A Quality Evaluation System for Dissertation Based on Fuzzy Analytic Hierarchy Process

A dissertation is a research report or scientific paper written by an author to obtain a certain degree. It reflects postgraduates’ research achievements and the educational quality of an institute, even a country. To construct an optimized quality evaluation system for postgraduate dissertation (QESPD), we summarized the influencing factors and invited 10 experienced specialists to rate and prioritize them based on fuzzy analytic hierarchy process. Four primary indicators (innovation, integrity, scientificity and normativity) and 16 sub-indicators were selected to form the evaluation system. The order of primary indicators by weight, was innovation (0.4269), scientificity (0.2807), integrity (0.1728) and normativity (0.1196). The top five sub-dimensions were theoretical originality, scientific value, data reliability, design rationality and evidence credibility. To demonstrate the effectiveness of the proposed system, a case study was performed. In the case study, it was demonstrated that the established two-index-hierarchy QESPD in this study was a more scientific and reasonable evaluation system worthy of promotion and application.

CuPc/FeNC双组分催化剂协同催化硝酸盐转化为氨

氨(NH_(3))作为重要的化学品和能源储存介质,需求量与日俱增.本文旨在通过电化学硝酸根还原反应(NO_(3)^(−)RR),将NO_(3)^(−)转化为NH3,不仅解决了NO_(3)^(−)引起的环境污染问题,又可以满足对NH_(3)的迫切需求.然而,NO_(3)^(−)RR涉及多个电子和质子转移过程,其中,NO_(2)^(−)是NO_(3)^(−)活化转化和深度还原合成NH_(3)的重要中间体.酞菁铜(CuPc)能够高效地活化转化NO_(3)^(−)为NO_(2)^(−),但在低过电位时无法有效地将NO2−还原为NH3,难以获得较高的氨法拉第效率(FENH3)和分电流密度.而氮配位的铁单原子催化剂(FeNC)则有较好的NO_(2)^(−)吸附活化特性.因此,利用双组分催化剂之间的协同作用以实现高效NO_(3)^(−)RR的活性和选择性是本文的主要研究思路.本文设计了CuPc/FeNC串联催化剂,利用CuPc和FeNC对NO_(3)^(−)和NO_(2)^(−)的吸附活化能力的差异,实现了高效的协同催化转化.X射线衍射、高角环形暗场扫描透射电镜、X射线光电子能谱及X射线吸收谱结果表明,FeNC催化剂中Fe原子均匀分布于ZIF-8热解后的基底.通过将FeNC和CuPc负载于气体扩散电极,在流动电解池中完成NO_(3)^(−)RR.CuPc/FeNC催化剂在较低电势区间中能够实现接近100%的NH3法拉第效率,同时在−0.57 V vs.RHE时达到273 mA cm–2的NH3分电流密度,并且在整个电势范围内有效地抑制了NO_(2)^(–)聚集.与单组分催化剂CuPc和FeNC对比结果表明,在−0.53 V vs.RHE时,CuPc/FeNC催化剂表现出较高的FE(NH_(3))/FE(NO_(2)^(−))比值,是CuPc催化剂的50倍;同时CuPc/FeNC催化剂上NH3分电流密度是FeNC催化剂的1.5倍.进一步研究了NO_(3)^(–)RR中的串联反应机制,其中FeNC催化剂表现出较高的NO_(2)^(–)RR活性,并且有效抑制了析氢反应.此外,CuPc/FeNC催化剂和FeNC催化剂在NO_(2)^(−)RR中表现出类似的NH3分电流密度,这表明在NO_(3)^(−)RR中,CuPc/FeNC催化剂性能的提高来源于FeNC位点能够进一步还原CuPc位点产生的NO_(2)^(–).理论计算结果表明,FeNC比CuPc表现出更强的NO_(2)^(–)吸附活化能力,说明NO_(2)^(−)在FeNC上更容易进行加氢还原.NO_(3)^(−)RR反应全路径分析结果表明,对于^(*)NO_(3)还原到*NO2过程,CuPc相对于FeNC位点具有明显降低的反应自由能,说明CuPc有利于NO_(2)^(−)的生成;而FeNC位点在后续的^(*)NO_(2)还原合成^(*)NH_(3)过程中具有更低的反应自由能,这与实验结果一致.一系列非原位和原位表征证明了CuPc催化剂在高电位下存在少量金属颗粒析出,与CuPc催化剂在高电位下NH_(3)分电流密度快速增加结果一致.综上,本工作中CuPc和FeNC催化剂之间的协同作用弥补了各自的不足,通过串联反应机制,在低过电位下有效增加了NH_(3)的法拉第效率和电流密度,实现了高效的协同催化转化,为设计和合成高效催化剂提供了新思路.

