Binary-Continuous Sum-of-ratios Optimization: Discretization, Approximations, and Convex Reformulations

We study a class of non-convex sum-of-ratios programs which can be used for decision-making in prominent areas such as product assortment and price optimization, facility location, and security games. Such an optimization problem involves both continuous and binary decision variables and is known to be highly non-convex and intractable to solve. We explore a discretization approach to approximate the optimization problem and show that the approximate program can be reformulated as mixed-integer linear or second-order cone programs, which can be conveniently handled by an off-the-shelf solver (e.g., CPLEX or GUROBI). We further establish (mild) conditions under which solutions to the approximate problem converge to optimal solutions as the number of discretization points increases. We also provide approximation abounds for solutions obtained from the approximated problem. We show how our approach applies to product assortment and price optimization, maximum covering facility location, and Bayesian Stackelberg security games and provide experimental results to evaluate the efficiency of our approach

A Study on Derailment at Railway Turnout Using the Multi-body Dynamics Simulation

In this study, the locomotive and the turnout were simulated with three-dimensional models. The purpose of this study is prediction the derailment phenomenon of the locomotive running on the turnout in Vietnam. Multi-body simulations were implemented by SIMPACK software to determine the derailment coefficient, the wheel unloading factor, and the lateral force. The interaction between the locomotive and the track structure at turnout was considered unified. The derailment coefficient, the wheel unloading factor, and the lateral force were calculated for locomotive-D19E at turnout (tg0.15) for 1000 mm gauge according to QCVN 18:2011/BGTVT, EN 14363:2016, and TCVN 8784:2011. The derailment coefficient, the wheel unloading factor, and the lateral force for the locomotive at max speed V=27.8 km/h are 0.94, 0.61, and 67.46 kN, respectively. These results show that the locomotive will not derail when it passes the turnout at a speed V 27.8 km/h

A Study on Derailment at Railway Turnout Using the Multi-body Dynamics Simulation

In this study, the locomotive and the turnout were simulated with three-dimensional models. The purpose of this study is prediction the derailment phenomenon of the locomotive running on the turnout in Vietnam. Multi-body simulations were implemented by SIMPACK software to determine the derailment coefficient, the wheel unloading factor, and the lateral force. The interaction between the locomotive and the track structure at turnout was considered unified. The derailment coefficient, the wheel unloading factor, and the lateral force were calculated for locomotive-D19E at turnout (tg0.15) for 1000 mm gauge according to QCVN 18:2011/BGTVT, EN 14363:2016, and TCVN 8784:2011. The derailment coefficient, the wheel unloading factor, and the lateral force for the locomotive at max speed V=27.8 km/h are 0.94, 0.61, and 67.46 kN, respectively. These results show that the locomotive will not derail when it passes the turnout at a speed V 27.8 km/h

Shortage in Access to Basic Social Services: A Case Study of Ethnic Minority Groups in Vietnam

The research uses shortages in the multi-dimensional poverty criteria and household living standards survey data collected by the General Statistic Office to evaluate the access to basic social services by ethnic minorities. The result shows significant differences in shortages between the Kinh and ethnic minorities, among ethnic minority groups and among localities. Differences in geographical location, level of development and lacking specific policies are the main causes. A number of policy recommendations has been made to narrow the gap in access to basic social services among ethnic minority groups in Vietnam. Keywords: Ethnic minorities, basic social services, shortage in access to basic social services, Vietnam DOI: 10.7176/EJBM/12-17-15 Publication date:June 30th 202

Economic, social and environmental disclosure, a theoretical framework and its application in Vietnam

This study focuses on the appraisal of firms performance and on its representation and reporting. Using interviews and inquiries in firms operating in the cement industry in Vietnam, two points are investigated. First, whether firms top executives consider that firms sustainable performance may include economic, social or environmental performance that is not integrated in financial statements. The theoretical framework is the stakeholder theory complemented with the institutional theory. Second, whether economic, social and environmental performance should be disclosed to answer the expectations of the various stakeholders. Therefore, our research contributes to corporate governance studies by focusing on reporting dedicated to all the stakeholders

Impact of Vocational Education and Training On Decent Job Opportunities Regarding Information and Communication Technology

Vocational education and training plays a crucial part in the creation of decent job. The fast growth of information and communication technology (ICT) during the past ten years has increased work opportunities for laborers. This research uses the yearly labor force survey data to study the impact of vocational education and training on decent job opportunities for employees in the context of Vietnam's information and communication technology development. The logit model results indicate that the 2020 rate of decent jobs is still low, at approximately 25.6 percent. However, vocational education and training and the advancement of ICT positively affect decent job opportunities. This long-lasting impact affects laborers in various areas, regions, and industries. These findings suggest that vocational education and training and ICT must play a significant role in transitioning from precarious to more secure employment, so laborers must acquire professional knowledge and information technology skills

Carrot hairy roots (Daucus carota L.) characterisation and optimisation for high β‐carotene extraction

