Palaeoenvironmental changes from pollen record in deep sea core PC-1 from northern Okinawa Trough, East China Sea during the past 24 ka

A pollen record of core PC-1 from the northern Okinawa Trough, East China Sea (ECS), provides information on vegetation and climate changes since 24 cal. kaBP. A total of 103 samples were palynologically analyzed at 8 cm intervals with a time resolution of 230 a. Four pollen zones are recognized: zone I (812-715 cm, 24.2-21.1 cal. kaBP), zone II (715-451 cm, 21.1-15.2 cal. kaBP), zone III (451-251 cm, 15.2-10.8 cal. kaBP), zone IV (251-0 cm, 10.8-0.3 cal. kaBP), corresponding to Late MIS 3, Last Glacial Maximum (LGM), deglaciation and Holocene, respectively. The LGM is characterized by the dominance of herbs, mainly Artemisia, and high pollen influx, implying an open vegetation on the exposed continental shelf and a cool and dry climate. The deglaciation is a climate warming stage with Pinus percentage increased and Artemisia percentage decreased and a rapid sea-level rise. The Holocene is characterized by predominance of tree pollen with rapid increase in Castanea-Castanopsis indicating the development of mixed evergreen and deciduous broad-leaved forest and a warm, humid climate. Low pollen influx during the Holocene probably implies submergence of the continental shelf and retreat of the pollen source area. The vegetation indicated by pollen assemblage found in this upper zone is consistent with the present vegetation found in Kyushu, Japan. Originating from the humid mountain area of North Luzon of the Philippines, Tasmania and New Zealand, Phyllocladus with sporadic occurrence throughout PC-1 core probably suggests the influence of Palaeo-Kuroshio Current or intense summer monsoon. The observed changes in Pinus and Herbs percentage indicate fluctuations of the sea level, and high Pinus percentage corresponds to high sea level. Spectrum analysis of the pollen percentage record reveals many millennial-scale periodicities, such as periodicities of 6.8, 3.85 2.2, 1.6 ka.

基于流域—库区—坝区模型“三重边界嵌套”方法的河南济源蟒河口水库渗漏数值模拟研究

Constructing reservoir in mountain area, in order to avoid dangerous reservoir and ensure long-term stable reservoir storage, study on reservoir leakage has been one of research hotspots. How to accurately predict the capacity of leakage and the effect of anti-seepage after reservoir impoundment under different anti-seepage measures is one of the most difficult problems of study on reservoir leakage. The paper took Manghekou Reservoir as a case study, which is located in Jiyuan City, Henan Province, China. Based on the system analysis of the geological and hydrogeological characters in the research area, the hydrogeological conceptual model was established. Then, according to the triplex boundary nested grid model method, using three-dimensional numerical simulation technique, the 3-D groundwater seepage flow numerical model was established in the study area. Based on the model, the change of seepage flow field, the capacity of leakage and the effect of anti-seepage are predicted after Manghekou reservoir impoundment under different condition. The reasonable and reliable anti-seepage measure is selected according to the model. All these provides scientific basis for the design and assessment of anti-seepage measure for the reservoir in mountain area.

