Diamond-shaped Block Research Articles

Preparation of Zn2+ doped NiCo2O4: Hole transport layer for high performance of perovskite solar cells

Inorganic hole transport materials (HTMs) play an important role for the stability and efficiency of planar perovskite solar cells (PSCs). Among the numerous inorganic HTMs, NiCo2O4 with its excellent performance is the emerging candidate for hole transport layers (HTLs) and is attracting increasing attention. However, the low electrical conductivity and optical transmittance of NiCo2O4 severely limit the device performance. Herein, the Zn2+ was used to dope NiCo2O4 to improve the electrical conductivity and optical transmittance of NiCo2O4. And the effects of the concentration of Zn2+ on the morphology, structure and properties of NiCo2O4 were investigated. The morphology and transparency of ZnxNi1-xCo2O4 would not be affected when the concentration of Zn2+ is below 0.1, but when it is up to 0.15 and 0.2, the morphology of NiCo2O4 clustered together or showed a diamond-shaped block, and the optical transmittance also decreased significantly. Meanwhile, with the increase of doping amount, the conductivity and hole mobility are gradually increased. As a result, the optimal concentration of Zn2+ is 0.1. Besides, the Zn0.1Ni0.9Co2O4 possessed a significant improvement in hole extraction and better band alignment compared to the NiCo2O4. And hence, the power conversion efficiency (PCE) of PSCs fabricated in open air is up to 13.41% by using Zn0.1Ni0.9Co2O4. This work develops a potential strategy for developing highly efficient and stable PSCs, opens up a new horizon for the development of inorganic HTMs.

Remnants of magma underplating by the Emeishan mantle plume within the lithosphere beneath southeastern margin of the Tibetan Plateau

The Emeishan Large Igneous Province (ELIP) is located along southeastern margin of the Tibetan Plateau, where long-wavelength crustal thickening and surface uplift have been attributed to the influx of weak crustal material from central Tibet into the lower crust beneath the Yangtze Craton. We have developed a new shear-wave velocity model for the lithosphere beneath eastern Tibet, based on a two-step linearized joint inversion technique of P-wave receiver functions (PRFs) with Rayleigh wave dispersion (10–60 s period) and Love wave dispersions (8–30 s period) for three dense seismic arrays. We applied bootstrap resampling technique to calculate the results of inversion. The resulting shear velocity model revealed two major low-velocity features in the middle–lower crust beneath southeastern Tibet. The horizontally extensive low-velocity zone (LVZ) beneath the northern Sichuan–Yunnan diamond-shaped block (SYDSB) can be interpreted as possible lower crustal flow from central Tibet, whereas the low-velocity anomaly observed beneath the Xiaojiang Fault is consistent with the presence of a partially molten layer enhanced by shear deformation along large faults. These two LVZs are separated by a lithospheric-scale high-velocity zone (HVZ) that is situated beneath the geologically inferred core of the ELIP. Based on other geophysical and geological evidence, we interpret this high-velocity anomaly body as remnants of the Emeishan plume-strengthened lithosphere that originally formed during the Permian volcanism, and we speculate that it has acted as a barrier to the hypothesized flow of lower crustal material from central Tibet since the late Cenozoic.

Upper mantle anisotropy in the southeastern margin of the Tibetan plateau and geodynamic implications

