Swelling characteristics of East-Africa black cotton soil based on computer molecular simulation

Black cotton soil in East Africa is not a stable engineering material for highway and railroad projects. Its strong swelling potential when it absorbs water causes distresses in subgrade of highway and railroad, and thus leads to failures of the projects. This paper presents study on the swelling characteristics of black cotton soil in East Africa. Lab tests were conducted to obtain its basic engineering properties, and the results show that black cotton soil contains high amount of montmorillonite and exchangeable cations and is strong expansive soil. Molecular modelling was exploited to further investigate water absorption ability of montmorillonite. Three different molecular models of montmorillonite were constructed and used for simulations, among which Types I and II montmorillonite represent the expansive soil montmorillonite in China, and Types II and III montmorillonite represent black cotton soil montmorillonite in East Africa. The results showed that the interlayer cations of Type III montmorillonite possessed the strongest water absorption ability based on analysis of radial distribution function(RDF) of cations. Interlayer compensatory cations of Na+ enhance the hydration ability of the other major cations, thus resulting in the strong swelling potential of East-Africa black cotton soil.

东非海岸盆地第四系深水沉积特征、过程及沉积模式

东非海岸盆地深水区的研究主要集中在油气富集的深部地层,缺乏对第四系深水沉积的研究。文中利用二维地震资料,对东非坦桑尼亚和鲁伍马盆地第四系深水区的深水沉积开展研究,查明了沉积类型,划分了沉积单元,对深水沉积建立了沉积模式。研究表明:1)研究区发育深水重力流沉积、等深流沉积、等深流与重力流交互作用沉积,分为峡谷、水道、漂积体及块状搬运复合体4种沉积单元。2)研究区深水沉积由北至南差异明显,坦中地区深水沉积规模较大,主要发育重力流水道及丘状漂积体;坦南地区发育峡谷,深水沉积规模整体较小;鲁北地区深水沉积规模较大,发育有峡谷、水道及席状漂积体。3)海底地形的差异导致坦中地区的重力流能量较弱,坦南地区和鲁北地区的重力流能量较强;在海底地貌的限制下,等深流沉积在坦中地区形成丘状漂积体,在鲁北地区形成席状漂积体;坦中南部的等深流与重力流发生交互作用,发育向南迁移的侧向迁移水道。

东非地区单线铁路隧道设备选型及交通组织研究

以东非肯尼亚恩贡山单线长隧道施工为依托,对隧道断面尺寸和施工作业空间进行统计分析,对比不同设备选型条件下的施工进度指标和经济指标,确定了单线铁路隧道相对合理的设备选型方案;通过扩大避车洞室,设计洞内交通运输,合理安排工序,实现了单线隧道快速施工。研究结果表明,分析不同设备选型的经济效益、工期影响、效率冗余和技术条件等,合理设计交通组织,是实现单线铁路隧道快速施工的关键。

东非鲁武马盆地气藏分布规律及主控因素

深水是全球油气来源的重要组成部分,快速寻找深水油气富集区可以大幅促进油气勘探开发进程。通过分析和解剖东非鲁武马盆地已发现气藏的分布特征,总结气藏类型及分布规律,进一步探讨气藏分布的主控因素。研究认为,鲁武马盆地古新世—渐新世主力含气层系的沉积类型与气藏类型具有一定的相关性,发育构造–断层气藏、岩性–构造气藏以及岩性气藏这3种主要气藏类型。气藏平面局部聚集、垂向多层叠置,表现出前渊缓坡汇聚、中–中高孔隙度浊积砂富集、高位体系域封盖的特征。控制盆地油气的富集有5个主要因素:①独特的三角洲改造型盆地的两期裂谷烃源岩为盆地提供了充足的油气来源;②充足的物源、窄陡的陆架边缘地貌以及底流作用,促成了厚层、粗粒、洁净的深水沉积储层的发育;③多期海侵形成的区域盖层及重力流沉积的细粒组成,构成了多个独立气藏的有效盖层;④东非沿海盆地陆上抬升作用间接促进大气田圈闭的形成;⑤断层的性质、活动期次等对天然气的输导发挥了重要作用。

