Electrochemical machining(ECM)is an economical and effective method for blisk manufacturing and includes two steps:channel machining and profile machining.The allowance distribution after the channel machining will di...Electrochemical machining(ECM)is an economical and effective method for blisk manufacturing and includes two steps:channel machining and profile machining.The allowance distribution after the channel machining will directly affect the profile machining.Therefore,to improve the uniformity of allowance distribution in the machining of channels,a method that incorporates a variable feed rate mode is developed.During the machining process,the feed rates are dynamically changed according to the needs of the side gap at the different feed depths.As a result,the side gaps at the different feed depths vary,contributing to a decrease in the allowance difference.In this study,the dissolution processes of a blisk channel are simulated using different feed rates,and prediction profiles are obtained.Based on the prediction profiles,the relationship among the feed rate,feed depth,and side gap is established.Then,the feed rates at different feed depths are adjusted according to the relationship.In addition,contrast experiments are conducted.Compared with blisk channel ECM using a constant feed rate of 1 mm/min,using the variable feed rate decreases the allowance differences in the convex and concave parts by 62.2%and 67.4%,respectively.This indicates that using the variable feed rate in the ECM process for a blisk channel is feasible and efficient.展开更多
A numerical model was established to calculate the cycle feed rate through studying the case of a cold pilger mill with the 304 stainless steel pipe. Firstly, the precise constitutive equation of 304 stainless steel w...A numerical model was established to calculate the cycle feed rate through studying the case of a cold pilger mill with the 304 stainless steel pipe. Firstly, the precise constitutive equation of 304 stainless steel was obtained through nonlinearly fitting the true stress-strain data from unidirectional tensile test. Then, the numerical method to calculate the equivalent deformation was determined according to the plastic deformation feature of the steel tube during cold rolling and the incremental theory. Finally, the cycle feed rate of cold roiled 304 stainless steel pipe was extracted when formulating springback through utilizing above results comprehensively and unloading law. Stress state, metal flow, finished pipe size and distribution of residual stress were obtained by finite element method to calculate the whole rolling process when the cycle feed rate was 10 mm, and the optimized model was verified through finished pipe size.展开更多
Considering machining efficiency, surface quality and wear of cutter and machine, it is necessary to maintain high, stable and constant surface feed rate as far as possible.The feed late control strategy for multi-axi...Considering machining efficiency, surface quality and wear of cutter and machine, it is necessary to maintain high, stable and constant surface feed rate as far as possible.The feed late control strategy for multi-axis CNC machining of free-form surfaces is presented. It comprises: ①the determination of effective feed rate; ②the adoption of suitable approaches to smooth feed rate. This strategy considers path geometry, actuator limitation and machine dynamics. The result shows that machining efficiency is improved effectively.展开更多
Friction stir processing （FSP）, a variation of FSW （friction stir welding） is an emerging surface engineering technology that can locally eliminate casting defects and refine microstructures, thereby improving the...Friction stir processing （FSP）, a variation of FSW （friction stir welding） is an emerging surface engineering technology that can locally eliminate casting defects and refine microstructures, thereby improving the mechanical properties of material. FSP can also produce fine grained microstructures through the thickness to impart superplasticity. The technology involves plunging a rapidly rotating, non consumable tool, comprising a profiled pin and larger diameter shoulder, into the surface and then traversing the tool across the surface. The pin and the shoulder friction heat the surface which alters the grain structure in the processed area thereby improving the mechanical properties. This paper presents the effects of FSP on microstructure and mechanical properties of extruded cast 2285 aluminum alloy at three different feed rates viz. 10, 12 and 15 mm/min. With the increase in the feed speed the material was observed to have increased impact strength. FSP also increased the tensile and yield strengths with increases in hardness and ductility values also. The observation has been listed in detail and pictorially represented.展开更多
In this paper, a model is proposed for the prediction of the width of arching in hoppers resulted from sudden changes in solid feed rates. Such changes in solid feed rate usually come from the collision on the surface...In this paper, a model is proposed for the prediction of the width of arching in hoppers resulted from sudden changes in solid feed rates. Such changes in solid feed rate usually come from the collision on the surface of the moving-bed in the standpipe. The model also takes into account the effect of the powder height in the standpipe of the hopper. The model proves to be adaptable for predicting operational conditions to avoid arching by keeping constant powder height in the main standpipe with interstitial gas flow.展开更多
