基于未确知测度的区域旅游风险危险性评价——以湖北省恩施土家族苗族自治州为例

从突发危机事件、旅游生态风险、旅游经济风险、旅游文化风险、旅游社会风险、旅游安全风险6个方面遴选出42项指标构建区域旅游风险因素识别指标体系。采用未确知数学方法、专家咨询法,从风险可能性和风险危害性两个方面构建区域旅游风险危险性评价模型,并对湖北省恩施土家族苗族自治州旅游发展中的风险进行综合评价。结果表明:在恩施州所面临的6大类旅游风险中,危险性程度最高的是旅游经济风险,其次是旅游文化风险。在42项风险因素中,自然灾害、旅游发展战略失误及盲目旅游开发导致的长期利益受损、旅游业导致的民族文化商品化/原真性丧失、旅游业导致的交通及人口拥挤等,对恩施州而言是危险性程度最高的几项风险因素。     

人工订正位涡改进模式初始场技术研究

面对数值天气预报模式发展中的制约,如今气象界提出了预报员数据同化(data assimilation,DA)的理念,即将预报员的能力有机地融入到数值预报模式中以便发挥各自的优势。人工订正位涡改进模式初始场技术即充分体现了这一理念,其原理是利用了在中、高纬度气旋性环流场中,位涡(potential vortictiy,PV)场和卫星水汽图像(satellite water vapor imagery,WV)较好的对应关系检验数值预报,进而利用位涡的可反演性通过人工修改位涡场来订正数值预报,并已在部分国家实践中证明有着显著的改进模式预报性能的效果。本研究将通过分析对流层中高层的动力活跃区、位涡分布和卫星水汽图像暗区的关系检验模式偏差,进而通过人工订正位涡场和位涡反演,实现对模式初始场的修改,为预报员主观订正模式初始场、改进模式预报能力提供完整的技术流程。     

数值模式预报调整趋势分析

对不同时效预报的调整趋势进行分析,是预估预报误差和对预报进行订正的一种思路。为了系统性检验这一思路的有效性,本文定义了西风槽强度和位置指数,以及西北太平洋副热带高压(简称副高)强度和位置等指数,运用2011年4月以来的500 hPa位势高度场预报资料,研究对比了ECMWF(简称EC)和T639模式对副高和我国不同区域西风槽的位置和强度,72 h时效内对同一时刻不同时效的预报,随预报时效的临近,预报调整趋势之间的相关性和一致性。研究结果显示,EC和T639模式对副高的预报,都存在西脊点偏东、范围偏小、强度偏弱和北界偏南的系统性偏差,且时效越长偏差越大,T639模式的偏差明显大于EC模式,但相关性分析和方差分析表明,不同时效的调整趋势之间并不存在较为显著的相关性,即不同时效的预报并没有较为明显的、一致的调整趋势。另外,副高的预报误差与西脊点所处的经度有关,从东印度洋到菲律宾以东洋面,西脊点越往东,预报误差和系统偏差越小,但西脊点位于不同的经度区间时,不同时效的调整趋势之间同样没有明显的相关性,且整体上以负的协方差为主。对于西风槽,两家模式北方槽的误差都明显大于南方槽的误差,强度的误差较小,且T639的误差明显大于EC模式,相邻时效的调整趋势之间以负的协方差为主,说明随时效的临近,槽的位置并没有较为一致的调整趋势。同时不同时期预报调整趋势之间的相关性分析显示,模式版本的升级,并没有改变调整趋势之间几乎无一致性的特征。     

Experimental Study on Displacement Field of Strata Overlying Goaf with Sloping Coal Seam

To study the displacement caused by underground mining, the displacement field in the strata overlying the mine was simulated in nine similar-material models with coal seam dip angles of 0°–80°. Digital close-range photogrammetry was employed to observe the displacement in these models and produce displacement vector diagrams of observation points set on the model surfaces. The movement boundary of the rock mass was extracted and determined. According to the displacement vectors’ direction, the displacement field within the movement boundary was divided into five zones: two zones with displacement vectors pointing towards the goaf center, two zones with vectors pointing towards the coal pillar, and one zone with displacement vectors pointing vertically downward. A symmetry index was defined to analyze the symmetry of the displacement field, and the results show that as the coal seam dip angle increased from 0° to 80°, the displacement field in the strata changed according to the following pattern: symmetric → asymmetric → nearly symmetric, with a transition angle of about 45°. The percentage of the area of the above-defined five zones relative to the displacement field’s total area also changed, showing a regular pattern. This study also revealed that the movement boundary inside the overlaying rock layers is not a straight line, but an S-shaped curve. These findings can enhance our understanding of the internal mechanism of ground subsidence and contribute to more effective prediction of the deformation occurring inside a given rock mass.     

