• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.38 no.6
• /
• pp.65-75
• /
• 2001

We proposed the detection method of pH variations by integrating a photocurrent characteristic curve, instead of finding an inflection point by differentiating it in LAPS system. By a simulation of the performance of the proposed method, we verified that it had 80 and 1000 times higher sensitivity and resolution than a conventional method. Then, with the implemented system based on the simulation results, we measured a pH variation which was given rise to a potential change on the LAPS surface exposed to 2-0.03125[mg/ml] enzyme solutions. As results, we observed that the proposed method has a higher sensitivity and resolution of 3.76-0.08[pH/min] pH variations than 3.79-0.27[pH/min] for conventional method with same samples.

• Journal of the Korean GEO-environmental Society
• /
• v.17 no.3
• /
• pp.27-35
• /
• 2016

Even if the various data analyzing methods were suggested to examine the measured slope behaviors, it is difficult to find methods or procedures for connecting the analyzed results of slope stability and measured slope data. This research suggests the analyzing methods combing the stability analysis and measured data based on progressive failure of slope. Slope failure analysis by time degradation were calculated by strength parameters composed of strength reduction coefficients, also which were compared to the measured data according to the variations of safety factor and displacement of slopes. The accumulated displacement curve were shown as 3rd degree polynomials by suggested procedures, which was the same as before researches. The reverse displacement velocity curves were shown as linear function for prediction of brittle slope failures, also they were shown as 3rd degree polynomials for ductile slope failures, which were the same as the suggested equation by Fukuzono (1985) and they were very similar behaviors to the in-situ failure cases.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.27 no.12
• /
• pp.609-619
• /
• 2015

A preprocessing scheme utilizing multi-division of the ROI (region of interest) in a chemiluminescence image during inversion is proposed. The resulting inverted image shows the flame's structure, which can be useful for studying combustion instability. The flame structure is often quantitatively visualized with PLIF (planar laser-induced fluorescence) images as well. The chemiluminescence image, which is a line-integral of the flame, needs to be preprocessed before inversion, mainly due to the inherent noise and the assumption of axisymmetry during the inversion. The feasibility of the multi-division preprocessing technique has been tested with experimentally-obtained OH PLIF and $OH^*$ chemiluminescence images of jet and swirl-stabilized flames burning substitute natural gas (SNG). It turns out that the technique outperforms two conventional methods, specifically, the technique without preprocessing and the one with uni-division, reconstructing the SNG flame structures much better than its two counterparts when compared using corresponding OH PLIF images. The characteristics of the optimum degree of polynomials to be applied for curve-fitting of the flame region data for the multi-division method involving two flames has also been investigated.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.20 no.7_spc
• /
• pp.485-494
• /
• 2016

The risk-based assessment, also called time-based assessment of structure is usually performed to provide seismic risk evaluation of a target structure for its entire life-cycle, e.g. 50 years. The prediction of collapse probability is the estimator in the risk-based assessment. While the risk-based assessment is the key in the performance-based earthquake engineering, its application is very limited because this evaluation method is very expensive in terms of simulation and computational efforts. So the evaluation database for many archetype structures usually serve as representative of the specific system. However, there is no such an assessment performed for building stocks in Korea. Consequently, the performance objective of current building code, KBC is not clear at least in a quantitative way. This shortcoming gives an unresolved issue to insurance industry, socio-economic impact, seismic safety policy in national and local governments. In this study, we evaluate the comprehensive seismic performance of an low-rise residential buildings with discontinuous structural walls, so called piloti-type structure which is commonly found in low-rise domestic building stocks. The collapse probability is obtained using the risk integral of a conditioned collapse capacity function and regression of current hazard curve. Based on this approach it is expected to provide a robust tool to seismic safety policy as well as seismic risk analysis such as Probable Maximum Loss (PML) commonly used in the insurance industry.

