不确定时滞系统非脆弱鲁棒H SymboleB@ 控制研究     

郝智红  俞鹏 《湖南农业大学学报(自然科学版)》2011,(3):24-28

以2004~2009 年间701家上市公司为样本,研究政府干预、政治关联对企业非效率投资行为的影响。研究发现：政府干预一方面会加剧有自由现金流量公司的过度投资,对国有企业过度投资的影响更为严重;另一方面可以有效地缓解融资约束企业的投资不足,尤其是国有企业的投资不足。这说明,出于自身的政策性负担或政治晋升目标,政府会损害或支持所控制的企业,这为政府“掠夺之手理论”和“支持之手理论”提供了实证支持。研究还发现,政治关联与过度投资和投资不足均负相关,这表明,政治关联可以作为法律保护的替代机制来保护企业产权免受政府损害,并为企业谋取利益。  相似文献   

二维方柱光子晶体的波导特性     

翦知渐  彭景翠  张高明 《湖南农业大学学报(自然科学版)》2007,34(4)

具有缺陷的光子晶体,光子频率带隙内将出现局域模,而线缺陷相应地形成一个传输效率很高的光波导.计算了空气中Al材料的旋转四边形直柱光子晶体存在线缺陷时的带结构和态密度,给出了二维方形光子晶体的波导的TM模的电场分布,并讨论了波导耦合的传输效率.  相似文献   

孕期心理干预对改善孕产妇心理状况的研究   总被引：6，自引：0，他引：6  

赵淑婷  陈月嫦  谭章云  李秀云 《湛江医学院学报》2003,21(1):36-37,40

目的：探讨孕期心理干预对改善孕产妇心理状况的可行措施。方法：随机将孕妇分为2组并随访至产后2周（非心理干预组402人，随访至产后2周者356人；心理干预组323人，随访至产后2周者287人），心理干预组孕妇分孕早期、孕中期和孕晚期进行三阶段的心理干预，孕期调查用医院焦虑和抑郁量表（HAD），产后2周调查用艾迪产后抑郁量表（EPDS）并增加本次有关妊娠、分娩前后的生活事件等内容并进行比较。结果：心理干预组孕妇临产前焦虑和抑郁情绪均分值明显低于非心理干预组，其焦虑和抑郁情绪发生率也明显低于心理干预组，差异非常显著（P＜0．01）；产后抑郁症发生率明显低于非心理干预组（P＜0．01）。对其潜在心理背景分析表明：心理干预组的孕产妇在妊娠心境、产后育儿、与社会家人关系等得到明显改善（P＜0．01）；而对来自分娩周围环境、分娩疼痛等压力无明显改善，与非心理干预组比较差异不显著（P＞0．05）。结论：孕期心理干预可明显改善孕产妇的心理状况和降低产后抑郁症的发生率。  相似文献   

基于MATLAB的数字信号基带传输系统仿真   总被引：1，自引：0，他引：1  

曲中水  王建卫  朱泳 《森林工程》2004,20(4):31-33

SIMULINK是MATLAB中动态系统建模、仿真和分析的一个集成环境 ,文中按照仿真过程基本步骤用MATLAB的仿真工具SIMULINK实现了数字信号基带传输系统的仿真过程 ,对系统性能进行了分析  相似文献   

草坪种子品种快速鉴定技术研究 II几种冷季型草坪草过氧化物同工酶谱计算机分析     

唐红  吕小瑞 《草业科学》2003,(6)

采用等电聚焦电泳技术对适于西北地区的几种冷季型草坪草种进行了品种真实性鉴定研究,并使用国际认证的计算机软件(ImageMaster1D)进行同工酶谱带分析,对检测结果进行了定性定量评定,充分表明了品种间基因多态性,证明此方法是草坪草品种鉴别的有效测定技术。  相似文献   

浅谈宽带的接入方式     

赵雪英 《林业科技情报》2004,36(4):35-36

本文从以电话铜缆为接入手段的xDSL技术、以五类双绞线为接入技术、及以无线为物理媒质的接入技术等几方面，阐述了宽带的主要接入技术及其特点。  相似文献   

Effects of method, rate and timing of slurry application to grassland on the preference by cattle for treated and untreated areas of pasture   总被引：1，自引：0，他引：1  

