拉萨市空气含氧量变化研究

对拉萨市空气含氧量进行了研究,分析了该值的日变化、逐日变化,并结合气象因子分析了可能导致该变化的原因。结果表明:拉萨市含氧量一天内有明显的峰值和谷值;含氧量变化与相对湿度显著负相关,与温度、气压不能通过相关性检验;与海平面地区含氧量相比,拉萨市含氧量变化不大;含氧量与每立方米空气中氧气的质量没有直接关系,不能用来衡量空气中氧气的绝对含量。      

近40 a西藏那曲当惹雍错湖泊面积变化遥感分析

西藏著名圣湖之一的当惹雍错,是藏北高原腹地内陆封闭大湖,对湖泊面积变化的长时间序列研究较少,本文通过高分辨率陆地资源卫星Landsat TM/ETM+数据源,利用遥感和地理信息系统软件,通过人工目视解译方法对1977-2014年当惹雍错湖泊面积变化进行系统分析,并结合流域临近气象站资料,流域冰川等辅助数据对其湖泊面积变化原因进行综合分析.结果表明,1977-2014年当惹雍错湖泊平均面积为835.75 km~2,1977-2014年湖泊面积总体呈上升趋势,1970s湖泊平均面积为829.15 km~2,1980s和1990s湖泊平均面积分别为827.50和826.42 km~2,2000年之后湖泊面积明显增加,2000s湖泊平均面积与1970s相比,增幅为8.04 km~2.当惹雍错湖泊空间变化特点是,位于最大河流入口处达尔果藏布的湖泊东南部扩大明显,湖泊西南部小湖1于2014年9月开始明显扩大并与当惹雍错有相连趋势;流域冰川融水是当惹雍错主要补给源,近40 a当惹雍错湖泊面积变化是在气温升高的背景下,冰川、降水量和蒸发量三者共同变化作用的结果.     

区域环境质量的层次模糊综合评价模型及应用

本文在模糊综合评判方法中引入层次分析法,对区域环境进行综合评价。在综合评判中,利用层次分析原理给各因素赋权,具有定性与定量相结合的特点。实例表明,该模型为区域环境质量综合评价提供了一条新的途径。     

Mg2B2O5晶须增强AZ91D镁基复合材料在Cl-溶液中腐蚀行为*

用电化学方法测量了Mg_2B_2O_5晶须增强AZ91D镁基复合材料在3.5%NaCl溶液中的开路电位、动电位极化曲线和交流阻抗,研究了晶须体积分数对镁合金基体耐腐蚀性能的影响,并利用SEM和XRD表征了腐蚀后复合材料表面的微观形貌和相组成。结果表明,随着Mg_2B_2O_5晶须体积分数的增加,AZ91D镁基复合材料的耐腐蚀性逐渐提高。当硼酸镁晶须的体积分数为35%时,材料的自腐蚀电位提高0.2V以上,自腐蚀流密度降低了1个数量级;SEM测试表明,复合材料表面生成了一层晶须增韧的腐蚀钝化膜,对基体起到保护作用。     

A computer-aided framework for subsurface identification of white shark pigment patterns

Subsurface video footage can be used as a successful identification tool for various marine organisms; however, processing of such information has proven challenging. This study tests the use of automated software to assist with photo-identification of the great white shark Carcharodon carcharias in the region of Gansbaai, on the south coast of South Africa. A subsurface photo catalogue was created from underwater video footage. Single individuals were identified by using pigmentation patterns. From this catalogue, two images of the head for each individual were inserted into automated contour-recognition software (Interactive Individual Identification System Beta Contour 3.0). One image was used to search the database, the other served as a reference image. Identification was made by means of a contour, assigned using the software to the irregular border of grey and white on the shark's head. In total, 90 different contours were processed. The output provided ranks, where the first match would be a direct identification of the individual. The method proved to be accurate, in particular for high-quality images where 88.24% and 94.12%, respectively, were identified by two independent analysts as first match, and with all individuals identified within the top 10 matches. The inclusion of metadata improved accuracy and precision, allowing identification of even low-quality images.     

盐生植物萌发期对盐胁迫和干旱胁迫的适应研究进展

目前我国盐渍土地面积较大,尤其是青藏高原的盐渍地,常伴有干旱、半干旱的生境,导致植物不易生长,生态环境日渐恶劣,这种生态现状亟待解决。盐生植物具有一定的耐盐性和耐旱性,是改善盐渍地的首选植物,种子的活力决定了种子萌发的情况,多数学者为改善严峻的生态环境开始了盐生植物引种的研究。测定种子活力有直接方法和间接方法,大多数学者采用的是直接方法,即在实验室模拟一定条件直接测定萌发率。本文简述了盐生植物的概况、制造胁迫的主要方法以及检测种子活力的指标,综述了近年来各位学者对盐爪爪、白刺等具有代表性的22种盐生植物在种子萌发期的耐盐性以及抗旱性的相关研究,为改善盐渍地的生态环境、提升盐渍地的生产量提供了理论依据。     

Near-IR Reflectance Spectroscopy of 433 Eros from the NIS Instrument on the NEAR Mission: I. Low Phase Angle Observations

