Large Hole Diameter Research Articles

Experimental and numerical study on the formation and detachment of bubbles at orifices under the impinging jet flow

Three detachment patterns, i.e. single bubble pattern, double bubble pattern, atomizing pattern, are observed as the jet velocity increases. The bubble formation and detachment model are established, and the intensification mechanisms of the impinging jet on the bubble formation and detachment is revealed: Instantaneous flow field fluctuations changes the direction of the pressure difference force, forcing the bubble to detach and shortening the bubble growth time. The fluctuations of the flow field cause the total force on the bubble in the radial direction to be non-zero and the displacement of the bubble in the radial direction appears, which reduces the axial drag and the resistance of bubble to leave the orifice. In summary, under the effect of the impinging jet, the growth time of the bubble is shortened and the detachment size is reduced, which provides the possibility of producing small bubbles through large-diameter holes.

Effect of thermoplastic mask hole diameter on dose distribution in the build-up region of medical LINAC

This study aims to investigate the effect of variations in the hole diameter of unstretched thermoplastic masks offered by a single company on the dose distribution in the build-up region. 2, 2.5, 3 and 4 mm hole diameters masks with the same properties were irradiated with 6 MV X-rays and dose distribution was analyzed according to the open field. Dose measurements were obtained with a parallel plane ionization chamber. All irradiations were repeated for 5 × 5, 8 × 8, 10 × 10 and 15 × 15 cm2 beam fields. It was observed that the mask had a bolus effect in all measurements. It was observed that this bolus effect varied especially depending on the hole diameter in the mask. In a 10 × 10 cm2 field, the dmax depth without mask was 15 mm, while the dmax for masks with 2, 2.5, 3 and 4 mm hole diameters was 11, 12, 13 and 13 mm, respectively. It was observed that the mask hole diameter affected the dmax depth. Thermoplastic masks with large hole diameters increase the surface dose less than those with small hole diameters.

Experiment analysis on defects in ultrasonic-assisted drilling of carbon fiber reinforced plastic with different diameter drills

Carbon fiber reinforced polymers (CFRP) are increasingly used in aerospace, military, and automotive applications due to their high specific strength and corrosion resistance. CFRP components usually require small-hole machining before assembly. CFRP parts are susceptible to defects such as tears and uncut fibers during hole machining. Ultrasonic-assisted drilling (UAD) contributes to the suppression of their defects. However, preliminary experiments revealed that the effect at different diameters is not the same. Therefore, this paper innovatively compares the effect of ultrasonic-assisted machining on the suppression of defects under different hole diameters and investigates the mechanism. The effects of machining parameters such as ultrasonic power, feed rate, and rotational speed on burr and tear defects of holes under different hole diameters are experimentally studied and theoretically analyzed. It was shown that the lowest defective machined holes were obtained at 50% (4 μm) ultrasonic power for all hole diameters, while higher ultrasonic power would result in an increase in machining defects. Compared with small hole diameters, there are relatively fewer uncut fibers at large hole diameters, but the tearing defects are more severe. The defect suppression effect of ultrasound is more pronounced at larger holes. The change in cutting force due to ultrasound is an important reason for the difference in machining defects. At a diameter of 6 mm, the longitudinal cutting force decreased by 58.7%, while uncut fibers and tearing defects decreased by 45.1% and 12.6%, respectively. This study can provide a theoretical basis for the selection of ultrasonic power and other parameters when machining holes of different diameters.

