Research of thermal characteristics has been a key issue in the development of high-speed feed system. Most of the work carried out thus far is based on the principle of directly mapping the thermal error against the ...Research of thermal characteristics has been a key issue in the development of high-speed feed system. Most of the work carried out thus far is based on the principle of directly mapping the thermal error against the temperature of critical machine elements irrespective of the operating conditions. But recent researches show that different sets of operating parameters generated significantly different error values even though the temperature of the machine elements generated was similar. As such, it is important to develop a generic thermal error model which is capable of evaluating the positioning error induced by different operating parameters. This paper ultimately aims at the development of a comprehensive prediction model that can predict the thermal characteristics under different operating conditions （feeding speed, load and preload of ballscrew） in a feed system. A novel wavelet neural network based on feedback linearization autoregressive moving averaging （NARMA-L2） model is introduced to predict the temperature rise of sensitive points and thermal positioning errors considering the different operating conditions as the model inputs. Particle swarm optimization（PSO） algorithm is brought in as the training method. According to ISO230-2 Positioning Accuracy Measurement and ISO230-3 Thermal Effect Evaluation standards, experiments under different operating conditions were carried out on a self-made quasi high-speed feed system experimental bench HUST-FS-001 by using Pt100 as temperature sensor, and the positioning errors were measured by Heidenhain linear grating scale. The experiment results show that the recommended method can be used to predict temperature rise of sensitive points and thermal positioning errors with good accuracy. The work described in this paper lays a solid foundation of thermal error prediction and compensation in a feed system based on varying operating conditions and machine tool characteristics.展开更多
The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the cu...The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the current research of the thermal characteristics of machines mainly focuses on steady simulation. To explore the influence of thermal characterizations on the precision of a jib boring machine assembled dual-drive feed system, the thermal equilibrium tests and the research on thermal-mechanical transient behaviors are carried out. A laser interferometer, infrared thermography and a temperature-displacement acquisition system are applied to measure the temperature distribution and thermal deformation at different feed speeds. Subsequently, the finite element method （FEM） is used to analyze the transient thermal behaviors of the boring machine. The complex boundary conditions, such as heat sources and convective heat transfer coefficient, are calculated. Finally, transient variances in temperatures and deformations are compared with the measured values, and the errors between the measurement and the simulation of the temperature and the thermal error are 2 ~C and 2.5 pm, respectively. The researching results demonstrate that the FEM model can predict the thermal error and temperature distribution very well under specified operating condition. Moreover, the uneven temperature gradient is due to the asynchronous dual-drive structure that results in thermal deformation. Additionally, the positioning accuracy decreases as the measured point became further away from the motor, and the thermal error and equilibrium period both increase with feed speeds. The research proposes a systematical method to measure and simulate the boring machine transient thermal behaviors.展开更多
The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleratio...The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleration and deceleration is an important step in improving the structural performance of vertical milling machines.The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates.Therefore,the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight.Thus,the system transmission stiffness also varies and affects the dynamics.In this study,a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direction of the inertial force is established for a ball screw feed system without counterweight.In addition,a calculation method for the system stiffness is provided.Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model.Finally,the influence of the spindle system position,the rated dynamic load of the screw-nut joint,and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied.The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration.The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.展开更多
Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented const...Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented constant current control which especially led to arc＂ blowout with the abrupt change oat＂ arc＂ length or downward welding. Therefore alterative wire-feed system based on arc voltage negative feedback was put forward to improve the .stability of arc＂ length in this paper. Double closed-loop and double fuzzy P1 regulation were adopted in this system. Fuzzy control of induced voltage was adopted in the inner-loop which improved the stability and fast response of wire-feed system. Fuzz）＂ control of arc＂ voltage negative feedback was used in the outer-loop whose output .served as the input of negative feedback regulation of inner-loop induced voltage. This method could remain arc＂ length and weld penetration unchan, ged on the basils of reducing spatter and improving formation and it was proved by downward welding tests.展开更多
Beijing Aerospace System Engineering Institute of China Academy of Launch Vehicle Technology (CALT) declared recently that theinstitute has set up a laboratory whichwould operate a newly
Robotic drilling technology for aircraft flexible assembly is challenging and is under active investigation.In this work,a feed system for robotic drilling end-effector is modeled.Two control algorithms with different...Robotic drilling technology for aircraft flexible assembly is challenging and is under active investigation.In this work,a feed system for robotic drilling end-effector is modeled.Two control algorithms with different computational complexity are proposed and compared.Based on reduced-order state observer,a pole placement controller is proposed firstly,and then a model reference adaptive controller is designed.An experiment platform is established in Matlab xPC environment to validate the effect of the two controllers.The experiment results show that the model reference adaptive controller delivers a higher tracking accuracy after the adaptive transient procedure than the pole placement controller does.展开更多
