Thermal conductivity of suspended pristine graphene measured by Raman spectroscopy

The thermal conductivity of suspended single-layer graphene was measured as a function of temperature using Raman scattering spectroscopy on clean samples prepared directly on a prepatterned substrate by mechanical exfoliation without chemical treatments. The temperature at the laser spot was monitored by the frequency of the Raman 2$D$ band of the Raman scattering spectrum, and the thermal conductivity was deduced by analyzing heat diffusion equations assuming that the substrate is a heat sink at ambient temperature. The obtained thermal conductivity values range from $\sim$1800 Wm$^{-1}$K$^{-1}$ near 325 K to $\sim$710 Wm$^{-1}$K$^{-1}$ at 500 K.Comment: 4pages, 3 figure

Cache-based Query Processing for the Boolean Retrieval Model

We propose a new method of processing general Boolean queries utilizing previous query results stored in a result cache in a mediator architecture. A simple but noble normalization form is developed to describe keyword-based Boolean queries and the content of the result cache. We propose Boolean query processing algorithms based on this form of presentation that utilizes the result cache. We show that the proposed method theoretically guarantees improved performance over the conventional query processing method without using a cache

DEVELOPMENT OF A NEW FATIGUE DAMAGE MODEL FOR QUARTER-MODAL SPECTRA IN FREQUENCY DOMAIN

Floating marine structures are exposed to various environmental loads. When the response of structures caused by these loads can be expressed as a multi-modal spectrum in the frequency domain. To estimate the fatigue damage by these loads, various fatigue damage models have been suggested by many previous researches. The offshore riser system, for example, that is a typical marine structure shows a quarter-modal response. However, existing fatigue damage models are suitable for spectrum with tri-modal in maximum. Consequently, it is necessary to develop a new fatigue damage model that can accurately calculate fatigue damage of quarter-modal spectrum. In this research, the Benasciutti and Tovo model was adopted for developing a new fatigue damage model. And 900 quarter-modal spectra are used to derive a new weighting factor in the Benasciutti and Tovo model by investigating the relationship between the linear weighting factor and the bandwidth parameters. Finally, a new linear weighting factor is derived using the least square method. The suitability of the new fatigue damage model with the derived weighting factor is evaluated by frequency domain and time domain results and their comparison with existing model’s results