• 자원환경지질
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• 제55권3호
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• pp.273-280
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• 2022

본 연구의 목적은 빅데이터 분석을 활용한 지질자원기술에 대한 사회적 인식을 바탕으로 지질자원기술에 대한 국민 인식 제고 방안을 논의하는 데 있다. 이를 위하여 2010년 1월 1일부터 2022년 4월 14일까지 54개 언론사를 대상으로 언론 기사 제목과 본문에 '지질자원기술'이 포함된 5,044건의 기사를 분석대상으로 삼았으며, 빅데이터 분석을 연구방법으로 채택하였다. 분석 결과, 연구소 중심, 미국·중국·일본 중심, 포항시 지진, 연구원 원장 중심으로 주제어가 구성되어 있었으며, 중요 주제어는 지질, 산업, 광물개발, 환경, 에너지, 원자력, 지하수 등으로 나타났다. 또한, 토픽 분석 결과, 토픽들은 개별적으로 위치하지 않고 전문가, 환경, 연구소 등을 중심으로 상호 연계되어 있고, 미래, 산업, 글로벌 토픽 등으로 확인되었다. 이러한 결과를 바탕으로 지질자원기술의 국민 인식 제고 방안을 논의하였다.

• 대한간호학회지
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• 제52권3호
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• pp.308-323
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• 2022

Purpose: This study aimed to construct and test a predictive model for the quality of life (QOL) in mothers of children with developmental disabilities (DB). The hypothesized model included severity of illness, distress, uncertainty, self-help, and parenting efficacy as influencing factors, QOL as a consequence based on the Braden's Self-Help Model. Methods: The data were collected through a direct and online surveys from 206 mothers in 8 locations, including welfare or daycare centers, developmental treatment centers, and The Parents' Coalition for the Disabled located in two provinces of Korea. Data were analysed using SPSS/WIN 23.0 and AMOS 21.0 program. Results: The fit indices of the predictive model satisfied recommended levels; 𝛘² = 165.79 (p < .001), normed 𝛘² (𝛘²/df) = 2.44, RMR = .04, RMSEA = .08, GFI = .90, AGFI = .85, NFI = .91, TLI = .93, CFI = .95. Among the variables, distress (β = - .46, p < .001), parenting efficacy (β = .22, p < .001), and self-help (β = .17, p = .018) had direct effects on QOL. Severity of illness (β = - .61, p = .010) and uncertainty (β = - .08, p = .014) showed indirect effects. The explanatory power of variables was 61.0%. Conclusion: The study results confirm the utility of Braden's Self-Help Model. They provide a theoretical basis for improving QOL in mothers of children with DB. Nursing intervention strategies that can relieve mothers' distress and uncertainty related to disease and enhance parenting efficacy and self-help behavior should be considered.

• 한국분말재료학회지
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• 제29권1호
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• pp.14-21
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• 2022

In the powder bed fusion (PBF) process, a 3D shape is formed by the continuous stacking of very fine powder layers using computer-aided design (CAD) modeling data, following which laser irradiation can be used to fuse the layers forming the desired product. In this method, the main process parameters for manufacturing the desired 3D products are laser power, laser speed, powder form, powder size, laminated thickness, and laser diameter. Stainless steel (STS) 316L exhibits excellent strength at high temperatures, and is also corrosion resistant. Due to this, it is widely used in various additive manufacturing processes, and in the production of corrosion-resistant components with complicated shapes. In this study, rectangular specimens have been manufactured using STS 316L powder via the PBF process. Further, the effect of heat treatment at 800 ℃ on the microstructure and hardness has been investigated.

