Leakage Minimization Research Articles

An environmental and economic assessment of bioplastic from urban biowaste. The example of polyhydroxyalkanoate

Bio-based and biodegradable plastics promise considerable reductions in our dependency on fossil fuels and in the environmental impacts of plastic waste. This study quantifies the environmental and economic consequences of diverting municipal food waste and wastewater sewage sludge from traditional management to the biorefinery-based production of polyhydroxyalkanoates (PHA) in five geographical regions. The results show that PHA can outperform fossil polyurethane and PHA from first-generation biomass (sugarcane and maize) with respect to both environmental impacts and societal costs (four times lower impacts and eight times lower costs than polyurethane). To outperform other fossil polymers like low-density polyethylene (LDPE), biorefinery performance should be improved further by more efficient utilization of sodium hypochlorite during PHA extraction, minimization of methane leakage in biogas facilities, upgrading of biogas to biomethane, and more effective handling of the liquid fraction from digestate dewatering.

Effectiveness enhancement of non-contact vacuum pumps working process

Three options of rotor profiles of Roots vacuum pump are considered: elliptic, circular, and involute. Rotor profiles are drawn in the same housing and are analyzed from point of view of backward leakage minimization through inter-rotor channel and geometric pumping speed increase. It is shown that coefficient of working volume use is only 3% higher for involute profile. Averaged over one revolution conductance of rotor mechanism channels is minimal for elliptic rotor profile. For inter-rotor channel it is 14% less than for involute profile. The presented approach makes it possible to choose the optimal rotor profile of Roots pump for particular purpose.

Design and Simulation of Reliable Low Power CMOS Logic Gates

In this paper, a circuit-level reliable low leakage design methodology is proposed for integrated circuits (ICs). Low leakage circuit design is the most challenging research area for very large-scale integration (VLSI) circuit designers due to the increased demand of battery-operated portable systems. Leakage power is increasing continuously with each new technology node generation in deep sub-micron (DSM) regime. Large power dissipation harms the device characteristics and affects the overall performance of the circuits. Proposed approach is extensively discussed and verified for the low power operation and reliability. The various logic circuits are simulated and compared with the available leakage minimization techniques at 22 nm technology node using predictive technology model (PTM) bulk CMOS BSIM4 on HSPICE tool. Proposed approach reduces leakage power by ≈81% in XOR2 and XNOR2 gates as compared to conventional CMOS gates. Reliability of the nanoscaled circuits is affected by several device parameters. Process, voltage and temperature (PVT) variations, aging and radiation effects are considered for reliability testing. The reliability of the proposed approach is improved by 77.45% for power delay product (PDP) metric for the ring oscillator as compared to conventional circuit.

GenMap: A Genetic Algorithmic Approach for Optimizing Spatial Mapping of Coarse-Grained Reconfigurable Architectures

Coarse-grained reconfigurable architectures (CGRAs) are expected to be used for embedded systems, Internet of Things (IoT) devices, and edge computing thanks to their high-energy efficiency and programmability. In essence, a CGRA is an array of numerous processing elements. To exploit this abundant computation resource, a compiler for CGRAs has to fulfill more tasks compared that for general-purpose processors. Therefore, many studies have proposed optimization methods, especially for application mapping, because the performance and energy efficiency strongly depend on optimization at compile time. However, many works focus only on performance improvement or resource minimization, although such optimization objectives are not always appropriate when considering various use cases. In this work, we propose GenMap, an application mapping framework using multiobjective optimization based on a genetic algorithm so that users can set optimization criteria as needed. Besides, it provides aggressive power optimization using our dynamic power model and leakage minimization technique. The proposed method is applied to three fabricated CGRA chips for evaluation. Experimental results show that GenMap achieves 15.7% reduction of wire length while keeping processing element utilization when compared with conventional methods. In addition, according to real chip experiments, 12.1%–46.8% of energy consumption is reduced, and up to $2\times $ speedup is archived for several architectures when compared with other two approaches.

