Long-Term Measurements of SO 2 Over Delhi,India

Long-term measurements (2011–2018) of ambient sulphur dioxide (SO2) and meteorology were carried out at an urban site of Delhi, India, to study the seasonal and inter-annual variations of SO2 over Delhi. The average mixing ratio of SO2 was estimated as 2.26 ± 0.48 ppb for the entire study period. Mixing ratio of ambient SO2 was estimated as 2.19 ± 0.64 ppb, 2.07 ± 0.89 ppb, 2.49 ± 1.05 ppb and 2.27 ± 0.71 ppb during winter, pre-monsoon, monsoon and post-monsoon seasons, respectively. SO2 mixing ratio was recorded maxima during monsoon (2.49 ± 1.05 ppb) season, whereas minima during pre-monsoon season (2.07 ± 0.89 ppb). The mixing ratio of SO2 showed slightly increase in the trend during observational period. Surface wind speed and wind directions analysis indicates the influence of local sources on the mixing ratio of SO2 at the study site. Backward trajectories and potential source contributing factor (PSCF) analysis also showed the local as well as the regional sources (industrial activities, coal burning and thermal power plants etc.,) influencing the mixing ratio of SO2 over Delhi.     

Correlation between interfacial microstructure and shear behavior of Sn–Ag–Cu solder ball joined with Sn–Zn–Bi paste

Sn–8Zn–3Bi solder paste was applied as a medium to joint Sn–3.2Ag–0.5Cu solder balls and Cu/Ni/Au metallized ball grid array substrates at 210 °C. Sn–Ag–Cu joints without Sn–Zn–Bi addition were also conducted for comparison. The shear behavior of the specimens was investigated after multiple reflow and thermal aging. For each strength test, more than 40 solder balls were sheared. The shear strength of Sn–Ag–Cu specimens kept constant ranging from 15.5 ± 1.3 N (single reflow) to 16.2 ± 1.0 N (ten reflows) and the fractures occurred in the solder. Shear strength of Sn–Ag–Cu/Sn–Zn–Bi specimens fell from 15.9 ± 1.7 N (single reflow) to 13.4 ± 1.6 N (ten reflows). After single reflow, Sn–Ag–Cu/Sn–Zn–Bi specimens fractured in the solder along Ag–Au–Cu–Zn intermetallic compounds and at Ni metallization. After ten reflows, fractures occurred in the solder and at solder/Ni–Sn–Cu–Zn intermetallic compound interface. The shear strengths of the Sn–Ag–Cu and Sn–Ag–Cu/Sn–Zn–Bi packages changed little after aging at 150 °C. Sn–Ag–Cu/Sn–Zn–Bi joints kept higher strength than Sn–Ag–Cu joints. Sn–Ag–Cu joints fractured in the solder after aging. But the fractures of Sn–Ag–Cu/Sn–Zn–Bi specimens shifted to the solder with aging time.     

Eliminating nuisance parameters: two characterizations

Given a statistical modelP = {P_θ : θ ∈ x} and a surjective functiong: ϑ→Λ the problem of transformingP into a new modelQ= {_λ : λ ∈ Λ} indexed by Λ is investigated. Two characterizations are given for those modelsQ of the form Q_λ = ∫ P_θ π_λ(dθ), where π_λ is some probability such that π_λ(g=λ)=1. The first is related to a geometric property ofQ, while the second rests on the inferential implications of adoptingQ. Also, in the first π_λ is allowed to be finitely additive, while in the second π_λ is σ-additive. Finally, integrated likelihoods are revisited in light of the second characterization.     

Introducing the concept of “uncertainty in measurement” into domestic metrological practice

There are four options for introducing the uncertainty concept in Russia. Preference is given to the gradual replacement of “error characteristic,” “total mean-square error,” and “confidence limits of error” by the terms “uncertainty,” “combined standard uncertainty,” and “expanded uncertainty,” respectively. The incorrect and widespread perception that “uncertainty in measurement” is an alternative for “error” is pointed out. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 27–28, May, 2000.     

