Ordinary Operation Research Articles

Real-time tracking of electromechanical oscillations in ENTSO-e Continental European Synchronous Area

Small signal stability is a crucial aspect of accurately keeping control in modern interconnected power systems, in order to ensure the required security and reliability standards. Such an aspect could represent a serious limiting factor in the search for ever higher power system exploitation levels. Hence, in order to exploit the existing networks as much as possible, ensuring at the same time adequate security levels, the system operators must monitor the electromechanical oscillations continuously, estimating their fundamental parameters (e.g. frequency, damping factor/ratio, amplitude and phase), and determining the actual dynamic stability margins. Nowadays, electromechanical oscillations tracking can be performed in real time thanks to the quick development of wide area measurement/monitoring systems, and the employment of so-called measurement-based methods (a.k.a. mode meters). In this regard, the paper presents a performance comparison among several measurement-based methods currently operating on the Italian Wide Area Monitoring (WAM) platform. The main objective of this investigation is to analyze the behavior of each of them with respect to actual critical/not critical electromechanical oscillations recorded on the European Network Transmission System Operators for Electricity (ENTSO-e) Continental Synchronous European System (CESA). The considered case studies cover a large variety of situations that can be encountered in the ordinary ENTSO-e CESA operation: local and inter-area oscillations; single mode and multi-mode power signals; ambient and ringdown data; and so on. By keeping in mind that usually no best estimator exists, owing to the lack of an optimality definition, the present analysis aims at examining whether some algorithms are generally more suitable than others, with respect to the variety of aforementioned situations. In detail, the measurement-based methods considered in this work are the Tufts–Kumaresan method, Hankel Singular Value Decomposition-VarPRO, Hilbert–Huang Transform, its refined Empirical Mode Decomposition with Fourier-Based Masking Technique (R-EMD), and a recently published Hilbert Transform-based estimation algorithm. Obviously, this set of estimation techniques cannot be considered exhaustive for the research problem under analysis. Nonetheless, it represents a collection of the major, recent and most fashionable methodologies implemented in actual WAM architectures.

Populism and Redistribution in Latin America. Conceptualizing a Threshold of Acceptance

Populism cannot be defined by an ideology or a set of policies, but rather by a style of governing. In Latin America, a longstanding tradition of populism has existed, which has adopted various discourses and policies, and has allied with different power-based sectors. However, an important strand of that tradition has consisted in movements and leaders that present themselves as outsider leftist political options, and argue that the ordinary operation of democracy inhibits the promotion of excluded sectors to the benefit of oligarchic elites. This type of Latin American populism posits a difficult challenge to liberal and social democrats committed to the value of equality. While populism may be criticized for its threats to pluralism, interest representation, checks and balances, and civil and political rights, the question remains whether it is worth defending for the redistribution and social incorporation that it allegedly delivers. In this paper we address this challenge by placing this form of populism’s arguments in the best possible light. We engage with the normative and positive question of whether and under what conditions a political arrangement that weakens some democratic traits for the purpose of promoting redistribution can be justified. We posit that, if populism wishes to be faithful to the democratic pedigree that it claims to have, it should tie its own hands by respecting certain conditions. As long as those conditions are met, it may be admissible for some democratic rules to be relaxed in order to achieve greater equality. Only by doing this would populism be true to its promise of strengthening democracy via social incorporation. Those conditions are thus the threshold of acceptance of populist redistributive projects. Very few populist governments, if any, comply with them.

Stable Quasiorderings on Some Permutable Inverse Monoids

Let G be an arbitrary group of bijections on a finite set. By I(G), we denote the set of all injections each of which is included in a bijection from G. The set I(G) forms an inverse monoid with respect to the ordinary operation of composition of binary relations. We study different properties of the semi-group I(G). In particular, we establish necessary and sufficient conditions for the inverse monoid I(G) to be permutable (i.e., ξ ○ φ = φ ○ ξ for any pair of congruences on I(G)). In this case, we describe the structure of each congruence on I(G). We also describe the stable orderings on I(A n ), where A n is an alternating group.

