Security Margin Research Articles

An Optimal N-1 Secure Operation Mode for Medium-voltage Loop Distribution Networks Considering Load Supply Capability and Security Distance

With many uncertainties, such as intermittent distributed generations and time-varying loads, penetrated into distribution networks, the load supply capability operating point has not been sufficient to guide power system operation for no security margin guarantee. To address this fundamental problem, an optimal operation model for interconnected distribution networks is proposed in this paper with the consideration of both security and efficiency of systems. The uncertainty, a feeder or substation transformer N-1 contingency, is taken into account and conductor thermal constraints after feeder or transformer failure are also incorporated into the formulated multi-objective model. The nonlinear optimization model is solved by a hybrid algorithm combining normal boundary intersection and sequential quadratic programming. The optimal load distribution solution on feeders and transformers can be obtained, which provides a trade-off between two defined indices, load supply capability adequacy and variation coefficient of security distance. Compared with conventional distribution loadability, case studies carried out on a test distribution network and a real urban distribution system in China demonstrate the effectiveness of the proposed model and solving method. The N-1 security margin is verified when increasing load demand.

Transmission Congestion Management using a Wind Integrated Compressed Air Energy Storage System

Transmission congestion is a vital problem in the power system security and reliability sector. To ensure the stable operation of the system, a congestion free power network is desirable. In this paper, a new Congestion Management (CM) technique, the Wind integrated Compressed Air Energy Storage (WCAES) system is used to alleviate transmission congestion and to minimize congestion mitigation cost. The CM problem has been solved by using the Generator Sensitivity Factor (GSF) and the Bus Sensitivity Factor (BSF). BSF is used for finding the optimal location of WCAES in the system. GSF with a Moth Flame Optimization (MFO) algorithm is used for rescheduling the generators to alleviate congestion and to minimize congestion cost by improving security margin. The impact of the WCAES system is tested with a 39 bus system. To validate this approach, the same problem has been solved with a Particle Swarm Optimization (PSO) algorithm and the obtained results are compared with the ones from the MFO algorithm.

The Influence of Load on Risk-Based Small-Disturbance Security Profile of a Power System

This paper establishes a generic severity function that can be used to produce power system security risk profiles. It is illustrated by analyzing the impacts of system load attributes on the small-disturbance rotor angle stability of a power system. The load attributes contributing to the oscillatory modes can be considered as inherent uncertain variables within power systems and include load power variations, load composition, and load model parameters. Uncertainty in the renewable power generation is also incorporated in the probabilistic modelling and risk assessment to demonstrate the flexibility of the approach. A novel approach is proposed to select the severity functions to logically represent small-disturbance security margin. The risk profile of a power system has been presented considering the probability density functions of power system critical modal damping and a selected set of severity functions. The analysis techniques developed are illustrated with a modified version of the 68-bus NETS-NYPS power system with a high amount of renewable power penetration. The relative importance of the load attributes and the impact of these attributes on stability boundaries have been identified at varying risk levels with respect to their contribution to small-disturbance stability.

Did the Introduction of Securities Margin Trading Decrease China’s A-Share Market Volatility?

Securities margin trading is a form of credit trading that is used extensively in mature securities markets. With the rapid development of its securities market, China introduced securities margin trading to its A-share market on 31st March 2010 for the purpose of reducing A-share market volatility. Owing to the fact that the introduction of securities margin trading in 2010 only applied to part of the A-share transaction targets, it can be treated as a natural experiment. This paper uses difference-in-differences analysis to investigate whether the introduction of securities margin trading in 2010 decreased China’s A-share market volatility. By selecting 50 underlying stocks of securities margin trading as a ‘treatment group’ and 50 non-underlying stocks as a ‘control group’, this paper utilizes a panel dataset comprising 100 stocks for the period 31st March 2009 – 31st March 2011. Results indicate that the introduction of securities margin trading in 2010 significantly decreased China’s A-share market volatility. In conclusion, this paper recommends that China reduces the barriers and transaction costs of securities margin trading, extends the supply of underlying stocks for securities lending, and enhances the capital supply of margin trading.

New Safety Margins for Melanoma Surgery: Nice Possibility for Drinking of "Just That Cup of Coffee"?

