Study on Joint Method of 3D Acoustic Emission Source Localization Simplex and Grid Search Scanning

Acoustic emission(AE)source localization is a fundamental element of rock fracture damage imaging.To improve the efficiency and accuracy of AE source localization,this paper proposes a joint method comprising a three-dimensional(3D)AE source localization simplex method and grid search scanning.Using the concept of the geometry of simplexes,tetrahedral iterations were first conducted to narrow down the suspected source region.This is followed by a process of meshing the region and node searching to scan for optimal solutions,until the source location is determined.The resulting algorithm was tested using the artificial excitation source localization and uniaxial compression tests,after which the localization results were compared with the simplex and exhaustive methods.The results revealed that the localization obtained using the proposed method is more stable and can be effectively avoided compared with the simplex localization method.Furthermore,compared with the global scanning method,the proposed method is more efficient,with an average time of 10%–20%of the global scanning localization algorithm.Thus,the proposed algorithm is of great significance for laboratory research focused on locating rupture damages sustained by large-sized rock masses or test blocks.

Transmission of Avian Influenza Virus by Humpback Whale and Its Stranding along the Atlantic Coast with CO₂Emissions

Humpback whales are migratory, spending summers in cooler, high-latitude waters and mating and calving in tropical and subtropical waters in 14 identified district population segments. It may be possible that the coastal areas are infected with low pathogenic avian influenza (LPAI) during the release of infected humpback whale feces. Therefore, humpback whales can be an effective reservoir of the avian influenza virus (AIV) from the Poles to the Continents to spread AIV to coastal animals. Strong ultraviolet (UV) exposure amidst CO2 emission increase and minimal sunspot number might cause mutations of aquatic virus and humpback whale in the Antarctic and the Arctic. LPAI or highly pathogenic avian influenza (HPAI) is expressed in the Continents under appropriate environmental factors. Since penguins are birds while humpback whales are marine mammals, the humpback whales infected by the mutant virus might cause interspecies transmission to a new host with evolutionary changes. The migration pattern is seasonally similar between migratory bird and humpback whale except: 1) different species of bird versus whale, 2) different landing area of land versus coast, 3) similar infection means of bird feces versus humpback whale feces. The contribution of AIV transmission by whales was several times larger than that by migratory birds. Therefore, the routes of humpback whales should be considered to prevent AIV outbreaks in addition to the flyways of migratory birds. Humpback whale stranding (y) along the Atlantic Coast of the USA was correlated with CO2 emissions (x) to have y = 0.3515x + 18.595 (R2 = 0.4069) during 1992-2016 while y = 0.0652x + 4.5847, (R2 = 0.6128) during 2016-2018. AIV outbreak in 2010 (y) along the Atlantic Coast was also correlated with humpback whale stranding (2016-2018) (x) as y = 0.1387x + 6.8184 (R2 = 0.3966). Since AIV outbreak was linearly (R2 = 0.9967) correlated with the minimum sunspot number, it was postulated that the unusual mortality events of humpback whale stranding might be caused by an infected mutant virus in the Arctic. Consequently, the humpback whales were stranded along major CO2 producing Atlantic Coast States toward the winter habitat of the West Indies during the CO2 emissions and the minimal sunspot number with strong UV radiation. The stranded dead whales should be burned as soon as possible to prevent further deadly viral interspecies transmission of AIV by the coastal animals. Since CO2 emissions were increased in 2017 and the sunspot number was minimal at the end of 2018, serious numbers of whales are expected to be stranded at the Gulf of Maine, States of North Carolina, New York, and Virginia from November 2018 till April 2019. To save humpback whales from the unusual mortality event along the Atlantic Coast, the reduction of CO2 emissions is suggested by replacement of fossil fuels combustion plants with nuclear power plants along the Atlantic Coast of the USA.

