Split Beam Method Research Articles

Split beam method for determining mode shapes of cantilever beams under multiple loading conditions

We have developed a general method, dubbed the split beam method, to solve Euler–Bernoulli equations for cantilever beams under multiple loading conditions. This kind of problem is, in general, a difficult inhomogeneous eigenvalue problem. The new idea is to split the original beam into two (or more) effective beams, each of which corresponds to one specific load and bears its own Young’s modulus. The mode shape of the original beam can be obtained by linearly superposing those of the effective beams. We apply the split beam method to simulating mechanical responses of an atomic force microscope probe in the “dynamical” operation mode, under which there are a stabilizing force at the positioner and a point-contact force at the tip. Compared with traditional analytical or numerical methods, the split beam method uses only a few number of basis functions from each effective beam, so a very fast convergence rate is observed in solving both the resonance frequencies and the mode shapes at the same time. Moreover, by examining the superposition coefficients, the split beam method provides a physical insight into the relative contribution of an individual load on the beam.

Holographic Measurement of a Tooth Model and Dental Composite Contraction

We have developed a real-time holographic technique to observe deformation induced by dental composite contraction. The standard split beam method was used, in conjunction with in situ holographic plate processing. Experiments were performed on a mechanical model of a human tooth with cavity. A silicone mold was used to manufacture a number of identical casts, using photoactivated composite. A LED lamp was used to induce photo-polymerization reaction in a composite. We have shown that the proposed method is ideal to analyze various polymerization strategies, with the purpose of recommending one which minimizes the polymerization contraction.

Robust analysis of single echo trace obtained by split beam sounder

The theory and method of the echo trace analysis of single echoes (ETA), which simultaneously analyze the shape and level of single echoes, are almost established. But, the method has not been extensively used. The major reasons are high‐quality echoes with a high signal‐to‐noise ratio (SNR) necessary for the analysis are some times difficult to obtain; the error introduced by transducer motion is large; and conditions for the theory sometimes could not be fulfilled. Therefore, we apply the ETA to the split beam method, which is most advantageous for the ETA, and make the method robust by introducing the following: careful echo selection considering SNR, correction of the effect of transducer motion, smoothing of the trace by regression analyses, introduction of indexes checking reliability, etc. The useful results of our ETA are the track, the swimming speed and orientation, the target strength as a function of tilt angle, and the estimated size of individual fish. The robust ETA was applied to echoes of...

The target strength of Antarctic krill (Euphausia superba) measured by the split-beam method in a small tank at 70 kHz

Abstract The target strengths (TS) of Antarctic krill (Euphausia superba) were measured at 70 kHz aboard the research and training vessel “Umitaka-maru” of Tokyo University of Marine Science and Technology in February 2003 during a Southern Ocean survey. The systematic variations of TS vs. the incident angle of the ensonified wave, henceforth called TS-patterns, were successfully measured for 12 live Antarctic krill. These measurements were compared with the theoretical TS-patterns predicted by the Distorted-Wave Born Approximation-based deformed-cylinder model (DWBA model). While there was good agreement near the main lobe, the measurements were higher than the model predictions in the side-lobe regions; this is consistent with the observations of others. Several possible causes of this discrepancy such as the bending of abdomen and scattering from pleopods were examined, but no single factor was identified as the cause. Rather, it is likely that the discrepancy is a result of a combination of several factors.

高周波スプリットビーム方式を用いたプランクトン計測装置の開発

We developed a high frequency split beam (SB) scientific echo sounder to measure the target strength of a zooplankton in situ. There are some issues for high frequency split beam method, namely, an accuracy of transducer, a high speed processing of phase detection and a calibration method. We discussed about the following provisions : Piezocomposite transducer, high speed phase detection device for mobile phone and tungsten carbide sphere.

