Sc Site Research Articles

Soft-x-ray-induced ionization and fragmentation dynamics of Sc3N@C80 investigated using an ion-ion-coincidence momentum-imaging technique

The fragmentation dynamics of an endohedral fullerene, $\mathrm{S}{\mathrm{c}}_{3}\mathrm{N}@{\mathrm{C}}_{80}$, after absorption of a soft-x-ray photon, has been studied with an ion-ion-coincidence momentum-imaging technique. Molecular inner-shell ionization at 406.5 eV, targeting the Sc ($2p$) shell of the encapsulated $\mathrm{S}{\mathrm{c}}_{3}\mathrm{N}$ moiety and the C ($1s$) shell of the ${\mathrm{C}}_{80}$ cage, leads to the cage fragmentation through evaporation of ${\mathrm{C}}_{2}$, emission of small molecular carbon ions (${\mathrm{C}}_{n}{}^{+}$, $n\ensuremath{\le}24$), and release of Sc and Sc-containing ions associated with the carbon cage opening or fragmentation. The predominant charge states of Sc and Sc-containing ionic fragments are $+1$ despite an effective Sc valence of 2.4, indicating that charge transfer or redistribution plays an important role in the fragmentation of the encaged $\mathrm{S}{\mathrm{c}}_{3}\mathrm{N}$. Sequential emission of two out of the three Sc atoms of the encaged moiety, via Coulomb explosion in the form of $\mathrm{S}{\mathrm{c}}^{+}$ or Sc-containing ions, is significant. We also find that the resonant excitation of the Sc ($2p$) shell electrons significantly increased the yield of the parent $\mathrm{S}{\mathrm{c}}_{3}\mathrm{N}@{\mathrm{C}}_{80}$ and its fragment ions, partially attributed to the collision of the energetic Auger electrons from the Sc site with the carbon cage.

Two Cl Ions and a Glu Compete for a Helix Cage in the CLC Proton/Cl− Antiporter

The ubiquitously expressed CLC chloride transporters are involved in a great variety of physiological functions. The CLC protein fold is shared by Cl− channels and 2Cl−:1H+ antiporters. The antiporters pump three charges per cycle across the membrane with two Cl ions moving in the opposite direction of one proton. Multiconformational continuum electrostatics was used to calculate the coupled thermodynamics of the protonation of the extracellular-facing gating Glu (Ex) and Cl− binding to the external (Sx) and central (Sc) sites in CLC-ec1, the Escherichia coli exchanger. Sx, Sc, and Ex are buried within the protein where the intersection of two helix N-termini creates a region with a strong, localized positive potential for anion binding. Our chemical potential titrations describe the thermodynamic linkage for binding the Cl− to each site and protons to Ex. We find that the 2Cl−:1H+ binding stoichiometry is a result of Cl− binding to Sx requiring H+ binding to Ex, whereas Cl− binding to Sc does not lead to proton uptake. When Sx binds a Cl−, the protonated Ex moves upward, out of the positive helix cage. The increasing Ex proton affinity on binding the first Cl− reduces the cost of binding the second Cl− at either Sx or Sc. Despite the repulsion among the anions, the lowest energy states have two anions bound in the helix cage. The state with no Cl− is not favored electrostatically, but relies on Ex blocking Sx and on the central residues Y445 and S107 blocking Sc.

Electronic structure, photoluminescence and phosphorescence properties in BaSc2Si3O10:Eu2+, RE3+ (RE3+ = Nd3+, Tm3+, Dy3+ and Tb3+) phosphors

Novel long lasting phosphorescence materials BaSc2Si3O10:Eu2+, RE3+ (RE3+ = Nd3+, Tm3+, Dy3+ and Tb3+) are designed and prepared by a solid state reaction. According to the density functional theory calculations, the conduction band is mostly composed of Sc 3d states, and Ba states have almost no contribution to the conduction band. Their photoluminescence emission spectra show a broad asymmetric blue emitting band peaking at about 443nm, attributed to the 5d-4f transitions of Eu2+ ion occupying Ba and Sc site respectively. According to the analysis on electronic structure and optical properties of the phosphors, it is believed that due to the special form of conduction band and the occupying situation of emission center, only the Eu2+ ion occupying the Sc site is involved in the long lasting phosphorescence process, resulting in the interesting phenomenon that the blue emitting phosphors show green phosphorescence. Additionally, the experimental results show that co-doping the trivalent rare earth ions, especially Nd3+ or Dy3+ ions, can improve the long lasting phosphorescence performance effectively in BaSc2Si3O10:Eu2+ system. This work shows up an interesting phosphorescence phenomenon, and provides a direct experimental evidence that conduction band plays an important role in the long lasting phosphorescence process.

