The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e.,the dynamic stiffness).However,the dynamic ...The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e.,the dynamic stiffness).However,the dynamic stiffness and its effect mechanism have been rarely incorporated in open studies of the rotor system.Therefore,this study theoretically reveals the effect mechanism of dynamic stiffness on the rotor system.Then,the numerical study and experimental verification are conducted on the dynamic stiffness characteristics of a squirrel cage,which is a common support structure for aero-engine.Moreover,the static stiffness experiment is also performed for comparison.Finally,a rotor system model considering the dynamic stiffness of the support structure is presented.The presented rotor model is used to validate the results of the theoretical analysis.The results illustrate that the dynamic stiffness reduces the critical speed of the rotor system and may lead to a new resonance.展开更多
In this article, a model of 3-D net is set up by using lumped mass method. Model test results made by Lader and Enerhaug are cited to verify the numerical model. The aim of this paper is to investigate the effects of ...In this article, a model of 3-D net is set up by using lumped mass method. Model test results made by Lader and Enerhaug are cited to verify the numerical model. The aim of this paper is to investigate the effects of weight system on the hydrodynamic behavior of 3-D net of gravity cage in current. Using the 3-D net model, with different styles and masses of weight system, hydrodynamic behavior of gravity cage net in current is simulated. In this article, two styles of common weight system are used, which include： （1） sinker system , （2） bottom collar-sinker system. Under each style, three different masses of weight system are adopted. The numerical results indicate that the bottom collar-sinker system is practically feasible in improving the cage net volume deformation. Results of this study will give references for better knowledge of hydrodynamic behavior of gravity cage.展开更多
The spatial distribution of laying hens in cage-free houses is an indicator of flock's health and welfare.While larger space allows chickens to perform more natural behaviors such as dustbathing,foraging,and perch...The spatial distribution of laying hens in cage-free houses is an indicator of flock's health and welfare.While larger space allows chickens to perform more natural behaviors such as dustbathing,foraging,and perching in cage-free houses,an inherent challenge is evaluating chickens'locomotion and spatial distribution(e.g.,realtime birds'number on perches or in nesting boxes).Manual inspection of hen's spatial distribution requires closer observation,which is labor intensive,time consuming,subject to human errors,and stress causing on birds.Therefore,an automated monitoring system is required to track the spatial distribution of hens for early detection of animal welfare and health concerns.In this study,a non–intrusive machine vision method was developed to monitor hens'spatial distribution automatically.An improved You Only Look Once version 5(YOLOv5)method was developed and trained to test hens'distribution in research cage-free facilities(e.g.,200 hens per house).The spatial distribution of hens the system monitored includes perch zone,feeding zone,drinking zone,and nesting zone.The dataset contains a whole growth period of chickens from day 1 to day 252.About 3000 images were extracted randomly from recorded videos for model training,validation,and testing.About 2400 images were used for training and 600 images for testing,respectively.Results show that the accuracy of the new model were 87–94%for tracking distribution in different zones for different ages of hens/pullets.Birds'age affected the performance of the model as younger birds had smaller body size and were hard to be detected due to blackness or occultation by equipment.The performance of the model was 0.891 and 0.942 for baby chicks(≤10 days old)and older birds(>10 days)in detecting perching behaviors;0.874 and 0.932 in detecting feeding/drinking behaviors.Miss detection happened when the flock density was high(>18 birds/m2)and chicken body was occluded by other facilities(e.g.,nest boxes,feeders,and perches).Further studies such as chicken be展开更多
Provision of nest boxes is necessary for laying hens,especially in non-cage systems.This study investigated the effects of nest width on nest utilization and mislaid eggs.Hy-Line Browns hens were transferred from conv...Provision of nest boxes is necessary for laying hens,especially in non-cage systems.This study investigated the effects of nest width on nest utilization and mislaid eggs.Hy-Line Browns hens were transferred from conventional cages to perchery pens at 12 weeks of age.Two experiments were conducted to mutually verify the hypothesis that narrowing group nests would improve nest utilization and reduce mislaid eggs.In experiment 1,group nests of 150 cm wide in two pens were partitioned at intervals of 50 cm and 37 cm,respectively.In experiment 2,partition panels were removed after acclimation.The number of mislaid eggs and nest eggs in each pre-set section were compared.Results indicated that narrowing group nests had positive effects on improving usage uniformity and efficiency of group nests.Nest eggs were more evenly distributed on the egg belt in both narrowed group nests,which was indicated by the significant decrease of variance among different sections(p<0.001).The proportion of mislaid eggs decreased by 3.5%in 37 cm treatment(p<0.05)and 4.7% in 50 cm treatment(p<0.001),respectively.As expected,reuse of the 150 cm group nests after removal of partition panels lowered the usage uniformity of group nests.A growth of three percentage points was found for the proportion of mislaid eggs after removing the partition panels in 50 cm treatment.The present results indicated that it is the width of the nest box that works for a better use of group nests.In conclusion,adding partition panels at intervals of 50 cm and 37 cm in group nests both are effective on nest usage and decreasing the occurrence of mislaid eggs.展开更多
基金the National Natural Science Foundation of China(Nos.11872148 and U1908217)the Fundamental Research Funds for the Central Universities of China(Nos.N2224001-4 and N2003013)the Basic and Applied Basic Research Foundation of Guangdong Province of China(No.2020B1515120015)。
文摘The support structure of a rotor system is subject to vibration excitation,which results in the stiffness of the support structure varying with the excitation frequency(i.e.,the dynamic stiffness).However,the dynamic stiffness and its effect mechanism have been rarely incorporated in open studies of the rotor system.Therefore,this study theoretically reveals the effect mechanism of dynamic stiffness on the rotor system.Then,the numerical study and experimental verification are conducted on the dynamic stiffness characteristics of a squirrel cage,which is a common support structure for aero-engine.Moreover,the static stiffness experiment is also performed for comparison.Finally,a rotor system model considering the dynamic stiffness of the support structure is presented.The presented rotor model is used to validate the results of the theoretical analysis.The results illustrate that the dynamic stiffness reduces the critical speed of the rotor system and may lead to a new resonance.