Interval Arithmetic and Self-Similarity Based RTL Input Vector Control for Datapath Leakage Minimization

With technology scaling, subthreshold leakage has dominated the overall power consumption in a design. Input vector control is an effective technique to minimize subthreshold leakage. Low leakage input vector determination is not often possible due to large design space and simulation time. Similarly, applying an appropriate minimum leakage vector (MLV) to each Register Transfer Level (RTL) module instance in a design often results in a low leakage state with significant area overhead. In this work, we propose a top-down and bottom-up approach for propagating the input vector interval to identify low leakage input vector at primary inputs of an RTL datapath. For each module, via Monte Carlo simulation, we identify a set of MLV intervals such that maximum leakage is within (say) 10% of the lowest leakage points. As the module bit width increases, exhaustive simulation to find the low leakage vector is not feasible. Further, we need to uniformly search the entire input space to obtain as many low leakage intervals as possible. Based on empirical observations, we observe self-similarity in the subthreshold leakage distribution of adder/multiplier modules with highly regular bit-slice architectures when input space is partitioned into smaller cells. This property enables the uniform search of low leakage vectors in the entire input space where the time taken for characterization increases linearly with the module size. We further process the reduced interval set with simulated annealing to arrive at the best low-leakage vector at the primary inputs. We also propose to reduce area overhead (in some cases to 0%) by choosing Primary Input (PI) MLVs such that resultant inputs to internal nodes are also MLVs. Compared to existing work, experimental results for DSP filters simulated in 16nm technology demonstrated leakage savings of 93.6% and 89.2% for top-down and bottom-up approaches with no area overhead.

Sum-Rate Optimization Constrained by Consumed Power for Multi- Antenna Non-Regenerative Relay Network

Background & Objective: This paper considers a multi-pair wireless network, which communicates peer-to-peer using some multi-antenna amplify-and-forward relays. Maximizing the throughput supposing that the total relay nodes’ power consumption is constrained, is the main objective of this investigation. We prove that finding the beamforming matrix is not a convex problem. Methods: Therefore, by using a semidefinite relaxation technique we find a semidefinite programming problem. Moreover, we propose a novel algorithm for maximizing the total signal to the total leakage ratio. Numerical analyses show the effectiveness of the proposed algorithm which offers higher throughput compared to the existing total leakage minimization algorithm, with much less complexity. Results and Conclusion: Furthermore, the effect of different parameters such as, the number of relays, the number of antennas in each relay, the number of transmitter/receiver pairs and uplink and downlink channel gains are investigated.

Comparison between two Hydraulic Control Valves Systems for Leakage Minimization in Water Distribution Networks Using Multi-Objective Memetic Algorithm . Dept C.(Irrigation )

This paper optimizes the selection, number, location, and sizing of hydraulic devices with the purposes of leakage reduction in water distribution network (WDN). A multi-objective memetic algorithm is adopted to effectively minimize the leakage problem in WDN through the regulation of two different hydraulic control valves systems: throttle control valves (TCVs) and flow control valves (FCVs). Two objective functions are simultaneously considered: the first one is to minimize the total leakage in the network and the second objective function is represented by the minimization of the number of valves (a surrogate for establishing valves cost) while accomplishing the required nodal pressure head restrictions. The great advantage of this study is that, in one run, several trade-off optimal solutions are acquired with a different level of compromise between the two objectives. Each solution from these optimal ones consists of minimum number of suggested valves, the best locations for the valves and optimum valves settings. The performance of the developed optimization model is evaluated by its application on a well-known WDN from literature. Then, the developed optimization model is applied on a real WDN of a new city, Egypt. Results show that the hydraulic performances of the two hydraulic control valves systems in leakage reduction are almost agreement for the same valves number, and the TCVs system is relatively better than the FCVs system

Comparison between two Hydraulic Control Valves Systems for Leakage Minimization in Water Distribution Networks Using Multi-Objective Memetic Algorithm