Complex field environments,diverse crop conditions,and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters.In order ...Complex field environments,diverse crop conditions,and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters.In order to overcome these problems,an electric-hydraulic concave clearance automatic control system for the threshing unit was developed based on the maize feed rate monitoring,which can automatically realize the best match between the concave clearance and diverse feed rates during harvesting.The threshing performance of the electric-hydraulic control system was evaluated for varying and uneven maize feed rate fluctuations,such as the feed rate increased(6-8-10 kg/s),the feed rate decreased after an increase(6-10-8 kg/s,8-10-6 kg/s),the feed rate increased after a decrease(8-6-10 kg/s,10-6-8 kg/s),and the feed rate decreased(10-8-6 kg/s).In particular,the threshing rotor shaft peak torque,the range of threshing rotor shaft torque,the rate of broken grains(BGR),and the rate of unthreshed grains(UGR)with and without the electric-hydraulic control system were tested.Treatments with the electric-hydraulic control system were adjustable concave clearance with the value of 45 mm,50 mm,and 55 mm.Treatments without the electric-hydraulic control system were constant concave clearance(50 mm).Results demonstrate that the threshing unit with the electric-hydraulic control system outperformed the one without the electric-hydraulic control system,with threshing rotor peak torque,the range of threshing rotor axis torque,the BGR,and the UGR decreasing by 18.38%,38.27%,2.08%,and 0.10%,respectively.Moreover,the rate of broken grains was lower than 5.00%,better than the national standard.Thus,the feed rate fluctuations and timely adjustment of the concave clearance were able to avoid blocking the rotor and improve the threshing performance compared to the constant concave clearance.展开更多
The growing interest in additive manufacturing of GH4169 alloy was accompanied by the demand on spherical GH4169 powders with high performance.The powder particles were treated by radio frequency plasma with the diffe...The growing interest in additive manufacturing of GH4169 alloy was accompanied by the demand on spherical GH4169 powders with high performance.The powder particles were treated by radio frequency plasma with the different feeding rates.The microstructure and morphology,the particle size distribution of as-treated powders were studied by scanning electron microscopy and laser particle size analysis.It was demonstrated that GH4169 powders with extremely fine followability were obtained by radio frequency plasma spheroidization technology.With the same plasma parameters,the spheroidization efficiency of the particles varied with the feeding rates.When the rate of the powder feeding rates was too small,the excessive absorption of the heating by the powders caused vaporization,then the collection decreased.When the feeding rates was too large,the powder particles were insufficiently absorbed,resulting in defects in the powders.The microstructure of the as-treated spherical particles was mainly cell crystals,columnar crystals,and even microcrystals.Under the suitable plasma parameters,the resulting powders haved a slightly increased average particle size,excellent spheroidization,surface smoothness,followability,and bulk ratio.展开更多
The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic particles.The effects of different feeding rates and ...The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic particles.The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment.The results indicate that as the powder feeding rate increases,the impact velocity of gas and particles gradually decreases,and the temperature of gas and particles increases,resulting in an increase in the difference between particle impact velocity and critical velocity.The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min,which is 343 MPa.As the powder feeding rate increases,the performance of the deposits decreases,but it significantly saves time and cost.As the particle diameter increases,the impact temperature first increases and then decreases,resulting in the critical velocity first decreasing and then increasing,and the mechanical performance first increasing and then decreasing.To some extent,the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.展开更多
