Eq Ratio Research Articles

The conformational behavior and structure of monosubstituted 1,3,5‐trisilacyclohexanes—Part III: 1‐Methyl‐1,3,5‐trisilacyclohexane

Abstract1‐Methyl‐1,3,5‐trisilacyclohexane was synthesized and its structure and conformational properties have been determined by gas‐phase electron diffraction (GED) and quantum chemical (QC) calculations. The molecule may exist in two forms differing from each other by the substituent's position. QC results show that the equatorial conformer is predicted to be slightly more stable than the axial conformer; note that one method (M06‐2X) with basis set 6‐311G** shows an equal amount of Ax and Eq conformers: ratio (Ax/Eq) = (30–50):(70–50)% (depending on the method and basis set). From the GED data, the molar fractions of the conformers were found to be Ax:Eq = 54(10):46(10) at 280(5) K. A temperature‐dependent Raman experiment resulted in an Ax:Eq ratio of 58(4):42(4). Conformational properties are compared in series of analogous 1‐X‐1‐(hetero)cyclohexanes.

Solidification Behavior of Duplex Stainless Steel (UNS S32205) Welds as a Function of WRC–1992 Diagram Equivalents and Cooling Rate

Duplex stainless steels solidify as 100 % Ferrite, however solidification of Duplex Stainless steel welds is a function of Chromium equivalent and Nickel equivalent alloying elements, filler metal and base metal composition and associated weld thermal cycle. Resultant solidification mode behavior and hence final weld metal microstructure is always a matter of interest among researcher because mechanical properties and corrosion properties are depending on weld metal ferrite content. The present research is to investigate the solidification mode behavior of duplex stainless steel welds with varying Chromium equivalent and Nickel equivalent ratios and associated weld cooling rate. In order to meet this objective, weld coupon were prepared using experimental Low Nickel, Medium Nickel and High Nickel electrodes using SMAW process, step wise increased in Nickel content from commercially available standard 09 weight percentage Nickel in E2209 design. WRC-1992 Diagram has been used to calculate Chromium Equivalent and Nickel equivalent and predict Ferrite Number using compositions of Base metal and Nickel enriched experimental electrodes. Microstructure characterization of all weld coupons is carried out using ASTM A 923 Method. Calculated values were correlated with the different microstructures developed. According to the findings of the studies, weld produced with higher Nickel content electrode, when cooled with maximum rate approximately 100.8 °C/ Sec , considered under study, exhibited FA-mode of solidification with as low as 1.71 Cr eq /Ni eq ratio and there was no noteworthy presence of intermetallic phases and precipitations in as-weld microstructures at approximate retained ferrite level of 15 Ferrite Number.

Effect of Ag doping and isothermal aging on phase transformation in 2205 duplex stainless steel

Abstract In this study, 0.2 wt% Ag-doped 2205 duplex stainless steel (DSS) was adopted to investigate the relationship between secondary precipitates and aging temperature. Before aging, 2205-0.2Ag samples were homogenized at 1200 °C for 12 h to resolve other secondary phases. The eutectoid reaction of α → γ 2 + σ and the formation of intergranular γ 2 at the α/γ interfaces were observed after aging at 900 °C for 2 h. Notable quantities of α-ferrite transferred to the γ 2 , χ, σ, and Cr 2 N phases, resulting in decreases of α-ferrite content during 900 °C aging. Because of decomposition of α-ferrite under 800 °C aging, the considerable Cr eq /Ni eq ratio difference between α-ferrite/γ-austenite facilitated the formation of the γ′ 2 phase and its growth at the α-ferrite/γ-austenite interface. This also indicated that doping DSS with silver can benefit the precipitation of γ 2 phases from α-ferrite. Furthermore, α-ferrite transferred to γ-austenite and the merger of primary austenitic grains facilitated the stabilization of phase constitution. Because the mutual solubility of silver and iron is very low, liquid silver solidified and caused silver particles to distribute at the α phase, γ phase, and α/γ interface. Furthermore, the solubility of silver in α, γ, and γ 2 phases decreased progressively as the aging temperature decreased. Moreover, the behavior of secondary precipitates was not affected by silver doping in 2205 DSS.

