Using directional antennas in wireless ad hoc networks is an attractive issue due to its potentia... more Using directional antennas in wireless ad hoc networks is an attractive issue due to its potential advantages such as spatial reuse, low power consumption and low chance of interference. To acquire these advantages, we propose a new routing scheme called DAPOS (Directional Antenna based Path Optimization Scheme). The proposed scheme enables us to acquire an efficient path by considering the characteristics of directional antennas, resulting a routing performance improvement. DAPOS focuses on shortening the length of routing path gradually by considering the higher gain of directional antennas at a receiver side. Simulation results show that DAPOS significantly reduces the number of hops in route, thereby it improves the overall network performance.
The binding of fluorescein isothiocyanate (FITC) conjugated lectins to gametes of Aglaothamnion o... more The binding of fluorescein isothiocyanate (FITC) conjugated lectins to gametes of Aglaothamnion oosumiense Itono during fertilization was studied by the use of confocal microscopy. The physiological effects of lectins and carbohydrates on gamete binding were also examined. Four different lectins, concanavalin A (ConA), soybean agglutinin (SBA), Dolichos biflorus agglutinin (DBA) and wheat germ agglutinin (WGA) bound to the surface of spermatia, but each lectin labelled a different region of the spermatium. SBA and DBA bound only to the spermatial appendages but ConA bound to all the spermatial surface except the spermatial appendages. WGA labelled a narrow region that connects the spermatial body and appendages. During fertilization, the ConA and WGA specific substances on the spermatial surface moved towards the area contacting the trichogyne and accumulated on the surface of the fertilization canal. Spermatial binding to trichogynes was inhibited by pre-incubation of spermat ia with SBA or ConA, while trichogyne receptors were blocked by the complementary carbohydrates, D-glucose or N-acetyl-galactosamine, respectively. WGA and DBA as well as their complementary carbohydrates had little effect on gamete binding. The inhibitory effects of ConA and SBA were increased when the two lectins were applied simultaneously. The inhibitory effects of both lectins were partially reversed (to 80–90% of controls) by addition of complementary carbohydrates at the same time. The results suggested that SBA and ConA receptors on the spermatial surface are involved in gamete recognition in Aglaothamnion oosumiense.
Memristors have been extensively studied for data storage and low-power computation applications.... more Memristors have been extensively studied for data storage and low-power computation applications. In this study, we show that memristors offer more than simple resistance change. Specifically, the dynamic evolutions of internal state variables allow an oxide-based memristor to exhibit Ca 2+ -like dynamics that natively encode timing information and regulate synaptic weights. Such a device can be modeled as a second-order memristor and allow the implementation of critical synaptic functions realistically using simple spike forms based solely on spike activity.
We demonstrate the use of an antibody (Ab) microarray for a comparative expression profiling of p... more We demonstrate the use of an antibody (Ab) microarray for a comparative expression profiling of proteins in an L-threonine biosynthetic pathway of Escherichia coli between a parental strain (W3110) and L-threonine overproducing mutant (TF5015). On the basis of a global comparative transcriptome analysis between the two strains, 28 analytical target proteins were selected and subjected to a production of polyclonal Abs against them. An Ab microarray was constructed by spotting a set of produced antibodies on a glass slide, and was employed for a comparative expression profiling of the proteins between the two strains by a two-color fluorescence assay method. The performance of the Ab microarray was evaluated with respect to cross-reactivity of the antibodies, dye-labeling efficiency, and the nature of antigenic proteins. Of these, the cross-reactivity of the used antibodies was found to mainly cause the deviation of the observed expression ratios from the expected ones. To offset the deviations, correction factors were derived from a statistical analysis and introduced. As a result, ten proteins were categorized to be up-regulated, while one was down-regulated in TF5015. Expression profiling of proteins using the Ab microarray was further verified by comparison with Western blotting and 2-DE.
