• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• 제32권1호
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• pp.3-9
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• 2021

Objectives: It is hard to accumulate research data on adolescents' suicide, because friends and family of the suicide completers might be reluctant to share the experience. To overcome the lack of information on adolescent suicide victims, the authors examined the risk and protective factors for adolescents' suicide from a character in a novel. Methods: Krystal, an adolescent female in the novel The Casual Vacancy by Joanne Rowling, failed to overcome her unfortunate circumstances and committed suicide. The authors analysed Krystal's case based on the guideline for patients with suicidal behaviours to address the complicated situation of her death. Results: Krystal grew up in a poor and dangerous environment. Despite the environmental hardships, she developed ego maturation with affectionate help from Mr Fairbrother, an assistant coach of the Girls' Rowing Team and a parish councillor. The sudden passing away of Mr Fairbrother brought on a crisis of identity for Krystal. In addition, a villainous character raped her and her brother drowned to death, which brought her great sorrow. She felt helpless and committed suicide. Conclusion: In spite of many risk factors for suicide, Krystal was able to keep her life with a few protective factors, a younger brother in the home, and a sense of responsibility for the family. After the loss of her brother, however, she collapsed in a moment. Krystal's suicide might not only be a personal choice but a breakdown of the social protection system for the youth.

• Applied Science and Convergence Technology
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• 제23권5호
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• pp.201-210
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• 2014

The influence of electron irradiation and hydrogen adsorption on the electronic structure of the $SrTiO_3$ (001) surface was investigated by ultraviolet photoemission spectroscopy (UPS). Upon electron irradiation of the surface, UPS revealed an electronic state within the band gap (in-gap state: IGS) with the surface kept at $1{\times}1$. This is considered to originate from oxygen vacancies at the topmost surface formed by electron-stimulated desorption of oxygen. Electron irradiation also caused a downward shift of the valence band maximum indicating downward band-bending and formation of a conductive layer on the surface. With oxygen dosage on the electron-irradiated surface, on the other hand, the IGS intensity was decreased along with upward band-bending, which points to disappearance of the conductive layer. The results indicate that electron irradiation and oxygen dosage allow us to control the surface electronic structure between semiconducting (nearly-vacancy free: NVF) and metallic (oxygen de cient: OD) regimes by changing the density of the oxygen vacancy. When the NVF surface was exposed to atomic hydrogen, in-gap states were induced along with downward band bending. The hydrogen saturation coverage was evaluated to be $3.1{\pm}0.8{\times}10^{14}cm^{-2}$ with nuclear reaction analysis. From the IGS intensity and H coverage, we argue that H is positively charged as $H^{{\sim}0:3+}$ on the NVF surface. On the OD surface, on the other hand, the IGS intensity due to oxygen vacancies was found to decrease to half the initial value with molecular hydrogen dosage. H is expected to be negatively charged as $H^-$ on the OD surface by occupying the oxygen vacancy site.

• Steel and Composite Structures
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• 제34권2호
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• pp.261-277
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• 2020

The main objective of this research paper is to consider vibration analysis of vacancy defected graphene sheet as a nonisotropic structure via molecular dynamic and continuum approaches. The influence of structural defects on the vibration of graphene sheets is considered by applying the mechanical properties of defected graphene sheets. Molecular dynamic simulations have been performed to estimate the mechanical properties of graphene as a nonisotropic structure with single- and double- vacancy defects using open source well-known software i.e., large-scale atomic/molecular massively parallel simulator (LAMMPS). The interactions between the carbon atoms are modelled using Adaptive Intermolecular Reactive Empirical Bond Order (AIREBO) potential. An isogeometric analysis (IGA) based upon non-uniform rational B-spline (NURBS) is employed for approximation of single-layered graphene sheets deflection field and the governing equations are derived using nonlocal elasticity theory. The dependence of small-scale effects, chirality and different defect types on vibrational characteristic of graphene sheets is investigated in this comprehensive research work. In addition, numerical results are validated and compared with those achieved using other analysis, where an excellent agreement is found. The interesting results indicate that increasing the number of missing atoms can lead to decrease the natural frequencies of graphene sheets. It is seen that the degree of the detrimental effects differ with defect type. The Young's and shear modulus of the graphene with SV defects are much smaller than graphene with DV defects. It is also observed that Single Vacancy (SV) clusters cause more reduction in the natural frequencies of SLGS than Double Vacancy (DV) clusters. The effectiveness and the accuracy of the present IGA approach have been demonstrated and it is shown that the IGA is efficient, robust and accurate in terms of nanoplate problems.