殖民时期德国在东非的森林政策及影响

19世纪末,德国逐渐在东非扩张其殖民统治。为实施所谓的科学森林政策和获得经济利益,德国殖民者基于自身经验最早在东非实施一系列森林管理政策。这些政策的实施破坏了当地原本人与自然和谐共生的关系,对当地的生态和社会产生深远的影响,引发非洲人的反抗。德国对东非殖民地森林管理的失败经历表明,生态治理必须尊重当地原本的人地关系、历史与文化。

The Impacts and Causes of Land Fragmentation on Farm Productivity: Case Review of East African Countries

This report provides an overall assessment of land fragmentation problems in East Africa. Many parts of East Africa have become highly fragmented, putting development systems and activities in these areas at risk of complete collapse. Land fragmentation occurs when land gets converted for agriculture, industrialization, or urbanization, invaded by non-local plants, or enclosed for individual use and by subdividing farmlands into subsequent smaller units called parcels with varying average farm sizes. Fragmentation results from inappropriate agricultural development processes and ineffective land use planning that fails to recognize how farmland is used, and the importance of its interconnected areas. Insecurity of tenure and resource rights are key factors in making this possible. Land fragmentation is one of the key reasons why the ability of most resources in East Africa becomes scarcer, and those remaining become “privatized” by more powerful community members—keen to maintain their access to them. Such individualistic attitudes are new and disadvantage the poorest even further by affecting the traditional customary safety nets and agricultural outputs. Neither the government nor customary governance systems effectively protect resource access for the poorest. This review summary report identifies the key causes, measures, and implications, government interventions, and the common remedies to land fragmentation problems in the East African Countries of Kenya, Uganda, Rwanda, and Tanzania including neighboring Ethiopia, and the Sudan. The findings indicated from 2005 to 2015, the population kept increasing for all the named countries in East Africa with Rwanda and Uganda having a substantial increase in population density. The study review further explores the trend in the performance of agriculture by average farm sizes within the intervals of five years by highlighting their strong linkages and found that the average farm size has declined drastically, especially for Kenya. This can only mean that small farms kept becoming smaller and smaller and that there were more small-scale farmers. The results further depicted that the major and commonly cultivated food crops among the East African countries include maize, sorghum, rice, cassava, sweet potatoes, bananas, Irish potatoes, beans, peas, etc., with maize yields (Mt/ha) in 2003 for Uganda being the highest (1.79 Mt/ha) and the lowest in Rwanda (0.77 Mt/ha) respectively. Therefore, from the review results, recommendations are being made as to how the negative impacts of land fragmentation on agricultural productivity can be reduced or mitigated. One way is by community sensitization and awareness about the importance of land consolidation and its proposition on farm productivity.

Spatio-Temporal Variability of Rainfall and Temperature and Their Effects on Pasture Variability over East Africa: Implication on the Cattle Grazing Areas

Understanding the spatiotemporal variability of climatic parameters and their effects on pasture variability is vital for pasture management interventions over East Africa. The present study aims to assess the spatial-temporal variability of rainfall, temperature and Normalized Difference Vegetation Index (NDVI) (which is being used to assess pasture quality and productivity) over the region, between the period of 1982 and 2019. This study used annual mean values for rainfall, temperature and NDVI which were calculated for the period mentioned above. NDVI was derived from National Oceanic and Atmospheric Administration (NOAA) Global Area Cover (GAC) (NOAA-07-GAC) data. The rainfall data was acquired from the Climate Hazards Group Infrared Precipitation with Station (CHIRPS) while temperature is ERA5 reanalysis data sourced from the European Centre for Medium-Range Weather Forecasts (ECMWF). The study utilized the empirical orthogonal function (EOF) to identify patterns and dominant relationships between the climate variables. The correlation was calculated between rainfall, temperature and NDVI to assess the relationship among them. A non-parametric Mann-Kendall trends test was used to determine whether annual precipitation, temperature and NDVI had statistically increasing or decreasing trend. Results revealed a positive correlation between rainfall and NDVI while a negative correlation between NDVI and temperature. Positive correlation between rainfall and NDVI indicates that pasture health (quality and productivity), will improve accordingly. A negative correlation between temperature and NDVI indicates that pasture health will decrease with increase in temperature while improving with decreasing temperature. Outcome from this study suggests that changes in climatic variables influence the distribution of pasture in East Africa’s cattle grazing areas. The study hence recommends prioritisation of climatic (weather) information during pasture management over East Africa.

