Joint Samples Research Articles

Investigation of the Nature of Damage to Welded Flexible Compensating Elements Made of Austenitic Stainless Steels

Welded flexible compensating elements made of austenitic stainless steels, such as metal hoses and bellows expansion joints, operate in a complex stress state; therefore, almost all corrosion damage of these products occurs in a stressed state. In addition, in welded joints, defects are possible associated with elastic-plastic deformations and stresses arising in the manufacturing process. Paper considers the defects of welded joints of multilayer bellows expansion joints made of stainless steels AISI 304 and AISI 316 types. The influence of the parameters of the argon tungsten electrode welding mode, with or without filler wire, on the mechanical characteristics of welded joints was studied. Mechanical tests of samples of welded joints were carried out on a tensile testing machine. The optimal range of variation of the parameters of the welding mode has been established, in which the plastic characteristics of the welded joints have maximum values. A metallographic study of the microstructure of welded joints of metal hoses and bellows expansion joints was carried out. The influence of the content of nonmetallic inclusions in the material of products on the conditions of melting and crystallization of the weld pool, contributing to the appearance of pores and hot cracks in the metal of the weld and the heat affected zone, has been established. To reduce the influence of the content of non-metallic inclusions in the weld metal and the heat-affected zone on the conditions of melting and crystallization of the weld pool, it is recommended to carry out preliminary heat treatment of the austenitic steel strip.

High-performance Ba1−x K x Fe2As2 superconducting joints for persistent current operation

High-performance superconducting joints are the key to achieving persistent-mode magnets. Herein, the superconducting joints between Ba1−x K x Fe2As2 (BaK-122) superconducting tapes were prepared by a simple cold-pressing method, and the joint resistance of the iron-based superconducting joint was estimated by field-decay method for the first time. Via the scanning electron microscope (SEM), electron backscattered diffraction (EBSD), electron probe microanalysis (EPMA) and x-ray computed tomography (XCT) measurements, it is found that the joint sample CP80 shows fine performance. At 4.2 K and 10 T, a transport critical current I c of 105 A for the joint sample CP80 was measured, and the critical current ratio (CCR = Ijoint c/Itape c) of the joint was 94.6%. On the other hand, the joints exhibit a pretty low joint resistance of 2.7 × 10−13 Ω in self-field at 4.2 K. Among iron-based superconductors, we are the first to estimate the accurate resistance of iron-based superconducting joint by the field-decay method. All these show the great prospective to apply BaK-122 in a series of practical applications that require superconducting joints as key components.

Research on the fracture mode and damage evolution model of sandstone containing pre-existing crack under different stress paths

To study the effect of creep loading on the fracture mode and damage evolution process of jointed rock masses during fatigue loading, a series of multilevel cyclic loading and unloading tests (MCT) and fatigue-creep tests (FCT) were carried out on jointed sandstone samples. First, a combined detection platform was built using acoustic emission (AE), scanning electron microscopy (SEM) and digital image-related (DIC) technologies. Then, the fracture mode of the sample is analyzed at the macro- and mesoscale. Finally, based on the loading and unloading response ratio (LURR) theory, assuming that the internal damage of the sample obeys the improved Harris distribution, a damage evolution model of the sandstone sample was established, and the applicability and validity of the model were verified. The test results show that applying creep load during the fatigue loading process can increase the axial strength, reduce the axial deformation, weaken the energy dissipation, and exhibit the phenomenon of early hardening. In terms of fracture mode, applying creep load can change the type of cracks that dominate the failure of the sample, improve the shear resistance, and increase the brittleness when the sample is broken. At the same time, the dislocation movement between the grains, pressure solution and splitting phenomenon will be enhanced, and the types of micro-defects will increase. In terms of the damage evolution process, a short-term low-stress level creep load can reduce the rate of damage growth, thereby increasing the fatigue life of the rock mass.