Influence of arsenic, antimony and phosphorous on the microstructure and corrosion behavior of brasses

The effect of minor additions of As, Sb and P on phase distribution and corrosion behavior has been studied in brasses. The alloys investigated were 60Cu–39Zn–1Pb, 48.95Cu–45Zn–5Pb–1Sn–0.05As, 48.90Cu–45Zn–5Pb–1Sn–0.05As–0.05Sb and 48.85Cu–45Zn–5Pb–1Sn–0.05As–0.05Sb–0.05P. Immersion tests in 1% CuCl₂ solution indicated that the addition of As improved corrosion resistance while the combined addition of As + Sb and As + Sb + P was not beneficial. The hardness increased significantly with the addition of As, Sb and P. Microstructural observations indicated an increase in β phase fraction in the As, Sb and P containing alloys. X-ray diffraction studies confirmed the formation of intermetallic compounds in As, Sb and P containing alloys. Based on the microstructural observations, the intermetallic compounds appear to be primarily precipitated in the β phase with As + Sb and As + Sb + P additions. The lower corrosion resistance of the alloys 48.90Cu–45Zn–5Pb–1Sn–0.05As–0.05Sb and 48.85Cu–45Zn–5Pb–1Sn–0.05As–0.05Sb–0.05P has been related to increase in β phase volume fraction and precipitation of intermetallic compounds in the β phase.     

Evaluation of cyclic elastoplastic strains near notches

On the basis of direct measurements of the opening displacements of notch contours, we develop an experimental-numerical procedure for the evaluation of the range of local elastoplastic strain Δε_τ. The experimental values of Δε_τ are compared with the data of numerical calculations performed by using formulas known from the literature (Δε). It is shown that, for Δε_τ(Δε)<2%, the experimental and theoretical values are in good agreement but only in the case where the gradients of strains near the tips of the notches are taken into account. For Δε_τ>2%, the theoretical values of Δε are higher than experimental Δε_τ and the smaller the radius of the notch ρ, the greater the difference between these values. Therefore, it reasonable to use the experimentally evaluated and approved values of the parameter Δε_τ. Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 33, No. 2, pp. 62–72, March–April, 1997.     

Nanostructural modification of an Al–C–Ti coating on alloy AZ91D under the multipulse action of Nd:YAG and Ng-glass lasers

Experimental results on the nanostructural modification of an Al–C–Ti coating on magnesium alloy AZ91D under the multipulse action of Nd:YAG lasers (λ = 1064 nm, τ = 20 ns, and E = 200 mJ) and Nd-glass lasers (λ = 1060 nm, τ = 85 ns, and E = 2 J) are given. It is shown that the formation of the found nanocrystalline coating structure with a grain size of 35 to 400 nm involves the process of background deposition of ablated particles and condensed clusters formed in the plasma plume.     

Properties of SnAgCu/SnAgCuCe soldered joints for electronic packaging

For quad flat packages (QFP256), lead-free soldered joints reliability in service is a critical issue. In this paper, soldering experiments of quad flat package (QFP256) devices were carried out by means of infrared reflow soldering system with Sn–3.8Ag–0.7Cu and Sn–3.8Ag–0.7Cu–0.03Ce lead-free solders, respectively, and the mechanical properties of micro-joints of the QFP devices were tested and studied by STR micro-joints tester. The results indicate that the tensile strength of Sn–Ag–Cu–Ce soldered joints is better than that of Sn–Ag–Cu soldered joints. In particular, the addition of trace Ce to the Sn–Ag–Cu solder can refine the microstructures and decrease the thickness of the intermetallic compound layer of Sn–Ag–Cu solder alloys. In addition, the stress–strain response of Sn–Ag–Cu/Sn–Ag–Cu–Ce soldered joints in quad flat packaging was investigated using finite element method based on Garofalo–Arrhenius model. The simulated results indicate creep distribution of soldered joints is not uniform, the heel and toe of soldered joints, the area between soldered joints and leads are the creep concentrated sites. The creep strain of Sn–Ag–Cu–Ce soldered joints is lower than that of Sn–Ag–Cu soldered joints.     

