Comparison of electrocoagulation and chemical coagulation with fiber filters for water treatment

A combined electrocoagulation(EC)-fiber filter system has been presented as a new technology for water treatment. The objective of this study was to evaluate the feasibility of applying an aluminum EC-fiber filter for water treatment. We compared the water treatment efficiency of the chemical coagulation (CC)-fiber filter and EC-fiber filter. A comparison of the EC and CC processes reveals that EC significantly outperformed CC when the water to be filtered using fiber filters was pretreated with aluminum. For particle size less than 6 μm, the removal efficiency was 66%, 43% for EC and CC, respectively, and the average removal efficiency of the total organic carbon (TOC) was 50%, 65% for CC and EC. Therefore, EC reduced the amount of aluminum utilized by 25%, and the effluent turbidity improved by approximately 0.11 NTU to 0.19 NTU. Also, the average log removal value (LRV) for heterotrophic plate count (HPC) was 2.5 and 1.9 for EC and CC. respectively. Therefore, the aluminum used for EC proved to be excellent for pretreating the water to be filtered by a fiber filter.     

Development of an evaluation parameter for physical protection in INPRO and its case study on Republic of Korea’s PWRs

Evaluation parameters (EP), including evaluation scales (ES), for assessing a physical protection status of an INS (innovative nuclear system) in the INPRO have been developed; and a case study on the Republic of Korea’s (ROK) PWRs, using the developed EPs, has been performed. The INPRO proliferation resistance (PR) and physical protection (PP) methodology (developed by the IAEA) is comprised of a BP (basic principle), a UR (user requirement), a CR (criterion) and an IN (indicator). In the case of the INPRO methodology for PR, an EP and an ES that may facilitate the evaluation process are provided with definitions in the manual; but they are not given for the area of PP. In this study, we have developed parameters which can be used to evaluate the PP status for both an INS and an existing nuclear power plant. The developed EPs and ESs contain all the possible components that may affect the PP status. They were made based on an IN and acceptance limits that are specified in the manual. The evaluation tables are provided for some EPs such as material type, insider attack and vulnerability tests to increase the reliability of the evaluation. A case study on this methodology had been performed on the ROK’s PWRs. The results showed that the physical protection status of the ROK’s PWRs satisfied most of the EPs; however, some parameters such as the DBT, and the QA system did not meet the requirements. It has been seen through the case study that the EPs and the ESs developed are very useful for evaluating the physical protection status of a nuclear facility.     

High-performance optical-label switching packet routers and smart edge routers for the next-generation Internet

This paper discusses the architecture, protocol, analysis, and experimentation of optical packet switching routers incorporating optical-label switching (OLS) technologies and electronic edge routers with traffic shaping capabilities. The core optical router incorporates all-optical switching with contention resolution in wavelength, time, and space domains. It is also capable of accommodating traffic of any protocol and format, and supports packet, flow, burst, and circuit traffic. The edge router is designed to achieve traffic shaping with consideration for quality of service and priority based class-of-service. Simulation results show packet loss rates below 0.3% at load 0.7 and jitter values below 18 /spl mu/s. The traffic shaping reduces the packet loss rate by a factor of /spl sim/5 while adding negligible additional latency. The OLS core routers and the electronic edge routers are constructed including the field-programmable-gate-arrays incorporating the wavelength-aware forwarding and contention resolution algorithms. The experiment shows optical-label-based packet switching with a packet loss rate near 0.2%.     

Isentropic compressibility of aqueous and methanolic electrolytic solution

We studied the effect of ion-solvent and ion-ion interactions on the isentropic compressibility of aqueous and methanolic electrolytic solutions. In aqueous electrolytic solutions a critical concentration is attained and correlated with the completion of the primary hydration shell. Such a situation is lacking in methanolic solutions. An expression has been derived for estimating the hydration numbers of the electrolyte in its solutions by using the isentropic compressibility data. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University.     

