Phân tích chi phí-lợi ích của đồng đốt sinh khối với than: Trường hợp nhà máy nhiệt điện Ninh Bình

National audienceĐồng đốt sinh khối với than là công nghệ tận dụng sinh khối để phát điện với mức chi phí thấp hơn rấtnhiều so với việc xây dựng nhà máy điện sinh khối. Đồng đốt giúp giảm bớt tác động của nhiệt điện thanđến kinh tế, môi trường và xã hội. Việt Nam có tiềm năng phát triển công nghệ này do có tiềm năng lớn vềsinh khối cũng như do Việt Nam sẽ tiếp tục phát triển các nhà máy nhiệt điện than trong vòng 2 thập kỷ tớitheo như Quy hoạch điện mới nhất.Trong số các công nghệ đồng đốt, đồng đốt trực tiếp là công nghệ phù hợp nhất đối với điều kiện Việt Namhiện nay. Mặc dù tỉ lệ đồng đốt thấp nhưng chi phí chuyển đối thấp nhất và có thể tận dụng hầu hết cácloại sinh khối. Việt Nam có nguồn sinh khối dồi dào, đặc biệt là nguồn phụ phẩm, phế phẩm nông nghiệp.Đây là các nguồn sinh khối nên được cân nhắc sử dụng trước tiên cho đồng đốt. Viên nén sinh khối cũnglà một lựa chọn tốt cho đồng đốt xét về các đặc tính kỹ thuật cũng như nguồn cung trong nước. Tuy nhiêngiá cả của viên nén chưa thực sự cạnh tranh được với than cũng như với nguồn phụ phẩm phế phẩm nôngnghiệp.Hiệu quả về mặt kinh tế của đồng đốt sinh khối với than sẽ cao hơn tại các nhà máy có các điều kiện nhưsau: sử dụng lò đốt than, tiếp cận được với nguồn cung sinh khối ổn định và có mức giá cạnh tranh, có giáthan cao, có các điều kiện ưu tiên về thị trường cũng như cơ chế đối với sử dụng năng lượng tái tạo vàgiảm rác thải. Việt Nam nên bắt đầu thí điểm với các nhà máy nhiệt điện than nằm tại các vùng có trữlượng sinh khối cao, thuận lợi cho việc thu gom và vận chuyển sinh khối, sử dụng than nhập khẩu có nguồncung than không ổn định và giá than cao như Vĩnh Tân 2, Duyên Hải 1, Long Phước 1...; hoặc các nhàmáy sắp hết thời gian khấu hao như Ninh Bình, Uông Bí hay Phả Lại 1 để tận dụng cơ sở hạ tầng sẵn có.Phân tích trường hợp đồng đốt 5% rơm với than tại nhà máy nhiệt điện Ninh Bình cho thấy đồng đốt đãmang lại hiệu quả kinh tế cho nhà máy trong điều kiện không có cơ chế chính sách hỗ trợ cho đồng đốtcũng như chưa có thị trường cacbon và doanh thu từ bán tro xỉ than. Mặt khác, lợi ích mà đồng đốt đemlại cho xã hội cũng như môi trường là rất đáng kể, đặc biệt là đối với người nông dân và sức khỏe cộngđồng. Các lợi ích này, nếu có cơ chế chia sẽ hợp lý sẽ có thể hỗ trợ cho nhà máy áp dụng đồng đốt đạthiệu quả cao hơn về mặt kinh tế

Socio-economic impacts of co-firing in Vietnam: The case of Ninh Binh Coal Power Plant

