Total Fatigue Life Estimation Of Aircraft Structural Components Using Strain Energy Density Method

This paper is aimed at developing a suitable computation method for estimating the fatigue life of structural elements exposed to the load spectrum. The total fatigue life can be divided into two parts, until the appearance of the initial damage and the other part represents the remaining life, i.e. until the effective fracture. The conventional approach to estimating the total life requires that low-cycle fatigue characteristics of the material be used until the initial damage occurs, and dynamic characteristics of the material for the remaining life. In order to obtain a more efficient method, the Strain Energy Density (SED) method was used in this paper. The essence of this approach is to use the same low - cycle fatigue characteristics of the material to estimate the life expectancy and the remaining life. This work is focused to developing efficient computation method and software for total fatigue life of metal aircraft structural components. To obtain efficient computation method, here the same fatigue low cyclic material properties for crack initiation and crack growth are used together with finite element method (FEM) for stress analyzes. To validate quality computation methods and in-house software for fatigue life estimations computation results are compared with experiments. The results show that the predicted results agree well with the test dat

Gluing together proof environments: Canonical extensions of LF type theories featuring locks

© F. Honsell, L. Liquori, P. Maksimovic, I. Scagnetto This work is licensed under the Creative Commons Attribution License.We present two extensions of the LF Constructive Type Theory featuring monadic locks. A lock is a monadic type construct that captures the effect of an external call to an oracle. Such calls are the basic tool for gluing together diverse Type Theories and proof development environments. The oracle can be invoked either to check that a constraint holds or to provide a suitable witness. The systems are presented in the canonical style developed by the CMU School. The first system, CLLF/p,is the canonical version of the system LLF p, presented earlier by the authors. The second system, CLLF p?, features the possibility of invoking the oracle to obtain a witness satisfying a given constraint. We discuss encodings of Fitch-Prawitz Set theory, call-by-value λ-calculi, and systems of Light Linear Logic. Finally, we show how to use Fitch-Prawitz Set Theory to define a type system that types precisely the strongly normalizing terms

Some aspects of design ventilation system in road tunnels

In the base, working of ventilation system can be analyzed in regular and incidental modes of operation. This paper concerns the specification of the longitudinal ventilation necessary to prevent upstream movement of combustion products in a tunnel fire. In this work the objective of the study is to analyze the road way tunnel ventilation system using CFD software to create comfort ventilation system in the tunnel. The comfort ventilation concept refers to the situation when air quality within the tunnel is reduced due to presence of polluted air in the tunnel. This paper is focused on ventilation system in a road traffic tunnel in moment of accident situation as fire. In this investigation numerical simulation of fire was carried out and determination of a critical air velocity depending on the power of the fire was conducted. The output results of the software developed for this purpose, which is also used in the realization of practical projects, are shown

Occupational exposure to blood and body fluids among health-care workers in Serbia

© 2014 S. Karger AG, Basel. Objectives: The aim of this study was to examine the epidemiology of occupational accidents and self-reported attitude of health-care workers (HCWs) in Serbia. Subjects and Methods: A cross-sectional study was conducted among HCWs in selected departments of five tertiary care hospitals and in one secondary care hospital in February 2012. A previously developed self-administered questionnaire was provided to HCWs who had direct daily contact with patients. χ2 test and Student's t test were used for statistical analysis of the data. Results: Of the 1,441 potential participants, 983 (68.2%) completed the questionnaire: 655 (66.7%) were nurses/medical technicians, 243 (24.7%) were physicians and 85 (8.6%) were other personnel. Of the 983 participants, 291 (29.6%) HCWs had had at least one accident during the previous year and 106 (40.2%) of them reported it to the responsible person. The highest prevalence (68.6%) of accidents was among nurses/technicians (p = 0.001). Accidents occurred more often in large clinical centers (81.1%; p < 0.001) and in the clinical ward, intensive care unit and operating theater (p = 0.003) than in other departments. Seventy-six (13.1%) nurses/medical technicians had an accident during needle recapping (p < 0.001). Of all the HCWs, 550 (55.9%) were fully vaccinated, including significantly more doctors (154, 63.4%) than participants from other job categories (p < 0.001). Conclusion: There was a relatively high rate of accidents among HCWs in our hospitals, most commonly amongst nurses and staff working in clinical wards, intensive care units and operating theaters. The most common types of accidents were needlestick injuries and accidents due to improper handling of contaminated sharp devices or occuring while cleaning instruments or by coming into contact with blood through damaged skin or through the conjunctiva/mucous membranes