First Detection of Methanogens in Orthopedic Prosthesis Infection: A Four-Case Founding Series

Orthopedic prosthesis infection must be medically managed after appropriate microbiological documentation. While bacteria and fungi are acknowledged to be causative opportunistic pathogens in this situation, the potential role of methanogens in orthopedic prosthesis infections is still unknown. In a retrospective study, a total of 100 joint and bone samples collected from 25 patients were screened by specific PCR assays for the detection of methanogens. PCR-positive samples were observed by autofluorescence, electron microscopy and tentatively cultured under specific culture conditions. Methanogens were detected by quantitative PCR in 4/100 samples, in the presence of negative controls. Sequencing identified Methanobrevibacter oralis in two cases, Methanobrevibacter smithii in one case and Methanobrevibacter wolinii in one case. Microscopic methods confirmed molecular findings and bacterial culture yielded two strains of Staphylococcus aureus, one strain of Staphylococcus epidermidis and one strain of Proteus mirabilis. These unprecedented data highlight the presence of methanogens in joint and bone samples of patients also diagnosed with bacterial orthopedic prosthesis infection, questioning the role of methanogens as additional opportunistic co-pathogens in this situation.

Enhancement of seismic behaviour of precast beam-to-column joints using engineered cementitious composite

Seismic activities can cause considerable damage to the integrity of the reinforced concrete and precast concrete structures, particularly in the beam-to-column joints. This article investigates the impact of using engineered cementitious composite (ECC) with different types of fibres on the performance behaviour of novel precast beam-to-column joints subjected to cyclic loading. Six samples of the novel precast hybrid joints, including one sample with a conventional joint, were tested to evaluate the seismic behaviour of the joints. The investigated precast joints were cast using ECC with 2% volume fraction of polyvinyl alcohol fibre (with two different aspect ratios), polyethylene fibre, hooked-end steel fibre, and hybrid fibre, while normal concrete was used to prepare the conventional monolithic joint. The seismic behaviour of the precast joints exhibited better performance than the conventional monolithic joint. This is as a result of the higher tensile and flexural strengths of the ECC fibres, better mechanical bridging in the crack area, adequate amount and distribution of the fibres, good bonding in the ECC produced, the increasing resistance to slippage for the reinforcing bars, and avoidance of the spalling concrete in the joint area, which may cause shear failure. The deformation capacity of the precast joints was 12.5% higher than that of the conventional monolithic joint. In addition, the ductility values and the hysteretic energy dissipations of the precast joints were 15.69–43.14% and 25.40–49.18%, respectively greater than that of the conventional monolithic joint. Furthermore, beam flexural failure was observed for the precast samples and there was less damage compared with the monolithic sample. Thus, the novel precast joints can be potentially implemented to withstand high earthquake activities due to their superior seismic performance.

Particularités des infections ostéo-articulaires tuberculeuses

Bone, articular or spinal tuberculosis is rare (200 to 300 cases per year in France) but should not be forgotten, in particular in patients with an osteoarticular infection, with negative initial bacteriology. The risk of tuberculosis is higher in foreign patients, immunosuppressed, homeless, prisoners or people living in precarious conditions. The destructive bone involvement of tuberculosis can mimic tumor pathology, emphasizing the importance of quality histological analysis, in front of a solid or multifocal lytic image. Tuberculous monoarthritis, subacute or chronic, looks like the onset of inflammatory rheumatism, justifying the performance, in the slightest doubt, of a synovial biopsy. The possibility of performing a PCR, from bone, joint or spinal samples, saves time for the initiation of a complex antibiotic therapy, which is effective but source of potentially serious side effects. Methodical, close, clinical, radiographic and biological monitoring is essential to support the patient for 6 to 9 months.

Decision Fusion Using Similarity-weighted JCR and Mid-level Features based ELM for Hyperspectral Image Classification with Limited Training Samples

ABSTRACT By combining the similarity-weighted joint collaborative representation (SJCR) and extreme learning machine based on mid-level features (MFELM), a decision fusion framework is constructed to classify hyperspectral images with limited training samples. First, the similarity-weighted matrix is obtained by calculating the Gaussian process-based distance between each testing sample and its surroundings, which can expose the spatial unequal contributions between samples. Based on this, the samples with the higher similarities are selected to construct the joint samples. Then, SJCR is exploited to classify the joint samples and calculate the related SJCR coefficients. Secondly, mid-level features with the rich spatial characteristics are formed by utilizing SJCR coefficients, which are introduced to conduct extreme learning machine for classification. Finally, the classification probabilities of SJCR and MFELM are combined in a multiplicative fusion manner to achieve the final classification results. Using different and limited amount of training samples, the proposed method is evaluated by comparing with the popular classifiers. The visual and numerical results indicate the effectiveness of the proposed method for classifying hyperspectral images with the limited training samples.

