Negative Input Research Articles

An Energy Buffer for Controllable Input Impedance of Constant Power Loads

Power electronic circuits often regulate load power and present a constant power profile to the utility or other electrical source. These constant power loads therefore exhibit a negative incremental input impedance and pose stability challenges when present in either dc or ac systems. This paper presents an energy buffer power converter for a constant power LED lighting load that presents a controllable input impedance to the electrical source. The use of an energy buffer allows the converter to independently control input and output power. The input power is controlled to resemble a resistive load, ensuring that the device exhibits a positive incremental input impedance over short-term input disturbances. Simultaneously, the output power is held constant through high-bandwidth regulation. The control scheme balances the power flow in the long term. Experimental results are presented that demonstrate independence between input and output performance, as well as long-term power balance.

Fast and efficient computation of directional distance estimators

Directional distances provide useful, flexible measures of technical efficiency of production units relative to the efficient frontier of the attainable set in input-output space. In addition, the additive nature of directional distances permits negative input or outputs quantities. The choice of the direction allows analysis of different strategies for the units attempting to reach the efficient frontier. Simar et al. (Eur J Oper Res 220:853–864, 2012) and Simar and Vanhems (J Econom 166:342–354, 2012) develop asymptotic properties of full-envelopment, FDH and DEA estimators of directional distances as well as robust order-m and order-$$\alpha $$ directional distance estimators. Extensions of these estimators to measures conditioned on environmental variables Z are also available (e.g., see Daraio and Simar in Eur J Oper Res 237:358–369, 2014). The resulting estimators have been shown to share the properties of their corresponding radial measures. However, to date the algorithms proposed for computing the directional distance estimates suffer from various numerical drawbacks (Daraio and Simar in Eur J Oper Res 237:358–369, 2014). In particular, for the order-m versions (conditional and unconditional) only approximations, based on Monte-Carlo methods, have been suggested, involving additional computational burden. In this paper we propose a new fast and efficient method to compute exact values of the directional distance estimates for all the cases (full and partial frontier cases, unconditional or conditional to external factors), that overcome all previous difficulties. This new method is illustrated on simulated and real data sets. Matlab code for computation is provided in an “Appendix”.

Quadruplet Network With One-Shot Learning for Fast Visual Object Tracking.

In the same vein of discriminative one-shot learning, Siamese networks allow recognizing an object from a single exemplar with the same class label. However, they do not take advantage of the underlying structure of the data and the relationship among the multitude of samples as they only rely on the pairs of instances for training. In this paper, we propose a new quadruplet deep network to examine the potential connections among the training instances, aiming to achieve a more powerful representation. We design a shared network with four branches that receive a multi-tuple of instances as inputs and are connected by a novel loss function consisting of pair loss and triplet loss. According to the similarity metric, we select the most similar and the most dissimilar instances as the positive and negative inputs of triplet loss from each multi-tuple. We show that this scheme improves the training performance. Furthermore, we introduce a new weight layer to automatically select suitable combination weights, which will avoid the conflict between triplet and pair loss leading to worse performance. We evaluate our quadruplet framework by model-free tracking-by-detection of objects from a single initial exemplar in several visual object tracking benchmarks. Our extensive experimental analysis demonstrates that our tracker achieves superior performance with a real-time processing speed of 78 frames/s. Our source code is available.

DC bus stabilization using passive damping network in distributed power system with constant power load

In distributed power system (DPS), the stability performance is always associated with the behaviour of constant power load (CPL). Since DPS large complex system build up from many power electronic converters, the DC bus of the system becomes unstable due to the strenuous action from power converters. When these converters tightly regulated, it behaves as constant power load and exhibit negative incremental input impedance which becomes the main reason in stability degradation of DPS. In this paper, four passive damping network topologies was proposed to reduce the DC bus instability. The best damping performance of the topologies was chosen and analysed using MATLAB/Simulink. The DC bus performances was studied in four cases which are damping behavior due to CPL power level, CPL disconnection, effects of filter and damping capacitor, and effects of filter cut-off frequency. Simulation results obtained shows that the DC bus was successfully stabilized and the resonance damped when passive damper installed. An experimental hardware tests was conducted to verify the proposed damping method and the results were compared with the simulated output waveforms. The analysis results in overshoot, settling time and steady state error of bus voltage shows system improvement with the proposed damper network.

