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Deep Value Function Networks for Large-Scale Multistage Stochastic Programs
No full textA neural networks-based stagewise decomposition algorithm called Deep Value Function Networks (DVFN) is proposed for large-scale multistage stochastic programming (MSP) problems. Traditional approaches such as nested Benders decomposition and its stochastic variant, stochastic dual dynamic programming (SDDP) approximates value functions as piecewise linear convex functions by gradually accumulating subgradient cuts from dual solutions of stagewise subproblems. Although they have been proven effective for linear problems, nonlinear problems may suffer from the increasing number of subgradient cuts as they proceed. A recently developed algorithm called Value Function Gradient Learning (VFGL) replaced the piecewise linear approximation with parametric function approximation, but its performance heavily depends upon the choice of parametric forms like most of traditional parametric machine learning algorithms did. On the other hand, DVFN approximates value functions using neural networks, which are known to have huge capacity in terms of their functional representations. The art of choosing appropriate parametric form becomes a simple labor of hyperparameter search for neural networks. However, neural networks are non-convex in general, and it would make the learning process unstable. We resolve this issue by using input convex neural networks that guarantee convexity with respect to inputs. We compare DVFN with SDDP and VFGL for solving large-scale linear and nonlinear MSP problems: production optimization and energy planning. Numerical examples clearly indicate that DVFN provide accurate and computationally efficient solutions
Safety analysis and evaluation of transport and storage container for very Low-Level liquid radioactive waste
No full textSafe temporary storage and transportation of the very low-level liquid radioactive waste generated during the Decommissioning and Decontamination (D&D) of nuclear power plants (NPPs) must be ensured. This study proposes a composite shielding transport container for very low-level liquid radioactive waste, which adheres to the industrial package (IP)-2 technical standards for packaging and transportation of radioactive materials. A shielding container based on barium sulfate (BaSO4) (a shielding material harmless to the human body) and a structurally reinforced frame were developed. Then, to confirm the structural safety of the container according to the regulations on the packaging and transportation of radioactive materials under drop weight and stacking tests, the Abaqus/Explicit program was used and on-site evaluations were performed. The maximum strains of about 8.8% and 2.2% were obtained in the drop-weight and stacking performance tests, respectively. Compared to the strain values of 40% at which high-density polyethylene (HDPE) could break, it was derived to be about 22% and 5.5%, respectively. The test satisfaction standard, that is, no loss or dispersion of radioactive contents and no shielding loss that could increase the radiation dose rate by more than 20% on the outer surface, were satisfied, confirming the safety of the container
Polythiophene-based terpolymers with modulated aggregation behaviors for high-performance organic solar cells with 16.6% efficiency
No full textPolythiophenes (PTs) are an attractive class of polymer donors (PDs) for organic solar cells (OSCs) owing to their relatively simple structures and scalable synthesis. Herein, a series of chlorinated thiazole-incorporated PT terpolymers are designed and high-performance OSCs with a power conversion efficiency (PCE) of 16.6% are demonstrated. By incorporating two different units, 3,3 & PRIME;-difluoro-2,2 & PRIME;-bithiophene (T2F2) and thieno[3,2-b] thiophene (TT), the aggregation properties of the terpolymers (PTz-FX; X = 0, 30, 50, 70, and 100, where X represents the mole percentage of T2F2 to total T2F2 +TT) are modulated. Among the PTz-FX series, PTz-F70 is found to be the optimal PD because its suitably tuned aggregation property leads to an optimized blend morphology with well-developed crystalline structures and donor-acceptor intermixed domains. The balanced morphology not only promotes charge generation/transport but also suppresses charge recombination in OSC devices. Thus, the PTz-F70-based OSCs achieve the highest PCE (16.6%), outperforming the OSCs based on PTz-FX with extremely strong (PTz-F100, PCE= 14.7%) or weak (PTz-F0, PCE = 12.0%) aggregation properties. The PCE of the PTz-F70-based OSCs is one of the highest performances among PT-based binary OSCs. This study highlights the importance of controlling the aggregation property of PTs for achieving high-performance PT-based OSCs
Ni(OH)(2)-SnO2 at the Hybrid Interface of Zeolite-Y and rGO for Electrochemical Oxidation of Methanol and Ethanol
No full textNickelhydroxide (Ni(OH)(2)) decorated in theframeworkof zeolite-Y and combined with SnO2, SnO2-Ni(OH)(2)-Y, was conceived as a cost-effective electrocatalyst forelectrochemical oxidation of methanol and ethanol (MOR and EOR). Significantenhancement in the current density was observed in both the electrochemicaloxidation processes on combining the SnO2-Ni(OH)(2)-Y with reduced graphene oxide (rGO). The maximum current densityin the case of the MOR was found to be 2.2 Amg(-1), while the same in the case of the EOR was found to be 2.0 Amg(-1). The prepared electrocatalyst SnO2-Ni(OH)(2)-Y/rGO was found to be superior in terms of stability comparedto SnO2-Ni(OH)(2)-Y. The current density did notdrop abruptly up to 1000 cycles, implying the high stability of thematerial under alkaline conditions. This was further evident fromthe chronoamperometry measurement. The linear relationship betweenthe current density and the square root of the scan rate also suggestedthat both the MOR and EOR followed the diffusion-controlled mechanism.The catalyst SnO2-Ni(OH)(2)-Y/rGO also exhibitedgood methanol and ethanol tolerance up to a maximum concentrationof 6 M