Network-Based Life Cycle Optimization of the Net Atmospheric CO2-eq Ratio (NACR) of Fuels and Chemicals Production from Biomass

A biofuels and bioproducts conversion network is optimized over unit cost and unit greenhouse gas emissions objectives. We use a multiobjective, functional unit approach based on the life cycle analysis methodology with simultaneous consideration of capital budget constraints. A novel functional unit of mass of input biogenic CO2-eq is proposed to capture common benefits of bioproducts and biofuels. A novel dimensionless net atmospheric carbon ratio (NACR) for bioconversion processes is defined that captures the life cycle carbon footprint of the process from feedstock cultivation to product end use. The model is formulated as a nonconvex multiobjective mixed integer nonlinear fractional programming problem. We address computational complexity by developing a novel global optimization algorithm that incorporates the parametric algorithm and successive piecewise linear approximations to estimate nonconvex terms, and we introduce nonlinear programming subproblems to ensure global convergence under capital c...

Temperature dependence of Uiso constraints in riding hydrogen treatments

"Anisotropic parametrisation of the thermal displacements of hydrogen atoms in single-crystal X-ray structure refinement is not possible with independent atom model (IAM) scattering factors. This is due to the weak scattering contribution of hydrogen atoms. Only when aspherical scattering factors are used can carefully measured Bragg data provide such information. For conventional structure determinations parameters of ""riding"" hydrogen atoms are frequently constrained to values of their ""parent"" heavy atom. Usually values of 1.2 and 1.5 times X-U_eq are assigned to H-U_iso in these cases. Such constraints yield reasonable structural models for room-temperature data. However, todays small molecule X-Ray diffraction experiments are usually carried out at significantly lower temperatures. To further study the temperature dependence of ADPs we have evaluated several data sets of N-Acetyl-L-4-Hydroxyproline Monohydrate at temperatures ranging from 9 K to 250 K. Methods compared were HAR [1], Invariom refinement [2], time-of-flight Neutron diffraction and the TLS+ONIOM approach [3]. In the TLS+ONIOM approach non-hydrogen ADPs from Invariom refinement provided ADPs for the TLS-fit. Hydrogen atoms in all methods were grouped and analyzed according to their Invariom name. We reach a good agreement of the temperature dependence of H-U_iso/X-U_eq. At very low temperatures the ratio H-U_iso/X-U_eq can be as high as 4, e.g. for Hydrogen attached to a sp3 carbon atom with three non-Hydrogen atom neighbors. Since all methods consistently show that the H-U_iso/X-U_eq ratio is temperature dependent, this effect should be taken into account in conventional structure determinations."

Influence of Heat Input on Martensite Formation and Impact Property of Ferritic-Austenitic Dissimilar Weld Metals

The effect of heat input on martensite formation and impact properties of gas metal arc welded modified ferritic stainless steel (409M) sheets (as received) with thickness of 4 mm was described in detail in this work. The welded joints were prepared under three heat input conditions, i.e. 0.4, 0.5 and 0.6 kJ/mm using two different austenitic filler wires (308L and 316L) and shielding gas composition of Ar + 5% CO 2 . The welded joints were evaluated by microstructure and charpy impact toughness. The dependence of weld metal microstructure on heat input and filler wires were determined by dilution calculation, Cr eq /Ni eq ratio, stacking fault energy (SFE), optical microscopy (OM) and transmission electron microscopy (TEM). It was observed that the microstructure as well as impact property of weld metal was significantly affected by the heat input and filler wire. Weld metals prepared by high heat input exhibited higher amount of martensite laths and toughness compared with those prepared by medium and low heat inputs, which was true for both the filler wires. Furthermore, 308L weld metals in general provided higher amount of martensite laths and toughness than 316L weld metals.

