• 한국정밀공학회지
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• 제2권2호
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• pp.43-59
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• 1985

In relation to the machinability of drilling operation, experiments were made to investigate the effect of cutting condition on static as well as dynamic cutting resistances in cutting plane carbon steel (SM 45 C) with H.S.S. twist drills. The results were as follows. 1) The static cutting resistances on carbon steel can practically be calculated by the following equations which were derived from experimental result. The deviation from the experimental values was less than 8% and 13% for cutting torque and thrust respectively. For cutting torque M: M=0.019 $H_B\;{f^{0.68}d^{1.68}$ For thrust T: T=0.400406 $r^{0.6}d^{0.68}$ + 0.1835 $H_BC^2$(where $H_B$: Brinnel hardness) 2) The static components of cutting resistance are increased exponentially with increasing drill diameter and feed rate. On the effect of drill diameter, the dynamic components of torque are decreased with increasing dirll diameter because of rigidity, the dynamic components of thrust being not effected with the changes. 3) As feed rates increase, the dynamic components of torque rather decrease although its changes on thrust components are unstable. 4) The static components of cutting resistance and dynamic component of torque are slightly decreased in accordance with the increase of spindle speed although its dynamic thrust components are not effected by the spindle speed.

• Journal of Astronomy and Space Sciences
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• 제17권2호
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• pp.151-162
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• 2000

근접촉쌍성을 분광형에 따라 A형과 F형으로 분류하여 각각의 물리적 특성과 진화를 조사하였다. 그 결과, 근접촉쌍성이 TRO 이론에 따른 진화 경로를 겪는다고 가정하면, F형이 A형에 비하여 더 접촉에 가까운 즉, W UMa형에 근접한 상태에 있을 가능성이 있음을 알 수 있었다. NCBs의 질량-반경 관계, 질량-광도 관계 및 H-R도를 조사하였는데 그 결과 A형이 F형에 비하여 질량교환이 활발할 것으로 생각된다. 근접촉쌍성은 ZAMS와 평행하게 나타나며 접촉쌍성의 진화 위치와 거의 일치하고 있다.

• International Journal of Automotive Technology
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• 제7권3호
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• pp.245-249
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• 2006

Accelerated aging of engine exhaust system components such as catalytic converters are traditionally performed using an engine/dynamometer test stand. $SwRI^{(R)}'s\;FOCAS^{(R)}$ system reduces or eliminates many of the engine based aging limitations. This paper will describe several studies. These include: 1) replication of engine based catalyst aging cycles with added precision and dependability; 2) catalyst aging with and without lubricating oil effects; 3) effects of lubricant phosphorus on catalyst performance; and 4) the potential to thermally age components beyond the capabilities of engine based systems. The first study includes the development of the SwRI FOCAS system to run programmed aging conditions with or without lubricating oil. A description of the subsystems is given. The second two studies used the SwRI FOCAS system to age catalysts. One study compared thermal-only aging using of the SwRI FOCAS system with equivalent aging on a traditional engine/dynamometer test stand. The other study examined the effect on catalyst performance of two lubricating oils containing different levels of phosphorus, and compared the results to field data generated using the same oils in a fleet of vehicles.

• Journal of Ginseng Research
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• 제44권5호
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• pp.690-696
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• 2020

Background: As the main metabolites of ginsenosides, 20(S, R)-protopanaxadiol [PPD(S, R)] and 20(S, R)-protopanaxatriol [PPT(S, R)] are the structural basis response to a series of pharmacological effects of their parent components. Although the estrogenicity of several ginsenosides has been confirmed, however, the underlying mechanisms of their estrogenic effects are still largely unclear. In this work, PPD(S, R) and PPT(S, R) were assessed for their ability to bind and activate human estrogen receptor α (hERα) by a combination of in vitro and in silico analysis. Methods: The recombinant hERα ligand-binding domain (hERα-LBD) was expressed in E. coli strain. The direct binding interactions of ginsenosides with hERα-LBD and their ERα agonistic potency were investigated by fluorescence polarization and reporter gene assays, respectively. Then, molecular dynamics simulations were carried out to simulate the binding modes between ginsenosides and hERα-LBD to reveal the structural basis for their agonist activities toward receptor. Results: Fluorescence polarization assay revealed that PPD(S, R) and PPT(S, R) could bind to hERα-LBD with moderate affinities. In the dual luciferase reporter assay using transiently transfected MCF-7 cells, PPD(S, R) and PPT(S, R) acted as agonists of hERα. Molecular docking results showed that these ginsenosides adopted an agonist conformation in the flexible hydrophobic ligand-binding pocket. The stereostructure of C-20 hydroxyl group and the presence of C-6 hydroxyl group exerted significant influence on the hydrogen bond network and steric hindrance, respectively. Conclusion: This work may provide insight into the chemical and pharmacological screening of novel therapeutic agents from ginsenosides.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1468-1475
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• 2023

Enhancement of wear resistance of components used in fast reactors is necessary for long service life of the components. Plasma nitriding is a promising surface modification technology to impart high hardness and improved wear resistance of various steel components. This study discusses the characterization of chrome nitrided SS316L casing ring used in secondary sodium pump of fast breeder reactor and its stability under long term sodium exposure. Microstructural and hardness analysis showed that stress relieved component could be chrome nitrided successfully to a thickness of about 100 ㎛. Assessment of in-sodium performance of the chrome nitrided casing ring subjected to long term exposure up to 5000h at 550℃, showed retention of chrome nitrided layer with a case depth almost similar to that before sodium exposure. A slight decrease in the hardness was observed due to prolonged high temperature sodium exposure. Tribological studies indicate very low coefficient of friction indicating the retention of good wear resistance of the coating even after long term sodium exposure.

