In modern times the increasing complexity of transistors and their constant decreasingsize require more effective techniques to display and interpret the processes that are inside of devices. In this work, we are modeling a two‐dimensional n‐MOSFET with a long channeland uniformly doped substrate. We assume that this device is a large geometry device so that short‐channel and narrow‐width effects can be neglected. As a result of the thesis, a demonstration program was built. In this executable file, the user can choose parameters of the MOSFET‐model: drain and gate voltage, and different geometrical parameters of the device (junction depth and effective channel length). In the advanced regime of the program, the user can also specify the model re‐calculation parameter, doping concentration in n+ and bulk regions. The program shows the channel between the source and drain region with surface diagrams of carrier density and potential energy as an output. It is possible to save all calculated results to a file and process it in any other program, for example, plot graphics in Matlab or Matematica. The model can be used in lectures that are related to semiconductor physics in order to explain the basic working mechanisms of MOSFETs as well as for further detailed analysis of the processes in MOSFETs. It is possible to use our modeling techniques to rebuild the model in another computer language, or even to build other models of transistors, performing similar calculations and approximations. It is possible to download the executable file of the model here: http://studentdevelop.com/projects/MOSFET_model.zip

In the thesis, LED driver circuits which are applied in low power lighting LED with constant output current and Power Factor Correction are presented. The non-isolated Buck converter are used for the LED drivers. According to different operating mode of inductance current, Power Factor Correction are realized with both the method of Voltage Follower Approach Control under Discontinuous Conduction Mode and the method of Nonlinear Carrier Control under Continuous Conduction Mode. NLC doesn¡¦t need the multiplier which is used in traditional power factor correction, therefore NLC can reduce the system cost. The designed circuits are verified by simulation of IsSpice software and practical experiments. From simulation and experimental results, it shows the proposed approaches achieve the goal with high power factor and constant output current.

Maritime is a very competitive industry in global market. In addition to political, economic and prosperity, container carriers have to confront oil prices and climate. It gets high risk and uncertainty in operation. The threat of oversupply of capacity will affect the operation and development of container carriers. Costs is aggravated on container carriers due to they brought too many new vessels when previous boom but economic declined soon. Fleet deployment is a big issue when making operational strategies and plans. Container carriers have to plan how to purchase and lease vessels. People said that the proportion of owned container vessels of Europe container carriers is lower than Asia container carriers. Europe container carries may not spend too much cost to purchase container vessels so it would be more flexible to lease container vessels and able to deploy container vessels in/out of route and create brand new service more mobility. For this reason, operating performance is better than Asia container carriers. This study is base on secondary data from Alphaliner, Containerisation International and American Shipper database and periodical in 2007 and 2008: net profit, total revenue, the numbers of owned, leased and operated container vessels. The 15 major container carriers are divided into three segments: Asia-Chinese, Asia-Non-Chinese and Non-Asia container carriers. The General Linear Mode is practiced on these to find out if any impact or correlation from the proportion of owned container vessel to performance. The conclusions of this study are as following. 1. It¡¦s no correlation between the proportion of owned container vessels and net profit and total revenue in 2007 and 2008 2. The proportion of owned container vessels can not be fixed at a value 3. The proportion of owned container vessels is dynamic, may not be operated by container carriers.

This thesis develops a power line carrier(PLC) communication module using FSK modulation technology by integration of PLC chip, with various hardware circuits such as DSP, signal coupling and amplifier circuits, filter. The communication performance and conduction EMI tests and executed for the communication module developed. The PLC module is then applied for appliance control of commercial customers to fulfill the demand response function for energy conservation by reducing the summer peak loading. Besides sending the load control command from central station in the smart grid, the power consumption of various appliances can also be collected and transmitted back to the control station via two way communication with the PLC communication module. Finally, the broadband PLC (BPLC) is applied for the CCTV supervision in system to support asset management of distribution room to prevent the power equipment from steal. With the remote control of light brightness and CCTV lens with high data transmission rate provided, the communication performance of PLC can therefore be verified in this study.

