Damage Assessment and Strength Predictions in S-Glass/Epoxy Laminates Subjected to Low Energy Impact

Composite materials have become one of the leading materials for manufacturing in the aerospace industry today. Compared to conventional aerospace metals, composites generally have higher strength-to-weight and stiffness-to-weight ratios, good fatigue and corrosion resistance and reduced parts count. However, like any other material, they also have disadvantages. They are inherently brittle and are thus prone to impact damage. Low energy/velocity impact damage, in particular, can be dangerous because the damage oftentimes goes undetected and can subsequently grow under load. Also known as barely visible impact damage (BVID), this area of concentration focuses on the small-scale damage that may be very difficult to detect yet can be lethal. The primary emphasis of this research is to predict the residual compressive strength of a 16-ply laminate [(0°/±45°/90°)2]s after experiencing low energy/velocity impact using combined technical approaches of ultrasonic C-scan and neural networks. To accomplish this, each test specimen was ultrasonically C-scanned after impact testing. A MATLAB computer program was then used to convert the image files into numeric data, which they were presented to a backpropagation neural network in order to predict the residual compressive strength. Microsoft Excel was used to take the average of the diagonal values of the normalized image data. Here the average prediction error turned out to be 3.9 percent, while the worst-case prediction error was 14.6 percent. This research also focused on identifying, sorting, and classifying how the composite laminates failed under compression after experiencing low energy/low velocity impact. Acoustic emission (AE) parameter data were collected during compression testing, and then inputted into an artificial neural network (ANN) for classification. Specifically a Kohonen Self Organizing Map (SOM) was used to sort and classify the failure mechanisms that occurred within the weakened composites. The associated BVID failure modes, otherwise known as failure mechanisms, were believed to consist primarily of transverse and longitudinal matrix cracks, delaminations, and occasionally fiber breaks. Even though delaminations are the most critical failure modes in BVID under compression, the other failure mechanisms also contribute significantly. Furthermore, it appeared that it was also possible to sort out and determine the transition regions between BVID and visible impact damage (VID) with AE data. Thus, it is important to know how the material fails so that necessary precautions can be taken to minimize these critical failure modes

Embedded Sensing and Control for High-Speed Electrohydraulic Soft Robots

Soft robotics is a field of robotic system design characterized by materials and structures that exhibit large-scale deformation, high compliance, and rich multifunctionality. The incorporation of soft and deformable structures endows soft robotic systems with the compliance and resiliency that makes them well-adapted for unstructured and dynamic environments. While actuation mechanisms for soft robots vary widely, soft electrostatic transducers such as dielectric elastomer actuators (DEAs) and hydraulically amplified self-healing electrostatic (HASEL) actuators have demonstrated promise due to their muscle-like performance. Despite significant leaps in design and modeling of HASEL actuators thus far, the actuators in and of themselves are limited in terms of estimating their own states and individually lacks useful system-level functionalities. To address the mentioned shortcomings, this body of research has enabled embedded perception and intelligence to electromechanical systems driven by electro-hydraulic actuators, by (i) developing capacitive self-sensing and magnetic sensing techniques to estimate shape changes of electro-hydraulic actuators in real-time; (ii) designing and implementing hardware and software controllers for an array of electrohydraulic actuators to enable complex motions and their collective useful functionalities; and (iii) demonstrating the integration of embedded sensing and control to bring soft robots driven by these actuators closer to practical, real-world applications. While not exhaustive, the introduced system technologies provide the fundamental building blocks for more advanced functionalities and features that can potentially integrate HASEL actuators to augment and enrich our daily lives

Assessing the Potential of Climate Smart Agriculture in Large Rice Field Models in Vietnam

