• Title/Summary/Keyword: soft core

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Acoustic Properties of Gassy Sediments: Preliminary Result of Jinhae Bay, Korea (가스함유퇴적물의 음향특성: 한국 진해만의 예비결과)

  • Kim, Gil-Young;Kim, Dae-Choul;Yeo, Jung-Yoon;Yoo, Dong-Geun
    • The Journal of the Acoustical Society of Korea
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    • v.26 no.1E
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    • pp.33-38
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    • 2007
  • Compressional wave velocity and shear wave velocity were measured for gassy sediments collected from Jinhae Bay, Korea. To distinguish inhomogeneities of gassy sediments, Computed Tomography (CT) was carried out for gassy sediment using CT Scanner. The cored sediments are composed of homogeneous and soft mud (greater than $8{\Phi}$ in mean grain size) containing clay content more than 50%. In depth interval of gassy sediments, compressional wave velocity is significantly decreased from 1480m/s to 1360m/s, indicating that the gas greatly affects compressional wave velocity due to a gas and/or degassing cracks. Shear wave velocity shows a slight increasing pattern from ${\sim}55\;m/s$ in the upper part of the core to ${\sim}58\;m/s$ at 320 cm depth, and then decreases to ${\sim}54\;m/s$ in the lower part of the core containing a small amount of gas. But shear wave velocity in the gassy sediments is slightly greater than that of non-gassy sediments in the upper part of the core. Thus, the Vp/Vs ratio is decreased (from 30 to 25) in gas charged zone. The Vp/Vs ratio is well correlated with shear wave velocity, but no correlation with compressional wave velocity. This suggests that low concentrations of gas have little affects on shear wave velocity. By CT images, the gas in the sediments is mostly concentrated around inner edge of core liner due to a long duration after sediment collection.

Arthroscopic assisted Core Decompression of Humeral Head Osteonecrosis - Technical Note - (상완 골두 골괴사증에서의 관절경하 핵심 감압술 - 수술 술기 -)

  • Cho, Chul-Hyun;Sohn, Sung-Won;Bae, Ki-Cheor;Kim, Dong-Hoo
    • Journal of the Korean Arthroscopy Society
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    • v.13 no.2
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    • pp.174-178
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    • 2009
  • Purpose: We introduce arthroscopic assisted core decompression for humeral head osteonecrosis. Operative technique: After diagnostic shoulder arthroscopy is performed using posterior and anterior portal, we make a 2 cm lateral skin incision approximately 3 cm distal to 1/3 of lateral margin of the acromion and place short gray cannula to prevent adjacent soft tissue injury when insert guide pin. Under C-arm fluoroscopic and arthroscopic guidance, 3 to 4 guide pins are inserted toward the necrotic area. Then we perform drilling using 7.0 mm reamer. Conclusion: We believe this technique is a less invasive approach and avoids the complications comparing to deltopectoral approach. Arthroscopic assisted core decompression is an effective procedure in management of early stage of the humeral head osteonecoris.

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Oral tissue response to soft tissue expanders prior to bone augmentation: in vitro analysis and histological study in dogs

  • Yoo, Jung Min;Amara, Heithem Ben;Kim, Min Kyoung;Song, Ju Dong;Koo, Ki-Tae
    • Journal of Periodontal and Implant Science
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    • v.48 no.3
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    • pp.152-163
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    • 2018
  • Purpose: To determine whether the swelling and mechanical properties of osmotic self-inflating expanders allow or not the induction of intraoral soft tissue expansion in dogs. Methods: Three different volumes (0.15, 0.25, and 0.42 mL; referred to respectively as the S, M, and L groups) of soft tissue expanders (STEs) consisting of a hydrogel core coated with a silicone-perforated membrane were investigated in vitro to assess their swelling behavior (volume swelling ratio) and mechanical properties (tensile strength, tensile strain). For in vivo investigations, the STEs were subperiosteally inserted for 4 weeks in dogs (n=5). Soft tissue expansion was clinically monitored. Histological analyses included the examination of alveolar bone underneath the expanders and thickness measurements of the surrounding fibrous capsule. Results: The volume swelling ratio of all STEs did not exceed 5.2. In tensile mode, the highest mean strain was registered for the L group ($98.03{\pm}0.3g/cm$), whereas the lowest mean value was obtained in the S group ($81.3{\pm}0.1g/cm$), which was a statistically significant difference (P<0.05). In addition, the S and L groups were significantly different in terms of tensile strength ($1.5{\pm}0.1g/cm$ for the S group and $2.2{\pm}0.1g/cm$ for the L group, P<0.05). Clinical monitoring showed successful dilatation of the soft tissues without signs of inflammation up to 28 days. The STEs remained volumetrically stable, with a mean diameter in vivo of 6.98 mm, close to the in vitro post-expansion findings (6.69 mm). Significant histological effects included highly vascularized collagen-rich fibrous encapsulation of the STEs, with a mean thickness of $0.67{\pm}0.12mm$. The bone reaction consisted of resorption underneath the STEs, while apposition was observed at their edges. Conclusions: The swelling and mechanical properties of the STEs enabled clinically successful soft tissue expansion. A tissue reaction consisting of fibrous capsule formation and bone loss were the main histological events.

