• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.4
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• pp.40-47
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• 2022

The present study aimed to examine the effectiveness of different techniques for controlling the diagonal cracks at the corners of openings on the strength, deformation, and crack propagation in reinforced concrete walls. The crack control strip proposed in this study, the conventional diagonal steel reinforcing bars, and stress-dispersion curved plates were investigated for controlling the diagonal cracks at the opening corners. An additional crack self-healing function was also considered for the crack control strip. To evaluate the volume change ratio and crack width propagation around the opening, downsized wall specimens with a opening were tested under the diagonal shear force at the opening corner. Test result showed that the proposed crack control strip was more effective in reducing the volume change and controlling the crack width around the opening when compared to the conventional previous methods. The crack control strip with crack healing feature displayed the superior performance in improving the strength of the wall and reducing the crack width while healing cracks occurred in the previous tests.

• Journal of the Korean Wood Science and Technology
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• v.10 no.3
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• pp.152-164
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• 1982

1. In order to make the improvement of plywood quality, this study has been made. The pretreatments applied to the veneers are as follows. a) The soaking treatment of the veneer in 30 percent methanol solution for 24 hours was applied to remove some resinous materials which may cause many stain discolouring on the face of finished plywood. b) The preservative treatment of the veneer in 2 percent malenit solution for 2 to 3 minutes was adopted to make resistance against decay and insect damages. c) The fire retardant treatment of the veneer in 40 percent ammonium phosphate solution for 2 hours was applied to give retardation effect against fire burning. 2. The results summarized in this study are as follows. a) One percent resinous materials was extracted, after the soaking of the veneers in 30 percent diluted methanol. b) No marks of the dirty stains of resinous materials on the face of the treated plywood was shown, although many quite dirty stains on the face of untreated plywood have contrary seen. c) However, the strip shear test strength of the treated plywood was not decreased. It means that there is no difference in the strength between the treated plywood and the untreated plywood. The strength values were 25.08 kg/$cm^2$ and 24.98 kg/$cm^2$, respectively. d) The strip shear test strength of plywood made of the treated veneers in 2 percent malenit solution was not decreased. e) The slight decrease of the strip shear test strength of the treated plywood made of the treated veneer in 40 percent ammonuim phosphate solution was shown. However, the remarkable difference of the fire retardation activities between the treated specimens and the untreated specimens has seen as in Table 10, that is, the fire proofed specimens had taken about 28 seconds to start to burn, while the untreated specimens had taken 15 seconds to reach to burning. This means that the fire retardation effect of the fire proofed plywood was greater than that of the unproofed plywood.

• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.299-305
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• 2008

The main goal of this study was to examine the shear behavior of reinforced concrete beams strengthened with CFRP strups. Seven rectangular beams were tested. The test variables were the configuration types, spacing length of CFRP strips and the amount of reinforced stirrups bars. From this experimental study, the shear capacity of beams strengthened with CFRP increased significantly compared to the beam without CFRP strip. Maximum increase of ultimate shear strength was found about 100% more than that of the beam without a CFRP strip and the CFRP strips attached in the shear region can resist the occurrence of the initial shear cracks and the propagation of major shear cracks. In this test, most of the shear strengthened beams failed suddenly due to the debonding of CFRP strips. A calculation of the shear strength of reinforced beams strengthened with CFRP strips based on the effective stresses was conducted and the comparisons were made with the test results.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.513-533
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• 1994

