Membership problems for data dependencies in relational expressions

In relational databases, a query can be formulated in terms of a relational algebra expression using projection, selection, restriction, cross product and union. In this paper, we consider a problem, called the membership problem, of determining whether a given dependency d is valid in a given relational expression E over a given database scheme R that is, whether every instance of the view scheme defined by E satisfies d (assuming that the underlying constraints in R are always satisfied).Consider the case where each relation scheme in R is associated with functional dependencies (FDs) as constraints, and d is an FD. Then the complement of the membership problem is NP-complete. However, if E contains no union, then the membership problem can be solved in polynomial time. Furthermore, if E contains neither a union nor a projection, then we can construct in polynomial time a cover for valid FDs in E, that is, a set of FDs which implies every valid FD in E.Consider the case where each relation scheme in R is associated with multivalued dependencies (MVDs) as well as FDs, and d is an FD or an MVD. Even if E consists of selections and cross products only, the membership problem is NP-hard. However, if E contains no union, and each relation scheme name in R occurs in E at most once, then the membership problem can be solved in polynomial time. As a corollary of this result, it can be determined in polynomial time whether a given FD or MVD is valid in $\text{R}{}_1\text{???R}{}_{\mathrm{s}}$, where R₁,…,R_s are relation schemes with FDs and MVDs, and $\text{R}{}_{\mathrm{i}}\text{?R}{}_{\mathrm{j}}$ is the natural join of R_i and R_j.     

Single-mode fibres with extremely high-Δ and small-dimensionpure GeO2 core for efficient nonlinear optical applications

Single-mode fibres with 8.2% Δ and a 1.4 μm diameter-GeO ₂ core have been prepared for efficient stimulated Raman effect. When pumping a 2.7 m-long fibre by a Q-switched and mode-locked Nd:YAG laser (λ=1.064 μm), the first Stokes light (λ=1.114 μm) and second Stokes light (λ=1.169 μm) have been observed at the input peak power levels of 24 W and 40 W, respectively. These results indicate that the above critical power levels are approximately 10^-2~10^-3 smaller than those for the high-silica single-mode fibre     

3 km-long single-polarisation single-mode fibre

A single-polarisation single-mode (SPSM) fibre with crosstalk of ?40 dB in a 3.2 km length has been demonstrated. No crosstalk degradation was found for lengths of more than 0.2 km. The two polarisations of the fundamental mode were split with a high modal birefringence of 8.5×10?4, which was produced by PANDA structure. The transmission loss was 2.8 dB/km at 1.56 ?m.     

Robust Computation of Intersection Graph between Two Solids

We propose a new robust algorithm for Boolean operations on solid models. The algorithm produces a consistent intersection graph between two input solids whose geometrical data are represented in floating point numbers. In order to prevent numerical calculation errors and inaccuracy of input data from causing inconsistency of the output, we put higher priority on symbolical connectivity of the edge-face intersection points than their numerical nearness. Each edge-face intersection point is symbolically represented using face names, which generate connectivity relations between the intersection points and the intersection line segments. The symbols with the same connectivity are made into clusters. The intersection line segments connected together at their end clusters form the intersection graph of two solids. Inconsistency of the connectivity of the clusters is detected and the intersection graph is corrected automatically. We describe the algorithm in detail for polyhedral solids, discuss extension to curves solids, and show its effectiveness by some examples of Boolean operations for two solids whose faces intersect at a very small angle.     

Vinyl polymerization: 414. Polymerization of vinyl monomer initiated by poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride

The polymerization of vinyl monomer initiated by an aqueous solution of poly(N,N,N-trimethyl-N-2-methacryloxyethyl)ammonium chloride (poly(Q-DMAEM-CI) has been carried out at 85°C. The effects of the amounts of vinyl monomer, poly(Q-DMAEM-CI) and water on the conversion of vinyl monomer have been studied. The overall activation energy in the polymerization of MMA is estimated as 41.9 kJ mol^?1. The polymerization proceeds through a radical mechanism. The location in which the polymerization occurs is discussed. The selectivity for vinyl monomer is explained by ‘the concept of hard and soft hydrophobic areas and monomers’.     

