Clemson University

About: Clemson University is a education organization based out in Clemson, South Carolina, United States. It is known for research contribution in the topics: Population & Control theory. The organization has 20556 authors who have published 42518 publications receiving 1170779 citations. The organization is also known as: Clemson Agricultural College of South Carolina.

Bullying in school: Evaluation and dissemination of the Olweus Bullying Prevention Program.

Abstract: The nature and extent of bullying among school children is discussed, and recent attention to the phenomenon by researchers, the media, and policy makers is noted. The Olweus Bullying Prevention Program (OBPP) is a comprehensive, school-wide program that was designed to reduce bullying and achieve better peer relations among students in elementary, middle, and junior high school grades. Several large-scale studies from Norway are reviewed, which provide compelling evidence of the program's effectiveness in Norwegian schools. Studies that have evaluated the OBPP in diverse settings in the United States have not been uniformly consistent, but they have shown that the OBPP has had a positive impact on students' self-reported involvement in bullying and antisocial behavior. Efforts to disseminate the OBPP in Norway and the United States are discussed. Language: en

A Composite from Poly(m‐phenylenevinylene‐co‐2,5‐dioctoxy‐p‐phenylenevinylene) and Carbon Nanotubes: A Novel Material for Molecular Optoelectronics

Abstract: As research progresses towards smaller and more efficient devices, the need to develop alternative molecular scale electronic materials becomes apparent. Integrated electronic component fabrication from organics has been recognized theoretically as the ultimate goal. In order to gain a comprehensive insight into these materials, extensive research has been carried out on conjugated carbon systems over the last few decades to optimize their optical and electrical properties. For example, doping polyacetylene with I2 has been shown to result in a large increase in conductivity compared to the pristine material. However, doping polymers tends to retard their optical properties as regards luminescence by reducing their bandgaps and introducing trapping sites such as solitons, polarons, or bipolarons. The simple lesson over the years is that if materials are to be considered for luminescence, doping should not be carried out despite the desire to improve charge transport properties. We report here the first physical adopingo, to use the traditional term, using small concentrations of multiwalled nanotubes in a conjugated luminescent polymer, poly(m-phenylenevinylene-co-2,5-dioctoxyp-phenylenevinylene) (PmPV), in a polymer/nanotube composite. This can increase electrical conductivity of the polymer by up to eight orders of magnitude. The nanotubes appear to act as nanometric heat sinks, preventing the buildup of large thermal effects, caused either optically (photobleaching) or electrically, which degrade these conjugated systems. We also report that electroluminescence was achieved from an organic light-emitting diode (LED) using the composite as the emissive layer in the device. Since initial work on conjugated systems, attempts have been made to find an area where polymers and/or fullerenes could be used as active semiconductor components. Although many new and interesting materials have been synthesized to this end, very few have found a practical application. One exception is polyphenylenevinylene (PPV), first reported by Burroughes et al. as being the light-emitting semiconductor in a Schottky diode. This encouraged scientists to study a wide variety of conjugated systems, including derivatives of this polymer, in order to optimize the efficiency of light emission from such devices. Polymers for use in LEDs must possess a number of important qualities. A high quantum yield of photoluminescence is necessary and the material must remain undoped, as dopants act as trapping sites, quenching the radiative decay of excitons. It is essential therefore to find a polymer that is reasonably conductive while maintaining its luminescent properties. Most undoped polymers possess a very low conductivity and so require high aturn-ono fields to generate sufficient carriers in order to produce the excitons, which decay radiatively. This is, in practical terms, very inefficient as fields generally induce large thermal effects, consequently causing device breakdown. There are other problems that must be addressed, but elimination of these very basic ones should substantially improve efficiencies and soon lead to applications for these polymers. The polymer used in our studies is PmPV, whose structure is a variation of the more common PPV. In this case the substitution pattern leads to dihedral angles in the chain and, according to molecular mechanics energy minimization calculations, the polymer chain tends to coil, forming a helical structure. The calculated diameter of this helix in vacuum is ca. 20 Š, whilst the pitch is ca. 6 Š. Multiwalled nanotubes were produced by the arc discharge method, resulting in multiwalled nanotubes of 20 nm average diameter and lengths between 500 nm and 1.5 mm. The nanotube powder and PPV were mixed together in toluene and sonicated briefly. It is probable that the coiled polymer conformation allows it to surround layers of nanotubes, permitting sufficiently close intermolecular proximity for p±p interaction to occur. The color change was dramatic in that the polymer has a bright yellow color while the composite, at high nanotube concentrations, possesses a deep green color. Photoluminescence studies were carried out using an Ar laser at the pump wavelength of 457 nm. Electrical conductivity was measured using a twopoint probe sandwich geometry and Pt electrodes. The LED was fabricated by casting the composite onto indium tin oxide (ITO) then sputtering an aluminum electrode on top. As the polymer structure possesses helicity, it is not surprising that it is able to wrap itself around the nanotubes and keep them suspended in solution indefinitely. The actual texture of the composite can be observed in Figure 1,

Bandgap-like strong fluorescence in functionalized carbon nanoparticles.

Abstract: Semiconductor quantum dots (QDs), especially the highly fluorescent CdSe-based core-shell nanostructures, have generated much excitement for their variety of potential applications in optical bioimaging and beyond.[1,2] These QDs are widely considered as being more advantageous over conventional organic dyes as well as genetically engineered fluorescent proteins in terms of optical brightness and photostability.[1,3–5] However, a serious disadvantage with these popular QDs is their containing heavy metals such as cadmium, whose significant toxicity and environmental hazard are well-documented.[6–9] Alternative benign (nontoxic) QD-like fluorescent nanomaterials have therefore been pursued, including the recent finding of fluorescent carbon nanoparticles (dubbed “carbon dots”).[10,11]

Test‐data generation using genetic algorithms

Abstract: This paper presents a technique that uses a genetic algorithm for automatic test-data generation. A genetic algorithm is a heuristic that mimics the evolution of natural species in searching for the optimal solution to a problem. In the test-data generation application, the solution sought by the genetic algorithm is test data that causes execution of a given statement, branch, path, or definition–use pair in the program under test. The test-data-generation technique was implemented in a tool called TGen, in which parallel processing was used to improve the performance of the search. To experiment with TGen, a random test-data generator called Random was also implemented. Both Tgen and Random were used to experiment with the generation of test-data for statement and branch coverage of six programs. Copyright © 1999 John Wiley & Sons, Ltd.