• Geomechanics and Engineering
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• 제30권3호
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• pp.259-272
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• 2022

Rockburst is a dynamic, multivariate, and non-linear phenomenon that occurs in underground mining and civil engineering structures. Predicting rockburst is challenging since conventional models are not standardized. Hence, machine learning techniques would improve the prediction accuracies. This study describes decision based uncertainty models to predict rockburst in underground engineering structures using gradient boosting algorithms (GBM). The model input variables were uniaxial compressive strength (UCS), uniaxial tensile strength (UTS), maximum tangential stress (MTS), excavation depth (D), stress ratio (SR), and brittleness coefficient (BC). Several models were trained using different combinations of the input variables and a 3-fold cross-validation resampling procedure. The hyperparameters comprising learning rate, number of boosting iterations, tree depth, and number of minimum observations were tuned to attain the optimum models. The performance of the models was tested using classification accuracy, Cohen's kappa coefficient (k), sensitivity and specificity. The best-performing model showed a classification accuracy, k, sensitivity and specificity values of 98%, 93%, 1.00 and 0.957 respectively by optimizing model ROC metrics. The most and least influential input variables were MTS and BC, respectively. The partial dependence plots revealed the relationship between the changes in the input variables and model predictions. The findings reveal that GBM can be used to anticipate rockburst and guide decisions about support requirements before mining development.

• Advances in nano research
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• 제12권5호
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• pp.515-527
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• 2022

The application of fibers in concrete obviously enhances the properties of concrete, also the application of natural fibers in concrete is raising due to the availability, low cost and environmentally friendly. Besides, predicting the mechanical properties of concrete in general and shear strength in particular is highly significant in concrete mixture with fiber nanocomposite reinforced concrete (FRC) in construction projects. Despite numerous studies in shear strength, determining this strength still needs more investigations. In this research, Adaptive Neuro-Fuzzy Inference System (ANFIS) have been employed to determine the strength of reinforced concrete with fiber. 180 empirical data were gathered from reliable literature to develop the methods. Models were developed, validated and their statistical results were compared through the root mean squared error (RMSE), determination coefficient (R²), mean absolute error (MAE) and Pearson correlation coefficient (r). Comparing the RMSE of PSO (0.8859) and ANFIS (0.6047) have emphasized the significant role of structural parameters on the shear strength of concrete, also effective depth, web width, and a clear depth rate are essential parameters in modeling the shear capacity of FRC. Considering the accuracy of our models in determining the shear strength of FRC, the outcomes have shown that the R² values of PSO (0.7487) was better than ANFIS (2.4048). Thus, in this research, PSO has demonstrated better performance than ANFIS in predicting the shear strength of FRC in case of accuracy and the least error ratio. Thus, PSO could be applied as a proper tool to maximum accuracy predict the shear strength of FRC.

• Nuclear Engineering and Technology
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• 제56권1호
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• pp.9-18
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• 2024

In-vessel retention through external reactor vessel cooling (IVR-ERVC) is a severe accident management (SAM) strategy that has been adopted and used in many nuclear reactors such as AP1000, APR1400, and light water reactor etc. Some reactor accidents have raised concerns about nuclear reactors among residents, leading to a decrease in residents' acceptability and many studies on SAM are being conducted. Experiments on IVR-ERVC are almost impossible due to its specificity, so fluid characteristics are analyzed through BALI experiments with similar condition. In this study, computational fluid dynamics (CFD) via Reynolds-averaged Navier-Stokes (RANS) and large eddy simulation (LES) for BALI experiments were performed. Steady-state CFD analysis was performed on three turbulence models, and SST k-ω model was in good agreement with the experimental measurement temperature within the maximum error range of 1.9%. LES CFD analysis was performed based on the RANS analysis results and it was confirmed that the temperature and wall heat flux for depth was consistent within an error range of 1.0% with BALI experiment. The LES CFD analysis results were compared with those of the Lagrangian-based solver. LES matched the temperature distribution better than SOPHIA, but SOPHIA calculated the position of boundary between stratified layer and convective layer more accurately. On the other hand, Lagrangian-based solver predicted several small eddy behaviors of the convective layer and LES predicted large vortex behavior. The vibration characteristics near the cooling part of the BALI experimental device were confirmed through Fast Fourier Transform (FFT) investigation. It was found that the power spectral density for pressure at least 10 times higher near the side cooling than near the top cooling.

