Incremental Conversion Research Articles

Effects of extensive-to-intensive pasture conversion on soil nitrogen availability and CO2 and N2O fluxes in a Brazilian oxisol

Brazilian beef production has been recognized as an important path to achieve environmental, social and economic sustainability, and to ensure food security. Although, traditionally, beef production in Brazil has relied on unmanaged pastures (i.e. extensive pasture), a growing demand for beef combined with increased competition for land to grow crops without increasing deforestation has led to the incremental conversion of pastures from unmanaged to intensive systems. To better understand the implications of changing pasture management on nitrogen availability and CO2 and N2O fluxes, a field experiment simulating the extensive-to-intensive pasture conversion was set up in São Paulo State, Brazil. Soil and gas samples were collected during two 6 months periods (October, 2013 to March, 2014 and December, 2014 to May, 2015) in an area of extensive pasture (EP), which served as a control, and also in two treatment areas where pasture intensification was simulated using practices typically adopted in the region. The treatment areas included conventionally tilled pasture without inorganic fertilizer (TP) and tilled pasture with inorganic fertilizer (IP). Environmental conditions and soil characteristics were also determined during the study period. The results clearly illustrated the impacts of commonly adopted pasture management systems in Brazil. Fluxes of CO2 and N2O fluxes increased with the application of fertilizer, with CO2 averaging about 4.1, 4.0 and 5.2 g m-2 day-1, and N2O fluxes averaging 0.2, 0.3 and 0.98 mg m-2 day-1 in EP, TP and IP, respectively. Despite equal rates of fertilizer application, differences in weather conditions and soil management resulted in different emission rates and dynamics for each pasture system type. Depending on the sampling period, emissions factors were 1.55% or 0.59%. The adoption of conservation management practices is vital to prevent “hot” moments of N2O emission arising from pasture intensification in Brazil.

Simulations of multiwavelength cladding pumping of high-power fiber Raman amplifiers

We numerically simulate and optimize a high-power fiber Raman amplifier cladding pumped by spectrally combined diode lasers at wavelengths from ∼0.9 to ∼1 μm in the continuous-wave regime. This amplified a signal at the first-Stokes wavelength of 1024 nm. We found that it was possible to add pumps over an increasingly wide wavelength span up to ∼90 nm, while still maintaining an incremental conversion efficiency higher than 60%, even though the Raman linewidth is only ∼15 nm. We investigated the dependence on the power of individual diode lasers and on the wavelength spacing and found that the total conversion efficiency reaches ∼70 % with realistic pump sources based on state-of-the-art diode lasers. We believe this study shows the potential for high-power fiber Raman lasers pumped by spectrally combined multiwavelength diode and fiber laser sources.

Digestibilidad aparente de dietas con torta de palmiste sobre el rendimiento productivo de la especie nativa Cichlasoma festae en la etapa de cría

El objetivo fue valorar el efecto de dietas a base de torta de palmiste sobre el rendimiento productivo, calculando el incremento de peso (IP), incremento de peso relativo (IPR), tasa de crecimiento (TC), tasa de crecimiento incremental (TCI), conversión alimenticia (CA), digestibilidad aparente de la materia seca (MS), proteína (PB) y energía bruta (EB), así como, el costo de esta alimentación y la mortalidad del pez nativo vieja colorada en la etapa de cría. Los peces fueron alimentados con cuatro dietas (0, 4, 8 y 12% de palmiste) y cuatro repeticiones por tratamiento, por 30 días, alojados en 16 jaulas en un estanque. Se determinaron: el peso final (PF), IP, IPR, TC, TCI, CA, los coeficientes de digestibilidad MS, PB y EB, costos de alimentación y mortalidad. No se encontraron diferencias significativas en el PF, IP, IPR, TC Y TCI de la vieja colorada, entre los tratamientos T1, T2 y T3 de inclusión de la torta de palmiste; solo la dieta con mayor porcentaje de inclusión (T4) mostró unos peores resultados con respecto a la dieta T1. La CA presentó un mayor valor en la dieta testigo en comparación con la dieta T2 (p<0,05). El T4 evidencio la peor conversión alimenticia (p>0,05). A medida que se incrementó el % de palmiste el costo de la dieta disminuyó significativamente. La inclusión en la dieta de la vieja colorada de hasta un 8% de palmiste no afectó a los parámetros de rendimiento productivo estudiados. Además, se abarata la dieta significativamente

