By solving the magneto-transport equation for excess minority charge carriers in the base of the series vertical-junction silicon cell, the phenomenological parameters of the cell can be determined from the boundary c...By solving the magneto-transport equation for excess minority charge carriers in the base of the series vertical-junction silicon cell, the phenomenological parameters of the cell can be determined from the boundary conditions. Photocurrent density and photovoltage are determined for each value of applied magnetic field and corresponding optimum thickness, to establish the current-voltage characteristic (Jph(Sf, Sb, z, B, Hop)-Vph(Sf, Sb, z, B, Hop) of the silicon cell under polychromatic illumination. This study will make it possible to reduce the material used (by reducing the optimum thickness), which will help to lower prices. It will also enable us to reduce betting effects (lower series resistance), thereby boosting solar cell efficiency.展开更多
Cabbage is today an economically important crop grown in more than 90 countries around the world. Production is constantly threatened by pests including the cabbage webworm, Hellula undalis (F.) (Lepidoptera: Pyralida...Cabbage is today an economically important crop grown in more than 90 countries around the world. Production is constantly threatened by pests including the cabbage webworm, Hellula undalis (F.) (Lepidoptera: Pyralidae) which just one or two larvae can cause severe damage by infesting the growing points or shoots of young plants. Hellula undalis is difficult to control by the use of chemical insecticides. The establishment of effective biological control is needed. The parasitoid species Pristomerus pallidus (Hymenoptera: Ichneumonidae: Cremastinae) was recorded for the first time in Senegal on larvae of Hellula undalis from cabbage fields infested with H. undalis. Laboratory observed parasitism was 7.4%. This is the first record of Pristomerus pallidus parasitizing Hellula undalis from Senegal. Furthermore, studies on the potential regulation of Hellula undalis under controlled and field conditions need to be evaluated for utilizing this parasitoid as a biocontrol agent against the cabbage webworm. .展开更多
This study investigates the effect of the magnetic field on the transient density of excess minority charge carriers in the base of a series-connected vertical junction silicon solar cell. The solar cell is presented ...This study investigates the effect of the magnetic field on the transient density of excess minority charge carriers in the base of a series-connected vertical junction silicon solar cell. The solar cell is presented in open circuit transient operation. The magnetic field through the Laplace force which deflects the photogenerated carriers from their initial trajectory towards the lateral surfaces reducing their mobility, diffusion and conduction, will certainly influence the decay time of the transient regime. The transient density of excess minority carriers in the base is a sum of infinite terms whose decay time of the different harmonics is studied.展开更多
Crop pests are a permanent threat to horticultural production. Several control methods are recommended for their control, including biological control. This method based on the use of natural enemies is not well estab...Crop pests are a permanent threat to horticultural production. Several control methods are recommended for their control, including biological control. This method based on the use of natural enemies is not well established. The objective of this study was to assess the diversity and abundance of natural enemies of crop pests. A survey of crops associated with pests was carried out on 144 fields in southern Senegal to measure the diversity and abundance of natural enemies of various crop pests, determine the native parasitoid complex and assess parasitism rates. Ecological indices were calculated to assess the diversity of natural enemies. A total of 25 natural enemy species were identified, including 15 parasitoids and 10 predators. Predatory Hemiptera and Parasitoid Hymenoptera were high biodiversity. The parasitism rates vary between 0 and 50% depending on the abundance of pests and parasitoid species. Knowledge of the diversity of natural enemies and the understanding of trophic interactions with pests are important in the development of biological crop protection in order to preserve resilience in agroecosystems.展开更多
文摘By solving the magneto-transport equation for excess minority charge carriers in the base of the series vertical-junction silicon cell, the phenomenological parameters of the cell can be determined from the boundary conditions. Photocurrent density and photovoltage are determined for each value of applied magnetic field and corresponding optimum thickness, to establish the current-voltage characteristic (Jph(Sf, Sb, z, B, Hop)-Vph(Sf, Sb, z, B, Hop) of the silicon cell under polychromatic illumination. This study will make it possible to reduce the material used (by reducing the optimum thickness), which will help to lower prices. It will also enable us to reduce betting effects (lower series resistance), thereby boosting solar cell efficiency.
文摘Cabbage is today an economically important crop grown in more than 90 countries around the world. Production is constantly threatened by pests including the cabbage webworm, Hellula undalis (F.) (Lepidoptera: Pyralidae) which just one or two larvae can cause severe damage by infesting the growing points or shoots of young plants. Hellula undalis is difficult to control by the use of chemical insecticides. The establishment of effective biological control is needed. The parasitoid species Pristomerus pallidus (Hymenoptera: Ichneumonidae: Cremastinae) was recorded for the first time in Senegal on larvae of Hellula undalis from cabbage fields infested with H. undalis. Laboratory observed parasitism was 7.4%. This is the first record of Pristomerus pallidus parasitizing Hellula undalis from Senegal. Furthermore, studies on the potential regulation of Hellula undalis under controlled and field conditions need to be evaluated for utilizing this parasitoid as a biocontrol agent against the cabbage webworm. .
文摘This study investigates the effect of the magnetic field on the transient density of excess minority charge carriers in the base of a series-connected vertical junction silicon solar cell. The solar cell is presented in open circuit transient operation. The magnetic field through the Laplace force which deflects the photogenerated carriers from their initial trajectory towards the lateral surfaces reducing their mobility, diffusion and conduction, will certainly influence the decay time of the transient regime. The transient density of excess minority carriers in the base is a sum of infinite terms whose decay time of the different harmonics is studied.
文摘Crop pests are a permanent threat to horticultural production. Several control methods are recommended for their control, including biological control. This method based on the use of natural enemies is not well established. The objective of this study was to assess the diversity and abundance of natural enemies of crop pests. A survey of crops associated with pests was carried out on 144 fields in southern Senegal to measure the diversity and abundance of natural enemies of various crop pests, determine the native parasitoid complex and assess parasitism rates. Ecological indices were calculated to assess the diversity of natural enemies. A total of 25 natural enemy species were identified, including 15 parasitoids and 10 predators. Predatory Hemiptera and Parasitoid Hymenoptera were high biodiversity. The parasitism rates vary between 0 and 50% depending on the abundance of pests and parasitoid species. Knowledge of the diversity of natural enemies and the understanding of trophic interactions with pests are important in the development of biological crop protection in order to preserve resilience in agroecosystems.
