基于不平衡数据的公司破产预测研究

整合创新数据预处理技术与集成算法利用不平衡数据探讨了公司破产预测问题。首先，运用冗余信息处理方法、不同抽样方法等对不平衡数据进行预处理。其次，以5.0分类器（Classifier 5.0,C5.0）决策树和单隐层前馈神经网络作为基分类器，分别与三类重抽样数据预处理技术结合，择出最优抽样法。再次，结合自助汇聚法提升分类效果，并运用十折交叉验证的受试者操作特征曲线的下方面积进行评价，对比了两基分类器的集成模型。最后，运用加利福尼亚大学尔湾分校数据库中一万多家波兰制造业公司的实际数据进行实验验证。实验结果表明：欠抽样或人工少数类过采样法与神经网络结合的集成模型分类效果最优，为企业实施破产预测提供积极支撑。     

The coconut pathosystem: weed hosts of nymphs of the American palm Cixiid Haplaxius crudus (Hemiptera: Fulgoroidea)

Lethal yellowing (LY) of coconut palm (Cocos nucifera L., Arecaceae) is a disease of economic importance that is caused by the phytoplasma ‘Candidatus Phytoplasma palmae’ and is transmitted by the planthopper Haplaxius crudus (Van Duzee) (Hemiptera: Cixiidae). This study explores the weeds used by H. crudus nymphs and other Cixiidae in a coconut pathosystem in southern Mexico. Nymphs were collected directly from the root system of each weed by hand or with the help of a vacuum after carefully opening the culm. This study included 11 species of weeds: nine Poaceae [Brachiaria decumbens Stapf, B. humidicola (Rendle) Schweick, B. mutica (Forssk.) Stapf, Digitaria abyssinica (Hochst. Ex A. Rich.) Stapf, Eustachys petraea (Sw.) Desv., Leersia hexandra Sw., Panicum laxum Sw., P. maximum Jacq., Paspalum notatum Flüggé]; one Cyperaceae [Cyperus ligularis L.], and one Portulacaceae: [Portulaca pilosa L.]. Brachiaria mutica, E. petraea, B. humidicola, P. maximum were identified as the principal host species for H. crudus nymphs. Brachiaria decumbens, D. abyssinica, and C. ligularis are new host records for the nymphs of H. crudus. Additionally, it was found that H. crudus may coexist with its cogeners H. skarphion Kramer (Cixiidae) and H. caldwelli Kramer (Cixiidae), on B. mutica. On C. ligularis, H. crudus may coexist with Oecleus snowi Ball (Cixiidae) nymphs. These results suggest that in the coconut pathosystem there is a complex of multitrophic interactions that should be considered in integrated management of LY.     

Comparative genetic differentiation study of three coexisting mangrove crabs in western Atlantic

ABSTRACT

A multispecies approach may reveal the factors influencing the genetic differentiation of coexisting species along a wide geographic area. Our aim was to compare the genetic differentiation of mangrove crabs coexisting along the western Atlantic in order to verify if there are common barriers, using two mitochondrial DNA markers to quantify genetic differentiation, variance and diversity. In addition, we included a mismatch distribution to check demographic history. Our data revealed that species with similar pelagic larval duration had either high genetic differentiation or the absence of genetic structure. These results can be explained by factors that contribute to genetic differentiation, such as the presence of large estuarine areas (acting as barriers), ocean currents, and larval behaviour. Also, historical events that promoted the isolation of some areas in the past, such as glacial cycles during the Pleistocene, could have caused the observed high levels of genetic divergence in some species.     

具预警状态的单模块可修复系统的指数稳定性

研究了具有预警状态的单模块可修复系统，将其动态变化过程用一组微分方程描述.通过选取适当的状态空间和系统算子的定义域，将方程化为Banach空间中的抽象柯西问题.利用泛函分析和线性算子半群理论证明了系统具有严格占优的单重的0本征值，说明系统的解满足渐近稳定性，并求出其稳态解.随后通过研究系统主算子的谱分布，证明了系统主算子的本质谱界为负.最后讨论了系统主算子在紧扰动下的本质谱界变化情况，结果表明系统的动态解是指数稳定的.     