Analysis of the Risk of Water Breakout in the Bottom Plate of High-Intensity Mining of Extra-Thick Coal Seams

In order to clarify the danger of water breakout in the bottom plate of extra-thick coal seam mining, 2202 working face of a mine in the west is taken as the research object, and it is proposed to use the on-site monitoring means combining borehole peeping and microseismic monitoring, combined with the theoretical analysis to analyze the danger of water breakout in the bottom plate. The results show that: 1) the theoretically calculated maximum damage depth of the bottom plate is 27.5 m, and its layer is located above the Austrian ash aquifer, which has the danger of water breakout;2) the drill hole peeping at the bottom plate of the working face shows that the depth of the bottom plate fissure development reaches 26 m, and the integrity of the water barrier layer has been damaged, so there is the risk of water breakout;3) for the microseismic monitoring of the anomalous area, the bottom plate of the return air downstream channel occurs in the field with a one-week lag, which shows that microseismic monitoring events may reflect the water breakout of the underground. This shows that the microseismic monitoring events can reflect the changes of the underground flow field, which can provide a reference basis for the early warning of water breakout. The research results can provide reference for the prediction of sudden water hazard.

Application of Horizontal Well Seismic Geo-Steering Technology in XX Block Development

During the development phase horizontal wells are very efficient way to improve the production in the deep coal bed methane. The 8# coal seam in the XX block on the eastern edge of the Ordos Basin has challenges such as deep burial depth (>2000 m), thin coal sweet spot (3 m), and significant short-distance structural fluctuations. The challenges caused a high risk of missing targets and running out of the target layers, as well as difficulties in cementing and completion due to uneven well trajectories. To address these challenges, this paper focuses on solving the issues through detailed precise geological modeling, optimized trajectory design, and accurate seismic geology Steerable Drilling. 1) Based on reasonable velocity field construction and Time-Depth transformation, a precise directional model is constructed using the layer-by-layer approximation principle with reference to marker layers, improving the accuracy of the target spot and avoiding premature or delayed entry into the target;2) Based on a precise geological model, the dip angle of the strata ahead and the development of sweet spots are clearly defined, enabling optimized trajectory design for horizontal wells;3) Using “1 + N” dynamic modeling to update the geological model in real-time during the drilling process, and actively guide the drill bit through the horizontal segment smoothly by using multi-information judgment of the drill bit position. The actual drilling of 80 completed horizontal wells in this area show: That this approach effectively ensures the smooth trajectory and high-quality drilling rate of the horizontal well in the coal seam, providing a basis for subsequent hydraulic fracturing and increasing single-well production. At the same time, it has certain potential value and significance for similar coalbed methane developments under similar geological conditions.

D-Psicose intake exacerbates dextran sulfate sodium-induced colitis in mice through alteration in the gut microbiota and dysfunction of mucosal barrier

