Search

Landslide is a common dynamic large-deformation disaster of mobilized soils, which poses a serious threat to the lives and economic properties of surrounding people. Both the strain-softening effect and spatial variability of soil are reported to have significant impacts on landslide behaviors. This study investigated the coupled effect of strain softening and spatial variability on the occurrence, evolution, and runout behavior of landslides induced by seismic loads, using three-dimensional (3D) large-deformation finite-element method. The results show that both the strain-softening behavior and spatial variability of soil dramatically affect the sliding velocity and runout distance. Their coupled effect further weakens the soil strength, resulting in a larger runout distance. Secondly, the runout distance in the 3D deterministic analysis is always smaller than the minimum value in the corresponding random analysis, which completely differs from the result from the two-dimensional (2D) analysis. This finding indicates that 2D analysis can result in a conservative estimation on the runout distance for spatially variable soils and highlights the advantages of 3D modeling on landslides. Thirdly, a linear formula was proposed to quantify the runout distance based on the horizontal peak acceleration, which can provide some guidelines for the safety design in practical slope engineering.

Reports have pointed out that nearly 50% of the global total energy demand for buildings is used for daily heating and cooling. Therefore, it is very important to develop various high-performance thermal management techniques with low energy consumption. In this work, we present an intelligent shape memory polymers (SMPs)-based device with programmable anisotropic thermal conductivity fabricated by a 4D printing technique to assist in thermal management with net zero energy. Highly thermal conductive BN nanosheets were textured in a poly (lactic acid) (PLA) matrix by 3D printing, and the printed composites lamina exhibited significant anisotropic thermal conductivity. The direction of heat flow in devices could be switched programmably, accompanying the light-activated deformation controlled by grayscale of composite, which was demonstrated by the “windows” arrays composed of in-plate thermal conductivity facets and SMPs-based hinge joints, achieving the programmable movement of opening and closing under different light conditions. Based on solar radiation-dependent SMPs coupled with the adjustment of heat flow along anisotropic thermal conductivity, the 4D printed device has been proved in concept for potential applications in thermal management in a building envelop for dynamic climate adaptation, taking place automatically based on the environment.

Earthwork excavator, as an all-terrain and high-efficiency earthwork excavation equipment, has been widely used in earthwork sites. It is very necessary to analyze the work of earthmoving excavator by means of machine vision. In this paper, the action segmentation method based on long video was applied to the analysis and recogniton of the excavator’s action, and compared with other two current best action segmentation models using the real construction site video. Firstly, the sequence features of the excavator’s work video obtained at the cnstruction site was extracted through 3D convolution method, and then two differernt networks with the extracted sequence features were trained and tested. The experimental results showed that the average frame accuracy of MS-TCN model and ASRF model in excavator action segmentation were 82.6490% and 86.1042% respectively. However, for the recognition task under different working environment, the performance of the two models is quite different. The experimental results manifest that the motion segmentation model based on long video reached good results in excavator motion recognition in earthmoving operation. And it is helpful to analyze the long video working behavior sequence of excavator. This research contributes to the identification of critical elements that explains serial action and to the development of a new application scenario for vision-based behavior segmentation network. Additionally, the results of this study were helpful to automatically analyze the working efficiency and monitor the productivity of earthmoving excavators. Using this kind of data-driven decision can improve the work efficiency of earthmoving excavator and promote the project progress.

The high intra class diversity of remote sensing image scene often leads to the problem of difficult classification of remote sensing image scenes. Therefore, this paper proposes the CA-EfficientNetV2 model, embedding the coordinate attention into the head of the EfficientNetV2 network to enhance the classification effect. The coordinate attention is used to generate the position relationship between image spaces and channels so as to learn features efficiently. We trained three improved models CA-EfficientNetV2-S, CA-EfficientNetV2-M and CA-EfficientNetV2-L on UC Merced remote sensing dataset respectively. The classification accuracy reached 99.55%, 97.49% and 97.09% respectively. Among them, CA-EfficientNetV2-S had the best effect, which was improved by 0.8% compared with the original network.

Full-flow penetrometers (ball and T-bar) are widely used for measurements of strength characteristics of clayey soils in offshore field investigations and laboratory tests. However, the accuracy of the estimated undrained shear strength is hampered by: (1) the drastic variation of the bearing factor for the penetrometer at shallow and transitional penetration depths where full-flow mechanisms are not achieved; and (2) the strain-softening of the soil, which results in a degradation of the estimated strength. This study conducted LDFE analyses to simulate the entire penetration process of full-flow penetrometers in strain-softening soils from shallow to deep embedment depths. Parametric studies were performed to investigate the effects of varied factors on the bearing factor and failure mechanism during the penetrometer penetration. Based on the LDFE analyses, empirical formulas are established to represent the critical penetration depths in the strain-softening soil, which are used to correct the bearing factor at shallow penetration depths. The discrepancies of the transitional failure mechanism and the trapped cavity bearing factor between ball and T-bar are emphasized. Finally, a back-analyses framework is proposed to estimate the strength parameters (including the original undrained shear strength prior to any strain-softening, and the strain-softening parameters) based on the measurements of the penetrometer during the first penetration from shallow to deep embedment depths. Through a series of model tests, the reliability of the back-analyses framework is validated.

