Dynamics of Active Magnetic Thrust Bearings

A linear model considering the effect of eddy currents is shown to be useful for the analysis of the dynamics of active magnetic thrust bearings in which electromagnet cores are composed of solid steel. The dynamics of the magnetic control force are modeled by the first-order time-lag system with unknown parameters : gain and time constant. The parameters are estimated from experimental results that indicate the static relation between the coil current and the magnetic control force, and the frequency response of magnetic flux for an input signal to a power amplifier. The effect of eddy currents on the dynamics is confirmed by the frequency characteristlcs of magnetic flux for the coil current. Model simulations with estimated parameters are compared with experimental results, and good agreement is obtained in frequency response in a linear range and in impulse responses with rotor displacements smaller than half the air gap

The Clinical Features of Patients Requiring Surgical Treatment for Pediatric Intussusception

Abstract Purpose : This study was conducted to examine the clinical features of pediatric intussusception requiring surgical treatment. Patiants and Methods : Between January 1, 1989 and Jane 30, 1999, a total of 140 children with intussusception were referred to Yamaguchi University Hospital, 13 (9.3%) of whom underwent surgical treatment. The age, sex, duration of symptoms and signs, type of intussusception, lead points, and other clinical features were examined. Result : The median age of onset was 1 year and the median duration of symptoms was 21 h. Ileo-ileo-colic, ileo-colic, and ileo-ileo type intussusception were present in 6(46.2%), 7(53.8%), 1(7.7%), and 1(7.7%) patiants (23.1%) underwent bowel resection for bowel necrosis or lead points. Conclusion : Pediatric intussusception necessitating surgical treatment was often associated with accompanying appendiceal intussusception or a marked ileocecal band, or both, apart from organic lesions

Our 10-year Experience in the Management of Newborn Infants with Multiple Congenital Anomalies

Purpose : The incidence of multiple congenital anomalies has increased as a result of advances in prenatal and prenatal treatment. A review of all infants born with more than two congenital anomalies was conducted to identify the clinical feature.Methods : Between January, 1989 and December, 1998, a total of 35 neonates with multiple congenital anomalies were referrred to Yamaguchi University Hospital. The Combination of anomalies, manalies, management and clinical course, prenatal diagnosis and treatment, chromosomal anomalies, outcome, and quality of life these infants were examined retrospectively.Rｅｓｕｌｔｓ : Of these 35 infants, 9(25.7%) had chromosomal abnormalities in the form of trisomy 21 in 8, and trisomy 18 in 1. Prenatal　diagnoses were established in 10 infants (28.6%) and a fetal treatment was preformed in 1. There were four deaths (11.4%) caused by trisomy 18, pulmonary hypoplasia, or cardiac anomalies. Among the survivingpatients, two(6.5%) suffered from mental retardation caused by trisomy 21 or a brain anomaly. A total of 18 children (58.1%) required as mental training, defecation training, or medication review. Conclusion : Approximately one fourth of infants with multiple congenital anomalies had chromosomal abnormalities. Chromosomal abnomalities or cardio-pulmonary anomalies were death causes. More than half of children required long-term forrow-up. We should aim to provide well-plannned management to promote good long-term quality of life of neonates with multiple congenital anomalies