Solid-State NMR Spectroscopy Proves the Presence of Penta-coordinated Sc Sites in MIL-100(Sc).

Advanced solid-state NMR methods and first-principles calculations demonstrate for the first time the formation of penta-coordinated scandium sites. These coordinatively unsaturated sites were shown during the thermal activation of scandium-based metal-organic frameworks (MOFs). A 45 Sc NMR experiment allows their specific observation in activated Sc3 BTB2 (H3 BTB=1,3,5-tris(4-carboxyphenyl)benzene) and MIL-100(Sc) MOFs. The assignment of the ScO5 groups is supported by the DFT calculations of NMR parameters. The presence of ScO5 Lewis acid sites in MIL-100(Sc) explains furthermore its catalytic activity. The first NMR experiment to probe 13 C-45 Sc distances is also introduced. This advanced solid-state NMR pulse sequence allows the demonstration of the shrinkage of the MIL-100(Sc) network when the activation temperature is raised.

Upconversion luminescence of CsScF4 crystals doped with erbium and ytterbium

Tetragonal CsScF4 crystals doped with (5 at.%) Er and Er/Yb (0.5 at.%/5 at.%) are grown and their crystal structure is determined to belong to Pmmn space group. Er and Yb ions are shown to occupy distorted octahedral Sc sites with the center of inversion. Bright visible upconversion luminescence was observed under 970–980 nm pumping with red (4F9/2), yellow (4S3/2) and green (2H11/2) bands of comparable intensity. UCL tuning curves maximize at 972 nm (CSF:Er) and at 969.7 nm (CSF:Er,Yb) pumping wavelengths. Different ratios between yellow-green and red luminescence intensities in CSF:Er and CSF:Er, Yb are explained by contribution of cross-relaxation in CSF:Er UCL. UC in CSF:Er is a three stage process while UC in CSF:Er, Yb is a two stage process. The peculiarities of power dependences are explained by the power-dependent repopulation between starting levels of UC.

Spectroscopic properties and laser performances of Yb:LGSB nonlinear optical crystal

Czochralski growth along with linear optical characterizations and near-infrared laser performances of ytterbium doped lanthanum and gadolinium scandium borate crystals (LaxGdYScZYbw(BO3)4 with x + y + z + w = 4) with acentric huntite-type structure are presented in this paper. Low-temperature spectroscopy analyses reveal two insertion sites for Yb3+ ions: a main one in Sc sites and the other one in lanthanide site. While absorption cross-section spectrum reveals broad bands with a maximum value of 7.8 × 10−21 cm2 at 981.5 nm for the σ state of polarization, the emission cross-section spectrum presents low anisotropy between the two polarization states over 1060 nm. Best laser performance is obtained in continuous-wave operation mode with 0.94W at 1070 nm for a 12.9-at% doped crystal.

First-principles calculation of point-defective structures of B2-NiSc intermetallics

ABSTRACTA pseudo-potential plane-wave method based on first principles was used to calculate the physical parameters of B2-NiSc intermetallics and the geometrical, energetic, and electronic structures of point defects. The possible types of point defects in B2-NiSc intermetallics were analyzed and predicted by comparing the formation enthalpy and formation energy for different kinds of point defect structures. The results show that Ni vacancy defects and Ni anti-position defects are the main point defects in the B2-NiSc intermetallics, and that these point defects emerge as double vacancy defects or double anti-position defects. When the double Ni atoms at Sc sites are in the first nearest neighborhood, the point defect structures are found to be the most stable. An analysis of the electronic structure of NiSc point defects shows that the Ni anti-position defect is more stable than the Sc vacancy defect in the Ni-rich alloy, and the Ni vacancy defect is more stable than the Sc anti-position defect in the Sc-rich alloy. These results are consistent with the energy calculation. Through analysis of C11–C12, G/B and Poisson's ratio, it was found that the NiSc point defect has little effect on crystal plasticity, and that the VNi point defect improves crystal plasticity.

