A study of the cutting performance of poly-crystalline oxygen free copper with single crystalline diamond micro-tools

A study was carried out to investigate the crystallographic effects on the performance of cutting poly-crystalline oxygen free copper C10200 (OFC) with single crystalline diamond (SCD) micro-tools. At both large cutting depth and cross-feed rate, as the micro-tool traversed a grain with a crystallographic orientation less favorable for a stable machining process, the work material in front of the rake face was found to be severely deformed. This may lead to a reduced shear angle, thick chip, striation at the back of the chip, high cutting forces, degraded machined surface and the possibility of burr formation. The results showed minimal variations in the machined surface integrity and cutting forces compared to cut amorphous NiP plating with micro-tools. For a high cutting depth, burrs were also observed due to material deformation and pile-up occurring at the groove edges since the localized stress probably built up in front of the rake face. Cutting strategies were demonstrated to improve the performance of cutting OFC with micro-tools and to generate high aspect ratio micro-pillar arrays.     

Evaluation of a hot oil immersion drying method for the upgrading of crushed low-rank coal

Coal is the most abundant fuel on earth, and low-rank coal (LRC) such as sub-bituminous coal and lignite makes up about half of all coal deposits. LRC is inconvenient to use due to its low caloric value and high content of moisture together with the strong tendency of spontaneous combustion due to these oxygen rich coals, etc. Solving these problems would substantially improve the efficiency of LRC usage. In this study, we describe a drying technique utilizing hot oil immersion. This upgrading process may be executed easily under relatively low temperature condition due to the difference of heat capacity and thereby pressure gradient between coal and heating oil. This results in greatly reducing its energy cost. Drying tests of Indonesian lignite were performed with refined waste oil and B-C heavy oil, which were heated to 120°C, 130°C or 140°C. Following 10 min of treatment, the moisture content of the upgraded coal was improved from 32% to 2.0–3.2%, and its high heating value from 3,000 kcal/kg to 6,000 kcal/kg.     

Characterization of nanoparticles prepared by acid hydrolysis of various starches

Various starches of different AM contents and origins such as wx maize, normal maize, high AM maize, potato, and mungbean starches were hydrolyzed using a H₂SO₄ solution (3.16 M) at 40°C for 7 days, and the starch particles were isolated from the hydrolysates by centrifugation. The hydrolysis rates varied from 61.4 to 90.9% depending on the starch type. Unexpectedly, A‐type starches were more resistant to the acid hydrolysis than B‐type starches. XRD results revealed that the starch particles with B‐crystalline type exhibited a decrease in peak intensity. In addition, in a DSC analysis, the crystals remaining in the B‐type starch particles were readily disrupted in the water dispersion so that no melting endotherm appeared. Electron microscopy confirmed that the starch particles had round or oval shapes with diameters ranging from 40 to 70 nm, which possibly represented the starch blocklets in granules. The acid degraded mainly AM and long AP chains, resulting in increasing the proportion of short chains.     

Microbial community analysis of Korean soybean pastes by next-generation sequencing

Soybean pastes, doenjang, have long been consumed as a fortified protein source in Korea. The quality of doenjang is determined by fermentation and Bacillus subtilis is suspected to be the main microorganism responsible. In the current culture-independent analysis, 17,675 bacterial sequences were derived from nine local and two commercial brands of doenjang samples by a barcoded pyrosequencing method targeting the hyper-variable regions V1/V2 of the 16S rRNA gene. In contrast to what has previously been found using plating or conventional molecular biology based methods, doenjang contains a diversity of bacterial species (total 208 species) and each doenjang reflects a region-specific bacterial community. While the Bacillus species was thought to be dominant in soybean pastes, we found that they were in high abundance (58.3-91.6%) only in samples from the central region of Korea, whereas lactic acid bacteria (LAB) (39.8-77.7%) were the dominant bacterial members of other doenjang samples. Compared to local brands of doenjang, commercial brands contain simple microbial communities dominated by Tetragenococcus and Staphylococcus that resemble the microbial communities of Japanese miso; this suggests that artificial inoculation was used for the quality control and standardization of doenjang. In this study, a massive sequencing approach was applied for the first time to analyze the microbial communities of different doenjang samples. Thus, we have determined that massive sequencing is a valid approach for assessing the overall microbial community of Korean fermented soybean pastes.     

