Optimalni model metode konačnih elemenata (MKE) konstrukcije strijele plovnog bagera

This paper is presentation of the development of advanced approach for modeling and structural analysis of jib structure which is usually part of waterway bucket dredgers. Object of analysis is a jib structure which will be reconstructed for the excavation of grain material from a river bed. Main goal of paper is to proof benefits of enough sophisticated i.e. “optimal” FEM model for structural analysis of this type of structures in comparison with simple, but not adequate models. Proper stress state is emphasized as primary, but not only condition. It is necessary to reach serviceability and durability state, as well as affordable financial construction circumstances.Rad je kratki prikaz razvitka naprednog pristupa u modeliranju i strukturnoj analizi konstrukcije strijele, koja je uobičajeni dio plovnih bagera. Predmet analize je konstrukcija strijele bagera vedričara rekonstruisanog za iskop šljunka sa dna vodotoka. Cilj rada je da dokaže prednosti dovoljno sofi sticiranog tj. “optimalnog” MKE modela za analizu ovog tipa konstrukcija u odnosu na jednostavne, ali neodgovarajuće modele. Odgovarajuće naponsko stanje je istaknuto kao primarni, ali ne i jedini uvjet za rabljenje bagera. Potrebno je osigurati i odgovarajuće stanje upotrebljivosti i trajnosti, kao i povoljne ekonomske uvjete izrade konstrukcije

Evolution of Conversations in the Age of Email Overload

Email is a ubiquitous communications tool in the workplace and plays an important role in social interactions. Previous studies of email were largely based on surveys and limited to relatively small populations of email users within organizations. In this paper, we report results of a large-scale study of more than 2 million users exchanging 16 billion emails over several months. We quantitatively characterize the replying behavior in conversations within pairs of users. In particular, we study the time it takes the user to reply to a received message and the length of the reply sent. We consider a variety of factors that affect the reply time and length, such as the stage of the conversation, user demographics, and use of portable devices. In addition, we study how increasing load affects emailing behavior. We find that as users receive more email messages in a day, they reply to a smaller fraction of them, using shorter replies. However, their responsiveness remains intact, and they may even reply to emails faster. Finally, we predict the time to reply, length of reply, and whether the reply ends a conversation. We demonstrate considerable improvement over the baseline in all three prediction tasks, showing the significant role that the factors that we uncover play, in determining replying behavior. We rank these factors based on their predictive power. Our findings have important implications for understanding human behavior and designing better email management applications for tasks like ranking unread emails.Comment: 11 page, 24th International World Wide Web Conferenc

Učinkovitost i kvaliteta indukcijskog zagrijavanja i kaljenja osovina startera dizel motora

Presented work discusses a complex process of inductive heating and quenching of carbon steel planetary shafts for diesel engine starters. On the measurements base of temperature fields on the surface of the planetary shafts by thermographic camera and theoretical knowledge, a mathematical model for temperature conditions determination in the shaft during the entire process of heating and quenching was carried out. On the basis of developed mathematical model a computer program was developed, and used for analyses and induction hardening process optimization of planetary shafts.U ovom se radu raspravlja o složenom procesu indukcijskog zagrijavanja i kaljenja osovina iz ugljičnog čelika za pokretanje dizelskih motora. Na temelju rezultata mjerenja temperaturnih polja na površini osovina termografskom kamerom i teorijskih spoznaja, razvijen je matematički model temperaturnih uvjeta tijekom procesa zagrijavanja i kaljenja osovina. Na temelju postavljenog matematičkog modela razvijen je računalni program koji je korišten za analizu i optimizaciju procesa zagrijavanja osovina

The analysis of particles emission during the process of grinding of steel EN 90MNV8

Metal grinding is a one of the manufacturing technologies that is greatly connected to particles emission. Particles generated during the grinding process are dangerous in terms of its potential penetration deeply into the lungs of an operator. The level of risk for human respiratory system is related to nature, shape and size of the particles, and for this reason it is important to have a quality characterization of emitted particles. This paper focuses on particles characterization on the bases of image analysis from scanning electron microscopy (SEM). The research was conducted during the process of grinding of steel EN 90MnV8, using personal sampler. Results of image analysis, consisted of Feret’s diameter and circularity, showed quite a wide range of sizes and significant deviation of particles from regular shape

The analysis of particles emission during the process of grinding of steel EN 90MNV8

Metal grinding is a one of the manufacturing technologies that is greatly connected to particles emission. Particles generated during the grinding process are dangerous in terms of its potential penetration deeply into the lungs of an operator. The level of risk for human respiratory system is related to nature, shape and size of the particles, and for this reason it is important to have a quality characterization of emitted particles. This paper focuses on particles characterization on the bases of image analysis from scanning electron microscopy (SEM). The research was conducted during the process of grinding of steel EN 90MnV8, using personal sampler. Results of image analysis, consisted of Feret’s diameter and circularity, showed quite a wide range of sizes and significant deviation of particles from regular shape

