Disinfection performance of an ultraviolet lamp: a CFD investigation

Ultraviolet (UV)-based devices have shown their effectiveness on various germicidal purposes. To serve their design optimisation, the disinfection effectiveness of a vertically cylindrical UV lamp, whose wattage ranges from P = 30 − 100 W, is numerically investigated in this work. The UV radiation is solved by the Finite Volume Method together with the Discrete Ordinates model. Various results for the UV intensity and its bactericidal effects against several popular virus types, i.e., Corona-SARS, Herpes (type 2), and HIV, are reported and analysed in detail. Results show that the UV irradiance is greatly dependent on the lamp power. Additionally, it is indicated that the higher the lamp wattage employed, the larger the bactericidal rate is observed, resulting in the greater effectiveness of the UV disinfection process. Nevertheless, the wattage of P ≤ 100W is determined to be insufficient for an effective disinfection performance in a whole room; higher values of power must hence be considered in case intensive sterilization is required. Furthermore, the germicidal effect gets reduced with the viruses less sensitive to UV rays, e.g, the bactericidal rate against the HIV virus is only ∼8.98% at the surrounding walls

GRADIENT KIẾN TẠO HIỆN ĐẠI KHU VỰC NINH THUẬN VÀ LÂN CẬN

The estimation of the present day tectonic movement and tectonic gradient (strain rate) has an important practical signification in the assessment of active fault and seismic hazards for the selection of Ninh Thuan nuclear power plant. Based on the three campaigns of GPS measurement between 2012 - 2013, we used BERNESE 5.0 software to determine present day slip rates of 13 stations in ITRF08 frame. The GPS stations move eastwards at the slip rates of 22 - 25 mm/yr, southwards at the velocities of 5 - 10 mm/yr. The standard errors in latitudinal and longitudinal directions are 1.2 mm/yr and 0.9 mm/yr, respectively. Combined with GPS data from the project of the study on actual geodynamics in Tay Nguyen TN3/06, we determined the strain rate ranging from 50 to 100 nanostrains with the standard error of 50 nanostrains. The direction of  maximum compressive strain rate is from northwest - southeast to east - west.Đánh giá vận tốc chuyển động kiến tạo hiện đại và gradient kiến tạo hiện đại có ý nghĩa thực tiễn quan trọng trong việc đánh giá đứt gãy hoạt động nguy hiểm động đất phục vụ xây dụng nhà máy điện hạt nhân Ninh Thuận. Trên cơ sở đo 3 chu kỳ GPS vào các năm 2012 - 2013, sử dụng phần mềm BERNESE 5.0, chúng tôi đã xác lập được vận tốc chuyển động kiến tạo hiện đại tại 13 điểm đo GPS trong khu vực lân cận bao gồm kéo dài từ Nha Trang tới đảo Phú Quý. Vận tốc chuyển dịch kiến tạo hiện đại về phía đông thay đổi từ 22 - 25 mm/năm và chuyển dịch về phía nam với vận tốc giao động từ 5 - 10 mm/năm trên hệ tọa độ toàn cầu ITRF08. Sai số vận tốc chuyển dịch kiến tạo về phía đông giao động trong khoảng 1,2 - 1,5 mm/năm và về phía nam giao động trong khoảng 0,9 - 1,2 mm/năm. Liên kết với giá trị đo GPS từ đề tài nghiên cứu địa động lực hiện đại khu vực Tây Nguyên mã số TN3/T06, chúng tôi đã xác định được giá trị vận tốc biến dạng giao động từ 50 nano tới 100 nano biến dạng với sai số giao động trong khoảng 50 nano biến dạng. Trục biến dạng nén cực đại giao động theo phương thay đổi từ bắc nam sang đông bắc - tây nam. Trục biến dạng căng cực đại có phương thay đổi từ tây bắc - đông nam sang phương đông - tây

Late Pleistocene-Holocene sequence stratigraphy of the subaqueous Red River delta and the adjacent shelf

