User centric cloud service model in public sectors: Policy implications of cloud services

This study examines the acceptance of cloud computing services in government agencies by focusing on the key characteristics that affect behavioral intent. The study expanded upon the technology acceptance model by incorporating contextual factors such as availability, access, security, and reliability. The research model was empirically verified by investigating the perception of users working in public institutions. Modeling results showed that user intentions and behaviors were largely influenced by the perceived features of cloud services. Also these features were found to be the significant antecedents of cloud computing usefulness and ease of use. The findings should guide governments' promotion of cloud public services to increase user awareness by enhancing usability and appeal and ensuring security

A socio-technical framework for Internet-of-Things design

This study presents a case application of a socio-technical framework to assess and predict the development of the Internet of Things (IoT) in Korea. Applying a socio-technical system approach to the IoT, this paper seeks a clear understanding of how the IoT will evolve and stabilize in a smart environment. It investigates the complex interaction between social and technical aspects of the IoT, by highlighting the co-evolution, interaction, and interface, which constitute the next generation network environment. It describes the challenges in designing, deploying, and sustaining the diverse components of the IoT, and provides a snapshot of Korea's current approach to meeting this challenge. Finally, the findings of this study provide insights into these challenges and opportunities, by offering a socio-technical analysis of IoT development. The insights help to conceptualize how the IoT can be designed and situated within human-centered contexts

High Lithium Ion Transport Through rGO-Wrapped LiNi0.6Co0.2Mn0.2O2 Cathode Material for High-Rate Capable Lithium Ion Batteries

In this work, we show an effective ultrasonication-assisted self-assembly method under surfactant solution for a high-rate capable rGO-wrapped LiNi0.6Co0.2Mn0.2O2 (Ni-rich cathode material) composite. Ultrasonication indicates the pulverization of the aggregated bulk material into primary nanoparticles, which is effectively beneficial for synthesizing a homogeneous wrapped composite with rGO. The cathode composite demonstrates a high initial capacity of 196.5 mAh/g and a stable capacity retention of 83% after 100 cycles at a current density of 20 mA/g. The high-rate capability shows 195 and 140 mAh/g at a current density of 50 and 500 mA/g, respectively. The high-rate capable performance is attributed to the rapid lithium ion diffusivity, which is confirmed by calculating the transformation kinetics of the lithium ion by galvanostatic intermittent titration technique (GITT) measurement. The lithium ion diffusion rate (DLi) of the rGO-wrapped LiNi0.6Co0.2Mn0.2O2 composite is ca. 20 times higher than that of lithium metal plating on anode during the charge procedure, and this is demonstrated by the high interconnection of LiNi0.6Co0.2Mn0.2O2 and conductive rGO sheets in the composite. The unique transformation kinetics of the cathode composite presented in this study is an unprecedented verification example of a high-rate capable Ni-rich cathode material wrapped by highly conductive rGO sheets

Smithing Processes Based on Hammer Scale Excavated from the Third- to Fourth-Century Ancient Iron-Making Sites of the Korean Peninsula

The by-products of iron smelting and smithing include slag, flake hammer scale, and spheroidal hammer scale. The analysis of such iron-making by-products reveals critical information regarding the development of iron culture and the process characteristics. Using a metallographic microscope, SEM-EDS, and Raman micro-spectroscopy, we investigated the manufacturing process by examining the microstructure and determining the composition of the flake hammer scale and spheroidal hammer scale excavated from Korean Peninsula sites of iron manufacture during the Proto-Three Kingdoms Period, in the third and fourth centuries CE. Microstructure analysis confirmed that as the process progressed, the flake hammer scale’s thickness decreased owing to forging, which flattened the structure. Additionally, three layers were observed, with the surface layer identified as hematite (Fe2O3), the middle layer identified as magnetite (Fe3O4), and the inner layer identified as wüstite (FeO). The analysis of hammer scales revealed that the forging process to create iron bars required repeated working, following a refining process to remove impurities, confirming the division of labor in the smithing process. Correspondingly, the smithing process stages can be deduced from the structural shape and thickness of the hammer scale produced during the iron manufacturing process. Thus, the findings of this study are expected to be invaluable in furthering our understanding of the smithing process in detail, through future research on hammer scale

Chemical Composition, Crystal Structure, and Microstructure of Slags on the Korean Peninsula from the First Copper Production Remains of the 9th Century

