• Korean Journal of Adult Nursing
• /
• v.27 no.1
• /
• pp.29-38
• /
• 2015

Purpose: The purpose of the study was to validate fall risk assessment scales among hospitalized adult patients in South Korea using the electronic medical records by comparing sensitivity, specificity, positive predictive values, and negative predictive values of Morse Fall Scale (MFS), Bobath Memorial Hospital Fall Risk Assessment Scale (BMFRAS), and Johns Hopkins Hospital Fall Risk Assessment tool (JHFRAT). Methods: A total of 120 patients who experienced fall episodes during their hospitalization from June 2010 to December 2013 was categorized into the fall group. Another 120 patients, who didn't experience fall episodes with age, sex, clinical departments, and the type of wards matched with the fall group, were categorized to the comparison group. Data were analyzed for the comparisons of sensitivity, specificity, positive and negative predictive values, and the area under the curve of the three tools. Results: MFS at a cut-off score of 48 had .806 for ROC curves, 76.7% for sensitivity, 77.5% for specificity, 77.3% for positive predictive value, and 76.9% for negative predictive value, which were the highest values among the three fall assessment scales. Conclusion: The MFS with the highest score and the highest discrimination was evaluated to be suitable and reasonable for predicting falls of inpatients in med-surg units of university hospitals.

• International Journal of Aeronautical and Space Sciences
• /
• v.16 no.1
• /
• pp.64-76
• /
• 2015

This paper suggests applying pseudospectral model predictive method for exo-atmospheric guidance. The method is a fusion of pseudospectral law and model predictive control, in which a two point boundary value problem is formulated using model predictive approach and solved by applying pseudospectral law. In this work, the method is applied to exo-atmospheric guidance with specific target requirement. The existing exo-atmospheric guidance methods suffice general requirements for guidance, but cannot ensure specific target constraints; whereas, the presented method is able to do so. The proposed guidance law is assessed through simulation of perturbed cases, and the tests suggest that the method is able to operate semi-autonomously under control and thrust vector perturbations.

• The Journal of the Korea Contents Association
• /
• v.11 no.10
• /
• pp.342-348
• /
• 2011

The study aimed to compare the validity between the abdominal ultrasonographic(US) grading system of fatty liver and histologic grading system of fatty liver in living liver donor candidates. As the fatty liver is defined as pathologic total fat >10%, US validity was sensitivity 64.6%, specificity 68%, positive predictive value 76.8%, negative predictive value 54%. As the strict data handling on US grading normal, mild fatty liver are negative, moderate fatty liver is positive, US validity was sensitivity 26.8%, specificity 100%, positive predictive value 100%, negative predictive value 45.5%. ROC curve analysis according to different cut off value of liver-to-kidney brightness ratio was Area under ROC curve=0.859(95% CI=0.795~0.922, state variable= total fat 10%). There were statistically significant difference( p<0.001). Ultrasonography for the fatty diagnosis showed a high validity to predict the result of histology grade of fatty liver.

• Journal of Chest Surgery
• /
• v.32 no.10
• /
• pp.910-915
• /
• 1999

Background: Positron emission tomography(PEFT) using fluorine-18 deoxyglucose(FDG), showing increased FDG uptake and retention in malignant cells, has been proven to be useful in differentiating malignant from benign tissues. We indertook the prospective study to compare the accuracy of the whole-body FDG PET with that of the conventional chest computed tomography(CT) for nodal staging of non-small-cell lung cancers(NSCLC). Material and Method: FDG PET and contrast enhanced CT were performed in 36 patients with potentially resectable NSCLC. Each Imaging study was evaluated independently, and nodal stations were localized according to the AJCC regional lymph nodes mapping system. Extensive lymph node dissection(1101 nodes) of ipsi- and contralateral mediastinal nodal stations was performed at thoracotomy and/or mediastinoscopy. Image findings were compared with the histopathologic staging results and were analyzed with the McNema test(p) and Kappa value(k). Result: The sensitivity, specificity, positive predictive value, and negative predictive value of CT for ipsilateral mediastinal nodal staging were 38%, 68%, 25%, 79%, and 61%, and those of PET were 88%, 71%, 47%, 95%, and 75%(p>0.05, K=0.29). When analyzed by individual nodal group(superior, aortopulmonary window, and inferior), the sensitivity, specificity, positive predictive value, and negative predictive value of CT were 27%, 82%, 22%, 85%, and 73%, and those of PET were 60%, 87%, 92%, and 82%(p<0.05, k=0.27). Conclusion: FDG PET in addition to CT appears to be superior to CT alone for mediastinal staging of non-small cell lung cancers.