Determining the suitable fish farming conditions for optimal growth is necessary for aquaculture production, but it is not very obvious because it requires a good understanding of species biology. Thus, this study aim...Determining the suitable fish farming conditions for optimal growth is necessary for aquaculture production, but it is not very obvious because it requires a good understanding of species biology. Thus, this study aims to evaluate the effects of different temperature regimes, stocking densities, and feeding rates on the growth of Nile tilapia, Oreochromis niloticus fingerlings that have been sex-reversed with 17α methyl testosterone. Three independent experiments were performed (with replicates) at the IRD Bel-Air fish farm (Dakar, Senegal) on 27-day-old fry maintained in six 25 L tanks with a batch of 100 individuals each. These fry were subjected to three different temperatures (26˚C, 28˚C, 30˚C;kept constant with thermostats), stocking densities (5, 10 and 15 ind/l) and feeding rates (5%, 10% and 15% of biomass;distributed three times a day). For the temperature and density treatments, fry was fed a pelleted feed containing 38% protein, distributed by hand at 10% of their total biomass, readjusted after each measurement. Growth performance (total weight, weight gain and daily weight gain), physicochemical parameters (temperature, oxygen, nitrite and phosphorus), feed conversion ratio (FCR) and survival rate (SR) were regularly monitored (weekly) during the experimental period. For the heat treatment, the results did not show an apparent relationship between growth performance and nitrite, phosphorus or dissolved oxygen (DO) contents. In contrast, there was a significant correlation between temperature and growth rates, with the best growth being obtained at 30˚C compared to 28˚C and 26˚C. Similarly, growth rates were correlated with stocking density and feeding rate but not with oxygen, temperature, nitrite or phosphorus levels. The best growth rates were observed at the lowest density (5 ind/l) and for the highest feeding rate (15% of biomass), which coincides with the best FCR and survival rates. Thus, 30˚C, 5 ind/l and 15% of biomass appeared to be the most favorable temperature, stocking density and feeding rate for optimal growth of Nile tilapia fry after inversion. The application of these results in the culture systems will allow to reach a good production of O. niloticus and thus to contribute to sustainable development of fish culture in Senegal.展开更多
Background: The optimal rate of feeding advancement after initiation of early enteral nutrition (EEN) for underweight, critically ill patients is unknown. Methods: We conducted a retrospective chart review in intensiv...Background: The optimal rate of feeding advancement after initiation of early enteral nutrition (EEN) for underweight, critically ill patients is unknown. Methods: We conducted a retrospective chart review in intensive care unit (ICU) patients with a body mass index (BMI) < 20.0 kg/m<sup>2</sup>. Patients were categorized into Group R, which reached the energy target within 3 days of EEN initiation, and Group S, which reached the energy target 4 or more days after EEN initiation. Results: A total of 65 patients with a median age of 73 years were included in the study. No significant differences were observed between the two groups for all-cause mortality, ICU-free days, or length of hospital stay. Ventilator-free days (VFDs) were significantly fewer in Group R than in Group S (18.0 [0.0 - 22.0] vs. 21.0 [16.3 - 24.8] days;P = 0.046). A significantly higher number of patients requiring mechanical ventilation (MV) at hospital discharge were observed in Group R than in Group S (29% vs. 8%;P = 0.030). Multivariable analyses with adjustment for confounders found that days required to reach target energy intake after EEN initiation were significantly and independently associated with the requirement for MV at hospital discharge, but not with VFDs. Conclusion: A slow rate of feeding advancement after initiation of EEN in critically ill patients having a BMI of <20.0 kg/m<sup>2</sup> might be associated with a reduced requirement for MV at hospital discharge. These results require confirmation in a large multicenter trial of underweight, critically ill patients.展开更多
The filtration rates of four kinds of bivalves that were cultivated dominantly around Xiamen sea area were measured by using a laboratory flowing system. The experimental results were shown below: (1) Filtration rates...The filtration rates of four kinds of bivalves that were cultivated dominantly around Xiamen sea area were measured by using a laboratory flowing system. The experimental results were shown below: (1) Filtration rates were measured in the range of 54 - 74.8 ml/ (g·min) among the four bivalves , sequencing descently Saccostrea cucullata > Sinonovacula constricta > Mytilus viridis > Rudi-tapes philippinarum. (2) The relationship between filtration rates on individual size showed a negative exponential function (FR = aW^b, FR'aW^(b-1), with b - 1 =- 0.435 6 and -0.392. (3) Filtration rates on Skeletonema costatum were much higher than on Alexandrium tamarensis and Scripp-silla trochoidea inS. cucullata and R. philippinarum. (4)FR'on algal densities was also shown a negative function(FR' = aD^(b-1), with b -1 =- 0.143 and -0.215 2 in S.cucullata and R.philippinarum , respectively.展开更多