BACKGROUND:The American Joint Committee on Cancer (AJCC’s) skin melanoma surgical treatment recommendations from 2011 are characterised by a prima facie “freedom of choice” regarding how extensive should be the excisions for melanomas with tumour thickness up to 2 mm and melanoma in situ. It is unclear why the recommended surgical security margins vary between 0.5 and 1 cm for melanoma in situ, whereas for melanomas with a tumour thickness of up to 1.99 mm, the range of variation is also between 1 and 2 cm, without specifying when the surgical field should be broader and, narrower, accordingly. This “uncertainty or lack of intent” of the guilders often leads to the same surgical approach to melanomas at different stages, or to a different approach in cases of melanomas at the same stage, in contrast. Therefore, this should be defined as wrong, logically.CASE PRESENTATION:We present 3 patients with cutaneous melanomas, treated with similar fields of surgical security. Current issues, generated within the framework of melanoma’s surgery guided by the recommendations of the AJCC are also discussed. A new surgical approach in patients with melanoma is recommended, discussed for the first time in world literature. We hypothesize that the introduction of a certain recommendations for a 2 cm surgical field in all directions during the initial excision, combined with the parallel performance of a sentinel lymph node biopsy, will lead in fact to several important advantages: 1) avoiding of the secondary excision in at least 70% - 90% of the patients (depending on the tumor thickness), 2) minimizing the risk of lymphatic effusion change and misinterpretation of the sentinel lymph node biopsy’s results in patients with secondary excision; 3) optimization of the surgical team’s work; 4) minimizing the possibility of unprepared/uninformed personnel to take part in decisions for treating a specific disease such as skin melanoma, 4) facilitating the appropriate patients’ group selection at the appropriate stage when involving them in different studies, leading to equal leveling of the initial positions;CONCLUSION:Whether the proposed approach will be subjected to a detailed discussion of AJCC’s expert’s remains currently unclear.

A study on analyzing side-channel resistant encoding schemes with respect to fault attacks

Recently, several software encoding countermeasures were proposed, utilizing the side-channel hiding concept for software implementations. While these schemes aim to protect the underlying code against various leakage models, they can also be utilized against fault injection attacks to some extent. This property comes from the data redundancy that is being employed in order to equalize the leakage. In this work, we analyze three different software encoding schemes with respect to fault injection attacks. We use a custom-made code analyzer to check the vulnerabilities in the assembly code, and we experimentally support our results using laser fault injection technique. Our results show that implementations based on table lookup operations provide reasonable security margin and thwart fault propagation.

Computing the closest small-signal security boundary in the control parameter space for large scale power systems

A constrained optimization algorithm is proposed for the determination of the minimum change in the parameter values of a set of controllers that locates a complex pair of eigenvalues of a linearized power system model at a user-defined small-signal security boundary. The intended practical use is to assess the combined robustness of the system controllers in maintaining adequately damped power system oscillations. The oscillation damping security margins, given an operating point and a set of fixed damping controller parameters, is the Euclidean norm of the relative parameter variation vector, also referred in the literature as the minimum distance in the control parameter space. The computational algorithm to find the Closest Security Boundary in the Control Parameter Space, CSBCPS, is based on the rigorous mathematical implementation of the non-linear programming method to the problem, including constraints on the parameter ranges. The resulting equations are solved by the Newton method. Numerical results for a large practical power system dynamic model are detailed described to illustrate the use of the proposed CSBCPS algorithm in small-signal applications involving multiple thyristor controlled series compensators and power system stabilizers.

An Approach to Solve Transient Stability-Constrained Optimal Power Flow Problem Using Support Vector Machines

The Transient Stability-Constrained Optimal Power Flow (TSC-OPF) is a challenging optimization problem, and is the subject of several recent researches. This paper proposes a novel approach to solve TSC-OPF. In the proposed framework, Support Vector Machines (SVMs) are used to classify whether an operating condition satisfies predefined transient contingencies. A novel classification strategy is proposed to ensure the optimal solution satisfies all considered contingencies with certain security margin. Besides, the weight coefficients of the SVM are used as sensitivity measures in order to help optimization solver find solutions more effectively. The proposed approach is demonstrated for the New England system and the IEEE 300 bus system.

The QARMA Block Cipher Family. Almost MDS Matrices Over Rings With Zero Divisors, Nearly Symmetric Even-Mansour Constructions With Non-Involutory Central Rounds, and Search Heuristics for Low-Latency S-Boxes

This paper introduces QARMA, a new family of lightweight tweakable block ciphers targeted at applications such as memory encryption, the generation of very short tags for hardware-assisted prevention of software exploitation, and the construction of keyed hash functions. QARMA is inspired by reflection ciphers such as PRINCE, to which it adds a tweaking input, and MANTIS. However, QARMA differs from previous reflector constructions in that it is a three-round Even-Mansour scheme instead of a FX-construction, and its middle permutation is non-involutory and keyed. We introduce and analyse a family of Almost MDS matrices defined over a ring with zero divisors that allows us to encode rotations in its operation while maintaining the minimal latency associated to {0, 1}-matrices. The purpose of all these design choices is to harden the cipher against various classes of attacks. We also describe new S-Box search heuristics aimed at minimising the critical path. QARMA exists in 64- and 128-bit block sizes, where block and tweak size are equal, and keys are twice as long as the blocks. We argue that QARMA provides sufficient security margins within the constraints determined by the mentioned applications, while still achieving best-in-class latency. Implementation results on a state-of-the art manufacturing process are reported. Finally, we propose a technique to extend the length of the tweak by using, for instance, a universal hash function, which can also be used to strengthen the security of QARMA.

