Predicting the electromechanical properties of small caliber projectile impact igniter using PZT dynamic damage constitutive model considering crack propagation

Block piezoelectric ceramics(PZTs)are often used in impact igniters to provide activation energy for electric initiators.Under the action of strong impact stress,PZTs release electric energy accompanied by crack initiation,propagation and crushing.At present,the electrical output performance of PZTs in projectile is usually calculated by quasi-static piezoelectric equation without considering the dynamic effect caused by strong impact and the influence of crack propagation on material properties.So the ignition parameters are always not accurately predicted.To tackle this,a PZT dynamic damage constitutive model considering crack propagation is established based on the dynamic impact test and the crack propagation theory of brittle materials.The model is then embedded into the ABAQUS subroutine and used to simulate the electromechanical response of the impact igniter during the impact of a small caliber projectile on the target.Meanwhile,the experiments of projectile with impact igniter impact on the target are carried out.The comparison between experimental and numerical simulation results show that the established dynamic damage model can effectively predict the dynamic electromechanical response of PZTs in the missile service environment.

云南省文山州40岁及以上壮族和苗族人群翼状胬肉患病率及其影响因素

目的:调查云南省文山州40岁及以上壮族和苗族人群的翼状胬肉患病率及其影响因素。方法:采用手持式裂隙灯和Keratograph-D眼表综合分析仪对云南省壮族和苗族目标人群进行流行病学调查,采用Logistic回归分析研究性别、年龄、职业、是否户外活动和民族等因素对翼状胬肉的影响。结果:于2019-03/11选取调查对象共1239人,确诊翼状胬肉437人,翼状胬肉总体患病率为35.27%。双眼翼状胬肉占59.27%,单眼翼状胬肉占40.73%。胬肉患病率在壮族人群为34.84%(224人),在苗族人群为35.74%(213人),两者无差异(P=0.740)。Logistic回归分析结果显示,睑板腺开口有无堵塞是翼状胬肉发生的影响因素(P=0.019),优势比OR=1.348。性别、年龄、受教育程度、是否户外活动、高血压和饮食习惯不是翼状胬肉的影响因素。用等级资料的Logistic回归进行胬肉侵入程度的多因素分析,结果显示泪河高度是翼状胬肉侵入程度的影响因素(P=0.048),泪河高度值越低,侵入程度越大。结论:云南省文山州40岁及以上壮族和苗族人群翼状胬肉患病率较高,睑板腺开口有无堵塞、泪河高度影响翼状胬肉的发生和侵入程度。

Magnifying narrow-band imaging endoscopy is superior in diagnosis of early gastric cancer

AIM:To evaluate the diagnostic effectiveness of white light endoscopy,magnifying endoscopy(ME),and magnifying narrow-band imaging endoscopy(ME-NBI) in detecting early gastric cancer(EGC).METHODS:From March 2010 to June 2012,a total of 3616 patients received screening for gastric cancer by magnifying endoscopy. There were 3675 focal gastric lesions detected using conventional high definition white light endoscopy(HD-WLE) in four different referentialhospitals that were recruited for further investigation using ME and ME-NBI. The images obtained from HD-WLE,ME,and ME-NBI were reviewed by four experienced endoscopists to evaluate their diagnostic effectiveness for EGC. The diagnosis of cancerous and non-cancerous lesions was conducted by evaluating the microvascular and microsurface patterns using the VS classification system. The final endoscopic diagnosis of each lesion was determined by consultation when a disagreement occurred. We used histopathological results as the gold standard for the diagnosis of EGC.RESULTS:Among the 3675 lesions found,1508 were validated by pathological findings as chronic gastritis,1279 as chronic gastritis with intestinal metaplasia,631 as low-grade neoplasia,and 257 as EGC. The sensitivity,specificity,positive predictive value,negative predictive value,and accuracy of HD-WLE for the diagnosis of EGC were 71.2%,99.1%,85.5%,97.9% and 97.1%,respectively. The results of ME for diagnosing EGC were 81.3%,98.8%,83.3%,98.6% and 97.6%,respectively. The results of ME-NBI for the diagnosis of EGC were 87.2%,98.6%,82.1%,99.0% and 97.8%,respectively. The diagnostic sensitivity and accuracy of paired ME and ME-NBI were significantly better than those of HD-WLE(P < 0.05).CONCLUSION:HD-WLE has a relatively high accuracy for diagnosing EGC and is an effective screening tool. Further investigations of ME and ME-NBI are required to achieve superior accuracy.

