• Geomechanics and Engineering
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• v.34 no.1
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• pp.103-113
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• 2023

This study focused on understanding the relationship between the design of a tunnel boring machine disc cutter ring and its rock-breaking efficiency, as well as the applicable conditions of different cutter ring types. The discrete element method was used to establish a numerical model of the rock-breaking process using disc cutters with different ring types to reveal the development of rock damage cracks and variation in cutter penetration load. The calculation results indicate that a sharp-edged (V-shaped) disc cutter penetrates a rock mass to a given depth with the lowest load, resulting in more intermediate cracks and few lateral cracks, which leads to difficulty in crack combination. Furthermore, the poor wear resistance of a conventional V-shaped cutter can lead to an exponential increase in the penetration load after cutter ring wear. In contrast, constant-cross-section (CCS) disc cutters have the highest quantity of crack extensions after penetrating rock, but also require the highest penetration loads. An arch-edged (U-shaped) disc cutter is more moderate than the aforementioned types with sufficient intermediate and lateral crack propagation after cutting into rock under a suitable penetration load. Additionally, we found that the cutter ring wedge angle and edge width heavily influence cutter rock-breaking efficiency and that a disc cutter with a 16 to 22 mm edge width and 20° to 30° wedge angle exhibits high performance. Compared to V-shaped and U-shaped cutters, the CCS cutter is more suitable for soft or medium-strength rocks, where the penetration load is relatively small. Additionally, two typical case studies were selected to verify that replacing a CCS cutter with a U-shaped or optimized V-shaped disc cutter can increase cutting efficiency when encountering hard rocks.

• Computers and Concrete
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• v.19 no.2
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• pp.211-216
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• 2017

Crack on concrete surface allows more rapid penetration of chlorides. Crack width and depth are dominant parameters for chloride behavior, however their effects on chloride penetration are difficult to quantify. In the present work, the previous anisotropic (1-D) model on chloride diffusion in concrete with single crack is improved considering crack shape and roughness. In the previous model, parallel-piped shape was adopted for crack shape in steady-state condition. The previous model with single crack is improved considering wedge shape of crack profile and roughness. For verifying the proposed model, concrete samples for nuclear power plant are prepared and various crack widths are induced 0.0 to 1.2 mm. The chloride diffusion coefficients in steady-state condition are evaluated and compared with simulation results. The proposed model which can handle crack shape and roughness factor is evaluated to decrease chloride diffusion and can provide more reasonable results due to reduced area of crack profile. The roughness effect on diffusion is evaluated to be 10-20% of reduction in chloride diffusion.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.1
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• pp.121-132
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• 1994

The aim of the present paper is to clarify the damage characteristics fur ship bottom stiffened platings in grounding. For this purpose, a series of tests are performed. A rigid wedge is quasi-statically pushed into the high tensile steel plates with two stiffeners. The aspect ratio of plates(a/B) is in the range from 1.0 to 2.5 and the thickness of plates is in the range from 3.4 to 7.0mm. Also other parameters, namely the shape of wedge tip, wedge angle and property/direction of stiffeners are varied. The test is carried out using the 100ton universal test machine. During the loading. both applied force and length of cutting(penetration) resulting in the grounding force-penetration response are measured.

• Restorative Dentistry and Endodontics
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• v.27 no.3
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• pp.257-269
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• 2002

Objective : The purpose of this study was to evaluate the resin infiltration into dentin of one-bottle adhesive systems and self-etching primer bonded to Class V cavities using confocal laser scanning microscope(CLSM). Material and Methods : Forty Class V cavities were prepared from freshly extracted caries-free Human teeth. These teeth were divided into two groups based on the presence of cervical abrasion: Group I, cervical abrasion : Group II, wedge-shaped cavity preparation. Resin-dentin interfaces were produced with two one-bottle dentin bonding systems-ONE COAT BOND(OCB; Coltene$^R$) and Syntac$^R$SPrint$^{TM}$(SS; VIVADENT)-, one self-etching priming system-CLEARFIL$^{TM}$ SE BOND (SB : KURARAY)- and one multi-step dentin bonding system-Scotchbond$^{TM}$Multi-Purpose (SBMP, 3M Dental Products)-as control according to manufacturers' instructions. Cavities were restored with Spectrum$^{R}$(Dentsply). Specimens were immersed in saline for 24 hours and sectioned longitudinally with a low-speed diamond disc. The resin-dentin interfaces were microscopically observed using CLSM. The quality of resin-infiltrated dentin layers were evaluated by five dentists using 0~4 scale. Results : Confocal laser scanning microscopal investigations using primer labeled with rhodamine B showed that the penetration of the primer occurred along the cavity margins. Statistical analysis using one-way ANOVA followed by Duncan's Multiple Range test revealed that the primer penetration of the group 2(wedge-shaped cavity preparation) was more effective than group 1(cervical abrasion) and that of the gingival interfaces was more effective than the occlusal interfaces. In the one-bottle dentin bonding systems, the resin penetration score of OCB was compatible to SBMP, but those of SS and self-etching priming system, SB were lower than SBMP.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.464-475
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• 2009

Electrical resistivity can be used for porosity estimation. In order to improve previously developed ERCP(Electrical Resistivity Cone Probe), 4ERP(4 Electrical Resistivity Probe), which has Wenner array at the tip of probes, has been developed. In properties of current flow Wenner array measures electrical properties of undisturbed area during penetration and relatively correct measurements are guaranteed without polarization. Furthermore, Wenner array equation can estimate electrical resistivity without extra calibration. 4ERP is developed into 2 types, penetration and fixation. Penetration type has wedge-shaped tip. Considering disturbance minimization, fixed type has plane tip. Fixed type 4ERP in consolidation cell measure electrical resistivity increment along porosity decrease, and penetration type 4ERP measured resistivity profile along the depth in chamber. Applying Archie's law, porosity profile was estimated with electrical resistivity. The tests result suggests that 4ERP can be new site investigation equipment with little disturbance.

