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• Assessing feasibility of inferring key track condition parameters using micro-electro-mechanical-system (MEMS) accelerometers. • Prototype of onboard data acquisition system designed and installed on a track recording car (TRC) and comparison of accelerometer-based results vs TRC recordings. • Accelerometers on the bogie are the best compromise between proximity to source and insensitivity to impulsive noise. • Two bogie accelerometers with two measurement axes can provide quantitative estimates of vertical alignment and trends in geographical distribution of horizontal alignment. • Frequency analysis of vertical/horizontal alignment formulas to justify choice of filtering parameters. The main objective of this paper is to assess the estimation of track condition parameters using onboard micro-electro-mechanical-system (MEMS) accelerometers. A prototype of an onboard data acquisition system was designed and installed on a track recording car (TRC) and a measurement campaign was conducted on an extensive portion of the Brisbane Suburban railway network. Comparison of the accelerometer-based results vs TRC recordings have shown that accelerometers installed on the bogie are the best compromise between proximity to the source and insensitivity to impulsive noise. It was found that two vertical bogie accelerometers (left and right) provide a good quantitative estimate of vertical alignment and that strong correlations with TRC measurements exist for lateral MEMS accelerometer measurements (horizontal alignment). These findings suggest that two bogie MEMS accelerometers with vertical and lateral measurement axes are effective in estimating geographical distributions of vertical/horizontal alignment. [ABSTRACT FROM AUTHOR]

The normal operation of various superconducting magnets is greatly influenced by the thermal stress of the insulating system, commonly made of epoxy resins with vacuum pressure impregnation (VPI) technology, throughout the curing and cooling processes. In this work, we developed a Fiber Bragg Grating (FBG) strain measurement method to monitor the real-time strain responses of an epoxy resin IR-3 and its glass fiber-reinforced composite during both curing and cooling processes. Then, we also monitored the same process of a Nb–Ti superconducting magnet coil prepared by VPI technology. With the help of FBG strain sensors, the residual strains of the coil at various positions and directions were investigated. The results show that the large residual strain occurred near the end of the coil in the axial direction. In addition, the interlaminar shear stress properties were measured at both room temperature and liquid nitrogen temperature. The strain characteristics of the epoxy resin IR-3 and the insulating system can provide useful guidance for the design and construction of high-field Nb–Ti superconducting magnets. [ABSTRACT FROM AUTHOR]

The database of thermal expansion behavior of closed-cell polyurethane rigid foam at very low temperatures is required for designing and manufacturing thermal insulation components of various cryogenic systems. In the present work, thermal expansion behaviors of closed-cell polyurethane rigid foams with different densities were investigated in the 20 K–270 K temperature range by means of a high-resolution extensometer technique, which has been verified through comparison with standard values of an AISI 304 stainless steel rod. The comparison result demonstrates that the maximum deviation from the standard coefficient of thermal expansion of the AISI 304 in cryogenic temperatures is less than 6.6%. Testing results indicate that the cryogenic thermal expansions of closed-cell polyurethane rigid foams depend reversely on density. Moreover, the thermal expansion behavior of closed-celled polyurethane rigid foams exhibits difference from that of bulky amorphous isotropic polymers, which have been attributed to several factors such as enclosed air and cellular structure. [ABSTRACT FROM AUTHOR]

(E) mRNA expression of BTLA in the kidney graft by qRT-PCR among the Allo + NC and Allo + BTLA groups. (A) IHC staining showed significantly upregulated BTLA expression in the kidney tissue of the SD rat by BTLA-overexpression adenovirus (Normal + BTLA) compared with the negative control vector (Normal + NC) and normal SD rat (Normal). [Extracted from the article]

• The two-dimensional temperature field of the tensile process was investigated based on Digital Image Correlation (DIC) technology and cooling heat transfer model. • The reconstructed temperature field is in good agreement with the temperature rise in the tensile process. • The observed trend of increased martensite production is consistent with the simulated predictions. To better understand the tensile fracture behavior and temperature variation during the tension testing of the 316LN at cryogenic temperatures, a two-dimensional temperature field solution method is developed based on two-dimensional strain field measured by the digital image correlation technology combined with the Taylor Quinney coefficient model and the intrinsic model of strain-induced martensitic phase transformation. The method allows for visualization of the strain field and temperature variation of the 316LN austenitic stainless steel at cryogenic temperature. By numerical simulation, the localized temperature elevation of the 316LN is determined to be 13.3 K during the tensile test at 77 K, which is in good agreement with the experimental result of 10.2 K. This model reconstructed the two-dimensional temperature field variation throughout the entire tensile test, which is beneficial for facilitating the analysis of the mutual relation between the mechanical properties and microstructural evolution of the 316LN and other metastable austenitic stainless steels in cryogenic temperatures. [ABSTRACT FROM AUTHOR]