Improved Cohen-Sutherland algorithm for TGS transmission imaging

Tomographic gamma scanner(TGS),an advancedγ-ray nondestructive analysis technique,can locate and analyze nuclides in radioactive nuclear waste,and TGS can be categorized into two processes:e.g.,transmission measurement and emission measurement.Specifically,transmission measurements provide the basis for accurate measurement of nonuniform radionuclide content in TGS scanning.The scan data were obtained using the Monte Carlo tool Geant4 simulation,and 25 voxels were divided into five lengths and five widths in a square barrel.In this study,an encoding cropping algorithm based on draped foot vector judgment was adopted to rapidly calculate the voxel trace matrix within a square bucket of nuclear waste,and the transmission images were reconstructed using ordered subset expectation maximization.The results indicated that the cropping speed of the improved coding algorithm was significantly higher than that of the original algorithm,and the relative mean deviation and root-mean-square error between the reconstructed attenuation coefficient and the reference standard value tended to decrease with an increase in the cropped line segments in the voxel;the Pearson correlation coefficient tended to converge to 1.0.The image quality evaluation parameters of the high media-density materials were better than those of the low media-density materials in the above three indexes.The reconstruction effect was relatively poor for more complex filling materials.When there were more than 10 cropped line segments in the voxel,the reconstruction data generally tended to be stable.The graphical trimming algorithm can rapidly calculate the trace matrix of the scanned voxels;it exhibits the advantages of speed and efficiency and can serve as a novel method to solve the trace matrix of TGS nuclear waste transmission scans.

Increase of brightness and transmission efficiency in fiat panel display through serial synchronous scanning mode with double buffers

This paper presents a serial synchronous scanning mode in fiat panel display （FPD） by adding a latch buffer between the serializer and the driving buffer. Comparing with conventional techniques, the proposed structure can efficiently reduce the brightness loss and improve the transmission performance. Theoretical analysis and experimental results show that the ratio between the lightest weight display time and the relative transmission time is a tradeoff between brightness loss and transmission efficiency.

Scanning transmission electron microscopy: A review of high angle annular dark field and annular bright field imaging and applications in lithium-ion batteries

Scanning transmission electron microscopy（STEM） has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field（HAADF） and annular bright field（ABF） imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries（LIBs）. The future prospects of the STEM are also discussed.

Highly specific characterization and discrimination of monosodium urate crystals in gouty arthritis based on aggregation-induced emission luminogens

Existing technologies used to detect monosodium urate(MSU)crystals for gout diagnosis are not ideal due to their low sensitivity and complexity of operation.The purpose of this study was to explore whether aggregation-induced emission luminogens(AIEgens)can be used for highly specific imaging of MSU crystals to assist in the diagnosis of gout.First,we developed a series of luminogens(i.e.,tetraphenyl ethylene(TPE)-NH_(2),TPE-2NH_(2),TPE-4NH_(2),TPE-COOH,TPE-2COOH,TPE-4COOH,and TPE-Ketoalkyne),each of which was then evenly mixed with MSU crystals.Next,optimal fluorescence imaging of each of the luminogens was characterized by a confocal laser scanning microscope(CLSM).This approach was used for imaging standard samples of MSU,hydroxyapatite(HAP)crystals,and mixed samples with 1:1 mass ratio of MSU/HAP.We also imaged samples from mouse models of acute gouty arthritis,HAP deposition disease,and comorbidities of interest.Subsequently,CLSM imaging results were compared with those of compensated polarized light microscopy,and we assessed the biosafety of TPE-Ketoalkyne in the RAW264.7 cell line.Finally,CLSM time series and three-dimensional imaging were performed on MSU crystal samples from human gouty synovial fluid and tophi.As a promising candidate for MSU crystal labeling,TPE-Ketoalkyne was found to detect MSU crystals accurately and rapidly in standard samples,animal samples,and human samples,and could precisely distinguish gout from HAP deposition disease.This work demonstrates that TPE-Ketoalkyne is suitable for highly specific and timely imaging of MSU crystals in gouty arthritis and may facilitate future research on MSU crystal-related diseases.

Utility of positron emission tomography-computed tomography scan in detecting residual hepatocellular carcinoma post treatment:Series of case reports

BACKGROUND Multi-phase computed tomography(CT)or magnetic resonance imaging(MRI)has been the standard of care for hepatocellular carcinoma(HCC)diagnosis for years.CASE SUMMARY We report a case series of four patients in whom positron emission tomographycomputed tomography(PET-CT)scan complemented the conventional CT/MRI scans in evaluating treatment response.In these four cases the conventional multi-phase CT and MRI failed to identify residual HCC disease post-treatment,while PET-CT complemented and aided in treatment response evaluation.In each case,the addition of PET-CT identified and located residual HCC disease,allowed retreatment,and altered medical management.CONCLUSION This case series suggests that PET-CT should perhaps play a role in the HCC management algorithm,in addition to the conventional contrast-enhanced multiphase scans.

