Search Results

You are looking at 1 - 10 of 114 items for

  • Author: Ivanov Ivanov x
Clear All Modify Search
Open access

Finica Ivanov

Reproductive Parameters of Porcellium Collicola (Verhoeff, 1907) and Trachelipus Arcuatus (Buddelund, 1885) (Crustacea: Isopoda: Oniscidea) in South Romania

Porcellium collicola (Verhoeff, 1907) and Trachelipus arcuatus (Budde-Lund, 1885) (Crustacea: Isopoda: Oniscidea) are two terrestrial isopod species inhabiting the leaf litter of oak forests in South Romania. This paper presents the size of reproductive females, fecundity (the number of eggs for a female for a brood), fertility (the number of larvae or mancas per female) and the relationship between the number of eggs or mancas per brood pouch and the total body length of pregnant females. In Porcellium collicola populations' reproductive females had a total body length of 3.3 to 7.3 mm, average fecundity was 18.60±7.10 eggs per female and average number of mancas per female was 10.29±8.05. In Trachelipus arcuatus the total body length of reproductive females was between 9.80 - 16.60 mm and the average number of eggs per brood per female was 55.60±21.71. A direct correlation between the size of pregnant females and fecundity and fertility was established for Porcellium collicola.

Open access

Vladimir N. Ivanov


This paper discusses the development of a complex device for Traffic Light Control. The device is based on a PicoBlaze microprocessor embedded in Spartan6 FPGA. Its benefits for the purposes of transport flows management are discussed.

Open access

Gheorghe Duca, Maria Nedealcov and Ivanov Ivanov


Although it is considered that the socio-economic impact over the last decades on surface water quality is significant, the role of changing regional climate that is manifested by the intensification of desertification process is crucial. In this context, it is important to know the current trends of change in total runoff of surface of surface waters in the context of increase of desertification degree of the regional climate attested in recent years

Open access

Kaspars Ivanovs


During the last century a large portion of small and medium-sized rivers in Latvia were channelized, hydroelectric power stations were also built, which led to changes in the hydrodynamic conditions, geomorphological structure, as well as a change in the fish fauna. Fish are an integral part of any community in natural or man-made bodies of water. They actively participate in maintaining the system, balancing/equilibrium, energy, substance transformation and biomass production. They are able to influence other organisms in the ecosystem in which they live. The aim of the paper “Pike distribution and feeding comparisons in natural and historically channelized river sections” is to find out what pike feed on in different environments in Latvian rivers, such as natural and straightened river sections, as well as what main factors determine the composition of their food. Several points were assessed during the course of the study: the impact of environmental conditions on the feeding habits and the distribution of pike; the general feeding habits of predators in Latvian rivers; the feeding differences of predators in natural and straightened river sections; and lastly, rhithral and pothamal habitats were compared. The study was based on data from 2014 and 2015 on fish fauna monitoring. During the study, 347 pike were collected from 136 plots using electrofishing method.

Open access

V. Ivanov


The paper discusses the aspects of building a system for color light effects in homes of the future using a FPGA-based embedded microprocessor. It is also discussed some opportunities for further development in order to improve the conditions of life of the inhabitants of the homes of the future.

Open access

V. Bobrovs and G. Ivanovs

Comparison of Different Modulation Formats and their Compatibility with WDM Transmission System

In the work, the intensity and phase modulation methods are compared for different versions of the wavelength division multiplexing (WDM) system. Binary and multilevel code formats are evaluated numerically, with OptSim simulation software at the bit rate of 10 and 40 Gbit/s, using long-fiber spans and dispersion compensation technique. The problems to be overcome at exploitation of multiterabit WDM systems based on 40 Gbit/s optical transmissions are: chromatic dispersion (CD), polarization-mode dispersion (PMD), dispersion slope, and nonlinear effects of the transmission line. We have investigated the potentialities of modulation formats for 40 Gbit/s WDM networks where most of the listed problems are avoided. It is shown that Duobinary and differential phase shift keying (DPSK) modulation formats are perfectly suitable for ultra-high spectral efficient WDM systems and possess high resistance to dispersion and nonlinear optical effects (NOE).

Open access

Ievgen Ivanov, Mykola Nikitchenko and Uri Abraham


Proving properties of distributed algorithms is still a highly challenging problem and various approaches that have been proposed to tackle it [1] can be roughly divided into state-based and event-based proofs. Informally speaking, state-based approaches define the behavior of a distributed algorithm as a set of sequences of memory states during its executions, while event-based approaches treat the behaviors by means of events which are produced by the executions of an algorithm. Of course, combined approaches are also possible.