Short-term liquid storage of ram semen in various extenders

The aim of this study was to investigate the effects of three extenders on ram sperm quality after short-term liquid storage (24 hours’ holding time). The study included 20 crossbred rams (Pirot Pramenka x Wurttemberg x Ile de France), 12 months old. Animals were housed at the experimental sheep farm of the Institute for Animal Husbandry in Belgrade, Serbia. Semen was collected through electro ejaculation. The ejaculates were obtained from single services and routine field analysis of the semen was performed immediately after the collection. The semen was split and diluted with three extenders, namely Optidyl®, Andromed® and ultrahigh temperature processed (UHT) milk, in ratios of 1 : 50 or 1 : 100. The ejaculates were examined for sperm motility variables (sperm cell motility percentage, the progressive motility percentage, curvilinear velocity (VCL), straight line velocity (VSL), average path velocity (VAP), sperm linearity (LIN), straightness (STR), amplitude of lateral sperm head displacement (ALH), beat cross frequency (BCF) and circular tracks), and sperm morphology (live sperm percentage, percentage of normal sperm forms with intact acrosome, percentage of abnormal sperm forms and total damaged acrosome) by computer-assisted sperm analysis (CASA) and classic sperm cytology after supravital eosin/nigrosine/trypan blue staining, respectively. It was observed that the type of extender used in diluting ram semen is an important factor in the successful short-term liquid preservation (at 4 °C) of ram spermatozoa. In conclusion, this study showed that egg yolk (Optidyl) and soybean (Andromed)-based extenders gave better results of both sperm morphology and sperm motility parameters compared with UHT milk.Keywords: Diluents, morphology, motility, sper

A possible connection between phosphate tungsten bronzes properties and briggs-rauscher oscillatory reaction response

The calcium phosphate tungsten bronze (Ca-PWB) has been synthesized and characterized (TGA, DSC, XRPD, FTIR, SEM). The influence of solid insoluble materials Ca-PWB, as well as lithium doped (Li-PWB) and cation free phosphate tungsten (PWB) bronzes on the oscillatory Briggs-Rauscher (BR) reaction dynamics, is compared. The results show that doping with Li and Ca reduces sensitivity of the BR reaction towards bronzes addition. These findings suggest the usage of the BR reaction as an innovative method for testing of different properties of bronze material. The behavior of PWB in the BR reaction is significantly changed with divalent cation (Ca2+) doping. The reasons for the different bronzes behavior were found in their calculated unit cell volumes. Namely, the compressed Ca-PWB unit cell volume indicates the difficult availability of the active site for heterogeneous catalysis. Hence, the linear correlation (slope) of the BR oscillogram’s length (τosc) vs. mass of bronze in BR reaction might be considered as a new parameter for the evaluation of the bronzes catalytic activity.У овом раду синтетисана је и окарактерисана (TGA, DSC, XRPD, FTIR, SEM) нова калцијумом допирана фосфат волфрамова бронза (Ca-PWB). Испитан је и упоређен утицај фосфат волфрамове бронзе (PWB), литијумом допиране фосфат волфрамове бронзе (Li-PWB) и калцијумом допиране фосфат волфрамове бронзе (Ca-PWB) на осцилаторну динамику Briggs-Rauscher (БР) реакције. Резултати показују да допирање катјонима Li+ и Ca2+ смањује осетљивост БР реакције на додатак нерастворних бронзи, што се огледа у смањивању нагиба праве осцилаторног времена (τosc) БР реакције у функцији масе додате допиране бронзе. Добијени резултати сугеришу употребу БР реакције као иновативне методе за испитивање различитих својстава допираних и недопиране фосфат волфрамове бронзе. Разлози за различито понашање бронзи у осцилаторној реакцији пронађени су у различитим величинама јединичних ћелија PWB, Li-PWB и Ca-PWB. Наиме, најмања вредност, тј. сабијање јединичне ћелије допирањем калицијумом указује на тежу доступност активних места за хетерогену катализу. Каталитичка активност бронзи усмерена је ка реакцијама оксидације које укључују водоник-пероксид (један од реактаната БР реакције). Стога би се линеарна корелација (нагиб) τosc у функцији масе бронзе у БР реакцији могла сматрати новим параметром за процену каталитичке активности бронзе, али и других материјала

