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AbstractThe characteristics of the radiation field around a consolidated interim spent nuclear fuel storage facility were investigated comprehensively through Monte Carlo simulations. Neutron and gamma-ray flux/dose contributions from multiple transport pathways, including direct, streaming, skyshine, groundshine, and multishine, were isolated using a modified version of the method that was originally developed by Oh et al. [J. Korean Phys. Soc., Vol. 69, 1057 (2016)] for the evaluation of neutron skyshine from a high-energy electron accelerator. The application of the methodology was demonstrated in this paper, and the flux/dose contributions of individual pathways were examined and compared. The results provided additional insight into how the radiation propagated from the source to off-site locations. The modified method for separating five transport pathways can provide valuable information for shielding optimization during the design phase and is generally applicable to Monte Carlo shielding analyses of other nuclear facilities.

Environmentally persistent free radicals (EPFR) are an emerging class of constituents in particulate matter (PM). They are relatively stable with lifetimes of days to years in the condensed phase, influence PM toxicity, and are involved in reactive oxygen species (ROS) generation and multiphase chemistry. The abundance of EPFR has been investigated in laboratory studies and outdoor locations globally, but their prevalence indoors was previously unstudied. In a case study home, EPFR were present at similar concentrations in indoor and outdoor PM, at 2.3 ± 2.8 × 1012and 3.6 ± 3.1 × 1012spins m−3, respectively. Indoor EPFR were observed at varying concentrations in airborne PM, dust, and surface samples, with the most concentrated surface loadings observed on windows. Overall, dust and indoor surfaces were estimated to be larger contributors to total in-home EPFR concentrations than PM. For comparison, combined estimates of total EPFR concentrations in indoor PM, dust, and on surfaces are similar to the range of typical indoor ozone concentrations. Due to the reactive nature of EPFR, they potentially undergo rapid cycling and may represent reservoirs of reactivity in these multiphase systems that influence the surface and multiphase chemistry of indoor environments. Here, the exposure of EPFR collected from some surfaces to nitrogen dioxide or ozone was shown to alter EPFR abundances and composition. In all, these results support further investigations of EPFR abundance, composition, and reactivity on indoor surfaces, including in accumulated organic coatings and dust.

Surface dose rate distribution over a spent nuclear fuel dry storage cask was realistically evaluated using the MONACO with Automated Variance Reduction using Importance Calculations (MAVRIC) computational sequence in the SCALE6 code system, with special emphasis on the effects of detailed modeling on the source term and cask geometry. The first storage cask in Taiwan has been fabricated and will be ready for loading of the designated spent fuels from Taiwan Power Company’s first nuclear power plant. A test run is scheduled for 2013.Neutron and gamma-ray source terms of the first batch of 56 spent fuels were determined one by one according to their specifications, burnup histories, and cooling times. The geometry of the cask was modeled in detail including the prescribed loading pattern of 56 spent fuels in the canister. MAVRIC was modified to allow specification of the source intensity and the axial distribution for each fuel bundle, and this resulted in a factor of 3 difference in the calculated surface dose rates from fuel gammas. The main purpose for such comprehensive and detailed modeling was to compare the results with a simplified model and to predict a dose rate distribution as realistically as possible in preparation for making a high-quality comparison with field measurements. In addition to checking assumptions adopted in the safety analysis report, the results of this study can provide useful guidance for the preparation of a health physics program during the test run and, more importantly, pave the way for establishing a valuable benchmark problem.

AbstractThis study reevaluates the dose rates at the site boundary of an independent spent-fuel storage installation (ISFSI) using the MAVRIC computational sequence in the SCALE6 code package. Based on advanced variance-reduction techniques and powerful geometry modeling capabilities, MAVRIC can tackle this large ISFSI shielding problem by directly simulating the radiation transport in a full-scale model. This study started with a benchmark calculation of a single storage cask and then investigated the impact of a fully loaded ISFSI on the dose rates at the site boundary. Because of the short distance to the nearest site boundary, additional shielding to the cask itself or the site is necessary to meet the stringent design dose limit. Compared to the two-step cask-by-cask approach adopted in the original safety analysis report, this method of analyzing the site boundary doses is straightforward and efficient enough to allow us to evaluate the effect of the cask design modification and to test various options for further improvement.

