Submarine canyons have been the subject of intense studies in recent years because of their close link to deepwater systems. The Central Canyon is a large unusual submarine canyon in the northwestern ...margin of the South China Sea, has a total length of about 425 km and is oriented sub-parallel to the continental slope. Using integrated 2D/3D seismic, well log, core, and biostratigraphy data, the current study documents the stratigraphic framework, internal architecture, depositional processes, and controlling factors of the segment of the Central Canyon located in the Qiongdongnan Basin.
The integrated analysis shows that the canyon fill consists of four 3
rd-order sequences, SQ4, SQ3, SQ2, and SQ1. Each of them is bounded by regionally important erosional surfaces (3
rd-order sequence boundaries). Within each 3
rd-order sequence there is maximum regressive surface separating a regressive systems tract in the lower part and a transgressive systems tract in the upper part. Nine facies are identified and are further grouped into five depositional units, DU1 through DU5.
The canyon evolved through four cut-and-fill stages, with a change from predominantly axial cut-and-fill to primarily side cut-and-fill. Axial cut-and-fill dominated during the first stage, and the slope-subparallel paleo Xisha Trough was intensely eroded by large-scale axial gravity flows. During the second cut-and-fill stage, the Central Canyon experienced both axial and side cut-and-fill. The third stage was dominated by side cut-and-fill. The canyon was eroded and fed by slope channels that transported sandy sediments from the shelf to the north during regression, and was covered by side-derived muddy MTCs during transgression. The last stage was also dominated by side cut-and-fill. The canyon, however, was filled predominantly by side-derived muddy MTCs.
Evolution and depositional processes in the Central Canyon were likely controlled by slope-subparallel negative-relief induced by paleo-seafloor morphology, structural inversion of the Red River Fault and the slope-subparallel basement faults. Additionally, Coriolis force, sea-level fluctuations, high sedimentation rate, and rapid progradation of the slope also controlled and influenced the depositional processes, and internal architectures of the canyon.
► The studied canyon consists of four 3rd-order sequences. ► Nine depositional facies are identified, and can be group into five depositional units. ► Four cut-and-fill stages are recognized. ► Possible controlling factors on the development of the studied canyon are examined.
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•A high-strength AlSi8.1 Mg1.4 aluminum alloy was specifically designed for SLM.•GP zones/Mg-Si clusters were formed in as-built alloy.•After direct aging, β″ nanoparticles were ...precipitated from α-Al cells.•The strength of present alloy was much higher than that of SLM AlSi10Mg alloys.
A high-strength AlSi8.1Mg1.4 aluminum alloy was specifically designed for selective laser melting (SLM) by doubling the Mg content of A357 alloy based on the rapid solidification characteristics of the SLM process. The alloy showed good processability with maximum density over casting alloy with the same composition. The microstructure of the as-built alloy was characterized by the formation of cell structure. The α-Al cells manifested GP zones/Mg-Si clusters. The yield strength (YS), ultimate tensile strength (UTS), and elongation to fracture of the as-built alloy were 341 ± 14 MPa, 518 ± 6 MPa, and 7.1 ± 0.4%, respectively. Due to the precipitation of β″ nanoparticles in α-Al cells, the strength of the SLM alloy was effectively improved after direct aging at 150 ℃ and 200 ℃, with a maximum YS of 446 ± 5 MPa and maximum UTS of 546 ± 1 MPa, which were much higher than those of Al-Si-based alloy produced by SLM. When the aging temperature exceeded 200 ℃, the strength of the alloys decreased rapidly, but the elongation increased significantly. Multiple strengthening mechanisms, including grain refinement, GP zones/Mg-Si clusters, and β″ nanoparticle precipitation contributed to the high strength of SLM AlSi8.1Mg1.4 alloy.
We present here a detailed study of the specific nanoparticle structures that give rise to single-molecule surface-enhanced Raman scattering (SMSERS). A variety of structures are observed, but the ...simplest are dimers of Ag nanocrystals. We chose one of these structures for detailed study using electrodynamics calculations and found that the electromagnetic SERS enhancement factors of 109 are easily obtained and are consistent with single-molecule SERS activity.