N_2O对乙烯自点火敏化作用的实验和理论研究

为了探究肼类自燃型火箭推进剂热解和氧化组分中不饱和烷烃与氮氧化物间是否存在直接交互作用,对C_2H_4和N_2O混合气的自着火过程进行了实验和理论研究。利用激波管反射激波方法,测量了化学计量比C_2H_4/O_2/N_2O/Ar混合气(N_2O与(O_2+N_2O)的摩尔分数比为0%、50%、80%和100%)在温度为1 214～1 817K、压力为0.12～1.01 MPa下的点火延迟期。实验结果表明,与纯O_2作为氧化剂比较,N_2O替换部分O_2显著降低了C_2H_4的反应活性,延长其点火延迟期,随着N_2O浓度的增加,抑制影响效果变化显著,在N_2O/O_2的摩尔分数比超过50%情况下尤为突出,单O原子N_2O在氧化不饱和烷烃时并未表现出优势。数值模拟结果表明,只有Aramco-Z可在整个研究工况下合理地预测当前实验结果。N_2O和C_2H_4之间并未发生直接化学交互作用,N_2O的添加对C_2H_3与O_2反应速率及活性自由基池浓度的抑制作用是其氧化能力弱于O_2的主要动力学机制。     

氟系替代工质R407C和R410A与R22在复合冷凝系统中的热力学特性对比研究

目前复合冷凝技术已经形成了行业标准,替代制冷剂在复合冷凝系统中的应用特性研究是一种趋势。有限时间热力学方法和分析方法和SIMULINK软件被引入建立氟系替代制冷剂R407C和R410A在复合冷凝系统的仿真模型,其对象为风冷热泵复合冷凝过程。氟系替代制冷剂R407C和R410A在复合冷凝系统中的热力学特性被模拟,并与原R22系统的性能做了对比。结果表明:R410A复合冷凝系统卫生热水水温上升速度比R22系统快,20 min时上升到约60℃,而R407C复合冷凝系统卫生热水上升速度比R22复合冷凝系统慢,约需50 min水温达到47℃左右。系统效率随用户要求的卫生热水水温温度升高而降低。R410A复合冷凝系统比R22复合冷凝系统略高3%～5%,而R407C复合冷凝系统比R22复合冷凝系统略低。     

两种维生素C注射液含量测定方法的比较

用折光法、碘量法两种方法测定了维生素C注射液的含量,并对两种方法进行了比较。结果显示两种方法所测的维生素C的含量、标示量百分比相近,误差均小于5%,碘量法的结果略低于折光法。折光法是一种可以快速、准确测定维生素C含量的方法。     

集值映射与层型结构空间(英文)

本论文利用半连续集值映射的插入给出具有层型结构空间的一些等价刻画.也引入了K-lower和K-upper集值映射,利用此概念给出了k-半层空间以及k-MCM的刻画.     

一株好氧反硝化细菌的筛选鉴定及其脱氮效果

经过富集培养和反硝化能力测定,从城市污水处理厂活性污泥中筛选得到1株好氧反硝化细菌。通过16S rDNA同源性分析对该菌进行分子鉴定,并将菌接种到模拟富营养化水体中以探究其对系统中硝态氮和总氮的去除能力。结果表明,该菌属于Klebsiella sp.,命名为HLNR05。菌株HLNR05在24 h内NO3--N的去除率达96.6%,TN去除率达92.1%,而且其从培养体系中完全去除的氮明显多于同化到细胞的氮。利用HLNR05处理模拟富营养化废水,结果发现其在24 h内对模拟废水中的NO3--N和TN去除率达91.4%和88.2%。表明菌株HLNR05具有较强的好氧反硝化能力。