Lateral Cross Section Research Articles

Independent control of aspect ratios in the axial and lateral cross sections of a focal spot for three-dimensional femtosecond laser micromachining

We theoretically and experimentally show that independent control of aspect ratios of cross-sectional shapes of a focal spot in both axial and lateral directions can be achieved for three-dimensional (3D) femtosecond laser micromachining by the use of a combination of a slit beam shaping technique and a temporal focusing technique. The simultaneous employment of the spatial and temporal beam shaping techniques allows us to achieve isotropic resolution in 3D space even for an objective lens of low numerical aperture. We also present analytical expressions of the peak-intensity distributions near the focus for the spatiotemporally focused femtosecond laser beams with and without utilizing the slit beam shaping technique.

Quantitative Measurement of Focused Ultrasound Pressure Field Using Subtraction Shadowgraph

In this study, the measurement of focused ultrasound pressure field by the subtraction shadowgraph method was investigated. Conventional shadowgraph is known as a fast, noninvasive, but qualitative method of ultrasound pressure field measurement. On the other hand, the subtraction shadowgraph method in this paper can provide quantitative projection images, from which the ultrasound pressure field can be reconstructed. Subtraction shadowgraph images of a focused ultrasound field were obtained, it was converted to the projection of the refractory distribution, and the focused ultrasound pressure field was reconstructed from the projection by computed tomography algorithm. The result was compared with that of hydrophone measurement, and successful reconstruction of the axi-symmetric pressure distribution of the focal field was confirmed in both lateral and axial cross sections.

Subwavelength leaky-wave optical nanoantennas: Directive radiation from linear arrays of plasmonic nanoparticles

We analyze here the leaky-wave properties of linear arrays of plasmonic nanoparticles. It is shown that such periodic arrays may support two orthogonal leaky-wave propagation regimes, respectively, with longitudinal and transverse polarization. Using closed-form dispersion relations derived in the complex domain, we analyze their properties in the leaky-wave regime and we derive general conditions under which a nanoparticle array with subwavelength lateral cross section may support a radiating leaky mode with directive properties, conical radiation, frequency scanning and sufficiently long propagation distance, paving the way to potential applications as a leaky-wave optical nanoantenna with subdiffractive properties. Realistic designs and configurations are presented, considering the material dispersion and absorption of optical materials, for which we determine propagation distance, near-field distribution and far-field leaky-wave radiation pattern.

순티타늄판의 Nd:YAG 레이저 용접성에 관한 연구(IV) - 겹치기 용접 및 실물 열교환기로의 적용 -

With large specific strength and outstanding corrosion resistance and erosion resistance in sea water, titanium and titanium alloy are widely used in heat exchanger production. In particular, pure titanium demonstrates outstanding molding performance and may be considered optimal for production of heat exchanger. Since titanium is very vulnerable to oxidation and embrittlement during welding, processes with less heat input are widely used, and laser welding is widely applied by considering production performance and shield etc in atmosphere. So far, 1st report and 2nd report compared and analyzed embrittlement degrees by bead colors of weldment through oxygen and nitrogen quantitative analysis and hardness measurement, and evaluated welding performance and mechanical properties of butt welding. This study evaluated field applicability of lap welding to heat exchange plate of LPG re-liquefaction device for ships through tensile stress test, hardness test and internal pressure test etc after deducing optimal weding condition and applying to actual heat exchange plate. In bead overlap area, the experiment produced sound welds with no porosity or defect by increasing and decreasing laser power, and tensile-shear test results indicated virtually the same tension and yield strength as base metal. As a result of measuring hardness at lateral cross section and bead overlap zone of actual heat exchanger welds, hardness difference within 20Hv was produced at base metal, HAZ and weldment, and as a result of pneumatic and hydraulic pressure test, no leakage occurred.

The SMALL AND ROUND SEED1 (SRS1/DEP2) gene is involved in the regulation of seed size in rice

The causal gene of a novel small and round seed mutant 1 (srs1) was identified in rice by map-based cloning and named SMALL AND ROUND SEED 1 (SRS1). The SRS1 gene is identical to the previously identified DENSE AND ERECT PANICLE 2 (DEP2). The SRS1/DEP2 gene encodes a novel protein of 1365 amino acids residues without known functional domains. In the longitudinal direction of the lemma, both cell length and cell number are reduced in srs1-1 compared to the wild type, whereas in the lateral cross section of the lemma, cell length in srs1-1 is greater than that in the wild type, but the cell number in srs1-1 is the same as that in wild type. These results suggest that the small and round seed phenotype of srs1-1 is due to the reduction in both cell length and cell number in the longitudinal direction, and the elongation of the cells in the lateral direction of the lemma. The SRS1 mRNA and proteins are abundant in wild type rice specifically in young organs, namely young leaves, internodes and panicles. Interestingly, the tissues expressing SRS1 are closely related to the tissues that exhibit abnormalities in the srs1 mutants.