D-Psicose,as a low-calorie rare sugar,has attracted a lot of attention in recent years for alternating to sucrose.The anti-obesity effect of D-psicose has been extensively confirmed in previous studies,however,the impact of D-psicose on colitis remains vague.Here,we firstly evaluated the effect of the D-psicose prophylactic intervention on dextran sulfate sodium-induced colitis in C57BL/6 mice.The pathological symptoms,inflammatory cytokines levels,gut microbiota composition,short chain fatty acids(SCFAs)production and colonic barrier integrity were comprehensively evaluated.The results confirmed that D-psicose intervention aggravated colitis,characterized by the exacerbation of colon shortening,increase of colonic inflammatory infiltration,and marked exaltation of disease activity indices and IL-6,IL-1βand TNF-αlevels.Further,the dysfunction of gut microbiota was identified in the psicose group.The abundance of pro-inflammatory bacteria Lachnospiraceae_NK4A136_group was significantly up-regulated while the abundance of probiotics Akkermansia and Lactobacillus were significantly down-regulated in the psicose group compared to the model group.Moreover,the production of SCFAs was suppressed in the psicose group,accompanied by a decrease in the level of mucin 2(Muc-2).Collectively,the underlying mechanism of the exacerbation of colitis by D-psicose intervention might be attributed to microbiota dysfunction accompanied by the reduction of SCFAs,which leads to the damage of the mucosal barrier and the intensifi cation of inflammatory invasion.

The research progress of an E//B neutral particle analyzer

An E//B neutral particle analyzer(NPA)has been designed and is under development at Sichuan University and Southwestern Institute of Physics.The main purpose of the E//B NPA is to measure the distribution function of fast ions in the HL-2A/3 tokamak.The E//B NPA contains three main units,i.e.the stripping unit,the analyzing unit and the detection unit.A gas stripping chamber was adopted as the stripping unit.The results of the simulations and beam tests for the stripping chamber are presented.Parallel electric and magnetic fields provided by a NdFeB permanent magnet and two parallel electric plates were designed and constructed for the analyzing unit.The calibration of the magnetic and electric fields was performed using a 50 kV electron cyclotron resonance ion source(ECRIS)platform.The detection unit consists of 32lutetium-yttrium oxyorthosilicate(LYSO)detector modules arranged in two rows.The response functions ofα,hydrogen ions(H^(+),H_(2)^(+)and H_(3)^(+))andγfor a detector module were measured with^(241)Am,^(137)Cs and^(152)Eu sources together with the 50 kV ECRIS platform.The overall results indicate that the designed E//B NPA device is capable of measuring the intensity of neutral hydrogen and deuteron atoms with energy higher than 20 keV.

m^(1)A inhibition fuels oncolytic virus-elicited antitumor immunity via downregulating MYC/PD-L1 signaling

N^(1)-methyladenosine(m^(1)A)RNA methylation is critical for regulating mRNA translation;however,its role in the development,progression,and immunotherapy response of head and neck squamous cell carcinoma(HNSCC)remains largely unknown.Using Tgfbr1 and Pten conditional knockout(2cKO)mice,we found the neoplastic transformation of oral mucosa was accompanied by increased m^(1)A modification levels.Analysis of m^(1)A-associated genes identified TRMT61A as a key m^(1)A writer linked to cancer progression and poor prognosis.Mechanistically,TRMT61A-mediated tRNA-m^(1)A modification promotes MYC protein synthesis,upregulating programmed death-ligand 1(PD-L1)expression.Moreover,m^(1)A modification levels were also elevated in tumors treated with oncolytic herpes simplex virus(oHSV),contributing to reactive PD-L1 upregulation.Therapeutic m^(1)A inhibition sustained oHSV-induced antitumor immunity and reduced tumor growth,representing a promising strategy to alleviate resistance.These findings indicate that m^(1)A inhibition can prevent immune escape after oHSV therapy by reducing PD-L1 expression,providing a mutually reinforcing combination immunotherapy approach.

The microbial community,nutrient supply and crop yields differ along a potassium fertilizer gradient under wheat-maize double-cropping systems

