Deterministic Mathematical Modelling of Platform Performance Degradation in Cyclic Operation Regimes

This paper considers the modelling of extreme-capability working platforms that are operated in periodic cycles, each cycle having a pre-defined number of operations that affect the working surfaces. A novel hypothesis is introduced about the platform-degrading effects that cause an equivalent decrease in the successful operations after repeated cycles. Deterministic modelling, based on the basic equations of Lanchester and Dinner, is generalized here to include coupling between parameters. The newly developed mathematical model of performance degradation is in good agreement with both experimental measurements and numerical simulations. It is assumed that the new variables and their correlations link the Gaussian distribution and the observed performances of the testing platforms. Relative probability dispersions of affected surfaces are derived, as a new indirect referencing figure of merit, to describe simulations and compare them to experimental test data. The model proves a hypothesis that the degrading effects are a function of the platform capacity, frequency of operations and the number of available cycles. Degradation effects are taken into account through an equivalent decrease of effective operation capacities, reflected on the properties of the affected operating surfaces. The obtained estimations of degradation could be used in the planning of platform capacity as well as in the selection of real affected surfaces in various machining systems and for a wide range of different materials

Comparison of the release of selenium nanoparticles from poly (є-caprolactone) microparticles in four different degradation mediums

One of the most prominent properties of poly (є-caprolactone) (PCL) as a biodegradable polymer is slow degradation rate. Due to this advantage the PCL is often used in versatile systems for drug delivery or tissue engineering. When it comes to drug delivery systems, this property of PCL provides the slow release of encapsulated medicaments in order to avoid acute toxicity i.e. to enhance therapeutic efficiency, or protects medicaments from "aggressive" environment and ensures prolonged effect. Selenium nanoparticles (SeNp) recently gained attention as a potential candidate for cancer therapy and prevention with antibacterial properties as well. The major drawback of SeNp is substantial risk of toxicity. Degradation itself is a function of several material properties as well as the nature of surrounding medium. In this work it is examined the release of SeNp from PCL microparticles during the degradation in four different mediums: phosphate buffered saline (PBS), solution of lipase isolated from porcine pancreas in PBS, 0.1 M hydrochloric acid (HCL) and Psseudomonas aeruginosa cell free extract in PBS. The main idea was to compare the release of the selenium nanoparticles in physiological conditions (the first three medium) and in the pathological conditions (the fourth medium), respectively. Firstly, the PCL/SeNp were suspended in adequate medium and placed in water bath at 37 °C. At exact times, samples were collected and examined by different techniques: X-ray diffraction (XRD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), differential scanning calorimetry (DSC). The release of selenium nanoparticles in physiological conditions occurred in a very slow manner without burst release while in the presence of bacterial extract the release was much more pronounced, even after 24 h

Repair welding of pressure equipment with unacceptable defects

The paper describes non-destructive testing and the repair welding technology for eliminating defects in the pressure equipment of RHE BB (Bajina Basta) (located in Serbia). The obtained results had justified the proposed technology

Repair welding of pressure equipment with unacceptable defects

The paper describes non-destructive testing and the repair welding technology for eliminating defects in the pressure equipment of RHE BB (Bajina Basta) (located in Serbia). The obtained results had justified the proposed technology

Assessment of integrity of pressure vessels for compressed air

Fracture mechanics approach for structural integrity assessment is described in the case of pressure vessels for compressed air. The results of non-destructive testing indicated unacceptable defects on the vessels and set a base for application of failure analysis diagrams (FAD) and risk-based analysis. Risk matrix are applied with the aim of assessment and analysis of the integrity of the vessels

Assessment of integrity of pressure vessels for compressed air

Fracture mechanics approach for structural integrity assessment is described in the case of pressure vessels for compressed air. The results of non-destructive testing indicated unacceptable defects on the vessels and set a base for application of failure analysis diagrams (FAD) and risk-based analysis. Risk matrix are applied with the aim of assessment and analysis of the integrity of the vessels

Analysis of cervical resistance during continuous controllable balloon dilatation: controlled clinical and experimental study