The efficiency and mechanism of hydrous iron oxide(HFO)and HFO/calcite mixture to inactivate the phosphorus in the overlying water(OW)/sediment system under the feed adding condition were explored,and the effect of HF...The efficiency and mechanism of hydrous iron oxide(HFO)and HFO/calcite mixture to inactivate the phosphorus in the overlying water(OW)/sediment system under the feed adding condition were explored,and the effect of HFO and HFO/calcite mixture addition on the diversity,composition and function of bacterial communities in the sediment was examined.HFO and HFO/calcite mixture direct addition can effectively lower the concentration of soluble reactive phosphorus(RSP)and diffusion gradient in thin film-unstable phosphorus(PD GT)in OW and inactivate the P DGTin the upper sediment.The elimination efficiencies of RSP by the direct HFO and HFO/calcite mixture addition were 48.9%-97.0%and 42.4%-95.4%,respectively.The alteration in the addition mode from the one-time to multiple direct addition was beneficial to the immobilization of RSP and PD GTin OW and P DGTin the upper sediment by HFO and HFO/calcite mixture under the feed input condition in the long run.Permeable fabric wrapping reduced the inactivation efficiency of RSP in OW by HFO and HFO/calcite mixture,but it made the recycling of these materials possible.Most of P immobilized by HFO and HFO/calcite mixture was relatively or very stable.After the HFO and HFO/calcite mixture addition,the composition of bacterial communities in the surface sediment changed.However,the bacterial communities in the amended sediments still can perform good ecological function.Our findings suggest that HFO and HFO/calcite mixture are promising phosphorus-immobilization materials for the inactivation of RSP and PD GTin OW and PD GTin the upper sediment under the feed inputting condition.展开更多
The Propellant Feed System(PFS)is a crucial component of Electric Propulsion System(EPS)which is widely used in satellites for its high reliability and specific impulse.The Switching and Proportional Hybrid-controlled...The Propellant Feed System(PFS)is a crucial component of Electric Propulsion System(EPS)which is widely used in satellites for its high reliability and specific impulse.The Switching and Proportional Hybrid-controlled Xenon Feed System(SPHXFS)is a novel type of PFS with high flow regulation precision.This study develops a system-level simulation model with 75 components for the SPHXFS.The accuracy of the model is validated through the comparison with test data,showing an error of less than 3%during the startup phase and less than 0.1%after stabilization.The study analyzes the startup process and finds that the two-stage pressure reduction system avoids two-phase flow interference downstream,achieving a regulation accuracy of±0.1%.A long-term operation simulation of the system is conducted,revealing that pressure fluctuations occur upstream at 4767 s due to Bang-Bang control.However,with proportional control adjustments,these fluctuations do not affect the flow supply.Further research examines the impact of synchronous and asynchronous control modes of the Bang-Bang Valve(TPBBV)under the tank pressures of 6-10 MPa on the system's dynamic characteristics.It is found that the asynchronous control scheme results in a flow supply settling time that is 7.2-10s longer than the synchronous control scheme,with an overshoot increase of 4.1%-4.9%.These insights provide valuable reference and guidance for system optimization design and the formulation of operational strategies.展开更多
In the face of constantly changing environments,the central nervous system(CNS)rapidly and accurately calculates the body's needs,regulates feeding behavior,and maintains energy homeostasis.The arcuate nucleus of ...In the face of constantly changing environments,the central nervous system(CNS)rapidly and accurately calculates the body's needs,regulates feeding behavior,and maintains energy homeostasis.The arcuate nucleus of the hypothalamus(ARC)plays a key role in this process,serv-ing as a critical brain region for detecting nutrition-related hormones and regulating appetite and energy homeostasis.Agouti-related protein(AgRP)/neuropeptide Y(NPY)neu-rons in the ARC are core elements that interact with other brain regions through a complex appetite-regulating network to comprehensively control energy homeostasis.In this review,we explore the discovery and research progress of AgRP neurons in regulating feeding and energy metabolism.In addition,recent advances in terms of feeding behavior and energy homeostasis,along with the redundant neural mecha-nisms involved in energy metabolism,are discussed.Finally,the challenges and opportunities in the field of neural regula-tion of feeding and energy metabolism are briefly discussed.展开更多
Microplastic(MP)pollution has spread from the mainland to the ocean.However,Haizhou Bay,which is one of the important land-ocean transition zones,has been reported relatively little about the enrichment of MPs.To prov...Microplastic(MP)pollution has spread from the mainland to the ocean.However,Haizhou Bay,which is one of the important land-ocean transition zones,has been reported relatively little about the enrichment of MPs.To provide fundamental data for MP pollution in Haizhou Bay,we studied the occurrence of microplastics in the intestines of 8 species of fish with different habits and feeding modes.The fish intestines were digested with a 10%KOH solution,and MPs are separated with a glass fiber filter.Then,the size,shape,color,and composition of the MPs were analyzed using a stereomicroscope and Fourier transform infrared spectrometer.The results showed the abundance of MP intake ranged from 0.02 items g^(-1) to 0.16 items g^(-1) and the detection rate of MPs ranged from 53.33% to 80% across different fish species.The MP intake in benthic fish and omnivorous fish was significantly higher than that of pelagic fish and predatory fish.Smaller MPs(<0.25 mm)were the dominant types and accounted for 62.50% of the total.The fiber was the prevailing shape of MPs,and the black MPs were the most common,followed by red and yellow ones.Polyethylene terephthalate(PET),polyamide(PA),and polystyrene(PS)were the main components of MPs,accounting for 34.9%,29.9%,and 16.4%,respectively.According to the composition analysis of MPs,the main sources of MPs in fish of Haizhou Bay were attributed to marine aquaculture and port construction.The results are helpful for our better understanding of the status of MP pollution in this area,and further aid in the development of the pointed measures to mitigate and prevent the MP pollution in this ecologically important area.展开更多
Feed efficiency(FE)is a crucial economic trait that significantly impacts profitability in intensive sheep production,and can be evaluated by the residual feed intake(RFI)and feed conversion ratio(FCR).However,the und...Feed efficiency(FE)is a crucial economic trait that significantly impacts profitability in intensive sheep production,and can be evaluated by the residual feed intake(RFI)and feed conversion ratio(FCR).However,the underlying genetic mechanisms that underlie FE-related traits in sheep are not fully understood.Herein,we measured the FE-related traits of 1,280 Hu sheep and conducted the phenotype statistics and correlation analysis,the result showcase that there was a large variation for FE-related traits,and RFI was significant positive correlation with average daily feed intake(ADFI)and FCR.Moreover,a genome-wide association study(GWAS)was conducted using whole-genome resequencing data to investigate the genetic associations of ADFI,FCR and RFI.For ADFI and FCR traits,2 and one single nucleotide polymorphisms(SNPs)exceeded the genome-wide significance threshold,whereas ten and 5 SNPs exceeded the suggestive significance threshold.For RFI traits,only 4 SNPs exceeded the suggestive significance threshold.Finally,a total of 8 genes(LOC101121953,LOC101110202,CTNNA3,IZUMO3,PPM1E,YIPF7,ZSCAN12and LOC105603808)were identified as potential candidate genes for FE-related traits.Simultaneously,we further analyzed the effects of 2 candidate SNPs associated with RFI on growth and FE traits in enlarged experimental population,the results demonstrated that these 2 SNPs was not significantly associated with growth traits(P>0.05),but significantly related to RFI traits(P<0.05).These findings will provide valuable reference data and key genetic variants that can be used to effectively select feed-efficient individual in sheep breeding programs.展开更多