AbstractBased on the Consistent Adjoint Driven Importance Sampling (CADIS) methodology, MAVRIC is a new computational sequence in the SCALE6 code package that is designed to perform efficient Monte Carlo simulation for a complicated and difficult shielding problem. This study aimed to evaluate the performance of MAVRIC with the latest cross-section library in calculating the surface dose rates of a realistic spent-fuel storage cask. Detailed dose rate profiles over the cask side and top surfaces were calculated, and the results were compared with our previous work using SAS4 and MCNP. In order to duplicate the same source model, the MAVRIC code has been modified to accommodate a user-defined axial source distribution. The comparison among the three codes was evaluated in terms of their accuracies and computational efficiencies. For the gamma-ray sources, the MAVRIC-calculated results are more accurate than SAS4 and consistent with those predicted by the continuous-energy MCNP calculations. Meanwhile, its computational efficiencies are comparable to the performance of the TORT-coupled MCNP calculations. For the fuel neutron source, the MAVRIC calculation with broad-group cross sections cannot give satisfactory result, and its computational performance is also a factor of ˜10 less efficient than that of TORT-coupled MCNP. With a fine-group cross-section library, MAVRIC can provide a better prediction but still underestimates the surface dose rates of the cask by 15 to 30%.

AbstractThis study investigates the characteristics of the prompt radiation field due to the operation of the proposed Taiwan Photon Source (TPS). Two extreme beam loss cases are considered to bound the possible beam loss scenarios in the tunnel; i.e., all electrons are lost at one point, or they are lost uniformly along the whole electron orbit. Energy spectra and dose distributions of the prompt radiation field for the shielding design of the TPS are studied using analytic estimations and Monte Carlo simulations. The radiation levels of photons and neutrons outside the shielding wall are estimated for various operation modes and beam loss scenarios. The calculated results show that the preliminary shielding design of the TPS is highly practicable to achieve its annual design dose limit of 1 mSv for personnel. Meanwhile, the radiation impact on the environment is also far below the regulatory requirement.

AbstractIn this study, discrete ordinates and Monte Carlo methods were applied to solve the radiation transport problem for a simplified spent fuel storage cask considering fixed neutron and gamma-ray sources. The results were compared, and the causes for their differences were investigated. In addition, a hybrid method based on the Consistent Adjoint Driven Importance Sampling (CADIS) methodology has been adopted to accelerate the Monte Carlo simulations. CADIS utilizes a deterministic adjoint function for variance reduction through source biasing and consistent transport biasing. The problem encountered and its possible solution for applying the source biasing in such a large volume source are described. Compared with the unbiased case, the computational efficiency is improved by a factor of several tens for neutron transport, and the efficiency is increased tremendously by about five orders of magnitude for gamma-ray transport. It has been demonstrated that the biasing scheme applied here is very effective in the shielding calculations for a spent fuel storage cask using the Monte Carlo method.

A series of PPV-based polyoxadiazoles have been synthesized by Horner and Suzuki coupling polymerization to investigate their structure−property relationship. These copolymers exhibit good thermal stability (decomposition temperature around 352−413 °C). Excimer formation in P4−P9 was confirmed by their absorption and PL spectral peak transition in solution at different concentrations and in thin films. Unusual absorption and fluorescence were observed in acid media and have been related to photoinduced charge transfer in alternating donor−acceptor architecture. The photoinduced charge transfer led to a blue shift in iminodibenzyl-containing copolymers (P1−P3) and a red shift in fluorene-containing copolymers (P9), reflecting the fact that iminodibenzyl is a stronger electron-donating unit. The electrochemical properties of the copolymers were evaluated by cyclic voltammetry and their highest occupied molecular orbital and the lowest unoccupied molecular orbit energy levels were estimated. The optical band gaps of the dioxadiazole-containing copolymers show great discrepancy with the electrochemical band gap energy due to the donor−acceptor feature of the dioxadiazole unit.

Systems of linear inequalities are important tools to formulate optimization problems. However, the feasibility of the whole system was often presumed true in most models. Even if an infeasible system could be detected, it is in general not easy to tell which part of the system caused it. This motivates the study of continuous linear inequalities, given no information whether it is feasible or not, what is the largest possible portion of the system that can be remained in consistency? We first propose a bisection-based algorithm which comes with an auxiliary program to answer the question. For further accelerating the algorithm, several novel concepts, one called “constraint weighting” and the other called “shooting technique”, are introduced to explore intrinsic problem structures. This new scheme eventually replaces the bisection method and its validity can be justified via a solid probabilistic analysis. Numerical examples and applications to fuzzy inequalities are reported to illustrate the robustness of our algorithm.

