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The flexural bearing capacities of three composite continuous box beams with different prestressing degrees were tested and studied to investigate the influences of local prestressing bundles on the deflection, relative slip of interface, strain, and redistribution of the internal force of the steel–concrete composite continuous box beam. Results show that the arrangement of local prestress can not only improve the bending stiffness at the mid-span of the composite continuous box beam, but also significantly enhance the ductility. In the design process of the local prestressed composite continuous box beam, the influence of the slip at the middle support should be fully considered, and the deflection could not be taken as a control factor. The internal force redistribution of the local prestressed continuous box beam is lower than that of the ordinary continuous box beam, but it still has good plastic internal force redistribution. The number of prestressing bundles in the negative moment region is the main factor that affects the internal force redistribution of the middle support.

This article focuses on two forged steel piston products of different structures and materials, through the mold stress analysis simulation mold structure optimization, die life is greatly improved, while solving the piston skirt crease, underfill, ejector pin distortion and other technical problems. Piston products for quenched and tempered steels and micro alloy have been adjusted to optimize the heat treatment process, reducing the proportion of scraps in the form of quenching cracks, skirt deformation, and uneven hardness distribution.

Centering on students' practical ability training, this paper puts forward a new teaching mode of BIM technology which is suitable for the current situation, and through the establishment of BIM skill level examination training point, organize students to participate in BIM graduation design, Establish BIM technology teaching practice base, reform BIM technology personnel training model, to further improve the teaching ideas and implementation plans of students' BIM technology application and practical ability, it provides a new idea for the BIM technology teaching in the same universities.

A series of Ba8Ga16Si30 clathrate samples were prepared by arc melting, ball milling, acid washing, and spark plasma sintering (SPS). X-ray diffraction analysis revealed that the lattice of the Ba8Ga16Si30 samples expanded as the SPS temperature was increased from 400 to 750°C. Lattice contraction recurred when the SPS temperature was further increased in the range of 750–1000°C. This phenomenon can be explained by the variation of Ga content in the lattice. The thermoelectric figure of the merit ZT value of clathrates increased with the increase in SPS temperature and reached a maximum when the sample was subjected to SPS at 800°C. A further increase in SPS temperature did not contribute to the improvement of ZT. The variation of the lattice parameter a vs. SPS temperature T was similar to the variation observed in the ZT-T curve.

A series of samples with the chemical formula Ba8Si46−xAlx (x = 2, 3, 5, 6, 7 and 8) were prepared by arc melting, ball milling and washing with diluted HCl. The lattice parameter of Ba8Si46−xAlx increases linearly with the increase of nominal Al content x. The composition analysis by energy-dispersive X-ray spectroscopy (EDS) shown that the actual Al contents in clathrates are lager than the nominal compositions because the dilute Al-contained impurity phases were washed out. The experimental results show that the minimum incorporation of Al into clathrate structure is expected to be about 3 at ambient pressure, which is in agreement with a first-principle simulation. The Al substitution for Si results in the decrease of superconducting transition temperature TC, which can be explained on the BCS theoretical frame. The electron density of state at Fermi level N(EF) decreases with the increment of x except for an abnormal increase for the sample x = 6. Such sample has a higher spatial symmetry of the structure in which all the six Si atoms at 6c sites were substituted by Al atoms. Its higher N(EF) causes to a higher TC. In addition, we calculated the phonon-dispersion relations and vibrational density of states for Al-doped silicon clathrates. The high frequency acoustic branch has a red shift from 430 cm−1 to 420 cm−1 with the doping of Al. The decreased frequency of bond-stretching vibration modes is another reason for the suppression of TC induced by Al substitution.

The potential thermoelectric and magnetic application of clathrate materials with rare-earth doping is the focus of much of the recent research activity in the synthetic material physics and chemistry. A series of clathrate samples with the chemical formula Ba 8− x Yb x Si 30 Ga 16 ( x = 0, 0.5, 0.7, 1 and 1.5) were prepared by combining arc melting, ball milling and spark plasma sintering (SPS) techniques. X-ray diffraction and scanning electronic microscopy combined with energy-dispersive X-ray spectroscopy (EDS) analysis showed the dominant phase to be the type-I clathrate. Whereas, X-ray structural refinement and EDS analysis indicated that some Yb atoms enter the clathrate lattice to replace Ba at 2 a sites, while other Yb atoms are oxidized as Yb 2 O 3 precipitated around grain boundaries. The solid solubility of Yb into clathrate lattice yielded x ∼ 0.3. Comparative analysis between Yb-doped and Yb-free clathrates showed that the thermal conductivity decreases with Yb-doping. Consequently, thermoelectric figure of merit ZT significantly increased.

