• Journal of computational fluids engineering
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• v.22 no.1
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• pp.95-102
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• 2017

Debris flow is a composition of solid objects of various sizes, suspension and water, which occurs frequently as the results of landslide following heavy rainfall. This often causes extensive damage in the form of socio-economic losses and casualties as witnessed during the incident around Mt. Umyeon, Seoul in 2011. There have been numerous investigation to mitigate the impacts from debris flow; however, the estimation as preparedness measure has not been successful due to nonlinear and multiphase characteristics of phenomena both in material and process inherent in the debris flow. This study presents a numerical approach to simulate the debris flow using open source code of computational fluid dynamics, OpenFOAM with non-Newtonian viscosity model for three phase material modeling. In order to validate the proposed numerical method, the quantitative evaluations were made by comparisons with experimental results and qualitative analysis for the dispersion characteristics was carried for the case of debris flow in the actual incident from Mt. Umyeon.

• Steel and Composite Structures
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• v.23 no.2
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• pp.173-186
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• 2017

Conceptual configuration and seismic performance of high-rise steel frame-brace structure are studied. First, the topology optimization problem of minimum volume based on truss-like material model under earthquake action is presented, which is solved by full-stress method. Further, conceptual configurations of 20-storey and 40-storey steel frame-brace structure are formed. Next, the 40-storeystructure model is developed in Opensees. Two common configurations are utilized for comparison. Last, seismic performance of 40-storey structure is derived using nonlinear static analysis and nonlinear dynamic analysis. Results indicate that structural lateral stiffness and maximum roof displacement can be improved using brace. Meanwhile seismic damage can also be decreased. Moreover, frame-brace structure using topology optimization is most favorable to enhance lateral stiffness and mitigate seismic damage. Thus, topology optimization is an available way to form initial conceptual configuration in high-rise steel frame-brace structure.

• Geomechanics and Engineering
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• v.16 no.3
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• pp.331-339
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• 2018

Worldwide growth in hydrocarbon and energy demand is driving the oil and gas companies to drill more wells in complex situations such as areas with high-pressure, high-temperature conditions. As a result, in recent years the number of wells in these conditions have been increased significantly. Wellbore instability is one of the main issues during the drilling operation especially for directional and horizontal wells. Many researchers have studied the wellbore stability in complex situations and developed mathematical models to mitigate the instability problems before drilling operation. In this work, a fully coupled thermoporoelastic model is developed to study the well stability in high-pressure, high-temperature conditions. The results show that the performance of the model is highly dependent on the truly evaluated rock mechanical properties. It is noted that the rock mechanical properties should be evaluated at elevated pressures and temperatures. However, in many works, this is skipped and the mechanical properties, which are evaluated at room conditions, are entered into the model. Therefore, an accurate stability analysis of high-pressure, high-temperature wells is achieved by measuring the rock mechanical properties at elevated pressures and temperatures, as the difference between the model outputs is significant.

• The Journal of Korean Medicine
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• v.24 no.2
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• pp.213-218
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• 2003

Objectives : There has been little report on the treatment of pulmonary hypertension on the basis of Oriental medicine. Several weeks ago we had a case of pulmonary hypertension, and found something in the treatment of the disease. A 60-year old man with hemoptysis was admitted to the Kyunghee Oriental Medical Center on April 23, 2002 and discharged May 4, 2002. During that time, we saw good results. Methods : On the oriental medical basis that Chuongsangboha-tang (Qingshangbuxia-tang) has an effect on chronic pulmonary disease, we treated him with that medicine three times a day for 12 days along with Roxithromycin 150mg/tab 1T qd, Digoxin 0.25mg/tab 0.5T qd, and Bambuterol Hel 1T qd. He was also given acupuncture therapy daily with tonifying SP3(太白), L9(太淵) and sedating H8(少府), L10(魚際). Results : The following data was observed from the therapy : hemoptysis volume decreased by 90%, general weakness by 40%m and ABGA results improved. Conclusions : As we managed pulmonary hypertension, we came to the conclusion that the oriental medical therapy can be of assistance to western medical therapy and can mitigate hemoptysis.

• Asian Journal of Atmospheric Environment
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• v.9 no.3
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• pp.187-193
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• 2015

Livestock is one of the major contributors of greenhouse gases (GHGs). It accounts for 14.5% of the global GHGs emissions like methane ($CH_4$) from enteric fermentation and manure, nitrous oxide ($N_2O$) from manure and fertilizer. Since enteric emissions are a major contributor of $CH_4$ than that of manure emissions hence primary efforts were made on reducing enteric emissions, with minor attention to dung emissions. Many researches were conducted by dietary manipulation to mitigate enteric $CH_4$ emission. However dietary manipulation also had significant effects on manure GHGs emissions too. Several works proved that manure $CH_4$ emissions were increased with high level of concentrate supplementation despite reduction in enteric $CH_4$. Fat and CP content of the diet has shown inconsistent results on manure $CH_4$ emissions. Amount of concentrate in the diet has shown little effect whereas dietary CP content exhibited conflicting effects on manure $N_2O$ emissions.

