Influence of Bed Temperature on Heat Shrinkage Shape Error in FDM Additive Manufacturing of the ABS-Engineering Plastic

In case of manufacturing hexahedral ABS (Acrylonitrile Butadiene Styrene) plastic components using a FDM (Fused Deposition Modeling)-based 3D printer, undesirable shape errors occur in the product due to heat shrinkage. This paper experimentally ob-served the influence of the bed temperature change on the deformed shape errors of a hexahedral specimen of 100 × 50 × 50 mm3 produced by using a 3D printer. During printing work, the head nozzle temperature was kept at 240?C and the head speed was set at 50 mm/s. The chamber was enclosed with a PC-plate. 3D printing was conducted at four different bed temperatures;50?C, 70?C, 90?C, and 110?C. After the produced specimens naturally cooled down to room temperature, their deformed shape errors were measured. As a result, the higher the bed temperature, the lower the deformed shape errors of the specimens were. However, if the bed temperature had exceeded 120?C, laminating adhesion became poor. That seems to occur because of the material phase change and can make 3D printing work very hard as a consequence. Results of this study can be helpful to set optimum bed temperature condition in FDM additive manufacturing.

Variations of OCT measurements corrected for the magnification effect according to axial length and refractive error in children

Purpose:The aim of this paper was to examine the distribution of macular,retinal nerve fiber layer(RNFL)thickness and optic disc parameters of myopic and hyperopic eyes in comparison withemmetropic control eyes and to investigate their variation according to axial length(AL)andspherical equivalent(SE)in healthy children.Methods:This study included 293 pairs of eyes of 293children(145 boys and 148 girks),ranging in age from 6 to 17 years,Subjects were dividedaccording to SE in control(emmetropia,99 children),myopia(100 children)and hyperopia(94children)groups and according to axial AL in 68 short(<22.00 mm,68),medium(from≥22.00 mmto 25.00 mm,189)and long eyes(>25.00 mm,36).Macular parameters,RNFL thickness and opticdisc morphology were assessed by the Cirrus^(TM) HD-OCT.AL was measured using the IOL-Mastersystem.Littmann's formula was used for calculating the corrected AL-related ocular magnification.Results Mean age(±SD)was 10.84±3.05 years;mean(±SD)SE was+0.14±0.51 D(range from8.75 to+8.25 D)and mean AL(±SD)was 23.12±1.49.Average RNFL thickness,averagemacular thickness and macular volume decreased as AL and myopia increased.No correlationsbetween AL/SE and optic disc parameters were found after correcting for magnification effect.Conclusions:AL and refractive error affect measurements of macular and RNFL thickness inhealthy children.To make a correct interpretation of ocT measurements,ocular magnificationeffect should be taken into account by clinicians or OCT manufacturers.

Practical Calculation of Thermal Deformation and Manufacture Error in Surface Grinding

The paper submits a method to calculate thermal deformation and manufacture error in surface grinding. The author established a simplified temperature field model, and derived the thermal deformation of the ground workpiece. It is found that there exists not only a upwarp thermal deformation, but also a parallel expansion thermal deformation. A upwarp thermal deformation causes a concave shape error on the profile of the workpiece, and a parallel expansion thermal deformation causes a dimension error in height. The calculations of examples are given and compared with presented experiment data.

On constructing symmetrical reversible variable-length codes independent of the Huffman code

Reversible variable length codes (RVLCs) have received much attention due to their excellent error resilient capabilities. In this paper, a novel construction algorithm for symmetrical RVLC is proposed which is independent of the Huffman code. The proposed algorithm's codeword assignment is only based on symbol occurrence probability. It has many advantages over symmetrical construction algorithms available for easy realization and better code performance. In addition, the proposed algorithm simplifies the codeword selection mechanism dramatically.

