• International Journal of Internet, Broadcasting and Communication
• /
• v.10 no.4
• /
• pp.6-11
• /
• 2018

As embedded memory technology evolves, the traditional Static Random Access Memory (SRAM) technology has reached the end of development. For deepening the manufacturing process technology, the next generation memory technology is highly required because of the exponentially increasing leakage current of SRAM. Non-volatile memories such as STT-MRAM (Spin Torque Transfer Magnetic Random Access Memory), PCM (Phase Change Memory) are good candidates for replacing SRAM technology in embedded memory systems. They have many advanced characteristics in the perspective of power consumption, leakage power, size (density) and latency. Nonetheless, nonvolatile memories have two major problems that hinder their use it the next-generation memory. First, the lifetime of the nonvolatile memory cell is limited by the number of write operations. Next, the write operation consumes more latency and power than the same size of the read operation.These disadvantages can be solved using the compiler. The disadvantage of non-volatile memory is in write operations. Therefore, when the compiler decides the layout of the data, it is solved by optimizing the write operation to allocate a lot of data to the SRAM. This study provides insights into how these compiler and architectural designs can be developed.

• 유체기계공업학회:학술대회논문집
• /
• 2000.12a
• /
• pp.145-152
• /
• 2000

A turbopump system composed of two pumps and one turbine is considered. The turbine composed of a nozzle and a rotor is used to drive the pumps while gas passes through the nozzle, potential energy is converted to kinematic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of turbine system is investigated using compressible fluid dynamic theories with some pre-determined design requirements (i.e., pressure ratio, rotational speed, required power etc.) obtained from liquid rocket engine (L.R.E.) system design. For simplicity of turbine system, impulse-type rotor blades for open type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow rate compared to close-type system. In this study, a partial admission nozzle Is adopted to maximize the efficiency of the open-type turbine system. A design methodology of turbine system has been introduced. Especially, partial admission nozzle has been designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design for a 10 ton thrust level of L.R.E is presented.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.11 no.2
• /
• pp.67-78
• /
• 2016

The emerging Spin-Transfer Torque RAM (STT-RAM) is a promising component that can be used to improve the efficiency as a result of its high storage density and low leakage power. However, the state-of-the-art STT-RAM is not ready to replace SRAM technology due to the negative effect of its write operations. The write operations require longer latency and more power than the same operations in SRAM. Therefore, a hybrid cache with SRAM and STT-RAM technologies is proposed to obtain the benefits of STT-RAM while minimizing its negative effects by using SRAM. To efficiently use of the hybrid cache, it is important to place write intensive data onto the cache. Such data should be placed on SRAM to minimize the negative effect. Thus, we propose a technique that optimizes placement of data in main memory. It drives the proper combination of advantages and disadvantages for SRAM and STT-RAM in the hybrid cache. As a result of the proposed technique, write intensive data are loaded to SRAM and read intensive data are loaded to STT-RAM. In addition, our technique also optimizes temporal locality to minimize conflict misses. Therefore, it improves performance and energy consumption of the hybrid cache architecture in a certain range.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1476-1477
• /
• 2008

This paper reports on a flexible flap valve actuated by electromagnetic force under a constant pressure source. The flexible flap valve consists of the three main components: a flexible flap with a steel disk embedded in PDMS, an electromagnetic actuator and two glass plates with inlet and outlet. Sealing lip structures for improving the valve characteristics are added on the outlet of the bottom glass substrate. The flap valve is fabricated by the spin-coating process, the EDM process, SU-8 mold process and oxygen plasma treatment. The dimension of an assembled flap valve is $12mm{\times}20mm{\times}28mm$. The stroke volume of the flap valve is measured for various pressures and open times. When the input voltage of 30 V is applied for 0.33 s, the minimum stroke volume of the flap valve is 70 ${\mu}L$ at 50 kPa.

• 한국전산유체공학회:학술대회논문집
• /
• 2006.05a
• /
• pp.94-99
• /
• 2006

As part of a Department of Defense Grand Challenge Project, advanced high performance computing (HPC) time-accurate computational fluid dynamics (CFD) techniques have been developed and applied to a new area of aerodynamic research on microjets for control of small and medium caliber projectiles. This paper describes a computational study undertaken to determine the aerodynamic effect of flow control in the afterbody regions of spin-stabilyzed projectiles at subsonic and low transonic speeds using an advanced scalable unstructured flow solver in various parallel computers such as the IBM SP4 and Linux Cluster. High efficiency is achieved for both steady and time-accurate unsteady flow field simulations using advanced scalable Navier-Stokes computational techniques. Results relating to the code's portability and its performance on the Linux clusters are also addressed. Numerical simulations with the unsteady microjets show the jets to substantially alter the flow field both near the jet and the base region of the projectile that in turn affects the forces and moments even at zero degree angle of attack. The results have shown the potential of HPC CFD simulations on parallel machines to provide to provide insight into the jet interaction flow fields leading to improve designs.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.541-541
• /
• 2012