Topology optimization of a swing arm type actuator using the response surface method

In the frame of topology optimization, the multi-objective ability has to be considered since structural design is usually required to satisfy more than one requirement. A modified topology optimization method based on the response surface method (RSM) is proposed to generate a structure of a small form factor (SFF) swing arm type actuator satisfying maximum compliance and maximum stiffness at the same time using the multi-objective optimization approach. The multi-objective function is defined to maximize the compliance in the direction of focusing as well as the eigen-frequency of the structure. The design of experiments (DOE) is performed to select sensitive variables. Based on DOE results, the response surface functions are formulated to construct the multi-objective function. The weight factors between conflicting objective functions are determined by the Pareto optimum method. By applying the optimal combination of design variables to the design domain, the optimized topology can be obtained.This work was supported by Korea Research Foundation (KRF) Grant KRF-2004-042-D00004.     

Developments of multibody system dynamics: computer simulations and experiments

It is an exceptional success when multibody dynamics researchers Multibody System Dynamics journal one of the most highly ranked journals in the last 10 years. In the inaugural issue, Professor Schiehlen wrote an interesting article explaining the roots and perspectives of multibody system dynamics. Professor Shabana also wrote an interesting article to review developments in flexible multibody dynamics. The application possibilities of multibody system dynamics have grown wider and deeper, with many application examples being introduced with multibody techniques in the past 10 years. In this paper, the development of multibody dynamics is briefly reviewed and several applications of multibody dynamics are described according to the author’s research results. Simulation examples are compared to physical experiments, which show reasonableness and accuracy of the multibody formulation applied to real problems. Computer simulations using the absolute nodal coordinate formulation (ANCF) were also compared to physical experiments; therefore, the validity of ANCF for large-displacement and large-deformation problems was shown. Physical experiments for large deformation problems include beam, plate, chain, and strip. Other research topics currently being carried out in the author’s laboratory are also briefly explained. Commemorative Contribution.     

Adaptive Dynamic Surface Control for Stabilization of Parametric Strict-Feedback Nonlinear Systems With Unknown Time Delays

The robust stabilization method via the dynamic surface control (DSC) is proposed for uncertain nonlinear systems with unknown time delays in parametric strict-feedback form. That is, the DSC technique is extended to state time delay nonlinear systems with linear parametric uncertainties. The proposed control system can overcome not only the problem of ldquoexplosion of complexityrdquo inherent in the backstepping design method but also the uncertainties of the unknown time delays by choosing appropriate Lyapunov-Krasovskii functionals. In addition, we prove that all the signals in the closed-loop system are semiglobally uniformly bounded. Finally, an example is provided to illustrate the effectiveness of the proposed control system.     

Scheduling algorithm for real-time tasks using multiobjective hybrid genetic algorithm in heterogeneous multiprocessors system

The scheduling problem for real-time tasks on multiprocessor is one of the NP-hard problems. This paper proposes a new scheduling algorithm for real-time tasks using multiobjective hybrid genetic algorithm (mohGA) on heterogeneous multiprocessor environment. In solution algorithms, the genetic algorithm (GA) and the simulated annealing (SA) are cooperatively used. In this method, the convergence of GA is improved by introducing the probability of SA as the criterion for acceptance of new trial solution.     

Properties of plasma enhanced chemical vapor deposited silicon nitride for the application in multicrystalline silicon solar cells

Hydrogenated films of silicon nitride (SiNx:H) were investigated by varying the deposition condition in plasma enhanced chemical vapor deposition (PECVD) reactor and annealing condition in infrared (IR) heated belt furnace to find the optimized condition for the application in multicrystalline silicon solar cells. By varying the gas ratio (ammonia to silane), the silicon nitride films of refractive indices 1.85-2.45 were obtained. Despite the poor deposition rate, silicon wafer with the film deposited at 450 °C showed the best minority carrier lifetime. The film deposited with the gases ratio of 0.57 showed the best peak of carrier lifetime at the annealing temperature of 800 °C. The performance parameters of cells fabricated by varying co-firing peak temperature also showed the best values at 800 °C. The multicrystalline silicon (mc-Si) solar cells fabricated in conventional industrial production line applying the optimized film deposition and annealing conditions on large area substrate (125 mm × 125 mm) was found to have the conversion efficiency of 15%.