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Over the course of the past 40-45 years of computational modeling in the fields of structures, structural acoustics, and vibrations, there have been extreme advancements made in numerous areas that have greatly increased and improved the size, accuracy, efficiency, and complexity of numerical solutions possible. Most of this progress has been made through a combination of improvements in the distinct areas of computer processing approaches/speed and available memory, primarily evolutionary enhancements in detailed numerical material and continuum mechanics models, development of entirely new physics-based numerical vibroacoustic modeling approaches, etc. This paper presents a historical review of the detailed progress made in computational structural acoustics and vibration from the “early days” in the 1980s through current state-of-the-art advanced numerical approaches, much of which would not have been dreamed possible back four decades ago! While most of the examples utilized in this talk are pulled from the speaker’s specific technical area of undersea vehicle/ system structural acoustics, the overall trends presented are certainly represented across the broad spectrum of vibro-acoustics modeling applications.

Throughout the course of a relatively long career in science and engineering, including advanced degrees, teaching, and a host of other external technical activities, there are numerous lessons learned and perspectives gained that are frequently much more important than specific technical advice. Oftentimes, the most important and critical teachings to be passed on to fellow present and future researchers are not narrowly-focused but wide-ranging and generally applicable. The most essential of these “pearls of wisdom” are learned occasionally out of successes yet more often out of apparent failures and frustrations. Almost invariably, the most valuable information is wide-ranging and universal and independent of any particular scientific discipline or field. This paper presents numerous technical and life-/career-related lessons that are hopefully of value and interest to current and upcoming scientists, engineers, and students. In addition, time permitting, a particular specific technical case study is presented.

This research offers an additional approach to the increased interest in information theoretic techniques utilized in the Theory of Communications, Electrical Engineering and Signal Processing disciplines for extracting nonlinear behavior in dynamical systems. This new approach was, in part, motivated by a diligent effort to create a man-made system that mimics the sound generation of a cicada. This insect has tremendous sound production capacity for its size. For the Okanagana and Magicicada species studied in this research, these cicadae ranged in size from five to six centimeters and produce sounds that are heard several hundred meters away. The evolution of this new signal processing algorithm from this bio-inspired research is explained in this article. This investigation initially examined the cicada hypothesized nonlinear system, by employing a number of numerical techniques in which to identify nonlinearity in a measurement times series. One such technique, the Nuttall modified-Volterra approach would serve as the validation and verification process for confirming that the inherent artificiality introduced by converting the sound production system of the biologic system to a man-made device did not corrupt the inherent dynamics of the cicada mating call. The technical advantage gained from quantification of the expansion kernels using the Nuttall approach, is the creation of more characterization clues by extending beyond the linear kernel response. This unique method is based on an extension of earlier developments of Vito Volterra and Norbert Wiener. The new Nuttall-Wiener-Volterra (NWV) method identifies the existence of nonlinearity in a measurement time series and determines the power distribution of individual nonlinear components. Moreover, the NWV method, unlike other methods that are likely less computationally efficient due to the Curse of Dimensionality (COD), significantly reduces the computational workload, thereby making characterizations of nonlinear systems with memory at higher orders possible. The nonlinear system kernel responses reveal identification and characterization of linear and nonlinear dynamics contained within the system under investigation. Thus, the nonlinear kernel responses computed for the cicada exposed a critical development for the NWV technique, namely that in order to obtain meaningful NWV kernel responses (i.e., to have physically and mathematically sound computational results), there are restrictive requirements for the system input excitation to be (a) band-limited, (b) white Gaussian and (c) zero mean. By studying the anatomical structures in the cicada sound production system and developing the wave propagation and finite element (FE) models this effort also then attempted an approach to confirm the accuracy of these models by employing the NWV nonlinear (and linear) analysis method.

This research has developed a mathematical model for characterizing nonlinear systems utilizing the earlier methods of Vito Volterra (1860-1940)1 and later by Norbert Wiener (1894-1964)2. More recently, Albert Nuttall, working with coauthors, has made significant improvements over the earlier methods. These enhancements include kernel estimation using a least-square approach for obtaining a best fit to the measured system response. These techniques, among others, include: maximally-sparse sampling of the kernels (for first-, second- and third-order), combatting ill-conditioning on its own terms, realizing an exponential decrease of the growth of the number of kernel coefficients, capturing frequency content beyond input excitation (transmit) band, and estimating the effects of noise on the kernel responses. Extensions of this theory are relevant to problems in acoustics.

The present article discusses novel improvements in nonlinear signal processing made by the prime algorithm developer, Dr. Albert H. Nuttall and co-authors, a consortium of research scientists from the Naval Undersea Warfare Center Division, Newport, RI. The algorithm, called the Nuttall-Wiener-Volterra or 'NWV' algorithm is named for its principal contributors [1], [2],[ 3] . The NWV algorithm significantly reduces the computational workload for characterizing nonlinear systems with memory. Following this formulation, two measurement waveforms are required in order to characterize a specified nonlinear system under consideration: (1) an excitation input waveform, x(t) (the transmitted signal); and, (2) a response output waveform, z(t) (the received signal). Given these two measurement waveforms for a given propagation channel, a 'kernel' or 'channel response', h= [h 0 ,h 1 ,h 2 ,h 3 ] between the two measurement points, is computed via a least squares approach that optimizes modeled kernel values by performing a best fit between measured response z(t) and a modeled response y(t). New techniques significantly diminish the exponential growth of the number of computed kernel coefficients at second and third order and alleviate the Curse of Dimensionality (COD) in order to realize practical nonlinear solutions of scientific and engineering interest.

Structural acoustics may be defined as a multidisciplinary coupled field of physics usually referring to the characterization of either (1) the sound power emitted by a vibrating structure subjected to external dynamic excitation or (2) the vibrational response of structures excited by incident sound fields or fluid excitation. The Structural Acoustics and Vibration (SAV) Technical Committee is a diverse group of scientists and engineers sharing a common interest and shared stewardship in the health and advancement of the SAV technical discipline. In addition to the fundamental scientific study of the underlying SAV physics which is important to all SAV practitioners, there is also interest on the practical real-world, application of the SAV science to predict, control, and potentially reduce the vibroacoustic response of given structural acoustic systems. This paper begins by providing a fundamental definition of the underlying physics governing the SAV technical discipline. The numerous categories and subdivisions within the general SAV area are then addressed, along with illustrations of the broad array of scientific and engineering real-world applications in the field. Following that, examples of interesting career options as well as exciting new research areas in SAV are presented. Finally, this paper concludes with information regarding the makeup, functioning, and administrative philosophy of the SAVTC.Structural acoustics may be defined as a multidisciplinary coupled field of physics usually referring to the characterization of either (1) the sound power emitted by a vibrating structure subjected to external dynamic excitation or (2) the vibrational response of structures excited by incident sound fields or fluid excitation. The Structural Acoustics and Vibration (SAV) Technical Committee is a diverse group of scientists and engineers sharing a common interest and shared stewardship in the health and advancement of the SAV technical discipline. In addition to the fundamental scientific study of the underlying SAV physics which is important to all SAV practitioners, there is also interest on the practical real-world, application of the SAV science to predict, control, and potentially reduce the vibroacoustic response of given structural acoustic systems. This paper begins by providing a fundamental definition of the underlying physics governing the SAV technical discipline. The numerous categories and s...

