Passively mode-locked 2-μm Tm:YAP laser with a double-wall carbon nanotube absorber

We report on a diode-pumped passively continuous wave （cw） mode-locked Tm：YAP laser with a double-wall carbon nanotube （DWCNT） absorber operating at a wavelength of 2023 nm for the first time, to the best our knowledge. The DWCNT absorber is fabricated on a hydrophilic quartz substrate by using the vertical evaporation technique. The output power is as high as 375 mW. A stable pulse train with a repetition rate of 72.26 MHz is generated with a highest single pulse energy of 5.2 μJ.

Experimental Study and Numerical Simulation of Hypervelocity Projectile Impact on Double-Wall Structure

Tests of hypervelocity projectile impact on double-wall structure were performed with the front wall ranging from 0.5 mm to 2.0 mm thick and different impact velocities. Smooth particle hydrodynamics (SPH) code in LS-DYNA was employed for the simulation of hypervelocity impact on the double-wall structure. By using elementary shock wave theory, the experimental results above are analyzed. The analysis can provide an explanation for the penetration mechanism of hypervelocity projectile impact on double-wall structure about the effect of front wall thickness and impact velocity..

A Continuum Shell Model Including van derWaals Interaction for Free Vibrations of Double-Walled Carbon Nanotubes

This paper proposes the free vibration analysis of Double-Walled Carbon NanoTubes(DWCNTs).A continuum elastic three-dimensional shell model is used for natural frequency investigation of simply supported DWCNTs.The 3D shell method is compared with beam analyses to show the applicability limits of 1D beam models.The effect of van der Waals interaction between the two cylinders is shown for different Carbon NanoTube(CNT)lengths and vibration modes.Results give the van der Waals interaction effect in terms of frequency values.In order to apply the 3D shell continuum model,DWCNTs are defined as two concentric isotropic cylinders(with an equivalent thickness and Young modulus)which can be linked by means of the interlaminar continuity conditions or by means of an infinitesimal fictitious layer which represents the van der Waals interaction.

Consecutive hybrid mechanism boosting Na+storage performance of dual-confined SnSe2 in N,Se-doping double-walled hollow carbon spheres

Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.

EFFECTS OF SPECTRAL DEPENDENCE IN PASS-THROUGH PHOTON-BASED BIOMEDICAL TRANSILLUMINATION

We have proposed an interferometric setup for biomedical analysis in transillumination modality.Wavelength dependence of optical properties must be considered for selecting source and sample.An expansion of the sample optical properties,around the central wavelength of emission,serves to account for spectral effects.Expected spectral values depend on the central moments of the source,and specific constants associated to the optical properties of the sample.By matching wavelength characteristics of source and sample,a first-order approximation is applicable.In such case,the expected values are exactly the optical properties evaluated at the central wavelength.Furthermore,in the first-order approximation,the transillumination interferometer yields the integrated attenuation of the sample at the central wavelength of emission.We verify the latter assertion by performing a wavelength-dependent Monte Carlo analysis to calculate the response of the transillumination interferometer.Recovered attenuation coefficients,for imaging and characterization scenarios,are in agreement with the value computed at the central wavelength of the source.

Properties of the incandescent light emitted from double-walled carbon nanotube filament

We have studied the radiation of a double-walled carbon nanotube （DWNT） filament with a length of 4.5 mm and a diameter of 10μm by applying an electric current through the filament. The DWNT filament starts emitting incandescent light at voltage U =6V. Emission spectra of the DWNT below temperature 1250K can well be fitted to those of the blackbody radiation. The intensity of the incandescent light shows an exponential dependence on the voltage applied on the DWNT filaments. The resistance of the DWNT filaments is very stable at high temperatures between 900 and 1250 K during the emission of light in the experiments.

Reasons and countermeasures for “marking problem” during the production of double-walled copper-brazed steel tubes

This study explores the reasons underlying the frequent appearance of ＂marking problem＂ during the production of double-walled copper-brazed steel tubes. To this end, we compared two types of copper-coated steel strips, of which one has almost no problem during production, whereas the other has higher number of incidences of ＂marking problem＂. We analyzed the chemical composition,mechanical properties,the cross-sectional metallographs, and surface quality of the trimmed edge in both types of specimen. After the roll forming process, the bonding condition between the steel layers of the tubes before and after brazing process has also been examined. Results indicate that the chemical composition and mechanical properties of the two kinds of strips are similar; however, the edge quality of the trimmed strips is significantly different. It is believed that the irregular shape of the edge portions in the strips will be more pronounced during the bevel treatment. Consequently, smooth and tight seams cannot be guaranteed by such uneven beveled edges,which lead to higher number of incidences of ＂marking problem＂ during production.

