Home About us Contact
|
Home About us Contact | ||
|
|
||
Rigorous Analysis (rigorous + analysis)
Selected AbstractsRigorous analysis of photonic crystals with periodic defectsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2005Hongting Jia Abstract A very efficient and simple formulation for analyzing 2D photonic crystals with periodic defects is presented. This method is a combination of lattice sums' matrices and a T-matrix of an isolated cylinder. The numerical examples show the convergence is very fast and the computing accuracy is very high. The scattering properties by three kinds of photonic crystals with periodic defects are investigated, and the propagating nature of a coupled-cavity waveguide are discussed. The validity and usefulness of this formulation is confirmed by the numerical experiments. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 256,261, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21140 [source] THE MACROEVOLUTIONARY DYNAMICS OF ANT DIVERSIFICATIONEVOLUTION, Issue 11 2009Marcio R. Pie The availability of increasingly comprehensive phylogenies has provided unprecedented opportunities to assess macroevolutionary patterns, yet studies on invertebrate diversification are few. In particular, despite the ecological and evolutionary importance of ants, little is known about their tempo and mode of diversification. Recent advances in ant phylogenetics can now provide a basis for rigorous analyses of the diversification of ant lineages. The goals of the present study are threefold. First, we demonstrate that a hypothesized disproportionate increase in ant diversification during the angiosperm radiation is largely artifactual. Rather, current evidence points to a fairly constant rate of lineage growth during its history. Moreover, an analysis of diversification patterns across the ant phylogeny indicates considerable rate heterogeneity among lineages. Indeed, and contrary to the expectation if lineages had experienced a single rate of lineage increase, we found no correspondence between genus age and diversity. Finally, we demonstrate a statistically significant phylogenetic signal in ant diversification: closely related genera have diversities that are more similar to one another than one would expect by chance. This suggests that the capacity for diversification may be itself a biological trait that evolved during the radiation of the family Formicidae. [source] In-situ Energy-Dispersive X-ray Diffraction Studies of Crystal Growth and Compound Conversion Under Solvothermal ConditionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2003Lars Engelke Abstract The results of in-situ energy-dispersive X-ray diffraction under solvothermal conditions performed on isostructural, layered thioantimonates Mn2Sb2S5·L (L = amine) demonstrate the great potential of the method. When the synthesis was carried out at low temperatures with L being 1,3-diaminopropane (DAP), two crystalline intermediate phases were detected which then grew and disappeared when product growth started. Surprisingly, when N -methyl-1,3-diaminopropane (MDAP) was used, no crystalline intermediates could be detected and the induction time was significantly shorter than for DAP. For reactions up to 100 °C and for higher temperatures with , < 0.8 (, is the extent of reaction), the crystallisation is predominantly controlled by nucleation. Further progress of crystallisation (, > 0.8) leads to a change of the dominant process and a diffusion-controlled mechanism is observed. During the reaction with diethylenetriamine (DIEN), three crystalline intermediates were detected prior to product growth. The induction time is longer than for the other two compounds. The crystallisation seems to be diffusion-controlled and is faster than for the DAP and MDAP compounds. In a solution of DIEN, the crystalline phases Mn2Sb2S5·L (L = DAP or MDAP) are transformed into the DIEN product under solvothermal conditions, and a rigorous analysis of the intensities of the reflections suggests a partial dissolution of the crystalline starting materials followed by crystallisation of the DIEN material. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] DO SUTURE ZONES EXIST?EVOLUTION, Issue 11 2004Nathan G. Swenson Abstract Remington (1968) argued that 13 suture zones exist in North America. Remington defined a suture zone as, "a band of geographic overlap between major biotic assemblages, including some pairs of species or semispecies which hybridize in the zone" (p. 322). Although initially controversial, the idea that suture zones exist has picked up momentum over the past decade, due largely to the phylogeographic work of Hewitt, Avise, and their colleagues. Nevertheless, the reality of suture zones has not yet been subjected to rigorous analysis using statistical and geographic information system (GIS) approaches. To test for the existence of Remington's suture zones, we first identified 117 terrestrial hybrid zones in Canada and