Soil microorganisms play critical roles in ecosystem function.However,the relative impact of the potassium(K)fertilizer gradient on the microbial community in wheat-maize double-cropping systems remains unclear.In this long-term field experiment(2008-2019),we researched bacterial and fungal diversity,composition,and community assemblage in the soil along a K fertilizer gradient in the wheat season(K0,no K fertilizer;K1,45 kg ha^(-1) K_(2)O;K_(2),90 kg ha^(-1)K_(2)O;K3,135 kg ha^(-1)K_(2)O)and in the maize season(K0,no K fertilizer;K_(1),150 kg ha^(-1) K_(2)O;K_(2),300 kg ha^(-1)K_(2)O;K_(3),450 kg ha^(-1)K_(2)O)using bacterial 16S rRNA and fungal internally transcribed spacer(ITS)data.We observed that environmental variables,such as mean annual soil temperature(MAT)and precipitation,available K,ammonium,nitrate,and organic matter,impacted the soil bacterial and fungal communities,and their impacts varied with fertilizer treatments and crop species.Furthermore,the relative abundance of bacteria involved in soil nutrient transformation(phylum Actinobacteria and class Alphaproteobacteria)in the wheat season was significantly increased compared to the maize season,and the optimal K fertilizer dosage(K2 treatment)boosted the relative bacterial abundance of soil nutrient transformation(genus Lactobacillus)and soil denitrification(phylum Proteobacteria)bacteria in the wheat season.The abundance of the soil bacterial community promoting root growth and nutrient absorption(genus Herbaspirillum)in the maize season was improved compared to the wheat season,and the K2 treatment enhanced the bacterial abundance of soil nutrient transformation(genus MND1)and soil nitrogen cycling(genus Nitrospira)genera in the maize season.The results indicated that the bacterial and fungal communities in the double-cropping system exhibited variable sensitivities and assembly mechanisms along a K fertilizer gradient,and microhabitats explained the largest amount of the variation in crop yields,and improved wheat?maize yields by 11.2-22.6 and 9.2-23.8%with K addition,respectively.These modes are shaped contemporaneously by the different meteorological factors and soil nutrient changes in the K fertilizer gradients.

从信号到知识——基于人工智能的医学影像裸数据诊断价值初探

Encouraging and astonishing developments have recently been achieved in image-based diagnostic technology.Modern medical care and imaging technology are becoming increasingly inseparable.However,the current diagnosis pattern of signal to image to knowledge inevitably leads to information distortion and noise introduction in the procedure of image reconstruction(from signal to image).Artificial intelligence(AI)technologies that can mine knowledge from vast amounts of data offer opportunities to disrupt established workflows.In this prospective study,for the first time,we develop an AI-based signal-toknowledge diagnostic scheme for lung nodule classification directly from the computed tomography(CT)raw data(the signal).We find that the raw data achieves almost comparable performance with CT,indicating that it is possible to diagnose diseases without reconstructing images.Moreover,the incorporation of raw data through three common convolutional network structures greatly improves the performance of the CT models in all cohorts(with a gain ranging from 0.01 to 0.12),demonstrating that raw data contains diagnostic information that CT does not possess.Our results break new ground and demonstrate the potential for direct signal-to-knowledge domain analysis.

Highly selective photocatalytic reduction of CO_(2) to CH_(4) on electron-rich Fe species cocatalyst under visible light irradiation

Efficient photocatalytic reduction of CO_(2) to high-calorific-value CH4,an ideal target product,is a blueprint for C_(1)industry relevance and carbon neutrality,but it also faces great challenges.Herein,we demonstrate unprecedented hybrid SiC photocatalysts modified by Fe-based cocatalyst,which are prepared via a facile impregnation-reduction method,featuring an optimized local electronic structure.It exhibits a superior photocatalytic carbon-based products yield of 30.0μmol g^(−1) h^(−1) and achieves a record CH_(4) selectivity of up to 94.3%,which highlights the effectiveness of electron-rich Fe cocatalyst for boosting photocatalytic performance and selectivity.Specifically,the synergistic effects of directional migration of photogenerated electrons and strongπ-back bonding on low-valence Fe effectively strengthen the adsorption and activation of reactants and intermediates in the CO_(2)→CH_(4) pathway.This study inspires an effective strategy for enhancing the multielectron reduction capacity of semiconductor photocatalysts with low-cost Fe instead of noble metals as cocatalysts.

