BER Performance of IM/DD FSO System with OOK using APD Receiver

In this paper, the performance of intensity-modulated with direct detection (IM/DD) free space optical (FSO) system using the on-off keying (OOK) and avalanche photodiode (APD) receiver is observed. The gamma-gamma model is used to describe the effect of atmospheric turbulence since it provides good agreement in the wide range of atmospheric conditions. In addition, the same FSO system with equal gain combining applied at the reception is analyzed. After theoretical derivation of the expression for the bit error rate (BER), the numerical integration with previously specified relative calculation error is performed. Numerical results are presented and confirmed by Monte Carlo simulations. The effects of the FSO link and receiver parameters on the BER performance are discussed. The results illustrate that the optimal APD gain in the minimum BER sense depends considerably on the link distance, atmospheric turbulence strength and receiver temperature. In addition, the value of this optimal gain is slightly different in the case of spatial diversity application compared with single channel reception

Impact of climatic factors to the percentage of young in the population of brown hare (Lepus europaeus P) in the Bačka district

Climatic factors, especially temperature and precipitations, greatly affect the dynamics of the hare number and population. Climatic factors directly affect the physiological and reproductive processes of both individuals and entire populations, or indirectly, through the availability of food, competition with other species, predators and other. The age structure of the hare population at the end of the period of reproduction is an important indicator of the population growth that is used for planning the level of explotation of the hare population (hunting). The rational use of the hare's population is one of the most important protection procedures and it should be well monitored and controlled by the hunting professionals. We used the average monthly temperature and the sum of monthly precipitations in the hare reproductive period (March-September) during ten years (2000 - 2009), together with the percent of young in the hare population, on the territory of Bačka, for multiple regression (stepwise) analysis. Results of the regression analysis show an association between the percentage of young hares and the influence of climatic factors. The average temperature and sum of precipitation in June, are the strongest predictor of the percent of young in the hare’s population in Bačka. According to the coefficient of determination (R2=0.50) climatic parameters account for 50% of variance in the percentage of young hares in Bačka. The regression correlation coefficient of all factors was R=0.70, which is on the border line between medium and high correlation

Effect of different types of stress on adrenal gland parameters and adrenal hormones in the blood serum of male Wistar rats

In the present study, we examined gross changes in the mass of whole adrenal glands and that of the adrenal cortex and medulla in mature male Wistar rats subjected to three different stress types: acute, chronic, and combined, i.e., chronic followed by acute stress. These parameters were correlated with adrenal activity as judged from serum levels of corticosterone and catecholamine, respectively, as well as with serum levels of ACTH and glucose. Under all three conditions, we observed bilaterally asymmetric and stress-type-independent hypertrophy of whole adrenals, as well as adrenal cortices and medullas. Under acute and combined stress, adrenal hypertrophy was followed by increase of adrenal hormones in the blood serum. However, under chronic stress, both cortical and medullar activities as judged from low or unaltered levels of the respective hormones and glucose were compromised and disconnected from the input signal of ACTH. Since all of the studied adrenal activities could be restored by subsequent acute stress, it is concluded that chronic isolation can be viewed as partly maladaptive stress with characteristics resembling stress resistance rather than the stress exhaustion stage of the general adaptation syndrome

Another Way for the Laboratory Preparation ofAnhydrous Chromium(III) Chloride

Two methods for the laboratory preparation of anhydrous chromium(III) chloride are described in the standard handbooks of inorganic syntheses, i. e. (i) the chromium metal is heated in a porcelain tube in a stream of chlorine at high temperature, (ii) the green aqua-chloride [CrCl2 (H2 0)4 ]Cl · 2H20 is heated and the resulting mass of oxide and basic chloride is then chlorinated with carbon tetrachloride

Combining high-resolution scanning tunnelling microscopy and first-principles simulations to identify halogen bonding

Scanning tunnelling microscopy (STM) is commonly used to identify on-surface molecular self-assembled structures. However, its limited ability to reveal only the overall shape of molecules and their relative positions is not always enough to fully solve a supramolecular structure. Here, we analyse the assembly of a brominated polycyclic aromatic molecule on Au(111) and demonstrate that standard STM measurements cannot conclusively establish the nature of the intermolecular interactions. By performing high-resolution STM with a CO-functionalised tip, we clearly identify the location of rings and halogen atoms, determining that halogen bonding governs the assemblies. This is supported by density functional theory calculations that predict a stronger interaction energy for halogen rather than hydrogen bonding and by an electron density topology analysis that identifies characteristic features of halogen bonding. A similar approach should be able to solve many complex 2D supramolecular structures, and we predict its increasing use in molecular nanoscience at surfaces

Nail metal connector plate - experimental determination of load-bearing capacity of timber member connections

This paper demonstrates the results of experimental determination of load-bearing capacity of structural timber member connections realized by nail metal connector plates which represent a new type of mechanical fasteners in load-bearing timber structures. The application of this type of metal connector should eliminate weakness of the standard metal connector plates produced by sheet perforating and pulling the teeth perpendicular to a sheet plane. The aim of the conducted experimental study was to determine the load-bearing capacity of connections realized by nail metal connector plates, in accordance with the provisions of Eurocode 5. Experimental testing was conducted by loading of multiple samples up to the limit bearing capacity of connection realized by nail metal connector plate. Discussion of the test results included the analysis of the limit bearing capacity of connection for different values of connection displacements, comparison of the obtained results with characteristic load-bearing capacity of standard type of metal connectors and with load-bearing capacity of nails calculated in accordance with limit state theory. Review of the determined limit bearing capacities of realized connections was given in the conclusion, together with the comment on test results, for the purpose of improving the application of metal connectors in modern systems of timber structures

Environmentally-based structural design criteria for buildings

Activities related to buildings contribute to a large degree to environmental degradation. It is necessary to reduce the negative environmental impact and resource consumption throughout the life cycle of the building. The aim is to optimize building performances in accordance with the integrated design objectives. The building structure, along with other elements of architectural space, determines the performances of the building. The building structure should be designed and evaluated as a sub-system of the building, whose behaviour is directed towards the aim of system-building ecological quality. This paper deals with the analysis of structural design in accordance with integrated design objectives, which are derived from quantitative and qualitative indicators of ecological quality of building, within the criteria of environmental protection throughout the life cycle of the building. The overall objective is to reduce harmful emissions to the air, water and soil, as well as to increase the efficiency of resource use, that is, to reduce the intensity of their use. Based on subject analysis, the environmentally-based criteria for the design and evaluation of building structures are derived, in the function of creating the environmentally acceptable building solutions. The present analysis points to the necessity of applying a complex and systemic approach to structural design, in function of achieving the ecological quality of buildings

Organizacijska djelatnost kao faktor uspješnog poslovanju

Nikad ranije, kao u ovom periodu nije postojala tako naznačena potreba da se organizaciji rada u mljekarstvu posvećuje posebna pažnja. Naime, sa narastajućim proizvodnim snagama i organizacija se mora razvijati, a kako mljekarska proizvodnja raste zamašnim koracima, to ova, poljoprivredno-prehrambena grana, stječe izvjestan prioritet

Obim i raspoređenost proizvodnje mlijeka kod nas kao osnov potrošnje

Krajnji cilj proizvodnje mlijeka i mliječnih proizvoda, jeste potrošnja, koja se manifestira kao široka (individualna) i reprodukciona. Osnovu ponude na tržištu čini kvantum proizvodnje mlijeka, kao i njegova raspoređenost u pojedinim regijama zemlje