Detection of cost leaders using non-central principal component analysis and data envelopment analysis

Purpose The purpose of this paper is to express the strategic positioning of a firm among its rivals based on an overall analysis. The proposed model uses data envelopment analysis (DEA) to determine the indexes due to cost leadership and differentiation. The model can be useful to identify the true cost leaders and those who are stuck in the middle. This work suggests the way how the strategic position can be explored from the consumption of resources (unlike the prevalent models like Banker et al., 2014). Design/methodology/approach Depending on the previous surveys, two inputs (spending per student and percentage of non-poor income group) and two outputs (average scores attained by students in science group and in language group in six private schools, located within the outskirt of Durgapur) were analyzed. Findings The classification made on the basis of the result of the proposed model reveals that out of the six schools (A, B, C, D, E and F), A, E and F occupy a strong position in this context, whereas B can be an example of stuck in the middle scenario. It not only has to reduce cost by 30 percent but also improve the differentiation index by 140 percent. C and D are lagging behind as they do not have enough differentiating qualities. Research limitations/implications Only six schools were taken for the analysis. Second, the input and output vectors had to be non-negative. In case of a negative input (output) set, separate treatment must be applied to them before the application of non-central PCA. Any decision-making unit producing an output of 0 will prohibit the use of the non-central PCA. Practical implications The extant study provides the indices to measure cost leadership and differentiation strategies for the classification as per the generic strategies. A firm which is lagging behind can adjust its consumption to remain successful. Social implications According to Hillman and Jenkner (2002), the developing countries lack the willingness of a primary school to impart education to children. The current study is used to explore whether any private primary school has the same goal or not. They also pointed out the possible future consequences while stating that the cost of educating children from the poorer section might be outweighed by the cost of not educating them and adults lacking basic skills had greater difficulty in finding well-paying jobs to escape poverty. So it is important to understand the role of a private primary school to offer seats to underprivileged students for educating them. The intention of six private primary schools toward educating the population of the small area within Durgapur is analyzed in this study, The study revealed that few schools spend more to serve the students belonging to upper classes to remain successful, whereas few schools as a differentiator make conscious attempts for providing services to poorer sections in an economical manner like a cost leader. Originality/value The extant research aims to formulate the determining methods of identifying strategic groups (proposed by Hunt, 1983) to make a parity between business definition view and strategic type concepts. The model can assess the rivals within an industry to explore the true cost leaders and those who are stuck in the middle using DEA. There are not enough kinds of literature which could effectively measure them.

On the drivers of cost changes in the Norwegian salmon aquaculture sector: a decomposition of a flexible cost function from 2001 to 2014

Since 2005, Norwegian salmon farmers have experienced increasing unit costs, contrasting pre-2005 trends characterized by innovations, rapid productivity growth, and diminishing unit costs. This article investigates these cost changes using a panel of salmon producers. The drivers behind cost changes in the industry are identified for the period of 2001–2014 using a flexible cost function. In particular, it is explored how cost changes can be attributable to scale economies, negative productivity shocks, production expansion, and input prices. The results indicate that cost increases in the sector are affected by external factors out of the control of individual firms such as input prices and environmental conditions like sea lice.

When Less Is More$\ldots$ Few Bit ADCs in RF Systems

Digitizing RF signals using few bit ADCs can provide system advantages in terms of reduced power dissipation, wider sampling bandwidth, and decreased demand for digital throughput. The diversity of established applications based on few bit ADCs, together with the recent surge of interest in the topic for 5G wireless communications and millimeter-wave radar, has created a need for practical design guidance governing their use in general RF systems. This paper, therefore, summarizes the state-of-the-art in few bit ADCs, comparing the dynamic range considerations involved with those of conventional RF receiver design. A simple analytic model for the monobit ADC is extended to multiple bits. Parametric analysis, independent of sampling considerations and system-specific signal processing, is used to illustrate the variation in the ADC output signal-to-noise-and-distortion ratio (SNDR) versus both the number of quantization bits and the input signal-to-noise ratio (SNR). At low and negative input SNR, increasing ADC resolution beyond 3-4 bits yields little advantage in output SNDR. Experiment confirms analytic predictions for the specific conditions under which the loss of signal fidelity due to quantization can be made negligible. In addition, parametric analysis of two-tone intermodulation distortion shows clear disadvantages to quantizing with <;4 bits in the presence of strong blockers. The results reported in this paper, which are general and independent of system application, can be used to customize the number of ADC bits in an RF system based on system-specific performance requirements for receiver dynamic range.

