Failure Characteristics of Rock-like Mortar Specimens with Arc-shaped Flaws under Freezing-thaw Cycles and Uniaxial Compression

To investigate the freeze-thaw(F-T)damages and failure characteristics of rock mass with arc-shaped joints in cold regions,three types of cement mortar specimens with different central angles and prefabricated arc-shaped flaws are subjected to uniaxial compressive tests under different F-T cycles.Experimental observations show that the uniaxial compressive strength of specimens are significantly influenced by F-T cycles and their failure modes are mainly affected by the central angleαof the prefabricated flaws.Unlike the specimens with a central angle of 60°,the specimens with a central angle of 120°and 180°have greater curvature of flaws,so tensile cracks occur in the arc-top area of their prefabricated flaws.According to experimental images observed by environmental scanning electron microscope(ESEM),as the number of F-T cycles increases,the deterioration effect of the specimen becomes more obvious,which is specifically reflected in the increase of the mass loss,peak stress loss,and damage variables as a power function,and the peak strain decreases as a quadratic polynomial.According to numerical results using two-dimensional particle flow code(PFC2D),it is found that F-T cycles cause more damage to the specimen in the early stages than in the later ones.The area of the concentrated compressive stress zone in the middle is decreased due to the increased number of F-T cycles,while the area of the surrounding tensile-shear stress zone is increased.The models appear different failure modes due to the release of concentrated stress in different tensile-shear zones.

The Origins of the Arc-Shaped Langshan Uplift and Linhe Trench

In the northern part of the Ordos Basin, there is a 325 km long arc-shaped Langshan uplift and a 15 km-deep Linhe Trench in front of Langshan, which are rare geological phenomena for which origins no one has explained. This article comprehensively analyzes the research achievements over the past 40 years of geology, geomorphology, seismic exploration, paleogeography, and oil and gas exploration in the Ordos Basin and Langshan. It recognizes that the northern part of the Ordos Basin experienced a meteorite impact in the Late Cretaceous period. The impact pushed the block northwest ward, subducting after colliding with igneous rocks in the north. This sudden event formed a clear arc-shaped mountain zone in the north and a wedge-shaped trench in front of the mountain. The chaotic layers, prolonged and continuous faults, and numerous thrust layers in the Langshan, a negative anomaly area in the center of the northern Ordos, abnormal orientation of crystalline basement structures in the north of Ordos, Moho uplift, and distribution of meteorite fragments in the northwest of Langshan, all of these geological phenomena support the occurrence of the meteorite impact event, forming the arc-shaped Langshan and the Trench.

Deep-subwavelength single grooves prepared by femtosecond laser direct writing on Si

It is well known that femtosecond laser pulses can easily spontaneously induce deep-subwavelength periodic surface structures on transparent dielectrics but not on non-transparent semiconductors.Nevertheless,in this study,we demonstrate that using high-numerical-aperture 800 nm femtosecond laser direct writing with controlled pulse energy and scanning speed in the near-damage-threshold regime,polarization-dependent deep-subwavelength single grooves with linewidths of~180 nm can be controllably prepared on Si.Generally,the single-groove linewidth increases slightly with increase in the pulse energy and decrease in the scanning speed,whereas the single-groove depth significantly increases from~300 nm to~600 nm with decrease in the scanning speed,or even to over 1μm with multi-processing,indicating the characteristics of transverse clamping and longitudinal growth of such deep-subwavelength single grooves.Energy dispersive spectroscopy composition analysis of the near-groove region confirms that single-groove formation tends to be an ultrafast,non-thermal ablation process,and the oxidized deposits near the grooves are easy to clean up.Furthermore,the results,showing both the strong dependence of groove orientation on laser polarization and the occurrence of double-groove structures due to the interference of pre-formed orthogonal grooves,indicate that the extraordinary field enhancement of strong polarization sensitivity in the deep-subwavelength groove plays an important role in single-groove growth with high stability and collimation.

Research on the Influence of Raceway Waviness on the Vibration Characteristics of Deep Groove Ball Bearings

The dynamics model of a 2-degree-of-freedom deep groove ball bearing is established by incorporating the raceway surface waviness model comprising multiple sinusoidal functions superposition.The model is solved using the fourth-order Runge-Kutta method to obtain the vibration characteristics including displacement,velocity,acceleration,and frequency of the bearing.Validation of the model is accomplished through comparison with theoretical vibration frequencies.The influence of the amplitude of waviness of the inner and outer ring raceway surfaces of deep groove ball bearings on the vibration displacement,peak-to-peak vibration displacement and root-mean-square vibration acceleration is analyzed,and the results show that as the amplitude of the inner and outer ring raceway surfaces waviness increases,all the vibration characteristic indexes increase,indicating that the vibration amplitude of the bearings as well as the energy of the waviness-induced shock waveforms increase with the increase of the amplitude of the waviness.