The Effects of Age and Ejaculatory Abstinence on Semen Quality and Reproductive Hormones in Africa and the Middle East

The aim of this study was to retrospectively evaluate the effects of male age and ejaculatory abstinence on semen parameters and reproductive hormones among men residing in Africa and the Middle East. A total of 70,142 semen analysis results were analysed and grouped according to the age intervals (16 - 20, 21 - 30, 31 - 40, 41 - 50, 51 - 60, >60) and ejaculatory abstinence (<2 days, 2 - 5 days and >5 days). Semen parameters i.e. volume, concentration, progressive motility, total progressively motile count, morphology, total normal sperm count, DNA fragmentation, viability, sORP, normed sORP were specifically evaluated. Additionally, for each age interval, reproductive hormones i.e. estradiol, luteinizing hormone, follicle stimulating hormone, testosterone and prolactin were evaluated. Semen volume, total progressively motile count, sperm morphology and total normal sperm count constantly decrease significantly after the age of 30 years. Sperm concentration started declining significantly after the age of 50 years. There was a constant age- related increase in number of spermatozoa with damaged DNA. sORP constantly increased up to 60 years. Furthermore, constantage-related decreases in FSH, serum testosterone and prolact in were observed from patients aged between 16 years and 60 years. Semen volume, sperm concentration, progressive motility and normal morphology were significantly higher in patients having > 5 days of abstinence. Patients having > 5 days of abstinence had the lowest normed sORP. Male age significantly affects sperm parameters and reproductive hormones in fertile and infertile men residing in Africa and the Middle East. Prolonged abstinence days provides better semen quality.

肯尼亚内罗毕快速路预制装配桥墩构造设计

肯尼亚内罗毕快速路项目是“一带一路”重要工程之一,是东非地区首次采用预制装配桥墩设计与施工的示范项目。结合项目的建设条件和特点,总结适用于当地城市高架桥预制装配桥墩的设计思路与要点,对构件连接方式进行研究和比选,同时对预制装配桥墩和传统现浇桥墩工程经济效益进行对比。对后续东非地区城市高架桥的建设具有参考意义。

The Relationship between Extreme Precipitation Events in East Africa during the Short Rainy Season and Indian Ocean Sea Surface Temperature

The East African short rainy season (October-November-December) is one of the major flood seasons in the East African region. The amount of rainfall during the short rainy season is closely related to the lives of the people and the socio-economic development of the area. By using precipitation data and sea surface temperature data, this study reveals the spatial and temporal variation patterns of extreme precipitation during the East African short rainy season. Key findings include significant rainfall variability, with Tanzania experiencing the highest amounts in December due to the southward shift of the Intertropical Convergence Zone (ITCZ), while other regions receive less than 100 mm. Extreme rainfall events (90th percentiles) are evenly distributed, averaging 2 to 10 days annually. Historical data shows maximum seasonal rainfall often peaks at 15 mm, with frequent occurrences of daily rainfall exceeding 10 mm during OND. Additionally, a positive correlation (0.48) between OND precipitation extremes and Indian Ocean Dipole (IOD) anomalies is statistically significant. These findings highlight the climatic variability and potential trends in extreme rainfall events in East Africa, providing valuable insights for regional climate adaptation strategies.

Potential Driving Systems Associated with Extreme Rainfall across East Africa during October to December (OND) Season 2019

The East African (EA) region highly experiences intra-seasonal and inter-annual variation in rainfall amounts. This study investigates the driving factors for anomalous rainfall events observed during the season of October-November-December (OND) 2019 over the region. The study utilized daily rainfall data from Climate Hazards Group InfraRed Precipitation with Station Data Version 2 (CHIRPSv2) and the driving systems data. Statistical spatiotemporal analysis, correlation, and composite techniques were performed to investigate the teleconnection between OND 2019 seasonal rainfall and global synoptic climate systems. The findings showed that the OND 2019 experienced seasonal rainfall that was twice or greater than its seasonal climatology and varied with location. Further, the OND 2019 rainfall showed a positive correlation with the Indian Ocean Dipole (IOD) (0.81), Nino 3 (0.51), Nino 3.4 (0.47), Nino 4 (0.40), Pacific Decadal Oscillation (PDO) (0.22), and North Tropical Atlantic (NTA) (0.02), while El Nino-Southern Oscillation (ENSO) showed a negative correlation (−0.30). The region was dominated by southeasterly warming and humid winds that originated from the Indian Ocean, while the geopotential height, vertical velocity, and vorticity anomalies were closely related to the anomalous rainfall characteristics. The study deduced that the IOD was the major synoptic system that influenced maximum rainfall during the peak season of OND 2019. This study therefore provided insights on the diagnosis study of OND 2019 anomalous rainfall and its attribution over the EA. The findings of the study will contribute to improvements in forecasting seasonal rainfall by regional climate centers and national meteorological centers within the region.

