Response of YBCO/PCBO/YBCO ramp type Josephson junctions to near MM wave irradiation

A high Tc Josephson device for high frequency detection applications is being developed, consisting of an YBCO/PBCO/YBCO ramp type junction and a broad band log-periodic antenna. In this contribution we present the response of such a device to (near) mm wave irradiation. Shapiro steps have been observed up to very high voltage values - nearly 4 mV at 10 K, at the maximum of the radiation power. The modulation of the step amplitudes shows very good resemblence with the predictions from the Resistively Shunted Junction model

Effect of Preliminary Torsional Strain on Low-Cycle Fatigue of Q345B Structural Steel

Effect of preliminary torsional strain on low-cycle fatigue of Q345B steel was studied. The specimens were first 0, 180, and 360° twisted, then the low-cycle fatigue of Q345B steel was evaluated in the strain range of 0.3–0.8% by the method of axisymmetrical strain. The cycling response, cyclic stress–strain relationship, strain–life relationship, fatigue life prediction model, and seismic stability at different torsion angles were obtained and analyzed. The strain–life curve is shown to slope down as a power function. The fatigue life comes down with preliminary torsional strain at a constant level. The cycling response varied from cyclic hardening to cyclic softening in preliminary torsion, and the cyclic hardening rate increased linearly with the strain amplitude. The parameters of the Coffin–Manson relation are corroborated with experimental data. After heat treatment, the seismic stability of the material is improved, with torsional strain greatly reducing this characteristic. Electron microscope examination of fatigue fracture revealed a fatigue crack initiating on the surface of the specimen. The propagating crack deviated from its direction, and plasticity of the material dropped as a result of preliminary torsional strain.Изучено влияние деформации предварительного кручения на малоцикловую усталость стали Q345B. Вначале образцы скручивали на 0, 180 и 360°, затем методом осесимметричной деформации определяли малоцикловую усталость стали Q345B в диапазоне деформаций 0.3 0.8%. Получены и проанализированы характеристика циклических изменений, зависимость циклического изменения напряжения от деформации, зависимость деформация долговечность, модель прогнозирования усталостной долговечности и сейсмостойкость при различных углах кручения. Показано, что кривая деформация долговечность идет вниз и описывается степенной функцией. Усталостная долговечность снижается с увеличением деформации предварительного кручения при постоянном уровне последней. Характеристика циклических изменений варьировала от циклического упрочнения до циклического разупрочнения при кручении, скорость циклического упрочнения возрастала линейно с повышением амплитуды деформации. Параметры зависимости Коффина Мэнсона подтверждаются экспериментальными данными. После термообработки сейсмостойкость материала улучшается, при этом деформация предварительного кручения существенно снижает ее. Электронно-микроскопическое исследование усталостного разрушения выявило зарождение усталостной трещины на поверхности образца. Растущая трещина отклонялась от своего направления, пластичность материала снижалась в результате деформации предварительного кручения.Вивчено вплив деформації попереднього кручення на малоціклову втому стали Q345B. Спочатку зразки скручували на 0, 180 і 360 °, потім методом вісесиметричної деформації визначали малоціклову втому стали Q345B в діапазоні деформацій 0.3-0.8%. Отримано і проаналізовано характеристику циклічних змін, залежність циклічної зміни напржень від деформації, залежність деформація-довговічність, модель прогнозування втомної довговічності і сейсмостійкості при різних кутах кручення. Показано, що крива деформація - довговічність йде вниз і описується ступеневою функцією. Втомна довговічність знижується зі збільшенням деформації попереднього кручення при постійному рівні останньої. Характеристика циклічних змін варіювала від циклічного зміцнення до циклічного знеміцнення при крученні, швидкість циклічного зміцнення зростала лінійно з підвищенням амплітуди деформації. Параметри залежності Коффина-Менсона підтверджуються експериментальними даними. Після термообробки сейсмостійкість матеріалу поліпшується, при цьому деформація попереднього кручення істотно знижує її. Електронно-мікроскопічне дослідження втомного руйнування виявило зародження втомної тріщини на поверхні зразка. Зростаюча тріщина відхилялася від свого напрямку, пластичність матеріалу знижувалася в результаті деформації попереднього кручення

Investigation on wear and rolling contact fatigue of wheel-rail materials under various wheel/rail hardness ratio and creepage conditions

The wear and rolling contact fatigue of wheel-rail materials were investigated through varying wheel/rail hardness ratios (Hw/Hr) and creepages. The results indicated that with the Hw/Hr increasing from 0.927 to 1.218, the wheel wear rate reduced significantly in the case of Hw/Hr = 1.218, the rail wear rate showed an increasing trend. Both the wheel and rail wear rates increased as the creepage enlarged. The synergistic results of Hw/Hr and creepage caused a transition of the wear and damage mechanisms on the wheel-rail steels. Besides, the fatigue damage of ER7 and CL60 wheel materials was dominated by slender multi-layer cracks, while the fatigue cracks were short and contained lots of interlayer broken materials on C-class wheel steel

Comparison of wear and rolling contact fatigue behaviours of bainitic and pearlitic rails under various rolling-sliding conditions

