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This paper mainly focuses on evaluating American options under regime-switching jump-diffusion models (Merton's and Kou's models). An efficient numerical method is designed for the concerned problems. The problem of American option pricing under regime-switching jump-diffusion models can be described as a free-boundary problem or a complementarity problem with integral and differential terms on an unbounded domain. By analyzing the relation of optimal exercise boundaries among several options, we truncate the solving domain of regime-switching jump-diffusion options, and present reasonable boundary conditions. For the integral terms of the truncated model, a composite trapezoidal formula is applied, which guarantees that the integral discretized matrix is a Toeplitz matrix. Meanwhile, a finite difference scheme is proposed for the resulting system, which leads to a linear complementary problem (LCP) with a unique solution. Moreover, we also prove the stability, monotonicity, and consistency of the discretization scheme and estimate the convergence order. In consideration of the characteristics of the discrete matrix, a projection and contraction method is suggested to solve the discretized LCP. Numerical experiments are carried out to verify the efficiency of the proposed scheme. [ABSTRACT FROM AUTHOR]

AlON transparent ceramics have broad application prospects in national defense and civil use due to its good light transmission, thermal shock stability, mechanical properties and good processability. The AlON powder were prepared in batches by an improved carbothermal reduction nitridation/fluidized bed method in this article. A single batch can prepare up to 2 kg, and no second phase was observed in the XRD patterns of AlON powder. Laser particle size analysis shows an average particle size of 1.54 µm and the particle size distribution is uniform. Green body with good uniformity and high density was obtained using the powder molded by cold isostatic pressing. AlON transparent ceramics with transmissivity of 82.3% and bending strength of 310 MPa were prepared by sintering temperature at 1 850 °C and nitrogen pressure of 5 MPa, which has certain practical significance for promoting the application of AlON transparent ceramics. [ABSTRACT FROM AUTHOR]

The sapphire single crystal plate with size of 485 mm x 985 mm x 12 mm was successfully prepared by a large-size edgedefined film-fed growth (EFG) furnace designed and developed independently. After cutting and grounding, the crystal was formed into transparent armors composited with glass and polycarbonate. The surface density with the size of 352 mm x 351 mm x 33 mm is 79. 27 kg/m², and the surface density of the other is 79.38 kg/m² with the size of 351 mm x 342 mm x 33 mm. Targeting tests were conducted on the transparent armors using incendiary shells with diameters of 7.62 mm and 12.7 mm, respectively. The experimental results show that the transparent armor based on sapphire crystal plate has excellent impact resistance during firing at a normal angle of 0° and with a distance of 100 m which from target to the armors. [ABSTRACT FROM AUTHOR]

The 14 mm x 12 mm AlN single crystal is synthesized by the homoepitaxial physical vapor transport method. The crystal sample sliced from the boule is processed by lapping and chemical mechanical processes (CMP). The sample is characterized by Raman spectrometer, high resolution X-ray diffractometer, X-ray photoelectron spectrometer and photoluminescence spectrometer. The Raman results show that the full width at half maximum (FWHM) of the E2 (high) phonon mode of Raman spectrum is 3.3 cm-1 in the central region of the sample, and the FWHM of the E2 (high) phonon mode of Raman spectrum is 4. 3 cm-1 in the edge of the sample, the AlN single crystal exhibits high crystal quality. The FWHM of the X-ray rocking curve increase to 100" in the central region of the homoepitaxial growth crystal, while the FWHM of the X-ray rocking curve is 205" in the edge region of the homoepitaxial growth crystal, which indicates defects exist in the crystal. XPS results show that there are C, O, Si impurity elements in the crystal, and the atomic concentration of the impurities is 0.74%, 1.43% and 2.14%, respectively. It is found that the mainly oxygen impurities exist in the crystal in the form of Al--O, N--Al--O bonding. PL spectra show that crystal contains VAl-ON compound defect and VAl point defect. [ABSTRACT FROM AUTHOR]

