MoS_(2)/Si tunnel diodes based on comprehensive transfer technique

Due to the pristine interface of the 2D/3D face-tunneling heterostructure with an ultra-sharp doping profile, the 2D/3D tunneling field-effect transistor(TFET) is considered as one of the most promising low-power devices that can simultaneously obtain low off-state current(IOFF), high on-state current(ION) and steep subthreshold swing(SS). As a key element for the 2D/3D TFET, the intensive exploration of the tunnel diode based on the 2D/3D heterostructure is in urgent need.The transfer technique composed of the exfoliation and the release process is currently the most common approach to fabricating the 2D/3D heterostructures. However, the well-established transfer technique of the 2D materials is still unavailable.Only a small part of the irregular films can usually be obtained by mechanical exfoliation, while the choice of the chemical exfoliation may lead to the contamination of the 2D material films by the ions in the chemical etchants. Moreover, the deformation of the 2D material in the transfer process due to its soft nature also leads to the nonuniformity of the transferred film,which is one of the main reasons for the presence of the wrinkles and the stacks in the transferred film. Thus, the large-scale fabrication of the high-quality 2D/3D tunnel diodes is limited. In this article, a comprehensive transfer technique that can mend up the shortages mentioned above with the aid of the water and the thermal release tape(TRT) is proposed. Based on the method we proposed, the MoS_(2)/Si tunnel diode is experimentally demonstrated and the transferred monolayer MoS_(2) film with the relatively high crystal quality is confirmed by atomic force microscopy(AFM), scanning electron microscopy(SEM), and Raman characterizations. Besides, the prominent negative differential resistance(NDR) effect is observed at room temperature, which verifies the relatively high quality of the MoS_(2)/Si heterojunction. The bilayer MoS_(2)/Si tunnel diode is also experimentally fabricated by repeating the transfer process we proposed, followed by the specific analysis of the electrical characteristics. This study shows the advantages of the transfer technique we proposed and indicates the great application foreground of the fabricated 2D/3D heterostructure for ultralow-power tunneling devices.

Consensus on the digestive endoscopic tunnel technique

With the digestive endoscopic tunnel technique(DETT), many diseases that previously would have been treated by surgery are now endoscopically curable by establishing a submucosal tunnel between the mucosa and muscularis propria(MP). Through the tunnel, endoscopic diagnosis or treatment is performed for lesions in the mucosa, in the MP, and even outside the gastrointestinal(GI) tract.At present, the tunnel technique application range covers the following:(1)Treatment of lesions originating from the mucosal layer, e.g., endoscopic submucosal tunnel dissection for oesophageal large or circular early-stage cancer or precancerosis;(2) treatment of lesions from the MP layer, per-oral endoscopic myotomy, submucosal tunnelling endoscopic resection, etc.; and(3) diagnosis and treatment of lesions outside the GI tract, such as resection of lymph nodes and benign tumour excision in the mediastinum or abdominal cavity. With the increasing number of DETTs performed worldwide, endoscopic tunnel therapeutics, which is based on DETT, has been gradually developed and optimized. However, there is not yet an expert consensus on DETT to regulate its indications, contraindications, surgical procedure, and postoperative treatment.The International DETT Alliance signed up this consensus to standardize the procedures of DETT. In this consensus, we describe the definition, mechanism,and significance of DETT, prevention of infection and concepts of DETTassociated complications, methods to establish a submucosal tunnel, and application of DETT for lesions in the mucosa, in the MP and outside the GI tract(indications and contraindications, procedures, pre-and postoperative treatments, effectiveness, complications and treatments, and a comparison between DETT and other operations).

Upper bound solution for supporting pressure acting on shallow tunnel based on modified tangential technique

Based on the nonlinear failure criterion and the upper bound theorem, the modified tangential technique method was proposed to derive the expression of supporting pressure acting on shallow tunnel. Instead of the same stress state, different normal stresses on element boundaries were used. In order to investigate the influence of different factors on supporting pressures, the failure mechanism was established. The solution of supporting pressure, with different parameters, was obtained by optimization theory. The corresponding failure mechanism and numerical results were presented. In comparison with the results using the single tangential technique method, it is found that the proposed method is effective, and the good agreement shows that the present solution of supporting pressure is reliable.

