A new write/erase method to improve the read disturbcharacteristics based on the decay phenomena of stress leakage currentfor flash memories

This paper describes a new write/erase method for flash memory to improve the read disturb characteristics by means of drastically reducing the stress leakage current in the tunnel oxide. This new write/erase operation method is based on the newly discovered three decay characteristics of the stress leakage current. The features of the proposed write/erase method are as follows: 1) the polarity of the additional pulse after applying write/erase pulse is the same as that of the control gate voltage in the read operation; 2) the voltage of the additional pulse is higher than that of a control gate in a read operation, and lower than that of a control gate in a write operation; and 3) an additional pulse is applied to the control gate just after a completion of the write/erase operation. With the proposed write/erase method, the degradation of the read disturb life time after 10⁶ write/erase cycles can be drastically reduced by 50% in comparison with the conventional bipolarity write/erase method used for NAND type flash memory. Furthermore, the degradation can he drastically reduced by 90% in comparison with the conventional unipolarity write/erase method fur NOR-, AND-, and DINOR-type flash memory. This proposed write/erase operation method has superior potential for applications to 256 Mb flash memories and beyond     

Digestion of crosslinked poly(vinylpyridinium halide) by activated sludge,and application to make poly(methyl methacrylate) biodegradable by incorporation of a pyridinium group into the main chain

Crosslinked poly(N-benzyl-4-vinyipyridinium bromide) has been found to be digested by activated sludge obtained from sewage works. As an extension of this work, the authors attempted to make poly(methyl methacrylate) biodegradable by incorporation of a pyridinium group. Poly(methyl methacrylate) containing a small amount of N-benzyl-4-vinylpyridinium chloride in the main chain showed remarkable reduction in molecular weight and gravimetric weight when placed in an aeration tank of a sewage works. Molecular weight reduction by activated sludge was more conspicuous when content of the pyridinium group was larger and the original molecular weight before the biological treatment was lower. Since insoluble pyridinium-type polymer captures microbial cells alive, this biodegradation appears to be facilitated by enhancement of affinity of the synthetic hydrophobic polymer with cells of microogranisms. © 1994 John Wiley & Sons, Inc.     

An improved prediction result of entropic‐FV model for vapor–liquid equilibria of solvent–polymer systems

In this work, entropic expressions of UNIFAC‐FV and Entropic‐FV models were evaluated by using an extensive database of infinite dilution vapor–liquid equilibrium (VLE) data of athermal systems containing polypropylene, polyethylene, and polyisobutylene. For the infinite dilution athermal systems, performance of the Entropic‐FV model was better than that of the UNIFAC‐FV model. Then, finite concentration VLE data of non‐athermal systems that consisted of 16 polymers and 36 solvents containing a large variety of solvent–polymer systems ranging from nonpolar to polar substances were considered to optimized 46 pairs of group interaction parameters of the Entropic‐FV model. For systems containing polar solvents of three types of solvents studied, revised group interaction parameters gave significant improvements from 17.9 to 13.0% average absolute deviation (AAD) of solvent activities. For overall results, improvements were achieved from 15.1 to 12.4% AAD. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1145–1153, 2005     

Pervaporation membranes for ethanol–water mixture prepared by plasma polymerization. III. Perfluorocarbon membranes

Pervaporation membranes for the ethanol–water mixture were prepared by plasma polymerization of tetrafluoroethylene, perfluoropropane, and perfluoropropylene onto porous substrates. The influence of the monomers on the elemental ratio (F/C) of the polymer depositions by X-ray photoelectron spectroscopy was rather small compared with that of the W/FM parameter (W = wattage for plasma excitation, FM = mass flow rate of a monomer). The optical emission spectroscopy indicated the similarity of gaseous species formed in the plasmas. The membranes were found ethanol-permselective, showing separation coefficients (α_EtOH) around 4–7 and a wide range of permeation rates (J), 10–10^?2 kg/m² h, for the 4.8 wt % ethanol solution at 40°C. The α_EtOH of the membranes with thicker depositions could be correlated to the F/C ratios as a measure of membrane hydrophobicity. It was thought that, by making a plot α_EtOH against J values for the perfluorocarbon membranes, they could be classified into three groups on thickness of deposition. The ethanol-separation mechanisms for each group, which may contain four kinds of mass transfer schemes, i.e., distillation through larger pores, flow of sorption layer at the liquid–membrane interface, and diffusions through deposition or substrate, were also discussed.     

