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A hybrid material created by mechanically combining polymers and aluminum foams is modeled and analyzed. The hybrid is manufactured by injection molding a polymer (polypropylene and acetal) into the open cells of Duocel® aluminum foam. Prior experimental work revealed that the combination of the polymer and the metal foam yields a hybrid that is stiffer than the polymer alone but has a reduced ultimate tensile strength. A finite element model using a tetrakaidecahedral unit cell is used to model the metal foam ligaments with the polymer occupying the remaining space. The resulting conclusions are that the aluminum ligaments oriented along the load direction cause an increase in stiffness but ligaments oriented laterally cause stress concentration that yield lower strength. The finite element model is used to give both qualitative and quantitative explanations of the physics of the interrelations between the metal foam and the polymer.

A type of interpenetrating phase composites was formed by impregnating 90%-porous open-cell aluminum foam with polypropylene through an injection molding process. Three aluminum foams were used having three distinct linear pore densities: 10, 20 and 40 pores per inch (ppi) or roughly 4, 8 and 16 pores per cm. Samples taken from these composites were tested for flexural strength and stiffness based on ASTM D790-03. Flexural modulus and strength of the composite are compared to those of unreinforced polypropylene. The results showed, in general, the combination of the polymer and metal foams to be stiffer than either of the two individual components. The stiffness of the composites was found to increase with decreasing pore size. The smaller pore size allowed more cells to exist across the thickness of the specimen, and thus increased the bending stiffness of the composite.

The paper presents how a U.S. university was able to implement curricular content in a specially designed engineering course to teach students critical non-technical skills of the engineers of 2020, as described by educational, industrial and governmental organizations. The course targeted issues that directly affect the engineering profession, i.e., nature of the knowledge-based economy, the nature and need for innovation, the various kinds and advantages of entrepreneurship and business models associated with it, public speaking and communication skills, working in teams, and the need for life-long learning. The course also included content targeting the ability for an engineer to manage his/herself with a corporate setting in today's knowledge-based economy. This paper describes the course design, content and rubric that were used to assess some of the course outcomes, as well as the results of the assessment. In general, the results show that the vast majority of students agreed that the course had been effective in teaching and making them aware of.

This paper presents experimental validations of the Helmholtz Equation Least Squares (HELS) method [Wang and Wu, J. Acoust. Soc. Am. 102, 2020-2032 (1997); Wu and Wang, U.S. Patent Number 5712805 (1998); Wu, J. Acoust. Soc. Am. 107, 2511-2522 (2000)] on reconstruction of the radiated acoustic pressures from a complex vibrating structure. The structure under consideration has geometry and dimensions similar to those of a real passenger vehicle front end. To simulate noise radiation from a vehicle, a high fidelity loudspeaker installed inside the structure at the location of the engine is employed to generate both random and harmonic acoustic excitations. The radiated acoustic pressures are measured over a finite planar surface above the structure by a microphone. The measured data are taken as input to the HELS formulation to reconstruct the acoustic pressures on the top surface of the structure as well as in the field. The reconstructed acoustic pressures are then compared with measured ones at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the surface. Results show that satisfactory reconstruction can be obtained on the top surface of the structure subject to both random and harmonic excitations. Moreover, the more measurements and the closer their distances to the source surface, the more accurate the reconstruction. The efficiency of the HELS method may decrease with increasing of the excitation frequency. This high frequency difficulty is inherent in all expansion theories.

The purpose of this study is to attempt the induction of early immunopotentiation of antibodies specific to fimbriae of Salmonella enterica serovar Enteritidis (SE), by administering thymulin and zinc to SE-vaccinated chicken breeders, and the improvement of protection against a controlled-live challenge by SE. The first two groups of breeders were administered subcutaneously at 15 and 19 weeks of age a killed SE vaccine. Breeders of the third and fourth groups were left unvaccinated. Breeders of the first group, immunopotentiated by thymulin and zinc, were able to induce the earliest antibodies in their pooled sera at 2 weeks post the first SE-vaccination, specific to fimbriae (approximately 21 KDa) of SE. However, the second group that was only vaccinated with the same SE-vaccine produced specific antibodies to fimbriae at 3 weeks following the second vaccination (22 weeks of age). Breeders of the third group, that were neither SE-vaccinated nor immunopotentiated by thymulin and zinc, but were challenged by live SE at 22 weeks of age, were able to show specific antibodies to fimbriae at 3 weeks post challenge (25 weeks of age). The fourth group that was deprived of SE-vaccination, immunopotentiators, and challenge didn't show any background antibodies specific to SE-fimbriae. The presence of the earliest antibody-immunopotentiation to fimbriae of SE in breeders of the first group, administered thymulin and zinc, was associated with the lowest frequency of SE-infected ceca (10%) among the challenged groups. In addition, breeders of the first group were the only challenged birds resulting in absence of SE infection in their cecal tonsils. The first group-vaccinated, immunopotentiated, and challenged, and the second group-vaccinated and challenged only resulted in breeders with absence of SE infection in their oviducts and spleens. In conclusion, immunopotentiation of chicken breeders by thymulin and zinc induces the earliest specific antibodies to fimbriae of SE associated with the lowest frequency of SE-infected ceca, and absence of SE infection from cecal tonsils, oviducts and spleens.

