• Journal of Magnetics
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• 제17권4호
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• pp.251-254
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• 2012

The electron paramagnetic resonance (EPR) of the $Eu^{2+}$ ion in $SrCl_2$:Eu single crystal has been investigated using an X-band spectrometer. The angular dependence of magnetic resonance positions for the $Eu^{2+}$ impurity ion in the crystallographic aa-plane is analyzed with effective spin-Hamiltonian. The EPR spectra of the isolated $Eu^{2+}$ center merged to each other. The hyperfine splitting of the isolated $Eu^{2+}$ center due to the $^{151}Eu$ nucleus is approximately 35 G. Three kinds of $Eu^{2+}$ centers except the isolated $Eu^{2+}$ center, $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters, are split from the fitting of the integrated experimental spectrum with the Gaussian curve. The calculated spectroscopic splitting parameters of the $Eu^{2+}$ pairs, $Eu^{2+}$ triples, and other $Eu^{2+}$ clusters in $SrCl_2$:Eu crystal are $g_1$ = 2.06, $g_2$ = 1.94, and $g_3$ = 1.93, respectively.

• Journal of Yeungnam Medical Science
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• 제21권2호
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• pp.143-150
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• 2004

A thromboembolic stroke is believed to be precipitated by a rupture of vulnerable atheromatous plaques. Until recently the assessment of a further risk of stroke in high-risk patients in whom atherosclerosis has presented with a transient ischaemic attack (TIA), has been confined to a quantitative assessment of the luminal patency of the internal carotid artery. These traditional stratification parameters are no longer believed to be the most accurate predictors of a thrombo-embolism. This is because the process of vessel wall remodeling can maintain a luminal patency, and consequently, quite large friable plaques may remain unidentified. Accordingly, there is a need for an improved risk assessment. The fibrous cap of a vulnerable plaque is thinner, and an intraplaque hemorrhage and inflammation can occur during the development of atherosclerotic plaque. Several imaging methods for identifying vulnerable plaques have been developed. Recently, high resolution magnetic resonance (MR) imaging has emerged as an accurate non-invasive tool that can characterize the carotid plaque components in vivo. A High resolution carotid magnetic resonance is capable of distinguishing an intact, thick fibrous cap from a thin and ruptured cap in carotid plaque. In addition, a plaque MR can identify the active inflammation and detect a hemorrhage. High resolution carotid MR imaging is a valuable noninvasive method for quantifying the plaque components and identifying vulnerable plaque.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.27-38
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• 2016

The purpose of this study is to investigate the influence of moving mass on the vibration characteristics and the dynamic response of the simply supported beam. The three types of the moving mass(moving load, unsprung mass, and sprung mass) are applied to the vehicle-bridge interaction analysis. The numerical analyses are then conducted to evaluate the effect of the mass, spring and damper properties of the moving mass on natural frequencies and dynamic responses of the simply supported beam. Particularly, in the case of the sprung mass, variations of the natural frequency of simply supported beam are explored depending on the position of the moving mass and the frequency ratio of the moving mass and the beam. Finally the parametric studies on the resonance phenomena are performed with changing mass, spring and damper parameters through the dynamic interaction analyses.

• 한국수소및신에너지학회논문집
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• 제24권6호
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• pp.566-572
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• 2013

In the present study, structure analysis has been performed to understand the deflection and stress distribution for a hybrid street-lamp having a vertical-axis wind turbine and a photovoltaic panel. Modal analysis is also evaluated to avoid resonance gerenerated by sychronism between a turbine and a lamppost. To analyze deflection, stress and frequency, general analysis code(ANSYS-Mechanical 13) is employed in the present work. Throughout structure analysis in the hybrid street-lamp, maximum stress is observed at the connecting position between a turbine blade and a blade supporter. Campbell diagram which is combined the natural frequency of turbine blades and blade passing frequency is presented to analyze a system resonance. It is found that the resonance of the system having a rotating turbine blade and a lamppost can avoid by the optimal selection of geometric parameters of a wind turbine.

• Steel and Composite Structures
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• 제37권1호
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• pp.51-73
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• 2020

The present paper investigates the simultaneous resonance behavior of spiral stiffened multilayer functionally graded (SSMFG) cylindrical shells with internal and external functionally graded stiffeners under the two-term large amplitude excitations. The structure is embedded within a generalized nonlinear viscoelastic foundation which is composed of a two-parameter Winkler-Pasternak foundation augmented by a Kelvin-Voigt viscoelastic model with a nonlinear cubic stiffness. The cylindrical shell has three layers consist of ceramic, FGM, and metal. The exterior layer of the cylindrical shell is rich ceramic while the interior layer is rich metal and the functionally graded material layer is located between these layers. With regard to classical shells theory, von-Kármán equation, and Hook law, the relations of stress-strain are derived for shell and stiffeners. The spiral stiffeners of the cylindrical shell are modeled according to the smeared stiffener technique. According to the Galerkin method, the discretized motion equation is obtained. The simultaneous resonance is obtained using the multiple scales method. Finally, the influences of different material and geometrical parameters on the system resonances are investigated comprehensively.