In this work, the microstructure evolution and magnetic properties of the 316LN austenitic stainless steels under high-cycle-fatigue loading at liquid helium temperature (4.2 K) were assessed by using the X-ray diffractometer (XRD), electron microscopy and magnetic measurements. The microstructure was composed of a single face-centered cubic (FCC) phase, and the high local misorientation was found near the grain boundaries. Observations through the high-resolution transmission electron microscopy reveals that the deformation was dominated by the dislocation and stacking faults. The magnetic susceptibility varies slightly after cyclic loading test at 4.2 K. [Display omitted] [ABSTRACT FROM AUTHOR]

• The evolving spall sizes were measured during run-to-failure experiments for REBs. • Four measurements (acceleration, AE, IAS, and displacement) were compared. • Displacement was the best for spall size estimation, and acceleration comes next. • IAS correlates well with spall size, albeit not a direct quantitative size. • AE was found poor in both quantification and tracking of natural spall size. Bearing prognostics is an important aspect in condition-based maintenance (CBM), and a key step to successful prognostic methods is the ability to quantify the fault severity of the bearing. Previous studies have resulted in some severity assessment methods based on certain types of signals, such as vibration, acoustic emission (AE) and instantaneous angular speed (IAS), however, their performances were not compared, especially in terms of their ability to track the severity of naturally growing spalls. In this paper, four measurement approaches were tested on the same rig for bearing run-to-failure experiments, and their signals were analysed individually and compared. It was found that IAS and radial load (a proxy for displacement) required less processing to provide a reliable assessment of bearing fault severity, acceleration required sophisticated techniques to extract spall-size estimates, whereas AE could not track fault evolution accurately. [ABSTRACT FROM AUTHOR]

• A Ne-liquefaction system cooled by a G-M cryocooler was developed and the refractive index and transmission of 940 nm infrared in liquid neon were also measured. • The neon gas was liquefied while the condenser chamber temperature was cooled down to 26.7 K and the production rate of liquid neon was 0.52 L/h. • The refractive index and transmittance of 940 nm infrared in liquid neon are 1.103 and 99.85%, respectively. A Ne-liquefaction system cooled by a G-M cryocooler was developed. The heat load and liquefied rate of the system were analyzed theoretically. The neon gas was liquefied over 340 min while the condenser chamber was cooled down to 26.7 K. The gas pressures of the heat exchanger inlet and condenser are directly proportional to its absolute temperature, which decreased with the reduction of cryostat system temperature. The pressure of the heat exchanger inlet decreased from 105 kPa to 100.4 kPa with the pressure of the condenser decreased from 101 kPa to 100.1 kPa. Neon gas with a purity of 99.999% was used in liquefaction and the mass flow is set to 0.173 g/s. The production rate of liquid neon is determined to be 0.52 L/h. The liquid neon was collected in a glass vacuum dewar with a transparent window, which allows to observe the liquid level and conduct the optical tests. The refractive index and transmittance of the 940 nm infrared in liquid neon are 1.103 and 99.85%, respectively. The parameters will provide a valuable database on infrared equipment with liquid neon as a cryogen. [ABSTRACT FROM AUTHOR]

• The sound welded joint was obtained with Ni interlayer for 316L/Cu dissimilar laser welding joint. • No welding defects and spherical particles were formed in the fusion zone. • The average tensile strength of dissimilar welded joint is 408 MPa at 77 K. To improve the quality of welded joints between copper and 316L stainless steel, laser welding with Ni interlayer was carried out. A sound welded joint was obtained and the microstructures as well as mechanical properties were investigated. Results indicate that no welding defects or spherical particles were formed in the fusion zone. The microstructures in the fusion zone were characterized as dendritic grains, and no macroscopic segregation was observed. The welded joint failed at copper base material with an average tensile strength of 408 MPa at 77 K, and ductile fracture mode with dimples on the fracture surface were presented. Moreover, the addition of Ni interlayer prevents formation of welding defects and spherical particles and improves mechanical properties of the joint. [ABSTRACT FROM AUTHOR]

• This paper proposes investigation of filament fracture of two types of Nb3Sn strands under different tensile strains by high energy X-ray. The influence of tensile strains on the filament fracture behavior was investigated and the results will be expected to provide reference for optimization of multifilamentary Nb3Sn strand, conductor and magnet design. Fracture of brittle filaments plays a crucial role in significant degradation of critical current density of multifilamentary Nb 3 Sn strand. Recent researches of distribution of filament factures mostly depend on photographic analysis with SEM or TEM. However, it is hard to obtain spatial distribution of filament fractures in the mulitifilamentary Nb 3 Sn strand. In addition, almost unavoidable filament fracture is introduced during the sample preparation procedure and it causes deviation of filament fracture distribution. X-ray microtomography is a non-invasive, non-destructive method, which allows determination and the discrimination of internal features without destructing the sample. It is widely used as a non-destructive test technology for its high penetrability and high resolution. This present work investigated filament fracture of two types of Nb 3 Sn strands under different tensile strains by high energy X-ray. The influence of tensile strain on the filament fracture behavior was investigated and the results will be expected to provide reference for optimization of multifilamentary Nb 3 Sn strand, conductor and magnet design. [ABSTRACT FROM AUTHOR]

