A Robust Approach to Optimal Matched Filter Design in Ultrasonic Non-Destructive Evaluation (NDE)

The matched filter was demonstrated to be a powerful yet efficient technique to enhance defect detection and imaging in ultrasonic non-destructive evaluation (NDE) of coarse grain materials, provided that the filter was properly designed and optimized. In the literature, in order to accurately approximate the defect echoes, the design utilized the real excitation signals, which made it time consuming and less straightforward to implement in practice. In this paper, we present a more robust and flexible approach to optimal matched filter design using the simulated excitation signals, and the control parameters are chosen and optimized based on the real scenario of array transducer, transmitter-receiver system response, and the test sample, as a result, the filter response is optimized and depends on the material characteristics. Experiments on industrial samples are conducted and the results confirm the great benefits of the method

Childbirth transformation and new style midwifery in Beijing, 1926 – 1937

This article offers a comparative analysis of the transformation of midwifery practices in Beijing city and its rural neighborhood in China between 1926 and 1937. From the 1920s onwards, impelled by supports of governments, academic groups and foreign foundations, a reform of midwifery practices was triggered across China. Beijing was one of the forerunners in this reform. Through examining the midwifery regulations, the new style midwifery service, the midwife education/training programs, as well as the consequential influences on birth attendants and birth outcomes (neonatal, infant and maternal mortality rates) in Beijing’s first health district and the nearby Qinghe district, this article shows that in the urban district the trained birth attendants performed better than the untrained personnel in preventing neonatal deaths. Also, the growing use of trained midwifery contributed to the reduction of infant and maternal mortality rates in the urban community. However, because of the paucity of sources of rural areas, such positive outcomes cannot be ascertained in the rural district. Yet an obvious urban-rural divergence in midwifery services and maternal care is still observed

Transforming childbirth practices:New style midwifery in China, 1912 – 1949

Over the last three centuries, childbirth has gradually become an issue of public concern worldwide, being linked increasingly to the welfare of populations and nations. During this process, medical improvements in obstetrics and midwifery have been introduced to daily childbirth practices by medical authorities and enforced by state governments in many countries, significantly contributing to the decline of childbirth-related mortality rates. This dissertation focuses on the transformation of childbirth practices in China during the Republican era (1912-1949) and its impacts on neonatal, infant, and maternal mortality rates. By using governmental archives, reports of hospitals and health stations, demographic and social surveys, and other historical sources, this dissertation first investigates how missionary and governmental initiatives pushed forward the institutionalization of childbirth in different parts of China from the late nineteenth to the early twentieth century. Then the dissertation presents case studies of Beijing (1926-1937) and Sichuan (1938-1949), as well as three comparisons regarding neonatal and maternal mortality rates in China and elsewhere in the world, through which it analyzes how biomedical approaches of the “new style midwifery” helped prevent neonatal, infant and maternal mortality by reducing infection-related diseases during and after childbirth. Combining qualitative and quantitative methods, this dissertation provides new insights into how childbirth became less risky across time and space

