Large Apex Angle Research Articles

Highly Reproducible Near-Field Optical Imaging with Sub-20-nm Resolution Based on Template-Stripped Gold Pyramids

With a template-stripping fabrication technique, we demonstrate the mass fabrication of high-quality, uniform, ultrasharp (10 nm) metallic probes suitable for single-molecule fluorescence imaging, tip-enhanced Raman spectroscopy (TERS), and other near-field imaging techniques. We achieve reproducible single-molecule imaging with sub-20-nm spatial resolution and an enhancement in the detected fluorescence signal of up to 200. Similar results are obtained for TERS imaging of carbon nanotubes. We show that the large apex angle (70.5°) of our pyramidal tip is well suited to scatter the near-field optical signal into the far-field, leading to larger emission enhancement and hence to a larger quantum yield. Each gold or silver pyramidal probe is used on-demand, one at a time, and the unused tips can be stored for extended times without degradation or contamination. The high yield (>95%), reproducibility, durability, and massively parallel fabrication (1.5 million identical probes over a wafer) of the probes hold promise for reliable optical sensing and detection and for cementing near-field optical imaging and spectroscopy as a routine characterization technique.

Investigation of Relationship between Instrumented Indentation Nominal Hardness and Reduced Elastic Modulus with Large Apex Angle Indenter

Based on dimensional analysis, finite element numerical calculation is undertaken on elastic–plastic solids to investigate the relationship between instrumented indentation nominal hardness Hn and reduced elastic modulus Er for three different apex angle indenters. The half-included angles of axisymetric conical indenter models are 62.9°, 70.3°and 85.566° which are corresponding to the real indenters of cube corner indenter with 60° face angle, Berkovich indenter with 65.27° face angle and cube corner indenter with 85° face angle, respectively. The relationship between a nominal hardness/reduced elastic modulus (Hn/Er) and elastic work/total indentation work (We/Wt) is established with a sixth-order polynomial form for each apex angle indenter. For rigid indenter of instrumented indentation model, reduced elastic modulus Er=1/[(1+v2)/E], where E and v are elastic modulus and Poisson’s ratio of the indented material. Therefore, Hn/Er–We/Wt relationship can be used to give estimates of E. Accuracy estimation for the each relationship of each half-included angle indenter shows that the large half-included angle of 85.566° gives better Er measurement error of +11.56% for a low yield strength material(e.g., materials for which σy=100MPa, n=0 and E=200GPa), while for the smaller half-included angle of 62.9° or 70.3° indenter, the measurement error is > ±12.74%. The research in this paper confirms that Hn/Er–We/Wt relationship of large apex angle indenter such as 85.566° half-included angle is recommended to be used for estimating the elastic modulus E of indented material.

Analysis of NC Data for Machining Test of Cone-Frustum under Simultaneous Five-Axis Control

NC data for machining the cone-frustum by means of five-axis machining centers with a tilting rotary table are analyzed in detail. The cone-frustum is machined by using a milling cutter at simultaneous five-axis control for inspecting the machining accuracy. However, the NC data have to be changed corresponding to the setting position of the workpiece on the rotary table. Thus, the moving range and velocity of each axis are analyzed by changing the apex angle and center position of the cone. It is found from the analyzed results that the larger apex angle gives the larger moving range and the higher velocity to all axes. When the center position moves along the Y-direction, every reversal point independently appears on a circular path. Therefore, it is recommended to offset the center position of the cone frustum along Y-direction to give the large moving ranges and the high velocities to the axes.

Occurrence of Taylor vortices in the flow between two rotating conical cylinders

The behavior of the flow between two coaxial conical cylinders with the inner one rotating and the outer one stationary is studied numerically. Special attention is paid to the occurrence of Taylor vortices in basic flow and unsteady helical vortices. It is found that, in basic flow, the vortices occur in the direction toward smaller radius, while toward bigger radius in unsteady helical vortices; moreover, the unsteady helical vortices can coexist with unstable steady Taylor vortices. The results suggest that the behavior of conical flow is dominated by a competition between the meridional flow and radial flow. The effect of meridional flow is most significant at small apex angle or in basic flow and helical vortices, while the radial flow dominates the structure at larger apex angle or in steady vortical flow. In order to get better understanding the competition and the transition of Taylor–Couette flow to conical flow, a velocity angle related to velocity components is defined, and the pattern evolution of velocity, streamlines and the velocity angle are examined with respect to apex angle, as well as Reynolds number. Finally, the statistical properties of turbulent conical flow are investigated.