Background: Hydraulic dilatation is a novel method of cervical dilatation that is based on continuous controllable dilatation (CCBD) by the pumping of fluid into the balloon extension of the system. The main advantage of this procedure is that it allows control of and insight into the process of cervical dilatation. Methods: For the purposes of our research, we created a new and upgraded system for CCBD which consists of a programmed hydrostatic pump connected to a balloon extension. With regard to our aim to precisely measure and determine the location of the cervical resistance, we placed two pressure-measuring films, one on the top and one on the bottom of the balloon extension. This study included 42 patients in whom cervical resistance was measured before suction curettage. Results: Cervical dilatation and measurement of cervical resistance were successful in all patients. The analysis of the pressure-measuring films showed that the points of highest resistance were located in the zone of the internal cervical os and that these values were much higher than those in the zone of the external cervical os (0.402 versus 0.264 MPa at the upper pressure-sensitive film; 0.387 versus 0.243 MPa at the lower pressure-sensitive film). This study also showed that an increase in cervical resistance in the zone of the internal cervical os was followed by an increase in cervical resistance in the zone of the external cervical os. Conclusions: During CCBD, the internal cervical os is the centre of cervical resistance, and the values do not decline with the number of miscarriages or the number of previous births

Nasal morphological characteristics of the serbian population

The aim of this study was to determine the nasal parameters in the population of central Serbia and to compare them with those determined in earlier studies in different populations. The research was conducted on 496 randomly selected persons (262 males and 234 females), aged 18-65 years. The measured parameters were nasal height and nasal breadth and the standard spreading caliper with scale was used for measurements. There were significant differences in the nasal parameters between male and female subjects. The nasal breadth was 34.72 mm in females, and in the male population it was 36.7 mm. The mean values of nasal height were 52.6 mm and 54.32 mm in females and males, respectively. The nasal index in females and males was 66.01 and 67.56, respectively, and the mean value of the nasal index of all respondents was 66.78. After conducting the research it was concluded that the dominant nasal type in the population of the central part of Serbia is leptorrhine. The present study showed the existence of sexual dimorphism in nasal morphology. The data obtained in our study may be useful in anthropological and forensic research, as well as in cosmetic planning and reconstructive surgery

Stiffener as a special design solution for pressure vessel repair

Prikazana je popravka posude 970, jer je rizik bio veoma visok, blizu najgoreg slučaja verovatnoće i posledica. Kako položaj greške nije bio pogodan za iskopavanje i reparaturno zavarivanje, odlučeno je da se napravi ukrutni prsten,kako bi se smanjio napon u zavarenom spoju, tako da se i faktor intenziteta napona i neto napon značajno smanjuju.The reparation of vessel 970 is shown, since the risk is very high (close to the worst case of both probability and consequence, being the highest). Since the defect location was not suitable for digging out and repair welding, it was decided to make a circumferential stiffener, to reduce the stress acting on the welded joint, so that both the stress intensity factor and net stress are reduced significantly

Termomehanička prerada mikrolegiranih čelika koncerna Sartid: III deo - poređenje Tnr temperatura određenih u laboratorijskim i industrijskim uslovima

The aim of this work was to compare the Tnr temperatures of microalloyed steels estimated on laboratory (Tnr**l) and industrial scale (Tnr**l). Laboratory and industrial scale are related to testing on high temperature torsion machine, and calculation based on rolling mill log data obtained from SARTID six stand Hot Strip Mill (HSM), respectively. Obtained results are in good agreement, showing the difference of about 30°C. It is assumed that TnrL has higher value due to use of average values in simulation.U radu su upoređene Tnr temperature dobijene u laboratorijskim (TnrL) i industrijskim uslovima (Tnr**l). U laboratorijskim uslovima Tnr**l temperatura je određena na uređaju za ispitivanje uvijanjem na povišenim temperaturama, a u industrijskim uslovima Tnr**l temperatura je određena na osnovu modela dobijenog analizom podataka sa završne pruge Tople valjaonice traka SARTID ad. Rezultati pokazuju dobro slaganje, uz napomenu da je Tnr**l viša od Tnr**l za oko 30 °C. Pretpostavljeno je da je razlika posledica korišćenja prosečnih vrednosti kojima je računala Tnr**l