• Child Health Nursing Research
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• v.4 no.2
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• pp.207-220
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• 1998

The purpose of this study was to build a substantive theory about the experience of the maternal uncertainty in childhood chronic illness. The qualitative research method used was grounded theory. The interviewees were 12 mothers who have cared for a child who had chronic illness. The data were collected through in-depth interviews with audiotape recording done by the investigator over a period of nine months. The data were analyzed simutaneously by a constant comparative method in which new data were continuously coded into categories and properties according to Strauss and Corbin's methodology. The 34 concepts were identified as a result of analyzing the grounded data. Ten categories emerged from the analysis. The categories were lack of clarity, unpredictability, unfamiliarity, negative change, anxiety, devotion normalization and burn-out. Causal conditions included : lack of clarity, unpredictability, unfamiliarity and change ; central phenomena : anxiety, being perplexed ; context. seriousness of illness, support ; intervening condition : belief action/interaction strategies devotion, overprotection ; consequences : normalization, burn-out. These categories were synthesized into the core concept-anxiety. The process of experiencing uncertainty was 1) Entering the world of uncertainty, 2) Struggling in the tunnel of uncertainty, 3) Reconstruction of the situation of uncertainty. Four hypotheses were derived from the analysis : (1) The higher the lack of clarity, unpredictability, unfamiliaity, change, the higher the level of uncertainty (2) The more serious the illness and the less the support, the higher the level of uncertainty. (3) The positive believes will influence the devoted care and normalization of the family life. Through this substantive theory, pediatric nurses can understand the process of experiencing maternal uncertainty in childhood chronic illness. Further research to build substantive theories to explain other uncertainties may contribute to a formal theory of how normalization is achieved in the family with chronically ill child.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.297-309
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• 2012

The stability assessment of abandoned gangway for the purpose of services was performed. Among the many factors that affect the stability of openings, the span of the opening in a given rock mass condition provides an important element of design. In this paper, the stability of gangway was assessed by the critical span curves proposed by Lang, the modified Mathews'stability graph method and using support measures of the Q system. In the evaluation of stability as a whole the gangway is considered as stable. But the rockfalls of wedge-shaped blocks were expected in the area in which the horizontal joints of low angle appear. The support measures such as local rock bolts are required to use for commercial purposes of the abandoned gangway. And entrance section may require the particular attention as unstable section. Since there are so many spalling due to bad blasting in the roof and sidewall of gangway, the scaling operations should be followed primarily.

• Tunnel and Underground Space
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• v.16 no.5 s.64
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• pp.405-412
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• 2006

It is well known that shotcrete is the most important support member for the construction of large underground spaces. Generally, the strength of the field shotcrete is heavily dependent on the field mixing and spraying conditions so that it is different from the strength of the shotcrete mixed in laboratories. As a support member, the early strength of shotcrete unlike concrete is very important to the initial stabilization of the underground spaces. Therefore, the field methods to efficiently test the early strength of shotcrete have been highly required. This paper aimed to verify the pneumatic pin penetration test and the point load test for measuring the early strength of the field shotcrete. As a result of the experiments through a series of uniaxial compression, pin penetration, and point load tests for the range of the early shotcrete strength, two equations to estimate reliably the uniaxial compressive strength by the pin penetration and the point load tests were acquired.

• Korean Journal of Construction Engineering and Management
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• v.9 no.5
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• pp.127-136
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• 2008

The initial step in the construction process, estimating appropriate construction time and expense is the most important factor that would influence the result of the construction. In order to enhance productivity and efficiency, there is a need to analyze and manage rationally. The purpose of this project is to make a simulation model for all subway tunnel construction based on the NATM method, also give an support equipment that would make available to plan and analyze the construction. The development of simulation model is based on a real case construction analysis process and also on the reference data. It reflects restrictive elements, make it possible to modify the conditions, and not only adapt to our project's construction but other projects as well. The model developed by this project will be able to reasonably predict the construction completion time and support the process of decision making during the planning. Therefore we can expect the productivity and efficiency of the whole construction projects.

• Journal of Korea Multimedia Society
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• v.5 no.1
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• pp.68-76
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• 2002

Multicast in mobile host has the problem of hast mobility, multicast decision, triangle routing, tunnel convergence, implosion of retransmission, and bandwidth waste. In particular, the bandwidth waste in radio is a definite factor that decreases transmission rate. To solve the problems, this paper proposes a new multicast transmission protocol called FIM(Forward Error Correction Integrated Multicast), which supports reliable packet recovery mechanism by integrating If Mobility Support for the host mobility, IGMP(Interned Group Management Protocol) for the group management, and DVMRP(Distance Vector Multicast Routing Protocol) for the multicast routing, and it also uses FEC and the local recovery method based on receiver. The performance measurement is performed by dividing the losses into the homogeneous independent loss, the heterogeneous independent loss, and the shared source link loss model.. The result shows that the performances improves in proportion to the size of local areal group when the size of transmission group exceeds designated size. This indicates FIM is effective in the environment where there are much of data and many receivers in the mobile host.

