Statistical characterization of frost zones: Case of tea freeze damage in the Kenyan highlands

Frequent frost occurrences in the Kenyan highlands have had devastating effects on agricultural productivity. With inadequate management systems to mitigate the impacts, farmers have often had to bear the burden of losses resulting from frost damage. While agriculture in Kenya remains dependent on weather and climate, the agricultural economy of Kenya continues to suffer, underscoring the need for building local knowledge as basis for development of early warning systems. The current paper attempts to delineate frost zones by statistically characterizing them based on known risk factors related to topography (elevation, convexity, aspect, upslope flow length) and Land Surface Temperature (LST) derived from Moderate Resolution Imaging Spectroradiometer (MODIS). Through binary logistic regression, a logistic regression model was developed utilizing observation data (frost occurrence and non-occurrence) as a binary dependent variable to estimate the probability of frost occurrence. Assuming a 0.5 probability cut-off threshold between frost occurrence and non-occurrence, an overall accuracy of 81% with area under Receiver Operating Characteristics (ROC) Curve of 0.88 was obtained. No evidence of lack of model fit was detected. This model outperforms the currently operational model that utilizes MODIS LST alone to detect frost zones in the Kenyan tea plantations. It provides an improved method for effective delineation of frost zones by incorporating local topographic characteristics.     

The Longmyndian Rocks of the Old Radnor Inlier,Welsh Borderland

Two formations are named in the presumed Precambrian sedimentary rocks of the Old Radnor Inlier. The Strinds Formation comprises fine- to medium-grained sandstones and pebbly sandstones. Grain-size, texture, clast types, and lithological invariance support correlation with the homogeneous and cross-bedded sandstone facies of the Bayston-Oakswood Formation of the Longmyndian, assigned to a braided alluvial plain environment. The Yat Wood Formation comprises fine-grained sandstones, siltstones, and laminated mudstones. It may be equivalent to some part of the Burway, Synalds, or Lightspout Formation. The Strinds and Yat Wood Formations are petrographically similar to each other and to the type Lonmyndian, and were sourced either directly or indirectly from a magmatic arc. The Strinds and Yat Wood Formations are seen only in faulted contact, and the inlier itself is partly or wholly bounded by strands of the Church Stretton fault zone. Similar faulted relationships are seen further northeast along the system at Pedwardine and in the Church Stretton area. A fault explanation for the juxtaposition of contrasting facies is favoured over that of an original unconformity of Strinds on Yat Wood Formation.     

Terrane sutures in the Maine Appalachians,USA and adjacent areas

Terrane sutures in the Maine Appalachians and adjacent areas are recognized as melange dominated, deformed accretionary prisms of Ordovician age, and as a broad synmetamorphic transcurrent fault zone of probable Late Silurian-Early Devonian age. Although the accretionary prisms are associated with present day aeromagnetic and Bouguer gravity anomalies, they are probably not associated with present day crustal penetrating boundaries. The geology of the accretionary prisms indicates subduction-obduction dominated regimes during which (1) the Gander and Boundary Mountain (Dunnage) terranes amalgamated and (2) the composite Boundary Mountain-Gander terrane accreted to the Laurentian margin. The Penobscottian orogeny produced and deformed the older of the two accretionary prisms. This accretionary prism indicates that the Penobscottian was a continuous or perhaps diachronous event which spanned the late Cambrian to early Late Ordovician. The younger accretionary prism was produced and deformed during the Taconian orogeny during late Middle to early Late Ordovician. Initial deformation of this accretionary prism may have overlapped the waning stages of the Penobscottian. Portions of the Taconian arc locally overlie the Penobscottian accretionary prism. A synmetamorphic fault zone lies within Precambrian(?) to Ordovician(?) bimodal metavolcanic and metapelitic rocks assigned here to the Avalon terrane. This zone is several kilometres wide and is interpreted to be the postsubduction suture between the Avalon and Gander terranes, and may, in part, represent a fossil transform fault system. The fault zone contains phyllonites as well as shear zones which generally record dextral motion. The phyllonites were previously interpreted as a stratigraphic unit, whereas the shear zones span or are contained within mappable compositional units. Formation of and movement along these phyllonites and shear zones ceased before the intrusion of Early Devonian plutons. Not all faults in south-western Maine are related to the suture. Younger dip and/or strike-slip and thrust faults are approximately parallel to, or may lie within, the older shear zones and they complicate the recognition of the older faults.     

