132 research outputs found
A Study of Reduced Order 4D-VAR with a Finite Element Shallow Water Model
No full textForecast models often depend on unknown parameters, such as model initial and boundary conditions, or other tunable parameters not necessarily having any physical meaning. Calibration of these parameters to minimize errors between forecasted and observed states is called data assimilation. A common approach in this context are variational methods, of which four dimensional data variation (4D-VAR) is studied in this thesis. In 4D-VAR, a cost function is defined that penalizes misfits between observations and the corresponding numerical model results, obtained by running the model with the chosen configuration. Performing optimization with regard to this cost function yields an improved initial parameter set. Associated with this type of methods, however, are difficulties in connection with programming the adjoint model, which is needed to compute the exact gradient of the cost function. Additionally, having to integrate the adjoint model backwards in time adds significantly to the computational cost of the data assimilation process. To avoid manual implementation of adjoint code and to reduce computational complexity, approximation of the gradient calculation is considered through the use of proper orthogonal decomposition (POD), a flexible data-driven order reduction method. To facilitate this, a finite element model of the shallow water equations is tested with both the full adjoint 4D-VAR method and two different POD-reduced approaches. Twin experiments are performed and comparisons are made in terms of accuracy, computational complexity and sensitivity to perturbation and number of observation points.Applied mathematicsElectrical Engineering, Mathematics and Computer Scienc
Model reduced variational data assimilation for shallow water flow models
No full textIdentifying uncertain parameters in large-scale numerical flow models can be done using the variational method. However, for implementing the variational method the adjoint model have to be available, which requires highly complex computer code and maintenance and thus hampers its applications. To ease this problem, this thesis has explored several methods for efficiently identifying uncertain parameters in a large-scale tidal model of the entire European continental shelf which does not require the implementation of these complex adjoint code. In this study, as a first step an estimation method based on model reduction is developed and investigated for the estimation of diffusion coefficient in a simple 2D-advection diffusion model. Two projection based model reduction methods were considered, namely proper orthogonal decomposition (POD) and Balanced proper orthogonal decomposition (BPOD). In the POD based estimation method an ensemble of forward model simulations is used to determine an approximation of the covariance matrix of the model variability and a small number of the leading eigenvectors of this matrix is used to define a model subspace. By projecting the original model onto this subspace an approximate linear reduced model is obtained. Once the reduced model is available its adjoint can be implemented easily and the minimization problem is solved completely in reduced space with very low computational cost. BPOD is also a model reduction method which considers both inputs and outputs of the system while determining the reduce subspace. The estimation method has been extended by including BPOD procedure into the estimation procedure. Numerical results from a simple pollution model demonstrate that the POD based estimation approach successfully estimate the diffusion coefficient for both advection dominated problems as for diffusion dominated problems. Another important message in this study, although lots of effort had been made in constructing a reduced order model by the BPOD method, the minimization results demonstrated that both the POD and the BPOD methods performed similarly. Preliminary results showed the validity of the POD based model reduction methods for parameter estimation. As a next step, the POD based estimation method is used to calibrate numerical tidal models. Results from (twin) numerical experiments showed that the POD based calibration method performed very efficiently to estimate depth values in the selected regions of the model domain. The computational costs of the POD based calibration method are dominated by the generation of an ensemble of forward model simulations where the simulation period of the ensemble is equivalent to the timescale of the original model. It has also been found in the study that it is not needed to use a full simulations of the original model for the generation of the ensemble. The POD based calibration method has also been implemented for the estimation of the water depth and space varying bottom friction coefficient values in a very large-scale DCSM model. The recently designed large-scale spherical grid based water level model for the northwest European continental shelf (around 1000000 computational grid points) has been used for this purpose. This has been the first application of the POD based calibration method to a very large-scale model and with real data. Results from numerical experiments showed that the calibration method performs very efficiently. An overall improvement of more than 50\% was observed after the calibration in comparison with the initial model. The results also demonstrated that the POD based calibration method offered a very efficient minimization technique