1,742 research outputs found
An analysis of short haul airline operating costs
The demand and supply characteristics of short haul air transportation systems are investigated in terms of airline operating costs. Direct, indirect, and ground handling costs are included. Supply models of short haul air transportation systems are constructed
Large amplitude acoustic excitation of swirling turbulent jets
A swirling jet with a swirl number of S = 0.12 is exited by plane acoustic waves at various Strouhal numbers (St = fD/U sub alpha). The maximum forcing amplitude of excitation was at 6.88 percent of the time-mean axial velocity at a Strouhal number of St = 0.39. The maximum time-mean tangential and axial velocities at the nozzle exit were 18 and 84 m/sec respectively. It was observed that the swirling jet was excitable by plane acoustic waves and the preferred Strouhal number based on the nozzle diameter and exit axial velocity of the jet was about 0.39. As a result of excitation at this frequency, the time-mean axial velocity decayed faster along the jet centerline, reaching about 89 percent of its unexcited value at x/D = 9. Also the half velocity radius and momentum thichness, at 7 nozzle diameters downstream, increased by 13.2 and 5.8 percent respectively, indicating more jet spread and enhanced mixing. To our knowledge, this is the first reported experimental data indicating any mixing enhancement of swirling jets by acoustic excitation
Effect of initial tangential velocity distribution on the mean evolution of a swirling turbulent free jet
An existing cold jet facility at NASA-Lewis was modified to produce swirling flows with controllable initial tangential velocity distribution. Distinctly different swirl velocity profiles were produced, and their effects on jet mixing characteristics were measured downstream of an 11.43 cm diameter convergent nozzle. It was experimentally shown that in the near field of a swirling turbulent jet, the mean velocity field strongly depends on the initial swirl profile. Two extreme tangential velocity distributions were produced. The two jets shared approximately the same initial mass flow rate of 5.9 kg/s, mass averaged axial Mach number and swirl number. Mean centerline velocity decay characteristics of the solid body rotation jet flow exhibited classical decay features of a swirling jet with S = 0.48 reported in the literature. It is concluded that the integrated swirl effect, reflected in the swirl number, is inadequate in describing the mean swirling jet behavior in the near field
Controlled excitation of a cold turbulent swirling free jet
Experimental results from acoustic excitation of a cold free turbulent jet with and without swirl are presented. A flow with a swirl number of 0.35 (i.e., moderate swirl) is excited internally by plane acoustic waves at a constant sound pressure level and at various frequencies. It is observed that the cold swirling jet is excitable by plane waves, and that the instability waves grow about 50 percent less in peak rms amplitude, and saturate further upstream compared to corresponding waves in a jet without swirl having the same axial mass flux. The preferred Strouhal number based on the mass-averaged axial velocity and nozzle exit diameter for both swirling and nonswirling flows is 0.4. So far no change in the mean velocity components of the swirling jet is observed as a result of excitation
Hermite-Hadamard type inequalities for operator geometrically convex functions
In this paper, we introduce the concept of operator geometrically convex
functions for positive linear operators and prove some Hermite-Hadamard type
inequalities for these functions. As applications, we obtain trace inequalities
for operators which give some refinements of previous results.Comment: Accepted for publishing in Monatshefte fur Mathemati
Facilitating and inhibiting factors related to treatment adherence in women with polycystic ovary syndrome: a qualitative study
Background: Adherence issues in PCOS patients have not been examined thoroughly. Patients report prolonged periods of treatment and side effects of drug as the most common reason for withdrawal from treatment. To improve the effective management of PCOS patients, it is fundamental to understand facilitating and inhibiting factors to treatment adherence.
Objective: to explore facilitating /inhibiting factors related to treatment adherence among PCOS patients.
Material and Methods: This was a qualitative study with a purposive sample of women with confirmed diagnosis of PCOS. The data were collected via 20 in-depth semi-structured interviews with women aged between 21 to 34. A qualitative content analysis was used to analyze the data.
Results: Five themes were identified which described different types of facilitating /inhibiting factors to treatment adherence. Inhibiting factors included financial issues, patient-related, disease-related, health care provider-related factors; social factors were found to be both facilitating and inhibiting.
Conclusion: The findings suggest that successful adherence to PCOS treatment is highly dependent on patients recognizing and adapting to financial, social, and health care related inhibiting factors. It is also crucial for clinicians and policy makers to recognize these key inhibiting factors in order to improve treatment outcomes
Keywords: polycystic ovarian syndrome, adherence, qualitative researc
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