Advanced sine wave modulation of continuous wave laser system for atmospheric CO2 differential absorption measurements

In this theoretical study, modulation techniques are developed to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described for making simultaneous online/offline differential absorption measurements. Amplitude and Phase Shift Keying (PSK) modulated IM carriers, in addition to a hybrid pulse technique are investigated that exhibit optimal autocorrelation properties. A method is presented to bandwidth limit the ML sequence based on a filter implemented in terms of Jacobi theta functions that does not significantly degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.Comment: Accepted for publication in Applied Optic

Modulated Sine Waves for Differential Absorption Measurements Using a CW Laser System

A continuous wave Light Detection and Ranging (CW LiDAR) system utilizes two or more laser frequencies and time or range shifted pseudorandom noise (PN) codes to discriminate between the laser frequencies. The performance of these codes can be improved by subtracting out the bias before processing. The CW LiDAR system may be mounted to an artificial satellite orbiting the earth, and the relative strength of the return signal for each frequency can be utilized to determine the concentration of selected gases or other substances in the atmosphere

Real-time predictive voltage control of a direct-current generating system, using a hybrid computer

Real-time predictive voltage control of a direct-current (d-c) generating system is achieved with the aid of a hybrid computer. Some assumptions were required to adequately simplify the simulation of the d-c generating system. A predictive controller is used to maintain the load voltage of the d-c generating system (the controlled system) at the desired level for any change in the load. This controller consists of a fast-time scale linearized analog model of the controlled system and a control logic, which is programmed on the digital part of the hybrid computer. In showing the applicability of the controller, the predictive control technique was first applied to the linearized analog simulation of the controlled system and the desired control was successfully achieved. Control of the real system was then attempted and satisfactory results were obtained

A study of the effect of the rotor coil couplings of a synchronous machine on its predicted transient response

The effect of the mutual inductances between the rotor coils of a synchronous machine on its defined reactances and predicted transients are investigated. Two linearized models of the machine are considered. One uses the Laplace-Transform approach, with minimum number of assumptions on the inter-coil couplings, in developing a model for the machine with short-circuited stator terminals. The other model is obtained by modifying the commonly used model and equivalent circuits given by Adkins (4). In the first model, the root-locus technique of classical control theory is used as a tool to investigate the effect of mutual inductances on the short-circuit eigenvalues of the general Park model. Transfer functions for the short-circuit stator and field current responses are derived in terms of the mutual inductances. Numerical examples are presented for two (solid rotor) turbogenerators and one (salient pole) hydrogenerator unit with dampers. In the second model, the effect of the rotor coil mutual inductances on the dynamic behavior of the synchronous machine are investigated for the machine connected to an infinite-bus via a transmission line. Small displacements around a fixed operating point are assumed in order to linearize the nonlinear model; and the state space approach is used for eigenvalue analysis and simulation of the model on a digital computer. A numerical example is given for a hydrogenerator unit. When the models studied were required to yield a fixed set of time constants and short-circuit reactances, it was noticed that the mutual couplings between the rotor coils did not affect the model eigenvalues. The rotor coil mutual couplings also hold no effect on the contribution of the eigenvalues to the short-circuit stator current components (i[subscript d], i[subscript q] ) when the field excitation voltage was fixed. On the other hand, the rotor currents were significantly affected by the mutual couplings between the rotor coils, and their effect should be included in any detailed investigation of synchronous machine

The relationship between job involvement and demographic characteristics in nurses in hospitals of Tehran and Kerman in 2013

Background and aim: Nowadays, job involvement is introduced as an important factor in the effectiveness of the organization, so that the high job involvement will increase the effectiveness of the organization. The aim of this study was to determine the relationship between job involvement and demographic characteristics of the nurses. Methods: In this cross - sectional descriptive-analytic study, 436 nurses from hospitals in Tehran and Kerman in 2013 were recruited by convenience sampling. The Job Involvement Questionnaire was used for data collection. The cutoff point for job involvement score was 40 and the relationship between job involvement and demographic characteristics of the nurses was evaluated. Results: Most the average age of participating nurses in the study 31-40 years. The mean score of job involvement was 36.07± 10.02. Among the demographic characteristics, in terms of gender, men had higher job involvement than women (P=0.01). Also, the job involvement of nurses in military hospitals was higher than civilian hospitals (P0.05). Conclusion: According to the low scores of job involvement, attention to the effective factors and motivation factors in environment variables to improve nurses' job involvement is recommended