Continued northeastward compression owing to the colliding Indian subcontinent has led to pronounced surface uplift and significant crustal and mantle deformation in the Sichuan–Yunnan region along the southeastern margin of the Tibetan Plateau. Seismic anisotropy is an effective physical property for characterising crustal and upper-mantle deformation, as these deformation mechanisms can be investigated by analysing the splitting of compressional-to-shear-wave (P-to-S) converted phases (XKS, which includes the SKS, SKKS, PKS and PKKS phases) at the core–mantle boundary. However, we cannot distinguish any crustal and/or mantle anisotropy variations owing to the relatively low vertical resolution of XKS splitting. Here we compute the P-wave receiver functions from teleseismic events recorded at 90 permanent and 350 mobile broadband seismic stations that were established by the ChinArray project in the Sichuan–Yunnan region and analyse the P-to-S converted phases at the Moho interface (Pms) to measure the crustal anisotropic parameters. The Pms splitting results are then regarded as the crustal anisotropic parameters, and the anisotropic parameters in the upper mantle beneath 347 stations are extracted from the XKS splitting parameters by removing this crustal anisotropy. The results indicate that an approximately E–W anisotropic fast-wave polarisation direction (FPD) exists in the upper mantle beneath the southeastern margin of the Tibetan Plateau, and that the splitting times range from 0.06 to 1.39 s, with an average splitting time of 0.93 s. The approximately E–W anisotropic FPD in the upper mantle is mainly due to asthenospheric flow induced by the eastward subduction of the Indian Plate beneath Myanmar. The small splitting times within the southern Sichuan–Yunnan diamond-shaped block (SYDSB) may be attributed to vertical growth of the lithosphere induced by mantle-plume-related magmatic uplift.

Crustal velocity, density structure, and seismogenic environment in the southern segment of the North-South Seismic Belt, China

The southern segment of the North-South Seismic Belt in China is a critical region for earthquake preparedness and risk reduction efforts. However, limited by the low density of seismic stations and the use of single-parameter physical structural models, the deep tectonic features and seismogenic environment in this area remain controversial. Thus, a comprehensive analysis based on high-resolution crustal structures and multiple physical parameters is required. In this study, we applied the ambient noise tomography method to obtain the three-dimensional (3D) crustal S-wave velocity structure using continuous waveform data from 112 permanent stations and 350 densely distributed temporary stations in the southern segment of the North-South Seismic Belt. Then, we obtained the high-resolution 3D density structure through wavenumber-domain 3D gravity imaging constrained by the velocity structure. The low-velocity and low-density anomalies in the upper crust of the study area were mainly distributed in the Sichuan Basin and around Dali and Simao, while the high-velocity and high-density anomalies were primarily distributed in the Panxi region, corresponding to the surface geological features. Two prominent low-velocity and low-density anomalies were observed in the middle and lower crust: one to the west of the Songpan-Garzê block and Sichuan-Yunnan diamond-shaped block, and the other near the Anninghe-Xiaojiang fault. Combined with the spatial distribution of seismic events in the study area, we found that previous earthquakes predominantly occurred in the transition zones between high and low anomaly regions and in the low-velocity and low-density zones in the upper crust. In contrast, moderate-to-strong earthquakes mainly occurred within the transition zones between high and low anomaly regions and close to the high-velocity and high-density regions, often with low-velocity and low-density layers below their hypocenters. Fluids play a critical role in the seismogenic process by reducing fault strength and destabilizing the stress state, which may be a triggering factor for earthquakes in the study area. Additionally, the upwelling of molten materials from the mantle may lead to energy accumulation and stress concentration, providing an important seismogenic background for moderate-to-strong earthquakes in this area.

Investigating the electromagnetic wave-absorbing capacity and mechanical properties of flexible radar-absorbing knitted compound materials

This study fabricated flexible radar-absorbing knitted compound materials by weft knitting and blending ferromagnetic nickel micron-fibers and cotton fiber into structures with a concave–convex surface, including rhombic, mat, wavy, and leno stitches. The electromagnetic wave-absorbing capability and mechanical properties of the flexible radar-absorbing knitted compound materials were evaluated. The results showed that the rhombic, mat, and wavy stitches displayed high mechanical properties with high bursting strength and there were no significant differences among them. The rhombic stitch flexible radar-absorbing knitted compound material with a ferromagnetic nickel micron-fiber content of 14% had a maximum bandwidth of 13 GHz and achieved a minimum reflectance of −20 dB at 7 GHz, which was 150% that of mat fabric, and 200% that of wavy fabric and leno fabric. This was ascribed to the fact that the concave–convex surface with regular diamond-shaped block improved the dispersion of the electromagnetic wave, weakened the wave strength, and increased the interference. Therefore, the rhombic stitch flexible radar-absorbing knitted compound material was the most suitable for flexible radar-absorbing material in this study. The development of flexible radar-absorbing materials, by combining aerospace technology, military technology and textile technology, is important for the application in stealth of aircraft and weapons.

