• The Journal of Engineering Geology
• /
• v.11 no.1
• /
• pp.1-11
• /
• 2001

The geological characteristics of Korea are that we can encounter the rock layer only after 10m of excavation, methods to presume the rock pressure distribution of the rock layer is urgently needed. When using the existing empiric science of Terzaghi-Peck, Tschebotarioff to measure the rock pressure of the rock layer, underestimate the real strength because of the cohesion is ignored. Therefore calculating the horizontal sliding force of wedge block, which includes the dips and shear strength of discontinuities and surcharge load etc., think to be to getting a closer rock stress of the real rock pressure acting upon the earth structure in rock mass. This research use Coulomb soil pressure theory assuming that the backfill soil will yield wedge failure when it has cohesion, applying Prakash-Saran(l963), and then it uses equilibrium of force and shear strength $\tau$=c+$\sigma$tan $\Phi$ of the cliscontinuities. Analyzing shear strength and dips of cliscontinuities using calculated theory according to the status of discontinuities aperture, we were able to find out that because the cohesion and friction angle of the rock layer itself is large enough, how the dip directions and dips facing the excavation face is the only factor deciding whether or not the rock stress is applied. The evaluated theory of this research should be strictly estimated, so that the many parameters such as c, $\Phi$value, types and structures of rock class, excessive lateral pressure, dynamic load, earthquake, needed later when calculating shear strength of discontinuities and especially the ground water effect acting on rock layer should be coumpted with many measuring data achieve at the insite to study the application.

• Journal of the Korean Arthroscopy Society
• /
• v.5 no.1
• /
• pp.7-12
• /
• 2001

Purpose : We observed usability of allograft by evaluating the clinical results, second look arthroscopic and histologic findings at last follow up after anterior cruciate ligament(ACL) reconstruction using by fresh frozen Achilles allograft. Materials and Methods : We analyzed in 58 patients(59 cases) by subjective and objective parameters, Telos stress arthrometer and Modified Feagin Scoring System. The average age and follow up period was 25 years(ranging from 18 to 49 years), and 15 months(ranging from 12 to 19 months). Among them we studied second look arthroscopic and histologic findings in 16 patients. Results : The mean Lysholm Score wits improved from 60 to 88.2 as well the anterior translation was improved from 7.1 min to 2.3mm at last follow up. The second look arthroscopic findings were close to normal in ligament thickness, tension and showed revasculization at the holly attachment site. Light microscope(LM) findings showed dense cellularity like a normal ligament. In electron microscope(EM) collagen fibrils showed parallel arrangement longitudinally and unimodal pattern diameter close to normal tissue in the transverse section. Conclusion : We think that the fresh frozen Achilles allograft is a good substitution of autograft in cruciate ligament reconstruction.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.40 no.2
• /
• pp.221-227
• /
• 2016

The main shaft is one of the key components connecting the rotor hub and gear box of a wind power generator. Typically, main shafts are manufactured by open die forging method. However, the main shaft for large MW class wind generators is designed to be hollow in order to reduce the weight. Additionally, the main shafts are manufactured by a casting process. This study aims to develop a manufacturing process for hollow main shafts by the open die forging method. The design of a forging process for a solid main shaft and hollow shaft was prepared by an open die forging process design scheme. Finite element analyses were performed to obtain the flow stress by a hot compression test at different temperature and strain rates. The control parameters of each forging process, such as temperature and effective strain, were obtained and compared to predict the suitability of the hollow main shaft forging process. Finally, high productivity reflecting material utilization ratio, internal quality, shape, and dimension was verified by the prototypes manufactured by the proposed forging process for hollow main shafts.

