Modelling of assembly sequences using hypergraph and directed graph

Rad se bavi problemom modeliranja tehnološkog procesa montaže proizvoda s posebnim naglaskom na sekvence kod povezivanja dijelova i cjelina. U radu se predstavljaju najvažniji parametri modeliranja sekvenci montaže, uključujući osnove heuristčkog postupka kojim bi se trebalo pojednostavniti pronalaženje racionalne varijante. Predložena metoda određivanja sekvenci montaže dijelova i cjelina strojeva primjenom hipergrafova i usmjerenih grafova sastoji se od: izbora glavnog osnovnog dijela i osnovnih dijelova pojedinih jedinica montaže, bilježenja strukture konstrukcije jedinice montaže u obliku usmjerenog hipergrafa i minimiziranja broja njegovih rubova do oblika digrafa, bilježenja matrice strukture konstrukcije jedinice montaže u obliku matrice stanja i matrice grafa, izbora ekstremne putanje u digrafu. Važan element rada je detaljni algoritam određivanja sekvenci montaže primjenom matrice hipergrafa i usmjerenog grafa, matrice stanja i grafa koji je primijenjen na računalnom softveru "Msassembly".The work concerns the problem of modelling technological process of product assembly, with particular stress on the sequences of connecting its parts and units. The work presents the most important parameters of modelling assembly sequences, including the bases of heuristic proceeding which has to simplify finding its rational variation. Suggested method of determining the sequences of assembly of parts and units of machines using hypergraphs and directed graphs consists of: selection of the main base part and base parts of particular assembly units, recording of construction structure of assembly unit in the form of directed hypergraph and minimization of the number of its edges to the form of digraph, matrix recording of construction structure of assembly unit in the form of state matrix and graph matrix, the selection of extreme path in digraph. An important element of the work is a detailed algorithm of determination of assembly sequences using the matrix of hypergraph and directed graph, state matrix and the graph which was implemented to computer software "Msassembly"

Production data collection, exposure and analysis in a small production enterprise

Rad uvodi čitatelja u osnovne probleme prikupljanja proizvodnih podataka. Pokazuje da postoji potreba prikupljanja podataka, opisuje moguće metode i prednosti dobivene analizom podataka. Također upućuje na sustave ERP klase. Isto tako demonstrira jednostavan način na koji se sustav prikupljanja podataka, izlaganja i analize može organizirati u malom poduzeću, te iznosi prednosti koje se na taj način mogu steći.The paper shows the reader to the basic problems involved in the collection of data on production. It shows that there is the necessity of data collecting describes possible methods and advantages resulting from data analysis. It also refers to the systems of class ERP. It demonstrates, too, a simple way in which the system of data collection, exposure and analysis can be organized in a small firm, with a discussion of advantages to be taken of it

Cutting wedge wear examination during turning of duplex stainless steel

Rad se bavi analizom topografskih karakteristika karbidne površine reznog alata. Istraživanjem je obuhvaćena detaljna analiza mehanizma trošenja rezne oštrice i prednje površine alata u procesu tokarenja duplex nehrđajućeg čelika. U stabilnom režimu uočeno je trošenje oba analizirana dijela reznog alata. Dokazana je pojava različitih mehanizama trošenja, primjerice abrazijskog trošenja. Trošenje površine analizirano je s pomoću elektronske pretražne mikroskopije (SEM) i optičkog uređaja Infinite Focus za trodimenzijsko mjerenje površina.The purpose of the study was to determine the coated carbide tool surface topography. The study included determining detailed identification of wear mechanisms occurring on the rake face and major flank in the process of turning the DSS. The results of wear occurring on the tool both points were compared for the period of the steady-state wear of the tool point. Occurrence of various mechanisms, such as abrasive wear, was proven. Scanning Electron Microscopy SEM and Infinite Focus optical device for 3D surface measurement were used for the wear analysis

Survival rate after acute myocardial infarction in patients treated with percutaneous coronary intervention within the left main coronary artery according to time of admission

The relationship regarding time of percutaneous coronary intervention (PCI) and clinical outcomes in patients with acute myocardial infarction (AMI) treated within the left main coronary artery (LMCA) is less investigated compared to the overall group of patientswith AMI. Therefore, we aimed to assess the relationship between time of PCI (day- vs night-time) and overall mortality rate in patients treated due to AMI within the LMCA. This cross-sectional study included 443,805 AMI patients hospitalized between 2006 and 2018 enrolled in the Polish Registry of Acute Coronary Syndromes. We extracted 5,404 patients treated within the LMCA. The number of patients were treated during daytime hours (7:00 am-10:59 pm) was 2809 while 473 patients underwent treatment during night-time hours (11:00 pm-6:59 am). Differences in cardiac mortality rates between night- and day-hours among patients treated with PCI during the follow-up period were assessed via the Kaplan-Meier method. The 30-day (20.3% vs 14.9%, P = .003) and 12-month (31.7% vs 26.2%, P=.001) overall mortality rates were significantly greater among patients treated during night-time, which was confirmed by comparison using Kaplan-Maier survival curves (P=.001). The time of PCI was not found among predictors of survival in multiple regression analysis (hazard ratio: 1.22; 95% confidence interval: 0.96-1.55, P=.099). Patients treated during night-time in comparison to the day-time are related to higher in-hospital, 30-day and 12-month mortality. This is probably largely a consequence that the night-time, in comparison to the day-time, of treatment of patients with AMI with PCI within the LMCA is and indicator of higher comorbidity and clinical acuity of patients undergoing therapy. Therefore, the night-time was not found to be an independent predictor of greater mortality rate during the 12-months follow-up period