GEN-Click: Genetically Encodable Click Reactions for Spatially Restricted Metabolite Labeling
No full textGEN-Click is a genetically encoded copper-click reaction.It enables spatial biotin labeling of the azide or alkyne-tagged biomoleculesin live cells. Chemical reactions for the in situ modificationof biomolecules within living cells are under development. Among thesereactions, bio-orthogonal reactions such as click chemistry usingcopper(I) and Staudinger ligation are widely used for specific biomoleculetracking in live systems. However, currently available live cell copper(I)-catalyzedazide/alkyne cycloaddition reactions are not designed in a spatiallyresolved manner. Therefore, we developed the "GEN-Click"system, which can target the copper(I)-catalyzed azide/alkyne cycloadditionreaction catalysts proximal to the protein of interest and can begenetically expressed in a live cell. The genetically controlled,spatially restricted, metal-catalyzed biorthogonal reaction can beused for proximity biotin labeling of various azido-bearing biomolecules(e.g., protein, phospholipid, oligosaccharides) in living cell systems.Using GEN-Click, we successfully detected local metabolite-transferringevents at cell-cell contact sites
Identification and reconstruction of low-energy electrons in the ProtoDUNE-SP detector
No full textMeasurements of electrons from ?e interactions are crucial for the Deep Underground Neutrino Experiment (DUNE) neutrino oscillation program, as well as searches for physics beyond the standard model, supernova neutrino detection, and solar neutrino measurements. This article describes the selection and reconstruction of low-energy (Michel) electrons in the ProtoDUNE-SP detector. ProtoDUNE-SP is one of the prototypes for the DUNE far detector, built and operated at CERN as a charged particle test beam experiment. A sample of low-energy electrons produced by the decay of cosmic muons is selected with a purity of 95%. This sample is used to calibrate the low-energy electron energy scale with two techniques. An electron energy calibration based on a cosmic ray muon sample uses calibration constants derived from measured and simulated cosmic ray muon events. Another calibration technique makes use of the theoretically well-understood Michel electron energy spectrum to convert reconstructed charge to electron energy. In addition, the effects of detector response to low-energy electron energy scale and its resolution including readout electronics threshold effects are quantified. Finally, the relation between the theoretical and reconstructed low-energy electron energy spectra is derived, and the energy resolution is characterized. The low-energy electron selection presented here accounts for about 75% of the total electron deposited energy. After the addition of lost energy using a Monte Carlo simulation, the energy resolution improves from about 40% to 25% at 50 MeV. These results are used to validate the expected capabilities of the DUNE far detector to reconstruct low-energy electrons
A VCO-Based 2nd-Order ???2????????? Modulator for Small-Size High Energy-Efficient Current Sensing Front-End
No full textIn this letter, a 2nd-order ?? 2-??\?? modulator consisting of a voltage-controlled-oscillator-based quantizer (VCOQ) and a current digital-to-analog converter (DAC) with a pulse width modulator (PWM) is presented for the precise acquisition of a wide-range photocurrent in an area-and energy-efficient form factor. The proposed ?? 2-modulation realized by the 2nd-order infinite impulse response (IIR) filter on the feedback significantly attenuates the magnitude of input signals, enhancing the DR and linearity. Moreover, an additional differentiator followed by the VCOQ features the negative feedback loop in the 2nd-order ??\?? modulator, improving noise shaping with no additional current DAC noise. In addition, a 1-bit PWM current DAC substituting the multibit current DAC is devised to mitigate the noise from the current DAC, realizing the high resolution of 1 pA with 500-Hz bandwidth. The prototype chip fabricated in a 110-nm CMOS occupies 0.0308 mm2 and achieves Walden FoM of 4.15 pJ/conv
Dose analysis of nearby residents and workers due to the emission accident of gaseous radioactive material at the spent resin mixture treatment facility
No full textThe dose from a possible accident at a microwave-based spent resin mixture treatment facility that was to be installed and operated at the Wolsong nuclear power plant was analyzed to evaluate the radiological safety prior to its installation and operation. The dose to which workers and nearby residents are likely to be exposed was calculated based on the atmospheric dispersion and deposition factors using the XOQDOQ code. The highest atmospheric dispersion factors were 1.349E-05 s/m3 (workers) and 1.534E-06 s/m3 (residents). The highest doses due to emissions from the mock-up tank before operation were 1.91E-06 mSv (workers) and 1.78E-07 mSv (residents). Even after 3 h of operation, emissions from the mock-up tank had the greatest impact ranging from 4.63E-08 to 1.24E-06 mSv (workers) and 2.74E-10 to 1.16E-07 mSv (residents), respectively. The doses were 7.09E-09???4.55E-07 mSv and 4.18E-11???4.25E-08 mSv at 4???5 h of operation, and the maximum doses after operation reached 5.69E-07 mSv and 5.31E-08 mSv for the workers and residents, respectively.
Even at the exclusion area boundary (EAB), 4.76E-08???9.51E-07 mSv (annual dose:9.52E-05???1.90E-03 mSv/y) was below the dose limit of the EAB, and the safety of the facility installation inside the NPP was confirmed
