The Lom Pangar dam, the largest reservoir in Cameroon with a storage capacity of 6 km3 and a 30 MW hydropower plant, primarily regulates the hydrologic regime of the Sanaga River to maintain hydropower efficiency duri...The Lom Pangar dam, the largest reservoir in Cameroon with a storage capacity of 6 km3 and a 30 MW hydropower plant, primarily regulates the hydrologic regime of the Sanaga River to maintain hydropower efficiency during dry seasons and enhance downstream hydropower plant performance. Understanding and managing sediments are crucial for the sustainability of dams, as indicated by numerous studies. This study assessed the granulometry of the sediments transported across the reservoir. For that purpose, 6 samples of fresh sediments were collected in the lacustrine and transitional sections of the reservoir using the standard method. Particles size was assessed using the laser diffusion technic after a 3 mm sieving. Various granulometric parameters were derived from the literature to analyze and characterize those sediments. Results show that silts are more than 70% of particles size and range between 2.19 - 60.26 µm. Size distribution also shows the same trend with D75 less than 51 µm. This is confirmed by the low values of Inman Skewness SkΦ (−0.168 to 0.303). The Sorting index S0 ranges from 0.31 to 0.53 µm, showing a very well-sorted sediments, aligning with low values of Krumbein index (0.906 - 1.683) that express the low heterometry of the particles. The consequence on the dam will be a quick clogging of the bottom of the reservoir. Their pH varies from 7.0 to 7.5. It also appears that the sandy fraction trend is higher in the right bank of the dam and reaches 22% on the right bank of Pangar River due to crystalline geology. Fraction greater than 3000 µm is negligible. The management of the dam has to keep attention to these results as siltation may close the safety outlet of the dam, damage turbines, and provoke recurrent technical and safety issues. Further, the clogging of the bottom of the reservoir may lead to an ecological problem with the limitation of hyporheic flow. Thus, water exchange with the underground water table and the natural purification of water reduce, while increasing sediments deposits change the biogeochemistry processes.展开更多
Aim: To describe the two-dimensional elastographic profile according to the Shearwave (2D-SWE) technique in patients with chronic liver disease in Lom. Materials and method: Cross-sectional, descriptive study conducte...Aim: To describe the two-dimensional elastographic profile according to the Shearwave (2D-SWE) technique in patients with chronic liver disease in Lom. Materials and method: Cross-sectional, descriptive study conducted over seven month at the Autel dElie Clinic in Lom, from January to August 2022, on adult patients with chronic liver disease who underwent abdominal ultrasound coupled with two-dimensional elastography. Results: The sample size was 54 patients. The mean age of the patients was 33 12 years, with extremes of 18 and 66 years. Patients aged 30 years or less accounted for 48.1% (n = 26). All patients (n = 54) had at least one transaminase assay with a mean of 69.3 78.3 IU/l (AST) and 59.3 82.8 IU/l (ALT). There was no statistically significant association between the biological parameters and the presence of fibrosis. Viral liver disease was the main cause, accounting for 81.5% (n = 44) of cases, with no significant association with the degree of fibrosis. Ultrasound revealed a dysmorphic liver (57.4%;n = 31) and portal hypertension (18.5%, n = 10). Fibrosis stages F1, F2 and F4 accounted for (48.1%, n = 26), (24.1%, n = 13) and (13%, n = 7) of cases respectively. Liver dysmorphia was significantly associated with the presence of fibrosis (p = 0.012) and portal hypertension was significantly associated with the degree of fibrosis (p = 0.0063). Conclusion: Assessment of liver fibrosis in patients with chronic liver disease using 2D-SWE elastography is essential for patient follow-up.展开更多
Meshes in the sheet of Laminated Object Manufacturing (LOM) are now designedwith the same size, and the length of mesh lines may be as several times as the outline length.The method of variablesize meshes is advanced ...Meshes in the sheet of Laminated Object Manufacturing (LOM) are now designedwith the same size, and the length of mesh lines may be as several times as the outline length.The method of variablesize meshes is advanced in this paper. Meshes in a sheet are designed ac-cording to the difficulty of removing the waste in or out of the outlines. The CAD model may bedivided into several segments in Z direction with different mesh sizes. The length of mesh lineswould be largely decreased and the manufacturing efficiency would be improved.展开更多
