• Title/Summary/Keyword: Sub-Zero

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Effect of Heat Treatment on Mechanical Properties of STD11 and STS3 (공구강의 열처리 조건에 빠른 기계적 성질)

  • 박지환;이종권;류근걸;이윤배
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.5 no.3
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    • pp.204-209
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    • 2004
  • Using STD11 and STS3 as a mold set, accuracy of a mold product could be improved by heat treatment. Results of Charpy impact test and measurement of retained austenite in STS3 and STD11, STD11 was superior than STS3 in effect of sub-zero treatment and stability of working and measure. Decrease of retain austenite by sub-zero treatment in STS3 did not occured.

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On a Numerical Homotopy Method for Solving Systems of Nonlinear Equations

  • Park, Chin-Hong
    • The Mathematical Education
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    • v.25 no.3
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    • pp.77-100
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    • 1987
  • Let G : R$^n$${\times}$R\longrightarrowR$^n$ be defined by a Homotopy solving a system F($\chi$)=0 of nonlinear equations. For the vector v$\^$k/ with G'(u$\sub$k/)v$\^$k/=0, ∥v$\^$k/∥=1 where uk is one point in Zero Curve let u$\sub$0/$\^$k/=v$\^$k/+$\tau$v$\^$k/ be the first prediction for the next point u$\^$k+1/, $\tau$$\in$(0, 1). When u$\sub$0/$\^$k/ approaching too losely to some unwanted point. to follow the Zero Curve may occur the returning or cycling. One lion for it is discussed and tile parametrizied Homotopy algorithm for solving F($\chi$)=0 with it been established. Also some theorems by means of the regular value have been discussed for Zero Curves of G(u)=0 and some theorems for algorithm have been obtained.

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Study on the Surface Treatment and Performance Evaluation of Mold Steel (금형강의 표면처리 및 성능평가에 관한 연구)

  • Lim, Kyu-seong;Choi, Seong-Dae
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.21 no.1
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    • pp.81-89
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    • 2022
  • It is necessary to increase the surface hardness and improve the wear resistance and peeling resistance through the surface treatment and performance evaluation of the mold steel. As a result of vacuum heat treatment analysis, residual austenite measurement and surface treatment wear test, retained austenite should be removed by sub-zero treatment, and retained austenite was completely removed by treatment at -196℃. The TiMon film coated on the sub-zero treated STD11 specimen showed the lowest coefficient of friction.

On the Representations of Finite Distributive Lattices

  • Siggers, Mark
    • Kyungpook Mathematical Journal
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    • v.60 no.1
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    • pp.1-20
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    • 2020
  • A simple but elegant result of Rival states that every sublattice L of a finite distributive lattice 𝒫 can be constructed from 𝒫 by removing a particular family 𝒥L of its irreducible intervals. Applying this in the case that 𝒫 is a product of a finite set 𝒞 of chains, we get a one-to-one correspondence L ↦ 𝒟𝒫(L) between the sublattices of 𝒫 and the preorders spanned by a canonical sublattice 𝒞 of 𝒫. We then show that L is a tight sublattice of the product of chains 𝒫 if and only if 𝒟𝒫(L) is asymmetric. This yields a one-to-one correspondence between the tight sublattices of 𝒫 and the posets spanned by its poset J(𝒫) of non-zero join-irreducible elements. With this we recover and extend, among other classical results, the correspondence derived from results of Birkhoff and Dilworth, between the tight embeddings of a finite distributive lattice L into products of chains, and the chain decompositions of its poset J(L) of non-zero join-irreducible elements.

SIMPLE ZEROS OF L-FUNCTIONS AND THE WEYL-TYPE SUBCONVEXITY

  • Peter Jaehyun Cho;Gyeongwon Oh
    • Journal of the Korean Mathematical Society
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    • v.60 no.1
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    • pp.167-193
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    • 2023
  • Let f be a self-dual primitive Maass or modular forms for level 4. For such a form f, we define Nsf(T):=|{ρ ∈ ℂ : |𝕵(ρ)| ≤ T, ρ is a non-trivial simple zero of Lf(s)}|.. We establish an omega result for Nsf(T), which is $N^s_f(T) = \Omega(T^{\frac{1}{6}-{\epsilon}})$ for any ∊ > 0. For this purpose, we need to establish the Weyl-type subconvexity for L-functions attached to primitive Maass forms by following a recent work of Aggarwal, Holowinsky, Lin, and Qi.

