bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hybrid channel estimation for MIMO relay systems with Doppler offset influences
Authors: Kaur Harmandar , Khosla Mamta , Sarin R. K. 
Published: November 2017

SummaryThe design of the channel estimation method in a multiple‐input multiple‐output (MIMO) relay system plays a highly crucial role in deciding the overall system performance. For the realistic scenarios specifically, with fast time‐varying channel conditions due to highly mobile communicating nodes, the degree of accuracy to which the channel estimates are obtained for MIMO relay systems influences the communication system reliability significantly. However, most of the channel estimation approaches proposed in literature for MIMO relay systems assume that the Doppler offset contributed by highly mobile nodes is already known to the receiver, ignoring the resulting nonlinear system dynamics. Hence, a novel hybrid algorithm is proposed to address the issue of time‐varying channel estimation under fast‐fading channel condition with Doppler offset influences contributed by high‐mobility communicating nodes for a 1‐way 2‐hop MIMO amplify‐and‐forward relaying system. The problem is first formulated as a nonlinear state‐space model, and then an algorithm is developed to estimate the individual source‐to‐relay and relay‐to‐destination channels in the presence of the associated dynamic Doppler offset. In the proposed method, a set of superimposed orthogonal pilots is used for aiding in the updation of the channel gains, since Kalman filter–based updation may lead to accumulation of estimation and prediction error. A detailed computational complexity analysis of the proposed hybrid algorithm is presented, which shows that the algorithm has moderate computational complexity with a good performance in fast time‐varying channel conditions with high node mobility in a dual‐hop MIMO relay system.
Identifiability inN‐mixture models: a large‐scale screening test with bird data
Authors: Kéry Marc 
Published: November 2017

AbstractBinomialN‐mixture models have proven very useful in ecology, conservation, and monitoring: they allow estimation and modeling of abundance separately from detection probability using simple counts. Recently, doubts about parameter identifiability have been voiced. I conducted a large‐scale screening test with 137 bird data sets from 2,037 sites. I found virtually no identifiability problems for Poisson and zero‐inflated Poisson (ZIP) binomialN‐mixture models, but negative‐binomial (NB) models had problems in 25% of all data sets. The corresponding multinomialN‐mixture models had no problems. Parameter estimates under Poisson and ZIP binomial and multinomialN‐mixture models were extremely similar. Identifiability problems became a little more frequent with smaller sample sizes (267 and 50 sites), but were unaffected by whether the models did or did not include covariates. Hence, binomialN‐mixture model parameters with Poisson and ZIP mixtures typically appeared identifiable. In contrast, NB mixtures were often unidentifiable, which is worrying since these were often selected by Akaike's information criterion. Identifiability of binomialN‐mixture models should always be checked. If problems are found, simpler models, integrated models that combine different observation models or the use of external information via informative priors or penalized likelihoods, may help.
Critical uncertainty parameters influencing seismic performance of bridges using Lasso regression
Authors: Mangalathu Sujith , Jeon Jong‐Su , DesRoches Reginald 
Published: November 2017

SummaryRecent efforts of regional risk assessment of structures often pose a challenge in dealing with the potentially variable uncertain input parameters. The source of uncertainties can be either epistemic or aleatoric. This article identifies uncertain variables exhibiting strongest influences on the seismic demand of bridge components through various regression techniques such as linear, stepwise, Ridge, Lasso, and elastic net regressions. The statistical results indicate that Lasso regression is the most effective one in predicting the demand model as it has the lowest mean square error and absolute error. As the sensitivity study identifies more than 1 significant variable, a multiparameter fragility model using Lasso regression is suggested in this paper. The proposed fragility methodology is able to identify the relative impact of each uncertain input variable and level of treatment needed for these variables in the estimation of seismic demand models and fragility curves. Thus, the proposed approach helps bridge owners to spend their resources judiciously (e.g., data collection, field investigations, and censoring) in the generation of a more reliable database for regional risk assessment. This proposed approach can be applicable to other structures.
Online numerical simulation: A hybrid simulation method for incomplete boundary conditions
Authors: Wu Bin , Ning Xizhan , Xu Guoshan , Wang Zhen , Mei Zhu , Yang Ge 
Published: November 2017

