In this paper, recent results of ongoing studies into the effectiveness and predictability of particle damping are discussed. Efforts have concentrated on characterizing and predicting the behavior of a wide range of potential particle materials, shapes, and sizes in the laboratory environment, as well as at elevated temperature. Methodologies used to generate data and extract the characteristics of the nonlinear damping phenomena are illustrated with interesting test results. Experimental results are compared to predictions from analytical simulations performed with an explicit code, based on the particle dynamics method, that has been developed in support of this work.

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In this paper, the coupled electromechanical behavior of piezoelectric (PZT) stack active members has been studied to determine power consumption characteristics. The electromechanical admittance of a PZT stack active member has been derived and shown to be dependent on it's structural dynamics as well as on the dynamic characteristics of the host structure, which may be represented as a driving point structural impedance. The derivation of the coupled elec-tromechanical admittance of the device includes detailed modeling of the influences of the actuator housing, fixture, and host structure. These theoretical predictions were tested experimentally and good correlation was found. Additionally, a simple numerical case study was performed to demonstrate the utility of the analysis technique presented in this paper by determining the power consumption of a mechanical system (modeled as a single-degree-of-freedom spring-mass-damper system) driven by the PZT stack active member. The analysis approach presented in this paper is important for the design of active control systems, in particular for the design of energy efficient active control systems for space structures.

The percentage of uncovered area in ultrathin diamond-like carbon (DLC) films on Si(001) wafers, which assesses the pinhole density of the carbon films, was quantified through angle-resolved X-ray photoelectron spectroscopy. The uncovered areas of the silicon substrate are oxidized upon contact with air, so the photoelectron signal from Si +4 could be used for this quantification. The pinhole density exhibited a strong dependence with the growing conditions of the carbon film, even for films of similar thickness. The detection limit of the technique is set by the photoelectron signal noise level, and by the accuracy in the accounting of the background signal. Copyright  2007 John Wiley & Sons, Ltd. KEYWORDS: carbon protective film; ARXPS; pinhole density; disk drive; DLC; FCA Ultrathin diamond-like carbon (DLC) films are suitable for surface protection due to their high degree of hardness and wear resistance, low friction coefficient and chemical inertness. In the data storage industry the DLC thin films are routinely employed to mechanically protect the magnetic heads and disks from corrosion and wearing. As the magnetic area density advances toward one terabit per square inch, it becomes necessary for a DLC film to provide sufficient protection in a thickness range of 1-2 nm. It is a grand challenge for both magnetic disk and head overcoats to achieve such a goal and to meet the industry magnetic spacing roadmap.1 The conformity and integrity of ultrathin DLC film is of particular interest because in 1-2 nm thickness ranges most DLC films fall short of corrosion protection (see Fig. 1). The quality of this protection is believed to be related to the pinhole density and/or the coverage of the ultrathin DLC films. The performance of the protective carbon films is influenced not only by the allotropic composition of the film but also by their distribution throughout the film thickness and the areas left uncovered (these unprotected areas are usually described as pinholes substrate (roughness and cleanliness in particular) and DLC film integrity. In this article, the application of the angle resolved X-ray photoelectron spectroscopy (ARXPS) on DLC pinhole study is described. ARXPS is a natural candidate because it is especially suitable to characterize films in this thickness range. In addition, it is a nondestructive technique.The three samples studied (FCA-C, DLC-E and DLC-M) were ultrathin carbon films grown under different conditions on Si(001) substrates. FCA-C sample was prepared with the filtered cathodic arc deposition technique; whereas the DLC-E and DLC-M samples were prepared with ion beam deposition using ethylene gas and methane gas, respectively. The Si(001) substrates were etched in ultrahigh vacuum to remove the naturally grown SiO 2 prior to the carbon deposition. The material properties of these films are summarized in Table 1. It should be noticed that these properties were measured in thicker films (¾500Å) grown under the same conditions but on Ge substrates, and that the actual numbers might d...