Short-term and long-term reliability studies in the deregulated power systems

The electric power industry is undergoing a restructuring process. The major goals of the change of the industry structure are to motivate competition, reduce costs and improve the service quality for consumers. In the meantime, it is also important for the new structure to maintain system reliability. Power system reliability is comprised of two basic components, adequacy and security. In terms of the time frame, power system reliability can mean short-term reliability or long-term reliability. Short-term reliability is more a security issue while long-term reliability focuses more on the issue of adequacy. This dissertation presents techniques to address some security issues associated with short-term reliability and some adequacy issues related to long-term reliability in deregulated power systems. Short-term reliability is for operational purposes and is mainly concerned with security. Thus the way energy is dispatched and the actions the system operator takes to remedy an insecure system state such as transmission congestion are important to shortterm reliability. Our studies on short-term reliability are therefore focused on these two aspects. We first investigate the formulation of the auction-based dispatch by the law of supply and demand. Then we develop efficient algorithms to solve the auction-based dispatch with different types of bidding functions. Finally we propose a new Optimal Power Flow (OPF) method based on sensitivity factors and the technique of aggregation to manage congestion, which results from the auction-based dispatch. The algorithms and the new OPF method proposed here are much faster and more efficient than the conventional algorithms and methods. With regard to long-term reliability, the major issues are adequacy and its improvement. Our research thus is focused on these two aspects. First, we develop a probabilistic methodology to assess composite power system long-term reliability with both adequacy and security included by using the sequential Monte Carlo simulation method. We then investigate new ways to improve composite power system adequacy in the long-term. Specifically, we propose to use Flexible AC Transmission Systems (FACTS) such as Thyristor Controlled Series Capacitor (TCSC), Static Var Compensator (SVC) and Thyristor Controlled Phase Angle Regulator (TCPAR) to enhance reliability

Feasibility Study of Synthetic Oil Based Nanofluids for Use in Thermal Oil Heaters

Paper presented at 2018 Canadian Society of Mechanical Engineers International Congress, 27-30 May 2018.Thermal oil heaters can be considered as an alternative to steam boilers for process heating use. Instead of boiling water, thermal oil heaters use heat transfer oils with high boiling points which allows operation at low pressures. To increase thermal oil heater efficiency, a nanofluid consisting of a common heat transfer oil, the synthetic TH66, and copper nanoparticles has been proposed. Based on existing correlations for nanofluids, a figure of merit (FOM) was created to evaluate heat transfer performance while factoring in pumping power increases. A maximum FOM increase of 13% was found for a thermal oil heater using the nanofluid when compared to one that uses the base fluid oil