Upper bound solutions of stability factor of shallow tunnels in saturated soil based on strength reduction technique

Based on the upper bound theorem of limit analysis,the factor of safety for shallow tunnel in saturated soil is calculated in conjunction with the strength reduction technique.To analyze the influence of the pore pressure on the factor of safety for shallow tunnel,the power of pore pressure is regarded as a power of external force in the energy calculation.Using the rigid multiple-block failure mechanism,the objective function for the factor of safety is constructed and the optimal solutions are derived by employing the sequential quadratic programming.According to the results of optimization calculation,the factor of safety of shallow tunnel for different pore pressure coefficients and variational groundwater tables are obtained.The parameter analysis shows that the pore pressure coefficient and the location of the groundwater table have significant influence on the factor of safety for shallow tunnel.

SURFACE OIL FLOW TECHNIQUE AND LIQUID CRYSTAL THERMOGRAPHY FOR FLOW VISUALIZATION IN IMPULSE WIND TUNNELS

This paper describes flow visualization techniques employing surface oil flow and liquid crystal thermography suitable for use in impulse wind tunnels.High spatial resolution photographs of oil flow patterns and liquid crystal thermograms have been obtained within test times ranging from 7 to 500 ms and have been shown to be very useful for revealing the detailed features of 3-D separated flow.The results from oil flow patterns,liquid crystal thermograms,schlieren photographs and heat flux measurements are shown to be in good agreement.

Tunneling Barrier Thickness Dependence of Spin Polarization of Ferromagnet in Magnetic Tunnel Junctions

For designing low-impedance magnetic tunnel junctions(MTJs),it has been found that tunneling magnetoresistance strongly correlates with the insulating barrier thickness,imposing a fundamental problem about the relationship between spin polarization of ferromagnet and the insulating barrier thickness in MTJs.Here,we investigate the influence of alumina barrier thickness on tunneling spin polarization(TSP)through a combination of theoretical calculations and experimental verification.Our simulating results reveal a significant impact of barrier thickness on TSP,exhibiting an oscillating decay of TSP with the barrier layer thinning.Experimental verification is realized on FeNi/AlO_(x)/Al superconducting tunnel junctions to directly probe the spin polarization of FeNi ferromagnet using Zeeman-split tunneling spectroscopy technique.These findings provide valuable insights for designs of high-performance spintronic devices,particularly in applications such as magnetic random access memories,where precise control over the insulating barrier layer is crucial.

Mechanical properties of steel mesh in anchor-mesh support for rocky tunnels

Underground geotechnical engineering encounters persistent challenges in ensuring the stability and safety of surrounding rock structures, particularly within rocky tunnels. Rock reinforcement techniques, including the use of steel mesh, are critical to achieving this goal. However, there exists a knowledge gap regarding the comprehensive understanding of the mechanical behavior and failure mechanisms exhibited by steel mesh under diverse loading conditions. This study thoroughly explored the steel mesh's performance throughout the entire loading-failure process, innovating with detailed analysis and modeling techniques. By integrating advanced numerical modeling with laboratory experiments, the study examines the influence of varying reinforcement levels and geometric parameters on the steel mesh strength and deformation characteristics. Sensitivity analysis, employing gray correlation theory, identifies the key factors affecting the mesh performance, while a BP (Backpropagation) neural network model predicts maximum vertical deformation with high accuracy. The findings underscore the critical role of steel diameter and mesh spacing in optimizing peak load capacity, displacement, and energy absorption, offering practical guidelines for design improvements. The use of a Bayesian Regularization (BR) algorithm further enhances the predictive accuracy compared to traditional methods. This research provides new insights into optimizing steel mesh design for underground applications, offering an innovative approach to enhancing structural safety in geotechnical projects.

Lateral femoral tunnel preparation and graft fixation for anterior cruciate ligament reconstruction–A discussion

This article provides a discussion and commentary around the recent advances in arthroscopic anterior cruciate ligament reconstruction(ACLR),with a focus on the aspects of lateral femoral tunnel preparation and graft fixation techniques.The paper explores and comments on a recently published review by Dai et al,titled"Research progress on preparation of lateral femoral tunnel and graft fixation in ACLR",while providing insight into its relevance within the field of ACLR,and recommendations for future research.

