Exploring multiple viewshed analysis using terrain features and optimisation techniques

The calculation of viewsheds is a routine operation in geographic information systems and is used in a wide range of applications. Many of these involve the siting of features, such as radio masts, which are part of a network and yet the selection of sites is normally done separately for each feature. The selection of a series of locations which collectively maximise the visual coverage of an area is a combinatorial problem and as such cannot be directly solved except for trivial cases. In this paper, two strategies for tackling this problem are explored. The first is to restrict the search to key topographic points in the landscape such as peaks, pits and passes. The second is to use heuristics which have been applied to other maximal coverage spatial problems such as location-allocation. The results show that the use of these two strategies results in a reduction of the computing time necessary by two orders of magnitude, but at the cost of a loss of 10% in the area viewed. Three different heuristics were used, of which Simulated Annealing produced the best results. However the improvement over a much simpler fast-descent swap heuristic was very slight, but at the cost of greatly increased running times. © 2004 Elsevier Ltd. All rights reserved

Magnetic Properties of Dilute Alloys: Equations for Magnetization and its Structural Fluctuations

The dilute Heisenberg ferromagnet is studied taking into account fluctuations of magnetization caused by disorder. A self-consistent system of equations for magnetization and its mean quadratic fluctuations is derived within the configurationally averaged two-time temperature Green's function method. This system of equations is analised at low concentration of non-magnetic impurities. Mean relative quadratic fluctuations of magnetization are revealed to be proportional to the square of concentration of impurities.Comment: 16 pages, LaTe

Top-down, bottom-up, or both? Toward an integrative perspective on operations strategy formation

Operations strategy is formed via complex processes that transpire in multiple directions at multiple organizational levels. While most previous studies focus on the “macro-level” process of strategy formation from the dominant top-down perspective, this study investigates the “micro-level” process of strategy formation that governs interactions among competitive priorities, objectives, and action plans within operations. Using 111 (59 top-down and 52 bottom-up) action plans collected from six German manufacturing plants, we build on Kim and Arnold's (1996) framework and propose an integrated process model of operations strategy formation that encompasses both top-down planning and bottom-up learning. We also identify a contingency factor that affects their balance: centralized versus decentralized organizational structure. Finally, based on the analysis of their respective strategic content, we provide evidence concerning the complementary roles of top-down and bottom-up action plans in operations strategy

Comparing Results of Five Glomerular Filtration Rate-Estimating Equations in the Korean General Population. MDRD Study, Revised Lund-Malmö, and Three CKD-EPI Equations

Estimated glomerular filtration rate (eGFR) is a widely used index of kidney function. Recently, new formulas such as the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations or the Lund-Malmö equation were introduced for assessing eGFR. We compared them with the Modification of Diet in Renal Disease (MDRD) Study equation in the Korean adult population. METHODS: The study population comprised 1,482 individuals (median age 51 [42-59] yr, 48.9% males) who received annual physical check-ups during the year 2014. Serum creatinine (Cr) and cystatin C (CysC) were measured. We conducted a retrospective analysis using five GFR estimating equations (MDRD Study, revised Lund-Malmö, and Cr and/or CysC-based CKD-EPI equations). Reduced GFR was defined as eGFR <60 mL/min/1.73 m². RESULTS: For the GFR category distribution, large discrepancies were observed depending on the equation used; category G1 (≥90 mL/min/1.73 m²) ranged from 7.4-81.8%. Compared with the MDRD Study equation, the other four equations overestimated GFR, and CysC-based equations showed a greater difference (-31.3 for CKD-EPI(CysC) and -20.5 for CKD-EPI(Cr-CysC)). CysC-based equations decreased the prevalence of reduced GFR by one third (9.4% in the MDRD Study and 2.4% in CKD-EPI(CysC)). CONCLUSIONS: Our data shows that there are remarkable differences in eGFR assessment in the Korean population depending on the equation used, especially in normal or mildly decreased categories. Further prospective studies are necessary in various clinical settings

Effects of polarization mode dispersion on polarization-entangled photons generated via broadband pumped spontaneous parametric down-conversion

