Fixed Power Supply Research Articles

Self‐Powered Electrically Controlled Drug Release Systems Based on Nanogenerator

AbstractPrecision medicine requires precise regulation of drugs in terms of time, space, and dosage. Exogenous control systems, such as electrical responsiveness, have made great progress. However, wearable or implantable controlled drug release devices still face major challenges due to limitations including limited battery life, large size, and fixed power supply. To overcome these limitations, the fabrication of autonomous devices is available to endure extended periods without reliance on external power sources. As a promising strategy, nanogenerators (NGs) turn body mechanical energy into electricity, powering long‐term drug release. In this review, the current status of drug delivery systems (DDS) is briefly outlined and the importance of self‐driven controlled drug release systems is emphasized. The main types and operational mechanisms of various nanogenerators are introduced. This review also focuses on summarizing the latest progress of self‐powered controlled drug release systems based on nanogenerators (NG‐based CDRs). Additionally, their applications in the field of drug release are introduced in detail. Finally, the existing challenges and future trends of self‐powered NG‐based CDRs are discussed from the perspectives of clinical needs and practical translation.

Evaluation of process conditions for methane pyrolysis applying the triple thermal plasma system

Among various thermal plasma sources for CH4 pyrolysis, singular direct current (DC) thermal plasma has limited capacity, erosion, and efficiency. However, the triple thermal plasma system has been applied for nanomaterial synthesis and exhibited results overcoming these limitations. This study used the triple thermal plasma system to investigate the most suitable conditions for CH4 pyrolysis. CH4 conversion rate and selectivity of H2 and C2H2 were analyzed by varying the CH4 flow rate and quenching conditions at a fixed power supply of approximately 30 kW, and the specific energy requirement (SER) per 1 kg H2 was compared with that of previous works. The maximum conversion rate was 97% at 50 L/min of CH4, which is approximately 7% higher than earlier studies under conditions with similar process enthalpy. In addition, the conversion of CH4 to C2H2 and further to heavier hydrocarbons proceeded one order of magnitude faster than the reaction time expected by the gas-phase reaction. This result is attributed to the easy penetration of CH4 into the core region with the highest temperature and the strong interaction between the processing gas and graphite surface due to the arrangement of the torches in the triple plasma system. C2H2 selectivity was relatively high, while it was less affected by the increase in the quenching gas than generally expected. This finding was attributed to the naturally fast quenching rate without quenching gas due to the structure expanding from the first to the second graphite. While quenching can enhance selectivity by stabilizing the radicals as intermediates such as H2 or C2H2, it depressed the following reaction with dehydrogenation. Thus, the quenching conditions must be optimized. Finally, we demonstrated that the triple thermal plasma enhanced CH4 pyrolysis regarding H2 production efficiency.

Battery Operated Portable Electric Kettle

Today, most of the homes have been fitted with electric kettles and heating systems. Electric kettles play a vital role in the development of hot water. Hot water is necessary to ensure good hygiene for everyone. Compared to drinking cold water, drinking hot water especially relieves congestion in the throat, and even encourages relaxing. Conventional electric kettles must be stored in a fixed location at the same time (which is not portable) with a fixed power source. On a trek, especially in cold countries, carrying enough drinking water is crucial to stay the person energized and feel well. On long hikes, it can be extremely dangerous to become dehydrated. Ice-covered hills freeze the water. There will be no electricity source available to heat the water while trekking on ice-covered hills. This condition has led to the proposed system i.e. battery operated portable kettle that can heat the water at any place. Without any fixed power supply, the proposed heating system will generate hot water that run on a battery source. The kettle can be shipped anywhere to make it more portable. This makes it very easy to use hot water safely with the battery management system. A battery management system (BMS) is an electronic regulator that monitors and controls the charging and discharging of rechargeable batteries. Battery management systems of various types are used in most devices that use rechargeable batteries.

