Characterization of the Insoluble Sludge from the Dissolution of Irradiated Fast Breeder Reactor Fuel

Insoluble sludge is generated in the reprocessing of spent fuel. The sludge obtained from the dissolution of irradiated fuel from the “Joyo” experimental fast reactor was analyzed to evaluate its chemical form. The sludge was collected by the filtration of the dissolved fuel solution, and then washed in nitric acid. The yields of the sludge weight were less than 1% of the total fuel weight. The chemical composition of the sludge was analyzed after decomposition by alkaline fusion. Molybdenum, technetium, ruthenium, rhodium, and palladium were found to be the main constituent elements of the sludge. X-ray diffraction patterns of the sludge were attributable to Mo₄Ru₄RhPd, regardless of the experimental conditions. The concentrations of molybdenum and zirconium in the dissolved fast reactor fuel solutions were low, indicating that zirconium molybdate hydrate is produced in negligible amounts in the process.     

Estimating Precision in Functional Images

Abstract

Functional imaging of biologic parameters like in vivo tissue metabolism is made possible by Positron Emission Tomography (PET). Many techniques have been suggested for extracting such images from dynamic time-course sequences of reconstructed PET scans. Quantitating the precision of these estimates is important for drawing inferences on the biologic parameters. Analytic variance formulas are not immediate owing to the nonlinear methods used in extraction. The usual resampling approach is infeasible because each image reconstruction in PET is a computationally demanding solution to a high-dimensional linear inverse problem. We suggest an alternative simulation approach that approximates the distribution of reconstructed PET scans and performs a parametric bootstrap in the imaging domain. Results on a simplified model chosen to match the characteristics of PET reconstruction are very encouraging. Mixture analysis is used to estimate functional images; however, the suggested approach is general enough to extend to other techniques or imaging methods.     

Off-resonance frequency filtered magnetic resonance imaging

One of the main problems with rapid magnetic resonance imaging (MRI) techniques is the artifacts that result from off-resonance effects. The proposed off-resonance frequency filtered MRI (OFF-MRI) method focuses on the elimination of off-resonance components from the image of the observed object. To maintain imaging speed and simultaneously achieve good frequency selectivity, MRI is divided into two steps: signal acquisition and post-processing.     

基于改进KNN算法的AVS到H.264/AVC 快速转码方法

尽管音视频编码标准(Audio and Video Coding Standard,AVS)的编码性能可以与H.264相媲美,但是H.264的应用范围更加广泛,因此视频由AVS标准转码成H.264标准具有很大的应用前景.目前,主流的转码方法是将AVS的分块模式与H.264的分块模式映射的方式降低转码复杂度,但是技术之间的差异导致这两种标准之间的分块模式并不是一一映射的关系,因此会导致编码效率大幅度降低.提出一种基于改进KNN(K最邻近节点)算法的AVS到H.264/AVC快速转码方法.充分利用了AVS码流中的各种信息,通过改进的KNN算法建立了中间信息和H.264分块模式之间的映射模型.根据AVS中运动矢量信息的差异自适应确定H.264可能的分块模式,实验结果表明上述问题得到有效解决,该算法在保证H.264编码效率的前提下大幅降低了转码复杂度.     

Pseudo-V2 control with adaptive compensation for fast-transient current-mode buck converter

A type of pseudo-V² control, with on-chip adaptive compensation to achieve fast transient (FT) response for current mode DC–DC buck converter, has been proposed and simulated using 0.18 μm CMOS technology in this paper. Based on a new on-chip capacitor multiplier, adaptive compensation is achieved by making the compensation capacitance to track the load current. The proposed pseudo-V² control utilizes the output ripple to determine the duty cycle during load transient. Thus the overshoot/undershoot voltage and the transient recovery time are effectively reduced. Simulation results demonstrate the transient ripple is smaller than 50 mV and the transient recovery time is shorter than 10 μs for a 450 mA load current step. The maximum power conversion efficiency is 94.6% at 1 MHz switching frequency when input and output voltages are 5 V and 1.8 V, respectively.     

SUPERPOROUS HYDROGELS: FAST RESPONSIVE HYDROGEL SYSTEMS

ABSTRACT

Superporous hydrogels, hydrogels with pore sizes in the range of 100 μm and larger, were synthesized using N-isopropyl-acrylamide (NIPAM) and acrylamide (AM). The superporous hydrogels were synthesized by crosslinking polymerization of monomers in the presence of gas bubbles. The pores of superporous hydrogels were connected to each other to form open capillary channels, which provided fast response to the changes in the environmental temperature. Upon increase in temperature from 10°C to 65°C, the superporous hydrogel made from a monomer solution of NIPAM:AM = 9:1 shrank from the fully swollen state (volume of 36 cm³) to the fully collapsed state (volume of 6.5 cm³) in 72±14 sec. When the temperature was changed back to 10°C, the superporous hydrogel swelled to 36 cm³ in 78±15 sec. This deswelling-swelling cycle was repeated many times without changes in the thermo-reversible property of the superporous hydrogel. The response time of the superporous hydrogels was thousand times faster than that of conventional hydrogels. The fast response of the superporous hydrogels is due to the rapid uptake or exclusion of water molecules through the extensive capillary channels. Because superporous hydrogels still maintain the open capillary structure even after drying, the dried superporous hydrogels can also swell to the equilibrium swelling state within minutes. These fast responsive hydrogels can find many pharmaceutical and medical applications.     

Characterization and kinetic performance of 2.1 × 100 mm production columns packed with new 1.6 μm superficially porous particles

The overall kinetic performance of three production columns (2.1 mm × 100 mm format) packed with 1.6 μm superficially porous CORTECS‐C₁₈+ particles was assessed on a low‐dispersive I‐class ACQUITY instrument. The values of their minimum intrinsic reduced plate heights (h_min = 1.42, 1.57, and 1.75) were measured at room temperature (295 K) for a small molecule (naphthalene) with an acetonitrile/water eluent mixture (75:25, v/v). These narrow‐bore columns provide an average intrinsic efficiency of 395 000 plates per meter. The gradient separation of 14 small molecules shows that these columns have a peak capacity about 25% larger than similar ones packed with fully porous BEH‐C₁₈ particles (1.7 μm) or shorter (50 mm) columns packed with smaller core–shell particles (1.3 μm) operated under very high pressure (>1000 bar) for steep gradient elution (analysis time 80 s). In contrast, because their permeabilities are lower than those of columns packed with larger core–shell particles, their peak capacities are 25% smaller than those of narrow‐bore columns packed with standard 2.7 μm core–shell particles.     

Microplasma electrochemistry (MIPEC) strategy for accelerating the synthesis of metal organic frameworks at room temperature

Metal organic frameworks(MOFs) are a kind of promising materials in many applications,while the fast and controllable synthesis of MOFs is still challenging.Here,taking HKUST-1 as illustration,a microplasma electrochemistry(MIPEC) strategy was developed to accelerate the synthesis process of MOFs with micro-plasma acting as cathode.Treating the HKUST-1 precursor solution with micro-plasma cathode could not only transfer the electrons into the solution leading to the deprotonation effect,but also generate radical species to trigger and accelerate the nucleation and growth of MOFs at the plasmaliquid interface.Thus,uniform and nanosize MOFs could be prepared within minutes.The obtained MOFs show similar excellent uranium adsorption properties compared with those obtained by other method,with a highly adsorption capability of uranium with 550 mg/g in minutes.The novel MIPEC strategy developed in this work provides an alternative for controllable synthesis of MOFs,and especially has potential application in accelerating traditional organic synthesis.