Enhanced rotordynamic performance under various structural arrangements of hole diaphragm labyrinth seal

In this study, we study the influence of five drilling hole arrangements on the rotordynamic and leakage performance of hole diaphragm labyrinth seal (HDLS) type seals with precise CFD analysis. Key findings reveal that hole distance significantly affects direct and cross-coupled stiffness, thereby impacting stability and leakage. Notably, the smallest hole in rectangle four holes(RF)-HDLS does not yield the minimum leakage. Vortex structure analysis, employing the Q-criterion, elucidate horizontal two holes(HT)-HDLS's superior leakage reduction owing to enhanced turbulence eddy dissipation. Seals with larger hole diameters, down single hole(DS)-HDLS and up single hole(US)-HDLS, demonstrate stable rotordynamic performance, with DS-HDLS exhibiting a notable 106.3% improvement in cross-coupled stiffness. In contrast, seals with holes positioned farther away, DS-HDLS, US-HDLS and vertical two holes(VT)-HDLS, experienced increased leakage with whirl frequency. HT-HDLS and RF-HDLS displayed a decrease, attributed to the stronger centrifugal effect. Comparing to center single hole(CS)-HDLS, VT-HDLS and US-HDLS achieved a significant 159.3% direct stiffness improvement and 432.7% reduction in cross-coupled stiffness. Despite a maximum 4.2% leakage increase, this substantial enhancement in rotor stability should not be overlooked. Moreover, all seals exhibited lower leakage rates than the traditional labyrinth seal.

Interlevel Connections as a Way to Increase the Ventilation Efficiency of a Mine Ventilation Network - a Case Study

The exploitation of the deposit necessitates continuous optimisation of the ventilation network, as well as the need to change fans. One way of optimising the network and increasing the efficiency of ventilation may be to make interlevel connections in the form of large-diameter openings. In this study, simulation calculations were carried out by assuming the drilling of large-diameter holes and the selection of parameters for the main ventilation fans. An evaluation of the ventilation network was carried out by checking the validity of the simulation data with the actual data. The ventilation calculations showed that it is possible to increase the ventilation efficiency through the aforementioned method. The results of the calculations are presented with tabular data and simplified ventilation diagrams. The creation of at least one large-diameter opening and the upgrading of the main ventilation fans will ensure a minimum of proper functioning of the ventilation system. The drilling of a further opening will ensure that there is sufficient air in each ventilation area - an increase of 50% in the mine's air volume will be achieved.

INVESTIGATION OF ELECTROEROSION MACHINING PERFORMANCE OF METAL MATRIX COMPOSITE MATERIALS PRODUCED USING STIR AND INDIRECT SQUEEZE METHOD

In this study, metal matrix composite (MMC) materials were made with an aluminum matrix (AA7075 alloy) and reinforcement silicon carbide (SiC) elements using molten metal stir and indirect squeeze casting. SiC was used as a reinforcing element in the making of MMC material in different amounts (10%, 14%, and 18%) by mass. Electro Discharge Machining (EDM), cut depth (0.5 mm), three different pulse-on times, three different discharge current values, and a fixed pulse-off time (20 s) were used to machine MMC materials. The effects of machining parameters on machining time, average surface roughness, hole diameter, and material wear difference after machining were studied. As a result of the study, the composite material with 75 [Formula: see text]s pulse-on time, 6A current value, and 10% reinforcement element had the lowest machining time, the largest hole diameter, and the smoothest average surface. These machining parameters and materials also had the shortest machining time (5 min). Based on the signal-to-noise ratios, the best parameters for average surface roughness, hole diameter, Processing time, and material wear amount (MMC, discharge current value, and impact time) were found to be [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text], respectively. Based on the ANOVA results, the [Formula: see text]2 values for the average surface roughness, hole diameter, machining time, and material wear loss value were 99.3%, 98.7%, 77.8%, and 97.3%, respectively.

