• Journal of the Korean Orthopaedic Association
• /
• v.54 no.4
• /
• pp.327-335
• /
• 2019

Purpose: To investigate the radiological efficacy of polymethylmethacrylate (PMMA) augmentation of pedicle screw operation in osteoporotic vertebral compression fractures (OVCF) patients. Materials and Methods: Twenty OVCF patients, who underwent only posterior fusion using pedicle screws with PMMA augmentation, were included in the study. The mean follow-up period was 15.6 months. The demographic data, bone mineral density (BMD), fusion segments, number of pedicle screws, and amount of PMMA were reviewed as medical records. To analyze the radiological outcomes, the radiologic parameters were measured as the time serial follow-up (preoperation, immediately postoperation, postoperation 6 weeks, 3, 6 months, and 1 year follow-up). Results: A total of 20 patients were examined (16 females [80.0%]; mean age, 69.1±8.9 years). The average BMD was -2.5±0.9 g/cm². The average cement volume per vertebral body was 6.3 ml. The mean preoperative Cobb angle of focal kyphosis was 32.7°±7.0° and was improved significantly to 8.7°±6.9° postoperatively (p<0.001), with maintenance of the correction at the serial follow-up, postoperatively. The Cobb angle of instrumented kyphosis, wedge angle, and sagittal index showed similar patterns. In addition, the anterior part of fractured vertebral body height averaged 11.0±5.0 mm and was improved to 18.5±5.7 mm postoperatively (p=0.006), with maintenance of the improvement at the 3-month, 6-month, and 1-year follow-up. Conclusion: The reinforcement of pedicle screws using PMMA augmentation may be a feasible surgical technique for OVCF. Moreover, it appears to be appropriate for improving the focal thoracolumbar/lumbar kyphosis and is maintained well after surgery.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.6 s.73
• /
• pp.769-780
• /
• 2004

This paper's objective is to evaluate the experimental behavior of gap N-joints made of cold-formed, square, hollow steel sections, with a connection plate as a tension member. The principal parameters for testing included the ratio of chord width to thickness, the ratio of brace width to chord width, eccentric ratio, the shape of the compression member, the branch angle, and the stiffening plate of the chord flange. The strength and failure mode were examined through the test for the gap N-joint, consisting of several parameters. Based on the results of the test, the gap N-joints were determined according to the capacity preceding the displacement of the tension, regardless of the width ratio, and the split failure mode-connected surface for a chord in joints. The strength of the gap N-joints increased proportionally as the $2\gamma$(B/T) ratio decreased, and as the width ratio(${\beta}$) of branch to chord increased. Particularly, $2\gamma$(B/T) decreased as the capacity of gap N-joint increased. The results of the test were summarized for the capacity, initial stiffness, ductility, and change of the failure mode of each gap N-joint.

• Science of Emotion and Sensibility
• /
• v.15 no.2
• /
• pp.201-208
• /
• 2012

The objectives of this study were to investigate the psychoacoustic properties of PTFE(Poly tetra Fluoroethylene) laminated vapor permeable water repellent fabrics which are frequently used for sportswear, to examine the relationship among fabrics' basic characteristics, mechanical properties and the psychoacoustic properties, and finally to propose the predicting model to minimize the psychoacoustic fabric sound. A total of 8 specimens' frictional sound were recorded and Zwicker's psychoacoustic parameters such as loudness(Z), sharpness(Z), roughness(Z), and fluctuation strength(Z) were calculated using the Sound Quality Program. Mechanical properties of specimens were measured by KES-FB system. Loudness(Z) of specimen D-1 was the highest, which means the rustling sound of the specimen D-1 was the most noisy. Statistically significant difference among film type was observed only in loudness(Z) for fabric sound. Based on ANOVA and post-hoc test, specimens were classified into less loud PTFE film group (groupI) and loud PTFE film group (groupII). Loudness(Z) was higher when staple yarn was used compared when filament yarn was used. According to the correlation between the mechanical properties of fabrics and loudness(Z) in groupI, the shear properties, compression properties and weight showed positive correlation with loudness(Z). According to the regression equation predicting loudness(Z) of groupI, the layer variable was chosen. In groupII, variables explaining the loudness(Z) were yarn types and shear hysteresis(2HG5).