High‐Precision Measurement of Molybdenum Isotopic Compositions of Selected Geochemical Reference Materials

Here we describe high‐precision molybdenum isotopic composition measurements of geological reference materials, performed using multi‐collector inductively coupled plasma‐mass spectrometry (MC‐ICP‐MS). Purification of Mo for isotopic measurements was achieved by ion exchange chromatography using Bio‐Rad AG^® 1‐X8 anion exchange resin. Instrumental mass bias was corrected using ¹⁰⁰Mo‐⁹⁷Mo double spiking techniques. The precision under intermediate measurement conditions (eighteen measurement sessions over 20 months) in terms of δ^98/95Mo was 0.10‰ (2s). The measurement output was approximately four times more efficient than previous techniques, with no compromise in precision. The Mo isotopic compositions of seven geochemical reference materials, seawater (IAPSO), manganese nodules (NOD‐P‐1 and NOD‐A‐1), copper‐molybdenum ore (HV‐2), basalt (BCR‐2) and shale (SGR‐1b and SCo‐1), were measured. δ^98/95Mo values were obtained for IAPSO (2.25 ± 0.09‰), NOD‐P‐1 (?0.66 ± 0.05‰), NOD‐A‐1 (?0.48 ± 0.05‰), HV‐2 (?0.23 ± 0.10‰), BCR‐2 (0.21 ± 0.07‰), SCo‐1 (?0.24 ± 0.06‰) and SGR‐1b (0.63 ± 0.02‰) by calculating δ^98/95Mo relative to NIST SRM 3134 (0.25‰, 2s). The molybdenum isotopic compositions of IAPSO, NOD‐A‐1 and NOD‐P‐1 obtained in this study are within error of the compositions reported previously. Molybdenum isotopic compositions for BCR‐2, SCo‐1 and SGR‐1b are reported for the first time.     

The transfer of oxygen isotopic signals from precipitation to drip water and modern calcite on the seasonal time scale in Yongxing Cave,central China

Stable isotope data of precipitation (δ¹⁸O_p and deuterium excess), drip water (δ¹⁸O_d), and modern calcite precipitates (δ¹⁸O_c and δ¹³C_c) from Yongxing Cave, central China, are presented, with monthly sampling intervals from June 2013 to September 2016. Moderate correlations between the monthly variation of δ¹⁸O_p values (from ??11.5 to ??0.7‰) and precipitation amount (r = ??0.59, n?=?34, p?<?0.01) and deuterium excess (r?=?0.39, n?=?31, p?<?0.01) imply a combined effect of changes in precipitation amount and atmospheric circulation. At five drip sites, the δ¹⁸O_d values have a much smaller variability (from ??9.1 to ??7.5‰), without seasonal signals, probably a consequence of the mixing in the karst reservoir with a deep aquifer. The mean δ¹⁸O_d value (??8.4‰) for all drip waters is significantly more negative than the mean δ¹⁸O_p value (??6.9‰) weighted by precipitation amount, but close to the wet season (May to September) mean value (??8.3‰), suggesting that a threshold of precipitation amount must be exceeded to provide recharge. Calculation based on the equilibrium fractionation factor indicates that the δ¹⁸O_c values are not in isotopic equilibrium with their corresponding drip waters, with a range of disequilibrium effects from 0.4 to 1.4‰. The δ¹⁸O_c and δ¹³C_c values generally increase progressively away from the locus of precipitation on glass plates. The disequilibrium effects in the cave are likely caused by progressive calcite precipitation and CO₂ degassing related to a high gradient of CO₂ concentration between drip waters and cave air. Our study provides an important reference to interpret δ¹⁸O_c records from the monsoon region of China.     

滇东北铅锌成矿带会泽金牛厂筇竹寺组含矿层的发现及意义

滇东北地区是我国铅、锌、银等有色金属矿产的重要产地之一,已发现铅锌矿床、矿点和矿化点多处。以前发现的赋矿层都是碳酸盐岩,而会泽金牛厂筇竹寺组含矿层是泥质粉砂岩,此含矿层是目前滇东北铅锌成矿带中新发现的铅锌矿含矿层位,它突破了滇东北成矿带中仅碳酸盐岩中含矿的历史,显示了滇东北筇竹寺组铅锌找矿的巨大潜力。文章对该含矿层的控矿特点及矿体规模、形态进行了详细研究,以期对滇东北筇竹寺组的找矿带来新的突破。     

地浸砂岩型铀矿镭—氡放射性平衡对伽玛测井解释结果的影响研究

地浸砂岩型铀矿钻探勘查过程中,由于钻孔内＂压氡现象＂的存在,使钻孔内铀矿层的镭—氡含量出现暂时的不平衡现象,往往会造成伽玛测井解释结果系统偏低,影响了铀矿资源量评价的准确程度。因此在地浸砂岩型铀矿勘查过程中,必须设计一定数量的物探参数孔,及时开展镭—氡放射性平衡系数的研究和评价。