The impact of land use on eco-environment in the Dianchi Basin.

(1) Studying the dynamic correlation between land use and the eco-environment in the Dianchi Basin is important for improving the basin's spatial layout and enhancing ecological development and conservation; (2) Through dynamic analysis and comprehensive evaluation of land use, the introduction of ecological and environmental quality index, and the use of FLUS models, the impacts on eco-environments in the Dianchi Basin for the recent 20 years were analyzed; (3) The past two decades witnessed a constant increase in the construction land in the Dianchi Basin and a decline in the farmland at an average annual rate of 0.93 %; The utilization level of land in the Dianchi Basin presented a negative correlation with the quality of the area's eco-environment, which reduces first and then increases; When natural production becomes a priority, both the construction land and farmland have witnessed growth. However, when ecological protection becomes a priority, it is projected that by 2035, the Dianchi Basin will achieve its highest eco-environmental quality index; (4) Studying how the change of land use types affects eco-environment is crucial for optimizing the current allocation of land resources and promoting sustainable development in the basin.

Evaluating and diagnosing ecosystem health of the "three-lake" watershed in Yuxi, Yunnan, China from 2010 to 2020 by PSR-KDE.

To carry out the diagnosis and evaluation of the ecosystem health in Yuxi three-lake watershed, this paper presents the changing trend of its health state, and predicts the future development. This also provides ideas for maintaining the regional ecosystem health, and then gradually improves the ecological environment quality. Taking Fuxian Lake, Qilu Lake and Xingyun Lake (the three-lake watershed) in Yuxi City, Yunnan Province, Southwest China as the research object, a model combining pressure-state-response and kernel density estimation (PSR-KDE) adopts to diagnose and evaluate the ecosystem health of the "three lake" watershed from 2010 to 2020, and the distribution map of ecosystem health index has obtained by the evaluation indexes integration based on GIS spatial analysis. Hence, the evaluation results have visualized on the map. The results show that: The distribution of ecosystem health index in the study area was 0.1530-0.7045 in 2010, 0.2056-0.7512 in 2015, and 0.2248-0.7662 in 2020. 0.12% was in the pathological area in 2010. After 2015, the pathological condition of ecosystem health has completely solved, and the proportion of unhealthy ecosystems was 11.95% in 2010, 7.38% in 2015, and 5.97% in 2020. The ecosystem health index of the study region was 0.5523 in 2010, 0.5807 in 2015, and 0.5815 in 2020, it indicates that the ecosystem was in a sub-health state. From 2010 to 2020, the ecosystem health around Qilu Lake was the most worrying, followed by the northwest of Fuxian Lake and the northern and southern regions of Xingyun Lake. The ecosystem health of the three-lake watershed showed significant improvement from 2010 to 2020. The study ecosystem health assessment and early warning in the three-lake watershed is significant to the ecological environment protection and management of the plateau lake basin, the restoration of the territorial space ecology and the economic development of the surrounding area.

An efficient molten steel slag gas quenching process: Integrating carbon solidification and waste heat recovery.

The iron and steel-making industries have garnered significant attention in research related to low-carbon transitions and the reuse of steel slag. This industry is known for its high carbon emissions and the substantial amount of steel slag it generates. To address these challenges, a waste heat recovery process route has been developed for molten steel slag, which integrates CO2 capture and fixation as well as efficient utilization of steel slag. This process involves the use of lime kiln flue gas from the steel plant as the gas quenching agent, thereby mitigating carbon emissions and facilitating carbonation conversion of steel slag while simultaneously recovering waste heat. The established carbonation model of steel slag reveals that the insufficient diffusion of CO2 gas molecules within the product layer is the underlying mechanism hindering the carbonation performance of steel slag. This finding forms the basis for enhancing the carbonation performance of steel slag. The results of Aspen Plus simulation indicate that 1 t of steel slag (with a carbonation conversion rate of 15.169 %) can fix 55.19 kg of CO2, process 6.08 kmol of flue gas (with a carbon capture rate of 92.733 %), and recover 2.04 GJ of heat, 0.43 GJ of exergy, and 0.68 MWh of operating cost. These findings contribute to the development of sustainable and efficient solutions for steel slag management, with potential applications in the steel production industry and other relevant fields.