REGULAR PAPERS-Silicon and Column IV Semiconductor Devices-An Extraction Method of the Energy Distribution of Interface Traps by an Optically Assisted Charge Pumping Technique
1 wileyonlinelibrary.com crystallographic defects and nonfl at interfaces with the polycrystallin... more 1 wileyonlinelibrary.com crystallographic defects and nonfl at interfaces with the polycrystalline electrode, it is generally improbable to ensure the uniform defect arrangements in all the memristor cells. Although several reports on the uniform multilevel switching have been made, this intrinsic uncertain and uncontrollable nature of RS behavior still remains unsolved. Nevertheless, switching uniformity can be ensured by confi guring an appropriate peripheral circuit with the memristive element as shown in this report. The nonuniformity has been induced during both set (switching from high-resistance state (HRS) to low-resistance state (LRS)) and reset (LRS → HRS) switching. It is well known that limiting the maximum current (compliance current) during the set switching is effective in forming a uniform LRS resistance ( R LRS ) and in protecting the device from permanent electrical damage. Moreover, by adjusting the maximum current level, multiple resistance states can be attained. However, actual device can hardly incorporate such complicated circuitry due to economical reasons. Therefore, achieving multilevel resistance values during the set switching is generally very challenging. Meanwhile, few studies have investigated methods of controlling the resistance of HRS ( R HRS ) during reset switching. In order to use the memristor as the analog circuit device or the multilevel information storage, however, the control of the reset switching is also important to attain the wider range of intermediate states. In addition, the reset switching could show a gradual resistance change behavior compared with the rapid resistance change during the set switching, and, thus, control the reset switching could be a viable method to achieve the uniform multilevel switching. In this study, therefore, a method of implementing "selflimited" reset switching is suggested and demonstrated. Then it is realized via a Ta 2 O 5 /TaO x ( x ≈ 2) structure. Using this method, both set and reset switching could be well regulated, which would allow self-limited R LRS and R HRS values. Here, the term "self-limited" refers to the circumstance where the R LRS and R HRS values were saturated at a certain value even when the degree of electrical stimulus varied. The circuit model for implementing self-limited switching was presented and the experimental results from the Ta 2 O 5 /TaO x memristor structure were precisely fi tted according to the circuit model. Finally, uniform and precise multilevel programming using self-limited switching was presented.
A comprehensive analysis of write operations (SET and RESET) in a resistance-change memory (resis... more A comprehensive analysis of write operations (SET and RESET) in a resistance-change memory (resistive random access memory) crossbar array is carried out. Three types of resistive switching memory cells-nonlinear, rectifying-SET, and rectifying-RESET-are compared with each other in terms of voltage delivery, current delivery, and power consumption. Two different write schemes, V/2 and V/3, were considered, and the V/2 write scheme is preferred due to much lower power consumption. A simple numerical method was developed that simulates entire current flows and node voltages within a crossbar array and provides a quantitative tool for the accurate analysis of crossbar arrays and guidelines for developing reliable write operation.
The nature of threshold switching (TS) in AsTeGeSiN-based selector devices is comprehensively inv... more The nature of threshold switching (TS) in AsTeGeSiN-based selector devices is comprehensively investigated. The scaling of the AC response is limited up to 5 ns due to a finite intrinsic delay time. An analytical model allows the accurate prediction of the TS nature, which can be merged to a numerical circuit simulation for providing essential guideline of the required selectivity performance. Introduction: A 3D stacked RRAM with a selector device is indispensable, as shown in , to overcome the scaling limit of the current NAND flash technology (<4F 2 ). Several promising types of selector devices, such as a bidirectional varistor, CRS, MIEC, and Schottky diode, have attracted attention, as summarized in
Tantalum-oxide-based bi-layered resistance-change memories (RRAMs) have recently improved greatly... more Tantalum-oxide-based bi-layered resistance-change memories (RRAMs) have recently improved greatly with regard to their memory performances. The formation and rupture of conductive filaments is generally known to be the mechanism that underlies resistive switching. The nature of the filament has been studied intensively and several phenomenological models have consistently predicted the resistance-change behavior. However, a physics-based model that describes a complete bi-layered RRAM structure has not yet been demonstrated. Here, a complete electro-thermal resistive switching model based on the finite element method is proposed. The migration of oxygen vacancies is simulated by the local temperature and electric field derived from carrier continuity and heat equations fully coupled in a 3-D geometry, which considers a complete bi-layered structure that includes the top and bottom electrodes. The proposed model accurately accounts for the set/reset characteristics, which provides an in-depth understanding of the nature of resistive switching.
Gate length (L G ) effects for program/erase (P/E) efficiency are investigated in a gate-all-arou... more Gate length (L G ) effects for program/erase (P/E) efficiency are investigated in a gate-all-around (GAA) SONOS structure. The experimental results show that P/E characteristics become worse at a shorter L G , and this trend is verified with numerical simulation. The down-scaling of L G gives rise to a change in the electric field in tunneling oxide and blocking oxide in the GAA-SONOS structure. For P/E efficiency, these results reveal that the fringing field via a low-k dielectric medium, which encapsulates a gate electrode as an inter-layer dielectric, favorably enhances the electric field of tunneling oxide. It also reduces the electric field of blocking oxide. Additionally, it is found that the electric field of tunneling and blocking oxide becomes more sensitive to the permittivity of the inter-layer dielectric as L G is more shortened.