Background This study was carried out to investigate the individual and combined contamination of aflatoxin B_(1)(AFB_(1)),deoxynivalenol(DON),and zearalenone(ZEN)in feeds in China between 2021 and 2024.A total of 23,...Background This study was carried out to investigate the individual and combined contamination of aflatoxin B_(1)(AFB_(1)),deoxynivalenol(DON),and zearalenone(ZEN)in feeds in China between 2021 and 2024.A total of 23,003 feed samples,including 17,489 feedstuff samples and 5,514 complete feed samples,were collected from different provinces of China for mycotoxin analysis.Results The analyzed mycotoxins displayed considerably high contamination in the feed samples,with the individual contamination of AFB_(1),DON,and ZEN were 20.0%–100%,33.3%–100%,and 85.0%–100%,respectively.The average concentrations of AFB_(1),DON,and ZEN were 1.2–728.7μg/kg,106–8,634.8μg/kg,and 18.1–3,341.6μg/kg,respectively.Notably,the rates over China’s safety standards for AFB_(1),DON,and ZEN in raw ingredients were 9.7%,2.7%,and 15.7%,respectively.Meanwhile,3.5%,1.1%,and 8.7%of analyzed complete feeds exceeded China’s safety standards for AFB_(1),DON,and ZEN,respectively.Moreover,the co-contamination rates of AFB_(1),DON,and ZEN in more than 70%of raw ingredients and 87.5%of complete feed products were 60.0%–100%and 61.5%–100%,respectively.Conclusion This study reveals that the feeds in China have commonly been contaminated with AFB_(1),DON,and ZEN alone and their combination during the past four years.These findings highlight the significance of monitoring mycotoxin contaminant levels in domestic animal feed and the importance of carrying out feed administration and remediation strategies for mycotoxin control.展开更多
Global warming and climate change have made food production through conventional agriculture inefficient, and their effects on livestock and crop cultivation are leading to disruptions in the food supply. The troubles...Global warming and climate change have made food production through conventional agriculture inefficient, and their effects on livestock and crop cultivation are leading to disruptions in the food supply. The troubles are severe in regions suffering from improper land management and unsustainable practices. The Bio-CircularGreen(BCG) economic model, designed to reduce and recycle resources by using environmentally friendly procedures, has been developed. The Azolla plant represents an interesting model for BCG and for enhancing community networks in Southeast Asia(SEA) because it provides multipurpose materials. Azolla can be used for various applications in agriculture such as biofertilizer and animal feed. However, our understanding and utilization of Azolla are limited. Moreover, collaboration among farmers is insufficient to maximize the benefits of Azolla. In this study, we provide a comprehensive review of the role of Azolla in agriculture. We review the main properties of Azolla as biofertilizers, especially regarding rice production and the interaction with cyanobacteria. For livestock, we discuss procedures to use Azolla in animal feed and evaluate the ingredients of the meal. In addition, we discuss product qualities from livestock treated with Azolla in the diet. This review also describes Azolla-based farming, which is designed for efficient land use and promotes nutrient cycling.Hence, we show that the Azolla plant is one of the key factors for farm-based agroecosystem services which can drive sustainable bioresource management in SEA. Moreover, we also propose the potential development of Azolla to improve its properties as a biofertilizer, a functional feed for animals and humans, and a feedstock for bio-oil production.展开更多
Background Intestinal oxidative stress serves as an endogenous host defense against the gut microbiota by increas-ing energy expenditure and therefore decreasing feed efficiency(FE).Several systems coordinately regula...Background Intestinal oxidative stress serves as an endogenous host defense against the gut microbiota by increas-ing energy expenditure and therefore decreasing feed efficiency(FE).Several systems coordinately regulate redox bal-ance,including the mitochondrial respiratory chain,nicotinamide adenine dinucleotide phosphate(NADPH)oxidase,and different antioxidants.However,it remains unclear which redox balance compartments in the intestine are crucial for determining FE.Results In this study,we first screened the key targets of different metabolites and redox balance-related gene expression in broiler ceca.We then constructed a mouse colitis model to explore malic acid(MA)ability to allevi-ate intestinal inflammation.We further used controlled release technology to coat MA and investigated its effects on the intestinal redox status and FE in vivo.Finally,we examined the underlying mechanism by which MA modulated redox status using a porcine intestinal epithelial cell jejunum 2(IPEC-J2)cell model in vitro.Our results demonstrated that the MA/malic enzyme 3(ME3)pathway may play an important role in reducing oxidative stress in the broiler cecum.In addition,colon infusion of MA attenuated inflammatory phenotypes in the dextran sulfate sodium salt(DSS)induced mouse colitis model.Then,dietary supplementation with controlled-release MA pellet(MAP)reduced the feed to gain(F/G)ratio and promoted chicken growth,with reduced oxidative stress and increased bacterial diver-sity.Finally,the in vitro IPEC-J2 cell model revealed that ME3 mediated the effect of MA on cellular oxidative stress.Conclusion In summary,our study firstly revealed the important role of the MA/ME3 system in the hindgut of broiler chickens for improving intestinal health and FE,which may also be crucial for the implications of colon inflammation associated diseases.展开更多
The radula is a crucial adaptation for food-processing in molluscs.A deeper understanding of the interaction between the radula and the preferred food is lacking,complicating the inference of the precise ecological ro...The radula is a crucial adaptation for food-processing in molluscs.A deeper understanding of the interaction between the radula and the preferred food is lacking,complicating the inference of the precise ecological roles of radular structures.This study presents the first experimental set-up that allows to study the influence of the radular morphology,specifically the degree of tooth-tooth interlocking(so-called collective effect),on the feeding efficiency.For this purpose,physical 3D models of the teeth were designed using CAD software and 3D printing technique.The feeding efficiencies with models of different degree of interlocking were determined by tensile tests,pulling the models trough agar gels with different viscosities.The forces generated by the models and the masses of the removed gel fragments were determined.We found,that radular models with a high degree of tooth–tooth interlocking performed best as they were able to remove most agar.We additionally broke the teeth and determined,that the teeth with the highest degree of interlocking could resist to highest force.Overall,the study highlights the complex interplay between radular morphology and its ecological function,suggesting that even minor morphological alterations can significantly impact the efficiency and effectiveness of food gathering.Understanding these interactions cannot only shed light on the ecological adaptations of molluscs,but provide further insights into development of more effective grinding,scraping,and cleaning technical devices.展开更多