Regional soil erosion assessment based on a sample survey and geostatistics

Soil erosion is one of the most significant environmental problems in China. From 2010 to 2012, the fourth national census for soil erosion sampled 32 364 PSUs (Primary Sampling Units, small watersheds) with the areas of 0.2–3 km2. Land use and soil erosion controlling factors including rainfall erosivity, soil erodibility, slope length, slope steepness, biological practice, engineering practice, and tillage practice for the PSUs were surveyed, and the soil loss rate for each land use in the PSUs was estimated using an empirical model, the Chinese Soil Loss Equation (CSLE). Though the information collected from the sample units can be aggregated to estimate soil erosion conditions on a large scale; the problem of estimating soil erosion condition on a regional scale has not been addressed well. The aim of this study is to introduce a new model-based regional soil erosion assessment method combining a sample survey and geostatistics. We compared seven spatial interpolation models based on the bivariate penalized spline over triangulation (BPST) method to generate a regional soil erosion assessment from the PSUs. Shaanxi Province (3116 PSUs) in China was selected for the comparison and assessment as it is one of the areas with the most serious erosion problem. Ten-fold cross-validation based on the PSU data showed the model assisted by the land use, rainfall erosivity factor (R), soil erodibility factor (K), slope steepness factor (S), and slope length factor (L) derived from a 1 : 10 000 topography map is the best one, with the model efficiency coefficient (ME) being 0.75 and the MSE being 55.8 % of that for the model assisted by the land use alone. Among four erosion factors as the covariates, the S factor contributed the most information, followed by K and L factors, and R factor made almost no contribution to the spatial estimation of soil loss. The LS factor derived from 30 or 90 m Shuttle Radar Topography Mission (SRTM) digital elevation model (DEM) data worsened the estimation when used as the covariates for the interpolation of soil loss. Due to the unavailability of a 1 : 10 000 topography map for the entire area in this study, the model assisted by the land use, R, and K factors, with a resolution of 250 m, was used to generate the regional assessment of the soil erosion for Shaanxi Province. It demonstrated that 54.3 % of total land in Shaanxi Province had annual soil loss equal to or greater than 5 t ha−1 yr−1. High (20–40 t ha−1 yr−1), severe (40–80 t ha−1 yr−1), and extreme ( \u3e  80 t ha−1 yr−1) erosion occupied 14.0 % of the total land. The dry land and irrigated land, forest, shrubland, and grassland in Shaanxi Province had mean soil loss rates of 21.77, 3.51, 10.00, and 7.27 t ha−1 yr−1, respectively. Annual soil loss was about 207.3 Mt in Shaanxi Province, with 68.9 % of soil loss originating from the farmlands and grasslands in Yan\u27an and Yulin districts in the northern Loess Plateau region and Ankang and Hanzhong districts in the southern Qingba mountainous region. This methodology provides a more accurate regional soil erosion assessment and can help policymakers to take effective measures to mediate soil erosion risks

Mechanism and influence factor of hydrocarbon gas diffusion in porous media with shale oil

Due to the compactness of shale reservoir matrix and the high conductivity of fractures, the hydrocarbon gas injection huff and puff method or displacement is the most realistic technology to improve shale oil recovery. The diffusion mechanism plays an important role in shale oil development; therefore, it is crucial to figure out the factors influencing diffusion, which could enhance shale oil recovery. In this paper, a physical simulation experiment is designed to evaluate the diffusion ability of  hydrocarbon gas. Diffusion experiments are conducted to simulate diffusion in the bulk fluid and in the porous media, to learn about how the pressure, permeability and fracture affect the diffusion behavior. The diffusion coefficients between the bulk diffusion and core sample diffusion are compared. The experimental results show that the diffusion coefficient and mass transfer capacity are positively correlated with permeability and pressure: increasing these parameters can promote the diffusion process. The diffusion coefficient of  hydrocarbon gas in a saturated oil core is significantly less than that in crude oil, which indicates that the porous media seriously affects the process of gas diffusion in crude oil. Fractures have little impact on the diffusion behavior. Combined with numerical simulation, the influencing factor of diffusion on the development effect of hydrocarbon gas injection is clarified. The recovery enhances and then decreases with the increasing diffusion  coefficient.Cited as: Wanyan, Z., Liu, Y., Li, Z., Zhang, C., Liu, Y., Xue, T. Mechanism and influence factor of hydrocarbon gas diffusion in porous media with shale oil. Advances in Geo-Energy Research, 2023, 7(1): 39-48. https://doi.org/10.46690/ager.2023.01.0

RLT Code Based Handshake-Free Reliable MAC Protocol for Underwater Sensor Networks

The characteristics of underwater acoustic channels such as long propagation delay and low bit rate cause the medium access control (MAC) protocols designed for radio channels to either be inapplicable or have low efficiency for underwater sensor networks (UWSNs). Meanwhile, due to high bit error, conventional end-to-end reliable transfer solutions bring about too many retransmissions and are inefficient in UWSN. In this paper, we present a recursive LT (RLT) code. With small degree distribution and recursive encoding, RLT achieves reliable transmission hop-by-hop while reducing the complexity of encoding and decoding in UWSN. We further propose an RLT code based handshake-free (RCHF) reliable MAC protocol. In RCHF protocol, each node maintains a neighbor table including the field of state, and packages are forwarded according to the state of a receiver, which can avoid collisions of sending-receiving and overhearing. The transmission-avoidance time in RCHF decreases data-ACK collision dramatically. Without RTS/CTS handshaking, the RCHF protocol improves channel utilization while achieving reliable transmission. Simulation results show that, compared with the existing reliable data transport approaches for underwater networks, RCHF can improve network throughput while decreasing end-to-end overhead