Efficacy and Safety of Lianhua Qingke Tablets in the Treatment of Long Coronavirus Disease (COVID) Cough: A Randomized, Double-Blind, Placebo-Controlled, Multicenter Clinical Study

Lianhua Qingke tablets,a patented traditional Chinese medicine that has validated clinical efficacy for treating cough caused by severe acute respiratory syndrome coronavirus 2 infection,lack rigorous evidence-based research evaluating their effect on long coronavirus disease(COVID)cough.A randomized,double-blind,placebo-controlled,multicenter clinical study was conducted among patients with long COVID cough from 19 hospitals and 23 community health centers in China.Patients were randomized 1:1 to receive either Lianhua Qingke tablets or placebo orally for 14 days(four tablets,1.84 g,three times a day).The primary endpoint indicator was the disappearance of cough,with the remission of cough also considered.Among 482 randomized patients,480(full analysis set 480;per-protocol set 470;safety set 480)were included in the primary analysis.According to the full analysis,the time until cough disappearance was significantly shorter in the trial group than in the control group,with a significant increase in the 14-day cough disappearance rate.Accordingly,the time to cough remission was significantly shorter in the trial group than in the control group.The change in the total symptom score was significantly greater in the trial group than in the control group on days 7 and 14,consistent with the results indicated by the visual analog scale(VAS)and cough evaluation test(CET)scores.No serious adverse events were recorded during the study.Lianhua Qingke tablets significantly improved the clinical symptoms of patients with long COVID cough.

Repeated inoculation with rumen fluid accelerates the rumen bacterial transition with no benefit on production performance in postpartum Holstein dairy cows

Background The dairy cow’s postpartum period is characterized by dramatic physiological changes,therefore imposing severe challenges on the animal for maintaining health and milk output.The dynamics of the ruminal microbiota are also tremendous and may play a crucial role in lactation launch.We aim to investigate the potential benefits of early microbial intervention by fresh rumen microbiota transplantation(RMT)and sterile RMT in postpartum dairy cows.Twelve fistulated peak-lactation dairy cows were selected to be the donors for rumen fluid collection.Thirty postpartum cows were divided into 3 groups as the transplantation receptors respectively receiving 10 L fresh rumen fluid(FR),10 L sterile rumen fluid(SR),or 10 L saline(CON)during 3 d after calving.Results Production performance,plasma indices,plasma lipidome,ruminal microbiome,and liver transcriptome were recorded.After fresh and sterile RMT,we found that the molar proportion of propionic acid was increased on d 7 in the FR and SR groups and the bacterial composition was also significantly changed when compared with the CON group.A similarity analysis showed that the similarities between the CON group and FR or SR group on d 7 were 48.40%or 47.85%,whereas the similarities between microbiota on d 7 and 21 in the FR and SR groups were 68.34%or 66.85%.Dry matter intake and feed efficiency were not affected by treatments.Plasmaβ-hydroxybutyrate concentration in the FR group was decreased and significantly different lipids mainly included phosphatidylcholine and lysophosphatidylcholine containing polyunsaturated fatty acids.Hepatic transcriptomics analysis indicated acutephase response pathways were upregulated in the SR group.Conclusions Our study suggests that RMT can shorten the transition process of the ruminal microbiota of postpartum dairy cows with no benefit on dry matter intake or feed efficiency.Inoculation with rumen fluid may not be a useful approach to promote the recovery of postpartum dairy cows.

Advantageous properties of halide perovskite quantum dots towards energy-efficient sustainable applications

As lead halide perovskite(LHP)semiconductors have shown tremendous promise in many application fields,and particularly made strong impact in the solar photovoltaic area,low dimensional quantum dot forms of these perovskites are showing the potential to make distinct marks in the fields of electronics,optoelectronics and photonics.The so-called perovskite quantum dots(PQDs)not only possess the most important features of LHP materials,i.e.,the unusual high defect tolerance,but also demonstrate clear quantum size effects,along with exhibiting desirable optoelectronic properties such as near perfect photoluminescent quantum yield,multiple exciton generation and slow hot-carrier cooling.Here,we review the advantageous properties of these nanoscale perovskites and survey the prospects for diverse applications which include lightemitting devices,solar cells,photocatalysts,lasers,detectors and memristors,emphasizing the distinct superiorities as well as the challenges.