EFFECTS OF POST WELD HEAT-TREATMENT ON MICROSTRUCTURE AND MECHANICAL BEHAVIOR OF DIS-SIMILAR MATERIALS PRODUCED BY GTAW PROCESS

Welding is a well-known economic fabrication process in that GTAW is one of the reliable and easy weld techniques compared with other fabrication techniques. The present research focused on the dissimilar metal welds, a weldment between ferrous and non-ferrous alloys taken into consideration. A part of experimental work, AA6061 with Ferrous alloys like EN8, SS302, SS316 welded with TIG welding process known as GTAW. Aluma steel filler rods are used for the weldment in a twostep process; the primary rod is used to fill the ferrous side, and the second filler is used to join them both. The structures for different samples of post welded joints to check the structural variation between all 3-zones, basemetal, Heat affected zone (HAZ), and weld zone using optical microscopy and scanning electron microscopy (SEM). The investigation further continued to check the mechanical properties of weld structures tensile and hardness. Hardness testing has been carried out like structures in 3- zones to check the hardness variation in HAZ and weldment. The results obtained are satisfactory based on weld strength and structures obtained in the sample analysis.

Unveiling the mystery of scale dependence of surface roughness of natural rock joints

Scale dependence of surface roughness of natural rock joints has long been an outstanding issue in rock mechanics. Controversial results were reported by various studies; however, the nature of scale dependency and the underlying mechanism for the conflicting observations remain unclear. Rock joints at different scales characterise two-order asperities, namely, waviness and unevenness; thus understanding how the individual roughness of waviness and unevenness vary as the joint size increases from the laboratory-scale to the large-scale is crucial for revealing the scale effect mystery. Here we digitise three natural granite joint surfaces with the same dimension of 1000 mm × 1000 mm through a high-resolution, three-dimensional scanner. Waviness and unevenness of each rock joint surface are quantitatively separated by selecting an appropriate sampling interval. The respective fractal dimensions of waviness and unevenness of joint surfaces sized from 100 mm × 100 mm to 1000 mm × 1000 mm are estimated through an improved roughness-length method. We find that the fractal dimensions of two-order roughness are scale-dependent but without generalised trends. The stationarity threshold beyond which the scale-dependency of roughness vanishes is absent for all the three joint samples, suggesting that the roughness of natural rock joints be assessed at the specific scale of the rock mass in-situ. We reveal that previous controversial results regarding scale effect are likely due to the composition of the roughness scaling of waviness and unevenness. Thus, accurate stability analysis of rock-engineering projects should consider separate contributions of multi-order asperities across scales to the strength and deformation of jointed rock masses.

Comparative Microbiomes of the Respiratory Tract and Joints of Feedlot Cattle Mortalities.

A comparative study of microbiota of the respiratory tract and joints of bovine respiratory disease (BRD) cattle mortalities was undertaken. Nasopharynx, trachea, lung and joint samples were collected from 32 cattle that died of BRD, “cases”, and 8 that died of other causes, “controls”. Bacterial diversity was lower (p < 0.05) in the nasopharynx, trachea and lungs of cases as compared to controls. In cases, alpha-diversity (p < 0.05) was lower in the lungs and joints than the nasopharynx. Proteobacteria, Tenericutes, Bacteroidetes, Firmicutes and Actinobacteria were the most abundant phyla in all samples. Relative abundances of Mycoplasma spp. in the lung, Pasteurella spp. in the trachea and lung, and Histophilus spp. in the lung, trachea and nasopharynx of cases were higher (p < 0.001) than controls. Mycoplasma spp. comprised 20.5% of bacterial flora in the joint, 36.0% in the lung, 22.4% in the trachea and 8.8% in the nasopharynx. Mannheimia spp. (21.8%) and Histophilus spp. (10.4%) were more abundant in lungs. Cattle that died of BRD possessed less diverse respiratory microbiomes with a higher abundance of respiratory pathogens. Mycoplasma spp. were prominent members of pneumonic lungs and joints displaying septic arthritis.

