Groove Walls Research Articles

Nanoimprint combination techniques

The combination of nanoimprint with optical lithography in a conventional mask aligner, both low-cost techniques, provides a number of novel but simple options for pattern definition with photoresists beyond nanoimprint or optical lithography. The effects exploited are based on two issues related to the interfaces at the bottom (substrate/resist) and at the top (resist/air); the bottom interface leads to a specific exposure situation with a reflective substrate like silicon, resulting in standing waves and a swing of the mean intensity in the resist; the top interface represents a pre-patterned surface providing phase shifting and diffraction when exposed. Both facts can be used to realize specific patterning results. We will show ‘residual layer free imprint’, frequency doubling with ‘residual layer lithography’, ‘hybrid lithography’ to overcome the pattern size dependence of nanoimprint as well as ‘multi-level structures’ resulting from diffraction patterns along the walls of lithography-defined grooves or inside the resist when thick layers are used. Major parameters for all effects are the resist thickness as well as the geometries of the stamp, in particular the stamp height. Furthermore, hierarchical wrinkling patterns can be induced by adding an exposure in the deep ultraviolet range to the hybrid process. The physical background of the effects will be addressed and examples of the single techniques are shown, indicating the requirements. With the physical understanding at hand the engineer is able either to make use of the effects shown or to avoid them, simply by choosing the boundary conditions of the combination process accordingly. The successful combination of nanoimprint with optical lithography relies on the fact that the imprint process does not change the properties of the imprinted material, in this case the optical ones, so that these can be exploited in a further processing step, namely lithography.

Understanding the friction and wear of KDP crystals by nanoscratching

Potassium dihydrogen phosphate (KDP) is an important nonlinear optical crystal material, and has been widely used in large-aperture high-power laser systems. This paper aims to explore the friction and wear mechanisms of KDP by nanoscratching using Berkovich and conical indentation tips. Two scratching loading modes, the ‘Constant’ and the ‘Continuous’, were applied. During the experiment, the moisture and temperature in the testing chamber were controlled. The study found that the adhesive force plays an important role when the scratching load is low. The lateral force or the friction coefficient fluctuates due to the non-uniform deformation of the KDP in front of the indentation tip. During a constant loading scratching, the frequency and amplitude of the fluctuation vary with the level of the scratching load and the type of the indenter, while the velocity effect seems to be trivial. The slip in the KDP crystal, which is very much affected by contact stress, could be a main mechanism of plastic deformation. The Berkovich tip produces more obvious wavy groove walls, while the conical tip brings about more ploughing deformation along the wear track. The strain rate in the range investigated in this study seems to have a little effect on the micro-plastic deformation.

Three-Dimensional Piston Ring–Cylinder Bore Contact Modeling

Increasing durability, preventing knocking combustion, improving fuel efficiency, and reducing pollutant emission characterize the needs for modern internal combustion engine design. These factors are highly influenced by the power cylinder system design. In particular, the piston ring to cylinder bore contact force distribution around the circumference of the piston rings must be optimized under all running conditions. To accomplish this, the ring manufacturers make the ring curvature nonconstant along the circumference. Most existing analytical tools are not able to simulate the variation along the ring circumference. In order to improve the understanding of this contact distribution and provide a high-fidelity ring design tool, a three-dimensional finite element piston ring model was developed to accomplish this variation. The modeling procedure and results are presented in this work. Experiments using a commercially available ring with negative ovality were conducted to validate the model. The ring free-shape profile and the ring cross section geometries were used as inputs to the model. Typical piston ring groove and cylinder wall temperatures were also model inputs to characterize thermal influences on the ring/bore interface forces. The ring/bore conformability was analyzed as a function of the ring radial displacements, cylinder bore constraint forces and thermal load changes to the ring. The model output showed radially separation gaps between the ring front face and the bore. This analysis provides an insight to evaluate the piston ring design. Together with an optimizer, the model can be used as a ring design tool to predict the ring free shape with a specified constraint force distribution pattern. Examples are given to demonstrate the capabilities of this numerical analytical tool. In addition, the 3D ring model can be used to improve the accuracy of existing lubrication, friction, and wear analysis tools and therefore improve the entire internal combustion engine power cylinder system design.

