• Korean Journal of Materials Research
• /
• v.25 no.7
• /
• pp.322-329
• /
• 2015

The magnitude of wear should be at a minimum for numerous automobile and aeronautical components. In the current work, composites were prepared by varying the cenosphere content using the conventional stir casting method. A uniform distribution of particles was ensured with the help of scanning electron microscopy (SEM). Three major parameters were chosen from various factors that affect the wear. A wear test was conducted with a pin-on-disc apparatus; the controlling parameters were volume percentages of reinforcement of 5, 10, 15, and 20%, applied loads of 9.8, 29.42, and 49.03 N, and sliding speeds of 1.26, 2.51, and 3.77 m/s. The design of the experiments (DOE) was performed by varying the different influencing parameters using the full factorial method. An analysis of variance (ANOVA) was used to analyze the effects of the parameters on the wear rate. Using regression analysis, a response curve was obtained based on the experimental results. The parameters in the resulting curve were optimized using the Genetic Algorithm (GA). The GA results were compared with those of an alternate efficient algorithm called Neural Networks (NNs).

• The Journal of the Korean dental association
• /
• v.53 no.4
• /
• pp.238-248
• /
• 2015

Sleep related breathing disorders(SRBDs) are a group of diseases accompanied by difficulties in respiration and ventilation during sleep. Central sleep apnea, obstructive sleep apnea(OSA), sleep-related hypoventilation, and hypoxemia disorder are included in this disease entity. OSA is known to be the most common SRBDs and studies show its significant correlation with general health problems including hypertension, arrhythmia, diabetes, and metabolic syndrome. The diagnostic process of OSA is composed of physical examinations of the head and neck area and also the oral cavity. Radiologic studies including cephalography, CT, MRI, and fluoroscopy assist in identifying the site of obstruction. However, polysomnography(PSG) is still considered the gold standard for the diagnosis of OSA since it offers both qualitative and quantitative recording of the events during a whole night's sleep. The dentist who is trained in sleep medicine can easily identify patients with the risk of OSA starting from simple questions and screening questionnaires. Diagnosis is the first step to treatment and considering the high rate of under-diagnosis for OSA the dentist may play a substantial role in the diagnosis and treatment of OSA which will eventually lead to the well-being of the patient as a whole person. So the objective of this article is to assist dental professionals in gaining knowledge and insight of the diagnostic measures for OSA including PSG.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
• /
• v.48 no.5
• /
• pp.259-266
• /
• 2022

The relationship between obstructive sleep apnea (OSA) and diverse types of pain conditions have been proposed. However, no consensus on the relationship between OSA and painful temporomandibular disorders (TMDs) has been established. Therefore, this systematic review has been conducted to review the existing literatures and provide comprehensive synthesis of such literatures about OSA and painful TMDs using the evidence-based methodology. A literature search was conducted using two electronic databases, Scopus, and PubMed. Risk of bias was assessed using the risk-of-bias assessment tool for non-randomized study version 2.0. A total of 158 articles were screened from the initial search and eventually, 5 articles were included in this systematic review. One study adopted both the longitudinal prospective cohort and case-control designs and other 4 articles adopted the cross-sectional design. Two studies employed polysomnography (PSG) for the diagnosis of OSA and mentioned the results from the PSG. All cross-sectional studies demonstrated higher OSA prevalence among patients with TMD, and one cohort study suggested OSA as a risk factor for TMD. OSA appears to have potential influences on the development of TMD; however, the role of TMD in the development of OSA remains to be unknown owing to the lack of high-quality evidences.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.16 no.1
• /
• pp.97-115
• /
• 2022

