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To verify that water-methane displacement effect in gassy coal exists objectively, a pseudo-triaxial experimental system of water-methane displacement was independently developed and tested. First, methane was injected into the standard cylindrical coal sample until the methane adsorption equilibrium state was reached. Then, the methane in the coal sample spontaneously desorbed. Finally, water was injected into the coal sample. It is shown that: 1) water-methane displacement effect exists objectively; 2) water-methane displacement effect includes the process of free methane generated by competitive adsorption and displacement desorption effect, the consumption caused by methane pressure increase, and water driving methane; 3) competitive adsorption and displacement desorption between methane and water can generate free methane. Due to water injection, the increase of methane pressure leads to consumption of free methane. The net free methane of the combined action provides methane source for the water-methane displacement effect. [Received: August 19, 2017; Accepted: February 2, 2018]

Based on use conditions and functional requirements of the UAV photodetector stabilized platform, an overall design scheme of its control system is given. This system is studied from hardware and software. Development of the platform is prospected.

According to the working principle of a UAV-borne photoelectric platform, as well as the main functions and characteristics of the photoelectric platform ground control system, the overall design scheme and target of this system are proposed with an introduction of its composition and working principle. On this basis, the design and research of the system are carried out from hardware and software. Specific schemes of the two aspects are given. Finally, the future of the photoelectric platform ground control system is predicted on the trend of UAV-borne photoelectric platform.

Hanging roofs can occur on a very large scale (generally can reach 15,000 m2) during the initial mining stages in longwall coal mining operations and are often a result of hard roof at the active mining face. Besides, when it suddenly fractures and caves, some risks and disasters would occur such as shock loading, wind blasts, and sudden gas extrusion from gob to working face. To control the size and competency of the hanging roof, Φ32-mm fracturing drills can create holes in the roof near the front and back coal walls, and Φ32-mm linear fracturing drills can be used to create holes in the roof at the face ends. The length of these drill holes is 3 to 5 times the height of the mining face and is based upon the principle that the gob should be fully filled with a caved roof to support vertical stresses, as well as the assumption that the broken-expansion coefficient of the rock is given as an empirical value. Considering the fracture propagation range and the support form of the cut, the drill-hole spacing is set to be between 1 and 2 times the single-hole crack propagation range. Hydraulic fracturing can generate main fractures and wing-shaped branching cracks inside the roof rock and can transform and weaken the roof structure, forming weak fracture plane favorable to roof caving. These fractures cause the roof to cave in a timely and adequate manner under in situ ground pressures. Successful field test in the no. 2 mine of Cuncaota, Shendong group indicated that the propagation range of hydraulic fractures is approximately 4–8 m. When the active face advanced 22.5 m, the roof beyond the hydraulic supports caves entirely, and gradually, the gob is fully filled with the caved roof and is absent of large voids. Thus, hazards such as shock loading, wind blasts, and sudden gas extrusion can be reduced or eliminated.

Nimonic super alloy are extensively used in the aerospace industry because of its unique properties. As they are quite costly and difficult to machine, the machining tool is easy to get worn. To solve the problem, an experiment was carried out on a numerical control slitting automatic lathe to analysis the tool wearing conditions and parts’ surface quality of nimonic super alloy GH2132 under different cutters. The selection of suitable cutter, reasonable cutting data and cutting speed is obtained and some conclusions are made. The excellent coating tool, compared with other hard alloy cutters, along with suitable cutting data will greatly improve the production efficiency and product quality, it can completely meet the process of nimonic super alloy GH2312.

Hydrodenitrogenation (HDN) of isoquinoline (IQ) over Ni and Pd/C were investigated at 200 and 300°C under pressurized hydrogen. The results show that Ni is less active at 200°C but more active at 300°C than Pd/C for HDN of IQ. Raising reaction temperature from 200 to 300°C significantly increased nitrogen removal selectivity. π-Electrondensity of pyridine ring and cleavage of C–N bond were investigated and found to play important roles in HDN of IQ.