• The duration of natural frequency perturbations is found informative of spall size. • The WVS is utilized to identify the cyclic behaviour of natural frequencies. • This approach overcomes the limitation of entry/exit-based methods for natural spalls. • The new approach is validated and compared with existing methods in three tests. Spalling caused by fatigue is the most common reason for rolling element bearing failure, and spall size can be a good indicator to predict the remaining useful life of the bearing. Previous studies reported that, in the acceleration signal, a low-frequency step response is caused by de-stressing or re-stressing of the rolling element during its entry into and exit from the spall zone, and a high-frequency impact response is often induced when the roller hits the trailing edge of the spall. The conventional spall size estimation methods thus attempt to capture these events (entry, impact, and exit) and use their time difference to estimate the spall size. But the limitation of these methods is that they were mostly built on artificial spalls and have proved scarcely effective in dealing with natural ones. A recent study investigated the effect of these events on bearing stiffness and reported that the stiffness of the bearing structure decreases when the rolling element traverses the spall zone. Inspired by the study, a novel approach is proposed in this paper, which utilises the duration of natural frequency perturbations (induced by stiffness variation) of the bearing structure to perform spall-size estimation. Compared to the existing methods, this approach investigates the instantaneous resonance frequency variation during the spall span instead of the signal events at the entry and exit points. This novel approach along with three other representative existing methods are tested on three experimental datasets: one obtained by an artificially induced spall and the other two by naturally extended spalls. The performance analysis results reveal that all the methods are effective for artificial spalls, but only the proposed approach is effective for naturally extended spalls. [ABSTRACT FROM AUTHOR]

• The internal 3D-view of two Nb 3 Sn strands were detected with a non-destructive way, high-resolution 3D X-ray micro tomography. • The Nb 3 Sn phase of WST strand has a poor crystallinity with high defect density and the filaments of OST strand were connected forming a large Nb 3 Sn bundle. • The higher J c of the OST strand than that of the WST is ensured not only by the overall Nb 3 Sn layers thickness, but also by smaller grain sizes and narrower zone of columnar grains. In the present work, microstructural and microchemical of Nb 3 Sn strands with the internal tin process produced by the Western Superconductor Technology co., Ltd (WST) and Oxford Instruments co., Ltd (OST) were analyzed. The internal 3D-view of two Nb 3 Sn strands were detected with a (sub-)micrometric resolution in a non-invasive, non-destructive way, i.e. high-resolution 3D X-ray micro tomography. The distribution of filaments and voids induced by the functional heat treatment of two strands were investigated. The elements distribution after heat reaction of two strands was investigated through elemental mapping by scanning electron microscope (SEM) and energy dispersive X-ray analysis. The filaments of the WST Nb 3 Sn strand distributed uniformly, whereas the filaments separated with clear copper boundary among filaments. However, the filaments of the OST Nb 3 Sn strand have serious overlap phenomenon and the copper isolation interface was not clear among filaments. In order to investigate the distinction of microstructure, the selected area electron diffraction was also performed by transmission electron microscopy (TEM) and the results indicated that obvious impurities were observed in the Nb 3 Sn phase of the WST strand compared to the OST strand. [ABSTRACT FROM AUTHOR]

• The 0.2% proof stress and ultimate tensile strength at 4.2 K for 35% pre-strained specimens increased respectively around 86% and 18% compared to those of the as-received material. • The elongation at fracture at both RT and 4.2 K decreased for the pre-strained 316LN SS compared to those of the as-received material. • The pre-strained 316LN SS fractured at 4.2 K exhibits a ductile fracture mode. In the present work, influences of room temperature tensile pre-strain on cryogenic tensile properties of 316LN austenitic stainless steel (SS) were investigated. The tensile properties of the 316LN SS with various tensile pre-straining amounts of 15%, 25% and 35% were measured at both room temperature (RT) and liquid helium temperature (4.2 K). Results indicated that both 0.2% proof strength (R p0.2) and ultimate tensile strength (R m) at both RT and 4.2 K of the pre-strained 316LN SS significantly increased compared to those of the as-received material. The R p0.2 and R m at 4.2 K for 35% pre-strained specimens increased around 86% and 18%, respectively, compared to those of the as-received material. However, the elongation at fracture (A) at both RT and 4.2 K decreased for the pre-strained 316LN SS compared to those of the as-received material. The fractured morphologies of the pre-strained 316LN SS were investigated by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Dimples in the surface fractured at both RT and 4.2 K of the as-received and pre-strained 316LN exhibited a ductile fracture mode. Moreover, fractographic results indicated that the pre-strain treatment considerably decreased the ductility at both RT and 4.2 K. TEM analyses revealed that pre-strain treatment at RT led to dislocation accumulation and stress-induced martensite phase occurred at 4.2 K, which interpreted the cryogenic tensile properties of the pre-strained 316LN SS. [ABSTRACT FROM AUTHOR]

