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The ground-based gravitational-wave telescopes such as LIGO, Virgo, and KAGRA are very complicated and sensitive compositions of advanced devices. Therefore, they are influenced not only by the mutual interaction among mechanical and electronics systems but also by the surrounding environment. To categorize and reduce noises from many channels interconnected by such instruments and environment for achieving the detection of gravitational waves, it needs to increase a signal-to-noise ratio and reduce false alarm rate from coincident spurious events. Therefore, it is of great importance to identify associations between inter-correlated channels. In this work, we present a novel tool called CAGMon for identifying (non-) linear couplings between inter-correlated channels, which can be applied to the practical cases of the gravitational-wave detector.

It has been suggested that the freshwater flux due to the recent melting of the Antarctic ice-sheet/shelf will suppress ventilation in the Southern Ocean (SO). In this study, we performed idealized earth-system simulations to examine the impacts of Antarctic meltwater on the biomass of surface phytoplankton in the Antarctic Ocean. The enhanced stratification due to the meltwater leads to a decrease in surface nitrate concentration, but an increase in the surface concentration of dissolved iron. These changes are associated with the reduced upwelling of nitrate-rich deep water and the trapped iron exported from terrestrial sediment. Because of the limited iron availability in the SO, the trapped iron in surface water enhances the chlorophyll concentration in the open ocean. However, in the marginal sea along the Antarctic coastline where the iron is relatively sufficient, a nitrate reduction induces a chlorophyll decrease, indicating a regime shift from iron-limited to nitrate-limited conditions.

A new 1200 V punch through-insulated gate bipolar transistor (PT-IGBT) with a protection circuit employing a lateral IGBT (LIGBT) and a floating p-well voltage sensing scheme is proposed and implemented by fabricating the main IGBT and gate voltage pull-down circuit using the widely used planar IGBT process. The detection of the fault and gate voltage pull-down operations is achieved using the floating p-well sensing scheme. The LIGBT used as a pull-down transistor reduces the area of the protection circuit due to the enhanced current handling capability. The voltage saturation effect of a floating p-well voltage under the high voltage condition provides the 1200 V PT-IGBT with a reliable and rapid protection by preventing the gate oxide failure of the pull-down LIGBT and eliminating the blanking filter.

This paper describes a single-aperture MEMS probe and a MEMS probe array for the measurement of biological properties. We designed and fabricated the single-aperture MEMS probe using surface micromachining and verified it by measuring the permittivity of a standard liquid before introducing the MEMS probe array. The actual aperture size of the single-aperture MEMS probe is only 390 µm × 80 µm, which is very small in comparison with the conventional laser-machined coaxial probe. In order to show the feasibility of the proposed single-aperture MEMS probe for permittivity measurements, we performed in vitro measurements of 0.9% saline. Once the single-aperture probe was verified, we proposed the concept of a probe array for biological measurements and experimentally showed the suitability of the MEMS probe array for biological applications through experiments using pork. The MEMS probe array consists of five microstrip feed lines, each of which is followed by open-ended strip lines, and the permittivity measurement of each port is separately performed through the use of a conventional multiport coaxial switch (Agilent, HP 87106 C), followed by a network analyzer (HP 8510 C). Through broadband measurements of 0.9% saline and pork using the MEMS probe array, we were able to discriminate the muscle and fat of pork through just one contact by placing the MEMS probe array on the boundary of muscle and fat. This newly proposed MEMS probe array has great potential in terms of disposability, low cost, integration with planar circuits and a short detection time for biological measurements.

We developed a silicon MEMS probe for permittivity measurements using an adhesive bonding process. Only two photolithographic masks are required to fabricate the probe, which can be implemented through simple bonding processes using silicon substrates and a benzo cyclo butene (BCB) adhesive layer. Undoped silicon substrates with thicknesses of 300 ?m are used as the dielectric layers of the proposed probe. BCB layers, which have good electrical properties at high frequencies as well as adhesive properties for the bonding process, play the role of bonding materials between the two silicon substrates. The length of the probe is 30 mm, and the aperture located at the tip of the probe is 1.1 mm ? 0.62 mm. The permittivity of 0.5% saline was measured, and the results agreed with the values obtained through the Cole?Cole equation. To validate the feasibility of this probe for practical biological applications, we also performed in vivo measurements of the muscle, skin and blood of mice. Due to the simple fabrication process, the cost of the probe can be reduced in comparison with the previous micromachined probe (Kim et al 2005 J. Micromech. Microeng. 15 543?50) as well as the conventional laser machined probe. Low cost leads to disposability, which is an important factor for practical biomedical applications; and thus, coupled with the probe's capabilities of MMIC integration and CMOS compatibility, this probe has excellent potential in the field of microwave permittivity measurements.

