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The main purpose of this study is to discuss whether online influencers can improve customer brand attitude and thus increase purchase intention as both of them are important performance indicators in a live show. Drawing on the persuasion theory, the authors aim to investigate the impacts of influencers’ attributes (professionalism, credibility, interactivity and attractiveness) on customers purchase intention from the perspective of attitude toward brand. Data were collected from 233 customers in China where the influencer centered livestreaming e-commerce is enjoying rapid growth. The hypotheses were tested via structural equation modeling. The findings indicate that the influencers’ credibility and attractiveness increase purchase intention directly. Further, customer brand attitude plays a mediating role in the relationship between the influencers’ attributes (attractiveness, credibility, and interactivity) and purchase intention. While, the professionalism improves neither favorable customer brand attitude nor purchase intention. The findings provide theoretical implications for scholars to rethink the role of internet influencers in influencing customer purchase intention.

Traditional ventilation methods consume excessive energy but still fail to meet requirements in underground tunnel group construction. Thus, a closed-loop intelligent control system for ventilation-on-demand (VOD) was developed. To address dynamic changes in ventilation load and reduce energy consumption, firstly, the developed system calculates the real-time ventilation load and establishes a ventilation-network-based control mode to represent the ventilation system structure. The deep deterministic policy gradient (DDPG) method was then employed for the closed-loop control ensuring the required air volume in each branch of tunnel groups while minimizing energy consumption. After that, the developed closed-loop intelligent ventilation control system encompasses comprehensive perception, real analysis, real-time control, and continuous optimization. This system treats decision-making, control, and feedback as subsystems that reflect the adaptability between ventilation efficiency, construction progress, and power consumption. Finally, the end-edge-cloud-based software of the system was developed to enable remote control and display on large screens, personal computers (PCs), and mobile applications (Apps) to ensure precise and timely operation. The system was employed in tunnel group under construction at the Xulong Hydropower Station in Southwestern China, and the obtained results validate its advanced closed-loop control based on reinforcement learning (RL) and confirm its feasibility in engineering practice.

Galloping-based piezoelectric energy harvesting systems are being used to supply renewable electricity for low-power wireless sensor network nodes. In this paper, a W-shaped bluff body is proposed as the core component of a piezoelectric wind energy harvester. Experiments and simulations have shown that the W-shaped bluff body can improve harvesting efficiency at low wind speeds. For the W-shaped structure, the finite element simulation results indicate that the structure can help improve the aerodynamic performance to obtain high aerodynamic force. The experimental results demonstrate that compared with the traditional bluff bodies, the piezoelectric wind energy harvester with the W-shaped bluff body (WEHW) can generate higher output voltages and has a lower cut-in speed. When the length L is 30 mm and the rear groove angle β is 30°, the W-shaped structure can induce the best harvesting performance. When an external load resistance of 820 KΩ is connected and the wind speed is 5 m/s, the WEHW generates an average output power of 0.28 mW.

The single-line-to-ground faults with line breaks (SLGFs-LBs) occur more and more frequently in distribution networks and can cause major safety accidents. It is difficult to distinguish the single-line-to-ground faults (SLGFs) in resonant grounding systems and ungrounding systems due to the same electrical characteristics on the source side and uncertain operation conditions of distribution networks. This paper proposes a method for distinguishing SLGFs-LBs and SLGFs. First, the source-side and load-side voltage characteristics of SLGFs and SLGFs-LBs are analyzed, and the phase difference between the voltages of the fault phase and non-fault phase on the load side is selected as the identification criterion. Phasor measurement units (PMUs) are selected as measuring devices. Then, the effects of operation conditions and external devices in distribution networks on the proposed method are discussed, and the phase errors caused by them are calculated to correct the identification method. Finally, the field testing and simulation experiments are conducted to verify the effectiveness and robustness of the proposed method.

