Smooth Side Research Articles

Fabrication of micro-optical components in polymer using proton beam micro-machining and modification

Proton beam micro-machining (PBM) is a direct write lithographic technique that utilizes a high energy (MeV) sub-micron focused proton beam to machine or modify a material, usually a polymer. The technique has been developed in recent years at the Research Centre for Nuclear Microscopy, National University of Singapore where structures with feature sizes of well below 1 μm have recently been demonstrated. The PBM technique has several desirable features that make it suitable for rapid prototyping of micro-optical components. Structures made using PBM have very smooth side walls, high aspect ratio, and a scale that can be easily matched to existing optical fiber technology (0.1–1000 μm). Furthermore, PBM can also be used to modify the optical properties of polymers, particularly if the end of range is used. In this paper we demonstrate the use of proton beam micro-machining and modification for manufacturing micro-optical components in positive and negative resist. The structures that are fabricated can be used for both rapid prototyping and for large scale replication.

Asymptotics Without Logarithmic Terms for Crack Problems†

We consider boundary value problems for elliptic systems in a domain complementary to a smooth surface with boundary, which models a crack with its edge. The same boundary conditions are prescribed on both sides of the surface. We prove that the singular functions appearing in the expansion of the solution along the crack edge all have the form in local polar coordinates: The logarithmic shadow terms predicted by the general theory do not appear. Moreover, we obtain that, for a smooth right hand side, the jump of the displacement across the crack surface is the product of r 1/2with a smooth vector function. We present two different, but complementing, approaches leading to these results, and providing distinct generalizations. The first one is based on a Wiener–Hopf factorization of the pseudodifferential symbol on the surface obtained after reduction of the boundary value problem. The second approach concerns directly the boundary value problem and is based on a closer look at the Mellin symbol at each point of the crack edge. †Dedicated to Prof. W. L. Wendland for his 65th anniversary.

Computer-Aided Integration of Motions of the Discontinuous Mechanical System

Consideration was given to computer-aided modeling of the dynamics of multiple-link manipulators and other mechanical systems. Various perturbing factors that can affect this process were examined. Conditions for correct modeling that provides motions close to those of the physical system were established. Motion of the mechanical system is often described by differential equations whose computer-aided integration is usually defined as difference schemes that occur, for example, if finiteness of the integration step is taken into account. For the differential equations with smooth right-hand sides, sufficiently efficient methods of constructing an adequate scheme of integration were developed. The present paper focused on the mechanical systems where the generalized forces may be discontinuous. Construction of an adequate integration scheme for them is a challenge. Established were the conditions for motions of the difference scheme to converge to those of the system of discontinuous differential equations of the mechanical system.

Explosion et normes [formula omitted] pour l'équation des ondes nonlinéaire cubique

We find blow-up solutions of nonlinear wave equations with cubic nonlinearity, in any number of space dimensions, and study the asymptotic behavior of their L p norms and “energy”. The L p norm blows up if the blow-up surface has an interior non-degenerate minimum and p⩾ n/2. For less smooth right-hand sides, and 0< ε<1, we give examples for which the L p norm blows up if p⩾ n/(1+ ε); their Cauchy data are unbounded, but blow-up is not instantaneous. Applications to nonlinear optics are briefly outlined. To cite this article: G. Cabart, S. Kichenassamy, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 903–908.

