Aerodynamic exciting forces have caused severe rotor whirl of axial compressors and turbines. One disturbing force investigated is due to circumferential variation of static pressure acting on the cylindrical surface of rotor, particularly within labyrinth seals. Another aerodynamic disturbing force is due to eccentricity of rotor causing circumferential variation of blade-tip clearance, and a corresponding variation of local efficiency and unbalanced torque. Seal deflection criteria and torque deflection criteria are presented as design guides for stable rotor systems. These criteria, the form of which comes from analysis of rotor dynamics, correlate design parameters of four examples of unstable rotor systems which exhibited whirl.
We present a brief measure of awareness of illness in schizophrenia and test whether awareness is related to perceived need for and adherence to outpatient psychiatric treatment. A prospective design assessed treatment adherence, awareness of the signs and symptoms of schizophrenia, symptoms, neurocognitive status, and substance abuse at baseline and 6-month follow-up in 89 persons with schizophrenia. Results indicate that persons with greater awareness perceived greater need for outpatient treatment and evidenced better adherence to outpatient treatment when adherence and awareness were measured concurrently. Awareness was not related to adherence at 6-month follow-up. In addition, neurocognitive impairment was associated with lower overall adherence to treatment when reported by collaterals at baseline and 6-month follow-up. Neurocognitive impairment was, however, associated with higher self-reported adherence to medication, which suggests that neurocognitive status may bias adherence reporting in persons with schizophrenia.
Resonance has been identified in several designs of stationary seals which have experienced failures. A resonant condition of the stationary seal occurs when the velocity of the rotating seal is equal to the velocity of propagation of the wave in the stationary seal. Self-excited vibrations have also caused fatigue failures particularly where damping is very small. Analysis of the mechanics of self-excited vibrations discloses a stability criterion which correlates pressure drop through seal with natural flexural frequency weight, and length. In addition to providing damping, the location of support of seal is shown to be of basic importance in preventing self-excited vibration.
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