the United States through a literature search for the key words "cline,""contact zone,""hybrid zone," and "hybridization" in articles published between 1970 and 2002. The 117 hybrid zones were mapped using a GIS approach and compared with a digitized version of Remington's original suture zone map. Overall, there does appear to be an association between hybrid zones and suture zones, but this association is largely attributable to clustering of hybrid zones in only two of the 13 suture zones recognized by Remington. The results suggest that evolutionary biologists should retain some skepticism toward Remington's suture zones. [source] An Empirical Investigation of Price Competition and Industry Specialisation in NHS Audit ServicesFINANCIAL ACCOUNTABILITY & MANAGEMENT, Issue 2 2005Ilias G. Basioudis The NHS audit market is regulated by the Audit Commission (AC) and has unique features. We develop a model for audit fees that includes rigorous analysis of the type of auditor. Poor financial standing does not give rise to higher audit fees. Despite regulation the study supports the existence of a Big Five price premium on the audit fee, but only one firm has a premium. We found no premium due to industry specialisation. The removal of performance audit from AC regulation will require improved audit fee reporting and control. [source] Risk-based decision making to manage contaminated sedimentsINTEGRATED ENVIRONMENTAL ASSESSMENT AND MANAGEMENT, Issue 1 2006Todd S Bridges Abstract This paper summarizes discussion among the 7 authors who served on an expert panel at the Third Battelle International Conference on Remediation of Contaminated Sediments held in New Orleans, Louisiana, USA, in January 2005. In this article, the authors review how sediment management decisions are currently made and address the question of how management decisions should be made in the future. It is arguably the case that sediment remediation presents greater challenges and more complexity than traditional land-based clean-ups. Although understanding of these challenges and complexities has grown over the last 25 y, there has been, until recently, relatively little innovation in the approaches used to manage the environmental risks posed by contaminated sediments. New methods that facilitate a more rigorous analysis of the multiple criteria considered in decision making have been developed. These methods, collectively known as multicriteria decision analysis (MCDA), coupled with the use of comparative-risk assessment and cost/benefit analysis, are proposed as an effective, efficient, and credible foundation for evaluating remedy alternatives at contaminated sediment sites. [source] Vector Hankel transform analysis of a tunable circular microstrip patchINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2005T. Fortaki Abstract In this paper, a rigorous analysis of the tunable circular microstrip patch is performed using a dyadic Green's function formulation. To make the theoretical formulation more general and hence valid for various antennas structures (not only limited to tunable microstrip patch); the dyadic Green's function is derived when the patch is assumed to be embedded in a multilayered dielectric substrate. A very efficient technique to derive the dyadic Green's function in the vector Hankel transform domain is proposed. Using the vector Hankel transform, the mixed boundary value problem is reduced to a set of vector dual integral equations. Galerkin's method is then applied to solve the integral equation where two sets of disk current expansions are used. One set is based on the complete set of orthogonal modes of the magnetic cavity, and the other consists of combinations of Chebyshev polynomials with weighting factors to incorporate the edge condition. Convergent results for these two sets of disk current expansions are obtained with a small number of basis functions. The calculated resonant frequencies and quality factors are compared with experimental data and shown to be in good agreement. Finally, numerical results for the air gap tuning effect on the resonant frequency and half-power bandwidth are also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source] Study of geometric degeneracies in electromagnetic characteristics of magnetron-type corrugated cavityINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 4 2002Andriy E. Serebryannikov Abstract A geometric degeneracy that can occur in natural frequencies and external Q factors of magnetron-type cavities is studied. We analyze the causes of its appearance and consider its feasibility to enhance the efficiency of the cavity design. Transcendental frequency-independent equations, the solutions of which can be easily obtained, and efficient estimates based on rigorous analysis are suggested to predict the existence of the degeneracy. