Wavelet Neural Network Based on NARMA-L2 Model for Prediction of Thermal Characteristics in a Feed System

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.

The effect of enzymes on release of trace elements in feedstuffs based on in vitro digestion model for monogastric livestock

Background: This experiment was conducted to study the effect of different feed enzymes(phytase,xylanase,β-glucanase) on release rate of trace elements(Fe,Cu,Mn and Zn) in 6 commonly used feedstuffs(corn,wheat,barley,soybean meal,wheat bran,wheat middlings) by using an in vitro model,simulating the digestive processes in stomach for 2 h and then in small intestine for 6 h at 39 °C.Results: Phytase raised(P < 0.05) the release rate of Cu and Zn in corn,Cu,Zn and Mn in wheat,Cu in barley,Cu,Zn and Mn in soybean meal,Zn,Fe in wheat bran and Zn,Fe,Mn in wheat middlings.The release rate of various trace elements in feedstuffs was increased after xylanase addition.Compared with the control group,the release rate of soluble Cu in corn,wheat,barley and soybean meal,soluble Zn in corn,wheat and wheat middlings and soluble of Mn in corn,wheat,barley and wheat bran increased(P < 0.05) after xylanase treatment.After the treatment of β-glucanase,the release rate of soluble Cu in corn,wheat and wheat bran,soluble Fe in barley,soybean meal and wheat bran and soluble Mn in corn and wheat bran all increased(P < 0.05) compared with the control group.In each feedstuff,after corresponding enzyme treatment,the contents of phytic acid,xylan and β-glucan were significantly lower than those of the control group(P < 0.05).Conclusions: Results showed that bound trace elements in feedstuffs can be released by feed enzymes.It may be necessary to take the trace elements in feedstuffs into account in the actual feed preparation including feed enzymes.

Development of a prediction model for enteral feeding intolerance in intensive care unit patients:A prospective cohort study

BACKGROUND Enteral nutrition(EN)is essential for critically ill patients.However,some patients will have enteral feeding intolerance(EFI)in the process of EN.AIM To develop a clinical prediction model to predict the risk of EFI in patients receiving EN in the intensive care unit.METHODS A prospective cohort study was performed.The enrolled patients’basic information,medical status,nutritional support,and gastrointestinal(GI)symptoms were recorded.The baseline data and influencing factors were compared.Logistic regression analysis was used to establish the model,and the bootstrap resampling method was used to conduct internal validation.RESULTS The sample cohort included 203 patients,and 37.93%of the patients were diagnosed with EFI.After the final regression analysis,age,GI disease,early feeding,mechanical ventilation before EN started,and abnormal serum sodium were identified.In the internal validation,500 bootstrap resample samples were performed,and the area under the curve was 0.70(95%CI:0.63-0.77).CONCLUSION This clinical prediction model can be applied to predict the risk of EFI.

Mathematical modeling and analytical solution for stretching force of automatic feed mechanism

Load of an automatic feed mechanism is composed of the stretching force of feed belt at the entrance to lower flexible guidance and the friction force between feed belt and flexible guidance. A mathematical model for computing the load was presented. An optimization problem was formulated to determine the attitude of the flexible guidance based on the principle that the potential energy stored in the system was the minimum at the equilibrium. Then the friction force was obtained according to the attitude of guide leaves and the moving velocity of the feed belt and the friction factor. Consequently, the load of the automatic feed mechanism can be calculated. Finally, an example was given to compute the load when the horizontal and elevating firing angles of the automation were respectively 45° and 30°. The computing result can be a criterion to determine the designing parameters of automat.

Model study of log feeding technology at the dam of Ertan Hydropower Station in China

The log float technology from timber depot at the reservoir to log feeding rolls was studied by model tests. The model test was taken with the rule of gravitation similitude and ratio of 1∶10. Main parameters, like the amount of tug boats, hydro-accelerators and the structure of feeding rolls, were determined. The more suitable float process is put forward and the reliable basis for the design is supplied.

OPTIMAL MODEL OF COMBINED PHASE CENTER FOR HORN FEEDS AND ITS COMPUTATIONAL METHOD

A definition of combined phase center for horn feeds is given.Formulas of E-planeand H-plane combined phase center for conical horns and the corresponding Optimal model arepresented,and a fast optimization method for solving this model is described.By using thismethod,the phase center of corrugated horn is discussed and calculated,and the variation of thephase center with distance and operating frequency is given.