Brain metabolism and the activity of the α-ketoglutarate dehydrogenase complex (KGDHC), a mitochondrial enzyme, are diminished in brains from patients with Alzheimer's disease (AD). In 109 subjects, the Clinical Dementia Rating (CDR) score was highly correlated with brain KGDHC activity. In AD patients who carried the epsilon 4 allele of the apolipoprotein E gene (ApoE4), the CDR score correlated better with KGDHC activity than with the densities of neuritic plaques or neuritic tangles. In contrast, in patients without ApoE4, the CDR score correlated significantly better with tangles and plaques than with KGDHC activity. The results suggest that mitochondrial/oxidative damage may be more important for the cognitive dysfunction in AD patients who carry ApoE4 than in those who do not. Ann Neurol 2000;48:297–303

Brain metabolism and the activity of the α‐ketoglutarate dehydrogenase complex (KGDHC), a mitochondrial enzyme, are diminished in brains from patients with Alzheimer's disease (AD). In 109 subjects, the Clinical Dementia Rating (CDR) score was highly correlated with brain KGDHC activity. In AD patients who carried the epsilon 4 allele of the apolipoprotein E gene (ApoE4), the CDR score correlated better with KGDHC activity than with the densities of neuritic plaques or neuritic tangles. In contrast, in patients without ApoE4, the CDR score correlated significantly better with tangles and plaques than with KGDHC activity. The results suggest that mitochondrial/oxidative damage may be more important for the cognitive dysfunction in AD patients who carry ApoE4than in those who do not. Ann Neurol 2000;48:297–303

The effect of the angular distribution of the equivalent point source on the analysis of the skyshine dose rates was investigated in detail. The dedicated skyshine codes SKYDOSE and McSKY were revised to include the capability of dealing with the anisotropic source. It was found that a replace of the cosine-distributed source by an isotropic source will overestimate the skyshine dose rates for large roof-subtended angles and cause underestimation for small roof-subtended angles. For building with roof shielding, however, replacing the cosine-distributed source by an isotropic source will always underestimate the skyshine dose rates. The skyshine dose rates from a volume source calculated by the dedicated skyshine code agree very well with those of the MCNP Monte Carlo calculation.

Neutron source characteristics, especially the spatial distribution and time variation, in electron synchrotron facilities are very complicated and can’t be well identified. The purpose of this study intends to evaluate the neutron source characteristics through the experimental measurements carried out outside the shielding wall, with a special emphasis on the angular distribution emerged from the shielding wall surface and locations of the neutron hot spots. A high-efficiency eight-channel neutron detector (8CND) had been designed to characterize the angular or energy information of the neutron field. The 8CND consists of eight BF3tubes and a polyethylene cylinder. The response function of each of the BF3tubes in the 8CND was examined in detail by using the Monte Carlo simulation. Based on the high-efficiency and distinct response function of each BF3tube in the 8CND, it had demonstrated that some valuable information about the neutron field could be extracted from the counting rates of these eight BF3tubes in the 8CND.

AbstractInterior point methods were originally designed to obtain the polynomial-time complexity for linear programming. Its extension to convex quadratic programming is straightforward because, when we take the first derivative of the quadratic Junction for use in KKT conditions, it becomes linear. However, further extension to convex programming remains a difficult task due to the nonlinearity. Here in this paper, we demonstrate a systematic way of interior point approach for solving this problem. General type of barrier functions are studied and conditions which ensure convergence and polynomality are exploited. As an interesting special case, we look into the logarithmic barrier function, and propose a standard Lipschitz notion for local analysis. A phase I procedure is also included to make this work complete.

In this paper, we study the minimization of the max function of qsmooth convex functions on a domain specified by infinitely many linear constraints. The difficulty of such problems arises from the kinks of the max function and it is often suggested that, by imposing certain regularization functions, nondifferentiability will be overcome. We find that the entropic regularization introduced by Li and Fang is closely related to recently developed path-following interior-point methods. Based on their results, we create an interior trajectory in the feasible domain and propose a path-following algorithm with a convergence proof. Our intention here is to show a nice combination of minmax problems, semi-infinite programming, and interior-point methods. Hopefully, this will lead to new applications.

In this paper, we study the search directions of three important interior-point algorithms, namely, the primal-affine scaling method (with logarithmic barrier function), the dual-affine scaling method (with logarithmic barrier function), and the primal-dual interior point method. From an algebraic point of view, we show that the search directions of these three algorithms are merely Newton directions along three different “paths” that lead to a solution of the Karush-Kuhn-Tucker conditions of a given linear programming problem. From a geometric point of view, we show that these directions can be obtained by solving certain well-defined subproblems. Both views provide a general platform for studying the existing interior-point methods and deriving new interior-point algorithms. We illustrate the derivation of new interior-point algorithms by replacing the logarithmic barrier function with an entropic barrier function. The results have been generalized and discussed.

