Study on the Snake Robot’s Rolling Motion and Driving Velocity

본 논문에서는 뱀을 모사한 로봇을 만들고 제자리에서 굴러가는 rolling motion을 개발하였다. 원활한 rolling motion을 수행하기 위해서 slip ring과 원형프레임이 이용되었으며, slip ring은 선이 꼬이지 않게 해주는 역할을 수행하고, 원형프레임은 모터가 바퀴처럼 굴러갈 수 있게 해주는 역할을 수행한다. Rolling motion을 수행하면 뱀 로봇의 형상은 활 모양을 이루게 되는데, 이때 gait parameter를 조정함으로써 활 모양이 변형된다. Gait parameter 중 amplitude, 즉 모터의 회전각도 범위를 조절함으로써 활의 휨 정도가 달라진다. 본 논문에서는 이와 같이 활모양의 몸의 형태와 모터의 회전각을 이용한 새로운 뱀로봇의 보행방식을 제안하고, 이에 대한 연구를 수행하였다. In this paper, we made a robot that mimics a snake and developed a rolling motion. A slip ring and a circular frame are used to perform a smooth rolling motion. The slip ring prevents the wires from being twisted, and the circular frame allows the motor to roll like a wheel. When rolling motion is performed, the shape of the snake robot becomes a bow shape. At this time, the bow shape is deformed by adjusting the gait parameter. Among the gait parameters, the degree of bending of the bow is changed by adjusting the amplitude, that is, the range of rotation angle of the motor. Comparing driving speeds according to these geometric shapes is the main content of this study. © 2022 The Korean Society of Mechanical Engineers.FALS

Protein Backbone Torsion Angle-Based Structure Comparison and Secondary Structure Database Web Server

Structural information has been a major concern for biological and pharmaceutical studies for its intimate relationship to the function of a protein. Three-dimensional representation of the positions of protein atoms is utilized among many structural information repositories that have been published. The reliability of the torsional system, which represents the native processes of structural change in the structural analysis, was partially proven with previous structural alignment studies. Here, a web server providing structural information and analysis based on the backbone torsional representation of a protein structure is newly introduced. The web server offers functions of secondary structure database search, secondary structure calculation, and pair-wise protein structure comparison, based on a backbone torsion angle representation system. Application of the implementation in pair-wise structural alignment showed highly accurate results. The information derived from this web server might be further utilized in the field of ab initio protein structure modeling or protein homology-related analyses

Organicferroelectric field-effect transistor with P(VDF-TrFE)/PMMA blend thin films for non-volatile memory applications

Among the many ferroelectrics polymers, poly(vinylidene fluoride-co-trifluoroethylene) [P(VDF-TrFE)] has drawn a great attention with its promising memory properties such as large remanent polarization, good fatigue and retention properties. Since the ferroelectric layer plays a critical role in the operation of memory device, it is important to control the structure of ferroelectric thin film. In order to improve the performance of a ferroelectric device, in this contribution we employed P(VDF-TrFE) layers blended with various compositions of an amorphous poly(methyl methacrylate) (PMMA) from 0 wt.% to 20 wt.%. In metal/ferroelectric/metal capacitor structure, we observed the decrease of remanent polarization from 9.13 mu C/cm(2) to 4.7 mu C/cm(2) and increase of coercive voltage from 9.5 V to 15.2 V with PMMA. Polarization switching time of the ferroelectric blend films estimated from the switched polarization vs. time curves increases with the amount of PMMA. Furthermore, ferroelectric field-effect transistors (FeFETs) based on ferroelectric P(VDF-TrFE) and PMMA blend films with single-crystalline tri-isopropylsilylethynyl pentacene (TIPS-PEN) channels show that both ON and OFF currents of the transistors are maintained with the PMMA contents despite the reduction of remanent polarization of P(VDF-TrFE)/PMMA films. (C) 2009 Elsevier B.V. All rights reservedclose6