The complex three-dimensional traffic construction often occur when the lower structure cannot bear the construction load and other special cases, indicating the need for temporary reinforcement of the lower structure. In this paper, combined with a project construction example, various temporary reinforcement technologies are adopted to solve the insufficient bearing capacity during understructure construction, which poses a serious danger, to ensure synchronous construction of the understructure and viaduct. Compared with the traditional construction technology, the temporary reinforcement technology proposed in this paper features the advantages of saving project cost and time and has achieved better economic and social benefits.

Geometrical frustration, which arises from the topology of a well-ordered structure rather than from disorder, has recently become a renewed interest. In particular, geometrical frustration among spins in the spinel oxides can lead to exotic low-temperature states. We reported a joint experimental and theoretical investigation of Fe-doping effect on LiMn 2 O 4 spinel oxide in which magnetic moments have geometrical frustration. The structural and physical properties of LiMn 1.5 Fe 0.5 O 4 were studied by means of Mossbauer spectroscopy, X-ray diffraction, scanning electron microscope (SEM), electrical and magnetic measurements. Electronic conductivity measurements showed that Verwey-type transition is absent in heavily Fe-doped LiMn 2 O 4 . In addition, LiMn 1.5 Fe 0.5 O 4 exhibits a semiconductor characteristic in resistivity with an energy gap E g =0.27 eV, which is consistent with our first-principle simulation. A large resistivity at room temperature for LiMn 1.5 Fe 0.5 O 4 indicates low concentration of conduction electrons corresponding to electronic localization behavior. X-ray diffraction refinement as well as Mossbauer analysis suggests that Fe ions preferentially substitute for Mn ions on the octahedral B-sites. Moreover, small amount of Fe replace for Li ions to form a site inversion in spinel structure. In contrast to the pure and low-Fe-doped LiMn 2 O 4 samples, LiMn 1.5 Fe 0.5 O 4 has an antiferromagnetic transition at T N =34 K. The Fe dopants enhance the antiferromagnetic interaction among moments accompanied by breaking the original moment equilibrium and suppressing the magnetic frustration in LiMn 2 O 4 .

The temperature-dependent structural changes were investigated by using the X-ray diffraction and the Ex- tended X-ray absorption fine spectroscopy (EXAFS) for layered perovskite manganites La2-2xSr1+2xMn2O7 (x=0.33 and 0.4). The anomalous changes of Mn-O bond length and Jahn-Teller (J-T) distortion of MnO6 octahedron were observed, corresponding to ferromagnetic transition temperature (~ 120 K). Around the temperature of 2D short-range magnetic or- dering (~ 235 K), there occurs an anomaly of the Jahn-Teller distortions of MnO6. These results indicate that magnetic properties of perovskite manganites La2-2xSr1+2xMn2O7 depend heavily on their microstructure change. The orbital state occupancy is involved in the observed Mn-O bond change.

Polycrystals of double-layered perovskite La2−2xSr1+2xMn2O7 ( x = 0.3 ,0.33,0.4) were prepared by solid-state reactions at the same temperature. We have performed resistance and magnetization measurements on these samples. They exhibit both colossal magnetoresistance (CMR) (MR>64% for H = 5 T ) near magnetic transition Tc, and 2D short-range magnetic order. Additionally, these compounds showed two distinct resistance peaks. The resistance peak near Tc was sharp, whereas the second peak below Tc was a broad one. Especially, it is notice that there are wide plateaus of CMR form Tc to 20 K for two samples.

