In this study the regeneration diversity of Syahkal forests afforestated and natural stands in north of Iran was studied and compared from the point of view of evenness and diversity index. In order to accomplish this...In this study the regeneration diversity of Syahkal forests afforestated and natural stands in north of Iran was studied and compared from the point of view of evenness and diversity index. In order to accomplish this study two natural and man-made stands that almost are located in the same height above the sea level were chosen. The area of each stand was 30 ha and the inventory was done by the random-systematic method with a 5R land measurement （500 m2） selected. Also, in order to study the regeneration in the center of each sample piece 125 square meters micro plots were formed. The results show that regeneration diversity index in natural stands is more than that in man-made stands which in this case Mc-Arthur index with 2.41 has the most amount while Simpson index with 0.543 has the least amount. But the evenness indexes in man-made stands are more than that in natural stand which the main reason is the purity of the man-made stand.展开更多
传统结构巴伦是一端开路的对称四端口网络,在奇偶模分析的基础上,对传统的巴伦结构进行改进,设计了一种工作于4 GHz的正方形微带巴伦。利用HFSS进行仿真分析,并加工成实物。测试结果表明,在3.7 GHz^5 GHz范围内,|S_(11)|大于10 d B;在...传统结构巴伦是一端开路的对称四端口网络,在奇偶模分析的基础上,对传统的巴伦结构进行改进,设计了一种工作于4 GHz的正方形微带巴伦。利用HFSS进行仿真分析,并加工成实物。测试结果表明,在3.7 GHz^5 GHz范围内,|S_(11)|大于10 d B;在工作频段内,|S_(21)|与|S_(31)|均小于4 d B,S_(21)与S_(31)之间的相位差在178°到183°范围内。该巴伦结构简单、实现成本较低,可应用于无线局域网、射频识别等领域。展开更多
文摘In this study the regeneration diversity of Syahkal forests afforestated and natural stands in north of Iran was studied and compared from the point of view of evenness and diversity index. In order to accomplish this study two natural and man-made stands that almost are located in the same height above the sea level were chosen. The area of each stand was 30 ha and the inventory was done by the random-systematic method with a 5R land measurement （500 m2） selected. Also, in order to study the regeneration in the center of each sample piece 125 square meters micro plots were formed. The results show that regeneration diversity index in natural stands is more than that in man-made stands which in this case Mc-Arthur index with 2.41 has the most amount while Simpson index with 0.543 has the least amount. But the evenness indexes in man-made stands are more than that in natural stand which the main reason is the purity of the man-made stand.
文摘传统结构巴伦是一端开路的对称四端口网络,在奇偶模分析的基础上,对传统的巴伦结构进行改进,设计了一种工作于4 GHz的正方形微带巴伦。利用HFSS进行仿真分析,并加工成实物。测试结果表明,在3.7 GHz^5 GHz范围内,|S_(11)|大于10 d B;在工作频段内,|S_(21)|与|S_(31)|均小于4 d B,S_(21)与S_(31)之间的相位差在178°到183°范围内。该巴伦结构简单、实现成本较低,可应用于无线局域网、射频识别等领域。
