• Journal of the Microelectronics and Packaging Society
• /
• v.12 no.2 s.35
• /
• pp.95-103
• /
• 2005

The interfacial reaction between 42Sn-58Bi solder (in wt.$\%$ unless specified otherwise) and electroless Ni-P/immersion Au has been investigated before and after thermal aging, with a focus on formation and growth of an intermetallic compound (IMC) layer, consumption of under bump metallurgy (UBM), and bump shear strength. The immersion Au layer with thicknesses of 0 (bare Ni), 0.1, and $1{\mu}m$ was plated on the $5{\mu}m$ thick electroless Ni-P ($14{\~}15 at.\%$P) layer. Then, the 42Sn-58Bi solder balls were fabricated on three different UBM structures by screen-printing and pre-reflow. The $Ni_3Sn_4$ layer (IMC1) was formed at the joint interface after pre-reflow for all the three UBM structures. On aging at $125^{\circ}C$, a quaternary phase (IMC2) was observed above the $Ni_3Sn_4$ layer in the Au-containing UBM structures, which was identified as $Sn_{77}Ni{15}Bi_6Au_2$ (in at.$\%$). The thick $Sn_{77}Ni{15}Bi_6Au_2$ layer deteriorated the integrity of the solder joint and the shear strength of the solder bump was decreased by about $40\%$ compared with non-aged joints.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.12
• /
• pp.25-33
• /
• 2019

In this study, the axial stiffness of existing piles (K_ve) of vertical extension remodeled building was quantified through theoretical and experimental approaches. Theoretically induced upper and lower boundary of the pile axial stiffness was estimated by using the formula proposed by Randolph and Wroth (1978), which can estimate the axial stiffness of rigid and flexible pile subjected under soil confinement. In addition, 38 cases of field measurement data on deteriorated piles with various diameters constructed in the period between 1995 - 1997 were taken in to account by overlapping the field data with the theoretical boundary of the axial stiffness. Through this the maximum axial stiffness of existing pile due to deterioration and long service time was presented for various slenderness ratio (L/D), which can be used in estimating the necessary axial stiffness of reinforcing piles(K_vr) for the vertical extension remodeling. The lower 95% value of the estimated axial stiffness of existing pile will be induced through statistical processing.

• Journal of Korean Society of Disaster and Security
• /
• v.5 no.1
• /
• pp.43-47
• /
• 2012

The asset management of infra facilities is a total framework for finally supporting a safe and comfortable service, which includes functions of supporting evaluation of condition and performance of infrastructures, making the decision method of repair or rehabilitation of deteriorated facilities, and lengthening the life cycle of structure through the decision of adequate cost and time of repair or reinforcement. In the range of the asset management, organization, human, the target, and information & data of company are included. Therefore, in this paper, appling the method of asset management analysis to the infra structures, the process of the risk assesment using BRE (Business Risk Exposure) and the basis of consisting ORDM (Optimized Renewal Decision-Making) are expressed.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.4
• /
• pp.343-350
• /
• 2011

Recently, as the catastrophic disasters due to earthquake happen frequently all over the world, it draws lots of attention to seismic capacity evaluation and/or structural integrity assessment of deteriorated civil infra-structures. However, there have been few studies on the existing dam flood gates, expecially in Korea. In this study, a proper vibration testing method applicable to a dam flood gate has been suggested, since the dynamic characteristics of a darn flood gate can be fundamental data for seismic capacity evaluation or structural integrity assessment. The frequency domain decomposition technique has been incorporated for modal parameter identification. Two kinds of vibration tests using an impact hammer and ambient vibration sources were carried out on two types of dam floodgates with different shapes. Through the field tests, the effectiveness of the ambient vibration tests were verified.

• The Journal of Engineering Geology
• /
• v.13 no.3
• /
• pp.309-320
• /
• 2003

Since the concrete covers most structures in modern architecture and it is composed of aggregates of about 75%, the appropriate selection of aggregates is valuable for the durability of concrete. A major cause of the expansion of mortar-bar measured by ASTM C 227-90 has been accounted by the alkali-aggregate reaction. This study carried out designed experiments on some aggregates including basalt and sandstone, to classify the expansion factors into the alkali-aggregate reaction, the increase of the gel pore volume, and the interstitial water that could expand physically the cracks or foliation developed in aggregates itself. The quantitative analyses of expansion by each factor indicated that the interstitial water and/or the alkali-aggregate reaction had major roles in the concrete expansion. Thus, if the supplied aggregates have deteriorated the structural framework, it is important to investigate the exact causes through this suggested method.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.9
• /
• pp.5844-5853
• /
• 2014

This paper presents the results of experimental investigations on the shear failure behaviors of reinforced concrete beams using ductile fiber reinforced cementitious composite (DFRCC). Total 10 RC beams of $150{\times}300{\times}1,000mm$ size were tested by 4-point bending under the displacement control. The main parameters of the experiment are surface treatment by grinding and preloading to the cracking point in the repair process. The load-displacement curves, diagonal tension cracking load, flexural cracking load, and shear strength were obtained. The test results showed that the DFRCC can be used effectively for restoring the shear strength approximately 99% to the original value under the condition that the appropriate thickness and surface treatment like grinding are assured. For further research, the specimens taken from real deteriorated structures will need to be tested after being repaired with DFRCC.