Liapunov Functions and Stability in Control Theory. Lecture Notes in Control and Information Sciences 267

Liapunov Functions and Stability in Control Theory. Lecture Notes in Control and Information Sciences 267

Transfer Wicking Mechanisms of Knitted Fabrics Used as Undergarments for Outdoor Activities

This study investigates liquid transfer from fabric layer to layer and liquid interaction between different fabrics in clothing systems. A higher external pressure leads to an early onset of transfer wicking. There exists an optimum value of external pressure for the maximum water transfer. The greater the water content initially held in wet fabric, the greater the amount of water transferred. For fleece fabrics, no significant transfer wicking occurs if the raised side of the dry layer contacts either side of a wet fleece fabric layer. If the smooth side of the dry layer contacts either side of the wet fleece fabric layer, the amount of water transferred from layer to layer is greater when the fabric setting is face to face rather than face to back. An investigation of liquid interaction within clothing systems shows that the amount of liquid transferred largely depends on the performance of individual fabrics as well as the way in which they contact each other. Integrated double-sided Aquator fabrics, which serve as the first layer in the clothing system, transfer more liquid from the wet layer to the clothing system than other fabrics. Introducing a fleece fabric into the clothing system where the Aquator fabrics serve as the first layer promotes liquid transfer into the clothing system, but if polyester eyelet knit fabric serves as the first layer, introducing a fleece fabric decreases the amount of liquid transfer from the wet layer to the clothing system.

Heat Transfer in Rotating Rectangular Cooling Channels AR=4 With Angled Ribs

An investigation into determining the effect of rotation on heat transfer in a rib-roughened rectangular channel with aspect ratio of 4:1 is detailed in this paper. A broad range of flow parameters have been selected including Reynolds number (Re=5000–40000), rotation number (Ro=0.04–0.3) and coolant to wall density ratio at the inlet Δρ/ρi=0.122. The rib turbulators, attached to the leading and trailing surface, are oriented at an angle α=45deg to the direction of flow. The effect of channel orientations of β=90 deg and 135 deg with respect to the plane of rotation is also investigated. Results show that the narrow rectangular passage exhibits a much higher heat transfer enhancement for the ribbed surface than the square and 2:1 duct previously investigated. Also, duct orientation significantly affects the leading and side surfaces, yet does not have much affect on the trailing surfaces for both smooth and ribbed surfaces. Furthermore, spanwise heat transfer distributions exist across the leading and trailing surfaces and are accentuated by the use of angled ribs. The smooth and ribbed case trailing surfaces and smooth case side surfaces exhibited a strong dependence on rotation number.

Heat transfer in high‐aspect‐ratio rectangular passage with skewed ribs

AbstractThe heat transfer characteristics and flow behavior in a rectangular passage with two opposite 45° skewed ribs for turbine rotor blade have been investigated for Reynolds numbers from 7800 to 19,000. In this blade, the spanwise coolant passage at the trailing edge region whose thickness is very thin is chosen, so the channel aspect ratio (=width/height of channel) is extremely high, 4.76. Therefore the heat transfer experiment in the high‐aspect‐ratio cooling channel was performed using thermochromic liquid crystal and thermocouples. Furthermore, the calculation of flow and heat transfer was carried out using CFD analysis code to understand the heat transfer experimental results. The enhanced heat transfer coefficients on the smooth side wall at the rib's leading end were the same level as those on the rib‐roughened walls. © 2002 Scripta Technica, Heat Trans Asian Res, 31(2): 89–104, 2002; DOI 10.1002/htj.10018

Selective growth of GaN on a SiC substrate patterned with an AlN seed layer by ammonia molecular-beam epitaxy

Highly selective growth of GaN on 4H–SiC using the SiC substrate as a pseudomask has been demonstrated using the ammonia molecular-beam-epitaxy technique. A total lack of nucleation on the bare SiC surface was observed under typical GaN growth conditions. The nucleation of the GaN layer occurred preferentially from a patterned thin (300 Å) AlN seed layer, which had been predeposited on the SiC surface using the magnetron-sputter-epitaxy technique and patterned into parallel stripes by photolithography and chemically assisted ion-beam etching. Evidence of lateral overgrowth was observed by scanning electron microscopy and x-ray diffraction studies. The GaN stripes grown show extremely smooth side facets due to the lateral growth.

