Experimental investigation of the effects of separate hydrogen and nitrogen addition on the emissions and combustion of a diesel engine

An experimental investigation of the effects of separate hydrogen and nitrogen addition on the emissions and combustion of a diesel engine was performed and the results are presented in the current paper.     

Decoupling and pole-zero assignment of singular systems with dynamic state feedback

This paper refers to the problem of designing a linear state feedback dynamic controller for single-input, single-output decoupling of linear, time-invariant, singular systems. Sufficient conditions are established for the state-feedback decoupling problem to have a solution. In the case where the system satisfies these conditions, the class of controller matrices which decouple the system is given. Finally a method is presented for pole-zero placement in the decoupled singular system and a structure is described for the realization of the generalized transfer function matrices.     

Residual grain-interaction stresses in zirconium alloys

Residual grain-interaction stresses develop during the thermomechanical treatment of Zr alloys due to the anisotropy of the mechanical and thermal properties of the hep lattice. The origin and characteristics of this type of residual stress are described in conjunction with underlying physical principles employed to measure grain-interaction strains by means of neutron diffraction. The effect of thermal treatments, deformation, and irradiation on the evolution of residual grain-interaction strains are reviewed, and the most up-to-date experimental results are presented. The effects of grain-interaction stresses on the plasticity and in-reactor deformation of ZIRCALOY-2 will be discussed. This paper is based on a presentation made in the symposium “Irradiation-Enhanced Materials Science and Engineering” presented as part of the ASM INTERNATIONAL 75th Anniversary celebration at the 1988 World Materials Congress in Chicago, IL, September 25–29, 1988, under the auspices of the Nuclear Materials Committee of TMS-AIME and ASM-MSD.     

Redox generation of nitric oxide to radiosensitize hypoxic cells

PURPOSE: Previous studies have shown that nitric oxide (NO) delivered from NO donor agents sensitizes hypoxic cells to ionizing radiation. In the present study, nitroxyl (NO-), a potential precursor to endogenous NO production, was evaluated for hypoxic cell radiosensitization, either alone or in combination with electron acceptor agents. METHODS AND MATERIALS: Radiation survival curves of Chinese hamster V79 lung fibroblasts under aerobic and hypoxic conditions were assessed by clonogenic assay. Hypoxia induction was achieved by metabolism-mediated oxygen depletion in dense cell suspensions. Cells were treated with NO- produced from the nitroxyl donor Angeli's salt (AS, Na2N2O3, sodium trioxodinitrate), in the absence or presence of electron acceptor agents, ferricyanide, or tempol. NO concentrations resulting from the combination of AS and ferricyanide or tempol were measured under hypoxic conditions using an NO-sensitive electrode. RESULTS: Treatment of V79 cells under hypoxic conditions with AS alone did not result in radiosensitization; however, the combination of AS with ferricyanide or tempol resulted in significant hypoxic radiosensitization with SERs of 2.5 and 2.1, respectively. Neither AS alone nor AS in combination with ferricyanide or tempol influenced aerobic radiosensitivity. The presence of NO generated under hypoxic conditions from the combination of AS with ferricyanide or tempol was confirmed using an NO-sensitive electrode. CONCLUSION: Combining NO- generated from AS with electron acceptors results in NO generation and substantial hypoxic cell radiosensitization. NO- derived from donor agents or endogenously produced in tumors, combined with electron acceptors, may provide an important strategy for radiosensitizing hypoxic cells and warrants in vivo evaluation.     

Impact of Statistical Multiplexing on Voice Quality in Cellular Networks

This paper examines the quality of transmission of voice over cellular, packet-switched networks. The medium access mechanism in the uplink is simulated under various statistical multiplexing scenarios in order to assess the effect of front-end clipping on voice quality. Moreover, the simulation is implemented in a real-time demonstration platform utilized to acquire subjective indicators of voice quality by performing Mean Opinion Score (MOS) tests. Results from the MOS tests are reported, and an analysis of the obtained speech samples is presented. Finally, the results are summarized and potential further directions for the simulation tool and the speech models are discussed.     

Research issues in developing compact pulsed power for high peak power applications on mobile platforms

Pulsed power is a technology that is suited to drive electrical loads requiring very large power pulses in short bursts (high-peak power). Certain applications require technology that can be deployed in small spaces under stressful environments, e.g., on a ship, vehicle, or aircraft. In 2001, the U.S. Department of Defense (DoD) launched a long-range (five-year) Multidisciplinary University Research Initiative (MURI) to study fundamental issues for compact pulsed power. This research program is endeavoring to: 1) introduce new materials for use in pulsed power systems; 2) examine alternative topologies for compact pulse generation; 3) study pulsed power switches, including pseudospark switches; and 4) investigate the basic physics related to the generation of pulsed power, such as the behavior of liquid dielectrics under intense electric field conditions. Furthermore, the integration of all of these building blocks is impacted by system architecture (how things are put together). This paper reviews the advances put forth to date by the researchers in this program and will assess the potential impact for future development of compact pulsed power systems.     

