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The scaling in tubing is a serious problem in Jingbian gas field, which leads to the increase of low production and low efficiency wells year by year. The production capacity of gas wells cannot be utilized effectively. In this paper, the scanning electron microscopy (SEM) was used to characterize the morphology of scale, and energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD) were utilized to analyze the composition of scaling products. According to the design of the plugging removal scheme, the scale-dissolving test of acid plugging remover was carried out. The results show that the scale samples have a three-layer structure, and the morphology of the three layers is quite different, but the chemical composition of the three layers is CaCO3. After adding acid plugging removal agent, the scale-like reaction is severe, a lot of gas escape, 40 h completely dissolved, no solid residue. Based on the test results and the production situation of Jingbian gas field, the scaling mechanism of gas wells is clarified, and the plugging removal scheme is optimized, which provides a basis for increasing production and efficiency of Jingbian gas field.

Jingbian gas-field is a low-permeability and lithological gas reservoir with strong reservoir heterogeneity and poorly physical properties. As the gas-field is getting older and older, its gas wells start to produce less, and have growing difficulties to lift water and finally fail to work normally and steadily. One inborn factor lies in the unstable liquid composition of Jingbian gas-field: salty formation water with easy-fouling ions and acidic gas such as CO 2 and H 2 S. Living in the underground for a long time these active materials prone to make the forming of water blocking and the solid deposition, which will weaken gas flow ability and threaten the production. After a detailed study on the plugging, there are three kinds of blocking divided: abruptly impurity blocking, slowly water locking, and energy deficiency. To relieve these blocking, methods have been put forth and carried out in field with achievement. The successful application has brought blockage gas wells solutions in Jingbian gas-field.

The pipeline conveying system as the gangue slurry filling technology lifeline. The occurrence of pipeline blockage will lead to the paralysis of the entire filling system; timely detection of pipeline blockage and early warning are needed to ensure the safe, stable, and efficient operation of the core elements of the coal gangue slurry filling system. Based on this, this paper summarizes and analyzes the classification of pipeline blockage and summarizes the current pipeline conveying blockage detection technologies. It elaborates in detail on the principles and advantages and disadvantages of existing pipeline blockage detection technologies, and points out that distributed optical fiber acoustic wave sensor (DAS), as an emerging fiber optic detection technology in recent years, can achieve high-precision, large-scale, real-time dynamic and distributed acoustic detection, Compared with traditional monitoring for pipeline blockage, it is more suitable for detecting blockage in coal gangue slurry pipeline conveying; then from the sensing principle of distributed fiber optic acoustic wave sensing technology, it discusses the current status of DAS technology application, analyzes the pipeline blockage DAS detection mechanism, and verifies the feasibility of pipeline conveying blockage detection based on the distributed fiber optic acoustic wave sensing technology by building a pipeline blockage DAS detection simulation experiment system; finally, it puts forward the feasibility of distributed fiber optic acoustic wave sensing technology; finally, it puts forward the feasibility of distributed fiber optic wave sensing technology detection. Finally, a pipeline blockage DAS detection and identification system is proposed, the function of each subsystem is introduced, and the core key technology involved in the pipeline blockage DAS detection and identification system is analyzed in detail, and the future development direction of gangue slurry pipeline conveying blockage DAS detection technology is also pointed out in order to provide reference for the development of the subsequent gangue slurry pipeline blockage and other pipeline conveying blockage DAS detection technology.

The blockage of natural gas pipelines caused by solid deposits such as hydrates is one of the major safety risks to transmission pipeline systems. The key to effective blockage relief or removal is to determine the location and severity of the blockage. In recent years, the pressure pulse wave method has been considered as a practical detection method due to its fast response time, simplicity of operation, and extended detection distance. Nevertheless, the current implementation of this method in pipelines indicates that the accuracy in detecting blockages is very low. To improve the accuracy of the pressure wave blockage detection technique in our experiments, a series of experiments were carried out to detect and locate hydrate blockages in natural gas pipelines based on the pressure wave method using a separate pipeline system of 22 mm diameter and 106 m length. The experimental results show that the accuracy of the blockage location prediction based on the pressure pulse wave method is within 5%. Still, the blockage’s cross-sectional shape can significantly affect the intensity of the reflected wave, with a maximum prediction error of 35%.

