Finite element modeling of free vibration problem of delaminated composite plates using Abaqus CAE

The aim of this paper is to discuss different finite element models of laminated composite plates with delaminations using the commercial software Abaqus CAE. Three-dimensional (solid), as well as two-dimensional (shell) models in Abaqus CAE, are considered. For comparison, the previously derived and validated numerical model of both intact and delaminated composite plates, based on the Generalized Layerwise Plate Theory of Reddy, is used. Influences of the finite element types and the mesh density on the free vibration response are analysed. Excellent agreement is achieved using the shell model in Abaqus CAE, while the limitations of solid models are noted

Softverski prototip za optimizaciju i upravljanje proizvodnim procesima

Modeling of manufacturing processes aimed at better understanding, optimization and process control is very important in manufacturing practice. This is usually achieved by integrating empirical models with classical mathematical and meta-heuristic algorithms. In this paper, software prototype “Function Analyzer” for optimization and control of manufacturing processes is presented. It is based on the mathematical iterative search of entire space of possible input values. This way, the developed software is able to determine global extreme points of the process model and corresponding input values (process optimization). Furthermore, it is able to determine the optimal input values that satisfy the specified requirements for output value and accuracy (process control). The developed software is characterized by extendible architecture, flexible user interface and efficient operation. The abilities of software prototype “Function Analyzer” were demonstrated on two case studies. The first one considers the regression based modeling of dry turning of cold rolled alloy steel. The second case study considers the artificial neural network based modeling of dry turning of unreinforced polyamide.Modeliranje proizvodnih procesa s ciljem boljeg razumijevanja, optimizacije i upravljanja procesa je vrlo važno u proizvodnoj praksi. U tu svrhu obično se vrši integracija empirijskih modela procesa s klasičnim matematičkim i meta-heurističkim algoritmima. U ovom radu je predstavljen softverski prototip “Function Analyzer” za optimizaciju i upravljanje proizvodnih procesa koji se temelji na matematičkom iterativnom pretraživanju cijelog prostora mogućih ulaznih vrijednosti. Na taj način razvijeni softver je u mogućnosti odrediti globalne ekstremne točke modela procesa i odgovarajuće ulazne vrijednosti (optimizacija procesa). Nadalje, u stanju je odrediti optimalne ulazne vrijednosti koje zadovoljavaju određene uvjete za izlazne vrijednosti i točnosti (upravljanje procesa). Razvijeni softver karakterizira nadogradiva arhitektura, fleksibilno korisničko sučelje i učinkovit rad. Sposobnosti softverskog prototipa “Function Analyzer” su demonstrirane na dvije studije slučaja. Prva razmatra regresijsko modeliranje procesa tokarenja hladno valjanog legiranog čelika. Druga studija slučaja razmatra modeliranje procesa tokarenja neojačanog poliamida pomoću umjetne neuronske mreže

Določevanje nekaterih elementov v sledovih v atmosferskih delcih

Determination of trace element concentrations in atmospheric aerosols is important because of their toxic effects on human health. Additionally, they are now widely used in source apportionment studies. There is a number of methods for sample preparation of ambient particulate matter. One of the most widely used is microwave-assisted digestion of filter-based samples. Since the water-soluble fraction is bioavaliable, the aim of our study was to determine the concentration of selected trace elements (V, Cr, Mn, Ni, Cu, Zn, As, Cd, Sb, Tl, and Pb) in this fraction and compare it to the amounts obtained by two different microwave digestion procedures – one using a mixture of H2O2 and HNO3 and the other using a mixture of HF, HCl, and HNO3. The recoveries of the digestion procedures used were tested on certified reference material (NIST SRM 1648 Urban Particulate Matter). The procedures were applied to filters containing PM10 particles collected at an urban background location in Ljubljana, Slovenia. Among the elements analysed, V, Zn, As, and Cd displayed the highest concentration within the water-soluble fraction, with Cr, Ni, Tl and Pb displaying the lowest concentrations. The comparison between the two applied digestion procedures showed that Cr, Ni, Sb and Tl were strongly bound to the sample matrix.Določevanje elementov v sledovih v atmosferskih delcih je pomembno zaradi njihovega toksičnega vpliva na človekovo zdravje. V zadnjem času se koncentracije teh elementov tudi zelo pogosto uporabljajo v študijah povezanih s porazdelitvijo po virih. Za določevanje elementov v sledovih se uporabljajo različne priprave vzorcev. Najpogostejši je razklop filtrov s pomočjo mikrovalovne peči. Ker je vodotopen delež tudi biološko dostopen, je bil namen naše študije določitev te frakcije posameznih elementov (V, Cr, Mn, Ni, Cu, Zn, As, Cd, Sb, Tl and Pb) in primerjava s koncentracijami po dveh različnih razklopih – prvi z mešanico H2O2 in HNO3 ter drugi z mešanico HF, HCl in HNO3. Izkoristke uporabljenih razklopov smo preverili s standardnim referenčnim materialom (NIST SRM 1648 Urban Particulate Matter). Preverjena postopka smo uporabili na filtrih, ki so vsebovali delce PM10, vzorčevane v Ljubljani, Slovenija. Med analiziranimi elementi so bili izrazito dobro topni v vodi V, Zn, As in Cd, najmanj pa Cr, Ni, Tl, in Pb. Primerjava med obema uporabljenima razklopoma je pokazala, da so Cr, Ni, Sb in Tl v delce izredno stabilno vezani