东非海域大型深水沉积体系及油气成藏特征

基于高品质三维地震和测井、录井等资料,对东非鲁伍马盆地古新统—渐新统深水沉积体系和赞比西坳陷上白垩统深水沉积体系特征进行了分析,并对二者的成藏条件进行了类比研究。研究结果表明:①鲁伍马盆地古新统—渐新统深水沉积体系中发育水道和朵体砂岩等大规模优质储层,等深流的改造作用是优质储层形成的关键因素。②赞比西坳陷上白垩统发育水道、朵体、块体搬运沉积等典型深水沉积,规模巨大的等深流漂积体多为优质储层。③赞比西坳陷主力烃源岩为下白垩统局限海相泥岩,油气生成后运移至邻近的上白垩统深水沉积砂体中,并被高位体系域深海泥岩封盖,深水砂岩上倾尖灭形成了岩性圈闭,具备良好的油气成藏条件,是未来油气勘探的有利区。

基于机器学习的东非植被变化因子重要性分析

[目的]基于机器学习算法对东非植被变化进行因子重要性分析,测度不同算法在各情况下的精度差异及适用性,为保护、恢复和促进可持续森林管理、水土流失综合防治提供科学依据。[方法]以东非9个国家2001—2020年的归一化植被指数(normalized difference vegetation index,NDVI)变化为研究对象,选取影响东非植被变化的2个气候因子及5个人类活动因子作为自变量,利用随机森林(random forest,RF)、BP神经网络(BP neural networks,BP)、支持向量机(support vector machines,SVM)、遗传算法(genetic algorithm,GA)、径向基神经网络(radial basis function,RBF)、卷积神经网络(convolutional neural networks,CNN)6种机器学习算法建立NDVI预测模型,以决定系数(R^(2))、平均绝对误差(MAE,mean absolute error)、平均相对误差(MRE,mean relative error)3个指标评价评估6种机器学习算法预测NDVI变化的潜力,并基于所得的最优模型即对选取的7个因子进行重要性分析。[结果]精度验证结果表明,研究区内在全因子的情况下,CNN算法的回归精度最差;经逐轮删除一个综合表现不佳的算法后,RF算法建立的模型在东非NDVI变化分析中回归精度较高;基于随机森林算法的不同因子变量对NDVI变化的重要性表明,年降水量、N_(2)O排放量、CH_(4)排放量、牲畜数量4个变量对NDVI变化回归的结果影响较大。[结论]随机森林算法的回归能力在东非NDVI模拟中具有相对优势,降水量是影响植被变化最重要的气候因子,同时,温室气体的排放对于东非植被的变化也具有一定的影响。东非各国应提高植被变化对气候环境、社会经济和政治制度相互依存关系的认识和理解,并制定适当的政策以促进可持续森林管理、防治荒漠化。

