• Journal of Korea Water Resources Association
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• 제43권10호
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• pp.921-932
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• 2010

In this study, the adjustment processes of the disturbed channels by sand or gravel mining were investigated by a two dimensional numerical model in the generalized coordinate system. As a numerical scheme, the CIP (cubic interpolated pseudoparticle method) method was used to calculate the advection term in the flow field and central difference method was used to the diffusion term in it. The pit of the channel was partially filled with sediment at the toe of the pit upstream. As time increased, the headcut erosion upstream in the pit was decreased due to the sediment inflow. The almost inflow sediment upstream was trapped into the pit and the sediment deposit wedge migrated downstream in the pit with the steep submerged angle of repose. The numerical model was reproduced well the evolution processes of the channel. The mining pit migrated with speed as the channel was steep, and the numerical results were in overall agreement with the experimental results.

• Journal of the Korea Safety Management & Science
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• 제17권2호
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• pp.215-228
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• 2015

A creative innovation and an innovative problem-solving of industrial companies can be achieved by overcoming the challenges of technical and physical contradictions. The approaches to address conflicting and paradoxical problems, such as technical and physical contradictions have a crucial role in advancing the quality assessment for manufacturer and service provider. The term, technical contradiction, depicts the state that improvement of one ends of IFR (Ideal Final Result) leads to unfavorable condition of the other ends, and results in conflicting problem. Another type of contradictions that's discussed in this study is a physical contradiction which is due to two mutually opposing states of the means of ends, and gives paradoxical situation. By integrating the means-ends chain perspectives, the physical contradiction that is a specifically root-causes, "means", can be initially addressed to resolve the downstream problem of technical contradiction which represents a general and abstract goals, "ends". This research suggests IFR resolution processes to handle both physical contradiction of means and technical contradiction of ends by employing causal relationship with IFR, effects and causes. In summary, the study represents three major processes that resolve such contradictions are demonstrated as follows: 1) Derivation of causal and hierarchical relationship among IFR, ends and means by considering CAED (Cause-And-Effect Diagram) and LT (Logic Tree). 2) Identification of causal relationship between physical contradiction and technical contradiction by using TPCT (TRIZ Physical Contradiction Tree) and TCD (Technical Contradiction Diagram). 3) Application of integrated TRIZ principles by classifying 40 inventive principles into 4 general conditions of the separation principle of mutually opposite states in space, in time, based on conditions, and between the parts and the whole. In order to validate the proof of proposed IFR resolution processes, the analysis of the TRIZ case studies from National Quality Circle Contest in the years, 2011 to 2014 have been proposed. The suggested guidelines that are built based on TRIZ principles can uniquely enhance the process of quality innovation and assessment for quality practitioners.

• Particle and aerosol research
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• 제5권4호
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• pp.189-197
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• 2009

Wet-type particulate removal system is employed in most of ironmaking processes. These de-dusting systems require additional downstream aggregates for treatment of water and for drying of the collected slurry. Thus dried slurry can be pressed in shape of briquettes and recycled in the steelmaking process. Different from the wet-type, the dry-type particulate removal systems generate no slurry. A high-temperature, high-pressure de-dusting system with inertial inlet was developed. The target application of this system was to remove particulate matter generated from the novel ironmaking process and other steelmaking processes. In this study we conducted tests with this newly developed system to evaluate the performance of the silica-carbide (SiC) ceramic filters. In addition, for purpose of comparison, we also conducted tests with a unit which has conventional direct inlet. Fe-Particles collected from the novel ironmaking process were used in our tests as test dusts. The temperature and the pressure were kept constant at their respective values $800^{\circ}C$ and $3kg_f/cm^2$.

• Biomolecules & Therapeutics
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• 제20권2호
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• pp.165-170
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• 2012

Cell migration plays a role in many physiological and pathological processes. Reactive oxygen species (ROS) produced in mammalian cells influence intracellular signaling processes which in turn regulate various biological activities. Here, we investigated whether melanoma cell migration could be controlled by ROS production under normoxia condition. Cell migration was measured by wound healing assay after scratching confluent monolayer of B16F10 mouse melanoma cells. Cell migration was enhanced over 12 h after scratching cells. In addition, we found that ROS production was increased by scratching cells. ERK phosphorylation was also increased by scratching cells but it was decreased by the treatment with ROS scavengers, N-acetylcysteine (NAC). Tumor cell migration was inhibited by the treatment with PD98059, ERK inhibitor, NAC or DPI, well-known ROS scavengers. Tumor cell growth as judged by succinate dehydrogenase activity was inhibited by NAC treatment. When mice were intraperitoneally administered with NAC, the intracellular ROS production was reduced in peripheral blood mononuclear cells. In addition, B16F10 tumor growth was significantly inhibited by in vivo treatment with NAC. Collectively, these findings suggest that tumor cell migration and growth could be controlled by ROS production and its downstream signaling pathways, in vitro and in vivo.

