期刊文献+
共找到26篇文章
< 1 2 >
每页显示 20 50 100
Attenuate Class Imbalance Problem for Pneumonia Diagnosis Using Ensemble Parallel Stacked Pre-Trained Models
1
作者 Aswathy Ravikumar Harini Sriraman 《Computers, Materials & Continua》 SCIE EI 2023年第4期891-909,共19页
Pneumonia is an acute lung infection that has caused many fatalitiesglobally. Radiologists often employ chest X-rays to identify pneumoniasince they are presently the most effective imaging method for this purpose.Com... Pneumonia is an acute lung infection that has caused many fatalitiesglobally. Radiologists often employ chest X-rays to identify pneumoniasince they are presently the most effective imaging method for this purpose.Computer-aided diagnosis of pneumonia using deep learning techniques iswidely used due to its effectiveness and performance. In the proposed method,the Synthetic Minority Oversampling Technique (SMOTE) approach is usedto eliminate the class imbalance in the X-ray dataset. To compensate forthe paucity of accessible data, pre-trained transfer learning is used, and anensemble Convolutional Neural Network (CNN) model is developed. Theensemble model consists of all possible combinations of the MobileNetv2,Visual Geometry Group (VGG16), and DenseNet169 models. MobileNetV2and DenseNet169 performed well in the Single classifier model, with anaccuracy of 94%, while the ensemble model (MobileNetV2+DenseNet169)achieved an accuracy of 96.9%. Using the data synchronous parallel modelin Distributed Tensorflow, the training process accelerated performance by98.6% and outperformed other conventional approaches. 展开更多
关键词 Pneumonia prediction distributed deep learning data parallel model ensemble deep learning class imbalance skewed data
下载PDF
Zeno’s Paradoxes and Lie Tzu’s Dichotomic Wisdom Explained with Alpha Beta (αβ) Asymptotic Nonlinear Math (Including One Example on Second Order Nonlinear Phenomena)
2
作者 Ralph W. Lai Melisa W. Lai-Becker Evgenios Agathokleous 《Journal of Applied Mathematics and Physics》 2023年第5期1209-1249,共41页
Zeno’s paradoxes are a set of philosophical problems that were first introduced by the ancient Greek philosopher Zeno of Elea. Here is the first attempt to use asymptotic approach and nonlinear concepts to address th... Zeno’s paradoxes are a set of philosophical problems that were first introduced by the ancient Greek philosopher Zeno of Elea. Here is the first attempt to use asymptotic approach and nonlinear concepts to address the paradoxes. Among the paradoxes, two of the most famous ones are Zeno’s Room Walk and Zeno’s Achilles. Lie Tsu’s pole halving dichotomy is also discussed in relation to these paradoxes. These paradoxes are first-order nonlinear phenomena, and we expressed them with the concepts of linear and nonlinear variables. In the new nonlinear concepts, variables are classified as either linear or nonlinear. Changes in linear variables are simple changes, while changes in nonlinear variables are nonlinear changes relative to their asymptotes. Continuous asymptotic curves are used to describe and derive the equations for expressing the relationship between two variables. For example, in Zeno’s Room Walk, the equations and curves for a person to walk from the initial wall towards the other wall are different from the equations and curves for a person to walk from the other wall towards the initial wall. One walk has a convex asymptotic curve with a nonlinear equation having two asymptotes, while the other walk has a concave asymptotic curve with a nonlinear equation having a finite starting number and a bottom asymptote. Interestingly, they have the same straight-line expression in a proportionality graph. The Appendix of this discussion includes an example of a second-order nonlinear phenomenon. . 展开更多
关键词 DICHOTOMY Asymptotic Concave and Convex Curve Upper and Bottom As-ymptote Cumulative and Demulative Numbers (Opposite to Cumulative Numbers) Coefficient of Determination Skewed Bell Sigmoid Curve
下载PDF
基于修正Sharpe指数的我国开放式基金业绩评价研究 被引量:4
3
作者 于天军 田金信 汪洋 《中国软科学》 CSSCI 北大核心 2010年第7期175-183,共9页
