Jung-Geun Han

Enhanced electrokinetic (E/K) remediation on copper contaminated soil by CFW (carbonized foods waste).

The E/K remediation method is presented to purify low permeable contaminated soils due to Cu(2+), and carbonized foods waste (CFW) was used as a permeable reactive barrier (PRB) material. For adsorption and precipitation of the Cu(2+) in the PRB during its motion, PRB was installed in a zone of rapidly changing pH values. The adsorption efficiency of CFW used as PRB material was found to be 4-8 times more efficient than that of Zeolite. Throughout the experiment, a voltage slope of 1V/cm was implemented and acetic acid was injected on the anode to increase the remediation efficiency. The electrode exchange was executed to more completely remove precipitated heavy metals in the vicinity of the cathode. The majority of Cu(2+) was adsorbed or sedimented by CFW prior to the exchange of the electrode, and the remaining quantity of precipitated Cu(2+) on the cathode had decreased with an increase in the operating time. Experiments of seven cases with different E/K operating times were performed, and the average removal ratios were 53.4-84.6%. The removal efficiencies for the majority of cases increased proportionally with an increase in the operating time. After the experiments were completed, the adsorbed Cu(2+) on CFW was 75-150 mg. This means that the role of CFW as the material in PRB for remediating heavy metals was confirmed. The cost of energies needed to remove Cu(2+), CFW, and acetic acid are estimated at US

The occurrence time estimation of oil contaminated source considering hydro-geological features

13.3-40/m(3).

Development of a Visual Monitoring System for Deformation Measuring of Welded Members and its Application

As industrial activities increase, the risk of geological contamination in Korea is becoming higher. The possibility of contamination is especially rising due to the increase of oil leakage and the corrosion of oil storage facilities. In this study, which was based on oil leakage cases in Korea, the occurrence time of oil contamination trace and source was hydro-geologically, such as groundwater flow considered soil composition, physical properties of soil and level of soil layers etc, estimated by examining the cause and ranges of an oil contamination event. It has been verified that the contamination history of potential contamination sources as well as the ranges and features of contamination sources were analyzed based on the test results of well, soil, and groundwater contamination status. The influential range of contaminated grounds and the occurrence time of oil leakage, considering hydro-geological features in the sites, can also be estimated. The occurrence time of oil leakage was estimated as 430 days when the mean void velocity was 0.52 m/day. The distance of pollutant migration was also estimated using the same method at 225 m.

An Investigation on Wetting Characteristics of Solder Particle for Solderable Electrically Conductive Adhesives (ECAs)

Recently, in the loading tests for steel members, the deformation value is measured by calculating a distance of both cross-heads. This measuring method encounters a test error due to various environmental factors, such as initial slip, etc.. Especially, in the case of welded members, the non-uniform deformation behavior in welded joints is observed because of the effect of welding residual stress and weld metal. This is mainly responsible for a test error and a loss of the reliability for used test instruments. Therefore, to improve the accuracy and the applicability of measuring system, it is necessary to employ a visual monitoring system which can accurately measure the local and overall deformation of welded members. In this paper, to accurately measure a deformation of welded members, a visual monitoring system (VMS) was developed by using three-dimensional digital photogrammetry. The VMS was applied to the loading tests of a welded member. The accuracy and the applicability of VMS was verified by comparing to the deformation value measured by a test instrument (MTS-810). The characteristics of the behavior near a welded joint were investigated by using VMS.

Application of a Photogrammetric System for Monitoring Civil Engineering Structures

A novel electrically conductive adhesives (ECAs) with solder particle have been developed. The kinetics of the curing reaction were investigated using isothermal differential scanning calorimeter (DSC). The dynamic DSC scans were also conducted to investigate the temperature dependant curing degree. The temperature dependant viscosity characteristic of polymer was investigated using rheometer. The wetting characteristic of two solders on two kinds of metals were investigated using an optical microscope. It was found that developed resin material showed good fluxing capacity against Sn-Bi solder on Ni/Au and the wetting angles was about 24º.