Millimeter wave (mmWave) technologies at 60 GHz and 100 GHz bands are currently gaining significant attention for its potential to meet the demanding needs of next-generation networks. These include ultra-high data rate, ultra-low latency, high spectral efficiency, and high end-to-end reliability. However, mmWave signals’ blockage remains a critical issue that affects the reliability of mmWave at 60 GHz and at 100 GHz bands due to the significant attenuations induced by the blockers (BLs). Not only blockers that have the size of a human body or even larger can affect the signal, but also smaller objects with much narrower dimensions, as narrow as 4 cm, can severely affect the signal strength and introduce an attenuation that reaches up to 12 dB at 100 GHz. In this paper we have conducted new measurements and presented results for three small copper sheets at each frequency band, aiming to investigate the blockage effect of small-sized metal objects on signal strength at these two frequency bands. Also, we have examined the performance of the knife-edge diffraction (KED) blockage model of the third-generation partnership project (3GPP) standards body and its evolved version named the mmMAGIC blockage model in such scenarios. Furthermore, we investigated the applicability of the two blockage models in capturing the attenuation characteristics of other materials-such as wood and glass. Experimental results supported by numerical models have shown that the induced peak attenuations are 5(12) dB, 10(23) dB, 23(23) dB for 4 × 4 cm, 8 × 8 cm, 16 × 16 cm copper blockers, respectively, at 60(100) GHz mmWave bands. Also, we have shown that both the 3GPP and mmMAGIC simulation models fail to accurately capture the attenuation characteristics of materials other than copper. The findings of this work highlight the importance of considering the dimensions and types of blockages when deploying reliable mmWave and sub-THz communications.

It is well known that a wake will develop downstream of a tidal stream turbine owing to extraction of axial momentum across the rotor plane. To select a suitable layout for an array of horizontal axis tidal stream turbines, it is important to understand the extent and structure of the wakes of each turbine. Studies of wind turbines and isolated tidal stream turbines have shown that the velocity reduction in the wake of a single device is a function of the rotor operating state (specifically thrust), and that the rate of recovery of wake velocity is dependent on mixing between the wake and the surrounding flow. For an unbounded flow, the velocity of the surrounding flow is similar to that of the incident flow. However, the velocity of the surrounding flow will be increased by the presence of bounding surfaces formed by the bed and free surface, and by the wake of adjacent devices. This paper presents the results of an experimental study investigating the influence of such bounding surfaces on the structure of the wake of tidal stream turbines.

【Background and objective】 Water-fertilizer integrated drip irrigation has advantages over traditional methods, including even fertilization, saving water and fertilizer, and precise control. However, emitter clogging is a problem limiting its widespread use. While emitter clogging is affected by various factors, the role of irrigation water temperature is poorly understood. This paper is to investigate the combined impact of temperature and working pressure on emitter blockage in a water-fertilizer integrated irrigation system. 【Method】 We used the plain channel emitter; the short-cycle intermittent irrigation clogging tests were conducted under temperature ranging from 15 to 30 ℃, and working pressures at 50 kPa (low) an 100 kPa (normal). Ammonium phosphates were used as the fertilizer and tap water as the irrigation water. Average water flow in the emitter was monitored; at the end of the experiment, the geometrical structure and composition of the clogging materials were analyzed using SEM; the blocking position in the emitter was also measured. 【Result】 Ammonium phosphate had a significant effect on clogging; irrigation reduced the average relative flow in the emitter by 15.03% 34.02%. Temperature rise increased the average relative flow, and the increase under the low pressure was greater than under the normal pressure. Irrigation increased the average relative flow by 18.55% under low pressure and 14.88% under normal pressure. The temperature did not affect the main components of the clogging material. The mechanisms underlying the blockage involve physical blockage by flocculation and replacement of ions in formation of the flocculation. However, increasing temperature weakened the flocculation and reduced surficial complexity of the blockage materials. In the emitter, the blockage was mainly located at the transition zone, the channel head, and the tail of the channel, which accounted for 29.75%, 22.31%, and 22.31% of the blockage, respectively. Changing temperature did not affect the blockage location. Therefore, it is recommended to optimize the structure of the transition zone, the channel head, and the tail of the channel to alleviate the blockage. 【Conclusion】 Increasing temperature can reduce flocculation thereby alleviating emitter blockage to some extent, regardless of working pressure.