In magnetic resonance electrical impedance tomography (MREIT), we measure the induced magnetic flux density inside an object subject to an externally injected current. This magnetic flux density is contaminated with noise, which ultimately limits the quality of reconstructed conductivity and current density images. By analysing and experimentally verifying the amount of noise in images gathered from two MREIT systems, we found that a carefully designed MREIT study will be able to reduce noise levels below 0.25 and 0.05 nT at main magnetic field strengths of 3 and 11 T, respectively, at a voxel size of 3 x 3 x 3 mm(3). Further noise level reductions can be achieved by optimizing MREIT pulse sequences and using signal averaging. We suggest two different methods to estimate magnetic flux noise levels, and the results are compared to validate the experimental setup of an MREIT system.

A multi-megawatt long pulse ion source (LPIS) was developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) neutral beam (NB) injector. Arc discharge characteristics of the ion source were investigated on the NB test stand. The ion source consists of a magnetic bucket plasma generator with multi-pole cusp fields and a set of tetrode accelerators with circular apertures. The inner volume of the ion source, including the accelerator column, is approximately 150 litres. Design requirements for the ion source were a 120 kV/65 A deuterium beam and a 300 s pulse length and initially an 80 kV/48 A hydrogen beam for a 20 s pulse length. Arc discharges of the plasma generator with hydrogen gases have been controlled by the emission-limited mode, operated by the applied heating voltage of the cathode filaments. Stable and efficient arc plasmas, with a maximum arc power of 110 kW, have been produced by a constant voltage (CV) mode operation of an arc power supply. The CV mode operation of the arc powers was more efficient than the constant power (CP) mode operation in the LPIS. A maximum ion density of 9.1 × 1011 cm−3 was measured by using electrostatic probes. The plasma non-uniformity of the ion source was less than 8% and was under the design limit. An optimum arc efficiency, defined by the ratio of extractible ion beam current to arc input power, of 0.46 A kW−1 was estimated for the CV mode operation and 0.44 A kW−1 for the CP mode operation. This arc efficiency is enough to extract the expected hydrogen beam of 48 A.

We present cross-sectional conductivity images of two biological tissue phantoms. Each of the cylindrical phantoms with both diameter and height of 140 mm contained chunks of biological tissues such as bovine tongue and liver, porcine muscle and chicken breast within a conductive agar gelatin as the background medium. We attached four recessed electrodes on the sides of the phantom with equal spacing among them. Injecting current pulses of 480 or 120 mA ms into the phantom along two different directions, we measured the z-component Bz of the induced magnetic flux density B = (Bx, By, Bz) with a magnetic resonance electrical impedance tomography (MREIT) system based on a 3.0 T MRI scanner. Using the harmonic Bz algorithm, we reconstructed cross-sectional conductivity images from the measured Bz data. Reconstructed images clearly distinguish different tissues in terms of both their shapes and conductivity values. In this paper, we experimentally demonstrate the feasibility of the MREIT technique in producing conductivity images of different biological soft tissues with a high spatial resolution and accuracy when we use a sufficient amount of the injection current.

