Showing papers by "Kwangwoon University published in 2010"

High-Performance a-IGZO TFT With $\hbox{ZrO}_{2}$ Gate Dielectric Fabricated at Room Temperature

Abstract: We have investigated the high-performance oxide thin-film transistor (TFT) with an amorphous indium gallium zinc oxide (a-IGZO) channel and ZrO2 gate dielectrics. The a-IGZO TFT is fully fabricated at room temperature without any thermal treatments. ZrO2 is one of the most promising high-k materials. The a-IGZO TFT (channel W/L = 240/30 ?m) with ZrO2 shows high performance such as high on current of 2.11 mA and high field effect mobility of 28 cm2/(V·s) at the gate voltage 10 V. The threshold voltage and the subthreshold swing are 3.2 V and 0.56 V/decade, respectively. Note that the high-performance a-IGZO TFT is higher than ever shown in previous researches.

A Watt-Level Stacked-FET Linear Power Amplifier in Silicon-on-Insulator CMOS

Abstract: A single-stage stacked field-effect transistor (FET) linear power amplifier (PA) is demonstrated using 0.28-?m 2.5-V standard I/O FETs in a 0.13-?m silicon-on-insulator (SOI) CMOS technology. To overcome the low breakdown voltage limit of MOSFETs, a stacked-FET structure is employed, where four transistors are connected in series so that their output voltage swings are added in phase. With a 6.5-V supply, the measured PA achieves a small-signal gain of 14.6 dB, a saturated output power of 32.4 dBm, and a maximum power-added efficiency (PAE) of 47% at 1.9 GHz. Using a reverse-link IS-95 code division multiple access modulated signal, the PA shows an average output power of up to 28.7 dBm with a PAE of 41.2% while meeting the adjacent channel power ratio requirement. Using an uplink wideband code division multiple access modulated signal, the PA shows an average output power of up to 29.4 dBm with a PAE of 41.4% while meeting the adjacent channel leakage ratio requirement. The stacked-FET PA is designed to withstand up to 9 V of supply voltage before reaching its breakdown limit. This is the first reported stacked-FET linear PA in submicrometer SOI CMOS technology that delivers watt-level output power in the gigahertz frequency range with efficiency and linearity performance comparable to those of GaAs-based PAs.

Silicon photonic temperature sensor employing a ring resonator manufactured using a standard CMOS process

Abstract: An ultra-small integrated photonic temperature sensor has been proposed and demonstrated which incorporates a silicon ring resonator linked to a vertical grating coupler. It was manufactured using a 0.18 μm standard CMOS process, rendering a homogeneous integration into other electrical/optical devices. The temperature variation was measured by monitoring the shift in the resonant wavelength of the silicon resonator, which was induced by the thermo-optic effect and the thermal expansion effect. The dependence of its sensing capability upon the waveguide width of the resonator was intensively probed both theoretically and experimentally. The best achieved sensitivity was about 83 pm/°C for a waveguide width of 500 nm, while the sensitivity was boosted by ~10 pm/°C by adjusting the waveguide width from 300 nm to 500 nm. Finally, the response speed of the sensor was as fast as ~6 μs.

Electrochemical nitric oxide sensors for physiological measurements

Abstract: The important biological roles of nitric oxide (NO) have prompted the development of analytical techniques capable of sensitive and selective detection of NO. Electrochemical sensing, more than any other NO detection method, embodies the parameters necessary for quantifying NO in challenging physiological environments such as blood and the brain. In this tutorial review, we provide a broad overview of the field of electrochemical NO sensors, including design, fabrication, and analytical performance characteristics. Both electrochemical sensors and biological applications are detailed.