Smart power grid is a user friendly system that transforms the traditional electric grid to the one that operates in a co-operative and reliable manner. Demand Response (DR) is one of the important components of the smart grid. The DR programs enable the end user participation by which they can communicate with the electricity service provider and shape their daily energy consumption patterns and reduce their consumption costs. The increasing demands of electricity owing to growing population stresses the need for optimal usage of electricity and also to look out alternative and cheap renewable sources of electricity. The solar and wind energy are the promising sources of alternative energy at present because of renewable nature and low cost implementation. The proposed work models a smart home with renewable energy units. The random nature of the renewable sources like wind and solar energy brings an uncertainty to the model developed. A stochastic dual descent optimization method is used to bring optimality to the developed model. The proposed work is validated using the simulation results. From the results it is concluded that proposed work brings a balanced usage of the grid power and the renewable energy units. The work also optimizes the daily consumption pattern thereby reducing the consumption cost for the end users of electricity.

• Journal of Korean Living Environment System
• /
• v.19 no.4
• /
• pp.479-488
• /
• 2012

This study investigated the influence of the indoor CO₂concentration level on sleep quality by polysomnography(PSG). One healthy female subject was selected among several subjects based on RI(Risk Indicator) value and BMI(Body Mass Index) value to evaluate judging the risk level of obstructive sleep apnea hypopnea. To get the impact of the indoor carbon dioxide concentration to sleep quality, both CO₂concentration levels were set up using ventilating form with 700~800 ppm and 2000~3000 ppm. Other environments were controlled in the comfortable sleep scope by previous researches. To measure the sleep quality, measurements have carried on polysomnography(PSG). In conclusion, it have shown that high carbon dioxide concentration leads arousal effect about central nervous system and to sustaining dreams and excited condition by bring about REM sleep split phenomenon.

• Proceedings of the Korean Society of Computer Information Conference
• /
• 2022.07a
• /
• pp.57-58
• /
• 2022

Sleep apnea (SA) is a common chronic sleep disorder that disrupts breathing during sleep. Clinically, the standard for diagnosing SA involves nocturnal polysomnography (PSG). However, this requires expert human intervention and considerable time, which limits the availability of SA diagnoses in public health sectors. Therefore, ECG-based methods for SA detection have been proposed to automate the PSG procedure and reduce its discomfort. We propose a preprocessing method to convert the one-dimensional time series of ECG into two-dimensional images using the Gramian Angular Field (GAF) algorithm, extract temporal features, and use a two-dimensional convolutional neural network for classification. The results of this study demonstrated that the proposed method can perform SA detection with specificity, sensitivity, accuracy, and area under the curve (AUC) of 88.89%, 81.50%, 86.11%, and 0.85, respectively. Our experimental results show that SA is successfully classified by extracting preprocessing transforms with temporal features.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.4
• /
• pp.1059-1074
• /
• 2024

The paper is an attempt to study the individual's intention to use mobile banking. In light of the results obtained from the study, the proposed model offers a better fit with the data and explains the intention of individuals to use mobile banking services. Government support, trust, and compatibility significantly contribute to the Perceived behavioral control of a bank customer to use mobile banking while Perceived ease of use, Perceived usefulness, Security and privacy, and risk have a significant positive impact on the attitude of the individuals to utilize mobile banking service. The study uses primary data and the final instrument was administered to 950 respondents, across the country of which 904 data were used for the analysis after editing to accommodate the missing values. The study has adopted structural equation modeling approach to analyze the relationships between the variables in the study. The proposed framework in this study can be utilized to identify the factors that promote the adoption of mobile banking practices and the study also has the potential to provide updated and comprehensive literature on mobile banking, which can accelerate future research in this field.

