• International Journal of Highway Engineering
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• v.18 no.6
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• pp.137-143
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• 2016

OBJECTIVES : Bituminous materials, such as tack coat, are utilized between pavement layers for improving the bond strength in pavement construction sites. The standards regarding the application of bituminous material are not clearly presented in the Korean construction guideline without RS(C)-4. Hence, the objective of this study is to determine the optimum content of bituminous materials by analyzing interlayer shear strength (ISS) from the direct shear tester, which was developed in this research. The shear strength of tack coat was defined with the sort of bituminous materials. METHODS : The mixtures for the shear test were made using marshall mix design. The specimens were vertically and horizontally separated for the direct shear test. The separated specimens were bonded using bituminous material. The objectives of the experiment are to determine the performance of bond and shear properties resulting from slippage, rutting, shovel, and corrugation of asphalt pavements. A machine based on the Louisiana interlayer shear strength tester (LISST) of NCHRP Report-712 was developed to determine the ISS. The applied types of tack coat were RS(C)-4, AP-3, QRS-4, and BD-coat with contents of $0.3{\ell}/m^2$, $0.45{\ell}/m^2$, $0.6{\ell}/m^2$, and $0.8{\ell}/m^2$, respectively. RESULTS : Table 2 gives the results of the direct shear test using the developed shear machine. The BD-coat type indicated the highest average ISS value compared to the others. Between the surface and binder course, optimum tack coat application rates for AP-3, RS(C)-4, QRS-4, and BD-Coat were $0.6{\ell}/m^2$, $0.3{\ell}/m^2$, $0.6{\ell}/m^2$, and $0.45{\ell}/m^2$, respectively. These optimum contents were determined using the ISS value. CONCLUSIONS : The ISS values of AP-3, RS(C)-4, and QRS-4 showed similar tendencies when ISS increased in the range $0.3{\sim}0.6{\ell}/m^2$, while ISS decreased when the applied rate exceeded $0.6{\ell}/m^2$. Similarly, the highest ISS value of the BD-coat was observed when the applied rate was $0.45{\ell}/m^2$. However, shear strength was similar to the maximum value of ISS when the tack-coat application rate of BD-Coat exceeded $0.45{\ell}/m^2$.

• Journal of Korean Neurosurgical Society
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• v.61 no.2
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• pp.212-218
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• 2018

Objective : Surgical clipping of the cerebral aenurysm is considered as a standard therapy with endovascular coil embolization. The surgical clipping is known to be superior to the endovascular coil embolization in terms of recurrent rate. However, a recurrent aneurysm which is initially treated by surgical clipping is difficult to handle. The purpose of this study was to research the management of the recurrent cerebral aneurysm after a surgical clipping and how to overcome them. Methods : From January 1996 to December 2015, medical records and radiologic findings of 14 patients with recurrent aneurysm after surgical clipping were reviewed retrospectively. Detailed case-by-case analysis was performed based on preoperative, postoperative and follow-up radiologic examinations and operative findings. All clinical variables including age, sex, aneurysm size and location, type and number of applied clips, prognosis, and time to recurrence are evaluated. All patients are classified by causes of the recurrence. Possible risk factors that could contribute to those causes and overcoming ways are comprehensively discussed. Results : All recurrent aneurysms after surgical clipping were 14 of 2364 (0.5%). Three cases were males and 11 cases were females. Mean age was 52.3. At first treatment, nine cases were ruptured aneurysms, four cases were unruptured aneurysms, and one case was unknown. Locations of recurrent aneurysm were determined; anterior communicating artery (A-com) (n=7), posterior communicating artery (P-com) (n=3), middle cerebral artery (n=2), anterior cerebral artery (n=1) and basilar artery (n=1). As treatment of the recurrence, 11 cases were treated by surgical clipping and three cases were treated by endovascular coil embolization. Three cases of all 14 cases occurred in a month after the initial treatment. Eleven cases occurred after a longer interval, and three of them occurred after 15 years. By analyzing radiographs and operative findings, several main causes of the recurrent cerebral aneurysm were found. One case was incomplete clipping, five cases were clip slippage, and eight cases were fragility of vessel wall near the clip edge. Conclusion : This study revealed main causes of the recurrent aneurysm and contributing risk factors to be controlled. To manage those risk factors and ultimately prevent the recurrent aneurysm, neurosurgeons have to be careful in the technical aspect during surgery for a complete clipping without a slippage. Even in a perfect surgery, an aneurysm may recur at the clip site due to a hemodynamic change over years. Therefore, all patients must be followed up by imaging for a long period of time.