This paper optimizes the selection, number, location, and sizing of hydraulic devices with the purposes of leakage reduction in water distribution network (WDN). A multi-objective memetic algorithm is adopted to effectively minimize the leakage problem in WDN through the regulation of two different hydraulic control valves systems: throttle control valves (TCVs) and flow control valves (FCVs). Two objective functions are simultaneously considered: the first one is to minimize the total leakage in the network and the second objective function is represented by the minimization of the number of valves (a surrogate for establishing valves cost) while accomplishing the required nodal pressure head restrictions. The great advantage of this study is that, in one run, several trade-off optimal solutions are acquired with a different level of compromise between the two objectives. Each solution from these optimal ones consists of: minimum number of suggested valves, the best locations for the valves and optimum valves settings. The performance of the developed optimization model is evaluated by its application on a well-known WDN from literature. Then, the developed optimization model is applied on a real WDN of a new city, Egypt. Results show that the hydraulic performances of the two hydraulic control valves systems in leakage reduction are almost agreement for the same valves number, and the TCVs system is relatively better than the FCVs system.

Using particle swarm optimization algorithm to optimally locating and controlling of pressure reducing valves for leakage minimization in water distribution systems

The main objective of pressure management in a water distribution system (WDS) is to minimize leakages, bursts and maintain the required pressure at every node. One of the methods for pressure management is using pressure-reducing valves (PRV). This paper outlines an optimization-simulation approach to determine the optimum location and settings of the PRVs to control the pressure and minimize the leakage in WDSs. To solve the problem, the particle swarm optimization (PSO) tool was coupled with EPANET hydraulic simulation software in MATLAB environment. The results revealed that by observing all the regulations of the problem, through utilizing the proposed method for finding optimal location and regulating the PRVs, the network average leakage rate in a 24-h utilization period dropped by 23%. The performance of the PSO-based model in pressure management was compared with models based on three specific types of powerful algorithms including a genetic algorithm (GA) from the evolutionary algorithms (EA), artificial bee colony (ABC) from the swarm intelligence, and cultural algorithm (CA) from human behavior. The PSO-based model with the lowest objective function call compared to the other three algorithms, was able to reduce leakage compared to GA, ABC, and CA by 1.63, 3.45, and 8.53%, respectively. That shows the presented method is successful in regulating the pressure level to minimize network leakage.

Energy-Efficient Group-Sparse Transceiver Design for Multiuser MIMO Relaying in C-RAN

This paper addresses the problem of centralized transceiver design for multiuser MIMO amplify-and-forward (AF) relaying within a cloud radio access network (C-RAN). The aim is to optimize AF matrices of remote radio heads (RRHs) acting as relays, in order to improve the reception quality at the destinations while reducing network power consumption and feedback overhead on the fronthaul links. A two-stage method is proposed to solve this problem efficiently. The first stage relies on interference leakage minimization subject to per-relay transmit power constraints along with signal preserving constraints. To reduce the total network power, RRH selection is achieved by incorporating in the objective function a regularization term that promotes group-sparsity among the RRHs. In the second stage, to reduce feedback overhead, a different penalty term is added that induces weight-level sparsity in the AF matrix of each active RRH. For both stages, low-complexity iterative algorithms based on the alternating direction method of multipliers (ADMM) are developed to solve the corresponding regularized problems with low complexity. Extensive simulations are performed to demonstrate the explicit benefits of the proposed design method, which results in notably lower power consumption, computational complexity and weight feedback overhead than conventional approaches.

Интенсификация работы систем водоснабжения и водоотведения г. Нижнеудинска

The paper proposes an approach to intensifying the operation of water supply and sanitation systems. The work was conducted using electronic modelling, calculation methods of hydraulic parameters and numerical modelling, as well as optimization of technical solutions for adjustment of operation modes, minimization of water leakage, pressure stabilization in the network, elimination of blockages and failures of regulating and stop valves. The efficacy of the proposed approach was demonstrated by the example of the city of Nizhneudinsk. As a result of the conducted research, information and computing systems and complexes were developed for simulating different modes of operation, assessing the performance, reliability and regime controllability of water supply and wastewater disposal systems, storing, analysing and accumulating information on the state of the system under analysis and its individual parameters. Such an approach served as a basis for developing a prospective scheme of development and reconstruction of the city water supply and sewage systems and provided an automated control system of its technological processes.