Catalytic behavior of V2O5 in rechargeable Li–O2 batteries

The possibility of using vanadium pentoxide (V₂O₅) as a catalyst in rechargeable lithium–oxygen (Li–O₂) batteries was studied. A V₂O₅-carbon composite was cast onto Ni foam to form a cathode. Electrochemical cells designed based on the flat cell manufactured by Hohsen Corporation were fabricated. The initial discharge capacity was 715 mA?h?g^?1, and the maximum discharge capacity reached 2,260 mA?h?g^?1 during the twelfth cycle. The cell had high capacity retention during cycling (1.24?% during cycles 2–8). V₂O₅ acted as a catalyst as well as an active material, improving the specific capacity and capacity retention of the non-aqueous Li–O₂ cell more effectively than do other materials.     

Pinch based approach to estimate CO2 capture and storage retrofit and compensatory renewable power for South Korean electricity sector

A pinch-based approach has been used to calculate optimum values of CO₂ capture and storage (CCS) retrofit and compensatory renewable power for the Korean electricity sector. Three cases are proposed. In the first case, KEPCO 2020 power generation forecast data were used to calculate CO₂ emissions and a 30% emission reduction target applied. For the second case, nuclear-free KEPCO 2020 forecast was used to calculate emissions along with 30% emissions reduction. In the third case, the emissions reduction target increased from 30% to 54.50% for case-2 scenario, in order to achieve 2005 emissions level. Results show that CCS retrofit and compensatory renewable power for case 3 is 2.6 times higher than case 1 and 1.8 times higher than case 2. According to sensitivity analysis results, CCS retrofit and compensatory renewable power for case 3 is more sensitive to CO₂ removal ratio and parasitic energy loss ratio, respectively, as compared to case 1 and case 2.     

A Robust and Cooperative MAC Protocol for IEEE 802.11a Wireless Networks

In wireless networks, it is well known that the interference of hidden nodes can interrupt frame receptions. Although several solutions have been proposed to alleviate the problem of DATA corruptions at receivers, control frame corruptions at transmitters have not been considered yet. In this paper, we propose an enhanced MAC protocol, called Robust and Cooperative Medium Access Control (RCMAC), to improve the network throughput and fairness by reducing control frame losses at transmitters. RCMAC uses a relay mechanism to allow transmitters of long distance links to receive control frames more robustly by relaying control frames via relay nodes. Furthermore, RCMAC improves the network throughput through fast two-hop DATA transmissions via relay nodes. Our extensive simulation results show that RCMAC has better performance than existing well-known MAC protocols.     

Evaluation of erosion resistance capacity on compacted weathered granite soil using non-destructive tests

This paper deals with the evaluation of the erodibility of compacted weathered granite soil through non-destructive tests. A rotating erosion cylinder test (RECT) was employed to evaluate the erosion resistance capacity of weathered granite soil with various relative densities and pre-consolidation pressures. In addition, non-destructive tests, i.e., electrical resistivity and bender element tests, were conducted to investigate a correlation between erosion resistance characteristic and non-destructive property. The results indicated that the critical shear stress increased with an increase in relative density and pre-consolidation pressure, and the threshold shear stress increased with an increase in relative density, while its increase was independent of an increase in pre-consolidation pressure. Thus, the relative density of weathered granite soil has a more significant effect on erosion resistance than its pre-consolidation pressure. The electrical resistivity and shear wave velocity increased with increases in relative density and pre-consolidation pressure, and these results had a good correlation with the porosity of weathered granite soils. The empirical equations for estimating the critical shear stress and the threshold shear stress of weathered granite soils, based on the relationship between the values of erosion resistance capacity normalized by those of non-destructive tests and porosity, were proposed. It is expected that the proposed correlation might be useful in determining the erosion resistance capacity of compacted weathered granite soil by using non-destructive tests.

     

Biopreservative potential of Lactobacillus plantarum YML007 and efficacy as a replacement for chemical preservatives in animal feed

Antifungal and biopreservation potentials of Lactobacillus plantarum YML007 isolated from Korean kimchi were analyzed. The biopreservative efficacy of the bacterium was analyzed using maize grains. Maize was divided into 3 groups and treated with a 5× concentrated cell-free supernatant of Lb. plantarum YML007 (T3R3), organic acids (T2R2), and a control group (T1R1) lacking treatment. All groups were stored for 30 days. Maize was tested for moisture and crude fat contents, mold growth, and aflatoxin production. The moisture content, mold count, and toxin production were higher in the control maize. The YML007 and acid treated maize remained uninfected after 30 days. Animals fed with YML007 treated maize showed more weight gain and less feed consumption. YML007 can be used to preserve the nutritional value of stored grain and to ensure better quality feedstuffs that are necessary for improving animal health and performance.