• Journal of Welding and Joining
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• v.11 no.4
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• pp.44-56
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• 1993

The arc welding processes are substantially nonlinear, in addition to being highly coupled multivariable systems, Frequently, not all the variables affecting the welding quality are known, nor may they be easily quantified. From this point of view, decoupling between the welding parameters from the welding quality is very difficult, which makes it also difficult to control the welding parameters for obtaining the desired welding quality. In this study, a neural network based on the backpropagation algorithm was implemented and adopted for the selection of gas metal arc welding parameters of the fillet joint, that is, welding current, arc voltage and welding speed. The performance of the neural network for modeling the relationship between the welding quality and welding parameters was presented and evaluated by using the actual welding data. To obtain the optimal neural network structure, various types of the neural network structures were tested with the experimental data. It was revealed that the neural network can be effectively adopted to select the appropriate gas metal arc welding parameter of fillet joints for a given weld quality.

• International Journal of Quality Innovation
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• v.6 no.1
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• pp.109-118
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• 2005

The parameter design is the most emphasized measure by researchers for a new products development. It is critical for makers to achieve simultaneously in both the time-to-market production and the quality enhancement. However, there are difficulties in practical application, such as (1) complexity and nonlinear relationships co-existed among the system's inputs, outputs and control parameters, (2) interactions occurred among parameters, (3) where the adjustment factors of Taguchi's two-phase optimization procedure cannot be sure to exist in practice, and (4) for some reasons, the data became lost or were never available. For these incomplete data, the Taguchi methods cannot treat them well. Neural networks have a learning capability of fault tolerance and model free characteristics. These characteristics support the neural networks as a competitive tool in processing multivariable input-output implementation. The successful fields include diagnostics, robotics, scheduling, decision-making, prediction, etc. This research is a case study of spherical annealing model. In the beginning, an original model is used to pre-fix a model of parameter design. Then neural networks are introduced to achieve another model. Study results showed both of them could perform the highest spherical level of quality.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.5
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• pp.973-981
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• 2012

In this paper, it suggest that nonlinear multivariable system control of induction motor using 'T-S Fuzzy Identification' 'T-S Fuzzy model of linearization' is not easy because of that arithmetic is difficult in computation of the function. Therefore 'T-S Fuzzy Identification' is suggested that the rules and functions through the estimation of high accuracy provides linearized model.

• Diabetes and Metabolism Journal
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• v.42 no.6
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• pp.538-543
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• 2018

Globally, diabetic retinopathy (DR) is one of the leading causes of blindness, that diminishes quality of life. This study aimed to describe the prevalence of DR, and its associated risk factors. This cross-sectional study was carried out among 478 diabetic patients in a referral center in Fars province, Iran. The mean${\pm}$standard deviation age of the participants was $56.64{\pm}12.45$ years old and DR prevalence was 32.8%. In multivariable analysis, lower education levels (adjusted odds ratio [aOR], 0.43; 95% confidence interval [CI], 0.24 to 0.76), being overweight (aOR, 1.70; 95% CI, 1.02 to 2.83) or obese (aOR, 1.88; 95% CI, 1.09 to 3.26), diabetes duration of 10 to 20 years (aOR, 2.35; 95% CI, 1.48 to 3.73) and over 20 years (aOR, 5.63; 95% CI, 2.97 to 10.68), receiving insulin (aOR, 1.99; 95% CI, 1.27 to 3.10), and having chronic diseases (aOR, 1.71; 95% CI, 1.02 to 2.85) were significantly associated with DR. In conclusion, longer diabetes duration and obesity or having chronic diseases are strongly associated with DR suggesting that control of these risk factors may reduce both the prevalence and impact of retinopathy in Iran.