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.1
• /
• pp.13-18
• /
• 2010

It is crucial to decide reasonably the parameters necessary for design through research on the characteristics of rock in order to analyze stability of rock structure. This article has conducted both pressure meter test, uniaxial and triaxial compression test to the areas of andesite or tuff located in local regions such as Yeosu, Gwangju, Yangsan, Busan, and Daejeon and has comparatively analyzed previously proposed estimative formulas. According to the result of estimating the deformation modulus through using the damping coefficient suggested by Nicholson & Bieniawski, when RMR is less than 60, it is desirable to use the result of the pressure meter test considering the damping coefficient. If the RMR value is over 60, however, the formula suggested by Kim Gyo-won has been proved to be the most applicable. Moreover, according to the result of comparing the RMR, adhesion, and angle of internal friction, both the adhesion and angle of internal friction best correspond to the formula proposed by Tsuchiya. Comparatively analyzing the relations between the rock deformation modulus and RMR and also suggesting the formula of calculating the shear strength parameter to use the RMR value, this study did not include the deformation modulus and shear strength parameter as factors to decide the RMR index. Since result can differ by several factors, it will be necessary afterwards to suggest practical estimative formulas applicable to the actual spots of Korea.

• Journal of the Korean GEO-environmental Society
• /
• v.9 no.6
• /
• pp.31-41
• /
• 2008

Consolidation characteristics of reclamated ground with dredged soil and methods of evaluating them are investigated in this paper. For a dredged and reclamated ground with a very high water content, self-weight consolidation being progressed, its consolidation characteristics are difficult to find since it is almost impossible to have a undisturbed sample. In order to overcome such a problem, methods of laboratory tests with disturbed sample were studied to obtain consolidation parameters required to analyze consolidation settlement in practices, using the conventional infinitesimal consolidation theory, were evaluated by carrying out various laboratory tests with disturbed soils such as oedometer test, constant rate of deformation test, Rowe-cell tests with ring diameters of 60 mm, 100 mm and 150 mm and the centrifuge model tests with 40 g-levels. Constitutive relations of void ratio - effective vertical stress - permeability were evaluated by using the inverse technique implemented with the finite strain consolidation theory and results of centrifuge model tests. Design soil parameters related to consolidation such as compression index, swelling index, coefficient of volume change and vertical and horizontal consolidation coefficients were proposed properly by analyzing the various test results comprehensively.

• The Journal of Engineering Geology
• /
• v.19 no.2
• /
• pp.153-163
• /
• 2009

In this study, a series of triaxial tests on Jeju basalt were carried out and then rock strength parameters were estimated by the Mohr-Coulomb failure criterion and the Hoek-Brown failure criterion using the test results. The characteristics of both failure criterions were investigated through comparing the estimated rock strength parameters. As the result of the Mohr-Coulomb criterion, the cohesions and the internal friction angles are determined as 5.35 MPa and $50.25^{\circ}$ of Pyoseonri basalt, 16.99 MPa and $60.66^{\circ}$ of Trachy-basalt, and 2.33 MPa and $37.05^{\circ}$ of Scoria, respectively. The cohesions and internal friction angles were estimated by the Hoek-Brown failure criterion in the basis of the results of regression analysis. The cohesions and the internal friction angles are determined as 4.77 MPa and $52.47^{\circ}$ of Pyoseonri basalt, 14.69 MPa and $60.70^{\circ}$ of Trachy-basalt, and 2.22 MPa and $47.60^{\circ}$ of Scoria, respectively. As the result of comparison between the Mohr-Coulomb failure criterion and the failure envelope predicted by the Hoek-Brown criterion, the cohesion estimated by the Hoek-Brown criterion is usually lower than that obtained from the Mohr-Coulomb criterion, whereas the friction angle estimated by the Hoek-Brown criterion is higher than that obtained from the Mohr-Coulomb criterion.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.4
• /
• pp.825-840
• /
• 2015