Web-building spiders that build detritus-based bell-shaped cobwebs are model organisms for studies on behavioral plasticity because their web architecture components are easily quantified and behavioral investments are clearly separated. We investigated the web architectures and behavioral investments of the cobwebs built by Campanicola campanulata under different weight (heavy, medium, and light) detritus to research its cobweb architecture variation and analyzed the investment trade-off between foraging and defense. The results showed that spiders could actively choose lighter detritus to build retreats to reduce material and energy cost. There was a clear trade-off between defense and foraging investment of spiders choosing different weight detritus for their webs. The total length of gumfooted lines (foraging investment) was longer for the spiders that chose lighter detritus, but the energy expenditure during web-building (defense investment) was higher for the spiders that chose heavier detritus.

Eight cobweb spider species building a detritus-based, bell-shaped retreat from China are reported in the current paper, including five new Campanicola species and three known species: Campanicola anguilliformis Li & Liu, sp. nov., Campanicola falciformis Li & Liu, sp. nov., Campanicola heteroidea Li & Liu, sp. nov., Campanicola tauricornis Li & Liu, sp. nov., Campanicola volubilis Li & Liu, sp. nov., Campanicola campanulata (Chen, 1993), Campanicola ferrumequina (Bösenberg & Strand, 1906), and Parasteatoda ducta (Zhu, 1998). Among them, the male of Parasteatoda ducta (Zhu, 1998) is described for the first time. We provide photographs of all species and descriptions for new species in the current paper. The type of bell-shaped retreat is rare in theridiid, and found only in four related genera. A natural next step upon completing this taxonomic study would be to analyse and understand the evolution of the retreat and related traits.

Ethanol (ETOH) affects many animals’ behaviour in nature; for example, honeybees become more aggressive after consuming ETOH. In previous studies, scientists have used honeybees and fruit flies as models to determine if they showed a strong preference to ETOH. Moreover, ETOH could affect their locomotion and learning abilities. However, whether and how ETOH affects spiders is unclear as of yet. In this study, we used empirical experiments to determine whether spiders showed preference for ETOH, as well as the potential benefits of spiders choosing ETOH, by using a common spider, Myrmarachne gisti, which has a high probability of contacting ETOH in their habitat. In our experiment, M. gisti showed a significant preference for ETOH. Although the success rate of the first attack was significantly decreased when M. gisti were exposed to ETOH, they had a significantly higher predation probability, since fruit flies also showed a significant preference for ETOH. Our findings suggested that ETOH could affect the prey capture efficiency of M. gisti, and indicated that spiders might evolve to use ETOH to locate a potential hunting place. Taken together, our findings suggested that M. gisti evolved to adapt to ETOH and could use it as a signal of the presence of food resources.

The construction of massive infrastructure projects in Africa suffers from a shortage in natural aggregate materials, such as coarse sand and gravel for cemented sand and gravel (CSG) for hydraulic projects, which would delay progress and raise costs. In response to the scarcity of CSG aggregates and the challenges in the environment-friendly disposal of excavation waste, a design method for the mix proportion of CSG by using jaw-crushed material was proposed, and this method was suitable for similar projects to be constructed in Africa. First, the target grading for coarse aggregates was set based on Fuller's ideal grading to determine the optimal ratio of jaw-crushed material and smaller stones for gradation adjustment. Second, the target grading for fine aggregates was determined to be the III zone fineness modulus and obtained by seeking the proper ratio of local ultrafine river sand and artificial sand produced from rock grinding. Then, considering the compressive strength, the optimal CSG mix proportion was determined, where both volcanic ash and cement were added as cementitious materials. Finally, the proposed design method for jaw-crushed-material-based CSG was applied in the construction of a temporary overflow cofferdam at the Julius Nyerere hydroelectric power station in Africa, and its feasibility and effectiveness were verified. The results indicate that the optimal ratio between the jawcrushed material and small stones for the coarse aggregate of CSG is 0.85:0.15 (by weight by default unless otherwise specified), the best ratio of ultrafine river sand and artificial sand for the fine aggregate of CSG is 4:6 by weight, the optimum sand content of CSG is 30%, the water-cement ratio is 1.11, and the optimal dosage of volcanic ash is 58.3 kg per cubic meters of CSG (kg/CSG m³). The engineering practice of the temporary CSG overflow cofferdam demonstrates that the use of jaw-crushed material for CSG is feasible, and the proposed CSG mix proportion design method achieved the efficient utilization of jaw-crushed material, which can reduce the environmental impact of excavation waste and ensure the completion of temporary high-quality overflow cofferdam for seasonal floods. This study provides valuable scientific and engineering references for similar CSG projects that may use jaw-crushed material for the design and construction and has important scientific and engineering significance. [ABSTRACT FROM AUTHOR]

