• Journal of the Korean Geosynthetics Society
• /
• v.12 no.2
• /
• pp.55-66
• /
• 2013

The experiment of model soil structures has been executed for the soil retaining wall in various conditions of excavation, in this study, to analyze the behavior of the corner of opening. The ground for experiment has been constituted with the sandy soil of relatively loose density, the construction condition has been divided into the opening length of corner, embedded depth, existence of strut, etc., and the excavation has been carried out for 4 stages in total. The behavior characteristics at the corner of opening area has been verified by concentrate analysis of the displacement of wall and the subsidence of ground surface, for each construction and excavation condition, using the measuring instrument mounted inside the model soil structure. In the result of experiment, it has been analyzed that the opening area of corner is unstable structurally compared to the linear area, as it shows that the wall displacement and subsidence of ground surface have been increased when the opening length of corner gets longer. The longer the embedded depth, ground surface settlement of coner was decreased 40%. To apply deeper embedded depth than designed estimate was an advantage in the safety. As a result of the analysis of coner behavior with added struts, maximum surface settlement and maximum horizontal displacement was evaluated 40% and 30%, respectively. Hence increased embedded depth with the added struts in coner edge was effective in the safety.

• Journal of the Society of Disaster Information
• /
• v.19 no.1
• /
• pp.161-172
• /
• 2023

Safety education delivered to construction workers in a lecture manner has limitations in concentration and immersion, so delivery power and interest are low. In order to improve unstable behavior through education and prevent safety accidents, it is necessary to change the paradigm to hands-on education. Purpose: Experiential safety education aims to contribute to preventing accidents for construction workers by quickly recognizing risks, improving emergency response skills, and verifying the effectiveness of pre- and post-learning. Method: Based on a survey of workers who experienced the same work environment as the actual construction site, an opinion survey on the pre- and post-safety experience education and a variable measurement tool were planned, and a research hypothesis was established. Results: The Bayesian theory and MC simulation analysis were used to analyze the structural equation model, and the change in construction worker behavior was confirmed through the intended safety (A), non-experiential education in the sub-area of anxiety (B), average, standard deviation, and minimum and maximum values. Conclusion: The effect of education and industrial accidents are reduced only when construction workers are motivated to participate.

• Journal of Consumption Culture
• /
• v.15 no.1
• /
• pp.93-118
• /
• 2012

The purpose of this study was to examine the effect of a householder's working type on household saving from the perspective of precautionary saving behavior theory and the determinants of household saving by householder's working type. The data for this study was from the 2009 year of the Korea Welfare Panel Survey (KOWEPS), consisting of 2,463 households with householders whose working type was regular or non-regular employment(temporary, daily or public work). OLS regression analyses and Chow-tests were performed. In the regression analyses, the dependent variables for household saving were precautionary saving and precautionary asset. Precautionary saving was operationalized with the amount of average monthly saving and the ratio of average monthly saving to average monthly disposable income, and precautionary asset was operationalized with the amount of financial assets and the ratio of financial assets to net assets. The independent variables were household income, household assets, householder's working type(regular, non-regular), householder's age, sex, education level and marriage status, income level, the number of household members, housing type, debt, and public transfer income. Monthly average total consumption expenditures for household income, and net assets for household assets, the existence of spouse for marriage status, poverty for income level were used. Public transfer income was classified into three, social insurance, basic assistance and government assistance. For the analyses, Stata 11.0 version was used. The results are as follows: Householder's working type was significantly related to the precautionary saving behavior of a household. However, the precautionary saving and the precautionary asset of a household with a householder in non-regular working type was lower than those of a household with a householder in regular working type. This result is not consistent with the expectation from the perspective of precautionary saving behavior that the saving of a household with a householder in non-regular working type is expected to be higher than that of a household with a householder in regular working type. According to the analyses of the determinants for precautionary saving behavior by householder's working type, monthly average total consumption expenditures, debt, net assets, poverty, the number of household members, basic assistance were statistically significant variables. The positive relation of basic assistance to precautionary saving(the amount of average monthly saving and the ratio of average monthly saving)is a noteworthy result in the analyses of the determinants for household saving by householder's working type. The above results suggest the followings. First, it is easy to predict the unstability of economic life of a household with a householder in non-regular working type because of relatively low precautionary saving and precautionary asset. The reason for the low precautionary saving and the low precautionary asset may be a low current income of the household in spite of its willingness to save. If this reasoning is possible, it suggests that policies are needed for households with householders in non-regular working type to save. Second, the relatively low precautionary saving and precautionary asset of a household with a householder in non-regular working type suggest also their long-term economic stability. This suggests they need to try a long-term financial planning even though they have limitations to save for future because of their low current income. It is necessary to develop the financial planning for the households with unstable incomes. Third, the determinants for precautionary saving behavior by householder's working type were mostly the ones which reflect the economic condition of a household. This suggests that the economic condition of a household is a core factor for household saving. Consequently, it emphasizes the efforts for a household to acquire the adequate level of income for saving. Forth, the positive relation of basic assistance to precautionary saving(the amount of average monthly saving and the ratio of average monthly saving) suggests the possibility for a household to accumulate the precautionary saving and the precautionary asset in the channel of basic assistance.