Application of Grooved Negative Pressure Drainage Tube in Surgical Stabilization of Rib Fractures

Objective: To explore the application value of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation. Methods: Seventy-five patients admitted to our Department of Trauma Surgery from June 2022 to April 2024 who underwent rib fracture osteotomy and internal fixation were selected. According to the types of drainage tubes left in the patients after the operation, they were divided into the observation group (35 cases who were left with disposable grooved negative pressure drainage tubes) and the control group (40 cases who were left with closed silicone thoracic drainage tubes). Comparison of chest drainage, pain, postoperative complications, secondary chest penetration rate, drain placement time, hospitalization time, and treatment costs were compared between the two groups. Results: The total postoperative chest drainage volume of the observation group was less than that of the control group (P < 0.05);the degree of pain, the incidence of postoperative complications, and the rate of secondary chest puncture in the observation group were lower than that of the control group three days after the operation (P < 0.05);and the time of drain placement in the observation group was shorter than that of the control group (P < 0.05). Conclusion: The application of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation can significantly improve patients’ postoperative pain and discomfort, reduce complications, lower the rate of secondary chest penetration, promote patients’ postoperative recovery, decrease the amount of postoperative chest drainage, and shorten the time of drain placement, which is worthy of clinical promotion and application.

Duodenojejunostomy treatment of groove pancreatitis-induced stenosis and obstruction of the horizontal duodenum:A case report

BACKGROUND Groove pancreatitis(GP)is a rare condition affecting the pancreatic groove region within the dorsal-cranial part of the pancreatic head,duodenum,and common bile duct.As a rare form of chronic pancreatitis,GP poses a diagnostic and therapeutic challenge for clinicians.GP is frequently misdiagnosed or not considered;thus,the diagnosis is often delayed by weeks or months.The treatment of GP is complicated and often requires surgical intervention,especially pancreatoduodenectomy.CASE SUMMARY A 66-year-old man with a history of long-term drinking was admitted to the gastroenterology department of our hospital,complaining of vomiting and acid reflux.Upper gastrointestinal endoscopy showed luminal stenosis in the descending part of the duodenum.Abdominal computed tomography showed slight exudation in the descending and horizontal parts of the duodenum with broadening of the groove region,indicating local pancreatitis.The symptoms of intestinal obstruction were not relieved with conservative therapy,and insertion of an enteral feeding tube was not successful.Exploratory laparoscopy was performed and revealed a hard mass with scarring in the horizontal part of the duodenum and stenosis.Intraoperative frozen section analysis showed no evidence of malignancy,and side-to-side duodenojejunostomy was performed.Routine pathologic examination showed massive proliferation of fibrous tissue,hyaline change,and the proliferation of spindle cells.Based on the radiologic and pathologic characteristics,a diagnosis of GP was made.The patient presented with anastomotic obstruction postoperatively and took a long time to recover,requiring supportive therapy.CONCLUSION GP often involves the descending and horizontal parts of the duodenum and causes duodenal stenosis,impaired duodenal motility,and gastric emptying due to fibrosis.

Pipe reduction of miniature inner grooved copper tubes through rotary swaging process

A rotary swaging machine was applied to fabricating pipe reduction for miniature inner grooved copper tube （MIGCT） heat pipes. Compared with conventional swaging method, the axial feed of the designed rotary swaging machine was reached by a constant pushing force. The deformation of grooves in pipe reduced section during rotary swaging was analyzed. The shrinkage and extensibility of pipe reduction were measured and calculated. Furthermore, four aspects, including outer diameter, surface roughness, extensibility and processing time of pipe reduction, which were influenced by the pushing force, were considered. The results show that the tube wall thickness increases gradually along the z-axis at sinking section. However, the outer diameters, surface roughness and micro-cracks at reduced section tend to decrease along the z-axis. Besides, the effect of variation in the pushing force on the extensibility is limited while an increase in the pushing force results in a decrease of surface roughness. Therefore, a large pushing force within the limit is beneficial to pipe reduction manufacturing during rotary swaging process.

Analysis of circular-to-circular groove waveguide junction

Mode matching method is used to analyze the scattering characteristics of thecircular-to-circular groove waveguide junction. Matching the electric fields and magnetic fields atthe boundary of the junction, and multiplying the mode functions of the circular waveguide andcircular groove waveguide on both sides of the boundary equation, the scattering matrix equation isobtained, the scattering coefficients can be obtained from the equation. Then the scatteringcharacteristics of the iris with circular window in circular groove waveguide are analyzed. At lastthe convergent problem is discussed; when choosing a suitable mode group, convergent numericalresults are obtained, and the frequency response of the iris' scattering coefficients is also given.

