Hydrogen and ammonia have attracted increasing attention as carbon-free fuels.Ammonia is considered to be an effective energy storage and hydrogen storage medium.However,a small amount of unremoved NH3 is still presen...Hydrogen and ammonia have attracted increasing attention as carbon-free fuels.Ammonia is considered to be an effective energy storage and hydrogen storage medium.However,a small amount of unremoved NH3 is still present in the product during the decomposition of ammonia to produce hydrogen.Therefore,it is very essential to investigate the self-ignition of hydrogen-ammonia mixtures in order to accommodate the various scenarios of hydrogen energy applications.In this paper,the effect of NH3 addition on the self-ignition of high-pressure hydrogen release is numerically investigated.The RNG k-εturbulence model,EDC combustion model,and 213-step detailed NH_(3)/H_(2) combustion mechanism are used.CHEMKIN-Pro programs for zero-dimensional homogeneous and constant volume adiabatic reactor models are used for sensitivity analysis and ignition delay time of the chemical reaction mechanism.The results showed that the minimum burst pressure required for self-ignition increased significantly after the addition of ammonia.The maximum temperature and shock wave intensity inside the tube decreases with increasing ammonia concentration.The ignition delay time and H,HO2,and OH radicals reduce with increasing ammonia concentration.H and HO2 radicals are suggested as indicators for tracking the second and third flame branches,respectively.展开更多
The thyroid, an endocrine gland located at the base of the neck, produces thyroid hormones (triiodothyronine (T3) and thyroxine (T4)). The production of these hormones is possible by iodine and other nutrients such as...The thyroid, an endocrine gland located at the base of the neck, produces thyroid hormones (triiodothyronine (T3) and thyroxine (T4)). The production of these hormones is possible by iodine and other nutrients such as selenium and certain vitamins. To assess the thyroid disturbances in the mountain population of Benin, a survey was conducted in Natitingou, a mountain town located in the department of Atacora, in the northwest of Benin, on a sample of thirty (30) adults (15 men and 15 women), most of whom are educated. The results of the questionnaire revealed that 43% of the surveyed population acknowledged having knowledge on the mentioned subject and have dietary habits based on the consumption of seafood, and also legumes (20%). The examination of the serum results of the dosage of T3, T4 and TSH hormones revealed cases of thyroid disturbances in the region (36.32% in men and 44.98% in women). The analysis of a comparative table including the “VEDALAB Easy Reader+” and five (05) other readers, presents the performance, reading techniques, principles, advantages and disadvantages of each device. Pending further studies, some recommendations were made at the end of this study to the academic authorities regarding probable cases of dysthyroidism for which additional examinations are required and an awareness for the improvement of dietary habits.展开更多
In the classical formulation, the problem of thermal explosion in a finite volume of the reacting material in the presence of harmonic oscillations of the ambient temperature has been solved. It is shown that in the o...In the classical formulation, the problem of thermal explosion in a finite volume of the reacting material in the presence of harmonic oscillations of the ambient temperature has been solved. It is shown that in the oscillation periods, commensurate with the adiabatic induction period of thermal explosion, implement a kind of resonance which corresponding with average ambient temperature. At both high and very low frequencies oscillations at ambient temperature, their influence on the critical condition and on the induction period of thermal explosion is negligible. However, at low-frequencies influence of ambient temperature oscillations, even a relatively low amplitude, on critical condition and especially on induction period of thermal explosion, can be very strong.展开更多
为了有效地解决多跳频信号的盲源分离问题,提出了一种变步长的EASI(Equivariant Adaptive Separation via Independence)盲源分离算法。该算法在传统EASI算法的等变化性基础上,用性能指标(串音误差)作为准则,通过改变函数的取值范围及形...为了有效地解决多跳频信号的盲源分离问题,提出了一种变步长的EASI(Equivariant Adaptive Separation via Independence)盲源分离算法。该算法在传统EASI算法的等变化性基础上,用性能指标(串音误差)作为准则,通过改变函数的取值范围及形状,自适应更新步长,使其在一个固定小的范围内,达到算法收敛速度和稳定性能的一个较理想的平衡点,改善了当步长固定时存在的缺陷。经过实验仿真,证明该算法对步长有很好的调整能力,性能稳定且收敛速度较快,能很好地将多个跳频信号进行分离,较传统的EASI算法有更高的适用性。展开更多
基金supported by the National Key R&D Program of China for Renewable Energy and Hydrogen Technology(Grant No.2021YFB4000403)the National Natural Science Foundation of China(Grant No.52204072)+3 种基金the National Natural Science Foundation of China(Grant No.22038002)the Science Fund for Creative Research Groups of the National Natural Science Foundation of China(Grant No.22221005)the Fujian Science and Technology Major Project(Grant No.2020HZ07009)the Natural Science Foundation of Fujian Province(Grant No.2020J05098).
