Leakage Minimization Research Articles

Multi-objective branch-and-bound for the design-for-control of water distribution networks with global bounds

This study investigates a design-for-control (DfC) problem formulation for the joint minimization of pressure-induced leakage, maximization of resilience, and minimization of cost in water distribution networks (WDN). The DfC problem, which consists in simultaneously installing new valves and/or pipes and optimizing valve control settings, results in a challenging optimization problem belonging to the class of non-convex multi-objective mixed-integer non-linear programs (MOMINLP). Due to their complex mathematical structure, multi-objective WDN design-for-control problems have previously been solved using general-purpose evolutionary algorithms or local deterministic methods, which do not provide guarantees on the quality of the returned solutions. While branch-and-bound (BB) frameworks have been proposed to approximate the Pareto fronts of MOMINLPs with global bounds, they rely on the availability of attainable solutions which, for WDN design-for-control problems, can be hard to identify. Moreover, in the absence of general-purpose solvers, the performance of multi-objective BB implementations depends, for a given application, on the choice of adequate branching and lower bounding strategies. In this study, we investigate a multi-objective BB algorithm based on tailored branching, lower bounding and additional upper bounding strategies to efficiently approximate the Pareto front of WDN design-for-control problems with bounds of ϵ\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\epsilon$$\\end{document}-non-dominance. The proposed algorithm is applied to the optimal DfC of two case study networks and is shown to outperform alternative solution methods.

Will the Green Credit Programme Incentivize Positive Environmental Actions?

The Government of India has launched the Green Credit Programme (GCP)—a market-based voluntary programme—to enhance energy and resource-use efficiency, foster conservation of resources, mitigate climate change, and strengthen adaptive capacity. The programme intends to incentivize the adoption of environmentally sustainable technologies and processes through fiscal and financial nudges and effect behavioural changes. The efficacy of a policy programme depends on its design and implementation, though, in theory, such programmes are designed to be cost-effective, environmentally favourable, as well as economically inclusive. The success of a tradable programme should be judged on the basis of four parameters: design of the programme, minimization of transaction costs, market volatility, and leakage and environmental degradation. The GCP administrators have yet to issue an effective design and implementation framework for the programme.

Cross-Terms and Spectral Leakage Minimization in Time-Frequency Distribution

Cross-Terms and Spectral Leakage Minimization in Time-Frequency Distribution

Privacy-aware document retrieval with two-level inverted indexing

Previous work on privacy-aware ranking has addressed the minimization of information leakage when scoring top k documents, and has not studied on how to retrieve these top documents and their features for ranking. This paper proposes a privacy-aware document retrieval scheme with a two-level inverted index structure. In this scheme, posting records are grouped with bucket tags and runtime query processing produces query-specific tags in order to gather encoded features of matched documents with a privacy protection during index traversal. To thwart leakage-abuse attacks, our design minimizes the chance that a server processes unauthorized queries or identifies document sharing across posting lists through index inspection or across-query association. This paper presents the evaluation and analytic results of the proposed scheme to demonstrate the tradeoffs in its design considerations for privacy, efficiency, and relevance.

Assessing the importance of drainage layers over geomembrane liners within engineered cover systems: Seven years of field monitoring at three mine waste rock piles

Geomembrane liners are commonly subject to defects that can allow water leakage through these openings and significantly undermine their performance. While defects are difficult to prevent and characterize, minimization of potential leakage can still be attained with appropriate lateral drainage over the liner. The objective of this study is to assess the performance of different drainage layer materials within HDPE-lined cover systems at three mine waste rock piles (WRPs) in the Sydney Coalfield, Nova Scotia, Canada. Natural soil, clean gravel and a geocomposite net were employed at the Summit, Victoria Junction and Franklin WRPs, respectively. Extensive field monitoring of precipitation (PPT), moisture content within the cover materials, and head of water above the liner, was performed. The head of water and moisture was consistently high at Summit throughout the year, while consistently low at Victoria Junction and Franklin, with the geocomposite net being just as effective as the gravel layer. Using typical assumptions of defect size/number, leakage rates at Victoria Junction and Franklin remained very low due to limited water head and flow gradient. Therefore, while the prevention of defects is highly challenging at HDPE-lined cover systems, potential defect leakage can be proactively controlled during cover system design with the implementation of adequate drainage layers above the liner.