国内外大量实证研究发现基金收益率呈明显的尖峰、厚尾性和有偏性的非正态分布。针对Sharpe指数前提假设是收益率服从正态分布及使用标准差来度量投资风险的缺陷。本文提出用能更好的刻画投资基金收益率分布的非对称性和尖峰、厚尾性的S... 国内外大量实证研究发现基金收益率呈明显的尖峰、厚尾性和有偏性的非正态分布。针对Sharpe指数前提假设是收益率服从正态分布及使用标准差来度量投资风险的缺陷。本文提出用能更好的刻画投资基金收益率分布的非对称性和尖峰、厚尾性的Skewed-t分布来拟合基金收益率分布。在此基础上分别给出了基于Skewed-t分布标准差和Skewed-t分布下的FIGARCH-SKST模型测算的VaR值的修正夏普指数;然后对22只开放式基金数据进行了实证分析。结果表明,基于Skewed-t分布修正的Sharpe指数是有效的。 展开更多
关键词 基金业绩评价 Skewed—t分布 FIGARCH—SKST模型 Sharpe指数
下载PDF
Neoplastic-Like CELL Changes of Normal Fibroblast Cells Associated with Evolutionary Conserved Maternal and Paternal Genomic Autonomous Behavior (Gonomery) 被引量:7
4
作者 Kirsten H. Walen 《Journal of Cancer Therapy》 2014年第9期860-877,共18页
The present comparative review discusses conservation of early evolutionary, relic genetics in the genome of man, which determine two different mechanistic reductive division systems expressed by normal, human diploid... The present comparative review discusses conservation of early evolutionary, relic genetics in the genome of man, which determine two different mechanistic reductive division systems expressed by normal, human diploid cells. The divisions were orderly and segregated genomes reductively to near-diploid daughter cells, which showed gain of a proliferative advantage (GPA) over cells of origin. This fact of GPA expression is a fundamental requirement for initiation of tumorigenesis. The division systems were responses to a carcinogen-free induction system, consisting of short (1 - 3 days) exposures of young cells to nutritional deprivation of amino acid glutamine (AAD). In recovery growth (2 - 4 days) endo-tetra/ochtoploid cells and normal diploid metaphase cells demonstrated chromosomal reductive divisions to respectively heterozygous and homozygous altered daughter cells. Both division systems showed co-segregating whole complements, which for reduction of the diploid metaphases could only arise from gonomeric-based autonomous behavior of maternal and paternal (mat/pat) genomes. The timely associated appearance with these latter divisions was fast growing small-cells (1/2 volume-size reduced from normal diploidy), which became homozygous from haploid, genomic doubling. Both reductive divisions thus produced genome altered progeny cells with GPA, which was associated with pre-cancer-like cell-phenotypic changes. Since both “undesirable” reductive divisions expressed orderly division sequences, their genetic controls were assumed to be “old genetics”, evolutionarily conserved in the genome of man. Support for this idea was a search for evidential material in the evolutionary record from primeval time, when haploid organisms were established. The theory was that endopolyploid and gonomery-based reductive divisions relieved the early eukaryotic organisms from accidental, non-proliferative diploidy and polyploidy, bringing the organism back to vegetative haploid proliferation. Asexual cycles were common for maintenance of propagating haploid and diploid early unicellular eukaryotes. Reduction of accidental diploidy was referred to as “one-step meiosis” which meant gonomeric-based maternal and paternal genomic independent segregations. This interpretation was supported by exceptional chromosomal behaviors. However, multiple divisions expressing non-disjunction was the choice-explanation from evolutionists, which today is also suggested for the rarer LL-1 near haploid leukemia. These preserved non-mitotic mechanistic divisions systems are today witnessed in apomixes and parthenogenesis in many animal phyla. Thus, the indications are the modern genome of man harbors, relic-genetics from past “good” evolvements assuring “stable” proliferation of ancient, primitive eukaryotes, but with cancer-like effects for normal human cells. 展开更多
关键词 CYTOGENETICS Pathologic Cytology ENDOMITOSIS Division skewedness Pathological Mitosis METAPHASE Rosettes HOMOZYGOUS LOH Growth Pattern Nutrition Amino Acid
下载PDF
基于偏态分布的风险度量计算
5
作者 王泓娜 宋立新 《大连理工大学学报》 EI CAS CSCD 北大核心 2012年第4期615-618,共4页
金融时间序列具有尖峰厚尾性,同时在股市中又存在着杠杆效应.对股票指数收盘价格的对数收益率序列建立ARMA-APARCH模型,在对数收益率序列分别满足Skewed-t分布和Skewed-GED的假设下,给出了在险价值及期望损失的计算方法.对t分布与Skewe... 金融时间序列具有尖峰厚尾性,同时在股市中又存在着杠杆效应.对股票指数收盘价格的对数收益率序列建立ARMA-APARCH模型,在对数收益率序列分别满足Skewed-t分布和Skewed-GED的假设下,给出了在险价值及期望损失的计算方法.对t分布与Skewed-t分布、GED与Skewed-GED分别进行对比性实证分析,结果表明,在两个偏态分布假设下计算得到的期望损失估计结果更为保守,更能够捕捉到股市的尾部风险. 展开更多
关键词 APARCH Skewed—t分布 Skewed—GED 在险价值 期望损失
