A large time step 1D upwind explicit scheme (CFL > 1): Application to shallow water equations

It is possible to relax the Courant–Friedrichs–Lewy condition over the time step when using explicit schemes. This method, proposed by Leveque, provides accurate and correct solutions of non-sonic shocks. Rarefactions need some adjustments which are explored in the present work with scalar equation and systems of equations. The non-conservative terms that appear in systems of conservation laws introduce an extra difficulty in practical application. The way to deal with source terms is incorporated into the proposed procedure. The boundary treatment is analysed and a reflection wave technique is considered. In presence of strong discontinuities or important source terms, a strategy is proposed to control the stability of the method allowing the largest time step possible. The performance of the above scheme is evaluated to solve the homogeneous shallow water equations and the shallow water equations with source terms.     

近红外光谱技术在奶酪品质评价中的应用

近红外光谱技术是一种快速、无损的分析方法,国外将该技术应用于奶酪品质的检测已有多年,国内在这方面的研究较少。通过本文介绍了近红外光谱技术分析奶酪成分和在奶酪的加工生产、缩水收缩控制、成熟过程、货架期、组成成分和品牌分类鉴别等几个方面的应用,表明近红外光谱技术在奶酪品质分析中应用潜力巨大,促进近红外光谱技术的应用和我国奶酪行业的发展是一项紧迫的任务。     

Some possible precursors of the main earthquakes of the Tornimparte (Central Italy) seismic sequence occurred in 1985

Summary Two tiltmeters installed at Peschiera site (Central Italy) generally showed trends that differ from the ones obtained at the network located in the Apennine region of Central Italy. Detrended tilt recordings reveal the presence of an anomalous variation during the first months of 1985. We propose to interpret this anomaly as a precursor of the main earthquakes of the seismic sequence occurred at Tornimparte area (Central Italy). The results of the deep-resistivity measurements obtained from June 1983 to December 1985 at Pizzoli area (Central Italy) reveal anomalous resistivity changes occurred at the end of May 1985. We propose that also this anomalous variation is connected with the Tornimparte seismic sequence.

---

Riassunto Due inclinometri installati in località Sorgenti del Peschiera (Italia Centrale) hanno evidenziato andamenti in generale diversi rispetto a quelli ottenuti dalla rete inclinometrica situata nella regione appenninica dell'Italia Centrale. Le tracce filtrate hanno messo in risalto la presenza di una variazione anomala verificatasi nei primi mesi del 1985. Si propone d'interpretare questa anomalia come precursore dei terremoti principali della sequenza sismica avvenuta nella zona di Tornimparte (Italia Centrale). I risultati delle misure di resistività profonda ottenuti da giugno 1983 a dicembre 1985 nell'area di Pizzoli (Italia Centrale) hanno evidenziato una variazione anomala di resistività alla fine di maggio 1985. Si propone che anche questa anomalia sia connessa alla sequenza sismica di Tornimparte.

---

Резюме Показания двух инклинометров, установленных в Пескиере (Центральная Италия) обычно отличаются от данных, полученных на станциях в Апеннинах Центральной Италии. Анализ данных обнаруживает аномальное отклонение в первые месяцы 1985 года. Мы предлагаем интерпретировать эту аномалию как предвестник главных змелятрясений сейсмической последовательности, наблюдавшейся в области Торнимпарте (Центральная Пталия). Результаты измерений глубинного сопротивления, полученные с июня 1983 г. по декабря 1985 г. в области Пиццоли (Центральная Италия), обнаруживают аномальные изменения сопротивления в конце мая 1985 г. Мы предполагаем, что это аномальное изменение также связано с сейсмической последовательностью в области Торнимпарте.

     

Theory of (e, 2e) reaction near solid surfaces: Application to Si

The use of the (e, 2e) technique in surface state spectroscopy is discussed. A general formulation based on Green function formalism is developed, that allows to take into account the electron-solid interaction. The case of the Si(111) surface is considered in detail. It is shown that the (e, 2e) cross section strongly depends on surface conditions; hence this technique could be an efficient tool for testing reconstruction models.     