• 한국자기공명학회논문지
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• 제24권1호
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• pp.9-15
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• 2020

Nitrogen vacancy center (NV center) in diamond has recently been appeared as a promising candidate for hyperpolarization applications due to its optical pumping property by laser. Optically Detected Magnetic Resonance (ODMR) has been used as a conventional method to obtain the resonance spectrum of NV centers. ODMR, however, has a shortcoming of sensitivity and a limitation of subjects, such that the degree of hyperpolarization can hardly be estimated, and that the spins other than NV centers are invisible. In contrast, Electron Spin Resonance (ESR) spectroscopy is known to proportionally reflect the degree of spin polarization. In this work, we successfully observed the optically-induced hyperpolarization of NV spins in diamond through CW-ESR spectroscopy with an X-band system. All the NV peaks were identified by calculating the eigenvalues of NV spin Hamiltonian. The intensities of NV peaks were enhanced over 240 times after optical pumping. The enhanced peaks corresponding to the transition from |m_s=0> to |m_s=-1> revealed inverted phases, while other peaks remained in-phase. The optically-induced hyperpolarization on NV spins can be a useful polarization source, leading to ¹³C nuclear hyperpolarization in diamond.

• Bulletin of the Korean Chemical Society
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• 제15권1호
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• pp.64-74
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• 1994

The nonstoichiometric chalcogenides with NaCl-type structure were prepared and the physical and structural properties were studied. The homogeneous range and the structural change were studied based on X-ray powder diffractions using Rietveld-type full-profile fitting technique. Wide homogeneous ranges were observed in Y-S and Y-Se systems, and relatively narrow homogeneous ranges were observed in Yb-S and Yb-Se systems. Both in $Yb_{1-x}S\;and\;Yb_{1-x}Se$, a vacancy ordering transition occurred in (111) plane direction. The ordered superstructure had cubic symmetry(Fm$\bar{3}m) with doubled unit cell "a" parameter compared to the original NaCl-type. The superlattice developed in a continuous second-order transitiion was characterized by the reduced waved vector k= $(a^*+b^*+c^*)/2$. Y-S system had metallic, and YSe, YbSe system had semiconducting properties in their homogeneous ranges. It was observed that the change of electronic transport properties in extended homogeneous range did not depend on the relativeratio of metal to nonmetal, but on the quantities of vacancies.

• Journal of Preventive Medicine and Public Health
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• 제31권4호
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• pp.786-800
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• 1998

This study has attempted to show general characteristics of health centre directors who have served the post of directorship during the last 40 years. Of 3,000 such health centre directors, information on about 2,500 directors was collected. While average length of service for health center directors has increased, that of vacancy period has decreased. Rural areas have a shorter average length of service than the urban area. Rural areas have twice longer length of vacancy period per health center. Kangwon-do has the longest average length of vacancy period since 1980(2.79 months/year), and Daejeon has the shortest length of vacancy period(0.21 months/year). Chung-buk has no physician directors. The civil servant's rank for the directorship has promoted from the fifth level to the fourth level since 1990. A comparison between the physician director & non-physician director was made as follows : first, the proportion of physician directors had maintained rather high before 1980 s; 62.5% in 1963, 78.3% in 1970, 70.4% in 1980. It decreased to 44.1% in 1990 and 47.6% in 1997. Instead, non-physician directors has abruptly increased since 1980s (12.4% in 1980, 55.4% in 1990 and 50.8% in 1997). Second, physician directors mainly locate in the urban area(58.0% in 1997), but non-physician directors mainly in the rural area(67.2% in 1997). Third, since 1980, the average length of service for physician directors and for non-physician directors has become similar. Fourth, the mean age of physician directors is 45.1 years, and that of non-physician directors 55.7 years. The latter is 10 years older than the former.

