Strength evaluation of unidirectional carbon fiber-reinforced plastic laminates based on tension–compression biaxial stress tests

Biaxial stress tests of carbon fiber-reinforced plastic (CFRP) laminates were performed to investigate failure criteria under biaxial loads. Specimens of unidirectional CFRP laminates were subjected to a tensile load in the longitudinal fiber direction and a compressive load in the transverse fiber direction. An exclusive jig was used to perform biaxial stress tests with a commonly used single-axis testing machine. Measurements were obtained by controlling the displacement ratio between compressive and tensile displacements. The critical tensile and compressive stresses were then calculated using a constitutive equation. The critical longitudinal tensile stress markedly dropped with increasing the compressive load. The failure criteria of the biaxial stress tests were expressed as the ellipse, of which the major and minor axes were the longitudinal tensile/transverse compressive strengths or fracture strains, respectively. Scanning electron microscope observations suggest that fiber/matrix interfacial debonding due to the compressive load could decrease the critical longitudinal tensile stress.     

Seminatural Occurrence of Fullerenes

In continuation to our search of fullerenes in usual soots, sixteen additional samples of Chinese ink stick have been analyzed by HPLC. When combined with our previous results, we recognize that C₆₀-content in Chinese ink sticks decreases with time following the first order rate law. This novel observation was interpreted in terms of diffusion-dissipation of C₆₀ molecules through the solid stick.     

Identification of BWR dynamics from autoregressive analysis of multivariable experiments

A method of time series analysis was applied to study dynamics of a boiling water reactor. The main aim of this work is to examine the usefulness of a multivariable autoregressive modelling technique for identifying a complicated reactor dynamics. Two kinds of experimental data were treated by this method; one from a perturbation experiment, and the other from a measurement of fluctuations of variables under normal operation conditions. Several open loop dynamics and closed loop dynamics were successfully identified from the perturbation experiment, and some specific open loop dynamics were also obtained from the measurement of fluctuations. The identified models were compared with each other in order to clarify the difference in identifiability of the reactor dynamics under these experimental conditions. An attempt was made to validate a theoretical model, and some uncertain parameters in the model were estimated by using the identified model. These results suggest that the present method is useful not only for study of dynamics but also for diagnosis and surveillance of nuclear power plants.     

On-column derivatization using redox activity of porous graphitic carbon stationary phase: an approach to enhancement of separation selectivity of liquid chromatography

A new on-column derivatization method based on the redox activity of porous graphitic carbon (PGC) packing materials was presented for enhancement of separation selectivity of HPLC. Two PGC packing materials were used as the solid redox agents as well as the stationary phase, and their redox activities were investigated using trans-1,2-diaminocyclohexanetetraacetate (DCTA) complexes of some metal ions as probe compounds. It was found that the redox property of PGC was modified by treating them with a solution containing a reducing agent, sodium sulfite or hydroxylammonium chloride. The original PGC packings oxidized Co(II)-DCTA to Co(III)-DCTA during elution, while the PGC treated with a reducing agent showed reduction activity converting Co(III)-DCTA to Co(II)-DCTA. These two cobalt complexes do not form their individual chromatographic zones but migrate as a single zone of their mixture on the PGC column contrary to the chromatographic behavior on a C18 bonded silica, on which Co(II)-DCTA and Co(III)-DCTA can be separated. Treatment of the PGC column with a reducing agent solution transforms the oxidative activity of the original PGC packing to a reductive one from the upper part of the column, so that the retention time of the cobalt complex can be controlled by changing the volume of the reducing agent solution to be used for treatment of the PGC column. The selective separation and determination of cobalt in a reference manganese nodule sample by the developed method was demonstrated.     

Lesser Bear—a light‐weight process library for SMP computers

We have designed and implemented a light‐weight process (thread) library called ‘Lesser Bear’ for SMP computers. Lesser Bear has high portability and thread‐level parallelism. Creating UNIX processes as virtual processors and a memory‐mapped file as a huge shared‐memory space enables Lesser Bear to execute threads in parallel. Lesser Bear requires exclusive operation between peer virtual processors, and treats a shared‐memory space as a critical section for synchronization of threads. Therefore, thread functions of the previous Lesser Bear are serialized. In this paper, we present a scheduling mechanism to execute thread functions in parallel. In the design of the proposed mechanism, we divide the entire shared‐memory space into partial spaces for virtual processors, and prepare two queues (Protect Queue and Waiver Queue) for each partial space. We adopt an algorithm in which lock operations are not necessary for enqueueing. This algorithm allows us to propose a scheduling mechanism that can reduce the scheduling overhead. The mechanism is applied to Lesser Bear and evaluated by experimental results. Copyright © 2001 John Wiley & Sons, Ltd.     