User-level incremental conversion ranking without A/B testing

The traditional approach to build incremental conversion prediction model has to rely on A/B test results. However, under certain intense business environment, A/B testing can be limited by technical support, platform, or budget, and become not practically available. In this paper, we propose an algorithm to rank users by incremental conversions resulted from advertising effects, which is based on user’s conversion history and the output from a conversion prediction model. By appropriately defining who an active user is, this algorithm is proven to work well with real data. In case where an A/B test is not available and incremental conversion-based user targeting is desired, this algorithm offers a practical solution.

New invariances for chemical reactions from Scaled Incremental Conversion (SIC)

For the two-step chemical reaction A ⇄ B ⇄ C, invariant dependences of a new type have been found. These invariants relate concentration dependences which are started from the single component (single-component-dependences). For constructing the invariants, a three-stage procedure is used:1.Scaled Incremental Conversion (SIC), χ, is determined for any substance as χ=X(t)-XoXeq-Xo, where Xeq and Xo are equilibrium and initial concentrations for any substance, A, B, or C, respectively; X(t) is the concentration at any moment of time.2.Differences of SIC terms Δχ are determined for different pairs of substances. SIC terms are calculated in experiments with symmetrical initial conditions.3.A generating function of invariants is constructed which produces invariants as ratios of different Δχ. These ratios remain constant at any time during the non-steady-state reaction.It is demonstrated that the variety of invariants obtained depends on the initial conditions used in the procedure. Explicit analytical expressions have been found assuming the same initial conditions, two, and three different initial conditions, respectively.All invariants are functions of three independent parameters which are ratios of kinetic coefficients. Two of them are equilibrium reaction constants, and the third one is the ratio of kinetic coefficients belonging to different reactions.

Performance Analysis of a Hybrid Incremental and Cyclic A/D Conversion Principle

This paper presents a new hybrid A/D conversion principle based on the combination of an incremental conversion for the most significant part of the result and on a cyclic conversion for the least significant part. The proposed approach exhibits a resolution comparable to a multiorder sigma-delta A/D converter (ADC), but with a higher conversion rate (typically a factor of two) and/or a lower complexity, at the cost of a more stringent antialiasing filter requirement. After having presented the basic equations of the conversion principle, a theoretical analysis of the resolution limitations is given, based on nonidealities and noise considerations. Finally, a switched-capacitor implementation example is given with the corresponding simulations, consisting of a low-complexity 14-b ADC suited for applications requiring medium-speed and very compact ADC.

Ancient Maya Agricultural Installations and the Development of Intensive Agriculture in NW Belize

Archaeological study of the spatial arrangement of agricultural features such as terraces and berms yields insight into the scale, mode, and tempo of farm production and the social organization of farming communities. Data from five regions of the Maya lowlands where such features have been extensively documented demonstrate the range of strategies employed by the ancient Maya to organize agricultural production. In some previously studied regions of the lowlands, spatial patterns suggest centralized management of farmland by state institutions, while in others a smallholder strategy seems evident. In the Río Bravo region of NW Belize, the organization of agricultural labor centered neither on the state nor on the individual farm family, but on the farm community. Moreover, the incremental conversion of open lands to terraced agricultural fields was part of a long-term interactive sequence of environmental change and human response over centuries of occupation. This sequence demonstrates that the ancient Maya not only adapted to a degraded environment but used it to their advantage, developing new technologies that were successful for several centuries prior to their ultimate failure. The agricultural history of the lowland Maya demonstrates that indigenous systems of resource management in fragile environments such as the tropics were not always deleterious. The innovations and successful adaptations of ancient farmers should also be recognized.