热察绥地区过去300年土地利用覆被变化

The historical land use and land cover changes is one of the key issues in LUCC research. However, the achievement of China in this field doesn't match her position in the world yet. And the reliability of the quantitive records in Chinese historical literature, the basic data for historical land use research, has been doubted. This research focuses on Re-Cha-Sui, a typical area for the farming-pastoral region in the north of China, to make a detailed case study in this field. Based on a deep mining and calibration on the data from massive historical documents and land-use surveys, the author gives a detailed analysis on the administrative region evolution, historical population dynamics, reclamation policy, and the land statistic system. According to textual researches, parallel validation and physical geographical analysis, a unified land use series for recent 300 years, which founded on the results of modern land-use surveys, is constructed. And the thematic maps on the cultivation index for different counties in several temporal sections are plotted. Based on the endeavor above, the dynamic of forest and steppe is reconstructed as well. The temporal-spatial patterns of land use/land cover changes in the area is analyzed. And the influence of different driving forces are discussed. The main conclusions of the research are as followed: 1. The quantitive records in literatures on Re-Cha-Sui area are reflection of real amounts of croplands. It is practical to reconstruct a result comparable with the modern land-use surveys, based of a deep mining and considerate validation on historical documents. The unexceptional negative attitude towards the numerical records in historical documents is unnecessary. 2. In recent 300 years, 3 climax of reclamation appeared in Re-Cha-Sui area and altered the pure pastoral area into a farming-pastoral region. The interval were respectively the early time till mid time of the Qing dynasty, the end of the Qing dynasty till early time of the Republic of China(ROC), and the time after A.D. 1949. After the first expansion, the area of cropland in this region reached 2.0 million ha. Among them, Guisui area, which was most densely cultivated, had a cultivation index over 30%, which is similar with modern situation. The second expansion covered broader area, and the amount of cropland reached 3.5 million ha. The increase of farming area after 1949 is due to the recultivation of abandoned farmland. The current area of cropland in this region is 5.6 million ha. In the southern area where the land was reclaimed early, the amount on of the cropland has some fluctuation in 300 years. While in the new reclaimed area in the north, the area of cropland has kept the trend of increasing. 3. Due to the different natural conditions, most forests in Re-Cha-Sui area distribute in the mountain area of North Hebei province, and the upland of West Liaoning province, especially the former, which has a forest coverage near 70%. However, most of these forests were destroyed before the end of the Qing dynasty. In 1949, the natural forest near Chengde was nearly cleared up. They were partly renewed after 1949 due to plantation. 4. In the steppe zone such as northern Rehe, Suiyuan and Chahar, the area of steppe has a negative correlation with that of cropland. With the expansion of cropland, the percentage of steppe has shrunk from over 80% to 53%. In the mountain area of North Hebei province, steppe expanded with the shrinkage of forest, though cropland was expanding. The percentage once reached 60%, and then fell with the renew of forest. However, in the upland of West Liaoning province, the steppe shrink slowly from original 50% to current 26%, with the expansion of cropland. 5. The land use and land cover change in Re-Cha-Sui area in recent 300 years is driven by various factors, including human dimensions such as population, policy of the government, disorder of the society, cultural tradition, and natural factors such as climate change and natural disasters. Among them, pressure from surplus population is the basic driving force.

贵州喀斯特山区植物营养元素和碳、氮、硫同位素组成研究--以贵阳花溪杨中流域为例

喀斯特的面积分布很广，占全球总面积的10%。我国喀斯特面积占国土面积的13%，主要集中在我国的南方。而贵州喀斯特山区位于西南喀斯特地貌最集中成片分布的中心区，是我国乃至世界热带、亚热带喀斯特地貌连续分布面积最大、发育最强烈的高原山区。和非喀斯特地区相比，贵州喀斯特山区由于碳酸盐岩的特殊理化特性，造成土层浅薄、土被不连续、岩石裸露率高、持水量低，适生树种少、群落结构单一、植被生长极其缓慢，生态环境十分的脆弱。加之人类不合理的活动，使得喀斯特山区植被退化非常严重。因此，开展贵州喀斯特山区植物的营养元素和碳、氮、硫同位素的研究是为了更好的了解该区植被的营养元素状况、生理生态特性以及营养元素的生物地球化学循环，更好地为该区森林、植被的治理、恢复以及生态系统的保护等提供决策依据。本研究选择典型喀斯特山区作为研究点，并以非喀斯特山区为对照。研究喀斯特山区植物的营养元素含量水平、分布状态、变异特征以及营养元素之间的相互关系和碳、氮、硫的同位素组成的种间差异、生境差异特征以及时空变化特征进行了研究。主要得到以下几点认识： 1、植物的N、P、K、Ca、Mg、S的平均含量大于1000 μg∙g-1； Fe、Mn、Al的平均含量在100 μg∙g¬-1～1000 μg∙g¬-1之间；Zn、Sr的平均含量为10 μg∙g¬-1～100 μg∙g¬-1之间；Cu和Mo的含量小于10 μg∙g¬-1，Mo最低(仅为0.17 μg∙g¬-1)。Ca、P、K、 Fe、Mn、S、Sr高于所报道的陆生植物元素的含量；Mg低于陆生植物的元素含量；其它元素在元素含量范围内。植物营养元素的特点为Ca>K>Mg型，和我国其它地区相比，喀斯特山区植被具有高钙的特征。 2、N、P、K、Mg为正态分布；Ca、Al、Fe、Mn、Cu、Zn、Sr、Mo、S为对数正态分布。Al、Fe、Mn、Sr的变异系数大于100%；N、P、K、Ca、Mg、S、Cu的变异系数小于60%。其中，Ca的变异系数最小(为11.8%)。P和K、P和Cu、Al和Fe、Al和Zn、Fe和Zn之间具有极显著的相关关系；N和P、P和Mg、K和Al、K和Cu、Ca和Sr、S和Mo之间具有显著的相关关系。 3、不同的生境下植物营养元素存在差异，差异在2倍范围内。其中，Mn、Al、Sr元素差异较大，分别达到2.1、1.5、1.4倍。 4、植物δ13C、δ15N、δ34S值的分布范围分别为-26.98‰～-29.15‰、-4.08‰～-0.79‰、-8.69‰～-6.04‰；平均值分别为-28.14‰、-2.41‰、-7.53‰。δ13C除了高于我国热带雨林区植物外，均低于其它地区，且变化范围较窄；不同地区之间植物的δ15N、δ34S值存在较大差异。 5、不同植物种之间的δ13C、δ15N、δ34S值存在较大的差异，不同生境条件下植物的δ13C、δ15N、δ34S值也存在差异。植物的δ13C值从生长初期到末期有降低的趋势；δ15N、δ34S则无一定的变化规律，不同的植物种的季节变化不同。植物的δ13C、δ34S随海拔的升高而增大，但δ15N随海拔的升高而降低。

