破坏包络面理论在多基础系统中的应用研究

由多个分离基础组成的多基础系统是常用的海洋结构基础型式。基于破坏包络面理论,分析了砂土地基多基础系统的失效模式,建立了相应的承载力计算方法,并验证了计算方法的可行性。对比分析了单一基础和多基础系统不同荷载路径下的荷载安全系数,探讨了破坏包络面理论与分项系数法相结合的基础承载力计算方法。失效模式的分析表明,由于水平荷载的增大,四腿平台结构迎浪侧基础首先到达破坏包络线,其失效模式属于滑动失稳,但由于基础间的运动约束,其并不会出现真正的滑移破坏。随着水平荷载进一步地增大,迎浪侧基础承担的水平和竖向荷载不断减小,导致背浪侧基础受到不断增大的荷载。最终,背浪侧基础也到达破坏包络线,多基础系统失效。分析表明,荷载路径对基础的荷载安全系数有决定性的影响,计算基础的荷载安全系数需指明相应的荷载路径。鉴于破坏包络面的大小和形状取决于众多因素,基础设计时需采用特定工况下的破坏包络面进行承载力计算。     

毛乌素沙地1960-2013年极端气温变化

毛乌素沙地处于多层次生态地理景观过渡带,拥有丰富的自然及人文资源.研究该生态脆弱区极端气温变化,有利于揭示全球气温变化与局地气温响应之间的复杂关系,为当地的可持续发展和气象灾害预防提供参考。通过线性趋势分析、累计距平、Mann-Kendall法、因子分析、R/S分析等方法,分析了该地极端气温指数的变化特征\,突变特点、相互关系,探讨了该地区气温变化的空间差异和极端气温未来的变化趋势。结果表明:(1)极端最低气温、极端最高气温、夏日日数、热夜日数、暖夜日数、暖日日数分别以不同的速率上升;冰日日数、霜冻日数、冷夜日数、冷日日数分别以不同的速率下降。(2)除极端最高气温、极端最低气温外,其余8项极端气温指数均发生突变,突变年份集中在20世纪90年代。(3)冷指数大幅下降是毛乌素沙地极端气温变化的主要特点,并且各冷指数间、各暖指数间相关关系显著。(4)毛乌素沙地极端气温在空间上表现出不同的变化特点,东北方向(榆林及鄂托克旗)冷指数呈现大幅减少,西南方向(横山及盐池)暖指数呈现大幅增加。(5)ENSO事件具有使毛乌素沙地极端最高气温降低的作用以及使极端最低气温升高的作用。(6)10项极端气温指数的Hurst指数均大于0.5,表明未来毛乌素沙地极端气温仍将呈现冷指数下降、暖指数上升的变化趋势。     

旧石器时期以来新疆文化遗址分布特征及驱动因素

运用最近邻指数和耦合分析方法,研究了旧石器时期至近现代新疆432处文化遗址时空分布特征及驱动因素。结果表明：（1）新疆文化遗址属于聚集分布模式,集中分布在以12个聚集区为主的丝绸之路南道、中道、北道和塔城-阿勒泰地区4个带。中道和北道的遗址数量约占总量的80.11%。（2）新疆文化遗址可划分为旧石器-商朝、西周-秦朝、汉代-南北朝、隋唐-五代、宋元明、清朝-近现代6个时期,不同时期遗址分布重心经历了塔城-阿勒泰→丝绸之路南道和中道→丝绸之路中道和北道→丝绸之路中道的演变。（3）文化遗址的格局演化与历史时期新疆自然和人文因素等有很好的耦合关系,文化遗址的快速发展期（如西汉、隋唐）与气候的相对凉湿期、中原政权的强盛、屯垦的高潮期、丝绸之路的繁荣期相对应。（4）文化遗址空间分布主要受控于自然因素,而时间变迁更多的是受人文因素的影响。早期自然因素的影响大,而后期人文力量起主导作用,是新疆文化遗址变迁与自然和人文耦合关系的总规律。     

Causes and effects of spatial and temporal variations of cold period in Chinese oases between 1960 and 2014

Based on daily average temperatures and observation data from 74 meteorological stations in Chinese oases, we calculate five-day (pentad) average temperature ≤0°C for the start and end pentad as well as pentads of cold period using linear regression analysis, nonparametric Mann-Kendall tests, the Morlet wavelet power spectrum, and correlation analysis. We also analyze spatial and temporal variations and their effects on the start and end pentad as well as pentads of cold period in Chinese oases. Results show that over the last 55 years, the start pentad of cold period has been postponed while the end pentad has been advanced. Overall, the pentads have gradually shortened over time at trend rates that are 0.3 p/10a,–0.27 p/10a, and–0.58 p/10a, respectively. Spatial differences are significant, especially for the Qaidam Basin oasis where the start pentad is the earliest, the end pentad is the latest, and the trend of change is most obvious. Mutation points for the start and end pentad as well as pentads of cold period were observed in 1990, 1998, and 1994, respectively. Of these, the start pentad and pentads of cold period show a periodic cycle, related to atmospheric circulation and El Nino events, while the end pentad exhibits a periodic cycle, related to solar activity. The Tibetan Plateau index (TPI), the Asian polar vortex area index (APVAI), and carbon dioxide emissions (CDE) are the main factors affecting cold period in the study area, whereas the South Asian summer monsoon (SASM) index exerts the greatest effect on the Qaidam Basin oasis. The start and end pentad as well as pentads of cold period increase in concert with latitude, longitude, and altitude; in response to these changes, the start pentad is advanced, the end pentad is postponed, and pentads of cold period are gradually extended. Results show that change in latitude is most significant. Overall, the start and end pentad as well as pentads of cold period show clear responses to regional warming, but there are different effects on each.     

