Measuring refractive index gradient of sugar solution

To measure refractive index at a particular altitude in a solution with vertical refractive index gradient, a transparent wedge-shaped container was constructed altogether with the development of mathematical formula derived from the Snell’s law. The refractive index of the solution can be calculated by measuring the angles of incoming and outgoing laser beams relative to respective normal line. By varying height of the laser beam, the refractive index as a function of height of a sugar solution was obtained. This technique is applied to investigate Fata Morgana which is a kind of superior mirage resulting from bending of light in a medium with density gradient.

Quality of Automated Stereotactic Radiosurgery Plans in Patients with 4 to 10 Brain Metastases

The purpose was to compare linac-based stereotactic radiosurgery and hypofractionated radiotherapy plan quality of automated planning, intensity modulated radiotherapy (IMRT) and manual dynamic conformal arc (DCA) plans as well as single- and multiple-isocenter techniques for multiple brain metastases (BM). For twelve patients with four to ten BM, seven non-coplanar linac-based plans were created: a manually planned DCA plan with a separate isocenter for each metastasis, a single-isocenter dynamic IMRT plan, an automatically generated single-isocenter volumetric modulated arc radiotherapy (VMAT) plan, four automatically generated single-isocenter DCA plans with three or five couch angles, with high or low sparing of normal tissue. Paddick conformity index, gradient index (GI), mean dose, total V12Gy and V5Gy of uninvolved brain, number of monitor units (MUs), irradiation time and pass rate were compared. The GI was significantly higher for VMAT than for separate-isocenter, IMRT, and all automatically generated plans. The number of MUs was lowest for VMAT, followed by automatically generated DCA and IMRT plans and highest for manual DCA plans. Irradiation time was the shortest for automatically planned DCA plans. Automatically generated linac-based single-isocenter plans for multiple BM reduce the number of MUs and irradiation time with at least comparable GI and V5Gy relative to the reference separate-isocenter DCA plans.

Planar refractive index patterning through microcontact photo-thermal annealing of a printable organic/inorganic hybrid material

We demonstrate proof-of-concept refractive-index structures with large refractive-index-gradient profiles, using a micro-contact photothermal annealing (CPA) process to pattern organic/inorganic hybrid materials comprising titanium oxide hydrate within a poly(vinyl alcohol) binder....

Synthesis methods for realistic images of three-dimensional scenes containing media with a refractive index gradient

The paper presents the results of a study of the possibility of implementing an effective and physically correct stochastic ray tracing in gradient media based on the Runge-Kutta method. For implementation in the photorealistic rendering system, the specifics of the ray tracing method in complex three-dimensional scenes were considered. One of the main features of ray tracing in geometrically complex scenes is the large volume of geometric primitives that need to be tested for the intersection of the ray segment with the primitives. A method of ray propagation in voxel space of the scene is proposed. The method allows significant speeding up the process of searching for ray intersections with geometry primitives. To implement these ray tracing features the special program interface for gradient media was proposed, which can become the basic interface for a media of all types. Methods for calculating the luminance of all lighting components in gradient media were considered. The results of modeling the propagation of rays and image synthesis in a fiber with a refractive index gradient are presented.

Hybrid Adaptive Wavelet-Based Optical Flow Algorithm for Background Oriented Schlieren (BOS) Experiments

Quantitative analysis of the flow field is an effective method to study hydrodynamics. As a flow field measurement technology, the Background Oriented Schlieren (BOS) is widely used. However, it is difficult to measure the complex transparent flow field (flow field with large refractive index gradient) using the BOS experiment. In order to overcome this difficulty and improve the accuracy of the BOS experiment, this paper presents a hybrid adaptive wavelet-based optical flow algorithm for the BOS. The current algorithm is a combination of the traditional optical flow algorithm and the wavelet-based optical flow algorithm. By adding the initial value constraints, the adaptive scale constraints, and the adaptive regularization constraints, the algorithm can effectively overcome the above-mentioned difficulty and also improve its accuracy. To further illustrate the feasibility of the proposed method, this paper uses the simulation data, the data of the DNS datasets, and the data of the BOS experiment to verify the performance of the algorithm. The experiment of comparing the proposed algorithm with the existing ones is carried out on the DNS datasets and the data of the BOS experiment. Finally, the proposed method is verified by a practical BOS experiment. The results show that the proposed algorithm can effectively improve the measurement accuracy of displacements.

High Homogeneity of Magnesium Doped LiNbO3 Crystals Grown by Bridgman Method

A series of LiNbO3 crystals doped with various MgO concentrations (0, 3%, and 5 mol%) was simultaneously grown in one furnace by the modified vertical Bridgman method. The wet chemistry method was used to prepare the polycrystalline powders, and the growth conditions were optimized. The full width at half maximum of high-resolution X-ray rocking curves for (001) reflection of 5 mol% Mg doped lithium niobate (LN) crystal was about 8″, which meant it possessed high crystalline quality. The OH− absorption spectra shifted to 3534.7 cm−1, and the UV absorption edge violet shift indicated that 5 mol% MgO successfully doped in LN and exceeded the threshold. The extraordinary refractive index gradient of 5 mol% Mg doped LN crystal was as small as 2.5 × 10−5/cm, which exhibited high optical homogeneity.