[Objective] In the future, China′s urban development will shift from construction-orientation to governance-orientation. As an important part of the Chinese-style modern social governance system, urban planning is an important lever and tool to improve urban governance. Prophase research on urban rail transit is a key component of urban planning and an important cut-in on urban planning improvement, construction and governance. It is the top-level design, key deployment and important guarantee of urban rail transit project construction. Analysis of research focuses at different stages of the prophase research is crucial to the collaborative development of urban planning and the construction of urban rail transit projects. [Method] The prophase research of urban rail transit mainly refers to the planning and research prior to the overall design, mainly including three aspects i.e. network planning, construction planning and project feasibility study. Based on the research characteristics and differences of the three aspects, research focuses at different stages of urban rail transit prophase works in the new era are analyzed. [Result & Conclusion] The above mentioned three aspects present characteristics of "stage-by-stage implementation, macro to micro working layer, and different emphasis for each work". Strengthening the prophase research on urban rail transit in the new era will help promote high-quality development of urban rail transit construction in China, and improve the governance level of urban planning and construction.

Abstract Background Malignant mesothelioma is a type of infrequent tumor that is substantially related to asbestos exposure and has a terrible prognosis. We tried to produce a fibroblast differentiation-related gene set for creating a novel classification and prognostic prediction model of MESO. Method Three databases, including NCBI-GEO, TCGA, and MET-500, separately provide single-cell RNA sequencing data, bulk RNA sequencing profiles of MESO, and RNA sequencing information on bone metastatic tumors. Dimensionality reduction and clustering analysis were leveraged to acquire fibroblast subtypes in the MESO microenvironment. The fibroblast differentiation-related genes (FDGs), which were associated with survival and subsequently utilized to generate the MESO categorization and prognostic prediction model, were selected in combination with pseudotime analysis and survival information from the TCGA database. Then, regulatory network was constructed for each MESO subtype, and candidate inhibitors were predicted. Clinical specimens were collected for further validation. Result A total of six fibroblast subtypes, three differentiation states, and 39 FDGs were identified. Based on the expression level of FDGs, three MESO subtypes were distinguished in the fibroblast differentiation-based classification (FDBC). In the multivariate prognostic prediction model, the risk score that was dependent on the expression level of several important FDGs, was verified to be an independently effective prognostic factor and worked well in internal cohorts. Finally, we predicted 24 potential drugs for the treatment of MESO. Moreover, immunohistochemical staining and statistical analysis provided further validation. Conclusion Fibroblast differentiation-related genes (FDGs), especially those in low-differentiation states, might participate in the proliferation and invasion of MESO. Hopefully, the raised clinical subtyping of MESO would provide references for clinical practitioners.

Due to the non-targeted release and low solubility of anti-gastric cancer agent, apatinib (Apa), a first-line drug with long-term usage in a high dosage often induces multi-drug resistance and causes serious side effects. In order to avoid these drawbacks, lipid-film-coated Prussian blue nanoparticles (PB NPs) with hyaluronan (HA) modification was used for Apa loading to improve its solubility and targeting ability. Furthermore, anti-tumor compound of gamabufotalin (CS-6) was selected as a partner of Apa with reducing dosage for combinational gastric therapy. Thus, HA-Apa-Lip@PB-CS-6 NPs were constructed to synchronously transport the two drugs into tumor tissue. In vitro assay indicated that HA-Apa-Lip@PB-CS-6 NPs can synergistically inhibit proliferation and invasion/metastasis of BGC-823 cells via downregulating vascular endothelial growth factor receptor (VEGFR) and matrix metalloproteinase-9 (MMP-9). In vivo assay demonstrated strongest anti-tumor growth and liver metastasis of HA-Apa-Lip@PB-CS-6 NPs administration in BGC-823 cells-bearing mice compared with other groups due to the excellent penetration in tumor tissues and outstanding synergistic effects. In summary, we have successfully developed a new nanocomplexes for synchronous Apa/CS-6 delivery and synergistic gastric cancer (GC) therapy.