S-Wave Velocity Images of the Crust in the Southeast Margin of Tibet Revealed by Receiver Functions

The southeast margin of Tibet is the region in clockwise rotation around the Eastern Himalayan Syntaxis due to the India–Eurasia collision and the resistance of the stable Sichuan Basin and South China block. However, the dynamic processes involved in the evolution and deformation of the region remain poorly understood due to a lack of reliable geophysical observations. We collected abundant seismic data recorded by 108 permanent broadband stations deployed in the SE margin of Tibet since 2000, and obtained 4536 pairs of P-wave receiver functions (PRFs) with high signal-to-noise ratio. In this study, we have implemented a novel two-step data inversion procedure that can reduce the dependence of the inversion results on the initial model. We first use low-frequency PRFs obtained by iterative deconvolution in the time domain, and then an initial model consisting of a series of 2-km-thick isotropic layers to fit velocity models, and thus determine an overall statistical solution by means of the bootstrap resampling technique. This statistical solution is then regarded as a new initial model to adjust high-frequency PRFs. Hence, the same resampling process is executed again to estimate the optimal S-wave velocity structure below each station. The results provide an accurate 3D image of the crust and uppermost mantle in the SE margin of Tibet. We infer a wide intra-crustal low-velocity zone that varies laterally and in depth, which is thinner or even absent in the most southern part of Yunnan. Our hypothesis is that this low-velocity zone is the result of the accumulation of lower crustal flow coming from central Tibet. Furthermore, we show that this lower crustal flow extends largely through the Sichuan–Yunnan diamond-shaped block, and that there are significant variations in both crustal velocity structure and deformation mechanism across the great strike-slip faults of the Jinshajiang–Red River and Xiaojiang fault systems.

Anisotropic H-k stacking and (revisited) crustal structure in the southeastern margin of Tibet

P receiver functions (PRFs) and the H-k stacking technique are tools often used to constrain the thickness of the crust and the ratio between the velocities of P and S waves. Both the crustal depth and the Poisson's ratio are very important parameters to study the tectonic evolution of the lithosphere, but they can be significantly affected by the presence of crustal anisotropy. In order to address this problem, we have extended the isotropic stacking approach to include six converted P-to-S phases that are generated in the anisotropic case, instead of only three phases considered in the isotropic case, and we have examined the feasibility of the stacking technique using synthetic and real data. Based on PRFs acquired by 108 permanent broadband seismic stations deployed in the southeastern margin of Tibet including the Sichuan and Yunnan areas, we have applied the anisotropic H-k stacking scheme to investigate the crustal thickness and Poisson’s ratio. The results reveal that the crustal thickness varies from ∼60 km in the Songpan-Ganzi fold system and the northern part of the Sichuan-Yunnan diamond-shaped block, near the Eastern Himalayan Syntaxis, to ∼33 km in southern Yunnan, and that the Poisson’s ratio varies mostly from 0.24 to 0.32. The highest values of 0.28–0.30 are found along the axis formed by the Longmenshan fault, the Lijiang-Jinhe fault and the Xiaojiang fault, and are attributed to the accumulation of lower crustal flow in front of the Sichuan Basin. The highest value of ∼0.32 is observed at the Tengchong volcano area to the north of the Indochina block, and is attributed to the upwelling of hot mantle associated to the eastward subduction of the Indian plate, rather than to the expansion of east Tibet. Comparing with the results provided by the isotropic stacking scheme, it is appreciated that the crustal depth determined by the anisotropic stacking method well adjusts the observed pattern of gravity anomaly. We conclude that the results obtained by anisotropic stacking yield a much better constraint on the estimation of the crustal depth and Poisson's ratio when compared to those achieved by isotropic stacking.

