Wireless Pressure Sensor Assisted Orthopedic Nursing Effectiveness Evaluation

This paper combines flexible pressure sensing technology, wireless sensor network, and cloud platform technology to design and manufacture a medical miniature pressure sensor and its supporting system. The problem of noninvasive monitoring of the syndrome encountered in the clinic is used for real-time monitoring and auxiliary diagnosis of the disease. Different from the current clinical use of “puncture” to measure intrafascial pressure, this system focuses on the noninvasive monitoring of compartment syndrome, using medical tape to paste a flexible microsensing unit on the injured area. The flexible sensor unit can measure the pressure here in real time and then can know the pressure in the fascia chamber. The flexible pressure sensor unit combines with the subsequent flexible circuit to send the measured data to the data in real time through wireless communication. The data aggregation node transmits the collected data to the upper computer through serial communication, and the upper computer software processes and stores the data and uploads it to the cloud server. In this experiment, it was observed that the concentrations of Ca and P showed the same fluctuating trend. With the gradual progress of the stretch, the concentrations of Ca and P increased with the increase in time, reaching approximately at the end of the extension. The peak value indicates that the osteoclast activity is enhanced at this time, the bone matrix is largely destroyed, and the Ca and P in the matrix are released into the serum in a large amount, thereby increasing the serum concentration. After the distraction ceases, it enters the healing period of the callus. At this time, the concentrations of Ca and P decrease with the increase in time and gradually reach a stable level, indicating that the osteoblast activity is enhanced at this time, the bone matrix begins to rebuild, and the Ca and P gradually increase. The deposited bone matrix gradually forms new bone and finally reaches a balance. Since the speed of extension in each experimental group is inconsistent, the time required to reach the same extension length is also inconsistent, so that the peak time is also inconsistent. After plotting the stress difference ( △ F ) before and after stretching against time and speed, it is found that the relationship is linear. However, these two variables affect △ F at the same time, so they cannot be isolated. Based on this, this subject uses multiple regression equations to fit the three relationships of stress difference ( △ F ), time, and speed. In the process of distraction osteogenesis, with each distraction, the bone stress presents a trend from high to low. And as the stretch progresses, the measured stress value increases linearly at the same time point every day.

Experimental and Numerical Simulation of Interlayer Propagation Path of Vertical Fractures in Shale

The complex fracture network formed by volume fracturing of shale gas reservoir is very important to the effect of reservoir reconstruction. The existence of bedding interface will change the propagation path of the hydraulic fracture in the vertical direction and affect the reservoir reconstruction range in the height direction. The three-point bending test is used to test and study the mechanical parameters and fracture propagation path of natural outcrop shale core. On this basis, a two-dimensional numerical model of hydraulic fracture interlayer propagation is established based on the cohesive element. Considering the fluid-solid coupling in the process of hydraulic fracturing, the vertical propagation path of hydraulic fracture under different reservoir properties and construction parameters is simulated. According to the results, the strength of the bedding interface is the weakest, the crack propagation resistance along the bedding interface is the smallest, and the crack propagation path is straight. When the crack does not propagate along the bedding interface, the fracture propagation resistance is large, and the fracture appears as an arc propagation path or deflection. The difference between vertical stress and minimum horizontal stress difference, interlayer stress difference and interface stiffness will have a significant impact on the propagation path of vertical fractures. Large injection rate and high viscosity fluid injection are helpful for vertical fractures to pass through the bedding interface, and low viscosity fracturing fluid is helpful to open the bedding interface. This research work is helpful to better understand the characteristics of bedding shale and the interlayer propagation law of vertical fractures, and to form the stimulation strategy of shale gas reservoir.

Development of Fracturing Technology for Deep Shale Gas in South Sichuan, China

Under the condition of high ambient temperature and high confining pressure，the physical & mechanical properties and in-situ stress state of deep shale will change noticeably. Normally, the deep-shale formation has high horizontal stress difference (about 11∼21 MPa, 1595∼3045 psi), high fracture-closure pressure gradient (about 0.023∼0.025 MPa/m, 1.017∼1.105 psi/ft), high breakdown pressure gradient (larger than 0.03 MPa/m, 1.327 psi/ft), low mechanical brittleness (about 42%∼55%), low difference between the vertical and the horizontal stresses (about 3∼5MPa, 435∼725 psi). The complex geological characteristics of deep shale increase the difficulity of fracturing: 1) effect of brittle/ductile transition under high confining pressure; 2) non-uniform propagation of multi-cluster fractures is more prominent; 3) the migration of proppant is difficult in narrow fracture network; 4) high friction and high pumping pressure; 5) more stringent requirements for fracturing tools; 6) high requirements for fracturing scale, efficiency and economy. To address above challenges, this paper presents a comprehensive overview of latest researching and applicable techniques about deep-shale fracturing (3500<TVD<3800 m, 11482∼12467 ft), including: 1) new evaluation methods on fractured shale quality and fracability, considering vertical stress difference coefficient and effective confining stress; 2) non-uniform propagation of fractures in multi-clusters perforation; 3) reveal the transport mechanism of proppant in narrow fracture network; 4) optimization of high performance fracturing fluid systems to enlarge the ESRV in deep shale; 5) development of a new staged fracturing tool for deep-shale fracturing, including dissoluble bridge plug and toe delayed sleeve; 6) an integrated geoscience and engineering simulation to optimize the treatment parameters and to achieve the best fracturing efficiency in the deep shale strata. The hydraulic fracturing technique for deep shale gas with the depth of 3500∼4500 m (11482∼14763 ft) has formed preliminarily. The hydraulic fracturing technology for deep shale gas (TVD≥3500∼3800 m, 11482∼12467 ft) have made a breakthrough in Sichuan basin, China, and significant progress has also made in 3800-4500m TVD (12467∼14763 ft). The research results and techniques introduced in the paper have been successfully applied to more than 100 wells in the Sichuan basin. The test production of part fractured well can reach (10∼31)×104 m3 per day (0.35∼1.09×107 SCF/day), which basically realizes the economical and effective development for deep shale gas.

