Identifying Counterexamples Without Variability in Software Product Line Model Checking

Product detection based on state abstraction technologies in the software product line(SPL)is more complex when compared to a single system.This variability constitutes a new complexity,and the counterexample may be valid for some products but spurious for others.In this paper,we found that spurious products are primarily due to the failure states,which correspond to the spurious counterexamples.The violated products correspond to the real counterexamples.Hence,identifying counterexamples is a critical problem in detecting violated products.In our approach,we obtain the violated products through the genuine counterexamples,which have no failure state,to avoid the tedious computation of identifying spurious products dealt with by the existing algorithm.This can be executed in parallel to improve the efficiency further.Experimental results showthat our approach performswell,varying with the growth of the system scale.By analyzing counterexamples in the abstract model,we observed that spurious products occur in the failure state.The approach helps in identifying whether a counterexample is spurious or genuine.The approach also helps to check whether a failure state exists in the counterexample.The performance evaluation shows that the proposed approach helps significantly in improving the efficiency of abstraction-based SPL model checking.

Binary Oriented Feature Selection for Valid Product Derivation in Software Product Line

Software Product Line(SPL)is a group of software-intensive systems that share common and variable resources for developing a particular system.The feature model is a tree-type structure used to manage SPL’s common and variable features with their different relations and problem of Crosstree Constraints(CTC).CTC problems exist in groups of common and variable features among the sub-tree of feature models more diverse in Internet of Things(IoT)devices because different Internet devices and protocols are communicated.Therefore,managing the CTC problem to achieve valid product configuration in IoT-based SPL is more complex,time-consuming,and hard.However,the CTC problem needs to be considered in previously proposed approaches such as Commonality VariabilityModeling of Features(COVAMOF)andGenarch+tool;therefore,invalid products are generated.This research has proposed a novel approach Binary Oriented Feature Selection Crosstree Constraints(BOFS-CTC),to find all possible valid products by selecting the features according to cardinality constraints and cross-tree constraint problems in the featuremodel of SPL.BOFS-CTC removes the invalid products at the early stage of feature selection for the product configuration.Furthermore,this research developed the BOFS-CTC algorithm and applied it to,IoT-based feature models.The findings of this research are that no relationship constraints and CTC violations occur and drive the valid feature product configurations for the application development by removing the invalid product configurations.The accuracy of BOFS-CTC is measured by the integration sampling technique,where different valid product configurations are compared with the product configurations derived by BOFS-CTC and found 100%correct.Using BOFS-CTC eliminates the testing cost and development effort of invalid SPL products.

Experimental,Numerical,and Analytical Studies on the Bending of Mechanically Lined Pipe

Mechanically lined pipe(MLP)is often used for offshore oil and gas transport because of its low cost and corrosion resistance.During installation and operation,the pipe may undergo severe bending deformation,which causes the liner to separate from the outer pipe and buckles,affecting the stability of the whole line.In this paper,the buckling response of MLP subjected to bending is investigated to clarify its bending characteristics by employing both experiments,numerical simulation,as theoretical methods.Two types of MLPs were manufactured with GB 45 carbon steel(SLP)and Al 6061(ALP)used as the outer pipe material,respectively.The hydraulic expansion and bending experiments of small-scale MLPs are conducted.In addition to the ovalized shape of the cross-section for the SLP specimens,the copper liner was found to wrinkle on the compressive side.In contrast,the liner of ALP remains intact without developing any wrinkling and collapse mode.In addition,a dedicated numerical framework and theoretical models were also established.It was found both the manufacturing and bending responses of the MLP can be well reproduced,and the predicted maximum moment and critical curvatures are in good agreement with the experimental results.

