Search

A synthesis and patterning process of luminescent graphene quantum dots (GQDs) is highly desirable in applications to industrial- and bio-fields. In this paper, a novel strategy to obtain GQDs is proposed and demonstrated by an ion-beam assisted chemical vapor deposition (CVD). Ion-beam irradiation provides catalyst sources for the GQD creation. The luminescent GQDs are generated using a Fe-implanted Si wafer by a two-step annealing process: i) A formation step of nano-sized Fe catalyst particles and ii) a synthesis step of GQDs by a CVD method. Under the 1st annealing step of the Fe-implanted Si wafer, Fe nanoparticles (FeNPs) are created by the diffusion and aggregation of Fe atoms. Due to the high temperature atmosphere in the 2nd annealing step, FeNPs are then completely removed, and thus only high-purity and -quality GQDs are finally produced. In our work, patterned GQDs were fabricated by using a metallic mask during the ion-beam irradiation. Furthermore, various GQD patterns were also demonstrated by combining the conventional semiconductor manufacturing process and our ion-beam assisted CVD technique.

A device approach to manage the emission color of the organic light-emitting diodes (OLEDs) which show two emission processes of thermally activated delayed fluorescence (TADF) and phosphorescence was developed by engineering the host of the emitter. The emitting material was phenyl(10-phenyl-10H-phenoselenazin-3-yl)methanone (PSeBz) which emitted at 496 nm by TADF process and at 559 nm by phosphorescence process. The phosphorescence of the PSeBz emitter was selectively switched by the host because the triplet excitons can be intentionally quenched by the low triplet energy host. Therefore, the color coordinate of the OLEDs could be tuned from (0.35, 0.52) to (0.41, 0.52) by just changing the host of the PSeBz emitter.

Recently an induction heating system comprising a pair of no-insulation high-temperature superconductor (HTS) racetrack coils was built and now it is commercially available. It generates a direct current (dc) magnetic field in which a conductive metallic billet rotates at a high speed. Most dc induction machines accommodate a “single” billet per operation. This paper proposes an alternative concept of a “multiple-billet” induction heater, where the multiple billets can be simultaneously heated. The system consists of eight pairs of HTS racetrack coils that are placed in a circular pattern. An arbitrary number of billets may be placed and rotate at the same time in the space between racetrack coil pairs. The main goal in this paper is to theoretically demonstrate the principle of operation of the new multibillet system. The paper presents: first, overall system configuration and the principle of operation; second, electromagnetic design of the eight-pole HTS magnet; third, analyses with key operation parameters to estimate the multibillet heater performance. Due to the “positive” mutual inductance among neighbor racetrack coils, the multibillet system is estimated to deliver a larger heating power per billet than that of its single-billet counterpart for given operating conditions. Also, due to the eddy-currents induced in each billet, the power per billet reduces when the number of billets increases beyond an optimal value.

In accordance with the decommissioning plan for the Kori Unit 1 NPP, the reactor coolant system will be chemically decontaminated as soon as possible after permanent shutdown. This study developed the chemical decontamination process though the development project of decontamination technology of reactor coolant system and dismantled equipment for NPP decommissioning, which has been carried out since 2014. In this study, Oxidation/reduction process was conducted using system decontamination process development equipment of lab scale and was divided into unit and continuous processes. The optimal process time was derived from the unit process, and decontamination agent and the number of process were derived through the continuous processes. Through the unit process, the oxidation process took 5 hours and the reduction process took 4 hours. As optimum decontamination agent, the oxidizing agent was 200 mg·L-1 Permanganic acid + 200 mg·L-1 Nitric acid and the reducing agent was 2000 mg·L-1 Oxalic acid. In the case of the number of processes, all oxide films were removed during the two-cycle chemical decontamination process of STS304 and SA508. In the case of Alloy600, all oxide films were removed when chemical decontamination was performed for three cycles or more.

