• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.2
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• pp.459-470
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• 2014

During ship design, welding-induced distortions are roughly estimated as a function of the size of the component as well as the welding process and residual stresses are assumed to be locally in the range of the yield stress. Existing welding simulation methods are very complex and time-consuming and therefore not applicable to large structures like ships. Simplified methods for the estimation of welding effects were and still are subject of several research projects, but mostly concerning smaller structures. The main goal of this paper is the application of a multi-layer welding simulation to the block joint of a ship structure. When welding block joints, high constraints occur due to the ship structure which are assumed to result in accordingly high residual stresses. Constraints measured during construction were realized in a test plant for small-scale welding specimens in order to investigate their and other effects on the residual stresses. Associated welding simulations were successfully performed with fine-mesh finite element models. Further analyses showed that a courser mesh was also able to reproduce the welding-induced reaction forces and hence the residual stresses after some calibration. Based on the coarse modeling it was possible to perform the welding simulation at a block joint in order to investigate the influence of the resulting residual stresses on the behavior of the real structure, showing quite interesting stress distributions. Finally it is discussed whether smaller and idealized models of definite areas of the block joint can be used to achieve the same results offering possibilities to consider residual stresses in the design process.

• Archives of Craniofacial Surgery
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• v.10 no.2
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• pp.91-96
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• 2009

Purpose: Frontal sinus fractures are relatively less common than other facial bone fractures. They are commonly concomitant with other facial bone fractures. They can cause severe complications but the optimal treatment of frontal sinus fractures remains controversial. Currently, many principles of treatment were introduced variously. The authors present valid and simplified protocols of treatment for frontal sinus fractures based on fracture pattern, nasofrontal duct injury, and complications. Methods: A retrospective chart review was performed on 36 cases of frontal sinus fractures between January, 2004 and January, 2009. The average age of patients was 33.7 years. Fracture patterns were classified by displacement of anterior and posterior wall, comminution, nasofrontal duct injury. These fractures were classified in 4 groups: I. anterior wall linear fractures; II. anterior wall displaced fractures; III. anterior wall displaced and posterior wall linear fractures; IV. anterior wall and posterior wall displaced fractures. Also, assessment of nasofrontal duct injury was conducted with preoperative coronal section computed tomographic scan and intraoperative findings. Patients were treated with various procedures including open reduction and internal fixation, obliteration, galeal frontalis flap and cranialization. Results: 12 patients are group I (33.3 percent), 14 patient were group II (38.8 percent), group III, IV were 5 each (13.9 percent). Frontal sinus fractures were commonly associated with zygomatic fractures (21.8 percent). 9 patients had nasofrontal duct injury. The complication rate was 25 percent (9 patients), including hypoesthesia, slight forehead irregularity, transient cerebrospinal fluid leakage. Conclusion: The critical element of successful frontal sinus fracture repair is precise diagnosis of the fracture pattern and nasofrontal duct injury. The main goal of management is the restoration of the sinus function and aesthetic preservation.

• Journal of Periodontal and Implant Science
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• v.43 no.5
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• pp.233-242
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• 2013

Purpose: Peri-implant sulcular fluid (PISF) has a production mechanism similar to gingival crevicular fluid (GCF). However, limited research has been performed comparing their behavior in response to inflammation. Hence, the aim of the present study was to comparatively evaluate PISF and GCF volume with varying degrees of clinical inflammatory parameters. Methods: Screening of patients was conducted. Based on the perimucosal inflammatory status, 39 loaded implant sites were selected from 24 patients, with equal numbers of sites in healthy, peri-implant mucositis, and peri-implantitis subgroups. GCF collection was done from age- and sex-matched dentate patients, selected with gingival inflammatory status corresponding to the implant sites. Assessment of the inflammatory status for dental/implant sites was performed using probing depth (PD), plaque index/modified plaque index (PI/mPI), gingival index/simplified gingival index (GI/sGI), and modified sulcular bleeding index (BI). Sample collection was done using standardized absorbent paper strips with volumetric evaluation performed via an electronic volume quantification device. Results: Positive correlation of the PISF and GCF volume was seen with increasing PD and clinical inflammatory parameters. A higher correlation of GCF with PD (0.843) was found when compared to PISF (0.771). PISF expressed a higher covariation with increasing grades of sGI (0.885), BI (0.841), and mPI (0.734), while GCF established a moderately positive correlation with GI (0.694), BI (0.696), and PI (0.729). Conclusions: Within the limitations of this study, except for minor fluctuations, GCF and PISF volumes demonstrated a similar nature and volumetric pattern through increasing grades of inflammation, with PISF showing better correlation with the clinical parameters.