This study assesses the economic, social, and environmental impacts of Large Field Models (LFMs) and their potential for promoting Climate-Smart Agriculture (CSA). In Vietnam, the government introduced the Large Field Model (LFM), a type of production organization, in which enterprises or cooperatives establish a cooperative relationship with farmers to apply a unification production procedure by providing production inputs (including material and technical support) and/or buying outputs from producers. These LFMs can be classified under three different forms based on the extent of those linkages: (1) farmers contribute land and/or labour to farmer cooperatives; (2) farmers sign contracts with cooperatives or enterprises and receive inputs; and (3) farmers lease out/sell their land to cooperatives or enterprises. Although the key objectives of constructing LFMs come from requirements in improving rice quality and rice production efficiency, these models also have potential for applying CSA to achieve three CSA pillars: productivity, resilience and mitigation. Productivity: the LFMs ensure integration between enterprises and farmers, wherein rice production is promoted, given that the output is sold at a more stable price. Therefore, farmers confidently manage their business to increase productivity. In addition, higher output price and lower production cost is observed from LFMs’ production. Better output price comes from the commitments of enterprises and higher rice quality produced from LFMs. The reduction in production costs is also achieved by taking advantage of economy of scale to apply modern agricultural machinery (such as tractors) and thus reduce labour costs. Resilience: this CSA pillar is created indirectly from LFMs. In general, as farmers use LFMs, they have a better chance to access certified seeds and follow the production procedures of enterprises under the direct support from technicians, and they are less likely to be exposed to disease epidemics than non-participant farmers. In addition, farmers who sign contracts with enterprises/cooperatives or work in LFMs tend to share their knowledge and discuss weather issues with technicians before deciding when to sow or harvest to reduce climate risks. Mitigation: the LFM production contributes to reduced GHG emissions. LFMs created a foundation to apply advanced cultivation methods and to follow strictly modern techniques such as: One Must Five Reductions (1M5Rs), Three Reductions Three Gain (3R3G), 4 Alternate Wetting and Drying (AWD), System of Rice Intensification (SRI), and Deep Fertilizer Placement (DPF). The synchronized irrigation timing or flattened surface field of LFMs also contributes more efficient water use. Moreover, this model changes farmer behaviours toward more efficient and environmentally friendly paddy straw treatment to mitigate environmental impacts. In sum, there are potentials for promoting CSA application in LFMs. The integration developed through LFMs will produce friendly and mutually beneficial networks of farmers to share knowledge and modern techniques. This also encourages farmers to improve cultivating skills and output quality to sustain their contracts with better enterprises in the long run. In addition, the pressure from climate risks will push farmers to act collectively to adapt and mitigate environmental impacts. These potentials should be accompanied by the strong support from the government through its response to climate changes in the Nationally Determined Contribution (NDCs). However, there are still many constraints for expanding CSA application into LFMs. First, traditional cultivation and small landholding habits make it difficult for enterprises to accumulate land to form LFMs. Even when farmers agree to contribute their land to cooperatives, this model is still struggling to establish the appropriate benefit-sharing method in order to keep it working smoothly in the long run, especially due to land price fluctuations. Second, there are infrastructure-related issues. Some types of CSA practices require infrastructure support, for example irrigation systems for applying Alternate Wetting and Drying (AWD). Finally, there is a need for a legal mechanism to bind contracts between enterprises and farmers, especially under high price volatility. Vietnam’s policy system to enhance CSA application and expand LFMs is still characterized by limitations related to effectiveness, validation and public-private participation. This requires a change to attract the participation of local government, enterprises, and farmers. For example, experience from other countries shows that in the case of small scale production, legal measures would not be feasible because of high transaction costs. Therefore, using community value to bind farmers to contracts is the most feasible measure that has been proven. In addition, support for developing agricultural insurance and infrastructure investment is important. However, before expanding CSA application into LFMs, detailed studies of LFMs in each region are required because each model might be more efficient for one specific region with a specific crop

Dairy Value Chain In Vietnam: Evidences from Bavi Area

Dairy farming, in Vietnam, existed in the early twentieth century thanks to the favorable natural advantage. During many difficult periods, the Vietnam’s dairy industry has developed constantly and contributed significantly to the food needs ensuring. However, Vietnam’s dairy industry still could not satisfy the domestic milk demand. Retail milk prices in Vietnam are very high, whereas the price of milk sold by the dairy farmers is very low. The cause stems from the control of dairy companies in the quantity and quality of milk. Moreover, that control caused an imbalance in the profits and benefits of each actor in the dairy value chain. This study, hence, finds out the distribution of benefits, costs, value-added among the actors, and problems in the practical management in dairy milk value chain with specific focus on Bavi as the case study

A framework for reviewing laws and policies for climate resilience – The case of the Vietnamese Mekong Delta