Modelling and evaluation of the post-hardness and forming limit diagram in the single point incremental hole flanging (SPIHF) process using ANN, FEM and experimental

In the single point incremental hole flanging (SPIHF) process, a sheet material with pre-cut holes is deformed using the SPIF technique to generate a flange, making it an effective approach for low volume manufacturing and quick prototyping. In the case of the SPIHF technique, the post-forming hardness property, the forming limit diagram (FLD), and spring-back phenomena are not completely evaluated. To this end, this paper employs experimental investigation and numerical validation to analyse the impact of SPIHF process parameters like tool diameter, feed rate, spindle speed, and initial hole diameter on these aspects for the truncated incrementally formed components made from AA1060 aluminium alloy and DC01 carbon steel. The plasticity behaviour of both sheet metals was simulated using the Workbench LS-DYNA model and ANSYS software version 18. Additionally, Cowper Symonds power-law hardening was added to the model to account for material properties. The average post-hardness of AA1060 and DC01 was evaluated using an SPIHF prediction model based on the performance of an artificial neural network (ANN). This ANN model was developed using a feed-forward back-propagation network trained using the Levenberg-Marquardt approach. The ANNs 4-n-1 were created by varying the transfer functions and the number of hidden neurons. Greater spindle speed and bigger pre-cut holes were shown to significantly increase the post-formed hardness of the truncated components, whereas the converse was seen when using a higher feed rate and a larger tool diameter. In addition, the FLD and spring-back improved dramatically with larger hole diameters. Employing correlation coefficient (R) and mean square error (MSE) as validation measures, it was shown that the established ANN models accurately predicted the SPIHF process response. Both the DC01 and AA1060 neural network models with a 4-8-1 network architecture performed very well, with MSE and R values of 0.0000105 and 1 for DC01 and 0.02613 and 0.99982 for AA1061.

A Study on the Relationship of Heat Exchanger Design Parameters with Water Lily Stem Profile by Robust Statistical Method

The study has successfully modeled and simulated a polymorphic tube based on the water lily stem using the robust statistical method and software. Taguchi analysis shows that the size factor E (Cross-section length of inner hole) with the effects values 39.89% has the most significant influence on the response temperature difference ((Δt) 0C). The size factor A (Peduncle diameter) has the most critical influence on the response pressure difference (ΔP (Pa)), with an effect value of 42.88%. The size factor C (Large inner hole diameter) with the significant effect value of 34.78% affects the response velocity difference (Δv (m/s)) the most. By ANOVA analysis, the results of response temperature difference analysis show that both the T-value and P-value of the size factor E (Cross-section length of inner hole) reach values that satisfy the setup requirements, with T-value reaching the most significant T-value 3.85 and the P-value 0.043 being smaller than the benchmark value 0.05, the final result indicated the size factor E (Cross-section length of inner hole) is the factor that has the most significant influence on the temperature difference of the model. For pressure difference, the results show that both the T-value and P-value of the size factor A (Peduncle diameter) reach values that satisfy the setup requirements, with the T-value reaching the largest T-value 12.19 and P-value 0.001 being smaller than the benchmark value of 0.05, the size factor A (Peduncle diameter) is the factor that has the most significant influence on the pressure difference of the model. For velocity difference, the results show that both the T-value and P-value of the size factor C (Large inner hole diameter) reach values that satisfy the set requirements, with the T-value reaching the largest T-value of 3.72 and the P-value 0.047 being smaller than the benchmark value 0.05, the size factor C (Large inner hole diameter) is the factor that has the most significant influence on the velocity difference of the model. Minitab software verification based on the Means graph drawn by Minitap17 software, the results show the best combination for response temperature difference is A3-B2-C1-D2-E2. Similarly, the best combination for response pressure and velocity differences is A2-B2-C3-D1-E1 and A2-B3-C2-D1-E3, respectively.

Discrete element study on mechanical response and pressure relief effect of rock containing variable hole

The traditional large-diameter hole pressure relief technology has the disadvantages of insufficient pressure relief in deep surrounding rock and damage to shallow surrounding rock. Therefore, an improved reaming hole pressure relief technology is proposed. A series of compression tests are conducted on numerical models with various hole parameters using the three-dimension particle flow code (PFC3D) to reveal the pressure relief mechanism of reaming hole technology. Firstly, numerical models for the pre-holed specimen are constructed, and the micro-parameters are calibrated based on the experimental results. Then, the evolution of crack initiation, propagation, and coalescence for pre-holed specimens are investigated by confined compression simulations in PFC3D. The relationships among the cracking process, stress-strain curve, and number of micro-crack are analyzed in detail. Finally, the spatial-temporal evolution of the stress field around the hole is discussed from the stress and force chain perspective. The research results could serve as a foundation for evaluating the pressure relief effect through stress and fracture monitoring methods on the surrounding rock mass.

