• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.745-752
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• 2009

In robust design, the mean and variance of design performance are frequently used to measure the design performance and its robustness under uncertainties. In this paper, we present the Gauss-type quadrature formula as a rigorous method for mean and variance estimation involving arbitrary input distributions and further extend its use to robust design optimization. One dimensional Gauss-type quadrature formula are constructed from the input probability distributions and utilized in the construction of multidimensional quadrature formula such as the tensor product quadrature (TPQ) formula and the univariate dimension reduction (UDR) method. To improve the efficiency of using it for robust design optimization, a semi-analytic design sensitivity analysis with respect to the statistical moments is proposed. The proposed approach is applied to a simple bench mark problems and robust topology optimization of structures considering various types of uncertainty.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.179-184
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• 2019

In this paper, we propose a design method of Active Noise Control (ANC) that reduces perceived level of the residual noise. A FELMS (Filtered-E Least Mean Squares) algorithm is used for the ANC system and the NC (noise criteria) is applied as an evaluation criterion of the residual noise. With this structure, we present the allowable spectral shape of the noise shaping filter that minimizes the NC index within the effective operating frequency band of the ANC, and showed that the filter satisfying in the criterion has a lower NC value than the psychoacoustic-based filter used in the previous studies.

• Journal of Korea Water Resources Association
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• v.57 no.3
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• pp.209-223
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• 2024

In the context of the fourth industrial revolution, data-driven decision-making has increasingly become pivotal. However, the integrity of data analysis is compromised if data quality is not adequately ensured, potentially leading to biased interpretations. This is particularly critical for water level data, essential for water resource management, which often encounters quality issues such as missing values, spikes, and noise. This study addresses the challenge of noise-induced data quality deterioration, which complicates trend analysis and may produce anomalous outliers. To mitigate this issue, we propose a noise removal strategy employing Wavelet Transform, a technique renowned for its efficacy in signal processing and noise elimination. The advantage of Wavelet Transform lies in its operational efficiency - it reduces both time and costs as it obviates the need for acquiring the true values of collected data. This study conducted a comparative performance evaluation between our Wavelet Transform-based approach and the Denoising Autoencoder, a prominent machine learning method for noise reduction.. The findings demonstrate that the Coiflets wavelet function outperforms the Denoising Autoencoder across various metrics, including Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), and Mean Squared Error (MSE). The superiority of the Coiflets function suggests that selecting an appropriate wavelet function tailored to the specific application environment can effectively address data quality issues caused by noise. This study underscores the potential of Wavelet Transform as a robust tool for enhancing the quality of water level data, thereby contributing to the reliability of water resource management decisions.

• Journal of the Korean Arthroscopy Society
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• v.10 no.1
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• pp.26-32
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• 2006

Purpose: We evaluated the result of the degree of reduction and anterior instability after arthroscopic treatment of tibial spine fractures. Materials and Methods: Thirty-two cases of tibial spine fractures treated with arthroscopic procedure could be evaluated and the mean follow-up period was $18\;(12{\sim}48)$ months. Evaluations included Lachman test, rotatory instability examination and side to side difference (SSD) using KT-2000 arthrometer. The degree of radiologic reduction was classified as accurate reduction, anterior elevation and reduction failure, according to which the degree of anterior instability was measured. Results: There were twenty three cases (71%) of accurate duction, eight cases (25%) of anterior elevation and one case (4%) of education failure. Eight (29%) of twenty eight cases with pull-out method showed anterior elevation. The SSDs of the accurate reduction and the anterior elevation group were 2.0 mm and 2.8 mm, respectively showing no significant difference. However, the percent age of grade 0 Lachman test and SSD less than 3 mm of the accurate reduction group were significantly higher. Conclusion: Accurate reduction is important in reducing anterior instability especially in unstable fractures. Therefore, arthroscopic pull-out method should be performed with great caution to avoid anterior elevation of the fracture fragment.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1314-1319
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• 2008

