Orbital instability and prediction of a Bunsen flame tip motion with burner rotation

An orbital instability of the unsteady flame tip motion with burner rotation and the possibility of the prediction of the flame tip motion are investigated from the viewpoint of nonlinear dynamics. A rich methane–air mixture of equivalence ratio 1.43 is used. The mean exit velocity from the burner tube, U, is varied from 0.6 to 1.3 m/s, keeping the swirl number S=1.14 constant. The variation in the flame tip motion is quantitatively evaluated by calculating the mean value of a parallel trajectory value Γ. At U0.7 m/s, the value of Γ is estimated to be approximately zero, indicating that periodic motion occurs. As U increases, the trajectory of the attractor becomes complicated and Γ gradually increases. The value of Γ approaches the value of the Fourier-transformed surrogate data with further increase in U. This suggests that the flame tip motion varies from periodic to chaotic due to the influence of phase randomness with increasing U. The short-term forward prediction method, that is based on the orbit of the attractor, first was used. Then the short-term forward prediction method was modified to successfully extend the prediction term. The results suggest that the modified short-term forward prediction method proposed in the present study provides a valid method for predicting the motion of unsteady flames.     

Independence of older adults in performing instrumental activities of daily living (IADLs) and the relation of this performance to visual abilities

A questionnaire study was undertaken of more than 2800 elderly people aged 60 years and over and living at home, to investigate the relationship between their performance of some instrumental activities of daily living (IADLs) and their visual abilities. The IADL measured the ability of elderly participants to pick up coins, manage monthly financial matters, use the telephone and take medication as recommended. Visual abilities were assessed by means of each subject's answers to questions relating to resolution, focus, adaptation to bright or to dim lighting, dynamic acuity, distance perception and colour vision. The types of visual functions that, together with age and gender, contribute to determining the level of independence in the performance of IADL activities were identified using logistic regression analysis. The results indicated that elderly participants who had problems with either distance perception or yellowish vision also tended to have difficulties in picking up coins, using the telephone and taking medication as recommended. In addition, problems with adaptation and dynamic acuity were associated with difficulty in managing monthly financial matters. From an analysis of all subjects, distance perception was the significant factor that determined whether an elderly subject could pick up coins or use a telephone unaided. Yellowish vision was also significantly associated with a need for assistance or with an inability to manage monthly financial matters, use the telephone or take medication as recommended.     

Effects of grain refinement on surface enhancement of thin-film chlorine-doped crystalline selenium

In this study, the surface enhancement of thin-film crystalline selenium (c-Se) is successfully demonstrated through grain refinement using chlorine (Cl) doping. We fabricated c-Se films via doping with various halogens, such as Cl, bromine (Br), and iodine (I). In particular, for Cl, we prepared c-Se films with different doping concentrations of 0, 50, and 500 ppm on glass substrates to investigate the details of concentration effects on surface enhancement. The long helical chains of Se atoms that comprise a large molecule in hexagonal Se, which is the most stable form of Se, are terminated via halogen doping into Se, leading to a marked reduction in the size of polycrystalline grains. In addition, the grain size of c-Se sharply decreases as the Cl doping concentration is increased. The mean surface roughness of a 500-ppm-Cl-doped c-Se film measured via atomic force microscopy decreased to approximately one-fourth that of the equivalent undoped c-Se film. This is a promising technology that could bring great benefits to c-Se-based imaging devices.     

