• Environmental Engineering Research
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• v.21 no.2
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• pp.196-202
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• 2016

Membrane bioreactor (MBR) technology has previously been used by water industry to treat high salinity wastewater. In this study, an anoxic-oxic biofilm-membrane bioreactor (AOB-MBR) system has been developed to treat mustard tuber wastewater of 10% salinity (calculated as NaCl). To figure out the effects of operating conditions of the AOB-MBR on membrane fouling rate ($K_V$), response surface methodology was used to evaluate the interaction effect of the three key operational parameters, namely time interval for pump (t), aeration intensity ($U_{Gr}$) and transmembrane pressure (TMP). The optimal condition for lowest membrane fouling rate ($K_V$) was obtained: time interval was 4.0 min, aeration intensity was $14.6 m^3/(m^2{\cdot}h)$ and transmembrane pressure was 19.0 kPa. And under this condition, the treatment efficiency with different influent loads, i.e. 1.0, 1.9 and $3.3kgCODm^{-3}d^{-1}$ was researched. When the reactor influent load was less than $1.9kgCODm^{-3}d^{-1}$, the effluent could meet the third discharge standard of "Integrated Wastewater Discharge Standard". This study suggests that the model fitted by response surface methodology can predict accurately membrane fouling rate within the specified design space. And it is feasible to apply the AOB-MBR in the pickled mustard tuber factory, achieving satisfying effluent quality.

• Bulletin of the Korean Mathematical Society
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• v.50 no.2
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• pp.639-648
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• 2013

In this paper, we study Finsler metrics of constant S-curvature. First we produce infinitely many Randers metrics with non-zero (constant) S-curvature which have vanishing H-curvature. They are counterexamples to Theorem 1.2 in [20]. Then we show that the existence of (${\alpha}$, ${\beta}$)-metrics with arbitrary constant S-curvature in each dimension which is not Randers type by extending Li-Shen' construction.

• Korean Journal of Hydrosciences
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• v.3
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• pp.105-113
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• 1992

Various modeling approaches to study a long term behavior of streamflow or groundwater storage have been conducted. In this study, a Multivariate AR (1) Model has been applied to generate monthly flows of the one key station which has historical flows using monthly flows of the three subordinate stations. The Model performance was examined using statistical comparisons between the historical and generated monthly series such as mean, variance, skewness. Also, the correlation coefficients (lag-zero, and lag-one) between the two monthly flows were compared. The results showed that the modeled generated flows were statistically similar to the historical flows.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.24-30
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• 2002

With the economic development in China, the utilization of silty and muddy coasts including the construction of deepwater harbors and channels are being carried out at a fast pace. In these projects, the key technology involved is sediment transport. Due to the complication of sediment problems under the actions of tidal currents and wind waves, physical experiments are necessary In addition to numerical model studies. (omitted)

• Journal of information and communication convergence engineering
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• v.1 no.1
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• pp.39-43
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• 2003

The technology required to advance the state of the art of ultra-high-intensity excimer amplifier construction to the 100 J/100fs output pulse level is identified. The preliminary design work for very large final amplifier pumped by electron beam module is described, and key design problems and approaches are presented and discussed in detail based on the recent experimental and theoretical results.

• Korean Journal of Construction Engineering and Management
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• v.10 no.3
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• pp.139-147
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• 2009

Accurate construction cost estimation in the initial stage of building project plays a key role for project success and for mitigation of disputes. Total construction cost(TCC) estimation of apartment projects in Vietnam has become more important because those projects increasingly rise in quantity with the urbanization and population growth. This paper presents the application of artificial neural networks(ANNs) in estimating TCC of apartment projects. Ninety-one questionnaires were collected to identify input variables. Fourteen data sets of completed apartment projects were obtained and processed for training and generalizing the neural network(NN). MATLAB software was used to train the NN. A program was constructed using Visual C++ in order to apply the neural network to realistic projects. The results suggest that this model is reasonable in predicting TCCs for apartment projects and reinforce the reliability of using neural networks to cost models. Although the proposed model is not validated in a rigorous way, the ANN-based model may be useful for both practitioners and researchers. It facilitates systematic predictions in early phases of construction projects. Practitioners are more proactive in estimating construction costs and making consistent decisions in initial phases of apartment projects. Researchers should benefit from exploring insights into its implementation in the real world. The findings are useful not only to researchers and practitioners in the Vietnam Construction Industry(VCI) but also to participants in other developing countries in South East Asia. Since Korea has emerged as the first largest foreign investor in Vietnam, the results of this study may be also useful to participants in Korea.