Effect of Measurement Error on the Multivariate CUSUM Control Chart for Compositional Data

Control charts(CCs)are one of the main tools in Statistical Process Control that have been widely adopted in manufacturing sectors as an effective strategy for malfunction detection throughout the previous decades.Measurement errors(M.E’s)are involved in the quality characteristic of interest,which can effect the CC’s performance.The authors explored the impact of a linearmodel with additive covariate M.E on the multivariate cumulative sum(CUSUM)CC for a specific kind of data known as compositional data(CoDa).The average run length(ARL)is used to assess the performance of the proposed chart.The results indicate that M.E’s significantly affects themultivariate CUSUM-CoDaCCs.The authors haveused theMarkov chainmethod to study the impact of different involved parameters using six different cases for the variance-covariance matrix(VCM)(i.e.,uncorrelated with equal variances,uncorrelated with unequal variances,positively correlated with equal variances,positively correlated with unequal variances,negatively correlatedwith equal variances and negatively correlated with unequal variances).The authors concluded that the error VCM has a negative impact on the performance of themultivariate CUSUM-CoDa CC,as the ARL increases with an increase in the value of the error VCM.The subgroup size m and powering operator b positively impact the proposed CC,as the ARL decreases with an increase in m or b.The number of variables p also has a negative impact on the performance of the proposed CC,as the values of ARL increase with an increase in p.For the implementation of the proposal,two illustrated examples have been reported formultivariate CUSUM-CoDaCCs inthe presence ofM.E’s.Onedealswith themanufacturingprocessof uncoated aspirin tablets,and the other is based on monitoring the machines involved in the muesli manufacturing process.

Estimating the Baseline Error of Wide-Swath Altimeters Using Nadir Altimeters via Numerical Simulation

The baseline roll and length errors for wide-swath altimeters are major error sources in sea surface measurements that exhibit strong spatial characteristics in the cross-track direction.These errors can be identified and estimated in accordance with height differences at crossover points generated with nadir altimeters after excluding the interference from other error sources.Most of the wide-swath altimeter baseline estimation methods considered only the roll error in previous studies.A numerical simulation was conducted in this study using nadir altimeters to estimate the roll and length errors simultaneously to provide a selectable scheme for baseline error estimation and correction for future wide-swath altimeters.Results based on the parameters of the surface water and ocean topography mission and Sentinel-3A show that the correlation coefficient of the roll error between the estimated and simulated values is 0.89,while the correlation coefficient of the length error is 0.85.The sea surface height root mean square error(RMSE)can be reduced from 12.18 cm to 6.45 cm based on the two estimated results.The estimation effect can be increased by using multiple nadir altimeters to form an observation constellation.The numerical simulation of the five nadir altimeter constellation shows that the correlation coefficients of the roll and length errors would increase to 0.97,which reduces the sea surface height RMSE to 2.88 cm.In addition,the stability of this method is indicated in simulation experiments,which introduce different degrees of sea state errors.

On Error Analysis and Refinement of the Measurement of Plane-to-Plane Perpendicularity

The principle of planc-to-plane perpendicularity measuring with coordinate measuring machine （CMM） is described and the main factors that influence the measuring precision are analyzed. The minimum condition method is adopted to eliminate the fitting error of the datum plane. In order to diminish the length error of the object plane, the tactics of measuring some part of the plane and then scale to the whole plane is employed. With large quantity of measuring experiments on fiat plates, the most appropriate number of points in measuring a plane is determined to reduce the sampling error.

Quasi-Static and Dynamic Behaviors of Helical Gear System with Manufacturing Errors

Time?varying mesh stiffness(TVMS) and gear errors include short?term and long?term components are the two main internal dynamic excitations for gear transmission. The coupling relationship between the two factors is usually neglected in the traditional quasi-static and dynamic behaviors analysis of gear system. This paper investigates the influence of short?term and long?term components of manufacturing errors on quasi?static and dynamic behaviors of helical gear system considering the coupling relationship between TVMS and gear errors. The TVMS, loaded static transmission error(LSTE) and loaded composite mesh error(LCMS) are determined using an improved loaded tooth contact analysis(LTCA) model. Considering the structure of shaft, as well as the direction of power flow and bearing location, a precise generalized finite element dynamic model of helical gear system is developed, and the dynamic responses of the system are obtained by numerical integration method. The results suggest that lighter loading conditions result in smaller mesh stiffness and stronger vibration, and the corresponding resonance speeds of the system become lower. Long?term components of manufacturing errors lead to the appearance of sideband frequency components in frequency spectrum of dynamic responses. The sideband frequency components are predominant under light loading conditions. With the increase of output torque, the mesh frequency and its harmonics components tend to be enhanced relative to sideband frequency components. This study can provide effective reference for low noise design of gear transmission.

