Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 1: Structural dynamics analysis

A theoretical investigation of structural vibration characteristics of rotor blades was carried out. Coupled equations of motion for flapwise bending and torsion were formulated for rotor blades with noncollinear elastic and mass axes. The finite element method was applied for a detailed representation of blade structural properties. Coupled structural mass and stiffness coefficients were evaluated. The range of validity of a set of coupled equations of motion linearized with respect to eccentricity between elastic and mass axes was investigated. The sensitivity of blade vibration characteristics to torsion were evaluated by varying blade geometric properties, boundary conditions, and eccentricities between mass and elastic axes

Sensitivity analysis of torsional vibration characteristics of helicopter rotor blades. Part 2: Aerodynamics and sensitivity analysis

A theoretical investigation of dynamic response characteristics of rotor blades was carried out with special emphasis on torsional degrees-of-freedom. Coupled equations of motion for flapwise bending and torsion were formulated at varying azimuth positions for rotor blades with noncollinear aerodynamic, elastic and mass axes. Both structural and aerodynamic mass, damping and stiffness coefficients were included. The variations of a sample blade at different flight conditions were investigated from these equations. The obtained numerical results were illustrated. The sensitivity of overall blade vibration characteristics to torsional oscillations was also investigated from the equations of motion for the sample blade. The illustrated results show the importance of torsional degrees-of-freedom in rotor blade analysis. Various possibilities of improving the overall response by tuning blade geometric, structural and aerodynamic characteristics are discussed

Finite element analysis of transonic flows in cascades: Importance of computational grids in improving accuracy and convergence

The finite element method is applied for the solution of transonic potential flows through a cascade of airfoils. Convergence characteristics of the solution scheme are discussed. Accuracy of the numerical solutions is investigated for various flow regions in the transonic flow configuration. The design of an efficient finite element computational grid is discussed for improving accuracy and convergence

Numerical calculations of velocity and pressure distribution around oscillating airfoils

An analytical procedure based on the Navier-Stokes equations was developed for analyzing and representing properties of unsteady viscous flow around oscillating obstacles. A variational formulation of the vorticity transport equation was discretized in finite element form and integrated numerically. At each time step of the numerical integration, the velocity field around the obstacle was determined for the instantaneous vorticity distribution from the finite element solution of Poisson's equation. The time-dependent boundary conditions around the oscillating obstacle were introduced as external constraints, using the Lagrangian Multiplier Technique, at each time step of the numerical integration. The procedure was then applied for determining pressures around obstacles oscillating in unsteady flow. The obtained results for a cylinder and an airfoil were illustrated in the form of streamlines and vorticity and pressure distributions

Logistics service provider selection for disaster preparation: a socio-technical systems perspective

Since 1990s, the world has seen a lot of advances in providing humanitarian aid through sophisticated logistics operations. The current consensus seems to be that humanitarian relief organizations (HROs) can improve their relief operations by collaborating with logistics service providers (CLSPs) in the commercial sector. The question remains: how can HROs select the most appropriate CLSP for disaster preparation? Despite its practical significance, no explicit effort has been done to identify the criteria/factors in prioritising and selecting a CLSP for disaster relief. The present study aims to address this gap by consolidating the list of criteria from a socio-technical systems (STS) perspective. Then, to handle the interdependence among the criteria derived from the STS, we develop a hybrid multi-criteria decision making model for CLSP selection in the disaster preparedness stage. The proposed model is then evaluated by a real-life case study, providing insights into the decision-makers in both HROs and CLSPs

The Relations between serum leptin levels and anthropometric measurements and hormon levels and chronic degenerative complications of diabetics in obese, diabetic and nonobese non diabetic cases

