Study of the relationship between fractures and highly productive shale gas zones, Longmaxi Formation, Jiaoshiba area in eastern Sichuan

Shale fractures are an important factor controlling shale gas enrichment and high-productivity zones in the Longmaxi Formation, Jiaoshiba area in eastern Sichuan. Drilling results have, however, shown that the shale fracture density does not have a straightforward correlation with shale gas productivity. Based on logging data, drilling and seismic data, the relationship between shale fracture and shale gas accumulation is investigated by integrating the results of experiments and geophysical methods. The following conclusions have been drawn：（1） Tracer diffusion tests indicate that zones of fracture act as favorable channels for shale gas migration and high-angle fractures promote gas accumulation.（2） Based on the result of azimuthal anisotropy prediction, a fracture system with anisotropy strength values between 1 and 1.15 represents a moderate development of high-angle fractures, which is considered to be favorable for shale gas accumulation and high productivity, while fracture systems with anisotropy strength values larger than 1.15 indicate over-development of shale fracture, which may result in the destruction of the shale reservoir preservation conditions.

Fracture prediction approach for oil-bearing reservoirs based on AVAZ attributes in an orthorhombic medium

Fracture systems in nature are complicated. Normally vertical fractures develop in an isotropic background. However, the presence of horizontal fine layering or horizontal fractures in reservoirs makes the vertical fractures develop in a VTI（a transversely isotropic media with a vertical symmetry axis） background. In this case, reservoirs can be described better by using an orthorhombic medium instead of a traditional HTI（a transversely isotropic media with a horizontal symmetry axis） medium. In this paper, we focus on the fracture prediction study within an orthorhombic medium for oil-bearing reservoirs. Firstly, we simplify the reflection coefficient approximation in an orthorhombic medium. Secondly, the impact of horizontal fracturing on the reflection coefficient approximation is analyzed theoretically. Then based on that approximation, we compare and analyze the relative impact of vertical fracturing, horizontal fracturing and fluid indicative factor on traditional ellipse fitting results and the scaled B attributes. We find that scaled B attributes are more sensitive to vertical fractures, so scaled B attributes are proposed to predict vertical fractures. Finally, a test is developed to predict the fracture development intensity of an oil-bearing reservoir. The fracture development observed in cores is used to validate the study method. The findings of both theoretical analyses and practical application reveal that compared with traditional methods, this new approach has improved the prediction of fracture development intensity in oil-bearing reservoirs.

Generalized Lanczos method for systematic optimization of tensor network states

We propose a generalized Lanczos method to generate the many-body basis states of quantum lattice models using tensor-network states （TNS）. The ground-state wave function is represented as a linear superposition composed from a set of TNS generated by Lanczos iteration. This method improves significantly the accuracy of the tensor-network algorithm and provides an effective way to enlarge the maximal bond dimension of TNS. The ground state such obtained contains significantly more entanglement than each individual TNS, reproducing correctly the logarithmic size dependence of the entanglement entropy in a critical system. The method can be generalized to non-Hamiltonian systems and to the calculation of low-lying excited states, dynamical correlation functions, and other physical properties of strongly correlated systems.

Flow stress and constitutive relations of ship plate steel continuous casting slab with solidification end reduction process

In order to describe the thermal–mechanical behavior of the ship plate steel continuous casting slab during solidification end heavy reduction(HR)process accurately,its constitutive behavior was investigated by a single-pass thermal compression experiment.According to the deformation features of wide thick continuous casting slab with HR,the simulation temperature ranged from 1173 to 1573 K with strain rates of 0.0001,0.001,0.01 and 0.1 s^(-1).Three different constitutive models,the modified Johnson–Cook(JC)model,the modified Zerilli–Armstrong(ZA)model and the Arrhenius model,were established according to the obtained true stress–strain curves.The average relative error of the modified JC model,the modified ZA model and the Arrhenius model are 10.82%,9.96%and 6.21%,respectively.Considering the obvious softening effect of the flow curve at a low strain rate,the secondary softening factor under the interaction of low strain rate and the temperature was introduced in the original Arrhenius model.Compared to the Arrhenius model,the modified Arrhenius model error decreased from 6.21%to 4.73%.

Nonlinear Forced Vibration of Cantilevered Pipes Conveying Fluid

The nonlinear forced vibrations of a cantilevered pipe conveying fluid under base excitations are explored by means of the full nonlinear equation of motion, and the fourth- order Runge-Kutta integration algorithm is used as a numerical tool to solve the discretized equations. The self-excited vibration is briefly discussed first, focusing on the effect of flow velocity on the stability and post-flutter dynamical behavior of the pipe system with parameters close to those in previous experiments. Then, the nonlinear forced vibrations are examined using several concrete examples by means of frequency response diagrams and phase-plane plots. It shows that, at low flow velocity, the resonant amplitude near the first-mode natural frequency is larger than its counterpart near the second-mode natural frequency. The second-mode frequency response curve clearly displays a softening-type behavior with hysteresis phenomenon, while the first-mode frequency response curve almost maintains its neutrality. At moderate flow velocity, interestingly, the first-mode resonance response diminishes and the hysteresis phenomenon of the second-mode response disappears. At high flow velocity beyond the flutter threshold, the frequency response curve would exhibit a quenching-like behavior. When the excitation frequency is increased through the quenching point, the response of the pipe may shift from quasiperiodic to periodic. The results obtained in the present work highlight the dramatic influence of internal fluid flow on the nonlinear forced vibrations of slender Pipes.