Geometry Design Method Considering Surcharge Load Behind Tiered Reinforced Soil Wall

Several traditional measuring apparatus are used to check the stability of civil engineering structures and maintenance of them. The measured results are applied for the deformation and stability analysis of civil engineering structures. Currently, precision and micro measuring instruments are used for stability evaluations of civil engineering structures. Furthermore, the measuring apparatus have been changed from manual systems to automatic systems. For example, total station, one of the traditional and manual measuring methods, is transferred to digital photogrammetry with high technology development. Especially, the movement of target points is able to be measured in real-time automatically because it can be obtained 3-dimensional coordinates by digital photogrammetry. The use of automatic measuring methods has been researched in several different industries (Hannah, 1989; Lee et al., 2006). The applications of digital photogrammetry are increased in various civil engineering structures (Han et al., 2001; Han & Song, 2003; Han et al., 2007, 2008). It shows that the automatic and high-tech measuring system likeVisual Monitoring System (VMS) based on digital photogrammetry is able to apply to the stability evaluations of large civil engineering structures.

Mechanical Property Enhancement of Water Soluble Polymer via PVP/LDPE Blend and SiO₂ Composite

The construction of reinforced soil wall is a recent trend in construction work due to the economical advantage and construction efficiency. However, there have been increasing numbers of large scale collapse accidents in tiered reinforced soil wall due to inconsistent in a design manual and uncertainty in stability evaluation. The surcharge load behind the wall has effects on the stability of tiered reinforced soil wall as well as the whole ground. Therefore, this study interpreted the method of surcharge load suggested in the typical design methods (i.e., NCMA and FHWA), which are applicable in Korea. The analysis resulted in the reasonable design method and the suggested method was applied in the field case using the numerical analysis. The numerical simulations confirmed that the surcharge load behind the wall should be considered for the slip failure surface to evaluate the tiered reinforced soil wall.

Determination of Cut Slope Reinforcement Using AHP Technique

Water-soluble polyvinylidene pyrrolidone/low density polyethylene (PVP/LDPE) blend polymer was fabricated for sinkhole restoration polymer pouch application. The mechanical property and water solubility were measured as a function of blended PVP and LDPE ratios. Increase of blended LDPE ratio caused the enhancement of tensile strength, elongation at break and storage modulus while water solubility decreased due to its non-soluble property. In order to enhance the mechanical properties, moreover, surface modified silica nanoparticle via silane coupling agent was adopted as a filler. As a result, the tensile strength was enhanced while water solubility was almost not influenced by additional silica filler.

Reliability Evaluation of QFP Solder Joint Using Sn-8Zn-3Bi Solder Paste during the Thermal Shock Test

Analysis was performed using AHP(Analytic Hierarchy Process) technique for the determination of priority on the effect factors and the preferences on cut-slope reinforcing methods. The results of data taken from professional group, researchers, design engineers and construction engineers, shows that stability, durability and environmental condition are most important effect factors. The retaining wall and the cutting methods were predominant for stability, economical efficiency, and maintenance/management in the preferences evaluation interpreted for the increasing method of safety factor on the cut-slope reinforcing methods.

Hybrid Interconnection Process Using Solderable ICAs (Isotropic Conductive Adhesives) with Low-Melting-Point Alloy Fillers

The reliability of QFP (Quad flat package) solder joint using Sn-8Zn-3Bi solder paste under the thermal shock test was investigated. Considering the environmental restriction such as ROHS, the QFP Cu LF (Lead-frame) was coated with lead-free materials (Sn, Sn-3Bi). To analyze the reliability under thermal shock treatment, the samples were placed in the thermal shock chamber (248K/423K, Dwell time: 30min). During the thermal shock test, the solder joint cross-sections were observed every 500 cycles. No crack initiation and propagation was observed through all type of plated Cu LF. The measured pull strength slightly decreased, as the number of cycles increased. After 1000 cycles, the pull strength of Sn and SnBi plated Cu LF reduced by 30% and 20%, respectively, compared with that of initial condition. Observing the fracture surface morphology by FE-SEM, the fracture mode changed and the IMC fractured area on the both fracture surface was increased. The IMC was identified as γ-Cu5Zn8 by chemical composition analysis using EDS. The reduced pull strength was affected by IMC fracture and fracture mode change. However, the pull strength does not decrease steeply but gradually. Consequently, the Sn-8Zn-3Bi solder joint shows the reliable solder joint strength, fracture mechanism, and compatibility with lead-free plated Cu LF during the thermal shock temperature of 248K to 423K.