Research and analysis of influential parameters on the operational characteristics of conveyor belts

Транспортна трака је по својој структури текстилни композит. Као носећи елемент транспортера са траком, трака подноси променљива оптерећења током свог рада. У циљу испитивања утицаја нивоа и амплитуде оптерећења на век трајања траке, извршена су испитивања на узорцима у лабораторијским условима. За ова испитивања је специјално пројектован и направљен уређај за испитивање који је омогућио прецизну контролу и праћење оптерећења као и броја циклуса оптерећења до лома. Ово истраживање даје преглед утицајних параметара на експлоатационе карактеристике транспортних трака. Објашњена је методологија спроведеног истраживања уз опис важних техничких параметара уређаја за испитивање. Физички експерименти и одговарајуће нумеричке симулације применом FEM методе су спроведене са више нивоа оптерећења узорака траке. На основу добијених резултата донети су одговарајући закључци – транспортне траке при оптерећењима близу 75% прекидне чврстоће имају економски оправдан век трајања, однос оптерећења R утиче на век трајања транспортних трака и врсту лома који настаје, могу се остварити значајне уштеде инвестиционих и експлоатационих трошковима применом добијених резултата.Transportna traka je po svojoj strukturi tekstilni kompozit. Kao noseći element transportera sa trakom, traka podnosi promenljiva opterećenja tokom svog rada. U cilju ispitivanja uticaja nivoa i amplitude opterećenja na vek trajanja trake, izvršena su ispitivanja na uzorcima u laboratorijskim uslovima. Za ova ispitivanja je specijalno projektovan i napravljen uređaj za ispitivanje koji je omogućio preciznu kontrolu i praćenje opterećenja kao i broja ciklusa opterećenja do loma. Ovo istraživanje daje pregled uticajnih parametara na eksploatacione karakteristike transportnih traka. Objašnjena je metodologija sprovedenog istraživanja uz opis važnih tehničkih parametara uređaja za ispitivanje. Fizički eksperimenti i odgovarajuće numeričke simulacije primenom FEM metode su sprovedene sa više nivoa opterećenja uzoraka trake. Na osnovu dobijenih rezultata doneti su odgovarajući zaključci – transportne trake pri opterećenjima blizu 75% prekidne čvrstoće imaju ekonomski opravdan vek trajanja, odnos opterećenja R utiče na vek trajanja transportnih traka i vrstu loma koji nastaje, mogu se ostvariti značajne uštede investicionih i eksploatacionih troškovima primenom dobijenih rezultata.The conveyor belt is by its structure a textile composite. As a load-supporting element of the conveyor, the belt withstands variable loads during its operations. In order to investigate the influence of the level and variability of loading on the life of the belt, tests were carried out on specimens in laboratory conditions. A testing device was specially designed and made for these tests that enabled precise control and monitoring of the loading as well as number of loading cycles up to fracture. This research provides an overview of influential parameters on the operational characteristics of conveyor belts. The methodology of the conducted research is explained with a description of important technical parameters of the testing device. Physical experiments and corresponding numerical simulations using the FEM method were carried out with multiple loading levels of belt specimens. Based on the obtained results, appropriate conclusions were made – conveyor belts at loads close to 75% of the breaking strength have economic justified lifetime, the load ratio R affects the lifetime of conveyor belts and the type of fracture which occurs, significant savings can be achieved in investment and exploitation costs by applying the obtained results

POLYSOMNOGRAPHIC SLEEP PATTERNS IN DEPRESSIVE, SCHIZOPHRENIC AND HEALTHY SUBJECTS

Background: Sleep disorders are frequent symptoms described in psychiatric patients with major depression and schizophrenia. These patients also exhibit changes in sleep architecture measured by polysomnography (PSG) during sleep. The aim of the present study was to identify potential biomarkers to facilitate diagnosis based on PSG measurements. Subjects and methods: Thirty (30) patients with schizophrenia, 30 patients with major depression and 30 healthy control subjects were investigated in the present study. All subjects underwent PSG measurements for a minimum time of 8 hours according to the criteria of Rechtscahffen & Kales (1968). We tested the potential of multiple sleep variables to predict diagnosis in different groups by using linear discriminant analysis (LDA). Results: There were significant differences in PSG variables between healthy control subjects and psychiatric patients (total sleep time, sleep latency, number of awakenings, time of awakening after sleep onset, REM 1 latency, REM 1 and index of endogenous periodicity). Importantly, LDA was able to predict the correct diagnosis in 88% of all cases. Conclusions: The presented analysis showed commonalities and differences in PSG changes in patients with major depressive disorder and in patients with schizophrenia. Our results underline the potential of PSG measurements to facilitate diagnostic processes

The analysis of influential parameters on calibration and feeding accuracy of belt feeders

Continual material feeding represents a process of great importance for process industries. Feeding with belt feeders represents one of the most common methods. Belt feeders are devices that require little space, they are not expensive and, most importantly, they do not interrupt material flow while feeding. Calibration of belt feeders, as well as other measuring devices, is a prerequisite for measuring and achieving a defined level of measurement accuracy. On the other hand, the defined level of measurement accuracy is often difficult to achieve in practice due to the multitude of factors that affect the operation of belt feeders. Existing mathematical models indicate a number of influential factors on measurement accuracy. The paper presents the measurement procedure performed on a belt feeder in laboratory conditions, with variable speeds and belt tensions and the known raised position of the measuring idler. Based on the obtained results, appropriate conclusions were made about the influences on calibration and measurement accuracy

Does facial attractiveness influence perception of epilepsy diagnosis? An insight into stigma in epilepsy

Background: Using a group of young healthy individuals and patients with multiple sclerosis (pMS), we aimed to investigate whether the physical attractiveness judgment affects perception of epilepsy. We tested hypothesis that subjects, in the absence of relevant clues, would catch upon the facial attractiveness when asked to speculate which person suffers epilepsy and select less attractive choices. Method: Two photo-arrays (7 photos for each gender) selected from the Chicago Face Database (180 neutral faces of Caucasian volunteers with unknown medical status) were shown to study participants. Photos were evenly distributed along a continuum of attractiveness that was estimated by independent raters in prestudy stage. In each photo-array, three photos had rating 1-3 (unattractive), one photo had rating 4 (neutral), and three photos had rating 5-7 (attractive). High-quality printed photo-arrays were presented to test subjects, and they were asked to select one person from each photo-array "who has epilepsy". Finally, all subjects were asked to complete questionnaire of self-esteem and 19-item Scale of stereotypes toward people with epilepsy. Results: In total, 71 students of psychology, anthropology, or andragogy (mean age: 21.6 +/- 1.7 years; female: 85.9%) and 70 pMS (mean age: 37.9 +/- 8 years; female: 71.4%) were tested. Majority of students or pMS had no previous personal experience with individuals with epilepsy (63.4%; 47.1%, p=0.052). Male photo was selected as epileptic in the following proportions: students -84.5% unattractive, 8.5% neutral, and 7% attractive; pMS -62.9% unattractive, 8.6% neutral, and 28.6% attractive (p=0.003). Female photo was selected as epileptic in the following proportions: students -38% unattractive, 52.1% neutral, and 9.9% attractive; pMS -32.9% unattractive, 34.3% neutral, and 32.9% attractive (0.003). Both groups showed very low potential for stigmatization: significantly lower in pMS in 10 items. Patients with multiple sclerosis showed significantly higher self-esteem than students (p=0.007). Conclusion: Facial attractiveness influences the perception of diagnosis of epilepsy. Both students and pMS were less willing to attribute epilepsy to attractive person of both genders