Christoffersensmall6741

Spectrophotometric measurement of particulate matter retained on filters is the most common and practical method for routine determination of the spectral light absorption coefficient of aquatic particles, a using the IS method. The relationships established for the three filter-pad methods are applicable to historical and ongoing measurements; for future work, the use of the IS method is recommended whenever feasible.In this paper, the impact of low-frequency noise on terahertz-computed tomography (THz-CT) is analyzed for several measurement configurations and pyroelectric detectors. We acquire real noise data from a continuous millimeter-wave tomographic scanner in order to figure out its impact on reconstructed images. Second, noise characteristics are quantified according to two distinct acquisition methods by (i) extrapolating from experimental acquisitions a sinogram for different noise backgrounds and (ii) reconstructing the corresponding spatial distributions in a slice using a CT reconstruction algorithm. Then we describe the low-frequency noise fingerprint and its influence on reconstructed images. Thanks to the observations, we demonstrate that some experimental choices can dramatically affect the 3D rendering of reconstructions. Thus, we propose some experimental methodologies optimizing the resulting quality and accuracy of the 3D reconstructions, with respect to the low-frequency noise characteristics observed during acquisitions.This paper proposes a staggered array to minimize heat concentration of an LED system. The purpose of this paper is to investigate temperature distribution with and without an optimized process of an LED system in various placements by experimental and numerical methods in order to improve thermal behavior. The proposed work develops an effective method to design an LED's placement for enhanced thermal uniformity and luminous efficacy, thus decreasing thermal concentrations and temperature of the LED system. Measured and calculated temperature distribution of the LED system shows good agreement.Tantalum pentoxide (Ta films has been estimated by Rutherford backscattering spectrometry (RBS). The variation of the optical constants of the films with changes in deposition parameters has been explained in the light of the change in average Ta-O bond lengths and oxygen coordination around Ta sites as obtained from EXAFS measurements. The trend in variation of the oxygen-to-tantalum ratio in the films obtained from RBS measurement, as a function of oxygen partial pressure used during sputtering, is found to follow the trend in variation of the oxygen coordination number around Ta sites obtained from EXAFS measurement.During the temporally and spatially modulated Fourier transform imaging spectrometer push-broom scanning process, the motion state of the spectrometer platform can vary. Thus, the target interferogram obtained from the image sequence deviates from the ideal interferogram obtained using high platform stability. The recovered target spectrum will not reflect the true target characteristics. We adopted target tracking to acquire the target position in the image sequence via a proposed kernel regression, with a relative deviation method for determining the target intensities, and the recovery of the spectrogram using the nonuniform fast Fourier transform algorithm. We tested our algorithm on simulated and experimentally obtained aerial images and, from comparison with accurate spectrograms, demonstrate the effectiveness of the proposed method.Two-dimensional materials such as MoS.Frequency variation in spatial frequency domain imaging is a powerful tool for adjusting the penetration depth of the imaging signal and the parameter sensitivity toward absorption and diffusive and subdiffusive scattering. Through our computational analysis, using an analytical solution of the radiative transfer equation, we add quantitation to this tool by linking the different spatial frequency regimes to their relative information content and to their absolute depth sensitivity. Special focus is placed on high spatial frequencies by analysis of the phase function parameter γ and its significance and ambiguity in describing subdiffusive scattering.Detecting objects in three-dimensional (3D) space may be useful for various applications. We present a method to detect the 3D locations of objects using computationally reconstructed images obtained by integral imaging. The new algorithm exploits the space-variant blurring properties of the reconstructed images to detect and isolate objects at their depth locations, while removing traces of objects from other depths. With regard to previous work, the proposed method is more efficient and more resistant to noise; it gives more information about the detected object's depth, and improves object isolation and presentation.A type of wave-breaking-free mode-locked dual-wavelength square pulse was experimentally observed in a figure-eight erbium-doped fiber laser with ultra-large net-anomalous dispersion. A 2.7 km long single-mode fiber (SMF) was incorporated as a nonlinear optical loop mirror (NOLM) and provided largely nonlinear phase accumulation and anomalous dispersion, which enhanced the four-wave-mixing effect to improve the stability of the dual-wavelength operation. In the NOLM, the long SMF with small birefringence supported the Sagnac interference as a filter to manage the dual-wavelength lasing. The dual-wavelength operation was made switchable by adjusting the intra-cavity polarization loss and phase delay corresponding to two square pulses. When the pump power was increased, the duration of the square pulse increased continuously while the peak pulse power gradually decreased. This square-type pulse can