8,030 research outputs found
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Evolving dynamic multiple-objective optimization problems with objective replacement
This paper studies the strategies for multi-objective optimization in a dynamic environment. In particular, we focus on problems with objective replacement, where some objectives may be replaced with new objectives during evolution. It is shown that the Pareto-optimal sets before and after the objective replacement share some common members. Based on this observation, we suggest the inheritance strategy. When objective replacement occurs, this strategy selects good chromosomes according to the new objective set from the solutions found before objective replacement, and then continues to optimize them via evolution for the new objective set. The experiment results showed that this strategy can help MOGAs achieve better performance than MOGAs without using the inheritance strategy, where the evolution is restarted when objective replacement occurs. More solutions with better quality are found during the same time span
An investigation of air and water dual adjustment decoupling control of surface heat exchanger
The terminal equipment of central cooling system accounts for a significant proportion of the total system's energy consumption. Therefore, it is important to reduce the terminal equipment energy consumption in central air conditioning system. In this study, the difference of the effect of the chilled water flow rate and air supply rate on the surface cooler during the heat transfer process is taken into full account. Matlab/Simulink simulation software is used to model and simulate the heat transfer of surface cooler of the main terminal equipment of air conditioning system. Simulation tests and experimental validations are conducted by using variable chilled water flow rate and variable air supply rate control mode separately. The experiment results show that the simulation model can effectively predict the heat transfer performance of heat exchanger. Further, the study introduced a dual feedback control mode, which synchronously regulates the chilled water flow rate and air supply rate. Also, under certain conditions, the complex heat transfer process of the surface cooler can be decoupled, and single variable control pattern is used to separately regulate the chilled water flow rate and air supply rate. This can effectively shorten the system regulation time, reduce overshoot and improve control performance
Centrifuge modelling of cone penetration tests in layered soils
Penetration problems are important in many areas of geotechnical engineering, such as the prediction of pile capacity and interpretation of in situ test data. The cone penetration test is a proven method for evaluating soil properties, yet relatively little research has been conducted to understand the effect of soil layering on penetrometer readings. This paper focuses on the penetration of a probe within layered soils and investigates the layered soil effects on both penetration resistance and soil deformation. A series of centrifuge tests was performed in layered configurations of silica sand with varying relative density in a 180° axisymmetric model container. The tests allowed for the use of a half-probe for observation of the induced soil deformation through a poly(methyl methacrylate) window as well as a full-probe for measurement of penetration resistance within the central area of the container. The variations of penetration resistance and soil deformation characteristics as they relate to penetration depth, soil density and soil layering are examined. The results of deformation are also compared with previous experimental data to examine the effect of the axisymmetric condition. The effects of soil layering on both resistance and soil deformation are shown to be dependent on the relative properties between soil layers
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Undescended retropharyngeal parathyroid adenoma with adjacent thymic tissue in a 13-year-old boy with primary hyperparathyroidism.
We describe a rare presentation of a symptomatic parathyroid adenoma located in an ectopic retropharyngeal position in a 13-year-old boy. Preoperative CT scan and MRI demonstrated the ectopic location of the parathyroid adenoma. The patient underwent successful parathyroidectomy with cure of his hyperparathyroidism. On pathologic exam, the specimen was made up of a parathyroid adenoma and adjacent thymic tissue, indicating that it was likely an undescended lower parathyroid gland arising from the third pharyngeal pouch. Ectopic retropharyngeal parathyroid adenomas are very rare and to our knowledge, none have been previously described in adolescents
Nature-Inspired, Computer-Assisted Optimization of Hierarchically Structured Zeolites
Zeolite catalysis is often affected by transport limitations, which significantly influence overall performance. Introducing wide pores as molecular transport highways can reduce transport limitations, control the product distribution, and mitigate effects of catalyst deactivation. Nevertheless, the importance to rationally design the mesoâ and macropore space remains underappreciated. This article reviews multiscale modelling approaches to optimize overall catalytic performance. It provides a general methodology and rules of thumb to guide catalyst synthesis with optimal pore network characteristics. Inspiration is taken from nature, such as the structure of leaves and tissues, with similar requirements and associated features. In optimal hierarchically structured zeolites, the added macroâ/mesopore volume fraction, connectivity, crystal size, and minimum wide pore size are crucial. The broad pore size distribution is secondary. No uncontrolled diffusion limitations should exist within the zeolite crystals. Surface barriers, however, can significantly affect, even dominate overall transport. Understanding their origin and ways to control them is an emergent research area. Synthesis methods to realize hierarchically structured zeolites are briefly reviewed. Significant gaps exist between laboratory synthesis methods and industrial requirements. Zeolite catalysis could benefit from computerâassisted design of their hierarchical pore network, embracing principles used by natural transport networks for scalable efficiency, selectivity, and robustness
