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Abstrak :
We report the effects of a transverse magnetic field (J⊥B) on the conductivity of quantum well tunneling structures based on AlGaAs/GaAs/AlGaAs quantum wells. The current voltage characteristics in the positive differential resistance regime show negative magnetoconductance for all values of B. The peak bias voltage increases monotonically with increasing B. For B≪6 T there is a decrease in the peak tunneling current, but then it increases for B≫6 T. The data also show dramatic magnetic field induced changes in the negative differential resistance (NDR) features. The behavior of the NDR changes from sharp hysteretic bistable like transitions to astable NDR transitions. Both the valley current and its bias voltage position increase with increasing magnetic field. This behavior is described by a simple model that includes magnetic field effects across the barriers.

Abstrak :
ABSTRAK
Pile breakwater is an effective type of breakwater to reduce wave energy. To find out the effectiveness of the structure of the pile breakwater can be carried out physical modeling experiments in the laboratory. The structure is tested based on the variation of gap between piles (rows)/Diameter (b/D), distance between piles (columns) / Diameter (B/D), arrangement of laying piles (N), and gap width between pile groups stake (G). Besides structure, period (T) and wave height (H) are also varied. This physical model test is carried out in a fume with regular wave at a depth of 60 cm. From the results of physical modeling it can be seen the value of the transmission coefficient (Kt) which is determined based on variations in the gap structure between the piles (rows) /Diameter (b/D), the arrangement of laying piles (N), and the width of the gap between the pile groups (G) which is used as a reference to determine the effectiveness of the pile breakwater structure. Physical modelling of the pile is the optimum value of the transmission coefficient (Kt) to reduce the waveform shown in the variation of the structure of the distance between the pile rows (b/D) 0.5, 58.1 cm Gap, and configuration of the pile structure N2 (three rows pile breakwater).