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Search Results: 1 - 10 of 542 matches for " Igi? Tomislav "
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Design of a System for Monitoring Reliability of Structures and Constructions in Civil Engineering
Tomislav S. Igi,Natasa ?. Veljkovi?
International Journal of Engineering Pedagogy , 2011, DOI: 10.3991/ijep.v1i2.1634
Abstract: Monitoring of civil engineering structures and constructions requires techniques which can produce high precision and accuracy, reliable measurements and fast processing speed. The development of information and communication systems as well as of microprocessor controllers has enabled a creation of monitoring systems that can be used for tracking reliability of structures and constructions in civil engineering, with described key features. This paper describes in detail the architecture of the Civil Engineering Structures Reliability Monitoring (CERM) system. The system has been designed for the purposes of the Technical Mechanics and Theory of Constructions Department at the Faculty of Civil Engineering and Architecture, University of Nis. Unlike general commercial monitoring systems, the CERM system has been specially designed for the purpose of reliability monitoring, and its potential will be further exploited in this paper. It is based on usage of universal microprocessor controllers Integraf of series 10X, along with specially designed software package. This system provides real time acquisition of measurements for observed civil engineering structures and analysis of received values based on developed mathematical models.
Structural safety determination methods
Zdravkovi? Slavko,IgiTomislav,Stoji? Radoslav
Facta Universitatis Series : Architecture and Civil Engineering , 2012, DOI: 10.2298/fuace1201097z
Abstract: For the purpose of determination of technical safety, and additional safety necessitated by public an social reasons, this paper considers methods of relations, probability and combined relation and probability. Also considered are functional failure and collapse failure, as well as the concept of designed service life of the structure. The ultimate safety degree is composed o the part for security regarding the technical and social consequences of collapse. The safety determination method, in technical terms too, strives to avoid the damage which would exceed the bearing capacity of the structure. The relation methods apply the safety degree which was obtained in cases when the similar structures of various dimensions were built, so it is necessary to determine the required dimensions to avoid the structural failure. The Probability method is widely applied using statistical data in the load and strength analysis. The combination of relation and probability methods provides the minimum safety degree as a reliable factor.
A bearing structure and finished construction behavior analysis based on the full-scale experimental research
Zdravkovi? Slavko,Zlatkov Dragan,Mladenovi? Biljana,IgiTomislav
Facta Universitatis Series : Architecture and Civil Engineering , 2010, DOI: 10.2298/fuace1001119z
Abstract: The paper deals with a brief presentation of a part of the performed experimental tests of the prefabricated reinforced concrete structural system 'AMONT' for construction of various types of modern industrial halls. The test results are analyzed for two industrial halls both constructed according to this structural system but in the different phases of construction, tested in the full scale by application of AMBIENT vibration method. From the obtained Fourier spectra for measured ambient vibrations in two orthogonal direction for the structure without walls and the other with fa ade and filling walls, a significant discrepancy in their natural frequencies has been observed, and some conclusions about the influence of panel walls on dynamic characteristic the frame structure have been drawn out. The paper used some data of the research after the earthquake in Montenegro which took place on 15th of April 1979.
Stability design of structures with semi-rigid connections
IgiTomislav,Zdravkovi? Slavko,Zlatkov Dragan,?ivkovi? Sr?an
Facta Universitatis Series : Architecture and Civil Engineering , 2010, DOI: 10.2298/fuace1002261i
Abstract: The paper points out to the differences of the First order theory and Second order theory and of the significance in practical calculations. The paper presents theoretical foundations and expressions of calculations of impacts on the stability of structure, that is, review of the Second order theory in a bridge with members semi-rigid connections in joints. In the real structures in general and the especially in the prefabricated structures the connection of members in the nodes can be partially rigid which can be very significant for the changes in tension and deformation. If the influence of the normal forces is significant and the structure is slender then it is necessary to carry out a calculation according to the Second order theory because the balance between internal and external forces really established on the deformed configuration and displacements in strict formation are also unreal. The importance and significance of the calculations and distribution of impact according to the Second order theory were presented in numerical examples as well as the calculation of critical load as well as the buckling length of members with semi-rigid connections in joint.
System identification approach application for evaluation of system properties degradation
Trajkovi? Marina,Bruhns Otto T.,Meyers Albert,IgiTomislav
Facta Universitatis Series : Architecture and Civil Engineering , 2004, DOI: 10.2298/fuace0401009t
Abstract: In respect to the subspace identification method as one of the possible variants of inverse dynamic analyses, behavior of real structural systems with real load and real noise contaminated input/output data was investigated in this work. A useful and non-destructive dynamic parameters evaluation tool - vibration monitoring of the structure - is proposed. The report of original investigation on real models excited by an impulse load in laboratory is also presented. A special contribution is a software program for experiment monitoring and for determination of relevant mechanical characteristics as well as of the location of a possible structural damage.
Can outstanding research be done under less than ideal conditions?