Effects of the liner materials on penetration capability of explosively formed projectiles

Numerical simulations are carried out to study the effects of the liner material (Al, Cu, Mo, W, Ta) on the shape, mass, velocity, kinetic energy, length-to-diameter ratio, penetration depth and hole-diameter of MCT-83 mine (explosively formed projectile). The results of these parameters present the potential capability of each liner material used to fabricate explosively formed projectiles. Cu has get the maximum penetration depth value while Mo has the largest hole-diameter. The research results help to choose the material of liner suitable for each type of EFP warhead and for each different purposes.

Theoretical analysis of drilling cuttings considering stress zoning of surrounding rock and its application in stress detection

AbstractDrilling cuttings method is a commonly used method to detect the risk of rockburst, which has been widely recognized and applied in coal mines. However, in the current theoretical research on the relationship between drilling cuttings method and coal stress, it is generally considered that the mechanical parameters of coal at different positions of roadway are unchanged, and the influence of surrounding rock plastic zone and elastic zone is not considered. Therefore, according to the secondary distribution characteristics of roadway side stress, the theoretical calculation formula of drilling cuttings in the plastic zone and elastic zone of the roadway side is established in this paper. The example shows that the distribution of cuttings on the roadway side is obviously consistent with the abutment pressure. The cuttings in the plastic zone and the elastic zone are in linear and power function with the coal stress, respectively, and the cuttings in the plastic zone are greater than those in the elastic zone. With the increase of the hole diameter, the slope of the relationship curve between the drill‐cutting weight and stress gradually increases, and the response of the drill‐cutting weight with a large hole diameter to the change of coal stress is more obvious. The numerical simulation results show that the error of the theoretical calculation formula of the drilling cuttings method is less than 9%, which can meet the engineering application needs of estimating the drill‐cutting weight in coal and the stress of coal. Using the theoretical formula, the stress field in the leading area of the working face is measured, and the leading influence range and the accurate position of the high stress concentration area are determined, which provides more comprehensive stress information for the early warning of impact danger and pressure relief.

Enhanced thermoelectric performance of holey silicon thin films using F4TCNQ surface doping

Silicon thin films have great potential as chip-integrated Peltier micro-coolers and thermoelectric power generators due to their industry compatibility and cost effectiveness. Improving the thermoelectric figure of merit, zT, and therefore the device efficiency can be achieved by increasing the power factor while decreasing the thermal conductivity. In this work, we study single crystalline silicon thin films with patterned nano-holes with sizes comparable to the phonon mean free path to suppress thermal conductivity. The holey silicon thin films are then surface doped with organic molecules F4TCNQ to create a three-dimensional modulation doping scheme. As the dopants are outside the host material, there is less impurity scattering, which improves carrier mobility and the overall power factor. We fabricate silicon thin films with periodic arrays of nano-sized holes, with a fixed pitch size of 300 nm. By changing the hole diameters, we vary the neck size from 169 nm to 22 nm. The in-plane thermal conductivity, measured using the heat diffusion imaging method, demonstrates an order of magnitude reduction compared to bulk silicon and a change from 26 Wm−1K−1 to 5 Wm−1K−1 at room temperature. The films with large hole diameters allow space for the relatively large F4TCNQ molecules and hence effective surface doping, which is evident by orders of magnitude improvement in the electrical conductivity and power factor.

