• Title, Summary, Keyword: range of confinement

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Size effect in concrete blocks under local pressure

  • Ince, R.;Arici, E.
    • Structural Engineering and Mechanics
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    • v.19 no.5
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    • pp.567-580
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    • 2005
  • Numerous tests on concrete structure members under local pressure demonstrated that the compressive strength of concrete at the loaded surface is increased by the confinement effect provided by the enveloping concrete. Even though most design codes propose specific criteria for preventing bearing failure, they do not take into consideration size effect which is an important phenomenon in the fracture mechanics of concrete/reinforced concrete. In this paper, six series of square prism concrete blocks with three different depths (size range = 1:4) and two different height/depth ratios of 2 and 3 are tested under concentrated load. Ultimate loads obtained from the test results are analysed by means of the modified size effect law (MSEL). Then, a prediction formula, which considers effect of both depth and height on size effect, is proposed. The developed formula is compared with experimental data existing in the literature. It is concluded that the observed size effect is in good agreement with the MSEL.

Ducitility Estimation of Exterior Beam-Column Joints using High-Strength Concrete (고강도 철근 콘크리트 보-기둥 접합부의 연성평가)

  • 장극관;서대원;황정현
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.415-418
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    • 1999
  • This paper presents a study in the ductility of reinforced concrete beam-column-slab joints Three assemblies were designed 2/3 scale (f'c=240kg/$\textrm{cm}^2$, f'c=700kg/$\textrm{cm}^2$) and tested to investigate seismic behavior. From the test results, 1) flexural cracks emerge to inside of beam deeply for high strength concrete member, 2) the high-strength specimens degraded in stiffness and strength, and unstable hysteretic behaviors were observed, owing to the brittleness of high-strength concrete beyond its range. 3) The confinement provided by the additional hoops to the column bar is probably the main reason for this improvement in behavior.

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Synthesis of Ultra-small PbS Nanocrystal Quantum Dots for Energy Applications

  • Choe, Hye-Gyeong;Jeong, So-Hui
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.535-535
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    • 2012
  • We present a new synthetic route and characterization for ultra small sized PbS quantum dots in extreme quantum confinement with 1.5 to 2.9 nm in diameter. We obtained a series of nanocrystals with first absorption wavelength ranging from 580 to 820 nm (2.1-1.5 eV). To get this result, PbS quantum dots size is finely controlled by adjusting the growth temperature in the range of $70-95^{\circ}C$. We demonstrate that photoluminescence (PL) shows a red shift with respect to the first absorption peak that increases with decreasing PbS quantum dots size and ranges from about 500 to 125 meV as the mean PbS quantum dots diameter increases from 1.5 to 2.9 nm. We further created the assembled PbS quantum dot solids and investigated the transport properties for energy applications.

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Dependency of Phonon-limited Electron Mobility on Si Thickness in Strained SGOI (Silicon Germanium on Insulator) n-MOSFET (Strained SGOI n-MOSFET에서의 phonon-limited전자이동도의 Si두께 의존성)

  • Shim Tae-Hun;Park Jea-Gun
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.42 no.9
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    • pp.9-18
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    • 2005
  • To make high-performance, low-power transistors beyond the technology node of 60 nm complementary metal-oxide-semiconductor field-effect transistors(C-MOSFETs) possible, the effect of electron mobility of the thickness of strained Si grown on a relaxed SiGe/SiO2/Si was investigated from the viewpoint of mobility enhancement via two approaches. First the parameters for the inter-valley phonon scattering model were optimized. Second, theoretical calculation of the electronic states of the two-fold and four-fold valleys in the strained Si inversion layer were performed, including such characteristics as the energy band diagrams, electron populations, electron concentrations, phonon scattering rate, and phonon-limited electron mobility. The electron mobility in an silicon germanium on insulator(SGOI) n-MOSFET was observed to be about 1.5 to 1.7 times higher than that of a conventional silicon on insulator(SOI) n-MOSFET over the whole range of Si thickness in the SOI structure. This trend was good consistent with our experimental results. In Particular, it was observed that when the strained Si thickness was decreased below 10 nm, the phonon-limited electron mobility in an SGOI n-MOSFT with a Si channel thickness of less than 6 nm differed significantly from that of the conventional SOI n-MOSFET. It can be attributed this difference that some electrons in the strained SGOI n-MOSFET inversion layer tunnelled into the SiGe layer, whereas carrier confinement occurred in the conventional SOI n-MOSFET. In addition, we confirmed that in the Si thickness range of from 10 nm to 3 nm the Phonon-limited electron mobility in an SGOI n-MOSFET was governed by the inter-valley Phonon scattering rate. This result indicates that a fully depleted C-MOSFET with a channel length of less than 15 m should be fabricated on an strained Si SGOI structure in order to obtain a higher drain current.