Acute rejection is a major risk for renal transplant failure. During this adverse process, activated T cells are considered the main effectors. Recently, B and T lymphocyte attenuator (BTLA), a member of the CD28 family receptor, was reported to be a novel inhibitory regulator of T cell activation in heart and pancreatic allograft rejection. Due to the similarity of acute rejection pathways among different organs, we hypothesized that BTLA might play a role in acute rejection of kidney transplant. In renal transplant patients, we observed that BTLA expression was significantly decreased in peripheral CD3+ T lymphocytes of biopsy-proven acute rejection (BPAR) recipients compared with control patients with stable transplanted kidney functions. Remarkably, overexpression of BTLA in the rat model was found to significantly inhibit the process of acute rejection, regulate the postoperative immune status, and prolong allograft survival. BTLA overexpression significantly suppressed IL-2 and IFN-γ production and increased IL-4 and IL-10 production both in vivo and in vitro. Moreover, vital factors in T-cell signaling pathways, including mitogen-associated protein kinases (MAPK), nuclear factor-kappa B (NF-κB) and nuclear factor of activated T cells (NFAT), were also significantly repressed by BTLA overexpression. Therefore, BTLA can suppress acute rejection and regulate allogeneic responses of kidney transplant by regulating TCR downstream signals and inflammatory cytokines production to improve allografts outcomes. [ABSTRACT FROM AUTHOR]

In recent years, the rapid development of convolutional neural networks (CNNs) has significantly advanced the progress of intelligent fault diagnosis. Most currently-available CNN-based diagnostic models are built on the premise that the monitored machine operates under stable conditions. However, in real-world scenarios, rotary machinery usually operates at varying speeds, making the fault-related pulse features susceptible to noise oversaturation. To extract discriminative features from mechanical signals under non-stationary conditions, a global contextual feature aggregation network (GCFAN) is developed in this paper. To begin with, a global contextual module (GCM) is embedded in the CNN architecture to explore multimodal features. Then, a multiscale attention module (MSAM) is introduced to guide the model to focus on global and local discriminative information. Further, a multiscale feature enhancement module (MFEM) is established to enlarge the receptive field and eliminate useless features. Finally, the GCFAN architecture is constructed based on these improvements. To achieve favourable diagnostic results under fluctuating variable speed conditions, we apply the label smoothing algorithm and the AMSGrad algorithm to assist the training of the model. Two case studies using the benchmark variable speed bearing dataset and the HF-MS variable speed gearbox dataset were carried out to test the practicality of the developed approach. Experimental results demonstrated that the developed GCFAN performs better than seven state-of-the-art approaches. [ABSTRACT FROM AUTHOR]

• An emissivity measurement system based on radiometric method was designed and built. • The radiation power signal received by detector can be switched by a stepping motor. • The emissivity of the blackbody coating (Nextel 811–21), 304 stainless steel and G10 were measured and discussed. Thermal radiation is a major part of heat transfer in cryogenic systems, especially in vacuum environment. The emissivity of materials is an essential factor of thermal radiation, which is difficult to be precisely predicted by theoretical calculation. Thus, the direct experimental measurement becomes an inevitable, reliable method. In this paper, a preliminary emissivity measurement system using the direct radiometric method was designed and built with a G-M (Gifford-McMahon) cryocooler as the cold source. The sample plate in the apparatus can be cooled to 9.2 K, while the sample thermal radiation shield and the optical path cover can respectively reach 46.7 K and 46.9 K. At present stage, MCT (HgCdTe) detector with an effective bandwidth 2–12 μm was used in this system, which achieved the measurements of emissivities of coating Nextel 811–21, 304 stainless steel and G10 composite from 240 K to 300 K. The reliability of the system was verified by comparing the measurement results with the data already published, and the dependence of the emissivities of these materials on temperature are analyzed. [ABSTRACT FROM AUTHOR]

• Mechanical properties of superconducting magnet insulation materials after reheat. • Strain responses during second Vacuum Pressure Impregnation process. • Monitoring by Fiber Bragg Grating sensors embedded in the insulation layers. • Additional strain introduced by the new added epoxy resin. In large-scale, high-field superconducting magnets used for magnetic confinement fusion, high energy accelerators, and magnetic resonance imaging, the insulating system made from glass fiber reinforced resin-based composites is the key component, which mainly plays the role of mechanical support, fixing and protecting superconducting conductors, as well as electrical insulation. Vacuum Pressure Impregnation (VPI) approach is widely used in the manufacturing of the insulation system. The second curing cycle is generally required after the first VPI and curing process. For example, after the superconducting coil is cured in the mold, the de-molding process requires the superconducting coil to be reheated according the curing temperature. Moreover, for large-scale superconducting magnets, the superconducting coil needs to undergo a second VPI process after the first VPI process to fix the coil in the coil case. In this work, the tensile and shear properties of pure epoxy resin and the glass fiber reinforced resin-based composite, were investigated at both room and cryogenic temperatures and the effect of the second curing cycle on the mechanical properties was analyzed. Additionally, the strain evolution of the Nb-Ti superconducting coil during the second curing cycle was measured using the Fiber Bragg Grating (FBG) sensors embedded in the composite. The results indicate that the second curing cycle will not introduce additional strain to the previously cured resin matrix, but the defective or weak parts of the resin matrix may be affected by the new added epoxy resin and a little extra strain has been observed. [ABSTRACT FROM AUTHOR]