The present article discusses some inroads in nonlinear signal processing made by the prime algorithm developer, Dr. Albert H. Nuttall and co-authors, a consortium of research scientists from the Naval Undersea Warfare Center Division, Newport, RI. The algorithm, called the Nuttall-Wiener-Volterra 'NWV' algorithm is named for its principal contributors [1], [2],[ 3] over many years of developmental research. The NWV algorithm significantly reduces the computational workload for characterizing nonlinear systems with memory. Following this formulation, two measurement waveforms on the system are required in order to characterize a specified nonlinear system under consideration: (1) an excitation input waveform, x(t) (the transmitted signal); and, (2) a response output waveform, z(t) (the received signal). Given these two measurement waveforms for a given propagation channel, a 'kernel' or 'channel response', h= [h 0 ,h 1 ,h 2 ,h 3 ] between the two measurement points, is computed via a least squares approach that optimizes modeled kernel values by performing a best fit between measured response z(t) and a modeled response y(t). New techniques significantly diminish the exponential growth of the number of computed kernel coefficients at second and third order in order to combat and reasonably alleviate the curse of dimensionality.

The Structural Acoustics and Vibration (SAV) Technical Committee is a broad group of scientists and engineers sharing a common interest and shared stewardship in the health and advancement of the SAV technical discipline. Structural acoustics may be defined as a multidisciplinary coupled field of physics usually referring to the characterization of either (1) the sound power emitted by a vibrating structure subjected to external dynamic excitation or (2) the vibrational response of structures excited by incident sound fields or fluid excitation. While the fundamental scientific study of the underlying SAV physics is certainly important to SAV practitioners, there is also interest on the practical application of the prediction, control, and potential reduction of the vibroacoustic response of given structural acoustic systems. This paper first provides a fundamental definition of the underlying physics behind the SAV technical discipline. The many categories and subdivisions within the general SAV area are then addressed, along with illustrations of the broad array of scientific and engineering real-world applications in the field. Following that, examples of interesting career options as well as exciting new research areas in SAV are presented. Finally, the paper concludes with information regarding the makeup, functioning, and administrative philosophy of the SAVTC.The Structural Acoustics and Vibration (SAV) Technical Committee is a broad group of scientists and engineers sharing a common interest and shared stewardship in the health and advancement of the SAV technical discipline. Structural acoustics may be defined as a multidisciplinary coupled field of physics usually referring to the characterization of either (1) the sound power emitted by a vibrating structure subjected to external dynamic excitation or (2) the vibrational response of structures excited by incident sound fields or fluid excitation. While the fundamental scientific study of the underlying SAV physics is certainly important to SAV practitioners, there is also interest on the practical application of the prediction, control, and potential reduction of the vibroacoustic response of given structural acoustic systems. This paper first provides a fundamental definition of the underlying physics behind the SAV technical discipline. The many categories and subdivisions within the general SAV area are...

Two major areas of current research focus in Structural Acoustics and Vibration (SAV) are in (1) the development of advancements in the Physics-Based Modeling (PBM) and simulation of real-world, large-scale vibroacoustic systems and also in (2) the development and incorporation of novel engineered materials to improve structural acoustic response performance from a broad array of perspectives. This paper presents examples from a wide survey of recent SAV computational PBM research, from the inclusion of additional complex, coupled modeled phenomena, to improvements in modeling efficiency, accuracy, and/or full frequency spectrum response prediction, through computational advances in the ability to solve extremely large-scale, previously intractable, structural acoustics models. Related to the second materials-based SAV research concentration, recent advancements and innovations in SAV-relevant materials including acoustic metamaterials, zero- and negative-Poisson’s ratio materials, single crystal ceramics, nanomaterials, etc., are also presented.

This study investigates laser beam propagation through an atmospheric boundary layer near the ocean surface. Objectives of this research are to ascertain feasibility limits for achieving maximum energy efficiency at extended ranges in the face of atmospheric and other distortions as the laser beam penetrates through transitional (anisotropic) and turbulent (isotropic) boundary layer regimes. Various aspects of turbulence modeling of laser beam propagation near the ocean surface are discussed including: Kolmogorov’s model of atmospheric turbulence, parameterized structure functions (e.g., velocity and temperature gradients, gradients in refractive index) and other important factors affecting near surface propagation such as humidity, aerosols, and wave slap. Various preliminary modeled propagation results are shown, and a new methodology is proposed for improving existing model estimates with new time domain measurement procedures.

A well-known mathematical model for characterizing nonlinear systems was originally proposed by Vito Volterra (1860-1940) and later developed by Norbert Wiener (1894-1964). More recently, Albert Nuttall, working with coauthors, has made substantial improvements to Wiener’s approach, in which kernel estimates are modeled directly rather than computed from Wiener functionals. Other enhancements made include kernel estimation using a least-square approach for obtaining a best fit to the measured system response, and procedural methods to obtain uncorrelated column-wise basis vectors in the design matrix. These techniques, among others, include: maximally-sparse sampling of the kernels (for first-, second- and third-order), combatting ill-conditioning on its own terms, and realizing an exponential decrease of the growth of the number of kernel coefficients.

Traditionally, solving structural-acoustics problems has posed significant computational challenges at very high wavenumbers because of the mesh refinement required. As such, instead of resolving each wavelength, the fundamental goal in Energy Finite Element Analysis (EFEA) is to average the energy over many wavelengths. The envelope of average energy behaves as a slowly varying exponential, which is much easier to solve numerically. EFEA thus computes the average energy over a region which can be used to determine undersea vehicle self- and radiated noise in much the same way as conventional FEA modeling but the size of the mesh does not suffer the same restrictions. In this talk, self-noise model predictions for a representative undersea vehicle are discussed to demonstrate the effectiveness of EFEA. This model includes an explicitly modeled acoustic domain to allow radiated energy to propagate in the acoustic medium and possibly reenter the vehicle structure. Results are validated with dense FEA models and the post-processing algorithms used for this purpose are discussed.

A basic model of a ribbed finite plate is first considered, with the plate connected to a parallel surface by a nonlinear spring. When individual ribs are placed under compression, the linearized version of the model predicts eventual exponential growth of the transverse displacement when the compressional load exceeds the buckling load. The nonlinear spring, however, stops this growth and a subsequent oscillation ensues. The anatomy of the cicada is, of course, much more complicated, and the basic model is extended to give a mathematical formulation of the model proposed by Bennet-Clark and Daws (J. Exper. Biol., 1999) for the Cyclochila australasiae (a relatively large species of cicada), with explicit elasto-mechanical parameters, a principal objective being the computational prediction of the observed far-field waveforms. Possible explanations are advanced for the anatomical cause of the nonlinear springs. Further extensions of the theory are applied to the development of mathematical models for species of cicadas (considerably smaller) commonly found in the United States.

