Calculation of nonlinear vibrations of piecewise-linear systems using the shooting method

In this paper, an explicit formulation of the shooting scheme for computation of multiple periodic attractors of a harmonically excited oscillator which is asymmetric with both stiffness and viscous damping piecewise linearities is derived. The numerical simulation by the shooting method is compared with that by the incremental harmonic balance method (IHB method), which shows that the shooting method is in many respects distinctively advantageous over the incremental harmonic balance method

Adaptation options for agricultural cultivation systems in the South Central Coast under the context of climate change: Assessment Report.

This report highlights the results of consultation meetings and field visits organized by the Department of Crop Production and the CGIAR Research Program on Climate Change, Agriculture and Food Security in Southeast Asia in association with the three offices of the Department of Agriculture and Rural Development in the South Central Coast provinces of Binh Thuan, Ninh Thuan, and Khanh Hoa, in combination with consultation with the provinces in the conference: “Summing up crops production in the Winter-Spring season in 2018-2019, implementing the Summer-Autumn season, Main rice season in 2019 for the South Central Coast and the Central Highlands” held by the Ministry of Agriculture and Rural Development in Tam Ky City, Quang Nam Province on 12 April 2019. The meetings underlined the progress made by the provinces on climate change adaptation and mitigation, options for risk reductions in agricultural production, and conversion of crop structure as results of implementing the guidelines of the provinces and the Sector, especially, solutions for reservation and efficient and economic use of water under the context of climate change. This assessment report also reviews some issues related to the agricultural transformation of the region in adapting to risks caused by climate change. They are based on comparative advantages in terms of geographical location and market of key agricultural products. This report also points out shortcomings in using land and unreasonable points in managing and using important natural resources, especially water, and provides recommendations for the agricultural transformation and inter-regional connection with the Central Highlands and the Southeast. The team also introduces climate-related risks maps and adaptation plans (CS MAP) which is applied in the five provinces in the Mekong Delta Region, and hopes this solution’s expansion shall be supported by the Ministry of Agriculture and Rural Development and the provinces

RESEARCH ON NEARSHORE WAVE CONDITIONS AT NHAT LE COASTAL AREA (QUANG BINH PROVINCE) BY USING MIKE21-SW

Research on marine dynamics, including coastal wave motions, is a concern of countries in the world in general and Vietnam in particular. Coastal wave dynamics has a direct impact on human activities including coastal construction, shipping, irrigation, aquatic resources exploitation, etc. The coastal area of Nhat Le, Quang Binh is one of the areas strongly influenced by the coastal wave regime which increases the risk of coastal erosion, estuarine sedimentation, destroys the economic life, affects marine fishing and directly affects the tourist beach area. This article aims to introduce some research results based on the application of MIKE21-SW model of the Danish Hydraulic Institute (DHI) to simulate coastal wave regime in Nhat Le coastal zone, Quang Binh province. The model results are verified by real-time wave data in long-term from the WaMoS® II Radar System at Quang Binh station. The results show that there are many similarities in wave height and direction between the computational model and the actual observation data from the radar system. This result will be an important basis for research and application for coastal protection, reduction in river mouth sedimentation, clearing and flood drainage in the study area

Facile synthesis of 3D Fe2O3 nanostructures: sponge-like cube shape and bird nest-like architecture

The hierarchical nanostructures (3D) with their large specific surface area and abundant pores usually possess unique physical and chemical properties for various important applications. In this report, we have introduced simple and scalable routes to successfully synthesize 3D iron oxide nanostructures, including porous cubes and bird nest-like architecture. The 3D sponge-like Fe2O3 nanocubes were formed by an annealing process of perfect Prussian Blue (PB) microcubes, which were built from small nanoparticles linked together. Whereas, the 3D bird nest-like Fe2O3 nanostructures were formed by the transformation of C@FeOOH nanoflower precursors, which were constructed by primary nanorods. The results indicated that the obtained materials show monodispersity, uniform morphology, ultra-porosity and extremely high specific surface area. With unique characteristics, the 3D Fe2O3 nanostructures could be potential candidates for various important fields such as catalysts, absorption and gas sensors