Entomophagy has gained popularity as a novel approach to addressing food and nutrition insecurity, particularly in sub-tropical and tropical countries. Cockroaches, for example, have the potential to alleviate nutriti...Entomophagy has gained popularity as a novel approach to addressing food and nutrition insecurity, particularly in sub-tropical and tropical countries. Cockroaches, for example, have the potential to alleviate nutritional deficiencies, as well as the erratic supply of protein in feeds. They can also be reared on locally available organic substrates. This study investigated growth performance and survival of german cockroach (Blattella germanica) reared on locally available organic matter substrates as treatments;spent brewers’ grain (Treatment A), Treatment B consisting of (40%: wheat bran: 40% spent brewers’ grain: 20% Caridina nilotica), wheat bran (Treatment C), and C. nilotica (Treatment D) and in a completely randomised design (CRD). Each treatment was replicated four times, while in each replicate 20 - 30 nymphs were reared for forty-two days. Feed intake for all the treatments was not significantly different. There was a significant difference (P 0.05) in mature weight, average daily weight gain, live weight, and survival during rearing period. Cockroach performed well on treatment B and recorded highest mature weight, overall performance index, survival was 90.25 mg, 197.35, 96%. The least perfomance was reported in Treatment C;1.78, 83, 143.17 and 72.5 for average growth rate, survival, overall perfomance and mature weight respectively. B. Based on these findings, a single feed as used in this study was inferior to the composite (Treatment B) in all parameters of growth performance and survival. The composite diet (Treatment B) could be suitable substrate for mass production of B. germanica for feed and food.展开更多
In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result...In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result that the appearance and quality of weld are not steady. To weaken the influence of the distance alteration, a method is put forward in the paper. The method is that the alternate wire-feed control is used for compensating the welding current. On the basis of theoretical analysis, a static numerical model for alternate wire-feed control is established. The experiments show that the model-based regulation of the wire feed rate can compensate the welding current and ensure the appearance of weld. When the alteration of vertical distance between the torch and the workpiece is greater, not only is the wire feed rate regulated, but the output voltage of the power source is adjusted to ensure the appearance and quality of weld.展开更多
基金the National Science and Technology Major Project(No.2017-VII-0004-0097)the Natural Science Foundation for Distinguished Young Scholars of Jiangsu Province(No.BK20170031)。
文摘Electrochemical machining(ECM)is an economical and effective method for blisk manufacturing and includes two steps:channel machining and profile machining.The allowance distribution after the channel machining will directly affect the profile machining.Therefore,to improve the uniformity of allowance distribution in the machining of channels,a method that incorporates a variable feed rate mode is developed.During the machining process,the feed rates are dynamically changed according to the needs of the side gap at the different feed depths.As a result,the side gaps at the different feed depths vary,contributing to a decrease in the allowance difference.In this study,the dissolution processes of a blisk channel are simulated using different feed rates,and prediction profiles are obtained.Based on the prediction profiles,the relationship among the feed rate,feed depth,and side gap is established.Then,the feed rates at different feed depths are adjusted according to the relationship.In addition,contrast experiments are conducted.Compared with blisk channel ECM using a constant feed rate of 1 mm/min,using the variable feed rate decreases the allowance differences in the convex and concave parts by 62.2%and 67.4%,respectively.This indicates that using the variable feed rate in the ECM process for a blisk channel is feasible and efficient.
基金The authors are grateful for the financial assis- tance from the National Science Foundation of China （U1710113）, the China Postdoctoral Science Foundation （2017M622903）, the Fund for Shanxi Key Subjects Construction, Excellent innovation projects of graduate students in Shanxi （2017SY077）, Heavy Machinery Engineering Research Center of Ministry of Education （20172004）.
文摘A numerical model was established to calculate the cycle feed rate through studying the case of a cold pilger mill with the 304 stainless steel pipe. Firstly, the precise constitutive equation of 304 stainless steel was obtained through nonlinearly fitting the true stress-strain data from unidirectional tensile test. Then, the numerical method to calculate the equivalent deformation was determined according to the plastic deformation feature of the steel tube during cold rolling and the incremental theory. Finally, the cycle feed rate of cold roiled 304 stainless steel pipe was extracted when formulating springback through utilizing above results comprehensively and unloading law. Stress state, metal flow, finished pipe size and distribution of residual stress were obtained by finite element method to calculate the whole rolling process when the cycle feed rate was 10 mm, and the optimized model was verified through finished pipe size.