Modeling and validation of nonlinear voltage-current characteristics of ITER PF joint sample tested in the SULTAN facility

The International Thermonuclear Experimental Reactor poloidal field (PF) coils are wound into double pancakes with NbTi cable-in-conduit conductors, which are connected by joints in shaking hands lap-type configuration. The coils are operating in pulsed mode with a maximum operating current of 55 kA and peak magnetic field of 6.4 T, utilizing electromagnetic load on the conductors and joints. A series of PF qualification joint samples modified in praying hands configuration is measured in the SULTAN facility. For some samples, a nonlinear voltage-current (VI) characteristic is observed during the assessment of joint resistance. The growth of joint resistance versus the B× I product is larger than what is expected from the magneto-resistant copper contribution. Two non-homogeneous contact resistance models are developed and combined to quantitatively evaluate the reason for the nonlinear VI behavior in combination with the relevant power dissipation and current redistribution in the joint. The simulations reveal that, for the particular pre-qualification PFJEU2 sample with resistance variation up to 3.5 nΩ, the most probable reason for the nonlinear VI characteristic is a widely spread defective connection between copper sole and shim. The electromagnetic force involves a separation effect on the mechanically and electrically weakly connected parts, resulting into a varying resistance depending on transport current and background field. The hypothesis and models are validated by an experiment on a similar sample PFJEU3 and a post-mortem examination of the PFJEU2 sample.

Graph Signal Compression by Joint Quantization and Sampling

Graph signals arise in various applications, ranging from sensor networks to social media data. The high-dimensional nature of these signals implies that they often need to be compressed in order to be stored and transmitted. The common framework for graph signal compression is based on sampling, resulting in a set of continuous-amplitude samples, which in turn have to be quantized into a finite bit representation. In this work, we study the joint design of graph signal sampling along with quantization, for graph signal compression. We focus on bandlimited graph signals, and show that the compression problem can be represented as a task-based quantization setup, in which the task is to recover the spectrum of the signal. Based on this equivalence, we propose a joint design of the sampling and recovery mechanisms for a fixed quantization mapping, and present an iterative algorithm for dividing the available bit budget among the discretized samples. Furthermore, we show how the proposed approach can be realized using graph filters combining elements corresponding the neighbouring nodes of the graph, thus facilitating distributed implementation at reduced complexity. Our numerical evaluations on both synthetic and real world data shows that the joint sampling and quantization method yields a compact finite bit representation of high-dimensional graph signals, which allows reconstruction of the original signal with accuracy within a small gap of that achievable with infinite resolution quantizers.

Meta-TR: Meta-Attention Spatial Compressive Imaging Network With Swin Transformer

As a flourishing research topic in the field of remote sensing, SCI (spatial compressive imaging) can utilize prior knowledge to recover high-dimensional signals from LR (low-resolution) measurements through joint sampling and compression, thus contributing to the bandwidth reduction of information transmission. However, most of the existing SCI methods based on deep learning cannot effectively utilize prior information, and difficult to perform deep extraction of image features, so the reconstruction is not ideal in the case of low sampling ratio. To address the above difficulty, we propose a SCI network based on MA (meta-attention) and swin transformer, named Meta-TR. We adopt the swin transformer as the network backbone, through the wide application of self-attention mechanisms, to achieve deeper extraction of image features, thereby improving the reconstruction quality under low sampling ratios. In addition, we design a meta-attention module, which adopts Squeeze-Excitation architecture to convert the metadata of SCI image degradation process to attention vectors. Then the attention vectors are used in the channel modulation of network feature maps to guide the network training. Extensive experiments are performed on different benchmark remote sensing datasets and different sampling ratios to confirm the superiority of the proposed Meta-TR method.

Dorso-ventral osteophytes of interphalangeal joints correlate with cartilage damage and synovial inflammation in hand osteoarthritis: a histological/radiographical study