Proizvodne karakteristike i telesne mere koza alpske rase gajenih na malim porodičnim gazdinstvima u centalnoj Srbiji

The purpose of this study was to evaluate present level of productivity and determine linear body traits of Alpine goats raised in Serbia on smallholder farms. Data were collected from 22 smallholder farms located in Belgrade district, with total of 330 purebred Alpine does 2-9 years of age, 145 yearling does and 476 kids. Traits measured were: body weight of does, body weight of kids at birth, 30 days of age and at weaning (90-120 days), prolificacy of mature and yearling (primiparous) does, six linear body traits of does (wither height, body length, hearth girth, chest depth, chest width, pelvic width) and milk production (milk yield, milk fat and milk protein content). The analysis showed the average body weight of does to be 54.96 kg, while the average body weight of kids at birth, 30 days of age and weaning was 2.73 kg, 8.7 kg and 18.3 kg., respectively. Prolificacy was 144% in mature and 125% in yearling does. Measurements of linear body traits were: wither height 67.87 cm, body length 71.92 cm, hearth girth 81.79 cm, chest depth 32.93, chest width 21.49 cm and pelvic width 17.63 cm. Among dairy production traits, following results were obtained: lactation length 220.73 days, total milk yield 531.66 kg, milk fat content 3.33% and milk protein content 3.16%. It was concluded that the overall productivity of Alpine goats raised under smallholder production systems in Serbia is satisfying. Giving the fact that these animals are usually kept under poor conditions, many of these productive traits are very good.Cilj ovog istraživanja bio je da se proceni postojeći nivo produktivnosti i da se utvrde vrednosti linearnih telesnih mera koza alpske rase koje se gaje u Srbiji kod individualnih poljoprivrednih proizvođača. U ispitivanje su uključena 22 poljoprivredna gazdinstva locirana u beogradskom okrugu, sa ukupno 330 koza alpske rase uzrasta 2-9 godina, 145 prvojarenica i 476 jaradi. Analizirane su sledeće osobine: telesna masa koza, telesna masa jaradi na rođenju, sa 30 dana uzrasta i pri odlučenju (90-120 dana), plodnost odraslih koza i prvojarenica, linearne telesne mere (visina grebena, dužina trupa, obim grudi, dubina grudi, širina grudi, širina karlice) i osobine mlečnosti (dužina laktacije, količina mleka za laktaciju, sadržaj mlečne masti i proteina). Prosečne vrednosti telesne mase i plodosti ispitivanih kategorija bile su: telesna masa koza 54,96 kg, telesna masa jaradi na rođenju 2,73 kg, telesna masa jaradi sa 30 dana 8,7 kg i telesna masa jaradi pri odlučenju 18,3 kg, plodnost odraslih koza 144%, plodnost prvojarenica 125%. Utvrđene su sledeće vrednosti telesnih mera: visina grebena 67,87 cm, dužina trupa 71,92 cm, obim grudi 81,79, dubina grudi 32,93 cm, širina grudi 21,49 cm i širina karlice 17,63 cm. Prosečna laktacijska mlečnost je iznosila 531,66 kg mleka u laktaciji od 221 dan, sa 3,33% mlečne masti i 3,16% proteina. Na osnovu utvrđenih rezultata i poređenjem sa rezultatima drugih autora zaključeno je da je produktivnost koza alpske rase gajenih na malim poljoprivrednim gazdinstvima zadovoljavajući. Plodnost koza je na nešto nižem nivou, kao i porođajne mase jaradi. Međutim, ako se ima u vidu da su uslovi gajenja ovih životinja često veoma skromni, mnoge od ovih proizvodnih osobina su veoma dobre. Prostora za poboljšanje ima, ali uz veća ulaganja koja uslovljavaju i veću cenu proizvodnje. Ipak, uz nepostojanje organizovanog i zagarantovanog otkupa mleka koza, kao ni zaštitnih cena mleka, što bi proizvođačima pružilo neku sigurnost u proizvodnji, sva veća ulaganja u ovom trenutku ne bi bila isplativa