METCAM/MUC18 is a novel tumor and metastasis suppressor for the human ovarian cancer SKOV3 cells.

BackgroundIncreased expression of METCAM/MUC18, a trans-membrane cell adhesion molecule in the Ig-like gene superfamily, has been associated with the malignant progression of epithelial ovarian carcinomas. To investigate if this is a fortuitous correlation or if METCAM/MUC18 actually plays a role in the progression of the cancer, we tested effects of enforced expression of METCAM/MUC18 on in vitro behaviors, in vivo tumorigenesis, and in vivo malignant progression of human ovarian cancer SK-OV-3 cells, which minimally expressed this protein.MethodsFor in vitro and in vivo tests, we transfected human METCAM/MUC18 cDNA gene into SK-OV-3 cells in a mammalian expression vector pcDNA3.1+ and obtained G418-resistant (G418R) clones, which expressed various levels of human METCAM/MUC18. To mimic physiological situations, we used pooled METCAM/MUC18-expressing and control (vector) clones for testing effects of human METCAM/MUC18 over-expression on in vitro motility and invasiveness, and on in vivo tumor formation and metastasis in female athymic nude mice. Effects of METCAM/MUC18 on the expression of various downstream key factors related to tumorigenesis were also evaluated by Western blot analyses.ResultsThe over-expression of METCAM/MUC18 inhibited in vitro motility and invasiveness of SK-OV-3 cells. SK-OV-3 cells of the control (vector) clone (3D), which did not express human METCAM/MUC18, supported the formation of a solid tumor after SC injection of the cells at dorsal or ventral sites and also formation of solid tumor and ascites after IP injection in the intraperitoneal cavity of nude mice. In contrast, SK-OV-3 cells from the METCAM/MUC18-expressing clone (2D), which expressed a high level of METCAM/MUC18, did not support the formation of a solid tumor at SC sites, or formation of ascites in the intraperitoneal cavity of nude mice. Expression levels of downstream key factors, which may affect tumor proliferation and angiogenesis, were reduced in tumors induced by the METCAM/MUC18-expressing clone (2D).ConclusionsWe conclude that increased human METCAM/MUC18 expression in ovarian cancer SK-OV-3 cells suppressed tumorigenesis and ascites formation in nude mice, suggesting that human METCAM/MUC18 plays a suppressor role in the progression of ovarian cancer, perhaps by reducing proliferation and angiogenesis.

Enhanced red upconversion emission, magnetoluminescent behavior, and bioimaging application of NaSc0.75Er0.02Yb0.18Gd0.05F4@AuNPs nanoparticles.

The present study reports significant enhancement in the red upconversion emission of Er(3+) in NaSc0.8Er0.02Yb0.18F4 upconversion nanoparticles (UCNPs), via a two step process, (i) codoping of Gd(3+) ion at Sc(3+) site and (ii) attaching gold nanoparticles (AuNPs) at the surface of these codoped nanostructures, and further probes the use of these Gd:UCNPs@AuNPs for bioimaging application. The Gd(3+) codoping tailors the particle size (reduces) of UCNPs and bring out Er(3+)-Yb(3+) ion pair in close proximity, which promotes the cross relaxation mechanism and boosts the population in red emitting level (4)F9/2. Further, attachment of AuNPs on the surface of UCNPs gives 2-fold advantages, that is, reduction in green band (through resonance energy transfer with efficiency 31.54%) and enhancement in red band (through plasmonic effect). It gives red to green (R/G) ratio nearly 20:1 (almost single band red UC), which is quite promising for imaging application. In addition to this, codoping of Gd(3+) enhances the magnetic moment appreciably and the obtained magnetic moment for NaSc0.75Er0.02Yb0.18Gd0.05F4 UCNPs (∼1.7 emu/g) is close to the reported values for bioseparation in case of NPs. This shows the potential of the material for multimodal (optical and magnetic both) imaging application. These magnetoluminescence particles were found safe up to 1 mg/mL dose as assessed by cytotoxicity measurement in human cervical cancer (HeLa) and lung cancer (A549) cells. Ultrafine nanoparticles, transparent, and stable colloidal solution and the unique red UC emission endow these NPs as optical probe for imaging applications.