SummaryHybrid simulation is a powerful and cost‐effective simulation technique to evaluate structural dynamic performance. However, it is sometimes rather difficult to guarantee all the boundaries on the physical substructures, especially when the boundary conditions are very complex, due to limited laboratory resources. Lacking of boundary conditions is bound to change the stress state of the structure and eventually result in an inaccurate evaluation of structural performance. A model updating‐based online numerical simulation method is proposed in this paper to tackle the problem of incomplete boundary conditions. In the proposed method, 2 sets of finite element models with the same constitutive model are set up for the overall analysis of the whole structure and the constitutive model parameter estimation of the physical substructure, respectively. The boundary conditions are naturally satisfied because the response is calculated from the overall structural model, and the accuracy is improved as the material constitutive parameters are updated. The effectiveness of the proposed method is validated via numerical simulations and actual hybrid tests on a RC frame structure, and the results show that the negative effect of incomplete boundary conditions is almost eliminated and the accuracy of hybrid simulation is very much improved.
Single-gene speciation: Mating and gene flow between mirror-image snails
Authors: Richards Paul M. , Morii Yuta , Kimura Kazuki , Hirano Takahiro , Chiba Satoshi , Davison Angus 
Published: November 2017

AbstractVariation in the shell coiling, or chirality, of land snails provides an opportunity to investigate the potential for “single-gene” speciation, because mating between individuals of opposite chirality is believed not possible if the snails mate in a face-to-face position. However, the evidence in support of single-gene speciation is sparse, mostly based upon single-gene mitochondrial studies and patterns of chiral variation between species. Previously, we used a theoretical model to show that as the chiral phenotype of offspring is determined by the maternal genotype, occasional chiral reversals may take place and enable gene flow between mirror image morphs, preventing speciation. Here, we show empirically that there is recent or ongoing gene flow between the different chiral types of Japanese Euhadra species. We also report evidence of mating between mirror-image morphs, directly showing the potential for gene flow. Thus, theoretical models are suggestive of gene flow between oppositely coiled snails, and our empirical study shows that they can mate and that there is gene flow in Euhadra. More than a single gene is required before chiral variation in shell coiling can be considered to have created a new species.
Influence of out‐of‐plane fiber orientation on reaction‐to‐fire properties of carbon fiber reinforced polymer matrix composites
Authors: Eibl S. , Swanson D. 
Published: November 2017

SummaryThis work investigates the influence of the out‐of‐plane orientation of carbon fibers on the reaction‐to‐fire characteristics of polymer matrix composites. A deep insight into combustion processes is gained, which is necessary to fully understand and assess advantages of composites with out‐of‐plane fiber angles. Epoxy‐based Hexply 8552/IM7 specimens with primarily low fiber angles between 0° and 15° are characterized by cone calorimetry. Heat release during fire is greatly affected by the out‐of‐plane fiber angle because of the thermal boundaries created by the fibers. The advancement of the pyrolysis front during fire was determined from peak heat release rates and validated by temperature measurements along the back surface of the panels, representing a novel method of determining position‐dependent pyrolysis migration velocity. These measurements show a transverse shift in pyrolysis front velocity for increasing out‐of‐plane fiber angles. Pyrolysis pathways between the fiber boundaries facilitate faster combustion through the composite thickness, especially for increasing angles from 0° to 15°. It was determined that under the chosen conditions, the pyrolysis front advances approximately 4 times faster when propagating parallel to the fibers than perpendicular.
Effects of opening edge treatment and EPS thickness on EPS external thermal insulation composite systems (ETICS) façade reaction‐to‐fire performance based on JIS A1310 standard façade fire test method
Authors: Zhou Biao , Yoshioka Hideki , Noguchi Takafumi , Ando Tatsuo 
Published: November 2017

