Sharpness Matching between Digital Image Display Devices

A method is presented for matching apparent sharpness between digital image display devices with different characteristics. The sharpness is most precisely described by the point spread function (PSF) as opposed to dot density such as DPI (dot per inch). The difference between devices is expressed as difference between transfer functions obtained from the PSFs. In the presented method, spatial frequency filtering for one digital image is carried out where the ratio of the transfer functions or its modified version is used as filter. The modification is introduced as a clipping operation to reduce excessive enhancement when the ratio of the transfer functions has a high pass characteristic with large gain. Through computer simulation including a subjective evaluation experiment and numerical evaluation, the effectiveness of filtering operation for sharpness matching is demonstrated.     

Dielectric relaxations and molecular motions in poly(vinylidene fluoride) with crystal form II

Molecular motions in poly(vinylidene fluoride) were studied by dielectric measurements. Of the three relaxation processes, the α_a and the α_c were studied. The α_a relaxation was attributed to the molecular motions in the amorphous regions and the α_c relaxation to molecular motions in the crystalline regions and their surfaces. The relaxation time and the magnitude of the α_a absorption were analyzed on the basis of the Adam-Gibbs theory of the temperature dependence of the size of the cooperatively rearranging region. As a result it was concluded that the molecular structure of crystal form II holds locally, even in the amorphous regions. The relaxation time and the magnitude for the α_c absorption were analysed on the basis of the two-site model. It was concluded that the α_c relaxation is attributable not only to molecular motions in the folds of the lamellar crystals, but also to those in the interior of the crystal; the folded chain is relatively mobile, while the molecular chain in the interior of the crystal executes restricted rotation around the chain axis.     

Relationship between structure and dielectric behavior of stereoregular poly(methyl methacrylate) in the glassy state

In order to elucidate the relationship between dielectric behavior and structure in solid polymers, we studied the dielectric relaxation of stereoregular poly(methyl methacrylate) (PMMA) in the glassy state. Assuming that the extremes of molecular structure are attained in the crystal and in solution, the most probable conformation of the main chain in the glassy state is estimated for isotactic and syndiotactic PMMA in terms of conformational analysis, the unperturbed mean-square end-to-end distance in solution, and the NMR second moment in the glassy state. Under the assumption that the molecular structure varies in a limited range near the most probable conformation and that the α-methyl group rotates freely, the energy barrier for the rotation of the side group is calculated. With the calculated energy barrier, the dielectric relaxation due to the side group is interpreted fairly satisfactorily by the barrier theory of Hoffman and Lauritzen, although the width of the relaxation curve is not. The experimental result that the loss peak of syndiotactic PMMA is located at higher temperature than that of isotactic PMMA is interpreted qualitatively in terms of different conformations for the syndiotactic and isotactic chains.     

A vector processing algorithm of auxiliary integral evaluation for two-electron Gaussian integrals

A six-term auxiliary integral expression for the two-electron Gaussian integral is derived on the basis of the Chebyshev polynomial approximation instead of the seven-term Taylor expansion. This expression and the related recurrence formula enable us to perform a high-speed calculation on a vector processing computer.     

Effects of annealing and isothermal crystallization upon crystalline forms of poly(vinylidene fluoride)

Poly(vinylidene fluoride) exists in three crystalline forms. Optimum conditions for preparing form III were established by infrared spectroscopy, differential scanning calorimetry, and x-ray diffraction measurements. Form III is easily obtained by annealing mats of solution-grown crystals of form II at 175–185°C and is also preferentially formed by isothermal crystallization from the melt between 165 and 175°C. Below 165° crystallization of form II is favored. The melting point of form III is higher than that of form II.     

Effects of diluent on molecular motion and glass transitions in polymers. III. The system poly(vinyl acetate)–toluene

Dielectric measurements, differential thermal analyses (DTA), and broad-line proton magnetic resonance (NMR) measurements are reported on the system poly(vinyl acetate)–toluene. Four dielectric relaxations were observed between 80 and 400°K. From proton NMR measurements on solutions in toluene and in deuterated toluene, the relaxation processes can be assigned, respectively, to segmental motion of poly(vinyl acetate), α; motion of side group, β′ rotation of toluene, β; local motions of poly(vinyl acetate) and toluene, γ, in order of appearance with decreasing temperature. Two stepwise changes in DTA traces have been observed and can be assigned as glass transition points T_gI and T_gII. Comparison of these glass transition points with temperatures at which dielectric relaxation times for the α and β processes are 100 sec, indicate that segmental motion of poly(vinyl acetate) and rotation of toluene are frozen-in at T_gI and T_gII, respectively. Activation plots for the α process conform to the Vogel–Tamman equation. In terms of the parameters A, B, and T₀ of the equation, T_gI can be represented by an expression of the form T_gI ≈ T₀ + B/(A + 3). In the range of concentration above 50% by weight, A and B are almost independent of concentration but T₀ varies strongly. The nature of the secondary dispersions is also discussed.     

Photoinduced change in the charge order pattern in the quarter-filled organic conductor (EDO-TTF)2PF6 with a strong electron-phonon interaction

The quasistable state in the photoinduced phase transition for the quasi-one-dimensional quarter-filled organic conductor (EDO-TTF)2PF6 has been examined by ultrafast reflective measurements and time-dependent model calculations incorporating both electron-electron and electron-phonon interactions. The transient optical conductivity spectrum over a wide probe photon-energy range revealed that photoexcitation induced a new type of charge-disproportionate state. Additionally, coherent and incoherent oscillations dependent on probe photon energies were found, as predicted by the calculation.