Modeling a high output marine steam generator feedwater control system which uses parallel turbine-driven feed pumps

Parallel turbine-driven feedwater pumps are needed when ships travel at high speed. In order to study marine steam generator feedwater control systems which use parallel turbine-driven feed pumps, a mathematical model of marine steam generator feedwater control system was developed which includes mathematical models of two steam generators and parallel turbine-driven feed pumps as well as mathematical models of feedwater pipes and feed regulating valves. The operating condition points of the parallel ttu-bine-driven feed pumps were calculated by the Chebyshev curve fit method. A water level controller for the steam generator and a rotary speed controller for the turbine-driven feed pumps were also included in the model. The accuracy of the mathematical models and their controllers was verified by comparing their results with those from a simulator.

Modified coupled map car-following model and its delayed feedback control scheme

A modified coupled map car-following model is proposed, in which two successive vehicle headways in front of the considering vehicle is incorporated into the optimal velocity function. The steady state under certain conditions is obtained. An error system around the steady state is studied further. Moreover, the condition for the state having no traffic jam is derived. A new control scheme is presented to suppress the traffic jam in the modified coupled map car-following model under the open boundary. A control signal including the velocity differences between the following and the considering vehicles, and between the preceding and the considering vehicles is used. The condition under which the traffic jam can be well suppressed is analysed. The results are compared with that presented by t^onishi et al. （the KKH model）. The simulation results show that the temporal behaviour obtained in our model is better than that in the KKH model. The simulation results are in good agreement with the theoretical analysis.

基于前馈非线性模型预测控制的类车机器人路径跟踪

类车机器人由于零件标准化程度低,侧偏刚度等轮胎力学参数难以准确获得,存在动力学建模十分困难的问题,因此现有研究工作通常以运动学模型作为类车机器人的控制模型,但由于其运动学模型存在模型失配,导致类车机器人与参考路径之间的误差、类车机器人的前轮转角和前轮转角速度出现剧烈振荡现象.针对前述问题,本文基于非线性模型预测控制(Nonlinear model predictive control,NMPC)的滚动优化原理,引入基于逆运动学模型的前馈转角信息,将前轮转向角作为预测模型的第四维,提出了一种基于前馈非线性模型预测控制(Feedforward NMPC,FNMPC)的类车机器人路径跟踪控制算法.并通过Simulink和CarSim进行了联合仿真,结果表明FNMPC有效减小了模型失配导致的振荡现象,同时具有较高的跟踪精度.其中前馈非线性模型预测控制器的位移误差幅值不超过0.1106 m,航向误差幅值不超过0.1253 rad.在相同工况下,线性模型预测控制、前馈线性模型预测控制、纯跟踪控制和Stanley控制误差发散,而本文提出的FNMPC相比已有NMPC跟踪精度更高,且控制增量绝对累计值相比NMPC控制器减小67.53%.通过线控类车机器人底盘作为实验平台完成的测试结果表明,NMPC系统在进入弯道时出现控制失控现象,在相同工况下,FNMPC系统能够有效完成对参考路径的跟踪,同时将位移误差幅值控制在0.1624 m以内,航向误差幅值控制在0.1138 rad以内.

Mechanism of burst feeding in ZL205A casting under mechanical vibration and low pressure

The burst feeding behavior of ZL205 A casting under mechanical vibration and low pressure was investigated by casting experiment and physical model. Experimental results indicated that the burst feeding appeared repeatedly during solidification and left a shrinkage cavity with layered structure under mechanical vibration. The castings with less shrinkage and higher density could be achieved through the vibration. The calculation results of physical model showed that the burst feeding could perform spontaneously under vibration while difficultly without vibration in low-pressure die casting. The obstruction of a casting could be broken and the grains could be rearranged by the vibration. And the obstruction could be carried away due to the inner and outer pressure difference, causing a burst feeding.

Untargeted metabolomics characteristics of nonobese nonalcoholic fatty liver disease induced by high-temperature-processed feed in Sprague-Dawley rats