Modeling of Water Distribution System for Reducing of Leakage

Water loss is a common phenomenon observed in all water distribution systems. The process of water loss reduction is a basic part to increase the performance of a water supply system. The means presented in this study is aimed at evaluating water distribution pressure for the minimizing leakages in Dilla town water supply system network. Water CAD software was used to evaluate water distribution system, fixed pressure reducing valves (PRV) were installed at the most effective set of water distribution systems to reduced pressure as well as leakage quantities of water. An average water distribution pressure in the existing water distribution system was 58 m. Then, after the pressure reduced by pressure reducing valves (PRVs) average pressure dropped to 44 m, therefore, leakage in average reduced by 24%. The study concluded that the application of PRVs in the water distribution system as a promising solution for leakage minimization by reducing pressure in the water distribution networks, such as Dilla town.

Analysis for the Minimization of Leakage and Common Mode Currents in Cascaded Half-Bridge PV Fed Multilevel Inverter

This paper gives the detailed study and analysis of the terminal voltage and the common mode voltage (CMV) for the photovoltaic fed cascaded half-bridge (CHB) multilevel inverter (MLI). The expression for the terminal voltage and CMV are also derived using switching function. The analytical waveforms obtained using the expression of the terminal voltage and CMV clearly indicate that the terminal voltage and CMV are not constant simultaneously. Thus, two pulsewidth modulation (PWM) schemes are proposed using redundant states concept for CHB nine-level MLI without the addition of any extra circuit element. The first PWM scheme reduces the high-frequency transitions in the terminal voltage and, thus, minimizes the leakage current. The other PWM scheme is designed to reduce the common mode current by maintaining CMV constant. Furthermore, the proposed PWM schemes are compared with the conventional PWM schemes. The effect of each PWM schemes on the terminal voltage and CMV is analyzed using the given switching function analysis. The given switching function analysis is also supported with the help of simulation and experimental results. The simulation and experimental results of the proposed PWM schemes are further compared with the conventional SPWM technique.

Optimal assets management of a water distribution network for leakage minimization based on an innovative index

Leakage reduction in water distribution networks is an absolute priority and several pressure management strategies have been proposed in the literature to tackle this issue. However, the definition of an effective relationship between leakage and relevant and measurable parameters still represents a challenge.This paper presented a novel performance parameter, the Leakage Performance Index (LPI), to minimize leakages starting from pressure and flow rate measurements. This parameter creates a ranking among the different nodes in the network, by properly weighting the pressure of each node with the output flow from the node in order to focus the pressure management strategy on those nodes whose impact, in terms of leakage, is expected to be greater.To verify the effectiveness of the proposed LPI, a model of an existing water distribution district in Italy was developed in EPAnet and validated by comparison with experimental results. The valve settings of the model were then used as variables of time-dependent optimization procedures aimed at minimizing different objective functions. Different scenarios were considered by varying the minimum guaranteed pressure at the customer points.The LPI minimization strategy was efficient insofar as it indirectly minimized the leakages, achieving the same results of the leakage minimization strategy.

