某型柴油机水泵、机油泵间隙调整工装的应用

为了方便某柴油机前端水泵和机油泵齿轮间隙的调整,改变以前传统的调整方法,通过长期在装配现场的观察和了解,设计出某柴油机前端水泵和机油泵齿轮间调整工作,经现场使用验证;该工装安全、小巧轻便精度高,改善了装配的劳动强度和装配质量。     

奥钢联板坯铸机驱动力报警问题的分析及改进

浇铸过程中，驱动力报警会导致紧急停浇甚至滞坯事故发生。为防止事故发生，通常采用降速、强冷等措施，但降速造成成本浪费，强冷又产生裂纹等质量缺陷，两者都难以满足生产需要。通过对铸机的各项参数对比分析，找到影响驱动力报警的主要原因为辊缝异常，轻压下模型参数、冷却工艺设置不合理等，通过调整二冷工艺、优化模型参数、加强轻压下区域扇形段辊缝维护，可以达到明显降低驱动力、消除报警的目的，从而保证连铸生产稳定。     

精密磨床转台静压轴承的强健化设计

针对精密磨床转台静压轴承性能仿真数据与其回转精度实测数据不一致的问题，为提高转台静压轴承的设计水平，提出了静压轴承的强健化设计方法。该方法考虑了轴承结构参数在轴承全生命周期内的变化，分析了半径间隙、油腔尺寸、节流比及润滑油黏度在设计、加工、装配和服役4个阶段的变化规律，重点研究了半径间隙在各阶段对轴承性能造成的影响，给出了转台静压轴承的强健化设计流程。通过一个径向轴承的设计实例对该强健化设计方法进行了说明，并将设计结果与传统设计进行了对比。对比的指标是轴承在4个阶段的刚度、承载力和温升，这3个指标对轴承回转精度有直接影响。研究表明：进行强健化设计后，在生命周期内静压轴承的刚度和承载力的变化量为10%~27%，温度的变化量为0.5%~1.6%，较传统设计更能保证转台回转精度的稳定。     

Transfer learning between crop types for semantic segmentation of crops versus weeds in precision agriculture

Agricultural robots rely on semantic segmentation for distinguishing between crops and weeds to perform selective treatments and increase yield and crop health while reducing the amount of chemicals used. Deep‐learning approaches have recently achieved both excellent classification performance and real‐time execution. However, these techniques also rely on a large amount of training data, requiring a substantial labeling effort, both of which are scarce in precision agriculture. Additional design efforts are required to achieve commercially viable performance levels under varying environmental conditions and crop growth stages. In this paper, we explore the role of knowledge transfer between deep‐learning‐based classifiers for different crop types, with the goal of reducing the retraining time and labeling efforts required for a new crop. We examine the classification performance on three datasets with different crop types and containing a variety of weeds and compare the performance and retraining efforts required when using data labeled at pixel level with partially labeled data obtained through a less time‐consuming procedure of annotating the segmentation output. We show that transfer learning between different crop types is possible and reduces training times for up to 80%. Furthermore, we show that even when the data used for retraining are imperfectly annotated, the classification performance is within 2% of that of networks trained with laboriously annotated pixel‐precision data.     

抽采孔液态CO2预裂效果显微CT实验研究

为研究液态CO2预裂爆破后,煤体内裂隙发育情况,采用高精度微焦点显微CT系统,对预裂后不同区域的煤样进行CT扫描,并利用Photoshop进行孔裂隙占比统计学分析。研究结果显示,距预裂孔4 m处的煤体裂隙发育明显,孔裂隙占比增加了一倍,而在5 m处的煤体裂隙则发育较弱。表明抽采孔内采取液态C2预裂技术后,4 m范围内的煤体裂隙得到了充分发育,为瓦斯抽采提供了有利条件。     

Top-down技术精密度法评定饮用水中氯酸钾含量的不确定度

目的使用Top-down技术精密度法评定饮用水中氯酸盐含量的不确定度。方法按照GB/T5750.10-2006《生活饮用水标准检验方法消毒副产物指标》规定的分析方法,通过对质控样品和能力验证样品的测定,基于Top-down精密度法的原理对数据进行检验和分析。结果通过偏移和精密度核查,在证明分析系统受控的情况下,计算得到不确定的结果U=0.056 mg/L。结论 Top-down技术用于化学分析不确定评估将不确定评估与实验室内部质量控制工作结合,减少了工作量,具有广泛的应用前景。     

Regression analysis of surface roughness and micro-structural study in rotary ultrasonic drilling of BK7

Ceramic materials have tremendous demand in manufacturing sectors. However, poor machinability impedes their widespread applications on an industrial scale. BK-7 falls in the same category and is normally processed by ultrasonic machining. But nowadays rotary ultrasonic machining is overtaking the ultrasonic machining for processing difficult to cut materials because of its superlative material removal mechanism. Current study aims to improve the surface quality of BK7 by studying the effect of input factors on surface roughness during rotary ultrasonic machining. Response surface methodology has been used to observe the effect of input variables ― spindle speed, feed rate and ultrasonic power ― on surface roughness (SR). Thereafter, central composite design was employed to estimate the regression coefficients of quadratic model for surface roughness. Fitness of developed quadratic model was checked by ANOVA test, which also revealed that all the model terms of input factors were significant except feed and speed interaction. Feed has the maximum impact over surface roughness descended by moderate impact of power and spindle speed. The study was further reinforced on observing the surface integrity of processed surfaces using scanning electron microscopic images. Mixed flow of material was observed to occur at lower feed rate and higher levels of rpm and ultrasonic power.     

Machining accuracy improvement for a dual-spindle ultra-precision drum roll lathe based on geometric error analysis and calibration

This paper performs a comprehensive analysis and calibration on the geometric error of the ultra-precision drum roll lathe with dual-spindle symmetrical structure and cross slider layout. Firstly, the volumetric error model which contains all geometric errors of the dual-spindle ultra-precision drum roll lathe (DSUPDRL) is developed based on the combination of the homogenous transfer matrix (HTM) and multi-body system (MBS) theory. Secondly, sensitivity analysis for the volumetric error model is conducted to identify the sensitive geometric error components of the DSUPDRL using an improved Sobol method based on the quasi-Monte Carlo algorithm. The result of sensitivity analysis laid the foundation for the subsequent geometric error calibration. Then, some sensitive error components along the X and Z directions are calibrated using a laser interferometer and a pair of inductance displacement probes. Besides the volumetric error model, the concentricity error caused by dual-spindle symmetrical structure is proposed and calibrated by the on-machine measurement using a classic reversal method. Finally, a large-scale roller mold with a diameter of 250 mm and a length of 600 mm is machined using the DSUPDRL after calibration. The experimental result shows that 1.4 μm/600 mm generatrix accuracy is obtained, which validate the effectiveness of the geometric error analysis and calibration.     

高精度大跨距同轴孔的精密研磨加工

对高精度大跨距同轴孔的加工现状进行了分析,确认采用现有加工方法无法满足要求。在此基础上,提出针对高精度大跨距同轴孔采用精密研磨加工,并改进了研磨工具。介绍了高精度大跨距同轴孔精密研磨加工的注意事项。这一方法可应用于加工孔距1 m以内的高精度大跨距同轴孔,加工效果良好。