BACKGROUND Nonalcoholic fatty liver disease(NAFLD)has become one of the most common chronic liver diseases in the world.In our early clinical data and questionnaire analysis of NAFLD,it was found that the body mass index of some patients did not meet the diagnostic criteria for overweight or obesity.The consumption of high-temperature-processed foods such as fried food,hot pot and barbecue is closely related to the occurrence of nonobese NAFLD.Reducing the intake of this kind of food can reduce disease severity and improve prognosis.AIM To explore the untargeted metabolomics characteristics of nonobese nonalcoholic fatty liver disease in Sprague-Dawley rats induced by high-temperatureprocessed feed.METHODS Fifty-four male Sprague-Dawley rats were divided into three groups:The control group received a standard diet;the nonfried soybeans(NDFS)group received 60%NDFS and 40%basic feed and the dry-fried soybeans(DFS)group received 60%DFS and 40%basic feed.Six rats were sacrificed at week 4,8,and 12 in each group.The food intake,body weight,Lee’s index,liver index,serological index and hepatic histopathology were assessed.Untargeted metabolomics characteristics were used to analyze the changes in liver metabolites of rats at week 12.Correlations between metabolites and pathology scores between the DFS and control groups and between the DFS and NDFS groups were analyzed.We selected some of the metabolites,both within the pathway and outside of the pathway,to explain preliminarily the difference in liver pathology in the three groups of rats.RESULTS There were no statistically significant differences in the food intake,body weight,Lee's index or serological index between the DFS group and the control group(P>0.05).At week 8 and week 12,the steatosis scores in the DFS group were significantly higher than those in the other two groups(P<0.05).At week 12,the liver index of the DFS group was the lowest(NDFS group vs DFS group,P<0.05).The fibrosis score in the DFS group was significantly higher than those in the other two groups(P<0.05).The correlation analysis of the liver pathology score and differential metabolites in the DFS and NDFS groups showed that there were 10 strongly correlated substances:Five positively correlated substances and five negatively correlated substances.The positively correlated substances included taurochenodeoxycholate-3-sulfate,acetylcarnitine,20a,22bdihydroxycholesterol,13E-tetranor-16-carboxy-LTE4 and taurocholic acid.The negatively correlated substances included choline,cholesterane-3,7,12,25-tetrol-3-glucuronide,nicotinamide adenine dinucleotide phosphate,lysoPC[16:1(9Z)]and glycerol 3-phosphate.The correlation analysis of the liver pathology score and differential metabolites in the DFS and control groups showed that there were 13 strongly correlated substances:Four positively correlated substances and 9 negatively correlated substances.The positively correlated substances included 4-hydroxy-6-eicosanone,3-phosphoglyceric acid,13-hydroxy-9-methoxy-10-oxo-11-octadecenoic acid and taurochenodeoxycholate-3-sulfate.The negatively correlated substances included lysoPC[16:1(9Z)],S-(9-hydroxy-PGA1)-glutathione,lysoPC[20:5(5Z,8Z,11Z,14Z,17Z)],SM(d18:1/14:0),nicotinamide adenine dinucleotide phosphate,5,10-methylene-THF,folinic acid,N-lactoylglycine and 6-hydroxy-5-methoxyindole glucuronide.CONCLUSION We successfully induced liver damage in rats by using a specially prepared hightemperature-processed feed and explored the untargeted metabolomics characteristics.

Numerical Simulation of Azimuthal Uniformity of Injection Currents in Single-Point-Feed Induction Voltage Adders

In order to investigate the injection current uniformity around the induction cell bores, two fully electromagnetic （EM） models are respectively established for a single-stage induction cell and an induction voltage adder （IVA） with three cells stacked in series, without considering electron emission. By means of these two models, some factors affecting the injection current uni- formity are simulated and analyzed, such as the impedances of adders and loads, cell locations, and feed timing of parallel driving pulses. Simulation results indicate that higher impedances of adder and loads are slightly beneficial to improve injection current uniformity. As the impedances of adder and loads increase from 5 Ω to 30Ω, the asymmetric coefficient of feed currents decreases from 10.3% to 6.6%. The current non-uniformity within the first cell is a little worse than that in other downstream cells. Simulation results also show that the feed timing would greatly affect current waveforms, and consequently cause some distortion in pulse fronts of cell output voltages. For a given driving pulse with duration time of 70-80 ns, the feed timing with a time deviation of less than 20 ns is acceptable for the three-cell IVAs, just causing the rise time of output voltages to increase about 5 ns at most and making the peak voltage decrease by 3.5%.

Acceleration-Dependent Analysis of Vertical Ball Screw Feed System without Counterweight

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.

Automatic control strategy for step feed anoxic/aerobic biological nitrogen removal process

Control of sludge age and mixed liquid suspended solids concentration in the activated sludge process is critical for ensuring effective wastewater treatment. A nonlinear dynamic model for a step-feed activated sludge process was developed in this study. The system is based on the control of the sludge age and mixed liquor suspended solids in the aerator of last stage by adjusting the sludge recycle and wastage flow rates respectively. The simulation results showed that the sludge age remained nearly constant at a value of 16 d in the variation of the influent characteristics. The mixed liquor suspended solids in the aerator of last stage were also maintained to a desired value of 2500 g/m3 by adjusting wastage flow rates.