• Journal of Pharmacopuncture
• /
• v.19 no.2
• /
• pp.137-144
• /
• 2016

Objectives: Several studies have revealed that systemic hypertension is strongly associated with cataractogenesis. However, the pathophysiology and treatment is often unclear. In this study, we evaluated the anti-cataractogenic effect of cinnamaldehyde (CA), a natural organic compound, in rats with fructose-induced hypertension. Methods: The rats were divided into six groups. For six weeks, the normal group received a suspension of 0.5% carboxy methyl cellulose (10 mL/kg/day, p.o.) while five other groups received a 10% (w/v) fructose solution in their drinking water to induce hypertension. By the end of the third week hypertension had been induced in all the animals receiving fructose. From the beginning of the fourth week to the end of the sixth week, one of those five groups (control) continued to receive only 10% (w/v) fructose solution, one group (standard) received ramipril (1 mg/kg/day, p.o.) plus 10% (w/v) fructose solution, and three groups (experimental) received CA at doses of 20, 30, and 40 mg/kg/day p.o., plus 10% (w/v) fructose solution. Blood pressure was measured weekly using a non-invasive blood pressure apparatus. After six weeks, the animals were sacrificed, and the anti-cataractogenic effects on the eye lenses were evaluated. Results: Administration of fructose elevated both the systolic and the diastolic blood pressures, which were significantly reduced by CA at all dose levels. In the control group, a significant increase in the malonaldehyde (MDA) level and decreases in the total protein, $Ca^{2+}$adenosine triphosphate (ATP)ase activity, glutathione peroxidase, catalase, superoxide dismutase and glutathione levels, as compared to the normal group, were observed. Administration of CA at all doses significantly restored the enzymatic, non-enzymatic, antioxidants, total protein, and $Ca^{2+}$ATPase levels, but decreased the MDA level, as compared to the control group. Conclusion: The present study revealed that CA modulated the antioxidant parameters of the serum and lens homogenates in hypertension-induced cataractogenic animals.

• Asian Journal of Turfgrass Science
• /
• v.26 no.2
• /
• pp.116-122
• /
• 2012

The study was conducted to know whether turfgrass wear tolerance, growth, and quality could be improved by the application of silicon and potassium. First, turf responses to silicate and potassium were evaluated by several parameters such as, turf visual quality, root length, shoot density, and dry weight under the field condition. Second, turf responses to traffic frequencies were examined by turf growth (root) length, shoot density and dry weight) and soil hardness under the field condition. Finally, under traffic stress condition, the effects of silica and potassium application on wear tolerance were evaluated through the methods described above. Creeping bentgrass (Agrostis stolonifera) rooting were significantly improved by silica. The root length was enhanced by an increase in potassium silicate application. Certain level of light traffic is beneficial while frequent traffic cause serious adverse effect on visual quality of bentgrass. Under a traffic stress condition with 10 times of footing a day for 30 days, silica and potassium increased turf visual quality by 6.38% and 10.25% respectively when compared to the control. Silica and potassium treatment on trafficked plot increased turf visual quality by 11.4% and 10.2% respectively in comparison with the control with significant reduction of wear injury from the traffic. A co-application of potassium silicate with potassium sulfate provided the enhanced visual quality of turf as compared to application of silica or potassium fertilizer, respectively.

• Journal of Korean Orthopaedic Sports Medicine
• /
• v.10 no.2
• /
• pp.54-60
• /
• 2011

Puropse: To evaluate the outcome of arthroscopic posterior cruciate ligament (PCL) reconstruction using fresh-frozen achilles allograft tendon with preservation of ligament remnant or elongated ligament. Materials and Methods: From October 2004 to March 2010, we performed PCL reconstruction with Achilles tendon allografts in 22 complete rupture patients. Mean age was 31.5 years. 14 cases were male and 8 cases were female. Average follow-up period was 3 years and 7 months, range from 1 year to 6 years and 4 months. Subjective and objective parameters were utilized in analyses, such as the mean range of motion, post. drawer test, Lysholm knee score, Tegner activity score, IKDC score, and second look arthroscopic examination. Results: Postoperative Lysholm knee score, IKDC scores, Tegner activity scale, and posterior displacement by the Telos stress test demonstrated statistically significant improvement compared to the preoperative state. Conclusion: Arthroscopic PCL reconstruction using fresh-frozen achilles allograft tendon with preservation of ligament remnant showed good clinical results and posterior stability.

• Korean Journal of Ichthyology
• /
• v.30 no.1
• /
• pp.1-8
• /
• 2018

We tried to determine the optimum salinity for a cultured of olive flounder (Paralichthys olivaceus) by investigating after exposing the fish at different salinity (10, 15, 20 and 25 psu) for 24 and 48 hours compared with control group (fish before transfer to experimental tank). As a control groups, we compared an analyzed with other experimental groups using olive flounder in natural sea water. Hematological parameters including hematocrit (Ht) and hemoglobin (Hb), cortisol and glucose, aspartate aminotransferase (AST) and alanine aminotransferase (ALT), $NH_3$, osmolality, total protein (TP), $Na^+$, $K^+$ and $Cl^-$ mostly exhibited significant changes at 10 and 15 psu groups compared with control groups for 24 and 48 hours exposed. Plasma SOD (superoxide dismutase) and CAT (catalase) activity also increased with experimental groups (10 and 15 psu) compared to the control groups. The expression of HSP70 mRNA was also higher at low-salinity (10 and 15 psu) than at control group. In particular, after 24 hours exposed, it expression to 15 psu groups showed a significant difference compared to the control group. However, after 48 hours exposed, it expression was higher in the 10 psu groups than the control. It is assumed that the changes in the hematological responses and hormone, homeostasis and metabolism were resulted in to protect fish body from stress. Based on these results, we are expected that it will be used as basic data for the culture of olive flounder prepared for low salinity.