ObjectiveTo detect dorsally located osteophytes (OP) on lateral x-ray views and to correlate their presence with the extent of structural joint damage, determined by histologic grading (cartilage damage and synovial inflammation) and radiographic scoring in hand osteoarthritis (HOA).MethodsDistal interphalangeal (DIP) and proximal interphalangeal (PIP) joints were obtained from post mortem specimens (n = 40). Multiplanar plain x-rays were taken (dorso/palmar (dp) and lateral views). Radiographic OA was determined by the Kellgren and Lawrence classification. Joint samples were prepared for histological analysis and cartilage damage was graded according to the Mankin scoring system. Inflammatory changes of the synovial membrane were scored using the general synovitis score (GSS). Spearman’s correlation was applied to examine the relationship between histological and radiographical changes. Differences between groups were determined by Mann-Whitney test.ResultsBony proliferations that were only detectable on lateral views but reminiscent of OPs on dp images were termed dorso-ventral osteophytes (dvOPs). All joints displaying dvOPs were classified as OA and the presence of dvOPs in DIP and PIP joints correlated with the extent of histological and radiographic joint damage, as well as with patient age. Joint damage in osteoarthritic DIP and PIP joints without any dvOPs was less severe compared to joints with dvOPs. Synovial inflammation was mainly present in joints displaying dvOPs and correlated with joint damage.ConclusiondvOPs are associated with increasing structural alterations in DIP and PIP joints and can be seen as markers of advanced joint damage. Detecting dvOPs can facilitate the diagnosis process and improve damage estimation in HOA.

The association of air pollutants (CO2, MTBE) on Candida albicans and Candida glabrata drug resistance

Abstract Introduction Therapeutic methods are very important in the prevalence of opportunistic fungal infections, which are an important cause of human diseases. In this study, air pollution agents that are in direct contact with microorganisms, and the effects of carbon sources using CO2 and MTBE on growth of fungi, and particularly the evaluation of changes in the expression of interfering genes in susceptibility and drug resistance in these fungi, were investigated. Materials and Methods Collecting samples and isolating Candida glabrata and Candida albicans with phenotypic methods were accomplished. We then evaluated the minimum inhibitory concentration (MIC) with the M27A4 protocol of CLSI. We adjusted 20 strains of C. albicans and 10 strains of C. glabrata whose sensitivity was evaluated in the MIC test with 5% CO2 and 5mg/ml methyl tert-butyl ether (MTBE) considered as air pollutants, and followed by re-evaluating MIC testing to separate azole-resistant strains. Interfering agents were also considered. Results Upregulation of some genes on the two mentioned yeasts had led to drug resistance in them; they were previously sensitive to both drugs. Correspondingly, 41% of C. glabrata samples in sputum showed sensitivity to these drugs. Upregulation of ERG11 (71%) and EPA1 (90%) were observed in resistant strains. Upregulation of genes associated with aspartate proteins and downregulation of SAP3 genes were recognized in C. glabrata in sputum and a 15% downregulation of bronchoalveolar lavage (BAL) isolate and 50% upregulation of SAP1 gene in C. albicans sensitive samples were observed and compared to fluconazole and itraconazole with the oral and joint sources. Remarkably, decreased SAP2 expression in oral sources and a 60% increase in resistant strains in C. albicans were observed. The downregulation of SAP3 expression showed in the joint samples. An increase in HWP1 expression (30%) was noted in isolated and drug-sensitive samples at the sputum and BAL source. CDR1 expression was increased in MTBE-affected species; however, it decreased in the vicinity of CT. Conclusions Air pollutants such as CO2 and MTBE eventually caused drug resistance in Candida, which can be one of the causes of drug resistance in candidiasis infections.

Influence of Fly Ash Geopolymer Ceramic Powder Addition on Sn-3.0Ag-0.5Cu Solder Joints

This paper reports the effect of 1.0 wt.% fly ash (FA) geopolymer ceramic powder addition in Sn-3.0Ag-0.5Cu (SAC305, in wt.%) solder joint. Powder metallurgy route was used to fabricate the new composite solder. Solder balls were formed from the new composite solder and reflowed on Cu substrate. The effect of FA as ceramic reinforcement on the bulk microstructure and the interfacial intermetallic compound layer formation of solder joints were investigated under optical microscope. Microstructure observation showed that the β-Sn dendrite size was refined in SAC305-1.0FA/Cu bulk solder joint sample than that in the non-reinforced sample. The addition of FA geopolymer ceramic powder into the solder matrix also produced a thinner intermetallic compound layer.