Background: Nowadays, renal allograft survival is confined by the development of allograft fibrosis. Previous studies have reported interleukin-33 (IL-33) upregulated significantly in patients with chronic renal allograft dysfunction, and it could induce renal tubular epithelial to mesenchymal transition (EMT), which eventually contributed to renal allograft fibrosis. Our study intended to detect the underlying association between single nucleotide polymorphisms (SNPs) of IL-33 gene and renal allograft fibrosis in kidney transplant recipients.Methods: We collected blood samples from 200 renal transplant recipients for the identification of SNPs and transplanted kidney tissue samples for identifying differentially expressed genes (DEGs). Intersection of SNP-related genes and DEGs was conducted for further analysis. Relationships between these SNPs and renal allograft fibrosis were evaluated by the inheritance models. Immunohistochemical (IHC) staining and western blotting (WB) were used to detect the expression of IL-33 and the markers of EMT in human kidney tissues obtained from control and chronic renal allograft dysfunction (CAD) patients. In vitro, we detected the progressions of EMT-related markers and the levels of MAPK signaling pathway mediators after transfecting IL-33 mutant plasmids in HK2 cells.Results: Three intersected genes including IL-33 genes were significantly expressed. IL-33 expression was validated in kidney tissues by IHC and WB. Thirty-nine IL-33-related SNPs were identified in targeted sequencing, in which 26 tagger SNPs were found by linkage disequilibrium analysis for further analysis. General linear models indicated sirolimus administration significantly influenced renal allograft fibrosis (P < 0.05), adjustment of which was conducted in the following analysis. By multiple inheritance model analyses, SNP rs10975519 of IL-33 gene was found closely related to renal allograft fibrosis (P < 0.005). Furthermore, HK2 cells transfected with mutated plasmid of rs10975519 showed stronger mobility and migration ability. Moreover, IL-33 mutant plasmids could promote the IL-33-induced EMT through the sustained activation of p38 MAPK signaling pathway in HK2 cells.Conclusion: In our study, rs10975519 on the IL-33 gene was found to be statistically associated with the development of renal allograft fibrosis in kidney transplant recipients. This process may be related to the IL-33-induced EMT and sustained activation of p38 MAPK signaling pathway. [ABSTRACT FROM AUTHOR]

To resist large electromagnetic loads, the ITER correction coils (CCs) are protected by a 20-mm thickness 316LN austenitic stainless steel case. Due to the strict tolerance requirement of the case manufacture, tungsten inert gas (TIG) welding technology was used for subcase assembly welding, whereas laser beam welding (LBW) technology was applied to enclosure welding of the cases. The case shall be operated at 4.2 K and shall undergo considerably cyclic stress due to magnet electromagnetization as well as interaction with the toroidal field (TF) and poloidal field (PF). This article focuses on the assessment of the mechanical properties of the welding joints at cryogenic temperature. Results indicated that the values of the ultimate tensile strength of the TIG welding joint and the LBW welding joint were 1555 and 1522 MPa, respectively, which reach to 99.7 and 97.6% of that of the base material (BM). The elongation at the fracture of both the TIG and LBW weldments was larger than 35%. The plane strain fracture toughness KIc(J) of the TIG and the LBW weldments was 210 and 241 MPa·m1/2, respectively. The fractographic analysis indicated that the fracture surface was composed of fine equiaxed dimples, which indicated that both welding joints fractured in a ductile manner. The welding joints survived the minimum of 30 000 cycles fatigue test at stress level and load ratio specified by the ITER document. In addition, the fatigue crack growth rates of both welding joints were lower than that of the BM. All mechanical properties of both the welding joints satisfied the ITER specifications. [ABSTRACT FROM AUTHOR]

