Subjects: Biology >> Botany >> Applied botany submitted time 2020-05-28 Cooperative journals: 《广西植物》
Abstract： This study explored the bole epiphytic bryophytes in the tropical rain forest and the tropical evergreen broad-leaved forest in Xishuangbanna, aimed to reveal their composition, diversity patterns, and maintenance mechanisms. The study site is located in Mengla County. Ten sampling plots (20 m×20 m) of each vegetation type were chosen, and about ten tree individuals were sampled in each plot to survey the bole epiphytic bryophytes. The results were as follows: (1) In total, 60 species belonging to 39 genera and 20 families were recorded. Among them, 48 species belonging to 33 genera and 19 families were recorded in the tropical rain forest, and 19 species belonging to 14 genera and 9 families were recorded in the tropical mountain evergreen broad-leaved forest; (2) The dominant family of the tropical rain forest is Neckeraceae, while the dominant family of the tropical mountain evergreen broad-leaved forest is Sematophyllaceae; (3) The species richness, βand γ diversity of the tropical rain forest were higher than the tropical mountain evergreen broad-leaved forest; (4) The coverage of epiphytic bryophytes was significantly different among different diameter classes and bark roughness; (5) Pendants, fans, wefts, and rough mats prefer the tropical rain forest, while turfs, cushions, smooth mats gather in the tropical mountain evergreen broad-leaved forest; (6) The results of redundancy analysis showed that host characteristics, especially bark roughness, significantly affected the composition and distribution of life forms. Tropical rainforests provide a greater diversity of microhabitats than tropical evergreen broad-leaved forests, and thus harbor more epiphytic bryophyte species than the latter. Considering different bryophyte life forms were recorded in different vegetation types or host characteristics, life forms can be considered as an important indicator for forest monitoring and management.
Subjects: Biology >> Botany >> Applied botany submitted time 2018-10-26 Cooperative journals: 《广西植物》
Abstract：附生苔藓在维持森林生态系统水分和养分循环中发挥着重要的生态作用。然而，由于访问技术的限制，附生苔藓多样性及其在林冠三维空间中的分布格局却鲜为人知。本研究首次借助林冠塔吊调查了西双版纳国家级自然保护区龙脑香热带雨林样地内69棵树13个垂直高度上的附生苔藓植物，通过统计不同垂直高度上的苔藓物种及其生活型，并利用典范相关分析法（CCA）和物种指示法对该区域附生苔藓植物沿宿主垂直梯度上的微生境偏好及其指示作用进行了分析。结果表明：该龙脑香热带雨林69棵树上共记录到隶属于25科60属的90种附生苔藓，其中细鳞苔科物种数最多，占比达25.6%。13个垂直高度上共划分出三种生态类型：喜阳苔藓(＞45m散生巨树的垂直高度上)，喜阴苔藓(＜15m的乔木树干上)，广布苔藓（通常广泛分布于各个宿主垂直高度上，生态位宽），并筛选出对微生境有特殊偏好的17种苔藓指示种（IndVal ≥ 0. 7，P ＜ 0. 05）。随宿主垂直高度的升高，扇型和交织型的苔藓占比降低，悬垂型苔藓占比先升高后降低，细平铺型和粗平铺型的苔藓占比升高。大气湿度、水汽压、胸径以及树皮粗糙度对附生苔藓生活型的分布偏好具有显著影响。总之，沿宿主垂直高度上的附生苔藓对微环境变化在生活型和形态结构上有着不同的响应方式，而同一种生态型的苔藓群落有相似的适应机制。因此，在森林林冠生境变化的监测和管理中，对微生境具有明显偏好的附生苔藓物种或生活型可作为有效的指示材料。
Subjects: Biology >> Botany >> Applied botany submitted time 2018-09-07 Cooperative journals: 《广西植物》