Post-rift volcanisms and fault activities are significant for understanding the tectonic-sedimentary evolution of rifted continental margins and associated hydrocarbon entrapments. In this study, a ...series of post-rift fault-associated volcanic activities have been found in the northern continental margin of the South China Sea (SCS). However, their episodes and relationships with the progressive continental breakup are still doubtful. Here, new 2D/3D seismic, borehole, dating, and biostratigraphic data are used to investigate the characteristics of the post-rift volcanism and fault activities in the Baiyun Sag (BYS), Pearl River Mouth Basin. The newly-found fault-associated volcanic complexes include thirteen submarine volcanic mounds and associated lava flows, together with igneous sills that are mainly composed of basalts and tuffs. Seismic stratigraphic analysis combined with KAr dating from cores confirms that post-rift volcanism in the BYS climaxed along with the breakup of the SCS mainly in three episodes: (1) the first episode near Oligocene/Miocene boundary (23.3 Ma); (2) the second at the middle Early Miocene (17.6 Ma); and (3) the new-found third episode at the late Early Miocene (17.1 Ma). Also, fifty-three syn-sedimentary faults are interpreted, which are characterized by a WNW trending normal fault group separated by an ENE trending transcurrent fault group. And there is evidence that these fifty-three faults were long-lived from ca. 32–17.1 Ma and served as important conduits for the upward migration of the magma. The three episodes of volcanism and tectonic fault activities are related to the progressive continental breakup in the northern SCS margin, and they represent the tectonic signature of the early stage of the post-rift subsidence after the lithospheric breakup which extends to the top of a hypothetical breakup sequence (32–17.1 Ma) in the BYS. Furthermore, this study proves that the diachronous continental breakup in the SCS margin can result in corresponding changes in depositional architectures, along with a breakup sequence characterized by the deposition of a ‘sandstone‑carbonate-shale’ regressive-transgressive cycle. The sedimentological changes and associated tectonic features recorded in the Baiyun Sag suggest an exceptionally active tectonic setting in the time of the formation of the breakup sequence (Early Oligocene-Early Miocene) along the northern SCS margin.
•3D characterization of the Early Miocene (17.1 Ma) volcanic complexes.•Investigation of post-rift fault activities (32–17.1 Ma) using 3D seismic data.•Discussion on the relationship between volcanic complexes and fault activities.•New insights into the breakup sequence of the northern South China Sea.
Underwater wireless acoustic positioning technology uses the geometric relationship between a target and a receiving array to determine the target’s position by measuring distances between the target ...and the array elements, that the receiving array is usually symmetry in space. It is an indirect measurement approach, so ranging errors can significantly impact positioning accuracy due to error transmission effects. To improve precision, a similarity-matched localization algorithm based on the L-p norm (LPM) is introduced. This algorithm constructs a distance vector model with environmental parameters and performs similarity analysis by computing the L-p norm of the distance vector and a reference copy vector for three-dimensional localization in the observation area. Unlike conventional methods, this technology directly matches distance vectors without coupling error transmission, thereby enhancing positioning accuracy even though it remains contingent upon ranging precision. To validate the algorithm’s efficacy, Monte Carlo simulations are employed to analyze the distribution patterns of positioning errors in both horizontal and three-dimensional spaces. The results show an improvement from a mean positioning error of 0.0475 m to 0.0250 m and a decrease in error standard deviation from 0.0240 m to 0.0092 m. The results indicate that LPM offers improved accuracy and robustness by circumventing traditional error transmission issues.
Pressure injury is a common complication after a spinal cord injury. Long-term multidisciplinary follow-up is difficult after such patients have been discharged. Telemedicine promises to provide ...convenient and effective support for the prevention and treatment of pressure injury, but previous attempts to demonstrate that have produced inconsistent results. The aim of this study is to evaluate the effectiveness of telemedicine in preventing and treating pressure injury among community-dwelling patients with spinal cord injury, and determine which telemedicine form is more effective. This systematic review was performed according to the PRISMA-NMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Network Meta-Analysis) standards. Ten databases were searched to identify randomized controlled trials and quasi-experimental studies related to the effectiveness of telemedicine intervention in patients with spinal cord injury. Two researchers worked independently and blindly selected studies, extracted data, and assessed the risk of bias. The results were described as relative risk (RR) and weighted mean difference and 95% CI. The 35 studies comprised 25 randomized controlled trials and 10 quasi-experimental studies involving 3131 patients. The results showed that telemedicine can significantly (P<.05) reduce the incidence of pressure injury (RR 0.24, 95% CI 0.14-0.41; P<.05; I sup.2=0%), promote faster healing (RR 0.73, 95% CI 0.62-0.85; P<.05; I sup.2=0%), and yield lower scores on the pressure ulcer scale of healing (weighted mean difference=–1.98, 95% CI –3.51 to –0.46; P<.05; I sup.2=0%). Cumulative ranking estimates showed that combining telemedicine with conventional intervention (93.5%) was the most effective approach. Telemedicine is a feasible way to prevent pressure injury among patients with spinal cord injuries. It can decrease the incidence and severity of pressure injury and accelerate patients’ healing without imposing economic burden. It is best used in tandem with other, more conventional interventions. Due to the limited quality and quantity of included studies, large-scale and well-designed randomized controlled trials are warranted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