基金This project is supported by National Natural Science Foundation of China and the Eight-Five Year Plan National Key Projects. Ma
文摘Considering machining efficiency, surface quality and wear of cutter and machine, it is necessary to maintain high, stable and constant surface feed rate as far as possible.The feed late control strategy for multi-axis CNC machining of free-form surfaces is presented. It comprises: ①the determination of effective feed rate; ②the adoption of suitable approaches to smooth feed rate. This strategy considers path geometry, actuator limitation and machine dynamics. The result shows that machining efficiency is improved effectively.
文摘Friction stir processing （FSP）, a variation of FSW （friction stir welding） is an emerging surface engineering technology that can locally eliminate casting defects and refine microstructures, thereby improving the mechanical properties of material. FSP can also produce fine grained microstructures through the thickness to impart superplasticity. The technology involves plunging a rapidly rotating, non consumable tool, comprising a profiled pin and larger diameter shoulder, into the surface and then traversing the tool across the surface. The pin and the shoulder friction heat the surface which alters the grain structure in the processed area thereby improving the mechanical properties. This paper presents the effects of FSP on microstructure and mechanical properties of extruded cast 2285 aluminum alloy at three different feed rates viz. 10, 12 and 15 mm/min. With the increase in the feed speed the material was observed to have increased impact strength. FSP also increased the tensile and yield strengths with increases in hardness and ductility values also. The observation has been listed in detail and pictorially represented.
基金Supported by the China Petrochemical Corporation.
文摘In this paper, a model is proposed for the prediction of the width of arching in hoppers resulted from sudden changes in solid feed rates. Such changes in solid feed rate usually come from the collision on the surface of the moving-bed in the standpipe. The model also takes into account the effect of the powder height in the standpipe of the hopper. The model proves to be adaptable for predicting operational conditions to avoid arching by keeping constant powder height in the main standpipe with interstitial gas flow.
基金This study was financially supported by the China Agriculture Research System of MOF and MARA,Mount Tai Industry Leading Talents Project(LJNY201708)the Soil-Machine-Plant Key Laboratory of the Ministry of Agriculture of China.
文摘Complex field environments,diverse crop conditions,and varying feed rate fluctuations commonly result in a decline in the threshing performance and the clogging of the threshing cylinder for maize harvesters.In order to overcome these problems,an electric-hydraulic concave clearance automatic control system for the threshing unit was developed based on the maize feed rate monitoring,which can automatically realize the best match between the concave clearance and diverse feed rates during harvesting.The threshing performance of the electric-hydraulic control system was evaluated for varying and uneven maize feed rate fluctuations,such as the feed rate increased(6-8-10 kg/s),the feed rate decreased after an increase(6-10-8 kg/s,8-10-6 kg/s),the feed rate increased after a decrease(8-6-10 kg/s,10-6-8 kg/s),and the feed rate decreased(10-8-6 kg/s).In particular,the threshing rotor shaft peak torque,the range of threshing rotor shaft torque,the rate of broken grains(BGR),and the rate of unthreshed grains(UGR)with and without the electric-hydraulic control system were tested.Treatments with the electric-hydraulic control system were adjustable concave clearance with the value of 45 mm,50 mm,and 55 mm.Treatments without the electric-hydraulic control system were constant concave clearance(50 mm).Results demonstrate that the threshing unit with the electric-hydraulic control system outperformed the one without the electric-hydraulic control system,with threshing rotor peak torque,the range of threshing rotor axis torque,the BGR,and the UGR decreasing by 18.38%,38.27%,2.08%,and 0.10%,respectively.Moreover,the rate of broken grains was lower than 5.00%,better than the national standard.Thus,the feed rate fluctuations and timely adjustment of the concave clearance were able to avoid blocking the rotor and improve the threshing performance compared to the constant concave clearance.