Incremental Conversion of Outer-Membrane Permeabilizers into Potent Antibiotics for Gram-Negative Bacteria

Cholic acid derivatives appended with amine groups have been prepared for use as permeabilizers of the outer membranes of Gram-negative bacteria. These compounds interact synergistically with antibiotics such as erythromycin and novobiocin to inhibit growth of Gram-negative bacteria. When a hydrophobic chain is included on the permeabilizers, they can be converted into potent antibiotics. The role of the hydrophobic chain is to facilitate self-promoted transport of the cholic acid derivatives across the outer membrane of Gram-negative bacteria. These compounds share activities found with polymyxin B and derivatives.

Co-processing of agricultural and biomass waste with coal

The liquefaction of Blind Canyon seam coal in the presence of one of four different types of co-liquefaction agents (CLAs) was studied at 350°C and 1000 psi (cold) hydrogen pressure. The role of tetralin as a solvent was studied. The four CLAs used include sawdust, horse manure, cow manure and commercial “Super Manure”. The conversion and the asphaltene-plus-preasphaltene yield were obtained by successive dissolution in tetrahydrofuran and hexane, respectively, with the oil-plus-gas yield obtained by difference. Results (on a dry, ash-free basis) are reported as both the overall values of conversion and yields, as well as the incremental differences in conversion and yields, relative to separate liquefaction of coal and the CLA. With or without the addition of tetralin, the overall conversion with cow manure is the smallest for the four co-liquefactions. In the absence of tetralin, the asphaltene-plus-preasphaltene yields are all similar. The presence of tetralin increases the overall conversions and the asphaltene-plus-preasphaltene yields. A study of the incremental differences in conversions and yields indicates that the four CLAs interact with coal and tetralin in different ways. The incremental conversion and the asphaltene-plus-preasphaltene yield appear to be related to the amount of hemi-cellulose in the CLAs, while the incremental oil-plus-gas yield appears to be related to the amount of lignin. Added inorganic compounds appear to negate incremental improvements in the oil-plus-gas yield when tetralin is present.

A computationally efficient technique for the solution of non‐isothermal nylon‐6 polymerization in batch reactors

AbstractThe kinetic scheme of nylon‐6 polymerization consists of ring opening, polyaddition, step growth, reaction with monofunctional acids and cyclization. A set of ordinary differential equations (initial value problem) governing the concentrations and moments of the reacting species and the energy balance for batch reactors has been solved. We proposed a semianalytic technique somewhat similar to the finite element method in which the conversion domain has been divided into sequential subdomains. A series solution for the state variables has been assumed in terms of the incremental conversion of caprolactam in that domain. The coefficients are obtained using the balance equations. This technique of solution takes care of the nonlinearity of the problem in a natural way and involves the sequential evaluation of constant coefficients of the series. It gives comparable results with those from Gear's algorithm (which involves the evaluation of functions) in far fewer steps. Our scheme can be easily implemented on a PC‐XT and is considerably faster and more efficient.

Tire Liquefaction and Its Effect on Coal Liquefaction

Liquefaction experiments were run using ground tire rubber and ground coal, individually and in combination. The runs, in a batch tubing-bomb reactor, were carried out in the presence and absence of tetralin as a solvent, and at high hydrogen pressures. The tire conversion is temperature dependent. At 400 °C in 30 min, almost all of the organic matter in the tire is converted to hexane-soluble material, in the absence of solvent and H 2 . The conversion of the tire-coal mixture is greater than the combination of the individual conversions. The incremental conversion, i.e., the difference between the conversion of the mixture and the combination of the individual conversions, increases with the tire/coal ratio

Modeling Tall Fescue Cultivar Response to Applied Nitrogen

AbstractModels can be used to estimate yields and nutrient utilization by forage grasses. The objective of this study was to model response of three cultivars of tall fescue (Festuca arundinacea Schreb.) to applied N over a 3‐yr period at Watkinsville, GA. The procedure uses analysis of variance to evaluate linear parameter A and the exponential parameters b and c for the logistic equation. It was shown that yields could be averaged across years and that all differences among cultivars could be assigned to the b (intercept) parameter. ‘All‐Triumph’ proved to be more efficient at converting soil N to dry matter without applied N than either ‘Johnstone’ or ‘Kentucky 31’ cultivars. Endophyte (Acremonium coenophialum Morgan‐Jones & Gams) infection did not affect dry matter response relationships of Kentucky 31. Maximum incremental conversion of applied N to dry matter occurred at N = 125 kg ha−1, where plant N utilization was ≈80%. The logistic model provides a very useful tool for evaluating response of tall fescue cultivars to applied N.