With hard roof conditions and the influence of side and front abutment pressures, pressure bump and large deformations periodically occur in the advanced support area of longwall face gob-side gateroads. To control the strong strata behaviours in gob-side gateroads, “directional hydraulic fracturing, to cut off the roof hanging over the adjacent gob area, and pre-fracturing of the roof, located behind the working face being extracted,” are performed. The directional initiation of hydraulic fracturing is controlled by pre-slotting, and this action guides the propagation of hydraulic fractures in three-dimensional space. The oriented fractures meet engineering requirements by cooperating with both the in situ ground stresses and the mining-induced stresses, as well as the technology of hydraulic fracturing. In field applications, hydraulic fracturing has proven to be a viable option for weakening hard roofs, destressing the side and front abutment pressures at the mining face and also transferring in situ and mining-induced stresses. Successful field tests in the Tongxin coal mine, Datong district, as well as other coal mines, show that hydraulic fracturing in both a hanging roof over an adjacent gob area and in the gob area behind the advancing working face controls the behaviour of strong strata material on the gob-side of gateroads in longwall mining and also guarantees safe extraction at the working face.

China is a country of vast territory with complicated geographical environment and climate conditions. With the rapid progress of the Chinese BeiDou satellite navigation system (BDS); more accurate tropospheric models must be applied to improve the accuracy of navigation and positioning. Based on the formula of the Saastamoinen and Callahan models; this study develops two single-site tropospheric models (named SAAS_S and CH_S models) for the Chinese region using radiosonde data from 2005 to 2012. We assess the two single-site tropospheric models with radiosonde data for 2013 and zenith tropospheric delay (ZTD) data from four International GNSS Service (IGS) stations and compare them to the results of the Saastamoinen and Callahan models. The experimental results show that: the mean accuracy of the SAAS_S model (bias: 0.19 cm; RMS: 3.19 cm) at all radiosonde stations is superior to those of the Saastamoinen (bias: 0.62 cm; RMS: 3.62 cm) and CH_S (bias: −0.05 cm; RMS: 3.38 cm) models. In most Chinese regions; the RMS values of the SAAS_S and CH_S models are about 0.51~2.12 cm smaller than those of their corresponding source models. The SAAS_S model exhibits a clear improvement in the accuracy over the Saastamoinen model in low latitude regions. When the SAAS_S model is replaced by the SAAS model in the positioning of GNSS; the mean accuracy of vertical direction in the China region can be improved by 1.12~1.55 cm and the accuracy of vertical direction in low latitude areas can be improved by 1.33~7.63 cm. The residuals of the SAAS_S model are closer to a normal distribution compared to those of the Saastamoinen model. Single-site tropospheric models based on the short period of the most recent data (for example 2 years) can also achieve a satisfactory accuracy. The average performance of the SAAS_S model (bias: 0.83 cm; RMS: 3.24 cm) at four IGS stations is superior to that of the Saastamoinen (bias: −0.86 cm; RMS: 3.59 cm) and CH_S (bias: 0.45 cm; RMS: 3.38 cm) models.

Considering the deficiencies of low accuracy and poor real-time capability in traditional UAV target location, a method of high precision localization of UAV image sequences based on DEM matching is proposed. By calculating the DEM data of aviation reconnaissance area in advance, the image sequences from UAV television reconnaissance are corrected, then by matching the DEM data again, the target location for sequence images is realized. The experiments show that this method can meet the requirements of high accuracy and real-time performance in target localization for image sequences.

Pocahontas No. 3 coal was extracted with CS2, n-hexane, benzene, methanol, acetone, and acetone/CS2 (1:1 vol/vol) mixed solvent sequentially. The resulting six extracts were analyzed with gas chromatography/mass spectrometer (GC/MS). Hexathiane, octathiocane, 23 sulfur-containing organic species, and 21 nitrogen-containing organic species were detected in the extracts. Sulfur-containing organic species detected in the extracts include dialkyl- and disulfides, dimexano, dibenzothiophene, benzonaphthothiophene, and their methyl-derivatives, among which dimexano and dixanthogen were seldom reported in any sediments. Methanol is effective for extracting sulfur-containing organic species without aromatic ring. Most of the nitrogen-containing organic species detected in the extracts are acridinone, carbazole and their methyl-derivatives, benzocarbazoles, amines, phenanthridinone, and piperidinone. The species number of nitrogen-containing organic compounds detected in the extracts increased with the in...