We present a joint experimental and theoretical study of the superconductivity and electronic structures in type-I Cu-doped silicon clathrates and germanium clathrates. The superconducting critical temperature in Ba8Si46–xCux is shown to decrease strongly with copper content increasing. These results are corroborated by CASTEP approach, first-principles simulations calculated from the density-functional theory with plane waves and pseudopotentials. The simulations show that Cu-doping results in a large decrease of electronic density of states in Fermi level, which can explain the superconducting critical temperature decrease with Cu-doping in the BCS theoretical frame. Further, comparison of Ba8Ge46 and Ba8Si46 within the CASTEP approach shows that the superconductivity is an intrinsic property of the s p 3 silicon and germanium clathrates without vacancy in the cage framework. By analysis of the density of states (DOS) and reported experimental results of the Zintl-like Ba8Ge43, a new mechanism of vacancy defect is suggested to explain the absence of superconductivity in Ge clathrates, which is of benefit to eliminating the divarication between theoretical prediction and the experimental observation for superconductivity in Ge clathrates. Keeping an entire Si and Ge cage structure without vacancy is the prerequisite for occurrence of superconductivity in clathrates.

This paper presents a new method to fabricate tungsten microelectrode instantaneously by means of the pressure difference of plasma between cathode and anode in a single electrical discharge. The influence of main machining parameters, such as electrode material, polarity, dielectric medium, discharge duration and peak current, is analyzed by detailed experiments to obtain the fabricating law of tungsten microelectrode. The fabricating principle is described clearly. As the result of experiments, a tungsten microelectrode about 350 μm in length and 30 μm in diameter can be fabricated on the top of the tungsten wire of 0.125 mm in diameter by this method. At the tip of the tungsten microelectrode, its radius is about 100 nm. This method can greatly shorten the microelectrode fabrication time and effectively improve the reliability of the microelectrode. Especially, this method can fabricate a nanometer level tip in general electrical discharge machining (EDM) machine tool and need not add any other apparatus. The fabricated microelectrode can be used as a drilling tool in micro-EDM or a probe for scanner and measurement devices.

The lattice distortion and local symmetry of bilayered perovskite manganites play an important role in its magnetoelectric transport properties, in particular, the effect of the colossal magnetoresistance (CMR) found in this new member of CMR family. In order to explore the structural origin, X-ray absorption fine structure (XAFS) spectra at both near edge and extended part were measured at Mn K-edge of the bilayered perovskite manganites, La2−2xSr1+2xMn2O7 with x = 0.2 , 0.3, 0.33, 0.4, 0.5 and 0.6. The XAFS oscillations from the first coordination shell of Mn–O were filtered out and analyzed in more detail aimed at investigating the lattice distortion with respect to this Mn–O octahedron. Despite lattice shrinkage due to substitution of La with Sr which has to be a close atom radius, the largest derivation from the Gaussian distribution of the Mn–O shell arose from the 0.33 doped sample. In a more sophisticated fit, we found that the JT distortion magnitude Δ JT and Debye-Waller factors σ 1 2 and σ 2 2 are the highest at the same doping concentration x = 0.33 .

Magnetocaloric and electronic properties of the layered perovskite La1.34Sr1.66Mn2O7 manganese oxide have been investigated. Broadening of the magnetic entropy change peak was observed above Curie temperature (Tc=118 K), which can be associated with the existence of two-dimensional short-range magnetic order in the bilayered perovskite. There is an additional reinforcement of the magnetization in a narrow range under Tc when magnetic field is above ∼2 T, leading to a positive magnetic entropy change. It is noticeable that a wide peak of magnetoresistance (MR ∼66%) near Tc as well as two field-dependent peaks in R–T curves was found in our sample.

The effects of Eu substituting for Ba on structural and superconducting properties were investigated for a series of superconductors Eu 1+ x Ba 2− x Cu 3 O 7− δ ( x =0, 0.02, 0.04, 0.06, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, and 0.2). With Eu content increasing, the random substitution of excessive Eu for Ba ion forms a Eu–Ba non-stoichiometric distribution on Ba site, which deviates from the ideal 123 phase stoichiometry. The analysis of crystallographic structure shows that the solid solubility x of Eu on Ba site is over 0.2. Eu 1+ x Ba 2− x Cu 3 O 7− δ take on an orthorhombic–tetragonal (O–T) phase transition from x =0.06, and end in x =0.18. Corresponding to the O–T phase transition, superconducting critical temperature T c rapidly decreases with Eu content increasing, which is attributed to the decline of carrier density and the proximity effects of non-superconducting clusters. The positron annihilation measurements show anomalous changes for lifetime spectra and Doppler-broadened radiation spectra when the O–T phase transition occurs. By the model of excessive oxygen defects in Cu–O chain regions, we discuss effects of Eu–Ba non-stoichiometric distribution on structural and superconducting properties.