This paper describes the design, construction, and simulation of a prototype, teleoperated, omnidirectional robotic ground vehicle. The design of a dynamic control system to assist the human operator of the vehicle is also presented. This work sought to test the feasibility of a novel vehicle architecture and to develop a dynamic multi-body simulation tool to assist in the development of future iterations of such a vehicle. The vehicle design seeks to achieve high-speed, omnidirectional mobility, and modest off-road capability. This paper presents results from the physical operation and simulation of the vehicle as well as describing some future work to achieve improved performance of the vehicle system.Copyright © 2012 by ASME

Asthma is a major cause of morbidity in childhood, restricting activity and causing absences from school. Theophylline, although effective in managing chronic asthma, has been reported to cause deficits in cognitive functioning and school performance. We therefore examined the effect of asthma and its treatment on academic achievement in a large, representative population of school-age children; matched sibling controls were used for comparison.We identified 255 consecutive children with asthma (mean age, 12.0 years) who had taken nationally standardized scholastic achievement tests administered routinely by the schools. One hundred one of these children had siblings without asthma with whom comparisons could be made in reading, mathematics, and a composite measure of achievement.Academic achievement among the children with asthma was similar to normative standards in Iowa and higher than national standards, as reflected in a mean composite T-score of 57.1 (expected mean [+/- SD], 50 +/- 10). For the 101 children with sibling controls, composite T-scores were 58.3 for the children with asthma and 57.5 for the siblings. Eighty-five of these 101 children with asthma were receiving daily maintenance medication for chronic asthma; 72 of these were receiving theophylline. The mean composite T-scores were 58.5 for the theophylline-treated patients and 58.4 for their siblings without asthma. None of the differences between the children with asthma and the sibling controls were statistically significant.Academic achievement among children with asthma, at least those whose status is closely monitored in a structured treatment program, generally appears to be unaffected by asthma or by its treatment with appropriate doses of theophylline.

A hybrid material consisting of an interpenetrating phase composite of aluminum foam and thermoplastic polymer was made and tested for its basic tensile mechanical properties. The material was made by injection molding a polymer (two polypropylenes and an acetal were used) through a Duocell aluminum foam (10% relative density and 10, 20 and 40 pores per inch linear densities). The material is referred to as an Aluminum Foam Polymer Composite (AFPC) and involves the aluminum foam and the polymer occupying the same volume. The continuous, interconnected morphologies of the two phases (aluminum foam and polymer) sets this type of material apart from regular composites. The AFPC exhibited an increase in stiffness, a reduction in strength and less ductility than the parent polymer. A basic mathematical model and a discussion of the physics were used to shed some light on the behavior of this material.Copyright © 2009 by ASME

The damping and basic dynamic properties of a novel type of multifunctional hybrid material known as Metal Foam-Polymer Composite are investigated. This material is obtained by injection molding a thermoplastic polymer through an open cell Aluminum Foam, in essence creating two contiguous morphologies; an Aluminum Foam interconnected “skeleton” with the open pores filled with a similarly interconnected polymer substructure. This coexistence of both materials allows each to contribute its salient properties (e.g. the plastics contributing surface toughness and the metal foams contributing thermal stability). Basic damping testing results are presented for various Aluminum Foam porosities and pore sizes as well as for three types of polymers. A basic mathematical model of the damping is also presented. The integrity of the interface between the Aluminum Foam and the Polymer is discussed in terms of its effect on the overall material damping.

This paper discusses the successes and struggles that we have encountered while integrating the two-semester capstone design sequence for both the electrical and computer engineering (ECE) and mechanical engineering (ME) departments at the University of Detroit Mercy (UDM). The ECE sequence has been based on a competition-motivated structure that focuses student efforts on the development of autonomous ground vehicles. The ME program, on the other hand, has used a model which tends to focus on product development. Two principal program changes are discussed - the integration and coordination of the two separate design programs to work on a single project and the addition of a parallel graduate-level design course. The program merger has yielded a stronger and more relevant student experience as well as better autonomous vehicle quality. It has also required the navigation of differences in design methodology, grading structures, and department/discipline cultures. The introduction of a graduate design course provided a strong multi-cultural influence and much needed technical sophistication that directly contributed to increased success at the competition. In this work then, we present the resulting design course structure and process, and provide a frank treatment of the associated successes and challenges.