From February 13 to May 13, 2000, the near-infrared spectrometer (NIS) instrument on the Near Earth Asteroid Rendezvous (NEAR) spacecraft obtained more than 200,000 spatially resolved 800- to 2500-nm reflectance spectra of the S-type asteroid 433 Eros. An important subset of the spectra was obtained during a unique opportunity on February 13 and 14, when the NEAR spacecraft flew directly through the 0° phase angle point between Eros and the Sun just prior to the orbital insertion maneuver. This low phase flyby (LPF) dataset consists of ∼2000 spectra of the northern hemisphere of Eros, obtained from 1° to 47° phase angle and at spatial resolutions of between 6×12 km to 1.25×2.50 km per spectrum. The spectra were calibrated to radiance factor (I/F, where I=observed radiance and πF=solar input radiance) and then photometrically corrected to normal albedo. The average northern hemisphere spectrum of Eros is similar to the asteroid's unresolved telescopic spectrum and exhibits absorption features near 1000 nm (Band I) and 2000 nm (Band II) consistent with an orthopyroxene to orthopyroxene+olivine (opx+ol) mixing ratio of approximately 0.38±0.08. The ensemble of NIS LPF spectra falls primarily within the S(IV) to upper S(III) fields of the Gaffey et al. (1993) S-asteroid classification scheme and exhibits Band I and Band II properties similar to those of ordinary chondrite meteorites. While some small spatially coherent spectral variations have been detected, neither the opx/opx+ol) mixing ratio nor other spectral parameters vary spatially by more than ∼1σ across the entire northern hemisphere of the asteroid, suggesting a remarkable homogeneity of the composition and mineralogy of the uppermost regolith. Spectral mixture modeling suggests that the presence of glass and/or a reddening agent like nanophase iron, likely formed from exposure of the regolith to the space environment, is a component of the surface of Eros. Reddening and darkening components could also explain the dissimilarity in overall spectral slope and albedo between Eros and other S(IV) asteroids and ordinary chondrite meteorites. The largest (but still weak) spectral variations across the surface are seen in the depths of Band I and Band II, which are greatest in and around the largest craters and at the 0° longitude “nose” of the asteroid, and in the Band II/Band I area ratio between the large impact craters Psyche and Himeros. These subtle NIS spectral variations are usually associated with albedo and surface slope variations seen in NEAR imaging and topographic data and appear to be related to downslope movement of regolith materials.     

Mineralogical interpretation of reflectance spectra of Eros from NEAR near‐infrared spectrometer low phase flyby

Abstract— High signal‐to‐noise near‐infrared spectrometer (NIS) spectra acquired during the low phase flyby of the near‐Earth asteroid rendezvous (NEAR) mission to 433 Eros are analyzed to determine mineral chemistry and proportions of mafic silicates across the asteroid's surface at 2.68 × 5.50 km spatial resolution. Spectral band parameters are derived, and compared with those of laboratory samples of known mineral composition, grain size distribution and terrestrial, meteoritic and lunar pyroxene spectral properties. The NIS derived band parameters are consistent with ordinary chondrite meteorites. We invoke the presence of a clinopyroxene component in the spectra, which is consistent with ordinary chondrite mineralogy and/or some degree of partial melting of ordinary chondritic material. Spectra measured across the surface of Eros can reveal small but real spectral variations. Most relative spectra are uniform to within 1–2%. Some areas suggest compositional variations of a few percent. Spectral slope variations of a few percent are seen indicating a non‐uniform distribution of materials affecting the slope parameter but with no resolved absorption bands. We find no correlation of slope with viewing geometry or compositional variation. The band parameter values do not consistently indicate a specific ordinary chondrite class but Eros is definitely undifferentiated with possible compositional variations of no more than 1–2%.     

黄河源区气候向暖湿转变的观测事实及其水文响应

基于黄河河源区干流各水文站和有关气象站、雨量站的气温、降水与径流观测资料, 分析了该区域的气候变化特征与趋势及其水文响应. 结果表明: 在全球变暖的大背景下, 自20世纪80年代后期开始西北地区西部新疆、甘肃河西走廊西部等地降水量显著增加、气候明显由"暖干"转向"暖湿"后, 到21世纪初的年代中期后黄河源区降水量亦出现明显的增长, 气候明显转向暖湿. 最新的观测数据显示, 2005年以来河源区平均年降水量已连续多年超过多年均值进入一个多雨期, 河源区各断面来水量也于2008年后连续多年超过多年均值, 进入一个连续丰水段, 并于2012年达到了自1989年以后20余年来的最大值. 这种变化的前景如何, 目前尚不能确定, 尚需对未来河源区气候在时间与空间上变化的速度和程度进一步观察和分析. 根据对与该区域气候关系密切的东亚季风活动的研究成果以及对河源区气候与径流变化的观测事实及趋势推测, 未来黄河源区气候向暖湿的转化在时间尺度上年代际的可能性较大.     

1971—2006年珠穆朗玛峰地区蒸发皿蒸发量的变化及其影响因素

升温率略高于平均最高气温的升温率.珠峰地区日照时数和平均风速的显著下降,以及相对湿度的明显增加可能是蒸发皿蒸发量下降的主要原因.