This article proposes a framework for reviewing to what extent laws and policies of a legal system support climate resilience. This article adopts the social-ecological system (SES) resilience theory and translates its core features into an operational framework which consists of four legal dimensions crucial for promoting climate resilience – adaptiveness of law, distributive justice, broad participation, and cross-scale interactions, and further identifies several indicators below each dimension. Then this article operationalizes the four legal dimensions via reviewing current Vietnamese climate adaptation laws and policies to assess to what extent they promote a climate-resilient Vietnamese Mekong Delta (VMD). While various barriers can be found in the current legal framework and policies which impede climate resilience, the latest National Climate Change Adaptation Plan demonstrates great improvement in facilitating climate resilience in a just, participatory and coordinated manner

Impacts of fallow conditions, compost and silicate fertilizer on soil nematode community in salt–affected paddy rice fields in acid sulfate and alluvial soils in the Mekong Delta, Vietnam

© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)Avoidance of intensive rice cultivation (IRC) and soil amendments are potential practices to enhance soil properties. There is only limited information on the effects of reduced IRC and its mixture with compost or silicate fertilizer (Si) on the soil nematode community in salt–affected soils. This study aimed to assess the shifts of soil nematode community by reducing a rice crop from triple rice system (RRR) to a double rice system and mixed with compost or Si in paddy fields in acid sulfate soil (ASS) and alluvial soil (AL) in the Mekong Delta, Vietnam. Field experiments were designed with four treatments in four replicates, including RRR and a proposed system of double–rice followed by a fallow (FRR) and with 3 Mg ha–1 crop−1 compost or 100 kg ha–1 crop−1 Si. Soils were collected at harvest after the 2 year experiment, reflecting the fifth and third consecutive rice crop in RRR and FRR system, respectively. Results showed that reduced IRC gave a significant reduction in abundance of plant–parasitic nematodes (PPN), dominated by Hirschmanniella and increased abundance bacterivorous nematodes when mixed to compost and silicate fertilizer in ASS. In addition, reduced IRC increased nematode biodiversity Hill’s indices and reduced herbivorous footprint in ASS. Proposed system having compost or Si had strongly increased in bacterivorous and omnivorous footprints. Particularly, reduced IRC mixture with Si increased abundance of Rhabdolaimus, Mesodorylaimus and Aquatides, metabolic footprints (structure footprint, bacterivorous, omnivorous and predator) and diversity Hill’s N1 index in ASS. Our results highlighted that reduced IRC was a beneficial practice for decreasing abundance of PPN in salt-affected soils and increasing abundance of FLN in ASS. IRC mixture with compost or Si had potential in structuring the nematode communities with increasing biodiversity, trophic structure, and metabolic footprintsPeer reviewedFinal Accepted Versio

Awareness And Risk Behaviors Towards Zoonotic Disease Among Ethnic Minority In Mountainous Area Of Central Vietnam

Background: As a result of the population explosion and rapid urbanization, human activities have been causing negative impacts on the environment. The changing patterns of transmissible diseases among wild animals, livestock and human have been getting more and more complicated in the context of climate change. Ethnic community from mountainous and isolated areas undoubtedly are the most vulnerable, with the high risk of emerging and re-emerging zoonosis. Objectives: To explore the awareness and risk behaviors of the residents in Nham commune, A Luoi district towards zoonosis transmission. To determine the factors related to the risk behaviors of the residents. Methods: A sectional-cross study was conducted among 230 residents whose ages range from 18 – 85, currently living in Nham commune, A Luoi district, adjacent to the Vietnam – Laos border. All participants were interviewed directly with a questionnaire including the following categories: demographics, household wealth, awareness of zoonosis, livestock management and behaviors related to wildlife animals. Descriptive analysis and multivariable logistic regression analysis were conducted to determine factors associated with risk behaviors. Results: The proportion of respondents who have heard about zoonotic diseases was 40%. The majority of subjects raise free-range livestock (83,4%), especially on poultry and cow. The percentage of participants who consumed culled sick and dead animals accounted for 26%, over 30% of villagers slept in forest and more than 50% consumed bushmeat. Risk behaviors related to management livestock and wildlife were statistically significantly associated with gender, age of subjects, educational background, household wealth, information approach on zoonosis, and the number of livestocks. Conclusions: The proportion of respondents who have heard about zoonotic diseases was 40%. The high-risk group falls on those who consume dead domestic animals, wildlife animals and sleep in the forest. Behaviors of human-wildlife contact and zoonosis are quite common with the Nham locals, which emphasizes the necessity for intervention programs in zoonotic disease control.