45°-tilted fiber gratings and their application in ultrafast fiber lasers

This chapter reviews the recentachievements of 45°-tilted fiber gratings (45°-TFGs) in all fiber laser systems, including the theory, fabrication, and characterization of 45° TFGs and 45° TFG-based ultrafast fiber laser systems working in different operating regimes at the wavelength of 1 µm, 1.5 µm, and 2 µm

Influenza A virus NS1 gene mutations F103L and M106I increase replication and virulence

<p>Abstract</p> <p>Background</p> <p>To understand the evolutionary steps required for a virus to become virulent in a new host, a human influenza A virus (IAV), A/Hong Kong/1/68(H3N2) (HK-wt), was adapted to increased virulence in the mouse. Among eleven mutations selected in the NS1 gene, two mutations F103L and M106I had been previously detected in the highly virulent human H5N1 isolate, A/HK/156/97, suggesting a role for these mutations in virulence in mice and humans.</p> <p>Results</p> <p>To determine the selective advantage of these mutations, reverse genetics was used to rescue viruses containing each of the NS1 mouse adapted mutations into viruses possessing the HK-wt NS1 gene on the A/PR/8/34 genetic backbone. Both F103L and M106I NS1 mutations significantly enhanced growth <it>in vitro </it>(mouse and canine cells) and <it>in vivo </it>(BALB/c mouse lungs) as well as enhanced virulence in the mouse. Only the M106I NS1 mutation enhanced growth in human cells. Furthermore, these NS1 mutations enhanced early viral protein synthesis in MDCK cells and showed an increased ability to replicate in mouse interferon β (IFN-β) pre-treated mouse cells relative to rPR8-HK-NS-wt NS1. The double mutant, rPR8-HK-NS-F103L + M106I, demonstrated growth attenuation late in infection due to increased IFN-β induction in mouse cells. We then generated a rPR8 virus possessing the A/HK/156/97 NS gene that possesses 103L + 106I, and then rescued the L103F + I106M mutant. The 103L + 106I mutations increased virulence by >10 fold in BALB/c mice. We also inserted the avian A/Ck/Beijing/1/95 NS1 gene (the source lineage of the A/HK/156/97 NS1 gene) that possesses 103L + 106I, onto the A/WSN/33 backbone and then generated the L103F + I106M mutant. None of the H5N1 and H9N2 NS containing viruses resulted in increased IFN-β induction. The rWSN-A/Ck/Beijing/1/95-NS1 gene possessing 103L and 106I demonstrated 100 fold enhanced growth and >10 fold enhanced virulence that was associated with increased tropism for lung alveolar and bronchiolar tissues relative to the corresponding L103F and I106M mutant.</p> <p>Conclusions</p> <p>The F103L and M106I NS1 mutations were adaptive genetic determinants of growth and virulence in both human and avian NS1 genes in the mouse model.</p

Numerical and experimental analysis of sensitivity-enhanced RI sensor based on Ex-TFG in thin cladding fiber

We report a highly sensitive refractive index (RI) sensor in the aqueous solution, which is based on an 81°-tilted fiber grating structure inscribed into a thin cladding fiber with 40 μm cladding radius. The numerical analysis has indicated that the RI sensitivity of cladding resonance mode of the grating can be significantly enhanced with reducing cladding size. This has been proved by the experimental results as the RI sensitivities of TM and TE resonance peaks in the index region of 1.345 have been increased to 1180 nm/RIU and 1150 nm/RIU, respectively, from only 200 and 170 nm/RIU for the same grating structure inscribed in standard telecom fiber with 62.5-μm cladding radius. Although the temperature sensitivity has also increased, the change in temperature sensitivity is still insignificant in comparison with RI sensitivity enhancement