An inexpensive and compact frequency multi-mode diode laser enables a compact two-photon polarization entanglement source via the continuous wave broadband pumped spontaneous parametric down-conversion (SPDC) process. Entanglement degradation caused by polarization mode dispersion (PMD) is one of the critical issues in optical fiber-based polarization entanglement distribution. We theoretically and experimentally investigate how the initial entanglement is degraded when the two-photon polarization entangled state undergoes PMD. We report an effect of PMD unique to broadband pumped SPDC, equally applicable to pulsed pumping as well as cw broadband pumping, which is that the amount of the entanglement degradation is asymmetrical to the PMD introduced to each quantum channel. We believe that our results have important applications in long-distance distribution of polarization entanglement via optical fiber channels.1111Ysciescopu

Heterogeneous PdAg alloy catalyst for selective methylation of aromatic amines with formic acid under an additive-free and solvothermal one-pot condition

The methylation of amines for the synthesis of methylamines and dimethylamines as platform chemicals has been attempted mostly by homogeneous catalysts with acid additives. However, there are scarcely any reports on heterogeneous catalytic methylation reactions except for a routine approach under high temperature and high pressure of CO2 and H-2 gases for extended reaction times. Here we report a heterogeneously catalyzed selective methylation of aromatic amines using reactive and nontoxic formic acid as the only source for the construction of methyl groups, under ambient pressure in an additive-free one-pot reaction condition. Equal proportions of Pd and Ag in the PdAg/Fe3O4/N-rGO catalyst deliver highly selective amine methylation without aromatic ring hydrogenation, as the strained Pd in the alloy is combined with the graphene-derived support, preventing nanoparticle agglomeration and the action of magnetite as a promoter. Both N-methylation and N, N-dimethylation of various substituted aromatic amines were performed with complete conversion and excellent 90-97% selectivity by controlling the reaction times in the range of 10-24 h at 140 degrees C without unwanted aromatic ring hydrogenation. Furthermore, the developed bimetallic catalyst provided high yields (88-91%) of methylation with CO2+H-2 gas under high pressure, which are as good as the results of homogenous catalysts with an acid additive. To the best of our knowledge, our use of this environmentally friendly methodology is the first time that this durable heterogeneous catalyst has readily performed highly selective methylation at ambient pressure, which is attractive for industrial applications.1193Ysciescopu

Experimental demonstration of high fidelity entanglement distribution over decoherence channels via qubit transduction

Quantum coherence and entanglement, which are essential resources for quantum information, are often degraded and lost due to decoherence. Here, we report a proof-of-principle experimental demonstration of high fidelity entanglement distribution over decoherence channels via qubit transduction. By unitarily switching the initial qubit encoding to another, which is insensitive to particular forms of decoherence, we have demonstrated that it is possible to avoid the effect of decoherence completely. In particular, we demonstrate high-fidelity distribution of photonic polarization entanglement over quantum channels with two types of decoherence, amplitude damping and polarization-mode dispersion, via qubit transduction between polarization qubits and dual-rail qubits. These results represent a significant breakthrough in quantum communication over decoherence channels as the protocol is input-state independent, requires no ancillary photons and symmetries, and has near-unity success probability.1132Ysciescopu

Pair interaction among adult EFL learners: A South Korean case study

The current study aims to investigate how pair work influences language learning in EFL lessons, in particular in a South Korean college. Specifically, the study addresses: (i) how learners interact with their partner in language learning activities, (ii) how they perceive their peer interaction, and (iii) how the interactive process of accomplishing the activities relates to language learning opportunities. Therefore, the study plan was to explore the type of peer interaction, learners’ perception of the interaction, and the relationship between the interaction and language learning opportunities. This study was classroom-based. Research was conducted in three EFL classroom settings in a Korean college where my own English courses were held for a period of seven weeks. Twelve learners (i.e. six pairs) participated in the study. Seven different activities related to the course syllabus were used as the main data collection instrument to record the processes of peer interaction undergone by learners while accomplishing the activities. Data for the study came from transcripts of audio-recorded pair talk as the participants completed seven different activities, from observation notes, and from a series of interviews such as individual post-activity interviews including stimulated recall and final interviews. What the findings of this study suggest is that learners need to have a willingness to collaboratively engage with their partner because language development seen as the internalisation of socially co-constructed or mutually accepted knowledge has more opportunities to occur in pair interaction with a collaborative orientation such as collaborative type and expert/novice type. Therefore, the important element that influences language learning is not pair work per se but engaging with a partner in collaborative type and expert/novice types of pair interaction that embody a collaborative orientation. These are more likely to lead to the development of socially co-constructed and mutually accepted language knowledge