549 research outputs found
Difference based Ridge and Liu type Estimators in Semiparametric Regression Models
No full textWe consider a difference based ridge regression estimator and a Liu type estimator of the regression parameters in the partial linear semiparametric regression model, y = Xβ + f + ε. Both estimators are analysed and compared in the sense of mean-squared error. We consider the case of independent errors with equal variance and give conditions under which the proposed estimators are superior to the unbiased difference based estimation technique. We extend the results to account for heteroscedasticity and autocovariance in the error terms. Finally, we illustrate the performance of these estimators with an application to the determinants of electricity consumption in Germany.Difference based estimator; Differencing estimator, Differencing matrix, Liu estimator, Liu type estimator, Multicollinearity, Ridge regression estimator, Semiparametric model
Pricing Chinese rain: a multi-site multi-period equilibrium pricing model for rainfall derivatives
No full textMany industries are exposed to weather risk which they can transfer on financial markets via weather derivatives. Equilibrium models based on partial market clearing became a useful tool for pricing such kind of financial instruments. In a multi-period equilibrium pricing model agents rebalance their portfolio of weather bonds and a risk free asset in each period such that they maximize the expected utility of their incomes constituted by possibly weather dependent profits and payoffs of portfolio positions. We extend the model to a multisite version and apply it to pricing rainfall derivatives for Chinese provinces. By simulating realistic market conditions with two agent types, farmers with profits highly exposed to weather risk and a financial investor diversifying her financial portfolio, we obtain equilibrium prices for weather derivatives on cumulative monthly rainfall. Dynamic portfolio optimization under market clearing and utility indifference of these representative agents determines equilibrium quantity and price for rainfall derivatives.rainfall derivatives, equilibrium pricing, space-time Markov model
A new fetal RHD genotyping test : costs and benefits of mass testing to target antenatal anti-D prophylaxis in England and Wales
No full textBackground
Postnatal and antenatal anti-D prophylaxis have dramatically reduced maternal sensitisations and cases of rhesus disease in babies born to women with RhD negative blood group. Recent scientific advances mean that non-invasive prenatal diagnosis (NIPD), based on the presence of cell-free fetal DNA in maternal plasma, could be used to target prophylaxis on "at risk" pregnancies where the fetus is RhD positive. This paper provides the first assessment of cost-effectiveness of NIPD-targeted prophylaxis compared to current policies.
Methods
We conducted an economic analysis of NIPD implementation in England and Wales. Two scenarios were considered. Scenario 1 assumed that NIPD will be only used to target antenatal prophylaxis with serology tests continuing to direct post-delivery prophylaxis. In Scenario 2, NIPD would also displace postnatal serology testing if an RhD negative fetus was identified. Costs were estimated from the provider's perspective for both scenarios together with a threshold royalty fee per test. Incremental costs were compared with clinical implications.
Results
The basic cost of an NIPD in-house test is £16.25 per sample (excluding royalty fee). The two-dose antenatal prophylaxis policy recommended by NICE is estimated to cost the NHS £3.37 million each year. The estimated threshold royalty fee is £2.18 and £8.83 for Scenarios 1 and 2 respectively. At a £2.00 royalty fee, mass NIPD testing would produce no saving for Scenario 1 and £507,154 per annum for Scenario 2. Incremental cost-effectiveness analysis indicates that, at a test sensitivity of 99.7% and this royalty fee, NIPD testing in Scenario 2 will generate one additional sensitisation for every £9,190 saved. If a single-dose prophylaxis policy were implemented nationally, as recently recommended by NICE, Scenario 2 savings would fall.
