Dual Semantic Fusion Network for Video Object Detection

Video object detection is a tough task due to the deteriorated quality of video sequences captured under complex environments. Currently, this area is dominated by a series of feature enhancement based methods, which distill beneficial semantic information from multiple frames and generate enhanced features through fusing the distilled information. However, the distillation and fusion operations are usually performed at either frame level or instance level with external guidance using additional information, such as optical flow and feature memory. In this work, we propose a dual semantic fusion network (abbreviated as DSFNet) to fully exploit both frame-level and instance-level semantics in a unified fusion framework without external guidance. Moreover, we introduce a geometric similarity measure into the fusion process to alleviate the influence of information distortion caused by noise. As a result, the proposed DSFNet can generate more robust features through the multi-granularity fusion and avoid being affected by the instability of external guidance. To evaluate the proposed DSFNet, we conduct extensive experiments on the ImageNet VID dataset. Notably, the proposed dual semantic fusion network achieves, to the best of our knowledge, the best performance of 84.1\% mAP among the current state-of-the-art video object detectors with ResNet-101 and 85.4\% mAP with ResNeXt-101 without using any post-processing steps.Comment: 9 pages,6 figure

Unraveling the nature of quasi van der Waals Epitaxy of magnetic topological insulators Cr: (BixSb1-x)2Te3 on a GaAs (111) substrate through coherently strained interface

Quasi van der Waals Epitaxy (qvdWE) has been realized for decades at the interfaces between 3D and 2D materials or van der Waals materials. The growth of magnetic topological insulators (MTI) Cr: (BixSb1-x)2Te3 (CBST) on GaAs (111) substrates for Quantum Anomalous Hall Effect (QAH) is actually one of the examples of qvdWE, which is not well noticed despite the fact that its advantages have been used in growth of various MTI materials. This is distinguished from the growth of MTIs on other substrates. Although the qvdWE mode has been used in many 2D growth on III-V substrates, the specific features and mechanisms are not well demonstrated and summarized yet. Here in this work, we have for the first time shown the features of both coherent interfaces and the existence of strain originating from qvdWE at the same time.Comment: 5 figures, 1 table. Already shown in APS March Meeting 2023 and 202

Giant Hall Switching by Surface-State-Mediated Spin-Orbit Torque in a Hard Ferromagnetic Topological Insulator

Topological insulators (TI) can apply highly efficient spin-orbit torque (SOT) and manipulate the magnetization with their unique topological surface states, and their magnetic counterparts, magnetic topological insulators (MTI) offer magnetization without shunting and are one of the highest in SOT efficiency. Here, we demonstrate efficient SOT switching of a hard MTI, V-doped (Bi,Sb)2Te3 (VBST) with a large coercive field that can prevent the influence of an external magnetic field and a small magnetization to minimize stray field. A giant switched anomalous Hall resistance of 9.2 $k\Omega$ is realized, among the largest of all SOT systems. The SOT switching current density can be reduced to $2.8\times10^5 A/cm^2$, and the switching ratio can be enhanced to 60%. Moreover, as the Fermi level is moved away from the Dirac point by both gate and composition tuning, VBST exhibits a transition from edge-state-mediated to surface-state-mediated transport, thus enhancing the SOT effective field to $1.56\pm 0.12 T/ (10^6 A/cm^2)$ and the spin Hall angle to $23.2\pm 1.8$ at 5 K. The findings establish VBST as an extraordinary candidate for energy-efficient magnetic memory devices

HIGH-MOBILITY 2DEGS AT ALGAN/GAN INTERFACES GROWN BY PA-MBE AND THE TRANSPORT STUDY

92 pagesAlGaN/GaN high-mobility transistor (HEMT) has been attracting people’s attention and is proved to have satisfactory performance due to its related properties such as high break-down voltage, high saturation velocity, high frequency, etc. Molecular Beam Epitaxy (MBE) is one of the methods used for growth of high-quality AlGaN/GaN heterostructure with a two-dimensional electron gas (2DEG) in between. The high mobility of the 2DEGs, which is essential for ideal device performance, is determined by the charge density of the 2DEG. It is influenced by not only Al composition and AlGaN thickness, but also by dislocation density and the MBE background impurity. In order to achieve a high mobility, the relationship of mobility and 2DEG charge density is studied systematically on samples with various Al composition and AlGaN thickness grown by plasma-assisted MBE. Hall measurement is adopted for the measurement of 2DEG mobility and corresponding charge density. GaN bulk substrate and GaN template substrate with different dislocation densities are used for MBE growth as a comparison study on the influence of dislocation density. A gate control method is also explored on one specific sample with fixed dislocation density and background impurity to experimentally study the relationship of mobility and 2DEG density. Temperature-dependent Hall measurement is conducted to study transport property at low-temperature where the mobility is mainly limited by dislocation and background impurity rather than phonons. By analyzing the experimental data and comparing with theoretical calculations, the influence of dislocation density and background impurity is explained