Strongly localized acoustic surface waves propagating along a V-groove

Strongly localized acoustic surface waves propagating along an immersed V-groove are numerically analyzed and experimentally demonstrated. We analyze the dispersion relation and the distribution of displacements of such groove waves using the compact two-dimensional finite-difference time-domain method. It is shown that they are dispersionless and strongly confined in the lateral cross section. The variations in their velocities as a function of the apex angle are also presented. Furthermore, we implement experimental observation by the near-field detection of these predicted waves in the 30° polymethyl methacrylate groove. The experimental measurements of the wave velocities agree very well with the numerical results.

Rotational CARS for simultaneous measurements of temperature and concentrations of N2, O2, CO, and CO2 demonstrated in a CO/air diffusion flame

Rotational coherent anti-Stokes Raman spectroscopy (CARS) has over the years demonstrated its strong potential to measure temperature and relative concentrations of major species in combustion. A recent work is the development and experimental validation of a CO2 model for thermometry, in addition to our previous rotational CARS models for other molecules. In the present work, additional calibration measurements for relative CO2/N2 concentrations have been made in the temperature range 294–1246K in standardized CO2/N2 mixtures. Following these calibration measurements, rotational CARS measurements were performed in a laminar CO/air diffusion flame stabilized on a Wolfhard–Parker burner. High-quality spectra were recorded from the fuel-rich region to the surrounding hot air in a lateral cross section of the flame. The spectra were evaluated to obtain simultaneous profiles of temperature and concentrations of all major species; N2, O2, CO, and CO2. The potential for rotational CARS as a multi-species detection technique is discussed in relation to corresponding strategies for vibrational CARS.

Circular and noncircular subsonic jets in cross flow

Experiments were conducted to investigate the impact of circular and noncircular injector nozzle geometries on the penetration, mixing, and structure of a jet injected perpendicular into subsonic cross flow. Circular, triangle, and elongated slot nozzles were studied including varying their orientations relative to the cross flow, to comprise a matrix of five different test cases. The cross-sectional areas of all geometries were equal. The interaction between the jets and the cross flow was strongly dependent on the different geometries and their orientations. Each of the injector geometries resulted in a distinctive region of backflow at the leeward side of the jet. The location and size of this region and the reverse flow magnitude were largely dependent on the aspect ratio and the jet cross section lateral dimension change in the axial direction. A combination of instantaneous and time-averaged particle image velocimetry images taken in the axial and lateral cross sections of the jet near the exit plane revealed several large scale turbulent structures downstream of the jets for two different blowing ratios r=3.2 and 8. Detailed flow field data are presented for the higher blowing ratio due to the better spatial resolution of the large scale structures in the near field. A counter-rotating vortex pair was identified in the near field of the jets resulting in a reverse flow region. These structures had an upright nature similar to the wake vortices with the exception that the former were attached to and constantly fed from jet fluid mixed with the cross flow. The latter was formed by the cross flow, fed from its boundary layer vorticity, and remained separate from the jet. It was attached to the surface of the flat plate at one end and to the trajectory of the bent jet at the other end. Both the shape and orientation of the nozzle geometries had a strong effect on the jet spread and penetration. Compared to the baseline circular nozzle, the slot major (slot nozzle’s major axis oriented along the cross stream) exhibited the highest penetration, whereas the slot minor penetrated the least. The triangular jets’ characteristics were significantly affected by their orientation relative to the cross flow. Several different scaling techniques were explored in order to compare the present jet trajectories with previously published data. Commonly used length scaling parameters of rd and r2d were shown to be inadequate to scale different experimental data. Newly proposed scaling that was based on the velocity profiles of the cross flow boundary layer and the jet, prior to their interaction, yielded better results.