Effect of Manufacturing Errors on Static Characteristics of Externally Pressurized Spherical Air Bearings

Externally pressurized spherical air bearings are the key component of the three-axis air bearing table, and the manufacturing errors of the bearing affects the performance of the air bearing table. However, the manufacturing errors are unavoidable, and the pursuit to enhance the manufacturing accuracy will increase the cost greatly. In order to provide some theoretical guideline for the tolerance choice in the design of the externally pressurized spherical air bearings with inherent compensation, the effects of several manufacturing errors on the static characteristics of the air bearing are studied. Due to the complex geometry of the computational domain, an unstructured meshing technology is used for mesh generation. A finite-volume method is adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations. A modified SIMPLE algorithm which is suitable for compressible flows is applied to solve the discretized governing equations. The effects of the dimension error and the roundness error of the ball head and the ball socket on the static characteristics are investigated. The investigation result shows that the positive dimension error and the oblate spheroid-type roundness error of the ball head as well as the negative dimension error and the prolate spheroid-type roundness error of the ball socket can improve the bearing capacity and static stiffness of the air bearings by reducing the mass flow. The calculation method proposed in this paper fits well for the general principle, which can be extended to the characteristics analysis of other air bearings.

The Variables and Invariants in the Evolution of Logic Optical Lithography Process

Photolithography has been a major enabler for the continuous shrink of the semiconductor manufacturing design rules.Throughout the years of the development of the photolithography,many new technologies have been invented and successfully implemented,such as image projection lithography,chemically amplified photoresist,phase shifting mask,optical proximity modeling and correction,etc.From 0.25μm technology to the current 7 nm technology,the linewidth has been shrunk from 250 nm to about 20 nm,or 12.5 times.Although imaging resolution is proportional to the illumination wavelength,with the new technologies,the wavelength has only been shrunk from 248 nm to 134.7 nm(193 nm immersion in water),less than 2 times.Would it mean that the imaging performance has been continuously declining?Or we have yet fully utilized the potential of the photolithography technology?In this paper,we will present a study on the key parameters and process window performance of the image projection photolithography from 0.25μm node to the current 7 nm node.

A Laser Scanner-Stage Synchronized System Supporting the Large-Area Precision Polishing of Additive-Manufactured Metallic Surfaces

This paper proposes a scanner–stage synchronized approach emphasizing a novel control structure for the laser polishing of Inconel 718 components manufactured by selective laser melting in order to address increasing demands for high surface quality in metal additive manufacturing.The proposed synchronized control system is composed of a motion decomposition module and an error synthesis module.The experimental results show that stitching errors can be avoided thanks to continuous motion during laser processing.Moreover,in comparison with the existing step-scan method,the processing efficiency of the proposed method is improved by 38.22%and the surface quality of the laser-polished area is significantly enhanced due to a more homogeneous distribution of the laser energy during the material phase change.The proposed synchronized system paves the way for high-speed,high-precision,and large-area laser material processing without stitching errors.