Bailout rotational atherectomy in patients with myocardial infarction is not associated with an increased periprocedural complication rate or poorer angiographic outcomes in comparison to elective procedures (from the ORPKI Polish National Registry 2015-2016)

Introduction: Many years of experience and refinement of existing rotational atherectomy (RA) techniques have resulted in improved clinical outcomes and a tendency to broaden the spectrum of RA usage. Aim: To compare the angiographic effectiveness and periprocedural complications in patients with stable angina (SA) and acute myocardial infarction (AMI) treated using RA. Material and methods: Data were prospectively collected using the Polish Cardiovascular Intervention Society national registry (ORPKI) on all percutaneous coronary interventions (PCIs) performed in Poland in 2015 and 2016. In total, 975 RA procedures were recorded out of 221,187 PCI procedures. Results: We compared angiographic effectiveness and periprocedural complications in 530 patients with SA and 245 with AMI in the RA group of patients, and 60,522 patients with SA and 91,985 with AMI in the non-RA group. The overall rate of periprocedural complications did not differ between SA and AMI patients in the RA group (2.3% vs. 2.0%; p = 0.84), while it was lower in AMI patients from the RA group compared to those from the non-RA group (2.0% vs. 3.0%; p = 0.34). The percentage of patients with angiographic success in the RA group was similar to the non-RA group in SA patients (97.3% vs. 97.1%; p = 0.75), whereas in the AMI group it was significantly higher compared to the non-RA group (96.7% vs. 92.6%; p < 0.001). Conclusions: The angiographic effectiveness of PCI with RA in patients with AMI was not worse than in patients with SA

Complete infarct-related artery revascularization in acute myocardial infarction patients : CORAMI Registry

Introduction: There are still limited data on the occurrence of multiple stenotic lesions within the infarct-related artery (IRA) in acute myocardial infarction (MI), and there is no consensus on the optimal treatment of this patient subgroup, which varies between centers and operators. Aim: To analyse the clinical efficacy of percutaneous coronary intervention (PCI) strategy of culprit lesion only in patients with myocardial infarction. Material and methods: Patients with acute MI with the presence of at least two significant lesions in the IRA – (1) the target culprit lesion which required immediate stenting (> 50–100% stenosis) and (2) a second distal critical lesion (70–90%) – were included in the registry. Both lesions in the IRA were considered to be independent lesions requiring two separate stent platforms to be covered (no overlap). The decision on the treatment strategy of either complete (CR) or culprit-lesion-only (CLO) revascularization was at the discretion of the operator. Results: There were altogether 95 patients enrolled in the registry, 63 (66%) in the group with CR of the IRA and 32 (34%) with CLO revascularization, which did not differ in terms of baseline demographics. In-hospital and long-term outcomes were similar between the groups. Stent thrombosis at 1 year occurred in 1.6% in CR and in 6.2% in CLO groups respectively (statistically not significant). There were no patients from the CLO group who had a planned percutaneous coronary intervention (PCI) of the 2nd lesion in the IRA during 1-year observation. Conclusions: At 1 year the clinical outcome was similar between those with complete and CLO PCI. Complete coverage of significant lesions did not increase the risk of stent thrombosis or need for repeated revascularization in long-term observation

Percutaneous left atrial appendage closure with Watchman LAA occluder device in a patient with persistent atrial fibrillation

We present a case of a 74-year-old male with persistent atrial fibrillation and ischaemic stroke despite vitamin-K antagonist treatment who underwent successful left atrial appendage closure with Watchman device

Diabetes and periprocedural outcomes in patients treated with rotablation during percutaneous coronary interventions

Background: This study is to assess differences in periprocedural outcomes among diabetic and non-diabetic patients treated with percutaneous coronary intervention (PCI) and rotational atherectomy (RA). Methods: Under assessment were 221,187 patients from the Polish Cardiovascular Intervention Society national registry (ORPKI) including all PCIs performed in Poland in 2015 and 2016. Data was extracted of 975 patients treated with RA — 336 (34.5%) diabetics and 639 (65.5%) non-diabetics. Periprocedural complications were defined as overall rate or particular complications such as deaths, no-reflows, perforations, dissections, cerebral strokes or bleedings. Multivariate analysis was performed to assess predictors of periprocedural complications. Results: The mean age was similar in diabetics and non-diabetics (70.9 ± 9.0 vs. 72.1 ± 9.9; p = 0.06). Diabetics were more often females (p &lt; 0.01), with arterial hypertension (p &lt; 0.01), kidney failure (p &lt; 0.01) and prior myocardial infarction (p = 0.01). No significant differences were observed in overall or individual periprocedural complications and angiographic success was expressed as thrombolysis in myocardial infarction grade 3 flow after PCI. At baseline, de-novo lesions accounted for 96.5% in diabetics and 99% in non-diabetics (p &lt; 0.01), while overall rate of restenosis was 3.5% and 1%, respectively (p &lt; 0.01). Diabetes was an independent predictor of periprocedural complications in the overall group of patients treated with PCI (OR 1.11, 95% CI 1.04–1.194; p &lt; 0.001). Conclusions: The negative impact of diabetes on the incidence of periprocedural complications and angiographic effectiveness in the group of patients treated with RA is mitigated in the comparison to the non-RA group