Space charge distributions in glass fibre/epoxy resin composites under dc 10 kV mm−1 electric field

In this paper, the authors discuss one- and three-dimensional space charge distributions in glass fibre/epoxy resin composites. By the conventional pulsed electroacoustic (PEA) method, only a one-dimensional distribution of the average charge over a whole area parallel to the two electrodes can be observed. Therefore, the authors have developed a new PEA system capable of measuring a three-dimensional space charge distribution. Using this system, they measured the charge distribution in glass fibre/epoxy resin composites made of lattice-woven glass fibre and epoxy resin. It has become clear that spatial variation in signal intensity observed depends on the internal structure of the composite. There appear repetitious positions where a high charge density is observed on the same lateral cross section along the vertical direction in the composite. Such positions are consistent with the intersections of the glass fibres. Accumulation of mobile charge carriers or appearance of polarization charge due to mismatch of the ratio of the conductivity and permittivity between the glass fibre and the epoxy resin is thought to be responsible for the PEA signals.

Evaluating the lateral resolution of the adaptive optics scanning laser ophthalmoscope

We present a statistical assessment of the lateral resolution of the adaptive optics scanning laser ophthalmoscope (AOSLO). We adopt a 2-D Gaussian function to approximate the AOSLO point spread function (PSF), which is dominated by the residual wavefront aberration and characterized by the Strehl ratio. Thus, we derive the lateral resolution in the presence of residual wave aberrations, which is inversely proportional to square root of the Strehl ratio. The modeling, while not sufficient in describing the fine structure of the real PSF, demonstrates good conformance to the lateral cross section of the real PSF. With this model, the lateral resolution of our current AOSLO was computed to be 1.65 to 2.33 microm, which agreed well with the actual result. We also reveal the relationships among the lateral resolution and other three measures of the AOSLO imaging property including the Strehl ratio, the PSF, and the root mean square (rms) of wavefront aberration.

The gene encoding the nucleocapsid protein of Gill-associated nidovirus of Penaeus monodon prawns is located upstream of the glycoprotein gene.

The ORF2 gene of Gill-associated virus (GAV) of Penaeus monodon prawns resides 93 nucleotides downstream of the ORF1a-ORF1b gene and encodes a 144-amino-acid hydrophilic polypeptide (15,998 Da; pI, 9.75) containing 20 basic (14%) and 13 acidic (9%) residues and 19 prolines (13%). Antiserum to a synthetic ORF2 peptide or an Escherichia coli-expressed glutathione S-transferase-ORF2 fusion protein detected a 20-kDa protein in infected lymphoid organ and gill tissues in Western blots. The GAV ORF2 fusion protein antiserum also cross-reacted with the p20 nucleoprotein in virions of the closely related Yellow head virus. By immuno-gold electron microscopy, it was observed that the ORF2 peptide antibody localized to tubular GAV nucleocapsids, often at the ends or at lateral cross sections. As GAV appears to contain only two structural protein genes (ORF2 and ORF3), these data indicate that GAV differs from vertebrate nidoviruses in that the gene encoding the nucleocapsid protein is located upstream of the gene encoding the virion glycoproteins.

On the electrostatic potential profile in biased molecular wires

The potential profile across a biased molecular junction is calculated within the framework of a simple Thomas–Fermi-type screening model. In particular, the relationship between this profile and the lateral molecular cross section is examined. We find that a transition from a linear potential profile to a potential that drops mainly near the molecule-metal contacts occurs with increasing cross-section width, in agreement with numerical quantum calculations.

Techniques for precision irradiation of the lateral half of the rat cervical spinal cord using 150 MeV protons

Techniques for high precision irradiation experiments with protons, to investigate the volume dependence of the tolerance dose of the rat cervical spinal cord are described. In the present study, 50% of the lateral cross section of the spinal cord was irradiated. The diameter of the cross section of this part of the rat spinal cord is at maximum 3.5 mm. Therefore, a dedicated procedure was developed to comply with the needs for a very high positioning accuracy and high spatial resolution dosimetry. By using 150 MeV protons a steep dose gradient (20–80% = 1 mm) in the centre of the spinal cord was achieved. This yields a good dose contrast between the left and right halves of the cord. A home-made digital x-ray imager with a pixel resolution of 0.18 mm/pixel was used for position verification of the spinal cord. A positioning accuracy of 0.09 mm was obtained by using information of multiple pixels. The average position stability during the irradiation was found to be 0.08 mm (1 SD) without significant systematic deviations. Profiles of the dose distribution were measured with a 2D dosimetry system consisting of a scintillating screen and a CCD camera. Dose volume histograms of the whole spinal cord as well as separately of the white and grey matters were calculated using MRI imaging of the cross section of the rat cervical spinal cord. From the irradiation of 20 animals a dose–response curve has been established. MRI showed radiation-induced damage at the high dose side of the spinal cord. Analysis of the preliminary dose–response data shows a significant dose–volume effect. With the described procedure and equipment it is possible to perform high precision irradiations on selected parts of the spinal cord.