Numerical Analyses of Exhaust and Refill Processes of aLaser Pulse Jet

The exhaust-refill processes in a laser pulse jet with a conical nozzle are simulated using computational fluid dynamics to clarify the analytically unpredictable decreasing tendency of a momentum-coupling coefficient with an increasing nozzle apex angle. Because the exhaust-refill processes result from an adiabatically expanding blast wave after laser heating, a valid explosion source based on a measurement is used to drive the blast wave instead of a laser-absorption process. Results of computations show that processes that occur until the shock front of a blast wave reaches the nozzle exit are similar, irrespective of the nozzle apex angle. However, after the blast wave leaves the nozzle edge, the behavior of the rarefaction wave induced behind the shock wave depends greatly on the nozzle apex angle. In the case of small apex angles, successive refilling mechanisms with a vortex are activated by the prominently evolved rarefaction wave. In contrast, in the case of large apex angles, this mechanism disappears, due to the moderate evolution of the rarefaction wave. This difference creates a tendency of the momentum-coupling coefficient to decrease with the apex angle.

Flow Fields of a Large-Angle, Spiked Blunt Cone at Hypersonic Mach Numbers

The flow fields around a large apex angle, spiked blunt cone have been analyzed at a hypersonic Mach number through experiments in a free piston-driven shock tunnel, and the results are compared with that of a laminar 2-dimensional axisymmetric unsteady Navier-Stokes solver developed in-house. The model geometry is a 120° apex angle blunt cone equipped with two types of spikes — a disc-tipped spike and a conical-tipped spike. The ratio of total length of the spike to model base diameter was kept at 1.00. The free-stream Mach number and Reynolds number (per unit length) in the free piston shock tunnel were 6.99 and 2.46×106, respectively. After measuring the aerodynamic forces on this model, time resolved visualization of the flow was attempted using a high-speed video camera in order to understand the characteristic features of the high-speed flow over the spiked body and to check if any unsteadiness existed in the flow fields. The experimental results indicate slight shock oscillations near the edge of the cone model when it is equipped with a disc spike, and the shock oscillations appear to be more pronounced when the model is equipped with a conical spike. However, the pulsation flow mode is not observed in the experimental results. The numerical results agree with the experimental results on the unsteadiness of the flow fields. The experimental results obtained in this case also serve as a database for the in-house CFD code validation for such high-speed spiked body flows.

衝撃波管を用いた円錐上での正常反射からマッハ反射への遷移(J12-1 流体情報学1(実験と計算の融合研究),J12 流体情報学と融合研究)

Shock wave reflections over large apex angle cones have been investigated in a diaphragm-less shock tube with an intention of studying the phenomenon of transition from regular to Mach reflection over the cone surface. It is believed that over large angle cones with semi-apex angles ranging from 43 to 48 degrees, the reflection of an incident shock wave at a moderate Mach number of 2.38 may undergo a transition from regular to Mach over the cone surface due to viscous effects. The experiments are carried out with two test gases, nitrogen and argon. Flow visualization experiments are planned to study this phenomenon in detail over cones of different apex angles in the above range. Measurement of surface heat flux using platinum thin film sensors has also be carried out in order to analyze the heat transfer history over the cone surface during these reflection phenomena. The experimental results have been compared with the numerical results obtained from a commercial N-S solver Fluent (Version 6.1, Fluent Inc.). The experimental results obtained in this study are expected to be useful in validating CFD codes.

Slugging fluidized beds in tapered vessels

The bed height and pressure drop of a tapered fluidized bed were well predicted by a model based on measurements for slugging fluidized beds in the fast bubble regime. Tapered vessels of large apex angle were effective in suppressing the development of square-nosed slugs.