The measurement of critical current for HTS tape at various temperature conditions if generally used by the conduction cooling system with dc power supply. However, the continuously increasing dc current affects the temperature rising of metallic parts such as copper terminal for conduction cooling, HTS tape holder, current leads, and contact parts by joule heating. The temperature increasing seriously affects the measuring factors, which are voltage, resistance, or temperature, and then users may get the wrong results. To minimize the heating effect, the authors considered the pulsed current instead of dc current for power supply. A cryostat for HTS tape has cryogenic refrigerant for conduction cooling and metallic current lead for 2500 A. The voltage and temperature variations by pulsed and DC current of the same HTS tape are given in this paper. The test results show the possibility of the measurement method for critical current using pulsed power supply with conduction cooling system.

T2 MRI contrast agents cannot be synthesized by using molecules but nanoparticles because appreciable magnetic moments at room temperature are needed. Recently, some of lanthanide (Ln) oxide nanoparticles have shown decent magnetic moments at room temperature and even at ultrasmall particle diameters. In this study, we explored D-glucuronic acid coated Ln2O3 nanoparticles (Ln = Ho and Er) with ultrasmall particle diameters. They showed decent magnetic moments at room temperature and as a result, appreciable transverse water proton relaxivities (r2s) at 1.5 tesla MR field. Clear dose-dependent contrast enhancements in R2 map images were observed in both samples. These results showed that D-glucuronic acid coated Ln2O3 nanoparticles (Ln = Ho and Er) would be potential T2 MRI contrast agents at high MR fields.

Recently, high-temperature superconductor (HTS)-based devices have been applied to practical electric power systems. In order to increase the critical currents of HTS wires, wide and stacked HTS wires are being extensively researched. However, general systems for testing critical currents via voltage taps are not accurate for measuring the critical currents of wide and stacked HTS wires. This paper proposes an induced current-based performance measurement system for wide and stacked HTS wires. The system consists of wide and stacked HTS wires and induction coils made of 2G HTS wire. The electromagnetic performance of the HTS wires and induction coil is analyzed using a finite element method program. The basic structure of the performance measurement system is designed and fabricated based on the electromagnetic analysis results. In the experiment, the characteristics of the HTS wire are analyzed under charge and discharge conditions from the viewpoint of induced currents. The current of the stacked HTS wires is measured by a Rogowski coil. As a result, we can accurately identify the characteristics of the wide and stacked HTS wires, such as critical current and joint resistance.

POSCO and the Research Institute of Industrial Science and Technology developed a 10-kW superconducting synchronous generator using high-temperature superconducting wire. The generator consists of four-pole racetrack-type superconducting coils using GdBCO wire for rotor and 24 slots copper windings for stator. The rated power of the generator was 10 kW at 600 r/min, and the operating temperature was 30 K by thermosyphon cooling method using liquid neon. The output power was measured when the generator was connected to a vector motor, and the detailed results were discussed in this paper.

The combined steam and CO2 reforming reaction of CH4 was investigated using LaSrNiOx mixed oxides supported on Al2O3-modified β-SiC to elucidate the largely enhanced CO2 conversion at an optimal concentration of Al2O3 modifier. The dispersion of Al2O3 on the SiC support simultaneously altered the dispersion of LaSrNiOx crystallites increasing their strength when combined with the Al2O3-modified SiC. Although all tested catalysts showed similar activation energies, the increased Al2O3 dispersion on SiC at around 10 wt % Al2O3 modifier was well-correlated with the increased dispersion of active perovskite-like La2NiO4 crystallites which resulted in an enhanced catalytic activity. The formation of smaller NiO and La2NiO4 crystallites through an intimate contact with Al2O3 particles seems to be responsible for the suppressed aggregation of nickel crystallites during higher temperature reforming reactions. The higher amounts of CO2 adsorption on the well-dispersed basic lanthanum and strontium oxides contained...

