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"Pan, Wenguo"
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Experimental Study and Failure Mechanism Analysis of Rubber Fiber Concrete under the Compression-Shear Combined Action
In order to examine the compression-shear combined mechanical properties of rubber fiber concrete, an experimental study was carried out on rubber fiber concrete of three different configurations using a material compression-shear testing machine by considering different axial compression ratios. The failure modes and shear stress-strain curves of rubber fiber concrete under different loading conditions were obtained. By comparatively analyzing the mechanical parameters of rubber fiber concrete under different axial compression ratios, the following conclusions were drawn. With the increase of the axial compression ratio, the failure mode in the shear direction gradually developed from a relatively straight crack to a main crack accompanied by a certain amount of axial cracks; meanwhile, the number of concrete slags on the shear failure section was gradually increased and the friction marks were gradually deepened. The addition of rubber particles increased the randomness and discreteness of the concrete upon failure, while fibers inhibited the development of oblique micro-cracks and the dropping of concrete slags. The shear stress of the concrete specimen containing rubber particles was significantly lower than those without rubber particles. Comparatively, fibers showed little effect on the shear stress. As the axial compression ratio increased, the shear stress and shear strain of rubber fiber concrete were gradually increased, but the increasing amplitude of shear stress tended to become flattened. Under the influence of the axial compression ratio, the shear stress of C-0%-0%, C-30%-0%, and C-30%-0.6% was increased by 4.57 times, 3.26 times, and 2.69 times, respectively, suggesting a gradually decreasing trend. At the same time, based on the principal stress space and the octahedral stress space, the compression-shear combined failure criterion was proposed for the three different rubber fiber concretes. The research findings are of great significance to the engineering application and development of rubber fiber concrete.
Journal Article
An Experimental Study on the Compressive Dynamic Performance of Rubber Concrete under Freeze-Thaw Cycles
An experimental study was conducted using a hydraulic servo machine to examine the compressive dynamic performance of rubber concrete under freeze-thaw cycles by considering 4 different numbers of freeze-thaw cycles and 8 different strain rates. The compressive stress-strain curves of rubber concrete under different loading conditions were obtained. By comparatively analyzing the mechanical characteristic parameters of the compressive stress-strain curves (i.e., peak stress, elastic modulus, and peak strain), the following conclusions were drawn: at the same loading strain rate, the compressive peak stress of rubber concrete is gradually decreased while the mass loss rate is gradually increased, as the number of freeze-thaw cycles increases. Compared to ordinary concrete, rubber concrete has a better frost resistance property. At the same number of freeze-thaw cycles, the compressive peak stress and elastic modulus of rubber concrete are gradually increased as the loading strain rate increases. The increase in the number of freeze-thaw cycles enlarges the increasing amplitude of the peak stress and elastic modulus under the action of loading strain rate. The compressive peak stress and elastic modulus dynamic increase factors of rubber concrete exhibit a linear relationship with the dimensionless logarithm of the loading strain rate. Meanwhile, a calculation model was proposed for the compressive peak stress dynamic increase factor of rubber concrete under the coupling effect of freeze-thaw cycles and loading strain rate, and the corresponding stress mechanism was discussed in detail. The research findings are of great significance to the application and development of antifreeze concrete in engineering practice.
Journal Article
An injectable self-healing coordinative hydrogel with antibacterial and angiogenic properties for diabetic skin wound repair
We report here an injectable, self-healing coordinative hydrogel with antibacterial and angiogenic properties for diabetic wound regeneration. The hydrogel was prepared by coordinative cross-linking of multi-arm thiolated polyethylene glycol (SH-PEG) with silver nitrate (AgNO3). Due to the dynamic nature of Ag-S coordination bond and bacteria-killing activity of Ag+, the resultant coordinative hydrogel featured self-healing, injectable and antibacterial properties. In this study, we synchronously loaded an angiogenic drug, desferrioxamine (DFO), in the coordinative hydrogel during cross-linking. We finally obtained a multifunctional hydrogel that is manageable, resistant to mechanical irritation, antibacterial and angiogenic in vitro. Our in vivo studies further demonstrated that the injectable self-healing hydrogel could efficiently repair diabetic skin wounds with low bacteria-infection and enhance angiogenic activity. In short, besides diabetic skin wound repair, such dynamic multifunctional hydrogel scaffolds would show great promise in the regeneration of different types of exposed wounds, in particular, in situations with disturbed physiological functions, high risk of bacterial infections, and external mechanical irritation.Wound repair: Self-healing materials step up to save feetSoft gels that can be injected into wounds to protect them from infection and promote blood vessel formation may benefit diabetic foot care. To create a scaffold-like substance tough enough to handle the mechanical stresses that feet experience, Hao Chen and colleagues from the Shanghai Jiao Tong University and Jiangsu University in China linked polyethylene glycol chains together using silver–sulfur chemical bonds that quickly re-join after being broken. This strategy produced a gel that returns to its original shape after being sliced or twisted, and which can be loaded with drugs to aid vascular network growth. Experiments in rat models revealed that direct injection of drug-containing gels to wounds decreased their size by 20% compared to control groups. The intrinsic antibacterial nature of silver ions also generated sterile inhibition zones around gel-treated lesions.