• Journal of Pharmaceutical Investigation
• /
• v.38 no.4
• /
• pp.241-247
• /
• 2008

Paclitaxel is a taxane diterpene amide, which was first extracted from the stem bark of the western yew, Taxus brevifolia. This natural product has proven to be useful in the treatment of a variety of human neoplastic disorders, including ovarian cancer, breast and lung cancer. Paclitaxel is a highly hydrophobic drug that is poorly soluble in water. It is mainly given by intravenous administration. Therefore, The pharmaceutical formulation of paclitaxel ($Taxol^{(R)}$; Bristol-Myers Squibb) contains 50% $Cremophor^{(R)}$ EL and 50% dehydrated ethanol. However the ethanol/Cremophor EL vehicle required to solubilize paclitaxel in $Taxol^{(R)}$ has a pharmacological and pharmaceutical problems. To overcome these problems, new formulations for paclitaxel that do not require solubilization by $Cremophor^{(R)}$ EL are currently being developed. Therefore this study utilized a supercritical fluid antisolvent (SAS) process for cremophor-free formulation. To select hydrophilic polymers that require solubilization for paclitaxel, we evaluated polymers and the ratio of paclitaxel/polymers. HP-${\beta}$-CD was used as a hydrophilic polymer in the preparation of the paclitaxel solid dispersion. Although solubility of paclitaxel by polymers was increased, physical stability of solution after paclitaxel/polymer powder soluble in saline was unstable. To overcome this problem, we investigated the use of surfactants. At 1/20/40 of paclitaxel/hydrophilic polymer/ surfactant weight ratio, about 10 mg/mL of paclitaxel can be solubilized in this system. Compared with the solubility of paclitaxel in water ($1\;{\mu}g/mL$), the paclitaxel solid dispersion prepared by SAS process increased the solubility of paclitaxel by near 10,000 folds. The physicochemical properties was also evaluated. The particle size distribution, melting point and amophorization and shape of the powder particles were fully characterized by particle size distribution analyzer, DSC, SEM and XRD. In summary, through the SAS process, uniform nano-scale paclitaxel solid dispersion powders were obtained with excellent results compared with $Taxol^{(R)}$ for the physicochemical properties, solubility and pharmacokinetic behavior.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.11 no.3
• /
• pp.181-188
• /
• 2011

With the rapid proliferation of wireless networks and mobile computing applications, the landscape of the network security has greatly changed recently. Especially, Vehicular Ad Hoc Networks maintaining network topology with vehicle nodes of high mobility are self-organizing Peer-to-Peer networks that typically have short-lasting and unstable communication links. VANETs are formed with neither fixed infrastructure, centralized administration, nor dedicated routing equipment, and vehicle nodes are moving, joining and leaving the network with very high speed over time. So, VANET-security is very vulnerable for the intrusion of malicious and misbehaving nodes in the network, since VANETs are mostly open networks, allowing everyone connection without centralized control. In this paper, we propose a weighted intrusion detection method using rough set that can identify malicious behavior of vehicle node's activity and detect intrusions efficiently in VANETs. The performance of the proposed scheme is evaluated by a simulation study in terms of intrusion detection rate and false alarm rate for the threshold of deviation number ${\epsilon}$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• v.y2005m4
• /
• pp.274-280
• /
• 2005

Experimental investigations were carried out in an atmospheric pressure, optically accessible and laboratory-scale dump combustor. The objective of this study is to obtain the phase-resolved gas temperatures at different phases of the oscillating pressure cycle during unstable combustion. To see the effect of incomplete fuel-air mixing on phase-resolved temperature characteristics, CARS temperature measurements were performed. Results including phase-resolved averaged temperature, normalized standard deviation and temperature probability distribution functions (PDFs) were provided in this paper. It could be found that the profile of mean temperature showed the in-phase relationship with pressure cycle. Temperature PDFs give an insight on the flame behavior as well as NOx emission characteristics. These results would be expected to play an important role in better understanding of driving mechanisms and thermo-acoustic interactions.

