• Restorative Dentistry and Endodontics
• /
• v.39 no.4
• /
• pp.276-281
• /
• 2014

Objectives: The purpose of this study was to compare the cutting efficiency of a newly developed microprojection tip and a diamond-coated tip under two different engine powers. Materials and Methods: The apical 3 mm of each root was resected, and root-end preparation was performed with upward and downward pressure using one of the ultrasonic tips, KIS-1D (Obtura Spartan) or JT-5B (B&L Biotech Ltd.). The ultrasonic engine was set to power-1 or -4. Forty teeth were randomly divided into four groups: K1 (KIS-1D / Power-1), J1 (JT-5B / Power-1), K4 (KIS-1D / Power-4), and J4 (JT-5B / Power-4). The total time required for root-end preparation was recorded. All teeth were resected and the apical parts were evaluated for the number and length of cracks using a confocal scanning micrscope. The size of the root-end cavity and the width of the remaining dentin were recorded. The data were statistically analyzed using two-way analysis of variance and a Mann-Whitney test. Results: There was no significant difference in the time required between the instrument groups, but the power-4 groups showed reduced preparation time for both instrument groups (p < 0.05). The K4 and J4 groups with a power-4 showed a significantly higher crack formation and a longer crack irrespective of the instruments. There was no significant difference in the remaining dentin thickness or any of the parameters after preparation. Conclusions: Ultrasonic tips with microprojections would be an option to substitute for the conventional ultrasonic tips with a diamond coating with the same clinical efficiency.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.4
• /
• pp.11-15
• /
• 2018

Torque tubes in High Temperature Superconducting (HTS) motor transfer torque from superconducting field winding rotor to the room temperature shaft. It should have minimum heat conduction property for minimizing the load on cryo-refrigerator. Generally, these torque tubes are made with stainless steel material because of high strength, very low outgassing and low thermal contraction properties at cryogenic temperatures and vacuum conditions. With recent developments in composite materials, these torque tubes could be made of composites such as Kevlar and S-Glass, which have the required properties like high strength and low thermal conductivity at cryogenic temperatures, but with a reduced weight. Development and testing of torque tubes made of these composites for HTS motor are taken up at Bharat Heavy Electricals Limited (BHEL), Hyderabad in collaboration with Central Institute of Plastics and Engineering Technology (CIPET), Chennai and Indian Institute of Technology (IIT), Kharagpur. As these materials are subjected to vacuum, it is important to measure their outgassing rates under vacuum conditions before manufacturing prototype torque tubes. The present study focusses on the outgassing characteristics of Kevlar and S-Glass, using an Outgassing Measurement System (OMS), developed at IIT Kharagpur. The OMS facility works under vacuum environment, in which the test samples are exposed to vacuum conditions over a sufficient period of time. The outgassing measurements for the composite samples were obtained using pressure-rise technique. These studies are useful to quantify the outgassing rate of composite materials under vacuum conditions and to suggest them for manufacturing composite torque tubes used in HTS motors.

• Journal of the Society of Naval Architects of Korea
• /
• v.58 no.4
• /
• pp.243-252
• /
• 2021

The present study aims to investigate the interaction of a wire-type turbulence stimulator and the laminar boundary layer on a flat plate by flow field measurement. For the towing tank tests, a one-dimensional Laser Doppler Velocimetry (LDV) attached on a two-axis traverse was used to measure the streamwise velocity component of the boundary layer flow in zero pressure gradient, disturbed by a turbulence stimulator. The wire diameter was 0.5 and 1.0 mm according to the recommended procedures and guidelines suggested by the International Towing Tank Conference. Turbulence development by the stimulator was identified by the skin friction coefficient, mean and Root Mean Square (RMS) of the streamwise velocity. The laminar boundary layer with the absence of the wire-type stimulator was similar to the Blasius solution and previous experimental results. By the stimulator, the mean and RMS of the streamwise velocity were increased near the wall, showing typical features of the fully developed turbulent boundary layer. The critical Reynolds number was reduced from 2.7×10⁵ to 1.0×10⁵ by the disturbances caused by the wire. As the wire diameter and the roughness Reynolds number (Rek) increased, the disturbances by the stimulator increased RMS of the streamwise velocity than turbulent boundary layer.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.6
• /
• pp.108-115
• /
• 2021