Single-Pass Object-Adaptive Data Undersampling and Reconstruction for MRI

There is much recent interest in techniques to accelerate the data acquisition process in MRI by acquiring limited measurements. Often sophisticated reconstruction algorithms are deployed to maintain high image quality in such settings. In this work, we propose a data-driven sampler using a convolutional neural network, MNet, to provide object-specific sampling patterns adaptive to each scanned object. The network observes very limited low-frequency k-space data for each object and rapidly predicts the desired undersampling pattern in one go that achieves high image reconstruction quality. We propose an accompanying alternating-type training framework with a mask-backward procedure that efficiently generates training labels for the sampler network and jointly trains an image reconstruction network. Experimental results on the fastMRI knee dataset demonstrate the ability of the proposed learned undersampling network to generate object-specific masks at fourfold and eightfold acceleration that achieve superior image reconstruction performance than several existing schemes. The source code for the proposed joint sampling and reconstruction learning framework is available at https://github.com/zhishenhuang/mri.

Cyclic behaviour of beam-column joints made of crumb rubberised concrete (CRC) and traditional concrete (TC)

Crumb rubberised concrete (CRC) is a sustainable material that recycles rubber particles from end-of-life tyres as partial fine aggregates in concrete. To promote the applications of CRC in building structures, this paper presents an experimental study on the cyclic behaviour of beam-column joints from both CRC and traditional concrete (TC) frame structures. CRC with 15% rubber content by sand volume was employed. Three full scale CRC joint samples and one full scale TC sample were tested. Varying axial loads were applied on the top of columns and anti-symmetrical low-frequency cyclic loads were applied at the two beam ends. The failure modes, hysteretic behaviour, stiffness degradation, bearing capacity degradation, shearing capacity, displacement ductility and strain response of CRC and TC joints were investigated and compared. Both CRC and TC joint samples reached their ultimate loads due to shear failure. When CRC and TC were with similar strengths, the first crack loads, yielding loads, ultimate loads and ultimate displacements for TC and CRC joints at the same axial compression ratios were comparable with slight differences within 5%. However, CRC joints exhibited an improved energy dissipation ability by up to 10.4% over TC samples.

Study of the Structural-Phase State of Pipeline Welded Metal

The issues of research of structural changes as applied to welded joints of steam pipelines are considered. The results of metallographic analysis of structural changes in the metal of steam pipelines are presented. There was carried out the analysis for a number of samples cut from different sections of the steam line at different operating time under creep and low-cycle fatigue conditions. In the analyzing process of the images of micro sections, the relative content of the structural-phase components and their distribution in the metal were revealed. A comparative analysis of the statistical characteristics of the distribution and the relative content of structural components for different sections of the metal of welded joints with different operating time is carried out. A scientifically substantiated description of structural changes in the metal of various sections of samples of welded joints is given, as well as the possibility of extending the service life of elements of steam pipelines with a degraded structure and the presence of damageability. The most promising, in the opinion of the authors, directions of further research of samples to provide conditions for extending the service life of steam pipelines have been formulated and substantiated.

Non-metallic inclusions interpretation technique for factory expertise of metal product defects

The technique of processing the results of factory experts&rsquo; reports has been developed to interpret the origin of nonmetallic inclusions (NMIs) detected in the defects of a welded pipe joints made of J55 API 5L (22GYu) steel. Thermodynamic simulation was performed to assess the possibility of the indigenous origin of these inclusions. The results of such a simulation were summarized using radar diagrams of four clusters uniting NMIs with similar composition of deoxidation and modification products. More than 130 compositions of actual inclusions detected on dozens of welded joints samples were processed and combined into four clusters in the same way. After a comparative analysis of these two types of radar diagrams, the origin of all clusters of actual inclusions was established, three of which are predominantly exogenous inclusions and the fourth is predominantly indigenous. None of the clusters contains only indigenous inclusions or only exogenous ones. The main source of inclusions in the discontinuities of welded joints is inclusions conglomerates, sorbed on the refractories surface, contacted with molten steel during its ladle treatment and pouring. These sintered conglomerates of indigenous and exogenous inclusions, that form three clusters of four ones, were out washed by the flow of steel melt into the crystallizer during steel pouring. The reasons for the formation of the fourth cluster are related to &ldquo;cold welding&rdquo;. The technique is implemented as a plug-in of Thixomet Pro image analysis system and allows to automate the process of metallographic conclusions generation in factory practice, as well as to accumulate all information in a database for its subsequent processing and analysis.