Silica films with a single-crystalline mesoporous structure

Films of mesoporous materials attract broad interest because of their wide applicability in the fields of optics and electronics. Although many of these films have a regular local porous structure, the structural regularity has not been used practically yet because of difficulties in its control on macroscopic scales. Here, we demonstrate the preparation of mesoporous silica films whose porous structure can be described as a single crystal, that is, a long-range order of cage-like pores is maintained over centimetre scales. These films have a three-dimensional hexagonal (space group P6(3)/mmc) porous structure, and the in-plane arrangement of the pores is strictly controlled by a polymeric substrate surface that has been treated by rubbing. This new class of single-crystalline films with mesoscopic periodic structure is a significant breakthrough in bottom-up nanotechnology, and could lead to novel devices, for example, optics in a soft X-ray region, and quantum electronics.     

CHAOTIC BEHAVIOR AND TRANSITION TO TURBULENCE IN POROUS MEDIA

An experimental study has been made of the chaotic behavior in the transition to turbulence of flow through porous media consisting of a bank of tubes in a narrow gap. Judging from the examination of the correlation dimension and the maximum Lyapunov exponents, we can identify the chaotic behavior in porous media for Re > ～60. Rapid increase in the maximum Lyapunov exponents was observed for Re > ～300. Also, the spatial distribution of the Lyapunov exponents is discussed.     

A high-density NAND EEPROM with block-page programming formicrocomputer applications

A high-density, 5-V-only, 4-Mb CMOS EEPROM with a NAND-structured cell using Fowler-Nordheim tunneling for programming is discussed. The block-page mode is utilized for high-speed programming and easy microprocessor interface. On-chip test circuits for shortening test time and for evaluating cell characteristics yield highly reliable EEPROMs. The NAND EEPROM has many applications for microcomputer systems that require small size and large nonvolatile storage systems with low power consumption     

Analytical Study on Impingement Heat Transfer with Single—Phase Free—Surface Circular Liquid Jets

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Critical Heat Flux of Boiling Heat Transfer in a Moderate Narrow Space

INTanDUCTI0NBoilingheattransferandcriticalheatflux(CHF)inaconfinednarrowspacehavebeenstudiedexperi-melltallybyanumberofinvestigatorsinthepastfewdecades.However,thereisnoanypopularlyacceptedmodelintheheattransferinnarrowspaceboiling,althoughsomepopularknowledgeabouttheboilingheattransferinthenarrowspacehavebeenacceptedbymanyresearchers.Theknowledgecanbecon-cludedasthatthenucleateboilingheattransferisenhancedatlowheatfluxregionanddeterioratedathighheatfiuxregi0nespeciallyatCHF.Theenhanceme…     

Characteristics of siliconn+-n--n+ diode with sub-micrometer n- region

In this paper, the I-V characteristics of silicon n⁺-n ^--n⁺ diode are investigated as a parameter of the length of the n^- region. This diode with shorter n^- region than 1 μm has the ohmic characteristics until reaching high electric field in spite of the existence of numerous space-charges in the n^- region, for the first time in this report. This conductance of the diode is inversely proportional to the third power of the length of the n^- region. The experimental results are in good agreement with an analytical calculation including the diffusion term of carriers injected from the n+ regions to the n^- region. However, the diode with longer n^- region than 2 μm shows the space-charge-limited conduction which is the same as earlier reports