• Geomechanics and Engineering
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• v.19 no.3
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• pp.283-293
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• 2019

Evaluating the stability of the excavation face of the cross-river shield tunnel with good accuracy is considered as a nonlinear and multivariable complex issue. Understanding the stability evaluation method of the shield tunnel excavation face is vital to operate and control the shield machine during shield tunneling. Considering the instability mechanism of the excavation face of the cross-river shield and the characteristics of this engineering, seven evaluation indexes of the stability of the excavation face were selected, i.e., the over-span ratio, buried depth of the tunnel, groundwater condition, soil permeability, internal friction angle, soil cohesion and advancing speed. The weight of each evaluation index was obtained by using the analytic hierarchy process and the entropy weight method. The evaluation model of the cross-river shield construction excavation face stability is established based on the idea point method. The feasibility of the evaluation model was verified by the engineering application in a cross-river shield tunnel project in China. Results obtained via the evaluation model are in good agreement with the actual construction situation. The proposed evaluation method is demonstrated as a promising and innovative method for the stability evaluation and safety construction of the cross-river shield tunnel engineerings.

• Quality Improvement in Health Care
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• v.26 no.2
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• pp.86-94
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• 2020

Purpose: This study aimed to identify current quality control (QC) practices of primary care clinics participating in the National Cancer Screening Program (NCSP) in Korea. Methods: A nationwide survey using a structured questionnaire was conducted among the primary care clinics participating in the NCSP, which were selected by a proportionate stratified sampling. The questionnaire consisted of general information about the responding clinics and the scope of QC activities undertaken. A total of 360 clinics responded and the set of data was then analyzed with Chi-square test and multivariable logistic regression analysis. Results: Among 360 respondents, 332 (92%) reported that they were involved in the QC activities. Most frequently performed QC activities were 'maintenance of facility and instruments' (89%) and 'staff training' (85%). The analysis revealed, with statistical significance (p<.05), that there was an association between certain characteristics of the clinics and the scope of QC activities. These findings also indicated that the diversity of QC practices varies according to the size of the clinics. The clinics screening more types of cancer, those with more screenees, and those with more employees were more likely to implement various QC activities including 'maintenance of facility and instruments', 'external quality control', and 'management of screening data'. Conclusion: To our knowledge, this is the first study to investigate the current status of QC activities conducted among primary care clinics participating in the NCSP. The results of this survey can be used as a basis for further development of policies on quality management of small- and medium-sized primary care clinics in Korea. However, further studies encompassing various aspects of QC activities and management of primary care clinics are needed to assess the current situation in a concise manner.

• Nutrition Research and Practice
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• v.12 no.1
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• pp.69-77
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• 2018

BACKGROUND/OBJECTIVES: Metabolic risk factors should be managed effectively in patients with type 2 diabetes mellitus (T2DM) to prevent or delay diabetic complications. This study aimed to compare the self-management levels of diet and metabolic risk factors in patients with T2DM, according to the duration of illness, and to examine the trends in self-management levels during the recent decades. SUBJECTS/METHODS: Data were collected from the Korea National Health and Nutrition Examination Surveys (KNHANES, 1998-2014). In our analysis, 4,148 patients with T2DM, aged ${\geq}30years$, were categorized according to the duration of their illness (< 5 years, 5-9 years, and ${\geq}10years$). Demographic and lifestyle information was assessed through self-administered questionnaires, and biomarker levels (e.g., fasting glucose level, blood pressure, or lipid level) were obtained from a health examination. Dietary intake was assessed by a 24-recall, and adherence level to dietary guidelines (meal patterns and intake levels of calories, carbohydrates, vegetable/seaweed, sodium, and alcohol) were assessed. Multivariable generalized linear regression and unconditional logistic regression models were used to compare the prevalence rates of hyperglycemia, dyslipidemia, and hypertension according to the duration of patients' illness, accounting for the complex survey design of the KNHANES. RESULTS: In the multivariable adjusted models, patients with a longer duration (${\geq}10years$) of T2DM had a higher prevalence of hyperglycemia than those with a shorter duration of T2DM (< 5 years) (odds ratio 2.20, 95% confidence interval 1.61-3.01, P for trend < 0.001). We did not observe any associations of disease duration with the prevalence of hypertension and dyslipidemia. In addition, the adherence levels to dietary recommendations did not significantly differ according to disease duration, except adherence to moderate alcohol consumption. There were significant decreasing trends in the prevalence of hyperglycemia in patients with a duration of illness ${\geq}10years$ (P for trend = 0.004). CONCLUSION: Although the proportion of patients with adequate control of glucose levels has improved in recent decades, poorer self-management has been found in those with a longer disease duration. These findings suggest the need for well-planned and individualized patient education programs to improve self-management levels and quality of life by preventing or delaying diabetic complications.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.28B no.10
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• pp.771-782
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• 1991