C++11 STANDARD REVIEW – MOVE SEMANTICS AND SMART POINTERS

Programski jezik C++ neprestano se razvija te je do sada objavljeno nekoliko C++ standarda. Međutim, zadnjim C++ 11 standardom ovaj programski jezik dobio je mnogo novih mogućnosti. Ispravljeni su određeni nedostatci samog programskog jezika te su dodane mnoge nove značajke koje olakšavaju način na koji se piše i dodatno optimizira programski kod. Popis svih značajki koje dolaze s C++ 11 standardom poprilično je velik. Stoga su u ovom radu opisane neke od najvažnijih poput semantike prijenosa i pametnih pokazivača. Upotrebom ovih novih značajki C++ programi postaju još brži i sigurniji za pisanje pa je zato i njihovo razumijevanje od ključne važnosti.C++ programming language is continuously being developed. Up to this date several C++ standards have been released. However, C++ 11 Standard has provided this programming language with many new possibilities. Certain disadvantages of the programming language have been corrected. Also, many new properties have been added, which makes it easier to write and additionally optimise the programming code. The list of new properties which come with C++ 11 Standard is quite long. Therefore, this paper will describe some of the most important properties such as move sematics and smart pointers. Using these new features C++ applications are becoming faster and safer for writing. Hence, their understandind is of key valu

Varijacije termičkih uvjeta u južnom Jadranu prema batitermografskim mjerenjima u periodu od listopada 2002. do lipnja 2003. godine

XBT measurements along two sections in the southern Adriatic carried out from the preconditioning through spreading phase of the deep convection in the season 2002/03 enabled us to describe in detail the process of dense water formation. In autumn, thermal conditions revealed a prominent doming structure and cyclonic circulation in the area that strengthened the inflow of Ionian waters. In March, the vertical convection reached 600 m depth but the air-sea heat and buoyancy losses were mitigated by the horizontal advection of buoyancy. Comparison with previously collected data reveals that the temperature of the mixed water patch shows a continuous interannual increasing trend noticed in the last decade.Redovna batitermografska mjerenja obavljana su dva puta mjesečno u južnom Jadranu u periodu od listopada 2002. do lipnja 2003., kako bi se analizirale vremenske promjene termičkih svojstava vezanih za formiranje pridnene vode. U jesenjem razdoblju prostorna raspodjela temperature ukazuje na pojačanu ciklonalnu cirkulaciju i intenziviranje utjecaja vode iz Jonskog mora. U ožujku vertikalno miješanje dosiže do 600 m dubine, ali je utjecaj gubitka topline na površini mora ublažen dotokom toplije vode s juga. Usporedba termičkih prilika u vertikalno izmiješanom stupcu vode ukazuje na nastavak višegodišnjeg porasta temperature mora uočenog u posljednjem desetljeću

Materials for production of protective boots for workers in forestry

Učinkovitost šumarskih čizama ponajprije ovisi o materijalima od kojih su izrađene, načinu i položaju ugradnje. Upotreba naprednih materijala, visokorazvijenih tehnoloških procesa i razvoj temeljen na znanju i tradiciji dobra su osnova proizvodnje kvalitetne šumarske čizme. U ovom je radu dan pregled tehnoloških faza izrade šumarskih čizama koje zadovoljavaju norme koje definiraju potpunu zaštitu čovjeka od mehaničkih i drugih ozljeda pri upotrebi motornih pila i mogućih prignječenja. Složenost izrade šumarskih čizama ogleda se u primjeni specijalnih visokokvalitetnih materijala, njihovih funkcija te načinu postavljanja u čizmu. Da bi se postigla potpuna zaštita stopala i potkoljenice, šumarska čizma sadržava višeslojne napredne kompozitne materijale, suvremeno obrađenu kožu, tkanine, čelik, netkani tekstil i vodonepropusne i paropropusne membrane.The effectiveness of forestry boots depends primarily on the materials of which they are made, the manner and location of incorporation. The use of highly sophisticated materials, highly developed technological processes and knowledge-based development provide a good basis for the production of quality forestry boots. This paper gives an overview of the technological phases of manufacturing forestry boots that meet the standards defining full human protection against mechanical and other injuries when using motor saws and possible crushing. The complexity of the manufacturing process of forestry boots is reflected in the use of special high-quality materials, their functions, and how to incorporate them into in the boot. To achieve full protection of the foot and lower leg, the forestry boot contains multi-layered advanced composite materials, appropriately processed leather, fabrics, steel, non-woven textiles, and waterproof and vapour-permeable membranes