Adaptive bitrate (ABR) streaming technology has become an important and prevalent feature in many multimedia delivery systems, with content providers such as Netflix and Amazon using ABR streaming to increase bandwidth efficiency and provide the maximum user experience when channel conditions are not ideal. Where such systems could see improvement is in the delivery of live video with a closed loop cognitive control of video encoding. In this paper, we present streaming camera system which provides spatially and temporally adaptive video streams, learning the user's preferences in order to make intelligent scaling decisions. The system employs a hardware based H.264/AVC encoder for video compression. The encoding parameters can be configured by the user or by the cognitive system on behalf of the user when the bandwidth changes. A cognitive video client developed in this study learns the user's preferences(i.e. video size over frame rate) over time and intelligently adapts encoding parameters when the channel conditions change. It has been demonstrated that the cognitive decision system developed has the ability to control video bandwidth by altering the spatial and temporal resolution, as well as the ability to make scaling decisions.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.6
• /
• pp.1417-1431
• /
• 1994

In this study, shear strength characteristics of the Nak-Dong river sand in Taegu area are investigated by triaxial compression test, considering shear strain control velocity, relative density, and confining pressure. The results from Lade model and Modified Lade model are compared with the measured value in the laboratory test. The results by the change of shear strain control velocity, relative density, and confining pressure are as follows; 1) The stress limit, which can be Coulomb's law about the Nak-Dong river sand, have ranged 120~200 kpa at 0.08%/min and 120~150 kpa at 0.5%/min. These limits are smaller than that of the calcareous sand and the well-graded, quartz sand. 2) The parameters needed to Lade model and Modified Lade model are much affected by the strain control velocity and the relative density. Consequently, in the field, it is important to use parameters aptly after accurately understanding both the loading condition and subsoil condition. 3) Overall, the principal stress ratio obtained from constitutive model equations is not affected by the control velocity, but both the relative density and confining pressure affect the result of constitutive model equations. Consequently, the study on the various conditions about the relative density and confining pressure is needed to accurately predict the stress-strain behavior on the Nak-Dong river sand. 4) For the range of the used confining pressure in the study, the Lade model shows better agreements with the measured value than the Modified Lade model, comparing the measured value with the principal stress ratio at failure and the internal friction angle of failure envelope obtained from the Lade model and Modified Lade model.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.39 no.2
• /
• pp.35-44
• /
• 2002

The translation and the rotation of camera occur global motion which affects all over the frame in video sequence. With the video sequences containing global motion, it is practically impossible to extract exact video objects and to calculate genuine object motions. Therefore, high compression ratio cannot be achieved due to the large motion vectors. This problem can be solved when the global motion compensated frames are used. The existing camera motion estimation methods for global motion compensation have a large amount of computations in common. In this paper, we propose a simple global motion estimation algorithm that consists of linear equations without any repetition. The algorithm uses information .of symmetric points in the frame of the video sequence. The discriminant conditions to distinguish regions belonging to distant view from foreground in the frame are presented. Only for the distant view satisfying the discriminant conditions, the linear equations for the panning, tilting, and zooming parameters are applied. From the experimental results using the MPEG test sequences, we can confirm that the proposed algorithm estimates correct global motion parameters. Moreover the real-time capability of the proposed technique can be applicable to many MPEG-4 and MPEG-7 related areas.

• The Journal of Engineering Geology
• /
• v.14 no.4 s.41
• /
• pp.371-379
• /
• 2004

Soil investigation data at 7 different locations around Honam costal region were analyzed and experimental correlations between soil properties and parameters of soft clay were presented. Most soils were classified as CL and CH by the Unified Soil Classification System and were unstable structurally because the water contents were generally greater than the liquid limits. The compression index has good correlations with water content, liquid limit and initial void ratio. The trend of these correlations were similar to the Skempton equation Cc = 0.009(LL -10) and other studies for Korean soft clays but the constants were small different. The slope of these correlations for Honam costal region were slightly greater than those for Kyunggi costal region and Kyungnam costal region. The correlation coefficient (R) between the liquid limit and the plastic index is 0.93. It is seen that not only the water content and the liquid limit but also the water content and the initial void ratio are correlate, therefore the experimental equations were presented for the practical purpose.