47 CFR 25.262 - Licensing and domestic coordination requirements for 17/24 GHz BSS space stations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... degree or less from an appendix F location, and may operate at the maximum power flux density limits defined in §§ 25.208(c) and (w) of this part, without coordinating its power flux density levels with... BSS U.S. licensee or permittee that does not comply with the power flux-density limits set forth in...

Optimization and Analysis of a U-Shaped Linear Piezoelectric Ultrasonic Motor Using Longitudinal Transducers

PubMed Central

Yu, Hongpeng; Quan, Qiquan; Tian, Xinqi; Li, He

2018-01-01

A novel U-shaped piezoelectric ultrasonic motor that mainly focused on miniaturization and high power density was proposed, fabricated, and tested in this work. The longitudinal vibrations of the transducers were excited to form the elliptical movements on the driving feet. Finite element method (FEM) was used for design and analysis. The resonance frequencies of the selected vibration modes were tuned to be very close to each other with modal analysis and the movement trajectories of the driving feet were gained with transient simulation. The vibration modes and the mechanical output abilities were tested to evaluate the proposed motor further by a prototype. The maximum output speed was tested to be 416 mm/s, the maximum thrust force was 21 N, and the maximum output power was 5.453 W under frequency of 29.52 kHz and voltage of 100 Vrms. The maximum output power density of the prototype reached 7.59 W/kg, which was even greater than a previous similar motor under the exciting voltage of 200 Vrms. The proposed motor showed great potential for linear driving of large thrust force and high power density. PMID:29518963

Optimization and Analysis of a U-Shaped Linear Piezoelectric Ultrasonic Motor Using Longitudinal Transducers.

PubMed

Yu, Hongpeng; Quan, Qiquan; Tian, Xinqi; Li, He

2018-03-07

A novel U-shaped piezoelectric ultrasonic motor that mainly focused on miniaturization and high power density was proposed, fabricated, and tested in this work. The longitudinal vibrations of the transducers were excited to form the elliptical movements on the driving feet. Finite element method (FEM) was used for design and analysis. The resonance frequencies of the selected vibration modes were tuned to be very close to each other with modal analysis and the movement trajectories of the driving feet were gained with transient simulation. The vibration modes and the mechanical output abilities were tested to evaluate the proposed motor further by a prototype. The maximum output speed was tested to be 416 mm/s, the maximum thrust force was 21 N, and the maximum output power was 5.453 W under frequency of 29.52 kHz and voltage of 100 V rms . The maximum output power density of the prototype reached 7.59 W/kg, which was even greater than a previous similar motor under the exciting voltage of 200 V rms . The proposed motor showed great potential for linear driving of large thrust force and high power density.

Modeling of a resonant heat engine

NASA Astrophysics Data System (ADS)

Preetham, B. S.; Anderson, M.; Richards, C.

2012-12-01

A resonant heat engine in which the piston assembly is replaced by a sealed elastic cavity is modeled and analyzed. A nondimensional lumped-parameter model is derived and used to investigate the factors that control the performance of the engine. The thermal efficiency predicted by the model agrees with that predicted from the relation for the Otto cycle based on compression ratio. The predictions show that for a fixed mechanical load, increasing the heat input results in increased efficiency. The output power and power density are shown to depend on the loading for a given heat input. The loading condition for maximum output power is different from that required for maximum power density.

Effect of salt concentration and mediators in salt bridge microbial fuel cell for electricity generation from synthetic wastewater.

PubMed

Sevda, Surajbhan; Sreekrishnan, T R

2012-01-01

The aim of this study was to investigate the feasibility of using agar salt bridges for proton transport in Microbial Fuel Cells (MFC). It also tries to elucidate and effect of mediators on electricity production from wastewaters through experimentation using a simulated wastewater. In order to offset the very high cost of proton exchange membrane, salt bridges have been used in dual chamber MFCs. When the concentration of salt was varied in agar salt bridges from 1% to 10%, the volumetric power density changed from 1.71 to 84.99 mW/m(3) with a concomitant variation in power density from 0.32 to 16.02 mW/m(2). The maximum power density was observed at 5% salt concentration with 10% agar, which was accompanied by 88.41% COD reduction. In the case of methylene blue (0.01 mM) as the electron mediator, the voltage and current generation were 0.551 V and 0.47 mA, respectively. A maximum open circuit voltage of 0.718 V was seen at 0.08 mM methylene blue concentration, whereas maximum power densities of 17.59 mW/m(2) and 89.22 mW/m(3) were obtained. Different concentrations of neutral red were also tried out as mediators. A maximum open circuit voltage of 0.730 V was seen at 0.01 mM neutral red, corresponding to a power density of 12.02 mW/m(2) (volumetric power density of 60.97 mW/m(3)). Biofilm formation on the electrode surface was not observed in the presence of mediators, but was present in the absence of mediators. The results clearly demonstrated the feasibility to use agar salt bridge for proton transport and role of mediators in MFCs to generate electricity.

Enhancing substrate utilization and power production of a microbial fuel cell with nitrogen-doped carbon aerogel as cathode catalyst.

PubMed

Tardy, Gábor Márk; Lóránt, Bálint; Lóka, Máté; Nagy, Balázs; László, Krisztina

2017-07-01

Catalytic efficiency of a nitrogen-doped, mesoporous carbon aerogel cathode catalyst was investigated in a two-chambered microbial fuel cell (MFC) applying graphite felt as base material for cathode and anode, utilizing peptone as carbon source. This mesoporous carbon aerogel containing catalyst layer on the cathode increased the maximum power density normalized to the anode volume to 2.7 times higher compared to the maximum power density obtained applying graphite felt cathode without the catalyst layer. At high (2 and 3) cathode/anode volume ratios, maximum power density exceeded 40 W m -3 . At the same time, current density and specific substrate utilization rate increased by 58% resulting in 31.9 A m -3 and 18.8 g COD m -3  h -1 , respectively (normalized to anode volume). Besides the increase of the power and the rate of biodegradation, the investigated catalyst decreased the internal resistance from the range of 450-600 to 350-370 Ω. Although Pt/C catalyst proved to be more efficient, a considerable decrease in the material costs might be achieved by substituting it with nitrogen-doped carbon aerogel in MFCs. Such cathode still displays enhanced catalytic effect.

Parametric design criteria of an updated thermoradiative cell operating at optimal states

NASA Astrophysics Data System (ADS)

Zhang, Xin; Peng, Wanli; Lin, Jian; Chen, Xiaohang; Chen, Jincan

2017-11-01

An updated mode of the thermoradiative cell (TRC) with sub-band gap and non-radiative losses is proposed, which can efficiently harvest moderate-temperature heat energy and convert a part of heat into electricity. It is found that when the TRC is operated between the heat source at 800 K and the environment at 300 K , its maximum power output density and efficiency can attain 1490 W m-2 and 27.2 % , respectively. Moreover, the effects of some key parameters including the band gap and voltage output on the performance of the TRC are discussed. The optimally working regions of the power density, efficiency, band gap, and voltage output are determined. The maximum efficiency and power output density of the TRC operated at different temperatures are calculated and compared with those of thermophotovoltaic cells (TPVCs) and thermionic energy converters (TECs), and consequently, it is revealed that the maximum efficiency of the TRC operated at the moderate-temperature range is much higher than that of the TEC or the TPVC and the maximum power output density of the TRC is larger than that of the TEC but smaller than that of the TPVC. Particularly, the TRC is manufactured more easily than the near-field TPVC possessing a nanoscale vacuum gap. The results obtained will be helpful for engineers to choose the semiconductor materials, design and manufacture TRCs, and control operative conditions.

The Evaluation of HOMER as a Marine Corps Expeditionary Energy Predeployment Tool

DTIC Science & Technology

2010-09-01

experiment was used to ensure the HOMER models were accurate. Following the calibration, the concept of expeditionary energy density as it pertains to power ...Brigade–Afghanistan xvi MEP Mobile Electric Power MPP Maximum Power Point MPPT Maximum Power Point Tracker NASA National Aeronautics and...process was used to analyze HOMER’s modeling capability: • Conduct photovoltaic (PV) experiment, • Develop a calibration process to match the HOMER

The Evaluation of HOMER as a Marine Corps Expeditionary Energy Pre-deployment Tool

DTIC Science & Technology

2010-11-21

used to ensure the HOMER models were accurate. Following the calibration, the concept of expeditionary energy density as it pertains to power ...MEP Mobile Electric Power MPP Maximum Power Point MPPT Maximum Power Point Tracker NASA National Aeronautics and Space Administration...process was used to analyze HOMER’s modeling capability: • Conduct photovoltaic (PV) experiment, • Develop a calibration process to match the HOMER

Design of experiments with four-factors for a PEM fuel cell optimization

NASA Astrophysics Data System (ADS)

Olteanu, V.; Pǎtularu, L.; Popescu, C. L.; Popescu, M. O.; Crǎciunescu, A.

2017-07-01

Nowadays, many research efforts are allocated for the development of fuel cells, since they constitute a carbon-free electrical energy generator which can be used for stationary, mobile and portable applications. The maximum value of the delivered power of a fuel cell depends on many factors as: the height of plates' channels, the stoichiometry level of the air flow, the air pressure for the cathode, and of the actual operating electric current density. In this paper, two levels, full four-factors factorial experiment has been designed in order to obtain the appropriate response surface which approximates the maximum delivered power dependence of the above-mentioned factors. The optimum set of the fuel-cell factors which determine the maximum value of the delivered power was determined and a comparison between simulated and measured optimal Power versus Current Density characteristics is given.

Cloth-Based Power Shirt for Wearable Energy Harvesting and Clothes Ornamentation.

PubMed

Li, Suling; Zhong, Qize; Zhong, Junwen; Cheng, Xiaofeng; Wang, Bo; Hu, Bin; Zhou, Jun

2015-07-15

Harvesting ambient mechanical energy from human body motion has attracted great research interest. In this work, a power shirt based on triboelectrification and the electrostatic induction effect between fluorinated ethylene propylene (FEP) and external objects is demonstrated. This power shirt can effectively convert the ambient mechanical energy into electric power, and the working mechanism is systematically discussed. A maximum short-circuit current density of ∼0.37 μA/cm2 and a maximum peak power density of ∼4.65 μW/cm2 were achieved. Simultaneously, 11 blue LEDs were lit by sliding the sleeve and power shirt, indicating the potential application of the power shirt in clothes ornamentation and risk warning. This study develops an efficient path for harvesting human body energy and promoting the development of wearable electronics and smart garments.

Single chamber microbial fuel cell with spiral anode for dairy wastewater treatment.

PubMed

Mardanpour, Mohammad Mahdi; Nasr Esfahany, Mohsen; Behzad, Tayebeh; Sedaqatvand, Ramin

2012-01-01

This study reports on the fabrication of a novel annular single chamber microbial fuel cell (ASCMFC) with spiral anode. The stainless steel mesh anode with graphite coating was used as anode. Dairy wastewater, containing complex organic matter, was used as substrate. ASCMFC had been operated for 450 h and results indicated a high open circuit voltage (about 810 mV) compared with previously published results. The maximum power density of 20.2 W/m(3) obtained in this study is significantly greater than the power densities reported in previous studies. Besides, a maximum coulombic efficiency of 26.87% with 91% COD removal was achieved. Good bacterial adhesion on the spiral anode is clearly shown in SEM micrographs. High power density and a successful performance in wastewater treatment in ASCMFC suggest it as a promising alternative to conventional MFCs for power generation and wastewater treatment. ASCMFC performance as a power generator was characterized based on polarization behavior and cell potentials. Copyright © 2012 Elsevier B.V. All rights reserved.

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Code of Federal Regulations, 2011 CFR

2011-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the... swept volume from the design specifications for the cylinders using enough significant figures to allow...

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Code of Federal Regulations, 2010 CFR

2010-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the... swept volume from the design specifications for the cylinders using enough significant figures to allow...

40 CFR 1042.140 - Maximum engine power, displacement, power density, and maximum in-use engine speed.

Code of Federal Regulations, 2014 CFR

2014-07-01

... ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM NEW AND IN-USE... procedures of 40 CFR part 1065, based on the manufacturer's design and production specifications for the... swept volume from the design specifications for the cylinders using enough significant figures to allow...

Uncooled pulsed zinc oxide semiconductor laser

NASA Astrophysics Data System (ADS)

Bogdankevich, O. V.; Darznek, S. A.; Zverev, M. M.; Kostin, N. N.; Krasavina, E. M.

1985-02-01

An optimized ZnO laser which operates at ambient temperature without cooling is reported, along with extension of the design to form a multielement high-power laser. ZnO single crystal plane-parallel wafers 0.22 mm thick, covered with total and semi-transparent coatings, were exposed to a 200 keV electron beam with a 10 nsec pulse and a current density up to 1 kA/sq cm. No damage was observed in the crystals at saturation. A 7 percent maximum efficiency at a reflection coefficient (RC) of 0.4 was associated with a maximum output of 25 kW and a light power density of 3 MW/sq cm. Cementing a ZnO wafer to a sapphire substrate, applying the same type of coatings and working with a RC of 0.6 yielded a maximum power of 300 kW/sq cm.

Bioelectricity generation in microbial fuel cell using natural microflora and isolated pure culture bacteria from anaerobic palm oil mill effluent sludge.

PubMed

Nor, Muhamad Hanif Md; Mubarak, Mohd Fahmi Muhammad; Elmi, Hassan Sh Abdirahman; Ibrahim, Norahim; Wahab, Mohd Firdaus Abdul; Ibrahim, Zaharah

2015-08-01

A double-chambered membrane microbial fuel cell (MFC) was constructed to investigate the potential use of natural microflora anaerobic palm oil mill effluent (POME) sludge and pure culture bacteria isolated from anaerobic POME sludge as inoculum for electricity generation. Sterilized final discharge POME was used as the substrate with no addition of nutrients. MFC operation using natural microflora anaerobic POME sludge showed a maximum power density and current density of 85.11mW/m(2) and 91.12mA/m(2) respectively. Bacterial identification using 16S rRNA analysis of the pure culture isolated from the biofilm on the anode MFC was identified as Pseudomonas aeruginosa strain ZH1. The electricity generated in MFC using P. aeruginosa strain ZH1 showed maximum power density and current density of 451.26mW/m(2) and 654.90mA/m(2) respectively which were five times higher in power density and seven times higher in current density compared to that of MFC using anaerobic POME sludge. Copyright © 2015 Elsevier Ltd. All rights reserved.

Thermodynamic, energy efficiency, and power density analysis of reverse electrodialysis power generation with natural salinity gradients.

PubMed

Yip, Ngai Yin; Vermaas, David A; Nijmeijer, Kitty; Elimelech, Menachem

2014-05-06

Reverse electrodialysis (RED) can harness the Gibbs free energy of mixing when fresh river water flows into the sea for sustainable power generation. In this study, we carry out a thermodynamic and energy efficiency analysis of RED power generation, and assess the membrane power density. First, we present a reversible thermodynamic model for RED and verify that the theoretical maximum extractable work in a reversible RED process is identical to the Gibbs free energy of mixing. Work extraction in an irreversible process with maximized power density using a constant-resistance load is then examined to assess the energy conversion efficiency and power density. With equal volumes of seawater and river water, energy conversion efficiency of ∼ 33-44% can be obtained in RED, while the rest is lost through dissipation in the internal resistance of the ion-exchange membrane stack. We show that imperfections in the selectivity of typical ion exchange membranes (namely, co-ion transport, osmosis, and electro-osmosis) can detrimentally lower efficiency by up to 26%, with co-ion leakage being the dominant effect. Further inspection of the power density profile during RED revealed inherent ineffectiveness toward the end of the process. By judicious early discontinuation of the controlled mixing process, the overall power density performance can be considerably enhanced by up to 7-fold, without significant compromise to the energy efficiency. Additionally, membrane resistance was found to be an important factor in determining the power densities attainable. Lastly, the performance of an RED stack was examined for different membrane conductivities and intermembrane distances simulating high performance membranes and stack design. By thoughtful selection of the operating parameters, an efficiency of ∼ 37% and an overall gross power density of 3.5 W/m(2) represent the maximum performance that can potentially be achieved in a seawater-river water RED system with low-resistance ion exchange membranes (0.5 Ω cm(2)) at very small spacing intervals (50 μm).

Power enhancement of piezoelectric transformers by adding heat transfer equipment.

PubMed

Su, Yu-Hao; Liu, Yuan-Ping; Vasic, Dejan; Wu, Wen-Jong; Costa, François; Lee, Chih-Kung

2012-10-01

It is known that piezoelectric transformers have several inherent advantages compared with conventional electromagnetic transformers. However, the maximum power capacity of piezoelectric transformers is not as large as electromagnetic transformers in practice, especially in the case of high output current. The theoretical power density of piezoelectric transformers calculated by stress boundary can reach 330 W/cm(3), but no piezoelectric transformer has ever reached such a high power density in practice. The power density of piezoelectric transformers is limited to 33 W/cm(3) in practical applications. The underlying reason is that the maximum passing current of the piezoelectric material (mechanical current) is limited by the temperature rise caused by heat generation. To increase this current and the power capacity, we proposed to add a thermal pad to the piezoelectric transformer to dissipate heat. The experimental results showed that the proposed techniques can increase by 3 times the output current of the piezoelectric transformer. A theoretical-phenomenological model which explains the relationship between vibration velocity and generated heat is also established to verify the experimental results.

47 CFR 15.407 - General technical requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... transmitting antennas of directional gain greater than 6 dBi are used, both the maximum conducted output power and the peak power spectral density shall be reduced by the amount in dB that the directional gain of... density shall not exceed 11 dBm in any 1 megahertz band. If transmitting antennas of directional gain...

47 CFR 15.407 - General technical requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... transmitting antennas of directional gain greater than 6 dBi are used, both the maximum conducted output power and the peak power spectral density shall be reduced by the amount in dB that the directional gain of... density shall not exceed 11 dBm in any 1 megahertz band. If transmitting antennas of directional gain...

47 CFR 15.407 - General technical requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... transmitting antennas of directional gain greater than 6 dBi are used, both the maximum conducted output power and the peak power spectral density shall be reduced by the amount in dB that the directional gain of... density shall not exceed 11 dBm in any 1 megahertz band. If transmitting antennas of directional gain...

Spatial Distribution of Oxygen Chemical Potential under Potential Gradients and Theoretical Maximum Power Density with 8YSZ Electrolyte

NASA Astrophysics Data System (ADS)

Lim, Dae-Kwang; Im, Ha-Ni; Song, Sun-Ju

2016-01-01

The maximum power density of SOFC with 8YSZ electrolyte as the function of thickness was calculated by integrating partial conductivities of charge carriers under various DC bias conditions at a fixed oxygen chemical potential gradient at both sides of the electrolyte. The partial conductivities were successfully taken using the Hebb-Wagner polarization method as a function of temperature and oxygen partial pressure, and the spatial distribution of oxygen partial pressure across the electrolyte was calculated based on Choudhury and Patterson’s model by considering zero electrode polarization. At positive voltage conditions corresponding to SOFC and SOEC, the high conductivity region was expanded, but at negative cell voltage condition, the low conductivity region near n-type to p-type transition was expanded. In addition, the maximum power density calculated from the current-voltage characteristic showed approximately 5.76 W/cm2 at 700 oC with 10 μm thick-8YSZ, while the oxygen partial pressure of the cathode and anode sides maintained ≈0.21 and 10-22 atm.

A novel high-density power energy harvesting methodology for transmission line online monitoring devices.

PubMed

Liu, Yadong; Xie, Xiaolei; Hu, Yue; Qian, Yong; Sheng, Gehao; Jiang, Xiuchen; Liu, Yilu

2016-07-01

This paper presents a novel energy-harvesting model which takes the primary current, secondary turns, dimension, the magnitude of magnetic flux density B, and the core loss resistance into consideration systematically. The relationship among the potential maximum output power, the dimension of energy harvesting coil (EHC), the load type of EHC, and the secondary turns is predicted by theoretical analysis and further verified by experiments. A high power density harvester is also developed and tested. It is shown that the power density of this novel harvester is 0.7 mW/g at 10 A, which is more than 2 times powerful than the traditional ones. Hence, it could lighten the half weight of the harvester at the same conditions.

Modeling of the thermal physical process and study on the reliability of linear energy density for selective laser melting

NASA Astrophysics Data System (ADS)

Xiang, Zhaowei; Yin, Ming; Dong, Guanhua; Mei, Xiaoqin; Yin, Guofu

2018-06-01

A finite element model considering volume shrinkage with powder-to-dense process of powder layer in selective laser melting (SLM) is established. Comparison between models that consider and do not consider volume shrinkage or powder-to-dense process is carried out. Further, parametric analysis of laser power and scan speed is conducted and the reliability of linear energy density as a design parameter is investigated. The results show that the established model is an effective method and has better accuracy allowing for the temperature distribution, and the length and depth of molten pool. The maximum temperature is more sensitive to laser power than scan speed. The maximum heating rate and cooling rate increase with increasing scan speed at constant laser power and increase with increasing laser power at constant scan speed as well. The simulation results and experimental result reveal that linear energy density is not always reliable using as a design parameter in the SLM.

New GaN based HEMT with Si3N4 or un-doped region in the barrier for high power applications

NASA Astrophysics Data System (ADS)

Razavi, S. M.; Tahmasb Pour, S.; Najari, P.

2018-06-01

New AlGaN/GaN high electron mobility transistors (HEMTs) that their barrier layers under the gate are divided into two regions horizontally are presented in this work. Upper region is Si3N4 (SI-HEMT) or un-doped AlGaN (UN-HEMT) and lower region is AlGaN with heavier doping compared to barrier layer. Upper region in SI-HEMT and UN-HEMT reduces peak electric field in the channel and then improves breakdown voltage considerably. Lower region increases electron density in the two dimensional electron gas (2-DEG) and enhances drain current significantly. For instance, saturated drain current in SI-HEMT is about 100% larger than that in the conventional one. Moreover, the maximum breakdown voltage in the proposed structures is 65 V. This value is about 30% larger than that in the conventional transistor (50 V). Also, suggested structure reduces short channel effect such as DIBL. The maximum gm is obtained in UN-HEMT and conventional devices. Proposed structures improve breakdown voltage and saturated drain current and then enhance maximum output power density. Maximum output power density in the new structures is about 150% higher than that in the conventional.

Cadmium recovery by coupling double microbial fuel cells.

PubMed

Choi, Chansoo; Hu, Naixu; Lim, Bongsu

2014-10-01

Cr(VI)-MFC of the double microbial fuel cell (d-MFC) arrangement could successfully complement the insufficient voltage and power needed to recover cadmium metal from Cd(II)-MFC, which operated as a redox-flow battery. It was also possible to drain electrical energy from the d-MFC by an additional passage. The highest maximum utilization power density (22.5Wm(-2)) of Cr(VI)-MFC, with the cathode optimized with sulfate buffer, was 11.3times higher than the highest power density directly supplied to Cd(II)-MFC (2.0Wm(-2)). Cr(VI)-MFC could generate 3times higher power with the additional passage than without it; and the current density for the former was 4.2times higher than the latter at the same maximum power point (38.0Am(-2) vs. 9.0Am(-2)). This boosting phenomenon could be explained by the Le Chatelier's principle, which addresses the rate of electron-hole pair formation that can be accelerated by quickly removing electrons generated by microorganisms. Copyright © 2014 Elsevier Ltd. All rights reserved.

Maximizing power generation from dark fermentation effluents in microbial fuel cell by selective enrichment of exoelectrogens and optimization of anodic operational parameters.

PubMed

Varanasi, Jhansi L; Sinha, Pallavi; Das, Debabrata

2017-05-01

To selectively enrich an electrogenic mixed consortium capable of utilizing dark fermentative effluents as substrates in microbial fuel cells and to further enhance the power outputs by optimization of influential anodic operational parameters. A maximum power density of 1.4 W/m 3 was obtained by an enriched mixed electrogenic consortium in microbial fuel cells using acetate as substrate. This was further increased to 5.43 W/m 3 by optimization of influential anodic parameters. By utilizing dark fermentative effluents as substrates, the maximum power densities ranged from 5.2 to 6.2 W/m 3 with an average COD removal efficiency of 75% and a columbic efficiency of 10.6%. A simple strategy is provided for selective enrichment of electrogenic bacteria that can be used in microbial fuel cells for generating power from various dark fermentative effluents.

High Performance Microbial Fuel Cells and Supercapacitors Using Micro-Electro-Mechanical System (MEMS) Technology

NASA Astrophysics Data System (ADS)

Ren, Hao

A Microbial fuel cell (MFC) is a bio-inspired carbon-neutral, renewable electrochemical converter to extract electricity from catabolic reaction of micro-organisms. It is a promising technology capable of directly converting the abundant biomass on the planet into electricity and potentially alleviate the emerging global warming and energy crisis. The current and power density of MFCs are low compared with conventional energy conversion techniques. Since its debut in 2002, many studies have been performed by adopting a variety of new configurations and structures to improve the power density. The reported maximum areal and volumetric power densities range from 19 mW/m2 to 1.57 W/m2 and from 6.3 W/m3 to 392 W/m 3, respectively, which are still low compared with conventional energy conversion techniques. In this dissertation, the impact of scaling effect on the performance of MFCs are investigated, and it is found that by scaling down the characteristic length of MFCs, the surface area to volume ratio increases and the current and power density improves. As a result, a miniaturized MFC fabricated by Micro-Electro-Mechanical System (MEMS) technology with gold anode is presented in this dissertation, which demonstrate a high power density of 3300 W/m3. The performance of the MEMS MFC is further improved by adopting anodes with higher surface area to volume ratio, such as carbon nanotube (CNT) and graphene based anodes, and the maximum power density is further improved to a record high power density of 11220 W/m3. A novel supercapacitor by regulating the respiration of the bacteria is also presented, and a high power density of 531.2 A/m2 (1,060,000 A/m3) and 197.5 W/m2 (395,000 W/m3), respectively, are marked, which are one to two orders of magnitude higher than any previously reported microbial electrochemical techniques.

Investigating the Effect of Titanium Dioxide (TiO2) Pollution on the Performance of the Mono-crystalline Solar Module

NASA Astrophysics Data System (ADS)

Ahmed Darwish, Zeki; Sopian, K.; Kazem, Hussein A.; Alghoul, M. A.; Alawadhi, Hussain

2017-11-01

This paper presents a study of titanium oxide TiO2 as one of the components of dust pollution affecting the PV performance. This pollutant can be found in various quantities in different locations around the world. The production of energy by different types of photovoltaic systems is very sensitive and depends on various environmental factors. Dust is one of the main contributing factors, yet the type of the dust is often neglected when studying the behaviour of the solar panel. In this experimental work we have studied the performance of the monocrystalline solar module as affected by the density of TiO2. The reduction of the PV module power caused by titanium dioxide under various mass densities was investigated. The results showed that the TiO2 has a significant effect on the PV output power. The dust density varied between 0-125 g.m-2. The corresponding reduction of the PV output power increased from 0 to 86.7%. This is based on various influencing parameters such as: short circuit current (Isc), maximum current (Im), open circuit voltage (Voc), maximum voltage (Vm), maximum power (Pm) and efficiency (E). Two functions are proposed as a mathematical model in order to explain this behaviour, namely the exponential and Fourier functions. The coefficients of all general models are valid for this type of dust with a density value ranging from 0-125 g.m-2.

Design and analysis of an unconventional permanent magnet linear machine for energy harvesting

NASA Astrophysics Data System (ADS)

Zeng, Peng

This Ph.D. dissertation proposes an unconventional high power density linear electromagnetic kinetic energy harvester, and a high-performance two-stage interface power electronics to maintain maximum power abstraction from the energy source and charge the Li-ion battery load with constant current. The proposed machine architecture is composed of a double-sided flat type silicon steel stator with winding slots, a permanent magnet mover, coil windings, a linear motion guide and an adjustable spring bearing. The unconventional design of the machine is that NdFeB magnet bars in the mover are placed with magnetic fields in horizontal direction instead of vertical direction and the same magnetic poles are facing each other. The derived magnetic equivalent circuit model proves the average air-gap flux density of the novel topology is as high as 0.73 T with 17.7% improvement over that of the conventional topology at the given geometric dimensions of the proof-of-concept machine. Subsequently, the improved output voltage and power are achieved. The dynamic model of the linear generator is also developed, and the analytical equations of output maximum power are derived for the case of driving vibration with amplitude that is equal, smaller and larger than the relative displacement between the mover and the stator of the machine respectively. Furthermore, the finite element analysis (FEA) model has been simulated to prove the derived analytical results and the improved power generation capability. Also, an optimization framework is explored to extend to the multi-Degree-of-Freedom (n-DOF) vibration based linear energy harvesting devices. Moreover, a boost-buck cascaded switch mode converter with current controller is designed to extract the maximum power from the harvester and charge the Li-ion battery with trickle current. Meanwhile, a maximum power point tracking (MPPT) algorithm is proposed and optimized for low frequency driving vibrations. Finally, a proof-of-concept unconventional permanent magnet (PM) linear generator is prototyped and tested to verify the simulation results of the FEA model. For the coil windings of 33, 66 and 165 turns, the output power of the machine is tested to have the output power of 65.6 mW, 189.1 mW, and 497.7 mW respectively with the maximum power density of 2.486 mW/cm3.

Analysis of chitin particle size on maximum power generation, power longevity, and Coulombic efficiency in solid-substrate microbial fuel cells

NASA Astrophysics Data System (ADS)

Rezaei, Farzaneh; Richard, Tom L.; Logan, Bruce E.

Microbial fuel cells (MFCs) produce bioelectricity from a wide variety of organic and inorganic substrates. Chitin can be used as a slowly degrading substrate in MFCs and thus as a long-term fuel to sustain power by these devices in remote locations. However, little is known about the effects of particle size on power density and length of the power cycle (longevity). We therefore examined power generation from chitin particles sieved to produce three average particle sizes (0.28, 0.46 and 0.78 mm). The longevity increased from 9 to 33 days with an increase in the particle diameter from 0.28 to 0.78 mm. Coulombic efficiency also increased with particle size from 18% to 56%. The maximum power density was lower for the largest (0.78 mm) particles (176 mW m -2), with higher power densities for the 0.28 mm (272 mW m -2) and 0.46 mm (252 mW m -2) particle sizes. The measured lifetimes of these particles scaled with particle diameter to the 1.3 power. Application of a fractal dissolution model indicates chitin particles had a three-dimensional fractal dimension between 2 and 2.3. These results demonstrate particles can be used as a sustainable fuel in MFCs, but that particle sizes will need to be controlled to achieve desired power levels.

Measurements of uranium mass confined in high density plasmas

NASA Technical Reports Server (NTRS)

Stoeffler, R. C.

1976-01-01

An X-ray absorption method for measuring the amount of uranium confined in high density, rf-heated uranium plasmas is described. A comparison of measured absorption of 8 keV X-rays with absorption calculated using Beer Law indicated that the method could be used to measure uranium densities from 3 times 10 to the 16th power atoms/cu cm to 5 times 10 to the 18th power atoms/cu cm. Tests were conducted to measure the density of uranium in an rf-heated argon plasma with UF6 infection and with the power to maintain the discharge supplied by a 1.2 MW rf induction heater facility. The uranium density was measured as the flow rate through the test chamber was varied. A maximum uranium density of 3.85 times 10 to the 17th power atoms/cu cm was measured.

Comparison of high-voltage ac and pulsed operation of a surface dielectric barrier discharge

NASA Astrophysics Data System (ADS)

Williamson, James M.; Trump, Darryl D.; Bletzinger, Peter; Ganguly, Biswa N.

2006-10-01

A surface dielectric barrier discharge (DBD) in atmospheric pressure air was excited either by low frequency (0.3-2 kHz) high-voltage ac or by short, high-voltage pulses at repetition rates from 50 to 600 pulses s-1. The short-pulse excited discharge was more diffuse and did not have the pronounced bright multiple cathode spots observed in the ac excited discharge. The discharge voltage, current and average power deposited into the discharge were calculated for both types of excitation. As a measure of plasma-chemical efficiency, the ozone number density was measured by UV absorption as a function of average deposited power. The density of ozone produced by ac excitation did not increase so rapidly as that produced by short-pulse excitation as a function of average power, with a maximum measured density of ~3 × 1015 cm-3 at 25 W. The maximum ozone production achieved by short-pulse excitation was ~8.5 × 1015 cm-3 at 20 W, which was four times greater than that achieved by ac excitation at the same power level.

Pulsed and CW adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser system for surgical laser soft tissue ablation applications.

PubMed

Huang, Yize; Jivraj, Jamil; Zhou, Jiaqi; Ramjist, Joel; Wong, Ronnie; Gu, Xijia; Yang, Victor X D

2016-07-25

A surgical laser soft tissue ablation system based on an adjustable 1942 nm single-mode all-fiber Tm-doped fiber laser operating in pulsed or CW mode with nitrogen assistance is demonstrated. Ex vivo ablation on soft tissue targets such as muscle (chicken breast) and spinal cord (porcine) with intact dura are performed at different ablation conditions to examine the relationship between the system parameters and ablation outcomes. The maximum laser average power is 14.4 W, and its maximum peak power is 133.1 W with 21.3 μJ pulse energy. The maximum CW power density is 2.33 × 10⁶ W/cm² and the maximum pulsed peak power density is 2.16 × 10⁷ W/cm². The system parameters examined include the average laser power in CW or pulsed operation mode, gain-switching frequency, total ablation exposure time, and the input gas flow rate. The ablation effects were measured by microscopy and optical coherence tomography (OCT) to evaluate the ablation depth, superficial heat-affected zone diameter (HAZD) and charring diameter (CD). Our results conclude that the system parameters can be tailored to meet different clinical requirements such as ablation for soft tissue cutting or thermal coagulation for future applications of hemostasis.

Collective effects on the wakefield and stopping power of an ion beam pulse in plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Ling-yu; University of Chinese Academy of Sciences, Beijing 100049; Zhao, Xiao-ying

A two-dimensional (2D) particle-in-cell simulation is carried out to study the collective effects on the wakefield and stopping power for a hydrogen ion beam pulse propagation in hydrogen plasmas. The dependence of collective effects on the beam velocity and density is obtained and discussed. For the beam velocity, it is found that the collective effects have the strongest impact on the wakefield as well as the stopping power in the case of the intermediate beam velocities, in which the stopping power is also the largest. For the beam density, it is found that at low beam densities, the collective contributionmore » to the stopping power increase linearly with the increase of the beam density, which corresponds well to the results calculated using the dielectric theory. However, at high beam densities, our results show that after reaching a maximum value, the collective contribution to the stopping power starts to decrease significantly with the increase of the beam density. Besides, at high beam densities, the wakefield loses typical V-shaped cone structures, and the wavelength of the oscillation wakefield increases as the beam density increases.« less

Air-Cooled Heat Exchanger for High-Temperature Power Electronics: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Waye, S. K.; Lustbader, J.; Musselman, M.

2015-05-06

This work demonstrates a direct air-cooled heat exchanger strategy for high-temperature power electronic devices with an application specific to automotive traction drive inverters. We present experimental heat dissipation and system pressure curves versus flow rate for baseline and optimized sub-module assemblies containing two ceramic resistance heaters that provide device heat fluxes. The maximum allowable junction temperature was set to 175 deg.C. Results were extrapolated to the inverter scale and combined with balance-of-inverter components to estimate inverter power density and specific power. The results exceeded the goal of 12 kW/L and 12 kW/kg for power density and specific power, respectively.

Regenerative braking systems with torsional springs made of carbon nanotube yarn

NASA Astrophysics Data System (ADS)

Liu, S.; Martin, C.; Lashmore, D.; Schauer, M.; Livermore, C.

2014-11-01

The demonstration of large stroke, high energy density and high power density torsional springs based on carbon nanotube (CNT) yarns is reported, as well as their application as an energy-storing actuator for regenerative braking systems. Originally untwisted CNT yarn is cyclically loaded and unloaded in torsion, with the maximum rotation angle increasing until failure. The maximum extractable energy density is measured to be as high as 6.13 kJ/kg. The tests also reveal structural reorganization and hysteresis in the torsional loading curves. A regenerative braking system is built to capture the kinetic energy of a wheel and store it as elastic energy in twisted CNT yarns. When the yam's twist is released, the stored energy reaccelerates the wheel. The measured energy and mean power densities of the CNT yarns in the simple regenerative braking system are up to 4.69 kJ/kg and 1.21 kW/kg, respectively. A slightly lower energy density of up to 1.23 kJ/kg and a 0.29 kW/kg mean power density are measured for the CNT yarns in a more complex system that mimics a unidirectional rotating regenerative braking mechanism. The lower energy densities for CNT yarns in the regenerative braking systems as compared with the yarns themselves reflect the frictional losses of the regenerative systems.

On the probability distribution function of the mass surface density of molecular clouds. I

NASA Astrophysics Data System (ADS)

Fischera, Jörg

2014-05-01

The probability distribution function (PDF) of the mass surface density is an essential characteristic of the structure of molecular clouds or the interstellar medium in general. Observations of the PDF of molecular clouds indicate a composition of a broad distribution around the maximum and a decreasing tail at high mass surface densities. The first component is attributed to the random distribution of gas which is modeled using a log-normal function while the second component is attributed to condensed structures modeled using a simple power-law. The aim of this paper is to provide an analytical model of the PDF of condensed structures which can be used by observers to extract information about the condensations. The condensed structures are considered to be either spheres or cylinders with a truncated radial density profile at cloud radius rcl. The assumed profile is of the form ρ(r) = ρc/ (1 + (r/r0)2)n/ 2 for arbitrary power n where ρc and r0 are the central density and the inner radius, respectively. An implicit function is obtained which either truncates (sphere) or has a pole (cylinder) at maximal mass surface density. The PDF of spherical condensations and the asymptotic PDF of cylinders in the limit of infinite overdensity ρc/ρ(rcl) flattens for steeper density profiles and has a power law asymptote at low and high mass surface densities and a well defined maximum. The power index of the asymptote Σ- γ of the logarithmic PDF (ΣP(Σ)) in the limit of high mass surface densities is given by γ = (n + 1)/(n - 1) - 1 (spheres) or by γ = n/ (n - 1) - 1 (cylinders in the limit of infinite overdensity). Appendices are available in electronic form at http://www.aanda.org

Neutral-depletion-induced axially asymmetric density in a helicon source and imparted thrust

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Takao, Yoshinori; Ando, Akira

2016-02-01

The high plasma density downstream of the source is observed to be sustained only for a few hundreds of microsecond at the initial phase of the discharge, when pulsing the radiofrequency power of a helicon plasma thruster. Measured relative density of argon neutrals inside the source implies that the neutrals are significantly depleted there. A position giving a maximum plasma density temporally moves to the upstream side of the source due to the neutral depletion and then the exhausted plasma density significantly decreases. The direct thrust measurement demonstrates that the higher thrust-to-power ratio is obtained by using only the initial phase of the high density plasma, compared with the steady-state operation.

Effect of the target power density on high-power impulse magnetron sputtering of copper

NASA Astrophysics Data System (ADS)

Kozák, Tomáš

2012-04-01

We present a model analysis of high-power impulse magnetron sputtering of copper. We use a non-stationary global model based on the particle and energy conservation equations in two zones (the high density plasma ring above the target racetrack and the bulk plasma region), which makes it possible to calculate time evolutions of the averaged process gas and target material neutral and ion densities, as well as the fluxes of these particles to the target and substrate during a pulse period. We study the effect of the increasing target power density under conditions corresponding to a real experimental system. The calculated target current waveforms show a long steady state and are in good agreement with the experimental results. For an increasing target power density, an analysis of the particle densities shows a gradual transition to a metal dominated discharge plasma with an increasing degree of ionization of the depositing flux. The average fraction of target material ions in the total ion flux onto the substrate is more than 90% for average target power densities higher than 500 W cm-2 in a pulse. The average ionized fraction of target material atoms in the flux onto the substrate reaches 80% for a maximum average target power density of 3 kW cm-2 in a pulse.

47 CFR 15.407 - General technical requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... maximum antenna gain does not exceed 6 dBi. In addition, the maximum power spectral density shall not exceed 17 dBm in any 1 megahertz band. If transmitting antennas of directional gain greater than 6 dBi... reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi. The maximum e.i.r.p...

Performance of air-cathode stacked microbial fuel cells systems for wastewater treatment and electricity production.

PubMed

Estrada-Arriaga, Edson Baltazar; Guillen-Alonso, Yvonne; Morales-Morales, Cornelio; García-Sánchez, Liliana; Bahena-Bahena, Erick Obed; Guadarrama-Pérez, Oscar; Loyola-Morales, Félix

2017-07-01

Two different air-cathode stacked microbial fuel cell (MFC) configurations were evaluated under continuous flow during the treatment of municipal wastewater and electricity production at a hydraulic retention time (HRT) of 3, 1, and 0.5 d. Stacked MFC 1 was formed by 20 individual air-cathode MFC units. The second stacked MFC (stacked MFC 2) consisted of 40 air-cathode MFC units placed in a shared reactor. The maximum voltages produced at closed circuit (1,000 Ω) were 170 mV for stacked MFC 1 and 94 mV for stacked MFC 2. Different power densities in each MFC unit were obtained due to a potential drop phenomenon and to a change in chemical oxygen demand (COD) concentrations inside reactors. The maximum power densities from individual MFC units were up to 1,107 mW/m 2 for stacked MFC 1 and up to 472 mW/m 2 for stacked MFC 2. The maximum power densities in stacked MFC 1 and MFC 2 connected in series were 79 mW/m 2 and 4 mW/m 2 , respectively. Electricity generation and COD removal efficiencies were reduced when the HRT was decreased. High removal efficiencies of 84% of COD, 47% of total nitrogen, and 30% of total phosphorus were obtained during municipal wastewater treatment.

Meta-analysis of Microbial Fuel Cells Using Waste Substrates.

PubMed

Dowdy, F Ryan; Kawakita, Ryan; Lange, Matthew; Simmons, Christopher W

2018-05-01

Microbial fuel cell experimentation using waste streams is an increasingly popular field of study. One obstacle to comparing studies has been the lack of consistent conventions for reporting results such that meta-analysis can be used for large groups of experiments. Here, 134 unique microbial fuel cell experiments using waste substrates were compiled for analysis. Findings include that coulombic efficiency correlates positively with volumetric power density (p < 0.001), negatively with working volume (p < 0.05), and positively with percentage removal of chemical oxygen demand (p < 0.005). Power density in mW/m 2 correlates positively with chemical oxygen demand loading (p < 0.005), and positively with maximum open-circuit voltage (p < 0.05). Finally, single-chamber versus double-chamber reactor configurations differ significantly in maximum open-circuit voltage (p < 0.005). Multiple linear regression to predict either power density or maximum open-circuit voltage produced no significant models due to the amount of multicollinearity between predictor variables. Results indicate that statistically relevant conclusions can be drawn from large microbial fuel cell datasets. Recommendations for future consistency in reporting results following a MIAMFCE convention (Minimum Information About a Microbial Fuel Cell Experiment) are included.

Nonimaging optical designs for maximum-power-density remote irradiation.

PubMed

Feuermann, D; Gordon, J M; Ries, H

1998-04-01

Designs for flexible, high-power-density, remote irradiation systems are presented. Applications include industrial infrared heating such as in semiconductor processing, alternatives to laser light for certain medical procedures, and general remote high-brightness lighting. The high power densities in herent to the small active radiating regions of conventional metal-halide, halogen, xenon, microwave-sulfur, and related lamps can be restored with nonimaging concentrators with little loss of power. These high fluxlevels can then be transported at high transmissivity with light channels such as optical fibers or lightpipes, and reshaped into luminaires that can deliver prescribed angular and spatial flux distributions onto desired targets. Details for nominally two- and three-dimensional systems are developed, along with estimates ofoptical performance.

Improving Power Density of Free-Piston Stirling Engines

NASA Technical Reports Server (NTRS)

Briggs, Maxwell H.; Prahl, Joseph; Loparo, Kenneth

2016-01-01

Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58 using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

Improving Free-Piston Stirling Engine Power Density

NASA Technical Reports Server (NTRS)

Briggs, Maxwell H.

2016-01-01

Analyses and experiments demonstrate the potential benefits of optimizing piston and displacer motion in a free piston Stirling Engine. Isothermal analysis shows the theoretical limits of power density improvement due to ideal motion in ideal Stirling engines. More realistic models based on nodal analysis show that ideal piston and displacer waveforms are not optimal, often producing less power than engines that use sinusoidal piston and displacer motion. Constrained optimization using nodal analysis predicts that Stirling engine power density can be increased by as much as 58% using optimized higher harmonic piston and displacer motion. An experiment is conducted in which an engine designed for sinusoidal motion is forced to operate with both second and third harmonics, resulting in a maximum piston power increase of 14%. Analytical predictions are compared to experimental data showing close agreement with indirect thermodynamic power calculations, but poor agreement with direct electrical power measurements.

A Study of a Two Stage Maximum Power Point Tracking Control of a Photovoltaic System under Partially Shaded Insolation Conditions

NASA Astrophysics Data System (ADS)

Kobayashi, Kenji; Takano, Ichiro; Sawada, Yoshio

A photovoltaic array shows relatively low output power density, and has a greatly drooping Current-Voltage (I-V) characteristic. Therefore, Maximum Power Point Tracking (MPPT) control is used to maximize the output power of the array. Many papers have been reported in relation to MPPT. However, the Current-Power (I-P) curve sometimes shows multi-local maximum points mode under non-uniform insolation conditions. The operating point of the PV system tends to converge to a local maximum output point which is not the real maximal output point on the I-P curve. Some papers have been also reported, trying to avoid this difficulty. However most of those control systems become rather complicated. Then, the two stage MPPT control method is proposed in this paper to realize a relatively simple control system which can track the real maximum power point even under non-uniform insolation conditions. The feasibility of this control concept is confirmed for steady insolation as well as for rapidly changing insolation by simulation study using software PSIM and LabVIEW. In addition, simulated experiment confirms fundament al operation of the two stage MPPT control.

Full scale hover test of a 25 foot tilt rotor

NASA Technical Reports Server (NTRS)

Helf, S.; Broman, E.; Gatchel, S.; Charles, B.

1973-01-01

The tilt rotor underwent a hover performance test on the Aero Propulsion Laboratory whirl stand at Wright-Patterson Air Force Base. The maximum thrust over density ratio measured at the design tip speed of 740 feet per second was 10,016 pounds. This occurred when the power over density ratio was 1721 horsepower. At the hover overspeed rpm, the thrust and power, over density ratio, were 11,008 pounds and 1866 horsepower. During the test, the maximum measured thrust coefficient was 0.177, and the rotor figure of merit exceeded 0.81. Measured lifting efficiency was 8.35 pounds per horsepower at the thrust a 13,000-pound aircraft would require for hover at sea level on a standard day. No effect of compressibility on performance is discernible in the test results (the range of tip Mach numbers tested was 0.55 to 0.71).

An innovative miniature microbial fuel cell fabricated using photolithography.

PubMed

Chen, You-Peng; Zhao, Yue; Qiu, Ke-Qiang; Chu, Jian; Lu, Rui; Sun, Min; Liu, Xian-Wei; Sheng, Guo-Ping; Yu, Han-Qing; Chen, Jie; Li, Wen-Jie; Liu, Gang; Tian, Yang-Chao; Xiong, Ying

2011-02-15

Recently microbial fuel cells (MFCs) have attracted increasing interests in both environmental and energy fields. Among the various MFC configurations, miniature microbial fuel cell (mini-MFC) has a great potential for the application in medical, communication and other areas because of its miniature volume and high output power density. In this work, a 25-μL single-chamber mini-MFC was fabricated using the photolithography technique. The plate-shaped gold anodic electrode in the mini-MFC showed a higher electrochemical activity than the stripe-shaped one. A biofilm of Shewanella oneidensis MR-1 was formed on the surface of gold electrode in this micro-liter-scale MFCs. As a result, a maximum power density of 29 mW/m(2) and a maximum current density of 2148 mA/m(2) were achieved by this single-chamber mini-MFC. Copyright © 2010 Elsevier B.V. All rights reserved.

Electricity generation directly using human feces wastewater for life support system

NASA Astrophysics Data System (ADS)

Fangzhou, Du; Zhenglong, Li; Shaoqiang, Yang; Beizhen, Xie; Hong, Liu

2011-05-01

Wastewater reuse and power regeneration are key issues in the research of bioregeneration life support system (BLSS). Microbial fuel cell (MFC) can generate electricity during the process of wastewater treatment, which might be promising to solve the two problems simultaneously. We used human feces wastewater containing abundant organic compounds as the substrate of MFC to generate electricity, and the factors concerning electricity generation capacity were investigated. The removal efficiency of total chemical oxygen demand (TCOD), Soluble chemical oxygen demand (SCOD) and NH4+ reached 71%, 88% and 44%, respectively with two-chamber MFC when it was fed with the actual human feces wastewater and operated for 190 h. And the maximum power density reached 70.8 mW/m 2, which implicated that MFC technology was feasible and appropriate for treating human feces wastewater. In order to improve the power generation of MFC further, human feces wastewater were fermented before poured into MFC, and the result showed that fermentation pretreatment could improve the MFC output obviously. The maximum power density of MFC fed with pretreated human feces wastewater was 22 mW/m 2, which was 47% higher than that of the control without pretreatment (15 mW/m 2). Furthermore, the structure of MFC was studied and it was found that both enlarging the area of electrodes and shortening the distance between electrodes could increase the electricity generation capacity. Finally, an automatic system, controlled by time switches and electromagnetic valves, was established to process one person's feces wastewater (1 L/d) while generating electricity. The main parts of this system comprised a pretreatment device and 3 one-chamber air-cathode MFCs. The total power could reach 787.1 mW and power density could reach the maximum of about 240 mW/m 2.

Electricity generation using an air-cathode single chamber microbial fuel cell in the presence and absence of a proton exchange membrane.

PubMed

Liu, Hong; Logan, Bruce E

2004-07-15

Microbial fuel cells (MFCs) are typically designed as a two-chamber system with the bacteria in the anode chamber separated from the cathode chamber by a polymeric proton exchange membrane (PEM). Most MFCs use aqueous cathodes where water is bubbled with air to provide dissolved oxygen to electrode. To increase energy output and reduce the cost of MFCs, we examined power generation in an air-cathode MFC containing carbon electrodes in the presence and absence of a polymeric proton exchange membrane (PEM). Bacteria present in domestic wastewater were used as the biocatalyst, and glucose and wastewater were tested as substrates. Power density was found to be much greater than typically reported for aqueous-cathode MFCs, reaching a maximum of 262 +/- 10 mW/m2 (6.6 +/- 0.3 mW/L; liquid volume) using glucose. Removing the PEM increased the maximum power density to 494 +/- 21 mW/m2 (12.5 +/- 0.5 mW/L). Coulombic efficiency was 40-55% with the PEM and 9-12% with the PEM removed, indicating substantial oxygen diffusion into the anode chamber in the absence of the PEM. Power output increased with glucose concentration according to saturation-type kinetics, with a half saturation constant of 79 mg/L with the PEM-MFC and 103 mg/L in the MFC without a PEM (1000 omega resistor). Similar results on the effect of the PEM on power density were found using wastewater, where 28 +/- 3 mW/m2 (0.7 +/- 0.1 mW/L) (28% Coulombic efficiency) was produced with the PEM, and 146 +/- 8 mW/m2 (3.7 +/- 0.2 mW/L) (20% Coulombic efficiency) was produced when the PEM was removed. The increase in power output when a PEM was removed was attributed to a higher cathode potential as shown by an increase in the open circuit potential. An analysis based on available anode surface area and maximum bacterial growth rates suggests that mediatorless MFCs may have an upper order-of-magnitude limit in power density of 10(3) mW/m2. A cost-effective approach to achieving power densities in this range will likely require systems that do not contain a polymeric PEM in the MFC and systems based on direct oxygen transfer to a carbon cathode.

Enhanced bioelectricity harvesting in microbial fuel cells treating food waste leachate produced from biohydrogen fermentation.

PubMed

Choi, Jeongdong; Ahn, Youngho

2015-05-01

Microbial fuel cells (MFCs) treating the food waste leachate produced from biohydrogen fermentation were examined to enhance power generation and energy recovery. In batch mode, the maximum voltage production was 0.56 V and the power density reached 1540 mW/m(2). The maximum Coulombic efficiency (CEmax) and energy efficiency (EE) in the batch mode were calculated to be 88.8% and 18.8%, respectively. When the organic loading rate in sequencing batch mode varied from 0.75 to 6.2 g COD/L-d (under CEmax), the maximum power density reached 769.2 mW/m(2) in OLR of 3.1 g COD/L-d, whereas higher energy recovery (CE=52.6%, 0.346 Wh/g CODrem) was achieved at 1.51 g COD/L-d. The results demonstrate that readily biodegradable substrates in biohydrogen fermentation can be effectively used for the enhanced bioelectricity harvesting of MFCs and a MFC coupled with biohydrogen fermentation is of great benefit on higher electricity generation and energy efficiency. Copyright © 2015 Elsevier Ltd. All rights reserved.

Integrating Reverse-Electrodialysis Stacks with Flow Batteries for Improved Energy Recovery from Salinity Gradients and Energy Storage.

PubMed

Zhu, Xiuping; Kim, Taeyoung; Rahimi, Mohammad; Gorski, Christopher A; Logan, Bruce E

2017-02-22

Salinity gradient energy can be directly converted into electrical power by using reverse electrodialysis (RED) and other technologies, but reported power densities have been too low for practical applications. Herein, the RED stack performance was improved by using 2,6-dihydroxyanthraquinone and ferrocyanide as redox couples. These electrolytes were then used in a flow battery to produce an integrated RED stack and flow battery (RED-FB) system capable of capturing, storing, and discharging salinity gradient energy. Energy captured from the RED stack was discharged in the flow battery at a maximum power density of 3.0 kW m -2 -anode, which was similar to the flow batteries charged by electrical power and could be used for practical applications. Salinity gradient energy captured from the RED stack was recovered from the electrolytes as electricity with 30 % efficiency, and the maximum energy density of the system was 2.4 kWh m -3 -anolyte. The combined RED-FB system overcomes many limitations of previous approaches to capture, store, and use salinity gradient energy from natural or engineered sources. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A miniature microbial fuel cell operating with an aerobic anode chamber

NASA Astrophysics Data System (ADS)

Ringeisen, Bradley R.; Ray, Ricky; Little, Brenda

A miniature microbial fuel cell (mini-MFC) is described that utilizes an aerobic culture of Shewanella oneidensis DSP10 as the active electrochemical species in the anode chamber. We find that the maximum aerobic mini-MFC power without the addition of exogenous mediators was 0.40 mW, a 33% decrease when compared with an anaerobic DSP10 culture (0.6 mW) operating in the mini-MFC. This decrease is most likely due to the presence of dissolved oxygen in the anode chamber that scavenges electrons to form water, thereby reducing the number of electrons donated to the anode. Aerobic power and current density at maximum power using the true surface area of the anode (611 cm 2) were calculated to be 6.5 mW m -2 and 13 mA m -2. The power density rises to 2.0 W m -2 and 330 W m -3 when calculated using the cross-sectional area and volume of the device (2 cm 2, 1.2 cm 3). The Coulombic efficiency was also reduced from 11 to 5% when using the aerobic versus anaerobic culture. Similar results were found when the external mediator anthraquinone-2,6-disulfonate (AQDS) was added to the aerobic culture, resulting in a maximum power of 0.54 mW, a 37% drop in power when compared to the anaerobic mediated system.

Maltodextrin-powered enzymatic fuel cell through a non-natural enzymatic pathway

NASA Astrophysics Data System (ADS)

Zhu, Zhiguang; Wang, Yiran; Minteer, Shelley D.; Percival Zhang, Y.-H.

Enzymatic fuel cells (EFCs) use a variety of fuels to generate electricity through oxidoreductase enzymes, such as oxidases or dehydrogenases, as catalysts on electrodes. We have developed a novel synthetic enzymatic pathway containing two free enzymes (maltodextrin phosphorylase and phosphoglucomutase) and one immobilized glucose-6-phosphate dehydrogenase that can utilize an oligomeric substrate maltodextrin for producing electrons mediated via a diaphorase and vitamin K 3 electron shuttle system. Three different enzyme immobilization approaches were compared based on electrostatic force entrapment, chemical cross-linking, and cross-linking with the aid of carbon nanotubes. At 10 mM glucose-6-phosphate (G6P) as a substrate concentration, the maximum power density of 0.06 mW cm -2 and retaining 42% of power output after 11 days were obtained through the method of chemical cross-linking with carbon nanotubes, approximately 6-fold and 3.5-fold better than those of the electrostatic force-based method, respectively. When changed to maltodextrin (degree of polymerization = 19) as the substrate, the EFC achieved a maximum power density of 0.085 mW cm -2. With the advantages of stable, low cost, high energy density, non-inhibitor to enzymes, and environmental friendly, maltodextrin is suggested to be an ideal fuel to power enzymatic fuel cells.

Immobilization of glucose oxidase into polyaniline nanofiber matrix for biofuel cell applications.

PubMed

Kim, Hyeongseok; Lee, Inseon; Kwon, Yongchai; Kim, Byoung Chan; Ha, Su; Lee, Jung-heon; Kim, Jungbae

2011-05-15

Glucose oxidase (GOx) was immobilized into the porous matrix of polyaniline nanofibers in a three-step process, consisting of enzyme adsorption, precipitation, and crosslinking (EAPC). EAPC was highly active and stable when compared to the control samples of enzyme adsorption (EA) and enzyme adsorption and crosslinking (EAC) with no step of enzyme precipitation. The GOx activity of EAPC was 9.6 and 4.2 times higher than those of EA and EAC, respectively. Under rigorous shaking at room temperature for 56 days, the relative activities of EA, EAC and EAPC, defined as the percentage of residual activity to the initial activity, were 22%, 19% and 91%, respectively. When incubated at 50°C under shaking for 4h, EAPC showed a negligible decrease of GOx activity while the relative activities of EA and EAC were 45% and 48%, respectively. To demonstrate the feasible application of EAPC in biofuel cells, the enzyme anodes were prepared and used for home-built air-breathing biofuel cells. The maximum power densities of biofuel cells with EA and EAPC anodes were 57 and 292 μW/cm(2), respectively. After thermal treatment at 60°C for 4h, the maximum power density of EA and EAPC anodes were 32 and 315 μW/cm(2), representing 56% and 108% of initially obtained maximum power densities, respectively. Because the lower power densities and short lifetime of biofuel cells are serious problems against their practical applications, the present results with EAPC anode has opened up a new potential for the realization of practical biofuel cell applications. Copyright © 2011 Elsevier B.V. All rights reserved.

Microwave emissions from police radar.

PubMed

Fink, J M; Wagner, J P; Congleton, J J; Rock, J C

1999-01-01

This study evaluated police officers' exposures to microwaves emitted by traffic radar units. Exposure measurements were taken at approximated ocular and testicular levels of officers seated in patrol vehicles. Comparisons were made of the radar manufacturers' published maximum power density specifications and actual measured power densities taken at the antenna faces of those units. Four speed-enforcement agencies and one transportation research institute provided 54 radar units for evaluation; 17 different models, encompassing 4 frequency bands and 3 antenna configurations, were included. Four of the 986 measurements taken exceeded the 5 mW/cm2 limit accepted by the International Radiation Protection Association and the National Council on Radiation Protection and Measurement, though none exceeded the American Conference of Governmental Industrial Hygienists, American National Standards Institute, Institute of Electrical and Electronic Engineers, or Occupational Safety and Health Administration standard of 10 mW/cm2. The four high measurements were maximum power density readings taken directly in front of the radar. Of the 812 measurements taken at the officers' seated ocular and testicular positions, none exceeded 0.04 mW/cm2; the highest of these (0.034 mW/cm2) was less than 1% of the most conservative current safety standards. High exposures in the limited region directly in front of the radar aperture are easily avoided with proper training. Results of this study indicate that police officer exposure to microwave radiation is apparently minimal. However, because of uncertainty in the medical and scientific communities concerning nonionizing radiation, it is recommended that law enforcement agencies implement a policy of prudent avoidance, including purchasing units with the lowest published maximum power densities, purchasing dash/rear deck-mounted units with antennae mounted outside the patrol vehicle, and training police officers to use the "stand-by" mode when not actually using radar.

Insect biofuel cells using trehalose included in insect hemolymph leading to an insect-mountable biofuel cell.

PubMed

Shoji, Kan; Akiyama, Yoshitake; Suzuki, Masato; Hoshino, Takayuki; Nakamura, Nobuhumi; Ohno, Hiroyuki; Morishima, Keisuke

2012-12-01

In this paper, an insect biofuel cell (BFC) using trehalose included in insect hemolymph was developed. The insect BFC is based on trehalase and glucose oxidase (GOD) reaction systems which oxidize β-glucose obtained by hydrolyzing trehalose. First, we confirmed by LC-MS that a sufficient amount of trehalose was present in the cockroach hemolymph (CHL). The maximum power density obtained using the insect BFC was 6.07 μW/cm(2). The power output was kept more than 10 % for 2.5 h by protecting the electrodes with a dialysis membrane. Furthermore, the maximum power density was increased to 10.5 μW/cm(2) by using an air diffusion cathode. Finally, we succeeded in driving a melody integrated circuit (IC) and a piezo speaker by connecting five insect BFCs in series. The results indicate that the insect BFC is a promising insect-mountable battery to power environmental monitoring micro-tools.

Room temperature microwave oscillations in GaN/AlN resonant tunneling diodes with peak current densities up to 220 kA/cm2

NASA Astrophysics Data System (ADS)

Encomendero, Jimy; Yan, Rusen; Verma, Amit; Islam, S. M.; Protasenko, Vladimir; Rouvimov, Sergei; Fay, Patrick; Jena, Debdeep; Xing, Huili Grace

2018-03-01

We report the generation of room temperature microwave oscillations from GaN/AlN resonant tunneling diodes, which exhibit record-high peak current densities. The tunneling heterostructure grown by molecular beam epitaxy on freestanding GaN substrates comprises a thin GaN quantum well embedded between two AlN tunneling barriers. The room temperature current-voltage characteristics exhibit a record-high maximum peak current density of ˜220 kA/cm2. When biased within the negative differential conductance region, microwave oscillations are measured with a fundamental frequency of ˜0.94 GHz, generating an output power of ˜3.0 μW. Both the fundamental frequency and the output power of the oscillator are limited by the external biasing circuit. Using a small-signal equivalent circuit model, the maximum intrinsic frequency of oscillation for these diodes is predicted to be ˜200 GHz. This work represents a significant step towards microwave power generation enabled by resonant tunneling transport, an ultra-fast process that goes beyond the limitations of current III-Nitride high electron mobility transistors.

Power density of piezoelectric transformers improved using a contact heat transfer structure.