Failure mechanism of continuous large deformation and a novel pressure relief control technology on the two sides of deep coal roadway

Traditional intensive drilling (or grooving) technology in a roadway destroys the rock mass and supporting structure in the shallow anchoring area while implementing pressure relief. In Dongpang coal mine, it is difficult to avoid the failure of the supporting system and continuous large deformations of the deep roadways influenced by disturbance, despite the application of strong bolt (cable) supporting systems and grouting reinforcements. Therefore, this study proposes a novel “anchoring and pressure relief” synergistic supporting technique to eliminate the dilemma among the anchoring supporting and pressure relief. With strong anchoring supporting in the shallow surrounding rock, this novel technology realizes pressure relief by excavating large-diameter holes in the deep peak stress area, to enable active regulation of the move of the peak stress area to the deep surrounding rock without impairing the shallow anchoring area. The path of coal body rheology and stress move is cut off by large-diameter holes using this novel technology, achieving the purpose of absorbing energy and deformation, decreasing the stress applied on the supporting structure in the anchoring area. The novel technology effectively solves the control problems of continuous large deformation in deep roadway and has a good engineering application prospect. This study findings will add scientific value for the improvement of surrounding rock control of deep roadway.

Structure optimization of Spindt-type emitter fabricated by triode high power pulsed magnetron sputtering

Spindt-type emitters were fabricated with cavities made of Al/Mo/SiO2 using the triode high power pulsed magnetron sputtering method. We explored the process parameters (gas pressure and voltage of the additional cap electrode) to optimize the sharpness of the emitter shape. We found that the intermediate pressure and voltage were suited to obtain sharp emitters. Further, we elucidated the crucial effect of the cavity dimensions, such as the cavity depth and hole diameter in the cavity ceiling, on the emitter shape. At a cavity depth of 480 nm, the aspect ratio (AR) of the emitter increased monotonously with an increase in the hole diameter. With a large hole diameter (900 nm) and even shallower cavity (380 nm depth), we attempted to reoptimize the process parameters. Consequently, a very sharp emitter cone structure with an AR exceeding 1.3 was obtained. The cap voltage that produced the optimum AR was found to decrease for the larger-hole and shallower-depth cavities. Finally, the applicability of the process for preparing a working emitter is discussed.

Experimental analysis of three essential types of hole making strategies in aircraft assembly technology concerning delamination factor

Large-diameter hole drilling for Carbon-Fibre-Reinforced-Polymer (CFRP) is challenging because of its non-homogeneity and anisotropic features. This research will illustrate the hand-laminated and unidirectional CFRP based on three-hole making strategies for helical milling, large hole and pilot hole drilling. In this article, CFRP analyzes and optimizes axial cutting force and Delamination Factor (DF) based on experimental data collected at different FR (Feed Rate). CFRP's large diameter hole quality analysis includes cutting speed (Rotational Tool Speed) and scanning electron microscopy (SEM) analysis of helical milling, pilot hole and large hole drilling. A comparative study between large hole diameter, pilot hole drilling, and helical milling of CFRP was also conducted to discover the better technology for hole calibration quality by analyzing Machining Force (MF) and DF. According to experimental tests of CFRP laminates, the MF is proportional to the FR. Compared to helical milling, pilot hole drilling with proper cutting parameters can create superior quality holes. As a result, it is recommended that pilot hole drilling be done at a low feed rate and a high rotational tool speed for optimum hole quality. The hole calibration was analyzed to distinguish the cutting parameters (Cutting Speed, FR, and MF) to reduce DF and improve hole quality. Low FR was necessary for CFRP high-speed drilling because delamination at the hole exit was a concern.