• Structural Monitoring and Maintenance
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• v.5 no.3
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• pp.363-377
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• 2018

The proper functioning of critical points on transport infrastructure is decisive for the entire network. Tunnels and bridges certainly belong to the critical points of the surface transport network, both road and rail. Risk management should be a holistic and dynamic process throughout the entire life cycle. However, the level of risk is usually determined only during the design stage mainly due to the fact that it is a time-consuming and costly process. This paper presents a simplified quantitative risk analysis method that can be used any time during the decades of a tunnel's lifetime and can estimate the changing risks on a continuous basis and thus uncover hidden safety threats. The presented method is a decision support system for tunnel managers designed to preserve or even increase tunnel safety. The CAPITA method is a deterministic scenario-oriented risk analysis approach for assessment of mortality risks in road tunnels in case of the most dangerous situation - a fire. It is implemented through an advanced risk analysis CAPITA SW. Both, the method as well as the resulting software were developed by the authors' team. Unlike existing analyzes requiring specialized microsimulation tools for traffic flow, smoke propagation and evacuation modeling, the CAPITA contains comprehensive database with the results of thousands of simulations performed in advance for various combinations of variables. This approach significantly simplifies the overall complexity and thus enhances the usability of the resulting risk analysis. Additionally, it provides the decision makers with holistic view by providing not only on the expected risk but also on the risk's sensitivity to different variables. This allows the tunnel manager or another decision maker to estimate the primary change of risk whenever traffic conditions in the tunnel change and to see the dependencies to particular input variables.

• The Korean Journal of Pain
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• v.33 no.2
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• pp.153-165
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• 2020

Background: Well-validated risk prediction models help to identify individuals at high risk of diseases and suggest preventive measures. A recent systematic review reported lack of validated prediction models for low back pain (LBP). We aimed to develop prediction models to estimate the 8-year risk of developing LBP and its recurrence. Methods: A population based prospective cohort study using data from 435,968 participants in the National Health Insurance Service-National Sample Cohort enrolled from 2002 to 2010. We used Cox proportional hazards models. Results: During median follow-up period of 8.4 years, there were 143,396 (32.9%) first onset LBP cases. The prediction model of first onset consisted of age, sex, income grade, alcohol consumption, physical exercise, body mass index (BMI), total cholesterol, blood pressure, and medical history of diseases. The model of 5-year recurrence risk was comprised of age, sex, income grade, BMI, length of prescription, and medical history of diseases. The Harrell's C-statistic was 0.812 (95% confidence interval [CI], 0.804-0.820) and 0.916 (95% CI, 0.907-0.924) in validation cohorts of LBP onset and recurrence models, respectively. Age, disc degeneration, and sex conferred the highest risk points for onset, whereas age, spondylolisthesis, and disc degeneration conferred the highest risk for recurrence. Conclusions: LBP risk prediction models and simplified risk scores have been developed and validated using data from general medical practice. This study also offers an opportunity for external validation and updating of the models by incorporating other risk predictors in other settings, especially in this era of precision medicine.

• Journal of Preventive Medicine and Public Health
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• v.38 no.3
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• pp.276-282
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• 2005

Objectives : To evaluate the predictive validity of three scoring systems; the acute physiology and chronic health evaluation(APACHE) III, simplified acute physiology score(SAPS) II, and mortality probability model(MPM) II systems in critically ill patients. Methods : A concurrent and retrospective study conducted by collecting data on consecutive patients admitted to the intensive care unit(ICU) including surgical, medical and coronary care unit between January 1, 2004, and March 31, 2004. Data were collected on 348 patients consecutively admitted to the ICU(aged 16 years or older, no transfer, ICU stay at least 8 hours). Three models were analyzed using logistic regression. Discrimination was assessed using receiver operating characteristic(ROC) curves, sensitivity, specificity, and correct classification rate. Calibration was assessed using the Lemeshow-Hosmer goodness of fit H-statistic. Results : For the APACHE III, SAPS II and MPM II systems, the area under the receiver operating characterist ic(ROC) curves were 0.981, 0.978, and 0.941 respectively. With a predicted risk of 0.5, the sensitivities for the APACHE III, SAPS II, and MPM II systems were 81.1, 79.2 and 71.7%, the specificities 98.3, 98.6, and 98.3%, and the correct classification rates 95.7, 95.7, and 94.3%, respectively. The SAPS II and APACHE III systems showed good calibrations(chi-squared H=2.5838 p=0.9577 for SAPS II, and chi-squared H=4.3761 p=0.8217 for APACHE III). Conclusions : The APACHE III and SAPS II systems have excellent powers of mortality prediction, and calibration, and can be useful tools for the quality assessment of intensive care units(ICUs).

