Derivation of Analytic Solution and MOC Calculation Procedure for Double Heterogeneity Treatment

The Sanchez-Pomraning method to resolve the double heterogeneity problem in the MOC transport calculation is described in detail. This method is founded on the collision probability method concepts which involves the collision and escape probabilities, and formally derived by using the statistical treatment of the neutron balance equation along a path. The statistical approach bring the concept of the chord and segment length distributions in the formulation of the integral equation for the grain surface and matrix fluxes, which later turns into collision and escape probabilities. For the analytic solution, a boundary layer of a grain thickness, in which no grain is present, is assumed within each flat source region. The analytic solution of the coupled integral equation which involves the convolution integral is derived first by Laplace transform, but finally by substitution. This solution introduces an effective cross section which represents the homogenized mixture of the matrix and grain. With observation that the resulting analytic solution for the matrix is the same as the MOC solution for the homogenized medium, the equivalent source is constructed so that the MOC calculation can be performed for the homogenized mixture. The assumption of the boundary layer causes, however, a problem in the neutron conservation which should be corrected by renormalization. This method requires very little modifications to the existing MOC code to implement the double heterogeneity treatment. Starting from the very basic collision probability relation, the exhaustive derivation and explanation of the all the solution and terms needed to establish the MOC calculation sequence with the double heterogeneity treatment are provided for complete understanding of the reader who might not have sufficient background on this subject

Multiobjective loading pattern optimization by simulated annealing employing discontinuous penalty function and screening technique

The problem of multiobjective fuel loading pattern (LP) optimization employing high-fidelity three-dimensional (3-D) models is resolved by introducing the concepts of discontinuous penalty function, dominance, and two-dimensional (2-D)–based screening into the simulated annealing (SA) algorithm. Each constraint and objective imposed on a reload LP design is transformed into a discontinuous penalty function that involves a jump to a quadratic variation at the point of the limiting value of the corresponding core characteristics parameter. It is shown that with this discontinuous form the sensitivity of the penalty coefficients is quite weak compared to the stochastic effect of SA. The feasible LPs found during SA update the set of candidate LPs through a dominance check that is done by examining multiple objectives altogether. The 2-D–based screening technique uses a precalculated database of the 2-D solution errors and is shown to be very effective in saving the SA computation time by avoiding 3-D evaluations for the unfavorable LPs that are frequently encountered in SA. Realistic applications of the proposed method to a pressurized water reactor reload LP optimization with the dual objectives of maximizing the cycle length and minimizing the radial peaking factor demonstrate that the method works quite well in practice.This work was supported by the project funded by the Ministry of Knowledge Economy of Korea to develop primary design codes for nuclear power plants

Maintained Seroprevalence of Toxoplasmosis among the Residents of Jeju Island, Korea

Seroepidemiological status of toxoplasmosis among the residents of Jeju island was surveyed and evaluated by ELISA with crude extract of Toxoplasma gondii. The sera of 2,348 residents (male 1,157 and female 1,191) were collected and checked for the IgG antibody titers, which showed 13.2% positive rate (309 sera). The positive rates were increasing gradually according to the age from 4.3% in teenage to 20.6% in seventies. The positive rates were significantly different between the sex by 16.2% for male and 10.2% for female (P<0.05). This positive rate of toxoplasmosis in Jeju island residents is regarded relatively higher than any other regions of Korea. And the high positive rate may be maintained continuously among Jeju island residents without any clear reasons until now but due to some parts peculiar socio-cultural tradition of Jeju island. Therefore, it is necessary to study further the epidemiology of toxoplasmosis of Jeju island

Radiofrequency Ablation of Benign Thyroid Nodules and Recurrent Thyroid Cancers: Consensus Statement and Recommendations

Thermal ablation using radiofrequency is a new, minimally invasive modality employed as an alternative to surgery in patients with benign thyroid nodules and recurrent thyroid cancers. The Task Force Committee of the Korean Society of Thyroid Radiology has developed recommendations for the optimal use of radiofrequency ablation for thyroid nodules. These recommendations are based on a comprehensive analysis of the current literature, the results of multicenter studies, and expert consensus

AI is a viable alternative to high throughput screening: a 318-target study

: High throughput screening (HTS) is routinely used to identify bioactive small molecules. This requires physical compounds, which limits coverage of accessible chemical space. Computational approaches combined with vast on-demand chemical libraries can access far greater chemical space, provided that the predictive accuracy is sufficient to identify useful molecules. Through the largest and most diverse virtual HTS campaign reported to date, comprising 318 individual projects, we demonstrate that our AtomNet® convolutional neural network successfully finds novel hits across every major therapeutic area and protein class. We address historical limitations of computational screening by demonstrating success for target proteins without known binders, high-quality X-ray crystal structures, or manual cherry-picking of compounds. We show that the molecules selected by the AtomNet® model are novel drug-like scaffolds rather than minor modifications to known bioactive compounds. Our empirical results suggest that computational methods can substantially replace HTS as the first step of small-molecule drug discovery