NGUỒN LỢI VÀ NGUỒN GIỐNG HẢI SẢN TRONG VỊNH NHA TRANG

Assessments of commercial and seed resources of target marine species exploited in Nha Trang bay were conducted in 2014 - 2015 through 8 consultations with 8 local communes/wards surrounding the bay in combination with 4 field surveys (December 2014; May, August and September 2015) to assess locations of important spawning and nursery grounds of target resources. Results from this study showed that there were 25 target resources of abalones, lambis and turbo snails, top shells, strawberry conch, scallops, squids and cuttlefish, swimming crab, spiny lobsters, sea cucumbers, rabbitfishes, anchovies, breams, scads and ponyfishes with an annual commercial catch and revenue of 651.3 tonnes and 65 billion VND respectively in 2014. The reef related resources contributed similar catch and higher revenue (323.9 tons and 21.56 billion VND) than the reef resources (327.4 tons and 11.11 billion VND), in which rabbitfish was the most important group. In addition, harvesting of seeds of spiny lobsters for marine aquaculture was also important activity to fishery in the bay, giving a total catch and revenue of  212.000 seeds and 32.34 billion VND per year and this revenue was 3 times higher than that of the commercial resources directly harvested from the reefs. The Sargassum beds and coral reefs in the bay were important spawning and nursery grounds for squids, abalones, turbo snails, top shells, spiny lobsters and rabbitfishes.Đánh giá hiện trạng nguồn lợi và nguồn giống hải sản khai thác trong vịnh Nha Trang được thực hiện thông qua việc tổ chức 8 cuộc tham vấn cộng đồng tại các xã/phường ven biển (tháng 12/2014) kết hợp với 4 đợt khảo sát thực địa (tháng 12/2014; tháng 5, 8 và 9/2015) nhằm xác định khu vực phân bố của các bãi nguồn giống hải sản quan trọng vào năm 2014 và 2015. Kết quả khảo sát ghi nhận trên 25 nhóm đối tượng nguồn lợi chủ yếu (bào ngư, ốc bàn tay, ốc đụn, ốc mặt trăng, ốc nhảy đỏ lợi, điệp nhật nguyệt, điệp quạt, điệp đỏ, điệp vỏ dày, mực lá, mực nang, mực ống, ghẹ ba chấm, tôm tít, tôm đất, tôm hùm, hải sâm nận, nhum sọ, cá dìa, cá giò, cá cơm săng, cá đổng, cá hanh, cá nục, cá liệt) được khai thác với sản lượng thương phẩm và doanh thu hàng năm ước đạt 651,3 tấn và 65 tỷ đồng, trong đó nguồn lợi ngoài rạn đóng vai trò quan trọng hơn nhiều (323,9 tấn và 21,56 tỷ đồng) so với trực tiếp trên rạn san hô (327,4 tấn và 11,11 tỷ đồng) và cá là nhóm nguồn lợi quan trọng nhất (đặc biệt là cá dìa và cá giò). Bên cạnh đó, khai thác nguồn lợi tôm hùm giống hàng năm trong vịnh ước đạt trên 212.000 con và doanh thu khoảng 32,34 tỷ đồng, cao gấp 3 lần so với doanh thu khai thác nguồn lợi thương phẩm trực tiếp trên rạn. Các thảm rong mơ và rạn san hô trong vịnh Nha Trang là khu vực bãi đẻ và ương giống của các nhóm đối tượng nguồn lợi quan trọng như mực lá, bào ngư, ốc đụn, ốc mặt trăng, tôm hùm, cá dìa và cá giò

An Efficient Method for Generating Synthetic Data for Low-Resource Machine Translation – An empirical study of Chinese, Japanese to Vietnamese Neural Machine Translation