Conclusions
Currently, NIPD testing to target anti-D prophylaxis is unlikely to be sufficiently cost-effective to warrant its large scale introduction in England and Wales. Only minor savings are calculated and, balanced against this, the predicted increase in maternal sensitisations may be unacceptably high. Reliability of NIPD assays still needs to be demonstrated rigorously in different ethnic minority populations. First trimester testing is unlikely to alter this picture significantly although other emerging technologies may
The meaning of handicrafts of children aged 4 to 5 in development of the fine motor skills
No full textDarba temats: Rokdarbu nozīme 4 - 5 gadus vecu bērnu sīkās motorikas attīstībā. Balstoties uz aktualitātēm izglītībā, personisko pieredzi, tika izvēlēts Pētījuma mērķis: Pētīt rokdarbu nozīmi sīkās motorikas apguvē 4 – 5 gadus veciem bērniem. Darbs sastāv no trijām nodaļām ar apakšnodaļām. Darbā tika analizētas pedagogu un psihologu atziņas par sīkās pirkstu muskulatūras attīstību vidējā pirmsskolas vecumā. Tāpat tika skatīts jautājums par 4 – 5 gadus vecu bērnu psiholoģiskajām īpatnībām, attīstību. Tika izpētīti materiāli rokdarbu nodarbību plānošanai un izstrādātas rekomendācijas darbam ar 4 – 5 gadus veciem bērniem rokdarbu nodarbībās. Tika veikts pētījums. Pētījumā izmantotas daudzveidīgas metodes. Darba vadītāja ir mag. paed., lektore: Ineta Aizporiete Darbs balstās uz ārzemju (Gabbard C., Rodrigies L., Козырева E., Вавилова А.Jermakovas un c.), kā arī uz Latvijas pedagogu un psihologu (D.Lieģenieces, D.Dzinteres, Šternfeldes I, Vidneres M., Ozoliņas I., Aizporietes I., Volānes E., I.Šternfelde un c.) teorētiskajām atziņām par bērna sīkās pirkstu muskulatūras attīstību un rokdarbu nozīmi 4 – 5 gadus veca bērna personības izaugsmē. Praktiskajā daļā veikti pedagoģiskie novērojumi, skolotāju intervijas, iegūto rezultātu analīze. Kvalifikācijas darbs sastāv no trīs nodaļām, 43 lpp, 4 pielikumiem, 5 attēliem, 43 literatūras avotiem.The title of qualification paper is „ The meaning of handicrafts of children aged 4 to 5 in development of the fine motor skills.” The author of the paper is Santa Osipenko, a student of the part – time first level professional study programme „Preschool education teacher” within the Faculty of Pedagogy of Riga, University of Latvia. The supervisor: Mg.paed., lect. Ineta Aizporiete. The aim of the research paper: to research the importance of the fine motor skills education for children aged 4 to 5. The paper consists of two main parts: theoretical and practical part. The research consists of three divisions with subdivisions. During the research the information made by educators and psychologists about the fine motor skills development and psyshological characteristics of children aged 4 to 5. Materials about lessons of handicraft planning werw researched. Based on the research there were made recommendations for work with children aged 4 to 5 during handicrafts lessons. The research was made using different kinds of methods. The theoretical part is based on the theoretical findings of both the foreign (Gabbard C., Rodrigies L., Козырева E., Вавилова А. ) and the Latvian pedagogues and psychologists (V. Hibnere, V.Jonīte, D.Lieģiniece, D.Dzintere ,E. Volāne, I.Šternfelde) about the development of childrens. The practical part is based on pedagogical observations, interview of teachers and analysis of results. The qualification paper consists of 3 chapters, 43 pages, 5 illustrations, literature and information – latvian and english authors, russian authors - 43
The Law of Attraction: Bilateral Search and Horizontal Heterogeneity
No full textWe study a matching model with heterogeneous agents, nontransferable utility and search frictions. Agents differ along a horizontal dimension (e.g. taste) and a vertical dimension (e.g. income). Agents’ preferences coincide only in the vertical dimension. This approach introduces individual preferences in this literature as seems suitable in applications like labor markets (e.g. regional preferences). We analyze how the notion of assortativeness generalizes to integration or segregation outcomes depending on search frictions. Contrary to results from the purely vertical analysis, here, agents continuously adjust their reservation utility strategies to changing search frictions. The model is easily generalizable in the utility specification, the distribution of taste-related payoffs and the number of vertical types. Extreme utility specifications can be treated as a case of horizontal heterogeneity only.Matching, Horizontal Differentiation , Marriage Markets
How Computational Statistics Became the Backbone of Modern Data Science
No full textThis first chapter serves as an introduction and overview for a collection of articles surveying the current state of the science of computational statistics. Earlier versions of most of these articles appeared in the first edition of Handbook of Computational Statistics: Concepts and Methods, published in 2004. There have been advances in all of the areas of computational statistics, so we feel that it is time to revise and update this Handbook. This introduction is a revision of the introductory chapter of the first edition.Discrete time series models, continuous time diffusion models, models with jumps, stochastic volatility, GARCH