Application of several optimization techniques for estimating TBM advance rate in granitic rocks

This study aims to develop several optimization techniques for predicting advance rate of tunnel boring machine(TBM)in different weathered zones of granite.For this purpose,extensive field and laboratory studies have been conducted along the 12,649 m of the Pahang-Selangor raw water transfer tunnel in Malaysia.Rock properties consisting of uniaxial compressive strength(UCS),Brazilian tensile strength(BTS),rock mass rating(RMR),rock quality designation(RQD),quartz content(q)and weathered zone as well as machine specifications including thrust force and revolution per minute(RPM)were measured to establish comprehensive datasets for optimization.Accordingly,to estimate the advance rate of TBM,two new hybrid optimization techniques,i.e.an artificial neural network(ANN)combined with both imperialist competitive algorithm(ICA)and particle swarm optimization(PSO),were developed for mechanical tunneling in granitic rocks.Further,the new hybrid optimization techniques were compared and the best one was chosen among them to be used for practice.To evaluate the accuracy of the proposed models for both testing and training datasets,various statistical indices including coefficient of determination(R^2),root mean square error(RMSE)and variance account for(VAF)were utilized herein.The values of R^2,RMSE,and VAF ranged in 0.939-0.961,0.022-0.036,and 93.899-96.145,respectively,with the PSO-ANN hybrid technique demonstrating the best performance.It is concluded that both the optimization techniques,i.e.PSO-ANN and ICA-ANN,could be utilized for predicting the advance rate of TBMs;however,the PSO-ANN technique is superior.

Real-time prediction of rock mass classification based on TBM operation big data and stacking technique of ensemble learning

Real-time prediction of the rock mass class in front of the tunnel face is essential for the adaptive adjustment of tunnel boring machines(TBMs).During the TBM tunnelling process,a large number of operation data are generated,reflecting the interaction between the TBM system and surrounding rock,and these data can be used to evaluate the rock mass quality.This study proposed a stacking ensemble classifier for the real-time prediction of the rock mass classification using TBM operation data.Based on the Songhua River water conveyance project,a total of 7538 TBM tunnelling cycles and the corresponding rock mass classes are obtained after data preprocessing.Then,through the tree-based feature selection method,10 key TBM operation parameters are selected,and the mean values of the 10 selected features in the stable phase after removing outliers are calculated as the inputs of classifiers.The preprocessed data are randomly divided into the training set(90%)and test set(10%)using simple random sampling.Besides stacking ensemble classifier,seven individual classifiers are established as the comparison.These classifiers include support vector machine(SVM),k-nearest neighbors(KNN),random forest(RF),gradient boosting decision tree(GBDT),decision tree(DT),logistic regression(LR)and multilayer perceptron(MLP),where the hyper-parameters of each classifier are optimised using the grid search method.The prediction results show that the stacking ensemble classifier has a better performance than individual classifiers,and it shows a more powerful learning and generalisation ability for small and imbalanced samples.Additionally,a relative balance training set is obtained by the synthetic minority oversampling technique(SMOTE),and the influence of sample imbalance on the prediction performance is discussed.

Soft ground tunnel lithology classification using clustering-guided light gradient boosting machine

During tunnel boring machine(TBM)excavation,lithology identification is an important issue to understand tunnelling performance and avoid time-consuming excavation.However,site investigation generally lacks ground samples and the information is subjective,heterogeneous,and imbalanced due to mixed ground conditions.In this study,an unsupervised(K-means)and synthetic minority oversampling technique(SMOTE)-guided light-gradient boosting machine(LightGBM)classifier is proposed to identify the soft ground tunnel classification and determine the imbalanced issue of tunnelling data.During the tunnel excavation,an earth pressure balance(EPB)TBM recorded 18 different operational parameters along with the three main tunnel lithologies.The proposed model is applied using Python low-code PyCaret library.Next,four decision tree-based classifiers were obtained in a short time period with automatic hyperparameter tuning to determine the best model for clustering-guided SMOTE application.In addition,the Shapley additive explanation(SHAP)was implemented to avoid the model black box problem.The proposed model was evaluated using different metrics such as accuracy,F1 score,precision,recall,and receiver operating characteristics(ROC)curve to obtain a reasonable outcome for the minority class.It shows that the proposed model can provide significant tunnel lithology identification based on the operational parameters of EPB-TBM.The proposed method can be applied to heterogeneous tunnel formations with several TBM operational parameters to describe the tunnel lithologies for efficient tunnelling.