Mechanism of Rock Burst and Its Dynamic Control Measures in Extra-Thick Coal Seam Mining from below the Residual Coal Seam to below the Gob

Abstract In this paper, aiming at the mechanism and regulation of overburden breakage induced by mining from the residual coal seam to the mined-out area, taking Kuangou Coal Mine as the background, the mechanism of rock burst from the residual coal seam to the mined-out area was revealed through the laws of overburden breakage and its structural evolution, ground pressure appearance, and energy release. The impact risk area is determined by the comprehensive evaluation results of multimethod face impact risk. A roof pressure relief and impact prevention control method using large-diameter empty hole combined with advanced deep hole blasting was formed, and the field verification was completed. The research results show that an obvious inverted trapezoid structure is formed when the residual coal seam of the W1123 working face is mined to the working face under the gob, which is related to the energy release caused by the occurrence of periodic pressure and the rupture of the critical layer. The shock ground pressure of the working face predicted by the neural network is mainly weak shock and medium shock risk; the numerical simulation analysis shows that the shock hazard area of the W1123 face below the solid coal is mainly located in the lower part of the working face near the transportation roadway and the shock below the W1145 gob. The dangerous area is about 32~72 m away from the return air alley. Through the plastic zone distribution and the orthogonal test, the optimal pressure relief scheme for large-diameter holes is 12 m in depth, 300 mm in diameter, and 2 m in spacing. When the blasting angle is consistent with the overlying rock fracture angle obtained from the simulation experiment, a better pressure relief can be achieved. When the bursting angle is consistent with the simulated overburden rupture angle, it has a better pressure relief effect. The pressure relief and anti-scour control method of large-diameter holes combined with advanced deep hole blasting reduce the daily average vibration frequency, energy, incoming pressure, and step distance of working face mining. The safe and efficient mining has a certain reference effect.

On the axial thrust and hydraulic performance of a multistage lifting pump for deep-sea mining

The multistage centrifugal lifting pumps are widely used for deep-sea mining to achieve high-head vertical transportation. However, the axial thrust caused by the multistage structure probably exceeds the carrying capacity of the deep-sea lifting pump. Mounting balance holes on the impeller reduces the axial thrust but also affects the pump’s hydraulic performance. In this research, the deep-sea mining pump’s axial thrust and hydraulic performance were studied. A computational fluid dynamics model of a two-stage centrifugal pump was established employing the whole-flow-field method. Numerical simulations on the transportation of pure liquid and solid–liquid mixtures were then carried out for an actual mining pump. Results reveal that the influence of balance hole position on hydraulic performance or thrust is insignificant. A larger hole diameter, contributing to an increased flow rate and ability to balance axial thrust, however, causes more flow losses and worse hydraulic performance. Furthermore, a test prototype pump was developed, and a non-destructive measuring device was exploited to acquire hydraulic parameters and axial thrust. The experimental results reveal the effectiveness of the proposed balancing scheme and numerical method. These findings could provide analytical methods and theoretical support for designing lifting pumps in deep-sea mining.

Impact of THT-hole dimensioning on manufacturability in selective wave soldering

Higher functional integration and increased electrical and reliability requirements are leading to increasingly complex printed circuit board (PCB) designs. Highly integrated PCBs with mixed SMT/THT assembly cause difficulties in soldering processes due to the thermal mismatch between heat demand and heat supply during soldering and the limited accessibility of THT-solder joints. This directly affects the manufacturability and robustness of the THT-soldering process with respect to sufficient hole fill according to typical quality standards like IPC-A-610. Partial hole fill also affects the mechanical reliability and fatigue resistance of a solder joint as well as its current carrying capacity and high frequency behavior. In the literature, several publications show the positive correlation between a larger hole diameter and vertical hole filling. In this paper, the fundamental relationships between hole diameter, hole filling and process robustness are investigated using design of experiments (DoE). It is shown that hole filling increases with increasing hole diameter, while keeping all other parameters constant. It was found that the process also becomes more robust at shorter solder contact times and lowers preheat temperatures. From these results, a general recommendation for larger THT holes in selective wave soldering can be derived. This is consistent with several other literature reports. In contrast to previous publications, it is not only shown how increasing the gap favors hole filling, but also what this means for the robustness of the soldering process to different PCB copper layer designs and soldering parameters. In addition, the impact of hole diameter is evaluated with respect to robotic component placement and back-end processes such as testing. A Gap-Ratio of 30–40 % is recommended for selective wave soldering to ensure robust soldering processes.