Simple FFH pilot experiment model based on DTT-like machine
No full textThe global need for energy in the world is constantly increasing. Critical fission reactors have proved great efficiency in the energy production, but the fear of nuclear wastes and accidents due to an uncontrolled chain reaction makes these unpleasant to public. More safe fusion reactors, on the opposite, have low efficiency. Hybrid reactors capable of using the advantages of both are studied, but not yet developed. In this paper, a simple fusion–fission pilot experiment model has been developed. A Tokamak with the same characteristics of DTT (Divertor Tokamak Test facility) has been considered as a reference machine for the fusion component. The fusion system has been coupled with a relatively simple low-power fission blanket configured into three different modes by using different fuels and materials. This model could be useful in order to investigate the properties of the fusion–fission hybrid coupling from a neutronic point of view
Novel hybrid pilot experiment proposal for a fusion-fission subcritical coupled system
No full textFusion-fission hybrid systems (FFH) represent a coupling between a fusion device and a subcritical fission reactor driven by neutrons produced by fusion reactions. This kind of systems, in principle, can be useful for different purposes, for example, as energy amplifier or as nuclear waste burner. In this work, the preliminary characteristics and potentialities of a FFH based on a tokamak device characterized by high magnetic field (B > 9 T) and high-density plasma (n > 10 14 cm –3 ) have been evaluated. During the years high magnetic field compact tokamaks have been designed, built and operated. Thanks to their characteristics, such as compactness, high field and high density plasma, these devices can produce intense neutron fluxes, and therefore are good candidates to be incorporated in FFH while operating in a sub-ignited regime. An additional advantage is that their design is based on relatively simple existing technology. In this work, a coupling between a tokamak (operating in DD-mode) and a subcritical molten salt fission blanket has been proposed. Molten salt reactor could be adapted for this purpose and could help the hybrid system to increase its energy balance. A model with a molten salt fission blanket (k eff = 0.92, P = 95 MW) instead of the lithium one, has been considered and studied in terms of neutronic evaluations. Presented preliminary numerical calculations based on a neutron Monte-Carlo code confirm the potentialities of the system
Novel hybrid pilot experiment proposal for a Fusion-fission subcritical coupled system
No full textFusion-fission hybrid systems (FFH) represent a coupling between a fusion device and a subcritical fission reactor driven by neutrons produced by fusion reactions. This kind of systems, in principle, can be useful for different purposes, for example, as energy amplifier or as nuclear waste burner. In this work, the preliminary characteristics and potentialities of a FFH based on a tokamak device characterized by high magnetic field (B > 9 T) and high-density plasma (n > 1014 cm-3) have been evaluated. During the years high magnetic field compact tokamaks have been designed, built and operated. Thanks to their characteristics, such as compactness, high field and high density plasma, these devices can produce intense neutron fluxes, and therefore are good candidates to be incorporated in FFH while operating in a sub-ignited regime. An additional advantage is that their design is based on relatively simple existing technology. In this work, a coupling between a tokamak (operating in DD-mode) and a subcritical molten salt fission blanket has been proposed. Molten salt reactor could be adapted for this purpose and could help the hybrid system to increase its energy balance. A model with a molten salt fission blanket (keff = 0.92, P = 95 MW) instead of the lithium one, has been considered and studied in terms of neutronic evaluations. Presented preliminary numerical calculations based on a neutron Monte-Carlo code confirm the potentialities of the system
Simple FFH pilot experiment model based on DTT-like machine
No full textThe global need for energy in the world is constantly increasing. Critical fission
reactors have proved great efficiency in the energy production, but the fear of nuclear wastes
and accidents due to an uncontrolled chain reaction makes these unpleasant to public. More
safe fusion reactors, on the opposite, have lowefficiency. Hybrid reactors capable of using the
advantages of both are studied, but not yet developed. In this paper, a simple fusion–fission
pilot experiment model has been developed. A Tokamak with the same characteristics of
DTT (Divertor Tokamak Test facility) has been considered as a reference machine for the
fusion component. The fusion system has been coupled with a relatively simple low-power
fission blanket configured into three different modes by using different fuels and materials.
This model could be useful in order to investigate the properties of the fusion–fission hybrid
coupling from a neutronic point of view
- …