DC reactors, made by aluminum busbar, are used to stabilize the arc of an electric furnace. In the conventional arc furnace, the transport current is several tens of kilo-amperes and enormous resistive loss is generated. To reduce the resistive loss at the DC reactor, a HTS DC reactor can be considered. It can dramatically improve the electric efficiency as well as reduce the installation space. Similar with other superconducting devices, the HTS DC reactor requires current leads from a power source in room temperature to the HTS coil in cryogenic environment. The heat loss at the metal current leads can be minimized through optimization process considering the geometry and the transport current. However, the transport current of the HTS DC reactor for the arc furnace is much larger than most of HTS magnets and the enormous heat penetration through the current lead should be effectively removed to keep the temperature around 70∼77 K. Current leads are cooled down by circulation of liquid nitrogen from the cooling system with a stirling cryocooler. The operating temperature of HTS coil is 30∼40 K and circulation of gaseous helium is used to remove the heat generation at the HTS coil. Gaseous helium is transported through the cryogenic helium blower and a single stage GM cryocooler. This paper describes design and experimental results on the cooling system for current leads and the HTS coil of 5 kA, 200 μH class DC reactor as a prototype. The results are used to verify the design values of the cooling systems and it will be applied to the design of scale-up cooling system for 50 kA, 200 μH class DC reactor.

For the conduction cooling application, epoxy impregnation is inevitable to enhance the thermal conduction. However, there have been several research results on the delamination problem with coated conductor and the main cause of the delamination is related with the different thermal contraction between epoxy, the insulation layer and the weak conductor. To avoid this problem, the amount of epoxy and insulation layer between conductors should be minimized or removed. Therefore, no insulation (NI) winding method and impregnation after dry winding can be considered to solve the problem. The NI coil winding method is very attractive due to high mechanical/thermal stability for the special purpose of DC magnets by removing the insulation layer. In this paper, the NI coil winding method and vacuum impregnation are applied to a HTS coil to avoid the delamination problem and enhance the mechanical/thermal stability for the conduction cooling application. Through the charging/discharging operation, electric/thermal characteristics are investigated at 77 K and 30 K.

Nanosized titanium oxide (TiO2) was synthesized in the channels of a porous coordination polymer (PCP) [La3+(1,3,5-benzenetrisbenzoate)]n by the sol–gel reaction of titanium tetraisopropoxide. XRD, IR, UV–vis, and gas sorption measurements demonstrated that nanosized TiO2 was formed in channels of the PCP. In this system, the resultant PCP⊃TiO2 composite showed enhancement of the adsorption of water. Furthermore, the sorption behavior of the composite could be changed by UV irradiation.

The water-soluble and biocompatible D-glucuronic acid coated Eu(OH)3 nanorods (average thickness x average length = 9.0 x 118.3 nm) have been prepared in one-pot synthesis. The D-glucuronic acid coated Eu(OH)3 nanorods showed a strong fluorescence at approximately 600 nm with a narrow emission band width. A cytotoxicity test by using DU145 cells showed that D-glucuronic acid coated Eu(OH)3 nanorods are not toxic up to 100 microM, making them a promising candidate for biomedical applications such as fluorescent imaging. The minimum Eu concentration needed for a conventional confocal imaging was estimated to be approximately 0.1 mM. Therefore, D-glucuronic acid coated Eu(OH)3 nanorods can be applied to fluorescent imaging. However, a very tiny magnetization of approximately 1.2 emu/g at room temperature and at an applied field of 5 tesla was observed. As a result, very small r1 and r2 water proton relaxivities were estimated, implying that surface coated Eu(OH)3 nanorods are not sufficient for MRI contrast agents.