• Structural Engineering and Mechanics
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• v.23 no.1
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• pp.97-113
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• 2006

A simply supported hybrid plate consisting of top and bottom functionally graded elastic layers and an intermediate actuating or sensing homogeneous piezoelectric layer is investigated by an elasticity (piezoelasticity) method, which is based on state space formulations. The general spring layer model is adopted to consider the effect of bonding adhesives between the piezoelectric layer and the two functionally graded ones. The two functionally graded layers are inhomogeneous along the thickness direction, which are approached by laminate models. The effect of interlaminar bonding imperfections on the static bending and free vibration of the smart plate is discussed in the numerical examples.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.5
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• pp.9-17
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• 2015

The development of wireless communication technology and change in the ICT market has led to the development of the M2M service and technology. Under these circumstances, the M2M environment has been the focus of communication environment construction between machines without control or direct intervention of human being. With characteristics of wireless communication environment, the possibility of being exposed to numerous security threats and safe communication security technology have becoming an issue an important requirements for problems such as data exposure, forgery, modulation, deletion, and privacy. This research analyzes requirements of trapdoor collision hash, generates keys between groups under the M2M environment by using the specificity of trapdoor, and suggests technology to exchange keys with session keys. Further, it also suggests techniques to confirm authentication of device and gateway in accordance with group key generation. The techniques herein suggested are confirmed as safe methods in that they have attack resistance such as Masquerade Attack, Man-in-the-Middle Attack, and Replay Attack in the group communication block by using the speciality of collision message and collision hash.

• Structural Engineering and Mechanics
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• v.81 no.6
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• pp.715-728
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• 2022

A new type of buckling-restrained braces (BRBs) with a longitudinally profiled steel plate working as the core (LPBRB) is proposed and experimentally investigated. Different from conventional BRBs with a constant thickness core, both stiffness and strength of the longitudinally profiled steel core along its longitudinal direction can change through itself variable thickness, thus the construction of LPBRB saves material and reduces the processing cost. Four full-scale component tests were conducted under quasi-static cyclic loading to evaluate the seismic performance of LPBRB. Three stiffening methods were used to improve the fatigue performance of LPBRBs, which were bolt-assembled T-shaped stiffening ribs, partly-welded stiffening ribs and stiffening segment without rib. The experimental results showed LPBRB specimens displayed stable hysteretic behavior and satisfactory seismic property. There was no instability or rupture until the axial ductility ratio achieved 11.0. Failure modes included the out-of-plane buckling of the stiffening part outside the restraining member and core plate fatigue fracture around the longitudinally profiled segment. The effect of the stiffening methods on the fatigue performance is discussed. The critical buckling load of longitudinally profiled segment is derived using Euler theory. The local bulging behavior of the outer steel tube is analyzed with an equivalent beam model. The design recommendations for LPBRB are presented finally.

• Korean Journal of Construction Engineering and Management
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• v.15 no.6
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• pp.83-91
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• 2014

The global community demands the reduction of environmental pollution such as greenhouse gas and carbon dioxide emissions. According to these requirements, the road construction project in the highest energy consuming industry is required the efficient way of reducing environmental pollution emissions. In this study, during the whole life cycle process, an environment impact assessment was performed for the several road construction projects in order to evaluate environmental stress through the road construction process. This study provides a proper process of environment impact assessment for life cycle assessment (LCA) analysis of road construction project, and figures the environmental stress regarding to the major construction materials for the case projects. In addition, this study conducted a sensitivity analysis for the key materials of environmental stress through the quantity analysis of major materials for the 1km section of a road construction. By this sensitivity analysis of total environmental stress change from the different volumes of constructing materials, it would be useful information for the environment impact assessment for the future road construction project.