N^(6)-腺苷甲基化修饰及其对LINE-1的调控机制

长散布元件-1(long interspersed elements-1,LINE-1)是现今在人类基因组中唯一具有自主转座能力的转座子,其转座会引起细胞基因组结构和功能的改变,是导致多种严重疾病的重要因素。在转座过程中,LINE-1 mRNA是转座中间体的核心,宿主细胞对其进行相关修饰直接影响转座。N^(6)-腺苷甲基化修饰(m^(6)A)是真核细胞RNA上最丰富且动态可逆的表观遗传修饰。目前发现m^(6)A修饰也存在于LINE-1 mRNA上,参与LINE-1整个生命周期的调控,影响其转座和基因组中LINE-1相邻基因的表达,进而影响基因组稳定性、细胞自我更新与分化潜能,在人类发育和疾病中具有重要作用。本文介绍了LINE-1 m^(6)A修饰的位置、功能以及相关机制,并总结了LINE-1的m^(6)A修饰对其转座调控的研究进展,以期为相关疾病发生发展的机制研究和治疗提供新的思路。

低压低氧对肠黏膜屏障及LINE-1核酸内切酶变异体GCRG213表达的影响

背景长散在核元件-1(long interspersed nuclear element-1,LINE-1或L1)是目前基因组中唯一活跃的自主反转录转座元件,低压低氧环境可以改变L1的甲基化程度。目的探究低压低氧环境对肠黏膜中L1核酸内切酶(L1 endonuclease,L1-EN)变异体GCRG213表达水平及以闭合蛋白(Occludin)和紧密连接蛋白-1(Claudin-1)表达水平为指标的肠黏膜机械屏障功能的影响。方法利用免疫组织化学染色(immunohistochemical staining,IHC)检测人正常小肠、结肠组织及小鼠正常结肠组织的GCRG213表达,观察GCRG213蛋白在正常肠道中的分布规律。将雄性C57BL/6小鼠随机分为实验组和对照组。实验组模拟海拔6000 m环境,饲养7 d构建低压低氧小鼠模型,对照组常压常氧饲养。将人正常结肠上皮细胞NCM-460随机分为常氧组以及低氧24 h、48 h组,常氧组于常氧环境正常培养,低氧组分别于0.3%O2浓度下培养24 h、48 h构建低氧细胞模型。使用qPCR、Western blot技术检测GCRG213、Occludin和Claudin-1在小鼠结肠组织及人NCM-460细胞中表达水平的变化。结果人正常小肠、结肠及小鼠结肠组织IHC结果一致显示,GCRG213表达于肠黏膜柱状上皮细胞胞质中,而在杯状细胞中未见表达。在动物实验中,与常氧组相比,低压低氧组小鼠结肠组织GCRG213在mRNA水平(P<0.05)和蛋白水平(P<0.01)均表达上调;同时,Occludin在蛋白水平表达下调(P<0.05)。在细胞实验中,低氧暴露后NCM-460细胞中GCRG213在mRNA(P<0.001)和蛋白水平(P<0.01)均表达上调,其中低氧24 h组GCRG213表达水平低于低氧48 h组,Occludin、Claudin-1在mRNA水平(P<0.01;P<0.001)表达下调,其中低氧24 h组表达水平均低于低氧48 h组,Occludin蛋白水平表达在低氧48 h组出现下调(P<0.05)。结论L1-EN变异体GCRG213在人和小鼠正常结肠组织黏膜柱状上皮细胞胞质内存在表达;在体内外模型中,低压低氧暴露下结肠黏膜上皮细胞GCRG213表达升高,同时观察到低压低氧对结肠黏膜紧密连接完整性产生影响,表现为Occludin、Claudin-1蛋白表达水平的降低。