Joint spectral efficiency optimization of uplink and downlink for massive MIMO-enabled wireless energy harvesting systems

This paper investigated the spectral efficiency (SE) in massive multiple-input multiple-output systems, where all terminals have no fixed power supply and thus need to replenish energy via the received signals from the base station. The hybrid wireless energy harvesting (EH) protocol is applied for each terminal, which can switch to either existing time-switching (TS) protocol or power-splitting (PS) protocol. Based on the hybrid wireless EH protocol, a general system model is developed, which can switch to either only uplink data transmission or only downlink data transmission. As a result, a general analytical framework is formulated. Then, closed-form lower bound expressions on SE for each terminal are obtained on the uplink and downlink, respectively. According to these expressions, the joint SE of uplink and downlink maximization problem is designed with some practical constraints. As the designed optimization problem is non-linear and non-convex, it is hard to solve directly. To provide a solution, an iteration algorithm is proposed by utilizing one-dimensional search technique and successive approximation method based on geometric program. Additionally, the convergence and complexity of the proposed algorithm are discussed as well. Finally, the feasibility of the proposed algorithm is analyzed by simulations. Numerical results manifest that the proposed algorithm can provide good SE by optimizing relevant system parameters, and the system model can help to discuss the TS, PS or hybrid protocol for only uplink data transmission, only downlink data transmission or joint data transmission of uplink and downlink in the considered system.

Precise Power Capping for Latency-Sensitive Applications in Datacenter

Power capping is widely used in cloud datacenters to mitigate power over-provisioning problem, thus improve datacenter capacity and cut off their operation cost. However, inappropriate or aggressive power capping may lead to performance degradation of applications (especially latency-sensitive ones), and there are few effective methods that can accurately evaluate and control such negative impact caused by aggressive power capping. In this paper, we propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Fine-Grained Differential Method</i> (FGD) to quantitatively analyze how inappropriate power capping degrades the performance of latency-sensitive applications. By using FGD, we can minimize the provisioned power for each server by setting a precise power budget according to application’s <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Service Level Agreement</i> (SLA). And we further propose <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Precise Power Capping</i> (PPCapping) which is designed to increase the datacenter capacity with a fixed power supply by means of FGD. Our research also provides an insight of precise tradeoff between applications’ SLAs and datacenter capacity. We verify FGD and PPCapping by using real world traces from Tencent’s datecenter with 25,328 servers. The experimental results show that FGD can accurately analyze the impact of power capping on the performance of latency-sensitive applications, and PPCapping can effectively increase datacenter capacity compared with the typical power provisioning strategy.

Proposing a Density‐Based Clustering Approach (DBCA) to Aggregate Data Collected from the Environment in Arid Area for Desertification

Nowadays, the expansion of desert areas has become one of the main problems in arid areas due to various reasons such as rising temperatures and vegetation fires. Establishment of wireless sensor networks in these areas can accelerate the process of environmental monitoring and integrate temperature and humidity information sending to base stations in order to make basic decisions on desertification. The main problem in this regard is the energy limitation of sensor nodes in wireless sensor networks, which is one of the main challenges in using these nodes due to the lack of a fixed power supply. Because the node consumes the most energy during data transmission, the node that transmits the most data or sends the packets over long distances runs out of energy faster than the others and the network work process is disrupted. Therefore, in this study, a density‐based clustering approach is proposed to integrate data collected from the environment in arid areas for desertification. In the proposed method at each step, the node that has the most residual energy and is highly centralized will be selected to transfer information. The results of experiments for evaluating the performance of the proposed method show that the proposed method balances the energy consumption of the nodes and optimizes the lifespan of the nodes in the wireless sensor network installed in the arid area.

An Improved Energy‐Aware Routing Protocol Using Multiobjective Particular Swarm Optimization Algorithm

The energy of sensor nodes in wireless sensor networks is limited, which is one of the most important challenges due to the lack of a fixed power supply. Because data transmission consumes the most energy of nodes, a node that transmits more packets runs out of energy faster than the others. When the energy of a node comes to the end of a network, the process of network operation may be disrupted. In this case, critical information in the network with the desired quality may not reach the hole and eventually the base stations. Therefore, considering the dynamic topology and distributed nature of wireless sensor networks, designing energy‐efficient routing protocols is the main challenge. In this paper, an energy‐aware routing protocol based on a multiobjective particle swarm optimization algorithm is presented. In the proposed particle swarm optimization algorithm method, the proportionality function for selecting the optimal threaded node is set based on the goals related to service quality including residual energy, link quality, end‐to‐end delay, and delivery rate. The simulation results show that the proposed method consumes less energy and has a longer lifespan compared with the state‐of‐the‐art methods due to balancing the goals related to service quality criteria.