文摘Hydrogen and ammonia have attracted increasing attention as carbon-free fuels.Ammonia is considered to be an effective energy storage and hydrogen storage medium.However,a small amount of unremoved NH3 is still present in the product during the decomposition of ammonia to produce hydrogen.Therefore,it is very essential to investigate the self-ignition of hydrogen-ammonia mixtures in order to accommodate the various scenarios of hydrogen energy applications.In this paper,the effect of NH3 addition on the self-ignition of high-pressure hydrogen release is numerically investigated.The RNG k-εturbulence model,EDC combustion model,and 213-step detailed NH_(3)/H_(2) combustion mechanism are used.CHEMKIN-Pro programs for zero-dimensional homogeneous and constant volume adiabatic reactor models are used for sensitivity analysis and ignition delay time of the chemical reaction mechanism.The results showed that the minimum burst pressure required for self-ignition increased significantly after the addition of ammonia.The maximum temperature and shock wave intensity inside the tube decreases with increasing ammonia concentration.The ignition delay time and H,HO2,and OH radicals reduce with increasing ammonia concentration.H and HO2 radicals are suggested as indicators for tracking the second and third flame branches,respectively.
文摘The thyroid, an endocrine gland located at the base of the neck, produces thyroid hormones (triiodothyronine (T3) and thyroxine (T4)). The production of these hormones is possible by iodine and other nutrients such as selenium and certain vitamins. To assess the thyroid disturbances in the mountain population of Benin, a survey was conducted in Natitingou, a mountain town located in the department of Atacora, in the northwest of Benin, on a sample of thirty (30) adults (15 men and 15 women), most of whom are educated. The results of the questionnaire revealed that 43% of the surveyed population acknowledged having knowledge on the mentioned subject and have dietary habits based on the consumption of seafood, and also legumes (20%). The examination of the serum results of the dosage of T3, T4 and TSH hormones revealed cases of thyroid disturbances in the region (36.32% in men and 44.98% in women). The analysis of a comparative table including the “VEDALAB Easy Reader+” and five (05) other readers, presents the performance, reading techniques, principles, advantages and disadvantages of each device. Pending further studies, some recommendations were made at the end of this study to the academic authorities regarding probable cases of dysthyroidism for which additional examinations are required and an awareness for the improvement of dietary habits.
文摘In the classical formulation, the problem of thermal explosion in a finite volume of the reacting material in the presence of harmonic oscillations of the ambient temperature has been solved. It is shown that in the oscillation periods, commensurate with the adiabatic induction period of thermal explosion, implement a kind of resonance which corresponding with average ambient temperature. At both high and very low frequencies oscillations at ambient temperature, their influence on the critical condition and on the induction period of thermal explosion is negligible. However, at low-frequencies influence of ambient temperature oscillations, even a relatively low amplitude, on critical condition and especially on induction period of thermal explosion, can be very strong.
文摘为了有效地解决多跳频信号的盲源分离问题,提出了一种变步长的EASI(Equivariant Adaptive Separation via Independence)盲源分离算法。该算法在传统EASI算法的等变化性基础上,用性能指标(串音误差)作为准则,通过改变函数的取值范围及形状,自适应更新步长,使其在一个固定小的范围内,达到算法收敛速度和稳定性能的一个较理想的平衡点,改善了当步长固定时存在的缺陷。经过实验仿真,证明该算法对步长有很好的调整能力,性能稳定且收敛速度较快,能很好地将多个跳频信号进行分离,较传统的EASI算法有更高的适用性。