Computational Analysis for Residue-Specific CDK2-Inhibitor Bindings

Cyclin-dependent kinase 2 (CDK2) is a key macromolecule in cell cycle regulation. In cancer cells, CDK2 is often overexpressed and its inhibition is an effective therapy of many cancers including breast carcinomas, leukemia, and lymphomas. Quantitative characterization of the interactions between CDK2 and its inhibitors at atomic level may provide a deep understanding of protein-inhibitor interactions and clues for more effective drug discovery. In this study, we have used the computational alanine scanning approach in combination with an efficient interaction entropy method to study the microscopic mechanism of binding between CDK2 and its 13 inhibitors. The total binding free energy from the method shows a correlation of 0.76?0.83 with the experimental values. The free energy component reveals two binding mode in the 13 complexes, namely van der Waals dominant, and electrostatic dominant. Decomposition of the total energy to per-residue contribution allows us to identify five hydrophobic residues as hot spots during the binding. Residues that are responsible for determining the strength of the binding were also analyzed.

Same-day single-dose vs large-volume split-dose regimens of polyethylene glycol for bowel preparation:A systematic review and meta-analysis

BACKGROUND Split-dose regimens(SpDs)of 4 L of polyethylene glycol(PEG)have been established as the“gold standard”for bowel preparation;however,its use is limited by the large volumes of fluids required and sleep disturbance associated with night doses.Meanwhile,the same-day single-dose regimens(SSDs)of PEG has been recommended as an alternative;however,its superiority compared to other regimens is a matter of debate.AIM To compare the efficacy and tolerability between SSDs and large-volume SpDs PEG for bowel preparation.METHODS We searched MEDLINE/PubMed,the Cochrane Library,RCA,EMBASE and Science Citation Index Expanded for randomized trials comparing(2 L/4 L)SSDs to large-volume(4 L/3 L)SpDs PEG-based regimens,regardless of adjuvant laxative use.The pooled analysis of relative risk ratio and mean difference was calculated for bowel cleanliness,sleep disturbance,willingness to repeat the procedure using the same preparation and adverse effects.A random effects model or fixed-effects model was chosen based on heterogeneity analysis among studies.RESULTS A total of 18 studies were included.There was no statistically significant difference of adequate bowel preparation(relative risk=0.97;95%CI:0.92-1.02)(14 trials),right colon Boston Bowel Preparation Scale(mean difference=0.00;95%CI:-0.04,0.03)(9 trials)and right colon Ottawa Bowel Preparation Scale(mean difference=0.04;95%CI:-0.27,0.34)(5 trials)between(2 L/4 L)SSDs and large-volume(4 L/3 L)SpDs,regardless of adjuvant laxative use.The pooled analysis favored the use of SSDs with less sleep disturbance(relative risk=0.52;95%CI:0.40,0.68)and lower incidence of abdominal pain(relative risk=0.75;95%CI:0.62,0.90).During subgroup analysis,patients that received low-volume(2 L)SSDs showed more willingness to repeat the procedure using the same preparation than SpDs(P<0.05).No significant difference in adverse effects,including nausea,vomiting and bloating,was found between the two arms(P>0.05).CONCLUSION Regardless of adjuvant laxative use,the(2 L/4 L)SSD PEG-based arm was considered equal or better than the large-volume(≥3 L)SpDs PEG regimen in terms of bowel cleanliness and tolerability.Patients that received low-volume(2 L)SSDs showed more willingness to repeat the procedure using the same preparation due to the low-volume fluid requirement and less sleep disturbance.

Searching for initial stage of massive star formation around the HⅡ region G18.2–0.3

Sometimes, early star formation can be found in cold and dense molecular clouds, such as an infrared dark cloud. Considering that star formation often occurs in clusters, H II regions may be triggering a new generation of star formation, so we can search for the initial stage of massive star formation around H II regions. Based on the above, this work introduces one method to search for the initial stage of massive star formation around H II regions. Towards one section of the H II region G18.2-0.3, multiwavelength observations are carried out to investigate its physical properties. Through analysis, we find three potential initial stages of massive star formation, suggesting that it is feasible to use in searching for the initial stage of massive star formation around H II regions.

