[en] Addition of lithium nitrate admixture to the fresh concrete mixture helps to minimize potential problems related to alkali-silica reaction. For this admixture to function as an effective ASR control measure, it is imperative that the lithium ions remain in the pore solution. However, it was found that about 50% of the originally added lithium ions are removed from the pore solution during early stages of hydration. This paper revealed that the magnitude of the Li⁺ ion loss is highly dependent on the concentration of Li⁺ ions in the pore solution and the hydration rate of the cementitious systems. Using these findings, an empirical model has been developed which can predict the loss of Li⁺ ions from the pore solution during the hydration period. The proposed model can be used to investigate the effects of mixture parameters on the loss of Li⁺ ions from the pore solution of cementitious system

[en] This paper presents the results of the investigation on the effects of Li⁺ ions on the chemical and physical changes in the cementitious system undergoing alkali-silica reaction (ASR). Specifically, this paper focuses on determining which chemical steps of ASR processes are affected by the presence of Li⁺ ions in the pore solution in order to provide better understanding of the role of Li⁺ ions in the mitigation process of ASR. The results presented in this paper strongly support the hypothesis that the Li⁺ ions facilitate the formation of a physical barrier on the surface of reactive silica, and thus prevent further attack on the reactive sites by hydroxyl ions.

[en] Thermal energy management, especially cooling, is becoming increasingly important in today’s high energy consumption world. Passive cooling, which does not require additional energy consumption, could be an effective approach to thermal energy management. We analyzed spectral selective thermal emitters by investigating the performance of a type of passive cooling known as radiative cooling. Our results can be used to improve radiative cooling. As we can control the radiation characteristics of Metal-dielectric-metal (MDM) structures, we developed an MDM-based spectral selective emitter. We measured the spectral emissivity of the fabricated MDM structure in the direction of the zenith and at an incline. We also simulated structures of different sizes to determine the effect of varying the size of the structure on the emissivity. Finally, we calculated the radiative cooling performance of the selectively emissive surface. In these calculations, we considered temperature changes caused by atmospheric and surface radiation. The radiative cooling performance of our MDM-based spectral selective emitter was better than the cooling performance of a non-selective emitter. The surface temperature of the best MDM spectral selective emitter was 38 °C below the ambient temperature.

[en] The soft materials, which are used as the main materials of cosmetics, self-assemble into various nanostructures depending on the external condition such as concentration, additives, temperature, and pH. The cosmetics, which is made of soft materials, can have a variety of properties according to their nanostructures. Therefore, it is essential to resolve the nanostructure of soft materials for the development of a new product in cosmetics. In this project, therefore, we characterized the nanostructure of the soft materials (surfactants, polymer, etc.) used to the raw materials of cosmetics and applied it to develop a new product and to enhance the production process in cosmetics. Furthermore, we tried to develop the new nanostructure probing methods and applied it to characterize the nanostructure of various soft materials. For this purpose, we used the various nanostructure probing methods such as neutron and X-ray small angle neutron scattering techniques, Dynamic Light Scattering, polarized optical microscopy, etc.

[en] Recently, a new radiation treatment method using a high-energy accelerator facility has attracted attention. High-energy particles used in radiation therapy react with structures in the treatment room and generate secondary radiation, X-rays, and neutrons. In particular, neutrons have a higher biological weight than photons and are more harmful to normal tissue. However, CR-39, a general-purpose neutron dosimeter, cannot measure high-dose and high-energy neutrons. Therefore, this study calculated the neutron effective dose inside the high-energy accelerator irradiation room using the WWS and WWR functions of MCNP 6.2 to confirm the effective neutron dose that can be generated inside the high-energy accelerator room. And this result can be used to evaluate the neutron effective dose when an accident occurs inside the high-energy accelerator irradiation room. (author)

[en] This paper presents the results of the investigation on the fundamental differences in the viscoelasticity between alkali-activated fly ash/slag materials (AAMs) and cement pastes. The effects of the precursor and the activator on the rheological behaviour of AAM pastes were studied. Given the specific precursor, the activator viscosity significantly affected the AAM paste viscosity. The high viscous activator increased the plastic viscosity of AAM pastes by 4–8 times higher than that of cement paste and drastically decreased the yield stress due to viscous effects and weak colloidal interactions. Temporal changes in viscoelasticity showed that the negligible colloidal interactions between particles in AAM paste made the system non-percolated until the initial setting. This resulted in very different viscoelastic behaviour compared to the one from the well-percolated network in cement paste. Considering all results obtained in this study, the paper describes the short-term evolution of the AAM paste from the fresh condition to the initial setting.