Modeling and Characterization of Piezoelectric $d_{33}$ -Mode MEMS Energy Harvester

Abstract: This paper presents the modeling, fabrication, and characterization of a piezoelectric microelectromechanical systems (MEMS) energy harvester using a d33 piezoelectric mode. A theoretical analysis and an analytical modeling for the d33-mode device were first performed to estimate the output power as a function of the material parameters and device geometry. A PbTiO3 seed layer was newly applied as an interlayer between the ZrO2 and Pb(Zr0.52Ti0.48)O3 (PZT) thin films to improve the piezoelectric property of the sol-gel spin-coated PZT thin film. The fabricated cantilever PZT film with an interdigital shaped electrode exhibited a remnant polarization of 18.5 C/cm2, a coercive field of less than 60 kV/cm, a relative dielectric constant of 1125.1, and a d33 piezoelectric constant of 50 pC/N. The fabricated energy-harvesting device generated an electrical power of 1.1 W for a load of 2.2 M with 4.4 Vpeak-to-peak from a vibration with an acceleration of 0.39 g at its resonant frequency of 528 Hz. The corresponding power density was 7.3 mW cm-3 · g-2. The experimental results were compared with those numerically calculated using the equations derived from the dynamic and analytical modeling. The fabricated device was also compared with other piezoelectric MEMS energy-harvesting devices.

Bacterial cytotoxicity of the silver nanoparticle related to physicochemical metrics and agglomeration properties.

Abstract: Silver particles are used in various consumer products due to their positive effects, which include sterilization and antibacterial properties. However, it has been reported that silver nanoparticles (AgNPs) have strongly acute toxic effects on various cells. Therefore, the cytotoxicity of AgNPs was investigated, using Escherichia coli as a model organism, from the standpoint of three key metrics (ionic ratio, size, and agglomeration) that are the most relevant physicochemical properties. The findings indicated that cytotoxicity is depressed by the agglomeration of AgNPs. The order of toxic sensitivity was as follows: total Ag concentration > ionic ratio > size, the order of which was inversely related to the extent of agglomeration. Environ. Toxicol. Chem. 2010;29:2154–2160. © 2010 SETAC

Morphable crowds

Abstract: Crowd simulation has been an important research field due to its diverse range of applications that include film production, military simulation, and urban planning. A challenging problem is to provide simple yet effective control over captured and simulated crowds to synthesize intended group motions. We present a new method that blends existing crowd data to generate a new crowd animation. The new animation can include an arbitrary number of agents, extends for an arbitrary duration, and yields a natural-looking mixture of the input crowd data. The main benefit of this approach is to create new spatio-temporal crowd behavior in an intuitive and predictable manner. It is accomplished by introducing a morphable crowd model that allows us to encode the formations and individual trajectories in crowd data. Then, its original spatio-temporal behavior can be reconstructed and interpolated at an arbitrary scale using our morphable model.

Transmission type color filter incorporating a silver film based etalon.

Abstract: Transmission type color filters based on a thin film Ag-SiO2-Ag etalon were built on a quartz substrate, enabling the infrared suppressed transmission and large effective area. They were designed by taking into account the influence of the dispersion characteristics and the thickness of the silver metal. Three different color filters were devised: The cavity length for the red, green and blue filter was 160 nm, 130 nm, and 100 nm respectively, while the metal layer was fixed at 25 nm. The observed spectral pass band was centered at 650 nm, 555 nm, and 480 nm for the red, green, and blue device; the corresponding bandwidth was about 120 nm, 100 nm, and 120 nm; and the peak transmission was all ~60%. For the oblique light incidence the angular dependence of the peak relative transmission was measured to be ~1%/degree. The spectral response of the device was also analyzed for two different polarizations as the tilt angle varied up to 12o, and it was found to be hardly polarization dependent. Finally, as for the positional dependence the relative transmission and the center wavelength were found to vary within 10% and 5 nm respectively over an effective area of 4x4 cm2.

Barnes-type multiple q-zeta functions and q-Euler polynomials

Abstract: The purpose of this paper is to present a systemic study of some families of multiple q-Euler numbers and polynomials and we construct multiple q-zeta functions which interpolate multiple q-Euler numbers at a negative integer. This is a partial answer to the open question in a previous publication (see Kim et al 2001 J. Phys. A: Math. Gen. 34 7633–8).

New approach to q-Euler polynomials of higher order

Abstract: In this paper, we present new generating functions related to q-Euler numbers and polynomials of higher order. Using those generating functions, we present new identities involving q-Euler numbers and polynomials of higher order.