The purpose of this study was to investigate the therapeutic effect of fludrocortisone in patients suffering from cervical spinal cord injury (SCI) with orthostatic hypotension (OH). Twenty-six patients with cervical SCI diagnosed with OH through a head-up tilt test were randomly assigned, and they were given either conservative treatment or additional fludrocortisone treatment. Fludrocortisone was administered for 2 weeks, increasing from 0.1 mg to 0.2 mg week . Blood pressure (BP), heart rate (HR), and blood parameters were measured at the beginning and after 2 weeks. After 2 weeks of treatment, there was a significant increase in the baseline BP of the treatment groups (p<.05). When analyzing the drop ratio, there was a tendency for a lower orthostatic BP drop in the treatment groups. Mild adverse events were reported in 7.69% of the treatment groups. Fludrocortisone exhibited therapeutic effects such as preventing cardiovascular complications and continuing rehabilitation through increased baseline BP and reduced OH, and can therefore be considered as a treatment option for OH in patients with SCI.

• Structural Engineering and Mechanics
• /
• v.78 no.5
• /
• pp.585-597
• /
• 2021

This paper presents a comparative study of analytical method, finite element method (FEM) and Multilayer Perceptron (MLP) for analysis of a contact problem. The problem consists of a functionally graded (FG) layer resting on a half plane and pressed with distributed load from the top. Firstly, analytical solution of the problem is obtained by using theory of elasticity and integral transform techniques. The problem is reduced a system of integral equation in which the contact pressure are unknown functions. The numerical solution of the integral equation was carried out with Gauss-Jacobi integration formulation. Secondly, finite element model of the problem is constituted using ANSYS software and the two-dimensional analysis of the problem is carried out. The results show that contact areas and the contact stresses obtained from FEM provide boundary conditions of the problem as well as analytical results. Thirdly, the contact problem has been extended based on the MLP. The MLP with three-layer was used to calculate the contact distances. Material properties and loading states were created by giving examples of different values were used at the training and test stages of MLP. Program code was rewritten in C++. As a result, average deviation values such as 0.375 and 1.465 was obtained for FEM and MLP respectively. The contact areas and contact stresses obtained from FEM and MLP are very close to results obtained from analytical method. Finally, this study provides evidence that there is a good agreement between three methods and the stiffness parameters has an important effect on the contact stresses and contact areas.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.12 no.1
• /
• pp.71-84
• /
• 2020

In order to improve the performance of marine centrifugal pump, a centrifugal pump whose specific speed is 66.7 was selected for the research. Outlet diameter D2, outlet width b2, blade outlet angle β2, blade wrap φ and blade number z of the impeller were chosen as the variables. The maximum weighted average efficiency and the minimum vibration intensity at the base were calculated as objectives. Based on the Latin Hypercube method, the impeller was numerically optimized. The numerical results show that after optimization, the amplitudes of pressure fluctuation on the main frequency at different monitoring points decrease in varying degrees. The radial force on impeller decreases obviously under off-design flow rates and is more symmetrical during the operation of the pump. The variation of the axial force is relatively small, which has no obvious relationship with the rotating angle of the impeller. The energy performance and vibration experiment was performed for verifying. The test results show that the weighted average efficiency under 0.8Qd, 1.0Qd and 1.2Qd increases by 4.3% after optimization. The maximal vibration intensity at M1-M4 on the pump base reduced from 0.36 mm/s to 0.25 mm/s, decreasing by 30.5%. In addition, the vibration velocities of bracket in pump side and outlet flange also have significant reductions.