下载PDF
投资组合行业配置的动态VaR研究——基于时变Copula-GJR-Skewed-t模型
6
作者 刘澄 张玲 《金融理论与实践》 CSSCI 北大核心 2013年第9期7-11,共5页
用时变Copula-GJR-Skewed-t模型研究了深证22个行业分类指数中任意两个投资组合的动态VaR,并与静态VaR比较。实证结果表明,时变t-Copula函数在众多Copula函数中对行业投资组合的拟合效果最优,给出了模型估计出的VaR最大和最小的5对行业... 用时变Copula-GJR-Skewed-t模型研究了深证22个行业分类指数中任意两个投资组合的动态VaR,并与静态VaR比较。实证结果表明,时变t-Copula函数在众多Copula函数中对行业投资组合的拟合效果最优,给出了模型估计出的VaR最大和最小的5对行业组合,不同行业组合的动态VaR在股市周期各阶段关系相对稳定,同一行业组合的动态VaR和静态VaR关系相对稳定,且略高于静态VaR。 展开更多
关键词 时变COPULA 动态VAR 行业组合 GJR—Skewed—t
下载PDF
Mobile bed thickness in skewed asymmetric oscillatory sheet flows 被引量:5
7
作者 Xin Chen Yong Li Fujun Wang 《Acta Mechanica Sinica》 SCIE EI CAS CSCD 2018年第2期257-265,共9页
A new instantaneous mobile bed thickness model is presented for sediment transport in skewed asymmetric oscillatory sheet flows. The proposed model includes a basic bed load part and a suspended load part related to t... A new instantaneous mobile bed thickness model is presented for sediment transport in skewed asymmetric oscillatory sheet flows. The proposed model includes a basic bed load part and a suspended load part related to the Shields parameter, and takes into account the effects of mass conservation, phase-lag, and asymmetric boundary layer development, which are important in skewed asymmetric flows but usually absent in classical models. The proposed model is validated by erosion depth and sheet flow layer thickness data in both steady and unsteady flows, and applied to a new instantaneous sediment transport rate formula. With higher accuracy than classical empirical models in steady flows, the new formula can also be used for instantaneous sediment transport rate prediction in skewed asymmetric oscillatory sheet flows. 展开更多
关键词 MOBILE BED thickness PHASE-LAG Sediment transport Sheet FLOW Skewed ASYMMETRIC OSCILLATORY FLOW
下载PDF
水下圆柱冲刷的时间演变 被引量:1
8
作者 Abhijit Rout Arindam Sarkar 《Journal of Marine Science and Application》 CSCD 2021年第1期85-101,共17页
Temporal evolutions of scour at submerged circular cylinders were investigated.Flow visualization was carried out around the cylinders over plane,under developed and equilibrium scour holes.Video analysis technique wa... Temporal evolutions of scour at submerged circular cylinders were investigated.Flow visualization was carried out around the cylinders over plane,under developed and equilibrium scour holes.Video analysis technique was used to formulate the equations for determining the diameter of the horseshoe vortex around the submerged cylinders,which is also verified from the vector diagrams drawn using the velocity measurements.The scour process similar to live bed scour was noticed around the downstream cylinder.The diameter of the horseshoe vortex is found to depend on the diameter of respective cylinder,submergence ratio,spacing between the cylinders and skew angle.This formulation along with the dislodgement and transportation of a single sediment particle is further incorporated in the proposed model for determining the time variation of scour around the submerged cylinders.It is evident from the results that the upstream cylinder shelters the downstream cylinder and thereby reduces the scour at the downstream cylinder.Proposed model is further extended to incorporate the effect of non-uniformity of the sediment particles on the time variation of scour depth.The results indicate significant reduction of scour depth of around 6%and 35%for upstream and downstream cylinders respectively due to the formation of the armor layer.The model is also compared with the local scour component of field data around cylindrical bridge piers to establish the differences in the scour process around a partially submerged cylinder and fully submerged tandem and skewed cylinders. 展开更多
关键词 SCOUR TANDEM Skewed Submerged cylinder SEDIMENT Time variation
下载PDF
Genomic Instability in Cancer I: DNA-Repair Triggering Primitive Hereditary 4n-Skewed, Amitotic Division-System, the Culprit in EMT/MET/Metaplasia Cancer-Concepts 被引量:3
9
作者 Kirsten H. Walen 《Journal of Cancer Therapy》 2018年第12期974-997,共24页