人工法off-line HDF对血液透析充分性和高同型半胱氨酸血症的影响

目的探究人工法off-line HDF对维持性血液透析(MHD)患者透析充分性、高同型半胱氨酸血症(HHcy)的影响。方法随机选取2021至2023年于南昌大学第一附属高新医院血液透析中心稳定透析6个月以上的MHD患者30例,进行单中心自身对照研究,时长6个月。前3个月维持每周2次高通量血液透析(HFHD)联合1次on-line HDF,后3个月维持每周2次人工法off-line HDF联合1次on-line HDF。于研究第3个月、第6个月时用全自动生化分析仪检测透析前后血尿素氮(BUN)、血肌酐(SCr)、β2-微球蛋白(β2MG)、同型半胱氨酸(Hcy)、白蛋白(Alb)、C反应蛋白(CRP)、血红蛋白(Hb)、甲状旁腺素(iPTH)、磷(P)、钾(K)水平;计算血清尿素清除指数(Kt/V)、尿素下降率(URR)和β2MG清除率。结果人工法off-line HDF模式透析的Kt/V、URR及β2MG清除率均较显著高于HFHD模式透析(P<0.05);人工法off-lineHDF模式透析Kt/V、URR及β2MG清除率达到透析充分的百分率分别为83.33%、83.33%和93.33%,均显著高于HFHD模式透析(P<0.05)。与HFHD模式透析时相比,人工法off-lineHDF模式透析结束后,患者透析前Hcy水平降低,Alb水平升高(P<0.05)。结论人工法off-line HDF模式透析可显著增加Kt/V、URR和β2MG清除率,提高MHD患者的透析充分性达标率,且对HHcy具有改善作用。

Toward a Direct Measurement of the Cosmic Acceleration:The Pilot Observation of HI 21 cm Absorption Line at FAST

This study presents results on detecting neutral atomic hydrogen(H I)21 cm absorption in the spectrum of PKS PKS1413+13 at redshift z=0.24670041.The observation was conducted by FAST,with a spectral resolution of10 Hz,using 10 minutes of observing time.The global spectral profile is examined by modeling the absorption line using a single Gaussian function with a resolution of 10 kHz within a 2 MHz bandwidth.The goal is to determine the rate of the latest cosmic acceleration by directly measuring the redshift evolution of the H I 21 cm absorption line with Hubble flow toward a common background quasar over a decade or longer time span.This will serve as a detectable signal generated by the accelerated expansion of the Universe at redshift z<1,referred to as redshift drift z(5)or the SL effect.The measured H I gas column density in this DLA system is approximately equivalent to the initial observation value,considering uncertainties of the spin temperature of a spiral host galaxy.The high signal-to-noise ratio of 57,obtained at a 10 kHz resolution,strongly supports the feasibility of using the H I 21 cm absorption line in DLA systems to accurately measure the redshift drift rate at a precision level of around 10~(-10)per decade.

Derivative Spectroscopy and its Application at Detecting the Weak Emission/Absorption Lines

The development of spectroscopic survey telescopes like Large Sky Area Multi-Object Fiber Spectroscopic Telescope(LAMOST),Apache Point Observatory Galactic Evolution Experiment and Sloan Digital Sky Survey has opened up unprecedented opportunities for stellar classification.Specific types of stars,such as early-type emission-line stars and those with stellar winds,can be distinguished by the profiles of their spectral lines.In this paper,we introduce a method based on derivative spectroscopy(DS)designed to detect signals within complex backgrounds and provide a preliminary estimation of curve profiles.This method exhibits a unique advantage in identifying weak signals and unusual spectral line profiles when compared to other popular line detection methods.We validated our approach using synthesis spectra,demonstrating that DS can detect emission signals three times fainter than Gaussian fitting.Furthermore,we applied our method to 579,680 co-added spectra from LAMOST Medium-Resolution Spectroscopic Survey,identifying 16,629 spectra with emission peaks around the Hαline from 10,963 stars.These spectra were classified into three distinct morphological groups,resulting in nine subclasses as follows.(1)Emission peak above the pseudo-continuum line(single peak,double peaks,emission peak situated within an absorption line,P Cygni profile,Inverse P Cygni profile);(2)Emission peak below the pseudo-continuum line(sharp emission peak,double absorption peaks,emission peak shifted to one side of the absorption line);(3)Emission peak between the pseudo-continuum line.