基金the National High Technology Research and Development Program of China (863 Program, Grant No. 2006AA100301)Program for Changjiang Scholars and Innovative Research Team in University (PCSIRT) (Grant No. IRT0420).
文摘In this article, a model of 3-D net is set up by using lumped mass method. Model test results made by Lader and Enerhaug are cited to verify the numerical model. The aim of this paper is to investigate the effects of weight system on the hydrodynamic behavior of 3-D net of gravity cage in current. Using the 3-D net model, with different styles and masses of weight system, hydrodynamic behavior of gravity cage net in current is simulated. In this article, two styles of common weight system are used, which include： （1） sinker system , （2） bottom collar-sinker system. Under each style, three different masses of weight system are adopted. The numerical results indicate that the bottom collar-sinker system is practically feasible in improving the cage net volume deformation. Results of this study will give references for better knowledge of hydrodynamic behavior of gravity cage.
基金sponsored by the Egg Industry CenterGeorgia Research Alliance(Venture Fund)+5 种基金UGA CAES Dean's Office Research FundUGA COVID Recovery Research FundUGA Provost Office Rural Engagement Fundand USDA-NIFAHatch projects:Future Challenges in Animal Production Systems:Seeking Solutions through Focused Facilitation(GEO00895,Accession Number:1021519)&Enhancing Poultry Production Systems through Emerging Technologies and Husbandry Practices(GEO00894Accession Number:1021518).
文摘The spatial distribution of laying hens in cage-free houses is an indicator of flock's health and welfare.While larger space allows chickens to perform more natural behaviors such as dustbathing,foraging,and perching in cage-free houses,an inherent challenge is evaluating chickens'locomotion and spatial distribution(e.g.,realtime birds'number on perches or in nesting boxes).Manual inspection of hen's spatial distribution requires closer observation,which is labor intensive,time consuming,subject to human errors,and stress causing on birds.Therefore,an automated monitoring system is required to track the spatial distribution of hens for early detection of animal welfare and health concerns.In this study,a non–intrusive machine vision method was developed to monitor hens'spatial distribution automatically.An improved You Only Look Once version 5(YOLOv5)method was developed and trained to test hens'distribution in research cage-free facilities(e.g.,200 hens per house).The spatial distribution of hens the system monitored includes perch zone,feeding zone,drinking zone,and nesting zone.The dataset contains a whole growth period of chickens from day 1 to day 252.About 3000 images were extracted randomly from recorded videos for model training,validation,and testing.About 2400 images were used for training and 600 images for testing,respectively.Results show that the accuracy of the new model were 87–94%for tracking distribution in different zones for different ages of hens/pullets.Birds'age affected the performance of the model as younger birds had smaller body size and were hard to be detected due to blackness or occultation by equipment.The performance of the model was 0.891 and 0.942 for baby chicks(≤10 days old)and older birds(>10 days)in detecting perching behaviors;0.874 and 0.932 in detecting feeding/drinking behaviors.Miss detection happened when the flock density was high(>18 birds/m2)and chicken body was occluded by other facilities(e.g.,nest boxes,feeders,and perches).Further studies such as chicken be
基金This study was financially supported by the Developing Key Equipment for Digital Management and Monitoring Environment in Animal Production Modern Agricultural Industry Technology System(2013AA10230602)the Special Fund for Cultivation and Evolution of Beijing Innovative Base(Z171100002217018).
文摘Provision of nest boxes is necessary for laying hens,especially in non-cage systems.This study investigated the effects of nest width on nest utilization and mislaid eggs.Hy-Line Browns hens were transferred from conventional cages to perchery pens at 12 weeks of age.Two experiments were conducted to mutually verify the hypothesis that narrowing group nests would improve nest utilization and reduce mislaid eggs.In experiment 1,group nests of 150 cm wide in two pens were partitioned at intervals of 50 cm and 37 cm,respectively.In experiment 2,partition panels were removed after acclimation.The number of mislaid eggs and nest eggs in each pre-set section were compared.Results indicated that narrowing group nests had positive effects on improving usage uniformity and efficiency of group nests.Nest eggs were more evenly distributed on the egg belt in both narrowed group nests,which was indicated by the significant decrease of variance among different sections(p<0.001).The proportion of mislaid eggs decreased by 3.5%in 37 cm treatment(p<0.05)and 4.7% in 50 cm treatment(p<0.001),respectively.As expected,reuse of the 150 cm group nests after removal of partition panels lowered the usage uniformity of group nests.A growth of three percentage points was found for the proportion of mislaid eggs after removing the partition panels in 50 cm treatment.The present results indicated that it is the width of the nest box that works for a better use of group nests.In conclusion,adding partition panels at intervals of 50 cm and 37 cm in group nests both are effective on nest usage and decreasing the occurrence of mislaid eggs.