Study on grooved wall flow under rarefied condition using the Lattice Boltzmann Method

Decreasing energy consumption is a key issue for stratospheric airship to maintain its high altitude long-endurance feature. The airship envelope covered micro-grooves is considered as a feasible way to reduce resistance in order to save energy. The key to using grooves as the drag reduction technique is to evaluate its drag reduction ability under the condition of rarefied gas which is different from the original continuum atmospheric state. In this paper, the drag reduction ability of V-shape and rectangular micro-grooves under both continuum and rarefied condition is evaluated using the Lattice Boltzmann Method (LBM). This method modified for rarefied flow has been validated by the analytical solution in this paper. The local vortices are obviously observed within the grooves in the continuum and slippery flow regimes. The mechanism of drag reduction with grooves is elucidated at first and the ability of drag reduction under the rarefied condition is then evaluated by comparison of that under continuum condition. In the end, both the V-shape and rectangular grooved wall flow with different height and width are simulated. The relationships of drag reduction ability and the groove geometry are also determined and evaluated. Our results reveal that the grooves can reduce the resistance with a drag reduction rate of about 6% in the continuum. The drag reduction ability of the same grooves, however, decreases to 2.5% or less in the slippery regime. The grooves with appropriate size which make the vortices full within grooves can reduce shear force between fluid and wall. The results obtained in this paper are good references to the design of stratospheric airship envelope and the drag reduction technique.

Research on cross-sectional deformation of double-ridged rectangular tube during H-typed rotary draw bending process

Based on the ABAQUS/Explicit, a three-dimensional elastic–plastic finite element model of the H96 brass double-ridged rectangular tube (DRRT) during H-typed rotary draw bending (RDB) was established and its reliability was validated by an experiment. With the model, distribution characteristic of cross-sectional deformation and effects of clearance and friction coefficient between tube and dies and core number on it were studied. The results show that the maximum cross-sectional height distortion ratio appears at the bending angle 60°. And the maximum cross-sectional width distortion ratio between side walls, as well as side walls of the ridge grooves, appears at the bending angle 80° and 60°, respectively. In addition, retracting mandrel has a great effect on the cross-sectional height distortion, but its influence on the cross-sectional width distortion can be ignored. And the maximum cross-sectional distortion ratio initially increases with increasing of clearance between tube and mandrel cm and friction coefficient μb between tube and bending die, and then decreases with their increase, and initially decreases with the increase of core number N, and then increases with increasing of N. Moreover, the reasonable value of N is taken as 4.

Silver-decorated ZnO hexagonal nanoplate arrays as SERS-active substrates: An experimental and simulation study

Abstract

Groove Stability of Diaphragm Wall Excavation in High Confined Water Stratum

Based on the construction of diaphragm wall groove of Hangzhou metro station engineering and combined with construction practice, detection and simulation, the groove stability of diaphragm wall in high confined water stratum was studied in aspects of construction parameters and geological conditions. Studies have shown that, the high confined water stratum is an important factor in the groove stability of diaphragm wall, the buried depth of head should be reduced; the deformation of groove wall reduces significantly with increasing in mud specific weight; and the width of groove should be control well.