Foreground removal of 21cm fluctuation with multifrequency fitting

The 21 centimeter （21 cm） line emission from neutral hydrogen in the intergalactic medium （IGM） at high redshifts is strongly contaminated by foreground sources such as the diffuse Galactic synchrotron emission and free-free emission from the Galaxy, as well as emission from extragalactic radio sources, thus making its observation very complicated. However, the 21 cm signal can be recovered through its structure in frequency space, as the power spectrum of the foreground contamination is expected to be smooth over a wide band in frequency space while the 21 cm fluctuations vary significantly. We use a simple polynomial fitting to reconstruct the 21 cm signal around four frequencies 50, 100, 150 and 200 MHz with an especially small channel width of 20 kHz. Our calculations show that this multifrequency fitting approach can effectively recover the 21 cm signal in the frequency range 100 - 200 MHz. However, this method doesn＇t work well around 50 MHz because of the low intensity of the 21 cm signal at this frequency. We also show that the fluctuation of detector noise can be suppressed to a very low level by taking long integration times, which means that we can reach a sensitivity of ≈ 10 mK at 150 MHz with 40 antennas in 120 hours of observations.

Modeling the WMAP large-angle anomalies as an effect of a local density inhomogeneity

We investigate large-angle scale temperature anisotropy in the Cosmic Microwave Background （CMB） with the Wilkinson Microwave Anisotropy Probe （WMAP） data and model the large-angle anomalies as the effect of the CMB quadrupole anisotropies caused by the local density inhomogeneities. The quadrupole caused by the local density inhomogeneities is different from the special relativity kinematic quadrupole. If the observer inhabits a strong inhomogeneous region, the lo- cal quadrupole should not be neglected. We calculate such local quadrupole under the assumption that there is a huge density fluctuation field in the direction （284°, 74°）, where the density fluctuation is 10-3, and its center is - 112 h-1 Mpc away from us. After removing such mock signals from WMAP data, the power in the quadrupole, C2, increases from the range （200 - 260 μK2） to - 1000 μK2. The quantity S, which is used to estimate the alignment between the quadrupole and the octopole, decreases from （0.7 - 0.74） to （0.31 - 0.37）, while the model predicts that C2 = 1071.5 μK2, and S = 0.412. So our local density inhomogeneity model can, in part, explain the WMAP low-l anomalies.

Prediction of contact resistance of electrical contact wear using different machine learning algorithms

H62 brass material is one of the important materials in the process of electrical energy transmission and signal transmission,and has excellent performance in all aspects.Since the wear behavior of electrical contact pairs is particularly complex when they are in service,we evaluated the effects of load,sliding velocity,displacement amplitude,current intensity,and surface roughness on the changes in contact resistance.Machine learning(ML)algorithms were used to predict the electrical contact performance of different factors after wear to determine the correlation between different factors and contact resistance.Random forest(RF),support vector regression(SVR)and BP neural network(BPNN)algorithms were used to establish RF,SVR and BPNN models,respectively,and the experimental data were trained and tested.It was proved that BP neural network model could better predict the stable mean resistance of H62 brass alloy after wear.Characteristic analysis shows that the load and current have great influence on the predicted electrical contact properties.The wear behavior of electrical contacts is influenced by factors such as load,sliding speed,displacement amplitude,current intensity,and surface roughness during operation.Machine learning algorithms can predict the electrical contact performance after wear caused by these factors.Experimental results indicate that an increase in load,current,and surface roughness leads to a decrease in stable mean resistance,while an increase in displacement amplitude and frequency results in an increase in stable mean resistance,leading to a decline in electrical contact performance.To reduce testing time and costs and quickly obtain the electrical contact performance of H62 brass alloy after wear caused by different factors,three algorithms(random forest(RF),support vector regression(SVR),and BP neural network(BPNN))were used to train and test experimental results,resulting in a machine learning model suitable for predicting the stable mean resistance of H62 brass alloy after wear.The prediction results showed that the BPNN model performed better in predicting the electrical contact performance compared to the RF and SVR models.

