• Investigative Magnetic Resonance Imaging
• /
• v.25 no.1
• /
• pp.10-22
• /
• 2021

Purpose: To overcome the difficulty in building a large data set with a high-quality in medical imaging, a concept of 'blended-transfer learning' (BTL) using a combination of both source data and target data is proposed for the target task. Materials and Methods: Source and target tasks were defined as training of the source and target networks to reconstruct cardiac CINE images from undersampled data, respectively. In transfer learning (TL), the entire neural network (NN) or some parts of the NN after conducting a source task using an open data set was adopted in the target network as the initial network to improve the learning speed and the performance of the target task. Using BTL, an NN effectively learned the target data while preserving knowledge from the source data to the maximum extent possible. The ratio of the source data to the target data was reduced stepwise from 1 in the initial stage to 0 in the final stage. Results: NN that performed BTL showed an improved performance compared to those that performed TL or standalone learning (SL). Generalization of NN was also better achieved. The learning curve was evaluated using normalized mean square error (NMSE) of reconstructed images for both target data and source data. BTL reduced the learning time by 1.25 to 100 times and provided better image quality. Its NMSE was 3% to 8% lower than with SL. Conclusion: The NN that performed the proposed BTL showed the best performance in terms of learning speed and learning curve. It also showed the highest reconstructed-image quality with the lowest NMSE for the test data set. Thus, BTL is an effective way of learning for NNs in the medical-imaging domain where both quality and quantity of data are always limited.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.10 no.6
• /
• pp.2851-2873
• /
• 2016

Cloud storage as a service provides high scalability and availability as per need of user, without large investment on infrastructure. However, data security risks, such as confidentiality, privacy, and integrity of the outsourced data are associated with the cloud-computing model. Over the year's techniques such as, remote data checking (RDC), data integrity protection (DIP), provable data possession (PDP), proof of storage (POS), and proof of retrievability (POR) have been devised to frequently and securely check the integrity of outsourced data. In this paper, we improve the efficiency of PDP scheme, in terms of computation, storage, and communication cost for large data archives. By utilizing the capabilities of JAR and ZIP technology, the cost of searching the metadata in proof generation process is reduced from O(n) to O(1). Moreover, due to direct access to metadata, disk I/O cost is reduced and resulting in 50 to 60 time faster proof generation for large datasets. Furthermore, our proposed scheme achieved 50% reduction in storage size of data and respective metadata that result in providing storage and communication efficiency.

• Nuclear Engineering and Technology
• /
• v.54 no.5
• /
• pp.1825-1834
• /
• 2022

Performing high-fidelity computational fluid dynamics (HF-CFD) to predict the flow and heat transfer state of the coolant in the reactor core is expensive, especially in scenarios that require extensive parameter search, such as uncertainty analysis and design optimization. This work investigated the performance of utilizing a multi-fidelity reduced-order model (MF-ROM) in PWR rod bundles simulation. Firstly, basis vectors and basis vector coefficients of high-fidelity and low-fidelity CFD results are extracted separately by the proper orthogonal decomposition (POD) approach. Secondly, a surrogate model is trained to map the relationship between the extracted coefficients from different fidelity results. In the prediction stage, the coefficients of the low-fidelity data under the new operating conditions are extracted by using the obtained POD basis vectors. Then, the trained surrogate model uses the low-fidelity coefficients to regress the high-fidelity coefficients. The predicted high-fidelity data is reconstructed from the product of extracted basis vectors and the regression coefficients. The effectiveness of the MF-ROM is evaluated on a flow and heat transfer problem in PWR fuel rod bundles. Two data-driven algorithms, the Kriging and artificial neural network (ANN), are trained as surrogate models for the MF-ROM to reconstruct the complex flow and heat transfer field downstream of the mixing vanes. The results show good agreements between the data reconstructed with the trained MF-ROM and the high-fidelity CFD simulation result, while the former only requires to taken the computational burden of low-fidelity simulation. The results also show that the performance of the ANN model is slightly better than the Kriging model when using a high number of POD basis vectors for regression. Moreover, the result presented in this paper demonstrates the suitability of the proposed MF-ROM for high-fidelity fixed value initialization to accelerate complex simulation.