• Geomechanics and Engineering
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• 제28권5호
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• pp.505-520
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• 2022

In recent years, geotextile-encased gravel columns (usually called stone columns) have become a popular method to increasing soil shear strength, decreasing the settlement, acceleration of the rate of consolidation, reducing the liquefaction potential and increasing the bearing capacity of foundations. The behavior of improved loose base-soil with gravel columns under shear loading and the shear stress-horizontal displacement curves got from large scale direct shear test are of great importance in understanding the performance of this method. In the present study, by performing 36 large-scale direct shear tests on sandy base-soil with different fine-content of zero to 30% in both not improved and improved with gravel columns, the effect of the presence of gravel columns in the loose soils were investigated. The results were used to predict the shear stress-horizontal displacement curve of these samples using support vector machines (SVM). Variables such as the non-plastic fine content of base-soil (FC), the area replacement ratio of the gravel column (Arr), the geotextile encasement and the normal stress on the sample were effective factors in the shear stress-horizontal displacement curve of the samples. The training and testing data of the model showed higher power of SVM compared to multilayer perceptron (MLP) neural network in predicting shear stress-horizontal displacement curve. After ensuring the accuracy of the model evaluation, by introducing different samples to the model, the effect of different variables on the maximum shear stress of the samples was investigated. The results showed that by adding a gravel column and increasing the Arr, the friction angle (ϕ) and cohesion (c) of the samples increase. This increase is less in base-soil with more FC, and in a proportion of the same Arr, with increasing FC, internal friction angle and cohesion decreases.

• Advances in nano research
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• 제12권1호
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• pp.81-99
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• 2022

The aim of current work is to evaluate thermo-electrical characteristics of graphene nanoplatelets Reinforced Composite (GNPRC) coupled with magneto-electro-elastic (MEE) face sheet. In this regard, a cylindrical smart nanocomposite made of GNPRC with an external MEE layer is considered. The bonding between the layers are assumed to be perfect. Because of the layer nature of the structure, the material characteristics of the whole structure is regarded as graded. Both mechanical and thermal boundary conditions are applied to this structure. The main objective of this work is to determine critical temperature and critical voltage as a function of thermal condition, support type, GNP weight fraction, and MEE thickness. The governing equation of the multilayer nanocomposites cylindrical shell is derived. The generalized differential quadrature method (GDQM) is employed to numerically solve the differential equations. This method is integrated with Deep Learning Network (DNN) with ADADELTA optimizer to determine the critical conditions of the current sandwich structure. This the first time that effects of several conditions including surrounding temperature, MEE layer thickness, and pattern of the layers of the GNPRC is investigated on two main parameters critical temperature and critical voltage of the nanostructure. Furthermore, Maxwell equation is derived for modeling of the MEE. The outcome reveals that MEE layer, temperature change, GNP weight function, and GNP distribution patterns GNP weight function have significant influence on the critical temperature and voltage of cylindrical shell made from GNP nanocomposites core with MEE face sheet on outer of the shell.

• 한국인터넷방송통신학회논문지
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• 제22권1호
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• pp.65-70
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• 2022

최근 고속 스토리지의 활성화로 인해 하드디스크를 전제로 설계된 메모리 관리 시스템에 대한 재고가 필요한 시점에 이르렀다. 본 논문은 고속 스토리지 환경에서 메모리 접근 시간이 페이지 크기에 민감한 점을 관찰하고, 그 이유가 페이지 폴트율보다 TLB 미스율이 메모리 접근시간에 미치는 영향력이 커졌기 때문임을 확인하였다. 또한, TLB 미스율과 페이지 폴트율이 페이지 크기 변화에 따라 상충관계를 나타냄을 확인하고 이를 모델링하는 함수를 설계하였다. TLB 미스율의 경우 파워 피팅을 통한 모델링을 하였으며, 페이지 폴트율의 경우 2개의 항을 가진 지수 피팅을 통한 모델링을 하였다. 검증 실험을 통해 설계된 모델 함수에 의한 예측치가 실제 결과값을 잘 반영함을 확인하였다.