Dislocation motion in the early stages of high-temperature low-stress creep in a single-crystal superalloy with a small lattice misfit

Dislocation configurations at different creep stages (1100 °C and 137 MPa) in a superalloy TMS-75(+Ru) were studied in transmission electron microscopy (TEM) and the movement path of these creep-produced dislocations could be fully illustrated. Due to the small value of γ/γ′ lattice misfit, these dislocations cannot glide in the horizontal γ matrix channels by cross slip, but they mainly move by climbing around the γ′ cuboids. In the primary stage, the dislocations first move by slip in the γ-matrix channels. When they reach the γ′ cuboids, they move by climbing along the γ′ cuboid surfaces. In the secondary creep stage, dislocation reorientation in the (001) interfacial planes happens slowly, away from the deposition orientation of 〈110〉 to the misfit orientation of 〈100〉. The velocity of the reorientation is lower and a perfect γ/γ′ interfacial dislocation network cannot be formed quickly. This factor results in a large creep rate of the alloy during the secondary creep stage. The path for dislocation motion during the early creep stages consists of the following sequences: (i) climbing along the γ′ cuboid surface, (ii) deposition onto the (001) γ/γ′ interfacial plane, and (iii) reorientation from the 〈110〉 direction to the 〈100〉 direction.     

Microstructure and corrosion properties of as sub-rapid solidification Mg–Zn–Y–Nd alloy in dynamic simulated body fluid for vascular stent application

Magnesium alloy stent has been employed in animal and clinical experiment in recent years. It has been verified to be biocompatible and degradable due to corrosion after being implanted into blood vessel. Mg–Y–Gd–Nd alloy is usually used to construct an absorbable magnesium alloy stent. However, the corrosion resistant of as cast Mg–Y–Gd–Nd alloy is poor relatively and the control of corrosion rate is difficult. Aiming at the requirement of endovascular stent in clinic, a new biomedical Mg–Zn–Y–Nd alloy with low Zn and Y content (Zn/Y atom ratio 6) was designed, which exists quasicrystals to improve its corrosion resistance. Additionally, sub-rapid solidification processing was applied for preparation of corrosion-resisting Mg–Zn–Y–Nd and Mg–Y–Gd–Nd alloys. Compared with the as cast sample, the corrosion behavior of alloys in dynamic simulated body fluid (SBF) (the speed of body fluid: 16 ml/800 ml min⁻¹) was investigated. The results show that as sub-rapid solidification Mg–Zn–Y–Nd alloy has the better corrosion resistance in dynamic SBF due to grain refinement and fine dispersion distribution of the quasicrystals and intermetallic compounds in α-Mg matrix. In the as cast sample, both Mg–Zn–Y–Nd and Mg–Y–Gd–Nd alloys exhibit poor corrosion resistance. Mg–Zn–Y–Nd alloy by sub-rapid solidification processing provides excellent corrosion resistance in dynamic SBF, which open a new window for biomedical materials design, especially for vascular stent application.     

Uncertainty of measurement results in various scales

The relationship between the concepts of “error” and “uncertainty” of measurement results is examined. The concepts of “standard uncertainty,” “combined standard uncertainty,” and “expanded uncertainty” are shown to be inapplicable in nonmetric scales of quantities and properties, in which the general concept of “uncertainty” in the broad sense is recommended. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 29–30, May, 2000.     

Formation of strain-induced martensite in chromium–nickel steels of the austenitic class

We investigate the formation of the first portions of strain-induced martensite in plastic uniaxial compression of 12Kh18N10T and 12Kh18N9T steels in which δ-ferrite is absent and present, respectively, in the initial state. The true deformation martensitic points ε _s are experimentally determined. It is established that, in 12Kh18N10T steel, there exist one-phase (A) and two-phase (A + M) states for ε < ε _s and ε > ε _s , respectively, whereas, in 12Kh18N9T steel, there exist two-phase (A + F) and three-phase (A + F + M) states for ε < ε _s and ε > ε _s , respectively. The effect of increase in the magnetization of paramagnetic austenite before the formation of strain-induced martensite is detected.     

