新冠疫情对中国国际航空网络连通性的影响及空间差异

航空运输在实现各国互联互通、推动全球经济发展中发挥着重要作用。突发公共卫生事件或恶劣天气等均易对航空网络的连通性造成影响。本研究以新冠疫情为例，从全球航空网络视角探讨新冠疫情对中国国际航空网络连通性的影响及地区差异。研究结果表明：疫情期间，中国境外通航城市、国际航班、国际航线数量均大幅缩减，航空网络连通效率显著降低，但其空间格局未发生根本性变化，东亚和东南亚仍是中国对外主要联系地区，经济联系与贸易仍然起着重要作用。航线停飞对中国与中亚、西亚和大洋洲航空网络的连通性影响最大，而航班缩减对中国与东亚、中亚和东南亚航空网络的连通性影响最大。在国内，北京、上海和广州仍然是中国对外联系的枢纽城市，且其聚集度在疫情期间得到提升。     

Application of Astronomic Time-latitude Residuals in Earthquake Prediction

After the earthquake (Ms = 6.1) occurred in Luquan county of Yunnan province on April 18, 1985, the relationship between major earthquakes and astronomical time-latitude residuals (ATLR) of a photoelectric astrolabe in Yunnan Observatory was analyzed. ATLR are the rest after deducting the effects of Earth’s whole motion from the observations of time and latitude. It was found that there appeared the anomalies of the ATLR before earthquakes which happened in and around Yunnan, a seismic active region. The reason of the anomalies is possibly from change of the plumb line due to the motion of the groundmass before earthquakes. Afterwards, using studies of the anomalous characters and laws of ATLR, we tried to provide the warning information prior to the occurrence of a few major earthquakes in the region. The significant synchronous anomalies of ATLR of the observatory appeared before the earthquake of magnitude 6.2 in Dayao county of Yunnan province, on July 21, 2003. It has been again verified that the anomalies possibly provide the prediction information for strong earthquakes around the observatory.     

Composite analytical solutions for a soil vapour extraction system

Soil vapour extraction (SVE) is a common remediation technique for cleaning up unsaturated soils contaminated by volatile organic compounds (VOCs). Analytical solutions, which result from simple mathematical models, can allow the fast approximation of the time‐dependent effluent concentration and the gaining of insight into the processes that take place during soil remediation. Deriving the analytical solutions to advection–dispersion equations that simultaneously take into account the mechanical dispersion and molecular diffusion is very difficult because of the variable dependence of governing equations' coefficients. In this study, we first present two simplified analytical solutions that only consider mechanical dispersion or molecular diffusion. The two developed analytical solutions are compared with the numerical solution that simultaneously considers both mechanical dispersion and molecular diffusion to examine the applicability of the two simplified analytical solutions and distinguishes the individual contribution of the mechanical dispersion and molecular diffusion to total VOCs transport in an SVE system. Results show that dispersion plays an important role during SVE decontamination and neither the diffusion‐dominated solution nor the dispersion‐dominated solution can agree well with the numerical solution when both mechanical dispersion and molecular diffusion have significant contributions to the total VOCs transport flux. A composite analytical solution that linearly couples the diffusion‐ and dispersion‐dominated analytical solutions, which is proposed herein to eliminate the discrepancy between the analytical solutions and the numerical solution. Results indicate that the proposed composite analytical solution agrees well with the numerical solution and is an effective tool for quickly and accurately evaluating the time‐dependent effluent concentration for parameters of the different ranges of interest in an SVE remedial system. Copyright © 2006 John Wiley & Sons, Ltd.     

新型知识观下高校旅游管理专业课程知识的构建思考

旅游管理专业是1998年新设置的高校本科专业,受学科专业特点和旅游职业需求的影响,其课程知识与传统的学科专业相比,具有很强的实践性.为此,其课程知识的构建,需要深入认识旅游管理专业课程知识的特点,建立起"科学-人本观"的构建价值取向,并充分唤醒教学参与者的主体意识,发挥课堂对课程知识的构建作用.     