Información contextual sobre el endogrupo nacional peruano y su efecto en las actitudes hacia una marca novedosa

The effect of contextual information about the national ingroup on explicit and implicit attitudes towards a novel brand was studied on a sample of university students from the Lima Metropolitana area (n = 59). The results show that the negative information about the ingroup exerts more influence on explicit attitudes towards a novel brand than the positive information. This effect is understood as a habituation of Peruvians towards the positive contextual information about their group, and an ingroup bias that acts when their national identity is threatened by the negative input. This bias guides them towards explicitly favoring a product they consider related to their social identity. On the other hand, the lack of visible results on the implicit attitudes is explained by the order effect of the Implicit Attitudes Test (IAT). These findings are relevant for advertising and marketing industries in Peru, which constantly develop campaigns that extol Peru and the Peruvian identity.

A Virtual Phase-Lead Impedance Stability Control Strategy for the Maritime VSC–HVDC System

In the maritime VSC-HVDC system supplying power to passive network on the island, the dc side of the system is prone to oscillation and even instability, which is resulted from the negative incremental input resistance characteristic of the inverter station. First, a virtual phase-lead impedance stability control strategy aiming at rectifier station is proposed. This control strategy can effectively mitigate the dc-side oscillation of the VSC–HVDC system without affecting the load performance of the inverter station. Then, the dc impedance model of the VSC–HVDC system is built, including the output impedance of the rectifier station, dc cable impedance, and the input impedance of the inverter station. In addition, the oscillation mechanism of the VSC–HVDC system is analyzed by impedance-based Nyquist stability criterion. The reason why rectifier station fails to mitigate the dc-side oscillation using traditional virtual resistance stability control is that the output impedance of the rectifier station exhibits negative damping characteristic outside the control bandwidth of voltage outer loop. For this issue, the proposed control strategy can correct the output impedance of the rectifier station to exhibit positive damping characteristic outside the control bandwidth of voltage outer loop, thus mitigating the dc-side oscillation of the VSC–HVDC system. Finally, simulation and experiment results validate the proposed control strategy and analysis.

Comparing forest governance models against invasive biological threats

In order to take account of the negative effects of invasive species and pathogens on networked forest areas, we study the dynamics of stochastic closed-loop input-output systems faced with the risk of external random perturbations. The extension of previous works on robustness is carried out by introducing a negative feedback mechanism, such that the output from an element contained in the system behaves as a negative input toward elements to which it is connected. Through the study of an overall network divided into compartments barely connected to one another, we first consider the pathway pertaining to monofunctional zoning. By looking at a single aggregated structure, we then move our focus to the pathway proper to multifunctionality. Our results show that, at significant time scales, the monofunctional-zoning mode of forest governance, generally applied in Australasia, performs robustly against invasive biological threats at all levels of outbreak probability. The multifunctional mode of forest governance, further practiced in Western Europe, is mainly sturdy when the probability of invasion verges into certainty. Should this not be the case, robustness is ensured would disturbers and perturbations be uncorrelated. Accordingly, the monofunctional pathway can afford adopting control strategies for outbreak avoidance, which is only acceptable in case the expected invasion can be halted. For the sake of maintaining low likelihood of invasion, the multifunctional pathway is compelled to applying preventive strategies.