The smooth surface after polishing of composite resin contributes to the patient's comfort, and appearance and longevity of the restoration. This study was performed for the quantitative analysis of the effects of the various finishing and polishing instruments on the surface roughness and reflectivity of the microfill, and hybrid composite resins. Cylindrical specimens 2mm thick and 10mm in diameter of Silux Plus, Durafill VS ; Z100, Prisma TPH, Brilliant, and Herculite XR composite resin were polymerized under the matrix strip. 18 specimens for each composite resin materials were divided into 6 groups ; 5 experimental groups were abraded with # 600 sand paper to remove resin-rich layer, except control. Thereafter, using diamond bur(Mani Dia-Burs), carbide bur(E. T. carbide set 4159), rubber point(Composite polishing kit), aluminum-oxide disk(Sof-Lex disk), polishing paste(Enhance system) ; each specimen was polished to its best achievable surface according to manufacturer's directions. Final polished surfaces were evaluated for the surface roughness with profilometer(${\alpha}$-step 200, Tencor instruments, USA) and for the reflectivity with image analyser(Omniment Image Analyser, Buehler, USA). The results were as follows. 1. Polishing paste or aluminum-oxide disk finish in the microfill, and hybrid composite resins was as smooth as matrix strip finish on the surface roughness test. 2. Polishing paste or aluminum-oxide disk finish in the microfill ; polishing paste finish in the hybrid composite resins was as reflective as matrix strip finish on the refectivity test. 3. For the polishing paste, there were no significant differences between the composite resin materials on the surface roughness and refectivity tests. 4. For the aluminum-oxide disk, the best result was obtained with the microfill composite resin on the surface roughness and reflectivity test. 5. Diamond bur, carbide bur, and rubber point were inappropriate for the final polishing instruments.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.6
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• pp.102-112
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• 2012

Recently, the near surface mounted (NSM) FRP strengthening technique has been actively applied to deteriorated concrete structures for rehabilitation purposes. However, the use of this conventional NSM technique could be restricted due to the insufficient height or strength of the concrete cover. In this study, the stirrup-Cutting Near Surface Mounted(CNSM) technique was considered as an alternative, whereby NSM strips are placed at a deeper level, namely at the level of the main steel reinforcement. A flexural test of a concrete beam strengthened with CNSM technique was performed and the results were then compared to those for a concrete beam strengthened by the conventional NSM technique. The embedment length of the CFRP strips was varied in order to increase the effect of the anchoring depth of the NSM and CNSM CFRP strips in the beam specimens. From the results of the test, the beam with the CNSM CFRP strip showed typical structural behavior similar to that of the beam with the NSM CFRP strip. Moreover, there was no apparent structural degradation resulting from the stirrup partial-cutting. Consequently, the CNSM strengthening technique can be suitably utilized for extensively damaged concrete structures where it is difficult to apply the conventional NSM technique.

• Journal of the Korean GEO-environmental Society
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• v.4 no.1
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• pp.67-75
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• 2003

In this study, the steel strip reinforcement bolted with braced angles expected to mobilize skin friction resistance as well as bearing resistance is proposed. Laboratory pullout tests are conducted to investigate the characteristics of pullout behavior. From the test results, friction effects between soil and reinforcement are evaluated with the width of reinforcement, magnitude of surcharge, and existence of bearing resistance member. Further to analyze interference effects for bearing resistance member, pullout tests are also carried by varing the number, the location, and the spacing of braced angles. Based on the test results, pullout resistance factor is evaluated under the consideration of location of braced angles and the degree of interference for spacing ratio.

• Journal of Microbiology and Biotechnology
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• v.13 no.4
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• pp.509-516
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• 2003

A model system for the immnunochemical detection of Escherichia coli O157:H7 using a combined immunomagnetic separation (IMS) and test-strip liposome immunoassay (LIA) procedure was developed. Immunomagnetic beads coated with anti-E. coli O157 IgG antibodies were used to separate the E. coli O157 (including the H7 serotype) from culture. Immunoliposomes, whose surface was conjugated to goat anti-E. coli O157:H7 IgG and which encapsulated the marker dye, sulforhodamine B, were used as a detection label. The test strip, onto which antibodies to goat IgG were immobilized, was the immunosensor capturing immunoliposomes that did not bind to E. coli O157:H7 on the immunomagnetic bead-E. coli O157:H7 complexes. In experiments, pure cell culture suspensions of $10^5 E.$ coli O157:H7 organisms per ml produced a measurable signal inhibition, whereas a weak yet detectable signal inhibition occurred with $10^3CFU/ml$. The inhibition signals increased, when the incubation time for IMS was extended to 90 min and higher IgG-tag density (0.4mol%) was used on the liposomes. With 0.2 and 0.4mol% IgG-tagged liposomes, the IMS-LIA procedure showed more improved signal inhibitions than those of a direct (no IMS) LIA. The combined assay, which measures the instantaneous signal from immunoliposomes, can be completed within 90 min, making it significantly faster than conventional plating methods and enzyme-linked immunosorbent assay (ELISA). Accordingly, it is quite feasible to use the combined immunoassay format of IMS and dye-loaded immunoliposomes for the detection of E. coli O157:H7.