Quasi-equilibrium and non-equilibrium adsorption in heterogeneous photocatalysis

Heterogeneous photocatalysis is a promising alternative for the removal of organic and inorganic pollutants in water. Some chemical species display a strong and slow surface adsorption kinetics reacting under non-equilibrium while others adsorb quickly and moderately with adsorption taking place under quasi-equilibrium. In the specific case of a given pollutant once the intrinsic kinetic constants are evaluated, one can establish a photochemical efficiency factor (PTEF), representing the efficiency of using absorbed photon energy in chemical transformations. Deviations between equilibrium and the more rigorous non-equilibrium adsorption models can be assessed with a PTEF non - eq / PTEF eq parameter. In the case of phenol photoconversion it is observed that the PTEF non - eq / PTEF eq ratio varies in a limited range (0.5–2) and this is consistent with quasi-equilibrium adsorption assumptions. On the other hand, for the photocatalytic conversion of methylene blue, 2-chlorophenol and pyrogallol, the PTEF non - eq / PTEF eq ratio changes from 3 to 18. This makes, in these cases, adsorption at quasi-equilibrium unsuitable given it leads to a severe underestimation of energy efficiency factors. As a result, this study emphasizes the critical importance of properly modeling photocatalytic degradation processes in terms of adsorption, reaction, kinetic parameters as well as for the evaluation of energy efficiency factors.

Evaluation of Water Resources in Dalmatia for Human Health

The purpose of this study was to monitor and evaluate the specific characteristics and properties of the most important water resources in Dalmatia, located in Southern Croatia, for a period of five years (1999–2003). The paper presents a detailed account of the water's chemical content, classification and concentration of salts. The bacteriological pollution levels are indicated by the total coliform bacterial levels (MPN coli/100 ml). The water characteristics are expressed by coefficients which represent the ratios between water ingredients. The Ca/Mg eq ratio, SO4/Cl eq ratio and K1, K2 for bicarbonate hardness were calculated. The hygienic characteristics of the water samples were expressed by the total coliform bacteria estimation (MPN coli/100 ml), the permanganate consumption (KMnO4) and biological oxygen demand (BOD5). Karst waters, i.e. rain waters, in Dalmatia are moderately hard, the SO4/Cl ratio is 0.38-1.6, non corrosive (K1 lower than 0.2) and not significantly mineralised (<500 mg/L minerals). Sulfate waters are generally hard, the SO4/Cl ratio is higher than 1.6, K1 is 0.2-0.65. Marine waters are quite hard or hard, particularly at the river estuaries, the SO4/Cl ratio is lower than 0.38, and K1 is higher than 0.65. Rain water direction equation, marine direction equation and sulfate direction equation are calculated on the base of SO4/Cl ratio. The groundwater and springs in Dalmatia are less polluted than surface waters. A majority of the water observed, 24 of 42 locations, have geometric average values of MPN coli<150/100 ml of water. This group includes the majority of springs in Dalmatia, as well as some sections of rivers studied. The highest bacteriological pollution was found at nine locations where MPN coli>1000/100 ml. Moderate pollution was found at nine locations where MPN coli is between 150–1000/100 ml of water. The water in Dalmatia is quite safe and mainly preserves its natural properties.

Influence of heat curing on the pore structure and compressive strength of self-compacting concrete (SCC)

The mechanical properties of self-compacting concrete (SCC) are well understood. But there are no scientific investigations available on the influence of a heat treatment on the properties of SCC. To evaluate the influence on the compressive strength, SCCs as powder type, combination type and viscosity-agent type in the strength classes between C20/25 and C70/85 were designed and exposed to heat treatment with different maximum temperatures. It has been found that there is an influence of the composition of the concrete, especially the ( w/ c) eq ratio, on the compressive strength after heat treatment. The reason for the substantial loss of strength in some cases compared to the strength of the concrete, which was stored under standard conditions, is a change of the pore size distribution. An empirical formula is presented to calculate the influence of the heat treatment on the compressive strength of the SCCs.

