[en] Sm₂Co_14.75Fe_1.5Ti_0.75 nano-flakes have been prepared by surfactant-assisted ball milling (SABM) in the organic solvent of heptane with the surfactants of oleic acid. The effects of ball milling time on phase composition and magnetic properties were systematically studied. The experimental results show that the synthesized nano-flakes have an amorphous phase and a hexagonal 2:17-type crystalline phase with [001] in-plane crystallographic texture induced by SABM without any external magnetic field. The coercivity value of the as-prepared nano-flakes was 5.0 kOe and then was enhanced to 6.0 kOe by the magnetic alignment for the sample ball-milled for 4 h. The remanence value of the un-aligned nano-flakes is lower than that of the magnetically aligned ones. In addition, the magnetically aligned nano-flakes exhibit a maximum energy product (BH) max of 56 kJ/m³ and a small misalignment angle h of 11°, which is the best value ever reported. The magnetic anisotropy behavior was also observed in both aligned and un-aligned nano-flakes. (author)

[en] Measurement of Thermal-hydraulic Data using simulated HANARO fuel assemblies. Triangular, square, and hexagonal test sections, which use 3, 4 and 7 fuel element simulators(FES) respectively, are developed to get bundle CHF data for HANARO. The thermal power was compared with supplied electric power identified as the product of voltage and current. A total of 36 bundle CHF data were produced. All data were believed to be reliable because of similar temperature history during experiments. Acoustic signals from the hydrophone were measured and analyzed before and after ONB. Frequency analysis showed clear differences in the power spectral density for 3 different frequencies before and after ONB. Analysis of Flow Field Calculational models of 3 important parts of the HANARO, i.e., inlet plenum, chimney and reactor pool are developed to analyze the flow field. The commercial CFX-4 code was used. Database Framework For end-users, the experimental data and analysis results from the project are loaded in a draft database and is installed in the homepage (//www.kaeri.re.kr/~rrad) of the research reactor analysis department of HANARO operation team. The heat transfer data obtained in the HANARO design stage is also included in the database with limited access

[en] In this paper, Bi(2223) silver clamp thick film with J_c=1.5x 10⁴A/cm² at 77 K and 0 T is fabricated by a physical deposition method. Voltage-current characteristics and magnetoresistance were investigated in detail at low magnetic fields. It can be concluded that the transport J_c limitation of the present samples was still dominated by weak links although their connectivity has been greatly improved in comparison with bulk materials. The weak links may exert an effective pinning on flux lines. When the transport current exceeds the critical current of weak links their resistances change, just as does the flux flow resistance of traditional type-II superconductors. A history effect of the magnetoresistivity below a certain field (about 1.0 kG) was found at various constant measuring currents and can be ascribed to the J_c (H) characteristics and flux trapping both in the weak link network and the grains

[en] The HANARO uses finned-element fuel bundles. For thermal-hydraulic safety analysis, used is the MATRA-h code which is a modified version of KAERI's MATRA-α. The subchannel analysis model was determined by using the in-core irradiation test results and hydraulic experiment results for fuel bundle. The validity of the analysis model was investigated by comparing the MATRA-h predictions with the experimental results from several bundle CHF tests. The comparison showed that the code predictions for the CHF power were very close to or less than the experimental results. Thus, it was confirmed that the subchannel analysis using MATRA-h is to be applicable to the prediction of CHF phenomenon in HANARO fuel bundle

[en] Microstructure evolution and properties were studied in a low carbon low alloyed hot-rolled bainitic steel by annealing and annealing plus tempering. Microstructure of the hot-rolled steel consists of lath bainite and martensite. By annealing at 720 °C for 30 min and water quenching, multi-phase microstructure consisting of intercritical ferrite, tempered bainite/martensite, retained austenite and fresh martensite was obtained. With increasing annealing temperature to 760 °C, microstructure of the steel consisted of intercritical ferrite, fresh martensite without retained austenite. After the second step of tempering at 680 °C for samples annealed both at 720 °C and 760 °C, ~ 8–9% volume fraction of retained austenite was obtained in the multi-phase microstructure. Moreover, fine precipitates of VC with size smaller than 10 nm and copper precipitates with size of ~ 10–50 nm were obtained after tempering. Results from scanning transmission electron microscopy (STEM) give evidence to support that the partitioning of Mn, Ni and Cu is of significance for retained austenite stabilization. Due to the combined contribution of multiphase microstructure, the transformation-induced-plasticity effect of retained austenite and strengthening effect of nanometer-sized precipitates, yield strength greater than 800 MPa, yield to tensile ratio of 0.9, uniform elongation of ~ 9% and good low temperature impact toughness of 147 J at − 40 °C were achieved. - Highlights: • Stable retained austenite was produced in a low alloyed steel. • Partition of Mn, Ni and Cu was confirmed by STEM for austenite stabilization. • Nano-sized VC and Cu precipitates were achieved by second tempering. • High strength–high toughness with low Y/T ratio was obtained.