• Advances in nano research
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• 제16권1호
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• pp.91-109
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• 2024

Carbon nanotubes are drawing wide attention of research communities and several industries due to their versatile capabilities covering mechanical and other multi-physical properties. However, owing to extreme operating conditions of the synthesis process of these nanostructures, they are often imposed with certain inevitable structural deformities such as single vacancy and nanopore defects. These random irregularities limit the intended functionalities of carbon nanotubes severely. In this article, we investigate the mechanical behaviour of double-wall carbon nanotubes (DWCNT) under the influence of arbitrarily distributed single vacancy and nanopore defects in the outer wall, inner wall, and both the walls. Large-scale molecular simulations reveal that the nanopore defects have more detrimental effects on the mechanical behaviour of DWCNTs, while the defects in the inner wall of DWCNTs make the nanostructures more vulnerable to withstand high longitudinal deformation. From a different perspective, to exploit the mechanics of damage for achieving defect-induced shape modulation and region-wise deformation control, we have further explored the localized longitudinal and transverse spatial effects of DWCNT by designing the defects for their regional distribution. The comprehensive numerical results of the present study would lead to the characterization of the critical mechanical properties of DWCNTs under the presence of inevitable intrinsic defects along with the aspect of defect-induced spatial modulation of shapes for prospective applications in a range of nanoelectromechanical systems and devices.

• Advances in nano research
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• 제7권3호
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• pp.209-221
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• 2019

Graphene, with impressive electronic properties, have high potential in the microelectronic field. However, graphene itself is a zero bandgap material which is not suitable for digital logic gates and its application. Thus, much focus is on graphene nanoribbons (GNRs) that are narrow strips of graphene. During GNRs fabrication process, the occurrence of defects that ultimately change electronic properties of graphene is difficult to avoid. The modelling of GNRs with defects is crucial to study the non-idealities effects. In this work, nearest-neighbor tight-binding (TB) model for GNRs is presented with three main simplifying assumptions. They are utilization of basis function, Hamiltonian operator discretization and plane wave approximation. Two major edges of GNRs, armchair-edged GNRs (AGNRs) and zigzag-edged GNRs (ZGNRs) are explored. With single vacancy (SV) defects, the components within the Hamiltonian operator are transformed due to the disappearance of tight-binding energies around the missing carbon atoms in GNRs. The size of the lattices namely width and length are varied and studied. Non-equilibrium Green's function (NEGF) formalism is employed to obtain the electronics structure namely band structure and density of states (DOS) and all simulation is implemented in MATLAB. The band structure and DOS plot are then compared between pristine and defected GNRs under varying length and width of GNRs. It is revealed that there are clear distinctions between band structure, numerical DOS and Green's function DOS of pristine and defective GNRs.

• 한국결정성장학회지
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• 제1권1호
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• pp.5-16
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• 1991

희토류 금속 산화물(RE=Ce, Pr, Nd, Eu, Er)을 1wt% 첨가한 큐빅 $ZrO_2(10 mol% Y_2O_3)$단결정을 스컬법으로 육성하였다. 육성된 단결정의 (111) 면에서의 임피던스 분석에 의한 전기적 성질을 조사하였다. 낮은 온도($500^{\circ}C$)에서 온도와 전기전도도와의 관계를 plot하였으며 $약300-400^{\circ}C$ 사이에서 전이를 관찰하였다. 저온 (전이전)과 고온(전이후 $50^{\circ}C$까지)산소 vacancy 이동에 관한 활성화 에너지를 구하였으며 전이로 인한 활성화 에너지의 차이는 안정제로 첨가한 이트륨 이온과 희토류 dopant 그리고 산소 vacancy와의 defect complexes를 붕괴하고 이온전도에 참여하게되는 산소 vacancy 형성에 관한 활성화 에너지로 볼 수 있다. yttria가 첨가됨에 따라, 또 희토류 산화물들의 첨가에 따른 활성화 에너지를 구하였으면 이온전도기구를 논의하였다. 육성된 단결정들은 첨가된 dopantdp 기인하여 Ce은 orang-red, Pr은 golden-yellow, Nd는 lilac, Eu는 옅은 pink, Er은 pink색으로 발현하였으며 가시광선 영역에서 광흡수 결과로서 나타내었다.

• 반도체디스플레이기술학회지
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• 제16권2호
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• pp.9-14
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• 2017

$ISnO_2$ thin films were prepared on p-type and n-type Si substrates to research the interface characteristics between $SnO_2$ and substrate. After the annealing processes, the amorphous structure was formed at the interface to make a Schottky contact. The O 1s spectra showed the bond of 530.4 eV as an amorphous structure, and the Schottky contact. The analysis by the deconvoluted spectra was observed the drastic variation of oxygen vacancies at the amorphous structure because of the depletion layer is directly related to the oxygen vacancy. $SnO_2$ thin film changed the electrical properties depending on the characteristics of substrates. It was confirmed that it is useful to observe the Schottky contact's properties by complementary using the XPS analysis and I-V measurement.