SIMULTANEOUS HEAT AND MASS TRANSFER IN MIXED CONVECTION ALONG A VERTICAL CONE UNDER UNIFORM HEAT AND UNIFORM MASS FLUXES

An analytical study is carried out to examine the combined heat and mass transfer characteristics under mixed convective flow along the external surface of a vertical circular cone. The analysis is limited to processes in which diffusion-thermo and thermo-diffusion effects can be neglected as well as limited to cones with large apex angles whereby the radial curvature effects can be neglected. The surface of the cone is subjected to uniform heat and mass fluxes. Numerical results of the local Sherwood number, the local Nusselt number and the local friction factor are obtained from the local similarity as well as local nonsimilarity approaches. Consideration is given to situations where the net buoyancy force assists and opposes the forced flow. Calculations are confined to diffusion of common gases and vapors into air.

Liquid fluidization in tapered vessels.

The flow regimes of a tapered fluidized bed were represented on a diagram with two lines which show positions of the minimum fluidization velocity and the terminal falling velocity. The diagram was used to calculate the bed height and pressure drop by a proposed method. The results were compared with measurements for two-dimensional tapered fluidized beds. Some hydraulic characteristics were discussed on the basis of the measured voidage distributions. The results show that the proposed method predicts the bed height and pressure drop on the basis of the empirical voidage, which is expressed as a power function of the local superficial velocity. The calculation procedure is also applicable to multi-species particle systems with an assumption of complete segregation of the species. The voidage in a tapered fluidized bed of large apex angle is smaller and its dependence on velocity is less than that for a cylindrical fluidized bed. This suppresses bed expansion and promotes mixing between different solid species.

The double cone fracture in flint

SummaryThis work proposes a mechanism for the formation of the characteristic ‘double cone’ cracking and ‘bulb of percussion with bulbar scar’ cracking caused by the artificial fracture of flint. The double cone fracture is observed as a large, small apex angle, cone that is truncated by a smaller cone of increased apex angle. The author considers that the large narrow apex angle truncated cone of the fracture is caused by Hertzian loading of the flint on impact and the upper complete cone is formed as a result of the unloading of the stressed flint. This mechanism has been deduced from work carried out in the fractography of glass by others and from some restricted laboratory experiments.

被削材除去過程における切りくずの観察

Metal removal mechanism by abrasive grit haven't investigated so much. But it is very important problem in grinding mechanism. In order to clear the action of abrasive grit which produce chips, we must get authentic informations about it. Then, a quick-stop technique has been developed to freeze the chip forming process effectively in nominal grinding speed. And the optical micrograph of longitudinal cross-section in the center of the groove has been got and observed in details. This paper concerns with an investigation into the chips produced in front of the rake surface of edge. The relations between the shape of chip and cutting condition have been discussed and as results followings were clarified:(1) The chips formed by the edges having apex angle of 100°-140° are consist of short segment with shear deformation. But the free ends of chips change depending on the apex angle of edges.(2) The chips are strongly compressed during the removing process between the material and the front surface of edge, and the free ends of chips shall get round in the case of large apex angle.(3) The number of cracks in the free end of chip shall increase when the oil is put on the work surface, and the change of chip-type is observed for small apex angle of cutting edge.(4) The increase of cutting speed makes the term of removing material as a chip short and makes the size of chip small accordingly.

Concepts of Multiphase Flow Related to the Jenike Design Method

Hypotheses are presented here for improving bulk solids flowability. They are directed toward a quantitative design goal for gas-solids flow systems. An effort is made to relate gas control in gas-solids flow systems to the Jenike design method. Cohesion and friction in slumped beds are frequent barriers to flow. Gas or liquid moving through bulk solids interstices can reduce interparticle cohesion. Changes in interstitial fluid pressure can modify friction angles and so change channel flow factors and bulk solid flow functions. Mass flow can be achieved in gas-solids flow systems using comparatively large hopper half apex angles.

Perturbed Open Resonators

The resonant frequencies and diffraction losses of two-mirror open resonators which depart somewhat from an ideal configuration are evaluated by a perturbative technique. Detailed results are derived and discussed for flat mirrors of rectangular or circular aperture with a parabolic phase perturbation as well as flat-roof and conical systems with large apex angle.

Infrared Absorption Spectra of Carbon Suboxide and Malononitrile in Solid Argon Matrices

The infrared spectra of carbon suboxide and malononitrile isolated in solid argon matrices at low temperatures have been measured in the spectral region 440–4400 cm—1. A detailed comparison with prior spectroscopic data is made. It is shown that the matrix spectra of C3O2 support the linear symmetric model. A comparison of the matrix spectra and vibrational assignments of the three isoelectronic molecules C3O2, CH2(CN)2, and B2O3 is shown to favor a large apex angle in B2O3.