Hairy roots are widely known as a biological system for the production of highly diverse biomolecules. β‐carotene – a precursor for vitamin A – is known to be an anti‐oxidant and anti‐gastric cancer and protection agent against cardiovascular disease, heart disease and stroke. β‐carotene has been chemically synthesised and consumed by humans. However, the chemical process often produces a by‐product that may be harmful to human health. Therefore, this study established a protocol to induce hairy roots (HRs) from a Vietnamese carrot variety and produce natural β‐carotene. The Rhizobium rhizogenes ATCC15834 harbouring Ri plasmid and a Vietnamese carrot variety were used as materials for genetic transformation and HR induction studies. The result showed that approximately 50 HR lines were obtained. Culture medium supplemented with 30 mg/L of sucrose that gave the highest biomass of HR was shown in carrot HR line 30, which had a doubling time of 6.5 days. The highest content of β‐carotene extraction, at 128 mg/100g hairy roots, was achieved with a ratio volume (v/v) of 2‐propanol and plant samples of 20:1, followed by two hours’ incubation with 2‐propanol at 60 °C. Our study reveals a highly efficient protocol for Vietnamese carrot hairy root establishment and multiplication. A very efficient protocol for β‐carotene extraction from the hairy root was established to produce natural β‐carotene that achieves the same β‐carotene quantity as that produced by normal roots. This study provides new insight into the production of high‐content and natural β‐carotene for therapeutic application

Using cassava waste of the cassava starch processing as food for raising African Nightcrawler (Eudrilus eugeniae) to obtain vermicomposting and earthworm biomass

The raising earthworms by cassava waste is a useful solution to reduce environmental pollution caused by cassava starch processing. In this study, cassava waste (including cassava peel, cassava pieces and soil) was used as a food source for raising African Nightcrawler (Eudrilus eugeniae) with three experiments: E1, earthworms were raised in crushed cassava waste right after being discharged; E2, earthworms raised in crushed cassava waste that had been incubated with organic matter after decomposing microbiological preparation for the previous two weeks; E3, earthworms were raised in crushed cassava waste that had self-decomposed naturally for the previous two weeks. The cassava waste was decomposed naturally for 4 weeks for control. The results showed that the content of organic matter, humic acid and total nitrogen in organic cassava humus, obtaining from experiments, increased compared to the control; the total organic matter content reached from 10.4%-15.7%, higher than the control (8.2%) from 1.27-1.92 times, humic acid content reached 0.6 - 0.8% and total nitrogen reached 0.3%. Experiment 3 had the highest quality of humus (organic matter content 15.7%, total nitrogen 0.3%, humic acid 0.7% and fulvic acid 0.5%). The experiment 3 also had the highest earthworm biomass (3.6kg), increasing 30.5% compared to experiment 1 and 19.4% comparing to experiment 2. Therefore, experiment 3 was proposed for application in treatment of cassava waste at larger scale. The organic humus obtaining from raising earthworms by cassava waste can be used as raw material for vermicompost production. The earthworm biomass can be used as protein-rich food for domestic animals (such as chicken, tortoise, eel, fish, etc) or used as nutritious fertilizer.Nuôi giun bằng phế liệu sắn là giải pháp hữu ích nhằm giảm thiểu ô nhiễm môi trường do chế biến tinh bột sắn gây ra. Trong nghiên cứu này, bã thải sắn (bao gồm vỏ, đầu mẩu sắn và bùn đất) được sử dụng làm nguồn thức ăn giun đất Châu Phi (African Nightcrawler (Eudrilus eugeniae) với các thí nghiệm như sau: Thí nghiệm 1: Giun quế được nuôi trong bã thải sắn nghiền ngay sau khi được loại bỏ; Thí nghiệm 2: giun đất được nuôi trong bã thải sắn nghiền đã được ủ với chế phẩm vi sinh phân hủy chất hữu cơ trong hai tuần trước đó; Thí nghiệm 3: Giun đất được nuôi trong bã thải sắn nghiền được để tự phân hủy tự nhiên trong hai tuần trước đó. Đối chứng là bã thải sắn để phân hủy tự nhiên trong 4 tuần. Bên cạnh đó, bã thải sắn nghiền còn được ủ bằng chế phẩm vi sinh phân hủy chất hữu cơ trong 4 tuần để cung cấp thêm số liệu so sánh giữa các thí nghiệm (Thí nghiệm 4). Các thí nghiệm được theo dõi trong 4 tuần. Kết quả cho thấy: Kết quả cho thấy: hàm lượng chất hữu cơ, axit humic và nitơ tổng trong mùn sắn hữu cơ thu được từ thí nghiệm đều tăng so với đối chứng: hàm lượng chất hữu cơ tổng số đạt từ 10,4% -15,7%, cao hơn đối chứng (8,2%) so với 1,27-1,92 lần, hàm lượng axit humic đạt 0,6 - 0,8% và nitơ tổng số đạt 0,3%. Trong đó, thí nghiệm 3 có chất lượng mùn cao nhất (hàm lượng chất hữu cơ 15,7%, đạm tổng số 0,3%, axit humic 0,7% và axit fulvic 0,5%). Thí nghiệm 3 cũng có sinh khối giun quế cao nhất (3,6kg), tăng 30,5% so với thí nghiệm 1 và 19,4% so với thí nghiệm 2. Do đó, thí nghiệm 3 đã được đề xuất ứng dụng để xử lý phế thải sắn ở quy mô lớn hơn. Chất mùn hữu cơ thu được từ việc nuôi trùn quế bằng phế thải sắn có thể được sử dụng làm nguyên liệu để sản xuất phân trùn quế. Sinh khối trùn quế có thể dùng làm thức ăn giàu đạm cho vật nuôi (như gà, ba ba, lươn, cá ...) hoặc làm phân bón dinh dưỡng

Synthesis of Cu+^+/bipyridyl Based Complex Towards Dye Sensitized Solar Cell Application

This study aims to synthesize the Cu+/bipyridyl-based complex using Sonogashira cross coupling. The structure of the ligand and the complex were investigated by nuclear magnetic resonance spectroscopy; by single crystal X-ray diffraction and by UV-VIS absorption spectroscopy. The obtained experimental results were in good agreement with the theoretical calculations. The complex is a potential candidate to be the photo sensitizer in dye-sensitized solar cells.