The scarcity of excavated early-stage smelting sites related to copper production presents significant challenges in gaining a comprehensive understanding of the copper production process. However, the archaeological site discovered in 2018 in Daeryang-ri, Jinan-gun, Jeollabuk-do, boasts a substantial number of copper smelting remains and related slags, marking it as the first copper manufacturing production site identified on the Korean Peninsula. Consequently, this study selected 10 slag samples, chosen based on surface color and characteristics indicative of a connection to copper smelting, for scientific analysis to accurately ascertain the site’s nature. The primary component analysis of the slags indicated that CuO content ranged from 0.30 to 3.29 wt%, which, although not high, reveals significant quantities of FeO and SiO2. X-ray diffraction analysis revealed the presence of minerals such as cristobalite, along with fayalite and wüstite, commonly found in slags, varying by sample. Furthermore, microstructural observation revealed circular copper particles containing sulfur and iron, indicating the presence of copper particles in a matte state that have not been refined. This analysis suggests that the slags recovered from Jinan Daeryang-ri bear evidence of iron smelting at the site, with the slag being produced as an intermediate by-product during copper production

Development of Bisphenol-A-Glycidyl-Methacrylate- and Trimethylolpropane-Triacrylate-Based Stereolithography 3D Printing Materials

The main advantages of the three-dimensional (3D) printing process are flexible design, rapid prototyping, multi-component structures, and minimal waste. For stereolithography (SLA) 3D printing, common photocurable polymers, such as bisphenol-A glycidyl methacrylate (Bis-EMA), trimethylolpropane triacrylate (TMPTMA), as well as urethane oligomers, have been widely used. For a successful 3D printing process, these photocurable polymers must satisfy several requirements, including transparency, a low viscosity, good mechanical strength, and low shrinkage post-ultraviolet curing process. Herein, we investigated SLA-type photocurable resins prepared using Bis-EMA, TMPTMA, and urethane oligomers. The flexural strength, hardness, conversion rate, output resolution, water absorption, and solubility of the printed materials were investigated. The degree of conversion of the printed specimens measured by infrared spectroscopy ranged from 30 to 60%. We also observed that 64–80 MPa of the flexural strength, 40–60 HV of the surface hardness, 15.6–29.1 MPa of the compression strength, and 3.3–14.5 MPa of the tensile strength. The output resolution was tested using three different structures comprising a series of columns (5–50 mm), circles (0.6–6 mm), and lines (0.2–5 mm). In addition, we used five different pigments to create colored resins and successfully printed complex models of the Eiffel Tower. The research on resins, according to the characteristics of these materials, will help in the design of new materials. These results suggests that acrylate-based resins have the potential for 3D printing

Implications of cation-disordered grain boundaries on the electrochemical performance of the LiNi0.5Co0.2Mn0.3O2 cathode material for lithium ion batteries

Although lithium-mixed transition metal oxides (LiTM) have promising properties suitable for practical applications, unavoidable cation disorder in their structure during their synthesis or their operation leads to complex effects on their electrochemical performance. The microscopic mechanism of the cation disorder remains elusive owing to the lack of information on the atomic structures with specific chemical identities. In this study, the Li-content-dependent cation disorder phenomenon near the grain boundary of LiNi0.5Co0.2Mn0.3O2 particles is uncovered using atom-resolved chemical and valence mapping techniques. LiTM with 1% excess Li (LiTM101) shows outstanding electrical conductivity at the grain boundary, whereas no enhancement in the electrical conductivity is manifested in LiTM with 7% excess Li. Remarkably, this superior property of LiTM101 is coupled to the combined cation disorder of Ni and Co in the Li layer with their increased valences, while the Mn ions in both samples are not labile to migrate. This work highlights the hitherto hidden role of highly oxidized Co ions in the Li layer as a key agent for enhancing the electrochemical performance, together with Ni ions acting as pillars to stabilize the layered structure, thus providing a new insight for engineering stable and durable cathode materials with high performance. © The Royal Society of Chemistry 201

Efficient Inverted Solar Cells Using Benzotriazole-Based Small Molecule and Polymers

We synthesized medium-band-gap donor-acceptor (D-A) -type conjugated polymers (PBTZCZ-L and PBTZCZ-H) consisting of a benzotriazole building block as an acceptor and a carbazole unit as a donor. In comparison with the polymers, a small conjugated molecule (BTZCZ-2) was developed, and its structural, thermal, optical, and photovoltaic properties were investigated. The power conversion efficiency (PCE) of the BTZCZ-2-based solar cell devices was less than 0.5%, considerably lower than those of polymer-based devices with conventional device structures. However, inverted solar cell devices configured with glass/ITO/ZnO:PEIE/BTZCZ-2:PC71BM/MoO3/Ag showed a tremendously improved efficiency (PCE: 5.05%, Jsc: 9.95 mA/cm2, Voc: 0.89 V, and FF: 57.0%). We believe that this is attributed to high energy transfer and excellent film morphologies