Millettia speciosa Champ. (MSCP), which is distributed and used in Southern China, is often sulfur-fumigated during postharvest handling to prevent insects and molds. In the present study, a comprehensive strategy was proposed by using ultrahigh-performance liquid chromatography-quadrupole/time-of-flight mass spectrometry (UHPLC–QTOF–MS/MS) with multivariate analysis to rapidly identify potential chemical sulfur-fumigated MSCP (SF-MSCP) samples, discover chemical transformation mechanisms and control the quality of SF-MSCP. Eighty-six compounds were tentatively assigned, and ten compounds were screened out as potential markers. Moreover, the chemical transformation mechanism was deduced by hydrolysis, esterification and dehydration reactions that occurred during the sulfur-fumigated process. The developed method was successfully applied to predict 16 commercial MSCP samples, and 9 samples were found to contain sulfur compounds, ranging in sulfur residues from 100 to 310 mg/kg. These research outcomes can not only be used to distinguish the nonfumigated MSCP from SF-MSCP by chemical markers but also provide a chemical basis for further comprehensive investigating in-depth safety and functional evaluations of SF-MSCP.

ObjectiveThe relationship between remnant-like particle cholesterol (RLP-C) levels and the progression of atrial fibrillation (AF) is not known. This research aimed to explore the association of RLP-C with long-term AF recurrence events post-radiofrequency catheter ablation (RFCA) of AF.MethodsIn total 320 patients with AF who were subjected to the first RFCA were included in this research. Baseline information and laboratory data of patients were retrospectively collected, and a 1-year follow-up was completed. The follow-up endpoint was defined as an AF recurrence event occurring after 3 months. Afterward, a multivariate Cox regression model was constructed to analyze the risk factors that affect AF recurrence.ResultsAF recurrence occurred in 103 patients (32.2%) within 3–12 months after RFCA. Based on the multivariate Cox regression analysis, Early recurrence (ER) [hazard ratio (HR) =1.57, 95% confidence interval (CI): 1.04–2.36, P = 0.032)], coronary artery disease (CAD) (HR = 2.03, 95% CI: 1.22–3.38, P = 0.006), left atrium anterior-posterior diameter (LAD) (HR = 1.07, 95% CI: 1.03–1.10, P 0.645 mmol/L group than in the ≤0.645 mmol/L group (Log-rank P

Millettia speciosa Champ. (MSCP) enjoys widespread recognition for its culinary and medicinal attributes. Despite the extensive history of MSCP cultivation, the disparities in quality and bioactivity between wild and cultivated varieties have remained unexplored. In this study, 20 wild and cultivated MSCP samples were collected from different regions in China. We embarked on a comprehensive investigation of the chemical constituents found in both wild and cultivated MSCP utilizing UHPLC-Q-Exactive Orbitrap-MS technology and multivariate analysis such as principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA). In total, 62 chemical components were unequivocally identified or tentatively characterized. Via the multivariate statistical analysis, we successfully pinpointed nine compounds with the potential to serve as chemical markers, enabling the differentiation between wild and cultivated MSCP varieties. Moreover, both genotypes exhibited substantial antioxidant and anti-fatigue properties. The bioactivities of wild MSCP were marginally higher when compared to their cultivated counterparts. This study illuminates the impressive antioxidant and anti-fatigue potential present in both wild and cultivated MSCP genotypes, further augmenting the allure of this species and opening new avenues for the economic valorization of MSCP. Hence, this study provides a valuable method for the identification and quality control of MSCP and a method in chemistry and pharmacology to assess an alternative possibility for cultivated MSCP.