An analysis of CSTRs in series for solution copolymerization

AbstractContinuous copolymerization is used in order to achieve a product of uniform composition. However, it is difficult to attain high conversions without resorting to very high residence times in a single tank. The way to avoid this is to use a series of stirred reactors with addition of one comonomer and initiator to each one after the first. The allowable half‐life of the initator is a function of the residence time. When all the reactors are equal in volume so that the residence time is the same in each, it can be shown that the incremental conversion in each successive reactor must decrease in a well‐ordered manner. As a specific example, a copolymerization is postulated with total polymer concentration restricted to the region where viscosity is manageable with conventional mixing equipment. Under these conditions the relative reactivity ratios are presumed to be constant and temperature can be held within narrow bounds.

U.S. Wetlands

Although the overall rate that the nation's wetlands are being converted to other uses is not alarming, the continued incremental conversion of wetlands, especially in certain inland regions of the country, may have significant adverse ecological effects over the next few decades. A comprehensive report on wetlands, requested by the Senate Committee on Environment and Public Works, was released recently by Senator John H. Chafee (R‐R.I.), chairman of the Subcommittee on Environmental Pollution. The report outlines options for new federal measures that could lead to more effective management of wetlands in the United States.Federal efforts to manage wetlands could be more effective if they were focused on higher value wetlands, although, because the value of individual wetlands in different regions of the country have not been evaluated at this time, priorities for protection have not been established.

MODELLING PROTEIN AND LIPID GAINS IN GROWING PIGS EXPOSED TO LOW TEMPERATURE

An existing energy partition model that relates protein and lipid retention in growing pigs (60 kg) to dietary energy intake was extended to include environmental temperature. The extended model for 45- to 75-kg pigs can be used to predict animal heat production at each feeding level, lower limit of the zone of thermoneutrality at each feeding level and incremental energy conversion efficiency over a range of feeding levels and environmental temperatures. The model predictions were validated in two ways. (1) Incremental energy conversion efficiencies over a range of feeding levels and environmental temperatures, as determined in three studies cited in the literature, were compared against the energy conversion efficiencies predicted by the model. (2) The rates of protein deposition and liveweight gains in growing pigs housed at 21 °C and 6 °C, were compared against the model predictions. While the model should receive further testing, both the above tests confirmed that low temperature can be related to feeding level and rates of tissue gain in pigs in a predictable manner. Key words: Pig, temperature, model, energy retention

A 20-GHz Integrated Balanced Mixer

An integrated balanced mixer for use in the receiver for the quasi-millimeter-wave digital radio transmission system is described. The following aspects of the mixer realization are discussed. 1) The characteristics of gallium arsenide Schottky barrier diodes and three types of diode mount construction are described. The least observed dc incremental conversion loss was about 4 dB in the range of 18-23 GHz. 2) The fabrication of waveguide to microstrip transition, using a ridged waveguide transducer, is described. A transition loss of less than 0.38 dB was obtained in the range of 18-21.75 GHz. 3) The microstrip circuit elements, such as the 3-dB directional coupler and the low-pass filter, are described. The minimum isolation and coupling values of the coupler were about 16 dB and 3-4 dB, respectively. 4) The effect of the undesirable electromagnetic mode propagation on the integrated mixer operations is discussed. 5) The performance of the integrated balanced mixer is presented. This mixer, operated at a signal frequency of 20 /spl plus mn/0.5 GHz and at a local oscillator frequency of 18.3 GHz, showed a single side-band noise figure of 4.8-5.8 dB. 6) The reliability of the mixer is also evaluated with high reliability under vibration and shock testing being exhibited.