• Journal of the Korean Geophysical Society
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• v.6 no.2
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• pp.79-87
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• 2003

An in-situ four-electrode contact resistivity probe system was designed, and field-tested in submarine sediments. Seismic survey was also performed to support and compare the results of electric survey. The probe was designed to be driven to selected depths below the seafloor using a Vibracore system. The four insulated electrodes were, spaced equidistant across the wedge, were extended beyond the probe tip to minimize effects of sediment disturbance by the wedge insertion. In-situ measurements of resistivity were recorded on board by precision electronic equipment consisting of signal generators and processors, and by temperature- monitoring systems. Overall limits of uncertainty at respective depths below the seafloor are up to ±10% of the measured values. Best estimates of conductivity are considered to be ±3 percent of the reported values. Resistivity measurements were made at six sites in carbonate sediments to a maximum depth of penetration of about 5 m. Average values of conductivity range between 0.88 and 1.21 mho/m. The results show the seabed is composed of alternating layers of relatively high-conductivity material (0.8 to 1.4 mho/m) in thicknesses of more or less one meter and layers about 30 cm thick having relatively low conductivities (0.4 to 0.8 mho/m).

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.719-724
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• 2001

In this study, wedge splitting tensile test(WST) using dye penetration method was carried out to investigate cracking criterion and fracture characteristics of concrete. For the this purpose, three levels of compressive strength of 180, 300 and 600 kgf/$\textrm{cm}^2$ and five testing age of 1, 3, 7, 14 and 28 days were selected as test variables. The specimen was loaded in a controlled manner and then dye was inserted at the load of 40%, 70% of the presumed peak load and at the load of 90% just after peak load. The fracture process zone was measured at each load step of a specimen. Test results were compared with analytic results by linear elastic fracture mechanics(LEFM) and numerical results through fictitious crack model(FCM) and finite element method(FEM).

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.56-62
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• 2000

The purpose of this study was to assess the effects of restorative materials on the marginal leakage of wedge-shaped class V cavity. The study was performed in vitro in 25 defect-free permanent, extracted teeth. Wedge-shaped class V cavities were prepared and then the teeth were randomly selected and restored according to the following. Group A : restoration with Tetric Ceram(composite resin) Group B : restoration with Tetric flow(flowable resin) Group C : restoration with Compoglass after acid etching(compomer) Group D : restoration with Compoglass(compomer) Group E : restoration with Fuji II LC improved(resin-modified GIC) After thermocycling, the specimens were immersed in 5% basic fuchsin solution for 6 hours and sectioned longitudinally through the center of the restoration. The degree of marginal leakage was measured as the extent of dye penetration under the stereomicroscope. The data were analysed using one-way ANOVA. When significant differences found, multiple comparisons were made using Duncan's Multiple Range Test. The results were as follows: 1. The occlusal margins of all groups except for Fuji II LC improved showed lesser leakage than gingival margins and there was statistically significant difference(p<0.05). 2. At the occlusal margins, group A, B showed same marginal leakage scores, and others were decreased as group C, D, E in that order. There were statistically significant difference between group A, Band group D, E, group C and group E(p<0.05). 3. At the gingival margins, group B, C showed same marginal leakage scores, and others were decreased as group A, D, E in that order. But there was statistically significant difference between group B, C and group E(p<0.05). 4. In the Compoglass restoration, acid-etching technique was beneficial for marginal sealing ability at all of margins. But there was no statistically significant difference (p>0.05). In the restorations for wedge-shaped class V cavities, resin restoration with acid etching technique is recommended.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.3C
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• pp.127-136
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• 2009

The objective of this study is the development and verification of the 4-electrode resistivity probe (4ERP) for the estimation of electrical properties of the saturated soils. The 4ERPs with wedge and plane types are manufactured to obtain the electrical resistivity without polarization at the electrodes by using Wenner array. The wedge type is for the penetration into the soil samples and the plane type is for the installation into the cells used for the laboratory tests. The consolidation tests are carried out by using 6 types of glass beads and 3 types of sands in size. The test results show that the electrical resistivity increases with a decrease in the porosity, and the constant m used in Archie's law is dependent on the particle shape rather particle size. The one dimensional liquefaction tests show that the porosity obtained by the 4ERP is similar to that determined by the volume fraction. The penetration of the 4ERP into the large scale calibration chamber produces the resistivity profiles. This study demonstrates that the 4ERP may effectively estimate the porosity of the saturated soils.

• Structural Engineering and Mechanics
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• v.18 no.4
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• pp.475-491
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• 2004

Anchorage devices play an important role in post-tensioned bridge structures since they must sustain heavy loads in order to permit the transfer of the prestressing force to the structure. In external prestressing, the situation is even more critical since the anchorage mechanisms, with the deviators, are the only links between the structure and the tendons throughout the service life of the structure. The behaviour of anchorage devise may be studied by using the finite element method. To do so, each component of the anchorage must be adequately represented in order to approximate the anchor mechanism as accurately as possible. In particular, the modelling of the jaw/tendon device may be carried out using the real geometry of these two components with an appropriate constitutive contact law or by replacing these components by a single equivalent. This paper presents the numerical study of a mono-strand anchorage device. The results of a comparison between two different representations of the jaw/tendon device, either as two distinct components or as a single equivalent, will be examined. In the double-component setup, the influence of the wedge configuration composing the jaw, and the influence of lubrication of the anchor, will be assessed.