Kun Tong, Sanjay Joshi and E. Amine Lehtihet
The purpose of this research is to extend the previous approach to software error compensation to fused deposition modeling (FDM) machines and explores the approach to apply…
Abstract
Purpose
The purpose of this research is to extend the previous approach to software error compensation to fused deposition modeling (FDM) machines and explores the approach to apply compensation by correcting slice files.
Design/methodology/approach
In addition to applying the stereolithography (STL) file‐based compensation method from earlier research; a new approach using the slice file format to apply compensation is presented. Under this approach, the confounded effects of all errors in a FDM machine are mapped into a “virtual” parametric machine error model. A 3D artifact is built on the FDM machine and differences between its actual and nominal dimensions are used to estimate the coefficients of the error functions. A slice file compensation method is developed and tested on two types of parts as a means for further improving the error compensation for feature form error improvement. STL file compensation is also applied to a specific FDM 3000 machine and the results are compared with those of a specific SLA 250 machine.
Findings
The two compensation methods are compared. Although, the slice file compensation method theoretically allows higher compensation resolution, the actual machine control resolution of the FDM machine can be a limitation which makes the difference between STL compensation and slice file compensation indistinguishable. However, as the control resolution is increased, this method will make it possible to provide a higher degree of compensation.
Originality/value
Compensation method applied to slice file format is developed for FDM machines and its limitations are explored. Based on the experimental study, dimensional accuracy of parts is considerably improved by the software error compensation approach.
Details
Keywords
Yixing Zhang, Xiaomeng Lu, Haitao Yin and Rui Zhao
Scholars have not agreed with each other on how people would behave after experiencing a catastrophic event. They could save more as a precautionary action for future difficulties…
Abstract
Purpose
Scholars have not agreed with each other on how people would behave after experiencing a catastrophic event. They could save more as a precautionary action for future difficulties or save less with a carpe diem attitude. This study aims to attempt to shed light on this debate with empirical observations on how the Covid-19 pandemic has affected household saving decisions.
Design/methodology/approach
The two waves of the survey data allowed us to investigate both instantaneous and ongoing effects of Covid-19 on household saving decisions. The instantaneous effect refers to the immediate impact of the crisis, while the ongoing effect refers to the lasting impact of the pandemic when economic recovery had started. The variation in the number of confirmed cases across cities during the two waves provides the source of power for identification. The authors extend their analyses of the impact of Covid-19 on the household saving decision by using ordinary least squares models. Due to the ordered nature of survey responses, the authors also rerun all baseline models using the ordered probit regression method.
Findings
This paper studied the impact of the Covid-19 pandemic on household saving decisions in China. This study found that households in the most affected cities would save more during the Covid-19 but tend to save less when the disaster started fading away. Combining findings in Kun et al. (2013) and Filipski et al. (2015), people do become more pessimistic during and after the Covid-19, possibly driving their observed precautionary and cape diem behaviors during the two points of time. Heterogeneity analysis shows that specific households would dramatically change their saving behavior. These observations might be useful for policymakers who concern the economic recovery after this pandemic disaster.
Originality/value
Understanding how the Covid-19 pandemic would affect household consumption vs saving decisions is important for the economic recovery after this disaster comes to an end. The analyses presented in this research could be useful for policymakers who concern appropriate policies aiming to boost consumption and economic activities after Covid.
Details
Keywords
Kun Tong, E. Amine Lehtihet and Sanjay Joshi
This paper is motivated by the need for a generic approach to evaluate the volumetric accuracy of rapid prototyping (RP) machines. The approach presented in this paper is inspired…
Abstract
This paper is motivated by the need for a generic approach to evaluate the volumetric accuracy of rapid prototyping (RP) machines. The approach presented in this paper is inspired in large part by the techniques developed over the years for the parametric evaluation of coordinate measuring machine (CMM) errors. In CMM metrology, the parametric error functions for the machine are determined by actual measurement of a master reference artifact with known characteristics. In our approach, the RP machine is used to produce a generic artifact, which is then measured by a master CMM, and measurement results are used to infer the RP machine's parametric error functions. The results presented demonstrate the feasibility of such an approach on a two‐dimensional model.
Details
Keywords
Seung-Han Yang and Kwang-Il Lee
The purpose of this study is to improve the accuracy of a fused deposition modeling three-dimensional (3D) printer by identifying and compensating for position-independent…
Abstract
Purpose
The purpose of this study is to improve the accuracy of a fused deposition modeling three-dimensional (3D) printer by identifying and compensating for position-independent geometric errors using a face-diagonal length test featuring a designed artifact and a Vernier caliper.
