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Jang, Jaegyu,Kee, Changdon Cambridge University Press 2009 The Journal of navigation Vol.62 No.3
<P>This paper describes the verification of a real-time attitude determination algorithm during GPS attitude receiver hardware development. The GPS attitude receiver of 24 channels had been already developed in Surrey University. However 24 channels were not enough for practical usage. For this reason, a 48-channel attitude receiver with 12 channels for each antenna has been developed. To estimate attitude in real time, precise relative positions of the GPS antenna array have to be determined as rapidly as possible. However, the calculation load based on the conventional algorithm is too burdensome to perform using the RISC microprocessor. Therefore, in this paper, the cycle ambiguities of each base vector are resolved using SNUGLAD (Seoul Nat Univ GNSS Lab Attitude Determination), the design focus of which is to allow the receiver to estimate the 10 Hz onboard solutions. To keep precise solutions continuously, after ambiguity removal, cycle slip must be detected or isolated. Otherwise, the receiver would output erroneous solutions after a short signal blockage or fading of the GPS signal. To prevent this, we defined the cycle slip detection and repair scheme using a standard extended Kalman filter, which can detect and repair cycle slip within one cycle. As a result, this paper shows that time synchronized measurement with good quality and a reliable solution can be provided by the hardware developed with inexpensive chipsets and that this may be a possible cost efficient sensor for UAV or microsatellites.</P>
AVERAGING FORMULA FOR NIELSEN NUMBERS OF MAPS ON INFRA-SOLVMANIFOLDS OF TYPE (R) - CORRIGENDUM
HA, KU YONG,LEE, JONG BUM Cambridge University Press 2016 Nagoya mathematical journal Vol.221 No.1
<P>First published online by Duke University Press 15 January 2010, subsequently published online by Cambridge University Press 11 January 2016, doi:10.1017/S0027763000009818</P>
Effects of the microstructure of ZnO seed layer on the ZnO nanowire density
Yang, Jaehyun,Lee, Myung Soo,Park, Kyung,Moon, Mi Ran,Jung, Donggeun,Kim, Hyoungsub,Lee, Hoo-Jeong Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.10
<▼1><B>Abstract</B><P/></▼1><▼2><P>In this study, we synthesized ZnO nanowires using Au catalytic particles formed on a ZnO seed layer. We modulated the microstructure of the ZnO seed layer by changing the sputtering power to investigate how the underlying ZnO film microstructure affects the distribution of ZnO nanowires. Examining the samples after each of the three key steps of the growth process (ZnO seed layer deposition, Au catalytic particle formation, and nanowire growth) using various characterization methods such as scanning electron microscopy, transmission electron microscopy, and x-ray diffraction helped us illuminate the profound impacts of the grain size of the seed layer on the nanowire density.</P></▼2>
Cao, Chunyan,Yang, Hyun Kyoung,Chung, Jong Won,Moon, Byung Kee,Choi, Byung Chun,Jeong, Jung Hyun,Kim, Kwang Ho Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.23
<▼1><B>Abstract</B><P/></▼1><▼2><P>Based on a citric acid-assisted hydrothermal method, series of Ce<SUP>3+</SUP>/Tb<SUP>3+</SUP> activated fluorides have been synthesized. By controlling the amount of KNO3, the final products evolve from the Ce<SUP>3+</SUP>/Tb<SUP>3+</SUP> codoped orthorhombic phase GdF3 to the Ce<SUP>3+</SUP>/Tb<SUP>3+</SUP> codoped cubic phase KGdF4. The concentration of Ce<SUP>3+</SUP> has great effects on the crystalline phases and the morphologies of final products. The Ce<SUP>3+</SUP> concentration dependent samples illustrate the appearance of the hexagonal phase solid solution CeF3-GdF3-TbF3 in the final products. When the Ce<SUP>3+</SUP> concentration is 20 mol%, the sample Ce20 presents the hexagonal phase CeF3 but the diffraction peaks move to higher degree. The x-ray diffraction patterns suggest the phase evolution of final products, the field emission scanning electron microscopy images present the variation in morphology of samples, and the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves illustrate the optical properties of samples.</P></▼2>
Atomistic modeling of the Al-H and Ni-H systems
Ko, Won-Seok,Shim, Jae-Hyeok,Lee, Byeong-Joo Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.12
<▼1><B>Abstract</B><P/></▼1><▼2><P>Second nearest-neighbor modified embedded-atom method (MEAM) interatomic potentials for the Al-H and Ni-H binary systems have been developed on the basis of previously developed MEAM potentials of pure Al, Ni, and H. The potentials can describe various fundamental physical properties of the relevant binary alloys (structural, thermodynamic, defect, and dynamic properties of metastable hydrides or hydrogen in face-centered cubic solid solutions) in good agreement with experiments or first-principles calculations. The applicability of the present potentials to atomic level investigations of dynamic behavior of hydrogen atoms in metal membranes is also discussed.</P></▼2>
Materials for stretchable electronics in bioinspired and biointegrated devices
Kim, Dae-Hyeong,Lu, Nanshu,Huang, Yonggang,Rogers, John A. Cambridge University Press (Materials Research Soc 2012 MRS bulletin Vol.37 No.3