电离层E_S层对综合射束污染的初步分析

本文考虑到干涉仪对电离层中不同尺度不规则性的滤波作用、结合密云米波综合孔径系统、提出了电离层E_(?)层是电离层不规则性影响该系统的主要根源。不规则性的尺度约在700～1000米的范围。再考虑到E_(?)层的漂移运动,提出了文中所描述的模型。用电子计算机进行了E_(?)层对综合射束污染的模拟计算,结果指出:射束主瓣的增益下降约10％,副瓣由13％增大到18％;综合射束在赤经方向出现不对称性,从而引起约0.6秒的赤经误差;射束的边缘处和两个扇形区出现了杂瓣。     

模糊评判法在公路黄土洞穴发育程度分区中的应用

阐述了影响黄土洞穴形成的黄土湿陷性、崩解性、地质构造、节理裂隙、微地形地貌和水文及气候条件等工程地质特性和地质因素;在公路沿线地区,公路工程质量及人类活动也是黄土洞穴形成的影响因素。洞穴发育程度分区预测和评价极具复杂性、随机性和模糊性,为此,在对各影响因素分析的基础上,借助模糊综合评判法,对黄土区公路沿线洞穴发育程度分区进行了研究。与实际情况对比分析表明,预测评价结果合理可靠,可作为黄土区已建公路洞穴灾害的防治依据。     

脊尾白虾蜕皮抑制激素基因全长cDNA的克隆及其对环境胁迫的响应

为研究脊尾白虾蜕皮抑制激素基因(MIH)在环境适应中的作用,本文采用RACE技术从蜕皮间期脊尾白虾眼柄中克隆获得MIH-like基因全长c DNA序列,命名为Ec MIH。该基因全长1218bp,包括360bp的开放阅读框,420bp的5'端非编码区和394bp的3'端非编码区;开放阅读框编码120个氨基酸,包括41个氨基酸组成的信号肽和79个氨基酸组成的成熟肽,预测蛋白分子量为13.71k Da,理论等电点p I为8.02。同源性比较分析发现,脊尾白虾MIH-like基因与日本沼虾和罗氏沼虾同源性最高,分别为87%和86%。荧光定量PCR分析结果表明,脊尾白虾MIH-like基因在眼柄中的表达量最高,在卵巢中的表达量最少,而在肝脏、肌肉、鳃和血细胞中不表达。环境胁迫后该基因具有明显的时序性。p H6.5胁迫后24h和48h,眼柄和腹神经节中MIH-like基因的表达量较对照组均显著增加(P0.05);4mg/L氨氮浓度组胁迫后12h和24h,眼柄和腹神经节中MIH-like基因的表达量较对照组均显著增加(P0.05);盐度39胁迫后12h和24h,眼柄和腹神经节中MIH-like基因的表达量较对照组均显著增加(P0.05)。本研究结果表明脊尾白虾mih基因参与了环境胁迫后的机体应激反应。     

南渡江河口洪、枯季节水文泥沙变化特征及台风“海鸥”对入海水沙的影响

基于2014年最新的洪、枯季节实测资料,分析了南渡江河口海域水文泥沙的季节性变化特征,借助台风"海鸥"过境期间的河道监测数据,研究了台风天气造成的洪水事件对河流入海水沙通量的影响。研究结果表明:(1)洪、枯季节河口海域的水体层化作用不强,洪季的水温高于枯季,但盐度低于枯季。水温呈现向海递减的趋势,而盐度整体分布较为均匀;(2)河口水体含沙量近岸大于远岸,枯季河口三角洲泥沙向西输运。洪季含沙量明显高于枯季,大量泥沙在台风季节被冲刷入海,而后向海或向西输运扩散;(3)河口海域为不规则全日潮,呈现东西向往复流特征。温度、盐度和浊度均呈现较强的潮汐性变化特征;(4)枯季河道内存在明显的盐水楔,锋面处的垂向梯度很大,在口门向陆大约12—15 km以远的河道水体不再受潮汐影响;(5)台风"海鸥"影响下,南渡江洪峰期间的径流量和含沙量均远远超过多年平均值,反映了南渡江河口地区"台风季节"的特点。     

菲律宾海北部四国海盆全新世沉积物源分析

对IODP333航次四国海盆北部地区C0011站位表层样品进行粒度和Sr-Nd同位素分析,并与前人发表的邻近海域同位素数据进行比较。经分离自生碳酸盐组分,四国海盆全新世沉积物呈现较好的陆源、火山源二端元组分特征。从地理位置看,四国海盆北部主要物质来源包括伊豆-小笠原海脊火山物质、日本列岛西南部的混合型沉积物以及由西向风或河流入海洋流输送而来的亚洲陆地沉积物,且日本列岛西南部对于该区域物质贡献最大。对四国海盆北部而言,与海盆中部沉积及日本海沉积相比,源自亚洲大陆的碎屑沉积物具有更多的贡献。沉积物中87Sr/86Sr与εNd、平均粒径的负相关关系反映了沉积物中陆源物质的相对贡献按时间顺序呈现增加、减小、增加、减少的多周期变化趋势。