BACKGROUND Esophageal cancer(EC)is an aggressive malignancy with low survival(10%-30%).Nutritional problems are present throughout the perioperative period and are key to prognosis.Home enteral nutrition appears to im...BACKGROUND Esophageal cancer(EC)is an aggressive malignancy with low survival(10%-30%).Nutritional problems are present throughout the perioperative period and are key to prognosis.Home enteral nutrition appears to improve the nutritional status of patients with EC.Few studies have addressed the experience of patients administering their own nutritional fluids and managing their own feeding tubes at home.The aim of this study was to explore the real-life experience of self-management of feeding tubes in patients at home after EC surgery in the first 3 months after discharge following surgery.AIM To explore feeding tube self-management experience of patients at home 3 months after discharge following EC surgery.METHODS Face-to-face semi-structured interviews were conducted with 18 patients using a feeding tube at home after EC surgery.Thematic analysis of the recordings identified themes related to feeding tube self-management.RESULTS Patients expressed similar feelings about their tube management experiences concerning three contextualized themes:Self-management dilemmas,distressing experiences,and self-management facilitators.CONCLUSION There are many dilemmas and problems in self-managing feeding tubes in postoperative homebound patients with EC.Clinical staff should provide guidance to promote a positive change in self-management behavior.展开更多
The feed industry serves as a critical intermediary between agriculture and animal husbandry,providing essential support for the modern breeding industry.Utilizing the annual financial report data from 19 publicly lis...The feed industry serves as a critical intermediary between agriculture and animal husbandry,providing essential support for the modern breeding industry.Utilizing the annual financial report data from 19 publicly listed companies within the feed industry in 2023,a comprehensive evaluation index system was developed to assess the financial performance of these companies from four dimensions:debt paying ability,operational ability,profitability,and development ability.Factor analysis and hierarchical cluster analysis were employed to assess the financial performance of publicly listed companies within the feed industry.By comparing the mean classifications and comprehensive scores,this study analyzed the strengths and weaknesses of these listed feed companies.Ultimately,it offered recommendations for improvement in areas such as product optimization and enhancement,reasonable liability management,and the advancement of company governance practices.展开更多
Rotational feeding combined with shift feeding electrochemical trepanning(RF-SF ECTr)is an effective method for machining aeroengine blisks.However,given the variable relative motion of the electrodes and the complex ...Rotational feeding combined with shift feeding electrochemical trepanning(RF-SF ECTr)is an effective method for machining aeroengine blisks.However,given the variable relative motion of the electrodes and the complex flow channels around the bending and twisting blades,the accessibility and uniformity of the flow field are poor in blisk RF-SF ECTr using the traditional electrolyte supply(TES)mode,resulting in poor machining stability and low machining efficiency.To improve the distribution of the flow field,a new multi-channel electrolyte supply(MCES)mode is proposed for blisk RF-SF ECTr,in which the position and volume of the electrolyte supply are controlled effectively by setting multiple inlet channels in the liquid inlet area.A flow-field simulation comparison between TES and MCES shows that better accessibility and uniformity of the flow-field distribution are achieved under MCES.To clarify further the flow-field distribution characteristics under RF-SF ECTr,a series of flow-field simulations was conducted at different machining depths.Based on the obtained dynamic change law for the flow field,to enhance further its uniformity and accessibility,a global coverage strategy for the electrolyte supply and a flow-field structure optimization method for MCES are proposed,which involve optimizing the number,diameter,and location of the inlet channels.After many simulations,the optimal MCES structure was achieved whereby the electrolyte covers all positions effectively in the processing area.To verify the proposed method as effective and correct,a series of RF-SF ECTr experiments was carried out.Under the optimized MCES mode,the feeding rate was increased from 0.8 mm/min with the TES mode to 2.0 mm/min,and the processing stability and efficiency were improved significantly.The methods presented here offer an effective guide for flow-field optimization when machining other components with complex spatial structures.展开更多
基金supported by National Key Basic Research Program of China(973Program,Grant No.2005CB724100,Grant No.2011CB706803)National Natural Science Foundation of China(Grant No.50675076,Grant No.50575087,Grant No.51075161)National Hi-tech Research and Development Program of China(863Program,Grant No.2008AA042802)
文摘Research of thermal characteristics has been a key issue in the development of high-speed feed system. Most of the work carried out thus far is based on the principle of directly mapping the thermal error against the temperature of critical machine elements irrespective of the operating conditions. But recent researches show that different sets of operating parameters generated significantly different error values even though the temperature of the machine elements generated was similar. As such, it is important to develop a generic thermal error model which is capable of evaluating the positioning error induced by different operating parameters. This paper ultimately aims at the development of a comprehensive prediction model that can predict the thermal characteristics under different operating conditions （feeding speed, load and preload of ballscrew） in a feed system. A novel wavelet neural network based on feedback linearization autoregressive moving averaging （NARMA-L2） model is introduced to predict the temperature rise of sensitive points and thermal positioning errors considering the different operating conditions as the model inputs. Particle swarm optimization（PSO） algorithm is brought in as the training method. According to ISO230-2 Positioning Accuracy Measurement and ISO230-3 Thermal Effect Evaluation standards, experiments under different operating conditions were carried out on a self-made quasi high-speed feed system experimental bench HUST-FS-001 by using Pt100 as temperature sensor, and the positioning errors were measured by Heidenhain linear grating scale. The experiment results show that the recommended method can be used to predict temperature rise of sensitive points and thermal positioning errors with good accuracy. The work described in this paper lays a solid foundation of thermal error prediction and compensation in a feed system based on varying operating conditions and machine tool characteristics.