AbstractExternal thermal insulation composite systems (ETICS) are quite common in constructions. However, the combustible insulation core induces serious fire disasters, especially considering thermoplastic expanded polystyrene (EPS) has been widely used as insulation core. Most of EPS ETICS building fire is caused by window spreading fire. The window opening edge treatment plays an important role in EPS ETICS fire prevention. Presently, in order to investigate optimal opening edge treatment and EPS thickness effects on EPS ETICS reaction‐to‐fire performance, façade fire tests based on JIS A 1310 standard façade fire test method were carried out by testing a series of EPS ETICS specimens varying EPS thickness, opening edge treatment methods and heating intensity. It is found that back‐wrapping is a good opening edge treatment method. When the EPS ETICS specimen is treated by back‐wrapping opening edge treatment method, the peak temperature, EPS burn area, time (20 minutes) averaged temperature, and heat flux density become low. The time (20 minutes) averaged temperature of each position from T1 to T5 versus EPS thickness is linear at heating intensity 300 or 600 kW. The averaged ratio of EPS burn area above opening (Sa) and below opening (Sb) is approaching 3.058.
Investigating motivation and engagement in an urban afterschool arts and leadership program
Authors: Chung He Len , Jusu Bentrice , Christensen Kirsten , Venescar Pierre , Tran Dan‐anh 
Published: November 2017

AbstractDespite the potential benefits of afterschool arts‐based programs on development, urban youth in low‐income areas are unlikely to participate in these activities. The aim of the current study was to investigate motivation and engagement in an arts and leadership afterschool program among 10 urban, predominantly African American youth. We took a mixed‐methods approach, as limited research has examined motivational processes in arts‐based programs. Youth identified program content, staff, and peers as important sources of motivation. Specifically, the program leader played multiple roles in youths’ lives, and it is critical to pay careful attention to how youth experience and learn to navigate these complex relationships. Youth especially valued opportunities to develop a sense of competence (e.g., learn teamwork skills) and engage in identity work (e.g., gain a better sense of themselves), and they envisioned their program participation having a positive influence on motivation in their everyday lives outside of program activities.
B1 artifact reduction in abdominal DCE‐MRI using kT‐points: First clinical assessment of dynamic RF shimming at 3T
Authors: Tomi‐Tricot Raphaël , Gras Vincent , Mauconduit Franck , Legou François , Boulant Nicolas , Gebhardt Matthias , Ritter Dieter , Kiefer Berthold , Zerbib Pierre , Rahmouni Alain , Vignaud Alexandre , Luciani Alain , Amadon Alexis 
Published: November 2017

BackgroundThe excitation inhomogeneity artifact occurring at 3T in the abdomen can lead to dramatic loss of signal and contrast, thereby hampering diagnosis.PurposeTo assess excitation homogeneity and image quality achieved by nonselective prototypical kT‐points pulses, compared to tailored static RF shimming, in clinical routine on a commercial dual‐transmit scanner.Study TypeRetrospective study with Institutional Review Board approval; informed consent was waived.PopulationFifty consecutive patients referred for liver MRI at a single hospital.Field Strength/Sequence3D breath‐hold dynamic contrast‐enhanced (DCE) MRI at 3T.AssessmentFlip angle homogeneity was estimated via numerical simulation based on measured static and RF field maps. In all, 20 of the 50 patients underwent DCE‐MRI while a pulse designer was present. The effect of RF shimming and kT‐point pulses could be compared by repeating the acquisition with each transmit scheme before injection and in the late phase. Signal homogeneity, T1 contrast, enhancement quality, structure details, and global image quality were assessed on a 4‐level scale (0 to 3) by two radiologists.Statistical testsMeans were compared using Wilcoxon signed‐rank tests.ResultsNormalized root mean square flip angle error was significantly reduced with kT‐points compared to static RF shimming (8.5% ± 1.5% [mean ± standard deviation, SD] vs. 20.4% ± 9.8%; P < 0.0001). The worst case (heavy ascites) led to 13.0% (kT‐points) vs. 54.9% (RF shimming). Global image quality was significantly higher for kT‐points (2.3 ± 0.5 vs. 1.9 ± 0.6; P = 0.008). One subject's examination was judged unusable with RF shimming by one reader, none with kT‐points. 85% of kT‐points acquisitions were graded at least 2/3, and only 55% for static RF shimming.Data ConclusionKT‐points reduce excitation inhomogeneity quantitatively and qualitatively, especially in patients with ascites and prone to B1 shading.Level of Evidence: 1Technical Efficacy: Stage 1J. Magn. Reson. Imaging 2018;47:1562–1571.
Microfinance development in Armenia: Sectoral characteristics and problems
Authors: Khachatryan Knar , Avetisyan Emma 
Published: November 2017