The objective was to gain proof of genome damage-repair induced mitotic slippage process (MSP) to 4n-diplochromosome skewed division-system, earlier suggested to have “cancer-deciding” consequences. Our damage-model... The objective was to gain proof of genome damage-repair induced mitotic slippage process (MSP) to 4n-diplochromosome skewed division-system, earlier suggested to have “cancer-deciding” consequences. Our damage-model showed two succeeding phases: molecular mutations for initiation of fitness-gained cells, and large chromosomal changes to aneuploidy from inherited DNA-breakage-repair inaccuracies. The mutations were gained while DNA-repair and DNA-replication, co-existed in the route to tetraploidy, a phenomenon also expressed for some existing unicellular organisms. These organisms also showed genome reductive, amitotic, meioticlike division, and was the origin of human genome conserved, self-inflicted 90° reorientation of the 4n nucleus relative to the cytoskeleton axis. In the in vitro DNA-damage model, this remarkable 4n-event deciding “flat-upright” cell-growth characteristics showed several consequences, for example, cancer-important, E-cadherin-β-catenin cell-to-cell adherence destruction, which gave diploid progeny cells, mobility freedom from cell contact inhibition, likely in renewal tissues. This 4n-skewed division-system with inheritance in progeny cells for repeat occurrences as mentioned for flat-up-right growth patterns is similar to claimed concepts of metaplasia-EMT/MET embryogenesis events in cancer evolution. A scrutiny of this literature, proof-wise invalidated this embryological concept by tetraploid 8C cells occurring in MET events and, was noted for small cell occurrence, i.e., diploidy from 4n-8C reductive division, an also event for tumor relapse cells, derived from genome damaging therapy agents. Pre-cancer hyperplasia reported MSP, cadherincatenin destruction and 90° perpendicularity to basal cell membrane. The DNA-damage-repair model can weed-out therapy-agents triggering 4n-skewed division. Cancer-control, beginning-information, is likely from mutational identity of the 4n derived fitness-gained cells. 展开更多
关键词 CANCER Evolution DNA-Damage-Repair Mitotic Slippage HEREDITARY PRIMITIVE Tetraploidy 90° Amitotic Skewed DIVISION Fitness-Gain Embryogenesis-Type EMT/MET Human Cell Conservation
下载PDF
Cancer Prevention? Fundamental Genomic Alterations Are Present in Preneoplasia, Including Function of High Frequency Selected Mutations (HFSMs) 被引量:2
10
作者 Kirsten H. Walen 《Journal of Cancer Therapy》 2016年第6期416-426,共11页
In a series of publications a special, tetraploid diplochromosomal division system to only two types of progeny cells (4n/4C/G1 and 2n/4C para-diploid) has been suggested to initiate preneoplasia that can lead to a ca... In a series of publications a special, tetraploid diplochromosomal division system to only two types of progeny cells (4n/4C/G1 and 2n/4C para-diploid) has been suggested to initiate preneoplasia that can lead to a cancerous pathway. Colorectal and other preneoplasia are known with the pathogenic, histological phases of hyperplasia to arrested adenoma/nevi that can give rise to dysplasia with high risk for cancer development. The present theme is to find solutions to tumorigenic unsolved, biological problems (queries), explainable from the tetraploid 4n-system, which would support its operation in the cancerous pathway. Presently admitted, the mutational sequencing of the cancer genome (cancer chemistry) cannot discover so-called “dark matter”, which herein is considered to be the queries. The solutions from the 4n-system were largely supported by mutated APC-induced same type of tetraploidy from the mitotic slippage process. But importantly, these behaviors and consequences could be linked to the beginning of hyperplastic lesions and their development to the arrest-phase of preneoplasia (polyps/nevi). Function of HFSMs is mostly unknown, but for Barrett’s esophagus, HFSMs (p53, p16ink4a) caused inactivation of the Rb gene, leading to dysplasia with 4n, aneuploid, abnormal cell cycles. In vitro models of the 4n-system from normal human cells recapitulated preneoplasia-like histopathological changes. It was speculated that the “cancer-crucial” step to dysplasia could be therapy-vulnerable to CRISPR-caspase editing, and perhaps antibody treatment. Additionally, the 4n-system with spontaneous cell-behaviors together with preneoplasia molecular data promises construction of a more truthful cancer-paradigm than from sequencing data alone. 展开更多