Design/methodology/approach
An artifact that does not require support when printing was designed and printed to allow performance of the face-diagonal length test. A Vernier caliper was used to measure the lengths of diagonals in the XY, YZ and ZX planes of the printed artifact specimen; this completed the face-diagonal length test. The relationships between position-independent geometric errors of the linear axes X, Y and Z and the measured diagonal lengths of the three planes were determined to identify geometric errors.
Findings
The approach was applied to a commercial fused deposition modeling 3D printer, and three position-independent geometric errors were rapidly identified. The artifact was re-printed after model-based compensation for these errors and the diagonal lengths were re-measured. The results were verified via coordinate measuring machine measurement of a simple test piece without and with model-based compensation for identified geometric errors. Furthermore, the proposed approach was applied to a commercial 3D printer.
Research limitations/implications
The measured diagonal lengths of the printed artifacts varied greatly. Thus, further studies should investigate the effects of printing materials and parameters on the length discrepancies of 3D printed artifacts.
Practical implications
A software-based compensation of identified position-independent geometric errors has to be used at commercial 3D printers for accuracy improvements of printed parts.
Originality/value
Thus, the approach is of practical utility; it can be periodically used to identify position-independent geometric errors and ensure that the 3D printer is consistently accurate.
Details
Keywords
Mariana Velykodna, Olha Charyieva, Natalia Kvitka, Kateryna Mitchenko, Oksana Shylo and Oksana Tkachenko
This study aims to develop and test multivariable psychosocial prediction models of perceived post-traumatic stress disorder (PTSD) and complex post-traumatic stress disorder…
Abstract
Purpose
This study aims to develop and test multivariable psychosocial prediction models of perceived post-traumatic stress disorder (PTSD) and complex post-traumatic stress disorder (CPTSD) symptoms development among trauma-exposed Ukrainian adults (n = 761) after 1.5 years of the 2022 Russian invasion of Ukraine.
Design/methodology/approach
This research was designed as a survey in line with the methodology of “Transparent reporting of a multivariable prediction model for individual prognosis or diagnosis” checklist. The survey included a questionnaire on sociodemographic characteristics and specifics of trauma exposure, as well as validated self-reported inventories: The International Trauma Questionnaire, Acceptance and Action Questionnaire – version 2, Connor–Davidson Resilience Scale-10 and the Modified BBC Subjective Well-being Scale.
Findings
Regression analysis revealed different prediction models for PTSD and CPTSD symptoms, explaining 18.4% and 41.4% of their variance with five and eight predictors, respectively. Four variables were similar in predicting PTSD and CPTSD: war-relatedness of trauma, living with a friend, perceived physical health and regret for the past. War-relatedness of trauma the respondents were exposed to was among the strongest predictors for PTSD and CPTSD severity. However, living with a friend was almost equally strong in mitigating these mental consequences. Regret for past and lowly rated physical health were assessed as relatively weaker but statistically significant predictors in this study.
Originality/value
Upon the original theoretical framework, two psychosocial prediction models were developed for PTSD and CPTSD symptoms in a non-clinical sample of trauma-exposed Ukrainian adults.
Gading Ekapuja Aurizki, Ferry Efendi and Retno Indarwati
The purpose of this paper is to analyze factors associated with post-traumatic stress disorder (PTSD) among elderly who live in a post-earthquake area.
Abstract
Purpose
The purpose of this paper is to analyze factors associated with post-traumatic stress disorder (PTSD) among elderly who live in a post-earthquake area.
Design/methodology/approach
This was a cross-sectional study involving 152 elder people who survived the disaster and were selected conveniently. The study was conducted in two worst-affected districts of Lombok Utara regency. PTSD was diagnosed using a modified version of the Clinician-Administered PTSD Scale version 5 (CAPS-5). The demographic data were assessed using a self-developed questionnaire consisting of 13 items. All data were analyzed by descriptive analysis, χ2 test and binary logistic regression with p<0.05.
Findings
Out of the 152 elder people, 91 (59.9 percent) suffered PTSD. Intrusion symptoms were the most common symptoms experienced by the respondents (94.1 percent). The factors associated with the PTSD in the elderly after the earthquake were having chronic illnesses (OR=2.490; 95% CI=1.151–5.385), public health center utilization (OR=2.200; 95% CI=1.068–4.535) and occupational status before the disaster (OR=2.726; 95% CI=1.296–5.730). These findings highlight that individual factors and access to health care services remain an important aspect of stress identification among the elderly following the disaster event.