PubMed

Shao, Wei Wei; Chen, Li Juan; Pan, Cheng Liang; Liu, Yong Bin; Feng, Zhi Hua

2012-01-01

Based on contact heat transfer, a novel method to increase power density of piezoelectric transformers is proposed. A heat transfer structure is realized by directly attaching a dissipater to the piezoelectric transformer plate. By maintaining the vibration mode of the transformer and limiting additional energy losses from the contact interface, an appropriate design can improve power density of the transformer on a large scale, resulting from effective suppression of its working temperature rise. A prototype device was fabricated from a rectangular piezoelectric transformer, a copper heat transfer sheet, a thermal grease insulation pad, and an aluminum heat radiator. The experimental results show the transformer maintains a maximum power density of 135 W/cm(3) and an efficiency of 90.8% with a temperature rise of less than 10 °C after more than 36 h, without notable changes in performance. © 2012 IEEE

A High-Density, High-Efficiency, Isolated On-Board Vehicle Battery Charger Utilizing Silicon Carbide Power Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whitaker, B; Barkley, A; Cole, Z

2014-05-01

This paper presents an isolated on-board vehicular battery charger that utilizes silicon carbide (SiC) power devices to achieve high density and high efficiency for application in electric vehicles (EVs) and plug-in hybrid EVs (PHEVs). The proposed level 2 charger has a two-stage architecture where the first stage is a bridgeless boost ac-dc converter and the second stage is a phase-shifted full-bridge isolated dc-dc converter. The operation of both topologies is presented and the specific advantages gained through the use of SiC power devices are discussed. The design of power stage components, the packaging of the multichip power module, and themore » system-level packaging is presented with a primary focus on system density and a secondary focus on system efficiency. In this work, a hardware prototype is developed and a peak system efficiency of 95% is measured while operating both power stages with a switching frequency of 200 kHz. A maximum output power of 6.1 kW results in a volumetric power density of 5.0 kW/L and a gravimetric power density of 3.8 kW/kg when considering the volume and mass of the system including a case.« less

Convection in an ideal gas at high Rayleigh numbers.

PubMed

Tilgner, A

2011-08-01

Numerical simulations of convection in a layer filled with ideal gas are presented. The control parameters are chosen such that there is a significant variation of density of the gas in going from the bottom to the top of the layer. The relations between the Rayleigh, Peclet, and Nusselt numbers depend on the density stratification. It is proposed to use a data reduction which accounts for the variable density by introducing into the scaling laws an effective density. The relevant density is the geometric mean of the maximum and minimum densities in the layer. A good fit to the data is then obtained with power laws with the same exponent as for fluids in the Boussinesq limit. Two relations connect the top and bottom boundary layers: The kinetic energy densities computed from free fall velocities are equal at the top and bottom, and the products of free fall velocities and maximum horizontal velocities are equal for both boundaries.

Electricity generation and microbial community in response to short-term changes in stack connection of self-stacked submersible microbial fuel cell powered by glycerol.

PubMed

Zhao, Nannan; Angelidaki, Irini; Zhang, Yifeng

2017-02-01

Stack connection (i.e., in series or parallel) of microbial fuel cell (MFC) is an efficient way to boost the power output for practical application. However, there is little information available on short-term changes in stack connection and its effect on the electricity generation and microbial community. In this study, a self-stacked submersible microbial fuel cell (SSMFC) powered by glycerol was tested to elucidate this important issue. In series connection, the maximum voltage output reached to 1.15 V, while maximum current density was 5.73 mA in parallel. In both connections, the maximum power density increased with the initial glycerol concentration. However, the glycerol degradation was even faster in parallel connection. When the SSMFC was shifted from series to parallel connection, the reactor reached to a stable power output without any lag phase. Meanwhile, the anodic microbial community compositions were nearly stable. Comparatively, after changing parallel to series connection, there was a lag period for the system to get stable again and the microbial community compositions became greatly different. This study is the first attempt to elucidate the influence of short-term changes in connection on the performance of MFC stack, and could provide insight to the practical utilization of MFC. Copyright © 2016 Elsevier Ltd. All rights reserved.

An Optimized Microfluidic Paper-Based NiOOH/Zn Alkaline Battery.

PubMed

Burrola, Samantha; Gonzalez-Guerrero, Maria Jose; Avoundjian, Ani; Gomez, Frank A

2018-05-29

In this paper, an alkaline Nickel Oxide Hydroxide/Zinc (NiOOH/Zn) battery featuring a cellulose matrix separator between electrodes is presented. The metallic electrodes and the paper separator are inserted in a layer-by-layer (LbL) assembly that provides mechanical stability to the system resulting in a lightweight and easy-to-use device. The battery was optimized for the amount of NiOOH-ink used at the cathode (11.1 mg/cm 2 ) and thickness of the paper membrane separating the electrodes (360 μm). The battery was able to function using a small volume (75 μL) of 1.5 M potassium hydroxide (KOH) producing a maximum voltage, current density and power density of 1.35 ± 0.05 V, 10.62 ± 0.57 mA/cm², and 0.56 ± 0.01 mW/cm², respectively. The system displayed a maximum current of 23.9 mA and a maximum power of 1.26 mW. Moreover, four batteries connected in series were able to power a small flameless candle for approximately 22 minutes. This work has potential in fulfilling the demands for short-term and lightweight power supplies. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

The coronal structure of active regions

NASA Technical Reports Server (NTRS)

Landini, M.; Monsignori Fossi, B. C.; Krieger, A.; Vaiana, G. S.

1975-01-01

A four-parameter model, which assumes a Gaussian dependence of both temperature and pressure on distance from center, is used to fit the compact part of coronal active regions as observed in X-ray photographs from a rocket experiment. The four parameters are the maximum temperature, the maximum pressure, the width of the pressure distribution, and the width of the temperature distribution. The maximum temperature ranges from 2.2 to 2.8 million K, and the maximum density from 2 to 9 by 10 to the 9th power per cu cm. The range of the pressure-distribution width is from 2 to 4 by 10 to the 9th power cm and that of the temperature-distribution width from 2 to 7.

Direct thermal to electrical energy conversion using 9.5/65/35 PLZT ceramics in the ergodic relaxor phase.

PubMed

Chin, Thomas K; Lee, Felix Y; McKinley, Ian M; Goljahi, Sam; Lynch, Christopher S; Pilon, Laurent

2012-11-01

This paper reports on direct thermal to electrical energy conversion by performing the Olsen cycle on 9.5/65/35 lead lanthanum zirconate titanate (PLZT). The Olsen cycle consists of two isothermal and two isoelectric field processes in the electric displacement versus electric field diagram. It was performed by alternatively dipping the material in hot and cold dielectric fluid baths under specified electric fields. The effects of applied electric field, sample thickness, electrode material, operating temperature, and cycle frequency on the energy and power densities were investigated. A maximum energy density of 637 ± 20 J/L/cycle was achieved at 0.054 Hz with a 250-μm-thick sample featuring Pt electrodes and coated with a silicone conformal coating. The operating temperatures varied between 3°C and 140°C and the electric field was cycled between 0.2 and 6.0 MV/m. A maximum power density of 55 ± 8 W/L was obtained at 0.125 Hz under the same operating temperatures and electric fields. The dielectric strength of the material, and therefore the energy and power densities generated, increased when the sample thickness decreased from 500 to 250 μm. Furthermore, the electrode material was found to have no significant effect on the energy and power densities for samples subject to the same operating temperatures and electric fields. However, samples with electrode material possessing thermal expansion coefficients similar to that of PLZT were capable of withstanding larger temperature swings. Finally, a fatigue test showed that the power generation gradually degraded when the sample was subject to repeated thermoelectrical loading.

High discharge efficiency of (Sr, Pb, Bi) TiO3 relaxor ceramics for energy-storage application

NASA Astrophysics Data System (ADS)

Chao, Mingming; Liu, Jingsong; Zeng, Mengshi; Wang, Debin; Yu, Hongtao; Yuan, Ying; Zhang, Shuren

2018-05-01

We report herein on the energy storage and discharge properties of the relaxor ferroelectric ceramic Sr0.8Pb0.1Bi0.1TiO3 (SPBT). This material has a slanted hysteresis loop, and all samples show low remnant polarization and low coercive field, which leads to a high discharge efficiency. The maximum polarization is 10.1 μC/cm2, the minimum coercive field is 0.229 kV/cm, and the maximum efficiency is 94.2%. The discharge current waveforms are sinusoidal, the first discharge period is 140 ns, and the power density is approximately 4.2 × 107 W/kg. The high discharge speed and high discharge power density indicate that SPBT ceramics are very promising materials for energy storage applications.

Are self-thinning constraints needed in a tree-specific mortality model?

Treesearch

Robert A. Monserud; Thomas Ledermann; Hubert Sterba

2005-01-01

Can a tree-specific mortality model elicit expected forest stand density dynamics without imposing stand-level constraints such as Reineke's maximum stand density index (SDImax) or the -3/2 power law of self-thinning? We examine this emergent properties question using the Austrian stand simulator PROGNAUS. This simulator was chosen...

700 F hybrid capacitors cells composed of activated carbon and Li4Ti5O12 microspheres with ultra-long cycle life

NASA Astrophysics Data System (ADS)

Ruan, Dianbo; Kim, Myeong-Seong; Yang, Bin; Qin, Jun; Kim, Kwang-Bum; Lee, Sang-Hyun; Liu, Qiuxiang; Tan, Lei; Qiao, Zhijun

2017-10-01

To address the large-scale application demands of high energy density, high power density, and long cycle lifetime, 700-F hybrid capacitor pouch cells have been prepared, comprising ∼240-μm-thick activated carbon cathodes, and ∼60-μm-thick Li4Ti5O12 anodes. Microspherical Li4Ti5O12 (M-LTO) synthesized by spray-drying features 200-400 nm primary particles and interconnected nanopore structures. M-LTO half-cells exhibits high specific capacities (175 mAhh g-1), good rate capabilities (148 mAhh g-1 at 20 C), and ultra-long cycling stabilities (90% specific capacity retention after 10,000 cycles). In addition, the obtained hybrid capacitors comprising activated carbon (AC) and M-LTO shows excellent cell performances, achieving a maximum energy density of 51.65 Wh kg-1, a maximum power density of 2466 W kg-1, and ∼92% capacitance retention after 10,000 cycles, thus meeting the demands for large-scale applications such as trolleybuses.

Experimental investigations of electron density and ion energy distributions in dual-frequency capacitively coupled plasmas for Ar/CF{sub 4} and Ar/O{sub 2}/CF{sub 4} discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Jia; Liu, Yong-Xin; Gao, Fei

2014-01-07

The electron density and ion energy distribution (IED) are investigated in low-pressure dual-frequency capacitively coupled Ar/CF{sub 4} (90%/10%) and Ar/O{sub 2}/CF{sub 4} (80%/10%/10%) plasmas. The relations between controllable parameters, such as high-frequency (HF) power, low-frequency (LF) power and gas pressure, and plasma parameters, such as electron density and IEDs, are studied in detail by utilizing a floating hairpin probe and an energy resolved quadrupole mass spectrometer, respectively. In our experiment, the electron density is mainly determined by the HF power and slightly influenced by the LF power. With increasing gas pressure, the electron density first goes up rapidly to amore » maximum value and then decreases at various HF and LF powers. The HF power also plays a considerable role in affecting the IEDs under certain conditions and the ion energy independently controlled by the LF source is discussed here. For clarity, some numerical results obtained from a two-dimensional fluid model are presented.« less

Voltage and power relationships in lithium-containing solar cells.

NASA Technical Reports Server (NTRS)

Faith, T. J.

1972-01-01

Photovoltaic characteristics have been measured on a large number of crucible-grown lithium-containing solar cells irradiated by 1-MeV electrons to fluences ranging from 3 x 10 to the 13th power to 3 x 10 to the 15th power electrons per sq cm. These measurements have established empirical relationships between cell photovoltaic parameters and lithium donor density gradient. Short-circuit current and maximum power measured immediately after irradiation decrease logarithmically with lithium gradient. Open-circuit voltage increases logarithmically with lithium gradient both immediately after irradiation and after recovery, the degree of recovery being strongly gradient-dependent at high fluence. As a result, the maximum power and the power at 0.43 V after recovery from 3 x 10 to the 15th power electrons per sq cm increase with increasing lithium gradient.

High-power quantum-dot tapered tunable external-cavity lasers based on chirped and unchirped structures.

PubMed

Haggett, Stephanie; Krakowski, Michel; Montrosset, Ivo; Cataluna, Maria Ana

2014-09-22

A high-power tunable external cavity laser configuration with a tapered quantum-dot semiconductor optical amplifier at its core is presented, enabling a record output power for a broadly tunable semiconductor laser source in the 1.2 - 1.3 µm spectral region. Two distinct optical amplifiers are investigated, using either chirped or unchirped quantum-dot structures, and their merits are compared, considering the combination of tunability and high output power generation. At 1230 nm, the chirped quantum-dot laser achieved a maximum power of 0.62 W and demonstrated nearly 100-nm tunability. The unchirped laser enabled a tunability range of 32 nm and at 1254 nm generated a maximum power of 0.97 W, representing a 22-fold increase in output power compared with similar narrow-ridge external-cavity lasers at the same current density.

Thermodynamic analysis of energy density in pressure retarded osmosis: The impact of solution volumes and costs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reimund, Kevin K.; McCutcheon, Jeffrey R.; Wilson, Aaron D.

A general method was developed for estimating the volumetric energy efficiency of pressure retarded osmosis via pressure-volume analysis of a membrane process. The resulting model requires only the osmotic pressure, π, and mass fraction, w, of water in the concentrated and dilute feed solutions to estimate the maximum achievable specific energy density, uu, as a function of operating pressure. The model is independent of any membrane or module properties. This method utilizes equilibrium analysis to specify the volumetric mixing fraction of concentrated and dilute solution as a function of operating pressure, and provides results for the total volumetric energy densitymore » of similar order to more complex models for the mixing of seawater and riverwater. Within the framework of this analysis, the total volumetric energy density is maximized, for an idealized case, when the operating pressure is π/(1+√w⁻¹), which is lower than the maximum power density operating pressure, Δπ/2, derived elsewhere, and is a function of the solute osmotic pressure at a given mass fraction. It was also found that a minimum 1.45 kmol of ideal solute is required to produce 1 kWh of energy while a system operating at “maximum power density operating pressure” requires at least 2.9 kmol. Utilizing this methodology, it is possible to examine the effects of volumetric solution cost, operation of a module at various pressure, and operation of a constant pressure module with various feed.« less

10 CFR 100.20 - Factors to be considered when evaluating sites.

Code of Federal Regulations, 2010 CFR

2010-01-01

... analysis or that may have an impact upon plant design (such as maximum probable wind speed and... for Stationary Power Reactor Site Applications on or After January 10, 1997 § 100.20 Factors to be... determining the acceptability of a site for a stationary power reactor: (a) Population density and use...

10 CFR 100.20 - Factors to be considered when evaluating sites.

Code of Federal Regulations, 2011 CFR

2011-01-01

... analysis or that may have an impact upon plant design (such as maximum probable wind speed and... for Stationary Power Reactor Site Applications on or After January 10, 1997 § 100.20 Factors to be... determining the acceptability of a site for a stationary power reactor: (a) Population density and use...

47 CFR 15.319 - General technical requirements.

Code of Federal Regulations, 2011 CFR

2011-10-01

... full bandwidth of the channel. (d) Power spectral density shall not exceed 3 milliwatts in any 3 kHz bandwidth as measured with a spectrum analyzer having a resolution bandwidth of 3 kHz. (e) The peak transmit power shall be reduced by the amount in decibels that the maximum directional gain of the antenna...

47 CFR 15.319 - General technical requirements.

Code of Federal Regulations, 2010 CFR

2010-10-01

... full bandwidth of the channel. (d) Power spectral density shall not exceed 3 milliwatts in any 3 kHz bandwidth as measured with a spectrum analyzer having a resolution bandwidth of 3 kHz. (e) The peak transmit power shall be reduced by the amount in decibels that the maximum directional gain of the antenna...

Optimization of intermittent microwave–convective drying using response surface methodology

PubMed Central

Aghilinategh, Nahid; Rafiee, Shahin; Hosseinpur, Soleiman; Omid, Mahmoud; Mohtasebi, Seyed Saeid

2015-01-01

In this study, response surface methodology was used for optimization of intermittent microwave–convective air drying (IMWC) parameters with employing desirability function. Optimization factors were air temperature (40–80°C), air velocity (1–2 m/sec), pulse ratio) PR ((2–6), and microwave power (200–600 W) while responses were rehydration ratio, bulk density, total phenol content (TPC), color change, and energy consumption. Minimum color change, bulk density, energy consumption, maximum rehydration ratio, and TPC were assumed as criteria for optimizing drying conditions of apple slices in IMWC. The optimum values of process variables were 1.78 m/sec air velocity, 40°C air temperature, PR 4.48, and 600 W microwave power that characterized by maximum desirability function (0.792) using Design expert 8.0. The air temperature and microwave power had significant effect on total responses, but the role of air velocity can be ignored. Generally, the results indicated that it was possible to obtain a higher desirability value if the microwave power and temperature, respectively, increase and decrease. PMID:26286706

Damage in Monolithic Thin-Film Photovoltaic Modules Due to Partial Shade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Silverman, Timothy J.; Mansfield, Lorelle; Repins, Ingrid

2016-09-01

The typical configuration of monolithic thin-film photovoltaic modules makes it possible for partial shade to place one or more cells in such a module in reverse bias. Reverse bias operation leads to high voltage, current density, and power density conditions, which can act as driving forces for failure. We showed that a brief outdoor shadow event can cause a 7% permanent loss in power. We applied an indoor partial shade durability test that moves beyond the standard hot spot endurance test by using more realistic mask and bias conditions and by carefully quantifying the permanent change in performance due tomore » the stress. With the addition of a pass criterion based on change in maximum power, this procedure will soon be proposed as a part of the module-type qualification test. All six commercial copper indium gallium diselenide and cadmium telluride modules we tested experienced permanent damage due to the indoor partial shade test, ranging from 4% to 14% loss in maximum power. We conclude by summarizing ways to mitigate partial shade stress at the cell, module, and system levels.« less

Ni2P Makes Application of the PtRu Catalyst Much Stronger in Direct Methanol Fuel Cells.

PubMed

Chang, Jinfa; Feng, Ligang; Liu, Changpeng; Xing, Wei

2015-10-12

PtRu is regarded as the best catalyst for direct methanol fuel cells, but the performance decay resulting from the loss of Ru seriously hinders commercial applications. Herein, we demonstrated that the presence of Ni2 P largely reduces Ru loss, which thus makes the application of PtRu much stronger in direct methanol fuel cells. Outstanding catalytic activity and stability were observed by cyclic voltammetry. Upon integrating the catalyst material into a practical direct methanol fuel cell, the highest maximum power density was achieved on the PtRu-Ni2P/C catalyst among the reference catalysts at different temperatures. A maximum power density of 69.9 mW cm(-2) at 30 °C was obtained on PtRu-Ni2P/C, which is even higher than the power density of the state-of-the-art commercial PtRu catalyst at 70 °C (63.1 mW cm(-2)). Moreover, decay in the performance resulting from Ru loss was greatly reduced owing to the presence of Ni2 P, which is indicative of very promising applications. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Study of emission spectra of N atom generated in multi-needle-to-plate corona discharge].

PubMed

Ge, Hui; Yu, Ran; Zhang, Lu; Mi, Dong; Zhu, Yi-Min

2012-06-01

The emission spectra of nitrogen (N) atom produced by multi-needle-to-plate negative corona discharge in air were detected successfully at one atmosphere, and the excited transition spectral line at 674.5 nm with maximum value of relative intensity was selected to investigate the influences of air and electrical parameters on N atom relative density. The results indicate that N atom relative density in ionization region increases with the increase in power; decreases with increasing discharge gap and relative humidity; and with the increase in N2 content, the relative density of N active atom firstly increases and then decreases. Under present experimental conditions, the maximum value of N atom relative density appears at the axial distance from needle point r = 1 mm.

A miniaturized human-motion energy harvester using flux-guided magnet stacks

NASA Astrophysics Data System (ADS)

Halim, M. A.; Park, J. Y.

2016-11-01

We present a miniaturized electromagnetic energy harvester (EMEH) using two flux-guided magnet stacks to harvest energy from human-generated vibration such as handshaking. Each flux-guided magnet stack increases (40%) the magnetic flux density by guiding the flux lines through a soft magnetic material. The EMEH has been designed to up-convert the applied human-motion vibration to a high-frequency oscillation by mechanical impact of a spring-less structure. The high-frequency oscillator consists of the analyzed 2-magnet stack and a customized helical compression spring. A standard AAA battery sized prototype (3.9 cm3) can generate maximum 203 μW average power from human hand-shaking vibration. It has a maximum average power density of 52 μWcm-3 which is significantly higher than the current state-of-the-art devices. A 6-stage multiplier and rectifier circuit interfaces the harvester with a wearable electronic load (wrist watch) to demonstrate its capability of powering small- scale electronic systems from human-generated vibration.

Graphite fiber brush anodes for increased power production in air-cathode microbial fuel cells.

PubMed

Logan, Bruce; Cheng, Shaoan; Watson, Valerie; Estadt, Garett

2007-05-01

To efficiently generate electricity using bacteria in microbial fuel cells (MFCs), highly conductive noncorrosive materials are needed that have a high specific surface area (surface area per volume) and an open structure to avoid biofouling. Graphite brush anodes, consisting of graphite fibers wound around a conductive, but noncorrosive metal core, were examined for power production in cube (C-MFC) and bottle (B-MFC) air-cathode MFCs. Power production in C-MFCs containing brush electrodes at 9600 m2/m3 reactor volume reached a maximum power density of 2400 mW/m2 (normalized to the cathode projected surface area), or 73 W/m3 based on liquid volume, with a maximum Coulombic efficiency (CE) of 60%. This power density, normalized by cathode projected area, is the highest value yet achieved by an air-cathode system. The increased power resulted from a reduction in internal resistance from 31 to 8 Q. Brush electrodes (4200 m2/m3) were also tested in B-MFCs, consisting of a laboratory media bottle modified to have a single side arm with a cathode clamped to its end. B-MFCs inoculated with wastewater produced up to 1430 mW/m2 (2.3 W/m3, CE = 23%) with brush electrodes, versus 600 mW/m2 with a plain carbon paper electrode. These findings show that brush anodes that have high surface areas and a porous structure can produce high power densities, and therefore have qualities that make them ideal for scaling up MFC systems.

An optimal design of magnetostrictive material (MsM) based energy harvester

NASA Astrophysics Data System (ADS)

Hu, Jingzhen; Yuan, Fuh-Gwo; Xu, Fujun; Huang, Alex Q.

2010-04-01

In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) has been designed to power the Wireless Intelligent Sensor Platform (WISP), developed at North Carolina State University. A linear MsM energy harvesting device has been modeled and optimized to maximize the power output. The effects of number of MsM layers and glue layers, and load matching on the output power of the MsM energy harvester have been analyzed. From the measurement, the open circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the 2nd natural frequency 324 Hz. The AC output power is 0.97 mW, giving power density 279 μW/cm3. Since the MsM device has low open circuit output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device has been implemented using a discontinuous conduction mode (DCM) buck-boost converter. The maximum output power after the voltage quadrupler is now 705 μW and power density reduces to 202.4 μW/cm3, which is comparable to the piezoelectric energy harvesters given in the literature. The output power delivered to a lithium rechargeable battery is around 630 μW, independent of the load resistance.

Are self-thinning contraints needed in a tree-specific mortality model.

Treesearch

Robert A. Monserud; Thomas Ledermann; Hubert Sterba

2005-01-01

Can a tree-specific mortality model elicit expected forest stand density dynamics without imposing stand-level constraints such as Reineke's maximum stand density index (SDI,) or the -312 power law of self-thinning? We examine this emergent properties question using the Austrian stand simulator PROGNAUS. This simulator was chosen specifically because it does not...

Air bio-battery with a gas/liquid porous diaphragm cell for medical and health care devices.

PubMed

Arakawa, Takahiro; Xie, Rui; Seshima, Fumiya; Toma, Koji; Mitsubayashi, Kohji

2018-04-30

Powering future generations of medical and health care devices mandates the transcutaneous transfer of energy or harvesting energy from the human body fluid. Glucose-driven bio fuel cells (bio-batteries) demonstrate promise as they produce electrical energy from glucose, which is a substrate presents in physiological fluids. Enzymatic biofuel cells can convert chemical energy into electrical energy using enzymes as catalysts. In this study, an air bio-battery was developed for healthcare and medical applications, consisting of a glucose-driven enzymatic biofuel cell using a direct gas-permeable membrane or a gas/liquid porous diaphragm. The power generation characteristics included a maximum current density of 285μA/cm 2 and maximum power density of 70.7μW/cm 2 in the presence of 5mmol/L of glucose in solution. In addition, high-performance, long-term-stabilized power generation was achieved using the gas/liquid porous diaphragm for the reactions between oxygen and enzyme. This system can be powered using 5mmol/L of glucose, the value of which is similar to that of the blood sugar range in humans. Copyright © 2017 Elsevier B.V. All rights reserved.

A membraneless biofuel cell powered by ethanol and alcoholic beverage.

PubMed

Deng, Liu; Shang, Li; Wen, Dan; Zhai, Junfeng; Dong, Shaojun

2010-09-15

In this study, we reported on the construction of a stable single-chamber ethanol/O(2) biofuel cell harvesting energy from the ethanol and alcoholic beverage. We prepared a composite film which consisted of partially sulfonated (3-mercaptopropyl)-trimethoxysilane sol-gel (PSSG) and chitosan (CHI). The combination of ion-exchange capacity sol-gel and biopolymer chitosan not only provided the attached sites for mediator MDB and AuNPs to facilitate the electron transfer along the substrate reaction, but also gave the suitable microenvironment to retain the enzyme activity in long term. The ethanol bioanode was constructed with the film coimmobilized dehydrogenase (ADH), Meldola's blue (MDB) and gold nanoparticles (AuNPs). The MDB/AuNPs/PSSG-CHI-ADH composite modified electrode showed prominent electrocatalytic activity towards the oxidation of ethanol. The oxygen biocathode consisted of laccase and AuNPs immobilized on the PSSG-CHI composite membrane. The AuNPs/PSSG-CHI-laccase modified electrode catalyzed four-electron reduction of O(2) to water, without any mediator. The assembled single-chamber biofuel cell exhibited good stability and power output towards ethanol. The open-circuit voltage of this biofuel cell was 860 mV. The maximum power density of the biofuel cell was 1.56 mWcm(-2) at 550 mV. Most interestingly, this biofuel cell showed the similar performance when the alcoholic beverage acted as the fuel. When this biofuel cell ran with wine as the fuel, the maximum power output density was 3.21 mAcm(-2) and the maximum power density was 1.78 mWcm(-2) at 680 mV of the cell voltage. Our system exhibited stable and high power output in the multi-component substrate condition. This cell has great potential for the development and practical application of bioethanol fuel cell. Copyright 2010 Elsevier B.V. All rights reserved.

Investigation of traveling ionospheric disturbances

NASA Technical Reports Server (NTRS)

Grossi, M.; Estes, R. D.

1981-01-01

Maximum entropy power spectra of the ionospheric electron density were constructed to enable PINY to compare them with the power independently obtained by PINY with in situ measurements of ionospheric electron density and neutral species performed with instrumentation carried by the Atmospheric Explorer (AE) satellite. This comparison corroborated evidence on the geophysical reality of the alleged electron density irregularities detected by the ASTP dual frequency Doppler link. Roughly half of the localized wave structures which are confined to dimensions of 1800 km or less (as seen by an orbiting Doppler baseline) were found to be associated with the larger crest of the geomagnetic anomaly in the Southern (winter) Hemisphere in the morning. The observed nighttime structures are also associated with local peaks in the electron density.

Satellite power system concept development and evaluation program. Volume 2: System definition

NASA Technical Reports Server (NTRS)

1981-01-01

The system level results of the system definition studies performed by NASA as a part of the Department of Energy/NASA satellite power system concept development and evaluation program are summarized. System requirements and guidelines are discussed as well as the major elements that comprise the reference system and its design options. Alternative system approaches including different system sizes, solid state amplifier (microwave) concepts, and laser power transmission system cost summaries are reviewed. An overview of the system analysis and planning efforts is included. The overall study led to the conclusion that the reference satellite power system concept is a feasible baseload source of electrical power and, within the assumed guidelines, the minimum cost per kilowatt is achieved at the maximum output of 5 gigawatts to the utility grid. Major unresolved technical issues include maximum allowable microwave power density in the ionosphere and performance/mass characteristics of laser power transmission systems.

MEANS FOR CONTROLLING A NUCLEAR REACTOR

DOEpatents

Wilson, V.C.; Overbeck, W.P.; Slotin, L.; Froman, D.K.

1957-12-17

This patent relates to nuclear reactors of the type using a solid neutron absorbing material as a means for controlling the reproduction ratio of the system and thereby the power output. Elongated rods of neutron absorbing material, such as boron steel for example, are adapted to be inserted and removed from the core of tae reactor by electronic motors and suitable drive means. The motors and drive means are controlled by means responsive to the neutron density, such as ionization chambers. The control system is designed to be responsive also to the rate of change in neutron density to automatically maintain the total power output at a substantially constant predetermined value. A safety rod means responsive to neutron density is also provided for keeping the power output below a predetermined maximum value at all times.

High charge-discharge performance of Pb{sub 0.98}La{sub 0.02}(Zr{sub 0.35}Sn{sub 0.55}Ti{sub 0.10}){sub 0.995}O{sub 3} antiferroelectric ceramics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Chenhong; University of the Chinese Academy of Sciences, Beijing 100049; Liu, Zhen

2016-08-21

The energy storage performance and charge-discharge properties of Pb{sub 0.98}La{sub 0.02}(Zr{sub 0.35}Sn{sub 0.55}Ti{sub 0.10}){sub 0.995}O{sub 3} (PLZST) antiferroelectric ceramics were investigated through directly measuring the hysteresis loops and pulse discharge current-time curves. The energy density only varies 0.2% per degree from 25 °C to 85 °C, and the energy efficiency maintains at about 90%. Furthermore, an approximate calculating model of maximum power density p{sub max} was established for the discharge process. Under a relatively high working electric field (8.2 kV/mm), this ceramics possess a greatly enhanced power density of 18 MW/cm{sup 3}. Moreover, the pulse power properties did not show degradation until 1500 timesmore » of charge-discharge cycling. The large released energy density, high energy efficiency, good temperature stability, greatly enhanced power density, and excellent fatigue endurance combined together make this PLZST ceramics an ideal candidate for pulse power applications.« less

Laser-induced electron source in a vacuum diode

NASA Astrophysics Data System (ADS)

Ghera, U.; Boxman, R. L.; Kleinman, H.; Ruschin, S.

1989-11-01

Experiments were conducted in which a high-power CO2 TEA laser interacted with metallic cathode in a high-vacuum (10 to the -8th Torr) diode. For power densities lower than 5 x 10 to the 7th W/sq cm, no current was detected. For power densities in the range of 5 x 10 to the 7th to 5 x 10 to the 8th W/sq cm, the Cu cathode emitted a maximum current of 40 mA. At a higher power density level, a circuit-limited current of 8 A was detected. The jump of a few orders of magnitude in the current is attributed to breakdown of the diode gap. The experimental results are similar to those of a triggered vacuum gap, and a thorough comparison is presented in this paper. The influence of the pressure in the vacuum chamber on the current magnitude shows the active role that adsorbed gas molecules have in the initial breakdown. When the cathode material was changed from metal to metal oxide, much lower laser power densities were required to reach the breakdown current region.

Carbon nanotube torsional springs for regenerative braking systems

NASA Astrophysics Data System (ADS)

Liu, Sanwei; Martin, Corbin; Lashmore, David; Schauer, Mark; Livermore, Carol

2015-10-01

The modeling and demonstration of large stroke, high energy density and high power density torsional springs based on carbon nanotube (CNT) yarns is reported, as well as their application as energy-storing actuators for regenerative braking systems. An originally untwisted CNT yarn is cyclically loaded and unloaded in torsion, with the maximum rotation angle increasing incrementally until failure. The measured average extractable energy density values are 2.9 kJ kg-1  ±  1.2 kJ kg-1 and 3.4 kJ kg-1  ±  0.4 kJ kg-1 for 1-ply CNT yarns and 2-ply CNT yarns, respectively. Additionally, a regenerative braking system is demonstrated to capture the kinetic energy of a wheel and store it as elastic energy in twisted CNT yarns. When the yarn’s twist is released, the stored energy reaccelerates the wheel. The measured energy and mean power densities of the CNT yarns in the simple regenerative braking setup are on average 3.3 kJ kg-1 and 0.67 kW kg-1, respectively, with maximum measured values of up to 4.7 kJ kg-1 and 1.2 kW kg-1, respectively. A slightly lower energy density of up to 1.2 kJ kg-1 and a 0.29 kW kg-1 mean power density are measured for CNT yarns in a more complex setup that mimics a unidirectional rotating regenerative braking mechanism.

Using live algae at the anode of a microbial fuel cell to generate electricity.

PubMed

Xu, Chang; Poon, Karen; Choi, Martin M F; Wang, Ruihua

2015-10-01

Live green microalgae Chlorella pyrenoidosa was introduced in the anode of a microbial fuel cell (MFC) to act as an electron donor. By controlling the oxygen content, light intensity, and algal cell density at the anode, microalgae would generate electricity without requiring externally added substrates. Two models of algal microbial fuel cells (MFCs) were constructed with graphite/carbon electrodes and no mediator. Model 1 algal MFC has live microalgae grown at the anode and potassium ferricyanide at the cathode, while model 2 algal MFC had live microalgae in both the anode and cathode in different growth conditions. Results indicated that a higher current produced in model 1 algal MFC was obtained at low light intensity of 2500 lx and algal cell density of 5 × 10(6) cells/ml, in which high algal density would limit the electricity generation, probably by increasing oxygen level and mass transfer problem. The maximum power density per unit anode volume obtained in model 1 algal MFC was relatively high at 6030 mW/m(2), while the maximum power density at 30.15 mW/m(2) was comparable with that of previous reported bacteria-driven MFC with graphite/carbon electrodes. A much smaller power density at 2.5 mW/m(2) was observed in model 2 algal MFC. Increasing the algal cell permeability by 4-nitroaniline would increase the open circuit voltage, while the mitochondrial acting and proton leak promoting agents resveratrol and 2,4-dinitrophenol would increase the electric current production in algal MFC.

Co(OH)2 nanosheet-decorated graphene–CNT composite for supercapacitors of high energy density

PubMed Central

Cheng, Qian; Tang, Jie; Shinya, Norio; Qin, Lu-Chang

2014-01-01

A composite of graphene and carbon nanotubes has been synthesized and characterized for application as supercapacitor electrodes. By coating the nanostructured active material of Co(OH)2 onto one electrode, the asymmetric supercapacitor has exhibited a high specific capacitance of 310 F g−1, energy density of 172 Wh kg−1 and maximum power density of 198 kW kg−1 in ionic liquid electrolyte EMI-TFSI. PMID:27877633

Co(OH)2 nanosheet-decorated graphene-CNT composite for supercapacitors of high energy density.

PubMed

Cheng, Qian; Tang, Jie; Shinya, Norio; Qin, Lu-Chang

2014-02-01

A composite of graphene and carbon nanotubes has been synthesized and characterized for application as supercapacitor electrodes. By coating the nanostructured active material of Co(OH) 2 onto one electrode, the asymmetric supercapacitor has exhibited a high specific capacitance of 310 F g -1 , energy density of 172 Wh kg -1 and maximum power density of 198 kW kg -1 in ionic liquid electrolyte EMI-TFSI.

Statistics of some atmospheric turbulence records relevant to aircraft response calculations

NASA Technical Reports Server (NTRS)

Mark, W. D.; Fischer, R. W.

1981-01-01

Methods for characterizing atmospheric turbulence are described. The methods illustrated include maximum likelihood estimation of the integral scale and intensity of records obeying the von Karman transverse power spectral form, constrained least-squares estimation of the parameters of a parametric representation of autocorrelation functions, estimation of the power spectra density of the instantaneous variance of a record with temporally fluctuating variance, and estimation of the probability density functions of various turbulence components. Descriptions of the computer programs used in the computations are given, and a full listing of these programs is included.

Power generation from furfural using the microbial fuel cell

NASA Astrophysics Data System (ADS)

Luo, Yong; Liu, Guangli; Zhang, Renduo; Zhang, Cuiping

Furfural is a typical inhibitor in the ethanol fermentation process using lignocellulosic hydrolysates as raw materials. In the literature, no report has shown that furfural can be utilized as the fuel to produce electricity in the microbial fuel cell (MFC), a device that uses microbes to convert organic compounds to generate electricity. In this study, we demonstrated that electricity was successfully generated using furfural as the sole fuel in both the ferricyanide-cathode MFC and the air-cathode MFC. In the ferricyanide-cathode MFC, the maximum power densities reached 45.4, 81.4, and 103 W m -3, respectively, when 1000 mg L -1 glucose, a mixture of 200 mg L -1 glucose and 5 mM furfural, and 6.68 mM furfural were used as the fuels in the anode solution. The corresponding Coulombic efficiencies (CE) were 4.0, 7.1, and 10.2% for the three treatments, respectively. For pure furfural as the fuel, the removal efficiency of furfural reached up to 95% within 12 h. In the air-cathode MFC using 6.68 mM furfural as the fuel, the maximum values of power density and CE were 361 mW m -2 (18 W m -3) and 30.3%, respectively, and the COD removal was about 68% at the end of the experiment (about 30 h). Increase in furfural concentrations from 6.68 to 20 mM resulted in increase in the maximum power densities from 361 to 368 mW m -2, and decrease in CEs from 30.3 to 20.6%. These results indicated that some toxic and biorefractory organics such as furfural might still be suitable resources for electricity generation using the MFC technology.

Improving performance of MFC by design alteration and adding cathodic electrolytes.

PubMed

Jadhav, G S; Ghangrekar, M M

2008-12-01

Performance of two microbial fuel cells (MFCs) was investigated under batch and continuous mode of operation using different cathodic electrolyte. The wastewater was supplied from the bottom port provided to the anode chamber in both the MFCs and the effluent left the anode chamber from the top port in MFC-1, whereas in MFC-2, the effluent exit was provided close to membrane. Stainless steel (SS) mesh anode was used in both the MFCs with surface area of 167 and 100 cm(2) in MFC-1 and MFC-2, respectively. Under batch mode and continuous mode of operation, these MFCs gave chemical oxygen demand removal efficiency more than 85% and about 68%, respectively. Under batch mode of operation, maximum power density of 39.95 and 56.87 mW/m(2) and maximum current density of 180.83 and 295 mA/m(2) were obtained in MFC-1 and MFC-2, respectively. Under continuous mode of operation, a reduction in power and current density was observed. Even with less surface area of the anode, MFC-2 produced more current (1.77 mA) than MFC-1 (1.40 mA). Among the cathodic electrolyte tested, these can be listed in decreasing order of power density as aerated KMnO(4) solution > KMnO(4) solution without aeration > aerated tap water > aerated tap water with NaCl.

47 CFR 15.319 - General technical requirements.

Code of Federal Regulations, 2012 CFR

2012-10-01

... bandwidth of the channel. (d) Power spectral density shall not exceed 3 milliwatts in any 3 kHz bandwidth as measured with a spectrum analyzer having a resolution bandwidth of 3 kHz. (e) The peak transmit power shall be reduced by the amount in decibels that the maximum directional gain of the antenna exceeds 3 dBi...

47 CFR 15.319 - General technical requirements.

Code of Federal Regulations, 2013 CFR

2013-10-01

... bandwidth of the channel. (d) Power spectral density shall not exceed 3 milliwatts in any 3 kHz bandwidth as measured with a spectrum analyzer having a resolution bandwidth of 3 kHz. (e) The peak transmit power shall be reduced by the amount in decibels that the maximum directional gain of the antenna exceeds 3 dBi...

47 CFR 15.319 - General technical requirements.

Code of Federal Regulations, 2014 CFR

2014-10-01

... bandwidth of the channel. (d) Power spectral density shall not exceed 3 milliwatts in any 3 kHz bandwidth as measured with a spectrum analyzer having a resolution bandwidth of 3 kHz. (e) The peak transmit power shall be reduced by the amount in decibels that the maximum directional gain of the antenna exceeds 3 dBi...

Electricity generation and microbial community analysis of alcohol powered microbial fuel cells.

PubMed

Kim, Jung Rae; Jung, Sok Hee; Regan, John M; Logan, Bruce E

2007-09-01

Two different microbial fuel cell (MFC) configurations were investigated for electricity production from ethanol and methanol: a two-chambered, aqueous-cathode MFC; and a single-chamber direct-air cathode MFC. Electricity was generated in the two-chamber system at a maximum power density typical of this system (40+/-2 mW/m2) and a Coulombic efficiency (CE) ranging from 42% to 61% using ethanol. When bacteria were transferred into a single-chamber MFC known to produce higher power densities with different substrates, the maximum power density increased to 488+/-12 mW/m2 (CE = 10%) with ethanol. The voltage generated exhibited saturation kinetics as a function of ethanol concentration in the two-chambered MFC, with a half-saturation constant (Ks) of 4.86 mM. Methanol was also examined as a possible substrate, but it did not result in appreciable electricity generation. Analysis of the anode biofilm and suspension from a two-chamber MFC with ethanol using 16S rDNA-based techniques indicated that bacteria with sequences similar to Proteobacterium Core-1 (33.3% of clone library sequences), Azoarcus sp. (17.4%), and Desulfuromonas sp. M76 (15.9%) were significant members of the anode chamber community. These results indicate that ethanol can be used for sustained electricity generation at room temperature using bacteria on the anode in a MFC.

Spatial-temporal characteristics of lightning flash size in a supercell storm

NASA Astrophysics Data System (ADS)

Zhang, Zhixiao; Zheng, Dong; Zhang, Yijun; Lu, Gaopeng

2017-11-01

The flash sizes of a supercell storm, in New Mexico on October 5, 2004, are studied using the observations from the New Mexico Lightning Mapping Array and the Albuquerque, New Mexico, Doppler radar (KABX). First, during the temporal evolution of the supercell, the mean flash size is anti-correlated with the flash rate, following a unary power function, with a correlation coefficient of - 0.87. In addition, the mean flash size is linearly correlated with the area of reflectivity > 30 dBZ at 5 km normalized by the flash rate, with a correlation coefficient of 0.88. Second, in the horizontal, flash size increases along the direction from the region near the convection zone to the adjacent forward anvil. The region of minimum flash size usually corresponds to the region of maximum flash initiation and extent density. The horizontal correspondence between the mean flash size and the flash extent density can also be fitted by a unary power function, and the correlation coefficient is > 0.5 in 50% of the radar volume scans. Furthermore, the quality of fit is positively correlated to the convective intensity. Third, in the vertical direction, the height of the maximum flash initiation density is close to the height of maximum flash extent density, but corresponds to the height where the mean flash size is relatively small. In the discussion, the distribution of the small and dense charge regions when and where convection is vigorous in the storm, is deduced to be responsible for the relationship that flash size is temporally and spatially anti-correlated with flash rate and density, and the convective intensity.

Self-consistent fluid modeling and simulation on a pulsed microwave atmospheric-pressure argon plasma jet

NASA Astrophysics Data System (ADS)

Chen, Zhaoquan; Yin, Zhixiang; Chen, Minggong; Hong, Lingli; Xia, Guangqing; Hu, Yelin; Huang, Yourui; Liu, Minghai; Kudryavtsev, A. A.

2014-10-01

In present study, a pulsed lower-power microwave-driven atmospheric-pressure argon plasma jet has been introduced with the type of coaxial transmission line resonator. The plasma jet plume is with room air temperature, even can be directly touched by human body without any hot harm. In order to study ionization process of the proposed plasma jet, a self-consistent hybrid fluid model is constructed in which Maxwell's equations are solved numerically by finite-difference time-domain method and a fluid model is used to study the characteristics of argon plasma evolution. With a Guass type input power function, the spatio-temporal distributions of the electron density, the electron temperature, the electric field, and the absorbed power density have been simulated, respectively. The simulation results suggest that the peak values of the electron temperature and the electric field are synchronous with the input pulsed microwave power but the maximum quantities of the electron density and the absorbed power density are lagged to the microwave power excitation. In addition, the pulsed plasma jet excited by the local enhanced electric field of surface plasmon polaritons should be the discharge mechanism of the proposed plasma jet.

Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors.

PubMed

Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

2016-09-23

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm(-2) at 1 mA cm(-2), good flexibility with a higher value (204.6 mF cm(-2)) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg(-1) (with a power density of 3.2 kW kg(-1)) and a maximum power density of 4.2 kW kg(-1) (with an energy density of 3.1 Wh kg(-1)). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

Development and investigation of silicon converter beta radiation 63Ni isotope

NASA Astrophysics Data System (ADS)

Krasnov, A. A.; Legotin, S. A.; Murashev, V. N.; Didenko, S. I.; Rabinovich, O. I.; Yurchuk, S. Yu; Omelchenko, Yu K.; Yakimov, E. B.; Starkov, V. V.

2016-02-01

In this paper the results of the creation and researching characteristics of, experimental betavoltaic converters (BVC), based on silicon are discussed. It was presented the features of structural and technological performance of planar 2 D- structure of BVC. To study the parameters of the converter stream the beta particles of the radioisotope was simulated by 63Ni electron flux from scanning electron microscope. It was investigated the dependence of the collecting electrons efficiency from the beam energy current-voltage characteristic was measured when irradiated by an electron beam, from which the value of the short-circuit current density equal to 126 nA / cm2 and the value of the open circuit voltage of 150 mV were obtained. The maximum power density at 70 mV is 9.5 nW / cm2, and the conversion efficiency is 2.1%. It was presented the results of experimental studies of the current-voltage characteristics of samples by irradiating a film 63Ni. The values of load voltage 111 mV and short circuit current density of 27 nA / cm2 were obtained. Maximum power density was 1.52 nW / cm2.

Enhancement in current density and energy conversion efficiency of 3-dimensional MFC anodes using pre-enriched consortium and continuous supply of electron donors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Borole, Abhijeet P; Hamilton, Choo Yieng; Vishnivetskaya, Tatiana A

2011-01-01

Using a pre-enriched microbial consortium as the inoculum and continuous supply of carbon source, improvement in performance of a three-dimensional, flow-through MFC anode utilizing ferricyanide cathode was investigated. The power density increased from 170 W/m3 (1800 mW/m2) to 580 W/m3 (6130 mW/m2), when the carbon loading increased from 2.5 g/l-day to 50 g/l-day. The coulombic efficiency (CE) decreased from 90% to 23% with increasing carbon loading. The CEs are among the highest reported for glucose and lactate as the substrate with the maximum current density reaching 15.1 A/m2. This suggests establishment of a very high performance exoelectrogenic microbial consortium atmore » the anode. A maximum energy conversion efficiency of 54% was observed at a loading of 2.5 g/l-day. Biological characterization of the consortium showed presence of Burkholderiales and Rhodocyclales as the dominant members. Imaging of the biofilms revealed thinner biofilms compared to the inoculum MFC, but a 1.9-fold higher power density.« less

Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

2016-09-01

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm-2 at 1 mA cm-2, good flexibility with a higher value (204.6 mF cm-2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg-1 (with a power density of 3.2 kW kg-1) and a maximum power density of 4.2 kW kg-1 (with an energy density of 3.1 Wh kg-1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

Electricity generation in a membrane-less microbial fuel cell with down-flow feeding onto the cathode.

PubMed

Zhu, Feng; Wang, Wancheng; Zhang, Xiaoyan; Tao, Guanhong

2011-08-01

A novel membrane-less microbial fuel cell (MFC) with down-flow feeding was constructed to generate electricity. Wastewater was fed directly onto the cathode which was horizontally installed in the upper part of the MFC. Oxygen could be utilized readily from the air. The concentration of dissolved oxygen in the influent wastewater had little effect on the power generation. A saturation-type relationship was observed between the initial COD and the power generation. The influent flow rate could affect greatly the power density. Fed by the synthetic glucose wastewater with a COD value of 3500 mg/L at a flow rate of 4.0 mL/min, the developed MFC could produce a maximum power density of 37.4 mW/m(2). Its applicability was further evaluated by the treatment of brewery wastewater. The system could be scaled up readily due to its simple configuration, easy operation and relatively high power density. Copyright © 2011 Elsevier Ltd. All rights reserved.

Encircling the dark: constraining dark energy via cosmic density in spheres

NASA Astrophysics Data System (ADS)

Codis, S.; Pichon, C.; Bernardeau, F.; Uhlemann, C.; Prunet, S.

2016-08-01

The recently published analytic probability density function for the mildly non-linear cosmic density field within spherical cells is used to build a simple but accurate maximum likelihood estimate for the redshift evolution of the variance of the density, which, as expected, is shown to have smaller relative error than the sample variance. This estimator provides a competitive probe for the equation of state of dark energy, reaching a few per cent accuracy on wp and wa for a Euclid-like survey. The corresponding likelihood function can take into account the configuration of the cells via their relative separations. A code to compute one-cell-density probability density functions for arbitrary initial power spectrum, top-hat smoothing and various spherical-collapse dynamics is made available online, so as to provide straightforward means of testing the effect of alternative dark energy models and initial power spectra on the low-redshift matter distribution.

Effects of lightning on trees: A predictive model based on in situ electrical resistivity.

PubMed

Gora, Evan M; Bitzer, Phillip M; Burchfield, Jeffrey C; Schnitzer, Stefan A; Yanoviak, Stephen P

2017-10-01

The effects of lightning on trees range from catastrophic death to the absence of observable damage. Such differences may be predictable among tree species, and more generally among plant life history strategies and growth forms. We used field-collected electrical resistivity data in temperate and tropical forests to model how the distribution of power from a lightning discharge varies with tree size and identity, and with the presence of lianas. Estimated heating density (heat generated per volume of tree tissue) and maximum power (maximum rate of heating) from a standardized lightning discharge differed 300% among tree species. Tree size and morphology also were important; the heating density of a hypothetical 10 m tall Alseis blackiana was 49 times greater than for a 30 m tall conspecific, and 127 times greater than for a 30 m tall Dipteryx panamensis . Lianas may protect trees from lightning by conducting electric current; estimated heating and maximum power were reduced by 60% (±7.1%) for trees with one liana and by 87% (±4.0%) for trees with three lianas. This study provides the first quantitative mechanism describing how differences among trees can influence lightning-tree interactions, and how lianas can serve as natural lightning rods for trees.

Magnetic-assisted triboelectric nanogenerators as self-powered visualized omnidirectional tilt sensing system

NASA Astrophysics Data System (ADS)

Han, Mengdi; Zhang, Xiao-Sheng; Sun, Xuming; Meng, Bo; Liu, Wen; Zhang, Haixia

2014-04-01

The triboelectric nanogenerator (TENG) is a promising device in energy harvesting and self-powered sensing. In this work, we demonstrate a magnetic-assisted TENG, utilizing the magnetic force for electric generation. Maximum power density of 541.1 mW/m2 is obtained at 16.67 MΩ for the triboelectric part, while the electromagnetic part can provide power density of 649.4 mW/m2 at 16 Ω. Through theoretical calculation and experimental measurement, linear relationship between the tilt angle and output voltage at large angles is observed. On this basis, a self-powered omnidirectional tilt sensor is realized by two magnetic-assisted TENGs, which can measure the magnitude and direction of the tilt angle at the same time. For visualized sensing of the tilt angle, a sensing system is established, which is portable, intuitive, and self-powered. This visualized system greatly simplifies the measure process, and promotes the development of self-powered systems.

Electronic and thermoelectric analysis of phases in the In 2O 3(ZnO) k system

DOE PAGES

Hopper, E. Mitchell; Zhu, Qimin; Song, Jung-Hwan; ...

2011-01-01

The high-temperature electrical conductivity and thermopower of several compounds in the In 2O 3(ZnO) k system (k = 3, 5, 7, and 9) were measured, and the band structures of the k = 1, 2, and 3 structures were predicted based on first-principles calculations. These phases exhibit highly dispersed conduction bands consistent with transparent conducting oxide behavior. Jonker plots (Seebeck coefficient vs. natural logarithm of conductivity) were used to obtain the product of the density of states and mobility for these phases, which were related to the maximum achievable power factor (thermopower squared times conductivity) for each phase by Ioffemore » analysis (maximum power factor vs. Jonker plot intercept). With the exception of the k = 9 phase, all other phases were found to have maximum predicted power factors comparable to other thermoelectric oxides if suitably doped.« less

Negative hydrogen ions in a linear helicon plasma device

NASA Astrophysics Data System (ADS)

Corr, Cormac; Santoso, Jesse; Samuell, Cameron; Willett, Hannah; Manoharan, Rounak; O'Byrne, Sean

2015-09-01

Low-pressure negative ion sources are of crucial importance to the development of high-energy (>1 MeV) neutral beam injection systems for the ITER experimental tokamak device. Due to their high power coupling efficiency and high plasma densities, helicon devices may be able to reduce power requirements and potentially remove the need for caesium. In helicon sources, the RF power can be coupled efficiently into the plasma and it has been previously observed that the application of a small magnetic field can lead to a significant increase in the plasma density. In this work, we investigate negative ion dynamics in a high-power (20 kW) helicon plasma source. The negative ion fraction is measured by probe-based laser photodetachment, electron density and temperature are determined by a Langmuir probe and tuneable diode laser absorption spectroscopy is used to determine the density of the H(n = 2) excited atomic state and the gas temperature. The negative ion density and excited atomic hydrogen density display a maximum at a low applied magnetic field of 3 mT, while the electron temperature displays a minimum. The negative ion density can be increased by a factor of 8 with the application of the magnetic field. Spatial and temporal measurements will also be presented. The Australian Research Grants Council is acknowledged for funding.

Understanding limiting factors in thick electrode performance as applied to high energy density Li-ion batteries

DOE PAGES

Du, Zhijia; Wood, David L.; Daniel, Claus; ...

2017-02-09

We present that increasing electrode thickness, thus increasing the volume ratio of active materials, is one effective method to enable the development of high energy density Li-ion batteries. In this study, an energy density versus power density optimization of LiNi 0.8Co 0.15Al 0.05O 2 (NCA)/graphite cell stack was conducted via mathematical modeling. The energy density was found to have a maximum point versus electrode thickness (critical thickness) at given discharging C rates. The physics-based factors that limit the energy/power density of thick electrodes were found to be increased cell polarization and underutilization of active materials. The latter is affected bymore » Li-ion diffusion in active materials and Li-ion depletion in the electrolyte phase. Based on those findings, possible approaches were derived to surmount the limiting factors. Finally, the improvement of the energy–power relationship in an 18,650 cell was used to demonstrate how to optimize the thick electrode parameters in cell engineering.« less

Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell

PubMed Central

Xu, Wei; Zhang, Huimin; Li, Gang; Wu, Zucheng

2014-01-01

Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm−2 when 0.33 M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm−2 with an open circuit voltage of 0.38 V at 60°C. PMID:25168632

Solar driven electrochromic photoelectrochemical fuel cells for simultaneous energy conversion, storage and self-powered sensing.

PubMed

Wang, Yanhu; Zhang, Lina; Cui, Kang; Xu, Caixia; Li, Hao; Liu, Hong; Yu, Jinghua

2018-02-15

One solar-driven electrochromic photoelectrochemical fuel cell (PFC) with highly efficient energy conversion and storage is easily constructed to achieve quantitative self-powered sensing. Layered bismuth oxyiodide-zinc oxide nanorod arrays (ZnO@BiOI NRA) with a core/shell p-n heterostructure are fabricated as the photoanode with electrochromic Prussian blue (PB) as the cathode. The core/shell p-n heterostructure for the ZnO@BiOI photoanode can effectively boost the photoelectrochemical (PEC) performance through the improvement of photon absorption and charge carrier separation. The optimal assembled PFC yields an open-circuit voltage (V OC ) of 0.48 V with the maximum power output density (P max ) as high as 155 μW cm -2 upon illumination. Benefitting from the interactive color-changing behavior of PB, the cathode not only exhibits cathodic catalytic activity in the PFC but also serves as an electrochromic display for self-powered sensing. The as-constructed PFC possesses multiple readable signal output nanochannels through the maximum power output density (P max ) of the PFC or the color change of PB. Meanwhile, the dual-signal-output makes the as-constructed self-powered sensor highly available in various operations demands with the enhanced reliability. With the advantages of high efficiency of PFCs, unique assay ability, and broad environmental suitability, the constructed self-powered platform shows broad application prospects as an integrated smart analytical device.

Helicon normal modes in Proto-MPEX

NASA Astrophysics Data System (ADS)

Piotrowicz, P. A.; Caneses, J. F.; Green, D. L.; Goulding, R. H.; Lau, C.; Caughman, J. B. O.; Rapp, J.; Ruzic, D. N.

2018-05-01

The Proto-MPEX helicon source has been operating in a high electron density ‘helicon-mode’. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the ‘helicon-mode’. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besides directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region. ).

Helicon normal modes in Proto-MPEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Piotrowicz, Pawel A.; Caneses, Juan F.; Green, David L.

Here, the Proto-MPEX helicon source has been operating in a high electron density 'helicon-mode'. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the 'helicon-mode'. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besidesmore » directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region.« less

Helicon normal modes in Proto-MPEX

DOE PAGES

Piotrowicz, Pawel A.; Caneses, Juan F.; Green, David L.; ...

2018-05-22

Here, the Proto-MPEX helicon source has been operating in a high electron density 'helicon-mode'. Establishing plasma densities and magnetic field strengths under the antenna that allow for the formation of normal modes of the fast-wave are believed to be responsible for the 'helicon-mode'. A 2D finite-element full-wave model of the helicon antenna on Proto-MPEX is used to identify the fast-wave normal modes responsible for the steady-state electron density profile produced by the source. We also show through the simulation that in the regions of operation in which core power deposition is maximum the slow-wave does not deposit significant power besidesmore » directly under the antenna. In the case of a simulation where a normal mode is not excited significant edge power is deposited in the mirror region.« less

EFFECTS OF LASER RADIATION ON MATTER: Melting and thermocapillary convection under the action of pulsed laser radiation with an inhomogeneous spatial distribution

NASA Astrophysics Data System (ADS)

Uglov, A. A.; Smurov, I. Yu; Gus'kov, A. G.; Aksenov, L. V.

1990-08-01

A theoretical study is reported of melting and thermocapillary convection under the action of laser radiation with a nonmonotonic spatial distribution of the power density. An analysis is made of changes in the geometry of the molten bath with time. The transition from a nonmonotonic boundary of a melt, corresponding to the spatial distribution of the radiation, to a monotonic one occurs in a time of the order of 1 ms when the power density of laser radiation is 105 W/cm2. The vortex structure of the flow in the molten bath is governed by the spatial distribution of the laser radiation in such a way that each local power density maximum corresponds to two vortices with oppositely directed velocity components.

High energy density propulsion systems and small engine dynamometer

NASA Astrophysics Data System (ADS)

Hays, Thomas

2009-07-01

Scope and Method of Study. This study investigates all possible methods of powering small unmanned vehicles, provides reasoning for the propulsion system down select, and covers in detail the design and production of a dynamometer to confirm theoretical energy density calculations for small engines. Initial energy density calculations are based upon manufacturer data, pressure vessel theory, and ideal thermodynamic cycle efficiencies. Engine tests are conducted with a braking type dynamometer for constant load energy density tests, and show true energy densities in excess of 1400 WH/lb of fuel. Findings and Conclusions. Theory predicts lithium polymer, the present unmanned system energy storage device of choice, to have much lower energy densities than other conversion energy sources. Small engines designed for efficiency, instead of maximum power, would provide the most advantageous method for powering small unmanned vehicles because these engines have widely variable power output, loss of mass during flight, and generate rotational power directly. Theoretical predictions for the energy density of small engines has been verified through testing. Tested values up to 1400 WH/lb can be seen under proper operating conditions. The implementation of such a high energy density system will require a significant amount of follow-on design work to enable the engines to tolerate the higher temperatures of lean operation. Suggestions are proposed to enable a reliable, small-engine propulsion system in future work. Performance calculations show that a mature system is capable of month long flight times, and unrefueled circumnavigation of the globe.

A continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit

NASA Technical Reports Server (NTRS)

Nerheim, N. M.; Bhanji, A. M.; Russell, G. R.

1978-01-01

Experimental characteristics of a continuously pulsed copper halide laser with a cable-capacitor Blumlein discharge circuit are reported. Quartz laser tubes 1 m in length and 1.5 and 2.5 cm in diameter were employed to study the effects of the electrical circuit, lasant, and buffer gas on laser performance. Measured properties of the Blumlein circuit are compared with an analytic solution for an idealized circuit. Both CuCl and CuBr with neon and helium buffer gas were studied. A maximum average power of 12.5 W was obtained with a 1.5 nF capacitor charged to 8 kV and discharged at 31 kHz with CuCl and neon buffer gas at 0.7 kPa in a 2.5-cm-diam tube. A maximum efficiency of 0.72 percent was obtained at 9 W average power. Measurements of the radial distribution of the power in the laser beam and the variation of laser power at 510.6 and 578.2 nm with halide vapor density are also reported. Double and continuously pulsed laser characteristics are compared, and the role of copper metastable level atoms in limiting the laser pulse energy density is discussed.

Design optimization of PVDF-based piezoelectric energy harvesters.

PubMed

Song, Jundong; Zhao, Guanxing; Li, Bo; Wang, Jin

2017-09-01

Energy harvesting is a promising technology that powers the electronic devices via scavenging the ambient energy. Piezoelectric energy harvesters have attracted considerable interest for their high conversion efficiency and easy fabrication in minimized sensors and transducers. To improve the output capability of energy harvesters, properties of piezoelectric materials is an influential factor, but the potential of the material is less likely to be fully exploited without an optimized configuration. In this paper, an optimization strategy for PVDF-based cantilever-type energy harvesters is proposed to achieve the highest output power density with the given frequency and acceleration of the vibration source. It is shown that the maximum power output density only depends on the maximum allowable stress of the beam and the working frequency of the device, and these two factors can be obtained by adjusting the geometry of piezoelectric layers. The strategy is validated by coupled finite-element-circuit simulation and a practical device. The fabricated device within a volume of 13.1 mm 3 shows an output power of 112.8 μW which is comparable to that of the best-performing piezoceramic-based energy harvesters within the similar volume reported so far.

[Performance of Electricity Generation and Feasibility of Discontinuous Power Supply of MFC by Using Pretreated Excess Sludge as Fuel].

PubMed

Zhao, Yan-hui; Zhao, Yang-guo; Guo, Liang

2016-03-15

The feasibility of treating pretreated excess sludge and capacity of supplying continuous power of microbial fuel cells (MFCs) were investigated. Two-chamber microbial fuel cells were started up and operated by using thermal pretreated excess sludge as the substrate. Potential fluctuations were achieved by changing the cathode electron acceptor. During the changes of electron acceptor, the operational stability of MFCs was assessed. The results indicated that the MFCs started successfully with oxygen as the cathode electron acceptor and reached 0.24 V after 148 hours. When the cathode electron acceptor was replaced by potassium ferricyanide, MFCs could obtain the maximum output voltage and maximum power density of 0.66 V and 4.21 W · m⁻³, respectively. When the cathode electron acceptor was changed from oxygen to potassium ferricyanide or the MFCs were closed circuit, the output power of MFCs recovered rapidly. In addition, changes of electron acceptor showed no effect on the removal of COD and ammonia nitrogen. Their removal efficiencies approached to 70% and 80%, respectively. This study concluded that MFC could treat the pretreated excess sludge and produce electricity simultaneously with a high power density. The MFC could also achieve discontinuous electricity supply during operation.

Direct alcohol fuel cells: toward the power densities of hydrogen-fed proton exchange membrane fuel cells.

