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Hydraulic fracturing is the most effective technology to increase the productivity of low permeability CBM wells and the main way to increase single well production is to increase the length of hydraulic fractures as much as possible. In order to increase single well production, multi-micro-fracturing stimulation technology is put forth by this paper. The experiments of the migration and precipitation of proppant are carried out in ideal artificial hydraulic fracture and the Multi-micro-fracturing is simulated by Meyer. The pilot comparison experiment also carried out to verify the effects of Multi-microfracturing on the increase of single-well production. The conclusions stated that the sanding times has great impact on the migration distance of sand in hydraulic fractures and the more the sanding times are, the longer the sand bank is. Conventional fracturing technology results in the accumulation of sand near the wellbore, however, multi-micro-fracturing technology can facilitate the further migration of sand. The three-times fracturing technology can form much longer effective fractures and larger effective stimulation volume of coal seam and can stop the hydraulic fracture penetrating into the floor slab of coal seam effectively. So the three-times fracturing technology gets gas production up to 4200m3/d, 4 times of that of Conventional fracturing. So multi-microfracturing technology can significantly improve single well production and three-times fracturing technology is appropriate for the CBM formation in Southern Qinshui Basin. [ABSTRACT FROM AUTHOR]

In order to optimize wellbore shear failure criteria, this article, comprehensively, evaluated the application characteristics of Mohr Coulomb criterion, Drucker-Prager criterion and modified Lade criterion. At present, the research on the stability of the wellbore is mainly based on the classic Mohr-coulomb criterion, but lots of experiments show that the intermediate principal stress still has a huge impact on the rock damage. In order to accurately describe the influence of intermediate principal stress on the borehole wall stability, this paper applies the modified Lade criterion to wellbore stability analysis for isotropic stratum. Results indicated that Mohr-Coulomb criterion, which is linear and neglects the effect of intermediate stress, underestimates the strength and estimates the highest minimum mud pressure required to stabilize the wellbore. The Drucker-Prager criterion can provide a better estimation compared with Mohr-Coulomb. However, the modified Lade criterion that considering the effect of intermediate stress is the best failure criterion for determination of safe mud weight window. The in-situ stress distribution and the actual space state of the borehole also largely determine the stability of the borehole. The wellbore collapse pressure cloud pictures showed that the changing regularity and sensitivity of wellbore collapse pressure with deviation angle and azimuth angle is different. The research can be used to optimize borehole trajectory, avoid drilling accident-prone areas and improve drilling efficiency. [ABSTRACT FROM AUTHOR]

Typically, the required mud weight is determined by a wellbore stability analysis in which the rock material is assumed to be linear elastic, homogeneous, and isotropic in mechanics and strength behaviors. This traditional stability analysis, however, may lead to erroneous results particularly for a well drilled into fractured carbonate formation, and ignoring the strength anisotropy associated with planes of weakness such as foliations, or schistosity presented in carbonated rocks. Therefore, based on the porous elastic mechanics model of borehole stability and the single weak-plane strength theory, borehole stability model for inclined wells in fractured carbonate formations is established. Based on those, this paper quantitatively analyzed the effects of attitude of fissures and system researched the hole collapse pressure under different well track along with the change of weak plane occurrence characteristics. The basis for wellbore stability during drilling and production was provided. The results showed that collapse pressure is controlled by weak plane occurrence characteristics. Compared with traditional hole stability analysis model, the method of this article can provide a scientific calculated means and methods for solving the carbonate borehole instability. [ABSTRACT FROM AUTHOR]

Shale wellbore instability is a major cause of high cost and long time drilling and completion for shale gas. The effect of working fluid soaking on shale crack propagation and mechanical properties was analyzed to optimize drilling technology and protect wellbore stability. Response surface methodology is applied to study the influencing factors under working fluid soaking. The results show that radial holes play a certain guiding role in the directional propagation of hydraulic fractures in low permeability reservoir. Fractures start to crack and propagate a certain distance along radial holes, and then gradually divert to the maximum principal insitu stress direction of reservoir. The expansion of shale cracks after fluid immersion can be divided into two stages: the rapid formation of cracks and the slow extension of existing fractures; the shale rock strength is reduced after soaking of different fluids, and the shale rock mechanical parameters are immersed by drilling fluid. Significant changes have occurred, showing a decrease in elastic modulus and an increase in Poisson's ratio. After soaking with the same drilling fluid, the longer the immersion time, the greater the reduction in shale rock strength. [ABSTRACT FROM AUTHOR]