Lesser Bear: A lightweight process library for SMP computers—scheduling mechanism without a lock operation

We have designed and implemented a lightweight process (thread) library called ‘Lesser Bear’ for SMP computers. Lesser Bear has thread‐level parallelism and high portability. Lesser Bear executes threads in parallel by creating UNIX processes as virtual processors and a memory‐mapped file as a huge shared‐memory space. To schedule thread in parallel, the shared‐memory space has been divided into working spaces for each virtual processor, and a ready queue has been distributed. However the previous version of Lesser Bear sometimes requires a lock operation for dequeueing. We therefore proposed a scheduling mechanism that does not require a lock operation. To achieve this, each divided space forms a link topology through the queues, and we use a lock‐free algorithm for the queue operation. This mechanism is applied to Lesser Bear and evaluated by experimental results. Copyright © 2002 John Wiley & Sons, Ltd.     

Generation of a regularly aligned surface pattern and control of cutter marks array by patch division milling

In this paper, a patch division milling technique that can generate a geometric surface pattern by means of a ball-end mill on a surface is proposed. The finished surface is divided into many same-size small patch segments such as triangles, quadrilaterals, or hexagons. The whole inside area of each patch is machined along a helical tool path with a high feed rate. A geometric surface pattern is generated by the cutting edges of the ball-end mill within the patch area, and after the machining of a series of patches, the machined surface is covered with many patches. It is shown that the aligned state of the cutter marks array on the patch can be controlled by the cross-feed, the feed speed per tooth, the number of teeth and the side length of the patch. A simulator was also developed to predict the aligned state of the cutter marks array in the patch. Comparing the machining on the patch division milling between an inclined flat surface and a cylindrical surface, the regularly aligned surface pattern and cutter marks array were found to agree well with the simulation results. The objective of this research is to establish the cutting method of generating regularly aligned surface pattern on the complex-shaped workpiece efficiently. If the surface pattern on the complex-shaped workpiece could be formed only by the ball-end milling with a machining center, it will be a very effective tool for the machinery industry.     

Oxygen Potential of U0.85Zr0.15O2+x Solid Solutions at 15000°C

Oxygen potentials for U_0.85Zr_0.15O_2+x solid solutions with the fluorite structure (prepared at 1500°C) were measured at 1500°C by a thermogravimetric technique. The oxygen potentials were 12 to 20 kJ/mol lower than those of pure UO_2+x at a given oxygen-to-metal ratio; they cannot be represented as a function of mean uranium valence .     

Optical half-band filters

This paper proposes two kinds of novel 2×2 circuit configuration for finite-impulse response (FIR) half-band filters. These configurations can be transformed into each other by a symmetric transformation and their power transmittance is identical. The configurations have only about half the elements of conventional FIR lattice-form filters. We derive a design algorithm for achieving desired power transmittance spectra. We also describe 2×2 circuit configurations for infinite-impulse response (IIR) half-band filters. These configurations are designed to realize arbitrary-order IIR half-band filter characteristics by extending the conventional half-band circuit configuration used in millimeter-wave devices. We discuss their filter characteristics and confirm that they have a power half-band property. We demonstrate design examples including FIR maximally flat half-band filters, an FIR Chebyshev half-band filter, and an IIR elliptic half-band filter     

Hypomethylation of CLDN4 Gene Promoter Is Associated with Malignant Phenotype in Urinary Bladder Cancer

The tight junction (TJ) protein claudin-4 (CLDN4) is overexpressed in bladder urothelial carcinoma (BUC) and correlates with cancer progression. However, the mechanism of CLDN4 upregulation and promotion of malignant phenotype is not clear. Here, we analyzed 157 cases of BUC and investigated the hypomethylation of CpG island in the CLDN4 promoter DNA and its correlation with cancer progression. In hypomethylated cases, CLDN4 expression, cell proliferation, stemness, and epithelial-mesenchymal transition were increased. Treatment of three human BUC cell lines with the demethylating agent aza-2′-deoxycytidine (AZA) led to excessive CLDN4 expression, and, specifically, to an increase in CLDN4 monomer that is not integrated into the TJ. The TJ-unintegrated CLDN4 was found to bind integrin β1 and increase stemness, drug resistance, and metastatic ability of the cells as well as show an anti-apoptosis effect likely via FAK phosphorylation, which reduces upon knockdown of CLDN4. Thus, CLDN4 is overexpressed in BUC by an epigenetic mechanism and the high expression enhances the malignant phenotype of BUC via increased levels of TJ-unintegrated CLDN4. CLDN4 promoter DNA methylation is expected to be a novel indicator of BUC malignant phenotype and a new therapeutic target.