3D seismic data from the northwestern South China Sea margin, coupled with the quantification of oceanographic processes and morphological results, were used to infer three-dimensional flow processes ...and in turn sedimentation in contourite channels. Contour currents resulting from the Northern Pacific Deep Water (NPDW-CCs) flowing through the bends of contourite channels around a topographic high lead to an imbalance in the transverse direction, around the bend, between three competing forces (i.e., upslope directed Coriolis forces versus downslope directed centrifugal and pressure-gradient forces). The interface deflection of NPDW-CCs by Coriolis, pressure gradient, and centrifugal forces yields a helical flow cell consisting of upper return flows directed downslope and basal flows orientated upslope. Ekman boundary layers, at the base and flow interface, are also likely present leading to flows in the downslope direction. The helical flow cell in the bulk of contour currents, and Ekman boundary layers, constitute a Coriolis force-induced helical flow circulation, which we suggest promoted asymmetric intra-channel deposition (i.e., downslope deposition versus upslope erosion), forcing contourite channels to consistently migrate in an upslope direction. Such Coriolis force-induced helical flow circulation is evidenced by occurrence of volumetrically significant overbank deposits along downslope margins and by asymmetric channel cross-sections with steepened channel walls and truncation terminations along upslope margins. It exhibits subcritical flow conditions (represented by internal Froude numbers estimated as 0.04 to 0.19), and is sufficiently deep to spill out of the studied contourite channels, yielding overbank deposits along downslope flanks of the contourite channels.
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•Coriolis force-induced helical flow cell consists of a large-scale secondary cell and Ekman boundary layers at the very base.•Coriolis force-induced helical flow cell exhibits unconfined, subcritical flow conditions.•Coriolis force-induced helical flow cell yields downslope deposition versus upslope erosion.
The basal plane dislocation (BPD) density is one of the most important defects affecting the application of SiC wafers. In this study, numerical simulations and corresponding experiments were ...conducted to investigate the influence of cooling processes, seed-bonding methods, and graphite crucible materials on the BPD density in an 8-inch N-type 4H-SiC single crystal grown by the physical vapor transport (PVT) method. The results showed that the BPD density could be effectively reduced by increasing the cooling rate, optimizing the seed-bonding method, and adopting a graphite crucible with a similar coefficient of thermal expansion as the SiC single crystal. The BPD density in the experiments showed that a high cooling rate reduced the BPD density from 4689 cm
to 2925 cm
; optimization of the seed-bonding method decreased the BPD density to 1560 cm
. The BPD density was further reduced to 704 cm
through the adoption of a graphite crucible with a smaller thermal expansion coefficient.
Moving target detection performance is seriously affected by missing array elements for multichannel synthetic aperture radar (Multi‐SAR) systems. Meanwhile, there is a contradiction between the ...accuracy of data recovery and the computational burden in traditional methods. To solve the problems, a moving target detection method based on CUR‐RPCA for missing array elements is proposed in this paper. First, key nodes of the echo data are extracted and rearranged into a low‐rank matrix. Then we uses the low‐rank characteristic to complete key nodes of data. Subsequently, complete echo data is constructed by utilising recovered key nodes of data and CUR decomposition. Therefore using the ideas of CUR and RPCA, a novel optimization problem is constructed to achieve separation of moving targets and clutter while recovering data. In addition, only key nodes of the data is completed to achieve the performance of all data recovery, so that the disadvantage of low computational efficiency has been overcome for traditional matrix completion methods. Finally, the superior clutter suppression performance of the proposed method is verified by several numerical simulations and comparative studies.
As the scarcity of frequency resources and the increasing wireless broadband requirements become very serious problems worldwide, more and more attention has been focused on TDD technology ...development, which is anticipated to provide desirable solutions to these problems. This has boosted standard evolution from TDSCDMA to TD-LTE and TD-LTE-Advanced in recent years, with a lot of innovative technologies contributed to the TDD-based cellular mobile communication world. This article mainly presents the evolution strategies from TDSCDMA to TD-LTE and TD-LTE-Advanced, including standardization progress, key technologies, performance evaluation, industry development, and commercial status. Some new technologies and challenging work for TD-LTE beyond are discussed as well.
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