OPTIMAL FEED RATE CONTROL FOR MULTI-AXIS CNC MACHINING OF FREE FORM SURFACES

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.

Effect of Low Feed Rate FSP on Microstructure and Mechanical Properties of Extruded Cast 2285 Aluminum Alloy

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.

Effect of Sudden Increase of Solid Feed Rate on the Arching in Hoppers Connected to a Moving-Bed Standpipe with Interstitial Gas Flow

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.

Electrochemical machining on blisk channels with a variable feed rate mode

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.

Numerical model establishment and verification of cold pilgering on cycle feed rate

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.

Development and performance evaluation of the electric-hydraulic concave clearance control system based on maize feed rate mon

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.

Effect of the feeding rate on microstructure and properties of plasma spheroidized GH4169 powder

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.

Suitable Temperature, Stocking Density and Feeding Rate for Optimal Growth of Sex Reversed Fry of Nile Tilapia Oreochromis niloticus (Senegal River Strain)

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.

The Impact of Rate of Feeding Advancement after Early Initiation of Enteral Nutrition in Critically Ill, Underweight Patients: A Single-Center Retrospective Chart Review

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/m2. 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/m2 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.

Studies on filtration rate in four species of suspension feeding bivalves

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.

Effects of Organic Substrates on Development and Survival of Blattela germanica for Food and Feed in Kenya

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.

Effects of Different Feeding Patterns on the Growth of Micropterus salmoides

Three experimental groups with different feeding frequencies,different feeding rates and compensatory feeding were set up to study their effects on the growth of Micropterus salmoides.The results showed that different feeding rates of 2%,3%and 4%had no significant effects on the growth of M.salmoides.Therefore,before the individual weight of 50 g,the fish could be fed with a feeding rate of 4%,which could be gradually decreased to 2%in the later period.Under the condition of relatively fixed feeding rate,different feeding frequencies had an impact on the growth of M.salmoides.Under the conditions of suitable water temperature,it is reasonable to feed twice daily.The experimental fish fed for 5 d and then deprived of feed for 1 d showed fully compensatory growth,and there were no significant differences in weight gain rate,daily weight gain and specific growth rate compared with the continuous feeding group(P>0.05).Therefore,according to the feeding conditions of fish in the breeding process,stopping feeding for 1 d every 5 d could save feed and labor and improve breeding efficiency.

人工饲料饲育家蚕5龄期的饲料效率研究

【目的】探明人工饲料饲育家蚕5龄期饲料效率与全龄桑叶育间的差异,为家蚕人工饲料的改进和饲育技术的优化提供技术支撑。【方法】以全龄桑叶育为对照(CK),研究家蚕5龄期不同饲育方式[1~5龄饲料育(5龄饲料育)、1~4龄饲料育5龄桑叶育(5龄桑叶育)]饲料效率间的差异。【结果】5龄饲料育家蚕第3天、第4天、第5天蚕体质量增量高于CK,第2天、第3天、第4天、第6天消化量低于CK,第2天、第3天、第4天、第5天体质转化率高于CK。5龄饲料育和5龄桑叶育的全茧转化效率、全茧生产效率、茧层转化效率和茧层生产效率均低于CK,5龄饲料育较CK分别低0.53百分点、0.10百分点、0.25百分点和0.08百分点,5龄桑叶育较CK分别低0.38百分点、0.14百分点、0.14百分点和0.06百分点;与5龄桑叶育相比,5龄饲料育除全茧生产效率高0.04百分点外,全茧转化效率、茧层转化效率、茧层生产效率分别低0.15百分点、0.11百分点和0.02百分点。【结论】全龄人工饲料育家蚕5龄期饲料效率低于全龄桑叶育,人工饲料饲育家蚕在饲料效率方面与全龄桑叶育有一定差距。

基于工程应用的CW-GMAW熔滴过渡形态表征

综述了涉及工程应用的冷丝熔化极气体保护焊(Cold wire gas metal arc welding,CW-GMAW)熔滴过渡形态特征。结果表明,在大电流、强规范、富氩混合气体保护下,CW-GMAW工艺的熔滴过渡形态呈喷射过渡;当电流较小、电弧电压较低时,可能为滴状过渡,甚至在弧压很低时,呈现短路过渡形态。该工艺电弧发生偏向冷丝的位移,弧长变短甚至发生短路,与冷丝送进速率比增高及冷丝在电弧中产生大量金属蒸气时弧柱电阻下降有关。在具有富氩混合保护气体的相同工艺参数下,CWGMAW转变电流比GMAW降低了4%~7%。焊接工艺参数对CW-GMAW和GMAW工艺熔滴过渡形态的影响规律大致相近,但前者因涉及冷丝送进速率比和电极焊丝送进速度,以及它们的匹配等,使焊接电流的影响更为复杂。

生物絮团的营养价值及其在水产养殖中的研究进展

规模化养殖背景下,水产养殖逐渐暴露出低效益、高污染等问题。为有效兼顾水产养殖的经济效益和环境效益,生物絮团技术应运而生,旨在调控水质,提高饲料利用率和水生动物成活率。虽然生物絮团被认为是最有效的养殖水体处理技术,且在欧美发达国家中得到广泛应用,但国内对生物絮团的研究尚处于起步阶段。因此,文章从生物絮团的营养价值出发,对前人的研究成果进行总结,力求为水产养殖的转型升级提供参考和借鉴。

