Search

For the flow interaction between the podded engine and the airframe of blended wing body configuration(BWB), taking the 300 seats class BWB civil transport NPU-BWB-300 designed by Northwestern Polytechnical University as the research object, the influence of the podded engines on the BWB airframe at typical high and low speed conditions were investigated by CFD method, and the airframe-nacelle interference mechanism was revealed. The results indicate that the podded engines mainly affect the high speed performance of BWB, but have little effect on the low speed performance. The flow interaction between the airframe and the nacelle at high speed condition is serious when podded the engines, which leads to strong shock wave and flow separation. The flow mechanism of the above-mentioned interaction is as follows: firstly, the large supersonic region and shock wave on the nacelle external surface interferes with airframe surface flow seriously, which induces shock wave and flow separation; secondly, a convergent-divergent channel is formed between the airframe and the nacelle, resulting in the "throat" effect, which produces shock wave and flow separation.

At present, the correlation analysis between the acoustic emission characteristics of the rock failure process and the fractal characteristics of sample fragments has been carried out. Some achievements have been obtained. But the quantitative description of the failure degree of coal samples with rock burst tendency under the condition of unidirectional loading with different strain rates and the quantitative relationship between the failure degree and the loading strain rate are few. In order to solve this problem, based on the MTS-C64. 106 electro-hydraulic servo system, the raw coal samples are subjected to uniaxial static load with different strain rates. In the test, the PCI-2 acoustic emission card is used to monitor the fracture process of the samples under load in real-time. The fractal theory is used to analyze the fracture fragments of the samples. The relationship between the fracture degree of the samples and the load strain rate is quantitatively evaluated. The results show the following points. ① On the basis of static load, the peak strength of sample failure increases with the increase of strain rate dynamic load. ② With the increase of the loading strain rate, the total number of AE decreases, and the number of high-energy AE events increases. The AE ringing count and energy amplitude undergo a consistent transition process of 'slow increase-rapid increase-sudden increase.' ③ The loading energy input rate of the sample is basically consistent with the increasing trend of acoustic emission ringing count and internal impact number. It will also experience the change of 'slow increase-rapid increase-sudden increase.' ④ The constant for the positive correlation between acoustic emission and vibration strength decreases with increasing loading strain rate. The constant which is negatively related to the ratio of the number of high and low energy vibrations, increases with increasing loading strain rate. The failure mode of the raw coal sample will experience a 'shear failure - splitting failure - bursting failure' transformation. ⑤ When the loading strain rate is low, the upper part of the sample is destroyed. When the strain rate increases, the sample is gradually destroyed from the middle to the lower part. The failure process of the raw coal sample under the action of dynamic strain rate is mainly the brittle propagation behavior of cracks. ⑥ The fractal dimension of the impact fragment mass of the sample has a quadratic function relationship with the loading strain rate. There is an extreme value of the loading strain rate that maximizes the damage to the sample, with the test showing a strain rate extreme value of 2.8×10−3 s−1.

Objective: Endoscopic surgery is an effective technique for preserving the nipple and areola, as well as for sentinel lymph node biopsy and breast implant reconstruction. However, the technical challenges associated with endoscopic surgery have limited its widespread adoption. Methods: In the normal single-port endoscopic surgery, the ultrasonic knife was accessed through the retractor. In our modified procedure, a tiny 5 mm incision was made at the lateral margin underneath the breast, serving as the second entry port for the ultrasonic scalpel, which was referred to as the "Haigui-1 hole". Preoperative and postoperative indicators such as blood loss, operative time, and postoperative drainage volume were collected. Differences between parameters were compared using Student's t test. Results: Endoscopic surgery with the assistance of the "Haigui-1 hole" led to preserved breast aesthetics with minimal scarring. Moreover, "Haigui-1 hole" surgery significantly reduced the operation time, intraoperative bleeding, and postoperative drainage volume compared to normal single-port endoscopic surgery. Conclusion: The "Haigui-1 hole" procedure, which involves the addition of a second entrance to improve the maneuverability of the ultrasonic knife, is worthy of further promotion. [ABSTRACT FROM AUTHOR]