The Analysis of Fatigue Damage to Glass-Fiber Reinforced Composites

We perform a complex investigation of the mechanism of fatigue fracture of epoxy–fiberglass compositions (with 80 wt.% of fiberglass) by using mechanical, fractographic, and acoustic-emission methods. Flat specimens are cyclically loaded by displacement-controlled console bending. As a criterion of loss of the fatigue strength of a specimen, we use an increase in its flexibility by 40%. The lateral surfaces and cross sections of the specimens are analyzed after the attainment of this criterion. Periodically, after different numbers of lading cycles, we record acoustic-emission signals. As the basic parameter, we use the so-called MARSE energy. Different energy levels of the signals are explained by the action of different fracture mechanisms (failures of the matrix and fibers and exfoliations along the fiber–matrix boundary). This enables us to establish the periodicity and intensity of each type of signals depending on the load.

Capelin TS: Effect of individual fish variability

Capelin (Mallotus villosus) is an important forage fish in northern latitudes. The effect of the individual biological variability on the target strength (TS) at various acoustic frequencies was investigated from a sample collected in the St. Lawrence estuary. The geometric properties of the fish and its swimbladder were measured from radiographs obtained from 45 anesthetized fish, from 12- to 16-cm total length. The data were input to a backscattering model exploring the effect of fish shape on TS as a function of acoustic frequency, length, and tilt angle. The swimbladder had similar cross sections in both lateral and dorsal views. It represented 5.5% (s.d. 1.1%) of lateral body cross section and 8.2% (s.d. 1.8%) of the dorsal body cross section. The swimbladder cross section was related to the fish total length but the variation around the mean for a given length was ±40%. This large variability is equivalent to the change in cross section between tilt angles of 0 and 90 deg for an average fish. The variability in shape parameters is paralleled with changes in the modeled backscatter patterns. The TS versus frequency relation exhibits substantial peaks and troughs, notably in the range of acoustic frequencies commonly used in fisheries acoustics (∼38–200 kHz).

EFFECT OF WALL SHEAR ON PARTICLE MOTION IN SEDIMENT LADEN OPEN CHANNEL FLOW

The paper deals with the concentration distributions of sediment particles in turbulent rectangular open channel flow. Special attention is paid on the effect of channel wall shear on the concentration profiles of sediment particles. Using the Reynolds strecc model, a mathematical model to describe the fluid and sic: din-mut motion in a prismatic open channel was presented. After confirming the validity of this model by laboratory experiments, sediment motions in a lateral cross section were discussed by this model. It was shown that the sediment particles flow downward with circularity trajectories like secondary current of fluid motion. Due to the settling of the sediment particles, the location of the center of the trajectory is somewhat near to the sidewall and to the bottom, compared with that of fluid motion. Experiments on sediment laden open channel flow, reported so far, were also reproduced numerically. In some cases of the reported paper, it was found that the circulatory motion of sediments spread almost over cross section. To the case of compound channels, the effect of relative height of the flood plane on sediment distributions were also investigated.

レーザー超音波による溶接状態の施工中監視 １ 溶接施工中における溶融深さ分布の計測

A new method for in-process monitoring of welding based on non-contacting ultrasonic technique is proposed. When a laser pulse is irradiated onto a surface of base metal, an ultrasonic pulse is generated due to ablation of material from the surface. The ultrasonic waves, which travel through both liquid and solid metal, are detected with a laser interferometer as micro displacement on the surface and then propagation time of the ultrasonic pulse is measured. Since sound velocity depends on the temperature distribution along the propagation path, it is capable to estimate the location of fusion point on the sound path from the propagation time with a temperature distribution model. Moreover, a configuration of the molten pool is reconstructed by scanning the laser beams on the surface which is being observed. Feasibility tests are performed with a pulsed Nd : YAG laser source (wavelength : 1064 nm, pulse energy : <450 mJ/pulse) for generating ultrasonic waves and Michelson interferometer for detecting. Molten pools are formed by static arc current using GTAW (welding current : 70-150 A) on type 304 stainless steel having 32 mm thickness. The estimated configurations molten pool are compared with lateral cross section views. Consequently, by applying the present method, it is found that ultrasonic signals are detected with good signal-to-noise ratio despite under welding operations and the molten pool configurations are estimated as a similar geometry within 1 mm or less accuracy. Accuracy of the estimated depth tends to be inferior as an increase of welding current ; therefore advanced temperature distribution model and simultaneous detection system of the propagation time over the observing area are required in order to determine the more accurate configurations.