Astrocytes support structure of central nervous system (CNS) and provide nutrients to neurons. When CNS is injured, astrocytes are activated and produce glia scar. There are debates if the reactive astrocytes give beneficial or harmful effects on neuronal regeneration. In vitro tissue culture systems successfully have been used to investigate how the astrocytes activity is regulated in response to environmental conditions. Physicochemical characteristics of supporting materials for tissue culture are one of the most important environmental conditions. Electrospun nanofiber has physical uniqueness such as high surface area to volume ratio and high porosity, which is favorable to tissue culture. However, cellular activities can also be regulated in response to surface chemistry, which can be modified easily and diversely. Poly(e-caprolactone) (PCL) is widely used for a scaffold for tissue culture. In this research, oxygen plasma-treated PCL nanofiber was assessed to ascertain whether it can have such potentials to regulate astrocytes activity. As a result, oxygen plasma treatment increased the hydrophilicity of the PCL nanofiber which made adhesion and viability of astrocytes enhanced without cytotoxicity Activation of astrocytes in the plasma treated scaffolds was confirmed by the fact of upregulation of glial fibrillary acidic protein. Above all, oxygenated nanofiber provides an initial culture environment which makes astrocytes activated. © 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 101B: 1267–1274, 2013.

Nanomaterials are attractive for use in biological systems due to their ability to control the microenvironment of cells. Additionally, nanofibers can mimic fibrous characteristics of natural tissues. This study was conducted to assess astrocyte activity and infiltration behavior on Spirulina extract-embedded polycaprolactone (SP-PCL) nanofiber. Astrocytes moved along with the nanofiber, and developed an elongated and stellate shape, which is similar to those in the natural neural tissue. In addition, the expression of GFAP, a biomarker representing the activation of astrocytes, was gradually up-regulated with the increase of the concentration of Spirulina extract, indicating that Spirulina extract can control astrocyte activation. Overall, the results presented herein indicate that SP-PCL nanofiber could be used in astrocyte tissue engineering for neuronal regeneration.

Porous coordination polymers (PCPs) have been recently highlighted because of their high synthetic designability in structure and functions. Because of their ordered nanoporous structures with a large surface area and tunable pore surface functionality, PCPs have emerged as a significant class of nanoporous materials with potential applications in gas storage, separation, catalysis, and chemical sensing. Recent research has shown the utility of PCPs as host materials for the confinement of nanoparticles of inorganic polymers (IPs), such as metals, metal oxides, and metal chalcogenides. The fabrication of IP nanoparticles in PCPs (PCP⊃IP) has been studied for manifesting specific nanosized-dependent properties and host-guest synergistic functions. In this review, we describe the recent progress in the accommodation of IPs in the nanochannels of PCPs and the remarkable functions of the composite materials.

The effect of the distribution of CeO2–ZrO2 on Ni/MgAl2O4 catalyst on the catalytic performance during the combined steam and carbon dioxide reforming of CH4 (CSCR) was investigated on two different catalysts prepared using a sequential impregnation and co-precipitation of Ni and CeO2–ZrO2 components. The CeO2–ZrO2 plays an important role in the CO2 conversion by enhancing a facile activation of CO2 with an adjacent contact with nickel crystallites. The CSCR catalysts prepared by the co-precipitation of nickel and CeO2–ZrO2 on MgAl2O4 support shows a catalytic activity superior to the catalyst prepared by sequential impregnation of nickel on the MgAl2O4 support with CeO2–ZrO2 due to the homogeneous distribution of CeO2–ZrO2 with the formation of small nickel crystallites and a large amount of active sites for CO2 adsorption.

This paper describes the design results, loss analysis, and experiment testing of the real manufactured toroid-type superconducting magnetic energy storage (SMES). We analysed heat load through the conduction and radiation of the cryostat and magnetization loss caused by the charging and discharging of the toroid-type SMES system. We also measured the characteristics of toroid-type SMES under three different types of operating conditions (steady state, one-cycle charging and discharging, series charging and discharging). The fundamental design specifications and the data obtained from the experiment will be applied to a large-scale toroid-type SMES system design.