Application of the SASW Method to the Evaluation of Grouting Performance for a Soft Ground of a Tunnel (터널 원지반의 그라우팅 보강 평가를 위한 SASW 기법의 적용)

  • 조미라;강태호
    • Journal of the Korean Geotechnical Society
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    • v.19 no.6
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    • pp.273-283
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    • 2003
  • Fissured rock and soft ground always suggest, problems in the construction of the underground space. The stress release of the weak underground material by opening the underground space with a soft ground, fissures and joints can lead to the failure of the opening. Grouting of the weak rock and the soft ground, which is a process of injecting some bonding agents into the soft ground, is one of the measures to reinforce the soft ground and to prohibit the failure of the underground construction due to the stress release. The proper installation of the grouting is essential to ensuring the safety of the tunneling operation, so that the evaluation of the grouting performance is very significant. The general procedure of evaluating the grouting is coring the grouted section and measuring the compression strength of the core. However, sometimes when the grouted section is at the crown of the tunnel and the grouting is installed at a wide section, the coring is not good enough. This study is oriented to propose a new and a non-destructive procedure of evaluating the grouting performance. The proposed method is based on the wave propagation of elastic waves, and evaluates the shear stiffness of the ground and investigates the anomalies such as voids and cracks. The SASW ( Spectral-Analysis-of-Surface-Waves) method is one of the candidate s to make the inspection of the pouting performance, and is adopted in this study. The practical grouting activity was monitored by SASW method, and the proposed method was applied to the inspection of the grouting performance to check the verification of the proposed method.

Laboratory Test and Field Study of Soft Ground Improvement Effect by Using Various PVDs (실내실험과 현장실험을 통한 다양한 PVD의 연약지반개량효과)

  • Shin, Eun-Chul;Nazarova, Zhanara
    • Journal of the Korean Geosynthetics Society
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    • v.7 no.2
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    • pp.15-21
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    • 2008
  • The advantages of prefabricated vertical drains over conventional sand drains include their relatively low costs, less disturbance to the soil mass, the easinees of installation, and their flexibility which ensures the integrity of the drains during installation. This study tested the change of discharge capacities with respect to the hydraulic gradients for each lateral pressure. From the test results, as increases the overburden pressure, the clay soil is being consolidated, and also lateral pressure to the PVD specimen is increased. Therefore, the discharge capacity is decreased. The size of opening space in the core of PVDs is proportionally related to the discharge capacity. The numerical analysis was performed with utilizing computer simulation with considering field conditions. The results of numerical analysis are compared well with the field measurements.

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A clinico-radiographic and histomorphometric analysis of alveolar ridge preservation using calcium phosphosilicate, PRF, and collagen plug

  • Tarun Kumar, AB;Chaitra, N.T.;Gayatri Divya, PS;Triveni, M.G.;Mehta, Dhoom Singh
    • Maxillofacial Plastic and Reconstructive Surgery
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    • v.41
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    • pp.32.1-32.7
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    • 2019
  • Background: Tooth extraction commonly leads to loss of residual alveolar ridge, thus compromising the room available for the implant placement. To combat the post-extraction alveolar loss, alveolar ridge preservation is practiced, with the advent of the biomaterial available. The purpose of this study was to assess the efficiency of calcium phosphosilicate biomaterial in alveolar ridge preservation. Twenty patients indicated for extraction were selected followed by socket grafting using calcium phosphosilicate. Implant placement was done 6 months postoperatively during which a core was harvested from the preserved sockets. Clinico-radiographic measurements of hard and soft tissues were taken at baseline and 6 months post-grafting. Results: There were no significant changes in the radiographic and soft tissue parameters while significant changes in hard tissue parameters with 1.9 mm (p = 0.013) gain in mid-buccal aspect and 1.1 mm (p = 0.019) loss in horizontal bone width were observed. The histomorphometric evaluation depicted the vital bone volume of 54.5 ± 16.76%, non-mineralized tissue 43.50 ± 15.80%, and residual material 2.00 ± 3.37%. Conclusion: The implants placed in these preserved ridges presented 100% success rate with acceptable stability after a 1-year follow-up, concluding calcium phosphosilicate is a predictable biomaterial in alveolar ridge preservation.