Journal Article
An Update on Adipose‐Derived Stem Cells for Regenerative Medicine: Where Challenge Meets Opportunity
Over the last decade, adipose‐derived stem cells (ADSCs) have attracted increasing attention in the field of regenerative medicine. ADSCs appear to be the most advantageous cell type for regenerative therapies owing to their easy accessibility, multipotency, and active paracrine activity. This review highlights current challenges in translating ADSC‐based therapies into clinical settings and discusses novel strategies to overcome the limitations of ADSCs. To further establish ADSC‐based therapies as an emerging platform for regenerative medicine, this review also provides an update on the advancements in this field, including fat grafting, wound healing, bone regeneration, skeletal muscle repair, tendon reconstruction, cartilage regeneration, cardiac repair, and nerve regeneration. ADSC‐based therapies are expected to be more tissue‐specific and increasingly important in regenerative medicine. Adipose‐derived stem cells (ADSCs) serve as an ideal candidate for regenerative medicine owing to their ability to differentiate into multilineages, facilitate angiogenesis, suppress apoptosis, and participate in immunoregulation. Numerous preclinical studies and clinical trials have demonstrated the therapeutic potential of ADSCs in fat grafting, wound healing, bone regeneration, skeletal muscle repair, tendon reconstruction, cartilage regeneration, cardiac repair, and nerve regeneration.
Journal Article
Reconstruction of Cropland for the Rikaze Area of China Since the Tubo Dynasty (AD 655)
The reconstruction of cropland across historical periods offers valuable insights into the relationship between climate change and human–environment interactions. By extracting key demographic and tax revenue data from historical documents, we estimated cropland data during the Tubo, Yuan, Ming, and Qing dynasties for the Rikaze area in China. Subsequently, according to the characteristics of cropland fragmentation in the Rikaze area, we employed geographically weighted regression (GWR) to reconstruct the 1 km × 1 km cropland cover datasets across the four dynasties for the Rikaze area. The findings are as follows. The amount of cropland showed that the change in cropland in the Rikaze area in the four periods was extremely high, which reflects the great instability of cropland in the Rikaze area. Under the combined action of social unification, cropland production policies, and a suitable climate, the Tubo dynasty was the most significant period of cropland development in the Rikaze area, with the area of cropland reaching 591,927 mu. However, under the influence of the nomadic regime and harsh climate in the Yuan dynasty, the cropland area was sharply reduced, reaching only 18,338 mu. During the Ming and Qing dynasties, the cropland area increased steadily, reaching 200,000 mu and 547,000 mu, respectively. The spatial distribution of cropland shows that the cropland in the Rikaze area is mainly distributed in the middle reaches of the Yarlung Zangbo River, the middle and lower reaches of the Nianchu River, and the Pengqu River Valley. Counties and districts with better agricultural conditions, such as Jiangzi, Bailang, and Renbu, are the main concentration areas of cropland in the Rikaze area. The overall spatial distribution pattern of cropland shows fragmented distribution along rivers, highlighting the characteristics of valley cropland. The research in this paper represents the active exploration of the reconstruction of cropland distribution under complex terrain conditions.