Visualization experiments for groove-wicked flat-plate heat pipes with various working fluids and powder-groove evaporator

This work experimentally compares the evaporation characteristics of three working fluids: water, methanol and acetone, in groove-wicked flat-plate heat pipes. In addition, the performance enhancement by filling copper powders in the evaporation section is investigated. The parallel, U-shaped grooves have a width of 0.25mm and a depth of 0.16mm. With stepwise increase of heat load, the behavior of the working fluid in the grooves is visualized and the evaporator resistances are measured. For all the three fluids, longitudinal liquid recession with a steep-sloped liquid front can be visualized above a certain heat load. Behind the short liquid front is the accommodation region where the meniscus appears to anchor on the top corners of the groove walls. Under a thermally stable situation, independent longitudinal oscillations of the liquid front exist in different grooves, forming a constantly varying zigzag front line. In response to increasing heat load, the liquid fronts gradually leave the heated zone, accompanied by increasing plate temperatures. Water exhibits the best performance with highest maximum heat loads and lowest evaporator resistances. However, the differences in the maximum heat loads for different fluids are much smaller than the differences in their figures of merit. No boiling is observed in the groove wick for all the three fluids. With the groove-powder evaporator, the evaporation performance is greatly improved for water. However, the improvements for methanol and acetone are not as significant as for water. Condensation modes for the three fluids are also compared. Dropwise condensation is observed for water, and film condensation for methanol and acetone.

STRUCTURE AND ULTRASTRUCTURE OF THE MOLLUSCAN PROSTATE

SUMMARY In Aplysia depilans Gmelin an actual and well differentiated prostate does not exist. The functions of this organ are probably accomplished by a large number of secretory cells placed along folds in the wall of the oviducal groove of the large hermaphrodite duct. Cells of the same kind are also contained inside diverticula arising from the external wall of the groove itself. This should be a first indication almost of the formation of a prostate as an organ in itself, placed outside the male gonoduct and independent of them within certain limits. Structure and ultrastructure of the prostatic tissue of the species examined so far by the Author, and represented, besides Aplysia depilans Gmelin, by Milax gagates (Draparnaud), Vaginulus borellianus (Colosi), and Laevicaulis alte (Ferussac), apart from a few differences in details, are quite similar. This tissue appears to be formed everywhere by two different types of epithelial cells: one secretory the other with no secretory activity, usually evenly...

Crack propagation under mode II dominance at stainless steel–epoxy interfaces with residual stresses and micro-scale roughness

This report describes investigations of grain boundary groove effects on mode II dominated interface fracture. The study focused on a specific interface between stainless steel and an epoxy adhesive. First, a finite element model was developed to simulate residual stresses and crack propagation. Second, the simulation results were compared with the experimental results from a previous study (Kanerva et al., 2013. Eng. Fract. Mech. 99, 147-158). Additional measurements were performed using atomic force microscopy. Based on the simulation, a 100-fold toughening effect due to the grain boundaries was determined. Implementation of flaws, in the form of interfacial voids, decreased the toughening effect by 35% and increased the mode II dominance significantly. The work underlines the practical importance of complete wetting by the adhesive and its necessary adherence to the grain boundary groove walls.

Development of a highly efficient hot-wire laser hybrid process for narrow-gap welding—welding phenomena and their adequate conditions

The purpose of this work is to develop hot-wire laser welding for narrow-gap joints. Test pieces of ASTM A 304 stainless steel with a gap width of 3 mm were used. With welding by tentative filler rod made of Inconel 600 alloy, melting phenomena of the molten pool and the weld bead formation during welding were investigated by in situ observation using a high-speed camera. Variations in the main welding parameters such as wire current, wire feeding position, laser irradiation angle, and wire feeding angle were investigated to determine appropriate conditions. Experiments showed that under the optimum welding conditions, hot-wire laser welding was able to produce complete weld deposition with very low dilution of the base metal. An experiment on laser beam reflection indicated that the laser beam reflected from the molten pool was a crucial phenomenon to explain the formation of the weld bead, especially in terms of melting the side groove wall of the base metal. Welding parameters as mentioned above significantly affected weld quality. Furthermore, in the case of welding with filler wire ER NiCrCoMo-1, the Vickers hardness distribution along the transverse welding direction was examined to evaluate weld properties and the bonding strength at the fusion interface was examined in a tensile test, and the results showed that there was no great difference in the hardness profile throughout the cross section of the weld plate. Additionally, metallurgical examination of the fracture surface revealed the rupture occurred at the weld metal, probably because the bonding at the fusion interface was stronger than the weld metal. Therefore, the development of laser welding with hot wire can advance the multi-pass weld for an ultra-narrow-gap joint.