Four-point bend adhesion measurements of copper and permalloy systems

Abstract The four-point bend split-beam method is used to quantitatively determine the interfacial fracture resistance and crack velocity as a function of mechanical energy release rate of the weakest interface in a thin film stack. Various interfaces of importance to magnetic storage devices are studied, including copper or nickel–iron (permalloy) on silicon oxynitride with additional adhesion promoters. The dynamics and kinetics of the four-point bend test are fully elucidated. A model for environmentally-controlled crack growth previously applied to bulk ceramics is used here as a model for interfacial crack growth and is found to fit the kinetic data.

スプリットビーム方式と小型水槽を用いる小型生物のターゲットストレングスの測定方法

オキアミ類のような小型生物のターゲットストレングス(TS)の姿勢特性を,小型水槽で精密に測定する方法を開発した。本方法では,70kHzのスプリットビーム方式音響計測システムと,ビデオカメラによる姿勢観測システムとを用いる。姿勢観測用窓を備えた小型水槽に,送受波器を下向きに設置し,TS測定と姿勢観測を同時に行う。物理モデル(銅円筒)のTS測定で精度を確認した上で,生きた小型エビのTS測定を行い,詳細なTSパターンを得ることができ,測定値と理論値がほぼ一致した。

Relation between electron exchange and nuclear vibrations in the H 2 + +H 2 + → H 3 + +p exothermic ion-molecular reaction

The effective cross section for the H2++H2+ → H3++p reaction in the energy range 5.7–11.5 eV is measured by the split beam method. The maximum of the cross section at an energy of ∼8 eV is related to the production of the H4++ compound system. The reaction threshold Wthr≈5 eV provides evidence in favor of the classical model of the H2+ ion with the charge fixed on one of the nuclei throughout the collision event.

Production of H 3 + ions in low-energy collisions between hydrogen molecular ions

The effective cross section for the H 2 + + H 2 + → H 3 + + p reaction in the energy range 5.7–11.5 eV is measured by the split beam method. The cross-section maximum at an energy of ∼8 eV is related to the production of the H 4 ++ compound system. The reaction threshold W thr ≈5 eV provides evidence in favor of the classical model with the H 2 + ion charge fixed on one of the two nuclei during the entire collision event.

Can stationary bottom split-beam hydroacoustics be used to measure fish swimming speed in situ?

We used split-beam hydroacoustics (Simrad EY500, 70 kHz) as a method for estimating fish swimming speed in situ. The method was first evaluated in the field using underwater video cameras (stereocinematographic method, SCG) to estimate accurate fish swimming speeds. The mean and distribution of swimming speeds of 15-cm brook trout ( Salvelinus fontinalis) obtained by the two methods were not statistically different (average 17.8 cm s –1with split-beam and 18.6 cm s –1with SCG). We then used the split-beam technique to measure swimming performance in situ for fish assumed to be yellow perch ( Perca flavescens) and alewives ( Alosa pseudoharengus) in two lakes in New York State, USA. The measured swimming speeds ranged from 0.5 to 6 body length (BL) per second for juvenile and adult fish. Other laboratory studies on swimming speeds have reported values in the same range. However, measured swimming speeds for smaller fish were unrealistically high (2–32 BL s −1) Advantages of the split-beam method are the ability of measuring swimming speed independently of visibility, with minimal disturbance and at large distances. Disadvantages are the inability to distinguish species observed and some variance in target location, which results in calculated average swimming speeds of 2.6 cm s –1 even for a stationary target.

A split beam method for measuring time-resolved circular dichroism

An improvement to the Lewis–Kliger method for measuring transient circular dichroism on the nanosecond time scale is described. The method uses a single-probe beam that is split into two different beams of plane polarized light entering the sample and a retarder from opposite directions in different succession. Rochon polarizers are used as high-quality polarizing beam splitters to select the slow axis component of the emerging elliptical polarized light beams. The intensities of the light beams are determined by an imaging spectrograph coupled to an intensified charge coupled device detector. The split beam method reduces the need for very precise calibration of the central strain plate acting as a retarder and controlling the ellipticity of the probe light. The necessary calculations are simple and can be shown to be equivalent to the formulas derived by Lewis and Kliger. The static CD spectrum of vitamin B12 is presented and compared to a spectrum obtained with a commercial instrument and standard technique. The time resolution of the instrument is demonstrated by observation of photobleaching of carbon monoxy myoglobin from horse heart muscle.

