Stress Analysis of Steel Structure Comprising Cylindrical Shell with Billboard Tower

In accordance with EN1993-1-1, in the definition of element classes, the tubular cross section elements are considered as class 3 for cross section that respects the relation: d/t ≤ 90ε2. If for any cross section this relation is not satisfied, the norm is not valid and the cross section is classified as a curved thin walled element – shell element. Thus the design is done according to EN 1993-1-6 normative. The paper presents some aspects regarding the shell design for a case study – a 30 m tall billboard pillar. The designing process is detailed in regard to the used analysis and the ultimate limit states checking. Considering the high stress concentration in the area of the segment joints, design of welded joints is also presented. The Finite Element Method (FEM) is applied as well, showing results in agreement with analytical ones

Calculation of the effective shear modulus of composite sandwich panels

U radu je predstavljena metoda proračuna efektivnog modula smicanja kompozitnih panela sa sendvič ispunom. Ovaj koeficijent elastičnosti predstavlja vrlo važnu karakteristiku materijala, posebno kod konstrukcija koje su izložene čistoj torziji ili kombinaciji savijanja i torzije. Strukture koje su ispitivane u ovom istraživanju su ravne ploče načinjene od gornjeg i donjeg kompozitnog lica i ispunom (jezgrom) od šestougaonog kompozitnog sendvič materijala. Polazeći od klasične teorije laminata određen je efektivni modul smicanja gornje i donje ploče za svaki sloj u stoku (laminatu). Ovi slojevi platana se svode u jedan kompozitni sloj sa različitim orijentacijama vlakana i debljine. Da bi se verifikovao ovaj prilaz korišćen je Metod konačnih elemenata da bi se odredila pomeranja, deformacije i naponi u kompozitnim pločama i sendvič ispuni. Dva tipa numeričkih modela su upoređivani: početni model, gde su svi spojevi ploče modelirani sa svojim karakteristikama i drugi model kod kojeg su spojeni u jednu celinu sa svojim ekvivalentnim karakteristikama.Calculation Method for the effective shear modulus of composite plates with sandwich cores is presented. This elastic coefficient represents one very important material property especially in constructions subjected to pure torsion and combined bending - torsion. The structures investigated in this research are flat plates made of top and bottom composite facesheets and hexagonal composite material sandwich core. Starting from classical Lamination theory the effective shear modulus of top and bottom plates was determined for each ply in the stack up sequence. These plies were 'lumped into a single composite layer for different fiber orientations and plies thicknesses. To verify this approach Finite element method was used to determine the displacement, stress and strain field on Composite plates with Sandwich Cores. Two types of models were compared: The initial model where all the material components, plates and the core were modeled with their intrinsic properties and 'lumped' model with calculated effective elastic coefficients

Stress Analysis of Steel Structure Comprising Cylindrical Shell with Billboard Tower

In accordance with EN1993-1-1, in the definition of element classes, the tubular cross section elements are considered as class 3 for cross section that respects the relation: d/t lt = 90 epsilon(2). If for any cross section this relation is not satisfied, the norm is not valid and the cross section is classified as a curved thin walled element - shell element. Thus the design is done according to EN 1993-1-6 normative. The paper presents some aspects regarding the shell design for a case study - a 30 m tall billboard pillar. The designing process is detailed in regard to the used analysis and the ultimate limit states checking. Considering the high stress concentration in the area of the segment joints, design of welded joints is also presented. The Finite Element Method (FEM) is applied as well, showing results in agreement with analytical ones

Identification of Crack Initiation Cause in Pylons Construction of the Excavator SchRs630

A crack occurred on gusset plate of pylon vertical truss of bucket wheel excavator (BWE) SchRs630. Numerical calculation model of pylons, slewing platform and undercarriage was formed. Calculations are done using finite element method (FEM) for different load cases. It was determined that the inertial forces caused by bucket wheel boom and counterweight boom masses while breaking slew drive cause the stress concentration in this spot. To complete the whole picture of the structure behaviour dynamic analysis was performed. Based on calculation and distribution of potential and kinetic energy on oscillation modes, using the reanalysis method, redesign of this part of the structure was proposed. The stress was reduced by over 20 % by the proposed redesign solution

Koncepcija razvoja ekoturizma u UNESCO rezervatima biosfere: Studije slučaja iz Hrvatske i Srbije