Analysis of the literature [1], [7], [12], [9], [13], [14], [15] shows that state-based approaches are more widely used than event-based approaches for proving properties of algorithms, and the difficulties in the event-based approach are often emphasized. We believe, however, that there is a certain naturalness and intuitive content in event-based proofs of correctness of distributed algorithms that makes this approach worthwhile. Besides, state-based proofs of correctness of distributed algorithms are usually applicable only to discrete-time models of distributed systems and cannot be easily adapted to the continuous time case which is important in the domain of cyber-physical systems. On the other hand, event-based proofs can be readily applied to continuous-time / hybrid models of distributed systems.

In the paper [2] we presented a compositional approach to reasoning about behavior of distributed systems in terms of events. Compositionality here means (informally) that semantics and properties of a program is determined by semantics of processes and process communication mechanisms. We demonstrated the proposed approach on a proof of the mutual exclusion property of the Peterson’s algorithm [11]. We have also demonstrated an application of this approach for proving the mutual exclusion property in the setting of continuous-time models of cyber-physical systems in [8].

Using Mizar [3], in this paper we give a formal proof of the mutual exclusion property of the Peterson’s algorithm in Mizar on the basis of the event-based approach proposed in [2]. Firstly, we define an event-based model of a shared-memory distributed system as a multi-sorted algebraic structure in which sorts are events, processes, locations (i.e. addresses in the shared memory), traces (of the system). The operations of this structure include a binary precedence relation ⩽ on the set of events which turns it into a linear preorder (events are considered simultaneous, if e 1e 2 and e 2e 1), special predicates which check if an event occurs in a given process or trace, predicates which check if an event causes the system to read from or write to a given memory location, and a special partial function “val of” on events which gives the value associated with a memory read or write event (i.e. a value which is written or is read in this event) [2]. Then we define several natural consistency requirements (axioms) for this structure which must hold in every distributed system, e.g. each event occurs in some process, etc. (details are given in [2]).

After this we formulate and prove the main theorem about the mutual exclusion property of the Peterson’s algorithm in an arbitrary consistent algebraic structure of events. Informally, the main theorem states that if a system consists of two processes, and in some trace there occur two events e 1 and e 2 in different processes and each of these events is preceded by a series of three special events (in the same process) guaranteed by execution of the Peterson’s algorithm (setting the flag of the current process, writing the identifier of the opposite process to the “turn” shared variable, and reading zero from the flag of the opposite process or reading the identifier of the current process from the “turn” variable), and moreover, if neither process writes to the flag of the opposite process or writes its own identifier to the “turn” variable, then either the events e 1 and e 2 coincide, or they are not simultaneous (mutual exclusion property).

Open access

O. Ozolins, V. Bobrovs and G. Ivanovs

Efficient Wavelength Filters for DWDM Systems

The authors investigate the best parameters of optical filters for dense wavelength division multiplexing (DWDM) systems. The investigation is based on the OptSim 5.0 simulation software using the method for solving a complex set of differential equations taking into account the optical and electrical noise as well as linear and nonlinear effects. It is shown that the bandwidth of optical filter extends as the data transmission speed increases, and that the most efficient are Supergaussian and Raised Cosine optical band-pass filters. It is also revealed that an ASK-RZ 40 Gbit/s data transmission system is impossible to realize with a channel interval less than 50 GHz because of wide spectral density and lower chromatic dispersion tolerance of this modulation format.

Open access

I. Lyashuk, A. Shchemelev and G. Ivanov

A Hybrid TDM/WDM-Pon System with FWM-Generated Source of Multiwavelength Optical Signals

A new approach to FTTx solutions is proposed, in the framework of which a hybrid TDM/WDM system using cascaded FWM-generated optical signals is evaluated by calculating the BER parameter and the optical power budget. Computer simulation is employed as the main method of calculations, with the results presented both in numerical and graphical forms. The results show that the use of a forward error correction allows the power margin of 4 dB to be achieved for the system to work reliably. The system can provide the total number of users up to 128 (8γx16 TDM users) with a bandwidth of multiple hundreds of Mbit/s p.u. by means of the existing passive optical networking infrastructure, with only minor improvements needed.

Open access

O. Ozoliņš, V. Bobrovs and G. Ivanovs

DWDM Transmission Based on the Thin-Film Filter Technology

A dense wavelength division multiplexing (DWDM) transmission scheme with two thin-film filters (FWHM bandwidth 100 GHz and 200 GHz) has been realized to evaluate the minimum channel interval needed for a satisfactory bit error ratio. For this purpose, detailed research was conducted into the impact of the filters on the optical signal's de-multiplexing in a DWDM system, in which the measurements of eye diagrams and the optical power spectral densities of a received signal were made. From the results of measurements the minimum channel interval has been found for the optical filters that ensures reliable data transmission and higher spectral efficiency of the whole system. It was found that for a DWDM system with a 100 GHz filter a sufficient channel interval is 75 GHz at 10 Gbit/s data transmission speed, which means that its spectral efficiency is increased from 0.1 bit/s/Hz to 0.1333 bit/s/Hz.