This paper proposes a quench detection method applied to a HTS coil and also discusses the results of tests on an HTS BSCCO wire and an HTS YBCO coil. A series-type thermocouple was fabricated to detect quench, where several thermocouples were welded in series. As the series-type thermocouple has many points of detection, variation in temperature was detected at each point by using thermo-electromotive force. The feasibility of the proposed method was investigated through the quench detection tests on the YBCO coil. This method has advantages such as a simple structure and cost effectiveness and also protects the HTS coil by detecting partial quench and its propagation.

The authors designed and manufactured a toroidal-type superconducting magnetic energy storage (SMES) system. The toroidal-type SMES was designed using a 3D CAD program. The toroidal-type magnet consists of 30 double pancake coils (DPCs). The single pancake coils (SPCs), which constitute the double pancake coils, are arranged at an angle of 6° from each other, based on the central axis of the toroidal-type magnet. The cooling method used for the toroidal-type SMES is the conduction cooling type. When the cooling method for the toroidal-type SMES was designed, the two-stage Gifford–McMahon (GM) refrigerator was considered. The Bi-2223 HTS wire, which was made by soldering brass on both sides of the superconductor, is used for the magnet winding. Finally, the authors connected the toroidal-type SMES to a real-time digital simulator (RSCAD/RTDS) to simulate voltage sag compensation in a power utility.

Superconducting magnetic energy storage (SMES) can overcome fluctuations in frequency because of its fast response time in charging and discharging energy. To stabilize the fluctuations in frequency of wind power generation systems (WPGSs), HTS SMES systems should be connected to the terminal of the WPGSs. Ulleung Island's power network in Korea was modeled with a real-time digital simulator (RTDS) to demonstrate the effectiveness of SMES at stabilizing frequency. A toroid-type HTS SMES cooled by conduction cooling and a DC/DC chopper to charge and discharge current were fabricated for the experiment. The simulation results show the frequency stabilization effected by the HTS SMES system with its operational characteristics such as real time variation in current and temperature.

Sol−gel polycondensation of tetramethoxysilane was performed in nanochannels of porous coordination polymers (PCPs), resulting in the formation of nanosized silica dispersed homogeneously inside the channels. In this system, the growth of silica was highly constrained, which increases the hydrophilic silanol moieties on the surface of silica particles. Deposition of silica particles into the nanochannels of PCPs could allow the remarkable alternations of the porous properties of the PCPs. Compared to the original PCP systems, adsorption of water was greatly enhanced because of the strong interaction between silica and water. The PCP−silica nanocomposites preferred to adsorb 1,4-dioxane rather than cyclohexane, showing the remarkable affinity of PCP−silica hybrids to hydrophilic molecules. It is noteworthy that pore dimensionality of PCPs have large effects on the adsorption properties of PCP−silica hybrids. Compared to a PCP with three-dimensional interconnecting nanochannels, a PCP with one-dimensional p...

This paper analyzed the heat characteristics of a conduction cooling toroidal-type SMES magnet. The authors designed and manufactured a conduction cooling toroidal-type SMES magnet which consists of 30 double pancake coils. One (a single pancake coil) of a double pancake coil is arranged at an angle of 6° from each other. The shape of the toroidal-type SMES magnet was designed by a 3D CAD program. The heat invasion was investigated under no-load condition and the thermal characteristic of the toroidal-type SMES magnet was analyzed using the Finite Elements Method program. Both the analyzed and the experiment results are compared and discussed in detail.

High temperature superconducting (HTS) power cables offer an innovative transmission line that differs from conventional technologies because HTS power cables can send bulk power with extremely low loss. This paper investigates the loss characteristic of HTS DC power cable considering harmonic current caused by power electronic devices in practical power systems. We focused on the losses of HTS DC power cables and designed a model cable using YBa 2 Cu 3 O 7 HTS wire. The losses under DC current with harmonic components at 77 K are measured. The lower DC transport current yields more losses with the same ripple current in the unsaturated region. If DC transport current is increased within the critical current, the high frequency ripple current will have less influence on the loss. It was clearly monitored that the losses are proportional to the magnitude of the ripple current and the frequency in this study.