Abstract: The magnetic resonance imaging (MRI) findings of 12 proven cases of peritoneal implants, mainly carcinomatosis, were reviewed for evidence of peritoneal seedings. The seeded sites include the pouch of Douglas, the ileocecal and retrocecal regions, the right and left paracolic gutters, Morison's pouch, the right subdiaphragmatic parietal peritoneum, the greater and lesser omentum, the gastrocolic, gastrosplenic, and phrenicocolic ligaments, the small bowel mesentery, the sigmoid and transverse mesocolons, and the small and large bowel walls. Sizes varied from less than 1 cm to omental cake and bulky tumors. The findings include linear or tiny nodular infiltrations of the omentum and subperitoneal fat (ligamentous, mesenteric, and mesocolic), focal or segmental wall thickenings, loss of unilateral colonie haustration with sacculation on the contralateral side, and nodular soft tissue masses along different locations of the peritoneal surfaces. Air was introduced via an antegrade or retrograde method to act as a gastrointestinal contrast agent and was found to be useful for delineating the seedings. As is true with computed tomography scan, miliary implants are also not detectable with MRI. The sensitivity and specificity of MRI in detecting peritoneal implants remain to be determined.

In order to evaluate the contribution of retrograde air insufflation in decreasing the occurrence of pseudotumor appearance and mimicked lymphadenopathy due to nonair-distended bowel loops, we retrospectively compared two groups of magnetic resonance (MR) examinations. In the group receiving retrograde air insufflation, 10.8% (67 of 619) of images showed a tumor-like lesion due to nonair-distended bowel loop(s), whereas in the group not receiving air introduction, a tumor-like lesion was simulated in 45.6% (140 of 307) of images. Furthermore, a collapsed bowel loop(s) mimicking an enlarged lymph node close to the aorta, inferior vena cava, or bilateral iliac vessels was found in 9.5% (24 of 252) of images of the latter group, in contrast to only 1.8% (9 of 505) of images of the former group. This study shows that retrograde air insufflation greatly reduces the occurrence of pseudotumor appearance and false impression of paraaortic, paracaval, or parailiac lymphadenopathy secondary to nonair-distended bowel loop(s).

The magnetic resonance (MR) images of 11 cases of gastrointestinal lymphoma are presented. The findings include irregularly thickened mucosal folds, irregular submucosal infiltration, annular constricting lesion, exophytic tumor growth, mesenteric masses, and mesenteric/retroperitoneal lymphadenopathy. The tumors were homogeneous and intermediate in signal intensity on T1-weighted images. Heterogeneously increased signal intensities were noted on T2-weighted images. There was mild to moderate enhancement after intravenous administration of gadolinium dimeglumine (Gd-DTPA). The submucosal tumor infiltration might be outlined between the strongly GD-DTPA-enhanced mucosa and the low-intensity muscular layer. In one case that received tumor resection, the pathological examination showed destruction of most parts of the muscular layer, and the MR images did not disclose the low intensity muscular zone.

Abstract: The appearance of gastrointestinal wall thickening of various entities is demonstrated on magnetic resonance imaging (MRI). The entities include benign gastric ulcer, gastric carcinoma, pancreatic carcinoma with direct invasion of stomach, duodenal leiomyoma, radiation enteritis, peritonitis, colonic carcinoma, recurrent carcinoma at the gastrojejunal anastomosis with direct extension to the transverse colon, colocolic intussusception, sigmoid diverticulitis with pericolonic abscess and fistula into the urinary bladder, and lymphoma of the stomach, duodenum, small bowel, and colon. Air was introduced antegradedly or retrogradedly into the alimentary tract to act as a contrast agent. When the bowel was distended by air, the normal bowel wall was barely visible or even invisible. Abnormal focal or segmental wall thickening was outlined between the intraluminal air and extraluminal fat. In some instances, the thickenings were better demonstrated on coronal or sagittal sections. The proper muscular layer of the bowel has a low-signal intensity and was delineated between the thickened mucosa—submucosa and extramural fat. Interruption of this low-intensity zone might represent tumor invasion through the muscular layer.

In this paper, we study a general path-following model for linear programming. Generalized barrier functions for linear programming are defined to create an ideal interior trajectory for path-following. The key components required for a generic algorithm, including the moving directions and criterion of closeness are discussed. A generic path-following algorithm is proposed and sufficient conditions for convergence and polynomality proofs are derived.

The trans‐butyrolactones (V) are prepared from the acetic acids (I) via the β‐hydroxy acids (III) and the β‐lactones (IV).