Some Considerations in Document Copying via Electrophotography

In designing equipment and materials suitable for electrophotographic reproduction of documents, it is necessary to consider very carefully each of the elements involved, including the design of mechanical components, the optical system, charging units, developing systems, fixing units, and the engineering of a recording medium which gives adequate performance. Each of these various units must be investigated not only from the standpoint of mechanically satisfactory functioning, but also with consideration for its interrelationship with the rest of the system. Some of the most important factors to be considered include contrast of the optical system and of the electrophotographic recording medium, selection of a suitable light source, proper design of a breakdown-free charging unit, reliability of the developing unit, and a high efficiency fixing unit. Compactness of equipment is also a major consideration, particularly for a desk-top office copier or similar small devices, if the electrophotographic copy is to be used as a lithographic master, additional problems are involved in adding this functional ability to that of good electrophotographic performance.     

Quantitative metallography of sigma phase precipitates in AISI 347 stainless steel – a comparison between different methods

Abstract

A reliable method to perform volume fraction measurements of sigma (σ) phase in a niobium stabilised steel (AISI 347) has been developed. The most accurate results of the tested methods were obtained using backscattered electrons in a scanning electron microscope (SEM) and samples etched with oxalic acid. Both optical microscopy (OM) and SEM either on polished samples or on etched samples have been evaluated to come to this conclusion. Several etchants were also tested and careful etching with oxalic acid gave a well defined rim. The measurement of σ-phase fraction has been performed using manual point counting and digital image analysis using manual threshold. It was concluded that image analysis is usually to be preferred since it is faster and also results in higher precision The phase boundary caused by etching was evaluated, and it was found that the boundary area should be included in the measurement when using the recommended SEM method.     

Quantification of precipitate fraction in maraging steels by X-ray diffraction analysis

Abstract

Quantification of precipitate fraction, a critical step in modelling precipitation hardening, is difficult to carry out for maraging steels because of the small precipitate size and its low volume fraction. A method is proposed in the present work to estimate the precipitate fraction in an 18 wt-%Ni C250 maraging grade based on simple X-ray diffraction (XRD) analysis. The estimation gives reasonable values of precipitate fraction, which increases when aging proceeds. The precipitate formed at 427°C may be of a type that has not been reported before. The method proposed may be applicable to other precipitate hardened alloys. The amount of reverted austenite formed was also estimated when applicable.     

PIV measurements for flow pattern and void fraction in cavitating flows of He II and He I

Cavitation phenomena in both He I and He II flows were investigated through pressure measurements, the optical visualization method, and particle image velocimetry analysis. Quasi two-dimensional cavitation flows of liquid helium under nearly saturated vapor pressure condition were generated downstream of the throat of a Venturi channel and of a converging jet nozzle. At a sufficiently high flow velocity, the throat pressure falls below the saturated vapor pressure, generating vapor bubbles downstream of the throat. The pressure loss of the He II flows was almost independent of temperature and was larger than that for He I. Large differences in the void fraction between He I and He II was concluded from the result of PIV measurements. The void fraction for He II was larger than that for He I, which was found to be in good agreement with the visualization results.     

Regional ejection fraction and regional area strain for left ventricular function assessment in male patients after first-time myocardial infarction

In this work, we present a method to assess left ventricle (LV) regional function from cardiac magnetic resonance (CMR) imaging based on the regional ejection fraction (REF) and regional area strain (RAS). CMR scans were performed for 30 patients after first-time myocardial infarction (MI) and nine age- and sex-matched healthy volunteers. The CMR images were processed to reconstruct three-dimensional LV geometry, and the REF and RAS in a 16-segment model were computed using our proposed methodology. The method of computing the REF was tested and shown to be robust against variation in user input. Furthermore, analysis of data was feasible in all patients and healthy volunteers without any exclusions. The REF correlated well with the RAS in a nonlinear manner (quadratic fit—R² = 0.88). In patients after first-time MI, the REF and RAS were significantly reduced across all 16 segments (REF: p < 0.05; RAS: p < 0.01). Moreover, the REF and RAS significantly decreased with the extent of transmural scar obtained from late gadolinium-enhanced CMR images. In addition, we show that the REF and RAS can be used to identify regions with compromised function in the patients with preserved global ejection fraction with reasonable accuracy (more than 78%). These preliminary results confirmed the validity of our approach for accurate analysis of LV regional function. Our approach potentially offers physicians new insights into the local characteristics of the myocardial mechanics after a MI.