compared to the classical adjoint method without the burden of implementation of the adjoint. As a concluding step, to estimate depth values in the model DCSM, a Simultaneous perturbation stochastic approximation (SPSA) method has been used. The method uses stochastic simultaneous perturbation of all model parameters to generate a search at each iteration. SPSA is based on a highly efficient and easily implemented simultaneous perturbation approximation to the gradient. This gradient approximation for the central difference method uses only two objective function evaluations independent of the number of parameters being optimized. The results from experiments showed that SPSA has a lower convergence rate than POD based calibration method, however the computational cost in each iteration of the SPSA method is usually far less then the POD based calibration method. The results also demonstrated that the SPSA algorithm proved to be a promising optimization algorithm for model calibration for cases where adjoint code is not available for computing the gradient of the objective function.Applied mathematicsElectrical Engineering, Mathematics and Computer Scienc
Thermal Hydraulic Analysis of 3 MW TRIGA Research Reactor of Bangladesh Considering Different Cycles of Burnup
No full textBurnup dependent steady state thermal hydraulic analysis of TRIGA Mark-II research reactor has been carried out utilizing coupled point kinetics, neutronics and thermal hydraulics code EUREKA-2/RR. From the previous calculations of neutronics parameters including percentage burnup of individual fuel elements performed so far for 700 MWD burnt core of TRIGA reactor showed that the fuel rod predicted as hottest at the beginning of cycle (fresh core) was found to remain as the hottest until 200 MWD of burn, but, with the progress of core burn, the hottest rod was found to be shifted and another rod in the core became the hottest. The present study intends to evaluate the thermal hydraulic parameters of these hottest fuel rods at different cycles of burnup, from beginning to 700 MWD core burnt considering reactor operates under steady state condition. Peak fuel centerline temperature, maximum cladding and coolant temperatures of the hottest channels were calculated. It revealed that maximum temperature reported for fuel clad and fuel centerline found to lie below their melting points which indicate that there is no chance of burnout on the fuel cladding surface and no blister in the fuel meat throughout the considered cycles of core burnt
The Folio: F. C. C. Magazine
No full textImtiaz Ahmad Khan-Editorial. pp. 1; Speech-Principal's Address at the Opening Assembly September, 1948. pp. 2-3; Poetic Flights. pp. 3; Imtiaz Ahmad Khan-Article-On Solving a Mathematics Problem. pp. 3-4; Mohd. Mubinur Rahman-Essay-Our Twentieth Century. pp. 5; Ishfaq Ahmad-Article-Atomic Energy. pp. 6-7; Butt, M. Naseer-Essay-Pessimistic Reverie! pp. 7-9; Falk, Clarence-Forests. pp. 9-10; Chandi, P.T.-Sports-Tennis. pp. 11; Sports-Basket Ball. pp. 11; Naseem Shujaat Mirza-Sports-Cricket. pp. 12-13; Acton, P. John-Essay-Religion in the 20th Century. pp. 13-14; Riaz Piracha-Old Boys' Reunion Dinner 1949. pp. 14-15; The Folio [Urdu] 34 p.Quaid e Azam, Muhammad Ali Jinnah. after page 1
Harpactus Shuckard 1837
No full textGenus Harpactus Shuckard, 1837 Arpactus Jurine, 1807: 192, junior homonym of Arpactus Panzer, 1805, and of Arpactus Panzer, 1806 (both junior synonyms of Gorytes Latreille, 1804). Type species: Arpactus formosus Jurine, 1807, designated by Shuckard 1837: 220. Harpactus Shuckard 1837: 221. Emendation of Arpactus Jurine, 107 on linguistic grounds, thus an available new name, with its own date and author (Articles 19 and 33.2). Since Harpactus is an emendation, it has the same type-species as Arpactus Jurine (Article 67.8). Harpactes Dahlbom 1843: 147, junior homonym of Harpactes Swainson, 1837 (Aves), and of Harpactes Templeton, 1834 (Arachnida). Emendation of Harpactus Shuckard. Dienoplus W.J. Fox 1894: 548. Type species: Dienoplus pictifrons Fox, 1894, by monotypy. Key to Harpactus species of India and adjacent territories 1. Head and mesosoma without distinct punctures............................................................. 2 - Head, mesosoma, [and T2] distinctly foveolate-punctate, with scattered foveae. [Kashmir].......... H. pulawskii sp. nov. 2. Propodeum with oblique and irregular striae................................................................ 3 - Propodeum with distinct coarse, longitudinal striae [Pakistan].................................. H. vividus (Turner) 3. Fore wing with fuscous patch in radial and cubital cells; propodeal enclosure red. [Northern India; Myanmar]................................................................................................. H. ornatus (Smith) - Fore wing usually without fuscous patch in radial and cubital cells; propodeal enclosure black. [Oriental India].............................................................................................. H. impudens (Nurse)Published as part of Binoy, C., Kumar, P. Girish, Monks, Joseph & Sheikh, Altaf Hussain, 2022, A review of digger wasp genus Harpactus Shuckard, 1837 (Hymenoptera Crabronidae) of the Indian subcontinent, with description of a new species and rediscovery of Harpactus impudens (Nurse, 1903), pp. 531-542 in Zootaxa 5190 (4) on page 532, DOI: 10.11646/zootaxa.5190.4.3, http://zenodo.org/record/713847
High-prevalence and high-estimated incidence of HIV infection among new injecting drug users in Estonia: need for large scale prevention programs.