Investigation of Impact of Carbon Surface Oxidation on Wettability of PEMFC Cathode Electrode

The oxidation reaction on carbon in proton exchange membrane fuel cells (PEMFCs) electrodes has been reported as carbon corrosion recently under several fuel-cell operation procedures [1-4]. The influence of cell design factors for the membrane electrode assembly (MEA) and gas transport in the gas diffusion layer and the catalyst layer were often investigated at start up and partial hydrogen starvation. These results suggested that the coexistence of oxygen in the anode is critical for carbon corrosion on the positive electrode. Although the impact of carbon loss under ordinary fuel-cell operation is less than during startup / shutdown and partial hydrogen starvation situations, it is estimated to be large enough to affect long-term durability of PEMFC. CO2generation on Pt/C catalyst in a PEMFC occurs under potential dynamic condition such as cyclic voltammetry. They each suggested that platinum accelerated the oxidation of carbon supports under potential dynamic condition. In order to elucidate the influence of platinum on carbon oxidation in more detail, carbon oxidation on Pt/C under potential dynamic model has been investigated. Four reactions were assigned as carbon oxidation reactions.C + H2O → CO2 + 4H+ + 4e- (1)C-C + H2O → C-COH + H+ + e- (2) C-COH + H2O → C-COOH + 2H+ + 2e- (3)C-COOH + Pt-OH → CO2 + Pt + COH + H+ + e- (4)Carboxyl group and phenol group species were induced from graphite structure carbon on carbon surface through the electrochemical reactions with water. High potential hold at 1.3V and potential cycling 0.1 V to 0.9 V were exposed to Pt/C catalyst under 0.1M H2SO4aq. in order to oxidize carbon surface. The carboxyl group and phenol group on carbon surface were measured before and after potential tests by Boehm method. Carbon groups were increased after 1.3V hold and potential cycling between 0.1 and 0.9V in Table 1. High potential hold caused high oxidation state carbon groups than lower potential cycling test. The increases in carbon groups on carbon surface is estimated to affect on the wettability on carbon surface and causes the suppress of PEFC performance.Acknowledgement Authors appreciated Dr. T. Abe and K. Miyazaki of Kyoto University for the discussion on this work.ReferencesL. M. Roen, C. H. Paik and T. D. Jarvi, Electrochem. Solid-State Lett., 7, A19 (2004).S. Maass, F. Finsterwlder, G. Frank, R. Jartmann and C. Merten, J. Power Sources, 176, 444 (2008).N. Takeuchi and T. F. Fuller, J. Electrochem. Soc., 155, B770 (2008).N. Takeuchi and T. F. Fuller, ECS Transactions, 16 (2) 1563 (2008).

Continuous Temperature Measurement of Liquid Iron and Slag Tapped from a Blast Furnace

Temperature measurements of liquid pig iron coming out of a blast furnace are essential for estimating the thermal condition in the hearth. The temperature is generally monitored by a disposable thermocouple on a runner. This paper proposes radiometric temperature measurement that targets an iron-slag-mixed stream in front of a taphole. It enables non-contact continuous thermometry. Liquid iron and slag are spatially separated on a thermal image obtained by a CCD camera with a high-speed electronic shutter. Molten iron temperature is calculated from the iron radiance detected automatically by means of histogram processing of the thermal image. Regarding optically semitransparent molten slag, its radiance varies as a function of the thickness. Slag temperature is determined from the highest radiance, presuming that the emittance of sufficiently thick slag converges on a constant. The authors performed an on-site test at a blast furnace in ordinary operation. It was confirmed that both iron and slag temperatures were continuously monitored. The temperature data obtained from the test showed findings such as unsteady temperature difference between the two liquids and discontinuous temperature fluctuation. This imaging thermometry technique is expected to be used in a new sensor for blast furnace operation.

RBS Activation Schemes for Minimum Power Consumption in Mobile Networks

Power consumption costs is a significant component in mobile network operators OPEX and recent research is focusing on energy efficient design and operation of the radio access network to decrease the economic and environmental consequences of operating such a vast number of Radio Base Stations (RBSs). In this work, we formulate the problem of power consumption in mobile networks as an ILP and propose a heuristic to determine the optimal, with respect to power consumption, subset of available RBS that should be active in order to serve a certain load of UEs, without violating QoS requirements for each user served. We exploit the results of this formulation setup and propose RBS activation schemes for network operation with acceptable levels of outage probability for the users. The results indicate that our RBS activation scheme which takes into account RBS coverage overlap achieves significant energy savings compared to ordinary network operation.

