Total Energy Transmission Research Articles

Design of waveguide with double layer diffractive optical elements for augmented reality displays

We investigated a diffraction optical waveguide structure with a double layer coupling configuration. This double layer-coupled diffraction optical waveguide structure modulates light information through wavefront modulation for propagation within the optical waveguide and then reproduces the light information through further wavefront modulation, thus achieving optical information transmission. Analysis indicates that the theoretical maximum field of view can reach 90° × 90°. With an actual field of view set to 53° × 53°, an entrance pupil size of 3.2 × 3.2 mm², an eye relief of 10 mm, and 50 pupil expansion, the system’s total energy transmission efficiency is 37%, with field of view uniformity at 91% and uniformity within the eye movement range reaching 97%.

Investigation of the Relationship between Vibration Signals Due to Oil Impurity and Cavitation Bubbles in Hydraulic Pumps

Although hydraulic pumps are frequently used in daily life, improper use due to oil analysis or oil contamination is ignored. There is no instantaneous inspection; instead, the oil is changed periodically at certain times, whether it is contaminated or not. Hydraulic systems operate based on Pascal’s law, which states that the fluid will distribute the pressure equally to every point in a closed area. The fluid oil taken from an oil reservoir is moved into the pump by engine power. During this movement, as it passes through different pressure areas and different sections, undesirable events such as viscosity change and gas formation occur in the hydraulic oil. These formations collide with the outer walls and cause cavitation with respect to unwanted oil impurities. This cavitation causes unwanted vibration signals to occur in the normal working order of the system. As a result of cavitation, the particles that affect the lubricity and fluidity of the oil in the oil are mixed into the liquid and circulate freely. At the connection points, the blockage caused by the liquid in the pump cylinder block or the valve plate and the collisions of particles is effective. As a result, it creates vibrations of different frequencies. The frequency and amplitudes of these vibrations differ according to the degree of oil contamination. A method has been developed to find the degree of contamination of the oil circulating in the pump by looking at the amplitude and frequency of these vibrations measured from the motor body. There exist standards about the pollution of hydraulic fluid. With these standards, the maximum number of particles allowed for a given pollution level is defined. This topic is discussed in the conclusion to this study. This method has also been proven experimentally. Error and vibration analysis studies on pumps using a different approach are available in the literature. In these studies, pressure variation, total energy transmission, or artificial intelligence models were used to detect anomalies in the pump. In this study, the impurity rate of the oil was set at five different levels and the operating regime of the pump at each level was investigated experimentally. Rayleigh–Plesset and Zwart–Gerber–Belamri models, which are the most common cavitation models, were used to explain the bubble formation in the moving oil and the relationship of these bubbles with vibration. Frequency components were examined by the Discrete Fast Fourier Analysis method, where the operation of the pump was affected by the increase in oil impurity.

Role of Interfacial Conditions on Blast Overpressure Propagation Into the Brain.

The complex interfacial condition between the human brain and the skull has been difficult to emulate in a surrogate system. Surrogate head models have typically been built using a homogeneous viscoelastic material to represent the brain, but the effect of different interfacial conditions between the brain and the skull on pressure transduction into the brain during blast has not been studied. In the present work, three interfacial conditions were generated in physical surrogate human head models. The first surrogate consisted of a gel brain separated from the skull by a layer of saline solution similar in thickness to the cerebrospinal fluid (CSF) layer in the human head: the fluid interface head model. The second surrogate head had the entire cranial cavity filled with the gel: the fixed interface head model. The third surrogate head contained a space-filling gel brain wrapped in a thin plastic film: the stick-slip interface head model. The human head surrogates were evaluated in a series of frontal blast tests to characterize the effect of skull-brain interfacial conditions on overpressure propagation into the gel brains. The fixed and the stick-slip interface head models showed nearly equal peak brain overpressures. In contrast, the fluid interface head model had much higher in-brain peak overpressures than the other two models, thus representing the largest transmission of forces into the gel brain. Given that the elevated peak overpressures occurred only in the fluid interface head model, the presence of the saline layer is likely responsible for this increase. This phenomenon is hypothesized to be attributed to the incompressibility of the saline and/or the impedance differences between the materials. The fixed interface head model showed pronounced high frequency energy content relative to the other two models, implying that the fluid and the stick-slip conditions provided better dampening. The cumulative impulse energy entering the three brain models were similar, suggesting that the interface conditions do not affect the total energy transmission over the positive phase duration of a blast event. This study shows that the fidelity of the surrogate human head models would improve with a CSF-emulating liquid layer.