Optimization of thermal deformation process parameters of 2219 Al matrix composites.

To investigate the deformation behavior and optimize the hot processing parameters for 2219 aluminum matrix composite, the constitutive equation and hot processing maps were established. Initially, hot compression experiments on 2219 aluminum alloy (2219A) were conducted using a Gleeble-3500 thermal simulation tester to obtain high-temperature rheological data. The deformation temperatures tested were 573, 623, 673, 723, and 773 K, with strain rates of 0.01, 0.1, 1, and 10 s-1, and a maximum deformation of 60 %. Subsequently, material parameters such as the activation energy, Zener-Hollomon parameter, power dissipation efficiency, and instability coefficient for 2219A were calculated. Analytical expressions for these material and deformation parameters were formulated, and a hot processing map for 2219A was constructed. The hot processing map, along with the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and the Entropy Weight Method (EWM), were used to optimize the thermal deformation process parameters. The stability processing area and the optimal processing area identified by both methods were largely consistent. According to the hot processing map, the stability processing areas were identified in the temperature ranges of 580-660 K and 690-773 K with strain rates of 0.01 s-1 and 0.01-0.6 s-1, respectively. Using the TOPSIS and EWM methods, the stability processing areas were defined between 573 and 640 K and 0.01 s-1, 640-690 K and 0.01-0.1 s-1, and 690-773 K and 0.01-1 s-1. The consistency and accuracy of these optimization results were confirmed through microstructure analysis.

Knowledge, attitude, and practice of healthcare providers on chronic refractory cough: A cross-sectional study.

Objective: Previous studies from outside China showed that the knowledge, attitudes, and practice (KAP) of chronic refractory cough (CRC) was moderate among physicians. This study examined the KAP toward CRC in Chinese healthcare providers. Methods: This single-center cross-sectional study was conducted at The Sixth Affiliated Hospital of Nantong University, Yancheng Third People's Hospital, from July 2022 to January 2023 and enrolled healthcare providers. The demographic characteristics and KAP scores were collected using a questionnaire (Cronbach's α = 0.934) developed based on CRC guidelines. Results: The study included 539 healthcare providers. The mean knowledge score was 8.27 ± 2.37 (maximum of 14, 59.07%), indicating poor knowledge. The highest rates of inaccuracies pertained to knowledge about the definition of chronic cough, empirical treatment methods, and potential risks of different treatments, suggesting a need for unified training in all aspects of CRC for medical staff. The mean attitude score was 49.74 ± 63.63 (maximum of 60, 82.90%), indicating favorable attitudes. Most healthcare providers believed that CRC affects normal work and life and that it would be necessary to provide more help to patients from the perspectives of drug treatment and psychological counseling. The mean practice score was 23.20 ± 6.28 (maximum of 35, 66.29%), indicating poor practice. Conclusion: This study suggests that healthcare providers in Yancheng have poor knowledge, favorable attitudes, and poor practice of CRC. This study provides points that should be targeted in future training and continuing education activities.

Research on the Hot Deformation Process of A100 Steel Based on High-Temperature Rheological Behavior and Microstructure.

To obtain the optimal hot deformation process, the rheological and dynamic recrystallization behaviors of A100 steel were researched through isothermal compression tests. Firstly, a Hensel-Spittel constitutive model was established based on the stress-strain curves. Secondly, dynamic recrystallization percentage and grain size models were established to identify the necessary conditions for complete dynamic recrystallization. Finally, microstructural analysis was employed to validate the accuracy of the recrystallization model. The results indicate that the flow stress is highly sensitive to both the strain rate and the temperature, and the HS model demonstrates a high predictive accuracy, with a correlation coefficient of 0.9914. There exists a contradictory relationship between decreasing the average grain size and increasing the recrystallization percentage. The higher the percentage of dynamic recrystallization, the larger the average grain size tends to be. This situation should be avoided when devising the actual processing procedures. The optimal hot working processes for achieving complete dynamic recrystallization and a smaller average grain size are as follows: a strain equal to or greater than 0.6, a temperature between 1193 and 1353 K, and a strain rate between 0.1 and 1 s-1.