关键词 DNA/Breakage/Repair Mitotic Slippage COHESIN Tetraploid System Segregation/Orderly Hyperplasia Dysplasia 4n-Cell-Cycles Skewed Cytoskeleton Antibody CRISPR-Caspase Therapy
下载PDF
On Tilings of Quadrants and Rectangles and Rectangular Pattern 被引量:2
11
作者 Viorel Nitica 《Open Journal of Discrete Mathematics》 2016年第4期351-371,共21页
The problem of tiling rectangles by polyominoes generated large interest. A related one is the problem of tiling parallelograms by twisted polyominoes. Both problems are related with tilings of (skewed) quadrants by p... The problem of tiling rectangles by polyominoes generated large interest. A related one is the problem of tiling parallelograms by twisted polyominoes. Both problems are related with tilings of (skewed) quadrants by polyominoes. Indeed, if all tilings of a (skewed) quadrant by a tile set can be reduced to a tiling by congruent rectangles (parallelograms), this provides information about tilings of rectangles (parallelograms). We consider a class of tile sets in a square lattice appearing from arbitrary dissections of rectangles in two L-shaped polyominoes and from symmetries of these tiles about the first bisector. Only translations of the tiles are allowed in a tiling. If the sides of the dissected rectangle are coprime, we show the existence of tilings of all (skewed) quadrants that do not follow the rectangular (parallelogram) pattern. If one of the sides of the dissected rectangle is 2 and the other is odd, we also show tilings of rectangles by the tile set that do not follow the rectangular pattern. If one of the sides of the dissected rectangle is 2 and the other side is even, we show a new infinite family of tile sets that follows the rectangular pattern when tiling one of the quadrants. For this type of dis-section, we also show a new infinite family that does not follow the rectangular pattern when tiling rectangles. Finally, we investigate more general dissections of rectangles, with. Here we show infinite families of tile sets that follow the rectangular pattern for a quadrant and infinite families that do not follow the rectangular pattern for any quadrant. We also show, for infinite families of tile sets of this type, tilings of rectangles that do not follow the rectangular pattern. 展开更多
关键词 POLYOMINO L-Shaped Polyomino Skewed L-Shaped Polyomino Tiling Rectangles Tiling Quadrants Tiling Parallelograms Rectangular Pattern for Tiling Quadrants/Rectangles
下载PDF
Signed Tilings by Ribbon L n-Ominoes, n Odd, via Gröbner Bases 被引量:1
12
作者 Viorel Nitica 《Open Journal of Discrete Mathematics》 2016年第4期297-313,共17页
We show that a rectangle can be signed tiled by ribbon L n-ominoes, n odd, if and only if it has a side divisible by n. A consequence of our technique, based on the exhibition of an explicit Gr&#246;bner basis, is... We show that a rectangle can be signed tiled by ribbon L n-ominoes, n odd, if and only if it has a side divisible by n. A consequence of our technique, based on the exhibition of an explicit Gr&#246;bner basis, is that any k-inflated copy of the skewed L n-omino has a signed tiling by skewed L n-ominoes. We also discuss regular tilings by ribbon L n-ominoes, n odd, for rectangles and more general regions. We show that in this case obstructions appear that are not detected by signed tilings. 展开更多
关键词 POLYOMINO Replicating Tile L-Shaped Polyomino Skewed L-Shaped Polyomino Signed Tilings Gröbner Basis Coloring Invariants
下载PDF
Signed Tilings by Ribbon L n-Ominoes, n Even, via Gröbner Bases 被引量:1
13
作者 Kenneth Gill Viorel Nitica 《Open Journal of Discrete Mathematics》 2016年第3期185-206,共22页
