Tests were performed on mechanical property and microstructure of joints on cold-formed high frequency induction welded (HFIW) pipes. The welding surface energy (WSE) is proposed to evaluate the combined effect of technological parameters including the welding speed, input power and wall-thickness. The optimum production technology was obtained. The Widmanstätten microstructure and coarse grains were observed in the overheated zone. The width of the heat-affected zone (HAZ) is proportional to the WSE. With increase of the WSE, the reversed V-shape was formed by the mean bend angle. The optimum WSE decreases with decreasing the opening angle. Rather than the standard tensile test, the cold-bending test is suitable for evaluating effect of technology on quality of joints on cold-formed HFIW pipe.
By using Gleeble1500-D thermal simulation machine, Rare Earth(RE) adding Q345B steel of single-pass compression test were carried out. A study had been made of the effect of different deformed conditions in hot rolling process on Nd-modified Q345B steel recrystallization behavior and microstructure evolution.The result shows that RE steel Q345B of single compression test are consistent with the general experimental rule. Rare Earth additions significantly increased hot- deformed resistance at low temperature compression, however, it is not obvious at high temperature. The increased hot-deformed resistance and the degree of the retardation is more obvious for heavy RE Tb than light RE Nd.
A series single-pass compression tests of HRB400 slab under the circumstances of different deformation temperature and deformation rate are carried out with Gleeble-1500D thermal simulation testing machine. The experimental results shows as follows. The true stress-true strain curves of the compression process are got from the tests. The state activation energy is 353.542kJ/mol and a mathematical model of high-temperature rheological stress is established. The calculated results by the rheological model are consistent with the experiments.
Cage roll-forming is an advanced roll-forming technique widely used in high frequency welding (HFW) pipes production. However, to the authors' knowledge, the real cage roll-forming production is mainly on experience rather than science. Few publications can be found on cage roll-forming for its complexity. In order to improve the understanding of the technique, a large deformation elastic-plastic finite element model for the HFW660 cage roll-forming mill was established and simulated through adopting the dynamic explicit algorithm. The distribution of effective plastic strain and the deformed geometry of the strip at the pre-forming and linear section were obtained. The simulation results were validated with the measurements. The results show that the biggest effective plastic strain (EPS) occurs at the center of strip. The distribution of EPS is far from uniform on the cross-section of the strip. This may owe to the uneven distribution of down-hill amount.
Introduction: The aim of this study was to explore the association between thyroid hormones and abdominal fat quantities in euthyroid post-menopausal women. Material and methods: Serum levels of thyroid stimulating hormone (TSH), free triiodothyronine (fT3), and free thyroxine (fT4) as well as body mass index (BMI) and waist circumference (WC) were collected from 540 euthyroid post menopausal women aged 45–65 years. Magnetic resonance imaging (MRI) was performed to measure visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) area. Multivariate linear regression analysis was used to determine whether abdominal fat was associated with thyroid hormones. Results: Weight, BMI, WC, fasting plasma glucose (FPG), fasting insulin (Fins), homeostasis model assessment of insulin resistance (HOMA-IR), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), TSH, and fT4 were higher in the obese group than in the nonobese group (p < 0.05). The study participants were divided into four groups according to quartiles in the light of TSH reference range (0.1–4.2 mU/L). Subcutaneous adipose tissue and VAT increased with the TSH levels. Adjusted for age, years since menopause (YSM), BMI, and HOMA-IR, VAT was negatively correlated with fT4 and positively correlated with fT3 and fT3-to-fT4 ratio (fT3/fT4) (p < 0.05), while no association was found between SAT and thyroid hormones. Similarly, we found no relation between body fat distribution and TSH. Furthermore, the association of common indicators of obesity and thyroid hormones showed no significance. Conclusions: In euthyroid post-menopausal women, VAT rather than SAT was negatively correlated with fT4, and positively correlated with fT3 and fT3/fT4.
In order to investigate section capacities of thick‐wall cold formed steel with square and rectangular hollow cross‐sections, experiments were carried out on mechanical properties of the flat coupons, corner coupons, parent steel coupons and full section stub columns. Strain hardening of cold forming thick‐wall cold formed sections was investigated. The stub column test strengths were compared with the design compressive strengths specified by the Australian/New Zealand and Chinese standards for the design of the cold formed steel structural members respectively. It has been shown that the strength predicted by the Australian/New Zealand standard using material properties and that forecasted by the Chinese standard based on the average design yield stress of the full section are a little conservative. The two mean strengths predicted by Australian/New Zealand standard based on the mean design yield stress and forecasted by the Chinese standard using material properties tests are identical, which are superior to the present thick‐wall cold formed steel tubes because of their safety and economy.
Three types of specimens (defect-free, with porosity defects, and with slag inclusions) were prepared via manual arc welding of Q355 steel. The effects of welding defects on the dynamic corrosion of ship pipeline systems under different conditions were revealed through macroscopic morphology, surface roughness test, atomic absorption spectroscopy test, microscopic morphology, and x-ray diffractometer detection of corrosion products. As the Cl− concentration increased, the color of the rust layer around the weld darkened, and uneven protrusions accumulated. The corrosion products are γ-FeOOH, α-FeOOH, and Fe3O4. Welding defects enhance the stratification of the rust layer and lead to more serious corrosion. Both the weld zone (WZ) and the heat-affected zone (HAZ) started from the corrosion pit and expanded, ultimately reaching into the flake corrosion zone. The degree of corrosion in the WZ was more severe than in the HAZ. The degrees of corrosion in the WZ and the HAZ of the sample with porosity defects were higher than those of the sample with slag inclusions, and the sample without defects exhibited the least corrosion.
In this work, we implemented a short-reach real-time optical communication system using MLP for pre-distortion. Lookup table (LUT) algorithms are commonly employed for pre-distortion in intensity modulation and direct detection (IM/DD) systems. However, storage limitations typically restrict the LUT pattern length to 9, limiting its effectiveness in compensating for nonlinear effects. A multilayer perceptron (MLP) can overcome this limitation by predicting errors and generating pre-distorted signals, thus replacing the extensive storage requirements of LUTs with minimal computational resources. The MLP-based digital pre-distortion (MLP-DPD) technique enables the creation of long-pattern LUTs for improved nonlinear compensation. In this work, an MLP-DPD scheme was implemented on a field-programmable gate array (FPGA). The FPGA was used to generate a 14.7456 GBaud pre-distorted pulse amplitude modulation 4-level (PAM4) signal. This signal was then transmitted over 20 km of standard single-mode fiber (SSMF). At the receiver, the parallel constant modulus algorithm (PCMA) was applied for signal processing. The bit error rate (BER) achieved met the 2.4 × 10
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