Non-volatile memory characteristics of epitaxially grown PVDF-TrFE thin films and their printed micropattern application

Highly ordered poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) ultrathin films epitaxially grown on friction-transferred polytetrafluoroethylene (PTFE) surface were incorporated in the Metal-Ferroelectric-Metal (MFM) and Metal-Ferroelectric-Insulator-Semiconductor (MFIS) memory structure. The non-volatile memory properties in epitaxially ordered ferroelectric films were characterized with polarization and capacitance hysteresis curves at low voltage sweep of +/- 12 V and +/- 5 V in each stacking structure of MFM and MFIS, respectively. Furthermore, we present the facile micro-and nano-patterning method of fabricating MFM arrays including highly ordered PVDF-TrFE films by microimprinting. Ultrathin ferroelectric polymer films grown by epitaxy were microimprinted with a silver coated poly-dimethylesiloxane (PDMS) mold at 170 degrees C with excellent quality and the simultaneous transfer of silver electrodes on the imprinted PVDF-TrFE enabled us to fabricate the arrays of MFM capacitors in which ferroelectricity in imprinted region was well-maintained after patterning process at high temperature above 170 degrees C with good thermal stability. (C) 2011 Elsevier B. V. All rights reservedclose101

Thin ferroelectric poly(vinylidene fluoride-chlorotrifluoro ethylene) films for thermal history independent non-volatile polymer memory

In this study, we investigated the molecular and microstructures of thin poly(vinylidene fluoride-chlorotrifluoro ethylene) (PVDF-CTFE) copolymer films with three different CTFE compositions of 10, 15, 20 wt% with respect to PVDF in relation with their ferroelectric properties. All PVDF-CTFE annealed at 130 degrees C showed consecutive TTTT trans conformation with beta type crystals while films molten and re-crystallized from a temperature above their melting points exhibited alpha type crystals with characteristic TGTG conformation. Microstructures of the films treated with the two different thermal histories also supported the formation of beta and alpha type crystals with hundreds of nanometer scale sphere caps and micron level spherulites, respectively. Interestingly, PVDF-CTFE films with both alpha and beta type crystals gave rise to relatively high remnant polarization of approximately 4 mu C/cm(2) in metal/ferroelectric/metal capacitors regardless of the composition of CTFE. The ferroelectric polarization of a PVDF-CTFE film independent of thermal processing history allowed a wide processing window and easy fabrication protocol, resulting in a nonvolatile ferroelectric field effect transistor memory which exhibited saturated hysteresis loops with the current ON/OFF ratio of approximately 10(3) at +/- 60 V sweep and reliable data retention. (C) 2011 Elsevier B. V. All rights reservedclose4

Tailored Single Crystals of Triisopropylsilylethynyl Pentacene by Selective Contact Evaporation Printing

Single crystalline triisopropylsilylethynyl pentacene (TIPS-PEN) arrays are fabricated with both size and shape of each patterned domain precisely tailored by selective contact evaporation printing (SCEP), which exhibit sufficient ON/OFF current ratio as well as high field effect mobility. [GRAPHICS]close252

Correlations Between the Incidence of National Notifiable Infectious Diseases and Public Open Data, Including Meteorological Factors and Medical Facility Resources

Objectives: This study was performed to investigate the relationship between the incidence of national notifiable infectious diseases (NNIDs) and meteorological factors, air pollution levels, and hospital resources in Korea. Methods: We collected and stored 660 000 pieces of publicly available data associated with infectious diseases from public data portals and the Diseases Web Statistics System of Korea. We analyzed correlations between the monthly incidence of these diseases and monthly average temperatures and monthly average relative humidity, as well as vaccination rates, number of hospitals, and number of hospital beds by district in Seoul. Results: Of the 34 NNIDs, malaria showed the most significant correlation with temperature (r=0.949, p<0.01) and concentration of nitrogen dioxide (r=-0.884, p<0.01). We also found a strong correlation between the incidence of NNIDs and the number of hospital beds in 25 districts in Seoul (r=0.606, p<0.01). In particular, Geumcheon-gu was found to have the lowest incidence rate of NNIDs and the highest number of hospital beds per patient. Conclusions: In this study, we conducted a correlational analysis of public data from Korean government portals that can be used as parameters to forecast the spread of outbreaks