九道岭井田聚煤规律及控煤因素分析

九道岭井田位于辽宁阜新煤田的西南部,勘查面积24km^2,煤炭资源量丰富,是一个具有远景发展的含煤地区。根据该区已有的勘探资料,研究其含煤地层的分布、含煤性及聚煤作用,并对其含煤岩系的沉积旋回结构及可采煤层的分布状况进行了分析。研究表明：九道岭井田沙海组聚煤作用可分为两个主要聚煤期,第一个聚煤期为第一旋回的上部4煤层及5煤层沉积时期：第二聚煤期为第三旋回顶部的二煤层沉积时期。该区的煤层发育主要受沉积环境、构造和古气候等因素控制。以上研究成果为今后矿山开采及外围找煤提供参考。     

宁夏灵武面子山山前区地下水中氟的富集及分布规律探讨

研究区东部属低山丘陵区及山前侵蚀堆积阶地,西部为黄河冲、洪积平原区,地下水资源丰富．是灵武矿区的主要水源地,但由于地下水中氟离子含量较高,给地下水的利用带来了影响。通过对该区水文地质条件和地下水中氟的水文地球化学特征的研究,认为研究区地下水中氟的含量与水化学类型关系不明显,与PH值及钠／钙值呈正相关关系。初步探讨了影响地下水中氟含量的富集因素及分布规律,研究发现：区内潜水含水层氟含量变化大,常发生突变;承压水含水层则多呈渐变形式;地下水中氟含量的高低主要与补给源中氟含量的高低有关．     

影响或控制平昌县地质灾害发育的因素分析

通过对四川平昌县滑坡、崩塌等地质灾害发育发育情况的介绍,分析了影响或控制该县地质灾害发育的因素。     

The dynamics of tourist excursion ratios in Slovakia show caves from 2000 to 2014

Show caves are one of the most important targets in developing local ecotourism strategies. This work focuses on a tourism visit rate incidence through an Attractiveness Index concerning 12 selected show caves in Slovakia. Our study focuses on visitor counts published from 2000 to 2014. A set of eight criteria were selected in order to analyse and determine the appeal that each cave may have for visitors. Establishing the “degree” of appeal as an indicator of the tourism and geographic absolute attractiveness value is based on a principal components factor analysis; the resultant single factor was correlated with our selected criteria. We find a strong correlation between touristic cave attractiveness and cave locations, ease of cave passage access (vehicle and trail) infrastructures, cave location in main tourism regions, and the growth of urban areas as they encroach on show cave locations. Similar studies in valorization of show caves tourism have not been attempted in Slovakia or Eastern Europe. The data and result from this study are also clearly important from a managerial perspective. This general framework could be easily expanded to include additional attributes that might be relevant for other market segments or other vacation experiences.     

中国能源消费增长特征及影响因素分析

以煤炭消费为主、总量增长迅速、结构演进缓慢、使用效率低下使得中国目前能源消费调控问题面临诸多困难。本文使用多元回归模型和通径分析法确定了中国能源消费增长的主要因子及各因子的作用机理,结果发现：影响中国能源消费的主要因素按照影响程度依次为经济增长、城市化水平、对外贸易、人口总量、能源消费结构及能源利用效率,其中经济增长、人口规模扩大是直接推动中国能源消费增长的原因,而城市化水平和对外贸易规模则通过间接作用推动能源消费增长,能源消费结构的改善和能源利用效率的提高表面上看起来会引发能源消费增加,但是其间接影响都是负的,从而使得这两个因素整体上表现为减缓了能源消费增长。     

Study of the seismic response of a recycled aggregate concrete frame structure

Based on six-degree-of-freedom three-dimensional shaking table tests, the seismic response of a recycled aggregate concrete （RAC） frame was obtained. The analysis results indicate that the maximum story shear force and overturning moment reduce proportionally along the height of the model under the same earthquake wave. The story shear force, base shear coefficient and overturning moment of the structure increase progressively as the acceleration amplitude increases. The base shear coefficient is primarily controlled by the peak ground acceleration （PGA）. The relationships between the PGA and the shear coefficient as well as between the PGA and the dynamic amplification factor are obtained by mathematical fitting. The dynamic amplification factor decreases rapidly at the elastic-plastic stage, but decreases slowly with the development of the elastic-plasticity stage. The results show that the RAC frame structure has reasonable deformability when compared with natural aggregate concrete frame structures. The maximum inter-story drift ratios of the RAC frame model under frequent and rare intensity 8 test phases are 1/266 and 1/29, respectively, which are larger than the allowable value of 1/500 and 1/50 according to Chinese seismic design requirements. Nevertheless, the RAC frame structure does not collapse under base excitations with PGAs from 0.066 g up to 1.170 g.