基金supported financially by Yangjiang City Hardware Knives and Scissors and Nickel Alloy Industry Additive Manufacturing Technology Innovation Platform Construction(No.2015B020221002)Guangdong Province‘Sailing Plan’Introduces Special Funding for Innovation and Entrepreneurship Team(No.2015YT02G090)+1 种基金High-end Knives and Scissors Additive Manufacturing(3D Printing)of Engineering Technology Research Center in Guangdong Province(Grant No.509153168061)Initial Construction Subsidy for New Research and Development Institutions of Yangjiang City Hardware Knives and Scissors Industry and Technology Research(Grant No.611229498090)。
文摘The growing interest in additive manufacturing of GH4169 alloy was accompanied by the demand on spherical GH4169 powders with high performance.The powder particles were treated by radio frequency plasma with the different feeding rates.The microstructure and morphology,the particle size distribution of as-treated powders were studied by scanning electron microscopy and laser particle size analysis.It was demonstrated that GH4169 powders with extremely fine followability were obtained by radio frequency plasma spheroidization technology.With the same plasma parameters,the spheroidization efficiency of the particles varied with the feeding rates.When the rate of the powder feeding rates was too small,the excessive absorption of the heating by the powders caused vaporization,then the collection decreased.When the feeding rates was too large,the powder particles were insufficiently absorbed,resulting in defects in the powders.The microstructure of the as-treated spherical particles was mainly cell crystals,columnar crystals,and even microcrystals.Under the suitable plasma parameters,the resulting powders haved a slightly increased average particle size,excellent spheroidization,surface smoothness,followability,and bulk ratio.
基金supported by the National Natural Science Foundation of China(Nos.52405356,52061135101,52071265)Jiangxi Provincial Natural Science Foundation Project,China(No.20242BAB20200)the National Key Research and Development Program,China(No.2021YFB3200500).
文摘The particle acceleration behavior and deposition mechanism of cold spraying aluminum matrix composites(Al_(2)O_(3)/2024)are complicated by the addition of ceramic particles.The effects of different feeding rates and particle diameters on critical velocity and mechanical properties were studied by numerical simulation and experiment.The results indicate that as the powder feeding rate increases,the impact velocity of gas and particles gradually decreases,and the temperature of gas and particles increases,resulting in an increase in the difference between particle impact velocity and critical velocity.The highest tensile strength of the deposit is achieved at a powder feeding rate of 1 r/min,which is 343 MPa.As the powder feeding rate increases,the performance of the deposits decreases,but it significantly saves time and cost.As the particle diameter increases,the impact temperature first increases and then decreases,resulting in the critical velocity first decreasing and then increasing,and the mechanical performance first increasing and then decreasing.To some extent,the best performance of the deposit is achieved when the size of the metal particle is close to that of the ceramic particle.
文摘Determining the suitable fish farming conditions for optimal growth is necessary for aquaculture production, but it is not very obvious because it requires a good understanding of species biology. Thus, this study aims to evaluate the effects of different temperature regimes, stocking densities, and feeding rates on the growth of Nile tilapia, Oreochromis niloticus fingerlings that have been sex-reversed with 17α methyl testosterone. Three independent experiments were performed (with replicates) at the IRD Bel-Air fish farm (Dakar, Senegal) on 27-day-old fry maintained in six 25 L tanks with a batch of 100 individuals each. These fry were subjected to three different temperatures (26˚C, 28˚C, 30˚C;kept constant with thermostats), stocking densities (5, 10 and 15 ind/l) and feeding rates (5%, 10% and 15% of biomass;distributed three times a day). For the temperature and density treatments, fry was fed a pelleted feed containing 38% protein, distributed by hand at 10% of their total biomass, readjusted after each measurement. Growth performance (total weight, weight gain and daily weight gain), physicochemical parameters (temperature, oxygen, nitrite and phosphorus), feed conversion ratio (FCR) and survival rate (SR) were regularly monitored (weekly) during the experimental period. For the heat treatment, the results did not show an apparent relationship between growth performance and nitrite, phosphorus or dissolved oxygen (DO) contents. In contrast, there was a significant correlation between temperature and growth rates, with the best growth being obtained at 30˚C compared to 28˚C and 26˚C. Similarly, growth rates were correlated with stocking density and feeding rate but not with oxygen, temperature, nitrite or phosphorus levels. The best growth rates were observed at the lowest density (5 ind/l) and for the highest feeding rate (15% of biomass), which coincides with the best FCR and survival rates. Thus, 30˚C, 5 ind/l and 15% of biomass appeared to be the most favorable temperature, stocking density and feeding rate for optimal growth of Nile tilapia fry after inversion. The application of these results in the culture systems will allow to reach a good production of O. niloticus and thus to contribute to sustainable development of fish culture in Senegal.