Self-assembled InAs quantum dots on InP nano-templates

InP nano-template structures with (0 0 1) top surfaces and atomically smooth crystallographic side facets have been controllably fabricated in situ for site-selective quantum dot nucleation studies using selective area chemical beam epitaxy. Deposition of a sub-critical layer of InAs on the nano-templates results in the nucleation of self-assembled quantum dots (SADs) exclusively on the (0 0 1) top surface as a result of the diffusion of InAs from the side facets onto the (0 0 1) surface. As the dimensions of the (0 0 1) top surface are decreased from 1000 down to 50 nm or less, scanning electron microscopy reveals a gradual increase in the spatial correlation between SADs, whilst linear arrays of uniform SADs are formed for dimensions below 200 nm. In addition, the density of SADs can be controllably varied by more than two orders of magnitude on the same sample by appropriate choice of nano-template dimension.

On a possible approximation of discontinuous dynamical systems

This work presents the arguments for the possibility of approximating some discontinuous dynamical systems with continuous or even smooth dynamical systems. The discontinuous differential equation, which describes the system, is transformed into a differential inclusion and then into a differential equation with continuous or smooth right-hand side. As an example a generalization of the equations governing Chua's circuit is presented.

PRELIMINARY STUDIES OF ASPHALTENE AGGREGATES BY LOW VACUUM SCANNING ELECTRON MICROSCOPY

A study of vacuum residue and asphaltenes from a Mexican oil refinery was performed using low vacuum scanning electron microscopy (LV-SEM) to determine the morphology of aggregates, and energy dispersive spectroscopy (EDS) to get the elemental composition of them. Irregular shaped particles were observed on vacuum residue, with a size range from 10 to 30 μm, that emerged from the oily fraction under the action of the electron beam. Those particles were sulphur and silicon rich. We also found some particles with important concentrations of Mg, Cl, K, and Fe. Asphaltenes precipitated with different n-alkane solvents showed slight differences in morphology. Fragile particles of several sizes were analyzed (230 × 130 μm to 730 × 240 μm); most of them presented a smooth face side by side with a rough one. Higher magnification of the smooth faces showed some randomly distributed pores. Rough facets tended to show larger pores. Some inclusions were also found; the sizes of those ranged from 7 to 25 μm. EDS revealed that sulphur and silicon are more abundant in the inclusions. Some Fe and Mg rich particles were also found. All the samples presented small amounts of V, and some of them Zn and Sn, whose concentration depends on the solvent used.

Shear Strength Characteristics of PVC Geomembrane-Geosynthetic Interfaces

Torsional ring shear and large-scale direct shear tests were conducted to investigate the shear behavior of polyvinyl chloride (PVC) geomembrane-geosynthetic interfaces. Specifically, the smooth and faille-finished sides of a 0.75 mm-thick PVC geomembrane were sheared against five different nonwoven geotextiles, a drainage composite, a geonet, and an unreinforced geosynthetic clay liner (GCL). Test results indicate that the smooth side of the PVC geomembrane yields a higher interface shear resistance than the faille-finished side due to the larger contact area and higher pliability of the smooth side. The interface shear behavior of the PVC geomembrane is compared to that of a high density polyethylene (HDPE) geomembrane and two very flexible polyethylene (VFPE) geomembranes. Faille-finished PVC geomembrane-nonwoven geotextile interfaces experience a post-peak strength loss of less than 25% at normal stresses between 100 and 400 kPa and no post-peak strength loss at normal stresses of 50 kPa and below. This behavior is attributed to the pliability of the PVC geomembrane, which enables (i) the geomembrane surface to be roughened, (ii) the other interface component to embed into the geomembrane as shearing progresses, and (iii) no texturing to be used that can damage the overlying geosynthetic. The effects of nonwoven geotextile fiber type, mass per unit area, and calendering on PVC geomembrane-nonwoven geotextile interface strength are also investigated.