Sum-Rate Maximization and Leakage Minimization for Multi-User Cell-Free Massive MIMO Systems

Sum-Rate Maximization and Leakage Minimization for Multi-User Cell-Free Massive MIMO Systems

Redundancy and Synergy of an Entangling Cloner in Continuous-Variable Quantum Communication

We address minimization of information leakage from continuous-variable quantum channels. It is known, that regime of minimum leakage can be accessible for the modulated signal states with variance equivalent to a shot noise, i.e., vacuum fluctuations, in the case of collective attacks. Here we derive the same condition for the individual attacks and analytically study the properties of the mutual information quantities in and out of this regime. We show that in such regime a joint measurement on the modes of a two-mode entangling cloner, being the optimal individual eavesdropping attack in a noisy Gaussian channel, is no more effective that independent measurements on the modes. Varying variance of the signal out of this regime, we observe the nontrivial statistical effects of either redundancy or synergy between the measurements of two modes of the entangling cloner. The result reveals the non-optimality of entangling cloner individual attack for sub-shot-noise modulated signals. Considering the communication between the cloner modes, we show the advantage of knowing the residual noise after its interaction with the cloner and extend the result to a two-cloner scheme.

Power leakage minimization in time‐modulated linear antenna array with optimized switching strategies employing modified harmony search algorithm

Time-modulated linear antenna array (TMLAA) with periodic time modulation of antenna elements radiates infinite inevitable harmonic beams. The infinite harmonic sideband radiation is a wastage of power unless the power is exploited. This paper aims to minimize inevitable power wastage in the harmonic beams radiated from TMLAA by employing an optimized periodic timing sequence. The optimization of the timing sequence is conducted employing harmony search (HS) to suppress the power wastage, However, conventional HS achieves an acceptable sidelobe level (SLL) below – 30 dB. Nevertheless, a modified harmony search algorithm (MHSA) is proposed to attain more power in the desired fundamental beam. The algorithm is validated using an array of 4-, 10-, and 16-element uniform half-wavelength spacing TMLAA. The optimization is conducted on the ON and OFF time instants and the real current of the elements. The simulation results exhibit that HS and MHSA perform potentially alike to suppress the SLL of fundamental below –30 dB. However, the further suppression of the sideband levels employing MHSA justifies the modification proposed in this work. The MHSA performance in terms of radiation parameters is compared with the HS and also with previous works to show the potentiality of the modification.

Optimal Steering of Matrix Product States and Quantum Many-Body Scars

Ongoing development of quantum simulators allows for a progressively finer degree of control of quantum many-body systems. This motivates the development of efficient approaches to facilitate the control of such systems and enable the preparation of non-trivial quantum states. Here we formulate an approach to control quantum systems based on matrix product states~(MPS). We compare counter-diabatic and leakage minimization approaches to the so-called local steering problem, that consists in finding the best value of the control parameters for generating a unitary evolution of the specific MPS state in a given direction. In order to benchmark the different approaches, we apply them to the generalization of the PXP model known to exhibit coherent quantum dynamics due to quantum many-body scars. We find that the leakage-based approach generally outperforms the counter-diabatic framework and use it to construct a Floquet model with quantum scars. We perform the first steps towards global trajectory optimization and demonstrate entanglement steering capabilities in the generalized PXP model. Finally we apply our leakage minimization approach to construct quantum scars in the periodically driven non-integrable Ising model.

TatA and TatB generate a hydrophobic mismatch important for the function and assembly of the Tat translocon in Escherichia coli

The twin-arginine translocation (Tat) system serves to translocate folded proteins across energy-transducing membranes in bacteria, archaea, plastids, and some mitochondria. In Escherichia coli, TatA, TatB, and TatC constitute functional translocons. TatA and TatB both possess an N-terminal transmembrane helix (TMH) followed by an amphipathic helix. The TMHs of TatA and TatB generate a hydrophobic mismatch with the membrane, as the helices comprise only 12 consecutive hydrophobic residues; however, the purpose of this mismatch is unclear. Here, we shortened or extended this stretch of hydrophobic residues in either TatA, TatB, or both and analyzed effects on translocon function and assembly. We found the WT length helices functioned best, but some variation was clearly tolerated. Defects in function were exacerbated by simultaneous mutations in TatA and TatB, indicating partial compensation of mutations in each by the other. Furthermore, length variation in TatB destabilized TatBC-containing complexes, revealing that the 12-residue-length is important but not essential for this interaction and translocon assembly. To also address potential effects of helix length on TatA interactions, we characterized these interactions by molecular dynamics simulations, after having characterized the TatA assemblies by metal-tagging transmission electron microscopy. In these simulations, we found that interacting short TMHs of larger TatA assemblies were thinning the membrane and—together with laterally-aligned tilted amphipathic helices—generated a deep V-shaped membrane groove. We propose the 12 consecutive hydrophobic residues may thus serve to destabilize the membrane during Tat transport, and their conservation could represent a delicate compromise between functionality and minimization of proton leakage.