文摘Background: The optimal rate of feeding advancement after initiation of early enteral nutrition (EEN) for underweight, critically ill patients is unknown. Methods: We conducted a retrospective chart review in intensive care unit (ICU) patients with a body mass index (BMI) < 20.0 kg/m<sup>2</sup>. Patients were categorized into Group R, which reached the energy target within 3 days of EEN initiation, and Group S, which reached the energy target 4 or more days after EEN initiation. Results: A total of 65 patients with a median age of 73 years were included in the study. No significant differences were observed between the two groups for all-cause mortality, ICU-free days, or length of hospital stay. Ventilator-free days (VFDs) were significantly fewer in Group R than in Group S (18.0 [0.0 - 22.0] vs. 21.0 [16.3 - 24.8] days;P = 0.046). A significantly higher number of patients requiring mechanical ventilation (MV) at hospital discharge were observed in Group R than in Group S (29% vs. 8%;P = 0.030). Multivariable analyses with adjustment for confounders found that days required to reach target energy intake after EEN initiation were significantly and independently associated with the requirement for MV at hospital discharge, but not with VFDs. Conclusion: A slow rate of feeding advancement after initiation of EEN in critically ill patients having a BMI of <20.0 kg/m<sup>2</sup> might be associated with a reduced requirement for MV at hospital discharge. These results require confirmation in a large multicenter trial of underweight, critically ill patients.
基金This work was supported by the Fourth Subject of the Major Project of Natural Sciences in the "Ninth Five-Year Plan" of the State under contract No.39790111 Fujian Province Natural Science Foundation under contract No. 49776308.
文摘The filtration rates of four kinds of bivalves that were cultivated dominantly around Xiamen sea area were measured by using a laboratory flowing system. The experimental results were shown below: (1) Filtration rates were measured in the range of 54 - 74.8 ml/ (g·min) among the four bivalves , sequencing descently Saccostrea cucullata > Sinonovacula constricta > Mytilus viridis > Rudi-tapes philippinarum. (2) The relationship between filtration rates on individual size showed a negative exponential function (FR = aW^b, FR'aW^(b-1), with b - 1 =- 0.435 6 and -0.392. (3) Filtration rates on Skeletonema costatum were much higher than on Alexandrium tamarensis and Scripp-silla trochoidea inS. cucullata and R. philippinarum. (4)FR'on algal densities was also shown a negative function(FR' = aD^(b-1), with b -1 =- 0.143 and -0.215 2 in S.cucullata and R.philippinarum , respectively.
文摘Entomophagy has gained popularity as a novel approach to addressing food and nutrition insecurity, particularly in sub-tropical and tropical countries. Cockroaches, for example, have the potential to alleviate nutritional deficiencies, as well as the erratic supply of protein in feeds. They can also be reared on locally available organic substrates. This study investigated growth performance and survival of german cockroach (Blattella germanica) reared on locally available organic matter substrates as treatments;spent brewers’ grain (Treatment A), Treatment B consisting of (40%: wheat bran: 40% spent brewers’ grain: 20% Caridina nilotica), wheat bran (Treatment C), and C. nilotica (Treatment D) and in a completely randomised design (CRD). Each treatment was replicated four times, while in each replicate 20 - 30 nymphs were reared for forty-two days. Feed intake for all the treatments was not significantly different. There was a significant difference (P 0.05) in mature weight, average daily weight gain, live weight, and survival during rearing period. Cockroach performed well on treatment B and recorded highest mature weight, overall performance index, survival was 90.25 mg, 197.35, 96%. The least perfomance was reported in Treatment C;1.78, 83, 143.17 and 72.5 for average growth rate, survival, overall perfomance and mature weight respectively. B. Based on these findings, a single feed as used in this study was inferior to the composite (Treatment B) in all parameters of growth performance and survival. The composite diet (Treatment B) could be suitable substrate for mass production of B. germanica for feed and food.
文摘In the automatic CO_2 arc welding, the alteration of the vertical distance between the welding torch and the workpiece has a strong effect on the welding parameters such as welding current and voltage, with the result that the appearance and quality of weld are not steady. To weaken the influence of the distance alteration, a method is put forward in the paper. The method is that the alternate wire-feed control is used for compensating the welding current. On the basis of theoretical analysis, a static numerical model for alternate wire-feed control is established. The experiments show that the model-based regulation of the wire feed rate can compensate the welding current and ensure the appearance of weld. When the alteration of vertical distance between the torch and the workpiece is greater, not only is the wire feed rate regulated, but the output voltage of the power source is adjusted to ensure the appearance and quality of weld.
