Printing parameter optimization of PLA material concerning geometrical accuracy and tensile properties relative to FDM process productivity

Mihajlo Popović,Miloš Pjević,Aleksa Milovanović,Goran Mladenović,Miloš Milošević 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.2

High demand for part customization shifts industries toward AM technologies. Part customization in high-volume manufacturing is developed to its limits, whereas low-volume production using AM is still economically unjustified. FDM technology is quite common in lowvolume AM production, but the main issue is poor printing parameter optimization which may result in insufficient final part quality. The subject of this paper is the experimental determination of the optimal parameters for the PLA polymer FDM parts, focusing on nozzle temperature and printing speed. Part geometry and mechanical properties are evaluated for the temperature range of 170-210 °C and speeds of 40, 80, and 120 mm/min. Roughness measurements for part geometrical accuracy assessment and tensile tests for mechanical property estimation have shown the clear advantage of 190 °C and 40 mm/min over the other parameter combinations. However, for higher FDM process productivity 80 mm/min speed may also be considered with 190 °C.

Xylella fastidiosa in Europe: From the Introduction to the Current Status

Vojislav Trkulja(Vojislav Trkulja ),Andrija Tomić(Andrija Tomić ),Renata Iličić(Renata Iličić ),Miloš Nožinić(Miloš Nožinić ),Tatjana Popović Milovanović(Tatjana Popović Milovanović ) 한국식물병리학회 2022 Plant Pathology Journal Vol.38 No.6

Xylella fastidiosa is xylem-limited bacterium capable of infecting a wide range of host plants, resulting in Pierce's disease in grapevine, citrus variegated chlorosis, olive quick decline syndrome, peach phony disease, plum leaf scald, alfalfa dwarf, margin necrosis and leaf scorch affecting oleander, coffee, almond, pecan, mulberry, red maple, oak, and other types of cultivated and ornamental plants and forest trees. In the European Union, X. fastidiosa is listed as a quarantine organism. Since its first outbreak in the Apulia region of southern Italy in 2013 where it caused devastating disease on Olea europaea (called olive leaf scorch and quick decline), X. fastidiosa continued to spread and successfully established in some European countries (Corsica and PACA in France, Balearic Islands, Madrid and Comunitat Valenciana in Spain, and Porto in Portugal). The most recent data for Europe indicates that X. fastidiosa is present on 174 hosts, 25 of which were newly identified in 2021 (with further five hosts discovered in other parts of the world in the same year). From the six reported subspecies of X. fastidiosa worldwide, four have been recorded in European countries (fastidiosa, multiplex, pauca, and sandyi). Currently confirmed X. fastidiosa vector species are Philaenus spumarius, Neophilaenus campestris, and Philaenus italosignus, whereby only P. spumarius (which has been identified as the key vector in Apulia, Italy) is also present in Americas. X. fastidiosa control is currently based on pathogen-free propagation plant material, eradication, territory demarcation, and vector control, as well as use of resistant plant cultivars and bactericidal treatments.

Characterization of Pseudomonas syringae pv. syringae, Causal Agent of Citrus Blast of Mandarin in Montenegro

Žarko Ivanović,Tatjana Perović,Tatjana Popović,Jovana Blagojević,Nenad Trkulja,Snježana Hrnčić 한국식물병리학회 2017 Plant Pathology Journal Vol.33 No.1

Citrus blast caused by bacterium Pseudomonas syringaeis a very important disease of citrus occuring inmany areas of the world, but with few data about geneticstructure of the pathogen involved. Consideringthe above fact, this study reports genetic characterizationof 43 P. syringae isolates obtained from planttissue displaying citrus blast symptoms on mandarin(Citrus reticulata) in Montenegro, using multilocus sequenceanalysis of gyrB, rpoD, and gap1 gene sequences. Gene sequences from a collection of 54 referencepathotype strains of P. syringae from the Plant Associatedand Environmental Microbes Database (PAMDB)was used to establish a genetic relationship with ourisolates obtained from mandarin. Phylogenetic analysesof gyrB, rpoD, and gap1 gene sequences showedthat P. syringae pv. syringae causes citrus blast inmandarin in Montenegro, and belongs to genomospecies1. Genetic homogeneity of isolates suggested thatthe Montenegrian population might be clonal whichindicates a possible common source of infection. Thesefindings may assist in further epidemiological studiesof this pathogen and for determining mandarin breedingstrategies for P. syringae control.