Coexistence of superconductivity and charge density wave instability in A15-Nb3Sn.

A15-type compound Nb3Sn has attracted much attention due to its relatively high critical temperature and critical field of superconductivity, making it a leading material for superconducting applications. In this study, we investigate the structural instability and superconductivity of Nb3Sn under hydrostatic pressure using first-principles calculations. We determine the electronic properties, phonon dispersion, electron-phonon coupling and the superconducting gap for Nb3Sn at pressures ranging from ambient to 9 GPa. Our results show that a significant electron density is present near the Fermi level due to the van Hove singularity, indicating the strong electron-phonon coupling. The phonon dispersion of Nb3Sn exhibits Kohn anomalies at three different wave vectors at a lower temperature. Moreover, above a pressure of 6 GPa, the charge density wave (CDW) instability disappeared, suggesting that pressure inhibits the CDW phase. The superconducting temperature is predicted to be TC = 18.62 K under ambient conditions, which is well consistent with the experimental results. We find that both the CDW and superconducting orders respond to pressure, with their transition temperatures decreasing as the pressure increases below 6 GPa. Above 6 GPa, the superconducting transition temperature increases slowly with pressure. Our results suggest that the instability in Nb3Sn is driven by the softening of the phonon modes due to the CDW caused by strong electron-phonon coupling. Therefore, the CDW phase and superconducting phase of Nb3Sn coexist at low pressure.

Concordance and Clinical Significance of Genomic Alterations in Progressive Tumor Tissue and Matched Circulating Tumor DNA in Aggressive-variant Prostate Cancer.

Sequencing of circulating tumor DNA (ctDNA) is a minimally invasive approach to reveal the genomic alterations of cancer; however, its comparison with sequencing of tumor tissue has not been well documented in real-world patients with aggressive-variant prostate cancer (AVPC). Concordance of genomic alterations was assessed between progressive tumor tissue and matched ctDNA by next-generation sequencing for 63 patients with AVPC. Associations of genomic alterations with progression-free survival (PFS) and overall survival (OS) were investigated using Kaplan-Meier and Cox regression analyses. A total of 161 somatic mutations (SMs) and 84 copy-number variants (CNVs) were detected in tumors, of which 97 were also found in ctDNA, giving concordance of 39.6% (97/245) across all SMs and CNVs, 49.7% for SMs only and 20.2% for CNVs only. Across all patients with AVPC, chemotherapy was associated with significantly longer median PFS (6 vs. 0.75 months, P = 0.001) and OS (11 vs. 8 months, P < 0.001) than next-generation hormonal therapy (NHT). Among types of chemotherapy, additional platinum-based chemotherapy was associated with significantly longer median PFS and OS than docetaxel only in patients with TP53, RB1, or PTEN alterations, and in those with ctDNA% ≥ 13.5%. The concordance analysis first provides evidence for combining the sequencing of ctDNA and tumor tissue in real-world patients with AVPC. Chemotherapy is associated with significantly better survival than NHT, and the benefit of additional platinum-based chemotherapy may depend on the presence of alterations in TP53, RB1, or PTEN and on a sufficiently high proportion of ctDNA in patients with AVPC. SIGNIFICANCE: AVPC is a highly malignant and heterogeneous disease. Sequencing of ctDNA is a minimally invasive approach to reveal genomic alterations. On the basis of the current real-world study, we found ctDNA does not fully recapitulate the landscape of genomic alterations from progressive tumor tissue in AVPC. We also revealed AVPC can benefit from chemotherapy, especially platinum-based regimens. TP53/RB1/PTEN alterations in ctDNA or tumor tissue could be biomarkers for platinum-based chemotherapy in this setting.

A review of sustainable utilization and prospect of coal gasification slag.

Currently, the storage of coal gasification slag (CGS) is continuously increasing, as the coal gasification technology develops, posing significant environmental hazards. Due to its volcanic ash characteristics and rich residual carbon, CGS has great potential for resource utilization, which has attracted the attentions of many scholars. This paper firstly introduces the compositions and properties of CGS. Then, it reviews the existing utilization methods of CGS, including Preparation of building materials, carbon-ash separation technology, ecological restoration, and cyclic blending. The advantages and disadvantages of various methods are compared. Subsequently, some high-value utilization methods of coal gasification slag are introduced, such as the preparation of high-performance activated carbon and zeolite, of which the feasibility and advantages are evaluated. Finally, some suggestions are put forward for future developing technologies. This paper aims to provide some references and inspiration for the utilization and environmental protection of CGS.

