Non-destructive testing of high strength concrete using spectral analysis of surface waves

Non-destructive testing is essential in the inspection of alteration, repair and new construction in construction industry. Researchers are exploring the performance of non-destructive testing method using spectral analysis of surface waves (SASW) in concrete structures. The method consists of the generation, measurement and processing of dispersive surface waves. In SASW test, the surface of the media under consideration is subject to an impact using, for example, a 12-mm steel ball, to generate surface wave energy at various frequencies. Two vertical accelerometer receivers detect the energy transmitted through the testing media. By recording signals in digitized form using a data acquisition system and processing them, surface wave velocity can be obtained using a dispersion curve. This study is to focus on understanding of the applicability and limitations of the SASW method in a high strength concrete. This study is also to characterize the material property of early age high strength concrete emphasizing compressive strength using non-destructive testing methods. Three high strength concrete slabs of 600, 850 and 1100 kg/cm² compressive strengths were prepared together with cylinders from same batches. Cylinder tests were performed at the ages of 7, 14, 21 and 28 days after pouring concrete. Using the impact-echo method, the compression wave velocities were obtained based on different high strength concrete ages and compressive strengths. The equation to obtain the compressive strengths of high strength concrete has been developed using the obtained compression wave velocities (f′_c=1.083V_p−3816.1143). Using the method, the equation has also been developed to obtain the compressive strengths of high strength concrete based on the surface wave velocities (f′_c=0.253V_p+16.271). This study can be utilized in examining structural elements of high strength concrete structures and be applied in the integrity analysis of high strength concrete structures with a finite thickness.     

Fabrication of a Continuously Oriented Porous Al2O3 Body and Its In Vitro Study

Continuously oriented porous Al₂O₃ bodies were fabricated by a multi-pass extrusion process using C powders and ethylene vinyl acetate as an agent for pore forming and as a binder, respectively. The main pore size can be easily controlled by increasing the number of extrusion passes. The edges of the pore frame showed a rough surface having many fine pores about 0.2–1 μm in size. In the continuously porous Al₂O₃ bodies having 150 μm pore size, the values of the relative density and bending strength were about 63% and 90 MPa, respectively. These values were higher than those of an Al₂O₃ porous body made by a common process. From the in vitro study using human osteoblast-like MG-63 cells, it was confirmed that the cells grew well and adhered to the top surface and inside pores, as well as the outside wall of the continuously porous Al₂O₃ body. Without the directionality, the cells showed some spindle-shaped, three-dimensional, and network-type structures.     

Spectral analysis of malfunction mode in endmilling

For the investigation of the chatter modes, the power spectrum of the parametric time series model was adopted and analyzed at several mixed conditions of different revolution. This paper describes a methodology for an application of several time series such asAR (forward-backward, burg, least square, Yule Walker, geometric lattice, instrumental variable),ARX (least square, instrumental variable),ARMAX, ARMA, Box Jenkins, Output Error. To estimate the chatter mode using their spectral analysis their results were compared with one another. As a result, it was proven that several time series methods can be used for chatter mode estimation. Among them, theARX, ARMAX and instrumental variable methods (iv4) are more desirable and reliable than the other algorithm for the exact calculation of the chatter mode in endmilling. Among three cutting forces, the z direction cutting force,Fz, has more powerful characteristics of chatter occurring than the cutting forces,Fx andFy, in the sense that weak mode is calculated exactly and there is no shifted or pseudo mode in the estimated power spectra of endmilling forces.     

Analyses of mutation and loss of heterozygosity of coding sequences of the entire transforming growth factor beta type II receptor gene in sporadic human gastric cancer

Mutations in the transforming growth factor beta type II receptor (TGFbetaRII) gene have been detected in several human cancer types exhibiting microsatellite instability. Using intron primers previously reported for examination of the entire coding region of the TGFbetaRII gene, 29 sporadic gastric cancers were screened with non-radioactive single strand conformation polymorphism and subsequent DNA sequencing analysis. Mutations of the TGFbetaRII gene were detected in three out of 29 tumors (10%). Two cases showed deletions in a polyadenine tract in both alleles and was positively associated with replication error. One case had an insertion of GA dinucleotide sequence in one allele. Mutations of the TGFbetaRII gene were restricted to exon 3 and other coding regions were not affected. Loss of heterozygosity was detected by analyzing a polymorphic site in intron 2. Three out of nine (33%) informative cases, which were all of intestinal type and advanced cases, showed loss of heterozygosity but neither TGFbetaRII mutation nor replication error was found in these cases. Immunoreactivity of TGFbetaRII in tumor tissues was reduced to a different extent in the gastric cancer with genetically abnormal transforming growth factor. Although the numbers studied are small, homozygous (A)10 deletion or loss of heterozygosity of TGFbetaRII is involved in tumorigenesis and progression of at least some part of sporadic gastric cancer.     