Numerical investigation of heat transfer and pressure drop in nuclear fuel rod with three-dimensional surface roughness

The paper focuses on the numerical studies of heat transfer and pressure drop in a simulated nuclear fuel rod with three-dimensional surface roughness. Two-dimensional numerical simulations utilizing SST k-ω turbulent model were performed to evaluate heat transfer and pressure drop on the smooth and rough section of the heater rod. The numerical results were compared with experimental data obtained from a heater element which simulates a single Inconel-Nickel fuel rod for pressurized water reactor (PWR). The length of the rod was 2152.6 mm, and an outer diameter 9.5 mm, of which the outer surface of a 304.8 mm long section of the Inconel fuel rod was modified with three-dimensional (Diamond-shaped blocks) surface roughness. The angle of corrugation for each diamond block was 45°, and the length of each side of the diamond block was 1 mm. The numerically computed local heat transfer coefficient, overall Nusselt number, and pressure drop across the test rod shows good agreement with the corresponding experimental results. For the simulated rough surface, heat transfer coefficient was enhanced by 86% at Re=4.18×105 as compared to the smooth surface, and pressure drop was found to increase by 15.75% within Re range of 4.50×104-1.07×105. Plausible reason of the heat transfer enhancement of the three-dimensional surface roughness was discussed in the paper.

Comprehensive crustal structure and seismological evidence for lower crustal flow in the southeastern margin of Tibet revealed by receiver functions

The lower crustal flow model has become an interesting proposal to describe the growth and expansion of eastern Tibet. To date, however, the geophysical results are not definitive due to the non-uniqueness of the solutions found through data inversion and the resolution limitations. In this study the polarity of P-to-S converted phases at intra-crustal interfaces are analyzed in order to reveal evidence for low seismic velocity and lower-crustal flow in southeastern Tibet. We are interested in a joint study that is both a mapping of the crustal structure (Moho topography and Poisson's ratio) and an attempt to constrain an ICLVZ. We have determined the crustal thickness and Poisson's ratio from P (PRFs) and S (SRFs) receiver functions acquired in 108 permanent seismic stations deployed in the Sichuan and Yunnan areas. Also, we have obtained 98 measurements of Pms-phase splitting parameters at the array stations. The crustal thickness provided by PRFs is consistent with that given by SRFs. It varies from ~60km in the Songpan-Ganzi (SG) fold system and the northern part of the Sichuan-Yunnan diamond-shaped block (SYDSB), near the Eastern Himalayan Syntaxis, to ~33km in southern Yunnan. The Poisson's ratio varies mostly from 0.24 to 0.32; the highest values 0.28–0.32 are found along the axis formed by the Longmenshan fault, the Lijiang-Jinhe fault and in the Tengchong volcano area. The value of ~0.28 observed in SYDSB and the SG fold system is attributed to the presence of a low-velocity zone in the lower crust, and partly to the great sediment thickness in Sichuan Basin. The crust is clearly anisotropic in the southeastern margin of Tibet: the fast-wave polarization direction exhibits a NW-SE regional bias, while the time delay varies between 0.07s and 1.27s, being the average 0.54s±0.12s, implying the existence a strong shear zone in the lower crust. Based on the negative polarity observed after the direct P-wave in teleseismic receiver functions, we have detected an intra-crustal low-velocity zone (ICLVZ) in a wide region including east and southeast of Tibet and southern Yunnan, so both the shear zone and ICLVZ suggest the existence of lower crustal flow. The reverberation PpPs and PsPs+PpSs phases at the Moho are clearly weaker in SYDSB and the SG fold system than in the Indochina Block and eastern Yunnan, implying that SYDSB has a structure and tectonic history different from Indochina on its west side and eastern Yunnan on its east side. The above results provide seismological evidence for a lower crustal flow spreading from the eastern Tibet and that in its advance southward has invaded SYDSB widely, crossed the Lijiang-Jinhe fault and reached southern Yunnan.