PubMed

Chen, Yanxin; Bellini, Marco; Bevilacqua, Manuela; Fornasiero, Paolo; Lavacchi, Alessandro; Miller, Hamish A; Wang, Lianqin; Vizza, Francesco

2015-02-01

A 2 μm thick layer of TiO2 nanotube arrays was prepared on the surface of the Ti fibers of a nonwoven web electrode. After it was doped with Pd nanoparticles (1.5 mgPd  cm(-2) ), this anode was employed in a direct alcohol fuel cell. Peak power densities of 210, 170, and 160 mW cm(-2) at 80 °C were produced if the cell was fed with 10 wt % aqueous solutions of ethanol, ethylene glycol, and glycerol, respectively, in 2 M aqueous KOH. The Pd loading of the anode was increased to 6 mg cm(-2) by combining four single electrodes to produce a maximum peak power density with ethanol at 80 °C of 335 mW cm(-2) . Such high power densities result from a combination of the open 3 D structure of the anode electrode and the high electrochemically active surface area of the Pd catalyst, which promote very fast kinetics for alcohol electro-oxidation. The peak power and current densities obtained with ethanol at 80 °C approach the output of H2 -fed proton exchange membrane fuel cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electron density and plasma dynamics of a colliding plasma experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wiechula, J., E-mail: wiechula@physik.uni-frankfurt.de; Schönlein, A.; Iberler, M.

2016-07-15

We present experimental results of two head-on colliding plasma sheaths accelerated by pulsed-power-driven coaxial plasma accelerators. The measurements have been performed in a small vacuum chamber with a neutral-gas prefill of ArH{sub 2} at gas pressures between 17 Pa and 400 Pa and load voltages between 4 kV and 9 kV. As the plasma sheaths collide, the electron density is significantly increased. The electron density reaches maximum values of ≈8 ⋅ 10{sup 15} cm{sup −3} for a single accelerated plasma and a maximum value of ≈2.6 ⋅ 10{sup 16} cm{sup −3} for the plasma collision. Overall a raise of the plasma density by a factor ofmore » 1.3 to 3.8 has been achieved. A scaling behavior has been derived from the values of the electron density which shows a disproportionately high increase of the electron density of the collisional case for higher applied voltages in comparison to a single accelerated plasma. Sequences of the plasma collision have been taken, using a fast framing camera to study the plasma dynamics. These sequences indicate a maximum collision velocity of 34 km/s.« less

X-Ray Emission from Supernovae in Dense Circumstellar Matter Environments: A Search for Collisionless Shock

NASA Technical Reports Server (NTRS)

Ofek, E.O; Fox, D.; Cenko, B.; Sullivan, M.; Gnat, O.; Frail A.; Horesh, A.; Corsi, A; Quimby, R. M.; Gehrels, N.;

Canonical Statistical Model for Maximum Expected Immission of Wire Conductor in an Aperture Enclosure

NASA Technical Reports Server (NTRS)

Bremner, Paul G.; Vazquez, Gabriel; Christiano, Daniel J.; Trout, Dawn H.

2016-01-01

Prediction of the maximum expected electromagnetic pick-up of conductors inside a realistic shielding enclosure is an important canonical problem for system-level EMC design of space craft, launch vehicles, aircraft and automobiles. This paper introduces a simple statistical power balance model for prediction of the maximum expected current in a wire conductor inside an aperture enclosure. It calculates both the statistical mean and variance of the immission from the physical design parameters of the problem. Familiar probability density functions can then be used to predict the maximum expected immission for deign purposes. The statistical power balance model requires minimal EMC design information and solves orders of magnitude faster than existing numerical models, making it ultimately viable for scaled-up, full system-level modeling. Both experimental test results and full wave simulation results are used to validate the foundational model.

Novel iron oxyhydroxide lepidocrocite nanosheet as ultrahigh power density anode material for asymmetric supercapacitors.

PubMed

Chen, Ying-Chu; Lin, Yan-Gu; Hsu, Yu-Kuei; Yen, Shi-Chern; Chen, Kuei-Hsien; Chen, Li-Chyong

2014-09-24

A simple one-step electroplating route is proposed for the synthesis of novel iron oxyhydroxide lepidocrocite (γ-FeOOH) nanosheet anodes with distinct layered channels, and the microstructural influence on the pseudocapacitive performance of the obtained γ-FeOOH nanosheets is investigated via in situ X-ray absorption spectroscopy (XAS) and electrochemical measurement. The in situ XAS results regarding charge storage mechanisms of electrodeposited γ-FeOOH nanosheets show that a Li(+) can reversibly insert/desert into/from the 2D channels between the [FeO6 ] octahedral subunits depending on the applied potential. This process charge compensates the Fe(2+) /Fe(3+) redox transition upon charging-discharging and thus contributes to an ideal pseudocapacitive behavior of the γ-FeOOH electrode. Electrochemical results indicate that the γ-FeOOH nanosheet shows the outstanding pseudocapacitive performance, which achieves the extraordinary power density of 9000 W kg(-1) with good rate performance. Most importantly, the asymmetric supercapacitors with excellent electrochemical performance are further realized by using 2D MnO2 and γ-FeOOH nanosheets as cathode and anode materials, respectively. The obtained device can be cycled reversibly at a maximum cell voltage of 1.85 V in a mild aqueous electrolyte, further delivering a maximum power density of 16 000 W kg(-1) at an energy density of 37.4 Wh kg(-1). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

An oxygen-independent and membrane-less glucose biobattery/supercapacitor hybrid device.

PubMed

Xiao, Xinxin; Conghaile, Peter Ó; Leech, Dónal; Ludwig, Roland; Magner, Edmond

2017-12-15

Enzymatic biofuel cells can generate electricity directly from the chemical energy of biofuels in physiological fluids, but their power density is significantly limited by the performance of the cathode which is based on oxygen reduction for in vivo applications. An oxygen-independent and membrane-less glucose biobattery was prepared that consists of a dealloyed nanoporous gold (NPG) supported glucose dehydrogenase (GDH) bioanode, immobilised with the assistance of conductive polymer/Os redox polymer composites, and a solid-state NPG/MnO 2 cathode. In a solution containing 10mM glucose, a maximum power density of 2.3µWcm -2 at 0.21V and an open circuit voltage (OCV) of 0.49V were registered as a biobattery. The potential of the discharged MnO 2 could be recovered, enabling a proof-of-concept biobattery/supercapacitor hybrid device. The resulting device exhibited a stable performance for 50 cycles of self-recovery and galvanostatic discharge as a supercapacitor at 0.1mAcm -2 over a period of 25h. The device could be discharged at current densities up to 2mAcm -2 supplying a maximum instantaneous power density of 676 μW cm -2 , which is 294 times higher than that from the biobattery alone. A mechanism for the recovery of the potential of the cathode, analogous to that of RuO 2 (Electrochim. Acta 42(23), 3541-3552) is described. Copyright © 2017 Elsevier B.V. All rights reserved.

Electron density modulation in a pulsed dual-frequency (2/13.56 MHz) dual-antenna inductively coupled plasma discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sirse, Nishant, E-mail: nishant.sirse@dcu.ie; Mishra, Anurag; Yeom, Geun Y.

The electron density, n{sub e}, modulation is measured experimentally using a resonance hairpin probe in a pulsed, dual-frequency (2/13.56 MHz), dual-antenna, inductively coupled plasma discharge produced in argon-C{sub 4}F{sub 8} (90–10) gas mixtures. The 2 MHz power is pulsed at a frequency of 1 kHz, whereas 13.56 MHz power is applied in continuous wave mode. The discharge is operated at a range of conditions covering 3–50 mTorr, 100–600 W 13.56 MHz power level, 300–600 W 2 MHz peak power level, and duty ratio of 10%–90%. The experimental results reveal that the quasisteady state n{sub e} is greatly affected by the 2 MHz power levels and slightly affected by 13.56 MHzmore » power levels. It is observed that the electron density increases by a factor of 2–2.5 on increasing 2 MHz power level from 300 to 600 W, whereas n{sub e} increases by only ∼20% for 13.56 MHz power levels of 100–600 W. The rise time and decay time constant of n{sub e} monotonically decrease with an increase in either 2 or 13.56 MHz power level. This effect is stronger at low values of 2 MHz power level. For all the operating conditions, it is observed that the n{sub e} overshoots at the beginning of the on-phase before relaxing to a quasisteady state value. The relative overshoot density (in percent) depends on 2 and 13.56 MHz power levels. On increasing gas pressure, the n{sub e} at first increases, reaching to a maximum value, and then decreases with a further increase in gas pressure. The decay time constant of n{sub e} increases monotonically with pressure, increasing rapidly up to 10 mTorr gas pressure and at a slower rate of rise to 50 mTorr. At a fixed 2/13.56 MHz power level and 10 mTorr gas pressure, the quasisteady state n{sub e} shows maximum for 30%–40% duty ratio and decreases with a further increase in duty ratio.« less

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes

NASA Astrophysics Data System (ADS)

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-01

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ˜75 F g-1, ˜987 kW kg-1 and ˜27 W h kg-1, respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (˜158 F g-1) and energy density (˜53 W h kg-1). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices.

Superconducting current injection transistor with very high critical-current-density edge-junctions

NASA Astrophysics Data System (ADS)

van Zeghbroeck, B. J.

1985-03-01

A Superconducting Current Injection Transistor (Super-CIT) was fabricated with very high critical current-density edge-junctions. The junctions have a niobium base electrode and a lead-alloy counter electrode. The length of the junctions is 30 microns and the critical-current density is 190KA/sq cm. The Super-CIT has a current gain of 2, a large signal transresistance of 100 mV/A, and the turn-on delay, inferred from the junction resonance, is 7ps. The power dissipation is 3.5 microwatts and the power-delay product is 24.5aJ. Gap reduction due to heating was observed, limiting the maximum power dissipation per unit length to 1.1 microwatt/micron. Compared to lead-alloy Super-CITs, the device is five times smaller, three times faster, and has a three times larger output voltage. The damping resistor and the contact junction could also be eliminated.

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes.

PubMed

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-20

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ~75 F g(-1), ~987 kW kg(-1) and ~27 W h kg(-1), respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (~158 F g(-1)) and energy density (~53 W h kg(-1)). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices. © 2012 IOP Publishing Ltd

Wind energy potential assessment of Cameroon's coastal regions for the installation of an onshore wind farm.

PubMed

Arreyndip, Nkongho Ayuketang; Joseph, Ebobenow; David, Afungchui

2016-11-01

For the future installation of a wind farm in Cameroon, the wind energy potentials of three of Cameroon's coastal cities (Kribi, Douala and Limbe) are assessed using NASA average monthly wind data for 31 years (1983-2013) and compared through Weibull statistics. The Weibull parameters are estimated by the method of maximum likelihood, the mean power densities, the maximum energy carrying wind speeds and the most probable wind speeds are also calculated and compared over these three cities. Finally, the cumulative wind speed distributions over the wet and dry seasons are also analyzed. The results show that the shape and scale parameters for Kribi, Douala and Limbe are 2.9 and 2.8, 3.9 and 1.8 and 3.08 and 2.58, respectively. The mean power densities through Weibull analysis for Kribi, Douala and Limbe are 33.7 W/m2, 8.0 W/m2 and 25.42 W/m2, respectively. Kribi's most probable wind speed and maximum energy carrying wind speed was found to be 2.42 m/s and 3.35 m/s, 2.27 m/s and 3.03 m/s for Limbe and 1.67 m/s and 2.0 m/s for Douala, respectively. Analysis of the wind speed and hence power distribution over the wet and dry seasons shows that in the wet season, August is the windiest month for Douala and Limbe while September is the windiest month for Kribi while in the dry season, March is the windiest month for Douala and Limbe while February is the windiest month for Kribi. In terms of mean power density, most probable wind speed and wind speed carrying maximum energy, Kribi shows to be the best site for the installation of a wind farm. Generally, the wind speeds at all three locations seem quite low, average wind speeds of all the three studied locations fall below 4.0m/s which is far below the cut-in wind speed of many modern wind turbines. However we recommend the use of low cut-in speed wind turbines like the Savonius for stand alone low energy needs.

Effect of acoustic frequency and power density on the aqueous ultrasonic-assisted extraction of grape pomace (Vitis vinifera L.) - a response surface approach.

PubMed

González-Centeno, María Reyes; Knoerzer, Kai; Sabarez, Henry; Simal, Susana; Rosselló, Carmen; Femenia, Antoni

2014-11-01

Aqueous ultrasound-assisted extraction (UAE) of grape pomace was investigated by Response Surface Methodology (RSM) to evaluate the effect of acoustic frequency (40, 80, 120kHz), ultrasonic power density (50, 100, 150W/L) and extraction time (5, 15, 25min) on total phenolics, total flavonols and antioxidant capacity. All the process variables showed a significant effect on the aqueous UAE of grape pomace (p<0.05). The Box-Behnken Design (BBD) generated satisfactory mathematical models which accurately explain the behavior of the system; allowing to predict both the extraction yield of phenolic and flavonol compounds, and also the antioxidant capacity of the grape pomace extracts. The optimal UAE conditions for all response factors were a frequency of 40kHz, a power density of 150W/L and 25min of extraction time. Under these conditions, the aqueous UAE would achieve a maximum of 32.31mg GA/100g fw for total phenolics and 2.04mg quercetin/100g fw for total flavonols. Regarding the antioxidant capacity, the maximum predicted values were 53.47 and 43.66mg Trolox/100g fw for CUPRAC and FRAP assays, respectively. When comparing with organic UAE, in the present research, from 12% to 38% of total phenolic bibliographic values were obtained, but using only water as the extraction solvent, and applying lower temperatures and shorter extraction times. To the best of the authors' knowledge, no studies specifically addressing the optimization of both acoustic frequency and power density during aqueous-UAE of plant materials have been previously published. Copyright © 2014 Elsevier B.V. All rights reserved.

High voltage series resonant inverter ion engine screen supply. [SCR series resonant inverter for space applications

NASA Technical Reports Server (NTRS)

Biess, J. J.; Inouye, L. Y.; Shank, J. H.

1974-01-01

A high-voltage, high-power LC series resonant inverter using SCRs has been developed for an Ion Engine Power Processor. The inverter operates within 200-400Vdc with a maximum output power of 2.5kW. The inverter control logic, the screen supply electrical and mechanical characteristics, the efficiency and losses in power components, regulation on the dual feedback principle, the SCR waveforms and the component weight are analyzed. Efficiency of 90.5% and weight density of 4.1kg/kW are obtained.

Full synergistic effect of hydrothermal NiCo2O4 nanosheets/CuCo2O4 nanocones supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Bai, Hongye; Shao, Rong; Xu, Wei; Shi, Weidong

2018-06-01

In this work, a series of NiCo2O4/CuCo2O4 composites were prepared by a two-step hydrothermal method. The optimized NiCo2O4/CuCo2O4 electrode shows more than 5 times area capacitance (4.97 F cm-2) than pure NiCo2O4 at the current density of 1 mA cm-2. The best performance of sample assembled an asymmetric supercapacitor could reach up to 42 F g-1 at the current density of 1 A g-1. In addition, the maximum energy density of 15 W h kg-1 was achieved with the power density of 814 W kg-1. The as-prepared active electrode material also reveals excellent cycling stability with 90.6% capacitance retention after 5000 cycles. These results indicate potential application in developing energy storage devices with high energy density power density.

A Numerical Simulation of the Energy Conversion Process in Microwave Rocket

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shibata, Teppei; Oda, Yasuhisa; Komurasaki, Kimiya

2008-04-28

In Microwave Rocket, a high power microwave beam ionizes atmospheric air inside of the thruster and the ionization front drives a shock wave. In this paper, CFD simulation was conducted using measured propagation velocity of the ionization front to evaluate the engine performance. As a result, maximum cycle efficiency was obtained at the power density of about 200 kW/m{sup 2} which is the transitional beam power condition between Microwave Supported Combustion and Microwave Supported Detonation regimes.

Magnetic-assisted triboelectric nanogenerators as self-powered visualized omnidirectional tilt sensing system

PubMed Central

Han, Mengdi; Zhang, Xiao-Sheng; Sun, Xuming; Meng, Bo; Liu, Wen; Zhang, Haixia

2014-01-01

The triboelectric nanogenerator (TENG) is a promising device in energy harvesting and self-powered sensing. In this work, we demonstrate a magnetic-assisted TENG, utilizing the magnetic force for electric generation. Maximum power density of 541.1 mW/m2 is obtained at 16.67 MΩ for the triboelectric part, while the electromagnetic part can provide power density of 649.4 mW/m2 at 16 Ω. Through theoretical calculation and experimental measurement, linear relationship between the tilt angle and output voltage at large angles is observed. On this basis, a self-powered omnidirectional tilt sensor is realized by two magnetic-assisted TENGs, which can measure the magnitude and direction of the tilt angle at the same time. For visualized sensing of the tilt angle, a sensing system is established, which is portable, intuitive, and self-powered. This visualized system greatly simplifies the measure process, and promotes the development of self-powered systems. PMID:24770490

Fluid simulation of the bias effect in inductive/capacitive discharges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Yu-Ru; Research Group PLASMANT, Department of Chemistry, University of Antwerp, Universiteitsplein 1, Wilrijk, BE-2610 Antwerp; Gao, Fei

Computer simulations are performed for an argon inductively coupled plasma (ICP) with a capacitive radio-frequency bias power, to investigate the bias effect on the discharge mode transition and on the plasma characteristics at various ICP currents, bias voltages, and bias frequencies. When the bias frequency is fixed at 13.56 MHz and the ICP current is low, e.g., 6 A, the spatiotemporal averaged plasma density increases monotonically with bias voltage, and the bias effect is already prominent at a bias voltage of 90 V. The maximum of the ionization rate moves toward the bottom electrode, which indicates clearly the discharge mode transition in inductive/capacitivemore » discharges. At higher ICP currents, i.e., 11 and 13 A, the plasma density decreases first and then increases with bias voltage, due to the competing mechanisms between the ion acceleration power dissipation and the capacitive power deposition. At 11 A, the bias effect is still important, but it is noticeable only at higher bias voltages. At 13 A, the ionization rate is characterized by a maximum at the reactor center near the dielectric window at all selected bias voltages, which indicates that the ICP power, instead of the bias power, plays a dominant role under this condition, and no mode transition is observed. Indeed, the ratio of the bias power to the total power is lower than 0.4 over a wide range of bias voltages, i.e., 0–300 V. Besides the effect of ICP current, also the effect of various bias frequencies is investigated. It is found that the modulation of the bias power to the spatiotemporal distributions of the ionization rate at 2 MHz is strikingly different from the behavior observed at higher bias frequencies. Furthermore, the minimum of the plasma density appears at different bias voltages, i.e., 120 V at 2 MHz and 90 V at 27.12 MHz.« less

Numerical modeling of heat and mass transfer in the human eye under millimeter wave exposure.

PubMed

Karampatzakis, Andreas; Samaras, Theodoros

2013-05-01

Human exposure to millimeter wave (MMW) radiation is expected to increase in the next several years. In this work, we present a thermal model of the human eye under MMW illumination. The model takes into account the fluid dynamics of the aqueous humor and predicts a frequency-dependent reversal of its flow that also depends on the incident power density. The calculated maximum fluid velocity in the anterior chamber and the temperature rise at the corneal apex are reported for frequencies from 40 to 100 GHz and different values of incident power density. Copyright © 2013 Wiley Periodicals, Inc.

Half-Heusler (TiZrHf)NiSn Unileg Module with High Powder Density.

PubMed

Populoh, Sascha; Brunko, Oliver C; Gałązka, Krzysztof; Xie, Wenjie; Weidenkaff, Anke

2013-03-27

(TiZrHf)NiSn half-Heusler compounds were prepared by arc melting and their thermoelectric properties characterized in the temperature range between 325 K and 857 K, resulting in a Figure of Merit ZT ≈ 0.45. Furthermore, the prepared samples were used to construct a unileg module. This module was characterized in a homemade thermoelectric module measurement stand and yielded 275 mW/cm² and a maximum volumetric power density of 700 mW/cm³. This was reached using normal silver paint as a contacting material; from an improved contacting, much higher power yields are to be expected.

Half-Heusler (TiZrHf)NiSn Unileg Module with High Powder Density

PubMed Central

Populoh, Sascha; Brunko, Oliver C.; Gałązka, Krzysztof; Xie, Wenjie; Weidenkaff, Anke

2013-01-01

(TiZrHf)NiSn half-Heusler compounds were prepared by arc melting and their thermoelectric properties characterized in the temperature range between 325 K and 857 K, resulting in a Figure of Merit ZT ≈ 0.45. Furthermore, the prepared samples were used to construct a unileg module. This module was characterized in a homemade thermoelectric module measurement stand and yielded 275 mW/cm2 and a maximum volumetric power density of 700 mW/cm3. This was reached using normal silver paint as a contacting material; from an improved contacting, much higher power yields are to be expected. PMID:28809212

Wind Power Generation Design Considerations.

DTIC Science & Technology

1984-12-01

DISTRIBUTION 4 I o ....................................... . . . e . * * TABLES Number Page I Wind Turbine Characteristics II 0- 2 Maximum Economic Life II 3...Ratio of Blade Tip Speed to Wind Speed 10 4 Interference with Microwave and TV Reception by Wind Turbines 13 5 Typical Flow Patterns Over Two...18 * 12 Annual Mean Wind Power Density 21 5 FIGURES (Cont’d) Number Page 13 Wind - Turbine /Generator Types Currently Being Tested on Utility Sites 22 14

Development of High Power Density Micro-Thermoelectric Generators

NASA Astrophysics Data System (ADS)

Zhang, Wenhua

Thermoelectric generators (TEGs) are promising for the waste heat recovery in virtue of the ability to directly convert heat to electricity. Despite of their relatively low energy conversion efficiency, TEGs have many advantages including high reliability, long lifetime, and environmental friendliness. Especially, compared to conventional heat engines, TEGs are compact, scalable, and can be easily driven by small temperature differences. Potential applications of TEGs include thermal sensing, thermal management, and thermal energy harvesting to power wireless sensors and microelectronic devices such as wearable medical sensors and wristwatches. This dissertation presents my work on development of high power density non-flexible and flexible micro-TEGs for thermal energy harvesting in the ambient environment. Micro- TEGs are developed by a bottom-up approach combing electroplating and microfabrication processes. Pulsed electroplating is mainly adopted to deposit thermoelectric materials in the device fabrication. First, I collaborated with Dr. Zhou in our lab and systematically studied the effect of deposition parameters on composition, microstructure, and thermoelectric properties of the electroplated Bi2Te3 and Sb2 Te3 thin films. We demonstrated that thermoelectric properties of both Bi2Te3 and Sb2Te3 films can be enhanced by tuning the pulse off-to-on ratio. After the fundamental study on the deposition conditions, morphology, and thermoelectric properties of the electroplated materials, we fabricated a high power density cross-plane micro-TEG on the SiO2/Si substrate by integrating the pulsed electroplating with microfabrication processes. The TEG consists of a total of 127 pairs of n-type Bi2Te3 and ptype Sb2Te3 thermoelectric pillars embedded in a SU-8 matrix to enhance the overall mechanical strength of the device. Both bottom and top electrical connections are formed by electroplating, which is advantageous because of facile and low cost fabrication and low parasitic electrical resistances. The device demonstrates a maximum power of 2990 muW at a temperature difference of 52.5 K, corresponding to a power density as high as 9.2 mW cm-2. The power density of our device is more than two times the highest value reported for the electroplated micro-TEGs in the literature, which can be attributed to the low internal resistance and high packing density of thermoelectric pillars. Based on my work on non-flexible micro-TEGs, I further modified the device fabrication process and developed an ultra-light high power density flexible micro-TEG. The flexible TEG demonstrates excellent flexibility. No obvious electrical resistance change was observed after bending to a curvature as small as 5 mm for 600 times. The flexible micro-TEG we developed demonstrates a maximum power of 1.5 mW at a temperature difference of 50.7 K, corresponding to a power density of 4.5 mW cm-2. More importantly, the flexible TEG is ultra-light and an unprecedentedly high power per unit mass of 60 mW g-1 is achieved, which might be beneficial for wearable technology.

Evaluation of electricity generation from ultrasonic and heat/alkaline pretreatment of different sludge types using microbial fuel cells.

PubMed

Oh, Sang-Eun; Yoon, Joung Yee; Gurung, Anup; Kim, Dong-Jin

2014-08-01

This study investigated the effects of different sludge pretreatment methods (ultrasonic vs. combined heat/alkali) with varied sources of municipal sewage sludge (primary sludge (PS), secondary excess sludge (ES), anaerobic digestion sludge (ADS)) on electricity generation in microbial fuel cells (MFCs). Introduction of ultrasonically pretreated sludge (PS, ES, ADS) to MFCs generated maximum power densities of 13.59, 9.78 and 12.67mW/m(2) and soluble COD (SCOD) removal efficiencies of 87%, 90% and 57%, respectively. The sludge pretreated by combined heat/alkali (0.04N NaOH at 120°C for 1h) produced maximum power densities of 10.03, 5.21 and 12.53mW/m(2) and SCOD removal efficiencies of 83%, 75% and 74% with PS, ES and ADS samples, respectively. Higher SCOD by sludge pretreatment enhanced performance of the MFCs and the electricity generation was linearly proportional to the SCOD removal, especially for ES. Copyright © 2014 Elsevier Ltd. All rights reserved.

Biological treatment of steroidal drug industrial effluent and electricity generation in the microbial fuel cells.

PubMed

Liu, Ru; Gao, Chongyang; Zhao, Yang-Guo; Wang, Aijie; Lu, Shanshan; Wang, Min; Maqbool, Farhana; Huang, Qing

2012-11-01

The single chamber microbial fuel cells (MFCs) were used to treat steroidal drug production wastewater (SPW) and generate electricity simultaneously. The results indicated that the maximum COD removal efficiency reached 82%, total nitrogen and sulfate removal rate approached 62.47% and 26.46%, respectively. The maximum power density and the Coulombic efficiency reached to 22.3Wm(-3) and 30%, respectively. The scanning electron microscope showed that the dominant microbial populations were remarkably different in morphology on the surface of SPW and acetate-fed anodes. PCR-denaturing gradient gel electrophoresis profiles revealed that the microbial community structure fed with different concentrations of SPW presented a gradual succession and unique bacterial sequences were detected on the SPW and acetate-fed anodes. This research demonstrates that MFCs fed with SPW achieved a high efficiency of power density and simultaneous nutrient removal, and the dominant microorganisms on the anode were related to the types and the concentrations of substrates. Copyright © 2012 Elsevier Ltd. All rights reserved.

Pt-Bi decorated nanoporous gold for high performance direct glucose fuel cell

PubMed Central

Guo, Hong; Yin, Huiming; Yan, Xiuling; Shi, Shuai; Yu, Qingyang; Cao, Zhen; Li, Jian

2016-01-01

Binary PtBi decorated nanoporous gold (NPG-PtBi) electrocatalyst is specially designed and prepared for the anode in direct glucose fuel cells (DGFCs). By using electroless and electrochemical plating methods, a dense Pt layer and scattered Bi particles are sequentially coated on NPG. A simple DGFC with NPG-PtBi as anode and commercial Pt/C as cathode is constructed and operated to study the effect of operating temperatures and concentrations of glucose and NaOH. With an anode noble metal loading of only 0.45 mg cm−2 (Au 0.3 mg and Pt 0.15 mg), an open circuit voltage (OCV) of 0.9 V is obtained with a maximum power density of 8 mW cm−2. Furthermore, the maximum gravimetric power density of NPG-PtBi is 18 mW mg−1, about 4.5 times higher than that of commercial Pt/C. PMID:27966629

Design and fabrication of vibration based energy harvester using microelectromechanical system piezoelectric cantilever for low power applications.

PubMed

Kim, Moonkeun; Lee, Sang-Kyun; Yang, Yil Suk; Jeong, Jaehwa; Min, Nam Ki; Kwon, Kwang-Ho

2013-12-01

We fabricated dual-beam cantilevers on the microelectromechanical system (MEMS) scale with an integrated Si proof mass. A Pb(Zr,Ti)O3 (PZT) cantilever was designed as a mechanical vibration energy-harvesting system for low power applications. The resonant frequency of the multilayer composition cantilevers were simulated using the finite element method (FEM) with parametric analysis carried out in the design process. According to simulations, the resonant frequency, voltage, and average power of a dual-beam cantilever was 69.1 Hz, 113.9 mV, and 0.303 microW, respectively, at optimal resistance and 0.5 g (gravitational acceleration, m/s2). Based on these data, we subsequently fabricated cantilever devices using dual-beam cantilevers. The harvested power density of the dual-beam cantilever compared favorably with the simulation. Experiments revealed the resonant frequency, voltage, and average power density to be 78.7 Hz, 118.5 mV, and 0.34 microW, respectively. The error between the measured and simulated results was about 10%. The maximum average power and power density of the fabricated dual-beam cantilever at 1 g were 0.803 microW and 1322.80 microW cm(-3), respectively. Furthermore, the possibility of a MEMS-scale power source for energy conversion experiments was also tested.

O Electromagnetic Power Waves and Power Density Components.

NASA Astrophysics Data System (ADS)

Petzold, Donald Wayne

1980-12-01

On January 10, 1884 Lord Rayleigh presented a paper entitled "On the Transfer of Energy in the Electromagnetic Field" to the Royal Society of London. This paper had been authored by the late Fellow of Trinity College, Cambridge, Professor J. H. Poynting and in it he claimed that there was a general law for the transfer of electromagnetic energy. He argued that associated with each point in space is a quantity, that has since been called the Poynting vector, that is a measure of the rate of energy flow per unit area. His analysis was concerned with the integration of this power density vector at all points over an enclosing surface of a specific volume. The interpretation of this Poynting vector as a true measure of the local power density was viewed with great skepticism unless the vector was integrated over a closed surface, as the development of the concept required. However, within the last decade or so Shadowitz indicates that a number of prominent authors have argued that the criticism of the interpretation of Poynting's vector as a local power density vector is unjustified. The present paper is not concerned with these arguments but instead is concerned with a decomposition of Poynting's power density vector into two and only two components: one vector which has the same direction as Poynting's vector and which is called the forward power density vector, and another vector, directed opposite to the Poynting vector and called the reverse power density vector. These new local forward and reverse power density vectors will be shown to be dependent upon forward and reverse power wave vectors and these vectors in turn will be related to newly defined forward and reverse components of the electric and magnetic fields. The sum of these forward and reverse power density vectors, which is simply the original Poynting vector, is associated with the total electromagnetic energy traveling past the local point. Another vector which is the difference between the forward and reverse power density vectors and which will be shown to be associated with the total electric and magnetic field energy densities existing at a local point will also be introduced. These local forward and reverse power density vectors may be integrated over a surface to determine the forward and reverse powers and from these results problems related to maximum power transfer or efficiency of electromagnetic energy transmission in space may be studied in a manner similar to that presently being done with transmission lines, wave guides, and more recently with two port multiport lumped parameter systems. These new forward and reverse power density vectors at a point in space are analogous to the forward and revoltages or currents and power waves as used with the transmission line, waveguide, or port. These power wave vectors in space are a generalization of the power waves as developed by Penfield, Youla, and Kurokawa and used with the scattering parameters associated with transmission lines, waveguides and ports.

Comparative study on power generation of dual-cathode microbial fuel cell according to polarization methods.

PubMed

Lee, Kang-yu; Ryu, Wyan-seuk; Cho, Sung-il; Lim, Kyeong-ho

2015-11-01

Microbial fuel cells (MFCs) exist in various forms depending on the type of pollutant to be removed and the expected performance. Dual-cathode MFCs, with their simple structure, are capable of removing both organic matter and nitrogen. Moreover, various methods are available for the collection of polarization data, which can be used to calculate the maximum power density, an important factor of MFCs. Many researchers prefer the method of varying the external resistance in a single-cycle due to the short measurement time and high accuracy. This study compared power densities of dual-cathode MFCs in a single-cycle with values calculated over multi-cycles to determine the optimal polarization method. External resistance was varied from high to low and vice versa in the single-cycle, to calculate power density. External resistance was organized in descending order with initial start-up at open circuit voltage (OCV), and then it was organized in descending order again after the initial start-up at 1000 Ω. As a result, power density was underestimated at the anoxic cathode when the external resistance was varied from low to high, and overestimated at the aerobic cathode and anoxic cathode when external resistance at OCV was reduced following initial start-up. In calculating the power densities of dual-cathode MFCs, this paper recommends the method of gradually reducing the external resistance after initial start-up with high external resistance. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of heat and particle fluxes nonlocality on spatial distribution of plasma density in two-chamber inductively coupled plasma sources

NASA Astrophysics Data System (ADS)

Kudryavtsev, A. A.; Serditov, K. Yu.

2012-07-01

This study presents 2D simulations of the two-chamber inductively coupled plasma source where power is supplied in the small discharge chamber and extends by electron thermal conductivity mechanism to the big diffusion chamber. Depending on pressure, two main scenarios of plasma density and its spatial distribution behavior were identified. One case is characterized by the localization of plasma in the small driver chamber where power is deposed. Another case describes when the diffusion chamber becomes the main source of plasma with maximum of the electron density. The differences in spatial distribution are caused by local or non-local behavior of electron energy transport in the discharge volume due to different characteristic scale of heat transfer with electronic conductivity.

Structural-electromagnetic bidirectional coupling analysis of space large film reflector antennas

NASA Astrophysics Data System (ADS)

Zhang, Xinghua; Zhang, Shuxin; Cheng, ZhengAi; Duan, Baoyan; Yang, Chen; Li, Meng; Hou, Xinbin; Li, Xun

2017-10-01

As used for energy transmission, a space large film reflector antenna (SLFRA) is characterized by large size and enduring high power density. The structural flexibility and the microwave radiation pressure (MRP) will lead to the phenomenon of structural-electromagnetic bidirectional coupling (SEBC). In this paper, the SEBC model of SLFRA is presented, then the deformation induced by the MRP and the corresponding far field pattern deterioration are simulated. Results show that, the direction of the MRP is identical to the normal of the reflector surface, and the magnitude is proportional to the power density and the square of cosine incident angle. For a typical cosine function distributed electric field, the MRP is a square of cosine distributed across the diameter. The maximum deflections of SLFRA linearly increase with the increasing microwave power densities and the square of the reflector diameters, and vary inversely with the film thicknesses. When the reflector diameter becomes 100 m large and the microwave power density exceeds 102 W/cm2, the gain loss of the 6.3 μm-thick reflector goes beyond 0.75 dB. When the MRP-induced deflection degrades the reflector performance, the SEBC should be taken into account.

Clostridium beijerinckii mutant obtained atmospheric pressure glow discharge generates enhanced electricity in a microbial fuel cell.

PubMed

Liu, Jun; Guo, Ting; Wang, Dong; Ying, Hanjie

2015-01-01

A Clostridium beijerinckii mutant M13 was derived from C. beijerinckii NCIMB 8052 by atmospheric pressure glow discharge. C. beijerinckii M13 generated a maximum output power density of 79.2 mW m(-2) and a maximum output voltage of 230 mV in a microbial fuel cell containing 1 g glucose l(-1) as carbon source and 0.15 g methyl viologen l(-1) as an electron carrier.

High breakdown voltage and high driving current in a novel silicon-on-insulator MESFET with high- and low-resistance boxes in the drift region

NASA Astrophysics Data System (ADS)

Naderi, Ali; Mohammadi, Hamed

2018-06-01

In this paper a novel silicon-on-insulator metal oxide field effect transistor (SOI-MESFET) with high- and low-resistance boxes (HLRB) is proposed. This structure increases the current and breakdown voltage, simultaneously. The semiconductor at the source side of the channel is doped with higher impurity than the other parts to reduce its resistance and increase the driving current as low-resistance box. An oxide box is implemented at the upper part of the channel from the drain region toward the middle of the channel as the high-resistance box. Inserting a high-resistance box increases the breakdown voltage and improves the RF performance of the device because of its higher tolerable electric field and modification in gate-drain capacitance, respectively. The high-resistance region reduces the current density of the device which is completely compensated by low-resistance box. A 92% increase in breakdown voltage and an 11% improvement in the device current have been obtained. Also, maximum oscillation frequency, unilateral power gain, maximum available gain, maximum stable gain, and maximum output power density are improved by 7%, 35%, 23%, 26%, and 150%, respectively. These results show that the HLRB-SOI-MESFET can be considered as a candidate to replace Conventional SOI-MESFET (C-SOI-MESFET) for high-voltage and high-frequency applications.

Electrophoretic deposition of multi-walled carbon nanotube on a stainless steel electrode for use in sediment microbial fuel cells.

PubMed

Song, Tian-Shun; Peng-Xiao; Wu, Xia-Yuan; Zhou, Charles C

2013-07-01

Sediment microbial fuel cells (SMFCs) could be used as power sources and one type of new technology for the removal of organic matters in sediments. In order to improve electrode materials and enhance their effect on the performance, we deposited multi-walled carbon nanotube (MWNT) on stainless steel net (SSN). Electrophoretic deposition technique as a method with low cost, process simplicity, and thickness control was used for this electrode modification and produced this novel SSN-MWNT electrode. The performances of SMFCs with SSN-MWNT as electrode were investigated. The results showed that the maximum power density of SMFC with SSN-MWNT cathode was 31.6 mW m(-2), which was 3.2 times that of SMFC with an uncoated stainless steel cathode. However, no significant increase in the maximum power density of SMFC with SSN-MWNT anode was detected. Further electrochemical analysis showed that when SSN-MWNT was used as the cathode, the cathodic electrochemical activity and oxygen reduction rate were significantly improved. This study demonstrates that the electrophoretic deposition of carbon nanotubes on conductive substrate can be applied for improving the performance of SMFC.

X-ray Emission from Supernovae in Dense Circumstellar Matter Environments: a Search for Collisionless Shocks

NASA Technical Reports Server (NTRS)

Ofek, E. O.; Fox, D.; Cenko, Stephen B.; Sullivan, M; Gnat, O.; Frail, D. A.; Horesh, A.; Corsi, A.; Quimby, R. M.; Gehrels, N.;

Bio-energy generation in an affordable, single-chamber microbial fuel cell integrated with adsorption hybrid system: effects of temperature and comparison study.

PubMed

Tee, Pei-Fang; Abdullah, Mohammad Omar; Tan, Ivy A W; Amin, Mohamed A M; Nolasco-Hipolito, Cirilo; Bujang, Kopli

2018-04-01

A microbial fuel cell (MFC) integrated with adsorption system (MFC-AHS) is tested under various operating temperatures with palm oil mill effluent as the substrate. The optimum operating temperature for such system is found to be at ∼35°C with current, power density, internal resistance (R in ), Coulombic efficiency (CE) and maximum chemical oxygen demand (COD) removal of 2.51 ± 0.2 mA, 74 ± 6 mW m -3 , 25.4 Ω, 10.65 ± 0.5% and 93.57 ± 1.2%, respectively. Maximum current density increases linearly with temperature at a rate of 0.1772 mA m -2  °C -1 , whereas maximum power density was in a polynomial function. The temperature coefficient (Q 10 ) is found to be 1.20 between 15°C and 35°C. Present studies have demonstrated better CE performance when compared to other MFC-AHSs. Generally, MFC-AHS has demonstrated higher COD removals when compared to standalone MFC regardless of operating temperatures. ACFF: activated carbon fiber felt; APHA: American Public Health Association; CE: Coulombic efficiency; COD: chemical oxygen demand; ECG: electrocardiogram; GAC: granular activated carbon; GFB: graphite fiber brush; MFC: microbial fuel cell; MFC-AHS: microbial fuel cell integrated with adsorption hybrid system; MFC-GG: microbial fuel cell integrated with graphite granules; POME: palm oil mill effluent; PTFE: polytetrafluoroethylene; SEM: scanning electron microscope.

Note: High-power piezoelectric transformer fabricated with ternary relaxor ferroelectric Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3 single crystal.

PubMed

Wang, Qing; Ma, Chuanguo; Wang, Feifei; Liu, Bao; Chen, Jianwei; Luo, Haosu; Wang, Tao; Shi, Wangzhou

2016-03-01

A plate-shaped piezoelectric transformer was designed and fabricated using ternary relaxor ferroelectric single crystal Pb(Mg(1/3)Nb(2/3))O3-Pb(In(1/2)Nb(1/2))O3-PbTiO3. Both the input and output sections utilized the transverse-extensional vibration mode. The frequency and load dependences of the electrical properties for the proposed transformer were systematically studied. Results indicated that under a matching load resistance of 14.9 kΩ, a maximum output power of 2.56 W was obtained with the temperature rise less than 5 °C. The corresponding power density reached up to 50 W/cm(3). This ternary single-crystal transformer had potential applications in compact-size converters requiring high power density.

Optimization principles and the figure of merit for triboelectric generators.

PubMed

Peng, Jun; Kang, Stephen Dongmin; Snyder, G Jeffrey

2017-12-01

Energy harvesting with triboelectric nanogenerators is a burgeoning field, with a growing portfolio of creative application schemes attracting much interest. Although power generation capabilities and its optimization are one of the most important subjects, a satisfactory elemental model that illustrates the basic principles and sets the optimization guideline remains elusive. We use a simple model to clarify how the energy generation mechanism is electrostatic induction but with a time-varying character that makes the optimal matching for power generation more restrictive. By combining multiple parameters into dimensionless variables, we pinpoint the optimum condition with only two independent parameters, leading to predictions of the maximum limit of power density, which allows us to derive the triboelectric material and device figure of merit. We reveal the importance of optimizing device capacitance, not only load resistance, and minimizing the impact of parasitic capacitance. Optimized capacitances can lead to an overall increase in power density of more than 10 times.

Porous glass membranes for vanadium redox-flow battery application - Effect of pore size on the performance

NASA Astrophysics Data System (ADS)

Mögelin, H.; Yao, G.; Zhong, H.; dos Santos, A. R.; Barascu, A.; Meyer, R.; Krenkel, S.; Wassersleben, S.; Hickmann, T.; Enke, D.; Turek, T.; Kunz, U.

2018-02-01

The improvement of redox-flow batteries requires the development of chemically stable and highly conductive separators. Porous glass membranes can be an attractive alternative to the nowadays most common polymeric membranes. Flat porous glass membranes with a pore size in the range from 2 to 50 nm and a thickness of 300 and 500 μm have been used for that purpose. Maximum values for voltage efficiency of 85.1%, coulombic efficiency of 97.9% and energy efficiency of 76.3% at current densities in the range from 20 to 60 mA cm-2 have been achieved. Furthermore, a maximum power density of 95.2 mW cm-2 at a current density of 140 mA cm-2 was gained. These results can be related to small vanadium crossover, high conductivity and chemical stability, confirming the great potential of porous glass membranes for vanadium redox-flow applications.

Effect of laser cavity parameters on saturation of light – current characteristics of high-power pulsed lasers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Veselov, D A; Pikhtin, N A; Lyutetskiy, A V

2015-07-31

We report an experimental study of power characteristics of semiconductor lasers based on MOVPE-grown asymmetric separate-confinement heterostructures with a broadened waveguide as functions of cavity length, stripe contact width and mirror reflectivities. It is shown that at high current pump levels, the variation of the cavity parameters of a semiconductor laser (width, length and mirror reflectivities) influences the light – current (L – I) characteristic saturation and maximum optical power by affecting such laser characteristics, as the current density and the optical output loss. A model is elaborated and an optical power of semiconductor lasers is calculated by taking intomore » account the dependence of the internal optical loss on pump current density and concentration distribution of charge carriers and photons along the cavity axis of the cavity. It is found that only introduction of the dependence of the internal optical loss on pump current density to the calculation model provides a good agreement between experimental and calculated L – I characteristics for all scenarios of variations in the laser cavity parameters. (lasers)« less

On the feasibility of increasing the energy of laser-accelerated protons by using low-density targets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brantov, A. V., E-mail: brantov@lebedev.ru; Bychenkov, V. Yu., E-mail: bychenk@lebedev.ru

2015-06-15

Optimal regimes of proton acceleration in the interaction of short high-power laser pulses with thin foils and low-density targets are determined by means of 3D numerical simulation. It is demonstrated that the maximum proton energy can be increased by using low-density targets in which ions from the front surface of the target are accelerated most efficiently. It is shown using a particular example that, for the same laser pulse, the energy of protons accelerated from a low-density target can be increased by one-third as compared to a solid-state target.

Effects of Ionization in a Laser Wakefield Accelerator

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGuffey, C.; Schumaker, W.; Matsuoka, T.

2010-11-04

Experimental results are presented from studies of the ionization injection process in laser wakefield acceleration using the Hercules laser with laser power up to 100 TW. Gas jet targets consisting of gas mixtures reduced the density threshold required for electron injection and increased the maximum beam charge. Gas mixture targets produced smooth beams even at densities which would produce severe beam breakup in pure He targets and the divergence was found to increase with gas mixture pressure.

Synthesis, characterization and electrochemical performance of graphene decorated with 1D NiMoO4.nH2O nanorods

NASA Astrophysics Data System (ADS)

Ghosh, Debasis; Giri, Soumen; Das, Chapal Kumar

2013-10-01

One-dimensional NiMoO4.nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4.nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4.nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g-1 at 5 A g-1 current density and a high energy density of 10.32 W h kg-1 at a power density of 1125 W kg-1 accompanied with long term cyclic stability.One-dimensional NiMoO4.nH2O nanorods and their graphene based hybrid composite with good electrochemical properties have been synthesized by a cost effective hydrothermal procedure. The formation of the mixed metal oxide and the composite was confirmed by XRD, XPS and Raman analyses. The morphological characterizations were carried out using FESEM and TEM analyses. The materials were subjected to electrochemical characterization through cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) studies with 6 M KOH as the supporting electrolyte. For NiMoO4.nH2O, a maximum specific capacitance of 161 F g-1 was obtained at 5 A g-1 current density, accompanied with an energy density of 4.53 W h kg-1 at a steady power delivery rate of 1125 W kg-1. The high utility of the pseudocapacitive NiMoO4.nH2O was achieved in its graphene based composite, which exhibited a high specific capacitance of 367 F g-1 at 5 A g-1 current density and a high energy density of 10.32 W h kg-1 at a power density of 1125 W kg-1 accompanied with long term cyclic stability. Electronic supplementary information (ESI) available: Materials used, characterization techniques and preparation of electrode, tables containing specific capacitance, coulombic efficiency, energy density and power density values at different current densities of NiMoO4.nH2O and Gr-NiMoO4.nH2O. See DOI: 10.1039/c3nr02444j

Full characterization of a three-photon Greenberger-Horne-Zeilinger state using quantum state tomography.

PubMed

Resch, K J; Walther, P; Zeilinger, A

2005-02-25

We have performed the first experimental tomographic reconstruction of a three-photon polarization state. Quantum state tomography is a powerful tool for fully describing the density matrix of a quantum system. We measured 64 three-photon polarization correlations and used a "maximum-likelihood" reconstruction method to reconstruct the Greenberger-Horne-Zeilinger state. The entanglement class has been characterized using an entanglement witness operator and the maximum predicted values for the Mermin inequality were extracted.

Pressed boride cathodes

NASA Technical Reports Server (NTRS)

Wolski, W.

1985-01-01

Results of experimental studies of emission cathodes made from lanthanum, yttrium, and gadolinium hexaborides are presented. Maximum thermal emission was obtained from lanthanum hexaboride electrodes. The hexaboride cathodes operated stably under conditions of large current density power draw, at high voltages and poor vacuum. A microtron electron gun with a lanthanum hexaboride cathode is described.

Synthesis of carbon core–shell pore structures and their performance as supercapacitors

DOE PAGES

Ariyanto, Teguh; Dyatkin, Boris; Zhang, Gui-Rong; ...

2015-07-15

High-power supercapacitors require excellent electrolyte mobility within the pore network and high electrical conductivity for maximum capacitance and efficiency. Achieving high power typically requires sacrificing energy densities, as the latter demands a high specific surface area and narrow porosity that impedes ion transport. Here, we present a novel solution for this optimization problem: a nanostructured core–shell carbonaceous material that exhibits a microporous carbon core surrounded by a mesoporous, graphitic shell. The tunable synthesis parameters yielded a structure that features either a sharp or a gradual transition between the core and shell sections. Electrochemical supercapacitor testing using organic electrolyte revealed thatmore » these novel core–shell materials outperform carbons with homogeneous pore structures. The hybrid core–shell materials showed a combination of good capacitance retention, typical for the carbon present in the shell and high specific capacitance, typical for the core material. These materials achieved power densities in excess of 40 kW kg -1 at energy densities reaching 27 Wh kg -1.« less

Facilitated charge transport in ternary interconnected electrodes for flexible supercapacitors with excellent power characteristics

NASA Astrophysics Data System (ADS)

Chen, Wanjun; He, Yongmin; Li, Xiaodong; Zhou, Jinyuan; Zhang, Zhenxing; Zhao, Changhui; Gong, Chengshi; Li, Shuankui; Pan, Xiaojun; Xie, Erqing

2013-11-01

Flexible and high performance supercapacitors are very critical in modern society. In order to develop the flexible supercapacitors with high power density, free-standing and flexible three-dimensional graphene/carbon nanotubes/MnO2 (3DG/CNTs/MnO2) composite electrodes with interconnected ternary 3D structures were fabricated, and the fast electron and ion transport channels were effectively constructed in the rationally designed electrodes. Consequently, the obtained 3DG/CNTs/MnO2 composite electrodes exhibit superior specific capacitance and rate capability compared to 3DG/MnO2 electrodes. Furthermore, the 3DG/CNTs/MnO2 based asymmetric supercapacitor demonstrates the maximum energy and power densities of 33.71 W h kg-1 and up to 22 727.3 W kg-1, respectively. Moreover, the asymmetric supercapacitor exhibits excellent cycling stability with 95.3% of the specific capacitance maintained after 1000 cycle tests. Our proposed synthesis strategy to construct the novel ternary 3D structured electrodes can be efficiently applied to other high performance energy storage/conversion systems.Flexible and high performance supercapacitors are very critical in modern society. In order to develop the flexible supercapacitors with high power density, free-standing and flexible three-dimensional graphene/carbon nanotubes/MnO2 (3DG/CNTs/MnO2) composite electrodes with interconnected ternary 3D structures were fabricated, and the fast electron and ion transport channels were effectively constructed in the rationally designed electrodes. Consequently, the obtained 3DG/CNTs/MnO2 composite electrodes exhibit superior specific capacitance and rate capability compared to 3DG/MnO2 electrodes. Furthermore, the 3DG/CNTs/MnO2 based asymmetric supercapacitor demonstrates the maximum energy and power densities of 33.71 W h kg-1 and up to 22 727.3 W kg-1, respectively. Moreover, the asymmetric supercapacitor exhibits excellent cycling stability with 95.3% of the specific capacitance maintained after 1000 cycle tests. Our proposed synthesis strategy to construct the novel ternary 3D structured electrodes can be efficiently applied to other high performance energy storage/conversion systems. Electronic supplementary information (ESI) available: Additional experimental details; calculations of the specific capacitances, and energy and power densities; additional SEM and optical images; XPS results; additional electrochemical results. See DOI: 10.1039/c3nr03923d

High-frequency resonant-tunneling oscillators

NASA Technical Reports Server (NTRS)

Brown, E. R.; Parker, C. D.; Calawa, A. R.; Manfra, M. J.; Chen, C. L.

1991-01-01

Advances in high-frequency resonant-tunneling-diode (RTD) oscillators are described. Oscillations up to a frequency of 420 GHz have been achieved in the GaAs/AlAs system. Recent results obtained with In0.53Ga0.47As/AlAs and InAs/AlSb RTDs show a greatly increased power density and indicate the potential for fundamental oscillations up to about 1 THz. These results are consistent with a lumped-element equivalent circuit model of the RTD. The model shows that the maximum oscillation frequency of the GaAs/AlAs RTDs is limited primarily by series resistance, and that the power density is limited by low peak-to-valley current ratio.

Optimization of hydrostatic pressure at varied sonication conditions--power density, intensity, very low frequency--for isothermal ultrasonic sludge treatment.

PubMed

Delmas, Henri; Le, Ngoc Tuan; Barthe, Laurie; Julcour-Lebigue, Carine

2015-07-01

This work aims at investigating for the first time the key sonication (US) parameters: power density (DUS), intensity (IUS), and frequency (FS) - down to audible range, under varied hydrostatic pressure (Ph) and low temperature isothermal conditions (to avoid any thermal effect). The selected application was activated sludge disintegration, a major industrial US process. For a rational approach all comparisons were made at same specific energy input (ES, US energy per solid weight) which is also the relevant economic criterion. The decoupling of power density and intensity was obtained by either changing the sludge volume or most often by changing probe diameter, all other characteristics being unchanged. Comprehensive results were obtained by varying the hydrostatic pressure at given power density and intensity. In all cases marked maxima of sludge disintegration appeared at optimum pressures, which values increased at increasing power intensity and density. Such optimum was expected due to opposite effects of increasing hydrostatic pressure: higher cavitation threshold then smaller and fewer bubbles, but higher temperature and pressure at the end of collapse. In addition the first attempt to lower US frequency down to audible range was very successful: at any operation condition (DUS, IUS, Ph, sludge concentration and type) higher sludge disintegration was obtained at 12 kHz than at 20 kHz. The same values of optimum pressure were observed at 12 and 20 kHz. At same energy consumption the best conditions - obtained at 12 kHz, maximum power density 720 W/L and 3.25 bar - provided about 100% improvement with respect to usual conditions (1 bar, 20 kHz). Important energy savings and equipment size reduction may then be expected. Copyright © 2014 Elsevier B.V. All rights reserved.

Supercapacitors based on self-assembled graphene organogel.

PubMed

Sun, Yiqing; Wu, Qiong; Shi, Gaoquan

2011-10-14

Self-assembled graphene organogel (SGO) with 3-dimensional (3D) macrostructure was prepared by solvothermal reduction of a graphene oxide (GO) dispersion in propylene carbonate (PC). This SGO was used as an electrode material for fabricating supercapacitors with a PC electrolyte. The supercapacitor can be operated in a wide voltage range of 0-3 V and exhibits a high specific capacitance of 140 F g(-1) at a discharge current density of 1 A g(-1). Furthermore, it can still keep a specific capacitance of 90 F g(-1) at a high current density of 30 A g(-1). The maximum energy density of the SGO based supercapacitor was tested to be 43.5 Wh kg(-1), and this value is higher than those of the graphene based supercapacitors with aqueous or PC electrolytes reported previously. Furthermore, at a high discharge current density of 30 A g(-1), the energy and power densities of the supercapacitor were measured to be 15.4 Wh kg(-1) and 16,300 W kg(-1), respectively. These results indicate that the supercapacitor has a high specific capacitance and power density, and excellent rate capability.

A Miniaturized 0.78-mW/cm2 Autonomous Thermoelectric Energy-Harvesting Platform for Biomedical Sensors.

PubMed

Rozgic, Dejan; Markovic, Dejan

2017-08-01

In order to use thermoelectric energy harvesters (TEHs) as a truly autonomous energy source for size-limited sensing applications, it is essential to improve the power conversion efficiency and energy density. This study presents a thin-film, array-based TEH with a surface area of 0.83 cm 2 . The TEH autonomously supplies a power management IC fabricated in a 65-nm CMOS technology. The IC utilizes a single-inductor topology with integrated analog maximum power point tracking (MPPT), resulting in a 68% peak end-to-end efficiency (92% converter efficiency) and less than 20-ms MPPT. In an in-vivo test, a 645-μW regulated output power (effective 3.5 K of temperature gradient) was harvested from a rat implanted with our TEH, demonstrating true energy independence in a real environment while showing a 7.9 × improvement in regulated power density compared to the state-of-the-art. The system showed autonomous operation down to 65-mV TEH input.

Performance Analysis of the Automotive TEG with Respect to the Geometry of the Modules

NASA Astrophysics Data System (ADS)

Yu, C. G.; Zheng, S. J.; Deng, Y. D.; Su, C. Q.; Wang, Y. P.

2017-05-01

Recently there has been increasing interest in applying thermoelectric technology to recover waste heat in automotive exhaust gas. Due to the limited space in the vehicle, it's meaningful to improve the TEG (thermoelectric generator) performance by optimizing the module geometry. This paper analyzes the performance of bismuth telluride modules for two criteria (power density and power output per area), and researches the relationship between the performance and the geometry of the modules. A geometry factor is defined for the thermoelectric element to describe the module geometry, and a mathematical model is set up to study the effects of the module geometry on its performance. It has been found out that the optimal geometry factors for maximum output power, power density and power output per unit area are different, and the value of the optimal geometry factors will be affected by the volume of the thermoelectric material and the thermal input. The results can be referred to as the basis for optimizing the performance of the thermoelectric modules.

Manganese dioxide decoration of macroscopic carbon nanotube fibers: From high-performance liquid-based to all-solid-state supercapacitors

NASA Astrophysics Data System (ADS)

Pendashteh, Afshin; Senokos, Evgeny; Palma, Jesus; Anderson, Marc; Vilatela, Juan J.; Marcilla, Rebeca

2017-12-01

Supercapacitors capable of providing high voltage, energy and power density but yet light, low volume occupying, flexible and mechanically robust are highly interesting and demanded for portable applications. Herein, freestanding flexible hybrid electrodes based on MnO2 nanoparticles grown on macroscopic carbon nanotube fibers (CNTf-MnO2) were fabricated, without the need of any metallic current collector. The CNTf, a support with excellent electrical conductivity, mechanical stability, and appropriate pore structure, was homogeneously decorated with porous akhtenskite ɛ-MnO2 nanoparticles produced via electrodeposition in an optimized organic-aqueous mixture. Electrochemical properties of these decorated fibers were evaluated in different electrolytes including a neutral aqueous solution and a pure 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ionic liquid (PYR14TFSI). This comparison helps discriminate the various contributions to the total capacitance: (surface) Faradaic and non-Faradaic processes, improved wetting by aqueous electrolytes. Accordingly, symmetric supercapacitors with PYR14TFSI led to a high specific energy of 36 Wh· kgMnO2-1 (16 Wh·kg-1 including the weight of CNTf) and real specific power of 17 kW· kgMnO2-1 (7.5 kW kg-1) at 3.0 V with excellent cycling stability. Moreover, flexible all solid-state supercapacitors were fabricated using PYR14TFSI-based polymer electrolyte, exhibiting maximum energy density of 21 Wh·kg-1 and maximum power density of 8 kW kg-1 normalized by total active material.

Production of electricity from acetate or butyrate using a single-chamber microbial fuel cell.

PubMed

Liu, Hong; Cheng, Shaoan; Logan, Bruce E

2005-01-15

Hydrogen can be recovered by fermentation of organic material rich in carbohydrates, but much of the organic matter remains in the form of acetate and butyrate. An alternative to methane production from this organic matter is the direct generation of electricity in a microbial fuel cell (MFC). Electricity generation using a single-chambered MFC was examined using acetate or butyrate. Power generated with acetate (800 mg/L) (506 mW/m2 or 12.7 mW/ L) was up to 66% higher than that fed with butyrate (1000 mg/L) (305 mW/m2 or 7.6 mW/L), demonstrating that acetate is a preferred aqueous substrate for electricity generation in MFCs. Power output as a function of substrate concentration was well described by saturation kinetics, although maximum power densities varied with the circuit load. Maximum power densities and half-saturation constants were Pmax = 661 mW/m2 and Ks = 141 mg/L for acetate (218 ohms) and Pmax = 349 mW/m2 and Ks = 93 mg/L for butyrate (1000 ohms). Similar open circuit potentials were obtained in using acetate (798 mV) or butyrate (795 mV). Current densities measured for stable power outputwere higher for acetate (2.2 A/m2) than those measured in MFCs using butyrate (0.77 A/m2). Cyclic voltammograms suggested that the main mechanism of power production in these batch tests was by direct transfer of electrons to the electrode by bacteria growing on the electrode and not by bacteria-produced mediators. Coulombic efficiencies and overall energy recovery were 10-31 and 3-7% for acetate and 8-15 and 2-5% for butyrate, indicating substantial electron and energy losses to processes other than electricity generation. These results demonstrate that electricity generation is possible from soluble fermentation end products such as acetate and butyrate, but energy recoveries should be increased to improve the overall process performance.

Probability density function characterization for aggregated large-scale wind power based on Weibull mixtures

DOE PAGES

Gomez-Lazaro, Emilio; Bueso, Maria C.; Kessler, Mathieu; ...

2016-02-02

Here, the Weibull probability distribution has been widely applied to characterize wind speeds for wind energy resources. Wind power generation modeling is different, however, due in particular to power curve limitations, wind turbine control methods, and transmission system operation requirements. These differences are even greater for aggregated wind power generation in power systems with high wind penetration. Consequently, models based on one-Weibull component can provide poor characterizations for aggregated wind power generation. With this aim, the present paper focuses on discussing Weibull mixtures to characterize the probability density function (PDF) for aggregated wind power generation. PDFs of wind power datamore » are firstly classified attending to hourly and seasonal patterns. The selection of the number of components in the mixture is analyzed through two well-known different criteria: the Akaike information criterion (AIC) and the Bayesian information criterion (BIC). Finally, the optimal number of Weibull components for maximum likelihood is explored for the defined patterns, including the estimated weight, scale, and shape parameters. Results show that multi-Weibull models are more suitable to characterize aggregated wind power data due to the impact of distributed generation, variety of wind speed values and wind power curtailment.« less

Dynamic Power Spectral Analysis of Solar Measurements from Photospheric, Chromospheric, and Coronal Sources

NASA Technical Reports Server (NTRS)

Bouwer, S. D.; Pap, J.; Donnelly, R. F.

1990-01-01

An important aspect in the power spectral analysis of solar variability is the quasistationary and quasiperiodic nature of solar periodicities. In other words, the frequency, phase, and amplitude of solar periodicities vary on time scales ranging from active region lifetimes to solar cycle time scales. Here, researchers employ a dynamic, or running, power spectral density analysis to determine many periodicities and their time-varying nature in the projected area of active sunspot groups (S sub act). The Solar Maximum Mission/Active Cavity Radiometer Irradiance Monitor (SMM/ACRIM) total solar irradiance (S), the Nimbus-7 MgII center-to-wing ratio (R (MgII sub c/w)), the Ottawa 10.7 cm flux (F sub 10.7), and the GOES background x ray flux (X sub b) for the maximum, descending, and minimum portions of solar cycle 21 (i.e., 1980 to 1986) are used. The technique dramatically illustrates several previously unrecognized periodicities. For example, a relatively stable period at about 51 days has been found in those indices which are related to emerging magnetic fields. The majority of solar periodicities, particularly around 27, 150 and 300 days, are quasiperiodic because they vary in amplitude and frequency throughout the solar cycle. Finally, it is shown that there are clear differences between the power spectral densities of solar measurements from photospheric, chromospheric, and coronal sources.

Vertically aligned carbon nanotubes as anode and air-cathode in single chamber microbial fuel cells

NASA Astrophysics Data System (ADS)

Amade, R.; Moreno, H. A.; Hussain, S.; Vila-Costa, M.; Bertran, E.

2016-10-01

Electrode optimization in microbial fuel cells is a key issue to improve the power output and cell performance. Vertically aligned carbon nanotubes (VACNTs) grown on low cost stainless-steel mesh present an attractive approach to increase the cell performance while avoiding the use of expensive Pt-based materials. In comparison with non-aligned carbon nanotubes (NACNTs), VACNTs increase the oxygen reduction reaction taking place at the cathode by a factor of two. In addition, vertical alignment also increases the power density up to 2.5 times with respect to NACNTs. VACNTs grown at the anode can further improve the cell performance by increasing the electrode surface area and thus the electron transfer between bacteria and the electrode. The maximum power density obtained using VACNTs was 14 mW/m2 and 160 mV output voltage.

The TELEC - A plasma type of direct energy converter. [Thermo-Electronic Laser Energy Converter for electric power generation

NASA Technical Reports Server (NTRS)

Britt, E. J.