A series of single crystals with starting composition Y1−xEuxBa2Cu3O7−δ (x=0, 0.1, 0.2, 0.3, 0.4, 0.5 and 1.0) were prepared in Al2O3 crucibles in the self-flux method. A home-made setup for crystal growth and a new flux separation method are introduced. Eu-doped Y-123 single crystals were characterized by means of X-ray diffraction, energy dispersive X-ray spectrometry, scanning electron microscopy (SEM), atomic force microscopy (AFM) and AC susceptibility. All single crystal samples maintain the crystallographical structure of the 123-phase. The SEM and AFM measurements indicate a growth anisotropy. The growth of the (0 0 1) surface is related to different growth mechanisms, and the spiral growth mechanism is the predominant one. For the first time, we observed a regular array of groove on (0 0 1) surface. A drastic suppression of the superconducting transition temperature with Eu concentration was observed. Al contamination from crucible corrosion and Eu substitution for the Ba site result in a heavy reduction of Tc in single crystals.

The effect of Sn-doping on (La 1− x Sr x ) 2 Cu 1− x Sn x O 4 ( x =0.075, 0.090 and 0.110) has been studied. Lattice parameters monotonically decrease with Sn dopant increasing. Sn atoms dominantly occupy Cu sites and form Sn–O clusters as point-like defects. Flux pinning properties of ceramic samples of (La 1− x Sr x ) 2 Cu 1− x Sn x O 4 have been investigated by magnetic measurements from 6 to 30 K up to 5 T. The current carrying scale-length analysis has been determined from the reverse leg of the magnetization hysteresis loops and compared to the actual dimensions of the sample. Magnetization hysteresis loops of the more richly Sn-doped sample exhibit stronger pinning behavior, especially in the higher temperature range. The intra-granular critical current J c in the rich Sn-doping sample has a significant increase. We discuss the experimental results within a pinning model of point-like defects. From our data we infer that the Sn–O cluster near Cu–O layers provides an effective pinning center.

Community acquired pneumonia (CAP) is one of the most common infectious disease in emergency department. In 2005 the concept of healthcare associated pneumonia (HCAP) was proposed by the ATS/IDSA guidelines. The clinical features and microbiology of HCAP are different from CAP, however, the initial antimicrobial treatment is still controversial. We aimed to compare the clinical efficacy between HCAP patients treated initially with HCAP guideline-concordant antimicrobial agents and those with CAP guideline-concordant antimicrobial agents.We conducted a retrospective observational study on HCAP patients who were admitted to emergency department between December 2011 and December 2012. Patients were divided into 2 groups according to their different initial antimicrobial treatment. We compared clinical features, distribution of pathogen, severity, days and spending on intravenous antimicrobial, length and charge of hospitalization and clinical outcomes, and meanwhile analyzed the clinical efficacy as well.Of the 125 HCAP patients, 55 patients received CAP guideline-concordant antimicrobial agents and 70 received HCAP agents. The major pathogens were Klebsiella pneumoniae, methicillin-resistant staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Escherichia coli. The 2 groups were similar at baseline, including old age, comorbidities, Pneumonia Severity Index scores, APACHE scores, and length of intravenous antimicrobial use and hospitalization duration, and in-hospital mortality. Overall efficacy rate occurred in 70.0% of HCAP agent patients and 50.9% of CAP agent patients (P = 0.029). Antimicrobial charge and total hospital charge for HCAP agent patients were significantly higher than that for CAP agent patients.Initial treatment of HCAP patients in emergency department with HCAP guideline-concordant antimicrobial could increase clinical efficacy rate, as well as antimicrobial charge and total hospital charge, but was not associated with shortening the length of stay, or lowering in-hospital mortality.