Multi-functional universal device using a band-engineered vertical structure
A multi-functional universal device based on a vertical channel is demonstrated as a total device... more A multi-functional universal device based on a vertical channel is demonstrated as a total device solution. Four different operation modes: conventional MOSFET, steep slope FET, multi-faceted volatile memory (1T-DRAM and 1T-SRAM), and non-volatile memory are implemented in a single transistor. The steep slope FET and volatile memory are boosted by a vertically inhomogeneous doped channel for spatial energyband-engineering, and non-volatile
A vertically integrated latch-up based n-p-n bidirectional diode, which is analogous to an open-b... more A vertically integrated latch-up based n-p-n bidirectional diode, which is analogous to an open-base bipolar junction transistor, is demonstrated for bipolar resistance-change memory selector application. A maximum current density of >50 MA/cm 2 and a selectivity of >10 4 are observed at a fast switching speed of within 10 ns. The high selectivity as a consequence of the sudden latch-up process is feasible owing to the positive-feedback process initiated by impact ionization. The optimization of the turn-on voltage is comprehensively investigated by numerical device simulation, which ensures the promising potential of the latch-up based selector device. V C 2013 AIP Publishing LLC. [http://dx.
A universal core model for multiple-gate field-effect transistors (Mug-FETs) is proposed. The pro... more A universal core model for multiple-gate field-effect transistors (Mug-FETs) is proposed. The proposed charge and drain current models are presented in Parts I and II, respectively. It is first demonstrated that an exact potential profile in the entire channel is not necessary for the derivation of accurate charge models in inversion-mode FETs. With application of this new concept, a universal charge model is derived for Mug-FETs by assuming an arbitrary channel potential profile, which simplifies the mathematical formulation. Thereafter, using the Pao-Sah integral, a drain current model is obtained from the charge model of Part I. The proposed model can be expressed as an explicit and continuous form for all operation regimes; therefore, it is well suited for compact modeling to support fast circuit simulations. The model shows good agreement with 2-D and 3-D numerical simulations for several multiple-gate structures, such as singlegate, double-gate, triple-gate, rectangular gate-all-around, and cylindrical gate-all-around FETs. Index Terms-Compact modeling, cylindrical gate-all-around FET (Cy-GAA-FET), double-gate FET (DG-FET), FinFET, multiple-gate FET (Mug-FET), Poisson's equation, rectangular gate-all-around FET (Re-GAA-FET), semiconductor device modeling, single-gate FET (SG-FET), triple-gate FET (TG-FET).
A universal core model for multiple-gate field-effect transistors (Mug-FETs) is proposed. The pro... more A universal core model for multiple-gate field-effect transistors (Mug-FETs) is proposed. The proposed charge and drain current models are presented in Parts I and II, respectively. It is first demonstrated that an exact potential profile in the entire channel is not necessary for the derivation of accurate charge models in inversion-mode FETs. With application of this new concept, a universal charge model is derived for Mug-FETs by assuming an arbitrary channel potential profile, which simplifies the mathematical formulation. Thereafter, using the Pao-Sah integral, a drain current model is obtained from the charge model of Part I. The proposed model can be expressed as an explicit and continuous form for all operation regimes; therefore, it is well suited for compact modeling to support fast circuit simulations. The model shows good agreement with 2-D and 3-D numerical simulations for several multiple-gate structures, such as singlegate, double-gate, triple-gate, rectangular gate-all-around, and cylindrical gate-all-around FETs. Index Terms-Compact modeling, cylindrical gate-all-around FET (Cy-GAA-FET), double-gate FET (DG-FET), FinFET, multiple-gate FET (Mug-FET), Poisson's equation, rectangular gate-all-around FET (Re-GAA-FET), semiconductor device modeling, single-gate FET (SG-FET), triple-gate FET (TG-FET).
A novel interface characterization technique is proposed to extract interface trap density N it i... more A novel interface characterization technique is proposed to extract interface trap density N it in fully depleted silicon-on-insulator MOSFETs. The proposed technique utilizes the temporal variation of the drain current, which is caused by the application of a single pulse to the gate in order to trigger charge pumping (CP). Vacant interface traps created as a result of recombination through the CP effect are gradually filled by carriers generated from a floating body (FB). By the characterization of this transient phenomenon, the interface trap density is directly extracted from FB devices without extra body contacts. Index Terms-Charge pumping (CP), drain current transient, floating body (FB), interface trap, silicon-on-insulator (SOI) MOSFET.
Charge pumping technique is investigated to identify biomolecular charge polarity using a nanogap... more Charge pumping technique is investigated to identify biomolecular charge polarity using a nanogap-embedded biotransistor. Biomolecules immobilized in a nanogap provide additional charges in the gate dielectric. They give rise to a change in the charge pumping current, as detected by applying a designed pulse waveform. The measured results are analyzed with the aid of numerical simulations. The proposed charge pumping technique represents an insightful method of investigating the electrical properties of biomolecules beyond biosensing.
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