Nonvolatile Polymer Memory with Nanoconfinement of Ferroelectric Crystals

We demonstrate significantly improved performance of a nonvolatile polymeric ferroelectric field effect transistor (FeFET) memory using nanoscopic confinement of poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) within self assembled organosilicate (OS) lamellae. Periodic OS lamellae with 30 nm in width and 50 nm in periodicity were templated using block copolymer self-assembly. Confined crystallization of PVDF-TrFE not only significantly reduces gate leakage current but also facilitates ferroelectric polarization switching. These benefits are due to the elimination of structural defects and the development of an effective PVDF-TrFE crystal orientation through nanoconfinement. A bottom gate FeFET fabricated using a single-crystalline triisopropylsilylethynyl pentacene channel and PVDF-TrFE/OS hybrid gate insulator shows characteristic source-drain current hysteresis that is fully saturated at a programming voltage of +/- 8 V with an ON/OFF current ratio and a data retention time of approximately 10(2) and 2 h, respectivelyclose455

Laser-Induced Nondestructive Patterning of a Thin Ferroelectric Polymer Film with Controlled Crystals using Ge₈Sb₂Te₁₁ Alloy Layer for Nonvolatile Memory

We present a simple but robust nondestructive process for fabricating micropatterns of thin ferroelectric polymer films with controlled crystals. Our method is based on utilization of localized heat arising from thin Ge₈Sb₂Te₁₁ (GST) alloy layer upon exposure of 650 nm laser. The heat was generated on GST layer within a few hundred of nanosecond exposure and subsequently transferred to a thin poly­(vinylidene fluoride-<i>co</i>-trifluoroethylene) film deposited on GST layer. By controlling exposure time and power of the scanned laser, ferroelectric patterns of one or two microns in size are fabricated with various shape. In the micropatterned regions, ferroelectric polymer crystals were efficiently controlled in both degree of the crystallinity and the molecular orientations. Nonvolatile memory devices with laser scanned ferroelectric polymer layers exhibited excellent device performance of large remnant polarization, ON/OFF current ratio and data retention. The results are comparable with devices containing ferroelectric films thermally annealed at least for 2 h, making our process extremely efficient for saving time. Furthermore, our approach can be conveniently combined with a number of other functional organic materials for the future electronic applications

Printable Ferroelectric PVDF/PMMA Blend Films with Ultralow Roughness for Low Voltage Non-Volatile Polymer Memory

Here, a facile route to fabricate thin ferroelectric poly(vinylidene fluoride) (PVDF)/poly(methylmethacrylate) (PMMA) blend films with very low surface roughness based on spin-coating and subsequent melt-quenching is described. Amorphous PMMA in a blend film effectively retards the rapid crystallization of PVDF upon quenching, giving rise to a thin and flat ferroelectric film with nanometer scale beta-type PVDF crystals. The still, flat interfaces of the blend film with metal electrode and/or an organic semi-conducting channel layer enable fabrication of a highly reliable ferroelectric capacitor and transistor memory unit operating at voltages as low as 15 V. For instance, with a TIPS-pentacene single crystal as an active semi-conducting layer, a flexible ferroelectric field effect transistor shows a clockwise I-V hysteresis with a drain current bistability of 10(3) and data retention time of more than 15 h at +/- 15 V gate voltage. Furthermore, the robust interfacial homogeneity of the ferroelectric film is highly beneficial for transfer printing in which arrays of metal/ferroelectric/metal micro-capacitors are developed over a large area with well defined edge sharpnessclose687