International audienceCo-firing biomass with coal is a relatively low-cost technology to utilize biomass for electricity production compared to dedicated biomass power plant. Co-firing could help to reduce the negative impact of coal power plants to economy, environment and society. Vietnam has potential to develop co-firing base on the abundant of biomass resources and because Vietnam will continue to build more coal-fired power plant in the next 2 decades as stated in the latest National Power Development Plan.Among the co-firing technologies, direct co-firing is the most suitable for Vietnam context. Despite of low biomass ratio, direct co-firing offers low investment cost and could utilize most of the biomass feedstock. Vietnam has huge biomass potential, especially the agriculture and forestry residues. These biomasses should be considered first as feedstock for co-firing. Biomass pellets is also a good choice in term of technical features and local supply. However, the price of pellets is not yet competitive with coal or agricultural residues.Economic benefit of co-firing would be higher in the plants that has following features: assess to stable biomass supply, biomass price competitive with coal, incentives and support in term of market for renewable energy utilization and waste reduction. Vietnam should start experimenting co-firing in the coal power plants that located in the area where biomass resource is available, easy to collect and deliver to the plant, using imported coal such as Vinh Tan 2, Duyen Hai 1, Long Phuoc 1…; or the plants that are soon or already depreciated such as Ninh Binh, Uong Bi or Pha Lai to utilize the existing infrastructures.The case study of co-firing 5% rice straw with coal in Ninh Binh Coal Power Plant shows that co-firing could bring benefit to the plant owner in the condition that lack supporting mechanism for co-firing as well as with the absent of carbon credit. Farmers and workers that work in biomass supply chain also benefit from co-firing, especially farmers. In addition, co-firing provide significant positive externalities, in which the most notable is health benefit from reducing air-borne pollutants. Greenhouse gas emissions reduction adds a small part to the overall benefit of co-firing

ROBUST DYNAMIC ID-BASED REMOTE MUTUAL AUTHENTICATION SCHEME

Dynamic ID based authentication scheme is more and more important in insecure wireless environment and system. Two of kinds of attack that authentication schemes must resist are stealing identity and reflection attack which is a potential way of attacking a challenge- response authentication system using the same protocol in both direc­tions. It must be guaranteed to prevent attackers from reusing informa­tion from authentication phase and the scheme of Yoon and Yoo satisfies those requirements. However, their scheme can not resist insider and impersonation attack by using lost or stolen smart card. In this paper, we demonstrate that Yoon and Yoo’s scheme is still vulnerable to those attacks. Then, we present an improvement to their scheme in order to isolate such problems

Automatic multi-camera extrinsic parameter calibration based on pedestrian torsors

Extrinsic camera calibration is essential for any computer vision task in a camera network. Typically, researchers place a calibration object in the scene to calibrate all the cameras in a camera network. However, when installing cameras in the field, this approach can be costly and impractical, especially when recalibration is needed. This paper proposes a novel, accurate and fully automatic extrinsic calibration framework for camera networks with partially overlapping views. The proposed method considers the pedestrians in the observed scene as the calibration objects and analyzes the pedestrian tracks to obtain extrinsic parameters. Compared to the state of the art, the new method is fully automatic and robust in various environments. Our method detect human poses in the camera images and then models walking persons as vertical sticks. We apply a brute-force method to determines the correspondence between persons in multiple camera images. This information along with 3D estimated locations of the top and the bottom of the pedestrians are then used to compute the extrinsic calibration matrices. We also propose a novel method to calibrate the camera network by only using the top and centerline of the person when the bottom of the person is not available in heavily occluded scenes. We verified the robustness of the method in different camera setups and for both single and multiple walking people. The results show that the triangulation error of a few centimeters can be obtained. Typically, it requires less than one minute of observing the walking people to reach this accuracy in controlled environments. It also just takes a few minutes to collect enough data for the calibration in uncontrolled environments. Our proposed method can perform well in various situations such as multi-person, occlusions, or even at real intersections on the street

Automatic extrinsic calibration of camera networks based on pedestrians

Extrinsic camera calibration is essential for any computer vision tasks in a camera network. Usually, researchers place calibration objects in the scene to calibrate the cameras. However, when installing cameras in the field, this approach can be costly and impractical, especially when recalibration is needed. This paper proposes a novel accurate and fully automatic extrinsic calibration framework for camera networks with partially overlapping views. It is based on the analysis of pedestrian tracks without other calibration objects. Compared to the state of the art, the new method is fully automatic and robust. Our method detects human poses in the camera images and then models walking persons as vertical sticks. We propose a brute-force method to determine the pedestrian correspondences in multiple camera images. This information along with 3D estimated locations of the head and feet of the pedestrians are then used to compute the camera extrinsic matrices. We verified the robustness of the method in different camera setups and for both single pedestrian and multiple walking people. The results show that the proposed method can obtain the triangulation error of a few centimeters. Typically, it requires 40 seconds of collecting data from walking people to reach this accuracy in controlled environments and a few minutes for uncontrolled environments. As well as compute relative extrinsic parameters connecting the coordinate systems of cameras in a pairwise fashion automatically. Our proposed method could perform well in various situations such as multi-person, occlusions, or even at real intersections on the street