Image cloud detection is an important part of high spatial resolution remote sensing imagery (HSRI) information processing and analysis. The spectral threshold selection of image cloud detection and the influence of cloud-like ground objects are two vital factors in determining cloud detection results of HSRI. With respect to these two issues, a novel cloud detection method for HSRI based on the spectrum and texture of superpixels is proposed in the paper. First, the adaptive image cloud detection spectral threshold is obtained according to the image equalization histogram. Second, the initial cloud detection result is obtained based on spectral threshold of the cloud detection and spectral attributes of superpixels. Third, the initial cloud detection result is refined based on the gray value and angular second moment of the superpixels local binary patterns texture to eliminate the influence of cloud-like ground objects. Finally, the cloud detection result is processed using the region growing algorithm and expansion algorithm to obtain an accurate cloud detection result. The experimental results show that the proposed method can obtain good cloud detection results. [ABSTRACT FROM AUTHOR]

Currently, students in higher vocational schools in China are passive in classrooms and depend too much on cellular phones. Thus, structural readjustment of the teaching organization is urgently needed. Increasing proportions of gamifying teaching and experiencing teaching is an effective way to solve this problem. However, only a few studies have discussed the gamification of teaching reform in colleges. To improve the effectiveness of teaching and increase the participation of students in classrooms, the teaching reform idea and scheme of gamifying teaching and experiencing teaching were discussed in a course entitled Layout and Management of Distribution Center. The teaching reform aims to integrate comprehensive gamifying into the teaching of an entire curriculum. Specifically, small games are designed in each class during the early period to help the students learn the corresponding knowledge in games. A game-driven model of curriculum design was proposed and applied in teaching reform practice of Shijiazhuang Posts and Telecommunications Technical College. Results demonstrated that gamification of teaching reform achieves outstanding effects. Students participate in classroom activities positively, and all evaluation indexes improve year by year. Results confirm that teachers need to pay attention to systemization, gamification, and immersion of teaching design, and ensure the attractiveness and acceptability of the teaching method. [ABSTRACT FROM AUTHOR]

A facile visible-light-assisted method has been demonstrated to synthesize palladium (Pd) nanoparticles (NPs) with single-crystalline multiple-twinned structures by reduction of PdCl 2 . The structures and electrochemical properties of Pd NPs were investigated by high resolution transmission electron microscopy (HRTEM), UV-visible spectroscopy, and cyclic voltammetry (CV). The results show that the formation of different nanostructures depends on the control of reduction rate. Unlike multiple-twinned Pd NPs, single-crystalline Pd NPs exhibit surface plasmon resonance (SPR) peaks in the visible region. By comparison of the electrochemical parameters in the oxidation process of Pd NPs with single-crystalline and multiple-twinned structures, multiple-twinned Pd NPs exhibit the better electrocatalytic activity and anti-poisoning capability for ethanol oxidation. [ABSTRACT FROM AUTHOR]

Backgrounds: The level of job satisfaction among clinical research associates (CRAs) is of importance because it may affect CRAs' retention, turnover, and then further affect the quality of clinical trials. Objectives: The objectives of this study were to (1) examine the level of job satisfaction among CRAs in China and (2) explore the association between CRAs' demographic and work-related characteristics and their job satisfaction. Methods: A Chinese CRA job satisfaction questionnaire was developed to measure CRAs' attitudes in relation to their job. The questionnaire contained 6 subcomponents, including work content, work reward, supervisors, coworkers, investigators, and organization administration. Then an anonymous cross-sectional web-based survey was conducted among CRAs in China. Results: 465 valid questionnaires were received (93% response rate). The overall job satisfaction of Chinese CRAs was moderate. As for the individual subcomponents, coworkers ranked the highest and work reward ranked the lowest. The female group was more satisfied with investigators than were the male group. Different scores with supervisors were seen among age groups. Different scores with overall satisfaction, work reward, and organizational administration were seen among geographic location groups and also among company type groups. There were no significant differences in job satisfaction based on marital status, education level, and working position of the respondents. Conclusions: Chinese CRAs were moderately satisfied with their job. They were most satisfied with coworkers and most dissatisfied with work reward. Further, Chinese CRAs' job satisfaction levels were more related with work-related characteristics, including geographic location and company type. [ABSTRACT FROM AUTHOR]