• Journal of the Korean Society of Safety
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• v.15 no.2
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• pp.111-117
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• 2000

In this study, the bearing capacity behavior of strip footing located above a continuous cavity in sand was investigated experimentally. The model footing test was performed in a model box made by using raining method in sand. The model footing test results were compared with those obtained from theoretically proposed equations. The results of the analysis indicate that there is a critical region under the footing. For strip footing, there exists a critical depth below which the presence of the cavity has negligible influence on the footing performance. Only when the cavity is located within this region will the footing performance be significantly affected by the presence of the cavity. The size of the critical region depends on several factors such as footing shape, soil property, cavity size and cavity shape. When the cavity is located within the critical region, the bearing capacity of the footing varies with various factors, such as the size and location of the cavity and the depth of foundation. Based on the experimental study, the following conclusions were induced. 1. The ultimate bearing capacity due to the eccentricity of a underground cavity increases at the rate of the small rather than that due to the depth of a underground cavity. This indicates that the bearing capacity of a strip footing is influenced on the depth rather than the eccentricity of a underground cavity. 2. The critical $depth(D/B)_{cr}$, by underground cavity in sand soil ground that is made by the relative density($D_r$)=55%, 65%, 75%, approaches a range of about 8~10 in case of W/B=1, and about 11~13 in case of W/B=2. 3. In case of the relative density($D_r$) 75%, the most outstanding differential settlement trend is shown in the depth of 4~8cm regardless of the size of cavity, namely, when the value of D/B is 1~2. Therefore, a underground cavity influences on not only the decrease of the bearing capacity but also the differential settlement of a strip footing.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.217-223
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• 2019

In this study, the acceleration changes of the surrounding ground when crushed stones were installed in a strip-type were analyzed using the 1-G shaking table test. The ground was constructed from clay, and the foundation was installed using crushed stone of strip-type form. The response acceleration and response spectrum for various input seismic motions were analyzed. The change in acceleration was examined according to the adjacent distance to the strip-type crushed stone foundation. In the Hachinohe seismic motion results, there was no significant decrease in acceleration, but the maximum response acceleration for the two seismic motions was inversely proportional to the distance from the crushed stone foundation. As a result of the response spectrum analysis, the attenuation period in the long period and the short period input wave were different from each other, and the change in response spectrum affected the maximum acceleration value. As the distance from the crushed stone foundation was increased, the attenuation was larger in the period between 0.08 and 0.5 sec in the Hachinohe seismic motion, the attenuation was larger in the period of less than 0.2 seconds in the Northridge seismic motion.

• Journal of Mechanical Science and Technology
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• v.17 no.3
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• pp.429-439
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• 2003

Counter-current two-phase flows of air- water in narrow rectangular channels with offset strip fins have been experimentally investigated in a 760 mm long and 100 mm wide test section with 3.0 and 5.0 mm gap widths. The two-phase flow regime, channel-average void fractions and two-phase pressure gradients were studied. Flow regime transition occurred at lower superficial velocities of air than in the channels without fins. In the bubbly and slug flow regimes, elongated bubbles rose along the subchannel formed by fins without lateral movement. The critical void fraction for the bubbly-to-slug transition was about 0.14 for the 3 mm gap channel and 0.2 for the 5 mm gap channel. respectively. Channel-average void fractions in the channels with fins were almost the same as those in the channels without fins. Void fractions increased as the gap width increased, especially at high superficial velocity of air. The presence of fins enhanced the two-phase distribution parameter significantly in the slug flow, where the effect of gap width was almost negligible. Superficial velocity of air dominated the two-phase pressure gradients. Liquid superficial velocity and channel gap width has only a minor effect on the pressure gradients.