With the explosive growth of mobile data demand, the fifth generation (5G) mobile network would exploit the enormous amount of spectrum in the millimeter wave (mmWave) bands to greatly increase communication capacity. There are fundamental differences between mmWave communications and existing other communication systems, in terms of high propagation loss, directivity, and sensitivity to blockage. These characteristics of mmWave communications pose several challenges to fully exploit the potential of mmWave communications, including integrated circuits and system design, interference management, spatial reuse, anti-blockage, and dynamics control. To address these challenges, we carry out a survey of existing solutions and standards, and propose design guidelines in architectures and protocols for mmWave communications. We also discuss the potential applications of mmWave communications in the 5G network, including the small cell access, the cellular access, and the wireless backhaul. Finally, we discuss relevant open research issues including the new physical layer technology, software-defined network architecture, measurements of network state information, efficient control mechanisms, and heterogeneous networking, which should be further investigated to facilitate the deployment of mmWave communication systems in the future 5G networks.

Worldwide, cerebrovascular accidents (stroke) are the second leading cause of death and the third leading cause of disability. Stroke, the sudden death of some brain cells due to lack of oxygen when the blood flow to the brain is lost by blockage or rupture of an artery to the brain, is also a leading cause of dementia and depression. Globally, 70% of strokes and 87% of both stroke-related deaths and disability-adjusted life years occur in low- and middle-income countries. Over the last four decades, the stroke incidence in low- and middle-income countries has more than doubled.

The arrangement of obstacles can significantly impact the deflagration behavior of combustible gases. In the actual pipeline accident site, liquefied petroleum gas (LPG) and other gases often show non-uniform distribution after leakage owing to diffusion and gravity, and the deflagration mechanism is also more complex. In this paper, based on the non-uniform distribution of combustible gases, the flame behavior and overpressure characteristics of LPG–air combustible gas deflagration are carried out by a combination of experiments and numerical simulations with obstacles arranged in increasing and decreasing blockage height. The results show that in the increasing blockage height arrangement, the flame forms a “straw hat” cavity, finally forming an elliptical region. In the decreasing blockage height arrangement, the flame appears as a “ribbon-shaped” narrow, blank area, which gradually becomes longer with time. By observing the overpressure and the structure of flame propagation in the coupled state, it is found that the explosion overpressure is maximum when the height of the obstacle is consistent, and the moment of the maximum area of flame appears slightly earlier than the appearance of the maximum overpressure peak. At the same time, without considering the change in height of the obstacle, the three arrangements all have an accelerating effect on the flame of deflagration. And the decreasing blockage height arrangement condition has the most obvious effect on the flame acceleration, which makes the peak of area of flame and the overpressure peak appear at first, and finally leads to the formation of a positive feedback mechanism among the speed of flame propagation, the area of flame and overpressure. In addition, in the case of the non-uniform distribution of combustible gases, the acceleration obtained by the flame at the initial stage is very important for the overall acceleration of the flame. The results of this paper can provide a reference for the placement of equipment and facilities in long and narrow spaces such as various pipe galleries, and to make predictions about the impact of the shape of some objects on the explosion and provide a theoretical basis for the prevention and management of gas explosions.