• Journal of Periodontal and Implant Science
• /
• v.44 no.2
• /
• pp.57-64
• /
• 2014

Purpose: Both chronic periodontitis (CP) and iron deficiency anemia (IDA) induce oxidative stress in the body and cause an imbalance between reactive oxygen species and antioxidants, such as superoxide dismutase (SOD). This study explored the SOD enzyme activity of saliva and serum in CP patients with and without IDA and analyzed the impact of IDA on CP. Methods: A total of 82 patients were divided into four groups: control group (CG, 22), periodontally healthy IDA patients (IDA-PH, 20), CP patients (CP, 20), and IDA patients with CP (IDA-CP, 20). After clinical measurements and samplings, serum and salivary SOD levels were determined using an SOD assay kit. Results: IDA-CP patients exhibited a higher gingival index, bleeding on probing, probing pocket depth, and percentage (%) of sites with a clinical attachment loss (CAL) of ${\geq}6mm$ (P<0.008) than CP patients. The mean salivary and serum SOD levels were significantly lower in the IDA-PH, CP, and IDA-CP patients than in the CG group (P<0.008). A significant positive correlation between salivary and serum SOD activity was observed in IDA (P<0.05). Furthermore, serum and salivary SOD levels were significantly and negatively correlated with all periodontal parameters including the percentage of sites with CAL of 4-5 and ${\geq}6mm$ (P<0.05) except the significant correlation between salivary SOD activity and mean CAL and the percentage of sites with CAL of 4-5 mm (P>0.05) in these patients. Conclusions: Within the limits of this study, it may be suggested that IDA patients with chronic periodontitis have more periodontal breakdowns than patients with chronic periodontitis. Serum and salivary SOD activity levels were lower in the IDA-PH, CP and IDA-CP groups than in the CG. Iron deficiency anemia influenced the serum SOD activity but did not seem to affect the salivary SOD activity in these patients.

• Journal of the Korea Concrete Institute
• /
• v.21 no.4
• /
• pp.489-499
• /
• 2009

It is quite difficult to predict the flexural strength of post-tensioned members with unbonded tendons (unbonded posttensioned members, UPT members) because of debonding behavior between concrete and prestressing tendons, which is different from that with bonded tendons. Despite many previous researches, our understanding on the flexural strength of UPT members is still insufficient, and thus, national codes use different methods to calculate the strength, which quite often give very different results. Therefore, this paper reviews various existing methods, and aims at proposing an improved rational strength model for UPT flexural members having better accuracy. Additionally, a database containing a large number of test data on UPT flexural members has been established and used for verification of the proposed flexural strength model. The analysis results show that the proposed method provides much better accuracy than many existing methods including the rigid-body model that utilizes the assumption of concentrated deformation and plastic hinge length, and that it also gives proper consideration on the effects of primary parameters such as reinforcement ratio, loading pattern, concrete strength, etc. Especially, the proposed method also well predicts the ultimate stress of unbonded tendons of over-reinforced members, which are often possible in construction fields, and high strength concrete members.

• Journal of the Korea Concrete Institute
• /
• v.28 no.2
• /
• pp.167-176
• /
• 2016

Shear friction strength model of concrete was proposed to explain the direct friction mechanism at the concrete interfaces intersecting two structural elements. The model was derived from a mechanism analysis based on the upper-bound theorem of concrete plasticity considering the effect of transverse reinforcement and applied axial loads on the shear strength at concrete interfaces. Concrete was modelled as a rigid-perfectly plastic material obeying modified Coulomb failure criteria. To allow the influence of concrete type and maximum aggregate size on the effectiveness strength of concrete, the stress-strain models proposed by Yang et al. and Hordijk were employed in compression and tension, respectively. From the conversion of these stress-strain models into rigidly perfect materials, the effectiveness factor for compression, ratio of effective tensile strength to compressive strength and angle of concrete friction were then mathematically generalized. The proposed shear friction strength model was compared with 91 push-off specimens compiled from the available literature. Unlike the existing equations or code equations, the proposed model possessed an application of diversity against various parameters. As a result, the mean and standard deviation of the ratios between experiments and predictions using the present model are 0.95 and 0.15, respectively, indicating a better accuracy and less variation than the other equations, regardless of concrete type, the amount of transverse reinforcement, and the magnitude of applied axial stresses.