Igi? Rajko
Srpski Arhiv za Celokupno Lekarstvo , 2004, DOI: 10.2298/sarh0410360i
Abstract: Great scientific discoveries rarely originate from small and poor countries. However, the lives and achievements of three Yugoslav scientists who were active in the biomedical sciences, Laza K. Lazarevi (1851-1891), Ivan Djaja (1884-1957), and Pavao Stern (1913-1976), serve as an example of success in this environment. These scientists, as well as the majority of other successful investigators in small and poor countries, were trained in foreign and developed countries and, upon return, were given the freedom to start a self dependent research program. They overcame many obstacles, including wars and civil unrests, to contribute significantly to certain medical fields. It is interesting that although a Jew, Stern was allowed to work during the World War II in Zagreb, which became capital of the so-called Independent State of Croatia, a puppet state under German control. Perhaps his good name among pharmacologists helped him to keep position during this tough period. Nowadays, new technologies requiring for biomedical research are rather expensive, and poor countries cannot afford to finance many scientists. Thus, selection of the most productive researchers is the challenge for those who finance scientific work.
Test of the Universal Rise of Hadronic Total Cross Sections at Super-high Energies
Ishida, Muneyuki;Igi, Keiji
High Energy Physics - Phenomenology , 2007, DOI: 10.1140/epjc/s10052-007-0392-6
Abstract: Saturation of the Froissart-Martin unitarity bound that the total cross sections increase like log2(s/s_0) appears to be confirmed. Due to this statement, the B log2(s/s_0) was assumed to extend the universal rise of all the total hadronic cross sections to reduce the number of adjustable parameters by the COMPETE Collaboration in the Particle Data Group (2006). Based on this assumption of parametrization, we test if the assumption on the universality of $B$ is justified through investigations of the value of B for pi p(K p)$ and pbar p, pp scatterings. We search for the simultaneous best fit to sigma(tot) and rho ratios, using a constraint from the FESR of the P' type for pi p scatterings and constraints which are free from unphysical regions for pbar p,pp and K p scatterings. By including rich informations of the low-energy scattering data owing to the use of FESR, the errors of B parameters decreases especially for pi p. The resulting value of B(pp) is consistent with B(pi p) within two standard deviation, which appears to support the universality hypothesis.
Universal Rise of Hadronic Total Cross Sections based on Forward pi p and pbarp(pp) Scatterings
Ishida, Muneyuki;Igi, Keiji
High Energy Physics - Phenomenology , 2008, DOI: 10.1016/j.physletb.2008.11.026
Abstract: Recently there are several evidences of the increase of the total cross section sigma(tot) to be log2 s consistent with the Froissart unitarity bound, and the COMPETE collaborations in the PDG have further assumed sigma(tot) = B log2(s/s0) to extend its universal rise with a common value of B for all the hadronic scatterings. However, there is no rigorous proof yet based only on QCD. Therefore, it is worthwhile to prove this universal rise of sigma(tot) even empirically. In this letter we attempt to obtain the value of B for pi p scattering, B(pi p), with reasonable accuracy by taking into account the rich pi p data in all the energy regions. We use the finite-energy sum rule(FESR) expressed in terms of the pi p scattering data in the low and intermediate energies as a constraint between high-energy parameters. We then have searched for the simultaneous best fit to the sigma(tot) and rho ratios, the ratios of the real to imaginary parts of the forward scattering amplitudes. The lower energy data are included in the integral of FESR, the more precisely determined is the non-leading term such as log s, and then helps to determine the leading terms like log2 s. We have derived the value of B(pi p) as B(pi p)=0.311 +- 0.044mb. This value is to be compared with the value of B for pbarp,pp scattering, B(pp), in our previous analysis[11], B(pp)=0.289 +- 0.023mb. Thus, our result appears to support the universality hypothesis.
Experimental verification of preset time count rate meters based on adaptive digital signal processing algorithms
igi? Aleksandar D.
Nuclear Technology and Radiation Protection , 2005, DOI: 10.2298/ntrp0502040z
Abstract: Experimental verifications of two optimized adaptive digital signal processing algorithms implemented in two pre set time count rate meters were per formed ac cording to appropriate standards. The random pulse generator realized using a personal computer, was used as an artificial radiation source for preliminary system tests and performance evaluations of the pro posed algorithms. Then measurement results for background radiation levels were obtained. Finally, measurements with a natural radiation source radioisotope 90Sr-90Y, were carried out. Measurement results, con ducted without and with radio isotopes for the specified errors of 10% and 5% showed to agree well with theoretical predictions.
Preset time count rate meter using adaptive digital signal processing
igi? Aleksandar D.
Nuclear Technology and Radiation Protection , 2005, DOI: 10.2298/ntrp0501064z
Abstract: Two presented methods were developed to improve classical preset time count rate meters by using adapt able signal processing tools. An optimized detection algorithm that senses the change of mean count rate was implemented in both methods. Three low-pass filters of various structures with adaptable parameters to implement the control of the mean count rate error by suppressing the fluctuations in a controllable way, were considered and one of them implemented in both methods. An adaptation algorithm for preset time interval calculation executed after the low-pass filter was devised and implemented in the first method. This adaptation algorithm makes it possible to obtain shorter preset time intervals for higher stationary mean count rate. The adaptation algorithm for preset time interval calculation executed before the low-pass filter was devised and implemented in the second method. That adaptation algorithm enables sensing of a rapid change of the mean count rate before fluctuations suppression is carried out. Some parameters were fixed to their optimum values after appropriate optimization procedure. Low-pass filters have variable number of stationary coefficients depending on the specified error and the mean count rate. They implement control of the mean count rate error by suppressing fluctuations in a controllable way. The simulated and realized methods, using the developed algorithms, guarantee that the response time shall not exceed 2 s for the mean count rate higher than 2 s-1 and that controllable mean count rate error shall be within the range of ±4% to ±10%.
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