The Approach of Compensation of Air Refractive Index in Thermal Expansion Coefficients Measurement Based on Laser Feedback Interferometry

We present the thermal expansion coefficient （TEC） measurement technology of compensating for the effect of variations in the refractive index based on a Nd： YA G laser feedback system, the beam frequency is shifted by a pair of aeousto-optic modulators and then the heterodyne phase measurement technique is used. The sample measured is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams hit perpendicularly and coaxially on each surface of the sample. The reference beams hit on the reference mirror and the high-refiectivity mirror, respectively. By the heterodyne configuration and computing, the influences of the vibration, distortion of the sample supporter and the effect of variations in the refractive index are measured and largely minimized. For validation, the TECs of aluminum samples are determined in the temperature range of 29-748K, confirming not only the precision within 5 × 10-7 K-1 and the accuracy within 0.4% from 298K to 448K but also the high sensitivity non-contact measurement of the lower reflectivity surface induced by the sample oxidization from 448 K to 748 K.

Spatial Characteristics Analysis of Urban Expansion in Luoyang, China

The characteristics of urban space expansion reflect the changes of urban spatial layout and structure, as well as the orientation of urban development in the future. This paper uses the regional sector division method to divide the urban land into 8 orientations, based on the urban land space compaction index, and designs a sector partition compaction index. Based on the remote sensing image data of 1990, 2000, 2010, and 2020, the spatial characteristics of urban land expansion of Luoyang are analyzed by using the partition compaction index, expansion intensity index, fractal dimension, and standard deviation ellipse. The results show that: from 1990 to 2020, the urban overall planning of Luoyang has effectively guided the urban development, the urban land expands rapidly, the urban land compaction has been maintained at a low level, and the urban form has been tending to be reasonable;the urban land centroid gradually shifts to the southwest, and the distribution axis rotates clockwise from southwest-northeast to northwest-southeast, and the directionality of distribution gradually disappears;the urban land has gone through the development process of land filling-enlarging-refilling. The urban land expansion is relatively active in the region with an azimuth of 90°- 225°, and the urban expansion in the north of Luo River is relatively stable and is always filling mode.

Study of Difference-Expansion Embedding Schemes

Difference expansion（DE） is one of the famous schemes in the field of reversible data hiding.With the high efficiency and simplicity,DE also has received more attention over the years.DE has a good information capacity,but due to its major location map,the pure payload is rather low.Therefore many scholars did relevant improvements which let n pixels as a unit instead of the original two pixels as a unit and can adaptively adjust the number of embedding secret information according to the smoothness degree of the block,which achieves the result of improving the information payload or the image quality.In this paper,the study of DE-based reversible data hiding schemes is comprehensively discussed.The performance of DEbased schemes is evaluated and compared in terms of embedding capacity and stego-image quality.

Application of Fourier Series Expansion Method with PMLs to the Microcavities on Two-Dimensional Photonic Crystals

By using a Fourier series expansion method combined with Chew＇s perfectly matched layers （PMLs）, we analyze the frequency and quality factor of a micro-cavity on a two-dimensional photonic crystal is analyzed. Compared with the results by the method without PML and finite-difference time-domain （FDTD） based on supercell approximation, it can be shown that by the present method with PMLs, the resonant frequency and the quality factor values can be calculated satisfyingly and the characteristics of the micro-cavity can be obtained by changing the size and permittivity of the point defect in the micro-cavity.

Driving Mechanism of Urban Space Expansion in Luoyang, China

Urban space expansion is the result of the interaction between internal and external forces of the urban. Based on the remote sensing image data of 1990, 2000, 2010, and 2020, and the social and economic development data, this paper analyzes the driving mechanism of the Luoyang space expansion characteristics and its correlation characteristics. By using urban land use efficiency index, urban expansion elastic index;urban allometric growth index, and grey correlation analysis in 4 times sections and 3 periods. The research results show that the urban space expansion of Luoyang mainly comes from the needs and support of economic development, the coordination between urban space expansion and population development is poor, and urban space expansion effectively attracts the inflow of external funds, and the settlement of migrants, drives the development of the tertiary industry, and increases the local revenue.

Improved Geometric Model of Extensional Fault–bend Folding

Extensional fault-bend folds, also called rollovers, are one of the most common structures in extensional settings. Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative modeling of geometric relations between normal faults and the strata in their hanging walls. However, the oblique simple shear has a rather serious issue derived from the shear direction, particularly above convex bends. We use geometric and experimental methods to study the deformation of extensional fault-bend folds on convex bends. The results indicate that whether the fault bends are concave or convex, the shear direction of the hanging wall dips toward the main fault. On this basis, we improve the previous geometric model by changing the shear direction above the convex bends. To illustrate basin history, our model highlights the importance of the outer limit of folding instead of the growth axial. Moreover, we propose a new expression for the expansion index that is applicable to the condition of no deposition on the footwall. This model is validated by modeling a natural structure of the East China Sea Basin.