Natural Gas Hydrate Decomposition Characteristics at the Exploitation Anaphase via Sediment Warming

Natural gas hydrates are typically deposited in low-permeability clayey-silty sediments with low gas production. The two main methods for enhancing gas production are complex structural wells and hydraulic fracturing. However, using only one of those methods does not significantly increase gas production. Herein, a method of combined multi-branch well with multi-stage fracturing was proposed. A novel evaluation method for increased gas production under fracturing was first proposed to reveal the effects of fracturing domain area and number. Then five fracturing distribution models were designed and analyzed. Results indicate that the combined method increased the gas recovery ratio by 829.13% and the hydrate dissociation ratio by 710.34% compared to branching wells because of enlarging pressure propagation and communicating deep thermal fluids. The dissociation of hydrates is enhanced by an increase in the area and the number of fractures, but the rangeability of the increased stimulating effect declines. Different fracture distributions influence production performances at different stages. Short-term production is beneficial when fractures are in the branch well centers. Long-term gas production can be improved when fractures are mainly located at the branch distal end. This novel study has important implications for commercial exploitation at different production stages. 

Enhanced gas production from silty clay hydrate reservoirs using multi-branch wells combined with multi-stage fracturing: Influence of fracture parameters

Experimental Study on the Depressurization of Methane Hydrate in the Clayey Silt Sediments via Hydraulic Fracturing

Progress and Application of Key Technologies on the Electronic Packaging Equipment Development

This article proposes a classifier-based approximator to compensate for friction in a high accelerated positioning system. Since friction function is globally non-smooth, an unsupervised k-means clustering algorithm is adopted to classify the friction into micro and macro motion segment, then the frictions are estimated with two sub-approximator in the corresponding segment respectively. Due to the unsupervised classification of friction, the classifier-based approximator can realize universal approximation of nonlinear friction with high precision. Finally, comparative experiments on a high accelerated position system driven by voice coil motors are conducted to verify the effectiveness of the proposed method. The proposed method can reduce the root mean square error (RMSE) of tracking by 57.2%, 19.1%, and 27.4% compared with a parametric model, recurrent neural network (RNN), and incremental extreme learning machine (I-ELM), respectively.

Classifier-Based Approximator for Friction Compensation in High Accelerated Positioning System

Reservoir stimulation offers the possibility to solve the problems of low single well production, small mining range, and short stabilized production in NGH field trials. Compared with traditional hydraulic fracturing, split grouting technology has the advantages of both enhancing the gas-water seepage capacity of the reservoir and maintaining the stability of the reservoir. In this study, a 2D discrete element method was used to establish a fine-scale model for NGH reservoir and numerical tests were conducted on split grouting. The pattern, direction and range of the grouting expansion were analyzed under different conditions of hydrate saturation, injection pressure, grout viscosity, injection well size, in-situ stress, and the number of injection wells. The results show that the grouting process can be roughly divided into two stages: squeeze grouting and split grouting. Squeeze grouting occurs in the early stages, and grout expansion is limited in the wellbore area. Subsequently, split grouting occurs always along the direction of the maximum principal stress when injection pressure is high enough, creating dendritic grout veins inside the reservoir and enhancing the connectivity inside the reservoir. Larger grouting range is achieved under lower in-situ stress, lower hydrate saturation or with lower viscous grout. The split grouting capacity can be enhanced with the increase of wellbore size or multiple wells. The results could help to deeply understand the grouting pattern and veins morphologies in natural gas hydrate reservoirs during split grouting and construct potential reservoir stimulation strategies. 

2D discrete element simulation on the marine natural gas hydrate reservoir stimulation by splitting grouting

The Z-axis motion acceleration of the wire bonding machine is very high (>100g) and may cause serious mechanical vibration and large impact force resulting in IC chip damage, optimal control of the impact force is one of the key factors to improve the bonding quality. How to reduce the vibration energy of the Z-axis motion in a very short time and reduce the force fluctuation is the main concern of this paper. Considering the effects of the mechanical motion, vibration and environment factor to the bonding control system, this paper proposed an improved fuzzy PID algorithm to control the overshot and fluctuation of the impact force. This algorithm inputs the deviation (e) of the system output and the variation rate(ec) of the system to the fuzzy controller, and outputs the fine-tuning value(ΔKp, ΔKi, ΔKd) of the parameters of the proportional, integral and differential gain. With the online adjustment of the PID parameters the system can rapidly adapt of any change. For the control scheme of the system, we adopted a Kalman filtering switch algorithm to predict the right switch condition for the fuzzy module control, which is based on the impedance current variation of the z-axis motor. The fuzzy PID control algorithm is simulated and compared with the conventional PID control algorithm through Matlab tool. The control algorithm is implemented and tested through bonding experiments. The experimental results indicated that the Z-axis impact force was reduced significantly and the force fluctuation was controlled within 3%, which will greatly improve the bonding quality of the wire bonding machine with high-speed motion.

Fuzzy PID control for impact force of high speed wire bonding process

This invention discloses a spatial cam mechanism assembly for feeding lead frame of chip adhering machine, which contains two-crossed spatial inclined plane for providing the driving force needed in XY plane and Z direction, the spatial cam rotated in one direction driven by step motor, through in turn starting, speeding, uniform speeding, reducing and stop etc process in one period, completing all action for feeding lead frame by rolling bearing, wrist support, slave arm and hook jaw of smooth level driving execution mechanism. Said invention can complete different productive demand by replacing cam.

Cylinder cam mechanism assembly for sticking machine lead frame feeding

Agriculture is a fundamental industry in China, contributing to economic and social development and historical progress. Therefore, China has also put forward the strategy of revitalizing the countryside to develop agriculture. And to achieve rural revitalization, rural infrastructure projects must be carried out. This paper elaborates on the development of rural infrastructure projects, and then identifies the current problems in the management of rural infrastructure projects in China: the legal system of project management has not yet been improved, the project management is not standardized, the construction cost, the construction schedule and the project quality are not coordinated, and the bidding is not rigorous enough. Finally, we propose measures to solve the problem: continuously improve the engineering management system, enhance the quality and knowledge of construction personnel, strengthen the safety supervision of rural infrastructure projects, and establish a warranty system for rural infrastructure projects to promote the construction of rural infrastructure projects in China.

Research on the Management of China's Rural Infrastructure Projects under the Background of Rural Revitalization Strategy

It was discussed the lead-frame driving structure moving along straight rail intermittently, especially the 3D cam in the designed Die Bonder. The driving part was controlled to fulfill scheduled moving rule by the curve of the 3D contour in the XY plane and Z directions. The contact structure was designed as two side slopes where contacted with the moving part of the 3D cam, by which the branched wrist rack could be forced by the two slopes and Z direction. In addition, the branched wrist could rotate around its geometry center axle, adjusting the contact state between the rollers and the cam surface automatically, to suit the turning movement of the slope contour of the 3D cam. The conveyor system could make the indexer insert the lead-frame, move forward, locate laterally, move back slight, exit from the lead-frame, and return to the start point in a circulation manner.

Design of Lead-Frame Driving Mechanical Structure of Die Bonder

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