Design Techniques for Power-Gated Nanoscale Low Power Circuits

Background: With the shrinking device-sizes in the present day world, the leakage power of the devices has also been increased significantly. Several techniques have been proposed to minimize the leakage power. However, the techniques have certain limitations, such as noise, delay or area of the chip. We have also proposed a leakage minimization technique which also minimizes the noise in the circuit. Objective: In this paper, we propose noise minimization circuit techniques for the distributed sleep transistor network in power-gated Multi-threshold CMOS circuits. The objective is to minimize leakage power as well as the noise associated with digital power-gated circuits. Methods: The proposed technique has been verified through simulations using the Cadence virtuoso tool. The proposed technique has been applied to a 16-bit adder circuit in 45 nm MTCMOS technology. Results: The proposed techniques i.e. HVT-ST and the Hybrid-ST techniques achieve 99%, 64.8% and 62.07% reduction in noise as compared to the All-ON, variable-width and variable gate-voltage techniques, respectively. The behavior of the circuit techniques has also been analyzed at higher temperatures. It has been shown through simulations that the proposed techniques effectively minimize noise at higher temperatures i.e. 75°C and 115°C. The proposed techniques also minimize leakage power and the on-time delay significantly. A layout of the section of the proposed circuit has also been drawn which occupies the chip area of 2.37 µm2. Conclusion: The proposed techniques i.e. HVT-ST and the Hybrid-ST techniques achieve a significant reduction in the noise as well as delay. In this paper, we propose leakage minimization techniques for the distributed sleep transistor network. The proposed techniques i.e. HVT-ST and the Hybrid-ST techniques achieve a significant reduction in noise as well as delay. The technique also reduces the leakage power significantly.

Features of the Vortex Flow Structure around a One Fin Shroud

Modern gas turbines have high efficiency. A further increase in their economic efficiency can be achieved, on the one hand, by enhancing the accuracy of the parameter prediction at the design stage and, on the other hand, by the possibility of improving the design for different components of the flow path based on the results of calculating the complicated viscous spatial structure of the flow. One of the tools for enhancing the efficiency of gas turbines is the minimization of the rotor-tip leakage, the rate of which is reduced by shrouding the rotor blades. In particular, using numerical methods and software tools based on the former, one can perform thorough computational analysis of the vortex structure of the flow in the vicinity of the tip shroud and sufficiently accurately determine the rotor-tip leakage rates and other parameters of the stage. Such an approach allows a more accurate assessment of the leakage than semiempirical approaches used in practice. In particular, the assessment by the correlation dependence showed that the leakage rate for the tip shroud design in question with a tip clearance of 5 mm exceeded the leakage rate calculated using the method that considers the specific features of the tip shroud design and the vortex structure of the flow in the vicinity of it by 8.65%. As exemplified by the last-stage rotor blade of a stationary gas turbine, the possibility of controlling the leakage of the main flow through the tip clearance is demonstrated based on results of a numerical experiment.

Cryogen-free apparatus for rapid thermal emissivity measurements at low temperature

Thermal radiation is a significant way of heat transfer among insulation parts. For minimization of heat leakage, the radiative properties of materials are essential for the design of cryogenic devices. Emissivity is a key element of radiation properties of materials. However, such experimental data are always not sufficient, especially at cryogenic temperature. In order to measure the radiative properties of material surfaces, a measurement device was presented. The device is based on a two-stage Gifford-McMahon refrigerator and the dismountable sample test rod has independent vacuum environment, which allows the sample to be replaced rapidly. In emissivity measurement, the temperature of examined samples can be controlled precisely between 15.4 K to room temperature.

Full-Bridge ZCS-Converter-Based High-Gain Modular DC-DC Converter for PV Integration With Medium-Voltage DC Grids

This paper presents a high-gain modular input-parallel output-series dc-dc converter for photovoltaic integration with medium-voltage dc grids. A new full-bridge zero-current-switching (FB-ZCS) converter proposed in this paper is used as a fundamental building block. Existing FB-ZCS converters utilize transformer leakage inductance and a shunt-connected resonant capacitor for achieving smooth resonant current commutation and ZCS. The shunt-connected capacitor requires dedicated charging interval in every switching cycle and stores full-load-rated resonant energy at all load/input conditions, resulting in significant duty-cycle loss. Moreover, it suffers from energy leakage through transformer winding and requires overrating. All these factors adversely impact the operation range of the converter, which is important for achieving a wide maximum power point tracking range. Novel improvements in the proposed converter include minimization of duty-cycle loss and resonant capacitor leakage and the realization of the current-adaptive resonant energy storage mechanism, without using additional switches or auxiliary circuits. Operation of the proposed converter is presented and validated with simulation and experimental results.