• 한국인터넷방송통신학회논문지
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• 제12권1호
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• pp.51-56
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• 2012

새롭게 발전시킨 등가 전송선로 해석법을 이용하여 원형 수직 캐비티 표면 광방출 레이저(VCSELs)의 공진특성을 연구되었다. VCSEL을 설계하기 위하여 필요한 광학변수들인 주기적인 Bragg 거울에서 나타나는 차단대역 특성과 반사율을 분석하였다. 또한, 설계된 VCSEL의 양자효율과 문턱 전류밀도를 평가하기 위하여 원형 모드 전송 선로 해석법의 횡방향 공진조건을 이용하였다. 이 해석법은 원형 VCSEL의 광학적 특성들을 분석하기 위한 수치해석 시간을 현저하게 줄여 주며, 명확한 설계개념을 제공한다.

• 한국초전도ㆍ저온공학회논문지
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• 제16권1호
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• pp.1-5
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• 2014

We calculated the resonance tunneling energy band in the BCS gap for Type-II superconductor in which periodic potential is generated by external magnetic flux. In this model, penetrating magnetic flux was assumed to be in a fixed lattice state which is not moving by an external force. We observed the existence of two subbands when we used the same parameters as for the $Nd_{1.85}Ce_{0.15}CuO_X$ thin film experiment. The voltages at which the regions of negative differential resistivity (NDR) started after the resonant tunneling ended were in a good agreement with the experimental data in the field region of 1 T - 2.2 T, but not in the high field regions. Discrepancy occurred in the high field region is considered to be caused by that the potential barrier could not be maintained because the current induced by resonant tunneling exceeds the superconducting critical current. In order to have better agreement in the low field region, more concrete designing of the potential rather than a simple square well used in the calculation might be needed. Based on this result, we can predict an occurrence of the electromagnetic radiation of as much difference of energy caused by the 2nd order resonant tunneling in which electrons transit from the 2nd band to the 1st band in the potential wells.

• Nuclear Engineering and Technology
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• 제51권4호
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• pp.1017-1023
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• 2019

The increase of the alternate current frequency results in increased rotational speed of the electrical motors and connected pumps. The consequence for the reactor coolant pumps is increased flow in primary coolant system. Increase of the current frequency can be initiated by the subsynchronous resonance phenomenon (SSR). This paper analyses the implications of the SSR and consequential increase of the frequency on the nuclear power plant safety. The Simulink $MATLAB^{(R)}$ model of the steam turbine and governor system and RELAP5 computer code of the pressurized water reactor are used in the analysis. The SSR results in fast increase of reactor coolant pumps speed and flow in the primary coolant system. The turbine trip value is reached in short time following SSR. The increase of flow of reactor coolant pumps results in increase of heat removal from reactor core. This results in positive reactivity insertion with reactor power increase of 0.5% before reactor trip is initiated by the turbine trip. The main parameters of the plant did not exceed the values of reactor trip set points. The pressure drop over reactor core is small discarding the possibility of core barrel lift.

• 한국자기공명학회논문지
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• 제23권1호
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• pp.12-19
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• 2019

A former study has shown that the spin-lattice relaxation time ($T_1$) in cancerous prostate tissue had enhanced contrast at an ultra-low magnetic field, $132{\mu}T$. To study the field dependence and the origin of the contrast we measured $T_1$ in pairs of ex-vivo prostate tissues at the Earth's magnetic field. A portable and coil-based nuclear magnetic resonance (NMR) system was adopted for $T_1$ measurements at $40{\mu}T$. The $T_1$ contrast, ${\delta}=1-T_1$ (more cancer)/$T_1$(less cancer), was calculated from each pair. Additionally, we performed pathological examinations such as Gleason's score, cell proliferation index, and micro-vessel density (MVD), to quantify correlations between the pathological parameters and $T_1$ of the cancerous prostate tissues.

• Current Applied Physics
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• 제18권11호
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• pp.1327-1337
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• 2018

This paper investigates the vibration behavior of pristine and defected triangular graphene sheets; which has recently attracted the attention of researchers and compare these two types in natural frequencies and sensitivity. Here, the molecular dynamics method has been employed to establish a virtual laboratory for this purpose. After measuring the different parameters obtained by the molecular dynamics approach, these data have been analyzed by using the frequency domain decomposition (FDD) method, and the dominant frequencies and mode shapes of the system have been extracted. By analyzing the vibration behaviors of pristine triangular graphene sheets in four cases (right angle of 45-90-45 configuration, right angle of 60-90-30 configuration, equilateral triangle and isosceles triangle), it has been demonstrated that the natural frequencies of these sheets are higher than the natural frequency of a square sheet, with the same number of atoms, by a minimum of 7.6% and maximum of 26.6%. Therefore, for increasing the resonance range of sensors based on 2D materials, nonrectangular structures, and especially the triangular structure, can be considered as viable candidates. Although the pristine and defective equilateral triangular sheets have the highest values of resonance, the sensitivity of defective (45,90,45) triangular sheet is more than other configurations and then, defective (45,90,45) sheet is the worst choice for sensor applications.