近60a来新疆不同海拔气候变化的时空特征分析

全球变暖是当前全球气候变化研究的热点之一,新疆深居亚欧大陆内陆,地形气候复杂,探讨该区域气候变化与海拔的关系对全球气候变化研究具有重要的参考意义。基于1958—2017年新疆41个气象站的月和年平均气候数据,采用一元线性回归、Mann Kendall（M-K）趋势分析和突变检验等方法分析该地区气候变化的时空分布与海拔的关系。结果表明：1958—2017年新疆年均气温、年均降水量均呈上升趋势,但增加幅度具有时间和空间差异。在时间上,北疆四季平均气温增温幅度均大于南疆（冬季除外）,四季降水量增幅北疆大于南疆（夏季除外）;在空间上,北疆气温和降水的增幅均大于南疆。研究区各个站点气温呈现出南部高而北部低的空间格局,年均降水量北部多,南部低。各个站点气温倾向率总体随海拔增加而减少,年均降水量变化率随海拔升高而增加,在不同海拔带内部存在差异。综上所述,受全球气候变暖的影响,近60 a来新疆年均气温和年均降水量均呈上升趋势,尤其是北疆对全球气候变暖的响应较为敏感。     

Formation control of multiple underwater vehicles subject to communication faults and uncertainties

This paper proposes a novel approach to analyze and design the formation keeping control protocols for multiple underwater vehicles in the presence of communication faults and possible uncertainties. First, we formulate the considered vehicle model as the Port-controlled Hamiltonian form, and introduce the spring-damping system based formation control. Next, the dynamics of multiple underwater vehicles under uncertain relative information is reformulated as a network of Lur’e systems. Moreover, the agents under unknown disturbances generated by an external system are considered, where the internal model is applied to tackle the uncertainties, which still can be regulated as the Lur’e systems. In each case, the formation control is derived from solving LMI problems. Finally, a numerical example is introduced to illustrate the effectiveness of the proposed theoretical approach.     

南海北部水合物富集区水道特征对比与成因分析

天然气水合物作为现今乃至未来的重要清洁能源之一,其沉积环境和成矿条件的研究一直是国内外地质学家关注的热点问题,我国2007年、2013年及2015年已先后在神狐、和东沙海域多次成功钻获了天然气水合物实物样品。由此南海北部陆坡成为探讨天然气水合物沉积成因与成矿条件的重要试验区。然而,南海北部陆坡区的神狐、东沙及琼东南三个海域均有不同程度的天然气水合物发现,其各自的水深、沉积特征、气源成因及水合物成矿条件各有特点。本文利用地震沉积学原理,结合不同沉积相和沉积演化和古地貌、海平面变化和构造运动等因素,识别出不同类型的地震相。通过对比南海北部陆坡区域的水道系统的MTDs,认为其发育位置、展布和控制因素的不同影响了沉积展布。其中东沙区域位于近物源的上陆坡,神狐区域位于正常的缓陆坡区域,琼东南区域位于远离物源的海底平原区域。并且,水道系统可以分成侵蚀型,侵蚀-加积型和加积型,MTDs也可以分成头部拉张型,中部过渡型和趾部挤压型。     

Late quaternary seismic stratigraphy and active faults of the Gulf of İzmit (NE Marmara Sea)