Assessment of arbuscular mycorrhizal fungi in flax production

Arbuscular mycorrhizal fungi (AMF) play an important role in nutrient cycling and growth of flax (Linum usitatissimum L.). However, limited information is available regarding the symbiotic association between flax and AMF in field environments. A study was conducted to survey AMF communities colonizing flax grown in Saskatchewan. Additionally, field and growth chamber studies investigated the impact of AMF inoculation on nutrient uptake and growth of flax. Eighteen commercial flax fields were surveyed to assess mycorrhizal colonization of flax and to assess the impact of agricultural practices and soil abiotic factors on AMF activity. The flax root-associated AMF communities were explored using a 454 sequencing method, together with microscopic-based measurements of root AMF colonization and soil spore density. High levels of root colonization were detected in most flax fields. Of the 222 AMF operational taxonomic units (OTUs) identified in flax roots, 181 OTUs clustered as Funneliformis-Rhizophagus, 19 as Claroideoglomus, 14 as Paraglomus, six as Diversisporales and two as Archaeospora. Results suggest that tillage influenced the composition of AMF communities colonizing flax, and reduced relative AMF abundance and species richness. Additionally, AMF community characteristics were related to soil abiotic factors such as pH, EC, available phosphorus and nitrogen. Field experiments were conducted over two years (two sites per year) using a commercial AMF inoculant applied at three rates (0, 1X, and 2X the recommended rate) with or without P fertilizer (16.8 kg ha-1). The response of flax cultivars to AMF inoculation was examined in a growth chamber experiment. In addition, 454 sequencing was employed to examine the impact of AMF inoculation on root-associated AMF communities. Under field conditions, only one site showed increased root colonization with AMF inoculation. Flax responded to AMF inoculation differently under different field conditions. At the two sites with intermediate initial soil P level, evidence of increased above-ground biomass and plant nutrient uptake with AMF inoculation was observed. However, such an effect was not detected when P fertilizer was combined with the inoculation. At a low P site and an irrigated site, P application accounted for all of the increases in plant nutrient uptake and biomass of flax, whereas no responses to AMF inoculation were detected. The 454 sequencing revealed different inoculation-induced changes in the diversity and composition of root-associated AMF communities between sites, which was possibly related to different field environments and native AMF communities. In the growth chamber, AMF inoculation resulted in general increases of plant nutrient uptake among cultivars, but only one cultivar showed enhanced biomass with inoculation. The diversity of AMF communities colonizing different flax cultivars was generally reduced by AMF inoculation. Community composition shifted under AMF inoculation, and the shifts appeared to be cultivar specific. These results suggested that benefits of AMF inoculation in flax production are limited and currently not predictable, and the degree of response is likely dependent on a myriad of soil and environmental conditions.

Autonomous navigation with constrained consistency for C-Ranger

Autonomous underwater vehicles (AUVs) have become the most widely used tools for undertaking complex exploration tasks in marine environments. Their synthetic ability to carry out localization autonomously and build an environmental map concurrently, in other words, simultaneous localization and mapping (SLAM), are considered to be pivotal requirements for AUVs to have truly autonomous navigation. However, the consistency problem of the SLAM system has been greatly ignored during the past decades. In this paper, a consistency constrained extended Kalman filter (EKF) SLAM algorithm, applying the idea of local consistency, is proposed and applied to the autonomous navigation of the C-Ranger AUV, which is developed as our experimental platform. The concept of local consistency (LC) is introduced after an explicit theoretical derivation of the EKF-SLAM system. Then, we present a locally consistency-constrained EKF-SLAM design, LC-EKF, in which the landmark estimates used for linearization are fixed at the beginning of each local time period, rather than evaluated at the latest landmark estimates. Finally, our proposed LC-EKF algorithm is experimentally verified, both in simulations and sea trials. The experimental results show that the LC-EKF performs well with regard to consistency, accuracy and computational efficiency

Fractal Dimension Analysis for Robust Ultrasonic Non-Destructive Evaluation (NDE) of Coarse Grained Materials

Over the recent decades, there has been a growing demand on reliable and robust non-destructive evaluation (NDE) of structures and components made from coarse grained materials such as alloys, stainless steels, carbon-reinforced composites and concrete; however, when inspected using ultrasound, the flaw echoes are usually contaminated by high-level, time-invariant, and correlated grain noise originating from the microstructure and grain boundaries, leading to pretty low signal-to-noise ratio (SNR) and the flaw information being obscured or completely hidden by the grain noise. In this paper, the fractal dimension analysis of the A-scan echoes is investigated as a measure of complexity of the time series to distinguish the echoes originating from the real defects and the grain noise, and then the normalized fractal dimension coefficients are applied to the amplitudes as the weighting factor to enhance the SNR and defect detection. Experiments on industrial samples of the mild steel and the stainless steel are conducted and the results confirm the great benefits of the method