Rare finding of primary aortoduodenal fistula on single-photon emission computed tomography/computed tomography of gastrointestinal bleeding: A case report

BACKGROUND Primary aortoduodenal fistula is a rare cause of gastrointestinal(GI)bleeding consisting of abnormal channels between the aorta and GI tract without previous vascular intervention that results in massive intraluminal hemorrhage.CASE SUMMARY A 67-year-old man was hospitalized for coffee ground vomiting,tarry stools,and colic abdominal pain.He was repeatedly admitted for active GI bleeding and hypovolemic shock.Intermittent and spontaneously stopped bleeders were undetectable on multiple GI endoscopy,angiography,computed tomography angiography(CTA),capsule endoscopy,and ^(99)mTc-labeled red blood cell(RBC)scans.The patient received supportive treatment and was discharged without signs of rebleeding.Thereafter,he was re-admitted for bleeder identification.Repeated CTA after a bleed revealed a small aortic aneurysm at the renal level contacting the fourth portion of the duodenum.A ^(99)mTc-labeled RBC singlephoton emission CT(SPECT)/CT scan performed during bleeding symptoms revealed active bleeding at the duodenal level.According to his clinical symptoms(intermittent massive GI bleeding with hypovolemic shock,dizziness,dark red stool,and bloody vomitus)and the abdominal CTA and ^(99)mTc-labeled RBC SPECT/CT results,we suspected a small aneurysm and an aortoduodenal fistula.Subsequent duodenal excision and duodenojejunal anastomosis were performed.A 7-mm saccular aneurysm arising from the anterior wall of the abdominal aorta near the left renal artery was identified.Percutaneous intravascular stenting of the abdominal aorta was performed and his symptoms improved.CONCLUSION Our findings suggest that ^(99)mTc-labeled RBC SPECT/CT scanning can aid the diagnosis of a rare cause of active GI bleeding.

Image charge effect on the light emission of rutile TiO2(110) induced by a scanning tunneling microscope

The plasmon-enhanced light emission of rutile TiO2（110） surface has been investigated by a low-temperature scanning tunneling microscope （STM）. We found that the photon emission arises from the inelastic electron tunneling between the STM tip and the conduction band or defect states of TiO2（110）. In contrast to the Au（111） surface, the maximum photon energy as a function of the bias voltage clearly deviates from the linear scaling behavior, suggesting the non-negligible effect of the STM tip on the band structure of TiO2. By performing differential conductance （dl/dV） measurements, it was revealed that such a deviation is not related to the tip-induced band bending, but is attributed to the image charge effect of the metal tip, which significantly shifts the band edges of the TiO2（110） towards the Femi level （EF） during the tunneling process. This work not only sheds new lights onto the understanding of plasmon-enhanced light emission of semiconductor surfaces, but also opens up a new avenue for engineering the plasmon-mediated interfacial charge transfer in molecular and semiconducting materials.

AN INVESTIGATION ON SECONDARY EMISSION PROPERTIES OF IMPREGNATED BARIUM SCANDATE DISPENSER CATHODE

A scanning electron probe is used to study the secondary emission properties of the im-pregnated barium scandate dispenser cathode, the influence of the activation on the secondary emis-sion property, the secondary emission image and the secondary emission distribution over the surfaceof the cathode. At optimal activation, δm=3.56 (Epm=700eV). The activation has a larger effect onδ when the activation temperature is higher than 1100℃. The distribution over the surface of thecathode is non-uniform. The half-peak width of the distribution curve over the surface is 0.4. Theexperimental phenomena are discussed in relation to surface analysis of the cathode. The theoreticallyderived binomial distribution curves over the surface fit much better with the experimental results.

Visualization of atomic scale reaction dynamics of supported nanocatalysts during oxidation and ammonia synthesis using in-situ environmental(scanning) transmission electron microscopy

Reaction dynamics in gases at operating temperatures at the atomic level are the basis of heterogeneous gas-solid catalyst reactions and are crucial to the catalyst function.Supported noble metal nanocatalysts such as platinum are of interest in fuel cells and as diesel oxidation catalysts for pollution control,and practical ruthenium nanocatalysts are explored for ammonia synthesis.Graphite and graphitic carbons are of interest as supports for the nanocatalysts.Despite considerable literature on the catalytic processes on graphite and graphitic supports,reaction dynamics of the nanocatalysts on the supports in different reactive gas environments and operating temperatures at the single atom level are not well understood.Here we present real time in-situ observations and analyses of reaction dynamics of Pt in oxidation,and practical Ru nanocatalysts in ammonia synthesis,on graphite and related supports under controlled reaction environments using a novel in-situ environmental(scanning) transmission electron microscope with single atom resolution.By recording snapshots of the reaction dynamics,the behaviour of the catalysts is imaged.The images reveal single metal atoms,clusters of a few atoms on the graphitic supports and the support function.These all play key roles in the mobility,sintering and growth of the catalysts.The experimental findings provide new structural insights into atomic scale reaction dynamics,morphology and stability of the nanocatalysts.