Micro-structural geometry of thin films intended for the inner lumen of nerve conduits affects nerve repair

Damage to peripheral nerves can cause significant motor or sensory injuries. In serious cases, a nerve is sacrificed from another part of the body to repair a damaged nerve (autograft). The development of biodegradable polymer conduits may offer an alternative to autografts. This study investigated the surface topography and mechanical properties of smooth, pitted and grooved structures of ultra-thin poly (ε-caprolactone)/poly lactic acid blended, solvent-cast films. We have investigated the effect of the groove shape on cell morphology and alignment. Photolithography and dry/wet etching was used to develop patterned silicon substrates with grooves with accurate geometries (V shaped, sloped walls and square shaped). Using a neural cell line (NG108-15), in vitro experiments confirmed good cell attachment and proliferation on all the polymer scaffolds. Imaging techniques demonstrated that there was different cellular responses and morphology according to the shape of the groove. Studies showed that the geometry, particularly the angle of the slope and the space between grooves, affected cellular responses. In addition, biomechanical studies showed that the patterned films had excellent mechanical properties and were stronger than the natural nerve. The conduit tubes were made by rolling the films around a mandrel and using a thermal welding technique to join the edges. The promising biomechanical and in vitro results demonstrate that nerve cell responses are affected by the shape of longitudinal grooves, and particularly by the angle of the slope of the groove walls.

Development of an automatic cumulative-lead error measurement system for ballscrew nuts

Ballscrew is a precision mechanical component used to convert rotational motion to linear motion in the precision linear stage. The precision measuring system for the screw's cumulative-lead error is already well known. Up to now, however, there is no suitable measuring equipment for internal cumulative-lead error of the nut. For a matching pair, it is not reasonable to understand the quality of only one piece. This paper presents a developed automatic cumulative-lead error measuring system for ballscrew nuts. The nut is clamped by a rotational stage, in which the moving angle is detected by a rotary encoder. The probing ball is inserted into the nut and remains in contact with the thread groove of the nut. The probe arm is mounted on a linear slide so that when rotating the nut, the probing ball will be pushed by the groove wall and moved axially. A high-resolution diffraction scale is employed to detect the linear movement of the probe to nanometer resolution. Combining the angular and linear motions, the cumulative-lead error of the nut can be realized. In practice, however, the nut will cause typical spindle errors during rotating, including axial slip, radial run out, and tilt motions. These errors have to be compensated in order to guarantee the accuracy of measurement results. A multi-sensor error compensation system is thus developed. Experimental results show the applicability of this developed measuring system.

Theoretical analysis of plasmonic black gold: periodic arrays of ultra-sharp grooves

Periodic arrays of tapered grooves in gold surfaces are theoretically considered for turning high-reflectivity (shiny) gold surfaces into broadband low-reflectivity (black) surfaces, when illuminated by light polarized perpendicular to the groove direction, by making use of nanofocusing and subsequent absorption of gap-plasmon modes excited in the tapered grooves. The importance of realization of the adiabatic regime of nanofocusing, i.e. without reflection of plasmonic modes by tapered walls, is emphasized, and the taper angle that can be used for a given groove width without causing significant reflection is quantified. It is shown that nearly parallel groove walls at the groove bottom, i.e. ultra-sharp grooves, are required in order to sufficiently suppress the light reflection. Periodic arrays of V-grooves, and grooves with profiles described by a power-formula, are demonstrated to have much higher reflectivity levels than ultra-sharp groove arrays. Reflectivity spectra of ultra-sharp groove arrays are presented for a wide range of parameters, including the groove depth, bottom groove width, period, width of a flat plateau, and the angle of light incidence. Similar surface geometries in other metals are shown to have higher or smaller reflectivity levels depending on whether the metals are more or less absorptive than gold.