Canine Myofascial Kinetic Lines: A Descriptive Dissection Study Including Related Function and Locomotion and Comparison of the Human and Equine Myofascial Kinetic Lines

Aim: This dissection study was conducted to verify if the Myofascial kinetic lines, outlined in detail in humans and recently documented in horses, were present in dogs. These dynamic lines present rows of interconnected muscles, myofascia and other fascia structures, which influence the biomechanics of the spine and limbs. Methods: Forty-two dogs of different breeds and genders were dissected, imaged, and videoed. Results: Similar kinetic lines were verified in the dog, as described in humans and horses, and additionally, three new branches of the lines were discovered. The kinetic lines described were three superficial lines: Dorsal, Ventral, and Lateral, which all started in the hindlimb and ended in the temporal and occipital regions. These lines act respectively in spinal extension, flexion, and lateral flexion. Three profound lines, which started in the tail and ended in the head. The Deep Dorsal Line followed the transversospinal myofascia. The Deep Ventral Line showed an additional start deep in the medial hind limb, continued in the hypaxial myofascia, and enveloped all the viscera. Also, the Deep Lateral Line started in the hindlimb but parted along the trunk in the deep lateral myofascial structures. Two helical lines crossed the midline two or three times and served to rotate the spine. The Functional Line established a sling from the axilla to the contralateral stifle and presented a new ipsilateral branch. The Spiral Line connected the head and the ipsilateral tarsus and additionally presented a new straight branch. The four front limb lines describe their motion: the Front Limb Protraction and Retraction, Adduction, and Abduction Lines. Conclusion: The canine lines mirrored the equine and human lines with exceptions due to differences in anatomy, foot posture, lumbosacral flexibility, and their biomechanical constitution as predator versus prey animals. Additionally, three new canine branches were verified and described.

Evaluation of red soil-bentonite mixtures for compacted clay liners

Compacted clay liners are an integral part of the waste landfills,which are provided to contain the leachate within the landfills and protect the surrounding environment.Generally,locally available natural soils are used for the construction of compacted clay liners if they satisfy the design criteria.However,not all soils in their natural state satisfy all the design criteria for the liner materials.Thus,there is a definite need to modify the locally available natural soils by blending with bentonite to meet the required design criteria for the liners.In view of this,the present study evaluates the suitability of an Indian red soil enhanced with bentonite as a liner material.To achieve this,a series of experiments were carried out using locally available red soil and bentonite.First,the suitability of the red soil was evaluated as a liner material.The experimental results showed that the red soil met all the selection criteria stipulated by the Environmental Protection Agencies(EPAs)for the liners except the hydraulic conductivity criterion.Therefore,the red soil was mixed with bentonite contents of 10%,20%and 30%,and the red soil-bentonite mixtures were evaluated for their suitability for liners in their compacted state.Further,as the liners in the arid and semi-arid regions are subjected to moisture variations due to seasonal moisture fluctuations and other factors,the red soil-bentonite mixtures were subjected to wetdry cycles,and their suitability was evaluated after wet-dry cycles.The experimental results revealed that all the red soil-bentonite mixtures met the stipulated EPA criteria for the liners in the as-compacted state.However,the red soil-bentonite mixtures with 20%and 30%bentonite contents only satisfied the hydraulic conductivity requirement even after wet-dry cycles.The experimental findings were supplemented with the microstructural insights captured through digital camera images,scanning electron microscopy(SEM),and mercury intrusion porosimetry(MIP)studies.

ST-LaneNet: Lane Line Detection Method Based on Swin Transformer and LaneNet

The advancement of autonomous driving heavily relies on the ability to accurate lane lines detection.As deep learning and computer vision technologies evolve,a variety of deep learning-based methods for lane line detection have been proposed by researchers in the field.However,owing to the simple appearance of lane lines and the lack of distinctive features,it is easy for other objects with similar local appearances to interfere with the process of detecting lane lines.The precision of lane line detection is limited by the unpredictable quantity and diversity of lane lines.To address the aforementioned challenges,we propose a novel deep learning approach for lane line detection.This method leverages the Swin Transformer in conjunction with LaneNet(called ST-LaneNet).The experience results showed that the true positive detection rate can reach 97.53%for easy lanes and 96.83%for difficult lanes(such as scenes with severe occlusion and extreme lighting conditions),which can better accomplish the objective of detecting lane lines.In 1000 detection samples,the average detection accuracy can reach 97.83%,the average inference time per image can reach 17.8 ms,and the average number of frames per second can reach 64.8 Hz.The programming scripts and associated models for this project can be accessed openly at the following GitHub repository:https://github.com/Duane 711/Lane-line-detec tion-ST-LaneNet.

