Stable automatic envelope estimation for noisy doppler ultrasound

Doppler ultrasound technology is widespread in clinical applications and is principally used for blood flow measurements in the heart, arteries and veins. A commonly extracted parameter is the maximum velocity envelope. However, current methods of extracting it cannot produce stable envelopes in high noise conditions. This can limit clinical and research applications using the technology. In this article, a new method of automatic envelope estimation is presented. The method can handle challenging signals with high levels of noise and variable envelope shapes. Envelopes are extracted from a Doppler spectrogram image generated directly from the Doppler audio signal, making it less device-dependent than existing imageprocessing methods. The method’s performance is assessed using simulated pulsatile flow, a flow phantom and in-vivo ascending aortic flow measurements and is compared with three state-of-the-art methods. The proposed method is the most accurate in noisy conditions, achieving on average for phantom data with SNRs below 10 dB, a bias and standard deviation 0.7% and 3.3% lower than the next-best performing method. In addition, a new method for beat segmentation is proposed. When combined, the two proposed methods exhibited the best performance using invivo data, producing the least number of incorrectly segmented beats and 8.2% more correctly segmented beats than the next best performing method. The ability of the proposed methods to reliably extract timing indices for cardiac cycles across a range of signal quality is of particular significance for research and monitoring applications

Effect of process parameters on the microstructure and mechanical properties of AA2024 fabricated using selective laser melting

Selective laser melting (SLM) offers significant benefits, including geometric freedom and rapid production, when compared with traditional manufacturing techniques. However, the materials available for SLM production remain limited, restricting the industrial adoption of the technology. The mechanical properties and microstructure of many aluminium alloys have not been fully explored, as their manufacturability using SLM is extremely challenging. This study investigates the effect of laser power, hatch spacing and scanning speed on the mechanical and microstructural properties of as-fabricated aluminium 2024 alloy (AA2024) manufactured using SLM. The results reveal that almost crack-free structures with high relative density (99.9%) and Archimedes density (99.7%) have been achieved. It is shown that when using low energy density (ED) levels, large cracks and porosities are a major problem, owing to incomplete fusion; however, small gas pores are prevalent at high-energy densities due to the dissolved gas particles in the melt pool. An inversely proportional relationship between ED and microhardness has also been observed. Lower ED decreases the melt pool size and temperature gradients but increases the cooling rate, creating a fine-grained microstructure, which restricts dislocation movement, therefore increasing the microhardness. The highest microhardness (116 HV0.2), which was obtained from one of the lowest EDs used (100 J/mm3), is 45% higher than as-cast AA2024-0, but 17% lower than wrought AA2024-T6 alloy

Ontology-based indexing of annotated images using semantic DNA and vector space model

The study presented in this paper focuses on the preprocessing stage of image retrieval by proposing an ontology-based indexing approach which captures the meaning of image annotations by extracting the semantic importance of the words in them. The indexing algorithm is based on the classic vector-space model that is adapted by employing index weighting and a word sense disambiguation. It uses sets of Semantic DNA, extracted from a lexical ontology, to represent the images in a vector space. As discussed in the paper, the use of Semantic DNA in text-based image retrieval aims to overcome some of the major drawbacks of well known traditional approaches such as `bags of words' and term frequency-(TF) based indexing. The proposed approach is evaluated by comparing the indexing achieved using the proposed semantic algorithm with results obtained using a traditional TF-based indexing in vector space model (VSM) with singular value decomposition (SVD) technique. The experimental results show that the proposed ontology-based approach generates a better-quality index which captures the conceptual meaning of the image annotation

Intuitive interaction with multifunctional mobile interfaces

This paper investigates intuitive interaction in the context of mobile phones. The aim is to identify what creates an intuitive interaction with an interface and therefore analyse how features may be designed to maximise the probability of an intuitive interaction. Three experimental studies were conducted. The first study recorded participants’ interaction with unmarked mobile phone button schematics with the aim of relating intuitiveness of interaction to the gestalt laws. It was demonstrated that intuitive interaction is facilitated when interfaces have layouts designed using the gestalt laws. The second study compared interactions using touchscreen and button phones to evaluate the significance of the touchscreen. It was found that participants who had never owned a touchscreen handset were still inclined to utilise the experiential knowledge of existing handsets for all of the tasks performed. The final study used the Immersion® CyberGlove® to record participants’ interactions with a prop in place of a touchscreen phone when carrying out various tasks. The aim was to determine which image schemata were prevalent in the use of a touchscreen handset. Six image schemata were identified, and it was concluded that these image schemata could improve the efficiency of inclusive design if taken into account. This research suggests that individual image schemata can be related to the continuum of knowledge sources in order to create design solutions that take advantage of the user’s basic sensorimotor experience