The model of Late Pleistocene-Holocene sequence stratigraphy of the subaqueous Red River delta and the adjacent shelf is proposed by interpretation of high-resolution seismic documents and comparison with previous research results on Holocene sedimentary evolution on the delta plain. Four units (U1, U2, U3, and U4) and four sequence stratigraphic surfaces (SB1, TS, TRS and MFS) were determined. The formation of these units and surfaces is related to the global sea-level change in Late Pleistocene-Holocene. SB1, defined as the sequence boundary, was generated by subaerial processes during the Late Pleistocene regression and could be remolded partially or significantly by transgressive ravinement processes subsequently. The basal unit U1 (fluvial formations) within incised valleys is arranged into the lowstand systems tract (LST) formed in the early slow sea-level rise ~19-14.5 cal.kyr BP, the U2 unit is arranged into the early transgressive systems tract (E-TST) deposited mainly within incised-valleys under the tide-influenced river to estuarine conditions in the rapid sea-level rise ~14.5-9 cal.kyr BP, the U3 unit is arranged into the late transgressive systems tract (L-TST) deposited widely on the continental shelf in the fully marine condition during the late sea-level rise ~9-7 cal.kyr BP, and the U4 unit represents for the highstand systems tract (HST) with clinoform structure surrounding the modern delta coast, extending to the water depth of 25-30 m, developed by sediments from the Red River system in ~3-0 cal.kyr BP.ReferencesBadley M.E., 1985. Practical Seismic Interpretation. International Human Resources Development Corporation, Boston, 266p.Bergh  G.D. V.D., Van Weering T.C.E., Boels J.F., Duc D.M, Nhuan M.T, 2007. Acoustical facies analysis at the Ba Lat delta front (Red River delta, North Vietnam. Journal of Asian Earth Science, 29, 532-544.Boyd R., Dalrymple R., Zaitlin B.A., 1992. Classification of Elastic Coastal Depositional Environments. Sedimentary Geology, 80, 139-150.Catuneanu O., 2002. Sequence stratigraphy of clastic systems: concepts, merits, and pitfalls. Journal of African Earth Sciences, 35, 1-43.Catuneanu O., 2006. Principles of Sequence Stratigraphy. Elsevier, Amsterdam, 375p.Catuneanu O., Abreu V., Bhattacharya J.P., Blum M.D., Dalrymple R.W., Eriksson P.G., Fielding C.R., Fisher W.L., Galloway W.E., Gibling M.R., Giles K.A., Holbrook J.M., Jordan R., Kendall C.G. St. C., Macurda B., Martinsen O.J., Miall A.D., Neal J.E., Nummedal D., Pomar L., Posamentier H.W., Pratt B.R., Sarg J.F., Shanley K.W., Steel R. J., Strasser A., Tucker M.E., Winker C., 2009. Towards the standardization of sequence stratigraphy. Earth-Science Reviews, 92, 1-33.Catuneanu O., Galloway W.E., Kendall C.G. St C., Miall A.D., Posamentier H.W., Strasser A. and Tucker M.. E., 2011. Sequence Stratigraphy: Methodology and Nomenclature. Newsletters on Stratigraphy, 44(3), 173-245.Coleman J.M and Wright L.D., 1975. Modern river deltas: variability of processes and sand bodies. In: Broussard M.L (Ed), Deltas: Models for exploration. Houston Geological Society, Houston, 99-149.Doan Dinh Lam, 2003. History of Holocene sedimentary evolution of the Red River delta. PhD thesis in Vietnam, 129p (in Vietnamese).Duc D.M., Nhuan M.T, Ngoi C.V., Nghi T., Tien D.M., Weering J.C.E., Bergh G.D., 2007. Sediment distribution and transport at the nearshore zone of the Red River delta, Northern Vietnam. Journal of Asian Earth Sciences, 29, 558-565.Dung B.V., Stattegger K., Unverricht D., Phach P.V., Nguyen T.T., 2013. Late Pleistocene-Holocene seismic stratigraphy of the Southeast Vietnam Shelf. Global and Planetary Change, 110, 156-169.Embry A.F and Johannessen E.P., 1992. T-R sequence stratigraphy, facies analysis and reservoir distribution in the uppermost Triassic-Lower Jurassic succession, western Sverdrup Basin, Arctic Canada. In: Vorren T.O., Bergsager E., Dahl-Stamnes O.A., Holter E., Johansen B., Lie E., Lund T.B. (Eds.), Arctic Geology and Petroleum Potential. Special Publication. Norwegian Petroleum Society (NPF), 2, 121-146.Funabiki A., Haruyama S.,  Quy N.V., Hai P.V., Thai D.H., 2007. Holocene delta plain development in the Song Hong (Red River) delta, Vietnam. Journal of Asian Earth Sciences, 30, 518-529.General Department of Land Administration., 1996. Vietnam National Atlas. General Department of Land Administration, Hanoi, 163p.Hanebuth T.J.J. and Stattegger K., 2004. Depositional sequences on a late Pleistocene-Holocene tropical siliciclastic shelf (Sunda shelf, Southeast Asia). Journal of Asian Earth Sciences, 23, 113-126.Hanebuth T.J.J., Voris H.K.., Yokoyama Y., Saito Y., Okuno J., 2011. Formation and fate of sedimentary depocenteres on Southeast Asia’s Sunda Shelf over the past sea-level cycle and biogeographic implications. Eath-Science Reviews, 104, 92-110.Hanebuth T., Stattegger K and Grootes P. M., 2000. Rapid flooding of the Sunda Shelf: a late-glacial sea-level record. Science, 288, 1033-1035.Helland-Hansen W and Gjelberg, J.G., 1994. Conceptual basis and variability in sequence stratigraphy: a different perspective. Sedimentary Geology, 92, 31-52.Hori K., Tanabe S., Saito Y., Haruyama S., Nguyen V., Kitamura., 2004. Delta initiation and Holocene sea-level change: example from the Song Hong (Red River) delta, Vietnam. Sedimentary Geology, 164, 237-249.Hunt D. and Tucker M.E., 1992. Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level fall. Sedimentology Geology, 81, 1-9.Hunt D. and Tucker M.E., 1995. Stranded parasequences and the forced regressive wedge systems tract: deposition during base-level fall-reply. Sedimentary Geology, 95, 147-160.Lam D.D. and Boyd W.E., 2000. Holocene coastal stratigraphy and model for the sedimentary development of the Hai Phong area in the Red River delta, north Vietnam. Journal of Geology (Series B), 15-16, 18-28.Lieu N.T.H., 2006. Holocene evolution of the Central Red River Delta, Northern Vietnam. PhD thesis of lithological and mineralogical in Germany, 130p.Luu T.N.M., Garnier J., Billen G., Orange D., Némery J., Le T.P.Q., Tran H.T., Le L.A., 2010. Hydrological regime and water budget of the Red River Delta (Northern Vietnam). Journal of Asian Earth Sciences, 37, 219-228.Mather S.J., Davies J., Mc Donal A., Zalasiewicz J.A., and Marsh S., 1996. The Red River Delta of Vietnam. British Geological Survey Technical Report WC/96/02, 41p.Mathers S.J. and Zalasiewicz J.A.,1999. Holocene sedimentary architecture of the Red River delta, Vietnam. Journal of Coastal Research, 15, 314-325.Milliman J.D. and Mead R.H., 1983. Worldwide delivery of river sediment to the oceans. Journal of Geology, 91, 1-21.Milliman J.D and Syvitski J.P.M., 1992. Geomorphic/tectonic control of sediment discharge to the Ocean: the importance of small mountainous rivers. Journal of Geology, 100, 525-544.Mitchum Jr. R.M., Vail P.R., 1977. Seismic stratigraphy and global changes of sea-level. Part 7: stratigraphic interpretation of seismic reflection patterns in depositional sequences. In: Payton C.E. (Ed.), Seismic Stratigraphy-Applications to Hydrocarbon Exploration, A.A.P.G. Memoir, 26, 135-144.Nguyen T.T., 2017. Late Pleistocene-Holocene sedimentary evolution of the South East Vietnam Shelf, PhD thesis (in Vietnamese), Hanoi University of Science, Vietnam, 169p.Nummedal D., Riley G.W., Templet P.T., 1993. High-resolution sequence architecture: a chronostratigraphic model based on equilibrium profile studies. In: Posamentier H.W., Summerhayes C.P., Haq B.U., Allen G.P. (Eds.), Sequence stratigraphy and Facies Associations. International Association of Sedimentologists Special Publication, 18, 55-58.Posamentier H.W. and Allen G.P., 1999. Siliciclastic sequence stratigraphy: concepts and applications. SEPM Concepts in Sedimentology and Paleontology, 7, 210p.Posamentier H.W., Jervey M.T. and Vail P.R., 1988. Eustatic controls on clastic deposition I-Conceptual framework. Sea-level changes-An Integrated Approach, The Society of Economic Paleontologists and Mineralogist. SEPM Special Publication, 42, 109-124.Reineck H.E., Singh I.B., 1980. Depositional sedimentary environments with reference to terrigenous clastics. Springer-Verlag Berlin Heidelberg New York, 551p. Ross K., 2011. Fate of Red River Sediment in the Gulf of Tonkin, Vietnam. Master Thesis. North Carolina State University, 91p.Saito Y., Katayama H., Ikehara K., Kato Y., Matsumoto E., Oguri K., Oda M., Yumoto M. 1998. Transgressive and highstand systems tracts and post-glacial transgression, the East China Sea. Sedimentary Geology, 122, 217-232.Stattegger K., Tjallingii R., Saito Y., Michelli M., Nguyen T.T., Wetzel A., 2013. Mid to late Holocene sea-level reconstruction of Southeast Vietnam using beachrock and beach-ridge deposits. Global and Planetary Change, 110, 214-222.Tanabe S., Hori K., Saito Y., Haruyama S., Doanh L.Q., Sato Y., Hiraide S., 2003a. Sedimentary facies and radiocarbon dates of the Nam Dinh-1 core from the Song Hong (Red River) delta, Vietnam. Journal of Asian Earth Sciences, 21, 503-513.Tanabe S., Hori K., Saito Y., Haruyama S., Phai V.V., Kitamura A., 2003b. Song Hong (Red River) delta evolution related to millennium-scale Holocene sea-level changes. Quaternary Science Reviews, 22(21-22), 2345-2361.Tanabe S., Saito Y., Lan V.Q., Hanebuth T.J.J., Lan N.Q., Kitamura A., 2006. Holocene evolution of the Song  Hong  (Red  River) delta system,  northern Vietnam. Sedimentary Geology, 187, 29-61.Thanh T.D. and Huy D.V., 2000. Coastal development of the modern Red River Delta. Bulletin of the Geological Survey of Japan, 5, 276.Tjallingii R., Stattegger K., Wetzel A., Phung VP., 2010. Infilling and flooding of the Mekong River incised valley during deglacial sea-level rise. Quaternary Science Reviews, 29, 1432-1444.Vail P.R., 1987. Seismic stratigraphy interpretation procedure. In: Bally, A.W. (Ed), Atlats of Seismic Stratigraphy. American Association of Petroleum Geologist Studies in Geology, 27, 1-10.Van Wagoner J.C., Posamentier H.W., Mitchum R.M., Vail P.R., Sarg P.R., Louit J.F., Hardenbol J., 1988. An overview of the fundamental of sequence stratigraphy and key definitions. An Integrated Approach, SEPM Special Publication, 42, 39-45.Veeken P.C.H., 2006. Seismic stratigraphy Basin Analysis and Reservoir Characterization. Handbook of geophysical exploration, Elsevier, Oxford, 37509p.Yoo D.G., Kim S.P., Chang T.S., Kong G.S., Kang N.K., Kwon Y.K., Nam S.L., Park S.C., 2014. Late Quaternary inner shelf deposits in response to late Pleistocene-Holocene sea-level changes: Nakdong River, SE Korea. Quaternary International, 344, 156-169.  