Rolling-sliding wear experiments were performed to investigate the wear and rolling contact fatigue (RCF) behaviours of a premium pearlitic rail (PH), a carbon-free bainitic rail (BH) and two standard pearlitic rails (U71Mn and U75V). The wear regime and RCF damage evolution of the PH and BH materials in terms of Tγ/A (i.e. creepages and contact pressures) were compared and analyzed. The high-hardness BH steel presented a wear resistance similar to U71Mn and U75V rail materials, whereas lower wear rate was shown by the PH steel. Concerning the RCF performance, the damage of BH steel (comparable to U75V) was more severe than that of PH steel (comparable to U71Mn). Finally, with the increase in creepages and pressures, the wear and RCF damage of both PH and BH steels increased. These information could provide a guide in choosing rail materials and in development of bainitic rails

High Altitude test of RPCs for the ARGO-YBJ experiment

A 50 m**2 RPC carpet was operated at the YangBaJing Cosmic Ray Laboratory (Tibet) located 4300 m a.s.l. The performance of RPCs in detecting Extensive Air Showers was studied. Efficiency and time resolution measurements at the pressure and temperature conditions typical of high mountain laboratories, are reported.Comment: 16 pages, 10 figures, submitted to Nucl. Instr. Met

Direct Measurements of the Branching Fractions for D0→K−e+νeD^0 \to K^-e^+\nu_e and D0→π−e+νeD^0 \to \pi^-e^+\nu_e and Determinations of the Form Factors f+K(0)f_{+}^{K}(0) and f+π(0)f^{\pi}_{+}(0)

The absolute branching fractions for the decays $D^0 \to K^-e ^+\nu_e$ and $D^0 \to \pi^-e^+\nu_e$ are determined using $7584\pm 198 \pm 341$ singly tagged $\bar D^0$ sample from the data collected around 3.773 GeV with the BES-II detector at the BEPC. In the system recoiling against the singly tagged $\bar D^0$ meson, $104.0\pm 10.9$ events for $D^0 \to K^-e ^+\nu_e$ and $9.0 \pm 3.6$ events for $D^0 \to \pi^-e^+\nu_e$ decays are observed. Those yield the absolute branching fractions to be $BF(D^0 \to K^-e^+\nu_e)=(3.82 \pm 0.40\pm 0.27)$ and $BF(D^0 \to \pi^-e^+\nu_e)=(0.33 \pm 0.13\pm 0.03)$. The vector form factors are determined to be $|f^K_+(0)| = 0.78 \pm 0.04 \pm 0.03$ and $|f^{\pi}_+(0)| = 0.73 \pm 0.14 \pm 0.06$. The ratio of the two form factors is measured to be $|f^{\pi}_+(0)/f^K_+(0)|= 0.93 \pm 0.19 \pm 0.07$.Comment: 6 pages, 5 figure

The σ\sigma pole in J/ψ→ωπ+π−J/\psi \to \omega \pi^+ \pi^-

Using a sample of 58 million $J/\psi$ events recorded in the BESII detector, the decay $J/\psi \to \omega \pi^+ \pi^-$ is studied. There are conspicuous $\omega f_2(1270)$ and $b_1(1235)\pi$ signals. At low $\pi \pi$ mass, a large broad peak due to the $\sigma$ is observed, and its pole position is determined to be $(541 \pm 39)$ - $i$ $(252 \pm 42)$ MeV from the mean of six analyses. The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL

Search for the Lepton Flavor Violation Processes J/ψ→J/\psi \to μτ\mu\tau and eτe\tau

The lepton flavor violation processes $J/\psi \to \mu\tau$ and $e\tau$ are searched for using a sample of 5.8$\times 10^7$ $J/\psi$ events collected with the BESII detector. Zero and one candidate events, consistent with the estimated background, are observed in $J/\psi \to \mu\tau, \tau\to e\bar\nu_e\nu_{\tau}$ and $J/\psi\to e\tau, \tau\to\mu\bar\nu_{\mu}\nu_{\tau}$ decays, respectively. Upper limits on the branching ratios are determined to be $Br(J/\psi\to\mu\tau)<2.0 \times 10^{-6}$ and $Br(J/\psi \to e\tau) < 8.3 \times10^{-6}$ at the 90% confidence level (C.L.).Comment: 9 pages, 2 figure

Observation of the decay \psip\rar\kstark

Using 14 million $\psi(2S)$ events collected with the BESII detector, branching fractions of \psip\rar\kstarkpm and \kstarknn are determined to be: \calB(\psip\rar\kstarkpm)=(2.9^{+1.3}_{-1.7}\pm0.4)\times 10^{-5} and \calB(\psip\rar\kstarknn)=(13.3^{+2.4}_{-2.7}\pm1.9)\times 10^{-5}. The results confirm the violation of the "12%" rule for these two decay channels with higher precision. A large isospin violation between the charged and neutral modes is observed.Comment: 5 pages, 3 figure

Fabrication of CuO nanoparticle interlinked microsphere cages by solution method

Here we report a very simple method to convert conventional CuO powders to nanoparticle interlinked microsphere cages by solution method. CuO is dissolved into aqueous ammonia, and the solution is diluted by alcohol and dip coating onto a glass substrate. Drying at 80 °C, the nanostructures with bunchy nanoparticles of Cu(OH)2can be formed. After the substrate immerges into the solution and we vaporize the solution, hollow microspheres can be formed onto the substrate. There are three phases in the as-prepared samples, monoclinic tenorite CuO, orthorhombic Cu(OH)2, and monoclinic carbonatodiamminecopper(II) (Cu(NH3)2CO3). After annealing at 150 °C, the products convert to CuO completely. At annealing temperature above 350 °C, the hollow microspheres became nanoparticle interlinked cages