Improved Bridgeless Interleaved Boost PFC Rectifier with Optimized Magnetic Utilization and Reduced Sensing Noise

  • Cao, Guoen;Kim, Hee-Jun
    • Journal of Power Electronics
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    • v.14 no.5
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    • pp.815-826
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    • 2014
  • An improved bridgeless interleaved boost power factor correction (PFC) rectifier to improve power efficiency and component utilization is proposed in this study. With combined conventional bridgeless PFC circuit and interleaved technology, the proposed rectifier consists of two interleaved and magnetic inter-coupling boost bridgeless converter cells. Each cell operates alternatively in the critical conduction mode, which can achieve the soft-switching characteristics of the switches and increase power capacity. Auxiliary blocking diodes are employed to eliminate undesired circulating loops and reduce current-sensing noise, which are among the serious drawbacks of a dual-boost PFC rectifier. Magnetic component utilization is improved by symmetrically coupling two inductors on a unique core, which can achieve independence from each other based on the auxiliary diodes. Through the interleaved approach, each switch can operate in the whole line cycle. A simple control scheme is employed in the circuit by using a conventional interleaved controller. The operation principle and theoretical analysis of the converter are presented. A 600 W experimental prototype is built to verify the theoretical analysis and feasibility of the proposed rectifier. System efficiency reaches 97.3% with low total harmonic distortion at full load.

Value Structure of Experiential Rental Hanbok Companies Based on Means-end Chain Theory (수단-목적 사슬이론에 따른 체험용 대여한복업체의 가치구조)

  • Kim, Min Ji;Kim, Soon-Young
    • Journal of the Korean Society of Clothing and Textiles
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    • v.46 no.2
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    • pp.331-348
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    • 2022
  • This study explores the value structure of experiential rental Hanbok companies using the means-end chain theory. For this, soft laddering was conducted for nine experiential rental Hanbok companies located in Jeonju Hanok Village. Next, the value structure was created. The results are as follows. First, the elicited values are in the following order: "creation of wealth," "promotion of Korean culture," "aesthetic value," "self-actualization," "community development," and "transmission of tradition." Second, most attributes are connected to "creation of wealth." Third, "promotion of Korean culture" and "community development" are similar to Holden's instrumental values. Fourth, some attributes linked to "aesthetic value" express what the experiential rental Hanbok companies consider to be beautiful. Fifth, the companies pursue "company satisfaction" through "consumer satisfaction" and "company differentiation," which leads to "self-actualization" and "aesthetic value." Sixth, it seems that "transmission of tradition" can be achieved through "expertise/expert training," indicating that some companies think expertise is necessary for the transmission of Hanbok and do it. This study is significant because it is a new attempt to understand the core values of experiential rental Hanbok companies and provides insights into their growth.

Development of Static Rock Penetrometer for Locating Rock Stratum During Construction of Drilled Shafts (암반에 근입된 현장타설말뚝 시공시 선단부 강도확인을 위한 정적암반관입기 개발연구)

  • Nam, Moon-S.
    • Journal of the Korean Geotechnical Society
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    • v.26 no.9
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    • pp.71-74
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    • 2010
  • During construction of deep foundation in soft rock under varying soil properties, it is essential to locate the rock stratum, especially when drilling with slurry. When slurry is used for drilling, the bottom of the borehole cannot be seen, thereafter soil cuttings cannot be differentiated from soft rock cuttings. A new static rock penetrometer, known as Rock Penetrometer was developed during this study. It could be a simple mechanical device that is attached to the bottom of a Kelly bar which is used to attach drilling tools such as augers and core barrels while drilling. After its calibration in the laboratory, the performance of the static rock penetrometer was verified in the several field test sites.

On the Evaluation of Construction Standards Based on Seismic Velocities Obtained In-Situ and through Laboratory Rock Tests (현장 및 실내 측정 탄성파 속도에 근거한 암반평가 기준에 대한 고찰)

  • Lee, Kang Nyeong;Park, Yeon Jun
    • Tunnel and Underground Space
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    • v.27 no.4
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    • pp.230-242
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    • 2017
  • Seismic velocities measured from in-situ tests (n=177) and through rock core samples (n=1,035) are reviewed in light of construction standards, widely used standards as a first-hand approximation of rock classification solely based on seismic velocities. In-situ down hole tests and refraction survey for soft rocks showed seismic velocities of 1,400~2,900 m/s which is faster than those specified in construction standards. For moderate~ hard rocks, in-situ down hole tests and refraction survey showed 2,300~3,800 m/s which roughly corresponds with the range specified in the construction standards. A similar trend is also observed for seismic velocities measured from rock core samples. The observed differences between construction standards and seismic velocities can be explained in two ways. If construction standards are correct the observed differences may be explained with seismic velocities affected by underlying fast velocities and also possibly with selection of intact cores for velocity measurement. Alternatively, construction standards may have intrinsic problems, namely artificial discrete boundaries between soft rocks and moderate rocks, application of foreign standards without consideration of geologic setting and lack of independent verification steps. Therefore, we suggest a carefully designed verification studies from a test site. We also suggest that care must be exercised when applying construction standards for the interpretation and accessment of rock mass properties.