Safety and efficacy of fluoxetine on functional outcome after acute stroke (AFFINITY): a randomised, double-blind, placebo-controlled trial

Background Trials of fluoxetine for recovery after stroke report conflicting results. The Assessment oF FluoxetINe In sTroke recoverY (AFFINITY) trial aimed to show if daily oral fluoxetine for 6 months after stroke improves functional outcome in an ethnically diverse population. Methods AFFINITY was a randomised, parallel-group, double-blind, placebo-controlled trial done in 43 hospital stroke units in Australia (n=29), New Zealand (four), and Vietnam (ten). Eligible patients were adults (aged ≥18 years) with a clinical diagnosis of acute stroke in the previous 2–15 days, brain imaging consistent with ischaemic or haemorrhagic stroke, and a persisting neurological deficit that produced a modified Rankin Scale (mRS) score of 1 or more. Patients were randomly assigned 1:1 via a web-based system using a minimisation algorithm to once daily, oral fluoxetine 20 mg capsules or matching placebo for 6 months. Patients, carers, investigators, and outcome assessors were masked to the treatment allocation. The primary outcome was functional status, measured by the mRS, at 6 months. The primary analysis was an ordinal logistic regression of the mRS at 6 months, adjusted for minimisation variables. Primary and safety analyses were done according to the patient's treatment allocation. The trial is registered with the Australian New Zealand Clinical Trials Registry, ACTRN12611000774921. Findings Between Jan 11, 2013, and June 30, 2019, 1280 patients were recruited in Australia (n=532), New Zealand (n=42), and Vietnam (n=706), of whom 642 were randomly assigned to fluoxetine and 638 were randomly assigned to placebo. Mean duration of trial treatment was 167 days (SD 48·1). At 6 months, mRS data were available in 624 (97%) patients in the fluoxetine group and 632 (99%) in the placebo group. The distribution of mRS categories was similar in the fluoxetine and placebo groups (adjusted common odds ratio 0·94, 95% CI 0·76–1·15; p=0·53). Compared with patients in the placebo group, patients in the fluoxetine group had more falls (20 [3%] vs seven [1%]; p=0·018), bone fractures (19 [3%] vs six [1%]; p=0·014), and epileptic seizures (ten [2%] vs two [<1%]; p=0·038) at 6 months. Interpretation Oral fluoxetine 20 mg daily for 6 months after acute stroke did not improve functional outcome and increased the risk of falls, bone fractures, and epileptic seizures. These results do not support the use of fluoxetine to improve functional outcome after stroke