The QARMA Block Cipher Family. Almost MDS Matrices Over Rings With Zero Divisors, Nearly Symmetric Even-Mansour Constructions With Non-Involutory Central Rounds, and Search Heuristics for Low-Latency S-Boxes

This paper introduces QARMA, a new family of lightweight tweakable block ciphers targeted at applications such as memory encryption, the generation of very short tags for hardware-assisted prevention of software exploitation, and the construction of keyed hash functions. QARMA is inspired by reflection ciphers such as PRINCE, to which it adds a tweaking input, and MANTIS. However, QARMA differs from previous reflector constructions in that it is a three-round Even-Mansour scheme instead of a FX-construction, and its middle permutation is non-involutory and keyed . We introduce and analyse a family of Almost MDS matrices defined over a ring with zero divisors that allows us to encode rotations in its operation while maintaining the minimal latency associated to {0, 1}-matrices. The purpose of all these design choices is to harden the cipher against various classes of attacks. We also describe new S-Box search heuristics aimed at minimising the critical path. QARMA exists in 64- and 128-bit block sizes, where block and tweak size are equal, and keys are twice as long as the blocks. We argue that QARMA provides sufficient security margins within the constraints determined by the mentioned applications, while still achieving best-in-class latency. Implementation results on a state-of-the art manufacturing process are reported. Finally, we propose a technique to extend the length of the tweak by using, for instance, a universal hash function, which can also be used to strengthen the security of QARMA.

Multi-key Analysis of Tweakable Even-Mansour with Applications to Minalpher and OPP

The tweakable Even-Mansour construction generalizes the conventional Even-Mansour scheme through replacing round keys by strings derived from a master key and a tweak. Besides providing plenty of inherent variability, such a design builds a tweakable block cipher from some lower level primitive. In the present paper, we evaluate the multi-key security of TEM-1, one of the most commonly used one-round tweakable Even-Mansour schemes (formally introduced at CRYPTO 2015), which is constructed from a single n-bit permutation P and a function f(k, t) linear in k from some tweak space to {0, 1} n. Based on giant component theorem in random graph theory, we propose a collision-based multi-key attack on TEM-1 in the known-plaintext setting. Furthermore, inspired by the methodology of Fouque et al. presented at ASIACRYPT 2014, we devise a novel way of detecting collisions and eventually obtain a memory-efficient multi-key attack in the adaptive chosen-plaintext setting. As important applications, we utilize our techniques to analyze the authenticated encryption algorithms Minalpher (a second-round candidate of CAESAR) and OPP (proposed at EUROCRYPT 2016) in the multi-key setting. We describe knownplaintext attacks on Minalpher and OPP without nonce misuse, which enable us to recover almost all O(2n/3) independent masks by making O(2n/3) queries per key and costing O(22n/3) memory overall. After defining appropriate iterated functions and accordingly changing the mode of creating chains, we improve the basic blockwiseadaptive chosen-plaintext attack to make it also applicable for the nonce-respecting setting. While our attacks do not contradict the security proofs of Minalpher and OPP in the classical setting, nor pose an immediate threat to their uses, our results demonstrate their security margins in the multi-user setting should be carefully considered. We emphasize this is the very first third-party analysis on Minalpher and OPP.

Multiset-Algebraic Cryptanalysis of Reduced Kuznyechik, Khazad, and secret SPNs

We devise the first closed formula for the number of rounds of a blockcipher with secret components so that these components can be revealed using multiset, algebraic-degree, or division-integral properties, which in this case are equivalent. Using the new result, we attack 7 (out of 9) rounds of Kuznyechik, the recent Russian blockcipher standard, thus halving its security margin. With the same technique we attack 6 (out of 8) rounds of Khazad, the legacy 64-bit blockcipher. Finally, we show how to cryptanalyze and find a decomposition of generic SPN construction for which the inner-components are secret. All the attacks are the best to date.