Improved Rate-Energy Trade-Off for SWIPT Using Chordal Distance Decomposition in Interference Alignment Networks

This paper investigates the simultaneous wireless information and power transfer (SWIPT) precoding scheme for K-user multiple-input-multiple-output (MIMO) interference channels (IC), for which interference alignment (IA) schemes provide optimal precoders to achieve full degrees-of-freedom (DoF) gain. However, harvesting RF energy simultaneously reduces the achievable DoFs. To study a trade-off between harvested energy and sum rate, the transceiver design problem is suboptimally formulated in literature via convex relaxations, which is still computationally intensive, especially for battery limited nodes running on harvested energy. In this paper, we propose a systematic method using chordal distance (CD) decomposition to obtain the balanced precoding, which improves the trade-off. Analysis shows that given the nonnegative value of CD, the achieved harvested energy for the proposed precoder is higher than that for perfect IA precoder. Moreover, energy constraints can be achieved, while maintaining a constant rate loss without losing DoFs via tuning the CD value and splitting factor. Simulation results verify the analysis and add that the IA schemes based on max-SINR or mean-squared error are better suited for SWIPT maximization than subspace or leakage minimization methods.

Stream level rank constrained transceiver design in MIMO interference channel networks

An interference leakage minimisation transceiver design for multiple-input multiple-output Interference Channel networks is proposed by making use of the full rank constraint of the desired signal, the low rank constraint and low power constraint of the interference signal. The objective is to suppress interference leakage caused by not only the signal from other users, but also the other streams from the same user. To do so, the transmit precoding matrix and the receive filtering matrix are iteratively optimised through convex optimisation tools at stream level. Furthermore, a Min–Max interference leakage algorithm is also proposed to suppress the maximum interference from user, with the purpose of guaranteeing the fairness among users. Simulation results demonstrate that taking inter-stream interference into consideration can significantly improve the effectiveness of multiple-input multiple-output Interference Channel networks, while the Min–Max method can slightly increase the system capacity under certain conditions. It can be also confirmed that the trade-off among effectiveness, fairness and robustness exists in the transceiver optimisation of multiple-input multiple-output Interference Channel networks.

Design of half adder using integrated leakage power reduction techniques

The necessity for the development of compact, portable, and reliable electronic devices of enhanced speed and efficiency has prompted the scaling of CMOS devices to be indispensable. However, the benefit of scaling CMOS devices comes at the cost of increased leakage current in circuits. The variance in power consumption by these circuits incites detrimental impacts on the operational characteristics of the entire device. So, in this work, a novel leakage power reduction technique obtained by combining the Leakage Control Transistor (LECTOR) approach and drain gating approach is proposed. Both these subthreshold leakage minimization approaches are prominently used in Complementary Metal Oxide Semiconductor (CMOS) devices for curtailing the leakage power. The effectiveness of the proposed Integrated Drain Gating Lector (IDGL) technique in mitigating the leakage power is ascertained by designing a half adder circuit. Hence the overall leakage power is of 3.16nW & delay 69.12 µs in 180 nm technology, and in low scale technology of 90 nm the same leakage power decline to 2.19nW & delay is 65.45 µs.