The magnetic properties of ceramic samples of Bi 2−2 x (PbSn) x Sr 2 CaCu 2 O y ( x =0,0.1,0.2,0.3 and 0.4) superconductors have been investigated using a vibrating sample magnetometer from 20 to 50 K and up to 8 T. Phase analysis shows that most of the (Pb,Sn) dopant enters the Bi-2212 lattice and occupies Bi sites. The current-carrying scale-length analysis has been determined from the reverse leg of the magnetization hysteresis loops and compared to the actual dimensions of the sample. Magnetization hysteresis loops of the (PbSn)-doped sample exhibit strong pinning behaviour in the higher temperature range. The effect of (Pb,Sn) doping on intragranular critical current J c was found to be enhanced by one order of magnitude at 50 K. We discuss the experimental results within a model of (PbSn) cluster pinning in blocking layers. Doping by (PbSn) clusters into the Bi–O layers provides effective pinning centres, as well as a large reduction of the resistivity anisotropy.

The magnetic properties of a series of superconductors (Eu1-xYx)Ba2Cu3O7-y (x = 0, 0.2, 0.3, 0.5, 0.7 and 0.8) have been investigated by magnetic measurements from 20 to 90 K. Magnetization hysteresis loops of the Y-doped sample exhibit a strongly developed second peak in the higher temperature range. We discuss the experimental results in the framework of a stress-field pinning model. The stress field induced by the lattice mismatch is also an effective pinning centre, in addition to pinning by 211 phase precipitates and oxygen vacancies. We further suggest that in the (Eu1-xYx)Ba2Cu3O7-y samples the oxygen deficient regions induced by the stress field in Cu-O chains also act as pinning centres, thus causing the second peak in the Jc-B curves of (Eu1-xYx)Ba2Cu3O7-y.

119Sn Mossbauer research is carried out on (La1-xSrx),Cu1-xSnxO4(x = 0.075 and 0.110) superconductors which are designed under a new concept. The Mossbauer spectra results show that Sn occupies Cu position in Sn4+ state, and there is no Sn2+ ion occupying La position. The local lattice deformation near Sn4+ site is small, but displays an increasing tendency with Sn doping. For La2CuO4 matrix, the simultaneous dopings of Sr/Sn induce holes and electrons on CuO2 layer in a new mechanism which influences superconductivity. Under a new mechanism of extra oxygen, the extra oxygen effect of Sn-doping on superconductivity is discussed

The Fe-doping effects on superconductivity, transport and microstructure are investigated by means of Hall coefficient measurements, thermogravimetric analysis, Mossbauer spectroscopy and the calculation of the point-charge-effective-valence model (PCEV model) in Fe-doped Tl 0.5 Pb 0.5 (Sr 0.8 Ba 0.2 ) 2 Ca 2 (Cu 1− x Fe x ) 3 O y (Tl-1223) superconductors. In the doping level of Fe ( x =0–0.05), both zero-resistance temperature T co and carrier concentration n H decrease linearly with Fe dopants increasing. The striking linear behavior of T co and n H suggests the potential effects of charge localization on the transport properties and also shows that Fe dopants occupy different Cu sites in a stable manner with Fe content increasing. The thermogravimetric analysis shows the Fe 3+ ions substituting for Cu 2+ ions can bring excess oxygen atoms into lattice and form some Fe–O defect clusters. Mossbauer measurements are performed to investigate the microstructure of Fe–O defects. In addition, the atomic position of Fe dopant and the electric field gradient (EFG) on Fe sites are investigated under the PCEV model. We found that the signs of the EFG on Fe sites are positive. According to quadrupole splittings deduced from Mossbauer spectroscopies and results of model calculation, it is further confirmed that there is a small shift of Fe ion relative to the original center of the CuO 2 network, and in some different kinds of Fe–O defect clusters, Fe dopants can lead to excess oxygen atoms entering lattice. These results provide a further support for the interpretation about the displacement of Fe dopant and the assignment of Fe site. Our discussion suggests that the microstructural distortion and the excess oxygen defect induced by Fe doping encourage in the localization of cruising carrier on CuO 2 planes, which is one of the reasons to explain the decrease of T c and carrier concentration.