Using high haze (> 90%) light-trapping film to enhance the efficiency of a-Si:H solar cells

The high haze light-trapping (LT) film offers enhanced scattering of light and is applied to a-Si:H solar cells. UV glue was spin coated on glass, and then the LT pattern was imprinted. Finally, a UV lamp was used to cure the UV glue on the glass. The LT film effectively increased the Haze ratio of glass and decreased the reflectance of a-Si:H solar cells. Therefore, the photon path length was increased to obtain maximum absorption by the absorber layer. High Haze LT film is able to enhance short circuit current density and efficiency of the device, as partial composite film generates broader scattering light, thereby causing shorter wave length light to be absorbed by the P layer so that the short circuit current density decreases. In case of lab-made a-Si:H thin film solar cells with v-shaped LT films, superior optoelectronic performances have been found (V_oc = 0.74 V, J_sc = 15.62 mA/cm², F.F. = 70%, and η = 8.09%). We observed ~ 35% enhancement of the short-circuit current density and ~ 31% enhancement of the conversion efficiency.     

Possible triggering of solar activity to big earthquakes (Ms ≥ 8) in faults with near west-east strike in China

This paper studies the relationship between solar activity and big earthquakes (Ms≥8) that occurred in China and western Mongolia. It is discovered that the occurrence dates of most of the big earthquakes in and near faults with west-east strike are close to the maximum years of sunspot numbers, whereas dates of some big earthquakes which are not in such faults are not close to the maximum years. We consider that it is possibly because of the appearance of many magnetic storms in the maximum years of solar activity. The magnetic storms result in anomalies of geomagnetic field and then produce eddy current in the faults gestating earthquake with near west-east strike. Perhaps the gestated big earthquakes occur easily since the eddy current heats the rocks in the faults and therefore decreases the shear resistant intensity and the static friction limit of the rocks.     

Triple differential cross-sections for near threshold (e, 2e) process for hydrogen

The resonance Raman (RR) spectra of nickel octaethyl porphyrin, Ni(OEP), in CH₂Cl₂ (solvent) at different excitations such as 514.5, 488.0, 441.6 and 406.7 nm are recorded and analysed. The results of the theory of distortion-induced RR intensity is applied to the observed spectra to determine the excited electronic state symmetry of porphyrin in Ni(OEP). It is concluded that the porphyrin molecule (D_4h structure) attains a non-polar distorted structure of D₂ symmetry rather than S₄ symmetry in CH₂Cl₂ solution.     

DWIA in the momentum space for (γ, π0) reaction near threshold

The differential and total cross-sections of neutral pion photoproduction off⁴He,¹²C and⁴⁰Ca nuclei are calculated in the framework of the DWIA in the momentum space. It is shown that the inclusion of pion wave distortion gives a less than 25% increase of the total cross sections. A good agreement with experimental data is achieved by using the full elementary amplitude that includes the pion-momentum nonlinear terms and the terms depending on nucleon momenta.     

The use of track registration detectors to reconstruct contemporary and historical airborne radon (RN) and radon progeny concentrations for radon-lung cancer epidemiologic study

Epidemiologic studies that investigate the relationship between radon and lung cancer require accurate estimates for the long-term average concentrations of radon progeny in dwellings. Year-to-year and home-to-home variations of radon in domestic environments pose serious difficulties for reconstructing an individual's long-term radon-related exposure. The use of contemporary radon gas concentrations as a surrogate for radon-related dose introduces additional uncertainty in dose assessment. Studies of glass exposed in radon chambers and in a home show that radon progeny deposited on, and implanted in, glass hold promise for reconstructing past radon concentrations in a variety of atmospheres. We developed an inexpensive track registration detector for the Iowa Radon Lung Cancer Study (IRLCS) that simultaneously measures contemporary airborne radon concentrations, surface deposited alpha activity density, and implanted ²¹⁰Po activity density. The implanted activity is used to reconstruct the cumulative radon and radon progeny exposure from the age of the glass and the ratios of the contemporary deposited activiteis to airborne radon gas activity. We placed over 2500 of these detectors in more than 1000 homes and retrieved 97% of them after a one-year exposure period. A preliminary analysis of the 1280 detectors that have undergone quality assurance review shows that the modules are meeting their accuracy and precision goals (10%). There is good correlation (r²0.5) between the total radon exposure estimated from contemporary radon gas measurements and historical average reconstructed from the implanted ²¹⁰Po surface activity. The linear regression slope of the airborne radon exposure to implanted activity is the same as the room model slope based on typical room parameters. This correlation improves (r²0.7) when the deposited surface activity measurements are added to the linear regression. Thus, track-registration detectors can contribute to accurate radon-related dose assessment in epidemiologic studies. Additional work is planned to incorporate the deposited activities in a more sophisticated reconstruction model.     