The Quality of Water Resources in Dalmatia

The purpose of this study was to monitor and record the specific characteristics and properties of most of the important water resources in Dalmatia located in Southern Croatia for a period of 5 years (1998-2002) according to established standards for drinking water. The paper presents a detailed account of their chemical content, the classification and the concentration of salts. The bacteriological pollution levels are indicated by the total coliform bacterial levels (MPN coli/100 mL). The water characteristics are expressed by coefficients, which represent the ratios between water ingredients. The Ca/Mg eq ratio, SO4/Cl eq ratio and K1, K2 for bicarbonate hardness were calculated. The hygienic characteristics of the water samples were expressed by the total coliform bacteria estimation (MPN coli/100 mL), the permanganate consumption (KMnO4) and biological oxygen demand (BOD5). Karst waters in Dalmatia are moderately hard, the SO4/Cl ratio is 0.38-1.6, non-corrosive (K1 lower than 0.2) and not significantly mineralised (< 500 mg/L minerals). Sulphate waters are generally hard, the SO4/Cl ratio is higher than 1.6, K1 is 0.2-0.65. Marine waters are quite hard or hard, particularly at the river estuaries, the SO4/Cl ratio is lower than 0.38, and K1 is higher than 0.65. The groundwater and springs in Dalmatia are less polluted than surface waters. A majority of these have a geometric average value of MPN coli < 150/100 mL of water observed in 24 of 42 locations studied. The highest bacteriological pollution was found in nine locations where MPN coli > 1000/100 mL and moderate pollution was found in nine locations where MPN coli is between 150 and 1000/100 mL of water. The physical and chemical parameters determined for the most sources in Dalmatia are safe below the international permissible limits.

Characteristics of water resources in Dalmatia according to established standards for drinking water

The purpose of this study was to monitor and record the specific characteristics and properties of most of the important water resources in Dalmatia (southern Croatia) for a period of 5 years (1994–1998). A detailed account of their chemical content classification and concentration of salts is presented. Bacteriological pollution levels are indicated by the total coliform bacterial levels (MPN coli/100 ml). The water characteristics are expressed by coefficients which represent the ratios between water components. The Ca/Mg eq ratio, SO4/Cl eq ratio and K 1 and K 2 for bicarbonate hardness were calculated. The concentration of anions shows a stability from which it is possible to predict probable content and availability of salts in these waters. The hygienic characteristics of the water samples were expressed by the total coliform bacteria estimation (MPN coli/100 ml), the permanganate consumption (KMnO4) and biological oxygen demand (BOD5). Typical karst waters in Dalmatia are moderately hard, the SO4/Cl ratio is 0.38–1.6, they are non-corrosive ( K 1 lower than 0.2), and not significantly mineralized (<500 mg/l minerals). Sulphate waters are generally hard, the SO4/Cl ratio is higher than 1.6, and K 1 is 0.2–0.65. Marine waters are quite hard or hard, particularly at the river estuaries, the SO4/Cl ratio is lower than 0.38, and K 1 is higher than 0.65. The groundwater and springs in Dalmatia are less polluted than surface waters. A majority of these have a geometric average value of MPN coli 1,000/100 ml, and moderate pollution was found in nine locations where MPN coli was between 150–1,000/100 ml of water. The overall changes in water quality can be correlated with the epidemiological prevalence of water-borne diseases, particularly bacterial diarrhoeas, and can reflect the demographic distribution of water-borne diseases, i.e. overall health status.

Effect of nitrogen addition on microstructure and fusion zone cracking in type 316L stainless steel weld metals

Nitrogen is known to have a significant effect on cracking behaviour of austenitic stainless steel during welding, although reports on its effects have often been controversial. A study was therefore undertaken to examine the effect of nitrogen on the weldability of two type 316L weld metals. Weldability was assessed using the longitudinal moving torch Varestraint test. The brittleness temperature range during solidification was calculated from crack length data. Nitrogen was added through the shielding gas to 316L (base N-0.036%) and 316LN (base N-0.073%) to produce weld metal nitrogen contents in the range 0.04–0.19%. In the primary austenitic solidification mode, nitrogen addition had little effect when the P+S levels were relatively low (316LN with 0.031%P, 0.001%S) while cracking increased for higher impurity levels (316L with 0.035%P, 0.012%S). Nitrogen additions also produced significant coarsening of the primary solidification structure. The study indicates that weldability effects of nitrogen may be influenced by the impurity levels, particularly S. The cracking data showed good correlation with the WRC Cr eq/Ni eq ratio.