基于网络药理学探寻银芩口服液治疗新型冠状病毒肺炎抑制机制的研究

目的探寻银芩口服液治疗儿童新型冠状病毒肺炎(Corona virus disease 2019,COVID-19)的潜在成分及作用机制。方法借助TCMSP和BATMAN-TCM数据库获取金银花、黄芩、柴胡、蝉蜕四味中药的活性成分和作用靶点。利用蛋白质数据库UniProt和人类基因数据库GeneCards进行靶点与基因的转换,借助Cytoscape3.7.2构建“活性成分-靶点”网络并进行拓扑分析,利用R软件进行GO和KEGG功能富集分析。结果银芩口服液共筛选出56个化合物和相应靶点266个,关键靶点涉及PTGS1、GSK3β、NCOA2、ESR2、ESR1等。GO富集共涉及237个生物过程、65种分子功能、54种细胞组成。KEGG通路66个条目,涉及网络神经信号传递通路、肿瘤相关通路、cAMP信号通路等。分子对接结果发现柴胡、黄芩、金银花中含有较多潜在抗COVID-19活性成分,其中以柴胡皂苷(A、D)、黄芩素、异黄蝶呤亲和力最强。结论银芩口服液中的有效成分可能通过抗病毒、抑制炎症因子、调节免疫等途径调控多条通路,为进一步阐明银芩口服液治疗新型冠状病毒肺炎的作用机制提供了研究方向。

Effect of temperature maintenance by forced-air warming blankets of different temperatures on changes in inflammatory factors in children undergoing congenital hip dislocation surgery

Background:Hypothermia is associated with many adverse clinical outcomes in pediatric patients,and thus,it is important to an effective and safe method for preventing peri-operative hypothermia and its associated adverse outcomes in pediatric patients.This study aimed to investigate the effect of forced-air warming blankets with different temperatures on changes in the transforming growth factor-β(TGF-β),tumor necrosis factor(TNF)-α,interleukin(IL)-1β,and IL-10 levels in children undergoing surgical treatment for developmental displacement of the hip(DDH).Methods:The study included 123 children undergoing surgery for DDH under general anesthesia.The patients were randomly assigned to three groups,using a random number table:the 32,38,and 43°C groups according to the temperature setting of the forced-air warming blankets.For each patient,body temperature was recorded immediately after anesthesia induction and intubation(T0),at initial incision(T1),at 1 h after incision(T2),at2 h after incision(T3),at the end of surgery(T4),immediately upon return to the ward after surgery(T5),and then at 12 h(T6),24 h(T7),36 h(T8),and 48 h(T9)after the surgery.The serum levels of TGF-β,TNF-α,IL-1β,and IL-10 were measured at To and T4 for all groups.Results:The number of patients with fever in the 38°C group was significantly less than those in the 32 and 43°C groups(x^2=6.630,P=0.036).At To,the body temperatures in the 38 and 43°C groups were significantly higher than that in the 32°C group(F=17.992,P<0.001).At T2,the body temperature was significantly higher in the 43°C group than those in the 32 and 38°C groups(F=12.776,P<0.001).Moreover,at T4,the serum levels of TGF-β(F=3286.548,P<0.001)and IL-10(F=4628.983,P<0.001)were significantly increased in the 38°C group,and the serum levels of TNF-α(F=911.415,P<0.001)and IL-10(F=322.191,P<0.001)were significantly decreased in the 38°C group,compared with the levels in the 32 and 43°C groups.Conclusion:Force-air warming blankets set at 38°C maintained stable body temperature with less adverse outcome and effectively inhibited the inflammatory response in pediatric patients undergoing surgery for DDH.

Parareal in Time Simulation of Morphological Transformation in Cubic Alloys with Spatially Dependent Composition

In this paper,a reducedmorphological transformation model with spatially dependent composition and elastic modulus is considered.The parareal in time algorithm introduced by Lions et al.is developed for longer-time simulation.The fine solver is based on a second-order scheme in reciprocal space,and the coarse solver is based on a multi-model backward Euler scheme,which is fast and less expensive.Numerical simulations concerning the composition with a randomnoise and a discontinuous curve are performed.Some microstructure characteristics at very low temperature are obtained by a variable temperature technique.