THE INFRASTRUCTURE AND ENVIRONMENT IN THE OLD TENEMENTS IN HANOI

Joint Research on Environmental Science and Technology for the Eart

Feasibility and sustainability of co-firing biomass in coal power plants in Vietnam

International audienceThe technology of co-firing biomass with coal is well-matured as demonstrated in many power plants in Europe and the US. It is considered as a relatively low-cost technology to utilize biomass in power generation as well as to reduce the greenhouse gases emissions and coal consumption in coal power plants. However, biomass co-firing is still a new concept in the context of Vietnam energy sector. By 2030, the capacity of coal power plants in Vietnam will be expanded to 75 GW, which accounts for 57% of total power generation. This will increase the greenhouse gases emissions and pose a great challenge on coal supply for Vietnam. This research aims to evaluate the feasibility and sustainability of co-firing biomass in coal power plants in Vietnam. The assessment is conducted using a set of indicators, which is divided into four categories: technical, economical, environmental and social aspects. The feasibility and sustainability assessment is then applied to a case study, a newly constructed 1000 MW fluidized bed coal power plant in Quang Ninh Province. In the case study, direct co-firing technology with 5% of biomass co-fired percentage is selected for the evaluation of the indicators

An investigation of online teaching and lecturers' online teaching competence in Vietnam: A case study at universities of technology and education

The rapid digital transformation and the widespread influence of the COVID-19 pandemic have impacted higher education in Vietnam. This social setting fosters online teaching and lecturers’ online teaching competencies.  The aim of this study is to investigate online teaching competence at two universities of technology and education in Vietnam through a survey. Based on a review of the literature, an online teaching competence scale for lecturers was developed and its validity and reliability were evaluated using exploratory component analysis and Cronbach's alpha coefficients with data from 311 lecturers at two public universities of technology and education. The online teaching competency scale for lecturers consists of 25 items organized into five component competencies: “Understanding student learning”, “online session administration”, “digital content development and learning facilitation”, “technology” and “online learning outcomes assessment”. With the exception of “technology”, the remaining component competencies were identified as good. Not only online teaching modes but also online teaching activities and productions were also deployed to maintain learning activities especially during the COVID-19 pandemic at two universities. Recommendations for developing lecturers' online teaching competence were also considered

Application of the cut-off projection to solve a backward heat conduction problem in a two-slab composite system

The main goal of this paper is applying the cut-off projection for solving one-dimensional backward heat conduction problem in a two-slab system with a perfect contact. In a constructive manner, we commence by demonstrating the Fourier-based solution that contains the drastic growth due to the high-frequency nature of the Fourier series. Such instability leads to the need of studying the projection method where the cut-off approach is derived consistently. In the theoretical framework, the first two objectives are to construct the regularized problem and prove its stability for each noise level. Our second interest is estimating the error in -norm. Another supplementary objective is computing the eigen-elements. All in all, this paper can be considered as a preliminary attempt to solve the heating/cooling of a two-slab composite system backward in time. Several numerical tests are provided to corroborate the qualitative analysis.Peer reviewe

Lecane (Rotifera: Lecanidae) community in psammon habitat in Central Coast Vietnam: Diversity and relation to environmental condition

Characteristics of the Lecane (Rotifera) community in psammon in Central Coast Vietnam were investigated. A total of 50 taxa were identified in samples collected at hygropsammon zones of temporary pools, contributing 4 new species to rotifers' record of Vietnam. Psammonxenic species accounted for the largest percentage of Lecane community with 82%, followed by psammophiles (12%) and psammonbionts (6%). Influences of some environmental factors on the distribution of psammic lecanids were also observed. This group of organisms showed a slight tendency towards sand with grain sizes larger than 125 µm. Besides, other abiotic factors including pH, total phosphorus (TP) and total dissolved solids (TDS) were also found to significantly related to the distribution of some common Lecane species