Dual-beam echo integration method for precise acoustic surveys

The echo integration method has been widely and effectively used for acoustic surveys of fisheries resources. In recent quantitative echo-sounders the dual-beam or split-beam method has been adopted, which improves the accuracy of in situ target strength (TS) measurement. The dual-beam method utilises a coaxial narrow and wide-beam pair. In ordinary dual-beam systems, echo integration is performed only for the narrow-beam signal, not for the wide-beam signal. If echo integration is also performed for the wide-beam signal, more information and better accuracy and precision of the acoustic survey of fish abundance can be gained. Comparing the integrator outputs of both beams, an index of avoidance behaviour of fish towards the surveying vessel can be compiled and unreliable measurements caused by, for example, noise contamination and failure in bottom detection can be found. Wide-beam integration is of better use when distributions of fish are shallow and sparse, because the sampling volume is greater. Furthermore, the error caused by transducer motion in bad weather conditions is smaller for the wide beam. By combining both beam echoes, the volume backscattering strength within individual fish schools can be measured precisely. The method is discussed theoretically. Experimental investigations were carried out on walleye pollock (Theragra chalcogramma (Pallas)), in the Bering Sea by our quantitative echo-sounding system, which provides independent echo integration results for both narrow and wide beams.

The development of an improved mode III delamination test for composites

A new test method for measuring the mode III interlaminar fracture toughness of composites has been devised. The method uses a specimen similar to the split cantilever beam method but the loading pattern is modified to ensure the unwanted mode II component is eliminated. A test jig has been manufactured and a series of tests to evaluate the new method has been conducted. Extensive finite element analyses have also been performed to investigate the performance of the test method. The results of these investigations confirmed that a mode III fracture was successfully achieved in the new test. Test results for an XAS/913C carbon-fibre/epoxy composite indicate that the critical mode III energy release rate is approximately six times the mode I value and two and a half times the mode II value.

Ontogenetic and Phylogenetic Variation of Form and Function of the Ocular Lens

AbstractThe crystalline lens of the eye is a unique optical structure that continues to develop within the eye throughout life. This process of development results in the formation of a lens with a gradient refractive index that has important optical consequences, particularly in the control of spherical aberration. The optical characteristics of the vertebrate crystalline lens are reviewed in terms of environmental concerns and spherical aberration. Lens shape and relative size are determined by such factors as whether the eye is to be used in air or water and whether it is to be used under scotopic or photopic conditions. The continued growth of the lens through life can be related to whether the lens exhibits positive or negative spherical aberration. In general, spherical aberration, as measured using a split laser beam method with excised lenses, is minimized in species with life histories indicating superior resolution ability. In addition, lens optical quality, as indicated by zonular differences in focal length, deteriorates with lens age. While the embryonic and post-embryonic lens undergoes significant change in size, shape and refractive index distribution, it appears that focal constancy is maintained, at least in certain species. This finding may indicate a means of simplifying the process of emmetropization.

Recrystallization of silicon film on insulating layers using a laser beam split by a birefringent plate

20-μm-wide, 1-mm-long, single-crystal Si films on SiO2 have been produced using a cw Ar laser beam split by a birefringent quartz plate. The single-scan recrystallized region width has been widened by multiple beam splitting. The resultant single-crystal region obtained by multiple scan from the seed is a 90-μm-wide and 100-μm-long area with rare grain boundaries. This split beam method uses the stable and highly efficient TEM00 mode and needs no prepatterned antireflection layers.