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Synthetic Aperture Radar (SAR) Tomography (TomoSAR) is a three-dimensional SAR imaging technique that uses multiple passes to process complex SAR images and obtain three-dimensional spatial scattering information to derive the elevation scattering distribution. Due to its own shortcomings, the elevation obtained by the traditional spectral estimation method has low resolution in the elevation direction and is affected by noise. The imaging algorithm based on compressed sensing can achieve super-resolution reconstruction in the elevation direction while reducing the number of observations. However, the CS algorithm still faces challenges when applied to real-world tomographic SAR imaging. In particular, it often requires numerous iterations to achieve satisfactory results, which significantly reduces its processing efficiency in large-scale tomography. To address the above issues, in this paper, we proposed an urban 3D reconstruction of VHR SAR images using an iterative optimization algorithm and layover fixed-order model. The iterative optimization algorithm and the layover fixed-order model consist of two parts: The TomoSAR imaging equation is solved by the two-step iterative shrinkage/thresholding (TwIST) algorithm, and the number of scatterers K is estimated by the Bayesian Information Criterion (BIC). In this paper, the effectiveness of TwIST-BIC in TomoSAR imaging in urban areas is verified with real TerraSARX data. By comparing with the OMP algorithm based on matching tracking and the FISTA algorithm based on gradient descent. The TWIST-BIC method is less complex, converges faster, and combines both execution speed and super-resolution, which can effectively solve the processing efficiency problem in large-area tomography and acquire high-resolution tomographic analysis.

In 3D digital urban planning applications, a model file may contain multiple building models, however, a single model or model component are very often needed to be used and operated independently. This paper studies 3D model segmentation and blanking technology in 3D urban planning. Three kinds of blanking and segmentation methods are in detail discussed. Finally, a 3D planning prototyping system is developed that include blanking and segmentation functions of the model. The experiment and their results verify the feasibility and efficiency of the method this paper proposed.

Differences of both amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) polymorphisms were compared between the 60-d-old rice (Oryza sativa L. cv. DH7) and F3 rice plants (SP3) derived from seed, which endured a 7-d-space flight in March 2002. Total leaf AFLP DNA bands amplified from 22 primer pairs were 537 in DH7, whereas 562 in SP3. From the total 267 SSR DNA bands generated by 267 primer pairs, 39 were polymorphic with 22 larger (56 %) or 17 smaller (44 %) fragment size bands. The greatest numbers of AFLP DNA bands were amplified by primer E1M1 in DH7 (33) and E3M1 in SP3 (35), whilst the least by E4M3 in DH7 (14) and E5M2 in SP3 (16).

A novel printed antenna with a frequency reconfigurable feed network is presented. The antenna consists of a bowtie structure patch radiating element in the inner space of an annulus that is on a nongrounded substrate with a ferroelectric (FE) Barium Strontium Titanate (BST) thin film. The bowtie patch is fed by a coplanar waveguide (CPW) transmission line that also includes a CPW-based BST shunt varactor. Reconfiguration of the compact 8 mm × 8 mm system has been demonstrated by shifting the antenna system’s operating frequency 500 MHz in the 7–9 GHz band by applying a DC voltage bias.

We have investigated the effect of the hydrostatic pressure on the electrical properties of the rhombohedral phase change material Sb2Te3 both experimentally and theoretically. The resistance can be reduced by 24.9% when the applied hydrostatic pressure reaches 0.377 GPa in the experiment, which is consistent with the results of the calculations by using the first principles theoretical method. The increase of the conductivity of Sb2Te3 under the hydrostatic pressure can be ascribed to the reduction of the electronic band gap.

The microstructures of TiN/SiN(sub x) films were studies by means of a Monte Carlo method. The findings show that the average size of TiN grains decreases with volume fraction of SiN(sub x) approximately according to a power law with a time-dependent exponent decreasing with growth time.

Research is done on two-phase nanocrystalline TiN/amorphous Si3N4 composite films, which were synthesized at room temperature by ion beam assisted deposition. In conclusion, the combination of hardness and grain size was correlated with film phase composition and structural examinations and the results have been revealed with the help of a Monte Carlo Potts model simulation.