The authors calculated the loss of the High Temperature Superconducting (HTS) model cable using Norris ellipse formula, and measured the loss of the model cable experimentally. Two kinds of measuring method are used. One is the electrical method, and the other is the calorimetric method. The electrical method can be used only in AC condition. But the calorimetric method can be used in both AC and DC bias conditions. In order to propose an effective measuring approach for Ripple Dependent Loss (RDL) under DC bias condition using the calorimetric method, Bismuth Strontium Calcium Copper Oxide (BSCCO) wires were used for the HTS model cable, and the SUS tapes were used as a heating tape to make the same pattern of the temperature profiles as in the electrical method without the transport current. The temperature-loss relations were obtained by the electrical method, and then applied to the calorimetric method by which the RDL under DC bias condition was well estimated.

This paper analyses operating characteristic of high temperature superconducting magnetic energy storage (HTS SMES) for frequency stabilization of dispersed power generation system. The wind power generation system (WPGS) fluctuates due to wind speed variation and affects the frequency and voltage fluctuations of the utility. SMES is probably a key technology to overcome these fluctuations. To stabilize power system frequency, a large-scale HTS SMES is connected to the terminal of the WPGS. The authors analysed the load side frequencies using two different configurations of SMES, one consisting of a single magnet and the other of a dual magnet. From the simulation results, it can be concluded that the SMES is a useful device for stabilizing the power system frequency fluctuations, and a dual magnet type SMES is more effective for frequency stabilizing but exhibits more AC loss due to the increased operating current than a single magnet type.

Studies on (YBCO) coated conductor (CC) are actively underway for the practical application of high temperature superconducting (HTS) devices such as magnets, cables and fault current limiting devices because the CC has higher critical current characteristics under high temperature and magnetic field. However, it is hard to make a long-length of YBCO CC tape with uniform critical current density using the present processing techniques. The hot spot will emerge in a local region if the critical current is non-uniform along the HTS tape, and eventually, the hot spots may cause serious damage to the HTS tape. Therefore, it is important to examine the thermal stability characteristic of the YBCO CC tape from the quench protection point of view. In this paper, the segmental critical current of a YBCO CC sample tape is measured in liquid nitrogen, and a heater is installed at the center of the sample tape in order to examine the normal zone propagation characteristics in the longitudinal direction under the adiabatic condition with a Gifford-McMahon cryocooler. Measurements are performed as a function of heat input and transport current for the operating temperatures of 77 K, 65 K and 40 K, respectively, and the results are discussed in detail.

This paper investigates the mechanical stresses of a toroidal-type superconducting magnet (TSM). The TSM is designed by 3D CAD program. The Bi-2223 high temperature superconducting (HTS) wire made by soldering brass on both sides of the superconductor is used for the magnet winding. The TSM consists of 30 double pancake coils (DPC). Single pancake coils (SPC) constituting the double pancake coils are arranged at an angle of 6 from each other based on the central axis of the TSM. The mechanical stresses due to the Lorentz force caused by the operating current are analyzed using FEM. These fundamental data will effectively be applied to design a toroidal-type superconducting magnetic energy storage.

The thermal stability of nickel silicide (NiSi) on a silicon-on-insulator (SOI) substrate after postsilicidation annealing (550–700 °C) is discussed in this paper. Nickel silicide technology, used for nanoscale complementary metal oxide semiconductor (CMOS) field-effect transistor (FET) devices, has a fundamental problem of thermal stability. Three different Pd concentrations in Ni–Pd alloy, 1, 5, and 10 at. %, were used to study the thermal stability of nickel silicide formed by a silicidation process. The Ni–Pd (10%) sample showed good thermal stability upon annealing at temperatures up to 700 °C for 30 min. Only a low-resistivity mononickel silicide (NiSi) phase peak was observed by X-ray diffraction (XRD) measurement, which was confirmed by Auger electron spectroscopy (AES) analysis. Uniformly formed nickel silicide with a good interface profile was obtained using the Ni–Pd (10%) sample according to field-emission scanning electron microscopy (FE-SEM) measurement. However, the Ni–Pd (5%) sample produced high-resistivity nickel disilicide (NiSi2) after annealing at 650 °C for 30 min. Four different layer structures, Ni, Ni/TiN, Ni/Co/TiN, and Ni–Pd (10%)/Co/TiN, were also used for further study. Among these structures, the Ni–Pd (10%)/Co/TiN layer structure had good thermal stability upon annealing at temperatures up to 700 °C, while the other structures deteriorated due to agglomeration above 550 °C.