Experimental Investigation on Space-dispersed Double-wall Jet Combustion System for DI Diesel Engine

A space-dispersed double-wall jet combustion system was developed by adopting the wall-guiding spray method and the stratification theory.The experimental test was carried out to optimize the structural parameters of the diesel-engine combustion system,including chamber structure,swirl ratio of cylinder head,included angle of jet orifice,number and diameter of jet orifice,fuel injection pressure and timing.The effect of double-wall jet combustion system on combustion and engine performance was tested to obtain the best performance indexes,and the double-wall jet combustion system was compared to the prototype.The results show that NOx is reduced from 712 PPm to 487 PPm at 2 100 r/min,and from 593 PPm to 369 PPm at 3 000 r/min,which are reduced by 31.6% and 37.7%,respectively.The smoke intensity was reduced form 3.67 BSU to 2.1 BSU,and the oil consumption was reduced from 240.5 g/(kW·h) to 225.4 g/(kW·h),which was decreased by 6.3% at low speed.The pressure in the cylinder was obviously reduced from 115 bar to 108 bar,which was reduced by 6%.

Pullout Behavior of Large-diameter Collapsed Double-walled Carbon Nanotubes

The pullout behavior of large-diameter collapsed double-walled carbon nanotubes（DWCNT） was studied by molecular dynamics simulations and compared with those in the circular cross-sectioned state. The pullout force-displacement curves of both are in good agreement with the same mean value of the pullout force during the steady pullout stage. The pullout force was mainly due to the formation of new surfaces; the friction between nested walls was negligible. The effects of different chiral combinations and inter-wall spacings on the pullout behavior for both section situations were investigated. The commensurate（zigzag/zigzag or armchair/armchair） bi-tube systems have a larger fluctuation in the pullout force. The smaller interspacing implies lower mean pullout force with stronger fluctuations.

Critical Length of Double-Walled Carbon Nanotubes Based Oscillators

The critical lengths of an oscillator based on double-walled carbon nanotubes(DWCNTs)are studied by energy minimization and molecular dynamics simulation.Van der Waals(vdW)potential energy in DWCNTs is shown to be changed periodically with the lattice matching of the inner and outer tubes by using atomistic models with energy minimization method.If the coincidence length between the inner and outer tubes is long enough,the restoring force cannot drive the DWCNT to slide over the vdW potential barrier to assure the DWCNT acts as an oscillator.The critical coincidence lengths of the oscillators are predicted by a very simple equation and then confirmed with energy minimization method for both the zigzag/zigzag system and the armchair/armchair system.The critical length of the armchair/armchair system is much larger than that of the zigzag/zigzag system.The vdW potential energy fluctuation of the armchair/armchair system is weaker than that of the zigzag/zigzag system.So it is easier to slide over the barrier for the armchair/armchair system.The critical lengths of zigzag/zigzag DWCNTbased oscillator are found increasing along with temperature,by molecular dynamics simulations.

Enhanced performance of solution-processed carbon nanotube transparent electrodes in foldable perovskite solar cells through vertical separation of binders by using eco-friendly parylene substrate

The successful utilization of an eco-friendly and biocompatible parylene-C substrate for high-performance solution-processed double-walled carbon nanotube(CNT)electrode-based perovskite solar cells(PSCs)was demonstrated.Through the use of a novel inversion transfer technique,vertical separation of the binders from the CNTs was induced,rendering a stronger p-doping effect and thereby a higher conductivity of the CNTs.The resulting foldable devices exhibited a power conversion efficiency of 18.11%,which is the highest reported among CNT transparent electrode-based PSCs to date,and withstood more than 10,000 folding cycles at a radius of 0.5 mm,demonstrating unprecedented mechanical stability.Furthermore,solar modules were fabricated using entirely laser scribing processes to assess the potential of the solution-processable nanocarbon electrode.Notably,this is the only one to be processed entirely by the laser scribing process and to be biocompatible as well as eco-friendly among the previously reported nonindium tin oxide-based perovskite solar modules.