Error Sensitivity Analysis for Machine Tool Based on Three-Dimensional Vector Chain

Error modeling and analysis can provide some important direction to the machining precision control. According to the characteristics of topology structure on machine tool, a space error model of machine tool and detailed modeling method are presented in this paper, which are based on three-dimensional vector chain. Taking a lathe as an example, the application method of this model in error sensitivity analysis is introduced. By this model, the relationship between the relative error of workpiece-tool and each source error can be solved by ordinary vector operation, and the analysis efficiency should be enhanced greatly.

PERICARDIOSCOPY

New methods of pericardioscopic electrocardiotherapy increasing the stability of electrodes and excluding X-ray irradiation of both the staff and a patient during an operation are suggested. On that ground, the operation does not require a cumbersome stationary radiographic equipment, it is reduced in time and becomes «mobile», in other words, it may be performed not only in a specially equipped center with an X-rayoperating theater, but in other, not specially equipped medical patient care institutions, as well as under the military field conditions, with an ordinary operating room. A new approach which makes it possible to adapt the method of pericardioscopy to the already existing treatment capabilities of a patient care institution, selecting a safe and reliable variant for a patient is introduced.

Low-NOx Modification of a Heavy Fuel Oil Swirl Burner Based on Semi-Industrial Scale Experimental Tests

A proposed swirl burner was modified from a burner used in a 300 MWe oil-fueled power plant. In particular, burner construction, including expanded nozzles, swirl numbers, and air ratios were changed. Then, experimental tests were carried out in a semi-industrial test rig with a horizontal cylindrical furnace with a single-swirl burner. The thermal input of the furnace was 9 MW. The species concentrations of O2, CO, and NOx in the flue gas were measured. NOx emission with the original burner was 320 ppm (3 vol % O2). However, NOx emission decreased to 195 ppm (3 vol % O2) with the proposed burner during optimal operation. Through a series of adjusting experiments, a 35–39% abatement of the NOx emission from the single-burner test could be maintained when the original burner was replaced by the proposed one. NOx emission measured from a full-scale industrial furnace is approximately 341 ppm (3 vol % O2) under ordinary operating conditions. The predicted NOx concentration from the industrial furnace could achieve 207.8 ppm (3 vol % O2) employing the proposed swirl burner under optimal operating conditions. The flow fields (including the recirculation zone and turbulent intensity) downstream of the two burners were compared on the basis of the numerical results. A CCD image system was applied to capture the flame structure downstream of the burner. A mushroom-shaped flame structure was observed with the proposed burner, whereas a fan-shaped diffusion flame was observed with the original burner. A strengthened division in the flame was formed at the burner outlet with the proposed burner. Temperatures ranged from 1184 to 2114 °C downstream of the burner, which was determined through the two-color pyrometry method for each burner. The minimum temperature of the reference section was reduced by 154 °C, and the average temperature was reduced by 76.9 °C when the proposed burner was applied. The proportion of the temperature region higher than 1500 °C in the reference section was calculated. The initial proportion was 94.96%, which was reduced to 80.91% when the proposed burner was applied. This represents a decrease of 14.05% through the modification.

Biological nutrients removal via nitrite from the supernatant of anaerobic co-digestion using a pilot-scale sequencing batch reactor operating under transient conditions

The short-cut nitrogen removal (SCNR) and denitrifying phosphorus removal via nitrite (DPRN) were studied using a pilot-scale sequencing batch reactor (SBR) for the treatment of the supernatant produced from the anaerobic co-digestion of waste activated sludge (WAS) and the organic fraction of municipal solid waste (OFMSW). The stability and behaviour of the biological via-nitrite processes were examined under transient conditions, imposed from the ordinary and extraordinary operation of the full-scale anaerobic digestion plant and the dewatering process of the anaerobic digestate. Nutrients removal was tested at low volumetric nitrogen loading rates (vNLR=0.2kgNm−3d−1), at the vNLR of the system’s nitrifying capacity (0.8kgNm−3d−1) and above its nitrifying capacity (1.1kgNm−3d−1). Complete absence of nitrite oxidizing bacteria (NOB) activity was accomplished, even when the free ammonia (FA) concentration in the reactor was very low (<0.45mgNH3–NL−1). The type of external carbon source critically impacted on the specific nitrite uptake rate (sNUR) and DPRN with fermentation liquid from OFMSW and from cattle manure and maize silage (CM&MS) to enhance these processes.