老年痴呆病人实施人手喂养的安全性及有效性的Meta分析

目的:系统评价老年痴呆病人实施人手喂养的安全性及有效性,为老年痴呆病人在其痴呆轻症期自预设医疗指示,为家属及临床医护在病人痴呆中、重度期是否实施人手喂养提供决策依据。方法:计算机检索中国知网、万方数据库、PubMed、CINAHL、EMbase、Web of Science、the Cochrane Library等数据库中关于老年痴呆病人实施人手喂养的随机对照研究、类试验研究、队列研究,检索时限为建库到2023年9月。由2名研究者进行文献筛选、资料提取及方法学质量评价,并运用RevMan 5.3软件进行统计分析。结果:纳入6项研究,涉及病人1796例,其中试验组(人手喂养)811例,对照组(鼻胃管喂养)985例。Meta分析结果显示,人手喂养可降低老年痴呆病人的肺炎发生率[RR=0.51,95%CI(0.33,0.77),P=0.002]和死亡率[RR=0.54,95%CI(0.32,0.93),P=0.030]。结论:现有证据表明,老年痴呆病人实施人手喂养,可降低其肺炎发生率及死亡率。

螺旋卸船机颗粒回流分析

为了研究螺旋卸船机在不同倾角下输送物料时颗粒在螺旋槽中的回流问题,文中通过离散元对物料输送过程进行模拟,分析颗粒的运动状态、波动程度和回流情况以及不同几何参数和物理参数对颗粒回流的影响。结果表明:螺旋转速对物料在螺旋槽中的波动程度与螺旋卸船机的倾角相关,螺旋转速的选取应与倾斜角度相匹配以达到降低回流率的目的;增加进料量和减小螺距均可减小颗粒的回流率但不会降低发生回流现象的频率;无论改变螺旋转速、进料量还是螺距,颗粒在稳定输送时间内回流率对主流量影响较小,故回流现象不会影响卸船机的输送效率。

石家庄市区3岁儿童乳牙患龋与家庭喂养习惯的相关性分析

目的了解石家庄地区3岁儿童龋齿的患病状况,探讨其与家庭喂养习惯的关系,对其预防和早期干预提供依据。方法在石家庄市区抽取1680名3岁儿童进行临床口腔检查并向接受检查的儿童监护人发放调查问卷,最终统计分析调查数据。结果共有1104名儿童患龋,患龋率为66.67%。单因素分析结果显示患龋儿童与未患龋儿童在孩子长牙后是否有含奶头或奶瓶入睡、长牙后孩子喂奶或进食后是否及时清洁牙面、孩子现在是否经常吃零食方面相比,差异均具有统计学意义(P<0.05);在对孩子采取的喂养方式以及母亲是否与孩子共用餐具两方面相比,差异均无统计学意义(P>0.05)。多因素分析结果显示孩子长牙后含奶头或奶瓶入睡、孩子现在经常吃零食是3岁儿童患龋的危险因素,孩子长牙后喂奶或进食后及时清洁牙面是3岁儿童患龋的保护因素。结论石家庄市区3岁儿童患龋率较高,孩子长牙后含奶头或奶瓶入睡、孩子现在经常吃零食均是低龄儿童龋的危险因素,应加强口腔护理。

投喂率对凡纳对虾中间培育生长、生理和水环境的影响

中间培育是凡纳对虾(Penaeus vannamei)养殖的重要阶段,投喂率是影响此阶段养殖成效的重要参数。本研究开展为期30 d的养殖实验,研究3组投喂率(投喂率分别为体重的5%、7.5%、10%,分别命名为T5、T7.5和T10)对凡纳对虾中间培育养殖水质、微生物群落结构、非特异性免疫指标及生长性能的影响。实验期间,水体pH、盐度、温度及溶解氧均保持在适宜对虾生长的范围内。结果显示,随着实验进行,总氨氮(TAN)、亚硝态氮(NO2--N)和化学需氧量(COD)浓度出现上升趋势,实验结束时,其浓度随投喂率升高呈现显著差异:T10>T7.5>T5。微生物群落结构分析表明,养殖水体的微生物群落丰富度和多样性随投喂率升高呈下降趋势,不同投喂率的优势门类均为变形菌门(Proteobacteria,50.36%~67.53%)和拟杆菌门(Bacteroidetes,12.09%~67.53%);在属水平上,对凡纳对虾有害的弧菌(Vibrio)相对丰度在T10组最高(37.33%)、T5组最低(0.13%);对其有益的假交替单胞菌(Pseudoalteromonas)相对丰度在T10组最低(0.28%)、T7.5组最高(9.78%)。凡纳对虾肝胰腺的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、酸性磷酸酶(ACP)和碱性磷酸酶(AKP)活性在T10组最低、T7.5组最高(P<0.05)。T7.5和T10组对虾的体长和体重均显著大于T5组(P<0.05),但T7.5和T10组之间无显著差异(P>0.05),投喂率与存活率呈负相关,且3组间存在显著差异(P<0.05)。利用因子分析对非特异性免疫指标和生长指标进行综合评价,结果表明,T7.5组得分最高,为0.92,凡纳对虾中间培育的投喂率在7.5%左右为宜。