A generalized model for characterizing nonlinear systems was originally proposed by Italian mathematician and physicist Vito Volterra (1860-1940). A further development by American mathematician and MIT Professor Norbert Wiener (1894-1964) was published in 1958. After direct involvement with Norbert Wiener publication, Albert H. Nuttall has recently made new inroads along with his coauthors in applying the Wiener-Volterra model. A general description of a nonlinear system to the third order is termed the Nuttall-Wiener-Volterra model (NWV) after its co-founders. In this formulation, two measurement waveforms on the system are required in order to characterize a specified nonlinear system under consideration: an excitation input, x(t) (the transmitted signal) and a response output, z(t) (the received signal). Given these two measurement waveforms for a given system, a kernel response, h= [h0,h1,h2,h3] between the two measurement points, is computed via a least squares approach that optimizes modeled kernel...

This study was designed to evaluate the relationship between marbling score and breed-type (Bos taurus vs .05) from Modest or Moderate marbling. In addition, variation in shear force was lower (P .05) by marbling score in either Bos taurus or Bos indicus cattle. Percentage yield of retail product decreased (P .05) to shear force or tenderness rating.(ABSTRACT TRUNCATED AT 250 WORDS)

Records from 12 breed groups col- lected from 1983 to 1991, included in the Germ Plasm Utilization project at the U.S. Meat Animal Research Center, were analyzed separately by breed group and combined to estimate heritabilities and genetic corre- lations for 320-d male and female pelvic width, height, and area, and for 320-d male pelvic and female 2-yr-old calving ease. Calving ease was analyzed as a trait of the dam using 1) actual and 2) binary scale calving ease scores with a covariate of calf birth weight. A bivariate animal model and derivative-free REML incorporating sparse matrix techniques were used. When breed groups were analyzed separately, heritability estimates of male and female 320-d pelvic traits varied by breed group and sex. Average genetic correlations between male and female 320-d pelvic width, pelvic height, and pelvic area were large and positive. When breed groups were combined (n = 26,071), heritability estimates for 320-d pelvic traits were moderate in size. Genetic correlations of .68, .48, and .61, between male and female 320-d pelvic width, height, and area, respectively, suggest male and female pelvic traits are largely under the same genetic control but are correlated traits rather than the same trait. Heritability estimates for actual calving ease in 2-yr-olds ranged from .OO to .49 in separate breed group analyses, and from .OO to .37 for binary measures. When breed groups were combined, herita- bility was .ll for actual calving ease and was .09 on the binary scale. Genetic correlations by breed groups between 320-d male pelvic traits and calving ease of 2-yr-old females were variable. When breed groups were combined, genetic correlation estimates between 320-d male pelvic traits and actual calving ease of 2-yr-old females (on a 6-point scale) were negative and moderate as were genetic correlations between male 320-d pelvic traits and binary calving ease of 2-yr-old females. A bull one phenotypic SD above the mean in pelvic area would be expected to increase his daughters' average pelvic area by 1.30 cm2 and improve its calving ease score by .03 of a score compared with an average breed bull.

Retained heterosis for meat traits was estimated in F3 generation castrate males in three composite populations of beef cattle finished on two levels of dietary energy density (2.82 Mcal of ME and 3.07 Mcal of ME and 11.50% CP) and serially slaughtered at four end points at intervals of 20 to 22 d. Breed effects were evaluated in nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, and 1/4 A). Breed effects were important (P < .01) for all carcass and meat traits evaluated. Dietary energy density and slaughter group affected (P < .05) most traits evaluated. The effects of retained heterosis were not consistent among composites. For the mean of the three composites, retained heterosis was significant only for percentage of 9-10-11th rib fat and for percentage of retail product. Phenotypic correlations indicated that marbling score was a poor predictor of palatability attributes of individual carcasses. Estimates of heritability were intermediate to high for measures of fatness but were generally low for palatability attributes. The high negative genetic correlation (-.56) between percentage of retail product and marbling score and the relatively low genetic correlations between percentage of retail product and palatability attributes suggests the need for simultaneous attention to percentage of retail product and palatability attributes rather than to marbling score. Correlations among breed group means were generally high for measures of fatness with palatability attributes and were high and negative for percentage of retail product with marbling score and with other measures of fatness. Limited opportunity exists for selecting among breeds to achieve high levels of marbling in the longissimus muscle simultaneously with a high percentage of retail product. These results suggest that the most logical approach to resolution of the genetic antagonism between favorable carcass composition and less favorable palatability attributes is to form composite breeds with breed contributions organized to achieve an optimum balance between favorable carcass composition and desirable palatability attributes at optimum slaughter weights.

Summary Data from nine parental breeds and three composite populations described in the preceding article were used to calculate heritabilities and phenotypic and genotypic correlations among carcass and meat traits. Phenotypic correlations indicated that marbling was a poor predictor of longissimus muscle palatability a ttributes of the individual carcasses. Heritability estimates were intermediate to high for fatness measures but generally low for palatability attributes. The high negative genetic correlation (-.56) between percentage of retail product and marbling score and the relatively low genetic correlations between percentage of retail product and palatability attributes suggest simultaneous selection for percentage of retail product and palatability, rather than for marbling score. Correlations among breed group means were generally high between measures of fatness and palatability attributes and were high and negative between percentage of retail product and marbling score or other fatness measures. Thus, opportunity is limited to select among breeds for high levels of marbling and a high percentage of retail product at the same time. The most logical approach to resolving that genetic antagonism is to form composites from breeds that contribute an optimum balance between favorable carcass composition and desirable meat palatability.

Experimental lifetime performance data obtained from 156 straightbred Hereford, Angus, and Shorthorn and 172 first-cross heifers were used to estimate heterosis for economic efficiency in a 100-cow herd at age equilibrium under three culling policies and at terminal ages from 6 to 12 yr. All nonpregnant heifers and cows greater than 9 yr of age were culled. The culling policy for removal of nonpregnant cows from second parity through 9 yr of age were 1) no culling, 2) after two consecutive years (actual), and 3) all (imposed). Efficiency was calculated as input cost per unit of output value. A 10-yr average was used for costs of replacement heifers, cow units, and the ratio of calf:cull cow prices (PR), plus higher and lower PR. Input included costs for both cow units and purchased replacements. Output value included both weaned calves and cull cows. Optimum terminal age was mainly a function of PR: 9 yr for average and high PR, but 6 through 9 yr when PR was low, regardless of culling policy or breed groups. Efficiency differences among culling policies were small for high or average PR, but more culling for infertility was beneficial when PR was low. Estimated reductions in unit costs of output value under any culling policy or terminal age were approximately 6% from crossbred cows plus another 6% from crossbred calves, or a total of 12% from specific three-breed crossing of these British breeds. Cost reductions would be somewhat less for rotation crossbreeding but greater for mating smaller crossbred cows with sires of superior growth-carcass breeds.