As more and more enterprises are willing to join the carbon emissions trading mechanism, it is necessary to explore a two-stage supply chain which includes upstream and downstream enterprises how to formulate the enterprise plans to reduce emissions. Through the study of internal carbon trading price of the carbon emissions trading alliance, we have a deep discussion for the decision of establishing the carbon emissions trading alliance. The results show that the upstream and downstream enterprises in the supply chain have respective optimal pricing and maximum profits before and after establishing the carbon emissions trading alliance. They choose to establish the carbon emissions trading alliance only in their respective alliance's internal carbon trading price range. Therefore, enterprises should obtain a mutually beneficial internal carbon trading price through negotiation to promote the establishment of carbon emissions trading alliance.

Considering the target location accuracy of the UAV airborne photoelectric platform, a parallelism detection method of optical axes was proposed, which including the design of collimating optical system and infrared up-conversion target. Digital image processing technology was utilized to realize the automatic, convenient and safe detection for the optical multi-axis parallelism.

Direct jet printing can assemble ceramic powder into a three dimensional shape by firing droplets of ink through a nozzle to build a multiple layered structure. As with stereolithography and selective laser sintering, the surface texture is expected to witness the layered assembly. The ability to create vertical walls by direct ink-jet printing was explored using a test piece based on a maze. The structure and topography are discussed in terms of droplet spreading and drying.

For a conventional SRAM, bit-lines dissipate the largest part of power consumption, since they are long lines with parasitical capacitance. Furthermore, the bit-lines consume more power in write cycle than in read cycle. A new charge-recycling method is proposed to reduce bit-line power consumption. The proposed SRAM pre-charge the bit-lines to VDD or GND respectively, they share the charge of adjacent bit-lines in write cycle. This is different from the former charge-recycling technique, because it does not need the additional voltage supply except VDD. SRAM cells also dissipate a lot of leakage power consumption in inactive cycle. The proposed SRAM uses non uniform cell method to reduce gate leakage. In this paper, a 64kb (4k∗16bits) 1-port SRAM is implemented with 100nm CMOS technology, the simulation results show that it reduces 32.9% leakage for SRAM cell in inactive mode, and 22% total power consumption to the conventional SRAM.

In order to study the seismic performance of steel frame with semi-rigid connections. Steel frames finite element model of engineering design was found using ANSYS finite element analysis software. Simulate to dynamic responses of steel frame with semi-rigid connections under seismic load. Numerical results show that seismic performance of steel frame with semi-rigid connections is well, and increase the ductility of steel frame, increase the natural periods of the lower modes, decrease the integral rigidity of steel frame, raise the structure lateral displacement within a certain range, reduce the column base shear.

An approach is proposed for medical three-dimensional reconstruction in view of the characteristics of modern medical image in this paper. The approach based on the traditional Marching Cubes algorithm combines with seed-occupying algorithm to expand isosurface for avoiding the detection of empty cubes and replaces cell edge interpolation by midpoint selection with DMC method. Finally, the isosurface is generated directly by polygons which are ordered by isopoints. Because the approach uses polygons instead of triangles without resorting to the pre-defined cases, it reduces the number of faces greatly and gives a good solution to the ambiguity problem. The experiment results show that the proposed approach makes a significant improvement in several aspects, including topological structure, storage space and processing speed than the traditional method. Therefore, it is propitious to real-time and interactive operation with computer by less hardware cost.

Improving brittle fracture prediction is crucial for structural integrity assessment. In current safety assessments, fracture mechanics treats polycrystalline steels as homogeneous continua. In reality, deformation of structural steels is heterogeneous. Part of this heterogeneity is due to the elastic and plastic anisotropy of their constituent (often randomly orientated) grains. This paper will compare the predicted failure stresses from tensile tests performed on a ferritic pressure vessel steel using the crystal plasticity finite element approach alongside measured carbide distribution and classical Beremin cleavage model. Available tensile data of 22NiMoCr37 steel at low temperature (−91°C and −154°C) were analysed using Bridgman solutions to account for the necking effect on the stress state at the centre of necking where brittle cracking initiates. This stress state imposed on representative volume element (RVE) made up of 10×10×10 randomly orientated grains, whose deformation is simulated using crystal plasticity finite element modelling (CPFEM). Randomly distributed carbides were produced based on the measured carbide size distribution and density for this steel. By assuming carbides as Griffith microcracks, the cleavage fracture stress in each grain can be assessed based the maximum principal stress on the cleavage crystal plane and an assumed surface energy. By repeating the random carbide distribution 1,000 times, brittle fracture probability can be calculated. Detailed examination shows that the above approach is actually a verification of the BEREMIN local approach model for cleavage fracture. The modelling results were compared with the available ductility data at −91°C and the interpolated ductility data at −154°C at the centre of necking. It is foreseen that this approach will lead to improvements in brittle fracture modelling in heterogeneous ferritic steels by introducing realistic surface energies and real defect distributions in specific materials, when used alongside the CPFEM submodelling approach.Copyright © 2008 by ASME