Evaluation of the effects of Ankaferd haemostat application on bone regeneration in rats with calvarial defects: histochemical, immunohistochemical and scintigraphic study.

Bone wax, a haemostatic agent, is widely used in craniospinal surgical procedures for a long time, in spite of controversial results regarding its negative influence upon bone regeneration. In this experimental study, the effects of Ankaferd Blood Stopper (ABS), as an alternative haemostatic agent, were evaluated through histochemical, immunohistochemical and scintigraphic studies. The total of 30 adult female Wistar albino rats was randomly divided into three groups: intact control group (n = 10), bone wax group (n = 10), and ABS group (n = 10). Surgically, a 3.0 mm hole in diameter was drilled on the right side of calvarium of the rats using a Class Mini Grinder set in all three groups, as described previously. At the end of 8 weeks, bone healing and connective tissue alterations surrounding drilled calvarial defect areas of the rats were determined via haematoxylin and eosin and the Mallory's trichrome staining and anti-bone sialoprotein immunohistochemistry. Image Pro Express 4.5 programme was used for histomorphometric calculation of new bone and fibrotic tissue areas. All statistical analyses were made with SPSS 25.0 and analysis of variance (one-way ANOVA) followed by Bonferroni post hoc test was performed, p < 0.001 was considered as significance level. Histomorphometrically, it was found that he had the largest hole diameter and the least fibrotic scar area in the bone-wax group. In the bone wax group, it was observed that the material closed the hole and there was only a fibrotic scar tissue in the area between the bone tissue at the edge of the hole and bone wax, and a fibrotic tissue was formed in the bone wax area. During the histological procedure, this bone-wax material was poured and the sections were seen as a gap in this area. In the ABS haemostat group, the smallest hole diameter and the least fibrotic scar tissue were observed. Fibrotic scar tissue close to each other was found in the ABS haemostat and bone wax groups. Histological analysis of samples also showed a statistical significance for fibrotic connective tissue area between groups (p < 0.05). Scintigraphically, osteoblastic activity related to blood flow in the animal taken from the group with application of ABS haemostat was more pronounced compared to the other two groups. In our study, it has been concluded that the ABS yields affirmative effects on the bone healing, while bone wax leads to negative impact on the bone regeneration. Scintigraphic, histochemical and immunohistochemical data support the affirmative impact of the ABS haemostat application upon the bone regeneration apart from the quick stop of haemorrhage.

Numerical Study on the Pressure Relief Characteristics of a Large-Diameter Borehole

Large-diameter drilling is an effective method for preventing rock burst disasters in coal mines. In this paper, the roadway stability of the W1123 fully mechanized caving work face of the Kuangou coal mine, located in northwest China, is investigated. A set of numerical modelling techniques were carried out to study the characteristics of stress, displacement, strain energy and the plastic zone of the roadway side rock with different parameters, including the large-diameter drilling hole diameter, depth and spacing. The results showed that: (1) after drilling, the peak values of the stress and strain energy are reduced and transferred to a deeper location, and the control effect presents a positive correlation with the diameter of the drilling hole; (2) when Lh &lt; LP, there are no pressure relief and energy release effects, which may induce impact, whereas when LP &lt; Lh ≤ 2.5LP, with the increase of the hole depth, the effects of pressure relief and energy release are enhanced, and further extension is not conducive to the long-term stability of the roadway; and (3) when the hole spacing decreases, the plastic zone and the broken zone between the holes are gradually penetrated, and the stress pattern transforms from a double peak to a saddle shape and then to single peak. Reducing the hole diameter reduces the efficiency of the plastic zone, failure zone and the stress form transformation between the boreholes, and weakens the pressure relief effect. Therefore, the main factor affecting the pressure relief effect is the hole diameter, and the secondary factor is the hole spacing. The engineering practice employed here showcases how a larger-diameter hole is an effective way of enhancing the effect of pressure relief and controlling the occurrence of rock burst. These research results are of great significance for guiding engineering practice.