• International Journal of Advanced Culture Technology
• /
• v.7 no.1
• /
• pp.89-95
• /
• 2019

One benefit of education for self-management of chronic diseases is to increase the use of cognitive techniques for coping with symptoms. Unfortunately, that benefit can deteriorate over time, and that phenomenon, which is sometimes called "decay of impact", has been studied only rarely. This study was done to understand the decay of impact with regard to the use of cognitive techniques for coping with symptoms, and especially to understand how that decay might be predicted. Data were analyzed from 381 adults suffering from chronic medical conditions, all of whom were involved in education to improve their self-management of their chronic condition(s). During the first year after the educational program, coping was measured four times. Variables associated with the decay of impact were found using statistical modeling (logistic regression). Decay of impact was found in almost half of the participants. The analysis provided moderately good predictions regarding the decay of impact. Given this new information, interventions to further improve coping with symptoms can be appropriately targeted to the people for whom they will be most beneficial.

• Journal of Korean Society of Water and Wastewater
• /
• v.32 no.5
• /
• pp.411-419
• /
• 2018

The residual chlorine concentration is an essential factor to secure reliable water quality in the water distribution systems. The chlorine concentration decays along the pipeline system and the main processes of the reaction can be divided into the bulk decay and the wall decay mechanisms. Using EPANET 2.0, it is possible to predict the chlorine decay through bulk decay and wall decay based on the pipeline geometry and the hydraulic analysis of the water distribution system. In this study, we tried to verify the predictability of EPANET 2.0 using data collected from experimental practices. We performed chlorine concentration measurement according to various Reynolds numbers in a pilot-scale water distribution system. The chlorine concentration was predicted using both bulk decay model and wall decay model. As a result of the comparison between experimental data and simulated data, the performance of the limited $1^{st}$-order model was found to the best in the bulk decay model. The wall decay model simulated the initial decay well, but the overall chlorine decay cannot be properly predicted. Simulation also indicated that as the Reynolds number increased, the impact of the wall.

• Journal of Aerospace System Engineering
• /
• v.9 no.2
• /
• pp.57-62
• /
• 2015

The satellite orbit is continuously changing due to space environment. Especially for low earth orbit, atmospheric drag plays an important role in the orbit altitude decay. Recently, solar activities are expected to be high, and relevant events are occurring frequently. In this paper, analysis on the impact of geomagnetic storm on LEO satellite orbit is presented. For this, real flight data of KOMPSAT-2, KOMPSAT-3, and KOMPSAT-5 are analyzed by using the daily decay rate of mean altitude is calculated from the orbit determination. In addition, the relationship between the solar flux and geomagnetic index, which are the metrics for solar activities, is statistically analyzed with respect to the altitude decay. The accuracy of orbit prediction with both the fixed drag coefficient and estimated one is examined with the precise orbit data as a reference. The main results shows that the improved accuracy can be achieved in case of using estimated drag coefficient.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.13 no.5
• /
• pp.334-340
• /
• 2003

Exponential window function Is widely used In impact hammer testing to reduce leakage error as well as to get a good S/N ratio. The larger its decaying rate is, the more effectively the leakage errors are reduced. But if the decay rate of the exponential window is too large, the FRF is distorted. And the modal parameters of the system can not be exactly identified by modal analysis technique. Therefore, it is a difficult problem to determine proper decay rate in impact hammer testing. In this paper, amount of the FRF distortion caused by exponential window is theoretically uncovered. A new circle fitting method is also proposed so that the modal parameters are directly extracted from impulse response spectrum distorted by the exponential-windowed impulse response data. The results by the conventional and proposed circle fitting method are compared through a numerical example.

• Nuclear Engineering and Technology
• /
• v.39 no.6
• /
• pp.683-690
• /
• 2007

Because of increasing concerns regarding global warming and the longevity of oil and gas reserves, the importance of nuclear energy as a major source of sustainable energy is gaining recognition worldwide. To make nuclear energy truly sustainable, it is necessary to ensure not only the sustainability of the fuel supply but also the sustained availability of waste repositories, especially those for high-level radioactive waste (HLW). From this perspective, the effort to maximize the waste loading density in a given repository is important for easing repository capacity problems. In most cases, the loading of a repository is controlled by the decay heat of the emplaced waste. In this paper, a comparison of the decay heat characteristics of HLW is made among the various fuel cycle options. It is suggested that, for a future fast breeder reactor (FBR) cycle, the removal and burning of minor actinides (MA) would significantly reduce the heat load in waste and would allow for a reduction of repository size by half.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.05c
• /
• pp.106-109
• /
• 2001