• Knowledge Management Research
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• v.17 no.1
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• pp.49-72
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• 2016

Extant research on firm innovation productivity is limited in measuring the innovation productivity, in which they measured firm innovation productivity by using either inputs or outputs of innovation. The present study complemented the extant research by employing Data Envelopment Analysis (DEA) approach to measure firm innovation productivity. Furthermore, this paper examined the effects of firms' external knowledge search, as one of open innovation practices, on firm innovation productivity, for open innovation activities are regarded as an influencing factor on firm innovation productivity in the previous literatures. Using the data of the Korean Innovation Survey (KIS) of manufacturing industries conducted in 2008, this study developed hypotheses in which we considered not only two dimensions of external knowledge search (breadth and depth) but also two subtypes of external knowledge search (market-driven and science-driven). The results found that searching deeply and market-driven search are positively related to firm innovation productivity, but science-driven search is somewhat negatively related to firm innovation productivity. Furthermore, market-driven search can mitigate the negative effect of science-driven search on innovation productivity.

• Journal of Korea Multimedia Society
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• v.5 no.5
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• pp.582-589
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• 2002

In this paper, we propose a new method that combines antenna array, which employs any beamforming algorithm, and successive interference cancelling multiuser detector which improves the performance of the receiver and analyse its performance. Antenna away receivers can improve the performance by spatially discriminating among the users and reducing the multiple access interference. But the performance of the receivers degrades when the difference of the direction of arrival of the users are too small. Many interference cancelling multiuser detectors have been suggested for DS/CDMA systems which have low complexity for their performance. In this paper, we show how to mitigate such a degradation by combining successive interference cancelling multiuser detector.

• The Journal of the Acoustical Society of Korea
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• v.11 no.3
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• pp.25-39
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• 1992

Undesired vibratory motion of a simply supported plate is controlled with piezoelectric sensors and actuators. Appropriate dynamic equations of the sensor and actuator are derived and coupled with the dynamic equation of the plate for the construction of an active feedback vibration control system. Analytic solutions are obtained for amplitude response of the plate, reflecting the combined effect of external driving forces and piezoelectric control moments. Numerical examples are presented to illustrate the effectiveness of this approach for two types of external forces, i.e. a concentrated point load and a piezoelectric plate driver. Calculation results show that the sensors and actuators can be efficient tools to mitigate the sensitivity of the structure to external sources of vibration. The method investigated in this work is applicable to arbitrary external loading conditions and control algorithms.

• Journal of Korean Academy of Nursing
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• v.46 no.2
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• pp.159-167
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• 2016

Purpose: This article provides an overview of current knowledge on the impact of caregiving on the psychological and physical health of family caregivers of intensive care unit (ICU) survivors and suggestions for future research. Methods: Review of selected papers published in English between January 2000 and October 2015 reporting psychological and physical health outcomes in family caregivers of ICU survivors. Results: In family caregivers of ICU survivors followed up to five years after patients' discharge from an ICU, psychological symptoms, manifested as depression, anxiety and post-traumatic stress disorder, were highly prevalent. Poor self-care, sleep disturbances and fatigue were identified as common physical health problems in family caregivers. Studies to date are mainly descriptive; few interventions have targeted family caregivers. Further, studies that elicit unique needs of families from diverse cultures are lacking. Conclusion: Studies to date have described the impact of caregiving on the psychological and physical health in family caregivers of ICU survivors. Few studies have tested interventions to support unique needs in this population. Therefore, evidence for best strategies is lacking. Future research is needed to identify ICU caregivers at greatest risk for distress, time points to target interventions with maximal efficacy, needs of those from diverse cultures and test interventions to mitigate family caregivers' burden.

• ALGAE
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• v.25 no.1
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• pp.27-35
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• 2010

Marked declines in seagrass meadows are increasingly being reported from coasts around Korea and many regions of the world. The transplantation of seagrasses has been attempted to mitigate and control their degradation from a range of anthropogenic factors. In this study, Zostera marina shoots, which were collected from a donor bed in Koje Bay, were transplanted in Jindong Bay in December 2004. In 2008, a comparative investigation of shoot morphology, growth, and reproduction strategy of Z. marina was carried out between the donor and transplant sites to assess their adaptation success. Shoot height, individual shoot weight, and leaf productivity at the transplant site were significantly greater than those at the donor site. However, below-/aboveground tissue ratio was significantly lower at the transplant site compared to the donor site. Z. marina survival was maintained through vegetative reproduction, while peak season for lateral shoot recruitment was late winter for both donor and transplant site populations. However, vegetative reproduction mainly occurred during late winter and spring at the transplant site, whereas lateral shoots were evident across all seasons except late spring in the donor site. More pronounced seasonal variations were found at the transplant site compared to the donor site. These results indicate that Z. marina populations at the two sites possess distinct phenotypic variations induced by different environmental conditions, and Z. marina transplants have adapted well to the new transplant environment.