Experimental and numerical stress and strain analysis of the boiler reversing chamber tube plate

Boilers are one of the most used units for both heat generation plants and industry systems. Their operation is subjected to different working loads and maintenance requirements. Exploitation experience points out critical boiler zones where failures and break downs typically occur. This paper analyzes critical zones in hot water fire-tube boiler. Experimental procedure was performed on the model of this type of boilers and its critical element. The tube plate of hot water boiler was identified as the most critical one. Experimental analysis and numerical model verification were performed using Aramis system based on 3-D digital image correlation method. Numerical analysis was done in ANSYS software package and verification of results was done based on measurements obtained by strain gauges and local measurements performed by the Aramis system. Stress-strain analysis indicates the critical zones of boiler tube plate. The character of change parameters such as strain and stress occurring in the critical zones can be verified both by experimental and numerical data. The paper presents a novel approach in experimental and numerical analyses that can be conducted in similar units and used for existing unit optimization, as well as for new product testing on different loads and provide opportunity for further development and improvement for practical industrial application

Basic seed germination characteristics of the endemic species Nepeta rtanjensis (Lamiaceae)

Nepeta rtanjensis is an endemic plant species that was first recorded in 1974 in the eastern part of Serbia. Because of the small number of discovered specimens and low seed viability, it has been difficult to determine the seed germination characteristics of this species. Using in vitro culture techniques, we obtained sufficient plants for successful reintroduction. In the first year approximately 500 000 seeds were collected and subjected to various seed germination tests. The seeds were positive photoblastic and germination was under the control of the phytochrome pigment system. The requirement for light could be substituted by gibberellins. The seeds were nitrate insensitive, but responded to treatment with liquid smoke.nul

The stimulatory effect of non-equilibrium (low temperature) air plasma pretreatment on light-induced germination of Paulownia tomentosa seeds

Light-induced germination of Paulownia tomentosa seeds was used as an experimental system to investigate the effect of pretreatments by non-equilibrium (low temperature) air plasma on the germination process. Dry P. tomentosa seeds exposed to the plasma changed their germination characteristics. Non-equilibrium plasma treatments significantly increased the light sensitivity of P. tomentosa seeds. These treatments could not substitute for the light-requirements of the seeds. After a short exposure to plasma (4 to 6 minutes) treated seeds had a germination of 75%, i.e. significantly higher than the 5-30% for seeds which did not undergo pretreatment. The results suggest that the stimulatory effect of the non-equilibrium air plasma pretreatment is not a direct photoreceptor-mediated phenomenon. Possible mechanisms of this effect are discussed.nul

Basic seed germination characteristics of the endemic species Nepeta rtanjensis (Lamiaceae)

Nepeta rtanjensis is an endemic plant species that was first recorded in 1974 in the eastern part of Serbia. Because of the small number of discovered specimens and low seed viability, it has been difficult to determine the seed germination characteristics of this species. Using in vitro culture techniques, we obtained sufficient plants for successful reintroduction. In the first year approximately 500 000 seeds were collected and subjected to various seed germination tests. The seeds were positive photoblastic and germination was under the control of the phytochrome pigment system. The requirement for light could be substituted by gibberellins. The seeds were nitrate insensitive, but responded to treatment with liquid smoke.nul

Stimulation of empress tree seed germination by liquid smoke

The germination of Empress tree (Paulownia tomentosa Steud.) seeds is phytochrome-controlled. Liquid smoke could not induce germination in darkness but red light irradiation of liquid smoke imbibed seeds induced a high percentage of germination. Maximum germination was achieved at liquid smoke concentration of 0.1% (v/v) when present during the imbibition phase or during the phase of phytochrome activity. The light requirement of these seeds could be completely substituted by exogenously applied gibberellins. In the presence of liquid smoke, optimal concentrations of GA(3), GA(4), and GA(9) necessary for inducing germination were several times lower than in the controls, while that of GA(7) was equally active when applied at a concentration one order of magnitude lower. The inhibitory effect of the applied growth retardants was strongly reduced and liquid smoke, in the presence of retardants, allowed light-induced germination, if applied simultaneously or after retardants treatment.nul