Mechanical properties of rapidly solidified ribbons of some AI–Si based alloys

Continuous uniform ribbons of Al–16 Si, Al–12.5 Si–1 Ni and Al–12.5 Si–1 Mg were prepared by melt spinning. Microhardness was measured. The as-melt spun values were 1280, 1370 and 1500 MN m-2 which relax on thermal ageing to 700, 700 and 800 MN m-2 for Al–16 Si, Al–Si–Ni and Al–Si–Mg, respectively. The hardness values of the melt spun ribbons are higher than the as-cast rods from which the ribbons were produced by a factor ranging from 1.8–2.2 times. Tensile testing at room temperature shows that the load–elongation curves are linear with a change of slope occurring in some of the specimens. These curves also show serrations in the case of as-melt spun and the intermediately annealed Al–Si specimens, while no serration was observed in the fully annealed samples. No serration was observed in the Al–Si–Ni and Al–Si–Mg alloys. UTS values were 420, 270 and 100 MN m-2 for Al–16 Si, Al–Si–Ni and Al–Si–Mg, respectively. These values show that the rapid solidification process improved the tensile properties significantly in Al–16 Si and Al–Si–Ni alloys while no significant improvement can be detected for Al–Si–Mg alloy. A discussion is given on hardness relaxation and tensile testing results in terms of silicon precipitation. This revised version was published online in November 2006 with corrections to the Cover Date.     

Analysis of the error of measurements of the active electric power in symmetrical three-phase electric networks

The error in measuring electric power for “three-element” and “two-element” transformer circuits including the electric power meter is analyzed. It is shown that, unlike a “ three-element” circuit, a “two-element” measurement circuit has somewhat larger values of the measurement error. __________ Translated from Izmeritel’naya Tekhnika, No. 4, pp. 68–70, April, 2006.     

Subcritical crack growth and power law exponent of Y–Si–Al–O(–N) glasses in aqueous environment

The subcritical crack growth resistance in water of a Y–Si–Al–O and Y–Si–Al–O–N glasses has been investigated with three point bending experiments. It has been shown that the SCG behaviour of the Y–Si–Al–O–N glass is superior to that of the Y–Si–Al–O glass. This is reflected by the power law exponent n which is 21 for the Y–Si–Al–O glass and 63 for the Y–Si–Al–O–N glass. Mechanistic implications of these observations are discussed.     

Suppressing the growth of interfacial Cu–Sn intermetallic compounds in the Sn–3.0Ag–0.5Cu–0.1Ni/Cu–15Zn solder joint during thermal aging

Evolution of interfacial phase formation in Sn–3.0Ag–0.5Cu/Cu (wt%), Sn–3.0Ag–0.5Cu–0.1Ni/Cu, Sn–3.0Ag–0.5Cu/Cu–15Zn, and Sn–3.0Ag–0.5Cu–0.1Ni/Cu–15Zn solder joints are investigated. Doping Ni in the solder joint can suppress the growth of Cu₃Sn and alter the morphology of the interfacial intermetallic compounds (IMCs), however it shows rapid growth of (Cu,Ni)₆Sn₅ at the Sn–3.0Ag–0.5Cu–0.1Ni/Cu interface. In comparison with the Cu substrates, the Cu–Zn substrates effectively suppress the formation of Cu–Sn IMCs. Among these four solder joints, the Sn–3.0Ag–0.5Cu–0.1Ni/Cu–15Zn solder joint exhibits the thinnest IMC, and only (Cu,Ni)₆(Sn,Zn)₅ formed at the interface after aging. It is revealed that the presence of Ni acts to enhance the effect of Zn on the suppression of Cu–Sn IMCs in the SAC305–0.1Ni/Cu–15Zn solder joint. The limited formation of IMCs is related to the elemental redistribution at the joint interfaces during aging. The Sn–3.0Ag–0.5Cu–0.1Ni/Cu–15Zn joint can act as a stabilized interconnection due to the effective suppression of interfacial reaction.     