Mathematical modelling and operation parameters analysis of proton exchange membrane fuel cell

The fuel cell is a device which can convert chemical energy from fuel into electrical and thermal energy directly. It has advantages like high power density, fast start-up and high conversion efficiency. Its prospects of application in transportation, fixed power supply and standby power generation are great. Fuel cell is a dynamic complex system with multi-phase, multi-scale and multi-physical fields. Based on the working mechanism of fuel cell, this paper establishes a mathematical model to simulate the electrochemical reaction, material and energy transfer process in fuel cell. The parameters such as temperature, pressure, concentration, current and potential, which are difficult to measure, are visualized to deepen the transfer and counter-reaction in fuel cell. In order to provide important scientific basis for the optimal design and system control of the stack, the mechanism should be understood and the optimum reaction conditions should be found.

Robust Beamforming and Time Allocation for Full-Duplex Wireless-Powered Communication Networks

We propose a joint optimization of beamforming and time allocation for full-duplex (FD) wireless-powered communication networks (WPCNs). In FD-WPCNs, an FD-enabled hybrid access point (HAP) having multiple antennas broadcasts radio frequency (RF) energy to users, and concurrently each user transmits its own information to the HAP. Due to a lack of fixed power supplies at the users, it is difficult for the HAP to have accurate channel state information (CSI) of all links. Therefore, in this letter, a robust algorithm is proposed to maximize the weighted sum rate of the users against the uncertainty of the CSI using the relationship between the weighted sum rate and the weighted sum of mean-square error. Numerical results demonstrate that the proposed algorithm provides robustness against imperfect channel knowledge and benefits of utilizing multiple antennas in the FD-WPCNs.

Throughput Maximization for Two-Way Buffer-Aided and Energy-Harvesting Enabled Multi-Relay Networks

For years, relay communications have been witnessed to extend the network coverage and improve the throughput and reliability of wireless systems. In this paper, we focus on throughput maximization for the two-way buffer-aided relay network with finite data buffers and limited energy battery, wherein relays have no fixed power supply and they replenish energy from the Radio Frequency (RF) signal radiated by source nodes. Specifically, by jointing the time switching and energy splitting for RF energy harvesting, we introduce a three time-subslot transmission model to balance the energy storage and the energy consumption for communication. On top of this transmission model, we formulate an optimization problem for throughput maximization of relay network. We purposely convert the non-convex optimization problem into a convex one by carefully decoupling and relaxing. Further, we theoretically derive the maximum throughput and apply an iterative algorithm to achieve the suboptimal solution based on relay selection and power allocation. In addition to solving the no-delay limited throughput maximization problem, we put forward the solution of the delay limited transmission in the two-way buffer-aided multi-relay networks. Extensive simulations have been conducted to demonstrate that our proposed strategy is able to significantly improve the sum-throughput under transmission energy and delay constraints.

Utility‐based cooperative spectrum leasing scheme for CR networks with hybrid energy supplies

As cognitive radio (CR) technologies developed, cooperative CR networks (CCRNs) have become a potential way to increase the spectrum efficiency. Moreover, as the authors face the problem of energy shortage nowadays, energy harvesting (EH) is considered to be an effective method to alleviate this problem. However, with fitful and random energy arrivals, the energy harvested from natural energy source cannot guarantee satisfactory quality of service in EH networks. Hybrid energy supplies system has emerged as a promising way to solve unstable power supply problems, which mean that the communication terminals in these networks are powered by both fixed power supply and harvested energy. In this study, they propose a novel utility-based cooperative spectrum leasing scheme for CCRNs with hybrid energy supplies. The secondary user (SU) is a cooperative relay powered largely by harvested energy extracted from the radio-frequency signal of the primary user (PU). In this way, SU can shorten the primary data transmission period, and then win the access opportunities for secondary data transmission. They formulate this model as a Stackelberg game. In such a scenario, the PU intends to enhance its revenue and save energy by cooperating with the SU, while the SU tries to improve throughput and minimise the fixed energy consumption. The Stackelberg equilibrium for the proposed scheme is analysed. The experimental results show that the utility of both PU and SU can be improved under this scheme.

Throughput Maximization for Multi-Hop Decode-and-Forward Relay Network With Wireless Energy Harvesting

In this paper, we consider multi-hop wireless networks with decode-and-forward relays. Intermediate relays have no fixed power supplies and thus need to replenish energy via wireless energy harvesting from the source signal. The technique of simultaneous wireless information and power transfer (SWIPT) is utilized between every two adjacent nodes to transport both information and energy. Three general protocols of SWIPT are considered: power-splitting (PS), time-switching (TS), and hybrid which is a combination of PS and TS protocols. For each protocol, we formulate optimization problems to decide optimal PS and TS ratios so as to maximize end-to-end throughput under two schemes. Scheme 1 allows different PS and TS ratios at each relay, and Scheme 2 uses uniform PS and TS ratios for all the relays. The proposed optimization problems are shown to be non-convex. With a series of transformations, we turn the proposed non-convex optimization problems to be convex ones. Insightful analysis of the system performance is presented in the part of numerical results.