• Journal of Veterinary Clinics
• /
• v.39 no.3
• /
• pp.144-148
• /
• 2022

A one-year-old spayed female Korean Shorthair cat presented to Kangwon National University Veterinary Hospital with vomiting, weight loss, lethargy, loss of appetite, and polyuria that lasted for more than two weeks. The body condition score, blood pressure, heart rate, and body temperature were abnormally low, and the physical examination findings were consistent with moderate dehydration. Hematological and biochemical tests demonstrated mild azotemia and a low Na:K ratio. Additional abdominal ultrasound imaging revealed reduced size of both adrenal glands. The adrenocorticotropic hormone (ACTH) stimulation test showed decreased post-ACTH cortisol and aldosterone levels and increased endogenous ACTH levels, confirming a diagnosis of primary hypoadrenocorticism. The cat was treated with subcutaneous injections of desoxycorticosterone pivalate (DOCP) and oral prednisolone supplementation, and subsequent electrolyte analysis showed a normal Na:K ratio. Clinical symptoms were also improved in response to treatment. Hypoadrenocorticism in cats is a very rare disease, but it should not be excluded as a potential diagnosis in favor of kidney diseases or other conditions, especially when the Na:K ratio is low. In addition, the prognosis for the disease and the response to DOCP treatment should be further evaluated in cats.

• Design & Manufacturing
• /
• v.16 no.4
• /
• pp.24-33
• /
• 2022

Fiber-reinforced plastics(FRPs) have excellent specific stiffness and strength, so they are usually used as automotive parts that require high rigidity and lightweight instead of metal. However, it is difficult to predict the mechanical properties of injection molded parts due to the fiber orientation and breakage of FRPs. In this paper, the fiber orientation characteristics and mechanical properties of injection molded specimens were evaluated in order to fabricate automotive transmission side covers with FRPs and design a rib structure for improvement of their rigidity. The test molds were designed and manufactured to confirm the fiber orientation characteristics of each position of the injection molded standard plate-shaped specimens, and the tensile properties of the specimens were evaluated according to the injection molding conditions and directions of specimens. A gusset-rib structure was designed to improve the additional structural rigidity of the target products, and a proper rib structure was selected through the flexural tests of the rib-structured specimens. Based on the evaluation of fiber orientation and mechanical characteristics, the optimization analyses of gate location were performed to minimize the warpage of target products. Also, the deformation analyses against the internal pressure of target product were performed to confirm the rigidity improvement by gusset-rib structure. As a result, it could be confirmed that the deformation was reduced by 27~37% compared to the previous model, when the gusset-rib structure was applied to the joining part of the target products.

• Explosives and Blasting
• /
• v.40 no.4
• /
• pp.1-14
• /
• 2022

To review the appropriateness of current regulations on the simple explosive storage facility, the effects of internal explosion on the structural stability of the standard storage facility were analyzed by means of both FEM analyses and field experiments. As a result, it was found that the explosion-proof performance of the existing storage structure was not sufficient for 15 kg of emulsion-type explosive. Thus, an alternative method of splitting explosives was tested by conducting sympathetic detonation experiments. This method worked properly as expected, and the proper amount of splitted explosive was determined according to the test results. In addition, a storage structure with open ceiling was found to be very effective because explosion pressure was released so rapidly that the damage of the facility could be reduced significantly. Hence, such a structural pattern was proposed as a new design scheme for simple explosive storage facility.

• Geomechanics and Engineering
• /
• v.29 no.5
• /
• pp.509-522
• /
• 2022

Tail-grouting is an effective measure in shield engineering for filling the gap at the shield tail to reduce ground deformation. However, the gap-filling ratio affects the value of the gap parameters, leading to different surface settlements. It is impossible to adjust the fill ratio indiscriminately to study its effect, because the allowable adjustment range of the grouting quantity is limited to ensure construction site safety. In this study, taking the shield tunnel section between Chaoyanggang Station and Shilihe Station of Beijing Metro Line 17 as an example, the correlation between the tail-grouting parameter and the surface settlement is investigated and the optimal grouting quantity is evaluated. This site is suitable for conducting field tests to reduce the tail-grouting quantity of shield tunneling over a large range. In addition, the shield tunneling under different grouting parameters was simulated. Furthermore, we analyzed the evolution law of the surface settlement under different grouting parameters and obtained the difference in the settlement parameters for each construction stage. The results obtained indicate that the characteristics of the grout affect the development of the surface settlement. Therefore, reducing the setting time or increasing the initial strength of the grout could effectively suppress the development of surface subsidence. As the fill ratio decreases, the loose zone of the soil above the tunnel expands, and the soil deformation is easily transmitted to the surface. Meanwhile, owing to insufficient grout support, the lateral pressure on the tunnel segments is significantly reduced, and the segment moves considerably after being removed from the shield tail.