High-Temperature Creep and Cavitation of Polycrystalline Aluminum Nitride

Dense, polycrystalline AlN samples of grain size between 1.8 and 19 μm were fabricated by hot-pressing. Bar-shaped samples were subjected to creep in four-point bending under static loads in nitrogen atmosphere. The outer fiber stress was varied between 20 and 140 MPa and the temperature between 1650 and 1940 K. Steady-state creep rate, dɛ/d t was proportional to σ ⁿ d ^{− m} where the stress exponent, n , was between 1.27 and 1.43 and grain-size exponent, m , between ∼ 2.2 and ∼ 2.4. The activation energy for creep ranged between 529 and 625 kJ/mol. Both round (r type) and wedgeshaped (w type) cavities were observed in electron micrographs of the deformed samples. No noticeable change in the dislocation density was observed. Contribution of cavitation to the creep rate was estimated using an unconstrained cavity model. Based on this study it is concluded that the dominant mechanism of creep in polycrystalline AlN is diffusional.     

Realumination of zeolite Y under acidic conditions

Dealuminated zeolites Y were treated with aqueous solutions of various acids and ammonium salts to investigate the realumination behavior under acidic conditions. From the results of ²⁷Al MAS NMR, ²⁹Si MAS NMR and FT-IR measurements, it was found that a part of non-framework aluminum species in the dealuminated zeolite Y is effectively reinserted into the zeolite framework in CH₃COONH₄ and C₆H₅COONH₄ aqueous solutions. Pyridine adsorption experiments also revealed that most of incorporated aluminum species generate tetrahedrally coordinated framework aluminum species, namely Brönsted acid sites. Although the realumination also proceeded in H₂SO₄ and CH₃COOH aqueous solutions, large amounts of incorporated aluminum species were not necessarily responsible for generation of Brönsted acid sites. Framework connected aluminum species, presumably as 3-fold-coordinated Lewis acidic framework aluminum species, were mainly generated. In the TEM image of the realuminated zeolite Y, needle-like crystals with ca. 25–80 nm in length were observed, which are probably due to AlOOH generated from non-framework aluminum species.     

A distance-based fuzzy time series model for exchange rates forecasting

Fuzzy time series model has been successfully employed in predicting stock prices and foreign exchange rates. In this paper, we propose a new fuzzy time series model termed as distance-based fuzzy time series (DBFTS) to predict the exchange rate. Unlike the existing fuzzy time series models which require exact match of the fuzzy logic relationships (FLRs), the distance-based fuzzy time series model uses the distance between two FLRs in selecting prediction rules. To predict the exchange rate, a two factors distance-based fuzzy time series model is constructed. The first factor of the model is the exchange rate itself and the second factor comprises many candidate variables affecting the fluctuation of exchange rates. Using the exchange rate data released by the Central Bank of Taiwan, we conducted several experiments on exchange rate forecasting. The experiment results showed that the distance-based fuzzy time series outperformed the random walk model and the artificial neural network model in terms of mean square error.     

Effect of the intercalation agent content of montmorillonite on the swelling behavior and drug release behavior of nanocomposite hydrogels

A series of novel dual functional nanocomposite hydrogels were prepared from N‐isopropylacrylamide (NIPAAm), acrylic acid (AA) that is neutralized 50 mol % by sodium hydroxide (SA50), and montmorillonite (MMT). MMT was intercalated with three different contents of intercalation agent of (3‐acrylamidopropyl) trimethyl ammonium chloride (TMAACl). Investigation of the effect of intercalated MMT with three contents of intercalation agent (TMAACl) in the present nanocomposite hydrogels on the swelling and drug release behaviors is the main purpose in this study. The microstructure was identified by X‐ray diffraction (XRD). Results showed that the swelling ratio for the present nanocomposite hydrogels decreased with an increase in the content of the intercalation agent. The gel strength of the present gels did not change obviously with an increase in the content of intercalation agent. XRD results indicated that exfoliation of MMT was achieved in the dry and swollen gel state. Finally, the drug release behaviors for these gels were accessed also. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 74–82, 2004     

The solubility of carbon dioxide and hydrogen sulfide in a 35 wt% aqueous solution of methyldiethanolamine

The solubility of hydrogen sulfide and carbon dioxide in an aqueous solution containing 35 wt% methyldiethanolamine (MDEA) (3.04 kmol/m³, 4.52 mol/kg) has been measured at 40° and 100°C at partial pressures of the acid gas up to 530 kPa. Some data for hydrogen sulfide in a 50 wt% solution of MDEA (4.38 kmol/m³, 8.39 mol/kg) were also obtained. Also, densities of CO₂-aqueous MDEA solutions were measured at 40°C.     