The Quadratic Constitutive Model Based on Partial Derivative and Taylor Series of Ti6242s Alloy and Predictability Analysis.

To solve the problem of insufficient predictability in the classical models for the Ti6242s alloy, a new constitutive model was proposed, based on the partial derivatives from experimental data and the Taylor series. Firstly, hot compression experiments on the Ti6242s alloy at different temperatures and different strain rates were carried out, and the Arrhenius model and Hensel-Spittel model were constructed. Secondly, the partial derivatives of logarithmic stress with respect to temperature and logarithmic strain rate at low, medium and high strain levels were analyzed. Thirdly, two new constitutive models with first- and second-order approximation were proposed to meet the requirements of high precision. In this new model, by analyzing the high-order differential data of experimental data and combining the Taylor series theory, the minimum number of terms that can accurately approximate the experimental rheological data was found, thereby achieving an accurate prediction of flow stress with minimal material parameters. In the new model, by analyzing the high-order differential of the experimental data and combining the theory of the Taylor series, the minimum number of terms that can accurately approximate the experimental rheological data was found, thereby achieving an accurate prediction of flow stress with minimal material parameters. Finally, the prediction accuracies for the classical model and the new model were compared, and the predictabilities for the classical models and the new model were proved by mathematical means. The results show that the prediction accuracies of the Arrhenius model and the Hensel-Spittel model are low in the single-phase region and high in the two-phase region. In addition, second-order approximation is required between the logarithmic stress and logarithmic strain rate, and first-order approximation is required between logarithmic stress and temperature to establish a high-precision model. The order of prediction accuracy of the four models from high to low is the quadratic model, Arrhenius model, linear model and HS model. The prediction accuracy of the quadratic model in all temperatures and strain rates had no significant difference, and was higher than the other models. The quadratic model can greatly improve prediction accuracy without significantly increasing the material parameters.

First assistant experience in total laparoscopic pancreaticoduodenectomy: accelerating the learning curve for an operator.

OBJECTIVE: Compare and analyze clinical data of total laparoscopic pancreaticoduodenectomy (TLPD) cases for surgeons with / without first assistant experience (FAE) in TLPD. Probe influence of FAE in TLPD on the learning curve for an operator. METHODS: The clinical data of 239 patients, that underwent TLPD performed by two surgeons between January 2017 and January 2022) in our department, were consecutively collected and divided into two groups (A and B). Group A cases were operated by Surgeon A, with FAE of 57 TLPDs in our department prior to initial TLPD as an operator. Group B cases were operated by Surgeon B with no FAE of TLPD. Cumulative sum (CUSUM) method developed learning curves. Clinical data and both surgeons' learning curves were statistically compared between both groups. RESULTS: Between both groups, no statistically significant variations were observed for pre-operative health conditions. Reduced surgical duration, blood loss and transfusion volume during surgery, together with reductions in major post-operative complication rates and reduced hospital/ICU stays were identified within Group A, having statistically significant variations. The technical plateau phases of the learning curves were approximately 25-41 cases and 35-51 cases, for Surgeon A and Surgeon B, respectively. CONCLUSION: FAE in TLPD can accelerate the learning curve of TLPD for an operator, with safer surgical procedures and enhanced post-operative recovery.

Study on Hot Tensile Deformation Behavior and Hot Stamping Process of GH3625 Superalloy Sheet.