Microstructural characterisation of a dissimilar weld of alloy D9 and AISI 316M stainless steel produced using a 2.5 kW CW CO 2 laser

The dissimilar weld, a fuel clad tube (D9 alloy) and an end plug made of AISI 316M forms a part of the fuel pin in the 500 MW Indian Prototype Fast Breeder Reactor (PFBR). The present study aimed at the development of a crack resistant microstructure of the dissimilar weld by optimisation of 2.5 kW CO 2 laser welding parameters. The D9 alloy, because of its low Cr eq /Ni eq ratio (close to 1), solidified first as primary austenite which makes its welds particularly susceptible to solidification cracking. In this study, the primary mode of solidification in the fusion zone was modulated by controlling the relative degree of fusion of the fuel clad tube and the end plug. A defect free weld with predominantly a primary ferrite mode of solidification was obtained by optimising laser parameters and displacing the focused laser beam towards the end plug side to achieve a greater contribution of end plug material to the fusion zone. The formation of a crater and associated defects at the termination site of laser welding were eliminated successfully by ramping the laser power during welding.

Modification of three-component bismaleimide resin by poly(phthaloyl diphenyl ether) and related copolymers

A three-component bismaleimide resin, composed of 4,4′-bismaleimidodiphenyl methane (BDM), o,o′-diallyl bisphenol A (DBA), and o,o′-dimethallyl bisphenol A (1.0/0.3/0.7 eq ratio) was used as a parent bismaleimide resin. Modification of the three-component bismaleimide resin was examined by blending it with poly(ether ketone ketone)s. Poly(ether ketone ketone)s include poly(phthaloyl diphenyl ether) (PPDE), poly(phthaloyl diphenyl ether-co-isophthaloyl diphenyl ether) (PPIDE), and poly(phthaloyl diphenyl ether-co-terephthaloyl diphenyl ether) (PPTDE). The PPIDE (51 mol % isophthaloyl) and PPTDE (44 mol % terephthaloyl) were more effective as modifiers for the bismaleimide resin than was PPDE. For example, the fracture toughness (KIC) for the modified resin increased 30% with no deterioration in the flexural strength and modulus with a 15 wt % inclusion of PPTDE (MW 23,400) compared to the parent three-component bismaleimide resin: the KIC increased 95% compared to the value for the Matrimid 5292 resin composed of BDM and DBA. The morphologies of the modified resins changed from particulate to cocontinuous phase structures, depending on the modifier structure and concentration. Toughening of the cured bismaleimide resin could be achieved because of the cocontinuous phase structure. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 2991–3000, 2001

Surface Melting Effect on the Corrosion Behaviour of Austenitic-Ferritic Stainless Steels Solidified in Various Modes

The aim of this study was to examine the effect of gas tungsten arc (GTA) surface melting on the pitting corrosion resistance of cast duplex stainless steels (DSSs) solidified in various modes. For this purpose, two commercial DSSs were selected. The low Cr eq /Ni eq ratio alloy solidified in primary ferrite with second-phase austenite mode (FA), while the solidification of the other high Cr eq /Ni eq ratio alloy is entirely ferritic mode (F mode) [1]. The surface melted DSSs were examined in the condition obtained after an air cooling to room temperature or water quenching from the elevated temperatures. The corrosion testing was performed in 0.5 M NaCI solution at room temperature by potentiodynamic and potentiostatic techniques. The obtained results clearly show that the surface melting treatment has proved effective in improving resistance to pitting corrosion. Especially in the condition after water quenching, the corrosion resistance was markedly improved. Furthermore, the F solidified alloy with a higher pitting index (PI= Cr+3.3Mo+16N) is more resistant to localized corrosion than the FA solidified alloy in both tested conditions.

