Authors: Tran, Nghi; Co-Author: 2007 (Vietnam has over 3200 km shoreline which extends from north to south of the country. Sea level changes were principal factors influenced on sedimentary environment and compositions. In Quaternary, cycles of sea level change and tectonic movement were main factor that created Red River delta, Nam Bo plain and Central plain. There are 5 sedimentary cycles corresponding to 5 cycles of sea level change of the Red River delta and Nam Bo plain. Sedimentary cycles were characterized by sedimentary coefficients such as: grain size, clay content, index of cation Fe2+/Fe3+ exchange, pH variation from the start to the end of cycles. They are represented by fluvial terraces, marine terraces, marine notches and peat layers. In central littoral plain, the relationship between sedimentary cycles and sea level is represented by five sandy cycles and distribution of coral terraces in shallow sea. There are 5 generations of ancient shoreline zones, which correlated with glacial and interglacial periods in Vietnamese continental shelf: the shoreline in 30 m water depth is correlated with (Q21-2). Up to 60 m water depth is correlated with (Q13b-Q21) and 100-120 m water depth is correlated with Wurm2 glaciation (Q13b)(?). In 200-300 m water depth correlated with Wurm1 glaciation (Q13a)(?), at 400-500 m water depth correlated with Riss glaciation (Q12b)(?), at 600-700 m water depth correlated with Mindel glaciation (Q12a)(?), and at 1000-1500 m water depth correlated with Gunz glaciation (Q11)(?). As such Quaternary sea level changes in mainland and continental shelf interacted and quite distinctive form each other by pendulum rule.)
Authors: Nguyen Ngoc, Thach; Co-Author: 2007 (Nowadays, there are many methods to study shoreline change in coastal engineering. Among them, mathematical methods are considered as effective ones that have been used for a long time. LITPACK is a numerical model in MIKE software package, developed by Danish Hydraulic Institute (DHI), for simulating non-cohesive sediment transport in wave and currents, littoral drift, coastline evolution and profile development along quasi-uniform beaches. In this paper, the authors apply the model for studying shoreline change in Cat Hai Island, Hai Phong City. Cat Hai is a famous island with dense population working with various coastal - tradition works locating at the centre of Hai Phong, where coastal line is changing with high speed and complicated cycles. Based on the analysis of hydrodynamic-lithologic conditions in this area, a coast protected structure system has been proposed, consisting of revetments, groynes, submerged breakwaters and emerged breakwaters. Results derived from LITPACK model show that they are reliable enough and suitable for use as remedial protecting measures.)
Authors: Tran Quoc, Binh; Co-Author: 2007 (Nowadays, digital terrain models (DTM) are an important source of spatial data for various applications in many scientific disciplines. Therefore, special attention is given to their main characteristic - accuracy. At it is well known, the source data for DTM creation contributes a large amount of errors, including gross errors, to the final product. At present, the most effective method for detecting gross errors in DTM source data is to make a statistical analysis of surface height variation in the area around an interested location. In this paper, the method has been tested in two DTM projects with various parameters such as interpolation technique, size of neighboring area, thresholds,... Based on the test results, the authors have made conclusions about the reliability and effectiveness of the method for detecting gross errors in DTM source data.)
Authors: Tong Dzuy, Thanh; Co-Author: 2007 (A lot of unconformities and stratigraphic gaps have been discovered in the Paleozoic and Mesozoic stratigraphy of Bac Bo region (North Viet Nam), but their role in the regional geology was not accessed yet in detail. This paper is the first attempt to describe the most significant unconformities and stratigraphic gaps and discussing their role in regional geology. The most important is the angular unconformity of Norian-Rhaetian formations upon various formations of different formations; it marked the change tectonic regime of the region resulting from the indosian orogeny in Viet Nam and in Southeast Asia in common. The gap of Lower Devonian red beds formations (Si Ka Formation, Song Cau Group) upon Lower Paleozoic formations (Upper Cambrian - Than Sa Formation, Lower Ordovician - Lutxia and Na Mo formations) is a regional unconformity, which had been taken place in the epicaledonian terranne of South China and North East of Viet Nam. The gap between the Da Mai Formation and the Dong Dang Formation was a result of a crust rising, but was not through the orogeny activity, although after this gap the structural plan was more differentiated. Other unconformities and stratigraphic gaps seems to be local unconformities, for instance, the one of the Tan Lap Formation (D2g-D3 fr tl) upon the Ban Pap Formation (D1p-D3 fr bp) and the unconformity between the Sinh Vinh (O3-S sv) and the Ben Khe (ε-O1 bk) formations.)