Three-dimensional S-velocity structure of the crust in the southeast margin of the Tibetan plateau and geodynamic implications

The lower crustal flow model is one of several competing models considered to interpret the growth and expansion of southeastern Tibet. However, the dynamic processes involved in the evolution and deformation of the Tibetan plateau remain poorly understood due to the absence of reliable geophysical observations. In this study, 159 earthquakes of magnitude Ms≥6.2 were selected, which were recorded by 50 permanent broadband stations deployed in southwest China, and 1873 pairs of P-wave receiver functions with high signal-to-noise ratio were isolated. On the basis of a linearized inversion algorithm, a two-step inversion procedure was implemented that not only reduced the dependence of the inversion results on the initial models, but also provided a statistical estimation of the solution. Thus, we obtained an accurate 3D image of the S-wave velocity structure of the crust and uppermost mantle in the southeast margin of the Tibetan plateau. Our results reveal that an extensive intracrustal low-velocity zone spreads beneath southwest China, and further suggest that a lower crustal flow coming from eastern Tibet is blocked by the Jinshajiang-Red River fault to the west and the Xiaojiang fault to the east and extends largely by the Sichuan-Yunnan diamond-shaped block. This crustal flow along the southeastern margin of Tibet does not appear to be restricted to two narrow low-velocity channels as was advanced, but rather reflects the southeastward extrusion of crustal material as a way of tectonic escape.

Seismic upper mantle discontinuities beneath Southeast Tibet and geodynamic implications

In this study, a total of 13,080 P receiver functions and 2800 S receiver functions recorded by 116 stations in Southeast Tibet, are used to determine the depths of the Moho, the lithosphere–asthenosphere boundary (LAB), and the 410km and 660km discontinuities. The results show that the LAB depth increases from 80–100km beneath southern Yunnan to 140–180km beneath Sichuan. Most of the 410km discontinuity is flat and at 410km depth, with a slight depression of 10–20km beneath the Longmenshan (LMS) Fault, the central Sichuan–Yunnan (SY) diamond-shaped block, and southeastern Yunnan. For the 660km discontinuity, the greatest depth occurs beneath the LMS and southern Yunnan, reaching 670–680km. The deepening of 660km discontinuity is attributed to compositional heterogeneity within the MTZ or dynamic pressure on the discontinuity. Additionally, the velocity of movement in the crust and upper mantle beneath SY is different. In Yunnan, crustal movement is southeastward, whereas across the Red-River fault, part of the crustal motion is redirected southwest by the westward rollback of the mantle beneath Myanmar. The interaction between the asthenosphere moving northeastward from Myanmar and southeastward from Tibet near latitude 26°N causes the crust and lithospheric mantle beneath southern Yunnan to have different movement directions.

Experimental study of a porous floating breakwater

The paper presents a novel configuration of floating breakwater and its performance in waves. The structure is fabricated with large numbers of diamond-shaped blocks so arranged to reduce transmitted wave height and the mooring force. Two mooring modes, directional mooring and bidirectional mooring are considered in the tests. The influence of an impermeable vertical sidewall on transmission coefficient is estimated. The results examined under the present investigations are: K t, wave transmission coefficient ( K t= H t/ H i, H t—transmitted wave height, H i—incident wave height); K r, reflection coefficient ( K r= H r/ H i, H r—reflected wave height); E loss ( E loss = 1 − K r 2 − K t 2 ) , the value of the dissipation of incident wave energy; and mooring force per unit length of the breakwater ( F w denotes windward mooring force and F l denotes leeward mooring force for directional mooring, and F 1, F 2, F 3 and F 4 are four mooring forces for bidirectional mooring) of two mooring modes without sidewall. For the case of floating breakwater with impermeable sidewall, measured transmission coefficient K T ( K T= H T/ H, H T—the measured wave height in front of the sidewall, H—the wave height without structure and sidewall) is offered. The experimental results show that the proposed floating breakwater can reduce incident wave height by dissipating wave energy more than reflecting it.