Experimental investigation on the degradation of SiGe LNAs under different bias conditions induced by 3 MeV proton irradiation

  • Li, Zhuoqi;Liu, Shuhuan;Ren, Xiaotang;Adekoya, Mathew Adefusika;Zhang, Jun;Liu, Shuangying
    • Nuclear Engineering and Technology
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    • v.54 no.2
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    • pp.661-665
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    • 2022
  • The 3 MeV proton irradiation effects on SiGe low noise amplifier (LNA) (NXP BGU7005) performance under different voltage supply VCC (0 V, 2.5 V) conditions were firstly experimental studied in this present work. The S parameters including S11, S22, S21, 1 dB compression point and noise figure (NF) of the test samples under different bias voltage supply were measured and compared before and after 3 MeV proton irradiation. The total proton irradiation fluence was 1 × 1015 protons/cm2. The maximum degradation quantities of the gain S21 and NF of the test samples under zero bias are measured respectively 1.6 dB and 1.2 dB. Compared with the samples under 2.5 V bias supply, the maximum degradation of S21 and NF are respectively 1.1 dB and 0.8 dB in the whole frequency band. It is noteworthy that the gain and NF of SiGe LNAs under zero-bias mode suffer enhanced degradation compared with those under normal bias supply. The key influence factors are discussed based on the correlation of the SiGe device and the LNA circuit. Different process of the ionization damage and displacement damage under zero-bias and 2.5 V bias voltage supply contributed to the degradation difference. The underlying physical mechanisms are analyzed and investigated.

Unsaturated Soil Properties of Compacted Soil at Sub-Zero Temperature (영하온도에서 다짐된 지반의 불포화 특성)

  • Lee, Jeonghyeop;Hwang, Bumsik;Cho, Wanjei
    • Journal of the Korean GEO-environmental Society
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    • v.19 no.3
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    • pp.5-13
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    • 2018
  • Recently, construction disasters in thawing season are increasing due to the ground collapse and it is related to the improper compaction during winter season. Compaction at sub-zero temperature reduces the compaction effect and the research of mechanical properties of thawed soil after winter compaction can be used as useful data to understand the behavior of the ground in the thawing season. On the other hand, the research interest in the unsaturated soil mechanics has been increasing in the field of the geotechnical engineering. Therefore, it is expected that the research of unsaturated characteristics under the compaction of sub-zero temperature and freezing & thawing condition provides information to the researchers in the related fields. Therefore, in this research, unsaturated soil-water characteristics test and unsaturated uniaxial compression test were conducted on the specimens compacted at sub-zero temperature and continuous freezing & thawing condition to investigate change of unsaturated characteristics and matric suction. Based on the test results, the change of matric suction and the decrease of strength and stiffness were observed with the freezing & thawing conditions. Especially in case of the weathered soil, the strength and matric suction were significantly reduced with lower temperature and more repetition of freezing & thawing cycles. This result implies that compaction of sub-zero temperature and freezing & thawing cycles will have a considerable influence on the stability of the ground.

The Generalized Instantaneous Power Theory Using Mapping Matrices (맵핑 매트릭스를 사용한 일반화 순시전력 이론)

  • Kim, Hyo-Sung;Choi, Jae-Ho
    • Proceedings of the KIEE Conference
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    • 1997.07f
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    • pp.1930-1932
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    • 1997
  • Instantaneous active/reactive powers are defined in three phase four wire systems. The definition can be generally applicable to any source conditions and load conditions including nonlinear circuits. The zero-sequence power resulted from the zero-sequence voltage and zero-sequence current between two sub-systems affects both to the instantaneous active and reactive powers. The zero-sequence current can be controlled by compensation of the reactive power without power storage elements.

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3-Phase Single Stage AC-DC Converter for Small Wind Turbine System (소형풍력발전을 위한 3상 단일전력단 교류-직류 컨버터)

  • Yu-Jin Moon;Beom-Su Park;Sang-Kyu Kim;Eun-Soo Kim;Deok-Jin Lim
    • The Transactions of the Korean Institute of Power Electronics
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    • v.28 no.1
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    • pp.68-75
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    • 2023
  • This paper proposes a three-phase single-stage AC-DC converter for the small wind generation system. Input power factor improvement and insulated output can be implemented with the proposed three-phase single-stage AC-DC converter under the wide power generation voltage (80-260 Vac) and frequency (10-42 Hz) in a small wind power generation (WPG) system. The proposed converter is also capable of zero-voltage switching in the primary-side switches and zero-current switching in the secondary-side diodes by phase-shift control at a fixed switching frequency. In addition, it is possible to control a wide output voltage (Vo: 39 VDC-60 VDC) by varying the link voltage and improving the input power factor (PF) and the total harmonic distortion factor (THDi). Simulation and experimental results verified the validity of the proposed converter.