Let T<sub>n </sub>be the set of ribbon L-shaped n-ominoes for some n≥4 even, and let T<sup>+</sup><sub>n</sub> be T<sub>n</sub> with an extra 2 x 2 square. We investiga... Let T<sub>n </sub>be the set of ribbon L-shaped n-ominoes for some n≥4 even, and let T<sup>+</sup><sub>n</sub> be T<sub>n</sub> with an extra 2 x 2 square. We investigate signed tilings of rectangles by T<sub>n</sub> and T<sup>+</sup><sub>n</sub> . We show that a rectangle has a signed tiling by T<sub>n</sub> if and only if both sides of the rectangle are even and one of them is divisible by n, or if one of the sides is odd and the other side is divisible by . We also show that a rectangle has a signed tiling by T<sup>+</sup><sub>n, </sub> n≥6 even, if and only if both sides of the rectangle are even, or if one of the sides is odd and the other side is divisible by . Our proofs are based on the exhibition of explicit Gr&Ouml;bner bases for the ideals generated by polynomials associated to the tiling sets. In particular, we show that some of the regular tiling results in Nitica, V. (2015) Every tiling of the first quadrant by ribbon L n-ominoes follows the rectangular pattern. Open Journal of Discrete Mathematics, 5, 11-25, cannot be obtained from coloring invariants. 展开更多
关键词 POLYOMINO Replicating Tile L-Shaped Polyomino Skewed L-Shaped Polyomino Signed Tilings Gröbner Basis Tiling Rectangles Coloring Invariants
下载PDF
Simulation Program to Determine Sample Size and Power for a Multiple Logistic Regression Model with Unspecified Covariate Distributions
14
作者 Naoko Kumagai Kohei Akazawa +2 位作者 Hiromi Kataoka Yutaka Hatakeyama Yoshiyasu Okuhara 《Health》 2014年第21期2973-2998,共26页
Binary logistic regression models are commonly used to assess the association between outcomes and covariates. Many covariates are inherently continuous, and have a variety of distributions, including those that are h... Binary logistic regression models are commonly used to assess the association between outcomes and covariates. Many covariates are inherently continuous, and have a variety of distributions, including those that are heavily skewed to the left or right. Existing theoretical formulas, criteria, and simulation programs cannot accurately estimate the sample size and power of non-standard distributions. Therefore, we have developed a simulation program that uses Monte Carlo methods to estimate the exact power of a binary logistic regression model. This power calculation can be used for distributions of any shape and covariates of any type (continuous, ordinal, and nominal), and can account for nonlinear relationships between covariates and outcomes. For illustrative purposes, this simulation program is applied to real data obtained from a study on the influence of smoking on 90-day outcomes after acute atherothrombotic stroke. Our program is applicable to all effect sizes and makes it possible to apply various statistical methods, logistic regression and related simulations such as Bayesian inference with some modifications. 展开更多
关键词 LOGISTIC Regression Model MONTE Carlo Simulation Non-Standard DISTRIBUTIONS Nonlinear POWER SAMPLE Size Skewed Distribution
下载PDF
Validation of Chaviaro Poulos and Hansen Stall Delay Model in the Case of Horizontal Axis Wind Turbine Operating in Yaw Conditions
15
作者 Abdelfattah Bouatem Ahmed Al Mers 《Energy and Power Engineering》 2013年第1期18-25,共8页
Operating in natural wind field, the horizontal axis wind turbines are subject to cyclical variation of aerodynamic loads. This cyclical loads fluctuation is a result of two aerodynamic phenomenon: the first one is th... Operating in natural wind field, the horizontal axis wind turbines are subject to cyclical variation of aerodynamic loads. This cyclical loads fluctuation is a result of two aerodynamic phenomenon: the first one is the advancing and retreating blade effect;the second one is related to the cyclical variation of induced velocity at the rotor plane. In these operating conditions, the correct prediction of this load variation is necessary to predict some important parameters linked to the fatigue and stability of free yawing turbines. The main objective of the present study is the evaluation of the azimuthal variation of normal force at different radial positions. To model the problem, the blade element momentum theory is used and wind turbine is supposed operate in yaw conditions. The aerodynamic coefficients are corrected using Chaviaropoulos and Hansen model to take into account the phenomenon of stall delay. A computer code was developed to obtain the numerical values and results are compared with measurements performed in the NASA Ames wind tunnel. 展开更多
