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891.
892.
吴文璐 《成都信息工程学院学报》2011,26(3):277-282
余代数为各种各样的模态逻辑提供一致的语义框架.Lutz Schr?der证明了任意自函子的余代数类都有一个rank-1的公理化.反过来,每一个rank-1的模态逻辑都有一个可靠的、强完备的余代数语义.另一方面,Clemens Kupke等提出模态逻辑可以描述成布尔代数上的自函子,并基于对偶理论研究余代数逻辑的可靠完备性.通过对偶理论重新证明了rank-1的模态逻辑都是余代数的,并且证明通过对偶理论构造出来的函子和Schr?der所构造的函子是等价的. 相似文献
893.
Suzuki G Kai S Yamashita H Suzuki K Iehisa Y Hayashibara T 《Marine pollution bulletin》2011,62(12):2803-2812
The initial factors that cause a decline in the survival of in situ settled corals remain poorly understood. In this study, we demonstrated through field experiments that the design of artificial grid plates may influence the initial survival of Acropora corals, with narrower grids being the most effective. In fact, grid plates with a 2.5-cm mesh presented the highest recorded survival rate (14%) at 6 months after settlement (representing approximately 50 corals per 0.25 m2 of plate). This is the first study where such high survival rates, matching those of cultures under aquarium conditions, were obtained in the field without using additional protective measures, such as guard nets against fish grazing after seeding. Therefore, our results provide a foundation for establishing new and effective coral restoration techniques for larval seeding, in parallel to clarifying the details of the early life stages of reef-building corals. 相似文献
894.
根据模型试验相似比尺和桩土间应力协调要求,用机制砂、河砂、水泥、石粉等配置了40组(每组6个)低强度、低弹性模量的圆柱形微混凝土相似材料试件。测试结果表明:微混凝土具有和原型混凝土大致相同的应力应变阶段和破坏模式,可以模拟原型结构的力学行为和变形、破坏特征。砂率和石粉取代率不同时,微混凝土试件的轴压强度和弹性模量在较大范围内变化;砂率较合适时,同一配合比微混凝土6个试件的强度和弹性模量一致性较好。微混凝土可以满足不同比尺模型试验对相似材料力学性质稳定、力学参数可以在较大范围内调整的要求。 相似文献
895.
896.
透明矿物绝大多数属于造岩矿物.本方法是从透明矿物中选取色泽纯正、易采集、便于加工的矿物作原材应用于玉板画工艺中,将其加工后与粘合胶液混合调配出能适应石板填充作画的填料,随之进行画面刻绘、填充、打磨、抛光等工序.工艺中采用雕刻深浅变化使画面显现出似透非透的,与石板背景色形成交相辉映、约隐约现如出天然之韵味的效果.这种透明... 相似文献
897.
898.
This paper demonstrates a practical step-wise method for modelling wave energy at the landscape scale using GIS and remote sensing techniques at Alphonse Atoll, Seychelles. Inputs are a map of the benthic surface (seabed) cover, a detailed bathymetric model derived from remotely sensed Compact Airborne Spectrographic Imager (CASI) data and information on regional wave heights. Incident energy at the reef crest around the atoll perimeter is calculated as a function of its deepwater value with wave parameters (significant wave height and period) hindcast in the offshore zone using the WaveWatch III application developed by the National Oceanographic and Atmospheric Administration. Energy modifications are calculated at constant intervals as waves transform over the forereef platform along a series of reef profile transects running into the atoll centre. Factors for shoaling, refraction and frictional attenuation are calculated at each interval for given changes in bathymetry and benthic coverage type and a nominal reduction in absolute energy is incorporated at the reef crest to account for wave breaking. Overall energy estimates are derived for a period of 5 years and related to spatial patterning of reef flat surface cover (sand and seagrass patches). 相似文献
899.
Pelayo Salinas-de-León Alba Costales-Carrera Stephen Zeljkovic David J. Smith James J. Bell 《Estuarine, Coastal and Shelf Science》2011
Recruitment is a key factor driving the population dynamics of scleractinian corals, but despite its importance, we still have a poor understanding of recruitment processes in the Coral triangle region, which contains the most biodiverse marine ecosystems in the world. This study aimed to compare settlement rates to artificial settlement panels with cleared areas of natural reef in order to assess whether panels are a suitable indicator of natural coral settlement rates. We recorded coral settlement rates to panels made of two different materials (concrete and terracotta), attached to the reef at two different orientations (vertical and horizontal), and compared these settlement rates to those on cleared areas of natural reef positioned on vertical reef walls, over a 12 month period. We examined settlement rates at four sites in the Wakatobi National Marine Park, south-east Sulawesi, Indonesia; two reefs were light-limited, highly sedimented sites with low coral cover (<10%) and two had moderate coral cover (approx. 40%) and lower sedimentation rates. Panels were directly attached to the reef at 6–7 m depth. The number of coral spat per tile ranged from 0 to 34 and no significant differences were reported between the settlement rates to cleared natural reef areas and settlement panels. Significantly higher numbers of spat settled on the cryptic (back) side of the panels, while no significant difference was found between settlement rates to the different panel materials, or between the different orientations or any combination of these two factors. There is, however, a significant difference in the settlement rates between sites, for both settlement panels and permanent cleared areas, with higher settlement rates at the sites with higher live coral cover. We conclude that both concrete and terracotta panels yield similar settlement rates, and orientation makes no difference to settlement rates when panels are directly attached to the reef. Our results demonstrate that artificial substrata provide comparable settlement rate data to natural substrata and therefore are suitable for monitoring coral settlement rates in the future. 相似文献
900.
忠县地面石质文物风化病害形式有:裂隙状风化、页片状风化、絮粉状风化、松胀状风化。其中以絮粉状风化对文物破坏最为严重。控制风化的主要因素是:岩性和岩体结构、气候和气象条件、人为的污染。现场简易强度测试数据表明,风化石材的力学强度明显下降。最后提出了三峡水库蓄水前,对石质文物搬迁和保护的建议。参加研究工作的还有王金华、陈超平、唐毅烈、邓修甫、卞大巍、黄明元等人。表13处文物概况Table1SurveyofthethreestoneculturalrelicsinZhongxianCounty表2石材的化学成分(%)Table2Chemicalcompositionsofrockmaterials注:丁房阙石样已非新鲜岩石。表3石材岩块的主要物理力学性质指标Table3Mainphysical-mechanicalparametersofrockmaterials注:灰绿色砂岩试验成果取自三峡工程库区环境地质研究有关资料。2石质文物的风化病害分析受自然地质环境及人文环境的制约,3处石质文物的主要环境病害是风化病害。2.1风化病害形式[1](1)裂隙状风化。这是一种典型的物理风化形式,见于无铭阙和临江岩摩崖造像。无 相似文献