We characterized and compared the electromagnetically induced transparency (EIT) response of superconducting niobium nitride (NbN) and NbN-Au hybrid metamaterials. In our design, the two resonators in a unit cell have strong coupling and are directly excited under terahertz (THz) radiation. A stronger slow light effect was achieved using superconducting metamaterials than hybrid metamaterials. The enhanced slow light effect could be attributed to the remarkably low Ohmic loss and strong interaction of the resonators. [ABSTRACT FROM AUTHOR]

Relaxation oscillations related to terahertz (THz) power detection in superconducting niobium nitride hot electron bolometers (HEBs) have been studied using microwaves as a probe. The reflected microwave signal, which is related to the impedance changes of the HEB irradiated by an incident THz signal, can be used to characterize relaxation oscillations. The frequency of relaxation oscillation switching between the superconducting and resistive states increases linearly with incident THz power but nonlinearly with bias voltage or bath temperature. The observed strong periodic pulse trains of relaxation oscillations have a maximum duty cycle of ∼50%. These strong switching pulses indicate that DC Joule heating, THz radiation or thermal energy is absorbed in the bi-stable region of the HEB intermittently. In addition to relaxation oscillations, we also see weaker oscillations when the device is in the resistive state, which we call intrinsic oscillations. These have a constant frequency at the order of 10 kHz which is independent of external stimuli. The weak periodic pulse trains at a constant frequency can be divided into mainly two types—one is the pulse train with a small duty cycle and the other is the quasi-square wave. Measurement of these oscillations in HEBs has some practical applications. Digital THz power measurement with frequencies below and above the gap frequency can be made based on the linearity between relaxation oscillation frequency and incident THz power. The relaxation oscillation frequency can be used to estimate the maximum speed of a THz direct detection system especially for a multi-pixel HEB array. In particular, extra noise induced by relaxation oscillations and intrinsic oscillations can be determined for the HEB operating as a THz direct detector. [ABSTRACT FROM AUTHOR]

Hopf insulators are intriguing three-dimensional topological insulators characterized by an integer topological invariant. They originate from the mathematical theory of Hopf fibration and epitomize the deep connection between knot theory and topological phases of matter, which distinguishes them from other classes of topological insulators. Here, we implement a model Hamiltonian for Hopf insulators in a solid-state quantum simulator and report the first experimental observation of their topological properties, including nontrivial topological links associated with the Hopf fibration and the integer-valued topological invariant obtained from a direct tomographic measurement. Our observation of topological links and Hopf fibration in a quantum simulator opens the door to probe rich topological properties of Hopf insulators in experiments. The quantum simulation and probing methods are also applicable to the study of other intricate three-dimensional topological model Hamiltonians. [ABSTRACT FROM AUTHOR]

The effect of liquid properties on gas bubble growth and motion characteristics in liquid films confined within a nanogap between a highly polished steel ball and a smooth glass disc under an electric field is reported. Experimental results show that the critical voltage for the appearance of bubbles has insignificant dependence on liquid viscosity and surface tension. The bubble size after detachment increases with liquid viscosity, and bubble instability and coalescence tend to occur when bubbles move some distance away from where they were formed. An increase in liquid surface tension results in larger bubbles at the growth stage. Also, the bubble motion characteristics are greatly influenced by liquid viscosity, and the dielectrophoresis force is demonstrated to be the dominant driving force for bubble movement. Theoretical models and analyses have been used to discuss the bubble formation and describe the bubble movement characteristics. [ABSTRACT FROM AUTHOR]

Iron is required for the Fe-S cluster assembly which occurs in chloroplasts, mitochondria, and cytosol and here we characterized 44 Fe-S cluster biosynthesis genes and investigated their expression profiles during different peach flowering stages. Quantitative real-time PCR analysis shows that the highest expression of most peach Fe-S cluster biosynthesis genes appeared in the full bloom stage. Also, the highest Fe accumulation occurred in the full bloom stage followed by beginning bloom, petal fall, and bud swell stages. Activities of nitrite reductase (NiR) and succinate dehydrogenase (SDH) were closely correlated to the flower Fe content, whereas the aconitase (ACO) activity kept steady during the whole flowering process. Moreover, shading treatment significantly reduced Fe accumulation and NiR, SDH, and ACO activities of the full blooming flowers. Seventeen Fe-S cluster biosynthesis genes were down-regulated in response to a shading treatment. In particular, plastid sulfur mobilization genes were sensitive to the shading treatment.

This study aimed to investigate the absorption mechanism of three curcumin constituents in rat small intestines. Self-emulsification was used to solubilize the three curcumin constituents, and the rat in situ intestinal perfusion method was used to study factors on drug absorption, including drug mass concentration, absorption site, and the different types and concentrations of absorption inhibitors. Within the scope of experimental concentrations, three curcumin constituents were absorbed in rat small intestines through the active transport mechanism.