• The Journal of the Korea Contents Association
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• v.18 no.4
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• pp.89-98
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• 2018

Due to the increasing global prevalence of dementia, such as Alzheimer disease, there is a growing public health concern about its prevention. The purpose of this study was to conduct a systematic review for a narrative synthesis and critical appraisal of current published research related to dementia prevention programs among Koreans. To conduct a systematic review, the data bases KoreaMed, Riss4u and 9 Nursing Journals were searched using the key words dementia prevention and cognitive function. Articles published between 2000~2014 and related to dementia prevention programs were reviewed. Two hundred-fifty references were searched but only 29 studies met our inclusion criteria to review. We found that dementia prevention programs focused on: exercise, 11 studies (37.9%); multi-therapy, 9 studies (31.0%); and cognitive enhancement activity, 4 studies(13.8%). The majority of studies (n=19, 65.5%) included adults over 65 while two studies targeted adults over 75. The current literature indicates that future research is needed to develop and provide appropriate and effective dementia prevention programs among Korean older adults.

• Health Policy and Management
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• v.28 no.4
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• pp.392-401
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• 2018

Background: Physical activity (PA) is critical for maintaining the health and well-being of older people in community and also institutional settings. The purpose of this study was to examine the current status of PA and related individual and organizational factors among older nursing home residents with and without dementia. Methods: This is a secondary data analysis study of a nationwide survey of 92 long-term care facilities in Korea, and the study sample includes older residents with dementia (n= 753) and without dementia (n= 480). The level of PA was measured by PA time and whether or not residents had an outdoor activity over the past 3 days. Multi-variate, multi-level analyses were conducted. Results: More than half of the sample in both groups had no or less than 1 hour of PA. About one out of four older people in our sample had no outdoor activity over the past 3 days regardless of whether or not they had dementia. Among the people without dementia, several individual-level factors were associated with PA, including dependency for activities of daily living, social activity participation, and caregivers' belief in the functional improvement of residents. Unlike the non-dementia group, individual- and organizationallevel factors including staffing level and having the relevant equipment for PA were associated with PA among those with dementia. Conclusion: Study findings provide evidence on the lack of PA among older nursing home residents, and the importance of institutional capacity with regard to human resources and physical equipment for promoting PA among people with dementia, in particular. Policies and supports are needed to promote the implementation of healthy aging programs including PA for older nursing home residents. Such programs should be person-centered with consideration to the physical and cognitive status of individual residents.

• Journal of the Korean Orthopaedic Association
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• v.55 no.4
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• pp.294-304
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• 2020

Anterior cruciate ligament (ACL) reconstruction is a successful procedure independently by patient selection, timing of surgery, surgical technique, choice of graft, and fixation methods. Among these factors, graft selection and fixation methods might be the most critical yet controversial questions for surgeons. Although recent studies showed that grafts have advantages and drawbacks, there is still no ideal graft. Similarly, many fixation methods of femoral and tibial tunnels have been proposed over the last few decades, with no clear superiority of one technique over another. Surgeons should be familiar with a variety of grafts, fixation techniques, and their specific associated surgical procedures as well as the advantages and disadvantages of each. Therefore, this article summarizes the current literature and discusses the current state of graft selection and fixation methods in the treatment of an ACL injury.

• Progress in Superconductivity and Cryogenics
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• v.22 no.1
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• pp.12-16
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• 2020

As high homogeneity in magnetic field is required to increase the resolution of MRI magnets, various shimming methods have been researched. Using one of them, the design of the superconducting active zonal shim coil for MRI magnets is discussed in this paper. The magnetic field of the MRI magnet is expressed as the sum of spherical harmonic terms, and the optimized current density of shim coils capable of removing higher-order terms is calculated by the Tikhonov regularization method. To investigate all potential designs derived from calculated current density, 4 sweeping parameters are selected: (1) axial length of shim coil zone; (2) radius of shim coils; (3) exact axial position of shim coils; and (4) operating current. After adequate designs are determined with constraints of critical current margin and homogeneity criterion, the total wire length required for each is calculated and the design with a minimum of them is chosen. Using the superconducting wire length of 9.77 km, the field homogeneity over 50 cm DSV is improved from 24 ppm to 1.87 ppm in the case study for 9.4 T whole-body MRI shimming. Finally, the results are compared with the finite element method (FEM) simulation results to validate the feasibility and accuracy of the design.