Subway construction activity influence on polycyclic aromatic hydrocarbons in fine particles: Comparison with a background mountainous site

Intensive construction activities worsened the surrounding atmospheric environment in China. Eighteen polycyclic aromatic hydrocarbons (PAHs) in fine particles (PM2.5) were collected at a subway construction site (SC) of Nanjing and compared with a regional background mountainous site (BM) to examine the influence of anthropogenic activities on concentrations, sources and health risks of PAHs. Average PAH concentrations at SC were higher than BM at a factor of about 5.9. All PAH species at SC were higher than BM, with the SC/BM ratios ranging from 1.3 (NaP) to 10.3 (BaP). PAH profiles differed for the two sites. The SC site had higher mass fractions of PAHs from coal combustion and vehicle emission, while the BM site held higher mass percentages of PAHs from long-range transported wood combustion and industrial activities. Lower temperature at BM may lead to the higher mass percentages of low ring PAHs. Coal combustion, traffic emissions and biomass burning were the common sources for PAHs at both SC and BM. Construction workers were exposed to higher BaPeq concentrations, nearly ten times of the background site and their lifetime cancer risk reached to 0.6 per 1,000,000 exposed worker, owing to the influence of coal combustion, vehicle emission and industrial activities at the surroundings of SC.

Consistent increase in abundance and diversity but variable change in community composition of bacteria in topsoil of rice paddy under short term biochar treatment across three sites from South China

Biochar functionality related to soil microbial community changes has not yet been fully understood. In this study, we present a cross site field experiment on bacterial community changes of rice paddies among three sites (Jiangxi province, JX; Hunan province, HN; and Sichuan province, SC) from South China with biochar amended (BSA) at 0, 20 and 40t ha−1 before rice plantation in 2010. Changes in bacterial abundance and diversity of topsoil (0-15cm) sampled at rice harvest were assessed. Increases in soil pH, soil organic carbon, total N, soil microbial biomass, as well as bacterial gene copy numbers and diversity indices (phylogenetic diversity, Shannon, Chao1 and OTU richness) were consistently observed under BSA at 40t ha−1, though generally insignificant at 20tha−1 across the sites. Cluster analysis of both terminal restriction fragment length polymorphism (T-RFLP) profiles and pyrosequencing of the 16S gene indicated a strong impact of biochar on bacterial community composition, though the changes were variable across the sites. In particular, BSA at 20 and 40tha−1 greatly increased the relative abundance of Betaproteobacteria (by 54% and 80%) and Deltaproteobacteria (by 164% and 151%) in JX while decreased Betaproteobacteria (by 46% and 52%) and increased Chloroflexi (by 27% and 61%) in SC site, respectively. However, no significant changes were detected in HN site. In addition, some significant but variable changes were observed in the abundance of nitrifying, denitrifying and N-fixing bacteria groups with biochar addition among sites. This study suggested a potential role of biochar in enhancing bacterial abundance, community diversity and modifying the community compositions, particularly of the bacteria involved in N cycling. However, changes in soil microbial structure and functioning related to biochar treatment deserve further studies.

Synthesis and structure of a new layered oxyfluoride Sr2ScO3F with photocatalytic property

A new Ruddlesden–Popper type scandium oxyfluoride, Sr2ScO3F, was synthesized by a conventional solid state reaction route. The detailed structure of Sr2ScO3F was investigated using X-ray diffraction (XRD) and selected area electron diffraction (SAED). The disorder distribution pattern of fluorine anions was determined by the 19F nuclear magnetic resonance (NMR) spectrum. The compound crystallizes in a K2NiF4-type tetragonal structure (space group I4/mmm) with O/F anions disordered over the apical sites of the perovskite-type Sc(O,F)6 octahedron layers interleaved with strontium cations. Ultraviolet–visible (UV–vis) diffuse reflection spectrum of the prepared Sr2ScO3F indicates that it has an absorption in the UV–vis region. The photocatalytic activity of Sr2ScO3F was further investigated, showing an effective photodegradation of Rhodamine-B (RB) within 2h under UV light irradiation.

Optical properties and energy transfer of a novel KSrSc2(PO4)3:Ce3+/Eu2+/Tb3+ phosphor for white light emitting diodes.