Hybrid Nonlinear Transmission Lines Used for RF Soliton Generation

Nonlinear transmission lines (NLTLs) have been studied for high-power RF generation with good prospects of applications in pulse radars for remote sensing (SARs) and disruption of communications in the battlefield, for instance. In this paper, two 30-section hybrid NLTLs built using nonlinear inductors and capacitors (2.2- and 10-nF barium titanate ceramic capacitors with 10- $\mu \text{H}$ ferrite bead inductors) will be described. For the test, the line is fed by a negative input pump pulse generated by a 1 kV discharge of a 0.75- $\mu \text{F}$ storage capacitor via a fast 50-ns switching system composed by an insulated gate bipolar transistor switch and its gate circuit driver. In the hybrid line tests, using 2.2-nF ceramic capacitors the maximum soliton generation packet obtained on the middle section had a frequency of the order of 33 MHz with voltage modulation depth (VMD) of around 700 V. For every single shot, approximately 10 RF cycles with small damping were noted. With the hybrid line using 10-nF ceramic capacitors the soliton generation obtained on the middle section reached a frequency of the order 10 MHz, and VMD of around 200 V. The main conclusion from this experiment is that hybrid lumped NLTLs may be used to achieve RF in megahertz range with higher VMD compared their counterparts (i.e., capacitive or inductive lines) because of their stronger nonlinearity with the use of both nonlinear elements.

An Active Damping Stabilization Scheme for the Suppression of the DC-Link Oscillation in Metro Traction Drive System

The dc-link oscillation is a typical phenomenon happening in the metro traction drive system (MTDS) due to the negative input impedance associated with the constant power load, which is considered as a thorny problem that needs to be resolved well. This paper proposes an active damping stabilization scheme based on inverter power regulation that can effectively eliminate the dc-link oscillation of the MTDS. The proposed stabilization scheme is mainly composed of two parts: 1) the generation of damping power; and 2) the inverter power control loop. The damping power, linked to the deviation of the dc-link voltage through the gain units, is fed back to the vector-controlled induction motor drive system to establish the inverter power control loop. From this control loop, the added q -axis current is obtained, which is regarded as the stabilization term. The additional stabilization term is combined with the q-axis current command of the induction motor for achieving the improvements of the drive performance and the system stability. The effectiveness of the proposed active damping stabilization scheme is verified by simulation and hardware-in-the-loop tests.

A modified slacks‐based ranking method handling negative data in data envelopment analysis

AbstractPerformance ranking for a set of comparable decision‐making units (DMUs) with multiple inputs and outputs is an important and often‐discussed topic in data envelopment analysis (DEA). Conventional DEA models distinguish efficient units from inefficient ones but cannot further discriminate the efficient units, which all have a 100% efficiency score. Another weakness of these models is that they cannot handle negative inputs and/or outputs. In this paper, a new modified slacks‐based measure is proposed that works in the presence of negative data and provides quantitative data that helps decision makers obtain a full ranking of DMUs in situations where other methods fail. In addition, the new method has the properties of unit invariance and translation invariance, and it can give targets for inefficient DMUs to guide them to achieve full efficiency. Two numerical examples are analysed to demonstrate the usefulness of the new method.

Multiple interfaces control activity of the Candida glabrata Pdr1 transcription factor mediating azole drug resistance.

The Cys6Zn2 DNA-binding domain transcription factor Pdr1 is a central regulator of drug resistance in the pathogenic yeast Candida glabrata. In this review, I discuss the multiple control mechanisms modulating the function of this positive transcriptional regulator. Available data suggest that Pdr1 activity is restrained by multiple negative inputs that can be lost by either mutagenesis of the protein or loss of trans-acting factors. Although extensive data are available on the C. glabrata transactivator as well as its cognate proteins in Saccharomyces cerevisiae, the physiological rationale underlying the regulation of these factors remains to be understood.

An Indicator for the Economic Performance and Ecological Sustainability of Nations

This document proposes a new indicator to assess countries’ sustainability. The indicator synthetises measures of economic and ecological efficiency. In other words, we assess the ability of countries to use resources to produce the maximum possible amounts of goods and services while keeping production activities’ impact on the environment as low as possible. The measure of ecological efficiency is the ecological reserve/deficit (ERD), which is based on the concept of ecological footprint. The new indicator is computed using the data envelopment analysis (DEA) model, a well-known non-parametric technique that delivers measures of productive efficiency by comparing outputs to inputs used in production. We modify the standard DEA model in two ways. Firstly, we allow for negative input and output data. Secondly, to increase DEA discriminating power of countries, we compute anti-efficiency measures. This allows us to obtain a ranking of countries based on the best and worst performances. Results show that the new efficiency indicator is valid and that high ERD positively influences the ranking of countries. Introducing anti-efficiency provides more plausible results and a more accurate ranking, for example high-polluting countries like China previously economically efficient are now ranked as low efficient when sustainability is taken into account.