We implemented a micromachined probe for the measurement of biological properties using MEMS technology, and experimentally showed the suitability of the micromachined probe in biological applications. The micromachined probe was fabricated on a silicon substrate, and to remove wave transmission through the silicon substrate, we etched the silicon substrate from beneath a lower ground and made the etched silicon surface conducting by using thermal evaporation of Cr/Au and a coating of conductive epoxy. The micromachined probe consists of a CPW and strip line between benzo cyclo butene (BCB) layers, which is known to be a material with high resistivity, low loss tangent, and low permittivity at high frequency. We measured the permittivity of a number of well-known liquids—0.5%, 0.9% and 1.3% saline, acetone, ethanol, and muscle and fat of pork—as biological samples using the micromachined probe after liquid calibration. The measured permittivity of 0.9% saline agreed well with the expected value of the Cole–Cole equation. In this paper, we first demonstrate that the micromachined probe can provide broadband measurement of measurable solid materials, such as biological samples, and also of well-known liquids at microwave frequencies. The size of the micromachined probe is 2000 µm (width) × 580 µm (thickness) × 30 000 µm (length), and the aperture size of the micromachined probe is only 650 µm × 70 µm. Therefore, we can extract the biological information from very small biological tissues and reduce radiation effects. Thus we show the feasibility of low-cost, small and portable permittivity measurement systems using a micromachined open-ended coaxial RF MEMS probe.

In magnetic resonance electrical impedance tomography (MREIT) we inject currents through electrodes placed on the surface of a subject and try to reconstruct cross-sectional resistivity (or conductivity) images using internal magnetic flux density as well as boundary voltage measurements. In this paper we present a static resistivity image of a cubic saline phantom (50 x 50 x 50 mm3) containing a cylindrical sausage object with an average resistivity value of 123.7 ohms cm. Our current MREIT system is based on an experimental 0.3 T MRI scanner and a current injection apparatus. We captured MR phase images of the phantom while injecting currents of 28 mA through two pairs of surface electrodes. We computed current density images from magnetic flux density images that are proportional to the MR phase images. From the current density images and boundary voltage data we reconstructed a cross-sectional resistivity image within a central region of 38.5 x 38.5 mm2 at the middle of the phantom using the J-substitution algorithm. The spatial resolution of the reconstructed image was 64 x 64 and the reconstructed average resistivity of the sausage was 117.7 ohms cm. Even though the error in the reconstructed average resistivity value was small, the relative L2-error of the reconstructed image was 25.5% due to the noise in measured MR phase images. We expect improvements in the accuracy by utilizing an MRI scanner with higher SNR and increasing the size of voxels scarifying the spatial resolution.

The on-line learning of a mixture-of-experts system is studied in the framework of statistical physics. The time dependence of the overlap-order parameters during training is calculated analytically in the thermodynamic limit. When the number of training examples is small each expert is in a symmetric state. As the number of time steps approaches a critical point, the symmetric state begins to disintegrate. This symmetry-breaking behaviour is accounted for by means of a gating network. In the symmetric state the gating network has little effect on the learning, but when the symmetry is broken the gating network assigns the experts to appropriate subspaces in the input space. A generalization curve shows a plateau between the symmetric- and broken-symmetry states. We also find that the learning curves show different behaviours depending on the stiffness of the gating function.

A neutral beam test-stand (NBTS) system has been developed for the extraction of a 300 s deuterium beam of 120 kV/65 A as an auxiliary heating system of Korea Superconducting Tokamak Advanced Research (KSTAR). The prototype long pulse ion source (LPIS) consists of a plasma generator and a set of tetrode accelerators. Beam extraction for 300 s was achieved at a maximum hydrogen beam power of 1.6 MW (70 kV/23 A) with an arc discharge power of 63 kW. The energy distribution of the ion source was analyzed by water-flow calorimetry (WFC) by monitoring the cooling-water temperature during the arc discharge. The power dissipation rate on the accelerator column was 0.97% of the total extracted ion beam power with a power loss of 0.2% caused by the collision of back stream electrons with the electron dump plate of the plasma generator. 74.2% of the total energy of was estimated to be distributed in the plasma generator and the accelerator for an arc discharge of 300 s. Also, 75.6% of the total energy was distributed in the ion source for an arc discharge of 2 s. The remaining energy was lost through the structures around the water-cooling path.

We study learning from examples by higher-order perceptrons, which realize polynomially separable rules. The model complexities of the networks are made 'tunable' by varying the relative orders of different monomial terms. We analyse the learning curves of higher-order perceptrons when the Gibbs algorithm is used for training. It is found that learning occurs in a stepwise manner. This is because the number of examples needed to constrain the corresponding phase-space component scales differently.