Turbulent Flow in D-Type Corrugated Pipes: Flow Pattern and Friction Factor

Turbulent flow in d-type corrugated pipes of various aspect ratios has been numerically investigated in terms of flow pattern and friction factor, for Reynolds numbers ranging from 5000 to 100,000. The present numerical model was verified by comparing the friction factor with experimental and numerical results from the literature. The numerical analysis suggested that d-type behavior exists for groove aspect ratios up to w/k = (groove width/rib height) = 2 independent of the pitch. However, for a ratio of w/k = 3 an important change in the flow pattern occurs so that the pressure drag exerted by the groove walls becomes important. It is shown that the friction factor is independent of the groove height as long as the flow is similar to a flow in a d-type corrugated pipe. Moreover, the friction factor curve for d-type pipes shows a logarithmic behavior as function of the Reynolds number, so that a simple method can be used to derive an expression for the friction factor as a function of the Reynolds number and the relative groove width only. The results may be useful to engineering projects that require a better prediction of the friction factor in d-type corrugated pipes.

Theoretical Study on Steric Effects of DNA Phosphorothioation: B-Helical Destabilization in Rp-Phosphorothioated DNA

Phosphorothioation, with sulfur replacing a nonbridging oxygen of phosphate, has surfaced in bacterial DNA electrophoresis. To understand structural characteristics of the thio-substituted DNA, we have investigated the correlation between the relative energy of phosphate/phosphorothioate linkage and the backbone torsions. The relative energies (R.E.) computed by the quantum mechanical method, the PBE1PBE(CPCM, solvent=water)//PBE1PBE/6-31+G(2df) level of theory, were used to construct energy-scoring functions against backbone torsion variables, resulting in the squared correlation coefficients r(2) of 0.90-0.95. Then, the DNA energy alteration by phosphorothioation is estimated with the relative energy difference (ΔR.E.) between phosphate and phosphorothioate of the phosphate linkages in the DNA crystallographic database (NDB). As a result, Rp-phosphorothioation shifts the relative energy of B-helical structures by 2.7 ± 3.4 kcal/mol, destabilizing about 95% linkages, while Sp-phosphorothioation by -1.4 ± 2.4 kcal/mol, stabilizing over 84% linkages in the data sets. The B-helical destabilization is likely caused by the steric effect between the sulfur atom of Rp-phosphorothioate and the neighboring C-H groups of deoxyribose on the groove wall in B-helix. The unfavorable interaction may be magnified by the increasing rigidness of P-O-involving backbone torsions α and ζ upon the nonbridging phosphorothioations. Since B-helix is the most prevalent DNA double-helical structure and Rp-phosphorothioation is the exclusive configuration in bacteria thio-DNA found to date, the observed stereospecificity-destabilization correlation may reflect a structure-function relationship of biological DNA-phosphorothiation.

Evolution of microstructure, texture and topography during additional annealing of cube-textured Ni–5at.%W substrate for coated conductors

Microstructure, texture and topography have been studied in a recrystallized Ni–5at.%W substrate before and after additional annealing at 1025°C for 1h. The initial recrystallized material contained a strong cube texture and a high fraction of low angle grain boundaries. Σ3 boundaries were also frequent in this substrate, including both coherent and incoherent twin boundary segments as well as non-twin Σ3 boundaries formed between twins and non-matrix neighbors of the cube texture component. A strong correlation between the boundary type and the average depth of grain boundary grooves was observed in this material. The smallest average groove depth was obtained for coherent twin boundaries, followed by low angle boundaries. Significantly greater average groove depths were found for the other boundary types. A similar correlation was also observed between the boundary type and the average inclination angle of groove walls. The additional annealing resulted in grain growth, texture strengthening and an increase in the fraction of low angle boundaries. Also, changes were observed in the extent of thermal grooving studied in the same regions before and after the additional annealing. Groove depths increased for a large number of stationary boundaries, whilst the majority of migrating boundaries developed shallower grooves compared to those before the additional annealing.