• Journal of Community Nutrition
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• 제5권4호
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• pp.209-217
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• 2003

The food and nutrition system is a network of processes linking agriculture, food, eating, nutrition, and health. The system includes a series of nine stages (production, processing, distribution, acquisition, preparation, consumption, digestion, transport, and utilization) and two types of contexts (biophysical and sociocultural). Analysis of whole food and nutrition systems provides information about the structure and processes involved in the complete scope of food and nutrition, assisting in the identification of ″upstream″ influences and ″downstream″ consequences in the system. The current analysis gathered existing data about the food and nutrition system in South Korea from public sources and professional publications, and interpreted that information to consider how different elements of the system contribute to health. The findings revealed that South Korea has substantial domestic food production and processing supplemented by imports, widespread food distribution in markets and a growing number of Korean and Western restaurants, a relatively low percentage of household income spent on food, growing use of new food preparation methods such as microwave ovens, a rice/vegetable/fish based three-meal consumption pattern, few recorded digestive problems, increasing calorie storage as body fat, and a relatively low chronic disease prevalence compared to other developed societies. Examination of the full scope of the food and nutrition system provides a broad perspective using whole system thinking that can identify potential strategies for future research and intervention.

• Molecules and Cells
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• 제44권12호
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• pp.861-878
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• 2021

The human genome contains many retroviral elements called human endogenous retroviruses (HERVs), resulting from the integration of retroviruses throughout evolution. HERVs once were considered inactive junk because they are not replication-competent, primarily localized in the heterochromatin, and silenced by methylation. But HERVs are now clearly shown to actively regulate gene expression in various physiological and pathological conditions such as developmental processes, immune regulation, cancers, autoimmune diseases, and neurological disorders. Recent studies report that HERVs are activated in patients suffering from coronavirus disease 2019 (COVID-19), the current pandemic caused by SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) infection. In this review, we describe internal and external factors that influence HERV activities. We also present evidence showing the gene regulatory activity of HERV LTRs (long terminal repeats) in model organisms such as mice, rats, zebrafish, and invertebrate models of worms and flies. Finally, we discuss several molecular and cellular pathways involving various transcription factors and receptors, through which HERVs affect downstream cellular and physiological events such as epigenetic modifications, calcium influx, protein phosphorylation, and cytokine release. Understanding how HERVs participate in various physiological and pathological processes will help develop a strategy to generate effective therapeutic approaches targeting HERVs.

• Journal of Korean Society on Water Environment
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• 제24권1호
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• pp.54-62
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• 2008

It is often believed that a more complex water quality model is better able to simulate reality. The more complex a model, however, the more parameters are involved thus increases the cost and uncertainty of modeling processes. The objective of this study was to compare the performance of two steady-state river water quality models, QUAL2E and QUAL-NIER, that have different complexity. QUAL-NIER is recently developed by National Institute of Environmental Research aiming to enhance the simulation capability of QUAL2E for eutrophic rivers. It is a carbon based model that considers different forms, such as dissolved versus particulate and labile versus refractory, of carbon and nutrients, and the contribution of autochthonous loading due to algal metabolism. The models were simultaneously applied to Nakdong River and their performance was evaluated by statistical verification with field data. Both models showed similar performance and satisfactorily replicated the longitudinal variations of BOD, T-N, T-P, Chl.a concentrations along the river. The algal blooms occurred at the stagnant reaches of downstream were also reasonably captured by the models. Although QUAL-NIER somewhat reduced the magnitude of errors, the hypothesis tests revealed no statistical evidence to justify its better performance. The contribution of autochthonous carbon and nutrient load by algal metabolism was insignificant because the hydraulic retention time is relatively short compare to the time scale of kinetic reactions. The results imply that the kinetic processes included in QUAL-NIER are too complex for the nature and scale of the real processes involved, thus needs to be optimized for improving the modeling efficiency.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제32권7호
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• pp.542-548
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• 2008

A thermal mass air flow sensor (MAFS), which consists of a micro-heater and thermo-resistive sensors on the silicon-nitride ($Si_3N_4$) thin membrane structure, is micro-fabricated by MEMS processes. Two thermo-resistive temperature sensors are located at $100{\mu}m$ upstream and downstream from the micro-heater respectively. The thermal characteristics are measured to find the best measurement indicator. The micro-heater is operated under constant power condition, and four flow indicators are investigated. The normalized temperature indicator shows good physical meaning and is easy to use in practice. It is found that the configurations and heating power of thermal-resistive elements are the dominant factors to determine the range of the flow measurement in the MAFS with higher sensitivity and accuracy.

• Management Science and Financial Engineering
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• 제1권1호
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• pp.39-66
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• 1995

This article presents a new model called the periodic square wave(PSW) to describe the material flow of periodic processes involving an intermediate buffer. The material flows into and out of the intermediate buffer are assumed to be periodic square shaped. By using this model, It is proved that the classical economic lot size model with finite supply rate, the so-called EPQ model, can be applicable to the arbitrary periodic demand case. This new model relaxes the original assumption of the constant demand. It is shown, as a unique application example, that the explicit solution for determining both upstream and downstream economic lot size can be obtained with the aid of the PSW model. The PSW model provides more accurate information on analyzing the inventory and production system than the classical approach, without losing simplicity and increasing the computational burden.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제27권11호
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• pp.1645-1654
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• 2003

When vortex shedding is locked-on to a single frequency oscillatory flow, the variations of vortex dynamics are investigated using a time-resolved PIV system. Wake regions of recirculation and vortex formation, dynamic behavior of the shed vortices and the Reynolds stress fields are measured in the wake-transition regime at the Reynolds number 360. In the lock-on state, reduction of the wake region occurs and flow energy distributed downstream moves upstream being concentrated near the cylinder base. To observe the dynamic behavior of the shed vortices, the trajectory of the vortex center extended to the inside of the wake bubble is considered, which describes well the formation and evolution processes. The Reynolds stresses and their contributions to overall force balance on the wake bubble manifest the increase of the drag force by the lock-on.