1978-01-01

The Thermo-Electronic Laser Energy Converter (TELEC) is a high-power density plasma device designed to convert a 10.6-micron CO2 laser beam into electric power. Electromagnetic radiation is absorbed in plasma electrons, creating a high-electron temperature. Energetic electrons diffuse from the plasma and strike two electrodes having different areas. The larger electrode collects more electrons and there is a net transport of current. An electromagnetic field is generated in the external circuit. A computer program has been designed to analyze TELEC performance allowing parametric variation for optimization. Values are presented for TELEC performance as a function of cesium pressure and for current density and efficiency as a function of output voltage. Efficiency is shown to increase with pressure, reaching a maximum over 45%.

NiCo2S4 nanosheet-decorated 3D, porous Ni film@Ni wire electrode materials for all solid-state asymmetric supercapacitor applications.

PubMed

Saravanakumar, Balasubramaniam; Jayaseelan, Santhana Sivabalan; Seo, Min-Kang; Kim, Hak-Yong; Kim, Byoung-Suhk

2017-12-07

Wire type supercapacitors with high energy and power densities have generated considerable interest in wearable applications. Herein, we report a novel NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode for high performance supercapacitor application. In this work, a facile method is introduced to fabricate a 3D, porous Ni film deposited on a Ni wire as a flexible electrode, followed by decoration with NiCo 2 S 4 as an electroactive material. The fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire electrode displays a superior performance with an areal and volumetric capacitance of 1.228 F cm -2 and 199.74 F cm -3 , respectively, at a current density of 0.2 mA cm -1 with a maximum volumetric energy and power density (E V : 6.935 mW h cm -3 ; P V : 1.019 W cm -3 ). Finally, the solid state asymmetric wire type supercapacitor is fabricated using the fabricated NiCo 2 S 4 -decorated 3D, porous Ni film@Ni wire as a positive electrode and N-doped reduced graphene oxide (N-rGO) as a negative electrode and this exhibits good areal and volumetric capacitances of C A : 0.12 F cm -2 and C V : 19.57 F cm -2 with a higher rate capability (92%). This asymmetric wire type supercapacitor demonstrates a low leakage current and self-discharge with a maximum volumetric energy (E V : 5.33 mW h cm -3 ) and power (P V : 855.69 mW cm -3 ) density.

Model analysis and electrical characterization of atmospheric pressure cold plasma jet in pin electrode configuration

NASA Astrophysics Data System (ADS)

Deepak, G. Divya; Joshi, N. K.; Prakash, Ram

2018-05-01

In this study, both model analysis and electrical characterization of a dielectric barrier discharge based argon plasma jet have been carried at atmospheric pressure in a pin electrode configuration. The plasma and fluid dynamics modules of COMSOL multi-physics code have been used for the modeling of the plasma jet. The plasma parameters, such as, electron density, electron temperature and electrical potential have been analyzed with respect to the electrical parameters, i.e., supply voltage and supply frequency with and without the flow of gas. In all the experiments, gas flow rate has been kept constant at 1 liter per minute. This electrode configuration is subjected to a range of supply frequencies (10-25 kHz) and supply voltages (3.5-6.5 kV). The power consumed by the device has been estimated at different applied combinations (supply voltage & frequency) for optimum power consumption at maximum jet length. The maximum power consumed by the device in this configuration for maximum jet length of ˜26 mm is just ˜1 W.

Activated Biomass-derived Graphene-based Carbons for Supercapacitors with High Energy and Power Density.

PubMed

Jung, SungHoon; Myung, Yusik; Kim, Bit Na; Kim, In Gyoo; You, In-Kyu; Kim, TaeYoung

2018-01-30

Here, we present a facile and low-cost method to produce hierarchically porous graphene-based carbons from a biomass source. Three-dimensional (3D) graphene-based carbons were produced through continuous sequential steps such as the formation and transformation of glucose-based polymers into 3D foam-like structures and their subsequent carbonization to form the corresponding macroporous carbons with thin graphene-based carbon walls of macropores and intersectional carbon skeletons. Physical and chemical activation was then performed on this carbon to create micro- and meso-pores, thereby producing hierarchically porous biomass-derived graphene-based carbons with a high Brunauer-Emmett-Teller specific surface area of 3,657 m 2  g -1 . Owing to its exceptionally high surface area, interconnected hierarchical pore networks, and a high degree of graphitization, this carbon exhibited a high specific capacitance of 175 F g -1 in ionic liquid electrolyte. A supercapacitor constructed with this carbon yielded a maximum energy density of 74 Wh kg -1 and a maximum power density of 408 kW kg -1 , based on the total mass of electrodes, which is comparable to those of the state-of-the-art graphene-based carbons. This approach holds promise for the low-cost and readily scalable production of high performance electrode materials for supercapacitors.

Flexible all-solid-state supercapacitors based on polyaniline orderly nanotubes array.

PubMed

Li, Huihua; Song, Juan; Wang, Linlin; Feng, Xiaomiao; Liu, Ruiqing; Zeng, Wenjin; Huang, Zhendong; Ma, Yanwen; Wang, Lianhui

2017-01-07

Flexible all-solid-state supercapacitors are crucial to meet the growing needs for portable electronic devices such as foldable phones and wearable electronics. As promising candidates for pseudocapacitor electrode materials, polyaniline (PANI) orderly nanotube arrays are prepared via a simple template electrodeposition method. The structures of the final product were characterized using various characterization techniques, including scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The obtained PANI nanotube film could be directly used as a flexible all-solid-state supercapacitor electrode. Electrochemical results show that the areal capacitance of a PANI nanotube-based supercapacitor with the deposition cycle number of 100 can achieve a maximum areal capacitance of 237.5 mF cm -2 at a scan rate of 10 mV s -1 and maximum energy density of 24.31 mW h cm -2 at a power density of 2.74 mW cm -2 . In addition, the prepared supercapacitor exhibits excellent flexibility under different bending conditions. It retains 95.2% of its initial capacitance value after 2000 cycles at a current density of 1.0 mA cm -1 , which displays its superior cycling stability. Moreover, the prepared flexible all-solid-state supercapacitor can power a light-emitting-diode (LED), which meets the practical applications of micropower supplies.

Quaternized poly(styrene ethylene butylene poly styrene)/multiwalled carbon nanotube composites for alkaline fuel cell applications.

PubMed

Vinodh, Rajangam; Sangeetha, Dharmalingam

2013-08-01

The present study is aimed at synthesizing a novel anion exchange composite membrane from quaternized polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene [QPSEBS] and functionalized multi walled carbon nanotubes (f-MWCNT) by solution casting method. The characteristic properties of the QPSEBS/f-MWCNT composite membranes were investigated using Fourier transform infrared (FTIR), UV-Visible spectroscopy, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction (XRD) studies and Raman spectroscopy. The water uptake, ion exchange capacity, ionic conductivity, methanol permeability and selectivity ratio of the membranes were also studied. The prepared composite membranes were tested in an in-house fabricated alkaline membrane fuel cell (AMFC) set up using Pt/C as the common anode catalyst and three different cathode catalysts namely Pt/C, Pd-Ni/C and Ag/C. Among all the three cathode catalysts, Pt/C for QPSEBS/5% f-MWCNT is found to show the maximum power density and open circuit voltage (OCV) of 187 mW cm(-2) and 0.73 V respectively. For direct methanol alkaline membrane fuel cells (DMAMFC), the OCV of QPSEBS/5% f-MWCNT is found to be 0.76 V and the maximum power density of 59.5 mW cm(-2) is achieved at a current density of 175 mA cm(-2).

Fully Enzymatic Membraneless Glucose|Oxygen Fuel Cell That Provides 0.275 mA cm(-2) in 5 mM Glucose, Operates in Human Physiological Solutions, and Powers Transmission of Sensing Data.

PubMed

Ó Conghaile, Peter; Falk, Magnus; MacAodha, Domhnall; Yakovleva, Maria E; Gonaus, Christoph; Peterbauer, Clemens K; Gorton, Lo; Shleev, Sergey; Leech, Dónal

2016-02-16

Coimmobilization of pyranose dehydrogenase as an enzyme catalyst, osmium redox polymers [Os(4,4'-dimethoxy-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) or [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) as mediators, and carbon nanotube conductive scaffolds in films on graphite electrodes provides enzyme electrodes for glucose oxidation. The recombinant enzyme and a deglycosylated form, both expressed in Pichia pastoris, are investigated and compared as biocatalysts for glucose oxidation using flow injection amperometry and voltammetry. In the presence of 5 mM glucose in phosphate-buffered saline (PBS) (50 mM phosphate buffer solution, pH 7.4, with 150 mM NaCl), higher glucose oxidation current densities, 0.41 mA cm(-2), are obtained from enzyme electrodes containing the deglycosylated form of the enzyme. The optimized glucose-oxidizing anode, prepared using deglycosylated enzyme coimmobilized with [Os(4,4'-dimethyl-2,2'-bipyridine)2(poly(vinylimidazole))10Cl](+) and carbon nanotubes, was coupled with an oxygen-reducing bilirubin oxidase on gold nanoparticle dispersed on gold electrode as a biocathode to provide a membraneless fully enzymatic fuel cell. A maximum power density of 275 μW cm(-2) is obtained in 5 mM glucose in PBS, the highest to date under these conditions, providing sufficient power to enable wireless transmission of a signal to a data logger. When tested in whole human blood and unstimulated human saliva maximum power densities of 73 and 6 μW cm(-2) are obtained for the same fuel cell configuration, respectively.

Material and cooling requirements for poly-Bitter resistive magnets and hybrid inserts generating continuous fields up to 50 T

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, B.J.; Bird, M.D.; Eyssa, Y.M.

1994-07-01

The new National High Magnetic Field Laboratory (NHMFL), equipped with a 40 MW DC power supply, will design and construct the next generation of high field resistive magnets and hybrid inserts generating DC fields up to 50 T. The authors present a study on the required materials and the necessary cooling characteristics, these magnets need. The configuration selected for this study consists of a combination of thin poly-Bitter and thick Bitter coils optimized in dimensions and power under constraint of maximum design stress and heat removal to obtain maximum field. The study shows that each design requires a different optimummore » ratio of conductor strength to electrical conductivity and that efficient cooling is only advantageous if strong copper alloys are used. For efficient use of the available power the development of new high strength, high conductivity materials will be necessary. Equally important are improvements in the heat transfer characteristics of these high power density magnets.« less

Measurements of Plasma Power Losses in the C-2 Field-Reversed Configuration Experiment

NASA Astrophysics Data System (ADS)

Korepanov, Sergey; Smirnov, Artem; Garate, Eusebio; Donin, Alexandr; Kondakov, Alexey; Singatulin, Shavkat

2013-10-01

A high-confinement operating regime with plasma lifetimes significantly exceeding past empirical scaling laws was recently obtained by combining plasma gun edge biasing and tangential Neutral Beam Injection in the C-2 field-reversed configuration (FRC) experiment. To analyze the power balance in C-2, two new diagnostic instruments - the pyroelectric (PE) and infrared (IR) bolometers - were developed. The PE bolometer, designed to operate in the incident power density range from 0.1-100 W/cm2, is used to measure the radial power loss, which is dominated by charge-exchange neutrals and radiation. The IR bolometer, which measures power irradiated onto a thin metal foil inserted in the plasma, is designed for the power density range from 0.5-5 kW/cm2. The IR bolometer is used to measure the axial power loss from the plasma near the end divertors. The maximum measurable pulse duration of ~ 10 ms is limited by the heat capacitance of the IR detector. Both detectors have time resolution of about 10-100 μs and were calibrated in absolute units using a high power neutral beam. We present the results of first direct measurements of axial and radial plasma power losses in C-2.

A Plasma Ultraviolet Source for Short Wavelength Lasers.

DTIC Science & Technology

1986-03-10

A high power blue-green laser was pumped with an array of the dense plasma focus . As the result of optimizing the operating conditions of the dense... plasma focus and laser system, the maximum untuned laser output exceeded 2.lmJ corresponding to the energy density 3J/cu cm which is much higher than

Electricity Generation in Microbial Fuel Cell (MFC) by Bacterium Isolated from Rice Paddy Field Soil

NASA Astrophysics Data System (ADS)

Fakhirruddin, Fakhriah; Amid, Azura; Salim, Wan Wardatul Amani Wan; Suhaida Azmi, Azlin

2018-03-01

Microbial fuel cell (MFC) is an alternative approach in generating renewable energy by utilising bacteria that will oxidize organic or inorganic substrates, producing electrons yielded as electrical energy. Different species of exoelectrogenic bacteria capable of generating significant amount of electricity in MFC has been identified, using various organic compounds for fuel. Soil sample taken from rice paddy field is proven to contain exoelectrogenic bacteria, thus electricity generation using mixed culture originally found in the soil, and pure culture isolated from the soil is studied. This research will isolate the exoelectrogenic bacterial species in the rice paddy field soil responsible for energy generation. Growth of bacteria isolated from the MFC is observed by measuring the optical density (OD), cell density weight (CDW) and viable cell count. Mixed bacterial species found in paddy field soil generates maximum power of 77.62 μW and 0.70 mA of current. In addition, the research also shows that the pure bacterium in rice paddy field soil can produce maximum power and current at 51.32 μW and 0.28 mA respectively.

Hybrid microfluidic fuel cell based on Laccase/C and AuAg/C electrodes.

PubMed

López-González, B; Dector, A; Cuevas-Muñiz, F M; Arjona, N; Cruz-Madrid, C; Arana-Cuenca, A; Guerra-Balcázar, M; Arriaga, L G; Ledesma-García, J

2014-12-15

A hybrid glucose microfluidic fuel cell composed of an enzymatic cathode (Laccase/ABTS/C) and an inorganic anode (AuAg/C) was developed and tested. The enzymatic cathode was prepared by adsorption of 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and Laccase on Vulcan XC-72, which act as a redox mediator, enzymatic catalyst and support, respectively. The Laccase/ABTS/C composite was characterised by Fourier Transform Infrared (FTIR) Spectroscopy, streaming current measurements (Zeta potential) and cyclic voltammetry. The AuAg/C anode catalyst was characterised by Transmission electron microscopy (TEM) and cyclic voltammetry. The hybrid microfluidic fuel cell exhibited excellent performance with a maximum power density value (i.e., 0.45 mW cm(-2)) that is the highest reported to date. The cell also exhibited acceptable stability over the course of several days. In addition, a Mexican endemic Laccase was used as the biocathode electrode and evaluated in the hybrid microfluidic fuel cell generating 0.5 mW cm(-2) of maximum power density. Copyright © 2014 Elsevier B.V. All rights reserved.

Photonic crystal enhanced silicon cell based thermophotovoltaic systems

DOE PAGES

Yeng, Yi Xiang; Chan, Walker R.; Rinnerbauer, Veronika; ...

2015-01-30

We report the design, optimization, and experimental results of large area commercial silicon solar cell based thermophotovoltaic (TPV) energy conversion systems. Using global non-linear optimization tools, we demonstrate theoretically a maximum radiative heat-to-electricity efficiency of 6.4% and a corresponding output electrical power density of 0.39 W cm⁻² at temperature T = 1660 K when implementing both the optimized two-dimensional (2D) tantalum photonic crystal (PhC) selective emitter, and the optimized 1D tantalum pentoxide – silicon dioxide PhC cold-side selective filter. In addition, we have developed an experimental large area TPV test setup that enables accurate measurement of radiative heat-to-electricity efficiency formore » any emitter-filter-TPV cell combination of interest. In fact, the experimental results match extremely well with predictions of our numerical models. Our experimental setup achieved a maximum output electrical power density of 0.10W cm⁻² and radiative heat-to-electricity efficiency of 1.18% at T = 1380 K using commercial wafer size back-contacted silicon solar cells.« less

Bioelectricity production from food waste leachate using microbial fuel cells: effect of NaCl and pH.

PubMed

Li, Xiao Min; Cheng, Ka Yu; Wong, Jonathan W C

2013-12-01

Microbial fuel cells are a promising technology for simultaneous treatment and energy recovery from food waste leachate. This study evaluates the effects of NaCl (0-150 mM) and pH on the treatment of food waste leachate using microbial fuel cells. The food waste leachate amended with 100mM NaCl enabled the highest maximum power density (1000 mW/m(3)) and lowest internal resistance (371Ω). Increasing the anodic pH gradually from acidic to alkaline conditions (pH 4-9) resulted in a gradual increase in maximum power density to 9956 mW/m(3) and decrease in internal cell resistance to 35.3Ω. The coulombic efficiency obtained under acidic conditions was only 17.8%, but increased significantly to 60.0% and 63.4% in the neutral and alkaline pH's MFCs, respectively. Maintaining a narrow pH window (6.3-7.6) was essential for efficient bioelectricity production and COD removal using microbial fuel cells for the treatment of food waste leachate. Copyright © 2013 Elsevier Ltd. All rights reserved.

Symmetrical solid oxide fuel cells with impregnated SrFe0.75Mo0.25O3-δ electrodes

NASA Astrophysics Data System (ADS)

Meng, Xie; Liu, Xuejiao; Han, Da; Wu, Hao; Li, Junliang; Zhan, Zhongliang

2014-04-01

Here we report nominally symmetrical solid oxide fuel cells that feature thin La0.9Sr0.1Ga0.8Mg0.2O3-δ (LSGM) electrolytes and impregnated SrFe0.75Mo0.25O3-δ (SFMO)-LSGM composite electrodes. Operation on hydrogen fuels and air oxidants can produce maximum power densities of 0.39 W cm-2 at 650 °C and 0.97 W cm-2 at 800 °C. Impedance measurements indicate that the anode and the cathode polarizations are 0.22 and 0.04 Ω cm2 at 800 °C, respectively. Hydrogen partial pressure and temperature dependence of impedance data in humidified hydrogen shows that hydrogen oxidation kinetics is largely determined by hydrogen adsorption on the SFMO catalysts at high temperatures and charge transfer reactions along the SFMO|LSGM interfaces at low temperatures. Carbon tolerance of the present fuel cells is also examined in iso-octane fuels balanced by nitrogen at 800 °C that yields stable maximum power densities of 0.39 W cm-2.

An analytic model for limiting high density LH transition by the onset of the tertiary instability

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Raghvendra, E-mail: rsingh129@gmail.com; Jhang, Hogun; Kaang, Helen H.

2016-07-15

We perform an analytic study of the tertiary instability driven by a strong excitation of zonal flows during high density low to high (LH) mode transition. The drift resistive ballooning mode is assumed to be a dominant edge turbulence driver. The analysis reproduces main qualitative features of early computational results [Rogers and Drake, Phys. Rev. Lett. 81, 4396 (1998); Guzdar et al., Phys. Plasmas 14, 020701 (2007)], as well as new characteristics of the maximum edge density due to the onset of the tertiary instability. An analytical scaling indicates that the density scaling of LH transition power may be determinedmore » by the onset condition of the tertiary instability when the operating density approaches to the Greenwald density.« less

Parametric dependence of ion temperature and relative density in the NASA Lewis SUMMA facility. [superconducting magnetic mirror

NASA Technical Reports Server (NTRS)

Snyder, A.; Lauver, M. R.; Patch, R. W.

1976-01-01

Further hot-ion plasma experiments were conducted in the SUMMA superconducting magnetic mirror facility. A steady-state ExB plasma was formed by applying a strong radially inward dc electric field between cylindrical anodes and hollow cathodes located near the magnetic mirror maxima. Extending the use of water cooling to the hollow cathodes, in addition to the anodes, resulted in higher maximum power input to the plasma. Steady-state hydrogen plasmas with ion kinetic temperatures as high as 830 eV were produced. Functional relations were obtained empirically among the plasma current, voltage, magnetic flux density, ion temperature, and relative ion density. The functional relations were deduced by use of a multiple correlation analysis. Data were obtained for midplane magnetic fields from 0.5 to 3.37 tesla and input power up to 45 kW. Also, initial absolute electron density measurements are reported from a 90 deg Thomson scattering laser system.

Elasto-Aerodynamics-Driven Triboelectric Nanogenerator for Scavenging Air-Flow Energy.

PubMed

Wang, Shuhua; Mu, Xiaojing; Wang, Xue; Gu, Alex Yuandong; Wang, Zhong Lin; Yang, Ya

2015-10-27

Efficient scavenging the kinetic energy from air-flow represents a promising approach for obtaining clean, sustainable electricity. Here, we report an elasto-aerodynamics-driven triboelectric nanogenerator (TENG) based on contact electrification. The reported TENG consists of a Kapton film with two Cu electrodes at each side, fixed on two ends in an acrylic fluid channel. The relationship between the TENG output power density and its fluid channel dimensions is systematically studied. TENG with a fluid channel size of 125 × 10 × 1.6 mm(3) delivers the maximum output power density of about 9 kW/m(3) under a loading resistance of 2.3 MΩ. Aero-elastic flutter effect explains the air-flow induced vibration of Kapton film well. The output power scales nearly linearly with parallel wiring of multiple TENGs. Connecting 10 TENGs in parallel gives an output power of 25 mW, which allows direct powering of a globe light. The TENG is also utilized to scavenge human breath induced air-flow energy to sustainably power a human body temperature sensor.

Analysis of hydrogen plasma in MPCVD reactor

NASA Astrophysics Data System (ADS)

Shivkumar, Gayathri

The aim of this work is to build a numerical model that can predict the plasma properties of hydrogen plasmas inside a Seki Technotron Corp. AX5200S MPCVD system so that it may be used to understand and optimize the conditions for the growth of carbon nanostructures. A 2D model of the system is used in the finite element high frequency Maxwell solver and heat trasfer solver in COMSOL Multiphysics, where the solvers are coupled with user defined functions to analyze the plasma. A simplified chemistry model is formulated in order to determine the electron temperature in the plasma. This is used in the UDFs which calculate the electron number density as well as electron temperature. A Boltzmann equation solver for electrons in weakly ionized gases under uniform electric fields, called BOLSIG+, is used to obtain certain input parameters required for these UDFs. The system is modeled for several reactor geometries at pressures of 10 Torr and 30 Torr and powers ranging from 300 W to 700 W. The variation of plasma characteristics with changes in input conditions is studied and the electric field, electron number density, electron temperature and gas temperature are seen to increase with increasing power. Electric field, electron number density and electron temperature decrease and gas temperature increases with increasing pressure. The modeling results are compared with experimental measurements and a good agreement is found after calibrating the parameter gamma in Funer's model to match experimental electron number densities. The gas temperature is seen to have a weak dependence on power and a strong dependence on gas pressure. On an average, the gas temperature at a point 5 mm above the center of the puck increases from about 1000 K at a pressure of 10 Torr to about 1500 K at 30 Torr. The inclusion of the pillar produces an increase in the maximum electron number density of approximately 50%; it is higher under some conditions. It increases the maximum electron temperature by about 70% and at 500 W and 30 Torr, the maximum gas temperature is seen to increase by 50%. The effect of susceptor position is studied and it is seen that the only condition favorable to growth would be to raise it by less than 25 mm from the initial reference position or to maintain it at the same level.

Convergent development of anodic bacterial communities in microbial fuel cells.

PubMed

Yates, Matthew D; Kiely, Patrick D; Call, Douglas F; Rismani-Yazdi, Hamid; Bibby, Kyle; Peccia, Jordan; Regan, John M; Logan, Bruce E

2012-11-01

Microbial fuel cells (MFCs) are often inoculated from a single wastewater source. The extent that the inoculum affects community development or power production is unknown. The stable anodic microbial communities in MFCs were examined using three inocula: a wastewater treatment plant sample known to produce consistent power densities, a second wastewater treatment plant sample, and an anaerobic bog sediment. The bog-inoculated MFCs initially produced higher power densities than the wastewater-inoculated MFCs, but after 20 cycles all MFCs on average converged to similar voltages (470±20 mV) and maximum power densities (590±170 mW m(-2)). The power output from replicate bog-inoculated MFCs was not significantly different, but one wastewater-inoculated MFC (UAJA3 (UAJA, University Area Joint Authority Wastewater Treatment Plant)) produced substantially less power. Denaturing gradient gel electrophoresis profiling showed a stable exoelectrogenic biofilm community in all samples after 11 cycles. After 16 cycles the predominance of Geobacter spp. in anode communities was identified using 16S rRNA gene clone libraries (58±10%), fluorescent in-situ hybridization (FISH) (63±6%) and pyrosequencing (81±4%). While the clone library analysis for the underperforming UAJA3 had a significantly lower percentage of Geobacter spp. sequences (36%), suggesting that a predominance of this microbe was needed for convergent power densities, the lower percentage of this species was not verified by FISH or pyrosequencing analyses. These results show that the predominance of Geobacter spp. in acetate-fed systems was consistent with good MFC performance and independent of the inoculum source.

A biohydrogen fuel cell using a conductive polymer nanocomposite based anode.

PubMed

Hoa, Le Quynh; Sugano, Yasuhito; Yoshikawa, Hiroyuki; Saito, Masato; Tamiya, Eiichi

2010-07-15

This paper introduces a newly designed biohydrogen fuel cell by integrating a bioreactor for hydrogen production with the anode chamber in a hydrogen fuel cell. Two different composites of platinum nanoparticles decorated on functionalised multi-walled carbon nanotubes (Pt/fMWCNTs) and polyaniline (PANI) were fabricated using the electrochemical polymerisation method and used as anodes. The biohydrogen fuel cell using a thin film of PANI nanofibres deposited on Pt/fMWCNTs/carbon paper as the anode showed much higher power density than the cell using a core-shell structure PANI/Pt/fMWCNTs and Pt/fMWCNTs without PANI based anodes. The structural differences between these two composites and their effects on the interaction with hydrogen gas inside the anode chamber leading to the difference in power density of the fuel cell were also discussed. The maximum power density was 613.5 mW m(-2), which was obtained at a current density of about 2.55 A m(-2) with a cell voltage of 0.24 V using 20 mL single-chamber air-cathode, compact biohydrogen fuel cell. Copyright (c) 2010 Elsevier B.V. All rights reserved.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Study of a volume discharge in inert-gas halides without preionisation

NASA Astrophysics Data System (ADS)

Erofeev, M. V.; Tarasenko, V. F.

2008-04-01

The energy characteristics of radiation of halides of inert gases excited by a volume discharge without additional preionisation are studied. The pressures of working mixtures and relations between the inert gas and halogen optimal for obtaining the maximum pulsed power and radiation efficiency are determined. The peak UV radiation power density achieved 5 kW cm-2 and the radiation efficiency was ≈5.5%. The pulse FWHM was 30—40 ns.

Effects of proton exchange membrane on the performance and microbial community composition of air-cathode microbial fuel cells.

PubMed

Lee, Yun-Yeong; Kim, Tae Gwan; Cho, Kyung-Suk

2015-10-10

This study investigated the effects of proton exchange membranes (PEMs) on performance and microbial community of air-cathode microbial fuel cells (MFCs). Air-cathode MFCs with reactor volume of 1L were constructed in duplicate with or without PEM (designated as ACM-MFC and AC-MFC, respectively) and fed with a mixture of glucose and acetate (1:1, w:w). The maximum power density and coulombic efficiency did not differ between MFCs in the absence or presence of a PEM. However, PEM use adversely affected maximum voltage production and the rate of organic compound removal (p<0.05). Quantitative droplet digital PCR indicated that AC-MFCs had a greater bacterial population than ACM-MFCs (p<0.05). Likewise, ribosomal tag pyrosequencing revealed that the diversity index of bacterial communities was greater for AC-MFCs (p<0.05). Network analysis revealed that the most abundant genus was Enterococcus, which comprised ≥62% of the community and was positively associated with PEM and negatively associated with the rate of chemical oxygen demand (COD) removal (Pearson correlation>0.9 and p<0.05). Geobacter, which is known as an exoelectrogen, was positively associated with maximum power density and negatively associated with PEM. Thus, these results suggest that the absence of PEM favored the growth of Geobacter, a key player for electricity generation in MFC systems. Taken together, these findings demonstrate that MFC systems without PEM are more efficient with respect to power production and COD removal as well as exoelectrogen growth. Copyright © 2015 Elsevier B.V. All rights reserved.

Power Peaking Effect of OTTO Fuel Scheme Pebble Bed Reactor

NASA Astrophysics Data System (ADS)

Setiadipura, T.; Suwoto; Zuhair; Bakhri, S.; Sunaryo, G. R.

2018-02-01

Pebble Bed Reactor (PBR) type of Hight Temperature Gas-cooled Reactor (HTGR) is a very interesting nuclear reactor design to fulfill the growing electricity and heat demand with a superior passive safety features. Effort to introduce the PBR design to the market can be strengthen by simplifying its system with the Once-through-then-out (OTTO) cycle PBR in which the pebble fuel only pass the core once. Important challenge in the OTTO fuel scheme is the power peaking effect which limit the maximum nominal power or burnup of the design. Parametric survey is perform in this study to investigate the contribution of different design parameters to power peaking effect of OTTO cycle PBR. PEBBED code is utilized in this study to perform the equilibrium PBR core analysis for different design parameter and fuel scheme. The parameters include its core diameter, height-per-diameter (H/D), power density, and core nominal power. Results of this study show that diameter and H/D effectsare stronger compare to the power density and nominal core power. Results of this study might become an importance guidance for design optimization of OTTO fuel scheme PBR.

Wearable Solid-State Supercapacitors Operating at High Working Voltage with a Flexible Nanocomposite Electrode.

PubMed

Li, Xiaoyan; Wang, Jun; Zhao, Yaping; Ge, Fengyan; Komarneni, Sridhar; Cai, Zaisheng

2016-10-05

The proposed approach for fabricating ultralight self-sustained electrodes facilitates the structural integration of highly flexible carbon nanofibers, amino-modified multiwalled carbon nanotubes (AM-MWNT), and MnO 2 nanoflakes for potential use in wearable supercapacitors. Because of the higher orientation of AM-MWNT and the sublimation of terephthalic acid (PTA) in the carbonization process, freestanding electrodes could be realized with high porosity and flexibility and could possess remarkable electrochemical properties without using polymer substrates. Wearable symmetric solid-state supercapacitors were further assembled using a LiCl/PVA gel electrolyte, which exhibit a maximum energy density of 44.57 Wh/kg (at a power density of 337.1 W/kg) and a power density of 13330 W/kg (at an energy density of 19.64 Wh/kg) with a working voltage as high as 1.8 V. Due to the combination of several favorable traits such as flexibility, high energy density, and excellent electrochemical cyclability, the presently developed wearable supercapacitors with wide potential windows are expected to be useful for new kinds of portable electric devices.

Low Li+ Insertion Barrier Carbon for High Energy Efficient Lithium-Ion Capacitor.

PubMed

Lee, Wee Siang Vincent; Huang, Xiaolei; Tan, Teck Leong; Xue, Jun Min

2018-01-17

Lithium-ion capacitor (LIC) is an attractive energy-storage device (ESD) that promises high energy density at moderate power density. However, the key challenge in its design is the low energy efficient negative electrode, which barred the realization of such research system in fulfilling the current ESD technological inadequacy due to its poor overall energy efficiency. Large voltage hysteresis is the main issue behind high energy density alloying/conversion-type materials, which reduces the electrode energy efficiency. Insertion-type material though averted in most research due to the low capacity remains to be highly favorable in commercial application due to its lower voltage hysteresis. To further reduce voltage hysteresis and increase capacity, amorphous carbon with wider interlayer spacing has been demonstrated in the simulation result to significantly reduce Li + insertion barrier. Hence, by employing such amorphous carbon, together with disordered carbon positive electrode, a high energy efficient LIC with round-trip energy efficiency of 84.3% with a maximum energy density of 133 Wh kg -1 at low power density of 210 W kg -1 can be achieved.

Hierarchical MoS2 nanowires/NiCo2O4 nanosheets supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Zhu, Fangfang; Shao, Rong; Xu, Wei

2018-01-01

The hierarchical MoS2 nanowires/NiCo2O4 nanosheets (MS/NCO) supercapacitor electrode materials supported on Ni foam were synthesized by a two-step hydrothermal method. The capacitance was investigated by using various electrochemical methods including cyclic voltammetry, constant-current galvanostatic charge/discharge curves and electrochemical impedance spectroscopy. The MS/NCO networks show 7 times more capacitance (7.1 F cm-2) than pure NiCo2O4 nanosheets by CV at a scan rate of 2 mV s-1. The specific capacitance of the assembled MS/NCO//active carbon (AC) asymmetric supercapacitor could reach up to 51.7 F g-1 at a current density of 1.5 A g-1. Also, the maximum energy density of 18.4 W h kg-1 at a power density of 1200.2 W kg-1 was achieved, with 98.2% specific capacitance retention after 8000 cycles. These exciting results exhibit potential application in developing energy storage devices with high energy density and high power density.

Enhancing power density of strained In0.8Ga0.2As/AlAs resonant tunneling diode for terahertz radiation by optimizing emitter spacer layer thickness

NASA Astrophysics Data System (ADS)

Shi, Xiangyang; Wu, Yuanyuan; Wang, Ding; Su, Juan; Liu, Jie; Yang, Wenxian; Xiao, Meng; Tan, Wei; Lu, Shulong; Zhang, Jian

2017-12-01

We demonstrate both theoretically and experimentally that the power density of resonant tunneling diode (RTD) can be enhanced by optimizing emitter spacer layer thickness, in addition to reducing barrier thickness. Compared to the widely used epitaxial structure with ultrathin emitter spacer layer thickness, appropriate increasing the thickness will increase the voltage drop in accumulation region, leading to larger voltage widths of negative differential resistance region. By measuring J-V characteristics, the specific contact resistivity, and the self-capacitance, we theoretically analyze the maximum output power of the fabricated RTDs. It shows that the optimized In0.8Ga0.2As/AlAs RTD with 20 nm emitter spacer thickness and 5 μm2 mesa area theoretically possesses the capability to reach 3.1 mW at 300 GHz and 1.8 mW at 600 GHz.

Enhanced power generation and energy conversion of sewage sludge by CEA-microbial fuel cells.

PubMed

Abourached, Carole; Lesnik, Keaton Larson; Liu, Hong

2014-08-01

The production of methane from sewage sludge through the use of anaerobic digestion has been able to effectively offset energy costs for wastewater treatment. However, significant energy reserves are left unrecovered and effluent standards are not met necessitating secondary processes such as aeration. In the current study a novel cloth-electrode assembly microbial fuel cell (CEA-MFC) was used to generate electricity from sewage sludge. Fermentation pretreatment of the sludge effectively increased the COD of the supernatant and improved reactor performance. Using the CEA-MFC design, a maximum power density of 1200 mW m(-2) was reached after a fermentation pre-treatment time of 96 h. This power density represents a 275% increase over those previously observed in MFC systems. Results indicate continued improvements are possible and MFCs may be a viable modification to existing wastewater treatment infrastructure. Copyright © 2014 Elsevier Ltd. All rights reserved.

Recycled tire crumb rubber anodes for sustainable power production in microbial fuel cells

NASA Astrophysics Data System (ADS)

Wang, Heming; Davidson, Matthew; Zuo, Yi; Ren, Zhiyong

One of the greatest challenges facing microbial fuel cells (MFCs) in large scale applications is the high cost of electrode material. We demonstrate here that recycled tire crumb rubber coated with graphite paint can be used instead of fine carbon materials as the MFC anode. The tire particles showed satisfactory conductivity after 2-4 layers of coating. The specific surface area of the coated rubber was over an order of magnitude greater than similar sized graphite granules. Power production in single chamber tire-anode air-cathode MFCs reached a maximum power density of 421 mW m -2, with a coulombic efficiency (CE) of 25.1%. The control graphite granule MFC achieved higher power density (528 mW m -2) but lower CE (15.6%). The light weight of tire particle could reduce clogging and maintenance cost but posts challenges in conductive connection. The use of recycled material as the MFC anodes brings a new perspective to MFC design and application and carries significant economic and environmental benefit potentials.

Observation of ultrahigh-energy electrons by resonance absorption of high-power microwaves in a pulsed plasma.

PubMed

Rajyaguru, C; Fuji, T; Ito, H; Yugami, N; Nishida, Y

2001-07-01

The interaction of high power microwave with collisionless unmagnetized plasma is studied. Investigation on the generation of superthermal electrons near the critical layer, by the resonance absorption phenomenon, is extended to very high microwave power levels (eta=E(2)(0)/4 pi n(e)kT(e) approximately 0.3). Here E0, n(e), and T(e) are the vacuum electric field, electron density, and electron temperature, respectively. Successive generation of electron bunches having maximum energy of about 2 keV, due to nonlinear wave breaking, is observed. The electron energy epsilon scales as a function of the incident microwave power P, according to epsilon proportional to P0.5 up to 250 kW. The two-dimensional spatial distribution of high energy electrons reveals that they are generated near the critical layer. However, the lower energy component is again produced in the subcritical density region indicating the possibility of other electron heating mechanisms.

Splitting of a vertical multiwalled carbon nanotube carpet to a graphene nanoribbon carpet and its use in supercapacitors.

PubMed

Zhang, Chenguang; Peng, Zhiwei; Lin, Jian; Zhu, Yu; Ruan, Gedeng; Hwang, Chih-Chau; Lu, Wei; Hauge, Robert H; Tour, James M

2013-06-25

Potassium vapor was used to longitudinally split vertically aligned multiwalled carbon nanotubes carpets (VA-CNTs). The resulting structures have a carpet of partially split MWCNTs and graphene nanoribbons (GNRs). The split structures were characterized by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. When compared to the original VA-CNTs carpet, the split VA-CNTs carpet has enhanced electrochemical performance with better specific capacitance in a supercapacitor. Furthermore, the split VA-CNTs carpet has excellent cyclability as a supercapacitor electrode material. There is a measured maximum power density of 103 kW/kg at an energy density of 5.2 Wh/kg and a maximum energy density of 9.4 Wh/kg. The superior electrochemical performances of the split VA-CNTs can be attributed to the increased surface area for ion accessibility after splitting, and the lasting conductivity of the structure with their vertical conductive paths based on the preserved GNR alignment.

Controlled synthesis of nanostructured molybdenum oxide electrodes for high performance supercapacitor devices

NASA Astrophysics Data System (ADS)

Maheswari, Nallappan; Muralidharan, Gopalan

2017-09-01

Well defined crystallographic and one dimensional morphological structure of molybdenum oxide were successfully synthesized by adjusting the duration of hydrothermal treatment. The prepared molybdenum oxide was examined through XRD, SEM, FTIR, TEM, BET and electrochemical studies. The XRD patterns illustrate that MoOx prepared by variying the hydrothermal reaction time are in different crystallographic structure of MoyOx (Mo8O23 and MoO3). SEM studies reveal the different morphological structures ranging from flake like morphology to nanorods. TEM images confirm the excellent nanorod structure. The nanorod structure ensures good cyclic behaviour with maximum capacitance of 1080 F g-1 at a current density of 2 A g-1. This large capacity of the MoO3 nanostructures enabled fabrication of symmetric and asymmertic supercapacitor devices. The asymmertic device exhibits a maximum specific capacitance of 145 F g-1 at 2 mV s-1 with highest energy density of 38.6 W h kg-1 at 374.7 W kg-1 power density.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kish, Edward R.; Desai, Tushar V.; Greer, Douglas R.

The authors have examined the nucleation of diindenoperylene (DIP) on SiO{sub 2} employing primarily atomic force microscopy and focusing on the effect of incident kinetic energy employing both thermal and supersonic sources. For all incident kinetic energies examined (E{sub i} = 0.09–11.3 eV), the nucleation of DIP is homogeneous and the dependence of the maximum island density on the growth rate is described by a power law. A critical nucleus of approximately two molecules is implicated by our data. A re-examination of the nucleation of pentacene on SiO{sub 2} gives the same major result that the maximum island density is determined by themore » growth rate, and it is independent of the incident kinetic energy. These observations are readily understood by factoring in the size of the critical nucleus in each case, and the island density, which indicates that diffusive transport of molecules to the growing islands dominate the dynamics of growth in the submonolayer regime.« less

Enhanced energy harvesting by concentration gradient-driven ion transport in SBA-15 mesoporous silica thin films.

PubMed

Hwang, Junho; Kataoka, Sho; Endo, Akira; Daiguji, Hirofumi

2016-09-21

Nanofluidic energy harvesting systems have attracted interest in the field of battery application, particularly for miniaturized electrical devices, because they possess excellent energy conversion capability for their size. In this study, a mesoporous silica (MPS)-based nanofluidic energy harvesting system was fabricated and selective ion transport in mesopores as a function of the salt gradient was investigated. Aqueous solutions with three different kinds of monovalent electrolytes-KCl, NaCl, and LiCl-with different diffusion coefficients (D + ) were considered. The highest power density was 3.90 W m -2 for KCl, followed by 2.39 W m -2 for NaCl and 1.29 W m -2 for LiCl. Furthermore, the dependency of power density on the type of cation employed indicates that the harvested energy increases as the cation mobility increases, particularly at high concentrations. This cation-specific dependency suggests that the maximum power density increases by increasing the diffusion coefficient ratio of cations to anions, making this ratio a critical parameter in enhancing the performance of nanofluidic energy harvesting systems with extremely small pores ranging from 2 to 3 nm.

Homogeneous coating of ionomer on electrocatalyst assisted by polybenzimidazole as an adhesive layer and its effect on fuel cell performance

NASA Astrophysics Data System (ADS)

Yang, Zehui; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2015-12-01

The fabrication of homogeneous ionomer distribution in fuel cell catalyst layers is necessary and important to improve the platinum utilization as well as the power density. Here, we focus on the effect of poly[2,2‧-(2,6-pyridine)-5,5‧-bibenzimidazole] (PyPBI) wrapped on multi-walled carbon nanotubes (MWNTs) for anchoring Nafion ionomer to the electrocatalyst, in which PyPBI functions as the binding sites for platinum nanoparticles (Pt-NPs) used as a catalyst. Based on the result using a control composite without having PyPBI, a strong interaction of the Nafion onto the PyPBI layer is recognized. Importantly, we find that the membrane-electrode assembly (MEA) shows a much higher maximum power density than that of the MEA without PyPBI. A homogeneous coating of Nafion on the electrocatalyst using the PyPBI forms a long-range network of the ionomer, leading to an improved Pt-NP utilization efficiency as well as an enhanced power density of the MEA.

Cosmic ray acceleration in magnetic circumstellar bubbles

NASA Astrophysics Data System (ADS)

Zirakashvili, V. N.; Ptuskin, V. S.

2018-03-01

We consider the diffusive shock acceleration in interstellar bubbles created by powerful stellar winds of supernova progenitors. Under the moderate stellar wind magnetization the bubbles are filled by the strongly magnetized low density gas. It is shown that the maximum energy of particles accelerated in this environment can exceed the "knee" energy in the observable cosmic ray spectrum.

Zero-CO2 emission and low-crossover 'rechargeable' PEM fuel cells using cyclohexane as an organic hydrogen reservoir.

PubMed

Kariya, Nobuko; Fukuoka, Atsushi; Ichikawa, Masaru

2003-03-21

High performance (open circuit voltage = 920 mV, maximum power density = 14-15 mW cm(-2)) of the PEM fuel cell was achieved by using cyclohexane as a fuel with zero-CO2 emission and lower-crossover through PEM than with a methanol-based fuel cell.

Effects of evolving quality of landfill leachate on microbial fuel cell performance.

PubMed

Li, Simeng; Chen, Gang

2018-01-01

Microbial fuel cell (MFC) is a novel technology for landfill leachate treatment with simultaneous electric power generation. In recent years, more and more modern landfills are operating as bioreactors to shorten the time required for landfill stabilization and improve the leachate quality. For landfills to operate as biofilters, leachate is recirculated back to the landfill, during which time the organics of the leachate can be decomposed. Continuous recirculation typically results in evolving leachate quality, which chronologically corresponds to evolution stages such as hydrolysis, acidogenesis, acetogenesis, methanogenesis, and maturation. In this research, variable power generation (160 to 230 mW m -2 ) by MFC was observed when leachate of various evolutionary stages was used as the feed. The power density followed a Monod-type kinetic model with the chemical oxygen demand (COD) equivalent of the volatile fatty acids (VFAs) ( p < 0.001). The coulombic efficiency decreased from 20% to 14% as the leachate evolved towards maturation. The maximum power density linearly decreased with the increase of internal resistance, resulting from the change of the conductivity of the solution. The decreased conductivity boosted the internal resistance and consequently limited the power generation. COD removal as high as 90% could be achieved with leachate extracted from appropriate evolutionary stages, with a maximum energy yield of 0.9 kWh m -3 of leachate. This study demonstrated the importance of the evolving leachate quality in different evolutionary stages for the performance of leachate-fed MFCs. The leachate extracted from acidogenesis and acetogenesis were optimal for both COD reduction and energy production in MFCs.

Photovoltaic Properties of Selenized CuGa/In Films with Varied Compositions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muzzillo, Christopher P.; Mansfield, Lorelle M.; Ramanathan, Kannan

2016-11-21

Thin CuGa/In films with varied compositions were deposited by co-evaporation and then selenized in situ with evaporated selenium. The selenized Cu(In, Ga)Se2 absorbers were used to fabricate 390 solar cells. Cu/(Ga+In) and Ga/(Ga+In) (Cu/III and Ga/III) were independently varied, and photovoltaic performance was optimal at Cu/III of 77-92% for all Ga/III compositions studied (Ga/III ~ 30, 50, and 70%). The best absorbers at each Ga/III composition were characterized with time-resolved photoluminescence, scanning electron microscopy, and secondary ion mass spectrometry, and devices were studied with temperature-dependent current density-voltage, light and electrical biased quantum efficiency, and capacitance-voltage. The best cells with Ga/IIImore » ~ 30, 50, and 70% had efficiencies of 14.5, 14.4, and 12.2% and maximum power temperature coefficients of -0.496, -0.452, and -0.413%/degrees C, respectively. This resulted in the Ga/III ~ 50% champion having the highest efficiency at temperatures greater than 40 degrees C, making it the optimal composition for practical purposes. This optimum is understood as a result of the absorber's band gap grading- where minimum band gap dominates short-circuit current density, maximum space charge region band gap dominates open-circuit voltage, and average absorber band gap dominates maximum power temperature coefficient.« less

Model calculations of kinetic and fluid dynamic processes in diode pumped alkali lasers

NASA Astrophysics Data System (ADS)

Barmashenko, Boris D.; Rosenwaks, Salman; Waichman, Karol

2013-10-01

Kinetic and fluid dynamic processes in diode pumped alkali lasers (DPALs) are analyzed in detail using a semianalytical model, applicable to both static and flowing-gas devices. The model takes into account effects of temperature rise, excitation of neutral alkali atoms to high lying electronic states and their losses due to ionization and chemical reactions, resulting in a decrease of the pump absorption, slope efficiency and lasing power. Effects of natural convection in static DPALs are also taken into account. The model is applied to Cs DPALs and the results are in good agreement with measurements in a static [B.V. Zhdanov, J. Sell and R.J. Knize, Electron. Lett. 44, 582 (2008)] and 1-kW flowing-gas [A.V. Bogachev et al., Quantum Electron. 42, 95 (2012)] DPALs. It predicts the dependence of power on the flow velocity in flowing-gas DPALs and on the buffer gas composition. The maximum values of the laser power can be substantially increased by optimization of the flowing-gas DPAL parameters. In particular for the aforementioned 1 kW DPAL, 6 kW maximum power is achievable just by increasing the pump power and the temperature of the wall and the gas at the flow inlet (resulting in increase of the alkali saturated vapor density). Dependence of the lasing power on the pump power is non-monotonic: the power first increases, achieves its maximum and then decreases. The decrease of the lasing power with increasing pump power at large values of the latter is due to the rise of the aforementioned losses of the alkali atoms as a result of ionization. Work in progress applying two-dimensional computational fluid dynamics modeling of flowing-gas DPALs is also reported.

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers

PubMed Central

2017-01-01

We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 1010 cm–2, the highest peak output power of 151 mW is found for 7.3 × 1010 cm–2. Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures. PMID:28470028

High-Power Growth-Robust InGaAs/InAlAs Terahertz Quantum Cascade Lasers.

PubMed

Deutsch, Christoph; Kainz, Martin Alexander; Krall, Michael; Brandstetter, Martin; Bachmann, Dominic; Schönhuber, Sebastian; Detz, Hermann; Zederbauer, Tobias; MacFarland, Donald; Andrews, Aaron Maxwell; Schrenk, Werner; Beck, Mattias; Ohtani, Keita; Faist, Jérôme; Strasser, Gottfried; Unterrainer, Karl

2017-04-19

We report on high-power terahertz quantum cascade lasers based on low effective electron mass InGaAs/InAlAs semiconductor heterostructures with excellent reproducibility. Growth-related asymmetries in the form of interface roughness and dopant migration play a crucial role in this material system. These bias polarity dependent phenomena are studied using a nominally symmetric active region resulting in a preferential electron transport in the growth direction. A structure based on a three-well optical phonon depletion scheme was optimized for this bias direction. Depending on the sheet doping density, the performance of this structure shows a trade-off between high maximum operating temperature and high output power. While the highest operating temperature of 155 K is observed for a moderate sheet doping density of 2 × 10 10 cm -2 , the highest peak output power of 151 mW is found for 7.3 × 10 10 cm -2 . Furthermore, by abutting a hyperhemispherical GaAs lens to a device with the highest doping level a record output power of 587 mW is achieved for double-metal waveguide structures.

Anomalous pH-Dependent Nanofluidic Salinity Gradient Power.

PubMed

Yeh, Li-Hsien; Chen, Fu; Chiou, Yu-Ting; Su, Yen-Shao

2017-12-01

Previous studies on nanofluidic salinity gradient power (NSGP), where energy associated with the salinity gradient can be harvested with ion-selective nanopores, all suggest that nanofluidic devices having higher surface charge density should have higher performance, including osmotic power and conversion efficiency. In this manuscript, this viewpoint is challenged and anomalous counterintuitive pH-dependent NSGP behaviors are reported. For example, with equal pH deviation from its isoelectric point (IEP), the nanopore at pH < IEP is shown to have smaller surface charge density but remarkably higher NSGP performance than that at pH > IEP. Moreover, for sufficiently low pH, the NSGP performance decreases with lowering pH (increasing nanopore charge density). As a result, a maximum osmotic power density as high as 5.85 kW m -2 can be generated along with a conversion efficiency of 26.3% achieved for a single alumina nanopore at pH 3.5 under a 1000-fold concentration ratio. Using the rigorous model with considering the surface equilibrium reactions on the pore wall, it is proved that these counterintuitive surface-charge-dependent NSGP behaviors result from the pH-dependent ion concentration polarization effect, which yields the degradation in effective concentration ratio across the nanopore. These findings provide significant insight for the design of next-generation, high-performance NSGP devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental advances and preliminary mathematical modeling of the Swiss-roll mixed-reactant direct borohydride fuel cell

NASA Astrophysics Data System (ADS)

Aziznia, Amin; Oloman, Colin W.; Gyenge, Előd L.

2014-11-01

The Swiss-roll single-cell mixed reactant (SR-MRFC) borohydride - oxygen fuel cell equipped with Pt/carbon cloth 3D anode and either MnO2 or Ag gas-diffusion cathodes is investigated by a combination of experimental studies and preliminary mathematical modeling of the polarization curve. We investigate the effects of four variables: cathode side metallic mesh fluid distributor, separator type (Nafion 112® vs. Viledon®), cathode catalyst (MnO2 vs. Ag), and the hydrophilic pore volume fraction of the gas-diffusion cathode. Using a two-phase feed of alkaline borohydride solution (1 M NaBH4 - 2 M NaOH) and O2 gas in an SR-MRFC equipped with Pt/C 3D anode, MnO2 gas diffusion cathode, Viledon® porous diaphragm, expanded mesh cathode-side fluid distributor, the maximum superficial power density is 2230 W m-2 at 323 K and 105 kPa(abs). The latter superficial power density is almost 3.5 times higher than our previously reported superficial power density for the same catalyst combinations. Furthermore, with a Pt anode and Ag cathode catalyst combination, a superficial power density of 2500 W m-2 is achieved with superior performance durability compared to the MnO2 cathode. The fuel cell results are substantiated by impedance spectroscopy analysis and preliminary mathematical model predictions based on mixed potential theory.

Increasing power-law range in avalanche amplitude and energy distributions

NASA Astrophysics Data System (ADS)

Navas-Portella, Víctor; Serra, Isabel; Corral, Álvaro; Vives, Eduard

2018-02-01

Power-law-type probability density functions spanning several orders of magnitude are found for different avalanche properties. We propose a methodology to overcome empirical constraints that limit the range of truncated power-law distributions. By considering catalogs of events that cover different observation windows, the maximum likelihood estimation of a global power-law exponent is computed. This methodology is applied to amplitude and energy distributions of acoustic emission avalanches in failure-under-compression experiments of a nanoporous silica glass, finding in some cases global exponents in an unprecedented broad range: 4.5 decades for amplitudes and 9.5 decades for energies. In the latter case, however, strict statistical analysis suggests experimental limitations might alter the power-law behavior.

Increasing power-law range in avalanche amplitude and energy distributions.

PubMed

Navas-Portella, Víctor; Serra, Isabel; Corral, Álvaro; Vives, Eduard

2018-02-01

Power-law-type probability density functions spanning several orders of magnitude are found for different avalanche properties. We propose a methodology to overcome empirical constraints that limit the range of truncated power-law distributions. By considering catalogs of events that cover different observation windows, the maximum likelihood estimation of a global power-law exponent is computed. This methodology is applied to amplitude and energy distributions of acoustic emission avalanches in failure-under-compression experiments of a nanoporous silica glass, finding in some cases global exponents in an unprecedented broad range: 4.5 decades for amplitudes and 9.5 decades for energies. In the latter case, however, strict statistical analysis suggests experimental limitations might alter the power-law behavior.

High Efficiency Thermoelectric Radioisotope Power Systems

NASA Technical Reports Server (NTRS)

El-Genk, Mohamed; Saber, Hamed; Caillat, Thierry

2004-01-01

The work performed and whose results presented in this report is a joint effort between the University of New Mexico s Institute for Space and Nuclear Power Studies (ISNPS) and the Jet Propulsion Laboratory (JPL), California Institute of Technology. In addition to the development, design, and fabrication of skutterudites and skutterudites-based segmented unicouples this effort included conducting performance tests of these unicouples for hundreds of hours to verify theoretical predictions of the conversion efficiency. The performance predictions of these unicouples are obtained using 1-D and 3-D models developed for that purpose and for estimating the actual performance and side heat losses in the tests conducted at ISNPS. In addition to the performance tests, the development of the 1-D and 3-D models and the development of Advanced Radioisotope Power systems for Beginning-Of-Life (BOM) power of 108 We are carried out at ISNPS. The materials synthesis and fabrication of the unicouples are carried out at JPL. The research conducted at ISNPS is documented in chapters 2-5 and that conducted at JP, in documented in chapter 5. An important consideration in the design and optimization of segmented thermoelectric unicouples (STUs) is determining the relative lengths, cross-section areas, and the interfacial temperatures of the segments of the different materials in the n- and p-legs. These variables are determined using a genetic algorithm (GA) in conjunction with one-dimensional analytical model of STUs that is developed in chapter 2. Results indicated that when optimized for maximum conversion efficiency, the interfacial temperatures between various segments in a STU are close to those at the intersections of the Figure-Of-Merit (FOM), ZT, curves of the thermoelectric materials of the adjacent segments. When optimizing the STUs for maximum electrical power density, however, the interfacial temperatures are different from those at the intersections of the ZT curves, but close to those at the intersections the characteristic power, CP, curves of the thermoelectric materials of the adjacent segments (CP = T(sup 2)Zk and has a unit of W/m). Results also showed that the number of the segments in the n- and p-legs of the STUs optimized for maximum power density are generally fewer than when the same unicouples are optimized for maximum efficiency. These results are obtained using the 1-D optimization model of STUs that is detailed in chapter 2. A three-dimensional model of STUs is developed and incorporated into the ANSYS commercial software (chapter 3). The governing equations are solved, subject to the prescribed

Composite plasma polymerized sulfonated polystyrene membrane for PEMFC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nath, Bhabesh Kumar; Khan, Aziz; Chutia, Joyanti, E-mail: jchutiaiasst@gmail.com

2015-10-15

Highlights: • Methyl methane sulfonate (MMS) is used as the sulfonating agent. • The proton conductivity of the membrane is found to be 0.141 S cm{sup −1}. • Power density of fuel cell with styrene/MMS membrane is 0.5 W cm{sup −2}. • The membrane exhibits thermal stability up to 140 °C. - Abstract: This work presents the introduction of an organic compound methyl methane sulfonate (MMS) for the first time in fabrication of polystyrene based proton exchange membrane (PEM) by plasma polymerization process. The membrane is fabricated by co-polymerizing styrene and MMS in capacitively coupled continuous RF plasma. The chemicalmore » composition of the plasma polymerized polymer membrane is investigated using Fourier Transform Infrared Spectroscopy which reveals the formation of composite structure of styrene and MMS. The surface morphology studied using AFM and SEM depicts the effect of higher partial pressure of MMS on surface topography of the membrane. The proton transport property of the membrane studied using electrochemical impedance spectroscopy shows the achievement of maximum proton conductivity of 0.141 S cm{sup −1} which is comparable to Nafion 117 membrane. Fuel cell performance test of the synthesized membrane shows a maximum power density of 500 mW cm{sup −2} and current density of 0.62 A cm{sup −2} at 0.6 V.« less

Phase-locked, high power, mid-infrared quantum cascade laser arrays

NASA Astrophysics Data System (ADS)

Zhou, W.; Slivken, S.; Razeghi, M.

2018-04-01

We demonstrate phase-locked, high power quantum cascade laser arrays, which are combined using a monolithic, tree array multimode interferometer, with emission wavelengths around 4.8 μm. A maximum output power of 15 W was achieved from an eight-element laser array, which has only a slightly higher threshold current density and a similar slope efficiency compared to a Fabry-Perot laser of the same length. Calculated multimode interferometer splitting loss is on the order of 0.27 dB for the in-phase supermode. In-phase supermode operation with nearly ideal behavior is demonstrated over the working current range of the array.

High performance terahertz metasurface quantum-cascade VECSEL with an intra-cryostat cavity

DOE PAGES

Xu, Luyao; Curwen, Christopher A.; Reno, John L.; ...

2017-09-04

A terahertz quantum-cascade (QC) vertical-external-cavity surface-emitting-laser (VECSEL) is demonstrated with over 5 mW power in continuous-wave and single-mode operation above 77 K, in combination with a near-Gaussian beam pattern with full-width half-max divergence as narrow as ~5° × 5°, with no evidence of thermal lensing. This is realized by creating an intra-cryostat VECSEL cavity to reduce the cavity loss and designing an active focusing metasurface reflector with low power dissipation for efficient heat removal. Compared with a conventional quantumcascade laser based on a metal-metal waveguide, the intra-cryostat QC-VECSEL exhibits significant improvements in both output power level and beam pattern. Also,more » the intra-cryostat configuration newly allows evaluation of QC-VECSEL operation vs. temperature, showing a maximum pulsed mode operating temperature of 129 K. While the threshold current density in the QC-VECSEL is worse in comparison to a conventional edge-emitting metal-metal waveguide QClaser, the beam quality, slope efficiency, maximum power, and thermal resistance are all significantly improved.« less

Domestic wastewater treatment and power generation in continuous flow air-cathode stacked microbial fuel cell: Effect of series and parallel configuration.

PubMed

Estrada-Arriaga, Edson Baltazar; Hernández-Romano, Jesús; García-Sánchez, Liliana; Guillén Garcés, Rosa Angélica; Bahena-Bahena, Erick Obed; Guadarrama-Pérez, Oscar; Moeller Chavez, Gabriela Eleonora

2018-05-15

In this study, a continuous flow stack consisting of 40 individual air-cathode MFC units was used to determine the performance of stacked MFC during domestic wastewater treatment operated with unconnected individual MFC and in series and parallel configuration. The voltages obtained from individual MFC units were of 0.08-1.1 V at open circuit voltage, while in series connection, the maximum power and current density were 2500 mW/m 2 and 500 mA/m 2 (4.9 V), respectively. In parallel connection, the maximum power and current density was 5.8 mW/m 2 and 24 mA/m 2 , respectively. When the cells were not connected to each other MFC unit, the main bacterial species found in the anode biofilms were Bacillus and Lysinibacillus. After switching from unconnected to series and parallel connections, the most abundant species in the stacked MFC were Pseudomonas aeruginosa, followed by different Bacilli classes. This study demonstrated that when the stacked MFC was switched from unconnected to series and parallel connections, the pollutants removal, performance electricity and microbial community changed significantly. Voltages drops were observed in the stacked MFC, which was mainly limited by the cathodes. These voltages loss indicated high resistances within the stacked MFC, generating a parasitic cross current. Copyright © 2018 Elsevier Ltd. All rights reserved.

47 CFR 27.53 - Emission limits.

Code of Federal Regulations, 2014 CFR

2014-10-01

... operations shall be limited to a maximum power flux density of −197 dBW/m2/4 kHz in the 2370-2390 MHz band at... displacement from the channel center frequency and measurement bandwidth. In the following tables, “(s... section of the printed volume and on GPO Access. Effective Date Note: At 79 FR 48539, Aug. 15, 2014, § 27...

Direct thrust measurement of a permanent magnet helicon double layer thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takahashi, K.; Lafleur, T.; Charles, C.

2011-04-04

Direct thrust measurements of a permanent magnet helicon double layer thruster have been made using a pendulum thrust balance and a high sensitivity laser displacement sensor. At the low pressures used (0.08 Pa) an ion beam is detected downstream of the thruster exit, and a maximum thrust force of about 3 mN is measured for argon with an rf input power of about 700 W. The measured thrust is proportional to the upstream plasma density and is in good agreement with the theoretical thrust based on the maximum upstream electron pressure.

Feasibility study of surface-modified carbon cloth electrodes using atmospheric pressure plasma jets for microbial fuel cells

NASA Astrophysics Data System (ADS)

Chang, Shih-Hang; Liou, Jyun-Sian; Liu, Jung-Liang; Chiu, Yi-Fan; Xu, Chang-Han; Chen, Bor-Yann; Chen, Jian-Zhang

2016-12-01

This study investigated the surface and electrochemical properties of carbon cloth electrodes surface-modified by using atmospheric pressure plasma jets (APPJs) for applications involving microbial fuel cells (MFCs). APPJ treatment made the carbon cloth highly hydrophilic and did not introduce any observable cracks or flaws. MFCs configured with APPJ-treated carbon cloth electrodes exhibited electrochemical performance (maximum power density of 7.56 mW m-2) superior to that of MFCs configured with untreated carbon cloth electrodes (maximum power density of 2.38 mW m-2). This boost in performance can be attributed to the formation of abundant carboxyl and ammonium functional groups on the surface of APPJ-treated carbon cloth, which promoted the formation of anodic biofilms and the adhesion of bacteria, while facilitating the transfer of electrons from the bacteria to the electrodes. APPJ surface modification is non-toxic and environmentally friendly (no exogenous chemicals are required), which is particularly beneficial as the introduction of toxins might otherwise inhibit bacterial growth and metabolism. The APPJ surface modification process is rapid, cost-effective, and applicable to substrates covering a large area, making it ideal for the fabrication of large-scale MFCs and bioelectrochemical bioenergy devices.