Motion planning for multi-agent dynamical systems in a variable environment

Cette thèse propose des solutions de commande basées sur la planification optimale de trajectoires pour des systèmes dynamiques multi-agents fonctionnant dans un environnement variable (avec obstacles statiques ou mobiles et des perturbations variables dans le temps).Cette planification de trajectoires repose sur l'utilisation combinée de la théorie des ensembles (en particulier des ensembles convexes bornés), de la commande prédictive non-linéaire (NMPC), du calcul de champs de potentiel et des méthodes basées sur des graphes. Elle se base sur la construction de champs de potentiel répulsifs associés à des fonctions de barrière marche-arrêt (on-off barrier functions) qui décrivent et activent ou désactivent les trajectoires libres (sans collision) calculées au préalable par une commande de type NMPC distribuée. Ces constructions sont ensuite utilisées pour maintenir la connectivité dans le groupe d'agents, tout en assurant le suivi du chemin pré-généré. En outre, un observateur pour l'estimation de perturbations non linéaires est intégré dans le schéma de commande afin de les rejeter.Les résultats théoriques obtenus sont validés en simulation, par des comparaisons avec des approches utilisant la programmation mixte en nombres entiers, à l'aide de données numériques réelles provenant d'une plateforme de navigation sécurisée pour les véhicules de surface non habités dans le fjord de Trondheim (Norvège).This thesis proposes optimization-based control solutions for the motion planning of multi-agent dynamical systems operating in a variable environment (with static/mobile obstacles and time-varying environmental disturbances).Collision-free paths are planned for the agents through the combined use of set theory (particularly, bounded convex sets), non(-linear) Model Predictive Control (MPC), Potential Field (PF) and graph-based methods. The contributions build on the proposal of repulsive potential field constructions together with on-off barrier functions which describe and, respectively, activate/deactivate the collision-free conditions introduced in a distributed NMPC framework. These constructions are further used for connectivity maintenance conditions among the group of agents while ensuring the tracking of the a priori generated path. Furthermore, a nonlinear disturbance observer is integrated within the control scheme for environmental disturbance rejection.Finally, the results are validated in simulation through comparisons with mixed-integer approaches and over a benchmark for the safe navigation of Unmanned Surface Vehicles (USVs) in the Trondheim fjord, Norway, using real numerical data

Planification de mouvement pour les systèmes dynamiques multi-agents dans un environnement variable