东非鲁伍马盆地中始新统深水沉积特征及层序界面识别方法

以层序地层学经典模式为指导,利用岩心、测井、录井及地震资料,总结了东非鲁伍马盆地深水区中始新统三级和四级层序界面特征,将深水沉积中发育的水道-朵体复合体与沉积相对应,划分了沉积亚相和微相,并在此基础上探讨了深水沉积的演化规律及其对储层的影响。研究结果表明:①鲁伍马盆地中始新统三级层序顶界位于凝缩段和偶发的碳酸盐碎屑流顶部,底界为逐期南向迁移的重力流底界;四级层序由半深海泥岩顶界和地震剖面上连续性好的沉积界面确定,但仅可以在水道-朵体复合体分布范围内开展解释。②研究区深水沉积可识别出水道复合体和朵体复合体2种沉积相,复合水道、朵体、决口扇和溢岸/漂积沉积4种亚相,水道轴部/边部充填、内天然堤、块体搬运沉积(MTD)、水道底部滞留沉积、朵体单元主体/边缘、决口扇和溢岸/漂积沉积等9种沉积微相;决口扇和溢岸/漂积沉积均分布于复合水道的北侧,受底流影响的决口扇在平面上呈向北发散的脉状。③研究区中始新统深水沉积的演化分为SQ1—SQ4共4个阶段,整体表现为先进积、后退积的过程,水道-朵体复合体受重力流与底流交互作用影响,逐期向南迁移。④研究区储层的发育主要受控于沉积微相,朵体单元主体和水道轴部充填微相发育的储层品质好,其中朵体单元主体微相中储层最发育、物性最好,孔隙度为13.00%~21.00%,渗透率为5.0~118.0 mD,水道轴部充填微相次之,储层孔隙度为13.00%~19.00%,渗透率为0.8~23.0 mD;溢岸/漂积沉积微相中发育的储层物性差,决口扇不发育储层。

中国与东非有机生产标准比对分析

有机产品作为“受信任”产品,对非洲国家优势创汇具有不何低估的积极作用。非洲重视并大力发展有机生产,有机产品生产和贸易在全球占有一席之地。有机产品作为中非农产品合作的重要组成部分,本文通过选取作物种植、畜禽养殖等关键指标,剖析我国有机产品标准与东非有机产品标准的异同,提出提升中国-非洲标准融合、合作发展的思路和建议,为提高中非经贸区贸易便利化水平提供技术参考。

另类殖民书写:《天堂》中东非沿海到内陆的生态研究

作为非裔移民作家,阿卜杜勒拉扎克·古尔纳的殖民书写可谓另类,迥异于以提安哥为代表的大多数非洲后殖民作家的惯有立场。其第四部小说《天堂》便将这种另类发挥得淋漓尽致。在书中古尔纳以求实态度揭示了广袤东非土地由沿海到内陆的复杂生态:天堂表象下的本土真实生态美丑交织;多元文化下的内部生态极具破碎性;殖民进程中潜藏着无孔不入的生态危机。殖民书写与生态描绘相互交织、彼此渗透。古尔纳将一度被忽略的东非殖民史化作文学现实,拒绝抹除非洲内部存在的文化差异,直指殖民症结所在,充满批判锋芒。

The Inter-Annual Variability of Rainfall Onset and Its Implication on Crop Planting in Selected East Africa Countries

The inter-annual variability of rainfall onset and crop replanting in East Africa (EA) was assessed using daily estimated rainfall data from climate hazard group infrared precipitation (CHIRPS Ver2.0) and monthly Sea Surface Temperature (SST) indices [Indian Ocean Dipole (IOD) and El-Ni?o Southern Oscillation (ENSO) at NINO3.4 region] from the National Center for Environmental Prediction (NCEP) and the National Center for Atmospheric Research (NCAR). The data covered a period of 40 years from1981 to 2020. The methods of cumulative of daily mean rainfall, percentage of onset date departure (PODD), Mann-Kendall (MK) trend test, student t-test, and correlation were applied in the analysis. The results showed that early onset with dry spell (WDS) consideration frequently occurs in Uganda between the first and second dekads of September, while late rainfall onset WDS occurs in the first and second dekads of December over central and Northern Kenya as well as in the Northeastern highlands, parts of the northern coast and unimodal regions in Tanzania. Rainfall onset with no dry spell (WnDS) portrayed an average of 10 days before the occurrence of true onset WDS, with maximum onset departure days (ODD) above 30 days across the Rift Valley area in Kenya and the Northeastern highlands in Tanzania. The high chance of minimum ODD is seen over entire Uganda and the area around Lake Victoria. However, few regions, such as Nakuru (Kenya) Gulu and Kibale (Uganda), and Gitega (Burundi), revealed a slight positive linear trend while others showed negative trend. Significant positive patterns for correlation between onset WDS and SST indices (IOD and NINO 3.4) were discovered in Northern and Northeastern Kenya, as well as areas along the Indian Ocean (over Tanzania’s Northern Coast). Inter-annual relationship between onset dates WDS and IOD (NINO3.4) indices exhibits a high correlation coefficient r = 0.23 (r = 0.48) in Uganda and r = 0.44 (r = 0.36) in Kenya. On the other hand, a negative correlation was revealed over Burundi and Tanzania (over a unimodal region). A high percentage of PODD was observed, ranging from 40% to 70% over the Rift Valley in Kenya and at the Northeastern highlands in Tanzania. However, a strong PODD above 70% was observed over Tanga and the Northern Pwani Region in Tanzania. These findings will help farmers to understand the appropriate time for crop planting, as well as help other socio-economic activities that strongly depend on rainfall.