A novel full-range soft-switching full-bridge (FSFB) cycloconverter-type high-frequency-link inverter (CHFLI) with active snubber network is proposed. By adding an auxiliary inductor in primary-side DC/AC converter and adopting centre-tapped transformer structure, the proposed FSFB-CHFLI achieves zero voltage switching (ZVS) for all switches under different operating conditions from light load to rated load, which benefits with high efficiency and high switching frequency. The secondary-side active snubber network is utilised to recycle leakage inductor energy and suppress voltage spikes caused by the resonance of the leakage inductor and the parasitic capacitance of switch. The commutation overlap strategy is adopted to guarantee complete ZVS turn-on and ZVS turn-off of bidirectional switches. Experimental results of a high efficient and high switching frequency (200 kHZ) prototype are presented to verify the analysis results of the proposed FSFB-CHFLI.

A novel soft-switching step-up/down DC–DC converter is proposed, which generates symmetric bipolar outputs while maintaining the grounded capability. The proposed converter consists of a zeta converter cell and a buck–boost converter cell, sharing an inductor and a power switch. High efficiency is achieved by zero voltage switching for all switches. Meanwhile, by connecting one load between positive and negative output terminals, high voltage gain can be achieved. Experimental results of a 3.7 V battery input and ±10 VDC/10 W outputs prototype are presented to verify the analysis results of the proposed converter.

A two-channel single-stage switching amplifier (SSA) based on high-frequency link inverter is proposed. The audio input signals are modulated by phase shift between primary-side switches and secondary-side switches, thus independent amplifications of two channels can be obtained. Benefiting from multiplexing of primary-side power switches for two channels, only a half bridge inverter is utilised at primary side. Clamp circuits at the secondary side of transformer eliminate spike voltages across the secondary-side switches during the current commutation of the cycloconverters. Zero voltage switching of primary-side switches and clamp switches are achieved by utilising magnetising inductor current. A 320 V/250W prototype is presented to verify the analysis results of the proposed two-channel SSA.

A high efficiency single-stage switching amplifier based on high-frequency link inverter is proposed. Bipolar phase shift modulation is adopted in the proposed switching amplifier. Auxiliary circuits including freewheeling diodes, clamp capacitors and active clamp bridge (ACB) are added to provide a current flowing path for the inductor current during the dead time of the bidirectional switches. The ACB is synchronised with primary-side switches to absorb the leakage inductor energy and clamp the secondary-side transformer voltages. With single-stage conversion and leakage inductor energy recycle, high efficiency of the proposed switching amplifier is achieved. A 5 V/25 W prototype is presented to verify the analysis results of the proposed switching amplifier.

The present study aimed to investigate the antiulcer activities and mechanisms of action of an active ingredient group (AIG) of Modified Xiao Chaihu Decoction (MXCD). The gastroprotective action of the AIG was studied in ethanol-induced, pylorus ligature-induced, and acetic acid-inducedin vivogastric ulcer models. The enzyme-linked immunoadsorbent assay (tumor necrosis factor-α(TNF-α), prostaglandin E2(PGE2), and epidermal growth factor (EGF)), nitrate reductase assay (nitric oxide (NO)), western blot analysis (Bax, Bcl-2, cleaved-caspase-3, and cleaved-PARP (poly (ADP-Ribose) polymerase)), histological analysis (HE), and immunohistochemical analysis (HSP-70, p-AKT, and PCNA) were used to evaluate the anti-inflammatory, antiapoptotic, and healing properties of AIG. Numerous mechanisms are involved in the antiulcer activity of AIG, including the increase of PGE2, NO, and EGF content and a reduction in TNF-αlevels. The upregulation of HSP-70, p-AKT, and PCNA seems to be directly linked to the healing effect of AIG. Bax, Bcl-2, cleaved-caspase-3, and cleaved-PARP also play a key role in this process. The AIG exerted gastroprotective effects by reducing antisecretory, anti-inflammatory, and antiapoptotic mechanisms. In addition, it promotes cell proliferation. Therefore, activation of the PI3K/AKT signaling pathway may play an important role in cell proliferation.

Full-flow penetrometers, Ball and T-bar, have been widely used to measure the undrained shear strength of offshore clayey soils in both laboratory and in situ tests. The penetration process of Ball or T-bar penetrometer is a large deformation geotechnical problem, which results in the surrounding soil partially remolding and softening. The soil disturbance influences the penetration resistance and hence leads to an underestimation of the undrained shear strength, which is a critical factor for offshore geotechnical design. To investigate the soil strain-softening behavior during the first penetration, large deformation finite element (LDFE) analyses were performed to simulate the penetration process of T-bar and Ball in the strain-softening clay. The thin layer element was employed to simulate the complex contact behavior between the penetrometer and the surrounding soil, thus the strain-softening behavior can be considered at the interface between penetrometer and soil. This study aims to investigate the effects of soil strain-softening and interface roughness on the penetration resistance during the first penetration of full-flow penetrometers. Based on the numerical results, relative comprehensive formulas considering the soil strain-softening parameters and the interface roughness factor have been proposed to evaluate the strain-softening factors, which can be used to estimate the soil intact undrained shear strength and the strain-softening parameters. Finally, the proposed formulas were verified by experimental results and were used to estimate the intact undrained strength of soft clay.