• 대한치과교정학회지
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• 제29권5호
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• pp.589-597
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• 1999

본 연구는 불소가 유리되는 교정용 전색제의 법랑질 탈회에 대한 효과를 미세경도법을 통해 실험적으로 규명하기 위해 112개의 치아를7개의 군으로 나누어 실험편을 제작한 뒤, 4개의 군에 광중합형 (L1군, L2군)및 자가 중합형 (S1군, S2군) 교정용 전색제인 $FluoroBond^{\circledR}$를 실험편에 도포하고 인공우식용액하에서 실험적으로 처리 완료된 실험편에 Knoop indenter를 부착한 Tukon microhardness tester를 이용해 미세경도를 측정하였고, 이를 KHN(Knoop hardness number)으로 환산하고 조직의 변성 여부를 검색하여 다음과 같은 결과를 얻었다. 1. 법랑질 깊이에 따른 미세경도는 모든군의 $50{\mu}m$ 깊이에서 최소였고, $200{\mu}m$에서 최고인 L2군을 제외한 모든군의 $300{\mu}m$ 깊이에서 최고의 수치를 보였으며, L2, S2군을 제외한 모든군에서 법랑질 깊이가 증가됨에 따라 미세경도치도 증가되었다. 2. 광중합형 및 자가중합형 교정용 전색제 군 모두 어느정도 치아우식에 저항하는 예방효과를 가지고 있었으나 통계학적인 유의성은 없었다(p>0.05). 3. 광중합형 교정용 전색제는 법랑질 깊이 $100{\mu}m,150{\mu}m,200{\mu}m$에서 치아우식 진행 억제효과가 있었다 (p<0.05). 4. 자가중합형 교정용 전색제는 법랑질 깊이 $150{\mu}m$에서 치아우식 진행 억제효과가 있었다 (p<0.05). 5. 광중합형 교정용 전색제 군과 자가중합형 교정용 전색제 군 사이의 법랑질 탈회 억제효과의 차이는 없었다 (p>0.05).

• Asian-Australasian Journal of Animal Sciences
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• 제10권2호
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• pp.245-250
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• 1997

Highly significant correlation (p < 0.001) was found between body weight and chest circumference of the local Katjang and cross-bred (local Katjang ♀ ${\times}$ German Fawn ♂ bucks under study. Increase in body length, chest circumference, depth of chest and height at withers (p < 0.001) reflected significantly the increase in body weight of the bucks. At the same age the cross-breds were bigger than the indigenous breed. No significant correlation was detected between body weight and scrotal circumference, or the latter with sperm counts in both buck types under study. However, the fluid portion of the semen increased in acidity and volume, the latter being significant (P < 0.01) in the local Katjangs, with increase in scrotal circumference. Although the effects of body condition on buck libido of both groups were not significant, the reaction time taken to mount the teaser females were significantly diminished (p < 0.001) with better body condition, at least in the local Katjangs. The reaction time gad an inverse, though not necessarily significant, relationship with semen characteristics such as volume, pH (in local Katjangs, p < 0.05), concentration, color (in cross-breds, p < 0.05), agglutination and mass movements in both phenotypes.

• 콘크리트학회논문집
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• 제11권6호
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• pp.57-67
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• 1999

Optimization scheme is presented for the design of precast prestressed double-tee beams used as slabs in the parking or market structures. The objective considered is defined by a function that minimizes the hight of the double-tee beam, including the prefabricated element and the concrete topping poured in a second phase. The Sequential Quadratic Programming method is adopted to solve the problem. As an example 12 double-tee beams are designed with the design loads of the current design code of our country. The results from optimization process show that at least 29cm less in overall height than that designed by PCI design handbook. The section determined from the optimization process was refined for practical considerations. A MathCad 7.0 Pro Spreadsheet was prepared to verify all ACI requirements for flexure, shear and deflections. Flexural tests are performed on four full-scale 12.5m prototype models and show that all the specimens are fully comply the flexural strength requirements as specified by ACI 318-95. The present optimization scheme can be used for wider application of the design of precast prestressed double-tee beams with different materials and configurations particularly for in a large scale or for important designs.

