Purpose: The purpose of this study was to introduce a new algorithm for automated measurement of the modulation transfer function (MTF) using an edge of a readily available phantom and to evaluate the effect of reconstruction filter and field of view (FOV) on the spatial resolution in the CT images.Methods: Our automated MTF measurement consisted of several steps. The center of the image was established and an appropriate region of interest (ROI) designated. The edge spread function (ESF) was determined, and a suitably interpolated ESF curve was differentiated to obtain the line spread function (LSF). The LSF was Fourier transformed to obtain the MTF. All these steps were accomplished automatically without user intervention. The results of the automated MTF from the edge phantom were validated by comparing them with a point image, and the results of the automated calculation were validated by the standard fitting method. The automated MTF calculation was then applied to the images of two polymethyl methacrylate (PMMA) phantoms and a wire phantom which had been scanned by a Toshiba Alexion 4‐slice CT scanner and reconstructed with various filter types and FOVs.Results: The difference in the 50% MTF values obtained from the edge and point phantoms were within ±4%. The values from the automated and fitted methods agreed to within ±2%, indicating that the automated MTF calculation was accurate. The automated MTF calculation was able to differentiate MTF curves for various filters. The spatial resolution values were 0.37 ± 0.00, 0.71 ± 0.01, and 0.78 ± 0.01 cycles/mm for FC13, FC30 and FC52 filters, respectively. The spatial resolution of the images decrease linearly (R² > 0.98) with increasing FOVs.Conclusion: An automated MTF method was successfully developed using an edge phantom, the PMMA phantom. The method is easy to implement in a clinical environment and is not influenced by user experience.

An experimental study has been carried out on the dynamical process taking place in the secondary plasma generated by a Q-switched Nd:YAG laser (80 mJ, 8 ns) on a copper target at reduced pressure. Accurate dynamical characterization of the cross-sectional view of the plasma has been made possible by the unique combination of a plasma confinement configuration and the time-resolved measurement technique. In addition to reaffirming the role of the blast-wave mechanism in the generation of secondary plasma, an analysis of the time-resolved spatial distributions of emission intensities and the time-resolved spatial distributions of temperature was made. As a result, the occurrence of two-stage emission processes, the “shock excitation stage” and “cooling stage,” has been proved. For instance, at 2 Torr it is shown that the emission process is initiated by a brief shock excitation process (∼ 1 μs) and followed by a longer cooling process (∼ 3 μs). The experimental results concerning the characteristics of the plasma can be well understood by considering the two-stage processes.

This research involves the study of two models of green facades and a model of bare wall. A house miniature was used as thermal lab. The aim of the project is evaluating the performance of energy transfer based on the various leaves densities on the green facade. Heat calculation was used to calculate heat transfer on the wall surface. There are two kinds of leaves densities, 50% and 90%. The data measurement show that the green facade has a significant cooling effect and more visible for the facade with higher leaves densities. Respectively, from experiment I to experiment III, the average of heat fluxes are 22.35 W/m², 8.76 W/m², and 0.60 W/m² where in experiment III, the negative heat flux occurred during day time due to interior surface temperature is higher than exterior surface temperature. Lastly, higher leaves densities possibility can create a better cooling effect but also has the risk of creating higher relative humidity, especially for the interior air layer.

Excitation mechanisms for copper and zinc atoms as well as their ionic species in the Q-switched (Q-sw) Nd:YAG laser-induced shock wave plasma have been investigated with a time-gated optical multichannel analyzer (OMA) system for various experimental conditions. It is demonstrated that the shock excitation process is the main mechanism responsible for the emission spectra for laser energy ranging from 8 to 86 mJ and surrounding air pressure from 2 to 50 Torr. At air pressure below 2 Torr, collision-induced excitation appears to take over and becomes the operative mechanism. In all cases, the neutral emission dominates over the ionic emission, leading to a high signal-to-background ratio, which tends to decrease, however, at higher laser energy and air pressure.