Privacy-Preserving Aggregate Mobility Data Release: An Information-Theoretic Deep Reinforcement Learning Approach

It is crucial to protect users’ location traces against inference attacks on aggregate mobility data collected from multiple users in various real-world applications. Most of the existing works on aggregate mobility data are focusing on inference attacks rather than designing privacy-preserving release mechanisms, and a few differential private release mechanisms suffer from poor utility-privacy tradeoffs. In this paper, we propose optimal centralized privacy-preserving aggregate mobility data release mechanisms (PAMDRMs) that minimize the leakage from an information-theoretic perspective by releasing perturbed versions of the raw aggregate location. Specifically, we use mutual information to measure user-level and aggregate-level privacy leakage separately, and formulate leakage minimization problems under utility constraints. As directly solving the optimization problems incur exponential complexity w.r.t. users’ trace length, we transform them into belief state Markov Decision Processes (MDPs), with a focus on the MDP formulation for the user-level privacy problem. We build reinforcement learning (RL) models and leverage the efficient Asynchronous Advantage Actor-Critic RL algorithm to derive the solutions to the MDPs as our optimal PAMDRMs. We compare them with two state-of-the-art privacy protection mechanisms PDPR (context-aware local design) and DMLM (context-free centralized design) in terms of mutual information leakage and adversary’s attack success (evaluated by her expected estimation error and Jensen-Shannon Divergence-based error). Extensive experimental results on both synthetic and real-world datasets demonstrate that the user-level PAMDRM performs the best on both measures thanks to its context-aware property and centralized design. Even though the aggregate-level PAMDRM achieves better privacy-utility tradeoff than the other two, it does not always perform better than them on adversarial success, highlighting the necessity of considering privacy measures from different perspectives to avoid overestimating the level of privacy offered to users. Lastly, we discuss an alternative, fully data-driven approach to derive the optimal PAMDRM by leveraging adversarial training on limited data samples.

Performance evaluation of low-GWP refrigerants in 1–100 ton scroll compressors

• Method to scale the scroll compressor for different cooling capacities and refrigerants. • Validation of scroll compressor model in PDSim. • Performance evaluation of low-GWP refrigerants in scroll compressor. Performance evaluation of low-GWP refrigerants in scroll compressor is carried out to aid the selection of suitable refrigerant for different applications. The open-source modeling platform PDSim, used for this study, is based on the mechanistic chamber model that has the accuracy comparable to the heuristic methods. A scaling model is developed to design and select the scroll geometry for 1–100 ton range of cooling capacity and seven refrigerants. This method is based on manufacturing constraints and minimization of leakage. Additionally, the ports and the bearings are scaled to make their effect fair for a range of capacities and refrigerants. The simulation model is validated using two example scroll compressors. The predicted mass flow rate and power are within 3% MAE while the isentropic efficiency is within 4% mean absolute error. A validated model and standard AHRI conditions are used for the performance evaluation of the refrigerants over a range of 1 to 100 tons of refrigeration capacity. Seven refrigerants are studied including low-pressure refrigerants, R1234ze(E) and R1234yf, medium-pressure refrigerants, R410A, R32, R454B, and R452B and high-pressure R744. The results suggest that an optimum range exists for each refrigerant to achieve good compressor performance. The leakage area is the primary contributor to the scroll compressor performance.

Minimization of information leakage in continuous-variable quantum key distribution

A communication protocol based on a Gaussian modulation of squeezed states in a single quadrature and measured via homodyne detection can completely eliminate information leakage to an eavesdropper in a pure-loss channel. However, the asymmetry of the protocol with respect to the quadratures of light presents security issues and the eavesdropper's information is not necessarily minimized for general asymmetric attacks. Here, we perform asymptotic security analysis of the asymmetric protocol against general asymmetric collective attacks and bound the eavesdropper's information via the Heisenberg uncertainty principle. The bound is not tight and therefore, we symmetrize the protocol in a heralding way, discarding the issues of asymmetry altogether. Our proposed heralding protocol asymptotically eliminates information leakage in a pure-loss channel and minimizes leakage in a noisy channel.

Multi-Objective Operation-Leakage Optimization and Calibration of Water Distribution Systems

This study aims to develop and solve a multi-objective water distribution systems optimization problem incorporating pumps’ optimal scheduling and leakage minimization. An iterative optimization model was presented for calibrating and computing leakages in water distribution systems to recognize the critical impact of leakage control on system operation. The multi-dimensional and nonlinear optimization model, incorporating pump control, consumer demands, storage, and other water distribution systems’ components, was constructed and was minimized using a multi-objective genetic algorithm coupled with hydraulic simulations. The model was demonstrated on two example applications with increasing complexity through base runs and sensitivity analyses. Results showed that leakage minimization competes against pumping, mainly when significant differences occur between demands during low and high energy tariffs. Pumping during the periods with high electricity tariffs (when the demands are high) generated pressure distribution that decreased the overall leakage related to pump scheduling that replicated the natural inclination to pump as much as possible at low tariffs (when the demands are low). The optimal fronts were found to be very sensitive to the leakage exponent value, and changing its value indeed contradicted the balance between minimizing the leakage and the energy cost significantly. Altogether, the idea presented in this paper was found capable of facilitating the decision-makers to conveniently select between the energy-efficient pump scheduling and pump scheduling reflecting minimum leakage based on the system operator’s preferences. The research also paves the way to rebuild the optimization model by incorporating water distribution reliability and water quality that, in some cases, may also contradict the choice between energy cost and leakage minimization.

