592 research outputs found

    Reconstruction of Long Anterior Urethral Strictures by Dorsally Quilted Penile Skin Flap

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    Objective. To present the results of reconstruction of long (>5 cm), penile, bulbar, and bulbopenile urethral strictures by penile skin flap as dorsal onlay in one-stage procedure. Patients and Methods. Between January, 1998 and December, 2004, 18 patients (aged from 28-65 years) presented with long urethral strictures, 5.6–13.2 cm (penile in 6, bulbar in 2 and combined in 10 cases), those were repaired utilizing long penile skin flaps placed as dorsal onlay flap in one stage (Orandi flap 6 cm in 6 cases, circular flaps 7–10 cm in 8, and spiral flaps 10–15 cm in 4). Followup of all patients after reconstruction included urine flow rate at weekly intervals, RUG at 6–12 weeks, and urethrocystoscopy at 12 and 18 months. Results. The urethral patency was achieved in 77% of patients. The complications were fistula in one patient (5.5%), restricture occurred in 3 patients (16.6%) that required visual internal urethrotomy and two patients (11%) showed curvature on erection that dose not interfere with sexual intercourse. Diverticulum (penile urethra) was seen in one patient (5.5%) containing stones and was excised surgically. There was penile skin loss in 3 patients (16.6%). All patients completed at least one-year followup period. Conclusion. Free penile skin flaps offer good results (functional and cosmetic) in long penile and/or bulbar urethral strictures. Meticulously fashioned longitudinal, circular or spiral penile skin flaps could bridge urethral defects up to 15 cm long

    Modeling the viscoplastic behavior of Inconel 718 at 1200 F

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    A large number of tests, including tensile, creep, fatigue, and creep-fatigue were performed to characterize the mechanical properties of Inconel 718 (a nickel based superalloy) at 1200 F, the operating temperature for turbine blades. In addition, a few attempts were made to model the behavior of Inconel 718 at 1200 F using viscoplastic theories. The Chaboche theory of viscoplasticity can model a wide variety of mechanical behavior, including monotonic, sustained, and cyclic responses of homogeneous, initially-isotropic, strain hardening (or softening) materials. It is shown how the Chaboche theory can be used to model the viscoplastic behavior of Inconel 718 at 1200 F. First, an algorithm was developed to systematically determine the material parameters of the Chaboche theory from uniaxial tensile, creep, and cyclic data. The algorithm is general and can be used in conjunction with similar high temperature materials. A sensitivity study was then performed and an optimal set of Chaboche's parameters were obtained. This study has also indicated the role of each parameter in modeling the response to different loading conditions

    Exact implicit Solution of Nonlinear Heat Transfer in Rectangular Straight Fin Using Symmetry Reduction Methods

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    In this paper, the exact implicit solution of the second order nonlinear ordinary differential equation which governing heat transfer in rectangular fin is obtained using symmetry reduction methods. General relationship among the temperature at the fin tip, the temperature gradient at the fin base, the mode of heat transfer, and the fin parameters and ℰ is obtained. Some numerical examples are discussed and it is shown that the temperature of fin increases when approaching from the heat source. The relationship between the fin efficiency and the temperature of fin tip is obtained for any value of the mode of heat transfer . The relationship between the fin efficiency and both the parameter and Δ the temperature gradient at the fin base is obtained. To our best knowledge, solutions obtained in this paper are new
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