• Journal of the Korean GEO-environmental Society
• /
• v.13 no.5
• /
• pp.25-33
• /
• 2012

In this study, gathered measuring data at fields constructed by IPS(Innovative Prestressed Support) system controls the ground displacement and improves the constructability of earth work and structure work greatly, and compared with horizontal displacement calculated by Elasto-plastic analysis program(EXCAV/W). As the result, displacement of calculated by pre-loading data is reduced 13.2% average of general method, and measuring displacement is also reduced 26.7% average of general method. Therefore that IPS system is more safe than conventional strut method in contrast to displacement of underground wall. In addition, horizontal displacement is reduced through the pre-loading effect used by IPS system.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2003.06a
• /
• pp.547-552
• /
• 2003

In mold machining, there are many concave machining regions where chatter and tool deflection occur since MRR (material removal rate) increases as curvature increases even though cutting speed and depth of cut are constant. Boolean operation between stock and tool model is widely used to compute MRR in NC milling simulation. In finish cutting, the side step is reduced to about 0.3mm and tool path length is sometimes over 300m. so Boolean operation takes long computation time and includes much error if the resolution of stock and tool model is larger than the side step. In this paper, curvature of CL(cutter location) surface and side step of tool path is used to compute the feedrate for constant MRR machining. The data structure of CL surface is Z-map generated from NC tool path. The algorithm to get local curvature from discrete data was developed and applied to compute local curvature of CL surface. The side step of tool path was computed by point density map which includes cutter location point density at each grid element. The feedrate computed from curvature and side step is inserted to new tool path to regulate MRR. The resultants wire applied to feedrate optimization system which generates new tool path with feedrate from NC codes for finish cutting. The system was applied to speaker mold machining. The finishing time was reduced to 12.6%. tool wear was reduced from 2mm to 1.1mm and chatter marks and over cut on corner were removed.

• Korea Journal of Hospital Management
• /
• v.14 no.3
• /
• pp.66-82
• /
• 2009

The purpose of this study is to investigate the determinants of caregiver's conflict experience in elderly care institutions. This study focused on the three key independent variable groups(e.g., socio-demographic, job-related, and individual personality). The sample used in this study are 311 caregivers who are randomly selected from 21 elderly care institutions in Korea. Data were collected with a structured questionnaire by mail from Oct. 15 to Nov. 30 in 2007. The collected data were analyzed using logistic regression. The major findings of the study are as follows: 1) Nearly 40% percent of the respondents reported that they had experienced conflicts with elderly patients. The conflict with other caregivers ranked as second(20.6%), followed by patients' families(18.6%) and hospital employees(15.1%). 2) The personality, especially uniqueness caused conflict with patients or other caregivers. The professional identity reduced conflict with patients. The negative work experiences caused conflict with patients or family. The service attitude reduced conflict with family. The service-centered culture reduced conflict with hospital employees. Those who lived with the elderly showed lower level of conflict with family or hospital employees.

• Safety and Health at Work
• /
• v.9 no.4
• /
• pp.462-467
• /
• 2018

Background: This study was conducted to investigate the effects of work on medical expenditures by the elderly. Methods: Data pertaining to individuals aged 65 or older collected by the Korean Health Panel 2008-2013 were used. The effects of work on medical expenditures were analyzed in a panel tobit model adjusted for several variables of demographic factors, socioeconomic factors, and health factors for health care. Data were also analyzed based on age groups (65-74, $75{\leq}$), type of work (waged or self-employed), and working time (daytime work or night time work). Results: Among the elderly older than 65 years, 34-37% were workers. Work among the elderly reduced medical expenditures relative to nonworking elderly. Specifically, medical expenditures were lower in individuals older than 75 years, as well as among those who were self-employed insured and had medical aid insurance and those who exercised. However, medical expenditures were higher among females, married individuals, those with a higher household income, and those with a chronic disease. Elderly wageworkers showed reduced medical expenditures than nonworking elderly and elderly daytime workers did. Conclusion: The elderly population's work, especially wage work and daytime work, reduced medical expenditures relative to no work. These results provide valuable information for policymakers by indicating that work was associated with lower medical expenditures than no work. If elderly work is to be encouraged, it is necessary to provide a variety of high-quality wage work.