Emissive characteristics of mesa-stripe lasers (λ=3.0–3.6 μm) made from InGaAsSb/InAsSbP double heterostructures

The directional patterns, current-voltage characteristics, and spectral characteristics of mesastripe lasers with InGaAsSb active layers, emitting at λ=3.0–3.6 μm (77 K) and having threshold currents ≥15 mA (j _th≥200 A/cm²), are investigated. The maximum output power is 1.4 mW (λ∼3.3 μm), the differential quantum efficiency ∼3%(τ=5–30 μs, f=500 Hz) for lasing in a longitudinal mode with beam divergences ΔΘ∥∼15° and ΔΘ ⊥ ∼30°. The relationship of the differential quantum efficiency to the order of the spatial mode of the lasing is demonstrated. A single-mode, current-tunable (−30 cm⁻¹/A) laser is used to measure the transmission of methane in the region of the ν ₃ absorption band. Pis’ma Zh. Tekh. Fiz. 24, 40–45 (June 26, 1998)     

Fluctuation-Induced Excess Conductivity in R1−x Ca x : 123 Superconductors

Fluctuation induced conductivity of Ca substitution at R sites of R_1−x Ca _x : 123 superconductors with various x and R is investigated. This work is done by using the reported data of Sedky et al. (Phys. Rev. B 58(18):12495, 1998). The logarithmic plots of Δσ and reduced temperature € reveal three different exponents corresponding to two different crossover temperatures. The first exponent at ln € (−1≥ln €≥−2) and its values are close to 1, for which order parameter dimensionalities (OPD) are two dimensional (2D). The second exponent at ln € (−2≥ln €≥−3.5) and its values are close to 2, for which OPD are neither two dimensional (2D) nor three dimensional (3D). The third exponent at ln € (−3.5≥ln €≥−8) and its values are close to 0.5, for which OPD are three dimensional (3D). The different values of the interlayer coupling are also calculated in the normal and mean field regions, respectively. Our results are discussed in terms of oxygen disorder and system anisotropy produced by Ca substitution in R _1−x Ca _x : 123 systems.     

Using direct hot-rolling approach to obtain dual-phase weathering steel Cu–P–Cr–Ni–Mo

A weathering steel Cu–P–Cr–Ni–Mo has been developed which exhibits special continuous cooling transformation characteristics which permit the desired dual-phase (DP) microstructure to be obtained by direct hot-rolling. Hot-rolling procedures to obtain DP microstructures have been designed based on the continuous cooling transformation diagram of weathering steel Cu–P–Cr–Ni–Mo. The results show that the microstructures of DP weathering steels Cu–P–Cr–Ni–Mo are characterized by an irregular distribution of island-shaped martensite–austenite in the matrix of polygonal ferrite grains. DP weathering steel Cu–P–Cr–Ni–Mo with favorable corrosion resistant property, weldability and mechanical properties, such as, high strain hardening exponent values, a lower ratio of yield to tensile strength, and higher strengths; and is obtained successfully by direct hot-rolling.     

The Kramers-Kronig relations for permittivity, “True” screening radius,and critical point of a coulomb system

A correlation between the peculiarities of the electric permittivity (EP) ɛ(q, ω) of a homogenous and isotropic Coulomb system (CS) in the limit of ω → 0, q → 0 and q → 0, ω → 0 is established on the basis of exact limiting relations; general expression for static EP ɛ(q, 0) of a CS is obtained in the region of small wave vectors q. The concepts of a “true” dielectric and “ideal” conductor are introduced. The definition of a “true” screening radius is considered. A critical point of two-component CS is shown to correspond to either the “true” dielectric state or the “ideal” conductor one.