• Journal of the Korean Geotechnical Society
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• v.31 no.4
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• pp.45-55
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• 2015

The stability of the adjcent structures or slopes under blasting is typically evaluated using an empirical vibration attenuation curve or dynamic numerical analysis. To perform a dynamic analysis, it is necessary to determine the blast load and the damping ratio of rock mass. Various empirical methods have been proposed for the blast load. However, a study on representative values of damping ratio of a rock mass has not yet been performed. Therefore, the damping ratio was either ignored or selected without a clear basis in performing a blast analysis. Selection of the dampring ratio for the rock mass is very difficult because the vibration propagation is influenced by the layout and properties of the rock joints. Besides, the vibration induced by blasting is propagated spherically, whereas plane waves are generated by an earthquake. Since the geometrical spreading causes additional attenuation, the damping ratio should be adjusted in the case of a 2D plane strain analysis. In this study, we proposed equivalent damping ratios for use in continuum 2D plane strain analyses. To this end, we performed 2D dynamic analyses for a wide range of rock stiffness and investigated the characteristics of blast vibration propagation. Based on numerical simulations, a correlation between the attenuation equation, shear wave velocity, and equivalent damping ratio of rock mass is presented. This novel approach is the first attempt to select the damping ratio from an attenuation relationship. The proposed chart is easy to be used and can be applied in practice.

• Journal of Korean Foot and Ankle Society
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• v.16 no.1
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• pp.47-52
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• 2012

Purpose: The purpose of this study is to evaluate the effect of axial shortening metatarsal osteotomy on the treatment of advanced rheumatoid arthritis patients with severe hallux valgus and claw toe deformity of lesser toes which is used for preserving the metatarsophalangeal joint. Materials and Methods: From January 2005 to June 2009, 18 cases of axial shortening metatarsal osteotomy in advanced rheumatoid arthritis were reviewed ; all of them followed up for more than 2 years after surgical procedures and the mean follow up period was 3.4 years. We performed axial shortening Scarf osteotomy and Akin osteotomy for hallux valgus and Weil osteotomy with soft tissue release for claw toe of lesser toes, respectively. We measured preoperative and postoperative hallux valgus angle, each metatarsal shortening length and the range of motion of the metatarsophalangeal joints through radiographic and clinical examination and compared them each other. Clinical results were evaluated by American Orthopedic Foot and Ankle Society (AOFAS) score and subjective satisfaction of the patients. Results: The hallux valgus angle was reduced from the preoperative mean value of 44.8 degree to 9.0 degree postoperatively and the range of motion of the metatarsophalangeal joint of great toe and lesser toes was increased from the mean of 21.7 degree and 11.0 degree preoperatively to 38.0 degree and 32.5 degree, respectively at postoperation. Also, the mean AOFAS score was improved from 26.5 points to 67.4 points. Conclusion: Axial shortening osteotomy is a useful method to correct the deformity and preserve the metatarsophalangeal joint for severe hallux valgus and claw toe deformity in advanced rheumatoid arthritis.

• Journal of the Korean GEO-environmental Society
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• v.2 no.1
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• pp.37-56
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• 2001

As a preliminary study to establish fracture network model in crystalline rocks, detail investigation on fracture characteristics were performed. Five fracture sets were determined on the basis of regional survey of geological structures and fractures on outcrops. Among the fracture sets, S1 set has the highest density and longest trace length of fractures which was identified on surface in the study area. S4 and S5 sets are composed of foliations and foliation parallel shear joints of gneisses, which are very important sets at the aspect of weighting of fracture length. For characterization of subsurface fractures, detail core logging was performed to identify fractures and fracture zones from five boreholes. Acoustic televiewer logging and borehole geophysical loggings produced images, orientations and geophysical properties of fractures which intersect with boreholes. According to the result of the investigations, subsurface fractures can be grouped as three preferred orientations(B1, B2 and B3), which correspond to S1, S2 and S4/S5 of surface fracture sets, respectively. Actually, B1 set is expected to be intensely developed at subsurface. However, it has low frequency of intersection with boreholes due to its parallel or sub-parallel direction to boreholes. According to the inference of conductive fractures, B1 and B3 sets have possibilities of water flow and their intersection lines are also thought to consist of important conduits of groundwater flow. In particular, faults which are parallel to foliations control major groundwater flow in the study area.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.1-9
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• 2002

