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Critical face pressure and backfill pressure in shield TBM tunneling on soft ground
Kim, Kiseok,Oh, Juyoung,Lee, Hyobum,Kim, Dongku,Choi, Hangseok Techno-Press 2018 Geomechanics & engineering Vol.15 No.3
The most important issue during shield TBM tunneling in soft ground formations is to appropriately control ground surface settlement. Among various operational conditions in shield TBM tunneling, the face pressure and backfill pressure should be the most important and immediate measure to restrain surface settlement during excavation. In this paper, a 3-D hydro-mechanical coupled FE model is developed to numerically simulate the entire process of shield TBM tunneling, which is verified by comparing with real field measurements of ground surface settlement. The effect of permeability and stiffness of ground formations on tunneling-induced surface settlement was discussed in the parametric study. An increase in the face pressure and backfill pressure does not always lead to a decrease in surface settlement, but there are the critical face pressure and backfill pressure. In addition, considering the relatively low permeability of ground formations, the surface settlement consists of two parts, i.e., immediate settlement and consolidation settlement, which shows a distinct settlement behavior to each other.
Variation of Structure and Composition of the TiO₂(001) Single Crystal Surfaces
Kim,Kiseok 嶺南大學校 工業技術硏究所 1994 工業技術硏究所論文集 Vol.22 No.1
TiO₂표면의 구조와 조성의 변화를 조사하기 위해서 (001) 방향의 TiO₂ 단결정을 AES, LEED, XPS와 같은 표면 과학기법들에 의하여 특성 분석하였다. ??으로 sputter 되어 산소가 결여된 표면에서는 산화 상태가 +3, +2인 Ti suboxides의 생성이 관찰되었다. ??으로 sputter된 표면은 600K 보다 낮은 온도에서 annealing 했을 경우 표면의 산화가 별로 일어나지 않은 반면, 650K에서 20분 동안 annealing 한 결과 Ti₂O₃ stoichiometry를 가지는 표면으로 산화되었다. 750K에서 20분동안 더 annealing한 결과 {011} facet 구조를 가지는 TiO₂ stoichiometry의 표면이 생성 되었다. 이 stoichiometry는 750K 보다 높은 annealing 온도에서도 유지 되었으나 950k 이상의 annealing 온도에서는 {114} facet 구조로의 변화가 관찰 되었다. In order to examine the variation of structure and composition of the TiO₂ surfaces, a (001)-oriented TiO₂ single crystal was characterized by surface science techniques including Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). The ??-bombarded, oxygen-deficient surface showed evidence for the formation of titanium suboxides, with Ti cations with oxidation states of +3 and +2 present. Whereas no significant surface oxidation was achieved by annealing the Ar-bombarded surface at 600K or below, annealing at 650K for 20 minutes resulted in oxidation of the surface to the nominal stoichiometry Ti₂O₃. Further annealing at 750K for 20 minutes resulted in formation of a stoichiometric TiO₂ surface with a structure previously identified as {011}-facetted. The surface remained stoichiometric above 750K, and a structural change to {114} facets was observed at 950K and above.
Metastable Ge<sub>1–<i>x</i></sub>C<sub><i>x</i></sub> Alloy Nanowires
Kim, Byung-Sung,Lee, Jae-Hyun,Son, Kiseok,Hwang, Sung Woo,Choi, Byoung Lyong,Lee, Eun Kyung,Kim, Jong Min,Whang, Dongmok AmericanChemical Society 2012 ACS APPLIED MATERIALS & INTERFACES Vol.4 No.2
<P>Carbon-containing alloy materials such as Ge<SUB>1–<I>x</I></SUB>C<SUB><I>x</I></SUB> are attractive candidatesfor replacing silicon (Si) in the semiconductor industry. The additionof carbon to diamond lattice not only allows control over the latticedimensions, but also enhances the electrical properties by enablingvariations in strain and compositions. However, extremely low carbonsolubility in bulk germanium (Ge) and thermodynamically unfavorableGe–C bond have hampered the production of crystalline Ge<SUB>1–<I>x</I></SUB>C<SUB><I>x</I></SUB> alloymaterials in an equilibrium growth system. Here we successfully synthesizedhigh-quality Ge<SUB>1–<I>x</I></SUB>C<SUB><I>x</I></SUB> alloy nanowires (NWs) by a nonequilibrium vapor–liquid–solid(VLS) method. The carbon incorporation was controlled by NW growthconditions and the position of carbon atoms in the Ge matrix (at substitutionalor interstitial sites) was determined by the carbon concentration.Furthermore, the shrinking of lattice spacing caused by substitutionalcarbon offered the promising possibility of band gap engineering forphotovoltaic and optoelectronic applications.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2012/aamick.2012.4.issue-2/am201446u/production/images/medium/am-2011-01446u_0006.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am201446u'>ACS Electronic Supporting Info</A></P>
A Current Transducer with Digital Output for Motor Drive
Kim Kiseok,Sohn Ho-Pyo,Lee Heekwang,Hong Sun-Ki 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.2
A current transducer is a device that converts a current measurement into a voltage. Conventional current transducers convert the measured current into an analog voltage as output. The conventional current transducer usually includes the noise generated by the impedance of the output signal. In this paper, a current transducer with digital output for motor control is proposed to overcome the problem. The proposed digital current transducer uses a SoC that includes an MCU. The transducer transmits measured current data to an inverter controller through SPI digital communication. It has no line noise and the advantage of being able to implement various additional functions including the parameter calculations with the measured current data, condition monitoring, etc. Motor control experiments were conducted to verify the suitability of the digital current transducer. The output voltage of a Hall sensor according to the output current of the inverter is converted to a digital value through the ADC function in the SoC. The converted digital value is transmitted to the motor inverter controller through SPI communication. The results were compared with those using an analog current transducer and validated the proposed transducer