The effect of molecular weight and casting solvent on the miscibility of polystyrene-poly(α-methyl styrene) blends

The glass transition temperatures (T_g) have been measured for blends of polystyrene and poly(α-methyl styrene) in the molecular weight ranges: polystyrene, 2030 < M < 250 000, and poly(α-methyl styrene), 17 000 < M < 250 000. The presence of either one T_g or two has been used as a criterion to determine the miscibility of each blend over a range of compositions, and the T_gs were obtained from measurements of the temperature dependence of the heat capacities of the blends. A sinlge T_g was observed over the entire composition range for blends in which the component molecular weights were both less than 70 000 g mol^?1, when these were cast from toluene solutions. When propylene oxide solutions were used to prepare the blends, this limit dropped to M = 50 000 g mol^?1. By using the appearance of two T_gs as an indication that phase separation had taken place, it was possible to establish regions of miscibility and immiscibility as a function of casting solvent and molecular weight for both components. The change in heat capacity at the glass transition was measured and it was found that for miscible blends the heat capacity changes are similar to the calculated values, but for immiscible systems the measured change is smaller than expected.     

The location of both upper and lower critical phase boundaries in a polystyrene-poly(vinyl methyl ether) blend

Summary A method has been developed for the location of both upper and lower critical cloudpoint curves in miscible polymer blends. Ternary, solvent (1)/polymer (2)/ polymer (3) systems have been used and the phase separation temperatures have been measured in solutions containing a fixed ratio of the two polymers. Extrapolation to zero solvent then gives the critical temperatures for the blend. By measuring these for several blend compositions a miscibility range can be established for a quasi-binary blend of components with specific molecular weights. Using this method, both upper and lower critical temperatures have been established for a polystyrene-poly(vinyl methyl ether) mixture.     

Global mapping of greenhouse gases retrieved from GOSAT Level 2 products by using a kriging method

Because a synoptic overview facilitates understanding of the temporal and spatial changes in the global distribution of greenhouse gases, we developed a statistical spatial estimation method using kriging. Level 3 (L3) data products for the Greenhouse Gases Observing Satellite (GOSAT) Thermal And Near infrared Sensor for Carbon Observation (TANSO) Fourier Transform Spectrometer (FTS) Short Wave Infrared (SWIR) were generated from column-averaged, dry-air mole fractions of carbon dioxide (XCO₂) and methane (XCH₄) TANSO-FTS SWIR Level 2 (L2) products using this method. Although there have been some reports on the use of kriging for analysing GOSAT products, the kriging method used in this research was specifically adapted to the statistical characteristics of GOSAT L2 products. In the context of using data for atmospheric research, spatially interpolated data (GOSAT L3 products) cannot be more accurate than model-simulated global distributions of gas concentrations (GOSAT Level 4B (L4B) products), which are generated using an atmospheric tracer transport model. However, the L3 product takes much less time to generate than the L4B. It would take about a year to produce the L4B after generation of an L2 product. The great advantage of the L3 product is that it gives a comprehensive and reasonable monthly global distribution of gas concentrations with little delay. The L3 product using the kriging method can be generated on a monthly basis by estimating global semi-variogram curves from the L2 products for each month and interpolating spatially within a region with a radius of 1000 km from existing L2 data locations. The main purpose of this paper is to describe the methodology and characteristics of kriging used to generate the GOSAT L3 product, not for strictly scientific use of the estimated values, but for a reasonable global map of gas concentrations derived statistically from the sparsely observed L2 products within a short time frame. The characteristics of this method are compared to XCO₂ products simulated with an atmospheric tracer transport model. The results show that the method proposed in this study is of practical use for generating L3 products from L2 products.     

High‐Performance Long‐Term‐Stable Dopant‐Free Perovskite Solar Cells and Additive‐Free Organic Solar Cells by Employing Newly Designed Multirole π‐Conjugated Polymers

Perovskite solar cells (PSCs) and organic solar cells (OSCs) are promising renewable light‐harvesting technologies with high performance, but the utilization of hazardous dopants and high boiling additives is harmful to all forms of life and the environment. Herein, new multirole π‐conjugated polymers (P1–P3) are developed via a rational design approach through theoretical hindsight, further successfully subjecting them into dopant‐free PSCs as hole‐transporting materials and additive‐free OSCs as photoactive donors, respectively. Especially, P3‐based PSCs and OSCs not only show high power conversion efficiencies of 17.28% and 8.26%, but also display an excellent ambient stability up to 30 d (for PSCs only), owing to their inherent superior optoelectronic properties in their pristine form. Overall, the rational approach promises to support the development of environmentally and economically sustainable PSCs and OSCs.     

