A direct numerical simulation study of vorticity transformation in weakly turbulent premixed flames

Database obtained earlier in 3D Direct Numerical Simulations (DNS) of statistically stationary, 1D, planar turbulent flames characterized by three different density ratios σ is processed in order to investigate vorticity transformation in premixed combustion under conditions of moderately weak turbulence (rms turbulent velocity and laminar flame speed are roughly equal to one another). In cases H and M characterized by σ = 7.53 and 5.0, respectively, anisotropic generation of vorticity within the flame brush is reported. In order to study physical mechanisms that control this phenomenon, various terms in vorticity and enstrophy balance equations are analyzed, with both mean terms and terms conditioned on a particular value c of the combustion progress variable being addressed. Results indicate an important role played by baroclinic torque and dilatation in transformation of average vorticity and enstrophy within both flamelets and flame brush. Besides these widely recognized physical mechanisms, two other effects are documented. First, viscous stresses redistribute enstrophy within flamelets, but play a minor role in the balance of the mean enstrophy Ω ¯ ¯ ¯ within turbulent flame brush. Second, negative correlation u ′ ⋅∇Ω ′ ¯ ¯ ¯ ¯ ¯ ¯ ¯ ¯ ¯ ¯ ¯ ¯ between fluctuations in velocity u and enstrophy gradient contributes substantially to an increase in the mean Ω ¯ ¯ ¯ within turbulent flame brush. This negative correlation is mainly controlled by the positive correlation between fluctuations in the enstrophy and dilatation and, therefore, dilatation fluctuations substantially reduce the damping effect of the mean dilatation on the vorticity and enstrophy fields. In case L characterized by σ = 2.5, these effects are weakly pronounced and Ω ¯ ¯ ¯ is reduced mainly due to viscosity. Under conditions of the present DNS, vortex stretching plays a minor role in the balance of vorticity and enstrophy within turbulent flame brush in all three cases

Regulation of Mitochondrial Dynamics and Neurodegenerative Diseases

Mitochondria are important cellular organelles in most metabolic processes and have a highly dynamic nature, undergoing frequent fission and fusion. The dynamic balance between fission and fusion plays critical roles in mitochondrial functions. In recent studies, several large GTPases have been identified as key molecular factors in mitochondrial fission and fusion. Moreover, the posttranslational modifications of these large GTPases, including phosphorylation, ubiquitination and SUMOylation, have been shown to be involved in the regulation of mitochondrial dynamics. Neurons are particularly sensitive and vulnerable to any abnormalities in mitochondrial dynamics, due to their large energy demand and long extended processes. Emerging evidences have thus indicated a strong linkage between mitochondria and neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Huntington's disease. In this review, we will describe the regulation of mitochondrial dynamics and its role in neurodegenerative diseases

A Study of Japanese Language Class With Conversation Activities for the Purpose During Learning Process

本研究の目的は，「走れメロス」（太宰治著）の読解プロセスの中で，授業のどのような場面でどのような対話活動をさせたら効果的なのかを，論じ合う対話「討論」に主眼を置きその効果を明らかにすることである。議論を通じて思考・理解を深めることができるという観点から、ペアやグループでの対話的活動を取り入れ，自分の意見とは異なる意見の存在を認識し，相互に取り入れ深めていく活動を日ごろから行い，集団としての学習力を高めていった。その結果，読解において主な中心発問や意見が対立する場合は討論を用いて読み深め，全体やペアなどの意見交流を毎時間取り入れた。これによって読みの深まりや多様化を見取ることができ，討論を中心とした対話的活動の効果があることが確認できた。The purpose of this study was to clarify what conversation activities would be efficient in what class situations, focusing on logical conversation―argumentation―a reading process of Run, Melos! written by Osamu Dazai. From the perspective that pupils could deepen their thoughts and understandings through discussion, the present study introduced conversation activities in pairs and groups in class. The activities helped the pupils recognize and accept various opinions of peers, leading them to enhance their learning ability as a group. The results showed positive effects of conversation activities on the pupils' deepened and varied reading

Structural analyses of RuO(2)-TiO(2)/Ti and IrO(2)-RuO(2)-TiO(2)/Ti anodes used in industrial chlor-alkali membrane processes

The morphology and composition of RuO(2)-TiO(2)/Ti and IrO(2)-RuO(2)-TiO(2)/Ti anodes, which have been used for the production of chlorine for more than 10 years, were analyzed by various methods; such as high-resolution scanning electron microscopy, high-resolution Auger electron spectroscopy, electron probe X-ray emission microanalysis and X-ray diffraction analysis. Drastic changes in the surface morphology, including partial exfoliation of a small amount of the oxide layer and a reduction in the content of ruthenium species through dissolution, were observed for the RuO(2)-TiO(2)/Ti anode. For the IrO(2)-RuO(2)-TiO(2)/Ti anode, on the other hand, there were moderate changes in the surface morphology and moderate dissolution of iridium and ruthenium species.ArticleJOURNAL OF APPLIED ELECTROCHEMISTRYjournal articl

The Effects of Conversation Activities with "Run, Melos !": Achieving Classes with Conversational and Deep Learning