Singularities Analysis of the Jacobian Matrix Modified in the Continuation Power Flow: Mathematical Modeling

In recent years, the concern for voltage stability issue has gained global highlighted when referring to the energy sector industry, this is because this issue is related to the operation and planning of electrical power systems. Factors such as the increasing energy demand, the transfer of large amounts of power to meet the consumption, combined with the economic and environmental requirements has led the systems operate in stressful conditions (close to their limits), i.e., with small margins of security that is a threat to its stable operating condition. The combination of these factors can be disastrous, enabling the vulnerability of electrical power systems, i.e., exposed to risk of a situation of instability. In the literature, a study to analyze stability and voltage instability is related to the P-V curve (power versus voltage magnitude) and the maximum loading point (MLP) (point on the curve that separates the stable operation of the unstable). The maximum loading point may be consequent to a saddle node bifurcation (SNB) related to transmission capacity limit in an electrical system where the Jacobian matrix is singular, or limit induced bifurcation (LIB), related the reactive power limit of the generator, where the matrix is not singular. In this sense, it is presented in this first part of the paper, an analysis of the modified Jacobian matrices (Jm) of the methods of continuation power flow (CPF) reported in the literature (parameterization methods), the study was developed in order to analyze the changes that the matrix conventional Jacobian (J) have to eliminate the singularity problems in the MLP and in the bifurcation points of each method.

Transmission capacity margin in market clearing

To ensure the secure operation of a power market, transmission networks must maintain an appropriate margin to account for various uncertainties. The uncertainties have increased significantly by the increasing penetration of renewable energy generation. A steady-state security distance (SSD) is an effective security margin that describes the distance of an operation point (OP) from steady-state security region boundaries. It captures both the available capacity and topological location of each transmission line that are important considerations for the ability of each line to withstand uncertainties. The proposed SSD-based transmission capacity margin is integrated into the market clearing model. The proposed SSD-constrained market clearing (SSDC-MC) model ensures that the SSD between the scheduled OP and security boundaries does not fall below a specified threshold. The SSDC-MC is formulated as a bi-level optimization problem. A novel algorithm is developed by dynamically identifying the binding constraints in the lower-level model. The SSDs are expressed as piecewise analytic functions of the scheduled OP. As a result, the bi-level problem is transformed into a single-level one. Two test cases are used to compare the SSDC-MC method with a different transmission margin determination method, which imposes constraints on loading of all transmission lines.

Déséquilibre de l’attachement et des émotions chez l’adolescent obèse

IntroductionObesity in adolescents remains little studied. Our clinical observations within center treatment of obesity in Franche-Comté, and inventory of various theories supporting a psychological origin of obesity with integrative spirit of research, led us to study capacities of emotional awareness and attachment representations compared to a control group. ObjectiveIn reference to developmental theory of alexithymia and clinical observations of Hilde Bruch, investigate the possible link between capacities of emotional awareness and representations and security of the bond of parent child attachment, among obese adolescents, that lead to hyperphagic behavior. MethodSeventeen obese adolescents, and 21 controls were tested. Participants completed the Level Emotional Awareness Scale (LEAS); the Inventory of parent and peer Attachment (IPPA), and the Relationships Scale Questionnaire (RSQ). ResultsThe group of obese adolescents presents a level of emotional awareness significantly lower than the control group. The results of this study show a peculiarity regarding the quality of parent child attachment. There seems to be an imbalance between the security of maternal bonding and paternal bonding perceived by the young obese. RSQ results support the hypothesis that those adolescents are at the margins of security from the perspective of attachment. DiscussionThe results support the interest of psychological treatments of obesity in the adolescent, by the implementation of therapy in the field of emotional regulation and family therapy.

Variable message encryption through blockcipher compression function

SummaryA constrained device is an emerging technology that has enormous applications in our daily life such as access control, inventory control, luggage tracking, bar‐code reader, and IoT. However, it has certain drawbacks of low memory and less computing power. Thus, one of the cracking challenges is to provide efficient and secure cryptographic solution for the constrained device in the aspect of security issue. An (n,n) blockcipher‐based cryptographic compression function is applicable to provide provable security to the constrained device. Though, there are many constructions of (n,n) blockcipher such as MDC‐2, MDC‐4, MJH, Bart‐12, and SKS‐15. However, most of the familiar schemes are not suitable for short and variable message encryption without padding because of their internal structures. Furthermore, the security margin is provided based on blocklength rather than the flexible size of message. In this paper, we present two different (n,n) blockcipher compression function schemes. The first scheme (FS) satisfies better efficiency such as less call of blockcipher, less key scheduling, and higher efficiency rate. On the contrary, the second scheme (SS) has upper security bound. Moreover, both of the schemes are suitable for small and variable message encryption (message size = tn|t < 1,n:blocklength), which is handy for the constrained device. The collision and preimage security bound of the FS are O(2tn/2) and O(2tn). In addition, the SS's collision resistance and preimage resistance are bounded by O(2tn) and O(22tn). Moreover, the efficiency rate of the proposed two schemes are respectively t and t/3. The numbers of key scheduling are 2 for the constructions of FS and SS. We use two calls of blockcipher in the FS. On the contrary, three calls of blockcipher are used in the SS. Copyright © 2016 John Wiley & Sons, Ltd.