A review of CoSb_(3)-based skutterudite thermoelectric materials

The binary skutterudite CoSb_(3) is a narrow bandgap semiconductor thermoelectric(TE)material with a relatively flat band structure and excellent electrical performance.However,thermal conductivity is very high because of the covalent bond between Co and Sb,resulting in a very low ZT value.Therefore,researchers have been trying to reduce its thermal conductivity by the different optimization methods.In addition,the synergistic optimization of the electrical and thermal transport parameters is also a key to improve the ZT value of CoSb_(3) material because the electrical and thermal transport parameters of TE materials are closely related to each other by the band structure and scattering mechanism.This review summarizes the main research progress in recent years to reduce the thermal conductivity of CoSb_(3)-based materials at atomic-molecular scale and nano-mesoscopic scale.We also provide a simple summary of achievements made in recent studies on the non-equilibrium preparation technologies of CoSb_(3)-based materials and synergistic optimization of the electrical and thermal transport parameters.In addition,the research progress of CoSb_(3)-based TE devices in recent years is also briefly discussed.

A gravity heat pipe for high voltage vacuum interrupter

To enhance nominal current of high voltage vacuum circuit breakers （VCBs）, a gravity heat pipe was proposed to replace stationary conducting rod of a high voltage vacuum interrupter. The heat pipe is composed of two coaxis tubes： the external tube is made of oxygen-free copper and the inner tube is made of stainless steel. The bottom end of the inner stainless steel tube is connected to the external copper tube by holes. Transient and static thermal performance of the heat pipe was measured, and the thermal resistance of it was compared with that of a solid copper rod with the same dimensions. Experimental results showed that thermal resistance of the heat pipe was about 1/3 of that of the copper rod, and it decreased slightly with the rising of the input heat flux. 3D thermal simulation on a 126 kV/2000 A single break VCB was done to compare the thermal performance between the proposed gravity heat pipe and the copper rod serving as the stationary conducting rod of the vacuum interrupter. Simulation results revealed that in the heat pipe case, the maximum temperature between contacts was 67 ℃ lower than that in the copper rod case.

Recent Advances on Neural Headline Generation

Recently, neural models have been proposed for headline generation by learning to map documents to headlines with recurrent neural network. In this work, we give a detailed introduction and comparison of existing work and recent improvements in neural headline generation, with particular attention on how encoders, decoders and neural model training strategies alter the overall performance of the headline generation system. Furthermore, we perform quantitative analysis of most existing neural headline generation systems and summarize several key factors that impact the performance of headline generation systems. Meanwhile, we carry on detailed error analysis to typical neural headline generation systems in order to gain more comprehension. Our results and conclusions are hoped to benefit future research studies.

Mineralization and osteoblast behavior of multilayered films on TiO_2 nanotube surfaces assembled by the layer-by-layer technique

In this paper,the multilayer films of poly-L-lysine（PLL） and DNA were created on TiO2 nanotube surfaces using the layer-by-layer（LBL） self-assembly technique.Chemical compositions of the assembled multilayered films were investigated by X-ray photoelectron spectroscopy.Biological properties of the multilayered films were evaluated by the biomimetic mineralization and osteoblast cell culture experiments.The results indicated that PLL and DNA were successfully assembled onto TiO2 nanotube surfaces by electrostatic attraction.Moreover,the samples of assembled PLL or/and DNA had better bioactivity in inducing HA formation and promoting osteoblast cells adhesion,proliferation and early differentiation.

Homogenization heat treatment for an additively manufactured precipitation-hardening high-entropy alloy

A precipitation-hardening high-entropy alloy(HEA),(FeCoNi)_(86)Al_(7) Ti_(7),was successfully fabricated using selective laser melting(SLM).Severe segregation of Ti occurred at the boundaries of dislocation cells.Therefore,homogenization heat treatment at 1150℃for 0.5 h was performed to alleviate the microsegregation.After homogenization,almost no dislocation cells were left in the grains,and recrystallization occurred as the average grain size increased from 37 to 54μm.Compared with the initial as-built HEA,the ductility of the HEA increases significantly from 29%to 40%,and the strength decreases slightly from 710 to 606 MPa.For further aging,pre-homogenization can decrease the precipitation of ordered L2_(1) phases.Because void has a high propensity to initiate from the matrix/L2_(1) incoherent interface,pre-homogenization reduced the number of weak points,thus considerably improving the plastic deformation ability of the aged HEA by 36%.In addition,the strengthening mechanism has also been analyzed for the aged HEA.It was revealed that the coherent L1_(2)precipitate contributed the most to the increased strength.