In order to meet the demand for low-absorption sapphire crystal materials in important national defense projects in China, a self-produced crystal growth apparatus is developed in this study and the successful growth of low-absorption sapphire crystal can be achieved. The as-obtained crystal exhibits excellent transparency in the ultraviolet, visible, and near to midinfrared wavelength ranges. The transmittance is above 83% as the wavelength in the range of 250 nm to 400 nm, while the transmittance is above 85% as the wavelength in the range of 400 nm to 4 200 nm. On the basis of the characterization tests conducted on different regions of the crystal, the average dislocation density of crystal can be determined as 253. 19 cm-2. The rocking curve shows symmetrical and sharp peaks with a full width at half maximum of 14". In addition, it is worth noting that the light absorption coefficient of crystal is (23.3 -30.4) x 10-6 cm-1 at the wavelength of 1 064 nm, indicating that the impurity elements inside the crystal can be effectively controlled. Accordingly, the outstanding optical properties crystal can be applied in high-energy laser systems, space camera lenses and other relevant fields. [ABSTRACT FROM AUTHOR]

Ce3+ doped gadolinium aluminum gallium garnet (GAGG:Ce) scintillation crystal has the advantages of high light output, high energy resolution, short decay time, no self radiation and non-deliquescence, which make it has a broad application prospect in nuclear medical imaging, security inspection and environment detection et al. This paper reported the Czochralski growth and scintillation properties of GAGG:Ce single crystal. GAGG:Ce raw material was synthesized by high temperature solid state reaction method. By means of XRD analysis, the raw material sintered at 1 500 °C for 12 h is verified to be pure GAGG phase. GAGG:Ce crystal with size of Φ50 mm x 90 mm was successfully grown by Czochralski method. The transmission spectrum, X-ray excited emission spectrum and pulse height spectrum of the crystal were tested. Results show that optical transmittance at 550 nm for the sample with thickness of 7 mm reaches as high as 81.5%. The X-ray excited emission peak central wavelength of the GAGG:Ce crystal is located at 550 nm. The light output of the GAGG:Ce crystal is 59 000 photons/ MeV and the energy resolution is 6.2%@662 keV. The decay time is 149 ns and a slow component of 748 ns. [ABSTRACT FROM AUTHOR]

Magnesium aluminate spinel, as an advanced transparent ceramic material, has excellent properties such as wide transmission band, high transmittance, isotropy, high hardness, high strength, high thermal conductivity, high thermal shock resistance, high corrosion resistance, and high-temperature stability. It can be widely applicated to the fields of national defense security and key high-performance equipment, such as infrared guidance windows, high Mach aircraft domes, transparent armor and photoelectronic equipment windows in extreme environments. In this paper, the basic properties and the development of magnesium aluminate spinel transparent ceramic are summarized, the research and development work of Sinoma Sythentic Crystal Co., Ltd. over the last three decades are focused on, including high-purity spinel powder synthesis, magnesium aluminate spinel transparent ceramic forming and sintering process, the performance and application. The difficulties encountered in material development and the challenges faced in the application development are analyzed. Based on these, the research directions and methods are considered, its application and development are prospected. [ABSTRACT FROM AUTHOR]

Highlights • SLT crystals with thickness of 3.2 mm were prepared by VTE method. • The chemical composition in SLT crystals is about 49.99 mol%. • The forward and reverse poling fields are 159 V/mm and 145 V/mm, respectively. Abstract A stoichiometric lithium tantalate (SLT) crystal, 3.2 mm in the thickness and approximate 56 mm in the diameter, was prepared employing improved vapor transport equilibration (VTE) method. The chemical composition in SLT crystals is about 49.99 mol%. The compositional depth profile and uniformity along the radial direction were characterized. The composition deviation in the whole wafer is less than 0.02 mol%. The poling fields for ferroelectric domain reversal of SLT crystals were measured by applying ramped voltages using liquid electrodes. The forward and reverse poling fields are 159 V/mm and 145 V/mm, respectively, and their uniformity in the whole SLT crystal is promising. [ABSTRACT FROM AUTHOR]

The twins were observed and investigated in vapor transport equilibration (VTE) treated lithium tantalate crystals by burying congruent lithium tantalate crystals (CLT) in a Li-rich polycrystalline powder. Twins and their etched patterns were observed under an optical polarizing microscope, and the geometry of the twins was discussed. Twin composition planes were the 01 1 ¯ 2 planes. The cause of twinning was analyzed and verified by experiment. The results indicate that the emergence of twins is due to sintering stress, which arises from sintered Li-rich polycrystalline powders at high temperature. 3.2 mm thick stoichiometric lithium tantalate (SLT) crystals without twins were obtained by setting corundum crucibles over the top of the crystals to make crystals free from the sintering stress. In addition, cracks were observed at the intersection of twin bands, and the stress caused by the dislocation pile-up was considered to be the reason for the formation of cracks. [ABSTRACT FROM AUTHOR]