Discotic liquid crystals (DLCs), which consist of disk-like molecules, have recently attracted considerable attention for their interesting electronic properties. One of the most significant of DLCs is their high charge carrier mobility in their columnar structure. Recently the number of researches have been increasing on applications such as organic light-emitting diodes (OLED), photovoltaic devices (OPV) and organic field-effect transistors (OFET). The purpose of the study is to investigate the mobility of different alignment of DLCs. The material used in the present study is HDBP-8. We will show that the stack of DLCs depended on temperature strongly. We will also discuss charge transport properties of homeotropic alignment. Carrier transport has been investigated in the hexagonal columnar (Colh) mesophase of HDBP-8 using time-of-flight (TOF) technique. The carrier mobilities are up to the order of 10-3 cm2V-1s-1 for both positive and negative charges with weak dependence on the electric fields.

A tunable erbium-doped fiber ring laser using an intra-cavity Fabry-Perot filter as the tuning element is investigated. Tuning is achieved by varying the applied voltage which controls the FP cavity length. The laser's wavelength is monitored using an optical spectrum analyzer to determine the laser's spectral characteristics under static conditions at different wavelengths over its tuning range of approximately 50nm. When the laser is tuned rapidly, the frequency versus time characteristic is determined using a fiber Fabry-Perot interferometer with a photodetector to convert the optical signal to an electrical signal. The core of the research is to determine the degree of spectral broadening of the laser as a function of the spectral tuning rate. The fringe contrast of fiber Fabry-Perot interferometer transmittance curves decreases with increase in the tuning frequency. The gain at a certain wavelength becomes a function of time putting an upper limit on the tuning frequency of the system. The carrier lifetime of erbium ions dictates the maximum achievable tuning speed.

The hot carrier dynamics of Zn0.91Cd0.09Se/ZnSe multi-quantum wells were studied using the femtosecond time-resolved photoluminescence upconversion technique. The carrier cooling behavior was investigated for different compositions at various lattice temperatures. The hot carriers generated photoexcitation by 405nm Ti:sapphire laser pulses release their excess energy primarily through carrier-LO-phonon interaction. As the excess energy reduce to the amount that lower than the energy of LO phonon, the excess energy was released by carrier-TA-phonon scattering before radiative recombination occurs. We have determined the scattering times of carrier-LO-phonon scattering at different lattice temperatures. No hot phonon effects was found at low photoexcited carrier density. The dependence of photoluminescence lifetime on wavelength was also discussed.

Abstract We have extended the spectral range of the current PL-upconversion apparatus to be operated in infrared. Using the IRPL-upconversion¡Awe study the behavior of carrier cooling of InN film and the relationship between the spacer and lifetime in InAs/GaAs stacked QDs . We excited InN film of the band gap of 0.74eV with ultrafast Ti:sapphire laser of the wavelength 404nm. We found the phonon emission time by hot carriers of InN is 14fs. The hot carriers release their excess energy to the lattice of 35K with a timescale of 100ps. We observed in InAs/GaAs QDs that the shorter life time for samples with thin spacer is due to tunneling effect.

Carrier dynamics of mullti-stacked quantum dots (MSQDs) have been studied by means of time-integrated and time-resolved photoluminescence (PL). The MSQD with different spacer thickness of 10, 15, 20 and 30 nm were grown by molecular beam epitaxy. Time-integrated PL exhibit red shift as spacer thickness increases. The red shift originated from the vertical coupling relaxes the strain in the MSQDs, leading to a decrease in the PL peak energy. From time-resolved PL, the MSQD with spacer thickness increased reveals the shorter lifetime of PL peak among samples studies. We attribute the maximum of lifetime to a better vertical alignment. We report on a measurement of the rise and decay of luminescence intensity in the MSQDs excited at 1.54 eV (808 nm) and 3.09 eV (404 nm). The results show a slow rise time of electrons from the L to the £F valley for high photoexcitation energies. The decay in luminescence is longest with photoexcitation at 3.09 eV, we demonstrate the importance of the penetration depth and carriers tunneling. In addition, the MSQDs strongly depends of on the carrier injection. The rise times decrease with increasing excitation density. The properties are characteristic features of Auger processes.

A successive interference cancellation (SIC) structure is proposed for multiuser interference cancellation (MUI) due to carrier frequency offsets (CFOs) in the uplink of orthogonal frequency division multiple access (OFDMA) systems. The proposed architecture adopts a circular convolution to suppress the impacts caused by CFOs. This paper demonstrates that, with 2 iterations, the SIC has better performance than that of the parallel interference cancellation (PIC), but system complexity is only 1/2K, where K is the number of users in the uplink of OFDMA system. This study also shows that system complexity can be significantly reduced if proper approximation is made.