Osteoarthritis (OA) is a highly prevalent whole-joint disease that causes disability and pain and affects a patient's quality of life. However, currently, there is a lack of effective early diagnosis and treatment. Although stem cells can promote cartilage repair and treat OA, problems such as immune rejection and tumorigenicity persist. Extracellular vesicles (EVs) can transmit genetic information from donor cells and mediate intercellular communication, which is considered a functional paracrine factor of stem cells. Increasing evidences suggest that EVs may play an essential and complex role in the pathogenesis, diagnosis, and treatment of OA. Here, we introduced the role of EVs in OA progression by influencing inflammation, metabolism, and aging. Next, we discussed EVs from the blood, synovial fluid, and joint-related cells for diagnosis. Moreover, we outlined the potential of modified and unmodified EVs and their combination with biomaterials for OA therapy. Finally, we discuss the deficiencies and put forward the prospects and challenges related to the application of EVs in the field of OA.

BackgroundPrimary squamous cell carcinoma of the thyroid (PSCCT) is a rare malignant tumor. The incidence rate of PSCCT is less than 1%. However, the diagnosis and treatment of PSCCT are limited. Surgical resection is considered to be one of the few effective intervention methods. In this article, we reported a case of taking tyrosine kinase inhibitors (TKIs) combined with immune checkpoint inhibitors (ICIs) for PSCCT.Case summaryAn 80-year-old male was admitted to our hospital with dyspnea, cough, wheezing, and hoarseness for a giant thyroid mass. He underwent bronchoscopy and tracheal stent implantation to alleviate the respiratory obstruction. Then he accepted right partial thyroid and right lymph node biopsy. Postoperative pathology revealed squamous cell carcinoma. Subsequently, he underwent an endoscopy to exclude upper gastrointestinal squamous cell carcinoma. Finally, he was diagnosed with PSCCT. The patient was tentatively treated with a combination of Anlotinib and Sintilimab. After two courses, the tumor volume significantly reduced in MRI images and shrank further after five courses of combined treatment. Unfortunately, the patient died of fulminant liver failure and autoimmune liver disease after 5-month-treatment.ConclusionTKIs combined with ICIs may be an effective and novel way for PSCCT treatment, but immune-related complications, especially liver damage, should be cared.

The reliability and safety of diesel engines gradually decrease with the increase in running time, leading to frequent failures. To address the problem that it is difficult for the traditional fault status identification methods to identify diesel engine faults accurately, a diesel engine fault status identification method based on synchro squeezing S-transform (SSST) and vision transformer (ViT) is proposed. This method can effectively combine the advantages of the SSST method in processing non-linear and non-smooth signals with the powerful image classification capability of ViT. The vibration signals reflecting the diesel engine status are collected by sensors. To solve the problems of low time-frequency resolution and weak energy aggregation in traditional signal time-frequency analysis methods, the SSST method is used to convert the vibration signals into two-dimensional time-frequency maps; the ViT model is used to extract time-frequency image features for training to achieve diesel engine status assessment. Pre-set fault experiments are carried out using the diesel engine condition monitoring experimental bench, and the proposed method is compared with three traditional methods, namely, ST-ViT, SSST-2DCNN and FFT spectrum-1DCNN. The experimental results show that the overall fault status identification accuracy in the public dataset and the actual laboratory data reaches 98.31% and 95.67%, respectively, providing a new idea for diesel engine fault status identification.

Summary: A small-scale delivery medium for CO2 laser energy with stable performance, flexibility, and high-strength is crucial in extreme laser processing environments, especially for minimally invasive surgery in high-humidity, twisty and narrow channels. Here, flexible and robust multimaterial infrared fibers made of selenium-based chalcogenide glasses and thermoplastic polymer were developed with a low loss of 7.18 dB/m at 10.6 μm. The resulting fibers were capable of stably delivering single-mode CO2 laser with 0.42 W average power. Moreover, to achieve precise control over the fibers in the practical clinical environment, customized co-polymers of polyphenylene sulfone resin and polyvinylidene fluoride were used as the fiber built-in jackets. Consequently, the fibers exhibited hydrophobicity, thermostability, high tensile strength, and low bending stiffness. The results demonstrated that the fibers can be used to deliver CO2 laser energy for fabric cutting and bio-tissues ablation, making them attractive for CO2 laser material processing and minimally invasive laser surgery.