Relationship between Refractive Error and Ocular Biometrics in Twin Children:the Guangzhou Twin Eye Study

Purpose:A cross-sectional study was conducted to explore the relationship between refractive error and ocular biometrics in children from the Guangzhou twin eye study.Methods:.Twin participants aged 7-15 years were selected from Guangzhou Twin Eye Study..Ocular examinations included visual acuity measurement, ocular motility evaluation, autorefraction under cycloplegia, and anterior segment, media, and fundus examination...Axial length(AL),..anterior cham ber depth(ACD), and corneal curvature radius were measured using partial coherence laser interferometry. A multivariate linear regression model was used for statistical analysis.Results:.Twin children from Guangzhou city showed a decreased spherical equivalent with age,.whereas both AL and ACD were increased and corneal curvature radius remained unchanged. When adjusted by age and gender, the data from77% of twins presenting with spherical equivalent changes indicated that these were caused by predictable variables.(R2=0.77, P<0.001). Primary factors affecting children's refraction included axial length(β=-0.97,P<0.001), ACD(β=0.33,P<0.001), and curvature radius(β=2.10,P<0.001). Girls had a higher tendency for myopic status than did boys(β=-0.26,P<0.001)..Age exerted no effect upon the changes in refraction(β=-0.01, P=0.25).Conclusion:.Refraction is correlated with ocular biometrics.Refractive status is largely determined by axial length as the major factor.

Smooth Operation with Manufacture Error and Modification of Cycloidal Pin Gearing

The paper considers the modification or the manufacture error of cycloidal gear, then analyzes the relationship of pin circle meshed with the modified cycloidal gear, discuases the amount of error that leads to destroying conjugate action and results in the changes of tbe instantaneous velocity ratio and so as to affect the smooth operation of cycloidal pin gearing. The idea of the relationship between amount of modification aud manufacture error and the smooth operation can be gotten from the curve diagrams of the instantaneous velocity ratio. Therefore, the directions for improving the reature of the cycloidal pin gear transmission are clear.

APL-based flexibility analysis of manufacturing grid

With the characteristics of diversity, randomness, concurrency and decomposability, tasks in manufacturing field are very complicated, and so manufacturing grid (MG) should have considerable flexibility to deal with this problem. With the definition of node and arc, MG structure is converted into a small-world network. Given construction cost constraint, the problem of shortest task waiting time is transformed into the constrained optimization problem, and a corresponding ?exibility analysis model based on average path length (APL) is proposed, and the premise of arc-length and node-distance are defined. The results of application example show that the analysis model is effiective.

Medication Error and Interprofessional Communication-Related Factors Contributing to Hospitalisation in Community-Dwelling Older Adults in Australia

Background: Population ageing is a worldwide phenomenon. It is common for older adults to develop multiple age-related illnesses and the prevalence of multimorbidity increases substantially with age. Multimorbid adults are frequently treated with several concurrent medications and the regimen may be complex requiring multiple steps in the preparation of a medication prior to its administration. Polypharmacy is a concerning trend and older adults have a 100% risk of experiencing adverse drug events when taking ten or more medications concurrently. Discharge summaries communicating the number of medications, changes made to medication regimens during hospitalisations and the requirement for ongoing monitoring in the community are often incomplete. The aim of this study was to investigate contributing factors to medication-related hospitalisation, length of stay or readmission in older community-dwelling persons and examine the quality of discharge summaries. Methods: Descriptive and correlational analyses of demographic, clinical, admission, readmission, length of stay and medication variables were examined in Australia in 2016-2018. Discharge summaries were analysed for completeness, timeliness and interprofessional communication. Results: There were 295 participants, mean age 80 years, 55% were female, taking an average of 11 prescribed medications and with a mean Medication Regimen Complexity Index score of 34. Medication errors that were unrecognised at the time of hospitalisation were present in 19% of the sample. Factors associated with medication error were older age and a longer median length of stay. Fewer than 52% of these older patients had detailed discharge summaries. Conclusion: The prevalence of polypharmacy and medication regimen complexity at admission was high. A high proportion of older adults on medical units may have unrecognised medication errors impacting their admission. Medical discharge summaries are inadequately addressing this issue for patients returning to the care of their family physician.

