When combustion instability occurs, fluctuation in the release of heat couples with oscillating pressure, while the sensitivity of flame to acoustic disturbance restricts the oscillation intensity. This paper investigates the efficacy of helium in suppressing combustion instability. The flame structure, its sensitivity to acoustic disturbance and the inhibition of oscillating pressure with the addition of helium were studied by means of open tests, external-excited and self-excited combustion instability experiments. First of all, the addition of helium made larger flame surface area, which shaped the distributed flame, and the heat was such released over a broader space. Then, the external-exited combustion instability experiments confirmed that adding helium to fuel could decrease the sensitivity of flame to acoustic disturbance. Finally, Helium was used in the case of self-excited combustion instability to further investigate its effectiveness on the oscillation suppression. Proper Orthogonal Decomposition (POD) and Dynamic Mode Decomposition (DMD) methods were used to study flame fluctuation intensity. The results showed that the amplitudes of oscillating pressure were greatly reduced by the added helium. For 250Hz mode, adding helium with 20% of fuel flow could significantly reduce the flame pulsation and reduce the pulsation pressure by more than half. However, for the 160hz mode, more helium should be added to achieve better results. When the helium flow exceeded 80% of fuel flow, the combustion instability could be converted to stable combustion.

This study investigates the stability of a surface flame burner using a photodiode and data acquisition system. The light intensity fluctuations were measured by the photodiode and, using fast Fourier transform, they were transferred from the temporal to the frequency space. To illustrate the dynamic behavior of premixed flames, flames are divided into two regions of cellular flames and surface flames. This classification is dependent on the flow rate and the equivalence ratio. In surface flames, as the flow rate increases, the oscillation frequency also increases because the hot burned gas velocity increases. In cellular flames, as the flow rate increases, oscillation frequency decreases. At identical flow rates, the sharp decrease in the oscillation frequency indicates the appearance of cellular flames so we can find the transition from the surface flame to the cellular flame. At a constant flow rate, with an increase in the equivalence ratio, there is no increase in the oscillation frequency, the transition from the cellular flame to the surface flame occurs. The initiation of the transition from the cellular flame to the surface flame occurs at flow rates of 1. 1, 1. 2, 1. 3, 1. 4, 1. 5, 1. 6 m3/h and at equivalence ratios of 0. 6, 0. 62, 0. 62, 0. 64, 0. 66, and 0. 67, respectively. The location of the transition corresponds to the start of the liftoff zone based on the image processing. This research is innovative because it is possible to evaluate flame stability using a non-intrusive method without disturbing the flame shape and damaging the flame regime.

Nowadays, the use of resistant and high melting point thermocouples is considered as an efficient and inexpensive tool for measuring the temperature of hot gases produced by combustion. Temperature measurement by thermocouples has inherited errors due to the radiation loss and conduction loss. Therefore, it is necessary to correct this error. In this research, the thermocouple is firstly modeled using a numerical method. The validity of the original code is accredited by comparing the results with a similar previous study. Then, the effects of thermocouple diameter and average flow velocity are investigated on the thermocouple error. The error increases about 50% with increasing the thermocouple diameter from 0. 5 to 1 mm. Besides, the error decreases about 41% with increasing the average velocity from 1 to 5 m/s. Based on a previous experimental study, the thermocouple modeling results indicate that the maximum errors for thermocouples with diameter of 300 and 500 microns are 30. 8% and 39. 6% under these conditions, respectively. In the following, a novel comprehensive solution is suggested to calculate the simultaneous distribution of temperature and velocity. Its results confirm that this algorithm has acceptable accuracy for high temperature flow conditions.

The purpose of this study is to identify the effect of stock tendency to deal with fluctuations and price fluctuation thresholds in creating fluctuations. The statistical population of the present study is the companies listed on the Tehran Stock Exchange that were present in the stock exchange during the years 2005 to 2018. In order to confirm and reject the research hypothesis, Eviews software has been used. In Tehran Stock Exchange, following severe stock price fluctuations, the stock price fluctuation mechanism is used to limit severe stock price fluctuations, and according to certain periods, the range of stock price fluctuations changes and over time the range of fluctuations increases. The basis of trial and error has been determined and in a short period of time there have been many changes in the procedures related to the application of stock price fluctuations, without really measuring the impact of these decisions in the market and investors' reaction to changes in price fluctuations. Findings showed that the number of times each share hits the price fluctuation Yield fluctuation has a significant effect.slow efficiency fluctuations have a significant effect; And in line with the concepts of hyper-reactive theory, it can be justified, that is, after the price reaches the range of fluctuation, the trend reverses and the basis of the fluctuation limit changes; It has changed the volatility of stock returns based on jump and price continuity.

Water stress considers as most important I environmental stresses. The effect of water stress in secondary metabolite fluctuation of Hypericum perforatum (hypericin) evaluated with performance of well water, mild and severs water stress treatments in Karaj research station. In this experiment a CRBD with 3 replications in 3 years was used. Well water (-0.3 bar), mild water stress (-3 bar) and sever water stress (-15bar) treatments according 17.4, 11.5 and 8.5 water weight percent relative to dry soil were performed respectively. Hypericin extracted in two stages by soxhelt (using CHCL3 and MeOH) and measured by UV spectrophotometer in 590 nm. The results showed that top yield, hypericin percentage and hypericin yield increased with well water. Mild and sever water stress caused to decreasing hypericin and yield of Hypericum perforatum. Top yield and hypericin amount in the first harvest was 2-3 folds to the second harvest. Correlation between hypericin amount and flowers per plant was significant and positive. In spite of Hypericum perforatum resistance to water stress, it produced lower tops and hypericin under water stress. Adequate and on time irrigation causes to completely growth and more flower which increases quality in H.perforatum.