potentially be utilized for signal transmission and sensing.In this paper, the use of three liquid crystal displays (LCDs) as targets for an experimental corneal topographer is proposed. The main advantage is that the geometrical pattern in the target can be modified without moving any mechanical part to apply the dynamic point shifting (DyPoS) method. Some results on the capabilities of the LCDs, obtained with photo frames, for measuring a 6.37 mm radius of curvature calibration sphere, and applying the DyPoS method, are presented. It is shown that the error in measuring the radius of curvature with DyPoS is reduced to 3% of the real value and the RMS in elevation or sagitta differences is around 15 μm, 30% or 66% of the values obtained without DyPoS, respectively.With graphene as a saturable absorber, the efficient and stable 1.4 μm dual-wavelength operation of NdYAG ceramic laser is demonstrated. A maximum total average output power of 601 mW is obtained under the pump power of 22.3 W, corresponding to an optical-optical conversion efficiency of 2.7%. The minimum pulse width and the highest pulse repetition rate are 470 ns and 101 kHz, respectively.We show, both theoretically and experimentally, that the propagation of optical vortices in free space can be analyzed by using the width [w(z)] of the host Gaussian beam and the inner and outer radii of the vortex beam at the source plane (z=0) as defined in [Opt. Lett.39, 4364 (2014)10.1364/OL.39.004364OPLEDP0146-9592]. We also studied the divergence of vortex beams, considered as the rate of change of inner or outer radius with the propagation distance (z), and found that it varies with the order in the same way as that of the inner and outer radii at z=0. These results may be useful in designing optical fibers for orbital angular momentum modes that play a crucial role in quantum communication.Link acquisition strategies are key aspects for interspacecraft laser interferometers. We present an optical fiber-based setup able to simulate the interspacecraft link for the laser ranging interferometer (LRI) on gravity recovery and climate experiment Follow-On. It allows one to accurately recreate the far-field intensity profile depending on the mispointing between the spacecraft, Doppler shifts, and spacecraft attitude jitter. Furthermore, it can be used in late integration stages of the mission, since no physical contact with the spacecraft is required. The setup can also be easily adapted to other similar missions and different acquisition algorithms.The mechanism of charge on the near-field intensity distribution is revealed for metallic and dielectric particles with sizes ranging from 10 nm to 10 μm. The theoretical foundation of near-field intensity perturbations is in the discontinuity of the tangential components of the magnetic fields on either side of the interface between the particle and its surrounding medium, since excess electrons form a thin metal-like layer with elevated conductivity. We have shown that the local fields alter marginally if charges are imposed on a surface of a metallic particle. But an intensity amplification is identified in the vicinity of charged dielectric particles with sizes smaller than the wavelength. Specifically, we have demonstrated that the electromagnetic field is amplified near the poles of the particle as a result of the oriented electric and incident fields. In contrast, a dielectric particle that is large compared to the wavelength becomes opaque with a deep shadow at the side opposite to the beam incidence. As a result, intensity damping is identified near a charged sphere in the geometric optics regime. At significant charge densities, the physical properties of a conductive layer play a dominant role in forming the 3D intensity distribution independent of conductivity or permittivity of the particle core. These findings suggest that some electrically chargeable particles have the potential to be used as optical devices with properties tunable through their net surface charge.This paper presents a new design of a planar solar concentrator with spectral splitting of light for space applications. https://www.selleckchem.com/products/fb23-2.html This concentrator spectrally splits the incident light into mainly two parts. Each part is then focused onto specific spatially separated photovoltaic cells allowing for independent control of respective cells' output power. These advantages of both spectral splitting and light focusing are combined here because of a specific diffraction grating superimposed on a Fresnel lens. The theoretical principle of the optical design is presented with optimization of each element and improvement steps including optimization of grating period evolution along the lens and testing of two kinds of gratings (a blazed and a lamellar one). First numerical results are presented highlighting the possibility to design a concentrator at about 10× or more for each cell with an output power larger than that of a classical concentrator focusing on a GaAs single junction cell and less than 10% of losses for tracking errors up to ±0.8°. Some experimental results are also presented.A technique for determining the optical path difference (OPD) between two Raman beams using a frequency-modulated continuous-wave method is investigated. This approach greatly facilitates the measurement and adjustment of the OPD when tuning the OPD is essential to minimize the effects of the diode laser's phase noise on Raman lasers. As a demonstration, the frequencies of the beat note with different OPDs are characterized and analyzed. When the measured beat frequency is 0.367 Hz, the OPD between Raman beams is zero. The phase noise of the Raman laser system after implementation of zeroing of the OPD is also measured.