Development of smart composite structures with small-diameter fiber Bragg grating sensors for damage detection: Quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing

The authors and Hitachi Cable, Ltd. have recently developed small-diameter optical fiber and its fiber Bragg grating (FBG) sensor for embedment inside a lamina of composite laminates without strength reduction. The outside diameters of the cladding and polyimide coating are 40 and 52 μm, respectively. First, a brief summary is presented for applications of small-diameter FBG sensors to damage monitoring in composite structures. Then, we propose a new damage detection system for quantitative evaluation of delamination length in CFRP laminates using Lamb wave sensing. In this system, a piezo-ceramic actuator generates Lamb waves in a CFRP laminate. After the waves propagate in the laminate, transmitted waves are received by an FBG sensor attached on or embedded in the laminate using a newly developed high-speed optical wavelength interrogation system. This system was applied to detect interlaminar delamination in CFRP cross-ply laminates. When the Lamb waves passed through the delamination, the amplitude decreased and a new wave mode appeared. These phenomena could be well simulated using a finite element analysis. From the changes in the amplitude ratio and the arrival time of the new mode depending on the delamination length, it was found that this system could evaluate the delamination length quantitatively. Furthermore, small-diameter FBG sensors were embedded in a double-lap type coupon specimen, and the debonding progress could be evaluated using the wavelet transform.     

同质外延CVD金刚石膜的室温边发射

利用高功率微波等离子体化学气相沉积方法及合适的预处理方法成功地合成了无生长丘的高品质金刚石膜，阴极荧光（CL）结果表明在本工作的同质外延金刚石膜中，边发射在室温下也是主峰之一。详细研究了室温下有异常粒子和无异常粒子的样品的CL谱和CL扫描图，发现边发射主要产生于无异常粒子区域。而大多数异常粒子主要对位于425nm的BandA发射起作用，因此抑制异常粒子的形成对提高同质外延金刚石摸的质量非常重要。     

Synthesis and improved electron field emission characteristics of Au-coated nano-carbon needle films

Nano-carbon needle films (NCNFs) coated with a 5-nm Au layer were prepared on p-type Si (100) substrates by means of quartz-tube type microwave plasma chemical vapor deposition (MWPCVD) at different total gas pressures and an electron beam (EB) method. The NCNF deposited at the total gas pressure of 60 Torr had better field emission (FE) characteristics due to the dense structure of carbon sheets, good direction and high density of carbon needles. The FE properties were obviously improved due to depositing Au thin layer on NCNFs. The FE current density at a macroscopic electric field, E, of 10 V/μm was increased from 68.2 mA/cm² to 154.6 mA/cm² and the threshold field was decreased from 2.4 V/μm to 2.1 V/μm for the Au-coated NCNF deposited at the total gas pressure of 60 Torr. The three-region E model was employed to reasonably explain the FE data.     

A comparative study of transcranial Doppler sonography and near-infrared spectroscopy for the assessment of cerebrovascular CO2 reactivity

Oleanolic acid (1) was identified as an anti-HIV principle from several plants, including Rosa woodsii (leaves), Prosopis glandulosa (leaves and twigs), Phoradendron juniperinum (whole plant), Syzygium claviflorum (leaves), Hyptis capitata (whole plant), and Ternstromia gymnanthera (aerial part). It inhibited HIV-1 replication in acutely infected H9 cells with an EC50 value of 1.7 microg/mL, and inhibited H9 cell growth with an IC50 value of 21.8 microg/mL [therapeutic index (T. I.) 12.8]. Pomolic acid, isolated from R. woodsii and H. capitata, was also identified as an anti-HIV agent (EC50 1.4 microg/mL, T. I. 16.6). Although ursolic acid did show anti-HIV activity (EC50 2.0 microg/mL), it was slightly toxic (IC50 6.5 microg/mL, T. I. 3.3). A new triterpene (11) was also isolated from the CHCl3-soluble fraction of R. woodsii, though it showed no anti-HIV activity. The structure of 11 was determined to be 1beta-hydroxy-2-oxopomolic acid by spectral examination. Based on these results, we examined the anti-HIV activity of oleanolic acid- or pomolic acid-related triterpenes isolated from several plants. In addition, we previously demonstrated that derivatives of betulinic acid, isolated from the leaves of S. claviflorum as an anti-HIV principle, exhibited extremely potent anti-HIV activity. Accordingly, we prepared derivatives of oleanolic acid and evaluated their anti-HIV activity. Among the oleanolic acid derivatives, 18 demonstrated most potent anti-HIV activity, with an EC50 value of 0. 0005 microg/mL and a T. I. value of 22 400.     

