厦门西海域浮游植物的生态

本文分析、鉴定了于1989年4月至1990年3月,逐月采自厦门西海域的7个站位的112份样品。结果表明,本海区浮游植物共129种,其中蓝藻1种,硅藻105种,金藻1种,甲藻22种。按其分布特点,可分为两大生态类群:广布种占57%,暖水种占43%。浮游植物细胞总量的季节分布是8月出现主高峰,5月为次高峰,3月是最低谷期。此外,对其数量分布和季节变化与海洋环境因素的关系,进行了较详细的讨论。     

以PC1井三维荧光光谱分析结果论油气垂向运移

本文以Pcl并不同深度岩心和地表土壤作为分析样品，通过三维全扫描荧光光谱等分析。揭示了该区油气垂向运移规律和地下油气的某些分布特征。研究表明，芳烃三维荧光光谱方法是研究芳烃组成变化最理想的手段之一，可以有效地解决油气运移等问题。     

低管电压与低对比剂量在肝脏CT增强中的应用

目的:探讨低管电压(110kVp)与低对比剂量(1.0mL/kg)在肝脏CT增强扫描中的可行性。方法:116例行肝脏CT增强扫描,且BMI<25kg/m²的患者,随机分成A、B两组进行研究,每组58例。A组:管电压110kVp,对比剂碘帕醇(300mgI/mL),对比剂量(1.0mL/kg),采用正弦迭代重建(SAFIRE)。B组:管电压130kVp,对比剂碘帕醇(300mgI/mL),对比剂量(1.2mL/kg),采用滤波反投影重建算法(FBP)。测量动脉期腹主动脉CT值、肝门脉期门静脉CT值及增强扫描3期(动脉期、门脉期、延迟期)的肝右叶肝实质CT值;计算两组图像的肝动脉期对比噪声比(CNR)、信噪比(SNR)及总有效辐射剂量ED;并对两组图像进行评分,进行统计学分析。结果:A组和B组CNR、SNR差异无统计学意义(P>0.05);两组分别在增强扫描3期测得肝右叶肝实质CT值及动脉期腹主动脉CT值差异亦无统计学意义(P>0.05);肝门脉期A组的门静脉CT值低于B组统计学差异有意义(P<0.05)。A组的3期总有效辐射剂量(ED)(9.88±3.56)mSv低于B组(13.91±4.71)mSv,统计学差异有显著意义(P<0.001);A组比B组的对比剂量减少17%。结论:128层MSCT在肝脏增强CT扫描中,应用低管电压(110kVp)和低对比剂量(1.0mL/kg),联合迭代重建技术(SAFIRE),可以得到较好的图像质量,同时降低辐射剂量及人体碘摄入量。     

大同火山群地质及岩石学特征

大同火山群以盆地为对称轴分布,中更新世晚期火山位于盆地的轴部,中更新世早期火山位于盆地两侧。计算的延伸和断裂速率分别为0.43cm/a和0.22cm/a。大同火山群主要属于碱性橄榄玄武岩系列,中更新世早期火山的一部分属于拉斑系列,夏威夷岩是大同火山岩的一个主要类型.中更新世早期火山岩的氧化物变异趋势可能是受高压下Ol+Opx的分离作用控制.中更新世晚期火山岩氧化物变异趋势暗示了是受岩浆混合作用的控制。     

Groundwater sustainability and groundwater/surface-water interaction in arid Dunhuang Basin,northwest China