Deep learning approaches to recover the plasma current density profile from the safety factor based on Grad–Shafranov solutions across multiple tokamaks

Many magnetohydrodynamic stability analyses require generation of a set of equilibria with a fixed safety factor q-profile while varying other plasma parameters.A neural network(NN)-based approach is investigated that facilitates such a process.Both multilayer perceptron(MLP)-based NN and convolutional neural network(CNN)models are trained to map the q-profile to the plasma current density J-profile,and vice versa,while satisfying the Grad–Shafranov radial force balance constraint.When the initial target models are trained,using a database of semianalytically constructed numerical equilibria,an initial CNN with one convolutional layer is found to perform better than an initial MLP model.In particular,a trained initial CNN model can also predict the q-or J-profile for experimental tokamak equilibria.The performance of both initial target models is further improved by fine-tuning the training database,i.e.by adding realistic experimental equilibria with Gaussian noise.The fine-tuned target models,referred to as fine-tuned MLP and fine-tuned CNN,well reproduce the target q-or J-profile across multiple tokamak devices.As an important application,these NN-based equilibrium profile convertors can be utilized to provide a good initial guess for iterative equilibrium solvers,where the desired input quantity is the safety factor instead of the plasma current density.

Integrated analysis of plasma rotation effect on HL-3 hybrid scenario

The hybrid scenario,which has good confinement and moderate MHD instabilities,is a proposed operation scenario for international thermonuclear experimental reactor(ITER).In this work,the effect of plasma rotation on the HL-3 hybrid scenario is analyzed with the integrated modeling framework OMFIT.The results show that toroidal rotation has no obvious effect on confinement with a high line averaged density of n_(bar)~(7)×10^(19)m^(-3).In this case,the ion temperature only changes from 4.7 keV to 4.4 keV with the rotation decreasing from 10^(5) rad/s to 10^(3) rad/s,which means that the turbulent heat transport is not dominant.While in the scenarios characterized by lower densities,such as n_(bar)~4×10^(19)m^(-3),turbulent transport becomes dominant in determining heat transport.The ion temperature rises from 3.8 keV to 6.1 keV in the core as the rotation velocity increases from 10^(3) rad/s to 10^(5) rad/s.Despite the ion temperature rising,the rotation velocity does not obviously affect electron temperature or density.Additionally,it is noteworthy that the variation in rotation velocity does not significantly affect the global confinement of plasma in scenarios with low density or with high density.

Critical behavior of quasi-two-dimensional ferromagnet Cr_(1.04)Te_(2)

The self-intercalation of Cr into pristine two-dimensional(2D) van der Waals ferromagnetic CrTe_(2),which forms chromium tellurides(Cr_(x)Te_(2)),has garnered interest due to their remarkable magnetic characteristics and the wide variety of chemical compositions available.Here,comprehensive basic characterization and magnetic studies are conducted on quasi-2D ferromagnetic Cr_(1.04)Te_(2) crystals.Measurements of the isothermal magnetization curves are conducted around the critical temperature to systematically investigate the critical behavior.Specifically,the critical exponents β=0.2399,γ=0.859,and δ=4.3498,as well as the Curie temperature T_(C)=249.56 K,are determined using various methods,including the modified Arrott plots,the Kouvel-Fisher method,the Widom scaling method,and the critical isotherm analysis.These results indicate that the tricritical mean-field model accurately represents the critical behavior of Cr_(1.04)Te_(2.A magnetic phase diagram with tricritical phenomenon is thus constructed.Further investigations confirm that the critical exponents obtained conform to the scalar equation near T_(C),indicating their self-consistency and reliability.Our work sheds light on the magnetic properties of quasi-2D Cr_(1.04)Te_(2),broadening the scope of the van der Waals crystals for developments of future spintronic devices operable at room temperature.