Shear Horizontal Phononic Metasurface for In-Liquid Gravimetric Biosensing

In-liquid wave attenuation is the major factor that limits the resolution of acoustic wave biosensors. Existing acoustic wave devices rely on shear mode operation to reduce the mechanical motion transferred to the liquid. However, the energy leakage still exists through acoustic radiation. In this article, we combined phononic metasurface based on local mechanical resonators with shear horizontal surface acoustic wave (SH-SAW) to address the above issue. The shear-horizontal phononic metasurface (SH-PM) resonator is made of periodic high-aspect-ratio electrode (HARE). It produces a slow phononic wave that cannot propagate in water due to its low velocity, which suppresses the acoustic radiation. Furthermore, as the particle motion of the HARE is polarized in shear mode, the SH-PM also reduces the mechanical motion transfer to water. The minimization of the total acoustic energy leakage in the SH-PM results in high quality factor (Q) resonance in water. Besides, the increased surface-to-volume ratio of the HAREs also enhances the mass sensitivity of the device. Experimental results show that the SH-PM resonator achieved an in-liquid Q factor of 230 and a normalized mass sensitivity of - 192.4 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">cm</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /g. The high in-liquid Q factor together with the high mass sensitivity makes the SH-PM a promising candidate for high-resolution gravimetric detection of biomolecules.

Assessing the Impact of Partitioning on Optimal Installation of Control Valves for Leakage Minimization in WDNs

This paper aims to assess the impact of partitioning on optimal installation of control valves for leakage minimization in water distribution networks (WDNs). The methodology used includes two main elements. The first element is a deterministic algorithm operating through the sequential addition of control valves, producing a Pareto front of optimal solutions in the trade-off between number of control valves installed and daily leakage volume, to be both minimized. The second element is a WDN partitioning algorithm based on the minimization of the transport function, for the partitioning of the WDN into a number of partitions equal to the number of WDN sources. The methodology is applied to two Italian WDNs with different characteristics. Due to variations in flow distribution induced by the partitioning, the valve locations optimally selected in the partitioned WDN prove slightly different from those in the unpartitioned WDN. Furthermore, the number of control valves being the same, better leakage reduction effects (up to 8%) are obtained in the partitioned WDN.

Cell leakage minimization by immobilization modulation of Chlorella sorokiniana NCIM 5561 and phosphate removal from wastewater

Microalgal cell leakage from immobilized beads due to mass transfer limitation and inert support matrix pose major problem during its application in the wastewater treatment process. To overcome this, Ca2+-alginate immobilization with water (AWIM—Alginate in Water Immobilized Microalgal system) and Blue Green (BG)-11 media (ABIM—Alginate in BG-11 Immobilized Microalgal system) using Chlorella sorokiniana NCIM 5561 was employed to determine their efficacy. Upon comparison of microalgal growth in the beads, ABIM resulted in better kinetic properties such as biomass yield, specific growth rate and productivity as 933.12 mg L−1, 0.42 day−1 and 77.78 mg L−1 day−1, respectively, as compared to AWIM. Flow cytometry and SEM analysis revealed that ABIM could hold up more cell density as compared to AWIM due to the reduced pore size and growth nutrient localization in the bead matrix. A novel strategy of co-cultivation of yeast along with microalgal cells under immobilized condition was attempted for improved phosphate uptake from the simulated wastewater. The results indicated that the co-cultivation resulted in minimum residual phosphate concentration of 0.75 mg L−1 as compared to ABIM and AWIM with corresponding concentration of 1.02 and 1.71 mg L−1, respectively. However, the rate of uptake was found to be superior with ABIM (0.41 h−1) than co-cultivation (0.29 h−1) and AWIM (0.23 h−1) that correlates to overall removal efficiency of 94.54%, 80.64% and 67.07%, respectively.