Effect of planet pin position errors on the fatigue reliability of large aviation planetary systems

Planet pin position errors significantly affect the mechanical behavior of planetary transmissions at both the power-sharing level and the gear tooth meshing level,and its tolerance properties are one of the key design elements that determine the fatigue reliability of large aviation planetary systems.The dangerous stress response of planetary systems with error excitation is analyzed according to the hybrid finite element method,and the weakening mechanism of large-size carrier flexibility to this error excitation is also analyzed.In the simulation and analysis process,the Monte Carlo method was combined to take into account the randomness of planet pin position errors and the coupling mechanism among the error individuals,which provides effective load input information for the fatigue reliability evaluation model of planetary systems.In addition,a simulation test of gear teeth bending fatigue intensity was conducted using a power flow enclosed gear rotational tester,providing the corresponding intensity input information for the reliability model.Finally,under the framework of stress-intensity interference theory,the computational logic of total formula is extended to establish a fatigue reliability evaluation model of planetary systems that can simultaneously consider the failure correlation and load bearing time-sequence properties of potential failure units,and the mathematical mapping of planet pin positional tolerance to planetary systems fatigue reliability was developed based on this model.Accordingly,the upper limit of planet pin positional tolerance zone can be determined at the early design stage according to the specific reliability index requirements,thus maximizing the balance between reliability and economy.

OFDM系统中有效信道长度跟踪方案

为获得更为精确的有效信道长度,在分析最大似然(ML)信道估计算法对有效信道长度具有依赖性的基础上,提出将粗搜索策略与逐次插值逼近法相结合的有效信道长度跟踪方案,跟踪信道长度的变化。理论分析和仿真结果表明,在时变信道环境下,该算法可以有效跟踪信道长度的变化,提高ML信道估计器的估计性能。

Locating Error Considering Dimensional Errors Modeling for Multistation Manufacturing System

Multistation machining process is widely applied in contemporary manufacturing environment. Modeling of variation propagation in multistation machining process is one of the most important research scenarios. Due to the existence of multiple variation streams, it is challenging to model and analyze variation propagation in a multi-station system. Current approaches to error modeling for multistation machining process are not explicit enough for error control and ensuring final product quality. In this paper, a mathematic model to depict the part dimensional variation of the complex multistation manufacturing process is formulated. A linear state space dimensional error propagation equation is established through kinematics analysis of the influence of locating parameter variations and locating datum variations on dimensional errors, so the dimensional error accumulation and transformation within the multistation process are quantitatively described. A systematic procedure to build the model is presented, which enhances the way to determine the variation sources in complex machining systems. A simple two-dimensional example is used to illustrate the proposed procedures. Finally, an industrial case of multistation machining part in a manufacturing shop is given to testify the validation and practicability of the method. The proposed analytical model is essential to quality control and improvement for multistation systems in machining quality forecasting and design optimization.

Effects of manufacturing errors on the characteristics of a polymer vertical coupling microring resonator

The effects of manufacturing errors on transmission characteristics are analyzed for a polymer vertical coupling microring resonator.Calculated results show that the errors cause a shift and shape change of the transmission spectrum compared to the designed case without errors.Furthermore,accumulation and compensation for the errors is researched.In order to realize the normal filtering for the fabricated microring resonator device,some allowed errors are discussed.

Feasibility of central loop TEM method for prospecting multilayer water-fi lled goaf

With deep mining of coal mines, prospecting multilayer water-filled goaf has become a new content that results from geophysical exploration in coalfields. The central loop transient electromagnetic （TEM） method is favorable for prospecting conductive layers because of the coupling relationship between its field structure and formation. However, the shielding effect of conductive overburden would not only require a longer observation time when prospecting the same depth but also weaken the anomalous response of underlying layers. Through direct time domain numerical simulation and horizontal layered earth forward modeling, this paper estimates the length of observation time required to prospect the target, and the distinguishable criterion of multilayer water-filled goal is presented with observation error according to the effect of noise on observation data. The observed emf curves from Dazigou Coal Mine, Shanxi Province can distinguish multilayer water-filled goaf. In quantitative inversion interpretation of observed curves, using electric logging data as initial parameters restrains the equivalence caused by coal formation thin layers. The deduced three-layer and two-layer water-filled goals are confirmed by the drilling hole. The result suggests that when observation time is long enough and with the anomalous situation of underlying layers being greater than the observation error, the use of the central loop TEM method to orosoect a multilaver water-filled goaf is feasible.