重复的意义:流行音乐中的Riff/Hook/Groove

流行音乐作为一种大众艺术,在现代音乐生活中扮演着极为重要的角色。与古典音乐依托调性布局构建起来的庞大结构和民间音乐建立在地域族群基础上的民族文化叙事不同,流行音乐以其结构短小、形式简单、内容通俗、具有明确商业化和跨文化特征,成为20世纪影响最为广泛的艺术形式之一。本文以流行音乐创作中的技术手段为切入点,致力于讨论流行音乐得以广泛传播的技术原因及其中所隐含的哲学/美学意义。

基于Groove的网络协作学习活动设计与实施

Groove作为一种协作工具,在网络协作学习中起到了举足轻重的作用。文章在分析Groove功能和特点的基础上,结合协作学习和网络协作学习的概念与要素,提出Groove支持下网络协作学习活动设计方式及设计出学习活动案例,以有效指导基于Groove的网络协作学习活动的开展。

基于Groove的虚拟学习社区研究

虚拟学习社区给学生创造了更为自由、开放的学习环境。应用Microsoft Office Groove 2007构建虚拟学习社区,设计了基于Groove虚拟学习社区的学习活动设计流程。为了验证其应用效果,以"城市总体布局"为教学内容实施了教学,并设计了调查问卷调查应用效果。通过实践,得出结论:①虚拟学习社区的资源应以文本资源为主;②教师应适当参与到虚拟学习社区中以保持学生的积极性、主动性和参与性。

基于Groove的智能商务协作模块的设计

Groove平台利用P2P技术来改善客户服务和员工的工作方式,设计了一个基于Groove和.Net编程的定制化商务协作模块,尝试为分布式工作提供更加自动化的解决方案。

计算机音乐中Groove的真正涵义

计算机音乐作为电子音乐的一个重要分支，近年来随着微机技术的发展与普及得到了很广泛的推广应用。从理论上讲，技术的发展必然带动新兴理论的诞生与发展，这同样适用于计算机音乐领域，但在我国由于在这方面起步较晚，所以计算机音乐领域中尚存很多的理论空白。本文试图从以下几个方面来探讨国内尚无统一认识的Groove技术。

Friction properties of groove texture on Cr12MoV surface

To analyze the influence of surface texture on friction properties of Crl2MoV＇, ordinary grinder and spinning technology were adopted to obtain the grooved surface morphology of samples, and then the impact of spindle speed and feed in z-direction on surface morphology in the process of spinning was studied. In addition, the corresponding friction coefficient of sample was obtained through friction and wear tests. The results show that the peak clipping and the valley filling were conducted on the grinding surface, which could improve the surface roughness effectively and make the grinding trench-type wear scar more uniform. Both the area ratio of groove and groove spacing increased initially and then decreased with the increase of the spindle speed or the feed in z-direction. As a kind of micro-process, the groove could influence the friction coefficient of sample surface, whose distribution was beneficial to the reduction of friction coefficient. Compared with the surface obtained through ordinary grinding, grooved surface morphology through spinning technology was more conductive to reduce the friction coefficient, which could be reduced by 25%. When the friction coefficient of sample was reduced to the minimum, the texture of groove corresponded had an optimal area ratio and an optimal groove spacing, 37.5% and 27.5 μm, respectively.

Characteristics of a 0.1μm SOI Grooved Gate pMOSFET

A 0. 1μm SOI grooved gate pMOSFET with 5.6nm gate oxide is fabricated and demonstrated. The groove depth is 180nm. The transfer characteristics and the output characteristics are shown. At Vds = -1. 5V,the drain saturation current is 380μA and the off-state leakage current is 1.9nA;the sub-threshold slope is 115mV/dec at Vds = -0. 1V and DIBL factor is 70. 7mV/V. The electrical characteristic comparison between the 0.1μm SOI groovedgate pMOSFET and the 0. 1μm bulk grooved gate one with the same process demonstrates that a 0. 1μm SOI grooved gate pMOSFET has better characteristics in current-driving capability and sub-threshold slope.

Numerical analysis of loaded stress and central displacement of deep groove ball bearing

The aim of this work is to develop a three-dimensional model of deep groove ball bearing to investigate the loaded stresses and central displacements of bearing rings. The equivalent stresses and central displacements of bearing rings are obtained based on the simulated analysis. Moreover, several parameters, such as load magnitude, raceway groove curvature radius(RGCR), thicknesses of outer and inner rings, are varied to investigate their effects on the equivalent stresses and central displacements of bearing rings. Research results provide useful guidelines for determining the design parameters.