Fatigue reliability problems are nowadays actively considered in the design of mechanical components. Recently, Dimension Reduction Method using Kriging approximation (KDRM) was proposed by the authors to efficiently calculate statistical moments of the response function. This method, which is more tractable for its sensitivity-free nature and providing the response PDF in a few number of analyses, is adopted in this study for the reliability analysis. Before applying this method to the practical fatigue problems, accuracies are studied in terms of parameters of the KDRM through a number of numerical examples, from which best set of parameters are suggested. In the fatigue reliability problems, good number of experimental data are necessary to get the statistical distribution of the S-N parameters. The information, however, are not always available due to the limited expense and time. In this case, a family of curves with prediction interval, called P-S-N curve, is constructed from regression analysis. Using the KDRM, once a set of responses are available at the sample points at the mean, all the reliability analyses for each P-S-N curve can be efficiently studied without additional response evaluations. The method is applied to a spring design problem as an illustration of practical applications, in which reliability-based design optimization (RBDO) is conducted by employing stochastic response surface method which includes probabilistic constraints in itself. Resulting information is of great practical value and will be very helpful for making trade-off decision during the fatigue design.

• Smart Structures and Systems
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• v.17 no.2
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• pp.209-230
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• 2016

The Canton Tower is a high-rise slender structure with a height of 610 m. A structural health monitoring system has been instrumented on the structure, by which data is continuously monitored. This paper presents an investigation on the identified modal properties of the Canton Tower using ambient vibration data collected during a whole day (24 hours). A recently developed Fast Bayesian FFT method is utilized for operational modal analysis on the basis of the measured acceleration data. The approach views modal identification as an inference problem where probability is used as a measure for the relative plausibility of outcomes given a model of the structure and measured data. Focusing on the first several modes, the modal properties of this supertall slender structure are identified on non-overlapping time windows during the whole day under normal wind speed. With the identified modal parameters and the associated posterior uncertainty, the distribution of the modal parameters in the future is predicted and assessed. By defining the modal root-mean-square value in terms of the power spectral density of modal force identified, the identified natural frequencies and damping ratios versus the vibration amplitude are investigated with the associated posterior uncertainty considered. Meanwhile, the correlations between modal parameters and temperature, modal parameters and wind speed are studied. For comparison purpose, the frequency domain decomposition (FDD) method is also utilized to identify the modal parameters. The identified results obtained by the Bayesian method, the FDD method and a finite element model are compared and discussed.

• Archives of Plastic Surgery
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• v.47 no.2
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• pp.171-177
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• 2020

Background Infrabrow blepharoplasty has become a common surgical method used to rejuvenate aged upper eyelids in Asians. In this paper, we describe the parallel excision method for infrabrow blepharoplasty as a useful alternative to the conventional elliptical excision method. The authors' experience over a 3-year period is presented and reviewed. Methods A retrospective review of parallel excision infrabrow blepharoplasty cases at our hospital between 2014 and 2017 was performed. Three oculoplastic surgeons compared preoperative and postoperative photographs using the Strasser grading system. Results From the medical records of 123 patients, a total of 93 patients with moderate-to-severe bilateral dermatochalasis were selected as subjects. The exclusion criterion was levator function less than 8 mm. The total mean follow-up period was 2 years (range, 0.5-3.5 years). The mean skin excision height and width were 9.75 mm (range, 5-16 mm) and 58.51 mm (range, 42-75 mm), respectively. All patients who underwent surgery recovered without major complications, and all patients had high levels of satisfaction and improvements in their visual field. In the Strasser evaluation performed by the oculoplastic surgeons, most patients were found to have excellent results. Conclusions The parallel excision method for infrabrow blepharoplasty is a safe and effective technique that yields more natural- and youthful-looking eyelids than the conventional elliptical excision method. In our method, more effective manipulation of the orbicularis oculi muscle led to a reduction in frontalis compensation, resolution of sunken eyelids, and correction of lateral hooding.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.10
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• pp.399-409
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• 2006