Proactive Risk-Based Integrity Assessment of Water Distribution Networks

Sustainable management of urban water distribution networks should include not only new methods for monitoring, repairing or replacing aging infrastructure, but also (and more importantly) expanded methods for modelling deteriorating infrastructure, for pro-actively assessing the risk of failure and for devising replace or repair strategies. The study presented herein describes a framework for proactive risk-based integrity monitoring of urban water distribution networks and the results obtained from a case-study based on a 5-year data sample. A combination of artificial neural network and statistical modelling techniques stemming from parametric and nonparametric survival analysis (Kaplan–Meier survival curves with Epanechnikov’s kernel) are utilized in the investigation of identified risk factors and for estimation of the forecasted time to failure metric. The data is stratified for different pipe groups for a more targeted analysis.     

ENDOW (efficient development of offshore wind farms): modelling wake and boundary layer interactions

While experience gained through the offshore wind energy projects currently operating is valuable, a major uncertainty in estimating power production lies in the prediction of the dynamic links between the atmosphere and wind turbines in offshore regimes. The objective of the ENDOW project was to evaluate, enhance and interface wake and boundary layer models for utilization offshore. The project resulted in a significant advance in the state of the art in both wake and marine boundary layer models, leading to improved prediction of wind speed and turbulence profiles within large offshore wind farms. Use of new databases from existing offshore wind farms and detailed wake profiles collected using sodar provided a unique opportunity to undertake the first comprehensive evaluation of wake models in the offshore environment. The results of wake model performance in different wind speed, stability and roughness conditions relative to observations provided criteria for their improvement. Mesoscale model simulations were used to evaluate the impact of thermal flows, roughness and topography on offshore wind speeds. The model hierarchy developed under ENDOW forms the basis of design tools for use by wind energy developers and turbine manufacturers to optimize power output from offshore wind farms through minimized wake effects and optimal grid connections. The design tools are being built onto existing regional‐scale models and wind farm design software which was developed with EU funding and is in use currently by wind energy developers. Copyright © 2004 John Wiley & Sons, Ltd.     

Minimization of the energy storage requirements of a stand‐alone wind power installation by means of photovoltaic panels

Autonomous wind power systems are among the most interesting and environmentally friendly technological solutions for the electrification of remote consumers. In many cases, however, the battery contribution to the initial or the total operational cost is found to be dominant, discouraging further penetration of the available wind resource. This is basically the case for areas possessing a medium–low wind potential. On the other hand, several isolated consumers are located in regions having the regular benefit of an abundant and reliable solar energy supply. In this context the present study investigates the possibility of reducing the battery size of a stand‐alone wind power installation by incorporating a small photovoltaic generator. For this purpose an integrated energy production installation based exclusively on renewable energy resources is hereby proposed. Subsequently a new numerical algorithm is developed that is able to estimate the appropriate dimensions of a similar system. According to the results obtained by long‐term experimental measurements, the introduction of the photovoltaic panels considerably improves the operational and financial behaviour of the complete installation owing to the imposed significant battery capacity diminution. Copyright © 2006 John Wiley & Sons, Ltd.     

The E3 architecture: enabling future cellular networks with cognitive and self‐x capabilities

Future mobile networks are expected to be complex heterogeneous systems. On the one hand this will enable users to take advantage of a number of different access technologies. On the other hand it will seriously affect network management procedures since more extensive operations and decisions will have to be dealt with. To tackle these challenges a number of new dynamic mechanisms need to be designed. It is imperative that certain network management tasks have to be performed without human intervention to reduce the OPEX costs and achieve faster responses in different events. To achieve this goal, the introduction of self‐x functionalities, combined with cognitive mechanisms and the ability to reconfigure network entities and terminals, is required. Moreover, the introduction of a new pilot channel needs to be considered to assist the terminals in selecting the most suitable radio access technology according to their requirements. We present the functional architecture of an evolved network that was designed in the context of the EU‐funded IP project ‘E³: End‐to‐End Efficiency’. This architecture aims to enhance existing procedures usually performed in traditional operation and maintenance systems (e.g. spectrum management, network planning, configuration actions). We explain the rationale of our design and provide specific examples to illustrate the role of the different functional entities and their interfaces. A considerable part of this architecture has recently been approved as a feasibility study by the ETSI Committee Reconfigurable Radio System. Copyright © 2010 John Wiley & Sons, Ltd.