简述曹魏迁都许昌的原因及对许昌的治理

通过黄巾起义发家的曹操,在不断地战争中有了统一天下的愿望。由于曹操的谋略、品行和军事才能,在其周围聚集了一批文臣武将,在他们的协助下,曹操的队伍不断地发展壮大,形成了独立的政权。建安元年,曹操建都许昌,以许昌为基点展开了统一天下的一系列军事征伐。曹魏政权对许昌也进行了一定的开发,一方面促进了许昌经济的发展,另一方面也为曹魏统一北方奠定了基础。     

超磁致伸缩作动器的磁路设计

论述了超磁致伸缩作动器的基本原理,根据三种偏置磁场优缺点,选用增加单独线圈产生偏置磁场。在磁路分析的基础上,采用有限元仿真的方法,分析了不同参数和结构对各个组成部分的磁场影响。     

辨《离骚》“溘死以流亡”

＂溘死＂和＂流亡＂在《离骚》中各见一例。＂溘死＂今者释义多为＂忽然死亡＂;而＂流亡＂释为何义,古今学者莫衷一是。然观文章前后之意,联接＂溘死＂、＂流亡＂的＂而＂应作顺接连词。＂溘死＂与＂流亡＂应为逻辑顺序关系,不宜为并列之序;且屈赋另亦三次出现类似句式,＂流亡＂皆为同义。联系屈子人生理想及其诗句,＂流亡＂应释为＂随流水消逝＂。     

浅谈高校电子阅览室的建设和管理

高等教育改革对高校图书馆工作提出了更高的要求,图书馆电子阅览室的建设和管理水平体现出高校的信息化透明程度,它的服务质量和管理状况对整个高校的教学和科研起着至关重要的作用,介绍了目前高校电子阅览室的现状,提出了优化管理的措施。     

Effect of epidermal growth factor on follicle-stimulating hormone-induced proliferation of granulosa cells from chicken prehierarchical follicles

The development of ovarian follicular cells is controlled by multiple circulating and local hormones and factors, including follicle-stimulating hormone (FSH) and epidermal growth factor (EGF). In this study, the stage-specific effect of EGF on FSH-induced proliferation of granulosa cells was evaluated in the ovarian follicles of egg-laying chickens. Results showed that EGF and its receptor (EGFR) mRNAs displayed a high expression in granulosa cells from the prehierarchical follicles, including the large white follicle (LWF) and small yellow follicle (SYF), and thereafter the expression decreased markedly to the stage of the largest preovulatory follicle. SYF represents a turning point of EGF/EGFR mRNA expression during follicle selection. Subsequently the granulosa cells from SYF were cultured to reveal the mediation of EGF in FSH action. Cell proliferation was remarkably increased by treatment with either EGF or FSH (0.1–100 ng/ml). This result was confirmed by elevated proliferating cell nuclear antigen (PCNA) expression and decreased cell apoptosis. Furthermore, EGF-induced cell proliferation was accompanied by increased mRNA expressions of EGFR, FSH receptor, and the cell cycle-regulating genes (cyclins D1 and E1, cyclin-dependent kinases 2 and 6) as well as decreased expression of luteinizing hormone receptor mRNA. However, the EGF or FSH-elicited effect was reversed by simultaneous treatment with an EGFR inhibitor AG1478. In conclusion, EGF and EGFR expressions manifested stage-specific changes during follicular development and EGF mediated FSH-induced cell proliferation and retarded cell differentiation in the prehierarchical follicles. These expressions thus stimulated follicular growth before selection in the egg-laying chicken.     

应用型本科院校植物学野外实习教学改革初探

植物学野外实习是应用型本科院校生物教学过程中必不可少的实践环节,结合野外实习经验,探索植物学野外实习模式的改革。强调在巩固和加强基础知识学习的同时,倡导野外实习与科研活动相结合,从而提高学生的基本技能和创新能力的培养。     

建构主义教学观在商务英语阅读教学的实践

传统的商务英语阅读教学不能很好的将语言教学和提高学生商务信息处理能力相融合。为改变这种现状,本文从建构主义理论的视角出发,阐述了建构主义模式在商务英语阅读教学中的实践,进而探讨如何在商务英语阅读教学中增进学生的积极性和主动参与意识,从而提高学生自主学习的能力。     

浅析现代产品设计中文化特征的符号表现形式——以传统符号在现代产品设计上的应用为例

产品设计本身就是文化的组成部分,因此设计必然反映和彰显文化。当设计创新与国家竞争力相联系的时候,涉及到文化层次是个必然的策略。通过分析传统符号在现代产品设计中的应用,我们应该认识到现代产品设计就不应只满足于套用传统符号来作为文化的装饰,而应该深入理解和应用传统文化元素,为产品设计增加附加价值。     

Lumped parameter model for resonant frequency estimation of a thermoacoustic engine with gas-liquid coupling oscillation

Gas-liquid coupling oscillation is a novel approach to reducing the resonant frequency and to elevating the pressure amplitude of a thermoacoustic engine. If a thermoacoustic engine is used to drive low-frequency pulse tube refrigerators, the frequency matching between the thermoacoustic engine and the refrigerator plays an important role. Based on an acoustic-electric analogy, a lumped parameter model is proposed to estimate the resonant frequency of a standing-wave thermoacoustic engine with gas-liquid coupling oscillation. Furthermore, a simplified lumped parameter model is also developed to reduce the computation complexity. The resonant frequency dependence on the mean pressure, the gas space volume, and the water column length is computed and analyzed. The impact of different working gases on the resonant frequency is also discussed. The effectiveness of the models is validated by comparing the computed results with the experimental data of the gas-liquid coupling oscillation system. An increase in the mean working pressure can lead to a rise in the resonant frequency, and a lower resonant frequency can be achieved by elongating the liquid column. In comparison with nitrogen and argon, carbon dioxide can realize a lower frequency due to a smaller specific heat ratio.     

高校经管类本科毕业论文选题类型的改革探索——调研型论文的教学实践

毕业论文是高等学校本科专业人才培养方案的重要组成部分。近年来论文质量不高,抄袭已经是一个非常普遍的问题。北京城市学院经济管理学部针对学生实际情况和学生就业需求,在毕业论文的改革方面进行了有益的尝试。本文提出了调研型论文的定位与内涵;阐述了调研型论文的过程控制、指导教师队伍建设;论述了调研型论文的突出特色。