Activities for Students: The Volume of a Pyramid: Low-Tech and High-Tech Approaches

This lesson came about spontaneously during a geometry unit on volume. I had used the lesson shown here in activity sheet 1, in which students use cubic blocks to rediscover the formulas for volumes of right prisms, that is, V = Bh and V = lwh. This lesson was a simple review for my tenth-grade class, and they completed it easily before the end of the period. With the wooden cubes still on their desks, most of them used the remaining time to build towers and other objects. I noticed that many students piled the cubes into bumpy pyramidal shapes. Because the next day's lesson involved studying the volume of pyramids, I wondered whether these bumpy shapes could be useful for discovering the volume of a real pyramid with smooth sides. Students could compare the volumes of these “pyramids of cubes” with the volumes of corresponding right prisms and perhaps discover the ratio 1/3 to obtain the formula for the volume of a pyramid, V = (1/3)Bh. As it turns out, the ratio of 1/3 does not become evident right away. To my students' delight, we found that using a spreadsheet is an excellent way to investigate this problem. My geometry classes had not used spreadsheets before, and the students enjoyed the experience of using the efficiency of technology to compare hundreds— and even thousands—of shapes with ease.

A Study of Ion Beam Etching of Polymethylmethacrylate Using N2 and N2/O2-Mixtures

The influence of process parameters such as gas composition, kinetic energy of the ions and sample temperatures was studied in order to discuss the dry etching mechanism of polymers. First, we investigated polymer dry etching using N2 gas and verified that the heating temperature was the critical parameter in the case of polymer dry etching. Next, polymer dry etching was carried out using N2–O2 gas for obtaining smooth vertical side walls. The experimental results revealed that the generation of neutralized reactive species needed to be suppressed to form smooth vertical side walls.

Physical features of grass leaves influence the placement of eggs within the plant by the Hessian fly

AbstractHessian fly eggs are more likely to be found on adaxial rather than abaxial surfaces of wheat leaves. These leaf surfaces differ in their physical features: the adaxial side of the leaf has parallel grooves and ridges while the abaxial side is relatively smooth. We used leaf models to investigate the relationship between Hessian fly egglaying and these physical features. When both sides of a green paper leaf model were treated with a wheat leaf extract, but only one side of the model was scored with parallel grooves, the grooved side received more eggs than the smooth side. As the number of grooves per surface increased from 0 to 10, eggs per model increased. When grooves and the wheat leaf extract were tested together and separately, the grooves significantly increased egg numbers in the presence, but not the absence, of wheat extract. In contrast, wheat extract increased egg numbers both in the absence and presence of grooves. Molding techniques were used to recreate the physical features of the adaxial and abaxial leaf surfaces of five grasses. For four of the grass genotypes (a triticale, two common wheats, and a durum wheat), patterns of egglaying on real leaves and molded models were similar, i.e., adaxial leaf surfaces and adaxial molded models were preferred over abaxial leaf surfaces and abaxial models. On the fifth grass, oat, preferences for the adaxial side of real leaves and for adaxial models were not as obvious. We conclude that the adult female Hessian fly obtains information about the leaf surface through her tactile and/or kinesthetic senses and uses this information when making egglaying decisions.

Laparoscopic treatment of an umbilical hernia using a new composite mesh

A case is reported of a recurrent umbilical hernia treated using an intraperitoneal Parietex® Composite mesh through a laparoscopic approach. Three trocars were inserted in the left flank. According to the size of the defects (3×5cm), a 15 × 10cm composite mesh was selected. The edges of the defects and the shape and size of the mesh centered on the hernia were drawn on the anterior abdominal wall. A reference point was positioned 1 cm outside each angle of the mesh. After the hydrophilic and absorbable film had been hydrated, the mesh was rolled, the film inside, and introduced within the peritoneal cavity. The mesh was carefully oriented with the smooth side on the viscera, porous side towards the wall. A 2mm cutaneous incision was performed at each reference point. An absorbable suture was inserted in the cutaneous incision, routed through the wall and the mesh, and finally brought out through the same incision. Using such a method, a transparietal subcutaneous suture was obtained in each corner and the mesh could be perfectly centered on the defect. The 1 cm distance between each corner of the mesh and the emerging tip of the needle induced a moderate tension within the mesh which balanced the relaxation of the wall during the exsufflation of the pneumoperitoneum. The final fixation of the mesh was then obtained using non-absorbable metallic devices. Hospital discharge was after 2 days and the patient returned to a normal activity within 10 days. After a three-month follow-up, no complication attributed to the laparoscopic approach or to the intraperitoneal position of the mesh had been reported.

