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Elastic nonlinearity in sandstones is given by the combination of slow and fast effects, leading to hysteresis and relaxation of the viscoelastic properties after the sample is perturbed (conditioning). While a lot of experimental evidences of slow dynamics are available, quantification of nonclassical nonlinearity is still difficult: nonlinear indicators must be introduced which are independent of both experimental configuration and on conditioning strain amplitude, which is often difficult to quantify in an accurate way. In this contribution, we introduce and analyze some possible quantities describing nonlinear viscoelasticity in sandstones, derived from a non-equilibrium strain model. We will show that they identify real material properties, in the sense that they are not dependent on experimental details (such as experiment duration, conditioning protocol, frequency,...) and can be measured easily with good repeatability. Highlights: We quantify the temporal relaxation of viscoelastic properties of sandstones; We introduce measurable indicators allowing to quantify hysteresis, anisotropy, and relaxation in sandstones; We propose a non-equilibrium strain model to describe observed hysteresis and anisotropy in nonlinear hysteretic viscoelastic properties; We show a linear correlation exists between modulus and damping evolution during relaxation in sandstones. [ABSTRACT FROM AUTHOR]

Materials with grain contacts or partially closed cracks exhibit anomalous elastic behavior: hysteresis in quasi-static experiments and slow dynamics in fast dynamic ones. Albeit the behavior in the two cases (which correspond to very different strain ranges) appears different, it should stem from the same physics and, thus, could be modeled by a universal equation of state. We propose a modification of the standard acoustoelastic theory, introducing the concept of conditioning induced non-equilibrium strain, which allows us to predict the evolution of elastic wave velocity in both quasi-static and dynamic ranges, including the velocity anisotropy induced by external uniaxial loading. [ABSTRACT FROM AUTHOR]

Surprisingly little is known about tooth removal procedures. This might be due to the difficulty of gaining reliable data on these procedures. To improve our understanding of these procedures, machine learning techniques were used to design a multiclass classification model of tooth removal based on force, torque, and movement data recorded during tooth removal. A measurement setup consisting of, among others, robot technology was used to gather high-quality data on forces, torques, and movement in clinically relevant dimensions. Fresh-frozen cadavers were used to match the clinical situation as closely as possible. Clinically interpretable variables or "features" were engineered and feature selection took place to process the data. A Gaussian naive Bayes model was trained to classify tooth removal procedures. Data of 110 successful tooth removal experiments were available to train the model. Out of 75 clinically designed features, 33 were selected for the classification model. The overall accuracy of the classification model in 4 random subsamples of data was 86% in the training set and 54% in the test set. In 95% and 88%, respectively, the model correctly classified the (upper or lower) jaw and either the right class or a class of neighboring teeth. This article discusses the design and performance of a multiclass classification model for tooth removal. Despite the relatively small data set, the quality of the data was sufficient to develop a first model with reasonable performance. The results of the feature engineering, selection process, and the classification model itself can be considered a strong first step toward a better understanding of these complex procedures. It has the potential to aid in the development of evidence-based educational material and clinical guidelines in the near future. [ABSTRACT FROM AUTHOR]

Background: Diabetes self-management is a mainstay of diabetes care, but the implementation of self-management regimens into daily life is complex and often results in discouragement and distress. Modern approaches such as smartphone-based self-management applications are therefore needed to support people with diabetes. Since reimbursability would increase the availability of such digital applications to people with diabetes, we designed a study that meets all scientific and methodological requirements set by the German Digital Healthcare Act to allow reimbursement for a specific application (mySugr PRO). Here, we report the protocol of this study that aims at evaluating the efficacy of the digital self-management application with regard to patient-reported outcomes and medical benefits.Methods/design: This multicenter, open-label, randomized, parallel-group, controlled trial will evaluate the health care effects and medical benefits of mySugr PRO. A total of 466 people with diabetes will be randomly allocated (2:1 randomization) to the interventional group (n = 311) that will use the digital self-management application during the 12-week study period or the control group (n = 155; no usage of the application). Baseline and follow-up examinations will assess diabetes distress as the primary endpoint as well as empowerment, HbA1c, blood glucose data, self-management, general well-being, and treatment satisfaction as secondary endpoints. Statistical analyses will use an intention-to-treat procedure (using multiple imputation for missing values) as well as a per-protocol approach for sensitivity analysis.Discussion: To the best of our knowledge, this study will be one of the largest diabetes-specific evaluations of a digital health application supporting people with diabetes in their diabetes self-management that follow the requirements of the German Digital Healthcare Act.Trial Registration: German Clinical Trial Register DRKS00022923 . Registered on 22 October 2020. [ABSTRACT FROM AUTHOR]

The Hopkinson split pressure bar (HSPB) was used for the testing of three polymers at strain rates between 102 to 10³ s-1. Higher strain rates were achieved using the direct Hopkinson test. Experimental data were evaluated in time as well as in the frequency domain. A more detailed analysis in the frequency domain showed that the description of tested polymers can be described in the framework of the linear viscoelasticity. The use of the direct Hopkinson test showed the occurrence of a permanent strain. [ABSTRACT FROM AUTHOR]