• Structural Engineering and Mechanics
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• v.45 no.4
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• pp.543-568
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• 2013

This study explores the floor micro-vibrations induced by the automated guided vehicles (AGVs) in liquid-crystal-display (LCD) factories. The relationships between moving loads and both the vehicle weights and speeds were constructed by a modified Kanai-Tajimi (MKT) power spectral density (PSD) function whose best-fitting parameters were obtained through a regression analysis by using experimental acceleration responses of a small-scale three-span continuous beam model obtained in the laboratory. The AGV induced floor micro-vibrations under various AGV weights and speeds were then assessed by the proposed regressional MKT model. Simulation results indicate that the maximum floor micro-vibrations of the target LCD factory fall within the VC-B and VC-C levels when AGV moves at a lower speed of 1.0 m/s, while they may exceed the acceptable VC-B level when AGV moves at a higher speed of 1.5 m/s. The simulated floor micro-vibration levels are comparable to those of typical LCD factories induced by AGVs moving normally at a speed between 1.0 m/s and 2.0 m/s. Therefore, the numerical algorithm that integrates a simplified sub-structural multi-span continuous beam model and a proposed regressional MKT moving force model can provide a satisfactory prediction of AGV-induced floor micro-vibrations in LCD factories, if proper parameters of the MKT moving force model are adopted.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.100-109
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• 2020

Pipelines subjected to ground movement would be easily exposed to large-scale deformation. Since such deformations may cause the pipeline failure, it is important to ensure the safety of pipelines in various operation conditions. However, crack in weld metal have been considered as one of the main causes that can deteriorate the structural integrity of the pipeline. For this reason, the structural integrity of the pipe containing the crack in the weld should be obtained. In order to assess cracked pipe, J-integral and crack-tip opening displacement(CTOD) have been applied widely as the elastic-plastic fracture mechanics parameters representing crack driving force. In this study, engineering solutions to calculate the J-integral and CTOD of pipes with a circumferential outer surface crack in the weld are proposed. For this purpose, 3-dimensional elastic-plastic finite element(FE) analyses have been performed considering the effect of overmatch and width of weld. The shape of the weld was simplified to I-groove, and axial displacement was employed as for loading condition. Based on FE results, the effects of crack size, material properties and width of weldment on J-integral and CTOD were investigated. Additionally, the J-integral and CTOD for I-groove were compared with those for V-groove to examine the effects of the weld shape, and a proportionality coefficient of J-integral and CTOD was calculated from the results of this paper.

• Nuclear Engineering and Technology
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• v.44 no.8
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• pp.897-910
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• 2012

Inappropriate communications can cause a lack of necessary information exchange between operators and lead to serious consequences in large process systems such as nuclear power plants (NPPs). In this regard, various kinds of taxonomies of inappropriate communications have been developed to prevent inappropriate communications. However, there seems to be difficult to identify inappropriate communications from verbal protocol data between operators. Because the existing taxonomies were developed for use in report analysis, there is a problem of 'uncertainty'. In consequence, this paper proposes a new taxonomy of inappropriate communications and provides some insights to prevent inappropriate communications. In order to develop the taxonomy, existing taxonomies for four industries from 1980 to 2010 were collected and a new taxonomy is developed based on the simplified one-way communication model. In addition, the ratio of inappropriate communications from 8 samples of audio-visual format verbal protocol data recorded during emergency training sessions by operating teams is compared with performance scores calculated based on the task analysis. As a result, inappropriate communications can be easily identified from the verbal protocol data using the suggested taxonomy, and teams with a higher ratio of inappropriate communications tend to have a lower performance score.

• Structural Engineering and Mechanics
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• v.61 no.4
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• pp.527-538
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• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.