Selective production of hydrogen by partial oxidation of methanol over catalysts derived from CuZnAl‐layered double hydroxides

Hydrogen production by partial oxidation of methanol (POM) reaction (CH₃OH + (1/2)O₂ ⇌ ₂H₂ + CO₂) was investigated over a series of CuZnAl ternary oxide catalysts derived from CuZnAl hydroxycarbonate precursors containing hydrotalcite‐like layered double hydroxide as a major phase. These catalysts exhibited a good catalytic activity and high H₂ selectivity. A methanol conversion of about 40–60% was obtained at 200°C with high selectivity of H₂ and CO₂. The undesirable by‐product, CO was virtually not produced over most of the catalysts at this temperature. The catalytic activity was found to decrease with increasing (Cu + Zn)/Al atomic ratio in the precursor and, was correlated with Cu metal surface areas, Cu dispersion and Cu particle sizes, which were calculated by both XRD and TPR‐N₂O passivation methods. The catalyst with higher Cu surface areas and Cu dispersion displayed a higher catalytic activity. Lifetime experiments showed that these catalysts were stable over a period of 24 h of continuous operation. Catalyst precursors containing hydroxycarbonates other than LDH as a major phase offered considerable amount of dimethyl ether as a by‐product. This revised version was published online in July 2006 with corrections to the Cover Date.     

Phase separation structure in poly(vinyl alcohol)/silk fibroin blend films

Blend films of a commercial poly(vinyl alcohol) (a-PVA) derived from vinyl acetate and silk fibroin (SF) obtained from degummed silk were prepared by mixing the aqueous solutions of both samples. A plain weave structure was recognized only in the blend films, whereas no structure was found for the superimposed films of both samples. The phase separation structure of the blend films was examined by microscopic observations elongation, tensile tests, and IR measurements. The microphase separation region increased with increase in the degree of polymerization of the PVA. In the IR spectra of the blend films with high PVA contents cast under certain conditions, the absorption peak attributed to the cross-β-form conformation of SF appeared strongly. Gelatin, a water-soluble and natural polymer, was also used for comparison with SF. The ternary phase diagram in an a-PVA/gelatin/H₂O system was obtained experimentally and the critical point was used to estimate the interaction parameter between PVA and gelatin molecules. The phase separation structure and the interaction between PVA and SF molecules were also discussed taking into consideration the results of the a-PVA/gelatin system. © 1998 SCI.     

Power-generating performance of alkali metal thermoelectric converter

The alkali metal thermoelectric converter (AMTEC) utilizing the sodium ion conducting β-alumina is a device to convert heat energy to electric energy directly. It is characterized by high conversion efficiencies, high power densities, no moving parts and low maintenance requirements. Because of these merits, AMTEC is one of the most promising candidates for aerospace power systems, remote power stations and dispersed small-scale power stations. In this paper, the experimental results of the series-connected cells and the theoretical considerations about internal resistances have been reported. For the single cell, the open voltage of 1.37 V and the maximum power of 7.89 W and maximum power density of 0.40 W/cm² at the sodium temperature of 1077 K have been obtained. For the two series-connected cells, the open voltage of 2.60 V and the maximum power of 12.3 W at the sodium temperature of 1016 K have been obtained. This power was about 90 percent of the sum power of two cells. This power decrease is due to the resistance of the current-collecting busbar. It is necessary to optimize the current-collecting busbar considering the electrical resistance and heat conductance.     

Macroscopic estimation method of the mixedness of Kenics type static mixer

We investigated the mixing process of the Kenics type static mixer, in which the mixing is enhanced by both advective mixing and mixing due to molecular diffusion in order to propose an estimation method of the mixedness. The results show that the element divides, folds and stretches the mixing fluids and forms a lamellar structure with striation width l _a . The value of l _a decreases with an increase in the number of elements by l _a -(2 ⁿ⁻¹)⁻¹, which represents the characteristics length of advective mixing. The characteristic length of mixing due to molecular diffusion l _d can be estimated by solving the one-dimensional unsteady species conservation equation analytically. The macroscopic estimation and prediction method of mixedness is proposed as function of l _a and l _d . When l _a >l _d , the advective mixing is dominant, while, when l _a <l _d , the mixing due to molecular diffusion plays an important role.     

Stochastic Behavior of a 2-Unit Parallel Fuel Charging System

In a contribution to this TRANSACTIONS, Buzacott (1973) discussed a fuel charge/discharge system for a nuclear reactor. We consider the same parallel fuel charging system and derive more detailed results by making use of Markov renewal processes and renewal-type equations.