Accuracy and Clinical Outcomes of Ultrasound-guided Glenohumeral joint Injection: Acromioclavicular Approach in Patients with Adhesive Capsulitis (초음파를 이용한 견관절 관절강내 주사의 정확성과 임상적 결과: 유착성 관절낭염 환자의 견봉 쇄골 접근법)

  • Lhee, Sang-Hoon;Hwang, Seok-Min
    • The Journal of Korean Orthopaedic Ultrasound Society
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    • v.5 no.1
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    • pp.9-14
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    • 2012
  • Purpose: The purpose of the study was to evaluate the accuracy and clinical outcome of ultrasound-guided glenohumeral joint steroid injection on adhesive capsulitis. Materials and Methods: Patients who were diagnosed as adhesive capsulitis by MRI and physical examination and did not improve their symptom with physical therapy and NSAIDS treatment more than 6 months were included in the study. Patients who showed any other shoulder pathology or history if trauma were excluded from the study. 33 patients including 15 males and 18 females were enrolled in the study, the average age being 55.1 (age 42~72). Cocktail of steroid, lidocaine, saline and contrast medium injected inside shoulder glenohumeral joint using novel approach (which we called acromioclavicular approach) under ultrasound guidance. Clinical outcome was measured through passive range of motion and VAS scoring system. Results: Based on radiographic findings, cases were classified according to the leakage of contrast medium; perfect confinement of contrast-medium inside the capsule, partial leakage of the medium and contrast-medium found at outside the joint. Total 25 cases (76%) out of 33 cases showed perfect confinement of contrast-medium inside the glenohumeral joint. Partial leakage was observed in 6 cases (18%), and contrast medium was observed outside of the glenohumeral joint in 2 cases (6%). Perfect-confinement group showed $111^{\circ}$($80{\sim}140^{\circ}$) of forward flexion and $48^{\circ}$($0{\sim}90^{\circ}$) of external rotation before injection, and improved to $134^{\circ}$($90{\sim}150^{\circ}$) of forward flexion and $70^{\circ}$($30{\sim}90^{\circ}$) of external rotation after injection (p<0.01). Partial leakage showed $120^{\circ}$($90{\sim}150^{\circ}$) of forward flexion and $70^{\circ}$($10{\sim}90^{\circ}$) of external rotation before injection, and improved to $139^{\circ}$($135{\sim}140^{\circ}$) of forward flexion and $78^{\circ}$($50{\sim}90^{\circ}$) of external rotation after injection (p<0.01). VAS score improved from 7.1 (score 3~9) to 2.6 (score 0~5) (p<0.01) in perfect confinement group, from 7.5 (score 7~9) to 3.3 (score 2~4) (p<0.01) in partial leakage group. Two group showed no significant difference. Conclusion: Accuracy of Acromioclavicular approach was 94% which is better than any other methods published so far. Partial leakage of the injection material did not show inferior result compared to perfect injection.

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Hole Mobility Enhancement in (100)- and (110)-surfaces of Ultrathin-Body Silicon-on-Insulator Metal-Oxide-Semiconductors (Ultrathin-Body SOI MOSFETs에서 면방향에 따른 정공의 이동도 증가)

  • Kim, Kwan-Su;Koo, Sang-Mo;Chung, Hong-Bay;Jung, Jong-Wan;Cho, Won-Ju
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.7-8
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    • 2007
  • We investigated the characteristics of UTB-SOI pMOSFETs with SOI thickness ($T_{SOI}$) ranging from 10 nm to 1 nm and evaluated the dependence of electrical characteristics on the silicon surface orientation. As a result, it is found that the subthreshold characteristics of (100)-surface UTB-SOI pMOSFETs were superior to (110)-surface. However, the hole mobility of (110)-surface were larger than that of (100)-surface. The enhancement of effective hole mobility at the effective field of 0.1 MV/ccm was observed from 3-nm to 5-nm SOI thickness range.