Seasonal forecasting of green water components and crop yield of summer crops in Serbia and Austria

A probabilistic crop forecast based on ensembles of crop model output estimates, presented here, offers an ensemble of possible realizations and probabilistic forecasts of green water components, crop yield and green water footprints (WFs) on seasonal scales for selected summer crops. The present paper presents results of an ongoing study related to the application of ensemble forecasting concepts in crop production. Seasonal forecasting of crop water use indicators (evapotranspiration (ET), water productivity, green WF) and yield of rainfed summer crops (maize, spring barley and sunflower), was performed using the AquaCrop model and ensemble weather forecast, provided by The European Centre for Medium-range Weather Forecast. The ensemble of estimates obtained was tested with observation-based simulations to assess the ability of seasonal weather forecasts to ensure that accuracy of the simulation results was the same as for those obtained using observed weather data. Best results are obtained for ensemble forecast for yield, ET, water productivity and green WF for sunflower in Novi Sad (Serbia) and maize in Gross-Enzersdorf (Austria) - average root mean square error (2006-2014) was lt 10% of observation-based values of selected variables. For variables yielding a probability distribution, capacity to reflect the distribution from which their outcomes will be drawn was tested using an Ignorance score. Average Ignorance score, for all locations, crops and variables varied from 1.49 (spring barley ET in Gross-Enzersdorf) to 3.35 (sunflower water productivity in Gross-Enzersdorf)

Morfologija poprečnog preseka prevlaka bakra dobijenih elektrohemijskim taloženjem u oblasti ko-depozicije vodonika

Cross-section analysis of copper deposits electrodeposited in the hydrogen co-deposition range at a constant overpotential and in a pulsating overpotential (PO) regime was performed. It was shown that a complete structural analysis of these technologically very important electrodes is impossible without an analysis of their internal structure. An insight into the compactness (or porosity) of the deposits, as well as into the depth of the holes, can only be obtained by this type of analysis.Urađena je analiza poprečnih preseka taloga bakra dobijenih u oblasti ko-depozicije vodonika na konstantnoj prenapetosti i režimom pulsirajuće prenapetosti. Pokazano je da kompletna strukturna analiza ovih tehnološki veoma važnih elektroda nije moguća bez analize njihove unutrašnje strukture. Uvid u kompaktnost (ili poroznost) taloga, kao i u dubinu rupa može da se dobije samo ovim tipom analize

Uticaj oblika i strukture čestica na tečljivost elektrolitičkog bakarnog praha IV - unutrašnja struktura čestica praha

The structure of powder particleswas analysed by considering their cross sections. It was shown that the structure of powder particles of nonsieved flowing powders is sufficiently dense to produce a continuous surface, which does not allow the particles to jam and hence permits the free flow of nonsieved powder. It was also shown that the representative powder particle the elementary cell of which can be presented by a 3D-cross, describes the properties of the powder relative to its flowability well.Analizirana je struktura čestica praha razmatranjem njihovog poprečnog preseka Pokazano je da je struktura čestica nesejanog praha koji teče dovoljno gusta da obrazuje kontinualnu površinu, koja ne dozvoljava zaglavljivanje čestica i samim tim omogućava slobodno tečenje nesejanih prahova. Takođe je pokazano da reprezentativna čestica praha, čija se elementarna ćelija može predstaviti 3D-krstom, dobro opisuje osobine praha koje se odnose na tečljivost