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12: 320,331, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10030 [source] Robust monotone gradient-based discrete-time iterative learning controlINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 6 2009D. H. Owens Abstract This paper considers the use of matrix models and the robustness of a gradient-based iterative learning control (ILC) algorithm using both fixed learning gains and nonlinear data-dependent gains derived from parameter optimization. The philosophy of the paper is to ensure monotonic convergence with respect to the mean-square value of the error time series. The paper provides a complete and rigorous analysis for the systematic use of the well-known matrix models in ILC. Matrix models provide necessary and sufficient conditions for robust monotonic convergence. They also permit the construction of accurate sufficient frequency domain conditions for robust monotonic convergence on finite time intervals for both causal and non-causal controller dynamics. The results are compared with recently published results for robust inverse-model-based ILC algorithms and it is seen that the algorithm has the potential to improve the robustness to high-frequency modelling errors, provided that resonances within the plant bandwidth have been suppressed by feedback or series compensation. Copyright © 2008 John Wiley & Sons, Ltd. [source] Theoretical study of the prion protein based on the fragment molecular orbital methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2009Takeshi Ishikawa Abstract We performed fragment molecular orbital (FMO) calculations to examine the molecular interactions between the prion protein (PrP) and GN8, which is a potential curative agent for prion diseases. This study has the following novel aspects: we introduced the counterpoise method into the FMO scheme to eliminate the basis set superposition error and examined the influence of geometrical fluctuation on the interaction energies, thereby enabling rigorous analysis of the molecular interaction between PrP and GN8. This analysis could provide information on key amino acid residues of PrP as well as key units of GN8 involved in the molecular interaction between the two molecules. The present FMO calculations were performed using an original program developed in our laboratory, called "Parallelized ab initio calculation system based on FMO (PAICS)". © 2009 Wiley Periodicals, Inc. J Comput Chem 2009 [source] Error modeling and calibration of exteroceptive sensors for accurate mapping applicationsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 1 2010James P. Underwood Reliable robotic perception and planning are critical to performing autonomous actions in uncertain, unstructured environments. In field robotic systems, automation is achieved by interpreting exteroceptive sensor information to infer something about the world. This is then mapped to provide a consistent spatial context, so that actions can be planned around the predicted future interaction of the robot and the world. The whole system is as reliable as the weakest link in this chain. In this paper, the term mapping is used broadly to describe the transformation of range-based exteroceptive sensor data (such as LIDAR or stereo vision) to a fixed navigation frame, so that it can be used to form an internal representation of the environment. The coordinate transformation from the sensor frame to the navigation frame is analyzed to produce a spatial error model that captures the dominant geometric and temporal sources of mapping error. This allows the mapping accuracy to be calculated at run time. A generic extrinsic calibration method for exteroceptive range-based sensors is then presented to determine the sensor location and orientation. This allows systematic errors in individual sensors to be minimized, and when multiple sensors are used, it minimizes the systematic contradiction between them to enable reliable multisensor data fusion. The mathematical derivations at the core of this model are not particularly novel or complicated, but the rigorous analysis and application to field robotics seems to be largely absent from the literature to date. The techniques in this paper are simple to implement, and they offer a significant improvement to the accuracy, precision, and integrity of mapped information. Consequently, they should be employed whenever maps are formed from range-based exteroceptive sensor data. © 2009 Wiley Periodicals, Inc. [source] On the complexity of Rocchio's similarity-based relevance feedback algorithmJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 10 2007Zhixiang Chen Rocchio's similarity-based relevance feedback algorithm, one of the most important query reformation methods in information retrieval, is essentially an adaptive learning algorithm from examples in searching for documents represented by a linear classifier. Despite its popularity in various applications, there is little rigorous analysis of its learning complexity in literature. In this article, the authors prove for the first