Automated fuzzy decision and control system for reservoir management

Traditional approaches to the management of an artificial reservoir involve the use of linear, dynamic, nonlinear or stochastic programming. Hence a purely model-based approach would be extremely difficult and thus, recently, a large number of papers devoted to the solution of reservoir management problems based on fuzzy logic approaches have appeared. In this work, two management problems of a reservoir are addressed with fuzzy logic: the definition of the water flow to supply to the user, a typical decision problem; and the regulation of the dam gate, which is a typical control problem. Both problems have been integrated in an Automated Fuzzy Decision and Control System (AFDCS) that is able to identify the ordinary and drought operating conditions. Fuzzy rules are developed from a database derived from the traditional experience of operators and they have been optimized with a genetic algorithm. Two cost functionals are used, able to weight user9s desiderata (water demand) with water waste (water spills and evaporation). Three strategies are developed for a case study and are validated in different scenarios, using Monte Carlo simulations and worst case situations. Results show a good performance of AFDCS to alleviate the consequences of drought and to control of the dam gate.

Supplement to “Consolidity: Moving opposite to built-as-usual systems practices”

A new updated conceptual systems change pathway graph for natural and man-made built-as-usual physical systems is developed following a joint two-level event-driven (or activity-driven) and time-driven framework. The events and activities “on and above” the normal systems operations are recognized in the form of high influencing level (referred to as the “event-driven or upper system layer(s)”) acting over the ordinary systems state equations denoted as the “time-driven or the basic system layer(s).” This is envisaged through the existence of some sort of an “Event clocklike register” that runs alongside with the ordinary “time clock”. Different than the ordinary continued operation of the time clock, the event clocklike register begins its operation with the original (or initial) system state, steps forward only with the occurrence of any coming event affecting the system, and stops at the final (or end) system state. The pathway graph reveals also the important finding that each system (including their parts and components) has autonomous self-recording consolidity-based scaled intelligent mechanisms (with infinite stacking) of their actions through continuously storing parameters changes internally with the occurrences of their varying environments or events. Conversely, it is envisioned that it is amenable under the existence of the reversibility conditions of the change functions to perform backtracking procedure (reversing direction of event clocklike register) at the event-driven or upper system layer(s) of the history of affected events through sequentially disclosing the internal overlaid stacking arrangements of systems parameters changes corresponding to such effects. The various stack-based system change classifications and categorizations are also scrutinized. The case study of the change pathway of the stabilized inverted pendulum is provided to thoroughly demonstrate the applicability of the suggested theory. Moreover, some selected explanatory applications to the theory are presented in the areas of biology, ecology, life sciences, medicine, materials engineering, psychiatry, religion, sociology and humanities. It is recommended that many of the related conventional techniques and approaches reported in the literature have to be mathematically reformulated once more and be applied for the pathway change analysis of the everywhere real life systems following the presented new generic stack-based representations. This could provide cutting-edge tools for the complete understanding of systems change pathways behavior in various sciences and disciplines all combined in a single global theory. Finally, the supplement leads to the very important finding that the universe by all means is not left unattended, but in fact is amazingly self-monitored since its creation through very high precision intelligent autonomous stack-based internal recordings with the given classifications and categorizations of self-events (or activities) inside each oneself (or itself).