We study a fully-connected parity machine with K hidden units for continuous weights. The geometrical structure of the weight space of this model is analysed in terms of the volumes associated with the internal representations of the training set. By examining the asymptotic behaviour of order parameters in the large K limit, we find the maximum number , the storage capacity, of patterns per input unit to be up to leading order, which saturates the mathematical bound given by Mitchison and Durbin. Unlike the committee machine, the storage capacity per weight remains unchanged compared with the corresponding tree-like architecture.

We present theoretical investigations via the replica theory of the storage capacities of committee machines with a large number M of hidden units and spherical weights. Difficulties arise in the solution of this problem in the limit of large M. In the case of overlapping receptive fields, as the number of patterns increases, both permutation symmetry and replica symmetry are broken, which leads to the appearance of many order parameters and causes additional difficulty. We observe that the relations among these order parameters yield a set of quantities which are small in the limit of large M, making the asymptotic calculation tractable. Using the one-step replica symmetry breaking scheme, we compute the asymptotic value of the storage capacity per input unit in the limit of large M. We find that . The shift to the case of non-overlapping receptive fields can be made easily; we then find . Both values satisfy the bound of Mitchison and Durbin.

The in vivo function and phenotype of ovarian follicle cells are determined by many factors. When these cells are removed from the in vivo microenvironment and grown in a 2D in vitro environment, the function of the follicular cells is difficult to preserve. A collagen hydrogel was used to examine the hormone and oocyte maturation of ovary follicles in a 3D culture system. Ovarian follicles from rats were isolated and cultured in various concentration of type I collagen hydrogels ranging from 1% to 7% (weight/volume). Differences in cell survival, follicle growth and development, sex hormone production, and oocyte maturation were seen with the modifications in the collagen hydrogel density and elasticity. The results show the significance of the collagen hydrogel properties on phenotype and function maintenance of the ovarian follicles in a 3D culture system.

We demonstrate the effects of overlap condition and surface wettability of dielectric layers on the drying process and crystalline structure of inkjet-printed semiconductor layers. 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS pentacene) was utilized to inkjet-print the semiconductor layer. Using various overlap conditions, semiconductor layers were inkjet-printed on dielectric layers with different surface wettabilities. It is observed that crystal growth and the resulting crystalline structures in inkjet-printed semiconductor layers are primarily determined by evaporation behavior, particularly the contact line movement of the drying semiconductor layers, which can be controlled via the overlap condition. With inappropriate overlap conditions, randomly oriented TIPS pentacene crystalline structures are generated in the semiconductor layer through irregular contact line recession. One-dimensionally oriented TIPS pentacene crystal structures can be obtained using the optimized overlap condition of 50% as a result of the uniform contact line movement. Relatively hydrophobic dielectric layers help to generate good crystallinity in the semiconductor layer. All-inkjet-printed organic thin film transistors (OTFTs) with well-oriented TIPS pentacene crystalline structures in the semiconductor layer show a high field effect mobility of ~0.1 cm2 V−1s−1, suggesting that, when printing inkjet semiconductor layers, the overlap condition and surface wettability of the dielectric layer are important factors for generating a well-oriented crystalline structure and thereby fabricating high-performance all-inkjet-printed OTFTs.

The paper aims to investigate the influence of bottom electrode configurations in all-inkjet-printed organic thin film transistors (OTFTs) on crystalline structures of semiconductor layers as well as the electrical performance of OTFTs. Two different types of all-inkjet-printed OTFTs were fabricated: one type with a new bottom-top contact configuration and the other type with a conventional bottom-bottom contact configuration. The crystal growth of semiconductor layer and the electrical characteristics of OTFTs were evaluated and compared between two different bottom electrode configurations. The resulting crystalline structures of semiconductor layers are mostly affected by the evaporation process of semiconductor layer. Randomly-oriented crystalline structures are generated in the semiconductor layer with a conventional bottom-bottom contact configuration due to irregular evaporation. However, a new bottom-top contact configuration leads to well-oriented crystalline structures because of controlled contact line movement. The average mobility of OTFTs with well-oriented crystalline structures is about 11 times as high as that with randomly-oriented crystalline structures.