Hot tensile tests of the GH3625 superalloy were carried out under the temperature range of 800-1050 °C and strain rates of 0.001, 0.01, 0.1, 1, and 10 s-1 on a Gleeble-3500 metallurgical processes simulator. The effect of temperature and holding time on grain growth was investigated to determine the proper heating schedule of the GH3625 sheet in hot stamping. The flow behavior of the GH3625 superalloy sheet was analyzed in detail. The work hardening model (WHM) and the modified Arrhenius model, considering the deviation degree R (R-MAM), were constructed to predict the stress of flow curves. The results showed that WHM and R-MAM have good prediction accuracy by evaluating the correlation coefficient (R) and the average absolute relative error (AARE). Additionally, the plasticity of the GH3625 sheet at elevated temperature drops with the increasing temperature and decreasing strain rate. The best deformation condition of the GH3625 sheet in the hot stamping is in the range of 800~850 °C and 0.1~10 s-1. Finally, a hot stamped part of the GH3625 superalloy was produced successfully, which had higher tensile strength and yield strength than the as-received sheet.

Perioperative Outcomes and Long-Term Survival of Laparoscopic Pancreaticoduodenectomy: A Retrospective Study of 653 Cases in a Single Institution.

Introduction: Laparoscopic pancreaticoduodenectomy (LPD) is gaining wide acceptance within pancreatic surgery. However, longitudinal data are lacking. The aim of this study was to analyze and assess the short-term outcomes and long-term survival of LPD over a duration of 8 years. Methods: Patients who underwent LPD in our institution between November 2013 and September 2021 were included in this study. The perioperative outcomes were statistically analyzed. The long-term survival was studied over a median follow-up duration of 13 months. Results: In total, 653 consecutive patients treated at our institution were included, of which 617 cases underwent standard LPD and 36 cases underwent LPD with vascular resection. The rate of death in hospital, reoperation, postpancreatectomy hemorrhage, postoperative pancreatic fistula, and delayed gastric emptying were 4.4%, 10.3%, 11.9%, 12.9%, and 6.1% respectively. There were statistical differences in the intraoperative blood loss and transfusion, operation time, and the R0 resection rate between the LPD cases and LPD with vascular resection cases. A total of 526 cases were pathologically diagnosed of cancer. The 1-, 3-, and 5-year survival rates were 49.2%, 17.9%, and 17.9%, respectively, for pancreatic cancer with the median survival time of 12 months. The 1-, 3-, and 5-year survival rates were 76.9%, 60.8%, and 52.5%, respectively, for bile duct cancer with the median survival time of 35 months. The 1-, 3-, and 5-year survival rates were 80.2%, 62.2%, and 52.9%, respectively, for duodenal cancer with the median survival time of 53 months. The 1-, 3-, and 5-year survival rates were 72.5%, 54.5%, and 50%, respectively, for ampullary cancer with the median survival time of 55 months. Conclusion: LPD is a feasible and oncologically acceptable procedure with satisfying perioperative outcomes and long-term survival in a high-volume institution.

Customer knowledge management competence evaluation of agritourism enterprises by using the balanced scorecard and fuzzy-AHP: Evidence from Chengdu-Chongqing economic circle.

This paper provides an evaluation framework to explore the linking mechanisms between customer knowledge management competence (CKMC) and Balanced Scorecard (BSC). With a case study from Chengdu-Chongqing Economic Circle of China, this paper attempts to empirically justify the framework. An index system was established for evaluating CKMC based on BSC and knowledge management process, the weight design and consistency check of the indexes were implemented by using the analytic hierarchy process (AHP), and the overall evaluation value and concrete index scores at all levels were obtained via the fuzzy evaluation method. Empirical results show that CKMC performance measurement indicators were ranked in order of importance as Business process performance dimensions (0.465), System support dimensions (0.289), Customer communication dimensions (0.152) and Market performance dimension (0.094). It also shows that the overall score of CKMC was 3.404, reflecting that the CKMC was in a state of general satisfaction. This research also identifies key factors hindering implementation of CKMC, including Attention from senior leaders (2.871), customer knowledge sharing efficiency (2.928), and information technology level (3.133). This research could contribute to CKM theory by extending customer knowledge management competence research with BSC initiatively. For practitioners, this study may provide useful suggestions to identify key factors promoting business CKMC, and finally promotes sustainable development of Agritourism.

Gradient Structure Design and Welding-Hammering Hybrid Remanufacturing Process of Continuous Casting Rollers.