Retained heterosis in F2 cows nursing F3 progeny was evaluated in 3-, 4-, and greater than or equal to 5-yr-old cows. Traits evaluated included milk yield at three stages of lactation and 200-d weight of progeny. Breed effects were evaluated in the nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Breed effects were significant for 12-h milk yield, estimated 200-d milk yield, and 200-d weight of progeny. Herefords were lowest (P less than .05) for 12-h milk yield and estimated 200-d milk yield, and Braunvieh produced significantly more milk than all breed groups except Pinzgauer and Simmental, for which the difference approached significance. The correlation among breed group means (nine parental breeds and three composites) for 12-h milk yield with 200-d weight of progeny was .91. When 200-d weight was adjusted to a common estimated 200-d milk yield, Hereford, Angus, Red Poll, and Limousin did not differ (P greater than .05); all were significantly lighter than Braunvieh, Pinzgauer, Gelbvieh, Simmental, and Charolais, which did not differ (P greater than .05) from each other.(ABSTRACT TRUNCATED AT 250 WORDS)

Heterosis effects in F1 dams producing F2 progeny and retained heterosis in combined F2 and F3 dams producing F3 and F4 progeny were evaluated in dams 2 yr old, in dams greater than or equal to 5 yr old, and in dams of all ages. Traits included pregnant percentage, calf crop born percentage, calf crop weaned percentage, 200-d calf weight per heifer or cow exposed, and 200-d calf weight. Breed effects were evaluated in the nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Breed effects were significant for all traits evaluated in the three age groupings and generally were greatest in 2-yr-old dams and smallest in dams greater than or equal to 5 yr old. Heterosis effects for 200-d calf weight were relatively uniform among age groupings and among the three composite populations and heterosis retained was equal to, or greater than, expectation based on retained heterozygosity. Heterosis effects in animals of all ages for reproductive traits in F1 dams producing F2 progeny differed among the three composite populations, as did heterosis retained in combined F2 and F3 dams producing F3 and F4 progeny. In dams of all ages, heterosis retained for reproductive traits in F2 and F3 dams producing F3 and F4 progeny did not differ (P greater than .05) from expectation based on retained heterozygosity in two of the three composite populations, but loss of heterosis was greater (P less than .05) than expectation based on retained heterozygosity in one of the three composite populations for calf crop born percentage, calf crop weaned percentage, and 200-d calf weight per heifer or cow exposed. This reduction was the result of increased fetal loss between pregnancy diagnosis and parturition.(ABSTRACT TRUNCATED AT 400 WORDS)

Records of Angus, Hereford, Shorthorn, and first-cross cows born from 1960 to 1963 were used to study the effect of age at first calving and culling policy on cumulative survival (SU), number of breeding seasons (BS), pregnancies (PG), calves born (CB) and alive at 72 h (C72) and at weaning (CW), calf weaning weights (WW), and input/output efficiency, up to 12 yr of age. The 155 cows born in 1960 and 1961 calved first at 3 yr of age (M3) and the 173 born in 1962 and 1963 calved at 2 yr of age (M2). Analyses included both actual culling of cows open in two consecutive years (AC) and imposed culling of any open cow (IC). Also, economic efficiency for no culling (NC) of cows for infertility after first calving and up to 10 yr of age was calculated. The model included cow birth year-sire breed of cow (Y-S), sires within Y-S, breed of cow's dam (D), and D x Y-S. Linear functions of Y-S were used to estimate means for M2 and M3 cows. Under AC, by 12 yr of age M2 exceeded M3 cows by 6.8% SU, 1.1 BS, 1.2 PG, 1.1 CB, 1.0 C72, .9 CW, and 138 kg WW (P less than .10). Under IC, M2 exceeded M3 cows by only .7% SU, .3 BS, .3 PG, .3 CB, .2 C72, and .1 CW; and M3 produced 24 kg more WW than M2 cows (P greater than .10). Economic efficiency was higher for M2 than for M3 cows (greater than 10% at 6 yr to greater than 5% at 12 yr culling age), regardless of culling policy. Economic efficiency was maximum when terminal age of cows was 6 to 9 yr for M2 and 8 to 9 yr for M3 cows. Repeatability of pregnancy was higher (P less than .05) for M3 (19%) than for M2 (2%) cows. Economic efficiency for M2 or M3 cows under NC was slightly poorer (2 to 3%) than under either AC or IC policies. Economic efficiency can be improved by managing heifers to calve first as 2-yr-olds under either mild or intense culling of open cows.

Heterosis effects were evaluated in F1, F2, and F3 generations of females and in the F1, F2, and combined F3 and F4 generations of males in three composite populations of beef cattle. Traits included weight, height, and condition scores at different ages, percentage of females reaching puberty at 368, 410, and 452 d, adjusted age, and adjusted weight of females at puberty and scrotal circumference and paired testicular volume of males. Breed effects were evaluated for the nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Breed effects were significant for all traits evaluated. Heterosis was significant for weight, height, and condition score at all ages and for most measures of puberty in each generation of each composite and for the mean of the three composite populations. Heterosis for age at puberty was largely independent of heterosis effects on 368-d weight. Heterosis was significant for scrotal circumference and paired testicular volume in each generation of each composite and for the mean of the three composite populations. Heterosis effects on scrotal measurements are mediated both through heterosis effects on growth rate and through factors that are independent of growth rate. Correlation coefficients among breed group means and correlations of breed rank for scrotal measurements with puberty traits of females were greater than or equal to .88 (P less than .01) for all puberty traits except weight at puberty, which was not associated with scrotal measurements. There was close agreement in heterosis observed for most traits and expectation based on retained heterozygosity. These results support the hypothesis that heterosis in cattle for size, puberty, and scrotal measurement traits is due to dominance effects of genes.

Experiments and analyses of Hughes et al., JASA, 2009 are the origins of this research where we study the in-air waveform generation and propagation of the acoustic signals generated by cicadas. The sound generation is studied in a Newtonian model and the sound propagation is analysis by a numerical solver for viscous Burgers’ equation. The time histories from the tymbal surface velocities recorded by a laser Doppler vibrometer to the microphones positioned near the cicadas provide the test data. The Newtonian model describes the sound production systems process to generate the mating call signal structure. The numerical solver employs weighted essentially non-oscillatory (WENO) reconstruction to approximate the first and second derivatives of the semi-discrete operator. The WENO is utilizes due to the non-smooth structure of the cicada propagating waveform. Principally, the cicada mating signal in question has sharp transitions, since spectral methods tend to produce spurious oscillations as a result of attempting to represent a discontinuous function by a Fourier basis expansion. Thus, these analytical models are computationally tested to determine if the results capture the sound production and the transmission of the cicada mating calls. To verify the models are meaningful, the simulations are verified with real experimental data.