Establishment and characterization of a canine chondrosarcoma cell line:Mango

In the global progress of bone tumor research,established stable and long-lasting transgenic chondrosarcoma(CSA)cell lines are rare,mainly of murine and human origin,while the establishment of canine CSA cell lines has yet to be reported.This study established a canine CSA cell line to facilitate the basic clinical study of canine CSA.Fifty fve cases of canine osteolytic disease were collected,and more than 10 bone tumor samples from dogs with typical clinical signs were used for primary cell culture.A cell line with stable passaging for more than 100 generations and mouse tumorigenic ability was successfully cultured.According to the clinical characteristics of the dog and the histopathological results of the primary tumor,CSA was diagnosed,and the CSA cell line was designated Mango.Immunohistochemical(IHC)results showed that the immunoreactivity of bone gamma-carboxyglutamate protein(BGLAP),secreted protein acidic and rich in cysteine(SPARC),alkaline phosphatase(ALPL),vimentin(VIM)and S100 were positive.However,the immunoreactivity of pan-cytokeratin(PCK),chromogranin A(CGA),and platelet endothelial cell adhesion molecule-1(CD31)was negative.Immunofuorescence(IF)results showed that the protein expressions in the Mango cell line were consistent with the IHC identifcation of the primary tumor.The Mango cell line’s doubling time was 43.92 h,and the cell formation rate exceeded 20%.There were abnormal chromosome numbers,hetero staining with toluidine blue,and certain calcifcation abilities.It could be passaged stably and continuously without changing the cell morphology and characteristics.In vivo,the cells were successfully injected into the nude mice model with a tumorigenic rate of 100%.The immunophenotype of the xenograft tumor was consistent with that of the primary tumor.Therefore,we efectively established a canine CSA cell line.As a promising cell material,this cell line can be used to construct a tumor-bearing model conducive to the subsequent basic research of canine CSA.Moreover,because of its similarity to human CSA,the animal model of CSA is also indispensable for investigating human CSA.

An Implementation of Multiscale Line Detection and Mathematical Morphology for Efficient and Precise Blood Vessel Segmentation in Fundus Images

Diagnosing various diseases such as glaucoma,age-related macular degeneration,cardiovascular conditions,and diabetic retinopathy involves segmenting retinal blood vessels.The task is particularly challenging when dealing with color fundus images due to issues like non-uniformillumination,low contrast,and variations in vessel appearance,especially in the presence of different pathologies.Furthermore,the speed of the retinal vessel segmentation system is of utmost importance.With the surge of now available big data,the speed of the algorithm becomes increasingly important,carrying almost equivalent weightage to the accuracy of the algorithm.To address these challenges,we present a novel approach for retinal vessel segmentation,leveraging efficient and robust techniques based on multiscale line detection and mathematical morphology.Our algorithm’s performance is evaluated on two publicly available datasets,namely the Digital Retinal Images for Vessel Extraction dataset(DRIVE)and the Structure Analysis of Retina(STARE)dataset.The experimental results demonstrate the effectiveness of our method,withmean accuracy values of 0.9467 forDRIVE and 0.9535 for STARE datasets,aswell as sensitivity values of 0.6952 forDRIVE and 0.6809 for STARE datasets.Notably,our algorithmexhibits competitive performance with state-of-the-art methods.Importantly,it operates at an average speed of 3.73 s per image for DRIVE and 3.75 s for STARE datasets.It is worth noting that these results were achieved using Matlab scripts containing multiple loops.This suggests that the processing time can be further reduced by replacing loops with vectorization.Thus the proposed algorithm can be deployed in real time applications.In summary,our proposed system strikes a fine balance between swift computation and accuracy that is on par with the best available methods in the field.