• Journal of Korean Society of Environmental Engineers
• /
• v.32 no.7
• /
• pp.730-737
• /
• 2010

It is very important to remove fluoride ion before treating semiconductor wastewater containing high concentration of ammonia, phosphates, and fluoride ions by struvite formation. Calcium ion was generally added for the removal of fluoride ion. However, calcium ions remained after removal of fluoride ion can deteriorate the performance of struvite crystalization. It should be removed completely before struvite formation. In this study, the effect of fluoride and calcium ion concentration on the struvite crystalization was investigated. Removal efficiencies of ortho-phosphate with struvite formation were more abruptly decreased than those of ammonium nitrogen, as increase of fluoride ion concentration in synthetic wastewater. The structures of struvite formed in synthetic wastewater containing calcium ion of up to 500 mg/L were identical. Purity of struvite was deteriorated as increase of calcium ion over 500 mg/L. Removal efficiencies of ammonium nitrogen were more decreased than those of phosphate ions as increase of cacium ion in synthetic wastewater.

• Proceeding of Spring/Autumn Annual Conference of KHA
• /
• 2009.04a
• /
• pp.222-225
• /
• 2009

The apartment housing in Korea has been rapidly constructed by adapting the most suitable construction methods as like wall structure, wet and united construction. But most of short-lived equipments usually filled in the structure which has longer life, and it causes not only to make difficult coping with the deterioration of equipments but also to let buildings remained deteriorate themselves. The buildings can be remodelled to slow down the terms of deterioration or reconstructed to give a new life of themselves, although the disposal of wastes or the lack of natural resources still be problems and unsolved that can occurred in pulling down and reconstructing the buildings. Furthermore, it is the time to need keeping with worldwide trends and movements as like sustainability or 'green growth' movements based on low carbon emissions. The researches for Long-Life Housing apartments which has durability and variation have been advanced up to now. Long-Life Housing apartments can separate their structures from equipments and interior or exterior materials of buildings. Therefore equipments or materials of buildings can be easily repaired and replaced with new ones, even if they are deteriorated themselves. Also, the construction process of Long-Life Housing apartments can be independent from the matter of proprietary rights, terms of durability, decision rights and so on. 'The law of Possession and Management of Collective Building' and the 'Regulation of Management of Collective Building' established by each local governments are already legislated for declaring the rights of using and ownership, responsibilities of each parts of apartment buildings. These laws and regulations classify the ownership of each parts of apartment buildings, and divide the ownership with public possession and exclusive possession. Therefore, this study will conduct comparative analysis between 'The law of Possession and Management of Collective Building' and 'the Regulation of Management of Collective Building' and find problems which can be occurred in future construction of Long-Life Housing apartments. It will be helpful to revise laws and regulations.

• Journal of the Korea Concrete Institute
• /
• v.18 no.3 s.93
• /
• pp.371-378
• /
• 2006

Recently sewage facilities mainly consisted of concrete structures are being deteriorated seriously by biodeterioration originated from sulfur-oxidizing bacteria. In this study, to prevent biochemical corrosion of the sewer concrete, antibiotics which prevent growth of sulfur-oxidizing bacteria were developed and antimicrobial performance of it was investigated. After that, to consider applicability of antibiotics to concrete, physical properties of concrete covered with antibiotics were investigated. As a results of the study, it was proved that the antimicrobial performance of antibiotics was available. Also compressive strength and bond strength of concrete didn't closely connected with antibiotics, and resistance to abrasion, water absorption, air permeability, carbonation, salt damage and chemical attack of concrete was improved remarkably by covering with it.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2009.04a
• /
• pp.295-303
• /
• 2009

The annals of Joseon dynasty, especially the volumes of King SeJong(1418-1450 A.D.), were heavily deteriorated by fungi. Investigations on the deteriorating and foxing fungi were carried out. Fungal structures on the beeswax, which were coated on the both side of Han-Ji, were suspected to be involved in the deterioration, and were observed by SEM. Isolation and culturing of these fungi were tried by scrubing swab samples and placing on the artificial media. Culture-independent approaches were used to identify the fungal strains associated with damages of beeswax and foxing of the paper by the analyses based on DNA sequences data from the specific ITS region of rDNA regions. In addition, well-known paper staining fungi(PSF), i.e., Aspergillus terreus var. terreus, Fusarium oxysporum, Chaetomium globosum, Cladosporium cladosporioides, and Alternaria solani, were compared in the mycelial growth and stain on beeswax and papers under different environmental conditions (temperature, light, moisture, etc). Fungal strains isolated from the air samples in the storage room and shelves were identified as Irpex sp., Arthrinium sacchari, Cladosporium tenuissimum, Aspergillus sclerotiorum, Sistotrema brinkmannii, and Hypoxylon bovei var. microsporum The isolated strains were compared in growth and stain patterns on beeswax and papers(Han-Ji, Hwa-Ji, and Yang-Ji) whether these can cause damage or foxing on the annals or not.