[en] Highlights: • Filtered and unfiltered sodium silicate solutions were synthesised from RHA. • The dissolution efficiency of RHA in NaOH solution was 76.3%. • RHA-derived activator showed a structural build-up comparable to the commercial activator in AAM pastes. • The undissolved residues in the unfiltered RHA-derived activator increased the yield stress. • Comparable compressive strength and early age gel formation were observed from both commercial and RHA-derived solutions. Waste-derived sodium silicates (SSs) were synthesised from rice husk ash (RHA) to produce alkali activated materials (AAMs) using fly ash and slag as precursors. The effects of these SSs on the structural build-up were investigated by monitoring the evolution of the viscoelasticity, ultrasonic pulse waves, setting time, and infrared spectra. Two types of RHA derived SSs (filtered SS and unfiltered SS) were prepared to investigate the effect of the undissolved residue on the hardening process. The derived SS contained a large portion of monomer silicate species. The results showed that the structural build-up mechanism was comparable between the AAMs activated by the filtered SS and a commercial SS. The unfiltered SS increased the yield stress of the paste by up to 10 times. However, the residues in the unfiltered SS had insignificant impacts on the gel formation and compressive strength when using identical SiO₂/Na₂O and Na₂O/binder ratios in the mix design.

[en] Small, uniform Ag nanoparticles (NPs) in ionic liquids (ILs) are synthesized via simple sputtering route. The NPs embedded in polymer film are coated on top of InGaN/GaN active multiple quantum-well light-emitting structures and their optical characteristics are compared. The InGaN structures coated with Ag NPs show a significant increase in photoluminescence efficiency, mainly caused by localized surface plasmon (LSPs) coupling. Time-resolved (TR) photoluminescence analysis demonstrates that the coupling efficiency is 47.2%. The increased luminescence is caused by good energy matching between the surface plasmon and the light emitter. The authors believe that present work takes a first step to utilize the advantages of metal NPs synthesized in ILs and has a great potential for use in various optoelectronic devices. (copyright 2018 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

[en] Tractography using diffusion tensor magnetic resonance imaging (DT-MRI) is a method to determine the architecture of axonal fibers in the central nervous system by computing the direction of greatest diffusion in the white matter of the brain. To reduce the noise in DT-MRI measurements, a tensor-valued median filter, which is reported to be denoising and structure preserving in the tractography, is applied. In this paper, we proposed the successive Fermat (SF) method, successively using Fermat point theory for a triangle contained in the two-dimensional plane, as a median filtering method. We discussed the error analysis and numerical study about the SF method for phantom and experimental data. By considering the computing time and the image quality aspects of the numerical study simultaneously, we showed that the SF method is much more efficient than the simple median (SM) and gradient descents (GD) methods

[en] In this study, we have investigated the shielding evaluation methodology for facilities using kV energy generators. We have collected and analysis of safety evaluation criteria and methodology for overseas facilities using radiation generators. And we investigated the current status of shielding evaluation of domestic industrial radiation generators. According to the statistical data from the Radiation Safety Information System, as of 2022, a total of 7,679 organizations are using radiation generating devices. Among them, 6,299 facilities use these devices for industrial purposes, which accounts for a considerable portion of radiation. The organizations that use these devices evaluate whether the exposure dose for workers and frequent visitors is suitable as per the limit regulated by the Nuclear Safety Act. Moreover, during this process, the safety shields are evaluated at the facilities that use the radiation generating devices. However, the facilities that use radiating devices having energy less than or equal to 6 MV for industrial purposes are still mostly evaluated and analyzed according to the National Council on Radiation Protection and Measurements 49 (NCRP 49) report published in 1976. We have investigated the technical standards of safety management, including the maximum permissible dose and parameters assessment criteria for facilities using radiation generating devices, based on the NCRP 49 and the American National Standards Institute/Health Physics Society N.43.3 reports, which are the representative reports related to radiation shielding management cases overseas