Motor development

A field eontrolled d.e. motor develops a torque Tm t) proportional to the field eurrent k t). The rotating parts have a moment of inertia / of 1.5 kg m and a viseous damping eoeffieient C of 0.5 Nm s/rad. 

Constant-speed motors are usually suited for a speed range of less than 3 to 1 by field control, but mechanical and electrical characteristics govern maximum safe speeds. With constant voltage on the armature, as the field is weakened the speed increases and the motor develops constant horsepower. 

The 1 hr, 50°C open motors develop constant horsepower over the entire speed range. Semienclosing covers can be added without changing the rating. 

The 40°C continuous-rated open motors develop the rated horsepower from 150% of minimum speed to the maximum speed. From minimum speed to 159% of minimum speed, the rated horsepower will be developed continuously without exceeding safe temperature limits. 

Tapered horsepower motors develop the maximum rated horsepower at three times the minimum speed, the horsepower decreasing in direct proportion to the decrease in speed down to the horsepower rating at 150% of the minimum speed. Figure 3-12 plots characteristics of shunt, series, and compound-wound direct-current motors. 

The evaluation results are mildly worrisome however, the quality of the infants behaviors are very worrisome. In the area of fine motor development, the infants performed in the low normal range. Furthermore, the items used to score fine motor behaviors do not identify deviant movements required for the fine motor act. For instance, each of these infants displayed abnormal movement... 

Bellinger DC, Needleman HL, Leviton A, et al. 1984. Early sensory-motor development and prenatal exposure to lead. Neurobehav Toxicol Teratol 6 387-402. 

Dietrich KN, Berger OG, Succop PA. 1993b. Lead exposure and the motor development status of urban six-year-old children in the Cincinnati Prospective study. Pediatrics 91 301-307. 

Duchenne and Becker muscular dystrophies (DMD and BMD) are X-linked, allelic, neuromuscular diseases. DMD/BMD are characterized by progressive muscular weakness and degeneration of skeletal muscle. DMD is the most common recessive lethal disease, with an incidence of approximately 1 in 3500 newborns, and according to estimates, one-third of the cases are linked with new mutations (M3). Clinical symptoms of the disease appear earlier, by 2 to 3 years of age, in the form of retarded motor development. Progressive symptomatic children show weakness and wasting of muscle and are usually wheelchair bound approximately by the age of 11-12 years. It has been reported that most patients die at about the age of 20 due to pneumonia, which is related to chronic respiratory insufficiency. BMD—being the rarer allelic disorder—has a milder clinical course with slower disease progression. The BMD-affected patients usually survive beyond the age of 30. 

Prenatal exposure to ethanol results in a spectrum of abnormalities including, at one extreme, fetal alcohol syndrome, which includes growth retardation, facial anomalies, mental retardation, and microencephaly. Children with less severe prenatal exposures often lack the characteristic facial features of fetal alcohol syndrome, but suffer from a similar pattern of cognitive deficits (Berman and Hannigan, 2000). Mild exposures are associated with variable deficits in motor development and functional delays (Levitt, 1998). 

Western States Sect Combust Inst, Paper, WSCI 65-23 (1965) 27) G.R. Mistier T.F. Seamans, Vacuum ignition characteristics of flox/diborane and oxygen difluoride/diborane, NASA Contract Report 1969, NASA-CR-100678. Avail CFSTI. From SciTechAerosp Rep 7 (12), 2196 (1969) 28) W.B. Powell et al, ClFj-Njli, liquid propellant evaluation and rocket motor development, TechRept 32-305, Jet Propulsion Lab, Calif Inst Tech, Pasadena, Ca, (May 1963) (NASA N63-21722) 29) H. Allen, Jr Pinna, Relative ignitability of typical solid propellants with C1F3, NASA TN-D-1533, NASA, Wash, DC, (Jan 1963) (NASA N63-11616) 30) R.F. Sawyer et al, AIAA J, 6, 11, 2111 (1968) CA 70, 13118 (1969) 31) M.C. Branch ... 

