Journal of Science and Technique
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DYNAMIC RESPONSE OF A SYSTEM OF 3 RIGID CONCRETE SLABS ON FOUNDATION TO A MOVING LOAD ON THE CONCRETE PAVEMENT USING FINITE ELEMENT ANALYSIS
Get PDFThe dynamic response of a concrete pavement system with load transfer dowels under the effects of moving loads is a topic of interest to many scholars. However, to fully understand the nature of the stress-strain state of the concrete slab, load transfer dowels, and the subgrade in the pavement structure, further research is needed. Using numerical methods with the commercial software ABAQUS 2020, this paper thoroughly investigates the dynamic behavior of rigid pavement structures under moving loads at a constant speed. The research results will provide road and airport engineers with valuable insights into the actual working conditions of rigid pavement structures
TRAJECTORY PLANNING FOR SEARCH-AND-RESCUE UAVs USING A GREEDY ALGORITHM
Get PDFThis article presents a trajectory-planning program for research-and-rescue UAVs based on the use of a local optimization greedy algorithm. Trajectories are generated over a search domain characterized by a probabilistic score map. For multiple-UAV systems, the program can assign each device to a search mission based on the probabilistic property or the geometry of the search domain. Some parameters such as the maximum travelled distance and trajectory resolusion could be input into the program. In this study, the program was tested to run for a two-UAV system over a given probabilistic score map. The input trajectory paremerters were selected based on the properties of each UAV and the requirement of a search-and-rescue mission. The program may be seamlessly integrated with UAV flight control software, enabling a direct translation of the obtained trajectories into autonomous mission execution.
INVESTIGATING LARGE-SCALE STRUCTURES IN TURBULENT MIXING LAYERS USING TWO-POINT CORRELATION
Get PDFThe formation and development of large-scale structures are primary research subjects in the study of turbulent mixing layers. Visualizing these structures based on published experimental data enhances the understanding of complex flow behaviors, which is the main objective of this article. The authors employed a two-point statistical correlation method to evaluate the size of large vortex structures along the interaction region. Additionally, the article provides a guide for analyzing the turbulent energy spectrum at selected fixed points. The calculations were performed using MATLAB software. The results indicate that at the beginning of the mixing layer, the vortices are small and highly anisotropic, with large-scale structures stretching in irregular directions. Further downstream, the vortices increase in size in all directions, and the degree of anisotropy decreases. In the self-similar region, isotropic states are almost achieved. The energy spectrum analysis findings align with Kolmogorov's theory of energy cascade in turbulent flow. The two-point statistical correlation method proves to be highly effective for analyzing structures within turbulent flows
VIBRATION CHARACTERISTIC CHANGES IN DAMAGED STRUCTURE WITH REDUCTION OF CROSS-SECTION
Get PDFThis article presents the study of the change in natural vibration frequency, which is determined with measured acceleration data of the structure when there is a weak reduction in a cross-section. Conducting a simulation with the initial structure and damaged structure has been evaluated the change of natural frequency and mode shape. The results can be used as the basic identification of the location and damage level of the structure. Because of reducing cross-section in different structural positions, the specific vibration form will appear suddenly at different positions. Hence, the level and location of damage can be determined based on the changing of the specific vibration pattern
EFFECTS OF IRON (III) OXIDE NANOPARTICLE ON THE BURNING CHARACTERISTICS OF THE PYROTECHNIC COMPOSITION FOR INFRARED EMISSION BASED ON MAGNESIUM-TEFLON-VITON
Get PDFNano additives are materials that have been widely used to increase the effectiveness of pyrotechnic compositions. This study examines the effects of iron (III) oxide (Fe2O3) nanoparticles on the burning characteristics (i.e., the heat of combustion, the burning rate, and the infrared radiance) of the pyrotechnic composition based on Magnesium-Teflon-Viton (MTV). The dispersion of nano additive in the pyrotechnic composition is evaluated using SEM and EDX. The experimental results demonstrate that the heat of combustion and the burning rate are increased while the spectral radiance is shifted to the shorter wavelength area with the complement of the additive Fe2O3 nanoparticle to the MTV composition
DESIGN AND EVALUATION OF A SEAWATER REVERSE OSMOSIS DESALINATION PLANT USING COMPUTER SOFTWARE
