High-Temperature Strength of Sinter-Forged Silicon Nitride with Lutetia Additive

A sinter-forging technique was successfully applied to fabricate a silicon nitride with a lutetia (Lu₂O₃) additive. The sinter-forged specimen had a strongly anisotropic microstructure where rodlike silicon nitride grains preferentially aligned perpendicular to the forging direction. The specimen exhibited superior strength of ∼700 MPa at 1500°C. This strength was highest when compared with previous silicon nitrides at temperatures >1400°C. Such superior high-temperature strength was attributed to grain alignment as well as to the refractory grain-boundary glassy phase and the existence of glass-free grain boundaries.     

Preparation of PMMA macromers by o-vinylbenzylmagnesium chloride and their polymerization

Summary Polymerization of MMA with o-vinylbenzylmagnesium chloride was examined in toluene and in tetrahydrofuran (THF) at various temperatures. The polymer formed in toluene at –78°C was highly isotactic (mm=94%) and containing one vinylbenzyl group at the -end of the chain, although the methanol-soluble fraction concomitantly formed in an appreciable amount was less isotactic. The PMMAs formed in THF at –78 and –98°C were mostly methanol-soluble and highly syndiotactic (rr=88% at –78°C and 96% at –98°C), and also contained one vinylbenzyl group. The methanol-soluble, isotactic and syndiotactic PMMA macromers were polymerized or copolymerized with styrene by AIBN in toluene at 60°C. The isotactic macromer exhibited slightly higher reactivity than the syndiotactic one.     

High pressure syntheses of copper oxychlorides with K2NiF4-type and related structures

Several new copper oxychlorides with the K₂NiF₄-type and related structures (the 02(n-1)n where n=1, 2 and 3, and the 0222 structures) are synthesized using a high pressure technique. These are (Ca,K)₂CuO₂Cl₂ (T_c = 24 K), Ba₂CuO₂Cl₂ for the 0201; (Sr,Ca)₃Cu₂O₄₊Cl_2–y (T_c = 80 K) for the 0212; (Sr,Ca)₄Cu₃O₆₊Cl_2–y (T_c = 46 K) for the 0223; CaLnCuO₃Cl (Ln=Y, Ho, Er) for the 0222. Hole carrier doping to induce superconductivity and size tuning of the CuO₂ sheet are attained in these new oxychlorides.     

Improvements of detection accuracy and its confidence of defective areas by YOLOv2 using a data set augmentation method

Artificial Life and Robotics - Recently, CNN (Convolutional Neural Network) and Grad-CAM (Gradient-weighted Class Activation Map) are being applied to various kinds of defect detection and position...     

Stereoregular polymerization of polysiobutylene macromonomer having methacryloyl function

Summary The polysiobutylene (PIB) macromonomer having methacryloyl function was prepared from a hydroxy-terminated PIB, -phenyl--(2-hydroxy-1-methylethyl)-poly(1,1-dimethylethylene) and methacryloyl chloride in the presence of triethylamine. The macromonomer was polymerized by various anionic initiators to form stereoregular polymacromonomers. The polymerization of the macromonomer with t-C₄H₉MgBr and n-C₄H₉Li in toluene gave isotactic polymacromonomers. On the other hand, syndiotactic-rich polymacromonomers were obtained in the polymerizations with 1,1-diphenylhexyllithium in tetrahydrofuran and with t-C₄H₉Li/(C₂H₅)₃Al in toluene.     

PMMA-block-polyisobutylene-block-PMMA prepared with α,ω-dilithiated polyisobutylene and its characterization

Summary A triblock copolymer of PMMA and polyisobutylene(PIB), PMMA-block-PIB-block-PMMA, was prepared by anionic polymerization of methyl methacrylate initiated with , -dilithiated poly(isobutylene) diisobutylate in tetrahydrofuran at -60°C. The molecular weight distribution of the block copolymer was close to that of the starting PIB. The stereoregularity of PMMA block was predominantly syndiotactic. Proton spin-lattice relaxation time and solution viscosity of the block copolymer in acetone, which is non-solvent for PIB, indicate that the block copolymer forms rigid spherical particles. Stereocomplex formation with isotactic PMMA was also studied.     