文摘The Lom Pangar dam, the largest reservoir in Cameroon with a storage capacity of 6 km3 and a 30 MW hydropower plant, primarily regulates the hydrologic regime of the Sanaga River to maintain hydropower efficiency during dry seasons and enhance downstream hydropower plant performance. Understanding and managing sediments are crucial for the sustainability of dams, as indicated by numerous studies. This study assessed the granulometry of the sediments transported across the reservoir. For that purpose, 6 samples of fresh sediments were collected in the lacustrine and transitional sections of the reservoir using the standard method. Particles size was assessed using the laser diffusion technic after a 3 mm sieving. Various granulometric parameters were derived from the literature to analyze and characterize those sediments. Results show that silts are more than 70% of particles size and range between 2.19 - 60.26 µm. Size distribution also shows the same trend with D75 less than 51 µm. This is confirmed by the low values of Inman Skewness SkΦ (−0.168 to 0.303). The Sorting index S0 ranges from 0.31 to 0.53 µm, showing a very well-sorted sediments, aligning with low values of Krumbein index (0.906 - 1.683) that express the low heterometry of the particles. The consequence on the dam will be a quick clogging of the bottom of the reservoir. Their pH varies from 7.0 to 7.5. It also appears that the sandy fraction trend is higher in the right bank of the dam and reaches 22% on the right bank of Pangar River due to crystalline geology. Fraction greater than 3000 µm is negligible. The management of the dam has to keep attention to these results as siltation may close the safety outlet of the dam, damage turbines, and provoke recurrent technical and safety issues. Further, the clogging of the bottom of the reservoir may lead to an ecological problem with the limitation of hyporheic flow. Thus, water exchange with the underground water table and the natural purification of water reduce, while increasing sediments deposits change the biogeochemistry processes.
文摘Aim: To describe the two-dimensional elastographic profile according to the Shearwave (2D-SWE) technique in patients with chronic liver disease in Lom. Materials and method: Cross-sectional, descriptive study conducted over seven month at the Autel dElie Clinic in Lom, from January to August 2022, on adult patients with chronic liver disease who underwent abdominal ultrasound coupled with two-dimensional elastography. Results: The sample size was 54 patients. The mean age of the patients was 33 12 years, with extremes of 18 and 66 years. Patients aged 30 years or less accounted for 48.1% (n = 26). All patients (n = 54) had at least one transaminase assay with a mean of 69.3 78.3 IU/l (AST) and 59.3 82.8 IU/l (ALT). There was no statistically significant association between the biological parameters and the presence of fibrosis. Viral liver disease was the main cause, accounting for 81.5% (n = 44) of cases, with no significant association with the degree of fibrosis. Ultrasound revealed a dysmorphic liver (57.4%;n = 31) and portal hypertension (18.5%, n = 10). Fibrosis stages F1, F2 and F4 accounted for (48.1%, n = 26), (24.1%, n = 13) and (13%, n = 7) of cases respectively. Liver dysmorphia was significantly associated with the presence of fibrosis (p = 0.012) and portal hypertension was significantly associated with the degree of fibrosis (p = 0.0063). Conclusion: Assessment of liver fibrosis in patients with chronic liver disease using 2D-SWE elastography is essential for patient follow-up.
文摘Meshes in the sheet of Laminated Object Manufacturing (LOM) are now designedwith the same size, and the length of mesh lines may be as several times as the outline length.The method of variablesize meshes is advanced in this paper. Meshes in a sheet are designed ac-cording to the difficulty of removing the waste in or out of the outlines. The CAD model may bedivided into several segments in Z direction with different mesh sizes. The length of mesh lineswould be largely decreased and the manufacturing efficiency would be improved.