• Journal of Preventive Medicine and Public Health
• /
• v.39 no.4
• /
• pp.309-316
• /
• 2006

Objectives: Korean epidemiological studies have used reduced samples according to the subject's characteristics, such as the health services provided, the historical note with asthma, and age, to examine the acute effect of air pollution on asthma using the Korean National Health Insurance records. However, there have been few studies on whether the effects shown in these reduced samples are different from those of all samples. This study compared the effects of air pollution on asthma attacks in three reduced samples with those of entire samples. Methods: The air pollution data for $PM_{10},\;CO,\;SO_2,\;NO_2,\;and\;O_3$, and weather conditions including temperature, relative humidity, and air pressure in Seoul, 2002, were obtained from outdoor monitoring stations in Seoul. The emergency hospital visits with an asthma attack in Seoul, 2002 were extracted from the Korean National Health Insurance records. From these, the reduced samples were created by health service, historical notes with asthma, and age. A case-crossover design was adopted and the acute effects of air pollution on asthma were estimated after adjusting for weather, time trend, and seasonality. The model was applied to each reduced sample and the entire sample. Results: With respect to the health service, the effects on outpatients were similar to those for the total sample but were different for inpatients. These similar effect sizes were also observed in the reduced samples according to the historical note with asthma and age. The relative risks of $PM_{10},\;CO,\;SO_2,\;NO_2,\;and\;O_3$, among the reduced and entire samples were 1.03, 1.04-1.05, 1.02-1.03, 1.04-1.06, and 1.10-1.17, respectively. Conclusions: There was no clear evidence to show a difference between the reduced samples and the entire samples.

• Journal of Family Resource Management and Policy Review
• /
• v.18 no.4
• /
• pp.1-26
• /
• 2014

This study analyzes the effects of the three types of flexible work arrangements (part-time, flexitime, and reduced working hours for childcare) available in Korea on work-family conflict, facilitation, and job satisfaction for married working women ages 15-49. The study employs a panel analysis based on the first to the fourth data from the Korean Longitudinal Survey of Women & Families (KLoWF). The major results are as follows. First, the availability of part-time jobs and reduced working hours to facilitate childcare is significantly related to work-family conflict for married women. If a married woman is employed in a part-time position or if reduced working hours for childcare are available, the conflict within the family caused by the job is reduced. Second, none of the three types of flexible work arrangements have a statistically significant influence on work-family facilitation for married women. Third, the availability of reduced working hours for childcare has a positive effect on the job satisfaction of married women. In conclusion, flexible working hours for women who are raising children are the main factor in reducing the negative effect of a job on a woman's family life as they contribute to work and family compatibility.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.21 no.2
• /
• pp.37-44
• /
• 2013

Generally, a reduced chemical mechanism of n-heptane is used as chemical fuel of a 3-D diesel engine simulation because diesel fuel consists of hundreds of chemical components and various chemical classes so that it is very complex and large to use for the calculation. However, the importance of fuel in a 3-D simulation increases because detailed fuel characteristics are the key factor in the recent engine research such as homogeneous charged compression ignition engine. In this study, normal paraffin, iso paraffin and aromatics were selected to represent diesel characteristics and n-dodecane was used as a representative normal paraffin to describe the heavy molecular weight of diesel oil (C10~C20). Reduced kinetics of iso-octane and toluene which are representative species of iso paraffin and aromatics respectively were developed in the previous study. Some species were selected based on the sensitivity analysis and a mechanism was developed based on the general oxidation scheme. The ignition delay times, maximum pressure and temperature of the new reduced n-dodecane chemical mechanisms were well matched to the detailed mechanism data.