The simultaneous measurements of Doppler-broadened radiation spectra and lifetime spectra have been performed on (Y 1− x Eu x )Ba 2 Cu 3 O 7− y ( x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1) superconductors. The mean lifetime and S -parameter, respectively show a characteristic significantly symmetric to Eu-doping concentration. Since lifetime and Doppler broadening spectroscopies are rather sensitive to the variation of the lattice distortion and defects induced by the stress-field of lattice mismatch, such symmetric behaviors of the S -parameter and the mean lifetime suggest a striking characteristic of stress in Y 1− x Eu x -123 superconductor. When the doping concentration x reaches 30%, the density of defects corresponding to stress-field appears the maximum, and there is an optimum distribution of the stress-field so as to increase critical current J c in Eu-doped Y-123 superconductors. Our results of the critical current density obtained by means of measurements of susceptibility χ ′( T , H AC ) and χ ″( T , H AC ) also suggest that the enhancement of the critical current density to reach an optimum when Eu doping x is 30%. We also qualitatively discuss experimental results in the framework of the model of stress-field pinning. The model calculating results also show the stress-field induced by lattice mismatch is an effective pinning center, and further conform that the stress pinning mechanism is dominant in RE-doped Y-123 superconductors.

The simultaneous measurements of Doppler-broadened radiation spectra and lifetime spectra were performed by positron annihilation analysis on Eu-doped Y-123 superconductors. When the doping concentration reaches 30% and 70%, the density of defeat and its stress-field reach the maximum for (Y1-x Eu x )Ba2CU3O7-y The pinning mechanism of such superconductors is discussed, and the results support the stress pinning mechanism.

The HgBa 2 CaCu 2 O 6+ x high temperature superconducting materials are synthesized under a high pressure of 30 kbar at 850 °C for 4 h. The zero resistance temperature of the materials measured by a four-probe method is 123 K. Using XRD, SEM, TEM and EDS the morphologies and features of the non-superconducting phases in the materials, such as phase stabilities, structure uniformities and transformations, were investigated. The decomposition of the CaHgO 2 phase under electron beam heating and bombardment was observed in-situ and an orientation evolution of the CaHgO 2 during decomposition was analysed. The special structures in some non-superconducting phases, such as the mosaic structure and the tweed structure in CaO and Ba 2 Cu 3 O 5+ x grains respectively, were investigated.

The superconductors HgBa2CaCu2O6+ delta (Hg-1212) and HgBa2Ca2Cu3O8+ delta (Hg-1223) have been synthesized by solid state reaction, carried out at 850 degrees C under 25 kbar, using the nominal composition of HgBa2Ca2Cu3Ox. The results indicate that the optimum sintering time for the Hg-1223 phase is about 0.5 h. With increasing sintering time, the Hg-1223 phase decomposes, and the Hg-1212 phase increases gradually. When the sintering time increased to 3.8 h, we obtained a sample with nearly a single phase of Hg-1212. We synthesized the HgBa2CaCu2O6+ delta superconductor under 27 kbar at various sintering temperatures using the nominal composition of HgBa2CaCu2Ox. The results indicate that the optimum sintering temperature for the Hg-1212 phase is 820-830 degrees C. The effect of annealing at various temperatures in flowing O2 on the superconductivity of HgBa2Ca2Cu3O8+ delta has been investigated.

A significant drop of the resistance around 235 K was observed in our experiment of mercury-based samples synthesized under high pressure and high temperature. The drop of the resistance alwaysappeared in samples containing tiny mercury droplets or HgAu alloys; it was sometimes also observed in samples with grains of Hg-1223 and grain boundaries containing an excess of Hg compared with the composition ratio of the superconducting phase of Hg-12(n-1)n. The measurements of DC magnetic susceptibility by a SQUID magnetometer did not demonstrate any diamagnetic behavior around 235 K although a very small drop in the AC magnetic susceptibility was observed at this temperature with a Lakeshore magnetometer. The paper will discuss if the drop in the resistance for the mercury-based compounds at 235 K is due to superconductivity; we rather believe that it is due to the presence of liquid mercury of its alloys in the sample.

