Topology optimisation of slow light coupling to photonic crystal waveguides

The slow light coupling efficiency in photonic crystal waveguides is enhanced by using the topology optimisation method. As much as 5 dB improvement in transmission can be achieved in the proximity of the spectrum cutoff. Moreover, the resemblance of the resulting two optimised spectra from different initial configurations indicates the possible convergence of the optimisations.     

Finite Element Modeling of Camber Evolution During Sintering of Bilayer Structures

The need for understanding the mechanisms and optimization of shape distortions during sintering of bilayers is necessary while producing structures with functionally graded architectures. A finite element model based on the continuum theory of sintering was developed to understand the camber developments during sintering of bilayers composed of La_0.85Sr_0.15MnO₃ and Ce_0.9Gd_0.1O_1.95 tapes. Free shrinkage kinetics of both tapes were used to estimate the parameters necessary for the finite element models. Systematic investigations of the factors affecting the kinetics of distortions such as gravity and friction as well as the initial geometric parameters of the bilayers were made using optical dilatometry experiments and the model. The developed models were able to capture the observed behaviors of the bilayers’ distortions during sintering. Finally, we present the importance of understanding and hence making use of the effect of gravity and friction to minimize the shape distortions during sintering of bilayers.     

Absorption efficiency of receiving antennas

A receiving antenna with a matched load will always scatter some power. This paper sets an upper and a lower bound on the absorption efficiency (absorbed power over sum of absorbed and scattered powers), which lies between 0 and 100% depending on the directivities of the antenna and scatter patterns. It can approach 100% as closely as desired, although in practice this may not be an attractive solution. An example with a small endfire array of dipoles shows an efficiency of 93%. Several examples of small conical horn antennas are also given, and they all have absorption efficiencies less than 50%.     

Sintering of Multilayered Porous Structures: Part II–Experiments and Model Applications

Experimental analyses of shrinkage and distortion kinetics during sintering of bilayered porous and dense gadolinium‐doped ceria Ce_0.9Gd_0.1O_1.95?δ structures are carried out, and compared with the theoretical models developed in Part I of this work. A novel approach is developed for the determination of the shear viscosities ratio of the layer fully dense materials. This original technique enables the derivation of all the input parameters for the bilayer sintering modeling from one set of optical dilatometry measurements, including the conversion between real and specific times of sintering, the layers’ relative sintering intensity, and the shear viscosities ratio of the layer fully dense materials. These optical dilatometry measurements are conducted simultaneously for each individual layer and for a symmetric trilayered porous structure based on the two layers utilized in the bilayered system. The obtained modeling predictions indicate satisfactory agreement with the results of sintering of a bilayered cerium–gadolinium oxide system in terms of distortion and shrinkage kinetics.     

Biodeterioration of synthetic materials – A brief review

Although synthetic polymers are part of our global waste problem because they are not sufficiently biologically degraded, microorganisms can severely impair the properties and functions of these materials. It seems as if consumers do not really acknowledge this cause of problems and there is only sparse systematic research about. Damaging mechanisms include (i) covering of surfaces (biofouling) which may be enhanced by leaching of biodegradable additives, (ii) depletion of such additives which can lead to loss of material properties, (iii) intrusion into materials by fungal hyphae, (iv) water uptake, and (v) discoloration. The common countermeasure is the addition of biocides or simply to tolerate the effects of biodeterioration and live on with them. It is suggested to encourage further systematic research, and to develop integrated strategies in order to avoid problems, e.g., based on nutrient and water limitation whenever possible.     

Zero impact: a large-scale study of uncitedness

This paper presents a large-scale study of the phenomenon ‘uncitedness’. A literature review indicates that uncitedness is related to at least three factors: Field, document type, and time. To explore these factors and their mutual influence further, and at much larger scale than previous studies, the paper focuses on seven subject areas (arts and humanities; social sciences; computer science; mathematics; engineering; medicine; physics and astronomy), seven document types (articles; reviews; notes; letters; conference papers; books; book chapters), and a 20-year publication window (1996–2015). Documents are searched in Scopus, and retrieved year-by-year, discipline-by-discipline, and for each individual document type (total: 29,472,184 documents; 7,508,741 uncited documents). The results show great variance in uncitedness ratios between subject areas and document types. This is probably caused by a somewhat tacitly agreed upon genre hierarchy existing in all subject areas, yet with important local traits and differences. The importance of the time-dimension is documented. Time to first citation varies a great deal between subject areas, and the uncitedness ratio is consequently shown to be quite sensitive to the length of citation windows.

     

Pathway analysis for BioAmbients

Systems Biology aims for a holistic understanding of biological processes. In order to make this understanding operational and testable it can be recorded into formal process calculus models. This is a difficult task, however, because such formal models and their, often infinitely many, consequences are hard to enumerate and understand. In this paper we define a pathway analysis, based on static analysis techniques from programming languages, and show how it can be used to establish useful, finite, approximations to the set of causal consequences of models. The Pathway Analysis can be used to great advantage in all phases of the modelling approach – serving as the basis of debugging during model development, postdiction during model validation, and, finally, prediction during model guided drug design.     

Disconnect in concept learning by rhesus monkeys (Macaca mulatta): Judgment of relations and relations-between-relations.

The authors investigated the role that entropy measures, discriminative cues, and symbolic knowledge play for rhesus monkeys (Macaca mulatta) in the acquisition of the concepts of same and different for use in a computerized relational matching-to-sample task. After repeatedly failing to perceive relations between pairs of stimuli in a 2-choice discrimination paradigm, monkeys rapidly learned to discriminate between 8-element arrays. Subsequent tests with smaller arrays, however, suggested that, although important for the initial acquisition of the concept, entropy is not a variable on which monkeys are dependent. Not only do monkeys choose a corresponding relational pair in the presence of a cue, but they also choose the cue itself in the presence of the relational pair--in essence, labeling those relations. Subsequent failure in the judgment of relations-between-relations, however, suggests that perhaps a qualitatively different cognitive component exists that prevents monkeys from behaving analogically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)