Mathematical Model. Initial attempts have been made to apply the least sophisticated form of the mathematical model of the curing process to some actual problems. Thus far, the results have served merely to provide qualitative guidance to the selection of the process variables for a limited number of new motor development programs. Sufficient experience with the use of the mathematical model has not yet been accumulated to provide quantitative verification of its validity. 

BA-107. Polybutadiene-Acrylic Acid Composite Propellant tot Rocket Motors developed by Thiokol Chemical Corp. Its compn and props are given in conf Propellant Manual ,SPIA/m2 (1959), Unit No 572 B(AM) or BAm(poudre). 

BF.122 BF.I51 are composite polysulfide pro-pints for rocket motors developed by the Thiokol Chem Corp. Their compn props are given in conf Propellant Manual,SPIA/M2( 1959),Unit Nos 570 571... 

Some patients exhibit cores that are smaller and shorter (longitudinally) than the cores observed in central core disease and that occur both in slow and fast type muscle fibers (Ferreiro 2002b Robinson 2006). These cores are referred to as multicores or minicores and patients with myopathic symptoms (e.g. proximal muscle weakness, delayed motor development, difficulty rising, etc.) along with these corelike structures are said to have multiminicore disease (MmD). Considerable overlap... 

Women who smoke marijuana during pregnancy may have low birth-weight babies who are at risk for developmental difficulties and are more susceptible to disease. Like other drugs, THC also crosses the placental barrier and affects the embryo as it grows some studies indicate that this may increase a baby s risk of developing leukemia. THC also passes into breast milk, where research has shown that it can affect a child s motor development. Toddlers whose parents smoke marijuana have been found to be angrier and to have more behavioral problems than children whose parents do not use marijuana. 

Richardson, G. A., Day, N. L., and Goldschmidt, L. (1995). Prenatal alcohol, marijuana, and tobacco use Infant mental and motor development. Neurotoxicol. Teratol. 17, 479-487. 

Gasoline containing tetraethyllead as an antiknock additive was first sold by General Motors Development Co. in Dayton, Ohio, in February, 1923. Ethyl Gasoline Corporation was formed to exploit the antiknock business by General Motors and Standard Oil in August of 1924. Commercial production of tetraethyllead was begun for them by... 

From this expression it is seen that the thrust does not depend at all on the combustion temperature Tr. but depends mainly on the dimensions of A , and A . and on the chamber pressure I. . In other words, the thrust that a rocket motor develops does not depend upon the particular choice of propellants, but upon the chamber pressure. The designer controls the pressure level of operation by the amount of propellants choSen to be injected. In fact, if it were not for the slight dependence of y on the combustion products, then the thrust level of a rocket engine could be considered entirely independent of the propellants used. 

In other words, the thrust that a rocket motor develops does not depend upon the particular choice of propellants, but upon the chamber pressure. 

Dancis, Levitz, and Westall (1960) collected further data that led them to propose the biochemical defect shown in Figure 18-28. In one case, they examined a patient whose urine first showed the maple syrup odor when he was 4 months old. At the age of 10 months (March 1956), the child was admitted to the hospital because he had a fever, and he showed grossly retarded motor development. 

PCBs with a more globular structure elicit effects similar to phenobarbital. These include induction of the isozyme CYP2B, carcinogenic promoter activity8 7 and neurotoxicity. Developmental neurotoxicity of PCBs in animals is consistent with findings in children and results in persistent behavioural and neurological effects, notably alterations in motor development and cognitive function.88 The... 

A second report from the Maternal Lifestyle Study focused on motor development in 392 children prenatally exposed to cocaine and 776 non-exposed control infants who were identified by meconium assay and mothers self-reporting (327). Motor skills were assessed at 1 month with the NICU Network Neurobehavioral Scale (NNNS), at 4 months with the posture and fine motor assessment of infants (PFMAI), at 12 months with the Bayley Scales of Infant Development-2nd edition (BSID-II), and at 18 months with the Peabody Developmental Motor Scales (PDMS). The infants with prenatal cocaine exposure had motor skill deficits at 1 month, but normal function at 18 months. Heavy cocaine use was associated with poorer motor performance. Both lower and higher nicotine exposures related to poorer motor performance. 

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