In the ear reconstruction field, tissue engineering enabling the regeneration of the ear's own tissue has been considered to be a promising technology. However, the ear is known to be difficult to regenerate using traditional methods due to its complex shape and composition. In this study, we used three-dimensional (3D) printing technology including a sacrificial layer process to regenerate both the auricular cartilage and fat tissue. The main part was printed with poly-caprolactone (PCL) and cell-laden hydrogel. At the same time, poly-ethylene-glycol (PEG) was also deposited as a sacrificial layer to support the main structure. After complete fabrication, PEG can be easily removed in aqueous solutions, and the procedure for removing PEG has no effect on the cell viability. For fabricating composite tissue, chondrocytes and adipocytes differentiated from adipose-derived stromal cells were encapsulated in hydrogel to dispense into the cartilage and fat regions, respectively, of ear-shaped structures. Finally, we fabricated the composite structure for feasibility testing, satisfying expectations for both the geometry and anatomy of the native ear. We also carried out in vitro assays for evaluating the chondrogenesis and adipogenesis of the cell-printed structure. As a result, the possibility of ear regeneration using 3D printing technology which allowed tissue formation from the separately printed chondrocytes and adipocytes was demonstrated.

In this paper, a two-step flash light sintering process for inkjet-printed Ag films is investigated with the aim of improving the quality of sintered Ag films. The flash light sintering process is divided into two steps: a preheating step and a main sintering step. The preheating step is used to remove the organic binder without abrupt vaporization. The main sintering step is used to complete the necking connections among the silver nanoparticles and achieve high electrical conductivity. The process minimizes the damage on the polymer substrate and the interface between the sintered Ag film and polymer substrate. The electrical conductivity is calculated by measuring the resistance and cross-sectional area with an LCR meter and 3D optical profiler, respectively. It is found that the resistivity of the optimal flash light-sintered Ag films (36.32 n? m), which is 228.86% of that of bulk silver, is lower than that of thermally sintered ones (40.84 n? m). Additionally, the polyimide film used as the substrate is preserved with the inkjet-printed pattern shape during the flash light sintering process without delamination or defects.

Resistive random access memory (RRAM) with a new structure which can effectively control switching area and electric field is proposed. It has been verified that the decrease in area of resistive material with the new structure increases electric field of switching area, and that such increased electric field makes initial forming at unipolar switching rather easier, resulting in effective decrease in forming voltage. Also, as the area in switching area is effectively reduced, decrease in reset current and set voltage in a limited area has also been verified. Excellent resistive switching characteristics are possible by decrease of conductive filament (CF) area in our structure. Random circuit breaker (RCB) simulation model which can effectively explain percolation switching similar to unipolar switching verifies such structural effect.

To analyze and explain the gradual reset switching property of the bipolar switching resistive random access memory (RRAM) for multilevel cell (MLC) operation, the effect of the amount of plasma oxidation on the gradual reset switching behavior of the Al/TiO2-based RRAM cell structure is investigated. The device that undergoes plasma oxidation in a shorter time has a better ON/OFF current (I ON/I OFF) ratio and shows increased ON current (I ON). The device that undergoes long plasma oxidation occasionally shows the step reset switching behavior because of the thick conductive filament formation in the ON state. This is clearly explained by the different conduction mechanisms during the ON state.

We firstly propose a novel resistive random access memory (RRAM) cell structure, which makes it possible to minimize the switching area and to maximize the electrical field where resistive switching occurs, resulting in the improvement of resistive switching characteristics. With excellent structural advantages, resistive switching characteristics such as reset current and set voltage fluctuation are improved through the enhancement of conductive filament (CF) controllability. A simple fabrication process is delivered and the device performance from the viewpoints of the forming voltage, set voltage, and reset current is investigated. Conducting defect effects are also investigated in comparison with the conventional RRAM cell structure. Numerical simulation is performed using a random circuit breaker (RCB) model to confirm the proposed structure.

A new technical improvement in understanding the resistive switching characteristics of unipolar resistive random access memory (RRAM) is investigated. It is possible to minimize reset current (I RESET), set voltage variation, and forming voltage (V FORMING), which results in a wide sensing margin and high density applications by using a conducting filament (CF) minimized structure up to a 10 nm technology node. Its structural advantages enable I RESET to be tuned with excellent manufacturability. Numerical simulation is also performed using a random circuit breaker (RCB) model, showing that the proposed structure elucidates the resistive switching improvement.