Assessment of candidates for target window material in accelerator-driven molybdenum-99 production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strons, Philip; Bailey, James; Makarashvili, Vakhtang

2016-10-01

NorthStar Medical Technologies is pursuing production of an important medical isotope, Mo-99, through a photo-nuclear reaction of a Mo-100 target using a high-power electron accelerator. The current target utilizes an Inconel 718 window. The purpose of this study was to evaluate other candidate materials for the target window, which separates the high-pressure helium gas inside the target from the vacuum inside the accelerator beamline and is subjected to significant stress. Our initial analysis assessed the properties (density, thermal conductivity, maximum stress, minimum window thickness, maximum temperature, and figure of merit) for a range of materials, from which the three mostmore » promising were chosen: Inconel 718, 250 maraging steel, and standard-grade beryllium. These materials were subjected to further analysis to determine the effects of thermal and mechanical strain versus beam power at varying thicknesses. Both beryllium and the maraging steel were calculated to withstand more than twice as high beam power than Inconel 718.« less

Characterization of atomic oxygen from an ECR plasma source

NASA Astrophysics Data System (ADS)

Naddaf, M.; Bhoraskar, V. N.; Mandale, A. B.; Sainkar, S. R.; Bhoraskar, S. V.

2002-11-01

A low-power microwave-assisted electron cyclotron resonance (ECR) plasma system is shown to be a powerful and effective source of atomic oxygen (AO) useful in material processing. A 2.45 GHz microwave source with maximum power of 600 W was launched into the cavity to generate the ECR plasma. A catalytic nickel probe was used to determine the density of AO. The density of AO is studied as a function of pressure and axial position of the probe in the plasma chamber. It was found to vary from ~1×1020 to ~10×1020 atom m-3 as the plasma pressure was varied from 0.8 to 10 mTorr. The effect of AO in oxidation of silver is investigated by gravimetric analysis. The stoichiometric properties of the oxide are studied using the x-ray photoelectron spectroscopy as well as energy dispersive x-ray analysis. The degradation of the silver surface due to sputtering effect was viewed by scanning electron spectroscopy. The sputtering yield of oxygen ions in the plasma is calculated using the TRIM code. The effects of plasma pressure and the distance from the ECR zone on the AO density were also investigated. The density of AO measured by oxidation of silver is in good agreement with results obtained from the catalytic nickel probe.

Frequency-tuning radiofrequency plasma source operated in inductively-coupled mode under a low magnetic field

NASA Astrophysics Data System (ADS)

Takahashi, Kazunori; Nakano, Yudai; Ando, Akira

2017-07-01

A radiofrequency (rf) inductively-coupled plasma source is operated with a frequency-tuning impedance matching system, where the rf frequency is variable in the range of 20-50 MHz and the maximum power is 100 W. The source consists of a 45 mm-diameter pyrex glass tube wound by an rf antenna and a solenoid providing a magnetic field strength in the range of 0-200 Gauss. A reflected rf power for no plasma case is minimized at the frequency of ˜25 MHz, whereas the frequency giving the minimum reflection with the high density plasma is about 28 MHz, where the density jump is observed when minimizing the reflection. A high density argon plasma above 1× {{10}12} cm-3 is successfully obtained in the source for the rf power of 50-100 W, where it is observed that an external magnetic field of a few tens of Gauss yields the highest plasma density in the present configuration. The frequency-tuning plasma source is applied to a compact and high-speed silicon etcher in an Ar-SF6 plasma; then the etching rate of 8~μ m min-1 is obtained for no bias voltage to the silicon wafer, i.e. for the case that a physical ion etching process is eliminated.

Interaction between the lower hybrid wave and density fluctuations in the scrape-off layer

NASA Astrophysics Data System (ADS)

Peysson, Y.; Madi, M.; Decker, J.; Kabalan, K.

2015-12-01

In the present paper, the perturbation of the launched power spectrum of the Lower Hybrid wave at the separatrix by electron density fluctuations in the scrape-off layer is investigated. Considering a slab geometry with magnetic field lines parallel to the toroidal direction, the full wave equation is solved using Comsol Multiphysics® for a fully active multi-junction like LH antenna made of two modules. When electron density fluctuations are incorporated in the dielectric tensor over a thin perturbed layer in front of the grill, it is shown that the power spectrum may be strongly modified from the antenna mouth to the plasma separatrix as the wave propagates. The diffraction effect leads to the appearance of multiple satellite lobes with randomly varying positions, a feature consistent with the recently developed model that has been applied successfully to high density discharges on the Tokamak Tore Supra corresponding to the large spectral gap regime [Decker J. et al. Phys. Plasma 21 (2014) 092504]. The perturbation is found to be maximum for the Fourier components of the fluctuating spectrum in the vicinity of the launched LH wavelength.

One-dimensional α-MoO3 nanorods for high energy density pseudocapacitor

NASA Astrophysics Data System (ADS)

Dutta, Shibsankar; Pal, Shreyasi; De, Sukanta

2018-04-01

Ultralong α-MoO3 nanorods having length of 500 nm to 1 µm and uniform width of around ˜50 nm have been synthesized by a simple one step hydrothermal route using a molybdenum organic salt precursor. An evaluation of the electrochemical properties of the nanorods was done by cyclic voltammetry (CV), and galvanometric charging- discharging (GCD) test. Because of the high active sites and rapid ion diffusion and electron transport of the electrodes using as prepared nanorods reveals energy density of 65 Wh/kg at a power density of 940 W/ kg and a maximum specific capacitance of 474 F/g. It also shows excellent cycling stability.

Analysis of longer period variation of the Kuroshio Current intrusion into the Luzon Strait using rectified wavelet power spectra

NASA Astrophysics Data System (ADS)

Yuan, Yaochu; Yang, Chenghao; Tseng, Yu-heng; Zhu, Xiao-Hua; Wang, Huiqun; Chen, Hong

2017-08-01

Longer period variation of the Kuroshio into the Luzon Strait (LS) was identified using acoustic Doppler current profiler (ADCP) observations as well as pressure and temperature time series data recorded by two TDs (manufactured by the RBR Ltd.) at mooring station N2 (20°40.441‧N, 120°38.324‧E). The ADCP was deployed at depths of 50-300 m between July 7, 2009 and April 10, 2011, and the TDs at around 340 and 365 m between July 9, 2009 and July 9, 2011. Observations provide strong evidence of longer period variation of the Kuroshio into the LS using the Vector rotary spectra (VRS) and Rectified wavelet power spectra analysis (RWPSA). RWPSA of the observations allowed the identification of two types of dominant periods. The first type, with the strongest power spectral density (PSD), had a dominant period of 112 d and was found throughout the upper 300 m. For example, the maximum PSD for western and northern velocity components time series were 3800 and 3550 at 50 m, respectively. The maximum power spectral density decrease with deeper depths, i.e., the depth dependence of maximum PSD. The 112 d period was also identified in the pressure and temperature time series data, at 340 m and 365 m. Combined RWPSA with VRS and mechanism analysis, it is clear that the occurrence of the most dominant period of 112 d in the upper 300 m is related to the clockwise meandering of the Kuroshio into the LS, which is caused by westward propagating stronger anticyclonic eddies from the interior ocean due to the interaction of Rossby eddies with the Kuroshio. The second type of dominant period, for example a 40 d period, is related to the anticlockwise meandering of the Kuroshio. The final dominant period of 14 d coincides with the fortnightly spring-neap tidal period.

Energetic Combustion Devices for Aerospace Propulsion and Power

NASA Technical Reports Server (NTRS)

Litchford, Ron J.

2000-01-01

Chemical reactions have long been the mainstay thermal energy source for aerospace propulsion and power. Although it is widely recognized that the intrinsic energy density limitations of chemical bonds place severe constraints on maximum realizable performance, it will likely be several years before systems based on high energy density nuclear fuels can be placed into routine service. In the mean time, efforts to develop high energy density chemicals and advanced combustion devices which can utilize such energetic fuels may yield worthwhile returns in overall system performance and cost. Current efforts in this vein are being carried out at NASA MSFC under the direction of the author in the areas of pulse detonation engine technology development and light metals combustion devices. Pulse detonation engines are touted as a low cost alternative to gas turbine engines and to conventional rocket engines, but actual performance and cost benefits have yet to be convincingly demonstrated. Light metal fueled engines also offer potential benefits in certain niche applications such as aluminum/CO2 fueled engines for endo-atmospheric Martian propulsion. Light metal fueled MHD generators also present promising opportunities with respect to electric power generation for electromagnetic launch assist. This presentation will discuss the applications potential of these concepts with respect to aero ace propulsion and power and will review the current status of the development efforts.

Nanoparticle-Mediated Physical Exfoliation of Aqueous-Phase Graphene for Fabrication of Three-Dimensionally Structured Hybrid Electrodes.

PubMed

Lee, Younghee; Choi, Hojin; Kim, Min-Sik; Noh, Seonmyeong; Ahn, Ki-Jin; Im, Kyungun; Kwon, Oh Seok; Yoon, Hyeonseok

2016-01-27

Monodispersed polypyrrole (PPy) nanospheres were physically incorporated as guest species into stacked graphene layers without significant property degradation, thereby facilitating the formation of unique three-dimensional hybrid nanoarchitecture. The electrochemical properties of the graphene/particulate PPy (GPPy) nanohybrids were dependent on the sizes and contents of the PPy nanospheres. The nanohybrids exhibited optimum electrochemical performance in terms of redox activity, charge-transfer resistance, and specific capacitance at an 8:1 PPy/graphite (graphene precursor) weight ratio. The packing density of the alternately stacked nanohybrid structure varied with the nanosphere content, indicating the potential for high volumetric capacitance. The nanohybrids also exhibited good long-term cycling stability because of a structural synergy effect. Finally, fabricated nanohybrid-based flexible all-solid state capacitor cells exhibited good electrochemical performance in an acidic electrolyte with a maximum energy density of 8.4 Wh kg(-1) or 1.9 Wh L(-1) at a maximum power density of 3.2 kW kg(-1) or 0.7 kW L(-1); these performances were based on the mass or packing density of the electrode materials.

Nanoparticle-Mediated Physical Exfoliation of Aqueous-Phase Graphene for Fabrication of Three-Dimensionally Structured Hybrid Electrodes

PubMed Central

Lee, Younghee; Choi, Hojin; Kim, Min-Sik; Noh, Seonmyeong; Ahn, Ki-Jin; Im, Kyungun; Kwon, Oh Seok; Yoon, Hyeonseok

2016-01-01

Monodispersed polypyrrole (PPy) nanospheres were physically incorporated as guest species into stacked graphene layers without significant property degradation, thereby facilitating the formation of unique three-dimensional hybrid nanoarchitecture. The electrochemical properties of the graphene/particulate PPy (GPPy) nanohybrids were dependent on the sizes and contents of the PPy nanospheres. The nanohybrids exhibited optimum electrochemical performance in terms of redox activity, charge-transfer resistance, and specific capacitance at an 8:1 PPy/graphite (graphene precursor) weight ratio. The packing density of the alternately stacked nanohybrid structure varied with the nanosphere content, indicating the potential for high volumetric capacitance. The nanohybrids also exhibited good long-term cycling stability because of a structural synergy effect. Finally, fabricated nanohybrid-based flexible all–solid state capacitor cells exhibited good electrochemical performance in an acidic electrolyte with a maximum energy density of 8.4 Wh kg−1 or 1.9 Wh L−1 at a maximum power density of 3.2 kW kg−1 or 0.7 kW L−1; these performances were based on the mass or packing density of the electrode materials. PMID:26813878

Starch-fueled microbial fuel cells by two-step and parallel fermentation using Shewanella oneidensis MR-1 and Streptococcus bovis 148.

PubMed

Uno, Megumi; Phansroy, Nichanan; Aso, Yuji; Ohara, Hitomi

2017-08-01

Shewanella oneidensis MR-1 generates electricity from lactic acid, but cannot utilize starch. On the other hand, Streptococcus bovis 148 metabolizes starch and produces lactic acid. Therefore, two methods were trialed for starch-fueled microbial fuel cell (MFC) in this study. In electric generation by two-step fermentation (EGT) method, starch was first converted to lactic acid by S. bovis 148. The S. bovis 148 were then removed by centrifugation, and the fermented broth was preserved for electricity generation by S. oneidensis MR-1. Another method was electric generation by parallel fermentation (EGP) method. In this method, the cultivation and subsequent fermentation processes of S. bovis 148 and S. oneidensis MR-1 were performed simultaneously. After 1, 2, and 3 terms (5-day intervals) of S. oneidensis MR-1 in the EGT fermented broth of S. bovis 148, the maximum currents at each term were 1.8, 2.4, and 2.8 mA, and the maximum current densities at each term were 41.0, 43.6, and 49.9 mW/m 2 , respectively. In the EGP method, starch was also converted into lactic acid with electricity generation. The maximum current density was 140-200 mA/m 2 , and the maximum power density of this method was 12.1 mW/m 2 . Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Public safety assessment of electromagnetic radiation exposure from mobile base stations.

PubMed

Alhekail, Z O; Hadi, M A; Alkanhal, M A

2012-09-01

Exposure of the general public to electromagnetic radiation originating from randomly selected GSM/WCDMA base stations in Riyadh, Kingdom of Saudi Arabia has been assessed in the context of the International Commission on Non-Ionising Radiation Protection (ICNIRP) guidelines. The purpose of the measurement was to record the maximum power density of signals to estimate possible worst case exposure at each measurement location. These power density measurements were carried out at 60 mobile base stations located in different regions of the city. For each of these sites, three sectors were operational, yielding a total of 180 sectors. Two positions were identified per site with the greatest power density values. Exposures from these base stations were generally found to be in the range of 0.313 to 0.00000149% of the ICNIRP general public reference level, and the greatest exposure near any of the base stations was 21.96 mW m(-2) for a wideband measurement in the 75-3000 MHz frequency range. Analysis of the measured data reveals several trends for different mobile bands with respect to maximum exposure in those locations. Additionally, a simplified calculation method for the electromagnetic fields was used to compare calculated and the measured data. It was determined, on the basis of both results of the measurements and calculations carried out for these selected base stations, that members of the public would not be exposed to in excess of a small fraction of the ICNIRP guidelines at any of those sites. These are first such measurements to be made in the Middle East and provide assurance that exposures in this region of the world do not seem to be any greater than elsewhere.

Simplified Solar Modulation Model of Inner Trapped Belt Proton Flux As a Function of Atmospheric Density

NASA Technical Reports Server (NTRS)

Wilson, Thomas L.; Lodhi, M. A. K.; Diaz, Abel B.

2005-01-01

No simple algorithm seems to exist for calculating proton fluxes and lifetimes in the Earth's inner, trapped radiation belt throughout the solar cycle. Most models of the inner trapped belt in use depend upon AP8 which only describes the radiation environment at solar maximum and solar minimum in Cycle 20. One exception is NOAAPRO which incorporates flight data from the TIROS/NOAA polar orbiting spacecraft. The present study discloses yet another, simple formulation for approximating proton fluxes at any time in a given solar cycle, in particular between solar maximum and solar minimum. It is derived from AP8 using a regression algorithm technique from nuclear physics. From flux and its time integral fluence, one can then approximate dose rate and its time integral dose. It has already been published in this journal that the absorbed dose rate, D, in the trapped belts exhibits a power law relationship, D = A(rho)(sup -n), where A is a constant, rho is the atmospheric density, and the index n is weakly dependent upon shielding. However, that method does not work for flux and fluence. Instead, we extend this idea by showing that the power law approximation for flux J is actually bivariant in energy E as well as density rho. The resulting relation is J(E,rho)approx.(sum of)A(E(sup n))rho(sup -n), with A itself a power law in E. This provides another method for calculating approximate proton flux and lifetime at any time in the solar cycle. These in turn can be used to predict the associated dose and dose rate.

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions.

PubMed

Martins, Vitor L; Rennie, Anthony J R; Sanchez-Ramirez, Nedher; Torresi, Roberto M; Hall, Peter J

2018-02-01

Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN) 4 ] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm -1 ). Herein, we report the use of ILs containing the [B(CN) 4 ] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two-electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g -1 @ 15 A g -1 ). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs.

Aligned carbon nanotube/zinc oxide nanowire hybrids as high performance electrodes for supercapacitor applications

NASA Astrophysics Data System (ADS)

Al-Asadi, Ahmed S.; Henley, Luke Alexander; Wasala, Milinda; Muchharla, Baleeswaraiah; Perea-Lopez, Nestor; Carozo, Victor; Lin, Zhong; Terrones, Mauricio; Mondal, Kanchan; Kordas, Krisztian; Talapatra, Saikat

2017-03-01

Carbon nanotube/metal oxide based hybrids are envisioned as high performance electrochemical energy storage electrodes since these systems can provide improved performances utilizing an electric double layer coupled with fast faradaic pseudocapacitive charge storage mechanisms. In this work, we show that high performance supercapacitor electrodes with a specific capacitance of ˜192 F/g along with a maximum energy density of ˜3.8 W h/kg and a power density of ˜ 28 kW/kg can be achieved by synthesizing zinc oxide nanowires (ZnO NWs) directly on top of aligned multi-walled carbon nanotubes (MWCNTs). In comparison to pristine MWCNTs, these constitute a 12-fold of increase in specific capacitance as well as corresponding power and energy density values. These electrodes also possess high cycling stability and were able to retain ˜99% of their specific capacitance value over 2000 charging discharging cycles. These findings indicate potential use of a MWCNT/ZnO NW hybrid material for future electrochemical energy storage applications.

One-step electroplating porous graphene oxide electrodes of supercapacitors for ultrahigh capacitance and energy density.

PubMed

Wang, Yongjie; Zhu, Jiaqi

2015-02-06

An electroplating method was used for the first time to synthesize 3D porous graphene oxide (PGO) architectures, exhibiting ultrahigh capacitance and energy density as electrodes of supercapacitors. Scanning electron microscopy illustrated the porous structures which promoted the stability and alleviated the stacking of the graphene oxide layers. As investigated in a three-electrode supercapacitor cell, PGO electrodes exhibited the maximum capacitance and energy of 973 F · g(-1) and 98.4 Wh · Kg(-1), which are better than current reports and comparable to batteries. At 4 A · g(-1) for high-power applications, PGO electrodes reached a capacitance, energy, and power density of 493 F · g(-1), 49.9 Wh · Kg(-1), and 1700 W · Kg(-1), and they retained ∼97.83% of capacitance after 10 000 charge/discharge processes. Furthermore, when the PGO was bent exaggeratedly, it still displayed identical properties, which is of important significance for supporting wearable devices.

Thermal treatment effects on charge storage performance of graphene-based materials for supercapacitors.

PubMed

Zhang, Hongxin; Bhat, Vinay V; Gallego, Nidia C; Contescu, Cristian I

2012-06-27

Graphene materials were synthesized by reduction of exfoliated graphite oxide and then thermally treated in nitrogen to improve the surface area and their electrochemical performance as electrical double-layer capacitor electrodes. The structural and surface properties of the prepared reduced graphite oxide (RGO) were investigated using atomic force microscopy, scanning electron microscopy, Raman spectra, X-ray diffraction pattern analysis, and nitrogen adsorption/desorption studies. RGO forms a continuous network of crumpled sheets, which consist of large amounts of few-layer and single-layer graphenes. Electrochemical studies were conducted by cyclic voltammetry, impedance spectroscopy, and galvanostatic charge-discharge measurements. The modified RGO materials showed enhanced electrochemical performance, with maximum specific capacitance of 96 F/g, energy density of 12.8 Wh/kg, and power density of 160 kW/kg. These results demonstrate that thermal treatment of RGO at selected conditions is a convenient and efficient method for improving its specific capacitance, energy, and power density.

Microwave decoration of Pt nanoparticles on entangled 3D carbon nanotube architectures as PEM fuel cell cathode.

PubMed

Sherrell, Peter C; Zhang, Weimin; Zhao, Jie; Wallace, Gordon G; Chen, Jun; Minett, Andrew I

2012-07-01

Proton-exchange membrane fuel cells (PEMFCs) are expected to provide a complementary power supply to fossil fuels in the near future. The current reliance of fuel cells on platinum catalysts is undesirable. However, even the best-performing non-noble metal catalysts are not as efficient. To drive commercial viability of fuel cells forward in the short term, increased utilization of Pt catalysts is paramount. We have demonstrated improved power and energy densities in a single PEMFC using a designed cathode with a Pt loading of 0.1 mg cm(-2) on a mesoporous conductive entangled carbon nanotube (CNT)-based architecture. This electrode allows for rapid transfer of both fuel and waste to and from the electrode, respectively. Pt particles are bound tightly, directly to CNT sidewalls by a microwave-reduction technique, which provided increased charge transport at this interface. The Pt entangled CNT cathode, in combination with an E-TEK 0.2 mg cm(-2) anode, has a maximum power and energy density of 940 mW cm(-2) and 2700 mA cm(-2), respectively, and a power and energy density of 4.01 W mg(Pt)(-1) and 6.35 A mg(Pt)(-1) at 0.65 V. These power densities correspond to a specific mass activity of 0.81 g Pt per kW for the combined mass of both anode and cathode electrodes, approaching the current US Department of Energy efficiency target. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Porous CrN thin films by selectively etching CrCuN for symmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wei, Binbin; Mei, Gui; Liang, Hanfeng; Qi, Zhengbing; Zhang, Dongfang; Shen, Hao; Wang, Zhoucheng

2018-05-01

Transition metal nitrides are regarded as a new class of excellent electrode materials for high-performance supercapacitors due to their superior chemical stability and excellent electrical conductivity. We synthesize successfully the porous CrN thin films for binder-free supercapacitor electrodes by reactive magnetron co-sputtering and selective chemical etching. The porous CrN thin film electrodes exhibit high-capacitance performance (31.3 mF cm-2 at 1.0 mA cm-2) and reasonable cycling stability (94% retention after 20000 cycles). Moreover, the specific capacitance is more than two-fold higher than that of the CrN thin film electrodes in previous work. In addition, a symmetric supercapacitor device with a maximum energy density of 14.4 mWh cm-3 and a maximum power density of 6.6 W cm-3 is achieved. These findings demonstrate that the porous CrN thin films will have potential applications in supercapacitors.

Field Trial on a Rack-mounted DC Power Supply System with 80-Ah Lithium-ion Batteries

NASA Astrophysics Data System (ADS)

Matsushima, Toshio

Using an industrial lithium-ion battery that has higher energy density than conventional valve-regulated lead-acid batteries, a rack-mounted DC-power-supply system was assembled and tested at a base transceiver station (BTS) offering actual services. A nominal output voltage and maximum output current of the system is 53.5V and 20A, respectively. An 80-Ah lithium-ion battery composed of 13 cells connected in series was applied in the system and maintained in a floating charge method. The DC-power-supply system was installed in a 19-inch power rack in the telecommunications equipment box at BTS. The characteristics of the 80Ah lithium-ion battery, specifications of the DC-power-supply system and field-test results were shown in this paper.

A microfabricated low cost enzyme-free glucose fuel cell for powering low-power implantable devices

NASA Astrophysics Data System (ADS)

Oncescu, Vlad; Erickson, David

In the past decade the scientific community has showed considerable interest in the development of implantable medical devices such as muscle stimulators, neuroprosthetic devices, and biosensors. Those devices have low power requirements and can potentially be operated through fuel cells using reactants present in the body such as glucose and oxygen instead of non-rechargeable lithium batteries. In this paper, we present a thin, enzyme-free fuel cell with high current density and good stability at a current density of 10 μA cm -2. A non-enzymatic approach is preferred because of higher long term stability. The fuel cell uses a stacked electrode design in order to achieve glucose and oxygen separation. An important characteristic of the fuel cell is that it has no membrane separating the electrodes, which results in low ohmic losses and small fuel cell volume. In addition, it uses a porous carbon paper support for the anodic catalyst layer which reduces the amount of platinum or other noble metal catalysts required for fabricating high surface area electrodes with good reactivity. The peak power output of the fuel cell is approximately 2 μW cm -2 and has a sustainable power density of 1.5 μW cm -2 at 10 μA cm -2. An analysis on the effects of electrode thickness and inter electrode gap on the maximum power output of the fuel cell is also performed.

Simulation and Experimental Study of Bipolar Plate on the Performance PEM Fuel cell

NASA Astrophysics Data System (ADS)

Chinnasa, Pornchai; Khamsuk, Pattama; Seechalee, Sarunya; Swatsitang, Ekaphan

2017-09-01

This research is a simulated and experimental study on effects of bipolar electrodes of a PEM fuel cell on its power conversion efficiency. The PEM fuel cell structure consists of bipolar electrodes, proton exchange membrane with catalysts, flow channels of gases. This research used fuel cell of 49 cm2 in active area as a research sample and the Comsol 4.4 was employed to simulate flow channels which are serpentine pattern for anode and parallel pattern for cathode. The parameters used were calculated effects of such parameters using Comsol 4.4. After the calculation has been completed, the prototype of the PEM fuel cell were fabricated using graphite plate as electrodes which had the channel height of 0.20 cm, proton exchange membrane using carbon-platinum catalyst. Finally, further it was found that the effect of temperature on the power conversion efficiency is not severely. And for anode, the concentration of hydrogen gas was reduced 64 wt% due to the reaction whereas in parallel channel of cathode the oxygen concentration was reduced by only 6 wt% from 23 wt% at the entrance to 17 wt% at the end. The maximum power output of the prototype operated under such condition was 0.28 W/cm2 calculated from maximum power output voltage (Vmp) of 0.70 V and maximum power output current density of 0.42 A/cm2 which was in good agreement with that simulated using Comsol 4.4 which revealed the power output of 0.29 W/cm2.

Improving energy conversion efficiency for triboelectric nanogenerator with capacitor structure by maximizing surface charge density.

PubMed

He, Xianming; Guo, Hengyu; Yue, Xule; Gao, Jun; Xi, Yi; Hu, Chenguo

2015-02-07

Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m(-2), which is 2.6 times as much as that of the pure polydimethylsiloxane film.

Compendium of Phase-I Mini-SHINE Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Youker, Amanda J.; Chemerisov, Sergey D.; Tkac, Peter

Argonne National Laboratory is assisting SHINE Medical Technologies in their efforts to develop the technology to become a domestic Mo-99 producer using low-enriched uranium (LEU). Mini-SHINE experiments are being performed with the high-current electron linear accelerator (linac) at Argonne. The target solution is a 90-150 g-U/L LEU uranyl sulfate at pH 1. In Phase 1, the convertor was tantalum with a maximum beam power on the convertor of 10 kW, and the target solution was limited to 5 L. This configuration generated a peak fission power density of 0.05 W/mL. Nine experiments were performed between February and October 2015. Resultsmore » are reported and discussed for each experiment regarding the off-gas analysis system, the sampling and Mo-recovery operation, and the Mo-product concentration and purification system. In Phase 2, the convertor will be depleted uranium; beam power will increase to 20 kW; and the solution volume will be 18 L. This configuration will generate a fission power density of up to 1 W/mL.« less

A state-of-the-art compact SiC photovoltaic inverter with maximum power point tracking function

NASA Astrophysics Data System (ADS)

Ando, Yuji; Oku, Takeo; Yasuda, Masashi; Ushijima, Kazufumi; Matsuo, Hiroshi; Murozono, Mikio

2018-01-01

We have developed a 150-W SiC-based photovoltaic (PV)-inverter with the maximum power point tracking (MPPT) function. The newly developed inverter achieved a state-of-the-art combination of the weight (0.79 kg) and the volume (790 mm3) as a 150-250 W class PV-inverter. As compared to the original version that we have previously reported, the weight and volume were decreased by 37% and 38%, respectively. This compactness originated from the optimized circuit structure and the increased density of a wiring circuit. Conversion efficiencies of the MPPT charge controller and the direct current (DC)-alternating current (AC) converter reached 96.4% and 87.6%, respectively. These efficiency values are comparable to those for the original version. We have developed a PV power generation system consisting of this inverter, a spherical Si solar cell module, and a 15-V Li-ion laminated battery. The total weight of the system was below 6 kg. The developed system exhibited stable output power characteristics, even when the weather conditions were fluctuated. These compactness, high efficiencies, and excellent stability clearly indicated the feasibility of SiC power devices even for sub-kW class PV power generation systems.

Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

NASA Astrophysics Data System (ADS)

Nayak, Gaurav; Santos Sousa, João; Bruggeman, Peter J.

2017-03-01

The production of singlet delta oxygen (O2(a 1Δg)) is of growing interest for many applications. We report on the measurement of O2(a 1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a 1Δg) production. Different O2(a 1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a 1Δg) densities are discussed. The flow rate also allows for control of the O2(a 1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

High power density cell using nanostructured Sr-doped SmCoO3 and Sm-doped CeO2 composite powder synthesized by spray pyrolysis

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Yamaguchi, Toshiaki; Suzuki, Toshio; Sumi, Hirofumi; Hamamoto, Koichi; Fujishiro, Yoshinobu

2016-01-01

High power density solid oxide electrochemical cells were developed using nanostructure-controlled composite powder consisting of Sr-doped SmCoO3 (SSC) and Sm-doped CeO2 (SDC) for electrode material. The SSC-SDC nano-composite powder, which was synthesized by spray pyrolysis, had a narrow particle size distribution (D10, D50, and D90 of 0.59, 0.71, and 0.94 μm, respectively), and individual particles were spherical, composing of nano-size SSC and SDC fragments (approximately 10-15 nm). The application of the powder to a cathode for an anode-supported solid oxide fuel cell (SOFC) realized extremely fine cathode microstructure and excellent cell performance. The anode-supported SOFC with the SSC-SDC cathode achieved maximum power density of 3.65, 2.44, 1.43, and 0.76 W cm-2 at 800, 750, 700, and 650 °C, respectively, using humidified H2 as fuel and air as oxidant. This result could be explained by the extended electrochemically active region in the cathode induced by controlling the structure of the starting powder at the nano-order level.

Immobilization of a Metal-Nitrogen-Carbon Catalyst on Activated Carbon with Enhanced Cathode Performance in Microbial Fuel Cells.

PubMed

Yang, Wulin; Logan, Bruce E

2016-08-23

Applications of microbial fuel cells (MFCs) are limited in part by low power densities mainly due to cathode performance. Successful immobilization of an Fe-N-C co-catalyst on activated carbon (Fe-N-C/AC) improved the oxygen reduction reaction to nearly a four-electron transfer, compared to a twoelectron transfer achieved using AC. With acetate as the fuel, the maximum power density was 4.7±0.2 W m(-2) , which is higher than any previous report for an air-cathode MFC. With domestic wastewater as a fuel, MFCs with the Fe-N-C/AC cathode produced up to 0.8±0.03 W m(-2) , which was twice that obtained with a Pt-catalyzed cathode. The use of this Fe-N-C/AC catalyst can therefore substantially increase power production, and enable broader applications of MFCs for renewable electricity generation using waste materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

QPO detection in superluminal black hole GRS 1915+105

NASA Astrophysics Data System (ADS)

Bhulla, Yashpal; Jaaffrey, S. N. A.

2018-05-01

We report on the first superluminal Black Hole GRS 1915+105 observed by the Rossi X-ray Timing Explorer - Proportion Counter Array (RXTE/PCA). We detect the Quasi Periodic Oscillations (QPOs) in the Power Density Spectrum (PDS) of source which have luminosity very near to Eddington limit and long variability in X-ray light curve. In power density spectrum, we deal with the study of highly variability amplitude, time evolution of the characteristic timescale, Quality Factor and Full Width at Half Maximum (FWHM). We find significant QPOs in 15 different observation IDs with frequency around 67 Hz although quality factor nearly 20 but in two IDs frequency is found just double. Typical fractional rms for GRS 1915+105 is dominating the hard band increasing steeply with energy more than 13% at 20-40 keV band.

Rubber muscle actuation with pressurized CO2 from enzyme-catalyzed urea hydrolysis

NASA Astrophysics Data System (ADS)

Sutter, Thomas M.; Dickerson, Matthew B.; Creasy, Terry S.; Justice, Ryan S.

2013-09-01

A biologically inspired pneumatic pressure source was designed and sized to supply high pressure CO2(g) to power a rubber muscle actuator. The enzyme urease served to catalyze the hydrolysis of urea, producing CO2(g) that flowed into the actuator. The actuator’s power envelope was quantified by testing actuator response on a custom-built linear-motion rig. Reaction kinetics and available work density were determined by replacing the actuator with a double-action piston and measuring volumetric gas generation against a fixed pressure on the opposing piston. Under the conditions investigated, urease catalyzed the generation of up to 0.81 MPa (117 psi) of CO2(g) in the reactor headspace within 18 min, and the evolved gas produced a maximum work density of 0.65 J ml-1.

Performance evaluation of tubular fuel cells fuelled by pulverized graphite

NASA Astrophysics Data System (ADS)

Kim, Jong-Pil; Lim, Ho; Jeon, Chung-Hwan; Chang, Young-June; Koh, Kwang-Nak; Choi, Soon-Mok; Song, Ju-Hun

A fuel cell fuelled by carbonaceous graphite is proposed. The tubular fuel cell, with the carbon in a fixed-bed form on the anode side, is employed to convert directly the chemical energy of carbon into electricity. Surface platinum electrodes are coated on the cell electrolyte, which is a yttria-stabilized zirconia (YSZ) tube of 1.5 mm thickness. The effect of using different sizes of graphite powder (in the range 0-180 μm) as fuel is analyzed. Power density and actual open-circuit voltage (OCV) values are measured as the temperature is varied from 0 to 950 °C. The cell provides a maximum power density of 16.8 mW cm -2 and an OCV of 1.115 V at the highest temperature condition (950 °C) tested in this study.

Maximizing the potential of cropping systems for nematode management.

PubMed

Noe, J P; Sasser, J N; Imbriani, J L

1991-07-01

Quantitative techniques were used to analyze and determine optimal potential profitability of 3-year rotations of cotton, Gossypium hirsutum cv. Coker 315, and soybean, Glycine max cv. Centennial, with increasing population densities of Hoplolaimus columbus. Data collected from naturally infested on-farm research plots were combined with economic information to construct a microcomputer spreadsheet analysis of the cropping system. Nonlinear mathematical functions were fitted to field data to represent damage functions and population dynamic curves. Maximum yield losses due to H. columbus were estimated to be 20% on cotton and 42% on soybean. Maximum at-harvest population densities were calculated to be 182/100 cm(3) soil for cotton and 149/100 cm(3) soil for soybean. Projected net incomes ranged from a $17.74/ha net loss for the soybean-cotton-soybean sequence to a net profit of $46.80/ha for the cotton-soybean-cotton sequence. The relative profitability of various rotations changed as nematode densities increased, indicating economic thresholds for recommending alternative crop sequences. The utility and power of quantitative optimization was demonstrated for comparisons of rotations under different economic assumptions and with other management alternatives.

Toward high-energy-density, high-efficiency, and moderate-temperature chip-scale thermophotovoltaics

PubMed Central

Chan, Walker R.; Bermel, Peter; Pilawa-Podgurski, Robert C. N.; Marton, Christopher H.; Jensen, Klavs F.; Senkevich, Jay J.; Joannopoulos, John D.; Soljačić, Marin; Celanovic, Ivan

2013-01-01

The challenging problem of ultra-high-energy-density, high-efficiency, and small-scale portable power generation is addressed here using a distinctive thermophotovoltaic energy conversion mechanism and chip-based system design, which we name the microthermophotovoltaic (μTPV) generator. The approach is predicted to be capable of up to 32% efficient heat-to-electricity conversion within a millimeter-scale form factor. Although considerable technological barriers need to be overcome to reach full performance, we have performed a robust experimental demonstration that validates the theoretical framework and the key system components. Even with a much-simplified μTPV system design with theoretical efficiency prediction of 2.7%, we experimentally demonstrate 2.5% efficiency. The μTPV experimental system that was built and tested comprises a silicon propane microcombustor, an integrated high-temperature photonic crystal selective thermal emitter, four 0.55-eV GaInAsSb thermophotovoltaic diodes, and an ultra-high-efficiency maximum power-point tracking power electronics converter. The system was demonstrated to operate up to 800 °C (silicon microcombustor temperature) with an input thermal power of 13.7 W, generating 344 mW of electric power over a 1-cm2 area. PMID:23440220

On the road to self-sputtering in high power impulse magnetron sputtering: particle balance and discharge characteristics

NASA Astrophysics Data System (ADS)

Huo, Chunqing; Lundin, Daniel; Raadu, Michael A.; Anders, André; Tomas Gudmundsson, Jon; Brenning, Nils

2014-04-01

The onset and development of self-sputtering (SS) in a high power impulse magnetron sputtering (HiPIMS) discharge have been studied using a plasma chemical model and a set of experimental data, taken with an aluminum target and argon gas. The model is tailored to duplicate the discharge in which the data are taken. The pulses are long enough to include both an initial transient and a following steady state. The model is used to unravel how the internal discharge physics evolves with pulse power and time, and how it is related to features in the discharge current-voltage-time characteristics such as current densities, maxima, kinks and slopes. The connection between the self-sputter process and the discharge characteristics is quantified and discussed in terms of three parameters: a critical target current density Jcrit based on the maximum refill rate of process (argon) gas above the target, an SS recycling factor ΠSS-recycle, and an approximation \\tilde{\\alpha} of the probabilities of ionization of species that come from the target (both sputtered metal and embedded argon atoms). For low power pulses, discharge voltages UD ⩽ 380 V with peak current densities below ≈ 0.2 A cm-2, the discharge is found to be dominated by process gas sputtering. In these pulses there is an initial current peak in time, associated with partial gas rarefaction, which is followed by a steady-state-like plateau in all parameters similar to direct current magnetron sputtering. In contrast, high power pulses, with UD ⩾ 500 V and peak current densities above JD ≈ 1.6 A cm-2, make a transition to a discharge mode where SS dominates. The transition is found not to be driven by process gas rarefaction which is only about 10% at this time. Maximum gas rarefaction is found later in time and always after the initial peak in the discharge current. With increasing voltage, and pulse power, the discharge can be described as following a route where the role of SS increases in four steps: process gas sputtering, gas-sustained SS, self-sustained SS and SS runaway. At the highest voltage, 1000 V, the discharge is very close to, but does not go into, the SS runaway mode. This absence of runaway is proposed to be connected to an unexpected finding: that twice ionized ions of the target species play almost no role in this discharge, not even at the highest powers. This reduces ionization by secondary-emitted energetic electrons almost to zero in the highest power range of the discharge.

Performance of an ion-cyclotron-wave plasma apparatus operated in the radiofrequency sustained mode

NASA Technical Reports Server (NTRS)

Swett, C. C.; Woollett, R. R.

1973-01-01

An experimental study has been made of an ion-cyclotron-wave apparatus operated in the RF-sustained mode, that is, a mode in which the Stix RF coil both propagates the waves and maintains the plasma. Problems associated with this method of operation are presented. Some factors that are important to the coupling of RF power are noted. In general, the wave propagation and wave damping data agree with theory. Some irregularities in wave fields are observed. Maximum ion temperature is 870 eV at a density of five times 10 to the 12th power cu cm and RF power of 90 kW. Coupling efficiency is 70 percent.

Critical fluctuations of the proton density in A+A collisions at 158A GeV

DOE PAGES

Anticic, T.; Baatar, B.; Bartke, J.; ...

2015-12-12

Here, we look for fluctuations expected for the QCD critical point using an intermittency analysis in the transverse momentum phase space of protons produced around midrapidity in the 12.5 % most central C+C, Si+Si and Pb+Pb collisions at the maximum SPS energy of 158A GeV. We find evidence of power-law fluctuations for the Si+Si data. The fitted power-law exponent Φ 2=0.96 +0.38 –0.25 (stat.) ± 0.16 (syst.) is consistent with the value expected for critical fluctuations. Power-law fluctuations had previously also been observed in low-mass π +π – pairs in the same Si+Si collisions.

Operating features of an ion-cyclotron-wave plasma apparatus running in the RF-sustained mode

NASA Technical Reports Server (NTRS)

Swett, C. C.

1972-01-01

An experimental study has been made of an ion-cyclotron-wave apparatus operated in the RF-sustained mode. This is a mode in which the Stix RF coil both propagates the waves and maintains the plasma. Problems associated with this method of operation are presented. Some factors that are important to the coupling of RF power are noted. In general, the wave-propagation and wave-damping data agree with theory. Some irregularities in wave fields are observed. Maximum ion temperature is 870 eV at a density of 5 times 10 to the 12th power per cubic centimeter and RF power of 90 kW. Coupling efficiency is 70 percent.

Potential efficiencies of open- and closed-cycle CO, supersonic, electric-discharge lasers

NASA Technical Reports Server (NTRS)

Monson, D. J.

1976-01-01

Computed open- and closed-cycle system efficiencies (laser power output divided by electrical power input) are presented for a CW carbon monoxide, supersonic, electric-discharge laser. Closed-system results include the compressor power required to overcome stagnation pressure losses due to supersonic heat addition and a supersonic diffuser. The paper shows the effect on the system efficiencies of varying several important parameters. These parameters include: gas mixture, gas temperature, gas total temperature, gas density, total discharge energy loading, discharge efficiency, saturated gain coefficient, optical cavity size and location with respect to the discharge, and supersonic diffuser efficiency. Maximum open-cycle efficiency of 80-90% is predicted; the best closed-cycle result is 60-70%.

Plasma density limits for hole boring by intense laser pulses.

PubMed

Iwata, Natsumi; Kojima, Sadaoki; Sentoku, Yasuhiko; Hata, Masayasu; Mima, Kunioki

2018-02-12

High-power lasers in the relativistic intensity regime with multi-picosecond pulse durations are available in many laboratories around the world. Laser pulses at these intensities reach giga-bar level radiation pressures, which can push the plasma critical surface where laser light is reflected. This process is referred to as the laser hole boring (HB), which is critical for plasma heating, hence essential for laser-based applications. Here we derive the limit density for HB, which is the maximum plasma density the laser can reach, as a function of laser intensity. The time scale for when the laser pulse reaches the limit density is also derived. These theories are confirmed by a series of particle-in-cell simulations. After reaching the limit density, the plasma starts to blowout back toward the laser, and is accompanied by copious superthermal electrons; therefore, the electron energy can be determined by varying the laser pulse length.

Cathodic reduction of hexavalent chromium [Cr(VI)] coupled with electricity generation in microbial fuel cells.

PubMed

Wang, Gang; Huang, Liping; Zhang, Yifeng

2008-11-01

A novel approach to Cr(VI)-contaminated wastewater treatment was investigated using microbial fuel cell technologies in fed-batch mode. By using synthetic Cr(VI)-containing wastewater as catholyte and anaerobic microorganisms as anodic biocatalyst, Cr(VI) at 100 mg/l was completely removed during 150 h (initial pH 2). The maximum power density of 150 mW/m(2) (0.04 mA/cm(2)) and the maximum open circuit voltage of 0.91 V were generated with Cr(VI) at 200 mg/l as electron acceptor. This work verifies the possibility of simultaneous electricity production and cathodic Cr(VI) reduction.

In situ synthesis of nanocomposite membranes: comprehensive improvement strategy for direct methanol fuel cells.

PubMed

Rao, Siyuan; Xiu, Ruijie; Si, Jiangju; Lu, Shanfu; Yang, Meng; Xiang, Yan

2014-03-01

In situ synthesis is a powerful approach to control nanoparticle formation and consequently confers extraordinary properties upon composite membranes relative to conventional doping methods. Herein, uniform nanoparticles of cesium hydrogen salts of phosphotungstic acid (CsPW) are controllably synthesized in situ in Nafion to form CsPW–Nafion nanocomposite membranes with both improved proton conductivity and methanol-crossover suppression. A 101.3% increase of maximum power density has been achieved relative to pristine Nafion in a direct methanol fuel cell (DMFC), indicating a potential pathway for large-scale fabrication of DMFC alternative membranes.

Feasibility of supersonic diode pumped alkali lasers: Model calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Barmashenko, B. D.; Rosenwaks, S.

The feasibility of supersonic operation of diode pumped alkali lasers (DPALs) is studied for Cs and K atoms applying model calculations, based on a semi-analytical model previously used for studying static and subsonic flow DPALs. The operation of supersonic lasers is compared with that measured and modeled in subsonic lasers. The maximum power of supersonic Cs and K lasers is found to be higher than that of subsonic lasers with the same resonator and alkali density at the laser inlet by 25% and 70%, respectively. These results indicate that for scaling-up the power of DPALs, supersonic expansion should be considered.

Likelihood reconstruction method of real-space density and velocity power spectra from a redshift galaxy survey

NASA Astrophysics Data System (ADS)

Tang, Jiayu; Kayo, Issha; Takada, Masahiro

2011-09-01

We develop a maximum likelihood based method of reconstructing the band powers of the density and velocity power spectra at each wavenumber bin from the measured clustering features of galaxies in redshift space, including marginalization over uncertainties inherent in the small-scale, non-linear redshift distortion, the Fingers-of-God (FoG) effect. The reconstruction can be done assuming that the density and velocity power spectra depend on the redshift-space power spectrum having different angular modulations of μ with μ2n (n= 0, 1, 2) and that the model FoG effect is given as a multiplicative function in the redshift-space spectrum. By using N-body simulations and the halo catalogues, we test our method by comparing the reconstructed power spectra with the spectra directly measured from the simulations. For the spectrum of μ0 or equivalently the density power spectrum Pδδ(k), our method recovers the amplitudes to an accuracy of a few per cent up to k≃ 0.3 h Mpc-1 for both dark matter and haloes. For the power spectrum of μ2, which is equivalent to the density-velocity power spectrum Pδθ(k) in the linear regime, our method can recover, within the statistical errors, the input power spectrum for dark matter up to k≃ 0.2 h Mpc-1 and at both redshifts z= 0 and 1, if the adequate FoG model being marginalized over is employed. However, for the halo spectrum that is least affected by the FoG effect, the reconstructed spectrum shows greater amplitudes than the spectrum Pδθ(k) inferred from the simulations over a range of wavenumbers 0.05 ≤k≤ 0.3 h Mpc-1. We argue that the disagreement may be ascribed to a non-linearity effect that arises from the cross-bispectra of density and velocity perturbations. Using the perturbation theory and assuming Einstein gravity as in simulations, we derive the non-linear correction term to the redshift-space spectrum, and find that the leading-order correction term is proportional to μ2 and increases the μ2-power spectrum amplitudes more significantly at larger k, at lower redshifts and for more massive haloes. We find that adding the non-linearity correction term to the simulation Pδθ(k) can fairly well reproduce the reconstructed Pδθ(k) for haloes up to k≃ 0.2 h Mpc-1.

Development of multi-ampered D{sup {minus}} source for fusion applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacquot, C.; Belchenko, Y.; Bucalossi, J.

1996-07-01

Large current and high current density deuterium negative ion sources are investigated on the MANTIS test bed with the objective of producing several amperes of D{sup {minus}} beams, at an accelerated current density in the range 10{endash}20 mA/cm{sup 2}, for possible application in future neutral beam injectors, e.g. ITER. As a first step, the DRAGON source, which was built by Culham Laboratory was tested on the MANTIS test bed in order to test this large source using only {open_quote}{open_quote}pure volume{close_quote}{close_quote} production of negative ions. The accelerated negative ion current is found to be a strong function of the source operatingmore » pressure and the arc power, and a significant isotopic effect is observed. The maximum accelerated currents are 1.3 A of H{sup {minus}} (3.3 mA/cm{sup 2}) and 0.5 A (1.3 mA/cm{sup 2}) at 110 kW of arc power. Cesium injection from a non conventional dispenser together with an improved extraction system, have significantly improved the D-current. A maximum of 14 mA/cm{sup 2} of D{sup {minus}1} are accelerated at 30 kV, which corresponds potentially, to more than 5 A for a full aperture extraction with an arc power of 140 kW (2250 A of arc current). {copyright} {ital 1996 American Institute of Physics.}« less

Laser-shock damage of iron-based materials

NASA Astrophysics Data System (ADS)

Chu, Jinn P.; Banas, Grzegorz; Lawrence, Frederick V.; Rigsbee, James M.; Elsayed-Ali, Hani E.

1993-05-01

The effects of laser shock processing on the microstructure and mechanical properties of the manganese (1 percent C and 14 percent Mn) steels have been low carbon (0.04 wt. percent C) and Hadfield studied. Laser shock processing was performed with a 1.054 micrometers wavelength Nd-phosphate laser operating in a pulse mode (600 ps pulse length and up to 200 J energy) with power densities above 10 to the 11th power W/cm2. Shock waves were generated by volume expansion of the plasma formed when the material was laser irradiated. Maximum shock wave intensities were obtained using an energy-absorbing black paint coating without a plasma-confining overlay. Maximum modification of compressive residual stresses were achieved when laser shock processing induced deformation occurred without melting. Mechanical properties were improved through modifying the microstructure by laser shock processing. High density arrays of dislocations (greater than 10 to the 11th power/cm2) were generated in low carbon steel by high strain-rate deformation of laser shock processing, resulting in surface hardness increases of 30 to 80 percent. In austenitic Hadfield steel, laser shock processing caused extensive formation of Epsilon-hcp martensite (35 vol. percent), producing increases of 50 to 130 percent in surface hardness. The laser shock processing strengthening effect in Hadfield steel was attributed to the combined effects of the partial dislocation/stacking fault arrays and the grain refinement due to presence of the Epsilon-hcp martensite.

Can a fermentation gas mainly produced by rumen Isotrichidae ciliates be a potential source of biohydrogen and a fuel for a chemical fuel cell?

PubMed

Piela, Piotr; Michałowski, Tadeusz; Miltko, Renata; Szewczyk, Krzysztof; Sikora, Radosław; Grzesiuk, Elzbieta; Sikora, Anna

2010-07-01

Bacteria, fungi and protozoa inhabiting the rumen, the largest chamber of the ruminants' stomach, release large quantities of hydrogen during the fermentation of carbohydrates. The hydrogen is used by coexisting methanogens to produce methane in energy-yielding processes. This work shows, for the first time, a fundamental possibility of using a hydrogen-rich fermentation gas produced by selected rumen ciliates to feed a low-temperature hydrogen fuel cell. A biohydrogen fuel cell (BHFC) was constructed consisting of (i) a bioreactor, in which a hydrogen-rich gas was produced from glucose by rumen ciliates, mainly of the Isotrichidae family, deprived of intra- and extracellular bacteria, methanogens, and fungi, and (ii) a chemical fuel cell of the polymer-electrolyte type (PEFC). The fuel cell was used as a tester of the technical applicability of the fermentation gas produced by the rumen ciliates for power generation. The average estimated hydrogen yield was ca. 1.15 mol H2 per mol of fermented glucose. The BHFC performance was equal to the performance of the PEFC running on pure hydrogen. No fuel cell poisoning effects were detected. A maximum power density of 1.66 kW/m2 (PEFC geometric area) was obtained at room temperature. The maximum volumetric power density was 128 W/m3 but the coulombic efficiency was only ca. 3.8%. The configuration of the bioreactor limited the continuous operation time of this BHFC to ca. 14 hours.

Efficiency Enhancement of a Cantilever-Based Vibration Energy Harvester

PubMed Central

Kubba, Ali E.; Jiang, Kyle

2014-01-01

Extracting energy from ambient vibration to power wireless sensor nodes has been an attractive area of research, particularly in the automotive monitoring field. This article reports the design, analysis and testing of a vibration energy harvesting device based on a miniature asymmetric air-spaced cantilever. The developed design offers high power density, and delivers electric power that is sufficient to support most wireless sensor nodes for structural health monitoring (SHM) applications. The optimized design underwent three evolutionary steps, starting from a simple cantilever design, going through an air-spaced cantilever, and ending up with an optimized air-spaced geometry with boosted power density level. Finite Element Analysis (FEA) was used as an initial tool to compare the three geometries' stiffness (K), output open-circuit voltage (Vave), and average normal strain in the piezoelectric transducer (εave) that directly affect its output voltage. Experimental tests were also carried out in order to examine the energy harvesting level in each of the three designs. The experimental results show how to boost the power output level in a thin air-spaced cantilever beam for energy within the same space envelope. The developed thin air-spaced cantilever (8.37 cm3), has a maximum power output of 2.05 mW (H = 29.29 μJ/cycle). PMID:24366177

Efficiency enhancement of a cantilever-based vibration energy harvester.

PubMed

Kubba, Ali E; Jiang, Kyle

2013-12-23

Extracting energy from ambient vibration to power wireless sensor nodes has been an attractive area of research, particularly in the automotive monitoring field. This article reports the design, analysis and testing of a vibration energy harvesting device based on a miniature asymmetric air-spaced cantilever. The developed design offers high power density, and delivers electric power that is sufficient to support most wireless sensor nodes for structural health monitoring (SHM) applications. The optimized design underwent three evolutionary steps, starting from a simple cantilever design, going through an air-spaced cantilever, and ending up with an optimized air-spaced geometry with boosted power density level. Finite Element Analysis (FEA) was used as an initial tool to compare the three geometries' stiffness (K), output open-circuit voltage (V(ave)), and average normal strain in the piezoelectric transducer (ε(ave)) that directly affect its output voltage. Experimental tests were also carried out in order to examine the energy harvesting level in each of the three designs. The experimental results show how to boost the power output level in a thin air-spaced cantilever beam for energy within the same space envelope. The developed thin air-spaced cantilever (8.37 cm3), has a maximum power output of 2.05 mW (H = 29.29 μJ/cycle).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobson, Paul T; Hagerman, George; Scott, George

This project estimates the naturally available and technically recoverable U.S. wave energy resources, using a 51-month Wavewatch III hindcast database developed especially for this study by National Oceanographic and Atmospheric Administration's (NOAA's) National Centers for Environmental Prediction. For total resource estimation, wave power density in terms of kilowatts per meter is aggregated across a unit diameter circle. This approach is fully consistent with accepted global practice and includes the resource made available by the lateral transfer of wave energy along wave crests, which enables wave diffraction to substantially reestablish wave power densities within a few kilometers of a linear array,more » even for fixed terminator devices. The total available wave energy resource along the U.S. continental shelf edge, based on accumulating unit circle wave power densities, is estimated to be 2,640 TWh/yr, broken down as follows: 590 TWh/yr for the West Coast, 240 TWh/yr for the East Coast, 80 TWh/yr for the Gulf of Mexico, 1570 TWh/yr for Alaska, 130 TWh/yr for Hawaii, and 30 TWh/yr for Puerto Rico. The total recoverable wave energy resource, as constrained by an array capacity packing density of 15 megawatts per kilometer of coastline, with a 100-fold operating range between threshold and maximum operating conditions in terms of input wave power density available to such arrays, yields a total recoverable resource along the U.S. continental shelf edge of 1,170 TWh/yr, broken down as follows: 250 TWh/yr for the West Coast, 160 TWh/yr for the East Coast, 60 TWh/yr for the Gulf of Mexico, 620 TWh/yr for Alaska, 80 TWh/yr for Hawaii, and 20 TWh/yr for Puerto Rico.« less

Preliminary Development of Electrodes for an Electric-Arc Wind Tunnel

NASA Technical Reports Server (NTRS)

Shepard, Charles E.; Boldman, Donald R.

1959-01-01

Two electrode configurations were tested in an electric-arc wind tunnel at the NASA Lewis Research Center. The results indicated approximately the same heat-loss rate per unit of arc power input for each of the configurations. Measured heat-loss rates were on the order of 40 percent of the arc power input. Nearly all this loss occurred at the anode. The power input and arc current limitations of the electrodes appear to be the critical design factors. Up to now, the maximum power to the stream has been 115 kilowatts with a cooled tungsten cathode and a cooled cylindrical anode incorporating a magnetic field. The maximum power input to this anode could not be established with the cooled tungsten cathode because cathode failures occurred at a gross power level of approximately 175 kilowatts. It was necessary to use a graphite cathode to seek the limitation of the anode. The results indicated that the anode limitation was primarily a function of arc current rather than power input. The anode was successfully operated at a power of 340 kilowatts at 1730 amperes; however, the anode failed with a power input of 324 kilowatts and a current of 2140 amperes. The magnetic flux density at the time of failure was 0.32 weber per square meter, or 3200 gauss. The graphite cathode was used only to establish the anode limitation; further investigation of graphite cathodes was discontinued because of the large amount of stream contamination associated with this type of electrode.

Enhancing Thermoelectric Performance Using Nonlinear Transport Effects

NASA Astrophysics Data System (ADS)

Jiang, Jian-Hua; Imry, Yoseph

2017-06-01

We study nonlinear transport effects on the maximum efficiency and power for both inelastic and elastic thermoelectric generators. The former device refers to phonon-assisted hopping in double quantum dots, while the latter device is represented by elastic tunneling through a single quantum dot. We find that nonlinear thermoelectric transport can lead to enhanced efficiency and power for both types of devices. A comprehensive survey of various quantum-dot energy, temperature, and parasitic heat conduction reveals that the nonlinear transport-induced improvements of the maximum efficiency and power are overall much more significant for inelastic devices than for elastic devices, even for temperature biases as small as Th=1.2 Tc (Th and Tc are the temperatures of the hot and cold reservoirs, respectively). The underlying mechanism is revealed as due to the fact that, unlike the Fermi distribution, the Bose distribution is not bounded when the temperature bias increases. A large flux density of absorbed phonons leads to a great enhancement of the electrical current, output power, and energy efficiency, dominating over the concurrent increase of the parasitic heat current. Our study reveals that nonlinear transport effects can be a useful tool for improving thermoelectric performance.

The effect of selective photosuppression of sensitized pathogenic microflora: Part II. Experimental validation on animals

NASA Astrophysics Data System (ADS)

Masychev, Viktor I.; Risovannaya, Olga N.

2005-03-01

Results of in vivo experiments have shown the maximum effectiveness of combined use of photo sensitizer 0,1% gel Radachlorine simultaneously with continuous and super pulse low energy irradiation of the diode laser with energy density 400 J/cm2, and power 1W. Given parameters have lead to complete elimination of Streptococcus pyogenes from inflammation foci in oral cavity of experimental animals.

Conditional Moment Closure of Mixing and Reaction in Turbulent Nonpremixed Combustion

NASA Technical Reports Server (NTRS)

Smith, Nigel S. A.

1996-01-01

Nonpremixed combustion is the process whereby fuel and oxidizer species, which are each nonflammable in isolation, concurrently mix to burn a flammable mixture, and chemically react in the flammable mixture. In cases of practical industrial interest, the bulk of nonpremixed combustion occurs in a turbulent mixing regime where enhanced mass transfer rates flow the maximum power density to be achieved in any given thermochemical device.

Synthesis and characterization of RuO(2)/poly(3,4-ethylenedioxythiophene) composite nanotubes for supercapacitors.

PubMed

Liu, Ran; Duay, Jonathon; Lane, Timothy; Bok Lee, Sang

2010-05-07

We report the synthesis of composite RuO(2)/poly(3,4-ethylenedioxythiophene) (PEDOT) nanotubes with high specific capacitance and fast charging/discharging capability as well as their potential application as electrode materials for a high-energy and high-power supercapacitor. RuO(2)/PEDOT nanotubes were synthesized in a porous alumina membrane by a step-wise electrochemical deposition method, and their structures were characterized using electron microscopy. Cyclic voltammetry was used to qualitatively characterize the capacitive properties of the composite RuO(2)/PEDOT nanotubes. Their specific capacitance, energy density and power density were evaluated by galvanostatic charge/discharge cycles at various current densities. The pseudocapacitance behavior of these composite nanotubes originates from ion diffusion during the simultaneous and parallel redox processes of RuO(2) and PEDOT. We show that the energy density (specific capacitance) of PEDOT nanotubes can be remarkably enhanced by electrodepositing RuO(2) into their porous walls and onto their rough internal surfaces. The flexible PEDOT prevents the RuO(2) from breaking and detaching from the current collector while the rigid RuO(2) keeps the PEDOT nanotubes from collapsing and aggregating. The composite RuO(2)/PEDOT nanotube can reach a high power density of 20 kW kg(-1) while maintaining 80% energy density (28 Wh kg(-1)) of its maximum value. This high power capability is attributed to the fast charge/discharge of nanotubular structures: hollow nanotubes allow counter-ions to readily penetrate into the composite material and access their internal surfaces, while a thin wall provides a short diffusion distance to facilitate ion transport. The high energy density originates from the RuO(2), which can store high electrical/electrochemical energy intrinsically. The high specific capacitance (1217 F g(-1)) which is contributed by the RuO(2) in the composite RuO(2)/PEDOT nanotube is realized because of the high specific surface area of the nanotubular structures. Such PEDOT/RuO(2) composite nanotube materials are an ideal candidate for the development of high-energy and high-power supercapacitors.

Design and operation of a bio-inspired micropump based on blood-sucking mechanism of mosquitoes

NASA Astrophysics Data System (ADS)

Leu, Tzong-Shyng; Kao, Ruei-Hung

2018-05-01

The study is to develop a novel bionic micropump, mimicking blood-suck mechanism of mosquitos with a similar efficiency of 36%. The micropump is produced by using micro-electro-mechanical system (MEMS) technology, PDMS (polydimethylsiloxane) to fabricate the microchannel, and an actuator membrane made by Fe-PDMS. It employs an Nd-FeB permanent magnet and PZT to actuate the Fe-PDMS membrane for generating flow rate. A lumped model theory and the Taguchi method are used for numerical simulation of pulsating flow in the micropump. Also focused is to change the size of mosquito mouth for identifying the best waveform for the transient flow processes. Based on computational results of channel size and the Taguchi method, an optimization actuation waveform is identified. The maximum pumping flow rate is 23.5 μL/min and the efficiency is 86%. The power density of micropump is about 8 times of that produced by mosquito’s suction. In addition to using theoretical design of the channel size, also combine with Taguchi method and asymmetric actuation to find the optimization actuation waveform, the experimental result shows the maximum pumping flowrate is 23.5 μL/min and efficiency is 86%, moreover, the power density of micropump is 8 times higher than mosquito’s.

A flexible electrostatic kinetic energy harvester based on electret films of electrospun nanofibers

NASA Astrophysics Data System (ADS)

Lu, Y.; Capo-Chichi, M.; Leprince-Wang, Y.; Basset, P.

2018-01-01

This paper reports a paper-based electrostatic kinetic energy harvester (e-KEH) implementing multilayered electret films based on electrospun nanofibrous material. It is the first time that a fully flexible electret-based e-KEH is reported. The proposed electret, PVDF-PTFD nanofibrous covered by Parylene C, has a faster stabilization of surface potential than a planar thin film of Parylene C, and a higher stability of charge storage. With a maximum force of 0.5 N and a 3-layer electret, the device capacitance increases from 25 to 100 pF during a pressing operation. Working with the optimal resistive load of 16 MΩ, the device pressed manually delivers a peak instantaneous power up to 45.6 μW and an average energy of 54 nJ/stroke, corresponding to a peak instantaneous power density of 7.3 μW cm-2 and an average energy density of 8.6 nJ cm-2/stroke. Within 450 manual strokes, a 10 nF capacitor is charged up to 8.5 V by the prototype through a full-wave diode bridge. On a 1 μF capacitor, the energy delivery of 9.9 nJ/stroke has been obtained with a 10 Hz pressing movement excited by a vibrator with a maximum force of 0.5 N.

Manufacturing Feasibility and Forming Properties of Cu-4Sn in Selective Laser Melting.

PubMed

Mao, Zhongfa; Zhang, David Z; Wei, Peitang; Zhang, Kaifei

2017-03-24

Copper alloys, combined with selective laser melting (SLM) technology, have attracted increasing attention in aerospace engineering, automobile, and medical fields. However, there are some difficulties in SLM forming owing to low laser absorption and excellent thermal conductivity. It is, therefore, necessary to explore a copper alloy in SLM. In this research, manufacturing feasibility and forming properties of Cu-4Sn in SLM were investigated through a systematic experimental approach. Single-track experiments were used to narrow down processing parameter windows. A Greco-Latin square design with orthogonal parameter arrays was employed to control forming qualities of specimens. Analysis of variance was applied to establish statistical relationships, which described the effects of different processing parameters (i.e., laser power, scanning speed, and hatch space) on relative density (RD) and Vickers hardness of specimens. It was found that Cu-4Sn specimens were successfully manufactured by SLM for the first time and both its RD and Vickers hardness were mainly determined by the laser power. The maximum value of RD exceeded 93% theoretical density and the maximum value of Vickers hardness reached 118 HV 0.3/5. The best tensile strength of 316-320 MPa is inferior to that of pressure-processed Cu-4Sn and can be improved further by reducing defects.