• A model coupling shaft torsional vibration and advanced injection angle is built to predict engine block vibration. • Formulas of block vibration excitation forces are analyzed and derived by taking in to account the coupling model. • An optimization method for block vibration mitigation by adjusting advanced injection angle is proved. Engine body vibration is an important safety concern for diesel engines as it can lead to severe engine damages and even catastrophic failures. Traditional methods for excitation computation assume that the rotational speed and the cylinder pressure remain stable under each working cycle, which makes it impossible to precisely predict vibration peaks at certain frequencies. But in practice, the existence of shafting torsional vibration will lead to the fluctuation of rotational speed and cylinder pressure. To predict engine block vibration more accurately, this paper proposes a novel method considering the instantaneous variations in rotational speed and cylinder pressure. It is implemented by two steps. Firstly, an innovative model considering the coupling effect between shaft torsional vibration and advanced injection angle is proposed, it particularly explains how the cylinder pressure and instantaneous rotational speed vary due to the coupling effects. Secondly, the excitation forces that cause block vibration are analyzed and their computational formulas are improved. This method also considers the offset of excitation loading position caused by torsional vibration. The coupling model is experimentally verified and the excitations are loaded into a finite element model of the diesel engine for vibration response prediction. The results reveal that the coupled model can predict vibration peaks at sideband frequencies and thus makes the frequency spectrum much richer than that of the traditional method. Furthermore, it shows that the acceleration results obtained by the coupled model have better prediction accuracy than those obtained from traditional methods, with the deviation percentage reducing from 6.31% and 8.41% to 0.64% and 0.32% in the X and Z direction. It indicates that the coupled model is more reliable in predicting the vibration response of the engine block. Finally, the effect of advanced injection angle on engine block vibration is investigated and the optimal value of the advanced injection angle is determined to be 29 CA, which makes the engine block vibration reduced by 3.60%, 2.72%, and 3.16% in the X, Y, and Z direction comparing to the original advanced injection angle. Overall, this study presents an improved approach for predicting engine block vibrations and offers valuable insights for the design of shafting structures and fuel injection parameters in marine diesel engines. [ABSTRACT FROM AUTHOR]

• Fatigue crack propagation behavior of 316LN tungsten inert gas (TIG) weldment and weldment with post weld heat treatment (PWHT) was investigated at liquid helium temperature. • Weldment with PWHT results in the highest fatigue crack propagation resistance, whereas the base material demonstrates the lowest fatigue crack propagation resistance. • The crack featured with a transgranular propagation characteristics for the base material, the weldments without and with PWHT. • More amount of strain-induced martensite near the crack tip in the base material compared to in the as-welded weldment and in the weldment with PWHT. • The strain-induced martensite transformation plays a crucial role in determining the fatigue crack propagation behavior at cryogenic temperature. In the present work, fatigue crack propagation behavior of 316LN tungsten inert gas (TIG) weldment and weldment with post weld heat treatment (PWHT) was investigated at liquid helium temperature. Results indicates that the weldment with PWHT results in the highest fatigue crack propagation resistance, whereas the base material demonstrates the lowest fatigue crack propagation resistance. Microstructure evolution reveals that the fatigue crack propagation is characterized as transgranular fracture for the base material as well as the as-welded weldments and the weldment with PWHT. Moreover, the crack propagation path of the weldments shows a zigzag crack extension, especially for the weldment with PWHT, whereas the crack extension of the base material is relative straight. Electron backscattered diffraction reveals more amount of strain-induced martensite near the crack tip in the base material compared to in the as-welded weldment and in the weldment with PWHT, which is considered to be a crucial factor in the fatigue crack propagation behavior at cryogenic temperature. [ABSTRACT FROM AUTHOR]

• The tree structures, inception probability, growth rates at 77 K were studied. • The Raman spectra of the degradation products within the tree channels at room temperature and 77 K were analyzed. • The effects of oxygen and graphitic carbon on the tree characteristics of epoxy resin were analyzed. The insulation structure which is mainly composed of epoxy resin is a key part of the superconducting magnet system. Due to the special operating environments, superconducting coils must address the challenges of cryogenic liquids and various kinds of high voltages. In this paper, the electrical tree characteristics of epoxy resin at 77 K were investigated. An experimental setup with a partial discharge (PD) device and a cryostat filled with liquid nitrogen (LN 2) was set up. Optical microscopy and confocal Raman spectrometer were applied to investigate the accumulation of degradation products within the tree channels. Each group of samples was tested at a range of AC voltages (50 Hz) from 8 kV rms (root mean square) to 20 kV rms and the PD experiments were carried out at both room temperature and 77 K. The results indicated that the color of electrical trees was darker and the tree structures were more complicated at 77 K compared with those at room temperature. The weak reaction between oxygen and the degradation products within the tree channels was responsible for the darker tree channels at 77 K. The density of electrical trees increased and the damage to materials caused by electrical trees was more serious at 77 K. Meanwhile, the tree inception probability decreased and the tree growth was inhibited obviously at 77 K. It's also revealed that the degradation products within the tree channels were confirmed to be graphitic carbon based on the corresponding Raman spectra. The size of graphitic domains within the tree channels at 77 K was more than 2 times of that at room temperature, which contributed to the tree growth acceleration in the later growth stage at 77 K. [ABSTRACT FROM AUTHOR]