改良膜龈手术在牙龈退缩治疗中的应用

随着人们对美观需求的日益提升,治疗牙龈退缩已经成为牙周科临床常见的患者诉求。临床上主要通过手术的方式治疗牙龈退缩,常见的手术包括游离龈移植术、带蒂瓣技术和双层瓣技术,适应证选择恰当时,通常可以获得满意的效果,但上述术式仍存在一定的不足,如根面覆盖效果不理想等。近年来,学者们针对这些不足陆续提出了一些改良方案来治疗不同程度的牙龈退缩,如改良游离龈移植术,即包含龈乳头及游离龈的牙龈单元移植,可改善受体区血供,提高根面覆盖效果,其针对轻度退缩的部位可获得良好的根面覆盖,同时可增宽角化龈和加深前庭沟,但应用于上颌美学区时可能存在术后牙龈颜色、形态不协调,美学效果欠佳的问题。牙龈瓣采用半厚-全厚-半厚的技术进行制备的改良冠向复位瓣,用于多颗牙牙龈退缩时,以退缩最严重牙为中心的改良切口设计的冠向复位信封瓣技术,可提高根面覆盖效果。不离断龈乳头,使龈瓣形成隧道,以容纳移植物的隧道技术及各种改良的隧道技术,可以有效减少术区的组织损伤,并促进创面愈合。本文通过对各类术式的阐述和文献回顾,总结改良膜龈手术治疗牙龈退缩的临床应用及注意事项,并提出牙龈退缩的治疗方案建议,同时强调牙龈退缩的对因治疗,以达到稳定的根面覆盖效果。创伤小、疗效稳定的手术方式和治疗方法是今后膜龈手术的发展方向。

高速铁路泥岩隧道仰拱底鼓控制技术研究

研究目的:为分析基底围岩劣化作用下泥岩隧道仰拱底鼓变形的控制效果,运用数值模拟的研究方法,建立高速铁路泥岩隧道有限元模型,考虑隧道开挖条件下模拟基底围岩吸湿膨胀和软化作用,选用底板与锁脚锚杆加固的控制技术,对比分析加固前后隧周围岩的竖向位移、填充层及仰拱的变形特性。研究结论:(1)锚杆加固基底可有效控制隧底围岩隆起,对隧底隆起的控制效果膨胀阶段优于软化阶段;(2)锚杆加固前后仰拱、填充层的底鼓位移曲线均呈“钟形”对称分布;(3)仰拱、填充层中心位置处的底鼓变形最大;(4)本研究结果可为高速铁路泥岩隧道仰拱底鼓病害防治与加固提供参考依据。

不同埋深下类矩形与圆形隧道施工诱发土体变形透明土试验对比研究

类矩形隧道因其内部空间优势在工程中逐步得到推广,但其施工引发周边土层变化规律与常规圆形隧道的差异尚缺乏深入研究,且该差异与隧道埋深紧密相关.为此自主设计组装了类矩形与圆形隧道开挖装置,以透明土模拟周边土层,并采用粒子图像测速(PIV)技术精准测定土层变形,对不同埋深下等面积类矩形与圆形隧道动态开挖过程中诱发上覆土体变化规律进行了深入分析.试验对比结果表明,两类隧道引发上覆土层变形的滑裂面基本一致,大致符合太沙基理论的竖直滑动面假定,滑裂角θ约等于45°+φ/2;不同埋深情况下,圆形隧道上覆土层竖向变形始终保持“V”型的正态分布,即存在最大值,而类矩形隧道随着地层深度的增加,上覆土层变形由“V”型转变为“W”型,即存在多个沉降最值,表明该类隧道比圆形隧道地层变形更为均匀,且在相同埋深情况下类矩形隧道开挖引发的地表沉降最大沉降值小于圆形隧道,该现象在浅埋状态下尤为明显,二者差异随着埋深增大逐渐缩小,该结论可为施工方案设计选择提供参考.