Stimulation of empress tree seed germination by liquid smoke

The germination of Empress tree (Paulownia tomentosa Steud.) seeds is phytochrome-controlled. Liquid smoke could not induce germination in darkness but red light irradiation of liquid smoke imbibed seeds induced a high percentage of germination. Maximum germination was achieved at liquid smoke concentration of 0.1% (v/v) when present during the imbibition phase or during the phase of phytochrome activity. The light requirement of these seeds could be completely substituted by exogenously applied gibberellins. In the presence of liquid smoke, optimal concentrations of GA(3), GA(4), and GA(9) necessary for inducing germination were several times lower than in the controls, while that of GA(7) was equally active when applied at a concentration one order of magnitude lower. The inhibitory effect of the applied growth retardants was strongly reduced and liquid smoke, in the presence of retardants, allowed light-induced germination, if applied simultaneously or after retardants treatment.nul

Comparative study on the effects of NaCl on selected moss and fern representatives

Salt demonstrates various osmotic and ionic effects on vascular plant growth, development and function, but very few data can be found on how salt affects non-tracheophytes. To explore this, gametophytes of two moss - Bryum argenteum Hedw. and Atrichum undulatum (Hedw.) P. Beauv., and three fern species - Asplenium viride Britton, Ceterach officinarum DC, and Phyllitis scolopendrium (L.) Newman, were treated for 3 days with different NaCl concentrations in growth medium under in vitro controlled conditions. Subsequently, these plants recovered for 18 days on NaCl-free medium, after which the following parameters were measured for mosses: presence of secondary protonema and shoots, protonemal radius and index of multiplication. Survival, chlorophyll a, b, total and a/b ratio were determined as well as total phenolic content, both for ferns and mosses. All species tolerated 50 and 100mMof NaCl-enriched media, quite well. On higher salt concentrations in the substrata, measured morphological parameters and chlorophyll content were reduced. In general, mosses exhibited higher NaCl tolerance than ferns. Change of phenolic content in ferns suggests these plants use antioxidative properties of phenolics as a mechanism of salt tolerance, in contrast with mosses whose phenolic content was stable.Serbian Ministry of Science [173024, 173030

Measurements of voltage-current characteristics of a plasma needle and its effect on plant cells

In this paper we present voltage-current-power characteristics of a plasma needle operating in the flow of helium at atmospheric pressure. In addition, we show some examples of how such a plasma affects plant tissues. In the characterization of the plasma needle, current and voltage waveforms were recorded by two derivative probes. These two probes are similar to the probes previously used by Puac et al for measuring transmitted power in low pressure CCP rf discharge. The instantaneous power was calculated from current and voltage waveforms and U-I characteristics of the discharge were determined. Regimes of operation with and without the grounding ring at the tip of the needle were considered. We have chosen two model systems to study the effect of the plasma needle on plant cells and tissues: sweet fern gametophyte (prothallus) and calli produced in vitro. Since the prothallus consists of a single layer of cells, the cytological effects could be easily examined. In addition, calli and prothallus are easy to manipulate and in vitro culture provides a possibility to work under constant and controlled conditions.nul

Measurements of voltage-current characteristics of a plasma needle and its effect on plant cells

In this paper we present voltage-current-power characteristics of a plasma needle operating in the flow of helium at atmospheric pressure. In addition, we show some examples of how such a plasma affects plant tissues. In the characterization of the plasma needle, current and voltage waveforms were recorded by two derivative probes. These two probes are similar to the probes previously used by Puac et al for measuring transmitted power in low pressure CCP rf discharge. The instantaneous power was calculated from current and voltage waveforms and U-I characteristics of the discharge were determined. Regimes of operation with and without the grounding ring at the tip of the needle were considered. We have chosen two model systems to study the effect of the plasma needle on plant cells and tissues: sweet fern gametophyte (prothallus) and calli produced in vitro. Since the prothallus consists of a single layer of cells, the cytological effects could be easily examined. In addition, calli and prothallus are easy to manipulate and in vitro culture provides a possibility to work under constant and controlled conditions.nul