• Journal of the Korean Chemical Society
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• v.46 no.6
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• pp.495-501
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• 2002

The critical micelle concentration(CMC) and the counterion binding constant(B) for the mixed micel-lization of sodium n-octanoate(SOC) with n-octylammonium chloride(OAC) were determined as a function of the overall mole fraction of $SOC({\alpha}_1).$ Various thermodynamic parameters($x_i$, $Y_i$, $C_i$, $${\alpha}_i^M$$, and $\Delta$$H_{mix}$) for the mixed micellization of the SOC/OAC systems have been calculated and analyzed by means of the equations derived from the nonideal mixed micellar model. The results show that there are great deviations from the ideal behavior for the mixed micellization of these systems. And other thermodynamic parameters(${\Delta}$$G^0_m$, ${\Delta}$$H^0_m$, and ${\Delta}$$S^0_m$) associated with the micellization of SOC,OAC, and their $mixture({\alpha}_1=0.5)$ have been also estimated from the temperature dependence of CMC and B values, and the significance of these parameters and their relation to the theory of the micelle formation have been considered and analyzed by comparing each other.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.473-481
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• 2015

The purpose of this research is to comprehend experimentally the characteristics of human strength for using as the basic data of impact resistance test method of lightweight wall. Human motions exerting static load are classified to 4 types. Pushes with two hands or shoulder are defined as the instantaneously forcing motions with hands or shoulder put on the force plate. Leanings back or one-hand against the wall are defined as motions of taking a rest in their respective comfortable posture. Human motions exerting dynamic load are classified to 3 types. Selecting 3 levels of motion strength (weak, middle, strong), 3 levels of force plate stiffness (A: 20kN/cm, B: 4.7kN/cm, C: 2.2kN/cm), and 30 male subjects, load was measured when they applied strength to the force plate. Results of this research are as follows: (1) The maximum load ratio (Pmax/W) of static load for each motion was 1.17-1.25 in two hands pushing, 0.95-0.99 in shoulder pushing, 0.16-0.18 in back leaning, and 0.12-0.15 in one hand leaning. (2) Human dynamic load and object collision were different in the load characteristics. (3) The maximum load ratio of dynamic load for each motion was 10.07 in heel kick, 4.46 in shoulder hitting, and 5.58 in fist blow.

• Journal of the Korea Institute of Building Construction
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• v.17 no.4
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• pp.349-360
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• 2017

In concrete construction work, formwork is an important process that accounts for 10% of the total construction cost. Recent buildings are becoming bigger and higher. In order to maximize the efficiency and safety of this formwork, the system of formworking has been systematized. However, the human accidents and the noise complaints arise from dismantling processes frequently occur. In order to solve these problems, most of them are dependent on foreign technology, but they do not take into consideration the conditions of domestic construction site. In this study, we developed a table type multi-drop system form for a slab and beam which can improve the process, safety and reduction of disassembly noise, and evaluated the physical properties of the main members which are used in the system. The results of this study show that there is sufficient strength to be used as a slab and a laying material for both a yoke beam and a supporting post. The noise level is improved compared to existing method.

• KSBB Journal
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• v.25 no.3
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• pp.277-282
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• 2010

This study was performed to investigate the composition of amino acids and biological properties with the ethanol extract of fruiting bodies of Pleurotus eryngii grown on the sawdust compost mix (400 g sawdust plus 200 g rice bran) supplemented with various dosages of monosodium glutamate (MSG). Amino acid composition analyses showed that arginine, glutamic acid, alanine and glycine increased as the dosage of MSG was increased, whereas histidine, serine, methionine, isoleucine, leucine and phenylalanine did not increase. $\gamma$-Aminobutyric acid (GABA) content increased significantly up to 1.18 mg/g extract when 6 g MSG was supplemented to the sawdust mix. Antioxidant activity of the extract was estimated and compared to the standard antioxidant (ascorbic acid). The antioxidant property such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity increased with the extract samples of increasing dosage of MSG. Although the extract showed low levels of nitrite scavenging activity, this activity increased up to 1.5-2.0 fold when MSG was supplemented to the sawdust mix above a dosage of 0.5 g. The results obtained from the present investigation would appear that Pleurotus eryngii grown on the MSG-enriched sawdust mix can be used more effectively as one of potential sources of functional foods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.803-810
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• 2011

The public interest of global warming and energy shortage is gradually increased, and the related industries also have become interested in developing eco-friendly material and technology. Warm-mix asphalt (WMA) is a result of the developments to alleviate global warming and energy problems. This WMA is produced at lower temperatures than the temperature at which hot mix asphalt (HMA) is produced. Because most tests in Superpave are developed only for the performance and maintenance of HMA produced by hot temperatures, it is difficult for the tests to identify properly the material properties and then evaluate the performances between HMA and WMA. This study deals with the development of a new protocol to differentiate HMA and WMA performance, and especially the interfacial properties between asphalt and aggregate are targeted as the performance indicator; thus, an evaluation method and guideline are suggested. The concept and idea of the test method applied in this study were modified from the DSR moisture damage test protocol. In addition, TSR test was performed to affirm the relation between the asphalt-aggregate interface and the asphalt-aggregate mixture performances. The followings are the results of this study. Shear stress at 85% linear visco-elastic complex modulus (LVE $G^*$) can be a better parameter than LVE $G^*$, which can assess the interfacial or bonding performance between asphalt and aggregate. Moreover, measuring the bonding performance in thinner film thicknesses will be a better way to evaluate the real and field situation between asphalt and aggregate. The interfacial properties' criteria to apply the newly developed test and parameter should be developed, after the asphalt mixture criteria relating to the interfacial properties are completed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.6D
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• pp.793-801
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• 2011