The effects of a strained silicon layer on the thermal stability of nickel (germano)silicide for nanoscale complementary metal oxide semiconductor field-effect transistor (CMOSFET) devices are discussed in this study. Three different thicknesses, 5, 13, and 40 nm, of silicon layers on silicon germanium (SiGe) were prepared for this experiment. The effects of the silicidation rapid thermal annealing (RTA) temperature and postsilicidation annealing temperature for the different silicon layer thicknesses were studied. For comparison, a bulk silicon substrate and a SiGe substrate were also used. Silicides with the thin strained silicon layers (5 and 13 nm) on SiGe showed good thermal stability in this study. However, the other silicides using bulk silicon, 40-nm-thick silicon on SiGe, and the SiGe substrate underwent degradation due to silicide agglomeration during annealing. A SiO2 layer was found on the silicide using the SiGe substrate. In this study, several analysis methods such as four-point probe measurement, field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and Auger electron spectroscopy (AES) were used for detailed study.

The 3D type, flower-like ZnO nanostructures from particle to flower-like or chestnut bur are fabricated on the GaN epitaxial layer substrate through the simple-route hydrothermal process. Structural characterization was made for the ZnO 3D nanostructures synthesized in different pH ranging from 9.5 to 11.0. The growth model was proposed and discussed regarding the fabrication mechanism and morphology of ZnO 3D flower-like nanostructure. The flower-like ZnO is composed of many thin single crystals ZnO nanorods. Bigger and thicker ZnO structure is fabricated with the increase of pH in solution. The enhanced UV emission in the PL measurement and the spectra in the Raman spectroscopy for ZnO–GaN heterojunction material were discussed.

The dependence of longitudinal (r1) and transverse (r2) water proton relaxivities of ultrasmall gadolinium oxide (Gd2O3) nanoparticles on the surface coating ligand-size was investigated. Both r1 and r2 values decreased with increasing ligand-size. We attributed this to the ligand-size effect. In addition the effectiveness of d-glucuronic acid-coated ultrasmall Gd2O3 nanoparticles as T1 magnetic resonance imaging (MRI) contrast agents was confirmed by measuring the in vitro cytotoxicity and using in vivo T1 MR images in a mouse in a 1.5 T MR field.

Tissue engineering using a biomaterial including bioactive compounds has been researched as a way to restore injured neural systems. Extracellular polymeric substances (EPS) extracted from marine seaweeds have been known to produce positive effects on physiological activities in human tissues. In this study, an electrospun nanofiber containing brown seaweed EPS was proven to be a candidate biomaterial for neural tissue engineering. Glial fibrillary acidic protein (GFAP) as a specific marker protein increased in the astrocytes cultured on the polycaprolactone (PCL) nanofiber containing EPS (EPS-PCL nanofiber), compared with PCL nanofiber. The upregulation of GFAP indicates that the EPS-PCL nanofiber induced astrocyte activation, which supports physiological agents favorable to restore injured neural tissue. Astrocytes could infiltrate into the EPS-PCL nanofiber mat without toxicity, comparable to PCL nanofiber. These results imply that EPS-PCL nanofiber could be a useful biomaterial to regulate astrocyte activity at a molecular level and could be considered as a novel therapeutic material for neural tissue engineering.