<▼1><B>Abstract</B><P/></▼1><▼2><P>Inorganic semiconductors such as silicon, gallium arsenide, and gallium nitride provide, by far, the most well-established routes to high performance electronics/optoelectronics. Although these materials are intrinsically rigid and brittle, when exploited in strategic geometrical designs guided by mechanics modeling, they can be combined with elastomeric supports to yield integrated devices that offer linear elastic responses to large strain (∼100%) deformations. The result is an electronics/optoelectronics technology that offers the performance of conventional wafer-based systems, but with the mechanics of a rubberband. This article summarizes the key enabling concepts in materials, mechanics, and assembly and illustrates them through representative applications, ranging from electronic “eyeball” cameras to advanced surgical devices and “epidermal” electronic monitoring systems.</P></▼2>
Jang, Yun-Guk,Kim, Won-Sik,Kim, Dai-Hong,Hong, Seong-Hyeon Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.17
<▼1><B>Abstract</B><P/></▼1><▼2><P>Ga2O3/SnO2 core-shell nanowires were synthesized by combining thermal evaporation and atomic layer deposition (ALD), and nanowire network sensors were fabricated by directly depositing them on the substrate with interdigitated Pt electrodes. Crystalline Ga2O3 nanowires of ∼20 nm diameter were grown on Au-catalyzed substrate at 800 °C. ALD-grown SnO2 shell layer was composed of interconnected nanoparticles of <10 nm, and its thickness was varied depending on the number of ALD cycles. The core-shell nanowire sensors exhibited the highest ethanol gas response at 400 °C, which was ∼200 °C lower than that for Ga2O3 nanowire sensor. The 100 cycle SnO2-coated nanowire sensor whose shell thickness was close to the Debye length of SnO2 had higher ethanol gas response in all the temperatures investigated. In addition, the core-shell nanowire sensors showed an order of magnitude higher gas response toward ethanol against other gases, such as H2, CO, and NH3.</P></▼2>
An investigation on photoluminescence and AC powder electroluminescence of ZnS:Cu,Cl,Mn,Te phosphor
Park, Bong Je,Seo, Hong Seok,Ahn, Joon Tae,Song, Jung Ho,Chung, Woon Jin,Jeon, Duk Young Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.18
<▼1><B>Abstract</B><P/></▼1><▼2><P>ZnS:Cu,Cl,Mn,Te, which shows red AC powder electroluminescence (ACPEL) emission, was synthesized using a conventional wet synthesis and a sealed vessel method. The photoluminescence (PL) and ACPEL were characterized. After the second firing, 0.5 wt% tellurium (Te)-doped ZnS:Cu,Cl,Mn,Te phosphor shows almost red PL emission from the <SUP>4</SUP>T1-<SUP>6</SUP>A1 transition of Mn<SUP>2+</SUP> ions, which are affected by the Te. Extended x-ray absorption fine structure analysis on the Mn K edge proved that the substitution of sulfur (S) with Te changes the local crystal field of the Mn<SUP>2+</SUP> ions and shifts an orange emission (∼588 nm) to a red emission (∼650 nm). A red ACPEL emission is first shown in 0.5 wt%Te-doped ZnS:Cu,Cl,Mn,Te after the third firing phosphor even though its luminance is not very high. The origin of the ACPEL emission is assumed to be not a Cu<I>x</I>S-ZnS p-n junction but a Cu<I>x</I>Te-ZnS p-n junction. Raman spectra were characterized to support that the red ACPEL emission is probably attributed to a Cu<I>x</I>Te-ZnS p-n junction.</P></▼2>
Park, Kyung-Tae,Nersisyan, Hayk H.,Chun, Byong-Sun,Lee, Jong-Hyeon Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.16
<▼1><B>Abstract</B><P/></▼1><▼2><P>Porous zirconium metal microspheres were synthesized successfully by a combustion technique using ZrO2 + 2Mg starting mixture. In this process, a controlled amount of KClO3 + 3Mg is mixed with ZrO2 + 2Mg to enable a self-sustaining combustion process and to promote a reduction of the ZrO2. The framework structure, morphology, and porosity of zirconium microspheres were determined using various techniques. Microscopic visualization suggested that the spherical structure has macroporous windows of diameter ∼0.5-5.0 μm and the space between the macropores has a wormhole-like mesoporous/microporous structure. The mesoporous structure had a pore diameter of ∼1.19 nm. This procedure provides an easy method for the synthesis of porous microspherical assemblies of Zr composed of submicrometer size particles.</P></▼2>
Elevated temperature intergranular cracking of heat-resistant alloy under tensile stress
Heo, Nam-Hoe,Chang, Jung-Chel Cambridge University Press (Materials Research Soc 2011 Journal of materials research Vol.26 No.8
<▼1><B>Abstract</B><P/></▼1><▼2><P>In a 2.25Cr1.5W heat-resistant alloy, it is shown that the time to intergranular failure under tensile stress <I>t</I> can be expressed by $t_0 \sigma ^{ - n} \exp \left({Q/RT} \right)$, where <I>t</I>0 is the constant of proportionality, <I>n</I> is the stress exponent, and <I>Q</I> is the activation enthalpy. It is shown that the dimples observed at elevated-temperature intergranular fracture surfaces are not the micro-ductile fracture areas but the interfaces between the grain boundary carbides and the neighboring grains. It is also shown that the segregation concentration of solute atoms is much higher at the grain boundary carbide interfaces than at the carbide-free grain boundaries. Under tensile stress, the elevated-temperature intergranular cracking occurs through the decohesion of grain boundary carbide interfaces, which is followed by the eventual carbide-free grain boundary cracking.</P></▼2>