Source Distinguishability Under Distortion-Limited Attack: An Optimal Transport Perspective

We analyze the distinguishability of two sources in a Neyman–Pearson setup when an attacker is allowed to modify the output of one of the two sources subject to an additive distortion constraint. By casting the problem in a game-theoretic framework and by exploiting the parallelism between the attacker’s goal and optimal transport theory, we introduce the concept of security margin defined as the maximum average per-sample distortion introduced by the attacker for which the two sources can be distinguished ensuring arbitrarily small, yet positive, error exponents for type I and type II error probabilities. Several versions of the problem are considered according to the available knowledge about the sources. We compute the security margin for some classes of sources and derive general bounds assuming that the distortion is measured in terms of the mean square error between the original and the attacked sequence. The analysis of the game and the study of the distinguishability of the sources are extended to the case in which the distortion constraint is defined in terms of the maximum distance.

Methodology to Evaluate the Electromechanical Effects of Electromagnetic Forces on Conductive Materials in Transformer Windings Using the Von Mises and Fatigue Criteria

A methodology based on computer simulations and aiming to estimate the lifespan of transformer windings after the occurrence of short circuits is presented in this paper. The Von Mises and fatigue criteria are employed to determine the failure proximity of the windings. The obtained results contribute to the evaluation of the influence of electromechanical effects in transformer windings and to the determination of the number of short circuits that a transformer winding can support. The simulation results may also be employed in the design of transformers and failure diagnosis, to increase the security margin against mechanical failures.

Withdrawal of maize protection by herbicides and insecticides increases mycotoxins contamination near maximum thresholds

Environmental and economic issues affect decision-making for whether or not to control small infestations of pests and pathogens in crops. Even where no crop yield loss is expected, other risks may be evident, such as the slow accumulation of pathogen inocula. The prevalence of toxins, arising from biotic interactions with fungal diseases, can alter crop quality rather than quantity. Thus, farmer decisions for whether to tolerate pest infestation must take into account several direct and immediate and/or delayed potential risks. Published scientific evidence on the co-occurrence of risk factors resulting from the presence of different pests and pathogens are largely absent, and this has stifled the adoption of integrated pest management. Here, we tested how the withdrawal of herbicide and insecticide protection in maize, alone and in combination, might induce higher prevalence of up to 23 mycotoxins in the crop at harvest. The experiment was conducted over 4 years in 29 fields in the south west of France. The test involved a comparison of paired samples collected from treated and untreated plots. All nine major mycotoxins that were observed in more than 4 % of the samples showed highly variable concentrations both between fields and years. The overall trend following the cessation of pesticide protection, however, is for higher levels of mycotoxins and up to a six-fold increased in nivalenol mean concentration (to 202.3 μg kg−1 of maize seeds) compared to its treated control. Overall mycotoxin concentrations approached 55–67 % of their maximum acceptable rate, a situation of reduced security margin that could lead to economic penalties and market restrictions. We found that the removal of herbicides had a greater impact than that of insecticides on the prevalence of mycotoxins, which differs from the expectation stated in the literature. This finding is further reinforced by the observation that certain species of weeds harbor several species of Fusarium. This means that weeds not only play a role as crop competitors but also as reservoirs of inoculum in the field. Our findings illustrate the importance of sanitary evaluation when the implementation of new cropping systems will alter the distribution and occurrence of pests and pathogens.

Potential for peat-to-power usage in Rwanda and associated implications

The persistent low-level access to modern energy in Rwanda is attributed to lack of investment in the energy sector. Accordingly, the investment in energy resources use is analyzed for electricity supply security. During a study period that spanned the years of 2013–2045, scenarios involving population and average GDP growth rates are used for the analysis of future electricity demand and supply. The introduction to the national grid of electricity from peat-fired plants helps phase out oil thermal power, thus the removal of electricity utility price subsidies. The supply of electricity security margin is also observed to be between 32% and 51%. In general, peat-to-power technology is cost competitive compared to the electricity utility price in Rwanda and the region.