An investigation into the effects of thermal errors of a machine tool on the dimensional accuracy of parts

The reduction of machining errors has become increasingly important in modern manufacturing in order to obtain the required quality of parts. Geometric error makes up the basic part of the inaccuracy of the machine tool at the cold stage; however, as the machine running time increases, thermally-induced errors start to play a major role in machined workpiece accuracy. Dimensional accuracy of machined parts could be affected by several factors, such as the machine tool’s condition, the workpiece material, machining procedures and the operator’s skill. Of these, the machine condition plays an important role in determining the machine’s performance and its effects on the final dimensions of machined parts. The machine’s condition can be evaluated by its errors which include the machine’s built-in geometric and kinematic error, thermal error, cutting force-induced error and other errors.This research represents a detailed study of the effects of thermal errors of a machine tool on the dimensional accuracy of the parts produced on it. A new model has been developed for the prediction of thermally-induced errors of a three-axis machine tool. By applying the proposed model to real machining examples, the dimensional accuracy of machined parts was improved. The research work presented in this thesis has the following four unique characteristics:• Investigated the thermal effects on the dimensional accuracy of machined parts by machining several components at different thermal conditions of a machine tool to establish a direct relationship between the dimensional accuracy of machined parts and the machine tool’s thermal status.• Developed a new model for calculating thermally-induced volumetric error where the three axial positioning errors were modelled as functions of ball screw nut temperature and travel distance. The influences of the other 18 error components were ignored due to their insignificant influence.• Employed a Laser Doppler Displacement Meter (LDDM) with three thermocouples, instead of the expensive laser interferometer and the large number of thermocouples required by the traditional model, to assess the thermally-induced volumetric errors of a three-axis CNC machining centre. The thermally-induced volumetric error predictions were in good agreement with the measured results.• Applied the newly developed thermally-induced volumetric error compensation model for drilling operations to improve the positioning accuracy of drilled holes. The results show that positioning accuracy of the drilled holes was improved significantly after compensation. The absolute reduction of the positioning errors of drilled holes was an average 30.44 μm at the thermal stable stage, while the average relative reduction ratio of these errors was 77%.Therefore, the proposed thermally-induced volumetric error compensation model can bean effective tool for enhancing the machining accuracy of existing machine tools used in the industry

Application of A Newly Developed Thermally Induced Volumetric Error Compensation Model in Improving Dimensional Accuracy of Parts

The thermally induced volumetric error of a machine tool has been recognised as a major contributor to the dimensional and geometric errors of component parts produced by that tool. Therefore, considerable research has focused on ways to compensate for this type of error. The traditional model of compensation for the thermally induced volumetric error of a three-axis machine tool requires the measurement of 21 geometric error components and their variations with temperature, which is difficult and time-consuming to conduct. In our previous research, we developed a simplified and economical method of compensation of thermally induced volumetric error by modeling the positioning error as functions of ball-screw nut temperature and travel distance. This paper describes the application of this newly developed compensation model in improving the dimensional accuracy of parts. The model was applied to reduce the positioning error of a number of drilled holes. The results showed an average reduction of absolute and relative errors by 30.44 µm and 77%, respectively

An investigation of thermal behaviour of a machine tool on the dimensional accuracy of parts

The thermal condition of machine tools can profoundly affect the dimensional accuracy of manufactured parts. Consequently, reducing its influence has become increasingly important to modern manufacturing. One of the most convenient and effective ways to reduce thermal error and enhance working accuracy is volumetric error compensation, especially for CNC machine tools. However, currently available compensation methods are highly complicated and difficult to apply in industry. They require a high-precision laser interferometer to measure 21 geometric error components and numerous thermocouples to monitor temperature variations. These requirements make such techniques costly and time consuming. This paper describes the development of a simplified and economical method of compensating for thermally induced errors. Compensation is implemented on the basis of only three axial positioning errors, which are assumed to be functions of ball screw nut temperature and travel distance. Instead of an expensive laser interferometer and many thermocouples, a simple laser Doppler displacement meter and only three thermocouples are required for the proposed method. Results show good agreement between measured and predicted thermally induced errors

Public Exposure to Live Animals, Behavioural Change, and Support in Containment Measures in response to COVID-19 Outbreak: a population-based cross sectional survey in China