• Nuclear Engineering and Technology
• /
• v.47 no.6
• /
• pp.712-718
• /
• 2015

Cast duplex stainless steels are susceptible to thermal aging during long-term service at temperatures ranging from $280^{\circ}C$ to $450^{\circ}C$. To analyze the effect of thermal aging on leak-before-break (LBB) behavior, three-dimensional finite element analysis models were built for circumferentially cracked pipes. Based on the elasticeplastic fracture mechanics theory, the detectable leakage crack length calculation and J-integral stability assessment diagram approach were carried out under different bending moments. The LBB curves and LBB assessment diagrams for unaged and thermally aged pipes were constructed. The results show that the detectable leakage crack length for thermally aged pipes increases with increasing bending moments, whereas the critical crack length decreases. The ligament instability line and critical crack length line for thermally aged pipes move downward and to the left, respectively, and unsafe LBB assessment results will be produced if thermal aging is not considered. If the applied bending moment is increased, the degree of safety decreases in the LBB assessment.

• Journal of the Korean Society for Precision Engineering
• /
• v.22 no.5 s.170
• /
• pp.130-137
• /
• 2005

Recently, the importance of CAE research is growing with the advances of the automotive and computer industry. In addition, multi-body dynamics and powertrain analysis are the most important factors in improving the vehicle design. Since engine torque with curve-data was used for analyzing full car simulation in the multi-body dynamics system for many years, it is impossible to assess the concurrent analysis of the engine and powertrain element included in a real full car system. In powertrain, since vehicle are usually modeled as a simple mass and a inertia, they can not be seen as real cars. Moreover, it is hard to obtain additional dynamics data other than the longitudinal velocity value in movement. Because of the reason that was previously discussed, it is necessary to consolidate the two parts as one routine program for design and development through the coordinate system connectivity, and presented here is a program named O-DYN. Using an object-oriented language C++, this program has a good structure with the valuable characteristics of objectivity, inheritance, and reusability. The reliability of this multi-body dynamics program is examined by DADS, which is the general dynamics program, using DAE solver and PECE integral function with the common coordinator separation method. As a result, we can obtain a better solution and total dynamics data in either area through this process. This program will be useful for analyzing full car simulation with powertrain.

• Journal of Korean Society of Steel Construction
• /
• v.14 no.6
• /
• pp.735-746
• /
• 2002

The task of plastic theory is twofold: first, to set up relationships between stress and strain that adequately describe the observed plastic deformation of metals, and second, to develop techniques for using these relationships in studying of the mechanics of metal forming processes, and the anlaysis and design of structures. One of the major problems in the theory of plasticity is to describe the behavior of work-hardening materials in the plastic range for complex loading histories. This can be achieved by formulating constitutive laws either in the integral or differential forms. To adequately predict the response of steel members during cyclic loading, the hardening rule must account for the features of cyclic stress-strain behavior. Neithe of the basic isotropic and kinematic hardening rules is suitable for describing cyclic streess-strain behavior, although a kinematic hardening rule describes the nearly linear portions of the stabilized hystersis loops. There is also a limited expansion of the yield surface as predicted by the isotropic hardening rule. Strong ground motions or wind gusts affect the complex and nonproportional loading histories in the inelastic behavior of structues rather than the proportional loading. Nonproportional loading is defined as externally applied forces on the structure, with variable ratios during the entire loading history. This also includes the rate of time-dependency of the loads. For nonproportional loading histories, unloading may take place along a chord instead of the radius of the load surface. In such cases, the shape of the stress-strain curve has to be determined experimentally for all non-radial loading conditions. The plasticity models including two surface models ae surveyed based on a yield surface and a bound surface that represent a state of maximum stress. This paper is concerned with the improvement of a plasticity models of the two-surface type for structural steel. This is follwed by an overview of plasticity models on structural steel. Finally the need for further research is identified.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2006.05a
• /
• pp.462-466
• /
• 2006