• Tunnel and Underground Space
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• v.31 no.6
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• pp.508-519
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• 2021

In this study, a model was developed to predict the peak particle velocity (PPV) that affects people and the surrounding environment during blasting. Four machine learning models using the k-nearest neighbors (kNN), classification and regression tree (CART), support vector regression (SVR), and particle swarm optimization (PSO)-SVR algorithms were developed and compared with each other to predict the PPV. Mt. Yogmang located in Changwon-si, Gyeongsangnam-do was selected as a study area, and 1048 blasting data were acquired to train the machine learning models. The blasting data consisted of hole length, burden, spacing, maximum charge per delay, powder factor, number of holes, ratio of emulsion, monitoring distance and PPV. To evaluate the performance of the trained models, the mean absolute error (MAE), mean square error (MSE), and root mean square error (RMSE) were used. The PSO-SVR model showed superior performance with MAE, MSE and RMSE of 0.0348, 0.0021 and 0.0458, respectively. Finally, a method was proposed to predict the degree of influence on the surrounding environment using the developed machine learning models.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.139-151
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• 2022

The mechanical properties of expansive soil are very unstable, highly sensitive to water, and thus easy to cause major engineering accidents. In this paper, the expansive soil foundation pit project of the East Huada Square in the eastern suburb of Chengdu was studied, the moisture content of the expansive soil was considered as an important factor that affecting the mechanics properties of expansive soil and the stability of the non-equal-length double-row piles in the foundation pit support. Three groups of direct shear tests were carried out and the quantitative relationships between the moisture content and shear strength τ, cohesion c, internal friction angle φ were obtained. The effect of cohesion and internal friction angle on the maximum displacement and the maximum bending moment of piles were analyzed by the finite element software MIDAS/GTS (Geotechnical and Tunnel Analysis System). Results show that the higher the moisture content, the smaller the matrix suction, and the smaller the shear strength; the cohesion and the internal friction angle are exponentially related to the moisture content, and both are negatively correlated. The maximum displacement and the maximum bending moment of the non-equal length double-row piles decrease with the increase of the cohesion and the internal friction angle. When the cohesion is greater than 33 kPa or the internal friction angle is greater than 25.5°, the maximum displacement and maximum bending moment of the piles are relatively small, however, once crossing the points (the corresponding moisture content value is 24.4%), the maximum displacement and the maximum bending moment will increase significantly. Therefore, in order to ensure the stability and safety of the foundation pit support structure of the East Huada Square, the moisture content of the expansive soil should not exceed 24.4%.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.586-597
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• 2022

In this study, a model was developed for the estimating the locational thickness information of the upper clay layer to be used for the consolidation vulnerability evaluation in the Nakdong river estuary. To estimate ground layer thickness information, we developed four spatial estimation models using machine learning algorithms, which are RF (Random Forest), SVR (Support Vector Regression) and GPR (Gaussian Process Regression), and geostatistical technique such as Ordinary Kriging. Among the 4,712 borehole data in the study area collected for model development, 2,948 borehole data with an upper clay layer were used, and Pearson correlation coefficient and mean squared error were used to quantitatively evaluate the performance of the developed models. In addition, for qualitative evaluation, each model was used throughout the study area to estimate the information of the upper clay layer, and the thickness distribution characteristics of it were compared with each other.

• Tunnel and Underground Space
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• v.19 no.3
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• pp.181-189
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• 2009

This study is to evaluate an effect of supports with respect to these supports after comparing the characteristic of support between rock bolt of a widely used type and spiral bolt of a new type. For these purposes, we performed pull-out test in laboratory about rock and spiral bolts in the case of cement-mortar grout curing periods, 7 and 28 days, then calculated pull-out load, displacement, external pressure, inner pressure and shear stress using data obtained from the results of pull-out test, respectively. In relation between pull-out load and displacement, displacement of spiral bolt is larger than one of rock bolt. It is considered that mechanical property of rock bolt is due to larger than one of spiral bolt. In addition, displacement of supports shows nearly same or decreasing with curing periods. We found that because adhesive force between supports and cement-mortar grout is increasing with compressive strength of grout according to curing periods. The inner pressure of spiral bolt is represented larger than one of rock bolt at a step of same pull-out load. It is suggested that spiral bolt is more stable than rock bolt, maintaining stability of ground or rock mass, when supports are installed in a ground or rock mass under the same condition. Putting together with above results, we can consider that spiral bolt as a new support on an aspect of pull-out load and inner pressure is larger than rock bolt in a ground or rock mass under the same condition. Moreover, spiral bolt is more effective support than rock bolt, considering an economical and constructive aspects of supports, as well as ground or rock stability before or after installing supports.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.626-631
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• 2018

An emergency evacuation support system is used to maintain evacuation routes by pressurizing a space inside screens. In cases of fire, it is important to understand the thermal distributions in the tunnel for preventing system failure. In this study, we numerically investigated the effect of fire on an emergency evacuation support system in a large fabric store with some fire scenarios with different combustibles. The critical temperature for system failures was assumed to be $200^{\circ}C$. As a result, the highest temperature was predicted in the ceiling part due to the effect of a ceiling jet, and the fire safety of the screen was secured at distances of 20 to 30 m according to the heat release rate. To prevent the inflow of smoke into the system, it is necessary to maintain more than 5 Pa if positive pressure inside the smoke screen. The results of this study could be useful for designing an emergency evacuation support system.