• 간호행정학회지
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• 제20권5호
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• pp.514-524
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• 2014

Purpose: The purpose of this study was to explore the experiences of clinical nurses over 40 years of age who were shift workers. Methods: Data were collected from in-depth interviews with 10 clinical nurses over 40 years of age who had at least 10 years of clinical experience and who worked in 5 acute care hospitals. The data were analyzed using Braun & Clark's thematic analysis. Results: One main theme, 3 themes, and 9 subthemes were derived. The main theme was "Sustaining a position still in conflict", and themes were as follows; "Being trained as a professional nurse", "Having unfavorable working conditions and damaged self-esteem", "Trying hard to get a sense of value as an experienced nurse" Conclusion: The results of this study show the issues of age and generational diversities in nurses in acute care hospitals. It is necessary to explore various ways to utilize the experience of older clinical nurses for the integrity of nursing organization and the development of the nursing profession.

• 한국지구과학회지
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• 제29권5호
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• pp.396-407
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• 2008

Hydrogeologic properties of a well field around middle mountainous areas in Pyosun, Jeju volcanic island were examined based on water level monitoring, geologic logging and pumping test data. Due to the alternating basaltic layers with varying permeability in the subsurface, it is difficult to analyze the hydraulic responses to artificial pumping and/or natural precipitation. The least permeable layer, detrital materials with clay, is found at a depth of 200 m below surface, but it is not an upper confining bed for lower main aquifer. Nevertheless, this layer may serve as a natural barrier to vertical percolation and to contaminant migration. Water levels of the production wells are dominantly affected by pumping frequently, while those of the remote observation wells are controlled by ambient precipitation. Results of pumping tests revealed a possible existence of horizontal anisotropy of transmissivity. However, some results of this study include inherent limitations enforced by field conditions such as the consistent of groundwater production and the set of time periods for the cessation of the pumping prior to pumping tests.

• 복식
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• 제50권
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• pp.97-118
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• 2000

The purposes of the present research were (1) to investigate the sociological factors influencing the increase of ambivalence and the relationship between, the ambivalence and fashion change(2) to categorize sets of the ambivalence expressed for contemporary fashion and (3) to examine the frequency and the patterns of ambivalence presented for contemporary fashion. This research was conducted through in depth literature review and content analysis. Data was collected from 806 colored pictures presented on 'Collections' from 1972 to 1988. Eight types of clothing cues were incluede: look color texture decorative motifs of clothing collar sleeve and wearer's headdress/hair style and make-up. The results of this study were as follows: 1 The popularization of culture has been accelerated by mass production mass consumption and mass media. Since the 1980s postmodernism and poststructuralism have resulted in the breakdown of dualistic distinction. As the ambiguity of meaning in appearance increases the meaning is negotiated constantly for identity. 2. The most frequenctly expressed ambivalence in clothing was feminity/masculinity and tradition/modernity and wealth/poverty was the least. The number of ambivalent expression were the highest during 1990s. The rapid growth in ambivalence of tradition/modernity was found in 1970s feminity/masculinity in 1980s and modesty/immodesty in 1990s. Within a clothing style ambivalence was manifested through feminine look in white for beauty/ugliness feminine look mainly in yellow/red for wealty/poverty sexy look dominantly in black for modesty/immodesty androgynous look in black for feminity/masculinity and through ecology look most frequently in black for tradition/modernity.

• 자원환경지질
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• 제33권1호
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• pp.61-75
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• 2000

Through modeling fault network using thin plate finite element technique in the San Andreas Fault system with slip rate over 1mm/year, as well as elevation, heat flow, earthquakes, geodetic data and crustal thickness, we compare the results with velocity boundary conditions of plate based on the NUVEL-1 plate model and the approximation of deformation in the Great Basin region. The frictional and dislocation creep constants of the crust are calculated to reproduce the observed variations in the maximum depth of seismicity which corresponds to the temperature ranging from $350^{\circ}C$ to $410^{\circ}C$. The rheologic constants are defined by the coefficient of friction on faults, and the apparent activation energy for creep in the lower crust. Two parameters above represent systematic variations in three experiments. The pattern of model indicates that the friction coefficient of major faults is 0.17~0.25. we test whether the weakness of faults is uniform or proportional to net slip. The geologic data show a good agreement when fault weakness is a trend of an additional 30% slip dependent weakening of the San Andreas. The results of study suggest that all weakening is slip dependent. The best models can be explained by the available data with RMS mismatch of as little as 3mm/year, so their predictions can be closely related with seismic hazard estimation, at least along faults where no data are available.