极端环境隧道建造面临的主要问题及发展趋势

聚焦艰险山区、深水海域与城市敏感区3类极端环境,全面梳理和总结了在此环境下隧道建造面临的主要问题、相关技术突破和未来发展趋势。针对艰险山区中极高地应力、高地温、高海拔以及活动断裂带等极端条件,总结分析围岩和隧道的变形机制、破坏机制及防护措施,并指出未来可通过大数据、机器学习等手段建立更精准的预测模型,以实现隧道建造过程的实时监控和风险评估;针对深水海域中高水压、高烈度地震、强侵蚀环境等极端条件,分析多因素耦合下沉管法及盾构法隧道管片及接头的劣损和破坏机制,总结提升其力学和耐久性能的主要技术措施,并提出未来仍需针对海底隧道管片接头的防水、抗震及抗侵蚀性能开展更深入的研究,以形成完整的理论和技术体系;针对城市敏感区隧道穿越既有隧道、敏感建构筑物、地下障碍物等挑战,总结分析盾构法和顶管法施工环境响应规律、地层变形评估方法和控制技术措施,提出未来可采用机器学习等技术辅助隧道建设,以提升预测和控制的准确性,减小建设过程对城市环境的扰动。目前,相关研究成果为极端环境下的隧道工程建设提供了重要支撑,但部分技术仍需进一步在实践中完善并形成规范,以指导后续的工程建设;而随着新一代信息技术的发展,未来隧道建造必将朝着数字化、智能化、自动化的方向发展,从而保障极端环境下隧道建设的安全、绿色、高效。

关节镜下“三缝线–三叉星”技术固定前交叉韧带下止点撕脱骨折

目的:探讨关节镜下“三缝线–三叉星”技术治疗前交叉韧带下止点撕脱骨折的临床疗效。方法:回顾性分析2019年1月至2022年1月期间,46例接受关节镜下“三缝线–三叉星”技术治疗的前交叉韧带(ACL)下止点撕脱骨折治疗患者的病例资料,包括术前和术后的体格检查(稳定性和活动度)、国际膝关节文献委员会(IKDC)评分、Tegner活动等级评分、疼痛视觉模拟评分(VAS)、术后满意度、并发症情况以及重返运动时间等。将术后6个月、术后12个月的样本数据分别与术前的样本数据进行比较。结果:46例患者中男性26例,女性20例,平均年龄37.6±10.3岁,平均随访时间为14.4±2.7个月。术前与术后6个月、12个月的IKDC评分分别为59.7±5.4、86.1±5.7、89.5±5.0(P<0.001);Lysholm评分分别为56.7±5.0、84.8±4.4、90.6±4.2(P<0.001);Tegner评分分别为0.5±0.3、4.6±1.7、6.6±2.1(P<0.001);VAS评分分别为7.1±1.1、1.7±1.0、0.7±0.8(P<0.001)。术后满意度评为优秀42例、良好3例、一般1例,优良率达97.8%。术后6个月、12个月随访时,体格检查的前抽屉试验、Lachman试验结果均为阴性;重返运动平均时间为8.3±2.5个月。所有患者撕脱骨折均一期愈合,未发生感染、关节僵硬、骨折块松动移位及畸形愈合等术后并发症,均无需二次手术。结论:关节镜下“三缝线–三叉星”技术对前交叉韧带下止点撕脱骨折患者具有显著的临床疗效,能有效恢复术后关节的稳定性和功能。

岩石隧道掘进机不良地质施工处置技术

岩石隧道掘进机(Tunnel Boring Machine,TBM)凭借其高效优质、作业安全等特点在铁路、公路、地铁、水利水电等领域广泛应用,在普通地质环境下推广顺利。复杂地质环境下致灾源多,如硬岩岩爆、软岩大变形、断层破碎带、涌水突泥等不良地质使TBM施工频繁出现围岩坍塌、支护失效、卡机淹井、设备损伤等问题。本文结合工程案例,从超前主动加固、注浆及锚固、管片支护、撑靴加固4个方面总结现有施工技术,以应对TBM穿越不良地质导致的刀盘卡机、护盾抱死、初期支护变形过大、撑靴打滑等问题,提升TBM在不良地质环境下的适应能力,为类似工程提供参考。