The Upper Quaternary seismic stratigraphy and active faults of the Gulf of İzmit were investigated by means of high-resolution shallow seismic profiling data in the source region of 1999 İzmit earthquake. High-resolution seismic reflection data correlated with borehole data indicate that the stratigraphy of İzmit Bay consists of three distinct depositional sequences formed in response to middle Pleistocene-Holocene sea-level changes. Reflector R, separating the pre-Holocene sequences (1 and 2) from the Holocene sequence (3), represents an erosional unconformity produced by the subaerial fluvial erosion of the continental shelves at the time of the last glacial maximum. Occasional, anomalous reflections (acoustic turbidity) observed within the Holocene sequence are interpreted as gas accumulations. The maximum thickness of the Holocene sediments is found to be about 25 m. The isopach map of Holocene sediment implies that the thickness of the Holocene decreases from the east towards the central and western basins of İzmit Bay. Two distinct fault systems are interpreted in İzmit Bay. The main fault system extending roughly in an E-W direction along the Gulf of İzmit is an active right lateral strike slip fault with a normal component. The secondary faults are normal faults striking in different directions and these are identified as being both active and inactive. In addition, prominent compressive features are identified in the seismic cross-sections of some profiles acquired to the east of Hersek Peninsula where the focal mechanisms of the aftershocks of the 1999 İzmit earthquake also reveal predominantly reverse faulting mechanisms, as identified by a local dense seismic network.     

Controlling factors on the morphology and spatial distribution of methane-related tubular concretions – Case study of an Early Eocene seep system

Up to 10 m in length and >1 m in diameter tubular, calcite-cemented sandstone concretions are hosted by the faulted Dikilitash unconsolidated sands and sandstones. These structures document shallow subsurface pathways of Early Eocene methane seepage in the Balkan Mountains foreland (NE Bulgaria). Their exceptional exposure allowed a unique study of the factors governing the morphology and spatial distribution of such fossilized fluid conduits. The large dimensions and subvertical, cylindrical shape of the most common tube type primarily reflects the buoyancy-driven, vertical path of an ascending gas-bearing fluid through permeable, mainly unconsolidated sandy host sediments. Tube morphology was also influenced by local stratigraphic anisotropies and might as well document differences in former seepage conditions. Mapping of >800 tubular concretions showed the NNW–NNE elongation and alignment of tube clusters and massive cemented sandstone structures. This suggests that Paleogene fault systems played a major role in directing the movement of fluids. However, within a single tube cluster, tubes are preferentially aligned, over distances up to 50 m along directions at an angle between 10° and 36° with respect to the inferred NNW–NNE, cluster parallel fault traces. In addition, cylindrical tubes of analogue dimensions are aligned over distances >100 m along N15° to N25°-oriented directions. It is hypothesized that this spatial geometry of tubular concretions reflects the complex geometry of deformations structures in fault damage zones along which fluids were preferentially channelled.     

南海东北部新构造运动及其动力学机制

南海东北部地处欧亚板块与菲律宾海板块的交汇区,新构造运动活跃。根据地震活动性、震源机制解和GPS资料对该区的新构造活动特征进行分析,在此基础上讨论该区新构造运动的动力学机制。分析发现,菲律宾海板块NW向俯冲对该区的影响最为显著,导致了该区较强的地震活动性以及与俯冲方向一致的构造应力场。而印藏碰撞产生的侧向应力传递也影响到该区,控制华南地块向SE方向运动,并与菲律宾海板块的NW向俯冲共同作用,使华南地块在SE向运动的同时伴有逆时针旋转。印藏碰撞的SE向应力传递对俯冲产生的NW向水平挤压的抵消作用,使得地震活动性自东向西减弱以及构造应力场P轴方位角顺时针旋转。在这一背景下,区内滨海断裂带的活动控制了该区的地震、海岸带构造升降等新构造运动。     

海洋主体功能区划与海洋功能区划关系研究

开展海洋主体功能区划与海洋功能区划的关系和衔接研究,是保障两者在我国海洋事业中充分发挥各自作用的基础.本文从编制及实施2个方面理顺海洋主体功能区划与海洋功能区划的关系,促进两者在实际工作中的相互结合.