First-Order Kinetic Gas Generation Model Parameters For Wet Landfills

Landfill gas collection data from wet landfill cells were analyzed and first-order gas generation model parameters were estimated for the US EPA landfill gas emissions model (LandGEM). Parameters were determined through statistical comparison of predicted and actual gas collection. The US EPA LandGEM model appeared to fit the data well, provided it is preceded by a lag phase, which on average was 1.5 years. The first-order reaction rate constant, k, and the methane generation potential, Lo, were estimated for a set of landfills with short-term waste placement and long-term gas collection data. Mean and 95% confidence parameter estimates for these data sets were found using mixed-effects model regression followed by bootstrap analysis. The mean values for the specific methane volume produced during the lag phase (Vsto), Lo, and k were 33 m3/Megagrams (Mg), 76 m3/Mg, and 0.28 year-1, respectively. Parameters were also estimated for three full scale wet landfills where waste was placed over many years. The k and Lo estimated for these landfills were 0.21 year-1, 115 m3/Mg, 0.11 year-1, 95 m3/Mg, and 0.12 year-1 and 87 m3/Mg, respectively. A group of data points from wet landfills cells with short-term data were also analyzed. A conservative set of parameter estimates was suggested based on the upper 95% confidence interval parameters as a k of 0.3 year-1 and a Lo of 100 m3/Mg if design is optimized and the lag is minimized. © 2006 Elsevier Ltd. All rights reserved

High-frequency and intrinsically stretchable polymer diodes

Skin-like intrinsically stretchable soft electronic devices are essential to realize next-generation remote and preventative medicine for advanced personal healthcare1-4. The recent development of intrinsically stretchable conductors and semiconductors has enabled highly mechanically robust and skin-conformable electronic circuits or optoelectronic devices2,5-10. However, their operating frequencies have been limited to less than 100 hertz, which is much lower than that required for many applications. Here we report intrinsically stretchable diodes-based on stretchable organic and nanomaterials-capable of operating at a frequency as high as 13.56 megahertz. This operating frequency is high enough for the wireless operation of soft sensors and electrochromic display pixels using radiofrequency identification in which the base-carrier frequency is 6.78 megahertz or 13.56 megahertz. This was achieved through a combination of rational material design and device engineering. Specifically, we developed a stretchable anode, cathode, semiconductor and current collector that can satisfy the strict requirements for high-frequency operation. Finally, we show the operational feasibility of our diode by integrating it with a stretchable sensor, electrochromic display pixel and antenna to realize a stretchable wireless tag. This work is an important step towards enabling enhanced functionalities and capabilities for skin-like wearable electronics.Agency for Science, Technology and Research (A*STAR)This work was partially supported by SAIT, Samsung Electronics Co., Ltd., and the Agency for Science, Technology and Research (A*STAR) under its Advanced Manufacturing and Engineering (AME) Programmatic Scheme (no. A18A1b0045). N.M. was partially supported by a Japan Society for the Promotion of Science (JSPS) overseas research fellowship. Part of this work was performed at the Stanford Nano Shared Facilities (SNSF), supported by the National Science Foundation under award ECCS-1542152. Experiments performed during revision were carried out in Keio University and was supported by JST, PRESTO Grant Number JPMJPR20B7, Japan