High throughput screening of small molecules and natural products is costly, requiring significant amounts of time, reagents, and operating space. Although microarrays have proven effective in the miniaturization of screening for certain biochemical assays, such as nucleic acid hybridization or antibody binding, they are not widely used for drug discovery in cell culture due to the need for cells to internalize lipophilic drug candidates. Lipid droplet microarrays are a promising solution to this problem as they are capable of delivering lipophilic drugs to cells at dosages comparable to solution delivery. However, the scalablility of the array fabrication, assay validation, and screening steps has limited the utility of this approach. Here we take several new steps to scale up the process for lipid droplet array fabrication, assay validation in cell culture, and drug screening. A nanointaglio printing process has been adapted for use with a printing press. The arrays are stabilized for immersion into aqueous solution using a vapor coating process. In addition to delivery of lipophilic compounds, we found that we are also able to encapsulate and deliver a water-soluble compound in this way. The arrays can be functionalized by extracellular matrix proteins such as collagen prior to cell culture as the mechanism for uptake is based on direct contact with the lipid delivery vehicles rather than diffusion of the drug out of the microarray spots. We demonstrate this method for delivery to 3 different cell types and the screening of 92 natural product extracts on a microarray covering an area of less than 0.1 cm2. The arrays are suitable for miniaturized screening, for instance in high biosafety level facilities where space is limited and for applications where cell numbers are limited, such as in functional precision medicine. [ABSTRACT FROM AUTHOR]

Master the dynamic instability response characteristics of underground coal and rock triggered by shock wave is a necessary condition to prevent disturbance rock burst. So, FLAC3D software was used to develop the dynamic function. And the instability response characteristics of roadways roof, floor and two groups were analyzed under the condition of different positions and magnitude of shock wave. The results show that maximum principal stress of roadway surrounding rock shocked wildly and the highest can reach 2 times of its initial state. The shock waves generated from the roadway floor have larger influence on the roof of the roadway (especially the top corner). The order of influence on the roof deformation under the 4 loading schemes is B1, B2, A1, A2. The plastic zones gradually extended to the roadway and eventually connected to the source area after shock wave exerted. The angles location of the roof and floor of rectangular tunnels is prone to disasters, such as rock burst.

In recent years, juvenile delinquency has attracted more and more attention from all walks of life. Youth at risk often accompany juvenile delinquency and violence, which will cause serious social problems if not intervened in time. Moreover, youth at risk lack basic life skills and life resources, which makes them unable to adapt to social development and stray from the edge of society. Therefore, the prevention of youth at risk should proceed from the background of youth at risk, understand the needs of youth at risk, link them with policy resources and social support, help them get rid of their predicament, and repay society. This paper studies the delinquency of youth at risk through data analysis. By looking for relevant policy support, it intervenes in youth at risk from the perspectives of behavior and psychology to prevent the delinquency of youth at risk.

Coal mine rockburst is closely related to the complex geological structure. Understanding the criterion of the fault activation instability and the disaster-causing mechanism of rockburst under the influence of mining is the theoretical premise and important guarantee of safe and efficient coal mining. In this paper, based on the theory of key stratum, the mechanical model of fault slip instability in the normal fault during the hanging wall mining was established, and the instability criterion was derived. It is concluded that the fault slip instability of the hanging wall is mainly controlled by two factors: (1) the distance between coal seams and key stratum and (2) the distance between working face and fault. Moreover, these two factors have an inverse relation to the occurrence of rockburst. Subsequently, three conceptual models of rockburst induced by the fault stress transfer, stress concentration of coal pillars, and fault structural instability were proposed. Based on the rock mechanics theory, the rockburst carrier system model of “roof-coal seam-floor” near the fault was established. The mechanical essence of fault rockburst was obtained as follows: under the action of fault, the static load of fault coal pillar was increased and superimposed with the fault activation dynamic load, leading to high-strength rockburst disaster. Based on the occurrence mechanism of fault rockburst, the monitoring and prevention concept and technical measures were proposed in three aspects, including the monitoring and control of fault activation dynamic loads, the monitoring of high static load in fault coal pillar and stress release, and the strengthening roadway support. These prevention and control measures were verified in the panel 103down02 of the Baodian Coal Mine in engineering, and the effectiveness of these measures was proved.