A self-converging atomized mist spray device using surface acoustic wave

This paper presents an innovative versatile method aiming at rapid fabrication of a master for polydimethylsiloxane (PDMS) molding. This technology is relying on liquid dielectrophoresis electromechanical microfluidic transduction for programmable ultraviolet (UV) glue manipulation. It enables formation of the master in a tailor-made approach, avoiding the need of micromachined structures unlike in conventional methods. The principle is simple: UV glue, while in liquid phase, is actuated onto an array of electrodes patterned on a Si substrate and cured afterward by UV exposure. The silicon chip and the glue microstructures defined atop of it then play the role of a master for PDMS molding. The glue microstructures’ shape is hemispherical which is of high interest for many microfluidic applications. This concept is assessed and validated with two different PDMS chip replica designs, both of them illustrating representative applications in continuous microfluidic: a T-junction design for inflow droplet generation and a “Quake” type valve. Lastly, this protocol has shown to be recyclable since the UV glue microstructures once formed can be easily removed by immersion in an acetone bath, such as the chip is reset and can be reprogrammed afterward to build another glue channels geometry.     

New Members of the Pb-based 1222 Superconductor Containing Phosphorus: (Pb0.75P0.25)Sr2(Ln1.9?x Ce x Sr0.1)Cu2O z (Ln=Sm and Gd)

We previously reported on the synthesis of new Pb-based 1222 superconductor containing phosphorus in the (Pb_0.75P_0.25)Sr₂(Eu_1.9−x Ce _x Sr_0.1)Cu₂O _z system. Recently, we have discovered new members of the Pb-based 1222 superconductor containing phosphorus in the (Pb_0.75P_0.25)Sr₂(Ln_1.9−x Ce _x Sr_0.1)Cu₂O _z (Ln=Sm and Gd) systems. In each system, it is found that the samples of almost the single 1222 phase can be obtained for a wide composition area of 0.3≤x≤1.0. After annealing under 143 atm O₂ atmosphere at 400 °C, each sample of Ln=Sm and Gd with x=0.3 is found to show an onset of resistivity-drop at about 28 K and at about 24 K, respectively. Moreover, each samples of Ln=Sm and Gd is found to show an onset of diamagnetic signal at about 25 K and about 22 K, respectively. From these facts, these samples of Ln=Sm and Gd are found to be new members of the Pb-based 1222 superconductor containing phosphorus.     

3D Scan matching for mobile robot localization over rough terrain

In order to enable an autonomous mobile robot to travel over rough terrain, it necessitates the capability to detect self‐position accurately even when the odometry errors are increased in traveling. The conventional method can keep high speed and precise localization using iterative closest point algorithms or feature matching techniques. However, effects of steep changes of a mobile robot position are not considered when it travels over rough terrain. In this article, we propose the method for efficient real‐time 6D pose tracking using a rotating 2D laser scanner in traveling over rough terrain. For adaptation to steep changes of the position, weighted point clouds are generated based on the angular and the linear velocity measured by sensors mounted on the robot. And the position and posture of the robot are sequentially optimized by the scan matching in increments of 10 scans. In indoor experiments, we evaluated accuracy of our method when the robot passes on rugged floor. As a result, our method was performed with less than 0.078 m RMS positional error in real time.     

Prototype of Phase-Change Channel Transistor for Both Nonvolatile Memory and Current Control

We prototyped phase-change (PC) channel transistors and demonstrated two functions of nonvolatile memory and channel current control. We have developed prototype transistors that use a PC channel instead of a silicon channel. The PC material of a Ge₂Sb₂Te₅ thin film with a thickness of 50 nm was used. We demonstrated a memory function whereby we achieved a reversible change between the crystalline and amorphous phases by applying a source-drain (SD) voltage for Joule heating. In the experiment, the applied voltages for PC between amorphous and crystalline phases were from 5 to 8 V. Control of the channel current was realized by applying a gate bias. The SD current was suppressed to less than 1/20 of that at a gate bias of -3 V by applying a gate bias of 0-3 V