L-精氨酸基姜黄素衍生物的合成及抑菌性评价

以4-二甲氨基吡啶(DMAP)为催化剂,1-(3-二甲氨基丙基)-3-乙基碳二亚胺(EDC)为脱水剂,琥珀酸(Sa)为连接臂,通过酯化和酰胺化反应将姜黄素接枝到L-精氨酸分子上,获得新型L-精氨酸基姜黄素(Cur-Sa-Arg)衍生物,产物经UV-Vis、FT-IR、1 H NMR和DSC表征,证明已成功合成.与姜黄素...     

关于Bernoulli多项式与Euler多项式线性组合的积和式

讨论了Bernoulli多项式与Euler多项式线性组合的乘积问题,给出了一组关于Bernoulli 多项式与Euler多项式乘积和的恒等式及一个推论.     

孪生组合恒等式(十六)--混合类型

孪生组合恒等式的混合类型简称孪生混合恒等式,这里每个恒等式中包含2种组合记号n与n,获得3组孪生混合恒等式.     

对乙烯基苯磺酸钠接枝聚丙烯纤维

利用超声波的分散原理,以二甲苯作为界面剂,把引发剂过氧化苯甲酰(BPO)分散到聚丙烯(PP)纤维表层里,然后在水溶液中接枝对乙烯基苯磺酸钠(VSB),得到接枝产物PP-g-VSB纤维．研究反应条件对接枝率的影响,以及接枝率对接枝纤维性能的影响,并用热重分析加以表征．结果表明,反应温度为90℃、VSB和 BPO质量分数分别为8％,4％,可得到接枝率34％、离子交换当量1．2 mmol·g-1的强酸型离子交换纤维．     

系统非线性组合预测方法及在黄河凌汛预测中应用

为了提高预测的精度,尤其是冰凌中长期预测的精度,基于工程模糊集、人工神经网络、遗传算法与组合预测理论,提出了系统非线性组合预测方法,给出了黄河内蒙段冰凌三种单一预测模型的非线性组合预测值．结果表明,所建立的非线性组合预测方法物理意义明确,数学推导过程严谨,预测精度高于任意单一预测模型．     

Does a lot help a lot? Forecasting stock returns with pooling strategies in a data‐rich environment

A variety of recent studies provide a skeptical view on the predictability of stock returns. Empirical evidence shows that most prediction models suffer from a loss of information, model uncertainty, and structural instability by relying on low‐dimensional information sets. In this study, we evaluate the predictive ability of various lately refined forecasting strategies, which handle these issues by incorporating information from many potential predictor variables simultaneously. We investigate whether forecasting strategies that (i) combine information and (ii) combine individual forecasts are useful to predict US stock returns, that is, the market excess return, size, value, and the momentum premium. Our results show that methods combining information have remarkable in‐sample predictive ability. However, the out‐of‐sample performance suffers from highly volatile forecast errors. Forecast combinations face a better bias–efficiency trade‐off, yielding a consistently superior forecast performance for the market excess return and the size premium even after the 1970s.     

Forecast Combination and Bayesian Model Averaging: A Prior Sensitivity Analysis

In this study we evaluate the forecast performance of model‐averaged forecasts based on the predictive likelihood carrying out a prior sensitivity analysis regarding Zellner's g prior. The main results are fourfold. First, the predictive likelihood does always better than the traditionally employed ‘marginal’ likelihood in settings where the true model is not part of the model space. Secondly, forecast accuracy as measured by the root mean square error (RMSE) is maximized for the median probability model. On the other hand, model averaging excels in predicting direction of changes. Lastly, g should be set according to Laud and Ibrahim (1995: Predictive model selection. Journal of the Royal Statistical Society B 57 : 247–262) with a hold‐out sample size of 25% to minimize the RMSE (median model) and 75% to optimize direction of change forecasts (model averaging). We finally apply the aforementioned recommendations to forecast the monthly industrial production output of six countries, beating for almost all countries the AR(1) benchmark model. Copyright © 2011 John Wiley & Sons, Ltd.     