Cross-sectional Specimen Preparation and Observation of a Plasma Sprayed Coating Using a Focused Ion Beam/Transmission Electron Microscopy System

A focused ion beam (FIB) technique was applied to cross-sectional specimen preparation to observe an interface between a plasma sprayed coating and an aluminum (Al) substrate by transmission electron microscopy (TEM). The surface of the sprayed coating film has a roughness of several tens of microns. Sputter rates for the coating film and the substrate are greatly different. The rough surface and the difference in sputter rate cause problems in making TEM specimens with smooth side walls. The top surface of the coating film was planerized by the FIB before fabricating the TEM specimen. The interfaces were investigated by TEM and energy-dispersive X-ray (EDX) analysis. The TEM observation revealed that there is a 10 nm thick amorphous layer at the interface between the coating film and substrate. The coating film consists of two kinds of sublayers with bright and dark contrast. The bright contrast sublayers were amorphous layers with thickness of 2 approximately 10 nm. The Al/Fe X-ray intensity ratio was larger in bright contrast sublayers than that in dark contrast sublayers.

Cross-sectional Specimen Preparation and Observation of a Plasma Sprayed Coating Using a Focused Ion Beam/Transmission Electron Microscopy System

Abstract A focused ion beam (FIB) technique was applied to cross-sectional specimen preparation to observe an interface between a plasma sprayed coating and an aluminum (Al) substrate by transmission electron microscopy (TEM). The surface of the sprayed coating film has a roughness of several tens of microns. Sputter rates for the coating film and the substrate are greatly different. The rough surface and the difference in sputter rate cause problems in making TEM specimens with smooth side walls. The top surface of the coating film was planerized by the FIB before fabricating the TEM specimen. The interfaces were investigated by TEM and energy-dispersive X-ray (EDX) analysis. The TEM observation revealed that there is a 10 nm thick amorphous layer at the interface between the coating film and substrate. The coating film consists of two kinds of sublayers with bright and dark contrast. The bright contrast sublayers were amorphous layers with thickness of 2~10 nm. The Al/Fe X-ray intensity ratio was larger in bright contrast sublayers than that in dark contrast sublayers.

Heat Transfer Enhancements in Rotating Two-Pass Coolant Channels With Profiled Ribs: Part 2—Detailed Measurements

Detailed heat/mass transfer distributions are presented inside a two-pass rotating ribbed coolant channel for two profiled-rib configurations. Several profiled-rib configurations have been studied (Acharya et al., 2000), and it was found that the best performance was achieved by saw-tooth ribs, and a pyramid–valley rib combination. The profiled ribs were placed directly opposite to each other on the leading and trailing surfaces. Smooth side walls were used in all the experiments. Heat transfer measurements were compared with straight ribs of equal blockage ratio. The measurements were made in a two-pass rotating facility using the naphthalene sublimation mass transfer technique, which provides highly resolved surface distributions. The results presented are for a Reynolds number of 30,000, two rotation numbers (0 and 0.3), and include average heat/mass transfer over the entire inter-rib module as well as detailed heat/mass transfer contours for two profiled-rib cases. Significant enhancement of up to 25 percent in heat/mass transfer was obtained with the pyramid–valley and saw-tooth shaped ribs under rotating conditions.