• Journal of the Korea Concrete Institute
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• v.28 no.5
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• pp.555-562
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• 2016

The objective of the present study is to evaluate the shear transfer capacity of transverse reinforcement at the concrete interfaces with smooth construction joint. The transverse reinforcing bars were classified into two groups: V-type for the arrangement perpendicular to the interface and X-type for inclined-crossing arrangement. The transverse reinforcement ratio at the interface varied from 0.0045 to 0.0135 for V-type and 0.0064 to 0.0045 for X-type. The mechanism analysis proposed for monolithic concrete interface, derived based on the upper-bound theorem of concrete plasticity, was modified to evaluate the shear friction capacity of concrete interfaces with smooth construction joint. Test results showed that the specimens with X-type reinforcement had lower amount of relative slippage at the interface and higher shear friction capacity than the companion specimens with V-type reinforcement. This observation was independent of the unit weight of concrete. The mean and standard deviation of the ratios between the experimental shear friction strength of smooth construction joints and predictions obtained from the proposed model are 1.07 and 0.14, respectively.

• Journal of Korean Neurosurgical Society
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• v.29 no.1
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• pp.51-57
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• 2000

Objective : For relief of back pain related to spondylolisthesis, fusion with or without internal fixation may be necessary. Currently, bilateral wide posterior decompression and fusion with or without internal fixation are used for treatment of spondylolisthesis. In case of severe osteoporosis, discectomy may be done without fusion to decompress the nerve roots. However, the procedure may aggravate radicular symptom because slippage may increase and thus foramen may become narrower. In these settings, inferomedial partial pediculectomy has been done in our institution, The object of this study was to evaltuate such cases with regard to per- and postoperative clinical courses. Patients and Methods : Fifteen patients complaining radicular pain with mild or no back pain underwent inferomedial partial pediculectomy. It was done in lytic spondylolisthesis after extension of isthmic defect. In degenerative spondylolisthesis of L4-5 interspace, intertransverse pediculectomy was done via paraspinal approach not to injure the posterior segment with intact isthmus. But, in degenerative spondylolisthesis of L5-S1 interspace however, partial pediculectomy was done after making artificial isthmic defect via midline approach. Then, reconstructive laminoplasty of L5 was performed to avoid iatrogenic instability resulted from artificial isthmic defect. They were followed up for average 14.4 months(3-31 months). Results : Radiating pain was relieved in all cases(100%). Postoperative result was excellent in 7 cases(46.7%), good in 7(46.7%) and fair in 1(6.6%). Only 1 case(6.7%) showed increase in slippage during follow-up period. Conclusion : Inferomedial partial pediculectomy is considered as a useful procedure for severely osteoporotic patients with spondylolisthesis with regards to keeping stability and decompressing the nerve roots.

• Steel and Composite Structures
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• v.6 no.6
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• pp.459-477
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• 2006

A theoretical research project is undertaken to develop integrated analysis and design tools for long span composite beams in modern high-rise buildings, and it aims to develop non-linear finite element models for practical design of composite beams. As the first paper in the series, this paper presents the development study as well as the calibration exercise of the proposed finite element models for simply supported composite beams. Other practical issues such as continuous composite beams, the provision of web openings for passage of building services, the partial continuity offered by the connections to columns as well as the behaviour of both unprotected and protected composite beams under fires will be reported separately. In this paper, details of the finite elements and the material models for both steel and reinforced concrete are first described, and finite element studies of composite beams with full details of test data are then presented. It should be noted that in the proposed finite element models, both steel beams and concrete slabs are modelled with two dimensional plane stress elements whose widths are assigned to be equal to the widths of concrete flanges, and the flange widths and the web thicknesses of steel beams as appropriate. Moreover, each shear connector is modelled with one horizontal spring and one vertical spring to simulate its longitudinal shear and pull-out actions based on measured load-slippage curves of push-out tests of shear connectors. The numerical results are then carefully analyzed and compared with the corresponding test results in terms of load mid-span deflection curves as well as load end-slippage curves. Other deformation characteristics of the composite beams such as stress and strain distributions across the composite cross-sections as well as distributions of shear forces and slippages in shear connectors along the beam spans are also examined in details. It is shown that the numerical results of the composite beams compare well with the test data in terms of various load-deformation characteristics along the entire deformation ranges. Hence, the proposed analysis and design tools are considered to be simple and yet effective for composite beams with practical geometrical dimensions and arrangements. Structural engineers are strongly encouraged to employ the models in their practical work to exploit the full advantages offered by composite construction.

• Asian Pacific Journal of Cancer Prevention
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• v.17 no.3
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• pp.1299-1308
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• 2016

