Geologic mapping and geochronological analysis in southwest (Kailas area) and southeast (Zedong area) Tibet reveal two major episodes of Tertiary crustal shortening along the classic Indus-Tsangpo suture in the Yalu River valley. The older event occurred between ca. 30 and 24 Ma during movement along the north-dipping Gangdese thrust. The development of this thrust caused extensive denudation of the Gangdese batholith in its hanging wall and underthrusting of the Xigaze forearc strata in its footwall. Examination of timing of major tectonic events in central Asia suggests that the initiation of the Gangdese thrust was approximately coeval with the late Oligocene initiation and development of north-south shortening in the eastern Kunlun Shan of northern Tibet, the Nan Shan at the northeastern end of the Altyn Tagh fault, the western Kunlun Shan at the southwestern end of the Altyn Tagh fault, and finally the Tian Shan (north of the Tarim basin). Such regionally synchronous initiation of crustal shortening in and around the plateau may have been related to changes in convergence rate and direction between the Eurasian plate and the Indian and Pacific plates. The younger thrusting event along the Yalu River valley occurred between 19 and 10 Ma along the south-dipping Great Counter thrust system, equivalent to the locally named Renbu-Zedong thrust in southeastern Tibet, the Backthrust system in south-central Tibet, and the South Kailas thrust in southwest Tibet. The coeval development of the Great Counter thrust and the North Himalayan granite-gneiss dome belt is consistent with their development being related to thermal weakening of the north Himalayan and south Tibetan crust, due perhaps to thermal relaxation of an already thickened crust created by the early phase of collision between India and Asia or frictional heating along major thrusts, such as the Main Central thrust, beneath the Himalaya.

This paper proposes a novel user cooperation approach in both computation and communication for mobile edge computing (MEC) systems to improve the energy efficiency for latency-constrained computation. We consider a basic three-node MEC system consisting of a user node, a helper node, and an access point (AP) node attached with an MEC server, in which the user has latency-constrained and computation-intensive tasks to be executed. We consider two different computation offloading models, namely the partial and binary offloading, respectively. For partial offloading, the tasks at the user are divided into three parts that are executed at the user, helper, and AP, respectively; while for binary offloading, the tasks are executed as a whole only at one of three nodes. Under this setup, we focus on a particular time block and develop an efficient fourslot transmission protocol to enable the joint computation and communication cooperation. Besides the local task computing over the whole block, the user can offload some computation tasks to the helper in the first slot, and the helper cooperatively computes these tasks in the remaining time; while in the second and third slots, the helper works as a cooperative relay to help the user offload some other tasks to the AP for remote execution in the fourth slot. For both cases with partial and binary offloading, we jointly optimize the computation and communication resources allocation at both the user and the helper (i.e., the time and transmit power allocations for offloading, and the central process unit (CPU) frequencies for computing), so as to minimize their total energy consumption while satisfying the user's computation latency constraint. Although the two problems are non-convex in general, we develop efficient algorithms to solve them optimally. Numerical results show that the proposed joint computation and communication cooperation approach significantly improves the computation capacity and energy efficiency at the user and helper, as compared to other benchmark schemes without such a joint design.

In Underwater Wireless Sensor Networks (UWSNs), localization is one of most important technologies since it plays a critical role in many applications. Motivated by widespread adoption of localization, in this paper, we present a comprehensive survey of localization algorithms. First, we classify localization algorithms into three categories based on sensor nodes’ mobility: stationary localization algorithms, mobile localization algorithms and hybrid localization algorithms. Moreover, we compare the localization algorithms in detail and analyze future research directions of localization algorithms in UWSNs.

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To better understand the mechanics of restraining double bends and the strike-slip faults in which they occur, we investigated the relationship between topography and bedrock structure within the Akato Tagh, the largest restraining double bend along the active, left-slip Altyn Tagh fault. The bend comprises a ~90-km long, east-west striking central fault segment fl anked by two N70°E-striking sections that parallel the regional strike of the Altyn Tagh system. The three segments form two inside corners in the southwest and northeast sectors of the uplift where they link. We fi nd that both the topography and bedrock structure of the Akato Tagh restraining bend are strongly asymmetric. The highest and widest parts of the uplift are focused into two topographic nodes, one in each inside corner of the bend. Structural mapping of the western half of the bend suggests the southwest node coincides with a region of anomalously high, bend-perpendicular shortening. We also fi nd that partitioned, transpressional deformation within the Akato Tagh borderlands is absorbed by bend-parallel strike-slip faulting and bend-perpendicular folding, unlike the thrusting reported from many other double bends. Synthesis of these results leads to three implications of general signifi cance. First, we show that focusing of bend-perpendicular shortening into the two inside corners of a restraining double bend may cause both the bend and the fault to undergo vertical-axis rotation, thereby reducing the bend angle and smoothing the trace during progressive deformation. Such vertical-axis rotation may help explain why fault trace complexity is inversely related to total displacement along strike-slip faults. Second, we calculate four independent age estimates for the Akato Tagh bend, all of which are much younger than the Altyn Tagh system. We use these estimates in a companion study to postulate that the Altyn Tagh and similarly multi-stranded strike-slip systems may evolve by net strain hardening. Third, comparison of the Akato Tagh with other restraining double bends highlights systematic differences in the style of borderland faulting and we speculate that these variations result from different states of stress adjacent to the bends. Strike-slip dominated bends such as the Akato Tagh may form where σ H = σ 1 , σ v = σ 2 , and σ h = σ 3 whereas thrust-dominated bends like the Santa Cruz bend along the San Andreas fault form when σ H = σ 1 , σ h = σ 2 , σ v = σ 3 . This hypothesis predicts that the style of faulting along a restraining double bend can evolve during progressive deformation, and we show that either weakening of borderland faults or growth of restraining bend topography can convert thrust-dominated bends into strike-slip dominated uplifts such as the Akato Tagh.