HYBRID DRYING OF GRANULAR MATERIALS BY COMBINED RADIATIVE AND CONVECTIVE HEATING

ABSTRACT

As one of the basic steps of the R&D on hybrid drying by combined radiative and convective heating, drying experiments of a stagnant horizontal wet granular layer heated simultaneously by infrared lamps and hot air were conducted throughout a whole period of the drying. An opaque model, in which the incident radiation is assumed to be absorbed only on the surface of the layer, was introduced to explain experimental trends. Then, the effects of combined heating on drying characteristics of three kinds of samples, a silica sand, a brick and a brown coal were discussed by comparing the experimental data with the calculated results.

The calculated results were found to be in a close agreement with the experimental data obtained on the time behaviors of the drying rate and the temperature distribution in the- layer during not only the preheating and the constant rate periods but also the falling rate period. In the case of the coal layer, however, the falling drying rate different from that in ordinary convective drying had to be considered since it appeared that the radiative heating had an effect to enhance the falling drying rate of the coal owing to some interactions of the coal and water.     

Deformation Behavior of Ceramic Slabs by Nonuniform Drying

ABSTRACT

The presenr paper is to study the transient deformation characteristics of molded ceramics undergoing nonunifom drying. The linear viscoelasticity was assumed for the strain-stress analysis. Three dimensional equations of the strain-stress as well as heat and moisture transfer werc solved numerically by the Galerkln finlle element melhod using isoparametric parameters of twenty-nodes so to allow easily the application to any feature of ceramics. Both the analysis and experiments were carried out to be compared on the behavior of drying and deformation for a slab clay in preheating and constant drying rare periods. When the bottom surface of the slab uras shielded to model the nonuniform drying. a warp phenomrnon to the opposite side of the shielded surface was observed experimentally as drying by hot air heating proceeds. The behavior could be successively simulaled by the present theoretical model. The degree of warp became rcmarkabel with a rise in air temperature or nonuniformity of drying. The surface area exposed to the atmosphere was subjected to a comparatively large tensional stress through drying. The tensile sltresses on the top surface were significantly larger than on the bottom surface.     

Novel IV-Group Based Diluted Magnetic Semiconductor: CrxGe1?x

Cr_xGe_1–x (x 0.08) films were grown on GaAs (001) and Ge (001) substrates using molecular beam epitaxy (MBE) method, and their magnetic and transport properties have been studied in the temperature range between 1.8 and 300 K. All of the films exhibited weak paramagnetic behavior. Transport measurements showed that magnetoresistance ratio and the anomalous Hall resistance depend on the Cr concentration x and the kinds of substrate.     

Influence of the Ionization Potential and of the Interfacial Electric Field on Photoinduced Hole Transfer Processes in Langmuir-Blodgett Films

The presence of a monolayer of ω-(2-anthryl)-alkanoic acid on an anthracene or perylene single crystal modifies the kinetics of photosensitized hole injection. An increase in the chain length of the ω-(2-anthryl)-alkanoic acid leads to a decrease in the quantum yield of the sensitized hole current (SHC). This effect becomes more important when the ionization potential of the dye is decreased. This argument supports the hypothesis that electron transfer is assisted by an interaction between the HOMO of the dye and that of the alkyl chain. The permanent electric field existing at the interface between the monolayer of ω-(2-anthryl)-alkanoic acid and the monolayer containing the dye is also expected to influence the free energy gain associated with this electron transfer process. When the dye is diluted by tripalmitine instead of arachidic acid, the change in the electrical potential difference at the interface with the monolayer of ω-(2-anthryl)-alkanoic acid leads to a tenfold decrease in the quantum yield of the SHC.     

Optical frequency spacing tunable four-channel integrated 1.55 mu m multielectrode distributed-feedback laser array

A four-channel integrated 1.55- mu m multielectrode distributed-feedback (DFB) laser array was fabricated using the metallorganic vapor-phase deposition/liquid-phase epitaxy (MOVPE/LPE) hybrid method. Simultaneous single-longitudinal mode operation was achieved in each multielectrode DFB laser on a single chip. Utilizing the frequency tunability of multielectrode DFB lasers, optical frequency spacings were controlled and set to within a few gigahertz. The drift of frequency spacings due to temperature fluctuation was in the range of +or-50 MHz for temperature control of +or-0.1 degrees .<>     

Narrow-beam divergence of the emission from low-threshold GaInAsP/InP double-heterostructure lasers

The angles of beam divergence perpendicular to the junction plane have been studied for low-threshold GaInAsP/InP double-heterostructure lasers with a thin active layer emitting at 1.31 ?m. The narrowest beam divergence obtained was 23° for a laser diode with an active-layer thickness of 0.05 ?m. At an active-layer thickness of 0.13 ?m, the beam divergence was 40° with a threshold current density of 770 A/cm2.     

Photoluminescence properties of dye-doped polymer multilayer films with periodic structure

We report the photoluminescence properties of polymer alternating multilayer films containing a fluorescent dye in one component. The alternating multilayer film with periodicity in both refractive indices and dye distribution showed 6 times higher intensity of amplified spontaneous emission than the multilayer film with periodicity in dye distribution only. Multilayer films that have a structure of Fabry-Perot resonator showed a lasing threshold of approximately 1.7 mJ cm^− 2.     

636 nm room temperature CW operation by heterobarrier blocking structure InGaAlP laser diodes

636 nm room temperature CW operation has been achieved by heterobarrier blocking structure InGaAlP laser diodes with a quaternary active layer. This structure was fabricated by two-step metal-organic chemical vapour deposition. The threshold current was 102 mA at 20 degrees C and CW operation of 3 mW was attained at up to 48 degrees C.<>     

The temperature dependence of the threshold current of GaInAsP/InP DH lasers

The temperature dependence of the threshold current of GaInAsP/InP lasers was considered in terms of linear gain, loss, and carder lifetime. The linear gain was calculated taking into account electronic intraband relaxation effects. The carrier lifetime, intraband relaxation time, loss in the active region, and dipole moment, all of which determine the threshold condition, were estimated from the experiments. The main loss mechanism which determines the temperature dependence of the differential quantum efficiency appears to be the absorption due to transitions between the split-off and heavy-hole valence bands. The temperature dependence of the theoretical threshold current Ithcalculated in terms of these parameters was compared with the measured results and reasonable agreement was obtained.     

Novel IV-Group Based Diluted Magnetic Semiconductor: Cr<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Ge<Subscript>1−</Subscript><Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

Cr _x Ge_{1? x} (x ～ 0.08) films were grown on GaAs (001) and Ge (001) substrates using molecular beam epitaxy (MBE) method, and their magnetic and transport properties have been studied in the temperature range between 1.8 and 300 K. All of the films exhibited weak paramagnetic behavior. Transport measurements showed that magnetoresistance ratio and the anomalous Hall resistance depend on the Cr concentration x and the kinds of substrate.