Data sparsity is one of the challenges for low-resource language pairs in Neural Machine Translation (NMT). Previous works have presented different approaches for data augmentation, but they mostly require additional resources and obtain low-quality dummy data in the low-resource issue. This paper proposes a simple and effective novel for generating synthetic bilingual data without using external resources as in previous approaches. Moreover, some works recently have shown that multilingual translation or transfer learning can boost the translation quality in low-resource situations. However, for logographic languages such as Chinese or Japanese, this approach is still limited due to the differences in translation units in the vocabularies. Although Japanese texts contain Kanji characters that are derived from Chinese characters, and they are quite homologous in sharp and meaning, the word orders in the sentences of these languages have a big divergence. Our study will investigate these impacts in machine translation. In addition, a combined pre-trained model is also leveraged to demonstrate the efficacy of translation tasks in the more high-resource scenario. Our experiments present performance improvements up to +6.2 and +7.8 BLEU scores over bilingual baseline systems on two low-resource translation tasks from Chinese to Vietnamese and Japanese to Vietnamese

Performance of Notched Connectors for CLT-Concrete Composite Floors

CLT-concrete composite floor systems are a solution for timber buildings with a long-span floor. It yields a reduction of carbon footprint and even eco-friendly structure at the end of its service life. This study will evaluate the structural performance of notched connectors in the CLT-concrete composite floor, comprised of the serviceability sti ness, maximum load, and behavior at failure. The parameters of the test plan are the loaded edge length, the notch depth, the concrete thickness, and the screw length. Other secondary variables are also assessed, such as di erent loading sequences, speed of test, and timber moisture content. Experimental results prove that the performance of the connector depends significantly but not linearly on the notch depth and the length of the loaded edge. The connector with a deeper notch and a shorter heel will be sti er and more robust, but it also tends to have a brittle rupture. The test results also help validate a solution for deconstructable connector systems. A nonlinear finite element model of the connector is built and validated versus the experimental results. It yields reasonably good predictions in terms of resistance and can capture the load-slip relationship

Fabrication and evaluation of some electrochemical properties of screen-printed electrodes for use in electrochemical analysis

Three types of conductive inks, including Ceres, Acheson carbon inks, and Ag/AgCl ink, were utilized to fabricate screen-printed electrodes (SPEs) on a 0.4 mm thick polyethylene terephthalate substrate using a screen-printing technique. To enhance the electrical conductivity, the printed electrodes were cured at 80°C for 90 minutes. The basic electrochemical properties of the self-made SPEs using these conductive inks were determined, evaluated, and compared with commercial SPEs from Metrohm. Although the electroactive surface areas of the self-made SPEs were not significantly different from those of the commercial SPEs, the heterogeneous electron transfer rates on the surfaces of self-made SPEs using Ceres and Acheson inks were inferior to those of the commercial SPEs. However, after pre-condition by applying a potential of +1.2 V for 180 s in a 2 M Na2CO3 solution, the electrochemical properties of the self-made SPEs, including the active surface areas and heterogeneous electron transfer rates, were significantly improved and became better than those of the commercial SPEs

Securing MIMO Wiretap Channel with Learning-Based Friendly Jamming under Imperfect CSI

Wireless communications are particularly vulnerable to eavesdropping attacks due to their broadcast nature. To effectively deal with eavesdroppers, existing security techniques usually require accurate channel state information (CSI), e.g., for friendly jamming (FJ), and/or additional computing resources at transceivers, e.g., cryptography-based solutions, which unfortunately may not be feasible in practice. This challenge is even more acute in low-end IoT devices. We thus introduce a novel deep learning-based FJ framework that can effectively defeat eavesdropping attacks with imperfect CSI and even without CSI of legitimate channels. In particular, we first develop an autoencoder-based communication architecture with FJ, namely AEFJ, to jointly maximize the secrecy rate and minimize the block error rate at the receiver without requiring perfect CSI of the legitimate channels. In addition, to deal with the case without CSI, we leverage the mutual information neural estimation (MINE) concept and design a MINE-based FJ scheme that can achieve comparable security performance to the conventional FJ methods that require perfect CSI. Extensive simulations in a multiple-input multiple-output (MIMO) system demonstrate that our proposed solution can effectively deal with eavesdropping attacks in various settings. Moreover, the proposed framework can seamlessly integrate MIMO security and detection tasks into a unified end-to-end learning process. This integrated approach can significantly maximize the throughput and minimize the block error rate, offering a good solution for enhancing communication security in wireless communication systems.Comment: 12 pages, 15 figure