• Environmental Engineering Research
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• v.23 no.2
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• pp.175-180
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• 2018

Box-Behnken Design (BBD) under response surface methodology (RSM) was implemented to optimization the operating parameters and assess the removal and recovery efficiencies of crude oil from contaminated soil using subcritical water extraction. The effects of temperature, extraction time and water flow rate were explored, and the results indicate that temperature has a great impact on crude oil removal and recovery. The correlation coefficients for oil removal ($R^2=0.74$) and recovery ($R^2=0.98$) suggest that the proposed quadratic model is useful. When setting the target removal and recovery (>99%), BBD-RSM determined the optimum condition to be a temperature of $250^{\circ}C$, extraction time of 120 min, and water flow rate of 1 mL/min. An experiment was carried out to confirm the results, with removal and recovery efficiencies of 99.69% and 87.33%, respectively. This result indicates that BBD is a suitable method to optimize the process variables for crude oil removal and recovery from contaminated soil.

• Journal of the Korean Society for Marine Environment & Energy
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• v.6 no.3
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• pp.54-62
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• 2003

This paper surveys a number of remotely operated recovery techniques and their recent applications in the removal of the toxic liquid from sunken ships, and suggests the appropriate recovery technique for our ocean environment, especially, in view of its cost and efficiency. Authors also give the technical requirements for the suggested remotely operated recovery system and the basic design result which is well-matched with such requirements.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.4A
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• pp.440-449
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• 2008

In this paper, we propose a 16-QAM carrier recovery loop which is suitable for the implementation of Inmarsat M4 system receiver. Because the frequency offset of ${\pm}924\;Hz$ on signal bandwidth 33.6 kHz is recommended in Inmarsat M4 system specification, carrier recovery loop having stable operation in the channel environment with large relative frequency offset is required. the carrier recovery loop which adopts only PLL can't be stable in relatively large frequency offset environment. Therefore, we propose a carrier recovery loop which has stable operation in large relative frequency offset environment for Inmarsat M4 system. The proposed carrier recovery loop employed differential filter-based noncoherent UW detector which is robust to frequency offset, CP-AFC for initial frequency offset acquisition using UW signal, and 16-QAM DD-PLL for phase tracking using data signal to overcome large relative frequency offset and achieve stable carrier recovery performance. Simulation results show that the proposed carrier recovery loop has stable operation and satisfactory performance in large relative frequency offset environment for Inmarsat M4 system.

• Proceedings of the Korean Society of Food Hygiene and Safety Conference
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• 2001.10a
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• pp.171-174
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• 2001

Solid phase micro-extraction (SPME), a solvent-free, rapid and inexpensive method for the extraction of organic compounds from aqueous sample matrices, was evaluated for determination of the 120 pesticides in vegetables such as crown daisy, perilla leaf, leafy lettuce and to mato. The analysis conditions were chosen for the SPME method: 15 min of immersion of the PDMS fiber in 10 ml of the solution with stirring at 1,000 rpm. The recovery tests were carried out in triplicate. The range of recoveries was 0-142% for organochlorine pesticides and $4.9\sim200\%$ for organophosphorus pesticides. The recoveries were very low in the pesticide groups with low solubility in water. The recoveries became lower in proportion to the interference materials in vegetables. The recovery in tomato was relatively higher than that in perilla Ie af and crown daisy. The recovery values obtained by SPE and SPME were compared. In leaf y lettuce, recovery obtained by SPE method ranged from $58.1\%\;to\;136.1\%$ and recovery by SPME ranged from $9.6\%\;to\;176.3\%$ In organophosphorus pesticides. The recovery in SPME method was satisfactory with $136\%$ for ethoprophos, $119\%$ for methidathion and $113\%$ for diazinon. Meanwhile, recovery of EPN, phenthoate and 2,4-DDT revealed relatively low value of $38\%,\;41\%\;and\;3.4\%,$ respectively. However, most of pesticides applied to SPME method sho wed constant recovery and precision. From these results, it can be concluded that solid phase micro-extraction might be an appropriate method for the screening test of pesticides in vegetables.