Nondisturbing and Stable SERS-Active Substrates with Increased Contribution of Long-Range Component of Raman Enhancement Created by High-Temperature Annealing of Thick Metal Films

High-temperature annealing of thick silver films (TSFs) deposited onto a smooth dielectric substrate leads to high-order self-organization of metal clusters on the film surface. A comparative atomic force microscopic (AFM) analysis of “as-deposited” and annealed TSFs (aTSFs) shows that uniform ellipsoidal roughness ∼41 × 25 nm in lateral cross section and ∼45 nm in height results after annealing. These metal clusters are mutually oriented so that the main lateral axes of the ellipsoids are nearly parallel. UV−visible data demonstrate a ∼300 nm hypsocromic shift of the bands corresponding to the collective surface plasmon modes. Additionally, a new (∼350 nm) band related to the normal component of the plasmon oscillations appears after annealing. This band was found to be strongly angle-dependent for p-polarized light. The aTSFs appeared extremely time- and organic solvent-stable versus as-deposited films. The aTSFs were found to be nondisturbing surface-enhanced Raman scattering (SERS)-active substrates in the application to studies of complexation of crown ether styryl dyes with metal ions. A pronounced SERS signal of the analyte rhodamine 6G was observed with aTSFs, even when the analyte was separated from the silver surface with five Langmuir−Blodgett monolayers of stearic acid. At the same time, depositing only a monolayer of stearic acid on the as-deposited film completely suppressed the SERS signal of the analyte. Finally, the self-assembling of Ag clusters on the surface of the aTSF, stimulated by the high-temperature annealing, results in the creation of a time- and organic solvent-stable SERS substrate with nanometer-scale quasi-periodical roughness, and this substrate exhibits an increased contribution of the electromagnetic component to the overall Raman enhancement.

On the cross‐sectional geometry of thermal erosion channels formed by turbulent lava flows

A new theoretical framework for interpreting the cross‐sectional geometry of self‐formed lava channels is introduced. The method may be applied to any lava channel, or tube, and is demonstrated by studying thermal erosion by a hot, turbulently flowing lava. The cross section of a thermal erosion channel is often characterized by undercutting of the channel walls when the upper surface of the lava flow falls beneath the original ground level. The degree of lateral undercutting is shown here to be a function of the flow parameters, which enables the shape of the channel cross section to be used to determine a lower bound upon the lava flow rate. The solution for the geometry of the lava channel is then coupled to an existing two‐dimensional model for thermal erosion by komatiite flows to determine the effects of lateral erosion and variable flow cross section upon cooling of the lava and contamination of the lava by assimilated ground material. Lateral thermal erosion is shown to lead to a thinning of the lava flow with time, even at a constant eruption rate, which reduces its erosive power and enhances cooling of the lava. Finally, a linear stability analysis of the evolution equation for the channel cross section suggests that inefficient lateral mixing in a thin lava flow can lead to a morphological instability and eventual splitting of the channel. The instability is suppressed at short wavelengths by the variation in melting rate with local wall curvature, and the fastest growing symmetric mode has a wavelength equal to half the channel width, which corresponds to the formation of midstream islands.

Investigation of Initial Oxide Growth on NiAl by Scanning Tunneling Microscopy

NiAl covered with native oxide is oxidized under UHV conditions with controlled oxygen exposures up to 22 × 103 L at T = 940 K and p = 4 × 10−4 Pa. Scanning tunneling spectroscopy and current imaging of oxidized samples reveal that the usual constant current image cannot be interpreted as height profile of the sample. As a consequence of a laterally varying oxide thickness or composition, constant current imaging is more sensitive to thickness and/or composition contrast than to height variations. As shown by I–z spectroscopy, the tip is in mechanical contact with the sample in regions of higher resistance of the oxide layer. For predominating thickness contrast, this effect permits to obtain a lateral cross section of the oxide thickness profile as a function of the oxygen exposure. AES depth profiling suggested the growth of an oxide layer of about 2 nm thickness, when exposing the sample to 22 × 103 L oxygen.