time that the learning complexity of Rocchio's algorithm is O(d + d2(log d + log n)) over the discretized vector space {0,,, n , 1}d, when the inner product similarity measure is used. The upper bound on the learning complexity for searching for documents represented by a monotone linear classifier over {0,,, n , 1}d can be improved to, at most, 1 + 2k (n , 1) (log d , log(n , 1)), where k is the number of nonzero components in q. Several lower bounds on the learning complexity are also obtained for Rocchio's algorithm. For example, the authors prove that Rocchio's algorithm has a lower bound on its learning complexity over the Boolean vector space {0, 1}d. [source] Finance and Firm Export in ChinaKYKLOS INTERNATIONAL REVIEW OF SOCIAL SCIENCES, Issue 1 2007Jun Du SUMMARY Using a rich panel data set, we provide a rigorous analysis of the relationship between access to external finance, foreign direct investment and the exports of private enterprises in China. We conclude that, in order to foster the exports of indigenous enterprises, the elimination of financial discrimination against private firms is likely to be a more effective policy tool than the reliance on spillovers from multinational firms. [source] Temperature characteristic analysis of a ferrite phase shifter in a grooved waveguideMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 3 2001Wenquan Che Abstract A rigorous analysis of the temperature characteristics of a ferrite phase shifter in a grooved waveguide is carried out by using a combination of analytical and numerical methods. The numerical results are found to be in agreement with our measurements. The results obtained provide valuable guidance for the simulation of the property of the device in the high-power case and for the optimization of the design of the device. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 156,159, 2001. [source] A method for quantifying rotational symmetryNEW PHYTOLOGIST, Issue 4 2007Frank M. Frey Summary ,,Here, a new approach for quantifying rotational symmetry based on vector analysis was described and compared with information obtained from a geometric morphometric analysis and a technique based on distance alone. ,,A new method was developed that generates a polygon from the length and angle data of a structure and then quantifies the minimum change necessary to convert that polygon into a regular polygon. This technique yielded an asymmetry score (s) that can range from 0 (perfect symmetry) to 1 (complete asymmetry). Using digital images of Geranium robertianum flowers, this new method was compared with a technique based on lengths alone and with established geometric morphometric methods used to quantify shape variation. ,,Asymmetry scores (s) more clearly described variation in symmetry and were more consistent with a visual assessment of the images than either comparative technique. ,,This procedure is the first to quantify the asymmetry of radial structures accurately, uses easily obtainable measures to calculate the asymmetry score and allows comparisons among individuals and species, even when the comparisons involve structures with different patterns of symmetry. This technique enables the rigorous analysis of polysymmetric structures and provides a foundation for a better understanding of symmetry in nature. [source] An enhanced-physics-based scheme for the NS-, turbulence modelNUMERICAL METHODS FOR PARTIAL DIFFERENTIAL EQUATIONS, Issue 6 2010William W. Miles Abstract We study a new enhanced-physics-based numerical scheme for the NS-alpha turbulence model that conserves both energy and helicity. Although most turbulence models (in the continuous case) conserve only energy, NS-alpha is one of only a very few that also conserve helicity. This is one reason why it is becoming accepted as the most physically accurate turbulence model. However, no numerical scheme for NS-alpha, until now, conserved both energy and helicity, and thus the advantage gained in physical accuracy by modeling with NS-alpha could be lost in a computation. This report presents a finite element numerical scheme, and gives a rigorous analysis of its conservation properties, stability, solution existence, and convergence. A key feature of the analysis is the identification of the discrete energy and energy dissipation norms, and proofs that these norms are equivalent (provided a careful choice of filtering radius) in the discrete space to the usual energy and energy dissipation norms. Numerical experiments are given to demonstrate the effectiveness of the scheme over usual (helicity-ignoring) schemes. A generalization of this scheme to a family of high-order NS-alpha-deconvolution models, which combine the attractive physical properties of NS-alpha with the high accuracy gained by combining ,-filtering with van Cittert approximate deconvolution. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2010 [source] MOSHER AWARD HONORABLE MENTION,THE LARYNGOSCOPE, Issue 4 2000Natural History of Acoustic Neuromas Abstract Objectives/Hypothesis 1) Develop a computerized technique to accurately compare acoustic neuroma size on routine computed tomography and magnetic resonance imaging (MRI) scans; 2) use this technique to determine the growth pattern in a large series of patients with acoustic neuroma who were conservatively managed; 3) describe the natural history of patients with acoustic neuromas who did not receive surgical intervention and those who underwent subtotal resection; 4) correlate the size and growth rate of acoustic neuromas to clinical presentation and auditory and vestibular testing; and 5) recommend guidelines for the management of patients with acoustic neuromas. Study Design A retrospective study from 1974 to 1999 of patients with unilateral acoustic neuromas who had conservative treatment by serial imaging studies (80 patients) or subtotal resection (49 patients). Methods All patient charts were evaluated for presenting symptoms, reasons for the type of management given, and clinical outcome. Charts were also reviewed with respect to serial audiological assessment, electronystagmography, and brainstem auditory evoked response. Imaging studies were analyzed using a computer technique so that serial studies could be compared to determine growth rates. Results Rigorous computer analysis of tumor size and growth rate was statistically the same as the radiologist's description of the tumor size and growth rate. Of 70 patients who were older than 65 years of age old at the time their tumor was discovered, 4 (5.7%) required intervention and 18 (26%) were dead of unrelated causes. These patients had a mean follow-up of 4.8 years (range, 0.01,17.2 y). Overall, growth rate for nonsurgical patients was 0.91 mm per year. Nonsurgical tumors did not grow or regressed in 42.3%. Overall postoperative growth rate for surgical subtotal resection patients was 0.35 mm per year. Surgical tumors did not grow or regressed after subtotal resection of acoustic neuroma in 68.5% of patients. Three patients (6.1%) required revision surgery because of tumor growth or the development of symptoms. Neither auditory nor vestibular testing was a reliable measure for determining tumor growth. Conclusion Measurement of the maximal tumor diameter on MRI scans is a reliable method for following acoustic neuroma growth. There is no need to perform a rigorous analysis of tumor size to determine whether the tumor is growing significantly. The vast majority of patients older than 65 years with acoustic neuromas do not require intervention. The indications for intervention should be based on a combination of rapid tumor growth with the development of symptoms. [source] Perils and possibilities: achieving best evidence from focus groups in public health researchAUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 2 2009Karen Willis Abstract Objective: Focus group research is often seen as a cost-effective way of gathering evidence from multiple research participants about the diversity of their views, experiences or beliefs. Our objective is to argue that focus group research only fulfils its potential if analysis of individual views is extended to include analysis of interaction between participants, so that we learn more why people hold these views. Approach: We outline the literature on focus group research, contrasting the ,quick-and-easy' approach with the demands of studies that are designed, conducted and analysed in a methodologically rigorous way to yield high quality public health evidence. Conclusion: Well-conducted focus groups contribute good evidence for public health decision making. The challenges of conducting high-quality studies should not be underestimated, and must involve rigorous analysis of both interaction and content. [source] Systematic review of early intervention programmes for children from birth to nine years who have a physical disabilityAUSTRALIAN OCCUPATIONAL THERAPY JOURNAL, Issue 4 2010Jenny Ziviani Aim:, To systematically review the literature on the effectiveness of early intervention programmes for children with physical disabilities. Methods:, Twelve electronic databases were searched for articles published between 1990 and April 2008. The quality of articles was appraised using an adapted version of the Checklist for the Evaluation of Research Articles and the Physiotherapy Evidence Database (PEDro) scale. Results:, Ten studies were included in the review. Cross-sectional and interrupted time-series studies were of moderate methodological quality, whereas the non-randomised control trial was of moderate-to-high methodological quality. Studies differed considerably with respect to participants, types of intervention and outcomes measured. Conclusions:, Positive outcomes for both children and families have resulted from early intervention. However, methodological limitations hamper a more rigorous analysis of findings across studies. [source] | ||||||||||||||||||||||