Efficient 1.6 Micron Laser Source for Methane DIAL

Methane is a potent greenhouse gas and on a per molecule basis has a warming influence 72 times that of carbon dioxide over a 20 year horizon. Therefore, it is important to look at near term radiative effects due to methane to develop mitigation strategies to counteract global warming trends via ground and airborne based measurements systems. These systems require the development of a time-resolved DIAL capability using a narrow-line laser source allowing observation of atmospheric methane on local, regional and global scales. In this work, a demonstrated and efficient nonlinear conversion scheme meeting the performance requirements of a deployable methane DIAL system is presented. By combining a single frequency 1064 nm pump source and a seeded KTP OPO more than 5 mJ of 1.6 m pulse energy is generated with conversion efficiencies in excess of 20%. Even without active cavity control instrument limited linewidths (50 pm) were achieved with an estimated spectral purity of ~95%. Tunable operation over 400 pm (limited by the tuning range of the seed laser) was also demonstrated. This source demonstrated the critical needs for a methane DIAL system motivating additional development of the technology

Assessing the Potential of Plug-in Electric Vehicles in Active Distribution Networks

A multi-objective optimization algorithm is proposed in this paper to increase the penetration level of renewable energy sources (RESs) in distribution networks by intelligent management of plug-in electric vehicle (PEV) storage. The proposed algorithm is defined to manage the reverse power flow (PF) from the distribution network to the upstream electrical system. Furthermore, a charging algorithm is proposed within the proposed optimization in order to assure PEV owner's quality of service (QoS). The method uses genetic algorithm (GA) to increase photovoltaic (PV) penetration without jeopardizing PEV owners' (QoS) and grid operating limits, such as voltage level of the grid buses. The method is applied to a part of the Danish low voltage (LV) grid to evaluate its effectiveness and capabilities. Different scenarios have been defined and tested using the proposed method. Simulation results demonstrate the capability of the algorithm in increasing solar power penetration in the grid up to 50%, depending on the PEV penetration level and the freedom of the system operator in managing the available PEV storage

A New Technique for the Retrieval of Near Surface Water Vapor Using DIAL Measurements

Water vapor is one of the most important atmospheric trace gas species and influences radiation, climate, cloud formation, surface evaporation, precipitation, storm development, transport, dynamics, and chemistry. For improvements in NWP (numerical weather prediction) and climate studies, global water vapor measurements with higher accuracy and vertical resolution are needed than are currently available. Current satellite sensors are challenged to characterize the content and distribution of water vapor in the Boundary Layer (BL) and particularly near the first few hundred meters above the surface within the BL. These measurements are critically needed to infer surface evaporation rates in cloud formation and climate studies. The NASA Langley Research Center Lidar Atmospheric Sensing Experiment (LASE) system, which uses the Differential Absorption Lidar (DIAL) technique, has demonstrated the capability to provide high quality water vapor measurements in the BL and across the troposphere. A new retrieval technique is investigated to extend these DIAL water vapor measurements to the surface. This method uses signals from both atmospheric backscattering and the strong surface returns (even over low reflectivity oceanic surfaces) using multiple gain channels to cover the large signal dynamic range. Measurements can be made between broken clouds and in presence of optically thin cirrus. Examples of LASE measurements from a variety of conditions encountered during NASA hurricane field experiments over the Atlantic Ocean are presented. Comparisons of retrieved water vapor profiles from LASE near the surface with dropsonde measurements show very good agreement. This presentation also includes a discussion of the feasibility of developing space-based DIAL capability for high resolution water vapor measurements in the BL and above and an assessment of the technology needed for developing this capability

Advanced Intensity-Modulation Continuous-Wave Lidar Techniques for ASCENDS O2 Column Measurements

Global atmospheric carbon dioxide (CO2) measurements for the NASA Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) space mission are critical for improving our understanding of global CO2 sources and sinks. Advanced Intensity- Modulated Continuous-Wave (IM-CW) lidar techniques are investigated as a means of facilitating CO2 measurements from space to meet the ASCENDS measurement requirements. In recent numerical, laboratory and flight experiments we have successfully used the Binary Phase Shift Keying (BPSK) modulation technique to uniquely discriminate surface lidar returns from intermediate aerosol and cloud contamination. We demonstrate the utility of BPSK to eliminate sidelobes in the range profile as a means of making Integrated Path Differential Absorption (IPDA) column CO2 measurements in the presence of optically thin clouds, thereby eliminating the need to correct for sidelobe bias errors caused by the clouds. Furthermore, high accuracy and precision ranging to the surface as well as to the top of intermediate cloud layers, which is a requirement for the inversion of column CO2 number density measurements to column CO2 mixing ratios, has been demonstrated using new hyperfine interpolation techniques that takes advantage of the periodicity of the modulation waveforms. This approach works well for both BPSK and linear swept-frequency modulation techniques. The BPSK technique under investigation has excellent auto-correlation properties while possessing a finite bandwidth. A comparison of BPSK and linear swept-frequency is also discussed in this paper. These results are extended to include Richardson-Lucy deconvolution techniques to extend the resolution of the lidar beyond that implied by limit of the bandwidth of the modulation, where it is shown useful for making tree canopy measurements