Oscillatory Motion of Viscoelastic Drops on Slippery Lubricated Surfaces

The introduction of slippery lubricated surfaces allows the investigation of the flow of highly viscous solutions which otherwise will hardly move on standard solid surfaces. Here we present the study of the gravity induced motion of small viscoelastic drops deposited on inclined lubricated surfaces. The viscoelastic fluids exhibit shear thinning and, more importantly, a significant first normal stress difference N1. Despite the homogeneity of the surface and of the fluids, drops of sufficiently high N1 move down with an oscillating instantaneous speed whose frequency is found to be directly proportional to the average speed and inversely to the drop volume. The oscillatory motion is caused by the formation of a bulge at the drop rear that starts rolling around the moving drop.

An Analysis of the Impact of Deviatoric Stress and Spherical Stress on the Stability of Surrounding Rocks in Roadway

In this study, a detailed analysis was conducted to evaluate the impacts of the deviatoric stress component and spherical stress component on the stability of surrounding rocks in the roadway via the theoretical analysis and calculation and numerical simulation. Based on the analysis, the distribution laws guiding the main stress differences, plastic zone, convergence of surrounding rocks, and third invariant of stress under various conditions (such as equal spherical stress and unequal deviatoric stress and equal deviatoric stress and unequal spherical stress) were developed, providing an optimization scheme for roadway support misunderstanding under the conditions of high spherical stress field and high deviator stress field. The study further reveals that under the circumstance of the constant spherical stress, the greater the deviatoric stress, the plastic zone range of the surrounding rock of the roadway, the range of tensile deformation of the surrounding rock, the amount of convergence of the surrounding rock, the probability of separation of the roof and floor of the roadway, and the principal stress difference and the main stress, the greater the concentration range of the maximum stress difference is, and the maximum principal stress difference is mainly concentrated in the roof and floor rocks of the roadway, and the greater the deviatoric stress, the greater the probability that the roof and floor rocks of the roadway will be separated, and the maximum principal stress difference is mainly concentrated in the roof and floor rocks of the roadway, the greater the deviator stress, the greater the concentration range of the maximum value of the principal stress difference and the principal stress difference; when the deviator stress is constant, the range of the plastic zone and the maximum principal stress difference concentration range of the surrounding rock of the roadway decrease with the increase of the ball stress, and the principal stress difference, the amount of convergence of the surrounding rock, and the range of tensile deformation increase with the increase of the ball stress. The maximum principal stress difference is mainly concentrated in the roof and floor rocks of the roadway. The principal stress difference increases with the increase of the spherical stress, and the maximum concentration range of the principal stress difference decreases with the increase of the spherical stress. After the method proposed in this paper optimizes the actual roadway support on site, the surrounding rock deformation of the roadway is small and the control is relatively ideal, which basically meets the engineering needs.

Numerical Simulation for Fracture Propagation in Elastoplastic Formations

Current hydraulic fracture models are mainly based on elastic theories, which fail to give accurate prediction of fracture parameters in plasticity formation. This paper proposes a fluid–solid coupling model for fracture propagation in elastoplastic formations. The rock plastic deformation in the model satisfies the Mohr-Coulomb yield criterion and plastic strain increment theory. The extended finite-element method (XFEM) combined with the cohesive zone method (CZM) is used to solve the coupled model. The accuracy of the model is validated against existing models. The effects of stress difference, friction angle, and dilation angle on fracture shape (length, width), injection pressure, plastic deformation, induced stress, and pore pressure are investigated through the model. The results indicate that compared with elastic formation, fracture propagation in elastoplastic formation is more difficult, the breakdown pressure and extending pressure are greater, and fracture shape is wider and shorter. The plastic deformation causes the fracture tip to become blunt. Under the condition of high stress difference or low friction angle formation, it is prone to occur large plastic deformation zones and form wide and short fracture. Compared with friction angle, dilation angle is less sensitive to plastic deformation, fracture parameters, and fracture geometry. For the formation with high stress difference and friction angle, the effect of plasticity deformation on fracture propagation should not be ignored.

Determination of Cyclic Filling Length in Gob-Side Entry Retained with Roadside Filling and Its Application

Gob-side entry retained with roadside filling (GER-RF) plays a key role in achieving coal mining without pillar and improving the coal resource recovery rate. Since there are few reports on the cyclic filling length of GER-RF, a method based on the stress difference method is proposed to determine the cyclic filling length of GER-RF. Firstly, a stability analysis mechanics model of the immediate roof above the roadside filling area was established, and then, the relationship between the roof stress distribution and the unsupported roof length was obtained by the stress difference method. According to the roof stability above the roadside filling area based on the relationship between the roof stress and its tensile strength, the maximum unsupported roof length and rational cyclic filling length were determined. Combined with the geological conditions of the 1103 thin coal seam working face of Heilong Coal Mine and the 1301 thick coal seam working face of Licun Coal Mine, the suggested method was applied to determine that the rational cyclic filling lengths were 2.4 m and 3.2 m, respectively. Field trial tests show that the suggested method can effectively control the surrounding rock deformation along with rational road-in support and roadside support and improve the filling and construction speed.