Couple analyzing the acoustic emission characters from hard composite rock fracture

Rock mass is fractured media. Its fracture is a nonlinear process. Theaccumulation of acoustic emission (AF) is closely related to the degree of damage. The dynamicsproblem is simply described based on the non-equilibrium statistical theory of crack evolvement,trying to use the hybrid analysis of the statistical theory and scan electron microscopy (SEM), thecharacters of AE signals from rock damage in a mined-out area is synthetically analyzed andevaluated. These provide an evidence to reverse deduce and accurately infer the position of rockfracture for dynamical hazard control.

Recent progress on advanced transmission electron microscopy characterization for halide perovskite semiconductors

Halide perovskites are strategically important in the field of energy materials. Along with the rapid development of the materials and related devices, there is an urgent need to understand the structure–property relationship from nanoscale to atomic scale. Much effort has been made in the past few years to overcome the difficulty of imaging limited by electron dose,and to further extend the investigation towards operando conditions. This review is dedicated to recent studies of advanced transmission electron microscopy(TEM) characterizations for halide perovskites. The irradiation damage caused by the interaction of electron beams and perovskites under conventional imaging conditions are first summarized and discussed. Low-dose TEM is then discussed, including electron diffraction and emerging techniques for high-resolution TEM(HRTEM) imaging. Atomic-resolution imaging, defects identification and chemical mapping on halide perovskites are reviewed. Cryo-TEM for halide perovskites is discussed, since it can readily suppress irradiation damage and has been rapidly developed in the past few years. Finally, the applications of in-situ TEM in the degradation study of perovskites under environmental conditions such as heating,biasing, light illumination and humidity are reviewed. More applications of emerging TEM characterizations are foreseen in the coming future, unveiling the structural origin of halide perovskite’s unique properties and degradation mechanism under operando conditions, so to assist the design of a more efficient and robust energy material.

Dynamic Model for the Z Accelerator Vacuum Section Based on Transmission Line Code

The transmission-line-circuit model of the Z accelerator, developed originally by W. A. STYGAR, P. A. CORCORAN, et al., is revised. The revised model uses different calculations for the electron loss and flow impedance in the magnetically insulated transmission line system of the Z accelerator before and after magnetic insulation is established. By including electron pressure and zero electric field at the cathode, a closed set of equations is obtained at each time step, and dynamic shunt resistance （used to represent any electron loss to the anode） and flow impedance are solved, which have been incorporated into the transmission line code for simulations of the vacuum section in the Z accelerator. Finally, the results are discussed in comparison with earlier findings to show the effectiveness and limitations of the model.

Preoperative [18]fluorodeoxyglucose-positron emission tomography/computed tomography in early stage breast cancer: Rates of distant metastases

AIM To investigate rates of distant metastases(DM) detected with [18]fluorodeoxyglucose-positron emissiontomography/computed tomography(^(18)FDG-PET/CT) in early stage invasive breast cancer.METHODS We searched the English language literature databases of PubM ed, EMBASE, ISI Web of Knowledge, Web of Science and Google Scholar, for publications on DM detected in patients who had ^(18)FDG-PET/CT scans as part of the staging for early stages of breast cancer(stage Ⅰ?and Ⅱ), prior to or immediately following surgery. Reports published between 2011 and 2017 were considered. The systematic review was conducted according to the PRISMA guidelines.RESULTS Among the 18 total studies included in the analysis, the risk of DM ranged from 0% to 8.3% and 0% to 12.9% for stage Ⅰ?and Ⅱ invasive breast cancer, respectively. Among the patients with clinical stage Ⅱ, the rate of occult metastases diagnosed by ^(18)FDG-PET/CT was 7.2%(range, 0%-19.6%) for stage ⅡA and 15.8%(range, 0%-40.8%) for stage ⅡB. In young patients(< 40-yearold), ^(18)FDG-PET/CT demonstrated a higher prevalence of DM at the time of diagnosis for those with aggressive histology(i.e., triple-negative receptors and poorly differentiated grade).CONCLUSION Young patients with poorly differentiated tumors and stage ⅡB triple-negative breast cancer may benefit from ^(18)FDG-PET/CT at initial staging to detect occult DM prior to surgery.

