Underwater sound radiation by a layered infinite elastic plate with discontinuity
The underwater sound radiation from layered structu re is determined by the properties of elastic waves in the structure and by interaction between structural/structur al waves and between structural/fluidal waves. In t his paper, a model of a layered infinite plate is used to addres s how the properties and interaction influence the near field and far field characteristics of the radiated sound. In par ticular, the effect of structural discontinuity int roduced to the layered plate by a finite signal conditioning plate on unde rwater sound radiation is investigated. The scatter ing of structural waves in the layered plate by the signal conditioni ng plate is used to explain the changes in the radi ated sound due to the discontinuity.
Acoustic radiation from an insonified elastic plate with a line discontinuity
This paper deals with the development of analytic models for the prediction of the acoustic radiated field from an infinite elastic plate with a single line force and line moment impedance discontinuity due to an incident plane acoustic wave. The solution is in the form of a Fourier integral with a kernel having ten poles. The integral is evaluated by three methods. The first uses the steepest descent path (SDP) method, leading to a solution that decays as 1/(k0r)1/2. The second method used conformal transformations and the modified saddle point (MSP) method, where all ten poles of the integrand are factored out. This second method yields a solution that has complementary error functions and an asymptotic series in (k0r). The third method employs a transformation of the integrand to effect an efficient and fastly convergent numerical integration algorithm. In general, the MSP asymptotic series solution and the numerical integration yielded numerically identical results. However, while the SDP solution pre...
Immune dysfunction following infection with chicken anemia agent and infectious bursal disease virus. II. Alterations of in vitro lymphoproliferation and in vivo immune responses.
To determine the functional impact of alterations in lymphocyte concentrations and ratios following infection with chicken anemia agent (CAA) alone or in combination with infectious bursal disease virus (IBDV) on the immune system of young chickens, in vitro lymphoproliferation assays and in vivo responses to vaccination with several common viral agents were assessed at various time intervals post-inoculation (PI). Concanavalin A (Con A), phytohemagglutinin (PHA) and pokeweed mitogen (PWM) stimulation of splenic lymphocytes (SPL) collected from control birds could not be detected until 10-14 days PI. Infection with CAA was characterized by significantly higher PWM stimulation of SPL at 17 days PI and significantly lower PWM stimulation of peripheral blood lymphocytes (PBL) at 14 days PI, compared with uninfected controls. Concanavalin A and PWM stimulation of SPL was significantly increased in birds inoculated with IBDV alone. Lymphocytes harvested from birds inoculated simultaneously with CAA and IBDV had significantly lower responses. Effects on humoral and cell-mediated immunity following CAA and/or IBDV were determined by evaluating vaccination responses to Newcastle disease virus (NDV), fowl pox virus (FPV) and infectious laryngotracheitis virus (ILTV) during the acute phase of CAA infection (2 weeks PI). Vaccination of birds 2 weeks following CAA infection at 1 day of age resulted in decreased protection against NDV (85.7%) and ILTV (7.1%) challenge compared with protection rates in control birds (100% and 53.3% respectively). Infectious bursal disease virus infection was associated with decreased protection against NDV (60%) only. Concomitant infection at 1 day of age resulted in a greater reduction in NDV challenge protection (33.3%), slightly decreased FPV protection (87.5%), increased numbers of persistent FPV vaccination lesions and increased protection against ILTV challenge (71.4%). Vaccination of birds 2 weeks following CAA infection at 2 weeks of age resulted in slightly decreased NDV humoral antibody, development of persistent FPV vaccination lesions (17%) and increased immunity to ILTV challenge compared with control birds (83.3% vs. 66.7%). Chickens inoculated with IBDV alone displayed a more severe depression in NDV antibody titers and only a slight decrease in ILTV protection. Vaccination following concomitant infection at 2 weeks of age resulted in a higher percentage of FPV persistent vaccination lesions (39%) and greatly enhanced immunity to ILTV challenge (100%).