Journal Article
Spider Silk-Improved Quartz-Enhanced Conductance Spectroscopy for Medical Mask Humidity Sensing
Spider silk is one of the hottest biomaterials researched currently, due to its excellent mechanical properties. This work reports a novel humidity sensing platform based on a spider silk-modified quartz tuning fork (SSM-QTF). Since spider silk is a kind of natural moisture-sensitive material, it does not demand additional sensitization. Quartz-enhanced conductance spectroscopy (QECS) was combined with the SSM-QTF to access humidity sensing sensitively. The results indicate that the resonance frequency of the SSM-QTF decreased monotonously with the ambient humidity. The detection sensitivity of the proposed SSM-QTF sensor was 12.7 ppm at 1 min. The SSM-QTF sensor showed good linearity of ~0.99. Using this sensor, we successfully measured the humidity of disposable medical masks for different periods of wearing time. The results showed that even a 20 min wearing time can lead to a >70% humidity in the mask enclosed space. It is suggested that a disposable medical mask should be changed <2 h.
Journal Article
Predicting the Impacts of Climate Change on the Potential Distribution of Major Native Non-Food Bioenergy Plants in China
Planting non-food bioenergy crops on marginal lands is an alternative bioenergy development solution in China. Native non-food bioenergy plants are also considered to be a wise choice to reduce the threat of invasive plants. In this study, the impacts of climate change (a consensus of IPCC scenarios A2a for 2080) on the potential distribution of nine non-food bioenergy plants native to China (viz., Pistacia chinensis, Cornus wilsoniana, Xanthoceras sorbifolia, Vernicia fordii, Sapium sebiferum, Miscanthus sinensis, M. floridulus, M. sacchariflorus and Arundo donax) were analyzed using a MaxEnt species distribution model. The suitable habitats of the nine non-food plants were distributed in the regions east of the Mongolian Plateau and the Tibetan Plateau, where the arable land is primarily used for food production. Thus, the large-scale cultivation of those plants for energy production will have to rely on the marginal lands. The variables of \"precipitation of the warmest quarter\" and \"annual mean temperature\" were the most important bioclimatic variables for most of the nine plants according to the MaxEnt modeling results. Global warming in coming decades may result in a decrease in the extent of suitable habitat in the tropics but will have little effect on the total distribution area of each plant. The results indicated that it will be possible to grow these plants on marginal lands within these areas in the future. This work should be beneficial for the domestication and cultivation of those bioenergy plants and should facilitate land-use planning for bioenergy crops in China.
Journal Article
Research on radial velocity and airspace position calculations of target in airborne active radar simulation
The detection of the target in the airborne active radar simulation is simplified to the calculations of the radial velocity, the maximum detecting range of the airborne active radar corresponding to the RCS, and the airspace position of the target. However, the coordinate transformations related to the calculations of the radial velocity and the airspace position are usually bewildering due to the different referenced coordinate systems. This paper introduces the radial velocity and airspace position calculations of the target in the airborne active radar simulation to illuminate the transformation process containing the specific rotation matrices, suggesting the unifying transformation to the north-up-east (NUE) rectangular coordinate system of the aircraft for both the radial velocity calculation and airspace position calculation of the target.
Journal Article
Experimental Investigation into the Impact of a Viscosity Reducer on the Crude Oil Recovery Rate in a Low-Permeability Reservoir
The relative permeability of oil and water is a key factor in assessing the production performance of a reservoir. This study analyzed the impact of injecting a viscosity reducer solution into low-viscosity crude oil to enhance fluid flow within a low-permeability reservoir. At 72°C, the oil-water dispersion solution achieved a viscosity reduction rate (f) of 92.42%, formulated with a viscosity reducer agent concentration (CVR) of 0.1% and an oil-water ratio of 5:5. The interfacial tension between the viscosity reducer solution and the crude oil remained stable at approximately 1.0 mN/m across different concentrations, with the minimum value of 4.07 × 10−1 mN/m recorded at a CVR of 0.2%. As the CVR increased, the relative permeability curve of the oil phase gradually decreased while the oil-water two-phase region (Ro-wtp) expanded significantly. At a CVR of 0.1%, the Ro-wtp peaked, making an increase of 7.93 percentage points compared to water flooding. In addition, the final displacement efficiency (ER, final) achieved with a 0.1% viscosity reducer solution reached 48.64%, exceeding water flooding by 15.46 percentage points, highlighting the effectiveness of the viscosity reducer solution in enhancing oil recovery.
Journal Article