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.

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.

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。

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.

Complete duodenal obstruction induced by groove pancreatitis: A case report

BACKGROUND Groove pancreatitis(GP)is a type of chronic pancreatitis occurring in an anatomic area between the duodenum,head of the pancreas,and common bile duct.Duodenal obstruction is always caused by malignant pancreatic diseases,such as pancreatic head carcinoma,while is rarely induced by benign pancreatic diseases,such as pancreatitis.CASE SUMMARY A 39-year-old man presented with a 1-mo history of upper abdominal discomfort.His concomitant symptoms were abdominal distension,postprandial nausea,and vomiting.Contrast-enhanced computed tomography of the abdomen showed thickening of the intestinal wall with enhancement of the descending segment of the duodenum,which could not be clearly differentiated from the head of the pancreas.Upper gastrointestinal radiographs and gastrointestinal endoscopy showed a complete obstruction of the descending duodenum.An operation found that a 3-cm mass was located in the“groove part”of the pancreas and oppressing the descending duodenum.Pancreaticoduodenectomy was performed to relieve the obstruction and thoroughly remove the pancreatic lesions.The pathologic diagnosis was pancreatitis.The patient had an uneventful recovery with no complications.CONCLUSION Because of the special location and the contracture induced by long-term chronic inflammation,our case reminds surgeons that some benign pancreatic diseases,such as GP,can also present with symptoms similar to those of pancreatic cancer.This knowledge can help to avoid an unnecessary radical operation.

SIMULATION AND EXPERIMENT OF BUBBLY FLOW INSIDE THROTTLING GROOVE

The relationship between pressure distribution and cavitation （noise） inside throttling groove is investigated by numerical simulation and experimental method. A valve pocket with several transducers is performed to detect the pressure distributions inside the valve chamber, and the results fit quite well with the computational fluid dynamics（CFD） analysis. High-speed imaging techniques are employed to investigate the cavitation mechanisms, in particular bubble inception and cluster formation near the throttling groove. A spectrum analyzer is used to measure the sound pressure level of noise generated by the bubble flow. It is found that the pressure distributions inside the groove are sensitive to the valve port configuration and back pressure. The pressure distribution determines the bubble size and number passing through the valve grooves and the sound pressure level of noise induced by collapsing bubbles. The inlet pressure mainly affects the saturation degree of bubbly flow inside the groove and the intensity of sound nressure level accordingly.

Firm embedding behavior of annular grooved projectiles impacting ductile metal targets

Annular grooved projectiles(AGPs)have drawn ongoing concerns as an advanced penetrator for their excellent anti-rebound capability in impacting metal plates.They could become embedded solidly in the target surface during low-velocity impact.In this investigation,the firm embedding behavior of AGP was observed by impact experiments.Corresponding numerical simulations provided a better understanding of this process.Experimental and numerical results indicated that the firm embedding behavior of AGP was mainly due to the filling-material in the groove rather than the friction between the projectile and target,unlike traditional shape such as conical projectile.According to observation,firm embedding process can generally be subdivided into four stages:initial-cratering stage,groove-filling stage,fillingmaterial failure stage and rebound vibration stage.Moreover,the damage mechanics of target material around crater was obtained through microscopic tests.A comparison of the cross-sectional figures between the experiment and simulation proved that the analysis and the proposed method were reasonable and feasible,which further demonstrated that the firm embedding behavior has application potential in new concept warheads.

Erosion of Grooved Surfaces by Cavitating Jet with Hydraulic Oil

To study the effect of impingement surface geometry, a cavitation erosion experiment was conducted using a submerged cavitating jet rig with hydraulic oil. The test setup comprised a test chamber with a long-orifice nozzle, a hydraulic pump with an electric motor, hydraulic auxiliaries, including valves, a cooler, a filter, a reservoir, and measuring instruments, including pressure gages and a thermometer. Hexahedral specimens made of aluminum alloy with flat and grooved surfaces and oblique angles were prepared. Hydraulic oil with a viscosity grade of 32 was used at 40&degC as the test fluid. The upstream absolute pressure was kept at 10.1 MPa and the cavitation numbers were set at 0.02 - 0.04. The results of this experiment yielded the following conclusions. The mass loss of the grooved specimens did not increase monotonically as the exposure time increased. The standoff distances at the maximum mass loss for the flat and grooved specimens were almost equivalent. The mass loss decreased as the oblique angle increased and the cavitation number increased, regardless of the presence of grooves. The surfaces were eroded in a ring-like region, but the region elongated as the angle increased. For the grooved specimens, the ridges on the ring were eroded, and when the directions of the grooves and the flow matched, the roots and flanks were severely eroded.

Oblique Y-groove cracking test of the welding cold cracking susceptibility of domestic X-70 pipeline steel

Gas Transmitting From West to East Project' is significant. It should ensure the welding quality and safety of pipeline. The task is very arduous to guarantee the quality of the project in the condition of long line, complex weather and geology features. In this paper, the welding cold cracking susceptibility of domestic X 70 pipeline steel adopted by the project, which is one of the most interesting questions of welding quality about petrol pipeline, was studied by means of oblique Y groove cracking test. The crack ratio of surface and section was tested under the conditions of different welding materials and preheat temperature .The thickness of plate steel was 14.7 mm and 10.3 mm . The results reveal that X 70 pipeline steel has good crack resistance. The research has important value for the construction of large scale pipeline engineering and the application of domestic X 70 pipeline steel.

The Solids Conveying Mechanism for Helically Grooved Single-screw Extruders

A novel particle-size conveying model was established to examine the effects of the dimension relationships of the groove depth and particle size on the solids conveying mechanism of the helically grooved feed section. In the model, one or two shear interfaces were proposed based on the dimension relationships of the groove depth and particle size, and the solid-plug embedded in the groove and screw channel were divided into two or three layers by the shear interfaces to consider the solids conveying mechanism of each layer by the boundary condition equation for positive conveying. By the particle-size model, the effects of different dimension relationships on the transformation of solids conveying mechanisms between the friction-drag conveying and the positive conveying were discussed and compared with the on-line measuring experimental data. The results showed that the shear interfaces among the solids existed indeed and the dimension relationships determined the conveying mechanism and the throughput of helically grooved extruders, which was well confirmed by the excellent consistence between the predicted and measured data.

Azimuthal anchoring of a nematic liquid crystal on a grooved interface with anisotropic polar anchoring

Zhang Y J et al.[Zhang Y J,Zhang Z D,Zhu L Z and Xuan L 2011 Liquid Cryst.38 355] investigated the effects of finite polar anchoring on the azimuthal anchoring energy at a grooved interface,in which polar anchoring was isotropic in the local tangent plane of the surface.In this paper,we investigate the effects of both isotropic and anisotropic polar anchoring on the surface anchoring energy in the frame of Fukuda et al.’s theory.The results show that anisotropic polar anchoring strengthens the azimuthal anchoring of grooved surfaces.In the one-elastic-constant approximation（K11 = K22 = K33 = K）,the surface-groove-induced azimuthal anchoring energy is entirely consistent with the result of Faetti,and it reduces to the original result of Berreman with an increase in polar anchoring.Moreover,the contribution of the surface-like elastic term to the Rapini-Papoular anchoring energy is zero.