Measurement of through-the-thickness variations of mechanical properties in SA508 Gr.3 pressure vessel steels using ball indentation test technique

The through-the-thickness variations of mechanical properties in SA508 Gr.3 pressure vessel steels were measured using the automated ball indentation (ABI) test technique. Key mechanical properties, such as the yield strength, ultimate strength, flow curve and hardness, were evaluated from indentation load-depth curves. The mechanical properties measured were location-dependent and the steepest gradients in the distributions of the mechanical properties appeared in the near-surface regions. The maximum through-the-thickness variations of the mechanical properties were in the range of 5–20% and they depended on the manufacturing process as well as the original wall thickness. It was concluded that the through-the-thickness variations in the mechanical properties were mainly caused by the location-dependent cooling rate during water quenching in the quality heat treatment which consisted of water quenching and tempering.     

Cooperative Hybrid‐ARQ Protocols: Unified Frameworks for Protocol Analysis

Cooperative hybrid‐automatic repeat request (HARQ) protocols, which can exploit the spatial and temporal diversities, have been widely studied. The efficiency of cooperative HARQ protocols is higher than that of cooperative protocols because retransmissions are only performed when necessary. We classify cooperative HARQ protocols as three decode‐and‐forward‐based HARQ (DF‐HARQ) protocols and two amplified‐and‐forward‐based HARQ (AF‐HARQ) protocols. To compare these protocols and obtain the optimum parameters, two unified frameworks are developed for protocol analysis. Using the frameworks, we can evaluate and compare the maximum throughput and outage probabilities according to the SNR, the relay location, and the delay constraint. From the analysis we can see that the maximum achievable throughput of the DF‐HARQ protocols can be much greater than that of the AF‐HARQ protocols due to the incremental redundancy transmission at the relay.     

Extraction and Regularization of Various Building Boundaries with Complex Shapes Utilizing Distribution Characteristics of Airborne LIDAR Points

This study presents an approach for extracting boundaries of various buildings, which have concave boundaries, inner yards, non‐right‐angled corners, and nonlinear edges. The approach comprises four steps: building point segmentation, boundary tracing, boundary grouping, and regularization. In the second and third steps, conventional algorithms are improved for more accurate boundary extraction, and in the final step, a new algorithm is presented to extract nonlinear edges. The unique characteristics of airborne light detection and ranging (LIDAR) data are considered in some steps. The performance and practicality of the presented algorithm were evaluated for buildings of various shapes, and the average omission and commission error of building polygon areas were 0.038 and 0.033, respectively     

Comparative study on the properties of amorphous carbon layers deposited from 1-hexene and propylene for dry etch hard mask application in semiconductor device manufacturing

Amorphous carbon layers (ACLs) were prepared by plasma enhanced chemical vapor deposition (PECVD) from 1-hexene (C₆H₁₂) and propylene (C₃H₆) as a carbon source at different temperatures for dry etch hard mask of semiconductor devices manufacturing process. The deposition rate of ACL deposited at 550 °C from C₆H₁₂ and C₃H₆ was 5050 Å/min and 6360 Å/min. Although the deposition rate of ACL deposited from C₆H₆ was lower than that from C₃H₆, normalized deposition rate of ACL deposited from C₆H₁₂ was 1.64 times higher than that from C₃H₆. The relative amount of hydrocarbon contents measured by FTIR (Fourier transformation infrared) and TDS (thermal desorption spectroscopy) was decreased with the increase of deposition temperature. Raman results showed that the numbers and size of graphite cluster of ACLs deposited from each source were increased with the increase of deposition temperature. The extinction coefficient of ACL deposited at 550 °C from C₆H₁₂ was 0.51 and that from C₃H₆ was 0.48. The density of ACL deposited at 550 °C from C₆H₁₂ was 1.48 g/cm³ and that from C₃H₆ was 1.45 g/cm³. The dry etching rate of ACL deposited at 550 °C from C₆H₁₂ was 1770 Å/min and that from C₃H₆ was 1840 Å/min. The deposition rate, dry etch rate and the amount of hydrocarbon contents of ACLs deposited from each carbon source were decreased with the increase of deposition temperature but extinction coefficient and density were increased with the increase of deposition temperature. We concluded that the variation behavior of the deposition characteristics and film properties of ACLs from C₆H₁₂ with the increase of deposition temperature was the same as those of ACLs from C₃H₆. The high density and low dry etch rate of ACL from C₆H₁₂ can be explained by less hydrocarbon incorporation during deposition and these properties are more favorable for the dry etch hard mask application in semiconductor device fabrication.     

Evaluation of transmitral flow velocity profile in supine and sitting positions by pulsed Doppler echocardiography in elderly hypertensives

To evaluate left ventricular diastolic filling properties in elderly hypertensive case with left ventricular hypertrophy (LVH), we investigated the influence of postural change from a supine to sitting position on transmitral flow velocity profile as assessed by pulsed Doppler echocardiography in 12 normotensives (N group) and 24 hypertensives, aged 65 to 80 years. Hypertensive subjects were divided into two groups on the basis of left ventricular mass index (LVMI): 12 hypertensives without LVH (H1 group; LVMI < 130 g/m2); 12 hypertensives with LVH (H2 group; LVMI > 130 g/m2). Peak early filling velocity (E), peak atrial filling velocity (A) and the E/A ratio were similar in the three groups in the supine position. The postural change decreased E and A in N and H1 groups. On the other hand, the change decreased E, but not A in the H2 group. The E/A ratio was decreased in the H2 group compared with both the N and H1 group in the sitting position. As a result, the sitting position increased atrial contribution to diastolic filling in the H2 group. These observations indicate that a reduction in preload changes the transmitral flow velocity profile in elderly hypertensives with left ventricular hypertrophy. The Doppler alterations may be related to impaired left ventricular diastolic function.     

Characterization of a polychromatic neutron beam diffracted by pyrolytic graphite crystals

The beam spectrum for polychromatic neutrons diffracted by pyrolytic graphite crystals was characterized. The theoretical beam spectrum was obtained using the diffraction model for a mosaic crystal. The lattice vibration effects were included in the calculation using the reported vibration amplitude of the crystal and the measured time-of-flight spectra in the thermal region. The calculated beam spectrum was compared with the results obtained in the absence of thermal motion. The lattice vibration effects became more important for the higher diffraction orders and a large decrease in the neutron flux induced by the vibrations was identified in the epithermal region. The validity of the beam spectrum was estimated by comparing with the effective quantities determined from prompt γ-ray measurements and Cd-ratios measured both for 1/ν and non-1/ν nuclides.