基金Supported by National Hi-tech Research and Development Program of China(863 Program,Grant No.2012AA040701)
文摘The machine tool equipped with the dual-drive servo feed system could realize high feed speed as well as sharp precision. Currently, there is no report about the thermal behaviors of the dual-drive machine, and the current research of the thermal characteristics of machines mainly focuses on steady simulation. To explore the influence of thermal characterizations on the precision of a jib boring machine assembled dual-drive feed system, the thermal equilibrium tests and the research on thermal-mechanical transient behaviors are carried out. A laser interferometer, infrared thermography and a temperature-displacement acquisition system are applied to measure the temperature distribution and thermal deformation at different feed speeds. Subsequently, the finite element method （FEM） is used to analyze the transient thermal behaviors of the boring machine. The complex boundary conditions, such as heat sources and convective heat transfer coefficient, are calculated. Finally, transient variances in temperatures and deformations are compared with the measured values, and the errors between the measurement and the simulation of the temperature and the thermal error are 2 ~C and 2.5 pm, respectively. The researching results demonstrate that the FEM model can predict the thermal error and temperature distribution very well under specified operating condition. Moreover, the uneven temperature gradient is due to the asynchronous dual-drive structure that results in thermal deformation. Additionally, the positioning accuracy decreases as the measured point became further away from the motor, and the thermal error and equilibrium period both increase with feed speeds. The research proposes a systematical method to measure and simulate the boring machine transient thermal behaviors.
基金Supported by Key Program of National Natural Science Foundation of China(Grant No.51235009)National Natural Science Foundation of China(Grant No.51605374).
文摘The distinguishing feature of a vertical ball screw feed system without counterweight is that the spindle system weight directly acts on the kinematic joints.Research into the dynamic characteristics under acceleration and deceleration is an important step in improving the structural performance of vertical milling machines.The magnitude and direction of the inertial force change significantly when the spindle system accelerates and decelerates.Therefore,the kinematic joint contact stiffness changes under the action of the inertial force and the spindle system weight.Thus,the system transmission stiffness also varies and affects the dynamics.In this study,a variable-coefficient lumped parameter dynamic model that considers the changes in the spindle system weight and the magnitude and direction of the inertial force is established for a ball screw feed system without counterweight.In addition,a calculation method for the system stiffness is provided.Experiments on a vertical ball screw feed system under acceleration and deceleration with different accelerations are also performed to verify the proposed dynamic model.Finally,the influence of the spindle system position,the rated dynamic load of the screw-nut joint,and the screw tension force on the natural frequency of the vertical ball screw feed system under acceleration and deceleration are studied.The results show that the vertical ball screw feed system has obviously different variable dynamics under acceleration and deceleration.The influence of the rated dynamic load and the spindle system position on the natural frequency under acceleration and deceleration is much greater than that of the screw tension force.
文摘Waveform control method was commonly adopted to reduce the spatter of CO2 arc welding and improve the weld formation. It certainly would reduce the self-regulation ability of arc due to the adoption of segmented constant current control which especially led to arc＂ blowout with the abrupt change oat＂ arc＂ length or downward welding. Therefore alterative wire-feed system based on arc voltage negative feedback was put forward to improve the .stability of arc＂ length in this paper. Double closed-loop and double fuzzy P1 regulation were adopted in this system. Fuzzy control of induced voltage was adopted in the inner-loop which improved the stability and fast response of wire-feed system. Fuzz）＂ control of arc＂ voltage negative feedback was used in the outer-loop whose output .served as the input of negative feedback regulation of inner-loop induced voltage. This method could remain arc＂ length and weld penetration unchan, ged on the basils of reducing spatter and improving formation and it was proved by downward welding tests.
文摘Beijing Aerospace System Engineering Institute of China Academy of Launch Vehicle Technology (CALT) declared recently that theinstitute has set up a laboratory whichwould operate a newly
基金the National Natural Science Foundation of China(No.51765031)Natural Science Foundation of Gansu Province(No.20JR5RA457).
文摘Robotic drilling technology for aircraft flexible assembly is challenging and is under active investigation.In this work,a feed system for robotic drilling end-effector is modeled.Two control algorithms with different computational complexity are proposed and compared.Based on reduced-order state observer,a pole placement controller is proposed firstly,and then a model reference adaptive controller is designed.An experiment platform is established in Matlab xPC environment to validate the effect of the two controllers.The experiment results show that the model reference adaptive controller delivers a higher tracking accuracy after the adaptive transient procedure than the pole placement controller does.