Research has been dedicated to the development of laboratory-scale simulation devices for studying mechanisms of gas migration. Cement-hydration analyzers (CHAs) are commercially available to assist industry in the design of gas-tight slurries. Although cement slurries under controlled conditions in the laboratory can be gas-tight, the in-situ performance of cement slurries is highly variable and difficult to predict. Therefore, a new approach has been designed to evaluate gas-migration potential under a range of representative borehole conditions. A laboratory-scale wellbore-simulation chamber (WSC) has been developed to replicate hydrostatic-pressure reduction in the cemented annulus and evaluate the potential for gas invasion under a range of borehole conditions. A discussion is presented on the development of the WSC that includes the details of the design and monitoring systems as well as the performance characteristics. Calibration-test results are examined to evaluate the performance of the WSC and the ability of the WSC to simulate in-situ wellbore conditions. Analysis of the results verifies the capability of the WSC in successfully recording the necessary parameters. [ABSTRACT FROM AUTHOR]

Objective. To analyze the role of PD-1/PD-L1 signaling pathway in regulating T cell activation and secretion of proinflammatory factors in atrial fibrillation. Methods. Forty-five patients with atrial fibrillation admitted to the cardiology department of our hospital from July 2019 to March 2021 were selected to be included in the atrial fibrillation group, and another 45 healthy volunteers were selected as the control group to compare the changes of T cell CD69 and human leukocyte antigen-DR (HLA-DR) expression in the peripheral blood of the two study groups; compare the changes of programmed death factor-1 on CD4+ and CD8+ lymphocytes in the peripheral blood of the two groups (PD-1) expression changes and PD-L1 and PD-L2 expression changes on peripheral blood myeloid dendritic cells (mDCs) cells; compare the changes of interleukin-2, interleukin-6, interleukin-10, and interleukin-17A (IL-2, IL-6, IL-10, and IL-17), tumor necrosis factor (TNF), and interferon gamma (IFN-γ) concentrations on peripheral blood inflammatory factors in the two groups; and isolate the two groups of peripheral blood mDCs cells; α interferon upregulated PD-L1 expression in the cells and analyzed the effect of PD-L1 expression on the ability of mDCs to stimulate T cells to secrete cytokines.Results. The positive expression rates of CD69 and HLA-DR on peripheral blood CD3+ T lymphocytes were significantly higher in patients in the atrial fibrillation group than in the control group, and the differences were statistically significant (P0.05). The positive expression rate of PD-L1 on mDCs cells was significantly lower in patients in the atrial fibrillation group than in the control group (P0.05). The concentrations of IL-2, IL-6, IL-10, and IFN-γ in peripheral blood were significantly higher in patients in the atrial fibrillation group than in the control group (P0.05). In the atrial fibrillation group, the ability of mDCs to stimulate T cells to secrete IL-2 and IFN-γ was significantly higher, and the ability to secrete IL-10 was significantly lower compared with the control group (P0.05). Conclusion. PD-1/PD-L1 signaling pathway may play an immunomodulatory role in the pathogenesis of atrial fibrillation by promoting increased secretion of inflammatory factors through regulating T cell activation.