Side-Coupling Scheme for a High-Power Laser Diode Array With Grating Couplers: Thermal and Geometrical Issues

Grating couplers for side coupling of the light from a high-power laser diode array (LDA) into the inner cladding of a double-clad fiber were studied theoretically and implemented experimentally. In the experiments, two types of grating couplers were designed and fabricated: a gold-coated surface relief grating coupler and a gold-embedded silica grating coupler. A suitable design for heat dissipation for each grating coupler was employed to minimize thermal expansion due to the heat accumulated from the light absorption by the metal part of the grating coupler. The experimental results show that the gold-embedded silica grating coupler is superior to the surface relief gold grating coupler, because of its higher resistance to thermal expansion and better heat removal capability. In addition, the grating pitch and groove width were optimized for the highest overall coupling efficiency by taking account the backward diffraction loss and the groove wall nonverticality due to fabrication distortion. The experimental results show that the gold-embedded silica grating coupler is capable of coupling light power up to 21 W from a 976-nm continuous-wave LDA into the inner cladding of a 400- m-diameter double-clad fiber with an overall coupling efficiency of 50%.

Direct Side Pumping of Double-Clad Fiber Laser by Laser Diode Array Through the Use of Subwavelength Grating Coupler

An electron-beam-fabricated subwavelength grating coupler for direct side coupling of light emission from a high-power laser diode array (LDA) was studied theoretically and implemented experimentally. A gold-embedded silica-based design for grating coupler was employed to minimize the thermal expansion caused by the accumulated heat from light absorption by metal part of the grating coupler. In addition, with the consideration of the backward diffraction loss and the groove wall nonverticality caused by fabrication distortion, the grating pitch and groove width were optimized for the highest coupling efficiency. According to the experimental results, the grating coupler is capable of coupling light power up to 21 W from a 976-nm continuous-wave-operated LDA into the inner clad of a 400-μm-diameter double-clad fiber with an overall coupling efficiency of 50%. Furthermore, an LDA side-pumped ytterbium-doped DCF laser by using the grating coupler was demonstrated. By fine tuning the slow-axis collimation lens array, the laser-pumping scheme can easily be switched between bidirectional pumping and unidirectional pumping. Compared with the unidirectionally pumped fiber laser of the same gain fiber length, the laser slope efficiency of the bidirectionally pumped fiber laser was increased by 18% because of a better gain distribution over the fiber length. Finally, the signal output power of 10 W with a slope efficiency of 61% was achieved for the bidirectional side-pumped fiber laser.

Visualization and evaporator resistance measurement for a groove-wicked flat-plate heat pipe

This work experimentally studied the evaporation characteristics in a groove-wicked flat-plate heat pipe charged with water. The parallel, U-shaped grooves had a width of 0.25mm and a depth of 0.16mm. Uniform heating was applied to the copper base plate near one end, and a cooling water jacket was connected at the other end. The evaporator resistance was calculated based on the difference of the plate temperature and the vapor temperature respectively under and above the center of the heated zone. With stepwise increase of heat load, the behavior of the working fluid in the grooves was visualized and the evaporator resistances were measured. Above a certain heat load, longitudinal liquid recession with a steep-sloped liquid front could be visualized. Behind the short liquid front is the accommodation region where the meniscus appeared to anchor on the top corners of the groove walls. Under a thermally stable situation, independent longitudinal oscillations of the liquid front existed in different grooves, forming a constantly varying zigzag front line. With increasing heat load, the liquid fronts gradually left the heated zone, accompanied by increasing plate temperatures. The evaporator resistance first remained at a low value before local dryout appearing beyond a certain heat load and then increased in a growing pace in response to the expanding dryout zone. No boiling was observed in all present tests.