Growth mechanism of thermally processed Cu(In,Ga)S2 precursors for printed Cu(In,Ga)(S,Se)2 solar cells

We investigate a process used for the selenisation of particle‐based precursors to prepare low‐cost Cu(In,Ga)(S,Se)₂ (CIGS) solar cells. It is suitable for high throughput with a short optimum selenisation duration of 3–5 min and employs a rapid thermal annealing system with elemental selenium vapour. Homogeneous crack‐free Cu(In,Ga)S₂ precursor films of up to 1 µm are obtained via doctor blading. The high selenium vapour pressure in the selenisation reaction chamber results in the formation of a compact Cu(In,Ga)(S,Se)₂ layer on top of a carbon‐rich underlayer. In order to investigate the phase development in the film, the selenisation process was interrupted at different stages and the samples were monitored via XRD and surface‐sensitive Raman measurements. We find the formation of a polycrystalline Cu(In,Ga)Se₂ phase already after 1 s at the target temperature of 550 °C. Furthermore, the effect of initial precursor thickness on solar cell parameters is discussed. Complete solar cells are prepared by conventional methods, leading to conversion efficiencies well above 8%. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Sonochemical synthesis of nano-scale mixed-ligands lead(II) coordination polymers as precursors for preparation of PbO and PbBr(OH) nano-structures; thermal,structural and X-ray powder diffraction studies

Nano-structures of two new lead(II) two-dimensional coordination polymers, [Pb₂(2-pyc)₂(I)₂]_n (1) and [Pb₂(2-pyc)₂(Br)₂]_n (2), {2-Hpyc = 2-pyridinecarboxilic acid } were synthesized by a sonochemical method that produce the coordination polymers at nano-size. The new nano-structures were characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. Compounds 1 and 2 were structurally characterized by single crystal X-ray diffraction and consist of two-dimensional polymeric units. The thermal stability of compounds 1 and 2 were studied by thermal gravimetric and differential thermal analyses. PbO and PbBr(OH) nano-structures were obtained by calcination of the nano-structures of compounds 1 and 2 at 400 °C, respectively.     

Interaction of hydrogen with (2 1 0)-oriented metal surfaces: Molecular precursors,chemisorbed atoms and subsurface states

Some selected aspects of hydrogen interaction with metal surfaces are surveyed with emphasis on the formation of molecular precursor states on surfaces that are normally known to readily and spontaneously dissociate hydrogen molecules (Ni, Pd, Rh). We will demonstrate that the crystallographic (2 1 0) orientation of the face-centered cubic (“f.c.c”) lattice seems to provide a particular route for stabilizing a (weakly) chemisorbed H₂ species notwithstanding the ordinary H₂ dissociative chemisorption and – in the Pd case – subsurface H state formation. This molecular hydrogen species – although or just because it is bound with an adsorption energy of merely ～20–25 kJ/mole may play an essential role both in heterogeneously catalysed surface and hydrogen uptake reactions that precede, e.g., H storage in solid materials.     

Microscopic (p,p′) calculations and polarization charges with large basis shell-model wave functions

Techniques have been developed for performing microscopic model DWBA calculations of inelastic nucleon-nucleus scattering using large basis shell-model wave functions to describe the nuclear states involved. For the case of ¹³⁸Ba at a bombarding energy of 30 MeV, we obtain good fits to the data by including the exchange amplitude in the DWBA and assuming a state and multipole independent polarization charge.     

电沉积Cu(In,Ga)Se_2预置层硫化退火制备Cu(In,Ga)(Se,S)_2薄膜及表征

在550℃下的H2S气氛中退火处理电沉积制备的Cu(In,Ga)Se2(CIGS)预置层,制备了太阳电池光吸收层Cu(In,Ga)(Se,S)2(CIGSS)薄膜.采用X射线能量色散谱、俄歇电子能谱、扫描电镜、X射线衍射和拉曼光谱对退火前后的薄膜进行表征.结果表明,H2S气氛下退火能够实现薄膜中O的去除和S的掺入,同时使得各元素的纵向分布更加均匀并可消除Cu-Se微相.此外,H2S退火还可改善薄膜的结晶性能,并使S和Ga进入黄铜矿结构,薄膜晶格参数变小.     