New three-port DC-AC inverter outputting a single-phase and a set of three-phase AC voltages

A conventional DC-AC inverter can only output either a single-phase AC voltage or a set of three-phase AC voltages. A new three-port DC-AC inverter which can simultaneously output a single-phase AC voltage and a set of three-phase AC voltages is proposed in this paper. This three-port DC-AC inverter is based on the three-port T-type multi-level power converter which is composed of three T-type power electronic legs, a decoupling transformer set, a filter inductor set, a single-phase filter capacitor, and a three-phase filter capacitor set. The DC port of the proposed power converter is connected to a DC power source to act as the input port, and the single-phase AC port and the three-phase AC port serve as two output ports to supply power to the single-phase load and the three-phase load, respectively. The zero-sequence transformer is used to decouple the single-phase and three-phase AC components, which are generated by the three T-type power electronic legs. The operation principle of this three-port DC-AC inverter is analyzed, and a hardware prototype is established to verify the performance of the proposed three-port DC-AC inverter. The experimental results are as expected.     

Time Dependent Origin-destination Estimation from Traffic Count without Prior Information

Existing research works on time-dependent origin-destination (O-D) estimation focus on the surveillance data usually assume the prior information of the O-D matrix (or transition matrix) is known (or at least partially known). In this paper, we relax such assumption by combining Gibbs sampler and Kalman filter in a state space model. A solution algorithm with parallel chain convergence control is proposed and implemented. To enhance its efficiency, a parallel structure is suggested with efficiency and speedup demonstrated using PC-cluster. Two numerical examples (one for Taipei Mass Rapid Transit network and the other for Taiwan Area National Freeway network) are included to show the proposed model could be effective of time-dependent origin-destination estimation.     

Degradation of Chlorobenzene in Water Using Nanoscale Cu Coupled with Microwave Irradiation

In this research, the microwave (MW) energy is used to generate heat directly inside the nanoscale copper particles that are suspended in aqueous chlorobenzene (CB) solution. The heat will reduce CB activation energy so that the CB can be more efficiently decomposed by the heat generated. Because the copper particle surface has pointed protuberances, more MW energy can be absorbed to result in higher solution temperature and lower CB activation energy. Laboratory results indicate that without MW irradiation, the CB solution temperature varies from 25 to 60°C with 19.5 to 41.3% removal of CB that has 21.4 kJ/mol activation energy. In the presence of 250-W MW, the CB activation energy is reduced to 15.8 kJ/mol, and the CB removal efficiency is raised by 1.8 times. Using MW energy to generate heat directly in nanoscale copper particles suspended in aqueous CB solution for reducing the activation energy of CB and enhancing its removal is a novel and efficient method for treating toxic organic substances.     

Automatic Verification Stimulus Generation for Interface Protocols Modeled With Non-Deterministic Extended FSM

Verifying if an integrated component is compliant with certain interface protocol is a vital issue in component-based system-on-a-chip (SoC) designs. For simulation-based verification, generating massive constrained simulation stimuli is becoming crucial to achieve a high verification quality. To further improve the quality, stimulus biasing techniques are often used to guide the simulation to hit design corners. In this paper, we model the interface protocol with the non-deterministic extended finite-state machine (NEFSM), and then propose an automatic stimulus generation approach based on it. This approach is capable of providing numerous biasing strategies. Experiment results demonstrate the high controllability and efficiency of our stimulus generation scheme.     

The discharge properties of Na/Ni3S2 cell at ambient temperature

The discharge properties of a Na/Ni₃S₂ cell using 1 M NaCF₃SO₃ in tetra(ethylene glycol)dimethyl ether liquid electrolyte were investigated at room temperature. The products were characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Electrochemical properties of Na/Ni₃S₂ cells were also presented by cyclic voltammetry and the galvanostatic current method. Na/Ni₃S₂ cells have an initial discharge capacity of 420 mAh g⁻¹ with a plateau potential at 0.94 V versus Na/Na⁺. After the first discharge, Ni₃S₂ and Na react at room temperature and then form sodium sulfide (Na₂S) and nickel. Sodium ion can be partially deintercalated from Na₂S charge reaction. The discharge process can be explained as follows: Ni₃S₂ + 4Na ↔ 3Ni + 2Na₂S.