The structural acoustics and vibration related to submerged, structurally driven elastic plates is germane to a wide range of applications in U.S. Navy undersea vehicle and system designs. Of particular interest to a recent specific Naval design application was the examination of effects on the acoustic radiation from a very large, fluid-loaded elastic plate joined with a “welded,” or strongly attached, smaller elastic plate subjected to force-loading excitation somewhere on the large plate. This paper presents the results following an examination of several theoretical approaches to predicting the radiated sound level (both levels and directivity) of an idealized infinite plate and perfectly attached thin, finite plate submerged in a heavy fluid and driven by a line-load at varying locations on the infinite plate. Parametric studies are also presented to both highlight the underlying basic physical mechanisms and also to investigate the effect on sound radiation of varying system parameters. Specifically, results of parametric variations in (a) location of the line force on the plate with respect to the attached finite plate, (b) length/size of the attached plate, (c) mass and/or stiffness of the attached plate, (d) frequency of the harmonic line-load, and, time permitting, and (e) the mechanical theory of the attached thin plate, are all presented herein.

Among a multitude of diverse applications, the acoustics of cylindrical shells is also an important area of study for its applicability to and representation of many US Navy undersea vehicles and systems. Examination of structural acoustic predictions of cylindrical-shell-based system designs are frequently made using a variety of analytical and computational approaches including closed-form 3D elasticity, numerous kinematic plate/shell theories, Finite Element Analysis (FEA), Energy-based FEA (EFEA) coupled with Energy Boundary Element Analysis (EBEA), and Statistical Energy Analysis (SEA). Each of these approaches has its own set of assumptions, advantages, and applicable frequency range which can make for confusion. This paper presents radiated noise solutions in the area of cylindrical shell structural acoustics from the above list of methodologies for the canonical problem of a point-excited, finite cylindrical shell with/without fluid loading. Specifically, far-field radiated sound power predictions...

The principal anatomical structures in the cicada that radiate sound are two platelets referred to as tymbals, which vibrate after being struck by ribs that have undergone buckling. This research effort investigates the sound of these ribbed finite plates connected to a parallel surface by a nonlinear spring. When individual ribs are placed under compression, the linearized version of the model predicts eventual exponential growth of the transverse displacement when the compressional load exceeds the buckling load. The nonlinear spring, however, stops this growth and a subsequent oscillation ensues. The actual anatomy of the cicada is more complicated than this basic model. However, this simplified mathematical explanation is given as a means to describe sound emitted in a sequence of closely spaced tone bursts. The energy from these sound impulses are stored in tensed muscles and released via buckling into the kinetic energy of ribs, which is similar to striking a drum. The tymbals “ring” at a frequency controlled by the mass of the tymbals and the air cavity “spring” within the abdomen. This ringing vibration affects the amplitude, cycles within each pulse, and the damping of the tymbal function to generate the efficiency of the cicada sound radiation.

Postweaning growth, puberty, and pregnancy traits were evaluated for 783 F1 heifers sired by Angus, Hereford, Charolais, Shorthorn, Galloway, Longhorn, Nellore, Piedmontese, and Salers bulls and out of Angus and Hereford dams in Cycle IV of the Germplasm Evaluation (GPE) Program at the U.S. Meat Animal Research Center. The Hereford and Angus sires included a sample of bulls born from 1982 to 1985 (1980s HA) as well as reference sires born from 1963 to 1970 (REF HA) used in previous cycles of the GPE program. Breed group of sire had a significant (P.01) effect on age and weight at puberty, on 200-, 400-, and 550-d weights, on ADG from 200 to 400 and from 400 to 550 d, and 550-d hip height, but it did not influence (P.05) pregnancy rate. Mean age and weight at puberty were predicted from the cumulative distribution because of censoring of data in each tail of the distribution. Sire breed group rankings (and predicted means in days) for age at puberty were as follows: Piedmontese (332), Shorthorn (338), Charolais (348), REF HA (348), Galloway (351), 1980s HA (352), Salers (355), Longhorn (357), and Nellore (405). Sire breed group rankings (and predicted means in kilograms) for weight at puberty were Longhorn (283), Piedmontese (298), Galloway (305), REF HA (309), Shorthorn (329), 1980s HA (330), Salers (338), Nellore (341), and Charolais (345). Sire breed group rankings (and least squares means in kilograms) for 200-d weight were Charolais (229), Salers (225), Nellore (221), Shorthorn (220), Piedmontese (215), 1980s HA (215), Galloway (209), REF HA (206), and Longhorn (197), with differences8.3 kg significant. Rankings for 400-d weight (kilograms) were Charolais (390), Shorthorn (384), Salers (380), 1980s HA (374), Nellore (364), REF HA (356), Piedmontese (353), Galloway (348), and Longhorn (321), with differences11.5 kg significant. Rankings for 550-d weight (kilograms) were Charolais (445), Salers (430), Shorthorn (429), 80's HA (422), Nellore (420), Piedmontese (401), REF HA (398), Galloway (389), and Longhorn (371), with differences11.7 kg significant. Rankings for 550-d hip height (centimeters) were Nellore (132.2), Charolais (131.9), Salers (129.9), Shorthorn (129.5), Piedmontese (126.7), 1980s HA (126.1), Longhorn (125.3), Galloway (121.7), and REF HA (121.5), with differences1.35 cm significant. Breed of sire had significant effects on growth and puberty traits of heifers.

The present work describes an integrated, two-phase computer-based method for fabricating marine propulsors using stereolithography. This new methodology seamlessly integrates stereolithography rapid prototyping techniques with the hydrodynamic design, structural design, and prototype testing of advanced marine propulsors in order to greatly increase the design process efficiency and reduce development time. Its use as applied to the design, fabrication, and testing of advanced propulsor prototypes for small weapon’s-scale undersea vehicles (e.g., Unmanned Underwater Vehicles (UUVs), lightweight and heavyweight torpedoes, etc.) is described in order to demonstrate specific strengths of the new method.

A quantitative explanation is given of features of noise emitted by cicadas (classed as the loudest of all insects). Microphone data shows sounds are emitted in a sequence of closely spaced tone bursts. Listeners do not perceive the individual pulses because of the finite integration time of the ear. The principal sound radiators are two platelets referred to as tymbals, which vibrate after being struck by ribs that have undergone buckling. The energy of each sound pulse is initially stored in tensed muscles and is initially released via buckling into the kinetic energy of ribs, which strike the tymbals in a manner similar to that of a drumstick striking a drum. The tymbals “ring” at a frequency controlled by the mass of the tymbals and the springiness of the air cavity within the abdomen of the cicada. The wavelengths of the radiated sound are much larger than the tymbal radii but comparable to the overall dimensions of the cicada. The detailed theory explains the radiation pattern of the sound radiation, the amplitude of the sound, the number of cycles in each pulse, the radiation damping of the tymbal vibrations, and why the cicada is such an efficient radiator of sound.