To improve the service life and reduce the repair cost of continuous casting rollers, a new welding-hammering hybrid remanufacturing process in which the roller was designed with a gradient structure was proposed, and corresponding equipment was developed. First, the failure modes and their causes for a continuous casting roller were analyzed by numerical simulation. The cyclic tension-compression shear stress, cyclic tension-compression normal stress, thermal cycle, and highly corrosive environment caused fatigue cracking and overall peeling of the roller surface. Second, the gradient structure composed of a base layer, transition layer, and strengthened layer of a continuous casting roller was designed, and materials for each layer were selected according to their different service conditions. Third, novel equipment for continuous welding-hammering composite remanufacturing was developed, and the optimized process parameters were obtained through welding experiments. Finally, an application test was carried out; the microscopic analysis showed that refined grains, fewer welding defects, and better surface toughness were obtained. Compared with traditional remanufacturing processes without hammering, the welding-hammering hybrid process achieved a forged structure instead of as-cast structure, which significantly improved the service life of the continuous casting roller by about 100%.

Do urban tourists prefer vegetarianism? An urban-rural comparison of vegetarian consumption in China.

The adoption of a vegetarian diet might have public health and environmental benefits. However, little is known about urban and rural Generation Z tourists' attitudes toward vegetarianism or vegetarian consumption within the Chinese urban and rural settings. Hence, to address this gap, the present study adopted a sequential and mixed research approach based on a survey (n = 212) and laddering interviews (n = 20) to validate post-millennial tourists' motives for adopting a vegetarian diet. The results identified the top four motives as environmental protection and resource conservation, ethical consideration, personal taste and choice, and personal healthcare issues. The top four barriers to vegetarianism were unavailability and limited choice, peer pressure, traditional prejudice/habit, and the inability to change. The results also demonstrated that both rural and urban tourists adopt vegetarianism mainly for environmental protection and ethical consideration, a subtle difference between them is that urban vegetarians emphasized ethical considerations more but rural ones emphasized food and variety. Urban consumers considered unavailability and limited choice as the topmost barriers to being vegetarian, while rural vegetarians found traditional prejudice to be restricting. Due to traditional dietary habits and peer influence, rural tourists face many more challenges when adopting a vegetarian diet. Understanding the perceived benefits and barriers to being vegetarian in different regions will not only enrich the theory of food nutrition but also expand Generation Z tourists' consumption behavior and practices.

Influence of Surfacing Fe-Based Alloy Layers on Wire Arc Additive Manufactured Ni-Based Superalloys Material on Its Microstructure and Wear Properties.

Wire arc additively manufactured (WAAM) Ni-based materials have good properties but are costly and hard to cut, leading to difficulties in machining after welding and wasting the materials. To overcome these shortcomings, this work proposes a method of surfacing Fe-based alloy layers on WAAM Ni-based material. The effect of this method on the microstructure and wear properties of WAAM Ni-based materials is discussed. In this work, a Fe-based alloy (JX103) was welded as the last layers of the WAAM Ni-based superalloy (JX201) material. The hardness, microstructure, and wear behavior of the material with different residual Fe-based materials were tested and analyzed. Our results indicate that the surface hardness was smoothly increased from HV350 to HV400 by overlaying Fe-based alloy layers. Microstructure analysis shows that γ-Fe gradually disappears, and the carbide form changes from WAAM Ni-based superalloys to Fe-based alloys. In the fusion boundary, the occurrence of cellular dendritic growth, a type -Ⅱ boundary, and low dilution indicate good crack resistance and good connection performance between these two materials. The wear test showed that the wear resistance of JX201 was decreased by changing the last layer to JX103. However, as the residual thickness of JX103 decreased, the influence gradually reduced. Meanwhile, the wear mechanism changed from severe abrasive and adhesive wear to light abrasive wear. When the thickness is less than 0.5 mm, the wear weight per minute is at the same level as the sample without JX103.

Path Generation Strategy and Wire Arc Additive Manufacturing of Large Aviation Die with Complex Gradient Structure.

