An experimental study was conducted on the response of V-shaped and M-shaped premixed flames to external acoustic excitation. Low emission premixed combustors with anchored V-flames are susceptible to combustion instabilities. V-flames attach to an anchoring rod at the centre of the burner, whereas M-flames attach to the anchoring rod as well as the burner rim. This is in contrast to conical flames which are anchored only on the burner rim. As a consequence, V-and M-shaped flames are more sensitive to external flow perturbations. In the present study, a mixture of propane-air was used. The mixture equivalence ratio was changed to determine the stability range of V-and M-shaped premixed flames. The results indicated that M-shaped flames have a narrower stability range compared to that of V-flames. This limited the equivalence ratios range for acoustic excitation experiments. In order to study the flame response to external acoustic excitations, a loud speaker was placed upstream of the flame to generate acoustic waves in a certain range of frequencies. Pressure fluctuations caused by the acoustically excited flame were measured by a microphone placed downstream of the burner. Flame imaging was done with a CCD high speed camera during acoustic excitations. These images were used for flame response determination. Image processing was accomplished using the MATLAB software to obtain the amplitude and phase of the flame response. Variations of the flame shape and the intensity of light emitted by the flame were examined during a period of excitation for various values of equivalence ratios and flow rates. The results indicated that the vortex shedding and roll-up due to the velocity perturbations play an important role on the flame response. The phase response of flames evolves quasi-linearly with excitation frequency, indicating a certain time delay for the fluctuations to reach the flame surface. Also, in a certain range of excitation frequency, the flame gain response exhibits more sensitivity to variation of the equivalence ratio. Observations of the V-flame behavior during a period of excitation have led to determination of the effects of nonlinear parameters on the flame response.

Hydrogen plays a key role in reducing reliance on fossil fuels in various energy production systems. While its use offers a promising alternative to carbon-based fuels, it presents significant challenges. The transition from carbon-rich hydrocarbons to hydrogen-based energy systems requires a thorough understanding of its dynamic effects. This study investigates the impact of hydrogen addition on the dynamic behavior of a partially premixed methane-air counterflow flame through experimental analysis and one-dimensional numerical simulations. The study examines the steady-state flame structure and response without acoustic excitation, assessing the influence of added hydrogen on the flame's heat release rate and thermal region thickness. Employing an acoustically excitable counterflow flame burner setup, the effects of increasing hydrogen content on methane-air flames are explored, and their dynamic response is analyzed using the CH* radical chemiluminescence method. The findings reveal that while hydrogen addition reduces the intensity of CH* radical emission in the absence of acoustic excitation, exposure to acoustic waves amplifies oscillations in the heat release rate and CH* radical emission intensity. This underscores the enhanced flame response function with hydrogen addition. 

In the present study, the flame response and the effect of equivalence ratio and inlet temperature on the flame response are numerically investigated using Weller flamelet combustion and LES turbulent models. The results show that with increasing excitation amplitude at a constant frequency, theheat release ratio increases; the increment is smaller at higher frequencies. Due to the combustor geometry, two recirculating zones are formed. Any change in the amplitude and frequency can affect these recirculation zones, especially the central recirculation zone. At the low frequencies (below 50Hz), increasing the excitation amplitude affects flame transfer functioninconsiderably, because of no influence of the recirculation zoneson the heat release. At higher frequencies, an increase in the amplitude has a more influence on value of flame transfer function. It is shown that by increasing the amplitude, up to frequency of 140 Hz, the phase of flame transfer function slightly reduced, while this is intensified with increasing the equivalence ratio or flame inlet temperature. Furthermore, by increasing the equivalence ratio or inlet temperature of the flame, heat release ratio and the flame transfer function are reduced.

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.

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.

Objective: CREB1 is an important downstream protein for many signaling pathways. By designing efficient siRNAs against CREB1, it may be possible to assess the role of molecules involved in signaling pathways in different cell types. In this research the efficiency of CREB1 knockdown by two different siRNAs in K562 cells has been studied. Materials and Methods: siRNAs have been designed according to the criteria suggested by Reynolds et al. K562 cells were transfected by siRNA using Lipofectamine 2000. The efficiency of CREB knockdown has been assessed by quantitative relative Real-time PCR. Results: Our results have shown that only one of the siRNAs has a high level of inhibitory effect on CREB1 gene expression. The expression of CREB1 by this siRNA was knocked-down by 87% in K562 cells. Conclusion: In this research, although two siRNAs were designed according to the Reynolds et al. criteria, only one showed an inhibitory effect. Reasons other than the aforementioned criteria may be involved in effectiveness of siRNAs.

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.