Experiments on the elastic size dependence of LPCVD silicon nitride

In classical elasticity, geometric dependence of the rigidities can be normalized and the normalized rigidities are size independent. Recent experimental observations showed significant elastic size effect in normalized bending rigidity in micron scale epoxy beams. Size effect in elastic behaviors can be described by surface stress theories and strain gradient elasticity theories. Surface effect on elastic properties is significant in nanometer scale, but recognized to be negligible in micron scale. The observed size effect in micron sized epoxy beams was found to agree with strain gradient elastic models. Besides epoxy films, effort is underway to characterize strain gradient behaviors in other material systems. Silicon nitride thin film is a widely used film in MEMS. Comprehensive understanding of the elastic deformation behaviors of silicon nitride thin films is essential for design and analysis of MEMS structures. In this thesis, submicron thick LPCVD silicon nitride thin films were fabricated. XPS and XRD analyses were conducted to determine elemental and micro-structural consistency of the as-fabricated thin films. XPS analyses showed element compositions were similar in films with different thicknesses. However, XRD analyses revealed that films had different crystalline phase fractions. Cantilever beams were fabricated from the films and elastic bending tests on the beams were conducted using nanoindenter to investigate the elastic bending behaviors of the films as a function of thickness. Analyses showed that beams with different thickness had fluctuating normalized bending rigidities. The fluctuations of normalized bending rigidities maybe related to varying crystalline phase fractions in the thin films. The beams were annealed and bending tests were conducted to investigate possible correlation between normalized bending rigidity fluctuations and crystalline phase fractions. Bending tests results showed similar level of fluctuations in normalized bending rigidities before and after annealing while XRD results of the annealed films showed increase in crystalline phase fractions for all thicknesses. This suggested crystalline phase fraction cannot be correlated with the fluctuations in normalized bending rigidities of the beams. Error analyses of experiment setup, geometries of the beams and data analysis were conducted. The fluctuations in normalized bending rigidity in different thickness were within the error range. While LPCVD silicon nitride may have size dependence in the nanometer scale, size dependence of normalized bending rigidity of LPCVD silicon nitride appears to be insignificant in submicron scale. Design of silicon nitride MEMS structures can be modeled with conventional elasticity without considerations for size effects

Soil Enzyme Activity Differs among Native Species and Continuously Planted Eucalyptus Plantations

In recent years, monoculture and multi-rotation successional Eucalyptus plantations have given rise to several environmental issues, including the degradation of soil quality and nutrient imbalance, and the conversion of logging sites to multi-rotation Eucalyptus plantations has attracted considerable attention from the scientists involved. However, the effects of different management strategies on soil extracellular enzyme activities (EEAs) and enzyme stoichiometry (ES) in degraded Eucalyptus plantations are not clear. In this study, we investigated the responses and mechanisms of soil physicochemical properties, microbial biomass, carbon, and nitrogen- and phosphorus-acquiring enzyme activities, as well as the microbial resource requirements of Eucalyptus plantations, under different management strategies. The findings revealed that second-rotation (TWE) and third-rotation (THE) continuous plantings of pure Eucalyptus plantations resulted in significant decreases in soil organic carbon (SOC), total nitrogen (TN) and effective available phosphorus (AP) contents, while soil nutrient contents increased after the introduction of Manglietia glauca to form mixed forests (EM) with Eucalyptus or pure Manglietia glauca (M). Meanwhile, phosphorus-acquiring enzymes significantly increased with successive rotations of Eucalyptus (TWE and THE), while EEAC:P and EEAN:P gradually decreased and phosphorus limitation gradually increased compared to that of a native-species-mixed plantation (CK). After the introduction of Manglietia glauca (EM and M), phosphorus-acquiring enzyme activities showed lower levels and there were significant increases in EEAC:P and EEAN:P compared to those of continuous plantings of pure Eucalyptus plantations, which reduced microbial phosphorus demand. Moreover, soil nutrients played a more significant role in altering the EEAs and ES than did microbial biomass (0–10 cm: 72.7% > 53.3%, 10–20 cm: 54.5% > 32.6%). The results showed that EM and M improved soil fertility quality conditions and alleviated soil nutrient phosphorus limitations for soil microorganisms. Therefore, the introduction of Manglietia glauca, either to form mixed forests with Eucalyptus or in rotation with Eucalyptus, can be used as technical means for the conversion of multi-rotation successive Eucalyptus plantations

Structural and enzymatic characterization of the choline kinase LicA from Streptococcus pneumoniae.