We attempt to provide a model calculation of the electric field gradient. With reference to the observed 57Fe Mossbauer hyperfine interaction parameters, the effective valence and electric field gradient on different Fe lattice sites have been computed for the Fe‐doped Y‐124 superconductor by means of the point‐charge‐effective‐valence model. According to the present calculations, the sign of electric‐field gradient for the pyramid Fe(B’) site and the quasioctahedral Fe(B) is estimated to be positive and negative, respectively, and furthermore Fe is found to be displaced relative to the CuO2 plane in Y‐124 superconductors.

High-temperature superconductors of the mercury-based system were synthesized under high temperature and high pressure. The measurements of resistance and DC magnetic susceptibility for the samples prepared at 20-35 kbar and 850-degrees-C for 1-3.5 h show that the as-synthesized sample (1) prepared at 20 kbar, 850-degrees-C for 1.5 h was a multiphase of Hg-1212 and Hg-1223 phases and showed superconducting transitions of both 132 and 120 K. The sample (2) prepared at 30 kbar, 850-degrees-C for 3.5 h has Hg-1212 as the major phase with only a small amount of impurity phase. The intergrowth of Hg-1212/Hg-1223 was found in the sample (1). The dependence of pressure on T(c) for the Hg-1212 and Hg-1223 phases, measured under hydrostatic pressure, shows that dT(c)/dp is 0.17 and 0.23 K/kbar, respectively, in the pressure range below 10 kbar.

The electronic structures of FeO 4 Ca 8 and FeO(1) 4 O(2)Ca 4 Sr 4 clusters in the Fe-doped Bi-systemhigh- T c phase are calculated using the SCF-Xα-SW method. From the calculated result, we find that the Fe atom does not contribute to the density of states near the Fermi energy in both clusters. Fe substitution for Cu sites of Bi-2233 phase is highly deleterious to superconducting behavior. The energy gap of FeO(1) 4 O(2)Ca 4 Sr 4 on the Fermi energy is about seven times larger than that of FeO 4 Ca 8 . Moreover, for the FeO(1) 4 O(2)Ca 4 Sr 4 cluster, the peak of the density of states (DOS) in the high energy range shifts to the low energy range and forms new DOS peaks, in contrast to the density of states in the FeO 4 Ca 8 cluster. The bonding of the hybridized orbital in FeO(1) 4 O(2)Ca 4 Sr 4 is stronger than in FeO 4 Ca 8 , namely the FeO(1) 4 O(2)Ca 4 Sr 4 is even stabler than the FeO 4 Ca 8 cluster. Such calculated result provides satisfactory agreement with Fe-doped experiments. It is observed that T c decreases with increasing iron content and Fe dopant gives rise to enhancement of the 2212 phase at expense of the 2223 in Bi-system superconductors. The calculated results can help us to understand the nature of Fe-doping for Cu on quantum mechanics background. Furthermore the theoretical value of the electric field gradient given by the SCF-Xα-SW method is agreement with the value deduced from quadrupole splittings by Mossbauer spectroscopy. This calculation can provide theoretical support for assignment of Fe species to Cu sites in high- T c superconductors.

The layered oxide LiVO2 recently has received more attention due to its interesting structural and magnetic behaviors involving the two-dimensional magnetic frustration in these systems. We synthesized a series of F-doped LiVO2 samples, and reported the F-doping effect on the structure and transition temperature Tt. The samples LiVO2-xFx (x=0, 0.1, 0.2 and 0.3) were characterized by X-ray diffraction, scanning electron microscope (SEM), differential scanning calorimetry (DSC), magnetic susceptibility and specific heat measurement. The structural analysis shows that with increasing x, the ratio of lattice parameter c/a increasing, i.e. in the a-b plane the lattice is compressed while in the c-axis direction the lattice expands. The DSC measurements show that a first-order phase transition happens at around 500 K, and the thermal hysteresis around phase transition temperature Tt increases with increasing x. Substitution of O with F ions results in a change of two dimensional characteristics and the distortion of the VO6 block in structure, which significantly influence the magnetic ordering transition temperature Tt.

57Fe Mossbauer measurement have been performed in the Fe-doped high-Tc phase of Bi-system superconductor. Isomer shifts display presence of Fe3+ ions in square and pyramidal coordinations. Regarding the high-Tc superconductors as primarily ionic crystals and using effective valence and point charge model, we have calculated the electric field gradients for Fe as a replacement for Cu in the high-Tc phase. Good agreement between theory and experiment is obtained.