基金supported by the Capacity Building Project of Local University of Shanghai Municipal Science and Technology Commission(No.10230502900)the Program for Shanghai Collaborative Innovation Center for Cultivating Elite Breeds and Green-culture of Aquaculture animals(No.2021-KJ-02-12)the Innovation Project for Chongming Agriculture Industry from Chongming District Agriculture Commission of Shanghai(No.2022CNKC-01-05)。
文摘The efficiency and mechanism of hydrous iron oxide(HFO)and HFO/calcite mixture to inactivate the phosphorus in the overlying water(OW)/sediment system under the feed adding condition were explored,and the effect of HFO and HFO/calcite mixture addition on the diversity,composition and function of bacterial communities in the sediment was examined.HFO and HFO/calcite mixture direct addition can effectively lower the concentration of soluble reactive phosphorus(RSP)and diffusion gradient in thin film-unstable phosphorus(PD GT)in OW and inactivate the P DGTin the upper sediment.The elimination efficiencies of RSP by the direct HFO and HFO/calcite mixture addition were 48.9%-97.0%and 42.4%-95.4%,respectively.The alteration in the addition mode from the one-time to multiple direct addition was beneficial to the immobilization of RSP and PD GTin OW and P DGTin the upper sediment by HFO and HFO/calcite mixture under the feed input condition in the long run.Permeable fabric wrapping reduced the inactivation efficiency of RSP in OW by HFO and HFO/calcite mixture,but it made the recycling of these materials possible.Most of P immobilized by HFO and HFO/calcite mixture was relatively or very stable.After the HFO and HFO/calcite mixture addition,the composition of bacterial communities in the surface sediment changed.However,the bacterial communities in the amended sediments still can perform good ecological function.Our findings suggest that HFO and HFO/calcite mixture are promising phosphorus-immobilization materials for the inactivation of RSP and PD GTin OW and PD GTin the upper sediment under the feed inputting condition.
基金supported by the Fundamental Research Funds for the Central Universities,China(No.JKF-2025009442288)the Excellent Youth Team Cultivation Project for Central Universities of the Ministry of Education,China(No.YWF-22/23/24-JT-106)。
文摘The Propellant Feed System(PFS)is a crucial component of Electric Propulsion System(EPS)which is widely used in satellites for its high reliability and specific impulse.The Switching and Proportional Hybrid-controlled Xenon Feed System(SPHXFS)is a novel type of PFS with high flow regulation precision.This study develops a system-level simulation model with 75 components for the SPHXFS.The accuracy of the model is validated through the comparison with test data,showing an error of less than 3%during the startup phase and less than 0.1%after stabilization.The study analyzes the startup process and finds that the two-stage pressure reduction system avoids two-phase flow interference downstream,achieving a regulation accuracy of±0.1%.A long-term operation simulation of the system is conducted,revealing that pressure fluctuations occur upstream at 4767 s due to Bang-Bang control.However,with proportional control adjustments,these fluctuations do not affect the flow supply.Further research examines the impact of synchronous and asynchronous control modes of the Bang-Bang Valve(TPBBV)under the tank pressures of 6-10 MPa on the system's dynamic characteristics.It is found that the asynchronous control scheme results in a flow supply settling time that is 7.2-10s longer than the synchronous control scheme,with an overshoot increase of 4.1%-4.9%.These insights provide valuable reference and guidance for system optimization design and the formulation of operational strategies.
基金supported by Grants from the Research Funds of the Center for Advanced Interdisciplinary Science and Biomedicine of IHM(QYPY20220018)the National Natural Science Foundation of China(31822026,32271063,31500860,and 32100821)the National Science and Technology Innovation 2030 Major Project of China(2021ZD0203900).
文摘In the face of constantly changing environments,the central nervous system(CNS)rapidly and accurately calculates the body's needs,regulates feeding behavior,and maintains energy homeostasis.The arcuate nucleus of the hypothalamus(ARC)plays a key role in this process,serv-ing as a critical brain region for detecting nutrition-related hormones and regulating appetite and energy homeostasis.Agouti-related protein(AgRP)/neuropeptide Y(NPY)neu-rons in the ARC are core elements that interact with other brain regions through a complex appetite-regulating network to comprehensively control energy homeostasis.In this review,we explore the discovery and research progress of AgRP neurons in regulating feeding and energy metabolism.In addition,recent advances in terms of feeding behavior and energy homeostasis,along with the redundant neural mecha-nisms involved in energy metabolism,are discussed.Finally,the challenges and opportunities in the field of neural regula-tion of feeding and energy metabolism are briefly discussed.
基金funded by research grants from the National Natural Science Foundation of China(Nos.41706142 and 32071615)the China Agriculture Research System of MOF and MARA(No.CARS-49)the Funding for School-Level Research Projects of Yancheng Institute of Technology(No.XJR2021035)。
文摘Microplastic(MP)pollution has spread from the mainland to the ocean.However,Haizhou Bay,which is one of the important land-ocean transition zones,has been reported relatively little about the enrichment of MPs.To provide fundamental data for MP pollution in Haizhou Bay,we studied the occurrence of microplastics in the intestines of 8 species of fish with different habits and feeding modes.The fish intestines were digested with a 10%KOH solution,and MPs are separated with a glass fiber filter.Then,the size,shape,color,and composition of the MPs were analyzed using a stereomicroscope and Fourier transform infrared spectrometer.The results showed the abundance of MP intake ranged from 0.02 items g^(-1) to 0.16 items g^(-1) and the detection rate of MPs ranged from 53.33% to 80% across different fish species.The MP intake in benthic fish and omnivorous fish was significantly higher than that of pelagic fish and predatory fish.Smaller MPs(<0.25 mm)were the dominant types and accounted for 62.50% of the total.The fiber was the prevailing shape of MPs,and the black MPs were the most common,followed by red and yellow ones.Polyethylene terephthalate(PET),polyamide(PA),and polystyrene(PS)were the main components of MPs,accounting for 34.9%,29.9%,and 16.4%,respectively.According to the composition analysis of MPs,the main sources of MPs in fish of Haizhou Bay were attributed to marine aquaculture and port construction.The results are helpful for our better understanding of the status of MP pollution in this area,and further aid in the development of the pointed measures to mitigate and prevent the MP pollution in this ecologically important area.