The sound absorption properties of open cell aluminum foams are understood to be significant (Ashby et al. Metal Foams: A Design Guide, 2000) with theoretical models presented in the literature [J. Acoust. Soc. Am. 108, 1697–1709 (2000)]. The pores that exist in metal foams, as artifacts of the manufacturing process, are left unfilled in the vast majority of cases. Work done by the US Navy (US patent 5895726 A) involved filling the voids with phthalonitrile prepolymer, resulting in a marked increase in sound absorption and vibration damping. The work presented here involves adding small amounts of elastomeric rubbers to the metal foam, thereby coating the ligaments of the foam with a thin layer of rubber. The goal is to achieve an increase in sound absorption without the addition of cost and weight. The work involves testing aluminum foam samples of various thicknesses and pore sizes in an impedance tube, with and without the added rubber. A design of experiment model was employed to gauge the effect of the various manufacturing parameters on the sound absorption and to set the stage for a physics-based predictive model.

This paper presents visualization of acoustic radiation from a vibrating bowling ball using the Helmholtz equation least squares (HELS) method. In conducting the experiments, the ball is excited by a vibration shaker using stationary random signals. The radiated acoustic pressures are measured using two microphones and taken as input to the HELS formulations. The reconstructed acoustic pressures on the bowling ball surface are compared with those measured at the same locations. Also shown are comparisons of the reconstructed and measured acoustic pressure spectra at various locations on the bowling ball surface. Results demonstrate that the accuracy of reconstruction based on measurements over a conformal surface is much higher than that over a finite planar surface. This is because the latter often extends beyond the near-field region, making the accuracy of measurements inconsistent. Nevertheless, satisfactory reconstruction of acoustic pressure fields over the entire bowling ball surface can still be obtained based on the measurements taken over a finite planar surface on one side of the source. In a similar manner, the normal component of the surface velocity is reconstructed. Once these acoustic quantities are determined, the time-averaged acoustic intensity is calculated. Also presented are the formulations for estimating a priori the numbers of expansion functions and measurements required by the HELS method and the guidelines for determining the reconstruction error and optimum measurement locations, given the overall dimensions of the source and the highest frequency of interest in reconstruction.

Spherical wave function expansions as means of describing the acoustic field radiated by arbitrarily shaped objects are very convenient and gaining popularity. The HELS method for acoustic holography is one methodology advocating the use of spherical wave functions as a basis for the solution of the inverse acoustic problem. Such methodologies only provide an approximation to the actual sound field and as such suffer from errors, albeit understood to be bounded and manageable in a large number of cases. Based on the sound radiation model of a volume distribution of monopole sources, these approximation errors are found to be due to the presence of monopole sources outside the largest inscribed virtual sphere. Monopole sources outside that virtual sphere are not accounted for in the expansion and thus come out as errors. These errors are greatly reduced if the spherical wave function expansion is modified to account for the largest number of monopole sources in the model. This is accomplished by employing the addition theorem for spherical harmonics. This modification complicates the problem mathematically and might require a greater rate of physical sampling, however the reduction in the reconstruction errors might prove beneficial.

The spherical harmonics in conjunction with the spherical Hankel functions form a complete set of spherical basis functions, which can fully describe the radiated sound field from a vibrating object. The vibrating object itself need not be spherical as long as the exterior region is beyond a minimum sphere that completely encloses the object. Such expansion solutions are not supposed to be valid inside the minimum sphere. However, experimental results [Rayess and Wu, J. Acoust. Soc. Am. 107] using the Helmholtz equation–least‐squares (HELS) method [Wang and Wu, J. Acoust. Soc. Am. 102] have shown that a modified set of spherical basis functions can accurately describe the sound field well inside the minimum sphere. That modified set is obtained by Gram–Schmidt orthonormalization of the spherical basis functions with respect to the source surface. It is shown that the velocity fields corresponding to these modified basis functions form an orthogonal and complete set, which can uniquely describe the velocit...

The damping and basic dynamic properties for a novel type of multifunctional hybrid material known as metal foam‐polymer composite are investigated. This material is obtained by injection molding a thermoplastic polymer through an open cell aluminum foam, in essence creating two contiguous morphologies, an aluminum foam interconnected “skeleton” with the open pores filled with a similarly interconnected polymer substructure. This coexistence of both materials allows each to contribute its salient properties (e.g., the plastics contributing surface toughness and the metal foams contributing thermal stability). Basic damping testing results are presented for various aluminum foam porosities and pore sizes as well as for three types of polymers. A basic mathematical model of the damping is also presented. The integrity of the interface between the aluminum foam and the polymer is discussed in terms of its effect on the overall material damping.

In most engineering applications, the acoustic fields are usually generated by multiple incoherent sources. When such acoustic fields are sampled and taken as input data to the Helmholtz equation least‐squares (HELS) formulations directly, the reconstruction might not be accurate. Hence there is a need to discriminate the contributions from individual sources and separate the composite sound field into a set of spatially coherent subfields that are also mutually incoherent. In this paper, we apply the principal component decomposition technique to the HELS method to reconstruct acoustic radiation from multiple incoherent sources in a free field. The key ingredients of this technique include a diagonalization by singular value decomposition (SVD) of the cross‐spectral matrices generated by a number of reference microphones. Each diagonal term corresponds to a subfield that results from a so‐called virtual sound source. Even though such virtual sources are not always representative of the actual sources, th...