吉林省长白山地区大气中不同形态汞的含量分布及沉降通量研究

汞是一种可以通过大气进行长距离跨国界进行传输的污染物，为了正确认识汞的全球大气循环演化规律，应该在全球不同区域内开展背景区大气不同形态汞含量的长期和高时间分辨率的观测研究。本论文工作利用高时间分辨率自动大气测汞仪（Tekran®2537A），于2005年8月～2006年7月对长白山地区大气气态总汞进行了连续一年的野外观测，同时按季节对该区大气中的颗粒态汞与活性气态汞进行了采集和分析。 研究结果表明，长白山地区大气气态总汞（TGM）的年平均含量为（3.22±1.78）ng•m-3。长白山地区大气气态总汞含量高于北半球大气汞含量的背景值(1.5~2.0 ng•m-3)，表明该地区已受到一定程度的大气汞污染。该区气态总汞表现出季节变化规律，含量高低按季节表现为：冬季（3.61ng•m-3）>春季（3.44ng•m-3）>秋季（3.15ng•m-3）>夏季（2.56ng•m-3）。在对长白山地区大气汞来源的解析中，该区频率最高的指示风向西南（SW）、西北（NW）和非主导风向东北（NE）方位上，城镇人为采暖、燃煤和对生物燃料的使用成为该地区的大气汞的主要人为来源，而土壤释汞和其他来源的大气汞经中长距离迁移也是造成该区大气汞含量偏高的原因。 对长白山地区不同时段的颗粒态汞（PM）与活性气态汞（RGM）含量的研究结果发现，采样期间颗粒态汞含量平均值为（77±136）pg•m-3，活性气态汞含量平均值为（65±84）pg•m-3。利用该结果计算了不同形态汞对长白山地区大气汞的组成。结果显示气态原子汞的贡献比例最大，约为94.0%；其次为颗粒态汞（PM<2.5），贡献比例为2.4%；活性气态汞的比例2.0%；贡献最小的是颗粒态汞（PM>2.5），所占比例1.6%。 论文工作还测定了长白山地区一年的大气降水中的总汞浓度，利用该雨水中的总汞含量估算该地区一年汞的湿沉降通量，同时用穿透雨（Throughfall）方法和模型法对大气中汞的干沉降进行估算。结果表明：长白山地区大气汞的干沉降通量大于湿沉降通量，干、湿沉降通量分别为16.5μg•m-2•a-1（模型计算为20.2μg•m-2•a-1）和8.4μg•m-2•a-1，且大气汞的总沉降通量为24.9μg•m-2•a-1。

Wavelength tunable distributed Bragg reflector laser integrated with electro-absorption modulator by a combined method of selective area growth and quantum well intermixing - art. no. 68240N