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The Genetic and Non-Genetic Aspects of Leg Weakness and Osteochondrosis in Pigs - Review -

  • Fukawa, K.;Kusuhara, S.
    • Asian-Australasian Journal of Animal Sciences
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    • v.14 no.1
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    • pp.114-122
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    • 2001
  • Leg weakness in pigs is one of the most serious problems in the pig industry. Leg weakness is responsible for an increase in the rate of culling of breeding pigs, which results in economic loss in the pig industry. Many researchers have investigated the cause of leg weakness, and that of osteochondrosis, in pigs, as well as in other mammals. For evaluating leg weakness, subjective scoring criteria have been applied, but the scoring systems varied widely. Subjective scoring systems have also been used in evaluating osteochondrosis lesions in leg joints. The lesions were scored optically, radiographically and histologically. Leg weakness and osteochondrosis are to some extent heritable traits. The heritability of leg weakness and joint lesion scores was found to range from 0.01 to 0.42. Leg weakness and osteochondrosis are associated with production traits (lean percentage and back fat depth). Nutritional aspects of leg weakness and osteochondrosis have also been extensively studied. Although the energy level of the diet may affect leg weakness and osteochondrosis, other nutritional factors seem to have very little effect. Confinement conditions also have an effect on leg weakness and osteochondrosis. Although studied extensively, the cause and etiology of leg weakness and osteochondrosis remain uncertain. It could be that there are multiple causes of leg weakness.

Vector Passive Harmonic Mode-locking Fiber Laser Based on Topological Insulator Bi2Se3 Interacting with Fiber Taper

  • Li, Jian Ping
    • Journal of the Optical Society of Korea
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    • v.20 no.1
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    • pp.135-139
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    • 2016
  • I propose a vector passive harmonic mode-locked fiber laser based on topological insulator Bi2Se3 interacting with a fiber taper with a diameter of 7 μm. The particles of topological insulator are deposited uniformly onto the fiber taper with light pressure effect. By incorporating the fabricated saturable absorber into an Er-doped fiber laser cavity, stable mode-locked fiber is obtained. Due to the intense evanescent field of the fiber taper, strong confinement of light enhances the nonlinearity of the laser cavity, and passive harmonic mode-locking is performed. I observe a maximum harmonic mode-locking of 356th, corresponding to a frequency of 3.57 GHz. The pulse duration is 824 fs, and the full width at half maximum of the spectrum is about 8.2 nm. The polarization dependent loss of the saturable absorber is ~ 2.5 dB in the wavelength range of the C band. As the cavity contains no other polarization dependent device, the mode-locked laser is functioning in the vector state. The harmonic order vs pump power is investigated. To the best of our knowledge, this report is the highest frequency mode-locked fiber laser based on Bi2Se3. Experimental results indicate that the topological insulator Bi2Se3 functioning with a thin fiber taper is effective for vector harmonic mode-locking.

Behavior of circular thin-walled steel tube confined concrete stub columns

  • Ding, Fa-xing;Tan, Liu;Liu, Xue-mei;Wang, Liping
    • Steel and Composite Structures
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    • v.23 no.2
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    • pp.229-238
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    • 2017
  • This paper presents a combined numerical and theoretical study on the composite action between steel and concrete of circular steel tube confined concrete (STCC) stub columns under axial compressive loading with a full theoretical elasto-plastic model and finite element (FE) model in comparison with experimental results. Based on continuum mechanics, the elasto-plastic model for STCC stub columns was established and the analysis was realized by a FORTRAN program and the three dimensional FE model was developed using ABAQUS. The steel ratio of the circular STCC columns were defined in range of 0.5% to 2% to analyze the composite action between steel tube and concrete, and make a further study on the advantages of the circular STCC columns. By comparing the results using the elasto-plastic methods with the parametric analysis result of FE model, the appropriate friction coefficient between the steel tube and core concrete was defined as 0.4 to 0.6. Based on ultimate balance theory, the formula of ultimate load capacity applying to the circular STCC stub columns was developed.

Preparation and Characterization of Surface Capped CdSe Nanoparticles from an Aqueous Solution (수용액으로부터 표면 수식된 CdSe 나노 입자의 제조 및 특성)

  • Kim, Shin-Ho;Lee, Yoon-Bok;Kim, Yong-Jin;Kim, Yang-Do;Kim, In-Bae
    • Korean Journal of Materials Research
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    • v.16 no.11
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    • pp.663-667
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    • 2006
  • CTAB(cetyltrimethylammonium bromide)-capped CdSe nanoparticles were prepared by using a 4 : 1(v/v) distilled water-isopropyl alcohol mixture. The cadmium chloride and sodium selenosulfate were used as the cadmium and selenium source. By the analysis of XRD and XPS, the resultant particle was confirmed to be cubic CdSe phase. TEM image showed CdSe nanoparticles with empty core. The CTAB-capped sample showed an maximum absorption at 418nm, blue-shifting compared with bulk CdSe, which indicated stronger quantum confinement effect compared with uncapped sample. From FT-IR analysis, it was found that the presence of the new peaks in the $850{\sim}1250cm^{-1}$ range indicated the existence of chemical bonding between CTAB and surface of CdSe nanoparticles. Also TG analysis indicated that there were two weight-loss steps for the CTAB-capped CdSe nanoparticles. It was suggested that CTAB played a significant role in protecting CdSe nanoparticles.