Size Reduction of Tunable Micromachined Filters for High Speed Operations

The size reduction of tunable micromachined filters is carried out for high-speed wavelength tuning. We fabricated micromachined filters having a miniature structure with an air gap of 300 nm and a short cantilever of 45 μm, exhibiting fast response of below 3 μs.     

Submillimeter-wave spectroscopy of HCN in excited vibrational states

Measurements of the rotational spectrum of HCN in excited vibrational states have been extended to higher-J values. The transitions reach J=8←7 around 710 GHz for most vibrational states studied in this investigation and J=22←21 near 2 THz for the (020) and (030) vibrational states. Using a pure sample of gaseous HCN at 350 K, selected states up to one quantum in the C–H stretching vibration at 3311.5 cm⁻¹ have been investigated. Even transitions having two quanta in the C–H stretch could be studied employing a glow discharge in a gas mixture of CH₄ and N₂. Molecular constants in 13 vibrational states have been obtained, several of which have been studied for the first time by rotational spectroscopy. The vibrational temperature in the discharge system is found to be about 1500 K for the stretching vibrational modes and about 600 K for the bending states.     

Metal matrix composite solidification in the presence of cooled fibers: numerical simulation and experimental observation

Attempts have been made to alter the solidification microstructures of fiber reinforced aluminum composites by cooling the ends of the fibers extending out of the mold. Experimental observations indicate that cooling the extended ends of the reinforcement results in finer microstructures in the matrix and changes the nature of the interface. In this paper, numerical simulation is performed on a two-dimensional axi-symmetric model to investigate the solidification process of metal matrix composite (MMC) with the extended ends of the fibers cooled by a heat sink. The numerical simulation is based on the source-based enthalpy method with finite volume discretization. The temperature profiles obtained by simulation are compared to the cooling curves measured experimentally in order to validate the current mathematical model. It is found that the simulation result matches the experimental data with reasonable agreement.     

Numerical simulation and experimental study of solidification of squeeze cast aluminum composites in the presence of cooled fibers

In order to improve the material properties of fiber-reinforced aluminum composites, experimental research has been carried out to create finer matrix microstructures and novel interfaces between aluminum matrix (A2014) and carbon fibers using a modified pressure infiltration technique. In this novel process the ends of the fibers extending outside the mold are cooled by using a variety of heat sinks. Solidification microstructures show that the dendrite arm spacing in between and around the fibers are much finer than in the region where there are no fibers. This suggests the possibility of refining the matrix microstructures by cooling the fibers extending out of the mold. A numerical simulation is also performed to study the solidification process of aluminum matrix by finite volume method. The cooling curves obtained by the simulation are compared with the experimentally measured cooling curves in order to validate the numerical model. It is found that the simulation result closely matches the experimentally obtained data.     

Immobilization of photosystem I or II complexes on electrodes for preparation of photoenergy-conversion devices

Photosystems, PSI and PSII isolated from Thermosynechococcus elongatus were successfully immobilized on a TiO₂ nanostructured film for use in dye-sensitized biosolar cells (DSBCs). The photosystem complexes were also immobilized on an ITO electrode modified with 3-aminopropyltriethoxysilane by utilizing the interactions between the electrode and the surface of the PSI or PSII polypeptide. Illumination of the PSI and PSII complexes immobilized on the ITO electrode resulted in action spectra in the presence of methyl viologen, which corresponded to the absorption spectra of the complexes. Compared with the ITO electrode, PSI or PSII complexes assembled on the TiO₂ electrode had much higher energy-conversion efficiency in the presence of an iodide/triiodide redox system of an ionic-liquid-based electrolyte. This could have interesting applications in the development of DSBCs.     

Determination of 129I/127I in environmental water before and after the 2011 Fukushima Daiichi nuclear power plant accident with a solid extraction disk

A Cs selective solvent composed of 0.08 M chlorinated cobalt dicarbollide and 0.5 % PEG 400 (polyethylene glycol of average molecular weight of 400) in phenyl trifluoromethyl sulphone (PTMS) was used for the extraction of Cs(I) and Sr(II) from nitric acid solution as well as synthetic pressurized heavy water reactor (PHWR) high level waste (HLW) solution. Comparison was also done with analogous solvent system in nitrobenzene and xylene diluent mixture. The various experiments included acid concentration variation and PEG-400 concentration variation. A sharp decrease in the Cs(I) and Sr(II) extraction was noticed with increasing nitric acid concentration. On the other hand, while PEG-400 concentration variation had very little effect on Cs(I) extraction, it has a very significant influence on Sr(II) extraction. Batch co-current extraction studies were carried out with solvents made from both the diluent systems and the results indicated that PTMS based solvent system was superior to that containing nitrobenzene and can be used for the recovery of the metal ions from actual PHWR-HLW. Radiolytic degradation studies were also carried out and the results suggested reasonably good stability of the solvent system.     

Simulation of metal matrix composite solidification in the presence of cooled fibers

Metal matrix composite (MMC) has been well known for its superior material properties compared with traditional composite. A new method is introduced to improve the properties of MMC in the sense that the ends of the reinforcement phase of the composite are allowed to extend out of the mold and cooled by a heat sink in order to promote the rate of heat transfer through the fibers and promote the formation of primary alpha phase around the reinforcement. This paper presents the experimental results obtained from the foundry in the University of Wisconsin-Milwaukee and some numerical simulation results of the solidification process in the cast mold.     

System for precise measurement in inverse Raman spectroscopy

A system for precise measurement was developed for inverse Raman spectroscopy, using a cw argon laser and a pulsed dye laser pumped by a YAG laser. The frequency accuracy was assured by monitoring the frequency of both of the lasers with an iodine fluorescence cell or a Fabry-Perot etalon dynamically calibrated by a stabilized HeNe laser. The spectrometer system employed a digitally controlled mechanism to handle the complicated measurement procedure and hence to reduce the overall measurement time. The performance of the system was tested by measuring the CH₄ v₁ lines and the H₂ Q(1) line.