Authors: Cung Thuong, Chi; Co-Author: 2007 (Available paleomagnetic data of Cretaceous redbed formations from Indochina and South China blocks are compiled and their tectonic significance is reviewed in a common reference frame of the Eurasian coeval paleopoles. The important factors that play a vital role in determining the tectonic significance of a paleomagnetic result have been taken into consideration and discussed. Review of the Cretaceous paleomagnetic data from the South China block further confirms the conclusion of the previous researchers that the present geographic position of the South China block has been relatively stable with respect to Eurasia since Cretaceous time and shows that the paleomagnetically detected motion of a coherent lithospheric block must be based on the representative data obtained from different places across the block; so the local tectonic movements can be distinguished. Cretaceous paleomagnetic data from the Indochina - Shan Thai block reveal complex intra-plate deformations that have been occurred due to the India - Eurasia collision. Paleomagnetically detected motions from the block-margin areas are mainly reflecting the displacement of upper crustal blocks due to folding and faulting processes, thus a rigid lithospheric block rotation and translation cannot be assumed. The paleomagnetic results from the areas located next to the south of the Red River fault suggest that the fault does not demarcate non-rotated and significantly rotated regions. Accordingly, given the difficulty in separating true lithospheric plate motions from those of superficial crustal blocks, we advocate extreme caution in interpreting the paleomagnetic record in regions such as Indochina where block interaction and strong deformation are known to have occurred.)
Authors: Dao Dinh, Bac; Co-Author: 2007 (This paper discusses debris and mud flash flood, which is a widespread phenomenon with different levels of damaging effects and repetition in the mountainous areas of Vietnam. There are some sites where the flash flood with severe debris components has recurred many times and it has always caused heavy loss of human and materials, such as Lay Nua Commune, the Former Muong Lay District, Dien Bien Province. During the 1990s, this kind of severe hazard is recorded to occur every two years in the town of Former Muong Lay District. This leads to the government’s decision to relocate the town to another place. Some characteristics of physiographical conditions such as climate, relief, lithologic and tectonic features, which are considered relevant to debris and mudflows activities, are analyzed, and then come to the conclusions on determinant agents of debris and mud flash flood in this area.)
Authors: Nguyễn Hữu, Dư; Co-Author: 2007 (Nghiên cứu dáng điệu nghiệm trong quá trình phát triển lâu dài của quần thể thú mồi chịu nhiễu ngẫu nhiên; Sự phát triển bền vững của các quần thể được mô tả bởi phương trình động học trên time-scale; Dáng điệu động học của quần thể thú - mồi với mô hình Modified Leslie - Gower và Holling - Type II Schemes. Kết quả nghiên cứu đạt được: Đối với quần thể thú mồi phát triển trong môi trường ngẫu nhiên, khi thời gian dần ra vô cùng, sự biến động của số lượng các loài rất lớn; Chỉ ra các điều kiện để hệ ổn định theo xấp xỉ ban đầu, sau đó chuyển định lý nổi tiếng Perron trong phương trình vi phân sang cho time-scale với giả thiết số lượng các cá thể của các loài của một quần thể được mô tả bởi phương trình động học trên time-scale; Chỉ ra điều kiện để hệ phát triển bền vững, ổn định hoặc phát triển tuần hoàn nếu quần thể thú mồi được mô hình hoá bởi mô hình Modified Leslie - Gower và Holling - Type II Schemes)
Authors: Lê Văn, Bính; Co-Author: 2007 (Khái quát lý luận về các mảng công việc của các bộ phận thuộc Phòng hành chính tổng hợp Khoa Luật, trực thuộc Đại học Quốc gia Hà Nội, các lĩnh vực quản lý trong công tác hành chính tổng hợp trong một đơn vị đào tạo luật chất lượng cao như: công tác tổ chức cán bộ, công tác hành chính - quản trị và cơ sở vật chất; công tác kế toán – tài vụ, công tác văn thư, công tác thư viện, công tác đối ngoại, công tác thanh tra, thi đua – khen thưởng. Phân tích thực trạng các mảng công việc mà Phòng Phòng hành chính tổng hợp phụ trách, qua đó đánh giá những mặt mạnh, những điểm yếu hoặc còn bất cập chưa thực sự hợp lý cũng như những nguyên nhân. Kiến nghị các giải pháp tương ứng với từng vấn đề đã được đánh giá thực trạng nhằm phục vụ tốt hơn cho công tác đào tạo và nghiên cứu khoa học tại một đơn vị đào tạo chất lượng cao như Khoa Luật, ĐHQGHN)