The Dunhuang Basin, a typical inland basin in northwestern China, suffers a net loss of groundwater and the occasional disappearance of the Crescent Lake. Within this region, the groundwater/surface-water interactions are important for the sustainability of the groundwater resources. A three-dimensional transient groundwater flow model was established and calibrated using MODFLOW 2000, which was used to predict changes to these interactions once a water diversion project is completed. The simulated results indicate that introducing water from outside of the basin into the Shule and Danghe rivers could reverse the negative groundwater balance in the Basin. River-water/groundwater interactions control the groundwater hydrology, where river leakage to the groundwater in the Basin will increase from 3,114?×?10⁴ m³/year in 2017 to 11,875?×?10⁴ m³/year in 2021, and to 17,039?×?10⁴ m³/year in 2036. In comparison, groundwater discharge to the rivers will decrease from 3277?×?10⁴ m³/year in 2017 to 1857?×?10⁴ m³/year in 2021, and to 510?×?10⁴ m³/year by 2036; thus, the hydrology will switch from groundwater discharge to groundwater recharge after implementing the water diversion project. The simulation indicates that the increased net river infiltration due to the water diversion project will raise the water table and then effectively increasing the water level of the Crescent Lake, as the lake level is contiguous with the water table. However, the regional phreatic evaporation will be enhanced, which may intensify soil salinization in the Dunhuang Basin. These results can guide the water allocation scheme for the water diversion project to alleviate groundwater depletion and mitigate geo-environmental problem.     

近年国外传统村镇旅游研究进展及启示

近年来,随着传统村镇旅游的日益兴起,有关传统村镇的旅游学研究日益受到学术界重视和关注.总结了国内外关于传统村镇的旅游学研究进展,指出国外研究成果主要集中在传统村镇旅游发展影响研究、传统村镇旅游发展与文化原真性保持之间的关系、传统村镇旅游可持续发展等方面.国内研究与之相比,在研究内容、方法、领域、深度等方面仍有很大差距,有待进一步扩展和深入.今后应注意以下几方面问题:研究内容流于表层,应加强研究领域的延伸和深度的扩展;研究方法、手段较为单一,研究理论和方法焏待提高;理论研究滞后于旅游发展实践的现状焏待改善.     

Waveform Characteristics of Earthquakes Induced by Hydraulic Fracturing and Mining Activities: Comparison with Those of Natural Earthquakes

Natural Resources Research - Some industrial activities, such as underground mining, hydraulic fracturing (HF), can cause microearthquakes and even damaging earthquakes. In recent years, with the...     

Effects of an ecological conservation and restoration project in the Three-River Source Region,China

The first-stage of an ecological conservation and restoration project in the Three-River Source Region (TRSR), China, has been in progress for eight years. However, because the ecological effects of this project remain unknown, decision making for future project implementation is hindered. Thus, in this study, we developed an index system to evaluate the effects of the ecological restoration project, by integrating field observations, remote sensing, and process-based models. Effects were assessed using trend analyses of ecosystem structures and services. Results showed positive trends in the TRSR since the beginning of the project, but not yet a return to the optima of the 1970s. Specifically, while continued degradation in grassland has been initially contained, results are still far from the desired objective, ‘grassland coverage increasing by an average of 20%–40%’. In contrast, wetlands and water bodies have generally been restored, while the water conservation and water supply capacity of watersheds have increased. Indeed, the volume of water conservation achieved in the project meets the objective of a 1.32 billion m³ increase. The effects of ecological restoration inside project regions was more significant than outside, and, in addition to climate change projects, we concluded that the implementation of ecological conservation and restoration projects has substantially contributed to vegetation restoration. Nevertheless, the degradation of grasslands has not been fundamentally reversed, and to date the project has not prevented increasing soil erosion. In sum, the effects and challenges of this first-stage project highlight the necessity of continuous and long-term ecosystem conservation efforts in this region.     

农牧交错带农田土壤风蚀PM10释放特征

粉尘释放是风蚀造成危害的一个重要过程。以农牧交错带沙区和非沙区农田土壤为研究对象,利用室内风洞模拟实验,实时监测了风蚀过程中释放的PM₁₀,分析了PM₁₀的动态变化特征,以深入认识土壤风蚀粉尘释放机理。结果表明：非沙区农田土壤风蚀强度远低于沙区农田,与风速呈指数函数关系;非沙区农田的土壤粉尘释放在不同风速下均以气流直接抬升模式为主,平均PM₁₀通量与风速呈线性函数关系,最大PM₁₀通量与风速呈幂函数关系;沙区农田的土壤粉尘释放在风速增大到一定程度后呈气流直接抬升和砂粒跃移冲击复合模式,最大PM₁₀通量增加不明显,但平均PM₁₀通量明显高于非沙区农田;对于沙区和非沙区农田而言,平均PM₁₀通量与风蚀速率呈对数函数关系。