• KSBB Journal
• /
• v.7 no.4
• /
• pp.308-316
• /
• 1992

Two-stage continuous culture system has been studied intensively to maximize the productivity of a cloned gene product in unstable recombinant microorganism. As an effort to optimize the two-stage process, transient behavior of the second-stage was studied theoretically as well as experimentally using Escherichia coli Kl2$\delta$Hl$\delta$trp. A mathematical model describing the transient response to a step change in dilution rate was developed based on the assumption that the adaptation rate of cell growth is proportional to the available growth potential, which is defined as the difference in dilution rates between before and after shift-up. The kinetic parameters appearing in the model equations were the dimensionless step increase in growth rate($\alpha$) and the adaptation rate constant(k). These parameters were evaluated for various dilution rates and temperatures by washout method. This relatively simple adaptation model could predict the specific growth rate of the second-stage successfully. Advantage and disadvantage of the proposed model are also discussed.

• Composites Research
• /
• v.16 no.4
• /
• pp.44-50
• /
• 2003

The damage zone around a crack tip occurring before the fracture is a significant domain. which affects the toughening mechanism of materials. In this study. the growth process of damage zone in the vicinity of crack tip for rubber-modified epoxy resin is investigated using an acoustic emission(AE) analysis. The weight fractions of rubber(CTBN 1300$\times$B) in rubber-modified epoxy resin are 5 wt% and 15 wt%. The fracture toughness($K_{IC}$) and the fracture energy($G_{IC}$) were measured using 3 point bending single-edge notched specimens. The damage zone and rubber particles distributed around the crack tip were observed by a polarized optical microscope and an atomic force microscope(AFM). The damage zone around crack tip of rubber-modified epoxy resin was formed at 13 % loading and developed until 57 % loading of the fracture load. The crack initiated at 57 % loading grew repeatedly in the stick-slip propagation behavior. Based on time-frequency analysis, it was confirmed that AE signals with frequency bands of 0.15~0.20 MHz and 0.20~0.30 MHz were generated from cavitation and stable/unstable cracking inside the damage zone.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.26 no.11
• /
• pp.2305-2311
• /
• 2002

The pressure tube is a major component of the CANDU reactor, which supports nuclear fuel bundle and heavy water coolant. Pressure tubes are installed horizontally inside the reactor and only selected samples are periodically examined during in-service inspection. In this respect, a probabilistic safety assessment method is more appropriate fur the assessment of overall pressure tube safety. The failure behavior of CANDU pressure tubes, however, is governed by delayed hydride cracking which is the major difference from pipings and reactor pressure vessels. Since the delayed hydride cracking has more widely distributed governing parameters, it is impossible to apply a general PFM methodology directly. In this paper, a PFM methodology for the safety assessment of CANDU pressure tubes is introduced by applying Monte Carlo simulation in determining failure probability Initial hydrogen concentration, flaw shape and depth, axial and radial crack growth rate and fracture toughness were considered as probabilistic variables. Parametric study has been done under the base of pressure tube dimension and hydride precipitation temperature in calculating failure probability. Unstable fracture and plastic collapse are used for the failure assessment. The estimated failure probability showed about three-order difference with changing dimensions of pressure tube.

• 한국신재생에너지학회:학술대회논문집
• /
• 2008.05a
• /
• pp.33-36
• /
• 2008

The transient behavior of a passive air breathing direct methanol fuel cell (DMFC) operated on vapor-feeding mode is studied in this paper. It generally takes 30 minutes after starting for the cell response to come to its steady-state and the response is sometimes unstable. A mathematical dynamic one-dimensional model for simulating transient response of the DMFC is presented. In this model a DMFC is decomposed into its subsystems using lumped model and divided into five layers, namely the anodic diffusion layer, the anodic catalyst layer, the proton exchange membrane (PEM), the cathodic catalyst layer and the cathodic diffusion layer. All layers are considered to have finite thickness, and within every one of them a set of differential-algebraic governing equations are given to represent multi-components mass balance, such as methanol, water, oxygen and carbon dioxide, charge balance, the electrochemical reaction and mass transport phenomena. A one-dimensional, isothermal and mass transport model is developed that captures the coupling between water generation and transport, oxygen consumption and natural convection. The single cell is supplied by pure methanol vapor from a methanol reservoir at the anode, and the oxygen is supplied via natural air-breathing at the cathode. The water is not supplied from external source because the cell uses the water created at the cathode using water back diffusion through nafion membrane. As a result of simulation strong effects of water transport were found out. The model analysis provides several conclusions. The performance drop after peak point is caused by insufficiency of water at the anode. The excess water at the cathode makes performance recovery impossible. The undesired crossover of the reactant methanol through the PEM causes overpotential at the cathode and limits the feeding methanol concentration.