SummaryBackgroundIn response to the COVID-19 outbreak, we aimed to investigate behavioural change on exposure to live animals before and during the outbreak, and public support and confidence for governmental containment measures.MethodsA population-based cross-sectional telephone survey via random dialing was conducted in Wuhan (the epicentre) and Shanghai (an affected city with imported cases) between 1 and 10 February, 2020. 510 residents in Wuhan and 501 residents in Shanghai were randomly sampled. Differences of outcome measures were compared before and during the outbreak, and between two cities.FindingsProportion of respondents visiting wet markets at usual was 23.3% (119/510) in Wuhan and 20.4% (102/501) in Shanghai. During the outbreak, it decreased to 3.1% (16) in Wuhan (p&lt;0·001), and 4.4% (22) in Shanghai (p&lt;0·001). Proportion of those consuming wild animal products declined from 10.2% (52) to 0.6% (3) in Wuhan (p&lt;0·001), and from 5.2% (26) to 0.8% (4) in Shanghai (p&lt;0·001). 79.0% (403) of respondents in Wuhan and 66.9% (335) of respondents in Shanghai supported permanent closure of wet markets (P&lt;0.001). 95% and 92% of respondents supported banning wild animal trade and quarantining Wuhan, and 75% were confident towards containment measures. Females and the more educated were more supportive for the above containment measures.InterpretationThe public responded quickly to the outbreak, and reduced exposure to live animals, especially in Wuhan. With high public support in containment measures, better regulation of wet markets and healthy diets should be promoted.FundingNational Science Fund for Distinguished Young Scholars, H2020 MOOD project.Research in contextEvidence before this studyOn February 19, 2020, we searched PubMed for papers published after January 1, 2020, containing the following terms: “2019 nCoV” or “COVID-19”. We identified 179 studies, most of which are research on clinical and epidemiological characteristics of COVID-19. To date there is no primary research to quantify public behavioural response and support in containment measures in response to the outbreak. Only four commentaries mentioned the influence of the outbreak on mental health. One commentary introduced the habit of consuming wild animal products in China. Another commentary briefly introduced isolation, quarantine, social distancing and community containment as public health measures in the outbreak. The Chinese government has introduced a series of strict containment measures, and societal acceptability of these measure is important for effective and sustained response. Evidence is urgently needed to help policy makers understand public response to the outbreak and support for the containment measures, but no evidence available to date.Added value of this studyWe conducted a population-based cross-sectional telephone survey via random digital dialing in Wuhan (the epicentre) and Shanghai (an affected city with imported cases) between 1 and 10 February, 2020. To date, this is the only few analyses on behavioural response to the outbreak and societal acceptability of governmental containment measures, which has been listed as the current priority of China CDC. We provide an assessment of behavioural change on exposure to live animals during the outbreak, by comparison before and during the outbreak, and between two cities with diverse exposure intensities to COVID-19. We also provide evidence on public support in governmental containment measures, including strict regulation on wet markets to reduce animal-to-human transmission and city quarantine to reduce human transmission.Implications of all the available evidenceWe found that wild animal consumption was more prevalent in Wuhan (10.2%) than in Shanghai (5.2%). The public responded quickly to the outbreak, and significantly reduced exposure to live animals and stopped wild animal consumption, especially in Wuhan. They were very supportive of governmental containment measures. With high public support, wet markets should be better regulated, and healthy diets, including changing the traditional habit of eating wild animal products, should be promoted. This can inform policy makers in China and other countries to implement and adjust containment strategies in response to the outbreak in the future.</jats:sec

Investigation into antiepileptic effect of ganoderic acid A and its mechanism in seizure rats induced by pentylenetetrazole

Ganoderic acid A (GAA) exhibited neuron protection in in vitro epilepsy study, but no study has been done in vivo. Rats were administered (i.p.) pentylenetetrazole daily for 28 days to induce seizure. Rats with grade II or above of epileptic score were divided into three groups and given placebo, sodium valproate, or GAA treatment, respectively, for 7 days. The electrical signals of brain were monitored with electroencephalography (EGG); epileptic behavior was assessed using the Racine scale; morphological changes and apoptosis rate of cortical neurons were assessed with H&E staining and TUNEL staining, respectively. Protein expression of calcium-sensing receptor, p-ERK, p-JNK, and p-p38 in hippocampal tissue and Bcl-2, cleaved caspase-3, and Bax in cortical tissues was observed by Western blot and immunohistochemistry assay, respectively. After GAA treatment, apparent seizure-like EEG with significant arrhythmic disorder and spike waves was reduced or disappeared, and wave amplitude of EEG was reduced significantly. GAA showed similar effect with sodium valproate treatments on epilepsy. There were an apparent improvement of the epileptic behavior and a significant increase in the epileptic latency and shortening of the epileptic duration in the treatment group compared to control. GAA treatment ameliorated the nuclear pyknosis of neurons which appeared seriously in the epilepsy group. GAA treatment significantly reduced the cortical neuron apoptosis of epilepsy and the expression of calcium-sensing receptor, p-P38, p-JNK, cleaved caspase-3, and Bax but increased the expression of both p-ERK and Bcl-2. In conclusion, GAA treatment showed strong antiepileptic effect by decreasing apoptosis in cortical neuron and the expression of calcium-sensing receptor and stimulating the MAPK pathwa

