1,444 research outputs found
S.R. Lewis letter to Z. Eastman, March 5, 1874
No full textBrief letter from S.R. Lewis to Z. Eastman, marking the announcement of an abolitionists' reunion to be held in Chicago in June of 1875. Lewis requests that Eastman, given his close acquaintance with Benjamin Lundy, prepare a public statement of remembrance on Lundy and his contributions to the anti-slavery movement. Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His Genius of Universal Emancipation was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
Modelling and optimization of a permanent-magnet machine in a flywheel
No full textThis thesis describes the derivation of an analytical model for the design and optimization of a permanent-magnet machine for use in an energy storage flywheel. A prototype of this flywheel is to be used as the peak-power unit in a hybrid electric city bus. The thesis starts by showing the feasibility of using a flywheel energy storage system for this application, as opposed to other energy storage technologies. It then continues by describing a prototype flywheel system and the required electrical machine: a radial-flux external-rotor permanent-magnet synchronous machine without slots in the stator iron and with a shielding cylinder. An analytical model for the machine is derived, based on 2D electromagnetic field calculations, including the reaction field of the eddy currents in the shielding cylinder. Torque and losses are calculated by means of the Theorem of Poynting and the Lorentz force. Such a machine was built and the analytical model has been validated by experimental measurements. Lastly, the thesis suggests and implements a machine optimization algorithm.Information Technology and System
Design metrics for evaluating the propulsive efficiency of future ships
No full textThere is an increasing need for the ship design process to take account of environmental issues such as the emission of greenhouse gases and the likely extension of a carbon dioxide charging mechanism to international shipping. These issues, together with the need for economic viability, provide further incentives to improve the efficiency of propulsion of ships. The main components of powering are firstly reviewed. Individual components and other power saving devices are identified which should contribute to improvements in the overall efficiency of propulsion. Suitable design metrics and procedures, taking into account economic and environmental factors, are recommended for the design of future ships
Description of S.R. Krom's system and machinery for dry crushing and concentrating ores.
No full textCover title.Mode of access: Internet.MAIN; TN500.K7 1876: Introduction signed by author, S.R. Krom
Growing up to be fearful? Social evaluative fears during adolescence
Get PDFThis thesis studies the normal developmental pattern of social evaluative fears from childhood to adolescence. We have investigated age differences in self-reported social fears and physical responses during a public speaking task. In addition, youth's perceptions of speaking in public were studied through a short interview. Finally, two aspects of adolescent development are highlighted, namely resistance to peer influence and self-restraint, in the two concluding chapters. The main finding of the thesis is that social evaluative fears seem to increase with age. However, future research needs to develop more developmentally sensitive measures and further investigate the underlying processes of this increase.LEI Universiteit LeidenDevelopmental pathways of social-emotional and cognitive functioning - ou
Psychosomatic complaints in adolescence: Untangling the relationship between offline and online peer victimization, psychosomatic complaints and social support
Get PDFOffline peer victimization has been linked to psychosomatic complaints. As peer victimization is no longer limited to adolescents’ offline relationships, it is crucial that we investigate whether online peer victimization has similar negative consequences. To date, no study systematically investigated the unique contribution of online vs. offline peer victimization on psychosomatic complaints, and the possible protective effect of social support. The current study disentangled offline and online peer victimization by distinguishing four victim types: non-victims, offline, online, and dual victims (N = 897, 9-to-18-year-olds). In addition, we assessed perceived social support from teachers, parents, friends and classmates. A main effect was found for victim type on psychosomatic complaints. Victims (offline or dual) reported more psychosomatic complaints than non-victims. Notably, online victims reported similar levels of psychosomatic complaints compared to non-victims. Furthermore, although social support from parents and classmates was related to fewer psychosomatic complaints, only limited support was found for a buffering effect of social support
Perceptions of love across the lifespan: differences in passion, intimacy, and commitment
No full textThis study investigated perceptions of love across the lifespan using Sternberg’s triangular theory of love, which distinguishes between passion, intimacy, and commitment. The study aimed to (a) investigate the psychometric properties of the short Triangular Love Scale (TLS-short) in adolescents and adults (see Appendix), and (b) track age and gender differences in the three love components of the TLS-short in a sample of 12- to 88-year-olds (N = 2791). The three-factor structure of the TLS-short was confirmed in both the adolescent and adult sample. Adolescents (12-17 years) reported lower levels of all love components compared to young adults (18-30 years). Late adults (50+) reported lower levels of passion and intimacy, but similar levels of commitment compared to young (18-30 years) and middle adults (30-50 years). Gender differences in the perceptions of all three love components were present but less sizeable than suggested in popular accounts and earlier academic research
Dealing with media distractions: An observational study of computer-based multitasking among children and adults in the Netherlands
Get PDFThe aim of this observational study was to investigate differences in computer-based multitasking among children and adults. Moreover, the study investigated how attention problems are related to computer-based multitasking and how these individual differences interact with age. Computer-based multitasking was observed for a 10-minute period among children (N = 164, aged 6–13) and adults (N = 160, aged 18–75) in the Netherlands. The findings indicated that individuals find it indeed difficult to focus their attention on a main activity in the presence of appealing media distractors. A main effect for age was qualified by an interaction effect between age and attention problems. There was a positive relationship between attention problems and computer-based multitasking only for children but not for adults. The findings indicate that particularly children with attention problems are easily distracted by other media activities
Navigating a muscular and sexualized Instagram feed: An experimental study examining how Instagram affects both heterosexual and nonheterosexual men’s body image
No full textDespite nearly equal Instagram use rates between men and women, research on the effects of Instagram use on body image has mainly focused on women, and continued research on visual social media is warranted. To fill this gap, we conducted a 2 (image muscularity; high vs. low) × 2 (image sexualization; high vs. low) + 1 (control) between-subjects online experiment among 133 young adult men. Among all participants, we examined the moderating effect of sexual orientation, hypermasculinity, and trait appearance-related social comparison. We considered internalized homophobia among men who did not identify as exclusively heterosexual. Results demonstrated no main or interaction effects of condition on intention to exercise. There was a small but significant main effect of condition on state body image, with scores significantly lower in the muscular/nonsexualized condition in comparison to the control. Further, the effect of exposure to muscular Instagram images was stronger among men higher in trait appearance-related social comparison and among nonheterosexual men higher in internalized homophobia. These results suggest that similar to findings among women, exposure to certain types of Instagram images can have small, negative body image effects on men, which are conditional on individual differences
Gender differences in online and offline self-disclosure in pre-adolescence and adolescence
No full textAlthough there is developmental research on the prevalence of offline self-disclosure in pre-adolescence and adolescence, it is still unknown (a) how boys’ and girls’online self-disclosure develops in this period and (b) how online and offline self-disclosure interact with each other. We formulated three hypotheses to explain the possible interaction between online and offline self-disclosure: the displacement, the rich-get-richer, and the rehearsal hypothesis. We surveyed 690 pre-adolescents and adolescents (10-17 years) at three time points with half-year intervals in between. We found significant gender differences in the developmental trajectories of self-disclosure. For girls, both online and offline self-disclosure increased sharply during pre- (10-11 years) and early adolescence (12-13 years), and then stabilized in middle and late adolescence. For boys, the same trajectory was found although the increase in self-disclosure started 2 years later. We found most support for the rehearsal hypothesis: Both boys and girls seemed to use online self-disclosure to rehearse offline self-disclosure skills. This particularly held for boys in early adolescence who typically have difficulty disclosing themselves offline
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