本研究の目的は，「走れメロス」（太宰治著）の学習過程の中で，授業のどのような場面でどのような対話的活動をさせることが深い学びにつながるのかを，論じ合う対話「討論」を取り入れながらその効果を明らかにすることである。本研究は昨年度から，議論を通じて思考・理解を深めることができるという観点から，ペアやグループでの対話的活動を，自分の意見とは異なる多様な意見の存在を認識し，相互に取り入れ集団としての学習力を高められるよう意識して行った。意見が対立する場合は討論を用いて読み深め，それ以外は毎時間全体やペアなどの意見交流を取り入れていった。その結果，読みの深まりや多様化を見とることができ，昨年度と比較しながら，討論を取り入れた対話的活動の効果があることが確認できた。The purpose of this study is to think of when and how to introduce the conversation activities which can lead to deepen learning into the classroom. In addition, the purpose of it is also to reveal the effect of the conversation activities in the process of learning "Run, Melos !" (written by Osamu Dazai) This study was used conversation activities which deepen the students' abilities of considering and understanding since last year. These activities did through recognizing the various opinions from other students and improving their learning abilities in pairs and in groups. They discussed their own opinions when they conflicted their views for reading deeply. Except for it, they had spent time to exchange their views in pairs. As a result, we found the effects of conversation activities on the pupils' 'deepened and varied reading', and also found the effects on conversation activities more than last year

Application of conditioned structure functions to exploring influence of premixed combustion on two-point turbulence statistics

International audienceIn order to investigate the influence of combustion-induced thermal expansion on turbulent flow within a premixed flame brush, a new method is introduced. The method consists in analyzing structure functions of the velocity field, which characterize velocity difference in two points A and B, with the structure functions being conditioned to various events; (i) unburned reactants in both points, (ii) combustion products in both points, (iii) intermediate states of the mixture in both points, (iv) the reactants in one point and the products in another point, (v) the reactants in one point and an intermediate state in another point, and (vi) the products in one point and an intermediate state in another point. Such structure functions and relevant probabilities are defined in the paper. Subsequently, the structure functions and the probabilities are extracted from Direct Numerical Simulation (DNS) data obtained from two statistically 1D, planar, fully-developed, weakly turbulent, premixed flames characterized by two significantly different (7.53 and 2.50) density ratios, with all other things being approximately equal. Obtained results indicate that (i) the conditioned structure functions differ significantly from the mean structure functions and (ii) the newly introduced approach could convey information important for understanding fundamentals of flame-turbulence interaction and finding issues that require further research. In particular, application of the approach to the aforementioned DNS data shows that the combustion-induced thermal expansion substantially affects small-scale two-point velocity statistics in the incoming constant-density turbulent flow of unburned reactants within a premixed flame brush

Preferential {100} etching of boron-doped diamond electrodes and diamond particles by CO2 activation

The etching behavior of polycrystalline boron-doped diamond (BDD) electrodes and diamond particles with gaseous CO2 at 800 and 900 degrees C was investigated by field-emission scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. Polycrystalline BDD (800 ppm), composed of a mixture of cubic {100} and triangular {111} orientated planes, was used so as to pursue the possibility of preferential etching by high temperature CO2 treatment. Nanometer sized pits were observed on the {100} planes while no change was observable for the {111} planes when the activation temperature was 800 degrees C. The difference in the etching behavior by CO2 with regard to the different planes was clarified using diamond particles and comparing with steam activation. The results demonstrate that CO2 activation leads to preferential {100} etching, whereas steam-activation results in preferential {111} etching.ArticleCARBON. 70:207-214 (2014)journal articl

A DNS study of the physical mechanisms associated with density ratio influence on turbulent burning velocity in premixed flames

International audienceData obtained in 3D direct numerical simulations of statistically planar, 1D weakly turbulent flames characterized by different density ratios σ are analyzed in order to study the influence of thermal expansion on flame surface area and turbulent burning rate. Obtained results show that, on the one hand, pressure gradient induced within the flame brush due to heat release in flamelets significantly accelerates unburned gas that deeply intrudes into combustion products in a form of an unburned mixture finger, thus, causing large-scale oscillations of the turbulent burning rate and flame brush thickness. Under conditions of the present simulations, contribution of this mechanism to creation of flame surface area is substantial and is increased by the density ratio, thus, implying an increase in the burning rate by σ. On the other hand, the total flame surface areas simulated at σ = 7.53 and 2.5 are approximately equal to one another. Apparent inconsistency between these results implies existence of another thermal expansion effect that reduces the influence of the density ratio on the flame surface area and burning rate. Investigation of the issue shows that the axial flow acceleration by the combustion-induced pressure gradient not only straightforwardly creates flame surface area by pushing a finger tip into products, but also mitigates wrinkling of the flame surface (the side surface of the finger) by turbulent eddies. The latter effect is attributed to a high-speed (at σ = 7.53) axial 1 flow (a jet) of unburned gas, which is induced by the axial pressure gradient within the flame brush (and the finger). This axial flow acceleration reduces a residence time of a turbulent eddy in an unburned zone of the flame brush (e.g. within the finger). Therefore, the capability of the eddy for wrinkling the flamelet surface (e.g. the side finger surface) is weakened due to a shorter residence time