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991.
Nancy Beller‐Simms 《The Professional geographer》2004,56(2):213-222
This study examines mitigation and preparation activities selected by four county and state governments in anticipation of the 1997–1998 El Ni1;o. It expands the knowledge of how state and local governments plan short‐term projects and mitigate with longer‐term activities in anticipation of a natural hazard. It also provides a preliminary understanding of divergent responses and plans under similar disaster warnings. It outlines stages that governments follow in determining their natural hazard mitigation and preparedness activities. This model should provide hazard planners, particularly those planning for slower onset hazards, with insights into their own local circumstances, allowing them to choose appropriate strategies. 相似文献
992.
ABSTRACT. The Pur1;pecha region of Michoacán State, in west‐central Mexico, has a strong tradition of craft production, especially wooden items. Transportation improvements in the region since the mid‐twentieth century have led to a higher level of integration of the regional economy, yet access to the broader Mexican market remains limited. Towns throughout the region have experienced substantial changes in the types of crafts produced, the extent of their local and external markets, and the location of craft production. Transportation improvements have, in part, led to agglomeration economies and a resultant contraction in the number of different types and an increase in the volume of the crafts produced. Market changes have led to the proliferation of craft storefronts in towns with higher levels of accessibility. Conversely, remote towns still rely heavily on distributors and have not been able to expand their markets. As a result, the region has seen the development of a two‐tiered system whereby towns with increased accessibility have viable craft industries and towns with limited accessibility struggle with stagnant craft industries. 相似文献
993.
上世纪70年代以来,由于雨花台组与其他砂砾层之间接触关系未被发现,南京—仪征地区新近纪地层层序及时代一直存在着争议。笔者对仪征大仪集新仪1孔剖面进行了重新整理划分,新近纪各地层叠置关系明显,同时结合其他剖面及岩相古地理分析,在前人工作的基础上,对新近纪地层层序及时代进行了讨论。该地区新近纪地层层序为中新世中期的洞玄观组(N1d)、中新世晚期的六合组(N1l)黄岗组(N1h)及上新世的雨花台组(N2γ)以及非正式岩石地层单位方山玄武岩(fb)。雨花台组沉积是位于六合组之上的另一套砂砾层,其沉积时代为上新世晚期。 相似文献
994.
轮南油田不同时代储层原油中检出了丰富的三甲基苯基类异戊二烯化合物。该类化合物被普遍认为是来自于高盐度和强还原水体沉积环境中绿硫菌体内的类胡萝卜素的特征性生物标志化合物。该类化合物的检出对轮南油田烃源岩研究具有重要的指示意义,暗示了具有分层水体或高盐度的强还原环境下发育的优势烃源岩,对该区烃类的主力生烃贡献不容忽视。基于C15-3,4,5-三甲基苯基类异戊二烯异构体在轮南油田原油中的分布规律,及C15-3,4,5/C13-2,3,6-比值与Pr/Ph,Ga/C31H和Ts/Tm等常规地球化学参数的对比,说明具有生源意义、能够指示沉积相特征的三甲基苯基类异戊二烯化合物分布,在一定程度上也受烃类热演化程度的影响。 相似文献
995.
时变参数PGM(1, 1)变形预测模型及其应用 总被引:7,自引:1,他引:7
汪孔政 《武汉大学学报(信息科学版)》2005,30(5):456-459
在GM(1,1)模型的基础上,考虑参数随时间的变化,用多项式逼近模型参数,同时针对GM(1,1)模型背景值取值方法的不足,引入背景值最佳生成系数,建立了时变参数PGM(1,1)变形预测模型。多项式中的待定系数采用最小二乘法确定,背景值最佳生成系数采用搜索法确定。实例计算表明,时变参数PGM(1,1)变形预测模型具有较高的模拟精度和预测精度,适合用于变形体的变形预测。 相似文献
996.
Sign-constrained robust least squares, subjective breakdown point and the effect of weights of observations on robustness 总被引:3,自引:1,他引:3
Peiliang Xu 《Journal of Geodesy》2005,79(1-3):146-159
The findings of this paper are summarized as follows: (1) We propose a sign-constrained robust estimation method, which can
tolerate 50% of data contamination and meanwhile achieve high, least-squares-comparable efficiency. Since the objective function
is identical with least squares, the method may also be called sign-constrained robust least squares. An iterative version
of the method has been implemented and shown to be capable of resisting against more than 50% of contamination. As a by-product,
a robust estimate of scale parameter can also be obtained. Unlike the least median of squares method and repeated medians,
which use a least possible number of data to derive the solution, the sign-constrained robust least squares method attempts
to employ a maximum possible number of good data to derive the robust solution, and thus will not be affected by partial near
multi-collinearity among part of the data or if some of the data are clustered together; (2) although M-estimates have been
reported to have a breakdown point of 1/(t+1), we have shown that the weights of observations can readily deteriorate such results and bring the breakdown point of
M-estimates of HuberR17;s type to zero. The same zero breakdown point of the L
1-norm method is also derived, again due to the weights of observations; (3) by assuming a prior distribution for the signs
of outliers, we have developed the concept of subjective breakdown point, which may be thought of as an extension of stochastic
breakdown by Donoho and Huber but can be important in explaining real-life problems in Earth Sciences and image reconstruction;
and finally, (4) We have shown that the least median of squares method can still break down with a single outlier, even if
no highly concentrated good data nor highly concentrated outliers exist.
