• 한국진공학회지
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• 제1권1호
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• pp.176-182
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• 1992

CVD 텅스텐의 응력 및 접합 누설전류 특성을 조사하였다. 응력-연속 어닐링온도 의 그래프는 냉각곡선의 응력이 가열곡선의 그것보다 더 높게 나타나는 이력현상을 보인다. SiH4 환원에 의하여 증착된 텅스텐 막이 수소환원에 의하여 증착된 막보다 전반적으로 내부 응력 뿐만 아니라 열 응력도 더 큰 것으로 나타났으며 전자가 후자에 비해 실리콘 기판과의 부착특성이 불량한 것도 이러한 응력차와 유관한 것으로 생각된다. SiH4 환원에 의하여 형 성된 텅스텐 막은 상온에서 인장 응력 상태에 있으며, 온도가 증가됨에 따라 응력이 감소하 다가 $700^{\circ}C$ 부근에서 압축 응력 상태로 바뀌고, 계속 더 온도가 증가됨에 따라 압축 응력 이 급격히 증가한다. SiH4 환원에 의한 텅스텐 막의 증착 온도가 증가함에 따라 n+/p 접합 의 누설전류가 크게 증가하며, 특히 $400^{\circ}C$로 온도가 증가함에 따라 누설전류의 증가폭이 크게 나타났는데, 이것은 수소환원 반응시와 유사하게 텅스텐의 침투(encroachment)에 의 한 실리콘 소모가 그 원인이다. SiH4/WF6 유속비의 증가에 따라서도 누설전류가 증가하는 데 그 효과는 미소한 것으로 나타났다.

• 대한간호학회지
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• 제49권6호
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• pp.701-712
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• 2019

Purpose: Despite the high drinking rates and the complexity of drinking behaviors in adolescents, insufficient attention has been paid to their drinking patterns. Therefore, we aimed to identify patterns of adolescent drinking behaviors and factors predicting the distinct subgroups of adolescent drinking behaviors. Methods: We analyzed nationally representative secondary data obtained in 2017. Our final sample included 24,417 Korean adolescents who had consumed at least one glass of alcohol in their lifetime. To investigate patterns of drinking behaviors, we conducted a latent class analysis using nine alcohol-related characteristics, including alcohol consumption levels, solitary drinking, timing of drinking initiation, and negative consequences of drinking. Furthermore, we investigated differences in demographics, mental health status, and characteristics of substance use across the latent classes identified in our study. To do so, we used the PROC LCA with COVARIATES statement in the SAS software. Results: We identified three latent classes of drinking behaviors: current non-drinkers (CND), binge drinkers (BD), and problem drinkers (PD). Compared to the CND class, both BD and PD classes were strongly associated with higher academic year, lower academic performance, higher levels of stress, suicidal ideation, lifetime conventional or electronic cigarette use, and lifetime use of other drugs. Conclusion: Health professionals should develop and implement intervention strategies targeting individual subgroups of drinking behaviors to obtain better outcomes. In particular, health professionals should consider different characteristics across subgroups of adolescent drinking behaviors when developing the interventions, such as poor mental health status and other substance use among binge and problem drinkers.

• 천문학논총
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• 제30권2호
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• pp.133-137
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• 2015

The Galactic center uniquely provides opportunities to resolve how star clusters form in neutral gas overdensities engulfed in a large-scale accretion flow. We have performed sensitive Green Bank 100m Telescope (GBT), Karl G. Jansky Very Large Array (JVLA), and Submillimeter Array (SMA) mapping observations of molecular gas and thermal dust emission surrounding the Galaxy's supermassive black hole (SMBH) Sgr $A^{\ast}$. We resolved several molecular gas streams orbiting the center on ${\gtrsim}10$ pc scales. Some of these gas streams appear connected to the well-known 2-4 pc scale molecular circumnuclear disk (CND). The CND may be the tidally trapped inner part of the large-scale accretion flow, which incorporates inflow via exterior gas filaments/arms, and ultimately feeds gas toward Sgr $A^{\ast}$. Our high resolution GBT+JVLA $NH_3$ images and SMA+JCMT 0.86 mm dust continuum image consistently reveal abundant dense molecular clumps in this region. These gas clumps are characterized by ${\gtrsim}100$ times higher virial masses than the derived molecular gas masses based on 0.86 mm dust continuum emission. In addition, Class I $CH_3OH$ masers and some $H_2O$ masers are observed to be well associated with the dense clumps. We propose that the resolved gas clumps may be pressurized gas reservoirs for feeding the formation of 1-10 solar-mass stars. These sources may be the most promising candidates for ALMA to probe the process of high-mass star-formation in the Galactic center.

• 한국식품위생안전성학회지
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• 제12권4호
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• pp.300-303
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• 1997

The present study was carried out to know the distribution of freshwater mollusk on the chinese liver fluke in the middle of August, 1997 at the upper area of Kyungan stream located in Yongin Kun, Kyungki province. The snails were collected from the shallow and irrigation route in a rural area located along the upper area of Kyungan stream. The snails collected by hand were brought to the laboratory and cercariae naturally shed from the snails, Parafossarulus manchouricus were examined. Parafossarulus manchouricus is medically important intermediated host of the transmission of digenetic trematoda to human. Each snail was placed in aerated tap water for the detection of ceracariae and examined for expelled cercariae. Infection rate of the cercariae of Clonorchis sinensis was 3 (1.5%) among 195 individuals collected in the habitat. The identification of the cercaria of Clonorchis sinensis was performed as described by Komiya and Tajimi.