A bonded concrete overlay of asphalt (BCOA), also known as whitetopping, is a thin concrete overlay placed upon a distressed asphalt pavement. The asphalt-resilient modulus is kept constant in current BCOA design procedures. This practice results in an underestimation of the damage as compared to when the hourly temperature variation of the asphalt is considered. The framework to establish an equivalent asphalt modulus involves generating a database of hourly middepth asphalt temperatures. This database should include hourly temperatures for different BCOA structures and a large range of geographical locations representing different climatic conditions. The hourly middepth asphalt temperatures are then used to generate hourly asphalt moduli using master curves. Through fatigue equivalency, the equivalent asphalt moduli are calculated for each month. In order to establish the relationship between the asphalt modulus and middepth temperature, the United States was divided into seven different zones according to their annual mean ambient temperatures. For each zone, models for predicting adjustment factors were developed for the asphalt modulus. Designers can calculate the monthly asphalt stiffness over the design life using the adjustment factor and reference month stiffness regression models. This asphalt stiffness is then corrected for aging and fatigue using the models incorporated into the AASHTO Pavement ME program. The methodology presented here has been incorporated into the recently developed BCOA mechanistic-empirical design and analysis procedure. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicle (UAV) ground-penetrating radar (GPR) is an important research topic for target detection in many fields. In this paper, we develop a UAV-mounted GPR system with a frequency band at 150 MHz–309 MHz. However, the received signal in the complex background is covered by various clutter and interference, leading to the serious obscuring of the target. To meet this challenge, a cross-correlation-based background subtraction (CCBS) method and an interference suppression technique are adopted in combination for more accurate detection. The CCBS method processes the raw echo by establishing a background-removal model and using the similarity between each A−Scan and a reference wave. In addition, a Butterworth filter is adopted to get rid of the active electromagnetic interference beyond the working frequencies of the system; then, a lateral Doppler filtering (LDF) technique is introduced to suppress the passive interference generated by the rotation of the UAV rotor itself. Moreover, a practical method for estimating the dielectric constant is introduced by the calibration process of the measured radar echo. Numerical simulations and experimental results by our UAV-GPR system demonstrate that the proposed method has presented a better performance than the traditional methods, and the system has great potential in detecting deeply buried targets.

Gases can migrate into the cemented annulus of a wellbore during early gelation when hydrostatic pressure within the cement slurry drops. Different means to describe hydrostatic-pressure reduction have been proposed and reported in the literature. Among them, static gel strength (SGS) is the most widely accepted concept in describing the strength development of hydrating cement. The classic shear-stress theory uses SGS to quantify the hydrostaticpressure reduction in the cement column. Approaches derived from the concept of SGS have contributed to understanding mechanisms of gas migration and methods of minimizing it. Unfortunately, these approaches do not accurately predict gas migration. Although SGS was originally adopted to describe the shear stress at interfaces, it has also been used to estimate the shear resistance required to deform slurry during the hydration period. Before early gelation, the hydrostatic pressure will overcome the formation gas pressure and prevent gas migrations. During gelation, the cement develops enough rigidity to withstand the gas invasion. This critical hydration period is defined as the transition time. API STD 65-2 (API 2010a) provides standards for determining the transition time by use of the concept of SGS. Current industry practice is to reduce the transition time, thereby lowering the potential for invading gas introducing migration pathways in the cemented annulus. This approach, although certainly helpful in reducing the risk for gas migration, does not eliminate its occurrence. Experimental results presented in this study demonstrate that the relationship between SGS and hydrostatic-pressure reduction is not linear. Characteristics of the transition-time endpoints depend on slurry properties and downhole conditions. Moreover, SGS is not able to characterize the gas-tight property of a cement slurry. When slurry gels, the mechanical properties are governed by its growing solid fraction. The gel can deform under shear loading, but gases and other fluids will need to break or fracture the bond between solids and push them aside for pathways to form within the cement/matrix domain at this point. To fully understand this process, the bond strength between solid particles and the compressibility of the cement matrix are needed. The bond strength and compressibility are mechanical properties dependent on the changing rigidity of the gelling cement. However, SGS does not address these important properties and, therefore, SGS is limited in its ability to predict gas-migration potential. A better means to characterize the cement/matrix strength by use of fundamental concepts and variables for replacing SGS is desired. [ABSTRACT FROM AUTHOR]

The electromagnetic scattering of an ultra-high-speed plasma covered target is simulated by the field discrete Monte Carlo method. The flow field network is used to simulate the trajectory of electromagnetic wave particles according to the electromagnetic distribution parameters, and the electromagnetic characteristics are calculated according to the statistical parameters of the reflected particles. The computational time-consumption is less correlated with the incident electromagnetic wave frequency [except for the Radar Cross Section (RCS) valley characteristics], and it is convenient for parallel calculation, which realizes the fast calculation of the electromagnetic scattering of the electrically large plasma-covered target. On this basis, the electromagnetic scattering characteristics of the blunt cone hypervelocity target are calculated, and the main RCS reduction and enhancement mechanisms are given.