基金supported by the National Key R&D Program of China(2021YFD1300901)the National Key R&D Young Scientists Project of China(2022YFD1302000)+1 种基金the Education Department of Gansu Province:Outstanding Postgraduate“Innovation Star”,China(2022CXZX-086)the Major Science and Technology Project of Gansu Province,China(22ZD6NC069)。
文摘Feed efficiency(FE)is a crucial economic trait that significantly impacts profitability in intensive sheep production,and can be evaluated by the residual feed intake(RFI)and feed conversion ratio(FCR).However,the underlying genetic mechanisms that underlie FE-related traits in sheep are not fully understood.Herein,we measured the FE-related traits of 1,280 Hu sheep and conducted the phenotype statistics and correlation analysis,the result showcase that there was a large variation for FE-related traits,and RFI was significant positive correlation with average daily feed intake(ADFI)and FCR.Moreover,a genome-wide association study(GWAS)was conducted using whole-genome resequencing data to investigate the genetic associations of ADFI,FCR and RFI.For ADFI and FCR traits,2 and one single nucleotide polymorphisms(SNPs)exceeded the genome-wide significance threshold,whereas ten and 5 SNPs exceeded the suggestive significance threshold.For RFI traits,only 4 SNPs exceeded the suggestive significance threshold.Finally,a total of 8 genes(LOC101121953,LOC101110202,CTNNA3,IZUMO3,PPM1E,YIPF7,ZSCAN12and LOC105603808)were identified as potential candidate genes for FE-related traits.Simultaneously,we further analyzed the effects of 2 candidate SNPs associated with RFI on growth and FE traits in enlarged experimental population,the results demonstrated that these 2 SNPs was not significantly associated with growth traits(P>0.05),but significantly related to RFI traits(P<0.05).These findings will provide valuable reference data and key genetic variants that can be used to effectively select feed-efficient individual in sheep breeding programs.
基金supported by the Chinese Natural Science Foundation projects(32272915 and 32472949)National Key Research and Development Programs of China(2023YFD1301003)+1 种基金the Fundamental Research Funds for the Central Universities(2662023DKPY002)Hebei Panshuo Biotechnolog Co.,Ltd.
文摘Background This study was carried out to investigate the individual and combined contamination of aflatoxin B_(1)(AFB_(1)),deoxynivalenol(DON),and zearalenone(ZEN)in feeds in China between 2021 and 2024.A total of 23,003 feed samples,including 17,489 feedstuff samples and 5,514 complete feed samples,were collected from different provinces of China for mycotoxin analysis.Results The analyzed mycotoxins displayed considerably high contamination in the feed samples,with the individual contamination of AFB_(1),DON,and ZEN were 20.0%–100%,33.3%–100%,and 85.0%–100%,respectively.The average concentrations of AFB_(1),DON,and ZEN were 1.2–728.7μg/kg,106–8,634.8μg/kg,and 18.1–3,341.6μg/kg,respectively.Notably,the rates over China’s safety standards for AFB_(1),DON,and ZEN in raw ingredients were 9.7%,2.7%,and 15.7%,respectively.Meanwhile,3.5%,1.1%,and 8.7%of analyzed complete feeds exceeded China’s safety standards for AFB_(1),DON,and ZEN,respectively.Moreover,the co-contamination rates of AFB_(1),DON,and ZEN in more than 70%of raw ingredients and 87.5%of complete feed products were 60.0%–100%and 61.5%–100%,respectively.Conclusion This study reveals that the feeds in China have commonly been contaminated with AFB_(1),DON,and ZEN alone and their combination during the past four years.These findings highlight the significance of monitoring mycotoxin contaminant levels in domestic animal feed and the importance of carrying out feed administration and remediation strategies for mycotoxin control.
基金Mahidol University for the support of a “Scholarship for PhD Student”, Thailandthe the cooperation with the National Science and Technology Development Agency and Mahidol University of “the Scholarship for the Development of High Quality Research Graduates in Science and Technology Project”, Thailand。
文摘Global warming and climate change have made food production through conventional agriculture inefficient, and their effects on livestock and crop cultivation are leading to disruptions in the food supply. The troubles are severe in regions suffering from improper land management and unsustainable practices. The Bio-CircularGreen(BCG) economic model, designed to reduce and recycle resources by using environmentally friendly procedures, has been developed. The Azolla plant represents an interesting model for BCG and for enhancing community networks in Southeast Asia(SEA) because it provides multipurpose materials. Azolla can be used for various applications in agriculture such as biofertilizer and animal feed. However, our understanding and utilization of Azolla are limited. Moreover, collaboration among farmers is insufficient to maximize the benefits of Azolla. In this study, we provide a comprehensive review of the role of Azolla in agriculture. We review the main properties of Azolla as biofertilizers, especially regarding rice production and the interaction with cyanobacteria. For livestock, we discuss procedures to use Azolla in animal feed and evaluate the ingredients of the meal. In addition, we discuss product qualities from livestock treated with Azolla in the diet. This review also describes Azolla-based farming, which is designed for efficient land use and promotes nutrient cycling.Hence, we show that the Azolla plant is one of the key factors for farm-based agroecosystem services which can drive sustainable bioresource management in SEA. Moreover, we also propose the potential development of Azolla to improve its properties as a biofertilizer, a functional feed for animals and humans, and a feedstock for bio-oil production.
基金supported by the local innovative and research teams project of Guangdong province(2019BT02N630)national key research and development program(2022YFD1300401)+2 种基金Double first-class discipline promoting project(2023B10564001)National Natural Science Foundation of China(32272954)Natural Science Foundation of Guangdong Province,China(2024A1515013131).