Tuning the pKa of the antihistaminic drug chlorpheniramine maleate by supramolecular interactions with water-soluble polymers

The interaction of the pharmacologically important chlorpheniramine maleate (CPM) with polyanions containing sulfonate groups such as poly(sodium 4-styrenesulfonate) (PSS), poly(sodium vinylsulfonate) (PVS), and the more hydrophobic poly(sodium 2-(N-acrylamido)-2-methyl-propanesulfonate) (PAMPS) has been studied by ¹H NMR. It was found that the pK_a of the low-molecular weight molecule (LMWM) may be modified by its interaction with the polyanions, changing from 3 to 5, due to electric charge compensation. Interestingly, the interaction of CPM with PSS produces changes in CPM resonances, such as a general broadening and upfield shifts of the signals, and NOE effects between the LMWM and the water-soluble polymer (WSP) that indicate the presence of π-π interactions.     

Digital copy milling—autonomous milling process control without an NC program

Conventional NC machine tools do not generally allow the change of cutting conditions such as depth of cut and stepover during machining operations, once they are given machining commands as NC programs. For that reason, the NC programs must be prepared adequately and verified in advance, which requires extensive time and effort. It is therefore necessary to develop functions to generate the cutter path autonomously and control the cutting conditions adaptively during machining to optimize the cutting process, maintain stable cutting, and avoid cutting trouble. This paper proposes a new architecture to realize autonomous control of the cutting process without using NC programs. A technique called digital copy milling is developed to control the NC machine tool in real time. The digital copy milling system can generate tool paths in real time, based on the principle of copy milling. In addition, a new control strategy is developed to control the cutting conditions adaptively. A prototype of an autonomous controller was implemented in a three-axis control machining center. Thereafter, experimental milling tests were carried out to verify the effectiveness of the proposed system. The cutter paths were generated autonomously by the digital copy milling system. Results show that the cutting depth and stepover can be changed during milling tests. Cutting conditions were controlled adaptively.     

Fabrication of wrinkled carbon nano-films with excellent field emission characteristics

B-doped nano-structured carbon films were deposited on Si substrates by means of chemical-vapour-deposition with 3.8-kW microwave-plasma. Scanning electron microscope images show that the deposited films were composed of wrinkled graphitic nano-sheets with considerable disorder structures. Field emission (FE) characteristics measured from such films yielded considerably high FE currents, being larger than 50 mA/cm² at a macroscopic electric field of 9.5 V/μm. A possible mechanism of the observed FEs is discussed in relation to a modified Fowler–Nordheim equation considering field-dependent parameters. As a result, it is found that the structure of the surface geometry mainly increased the FE current densities. Adding a suitable amount of B-component gas to the carbon source gas resulted in a considerable increase in the FE areas of the wrinkled carbon nano-films.     

Further Characterization of 394-GHz Gyrotron FU CW GII with Additional PID Control System for 600-MHz DNP-SSNMR Spectroscopy

A 394-GHz gyrotron, FU CW GII, has been designed at the University of Fukui, Japan, for dynamic nuclear polarization (DNP)-enhanced solid-state nuclear magnetic resonance (SSNMR) experiments at 600-MHz ¹H resonant frequency. After installation at the Institute for Protein Research (IPR), Osaka University, Japan, a PID feedback control system was equipped to regulate the electron gun heater current for stabilization of the electron beam current, which ultimately achieved stabilization of output power when operating in continuous wave (CW) mode. During exploration to further optimize operating conditions, a continuous tuning bandwidth of approximately 1 GHz was observed by varying the operating voltage at a fixed magnetic field. In the frequency range required for positive DNP enhancement, the output power was improved by increasing the magnetic field and the operating voltage from their initial operational settings. In addition, fine tuning of output frequency by varying the cavity cooling water temperature was demonstrated. These operating conditions and ancillary enhancements are expected to contribute to further enhancement of SSNMR signal.     

A novel meshing algorithm for dynamic finite element analysis

This paper describes a new algorithm to handle problems in dynamic finite element analysis and run-time simulation, where mesh re-generation or dynamic adjustment is required. Based on a concept called coded box cell (CBC) substitution, this algorithm can be applied to both initial mesh generation and dynamic mesh adjustment along the border zones of multiple primitives that form an entire model. During the initial mesh generation, appropriate labels are assigned to the nodes and the faces of each finite element. These labels are used to facilitate decision-making in dynamic mesh adjustment. A mapping technique is adopted to transform curved surfaces to plain surfaces for the ease of automatic mesh adjustment while still using the same algorithm. The results of a case study show that a finite element mesh can be adjusted dynamically and locally around its border zone; and the algorithm can be utilized effectively to simulate the thermal behavior of a device under real operating conditions.