Our previous studies clearly demonstrated that a combination of WP 631 and Epo B has higher activity against ovarian cancer cells than either of these compounds used separately. In order to fully understand the exact mechanism of action in combination, we assessed effects on the cell cycle of SKOV-3 cells. We evaluated three control points essential for WP 631 and Epo B action to determine which cell cycle-regulating proteins (CDK1/cyclin B complex, EpCAM or HMGB1) mediate activity. The effects of the drug on the cell cycle were measured based on the nuclear DNA content using flow cytometry. Expression of cell cycle-regulating genes was analyzed using real-time PCR. It was discovered that WP 631, at the tested concentration, did not affect the SKOV-3 cell cycle. Epo B caused significant G2/M arrest, whereas the drug combination induced stronger apoptosis and lower mitotic arrest than Epo B alone. This is very important information from the point of view of the fight against cancer, as, while mitotic arrest in Epo B-treated cells could be overcame after DNA damage repair, apoptosis which occurs after mitotic slippage in combination-treated cells is irreversible. It clearly explains the higher activity of the drug combination in comparison to Epo B alone. Epo B acts via the CDK1/cyclin B complex and has the ability to inhibit CDK1, which may be a promising strategy for ovarian cancer treatment in the future. The drug combination diminishes EpCAM and HMGB1 expression to a greater degree than either WP 631 and Epo B alone. Owing to the fact that the high expression of these two proteins is a poor prognostic factor for ovarian cancer, a decrease in their expression, observed in our studies, may result in improved efficacy of cancer therapy. The presented findings show that the combination of WP 631 and Epo B is a better therapeutic option than either of these drugs alone.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.1
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• pp.109-117
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• 2016

This paper is focused on the determination of friction parameter which is a predominant factor in the design of inflatable structure system. This inflatable structure system is very valuably used to protect passively and rapidly the possibilities of tunnel damages by flooding threats and unusual leakage to be occurred during and after underground infrastructure construction. In particular, this system should be necessary in subsea tunnel. This study presents the experimental results obtained from the relative friction characteristics tests of the fabric materials that constitute the inflatable structure. In order to evaluate the relative friction behaviour of the inflatable structure system, friction tests and scaled model tunnel friction tests are carried out. The friction tests are carried out to determine the friction coefficient for different surface conditions between tunnel and inflatable structure. These friction coefficients are then evaluated and compared with the result obtained from the model tunnel friction tests. Interaction behaviours between tunnel and system are also reviewed and described in this study. The results clearly show that the friction coefficients derived from scaled model slippage tests are about 12% lower than values obtained from the friction tests. In addition, this study will be necessary to verify the real friction behaviour with prototype tests before applying in practice.

• Korean Journal of Applied Biomechanics
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• v.19 no.1
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• pp.149-157
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• 2009

The purpose of this project was to determine biomechanical differences between Type A(Korean brand) and Type B(world top brand) badminton shoes and to make recommendations to improve the fit and function of Type A badminton shoes. Measurements of shoe shape and dimensions, foot movement within the shoe, cushioning of ground reaction forces, in-shoe pressure and outsole traction were performed. In addition, subjective feedback of the fit and function of the shoes was quantified for 17 recreational badminton players. Type A shoe had a much higher heel and shallower heel cup, so the heel was not secured well in the shoe and the ankle joint was higher off the ground. Foot slippage was up to 40% greater in Type A shoe than Type B shoe. Impact forces and peak pressures under the foot were generally higher with Type A shoe compared to Type B shoe. The flexion axis of Type A shoe occurred in the midfoot, not at the ball of the foot like Type B shoe, where you would want the shoe flexion to occur. In summary, there are several characteristics where A Type shoe and B Type differ. Therefore, a few recommendations are provided to help improve the fit and function of A Type shoe.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6D
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• pp.737-743
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• 2009

Shield TBM, since it was employed for Suyoungman Bay riverbed tunnel of Busan Subway in 2000,has been increasingly adopted in Korea, and in line with growing popularity, the study on Shield TBM has been expanded. However the studies mostly focus on ground condition in a bid to estimate the advancement rate and develop the model for calculating the excavation efficiency, whereas the efforts to analyze the cause of delay and to develop the improvement measures have been neglected. Thus the studies were mostly intended to analyze the schedule slippage focusing on ground conditions, while the study on schedule behind due to equipment itself and related facilities have yet to be attempted in earnest. This study hence was aimed at evaluating the troubles and schedule slippage caused by mechanical elements such as shield TBM equipment and tools and ground conditions, making use of FMEA approach so as to analyze the risk of schedule delay by such elements, thereby proposing the preventive measures to deal with high-risk factors. So, this study suggest the solution to highly ranked trouble factor for the purpose of enhance the efficiency on Shield TBM.

• Earthquakes and Structures
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• v.3 no.2
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• pp.169-180
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• 2012

The performance of pure friction isolation system with respect to the frequency bandwidth of excitation and the predominant frequency is investigated. A set of earthquake ground motions (artificial as well as recorded [with different combinations of magnitude-distance and local site geology]) is considered for investigating effectiveness of pure friction isolators. The results indicate the performance of pure friction base isolated system does not only depend upon coefficient of friction and mass ratio but the stick-slip behaviour depends upon the frequency content of the excitation as well. Slippage prevails if the excitation frequency lies in a suitable frequency range. This range widens with increasing mass ratio. For larger mass ratios, the sliding effect is more pronounced and the maximum acceleration response is further reduced in the neighbourhood of frequency ratio (${\omega}/{\omega}_n$) of unity. The pure friction isolation system is effective in the case of broadband excitations only and that too, in the acceleration sensitive range of periods. The pure friction system is not effective for protection against narrow band motions for which the system response is quasi-periodic.