Projection systems are considered where two or three frequencies (e.g., f1, f2, and/or f3) are simultaneously projected into water in a parallel fashion. High near-field amplitudes produce beams of frequencies equal to any linear combination of f1, f2, and f3, with integer coefficients n1, n2, and n3 (possibly zero or negative). Interest here is in the case where the magnitudes of the coefficients sum to three, associated with a third-order nonlinearity. The question addressed is that of how large the amplitude of the far-field signal will be. The considered causes of the nonlinearities are (1) the convective derivative term in the total time derivative of the fluid velocity, and (2) the higher coefficients in the expansion of the fluid density in terms of the deviation of the pressure from its ambient value. These coefficients are derived from data reported by Holton et al. [J. Acoust. Soc. Am. (1968)] on the sound speed in water. A perturbation technique is explored starting with the basic nonlinear equations of compressible time-dependent fluid dynamics, where at each step one has a simultaneous set of coupled linear and homogeneous equations with the source terms dependent on the solutions of the analogous equations corresponding to the previously considered orders.

Least squares means, genetic ( ug) and phenotypic ( ap) standard deviations, and pheno- typic coefficients of variation (CV) were estimated for growth traits of intact males from 12 breed groups combined, for nine purebreds combined, and for the F1, Fa, F3, and F4 generations of three composite populations to which the nine purebreds contributed. Heritabilities (h2) and genetic (rg) and phenotypic (Ip) correlations were estimated for growth traits, calving difficulty of calves with dams of different ages, and gestation length. Coefficients of variation and ug generally were similar for composites and contributing purebreds. Generally, estimates of h2 were similar for all breed groups combined, contributing purebreds combined, and composites combined. Estimates of h2 for calving difficulty were higher for calves with 2-yr-old dams than for calves with dams 2 3 yr old and were sufficiently high (.27 and .3 1) to be a useful selection criterion for reducing calving difficulty. Mean h2 pooled within all breed groups ranged from .35 for 200-d weight and 368-d weight to .48 for 368-d height. Estimates of h2 for subjective scores of anatomical traits were only slightly lower than those for growth and size traits. The h2 of scrotal circumfer- ence ( .43) was similar to those for growth and size traits. Genetic correlations between birth weight and calving difficulty were similar for 1 ) calves with dams of all ages, 2) calves with 2-yr-old dams, and 3) calves with dams 2 3 yr old. The rg of gestation length with birth weight was low (. 2 1) and was .57 and 54, respectively, with calving difficulty score and with percentage calving difficulty for calves with dams 2 3 yr old. Phenotypic correlations were relatively high among growth and size traits and were intermediate between birth weight and both expressions of calving difficulty in calves with 2-yr-old dams (.53 and .42) but were lower for calves with dams in other age classes.

Least squares means, genetic (sigma g), and phenotypic (sigma p) standard deviations, and phenotypic coefficients of variation (CV) were estimated on an age-constant basis for growth, carcass, and meat traits of castrate males from 12 breed groups combined, for 9 purebreds combined, and for the F3 generation of three composite populations combined to which the nine purebreds contributed. Also, heritabilities (h2) and genetic (rg) and phenotypic (rp) correlations were estimated among growth, carcass, and meat traits for all breed groups combined involving 1,594 individuals that were the progeny of 306 sires (214 purebred and 92 composites). Coefficients of variation and sigma g generally were similar for composites and contributing purebreds for growth and size-related traits. For traits relating to carcass composition and meat quality, means, sigma p, or CV for composites and contributing purebreds generally were similar. Generally, estimates of sigma g and h2 were similar among all breed groups combined, contributing purebreds combined, and composites combined. Generally, rg were high among all measures of carcass fat, indicating major difficulty in achieving a high percentage of retail product simultaneously with a high fat content of the longissimus muscle that is required for carcass quality grade. Generally, rp were of smaller magnitude than rg. All rp of marbling score or percentage of ether-extracted fat in the longissimus muscle with all end-use properties relating to palatability including shear force, and sensory evaluation of tenderness, juiciness, and flavor were below .30.

Since the pioneering work of Preston Smith, Jr. and Richard Lyon in 1959 in the development of the theory of Statistical Energy Analysis (SEA), followed by many others in the 1960’s on through today, the US Navy has utilized the important SEA vibro-acoustic simulation approach for high frequency self- and radiated-noise predictions of a multitude of undersea vehicles and systems. As a tribute to Preston Smith, this talk will review the current state of research in the determination of the variance/probability distribution about the mean response of a system modeled in SEA. While the subject of system response variance (or confidence interval) has obviously been of interest since the inception of this energy-based statistical method, there has been significant recent research in the literature advancing this area that is worth reviewing. As an additional acknowledgement of Preston Smith’s later important work in the area of underwater cylindrical shell acoustics, the current presentation will also revisit ...

Retained heterosis for different measures of gain efficiency was estimated in F3 generation castrate male progeny in three composite populations finished on two levels of dietary energy density (2.82 and 3.07 Mcal of ME and 11.50% CP) and serially slaughtered at four end points at intervals of 20 to 22 d. Breed effects were evaluated in nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 B, 1/4 C, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, and 1/4 A). Gain efficiency was evaluated in time constant (0 to 207 d), gain constant (310 to 540 kg), carcass weight constant (333 kg), and retail product weight constant (225 and 210 kg) end points and to different marbling score and longissimus muscle fat end points. Expressions of gain efficiency included live weight gain/megacalories of ME and retail product weight/megacalories of ME. Significant differences were observed among breeds in all measures of gain efficiency. Breeds that had the smallest weight to maintain tended to be more efficient in live weight gain in the time constant period, whereas breeds with the highest rate of gain tended to be more efficient in the gain constant period. To marbling score or longissimus muscle fat end points, breeds with the lowest marbling scores and smallest percentage fat in the longissimus muscle on an age constant basis (e.g., Limousin and Gelbvieh) tended to be less efficient, whereas breeds with the highest marbling score and highest percentage of fat in the longissimus muscle on an age constant basis (e.g., Hereford and Angus) tended to be more efficient. Breeds with the highest percentage of retail product (Limousin and Gelbvieh) were more efficient to retail product weight end points, or when retail product weight was the measure of output. Steers fed the higher energy density diet were more efficient in live weight gain to time constant, live weight gain constant, marbling score constant, and longissimus fat constant end points and were more efficient in the production of retail product weight to retail product weight end points because of the shorter period of maintenance. Retained heterosis was not consistent among composites in different measures of gain efficiency. Higher initial weights resulting in greater requirements for maintenance had a negative effect in composites for most measures of gain efficiency.