Numerical Modeling and Analysis of Grooved Surface Applied to Film Cooling

In order to improve the efficiency of film cooling, numerical investigation was carried out to study the effects of different film-cooled plates on surface heat transfer. Both grooved and non-grooved surfaces were concerned. The modeling was per- formed using Fluent software with the adoption of Shear-Stress Transport （SST） k-ωmodel as the turbulence closure. The coolant was supplied by a single film cooling hole with an inclination angle of 30°. The Mach numbers for the coolant flow and the mainstream flow were fixed at 0 and 0.6, respectively. At three blowing ratios of 0.5, 1.0 and 1.5, the aerodynamic behaviour of the mixing process as well as the heat transfer performance of the film cooling were presented. The numerical results were validated using experimental data extracted from a benchmark test. Good agreements between numerical results and the ex- perimental data were observed. For the film cooling efficiency, it shows that both local and laterally averaged cooling effectiveness can be improved by the non-smooth surface at different blowing ratios. Using the grooved surface, the turbulence intensity upon the plate can be reduced notably, and the mixing between the two flows is weakened due to the reduced turbu lence level. The results indicate that the cooling effectiveness of film cooling can be enhanced by applying the grooved surface.

Leakage and Stiffness Characteristics of Bionic Cluster Spiral Groove Dry Gas Seal

Spiral groove dry gas seal(S?DGS), the most widely used DGS in the world, encounters the problem of high leakage rate and inferior film stability when used in high?speed machinery equipment, which could not be well solved by optimization of geometrical parameters and molded line of spiral groove. A new type of bionic cluster spiral groove DGS(CS?DGS) is proved to have superior film stability than S?DGS at the condition of high?speed and low?pressure numerically. A bionic CS?DGS is experimentally investigated and compared with common S?DGS in order to provide evidence for theoretical study. The film thickness and leakage rate of both bionic spiral groove and common spiral groove DGS are measured and compared with each other and with theoretical values under different closing force at the condition of static pressure, high?speed and low?pressure, and the film stiffness and stiffness?leakage ratio of these two face seals are derived by the relationship between closing force and film thickness at the steady state. Experimental results agree well with the theory that the leakage and stiffness of bionic CS?DGS are superior to that of common S?DGS under the condition of high?speed and low?pressure, with the decreasing amplitude of 20% to 40% and the growth amplitude of 20%, respectively. The opening performance and stiffness characteristics of bionic CS?DGS are inferior to that of common S?DGS when rotation speed equals to 0 r/min. The proposed research provides a new method to measure the axis film stiffness of DGS, and validates the superior performance of bionic CS?DGS at the condition of high?speed and low?pressure experimentally.

Ejecta from periodic grooved Sn surface under unsupported shocks

Dynamic failure and ejection characteristics of a periodic grooved Sn surface under unsupported shock loading are studied using a smoothed particle hydrodynamics method. An ＂Eiffel Tower＂ spatial structure is observed, which is com- posed of high-speed jet tip, high-density jet slug, longitudinal tensile sparse zone, and complex broken zone between grooves. It is very different from the spike-bubble structure under supported shocks, and has been validated by detonation loading experiments. In comparison with that under supported shocks at the same peak pressure, the high-speed ejecta decreases obviously, whereas the truncated location of ejecta moves towards the interior of the sample and the total mass of ejecta increases due to the vast existence of low-speed broken materials. The shock wave profile determines mainly the total ejection amount, while the variation of V-groove angle will significantly alter the distribution of middle- and high-speed ejecta, and the maximum ejecta velocity has a linear corretation with the groove angle.

Influence Analysis of Secondary O-ring Seals in Dynamic Behavior of Spiral Groove Gas Face Seals

The current research on secondary O-ring seals used in mechanical seals has begun to focus on their dynamic properties. However, detailed analysis of the dynamic properties of O-ring seals in spiral groove gas face seals is lacking. In particular a transient study and a difference analysis of steady-state and transient performance are imperative. In this paper, a case study is performed to gauge the effect of secondary O-ring seals on the dynamic behavior（steady-state performance and transient performance） of face seals. A numerical finite element method（FEM） model is developed for the dynamic analysis of spiral groove gas face seals with a flexibly mounted stator in the axial and angular modes. The rotor tilt angle, static stator tilt angle and O-ring damping are selected to investigate the effect of O-ring seals on face seals during stable running operation. The results show that the angular factor can be ignored to save time in the simulation under small damping or undamped conditions. However, large O-ring damping has an enormous effect on the angular phase difference of mated rings, affecting the steady-state performance of face seals and largely increasing the possibility of face contact that reduces the service life of face seals. A pressure drop fluctuation is carried out to analyze the effect of O-ring seals on the transient performance of face seals. The results show that face seals could remain stable without support stiffness and O-ring damping during normal stable operation but may enter a large-leakage state when confronting instantaneous fluctuations. The oscillation-amplitude shortening effect of O-ring damping on the axial mode is much greater than that on the angular modes and O-ring damping prefers to cater for axial motion at the cost of angular motion. This research proposes a detailed dynamic-property study of O-ring seals in spiral groove gas face seals, to assist in the design of face seals.