AbstractThe heavy‐handed regulation enforced a commercialization process and as a result pushed microfinance institutions in Armenia towards a commercial logic, which diminished the importance of the social component. Sector development problems include unfair fees, limit on annual interest rate, late cooperation between credit organizations, and regulated microfinance operations. Because of the high interest rates and difficult economic situation, micro‐loans do not necessarily help poor people in Armenia to escape poverty, but instead push them further down into greater poverty.
Comparisons of glyphosate adsorption properties of different functional Cr‐based metal–organic frameworks
Authors: Feng Dan , Xia Yan 
Published: November 2017

AbstractA Cr‐based metal–organic framework, namely, MIL‐101(Cr), was modified with amino (NH2–) and urea (UR2–) groups, and the materials were evaluated as adsorbents for glyphosate, and a comparison with commercial activated carbon was also discussed. The effects of the adsorption factors, such as adsorbent concentration, adsorption time, pH and ionic strength were mainly investigated. The results showed that a pseudo‐second‐order rate equation described the adsorption kinetics mechanisms well, while the Langmuir model and the Freundlich model fitted different adsorption isotherms, respectively. Among the adsorbents we studied, NH2‐MIL‐101(Cr) showed the maximum adsorbing capacity, which is 64.25 mg/g when pH = 3.0, while UR2‐MIL‐101(Cr) did not reach the best adsorption performance due to the steric hindrance. The work opens up a new way for the modification of metal–organic frameworks for adsorption process.
Defining the Field of Sequence‐Controlled Polymers
Authors: Lutz Jean‐François 
Published: November 2017

AbstractOver the last ten years, the development of synthetic polymers containing controlled monomer sequences has become a prominent topic in fundamental and applied polymer science. This emerging area is particularly broad and combines classical polymer chemistry tools with techniques imported from other domains such as biology, biochemistry, organic synthesis, engineering, and bioanalytics. Consequently, it also generates new structures, terminologies, and applications that are not within the traditional scope of polymer science. The term “sequence‐controlled polymers” (SCPs) was recently proposed as a generic name to describe all these recent trends. However, since the field of SCPs has been growing very rapidly in recent literature, it is urgent to accurately define its scientific frontiers. In this important context, this review is an attempt to define, rationalize, and classify the field of SCPs. In particular, all synthetic approaches that have been reported for the synthesis of SCPs are discussed and categorized. In addition, the characterization tools, properties, and potential applications of these new polymers are described herein. Overall, this review serves as a reference guide for understanding the burgeoning field of SCPs.
Performance of a hybrid Monte Carlo‐Pencil Beam dose algorithm for proton therapy inverse planning
Authors: Barragán Montero Ana María , Souris Kevin , Sanchez‐Parcerisa Daniel , Sterpin Edmond , Lee John Aldo 
Published: November 2017