• Journal of Communications and Networks
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• 제16권6호
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• pp.667-676
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• 2014

Connectivity is a crucial quality of service measure in wireless sensor networks. However, the network is always at risk of being split into several disconnected components owing to the sensor failures caused by various factors. To handle the connectivity problem, this paper introduces an in-advance mechanism to prevent network partitioning in the initial deployment phase. The approach is implemented in a distributed manner, and every node only needs to know local information of its 1-hop neighbors, which makes the approach scalable to large networks. The goal of the proposed mechanism is twofold. First, critical nodes are locally detected by the critical node detection (CND) algorithm based on the concept of maximal simplicial complex, and backups are arranged to tolerate their failures. Second, under a greedy rule, topological holes within the maximal simplicial complex as another potential risk to the network connectivity are patched step by step. Finally, we demonstrate the effectiveness of the proposed algorithm through simulation experiments.

• Structural Engineering and Mechanics
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• 제87권6호
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• pp.601-614
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• 2023

In this study, the uniaxial ratcheting effect of Z2CND18.12N austenitic stainless steel at room and elevated temperatures is firstly simulated based on the Ahmadzadeh-Varvani hardening rule (A-V model), which is embedded into the finite element software ABAQUS by writing the user material subroutine UMAT. The results show that the predicted results of A-V model are lower than the experimental data, and the A-V model is difficult to control ratcheting strain rate. In order to improve the predictive ability of the A-V model, the parameter γ2 of the A-V model is modified using the isotropic hardening criterion, and the extended A-V model is proposed. Comparing the predicted results of the above two models with the experimental data, it is shown that the prediction results of the extended A-V model are in good agreement with the experimental data.

• Steel and Composite Structures
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• 제20권4호
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• pp.931-950
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• 2016

Ratcheting deformation of pressurized Z2CND18.12N stainless steel $90^{\circ}$ elbow pipe with local wall thinning subjected to constant internal pressure and reversed bending was studied using finite element analysis. Chen-Jiao-Kim (CJK) kinematic hardening model, which was used to simulate ratcheting behavior of pressurized $90^{\circ}$ elbow pipe with local wall thinning at extrados, flanks and intrados, was implemented into finite element software ANSYS. The local wall thinning was located at extrados, flanks and intrados of $90^{\circ}$ elbow pipe, whose geometry was rectangular cross-section. The effect of depth, axial length and circumferential angle of local wall thinning at extrados, flanks and intrados on the ratcheting behaviors of $90^{\circ}$ elbow pipe were studied in this paper. Three-dimensional elastic-plastic analysis with Chen-Jiao-Kim (CJK) kinematic hardening model was carried out to evaluate structural ratcheting behaviors. The results indicated that ratcheting strain was generated mainly along the hoop direction, while axial ratcheting strain was relatively small.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(1)
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• pp.117-120
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• 2004

As the maximum power operating point (MPOP) of photovoltaic (PV) power generation systems changes with varying atmospheric conditions such as solar radiation and temperature, an important consideration in the design of efficient PV system is to track the MPOP correctly. Although the efficiency of these Maximum Power Point Tracking algorithms is usually high, it drops noticeably in case of rapidly changing atmospheric conditions. This paper describes common MPPT control algorithm: Constant Voltage Control, Perturbation and Observation(P&O), Incremental Conductance (IncCnd) and proposes a new MPPT algorithm based on P&O algorithm. The conception and control principles of the proposed MPPT method are explained in detail and its validity of the proposed method is verified through several simulated results. As it doesn't use digital signal processor, this MPPT method has the merits of both a cost efficiency and a simple control circuit design. Therefore, it is considered that the proposed MPPT method is proper to low power, low cost PV applications.

• Journal of Information Display
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• 제7권2호
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• pp.16-21
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• 2006

The effect of improvement on the surface morphology of screen-printed carbon nanotube (CND) films was studied by using the optically clear poly-dimethylsiloxane (PDMS) elastomer for surface treatment. After the PDMS activation treatment was applied to the diode-type CNT cathode, the entangled carbon nanotube (CNT) bundles were broken up into individual free standing nanotubes to remarkably improve the field-emission characteristics over the as-deposited CNT film. Also, the cathode film morphology of a top gated triode-type structure can be treated by using the proposed surface treatment technique, which is a low-cost process, simple process. The relative uniform emission image showed high brightness with a high anode current. This result shows the possibility of using this technique for surface treatment of large-size field emission displays (FEDs) in the future.

• Journal of Advanced Marine Engineering and Technology
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• 제33권4호
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• pp.588-594
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• 2009

The maximum power point operation point(MPPOP) of photovoltaic(PV) power generation systems changes with varying atmospheric conditions such as temperature, solar radiation. For achieving a high efficiency in PV system, it is very important for PV system to track the MPPOP correctly according to operation condition. Although the MPPT(maximum power point tracking) algorithm which applied P&O(Perturbation & Observation) or IncCnd(Incremental Conductance) algorithm tracks the MPPOP efficiently, its efficiency drops noticeably in case that the incidence angle of PV panel on buoy changes rapidly. To solve this problem, this paper proposes maximum power point searching and tracking algorithm(MPPST). The proposed algorithm set the specific area and measures the PV voltage at the same interval. The proposed algorithm have been obtained high efficiency than P&O algorithm through ocean experiment.