油气压力管道DR数字成像检测系统研发技术

应用油气压力管道DR数字成像检测系统研发技术,实现了大口径油气压力管道DR检测,提升了检测透照能力,提高了检验检测质量和工效,为油气压力管道的检验检测提供了技术支撑,推广应用前景广阔。

原发性开角型青光眼患者外路巩膜静脉窦精准定位方法

目的探讨原发性开角型青光眼(POAG)患者外路巩膜静脉窦精准定位方法。方法选取2020年8月至2021年10月于潍坊眼科医院就诊,确诊为POAG需行外路巩膜静脉窦相关手术治疗的患者40例(40眼)。根据术中测量方法不同将患者随机分为两组,每组各20例(20眼)患者。高清图像组患者采用显微镜截取高清图像后划线测量;无菌图纸组患者采用测绘圆规标记于无菌图纸后完成显微镜下测量。采用角巩膜分光照明法标记巩膜床半透明与不透明组织交界线并将其作为基线,内窥镜光纤前房内透照可于巩膜床清晰透见巩膜静脉窦返流血带,定位巩膜静脉窦后完整切除其外侧壁进行相关指标的长度测量。术前采用IOL-Master记录患者白到白距离(WTW)、眼轴长度(AL),术中测量患者巩膜静脉窦宽度(SW)、基线到巩膜静脉窦后缘距离(d1)、球结膜反折线到巩膜静脉窦前缘距离(d2)、基线到球结膜反折线距离(d3);分析各指标间差异及相关性。结果高清图像组患者d2[(1.85±0.28)mm]和d3[(2.63±0.30)mm]均高于无菌图纸组[分别为(1.61±0.37)mm和(2.41±0.38)mm],差异均有统计学意义(均为P<0.05)。高清图像组和无菌图纸组患者WTW、d1与AL均呈正相关关系(均为P<0.05),d1、d2与d3亦均呈正相关关系(均为P<0.05),其余指标间均无明显相关性(均为P>0.05)。将40眼按照AL不同划分为3组:AL<23 mm为短眼轴组,23 mm≤AL<25 mm为中眼轴组,AL≥25 mm为长眼轴组。短、中、长眼轴组患者d1分别为(0.30±0.08)mm、(0.37±0.10)mm、(0.57±0.09)mm,组间差异有统计学意义(F=14.915,P<0.05);长眼轴组患者d1较短、中眼轴组更长(均为P<0.05)。结论采用内透照法可于深层巩膜床上清晰透见巩膜静脉窦返流血带从而实现术中对巩膜静脉窦的精准定位;d1与POAG患者AL呈正相关关系。

Deformation characterization method of typical double-walled turbine blade structure during casting process

To address the complex structures,large out-of-tolerance issues,and inconsistent quality of double-walled turbine blades,a mapping relationship between the structure and deformation was established based on a structural correlation study.Numerical simulations and pouring experiments were carried out based on the designed double-walled model,and a reliable displacement field model of the double-walled blade was established.A decoupling method for the displacement field of the double-walled blade castings was proposed,which decoupled the displacement field into bending,torsion,and expansion/shrinkage deformation vectors.Based on the displacement field analysis of the theoretical and physical models,an expansion/shrinkage model of double-walled blade structure castings was established.Furthermore,an experiment to determine the mapping relationship between double-walled construction and deformation was designed,which included the characteristic distribution distance and designed angle as structural parameters.The functional relationship between the deformation and the structural parameters was established based on a nonlinear regression method.

Insight into deformation allocation in the multi-pass roll forming of a double-walled brazed tube

Deformation allocation is an important factor that affects 720°curling forming from copper-coated steel strips to double-walled brazed tubes(DWBTs).In this study,four schemes of deformation allocation,considering different weights of the total feed distance,are proposed,and a 3D finite element(FE)model of the multi-pass roll forming process for DWBT is developed and verified to investigate the cross-sectional evolution and deformation features.The results show the following.(i)In the 720°curling forming process from the steel strip into double-walled tubes,the curvature of the formed circular arc initially increases and then remains stable with roll forming,and the inner and outer tubes of the DWBT are formed in the third and fifth forming passes.Size forming can eliminate the gap between the double walls and improve the overall roundness.(ii)For different deformation allocations,the cross-sectional profiles of the roll-formed parts exhibit a discrepancy,and the deformation amount varies with the roll-forming process.The deformation amount in Scheme three is the maximum,and the cross-sectional profile deviates significantly from the ideal shape and fails to form a DWBT,which indicates that the deformation allocation is unsuitable.(iii)The roundness of the outer tube is better than that of the inner tube.Therefore,the roundness of the inner tube is the key to restricting the forming accuracy of the DWBT.Compared with Schemes one and two,Scheme four with a linear allocation of the total feed distance exhibits the best roundness,and the deformation allocation is reasonable;i.e.,when the contact points between the rollers and steel strip are in a straight line,the roundness of the DWBT is in good agreement with the ideal condition.