Graphene oxide electrocatalyst on MnO2 air cathode as an efficient electron pump for enhanced oxygen reduction in alkaline solution

NASA Astrophysics Data System (ADS)

Basirun, Wan Jeffrey; Sookhakian, Mehran; Baradaran, Saeid; Endut, Zulkarnain; Mahmoudian, Mohammad Reza; Ebadi, Mehdi; Yousefi, Ramin; Ghadimi, Hanieh; Ahmed, Sohail

2015-03-01

Graphene oxide (GO) was deposited on the surface of a MnO2 air cathode by thermal evaporation at 50°C from a GO colloidal suspension. Fourier transformed infrared spectroscopy and field emission scanning electron microscopy confirmed the presence of GO on the MnO2 air cathode (GO-MnO2). Voltammetry and chrono-amperometry showed increased currents for the oxygen reduction reaction (ORR) in 6 M KOH solution for GO-MnO2 compared to the MnO2 cathode. The GO-MnO2 was used as an air cathode in an alkaline tin-air cell and produced a maximum power density of 13 mW cm-2, in contrast to MnO2, which produced a maximum power density of 9.2 mW cm-2. The electrochemical impedance spectroscopy results suggest that the chemical step for the ORR is the rate determining step, as proposed earlier by different researchers. It is suggested that the presence of GO and electrochemically reduced graphene oxide (ERGO) on the MnO2 surface are responsible for the increased rate of this step, whereby GO and ERGO accelerate the process of electron donation to the MnO2 and to adsorbed oxygen atoms.

A Simple Prelithiation Strategy To Build a High-Rate and Long-Life Lithium-Ion Battery with Improved Low-Temperature Performance.

PubMed

Liu, Yao; Yang, Bingchang; Dong, Xiaoli; Wang, Yonggang; Xia, Yongyao

2017-12-22

Lithium-ion batteries (LIBs) are being used to power the commercial electric vehicles (EVs). However, the charge/discharge rate and life of current LIBs still cannot satisfy the further development of EVs. Furthermore, the poor low-temperature performance of LIBs limits their application in cold climates and high altitude areas. Herein, a simple prelithiation method is developed to fabricate a new LIB. In this strategy, a Li 3 V 2 (PO 4 ) 3 cathode and a pristine hard carbon anode are used to form a primary cell, and the initial Li + extraction from Li 3 V 2 (PO 4 ) 3 is used to prelithiate the hard carbon. Then, the self-formed Li 2 V 2 (PO 4 ) 3 cathode and prelithiated hard carbon anode are used to form a 4 V LIB. The LIB exhibits a maximum energy density of 208.3 Wh kg -1 , a maximum power density of 8291 W kg -1 and a long life of 2000 cycles. When operated at -40 °C, the LIB can keep 67 % capacity of room temperature, which is much better than conventional LIBs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of hydraulic pressure on the performance of single chamber air-cathode microbial fuel cells.

PubMed

Cheng, Shaoan; Liu, Weifeng; Guo, Jian; Sun, Dan; Pan, Bin; Ye, Yaoli; Ding, Weijun; Huang, Haobin; Li, Fujian

2014-06-15

Scaling up of microbial fuel cells (MFCs) without losing power density requires a thorough understanding of the effect of hydraulic pressure on MFC performance. In this work, the performance of an activated carbon air-cathode MFC was evaluated under different hydraulic pressures. The MFC under 100 mmH2O hydraulic pressure produced a maximum power density of 1260 ± 24 mW m(-2), while the power density decreased by 24.4% and 44.7% as the hydraulic pressure increased to 500 mmH2O and 2000 mmH2O, respectively. Notably, the performance of both the anode and the cathode had decreased under high hydraulic pressures. Electrochemical impedance spectroscopy tests of the cathode indicated that both charge transfer resistance and diffusion transfer resistance increased with the increase in hydraulic pressure. Denaturing gradient gel electrophoresis of PCR-amplified partial 16S rRNA genes demonstrated that the similarity among anodic biofilm communities under different hydraulic pressures was ≥ 90%, and the communities of all MFCs were dominated by Geobacter sp. These results suggested that the reduction in power output of the single chamber air-cathode MFC under high hydraulic pressures can be attributed to water flooding of the cathode and suppression the metabolism of anodic exoelectrogenic bacteria. Copyright © 2014 Elsevier B.V. All rights reserved.

Peculiarities of light absorption by spherical microcapsules

NASA Astrophysics Data System (ADS)

Geints, Yurii E.; Panina, Ekaterina K.; Zemlyanov, Alexander A.

2018-04-01

Optical radiation absorption in the poly-layer spherical microparticles simulating the inorganic/organic polyshell absorbing microcapsules is considered. With the aim of the finite-difference time-domain technique, the spatial distribution of the absorbed light power in microcapsules of various sizes and internal structure is numerically calculated. For the purpose of light absorption enhancement, we have engineered the optimal structure of a capsule consisting of a strong-refracting transparent outer coating and an absorbing layer which covers a liquid core. The proposed microcapsule prototype provides for a manifold increase in the absorbed light power density in comparison with the usual single-layer absorbing capsule. We show that for light-wavelengths-scaled microcapsules it is optimal to use a material with the refractive index larger than two as an outer shell, for example, titanium dioxide (TiO2). The highest values of the absorbed power density can be obtained in microcapsules with absorbing shell thickness of approximately a tenth of a laser wavelength. When laser radiation is scattered by a dimer constituted by two identical absorbing microcapsules the absorbed power density can be maximized by the choosing of proper dimer spatial configuration. In the case of strongly absorbing particles, the absorption maximum corresponds to a shift of the capsules to a distance of about their diameter, and in the case of weakly absorbing particles the absorption is maximal when particles are in geometrical shades of each other.

Pillared Structure Design of MXene with Ultralarge Interlayer Spacing for High-Performance Lithium-Ion Capacitors.

PubMed

Luo, Jianmin; Zhang, Wenkui; Yuan, Huadong; Jin, Chengbin; Zhang, Liyuan; Huang, Hui; Liang, Chu; Xia, Yang; Zhang, Jun; Gan, Yongping; Tao, Xinyong

2017-03-28

Two-dimensional transition-metal carbide materials (termed MXene) have attracted huge attention in the field of electrochemical energy storage due to their excellent electrical conductivity, high volumetric capacity, etc. Herein, with inspiration from the interesting structure of pillared interlayered clays, we attempt to fabricate pillared Ti 3 C 2 MXene (CTAB-Sn(IV)@Ti 3 C 2 ) via a facile liquid-phase cetyltrimethylammonium bromide (CTAB) prepillaring and Sn 4+ pillaring method. The interlayer spacing of Ti 3 C 2 MXene can be controlled according to the size of the intercalated prepillaring agent (cationic surfactant) and can reach 2.708 nm with 177% increase compared with the original spacing of 0.977 nm, which is currently the maximum value according to our knowledge. Because of the pillar effect, the assembled LIC exhibits a superior energy density of 239.50 Wh kg -1 based on the weight of CTAB-Sn(IV)@Ti 3 C 2 even under higher power density of 10.8 kW kg -1 . When CTAB-Sn(IV)@Ti 3 C 2 anode couples with commercial AC cathode, LIC reveals higher energy density and power density compared with conventional MXene materials.

Influence of template properties and quantum well number on stimulated emission from Al0.7Ga0.3N/Al0.8Ga0.2N quantum wells

NASA Astrophysics Data System (ADS)

Jeschke, J.; Martens, M.; Hagedorn, S.; Knauer, A.; Mogilatenko, A.; Wenzel, H.; Zeimer, U.; Enslin, J.; Wernicke, T.; Kneissl, M.; Weyers, M.

2018-03-01

AlGaN multiple quantum well laser heterostructures for emission around 240 nm have been grown by metalorganic vapor phase epitaxy on epitaxially laterally overgrown (ELO) AlN/sapphire templates. The edge emitting laser structures showed optically pumped lasing with threshold power densities in the range of 2 MW cm-2. The offcut angle of the sapphire substrates as well as the number and the width of the quantum wells were varied while keeping the total thickness of the gain region constant. A larger offcut angle of 0.2° leads to step bunching on the surface as well as Ga accumulation at the steps, but also to an increased inclination of threading dislocations and coalescence boundaries resulting in a reduced dislocation density and thus a reduced laser threshold in comparison to lasers grown on ELO with an offcut of 0.1°. For low losses, samples with fewer QWs exhibited a lower lasing threshold due to a reduced transparency pump power density while for high losses, caused by a higher threading dislocation density, the quadruple quantum well was favorable due to its higher maximum gain.

Density and beta limits in the Madison Symmetric Torus Reversed-Field Pinch

NASA Astrophysics Data System (ADS)

Caspary, Kyle Jonathan

Operational limits and the underlying physics are explored on the Madison Symmetric Torus (MST) Reversed-Field Pinch (RFP) using deuterium pellet fueling. The injection of a fast pellet provides a large source of fuel in the plasma edge upon impact with the vessel wall, capable of triggering density limit terminations for the full range of plasma current, up to 600 kA. As the pellet size and plasma density increase, approaching the empirical Greenwald limit, plasma degradation is observed in the form of current decay, increased magnetic activity in the edge and core, increased radiation and plasma cooling. The complete termination of the plasma is consistent with the Greenwald limit; however, a slightly smaller maximum density is observed in discharges without toroidal field reversal. The plasma beta is the ratio of the plasma pressure to the confining magnetic pressure. Beta limits are known to constrain other magnetic confinement devices, but no beta limit has yet been established on the RFP. On MST, the highest beta values are obtained in improved confinement discharges with pellet fueling. By using pellet injection to scan the plasma density during PPCD, we also achieve a scan of Ohmic input power due to the increase in plasma resistivity. We observe a factor of 3 or more increase in Ohmic power as we increase the density from 1*1019 to 3*10 19 m-3. Despite this increased Ohmic power, the electron contribution to beta is constant, suggesting a confinement limited beta for the RFP. The electrons and ions are classically well coupled in these cold, dense pellet fueled plasmas, so the increase in total beta at higher density is primarily due to the increased ion contribution. The interaction of pellet fueling and NBI heating is explored. Modeling of MST's neutral heating beam suggests an optimal density for beam power deposition of 2-3*1019 m-3. Low current, NBI heated discharges show evidence of an increased electron beta in this density range. Additionally, the fast ion population can enhance ablation as well as cause pellet deflection. Other exploratory experiments with the pellet injection system explore additional injection scenarios and expand the injector capabilities.

An intelligent maximum permissible exposure meter for safety assessments of laser radiation

NASA Astrophysics Data System (ADS)

Corder, D. A.; Evans, D. R.; Tyrer, J. R.

1996-09-01

There is frequently a need to make laser power or energy density measurements when determining whether radiation from a laser system exceeds the Maximum Permissible Exposure (MPE) as defined in BS EN 60825. This can be achieved using standard commercially available laser power or energy measurement equipment, but some of these have shortcomings when used in this application. Calculations must be performed by the user to compare the measured value to the MPE. The measurement and calculation procedure appears complex to the nonexpert who may be performing the assessment. A novel approach is described which uses purpose designed hardware and software to simplify the process. The hardware is optimized for measuring the relatively low powers associated with MPEs. The software runs on a Psion Series 3a palmtop computer. This reduces the cost and size of the system yet allows graphical and numerical presentation of data. Data output to other software running on PCs is also possible, enabling the instrument to be used as part of a quality system. Throughout the measurement process the opportunity for user error has been minimized by the hardware and software design.

Design of activated carbon/activated carbon asymmetric capacitors

NASA Astrophysics Data System (ADS)

Piñeiro-Prado, Isabel; Salinas-Torres, David; Ruiz Rosas, Ramiro; Morallon, Emilia; Cazorla-Amoros, Diego

2016-03-01

Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

Airfoil-based electromagnetic energy harvester containing parallel array motion between moving coil and multi-pole magnets towards enhanced power density.

PubMed

Leung, Chung Ming; Wang, Ya; Chen, Wusi

2016-11-01

In this letter, the airfoil-based electromagnetic energy harvester containing parallel array motion between moving coil and trajectory matching multi-pole magnets was investigated. The magnets were aligned in an alternatively magnetized formation of 6 magnets to explore enhanced power density. In particular, the magnet array was positioned in parallel to the trajectory of the tip coil within its tip deflection span. The finite element simulations of the magnetic flux density and induced voltages at an open circuit condition were studied to find the maximum number of alternatively magnetized magnets that was required for the proposed energy harvester. Experimental results showed that the energy harvester with a pair of 6 alternatively magnetized linear magnet arrays was able to generate an induced voltage (V o ) of 20 V, with an open circuit condition, and 475 mW, under a 30 Ω optimal resistance load operating with the wind speed (U) at 7 m/s and a natural bending frequency of 3.54 Hz. Compared to the traditional electromagnetic energy harvester with a single magnet moving through a coil, the proposed energy harvester, containing multi-pole magnets and parallel array motion, enables the moving coil to accumulate a stronger magnetic flux in each period of the swinging motion. In addition to the comparison made with the airfoil-based piezoelectric energy harvester of the same size, our proposed electromagnetic energy harvester generates 11 times more power output, which is more suitable for high-power-density energy harvesting applications at regions with low environmental frequency.

Dynamic response and residual stress fields of Ti6Al4V alloy under shock wave induced by laser shock peening

NASA Astrophysics Data System (ADS)

Sun, Rujian; Li, Liuhe; Zhu, Ying; Zhang, Lixin; Guo, Wei; Peng, Peng; Li, Bo; Guo, Chao; Liu, Lei; Che, Zhigang; Li, Weidong; Sun, Jianfei; Qiao, Hongchao

2017-09-01

Laser shock peening (LSP), an innovative surface treatment technique, generates compressive residual stress on the surface of metallic components to improve their fatigue performance, wear resistance and corrosion resistance. To illustrate the dynamic response during LSP and residual stress fields after LSP, this study conducted FEM simulations of LSP in a Ti6Al4V alloy. Results showed that when power density was 7 GW cm-2, a plastic deformation occurred at 10 ns during LSP and increased until the shock pressure decayed below the dynamic yield strength of Ti6Al4V after 60 ns. A maximum tensile region appeared beneath the surface at around 240 ns, forming a compressive-tensile-compressive stress sandwich structure with a thickness of 98, 1020 and 606 μm for each layer. After the model became stabilized, the value of the surface residual compressive stress was 564 MPa at the laser spot center. Higher value of residual stress across the surface and thicker compressive residual stress layers were achieved by increasing laser power density, impact times and spot sizes during LSP. A ‘Residual stress hole’ occurred with a high laser power density of 9 GW cm-2 when laser pulse duration was 10 ns, or with a long laser pulse duration of 20 ns when laser power density was 7 GW cm-2 for Ti6Al4V. This phenomenon occurred because of the permanent reverse plastic deformation generated at laser spot center.

Hierarchical porous nickel oxide-carbon nanotubes as advanced pseudocapacitor materials for supercapacitors

NASA Astrophysics Data System (ADS)

Su, Aldwin D.; Zhang, Xiang; Rinaldi, Ali; Nguyen, Son T.; Liu, Huihui; Lei, Zhibin; Lu, Li; Duong, Hai M.

2013-03-01

Hierarchical porous carbon anode and metal oxide cathode are promising for supercapacitor with both high energy density and high power density. This Letter uses NiO and commercial carbon nanotubes (CNTs) as electrode materials for electrochemical capacitors with high energy storage capacities. Experimental results show that the specific capacitance of the electrode materials for 10%, 30% and 50% CNTs are 279, 242 and 112 F/g, respectively in an aqueous 1 M KOH electrolyte at a charge rate of 0.56 A/g. The maximum specific capacitance is 328 F/g at a charge rate of 0.33 A/g.

GaN MOSFET with Boron Trichloride-Based Dry Recess Process

NASA Astrophysics Data System (ADS)

Jiang, Y.; Wang, Q. P.; Tamai, K.; Miyashita, T.; Motoyama, S.; Wang, D. J.; Ao, J. P.; Ohno, Y.

2013-06-01

The dry recessed-gate GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) on AlGaN/GaN heterostructure using boron trichloride (BCl3) as etching gas were fabricated and characterized. Etching with different etching power was conducted. Devices with silicon tetrachloride (SiCl4) etching gas were also prepared for comparison. Field-effect mobility and interface state density were extracted from current-voltage (I-V) characteristics. GaN MOSFETs on AlGaN/GaN heterostructure with BCl3 based dry recess achieved a high maximum electron mobility of 141.5 cm2V-1s-1 and a low interface state density.

Note: High turn density magnetic coils with improved low pressure water cooling for use in atom optics.

PubMed

McKay Parry, Nicholas; Baker, Mark; Neely, Tyler; Carey, Thomas; Bell, Thomas; Rubinsztein-Dunlop, Halina

2014-08-01

We describe a magnetic coil design utilizing concentrically wound electro-magnetic insulating (EMI) foil (25.4 μm Kapton backing and 127 μm thick layers). The magnetic coils are easily configurable for different coil sizes, while providing large surfaces for low-pressure (0.12 bar) water cooling. The coils have turn densities of ~5 mm(-1) and achieve a maximum of 377 G at 2.1 kW driving power, measured at a distance 37.9 mm from the axial center of the coil. The coils achieve a steady-state temperature increase of 36.7°C/kW.

Effective Ice Particle Densities for Cold Anvil Cirrus

NASA Technical Reports Server (NTRS)

Heymsfield, Andrew J.; Schmitt, Carl G.; Bansemer, Aaron; Baumgardner, Darrel; Weinstock, Elliot M.; Smith, Jessica

2002-01-01

This study derives effective ice particle densities from data collected from the NASA WB-57F aircraft near the tops of anvils during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers (CRYSTAL) Florida Area Cirrus Experiment (FACE) in southern Florida in July 2002. The effective density, defined as the ice particle mass divided by the volume of an equivalent diameter liquid sphere, is obtained for particle populations and single sizes containing mixed particle habits using measurements of condensed water content and particle size distributions. The mean effective densities for populations decrease with increasing slopes of the gamma size distributions fitted to the size distributions. The population-mean densities range from near 0.91 g/cu m to 0.15 g/cu m. Effective densities for single sizes obey a power-law with an exponent of about -0.55, somewhat less steep than found from earlier studies. Our interpretations apply to samples where particle sizes are generally below 200-300 microns in maximum dimension because of probe limitations.

Statistical results from 10 years of Cassini Langmuir probe plasma measurements

NASA Astrophysics Data System (ADS)

Holmberg, M.; Shebanits, O.; Wahlund, J. E.; Morooka, M.; Andre, N.

2016-12-01

We use a new analysis method to obtain 10 years of Cassini RPWS Langmuir probe (LP) measurements to study the structure and dynamics of the inner plasma disk of Saturn. The LP plasma density measurements show good agreement with electron densities derived from the RPWS electric field power spectra and confirms and/or improves a number of previous findings about the structure of the plasma disk. E.g., the Enceladus plume is detected as a localised density maximum at the orbit of Enceladus, but the peak density of the inner plasma disk, excluding Enceladus plume passages, is located closer to 4.7 Rs. No density peaks are recorded at the orbits of the moons Mimas, Tethys, Dione, and Rhea. We confirm the previously detected plasma density dayside/nightside asymmetry, which is likely due to a particle drift in the dusk to dawn direction. Presented is also the LP result on the seasonal dependence of the plasma disk within Enceladus' orbit.

Modeling and Numerical Simulation of Microwave Pulse Propagation in Air Breakdown Environment

NASA Technical Reports Server (NTRS)

Kuo, S. P.; Kim, J.

1991-01-01

Numerical simulation is used to investigate the extent of the electron density at a distant altitude location which can be generated by a high-power ground-transmitted microwave pulse. This is done by varying the power, width, shape, and carrier frequency of the pulse. The results show that once the breakdown threshold field is exceeded in the region below the desired altitude location, electron density starts to build up in that region through cascading breakdown. The generated plasma attenuates the pulse energy (tail erosion) and thus deteriorates the energy transmission to the destined altitude. The electron density saturates at a level limited by the pulse width and the tail erosion process. As the pulse continues to travel upward, though the breakdown threshold field of the background air decreases, the pulse energy (width) is reduced more severely by the tail erosion process. Thus, the electron density grows more quickly at the higher altitude, but saturates at a lower level. Consequently, the maximum electron density produced by a single pulse at 50 km altitude, for instance, is limited to a value below 10(exp 6) cm(exp -3). Three different approaches are examined to determine if the ionization at the destined location can be improved: a repetitive pulse approach, a focused pulse approach, and two intersecting beams. Only the intersecting beam approach is found to be practical for generating the desired density level.

Optimized anion exchange membranes for vanadium redox flow batteries.

PubMed

Chen, Dongyang; Hickner, Michael A; Agar, Ertan; Kumbur, E Caglan

2013-08-14

In order to understand the properties of low vanadium permeability anion exchange membranes for vanadium redox flow batteries (VRFBs), quaternary ammonium functionalized Radel (QA-Radel) membranes with three ion exchange capacities (IECs) from 1.7 to 2.4 mequiv g(-1) were synthesized and 55-60 μm thick membrane samples were evaluated for their transport properties and in-cell battery performance. The ionic conductivity and vanadium permeability of the membranes were investigated and correlated to the battery performance through measurements of Coulombic efficiency, voltage efficiency and energy efficiency in single cell tests, and capacity fade during cycling. Increasing the IEC of the QA-Radel membranes increased both the ionic conductivity and VO(2+) permeability. The 1.7 mequiv g(-1) IEC QA-Radel had the highest Coulombic efficiency and best cycling capacity maintenance in the VRFB, while the cell's voltage efficiency was limited by the membrane's low ionic conductivity. Increasing the IEC resulted in higher voltage efficiency for the 2.0 and 2.4 mequiv g(-1) samples, but the cells with these membranes displayed reduced Coulombic efficiency and faster capacity fade. The QA-Radel with an IEC of 2.0 mequiv g(-1) had the best balance of ionic conductivity and VO(2+) permeability, achieving a maximum power density of 218 mW cm(-2) which was higher than the maximum power density of a VRFB assembled with a Nafion N212 membrane in our system. While anion exchange membranes are under study for a variety of VRFB applications, this work demonstrates that the material parameters must be optimized to obtain the maximum cell performance.

Maximum value of the pulse energy of a passively Q-switched laser as a function of the pump power.

PubMed

Li, Jianlang; Ueda, Ken-ichi; Dong, Jun; Musha, Mitsuru; Shirakawa, Akira

2006-07-20

The finite recovery time Ts of the bleached absorber is presented as one of the possible mechanisms accounting for the increase-maximum-decrease in pulse energy E with the pumping rate Wp in cw-pumped passively Q-switched solid-state lasers, by analytically evaluating the sign of the derivative partial differentialE/ partial differentialWP. The results show that, in the low pump regime (T>Ts, T is the interpulse period), the initial population density ni remains constant, the final population density nf decreases with Wp, and this results in a monotonic increase of E with Wp. In the high pump regime (T

Electricity generation and wastewater treatment of oil refinery in microbial fuel cells using Pseudomonas putida.

PubMed

Majumder, Dip; Maity, Jyoti Prakash; Tseng, Min-Jen; Nimje, Vanita Roshan; Chen, Hau-Ren; Chen, Chien-Cheng; Chang, Young-Fo; Yang, Tsui-Chu; Chen, Chen-Yen

2014-09-22

Microbial fuel cells (MFCs) represent a novel platform for treating wastewater and at the same time generating electricity. Using Pseudomonas putida (BCRC 1059), a wild-type bacterium, we demonstrated that the refinery wastewater could be treated and also generate electric current in an air-cathode chamber over four-batch cycles for 63 cumulative days. Our study indicated that the oil refinery wastewater containing 2213 mg/L (ppm) chemical oxygen demand (COD) could be used as a substrate for electricity generation in the reactor of the MFC. A maximum voltage of 355 mV was obtained with the highest power density of 0.005 mW/cm² in the third cycle with a maximum current density of 0.015 mA/cm² in regard to the external resistor of 1000 Ω. A maximum coulombic efficiency of 6 × 10⁻²% was obtained in the fourth cycle. The removal efficiency of the COD reached 30% as a function of time. Electron transfer mechanism was studied using cyclic voltammetry, which indicated the presence of a soluble electron shuttle in the reactor. Our study demonstrated that oil refinery wastewater could be used as a substrate for electricity generation.

Electricity Generation and Wastewater Treatment of Oil Refinery in Microbial Fuel Cells Using Pseudomonas putida

PubMed Central

Majumder, Dip; Maity, Jyoti Prakash; Tseng, Min-Jen; Nimje, Vanita Roshan; Chen, Hau-Ren; Chen, Chien-Cheng; Chang, Young-Fo; Yang, Tsui-Chu; Chen, Chen-Yen

2014-01-01

Microbial fuel cells (MFCs) represent a novel platform for treating wastewater and at the same time generating electricity. Using Pseudomonas putida (BCRC 1059), a wild-type bacterium, we demonstrated that the refinery wastewater could be treated and also generate electric current in an air-cathode chamber over four-batch cycles for 63 cumulative days. Our study indicated that the oil refinery wastewater containing 2213 mg/L (ppm) chemical oxygen demand (COD) could be used as a substrate for electricity generation in the reactor of the MFC. A maximum voltage of 355 mV was obtained with the highest power density of 0.005 mW/cm2 in the third cycle with a maximum current density of 0.015 mA/cm2 in regard to the external resistor of 1000 Ω. A maximum coulombic efficiency of 6 × 10−2% was obtained in the fourth cycle. The removal efficiency of the COD reached 30% as a function of time. Electron transfer mechanism was studied using cyclic voltammetry, which indicated the presence of a soluble electron shuttle in the reactor. Our study demonstrated that oil refinery wastewater could be used as a substrate for electricity generation. PMID:25247576

Optimization of electrode characteristics for the Br₂/H₂ redox flow cell

DOE PAGES

Tucker, Michael C.; Cho, Kyu Taek; Weber, Adam Z.; ...

2014-10-17

The Br₂/H₂ redox flow cell shows promise as a high-power, low-cost energy storage device. The effect of various aspects of material selection, processing, and assembly of electrodes on the operation, performance, and efficiency of the system is determined. In particular, (+) electrode thickness, cell compression, hydrogen pressure, and (–) electrode architecture are investigated. Increasing hydrogen pressure and depositing the (–) catalyst layer on the membrane instead of on the carbon-paper backing layers have a large positive impact on performance, enabling a limiting current density above 2 A cm -2 and a peak power density of 1.4 W cm -2. Maximummore » energy efficiency of 79% is achieved. In addition, the root cause of limiting-current behavior in this system is elucidated, where it is found that Br - reversibly adsorbs at the Pt (–) electrode for potentials exceeding a critical value, and the extent of Br - coverage is potential-dependent. This phenomenon limits maximum cell current density and must be addressed in system modeling and design. These findings are expected to lower system cost and enable higher efficiency.« less

Characterization of perovskite solar cells: Towards a reliable measurement protocol

NASA Astrophysics Data System (ADS)

Zimmermann, Eugen; Wong, Ka Kan; Müller, Michael; Hu, Hao; Ehrenreich, Philipp; Kohlstädt, Markus; Würfel, Uli; Mastroianni, Simone; Mathiazhagan, Gayathri; Hinsch, Andreas; Gujar, Tanaji P.; Thelakkat, Mukundan; Pfadler, Thomas; Schmidt-Mende, Lukas

2016-09-01

Lead halide perovskite solar cells have shown a tremendous rise in power conversion efficiency with reported record efficiencies of over 20% making this material very promising as a low cost alternative to conventional inorganic solar cells. However, due to a differently severe "hysteretic" behaviour during current density-voltage measurements, which strongly depends on scan rate, device and measurement history, preparation method, device architecture, etc., commonly used solar cell measurements do not give reliable or even reproducible results. For the aspect of commercialization and the possibility to compare results of different devices among different laboratories, it is necessary to establish a measurement protocol which gives reproducible results. Therefore, we compare device characteristics derived from standard current density-voltage measurements with stabilized values obtained from an adaptive tracking of the maximum power point and the open circuit voltage as well as characteristics extracted from time resolved current density-voltage measurements. Our results provide insight into the challenges of a correct determination of device performance and propose a measurement protocol for a reliable characterisation which is easy to implement and has been tested on varying perovskite solar cells fabricated in different laboratories.

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions

PubMed Central

Martins, Vitor L.; Rennie, Anthony J. R.; Sanchez‐Ramirez, Nedher; Torresi, Roberto M.; Hall, Peter J.

2018-01-01

Abstract Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN)4] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm−1). Herein, we report the use of ILs containing the [B(CN)4] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two‐electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g−1 @ 15 A g−1). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs. PMID:29577008

A Thermally-Regenerative Ammonia-Based Flow Battery for Electrical Energy Recovery from Waste Heat.

PubMed

Zhu, Xiuping; Rahimi, Mohammad; Gorski, Christopher A; Logan, Bruce

2016-04-21

Large amounts of low-grade waste heat (temperatures <130 °C) are released during many industrial, geothermal, and solar-based processes. Using thermally-regenerative ammonia solutions, low-grade thermal energy can be converted to electricity in battery systems. To improve reactor efficiency, a compact, ammonia-based flow battery (AFB) was developed and tested at different solution concentrations, flow rates, cell pairs, and circuit connections. The AFB achieved a maximum power density of 45 W m(-2) (15 kW m(-3) ) and an energy density of 1260 Wh manolyte (-3) , with a thermal energy efficiency of 0.7 % (5 % relative to the Carnot efficiency). The power and energy densities of the AFB were greater than those previously reported for thermoelectrochemical and salinity-gradient technologies, and the voltage or current could be increased using stacked cells. These results demonstrated that an ammonia-based flow battery is a promising technology to convert low-grade thermal energy to electricity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Pyrolyzed binuclear-cobalt-phthalocyanine as electrocatalyst for oxygen reduction reaction in microbial fuel cells.

PubMed

Li, Baitao; Wang, Mian; Zhou, Xiuxiu; Wang, Xiujun; Liu, Bingchuan; Li, Baikun

2015-10-01

A novel platinum (Pt)-free cathodic materials binuclear-cobalt-phthalocyanine (Bi-CoPc) pyrolyzed at different temperatures (300-1000 °C) were examined as the oxygen reduction reaction (ORR) catalysts, and compared with unpyrolyzed Bi-CoPc/C and Pt cathode in single chamber microbial fuel cells (SCMFCs). The results showed that the pyrolysis process increased the nitrogen abundance on Bi-CoPc and changed the nitrogen types. The Bi-CoPc pyrolyzed at 800 °C contained a significant amount of pyrrolic-N, and exhibited a high electrochemical catalytic activity. The power density and current density increased with temperature: Bi-CoPc/C-800 > Bi-CoPc/C-1000 > Bi-CoPc/C-600 > Bi-CoPc/C-300 > Bi-CoPc/C. The SCMFC with Bi-CoPc/C-800 cathode had a maximum power density of 604 mW m(-2). The low cost Bi-CoPc compounds developed in this study showed a potential in air-breathing MFC systems, with the proper pyrolysis temperature being chosen. Copyright © 2015 Elsevier Ltd. All rights reserved.

Plasma density behavior with new graphite limiters in the Hefei Tokamak-7

DOE Office of Scientific and Technical Information (OSTI.GOV)

Asif, M.; Gao, X.; Li, J.

A new set of actively cooled toroidal double-ring graphite limiters has been developed in the Hefei Tokamak-7 (HT-7) [X. Gao et al., Phys. Plasmas 7, 2933 (2000)] for long pulse operation. The extension of operational region and density behavior with graphite (C) limiters have been studied in this paper. Extended high-density region at the high plasma current low-q{sub a} was obtained. The density profile with the C limiter was studied to compare with the previous molybdenum (Mo) limiter. The critical density of multifaceted asymmetric radiation from the edge (MARFE) onset is observed in the region of Z{sub eff}{sup 1/2}f{sub GW}=0.9{approx}1.2,more » where f{sub GW}=n{sub e}/n{sub GW}. (Here n{sub e} is the maximum line average electron density and n{sub GW} is the Greenwald density.) Under the same injected power, the critical density of MARFE onset with the new C limiter is much higher than the previous Mo limiter.« less

Modeling of four-terminal solar photovoltaic systems for field application

NASA Astrophysics Data System (ADS)

Vahanka, Harikrushna; Purohit, Zeel; Tripathi, Brijesh

2018-05-01

In this article a theoretical framework for mechanically stacked four-terminal solar photovoltaic (FTSPV) system has been proposed. In a mechanical stack arrangement, a semitransparent CdTe panel has been used as a top sub-module, whereas a μc-Si solar panel has been used as bottom sub-module. Theoretical modeling has been done to analyze the physical processes in the system and to estimate reliable prediction of the performance. To incorporate the effect of material, the band gap and the absorption coefficient data for CdTe and μc-Si panels have been considered. The electrical performance of the top and bottom panels operated in a mechanical stack has been obtained experimentally for various inter-panel separations in the range of 0-3 cm. Maximum output power density has been obtained for a separation of 0.75 cm. The mean value of output power density from CdTe (top panel) has been calculated as 32.3 Wm-2 and the mean value of output power density from μc-Si, the bottom panel of four-terminal photovoltaic system has been calculated as ˜3.5 Wm-2. Results reported in this study reveal the potential of mechanically stacked four-terminal tandem solar photovoltaic system towards an energy-efficient configuration.

A symmetric supercapacitor/biofuel cell hybrid device based on enzyme-modified nanoporous gold: An autonomous pulse generator.

PubMed

Xiao, Xinxin; Conghaile, Peter Ó; Leech, Dónal; Ludwig, Roland; Magner, Edmond

2017-04-15

The integration of supercapacitors with enzymatic biofuel cells (BFCs) can be used to prepare hybrid devices in order to harvest significantly higher power output. In this study, a supercapacitor/biofuel cell hybrid device was prepared by the immobilisation of redox enzymes with electrodeposited poly(3,4-ethylenedioxythiophene) (PEDOT) and the redox polymer [Os(2,2'-bipyridine) 2 (polyvinylimidazole) 10 Cl] +/2+ (Os(bpy) 2 PVI) on dealloyed nanoporous gold. The thickness of the deposition layer can be easily controlled by tuning the deposition conditions. Once charged by the internal BFC, the device can be discharged as a supercapacitor at a current density of 2mAcm -2 providing a maximum power density of 608.8μWcm -2 , an increase of a factor of 468 when compared to the power output from the BFC itself. The hybrid device exhibited good operational stability for 50 charge/discharge cycles and ca. 7h at a discharge current density of 0.2mAcm -2 . The device could be used as a pulse generator, mimicking a cardiac pacemaker delivering pulses of 10μA for 0.5ms at a frequency of 0.2Hz. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhancing the performance of NaNbO3 triboelectric nanogenerators by dielectric modulation and electronegative modification

NASA Astrophysics Data System (ADS)

Lai, Meihui; Cheng, Lu; Xi, Yi; Wu, Yinghui; Hu, Chengguo; Guo, Hengyu; Du, Bolun; Liu, Guanlin; Liu, Qipeng; Liu, Ruchuan

2018-01-01

Increasing the triboelectric charge density on the friction layer of polydimethylsiloxane (PDMS) is a basic approach towards improving the output performance of a triboelectric nanogenerator (TENG). Most previous work focuses on the surface structure or dielectric properties, nonetheless, a few studies have focused on electronegative modification. NaNbO3-PDMS TENG (N-TENG) devices are fabricated by dispersing cubic NaNbO3, which is a lead-free piezoelectric material with molecular oxygen dangling bonds on the surface of the crystal, into the PDMS at different mass ratios. When the mass ratio is 7 wt%, the maximum output performance of the N-TENG is obtained. The open-circuit voltage is 550 V, the short-circuit current is 16 µA, and the effective power densities reach up to 5.5 W m-2 at a load resistance of ~100 MΩ. The N-TENG has been used to assemble self-powered electronic watches and illuminate commercial light-emitting diodes, respectively. Its fundamental mechanism has also been discussed in detail from the perspective of dielectric modulation and electronegative modification. This N-TENG technology is revealed to be a splendid candidate for application in large-scale device fabrication, flexible sensors and biological devices thanks to its easy fabrication process, low consumption, high output power density and biocompatibility.

Measurement of solubility and water sorption of dental nanocomposites light cured by argon laser.

PubMed

Mirsasaani, Seyed Shahabeddin; Ghomi, Farhad; Hemati, Mehran; Tavasoli, Tina

2013-03-01

Different parameters used for photoactivation process and also composition provide changes in the properties of dental composites. In the present work the effect of different power density of argon laser and filler loading on solubility (SL) and water sorption (WS) of light-cure dental nanocomposites was studied. The resin of nanocomposites was prepared by mixing bisphenol A glycol dimethacrylate (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) with a mass ratio of 65/35. 20 wt.% and 25 wt.% of nanosilica fillers with a primary particle size of 10 nm were added to the resin. Camphorquinone (CQ) and DMAEMA were added as photoinitiator system. The nanocomposites were cured by applying the laser beam at the wavelength of 472 nm and power densities of 260 and 340 mW/cm(2) for 40 sec. Solubility and water sorption were then measured according to ISO 4049, which in our case, the maximums were 2.2% and 4.3% at 260 mW/cm(2) and 20% filler, respectively. The minimum solubility (1.2%) and water sorption (3.8%) were achieved for the composite containing 25% filler cured at 340 mW/cm(2). The results confirmed that higher power density and filler loading decreased solubility of unreacted monomers and water sorption and improved physico-mechanical properties of nanocomposites.

Evaluation of power density on the bioethanol production using mesoscale oscillatory baffled reactor and stirred tank reactor

NASA Astrophysics Data System (ADS)

Yussof, H. W.; Bahri, S. S.; Mazlan, N. A.

2018-03-01

A recent development in oscillatory baffled reactor technology is down-scaling the reactor, so that it can be used for production of small-scale bioproduct. In the present study, a mesoscale oscillatory baffled reactor (MOBR) with central baffle system was developed. The reactor performance of the MOBR was compared with conventional stirred tank reactor (STR) to evaluate the performance of bioethanol fermentation using Saccharomyces cerevisiae. Evaluation was made at similar power density of 24.21, 57.38, 112.35 and 193.67 Wm-3 by varying frequency (f), amplitude (xo) and agitation speed (rpm). It was found that the MOBR improved the mixing intensity resulted in lower glucose concentration (0.988 gL-1) and higher bioethanol concentration (38.98 gL-1) after 12 hours fermentation at power density of 193.67 Wm-3. Based on the results, the bioethanol yield obtained using MOBR was 39% higher than the maximum achieved in STR. Bioethanol production using MOBR proved to be feasible as it is not only able to compete with conventional STR but also offers advantages of straight-forward scale-up, whereas it is complicated and difficult in STR. Overall, MOBR offers great prospective over the conventional STR.

A thermally self-sustained micro-power plant with integrated micro-solid oxide fuel cells, micro-reformer and functional micro-fluidic carrier

NASA Astrophysics Data System (ADS)

Scherrer, Barbara; Evans, Anna; Santis-Alvarez, Alejandro J.; Jiang, Bo; Martynczuk, Julia; Galinski, Henning; Nabavi, Majid; Prestat, Michel; Tölke, René; Bieberle-Hütter, Anja; Poulikakos, Dimos; Muralt, Paul; Niedermann, Philippe; Dommann, Alex; Maeder, Thomas; Heeb, Peter; Straessle, Valentin; Muller, Claude; Gauckler, Ludwig J.

2014-07-01

Low temperature micro-solid oxide fuel cell (micro-SOFC) systems are an attractive alternative power source for small-size portable electronic devices due to their high energy efficiency and density. Here, we report on a thermally self-sustainable reformer-micro-SOFC assembly. The device consists of a micro-reformer bonded to a silicon chip containing 30 micro-SOFC membranes and a functional glass carrier with gas channels and screen-printed heaters for start-up. Thermal independence of the device from the externally powered heater is achieved by exothermic reforming reactions above 470 °C. The reforming reaction and the fuel gas flow rate of the n-butane/air gas mixture controls the operation temperature and gas composition on the micro-SOFC membrane. In the temperature range between 505 °C and 570 °C, the gas composition after the micro-reformer consists of 12 vol.% to 28 vol.% H2. An open-circuit voltage of 1.0 V and maximum power density of 47 mW cm-2 at 565 °C is achieved with the on-chip produced hydrogen at the micro-SOFC membranes.

Power production and wastewater treatment simultaneously by dual-chamber microbial fuel cell technique.

PubMed

Izadi, Paniz; Rahimnejad, Mostafa; Ghoreyshi, Ali

2015-01-01

Microbial fuel cell (MFC) is a novel technology that is able to convert the chemical energy of organic and inorganic substrates to electrical energy directly. The use of fossil fuels and recent energy crisis bring increasing attention to this technology. Besides electricity generation, wastewater treatment is another application of MFCs. Sulfide is a hazardous ion that is common in wastes. In this article, dual-chamber MFC was fabricated and a mixed culture of microorganisms was used as an active biocatalyst in an anaerobic anodic chamber to convert substrate to electricity. The obtained experimental results indicate that this MFC can successfully alter sulfide to elementary sulfur and power generation. The initial concentration of sulfide in wastewater was 1.5 g L(-1) , and it was removed after 10 days of MFC operation. Maximum produced power and current density were 48.68 mW⋅m(-2) and 231.47 mA⋅m(-2) , respectively. Besides, the influences of a biocathode were investigated and accordingly the data obtained for power and current density were increased to 372.27 mW⋅m(-2) and 1,665.15 mA⋅m(-2) , respectively. © 2015 International Union of Biochemistry and Molecular Biology, Inc.

Proof of principle experiments for helicon discharges in hydrogen

NASA Astrophysics Data System (ADS)

Briefi, Stefan; Fantz, Ursel

2013-09-01

In order to reduce the amount of power required for generating CW hydrogen discharges with high electron densities and a high degree of dissociation via RF coupling, the helicon concept is investigated. For this purpose a small laboratory experiment (length of the discharge vessel 40 cm, diameter 10 cm) has been built up. The RF generator has a maximum power of 600 W (frequency 13.56 MHz) and a Nagoya type III antenna is applied. As water cooling was avoided in constructing the experiment for simplicity, the induction coils can only generate a rather low magnetic field up to 14 mT. The performed investigations cover a variation of the RF power and the magnetic field in a pressure range between 0.3 and 10 Pa. Around a magnetic field of 3 mT the low field peak which is typical for helicon discharges could be observed. As the high density mode of helicon discharges has not yet been reached, a different RF generator (2 MHz, 2 KW) and water cooled induction coils will be applied in a next step in order to increase the available power and the magnetic field.

NATIONAL GEODATABASE OF TIDAL STREAM POWER RESOURCE IN USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Brennan T; Neary, Vincent S; Stewart, Kevin M

2012-01-01

A geodatabase of tidal constituents is developed to present the regional assessment of tidal stream power resource in the USA. Tidal currents are numerically modeled with the Regional Ocean Modeling System (ROMS) and calibrated with the available measurements of tidal current speeds and water level surfaces. The performance of the numerical model in predicting the tidal currents and water levels is assessed by an independent validation. The geodatabase is published on a public domain via a spatial database engine with interactive tools to select, query and download the data. Regions with the maximum average kinetic power density exceeding 500 W/m2more » (corresponding to a current speed of ~1 m/s), total surface area larger than 0.5 km2 and depth greater than 5 m are defined as hotspots and documented. The regional assessment indicates that the state of Alaska (AK) has the largest number of locations with considerably high kinetic power density, followed by, Maine (ME), Washington (WA), Oregon (OR), California (CA), New Hampshire (NH), Massachusetts (MA), New York (NY), New Jersey (NJ), North and South Carolina (NC, SC), Georgia (GA), and Florida (FL).« less

Exploring packaging strategies of nano-embedded thermoelectric generators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singha, Aniket; Muralidharan, Bhaskaran, E-mail: bm@ee.iitb.ac.in; Mahanti, Subhendra D.

2015-10-15

Embedding nanostructures within a bulk matrix is an important practical approach towards the electronic engineering of high performance thermoelectric systems. For power generation applications, it ideally combines the efficiency benefit offered by low dimensional systems along with the high power output advantage offered by bulk systems. In this work, we uncover a few crucial details about how to embed nanowires and nanoflakes in a bulk matrix so that an overall advantage over pure bulk may be achieved. First and foremost, we point out that a performance degradation with respect to bulk is inevitable as the nanostructure transitions to a multimore » moded one. It is then shown that a nano embedded system of suitable cross-section offers a power density advantage over a wide range of efficiencies at higher packing fractions, and this range gradually narrows down to the high efficiency regime, as the packing fraction is reduced. Finally, we introduce a metric - the advantage factor, to elucidate quantitatively, the enhancement in the power density offered via nano-embedding at a given efficiency. In the end, we explore the maximum effective width of nano-embedding which serves as a reference in designing generators in the efficiency range of interest.« less

A micro-sized bio-solar cell for self-sustaining power generation.

PubMed

Lee, Hankeun; Choi, Seokheun

2015-01-21

Self-sustainable energy sources are essential for a wide array of wireless applications deployed in remote field locations. Due to their self-assembling and self-repairing properties, "biological solar (bio-solar) cells" are recently gaining attention for those applications. The bio-solar cell can continuously generate electricity from microbial photosynthetic and respiratory activities under day-night cycles. Despite the vast potential and promise of bio-solar cells, they, however, have not yet successfully been translated into commercial applications, as they possess persistent performance limitations and scale-up bottlenecks. Here, we report an entirely self-sustainable and scalable microliter-sized bio-solar cell with significant power enhancement by maximizing solar energy capture, bacterial attachment, and air bubble volume in well-controlled microchambers. The bio-solar cell has a ~300 μL single chamber defined by laser-machined poly(methyl methacrylate) (PMMA) substrates and it uses an air cathode to allow freely available oxygen to act as an electron acceptor. We generated a maximum power density of 0.9 mW m(-2) through photosynthetic reactions of cyanobacteria, Synechocystis sp. PCC 6803, which is the highest power density among all micro-sized bio-solar cells.

Deep space telecommunications and the solar cycle: A reappraisal

NASA Technical Reports Server (NTRS)

Berman, A. L.

1978-01-01

Observations of density enhancement in the near corona at solar cycle (sunspot) maximum have rather uncritically been interpreted to apply equally well to the extended corona, thus generating concern about the quality of outer planet navigational data at solar cycle maximum. Spacecraft have been deployed almost continuously during the recently completed solar cycle 20, providing two powerful new coronal investigatory data sources: (1) in-situ spacecraft plasma measurements at approximately 1 AU, and (2) plasma effects on monochromatic spacecraft signals at all signal closest approach points. A comprehensive review of these (solar cycle 20) data lead to the somewhat surprising conclusions that for the region of interest of navigational data, the highest levels of charged particle corruption of navigational data can be expected to occur at solar cycle minimum, rather than solar cycle maximum, as previously believed.

Maximum stand density for ponderosa pine and red and white fir in northern California

Treesearch

William.W. Oliver; Fabian C.C. Uzoh

1997-01-01

Why are forest managers interested in quantifying maximum stand density? Nearly all conceivable management objectives dictate a stand density less than a biological maximum. Certainly, the notion that thinning dense stands increases growth on the remaining trees and reduces mortality is well-established in the literature. The interest in quantifying maximum stand...

Residual Stress Distribution and Microstructure of a Multiple Laser-Peened Near-Alpha Titanium Alloy

NASA Astrophysics Data System (ADS)

Umapathi, A.; Swaroop, S.

2018-04-01

Laser peening without coating (LPwC) was performed on a Ti-2.5 Cu alloy with multiple passes (1, 3 and 5), using a Nd:YAG laser (1064 nm) at a constant overlap rate of 70% and power density of 6.7 GW cm-2. Hardness and residual stress profiles indicated thermal softening near the surface (< 100 μm) and bulk softening due to adiabatic heating. Maximum hardness (235 HV at 500 μm) and maximum residual stress (- 890 MPa at 100 μm) were observed for LPwC with 1 pass. Surface roughness and surface 3-D topography imaging showed that the surface roughness increased with the increase in the number of passes. XRD results indicated no significant β phases. However, peak shifts, broadening and asymmetry were observed and interpreted based on dislocation activity. Microstructures indicated no melting or resolidification or refinement of grains at the surface. Twin density was found to increase with the increase in the number of passes.

Residual Stress Distribution and Microstructure of a Multiple Laser-Peened Near-Alpha Titanium Alloy

NASA Astrophysics Data System (ADS)

Umapathi, A.; Swaroop, S.

2018-05-01

Laser peening without coating (LPwC) was performed on a Ti-2.5 Cu alloy with multiple passes (1, 3 and 5), using a Nd:YAG laser (1064 nm) at a constant overlap rate of 70% and power density of 6.7 GW cm-2. Hardness and residual stress profiles indicated thermal softening near the surface (< 100 μm) and bulk softening due to adiabatic heating. Maximum hardness (235 HV at 500 μm) and maximum residual stress (- 890 MPa at 100 μm) were observed for LPwC with 1 pass. Surface roughness and surface 3-D topography imaging showed that the surface roughness increased with the increase in the number of passes. XRD results indicated no significant β phases. However, peak shifts, broadening and asymmetry were observed and interpreted based on dislocation activity. Microstructures indicated no melting or resolidification or refinement of grains at the surface. Twin density was found to increase with the increase in the number of passes.

Nickel-phendione complex covalently attached onto carbon nanotube/cross linked glucose dehydrogenase as bioanode for glucose/oxygen compartment-less biofuel cell

NASA Astrophysics Data System (ADS)

Korani, Aazam; Salimi, Abdollah; Hadadzadeh, Hasan

2015-05-01

Here, [Ni(phendion) (phen)]Cl2 complex, (phendion and phen are 1,10-phenanthroline-5,6-dione and 5-amino-1, 10-phenanthrolin) covalently attached onto carboxyl functionalized multi walls carbon nanotube modified glassy carbon electrode (GCE/MWCNTs-COOH) using solid phase interactions and combinatorial approaches.The attached [Ni(phendion) (phen)]Cl2 complex displays a surface controlled electrode process and it acts as an effective redox mediator for electrocatalytic oxidation of dihydronicotinamide adenine dinucleotide (NADH) at reduced overpotentials. With co-immobilization of glucose dehydrogenase enzyme (GDH) by crosslinking an effective biocatalyst for glucose oxidation designed. The onset potential and current density are -0.1 V versus Ag/AgCl electrode and 0.550 mA cm-2, which indicate the applicability of the proposed system as an efficient bioanode for biofuel cell (BFC) design. A GCE/MWCNTs modified with electrodeposited gold nanoparticles (AuNPs) as a platform for immobilization of bilirubin oxidase (BOD) and the prepared GCE/MWCNTs/AuNPs/BOD biocathode exhibits an onset potential of 0.56 V versus Ag/AgCl. The performance of the fabricated bioanode and biocathode in a membraneless enzyme based glucose/O2 biofuel cell is evaluated. The open circuit voltage of the cell and maximum current density are 520 mV and 0.233 mA cm-2, respectively, while maximum power density of 40 μWcm-2 achieves at voltage of 280 mV with stable output power after 24 h continues operation.

Performance of polyacrylonitrile-carbon nanotubes composite on carbon cloth as electrode material for microbial fuel cells.

PubMed

Kim, Sun-Il; Lee, Jae-Wook; Roh, Sung-Hee

2011-02-01

The performance of carbon nanotubes composite-modified carbon cloth electrodes in two-chambered microbial fuel cell (MFC) was investigated. The electrode modified with polyacrylonitrile-carbon nanotubes (PAN-CNTs) composite showed better electrochemical performance than that of plain carbon cloth. The MFC with the composite-modified anode containing 5 mg/cm2 PAN-CNTs exhibited a maximum power density of 480 mW/m2.

Advanced Neutron Radiographic Equipment within the US Army

DTIC Science & Technology

2014-01-29

generator was then placed into a moderator assembly made mainly of high density polyethylene ( HDPE ), with a collimator that was a gadolinium (Gd) coated...port made with various slabs, bricks, sheets, and foils of materials containing lead, boron, and HDPE . This port merely functioned as a scatter...conical inserts made of HDPE , lead, and Gd infused paint. The trial experiments have shown that with the system running at its designed maximum power

Formation of Platinum Catalyst on Carbon Black Using an In-Liquid Plasma Method for Fuel Cells.

PubMed

Show, Yoshiyuki; Ueno, Yutaro

2017-01-31

Platinum (Pt) catalyst was formed on the surface of carbon black using an in-liquid plasma method. The formed Pt catalyst showed the average particle size of 4.1 nm. This Pt catalyst was applied to a polymer electrolyte membrane fuel cell (PEMFC). The PEMFC showed an open voltage of 0.85 V and a maximum output power density of 216 mW/cm2.

Formation of Platinum Catalyst on Carbon Black Using an In-Liquid Plasma Method for Fuel Cells

PubMed Central

Show, Yoshiyuki; Ueno, Yutaro

2017-01-01

Platinum (Pt) catalyst was formed on the surface of carbon black using an in-liquid plasma method. The formed Pt catalyst showed the average particle size of 4.1 nm. This Pt catalyst was applied to a polymer electrolyte membrane fuel cell (PEMFC). The PEMFC showed an open voltage of 0.85 V and a maximum output power density of 216 mW/cm2. PMID:28336864

Volume and Mass Estimation of Three-Phase High Power Transformers for Space Applications

NASA Technical Reports Server (NTRS)

Kimnach, Greg L.

2004-01-01

Spacecraft historically have had sub-1kW(sub e), electrical requirements for GN&C, science, and communications: Galileo at 600W(sub e), and Cassini at 900W(sub e), for example. Because most missions have had the same order of magnitude power requirements, the Power Distribution Systems (PDS) use existing, space-qualified technology and are DC. As science payload and mission duration requirements increase, however, the required electrical power increases. Subsequently, this requires a change from a passive energy conversion (solar arrays and batteries) to dynamic (alternator, solar dynamic, etc.), because dynamic conversion has higher thermal and conversion efficiencies, has higher power densities, and scales more readily to higher power levels. Furthermore, increased power requirements and physical distribution lengths are best served with high-voltage, multi-phase AC to maintain distribution efficiency and minimize voltage drops. The generated AC-voltage must be stepped-up (or down) to interface with various subsystems or electrical hardware. Part of the trade-space design for AC distribution systems is volume and mass estimation of high-power transformers. The volume and mass are functions of the power rating, operating frequency, the ambient and allowable temperature rise, the types and amount of heat transfer available, the core material and shape, the required flux density in a core, the maximum current density, etc. McLyman has tabulated the performance of a number of transformers cores and derived a "cookbook" methodology to determine the volume of transformers, whereas Schawrze had derived an empirical method to estimate the mass of single-phase transformers. Based on the work of McLyman and Schwarze, it is the intent herein to derive an empirical solution to the volume and mass estimation of three-phase, laminated EI-core power transformers, having radiated and conducted heat transfer mechanisms available. Estimation of the mounting hardware, connectors, etc. is not included.

Triboelectrification-Enabled Self-Powered Data Storage.

PubMed

Kuang, Shuang Yang; Zhu, Guang; Wang, Zhong Lin

2018-02-01

Data storage by any means usually requires an electric driving power for writing or reading. A novel approach for self-powered, triboelectrification-enabled data storage (TEDS) is presented. Data are incorporated into a set of metal-based surface patterns. As a probe slides across the patterned surface, triboelectrification between the scanning probe and the patterns produces alternatively varying voltage signal in quasi-square wave. The trough and crest of the quasi-square wave signal are coded as binary bits of "0" and "1," respectively, while the time span of the trough and the crest is associated with the number of bits. The storage of letters and sentences is demonstrated through either square-shaped or disc-shaped surface patterns. Based on experimental data and numerical calculation, the theoretically predicted maximum data storage density could reach as high as 38.2 Gbit in -2 . Demonstration of real-time data retrieval is realized with the assistance of software interface. For the TEDS reported in this work, the measured voltage signal is self-generated as a result of triboelectrification without the reliance on an external power source. This feature brings about not only low power consumption but also a much more simplified structure. Therefore, this work paves a new path to a unique approach of high-density data storage that may have widespread applications.

Enhancing low-grade thermal energy recovery in a thermally regenerative ammonia battery using elevated temperatures.

PubMed

Zhang, Fang; LaBarge, Nicole; Yang, Wulin; Liu, Jia; Logan, Bruce E

2015-03-01

A thermally regenerative ammonia battery (TRAB) is a new approach for converting low-grade thermal energy into electricity by using an ammonia electrolyte and copper electrodes. TRAB operation at 72 °C produced a power density of 236 ± 8 Wm(-2), with a linear decrease in power to 95 ± 5 Wm(-2) at 23 °C. The improved power at higher temperatures was due to reduced electrode overpotentials and more favorable thermodynamics for the anode reaction (copper oxidation). The energy density varied with temperature and discharge rates, with a maximum of 650 Wh m(-3) at a discharge energy efficiency of 54% and a temperature of 37 °C. The energy efficiency calculated with chemical process simulation software indicated a Carnot-based efficiency of up to 13% and an overall thermal energy recovery of 0.5%. It should be possible to substantially improve these energy recoveries through optimization of electrolyte concentrations and by using improved ion-selective membranes and energy recovery systems such as heat exchangers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A membraneless single compartment abiotic glucose fuel cell

NASA Astrophysics Data System (ADS)

Slaughter, Gymama; Sunday, Joshua

2014-09-01

A simple energy harvesting strategy has been developed to selectively catalyze glucose in the presence of oxygen in a glucose/O2 fuel cell. The anode consists of an abiotic catalyst Al/Au/ZnO, in which ZnO seed layer was deposited on the surface of Al/Au substrate using hydrothermal method. The cathode is constructed from a single rod of platinum with an outer diameter of 500 μm. The abiotic glucose fuel cell was studied in phosphate buffer solution (pH 7.4) containing 5 mM glucose at a temperature of 22 °C. The cell is characterized according to its open-circuit voltage, polarization profile, and power density plot. Under these conditions, the abiotic glucose fuel cell possesses an open-circuit voltage of 840 mV and delivered a maximum power density of 16.2 μW cm-2 at a cell voltage of 495 mV. These characteristics are comparable to biofuel cell utilizing a much more complex system design. Such low-cost lightweight abiotic catalyzed glucose fuel cells have a great promise to be optimized, miniaturized to power bio-implantable devices.

Study of different carbon materials for their use as bioanodes in microbial fuel cells.

PubMed

González-Nava, Catalina; Godínez, Luis A; Chávez, Abraham U; Cercado, Bibiana; Arriaga, Luis G; Rodríguez-Valadez, Francisco J

2016-01-01

Microbial fuel cells (MFCs) are capable of removing the organic matter contained in water while generating a certain amount of electrical power at the same time. One of the most important aspects in the operation of MFCs is the formation of biofilms on the anode. Here, we report the characterization of different carbon electrodes and biofilm using a rapid and easy methodology for the growth of biofilms. The biofilms were developed and generated a voltage in less than 4 days, obtaining a maximum of 0.3 V in the cells. Scanning electron microscopy images revealed that growth of the biofilm was only on the surface of the electrode, and consequently both carbon cloth Electrochem and carbon cloth Roe materials showed a greater quantity of volatile solids on the surface of the anode and power density. The results suggested that the best support was carbon cloth Electrochem because it generated a power density of 13.4 mW/m(2) and required only a few hours for the formation of the biofilm.

30 nm T-gate enhancement-mode InAlN/AlN/GaN HEMT on SiC substrates for future high power RF applications

NASA Astrophysics Data System (ADS)

Murugapandiyan, P.; Ravimaran, S.; William, J.

2017-08-01

The DC and RF performance of 30 nm gate length enhancement mode (E-mode) InAlN/AlN/GaN high electron mobility transistor (HEMT) on SiC substrate with heavily doped source and drain region have been investigated using the Synopsys TCAD tool. The proposed device has the features of a recessed T-gate structure, InGaN back barrier and Al2O3 passivated device surface. The proposed HEMT exhibits a maximum drain current density of 2.1 A/mm, transconductance {g}{{m}} of 1050 mS/mm, current gain cut-off frequency {f}{{t}} of 350 GHz and power gain cut-off frequency {f}\\max of 340 GHz. At room temperature the measured carrier mobility (μ), sheet charge carrier density ({n}{{s}}) and breakdown voltage are 1580 cm2/(V \\cdot s), 1.9× {10}13 {{cm}}-2, and 10.7 V respectively. The superlatives of the proposed HEMTs are bewitching competitor or future sub-millimeter wave high power RF VLSI circuit applications.

Facilitated charge transport in ternary interconnected electrodes for flexible supercapacitors with excellent power characteristics.

PubMed

Chen, Wanjun; He, Yongmin; Li, Xiaodong; Zhou, Jinyuan; Zhang, Zhenxing; Zhao, Changhui; Gong, Chengshi; Li, Shuankui; Pan, Xiaojun; Xie, Erqing

2013-12-07

Flexible and high performance supercapacitors are very critical in modern society. In order to develop the flexible supercapacitors with high power density, free-standing and flexible three-dimensional graphene/carbon nanotubes/MnO2 (3DG/CNTs/MnO2) composite electrodes with interconnected ternary 3D structures were fabricated, and the fast electron and ion transport channels were effectively constructed in the rationally designed electrodes. Consequently, the obtained 3DG/CNTs/MnO2 composite electrodes exhibit superior specific capacitance and rate capability compared to 3DG/MnO2 electrodes. Furthermore, the 3DG/CNTs/MnO2 based asymmetric supercapacitor demonstrates the maximum energy and power densities of 33.71 W h kg(-1) and up to 22,727.3 W kg(-1), respectively. Moreover, the asymmetric supercapacitor exhibits excellent cycling stability with 95.3% of the specific capacitance maintained after 1000 cycle tests. Our proposed synthesis strategy to construct the novel ternary 3D structured electrodes can be efficiently applied to other high performance energy storage/conversion systems.

Polydopamine as a new modification material to accelerate startup and promote anode performance in microbial fuel cells

NASA Astrophysics Data System (ADS)

Du, Qing; An, Jingkun; Li, Junhui; Zhou, Lean; Li, Nan; Wang, Xin

2017-03-01

The bacterial anode material is important to the performance of microbial fuel cells (MFCs) because its characteristics affect the biofilm formation and extracellular electron transfer. Here we find that a superhydrophilic semiconductor, polydopamine (PDA), is an effective modification material for the anode to accelerate startup and improve power density. When the activated carbon anode is added with 50% (wt.) PDA, the startup time is 14% shorter than the control (from 88 h to 76 h), with a 31% increase in maximum power density from 613 ± 9 to 803 ± 6 mW m-2, and the Columbic efficiency increases from 19% to 48%. These can be primarily attributed to the abundant functional groups (such as amino group, and catechol functions) introduced by PDA that improve hydrophilicity and extracellular electron transfer. PDA also increases proportions of Proteobacteria and Firmicutes families, indicating that PDA has a selective effect on anode microbial community. Our findings provide a new approach to accelerate anode biofilm formation and enhance MFC power output by modification of biocompatible PDA.