Mathematical Models of Block Media in Problems of Geomechanics. Part III: Diamond-Shaped Blocks

The mathematical and mechanical models of elastic and elastoplastic deformation of block rock mass are developed. The problems of rigid punch indentation into a rock mass and the stress-strain state around a cylindrical working are considered.

Ising-Model, Block-Spin Distributions by the Markov Property Method

The idea that near the critical point each block of spins behaves just like a single big spin is investigated. The case where a diamond-shaped block of spins is embedded in a (small) sea of spins is studied. Use is made of the Markov property method to make exact computations of the various spin moments needed to test this hypothesis. The residual fluctuation about the mean value of the block spin is seen to tend to a finite fraction of the length of the mean block-spin. This result is in line with previous studies which used different types of boundary conditions.

Role of Fault Rejuvenation in Hydrocarbon Accumulation and Structural Evolution of Reconcavo Basin, Northeastern Brazil

From a geometric analysis of the fault pattern in the Reconcavo basin, Brazil, supported by a reinterpretation of the early opening history of the South Atlantic Ocean, it is inferred that the basin formed as a result of Valanginian (Early Cretaceous) motion on a major N40°E-striking left-lateral transform fault located offshore between Salvador and Recife. This left-lateral motion was due to the location of the Valanginian pole of South American-African plate rotation within northern Brazil, at 2.5°S, 45.0°W, rather than farther north as interpreted previously. Left-lateral movement along the inferred transform created three fault sets: (1) a predominant set striking N30°E ± 20° (1^sgr); and two lesser developed sets striking (2) N13°W ± 6° and (3) N37°W ± 12° (1^sgr). Sets (1) and (3) are interpreted, respectively, as Riedel and conjugate Riedel shears (with an extensional component) to the N40°E-trending left-lateral transform fault. Set (2) formed as an extensional fault system. Intersections of these three sets subdivide the basin into triangular and diamond-shaped blocks. The Reconcavo basin continues northward in northeastern Brazil into the Tucano and Jatoba basins. These basins collectively form a north-south-trending, mega half-graben within continental crust. Geohistory curves for Early Cretaceous units in the Reconcavo basin indicate that the syn-tectonic Valanginian shales of the lacustrine Candeias Formation began to generate hydrocarbons during the earliest subsequent deposition of the Ilhas Formation (?Hauterivian). Because diamond-shaped structural traps had formed earlier during the Valanginian, hydrocarbons generated in the Candeias Formation are believed to have then migrated into the Sergi Formation (?Upper Jurassic) reservoir units in structurally juxtaposed fault blocks. During Barremian to Aptian time, deposition of fluvial, lacustrine, and alluvial sediments of the Ilhas and Sao Sebastiao Formations occurred. Rejuvenation as normal faults of earlier formed strike-slip and normal faults occurred in the latest Aptian (106 Ma) when the pole of South American-African plate rotations jumped to 41.3°N, 43.8°W. This pole jump caused extension along the previously formed transform margin between Salvador and Recife and the abandonment of rifting in the Reconcavo basin. Rejuvenated faults tapped earlier filled Sergi Formation reservoirs, which then leaked earlier reservoired hydrocarbons up these fault planes into higher reservoirs in the Ilhas and Sao Sebastiao Formations. This structural history thus explains the frequency distribution and orientation of faults in the basin, Sergi Formation production from corners of diamond-shaped fault blocks, and production from stratigraphically and structurally higher reservoirs (Ilhas and Sao Sebastiao Formations) in rollover folds and stratigraphic traps charged by second-phase faulting.