J. A. Laws  B. F. Pain 《Grass and Forage Science》2002,57(2):93-104

Two experiments were conducted in the UK to investigate preference by cattle for areas of pasture treated or untreated with dairy cow slurry. Experiment 1 examined the effects of method and rate of slurry applied to a grass pasture in March (Spring); Experiment 2 examined the effects of method and timing of slurry application after cutting for silage in June (Summer). In both experiments, beef steers grazed grassland plots that had been treated with slurry on one half only of the plots for 4 weeks. Slurry was applied by shallow injection (I), trailing shoe (T) or conventional surface broadcasting (S) techniques. In Experiment 1, slurry was applied at 40 m³ ha^?1 (HI) or 20 m³ ha^?1 (LO) 21 d before grazing commenced; in Experiment 2, slurry was applied at 20 m³ ha^?1 either 32 d (E) or 10 d (L) before grazing commenced. Sward height was measured and animal behaviour was recorded during 8 × 24 h measurement periods in each experiment. Preference for slurry‐treated or untreated swards was indicated by a comparison of post‐grazing sward height on each sward and the proportion of total grazing time spent on the slurry‐treated swards. In Experiment 1, a smaller proportion of grazing time was spent on slurry‐treated areas of swards compared with untreated areas of swards on all treatments, but the proportion of time spent grazing the slurry‐treated sward was greater on method T than on methods I or S (0·28, 0·31 and 0·39 for methods S, I and T, respectively, s.e.d. = 0·035, P < 0·05). Steers showed no preference between slurry‐treated and untreated swards by 49, 45 and 44 d after slurry application for methods S, I and T respectively. Differences between HI and LO were not significant (P > 0·05). In Experiment 2, aversion to slurry‐treated swards compared with untreated swards was less for treatment E than for L, with a greater proportion of both residence and grazing time spent on the slurry‐treated sward of treatment E than L (0·43 and 0·28, respectively, for residence time, s.e.d. = 0·025, P < 0·001, and 0·47 and 0·30, respectively, for grazing time, s.e.d. = 0·021, P < 0·001). Significant differences were shown between the methods of slurry application for treatment E, with a greater proportion of grazing time spent on the slurry‐treated swards of methods I and T than method S (0·40, 0·52 and 0·49 for S, I and T, respectively, s.e.d. = 0·032, P < 0·001), and a greater difference between post‐grazing heights on slurry‐treated and untreated swards for method S than for I or T (30, 12 and 15 mm, respectively, s.e.d. = 4·8, P < 0·001). For treatment L, differences in the proportion of time spent grazing on slurry‐treated swards compared with untreated swards were not significant between treatments (0·26, 0·34 and 0·31 for methods S, I and T, respectively, s.e.d. = 0·040, P > 0·05) and indifference between slurry‐treated and untreated swards was achieved 77, 60 and 58 d after slurry spreading for methods S, I and T respectively. These results show that, when slurry is applied to pasture in a grazing rotation, the adverse effects on grazing behaviour associated with conventional surface broadcasting may be overcome by the use of novel slurry application techniques.  相似文献   

猪(Svs scrofa domastica L)染色体高分辨G带带型     

于汝梁  辛彩云 《畜牧兽医学报》1989,(4)

利用加入氨甲喋呤和胸苷使细胞分裂同步化并结合胰酶G带技术,分析了猪前中期染色体高分辨G带。单套染色体的G带数目,包括x和y染色体,前中期为503条,中期为300条。绘制了前中期和中期G带带型图。  相似文献   

黄花菜染色体核型及C-带G-带带型的研究     

何立珍  贾大勇 《湖南农业大学学报(自然科学版)》1988,(2)

本试验较系统地研究了黄花菜根尖细胞染色体的核型特征和带型特征,其中,对黄花菜G—带带型的研究,为国内首次报道。  相似文献   

Experimental use of polyamide bands in combination with intramedullary pinning for repair of oblique femoral fractures in rabbits     

Carrillo JM  Sopena JJ  Rubio M  Redondo JI  Serra I  Soler C 《Veterinary surgery : VS》2005,34(4):387-392

OBJECTIVE: To evaluate the use of polyamide bands, manufactured for securing electrical cables, for repair of oblique femoral fractures in rabbits. STUDY DESIGN: Experimental study. ANIMALS: Twelve nulliparous, 21-25-week-old, California female rabbits. METHODS: Rabbits were divided into 3 groups (n=4) and studied for 14, 28, or 56 days. A Z-shaped mid-diaphyseal femoral osteotomy was repaired with a 2.5 mm intramedullary pin and a polyamide 6.6 cerclage band. Healing was evaluated at intervals by physical examination, limb use, femoral radiographs, and callus histology. RESULTS: Rabbits had early limb use with good wound healing. From the 1st day, movement of the hip and stifle joints was satisfactory. Radiographically, fractures were healed at 28 days. Histologically, there was no foreign body reaction and bone healing was normal. CONCLUSION: Nylon cerclage band application was accomplished easily, maintained reduction, and resulted in good healing and limb use. CLINICAL RELEVANCE: Sterilized nylon bands, manufactured for electrical use, can be used for cerclage in rabbits.  相似文献