A Prediction of the Probability of Default of SMEs on the Credit Guarantee Schemes

SMEs (small and medium enterprises) have had a significant impact in improving economic development and social stability in Taiwan. However, due to weaker management constitutions than large enterprises, SMEs usually encounter more financing when running their business. Through the Small and Medium Enterprise Credit Guarantee Fund of Taiwan (SMEG[11]), the government provides a credit guarantee service to SMEs that have development potential, an ordinary operation status, and good credit history. With government help, SMEs can receive financing from banks without worrying about their lack of collateral. Due to SMEG, the rate of SMEs using financing from banks has gradually increased recently; this demonstrated the importance of the credit guarantee scheme to SMEs. However, the guarantee multiple (guaranteed balance/net worth value) of the SMEG almost reaches to a maximum limit of 20 times, indicating that SMEG is undertaking overly high financial risk. In addition to continuously replenishing the fund amount, the SMEG in Taiwan should also actively improve its risk management capability of underwriting loans to support the guarantee balance with its current guarantee capacity. This study uses companies that have applied for special guarantee loans as samples. This study referenced the Private Firm Model (PFM) developed by Moody's KMV company and established a modified model of default probability using a threshold regression model to redefine default point (DP) to examine the adaptability of the credit risk assessment methods for the Taiwan SMEs. Using the receiver operating characteristic curve (ROC curve) to assess the subject companies, the model proposed by this study is believed to provide better identification when used to predict SMEs’ credit quality. The results of this study will hopefully provide a new method of predicting the credit risk of SMEs that do not share their trading information, and assist the credit guarantee scheme in Taiwan in improving its development and management.

Two-Stage Start-Up to Achieve the Stable via-Nitrite Pathway in a Demonstration SBR for Anaerobic Codigestate Treatment

The supernatant effluent from full scale anaerobic codigestion of waste-activated sludge and the organic fraction of municipal solid waste was treated by a demonstration sequencing batch reactor for short-cut nitrogen removal. After inoculation with conventional municipal activated sludge, the strategy of two-stage start-up allowed us the fast speciation of ammonia oxidizing bacteria (achieved within 20 days), then the achievement of the maximal treatment potential (0.8 kgN m–3 d–1) for nitritation–denitritation. By automatic indirect control of the free ammonia and the free nitrous acid concentrations, the via-nitrite pathway was fully and stably achieved under aerobic conditions (DO of 1.5 mg L–1) and T of 15 °C. Under ordinary operation, the specific nitritation rates were 15–20 mgN gMLVSS–1h–1, while the denitritation rate was 45–50 mgN gMLVSS–1h–1. In-situ and ex-situ respirometry and gene-based molecular techniques demonstrated the stable presence of a dominant, restricted ammonia oxidizing bacteria...

TOWARDS A CALCULUS FOR NONDETERMINISTIC SCHEMAS IN Z

In our previous work, we presented a Z-based formalism, called NZ, by which one can explicitly specify bounded, unbounded, erratic, angelic, demonic, loose, strict, singular, and plural nondeterminism. The NZ notation is mainly based on a new notion of operation schemas, called multi-schema. Since the operations of the Z schema calculus do not work on multi-schemas anymore, in this paper we augment NZ with a new set of schema calculus operations that can be applied on multi-schemas as well as ordinary operation schemas. To demonstrate the usability of the resulting formalism, we show how this formalism can assist to model game-like situations and concurrent systems as two well-known classes of nondeterministic systems.

A Z-Based Formalism to Specify Markov Chains

Probabilistic techniques in computer programs are becoming more and more widely used. Therefore, there is a big interest in methods for formal specification, verification, and development of probabilistic programs. In this paper, we introduce a Z-based formalism that assists us to specify probabilistic programs simply. This formalism is mainly based on a new notion of Z operation schemas, called probabilistic schemas, and a new set of schema calculus operations that can be applied on probabilistic schemas as well as ordinary operation schemas. To demonstrate the applicability of this formalism, we show that any probabilistic system modelled with Markov chains can be formally specified using the new formalism. More precisely, we show the resulting formalism can be used to specify any discrete-time and continues-time Markov chain. Since our formalism is obtained from enriching Z with probabilistic notions, unlike notations such as Markov chains, it is appropriate for modelling both probabilistic and functional requirements simultaneously. In addition, since we provide an interpretation of our formalism in the Z notation itself, we can still use Z tools, such as Z-eves to check the type and con- sistency of the written specifications formally. For the same reason, we can still use various methods and tools which are targeted for formal validation, verification and program development based on the Z specification language.