Benchmark solutions of large-strain cavity contraction for deep tunnel convergence in geomaterials
To provide precise prediction of tunnelling-induced deformation of the surrounding geomaterials, a framework for derivation of rigorous large-strain solutions of unified spherical and cylindrical cavity contraction is presented for description of confinement-convergence responses for deep tunnels in geomaterials. Considering the tunnelling-induced large deformation, logarithmic strains are adopted for cavity contraction analyses in linearly elastic, non-associated MohrâCoulomb, and brittle HoekâBrown media. Compared with approximate solutions, the approximation error indicates the importance of release of small-strain restrictions for estimating tunnel convergence profiles, especially in terms of the scenarios with high stress condition and stiffness degradation under large deformation. The ground reaction curve is therefore predicted to describe the volume loss and stress relaxation around the tunnel walls. The stiffness of circular lining is calculated from the geometry and equivalent modulus of the supporting structure, and a lining installation factor is thus introduced to indicate the time of lining installation based on the prediction of spherical cavity contraction around the tunnel opening face. This study also provides a general approach for solutions using other sophisticated geomaterial models, and serves as benchmarks for analytical developments in consideration of nonlinear large-deformation behaviour and for numerical analyses of underground excavation
Genome-Wide Localization of Protein-DNA Binding and Histone Modification by a Bayesian Change-Point Method with ChIP-seq Data
Next-generation sequencing (NGS) technologies have matured considerably since their introduction and a focus has been placed on developing sophisticated analytical tools to deal with the amassing volumes of data. Chromatin immunoprecipitation sequencing (ChIP-seq), a major application of NGS, is a widely adopted technique for examining protein-DNA interactions and is commonly used to investigate epigenetic signatures of diffuse histone marks. These datasets have notoriously high variance and subtle levels of enrichment across large expanses, making them exceedingly difficult to define. Windows-based, heuristic models and finite-state hidden Markov models (HMMs) have been used with some success in analyzing ChIP-seq data but with lingering limitations. To improve the ability to detect broad regions of enrichment, we developed a stochastic Bayesian Change-Point (BCP) method, which addresses some of these unresolved issues. BCP makes use of recent advances in infinite-state HMMs by obtaining explicit formulas for posterior means of read densities. These posterior means can be used to categorize the genome into enriched and unenriched segments, as is customarily done, or examined for more detailed relationships since the underlying subpeaks are preserved rather than simplified into a binary classification. BCP performs a near exhaustive search of all possible change points between different posterior means at high-resolution to minimize the subjectivity of window sizes and is computationally efficient, due to a speed-up algorithm and the explicit formulas it employs. In the absence of a well-established "gold standard" for diffuse histone mark enrichment, we corroborated BCP's island detection accuracy and reproducibility using various forms of empirical evidence. We show that BCP is especially suited for analysis of diffuse histone ChIP-seq data but also effective in analyzing punctate transcription factor ChIP datasets, making it widely applicable for numerous experiment types
Organoaluminium complexes of ortho-, meta-, para-anisidines: synthesis, structural studies and ROP of Δ-caprolactone (and rac-lactide)
Reaction of MeâAl (two equivalents) with ortho-, meta- or para-anisidine, (OMe)(NHâ)CâHâ, affords the complexes {[1,2-(OMe),NCâHâ(ÎŒ-MeâAl)](ÎŒ-MeâAl)}â (1), [1,3-(MeâAlOMe),NHCâHâ(ÎŒ-MeâAl)]2 (2) or [1,4-(MeâAlOMe),NHCâHâ(ÎŒ-MeâAl)]â (3), respectively. The molecular structures of 1â3 have been determined and all three complexes were found to be highly active for the ring opening polymerization (ROP) of Δ-caprolactone. 1 was found highly active either with or without benzyl alcohol present; at various temperatures, the activity order 1 > 2 â 3 was observed. For the ROP of rac-lactide results for 1â3 were poor
Real Scalar Field Scattering with Polynomial Approximation around Schwarzschild-de Sitter Black-hole
As one of the fitting methods, the polynomial approximation is effective to
process sophisticated problem. In this paper, we employ this approach to handle
the scattering of scalar field around the Schwarzschild-de Sitter black-hole.
The complex relationship between tortoise coordinate and radial coordinate is
replaced by the approximate polynomial. The Schrdinger-like equation,
the real boundary conditions and the polynomial approximation construct a full
Sturm-Liouville type problem. Then this boundary value problem can be solved
numerically according to two limiting cases: the first one is the Nariai
black-hole whose horizons are close to each other, the second one is when the
horizons are widely separated. Compared with previous results (Brevik and
Tian), the field near the event horizon and cosmological horizon can have a
better description.Comment: revtex4 source file, 11 pages, 8 figure
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