Brittle fracture can have potentially catastrophic consequences on the safety and integrity of engineering components. For this reason, the accurate prediction of cleavage failure probability is of importance in assessing the defect tolerance of high-integrity ferritic steel components, given the possibility of operation in the presence of significant loads at temperatures in the ductile-brittle transition range. In current safety assessments, fracture mechanics treats polycrystalline steels as homogeneous continua. In reality, deformation is heterogeneous, due to the elastic and plastic anisotropy of their constituent (often randomly orientated) grains. Heterogeneity at the micro (grain) scale is currently not considered by conventional fracture mechanics. This paper describes the initial results of a programme of work on a 22NiMoCr37 steel forging to assess the effect of micro-scale heterogeneity on cleavage fracture probability using an adaptation of the Beremin local approach model. The results of cleavage fracture modelling allowing for the effects of micro-scale heterogeneity are compared with the results of modelling based on the assumption of homogeneous materials behaviour. Application of the micro-scale heterogeneity model is providing some new insights into the prediction of cleavage fracture probability.Copyright © 2007 by ASME

A neural network based method of modeling hysteresis in piezo-electrical actuator is proposed. In this method, a hysteretic operator is introduced to transform the multi-valued mapping of hysteresis into a one-to-one mapping so that neural networks can be utilized to approximate the characteristic of hysteresis. The result of modeling the hysteresis exists in a piezo-electrical actuator using the proposed method is finally presented.

This study is an experiment of a new instructional model in classroom of higher education. Quantitative research methodology is employed in this study. Data are collected from 22 college students in the school of educational technology of a university. Findings indicate that 'many to one' mode participated by two to three students sharing one computer has a positive effect on the quality of learning. This contributes to the improvement in instructional quality of the college. As a result of this study, this paper advocates for an emphasis on experience-based computer-supported cooperative learning (ECSCL) in F2F classroom to facilitate the reform in higher education.

Microstructural observations of the 22NiMoCr37 “EURO” reactor pressure vessel (RPV) steel ring forging reveal that there is a banded structure along the radial direction, composed of alternate layers rich in bainite and ferrite of wavelength ∼1.5 ±0.75 mm. Heterogeneity at this meso (millimetre)-scale as well as at the micro (micrometre)-scale is currently not considered by conventional fracture mechanics. This paper describes the development of two numerical approaches aimed at incorporating such heterogeneity into the Beremin local approach model of cleavage failure, a model that has been used extensively for predicting the brittle fracture of ferritic RPV steels. The approaches developed combine the crystal plasticity finite element method (CPFEM) with continuum finite element analysis (FEA). CPFEM is applied to predict stress distributions at the microscale and to obtain phase-specific yield and flow properties for continuum FEA that derives stresses at the mesoscale. The results confirm that deformation heterogeneity on the micro- and mesoscales influences the local development of stress. At the microscale, the stress distribution within a representative volume of material located within the crack-tip plastic zone is shown to follow a normal distribution with a ratio of mean stress to standard deviation tending towards 0.1. These results indicate local stress levels that are within approximately ±20 % of those derived using continuum FEA. At the mesoscale, a periodic variation of stress is predicted within the larger representative volume. This variation is less dramatic than that observed at the microscale, though it still gives a spatial variation in maximum principal stress of approximately ±7 % between bainite- and ferrite-rich microstructural regions. These results suggest a significant influence of deformation heterogeneity on local stress levels, particularly at the microscale. However, the conventional Beremin cleavage fracture model, modified to account for microscale stress distribution, predicts only a modest influence of deformation heterogeneity on cleavage fracture probability, increasing Pf by just 5 %. This highlights the need to account for both the spatial variation in cleavage initiation sites as well as the distribution in stress throughout the microstructure. The paper describes one approach for this development.