In vitro T cell unresponsiveness following low-dose injection of anti-CD3 MoAb

Anti-CD3 MoAb treatment is widely used as an immunosuppressive therapy. In the present study we examined the in vitro T cell response in mice having received 24 h before a single i.v. injection of 10 microgram of anti-CD3 MoAb. We found that splenocytes from these mice displayed a dramatically decreased proliferative response to the T cell mitogens concanavalin A (Con A), anti-CD3, phytohaemagglutinin (PHA) and phorbol myristate acetate (PMA) + calcium ionophore, while the effect of lipopolysaccharide (LPS) was not impaired. T cell suppression persisted for about 10 days after anti-CD3 injection, returning to normal within 15 days. The F(ab')2 fragment of anti-CD3 had no such effect, indicating the requirement for in vivo activation. At the dose used, anti-CD3 resulted neither in T cell depletion nor in down-modulation of the CD3/T cell receptor (TCR) complex. The low proliferation was also not explained by apoptosis, following secondary challenge with Con A. Splenocytes from anti-CD3-injected mice were highly responsive to IL-2, but generated little or no IL-2, IL-3, IL-4 and interferon-gamma (IFN-gamma) when exposed to Con A. Normal cytokine production could not be restored by the addition of optimal doses of IL-2 during Con A stimulation. Transforming growth factor-beta (TGF-beta) was the only cytokine whose mRNA expression was not modified in stimulated splenocytes from anti-CD3-injected mice. Furthermore, anti-TGF-beta antibodies increased Con A-induced T cell proliferation, but not cytokine production.     

Zero-voltage and zero-current-switching full bridge PWM converterfor high-power applications

A novel zero-voltage and zero-current-switching (ZVZCS) full-bridge (FB) pulse-width modulated (PWM) converter is proposed. The new converter overcomes the limitations of the zero-voltage-switching (ZVS)-FB-PWM converter, such as high circulating energy, loss of duty cycle, and limited ZVS load range for the lagging-leg switches. By using the DC blocking capacitor and adding a saturable inductor, the primary current during the freewheeling period is reduced to zero, allowing the lagging-leg switches to be operated with zero-current-switching (ZCS). Meanwhile, the leading-leg switches are still operated with ZVS. The new converter is attractive for high-voltage (400-800 V), high-power (2-10 kW) applications where IGBTs are predominantly used as the power switches. The principle of operation, features, and design considerations of the new converter are described and verified on a 2-kW, 100-kHz, IGBT-based experimental circuit     

Kinetics of copper drift in PECVD dielectrics

We quantified the drift of Cu ions into various PECVD dielectrics by measuring shifts in capacitance-voltage behavior after subjecting Cu-gate MOS capacitors to bias-temperature stress. At a field of 1.0 MV/cm and temperature of 100°C, Cu ions drift readily into PECVD oxide with a projected accumulation of 2.7×10¹³ ions/cm ² after 10 years. However, in PECVD oxynitride, the projected accumulation under the same conditions is only 2.3×10¹⁰ ions/cm². These findings demonstrate the necessity of integrating drift barriers, such as PECVD oxynitride layers, in Cu interconnection systems to ensure threshold stability of parasitic field n-MOS devices     

Whole-body [18F]FDG PET in the management of metastatic brain tumours

BACKGROUND: To determine its roles in the diagnosis and the systemic evaluation of metastatic brain tumours, whole-body positron emission tomography (PET) using [18F]FDG was performed in 20 consecutive patients. METHODS: All patients were thought to be suffering or needing to be differentiated from metastatic brain tumours. Nine patients had multiple brain lesions; six were older and showed a rim-enhancing lesion with surrounding oedema; seven had homogeneously enhancing periventricular lesion(s) on computed tomography (CT) and/or magnetic resonance (MR) imaging, thought to be central nervous system lymphomas. Two patients had skull mass(es) and two patients had a solid mass suspected to be, respectively, a haemorrhagic metastasis and a metastatic malignant melanoma. All of them received whole-body [18F]FDG PET and conventional systemic work-up for metastasis in order to compare the results of the two methods. RESULTS: Metastatic brain tumours were diagnosed on whole-body [18F]FDG PET in eleven patients who had extracranial and intracranial hypermetabolic lesions. In nine of these, a conventional work-up also detected primary lesions which on whole-body [18F]FDG PET were seen to be hypermetabolic foci. Systemic lymph node metastases were detected by whole-body [18F]FDG PET only in two patients and histological diagnosis was possible by biopsy of lymph nodes rather than of brain lesions. In the remaining nine patients who had only intracranial hypermetabolic foci, histological diagnosis was made by craniotomy or stereotactic biopsy. It was confirmed that seven of nine patients were suffering from a primary brain tumour and two from metastatic carcinoma. None of the nine showed evidence of systemic cancer on conventional work-up. Histological diagnoses of the primary brain tumours were four cases of primary central nervous system lymphoma and one each of multifocal glioblastoma, Ewing's sarcoma, and cavernous angioma. Patients felt no discomfort during the whole-body [18F]FDG PET procedure and there were no complications. The false negative rate in [18F]FDG PET and in conventional work-up was 15.4% and 30.7% respectively. There were no false positives on either [18F]FDG PET or conventional work-up. CONCLUSION: It is suggested that whole-body [18F]FDG PET is a safe, reliable, and convenient method for the diagnosis and systemic evaluation of patients thought to be suffering or needing to be differentiated from a metastatic brain tumour.