Abstract： Bryophytes are typically poikilohydric plants and water availability for growth of bryophytes is particularly important. In order to explore ecological adaptation strategies of bryophytes for different water conditions, we determined the water loss characteristics during natural desiccation and water use efficiency of 18 dominated or common bryophytes species from terrestrial, trunk and branch in a moist evergreen broad-leaved forest in Ailao Mts. Our results demonstrated that weft, fan and pendant life-forms were dominated in terrestrial, bole epiphytic and branch epiphytic bryophytes respectively. Bryophytes from different microhabitats exhibited great variance of water-holding capacity and water loss rate: Water-holding capacity of bryophytes from three microhabitats was 476%DW, 210.98%DW and 238.95%DW respectively; Water-holding capacity and water loss rate of terrestrial bryophytes were higher than these of the trunk- and branch-dwellers. Compared with branch-dwellers, the bole epiphytic bryophytes had lower water-holding capacity and higher water loss rate. Water holdingcapacityandwaterlossrateofbryophytesamongdifferent life-formsalso exhibitedsignificantdifferences: Weft life-form bryophytes exhibited higher water-holding capacity and higher water loss rate, indicating their weaker water retention capacity, followed by pendant bryophytes, and fan bryophytes had lowest water holding capacity and highest water loss rate. Water use efficiency of terrestrial bryophytes and bole epiphytic bryophytes were significantly higher than branch-dwellers. Weft and fan life-form bryophytes had higher water use efficiency than that of pendant bryophytes. The results indicated that water-holding capacity and water use efficiency of terrestrial bryophytes was higher while water retention capacity was poor; water retention capacity of branch-dwellers was higher while water-holding capacity and water use efficiency was lower; water use efficiency of trunk-dwellers was higher while both water-holding capacity and water retention capacity was poor. Life-form composition and water characteristics of bryophytes from terrestrial bryophytes, bole and branch epiphytic bryophytesindicated theiradaptation strategies to different habitats toa certain extent. The resultswould providea scientific basis ofelucidating hydrological features ofbryophytes under different microhabitats, and understanding ecologicaladaptationstrategiesofbryophyte.
Subjects: Geosciences >> Space Physics submitted time 2017-03-10
Abstract：三极管倍频器是根据晶体三极管的非线性特性，得到输入信号的各次谐波，然 后通过带通滤波器选出所需要的频率，从而实现输入信号的倍频。文中详细阐述了三极 管倍频电路的设计，实现了对 10MHz 输入信号的四倍频，通过电路测试，结果证明输 出信号的相噪没有明显恶化，在 1MHz 带宽内相噪优于-80.87 dBc/Hz，在 100kHz 内杂 散抑制可达-79.54dBc/Hz，满足设计需求。
Peer Review Status:
Awaiting Review
Subjects: Materials Science >> Nanoscience and Nanotechnology submitted time 2016-12-22
Abstract：以 AlGaN/GaN HEMT为代表的 GaN基功率晶体管由于具有宽带隙、高工作结温、高摘要：以 AlGaN/GaN HEMT为代表的 GaN基功率晶体管由于具有宽带隙、高工作结温、高击穿场强和高电子迁移率等优点，成为当前功率器件研究的热点。当 GaN 基功率晶体管应用到大功率开关电路中时，为了电路的设计简单和安全方面考虑，一般要求开关器件具有常关特性即需要器件为增强型器件。通过 Ar离子注入实现具有工艺简单、重复性好、稳定可控的优点。本实验通过调整 Ar 离子注入能量、剂量来研究 Ar 离子注入能否实现增强型HEMT器件，同时研究了 LP-SiNx作为能量阻挡层的效果。实验发现 Ar离子注入能实现增强型，但存在着饱和电流小的问题，退火能够修复损伤，一定程度上提高饱和电流。而采用LP-SiNx作为能量阻挡层，可以减小损伤，饱和电流相对提高，但存在着回滞的问题。作为增强型实现方法，Ar离子注入尚需进一步研究并改进。
Peer Review Status:Awaiting Review
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