An evolutionary system for the prediction of high performance concrete strength based on semantic genetic programming

Mauro Castelli,Leonardo Trujillo,Ivo Gonçalves,Aleš Popovič 사단법인 한국계산역학회 2017 Computers and Concrete, An International Journal Vol.19 No.6

High-performance concrete, besides aggregate, cement, and water, incorporates supplementary cementitious materials, such as fly ash and blast furnace slag, and chemical admixture, such as superplasticizer. Hence, it is a highly complex material and modeling its behavior represents a difficult task. This paper presents an evolutionary system for the prediction of high performance concrete strength. The proposed framework blends a recently developed version of genetic programming with a local search method. The resulting system enables us to build a model that produces an accurate estimation of the considered parameter. Experimental results show the suitability of the proposed system for the prediction of concrete strength. The proposed method produces a lower error with respect to the state-of-the art technique. The paper provides two contributions: from the point of view of the high performance concrete strength prediction, a system able to outperform existing state-of-the-art techniques is defined; from the machine learning perspective, this case study shows that including a local searcher in the geometric semantic genetic programming system can speed up the convergence of the search process.

Relationship between Right Ventricular Longitudinal Strain, Invasive Hemodynamics, and Functional Assessment in Pulmonary Arterial Hypertension

박재형,Kenya Kusunose,Deborah H. Kwon,Margaret M. Park,Serpil C. Erzurum,James D. Thomas,Richard A. Grimm,Brian P. Griffin,Thomas H. Marwick,Zoran B. Popović 대한심장학회 2015 Korean Circulation Journal Vol.45 No.5

Background and Objectives: Right ventricular longitudinal strain (RVLS) is a new parameter of RV function. We evaluated the relationship of RVLS by speckle-tracking echocardiography with functional and invasive parameters in pulmonary arterial hypertension (PAH) patients. Subjects and Methods: Thirty four patients with World Health Organization group 1 PAH (29 females, mean age 45±13 years old). RVLS were analyzed with velocity vector imaging. Results: Patients with advanced symptoms {New York Heart Association (NYHA) functional class III/IV} had impaired RVLS in global RV (RVLSglobal, -17±5 vs. -12±3%, p<0.01) and RV free wall (RVLSFW, -19±5 vs. -14±4%, p<0.01 to NYHA class I/II). Baseline RVLSglobal and RVLSFW showed significant correlation with 6-minute walking distance (r=-0.54 and r=-0.57, p<0.01 respectively) and logarithmic transformation of brain natriuretic peptide concentration (r=0.65 and r=0.65, p<0.01, respectively). These revealed significant correlations with cardiac index (r=-0.50 and r=-0.47, p<0.01, respectively) and pulmonary vascular resistance (PVR, r=0.45 and r=0.45, p=0.01, respectively). During a median follow-up of 33 months, 25 patients (74%) had follow-up examinations. Mean pulmonary arterial pressure (mPAP, 54±13 to 46±16 mmHg, p=0.03) and PVR (11±5 to 6±2 wood units, p<0.01) were significantly decreased with pulmonary vasodilator treatment. RVLSglobal (-12±5 to -16±5%, p<0.01) and RVLSFW (-14±5 to -18±5%, p<0.01) were significantly improved. The decrease of mPAP was significantly correlated with improvement of RVLSglobal (r=0.45, p<0.01) and RVLSFW (r=0.43, p<0.01). The PVR change demonstrated significant correlation with improvement of RVLSglobal (r=0.40, p<0.01). Conclusion: RVLS correlates with functional and invasive hemodynamic parameters in PAH patients. Decrease of mPAP and PVR as a result of treatment was associated with improvement of RVLS

Relationship between Right Ventricular Longitudinal Strain, Invasive Hemodynamics, and Functional Assessment in Pulmonary Arterial Hypertension

박재형,Kenya Kusunose,Deborah H. Kwon,Margaret M. Park,James D. Thomas,Richard A. Grimm,Brian P. Griffin,Thomas H. Marwick,Zoran B. Popović 대한심장학회 2016 Korean Circulation Journal Vol.46 No.2