• 한국음향학회지
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• 제21권7호
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• pp.665-670
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• 2002

프리엠퍼시스 필터의 일반적인 형태는 y(n)=s(n)-As(n-1)이고, 여기서 A값은 유성음의 경우 0.9∼l.0사이의 값이다. 또한 A값은 프리엠퍼시스의 기울기 값을 반영하고 기존의 방법에서는 자기상관계수 값인 R(1)/R(0)를 사용한다. 본 논문에서는 성문특성으로 인해 고주파특성이 약화되는 것을 보상하기 위하여 새로운 평탄화 기법을 제안한다. 우선 포만트 주파수 예측을 위해 LSP 파라미터의 간격정보를 사용하였다. 찾아진 포만트 주파수들간의 선형보간을 통해 기울기와 역기울기 값을 구하여 평탄화 과정을 수행한다. 실험결과에서는 제안한 방법이 기존의 방법보다 평탄화 특성이 우수한 것으로 나타났다. 즉 본 논문에서는 약화된 고주파 성분을 보상하는 과정에서 평탄화 요소로 LSP의 간격정보를 사용하였다.

• Journal of applied mathematics & informatics
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• 제12권1_2호
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• pp.81-105
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• 2003

This paper deals with the very interesting problem about the influence of piecewise smooth boundary conditions on the distribution of the eigenvalues of the negative Laplacian in R$^3$. The asymptotic expansion of the trace of the wave operator (equation omitted) for small ｜t｜ and i=√-1, where (equation omitted) are the eigenvalues of the negative Laplacian (equation omitted) in the (x$^1$, x$^2$, x$^3$)-space, is studied for an annular vibrating membrane $\Omega$ in R$^3$together with its smooth inner boundary surface S$_1$and its smooth outer boundary surface S$_2$. In the present paper, a finite number of Dirichlet, Neumann and Robin boundary conditions on the piecewise smooth components (equation omitted)(i = 1,...,m) of S$_1$and on the piecewise smooth components (equation omitted)(i = m +1,...,n) of S$_2$such that S$_1$= (equation omitted) and S$_2$= (equation omitted) are considered. The basic problem is to extract information on the geometry of the annular vibrating membrane $\Omega$ from complete knowledge of its eigenvalues by analysing the asymptotic expansions of the spectral function (equation omitted) for small ｜t｜.

• Kyungpook Mathematical Journal
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• 제58권1호
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• pp.9-17
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• 2018

Let $R ={\oplus}_{n{\in}Z}R_n$ be a graded commutative Noetherian ring and let I be a graded ideal of R and J be an arbitrary ideal. It is shown that the i-th generalized local cohomology module of graded module M with respect to the (I, J), is graded. Also, the asymptotic behaviour of the homogeneous components of $H^i_{I,J}(M)$ is investigated for some i's with a specified property.

• Journal of Communications and Networks
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• 제14권6호
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• pp.692-702
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• 2012

Supporting quality of service (QoS) guarantees for diverse multimedia services are the primary concerns for WiMAX (IEEE 802.16) networks. A scheduling scheme that satisfies QoS requirements has become more important for wireless communications. We propose a downlink scheduling scheme called adaptive priority-based downlink scheduling (APDS) for providing QoS guarantees in IEEE 802.16 networks. APDS comprises two major components: Priority assignment and resource allocation. Different service-type connections primarily depend on their QoS requirements to adjust priority assignments and dispatch bandwidth resources dynamically. We consider both starvation avoidance and resource management. Simulation results show that our APDS methodology outperforms the representative scheduling approaches in QoS satisfaction and maintains fairness in starvation prevention.

• 한국주거학회논문집
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• 제17권3호
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• pp.123-131
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• 2006

This study examined types and color conditions of street views through relationship of high-storied apartment house to street components which has great visual influence on urban street view and requires harmony with street environment as background factor and conducted positive experiment with high-storied apartment houses located at housing site development districts in Gwangju Metropolitan City since 1990s in order to set applicable color ranges in designing external colors of high-storied apartment houses which became background of street view by types. Consequently, in image changes of four factors of main colors in classified street types, P, RP, R and YR colors showed high average values in naturalness, harmony and unity and GY, G, BG and B colors showed dichotomy with low average value, but image of personality showed generally low average value. RP, R and YR colors showed higher adaptability and GY, G and BG colors showed lower adaptability. It was confirmed that according to adaptability of main colors used in high-storied apartment houses by street types, there was difference of appropriate color range in street components and external colors of high-storied apartment houses by street types.