Close-to-nature stream evaluation is one of the processing to make the streams over in order to keep them natural. It is integral to evaluate and make an accurate analysis of them on the purpose of maintaining streams healthy. For many instances, there are, stream organization evaluation for restoration by German government, evaluation for ecosystem protection in natural preserves by New Zealand government, and stream-view evaluation for restoration by Britain government so on. In case of the country there are analysis and evaluation of stream physical organization by Cho, Yong-hyun, Close-to-nature stream evaluation for restoration by Kim, Dong-chan, evaluation of stream properties in korea by Park, Bong-jin. Close-to-nature evaluation by Lim, Chan-uk, that is advanced version of Park, Bong-jin's, shows form of stream including waterway curve, sand bar, diversity of flow, river bed material, diversity of minor bed, minor bed bank protection works, bank protection material. It also does environment of stream including side of minor bed vegetation, width of surface of the water/width of the river etc.. By the way, this evaluation does not have free access to apply those details above in the field, it often happens that you get various outcome from the one spot. so you must need more realistic testing method to obtain more accurate data. Remote sensing method is highly recommended because this is very useful for collecting realistic data of vegetation index. what is more, it can not only scan even the minimum area within its resolving power but also do obtain data anytime. Vegetation index indicates Ratio vegetation index, Normalized difference vegetation index, Soil adjusted vegetation index, Atmospherically resistant vegetation index etc.. The research is focusing on Cheokgwa stream which is the branch of Taehwa river and shows 19 sectioned Close-to-nature stream performed according to the method by Lim, chan-uk. Besides let you know vegetation index came from image data of satellite landsat 7 with the variation of buffering area, of the day 9. may. 2003. Of all, the outcome 0.758 at 200m buffer-zone of NDVI was the best we have got so far.

• Journal of Forest and Environmental Science
• /
• v.36 no.3
• /
• pp.175-186
• /
• 2020

This study approaches, from a floristic perspective, the under-researched human-primate competition for forest resources. Investigating the human impact on fruit trees edible for Kinda baboons (Papio kindae Lönnberg), we have collated dietary data on a free-ranging troop and floristic information on two forest sites of the Kundelungu National Park (KNP), Democratic Republic of Congo: the relatively intact Integral Zone (IZ) and the human-disturbed Annex Zone (AZ). Trees with DBH≥10 cm have been identified, counted and measured throughout 22 sample plots (11 per site), each measuring 1,000 ㎡. A total of seven woody species whose fruits are eaten by Kinda baboons were recorded. Four of them, namely the Sycamore fig Ficus sycomorus L., the Mobola plum Parinari curatellifolia Planch. ex Benth, the Kudu berry Pseudolachnostylis maprouneifolia Pax and the Monkey orange Strychnos innocua Delile were found in both sites, while the Large-leaved jackal-berry Diosyros kirkii Hiern and the Buffalo thorn Ziziphus mucronata Willd. were exclusively in the IZ, and Strychnos cocculoides Baker only in the AZ. Compared to the IZ, the AZ had lower values of stem density, species richness and diversity indices, suggesting a negative human impact on baboon-edible trees, in line with our hypothesis. Moreover, as was expected, human activities decreased the abundance of larger baboon-edible fruit trees. However, the size-class distribution of P. curatellifolia depicted a reverse J-curve in the AZ. The abundant younger P. curatellifolia trees remaining in that human-disturbed site constitute an important food stock for baboons, if well preserved. These results also illustrate the critical role of rangers' patrols, formerly more frequent (and presumably efficient) in the IZ than in the AZ of the Park. Their implications on baboons and miombo forests are discussed from both the research and conservation perspectives.

• Fire Science and Engineering
• /
• v.15 no.1
• /
• pp.84-92
• /
• 2001

In today's world, rise in the establishment of social infrastructure resulting from population saturation in large cities has led to more extensive and frequent use of chemical materials on facilities. A result, unexpected and serious accidents, hazards, contingencies and disasters are more prevalent than ever. Such phenomenon calls for more devoted and concerted efforts towards finding ways to reduce the safety hazards that are seen to take place more often than before with the increase in the number of facilities that are prone to bring disaster and hazard coupled with the conventional safety problems that continue to exist even today. In developed countries, such challenge is addressed by various appropriate countermeasures drawn up by local professional committees on industrial facilities, whose members conduct offsite and onsite evaluation un the potential industrial disasters and its seriousness and provide their advice thereof. Against this backdrop, this study aims at identifying a comprehensive safety allowance level (safety acceptable level) when imposing limitation on the development of conventional or new facilities, for the fur pose of establishing a safety allowance level of disastrous and dangerous facilities in Korea. This is done by assessing and applying the level of danger each individual is exposed to in a randomly selected region (disastrous and dangerous areas in Seoul) based on probability of quantitative hazards, as well as simulation and calculation methods which include: i) social disaster evaluation method applying Quantified Risk Assessment of Health & Safety Executive of UK and Matrix of Risk of Evaluated Sources of Hazard; ii) Fault Tree or Event Tree Analysis and etc.