Infrared Absorption Spectra of B2O3, B2O2, and BO2 in Solid Argon Matrices

The infrared absorption spectra of B2O3, B2O2, and BO2 isolated in solid argon matrices have been investigated in the region 350–4000 cm—1. The visible absorption spectrum of matrix-isolated BO2 was observed in the region 4000–5500 Å. The gaseous species were generated in a high-temperature effusion cell and trapped under conditions of moderate to high dilution in solid argon matrices at approximately 4°K. Bands were found at 1955, 1921, 1899, 1323, and 1276 cm—1 in the infrared spectra of B210O2, B10B11O2, B211O2, and B10O2, and B11O2, respectively. For both B210O3 and B211O3 infrared spectra of the most dilute matrices show seven distinct bands in the region 450–2100 cm—1. Six of these can be readily assigned as fundamentals and their relative intensities explained if the known ``V'' structure of B2O3 is supposed to have a larger apex angle than that determined by electron diffraction, and the correlation of the normal vibrations and selection rules with those for the linear symmetric (D∞h) model is considered. With additional help from the measured B10–B11 isotope shifts and force constant calculations the following complete assignment was obtained (all frequencies in cm—1): B210O3: 2128(A1),733(A1),536(A1);[172](A1),or [260](A1);[476](A2) 2128(B1),1242(B1),471(B1);493(B2);B211O3: 2060(A1),729(A1),518(A1),[172](A1), or [259](A1);[456](A2),2060(B1),1239(B1),454(B1);477(B2);where the bracketed frequencies were not observed directly. Thermal functions have been computed for B2O3 and compared with the available calorimetric data. Structural parameters and a complete vibrational assignment have been estimated for B2O2. The infrared and green bands observed for BO2 are in agreement with the high-resolution results of Johns. Thermal functions for B2O2 and BO2 have also been computed.

閉合現象の閾値測定に関する研究

The concept of closure means a tendency on the part of an organism perceptually to complete stimulus presentations which are physically incomplete. But, when any one outline figure is very incomplete the tendency to perceive each part separately is stronger than to see the parts in a unitary manner. The general purpose of the present study is to determine whether or not, in the case of a diamond outline figure, the tendency toward closure could be psychophysically measured. It is possible, in the case of a diamond, to measure the threshold of closure as the percentage of the perimeter of the figure presented compared with that of a complete one. The threshold of closure was defined by Bobbitt (1) as that point in the series which represents the transition between forms having the quality of twoness and those having the quality of oneness. In the present study, the threshold of closure was measured for six different kinds of diamond having small or large apex angle. The apex angles (vertical angles) were respectively 40°, 50°, 60°, 70°, 80° and 90°. The exposure time interval of stimulus figures was a tenth of a second.The main results were as follows:1) Since the threshold of closure, in the case of diamond figures, is a very stable one, it is possible psychophysically to measure the phenomenon of closure.2) For the diamonds used here, the size of threshold varied directly with the size of the apex angle, i.e., the figure with the smallest apex angle had the lowest threshold, the figure with the largest apex angle had the highest one.3) However, the data of this study indicate that the important determinants of the location of the threshold include not only the angular characteristics of the figure, but the degree of proximity between the angles of the two jointed lines representing the opposite side of the diamond, and that the larger the angle of the opposite sidelines are, the more effective the factor of proximity is.4) It must be emphasized that the angular characteristics which are important are those of the really perceived lines, not of the imaginary ones.

Backscattering from Wide-Angle and Narrow-Angle Cones

Solutions are obtained for the diffraction of the waves radiated by scalar and vector point sources on the axis of a semi-infinite cone. The scalar problems are solved by the method of characteristic Green's functions to yield directly various alternative representations whose different convergence properties are discussed; the vector problem is solved by an application of spherical transmission line theory. To evaluate the plane wave scattering observed far from the cone tip, a highly convergent contour integral representation is selected and evaluated approximately for the special case of backscattering from cones having large and small apex angles. The results for the large-angle cone exhibit the transition from a backscattered spherical wave to a plane wave as the cone degenerates into an infinite plane.