大尺寸自由活塞激波风洞自由流参数诊断方法

高焓激波风洞自由流具有一定程度的热化学非平衡,使得流场参数的确定存在困难。针对大尺寸自由活塞高焓激波风洞的总温2 700~4 700 K、总压5.6~20.3 MPa条件,采用非接触吸收光谱技术、接触测量技术等测试技术,结合多温度多组分数值模拟方法,共同诊断喷管名义马赫数10出口自由流的参数。结果显示,温度测量值与计算值最大偏差小于7.5%,速度测量值与计算值最大偏差小于5%,NO浓度测量值与计算中最大偏差小于12%。

经跟骨骨隧道线扣技术对跟腱止点或近止点断裂患者手术效果和术后炎症及应激反应的影响

目的 探讨经跟骨骨隧道线扣技术对跟腱止点或近止点断裂患者手术效果和术后炎症及应激反应的影响。方法 采用回顾性病例对照研究方法,收集2012年6月至2022年10月于衡水市第四人民医院接受手术治疗的106例跟腱止点或近止点断裂患者的病例资料,根据手术方案的不同分为锚钉组和线扣组,锚钉组(53例)采取带线锚钉技术治疗,线扣组(53例)接受经跟骨骨隧道线扣技术治疗。比较两组的术中出血量、手术时间、住院时间、住院费用和跟腱愈合时间,术前和术后12个月踝关节活动度和跟腱完全断裂评分系统(Achilles tendon rupture scoring system, ATRS)、美国足与踝关节协会(American Foot and Ankle Association, AOFAS)踝-后足评分系统评分,术前和术后1 d血清炎症及应激指标[白细胞介素(IL)-1β、去甲肾上腺素(NE)等]水平。统计两组术后并发症情况。结果 所有患者均顺利完成手术并获得随访,随访时间12~23个月,平均(16.62±2.79)个月。线扣组的术中出血量、住院时间、住院费用、跟腱愈合时间均明显少于锚钉组,手术时间明显长于锚钉组,差异有统计学意义(P<0.05)。术后12个月,两组踝关节背屈、跖屈角度及ATRS、AOFAS踝-后足评分系统评分均显著优于术前(P<0.05)。其中,两组踝关节背屈、跖屈角度及ATRS评分组间同期比较差异无统计学意义(P>0.05);术后12个月,线扣组AOFAS踝-后足评分系统评分显著高于锚钉组(P<0.05)。两组术后1 d血清IL-1β、IL-6、NE、血管紧张素Ⅱ(AngⅡ)水平均显著高于术前(P<0.05),但线扣组术后1 d血清IL-1β、IL-6、NE、AngⅡ水平均显著低于同期锚钉组(P<0.05)。术后仅锚钉组出现了2例切口红肿,经伤口换药及延迟拆线,切口均为Ⅰ期愈合。随访12个月内,所有患者均未出现跟腱再次断裂、腓肠神经损伤、切口周围皮肤坏死等其他并发症。结论 跟腱止点或近止点断裂患者采用经跟骨骨隧道线扣技术治疗能明显减轻患者术后机体炎症及应激反应,利于术后康复;与带线锚钉技术相比,该线扣技术具有创伤小、住院费用少等优势,同时还能达到更好的治疗效果。

盾构隧道长联络通道冻结法施工技术与应用

本文以郑州市轨道交通8号线五龙口站—同乐站区间隧道3#联络通道冻结工程为背景,详细总结了长距离联络通道施工关键技术,包括冻结加固方案、冻结施工技术要点、施工风险及应对措施等,并通过现场施工情况及实测数据进行了验证。针对长距离联络通道的冻结施工,采用双侧搭接布置冻结管、实时压力监测并打设泄压孔、解冻期及时跟进补浆、必要情况下施作钢拱架等措施,可以有效降低长距离联络通道冻结施工中的风险。在本工程冻结施工期间,实测地表冻胀位移及管片竖向隆起位移均小于6mm,解冻后融沉量小于10mm,联络通道初期支护竖向位移小于2.1mm,验证了本工程施工技术的可靠性,可以为类似的长联络通道冻结开挖工程提供参考。