• Sleep Medicine and Psychophysiology
• /
• v.14 no.2
• /
• pp.86-91
• /
• 2007

Background: Actigraphy is a reliable and valid method for assessing sleep in normal, healthy populations, but it may be less reliable and valid for detecting disturbed sleep in patients. In this study, we attempted to assess the utility of actigraphy in the estimation of sleep quality in patients with obstructive sleep apnea syndrome (OSAS), a major sleep disorder. Method: We analyzed the data of patients who underwent polysomnography (PSG) and actigraphy simultaneously for one night at the Center for Sleep and Chronobiology, Seoul National University Hospital from November 2004 to March 2006. Eighty-nine subjects with OSAS alone and 21 subjects with OSAS and periodic limb movement disorder (PLMD) were included for final data analyses between groups. Polysomnographic and actigraphic data were also compared. Results: In subjects with mild OSAS (RDI<15), modretae ($15{\leq}RDI$<30), and OSAS with PLMD, PSG and actigraphy did not show significant difference in total sleep time and sleep efficiency. However in severe ($30{\leq}RDI$) OSAS subjects, PSG and actigraphy showed significant difference in total sleep time and sleep efficiency. In all patients, no correlations were found between sleep parameters from PSG and from those using actigraphy. Conclusions: We suggest that in severe OSAS patients, PSG is the diagnostic tool. In mild and moderate cases, actigraphy might be used as a screening tool.

• Sleep Medicine and Psychophysiology
• /
• v.2 no.1
• /
• pp.73-81
• /
• 1995

Objective : Patients with sleep apnea should be diagnosed with polysomnography(PSG). However, it is not easy to recommend PSG for all patients suspected with sleep apnea in practice. Therefore, we tried to develop the screening test for referral of PSG. Method : 140 patients with snoring and sleep apnea syndrome were studied by the PSG. Sleep apnea questionnaire. Zung's scale for depression. Stanford Sleepiness Scale(SSS), insomnia scale and neuropsychological test were administered. Also, blood pressure, height, weight and neck circumference were measured and some histories were taken. Correlations between respiratory disturbance index(RDI) and various parameters mentioned above and discriminant coefficients of the parameters to RDI were computed. And, we investigated sensitivities of screening tests for selection of the patients with RDI above 20. Results : Using six parameters(neck circumference, systolic blood pressure before sleep, degree of alcohol drinking, frequency of breath-holding during sleep, degree of dry mouth during sleep, sleep apnea score), the patients with RDI above 20 could be discriminated in 92.8% sensitivity. In case of more than two among six parameters(neck circumference of above 40cm, systolic blood pressure of above 125mmHg, frequent alcohol drinking, frequent breath-holding during sleep, frequent dry mouth during sleep, sleep apnea score of above 35), same patients could be discriminated in 87.6% sensitivity. And, in case of more than one among four parameters(neck circumference of above 40cm. systolic blood pressure of above 125mmHg, frequent alcohol drinking, body weight of above 80kg), discrimination sensitivity was 83.5%. Conclusions : Patients with RDI above 20 could be discriminated by above parameters with high sensitivity. Therefore, the screening test using above parameters can be applied in selection of the patients with sleep apnea for PSG in practice.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.42 no.3 s.303
• /
• pp.47-52
• /
• 2005

Obstructive Sleep Apnea (OSA) is a representative symptom of sleep disorder caused by the obstruction of upper airway. Because OSA causes not only excessive daytime sleepiness and fatigue, hypertension and arrhythmia but also cardiac arrest and sudden death during sleep in the severe case, it is very important to detect the occurrence and the frequency of OSA. OSA is usually diagnosed through the laboratory-based Polysomnography (PSG) which is uncomfortable and expensive. Therefore researches to improve the disadvantages of PSG are needed and studies for the detection of OSA using only one or two parameters are being made as alternatives to PSG. In this paper, we developed an algorithm for the detection of OSA based on Heart Rate Variability (HRV). The proposed method is applied to the ECG data sets provided from PhysioNet which consist of learning set and training set. We extracted features for the detection of OSA such as average and standard deviation of 1 minute R-R interval, power spectrum of R-R interval and S-peak amplitude from data sets. These features are applied to the input of neural network. As a result, we obtained sensitivity of $89.66\%$ and specificity of $95.25\%$. It shows that the features suggested in this study are useful to detect OSA.