Existing specifications of road pavement require contractors to meet only materials and construction conditions regardless of pavement life. There are limitation of developing road pavement technology and possibility causing dispute between ordering organization and contractor with this type of specification. Research efforts to introduce performance warranty contracting are in progress in the field of road pavement to improve the problems. The performance warranty contracting gives the contractors opportunity to select materials and construction methods as they like. But they should satisfy a certain level of performance during a given period. The performance indicator and threshold value of pavement which are main elements of the warranty specification should be defined first to introduce the performance warranty contracting successfully. In this study, the performance indicator, threshold value, and warranty duration of asphalt pavement were investigated by reviewing literatures on performance warranty contracting of some states of the US. Major distresses influencing the performance of the asphalt pavement were investigated at 24 national expressway lines and national highway lines in 16 regions, and the data were analyzed to be compared to the cases of the US. Development of rational performance warranty specification for domestic asphalt pavement is expected based on the research results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4C
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• pp.137-145
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• 2011

The amount of material upheaved owing to the installation of a granular compaction pile (GCP) in the seabed was analyzed by a field execution. The amount of material upheaved was predicted by existing equations, proposed by the Korea Construction New-Technology Association (KCNET; 2003) and Shiomi and Kawamoto (1986), and compared with the amount measured by bathymetry in the field. As a result, the upheaval heights were found to show a clear increase with increasing replacement ratio. The measured amount was larger than the amount predicted by the equations, but the amount predicted from the equation proposed by KCNET (2003) was relatively close to the measured amount. The upheaval heights were found to be more sensitive to the replacement ratio than the installation depth. The increasing trends of the upheaval heights with the installation depth as predicted by the equation of KCNET (2003) were in agreement with the measured trends at a replacement ratio of 25%. As a result of comparing the coefficients of upheaval by the equations, the coefficients of upheaval determined by the equation of KCNET (2003) were larger than those determined by the equation proposed by Shiomi and Kawamoto (1986), which were relatively close to the measured trends. Specifically, the difference between results obtained by both these equations was large when the replacement ratio was relatively low.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.40 no.5
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• pp.455-463
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• 2020

Road facilities with a service life of more than 30 years are expected to triple in the next ten years. The seismic performance of road facilities should be reviewed with consideration of the "Common Application of Seismic Design Standards" issued by Korea's Ministry of Public Administration and Security in 2017. These standards should be applied to all existing road facilities, including retrofitted or seismic-designed facilities, for evaluating seismic performance. In order to manage seismic performance for a large number of facilities, decision-support technology that can provide economic and reliable results is needed. However, the indices method currently used in Korea is a deterministic method, and the seismic performance of individual facilities is evaluated based on qualitative indices so that only retrofitting among road facilities is prioritized. In turn, with the indices method, it is difficult to support decisions other than the decision to prioritize retrofitting. Therefore, it is necessary to use the seismic risk assessment method to overcome such shortcomings and provide useful information such as direct loss, indirect socio-economic loss, and benefit of the investment.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.3
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• pp.170-179
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• 2020

Tidal asymmetry would occur owing to shallow water tides at the Western Coast of macro tidal area. Especially, as ebb dominance of Mokpo coastal zone is known as the most prominent in Korea, it had been studied by domestic researchers. The cause of ebb dominance in Mokpo area is considered due to extensive inter-tidal zone in Muan Bay, and this has been studied based on amplification ratio, relative phase and skewness of tide/tidal flow curves in order to analyze qualitative tidal asymmetry. Furthermore, it was possible to figure out tidal characteristics with the difference of tidal amplitude and phase with Mokpo Harbor by observing the tide for 15 days in Muan Bay, which showed 40 minutes shorter ebbing time than at Mokpo Harbor. In addition, tidal flow prediction data in Mokpo North Harbor and Mokpo-Gu were analyzed. Meanwhile, the basis regarding qualitative interpretation of bed sediment and suspended sediment was provided by examining the qualitative changes in tidal asymmetry for spring-neap tidal cycle through the PCA/SWA indices. In addition, by examining long-term changes of ebb dominance in Mokpo Port, tidal characteristics of the past, present and future in this area, which is related to tidal asymmetry, is also provided.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.4
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• pp.423-428
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• 2016

The last stage blades of a low pressure (LP) turbine get frequently fractured because of stress corrosion cracking. This is because they operate in a severe corrosive environment that is caused by the impurities dissolved in condensed steam and high stress due to high speed rotation. To improve the reliability of the blades under severe conditions, 12% Cr martensitic stainless steel, having excellent corrosion resistance and higher strength, is widely used as the blade material. This paper shows the result of root cause analysis on a blade which got fractured suddenly during normal operation. Testing of mechanical properties and microstructure examination were performed on the fractured blade and on a blade in sound condition. The results of testing of mechanical properties of the fractured blade showed that the hardness were higher but impact energy were lower, and were not meeting the criteria as per the material certificate specification. This result showed that the fractured blade became embrittled. The branch-type crack was found to have propagated through the grain boundary and components of chloride and sulfur were detected on the fractured surface. Based on these results, the root cause of fracture was confirmed to be stress corrosion cracking.