Recent research in very high speed underwater vehicles shows they require a much more streamlined vehicle nose than the present rather flat tactical scale vehicle nose. It has been found that the common forward‐facing transducer array with a constant thickness array window utilized on current lower speed vehicles is inadequate. Two newer alternate front‐end array concepts suitable for lower drag, higher speed vehicles being investigated are (a) a variable thickness, streamlined array window on a flat forward facing array and (b) a streamlined vehicle nose structure consisting of a built‐in distributed, conformal array. While these highly streamlined concepts are attractive from the standpoint of reducing vehicle drag at higher speeds, both require reexamination of the effects of high curvature on front‐end sonar array performance. In the present paper, both above streamlined array concepts are numerically examined using the sara2d dynamic structural‐acoustic Finite Element Analysis (FEA) code. First, the ...

Statistical energy analysis (SEA) modeling has been utilized for decades toward the prediction of both self‐ and radiated noise behaviors of undersea vehicles such as submarines, torpedoes, and unmanned underwater vehicles. Since these vehicles operate in a semi‐infinite or infinite seawater environment, it is difficult in SEA to account for any “intra‐model” acoustic propagation through this infinite seawater path. For example, an important source of undersea vehicle self‐noise arises due to acoustic propagation through the seawater environment from the vehicle’s aft propulsion system to the vehicle’s nose where the array is oftentimes located. To date, there has been no standard method published in the literature for how to accurately handle this important acoustic propagation path in SEA. The present paper investigates and compares several approaches that have been employed for properly accounting for aft‐to‐forward acoustic propagation through this infinite seawater environment path both for fully‐wetted and supercavitating, high‐speed undersea vehicle SEA models. A new hybrid method employing both finite acoustic volume and semi‐infinite SEA acoustic elements has recently shown promise and is presented for discussion.

Heterosis effects were evaluated as traits of the dam in F2 progeny of F1 dams and F3 and 4 progeny of F2 and 3 dams in three composite populations of beef cattle. Traits included birth weight, birth date, calving difficulty percentage, and survival percentage at birth, 72 h, and weaning for calves with dams of different age classes. Breed effects were evaluated for the nine parental breeds (Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 C, 1/4 B, 1/4 L, 1/4 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Among calves with 2-yr-old dams, breed effects were significant for birth weight, birth date, calving difficulty percentage, and survival percentage at birth but not at 72 h and weaning. Calf survival at weaning was lowest for smallest (less than mu - 1.5 sigma) and largest (greater than mu + 1.5 sigma) birth weight classes and did not differ among intermediate birth weight classes. Calves with difficult births with 2-yr-old dams were significantly heavier at birth (39.6 vs 35.4 kg) and had significantly lower survival at 72 h (87.1 vs 92.2%) and at weaning (77.4 vs 85.1%) than calves with 2-yr-old dams that did not experience difficult births. Among calves with dams greater than or equal to 3 yr old and from dams of all ages, breed group effects generally were significant for the traits analyzed. Important breed group effects on dystocia and survival traits were observed independent of breed group effects on birth weight. Effects of heterosis were significant for birth weight for each generation of each composite population and for the mean of the three composite populations. Generally, heterosis effects for calving difficulty percentage were not significant. Effects of heterosis generally were significant for date of birth (earlier) for each composite population and for the mean of the three composite populations. Heterosis effects on survival to weaning percentage generally were positive but generally were not significant. Heterosis retained for birth weight, birth date, and survival percentage in combined F3 and 4 generation progeny of combined F2 and 3 generation dams did not differ (P greater than .05) from expectation based on retained heterozygosity. These results support the hypothesis that heterosis in cattle for these traits is the result of dominance effects of genes.

Heterosis effects for birth weight, ADG from birth to weaning, 200-d weight, ADG from weaning to 368 d, 368-d weight, 368-d height, 368-d condition score, and 368-d muscling score (males only) were evaluated separately for each sex in F1, F2, and combined F3 and F4 generations in three composite beef cattle populations. Breed effects were evaluated for the nine parental breeds (i.e., Red Poll [R], Hereford [H], Angus [A], Limousin [L], Braunvieh [B], Pinzgauer [P], Gelbvieh [G], Simmental [S], and Charolais [C]) that contributed to the three composite populations (MARC I = 1/4 C, 1/4 B, 1/4 L, 1/8 H, 1/8 A; MARC II = 1/4 G, 1/4 S, 1/4 H, 1/4 A; and MARC III = 1/4 R, 1/4 P, 1/4 H, 1/4 A). Breed effects were significant for all traits evaluated. The large differences among breeds for growth and size traits in combined additive direct and additive maternal genetic effects (Gi + Gm) provide an opportunity to use genetic differences among breeds to achieve and maintain optimum additive genetic (breed) composition for growth and size traits to match cattle genetic resources to a wide range of production and marketing situations. Combined individual and maternal heterosis was significant in the F1, F2, and combined F3 and F4 generations for each composite population and for the mean of the three composite populations in both sexes for most of the traits evaluated. In both sexes, heterosis retained in combined F3 and F4 generations was greater (P less than .05) than expected based on retained heterozygosity for birth weight, ADG from weaning to 368 d, and for 368-d weight and did not differ (P greater than .05) from expectation for other traits. These results support the hypothesis that heterosis in cattle for traits related to growth and size is due to dominance effects of genes.

Records of 328 Angus, Hereford, Shorthorn, and first-cross cows produced from 1960 to 1963 were used to estimate heterosis (h) and individual (gI) and maternal (gM) average breed effects on cumulative survival (CS) by ages to 12 yr, longevity (L), and size (SI) and condition of incisors at 10 to 15 yr of age. Reasons for cow disposal were also studied. The 155 cows born in 1960 and 1961 first calved at 3 yr of age, and the 173 born in 1962 and 1963 first calved at 2 yr of age. Analyses for CS and L were done for both actual culling of cows open in two consecutive years (AC) and imposed culling of any open cow (IC). The model for CS and L included cow birth year-breed of cow's sire (Y-S), sires within Y-S, breed of dam (D), and D x Y-S. For SI, the model included breed of cow, year of recording, and quadratic effect of age. Linear contrasts were used to estimate h, gI, and gM for quantitative variables, and chi-square was used for discrete variables. Under both AC (P less than .05) and IC, crossbreds exceeded straightbreds in CS to 12 yr (16.7 and 8.5%) and L (1.36 and .99 yr). Estimates of gI and gM for CS and L were generally small, except for the low (P less than .05) gM of Shorthorn cows under IC. Mortality and culling for emaciation, cancer eye, or prolapse was less for crossbreds than for straightbreds and increased with age. Crossbreds had longer (P less than .01) and better (P less than .001) teeth than straightbreds. The longer productive life of crossbred cows reduces rearing costs for replacements and increases sales of calves and cull cows.