The dark state of homogeneously aligned liquid crystal displays (LCDs) associated with the in-plane switching of a LC director depends on their molecular ordering. We propose a new approach to reduce the light leakage in the dark state of homogeneously aligned LCDs. A very small amount of reactive mesogen (RM) is mixed with the LC material and polymerized at room temperature and also at a low temperature (−20 °C) to strengthen the surface-anchoring energy. The contrast ratio of the low-temperature cured cell is improved by about 50% over that of the pure LC cell and the room temperature cured RM-mixed LC cell due to an enhanced order parameter.

The first neutral beam injector (NBI-1) has been developed for the Korea Superconducting Tokamak Advanced Research (KSTAR) tokamak. The first long pulse ion source (LPIS-1) has been installed on the NBI-1 for an auxiliary heating and current drive of KSTAR plasmas. The performance of ion and neutral beam extractions in the LPIS-1 was investigated initially on the KSTAR NBI-1 system, prior to the neutral beam injection into the main plasmas. The ion source consists of a magnetic bucket plasma generator with multipole cusp fields and a set of prototype tetrode accelerators with circular apertures. The inner volume of the plasma generator and accelerator column in the LPIS-1 is approximately 123 L. Design requirements for the ion source were a 120 kV/65 A deuterium beam and a 300 s pulse length. The extraction of ion beams was initiated by the formation of arc plasmas in the LPIS-1, called the arc-beam extraction method. A stable ion beam extraction of the LPIS-1 was achieved up to 85 kV/32 A for a 5 s pulse length and 80 kV/25 A for a 14 s pulse length. An optimum beam perveance of 1.15 µperv was observed at an acceleration voltage of 60 kV. Neutralization efficiency was measured by a water-flow calorimetry (WFC) method using a calorimeter and the operation of a bending magnet. The full-energy species of ion beams were detected by using the diagnostic method of optical multichannel analyzer (OMA). An arc efficiency of the LPIS was 0.6–1.1 A/kW depending on the operating conditions of arc discharge. A neutral beam power of ∼1.0 MW must be sufficiently injected into the KSTAR plasmas from the LPIS-1 at a beam energy of 80 keV.

We firstly propose a novel U-shape resistive cell structure which is the best fit for generating low power resistive random access memory (RRAM) with forming-less process. We find that irregular resistive switching behavior in the initial transition and the characteristics associated with it. Controlling the conducting filament (CF) dimension and deposition orientation of resistive material are expected to reduce the distribution and forming voltage, which enables low power RRAM to be feasible without forming state. Simple fabrication flow and device performances are also evaluated in the aspect of forming-less process. Numerical simulation is performed using random circuit breaker model (RCB) to confirm the proposed structure.

The shape changes of inkjet-printed dots and lines were investigated by varying the primary solvent of nanosilver colloids, surface wettability and substrate temperature. The morphological changes in dots and lines in array patterns due to the interaction between neighboring dots or lines during evaporation was also examined for two different nanosilver colloids. In order to examine the effect of solvent evaporation rate, two different solvents with different boiling points (BP) were employed for nanosilver inks. With a fluorocarbon film coating and subsequent ultraviolet ozone (UV/O3) treatment, various surface wettability conditions were obtained on silicon (Si) wafers. Substrate temperature was varied from room temperature to 80 °C, and droplets from a 50 µm diameter nozzle were printed onto the substrate after optimizing the ejection of individual droplets. The results indicate that the shapes and sizes of dots and lines are sensitive to changes in both surface energy and substrate temperature, and the ink with a higher BP solvent produces larger dots under the same surface condition due to its slower evaporation. Dots and lines with better quality are achieved using the ink with a lower BP solvent. The morphological changes in dot and line arrays are dependent on the evaporation rate of the primary solvent as well as the distance between neighboring features. As a result, selecting a proper solvent for nanosilver ink is very crucial for controlling the shape and morphology of inkjet-printed patterns.