PurposeAnalytical algorithms have a limited accuracy when modeling very heterogeneous tumor sites. This work addresses the performance of a hybrid dose optimizer that combines both Monte Carlo (MC) and pencil beam (PB) dose engines to get the best trade‐off between speed and accuracy for proton therapy plans.MethodsThe hybrid algorithm calculates the optimal spot weights (w) by means of an iterative optimization process where the dose at each iteration is computed by using a precomputed dose influence matrix based on the conventional PB plus a correction term c obtained from a MC simulation. Updates of c can be triggered as often as necessary by calling the MC dose engine with the last corrected values of w as input. In order to analyze the performance of the hybrid algorithm against dose calculation errors, it was applied to a simplistic water phantom for which several test cases with different errors were simulated, including proton range uncertainties. Afterwards, the algorithm was used in three clinical cases (prostate, lung, and brain) and benchmarked against full MC‐based optimization. The influence of different stopping criteria in the final results was also investigated.ResultsThe hybrid algorithm achieved excellent results provided that the estimated range in a homogeneous material is the same for the two dose engines involved, i.e., PB and MC. For the three patient cases, the hybrid plans were clinically equivalent to those obtained with full MC‐based optimization. Only a single update of c was needed in the hybrid algorithm to fulfill the clinical dose constraints, which represents an extra computation time to obtain c that ranged from 1 (brain) to 4 min (lung) with respect to the conventional PB‐based optimization, and an estimated average gain factor of 14 with respect to full MC‐based optimization.ConclusionThe hybrid algorithm provides an improved trade‐off between accuracy and speed. This algorithm can be immediately considered as an option for improving dose calculation accuracy of commercial analytical treatment planning systems, without a significant increase in the computation time (≪5 min) with respect to current PB‐based optimization.
Synthesized tissue‐equivalent dielectric phantoms using salt and polyvinylpyrrolidone solutions
Authors: Ianniello Carlotta , de Zwart Jacco A. , Duan Qi , Deniz Cem M. , Alon Leeor , Lee Jae‐Seung , Lattanzi Riccardo , Brown Ryan 
Published: November 2017

PurposeTo explore the use of polyvinylpyrrolidone (PVP) for simulated materials with tissue‐equivalent dielectric properties.MethodsPVP and salt were used to control, respectively, relative permittivity and electrical conductivity in a collection of 63 samples with a range of solute concentrations. Their dielectric properties were measured with a commercial probe and fitted to a 3D polynomial in order to establish an empirical recipe. The material's thermal properties and MR spectra were measured.ResultsThe empirical polynomial recipe (available at https://www.amri.ninds.nih.gov/cgi-bin/phantomrecipe) provides the PVP and salt concentrations required for dielectric materials with permittivity and electrical conductivity values between approximately 45 and 78, and 0.1 to 2 siemens per meter, respectively, from 50 MHz to 4.5 GHz. The second‐ (solute concentrations) and seventh‐ (frequency) order polynomial recipe provided less than 2.5% relative error between the measured and target properties. PVP side peaks in the spectra were minor and unaffected by temperature changes.ConclusionPVP‐based phantoms are easy to prepare and nontoxic, and their semitransparency makes air bubbles easy to identify. The polymer can be used to create simulated material with a range of dielectric properties, negligible spectral side peaks, and long T2 relaxation time, which are favorable in many MR applications. Magn Reson Med 80:413–419, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Understanding the metabolic burden of recombinant antibody production in Saccharomyces cerevisiae using a quantitative metabolomics approach
Authors: de Ruijter Jorg C. , Koskela Essi V. , Nandania Jatin , Frey Alexander D. , Velagapudi Vidya 
Published: November 2017

AbstractThe cellular changes induced by heterologous protein expression in the yeast Saccharomyces cerevisiae have been analysed on many levels and found to be significant. However, even though high‐level protein production poses a metabolic burden, evaluation of the expression host at the level of the metabolome has often been neglected. We present a comparison of metabolite profiles of a wild‐type strain with those of three strains producing recombinant antibody variants of increasing size and complexity: an scFv fragment, an scFv–Fc fusion protein and a full‐length IgG molecule. Under producing conditions, all three recombinant strains showed a clear decrease in growth rate compared with the wild‐type strain and the severity of the growth phenotype increased with size of the protein. The levels of 76 intracellular metabolites were determined using a targeted (semi) quantitative mass spectrometry based approach. Based on unsupervised and supervised multivariate analysis of metabolite profiles, together with pathway activity profiling, the recombinant strains were found to be significantly different from each other and from the wild‐type strain. We observed the most prominent changes in metabolite levels for metabolites involved in amino acid and redox metabolism. Induction of the unfolded protein response was detected in all producing strains and is considered to be a contributing factor to the overall metabolic burden on the cells.