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We consider the numerical solution of competitive exothermic and endothermic reactions in the presence of a chaotic advection flow. The resulting behaviour is characterized by a strong dependence on the competitive reaction history. The burnt temperature is not immediately connected to simple enthalpy calculations, so there is a subtlety in the interplay between the major parameters, notably the Damköhler number, the ratio of the heats of exothermic and endothermic reactions, as well as the ratio of their respective activation energies. This paper seeks to explore the way these parameters affect the steady states of these reaction fronts and their stability. [ABSTRACT FROM AUTHOR]

Cotton–wheat (CW) is an important cropping system in South Asia. Wheat yields under a conventional CW system are generally lower compared to a rice–wheat system due to delayed seeding. Relay seeding of wheat can help timely sowing, capturing residual soil moisture of last irrigation to cotton, and increase the productivity and profitability of CW system. The field experiment included two Bt-cotton genotypes having different canopy cover (RCH 776 and MRC 7017), two types of relay seeders (RSs) for cotton planted at 67.5-cm and 101-cm row spacing and four types of relay seeding methods (manual broadcast, strip rotor (SR) and zero-till double disc and conventional till). Relay planting of wheat allowed one additional boll picking, which increased seed cotton yield by 12% compared with conventional tillage wheat. Cotton genotypes and RSs had no effect on emergence and yield of wheat. The RSs with SR and zero till double disc furrow openers performed better in terms of wheat emergence and grain yield compared to zero-till tine openers. Under relay seeding, wheat sowing was advanced by 31 days, which increased grain yield by 18.8% compared with conventional tillage practice. Net returns from the CW system with relay seeding of wheat were higher by US$ 311 to 425 ha−1 compared with the conventional CW system. [ABSTRACT FROM PUBLISHER]

Cotton–wheat (CW) is the second most important cropping system after rice–wheat in South Asia. Sowing of wheat after cotton is usually delayed due to late pickings coupled with time needed for seedbed preparation, resulting in low wheat yield. Lack of suitable machinery is a major constraint to direct drilling of wheat into the heavy cotton stubbles. An innovative approach with much promise is the ‘2-wheel tractor-based self-propelled relay seeder’ with seed-cum-fertilizer attachment. On-farm trials were conducted at four locations during 2009–2010 and at 10 locations during 2010–2011 to evaluate the following four wheat establishment methods in CW-dominated areas of south-western Punjab, India: (1) zero till seeding in standing cotton using a self-propelled relay seeder, (2) relay seeding in standing cotton with a manual drill without prior tillage (2010 only), (3) relay broadcast seeding in standing cotton following light manual tillage and (4) conventional sowing of wheat after cotton harvest (conventional tillage and sowing with a seed–fertilizer drill). Planting of wheat under conventional practice was delayed by 20–44 days compared with relay seeding. Seed cotton yield was also significantly higher with relay seeding due to opportunity for one additional picking. Yield of wheat sown with the self-propelled relay seeder was 41.2% and 11.8% higher than with conventional practice in 2009–2010 and 2010–2011 respectively. The increase in wheat yield under relay seeding of wheat was primarily due to higher spike density and more grains per spike. The net income from the CW system was 28.2% higher for the self-propelled relay seeder than with conventional sowing. [ABSTRACT FROM AUTHOR]

There are many ways to define how long diffusive processes take, and an appropriate “critical time” is highly dependent on the specific application. In particular, we are interested in diffusive processes through multilayered materials, which have applications to a wide range of areas. Here we perform a comprehensive comparison of six critical time definitions, outlining their strengths, weaknesses, and potential applications. A further four definitions are also briefly considered. Equivalences between appropriate definitions are determined in the asymptotic limit as the number of layers becomes large. Relatively simple approximations are obtained for the critical time definitions. The approximations are more accessible than inverting the analytical solution for time, and surprisingly accurate. The key definitions, their behaviour and approximations are summarized in tables. [ABSTRACT FROM PUBLISHER]