Validation of a dew-point generator for pressures up to 6 MPa using nitrogen and air

A new primary humidity standard was developed at VSL that, in addition to ordinary operation with air and nitrogen at atmospheric pressure, can be operated with other carrier gases such as natural gas at pressures up to 6 MPa and SF6 at pressures up to 1 MPa. The temperature range of the standard is from −80 °C to +20 °C. In this paper, we report the validation of the new primary dew-point generator in the temperature range −41 °C to +5 °C and the pressure range 0.1 MPa to 6 MPa using nitrogen and air. For the validation the flow through the dew-point generator was varied up to 10 l min−1 (at 23 °C and 1013 hPa) and the dew point of the gas entering the generator was varied up to 15 °C above the dew point exiting the generator. The validation results showed that the new generator, over the tested temperature and pressure range, can be used with a standard uncertainty of 0.02 °C frost/dew point.The measurements used for the validation at −41 °C and −20 °C with nitrogen and at +5 °C with air were also used to calculate the enhancement factor at pressures up to 6 MPa. For +5 °C the differences between the measured and literature values were compatible with the respective uncertainties. For −41 °C and −20 °C they were compatible only up to 3 MPa. At 6 MPa a discrepancy was observed.

Development of a Dew-Point Generator for Gases Other than Air and Nitrogen and Pressures up to 6 MPa

A new primary humidity standard is currently being developed at VSL that, in addition to ordinary operation with air and nitrogen at atmospheric pressure, can be operated also with special carrier gases such as natural gas and SF6 and at pressures up to 6 MPa. In this paper, the design and construction of this new primary dew-point generator and the preliminary tests performed on the generator are reported. The results of the first efficiency tests, performed for the dew-point temperature range from −50 °C to 20°C, for pressures up to 0.7MPa and for carrier gas flow rates up to 4L· min−1, showed satisfactory generator performance when used in the single-pass mode, i.e., with no recirculation of the carrier gas.

Evacuation Criteria after a Nuclear Accident: A Personal Perspective

In any decision involving radiation a risk-risk or risk-benefit comparison should be done. This can be either explicit or implicit. When the adverse effect of an alternate action is less than the planned action, such as medical use of X rays or nuclear power in ordinary operation, the comparison is simple. But in this paper I argue that with the situation faced by the Japanese in Fukushima, the assumption that the risk of an alternate action is small is false. The risks of unnecessary evacuation exceeded the risk of radiation cancers hypothetically produced by staying in place. This was not realized by those that had to make a decision within hours. This realization suggests important changes, worldwide, in the guidelines for radiation protection in accident situations.

Numerical investigation of antegrade flow effects on flow pulsations in Fontan operation

This study considers blood flow in Total Cavopulmonary Connection (TCPC) morphology, created in Fontan surgical procedure in patients with single ventricle heart disease. Ordinary process of TCPC operation reduces pulmonary blood flow pulsatility; because of right ventricle being bypassed. This reduction may limit the long term outcome of Fontan circulation. There is an idea stating that keeping Main Pulmonary Artery (MPA) partially open, would increase pulmonary flow pulsations. MPA gets closed in ordinary TCPC operation. The purpose of current study is to verify effects of Antegrade Flow (AF) coming through stenosed MPA on pulmonary flow pulsations, by means of Computational Fluid Dynamics (CFD). The 3-D geometry is reconstructed from CT Angiography (CTA) scan of a patient who has undergone an ordinary TCPC procedure. The stenosed MPA or Pulmonary Stenosis (PS) is virtually added to the original geometry. Inlet velocity profiles are obtained from Echocardiography data of the same patient. AF profile in a cardiac cycle is obtained from a general pressure cycle of left ventricle, assuming a linear relationship between pressure gradient and flow rate in PS. Flow field is studied in six different models in which average AF increasingly changes from 0 to 14% of total cardiac flow, using FLUENT. The results show that adding AF increases Pulsatility Index (PI) in both left and right pulmonary artery (LPA and RPA respectively), with a maximum amount of 140% in LPA. Moreover, adding AF leads to an increase in energy loss of the TCPC region, with a maximum amount of 67%. The addition of AF also increases pulmonaryto- systemic flow ratio which leads to an increase in total cardiac flow rate and hence heart power.