InP quantum dots capped by myristic acid (InP-MA QDs) were synthesized by a typical hot injection method using MA as stablizing agent. The current density across the InP-MA QDs thin film which was fabricated by spin-coating method is about $10^{-4}A/cm^2$ at the electric field of 0.1 MV/cm from I-V measurement on a metal-insulator-metal (MIM) device. The low conductivity of the InP-MA QDs thin film is interpreted as due to the long interdistances among the dots governed by the MA molecules. Therefore, replacing the MA with thioacetic acid (TAA) by biphasic ligand exchange was conducted in order to obtain TAA capped InP QDs (InP-TAA). InP-TAA QDs were designed due to: 1) the TAA is very short molecule; 2) the thiolate groups on the surface of the InP-TAA QDs are expected to undergo condensation reaction upon thermal annealing which connects the QDs within the QD thin film through a very short linker -S-; and 3) TAA provides better passivation to the QDs both in the solution and thin film states which minimizing the effect of surface trapping states.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.350-350
• /
• 2011

The spin structure of Fe over layers on Cu (001), especially in region II is one of the unsolved problem for many years. We study the out - of - plane (OP) Fermi surfaces (FSs) of 7 monolayer Fe/Cu (001) films using angle resolved photo emission spectroscopy (ARPES). Ultrathin Fe was grown on Cu (001) substrate at room temperature and the experimental measurements were carried out at room temperature and low temperature. Fermi surfaces measured about $\frac{1}{4}$ of the Brillouin Zone (BZ) using photon energies ranging from 170 eV to 280 eV. Our results confirmed that ferromagnetic signal at 7 ML Fe on Cu (001) is nearly zero. These results are consistent with our recent x-ray magnetic circular dichroism (XMCD) and surface magneto - optic Kerr effect (SMOKE) experiments. Based on our observations we have made a simple model of this system, which explains all the experimental results.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.108-108
• /
• 2011

Organometallic complexes containing unpaired spins, such as metalloporphyrin or metallophthalocyanine, have extensively studied with increasing interests of their promising model systems in spintronic applications. Additionally, the use of these complexes as an acceptor molecule in chemical sensors has recently received great attentions. In this presentation, we have investigated adsorption of nitric oxide (NO) molecules at Co-porphyrin molecules on Au(111) surfaces with scanning tunneling microscopy and spectroscopy at low temperature. At the location of Co atom in Co-porphyrin molecules, we could observe a Kondo resonance state near Fermi energy in density of states (DOS) before exposing NO molecules and the Kondo resonance state was disappeared after NO exposing because the electronic spin structure of Co-porphyrin were modified by forming a cobalt-NO bonding. Furthermore, we could locally control the chemical reaction of NO dissociations from NO-CoTPP by electron injections via STM probe. After dissociation of NO molecules, the Kondo resonance state was recovered in density of state. With a help of density functional theory (DFT) calculations, we could understand that the modified electronic structures for NO-Co-porphyrin could be occurred by metal-ligand hybridization and the dissociation mechanisms of NO can be explained in terms of the resonant tunneling process via molecular orbitals.

• Journal of Powder Materials
• /
• v.8 no.3
• /
• pp.201-206
• /
• 2001

$>LaMnO_3$$(La, Sr)MO_3$, and $(La, Sr)MO_3/YSZ$ gel films were deposited by spin-coating technique on scandium-doped zirconia (YSZ) substrate using the precursor solution prepared from $La(O-i-C_3H_7)_3$, $Co(CH_3COO)_2$or $Mn(O-i-C_3H_7)_2$,2-methoxyethanol, and polyethylene glycol. By heat-treating the gel films, the electrochemical cells, $(La, Sr)MnO_3{\mid}ScSZ{\mid}Pt$ were fabricated. The effect of polyethylene glycol on the microstructure evolution of $$LaCoO_3and $LaMnO_3$thin films was investigated, and NOx decomposition characteristics of the electrochemical cells were investigated at $500^{\circ}C$ to $600^{\circ}C$. By applying a direct current to the $(La, Sr)MnO_3{\mid}ScSZ{\mid}Pt$ electrochemical cell, good NOx conversion rate could be obtained relatively at low current value even if excess oxygen is included in the reaction gas mixture.

• Journal of the Korean Society of Safety
• /
• v.19 no.3 s.67
• /
• pp.51-56
• /
• 2004

Conductive polymer blends and composites are widely used for different safety application such as electrostatic charge dissipation(ESD), electromagnetic interference(EMI) shielding, electrostatic prevention and safety chemical sensor. In order to prepare a impedance-type humidity sensor that is durable at high humidities and high temperature, electically conductive polymer blends based on diallyldimethylammonium chloride(DADMAC) and epoxy were prepared in this study. The polymer blends type conductive ionomer exhibits reaction each other DADMAC and epoxy in FT-IR and DSC analysis. The blends material was traced by new peak at 1600cm-1 and appeard improvement of thermal resistance by melting point shift. Alumina substrate was deposited a pair of gold electrodes by screen printing. The blend material were spin-coated with a thin film type on the surface of alumina substrate. The polymer bleld type sensor exhibits a linear impedance increasing better than DADMAC coated humidity sensor. Also it shows good sensitivity, low hysteresis and durability against high humidity.