Background and Objectives Right ventricular longitudinal strain (RVLS) is a new parameter of RV function. We evaluated the relationship of RVLS by speckle-tracking echocardiography with functional and invasive parameters in pulmonary arterial hypertension (PAH) patients. Subjects and Methods Thirty four patients with World Health Organization group 1 PAH (29 females, mean age 45±13 years old). RVLS were analyzed with velocity vector imaging. Results Patients with advanced symptoms {New York Heart Association (NYHA) functional class III/IV} had impaired RVLS in global RV (RVLSglobal, -17±5 vs. -12±3%, p<0.01) and RV free wall (RVLSFW, -19±5 vs. -14±4%, p<0.01 to NYHA class I/II). Baseline RVLSglobal and RVLSFW showed significant correlation with 6-minute walking distance (r=-0.54 and r=-0.57, p<0.01 respectively) and logarithmic transformation of brain natriuretic peptide concentration (r=0.65 and r=0.65, p<0.01, respectively). These revealed significant correlations with cardiac index (r=-0.50 and r=-0.47, p<0.01, respectively) and pulmonary vascular resistance (PVR, r=0.45 and r=0.45, p=0.01, respectively). During a median follow-up of 33 months, 25 patients (74%) had follow-up examinations. Mean pulmonary arterial pressure (mPAP, 54±13 to 46±16 mmHg, p=0.03) and PVR (11±5 to 6±2 wood units, p<0.01) were significantly decreased with pulmonary vasodilator treatment. RVLSglobal (-12±5 to -16±5%, p<0.01) and RVLSFW (-14±5 to -18±5%, p<0.01) were significantly improved. The decrease of mPAP was significantly correlated with improvement of RVLSglobal (r=0.45, p<0.01) and RVLSFW (r=0.43, p<0.01). The PVR change demonstrated significant correlation with improvement of RVLSglobal (r=0.40, p<0.01). Conclusion RVLS correlates with functional and invasive hemodynamic parameters in PAH patients. Decrease of mPAP and PVR as a result of treatment was associated with improvement of RVLS.

SiC JFET Switching Behavior in a Drive Inverter under Influence of Circuit Parasitics

I. Josifovi?,J. Popovi?-Gerber,J.A. Ferreira 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5

This paper investigates the switching behaviour of normally-off SiC JFETs in an inverter for a motor drive. The parasitic ringing caused by different parasitic effects is analysed. Two different methods, the use of an RC snubber and the use of a ferrite bead, are proposed for dampening the parasitic oscillations. It is found that applying a ferrite bead not only dampens the parasitic oscillations but also results in significantly lower switching losses. Furthermore, it is shown that the capacitive coupling between SiC devices and heat sinks significantly deteriorates the JFETs’ switching performance. The effect of two substrates, an IMS and a PCB, on the capacitive coupling is investigated. A method in which the use of two separate heat sinks minimises the capacitive coupling thus exploiting the full potential of fast SiC JFETs is proposed.

Accurate High Performance Concrete Prediction with an Alignment-Based Genetic Programming System

Leonardo Vanneschi,Mauro Castelli,Kristen Scott,Ale? Popovi? 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.7

In 2013, our research group published a contribution in which a new version of genetic programming, called Geometric Semantic Genetic Programming (GSGP), was fostered as an appropriate computational intelligence method for predicting the strength of high-performance concrete. That successful work, in which GSGP was shown to outperform the existing systems, allowed us to promote GSGP as the new state-of-the-art technology for high-performance concrete strength prediction. In this paper, we propose, for the first time, a novel genetic programming system called Nested Align Genetic Programming (NAGP). NAGP exploits semantic awareness in a completely different way compared to GSGP. The reported experimental results show that NAGP is able to significantly outperform GSGP for high-performance concrete strength prediction. More specifically, not only NAGP is able to obtain more accurate predictions than GSGP, but NAGP is also able to generate predictive models with a much smaller size, and thus easier to understand and interpret, than the ones generated by GSGP. Thanks to this ability of NAGP, we are able here to show the model evolved by NAGP, which was impossible for GSGP.

Spin Excitations in a 4f−3d Heterodimer on MgO

Singha, A.,Donati, F.,Natterer, F. D.,Wä,ckerlin, C.,Stavrić,, S.,Popović,, Z. S.,Š,ljivanč,anin, Ž,.,Patthey, F.,Brune, H. American Physical Society 2018 Physical review letters Vol.121 No.25