Mossbauer measurements were performed in the temperature range from 77 to 300K. Temperature-dependent57Fe Mossbauer recoil-free fraction in high-Tc superconducting phase of Bi-system display cvidence of a softening in lattice vibrations, which appears at T

Long-term tests (864 days) were conducted on three types of columns, including plain concrete (PC) columns, reinforced concrete (RC) columns and concrete-filled steel tube (CFST) columns. The shrinkage and creep performance and the ultimate strength of the columns were tested and analyzed. The results show that the shrinkage strain of RC columns is about 87.6% of that of PC columns, the shrinkage strain of the CFST columns is about 34.8% of that of PC columns, and that the effect of expansion agent on shrinkage strain is about 2% for the PC columns. It was also found that the smaller the loading age, the greater the creep coefficient. Reinforcement can significantly reduce the creep deformation of PC columns. The creep coefficient of steel pipe surface is larger than that of inner concrete for CFST columns, leading to a longer life due to the creep of inner concrete to achieve stability. The loading age and the reinforcement have great impact on extreme compressive strain and ultimate strength. The hoop effect of RC columns is obvious. Loading rate influences the stress redistribution of CFST columns. The stress redistribution effect is relatively small for columns with loading course. However, the effect on the ultimate strength is very small for columns with or without loading courses. The difference of two is only 2.4%.

57 Fe Mossbauer measurements have been performed on Fe-doped samples of Bi 1.6 Pb 0.4 Sr 2 Ca 3 Cu 4- x Fe x O y ( x =0.06 and 0.08) at room temperature. The Mossbauer spectra show three quadrupole doublets that can be related to different Cu sites. Two doublets (B and C) with larger quadrupole splitting (QS) are assigned with a 57 Fe probe atom on the Cu-O square planar sites of the compound with different local charge environments. Another doublet A with smallest quadrupole splitting is associated with a Fe atom in a planar pyramid site. the doublet with smallest QS possesses relatively the smaller area indicating that the Fe atom preferentially occupies a square planar site rather than a pyramid site. To assure our assignment, we calculated the EFG (electric field gradient) on different Cu sites with the use of the point charge model and of the calculation of an effective ions valence.

We report a joint experimental and theoretical investigation of superconductivity in Ga-substituted type-I silicon clathrates. We prepared samples of the general formula Ba8Si46�xGax, with different values of x .W e show that Ba8Si40Ga6 is a bulk superconductor, with an onset at TC 3.3 K. For x = 10 and higher, no superconductivity was observed down to T = 1.8 K. This represents a strong suppression of superconductivity with increasing Ga content, compared to Ba8Si46 with TC 8 K. Suppression of superconductivity can be attributed primarily to a decrease in the density of states at the Fermi level, caused by a reduced integrity of the sp 3 -hybridized networks as well as the lowering of carrier concentration. These results are corroborated by first-principles calculations, which show that Ga substitution results in a large decrease of the electronic density of states at the Fermi level, which explains the decreased superconducting critical temperature within the BCS framework. To further characterize the superconducting state, we carried out magnetic measurements showing Ba8Si40Ga6 to be a type-II superconductor. The critical magnetic fields were measured to be HC1 35 Oe and HC2 8.5 kOe. We deduce the London penetration depth 3700 A and the coherence length c 200 A. Our estimate of the electron-phonon coupling reveals that Ba8Si40Ga6 is a moderate phonon-mediated BCS superconductor.

Micro-EDM milling has become one of the powerful means of 3D micromachining for MEMS. However, for micro- EDM milling, there isn't a general electrode wear compensation strategy matched to arbitrary materials of workpiece and electrode. In this paper, the machinability of platinum metal is evaluated by taking latent heat of fusion and evaporation into account firstly. And then, a general electrode wear compensation strategy based on above-mentioned evaluation is proposed. The two characters of this strategy are employing an unequal thickness lamination for milling path and using a fixed flat surface as compensation reference. As a result, a 0100 mum micro platinum hemisphere is machined successfully. The surface quality of the platinum hemisphere is better than that of micro steel hemisphere. It is proved that platinum is feasible to be machined by micro-EDM.