A new langbeinite-type phosphate KSrSc2(PO4)3 has been synthesized by conventional high temperature solid state reaction. Rietveld structure refinement, a field emission scanning electron microscope, photoluminescence spectra, quantum efficiency as well as lifetimes were used to characterize the samples. Structure refinement reveals that KSrSc2(PO4)3 has two kinds of Sr(2+) and Sc(3+) sites for the doped ions to occupy, forming emission centers. The KSrSc2(PO4)3:Ce(3+) and KSrSc2(PO4)3:Eu(2+) phosphors both have broad excitation and emission bands due to spin- and orbit-allowed electron transitions. Phosphors with tunable blue to blue-green colors were obtained by codoping the Tb(3+) ions into the KSrSc2(PO4)3:0.03Ce(3+) and KSrSc2(PO4)3:0.03Eu(2+) phosphors with varying contents. The mechanism of Eu(2+)→Tb(3+) energy transfer is determined to be a dipole-quadrupole interaction in terms of the experimental results and analysis of photoluminescence spectra and decay curves of the phosphors by using the Inokuti-Hirayama theoretical model. Our prepared KSrSc2(PO4)3:Ce(3+),Tb(3+) and KSrSc2(PO4)3:Eu(2+),Tb(3+) phosphors are of potential value for UV excited WLEDs.

Transplantation of mouse ovarian tissue: Comparison of the transplantation sites

Many studies have shown that ischemic injuries during the transplantation process were more detrimental than cryoinjuries for follicle survival and death, and it has been reported that transplantation sites can affect the outcomes of grafted ovarian tissue (OT). The purpose of this study was to assess the impact of different OT transplantation sites on follicular integrity and function of OT grafts. B6D2F1 mice were randomly assigned to control (sham) and four experimental groups according to transplantation sites (back muscle [BM], fat pad [FP], kidney capsule [KC], and subcutaneous [SC]). The ovaries from four groups were autotransplanted to each site. The OT recovery ratios on Days 2, 7, and 21 were significantly decreased in the FP group. The mean numbers of follicles were significantly lower in all the grafting groups compared with the sham group, except in the KC group on Days 7 and 21 and the BM group on Day 21. On Day 2, all the experimental groups showed low intact (G1) follicle ratio when compared with the sham group; however, the BM, KC, and FP groups recovered their morphologic integrity on Day 7, and only the SC group presented a significant decrease in G1 follicle ratios. On Day 21, the G1 follicle ratios of the FP and KC groups were greater than the sham control group. The proportion of apoptotic follicles of the four OT graft groups was higher than in the sham group on Day 2, followed by a significant decrease in the KC group and an increase in the SC group on Day 7. The serum follicle-stimulating hormone levels were significantly increased in all grafting groups on Day 2. On Day 7, only the SC group showed the high follicle-stimulating hormone level compared with the other groups. The mean numbers of oocytes from OT grafts were the highest in the KC group, except in the control group, and the lowest in the SC group. The ratios of mature oocytes were also significantly greater in the sham and KC groups. However, the ratios of normal spindle did not differ among the five groups. In conclusion, the KC was the optimal site for OT transplantation in this murine model, whereas the SC site was unfavorable for this procedure. In this study, we confirmed that the different grafting sites influenced the outcomes of transplantation.

Vacancy association energy in scandium doped ceria: 45Sc MAS NMR and 2D exchange spectroscopy study

Oxygen vacancy exchange between Sc ions in 0.5% Sc-doped ceria Sc0.005Ce0.995O0.9975 is investigated by means of 2D exchange spectroscopy (EXSY). 45Sc NMR spectrum of Sc-doped ceria contains two peaks—one corresponding to Sc ions coupled with an oxygen vacancy (Sc-7), and the other corresponding to Sc ions in a regular lattice site surrounded by eight oxygen ions (Sc-8). The vacancy exchange between these two Sc sites generates the cross-peaks in the EXSY spectrum. Relative amplitudes of the cross-peaks provide direct values of the exchange frequency at a given temperature. Arrhenius analysis of the exchange frequency gives the activation energy Ea=1.18eV for the vacancy hopping between Sc sites. Most of this energy barrier is due to association energy which binds the vacancy to Sc3+. Large dopant–vacancy association energy in Sc doped ceria is demonstrated by 45Sc NMR spectrum of La/Sc doubly doped sample, ScxLaxCe1−2xO2−x, x=0.005, where the only line of Sc-7 site shows that all vacancies are bound by Sc3+ ions.

Zero thermal expansion and ferromagnetism in cubic Sc(1-x)M(x)F3 (M = Ga, Fe) over a wide temperature range.