• The Journal of Society for e-Business Studies
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• v.4 no.3
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• pp.159-178
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• 1999

As Electronic Commerce is getting larger, the volume of Internet-based commerce by enterprise is also getting larger. This phenomenon applies to Internet EDI, Global Internet Business, and CALS information services. In this paper, a new type of cryptographic key recovery mechanism satisfying requirements of business environment is proposed. It is also applied to enterprise information infrastructure for managing employees' task related to handling official properties of electronic enterprise documents exchange. This technology needs to be complied to information management policy of a certain enterprise environment because behavior of cryptographic key recovery can cause interruption of the employees' privacy. However, the cryptographic key recovery mechanism is able to applied to any kind of information service, the application areas of key recovery technology must be seriously considered as not disturbing user's privacy It will depend on the policy of enterprise information management of a specific company.

• Journal of Advanced Navigation Technology
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• v.14 no.1
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• pp.74-79
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• 2010

This paper explains the design and implementation of nested session management based the FRA(Fault Recovery Agent). FRA is a system that is suitable for recovering software error for multimedia remote control based on industry safety environment. In this paper, we discuss a method for increasing reliability through organization of nested session.

• Journal of Korean Society for Atmospheric Environment
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• v.29 no.6
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• pp.801-810
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• 2013

A field study was conducted to evaluate air quality from gas stations with and without Stage II vapor recovery systems that are currently used to reduce VOCs. The THC and VOCs levels were monitored for the test at three locations (inside office, around refueling area, site boundary) from a total of five gas stations. The results showed a considerable reduction in THC concentration which ranged from 48.7% to 81.8% with and without the operation of the Stage II VRS. Acoording to our comparative analysis, BTEX and other 19 VOCs levels were also significantly reduced with Stage II vapor recovery systems.

• Journal of Advanced Navigation Technology
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• v.11 no.4
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• pp.479-484
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• 2007

This paper explains the design and implementation of the FRA(Fault Recovery Agent). FRA is a system that is suitable for recovering software error for multimedia distance education based on home network environment. In terms of distributed multimedia systems, the most important catagories for quality of service are a timeless, volume, and reliability. In this paper, we discuss a method for increasing reliability through fault tolerance. This paper explains a performance analysis of an error recovery system running on distributed multimedia environment using rule-based DEVS modeling and simulation techniques. In DEVS, a system has a time base, inputs, states, outputs, and functions. The proposed method is more efficient than the other method in comparison with error ration and processing time.

• Journal of Korean Society on Water Environment
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• v.20 no.2
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• pp.183-189
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• 2004

The performance of a membrane-coupled anaerobic fermenter system for the recovery of volatile fatty acids (VFAs) from liquid organic sludge was experimentally investigated. Permeation flux was stably kept around $0.2(m^3/m^2/day)$ during operational period. The membrane-coupled fermenter showed 2.2 times higher VFAs concentration and higher VFAs forming rate than those of fermenter without membrane. The fermenter with membrane proved to be an effective system for the recovery of soluble organic materials from liquid sludge.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.2
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• pp.131-143
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• 2018

Phosphorus (P) is a limited, essential, and irreplaceable nutrient for the biological activity of all the living organisms. Sewage sludge ash (SSA) is one of the most important secondary P resources due to its high P content. The SSA has been intensively investigated to recover P by wet chemicals (acid or alkali). Even though $H_2SO_4$ was mainly used to extract P because of its low cost and accessibility, the formation of $CaSO_4$ (gypsum) hinders its use. Heavy metals in the SSA also cause a significant problem in P recovery since fertilizer needs to meet government standards for human health. Therefore, P recovery process with selective heavy metal removal needs to be developed. In this paper some of the most advanced P recovery processes have been introduced and discussed their technical characteristics. The results showed that further research is needed to identify the chemical mechanisms of P transformation in the recovery process and to increase P recovery efficiency and the yields.