Proposal for new catalytic roles for two invariant residues in Escherichia coli ribonuclease HI

Three mutants of Escherichia coli ribonuclease HI, in whichan invariant acidic residue Asp134 was replaced, were crystallized,and their three-dimensional structures were determined by X-raycrystallography. The D134A mutant is completely inactive, whereasthe other two mutants, D134H and D134N, retain 59 and 90% activitiesrelative to the wild-type, respectively. The overall structuresof these three mutant proteins are identical with that of thewild-type enzyme, except for local conformational changes ofthe flexible loops. The ribonuclease H family has a common activesite, which is composed of four invariant acidic residues (Asp10,G1u48, Asp70 and Asp134 in E.coli ribonuclease HI), and theirrelative positions in the mutants, even including the side-chainatoms, are almost the same as those in the wild-type. The positionsof the -polar atoms at residue 134 in the wild-type, as wellas D134H and D134N, coincide well with each other. They arelocated near the imidazole side chain of His124, which is assumedto participate in the catalytic reaction, in addition to thefour invariant acidic residues. Combined with the pH profilesof the enzymatic activities of the two other mutants, H124Aand H124A/D134N, the crystallographic results allow us to proposea new catalytic mechanism of ribonuclease H, which includesthe roles for Asp134 and His124.     

Studies on melt spinning. II. Steady-state and transient solutions of fundamental equations compared with experimental results

In the part installment of the present paper, the authors formulated the dynamics of melt spinning by introducing a set of fundamental equations that consist of the equations of heat, force, and material balances. Some steady-state solutions were also given. Additional steady-state solutions corresponding to many different spinning conditions for polyester and polypropylene filament yarns consistently show good agreement with experimental results. These steady-state solutions that give filament cross-section A (x) and filament temperature t(x) as functions of position x are correlated with yarn qualities: yarn density and birefringence, crystallinity and molecular orientation, are correlated respectively with the speed of Polymer cooling at 100°C. and the maximum tensile stress (F/A)_w acting on the filament. A transient solution of the fundamental equations computed on an IBM 1401 machine shows that the filament cross-section A at the take-up roll forms a large transient peak after a stepwise increase in the speed v_y of cooling air. This agrees with experiments fairly well. The fundamental equations, therefore, clarify the dynamic relations between cooling air speed and yarn weight variations.     

A 209 K-transistor ECL gate array with RAM

A 12 K-gate ECL gate array with 36 kbit of dedicated RAM has been developed. An ECL logic cell structure with an extra transistor buried under a V/sub cc/ power bus is proposed to implement both the logic function and a memory cell. The logic part has the capability of implementing configurable RAM with up to 5.8 kbit. By employing 0.6- mu m double-polysilicon self-aligned technology, the intrinsic gate delay is 110 ps at a power consumption of 1.8 mW/gate. The address access times of dedicated RAM and configurable RAM are 3.0 and 1.8 ns, respectively. The gate array is applied to 9 K-gate logic circuitry with 35-kbit table look-aside buffer (TLB) memory using dedicated RAM and a 16-word*18-bit register file using configurable RAM.<>     

High-Performance Boron Nitride-Containing Composites by Reaction Synthesis for the Applications in the Steel Industry

In this study boron nitride-containing composites (BNCC) with high strength, low Young's modulus and highly improved strain tolerance have been developed by reaction synthesis technology. The in situ formed BN particles with fine (nanosized) particle size were distributed homogeneously and isotropically in the matrixes, which decreased the negative effect of the BN phase on the composite properties. In order to be relevant to the wide applications in the steel industry such as break rings for horizontal casting of steel, the BNCC (i.e., AlON–BN composites) were evaluated in terms of the corrosion resistance to molten steel, wear and thermal shock resistance. The results demonstrate that the AlON–BN composites outperform those of the currently employed materials especially with respect to corrosion resistance.