• Journal of Power Electronics
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• v.19 no.4
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• pp.846-857
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• 2019

Voltage step-down converters are very popular in distributed power systems, voltage regular modules, electric vehicles, etc. However, a high step-down voltage ratio is required in many applications to prevent the traditional buck converter from operating at extreme duty cycles. In this paper, a series capacitor interleaved buck converter with a soft switching technique is proposed. The DC voltage ratio of the proposed converter is half that of the traditional buck converter and the voltage stress across the one main switch and the diodes is reduced. Moreover, by paralleling the series connected auxiliary switch and the auxiliary inductor with the main inductor, zero voltage transition (ZVT) of the main switches can be obtained without increasing the voltage or current stress of the main power switches. In addition, zero current turned-on and zero current switching (ZCS) of the auxiliary switches can be achieved. Furthermore, owing to the presence of the auxiliary inductor, the turned-off rate of the output diodes can be limited and the reverse-recovery switching losses of the diodes can be reduced. Thus, the efficiency of the proposed converter can be improved. The DC voltage gain ratio, soft switching conditions and a design guideline for the critical parameters are given in this paper. A loss analysis of the proposed converter is shown to demonstrate its advantages over traditional converter topologies. Finally, experimental results obtained from a 100V/10V prototype are presented to verify the analysis of the proposed converter.

• Tuberculosis and Respiratory Diseases
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• v.71 no.6
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• pp.400-407
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• 2011

Background: There were a few studies which were conducted to know about the behavior of the chronic obstructive pulmonary diseases (COPD) patients. The aims of this study was to explore the behaviour of COPD patients, such as awareness and impact of disease, the pathway of visiting doctors, and the treatment pattern and preference. Methods: A face-to-face interview of 300 subjects with COPD was conducted. Results: The most concerned symptom which made the respondents to visit the hospital was 'breathlessness' (78%). Only 58% of them knew the exact diagnosis. Seventy-three percent of them visited the hospital 'once a month' or 'once every 2 month'. They have made 12.8 prescheduled visits to the hospital in the past 1 year. Unscheduled visits and hospital stay figured to two in the past year. Only 11% of respondents felt they were currently in good health. 'Severe' and 'very severe' COPD patients perceived their health to be in a worse condition than 'mild' and 'moderate' COPD patients. When conditions worsened, 42% of patients were hospitalized. The most common prescription treatment was a fixed combination of inhaled corticosteroids and long-acting ${\beta}2$ agonists (48%), followed by a long acting anticholinergics (38%). Conclusion: Over forty percent of the patients didn't know exactly about their condition. Most of them had a negative attitude toward their current health status. Doctors need to know more about COPD patients in terms of their attitude toward the disease, impact of the disease, interaction with healthcare professionals and treatment related problems.

• Ocean and Polar Research
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• v.41 no.3
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• pp.159-168
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• 2019