LicA plays a key role in the cell-wall phosphorylcholine biosynthesis of Streptococcus pneumonia. Here we determined the crystal structures of apo-form LicA at 1.94 Å and two complex forms LicA-choline and LicA-AMP-MES, at 2.01 and 1.45 Å resolution, respectively. The overall structure adopts a canonical protein kinase-like fold, with the active site located in the crevice of the N- and C-terminal domains. The three structures present distinct poses of the active site, which undergoes an open-closed-open conformational change upon substrate binding and product release. The structure analyses combined with mutageneses and enzymatic assays enabled us to figure out the key residues for the choline kinase activity of LicA. In addition, structural comparison revealed the loop between helices α7 and α8 might modulate the substrate specificity and catalytic activity. These findings shed light on the structure and mechanism of the prokaryotic choline kinase LicA, and might direct the rational design of novel anti-pneumococcal drugs

A Pressure Sensing System for Heart Rate Monitoring with Polymer-Based Pressure Sensors and An Anti-Interference Post Processing Circuit

Heart rate measurement is a basic and important issue for either medical diagnosis or daily health monitoring. In this work great efforts have been focused on realizing a portable, comfortable and low cost solution for long-term domestic heart rate monitoring. A tiny but efficient measurement system composed of a polymer-based flexible pressure sensor and an analog anti-interference readout circuit is proposed; manufactured and tested. The proposed polymer-based pressure sensor has a linear response and high sensitivity of 13.4 kPa−1. With the circuit’s outstanding capability in removing interference caused by body movement and the highly sensitive flexible sensor device, comfortable long-term heart rate monitoring becomes more realistic. Comparative tests prove that the proposed system has equivalent capability (accuracy: <3%) in heart rate measurement to the commercial product

Dynamic Simulation Analysis of the Working Process of the Picking Mechanism of a Sugarcane Leaf Cutting and Returning Machine

Leaf–device interaction can effectively be modeled with a finite element model when proper finite element model parameters are applied. In order to investigate the contact mechanism of picking up sugarcane leaf during the operation of a sugarcane leaf cutting and returning machine, a geometric solid model of sugarcane leaf picking was established. A finite element numerical model to analyze the large deformation problem of flexible bodies was developed in LS-DYNA to simulate the picking process of the returning machine. A dynamic simulation of the sugarcane leaf-picking process was carried out to obtain the change of stress field and the motion posture of the sugarcane leaf and the elastic teeth. The picking process of the picking mechanism, the change in posture of the sugarcane leaves, the change in stress on the sugarcane leaf, the change in the bending angle of the sugarcane leaf and the change in stress on the elastic teeth were analyzed in detail. The results showed that the picking process can be divided into four stages: picking, lifting, pushing and retrieving. The posture changes of sugarcane leaf are “C”, logarithmic curve, wavy shape and “V”, in turn. During the picking process, the sugarcane blade showed some breakage, the sugarcane vein remained intact, and the elastic teeth did not fail. During the whole picking cycle, the maximum Von Mises stress of the blade, vein and elastic teeth were 22.8 MPa, 17.5 MPa and 900 MPa, respectively. An evaluation criterion of bending angle was creatively put forward to measure the bending deformation of leaves. The trend in the sugarcane leaf bending angle shows that it is largely variable, gradually decreasing, fluctuating and increasing with interval fluctuations. The working process of the picking mechanism was observed through a quick camera experiment. Comparing the experiment with the simulation, the changing trend of the simulation data and experimental data was generally similar. The experimental and simulation values of the average sugarcane leaf bending angle were 27° and 19°, respectively. The relative error of the average bending angle was 29.6%. It was concluded that the developed finite element model is substantial and could be applied to optimize and improve the picking mechanism. In addition, some references were provided for the contact mechanism between the picking mechanism and the sugarcane leaf

Research on Lateral Bearing Behavior of Spliced Helical Piles with the SPH Method

The length of a spliced pile is 2 m assembled from an original spiral pile using a connector. The whole pile is the structure of the upper straight pipe and the lower spiral. The pile–soil model is established with FEM-SPH by LS-DYNA to simulate and analyze the characteristics of the spliced piles. When the helical pile is subjected to a horizontal load, the pile rotates around the point of rotation, and the contact force position of the soil in the model is as expected. During the process of pile driving, the soil forms an inverted cone stress-area, and the maximum particle stress area near the pile tip and the ground surface is 400 Kpa, which is highly concentrated. When loaded laterally, the area of the interaction stress of the soil particles is divided into three regions: the stress effect region; the transition region; and the critical region. Then, 7° is defined as the ultimate horizontal bearing-capacity of the spliced pile, and the numerical simulation of the horizontal bearing-capacity fundamentally matches the test results. The simulation model realizes the transition from the pile installation to the lateral loading, predicts the ultimate horizontal bearing-capacity, and analyzes the stress distribution of the soil particles and the time-development of the soil displacement