关键词 WIND TURBINE WAKE Yaw STALL STALL DELAY Skewed WAKE RENEWABLE Energy
下载PDF
Every Tiling of the First Quadrant by Ribbon <i>L n</i>-Ominoes Follows the Rectangular Pattern
16
作者 Viorel Nitica 《Open Journal of Discrete Mathematics》 2015年第2期11-25,共15页
Let and let be the set of four ribbon L-shaped n-ominoes. We study tiling problems for regions in a square lattice by . Our main result shows a remarkable property of this set of tiles: any tiling of the first quadran... Let and let be the set of four ribbon L-shaped n-ominoes. We study tiling problems for regions in a square lattice by . Our main result shows a remarkable property of this set of tiles: any tiling of the first quadrant by , n even, reduces to a tiling by and rectangles, each rectangle being covered by two ribbon L-shaped n-ominoes. An application of our result is the characterization of all rectangles that can be tiled by , n even: a rectangle can be tiled by , n even, if and only if both of its sides are even and at least one side is divisible by n. Another application is the existence of the local move property for an infinite family of sets of tiles: , n even, has the local move property for the class of rectangular regions with respect to the local moves that interchange a tiling of an square by n/2 vertical rectangles, with a tiling by n/2 horizontal rectangles, each vertical/horizontal rectangle being covered by two ribbon L-shaped n-ominoes. We show that none of these results are valid for any odd n. The rectangular pattern of a tiling of the first quadrant persists if we add an extra tile to , n even. A rectangle can be tiled by the larger set of tiles if and only if it has both sides even. We also show that our main result implies that a skewed L-shaped n-omino, n even, is not a replicating tile of order k2 for any odd k. 展开更多
关键词 POLYOMINO Replicating Tile L-Shaped POLYOMINO Skewed L-Shaped POLYOMINO Local Move Property TILING Rectangles RECTANGULAR PATTERN TILING First QUADRANT
下载PDF
Reconstructing a Six-Leg Intersection into Mohave County’s First Roundabout
17
作者 Steven P.Latoski 《Journal of Traffic and Transportation Engineering》 2018年第2期53-60,共8页
Mohave County,Arizona maintains a six-leg intersection in the Golden Shores area bisected by an uncontrolled regional County highway,County Route 1,where two STOP-controlled section line local roads converge.The two-l... Mohave County,Arizona maintains a six-leg intersection in the Golden Shores area bisected by an uncontrolled regional County highway,County Route 1,where two STOP-controlled section line local roads converge.The two-lane,rural CR 1 serves commuter and visitor traffic traveling between population centers of Lake Havasu City,AZ and Bullhead City,AZ/Laughlin,NV on the Colorado River and its desert lakes.The intersection features 180 total vehicle-to-vehicle conflict points inclusive of 126 crossing conflicts.This paper presents the County’s technical and administrative approach and techniques in planning and developing the CR 1“Six Points”roundabout given the(1)absence of fatal and incapacitating injury crash history and(2)backdrop of this improvement representing the County’s first roundabout.Project initiation entailed the County securing a Federal share of Highway Safety Improvement Program funding at 100-percent.Project design commenced with a preliminary engineering study to identify,evaluate,and solicit public input on alternative improvement solutions as part of validating the roundabout improvement as superior for traffic operations,community and business function,sitting,and constructability.Public input targeted preference for maintaining CR 1 uninterrupted flow versus interrupted flow introduced under roundabout circulation.This simple decision tree enabled the County to understand existing operational and access conditions important to the public,business owners,and public safety providers for purpose of configuring a roundabout improvement satisfying local motorist and community needs,which stoked stakeholder buy-in on the project. 展开更多
关键词 ROUNDABOUT thru-about safety skewed INTERSECTIONS PREDICTIVE modeling benefit-cost