An erratum to this article is available at . 相似文献
997.
Satoko Niimi Michio X. Watanabe Eun-Young Kim Hisato Iwata Genta Yasunaga Yoshihiro Fujise Shinsuke Tanabe 《Marine pollution bulletin》2005,51(8-12):784
This study presents full-length cDNA sequences of CYP1A1 and 1A2, in common minke whale (Balaenoptera acutorostrata) from the North Pacific. Both CYP1A1 and CYP1A2 cDNAs had an open reading frame of 516 amino acid residues, and predicted molecular masses were 58.3 kDa and 58.1 kDa, respectively. The deduced full-length amino acid sequence of CYP1A1 revealed higher identities with those of sheep (86%) and pig (87%), and that of CYP1A2 was most closely related to human (82%) and monkey CYP1A2 (82%) among species from which CYP1A2 has been isolated so far. Differences in certain conserved and functional amino acid residues of CYP1A1 and 1A2 between common minke whale and other mammalian species indicate the possibility of their specific metabolic function. Concentrations of organochlorine compounds (OCs) including PCBs and DDTs analyzed in common minke whale liver showed no significant correlation with hepatic mRNA expression levels of CYP1A1 and CYP1A2, indicating no induction of these enzymes by such OCs. 相似文献
998.
WANG Rujian & CHEN Ronghua . State Key Laboratory of Marine Geology Tongji University Shanghai China . The Key Laboratory of Submarine Geoscience State Oceanic Administration Hangzhou China 《中国科学D辑(英文版)》2005,48(10)
The Bering Sea, located in the Subarctic Northern Pacific Ocean, plays an important role in the global carbon cycle and modern and past global climatic sys-tems, which originates from a very effective biological pump, indicating much higher biogenic opal produc-tion than calcium carbonate[1]. Measured biological particular fluxes show that the flux in the Bering Sea is twice over that in the open ocean. Thereby, the Ber-ing sea is thought as a CO2 sink[2]. At the same time, the Bering Sea… 相似文献
999.
Alzheimer's disease (AD) is the most common form of dementia. Populations migrating from developing to industrialized countries seem to elicit a higher incidence and prevalence rate of AD, suggesting lifestyle and environmental factors to have a role in the pathophysiology of AD. One of its major neuropathological hallmarks is the deposition of Aβ peptides as amyloid plaques in the brain of AD patients. Aβ is proteolytically cleaved out of the larger amyloid precursor protein (APP). Cu and Mn are often found in drinking water and may have a neurotoxic potential. APP is involved in Cu homeostasis in mouse and man. In vitro observations and in vivo data obtained from APP mouse models provide strong evidence that APP overexpression enables intracellular Cu to be transported out of the cell. Disturbed metal‐ion homeostasis with elevated serum Cu levels occurs in Alzheimer and Down's patients and lowered levels in post‐mortem AD brain. We observed that bioavailable Cu has specific beneficial effects in an Alzheimer's disease mouse model. This should be regarded as a proof‐of‐concept for a prophylactic approach to overcome the observed CNS Cu deficiency in the brain of Alzheimer's disease patients. Manganism is a disorder with symptoms similar to that of Parkinson's disease. The precise mechanism how manganese can damage the nervous system is unknown. There is some evidence that iron and manganese may utilize similar transport systems. Epidemi ologic data strongly suggests that manganese enters the body primarily via inhalation and through the ingestion of manganese in drinking water. 相似文献
1000.
1 INTERNAL HYDRAULIC JUMPS AND LOCAL WATER ENTRAINMENT Traveling and stationary internal hydraulic jumps in two-layer flow can occur in the following situations (Fig. 1). When a stratified fluid flows over an obstacle created by a sudden blockage, the layer of increased depth within the heavier fluid will propagate upstream as a traveling hydraulic jump. When the heavier fluid overtops the obstacle it will flow along the downstream face of the obstacle as a supercritical flow… 相似文献