Optimal Energy Harvesting Protocols for Wireless Relay Networks

In this paper, we consider a relay network over a flat-fading channel, where the relay has no fixed power supply and thus needs to replenish energy via wireless energy harvesting (EH) from the signals transmitted by the source. We propose a novel hybrid protocol, which is a combination of existing EH protocols, such as power splitting (PS) and time switching (TS). We formulate the optimization problems and derive some explicit results. In particular, we derive the optimal PS and TS ratios at the relay for all three EH protocols to achieve the maximum throughput for information transfer from the source to the destination for both decode-and-forward and amplify-and-forward relaying schemes. We show that the proposed hybrid protocol outperforms both PS and TS protocols.

Diversity-Multiplexing Tradeoff of Dynamic Harvest-and-Forward Cooperation

We analyze the diversity-multiplexing tradeoff (DMT) of the dynamic harvest-and-forward (DHF) cooperation to clearly explain the achievable diversity order. Surprisingly, DHF cooperation with a relay that harvests energy from a wireless source achieves the same DMT as when the relay is connected to a fixed power supply, by supplying the energy harvesting (EH) period to be asymptotically small. For nontrivial EH period, however we show that the same DMT is achieved for a sufficiently small multiplexing gain (or corresponding large diversity gain), beyond which the DMT degrades.

Outage performance of relay selection with spatially random relays using RF energy harvesting

AbstractTo enable green wireless networks, one appealing approach is to deploy energy harvesting (EH) relays to assist the source transmission. Unlike conventional relays relying on fixed power supplies, EH relays make use of the energy collected from the RF radiation of the source node, and thus, they do not introduce extra energy cost to the network. This paper presents an analytical study to assess the efficacy of EH relays when the one with the maximal end‐to‐end signal‐to‐noise ratio is selected to perform data relaying while others perform EH. Because the action (either harvesting energy or forwarding data) of one EH relay affects those of others, exact performance analysis is not tractable. Additionally, relay density and positions may be random, which further complicates the analysis. Our analysis is conducted based on the hypothesis that each EH relay has an equal chance to be selected. This hypothesis allows for analytical tractability and is of importance to EH relays because otherwise some may drain their batteries fast. We identify the conditions under which the aforementioned hypothesis is valid. Our analysis also considers two variants of amplify‐and‐forward relays with and without using channel state information. Numerical results are presented to validate the analysis accuracy along with extensive discussions on the impact of numerous system parameters. Copyright © 2015 John Wiley &amp; Sons, Ltd.

A general utility optimization framework for energy-harvesting-based wireless communications

In recent years, wireless communication systems are expected to achieve more cost-efficient and sustainable operations by replacing conventional fixed power supplies such as batteries with energy harvesting (EH) devices, which could provide electric energy from renewable energy sources (e.g., solar and wind). Such EH power supplies, however, are random and instable in nature, and as a result impose new challenges on reliable communication design and have triggered substantial research interests in EH based wireless communications. Building upon existing works, in this article, we develop a general optimization framework to maximize the utility of EH wireless communication systems. Our framework encapsulates a variety of design problems, such as throughput maximization and outage probability minimization in single-user and multiuser setups, and provides useful guidelines to the practical design of general EH based communication systems with different assumptions over the knowledge of time-varying wireless channels and EH rates at the transmitters.

Analysis of simulation approaches for the breakdown characteristics of SOI high-voltage PMOS in a fixed power supply

A novel simulation approach for the breakdown characteristics of SOI high-voltage (HV) PMOS in a fixed power supply application is proposed. The different optimized parameters for the SOI HV PMOS can be achieved by the conventional and proposed simulation approaches. A SOI variation of lateral doping (VLD) field PMOS, which is widely used in the level-shift circuit is investigated by the conventional and novel simulation approaches. For the level-shift circuit with power supply of 400V, the breakdown voltage (BV) of the optimized SOI VLD field PMOS increases from 520V with the conventional simulation approach to 646V with the proposed simulation approach. Moreover, the corresponding optimized doping concentration of p-drift region with the proposed approach is higher than that with the conventional approach, thus greatly reducing the specific on-resistance (Ron,sp). The SOI VLD field PMOS actually has a more robust breakdown voltage and lower Ron,sp in the fixed power supply. The BV and Ron,sp of SOI HV PMOS can be truly reflected and the effect of reduced bulk field (REBULF) is revealed in the fixed HV power supply by employing the novel simulation approach.

