28,777 research outputs found

    A Judicial Postscript to the Church-State Debates of 1989: How Porous the Wall, How Civil the State?

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    This work is a continuation of the debate regarding the Establishment Clause. The focus lies with Justice O’Connor’s concurrence in County of Allegheny v. ACLU and how this opinion harkens back to a concept shared by Jefferson and Madison, that the establishment clause is designed to prevent government favoritism

    Confidence intervals for tourism demand elasticity

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    2009-2010 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

    Correlated EEMD and effective feature extraction for both periodic and irregular faults diagnosis in rotating machinery

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    © 2017 by the authors. Licensee MDPI, Basel, Switzerland. Intelligent fault diagnosis of complex machinery is crucial for industries to reduce the maintenance cost and to improve fault prediction performance. Acoustic signal is an ideal source for diagnosis because of its inherent characteristics in terms of being non-directional and insensitive to structural resonances. However, there are also two main drawbacks of acoustic signal, one of which is the low signal to noise ratio (SNR) caused by its high sensitivity and the other one is the low computational efficiency caused by the huge data size. These would decrease the performance of the fault diagnosis system. Therefore, it is significant to develop a proper feature extraction method to improve computational efficiency and performance in both periodic and irregular fault diagnosis. To enhance SNR of the acquired acoustic signal, the correlation coefficient (CC) method is employed to eliminate the redundant intrinsic mode functions (IMF), which comes from the decomposition procedure of pre-processing known as ensemble empirical mode decomposition (EEMD), because the higher the correlated coefficient of an IMF is, the more significant fault signatures it would contain, and the redundant IMF would compromise both the SNR and the computational cost performance. Singular value decomposition (SVD) and sample Entropy (SampEn) are subsequently used to extract the fault feature, by exploiting their sensitivities to irregular and periodic fault signals, respectively. In addition, the proposed feature extraction method using sparse Bayesian based pairwise coupled extreme learning machine (PC-SBELM) outperforms the existing pairwise-coupling probabilistic neural network (PC-PNN) and pairwise-coupling relevance vector machine (PC-RVM) by 1.8%and 2%, respectively, to achieve an accuracy of 93.9%. The experiments conducted on the periodic and irregular faults in the gears and bearings have demonstrated that the proposed hybrid fault diagnosis system is effective

    华北克拉通北缘晚中生代火山岩Sr-Nd-Pb同位素填图及其构造意义

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    辽宁西部广泛分布着晚中生代火山岩,横跨华北克拉通和兴> 蒙造山带两大构造单元,一般认为它们是以在这一地区发育的两条主要断裂———西拉木伦河断裂和赤峰> 开源断裂为界。这些火山作用曾被认为是中生代伊泽奈崎板块西向或西北向消减作用的结果。在岩性上它们主要以中酸性岩石为主,玄武岩等中基性岩石较少。为查明下伏岩石圈对这些岩浆作用成因的影响,对其中的SiO2 含量 开源断裂两侧为界,两侧火山岩的同位素特征存在显著区别。南区有明显的EMI 特征并具EMI-PM 混合趋势,而北区则显示了原始或略亏损的特征。南北两区之间的过渡带(介于西拉木伦河断裂和赤峰> 开源断裂之间)则表现了同位素组成上相应的过渡特征。这一地球化学观测与已有的地质和地球物理资料颇为吻合。基于新生代幔源岩石化学反演的中国东部陆下地幔化学区划研究揭示了克拉通下(subcratonic)岩石圈地幔与EMI 存在着密切关系。本研究所提供的地球化学证据说明了采用中生代中基性岩类作为类似研究途径的可行性,并进一步提出对华北克拉通边缘中生代火山作用成因另一种可能的解释,即古消减带物质的活化有可能对华北北缘火山岩源区物质组成产生重要影响。Late Mesozoic volcanic rocks are extensively spread on both sides of northern margin of the North China Craton (NCC), where is the boundary between an Archean craton to the south and a Paleozoic orogenic belt, Xing an- Mongolia Orogenic Belt (XMOB), to the north. Two major east- west trending faults, Kaiyuan- Chifeng Fault (KCF) and Xar Moron He Fault (XHF) develop in this margin zone as a boundary between two tectonic domains. The volcanism has been thought to be the magmatic response to the west- , or no...published_or_final_versio

    Benchmark performance of low-cost Sb2Se3 photocathodes for unassisted solar overall water splitting

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    Determining cost-effective semiconductors exhibiting desirable properties for commercial photoelectrochemical water splitting remains a challenge. Herein, we report a Sb2Se3 semiconductor that satisfies most requirements for an ideal high-performance photoelectrode, including a small band gap and favourable cost, optoelectronic properties, processability, and photocorrosion stability. Strong anisotropy, a major issue for Sb2Se3, is resolved by suppressing growth kinetics via close space sublimation to obtain high-quality compact thin films with favourable crystallographic orientation. The Sb2Se3 photocathode exhibits a high photocurrent density of almost 30mAcm(-2) at 0V against the reversible hydrogen electrode, the highest value so far. We demonstrate unassisted solar overall water splitting by combining the optimised Sb2Se3 photocathode with a BiVO4 photoanode, achieving a solar-to-hydrogen efficiency of 1.5% with stability over 10h under simulated 1 sun conditions employing a broad range of solar fluxes. Low-cost Sb2Se3 can thus be an attractive breakthrough material for commercial solar fuel production. While photoelectrochemical water splitting offers an integrated means to convert sunlight to a renewable fuel, cost-effective light-absorbers are rare. Here, authors report Sb2Se3 photocathodes for high-performance photoelectrochemical water splitting devices

    Ultrasonic Sizing of Voids Using Area Functions

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    We present a simple technique for determining the size of voids by the inversion of backscattered ultrasonic signals using the area function formula. The formulation of this method is based on the Born approximation, which is a weak scattering approximation, but the method works well for voids. The area function has been widely used as a method for determining the position of the flaw centroid to assist implementation of some inversion algorithms. The method has been reported in [6]. Here, we report some further studies, and more experimental results in detail

    Nanofibers Fabricated Using Triaxial Electrospinning as Zero Order Drug Delivery Systems

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    A new strategy for creating functional trilayer nanofibers through triaxial electrospinning is demonstrated. Ethyl cellulose (EC) was used as the filament-forming matrix in the outer, middle, and inner working solutions and was combined with varied contents of the model active ingredient ketoprofen (KET) in the three fluids. Triaxial electrospinning was successfully carried out to generate medicated nanofibers. The resultant nanofibers had diameters of 0.74 ± 0.06 μm, linear morphologies, smooth surfaces, and clear trilayer nanostructures. The KET concentration in each layer gradually increased from the outer to the inner layer. In vitro dissolution tests demonstrated that the nanofibers could provide linear release of KET over 20 h. The protocol reported in this study thus provides a facile approach to creating functional nanofibers with sophisticated structural features
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