Characterization of the infectivity of an Indonesian Zika virus strain in mammalian cell lines

Objective:To characterize the infection patterns and growth characteristics of the Zika virus(ZIKV)strain JMB-185 from Indonesia in various mammalian cell lines.Methods:ZIKV was grown in human(A549,HEK293,HepG2,Huh7,Jurkat,and THP-1)and non-human mammalian(RAW264.7,Vero,and Vero76)cell lines.Viral replication kinetics were measured using plaque assay,while intra-and extracellular viral RNA concentrations were assessed using RT-PCR.Flow cytometry was used to quantify the infected cells and cell viability was measured using an MTT assay.The ability of ZIKV to infect cell lines was visualized using a fluorescence immunostaining assay.Results:This ZIKV strain preferentially infected the lung,kidney,and liver cell lines A549,HEK293,Huh7,Vero,and Vero76,but not the immune cells Jurkat,RAW264.7,and THP-1.By contrast,the ZIKV showed no sign of infection in HepG2 cells,while maintaining viral titer over 3 days post-infection,with no infection recorded in immunostaining,no increase in viral RNA,and no indication of cell deterioration.Conclusions:The Indonesian ZIKV strain has a similar infection profile as other strains,except for its poor infectivity on HepG2 cells.Information on the growth characteristics of Indonesia ZIKV will help expand our understanding of the biology of ZIKV which will be useful for various applications including antiviral discovery.

Optimizing profile line interval for enhanced accuracy in rock joint morphology and shear strength assessments

2D profile lines play a critical role in cost-effectively evaluating rock joint properties and shear strength.However, the interval(ΔI_(L)) between these lines significantly impacts roughness and shear strength assessments. A detailed study of 45 joint samples using four statistical measures across 500 different ΔI_(L)values identified a clear line interval effect with two stages: stable and fluctuation-discrete.Further statistical analysis showed a linear relationship between the error bounds of four parameters,shear strength evaluation, and their corresponding maximum ΔI_(L)values, where the gradient k of this linear relationship was influenced by the basic friction angle and normal stress. Accounting for these factors,lower-limit linear models were employed to determine the optimal ΔI_(L)values that met error tolerances(1%–10%) for all metrics and shear strength. The study also explored the consistent size effect on joints regardless of ΔI_(L)changes, revealing three types of size effects based on morphological heterogeneity.Notably, larger joints required generally higher ΔI_(L)to maintain the predefined error limits, suggesting an increased interval for large joint analyses. Consequently, this research provides a basis for determining the optimal ΔI_(L), improving accuracy in 2D profile line assessments of joint characteristics.

On traceable iterated line graph and hamiltonian path index

Xiong and Liu[21]gave a characterization of the graphs G for which the n-iterated line graph L^(n)(G)is hamiltonian,for n≥2.In this paper,we study the existence of a hamiltonian path in L^(n)(G),and give a characterization of G for which L^(n)(G)has a hamiltonian path.As applications,we use this characterization to give several upper bounds on the hamiltonian path index of a graph.

Imaging of human parafoveal area with large field of view in adaptive optics line scanning ophthalmoscope

The parafoveal area,with its high concentration of photoreceptors andfine retinal capillaries,is crucial for central vision and often exhibits early signs of pathological changes.The current adaptive optics scanning laser ophthalmoscope(AOSLO)provides an excellent tool to acquire accurate and detailed information about the parafoveal area with cellular resolution.However,limited by the scanning speed of two-dimensional scanning,thefield of view(FOV)in the AOSLO system was usually less than or equal to 2,and the stitching for the parafoveal area required dozens of images,which was time-consuming and laborious.Unfortunately,almost half of patients are unable to obtain stitched images because of their poorfixation.To solve this problem,we integrate AO technology with the line-scan imaging method to build an adaptive optics line scanning ophthalmoscope(AOLSO)system with a larger FOV.In the AOLSO,afocal spherical mirrors in pairs are nonplanar arranged and the distance and angle between optical elements are optimized to minimize the aberrations,two cylinder lenses are orthogonally placed before the imaging sensor to stretch the point spread function(PSF)for sufficiently digitizing light energy.Captured human retinal images show the whole parafoveal area with 55FOV,60 Hz frame rate and cellular resolutions.Take advantage of the 5FOV of the AOLSO,only 9 frames of the retina are captured with several minutes to stitch a montage image with an FOV of 99,in which photoreceptor counting is performed within approximately 5eccentricity.The AOLSO system not only provides cellular resolution but also has the capability to capture the parafoveal region in a single frame,which offers great potential for noninvasive studying of the parafoveal area.