Nondiabetik obez, diabetik ve nonobez-nondiabetik kontrol grubunda çeşitli antropometrik ölçümlerle serum lipid, bazı hormonlar ve leptin düzeylerinin gruplar arasında ve grup içindeki ilişkilerini araştırmak amacıyla bu araştırma yapıldı. Olgular ve metod: Çalışmaya alman toplam 149 kişi nondiabetik obez, diabetik ve nonobez nondiabetik kontrol grubu olarak ayrıldı. Obez olgular kendi arasında hafif, orta ve ağır olarak diabetikler de yeni tanı konulan ve oral antidiabetik kullanan eski diabetikler olarak ayrıldı. Olguların tümünün boy, kilo, bel, kalça ve ayak bileği ölçümleri yapılarak BKİ ve BKO hesaplandı. Ayrıca biseps, triseps, suprailiak ve subskapular deri kıvrım kalınlıkları ölçülerek standart tablodan VYY'leri bulundu. Çalışmaya alınanların kan basınçları ölçüldü. Labaratuvar incelemeleriyle serum lipid düzeyleri, açlık kan şekerleri, tiroid hormonları, TSH, kortizol, ACTH, GH, erkeklerde total ve serbest testosteron postmenapozal kadınlarda östrojen, progesteron, FSH, LH ve leptin düzeyleri çalışıldı. Obez ve kontrol grubunda OGTT yapılarak glukoz metabolizmaları, diabetiklerde ise HbAlc ve fruktozamin ölçümleri ile metabolik durumları araştırıldı ve kronik dejeneratif komplikasyonlar değerlendirildi. Sonuç: Obezitenin artmış dereceleriyle insülin ve kan basınçlarının arttığı, diabetiklerin BKO'nın kontrol grubundan fazla olduğu, obezlerdeki BKO ile total kolesterol ve LDL düzeylerinin ilişkili olduğu, android obez kadınlarda total kolesterol, LDL, TG ve kortizol düzeylerinin arttığı ve obez erkeklerde serbest testosteronun azaldığı bulundu. Serum leptin düzeyleri obezite derecesiyle ve antropometrik ölçümlerle pozitif ilişkili bulundu. Kadınlarda leptin düzeyleri erkeklerden oldukça yüksek bulunmasına rağmen ilerleyen yaşla leptin düzeyleri arasında ilişki bulunmadı. Postmenapozal obez kadınlarda menapoz leptin ilişkisi bulunmazken diabetiklerde istatistiksel anlamlı olmayan leptin düşüklüğü olduğu saptandı. Leptin'in insülin ile pozitif serbest T 4 negatif ilişkili bulunması dışında diğer hormonlarla arasında ilişkisi bulunmadı. Serum leptin düzeyi sistolik ve diastolik kan basınçları ile oldukça kuvvetli pozitif ilişkili bulundu.The relations between serum leptin levels and anthropometric measurements and hormon levels and choronic degenerative complications of diabetics in obese, diabetic and nonobese nondiabetic cases. Intraduction: This study is performed in order to investigate the relations between several anthropometric measurements and serum lipids, some hormones and serum leptin levels of the nondiabetic obese, diabetic and nondiabetic nonobese control groups. Cases and methods : A total of 149 cases were divided as nondiabetic obese, diabetic and nondiabetic nonobese control groups. The obese cases were classified as mild, moderete and severe obese. The diabetic cases were grouped as those diagnosed recently and old diabetics on oral antidiabetic agents. The weight, height and waist, hip and ankle circumperences were measured and BMI and WHR as values were calculated. In all cases biceps, triceps, suprailiac and subscapular skinfold measurements were performed and body fat percentages were found comparing standard tables; and blood pressure were measured ; serum lipid levels, fasting blood glucose, thyroid hormons, TSH, Cortisol, ACTH, GH and leptin levels, total and free testosteron in male, estrogen, progesteron, FSH, LH levels in postmenaposal fameles were determined. In obese and control groups OGTT was used to determine glucose metabolism, and in diabetic group HbAlc and fructosamin levels were used to define metabolic control state and chronic degenerative complications were evaluated. Resuls : It was found that insulin levels and blood pressure elevated with increased obesity grade and WHR' s of diabetic were more than those of control group. Also WHR of obese cases were positively correlated with the levels of total colesterol and LDL; total colesterol, LDL, TG and Cortisol levels were increased in android type obese women, and free testosteron were decreased in obese males. Serum leptin levels were found to be positively correlated with the grade of obesity and anthropometric measurements. Leptin levels were higher in females comparing to males, but leptin levels were not correlated with increasing age. There were no relations between serum leptin levels and serum hormone levels except positive with insulin and negative correlation with free T 4 levels. Serum leptin levels were found to be strongly positively correlated with systolic and diastolic blood pressure