Wall-PIV as a near wall flow validation tool for CFD: Application in a pathologic vessel enlargement (aneurysm)

Flow visualization of a near wall flow is of great importance in the field of biofluid mechanics in general and for studies of pathologic vessel enlargements (aneurysms) particularly. Wall shear stress (WSS) is one of the important hemodynamic parameters implicated in aneurysm growth and rupture. The WSS distributions in anatomically realistic vessel models are normally investigated by computational fluid dynamics (CFD). However, the results of CFD flow studies should be validated. The recently proposed Wall-PIV method was first applied in an enlarged transparent model of a cerebri anterior artery terminal aneurysm made of silicon rubber. This new method, called Wall-PIV, allows the investigation of a flow adjacent to transparent surfaces with two finite radii of curvature (vaulted walls). Using an optical method which allows the observation of particles up to a predefined depth enables the visualization solely of the boundary layer flow. This is accomplished by adding a specific molecular dye to the fluid which absorbs the monochromatic light used to illuminate the region of observation. The results of the Wall-PIV flow visualization were qualitatively compared with the results of the CFD flow simulation under steady flow conditions. The CFD study was performed using the program FLUENT®. The results of the CFD simulation were visualized using the line integral convolution (LIC) method with a visualization tool from AMIRA®. The comparison found a very good agreement between experimental and numerical results.     

Thermal decomposition mechanisms of tungsten nitride CVD precursors on Cu(1 1 1)

Chemisorption and thermal decomposition of metallorganic chemical vapor deposition precursors, (t-BuN)₂W(NHBu-t)₂, bis(tert-butylimido)bis(tert-butylamido)tungsten (BTBTT) and (t-BuN)₂W(NEt₂)₂, bis(tert-butylimido)bis(diethylamido)tungsten (BTBDT), on Cu(1 1 1) have been investigated by means of thermal desorption spectroscopy (TDS) and synchrotron-based X-ray photoelectron spectroscopy (SR-XPS) under ultrahigh vacuum conditions. The precursors remain intact upon chemisorption on Cu(1 1 1) at 100 K, and at 300 K both precursors decompose readily via the characteristic hydride abstraction/elimination pathways to produce two stable surface intermediates for each precursor. For BTBTT, one species is W(=NBu-t)₃ and the other is proposed to be a bridged amido complex, [(t-BuN)₂W(μ-NBu-t)]₂. In comparison, a W-imine complex and a W-N-C metallacycle are two intermediates produced from BTBDT. Annealing toward 800 K further decomposes the intermediates and the detectable desorption species are completely derived from the ligands. The desorption products from BTBTT include t-butylamine generated from α-H abstraction, isobutylene from γ-H elimination, acetonitrile from β-methyl elimination, and molecular hydrogen. In addition to these desorption species, BTBDT produces hydrogen cyanide and imine (EtN = CHMe) via β-H elimination, not possible with BTBTT due to the absence of β-H in the ligands. Eventually, tungsten nitrides incorporating oxygen atoms and a small amount of graphitic carbons are formed and the stoichiometry is approximated as WN_1.5O_0.1. Oxygen incorporation, driven by a large oxide formation enthalpy, is sensitively dependent on the moisture exposure in UHV environment.     

The ANC of O subthreshold states from C(Li, d) reaction at energies near the barrier

The ANC of the ²⁺ (6.92 MeV) and ¹⁻ (7.12 MeV) subthreshold states of ¹⁶O have been extracted from the normalization of ¹²C(⁶Li, d) angular distribution to a Finite Range Distorted Wave Born Approximation (FRDWBA) calculation. The theoretical analysis indicates a peripheral reaction and the extracted ANCs are not sensitive to the number of nodes in the bound state potential. The uncertainty from the entrance channel potential is minimized to 8% for the 6.92 and 11% for the 7.12 MeV state if the normalization is performed at the grazing angle. The uncertainty from the exit channel potential at the grazing angle is found to be 10% and 12% respectively for the 7.12 and 6.92 MeV states.     

Exclusive measurement of the pp --> pppi(+)pi(-) reaction near threshold

The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant contributions from p(*)-->Delta(++)pi(-)-->psigma. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance (3sigma) are found.