小梁切除术治疗色素性青光眼的中远期疗效

目的:观察小梁切除术治疗色素性青光眼的中远期临床效果。方法:回顾性分析2010-01/2022-09于云南大学附属医院行小梁切除术治疗的色素性青光眼患者38例51眼的临床资料。术后随访3~144mo,分析纳入患者的眼压、视力及屈光状态,记录并发症情况,评估手术疗效。结果:纳入患者术前平均使用降眼压药物种类2.90±0.12种,平均眼压18.89±7.40mmHg,术后3d, 1、3、6mo, 1a、末次随访时平均眼压分别为14.68±5.08、13.99±2.95、14.25±2.50、14.36±2.83、14.33±2.66、14.94±1.95mmHg,术后各时间点眼压均较术前明显降低(P<0.05),术后各时间点眼压均无明显差异(P>0.05)。随访期间,纳入患者视力基本保持稳定,均无眼内炎、恶性青光眼发生。末次随访时,手术完全成功率为90%,部分成功率为8%,失败率为2%。结论:小梁切除术治疗色素性青光眼可以解除反向瞳孔阻滞,有效控制眼压、稳定视力,是安全有效的治疗方法。

基于DDA检测技术的管道焊缝一次透照长度计算

以数字探测器阵列(DDA)检测技术为研究对象,对压力管道数字射线检测中的纵缝透照、环焊缝中心透照、环焊缝源在外双壁单影透照、环焊缝源在内单壁单影透照的一次透照长度进行了推导计算,为压力管道焊缝的DDA检测提供理论和实践依据。

乳腺疾病的近红外扫描诊断

透照法经加用计算机技术并发挥近红外光的特点以来,在诊断乳腺疾病方面更具科学性。我院用该方法检查乳腺疾病300例,均经病理证实,并与触诊和钼靶X线摄影行双盲对比分析。结果表明,近红外扫描诊断乳腺恶性肿瘤的阳性符合率为88％,明显高于X线的71％(P<0.05)。但对直径≤2cm的恶性肿瘤诊断符合率为60％,尚待提高。在不同病理类型的乳腺恶性肿瘤中,恶性度越低,近红外影像的恶性特征越不典型。假阳性和假阴性均占12％。著者建议,该方法有一定实用价值,可作为检诊乳腺疾病,尤其乳腺癌的常规手段之一。

不同微创方式治疗下肢静脉曲张的临床疗效比较

目的:比较不同微创手术方式治疗下肢静脉曲张的临床疗效,探讨其临床价值。方法:选择201例下肢静脉曲张患者,采用不同的治疗方式,其中腔内激光灼闭术(EVLA)组52例、透光旋切术(TIPP)组46例、EVLA联合腔镜下交通支离断术(SEPS)(EVLA+SEPS)组49例和TIPP+SEPS组54例。比较各组患者手术时间、术中出血量、术后住院费用、住院时间以及术后并发症(残留静脉曲张、皮下硬结、浅静脉炎、隐神经损伤、瘀斑、伤口血肿、皮肤麻木和下肢肿胀)的发生率。结果:各组患者手术时间、术中出血量及术后住院时间和住院费用比较差异均有统计学意义(P<0.05)。与EVLA组比较,TIPP组患者残留静脉曲张、浅静脉炎、下肢肿胀和瘀斑发生率降低(P<0.05);皮下硬结、伤口血肿、隐神经损伤和皮肤麻木发生率略高,但差异无统计学意义(P>0.05);与EVLA组和TIPP组比较,EVLA+SEPS组和TIPP+SEPS组残留静脉曲张和浅静脉炎发生率下降(P<0.05)。与EVLA组比较,TIPP组、EVLA+SEPS组和TIPP+SEPS组术后3个月愈合率明显升高(P<0.05);TIPP组、EVLA+SEPS组和TIPP+SEPS组术后1年复发率明显降低(P<0.05)。结论:EVLA联合SEPS和TIPP联合SEPS治疗下肢静脉曲张的疗效优于单独EVLA和TIPP治疗方法,具有安全可靠、曲张静脉切除彻底、溃疡愈合快及复发率低等优点。

无线电波透视法及其应用

无线电波透视法是利用无线电波在钻孔中的发射和接收来确定地下介质特性和地质构造的一种物探方法。当电磁波在地下有耗介质中传播时,遇到岩性不同的分界面就会产生不同的电磁波反射、折射、透射和频散、吸收等,通过研究接收到的电磁波的性质达到探测地下目标物的目的。本文简述了该方法的理论,描述了方法的分类,概述了目前使用的发射天线、接收天线和常用的仪器,总结了野外工作方法和解释方法,最后给出了应用实例说明其应用效果。