To realize automatic wire arc additive manufacturing (WAAM) of a large aviation die with a complex gradient structure, a new contour-parallel path generation strategy was proposed and practically applied. First, the planar curve was defined as a vertical slice of a higher-dimensional surface and a partial differential equation describing boundary evolution was derived to calculate the surface. The improved Finite Element Method (FEM) and Finite Difference Method (FDM) were used to solve this partial differential equation. Second, a cross section of a large aviation die was used to test the path-generation algorithms. The results show that FEM has a faster solving speed than FDM under the same solving accuracy because the solving domain of FEM mesh was greatly reduced and the boundary mesh could be refined. Third, the die was divided into three layers: base layer, transition layer (Fe-based material) and strengthening layer (Co-based material) according to the difference of the temperature and stress field, and corresponding WAAM process parameters has been discussed. The optimum welding parameters are obtained as follows: voltage is 28 V, wire feeding speed is 8000 mm/min and welding speed is 450 mm/min. Finally, the path generation strategy was practically applied to the remanufacture of the large aircraft landing gear die with a three-layer structure. The application test on aircraft landing gear dies justified the effectiveness of the algorithms and strategy proposed in this paper, which significantly improved the efficiency of the WAAM process and the service life of large aviation dies with complex gradient structures. The microstructure of the fusion zone shows that the base metal and welding material can be fully integrated into the welding process.

Clarification of Temperature Field Evolution in Large-Scale Electric Upsetting Process of Ni80A Superalloy through Finite Element Method.

Electric upsetting has been widely employed to manufacture the preformed workpiece of large-scale exhaust valves. The temperature field in the electric upsetting process plays an important role in microstructure evolution and defect formation. In order to uncover the temperature evolution in a larger-scale electric upsetting process, the electric-thermal-mechanical multi-field coupling finite element model was developed to simulate the electric upsetting forming process of Ni80A superalloy. The temperature distribution characteristics and their formation mechanisms under different stages were analyzed systematically. Results indicate that at the preheating stage, the billet temperature increases from 20 °C to 516.7 °C, and the higher temperature region firstly appears at the contact surface between billet and anvil due to the combined effects of contact resistance and volume resistance. With increasing preheating time, the higher temperature region is transferred to the interior of the billet because the contact resistance is reduced with increasing temperature. As for the forming process, the billet is gradually deformed into an onion shape. The highest billet temperature increases to 1150 °C and keeps relatively constant. The high temperature region always appears at the neck of the onion due to the relatively higher current density at this place. It enlarges continuously in the primary stage and intermediate stage, and then decreases at the stable deformation stage. The low temperature regions lie in the contact surface and the outer surface of the onion because a lot of heat is lost to the anvil and surroundings through thermal conduction and radiation. Finally, the established finite element model was verified by an actual electric upsetting experiment. The average relative error between simulated temperatures and experimental ones was estimated as 7.54%. The longitudinal and radial errors between simulated onion shape and the experimental one were calculated as 1.38% and 2.70%, respectively.

Study on Chip Formation Mechanism of Single Crystal Copper Using Molecular Dynamics Simulations.

Nano-cutting is an important development direction of the modern manufacturing technology. However, the research on the mechanism underlying nano-cutting lags far behind the practical application, which restricts the development of this advanced manufacturing technology. The chip formation process is the basic process of nano-cutting, and it is of key importance for the mechanism research of nano-cutting. In this paper, the nano-tensile behavior of single crystal copper was studied based on the molecular dynamics simulations. The toughness and brittleness characteristics of the copper at different temperatures were analyzed. Then, the molecular dynamics simulations of nano-cutting for single crystal copper with different toughness and brittleness were studied. The crystal structure, cutting force, stress-strain distribution and atomic motion characteristics were systematically investigated. The nano-chip formation mechanism of single crystal copper was revealed. The results show that the chip is formed through two ways, namely the shear and extrusion. The material near the free surface of the workpiece undergoes continuous shear slip and periodic long-distance slippage along the primary shear direction, forming the block chip in which the FCC and HCP structures are orderly distributed. The material near the tool-chip interface is extruded by the tool, block chip and stagnation zone to form the flowing chip with amorphous structure. As the temperature increases, the occurrence frequency of long-distance slippage in the block chip increases, while the slippage degree decreases. Besides, with the increase in temperature, the thickness of block chip formed by shear slip decreases, while the thickness of flowing chip formed by extrusion increases.