Phase transformation and densification during pressureless sintering of Si3N4 with MgO and Y3Al5O12 additives

The - transformation of Si₃N₄ during liquid-phase sintering appears to be controlled by the growth of the -Si₃N₄ grains in the direction perpendicular to thec-axis in the case of MgO additive. The diffusion through the liquid is the rate-controlling step in the case of the Y₄Al₅O₁₂ additive. The density of the sintered body at the solid skeleton stage was influenced by the change in the - transformation rate and/or by a change of the transformation mechanism. The indirect proportionality between the -phase content in the starting powder and the density at the solid skeleton stage was found. The microstructure of the sintered body is influenced by both the -phase content in the starting powder and the chemical composition of the additive. Fine, uniform microstructure with a high aspect ratio of -grains is obtained, when the -phase content in the starting powder is as small as possible and when the - transformation is controlled by grain growth.     

Challenges and opportunities of multimodal data in human learning: The computer science students' perspective

Multimodal data have the potential to explore emerging learning practices that extend human cognitive capacities. A critical issue stretching in many multimodal learning analytics (MLA) systems and studies is the current focus aimed at supporting researchers to model learner behaviours, rather than directly supporting learners. Moreover, many MLA systems are designed and deployed without learners' involvement. We argue that in order to create MLA interfaces that directly support learning, we need to gain an expanded understanding of how multimodal data can support learners' authentic needs. We present a qualitative study in which 40 computer science students were tracked in an authentic learning activity using wearable and static sensors. Our findings outline learners' curated representations about multimodal data and the non-technical challenges in using these data in their learning practice. The paper discusses 10 dimensions that can serve as guidelines for researchers and designers to create effective and ethically aware student-facing MLA innovations.     

A case of using the Semantic Interoperability Framework for custom orthopedic implants manufacturing

The efficiency and effectiveness of the daily practice in orthopedic surgery depend on the availability, interoperability and unique access to a wide set of information, related to the patient’s medical record and diagnosis, domain knowledge and available resources and staff. The most important of the tangible resources, needed for the therapeutic or preventive actions are orthopedic implants. In some cases, the implants may be highly complex and customized products, which need to be manufactured (assembled) on basis of the above information in a shortest possible timeframe. In this paper, the case of the custom orthopedic implants manufacturing is described from the perspective of the collaborative enterprising, with special consideration of the interoperability issues of the involved enterprise collaboration. It is shown how the previously developed Semantic Interoperability Framework can be used to improve the efficiency of the manufacturing and other relevant processes.     

Automatic recognition of gait-related health problems in the elderly using machine learning

This paper proposes a system for the early automatic recognition of health problems that manifest themselves in distinctive form of gait. Purpose of the system is to prolong the autonomous living of the elderly at home. When the system identifies a health problem, it automatically notifies a physician and provides an explanation of the automatic diagnosis. The gait of the elderly user is captured using a motion-capture system, which consists of body-worn tags and wall-mounted sensors. The positions of the tags are acquired by the sensors and the resulting time series of position coordinates are analyzed with machine-learning algorithms in order to recognize a specific health problem. Novel semantic features based on medical knowledge for training a machine-learning classifier are proposed in this paper. The classifier classifies the user’s gait into: 1) normal, 2) with hemiplegia, 3) with Parkinson’s disease, 4) with pain in the back and 5) with pain in the leg. The studies of 1) the feasibility of automatic recognition and 2) the impact of tag placement and noise level on the accuracy of the recognition of health problems are presented. The experimental results of the first study (12 tags, no noise) showed that the k-nearest neighbors and neural network algorithms achieved classification accuracies of 100%. The experimental results of the second study showed that classification accuracy of over 99% is achievable using several machine-learning algorithms and 8 or more tags with up to 15 mm standard deviation of noise. The results show that the proposed approach achieves high classification accuracy and can be used as a guide for further studies in the increasingly important area of Ambient Assisted Living. Since the system uses semantic features and an artificial-intelligence approach to interpret the health state, provides a natural explanation of the hypothesis and is embedded in the domestic environment of the elderly person; it is an example of the semantic ambient media for Ambient Assisted Living.     

Prevention of dark-cutting (DFD) beef in penned bulls at the abattoir

There is a large body of evidence indicating that activities associated with regrouping of bulls before slaughter, which leads to physical exhaustion mainly from mounting, are primary factors inducing dark-cutting (DFD) in beef. The aim of this study was to test several methods to control activity when regrouping cannot be avoided. Fifty bulls previously individually tied for at least 16 months were drafted into groups of five animals and released in a pen at the abattoir. After 18 to 22 h they were slaughtered. According to environmental conditions in the pen, the bulls were divided into four groups: Control group (n = 10, no experimentation); Electricity group (n = 10, an electric fence was constructed above the pen so that a mounting bull would receive an electric shock); Darkness group (n = 10, the whole stall was in darkness); and Combination group (n = 20, both treatments, of the electricity and darkness groups were applied). During the first hour of penning the behaviour of the bulls was videorecorded. After slaughter meat quality characteristics were measured. Dark-cutting was found in Control (70%), Electricity (30%) and Darkness (70%) groups, but not in the Combination group (0%). No treatment altered the repertoire of agonistic activity, but under the combined treatments the number of agonistic interactions was significantly lower than in any other group.     

Thermodynamic analysis of the refining of technical boron nitride

The efficiency of the process of refining technical boron nitride was assessed based on calculations of the chemical equilibrium in the B-N-O-C-Cl-H system. Three refining mixtures, CCl₄ + H₂, CCl₄ + NH₃ and CHCl₃ + NH₃, were considered. The analysis indicates that the use of ammonia-containing mixtures is more convenient, a lower residual oxygen content, lower contamination of the product by carbon and a better overall boron balance emerging. The calculations of the equilibrium composition of the solid phase enabled suitable technological conditions of the refining process (temperature and starting composition of the gaseous phase) to be established. The calculated results are compared with experimental data, and some observed differences are discussed.     

Observation of higher order NMR larmor lines by SQUID in solids at low magnetic field

We describe an apparatus allowing the observation of the NMR static longitudinal component of nuclear magnetizationM _z by a SQUID at low magnetic fields and atT=4.2 K in Plexiglas, Teflon, and CaF₂. The higher order NMR Larmor lines at 2f ₀, 3f ₀, and 4f ₀, wheref ₀ is the Larmor frequency of the allowed NMR line, were measured. These lines correspond to a flip of two, three, and four spins, respectively, by one photon. The amplitudes of 2f ₀ and 3f ₀ lines and their field dependences show that the common assertion that the forbidden lines at 2f ₀ and 3f ₀ appear in the same order of perturbation theory and that their intensity decreases with static magnetic fieldB ₀ asB ₀ ^–2 is wrong. In fact, the third Larmor line 3f ₀ appears at higher order than the second Larmor line 2f ₀ and its intensity decreases asB ₀ ^–4 . This is also shown by a theoretical calculation of its intensity. For the first time the NMR SQUID technique allowed the detection of the 4f ₀ line, corresponding to the simultaneous flip of four spins by one photon.