In this paper, we have investigated the degradation of shed materials of outdoor insulators by UV-radiation by using corona-charging and XPS analysis. The accumulated charges on polymeric surface having intrinsic hydrophobic property have a negative impact on retaining its hydrophobicity. Therefore, shorter decay times of surface charges are preferred. The surface voltage decay on UV-treated silicone rubber and EPDM show a different decay trend with UV treated time. From the XPS analysis, the oxidized groups of silica-like structure in silicone rubber increase with UV treatment time. For EPDM, the oxidized carbon groups of C=O, O=C-O increase as elapse of UV radiation time. These oxidized surface for each material have different electrostatic characteristics, so deposited charges may be expected to have different impacts on their surface hydrophobicity. The degradation mechanism based on our results is discussed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2014.10a
• /
• pp.7-9
• /
• 2014

An auditory experiment was conducted to establish annoyance criteria for floor impact noise in apartment buildings. Heavyweight floor impact sounds were recorded using an impact ball; the impact sound pressure level (SPL) together with the temporal decay rate (DR), which is quantified by the dB drop per second, was analyzed. For the experiment, A-weighted exposure levels of the heavy-weight floor impact sounds ranging 34~73 dB were evaluated at 3 dB intervals. Participants used a 7-point verbal scale to evaluate the level of annoyance from floor impact noise. The results show that the annoyance increases with increasing impact SPL and decreasing DR. Consequently, a classification and an acceptable level of floor impact sounds were proposed.

• Journal of Korean Society on Water Environment
• /
• v.24 no.6
• /
• pp.793-800
• /
• 2008

Recently domestic drinking water industry has recognized membrane-based technology as a promising alternative for water treatment. To ensure successful application of membrane processes, the integrity of membrane systems should be maintained. According to US EPA guidance, the pressure decay test based on the bubble point theory is recommended to detect any membrane defection of which size is close to the smallest diameter of Cryptosporidium oocysts, $3{\mu}m$. Proper implementation of the pressure decay test is greatly affected by initial test pressure, and the interpretation of the test results is associated with upper control limit. This study is conducted to investigate various factors affecting determination of initial test prtessure and upper control limit, including membrane-based parameters such as pore shape correction factor, surface tension and contact angle, and system-based parameters, such as volumetric concentration factor and total volume of system. In this paper, three different hollow fibers were used to perform the pressure decay test. With identical initial test pressure applied, their pressure decay tendency were different from each other. This finding can be explained by the micro-structure disparity of those membranes which is verified by FESEM images of those membranes. More specifically, FESEM images revealed that three hollow fibers have asymmetry, deep finger, shallow finger pore shape, respectively. In addition, sensitivity analysis was conducted on five parameters mentioned above to elucidate their relation to determination of initial test pressure and upper control limit. In case of initial pressure calculation, the pore shape correction factor has the highest value of sensitivity. For upper control limit determination, system factors have greater impact compared to membrane-based parameters.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.6
• /
• pp.688-696
• /
• 2023

In the present study, free roll decay and resistance performances of fishing vessels were evaluated with the combinations and variations of in the parameters of appendages which are attached to improve motion performance of fishing vessels. Computational Ffluid Ddynamics was used to perform free roll decay and resistance analysis. The roll period and decay coefficient were derived by the variations in the combination and dimensions of the primary appendages of the bilge keel and the under keel. It was observed thatThe variations of in the length of the under keel did not significantly impact to the roll damping coefficient. Conversely, for the bilge keel, an increase in the length and angle resulted in an increase in the roll damping coefficient. Comparison of resistance performance was additionally assessed among the selected hulls with the appendages and bare hull. The resistance of the hull with the appendages was higher than that of the bare hull due owing to the changes of in the pressure on the surface of the hull and trim angle. Throughout the present study, the impact of appendage parameter and arrangement on the free roll decay and resistance performance of fishing vessels were was assessed,. which This will be beneficial for the application of appendages to fishing vessels.

• The Korean Journal of Ecology
• /
• v.13 no.1
• /
• pp.51-58
• /
• 1990

The rates of litter production and decomposition of litters from grasslands and forests in Mt. Guryong were studied. The annual litter production of Glycine soja showed the highest value 1950.88 g/$m^2$/yr in the grasslands and that in Quercus acutissima, as 2202.38 g/$m^2$/yr in the forests. The highest decay rate of the grasslands was found in G. soja as k=0.713 and that of the forests was in Salix koreensis as k=0.319. The Z values of k in the grasslands was higher than that in the forests. The shortest half-time of the litter decay in the grasslands was 0.9 years in G. soja and the longest one of the forests was S. koreensis as 2.1 years and the longest of all was Q. mongolica as 5.2 years. In the amount of total nitrogen of litters, G. soja was the highest of the grasslands and S. koreensis was the highest of the forest. The content of the total nitrogen in litters was directly propotional to the decay rates.