An Individual-Based Modeling Approach to Investigate Sympatric Speciation via Specialized Resource Usage

An individual-based model, EcoSim, was employed to investigate if specialized resource use could promote sympatric speciation. Prey individuals in the original version of EcoSim were supplied with a single primary food resource. A dual resource version with different food resources (Food 1 and Food 2) was also developed to create favorable conditions for the emergence of specialized food consumption among prey individuals. The single resource version was used as the control to determine the impact of the presence of multiple food resources on the occurrence of sympatric speciation. Each unit of Food 2 contained a higher amount of energy than Food 1, and Food 1 was more accessible than Food 2. Initially, prey individuals mostly fed on Food 1. How-ever, after the emergence of food specialization, the consumption rate of Food 2 signifi-cantly exceeded the consumption rate of Food 1;although prey individuals more frequently encountered Food 1. While sympatric speciation was observed in the dual resource version runs, we could not identify any sympatric species in the single resource version runs. Machine learning techniques were also employed to identify the most influential initial conditions leading to sympatric speciation. According to the obtained results, in most lineages sympatric speciation occurred at the beginning of the food specialization pro-cess. When the lineage had a high special diversity, the lineage needed two different criteria to diverge sympatrically: possessing high genetic diversity and a large population size. In support of previous findings, this study demonstrated that the most accurate determination of initial conditions leading to sympatric speciation can be obtained from lineages that are at the beginning of the divergence process. In conclusion, this study indicated that divergent foraging behavior could potentially lead to the sympatric emergence of new species in the absence of geographic isolation.

Simulation of Artificial Grain Feeding in Order to Reach Dynamical Bed Stabilisation Along the River Rhine

The Wesel-Xanten stretch of the fiver Rhine between km-812.5 and km-821.5 is one of the reaches where strong erosion leads to high maintenance efforts conceming navigability.In order to improve the naviga- tion conditions without aggravating the flood protection,but also ensuring that the ecological system of the river is not damaged,investigations of the morphodynamical processes in connection with artificial grain feeding ac- tivities have to be carried out by Federal Waterways Engineering and Research...

Dynamic control for the feed system of a robotic drilling end-effector

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.

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.

Measurement and Simulation of Energy Consumption of Feed Drive Systems

In this study, in order to investigate the power consumption of feed drive system, mathematical models for the single-axis experimental apparatus are developed. This apparatus can be driven by either of ball screw or linear motor and it is possible to change the mechanical properties of such as grease viscosity of the table. Then, the power consumption is simulated by proposed method based on the mathematical model of feed drive systems and the simulated results are compared with the measured results of the experimental apparatus to confirm the validity of the proposed method. In addition, it is clarified that the energy usages of the feed drive system. The energy losses of the feed drive system are divided into the loss of each part and these energy losses are calculated by the proposed method. Then, it is investigated that the influence of the velocity and friction to the energy consumption of feed drive system. As the results, it is confirmed that proposed method can accurately predict the power consumption of the ball-screw feed drive system. It is also clarified that the energy usage for both of ball-screw and linear motor drive systems.

上消化道肿瘤患者术后早期肠内营养喂养不耐受风险预测模型的构建

目的分析上消化道肿瘤患者术后发生早期肠内营养喂养不耐受的危险因素,建立风险预测模型。方法回顾性分析2021年5月至2022年12月收治于上海市某二级甲等医院普外科的210例上消化道肿瘤患者病例资料,所有患者术后均行早期肠内营养支持治疗。根据是否发生术后早期肠内营养喂养不耐受,分为不耐受组(n=121)与耐受组(n=89),比较两组患者间的差异。运用logistic回归分析上消化道肿瘤患者术后早期肠内营养喂养不耐受的危险因素,并构建风险预测模型,同时通过受试者工作特征(ROC)曲线下面积和霍斯默-莱梅肖(H-L)评价模型的校准度及区分度。结果上消化道肿瘤患者术后早期肠内营养喂养不耐受的发生率为57.62%,多因素logistic回归分析结果显示,低蛋白血症、高血糖、胃肠内补钾、术后疼痛评分≥4分、术后3 d后下床活动为上消化道肿瘤患者术后发生早期肠内营养喂养不耐受的独立危险因素。H-L检验结果显示,χ^(2)=6.523(P=0.367),模型ROC曲线下面积为0.916(P<0.001),灵敏度为0.857,特异度为0.832。结论上消化道肿瘤患者术后早期肠内营养喂养不耐受的发生率较高,本研究所构建的风险预测模型预测效能较好,能够帮助临床医护人员识别肠内营养喂养不耐受高危人群,为早期采取护理干预措施提供参考依据。