In this work, we investigated the effects of single-walled carbon nanotubes (SWNTs) on the device performance of organic photovoltaic devices (OPVs) according to the location of the added SWNTs. When SWNTs were incorporated in OPVs, we found that the power conversion efficiency (PCE) of OPVs depended on the device structure, resulting in improved PCE of 1.89% in SWNTs network layer cell (SNC) at 0.5 wt % SWNTs (37% increase) and 1.57% in SWNTs doped cell (SDC) at 0.25 wt % SWNTs (14% increase) compared to that of 1.38% in the reference device. We concluded that superior performance of SNC was due to more efficient carrier extracting and improved transport behaviors by suppressing the recombination losses without disturbing the intimate conformations of photoactive materials.

In this paper, we propose a novel fin and recess-channel metal oxide semiconductor field effect transistor (MOSFET) for sub-50 nm dynamic random access memory (DRAM) cell application. Also, it is compared with the recess-channel-array transistor (RCAT). In the proposed device, a silicon fin region is added to the recessed channel MOSFET. Thanks to the additional current path through the silicon fin with the wide source/drain width, the FiReFET shows excellent current drivability. To reduce gate-induced drain leakage (GIDL) current, we adopt an underlapped device structure. As a result, it is found that the optimized underlap structure helps to prevent the OFF state leakage current induced by the increase of the gate work function.

The effect of plasma surface treatment on the dried diameter of droplets inkjet-printed on the PI substrate was investigated by varying the plasma process parameters. The sequential design of the experiments technique combining a factorial design with a response surface method was introduced to systematically estimate an accurate empirical response model for two independent design variables: radio frequency (RF) power and gas pressure. C4F8 gas was used for the plasma surface treatment of 90 mm × 90 mm polyimide substrates. Ag ink droplets ejected from a 30 µm nozzle were printed on the plasma-treated substrates, and their measured diameter and standard deviation were used as the response variables. The plasma-treated substrate was also characterized by contact angles and x-ray photoelectron spectroscopy. The results indicate that the droplet diameters and their uniformity are sensitive to changes in both RF power and gas pressure, lower droplet diameters on PI substrates correspond to lower surface energies, and the process condition producing higher F content results in more hydrophobic surface. The resolution of the inkjet printing can be precisely controlled by varying the droplet diameter and uniformity through the C4F8 plasma surface treatment.

The dynamic properties of inkjet-printed thin films on flexible polyimide (PI) substrates were investigated using the vibration analysis adopting wave approach. In order to fabricate the test specimens, the Ag nanoparticle suspension was inkjet printed on the plasma-treated PI substrate and sintered at different temperatures. The beam-shaped Ag-printed PI specimens with 30 mm length and 0.6 mm width were prepared by pico-second laser pulse cutting and were used as the cantilever beam in the vibration test. From the base-excited response of the beam, the frequency-dependent bending stiffness and loss factor were obtained, which were used to calculate Young's modulus and loss factor of the inkjet-printed thin films. The influence of the sintering temperature and film thickness on the dynamic properties was investigated and the nanoindentation test was also performed to compare results from each test. Young's modulus increased and loss factor decreased with increasing sintering temperature and the effect of the film thickness was not significant. Young's modulus from the vibration analysis was in comparable agreement with that from the nanoindentation test. The proposed method enables the direct determination of the dynamic characteristics of thin films without damaging the thin films as well as removing the substrate.

The Gas Diffusion Layer(GDL) of fuel cell, are required to provide both delivery of reactant gases to the catalyst layer and removal of water in either vapor or liquid form in typical PEMFCs. In this study, the fabrication of GDL containing Micro Porous Layer(MPL) made of the slurry of PVDF mixed with carbon black is investigated in detail. Physical properties of GDL containing MPL, such as electrical resistance, gas permeability and microstructure were examined, and the performance of the cell using developed GDL with MPL was evaluated. The results show that MPL with PVDF binder demonstrated uniformly distributed microstructure without large cracks and pores, which resulted in better electrical conductivity. The fuel cell performance test demonstrates that the developed GDL with MPL has a great potential due to enhanced mass transport property due to its porous structure and small pore size.

Using Monte Carlo simulation, random walks on a two-dimensional Sierpinski gasket in the presence of an external field were studied. It was observed that the random walk motion of a particle displayed a crossover from anomalous diffusion to drift for a non-zero bias field, and the crossover time tcr was a decreasing function of the external bias field. The associated dynamic exponents obtained in a computer simulation agree with the predictions of Stinchcombe's scaling treatment (1985).