The rare physical property of zero thermal expansion (ZTE) is intriguing because neither expansion nor contraction occurs with temperature fluctuations. Most ZTE, however, occurs below room temperature. It is a great challenge to achieve isotropic ZTE at high temperatures. Here we report the unconventional isotropic ZTE in the cubic (Sc1-xMx)F3 (M = Ga, Fe) over a wide temperature range (linear coefficient of thermal expansion (CTE), αl = 2.34 × 10(-7) K(-1), 300-900 K). Such a broad temperature range with a considerably negligible CTE has rarely been documented. The present ZTE property has been designed using the introduction of local distortions in the macroscopic cubic lattice by heterogeneous cation substitution for the Sc site. Even though the macroscopic crystallographic structure of (Sc0.85Ga0.05Fe0.1)F3 adheres to the cubic system (Pm3̅m) according to the results of X-ray diffraction, the local structure exhibits a slight rhombohedral distortion. This is confirmed by pair distribution function analysis of synchrotron radiation X-ray total scattering. This local distortion may weaken the contribution from the transverse thermal vibration of fluorine atoms to negative thermal expansion, and thus may presumably be responsible for the ZTE. In addition, the present ZTE compounds of (Sc1-xMx)F3 can be functionalized to exhibit high-Tc ferromagnetism and a narrow-gap semiconductor feature. The present study shows the possibility of obtaining ZTE materials with multifunctionality in future work.

Cs3ScCl6.

Crystals of tricaesium scandium(III) hexa­chloride were obtained as a side product from the reaction of U, SnCl2, Sc, and S in a CsCl flux at 1073 K. Cs3ScCl6 crystallizes in the Rb3YCl6 structure type. The asymmetric unit comprises three Cs sites, two Sc sites, and six Cl sites, all of which have site symmetry 1, except for the two Sc sites that have site symmetries of 2 and -1, respectively. The structure is composed of isolated [ScCl6]3− octa­hedra that are surrounded by Cs+ cations. Two Cs+ cations have inter­actions with eight Cl− anions, while the third has inter­actions with ten Cl− anions.

Low-Temperature Fluorination Route to Lanthanide-Doped Monoclinic ScOF Host Material for Tunable and Nearly Single Band Up-Conversion Luminescence

Lanthanide upconversion (UC) materials that convert near-infrared excitations into visible emissions are of extensive current interest owing to their potential applications in biosensing, 3D displays, and solar cells. A wise choice of the host lattice is crucial for high-quality UC luminescence with desired emission wavelengths. From the viewpoint of structural chemistry, here we propose monoclinic scandium oxyfluoride (M-ScOF) as a promising UC host material for the following reasons: (1) the shortest Sc3+–Sc3+ distance (3.234 Å, versus 3.584 Å of Y3+–Y3+ in hexagonal NaYF4); (2) the unique crystallographic site of Sc in the structure; (3) specific coordination environment of Sc with 4O + 3F in C1 symmetry. Lanthanide doping in an individual host with such structural features is highly expected to achieve single band emission and fast energy migration for high-efficiency UC process. Experimentally, we employ a low temperature fluorination method to synthesize pure and lanthanides doped M-ScOF samples successfully by using polytetrafluoroethylene as the fluridizer. The Yb3+/Ho3+-codoped M-ScOF nanoparticles exhibit tunable UC emissions with various red/green ratios under excitation of λex = 980 nm. Nearly single-band red (∼660 nm) and near-infrared (∼805 nm) UC luminescence have been achieved in Yb3+/Er3+- and Yb3+/Tm3+-incorporated samples, respectively. We believe that more attention to M-ScOF and the search for other advanced host materials based on structural chemistry perspective will greatly boost the development of high-efficiency UC phosphors in various applications such as bioprobes and chromatic displays.