Development of banded microstructure in 34CrNiMo6 steel

In this paper the development of a banded microstructure in hot-rolled 34CrNiMo6 steel which consisted of bainitic and martensitic bands is explained. The chemical compositions of the bands were measured with energy dispersive x-ray spectroscopy (EDS), which showed that the martensitic bands contained more alloying elements (Mn, Cr, Mo, Si) than bainitic bands. By using Oberhoffer reagent, the segregations of phosphorus were also revealed. These phosphorus segregations coincided with the positive segregations of the alloying elements. The continuous cooling transformation (CCT) diagrams of steel were calculated. They confirmed the formation of martensite in positive segregations and the formation of bainite in negative segregations

Reconstruction of 3D models of cast sculptures using close-range photogrammetry

This paper presents the possibilities of application of close-range photogrammetry, based on the Structure-from- Motion (SfM) approach, in 3D model’s reconstruction of bronze cast sculptures. Special attention was dedicated to the analysis of image processing strategy, and its impact on the 3D model reconstruction quality. For the purpose of analysis a bust of Nikola Tesla, placed in front of the Faculty of Technical Sciences University of Novi Sad was used. Experimental results indicate that the strategy employing multi-group photo processing provides substantial reductions in processing time while providing satisfactory results in 3D reconstruction

Unique and conserved MicroRNAs in wheat chromosome 5D revealed by next-generation sequencing

MicroRNAs are a class of short, non-coding, single-stranded RNAs that act as post-transcriptional regulators in gene expression. miRNA analysis of Triticum aestivum chromosome 5D was performed on 454 GS FLX Titanium sequences of flow sorted chromosome 5D with a total of 3,208,630 good quality reads representing 1.34x and 1.61x coverage of the short (5DS) and long (5DL) arms of the chromosome respectively. In silico and structural analyses revealed a total of 55 miRNAs; 48 and 42 miRNAs were found to be present on 5DL and 5DS respectively, of which 35 were common to both chromosome arms, while 13 miRNAs were specific to 5DL and 7 miRNAs were specific to 5DS. In total, 14 of the predicted miRNAs were identified in wheat for the first time. Representation (the copy number of each miRNA) was also found to be higher in 5DL (1,949) compared to 5DS (1,191). Targets were predicted for each miRNA, while expression analysis gave evidence of expression for 6 out of 55 miRNAs. Occurrences of the same miRNAs were also found in Brachypodium distachyon and Oryza sativa genome sequences to identify syntenic miRNA coding sequences. Based on this analysis, two other miRNAs: miR1133 and miR167 were detected in B. distachyon syntenic region of wheat 5DS. Five of the predicted miRNA coding regions (miR6220, miR5070, miR169, miR5085, miR2118) were experimentally verified to be located to the 5D chromosome and three of them : miR2118, miR169 and miR5085, were shown to be 5D specific. Furthermore miR2118 was shown to be expressed in Chinese Spring adult leaves. miRNA genes identified in this study will expand our understanding of gene regulation in bread wheat

Immunological reactions and ventilatory capacity in hemp workers

Odnos imunološkog statusa i respiratornih nalaza ispitivan je u 42 radnice profesionalno izložene prašini konoplje i u 49 radnica kontrolne skupine. Najviša prevalencija pozitivnih kožnih prick testova u radnica na preradi konoplje utvrđena je za mješavinu konoplje i lana (64% ), zatim za lan (48% ), konoplju s češljara (41%), konoplju s karda (38%), konoplju s predilica i tkalačkih strojeva (33%) i konoplju s omekšivača (20%). Prevalencija pozitivnih kožnih tekstova u radnica kontrolne skupine bila je znatno niža i varirala je od 21% do 5%. Povišen ukupni IgE utvrđen je u 35,7% radnica na preradi konoplje i u 4,1% radnica kontrolne skupine (P<0,05). U radnica na preradi konoplje s pozitivnim kožnim testovima utvrđena je značajno viša prevalencija kroničnih respirator-nih simptoma nego u onih s negativnim kožnim testovima. Akutne promjene ventilacijske funkcije pluća nisu se razlikovale prema imunološkom statusu. Vodeni ekstrakt prašine konoplje uzrokovao je kontrakciju glatke muskulature traheje u eksperimentu in vitro na nesenzibiliziranoj zamorčadi. Naši rezultati upućuju na to da prašina konoplje osim imunološkim mehanizmom može djelovati i iritativno na respiratorni sustav izloženih radnika.The relationship between immunological status and respiratory function was studied in 42 hemp workers and in 49 control workers. The highest prevalence of positive skin tests was recorded for a mixture of hemp and flax (64%), followed by flax (48%), hemp on a combing machine (41%), hemp on a carding machine (38% ), hemp on spinnin~ and weaving machines (33% ), and hemp on a softening machine (20%). The prevalence of positive skin tests in control workers was smaller and varied from 21 to 5%. Increased lgE was found in 35.7% of the hemp workers and in 5.0% of the controls (P<0.05). Hemp workers with positive skin tests had a significantly higher prevalence of chronic respiratory symptoms than those with negative skin tests. Acute ventilatory capacity reductions did not differ in respect to the immunological status. An extract of hemp dust caused a constriction of an isolated guinea pig tracheal smooth muscle in vitro. Our data suggest that hemp dust as well as producing an immunological effect may exert an irritant effect on the respiratory system in exposed textile workers