Bulk Fill Resin Composite Materials Cured with Single-Peak versus Dual-Peak LED LCUs

Abstract Introduction: Manufactures claim that recently introduced bulk fill materials (BFM) can be cured adequately in 4 mm increments. This requires adequate light energy to be transmitted through the material to ensure adequate polymerization at the bottom of the increment. Aim: To compare the total light energy transmission through three BFMs and bottom/top (B/T) surface Vickers hardness (VH) when cured with single-peak versus dual-peak LED LCUs. Methods and Materials: Samples (n=5) of two viscous BFMs, Tetric EvoCeram® Bulk Fill X-tra fil® [XF] flowable SureFil, were prepared. A conventional RBC, Tetric EvoCeram® was used as a control. Using MARC® RC, the irradiance delivered to top surface of samples was adjusted to 1200 mW/cm2. Samples were cured with singlepeak EliparTM S10 or dual-peakBluephase® G2 for 10 seconds and irradiance transmitted to the bottom surface measured. Samples were stored for 24 hours, prior to VH measurements B/T VH ratios were calculated. Statistically analysed used oneway ANOVA (α=0.05). Results: There was no statistically significant difference for B/T total energy transmission between materials except XF with EliparTM S10 (P<0.001). Total energy transmission ranged from 0.7 J/cm2 to 1.5 J/cm2. There was no statistically significant difference for B/T VH ratios between materials (P>0.05) when materials were cured with single-peak versus dual-peak LCU’s, XF>SDR>TEC>TBF. TBF alone, did not reach the generally accepted B/T VH of 80%. Conclusions: Both single-peak and dual-peak LCU’s were equally effective for curing the studied bulk fill materials. Manufacture’s recommended total energy delivered to the top surface may not always be sufficient for effective curing.

Effect of curing time on Vickers microhardness of bulk-fill materials

Purpose: To compare the total light energy transmission (J/cm2) through bulk fill composite materials (BFMs) and Vickers microhardness (VH) when cured with a single peak LED LCU at two different exposure times. Methods and materials: Two viscous BFMs, Tetric EvoCeram Bulkfil (Ivoclar Vivadent) [TBF], XtraFil (Voco) [XF], and two flowable BFMs, Surefil SDR (Dentsply) [SDR], XtraBase (Voco) [XB] were prepared in 4mmdeep Delrin® rings (DuPont, Mississauga, Ontario, Canada). Tetric Evoceram [TEC], a conventional composite (Ivoclar Vivadent) was used as a control. Using MARC® RC, the irradiance delivered to the top surface of the samples was adjusted to either 800mW/cm2 and delivered for 2 s (16 J/cm2) or 1600mW/cm2 for 10 s (16 J/cm2). The irradiance (mW/cm2) transmitted to the bottom surface was measured with MARC® and the internal software converted this to J/cm2. Samples were stored post-irradiation in a dry, sealed, light-proof container at room temperature (21± 10 ◦C) for 24h. Three measurements were taken from both top and bottom surfaces of each sample using a Vickers Hardness TestingMachine (HM-200 Series, Mitutoyo Corporation, Tokyo, Japan) with 200g load applied for 10 s. Bottom to top (B/T) VH ratios were calculated. Data were statistically analysed using one-way ANOVA (a=0.05). Results: Table 1. For B/T total energy transmission, comparing each material when cured with 800mW/cm2 × 20 s versus 1600mW/cm2 × 10 s, there was extremely statistical significant difference for all materials used with more total energy transmitted at 800mW/cm2 × 20 s (P TEC>XF>TBF>XB. For B/T VH ratios. Comparing each material when cured with 800mW/cm2 × 20 s versus 1600mW/cm2 × 10 s, XB and TEC showed extremely significant difference with higher B/T VH ratio when cured with 800mW/cm2 × 20 s (P 0.05). XB did not reach the generally accepted [1] 80% B/T VH ratio (74.8% @ 800mW/cm2 × 20 s, 64.0% @ 1600mW/cm2 × 10 s). Comparing B/T VH ratios ranged from 74.8% to 91.6%(TEC>XF>SDR>TBF>XB @800mW/cm2 × 20 s) and ranged from 64.0% to 88.3% (XF>SDR>TEC>TBF>XB @1600mW/cm2 × 10 s).

Cylindrically polarized vortex beams generated by subwavelength concentric Al metallicgratings

Cylindrically polarized vortex beams generated by subwavelength concentric Al metallicgratings are studied in numerical simulations and experiments. The simulation results showthe performances of Al subwavelength metallic gratings as polarizing beamsplitters inthe visible light band are better than those of the generally used Au and Agsubwavelength metallic gratings. A subwavelength concentric Al metallic grating witha period of 200 nm and an etched depth of 100 nm is fabricated using e-beamlithography and RIE etching technology. Next, the intensity and polarizationdistributions of the generated beam are measured at three visible wavelengths 488, 532and 633 nm, which show a good performance of polarization purities beyond 93%and total energy transmission efficiencies beyond 32%. In addition, the focusedfield intensity distributions of the generated beam are also measured based ona confocal microscopy system, which also confirms the existence of the spiralgeometrical phase and the influence of the geometrical phase on focused fields.

