排序方式: 共有83条查询结果,搜索用时 15 毫秒
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近十几年来,我国出现了前所未有的“申遗热”,这固然有利益驱动的因素,但遗产保护意识不断增强也是一个重要原因。被列入世界遗产名录能够提高一个国家、一个地区或一个城市在世界范围内的知名度,但更为重要的是,遗产保护事业在一定程度上还展示了一个国家文明进步的程度和教育科技文化发展的水平。需要指出的是, 相似文献
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东太湖全新世水下河道沉积特征及环境演变 总被引:7,自引:0,他引:7
在详细研究东太湖E2孔全新世沉积基础上,总结和归纳了水下河道的沉积特征和相组合规律。识别出高湖面型和低湖南型两种沉积层序,划分了东太湖晚更新世末以来环境演变阶段:1)15885-6575aB.P.冲积黄土基础上发育而成的古河道;2)6575-5800aB.P.高湖面时期水下河道沉积环境;3)5800aB.P.后,演化为低湖面型水下河道,并逐渐淤积形成开敞湖缘环境。结合西太湖W1孔沉积特征和层位对比 相似文献
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为探究水下噪音对杂交鲟行为变化(游泳速率、摄食速率、空间分布)及其肠道微生物的影响,在(145±5) dB, 400 Hz的噪音条件下对杂交鲟进行了0、24h、48h、7d和14d的噪音刺激,随后置于无胁迫噪音的自然环境中恢复48h。结果显示,噪音刺激后杂交鲟游泳速度和摄食速度显著减慢,空间分布发生改变,噪音刺激开始时杂交鲟聚集于远离噪音源的一侧, 3min后却逐渐接近噪音源。噪音对杂交鲟的肠道微生物的丰富度无显著性影响;不同时间段的各组肠道微生物的优势种群存在差异,且随时间变化优势种群反复改变;以上微生物分析结果通过COG预测显示,噪音胁迫48h和7d时“细胞信号传递过程”,“碳水化合物的转运”及“氨基酸的运输和代谢功能”显著低于其他组。结果表明,噪音对杂交鲟摄食速率、游泳速率及空间分布影响显著,改变了其肠道微生物组成和占比,影响了其氨基酸代谢等多条生命活动相关通路。实验模拟了水下各类噪音源的混合噪音对杂交鲟行为和肠道微生物的影响,为探讨杂交鲟的健康生态养殖和逆境生理响应机制提供基础资料。 相似文献
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Computational Research on Modular Undulating Fin for Biorobotic Underwater Propulsor 总被引:2,自引:1,他引:1
Biomimetic design employs the principles of nature to solve engineering problems. Such designs which are hoped to be quick, efficient, robust, and versatile, have taken advantage of optimization via natural selection. In the present research, an environment-friendly propulsion system mimicking undulating fins of stingray was built. A non-conventional method was considered to model the flexibility of the fins of stingray. A two-degree-of-freedom mechanism comprised of several linkages was designed and constructed to mimic the actual flexible fin, The driving linkages were used to form a mechanical fin consisting of several fin segments, which are able tO produce undulations, similar to those produced by the actual fins. Owing to the modularity of the design of the mechanical fin, various undulating patterns can be realized. Some qualitative observations, obtained by experiments, predicted that the thrusts produced by the mechanical fin are different among various undulating patterns. To fully understand this experimental phenomenon is very important for better performance and energy saving for our biorobotic underwater propulsion system. Here, four basic undulating patterns of the mechanical fin were performed using two-dimensional unsteady computational fluid dynamics (CFD) method. An unstructured, grid-based, unsteady Navier-Stokes solver with automatic adaptive re-meshing was used to compute the unsteady flow around the fin through twenty complete cycles. The pressure distribution on fin surface was computed and integrated to provide fin forces which were decomposed into rift and thrust. The pressure force and friction force were also computed throughout the swimming cycle. Finally, vortex contour maps of these four basic fin undulating patterns were displayed and compared. 相似文献
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线性文化遗产保护的重要性和迫切性已成为共识。以明长城大同段为研究案例,综合现有文化遗产分类方法进行遗产要素分类与识别,利用空间信息技术和不同遗产价值评价体系进行资源评价与分析,并总结多级别遗产点的地理空间分布规律。基于“核心保护与多级别缓冲”保护格局,结合实际问题和相关法规文件从宏观层面提出横向层级式、纵向组团式的空间格局,最后针对不同层次的遗产区域组合,制定实操性较强的保护策略。借此为中国线性文化遗产保护的空间格局规划理论与技术研究提供经验,以完善中国文化遗产保护体系。 相似文献
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文物是人类历史的结晶,是不可再生、不可替代的资源。微生物广泛定殖于古代壁画、石质文物及其他类型文化遗产上并造成危害,其中优势病害真菌白色侧齿霉菌的分布尤为广泛,其可在多种文物和极端环境中生存,严重威胁着珍贵文化遗产的长久保存。白色侧齿霉菌的分类命名经历了几次变化,导致其对文物的影响尚未被特别关注。本文以白色侧齿霉菌为主线,梳理了其分类发展简史、分布范围、文化遗产类型偏好,分析了其生理、生化、生态特征及潜在的生物退化机制,提出了其可作为文化遗产微生物危害的指示物种,讨论了此类典型壁画微生物的防治对策,并展望了该领域未来的重点研究方向。 相似文献
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