This paper presents a novel method for satisfying the thermal comfort of indoor environment and reducing the summer peak demand power by minimizing the power consumption for an Air-conditioner within a space. Korea Electric Power Corporation (KEPCO) use the fixed duty cycle control method regardless of the indoor thermal environment. However, this method has disadvantages that energy saving depends on the set-point value of the Air-Conditioner and direct load control (DLC) has no net effects on Air-conditioners if the appliance has a lower operating cycle than the fixed duty cycle. In this paper, the variable duty cycle control method is proposed in order to compensate the weakness of conventional fixed duty cycle control method and improve the satisfaction of residents and the reduction of peak demand. The proposed method estimates the predict mean vote (PMV) at the next step with predicted temperature and humidity using the back propagation neural network model. It is possible to reduce the energy consumption by maintaining the Air-conditioner's OFF state when the PMV lies in the thermal comfort range. To verify the effectiveness of the proposed variable duty cycle control method, the case study is performed using the historical data on Sep. 7th, 2001 acquired at a classroom in Seoul and the obtained results are compared with the fixed duty cycle control method.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.34 no.2
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• pp.230-236
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• 2008

Purpose: This study was performed to investigate the incidence, types of fracture, treatment, associated fracture and complications in patients with nasal bone fracture. Materials and methods: Clinical examination, patient's records and radiographic images were evaluated in 230 cases of nasal bone fractures who were treated at the Department of Oral and Maxillofacial Surgery, Chonnam National University Hospital for recent 5 years; from January 2002 to December 2006. Results: 1. The age of patient was ranged from 4 to 77 years (mean age=36.6 years); Males was 75.7% (n=174), and females 24.3% (n=56). 2. The cause of the nasal bone fracture in this study was a fall or slip down (28.8%, n=66), sports accident (26.0%, n=60), fighting (21.3%, n=49), traffic accident (9.6%, n=22), industrial trauma (7.8%, n=18), and the others (6.6%, n=15). 3. For the patterns of fracture, simple fracture without displacement occured in 10.4% (n=24). Simple fracture with displacement without septal bone fracture was found in 49.5% (n=114). Simple fracture with displacement in company with septal bone fracture showed in 32.6% (n=75). Commiuted fracture with severe depression was presented in 7.4% (n=17). 4. The reduction the displaced nasal bone was carried out in 2 to 10 days (mean 6.8 days) after the injury. 5. Nasal bone fracture associated with Le Fort I fracture (6.5%, n=6.5), Le Fort II fracture (7.4%, n=17), Le Fort III fracture (1.3%, n=3), NOE fracture (13.9%, n=32), ZMC fracture (17.4%, 40), maxillary bone fracture (8.3%, n=19), orbital blow-out fracture (15.7%, n=36), frontal bone fracture (1.3%, n=3) and alveolar bone fracture (10.9%, n=25). 6. The major type of treatment method was closed reduction in 90% (n=207), open reduction in 3% (n=7), and observation in 7% (n=16). 7. There were some complications such as ecchymosis, hyposmia, hypo esthesia and residual nasal deformity which are compatible. Open rhino-plasty was conducted for 3 patients who had residual nasal deformity. Conclusions: These results suggest that most of nasal bone fractures are occurred physically active aged groups(age 10-49 years) and could be treated successfully with closed reduction at 7 days after the injury.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.6
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• pp.663-673
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• 2021

Normally, allowable mean overtopping discharge is used as a design parameter for coastal structures. The crest elevation of a structure must ensure wave overtopping discharge within acceptable limits for structural safety and the safety of pedestrians, vehicles, operations, and so on. Some researchers have alternatively proposed using the maximum individual wave overtopping volumes as design criteria during a design storm, since these can provide a better design measure than the mean overtopping rate. This study contributes to the knowledge on maximum individual overtopping volumes in Rayleigh-distributed wave conditions. Two-dimensional physical model tests on typical rubble mound structure geometries were performed, and the new measurement method for individual overtopping was adopted. An empirical formula was proposed to predict the maximum individual overtopping volumes based on the mean overtopping rate, and the reduction effects by the armor crest width on the mean wave overtopping discharge were assessed.