scholarly journals The intrinsic phenomena of concentration and cavitation on the Riemann solutions for the perturbed macroscopic production model

Author(s):  
Yunfeng Zhang ◽  
Meina Sun
Author(s):  
Yunfeng Zhang ◽  
Meina Sun

The exact solutions of the Riemann problems for the two different perturbed macroscopic production models are considered and constructed respectively for all the possible cases. It is found that the asymptotic limits of solutions to the Riemann problem for the first kind of perturbed macroscopic production model do not coverage to those of the pressureless gas dynamics model, because the delta shock wave in the limiting situation has different propagation speed and strength from those for the pressureless gas dynamics model. In order to remedy it, the second kind of perturbed macroscopic production model is proposed, whose asymptotic limits of Riemann solutions are identical with those of the pressureless gas dynamics model.


2020 ◽  
Vol 26 (1-2) ◽  
pp. 79-102
Author(s):  
NR Sarker ◽  
F Tabassum D Yeasmin ◽  
MA Habib ◽  
MR Amin

This study was undertaken to develop a year round fodder production model for small scale dairy farmers. Five pregnant dairy cows of Red Chittagong Cattle (RCC) genotype were selected. For rearing five cows, 66 decimal of land was selected from existing fodder plots under Pachutia Research Farm at Bangladesh Livestock Research Institute (BLRI), Savar, Dhaka. The selected land was divided into two parts (33 decimal in each). One part was brought under perennial (Napier-4 and Splendida) and the 2nd part of land for seasonal (Maize & Matikalai) fodder production. Data on live weight and live weight gain of cows, birth weight of calves, feed intake, milk production, actual biomass yield for both perennial and seasonal fodder, yearly manure production were recorded and calculated. Napier-4 grass, splendida, maize, straw, silage were supplied to the experimental cows according to the seasonal availability in different months. Concentrate mixture were also supplied consisting of wheat bran, kheshari (red gram), soybean meal, maize crushed, til oil cake, DCP and common salt. Economics of the model revealed that considering the sale of milk, calves and manure and cost included only feed and land leased, a farm/family rearing 5 indigenous dairy cows with his/her family labours, he/she could earn around BDT 98 thousand in a year (1$ = 85 BDT) and the benefit cost ratio of the model on total variable cost and total cost were 1.86 and 1.66, respectively. Therefore, it may be recommended that a farmer having 5 adult dairy cows with 66 decimal land under fodder cultivation may earn substantial share of his/her family income as small-scale rural dairying. Bang. J. Livs. Res. Vol. 26 (1&2), 2019: P. 89-102


Author(s):  
Olga Olegovna Eremenko ◽  
Lyubov Borisovna Aminul ◽  
Elena Vitalievna Chertina

The subject of the research is the process of making managerial decisions for innovative IT projects investing. The paper focuses on the new approach to decision making on investing innovative IT projects using expert survey in a fuzzy reasoning system. As input information, expert estimates of projects have been aggregated into six indicators having a linguistic description of the individual characteristics of the project type "high", "medium", and "low". The task of decision making investing has been formalized and the term-set of the output variable Des has been defined: to invest 50-75% of the project cost; to invest 20-50% of the project cost; to invest 10-20% of the project cost; to send the project for revision; to turn down investing project. The fuzzy product model of making investment management decisions has been developed; it adequately describes the process of investment management. The expediency of using constructed production model on a practical example is shown.


2021 ◽  
Vol 13 (11) ◽  
pp. 6275
Author(s):  
Weiwei Zhang ◽  
Donglan Zhang ◽  
Lawrence Jun Zhang

This mixed-methods study investigated English-as-a-foreign-language (EFL) learners’ perceptions of task difficulty and their use of metacognitive strategies in completing integrated speaking tasks as empirical evidence for the effects of metacognitive instruction. A total of 130 university students were invited to complete four integrated speaking tasks and answer a metacognitive strategy inventory and a self-rating scale. A sub-sample of eight students participated in the subsequent interviews. One-way repeated measures MANOVA and structure coding with content analysis led to two main findings: (a) EFL learners’ use of metacognitive strategies, in particular, problem-solving, was considerably affected by their perceptions of task difficulty in completing the integrated speaking tasks; (b) EFL learners were not active users of metacognitive strategies in performing these tasks. These findings not only support the necessity of taking into account learners’ perceptions of task difficulty in designing lesson plans for metacognitive instruction, but also support a metacognitive instruction model. In addition, the findings provide empirical support for the utility of Kormos’ Bilingual Speech Production Model. As the integrated speaking tasks came from a high-stakes test, these findings also offer validity evidence for test development in language assessment to ascertain sustainable EFL learning for nurturing learner autonomy as an ultimate goal.


Sign in / Sign up

Export Citation Format

Share Document