电诱导自修复纳米复合水凝胶的制备及性能研究

采用表面修饰N,N-双丙烯酰胱胺(BACA)的金纳米颗粒(Au NP)为多功能交联剂,聚邻苯二胺纳米带(PoPd nanobelt)为导电掺杂剂,N-异丙基丙烯酰胺(NIPAm)为可聚合单体,在热引发剂和催化剂存在下,发生自由基聚合反应,成功合成导电性纳米复合水凝胶.采用扫描电子显微镜、透射电子显微镜及元素成像技术、紫外可见吸收光谱仪、直流四探针等对PoPd nanobelt和Au@BACA表征结果表明:PoPd nanobelt长度约100μm,直径约200 nm;对PoPd nanobelt进行化学掺杂,其导电率可增加至5.5 S/m;Au NP直径约15 nm,且成功与BACA分子发生复合.采用扫描电子显微镜及元素成像技术、透射电子显微镜、万能试验机、红外热成像仪、显微镜等对水凝胶样品表征结果表明:凝胶呈现均匀、致密的聚合物网络;Au NPs均匀分散在聚合物网络中;凝胶导电率高达1.47 S/m;凝胶拉伸应变高达2400%,断裂强度高达1.2 MPa;修复电流强度为0.05 A,通电时间15 min时,自修复效率接近90%.可快速、高效电诱导自修复性的高强度纳米复合水凝胶对发展智能、柔性可穿戴电子器件具有重要意义.

Superhydrophobic coating on heat-resistant steel surface fabricated by a facile method

Industrial application of superhydrophobic surfaces is often hindered by complicated process and sophisticated machines. A facile wet etching method （sandblast, HCl and sandblast/HCl） with vapor deposition of PFDS （1H, 1H, 2H, 2H- perfluorodecyltriethoxysilane） was applied to fabricate superhydrophobic surface of heat-resistant steel used for vane. The coating component, surface morphology and surface roughness parameters of sample were observed by attenuated total reflectance Fourier transform infrared spectroscopy, scanning electron microscopy and atomic force microscopy. Static water contact angle （WCA） of samples with and without PFDS coating was measured by contact angle goniometer. The results showed that WCA values of polished, sandblast, HCl and sandblast/HCl-etched samples are 98°, 97°, 100° and 101°, respectively, and increase to 112°, 148°, 151 ° and 154v after vapor deposition of PFDS. The sandblast/HCl-etched sample with PFDS coating shows higher superhydrophobicity because of very large surface roughness and lotus protrusionlike structure. The superhydrophobicity of this fabricated surface has no obvious change after 38 cycles of the film adhesion test, indicating excellent durability.

Influence Factors Analysis of Fe-C Alloy Blocking Layer in the Electromagnetic Induction-Controlled Automated Steel Teeming Technology

In the electromagnetic induction-controlled automated steel teeming(EICAST)technology of ladle,the height and location of the blocking layer are critical factors to determine the structure size and installation location of induction coil.And,they are also the key parameters affecting the successful implementation of this new technology.In this paper,the influence of the liquid steel temperature,the holding time and the alloy composition on the height and location of the blocking layer were studied by numerical simulation.The simulation results were verified by 40 t ladle industrial experiments.Moreover,the regulation approach of the blocking layer was determined,and the determination process of coil size and its installation location were also analyzed.The results show that the location of the blocking layer moves down with the increase in the liquid steel temperature and the holding time.The height of the blocking layer decreases with the increase in the liquid steel temperature;however,it increases with the increase in the holding time.The height and location of the blocking layer can be largely adjusted by changing the alloy composition of filling particles in the upper nozzle.When the liquid steel temperature is 1550℃,the holding time is 180 min and the alloy composition is confirmed,the melting layer height is 120 mm,and the blocking layer height is 129 mm,which are beneficial to design and installation of induction coil.These results are very important for the industrial implementation of the EICAST technology.

Development of Monofluoroalkenes as Molecular Platform for Diversity-Oriented Syntheses of Tertiary Aliphatic Fluorides via Nickel/Manganese-Dual Catalysis

The selective introduction of fluorine atoms into drug candidates has long been used as a common strategy in drug discovery.Most methods used for the synthesis of tertiary aliphatic fluorides rely on C–F bond formation by fluorinating relatively stable tertiary carbon cation or radical intermediates,where the stoichiometric amounts of corrosive/expensive electrophilic fluorinating reagents were required.

Critical Shear Offset of Fracture in a Zr-based Metallic Glass

The nanoscale shear band operation process of Zr_（55）Pd_（10）Cu_（20）Ni_5Al_（10） metallic glass（MG）was reined in by constant force during well-designed loading-holding-unloading cyclic microcompression test.Through the test,it is revealed that the whole shear banding process involves three stages：shear band initiation,shear sliding and shear band arrest.Based on the energy balance principle,the size-affected speed of shear sliding is interpreted.The energy originated from the shear sliding leads to heat-up of the shear plane;therefore,the temperature in shear band increases with the size of shear offset caused by the energy accumulation during shear sliding.Taking the glass transition temperature as the critical temperature of fracture for the Zr-based MG,the critical shear offset is predicted to be approximately 190μm,fully in line with the experimental observation.This directly proved that the fracture of the MG is caused by the temperature rise during shear sliding.