• Steel and Composite Structures
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• 제46권4호
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• pp.471-483
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• 2023

This paper presents an analytical hyperbolic theory based on the refined shear deformation theory for mechanical stability analysis of the simply supported advanced composites plates (exponentially, sigmoidal and power-law graded) under triangular, trapezoidal and uniform uniaxial and biaxial loading. The developed model ensures the boundary condition of the zero transverse stresses at the top and bottom surfaces without using the correction factor as first order shear deformation theory. The mathematical formulation of displacement contains only four unknowns in which the transverse deflection is divided to shear and bending components. The current study includes the effect of the geometric imperfection of the material. The modeling of the micro-void presence in the structure is based on the both true and apparent density formulas in which the porosity will be dense in the mid-plane and zero in the upper and lower surfaces (free surface) according to a logarithmic function. The analytical solutions of the uniaxial and biaxial critical buckling load are determined by solving the differential equilibrium equations of the system with the help of the Navier's method. The correctness and the effectiveness of the proposed HyRPT is confirmed by comparing the results with those found in the open literature which shows the high performance of this model to predict the stability characteristics of the FG structures employed in various fields. Several parametric analyses are performed to extract the most influenced parameters on the mechanical stability of this type of advanced composites plates.

• 응용통계연구
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• 제36권4호
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• pp.295-307
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• 2023

HAR 모형은 간단한 선형 모형으로 실현 변동성의 장기기억성을 비교적 잘 설명할 수 있어 널리 쓰이고 있다. 하지만, 실현 변동성은 조건부 이분산성, 레버리지 효과, 변동성 집중 등과 같은 복잡한 특징을 보이고 있기에 단순 HAR 모형을 확장할 필요가 있다. 따라서 본 연구는 조건부 이분산성을 설명하는 GARCH 모형에 임계값에 따라 계수가 달라지는 비선형 모형인 임계 HAR 모형(THAR-GARCH)을 제안하고 그 추정 방법 및 예측 성능에 대해서 살펴보고자 한다. 보다 구체적으로 오차항의 등분산 가정을 벗어났기 때문에 모형의 계수를 추정하기 위해서 반복적인 가중최소제곱추정법을 제안하고 모의실험을 통해 일치성을 보였다. 또한 전세계 21개의 주요 주가 지수의 실현 변동성에 대한 예측 오차를 비교함으로써 제안한 GARCH 오차를 가지는 임계 HAR 모형이 일반적으로 더 우수한 예측력을 보임을 확인하였다.

• 한국정밀공학회지
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• 제13권9호
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• pp.114-129
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• 1996

This paper describes the whole development phase for the underwater vehicle actuating system with high hydroload torque disturbance. This includes requirement analysis, system modeling, control algorithm design, real time implementation, test and performance evaluations. As for driving control algorithms, fuzzy logic, variable structure and PD(Proportional-Differential) algorithm were designed and implemented on board controller using a single chip microprocessor. Intel 8797. And test and performance evaluation is carried out both single test and wystem integration test. We could confirm the basic performance of actuating system through the single test and gereral developing work of any actuating systems was finished with a single performance test of actuating system without system integration test. But, we suggested that system integration test be needed. System integration test is carried out using G/C HILS(Guidance and Control Hardware-In-the -Loop Simulation) which is constituted flight motion simulator, load simulator, real time host computer and the related subsystems such as inertial navigation system, power supply system and Guidance and Control Computer etc.. The most important practical contribution of this paper is that full system characteristics such as minimal control effort, enhancement of guidance and autopilot performance by the actuating system using G/C HILS technique are investigated. Through full running G/C HILS, in spite of the passing to single tests, some control algorithm resulted in failure as to stability of full system and system time frame.

• Nuclear Engineering and Technology
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• 제55권2호
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• pp.460-474
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• 2023

A simple but accurate mathematical model is crucial for dynamic simulations and controller design of helical coil once-through steam generator (OTSG). This paper presents a three-region movable boundary dynamic model of the helical coil OTSG. Based on the secondary side fluid conditions, the OTSG is divided into subcooled region (two control volumes), two-phase region (two control volumes) and superheated region (three control volumes) with movable boiling boundaries between each region. The nonlinear dynamic model is derived based on mass, energy and momentum conservation equations. And the linear model is obtained by using the transfer function and state space transformation, which is a 37-order model of five input and three output. Validations are made under full-power steady-state condition and four transient conditions. Results show good agreements among the nonlinear model, linear model and the RELAP5 model, with acceptable errors. This model can be applied to dynamic simulations and controller design of helical coil OTSG with constant primary-side flow rate.