In the present work, a cryogenic mechanical property testing system conduction-cooled by two G-M cryocoolers was developed. The testing sample can be cooled from room temperature to 2.7 K within 7.5 h. The sample was first cooled down to 11.1 K directly by the two G-M cryocoolers and then cooled down to 2.7 K by decompressing the chamber. Instead of liquid helium, the cooling process is characterized by cooling with recycled helium gas as heat transfer medium. The heat load of the system was analyzed and optimizations were adopted in terms of material selections and design. The static load capacity of the system reaches 200 kN and the fatigue load capacity can reach 50 kN. This system can be installed onto an electronic universal testing machine or a fatigue testing machine to characterize static tension, fracture mechanics or fatigue properties at tunable low temperatures. Tensile properties of 316L austenitic stainless steels at 4.2 K were tested with the system and the results were compared with those obtained by cooled using liquid helium, which demonstrates high reliability. [ABSTRACT FROM AUTHOR]

• Mechanical properties of 316LN stainless steel with cryogenic pre-strain were studied at different temperatures (RT, 77 K and 4.2 K). • The pre-strained samples stretched at cryogenic temperature obtain higher mechanical strength. • The samples stretched at 77 K possess higher elongation and hardness than RT and 4.2 K, the mechanism was explained. • The results are attributed to the changes in dislocation density and martensite transformation due to temperature and cryogenic pre-strain. The 316LN stainless steel (SS) used for TF conduits in the ITER must undergo a series of pre-deformation during the fabrication. In order to investigate the variation of mechanical properties of 316LN SS with different temperature and cryogenic pre-strain, the cryogenic pre-strained samples with 0%, 15%, 25%, and 35% pre-strain were prepared and stretched at room temperature (RT), 77 K and 4.2 K, respectively. The yield strength (YS), ultimate tensile strength (UTS), elongation and microhardness of the samples were measured. Besides, the Scanning Electronic Microscopy (SEM) and Transmission Electronic Microscopy (TEM) were applied to observe the microstructure of 316LN SS. The magnetic measurements for the samples were carried out to investigate the volume percent of phase transformation. The results indicate that the YS, UTS and microhardness of 316LN SS are improved by means of cryogenic pre-strain and the decrease of elongation of pre-strained samples is different at different temperatures. All 316LN samples show the ductile fracture. The dislocation of samples promotes by cryogenic pre-strain and hinders by cryogenic temperatures. The martensitic transformation occurs after all pre-strained samples were stretched. The volume percent of α' martensite is minimal at RT and increases dramatically at cryogenic temperatures (77 K and 4.2 K). The combination of dislocation density and martensitic transformation results in changes in the 316LN SS mechanical properties. [ABSTRACT FROM AUTHOR]

• A cryogenic system for measuring electrical properties of insulation materials has been established. • The thermal switch in the cryostat shortens the time of precooling and saves a lot of helium gas. • Two modes in the cryogenic system: 4.2 K mode and 1.65 K mode. • The cryogenic system realizes the coupling of low temperature and high voltage. A cryogenic system has been established to measure electrical properties of insulation materials. The cryostat in the system contains two operating modes: 4.2 K and 1.65 K. A G-M cryocooler is used as cold source in these two modes. In 4.2 K mode, samples were directly cooled by the copper plates connected to the second stage of the cryocooler. In the 1.65 K mode, the helium gas is liquefied. The superfluid 4He (He-Ⅱ) of 1.65 K was obtained by throttling and depressurizing the liquid 4He (He-Ⅰ). The thermal switch in the 1.65 K mode can reduce the precooling time by 11.6 h and saved 22.5 L of helium. The transforming of the two modes is controlled by four threaded rods which are connected to the first and the second stage flange. The electrical test unit is designed, including the breakdown strength test and the flashover characteristics test with the voltage from 0 to 100 kV, which realizes the coupling of low temperature and high voltage. [ABSTRACT FROM AUTHOR]

• The system can quantitatively detect internal and external leakage within a wide range of operating temperatures (20–300 K). • This system using the GM cryocooler instead of cryogen is a benefit for its low operating cost, simple structure, and safe handling. • Five sample valves can be cooled simultaneously and tested in sequence to improve efficiency. • The helium mass spectrometry leak detector was used for its sensitive response and high precision. • The external leakage of the sample valves was detected at LH 2 temperature for the first time. Sealing performance under cryogenic temperatures should be a consideration in the development of a cryogenic valve for use in cryogenic engineering. In the present work, a cryogen-free leak detection system at 20 K to conduct leakage testing of cryogenic valves was developed. The experimental system was composed of a cooling system, a leak detection system, and a PLC (Programmable Logic Controller) system. Compared with the traditional cryogenic leak detection systems, this system using the GM cryocooler instead of cryogen is beneficial for the application for its low operating cost, simple structure, and safe handling. Five valves can be installed simultaneously and tested in sequence. The helium mass spectrometer leak detector is used for its sensitive response and high precision. The reliability of this system was verified by testing the leak rate of the system itself. Three high-pressure cryogenic solenoid valves were tested using helium gas under the pressure varied from approximately 2.5 bar to 80 bar and at both room temperature (300 K) and liquid hydrogen temperature (20 K). The tested valves can be cooled from room temperature to 18 K within 6 h. The test results of the internal leakage rate and the external leakage rate of the samples were discussed. This system will aid in the inspection of many critical cryogenic components such as liquid oxygen and liquid hydrogen valve assemblies for which leakage may lead to serious consequences. [ABSTRACT FROM AUTHOR]

