Search

Precision tilt and rotational isolation system design for inertial navigation sensor testing

The report is the result of a research study conducted on the Dynamic Antiresonant Vibration Isolator (DAVI). Theoretical analysis and experimental model correlation show the DAVI to be capable of over 98 percent isolation at very low frequencies with low static deflections; and at a tuned frequency, the transmissibility is independent of the isolated mass. Analysis and drop tests show that the DAVI gives better shock transmissibility for its fundamental mode than a conventional isolation system with the same spring rate.

Isolation chambers are considered essential for the study of methods of transmission of diseases among chickens. Drury et al. (1969) described an isolation system consisting of metal cabinets similar to the Horsfall-Bauer units, suitable for positive or negative pressure operation. Prince et al. (1967) described a plywood cabinet system used for isolating infectious bronchitis virus. While this system was used for some of the earlier experiments on the transmission of Marek’s disease, it had the disadvantage of providing an inadequate number of cabinets which were too large for the number of birds housed. The cabinets were difficult to clean which caused delays between experiments. It became necessary to develop a simple inexpensive isolation chamber which could be discarded after a single occupancy and yet provide a barrier against the transmission of Marek’s disease. The chambers were to house 5 to 10 chicks to four weeks of age. They were to…

Magneto-sensitive (MS) rubber is a kind of smart material, the shear modulus of it can be changed rapidly and reversibly by a magnetic field applied. A smart MS rubber-based isolation system and a nonlinear model based on this MS rubber-based vibration isolation system are developed in this paper. The influence of the amplitude, frequency and magnetic dependency for MS rubber, the mechanical inertance of infinite extended foundation, the mass of solid block and the dimension of MS rubber isolators are all considered in this model. The feasibility of two control strategies aimed at reducing the energy transmitted to the foundation and protecting machine against foundation motion, respectively, is investigated based on this smart vibration isolation system. It is found that compared to the traditional passive rubber isolators, an enhanced vibration isolation effect can be achieved by using MS rubber isolators after control strategies applied. Furthermore, the influence of the amplitude dependency and the response time of MS rubber to the isolation effect is studied. The nonlinear model established for MS rubber isolation system, the control strategies developed and the investigation for the amplitude dependency and the response time of MS rubber to the isolation effect in this paper provide fundamentals for the application of MS rubber in the field of vibration reduction.

An optimal design method based on closed-form analytical solutions is proposed for a liquid storage tank with inerter isolation system. The storage tank is modeled accounting for the flexibility of the tank wall, and isolated by the inerter isolation system composed of an inerter, a damping element, and a spring element connected between the same two terminals in parallel. The stochastic response of the storage tank with inerter isolation system, in terms of sloshing height and isolation displacement, is derived in closed form under the assumption of white-noise excitation. These analytical results are then used in an extensive parametric analysis to investigate the response variation pattern with respect to changes in the parameters of inerter system. In the extremum condition that represents the most efficient parameter set of inertance-mass ratio and damping ratio for response mitigation, an optimal design method is developed by exploiting a performance-demand-oriented design philosophy. The optimal design formulae of the inerter system are derived on the basis of target sloshing height mitigation ratio in analytical form. Moreover, a series of examples are provided to verify the proposed analytical design formulae and design criterion. Based on results from response history analysis under both artificial and natural ground motion records, the design method proves to be effective to meet the desired demand of sloshing height response, while simultaneously reducing base shear force and isolation displacement. The derived analytical design formulae are practical and convenient for preliminary design purposes and substantially explain the mechanism of inerter system for vibration control of liquid storage tank.

In the first part of this paper the objectives of an isolation system for a bridge structure are discussed, in relation to modelling options and modification of the traditional capacity design prin...

The burn eschar is the major source of infection in the severely burned patient, and it hampers healing and prevents skin grafting. Tangenital excision has been shown to be safe for rapid removal of the eschar. For the last 14 months we have used this method beginning about 7 days postinjury. Our burn unit is composed of a four-bed, horizontal, laminar airflow isolation system, and transfer out of the sterile environment to the operating room would expose the patient to airborne contamination. Intramuscular ketamine anesthesia was used to allow major debridement to be carried out in the unit itself. Forty-five patients aged 18 months to 71 years have undergone 150 excisions in the burn unit under anesthesia with no complications. The burns ranged from 20 to 75% of body surface (mean, 40%). Because ketamine is a cardiorespiratory stimulant, ventilation and vital signs were well maintained. Psychological side effects of ketamine were minimal, particularly in the younger age group.

Two tracks are mounted between a vibratory source of shear, or horizontally travelling, wave siesmic energy and its transport vehicle. The tracks are parallel to each other in the direction of horizontal movement of the source when vibrating. One track is attached to the source, and the other to the vehicle. Pressurized rounded resilient members, which may be either spherical bags or wide tires, are mounted between the tracks to isolate the vehicle from vibrations, insuring that the seismic energy enters the earth.

A vibration isolation system in which a supported body is supported from a vibration excitation body which is prone to vibrate at a predominant frequency and to impart such vibratory forces and motions to the supported body. The isolation system is of the antiresonant type and operable to provide vibration force and motion isolation of the supported body from the vibration excitation body both axially along and rotationally about three mutually perpendicular axes, thereby giving the supported body six degrees of vibration isolation from the vibration excitation body.

A National Research Council (NRC) panel has concluded that the technology for safely storing radioactive waste is ready for confirmation in a test facility. At the same time, the panel proposed safety standards that are more stringent than standards currently proposed by some government agencies. The report, Study of the Isolation System for the Geologic Disposal of Radioactive Wastes, was funded by the Department of Energy as part of its effort to comply with a Congressional mandate to open a national radioactive waste storage facility by the end of the century. The Waste Isolation Panel of the NRC's Board on Radioactive Waste Management did not choose a specific site for the first U.S. repository because the state of current technology does not allow the U.S. to design, construct, and safely operate a full-fledged site. However, the panel's chairman, Thomas H. Pigford, of the University of California at Berkeley, believes that the goal established by Congress can be met.

The effective rotational and translational stiffnesses of a set of isolators arbitrarily oriented with respect to the c.g. of an isolated rigid mass are developed by matrix techniques. Influence coefficients for determining isolator loadings due to arbitrary g loads are also presented in matrix form. Matrix equations of rigid‐body motion for a general isolation system are presented and conditions for decoupling translational and rotational motions are determined. The application of the matrix techniques developed to the design of vibration isolation systems is illustrated through several examples.

In estimating file effectiveness of a multimount isolation system, it is necessary to know the mobility or impedance characteristics of the machine, the mounts, and the foundation structure. As a first step in the study of estimating mount effectiveness, this paper considers the mobility characteristics of a machine idealized as a rigid body of simple geometrical shape having an arbitrary number of mounting points. Equations are presented for calculating the point and transfer mobilities at the mounting points of such idealized machines. Mobility measurements on a steel rectangular parallelopiped (an idealized model of a machine with approximately a block shape) of dimensions ratio 3×5×7 are compared with theoretical values. Several recommendations are made relevant to mobility‐coefficient calculation and to the problem of mount‐effectiveness estimation.