동적 원심모형실험에 의한 점성토 지반에 근입된 말뚝지지 기초의 응답 스펙트럼 분석

현재 국내 내진설계기준에서 제시하고 있는 지반분류 방법 및 지반 증폭계수는 기반암이 주로 30m 이내에 위치하는 일반적인 국내 지반특성을 제대로 반영하지 못하고 있다. 따라서, 본 연구에서는 점성토 지반에 근입된 비정형 말뚝기초(PHC 500, 중심 간격 3D)에 대한 동적 원심모형 실험을 실시하여 자유장과 기초판의 응답 스펙트럼 결과를 비교하였다. 장주기 영역에서는 SE 지반의 설계 스펙트럼 가속도보다 기초와 자유장에서 계측된 실제 스펙트럼 가속도가 작게 나타났고, 기초에서 발생한 스펙트럼 가속도는 지진 하중이 커지면 SD 지반의 설계 스펙트럼 가속도와 유사해지는 것을 확인할 수 있었다. 이것은 연약한 지반(SE 지반)에 대한 현행 설계기준이 지진 하중을 과대평가하고 있으며 비경제적 설계를 할 수 있음을 의미한다. 1.5초 이상의 장주기 영역에서는 실험에서 측정된 스펙트럼 가속도가 SC 지반의 표준설계응답스펙트럼 가속도보다 작게 나타났고 기초 및 자유장 조건에 의한 스펙트럼 가속도 차이가 거의 발생하지 않았다. 따라서, 실제 아파트에 해당하는 1.5초 이상의 장주기에서는 국내 지반조건을 고려하여 실험에서 측정된 스펙트럼 가속도를 설계에 적용하면 표준설계스펙트럼을 적용할 때 보다 경제적인 설계가 가능한 것으로 나타났다. Site coefficient and amplification factor of current domestic Seismic Design Code (KBC-2009) have no consideration for the domestic ground condition in which the base rock is normally placed within 30m form the surface. Accordingly, in this study dynamic centrifugal test and analysis for pile foundation into clay were achieved. and the response spectrums of free surface and basement were compared with each other. Within the period 1sec., the measured spectral acceleration of free surface and basement was bigger than the design spectral acceleration of SC and SD site. However the measured spectral acceleration of free surface and basement for the period over 1.5sec. was smaller than the design spectral acceleration of SC site. There was no severe difference of spectral acceleration according to the upper structure, embedded depth of foundation and free surface conditions. Consequently, normal domestic apartment housing for the period range over 1.5sec. could be design more economically applying these test result.

동적 원심모형실험에 의한 사질토에 근입된 말뚝지지 기초의 응답 스펙트럼 분석

현재 국내 내진설계기준에서 제시하고 있는 지반분류 방법 및 지반 증폭계수는 기반암이 주로 30m 이내에 위치하는 일반적인 국내 지반특성을 제대로 반영하지 못하고 있다. 따라서, 본 연구에서는 사질토 지반에 근입된 비정형 말뚝기초(PHC 500, 중심 간격 3D, 4D, 5D)와 상부 구조물에 대한 동적 원심모형 실험을 실시하여 자유장과 기초판의 응답 스펙트럼 결과를 비교하였다. 단주기 영역인 1초 이내 주기에서는 기초판 및 지표면 자유장의 측정 스펙트럼이 SC 및 SD 지반의 표준설계스펙트럼 가속도보다 크게 나타났다. 1.5초 이상의 장주기 영역에서는 실험에서 측정된 스펙트럼 가속도가 SC 지반의 표준설계응답스펙트럼 가속도보다 작게 나타났고 상부구조물 유무, 지반 근입 심도, 기초 및 자유장 조건에 의한 스펙트럼 가속도 차이가 거의 발생하지 않았다. 따라서, 실제 아파트에 해당하는 1.5초 이상의 장주기에서는 국내 지반조건을 고려하여 측정된 스펙트럼 가속도를 설계에 적용하면 표준설계스펙트럼을 적용할 때 보다 경제적인 설계가 가능한 것으로 나타났다. Site coefficient and amplification factor of current domestic Seismic Design Code (KBC-2009) have no consideration for the domestic ground condition in which the base rock is normally placed within 30m form the surface. Accordingly, in this study dynamic centrifugal test and analysis for pile foundation into sand and upper structure were achieved. and the response spectrums of free surface and basement were compared with each other. Within the period 1 sec., the measured spectral acceleration of free surface and basement was bigger than the design spectral acceleration of SC and SD site. However the measured spectral acceleration of free surface and basement for the period over 1.5 sec. was smaller than the design spectral acceleration of SC site. There was no severe difference of spectral acceleration according to the upper structure, embedded depth of foundation and free surface conditions. Consequently, normal domestic apartment housing for the period range over 1.5sec. could be design more economically applying these test result.