[en] The reduced order model methods are very useful for real-time or many-query simulations of nuclear reactors. The common way for the reduced order models construction is a reduction of the preliminary calculated snapshots by the proper orthogonal decomposition methods. But an implementation of this approach for the high-fidelity real-size problems becomes very expensive due to a large computation cost of the one snapshot. To escape this problem the reduced basis element method is suggested to use. The method is based on a spatial decomposition of the reactor core and computation of the reduced bases on each subdomain. An efficiency of the method is confirmed by calculations of the two-dimensional core with pin-level resolution. (authors)

[en] We have studied the sequence of phase transformations induced in the Zr-Al binary system by mechanical alloying of mixed Zr and Al powders. The structure of these materials has been studied by transmission electron microscopy and by x-ray diffraction measurements. Three different metastable phases have been found experimentally with variation of the initial composition x_Al: (1) a nanocrystalline supersaturated solid solution of α-Zr for x_Al≤0.15, (2) an amorphous phase for 0.15< x_Al≤0.4, and (3) a metastable face-centered-cubic phase for x_Al=0.5 with a grain size of 4 nm. The crystallization reaction of the amorphous phase was monitored by differential scanning calorimetry, and the kinetics of the reaction have been examined as well. A possible explanation based on thermodynamic arguments is given for the defect-driven vitrification of the crystalline Zr phase

[en] Electrocardiogram (ECG) signal is nonlinear and non-stationary weak signal which reflects whether the heart is functioning normally or abnormally. ECG signal is susceptible to various kinds of noises such as high/low frequency noises, powerline interference and baseline wander. Hence, the removal of noises from ECG signal becomes a vital link in the ECG signal processing and plays a significant role in the detection and diagnosis of heart diseases. The review will describe the recent developments of ECG signal denoising based on Empirical Mode Decomposition (EMD) technique including high frequency noise removal, powerline interference separation, baseline wander correction, the combining of EMD and Other Methods, EEMD technique. EMD technique is a quite potential and prospective but not perfect method in the application of processing nonlinear and non-stationary signal like ECG signal. The EMD combined with other algorithms is a good solution to improve the performance of noise cancellation. The pros and cons of EMD technique in ECG signal denoising are discussed in detail. Finally, the future work and challenges in ECG signal denoising based on EMD technique are clarified.

[en] A volume reduction of the concrete waste by appropriate treatment technologies will decrease the amount of waste to be disposed of and result in a reduction of the disposal cost and an enhancement of the efficiency of the disposal site. Our group has developed a decontamination process for uranium-contaminated (U-contaminated) concrete, and some experiments were performed to reduce the second radioactive waste. A decontamination process was developed to remove uranium from concrete waste. The yellow or brown colored surface of the wall brick with high concentration of uranium was removed by a chisel until the radioactivity of remaining block reached less than 1 Bq/g. The concrete waste coated with epoxy was directly burned by an oil flame, and the burned surface was then removed using the same method as the treatment of the brick. The selective mechanical removal of the concrete block reduced the amount of secondary radioactive waste. The concrete blocks without an epoxy were crushed to below 30 mm and sifted to 1 mm. When the concrete pieces larger than 1 mm were sequentially washed with a clear recycle solution and 1.0 M of nitric acid, their radioactivity reached below the limit value of uranium for self-disposal. For the concrete pieces smaller than 1 mm, a rotary washing machine and electrokinetic equipment were also used

[en] The numerical models for HANARO have been coded in simulation program. The program simulates the core kinetics, the cooling systems, the reactivity control systems, and the digital controllers at the personal computers. The various initial conditions can be set. Because the simulator can be controlled by the operator in accordance with the HANARO operation principles, it will be used as a tool for the operator training. And it can be upgraded to dynamic test bed for the control system development if the I/O features are extended