) simulation models. In case of UWB antennas, the feature points are defined, among others, as the levels of the reflection characteristic at its local in‐band maxima, as well as location of the frequency point which corresponds to acceptable reflection around the lower corner frequency within the UWB band. Also, the number of characteristic points depends on antenna topology and its dimensions. Performance of FBO‐based design optimization is demonstrated using two examples of planar UWB antennas. Moreover, the computational cost of the approach is compared with conventional optimization driven by a pattern search algorithm. Experimental validation of the numerical results is also provided.     

Structure generation and performance comparison of elliptic Gm‐C filters

Starting from a set of matrices describing a general G_m‐C filter topology, a procedure is developed for generating structures of lowpass filters. As the matrices and the filter topologies have a one‐to‐one correspondence, an algebraic method is used to identify filter topologies with desired properties, here, transfer functions with finite jω‐axis transmission zeros, specifically elliptic filters. Sensitivity expressions for these structures are derived and a performance comparison based on a set of chosen criteria is made. For a specified elliptic transfer function, filters with only grounded capacitors and those containing also floating capacitors emerge as alternative realizations, as are filters with a single input and those with distributed inputs. For third‐order functions, a detailed comparison is performed of leapfrog (LF) and inverse follow‐the‐leader‐feedback (IFLF), the most popular special cases, and of topologies that have also floating capacitors (LF_f, IFLF_f), as well as of a novel configuration that uses also distributed inputs (DI_f) and leads to a reduced element count. Design guidelines and restrictions are given, which follow from the derived results with focus on the circuits' sensitivity performance and other properties important for IC implementation. Copyright © 2004 John Wiley & Sons, Ltd.     

Role of Obesity,Physical Exercise,Adipose Tissue-Skeletal Muscle Crosstalk and Molecular Advances in Barrett’s Esophagus and Esophageal Adenocarcinoma

Both obesity and esophageal adenocarcinoma (EAC) rates have increased sharply in the United States and Western Europe in recent years. EAC is a classic example of obesity-related cancer where the risk of EAC increases with increasing body mass index. Pathologically altered visceral fat in obesity appears to play a key role in this process. Visceral obesity may promote EAC by directly affecting gastroesophageal reflux disease and Barrett’s esophagus (BE), as well as a less reflux-dependent effect, including the release of pro-inflammatory adipokines and insulin resistance. Deregulation of adipokine production, such as the shift to an increased amount of leptin relative to “protective” adiponectin, has been implicated in the pathogenesis of BE and EAC. This review discusses not only the epidemiology and pathophysiology of obesity in BE and EAC, but also molecular alterations at the level of mRNA and proteins associated with these esophageal pathologies and the potential role of adipokines and myokines in these disorders. Particular attention is given to discussing the possible crosstalk of adipokines and myokines during exercise. It is concluded that lifestyle interventions to increase regular physical activity could be helpful as a promising strategy for preventing the development of BE and EAC.     

The Combination of Intestinal Alkaline Phosphatase Treatment with Moderate Physical Activity Alleviates the Severity of Experimental Colitis in Obese Mice via Modulation of Gut Microbiota,Attenuation of Proinflammatory Cytokines,Oxidative Stress Biomarkers and DNA Oxidative Damage in Colonic Mucosa

Inflammatory bowel diseases (IBD) are commonly considered as Crohn’s disease and ulcerative colitis, but the possibility that the alterations in gut microbiota and oxidative stress may affect the course of experimental colitis in obese physically exercising mice treated with the intestinal alkaline phosphatase (IAP) has been little elucidated. Mice fed a high-fat-diet (HFD) or normal diet (ND) for 14 weeks were randomly assigned to exercise on spinning wheels (SW) for 7 weeks and treated with IAP followed by intrarectal administration of TNBS. The disease activity index (DAI), grip muscle strength test, oxidative stress biomarkers (MDA, SOD, GSH), DNA damage (8-OHdG), the plasma levels of cytokines IL-2, IL-6, IL-10, IL-12p70, IL-17a, TNF-α, MCP-1 and leptin were assessed, and the stool composition of the intestinal microbiota was determined by next generation sequencing (NGS). The TNBS-induced colitis was worsened in obese sedentary mice as manifested by severe colonic damage, an increase in DAI, oxidative stress biomarkers, DNA damage and decreased muscle strength. The longer running distance and weight loss was observed in mice given IAP or subjected to IAP + SW compared to sedentary ones. Less heterogeneous microbial composition was noticed in sedentary obese colitis mice and this effect disappeared in IAP + SW mice. Absence of Alistipes, lower proportion of Turicibacter, Proteobacteria and Faecalibacterium, an increase in Firmicutes and Clostridium, a decrease in oxidative stress biomarkers, 8-OHdG content and proinflammatory cytokines were observed in IAP + SW mice. IAP supplementation in combination with moderate physical activity attenuates the severity of murine colitis complicated by obesity through a mechanism involving the downregulation of the intestinal cytokine/chemokine network and oxidative stress, the modulation of the gut microbiota and an improvement of muscle strength.