Understanding the interaction between climate and the water cycle is critical especially in a drought sensitive region such as California. This study explored hydrologic changes in central and southern California in relation to the glacial-interglacial climate cycles over the last 30 thousand years. To do this, we reconstructed paleovegetation using plant wax carbon isotopic compositions (${\delta}^{13}C$) preserved in marine sediment cores retrieved from the central California continental shelf (ODP Site 1018) and Santa Barbara Basin (ODP Site 893A). The results were then compared to the existing sea surface temperature (SST) and pollen records from the same cores to understand terrestrial hydrology in relation to oceanographic processes. The Last Glacial was generally dry both in central and southern California, indicated by grassland expansion, confirming the previously suggested notion that the westerly storm track that supplies the majority of the precipitation in California may not have moved southward during the glacial period. Southern California was drier than central California during the Last Glacial Maximum (LGM). This drying trend may have been associated with the weakening of the California Current and northerly winds leading to the early increase in SST in southern California and decline in both offshore and coastal upwelling. The climate was wetter during the Holocene in both regions compared to the glacial period and forest coverage increased accordingly. We attribute this wetter condition to the precipitation contribution increase from the tropics. Overall, we found a clear synchronicity between the terrestrial and marine environment which showed that the terrestrial vegetation composition in California is greatly affected by not only the global climate states but also regional oceanographic and atmospheric conditions that regulate the timing and amount of precipitation over California.

• Biomaterials and Biomechanics in Bioengineering
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• v.2 no.3
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• pp.127-141
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• 2015

Silver-based systems activated by low intensity direct current continue to be investigated as an alternative antimicrobial for infection prophylaxis and treatment. However there has been limited research on the quantitative characterization of the antimicrobial efficacy of such systems. The objective of this study was to develop a semi-mechanistic pharmacokinetic/pharmacodynamic (PK/PD) model providing the quantitative relationship between the critical system parameters and the degree of antimicrobial efficacy. First, time-kill curves were experimentally established for a strain of Staphylococcus aureus in a nutrientrich fluid environment over 48 hours. Based on these curves, a modified PK/PD model was developed with two components: a growing silver-susceptible bacterial population and a depreciating bactericidal process. The test of goodness-of-fit showed that the model was robust and had good predictability ($R^2>0.7$). The model demonstrated that the current intensity was positively correlated to the initial killing rate and the bactericidal fatigue rate of the system while the anode surface area was negatively correlated to the fatigue rate. The model also allowed the determination of the effective range of these two parameters within which the system has significant antimicrobial efficacy. In conclusion, the modified PK/PD model successfully described bacterial growth and killing kinetics when the bacteria were exposed to the electrically activated silver-titanium implant system. This modeling approach as well as the model itself can also potentially contribute to the development of optimal design strategies for other similar antimicrobial systems.

• Progress in Superconductivity
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• v.3 no.1
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• pp.23-27
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• 2001

We have investigated the mixed-state magnetoresistance of high quality c-axis-oriented MgB2 thin film for magnetic field from 0.5 T to 5.0 T, applied normal to ab-plane. The temperature dependence of magnetoresistance was well described by vortex glass and fluctuation theories for different temperature regimes. We observed glassy exponent of v(z-1)~3 and upper critical field of $H_{c2}$(0)~35 T, which is consistent with previous data obtained from direct $H_{c2}$(0) measurements. Interestingly, the thermally activated flux flow region was observed to be very narrow, suggesting that the pinning strength of this compound is very strong. This finding is closely related to the recent reports that the bulk pinning is dominant in $MgB_2$and the critical current density of $MgB_2$ thin film is very high, comparable to that of cuprate superconductor. The present results further suggest that $MgB_2$is beneficial to technical applications.ons.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.7
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• pp.797-803
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• 2012

Proportional solenoid valves are a modulating type that can control the displacement of valves continuously by means of electromagnetic forces proportional to the solenoid coil current. Because the solenoid-type modulating valves have the advantages of fast response and compact design over air-operated or motor-operated valves, they have been gaining acceptance in chemical and power plants to control the flow of fluids such as water, steam, and gas. This paper deals with the auto tuning of the position controller that can provide the proportional and integral gain automatically based on the dynamic system identification. The process characteristics of the solenoid valve are estimated with critical gain and critical period at a stability limit based on implemented relay feedback, and the controller parameters are determined by the classical Ziegler-Nichols design method. The auto-tuning algorithm was verified with experiments, and the effects of the operating point at which the relay control is activated as well as the relay amplitude were investigated.