In coal mining, the rockburst intensity triggered by the mine earthquake is often greater in the mining area, and the precursor information is more difficult to capture. In this paper, this kind of rockburst is called shock-type rockburst and studied as the research object. Based on the evolution process and the theoretical model of the carrier system, the energy criterion of the occurrence of shock-type rockburst was deduced based on the theories of mathematics and statistical physics. The results showed that the process of shock-type rockburst can go through four stages: inoculation stage, occurrence stage, development stage, and termination stage, and the secondary triggering phenomenon may occur in the occurrence stage. The theoretical model of the shock-type rockburst carrier system was constructed, and the key characteristic parameter of shock-type rockburst was put forward. Then, the energy of mine earthquake was quantitatively characterized in the form of kinetic energy of rock block. Through the combination of the two parameters, the energy criterion of shock-type rockburst was obtained as follows: once the energy of mine earthquake acting on the rockburst source area was 2%–9% of the static energy, shock-type rockburst can occur. Then, this criterion was verified by three typical cases. Finally, based on the distribution conditions of “red seam” overburden in the Yanzhou mining area of China, the secondary triggering principle of rockburst was expounded, that is, the secondary triggering principle of rockburst caused by the shear fracture and sliding settlement of “red seam” overburden. To sum up, a theoretical system for judging the instability of the shock-type rockburst carrier system was formed. This study provides a theoretical basis for earthquake prevention and disaster reduction in coal mining.

To effectively monitor and control the severe mining-induced rockburst in deep fault area, the fault activation law and the mechanical essence of rockburst induced by crossing fault mining were studied through theoretical analysis, microseismic monitoring, field investigation, and other methods; numerical simulation was employed to verify the obtained fault activation law and the mechanical nature. First, the distribution of microseismic sources at different mining locations and the fault activation degree were analyzed. According to the microseismic frequency and the characteristics of the energy stage, the fault activation degree was divided into three stages: fault stress transfer, fault pillar stress behavior, and fault structure activation. It was determined that the impact disaster risk was the strongest in the stage of the fault pillar stress behavior. Based on the periodic appearance law of microseisms in fault area, three types of conceptual models of fault-type rockburst were proposed, and the rockburst carrier system model of “roof-coal seam-floor” in the fault area was established. The mechanical essence of fault-type rockburst was obtained as follows: under the action of fault structure, the static load of the fault coal pillar was increased and superimposed with the active dynamic load of the fault, leading to high-strength impact disaster. Finally, the prevention and treatment concepts of fault-type rockburst were proposed. The monitoring and prevention measures of fault-type rockburst were taken from two aspects: the monitoring and characterization of fault rockburst and weakening control of the high static load of the fault coal pillar and dynamic load of fault activation. The proposed concepts and technical measures have been verified in the working face 14310 of Dongtan Coal Mine with sound results. The research results have a guiding significance for the prevention and control of rockburst in a similar mining face under crossing fault mining.

For new concept of wisdom mine, its development course, existing status and problems in construction process in China were summarized through its association with automation mine, informatization mine and digital mine. A new definition of wisdom mine was put forward, which emphasized that the wisdom mine was a set of wisdom system and could make the optimal regulation for each part automatically. Vision of the wisdom mine was prospected from five aspects of mine design, safety guarantee, efficient production, economic operation and green environmental protection. Construction planning of the wisdom mine was proposed, which mainly included four aspects: establishing wisdom mine industrial alliance, formulating relevant technical specifications and standards, researching and developing intelligent equipment and developing wisdom decision applications.