下载PDF
Some Financial Problems in the Light of EMM Results:Asset Pricing and Efficient Portfolio Allocation
18
作者 Valery V.Shemetov 《Management Studies》 2022年第5期294-324,共31页
Discussing results in asset pricing and efficient portfolio allocation,we show that mixed success and errors in these results often follow from a lack of information about the asset return distribution and wrong assum... Discussing results in asset pricing and efficient portfolio allocation,we show that mixed success and errors in these results often follow from a lack of information about the asset return distribution and wrong assumptions about its properties.Some mistakes in asset pricing come from the assumption of symmetry in return distributions.Some errors in efficient portfolio allocation follow from Markowitz’s approach when applying it to portfolio optimization of skewed asset returns.The Extended Merton model(EMM),generating skewed return distributions,demonstrates that(i)in skewed asset returns,the variance is not an adequate measure of risks and(ii)positive skewness in the asset returns comes together with a high default probability.Thus,the maximization of the mean portfolio returns and skewness with controlled variance used in mainstream papers can critically increase portfolio risks.We present the new settings of the optimal portfolio allocation problem leading to less risky efficient portfolios than the solutions suggested in all previous papers. 展开更多
关键词 asset pricing efficient portfolio allocation skewed returns default probability Extended Merton model
下载PDF
基于Skewed Miura构型的周期可展结构变带隙分析研究
19
作者 郭书瑜 喻莹 彭肖桐 《空间结构》 CSCD 北大核心 2023年第4期57-64,79,共9页
基于折纸构型的周期结构在一定条件下具有带隙特性,能阻止特定频率的弹性波在结构中传播,这种带隙特征可以调节,为减振结构的开发提供了新思路.对基于Skewed Miura折纸构型的周期性可展结构变带隙机理进行研究.推导了Skewed Miura折纸... 基于折纸构型的周期结构在一定条件下具有带隙特性,能阻止特定频率的弹性波在结构中传播,这种带隙特征可以调节,为减振结构的开发提供了新思路.对基于Skewed Miura折纸构型的周期性可展结构变带隙机理进行研究.推导了Skewed Miura折纸构型的几何关系,并利用布洛赫波分析框架研究了该构型的带隙情况.将Skewed Miura单元的几何形状和折纸构型的折叠状态作为设计变量,找出该构型的最大带隙值和相应的折展状态.对比发现,Skewed Miura构型带隙的数量及大小明显大于Miura构型,且带隙位置所处频率范围较低.本研究为减振结构的开发提供了新的结构形式. 展开更多
关键词 Skewed Miura折纸构型 周期性可展结构 变带隙机理
原文传递
Stability management of high speed axial flow compressor stage through axial extensions of bend skewed casing treatment 被引量:3
20
作者 Dilipkumar Bhanudasji Alone S.Satish Kumar +4 位作者 Shobhavathy M.Thimmaiah Janaki Rami Reddy Mudipalli A.M.Pradeep Srinivasan Ramamurthy Venkat S.Iyengara 《Propulsion and Power Research》 SCIE 2016年第3期236-249,共14页
This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend s... This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend skewed casing treatment with moderate porosity.The bend skewed casing treatment of 33%porosity was coupled with rectangular plenum chamber of depth equal to the slots depth.The five axial extensions of 20%,40%,60%,80%and 100%were used for the experimental evaluations of compressor performance.The main objective was to identify the optimum extension of the casing treatment with reference to rotor leading edge which results in maximum stall margin improvements with minimum loss in the stage efficiency.At each axial extension the compressor performance is distinctive.The improvement in the stall margin was very significant at some axial extensions with 4%–5%penalty in the stage efficiency.The compressors stage shows recovery in terms of efficiency at lower axial extensions of 20%and 40%with increase in the peak stage efficiency.Measurements of flow parameters showed the typical behaviors at near stall flow conditions.Hot wire sensor was placed at the rotor upstream in the tip region to capture the oscillations in the inlet axial and tangential velocities at stall conditions.In the absence of casing treatment the compressor exhibit abrupt stall with very high oscillations in the inlet axial and tangential velocity of the flow.The extents of oscillations reduce with bend skewed casing treatment.Few measurements were also performed in the plenum chamber and salient results are presented in this paper. 展开更多
关键词 High speed compressor Bend skewed casing treatments Axial extensions Stall margin improvements Peak stage efficiency Hot wire probe STALL ABRUPT
原文传递
上一页 1 2 下一页 到第
使用帮助 返回顶部