The metallurgical reaction properties between the pad consisted of 0.5 $\mu\textrm{m}$Au/5 $\mu\textrm{m}$Ni/Cu layers on a conventional ball grid array (BGA) substrate and In-15 (wt.%)Pb-5Ag solder ball were characterized during the reflow process and solid aging. During the reflow process of 1 to 5 minutes, it was observed that thin $AuIn_2$ or Ni-In intermetallic layer was formed at the interface of solder/pad. The dissolution rate of the Au layer into the molten solder was about $2\times 10^{-3}$ $\mu\textrm{m}$/sec which is remarkably low in comparison with a eutectic Sn-37Pb solder. After solid aging treatment for 500 hrs at $130^{\circ}C$, the thickness of $Ni_{28}In_{72}$ intermetallic layer was increased to about 3 $\mu\textrm{m}$ in all the conditions nevertheless the initial reflow time was different. These result show that In atoms in the solder alloy were diffused through the $AuIn_2$ phase to react with underlaying Ni layer during solid aging treatment. From the microstructural observation and shear tests, the reaction properties between In-15Pb-5Ag alloy and Au/Ni surface finish were analyzed not to trigger Au-embrittlement in the solder joints unlike Sn-37Pb composition.

• Journal of the Microelectronics and Packaging Society
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• v.16 no.3
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• pp.67-73
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• 2009

Compared to the chip-bonding process utilizing solder bumps, flip chip process using Cu pillar bumps can accomplish fine-pitch interconnection without compromising stand-off height. Cu pillar bump technology is one of the most promising chip-mounting process for RF packages where large gap between a chip and a substrate is required in order to suppress the parasitic capacitance. In this study, Cu pillar bumps and Sn bumps were electroplated on a chip and a substrate, respectively, and were flip-chip bonded together. Contact resistance and chip shear force of the Cu pillar bump joints were measured with variation of the electroplated Sn-bump height. With increasing the Sn-bump height from 5 ${\mu}m$ to 30 ${\mu}m$, the contact resistance was improved from 31.7 $m{\Omega}$ to 13.8 $m{\Omega}$ and the chip shear force increased from 3.8 N to 6.8 N. On the contrary, the aspect ratio of the Cu pillar bump joint decreased from 1.3 to 0.9. Based on the variation behaviors of the contact resistance, the chip shear force, and the aspect ratio, the optimum height of the electroplated Sn bump could be thought as 20 ${\mu}m$.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.23-27
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• 2017

This paper proposes an approach to predict the reliability of high temperature heaters by identifying their primary failure modes and mechanisms in the field. Test specimens were designed to have the equivalent stress conditions with the high temperature heaters in the field in order to examine the effect of stress conditions on the solder joint failures. There failures often result from cracking due to intermetallic compound (IMC) or void formation within a solder joint. Aging tests have been performed by exposing the test specimens to a temperature of $170^{\circ}C$ in order to reproduce solder joint failures in the field. During the test, changes in IMC formation were investigated by scanning electron microscopy (SEM) on the cross-sections of the test specimens, while changes in void formation were monitored both by resistance spectroscopy and by micro-computed tomography (microCT), alternately. The test results demonstrated the void volume within the solder increased as the time at the high temperature increased. Also, the phase shift of high frequency resistance was found to have high correlation with the void volume. These results implied the failure of high temperature heaters can be non-destructively predicted based on the correlation.

• Journal of the Korean Society of Safety
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• v.18 no.2
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• pp.132-138
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• 2003

The use of long rails in high-speed railway bridges causes additional stresses due to nonlinear behaviours between the rail and bridge decks in the neighbourhood of the deck joints. In the seismic response analysis of high-speed railway bridges, since structural response is highly sensitive to properties of the ground motion, spatial variation of the ground excitation affects responses of the bridges, which in turn affect stresses in the rails. In addition, it is shown that high-speed trains need very long distances to stop when braking under seismic occurrence corresponding to operational earthquake performance level so that verification of the safe stoppage of the train is also required. In view of such additional stresses due to long rails, sensibility of structural response to the properties of the ground motion and braking distance needed by the train to stop safely, this paper proposes and establishes a time domain nonlinear dynamic analysis method that accounts for braking loads, spatial variation of the ground motion and material nonlinearities of rails to analyze long rail stresses in high-speed railway bridges subjected to seismic event. The accuracy of the proposed method is demonstrated through an application on a typical site of the Korean high-speed railway.