Power output of microbial fuel cell emphasizing interaction of anodic binder with bacteria

NASA Astrophysics Data System (ADS)

Li, Hongying; Liao, Bo; Xiong, Juan; Zhou, Xingwang; Zhi, Huozhen; Liu, Xiang; Li, Xiaoping; Li, Weishan

2018-03-01

Electrochemically active biofilm is necessary for the electron transfer between bacteria and anodic electrode in microbial fuel cells and selecting the type of anodic electrode material that favours formation of electrochemically active biofilm is crucial for the microbial fuel cell operation. We report a new finding that the interaction of anodic binder with bacteria plays more important role than its hydrophilicity for forming an electrochemically active biofilm, which is emphasized by applying poly(bisphenol A-co-epichorohydrin) as an anodic binder of the microbial fuel cell based on carbon nanotubes as anodic electrode and Escherichia coli as bacterium. The physical characterizations and electrochemical measurements demonstrate that poly(bisphenol A-co-epichorohydrin) exhibits a strong interaction with bacteria and thus provides the microbial fuel cell with excellent power density output. The MFC using poly(bisphenol A-co-epichorohydrin) reaches a maximum power density output of 3.8 W m-2. This value is larger than that of the MFCs using polytetrafluoroethylene that has poorer hydrophilicity, or polyvinyl alcohol that has better hydrophilicity but exhibits weaker interaction with bacteria than poly(bisphenol A-co-epichorohydrin).

Gravitational potential energy of the earth: A spherical harmonic approach

NASA Technical Reports Server (NTRS)

Rubincam, D. P.

1977-01-01

A spherical harmonic equation for the gravitational potential energy of the earth is derived for an arbitrary density distribution by conceptually bringing in mass-elements from infinity and building up the earth shell upon spherical shell. The zeroth degree term in the spherical harmonic equation agrees with the usual expression for the energy of a radial density distribution. The second degree terms give a maximum nonhydrostatic energy in the mantle and crust of -2.77 x 10 to the twenty-ninth power ergs, an order of magnitude. If the earth is assumed to be a homogeneous viscous oblate spheroid relaxing to an equilibrium shape, then a lower limit to the mantle viscosity of 1.3 x 10 to the twentieth power poises is found by assuming the total geothermal flux is due to viscous dissipation. If the nonequilibrium figure is dynamically maintained by the earth acting as a heat engine at one per cent efficiency, then the viscosity is ten to the twenty second power poises, a number preferred by some as the viscosity of the mantle.

Comparing methods to estimate Reineke’s maximum size-density relationship species boundary line slope

Treesearch

Curtis L. VanderSchaaf; Harold E. Burkhart

2010-01-01

Maximum size-density relationships (MSDR) provide natural resource managers useful information about the relationship between tree density and average tree size. Obtaining a valid estimate of how maximum tree density changes as average tree size changes is necessary to accurately describe these relationships. This paper examines three methods to estimate the slope of...

Metal Amorphous Nanocomposite Soft Magnetic Material-Enabled High Power Density, Rare Earth Free Rotational Machines [Metal Amorphous Nanocomposite (MANC) Soft Magnetic Material (SMM) Enabled High Power Density, Rare Earth Free Rotational Machines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simizu, Satoru; Ohodnicki, Paul R.; McHenry, Michael E.

Metal amorphous nanocomposites (MANCs) are promising soft magnetic materials (SMMs) for power electronic applications offering low power loss at high frequency and maintaining a relatively high flux density. While applications in certain motor designs have been recently modeled, their widespread application awaits scaled manufacturing of MANC materials and proliferation of new higher speed motor designs. A hybrid motor design based on permanent magnets and doubly salient stator and rotor is reported here to develop a compact (a factor of 10 smaller than currently possible in Si steels), high-speed (>1 kHz, electrical), high-power (>2.5 kW) motor by incorporating low loss (<10more » W/kg at 1 kHz) MANCs such as recently reported Fe-Ni-based alloys. A feature of this motor design is flux focusing from the permanent magnet allowing use of lower energy permanent magnet chosen from among non-rare earth containing compositions and attractive due to constraints posed by rare earth criticality. A 2-D finite element analysis model reported here indicates that a 2.5 kW hybrid motor may be built with a permanent magnet with a 0.4 T remanence at a rotor speed of 6000 rpm. At a magnetic switching frequency of 1.4 kHz, the core loss may be limited to <3 W by selecting an appropriate MANC SMM. The projected efficiency exceeds 96% not including power loss in the controller. Under full load conditions, the flux density distributions for the SMM stay predominantly <1.3 T, the saturation magnetization of optimized FeNi-based MANC alloys. As a result, the maximum demagnetizing field in the permanent magnet is less than 2.2 × 10 5 A/m sustainable, for example, with a high-grade hard ferrite magnet.« less

Metal Amorphous Nanocomposite Soft Magnetic Material-Enabled High Power Density, Rare Earth Free Rotational Machines [Metal Amorphous Nanocomposite (MANC) Soft Magnetic Material (SMM) Enabled High Power Density, Rare Earth Free Rotational Machines

DOE PAGES

Simizu, Satoru; Ohodnicki, Paul R.; McHenry, Michael E.

2018-02-27

Metal amorphous nanocomposites (MANCs) are promising soft magnetic materials (SMMs) for power electronic applications offering low power loss at high frequency and maintaining a relatively high flux density. While applications in certain motor designs have been recently modeled, their widespread application awaits scaled manufacturing of MANC materials and proliferation of new higher speed motor designs. A hybrid motor design based on permanent magnets and doubly salient stator and rotor is reported here to develop a compact (a factor of 10 smaller than currently possible in Si steels), high-speed (>1 kHz, electrical), high-power (>2.5 kW) motor by incorporating low loss (<10more » W/kg at 1 kHz) MANCs such as recently reported Fe-Ni-based alloys. A feature of this motor design is flux focusing from the permanent magnet allowing use of lower energy permanent magnet chosen from among non-rare earth containing compositions and attractive due to constraints posed by rare earth criticality. A 2-D finite element analysis model reported here indicates that a 2.5 kW hybrid motor may be built with a permanent magnet with a 0.4 T remanence at a rotor speed of 6000 rpm. At a magnetic switching frequency of 1.4 kHz, the core loss may be limited to <3 W by selecting an appropriate MANC SMM. The projected efficiency exceeds 96% not including power loss in the controller. Under full load conditions, the flux density distributions for the SMM stay predominantly <1.3 T, the saturation magnetization of optimized FeNi-based MANC alloys. As a result, the maximum demagnetizing field in the permanent magnet is less than 2.2 × 10 5 A/m sustainable, for example, with a high-grade hard ferrite magnet.« less

A low-frequency MEMS piezoelectric energy harvester with a rectangular hole based on bulk PZT film

NASA Astrophysics Data System (ADS)

Tian, Yingwei; Li, Guimiao; Yi, Zhiran; Liu, Jingquan; Yang, Bin

2018-06-01

This paper presents a high performance piezoelectric energy harvester (PEH) with a rectangular hole to work at low-frequency. This PEH used thinned bulk PZT film on flexible phosphor bronze, and its structure included piezoelectric layer, supporting layer and proof mass to reduce the resonant frequency of the device. Here, thinned bulk PZT thick film was used as piezoelectric layer due to its high piezoelectric coefficient. A Phosphor bronze was deployed as supporting layer because it had better flexibility compared to silicon and could work under high acceleration ambient with good durability. The maximum open-circuit voltage of the PEH was 15.7 V at low resonant frequency of 34.3 Hz when the input vibration acceleration was 1.5 g (g = 9.81 m/s2). Moreover, the maximum output power, the output power density and the actually current at the same acceleration were 216.66 μW, 1713.58 μW/cm3 and 170 μA, respectively, when the optimal matched resistance of 60 kΩ was connected. The fabricated PEH scavenged the vibration energy of the vacuum compression pump and generated the maximum output voltage of 1.19 V.

Development of advanced polymer nanocomposite capacitors

NASA Astrophysics Data System (ADS)

Mendoza, Miguel

The current development of modern electronics has driven the need for new series of energy storage devices with higher energy density and faster charge/discharge rate. Batteries and capacitors are two of the most widely used energy storage devices. Compared with batteries, capacitors have higher power density and significant higher charge/discharge rate. Therefore, high energy density capacitors play a significant role in modern electronic devices, power applications, space flight technologies, hybrid electric vehicles, portable defibrillators, and pulse power applications. Dielectric film capacitors represent an exceptional alternative for developing high energy density capacitors due to their high dielectric constants, outstanding breakdown voltages, and flexibility. The implementation of high aspect ratio dielectric inclusions such as nanowires into polymer capacitors could lead to further enhancement of its energy density. Therefore, this research effort is focused on the development of a new series of dielectric capacitors composed of nanowire reinforced polymer matrix composites. This concept of nanocomposite capacitors combines the extraordinary physical and chemical properties of the one-dimension (1D) nanoceramics and high dielectric strength of polymer matrices, leading to a capacitor with improved dielectric properties and energy density. Lead-free sodium niobate (NaNbO3) and lead-containing lead magnesium niobate-lead titanate (0.65PMN-0.35PT) nanowires were synthesized following hydrothermal and sol-gel approaches, respectively. The as-prepared nanowires were mixed with a polyvinylidene fluoride (PVDF) matrix using solution-casting method for nanocomposites fabrication. The dielectric constants and breakdown voltages of the NaNbO3/PVDF and 0.65PMN-0.35PT/PVDF nanocomposites were measured under different frequency ranges and temperatures in order to determine their maximum energy (J/cm3) and specific (J/g) densities. The electrical properties of the synthesized nanoceramics were compared with commercially available barium titanate (BaTiO3) and lead zirconate titanate Pb(ZrxTi1-x)O3 powders embedded into a PVDF matrix. The resulting dielectric film capacitors represent an excellent alternative energy storage device for future high energy density applications.

Tolerant chalcogenide cathodes of membraneless micro fuel cells.

PubMed

Gago, Aldo Saul; Gochi-Ponce, Yadira; Feng, Yong-Jun; Esquivel, Juan Pablo; Sabaté, Neus; Santander, Joaquin; Alonso-Vante, Nicolas

2012-08-01

The most critical issues to overcome in micro direct methanol fuel cells (μDMFCs) are the lack of tolerance of the platinum cathode and fuel crossover through the polymer membrane. Thus, two novel tolerant cathodes of a membraneless microlaminar-flow fuel cell (μLFFC), Pt(x)S(y) and CoSe(2), were developed. The multichannel structure of the system was microfabricated in SU-8 polymer. A commercial platinum cathode served for comparison. When using 5 M CH(3)OH as the fuel, maximum power densities of 6.5, 4, and 0.23 mW cm(-2) were achieved for the μLFFC with Pt, Pt(x)S(y), and CoSe(2) cathodes, respectively. The Pt(x)S(y) cathode outperformed Pt in the same fuel cell when using CH(3)OH at concentrations above 10 M. In a situation where fuel crossover is 100 %, that is, mixing the fuel with the reactant, the maximum power density of the micro fuel cell with Pt decreased by 80 %. However, for Pt(x)S(y) this decrease corresponded to 35 % and for CoSe(2) there was no change in performance. This result is the consequence of the high tolerance of the chalcogenide-based cathodes. When using 10 M HCOOH and a palladium-based anode, the μLFFC with a CoSe(2) cathode achieved a maxiumum power density of 1.04 mW cm(-2). This micro fuel cell does not contain either Nafion membrane or platinum. We report, for the first time, the evaluation of Pt(x)S(y)- and CoSe(2)-based cathodes in membraneless micro fuel cells. The results suggest the development of a novel system that is not size restricted and its operation is mainly based on the selectivity of its electrodes. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Removal of pollutants with determination of power consumption from landfill leachate wastewater using an electrocoagulation process: optimization using response surface methodology (RSM)

NASA Astrophysics Data System (ADS)

Asaithambi, Perumal; Beyene, Dejene; Aziz, Abdul Raman Abdul; Alemayehu, Esayas

2018-05-01

Treatment of landfill leachate wastewater by electrocoagulation process using an aluminium electrode was investigated in a batch electrochemical cell reactor. Response surface methodology based on central composite design was used to optimize the operating parameters for the removal of % color and % total organic carbon (TOC) together with power consumption from landfill leachate. Effects of three important independent parameters such as current density ( X 1), inter-electrode distance ( X 2) and solution pH ( X 3) of the landfill leachate sample on the % color and % TOC removal with power consumption were investigated. A quadratic model was used to predict the % color and % TOC removal with power consumption in different experimental conditions. The significance of each independent variable was calculated by analysis of variance. In order to achieve the maximum % color and % TOC removal with minimum of power consumption, the optimum conditions were about current density ( X 1)—5.25 A/dm2, inter-electrode distance ( X 2)—1 cm and initial solution of effluent pH ( X 3)—7.83, with the yield of color removal of 74.57%, and TOC removal of 51.75% with the power consumption of 14.80 kWh/m3. Electrocoagulation process could be applied to remove pollutants from industrial effluents and wastewater.

Thermodynamic and energy efficiency analysis of power generation from natural salinity gradients by pressure retarded osmosis.

PubMed

Yip, Ngai Yin; Elimelech, Menachem

2012-05-01

The Gibbs free energy of mixing dissipated when fresh river water flows into the sea can be harnessed for sustainable power generation. Pressure retarded osmosis (PRO) is one of the methods proposed to generate power from natural salinity gradients. In this study, we carry out a thermodynamic and energy efficiency analysis of PRO work extraction. First, we present a reversible thermodynamic model for PRO and verify that the theoretical maximum extractable work in a reversible PRO process is identical to the Gibbs free energy of mixing. Work extraction in an irreversible constant-pressure PRO process is then examined. We derive an expression for the maximum extractable work in a constant-pressure PRO process and show that it is less than the ideal work (i.e., Gibbs free energy of mixing) due to inefficiencies intrinsic to the process. These inherent inefficiencies are attributed to (i) frictional losses required to overcome hydraulic resistance and drive water permeation and (ii) unutilized energy due to the discontinuation of water permeation when the osmotic pressure difference becomes equal to the applied hydraulic pressure. The highest extractable work in constant-pressure PRO with a seawater draw solution and river water feed solution is 0.75 kWh/m(3) while the free energy of mixing is 0.81 kWh/m(3)-a thermodynamic extraction efficiency of 91.1%. Our analysis further reveals that the operational objective to achieve high power density in a practical PRO process is inconsistent with the goal of maximum energy extraction. This study demonstrates thermodynamic and energetic approaches for PRO and offers insights on actual energy accessible for utilization in PRO power generation through salinity gradients. © 2012 American Chemical Society

Quiet-Time Suprathermal (˜0.1 - 200 keV) Electrons in the Solar Wind

NASA Astrophysics Data System (ADS)

Wang, Linghua; Yang, Liu; Tao, Jiawei; Zong, Qiugang; Li, Gang; Wimmer-Schweingruber, Robert; He, Jiansen; Tu, Chuanyi; Bale, Stuart

2017-04-01

We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-200 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. The observed energy spectrum of both (beaming) strahl and (isotropic) halo electrons at ˜0.1-1.5 keV generally fits to a Kappa distribution function with an index κ and effective temperature Teff, while the observed energy spectrum of nearly isotropic superhalo electrons at ˜20-200 keV generally fits to a power-law function, J ˜ E-β. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl density and halo density. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. For the superhalo population, the spectral index β ranges from ˜1.6 to ˜3.7 and the integrated density nsup ranges from 10-8 cm-3 to 10-5 cm-3, with no clear association with the sunspot number. In solar cycle 23 (24), the distribution of β has a broad maximum between 2.4 and 2.8 (2.0 and 2.4). All the strahl, halo and superhalo populations show no obvious correlation with the solar wind core population. These results reflect the nature of the generation of solar wind suprathermal electrons.

Propane spectral resolution enhancement by the maximum entropy method

NASA Technical Reports Server (NTRS)

Bonavito, N. L.; Stewart, K. P.; Hurley, E. J.; Yeh, K. C.; Inguva, R.

1990-01-01

The Burg algorithm for maximum entropy power spectral density estimation is applied to a time series of data obtained from a Michelson interferometer and compared with a standard FFT estimate for resolution capability. The propane transmittance spectrum was estimated by use of the FFT with a 2 to the 18th data sample interferogram, giving a maximum unapodized resolution of 0.06/cm. This estimate was then interpolated by zero filling an additional 2 to the 18th points, and the final resolution was taken to be 0.06/cm. Comparison of the maximum entropy method (MEM) estimate with the FFT was made over a 45/cm region of the spectrum for several increasing record lengths of interferogram data beginning at 2 to the 10th. It is found that over this region the MEM estimate with 2 to the 16th data samples is in close agreement with the FFT estimate using 2 to the 18th samples.

Regimes of an atmospheric pressure nanosecond repetitively pulsed discharge for methane partial oxidation

NASA Astrophysics Data System (ADS)

Maqueo, P. D. G.; Maier, M.; Evans, M. D. G.; Coulombe, S.; Bergthorson, J. M.

2018-04-01

The operation of a nanosecond repetitively pulsed discharge for partial oxidation of CH4 is characterized at atmospheric pressure and room temperature. Two regimes are observed: diffuse and filamentary. The first is a low power regime, characterized by low rotational temperatures around 400 K. The second is much more energetic with rotational temperatures close to 600 K. Both have vibrational temperatures of at least 10 times their rotational temperatures. The average electron number density was determined to be 8.9×1015 and 4.0×1017 cm-3, respectively, showing an increase in the ionization fraction in the more powerful filamentary regime. Results of CH4 conversion to H2, CO, CO2 and C2H6 are presented for the filamentary regime, while the diffuse regime shows no measurable conversion ability. As expected, oxidative mixtures show higher conversion ability than pure CH4. A maximum conversion efficiency of 26.3% and a maximum energy efficiency of 19.7% were reached for the oxidative mixtures.

Effect of distribution, interface property and density of hydrogel-embedded vertically aligned carbon nanotube arrays on the properties of a flexible solid state supercapacitor

NASA Astrophysics Data System (ADS)

Zhu, Qi; Yuan, Xietao; Zhu, Yihao; Ni, Jiangfeng; Zhang, Xiaohua; Yang, Zhaohui

2018-05-01

In this paper we fabricate a robust flexible solid-state supercapacitor (FSC) device by embedding a conductive poly(vinyl alcohol) hydrogel into aligned carbon nanotube (CNT) arrays. We carefully investigate the effect of distribution, interface properties and densification of CNTs in the gel matrix on the electrochemical properties of an FSC. The total electrochemical capacitance of the device is measured to be 227 mF cm‑3 with a maximum energy density of 0.02 mWh cm‑3, which is dramatically enhanced compared with a similar device composed of non-parallel CNTs. Additionally, controllable in situ electrochemical oxidation greatly improved the compatibility between the hydrophobic CNTs and the hydrophilic hydrogel, which decreased the resistance of the device and introduced extra pseudocapacitance. After such oxidation treatment the energy storage ability further doubled to 430 mF cm‑3 with a maximum energy density of 0.04 mWh cm‑3 . The FSCs based on densified CNT arrays exhibited a much higher volumetric capacitance of 1140 mF cm‑3 and a larger energy density of 0.1 mWh cm‑3, with a large power density of 14 mW cm‑3. All devices show excellent stability of capacitance after at least 10 000 charge–discharge cycles with a loss of less than 2%. These easy-to-assemble hybrid arrays thus potentially provide a new method for manufacturing wearable devices and implantable medical devices.

Effect of distribution, interface property and density of hydrogel-embedded vertically aligned carbon nanotube arrays on the properties of a flexible solid state supercapacitor.

PubMed

Zhu, Qi; Yuan, Xietao; Zhu, Yihao; Ni, Jiangfeng; Zhang, Xiaohua; Yang, Zhaohui

2018-05-11

In this paper we fabricate a robust flexible solid-state supercapacitor (FSC) device by embedding a conductive poly(vinyl alcohol) hydrogel into aligned carbon nanotube (CNT) arrays. We carefully investigate the effect of distribution, interface properties and densification of CNTs in the gel matrix on the electrochemical properties of an FSC. The total electrochemical capacitance of the device is measured to be 227 mF cm -3 with a maximum energy density of 0.02 mWh cm -3 , which is dramatically enhanced compared with a similar device composed of non-parallel CNTs. Additionally, controllable in situ electrochemical oxidation greatly improved the compatibility between the hydrophobic CNTs and the hydrophilic hydrogel, which decreased the resistance of the device and introduced extra pseudocapacitance. After such oxidation treatment the energy storage ability further doubled to 430 mF cm -3 with a maximum energy density of 0.04 mWh cm -3 . The FSCs based on densified CNT arrays exhibited a much higher volumetric capacitance of 1140 mF cm -3 and a larger energy density of 0.1 mWh cm -3 , with a large power density of 14 mW cm -3 . All devices show excellent stability of capacitance after at least 10 000 charge-discharge cycles with a loss of less than 2%. These easy-to-assemble hybrid arrays thus potentially provide a new method for manufacturing wearable devices and implantable medical devices.

Electricity generation through a photo sediment microbial fuel cell using algae at the cathode.

PubMed

Neethu, B; Ghangrekar, M M

2017-12-01

Sediment microbial fuel cells (SMFCs) are bio-electrochemical devices generating electricity from redox gradients occurring across the sediment-water interface. Sediment microbial carbon-capture cell (SMCC), a modified SMFC, uses algae grown in the overlying water of sediment and is considered as a promising system for power generation along with algal cultivation. In this study, the performance of SMCC and SMFC was evaluated in terms of power generation, dissolved oxygen variations, sediment organic matter removal and algal growth. SMCC gave a maximum power density of 22.19 mW/m 2 , which was 3.65 times higher than the SMFC operated under similar conditions. Sediment organic matter removal efficiencies of 77.6 ± 2.1% and 61.0 ± 1.3% were obtained in SMCC and SMFC, respectively. With presence of algae at the cathode, a maximum chemical oxygen demand and total nitrogen removal efficiencies of 63.3 ± 2.3% (8th day) and 81.6 ± 1.2% (10th day), respectively, were observed. The system appears to be favorable from a resources utilization perspective as it does not depend on external aeration or membranes and utilizes algae and organic matter present in sediment for power generation. Thus, SMCC has proven its applicability for installation in an existing oxidation pond for sediment remediation, algae growth, carbon conversion and power generation, simultaneously.

A real-time laser feedback control method for the three-wave laser source used in the polarimeter-interferometer diagnostic on Joint-TEXT tokamak

NASA Astrophysics Data System (ADS)

Xiong, C. Y.; Chen, J.; Li, Q.; Liu, Y.; Gao, L.

2014-12-01

A three-wave laser polarimeter-interferometer, equipped with three independent far-infrared laser sources, has been developed on Joint-TEXT (J-TEXT) tokamak. The diagnostic system is capable of high-resolution temporal and phase measurement of the Faraday angle and line-integrated density. However, for long-term operation (>10 min), the free-running lasers can lead to large drifts of the intermediate frequencies (˜100-˜500 kHz/10 min) and decay of laser power (˜10%-˜20%/10 min), which act to degrade diagnostic performance. In addition, these effects lead to increased maintenance cost and limit measurement applicability to long pulse/steady state experiments. To solve this problem, a real-time feedback control method of the laser source is proposed. By accurately controlling the length of each laser cavity, both the intermediate frequencies and laser power can be simultaneously controlled: the intermediate frequencies are controlled according to the pre-set values, while the laser powers are maintained at an optimal level. Based on this approach, a real-time feedback control system has been developed and applied on J-TEXT polarimeter-interferometer. Long-term (theoretically no time limit) feedback of intermediate frequencies (maximum change less than ±12 kHz) and laser powers (maximum relative power change less than ±7%) has been successfully achieved.

A real-time laser feedback control method for the three-wave laser source used in the polarimeter-interferometer diagnostic on Joint-TEXT tokamak.

PubMed

Xiong, C Y; Chen, J; Li, Q; Liu, Y; Gao, L

2014-12-01

A three-wave laser polarimeter-interferometer, equipped with three independent far-infrared laser sources, has been developed on Joint-TEXT (J-TEXT) tokamak. The diagnostic system is capable of high-resolution temporal and phase measurement of the Faraday angle and line-integrated density. However, for long-term operation (>10 min), the free-running lasers can lead to large drifts of the intermediate frequencies (∼100-∼500 kHz/10 min) and decay of laser power (∼10%-∼20%/10 min), which act to degrade diagnostic performance. In addition, these effects lead to increased maintenance cost and limit measurement applicability to long pulse/steady state experiments. To solve this problem, a real-time feedback control method of the laser source is proposed. By accurately controlling the length of each laser cavity, both the intermediate frequencies and laser power can be simultaneously controlled: the intermediate frequencies are controlled according to the pre-set values, while the laser powers are maintained at an optimal level. Based on this approach, a real-time feedback control system has been developed and applied on J-TEXT polarimeter-interferometer. Long-term (theoretically no time limit) feedback of intermediate frequencies (maximum change less than ±12 kHz) and laser powers (maximum relative power change less than ±7%) has been successfully achieved.

Membraneless glucose/oxygen enzymatic fuel cells using redox hydrogel films containing carbon nanotubes.

PubMed

MacAodha, Domhnall; Ó Conghaile, Peter; Egan, Brenda; Kavanagh, Paul; Leech, Dónal

2013-07-22

Co-immobilisation of three separate multiple blue copper oxygenases, a Myceliophthora thermophila laccase, a Streptomyces coelicolor laccase and a Myrothecium verrucaria bilirubin oxidase, with an [Os(2,2'-bipyridine)2 (polyvinylimidazole)10Cl](+/2+) redox polymer in the presence of multi-walled carbon nanotubes (MWCNTs) on graphite electrodes results in enzyme electrodes that produce current densities above 0.5 mA cm(-2) for oxygen reduction at an applied potential of 0 V versus Ag/AgCl. Fully enzymatic membraneless fuel cells are assembled with the oxygen-reducing enzyme electrodes connected to glucose-oxidising anodes based on co-immobilisation of glucose oxidase or a flavin adenine dinucleotide-dependent glucose dehydrogenase with an [Os(4,4'-dimethyl-2,2'-bipyridine)2(polyvinylimidazole)10Cl](+/2+) redox polymer in the presence of MWCNTs on graphite electrodes. These fuel cells can produce power densities of up to 145 μW cm(-2) on operation in pH 7.4 phosphate buffer solution at 37 °C containing 150 mM NaCl, 5 mM glucose and 0.12 mM O2. The fuel cells based on Myceliophthora thermophila laccase enzyme electrodes produce the highest power density if combined with glucose oxidase-based anodes. Although the maximum power density of a fuel cell of glucose dehydrogenase and Myceliophthora thermophila laccase enzyme electrodes decreases from 110 μW cm(-2) in buffer to 60 μW cm(-2) on testing in artificial plasma, it provides the highest power output reported to date for a fully enzymatic glucose-oxidising, oxygen-reducing fuel cell in artificial plasma. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

ASSESSMENT OF PUBLIC EXPOSURE FORM WLANS IN THE WEST BANK-PALESTINE.

PubMed

Lahham, Adnan; Sharabati, Afifeh; ALMasri, Hussein

2017-11-01

A total of 271 measurements were conducted at 69 different sites including homes, hospitals, educational institutions and other public places to assess the exposure to radiofrequency emission from wireless local area networks (WLANs). Measurements were conducted at different distances from 40 to 10 m from the access points (APs) in real life conditions using Narda SRM-3000 selective radiation meter. Three measurements modes were considered at 1 m distance from the AP which are transmit mode, idle mode, and from the client card (laptop computer). All measurements were conducted indoor in the West Bank environment. Power density levels from WLAN systems were found to vary from 0.001 to ~1.9 μW cm-2 with an average of 0.12 μW cm-2. Maximum value found was in university environment, while the minimum was found in schools. For one measurement case where the AP was 20 cm far while transmitting large files, the measured power density reached a value of ~4.5 μW cm-2. This value is however 221 times below the general public exposure limit recommended by the International Commission on Non-Ionizing Radiation Protection, which was not exceeded in any case. Measurements of power density at 1 m around the laptop resulted in less exposure than the AP in both transmit and idle modes as well. Specific absorption rate for the head of the laptop user was estimated and found to vary from 0.1 to 2 mW/kg. The frequency distribution of measured power densities follows a log-normal distribution which is generally typical in the assessment of exposure resulting from sources of radiofrequency emissions. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Performance of a vanadium redox flow battery with tubular cell design

NASA Astrophysics Data System (ADS)

Ressel, Simon; Laube, Armin; Fischer, Simon; Chica, Antonio; Flower, Thomas; Struckmann, Thorsten

2017-07-01

We present a vanadium redox flow battery with a tubular cell design which shall lead to a reduction of cell manufacturing costs and the realization of cell stacks with reduced shunt current losses. Charge/discharge cycling and polarization curve measurements are performed to characterize the single test cell performance. A maximum current density of 70 mAcm-2 and power density of 142 Wl-1 (per cell volume) is achieved and Ohmic overpotential is identified as the dominant portion of the total cell overpotential. Cycling displays Coulomb efficiencies of ≈95% and energy efficiencies of ≈55%. During 113 h of operation a stable Ohmic cell resistance is observed.

Rational design of octahedron and nanowire CeO2@MnO2 core-shell heterostructures with outstanding rate capability for asymmetric supercapacitors.

PubMed

Zhu, Shi Jin; Jia, Jia Qi; Wang, Tian; Zhao, Dong; Yang, Jian; Dong, Fan; Shang, Zheng Guo; Zhang, Yu Xin

2015-10-14

Two kinds of novel CeO2@MnO2 nanostructures have been synthesized via a self-assembly strategy. The as-prepared CeO2 nanowire@MnO2 nanostructures exhibited unprecedented pseudocapacitance performance (255 F g(-1)) with outstanding rate capability. A new mechanism based on the synergistic effect between CeO2 and MnO2 was proposed to interpret this phenomenon. When assembled as an asymmetric supercapacitor, an energy density of 27.5 W h kg(-1) with a maximum power density of 1.6 kW kg(-1) was achieved for CeO2 nanowire@MnO2 nanostructures.

Comparison of Fatigue Life Estimation Using Equivalent Linearization and Time Domain Simulation Methods

NASA Technical Reports Server (NTRS)

Mei, Chuh; Dhainaut, Jean-Michel

2000-01-01

The Monte Carlo simulation method in conjunction with the finite element large deflection modal formulation are used to estimate fatigue life of aircraft panels subjected to stationary Gaussian band-limited white-noise excitations. Ten loading cases varying from 106 dB to 160 dB OASPL with bandwidth 1024 Hz are considered. For each load case, response statistics are obtained from an ensemble of 10 response time histories. The finite element nonlinear modal procedure yields time histories, probability density functions (PDF), power spectral densities and higher statistical moments of the maximum deflection and stress/strain. The method of moments of PSD with Dirlik's approach is employed to estimate the panel fatigue life.

Development of Electrochemical Supercapacitors for EMA Applications

NASA Technical Reports Server (NTRS)

Kosek, John A.; Dunning, Thomas; LaConti, Anthony B.

1996-01-01

A limitation of the typical electrochemical capacitor is the maximum available power and energy density, and an improvement in capacitance per unit weight and volume is needed. A solid-ionomer electrochemical capacitor having a unit cell capacitance greater than 2 F/sq cm and a repeating element thickness of 6 mils has been developed. This capacitor could provide high-current pulses for electromechanical actuation (EMA). Primary project objectives were to develop high-capacitance particulates, to increase capacitor gravimetric and volumetric energy densities above baseline and to fabricate a 10-V capacitor with a repeating element thickness of 6 mils or less. Specific EMA applications were identified and capacitor weight and volume projections made.

Estimation of Reineke and Volume-Based Maximum Size-Density Lines For Shortleaf Pine

Treesearch

Thomas B. Lynch; Robert F. Wittwer; Douglas J. Stevenson

2004-01-01

Maximum size-density relationships for Reineke's stand density index as well as for a relationship based on average tree volume were fitted to data from more than a decade of annual remeasurements of plots in unthinned naturally occurring shor tleaf pine in southeaster n Oklahoma. Reineke's stand density index is based on a maximum line of the form log(N) = a...

Photonic surgery with noncoherent light

NASA Astrophysics Data System (ADS)

Feuermann, Daniel; Gordon, Jeffrey M.; Ng, Tuck Wah

2006-03-01

Extensive photothermal surgical effects have been generated with artificial noncoherent light. Our ex vivo experiments produced the same type and extent of tissue damage ordinarily achieved with laser fiber-optic surgery, at comparable surgical efficacy, the motivation being the possibility of supplanting surgical lasers with a potentially far less expensive device. Maximum-flux optics reconstitute the immense power density at the core of an ultrabright discharge lamp inside an optical fiber the distal tip of which couples light into the organ.

Molecular-Beam-Epitaxy Program

NASA Technical Reports Server (NTRS)

Sparks, Patricia D.

1988-01-01

Molecular Beam Epitaxy (MBE) computer program developed to aid in design of single- and double-junction cascade cells made of silicon. Cascade cell has efficiency 1 or 2 percent higher than single cell, with twice the open-circuit voltage. Input parameters include doping density, diffusion lengths, thicknesses of regions, solar spectrum, absorption coefficients of silicon (data included for 101 wavelengths), and surface recombination velocities. Results include maximum power, short-circuit current, and open-circuit voltage. Program written in FORTRAN IV.

Study of poly(vinyl alcohol)/titanium oxide composite polymer membranes and their application on alkaline direct alcohol fuel cell

NASA Astrophysics Data System (ADS)

Yang, Chun-Chen; Chiu, Shwu-Jer; Lee, Kuo-Tong; Chien, Wen-Chen; Lin, Che-Tseng; Huang, Ching-An

The novel poly(vinyl alcohol)/titanium oxide (PVA/TiO 2) composite polymer membrane was prepared using a solution casting method. The characteristic properties of the PVA/TiO 2 composite polymer membrane were investigated by thermal gravimetric analysis (TGA), a scanning electron microscopy (SEM), a micro-Raman spectroscopy, a methanol permeability measurement and the AC impedance method. An alkaline direct alcohol (methanol, ethanol and isopropanol) fuel cell (DAFC), consisting of an air cathode based on MnO 2/C inks, an anode based on PtRu (1:1) black and a PVA/TiO 2 composite polymer membrane, was assembled and examined for the first time. The results indicate that the alkaline DAFC comprised of a cheap, non-perfluorinated PVA/TiO 2 composite polymer membrane shows an improved electrochemical performances. The maximum power densities of alkaline DAFCs with 4 M KOH + 2 M CH 3OH, 2 M C 2H 5OH and 2 M isopropanol (IPA) solutions at room temperature and ambient air are 9.25, 8.00, and 5.45 mW cm -2, respectively. As a result, methanol shows the highest maximum power density among three alcohols. The PVA/TiO 2 composite polymer membrane with the permeability values in the order of 10 -7 to 10 -8 cm 2 s -1 is a potential candidate for use on alkaline DAFCs.

In situ formation of graphene layers on graphite surfaces for efficient anodes of microbial fuel cells.

PubMed

Tang, Jiahuan; Chen, Shanshan; Yuan, Yong; Cai, Xixi; Zhou, Shungui

2015-09-15

Graphene can be used to improve the performance of the anode in a microbial fuel cell (MFC) due to its good biocompatibility, high electrical conductivity and large surface area. However, the chemical production and modification of the graphene on the anode are environmentally hazardous because of the use of various harmful chemicals. This study reports a novel method based on the electrochemical exfoliation of a graphite plate (GP) for the in situ formation of graphene layers on the surface of a graphite electrode. When the resultant graphene-layer-based graphite plate electrode (GL/GP) was used as an anode in an MFC, a maximum power density of 0.67 ± 0.034 W/m(2) was achieved. This value corresponds to 1.72-, 1.56- and 1.26-times the maximum power densities of the original GP, exfoliated-graphene-modified GP (EG/GP) and chemically-reduced-graphene-modified GP (rGO/GP) anodes, respectively. Electrochemical measurements revealed that the high performance of the GL/GP anode was attributable to its macroporous structure, improved electron transfer and high electrochemical capacitance. The results demonstrated that the proposed method is a facile and environmentally friendly synthesis technique for the fabrication of high-performance graphene-based electrodes for use in microbial energy harvesting. Copyright © 2015 Elsevier B.V. All rights reserved.

A screen-printed Ce 0.8Sm 0.2O 1.9 film solid oxide fuel cell with a Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ cathode

NASA Astrophysics Data System (ADS)

Zhang, Yaohui; Huang, Xiqiang; Lu, Zhe; Liu, Zhiguo; Ge, Xiaodong; Xu, Jiahuan; Xin, Xianshuang; Sha, Xueqing; Su, Wenhui

Screen-printing technology was developed to fabricate Ce 0.8Sm 0.2O 1.9 (SDC) electrolyte films onto porous NiO-SDC green anode substrates. After sintering at 1400 °C for 4 h, a gas-tight SDC film with a thickness of 12 μm was obtained. A novel cathode material of Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ was subsequently applied onto the sintered SDC electrolyte film also by screen-printing and sintered at 970 °C for 3 h to get a single cell. A fuel cell of Ni-SDC/SDC (12 μm)/Ba 0.5Sr 0.5Co 0.8Fe 0.2O 3- δ provides the maximum power densities of 1280, 1080, 670, 370, 180 and 73 mW cm -2 at 650, 600, 555, 505, 455 and 405 °C, respectively, using hydrogen as fuel and stationary air as oxidant. When dry methane was used as fuel, the maximum power densities are 876, 568, 346 and 114 mW cm -2 at 650, 600, 555 and 505 °C, respectively. The present fuel cell shows excellent performance at lowered temperatures.

Activity of platinum/carbon and palladium/carbon catalysts promoted by Ni2 P in direct ethanol fuel cells.

PubMed

Li, Guoqiang; Feng, Ligang; Chang, Jinfa; Wickman, Björn; Grönbeck, Henrik; Liu, Changpeng; Xing, Wei

2014-12-01

Ethanol is an alternative fuel for direct alcohol fuel cells, in which the electrode materials are commonly based on Pt or Pd. Owing to the excellent promotion effect of Ni2 P that was found in methanol oxidation, we extended the catalyst system of Pt or Pd modified by Ni2 P in direct ethanol fuel cells. The Ni2 P-promoted catalysts were compared to commercial catalysts as well as to reference catalysts promoted with only Ni or only P. Among the studied catalysts, Pt/C and Pd/C modified by Ni2 P (30 wt %) showed both the highest activity and stability. Upon integration into the anode of a homemade direct ethanol fuel cell, the Pt-Ni2 P/C-30 % catalyst showed a maximum power density of 21 mW cm(-2) , which is approximately two times higher than that of a commercial Pt/C catalyst. The Pd-Ni2 P/C-30 % catalyst exhibited a maximum power density of 90 mW cm(-2) . This is approximately 1.5 times higher than that of a commercial Pd/C catalyst. The discharge stability on both two catalysts was also greatly improved over a 12 h discharge operation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Resonant wave energy harvester based on dielectric elastomer generator

NASA Astrophysics Data System (ADS)

Moretti, Giacomo; Pietro Rosati Papini, Gastone; Righi, Michele; Forehand, David; Ingram, David; Vertechy, Rocco; Fontana, Marco

2018-03-01

Dielectric elastomer generators (DEGs) are a class of capacitive solid-state devices that employ highly stretchable dielectrics and conductors to convert mechanical energy into high-voltage direct-current electricity. Their promising performance in terms of convertible energy and power density has been mostly proven in quasi-static experimental tests with prescribed deformation. However, the assessment of their ability in harvesting energy from a dynamic oscillating source of mechanical energy is crucial to demonstrate their effectiveness in practical applications. This paper reports a first demonstration of a DEG system that is able to convert the oscillating energy carried by water waves into electricity. A DEG prototype is built using a commercial polyacrylate film (VHB 4905 by 3M) and an experimental campaign is conducted in a wave-flume facility, i.e. an artificial basin that makes it possible to generate programmed small-scale waves at different frequencies and amplitudes. In resonant conditions, the designed system demonstrates the delivery of a maximum of 0.87 W of electrical power output and 0.64 J energy generated per cycle, with corresponding densities per unit mass of dielectric elastomer of 197 W kg-1 and 145 J kg-1. Additionally, a notable maximum fraction of 18% of the input wave energy is converted into electricity. The presented results provide a promising demonstration of the operation and effectiveness of ocean wave energy converters based on elastic capacitive generators.

Optimized Kernel Entropy Components.

PubMed

Izquierdo-Verdiguier, Emma; Laparra, Valero; Jenssen, Robert; Gomez-Chova, Luis; Camps-Valls, Gustau

2017-06-01

This brief addresses two main issues of the standard kernel entropy component analysis (KECA) algorithm: the optimization of the kernel decomposition and the optimization of the Gaussian kernel parameter. KECA roughly reduces to a sorting of the importance of kernel eigenvectors by entropy instead of variance, as in the kernel principal components analysis. In this brief, we propose an extension of the KECA method, named optimized KECA (OKECA), that directly extracts the optimal features retaining most of the data entropy by means of compacting the information in very few features (often in just one or two). The proposed method produces features which have higher expressive power. In particular, it is based on the independent component analysis framework, and introduces an extra rotation to the eigen decomposition, which is optimized via gradient-ascent search. This maximum entropy preservation suggests that OKECA features are more efficient than KECA features for density estimation. In addition, a critical issue in both the methods is the selection of the kernel parameter, since it critically affects the resulting performance. Here, we analyze the most common kernel length-scale selection criteria. The results of both the methods are illustrated in different synthetic and real problems. Results show that OKECA returns projections with more expressive power than KECA, the most successful rule for estimating the kernel parameter is based on maximum likelihood, and OKECA is more robust to the selection of the length-scale parameter in kernel density estimation.

Improving bioelectricity generation and COD removal of sewage sludge in microbial desalination cell.

PubMed

Ebrahimi, Atieh; Yousefi Kebria, Daryoush; Darzi, Ghasem Najafpour

2018-05-01

Improving wastewater treatment process and water desalination are two important solutions for increasing the available supply of fresh water. Microbial desalination cells (MDCs) with common electrolytes display relatively low organic matter removal and high cost. In this study, sewage sludge was used as the substrate in the Microbial desalination cell (MDC) under three different initial salt concentrations (5, 20 and 35 g.L -1 ) and the maximum salt removal rates of 50.6%, 64% and 69.6% were obtained under batch condition, respectively. The MDC also produced the maximum power density of 47.1 W m -3 and the averaged chemical oxygen demand (COD) removal of 58.2 ± 0.89% when the initial COD was 6610 ± 83 mg L -1 . Employing treated sludge as catholyte enhanced COD removal and power density to 87.3% and 54.4 W m -3 , respectively, with counterbalancing pH variation in treated effluent. These promising results showed, for the first time, that the excess sewage sludge obtained from biological wastewater treatment plants could be successfully used as anolyte and catholyte in MDC, achieving organic matter biodegradation along with salt removal and energy production. In addition, using treated sludge as catholyte will improve the performance of MDC and introduce a more effective method for both sludge treatment and desalination.

Electrostatic-probe measurements of plasma parameters for two reentry flight experiments at 25000 feet per second

NASA Technical Reports Server (NTRS)

Jones, W. L., Jr.; Cross, A. E.

1972-01-01

Unique plasma diagnostic measurements at high altitudes from two geometrically similar blunt body reentry spacecraft using electrostatic probe rakes are presented. The probes measured the positive ion density profiles (shape and magnitude) during the two flights. The probe measurements were made at eight discrete points (1 cm to 7 cm) from the vehicle surface in the aft flow field of the spacecraft over the altitude range of 85.3 to 53.3 km (280,000 to 175,000 ft) with measured densities of 10 to the 8th power to 10 to the 12th power electrons/cu cm, respectively. Maximum reentry velocity for each spacecraft was approximately 7620 meters/second (25,000 ft/sec). In the first flight experiment, water was periodically injected into a flow field which was contaminated by ablation products from the spacecraft nose region. The nonablative nose of the second spacecraft thereby minimized flow field contamination. Comparisons of the probe measured density profiles with theoretical calculations are presented with discussion as to the probable cause of significant disagreement. Also discussed are the correlation of probe measurements with vehicle angle of attack motions and the good high altitude agreement between electron densities inferred from the probe measurements, VHF antenna measurements, and microwave reflectometer diagnostic measurements.

Storing Renewable Energy in the Hydrogen Cycle.

PubMed

Züttel, Andreas; Callini, Elsa; Kato, Shunsuke; Atakli, Züleyha Özlem Kocabas

2015-01-01

An energy economy based on renewable energy requires massive energy storage, approx. half of the annual energy consumption. Therefore, the production of a synthetic energy carrier, e.g. hydrogen, is necessary. The hydrogen cycle, i.e. production of hydrogen from water by renewable energy, storage and use of hydrogen in fuel cells, combustion engines or turbines is a closed cycle. Electrolysis splits water into hydrogen and oxygen and represents a mature technology in the power range up to 100 kW. However, the major technological challenge is to build electrolyzers in the power range of several MW producing high purity hydrogen with a high efficiency. After the production of hydrogen, large scale and safe hydrogen storage is required. Hydrogen is stored either as a molecule or as an atom in the case of hydrides. The maximum volumetric hydrogen density of a molecular hydrogen storage is limited to the density of liquid hydrogen. In a complex hydride the hydrogen density is limited to 20 mass% and 150 kg/m(3) which corresponds to twice the density of liquid hydrogen. Current research focuses on the investigation of new storage materials based on combinations of complex hydrides with amides and the understanding of the hydrogen sorption mechanism in order to better control the reaction for the hydrogen storage applications.

Wind energy potential assessment to estimate performance of selected wind turbine in northern coastal region of Semarang-Indonesia

NASA Astrophysics Data System (ADS)

Premono, B. S.; Tjahjana, D. D. D. P.; Hadi, S.

2017-01-01

The aims of this paper are to investigate the characteristic of the wind speed and wind energy potential in the northern coastal region of Semarang, Central Java, Indonesia. The wind data was gained from Meteorological Station of Semarang, with ten-min average time series wind data for one year period, at the height of 10 m. Weibull distribution has been used to determine the wind power density and wind energy density of the site. It was shown that the value of the two parameters, shape parameter k, and scale parameter c, were 3.37 and 5.61 m/s, respectively. The annual mean wind speed and wind speed carrying the maximum energy were 5.32 m/s and 6.45 m/s, respectively. Further, the annual energy density at the site was found at a value of 103.87 W/m2, and based on Pacific North-west Laboratory (PNL) wind power classification, at the height of 10 m, the value of annual energy density is classified into class 2. The commercial wind turbine is chosen to simulate the wind energy potential of the site. The POLARIS P25-100 is most suitable to the site. It has the capacity factor 29.79% and can produce energy 261 MWh/year.

Operation of the ORNL High Particle Flux Helicon Plasma Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goulding, R. H.; Biewer, T. M.; Caughman, J. B. O.

2011-12-23

A high power, high particle flux rf-based helicon plasma source has been constructed at ORNL and operated at power levels up to 30 kW. High-density hydrogen and helium plasmas have been produced. The source has been designed as the basis for a linear plasma materials interaction (PMI) test facility that will generate particle fluxes {Gamma}{sub p}10{sup 23} m{sup -3} s{sup -1}, and utilize additional ion and electron cyclotron heating to produce high parallel (to the magnetic field) heat fluxes of {approx}10 MW/m{sup 2}. An rf-based source for PMI research is of interest because high plasma densities are generated with nomore » internal electrodes, allowing true steady state operation with minimal impurity generation. The ORNL helicon source has a diameter of 15 cm and to-date has operated at a frequency f = 13.56 MHz, with magnetic field strength |B| in the antenna region up to {approx}0.15 T. Maximum densities of 3x10{sup 19} m{sup -3} in He and 2.5x10{sup 19} m{sup -3} in H have been achieved. Radial density profiles have been seen to be dependent on the axial |B| profile.« less

Operation of the ORNL High Particle Flux Helicon Plasma Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goulding, Richard Howell; Biewer, Theodore M; Caughman, John B

2011-01-01

A high power, high particle flux rf-based helicon plasma source has been constructed at ORNL and operated at power levels up to 30 kW. High-density hydrogen and helium plasmas have been produced. The source has been designed as the basis for a linear plasma materials interaction (PMI) test facility that will generate particle fluxes Gamma(p) > 10(23) M-3 s(-1), and utilize additional ion and electron cyclotron heating to produce high parallel (to the magnetic field) heat fluxes of similar to 10 MW/m(2). An rf-based source for PMI research is of interest because high plasma densities are generated with no internalmore » electrodes, allowing true steady state operation with minimal impurity generation. The ORNL helicon source has a diameter of 15 cm and to-date has operated at a frequency f = 13.56 MHz, with magnetic field strength vertical bar B vertical bar in the antenna region up to similar to 0.15 T. Maximum densities of 3 x 10(19) M-3 in He and 2.5 x 10(19) m(-3) in H have been achieved. Radial density profiles have been seen to be dependent on the axial vertical bar B vertical bar profile.« less

New materials for polymer electrolyte membrane fuel cell current collectors

NASA Astrophysics Data System (ADS)

Hentall, Philip L.; Lakeman, J. Barry; Mepsted, Gary O.; Adcock, Paul L.; Moore, Jon M.

Polymer Electrolyte Membrane Fuel cells for automotive applications need to have high power density, and be inexpensive and robust to compete effectively with the internal combustion engine. Development of membranes and new electrodes and catalysts have increased power significantly, but further improvements may be achieved by the use of new materials and construction techniques in the manufacture of the bipolar plates. To show this, a variety of materials have been fabricated into flow field plates, both metallic and graphitic, and single fuel cell tests were conducted to determine the performance of each material. Maximum power was obtained with materials which had lowest contact resistance and good electrical conductivity. The performance of the best material was characterised as a function of cell compression and flow field geometry.

[Electricity generation using high concentration terephthalic acid solution by microbial fuel cell].

PubMed

Ye, Ye-Jie; Song, Tian-Shun; Xu, Yuan; Chen, Ying-Wen; Zhu, She-Min; Shen, Shu-Bao

2009-04-15

The high concentration terephthalic acid (TA) solution as the substrate of microbial fuel cell (MFC) was studied to generate electricity. The open circuit voltage was 0.54 V after inoculating for 210 h with anaerobic activated sludge, which proved that TA can be the substrate of microbial fuel cell to generate electricity. The influence of pH and substrate concentration on generating electricity was studied deeply. The voltage output of external resistance (R = 1,000 Omega) was the highest when pH was 8.0. It increased as the substrate concentration increasing and tended towards a maximum value. The maximum voltage output Umax was 0.5 V and Ks was 785.2 mg/L by Monod equation regression. When the substrate concentration (according to COD) was 4000 mg/L, the maximum power density was 96.3 mW/m2, coulomb efficiency was 2.66% and COD removal rate was 80.3%.

Electricity generation from food wastes and microbial community structure in microbial fuel cells.

PubMed

Jia, Jianna; Tang, Yu; Liu, Bingfeng; Wu, Di; Ren, Nanqi; Xing, Defeng

2013-09-01

Microbial fuel cell (MFC) was studied as an alternate and a novel way to dispose food wastes (FWs) in a waste-to-energy form. Different organic loading rate obviously affected the performance of MFCs fed with FWs. The maximum power density of ~18 W/m(3) (~556 mW/m(2)) was obtained at COD of 3200±400 mg/L and the maximum coulombic efficiency (CE) was ~27.0% at COD of 4900±350 mg/L. The maximum removals of COD, total carbohydrate (TC) and total nitrogen (TN) were ~86.4%, ~95.9% and ~16.1%, respectively. Microbial community analysis using 454 pyrosequencing of 16S rRNA gene demonstrated the combination of the dominant genera of the exoelectrogenic Geobacter and fermentative Bacteroides effectively drove highly efficient and reliable MFC systems with functions of organic matters degradation and electricity generation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Efficiency droop suppression of distance-engineered surface plasmon-coupled photoluminescence in GaN-based quantum well LEDs

NASA Astrophysics Data System (ADS)

Li, Yufeng; Wang, Shuai; Su, Xilin; Tang, Weihan; Li, Qiang; Guo, Maofeng; Zhang, Ye; Zhang, Minyan; Yun, Feng; Hou, Xun

2017-11-01

Ag coated microgroove with extreme large aspect-ratio of 500:1 was fabricated on p-GaN capping layer to investigate the coupling behavior between quantum wells and surface plasmon in highly spatial resolution. Significant photoluminescence enhancement was observed when the distance between Ag film and QWs was reduced from 220 nm to about 20 nm. A maximum enhancement ratio of 18-fold was achieved at the groove bottom where the surface plasmonic coupling was considered the strongest. Such enhancement ratio was found highly affected by the excitation power density. It also shows high correlation to the internal quantum efficiency as a function of coupling effect and a maximum Purcell Factor of 1.75 was estimated at maximum coupling effect, which matches number calculated independently from the time-resolved photoluminescence measurement. With such Purcell Factor, the efficiency was greatly enhanced and the droop was significantly suppressed.

8.76 W mid-infrared supercontinuum generation in a thulium doped fiber amplifier

NASA Astrophysics Data System (ADS)

Michalska, Maria; Grzes, Pawel; Swiderski, Jacek

2018-07-01

A stable mid-infrared supercontinuum (SC) generation with a maximum average power of 8.76 W in a spectral band of 1.9-2.65 μm is reported. To broaden the bandwidth of SC, a 1.55 μm pulsed laser system delivering 1 ns pulses at a pulse repetition frequency of 500 kHz was used as a seed source for one-stage thulium-doped fiber amplifier. The power conversion efficiency for wavelengths longer than 2.4 μm and 2.5 μm was determined to be 28% and 18%, respectively, which is believed to be the most efficient power distribution towards the mid-infrared in SC sources based on Tm-doped fibers. The power spectral density of the continuum was calculated to be >13 mW/nm with a potential of further scaling-up. A long-term power stability test, showing power fluctuations <3%, proved the robustness and reliability of the developed SC source.

High Efficiency, Low Power-Consumption DFB Quantum Cascade Lasers Without Lateral Regrowth

NASA Astrophysics Data System (ADS)

Jia, Zhi-Wei; Wang, Li-Jun; Zhang, Jin-Chuan; Liu, Feng-Qi; Zhou, Yu-Hong; Wang, Dong-Bo; Jia, Xue-Feng; Zhuo, Ning; Liu, Jun-Qi; Zhai, Shen-Qiang; Wang, Zhan-Guo

2017-04-01

Very low power-consumption distributed feedback (DFB) quantum cascade lasers (QCLs) at the wavelength around 4.9 μm were fabricated by conventional process without lateral regrowth of InP:Fe or using sidewall grating. Benefitted from the optimized materials and low waveguide loss, very low threshold current density of 0.5 kA/cm2 was obtained for a device with cavity length of 2 mm. Combined with the partial-high-reflection coating, the 1-mm-long DFB QCL achieved low power-consumption continuous wave (CW) operation up to 105 °C. The CW threshold power-consumptions were 0.72 and 0.78 W at 15 and 25 °C, respectively. The maximum CW output power was over 110 mW at 15 °C and still more than 35 mW at 105 °C. At 15 °C, wall-plug efficiency of 5.5% and slope efficiency of 1.8 W/A were deduced, which were very high for low power-consumption DFB QCLs.

Self-powered fluorescence display devices based on a fast self-charging/recharging battery (Mg/Prussian blue).

PubMed

Zhang, Hui; Yu, You; Zhang, Lingling; Zhai, Yiwen; Dong, Shaojun

2016-11-01

Stimuli-responsive (such as voltage and/or light) fluorescence display systems have attracted particular attention in their promising fields of application. However, there are few examples of self-powered fluorescence display devices. Here we designed and fabricated a self-powered fluorescence display device based on a fast-charging/recharging battery. The specially designed battery was composed of a Prussian blue (PB) cathode and a magnesium metal anode with a high theoretical redox potential difference (∼2.8 V). Moreover, smartly adding a trace amount of NaClO in the electrolyte could realize oxidizing PW to PB ∼480 times faster than when oxidizing without NaClO, leading to the fast self-charging and high power density (maximum power density of 13.34 mW cm -2 , about two to three orders of magnitude larger than previous bio-fuel cells) of the Mg/PB battery. Most importantly, PB was used as not only the cathodic catalyst but also as an electrochromic material, making it possible to construct a self-powered and rechargeable electrochromic fluorescence display with only two electrodes. Besides, fluorescent [Ru(bpy) 3 ] 2+ -doped silica nanoparticles (Ru@SiO 2 ), were selected as the fluorescence resonance energy transfer (FRET) donor to match PB (FRET acceptor). To the best of our knowledge, we demonstrated a self-powered and rechargeable electrochromic fluorescence display with only two electrodes for the first time.

Achieving High Current Density of Perovskite Solar Cells by Modulating the Dominated Facets of Room-Temperature DC Magnetron Sputtered TiO2 Electron Extraction Layer.

PubMed

Huang, Aibin; Lei, Lei; Zhu, Jingting; Yu, Yu; Liu, Yan; Yang, Songwang; Bao, Shanhu; Cao, Xun; Jin, Ping

2017-01-25

The short circuit current density of perovskite solar cell (PSC) was boosted by modulating the dominated plane facets of TiO 2 electron transport layer (ETL). Under optimized condition, TiO 2 with dominant {001} facets showed (i) low incident light loss, (ii) highly smooth surface and excellent wettability for precursor solution, (iii) efficient electron extraction, and (iv) high conductivity in perovskite photovoltaic application. A current density of 24.19 mA cm -2 was achieved as a value near the maximum limit. The power conversion efficiency was improved to 17.25%, which was the record value of PSCs with DC magnetron sputtered carrier transport layer. What is more, the room-temperature process had a great significance for the cost reduction and flexible application of PSCs.

Optimal design of a vibration-based energy harvester using magnetostrictive material (MsM)

NASA Astrophysics Data System (ADS)

Hu, J.; Xu, F.; Huang, A. Q.; Yuan, F. G.

2011-01-01

In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) was designed and tested to enable the powering of a wireless sensor. In particular, the conversion efficiency, converting from magnetic to electric energy, is approximately modeled from the magnetic field induced by the beam vibration. A number of factors that affect the output power such as the number of MsM layers, coil design and load matching are analyzed and explored in the design optimization. From the measurements, the open-circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the second natural frequency 324 Hz. The AC output power is 970 µW, giving a power density of 279 µW cm - 3. The attempt to use electrical reactive components (either inductors or capacitors) to resonate the system at any frequency has also been analyzed and tested experimentally. The results showed that this approach is not feasible to optimize the power. Since the MsM device has low output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device is implemented using a discontinuous conduction mode (DCM) buck-boost converter. The DC output power after the voltage quadrupler reaches 705 µW and the corresponding power density is 202 µW cm - 3. The output power delivered to a lithium rechargeable battery is around 630 µW, independent of the load resistance.

Area-Efficient 60 GHz +18.9 dBm Power Amplifier with On-Chip Four-Way Parallel Power Combiner in 65-nm CMOS

NASA Astrophysics Data System (ADS)

Farahabadi, Payam Masoumi; Basaligheh, Ali; Saffari, Parvaneh; Moez, Kambiz

2017-06-01

This paper presents a compact 60-GHz power amplifier utilizing a four-way on-chip parallel power combiner and splitter. The proposed topology provides the capability of combining the output power of four individual power amplifier cores in a compact die area. Each power amplifier core consists of a three-stage common-source amplifier with transformer-coupled impedance matching networks. Fabricated in 65-nm CMOS process, the measured gain of the 0.19-mm2 power amplifier at 60 GHz is 18.8 and 15 dB utilizing 1.4 and 1.0 V supply. Three-decibel band width of 4 GHz and P1dB of 16.9 dBm is measured while consuming 424 mW from a 1.4-V supply. A maximum saturated output power of 18.3 dBm is measured with the 15.9% peak power added efficiency at 60 GHz. The measured insertion loss is 1.9 dB at 60 GHz. The proposed power amplifier achieves the highest power density (power/area) compared to the reported 60-GHz CMOS power amplifiers in 65 nm or older CMOS technologies.

Performance of an annular solid-oxide fuel cell micro-stack array operating in single-chamber conditions

NASA Astrophysics Data System (ADS)

Liu, Mingliang; Lü, Zhe; Wei, Bo; Huang, Xiqiang; Zhang, Yaohui; Su, Wenhui

An annular micro-stack array consisting of four fuel cells has been fabricated and operated successfully in single-chamber conditions using a nitrogen-diluted oxygen-methane mixture as the operating gas. The single cells consist of a state-of-the-art porous NiO/Y 2O 3-stabilized ZrO 2 (YSZ) anode support, a YSZ electrolyte membrane and a modified La 0.7Sr 0.3MnO 3 (LSM) cathode. The annular configuration of the array is favorable for utilizing the heating effect. The maximum power output of the annular stack decreases with increasingCH 4/O 2 ratio. Its performance increases with increasing CH 4 flow rate and decreases with increasing N 2 flow rate. The power output of the stack is ∼380 mW at CH 4/O 2 = 1 and an N 2 flow rate of 100 sccm and the average maximum power density of each cell is ∼190 mW cm -2. The average performance of each cell in the annular micro-stack array is higher than that of an additional single cell placed next to the stack.

Design and testing of a high power spacecraft thermal management system

NASA Technical Reports Server (NTRS)

Mccabe, Michael E., Jr.; Ku, Jentung; Benner, Steve

1988-01-01

The design and test results are presented of an ammonia hybrid capillary pumped loop thermal control system which could be used for heat acquisition and transport on future large space platforms and attached payloads, such as those associated with the NASA Space Station. The High Power Spacecraft Thermal Management System (HPSTM) can operate as either a passive, capillary pumped two phase thermal control system, or, when additional pressure head is required, as a mechanically pumped loop. Testing has shown that in the capillary mode, the HPSTM evaporators can acquire a total heat load of between 600 W and 24 kW, transported over 10 meters, at a maximum heat flux density of 4.3 W/sq cm. With the mechanical pump circulating the ammonia, a heat acquisition potential of 52 kW was demonstrated for 15 minutes without an evaporator failure. These results represent a significant improvement over the maximum transport capability previously displayed in other capillary systems. The HPSTM system still retains the proven capillary capabilities of heat load sharing and flow control between evaporator plates, rapid power cycling, and nonuniform heating in both the capillary and hybrid operating modes.

Fuel Pin Behavior Under the Slow Power Ramp Transients in the CABRI-2 Experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Charpenel, Jean; Lemoine, Francette; Sato, Ikken

Slow ramp-type transient-overpower tests were performed within the framework of the international CABRI-2 experimental program. The implemented power transients of {approx}1% nominal power/s correspond to a control rod withdrawal-type accident in a liquid-metal-cooled fast breeder reactor (FBR). The analysis of the tests includes the information elements derived from the hodoscope signals, which were assessed quantitatively and supported by destructive and nondestructive posttest examinations. These tests, performed with fuels of various geometries, demonstrated the high margin to failure of such FBR fuel pins within the expected power level before the emergency reactor shutdown. At the same time, these tests performed withmore » high- and low-smear-density industrial pins led to clarification of the influence of pellet design on fuel pin behavior under high overpower condition. With the high-smear-density solid fuel pellet pin of high burnup level, the retained gaseous fission products played an important role in the solid fuel swelling, leading to clad deformation and failure at a maximum heating rate of 81 kW.m{sup -1}, which is much greater than the end-of-life (EOL) linear rating of the pin. With the low smear-density annular pellet pin, an important fuel swelling takes place, leading to degradation of the fuel thermal conductivity. This effect was detected at the power level around 73 kW.m{sup -1}, which is also much higher than the EOL value of the pin. Furthermore, the absence of clad deformation, and consequently of failure even at the power level going up to 134.7 kW.m{sup -1}, confirmed the very high margin to failure. In consequence, it was clarified that gaseous fission products have significant effects on failure threshold as well as on thermal performance during overpower condition, and such effects are significantly dependent on fuel design and power operation conditions.« less

Maximum Power Training and Plyometrics for Cross-Country Running.

