Simulation of 2-way fluid structure interaction in a 3D model combustor

The liner of a gas turbine combustor is a very flexible structure that is exposed to the pressure oscillations that occur in the combustor. These pressure oscillations can be of very high amplitude due to thermoacoustic instability, when the fluctuations of the rate of heat release and the acoustic pressure waves amplify each other. The liner structure is a dynamic mechanical system that vibrates at its eigenfrequencies and at the frequencies by which it is forced by the pressure oscillations to which it is exposed. On the other hand the liner vibrations force a displacement of the flue gas near the wall in the combustor. The displacement is very small but this acts like a distributed acoustic source which is proportional to the liner wall acceleration. Hence liner and combustor are a coupled elasto-acoustic system. When this is exposed to a limit cycle oscillation the liner may fail due to fatigue. In this paper the method and the results will be presented of the partitioned simulation of the coupled acousto-elastic system composed of the liner and the flue gas domain in the combustor. The partitioned simulation uses separate solvers for the flow domain and the structural domain, that operate in a coupled way. In this work 2-way fluid structure interaction is studied for the case of a model combustor for the operating conditions 40–60 kW with equivalence ratio of 0.625. This is done in the framework of the LIMOUSINE project. Computational fluid dynamics analysis is performed to obtain the thermal loading of the combustor liner and finite element analysis renders the temperature, stress distribution and deformation in the liner. The software used is ANSYS workbench V13.0 software, in which the information (pressure and displacement) is also exchanged between fluid and structural domain transiently.</jats:p

Eco-sectarianism: From ecological disasters to sectarian violence in Syria

YesThis study introduces ‘eco-sectarianism’, which is a new concept that explains the relationship between sectarian violence and environmental pressures in divided societies in the Middle East. Against the backdrop of climate change, ‘eco-sectarianism’ poses a challenge to many fragmented and unequal societies where the sense of national consciousness is weak and nation-building projects are incomplete. This paper draws attention to the links between politicisation of sub-national identities and emerging ecological challenges in Syria

Information technology governance domains in hospitals: a case study in Iran

IT governance is a set of organizational structures ensuring decision-making rights and responsibilities with regard to the organization's IT assets. This qualitative study was carried out to identify the IT governance domains in teaching hospitals affiliated to Iran University of Medical Sciences. There were 10 heads of IT departments and 10 hospital directors. Semi structured interviews used for data collection. To analyze the data content analysis was applied. All the interviewees (100) believed that decisions upon hospital software needs could be made in a decentralized fashion by the IT department of the university. Most of the interviewees (90) believed that there were policies for logistics and maintenance of networks, purchase and maintenance, standards and general policies in the direction of the policies of the ministry of health and medical education. About 80 of the interviewees believed that the current emphasis of the hospital's IT unit and the hospital management for outsourcing of services were in the format of specialized contracts and under supervision of the university Statistic and IT department. A hospital strategic committee is an official organizational group consisting of hospital executives, heads of IT and multiple functional areas and business units in a hospital. In this committee, "the head of hospital" acts as the director of IT activities and ensures that IT strategies are alignment with the hospital business strategies

The relation between severe density of Helicobacter pylori in biopsy with cigarette smoking and age in infected patients

Background and Aim: Helicobacter pylori infection is currently endemic worldwide health problem. The infection causes variety of gastrointestinal (GI) symptoms such as chronic gastritis, peptic ulcer, and gastric adenocarcinoma. It is clear that smoking is important to the development of disorders like intestinal disease. This study determines the relationship between H.pylori density and smoking. Materials and Methods: The study was performed in 247 patients (20-80 years) both sexes, with dyspepsia symptoms referred to Hajar hospital. Demographic data were recorded, such as age and smoking history. Patients were checked by 16 SrRNA and glmM genes polymerase chain reaction for H. pylori. Density of H.pylori graded according to the number of H.pylori bacteria counted in light microscopy by (x1000 magnified).also patient had to have smoked for more than 1 year. Results: We observed 67.61% of patients (167 of 247) were positive for H. pylori, and 32.39% were negative (80 of 247). In patients with dyspepsia, 36.4% in 20-40 age range, 42.1% in 41-61 and 21.5% in 62-80. Of total patients, 57.1% were smokers and in this number, 78.01% were H. pylori positive. Also study showed, in smokers and 3th age range, sever density of H.pylori was more than nonsmokers and other ranges. A significant difference (P<0.05) was observed when we compared density of bacteria by age and smoker with nonsmoker groups. Conclusions: H.pylori sever density can be related by cigarette smoking and age

Study of association between helicobacter pylori infection and microalbuminuria in type-2 diabetic patients