Surface energy fluxes of Phragmites australis in a prairie wetland

Components of the surface energy balance were measured in three communities ( Phragmites australis, Scirpus acutus, and open water) in a wetland located in northcentral Nebraska, USA, during the growing season of 1994. This paper includes results from the area covered by Phragmites australis (reedgrass). The Bowen ratio – energy balance method was used to calculate sensible and latent heat fluxes. During daytime, with a water depth of about 0.5 m, the heat storage term ( G) consumed 20–30% of the net radiation ( R n). At night, G was a significant source of energy (on average, about – 40 W m −2). The magnitude of the daily (24 h) averaged G was small. Evapotranspiration (ET) was a major consumer of the incoming solar energy. During early and peak growth, the daily ET ranged between 2.5 and 6.5 mm per day. During senescence, evapotranspiration was between 0.5 and 3.1 mm per day. ET was partitioned into transpiration ( E v) and evaporation ( E s) using a dual-source modification of the Penman–Monteith equation. Results indicated that transpiration contributed 40–45% of the total ET in the beginning of the early growth stage. During the second half of the early growth stage and the entire peak growth stage, it contributed 53–62% of ET. The contribution decreased to 50% in the beginning of senescence, and to near zero in late senescence. The daytime variation of E s did not follow R n, and seemed to be controlled by thermal stability and air dryness. Before senescence, the ratio of the actual to equilibrium evapotranspiration (ET/ET eq) averaged 1.3. It decreased to about 0.5 during senescence. The McNaughton and Spriggs (1989, IAHS Publ. 177, 86–101) model, developed primarily for dryland vegetation, significantly overestimated the ET/ET eq ratio in Phragmites when the canopy stomatal resistance was larger than 150 s m −1. The model prediction improved significantly when the contribution of evaporation was eliminated by substituting the ET/ET eq ratio by E v/ E veq (transpiration/equilibrium transpiration).

H ax vs. H eq migrations in tetrahydropyranylidenes generated by Bamford-Stevens reactions. Temperature dependence and non-stereoselective activation by ring oxygen

For 1,2-shifts in singlet carbenes, a tetrahydropyranyl oxygen strongly activates its adjacent H's. To determine whether this activation is stereoselective for H ax or H eq, we studied d-labeled analogs of 17a-oxa-D-homosteroidal C- 16 ketones ( 6a). A putative carbene center was generated at C-16 by thermal and photic Bamford-Stevens reactions, and the relative proportions of H and D shift from C-17 were assayed. After correction for primary H/D isotope effects, the H ax/H eq migration ratios in thermolysis were 2.2 at 170°C, 3.3 at 120°C, and 4.1 at 95°C; and in photolysis it was 4.4 at −70°C. The ratio at 170°C is virtually the same as for ordinary cyclohexylidenes under comparable thermal conditions, so the ring oxygen activates H ax and H eq non-stereoselectively. Graphical analysis of the temperature dependence in thermolysis gave ΔE a (or Δ(ΔH ‡)) = 2.7 k cal/mol (in favor of H ax) and Δ(ΔS ‡) 4.5 e.u. (in favor of H eq). Extrapolation indicates the H ax/H eq ratio would be ca. 10 at room temperature, corresponding to Δ(ΔG ‡) = ca. 1.35 kcal/mol.

Effect of weld cooling rate on delta-ferrite content of austenitic weld metals

The present study attempts to vary the weld cooling rate by the use of water-cooled copper backing (so far not tried) by keeping the heat input constant. It also takes into account the Cr eq /Ni eq ratio. In the present study two austenitic stainless steel strips (0.5 mm thick), type 308 Cb and 309 Cb (Table I) were used. Microplasma arc welding (5 A, 20 V, 20 cm min -1 , direct current electrode negative) was used to make autogenous beads using the melt-in technique

Seasonal variations in glycolysis in Mytilus galloprovincialis Lmk

1. 1. In the hepatopancreas and mantle of the sea mussel Mytilus galloprovincialis Lmk glycolysis shows seasonal variations. 2. 2. In both these tissues, glycolytic activity shows a maximum in winter and a minimum in summer. 3. 3. Smaller fluctuations also take place in the posterior adductor muscle. 4. 4. In all three tissues, Fru 2,6-P 2 indicates the direction and strength of glycolysis, correlating well with other parameters such as energy charge or the phosphoenolpyruvate/pyruvate ratio. 5. 5. In the posterior adductor muscle, however, Fru 2,6-P 2 does not correlate with the MAR/K eq ratio from phosphofructokinase owing to the synergic activation of the enzyme by both Fru 2,6-P 2 and AMP.