Wavelength tunable electro-absorption modulated distributed Bragg reflector lasers (TEMLs) are promising light source in dense wavelength division multiplexing (DWDM) optical fiber communication system due to high modulation speed, small chirp, low drive voltage, compactness and fast wavelength tuning ability. Thus, increased the transmission capacity, the functionality and the flexibility are provided. Materials with bandgap difference as large as 250nm have been integrated on the same wafer by a combined technique of selective area growth (SAG) and quantum well intermixing (QWI), which supplies a flexible and controllable platform for the need of photonic integrated circuits (PIC). A TEML has been fabricated by this technique for the first time. The component has superior characteristics as following: threshold current of 37mA, output power of 3.5mW at 100mA injection and 0V modulator bias voltage, extinction ratio of more than 20 dB with modulator reverse voltage from 0V to 2V when coupled into a single mode fiber, and wavelength tuning range of 4.4nm covering 6 100-GHz WDM channels. A clearly open eye diagram is observed when the integrated EAM is driven with a 10-Gb/s electrical NRZ signal. A good transmission characteristic is exhibited with power penalties less than 2.2 dB at a bit error ratio (BER) of 10(-10) after 44.4 km standard fiber transmission.

An Improved Selective Area Growth Method in Fabrication of Electroabsorption Modulated Laser

An improved selective area growth (SAG) method is proposed to better the fabrication and performance of the Electroabsorption modulated laser The typical threshold current of the EML is 18mA, and the output power is 5.6mW at EAM facet.

Tandem electroabsorption modulators integrated with DFB laser by ultra-low-pressure selective-area-growth MOCVD for 10 GHz optical short pulse generation - art. no. 60200O

A novel device of tandem multiple quantum wells (MQWs) electroabsorption modulators (EAMs) monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22 mbar) selective area guowth (SAG) MOCVD technique. Experimental results exhibit superior device characteristics with low threshold of 19 mX output light power of 4.5 mW and over 20 dB extinction ratio when coupled into a single mode Fiber. Moreover, over 10 GHz modulation bandwidth is developed with a driving voltage of 2 V. Using I this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with a width of 13.7 ps without any compression elements is obtained.

Microorganisms linked to Neoproterozoic microspar carbonate sedimentation in the Jilin-Liaoning area

Molar-tooth carbonate refers to a sort of rock that has ptygmatical folded structure comparable to the ivory. This kind of carbonate exists in a special time range (from Middle to Neoproterozoic). Its origin and the possibility to use it in stratigraphic correlation of the paleocontinent is the key task of the IGCP447, a project on Proterozoic molar tooth carbonates and the evolution of the earth (2001-2005). The importance lies in that the molar-tooth structure is the key to solving problems related to Precambrian biological and global geochemical events. The molar-tooth structure is associated with microorganisms. Development and recession of such carbonates have relations with the evolution process of early lives and abrupt changes in sea carbonate geochemistry. In recent years, based on researches on petrology, geochemistry and Sr isotope of molar-tooth carbonate in the Jilin-Liaoning and Xuzhou-Huaiyang area, the authors hold that it can be used as a marker for stratigraphic sequence and sedimentary facies analyses.

Tunable MQW-DBR lasers using selective area growth

The tunable ridge waveguide distributed Bragg reflector (DBR) lasers designed for wavelength-division-multiplex (WDM) communication systems at 1.55 um by using selective area growth (SAG) is reported. The threshold current of the DBR laser is 62mA and the output power is more than 8mW. The isolation resistance between the active region and the Bragg region is 30K Ohm. The total tuning range is 6.5nm and this DBR laser can provide 6 continuous standard WDM channels with 100GHz channel spacing; in the tuning range, the single mode suppression ratio (SMSR) is maintained more than 32dB and the maximum output power variation is less than 3dB.

Design, simulation and testing of large area silicon drift detectors and detector array for X-ray spectroscopy

Large area (25 mm(2)) silicon drift detectors and detector arrays (5x5) have been designed, simulated, and fabricated for X-ray spectroscopy. On the anode side, the hexagonal drift detector was designed with self-biasing spiral cathode rings (p(+)) of fixed resistance between rings and with a grounded guard anode to separate surface current from the anode current. Two designs have been used for the P-side: symmetric self-biasing spiral cathode rings (p(+)) and a uniform backside p(+) implant. Only 3 to 5 electrodes are needed to bias the detector plus an anode for signal collection. With graded electrical potential, a sub-nanoamper anode current, and a very small anode capacitance, an initial FWHM of 1.3 keV, without optimization of all parameters, has been obtained for 5.9 keV Fe-55 X-ray at RT using a uniform backside detector.