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A NbOx layer features forming-free bipolar threshold switching for the application to selector devices in crossbar array architectures through controlling conducting phases in the layer by precise deposition and interaction with a niobium electrode.

Fouling mechanisms associated with membrane-based polysaccharide enrichment were determined using a dense ultrafiltration (UF) membrane. Dextran with different molecular weights (MWs) was used as a surrogate for polysaccharides. The influence of dextran MW on fouling mechanisms was quantified using the Hermia model. Flux data obtained with different dextran MWs and filtration cycles were plotted to quantify the more appropriate fouling mechanisms among complete pore blocking, standard pore blocking, intermediate pore blocking, and cake filtration. For 100,000 Da dextran, all four mechanisms contributed to the initial fouling. As the filtration progressed, the dominant fouling mechanism appeared to be cake filtration with a regression coefficient (R2) of approximately 0.9519. For 10,000 Da, the R2 value for cake filtration was about 0.8767 in the initial filtration. Then, the R2 value gradually decreased as the filtration progressed. For 6000 Da, the R2 values of the four mechanisms were very low in the initial filtration. However, as the filtration progressed, the R2 value for cake filtration reached 0.9057. These results clearly show that the fouling mechanism of dense UF membranes during polysaccharide enrichment can be quantified. In addition, it was confirmed that the dominant fouling mechanism can change with the size of the polysaccharide and the duration of filtration.

The management of oyster shell disposal is an ongoing challenge in the southern coast of Korea because of continuously dumping the oyster shell in environment. Oyster shell wastes could be a biocidal alternative after calcination using a heat treatment. Calcined oyster shell is normally obtained through thermally conversion of CaCO3 (main component in oyster shell (96%)) into CaO. This study provides a brief overview of oyster shell disposal and its potential as an antimicrobial agent with a focus on calcination process, antimicrobial mechanisms, and packaging applications.

Owing to its biodegradability, non-toxicity, and biocompatibility, chitosan (Cs) is a ubiquitous biopolymer. However, applications of Cs are limited owing to the existence of strong inter- and intra-molecular hydrogen bonds within its network. To address this issue, we regenerated medium-molecular-weight Cs to enhance the physico-chemical and functional properties using a cationic approach. Accordingly, alkaline modification was employed to introduce an additional positive charge to the amine functional groups of Cs and moderately disintegrate the inter- and intra-hydrogen bonds. The chemical structure of Cs and regenerated chitosan (RCs) was confirmed through Fourier transform infrared and 1H-NMR spectroscopy. RCs showed higher zeta potential value compared to Cs. Additionally, using X-ray diffraction, RCs exhibited low crystallinity, which can be attributed to the repulsive force caused by the positive surface charge and the destruction of hydrogen bonds. The RCs exhibited stronger antioxidant activity than Cs. Furthermore, the minimum inhibition concentrations (MICs) of RCs against Escherichia coli and Staphylococcus aureus were reduced by almost four times compared with those of Cs. The superior functional properties of RCs can be attributed to the formation of a polycationic structure after alkaline modification. Thus, RCs can be introduced as potent agents for various biomedical purposes.

In South Korea, a reasonable rate system that can be domestically applied to calculate sewage and stormwater separately from the domestic sewage fee system is needed. This study proposed a phased pricing scenario to separate sewage and stormwater in Bupyeong-gu, Incheon, and the rate changes were compared based on a simulated calculation of the stormwater utility fee. In this investigation, stormwater runoff cases from other countries and the current domestic system were analyzed. A stormwater utility fee introduction scenario was presented that considers the impervious surface area. Water and sewage usage statistics and hydrant spatial data were collected from the Incheon Metropolitan City Waterworks Authority, and the total amount of water and sewage fees from the land use area were calculated. The stormwater utility fee was calculated, and the rates of each step were compared. The total sewage fee of Bupyeong-gu during 2014 was KRW 21,685,446,578, and the phased stormwater utility fee was calculated, assuming that 40% represents the stormwater cost. The sewage fee for the residential area in phase 3 decreased by 0.77% compared to phase 1. For the commercial areas, the sewage fee decreased by 36.87%. Because the impervious surface ratio was high, the overall area contributing to the impervious surface area was small. In the industrial area, the sewage fee increased by 8.35%. In the green area, the sewage fee increased by 37.46%. The sewage fee for the apartment complexes decreased by 10.6%. Finally, the possibility of estimating the actual stormwater utility fee was confirmed.

In this paper, a conceptual design for a reusable unmanned space vehicle was studied with multiple objective functions. To achieve this goal, a multi-objective genetic algorithm was used, and the performance of the space vehicle was evaluated based on weight, propulsion, aerothermodynamics, and trajectory analysis. Minimization of weight and landing speed and maximization of the highest CL in the supersonic flight regime were selected as the objective functions. The maximum limits in the dynamic pressure and the heat flux were applied as constraints. All objective functions are in trade-off relationships with each other. The geometry that produced the smallest weight had a very small wing size. Also, the vehicle that had the maximum CL in the supersonic flight regime had a closer angle between the flow and the lower surface of the wing, which showed the highest CL on the flat surface. The vehicle design with the lowest landing speed had the largest wing, which generated sufficient lift.