• Journal of the Korean Data and Information Science Society
• /
• v.16 no.2
• /
• pp.419-428
• /
• 2005

The screening test is increasingly being used for predicting future disease in the person screened and has raised concerns about reliability of the result of its procedure. We propose an improved estimator of the confidence interval for the positive predictive value(PPV) in screening test by simply taking inverse sinh transformation comparing to Gastwirth(1987) estimator and show its efficiency through the simulation study.

• Proceedings of the Korean Reliability Society Conference
• /
• 2000.04a
• /
• pp.177-183
• /
• 2000

As monitoring, testing, and measuring techniques develop, predictive control of components and complete systems have become more practical and affordable. In this paper we develop a statistics-based approach assuming nonlinear degradation paths and time-dependent standard deviation. This approach can be extended to provide reliability estimates and limit value determination in the censoring case fur predictive maintenance policy.

• Advances in Energy Research
• /
• v.5 no.1
• /
• pp.79-90
• /
• 2017

The main objective of load frequency control (LFC) is to keep the frequency value at nominal value and force deviation of the frequency to zero in case of load change. This paper suggests LFC by using a model predictive control (MPC), based on Integral Square Error (ISE) method designed to optimize the damping of oscillations in a two-area power system. The MPC is designed and simulated with a model system in state space, for robust performance in the system response. The proposed MPC is tuned by ISE to achieve superior efficiency. Moreover, its performance has been assessed and compared with the PI and PID conventional controllers. The settling time and overshoot with MPC are extremely minimized as compared with conventional controllers.

• Proceedings of the KIEE Conference
• /
• 2000.11d
• /
• pp.621-623
• /
• 2000

In this paper, the effective design method of the predictive controller using fuzzy neural networks(FNNs) is presented for the Intelligent control of chaotic nonlinear systems. In our design method of controller, predictor parameters are tuned by the error value between the actual output of a chaotic nonlinear system and that of a fuzzy neural network model. And the parameters of predictive controller using fuzzy neural network are tuned by the gradient descent method which uses control error value between the actual output of a chaotic nonlinear system and the reference signal. In order to evaluate the performance of our controller, it is applied to the Duffing system which are the representative continuous-time chaotic nonlinear systems and the Henon system which are representative discrete-time chaotic nonlinear systems.

• Communications for Statistical Applications and Methods
• /
• v.27 no.2
• /
• pp.211-224
• /
• 2020

Sensitivity and specificity are popular measures described by the receiver operating characteristic (ROC) curve. There are also two other measures such as the positive predictive value (PPV) and negative predictive value (NPV); however, the PPV and NPV cannot be represented by the ROC curve. Based on the total operating characteristic (TOC) curve suggested by Pontius and Si (International Journal of Geographical Information Science, 97, 570-583, 2014), explanatory methods are proposed to geometrically describe the PPV and NPV by the TOC curve. It is found that the PPV can be regarded as the slope of the right-angled triangle connecting the origin to a certain point on the TOC curve, while 1 - NPV can be represented as the slope of the right-angled triangle connecting a certain point to the top right corner of the TOC curve. When the neutral zone exists, the PPV and 1-NPV can be described as the slopes of two other right-angled triangles of the TOC curve. Therefore, both the PPV and NPV can be estimated using the TOC curve, whether or not the neutral zone is present.

• Proceedings of the KIEE Conference
• /
• 2005.05a
• /
• pp.236-238
• /
• 2005

In this paper, we propose a new discrete-time predictive current controller for a PMLSM(permanent magnet linear synchronous motor). The main objectives of the current controllers are that the measured stator current is tracked the command current value accurately and the transient interval is shorten as much as possible, in order to obtain high-performance of ac drive system. The conventional predictive current controller is hard to implement in full digital current controller since a finite calculation time causes a delay between the current sensing time and the time that take to apply the voltage to motor. A new control strategy is the schema that gets the fast adaptation of transient current change, the fast transient response tracking. Moreover, the simulation results will be verified the improvements of Predictive controller and accuracy of the current controller.