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

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

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

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

Thermal and fluid dynamic analysis of partially premixed turbulent combustion driven by thermo acoustic effects

Thermo-acoustic instability can be caused by the feedback mechanism between unsteady heat release, acoustic oscillations and flow perturbations. In a gas turbine combustor limit cycles of pressure oscillations at elevated temperatures generated by the unstable combustion process enhance the structural vibration levels of the combustor. In this paper, the behavior of turbulent partially premixed flames in a laboratory-scale lean partially premixed combustor (called as LIMOUSINE combustor) operating on natural gas- methane fuel mixtures is studied by using CFD methods. Depending on the operating conditions, the flame shows a stable or an unstable behavior. In order to predict the frequency and magnitude of the thermo-acoustic instability, and also to capture the reacting flow physics within the combustor, the influence of operating conditions on combustion characteristics is examined by using unsteady three-dimensional RANS solution of the conservation equations. To understand the effects of operating conditions on the observed stability characteristics, the time averaged velocity fields were measured with Particle Image Velocimetry (PIV) for the thermoacoustically stable and unstable operating conditions of the combustor. The comparison of the CFD calculations with the mean velocity fields shows good agreement. The results of the present study demonstrate the relationship between the flame structure, the mean velocity filed and pressure fluctuations under different operating conditions

Incidence of Snake Bites in Kashan, Iran During an Eight Year Period (2004-2011)

Background: Snake bites are one of the significant health problems in the tropical and subtropical regions. Snake bite is a common medical emergency in Iran, and the epidemiological features and management of such cases vary from region to region. Objectives: This present research study was conducted to obtain new information about the epidemiology of snake bites in the region of Kashan, located in the central part of Iran. Patients and Methods: This research was a descriptive retrospective study. Data from 2004 to 2011 of snakebite cases were collected from case reports. Information included; age and sex of the victim, district, month of incident, mortality, and time of bite. Results: The results of this study showed that the majority of snake bite patients were male (96%). The age distribution of patients indicated that the greatest rate of snake bites occurred among the 15-24 year old group. Data collected in this study revealed that the highest incidence of snake bite cases took place in summer (60%) and the lowest number occurred in winter, with no snake bite cases being recorded. The peak number of snakebite cases was seen during June-September. Conclusions: It was concluded that snake bite cases in Kashan are similar to other areas in Iran from an epidemiological point of view, including; age distribution rates, gender and site of the bites. The existence of Macrov ipera lebetina, a dangerous venomous snake, can cause a range of clinical effects among residents in central parts of Iran, such as Kashan area

Drosophila modifier screens to identify novel neuropsychiatric drugs including aminergic agents for the possible treatment of Parkinson's disease and depression.

Small molecules that increase the presynaptic function of aminergic cells may provide neuroprotection in Parkinson's disease (PD) as well as treatments for attention deficit hyperactivity disorder (ADHD) and depression. Model genetic organisms such as Drosophila melanogaster may enhance the detection of new drugs via modifier or 'enhancer/suppressor' screens, but this technique has not been applied to processes relevant to psychiatry. To identify new aminergic drugs in vivo, we used a mutation in the Drosophila vesicular monoamine transporter (dVMAT) as a sensitized genetic background and performed a suppressor screen. We fed dVMAT mutant larvae ∼ 1000 known drugs and quantitated rescue (suppression) of an amine-dependent locomotor deficit in the larva. To determine which drugs might specifically potentiate neurotransmitter release, we performed an additional secondary screen for drugs that require presynaptic amine storage to rescue larval locomotion. Using additional larval locomotion and adult fertility assays, we validated that at least one compound previously used clinically as an antineoplastic agent potentiates the presynaptic function of aminergic circuits. We suggest that structurally similar agents might be used to development treatments for PD, depression and ADHD, and that modifier screens in Drosophila provide a new strategy to screen for neuropsychiatric drugs. More generally, our findings demonstrate the power of physiologically based screens for identifying bioactive agents for select neurotransmitter systems

Decoupling of a Neutron Interferometer from Temperature Gradients

Neutron interferometry enables precision measurements that are typically operated within elaborate, multi-layered facilities which provide substantial shielding from environmental noise. These facilities are necessary to maintain the coherence requirements in a perfect crystal neutron interferometer which is extremely sensitive to local environmental conditions such as temperature gradients across the interferometer, external vibrations, and acoustic waves. The ease of operation and breadth of applications of perfect crystal neutron interferometry would greatly benefit from a mode of operation which relaxes these stringent isolation requirements. Here, the INDEX Collaboration and National Institute of Standards and Technology demonstrates the functionality of a neutron interferometer in vacuum and characterize the use of a compact vacuum chamber enclosure as a means to isolate the interferometer from spatial temperature gradients and time-dependent temperature fluctuations. The vacuum chamber is found to have no depreciable effect on the performance of the interferometer (contrast) while improving system stability, thereby showing that it is feasible to replace large temperature isolation and control systems with a compact vacuum enclosure for perfect crystal neutron interferometry