A KELM-Based Ensemble Learning Approach for Exchange Rate Forecasting

In this paper, a KELM-based ensemble learning approach, integrating Granger causality test, grey relational analysis and KELM(Kernel Extreme Learning Machine), is proposed for the exchange rate forecasting. The study uses a set of sixteen macroeconomic variables including, import,export, foreign exchange reserves, etc. Furthermore, the selected variables are ranked and then three of them, which have the highest degrees of relevance with the exchange rate, are filtered out by Granger causality test and the grey relational analysis, to represent the domestic situation. Then, based on the domestic situation, KELM is utilized for medium-term RMB/USD forecasting. The empirical results show that the proposed KELM-based ensemble learning approach outperforms all other benchmark models in different forecasting horizons, which implies that the KELM-based ensemble learning approach is a powerful learning approach for exchange rates forecasting.     

一种新的体细分格式

近二十年来,对曲线和曲面的细分方法(Subdivision)的研究和应用在计算机图形学和造型领域中相当流行,然而对于实体的细分方法却研究得较少.在本文中,我们设计了一种基于六面体的逼近细分格式在张量积网格上表现为张量积格式,在体网格上生成光滑的极限实体,并能在实体上引入边界和折痕.根据已有的在简单六面体网格上的基于六面体的逼近格式,如果不采用一些特殊规则,设计者很难得到实体模型.我们设计了一套针对实体模型的细分规则来简化细分过程.大体上,我们的细分过程结合了简单线性细分和二层平均,对网格的局部拓扑结构没有严格要求.特别地,我们的格式可以不加修改地应用到非流形拓扑网格上.同时,我们引入了用于控制模型形状的自由参数,使模型设计更具弹性.     

Substrate-targeting gamma-secretase modulators

Selective lowering of Abeta42 levels (the 42-residue isoform of the amyloid-beta peptide) with small-molecule gamma-secretase modulators (GSMs), such as some non-steroidal anti-inflammatory drugs, is a promising therapeutic approach for Alzheimer's disease. To identify the target of these agents we developed biotinylated photoactivatable GSMs. GSM photoprobes did not label the core proteins of the gamma-secretase complex, but instead labelled the beta-amyloid precursor protein (APP), APP carboxy-terminal fragments and amyloid-beta peptide in human neuroglioma H4 cells. Substrate labelling was competed by other GSMs, and labelling of an APP gamma-secretase substrate was more efficient than a Notch substrate. GSM interaction was localized to residues 28-36 of amyloid-beta, a region critical for aggregation. We also demonstrate that compounds known to interact with this region of amyloid-beta act as GSMs, and some GSMs alter the production of cell-derived amyloid-beta oligomers. Furthermore, mutation of the GSM binding site in the APP alters the sensitivity of the substrate to GSMs. These findings indicate that substrate targeting by GSMs mechanistically links two therapeutic actions: alteration in Abeta42 production and inhibition of amyloid-beta aggregation, which may synergistically reduce amyloid-beta deposition in Alzheimer's disease. These data also demonstrate the existence and feasibility of 'substrate targeting' by small-molecule effectors of proteolytic enzymes, which if generally applicable may significantly broaden the current notion of 'druggable' targets.     

Differential response of root morphology to potassium deficient stress among rice genotypes varying in potassium efficiency

Disparity in the root morphology of six rice （Oryza sativa L.） genotypes varying in potassium （K） efficiency was studied with three K levels： 5 mg/L （low）, 10 mg/L （moderate） and 40 mg/L （adequate） in hydroponic culture. Morphological parameters included root length, surface area, volume and count of lateral roots, as well as fine （diameter〈0.2 mm） and thick （diameter〉0.2 mm） roots. The results indicate that the root growth of all genotypes was reduced under low K, but moderate K deficiency increased the root length of the efficient genotypes. At deficient and moderate K levels, all the efficient rice genotypes developed more fine roots （diameter〈0.2 mm） than the inefficient ones. Both fine root count and root surface area were found to be the best parameters to portray K stress in rice. In accordance with the root morphology, higher K concentrations were noted in shoots of the efficient genotypes when grown at moderate and deficient K levels, indicating that root morphology parameters are involved in root uptake for K and in the translocation of K up to shoots. K deficiency affected not only the root morphology, but also the root ultra-structure. The roots of high-efficient genotypes had stronger tolerance to K deficient stress for root membrane damage, and could maintain the developed root architecture to adapt to the low K growth medium.     

求解Burger''s方程带限制算子的傅立叶拟谱方法

采用带限制算子的傅立叶拟谱方法近似求解了Burgers方程，分别证明了它的(Burgers方程)一般化的稳定性和收敛性，并获得了数值结果．     

Return and Volatility Spillovers Effects:Study of Asian Emerging Stock Markets

This paper examines the extent of contagion and interdependence across the six Asian emerging countries stock markets(e.g., Bangladesh, China, India, Malaysia, the Philippine, and South Korea) and then try to quantify the extent of the Asian emerging market fluctuations which are described by intra-regional contagion effect. These markets experienced both fast growth and key upheaval during the sample period, and thus, provide potentially rich information on the nature of border market interactions. Using the daily stock market index data from January 2002 to December 2016(breaking the 15 years data set into three sub periods; pre-crisis, crisis, and post crisis periods);particularly make attention to the global financial crisis of 2007~2008. The return and volatility spillovers are modeled through the GARCH(generalized autoregressive conditional heteroscedasticity),pairwise Granger causality tests, and the forecast error variance decomposition in a generalized VAR(vector auto regression) models. This paper shows that volatility and return spillovers behave very differently over time, during the pre-crisis, crisis, and post crisis periods. Importantly, Asian emerging stock markets interaction is less before the global financial crisis period. The return and volatility spillover indices touch their respective historical peaks during the global financial crisis 2007~2008,however Bangladeshi market faces this condition in 2009~2010.     

Effect of Co substitution on the structural, electrical, and magnetic properties of Bi0.9La0.1FeO3 by sol-gel synthesis

Cobalt (Co)-doped Bi_0.9La_0.1FeO₃ multiferroics were synthesized by a sol-gel method based on the autocombustion technique. As-synthesized powder was examined using various characterization techniques to explore the effect of Co substitution on the properties of Bi_0.9La_0.1FeO₃. X-ray diffraction reveals that Co-doped Bi_0.9La_0.1FeO₃ preserves the perovskite-type rhombohedral structure of BiFeO₃, and the composition without Co preserves the original structure of the phase; however, a second-phase Bi₂Fe₄O₉ has been identified in all other compositions. Surface morphological studies were performed by scanning electron microscopy. Temperature-dependent resistivity of the samples reveals the characteristic insulating behavior of the multiferroic material. The resistivity is found to decrease with the increase both in temperature and Co content. Room temperature frequency-dependent dielectric measurements were also reported. Magnetic measurements show the enhancement in magnetization with the increase in Co content.     

(√3)细分曲面的误差界

给出了(√3)细分曲面和其k次细分后控制网之间的误差界估计.误差界是用初始控制点序列的一阶向前极大差分和常数表示的.采用的方法是对四边形细分框架中已有技术的推广.