A study of Platyplectrus Ferrière (Hymenoptera: Eulophidae) in mainland China

This paper reviews the Chinese species of Platyplectrus Ferrière. Twelve valid species are recognized from mainland China and a key to species is provided. Trichoplectrus Erdös (1951 Erdös, J, 1951. "Eulophidae novae. Acta Biologica". 1951, Academiae Scientiarum Hungaricae, 2(1–3), 169–237. [Google Scholar]) is newly synonymized with Metaplectrus Ferrière (1941 Ferrière, C, 1941. New species of Euplectrini (Hym. Chalcidoidea) from Europe, Africa and Asia, Bulletin of Entomological Research 32 (1941), pp. 17–48.[Crossref] , [Google Scholar]) and three new combinations are proposed: Metaplectrus szepligetii (Erdös) from Platyplectrus, Platyplectrus bussy (Crawford) from Euplectrus and P. politus (Lin) from Metaplectrus. Four species of Platyplectrus were known previously from China: P. politus (Lin), P. odontogaster (Lin), P. papillata Lin and P. medius Zhu and Huang. Six species, P. bussyi (Crawford), P. laeviscuta (Thomson), P. natadae Ferrière, P. orthocraspedae Ferrière, P. pannonica (Erdös) and P. viridiceps (Ferrière) are newly recorded from China and re-described. Five new species, P. pulcher, P. setulosus, P. peculiaris, P. obtusiclavatus and P. variflagellum are described and compared with related species. Several species are also newly recorded from other regions: P. orthocraspedae Ferrière from the Afrotropical region, P. bussyi (Crawford) and P. laeviscuta (Thomson) from the Australian/Pacific region, P. laeviscuta (Thomson) from the Oriental region and P. viridiceps from the Palearctic region.     

Revision of the genus Mimopodabrus Wittmer (Coleoptera,Cantharidae)

The genus Mimopodabrus Wittmer is reviewed, and the genus diagnosis is re-described. Three new species are described, M. multidentatus sp. nov. (Guangdong, China), M. variabilis sp. nov. (Yunnan, China) and M. diversefoveolatus sp. nov. (Lao Cai, Vietnam), with illustrations of habitus, antennae and aedeagus. A species is transferred from Micropodabrus to this genus, M. bicoloriceps (Wittmer, 1989 Wittmer, W. 1989. 42. Beitrag zur Kenntnis der indo-malaiischen Cantharidae und Malachiidae (Coleoptera). Entomol Basil., 13: 209–237.  [Google Scholar]) comb. nov. A species is synonymized, M. bicoloriceps (Wittmer, 1989 Wittmer, W. 1989. 42. Beitrag zur Kenntnis der indo-malaiischen Cantharidae und Malachiidae (Coleoptera). Entomol Basil., 13: 209–237.  [Google Scholar]) comb. nov.?=?M. bicoloriceps Wittmer, 1997 syn. nov. and the definition of M. yunnanus (Wittmer, 1993 Wittmer, W. 1993. Zur Kenntnis der palaearktischen und indo-malaiischen Cantharidae (Coleoptera). Entomol Basil., 16: 203–253.  [Google Scholar]) is restricted. A key to all known species of this genus is provided.     

基于动态组合残差修正的预测方法

本文建立了一种基于残差修正的组合预测方法,并基于该方法证明了针对多个单一的预测方法根据其在某个时间段的相对预测误差的大小选择组合选项可以进一步提高预测精度.提出了针对不同时间段可根据各种单项预测模型的相对预测误差的大小动态选取相对预测误差最小的两种模型构成组合残差来修正基本方法的预测误差,以提高预测精度.最后通过实际空调负荷预测对其进行了验证,结果表明这种动态组合残差修正的预测方法相对于基于多个固定单一预测方法的组合预测方法,可以进一步改善预测效果.