Wireless Information and Power Transfer: A Dynamic Power Splitting Approach

Energy harvesting is a promising solution to prolong the operation time of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the flat-fading channel, where the receiver has no fixed power supplies and thus needs to replenish energy via WEH from the signals sent by the transmitter. We first consider a SISO (single-input single-output) system where the single-antenna receiver cannot decode information and harvest energy independently from the same signal received. Under this practical constraint, we propose a dynamic power splitting (DPS) scheme, where the received signal is split into two streams with adjustable power levels for information decoding and energy harvesting separately based on the instantaneous channel condition that is assumed to be known at the receiver. We derive the optimal power splitting rule at the receiver to achieve various trade-offs between the maximum ergodic capacity for information transfer and the maximum average harvested energy for power transfer, which are characterized by the boundary of a so-called "rate-energy (R-E)" region. Moreover, for the case when the channel state information is also known at the transmitter, we investigate the joint optimization of transmitter power control and receiver power splitting. The achievable R-E region by the proposed DPS scheme is also compared against that by the existing time switching scheme as well as a performance upper bound by ignoring the practical receiver constraint. Finally, we extend the result for optimal DPS to the SIMO (single-input multiple-output) system where the receiver is equipped with multiple antennas. In particular, we investigate a low-complexity power splitting scheme, namely antenna switching, which achieves the near-optimal rate-energy trade-offs as compared to the optimal DPS.

Wireless Information Transfer with Opportunistic Energy Harvesting

Energy harvesting is a promising solution to prolong the operation of energy-constrained wireless networks. In particular, scavenging energy from ambient radio signals, namely wireless energy harvesting (WEH), has recently drawn significant attention. In this paper, we consider a point-to-point wireless link over the narrowband flat-fading channel subject to time-varying co-channel interference. It is assumed that the receiver has no fixed power supplies and thus needs to replenish energy opportunistically via WEH from the unintended interference and/or the intended signal sent by the transmitter. We further assume a single-antenna receiver that can only decode information or harvest energy at any time due to the practical circuit limitation. Therefore, it is important to investigate when the receiver should switch between the two modes of information decoding (ID) and energy harvesting (EH), based on the instantaneous channel and interference condition. In this paper, we derive the optimal mode switching rule at the receiver to achieve various trade-offs between wireless information transfer and energy harvesting. Specifically, we determine the minimum transmission outage probability for delay-limited information transfer and the maximum ergodic capacity for no-delay-limited information transfer versus the maximum average energy harvested at the receiver, which are characterized by the boundary of so-called outage-energy region and region, respectively. Moreover, for the case when the channel state information (CSI) is known at the transmitter, we investigate the joint optimization of transmit power control, information and energy transfer scheduling, and the receiver's mode switching. The effects of circuit energy consumption at the receiver on the achievable rate-energy trade-offs are also characterized. Our results provide useful guidelines for the efficient design of emerging wireless communication systems powered by opportunistic WEH.

An Energy-Efficient, Adiabatic Electrode Stimulator With Inductive Energy Recycling and Feedback Current Regulation

In this paper, we present a novel energy-efficient electrode stimulator. Our stimulator uses inductive storage and recycling of energy in a dynamic power supply. This supply drives an electrode in an adiabatic fashion such that energy consumption is minimized. It also utilizes a shunt current-sensor to monitor and regulate the current through the electrode via feedback, thus enabling flexible and safe stimulation. Since there are no explicit current sources or current limiters, wasteful energy dissipation across such elements is naturally avoided. The dynamic power supply allows efficient transfer of energy both to and from the electrode and is based on a DC-DC converter topology that we use in a bidirectional fashion in forward-buck or reverse-boost modes. In an exemplary electrode implementation intended for neural stimulation, we show how the stimulator combines the efficiency of voltage control and the safety and accuracy of current control in a single low-power integrated-circuit built in a standard .35 μm CMOS process. This stimulator achieves a 2x-3x reduction in energy consumption as compared to a conventional current-source-based stimulator operating from a fixed power supply. We perform a theoretical analysis of the energy efficiency that is in accord with experimental measurements. This theoretical analysis reveals that further improvements in energy efficiency may be achievable with better implementations in the future. Our electrode stimulator could be widely useful for neural, cardiac, retinal, cochlear, muscular and other biomedical implants where low power operation is important.