Vibration characteristics of bone conducted sound in vitro.

A dry skull added with damping material was used to investigate the vibratory pattern of bone conducted sound. Three orthogonal vibration responses of the cochleae were measured, by means of miniature accelerometers, in the frequency range 0.1-10 kHz. The exciter was attached to the temporal, parietal, and frontal bones, one at the time. In the transmission response to the ipsilateral cochlea, a profound low frequency antiresonance (attenuation) was found, verified psycho-acoustically, and shown to yield a distinct lateralization effect. It was also shown that, for the ipsilateral side, the direction of excitation coincides with that of maximum response. At the contralateral cochlea, no such dominating response direction was found for frequencies above the first skull resonance. An overall higher response level was achieved, for the total energy transmission in general and specifically for the direction of excitation, at the ipsilateral cochlea when the transducer was attached to the excitation point closest to the cochlea. The transranial attenuation was found to be frequency dependent, with values from -5 to 10 dB for the energy transmission and -30 to 40 dB for measurements in a single direction, with a tendency toward higher attenuation at the higher frequencies.

Effect of secondary electron emission on sheath potential in an electron cyclotron resonance plasma

The sheath potential φM is calculated from the difference between the plasma potential and the floating potential. The plasma potential has been measured by using a retarding field analyzer with an entrance slit located in front of it. The electron temperature Te and ion temperature Ti are also measured with the same analyzer in an electron cyclotron resonance plasma. Comparing the normalized sheath potential, −eφM/kTe, with the different theoretical values, it is found that the secondary electron emission could not be neglected in our experiment and is noncritical. The critical emission corresponds to zero electric field at the emitter. The various calculations have shown that the thermionic electron emission need not be required to be taken into consideration. The total energy transmission factors δT(=W/FTe, where W is the energy flux from the plasma, F is the ion flux, and Te is the electron temperature at the sheath edge) for hydrogen, nitrogen, and argon plasmas are calculated from the estimated secondary electron emission coefficient and the sheath potential, respectively.

Upgrade of the Vapor Shield Modeling Code MAGFIRE

An upgrade of the MAGFIRE code used to model the vapor shield (VS) effect was needed to include: higher disruption heat fluxes of interest to ITER, a comparison of carbon to beryllium erosion depths and the effects of ion/electron beam charge separation in the VS. Results show that higher heat fluxes give a lower total energy transmission factor (f) as expected. Beryllium divertor plates have much higher erosion depths than do carbon as well as a higher f. Charge separation has a small effect on the VS stopping power for electrons and on the distribution of deposited energy in the VS. However, the effect will be more important as the disruption particle energy increases.

Two-Photon Absorption in Polybenzidine

AbstractPolymers of Benzidine were synthesized by hydrogen peroxide reaction catalyzed by horseradish peroxidase enzyme. The polymerization reaction was carried out at room temperature in a monophasic organic solvent with a small amount of water at pH 7.5.The technique of degenerate four-wave mixing (DFWM) with nanosecond and picosecond pulses was employed to measure the third-order nonlinear optical susceptibility χ. The samples were studied in solution in Dimethyl sulfoxide:Methanol in volume ratio 4:1. The observed values are of order 10−9 to 10−8esu. Measurements on a thin film agree approximately with the extrapolated values fron solution measurements. Picosecond time resolved measurements indicate a pulse-width limited response followed by a small slow component. Investigation of the total energy transmission as a function of the incident intensity and fluence at 532 nm for pico- and nanosecond pulses indicates reverse saturable absorption. As we observe the nanosecond and picosecond curves to be superimposed for the intensity plot but not for fluence, we conclude that the nonlinearity is predominantly due to two-photon absorption. Numerical analysis of the data yields a value of 12.25 cm/GW for the two-photon absorption coefficient β. The imaginary component of χ obtained is 5 × 10−9esu. The material appears to be a good candidate for applications in optical power limiting and switching.

The Most Favorable Absorption of the Phase Plate in Phase Contrast Microscopy

Accepting the conclusion of Zernike that phase structures in an object may be converted into apparent amplitude structures in its image by alteration of phase of portions of the light at the Fraunhofer diffraction spectrum, a simple relationship between intrinsic object contrast and optimum absorption of the phase plate is developed. For this purpose, the definition of contrast as the ratio of the brightness difference between adjacent small areas in the image to the greater brightness of the two is employed, and considered more suitable than the simple ratio of the brightest area to the darkest. The departure of biologic structures from the periodicity and grating constants characteristic of perfect object gratings is handled by means of a parameter defined as the ratio of the energy transmission by the null order of the diffraction spectrum to the total energy transmission by all orders admitted by the limited apertures of the microscope. Calculations based on the formula developed are given in the form of tables and graphs.