Temperature dependence of polymer chain dimensions in the polystyrene-cyclopentane system

The limiting viscosity number in polystyrene-cyclopentane system has been determined over the temperature range of θ_u to θ_l in which θ_u and θ_l are the θ or Flory temperature for the upper and lower critical solution temperatures. The temperature coefficient of unperturbed mean square end-to-end distance observed for the polystyrene (M_w=20×10⁴, $\text{M}{}_{\mathrm{w}}\text{M}{}_{\mathrm{n}}\text{<1·06}$ and M_w=67×10⁴, $\text{M}{}_{\mathrm{w}}\text{M}{}_{\mathrm{n}}\text{<1·10}$) in cyclopentane is negligibly small. The observed temperature dependence of the polymer chain dimension over the temperature range of θ_u=19·6° to θ_l=154·2°C shows a parabolic curve with a maximum in the neighbourhood of 90°C and is qualitatively interpreted by the free volume theory of polymer solution, which gives a new χ₁-temperature function.     

The cleaning at a back surface and edge of a wafer for introducingCu metallization process

Cu metallization has been introduced in high-speed complementary metal-oxide-semiconductor (CMOS) large scale integration (LSI) in order to achieve low electrical resistivity. This means Cu contamination can be spread all over semiconductor equipment by the wafers, even though Cu has been thoroughly eliminated from semiconductor manufacturing for a long time. To protect the other wafers without Cu from Cu cross-contamination, we have demonstrated a method that can clean the back surface and selectively clean the edge of a wafer simultaneously without any masks. This method performs the cleaning by optimizing the overhang of chemicals in the single-wafer system with the Bernoulli chuck. We have also demonstrated a new edge extractor that can be used to perform the quantitative evaluation of Cu contamination at the wafer edge. The combination of the edge cleaning and the edge evaluation is useful for introducing not only Cu, but also new exotic materials such as Ta₂O₅ and BST     

Assessment of snowmelt triggered landslide hazard and risk in Japan

This study is pertaining to an evaluation of landslide occurrence on natural terrain due to snowmelt in Japan, using a probabilistic model based on multiple logistic regression analysis. The evaluation concerns several physical parameters such as hydraulic parameters, geographical parameters and geological parameters which are considered to be influential in the occurrence of landslides. A Snow Water Equivalent model (SWE) is utilized to estimate snowmelt and associated infiltration in light, heavy and normal snow years. Using the constructed spatial data-sets, we apply a multiple logistic regression model to produce landslide susceptibility maps showing the spatial–temporal distribution of landslide hazard probabilities throughout Japan using 1 km × 1 km resolution grid cells. The results have revealed that, over 95% landslide hazard probability exists in the mountain ranges on the western side of Japan (the Japan Sea side). In particular, this study is dealing with the Aizu region of Fukushima prefecture in order to verifying the landslide hazard probability. Verification proved that, the areas identified as high risk areas (having over 90% landslide hazard probability in numerical modeling) show 87% agreement with observed landslides in the Aizu region. Also we evaluated the relationship between landslides and snow melting process giving special concern to change of temperature in the spring.     

A 1.3-cycle lock time, non-PLL/DLL clock multiplier based on directclock cycle interpolation for “clock on demand”

A 1.3-cycle lock-in time, non-PLL/DLL clock multiplier based on direct clock cycle interpolation is proposed with an array structure of short-circuit-current-suppression interpolators. The circuits have been fabricated with a 0.25-μm digital CMOS and operated in any condition where digital CMOS circuits operate. Measured results have achieved 1.3 clock cycle lock time and cycle-to-cycle jitter suppression characteristics. The circuits have been verified in 622-Mb/s clock and data recovery that satisfied the ITU-T G.958 jitter tolerance specification     

Constant-charge-injection programming: a novel high-speed programming method for multilevel flash memories

Constant-charge-injection programming (CCIP) has been proposed as a way to achieve high-speed multilevel programming in flash memories. In order to achieve high programming throughput in multilevel flash memory, programming method must provide: 1) high-speed cell-programming; 2) high programming efficiency; and 3) highly uniform programming characteristics. Conventional source-side channel-hot-electron injection (SSI) programming realizes both fast cell-programming and high programming efficiency, but the large cell-to-cell variation in programming speed with SSI is a problem. CCIP reduces the characteristic variation of SSI programming and satisfies all of the above requirements. By applying CCIP to 2-bit/cell AG-AND flash memory, the high programming throughput of 10.3 MB/s is obtained with no area penalty. This is 1.8 times faster than the throughput with conventional SSI programming.