Enhanced photon emission by field emission resonances and local surface plasmon in tunneling junction

We investigated the photon emission spectra on Ag(111)surface excited by tunneling electrons using a low temperature scanning tunneling microscope in ultrahigh vacuum.Characteristic plasmon modes were illustrated as a function of the bias voltage.The one electron excitation process was revealed by the linear relationship between the luminescence intensity and the tunneling current.Luminescence enhancement is observed in the tunneling regime for the relatively high bias voltages,as well as at the field emission resonance with bias voltage increased up to 9 V.Presence of a silver(Ag)nanoparticle in the tunneling junction results in an abnormally strong photon emission at the high field emission resonances,which is explained by the further enhancement due to coupling between the localized surface plasmon and the vacuum.The results are of potential value for applications where ultimate enhancement of photon emission is desired.

Secondary electron emission yield from vertical graphene nanosheets by helicon plasma deposition

The secondary electron emission yields of materials depend on the geometries of their surface structures.In this paper,a method of depositing vertical graphene nanosheet(VGN)on the surface of the material is proposed,and the secondary electron emission(SEE)characteristics for the VGN structure are studied.The COMSOL simulation and the scanning electron microscope(SEM)image analysis are carried out to study the secondary electron yield(SEY).The effect of aspect ratio and packing density of VGN on SEY under normal incident condition are studied.The results show that the VGN structure has a good effect on suppressing SEE.

Nonlinear Change in Refractive Index and Transmission Coefficient of ZnSe:Fe²⁺at Long-Pulse 2.94-μm Excitation

An experimental study of the nonlinear changes in refractive index and transmission coefficient of single-crystal ZnSe:Fe2+, fabricated through the Fe-diffusion method, at long-pulse (~300 ns), sub-mJ, 2.94-mm Z-scan probing is reported. As well, a theoretical model based on the generalized Avizonis-Grotbeck equations is developed and applied for straightforward fitting of the open- and closed-aperture Z-scans, obtained for ZnSe:Fe2+ with different Fe2+ centers concentrations. The modeling results reveal that the contributions in the absorption and refractive index nonlinearities of ZnSe:Fe2+ are “common” resonant-absorption saturation (the minor part) and pulse-induced heating of the samples (the major part), which are strongly dependent on Fe2+ concentrations. Large values of the index change (>~10-3) and partial resonant-absorption bleaching (limited by ~50%), both produced via the thermal effect mainly, are the features of the ZnSe:Fe2+ samples inherent to this type of excitation.

中国实现碳中和:降碳风险的识别与应对

中国实现碳中和目标必将引发能源利用模式的深度变革,重塑各领域生产生活方式既是一场系统性变革,也面临微观与宏观的转型风险。从系统视角阐释中国零碳转型过程中降碳风险及其风险的系统传导机制,并基于低碳/零碳/负碳技术创新及转化的“研发—应用—推广”的阶段过程,解析了零碳转型过程中风险因素的传导路径;指出技术成熟度、产品绿色溢价、资产沉没成本、技术应用及供应链保障五类主要降碳风险,评估其对中国碳中和目标实现和社会经济发展的影响。提出中国需从系统视角慎重把握目标实现过程中的降碳风险,从政策引领、监测核算、科技人才、创新环境、国际合作等多方面共同发力和协同推进,全局把控设计应对政策措施,应深入实施低碳技术领跑者政策、加强碳排放核算与碳减排风险评估、积极培育壮大低碳技术研发力量、营造有利于低碳创新的社会环境。

基于孢粉学及花瓣微观形态学的玫瑰花品种的鉴定

目的对6种玫瑰花花粉粒、花瓣进行显微特征观察,以期为玫瑰花显微鉴定与品种划分提供参考。方法通过使用光学显微镜及扫描电子显微镜对6种玫瑰花的花粉粒和花瓣形貌进行观察,并对花粉粒的9个孢粉学特征指标进行量化分析。结果6种玫瑰花的花粉粒类型均为等级单粒的N_(3)P_(4)C_(5)型,均具沿极轴方向向两极延伸的条状纹饰。其孢粉学数据结果显示:内孔宽度(We)变异系数过大,不能作为鉴别依据;其它指标包括极轴长(P)、赤道轴长(E)、P/E值、外孔长度(Le)、花粉壁沿极轴长度(Exp)、花粉壁沿赤道轴长度(Exe)、花粉壁沿极轴相对厚度(Exe/P)以及花粉壁沿赤道轴相对厚度(Exe/E)差异明显,可综合应用对6种玫瑰花进行品种鉴定。6种玫瑰花花瓣近轴面乳突结构及远轴面条纹形成的盘状结构差异较大,可作为6个品种的鉴别依据。结论从微观角度对6种玫瑰花花瓣微形貌、花粉粒特征及孢粉学研究,为不同品种玫瑰花的鉴别提供了参考依据。