Ultra-wide band gap and wave attenuation mechanism of a novel star-shaped chiral metamaterial

A novel hollow star-shaped chiral metamaterial(SCM)is proposed by incorporating chiral structural properties into the standard hollow star-shaped metamaterial,exhibiting a wide band gap over 1500 Hz.To broaden the band gap,solid single-phase and two-phase SCMs are designed and simulated,which produce two ultra-wide band gaps(approximately 5116 Hz and 6027 Hz,respectively).The main reason for the formation of the ultra-wide band gap is that the rotational vibration of the concave star of two novel SCMs drains the energy of an elastic wave.The impacts of the concave angle of a single-phase SCM and the resonator radius of a two-phase SCM on the band gaps are studied.Decreasing the concave angle leads to an increase in the width of the widest band gap,and the width of the widest band gap increases as the resonator radius of the two-phase SCM increases.Additionally,the study on elastic wave propagation characteristics involves analyzing frequency dispersion surfaces,wave propagation directions,group velocities,and phase velocities.Ultimately,the analysis focuses on the transmission properties of finite periodic structures.The solid single-phase SCM achieves a maximum vibration attenuation over 800,while the width of the band gap is smaller than that of the two-phase SCM.Both metamaterials exhibit high vibration attenuation capabilities,which can be used in wideband vibration reduction to satisfy the requirement of ultra-wide frequencies.

Low-frequency bandgap and vibration suppression mechanism of a novel square hierarchical honeycomb metamaterial

The suppression of low-frequency vibration and noise has always been an important issue in a wide range of engineering applications.To address this concern,a novel square hierarchical honeycomb metamaterial capable of reducing low-frequency noise has been developed.By combining Bloch’s theorem with the finite element method,the band structure is calculated.Numerical results indicate that this metamaterial can produce multiple low-frequency bandgaps within 500 Hz,with a bandgap ratio exceeding 50%.The first bandgap spans from 169.57 Hz to 216.42 Hz.To reveal the formation mechanism of the bandgap,a vibrational mode analysis is performed.Numerical analysis demonstrates that the bandgap is attributed to the suppression of elastic wave propagation by the vibrations of the structure’s two protruding corners and overall expansion vibrations.Additionally,detailed parametric analyses are conducted to investigate the effect ofθ,i.e.,the angle between the protruding corner of the structure and the horizontal direction,on the band structures and the total effective bandgap width.It is found that reducingθis conducive to obtaining lower frequency bandgaps.The propagation characteristics of elastic waves in the structure are explored by the group velocity,phase velocity,and wave propagation direction.Finally,the transmission characteristics of a finite periodic structure are investigated experimentally.The results indicate significant acceleration amplitude attenuation within the bandgap range,confirming the structure’s excellent low-frequency vibration suppression capability.

Effect of icosahedral phase formation on the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li(in wt.%)based alloys

Through exploring the stress corrosion cracking(SCC)behaviors of the as-cast Mg-8%Li and Mg-8%Li-6%Zn-1.2%Y alloys in a 0.1 M NaCl solution,it revealed that the SCC susceptibility index(I_(SCC))of the Mg-8%Li alloy was 47%,whilst the I_(SCC)of the Mg-8%Li-6%Zn-1.2%Y alloy was 68%.Surface,cross-sectional and fractography observations indicated that for the Mg-8%Li alloy,theα-Mg/β-Li interfaces acted as the preferential crack initiation sites and propagation paths during the SCC process.With regard to the Mg-8%Li-6%Zn-1.2%Y alloy,the crack initiation sites included the I-phase and the interfaces of I-phase/β-Li andα-Mg/β-Li,and the preferential propagation paths were the I-phase/β-Li andα-Mg/β-Li interfaces.Moreover,the SCC of the two alloys was concerned with hydrogen embrittlement(HE)mechanism.

Plasma current tomography for HL-2A based on Bayesian inference

An accurate plasma current profile has irreplaceable value for the steady-state operation of the plasma.In this study,plasma current tomography based on Bayesian inference is applied to an HL-2A device and used to reconstruct the plasma current profile.Two different Bayesian probability priors are tried,namely the Conditional Auto Regressive(CAR)prior and the Advanced Squared Exponential(ASE)kernel prior.Compared to the CAR prior,the ASE kernel prior adopts nonstationary hyperparameters and introduces the current profile of the reference discharge into the hyperparameters,which can make the shape of the current profile more flexible in space.The results indicate that the ASE prior couples more information,reduces the probability of unreasonable solutions,and achieves higher reconstruction accuracy.