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This study deals with the perceptual sensitivity to Head-Related Impulse Responses (HRIRs) in the median plane based on a series of subjective listening tests using a pair of headphones. First, the non-individualized HRIRs were modeled from 12 principal components (PCs) extracted from Principal Components Analysis (PCA) of the CIPIC HRTF database. The Just Noticeable Difference (JND) in weight of PCs (PCWs) at each elevation was estimated. It was not observed the common elevation-dependent tendency or PCW-dependent tendency of JND in PCWs across the five subjects who participated in the tests, and the inter-subject variation of JND in PCWs was large. The JND in HRIRs can be estimated indirectly from the JND in PCWs because the HRIRs can be represented by a linear summation of the PCs weighted by PCWs. The common elevation-dependent tendency of JND in Directional Impulse Responses (DIRs), which are the mean-subtracted HRIRs, across the five subjects can be found. The change in PCWs does not seem to contribute to our perception of sound source characteristics; however, the resulting change in HRIRs due to the change in PCWs seems to contribute. The subjects showed larger JND in DIRs in the frontal region than in the rear region. This means that our perception of sound source characteristics is more sensitive for frontal sources than rear sources. [ABSTRACT FROM AUTHOR]

Preview control involves using forward road information acquired from preview sensors in designing a controller. Preview control, which is composed of feedback and feed-forward input parts can lead to better performance than feedback control alone. In this paper, application of the preview control based on the active suspension to tracked vehicles will be introduced. The suspension unit of the tracked vehicle is in the form of a trailing arm type to increase the wheel travel. Because the preview control has been developed for the linear time-invariant system, a linearized model of the system is required. A linear model of the tracked vehicle, which the preview controller is designed based upon, is generated without considering the dynamics of the track elements for simplification. On the other hand, the nonlinear model, which the performance of the controlled system is investigated based upon, is generated by using Recurdyn™, commercial software. The nonlinear model includes nonlinear damping and stiffness characteristics of hydraulic suspension units(HSUs). From the simulation results for RRC 9, performance enhancement of the preview control will be shown in terms of ride comfort by using ISO 2631 under the assumption that actuators are ideal and the velocity of the vehicle is constant. [ABSTRACT FROM AUTHOR]

Recently the authors tried to find damage position only using measured frequency response functions. According to their work, it seems that the algorithm is very practical since it needs only measured frequency responses while other methods require exact analytic model. But when applying the method to a real structure, it requires lots of experiment. The authors, in this time, propose a method to reduce its experimental load by detecting damage within a substructure. This method searches damages not within an entire structure but within substructures. In addition, damage severity was treated in this paper since it is worthy to know damage severity. Optimization technique is used to estimate damage level using measured responses and damage model. Two test examples, a plate and a jointed structure, are chosen to verify the suggesting method. [ABSTRACT FROM AUTHOR]

In this paper, the motion of a finger-follower type cam valve system with a hydraulic tappet was analytically and experimentally studied. First, the exact contact point between cam and follower for each corresponding cam angle was searched by kinematic analysis. Then a 6 degree of freedom lumped spring-damper-mass model was constructed to simulate the valve motion analytically. When constructing the model, most of the parameters were experimentally determined. But several values which are difficult to derive experimentally such as damping coefficients were determined with engineering intuition. In order to show the effectiveness of the analytical model, the predicted cam-valve motion was directly compared with the measured valve and tappet motions. [ABSTRACT FROM AUTHOR]