BACKGROUND/AIMS: As default, Helicobacter pylori infection may cause systemic inflammation and vascular endothelial damage. Therefore, it can be assumed that the glomerular damage as a result may lead to an increase in urinary albumin excretion. In this study, this hypothesis was set, and the relationship between Helicobacter pylori infection and microalbuminuria was examined. METHODS: Ninety-three patients with type 2 diabetes were included in the study. These patients were divided into two groups as Helicobacter pylori infection-positive (Group 1) or -negative (Group 2). In all infected and non-infected patients, urinary albumin excretion and other parameters were compared. RESULTS: The presence of Helicobacter pylori infection was detected in 53 of 93 diabetic patients (56.98%). Diabetic patients infected by Helicobacter pylori (Group 1; 186.7±24.2 mg/24 h) showed significantly higher microalbuminuria than non-infected patients (Group 2; 131.2±11.6 mg/24 h) (p=0.012). Diabetics infected with Helicobacter pylori had significantly higher inflammation marker levels than non-infected patients (p<0.05). It has been concluded that the relation between microalbuminuria level and Helicobacter pylori infection in diabetics is independent from other study variables. CONCLUSIONS: Helicobacter pylori infection, because of the systemic inflammatory response, may play an important role in the progression of diabetic nephropathy or its development. In this study, demonstrating the relationship between Helicobacter pylori infection with diabetic microalbuminuria, due to the small number of patients, is inadequate. Therefore, clinical and molecular studies involving more patients should be supported

Study of antioxidant activity and free radical scavenging power of Physalis alkekengi flower extract

According to the undesirable effects of many chemical preservatives in food products such as oilseed extraction industry, the possibility of substituting these materials with effective compounds of herbal plants have been considered by the researchers. In this study, at first, the Physalis Alkekengi flower extract was extracted by using maceration method with methanol. The Phenolic compounds and the amount of free radical scavenging activity of the flower extract were investigated in different concentrations (200, 400, 600, 800 and 1000 ppm), respectively by Folin–Ciocalteu method and DPPH test and were compared with the synthetic antioxidant activity (BHT) at 200 ppm. The results showed a significant difference between different concentrations of Physalis Alkekengi flower extract, in terms of the rate of Phenolic compounds and free radical scavenging activity of flower extract (p &lt; 0.05). In general, the results of this study showed that the methanol extract of Physalis Alkekengi flower, as a source of cheap and available natural antioxidant, after conducting supplementary experiments can be used in food industry.Keywords: Physalis Alkekengi flower, Free radical scavenging power, Natural antioxidants,Phenolic compounds

Fluid-structure interaction on the combustion instability

The multi-domain problem, the limit cycle behaviour of unstable oscillations in the LIMOUSINE model combustor has been investigated by numerical and experimental studies. A strong interaction between the aerodynamics-combustion-acoustic oscillations has been observed during the operation. In this regime, the unsteady heat release by the flame is the acoustic source inducing pressure waves and subsequently the acoustic field acts as a pressure load on the structure. The vibration of the liner walls generates a displacement of the flue gas near the wall inside the combustor which generates an acoustic field proportional to the liner wall acceleration. The two-way interaction between the oscillating pressure load in the fluid and the motion of the structure under the limit cycle oscillation can bring up elevated vibration levels, which accelerates the degradation of liner material at high temperatures. Therefore, fatigue and/or creep lead the failure mechanism. In this paper the time dependent pressures on the liner and corresponding structural velocity amplitudes are calculated by using ANSYS workbench V13.1 software, in which pressure and displacement values have been exchanged between CFD and structural domains transiently creating two-way fluid-structure coupling. The flow of information is sustained between the fluid dynamics and structural dynamics. A validation check has been performed between the numerical pressure and liner velocity results and experimental results. The excitation frequency of the structure in the combustor has been assessed by numerical, analytical and experimental modal analysis in order to distinct the acoustic and structural contribution

Inflationary Expectations and Monetary Adjustment in Nigeria: 1960-1978

Short-run money demand functions are estimated and elasticities of price expectations and real cash balance adjustment arc determined. By examining the hypothesis that inflation m Nigeria is self-generating, the study concludes that explanations for the rise in price level should be sought in factors other than money supply alone

A novel multi-reactor system for thermochemical heat storage through detailed modeling of K₂CO₃ particles

Thermochemical energy storage (TCES) is becoming increasingly important in the energy transition, as it can effectively bridge the gap between renewable energy supply and demand. In this study, the reaction kinetics of K2CO3 were characterized and validated. Based on this kinetic model, a numerical model of a packed bed of particles was developed using a coupled CFD-DEM approach. The results of the model were validated against experimental data of a particle bed, showing good agreement. The reaction rate of the system was found to be limited by the diffusion of water vapor into the material, which led to unsatisfactory performance on the bed scale due to significant temperature drop-offs. Although reducing particle size was found to be an effective way to improve system performance, practical concerns such as agglomeration and bed permeability limited its effectiveness. As an alternative, a multi-reactor system with adaptive flow rates was proposed, which improved system performance without the limitations of reducing particle size. The proposed modular system is capable of delivering 10 kW power at the temperature of 45 degrees for a duration of 19.5 h