This thesis proposes optimization-based control solutions for the motion planning of multi-agent dynamical systems operating in a variable environment (with static/mobile obstacles and time-varying environmental disturbances).Collision-free paths are planned for the agents through the combined use of set theory (particularly, bounded convex sets), non(-linear) Model Predictive Control (MPC), Potential Field (PF) and graph-based methods. The contributions build on the proposal of repulsive potential field constructions together with on-off barrier functions which describe and, respectively, activate/deactivate the collision-free conditions introduced in a distributed NMPC framework. These constructions are further used for connectivity maintenance conditions among the group of agents while ensuring the tracking of the a priori generated path. Furthermore, a nonlinear disturbance observer is integrated within the control scheme for environmental disturbance rejection.Finally, the results are validated in simulation through comparisons with mixed-integer approaches and over a benchmark for the safe navigation of Unmanned Surface Vehicles (USVs) in the Trondheim fjord, Norway, using real numerical data.Cette thèse propose des solutions de commande basées sur la planification optimale de trajectoires pour des systèmes dynamiques multi-agents fonctionnant dans un environnement variable (avec obstacles statiques ou mobiles et des perturbations variables dans le temps).Cette planification de trajectoires repose sur l'utilisation combinée de la théorie des ensembles (en particulier des ensembles convexes bornés), de la commande prédictive non-linéaire (NMPC), du calcul de champs de potentiel et des méthodes basées sur des graphes. Elle se base sur la construction de champs de potentiel répulsifs associés à des fonctions de barrière marche-arrêt (on-off barrier functions) qui décrivent et activent ou désactivent les trajectoires libres (sans collision) calculées au préalable par une commande de type NMPC distribuée. Ces constructions sont ensuite utilisées pour maintenir la connectivité dans le groupe d'agents, tout en assurant le suivi du chemin pré-généré. En outre, un observateur pour l'estimation de perturbations non linéaires est intégré dans le schéma de commande afin de les rejeter.Les résultats théoriques obtenus sont validés en simulation, par des comparaisons avec des approches utilisant la programmation mixte en nombres entiers, à l'aide de données numériques réelles provenant d'une plateforme de navigation sécurisée pour les véhicules de surface non habités dans le fjord de Trondheim (Norvège)

Improving User Interface and User Experience of MathSpring Intelligent Tutoring System for Students

MathSpring is an intelligent tutoring system that assists students in studying mathematics. - Given the complex interactions between students and MathSpring system together with suggestions from students, we believe that its user interface and user experience have room for improvements. To learn the students’ experience and determine our improvement strategy, we quantitatively analyze the students’ suggestions and interview a teacher who uses the system for his class. We then use the results of our analysis and design principles to devise a new design for MathSpring. Lastly, we conduct a user study to evaluate the new design. The results of this study demonstrate that our new design has succeeded at improving the user experience to some extent

Distributed nonlinear optimization-based control for multi-agent systems navigation in a coastal environment

International audienc

Nonlinear optimization for multi-agent motion planning in a multi-obstacle environment

International audienc

Safe navigation in a coastal environment of multiple surface vehicles under uncertainties: A combined use of potential field constructions and NMPC

International audienceThis paper deals with the motion planning problem for surface vehicles in the presence of varying environmental disturbances. The goal is to steer the vehicles from an initial to a final destination while ensuring connectivity and avoiding collision with fixed and moving obstacles. The novelty lies in the coherent combination among various ingredients for path generation and potential field constructions for collision avoidance and connectivity maintenance, all gathered in a distributed NMPC (Nonlinear Model Predictive Control) framework: i) LOS (Line-of-Sight) guidance and RRT* (optimal Rapidly-exploring Random Tree) algorithms are employed for generating a collision-free path considering static surroundings; ii) on-off barrier functions activate the proposed potential field components which are in the view range of the agents, hence ensuring safe navigation in a dynamic coastal environment with a low computation demand; iii) a NDO (Nonlinear Disturbance Observer) is integrated in the NMPC design to compensate the environmental disturbances. The proposed algorithm is validated through simulations and comparisons carried out over a benchmark for USVs (Unmanned Surface Vehicles) safe navigation in the Trondheim fjord, Norway