• The epoxy resin has a low viscosity and long pot life. • At 77 K, the epoxy resin offers high tensile strength and modulus. • The superconducting magnet exhibits high shear and compressive strength at 77 K. Superconducting magnet is a key component in magnetic resonance imaging (MRI). In general, vacuum pressure impregnation (VPI) technology is used for insulating system of the superconducting magnet. Performance of the superconducting magnets is affected by the adhesion strength between superconducting wires and resins at cryogenic temperature. In this study, experimental superconducting coil was prepared by modified bisphenol-A type epoxy resin and the VPI technology. Tensile, shear, and compressive properties of the samples cut from the superconducting coil were measured at both room temperature (RT) and liquid nitrogen temperature (77 K), and the bonding properties between the superconducting wire and the resin were discussed. The results show that the resin exhibits low viscosity, long pot life and higher mechanical strength, and it is suitable for impregnating superconducting magnets by VPI technology. Moreover, the shear and compressive strength of the impregnated superconducting magnet at 77 K are significantly higher than that at room temperature, with the increase of 132% in radial compressive strength, 170% in axial compressive strength, 63% in radial shear strength and 70% in axial shear strength, respectively. This study provides references for the design of insulation for superconducting magnet system and the manufacture of insulating materials for MRI superconducting magnets. [ABSTRACT FROM AUTHOR]

The present work describes the monitoring system of the real-time strain response on the curing process of epoxy resin from the initial point of curing to the end, and the change in strain during temperature changes. A simple mould was designed to embed the strain gauge, thermometer, and quartz standard sample into the epoxy resin, so that the strain and the temperature were simultaneously measured and recorded. A cryogenic-grade epoxy resin was tested and the Differential Scanning Calorimetry (DSC) was used to analyse the curing process. Based on the DSC results, three curing processes were adopted to investigate their influence on strain response as well as residual strain of the epoxy resin. Moreover, impact strength of the epoxy resin with various curing temperatures were tested and the results indicate that the curing plays a crucial role on the mechanical properties. The method will find cryogenic application of epoxy adhesives and epoxy resin based composites to monitor the strain during the curing process as well as the cryogenic service. [ABSTRACT FROM AUTHOR]

Solid organ transplantation is a lifesaving therapy for patients with end-organ disease. Current immunosuppression protocols are not designed to target antigen-specific alloimmunity and are uncapable of preventing chronic allograft injury. As myeloid-derived suppressor cells (MDSCs) are potent immunoregulatory cells, we tested whether donor-derived MDSCs can protect heart transplant allografts in an antigen-specific manner. C57BL/6 (H2Kb, I-Ab) recipients pre-treated with BALB/c MDSCs were transplanted with either donor-type (BALB/c, H2Kd, I-Ad) or third-party (C3H, H2Kk, I-Ak) cardiac grafts. Spleens and allografts from C57BL/6 recipients were harvested for immune phenotyping, transcriptomic profiling and functional assays. Single injection of donor-derived MDSCs significantly prolonged the fully MHC mismatched allogeneic cardiac graft survival in a donor-specific fashion. Transcriptomic analysis of allografts harvested from donor-derived MDSCs treated recipients showed down-regulated proinflammatory cytokines. Immune phenotyping showed that the donor MDSCs administration suppressed effector T cells in recipients. Interestingly, significant increase in recipient endogenous CD11b+Gr1+ MDSC population was observed in the group treated with donor-derived MDSCs compared to the control groups. Depletion of this endogenous MDSCs with anti-Gr1 antibody reversed donor MDSCs-mediated allograft protection. Furthermore, we observed that the allogeneic mixed lymphocytes reaction was suppressed in the presence of CD11b+Gr1+ MDSCs in a donor-specific manner. Donor-derived MDSCs prolong cardiac allograft survival in a donor-specific manner via induction of recipient's endogenous MDSCs. [ABSTRACT FROM AUTHOR]

Laser welding of modified 316LN steel with a thickness of 20 mm was conducted using a YLS-20000 fiber laser. The microstructure of the weld joint was characterized and tensile and fracture toughness tests were carried out. The microstructure evolution of the fracture specimens was studied systematically to elucidate the fracture mechanism. The weld was composed of the single austenite phase and was characterized by cellular and columnar grains, and the grain size became coarser with a weak orientation. The R m values of the laser welded joints were almost equal to that of the base metal both at RT and 4.2 K, and the fracture surfaces were featured by ductile fracture with quantities of dimples and microvoids. The fracture toughness of the weldments decreased to ˜84% of that of the parent metal at 4.2 K. Enhancement of the fracture toughness was attributed predominantly to the presence of twins and to the fine grain size, and the reduction was caused by the partially stress-induced phase transformation of the austenite to martensite. The synergistic effects of these factors result in a favorable improvement in the fracture toughness of the weldment. [ABSTRACT FROM AUTHOR]