Thermodynamic calculations of the combustion heat release, specific impulse, and volumetric specific impulse show that metal fuels can exceed hydrocarbon fuels in volumetric energy content and in the case of boron exceeds conventional fuels on a mass basis as well. The refractory nature of metal fuels and their combustion products also suggest that they may permit ramjets utilizing subsonic combustion to extend their operation to hypersonic Mach numbers. In this paper, formation of stabilized flame using a pure powdered metal fuel without the use of hydrocarbons is investigated experimentally. The ability to effectively inject powdered, metal into a combustor is demonstrated using a laboratory-scale dispersion apparatus. Dynamic parameters of burning time and flame speed of aluminum dust flame have been measured by dust combustion apparatus. Results imply that the burning time is decreased, while the oxygen concentration is increased.Also, the replacement of nitrogen with argon increases burning time. This is, because of the increase in aluminum dust reaction rate. The flame speed of aluminum dust is near the diffusion flame and its differences with hydrocarbon fuel flame are to stabilize the dust flame in rich mixtures.

Embryogenic calli production in Vitis is mainly possible by use of such regenerative tissues as anther and ovary. Because of long periods of time required for obtaining such tissues, use of such vegetative organs as leaf explant would be a promising alternative. Towards this end, leaf explants were taken from two varieties of ‘Flame Seedless’ and ‘Red Sultanina’ to be raised in. MS medium, consisting of 2.5 mM 2, 4-D, 1.1 mM BAP, 1 g/l Cazein Hydrolizate, 20 g/l sucrose, and 7 gr/l of agar. After two months, calli were transferred to the same medium except for 2-4, D which was replaced by NAA. Three months after explants' culture, calli were transferred to MS medium containg varied concentrations of BAP (1, 2 & 3.5 mg/l), and IAA (2, 5 & 15 mg/l). Results showed that among different hormonal treatments, the fifth medium (BAP 5 mg/l & IAA 2 mg/l) induced a maximum embryogenesis in calli of cv. Flame Seedless.

Nezami's Poem is in the front rank of poetry. He always attempted to choose the best words- fine words using beautiful words and expressions. His poetry is enriched by his power of imagination and awareness of the common knowledge and beliefs of the time. The common features of his speech includes a unique use of the words-word choice, creating new compounds, compounding- description, repetition, emphasis, transformation, omission, using Quranic verses, Islamic hadiths and Arabic compounds, expressions of astrology and medicine, adages, proverbs and idioms regularly used by ordinary people. He is a poet familiar with the language of ordinary people and their beliefs, customs and traditions. Since he rightfully attended to the spoken language and because of his particular style of speech, his works are full of street talks to the extent that this propery can be viewed as the prominent stylistic feature of his poems. He took advantage of the common sciences of the time and utilized the scientific, astrological and medical terms and also the technical meanings and themes of these sciences. His imagination and awareness of the sciences and beliefs made his poems productive. Some of the features of his poems are as follow:1- Imagery: Imagery refers to producing pictures, paintings or shows in the mind of readers /listeners using words. That is, the poet or writer should have such mastery over using words, space, meanings and their relations that makes him able to effectively use the sentences and words to create paintings, pictures or shows in the mind of readers or listener, to enable the reader to imagine a real painting or picture when he is over with his reading.2- Diction: Experts of language issues and grammar beliefs that word coining can strengthen the foundation of language. So, the first premise in creating fine text is to choose musical words appropriate for the given text and meaning. In the first step, melodic, expressive, rich words compatible with the spatial totality should be choosen. This powerful diction is one of the major reasons for the immortality of Nezami's poems.  3- Compounding: In addition to words which need to be musical and melodic, literary compound should supplement the musical quality of the text. Since compounding is one the major features of Persian language, Nezami effectively utilized his power of compounding and its one of the prominent features of his poetry.4- Description: In his poems, description of the nature is done through personifications, descriptions, similies and metaphors, and this description is indispensible feature of the theme that improves the manifestation of the heroes and events from the poetic perspective. Since His poems are full of personifications, all the manifestations of the nature simply represent characteristics, attitudes and thoughts of human beings. A plentiful supply of finest descriptions can be found in his Masnavi-e Khosro va Shirin 5- Repetition:Repetition of a morpheme, word or picture proves to be one of the main characteristics of his poems. Nezami uses a large variety of repetitions in his poems and this variety in repetition enriches his works. Reading the poems of Nezami, one can understand that the initial words determine the following morphs and words. In fact, words are chosen based on their melodic properties.Conclusion: Generally speaking, in a noble poem, imagination, melody and form should be consistent in order to reach the optimal goal. If they are not consistent with each other the poem may not be influential as well as possible. So, the music of the poem should be compatible with the imagination and the language of the poem. A successful poet attends both to the form and meaning of the poem and does not strengthen one at the expense of the other one. Nezami attends to both form and meaning.