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We present here an 11,000-year palaeomonsoonal record from a sediment core (SS-1) from Shantisagara (SS) Lake in Peninsular India, which is the longest published so far from the region. This is also a region with limited palaeoclimate records. Environmental magnetic, organic geochemical, sedimentological and carbon isotopic studies were carried out on the SS-1 sediments to reconstruct the Indian summer monsoon (ISM) variability during the Holocene. The chronology of the sediments is constrained by three AMS 14C dates. Environmental magnetic data reveal that there is no contribution from bacterial magnetite, greigite and anthropogenic magnetite/lithogenic grains and that the magnetic signal is contributed mainly by the pedogenic component. The environmental magnetic data also depict variations in pedogenic magnetite production in the catchment and detrital influx to the lake, which in turn is related to monsoonal rainfall amount. The sedimentological data reveal variations in sediment size related to monsoon. The Corg/N ratio and δ13C indicate palaeovegetational variations in the SS catchment. Periods of strong monsoon are characterized by high values of concentration-dependent magnetic parameters like χlf, χfd, χARM and SIRM, high sand content, low Corg/N ratio (fully aquatic-deep water conditions), relatively depleted δ13C values (more C3 but less C4 land plants) and vice versa. The prominent palaeomonsoon events documented in this study are: (i) 11,100–10,700 cal yr BP with a weak ISM, (ii) 10,700 to 8600 cal yr BP characterized by intensified ISM, corresponding to the Early Holocene Optimum, (iii) 8600 to 4500 cal yr BP with a weakened ISM, (iv) 4500 to 3300 cal yr BP characterized by fluctuating monsoonal conditions, (v) 3300 cal yr BP to the Present with a slight increasing trend in ISM. A similar pattern is also documented in many palaeomonsoon records from the region, which indicate that Shantisagara sediments were able to record regional climatic variations as well.

Sediments from Pookot Lake (PK) in southern India have provided a record of local environmental changes and catchment processes during the past 3100 cal. years B.P. Variations in the rock magnetic parameters (χlf, χfd, χARM and IRM's at different field strengths) of sediments from two AMS 14C-dated cores reflect climate-induced changes in the catchment of Pookot Lake. Assuming that rainfall is most likely the dominant driving mechanism behind the rock magnetic variations of PK sediments, the environmental history of the site has been reconstructed. Rock magnetic parameters exhibit significant variations during the past 3100 years. The palaeoenvironmental history of the Pookot Lake region may be divided into three phases. During the first phase (~ 3100 to 2500 cal. years B.P.), catchment erosion and detrital influx were high, indicating a strong monsoon. The second phase, which lasted from 2500 to 1000 cal. years B.P., was characterised by low and steady rainfall, resulting in a low and uniform catchment erosion and detrital influx. Phase 2 was interspersed with brief intervals of strong monsoon and characterised by frequent drying up of the lake. During Phase 3 (~ 1000 cal. years B.P. to the present), catchment erosion was high, indicating a shift to strong monsoonal conditions. It appears that monsoonal rainfall in the region is influenced by solar activity, with periods of high total solar irradiance being characterised by high rainfall and vice versa; it was relatively low during the Little Ice Age and high during the Medieval Warm Period. The magnetic susceptibility (χlf) data exhibit a number of periodicities which might have a solar origin. The χlf record exhibits similarities with other continental and marine palaeoclimatic records from the region, indicating that regional trends in the monsoon during the Late Holocene are broadly similar.

A scalable Gummel-Poon model for high-speed SiGe HBTs is developed based on Gummel-Poon model in this paper. This model is well applied to simulation software of ADS and Hspice. The scaling is mainly based on different physical dimension of individual devices, all the scaling parameters in the scaling equations are extracted directly from the measurement data of various dimension. The correctness of this scalable model is further verified by the quite good fit between measured and simulated results on DC, CV, Ft and S parameters at the frequency up to 30 GHz.

A novel composite-channel AlxGa1-xN/AlyGa1-yN/GaN high electron mobility transistor has designed and optimized. The influence of the two-dimensional electron gas and electric field on device structure parameter is obtained from the self-consistent solution based on the theory of semiconductor energy band and quantum well. The influence of the layer structure of the device on its performance is obtained from simulation using TCAD software. Combining the results of theoretical analysis and simulation, the optimized structure Al0.31Ga0.69N/Al0.04Ga0.96N/GaN HEMT is proposed. The simulation results show that the device with gate length of 1 μm and gate width of 100 μm has the maximum transconductance of 300 mS/mm and small fluctuation in the gate voltage of from -2 V to 1 V, which shows the excellent linearity of the device. The maximum current density of 1300 mA/mm, the cut-off frequency of 11.5 GHz and a maximum oscillation frequency of 32.5 GHz are obtained.