Get PDFSeawater and brackish desalination using reverse osmosis (RO) has been a pragmatic approach to mitigating fresh water shortage in many water-stressed areas worldwide. Compared with other desalination technologies, RO has several attributes including high energy efficiency and system modularization. To achieve these notable attributes, for large-scale seawater RO plants, it is critical to accurately design and evaluate the RO process before plant installation and operation. In this study, the IMSDesign software is applied to design a seawater RO plant with a capacity of 100 m3 of fresh water per hour. The software allows to customize the design parameters and operating conditions of the RO plant to meet the design requirements. After inputting design parameters and operating conditions, the RO plant operation can be simulated to obtain its performance indexes for plant design evaluation. The evaluation results reveal that the RO plant with membrane trains arranged in 2-passes configuration can obtain high quality permeate that meets the required standards for drinking water at energy consumption and water cost of 10.66 kWh/m3 and 2.48 USD/m3, respectively
INVESTIGATION OF EFFICACY OF A DCBRN-01VN SKIN DECONTAMINANT AGAINST ORGANOPHOSPHATE AGENT
Get PDFThis research has been initiated to examine the effectiveness of DCBRN-01VN lotion in degrading some readily available organic phosphorous (OP). UPLC-MS/MS technique was used to measures the amount of residual pesticide via selected ion monitoring. The results showed that lotion effectively degrades OP expediently. The removal efficiency is nearly 100% with MP at 6th min and MT at 2nd min when the molar ratio of KBDO and OP is 10:1. The results in vivo test with both solutions (MP and MT) on pig skin showed that the toxic removal efficiency was over 90%, for MP was over 98%
NGHIÊN CỨU DAO ĐỘNG CỦA DẦM CẦU TRỤC KHI CÁC THAM SỐ MÔ HÌNH LÀ ĐẠI LƯỢNG NGẪU NHIÊN
Get PDFTheo phương pháp thiết kế ngẫu nhiên, hàm trạng thái của các điều kiện thiết kế thường được xây dựng với sự xuất hiện của các biến ngẫu nhiên đầu vào tuân theo các hàm phân bố giả định và các đáp ứng ngẫu nhiên thu được từ việc giải mô hình tính toán. Bài báo tập trung nghiên cứu các đặc trưng động lực học của cầu trục khi các tham số mô hình là đại lượng ngẫu nhiên. Đầu tiên, mô hình vật lý và hệ phương trình vi phân chuyển động của cơ hệ được thiết lập sử dụng phương trình Lagrange. Tiếp đến, phương pháp số Newmark- được áp dụng để tìm các ứng xử dao động của hệ thống. Cuối cùng, các đáp ứng dao động của dầm chính cầu trục sẽ được khảo sát khi xem xét các tham số mô hình tuân theo phân bố chuẩn. Kết quả nhận được cho thấy các đặc trưng phân bố của các tham số đáp ứng dao động của dầm cầu phụ thuộc vào độ lệch chuẩn của tham số đầu vào và vị trí của xe tời trong quá trình khảo sát. Cụ thể, với giá trị độ lệch chuẩn 0,15 thì có thể gây ra mức bất định ~75 % của chuyển vị ở mặt cắt giữa dầm
EFFECT OF SEA SAND WITH DIFFERENT CHLORIDE ION CONTENTS ON THE PROPERTIES OF CONCRETE
Get PDFThis article presents the results of a study that evaluated the effects of using sea sand with varying contents of chloride ions on the properties of concrete, including physical and mechanical properties as well as durability. The study was carried out on the sea sand samples with different chloride ion contents, including as-received sea sand samples with a chloride ion content of approximately 0.15%, two washed (desalted) sea sand samples with chloride ion content of 0.024% and 0.05%, and sea sand samples added with chloride salt (0.375%), which were then compared with river sand samples. The sand samples had approximately the same fineness modulus ranging from 2.3-2.5. The research results indicated that compared with washed sea sand and river sand, concrete mixes using sea sand with high chloride ion content increased the mixing water and reduced the slump retainability of the fresh concrete. Furthermore, early compressive strength (7 days) increased but late age strength (91 and 365 days) decreased in both standard curing and wet-dry circle curing cases. Additionally, the impermeability (water and chloride ion) and the ability to protect the reinforcement from corrosion in concrete were reduced when using sea sand with high chloride ion content compared to washed sea sand and river sand
THERMAL BEHAVIOR OF MASS CONCRETE STRUCTURES WITH DIFFERENT MATERIAL PROPERTIES
Get PDFIn mass concrete constructions, cement hydration produces much heat at an early age. Because of the different distribution of temperature in their parts, which leads to a significant temperature difference between the concrete block’s center and outer surface. When the temperature difference among structural parts surpasses the permissible temperature difference, thermal cracks can occur. Hence, this article presents the development of the temperature field in mass concrete structures with two different concrete mixes M1 and M2. M1 consists of 100% ordinary Portland cement, and M2 consists of 65% ordinary Portland cement and 35% fly ash. Furthermore, by using the finite element method, the effect of the initial temperature of concrete mixtures (M1, M2) on the temperature field in the structure has been investigated. The researched results can be used to reduce the risk of thermal crack formation in mass concrete