Enhancement of East African Monsoon Long Rainfall (March to May) Variability from Weekly to Annual Scale by Climatic Extremes

As global warming increasingly affects vulnerable regions such as Central East Africa, it is crucial to understand future changes in rainfall variability to reduce vulnerability. Despite the importance of rainfall variability, it has received less attention compared to changes in mean and extreme rainfall. This study evaluates the amplification of synoptic (weekly) to annual variability of East African Monsoon (EAM) Long Rainfall (March to May) by climatic extremes. Using band-pass filtered daily rainfall data, we found that EAM rainfall variability is anticipated to increase by 20% - 60% across the region under global warming conditions. The majority of the intermodal variability in Long Rain EAM rainfall forecasting is explained by differences in mean rainfall. Our results show that the synoptic variability of Long Rain for EAM rainfall is likely to amplify, resulting in more extreme rainfall events and longer dry spells under global warming. This amplification is attributed to the warming of the Indian Ocean and the associated changes in atmospheric circulation patterns. The projected increase in synoptic to annual variability of Long Rain for EAM rainfall has significant implications for water resources management and agriculture in the region, challenging policymakers to develop adaptive strategies that can mitigate the impacts of these extreme events. This study emphasizes the potential impacts of projected climate changes in rainfall variability on the East African region at all periods and underscores the need for effective adaptation strategies to ensure sustainable development.

东非大裂谷区地裂缝成因及铁路路基防治技术

东非大裂谷地裂缝为活动性构造。通过地质调绘、钻探、挖探、综合物探等勘察手段,选取内马铁路DK76+819.50~+933.80段典型地裂缝工点,研究东非大裂谷地裂缝的成因;在此基础上,分析地裂缝下的路基破坏特点,提出地裂缝防治措施。

Tectonic Related Lithium Deposits Another Major Region Found North East Tanzania—A New Area with Close Association to the Dominant Areas: The Fourth of Four

The current “mega” interest in Lithium resources was spurred by the development of Lithium-Ion batteries to aid in restructuring the world’s reliance on carbon spewing power petroleum reserves. Current resources of lithium recovery have fallen into two main categories—Pegmatite, found worldwide associated with felsic intrusions and Brine Related, and now with development in the Southwest United States of America (SWUS), a third category— Tertiary Volcanic clays, are specifically associated with Tertiary volcanics and major Tectonic Plate interactions. “Active” Plate tectonics is important as both the SWUS, the Lithium Triangle of South America (LTSA) and the Tibetan Plateau of China (TPC) producing tertiary (Miocene) volcanism that is important to the development of Lithium resources. The Tanzanian part of the East Africa Rift System (EARS) has features of both the SWUS, tertiary volcanic related “playas” and Continental rifting, the LTSA, tertiary volcanic related “Brines” and a major Tectonic plate event (subduction of an Oceanic Plate beneath the Continental South American Plate) and the TPC, tertiary volcanics (?) and major tectonic plate event (subduction of the Indian Continental Plate under the Eurasian Continental Plate). As well as the association of peralkaline and metaluminous felsic volcanics with Lithium playas of the SWUS and the EARS (Tanzania) “playas”. These similarities led to an analysis of a volcanic rock in Northeast Tanzania. When it returned 1.76% Lithium, a one-kilometer spaced soil sampling program returned, in consecutive samples over 0.20% Lithium (several samples over 1.0% lithium and a high of 2.24% lithium). It is proposed that these four regions with very similar past and present geologic characteristics, occur nowhere else in the world. That three of them have produced Lithium operations and two of them have identified resources of Lithium clay and “highly” anomalous Lithium clays should be regarded as more than “coincidental”.