Electrochemical behavior of Ce(III) and underpotential deposition of Al-Ce alloys were investigated at an Al active electrode in LiCl-KCl-CeCl 3 melts. Compared with the cyclic voltammetry curves on a Mo electrode, the redox potential of Ce(III)/Ce at the Al electrode is more positive; there are two new plateaus between the deposition plateau of Al and Ce metal by open circuit chronopotentiometry, which means two kinds of intermetallic compounds. All above show Ce(III) forms intermetallic compound by underpotential deposition electrochemically. Furthermore, it is also confirmed by Al-Ce alloys, which are obtained at the Al active electrode in LiCl-KCl-CeCl 3 melts after potentiostatic deposition under the same condition. The formation of AlCe and AlCe 3 is illuminated by X-ray diffraction (XRD). The reasons of AlCe and AlCe 3 formation were explained by XRD and phase diagram of Al-Ce. The standard Gibbs free energies of AlCe and AlCe 3 formation were calculated by XRD and open circuit chronopotentiometry. The analysis of scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) reveals that cerium exists at the surface of Al electrode to form an Al-Ce alloys layer, which is about 28 μm in thickness, and evenly coated the Al electrode. [ABSTRACT FROM AUTHOR]

In this paper, Pt-Cu (Ni, Co)/GNs-CD composites were prepared through aqueous solution synthesis method with NaBH4 as the reducing agent and β-Cyclodextrin (CD) functionalized graphene nanosheets (GNs-CD) as supporting materials. The introduction of the second metal (Cu, Ni, Co) makes bimetal alloy particles smaller in favor of high surface-to-volume ratios. Catalytic performances of as-prepared Pt-Cu (Ni, Co)/GNs-CD for methanol oxidation reaction (MOR) were investigated by cyclic voltammetry (CV), chronoamperometry, COads stripping voltammetry and electrochemical impedance spectrum (EIS). Compared with Pt/GNs-CD and commercial Pt/C, the Pt-Cu (Ni, Co)/GNs-CD composites exhibit an improved catalytic performance for MOR, suggesting that the introduction of non-precious metal is an effective strategy to improve Pt catalytic capacity. Especially, Pt-Cu/GNs-CD composite shows the best electro-catalytic performance among the as-tested three bimetal alloy catalysts. The superior catalytic activity of Pt-Cu/GNs-CD for MOR derives from the better modification of the electronic properties of Pt atoms and the stability of Pt-Cu alloy in acid media. [ABSTRACT FROM AUTHOR]

A two-bar thermal ratcheting procedure has been implemented to Alloy 617 at very high temperatures. The procedure is based on two bars tested on two coupled servo hydraulic machines to achieve equal displacement and constant total applied load, mimicking the behavior of a pressurized cylinder subjected to through wall thermal transients. The bars were heated and cooled out of phase to generate thermally induced loading superimposed on a constant mean stress. Scoping test results at slow heating and cooling rates are presented for different mean stresses and thermal histories. [ABSTRACT FROM AUTHOR]

This is Part II of a study on two-bar thermal ratcheting for Alloy 617. The ratcheting strains were evaluated for conditions with the same temperature range but with different mean stresses, heating and cooling rates, time delays, and thermal histories. These testing conditions were designed to be closely aligned to the development of design rules for strain limits at very high temperatures for Alloy 617. These new design rules have been formulated to address the fact that the effects of plastic deformation and creep deformation on the ratcheting strains are not separable at very high temperatures for this alloy. [ABSTRACT FROM AUTHOR]

The simplified model test (SMT) method is an alternate approach to determine the cyclic life at elevated temperature. It is based on the use of creep-fatigue hold time test data from test specimens with elastic follow-up conservatively designed to bound the response of general structural components. In this paper, the previously documented development of the SMT approach and applicable restrictions are reviewed; the design of the Alloy 617 SMT specimen, measurement issues and constraints are presented; initial test results and their application to a prototypic design curve are presented; and further testing and analysis for ASME code incorporation are discussed. [ABSTRACT FROM AUTHOR]

With advances in satellite maneuvering imaging capability, stereoscopic images with large roll and pitch angles can be captured to improve the efficiency of observations. At the same time, the influences of light aberration and atmospheric refraction on image positioning accuracy will be more significant. However, these errors are not accounted for in the traditional imaging and calibration model for optical agile satellites. In this study, the formation mechanisms of the aberration and atmospheric refraction errors in optical remote sensing satellite Earth observation imaging were analyzed quantitatively, and correction models were constructed. From this, the traditional geometric imaging model was refined by introducing a correction model for aberration and atmospheric refraction errors to create a more comprehensive geometric imaging model. The feasibility of an extended rational function model, based on the constructed more comprehensive geometric imaging model, was verified quantitatively. [ABSTRACT FROM AUTHOR]