文摘Background Intestinal oxidative stress serves as an endogenous host defense against the gut microbiota by increas-ing energy expenditure and therefore decreasing feed efficiency(FE).Several systems coordinately regulate redox bal-ance,including the mitochondrial respiratory chain,nicotinamide adenine dinucleotide phosphate(NADPH)oxidase,and different antioxidants.However,it remains unclear which redox balance compartments in the intestine are crucial for determining FE.Results In this study,we first screened the key targets of different metabolites and redox balance-related gene expression in broiler ceca.We then constructed a mouse colitis model to explore malic acid(MA)ability to allevi-ate intestinal inflammation.We further used controlled release technology to coat MA and investigated its effects on the intestinal redox status and FE in vivo.Finally,we examined the underlying mechanism by which MA modulated redox status using a porcine intestinal epithelial cell jejunum 2(IPEC-J2)cell model in vitro.Our results demonstrated that the MA/malic enzyme 3(ME3)pathway may play an important role in reducing oxidative stress in the broiler cecum.In addition,colon infusion of MA attenuated inflammatory phenotypes in the dextran sulfate sodium salt(DSS)induced mouse colitis model.Then,dietary supplementation with controlled-release MA pellet(MAP)reduced the feed to gain(F/G)ratio and promoted chicken growth,with reduced oxidative stress and increased bacterial diver-sity.Finally,the in vitro IPEC-J2 cell model revealed that ME3 mediated the effect of MA on cellular oxidative stress.Conclusion In summary,our study firstly revealed the important role of the MA/ME3 system in the hindgut of broiler chickens for improving intestinal health and FE,which may also be crucial for the implications of colon inflammation associated diseases.
基金Open Access funding enabled and organized by Projekt DEALfinanced by the Deutsche Forschungsgemeinschaft(DFG)grant 470833544 to WK.
文摘The radula is a crucial adaptation for food-processing in molluscs.A deeper understanding of the interaction between the radula and the preferred food is lacking,complicating the inference of the precise ecological roles of radular structures.This study presents the first experimental set-up that allows to study the influence of the radular morphology,specifically the degree of tooth-tooth interlocking(so-called collective effect),on the feeding efficiency.For this purpose,physical 3D models of the teeth were designed using CAD software and 3D printing technique.The feeding efficiencies with models of different degree of interlocking were determined by tensile tests,pulling the models trough agar gels with different viscosities.The forces generated by the models and the masses of the removed gel fragments were determined.We found,that radular models with a high degree of tooth–tooth interlocking performed best as they were able to remove most agar.We additionally broke the teeth and determined,that the teeth with the highest degree of interlocking could resist to highest force.Overall,the study highlights the complex interplay between radular morphology and its ecological function,suggesting that even minor morphological alterations can significantly impact the efficiency and effectiveness of food gathering.Understanding these interactions cannot only shed light on the ecological adaptations of molluscs,but provide further insights into development of more effective grinding,scraping,and cleaning technical devices.
文摘BACKGROUND Esophageal cancer(EC)is an aggressive malignancy with low survival(10%-30%).Nutritional problems are present throughout the perioperative period and are key to prognosis.Home enteral nutrition appears to improve the nutritional status of patients with EC.Few studies have addressed the experience of patients administering their own nutritional fluids and managing their own feeding tubes at home.The aim of this study was to explore the real-life experience of self-management of feeding tubes in patients at home after EC surgery in the first 3 months after discharge following surgery.AIM To explore feeding tube self-management experience of patients at home 3 months after discharge following EC surgery.METHODS Face-to-face semi-structured interviews were conducted with 18 patients using a feeding tube at home after EC surgery.Thematic analysis of the recordings identified themes related to feeding tube self-management.RESULTS Patients expressed similar feelings about their tube management experiences concerning three contextualized themes:Self-management dilemmas,distressing experiences,and self-management facilitators.CONCLUSION There are many dilemmas and problems in self-managing feeding tubes in postoperative homebound patients with EC.Clinical staff should provide guidance to promote a positive change in self-management behavior.
文摘The feed industry serves as a critical intermediary between agriculture and animal husbandry,providing essential support for the modern breeding industry.Utilizing the annual financial report data from 19 publicly listed companies within the feed industry in 2023,a comprehensive evaluation index system was developed to assess the financial performance of these companies from four dimensions:debt paying ability,operational ability,profitability,and development ability.Factor analysis and hierarchical cluster analysis were employed to assess the financial performance of publicly listed companies within the feed industry.By comparing the mean classifications and comprehensive scores,this study analyzed the strengths and weaknesses of these listed feed companies.Ultimately,it offered recommendations for improvement in areas such as product optimization and enhancement,reasonable liability management,and the advancement of company governance practices.
基金Supported by National Natural Science Foundation of China(Grant Nos.52275435,52075465,52375519)Open Fund Project of Jiangsu Key Laboratory of Precision and Micro-manufacturing Technology(Grant No.JSKL2324K03)Key Research and Development Program of Hunan Province of China(Grant No.2023GK2026)。
文摘Rotational feeding combined with shift feeding electrochemical trepanning(RF-SF ECTr)is an effective method for machining aeroengine blisks.However,given the variable relative motion of the electrodes and the complex flow channels around the bending and twisting blades,the accessibility and uniformity of the flow field are poor in blisk RF-SF ECTr using the traditional electrolyte supply(TES)mode,resulting in poor machining stability and low machining efficiency.To improve the distribution of the flow field,a new multi-channel electrolyte supply(MCES)mode is proposed for blisk RF-SF ECTr,in which the position and volume of the electrolyte supply are controlled effectively by setting multiple inlet channels in the liquid inlet area.A flow-field simulation comparison between TES and MCES shows that better accessibility and uniformity of the flow-field distribution are achieved under MCES.To clarify further the flow-field distribution characteristics under RF-SF ECTr,a series of flow-field simulations was conducted at different machining depths.Based on the obtained dynamic change law for the flow field,to enhance further its uniformity and accessibility,a global coverage strategy for the electrolyte supply and a flow-field structure optimization method for MCES are proposed,which involve optimizing the number,diameter,and location of the inlet channels.After many simulations,the optimal MCES structure was achieved whereby the electrolyte covers all positions effectively in the processing area.To verify the proposed method as effective and correct,a series of RF-SF ECTr experiments was carried out.Under the optimized MCES mode,the feeding rate was increased from 0.8 mm/min with the TES mode to 2.0 mm/min,and the processing stability and efficiency were improved significantly.The methods presented here offer an effective guide for flow-field optimization when machining other components with complex spatial structures.
