Resistance curves for crack growth under plane-stress conditions in an elastic perfectly-plastic material

A recently developed solution for the plastic strain, ε^P_y(x, t), on the crack line is used in conjunction with a critical strain criterion to construct curves for k_R(a) versus a, where a is the increase in crack length. Resistance curves have been computed for various values of the critical plastic strain. They show a monotonic increase of K_R(a) with increase in crack length, to a constant steady-state value.     

Behavioral and emotional problems among Thai and American adolescents: parent reports for ages 12-16

We studied adolescents' behavioral and emotional problems in the United States and in Thailand, a Buddhist country in which, reportedly, aggression is discouraged and self-control, emotional restraint, and social inhibition are encouraged. Standardized parent reports on 118 problems revealed 45 Thai-U.S. differences. Thai adolescents were reported to show more overcontrolled problems (e.g., shyness, compulsivity, inhibition of talking, fearfulness, and constipation) than American adolescents (p < .0001). The two groups did not differ reliably in total undercontrolled problems, but Americans showed higher levels of direct, overt, and interpersonally aggressive undercontrol (e.g., fighting and bullying), whereas Thais showed more indirect and subtle undercontrol that was not interpersonally aggressive (e.g., sulking and sullenness). The findings suggest that different cultures may be linked to different styles of adolescent problem behavior.     

Three-year course of behavior/emotional problems in a national sample of 4- to 16-year-olds: III. Predictors of signs of disturbance.

Tested parent-reported family variables, problems, competencies, and stress as predictors of (1) academic problems, (2) school behavior problems, (3) receipt of mental health services, (4) child's need for additional help, (5) suicidal behavior, (6) police contacts, and (7) the sum of these 6 outcomes. Included in the study were 995 cases manifesting at least 1 sign of disturbance (from Outcomes 1–6) and 995 matched controls from a national sample of 2,479 children assessed twice over a 3-yr interval. Path analyses identified predictors that were significant across age and sex plus those specific to particular groups. The predictive models accounted for medium to large effects in Time 2 signs of disturbance. Time 2 Child Behavior Checklist scores were significantly associated with all Time 2 disturbance scores. The multiple significant risk factors associated with signs of disturbance indicated variations in pathways leading to particular signs of disturbance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

About objective 3-d analysis of airway geometry in computerized tomography

The technology of multislice X-ray computed tomography (MSCT) provides volume data sets with approximately isotropic resolution, which permits a noninvasive 3-D measurement and quantification of airway geometry. In different diseases, like emphysema, chronic obstructive pulmonary disease (COPD), or cystic fribrosis, changes in lung parenchyma are associated with an increase in airway wall thickness. In this paper, we describe an objective measuring method of the airway geometry in the 3-D space. The limited spatial resolution of clinical CT scanners in comparison to thin structures like airway walls causes difficulties in the measurement of the density and the thickness of these structures. Initially, these difficulties will be addressed and then a new method is introduced to circumvent the problems. Therefore the wall thickness is approximated by an integral based closed-form solution, based on the volume conservation property of convolution. We evaluated the method with a phantom containing 10 silicone tubes and proved the repeatability in datasets of eight pigs scanned twice. Furthermore, a comparison of CT datasets of 16 smokers and 15 nonsmokers was done. Further medical studies are ongoing.     

Child/adolescent behavioral and emotional problems: Implications of cross-informant correlations for situational specificity.

Our purpose in this article was to determine the degree of consistency between different informants' reports of the behavioral/emotional problems of subjects aged from 1? to 19 years. We found 269 samples in 119 studies for meta-analyses of Pearson rs between ratings by parents, teachers, mental health workers, observers, peers, and the subjects themselves. The mean rs between all types of informants were statistically significant. The mean rs were .60 between similar informants (e.g., pairs of parents), .28 between different types of informants (e.g., parent/teacher), and .22 between subjects and other informants. Correlations were significantly higher for 6- to 11-year-olds than for adolescents, and for undercontrolled versus overcontrolled problems, although these differences were not large. The modest correlations between informants indicate that child and adolescent problems are not effectively captured by present-versus-absent judgments of problems. Instead, the variations between reports by different informants argue for assessment in terms of multiple axes designed to reflect the perceived variations in child and adolescent functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A dense electron target for the study of electron-ion collisions