• Journal of the Korean Institute of Oriental Medical Informatics
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• v.17 no.2
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• pp.82-129
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• 2011

"Beijijiufa" is a medical book republished by Sun Ju Qing in 1245. He compiled this book having added "Qizhumajiufa" and "Zhugejingyanbeijiyaofang" to the contents of "Beijijiufa" authored by Wen Ren Qi Nian. In "Beijijiufa" the author described treatment methods making use of moxibustion methods in connection with 22 cases of acute diseases. The author had collected the moxibustion methods used to treat acute diseases, which had been practiced by the medical practitioners of many generations, and quoted total 13 medical men's practices. In the book, the greatest parts of details were quoted especially from the writings of Sun Si Miao and Ge Hong, and this shows that the medical philosophies of both Sun Si Miao and Ge Hong were reflected onto "Beijijiufa". He had differed on his moxibustion practice: the size of moxa wool, the number of moxibustion treatment, and method of moxibustion for male and female were differed from one another according to the disease. As to the area of moxibustion, he chose the body parts around under four limbs and joints, and mostly used extraordinary acupoints rather than twelve main meridians. In his descriptions of finding meridian points, he did not describe it by its specific name of the reaction point, but explained the location of moxibustion points in detail through pictures. "Qizhumajiufa" is related to moxibustion method and prescriptions to treat surgical diseases, like skin boils or furuncle on the back, etc. He easily explained the method to find the meridian points for moxibustion treatment by using particular way through diagrams and pictures. Eight prescriptions he used were the collections among the historical practices of medical practitioners of many generations for skin boils which showed excellent therapeutic actions. In "Zhugejingyanbeijiyaofang", there are prescribed for 36 disease, also is the records of treatment methods for medical emergency which would be encountered easily in everyday life. As to therapeutic remedies, varied treatment methods, including the treatment by means of pasting and attaching medicinal substance to the spot, the treatment by means of mixing medicinal substance with alcoholic beverage, cleansing method, smoke inhalation remedy etc. were introduced. In "Beijijiufa" moxibustion was regarded as a top priority for treatment of acute disease, and the author strived to present remedies to the readers as easily as possible through 19 pictures. Regarding prescriptions, the author introduced diverse treatment methods with respect to various disease symptoms, and described the method to treat disease symptoms making use of medicinal ingredients which can easily be found in daily life. Likewise, "Beijijiufa" compiled by Sun Ju Qing was intended for clinical practice, and was indeed a medical book having been utilized for treatment of acute diseases in those days.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.114-120
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• 2017

In this paper, the effect of the masonry infill walls on the seismic performance of the reinforced concrete(RC) frames with non-seismic details was evaluated through the static test of an masonry infilled RC frame sub-assemblage with non-seismic details of real size, and comparison with the test results of the RC frame sub-assemblage with non-seismic details. As the test results, lots of cracks occurred on the surface of the entire frame due to the compression of the masonry infilled wall, and the beam-column joint finally collapsed with the expansion of the shear crack and buckling(exposure) of the reinforcement. On the other hand, the stiffness of the shear force-story drift relationship decreased due to the wall sliding crack and column flexural cracks, and the strength finally decreased by around 60% of the maximum strength. The damage that concentrated on the upper and lower parts of columns was dispersed in the entire frame such as columns, a beam, and beam-column joints due to the wall, and the specimen was finally collapsed by expansion of the shear crack of the joint, not the shear crack of the column. Also, the stiffness of RC frame increased by 12.42 times and the yield strength by 3.63 times, while the story drift at maximum strength decreased by 0.18 times.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.121-129
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• 2017

In this paper, the shake table test for the masonry infilled reinforced concrete frame with non-seismic details was carried out in order to evaluate its dynamic behaviour and damage under seismic condition. The tested specimens were the RC frame and the masonry infilled RC frame and the dynamic characteristics, such as a resonant period, acceleration response, displacement response and base shear force response, were compared between them. As a result of the shake table test, RC frame specimen had flexural cracks at the top and bottom of the column and shear cracks at the joints. In the case of masonry infilled RC frame, the damage of the frame was relatively minor but the sliding cracks and diagonal shear cracks on the masonry wall were severe at the final excitation. The resonant period of infilled RC frame specimen was shorter than that of the RC frame specimen because the masonry infill contributed to increase the stiffness. The maximum displacement response of the infilled RC frame specimen was decreased by about 20% than the RC frame specimen. It was analyzed that the masonry infill wall applied in this study contributed to increase the lateral strength of the RC frame with non - seismic detail by about 2.2 times and the stiffness by about 1.6 times.