Dual-Band Branch-Line Coupler With Port Extensions

Abstract: A new branch-line coupler structure with port extensions is proposed for the dual-band operation. The conventional branch-line coupler structure is adapted to the dual-band operation by inserting a transmission line section at the input ports and modifying the branch parameters. The dual-band performance of the proposed coupler is verified theoretically through the rigorous microwave circuit analysis and the exact design equations are derived in concise form. The design, simulation, and measurement results validate the dual-band capability of the proposed coupler with the same quadrature phase relation between the two band frequencies.

A New VLSI Architecture of Parallel Multiplier–Accumulator Based on Radix-2 Modified Booth Algorithm

Abstract: In this paper, we proposed a new architecture of multiplier-and-accumulator (MAC) for high-speed arithmetic. By combining multiplication with accumulation and devising a hybrid type of carry save adder (CSA), the performance was improved. Since the accumulator that has the largest delay in MAC was merged into CSA, the overall performance was elevated. The proposed CSA tree uses 1's-complement-based radix-2 modified Booth's algorithm (MBA) and has the modified array for the sign extension in order to increase the bit density of the operands. The CSA propagates the carries to the least significant bits of the partial products and generates the least significant bits in advance to decrease the number of the input bits of the final adder. Also, the proposed MAC accumulates the intermediate results in the type of sum and carry bits instead of the output of the final adder, which made it possible to optimize the pipeline scheme to improve the performance. The proposed architecture was synthesized with 250, 180 and 130 ?m, and 90 nm standard CMOS library. Based on the theoretical and experimental estimation, we analyzed the results such as the amount of hardware resources, delay, and pipelining scheme. We used Sakurai's alpha power law for the delay modeling. The proposed MAC showed the superior properties to the standard design in many ways and performance twice as much as the previous research in the similar clock frequency. We expect that the proposed MAC can be adapted to various fields requiring high performance such as the signal processing areas.

A Fast and High-Precision VCO Frequency Calibration Technique for Wideband $\Delta \Sigma $ Fractional-N Frequency Synthesizers

Abstract: A VCO frequency calibration technique suitable for a wideband fractional-N PLL is presented. It provides a fast and high-precision search for an optimal discrete tuning curve of an LC VCO during the coarse tuning process in a fractional-N PLL. A high-speed frequency error detector (FED) converts the VCO frequency to a digital value and computes the exact frequency difference from a target frequency. A minimum error code finder finds an optimal code that is closest to the target frequency. Due to the pure digital domain operation, a ΔΣ modulator in PLL can be deactivated during the calibration process, which makes this technique fast and accurate especially for a ΔΣ fractional-N PLL. We achieve a single-bit calibration time of only kTREF for obtaining a frequency resolution of fREF/k, and compared to the conventional techniques, which is the best performance in terms of the calibration time versus resolution. Such fast VCO frequency calibration can greatly reduce the total lock time in a PLL. A 2.3-3.9 GHz fractional-N PLL employing the proposed calibration technique is implemented in 0.13 μm CMOS. Successful operation is verified through experimental results. The measured calibration time for a 6-bit capbank is 1.09 and 2.03 μs for a frequency resolution of 19.2 and 4.8 MHz, respectively.

Large resistive-switching phenomena observed in Ag/Si3N4/Al memory cells

Abstract: An effective resistive-switching effect has been observed in silicon nitride (Si3N4) dielectrics in Ag/Si3N4/Al memory cells. The ratio of the low resistance to high resistance state was larger than 107 at ±1.2 V for a 10 nm thick Si3N4 layer. This switching behavior is attributed to a change in the conductivity of the Si3N4 dielectrics, depending on whether nitride-related traps are filled with electrons under positive biases or unfilled under negative biases. This assertion is experimentally confirmed from the relationship between the amount of charges trapped in the Si3N4 layer and the corresponding changes in its resistance with respect to bias voltages. In addition, the formation or dissolution of the conductive path is confirmed by conductive atomic force microscopy current images.

Adaptive duty-cycle based congestion control for home automation networks

Abstract: There is a growing interest in the wireless sensor network technology in the home automation field, but as the number of sensor nodes in the home increases and as the data traffic generated by such nodes grows, the network becomes more congested. Due to resource constraints, a congestion control scheme for wireless sensor network should be designed with simplicity and operate energy efficiently. In this paper, we propose ADCC(Adaptive Duty-cycle Based Congestion Control), a lightweight congestion control scheme using duty-cycle adjustment for wireless sensor networks. This scheme uses both the resource control and traffic control approaches according to the amount of network traffic for the congestion avoidance. Our simulation results show that the ADCC improves the reliability and energy efficiency of duty-cycle based congestion control in wireless sensor networks.