In industrial multivariable plants, it is ofte the case that the plant outputs are measured in similar components not simultaneously but serially. In this paper, the problem of estimating the state vector of the plant based on the data obtained from such a measuring scheme is considered, and a special type of observer(referred to as a $'$multiple serial-sampling$'$ type observer) which renews its internal states whenever a new group of data is obtained is proposed. It is proved that such an observer can be constructed for almost every sampling period if the palnt is observable as a continuous-time multivariable system, and that the poles of the closed-loop system using the multiple serial-sampling type observer consist of the poles of the observer and those of the state feedback system. The behaviors of the observer and the closed-loop system are studied by simulation. The results of simulation indicate that a multiple serial-ampling type observer can estimate the state of the plant more accurately than the ordinary type observers and improve the closed-loop performance, especially, in the existence of measuring noise.ng noise.

• Journal of Trauma and Injury
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• v.37 no.1
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• pp.28-36
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• 2024

Purpose: Recent advancements in interventional radiology have made angioembolization an invaluable modality in trauma care. Angioembolization is typically performed by interventional radiologists. In this study, we aimed to investigate the safety and efficacy of emergency angioembolization performed by trauma surgeons. Methods: We identified trauma patients who underwent emergency angiography due to significant trauma-related hemorrhage between January 2020 and June 2023 at Jeju Regional Trauma Center. Until May 2022, two dedicated interventional radiologists performed emergency angiography at our center. However, since June 2022, a trauma surgeon with a background and experience in vascular surgery has performed emergency angiography for trauma-related bleeding. The indications for trauma surgeon-performed angiography included significant hemorrhage from liver injury, pelvic injury, splenic injury, or kidney injury. We assessed the angiography results according to the operator of the initial angiographic procedure. The term "failure of the first angioembolization" was defined as rebleeding from any cause, encompassing patients who underwent either re-embolization due to rebleeding or surgery due to rebleeding. Results: No significant differences were found between the interventional radiologists and the trauma surgeon in terms of re-embolization due to rebleeding, surgery due to rebleeding, or the overall failure rate of the first angioembolization. Mortality and morbidity rates were also similar between the two groups. In a multivariable logistic regression analysis evaluating failure after the first angioembolization, pelvic embolization emerged as the sole significant risk factor (adjusted odds ratio, 3.29; 95% confidence interval, 1.05-10.33; P=0.041). Trauma surgeon-performed angioembolization was not deemed a significant risk factor in the multivariable logistic regression model. Conclusions: Trauma surgeons, when equipped with the necessary endovascular skills and experience, can safely perform angioembolization. To further improve quality control, an enhanced training curriculum for trauma surgeons is warranted.

• Korean Chemical Engineering Research
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• v.52 no.5
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• pp.592-602
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• 2014

In the Integrated Gasification Combined Cycle (IGCC), the stability of the gasifier has strong influences on the rest of the plant as it supplies the feed to the rest of the power generation system. In order to ensure a safe and stable operation of the entrained-flow gasifier and for protection of the gasifier wall from the high internal temperature, the solid slag layer thickness should be regulated tightly but its control is hampered by the lack of on-line measurement for it. In this study, a previously published dynamic simulation model of a Shell-type gasifier is reproduced and two different linear model predictive control strategies are simulated and compared for multivariable control of the entrained-flow gasifier. The first approach is to control a measured secondary variable as a surrogate to the unmeasured slag thickness. The control results of this approach depended strongly on the unmeasured disturbance type. In other words, the slag thickness could not be controlled tightly for a certain type of unmeasured disturbance. The second approach is to estimate the unmeasured slag thickness through the Kalman filter and to use the estimate to predict and control the slag thickness directly. Using the second approach, the slag thickness could be controlled well regardless of the type of unmeasured disturbances.