Ecotourism is a sustainable form of tourism in protected areas that provides support for nature protection and sustainable development of local communities. Biosphere reserves are special areas with a relatively original nature and active socio-economic development, as well as with cultural characteristics that must be in harmony with the ecological environment. Understanding the interaction of environmental, economic and social factors in a biosphere reserve is the basis for setting the concept of sustainable development of ecotourism. In respect to that, this paper includes an analysis of the concepts of ecotourism within the protected areas Kopački rit (Croatia) and Gornje Podunavlje (Serbia), in the biosphere reserves Mura – Drava – Dunav (Croatia) and Bačko Podunavlje (Serbia), with the main aim of making a comparative analysis of their organization. The main findings are providing the knowledge basis in terms of nature protection according to the national legislation and international nature protection statuses, nature degradation and challenges of protected area management, organization of tourism, cooperation between nature protection and tourism development, projects supporting the nature protection and ecotourism development and involvement of the local population.Ekoturizam je održivi oblik turizma koji u zaštićenim područjima pruža podršku zaštiti prirode i održivom razvoju lokalnih zajednica u njihovu okruženju. Rezervati biosfere posebna su područja s relativno izvornom prirodom i aktivnim društveno-ekonomskim razvojem, kao i s kulturnim osobnostima koje moraju biti suglasne s ekološkim okruženjem. Spoznaja o interakciji ekoloških, ekonomskih, kulturnih i društvenih čimbenika u nekom rezervatu biosfere predstavlja temelj za postavljanje koncepcije održivog razvoja ekoturizma. Ovaj rad obuhvaća analizu koncepcija razvoja ekoturizma zaštićenih područja Kopački rit (Hrvatska) i Gornje Podunavlje (Srbija), u rezervatima biosfere Mura – Drava – Dunav (Hrvatska) i Bačko Podunavlje (Srbija), s glavnim ciljem da se napravi usporedna analiza njihove opće organizacije. Rezultati istraživanja pružaju ključne informacije o zaštiti prirode u skladu s nacionalnim zakonodavstvima i međunarodnim standardima zaštite prirode, degradacije prirode i izazova upravljanja zaštićenim područjima, organizacije ekoturizma, povezanosti između zaštite prirode i razvoja ekoturizma, projekata koji podržavaju zaštitu prirode i razvoj ekoturizma i uključivanja lokalnog stanovništva u daljnji razvoj

The significance of interleukin - 6 and tumor necrosis factor - alpha levels in patients with schizophrenia

Uvod: Alteracije proinflamatornih citokina (Interleukina -6 i Tumor nekrozis faktora-alfa) se ĉesto povezuju sa shizofrenijom i depresijom, duţinom bolesti, psihopatologijom i tretmanom. Prema „citokinskoj hipotezi“ proinflamatorni citokini su oznaĉeni kao kljuĉne neuromodulatorne supstance koje imaju ulogu u centralnoj koordinaciji bihejvioralnih, neuroendokrinih i neurohemisjkih ispoljavanja kod obolelih. Cilj: Ispitati razlike u serumskim koncentracijama IL-6 i TNF-: kod obolelih od shizofrenije u akutnoj fazi bolesti i u fazi remisije; izmedju obolelih od shizofrenije u akutnoj fazi bolesti i u fazi remisije u poredjenju sa kontrolnom grupom depresivnih pacijenata. Ispitati povezanost koncentracija ispitivanih citokina sa godinama poĉetka bolesti, periodom neleĉenosti, duţinom leĉenja i duţinom bolesti medju obolelima od shizofrenije i depresije. Ispitati povezanost koncentracija IL-6 i TNF- i psihopatoloških korelata shizofrenije (nivoa opšte psihopatologije, intenziteta pozitivnih i negativnih simptoma). Metod: U istraţivanje je ukljuĉeno 80 subjekata (43 obolela od shizofrenije i 37 obolelih od depresije). Shizofreni pacijenti su posmatrani kao studijska grupa (S) u dve faze bolesti akutna faza -T1 i remisija -T2), dok su depresivni bili kontrolna grupa i posmatrani su samo u akutnoj fazi...Introduction: Alterations in serum levels of pro-inflamatory cytokines (Interleukin-6 and Tumor Necrosis Factor-Alpha ) are fequently associated with schizophrenia and depression, duration of the illnesses, their psychopatology and treatment. According to the „cytokine hypothesis“ pro-inflamatory cytokines are considered as crutial neuromodulatory substances which take part in central coordination of behavioural , neuroendocrine and neurochemical clinical manifestations in patients suffering from these illnesses. Aim: Comparissson of the differences in serum concentrations of IL-6 and TNF-: a) in schizophrenic patients in the acute phase of the illness and in remission; b) in schizophrenic patients in the acute phase of the illness and in remission compared to the control group of depressive patients. Investigation of the connection between the studied cytokines and the age of the patients at the onset of the illness, with periods of time without treatment, duration of treatment, and total illness duration in both schizophrenic and depressive patients. Investigation of the connection between concetrations of IL-6 and TNF- in serum and psychopathological correlations of schizophrenia (level of general psychopathology, intensity of positive and negative symptoms)..