A Bidirectional-Current CMOS Potentiostat for Fast-Scan Cyclic Voltammetry Detector Arrays.

A potentiostat circuit for the application of bipolar electrode voltages and detection of bidirectional currents using a microelectrode array is presented. The potentiostat operates as a regulated-cascode amplifier for positive input currents, and as an active-input regulated-cascode mirror for negative input currents. This topology enables constant-potential amperometry and fast-scan cyclic voltammetry (FSCV) at microelectrode arrays for parallel recording of quantal release events, electrode impedance characterization, and high-throughput drug screening. A 64-channel FSCV detector array, fabricated in a 0.5-$\mu$m, 5-V CMOS process, is also demonstrated. Each detector occupies an area of 45 $\mu$m $\times$ 30$\mu$m and consists of only 14 transistors and a 50-fF integrating capacitor. The system was validated using prerecorded input stimuli from actual FSCV measurements at a carbon-fiber microelectrode.

Measuring the Road Traffic Intensity using Neural Network with Computer Vision

Traffic congestion plagues all driver around the world. To solve this problem computer vision can be used as a tool to develop alternative routes and eliminate traffic congestions. In the current generation with increasing number of cameras on the streets and lower cost for Internet of Things(IoT) this solution will have a greater impact on current systems. In this paper, the Macroscopic Urban Traffic model is used using computer vision as its source and traffic intensity monitoring system is implemented. The input of this program is extracted from a traffic surveillance camera and another program running a neural network classification which can classify and distinguish the vehicle type is on the road. The neural network toolbox is trained with positive and negative input to increase accuracy. The accuracy of the program is compared to other related works done and the trends of the traffic intensity from a road is also calculated.

Negative Input Shaped Commands for Unequal Acceleration and Braking Delays of Actuators

A negative input shaped command is presented for flexible systems to reduce the residual oscillation under unequal acceleration and braking delays of actuators that are common issues in industrial applications. Against this nonlinearity, a compensated unit magnitude zero vibration (UMZV) shaper is analytically developed with a phasor vector diagram and a ramp-step function to approximate the dynamic response of the unequal acceleration and braking delays of actuators. A closed-form solution is presented with a benchmark system without sacrificing the generality and simplicity for industrial applications. The robustness and control performance of the exact solution are numerically evaluated and compared with those of an existing negative input shaper in terms of the switch-on time, command interference, and effects of the shaper parameters. The proposed negative input shaped commands are experimentally validated with a mini-bridge crane.

Stabilization and Performance Preservation of DC–DC Cascaded Systems by Diminishing Output Impedance Magnitude

DC–DC cascaded systems are vulnerable to instability and dynamic performance deterioration. These problems arise due to the nonideality in the source converter output impedance and to the negative input impedance of the load converter. Any overlap in magnitude between these two impedances will destabilize the voltage at the dc bus. Thus, we introduce a method to diminish the magnitude of source-converter output impedance such that the source converter will act as an ideal voltage source. As a consequence, the dynamic performance of the source and load converters will be intact, leading to ensuring the bus voltage stability. In addition, the controller is independent of the number of converters that form the load subsystem. To validate the proposed method, an experimental cascaded system was analyzed, simulated, and experimentally tested. Collectively, all of the outcomes proved the effectiveness of the proposed method.

An Active Damping Control Method for Reduced DC-Link Capacitance IPMSM Drives

In order to mitigate harmonics of the grid input current, passive filters are applied widely in the power electric systems. The LC resonance and the negative input impedance are important concerns in the reduced dc-link capacitance motor drive system. In this paper, an active damping control method is proposed to suppress the LC resonance by the direct damping current approach, which can formulate the pole distribution of the drive system. Different control laws have been analyzed, and the stability analysis is evaluated by the Routh–Hurwitz criterion. Meanwhile, the active damping control method is realized by the voltage command, which can overcome the limited bandwidth of the current controller. Since the generation of the direct damping current only depends on the dc-link voltage, the proposed active damping control method is robust. Compared with the virtual impedance methods, parameters can be accurately optimized by Bode diagrams after adopting the proposed active damping method. Simulation and experimental results are provided to verify the effectiveness of the proposed method.