Employee involvement and group incentives in manufacturing companies: a multi‐level analysis

Abstract: The effects of employee involvement and group incentives on organisational commitment and turnover intention were examined using data from a survey of over 4,000 employees in 29 manufacturing companies. Using the mediated moderation model, we investigated the moderating role of capital intensity on the relationships between employee involvement and group incentives and these outcomes, and the mediating role of organisational commitment on the effects of employee involvement and group incentives on turnover intention. The findings revealed that employee involvement is more effective in capital-intensive companies than in labour-intensive companies, but group incentives are more effective in labour-intensive companies. The moderated effects on turnover intention were mediated through organisational commitment. Implications for company policies and future research are discussed.

Biosensor system-on-a-chip including CMOS-based signal processing circuits and 64 carbon nanotube-based sensors for the detection of a neurotransmitter

Abstract: We developed a carbon nanotube (CNT)-based biosensor system-on-a-chip (SoC) for the detection of a neurotransmitter. Here, 64 CNT-based sensors were integrated with silicon-based signal processing circuits in a single chip, which was made possible by combining several technological breakthroughs such as efficient signal processing, uniform CNT networks, and biocompatible functionalization of CNT-based sensors. The chip was utilized to detect glutamate, a neurotransmitter, where ammonia, a byproduct of the enzymatic reaction of glutamate and glutamate oxidase on CNT-based sensors, modulated the conductance signals to the CNT-based sensors. This is a major technological advancement in the integration of CNT-based sensors with microelectronics, and this chip can be readily integrated with larger scale lab-on-a-chip (LoC) systems for various applications such as LoC systems for neural networks.

Development of Batch and Continuous Processes on Biodiesel Production in a Packed-Bed Reactor by a Mixture of Immobilized Candida rugosa and Rhizopus oryzae Lipases

Abstract: In this study, transesterification and esterification were investigated in batch and continuous process using immobilized Candida rugosa and Rhizopus oryzae lipases. In the case of batch process, stepwise reaction method was investigated to prevent the lipase deactivation. Reaction conditions were as follows: temperature, 45 °C; agitation speed, 250 rpm; enzyme concentration, 20%; and water contents 10%. And then, conversion yield was 98.33% at 4 h. In the case of continuous process, circulation and long-term continuous system were investigated for development of efficient mass transfer system. Optimal reaction conditions were as follows: temperature, 45 °C; flow rate, 0.8 mL/min; and water contents, 10%. And then, conversion yield of biodiesel was 97.98% at 3 h. Especially, the maximum conversion yield using a mixture of immobilized lipases exceeded over 90% for 108 h in long-term continuous system under optimal reaction conditions (45 °C; flow rate, 0.8 mL/min; and water contents, 10%). These results should help in determining the best method for the biodiesel production and improving the design and operation of large scale by enzymatic systems.

Micro-Fabricated Electromagnetic Power Generator to Scavenge Low Ambient Vibration

Abstract: In this paper, micro-fabricated electromagnetic power generator is presented to convert the low level ambient vibration into electric energy. The proposed micro-power generator is comprised of three micro-components such as bulk-micromachined silicon spiral spring, low loss copper micro-coil, and NdFeB magnet to be assembled with low cost PDMS packaging substrate. In order to maximize the output power, magnet is applied as inertial mass at the center of silicon spiral spring to adjust its resonant frequency. Especially, NdFeB discrete/miniaturized magnet and copper wire wounded micro-coil were utilized to avoid the performance deterioration of the proposed device due to its miniaturization. It was specially designed for scavenging low ambient vibration of several tens of hertz and low acceleration under 1g. The fabricated device generated output power of 115.1 W and load voltage of 68.2 mV to the load resistance of 18.1 from the vibration of 54 Hz with acceleration of 0.57 g. The normalized power density was 590.4 ?W/cm3g2.