STR loci D19S216, D20S502 and D20S842 analysis in the Serbian population using dentin DNA

Dentin provides a protective enclosure for genomic and mitochondrial DNA. In the present study, DNA was obtained from pulverized or ground teeth. The quality of the DNA extracted from the teeth of 70 unrelated individuals was tested in the context of assessing the allelic and genotypic frequencies of autosomal loci D19S216, D20S502 and D20S842, and calculating a number of parameters of population genetics and forensic interest. This study illustrates that teeth can be a convenient tissue to extract DNA from large numbers of individuals for population genetic studies as well as for forensic case work

Prothrombin expression in cancer-derived cell lines

The link between thrombotic disorders and cancer has been known for over 150 years, although the precise mechanism of this relationship has not yet been resolved. Current data show that thrombin has a significant role in cancer metabolism, invasiveness, adhesion and survival. However, data regarding the expression of the thrombin precursor prothrombin in various cancer cell lines are scarce. Therefore, it was our objective to determine whether common cancer-derived cell lines (Caco-2, MCF-7, SK-BR-3, U-87 and U-251) express prothrombin. The prothrombin RNA expression level was assessed by qPCR, and the presence of prothrombin was analyzed by Western blot analysis. Our results show that Caco-2 cells originating from colorectal adenocarcinoma express prothrombin, whereas other analyzed cell lines do not. Our results provide a background for further research into the role of (pro) thrombin in cancer etiopathology

The effect of prothrombin, the precursor of thrombin, on the proliferation and migration of colorectal cancer cells

Thrombotic disorders are some of the main comorbidities in cancer patients. So far, research has indicated that thrombin, a key regulator of hemostasis, contributes to cancer progression. However, data on its origin in tumor microenvironments remain elusive. Based on previous research, we analyzed the RNA and protein expression of prothrombin, a precursor of thrombin, in selected colorectal cancer (CRC) cell lines. Since the effect of prothrombin in cancer development has not been previously reported, we treated the cells for 24 h and 48 h with different prothrombin concentrations and assessed the effect on cell proliferation and migration. Our results show that the tested CRC cell lines expressed prothrombin and that prothrombin inhibited proliferation and migration. The presented results suggest that prothrombin may contribute to CRC etiopathology and could serve as a potential diagnostic biomarker and therapeutic target. The mechanisms underlying prothrombin expression in cancer cells, potential prothrombin activation, and the underlying processes driving the described effects warrant further investigation

Professional stress in general practitioners and psychiatrists: The level of psycologic distress and burnout risk

Background/Aim. So far, studies of stress have shown that physicians are at a high risk of sickness from psychic and somatic disorders related to professional stress, that can lead to important disturbance of personal, familiar and professional functionating. The aim of this study was to investigate the doctors exposition level to professional stress, to compare stress level in general practitioners (GP) group with that in the group of psychiatrists and risk level for the apperance of burnout syndrome. Methods. This cross-section study included subjects recruited by a random sample method. Thirty General Practice doctors and 30 psychiatrists (totally 60 doctors) filled the set of 3 questionnaires: Sociodemographics features, General Health Questionnaire (GHQ; Goldberg D, 1991), and Maslach Burnout Inventory (MBI; Maslach C, 1996). Appropriate statistical procedures (Pearson test, t-test, variance analysis) in interpretation of the results were used. Results. A total level of psychic distress measured with the GHQ test in both groups of physicians was very low implying their good mental health. A difference in Burnout risk based on MBI test between the groups was statistically significant (χ2 = 4,286; p < 0.05) only at subscale Personal Accomplishment (MBI-PA); it was a consequence of a higher number of GPs with medium burnout risk (13.3 : 0.0%). However, even 35 physicians from the sample were affected with a high burnout risk measured with subscales Emotional Ehausation (MBI-EE) and MBI-DP, showing that both groups of physicians had risk for the appearance of burnout syndrome. Conclusion. The obtained results showed a high burnout risk level in both, GPs and psychiatrists, groups. In both groups there was no presence of psychic disorders (anxiety, depression, insomnia), while there was a high level of emotional ehausation and overtension by job, and also a lower total personal accomplishment. Level of exposition to professional stress is higher in GPs than in psychiatrists, but the difference was not statistically significant