No full textOBJECTIVE: To examine HIV risk behavior and HIV infection among new injectors in Tallinn, Estonia. Design and methods Data from two cross-sectional surveys of injecting drug users (IDUs) recruited from a syringe exchange program (N = 162, Study 1) or using respondent driven sampling (N = 350, Study 2). Behavioral surveys were administered; serum samples were collected for HIV testing. Subjects were categorized into new injectors (injecting 3 years). RESULTS: Twenty-eight of 161 (17%, Study 1) and 73/350 (21%, Study 2) of the study subjects were new injectors. HIV infection was substantial among the newer injectors: HIV prevalence was 50% (Study 1) and 34% (Study 2), and estimated HIV incidence 31/100 PY and 21/100 PY, respectively. In Study 2, new injectors were more likely to be female and ethnic Estonian and less likely to be injecting daily compared with long-term injectors. No significant difference was found among two groups on sharing injecting equipment or reported number of sexual partners. CONCLUSIONS: A continuing HIV epidemic among new injectors is of critical public health concern. Interventions to prevent initiation into injecting drug use and scaling up HIV prevention programs for IDUs in Estonia are of utmost importance
RIA Analysis of Unprotected TRIGA Reactor
No full textAn RIA (reactivity initiated accident) analysis has been carried out for the TRIGA Mark II research reactor considering both step and ramp reactivity ranges within 0.5 % dk/k (< 2). The insertion time was set at 10 s. Based on the fact that a reactor becomes unprotected if scram does not work at the event of danger, to define unprotected conditions, the time to actuate scram (trip) was taken as close to total simulation time. In this long duration of scram inactivity, it is obtained from the present analysis that the reactor remained safe to up to 1.8 % dk/k (2.84) for ramp reactivity. In addition to negative temperature coefficient of reativity, probably the longer time of reactivity insertion keeps TRIGA safe even at larger magnitudes of reactivity during unprotected reactor transients. Coupled point kinetics, neutronics, and thermal hydraulics code EUREKA-2/R has been utilized for this work. It appears that EUREKA-2/RR predicts the sequence of unprotected transient scenario of TRIGA core with good approximation and the results will definitely be helpful for the reactor operators.</p
سرسیدکامقام:حالی وشبلی کی اردوشاعری کی روشنی میں
No full textSir Syed Ahmed Khan is known as a Muslim reformer of the 19th century. He played an important role in introducing modern Urdu verse and prose. He himself was a prominent author, editor and compiler. Altaf Husain Hali is a well known poet, prose writer and critic etc. Shibli Naumani is another great name of Urdu literature. Shibli was a distinguished scholar, writer and poet. Hali and Shibli were close companions of Sir Syed. They discussed the personality and achievements of Sir Syed in their verses. The article analyses the status of Sir Syed in the light of the verse of the said two great names of Urdu.
Socio-economic determinants of employment in Mahatma Gandhi National Rural Employment Guarantee Scheme (MGNREGS) in Jammu and Kashmir
No full textPurposeThe purpose of this paper is to look at the socio-economic determinants of employment in Mahatma Gandhi National Rural Employment Guarantee Scheme (MGNREGS) in Jammu and Kashmir (J&K) at both household and individual level. My results show that there is no discrimination in provision of employment to backward classes. Out of all the Indian States, J&K has lowest female participation in the scheme. My results show that women are discriminated against in provision of employment. Worksite facilities, like creche, can positively affect female participation in the scheme.Design/methodology/approachThe author uses multi-variate OLS regression model to analyse the data collected through primary survey of three heterogenous villages of district Ganderbal of J&K.FindingsThe author finds clear evidence of discrimination against females in provision of employment along with slight evidence of elite capture of the scheme. The author also finds negative relationship between the number of children in a household and the number of workdays which highlights the importance of worksite facilities to increase female and overall participation for the scheme to be successful.Research limitations/implicationsThe possible limitation could be small sample size but given that this is the first study of its kind in the J&K State, researchers can build up on it.Originality/valueThis is one of the first research papers which looks at the performance of MGNREGS in J&K in such detail. No comprehensive study of this magnitude and rigour has been undertaken in J&K till now.</jats:sec
PENGARUH ATRIBUT RESTORAN (DINESERV) TERHADAP KEPUASAN PELANGGAN, NIAT DATANG KEMBALI, DAN REKOMENDASI DENGAN PENDEKATAN SEM-PLS (STUDI KASUS: NICE BOX SIGURA-GURA MALANG)
No full textJika membutuhkan abstrak atau isi jurnal silahkan menghubungi author melalui e-mail [email protected] atau [email protected]
Dipublikasikan tanggal: 13 Juli 202
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