基于Hessian矩阵的改进EDlines输电线识别算法

随着电力网络的飞速发展,采用无人机搭载高清摄像头来进行输电线巡检已成常态。为提高巡检的实时性和准确性,本研究提出了一种基于Hessian矩阵的改进EDlines输电线识别算法。首先,通过伽马变换对输电线图像进行预处理,利用Hessian矩阵特征值和特征向量以求取像素点主方向和主曲率,并获得输电线主体轮廓,从而摒弃了传统方法中梯度计算锚点和像素方向的繁琐步骤。接着,在主体轮廓基础上连接锚点以得到潜在直线线段像素链,并运用随机抽样一致性(RANSAC)算法来进行线段拟合。最后,根据直线间的距离和角度,迭代拟合以得到最终的输电线。实验结果表明,该方法能应对多种复杂环境下的输电线识别任务,抗干扰能力强,误检率显著降低,为高空输电线巡检提供了可靠的技术支持,具有重要的工程应用价值。

Analysis of mechanical strengths of extreme line casing joint considering geometric, material, and contact nonlinearities

To address the challenges associated with difficult casing running,limited annular space,and poor cementing quality in the completion of ultra-deep wells,the extreme line casing offers an effective solution over conventional casings.However,due to its smaller size,the joint strength of extreme line casing is reduced,which may cause failure when running in the hole.To address this issue,this study focuses on the CST-ZTΦ139.7 mm×7.72 mm extreme line casing and employs the elastic-plastic mechanics to establish a comprehensive analysis of the casing joint,taking into account the influence of geometric and material nonlinearities.A finite element model is developed to analyze the forces and deformations of the extreme line casing joint under axial tension and external collapse load.The model investigates the stress distribution of each thread tooth subjected to various tensile forces and external pressures.Additionally,the tensile strength and crushing strength of the extreme line casing joint are determined through both analytical and experimental approaches.The findings reveal that,under axial tensile load,the bearing surface of each thread tooth experiences uneven stress,with relatively high equivalent stress at the root of each thread tooth.The end thread teeth are valuable spots for failure.It is observed that the critical fracture axial load of thread decreases linearly with the increase of thread tooth sequence.Under external pressure,the circumferential stress is highest at the small end of the external thread,leading to yield deformation.The tensile strength of the joint obtained from the finite element model exhibits a relative error of less than 7%compared to the analytical and experimental values,proving the reliability of the finite element model.The tensile strength of the joint is 3091.9 k N.Moreover,in terms of anti-collapse capability,the joints demonstrate higher resistance to collapse compared to the casing body,which is consistent with the test results where the pipe body experiences collapse and failure while the joints remain intact during the experiment.The failure load of the casing body under external collapse pressure is 87.4 MPa.The present study provides a basic understanding of the mechanical strengths of extreme line casing joint.

FAST Observations of Four Comets to Search for the Molecular Line Emissions between 1.0 and 1.5 GHz Frequencies

We used the Five-hundred-meter Aperture Spherical radio Telescope(FAST)to search for the molecular emissions in the L-band between 1.0 and 1.5 GHz toward four comets,C/2020 F3(NEOWISE),C/2020 R4(ATLAS),C/2021 A1(Leonard),and 67P/Churyumov-Gerasimenko during or after their perihelion passages.Thousands of molecular transition lines fall in this low-frequency range,many attributed to complex organic or prebiotic molecules.We conducted a blind search for the possible molecular lines in this frequency range in those comets and could not identify clear signals of molecular emissions in the data.Although several molecules have been detected at high frequencies of greater than100 GHz in comets,our results confirm that it is challenging to detect molecular transitions in the L-band frequency ranges.The non-detection of L-band molecular lines in the cometary environment could rule out the possibility of unusually strong lines,which could be caused by the masers or non-LTE effects.Although the line strengths are predicted to be weak,for FAST,using the ultra-wide bandwidth receiver and improving the radio frequency interference environments would enhance the detectability of those molecular transitions at low frequencies in the future.