There is no doubt that the molecular imaging is an extremely important technique in diagnosing diseases. Dual imaging is emerging as a step forward in molecular imaging technique because it can provide us with more information useful for diagnosing diseases than single imaging. Therefore, diverse dual imaging modalities should be developed. Molecular imaging generally relies on imaging agents. Mixed lanthanide oxide nanoparticles could be valuable materials for dual magnetic resonance imaging (MRI)-fluorescent imaging (FI) because they have both excellent and diverse magnetic and fluorescent properties useful for dual MRI-FI, depending on lanthanide ions used. Since they are mixed nanoparticles, they are compact, robust, and stable, which is extremely useful for biomedical applications. They can be also easily synthesized with facile composition control. In this study, we explored three systems of ultrasmall mixed lanthanide (Dy/Eu, Ho/Eu, and Ho/Tb) oxide nanoparticles to demonstrate their usefulness as dual T-2 MRI-FI agents.

were between 20 ~ 30 years old. The hairs were burned in a furnace at 300 o C for 1 h in the presence of air atmosphere. BHH was immersed in water, and the solution was analyzed for metals content. The mixture was stirred for 1 h at room temperature. Then, the solution was filtered off, and the solution was analyzed for metal concentrations and the amount of metal adsorbed was estimated. BHH was characterized by EDX, IR, TGA, and SEM. BHH is a brittle stable solid under air and moisture. SEM images show that BHH has a main channel with diameters in the range of 20 ~ 40 µm and satellite channels with diameters in the range of 1 ~ 2 µm as shown in Figure 1 and Supporting Information. The formation of channels indicates that the surface of hairs is different from the bulk of hairs in chemical properties. The human hairs take a weight-loss of 23% at 300 o C, and then a weight-loss of 76% at 600 o C (Figure S2). According to EDX results (Supporting Information), BHH [C (66%), O (30%), S (4%)] shows increase in oxygen, and decrease in sulfur, relative to non-burned human hairs [C (64%), O (21%), S (15%)]. Such a porous morphology has wide surface area, and thus may be a driving force for metal-adsorption. Of course, the formation and preservation of porous morphology may be indebted to the part burning rather than the complete burning of the human hairs.

The characteristics of the tri-axial high temperature superconducting (HTS) power cable are different from a general copper cable, depending on whether the cable is under steady state or transient state, which is caused by quench. Before applying the tri-axial HTS power cable to a real utility, the system should be analyzed using certain simulation tools in order to confirm the effects of the cable on the real utility. However, a component that has the same impedance characteristics as the real tri-axial HTS power cable is not provided in simulation tools. In this paper, a model component for the tri-axial HTS power cable was developed in PSCAD/EMTDC. The developed model component included characteristics of the HTS cable, such as resistance, reactance, and temperature variation. The model component for the tri-axial HTS power cable was applied to a model power system and a simulation was performed under transient state. The simulation results show the effect of the tri-axial HTS power cable on the power system, the variation of quench resistance, and the temperature of the cable under fault conditions according to superconducting characteristics. The results of this work will be used to analyze the transient characteristics of other types of HTS power cables.

This paper considers the insulationless high-temperature superconducting (HTS) magnet as a new and innovative concept for dc applications due to its benefits as compared to conventional HTS magnets with insulation layers between HTS conductors. The purpose of this paper is to study the operating characteristics of an insulationless HTS magnet. The normal operating characteristics of the insulationless HTS magnet were investigated according to the various current levels. Thermal stability of the insulationless HTS magnet was also analyzed. The critical current of the insulationless HTS magnet was measured at 40 K. The temperature distribution of the insulationless HTS magnet was measured using thermocouples. The experiment results demonstrate superior thermal stability characteristics in the insulationless HTS magnet. Thus, it is confirmed that the thermal performance of large-scale HTS magnets can be enhanced by applying insulationless magnets instead of general insulated HTS magnets.