Recently, interest in the development of alternative water resources has been increasing rapidly due to environmental pollution and depletion of water resources. In particular, seawater desalination has been attracting the most attention as alternative water resources. As seawater desalination consumes a large amount of energy due to high operating pressure, many researches have been conducted to improve energy efficiency such as energy recovery device (ERD). Consequently, this study aims to compare the energy efficiency of RO process according to ERD of isobaric type which is applied in scientific control pilot plant process of each 100 ㎥/day scale based on actual RO product water. As a result, it was confirmed that efficiency, mixing rate, and permeate conductivity were different depending on the size of the apparatus even though the same principle of the ERD was applied. It is believed that this is caused by the difference in cross-sectional area of the contacted portion for pressure transfer inside the ERD. Therefore, further study is needed to confirm the optimum conditions what is applicable to the actual process considering the correlation with other factors as well as the factors obtained from the previous experiments.

Continuous measurement of atmospheric nanoparticles down to 3 nm was conducted in the Arctic (Zeppelin) from Oct 2016 to Dec 2018. The measured size distributions of particles from 3 nm to 60 nm were classified into distinct clusters with mode diameters of 10 nm (cluster 1), 20 nm (cluster 2), 30 nm (cluster 3), and 50 nm (cluster 4). Cluster 1 includes newly formed particles with high population which was often observed in summer season. A significant amount of nanoparticles down to 3 nm often appeared during new particle formation (NPF), suggesting that the NPF happened near the site rather than being transported from other regions after growth. The average NPF occurrence frequency per year was found to be 28%. The particle formation rate (J3-7) for particles in 3 nm to 7 nm was 0.044 cm-3 s-1 on average, ranging from 0.001 to 0.714 cm-3 s-1. The average growth rate (GR3-25) was around 2.62 nm h-1. Even though the NPF occurrence frequency in the Arctic was comparable to other areas (highly or moderately polluted areas), the intensity of NPF events (e.g. J3-7 and GR3-25) was much smaller than other continental areas. The increase of nanoparticles occurred more frequently when the air mass passed over the south and southwest ocean region, and concentration of NH3 increased in the NPF event days compared to non-event days, suggesting that that the marine biogenic and animal sources played important roles in the NPF. The NPF occurrence criteria previously developed was also applicable for the NPF in the Arctic.

Significance This report describes an opportunity for the bacterial cellulose nanofiber (BCNF) membrane, which has recently been attracting much attention due to its sustainability and high thermal stability, as a “single-layer,” good alternative membrane to the existing chemical-derived one in batteries, and thus allows us to find possible solutions to the environmental and safety issues. We achieved highest BCNF yield ever reported so far and fabricated a cylindrical lithium ion battery (LIB) by roll-to-roll process to realize remarkable cycle stability with 80% capacity retention even after 1,000 cycles, which is comparable to those of commercialized batteries. Finally, we introduced a Lewis base to improve thermal safety of the battery to a level comparable to that of a commercial ceramic-coated separator.

The increase in atmospheric CO2 concentration is responsible for progressive ocean acidification and has potential widespread effects on organic matter production and degradation. In order to understand the effect of elevated CO2 concentrations on organic matter dynamics, we conducted an in-situ mesocosm study in the mid-latitude coastal seas. Changes in the concentration and characteristics of organic matter, including particulate and dissolved fractions, as well as extracellular enzymatic hydrolysis of polysaccharides, were determined at six pCO2 levels ranging from 260 to 1040 ppmv over 19 days. The phytoplankton bloom and accumulation of dissolved organic carbon were observed in all pCO2 treatments. In the present study, although the elevated pCO2 positively influenced the quantity of organic matter, it did not affect its fluorescence characteristics and biodegradability. The highest hydrolysis potentials for polysaccharide degradation were recorded under highly acidified conditions (890 and 1040 ppmv). Our findings suggest that elevated CO2 concentrations could stimulate organic matter production and degradation, which in turn could lead to increased rates of organic carbon cycling.

Most memory-chip manufacturers keep trying to supply cost-effective storage devices with high-performance characteristics such as shorter tPROG, lower power consumption and higher endurance. For many years, every effort has been made to shrink die size to lower cost and to improve performance. However, the previously used node-shrinking methodology is facing challenges due to increased cell-to-cell interference and patterning difficulties caused by decreasing dimension. To overcome these limitations, 3D-stacking technology has been developed. As a result of long and focused research in 3D stacking technology, we succeed in developing 128 Gb 3b/cell Vertical NAND with 32 stack WL layers for the first time, which is the smallest 128 Gb NAND Flash. The die size is 68.9 mm $^{2}$ , program time is 700 us and I/O rate is 1 Gb/s.

In a memory hierarchy, there are various classes of memory systems depending on the access latency. A typical memory hierarchy consists of a CPU cache, DRAM, and an SSD or HDD. The DRAM has an access latency of 100ns, while flash memory has a latency of about 50μs [1]. Recently, new non-volatile memories with latencies of less than 10μs, including PRAM, MRAM, and ReRAM [2], are getting attention for business-critical systems such as big-data analysis and storage caches. To meet the low latency requirements, a new type of NAND flash, Z-NAND, with a read time (t R ) of 3μs has also been introduced [3]. Figure 20.2.1 shows a feature comparison between Z-NAND and conventional 3D NAND [4,5]. The Z-NAND achieves a read time of 3μs, which is 15–20 times faster than conventional NAND. Write throughput reaches up to 160MB/s with a 100μs program time. To further minimize read latency, I/O circuit support a DDR interface for both x8 and x16 mode. To take full advantage of such low-latency memory devices, reduction of memory access overhead is necessary. In this paper, we introduce an NVMe SSD controller which leverages the advantages of the low-latency NAND and enables the reduction of total memory access time, thereby minimizing overall system latency.