Social implications
Elder people constitute a vulnerable group that is often forgotten and neglected during post-disaster recovery, though they have potentially higher psychosocial distress than younger age groups. This study was conducted to raise awareness about mental health problems suffered by the elderly.
Originality/value
This is the first study to apply CAPS-5 to assess PTSD among Indonesian elderly people following a natural disaster. This paper also provides insights that can be used by governments and other relevant parties to address PTSD problems suffered by many elderly people in a post-disaster area.
Details
Keywords
Kun Wang and Juntong Xi
This paper aims to present an optimization method of the input driving signal of a piezoelectric inkjet printhead to improve droplet consistency and increase jetting frequency.
Abstract
Purpose
This paper aims to present an optimization method of the input driving signal of a piezoelectric inkjet printhead to improve droplet consistency and increase jetting frequency.
Design/methodology/approach
The optimization target is the transient pressure in the nozzle caused by the input driving signal, which directly generates the droplets. After demonstrating the linearity of the driving input and system pressure, an analytic model as a transfer function was developed, allowing calculation of the pressure vibration in the nozzle for an arbitrary input. Different patterns of input signal were parameterized and applied into the optimizing function, which represents the difference between the ideal and the actual pressure vibration. By determining the function minimum, the optimized parameters of the input signal were estimated.
Findings
Optimization results of different input patterns were compared and verified by the numerical model of the printhead, and it was revealed that the optimization method that combined the quenching pulse and an increased falling time interval was more effective than use of a single method.
Originality/value
After the process of optimization, a new type of input signal to the piezoelectric inkjet printhead was showed. By this method, the frequency of the printhead could be increased without losing consistency of droplets.
Details
Keywords
Kun Wang and Juntong Xi
This paper aims to present a method based on dynamics to find the transient pressure at the nozzle area of a piezoelectric inkjet printer. This pressure responds to input signals…
Abstract
Purpose
This paper aims to present a method based on dynamics to find the transient pressure at the nozzle area of a piezoelectric inkjet printer. This pressure responds to input signals of the piezoelectric driver deformation. The pressure at the nozzle is the boundary condition of the computational fluid dynamics model of the inkjet printer nozzle, and serves as the “bridge” between the piezoelectric driver actuation and the droplet generation of an inkjet printer.
Design/methodology/approach
The transient pressure was estimated using a fluid-solid coupling numerical model of the printerhead. In this study, a simple step-shape signal was applied. The printerhead chamber was considered to act as a linear Helmholtz resonator to determine the system transfer function between the input of driver deformation and the output of pressure. By decomposing the input signal into several simple signals, the transient pressure is the superposition of those calculated pressures.
Findings
The pressure values determined by transfer function and by superposition match the pressure values directly calculated by a fluid-solid coupling model. This demonstrates the rationality and practicability of the method.
Originality/value
This paper proposes a method to identify a proper boundary condition of pressure for numerical models that only include the fluid field around the nozzle. This strategy eliminates the need to calculate the complex and unstable fluid-solid coupling for every pattern of input. Additionally, the suitable boundary condition of transient pressure can be set rather than relying on the shape of the PZT driver deformation signal.
Details
Keywords
Cong Liu, Baohong Tong, Guotao Zhang, Wei Wang, Kun Liu and Peimin Xu
This paper aims to investigate the influence of oil–air lubrication flow behavior on point contact sliding wear characteristics.
Abstract
Purpose
This paper aims to investigate the influence of oil–air lubrication flow behavior on point contact sliding wear characteristics.
Design/methodology/approach
Oil–air lubrication equations between point contact counterparts were established on the basis of volume of fluid model. The effects of oil supply and injection azimuth on oil-phase volume fraction and its pressure distribution were simulated with commercial software Fluent. Characteristics of point contact sliding wear were then tested with an MFT-3000 friction tester under oil–air lubrication condition. The influence of flow behavior on wear characteristic was investigated combined with numerical and experimental results. The wear mechanism was revealed using SEM, EDS and ferrography.
Findings
When air supply speed is constant, the oil-phase volume fraction increases with the increase in oil supply, which helps form continuous oil film and decrease the sliding wear evidently. The injection angle and distance considerably influence the oil–air flow behavior. When injecting at a certain distance and angle, the oil-phase volume fraction reaches its maximum, and the abrasion loss is minimal. Under the test conditions in this study, abrasive particles are mainly debris and a few spiral cuttings. The wear mechanism is abrasive wear.
Originality/value
The influence of the behavior of oil–air lubrication flow on the characteristic of point contact sliding wear is analyzed. This work provides guidance for the application of oil–air lubrication technology in point contact friction pairs.