Energy Flux Manipulation in Upconversion Nanosystems.

Lanthanide-doped upconversion nanoparticles (UCNPs) exhibit unique optical characteristics, including a large anti-Stokes shift, a long luminescence lifetime, sharp emission bands, and high photostability. These virtues make UCNPs highly useful in many emerging applications such as biolabeling, security, multicolor displays, and optogenetics. Despite the enticing prospects of UCNPs, their practical utility is greatly hindered by the low efficiency of the conversion from near-infrared (NIR) excitation to visible emission. In a typical nanosystem codoped with sensitizers and activators, upconversion processes occur through NIR light sensitization, energy transfer from sensitizers to activators, sequential energy population at the excited states of the activators, and eventually the release of higher-energy photons. In fact, in the upconversion nanosystem, each step in the energy flux, including NIR energy injection, energy transfer and migration, and energy dissipation, has a decisive effect on the resulting luminescence intensity. Important in-depth studies have been conducted in pursuit of brighter UCNPs. Specifically, lanthanide ions possessing larger absorption cross sections (Nd3+) or organic dye molecules have been chosen as NIR light sensitizers to improve the light harvesting ability of upconversion nanostructures. The doping concentration and spatial distribution of lanthanide ions are strictly managed to mitigate detrimental energy cross-talk processes. The surfaces of UCNPs are passivated with epitaxially grown layers to block surface quenching. Therefore, rational design of energy flux manipulation, through control of excitation energy collection, transmission, and release in a three-dimensional nanospace of UCNPs, is crucial in constructing nanosystems with high upconversion efficiencies. In this Account, from an energy flux manipulation perspective, we attempt to provide an overview of general and emerging strategies for the design of efficient lanthanide-mediated photon upconversion nanosystems. With the significant progress made over the past several years, we are now able to design a series of upconversion nanoplatforms with efficient NIR light harvesting ability, sufficient energy transmission channels, and low levels of luminescence quenching at the particle's surface. In addition to providing a deep understanding of the underlying mechanism of energy flux, these discoveries will guide the development of upconversion nanosystems with significantly improved performance. The key aspects of this Account of energy flux manipulation in upconversion nanosystems mainly include the management of NIR photon energy injection, the optimization of efficient energy transfer pathways, and the minimization of energy flux leakage. Future challenges and opportunities for the development of efficient upconversion nanosystems are also discussed.

Beamformer Design for MIMO Interference Broadcast Channels With Semidefinite Programming

We consider beamformer design for multiuser multiple-input multiple-output (MIMO) interference channels where each transmitter communicates to its intended receivers while sharing the same spectro-temporal resources with some other unintended receivers. This scenario is often referred to as MIMO interference broadcast channel (IBC) where by using interference alignment (IA), it is possible to cancel out inter and intracell interferences so that the achievable degrees of freedom could be linearly scaled up with the number of users. In this paper, we propose two distinct and novel IA algorithms, one of which is IA via signal matching (SIGMA) that revolves around interference leakage minimization and further takes the desired signal subspaces into account to output higher sum rates. The second algorithm is called bipartite rank fitting, which is founded on the prior knowledge of the rank of receive beamformers and interference matrices. Therefore, this algorithm is quite a unique approach towards interference alignment in MIMO IBCs since it performs the optimization over only receive beamformers. Furthermore, we propose a robust design of SIGMA algorithm to achieve better performance in the presence of imperfect channel state information (CSI). The key tenet of our design is that we formulate the optimization problems involved in these two algorithms as plain semidefinite programs. It is shown that the proposed algorithms are able to outperform state-of-the-art IA techniques under perfect and imperfect CSI, and the suitability of each algorithm for different network configurations is further discussed.