Minimum Message Length in Hybrid ARMA and LSTM Model Forecasting

Modeling and analysis of time series are important in applications including economics, engineering, environmental science and social science. Selecting the best time series model with accurate parameters in forecasting is a challenging objective for scientists and academic researchers. Hybrid models combining neural networks and traditional Autoregressive Moving Average (ARMA) models are being used to improve the accuracy of modeling and forecasting time series. Most of the existing time series models are selected by information-theoretic approaches, such as AIC, BIC, and HQ. This paper revisits a model selection technique based on Minimum Message Length (MML) and investigates its use in hybrid time series analysis. MML is a Bayesian information-theoretic approach and has been used in selecting the best ARMA model. We utilize the long short-term memory (LSTM) approach to construct a hybrid ARMA-LSTM model and show that MML performs better than AIC, BIC, and HQ in selecting the model—both in the traditional ARMA models (without LSTM) and with hybrid ARMA-LSTM models. These results held on simulated data and both real-world datasets that we considered.We also develop a simple MML ARIMA model.     

Preparation of carbon composite from coconut fiber for gas diffusion layer

A natural carbon from coconut fiber is used as a main composite material of gas diffusion layer (GDL) for fuel cell electrode. The composite comprise of polymer (ethylene vinyl acetate and poly ethylene glycol) and carbon in various compositions. The materials are mixed in xylene and printed using casting method. The composite is coated with polytetrafluoro ethylene (PTFE) to achieve hydrophobic requirement as GDL. The electrical properties of composite were measured by using LCR-meter, the porosity was obtained by immersion method, and the hydrophobic properties were observed by measuring its contact angle. The results show the electrical conductivity of GDL prepared corresponds to its carbon content. The electrical conductivity of GDLs is 22.17, 26.89, 35, 43, and 52 S/m for the carbon composition of 65, 70, 75, 80, and 85 %, respectively. The composite of 80 % carbon content and coated with PTFE contains 74 % porosity and has desired hydrophobic properties revealed from its high contact angle, i.e., 120°.     

On Generalizations of Ostrowski Inequality and Some Related Results

Some generalizations of the Ostrowski inequality, the Milovanovi-Peari-Fink inequality, the Dragomir-Agarwal inequality and the Hadamard inequality are given.     

Efficient palladium-mediated or base-induced 5-endo-dig cyclisation of C5-alkynylated pyrimidine derivatives: conventional and microwave-assisted synthesis of novel furo[2,3-d]pyrimidines

A series of the novel 5-alkynyl- and furo[2,3-d]pyrimidine derivatives in which the sugar moiety is replaced by a methoxymethyl (MOM) group is synthesised using the Sonogashira cross-coupling reaction under both conventional and microwave conditions, in good to excellent yields. The 5-endo-dig cyclisation of 5-alkynylpyrimidine derivatives promoted by a Pd-catalyst or base gives the corresponding furo[2,3-d]pyrimidines in good yields.     

Exploring the possible interlinked structures in single‐wall carbon nanotubes under pressure by Raman spectroscopy

High‐pressure Raman measurements on single‐wall carbon nanotubes (SWNTs) have been carried out in a diamond anvil cell by using two wavelength lasers: 830 and 514.5 nm. Irrespective of using a pressure transmitting medium (PTM) or not, we found that nanotubes undergo similar transformations under pressure. The pressure‐induced changes in Raman signals at around 2 and 5 GPa are attributed to the nanotube cross‐section transitions from circle to ellipse and then to a flattened shape, respectively. Especially with pressure increasing up to 15–17 GPa, we observed that the third transition takes place in both the Raman wavenumber and the linewidth of G‐band. We propose explanations that the interlinked configuration with sp³ bonds forms in the bundles of SWNTs under pressure, which was the cause for the occurrence of those Raman anomalies, similar to the structural‐phase transition of graphite above 14 GPa. Our TEM observations and Raman measurements on the decompressed samples support this transition picture. Copyright © 2012 John Wiley & Sons, Ltd.     

In situ Raman and photoluminescence study on pressure‐induced phase transition in C60 nanotubes

Single crystalline C₆₀ nanotubes having face‐centered‐cubic structure with diameters in the nanometer range were synthesized by a solution method. In situ Raman and photoluminescence spectroscopy under high pressure were employed to study the structural stabilities and transitions of the pristine C₆₀ nanotubes. A phase transition, probably because of the orientational ordering of C₆₀ molecules, from face‐centered‐cubic structure to simple cubic structure occurred at the pressure between 1.46 and 2.26 GPa. At above 20.41 GPa, the Raman spectrum became very diffuse and lost its fine structure in all wavenumber regions, and only two broad and asymmetry peaks initially centered at 1469 and 1570 cm^–1 were observed, indicating an occurrence of amorphization. This amorphous phase remained to be reversible until 31.1 GPa, and it became irreversible to the ambient pressure after the pressure cycle of 34.3 GPa was applied. Copyright © 2012 John Wiley & Sons, Ltd.     

Lucidumol D,a new lanostane-type triterpene from fruiting bodies of Reishi (Ganoderma lingzhi)

A new lanostane-type triterpenoid, lucidumol D (1) was isolated from the fruiting bodies of Ganoderma lingzhi. Its structure was elucidated on the basis of extensive 1D- and 2D-NMR studies as well as mass spectrometry. The cytotoxicity of lucidumol D against proliferation of several cancer cells were assayed by using MTT method and the obtained result suggested selective anti-proliferative and cytotoxic effects against MCF-7, HepG2, HeLa, Caco-2, and HCT-116. In comparison to lucidumol C (2) isolated previously by our group, the structure-activity relationship indicated that carbonyl function at C-11 is necessary to enhance the cytotoxicity.