Autoinflammatory mutation in NLRC4 reveals a leucine-rich repeat (LRR)-LRR oligomerization interface

Background Monogenic autoinflammatory disorders are characterized by dysregulation of the innate immune system, for example by gain-of-function mutations in inflammasome-forming proteins, such as NOD-like receptor family CARD-containing 4 protein (NLRC4). Objective Here we investigate the mechanism by which a novel mutation in the leucine-rich repeat (LRR) domain of NLRC4 (c.G1965C, p.W655C) contributes to autoinflammatory disease. Methods: We studied 2 unrelated patients with early-onset macrophage activation syndrome harboring the same de novo mutation in NLRC4. In vitro inflammasome complex formation was quantified by using flow cytometric analysis of apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) specks. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 techniques and lentiviral transduction were used to generate THP-1 cells with either wild-type or mutant NLRC4 cDNA. Cell death and release of IL-1β/IL-18 were quantified by using flow cytometry and ELISA, respectively. Results The p.W655C NLRC4 mutation caused increased ASC speck formation, caspase-1–dependent cell death, and IL-1β/IL-18 production. ASC contributed to p.W655C NLRC4–mediated cytokine release but not cell death. Mutation of p.W655 activated the NLRC4 inflammasome complex by engaging with 2 interfaces on the opposing LRR domain of the oligomer. One key set of residues (p.D1010, p.D1011, p.L1012, and p.I1015) participated in LRR-LRR oligomerization when triggered by mutant NLRC4 or type 3 secretion system effector (PrgI) stimulation of the NLRC4 inflammasome complex. Conclusion This is the first report of a mutation in the LRR domain of NLRC4 causing autoinflammatory disease. c.G1965C/p.W655C NLRC4 increased inflammasome activation in vitro. Data generated from various NLRC4 mutations provides evidence that the LRR-LRR interface has an important and previously unrecognized role in oligomerization of the NLRC4 inflammasome complex

Genome-Wide Analyses of Nkx2-1 Binding to Transcriptional Target Genes Uncover Novel Regulatory Patterns Conserved in Lung Development and Tumors

The homeodomain transcription factor Nkx2-1 is essential for normal lung development and homeostasis. In lung tumors, it is considered a lineage survival oncogene and prognostic factor depending on its expression levels. The target genes directly bound by Nkx2-1, that could be the primary effectors of its functions in the different cellular contexts where it is expressed, are mostly unknown. In embryonic day 11.5 (E11.5) mouse lung, epithelial cells expressing Nkx2-1 are predominantly expanding, and in E19.5 prenatal lungs, Nkx2-1-expressing cells are predominantly differentiating in preparation for birth. To evaluate Nkx2-1 regulated networks in these two cell contexts, we analyzed genome-wide binding of Nkx2-1 to DNA regulatory regions by chromatin immunoprecipitation followed by tiling array analysis, and intersected these data to expression data sets. We further determined expression patterns of Nkx2-1 developmental target genes in human lung tumors and correlated their expression levels to that of endogenous NKX2-1. In these studies we uncovered differential Nkx2-1 regulated networks in early and late lung development, and a direct function of Nkx2-1 in regulation of the cell cycle by controlling the expression of proliferation-related genes. New targets, validated in Nkx2-1 shRNA transduced cell lines, include E2f3, Cyclin B1, Cyclin B2, and c-Met. Expression levels of Nkx2-1 direct target genes identified in mouse development significantly correlate or anti-correlate to the levels of endogenous NKX2-1 in a dosage-dependent manner in multiple human lung tumor expression data sets, supporting alternative roles for Nkx2-1 as a transcriptional activator or repressor, and direct regulator of cell cycle progression in development and tumors