The effects of heterosis for gestation length, dystocia, calf survival, birth weight, 200-d weight, and ADG from birth to weaning were evaluated in F1, F2, and combined F3 and F4 generations in three composite populations. Breed effects were evaluated for the nine parental breeds (Red Poll, Hereford, Angus, Limousin, Braunvieh, Pinzgauer, Gelbvieh, Simmental, and Charolais) that contributed to the three composite populations. Breed effects were significant for all traits evaluated except survival at birth. The large differences among breeds in additive direct and additive maternal genetic effects offer a great opportunity to use the genetic differences among breeds to achieve and maintain optimum additive genetic (breed) composition to match genetic resources to a wide range of production-marketing ecosystems. There was no heterosis for gestation length. Mean heterosis for dystocia was significant estimated in F1 but not in F2 or in the combined F3 and F4 generations. Mean heterosis was not significant in any generation for survival at birth, to 72 h, and to weaning for the F1 generation; mean heterosis was significant for survival to weaning for the F2 generation and approached significance (P = .06) for the combined F3 and F4 generations. Mean heterosis over all composite populations and heterosis for each composite population were significant in all generations for weight at birth and at 200 d and for ADG from birth to weaning. Retained heterosis was not less than expected from retained heterozygosity in composite populations for the traits evaluated. These results suggest that heterosis for these traits likely is due to dominance effects and, thus, can be attributed to the recovery of accumulated inbreeding depression in the parental breeds.

The literature is full of technical papers that have examined the free vibration of cantilevered Bernoulli‐Euler beams with both rigidly and elastically‐attached point masses at the free end. Additionally, much work has been published in the last ten years on cantilevered Timoshenko beams (which includes the effects of shear deformation and rotatory inertia) with a similar, yet more restricted, set of free end boundary conditions. Rossit and Laura published in the Journal of the Acoustical Society of America in 2001 a formulation for a Timoshenko beam with a simple single DOF spring‐mass system attached to the free end. The present paper extends Rossit and Laura's mathematical formulation to account for a general, damped, multi‐DOF system point‐connected to a cantilevered Timoshenko beam's free end. To demonstrate the formulation, mathematical relations and numerical results for a single DOF damped system and both damped/undamped 2DOF vibration absorbers are presented.

An evaluation of natural twinning in beef cattle revealed that cows birthing twins had shorter (P less than .01) gestation lengths, more (P less than .01) retained placentas, more (P less than .01) dystocia, more (P less than .01) days to estrus, lower (P less than .01) conception rates and more (P less than .01) days to pregnancy than cows birthing singles. Days to estrus, conception rate and days to pregnancy were not affected by number of calves reared (1 vs 2) in cows birthing twins. Survival at birth was greater (P less than .01) for single- than for twin-born calves, but twins and singles did not differ (P greater than .05) in postnatal survival. When dystocia was experienced, calf survival at birth was 95% vs 73% for singles vs twins compared with 99% vs 92% when no dystocia was experienced. Calves born twins were lighter (P less than .01) at birth, 100 d and 200 d, but twins and singles did not differ in postweaning gains. Total calf weights at 100 d per cow calving were 12% greater (P less than .01) in cows birthing twins vs singles when twin calves reared by foster dams were excluded. The potential increase in cow productivity for total calf weight at 100 d is 40% if calf survival rates of twins with dystocia relative to survival rates of twins without dystocia were comparable to survival rates of singles with and without dystocia, and if cows birthing twins were fed and managed to obtain conception rates equal to those of cows birthing singles. Identification of cows gestating twins to provide for their higher prepartum nutritive requirements and calving assistance at parturition is necessary to make twinning in cattle an economically viable technology.

Foundation cows were selected using prior records from one of two sources, private herds or other projects at the Research Center. Comparing twinning rates before and after selection, the repeatability was lower for those from the first (.08) than for those from the second (.16) source with a combined value of .12. Realized heritability of single-parity twinning rate estimated from selection of parents and response in daughters of foundation females was .06. Paternal half-sib estimate of heritability of twinning rate was .02 +/- .07. Estimates of repeatability computed from calving records of females born in the project indicate that permanent environmental effects on twinning rate in cattle are small. Mean calving rate of females born in the project was 1.11 in the data set that included all data and 1.09 in the data set that excluded females from highly selected parents. Twinning rate was greater (P less than .05) in fall than in spring calving (1.13 vs 1.06). Data on twinning rate of a sample of the Swedish Friesian breed were summarized. Mean twinning rate of the Swedish Friesian breed is 2.57%. Age adjusted mean twinning rate of daughters of 32 half-sib sons of one particular Swedish Frieisan sire averaged 5.4% and ranged from .9% to 13.6%. There was no indication of a bimodal distribution, which would be expected if a single gene with a major effect on twinning rate were segregating. The estimated genetic standard deviation (sigma-xn) for mean twinning rates of the 32 sire progeny groups was 1.8%. Observed range among son progenies was .127 or 7.2 sigma-xn, in reasonable agreement with the hypothesis that twinning rate in this population is inherited as a quantitative trait.

This 20-yr study, using 584 beef heifers born in the spring of 1984 or 1985, was conducted to determine whether selection for growth traits affected age and weight at puberty. Heifers were from three Hereford lines selected for weaning weight, final weight, and final weight plus muscling score, a control line and a line of Angus cattle. In addition, heifers from reciprocal crosses among the selection lines, control and Angus groups were evaluated. Intact bulls and androgenized heifers fitted with marking harnesses were used to aid in detection of estrus for heifers born in 1984 and 1985, respectively. The time of puberty was identified by the first behavioral estrus. During both years, heifers were weighed at 56-d intervals; these weights were used to calculate weight at puberty. Mean age at puberty was determined using survival analysis; percentages of heifers that were pubertal by the end of the study were transformed to logits for analysis. Heifers born in 1985 were heavier (P less than .05) at puberty than those born in 1984. Heifers in lines selected for growth traits were younger at puberty (P less than .05; 20 d) than were heifers in the control line because of combined direct and maternal genetic effects. Heifers from the final weight, control (P less than .05) and weaning weight lines (P less than .10) weighed less at puberty than Angus heifers; selection line x Angus crossbred heifers were heavier at puberty (P less than .05) than their respective pureline or purebred contemporaries due to heterotic effects. Selection for weaning weight, final weight or final weight plus muscling score did not have a detrimental effect on age at puberty in heifers.

The coupled structural, acoustic, and piezoelectric noise propagation physics within a layered 1‐3 composite, half‐wavelength resonator transducer array for high‐frequency, broadband underwater applications is modeled herein using dynamic finite element analysis (FEA). This analysis is being performed primarily to evaluate the complex steady‐state dynamic response of the multiple‐layered composite array in order to ensure bond structural integrity during high‐frequency operation. Specifically, various geometric configurations of the individual array layers will be examined to determine their effect on both array performance and structural integrity (e.g., relative PZT element spacing between layers, bond materials, joining layer thickness). The results of the present analysis will also be compared to experimental data being collected on prototype layered 1‐3 composite arrays.