Current metal additive manufacturing (AM) technologies imply complicated processes, with many variable parameters determining their performance and the quality of the resulting product. Process optimisation requires feedback from nondestructive evaluation (NDE) of the additively manufactured parts. The presence of a complicated internal structure and complex shapes and geometries are limiting factors in the application of standard, preferably online, NDE techniques for quantitative assessment of process-related defects such as irregular internal structure, porosity, etc. In this study, potential non-linear elastic wave spectroscopy (NEWS) methods were tested to classify two types of artificially created defect in Ti-6Al-4V prismatic samples fabricated by an electron beam melting (EBM) system. Two series of samples with variable internal defects were tested: samples with central circular defects (missing material gaps) and samples with gradually growing stochastic porosity. Each group of samples also contained a fully compact sample for comparison. Additional ultrasonic NEWS procedures were then tested to classify the variability of defects. A relatively simple experimental facility with two piezoelectric transducers allowed samples to be analysed and the results recorded. The best results, documented in this paper, were obtained using two modifications of the non-linear wave modulation spectroscopy (NWMS) procedure. One group was successfully classified with two mixed excitation frequencies; slopes of amplitude-dependent inter-modulation sidebands identified samples with growing defect thickness. For the second group, longer chirp excitation was used mixed with signals of constant frequency and/or without any mixing. Growing dispersed stochastic porosity was successfully classified using these methods. The results of NEWS tests indicate that selected NEWS procedures can also be used for online AM monitoring. [ABSTRACT FROM AUTHOR]

Since the official registration of the word "Mechatronics" as a trademark by Yaskawa Electric Corporation in 1971, explosive growth has been observed in mechatronics research and product development activities. Nowadays, mechatronics and mechatronic design methodologies play increasingly important roles in computer, communication, control, and consumer product (4C) technologies. As such, it is fair to agree that mechatronics technology has profoundly affected almost all aspects of human life, particularly, of engineering realities ranging from rehabilitation devices to ground and underwater robots, and from unmanned aerial vehicles to intelligent manufacturing facilities, constituting a rapidly progressing frontline. [ABSTRACT FROM AUTHOR]

Time reversal (TR) processing of acoustic and ultrasonic signals is effective tool for complicated problems solution in NDT/E and structural health monitoring. TR enables space-time focusing of elastic wave and thereby relatively easy location and partial reconstruction of both burst and continuous acoustic emission (AE) sources. AE source location problems come up in situations with high external noise, wave dispersion in thin-wall structures, and wave velocity changes in complex structures containing welds, flanges, branches, etc. Localization problems in such cases mostly require large sensor arrays and sophisticated signal processing and filtration. A new solution with using TR approach is suggested in this paper. This approach allows planar location of burst AE sources with only one transducer, and continuous AE sources with two transducers, both under high background noise from other sources. TR procedure is in this paper applied to long random noise (leakage) signals for the first time. Suggested method was experimentally verified by simulated burst and continuous AE sources on a thick steel plate and thin Al-plate with various holes. Source location results certified high robustness of suggested approach. Need of detailed scanning of a region around a pre-localized source constitutes certain disadvantage of that method. Numerical simulations shown that scanning can be omitted by inserting experimental TR signals into the computer model of monitored structure ("digital twin") and perform the source location in the model. Localization accuracy of suggested procedure proved by LDV is about one mm, which is better than the wavelength and transducer aperture. [ABSTRACT FROM AUTHOR]

Background: Deep excision down to the muscle fascia and split-thickness skin grafting is a necessary part in modern surgical care of adult burn patients presenting with full-thickness wounds. We evaluated a new surgical approach combining a dermal matrix, autologous fat-transfer, and split-thickness skin grafting. Methods: Full thickness burn wounds of five consecutive patients were excised down to the muscle fascia. Parts of the excised adipose tissues were harvested for in vitro analysis of preadipocyte viability and its potential for proliferation and differentiation. The excised fatty tissue was manually harvested by use of a Coleman Liposuction needle mounted on 10 ml syringes, and spread onto a bovine collagen-elastin scaffold (Matriderm). The sheet was put upside down onto the wound and covered with split-thickness grafts during the same operation. Skin biopsies for histological evaluation were taken on days 30 and 90 postoperatively. Results: Preadipocytes from excised burn wounds showed cell behavior comparable to healthy fat tissue. FACS Analysis showed 75 % viable cells in the samples which is comparable to healthy fat tissue. Three patients showed more than 90 % vital split thickness skin grafts 10 days after surgery. All skin biopsies confirmed the presence of adipose tissue. Conclusions: Autologous fat-transfer in combination with a dermal substitute and split-thickness skin grafts seems to be a possible reconstructive procedure for covering defects after deep excision down to the fascia in a single step approach. [ABSTRACT FROM AUTHOR]

An abstract of the study "Assessment of the Right Ventricular (RV) Function by Doppler Tissue Imaging (TDI) in Patients With Pulmonary Arterial Hypertension (PAH)," by J. Kober and colleagues is presented.