A new high current (0.5 A), high density (0.3 $\text{A}\text{cm}{}^2$) electron gun has been designed for crossed beams electron-ion-experiments to yield high signal to background counting rates in the energy range 10–1000 eV. Comprehensive computer runs were performed to assure a uniform electrostatic potential in spite of the high electronic space charge. Trapped ions can be used to compensate this space charge, because their contribution to the counting rate is well discriminated below the threshold of the process to be studied. The overlap integral is determined by sweeping the whole electron gun perpendicular to both beams across the ion beam, which is possible, because the interaction region potential extends in perpendicular direction of both beams and sweeping therefore does not affect ion beam transmission. The accuracy and the reproducibility of cross section measurements with this new gun is demonstrated by a comparison with data from Harrison's group, exhibiting “perfect” agreement.     

The propagation of stress discontinuities according to the coupled equations of thermoelasticity

Summary The method of the characteristics is used to study the influence of thermomechanical coupling on the magnitudes of discontinuities at the wavefronts of dilatational waves. A set of unified equations is employed, which is applicable to plane, cylindrical and spherical waves. The thermal conductivity is taken as a function of the space coordinate. For cylindrical and spherical symmetry the discontinuity at the wavefront of a diverging wave is subjected to both material damping and decay due to geometry. The sharp wavefront is attenuated over a very short distance. For converging waves the material damping is counteracted by an increase in magnitude due to geometry. It is shown that material damping is predominant, except at extremely small distances from the center which fall outside the realm of continuum theory.

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Zusammenfassung Die Charakteristikenmethode wird benützt, um den Einfluß der thermomechanischen Kopplung auf die Größe der Unstetigkeiten an den Fronten von Dilatationswellen zu studieren. Ein System vereinheitlichter Gleichungen, das auf ebene, zylindrische und sphärische Wellen anwendbar ist, wird aufgestellt. Die Wärmeleitfähigkeit wird als Funktion des Ortes angenommen. Bei Zylinder- und Kugelsymmetrie ist die Unstetigkeit der Front einer divergierenden Welle sowohl der Materialdämpfung als auch einer geometrisch bedingten Abnahme unterworfen. Die steile Wellenfront wird entlang eines sehr kurzen Weges abgemindert. Bei konvergenten Wellen wirkt die geometrisch bedingte Amplitudenvergrößerung der Materialdämpfung entgegen. Es wird gezeigt, daß die Materialdämpfung überwiegt; ausgenommen sind extrem kleine Gebiete um das Wellenzentrum, die außerhalb des Geltungsbereiches der Kontinuumstheorie liegen.

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The work presented in this paper was supported by the Advanced Research Project Agency of the Department of Defense through the Northwestern University Materials Research Center.     

Effects of IQ and mental age on hypothesis behavior in normal and retarded children.

156 mental-age-matched normal and retarded Ss at mental-age (MA) levels of 5.5, 7.5, and 9.5 yrs received blank-trial discrimination problems designed to expose hypothesis behavior. There was evidence that Ss at all MA levels used hypotheses. Use of feedback indicating that a response was wrong increased significantly with MA, while use of feedback indicating that a response was right increased significantly with IQ. On simple problems involving 2 stimulus dimensions, retarded and normal groups used about equal numbers of hypotheses, but on 4-dimensional problems the retarded used fewer hypotheses than normals. It is suggested that this IQ Level * Problem Complexity interaction may explain contradictions among previous findings regarding IQ effects on learning. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The teacher version of the Child Behavior Profile: I. Boys aged 6–11.

Reports the development and standardization of the teacher version of the Child Behavior Profile for boys aged 6–11 yrs. The teacher profile is scored from the Teacher's Report Form (TRF). Factor analysis of TRFs completed on 450 clinically referred boys yielded 8 behavior problem syndromes: anxious, social withdrawal, unpopular, self-destructive, obsessive-compulsive, inattentive, nervous-overactive, and aggressive. Norms were constructed from a sample of 300 randomly selected nonreferred boys. Compared to normal Ss, disturbed Ss scored significantly higher on all behavior problem scales and significantly lower on teacher-reported school performance and adaptive functioning. One-week test–retest reliability averaged .89 for the behavior problem scales, whereas 2- and 4-mo stability averaged .77 and .64, respectively. Computer- and hand-scored versions of the new teacher profile are described. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)