ERIC Educational Resources Information Center

Ebben, William P.

2001-01-01

Provides a rationale for maximum power training and plyometrics as conditioning strategies for cross-country runners, examining: an evaluation of training methods (strength training and maximum power training and plyometrics); biomechanic and velocity specificity (role in preventing injury); and practical application of maximum power training and…

Four-junction AlGaAs/GaAs laser power converter

NASA Astrophysics Data System (ADS)

Huang, Jie; Sun, Yurun; Zhao, Yongming; Yu, Shuzhen; Dong, Jianrong; Xue, Jiping; Xue, Chi; Wang, Jin; Lu, Yunqing; Ding, Yanwen

2018-04-01

Four-junction AlGaAs/GaAs laser power converters (LPCs) with n+-GaAs/p+-Al0.37Ga0.63As heterostructure tunnel junctions (TJs) have been designed and grown by metal-organic chemical vapor deposition (MOCVD) for converting the power of 808 nm lasers. A maximum conversion efficiency η c of 56.9% ± 4% is obtained for cells with an aperture of 3.14 mm2 at an input laser power of 0.2 W, while dropping to 43.3% at 1.5 W. Measured current–voltage (I–V) characteristics indicate that the performance of the LPC can be further improved by increasing the tunneling current density of TJs and optimizing the thicknesses of sub-cells to achieve current matching in LPC. Project financially supported by the National Natural Science Foundation of China (No. 61376065) and Zhongtian Technology Group Co. Ltd.

Design and analysis of a MEMS-based bifurcate-shape piezoelectric energy harvester

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yuan; Gan, Ruyi, E-mail: 2471390146@qq.com; Wan, Shalang

This paper presents a novel piezoelectric energy harvester, which is a MEMS-based device. This piezoelectric energy harvester uses a bifurcate-shape. The derivation of the mathematical modeling is based on the Euler-Bernoulli beam theory, and the main mechanical and electrical parameters of this energy harvester are analyzed and simulated. The experiment result shows that the maximum output voltage can achieve 3.3 V under an acceleration of 1 g at 292.11 Hz of frequency, and the output power can be up to 0.155 mW under the load of 0.4 MΩ. The power density is calculated as 496.79 μWmm{sup −3}. Besides that, itmore » is demonstrated efficiently at output power and voltage and adaptively in practical vibration circumstance. This energy harvester could be used for low-power electronic devices.« less

Utilizing Maximum Power Point Trackers in Parallel to Maximize the Power Output of a Solar (Photovoltaic) Array

DTIC Science & Technology

2012-12-01

photovoltaic (PV) system to use a maximum power point tracker ( MPPT ) to increase... photovoltaic (PV) system to use a maximum power point tracker ( MPPT ) to increase the power output of the solar array. Currently, most military... MPPT ) is an optimizing circuit that is used in conjunction with photovoltaic (PV) arrays to achieve the maximum delivery of power from the array

Determination of the neutral oxygen atom density in a plasma reactor loaded with metal samples

NASA Astrophysics Data System (ADS)

Mozetic, Miran; Cvelbar, Uros

2009-08-01

The density of neutral oxygen atoms was determined during processing of metal samples in a plasma reactor. The reactor was a Pyrex tube with an inner diameter of 11 cm and a length of 30 cm. Plasma was created by an inductively coupled radiofrequency generator operating at a frequency of 27.12 MHz and output power up to 500 W. The O density was measured at the edge of the glass tube with a copper fiber optics catalytic probe. The O atom density in the empty tube depended on pressure and was between 4 and 7 × 1021 m-3. The maximum O density was at a pressure of about 150 Pa, while the dissociation fraction of O2 molecules was maximal at the lowest pressure and decreased with increasing pressure. At about 300 Pa it dropped below 10%. The measurements were repeated in the chamber loaded with different metallic samples. In these cases, the density of oxygen atoms was lower than that in the empty chamber. The results were explained by a drain of O atoms caused by heterogeneous recombination on the samples.

Importance of polypyrrole in constructing 3D hierarchical carbon nanotube@MnO2 perfect core-shell nanostructures for high-performance flexible supercapacitors

NASA Astrophysics Data System (ADS)

Zhou, Jinyuan; Zhao, Hao; Mu, Xuemei; Chen, Jiayi; Zhang, Peng; Wang, Yaling; He, Yongmin; Zhang, Zhenxing; Pan, Xiaojun; Xie, Erqing

2015-08-01

This study reports the preparation of 3D hierarchical carbon nanotube (CNT) @MnO2 core-shell nanostructures under the assistance of polypyrrole (PPy). The as-prepared CNT@PPy@MnO2 core-shell structures show a perfect coating of MnO2 on each CNT and, more importantly, a robust bush-like pseudocapacitive shell to effectively increase the specific surface area and enhance the ion accessibility. As expected, a high specific capacity of 490-530 F g-1 has been achieved from CNT@PPy@MnO2 single electrodes. And about 98.5% of the capacity is retained after 1000 charge/discharge cycles at a current density of 5 A g-1. Furthermore, the assembled asymmetric CNT@PPy@MnO2//AC capacitors show the maximum energy density of 38.42 W h kg-1 (2.24 mW h cm-3) at a power density of 100 W kg-1 (5.83 mW cm-3), and they maintain 59.52% of the initial value at 10 000 W kg-1 (0.583 W cm-3). In addition, the assembled devices show high cycling stabilities (89.7% after 2000 cycles for asymmetric and 87.2% for symmetric), and a high bending stability (64.74% after 200 bending tests). This ability to obtain high energy densities at high power rates while maintaining high cycling stability demonstrates that this well-designed structure could be a promising electrode material for high-performance supercapacitors.This study reports the preparation of 3D hierarchical carbon nanotube (CNT) @MnO2 core-shell nanostructures under the assistance of polypyrrole (PPy). The as-prepared CNT@PPy@MnO2 core-shell structures show a perfect coating of MnO2 on each CNT and, more importantly, a robust bush-like pseudocapacitive shell to effectively increase the specific surface area and enhance the ion accessibility. As expected, a high specific capacity of 490-530 F g-1 has been achieved from CNT@PPy@MnO2 single electrodes. And about 98.5% of the capacity is retained after 1000 charge/discharge cycles at a current density of 5 A g-1. Furthermore, the assembled asymmetric CNT@PPy@MnO2//AC capacitors show the maximum energy density of 38.42 W h kg-1 (2.24 mW h cm-3) at a power density of 100 W kg-1 (5.83 mW cm-3), and they maintain 59.52% of the initial value at 10 000 W kg-1 (0.583 W cm-3). In addition, the assembled devices show high cycling stabilities (89.7% after 2000 cycles for asymmetric and 87.2% for symmetric), and a high bending stability (64.74% after 200 bending tests). This ability to obtain high energy densities at high power rates while maintaining high cycling stability demonstrates that this well-designed structure could be a promising electrode material for high-performance supercapacitors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03426d

Thermospheric mass density model error variance as a function of time scale

NASA Astrophysics Data System (ADS)

Emmert, J. T.; Sutton, E. K.

2017-12-01

In the increasingly crowded low-Earth orbit environment, accurate estimation of orbit prediction uncertainties is essential for collision avoidance. Poor characterization of such uncertainty can result in unnecessary and costly avoidance maneuvers (false positives) or disregard of a collision risk (false negatives). Atmospheric drag is a major source of orbit prediction uncertainty, and is particularly challenging to account for because it exerts a cumulative influence on orbital trajectories and is therefore not amenable to representation by a single uncertainty parameter. To address this challenge, we examine the variance of measured accelerometer-derived and orbit-derived mass densities with respect to predictions by thermospheric empirical models, using the data-minus-model variance as a proxy for model uncertainty. Our analysis focuses mainly on the power spectrum of the residuals, and we construct an empirical model of the variance as a function of time scale (from 1 hour to 10 years), altitude, and solar activity. We find that the power spectral density approximately follows a power-law process but with an enhancement near the 27-day solar rotation period. The residual variance increases monotonically with altitude between 250 and 550 km. There are two components to the variance dependence on solar activity: one component is 180 degrees out of phase (largest variance at solar minimum), and the other component lags 2 years behind solar maximum (largest variance in the descending phase of the solar cycle).

Extremely fine structured cathode for solid oxide fuel cells using Sr-doped LaMnO3 and Y2O3-stabilized ZrO2 nano-composite powder synthesized by spray pyrolysis

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Yamaguchi, Toshiaki; Sumi, Hirofumi; Nomura, Katsuhiro; Yamaguchi, Yuki; Fujishiro, Yoshinobu

2017-02-01

A solid oxide fuel cell (SOFC) for high power density operation was developed with a microstructure-controlled cathode using a nano-composite powder of Sr-doped LaMnO3 (LSM) and Y2O3-stabilized ZrO2 (YSZ) synthesized by spray pyrolysis. The individual LSM-YSZ nano-composite particles, formed by crystalline and amorphous nano-size LSM and YSZ particles, showed spherical morphology with uniform particle size. The use of this powder for cathode material led to an extremely fine microstructure, in which all the LSM and YSZ grains (approximately 100-200 nm) were highly dispersed and formed their own network structures. This microstructure was due to the two phase electrode structure control using the powder, namely, nano-order level in each particle and micro-order level between particles. An anode-supported SOFC with the LSM-YSZ cathode using humidified H2 as fuel and ambient air as oxidant exhibited high power densities, such as 1.29 W cm-2 under a voltage of 0.75 V and a maximum power density of 2.65 W cm-2 at 800 °C. Also, the SOFC could be stably operated for 250 h with no degradation, even at a high temperature of 800 °C.

A highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes

PubMed Central

Berber, Mohamed R.; Hafez, Inas H.; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2015-01-01

Driven by the demand for the commercialization of fuel cell (FC) technology, we describe the design and fabrication of a highly durable FC electrocatalyst based on double-polymer-coated carbon nanotubes for use in polymer electrolyte membrane fuel cells. The fabricated electrocatalyst is composed of Pt-deposited polybenzimidazole-coated carbon nanotubes, which are further coated with Nafion. By using this electrocatalyst, a high FC performance with a power density of 375 mW/cm2 (at 70 ˚C, 50% relative humidity using air (cathode)/H2(anode)) was obtained, and a remarkable durability of 500,000 accelerated potential cycles was recorded with only a 5% loss of the initial FC potential and 20% loss of the maximum power density, which were far superior properties compared to those of the membrane electrode assembly prepared using carbon black in place of the carbon nanotubes. The present study indicates that the prepared highly durable fuel cell electrocatalyst is a promising material for the next generation of PEMFCs. PMID:26594045

A highly durable fuel cell electrocatalyst based on double-polymer-coated carbon nanotubes.

PubMed

Berber, Mohamed R; Hafez, Inas H; Fujigaya, Tsuyohiko; Nakashima, Naotoshi

2015-11-23

Driven by the demand for the commercialization of fuel cell (FC) technology, we describe the design and fabrication of a highly durable FC electrocatalyst based on double-polymer-coated carbon nanotubes for use in polymer electrolyte membrane fuel cells. The fabricated electrocatalyst is composed of Pt-deposited polybenzimidazole-coated carbon nanotubes, which are further coated with Nafion. By using this electrocatalyst, a high FC performance with a power density of 375 mW/cm(2) (at 70 ˚C, 50% relative humidity using air (cathode)/H2(anode)) was obtained, and a remarkable durability of 500,000 accelerated potential cycles was recorded with only a 5% loss of the initial FC potential and 20% loss of the maximum power density, which were far superior properties compared to those of the membrane electrode assembly prepared using carbon black in place of the carbon nanotubes. The present study indicates that the prepared highly durable fuel cell electrocatalyst is a promising material for the next generation of PEMFCs.

Bioelectricity generation in continuously-fed microbial fuel cell: effects of anode electrode material and hydraulic retention time.

PubMed

Akman, Dilek; Cirik, Kevser; Ozdemir, Sebnem; Ozkaya, Bestamin; Cinar, Ozer

2013-12-01

The main aim of this study is to investigate the bioelectricity production in continuously-fed dual chambered microbial fuel cell (MFC). Initially, MFC was operated with different anode electrode material at constant hydraulic retention time (HRT) of 2d to evaluate the effect of electrode material on electricity production. Pt electrode yielded about 642 mW/m(2) power density, which was 4 times higher than that of the MFC with the mixed metal oxide titanium (Ti-TiO2). Further, MFC equipped with Pt electrode was operated at varying HRT (2-0.5d). The power density generation increased with decreasing HRT, corresponding to 1313 mW/m(2) which was maximum value obtained during this study. Additionally, decreasing HRT from 2 to 0.5d resulted in increasing effluent dissolved organic carbon (DOC) concentration from 1.92 g/L to 2.23 g/L, corresponding to DOC removal efficiencies of 46% and 38%, respectively. Copyright © 2013 Elsevier Ltd. All rights reserved.

B{sub 4}C protective coating under irradiation by QSPA-T intensive plasma fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buzhinskij, O. I.; Barsuk, V. A.; Begrambekov, L. B., E-mail: lbb@plasma.mephi.ru

The effect of the QSPA-T pulsed plasma irradiation on the crystalline boron carbide B{sub 4}C coating was examined. The duration of the rectangular plasma pulses was 0.5 ms with an interval of 5–10 min between pulses. The maximum power density in the central part of plasma stream was 1 GW/m{sup 2}. The coating thickness varied from 20 to 40 μm on different surface areas. Modification of the surface layers and transformation of the coating at elevated temperature under plasma pulse irradiation during four successive series of impulses are described. It is shown that the boron carbide coating withstood the fullmore » cycle of tests under irradiation with 100 plasma pulses with peak power density of 1GW/m{sup 2}. Constitutive surface deterioration was not detected and the boron carbide coating kept crystal structure B{sub 4}C throughout the irradiation zone at the surface depth no less 2 μm.« less

A lithographically patterned capacitor with horizontal nanowires of length 2.5 mm.

PubMed

Yan, Wenbo; Thai, Mya Le; Dutta, Rajen; Li, Xiaowei; Xing, Wendong; Penner, Reginald M

2014-04-09

A symmetrical hybrid capacitor consisting of interdigitated, horizontal nanowires is described. Each of the 750 nanowires within the capacitor is 2.5 mm in length, consisting of a gold nanowire core (40 × ≈200 nm) encapsulated within a hemicylindrical shell of δ-phase MnO2 (thickness = 60-220 nm). These Au@δ-MnO2 nanowires are patterned onto a planar glass surface using lithographically patterned nanowire electrodeposition (LPNE). A power density of 165 kW/kg and energy density of 24 Wh/kg were obtained for a typical nanowire array in which the MnO2 shell thickness was 68 ± 8 nm. Capacitors incorporating these ultralong nanowires lost ≈10% of their capacity rapidly, during the first 20 discharge cycles, and then retained 90% of their maximum capacity for the ensuing 6000 cycles. The ability of capacitors consisting of ultralong Au@δ-MnO2 nanowires to simultaneously deliver high power and high capacity with acceptable cycle life is demonstrated.

Effect of the depth base along the vertical on the electrical parameters of a vertical parallel silicon solar cell in open and short circuit

NASA Astrophysics Data System (ADS)

Sahin, Gokhan; Kerimli, Genber

2018-03-01

This article presented a modeling study of effect of the depth base initiating on vertical parallel silicon solar cell's photovoltaic conversion efficiency. After the resolution of the continuity equation of excess minority carriers, we calculated the electrical parameters such as the photocurrent density, the photovoltage, series resistance and shunt resistances, diffusion capacitance, electric power, fill factor and the photovoltaic conversion efficiency. We determined the maximum electric power, the operating point of the solar cell and photovoltaic conversion efficiency according to the depth z in the base. We showed that the photocurrent density decreases with the depth z. The photovoltage decreased when the depth base increases. Series and shunt resistances were deduced from electrical model and were influenced and the applied the depth base. The capacity decreased with the depth z of the base. We had studied the influence of the variation of the depth z on the electrical parameters in the base.

On the modulation of low-frequency quasi-periodic oscillations in black hole transients

NASA Astrophysics Data System (ADS)

Pawar, Devraj D.; Motta, Sara; Shanthi, K.; Bhattacharya, Dipankar; Belloni, Tomaso

2015-04-01

We studied the properties of the low-frequency quasi-periodic oscillations detected in a sample of six black hole candidates (XTE J1550-564, H 1743-322, XTE J1859+226, 4U 1630-47, GX 339-4, XTE J1650-500) observed by the Rossi XTE satellite. We analysed the relation between the full width at half-maximum and the frequency of all the narrow peaks detected in power density spectra where a type-C QPO is observed. Our goal was to understand the nature of the modulation of the signal by comparing the properties of different harmonic peaks in the power density spectrum. We find that for the sources in our sample the width of the fundamental and of the first harmonic are compatible with a frequency modulation, while that of the sub-harmonic is independent of frequency, possibly indicating the presence of an additional modulation in amplitude. We compare our results with those obtained earlier from GRS 1915+105 and XTE J1550-564.

Electrochemical Performance of Glucose/Oxygen Biofuel Cells Based on Carbon Nanostructures.

PubMed

Koo, Min-Hye; Das, Gautam; Yoon, Hyon Hee

2016-03-01

The electrochemical performance of glucose/oxygen biofuel cells based on carbon nanostructures was investigated in the present study. Different types of carbon nanomaterials, including multi-walled carbon nanotubes (MWCNT), functionalized MWCNT (f-MWCNT), carbon nanofibers (CNF), and functionalized CNF (f-CNF) were examined for electrode fabrications. The anode for glucose/oxygen biofuel cells were prepared by sequential coating of carbon nanomaterials, charge transfer complex (CTC), glucose oxidase (GOx) and nafion membrane. The anode was then integrated with a bilirubin oxidase-immobilized cathode for the biofuel cell test. It was found that the electrochemical performance of the enzyme electrodes was remarkably enhanced by the amalgamation of carbon nanomaterials with the CTC. The biofuel cell with anode comprising of f-CNF and the cathode with MWCNT exhibited the best electrochemical performance with a maximum power density of 210 μW/cm2 at a cell voltage of 0.44 V for 20 mM glucose concentration, which is comparable with the best power density value reported earlier.

Estimating maximum instantaneous distortion from inlet total pressure rms and PSD measurements. [Root Mean Square and Power Spectral Density methods

NASA Technical Reports Server (NTRS)

Melick, H. C., Jr.; Ybarra, A. H.; Bencze, D. P.

1975-01-01

An inexpensive method is developed to determine the extreme values of instantaneous inlet distortion. This method also provides insight into the basic mechanics of unsteady inlet flow and the associated engine reaction. The analysis is based on fundamental fluid dynamics and statistical methods to provide an understanding of the turbulent inlet flow and quantitatively relate the rms level and power spectral density (PSD) function of the measured time variant total pressure fluctuations to the strength and size of the low pressure regions. The most probable extreme value of the instantaneous distortion is then synthesized from this information in conjunction with the steady state distortion. Results of the analysis show the extreme values to be dependent upon the steady state distortion, the measured turbulence rms level and PSD function, the time on point, and the engine response characteristics. Analytical projections of instantaneous distortion are presented and compared with data obtained by a conventional, highly time correlated, 40 probe instantaneous pressure measurement system.

EFFECTS OF LASER RADIATION ON MATTER. LASER PLASMA: Temporal and thermodynamic characteristics of plasma formation

NASA Astrophysics Data System (ADS)

Ignatavichyus, M. V.; Kazakyavichyus, É.; Orshevski, G.; Danyunas, V.

1991-11-01

An investigation was made of plasma formation accompanying the interaction with aluminum, iron, and VK-6 alloy targets of nanosecond radiation from a YAG:Nd3+ laser (Emax = 50 mJ, τ = 3-8 ns). The duration of the plasma formation process depended weakly on the laser radiation parameters [the power density was varied in the range 1-3 GW/cm2, the pulse rise time in the range 2-8 ns, or the rate of rise of the power density in the range (1-8) × 108 W · cm - 2 · ns -1]. A study was made of the establishment of a local thermodynamic equilibrium in a plasma jet excited by radiation from nanosecond and picosecond (E = 30 mJ, τ = 40 ps) lasers. The maximum of the luminescence from an aluminum plasma excited by picosecond laser radiation was found to correspond to a local thermodynamic equilibrium. A local thermodynamic equilibrium could be absent in the case of excitation by nanosecond laser radiation.

[Effects of Oil Pollutants on the Performance of Marine Benthonic Microbial Fuel Cells and Its Acceleration of Degradation].

PubMed

Meng, Yao; Fu, Yu-bin; Liang, Sheng-kang; Chen, Wei; Liu, Zhao-hui

2015-08-01

Degradation of oil pollutants under the sea is slow for its oxygen-free environment which has caused long-term harm to ocean environment. This paper attempts to accelerate the degradation of the sea oil pollutants through electro catalysis by using the principle of marine benthonic microbial fuel cells (BMFCs). The influence of oil pollutants on the battery performance is innovatively explored by comparing the marine benthonic microbial fuel cells ( BMFCs-A) containing oil and oil-free microbial fuel cells (BMFCs-B). The acceleration effect of BMFCs is investigated by the comparison between the oil-degrading rate and the number of heterotrophic bacteria of the BMFCs-A and BMFCs-B on their anodes. The results show that the exchange current densities in the anode of the BMFCs-A and BMFCs-B are 1. 37 x 10(-2) A x m(-2) and 1.50 x 10(-3) A x m(-2) respectively and the maximum output power densities are 105.79 mW x m(-2) and 83.60 mW x m(-2) respectively. The exchange current densities have increased 9 times and the maximum output power density increased 1. 27 times. The anti-polarization ability of BMFCs-A is improved. The heterotrophic bacteria numbers of BMFCs-A and BMFCs-C on their anodes are (66 +/- 3.61) x 10(7) CFU x g(-1) and (7.3 +/- 2.08) x 10(7) CFU x g(-1) respectively and the former total number has increased 8 times, which accelerates the oil-degrading rate. The degrading rate of the oil in the BMFCs-A is 18.7 times higher than that in its natural conditions. The BMFCs can improve its electrochemical performance, meanwhile, the degradation of oil pollutants can also be accelerated. A new model of the marine benthonic microbial fuel cells on its acceleration of oil degradation is proposed in this article.

Behavioral Intervention, Exercise, and Nutrition Education to Improve Health and Fitness (BENEfit) in Adolescents With Mobility Impairment Due to Spinal Cord Dysfunction

PubMed Central

Liusuwan, Rungsinee Amanda; Widman, Lana M; Abresch, Richard Ted; Johnson, Allan J; McDonald, Craig M

2007-01-01

Background/Objective: Determine the effects of a nutrition education and exercise intervention on the health and fitness of adolescents with mobility impairment due to spinal cord dysfunction from myelomeningocele and spinal cord injury. Subjects participated in a 16-week intervention consisting of a behavioral approach to lifestyle change, exercise, and nutrition education to improve fitness (BENEfit) program. Participants were given a schedule of aerobic and strengthening exercises and attended nutrition education and behavior modification sessions every other week along with their parent(s). Subjects: Twenty adolescents (aged 11–18 years, mean 15.4 ± 2.2 years) with spinal cord dysfunction. Methods: Subjects were tested immediately prior to starting and upon completion of the program. Aerobic fitness was measured using a ramp protocol with an arm ergometer. Heart rate and oxygen uptake were measured. Values at anaerobic threshold and maximum oxygen uptake were recorded. Peak isokinetic arm and shoulder strength were determined with a dynamometer. Body composition was estimated with dual-energy x-ray absorptiometry. Serum chemistry included measures of cholesterol, high-density lipoprotein, low-density lipoprotein, and triglycerides. Results: Fourteen individuals completed all testing sessions. There was no significant overall change in weight, body mass index, body mass index z-scores, or serum chemistry. Overall, there was a significant increase in whole body lean tissue without a concomitant increase in whole body fat. Fitness measures revealed a significant increase in maximum power output, work efficiency as measured by the amount of power output produced aerobically, and resting oxygen uptake. Strength measurements revealed a significant increase in shoulder extension strength and a trend towards increased shoulder flexion strength. There were no significant changes in high-density lipoprotein, low-density lipoprotein, total cholesterol, or triglycerides. Conclusions: The BENEfit program shows promise as a method for improving the health and fitness of adolescents with mobility impairments who are at high risk for obesity and obesity-related health conditions. PMID:17874697

A Novel Electrophototrophic Bacterium Rhodopseudomonas palustris Strain RP2, Exhibits Hydrocarbonoclastic Potential in Anaerobic Environments

PubMed Central

Venkidusamy, Krishnaveni; Megharaj, Mallavarapu

2016-01-01

An electrophototrophic, hydrocarbonoclastic bacterium Rhodopseudomonas palustris stain RP2 was isolated from the anodic biofilms of hydrocarbon fed microbial electrochemical remediation systems (MERS). Salient properties of the strain RP2 were direct electrode respiration, dissimilatory metal oxide reduction, spore formation, anaerobic nitrate reduction, free living diazotrophy and the ability to degrade n-alkane components of petroleum hydrocarbons (PH) in anoxic, photic environments. In acetate fed microbial electrochemical cells, a maximum current density of 305 ± 10 mA/m2 (1000Ω) was generated (power density 131.65 ± 10 mW/m2) by strain RP2 with a coulombic efficiency of 46.7 ± 1.3%. Cyclic voltammetry studies showed that anaerobically grown cells of strain RP2 is electrochemically active and likely to transfer electrons extracellularly to solid electron acceptors through membrane bound compounds, however, aerobically grown cells lacked the electrochemical activity. The ability of strain RP2 to produce current (maximum current density 21 ± 3 mA/m2; power density 720 ± 7 μW/m2, 1000 Ω) using PH as a sole energy source was also examined using an initial concentration of 800 mg l-1 of diesel range hydrocarbons (C9-C36) with a concomitant removal of 47.4 ± 2.7% hydrocarbons in MERS. Here, we also report the first study that shows an initial evidence for the existence of a hydrocarbonoclastic behavior in the strain RP2 when grown in different electron accepting and illuminated conditions (anaerobic and MERS degradation). Such observations reveal the importance of photoorganotrophic growth in the utilization of hydrocarbons from contaminated environments. Identification of such novel petrochemical hydrocarbon degrading electricigens, not only expands the knowledge on the range of bacteria known for the hydrocarbon bioremediation but also shows a biotechnological potential that goes well beyond its applications to MERS. PMID:27462307

20 kHz, 25 kVA node power transformer

NASA Technical Reports Server (NTRS)

Hussey, S.

1989-01-01

The electrical and mechanical design information and the electrical and thermal testing performed on the 440-208-V rms, 20-kHz, 25-kVa prototype node transformer are summarized. The calculated efficiency of the node transformer is 99.3 percent based on core loss and copper loss test data, and its maximum calculated load regulation is 0.7 percent. The node transformer has a weight of 19.7 lb and has a power density of 0.8 lb/kW. The hot-spot temperature rise is estimated to be 33 C above the cold plate mounting base. This proof-of-concept transformer design is a viable candidate for the space station Freedom application.

High-power terahertz quantum cascade lasers with ∼0.23 W in continuous wave mode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xuemin; Shen, Changle; Jiang, Tao

2016-07-15

Terahertz quantum cascade lasers with a record output power up to ∼0.23 W in continuous wave mode were obtained. We show that the optimal 2.9-mm-long device operating at 3.11 THz has a low threshold current density of 270 A/cm{sup 2} at ∼15 K. The maximum operating temperature arrived at ∼65 K in continuous wave mode and the internal quantum efficiencies decreased from 0.53 to 0.19 for the devices with different cavity lengths. By using one convex lens with the effective focal length of 13 mm, the beam profile was collimated to be a quasi Gaussian distribution.

An analysis of quantum coherent solar photovoltaic cells

NASA Astrophysics Data System (ADS)

Kirk, A. P.

2012-02-01

A new hypothesis (Scully et al., Proc. Natl. Acad. Sci. USA 108 (2011) 15097) suggests that it is possible to break the statistical physics-based detailed balance-limiting power conversion efficiency and increase the power output of a solar photovoltaic cell by using “noise-induced quantum coherence” to increase the current. The fundamental errors of this hypothesis are explained here. As part of this analysis, we show that the maximum photogenerated current density for a practical solar cell is a function of the incident spectrum, sunlight concentration factor, and solar cell energy bandgap and thus the presence of quantum coherence is irrelevant as it is unable to lead to increased current output from a solar cell.

Emergent traffic jams

NASA Astrophysics Data System (ADS)

Nagel, Kai; Paczuski, Maya

1995-04-01

We study a single-lane traffic model that is based on human driving behavior. The outflow from a traffic jam self-organizes to a critical state of maximum throughput. Small perturbations of the outflow far downstream create emergent traffic jams with a power law distribution P(t)~t-3/2 of lifetimes t. On varying the vehicle density in a closed system, this critical state separates lamellar and jammed regimes and exhibits 1/f noise in the power spectrum. Using random walk arguments, in conjunction with a cascade equation, we develop a phenomenological theory that predicts the critical exponents for this transition and explains the self-organizing behavior. These predictions are consistent with all of our numerical results.

Characterization of a novel strain phylogenetically related to Kocuria rhizophila and its chemical modification to improve performance of microbial fuel cells.

PubMed

Luo, Jianmei; Li, Ming; Zhou, Minghua; Hu, Youshuang

2015-07-15

It is certainly an important research area to discovery new exoelectrogens for microbial fuel cells (MFCs), and how to effectively manipulate its cell property to improve power performance is still a great challenge. In this study, a new electrochemically active bacterium phylogenetically related to Kocuria rhizophila was first isolated and found electrogenic in MFCs, which was identified through the combination methods of molecular biology, physiological, biochemical and morphological characteristics. The MFCs inoculated with this strain generated power from a wide variety of substrates, reached a maximum power density of 75mW/m(2) in the substrate of 1g/L glucose. And the electron transfer mechanism was confirmed to be dominantly direct biofilm mechanism. Chemical treatment with five reagents was verified to be a feasible strategy to improve the power density of MFCs, increasing approximately 1.75 fold at most after treated with lysozyme. This enhancement was contributed to the significant enhancement on cell permeability, cell membrane fluidity and Coenzyme Q10 (the electron carrier). Thus this work offered a novel Gram-positive electrogenic bacterium and proved chemical treatment was a feasible strategy to improve electron transfer for application in MFCs. Copyright © 2015 Elsevier B.V. All rights reserved.

A flat-panel-shaped hybrid piezo/triboelectric nanogenerator for ambient energy harvesting

NASA Astrophysics Data System (ADS)

Hassan, Gul; Khan, Fasihullah; Hassan, Arshad; Ali, Shawkat; Bae, Jinho; Lee, Chong Hyun

2017-04-01

Recently, many researchers have been paying attention to nanogenerators (NGs) as energy sources for self-powered mirco-nano systems, and studying how to achieve their higher power generation. Hence, we propose a hybrid-type NG for harvesting both the piezoelectric and triboelectric effect simultaneously. In the proposed hybrid NG, the piezoelectric NG (PNG) and triboelectric NG (TENG) are fabricated using polydimethylsiloxane (PDMS) and perovskite zinc stannite (ZnSnO3) nanocubes with a high charge polarization of 59 uC cm-2 composite (PDMS + ZnSnO3) and UV surface-treated PDMS, respectively. To effectively combine a high output current of PNG and a high voltage of TENG, these two NGs are stacked upon each other, and separated by sponge spacers providing a uniform air gap for the triboelectric effect. In particular, this fabricated structure has a low Young’s modulus for piezoelectricity. The proposed hybrid NG device effectively achieves a combined peak voltage of 300 V on an open circuit, a power density of 10.41 mW cm-2 at 1 MΩ load, and a maximum short circuit current density of 16 mA cm-2 at 50 Ω load. It is feasible that the proposed NG can be utilized as a source for various self-powered systems.

Flexible and Robust Thermoelectric Generators Based on All-Carbon Nanotube Yarn without Metal Electrodes.

PubMed

Choi, Jaeyoo; Jung, Yeonsu; Yang, Seung Jae; Oh, Jun Young; Oh, Jinwoo; Jo, Kiyoung; Son, Jeong Gon; Moon, Seung Eon; Park, Chong Rae; Kim, Heesuk

2017-08-22

As practical interest in flexible/or wearable power-conversion devices increases, the demand for high-performance alternatives to thermoelectric (TE) generators based on brittle inorganic materials is growing. Herein, we propose a flexible and ultralight TE generator (TEG) based on carbon nanotube yarn (CNTY) with excellent TE performance. The as-prepared CNTY shows a superior electrical conductivity of 3147 S/cm due to increased longitudinal carrier mobility derived from a highly aligned structure. Our TEG is innovative in that the CNTY acts as multifunctions in the same device. The CNTY is alternatively doped into n- and p-types using polyethylenimine and FeCl 3 , respectively. The highly conductive CNTY between the doped regions is used as electrodes to minimize the circuit resistance, thereby forming an all-carbon TEG without additional metal deposition. A flexible TEG based on 60 pairs of n- and p-doped CNTY shows the maximum power density of 10.85 and 697 μW/g at temperature differences of 5 and 40 K, respectively, which are the highest values among reported TEGs based on flexible materials. We believe that the strategy proposed here to improve the power density of flexible TEG by introducing highly aligned CNTY and designing a device without metal electrodes shows great potential for the flexible/or wearable power-conversion devices.

High rate copper and energy recovery in microbial fuel cells

PubMed Central

Rodenas Motos, Pau; ter Heijne, Annemiek; van der Weijden, Renata; Saakes, Michel; Buisman, Cees J. N.; Sleutels, Tom H. J. A.

2015-01-01

Bioelectrochemical systems (BESs) are a novel, promising technology for the recovery of metals. The prerequisite for upscaling from laboratory to industrial size is that high current and high power densities can be produced. In this study we report the recovery of copper from a copper sulfate stream (2 g L-1 Cu2+) using a laboratory scale BES at high rate. To achieve this, we used a novel cell configuration to reduce the internal voltage losses of the system. At the anode, electroactive microorganisms produce electrons at the surface of an electrode, which generates a stable cell voltage of 485 mV when combined with a cathode where copper is reduced. In this system, a maximum current density of 23 A m-2 in combination with a power density of 5.5 W m-2 was produced. XRD analysis confirmed 99% purity in copper of copper deposited onto cathode surface. Analysis of voltage losses showed that at the highest current, most voltage losses occurred at the cathode, and membrane, while anode losses had the lowest contribution to the total voltage loss. These results encourage further development of BESs for bioelectrochemical metal recovery. PMID:26150802

Soybean Root-Derived Hierarchical Porous Carbon as Electrode Material for High-Performance Supercapacitors in Ionic Liquids.

PubMed

Guo, Nannan; Li, Min; Wang, Yong; Sun, Xingkai; Wang, Feng; Yang, Ru

2016-12-14

Soybeans are extensively cultivated worldwide as human food. However, large quantities of soybean roots (SRs), which possess an abundant three-dimensional (3D) structure, remain unused and produce enormous pressure on the environment. Here, 3D hierarchical porous carbon was prepared by the facile carbonization of SRs followed by chemical activation. The as-prepared material, possessing large specific surface area (2143 m 2 g -1 ), good electrical conductivity, and unique 3D hierarchical porosity, shows outstanding electrochemical performance as an electrode material for supercapacitors, such as a high capacitance (276 F g -1 at 0.5 A g -1 ), superior cycle stability (98% capacitance retention after 10,000 cycles at 5 A g -1 ), and good rate capability in a symmetric two-electrode supercapacitor in 6 M KOH. Furthermore, the maximum energy density of as-assembled symmetric supercapacitor can reach 100.5 Wh kg -1 in neat EMIM BF 4 . Moreover, a value of 40.7 Wh kg -1 is maintained at ultrahigh power density (63000 W kg -1 ). These results show that the as-assembled supercapacitor can simultaneously deliver superior energy and power density.

Modeling and Simulation of Linear and Nonlinear MEMS Scale Electromagnetic Energy Harvesters for Random Vibration Environments

PubMed Central

Sassani, Farrokh

2014-01-01

The simulation results for electromagnetic energy harvesters (EMEHs) under broad band stationary Gaussian random excitations indicate the importance of both a high transformation factor and a high mechanical quality factor to achieve favourable mean power, mean square load voltage, and output spectral density. The optimum load is different for random vibrations and for sinusoidal vibration. Reducing the total damping ratio under band-limited random excitation yields a higher mean square load voltage. Reduced bandwidth resulting from decreased mechanical damping can be compensated by increasing the electrical damping (transformation factor) leading to a higher mean square load voltage and power. Nonlinear EMEHs with a Duffing spring and with linear plus cubic damping are modeled using the method of statistical linearization. These nonlinear EMEHs exhibit approximately linear behaviour under low levels of broadband stationary Gaussian random vibration; however, at higher levels of such excitation the central (resonant) frequency of the spectral density of the output voltage shifts due to the increased nonlinear stiffness and the bandwidth broadens slightly. Nonlinear EMEHs exhibit lower maximum output voltage and central frequency of the spectral density with nonlinear damping compared to linear damping. Stronger nonlinear damping yields broader bandwidths at stable resonant frequency. PMID:24605063

High-injection effects in near-field thermophotovoltaic devices.

PubMed

Blandre, Etienne; Chapuis, Pierre-Olivier; Vaillon, Rodolphe

2017-11-20

In near-field thermophotovoltaics, a substantial enhancement of the electrical power output is expected as a result of the larger photogeneration of electron-hole pairs due to the tunneling of evanescent modes from the thermal radiator to the photovoltaic cell. The common low-injection approximation, which considers that the local carrier density due to photogeneration is moderate in comparison to that due to doping, needs therefore to be assessed. By solving the full drift-diffusion equations, the existence of high-injection effects is studied in the case of a GaSb p-on-n junction cell and a radiator supporting surface polaritons. Depending on doping densities and surface recombination velocity, results reveal that high-injection phenomena can already take place in the far field and become very significant in the near field. Impacts of high injection on maximum electrical power, short-circuit current, open-circuit voltage, recombination rates, and variations of the difference between quasi-Fermi levels are analyzed in detail. By showing that an optimum acceptor doping density can be estimated, this work suggests that a detailed and accurate modeling of the electrical transport is also key for the design of near-field thermophotovoltaic devices.

Comparative study of cluster Ag17Cu2 by instantaneous normal mode analysis and by isothermal Brownian-type molecular dynamics simulation.

PubMed

Tang, Ping-Han; Wu, Ten-Ming; Yen, Tsung-Wen; Lai, S K; Hsu, P J

2011-09-07

We perform isothermal Brownian-type molecular dynamics simulations to obtain the velocity autocorrelation function and its time Fourier-transformed power spectral density for the metallic cluster Ag(17)Cu(2). The temperature dependences of these dynamical quantities from T = 0 to 1500 K were examined and across this temperature range the cluster melting temperature T(m), which we define to be the principal maximum position of the specific heat is determined. The instantaneous normal mode analysis is then used to dissect the cluster dynamics by calculating the vibrational instantaneous normal mode density of states and hence its frequency integrated value I(j) which is an ensemble average of all vibrational projection operators for the jth atom in the cluster. In addition to comparing the results with simulation data, we look more closely at the entities I(j) of all atoms using the point group symmetry and diagnose their temperature variations. We find that I(j) exhibit features that may be used to deduce T(m), which turns out to agree very well with those inferred from the power spectral density and specific heat. © 2011 American Institute of Physics

Metal-Organic-Framework-Derived Dual Metal- and Nitrogen-Doped Carbon as Efficient and Robust Oxygen Reduction Reaction Catalysts for Microbial Fuel Cells.

PubMed

Tang, Haolin; Cai, Shichang; Xie, Shilei; Wang, Zhengbang; Tong, Yexiang; Pan, Mu; Lu, Xihong

2016-02-01

A new class of dual metal and N doped carbon catalysts with well-defined porous structure derived from metal-organic frameworks (MOFs) has been developed as a high-performance electrocatalyst for oxygen reduction reaction (ORR). Furthermore, the microbial fuel cell (MFC) device based on the as-prepared Ni/Co and N codoped carbon as air cathode catalyst achieves a maximum power density of 4335.6 mW m -2 and excellent durability.

New Materials Developments for Military High Power Electronics and Capacitors

DTIC Science & Technology

2009-04-27

parameters, permittivity and breakdown field strength, and can be given by equation 1. (1) Where U - energy density (J/ cm3), ε - relative material... permittivity εo - permittivity of free space (8.85418782 × 10-12 m-3 kg-1 s4 A2) Emax (V/µm) - maximum field strength before material breakdown... Permittivity can be described as the ability of the material to polar- ize in response to an electric field through separation of ions, twist- ing permanent

Methods for utilizing maximum power from a solar array

NASA Technical Reports Server (NTRS)

Decker, D. K.

1972-01-01

A preliminary study of maximum power utilization methods was performed for an outer planet spacecraft using an ion thruster propulsion system and a solar array as the primary energy source. The problems which arise from operating the array at or near the maximum power point of its 1-V characteristic are discussed. Two closed loop system configurations which use extremum regulators to track the array's maximum power point are presented. Three open loop systems are presented that either: (1) measure the maximum power of each array section and compute the total array power, (2) utilize a reference array to predict the characteristics of the solar array, or (3) utilize impedance measurements to predict the maximum power utilization. The advantages and disadvantages of each system are discussed and recommendations for further development are made.

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based on Vertically Aligned CuSe@Co(OH) 2 Nanosheet Arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Jiangfeng; Tian, Yazhou; Yang, Ziyuan

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. In this paper, we demonstrate a novel vertically aligned CuSe@Co(OH) 2 nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH) 2 nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g -1 at a current density of 1 A g -1. A flexible asymmetric all-solid-state supercapacitor is fabricated usingmore » CuSe@Co(OH) 2 nanosheet arrays as the positive electrode and activated carbon as the negative electrode. The device delivers a volumetric capacitance of 441.4 mF cm -3 with maximum energy density and maximum power density is 0.17 and 62.1 mW cm -3, as well as robust cycling stability (~80.4% capacitance retention after 10 000 cycles), excellent flexibility, and mechanical stability. Finally, the excellent electrochemical performance can be attributed to its unique vertically aligned configuration.« less

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based on Vertically Aligned CuSe@Co(OH) 2 Nanosheet Arrays

DOE PAGES

Gong, Jiangfeng; Tian, Yazhou; Yang, Ziyuan; ...

2018-01-04

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. In this paper, we demonstrate a novel vertically aligned CuSe@Co(OH) 2 nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH) 2 nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g -1 at a current density of 1 A g -1. A flexible asymmetric all-solid-state supercapacitor is fabricated usingmore » CuSe@Co(OH) 2 nanosheet arrays as the positive electrode and activated carbon as the negative electrode. The device delivers a volumetric capacitance of 441.4 mF cm -3 with maximum energy density and maximum power density is 0.17 and 62.1 mW cm -3, as well as robust cycling stability (~80.4% capacitance retention after 10 000 cycles), excellent flexibility, and mechanical stability. Finally, the excellent electrochemical performance can be attributed to its unique vertically aligned configuration.« less

Scaling properties of fractional momentum loss of high-pT hadrons in nucleus-nucleus collisions at √{sN N} from 62.4 GeV to 2.76 TeV

NASA Astrophysics Data System (ADS)

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Akimoto, R.; Al-Bataineh, H.; Alexander, J.; Alfred, M.; Al-Ta'Ani, H.; Angerami, A.; Aoki, K.; Apadula, N.; Aphecetche, L.; Aramaki, Y.; Armendariz, R.; Aronson, S. H.; Asai, J.; Asano, H.; Aschenauer, E. C.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Baldisseri, A.; Bandara, N. S.; Bannier, B.; Barish, K. N.; Barnes, P. D.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Batsouli, S.; Baublis, V.; Baumann, C.; Baumgart, S.; Bazilevsky, A.; Beaumier, M.; Beckman, S.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bickley, A. A.; Blau, D. S.; Boissevain, J. G.; Bok, J. S.; Borel, H.; Boyle, K.; Brooks, M. L.; Bryslawskyj, J.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Castera, P.; Chang, B. S.; Charvet, J.-L.; Chen, C.-H.; Chernichenko, S.; Chi, C. Y.; Chiba, J.; Chiu, M.; Choi, I. J.; Choi, J. B.; Choi, S.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Churyn, A.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cleven, C. R.; Cole, B. A.; Comets, M. P.; Connors, M.; Constantin, P.; Csanád, M.; Csörgő, T.; Dahms, T.; Dairaku, S.; Danchev, I.; Danley, T. W.; Das, K.; Datta, A.; Daugherity, M. S.; David, G.; Deaton, M. B.; Deblasio, K.; Dehmelt, K.; Delagrange, H.; Denisov, A.; D'Enterria, D.; Deshpande, A.; Desmond, E. J.; Dharmawardane, K. V.; Dietzsch, O.; Ding, L.; Dion, A.; Diss, P. B.; Do, J. H.; Donadelli, M.; D'Orazio, L.; Drapier, O.; Drees, A.; Drees, K. A.; Dubey, A. K.; Durham, J. M.; Durum, A.; Dutta, D.; Dzhordzhadze, V.; Edwards, S.; Efremenko, Y. V.; Egdemir, J.; Ellinghaus, F.; Emam, W. S.; Engelmore, T.; Enokizono, A.; En'yo, H.; Esumi, S.; Eyser, K. O.; Fadem, B.; Feege, N.; Fields, D. E.; Finger, M.; Finger, M.; Fleuret, F.; Fokin, S. L.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fusayasu, T.; Gadrat, S.; Gainey, K.; Gal, C.; Gallus, P.; Garg, P.; Garishvili, A.; Garishvili, I.; Ge, H.; Giordano, F.; Glenn, A.; Gong, H.; Gong, X.; Gonin, M.; Gosset, J.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Guo, L.; Gustafsson, H.-Å.; Hachiya, T.; Hadj Henni, A.; Haegemann, C.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamblen, J.; Hamilton, H. F.; Han, R.; Han, S. Y.; Hanks, J.; Harada, H.; Hartouni, E. P.; Haruna, K.; Hasegawa, S.; Haseler, T. O. S.; Hashimoto, K.; Haslum, E.; Hayano, R.; He, X.; Heffner, M.; Hemmick, T. K.; Hester, T.; Hiejima, H.; Hill, J. C.; Hobbs, R.; Hohlmann, M.; Hollis, R. S.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hori, Y.; Hornback, D.; Hoshino, T.; Hotvedt, N.; Huang, J.; Huang, S.; Ichihara, T.; Ichimiya, R.; Ide, J.; Iinuma, H.; Ikeda, Y.; Imai, K.; Imrek, J.; Inaba, M.; Inoue, Y.; Iordanova, A.; Isenhower, D.; Isenhower, L.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanishchev, D.; Jacak, B. V.; Javani, M.; Jezghani, M.; Jia, J.; Jiang, X.; Jin, J.; Jinnouchi, O.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kanda, S.; Kaneta, M.; Kaneti, S.; Kang, B. H.; Kang, J. H.; Kang, J. S.; Kanou, H.; Kapustinsky, J.; Karatsu, K.; Kasai, M.; Kawall, D.; Kawashima, M.; Kazantsev, A. V.; Kempel, T.; Key, J. A.; Khachatryan, V.; Khanzadeev, A.; Kijima, K. M.; Kikuchi, J.; Kim, B. I.; Kim, C.; Kim, D. H.; Kim, D. J.; Kim, E.; Kim, E.-J.; Kim, G. W.; Kim, H. J.; Kim, K.-B.; Kim, M.; Kim, S. H.; Kim, Y.-J.; Kim, Y. K.; Kimelman, B.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Kitamura, R.; Kiyomichi, A.; Klatsky, J.; Klay, J.; Klein-Boesing, C.; Kleinjan, D.; Kline, P.; Koblesky, T.; Kochenda, L.; Kochetkov, V.; Komatsu, Y.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kotov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Krizek, F.; Kubart, J.; Kunde, G. J.; Kurihara, N.; Kurita, K.; Kurosawa, M.; Kweon, M. J.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, B.; Lee, D. M.; Lee, J.; Lee, K.; Lee, K. B.; Lee, K. S.; Lee, M. K.; Lee, S.; Lee, S. H.; Lee, S. R.; Lee, T.; Leitch, M. J.; Leite, M. A. L.; Leitgab, M.; Leitner, E.; Lenzi, B.; Lewis, B.; Li, X.; Liebing, P.; Lim, S. H.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Love, B.; Luechtenborg, R.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Makek, M.; Malakhov, A.; Malik, M. D.; Manion, A.; Manko, V. I.; Mannel, E.; Mao, Y.; Mašek, L.; Masui, H.; Masumoto, S.; Matathias, F.; McCumber, M.; McGaughey, P. L.; McGlinchey, D.; McKinney, C.; Means, N.; Meles, A.; Mendoza, M.; Meredith, B.; Miake, Y.; Mibe, T.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Miller, T. E.; Milov, A.; Mioduszewski, S.; Mishra, D. K.; Mishra, M.; Mitchell, J. T.; Mitrovski, M.; Miyachi, Y.; Miyasaka, S.; Mizuno, S.; Mohanty, A. K.; Mohapatra, S.; Montuenga, P.; Moon, H. J.; Moon, T.; Morino, Y.; Morreale, A.; Morrison, D. P.; Motschwiller, S.; Moukhanova, T. V.; Mukhopadhyay, D.; Murakami, T.; Murata, J.; Mwai, A.; Nagae, T.; Nagamiya, S.; Nagashima, K.; Nagata, Y.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakagomi, H.; Nakamiya, Y.; Nakamura, K. R.; Nakamura, T.; Nakano, K.; Nattrass, C.; Nederlof, A.; Netrakanti, P. K.; Newby, J.; Nguyen, M.; Nihashi, M.; Niida, T.; Nishimura, S.; Norman, B. E.; Nouicer, R.; Novák, T.; Novitzky, N.; Nyanin, A. S.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Ohnishi, H.; Oka, M.; Okada, K.; Omiwade, O. O.; Onuki, Y.; Orjuela Koop, J. D.; Osborn, J. D.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Pal, D.; Palounek, A. P. T.; Pantuev, V.; Papavassiliou, V.; Park, B. H.; Park, I. H.; Park, J.; Park, J. S.; Park, S.; Park, S. K.; Park, W. J.; Pate, S. F.; Patel, L.; Patel, M.; Pei, H.; Peng, J.-C.; Pereira, H.; Perepelitsa, D. V.; Perera, G. D. N.; Peresedov, V.; Peressounko, D. Yu.; Perry, J.; Petti, R.; Pinkenburg, C.; Pinson, R.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ramson, B. J.; Ravinovich, I.; Read, K. F.; Rembeczki, S.; Reuter, M.; Reygers, K.; Reynolds, D.; Riabov, V.; Riabov, Y.; Richardson, E.; Rinn, T.; Roach, D.; Roche, G.; Rolnick, S. D.; Romana, A.; Rosati, M.; Rosen, C. A.; Rosendahl, S. S. E.; Rosnet, P.; Rowan, Z.; Rubin, J. G.; Rukoyatkin, P.; Ružička, P.; Rykov, V. L.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakai, S.; Sakashita, K.; Sakata, H.; Sako, H.; Samsonov, V.; Sano, M.; Sano, S.; Sarsour, M.; Sato, S.; Sato, T.; Sawada, S.; Schaefer, B.; Schmoll, B. K.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Semenov, V.; Sen, A.; Seto, R.; Sett, P.; Sexton, A.; Sharma, D.; Shein, I.; Shevel, A.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Skutnik, S.; Slunečka, M.; Snowball, M.; Soldatov, A.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Sparks, N. A.; Staley, F.; Stankus, P. W.; Stenlund, E.; Stepanov, M.; Ster, A.; Stoll, S. P.; Sugitate, T.; Suire, C.; Sukhanov, A.; Sumita, T.; Sun, J.; Sziklai, J.; Tabaru, T.; Takagi, S.; Takagui, E. M.; Takahara, A.; Taketani, A.; Tanabe, R.; Tanaka, Y.; Taneja, S.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Tennant, E.; Themann, H.; Thomas, T. L.; Tieulent, R.; Timilsina, A.; Todoroki, T.; Togawa, M.; Toia, A.; Tojo, J.; Tomášek, L.; Tomášek, M.; Torii, H.; Towell, C. L.; Towell, R.; Towell, R. S.; Tram, V.-N.; Tserruya, I.; Tsuchimoto, Y.; Tsuji, T.; Vale, C.; Valle, H.; van Hecke, H. W.; Vargyas, M.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vossen, A.; Vrba, V.; Vznuzdaev, E.; Wagner, M.; Walker, D.; Wang, X. R.; Watanabe, D.; Watanabe, K.; Watanabe, Y.; Watanabe, Y. S.; Wei, F.; Wei, R.; Wessels, J.; White, A. S.; White, S. N.; Winter, D.; Wolin, S.; Wood, J. P.; Woody, C. L.; Wright, R. M.; Wysocki, M.; Xia, B.; Xie, W.; Xue, L.; Yalcin, S.; Yamaguchi, Y. L.; Yamaura, K.; Yang, R.; Yanovich, A.; Yasin, Z.; Ying, J.; Yokkaichi, S.; Yoo, J. H.; Yoon, I.; You, Z.; Young, G. R.; Younus, I.; Yu, H.; Yushmanov, I. E.; Zajc, W. A.; Zaudtke, O.; Zelenski, A.; Zhang, C.; Zhou, S.; Zimamyi, J.; Zolin, L.; Zou, L.; Phenix Collaboration

2016-02-01

Measurements of the fractional momentum loss (Sloss≡δ pT/pT ) of high-transverse-momentum-identified hadrons in heavy-ion collisions are presented. Using π0 in Au +Au and Cu +Cu collisions at √{sNN}=62.4 and 200 GeV measured by the PHENIX experiment at the Relativistic Heavy Ion Collider and and charged hadrons in Pb +Pb collisions measured by the ALICE experiment at the Large Hadron Collider, we studied the scaling properties of Sloss as a function of a number of variables: the number of participants, Npart, the number of quark participants, Nqp, the charged-particle density, d Nch/d η , and the Bjorken energy density times the equilibration time, ɛBjτ0 . We find that the pT, where Sloss has its maximum, varies both with centrality and collision energy. Above the maximum, Sloss tends to follow a power-law function with all four scaling variables. The data at √{sNN}=200 GeV and 2.76 TeV, for sufficiently high particle densities, have a common scaling of Sloss with d Nch/d η and ɛBjτ0 , lending insight into the physics of parton energy loss.

Homogeneous deposition-assisted synthesis of iron-nitrogen composites on graphene as highly efficient non-precious metal electrocatalysts for microbial fuel cell power generation

NASA Astrophysics Data System (ADS)

Liu, Yuan; Jin, Xiao-Jun; Dionysiou, Dionysios D.; Liu, Hong; Huang, Yu-Ming

2015-03-01

This work proposed a novel strategy for synthesizing highly efficient non-precious metal oxygen reduction reaction (ORR) electrocatalysts. Fe complexes were homogeneously deposited (HD) on graphene oxide through in situ hydrolysis of urea, followed by two-step pyrolysis under Ar and NH3 atmospheres, resulting in formation of Fe- and N-functionalized graphene (HD-FeN/G). The morphology, crystalline structure and elemental composition of HD-FeN/G were characterized. ORR activity was evaluated by using a rotary disk electrode (RDE) electrochemical system. HD improved the loading and distribution of the Fe-Nx composites on graphene. The ORR activity of the as-prepared HD-FeN/G in neutral medium was comparable to that of the state-of-the-art commercial Pt/C and significantly superior to a FeN/G counterpart produced via traditional approach. The ORR electron transfer number of HD-FeN/G was as high as 3.83 ± 0.08, which suggested that ORR catalysis proceeds through a four-electron pathway. HD-FeN/G was used as a cathodic electrocatalyst in microbial fuel cells (MFCs), and the resultant HD-FeN/G-MFC showed comparable voltage output and maximum power density to those of Pt/C-MFC. The HD-FeN/G-MFC achieved a maximum power density of 885 mW m-2, which was much higher than that of FeN/G-MFC (708 mW m-2). These findings demonstrate that HD-FeN/G produced through the novel synthesis strategy proposed in this work would be a good candidate as cathodic electrocatalyst in MFCs.

Proton exchange membrane and electrode surface areas as factors that affect power generation in microbial fuel cells.

PubMed

Oh, Sang-Eun; Logan, Bruce E

2006-03-01

Power generation in microbial fuel cells (MFCs) is a function of the surface areas of the proton exchange membrane (PEM) and the cathode relative to that of the anode. To demonstrate this, the sizes of the anode and cathode were varied in two-chambered MFCs having PEMs with three different surface areas (A (PEM)=3.5, 6.2, or 30.6 cm(2)). For a fixed anode and cathode surface area (A (An)=A (Cat)=22.5 cm(2)), the power density normalized to the anode surface area increased with the PEM size in the order 45 mW/m(2) (A (PEM)=3.5 cm(2)), 68 mW/m(2) (A (PEM)=6.2 cm(2)), and 190 mW/m(2) (A (PEM)=30.6 cm(2)). PEM surface area was shown to limit power output when the surface area of the PEM was smaller than that of the electrodes due to an increase in internal resistance. When the relative cross sections of the PEM, anode, and cathode were scaled according to 2A (Cat)=A(PEM)=2A (An), the maximum power densities of the three different MFCs, based on the surface area of the PEM (A (PEM)=3.5, 6.2, or 30.6 cm(2)), were the same (168+/-4.53 mW/m(2)). Increasing the ionic strength and using ferricyanide at the cathode also increased power output.

Polymer bulk heterojunction solar cells with PEDOT:PSS bilayer structure as hole extraction layer.

PubMed

Kim, Wanjung; Kim, Namhun; Kim, Jung Kyu; Park, Insun; Choi, Yeong Suk; Wang, Dong Hwan; Chae, Heeyeop; Park, Jong Hyeok

2013-06-01

A high current density obtained in a limited, nanometer-thick region is important for high efficiency polymer solar cells (PSCs). The conversion of incident photons to charge carriers only occurs in confined active layers; therefore, charge-carrier extraction from the active layer within the device by using solar light has an important impact on the current density and the related to power conversion efficiency. In this study, we observed a surprising result, that is, extracting the charge carrier generated in the active layer of a PSC device, with a thickness-controlled PEDOT:PSS bilayer that acted as a hole extraction layer (HEL), yielded a dramatically improved power conversion efficiency in two different model systems (P3HT:PC₆₀BM and PCDTBT:PC₇₀BM). To understand this phenomenon, we conducted optical strength simulation, photocurrent-voltage measurements, incident photon to charge carrier efficiency measurements, ultraviolet photoelectron spectroscopy, and AFM studies. The results revealed that approximately 60 nm was the optimum PEDOT:PSS bilayer HEL thickness in PSCs for producing the maximum power conversion efficiency. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A direct ascorbate fuel cell with an anion exchange membrane

NASA Astrophysics Data System (ADS)

Muneeb, Omar; Do, Emily; Tran, Timothy; Boyd, Desiree; Huynh, Michelle; Ghosn, Gregory; Haan, John L.

2017-05-01

Ascorbic Acid (Vitamin C) is investigated as a renewable alternative fuel for alkaline direct liquid fuel cells (DLFCs). The environmentally- and biologically-friendly compound, L-ascorbic acid (AA) has been modeled and studied experimentally under acidic fuel cell conditions. In this work, we demonstrate that ascorbic acid is a more efficient fuel in alkaline media than in acidic media. An operating direct ascorbate fuel cell is constructed with the combination of L-ascorbic acid and KOH as the anode fuel, air or oxygen as the oxidant, a polymer anion exchange membrane, metal or carbon black anode materials and metal cathode catalyst. Operation of the fuel cell at 60 °C using 1 M AA and 1 M KOH as the anode fuel and electrolyte, respectively, and oxygen gas at the cathode, produces a maximum power density of 73 mW cm-2, maximum current density of 497 mA cm-2 and an open circuit voltage of 0.90 V. This performance is significantly greater than that of an ascorbic acid fuel cell with a cation exchange membrane, and it is competitive with alkaline DLFCs fueled by alcohols.

High performance asymmetric supercapacitor based on molybdenum disulphide/graphene foam and activated carbon from expanded graphite.

PubMed

Masikhwa, Tshifhiwa M; Madito, Moshawe J; Bello, Abdulhakeem; Dangbegnon, Julien K; Manyala, Ncholu

2017-02-15

Molybdenum disulphide which has a graphene-like single layer structure has excellent mechanical and electrical properties and unique morphology, which might be used with graphene foam as composite in supercapacitor applications. In this work, Molybdenum disulphide (MoS 2 )/graphene foam (GF) composites with different graphene foam loading were synthesized by the hydrothermal process to improve on specific capacitance of the composites. Asymmetric supercapacitor device was fabricated using the best performing MoS 2 /GF composite and activated carbon derived from expanded graphite (AEG) as positive and negative electrodes, respectively, in 6M KOH electrolyte. The asymmetric MoS 2 /GF//AEG device exhibited a maximum specific capacitance of 59Fg -1 at a current density of 1Ag -1 with maximum energy and power densities of 16Whkg -1 and 758Wkg -1 , respectively. The supercapacitor also exhibited a good cyclic stability with 95% capacitance retention over 2000 constant charge-discharge cycles. The results obtained demonstrate the potential of MoS 2 /GF//AEG as a promising material for electrochemical energy storage application. Copyright © 2016 Elsevier Inc. All rights reserved.

Perspective use of direct human blood as an energy source in air-breathing hybrid microfluidic fuel cells

NASA Astrophysics Data System (ADS)

Dector, A.; Escalona-Villalpando, R. A.; Dector, D.; Vallejo-Becerra, V.; Chávez-Ramírez, A. U.; Arriaga, L. G.; Ledesma-García, J.

2015-08-01

This work presents a flexible and light air-breathing hybrid microfluidic fuel cell (HμFC) operated under biological conditions. A mixture of glucose oxidase, glutaraldehyde, multi-walled carbon nanotubes and vulcan carbon (GOx/VC-MWCNT-GA) was used as the bioanode. Meanwhile, integrating an air-exposed electrode (Pt/C) as the cathode enabled direct oxygen delivery from air. The microfluidic fuel cell performance was evaluated using glucose obtained from three different sources as the fuel: 5 mM glucose in phosphate buffer, human serum and human blood. For the last fuel, an open circuit voltage and maximum power density of 0.52 V and 0.20 mW cm-2 (at 0.38 V) were obtained respectively; meanwhile the maximum current density was 1.1 mA cm-2. Furthermore, the stability of the device was measured in terms of recovery after several polarization curves, showing excellent results. Although this air-breathing HμFC requires technological improvements before being tested in a biomedical device, it represents the best performance to date for a microfluidic fuel cell using human blood as glucose source.

Performance of steel wool fiber reinforced geopolymer concrete

NASA Astrophysics Data System (ADS)

Faris, Meor Ahmad; Abdullah, Mohd Mustafa Al Bakri; Ismail, Khairul Nizar; Muniandy, Ratnasamy; Ariffin, Nurliayana

2017-09-01

In this paper, performance of geopolymer concrete was studied by mixing of Class F fly ash from Manjung power station, Lumut, Perak, Malaysia with alkaline activator which are combination of sodium hydroxide and sodium silicate. Steel wool fiber were added into the geopolymer concrete as reinforcement with different weight percentage vary from 0 % - 5 %. Chemical compositions of Malaysian fly ash was first analyzed by using X-ray fluorescence. All geopolymer concrete reinforced with steel wool fiber with different weight percentage were tested in terms of density, workability, and compression. Result shows Malaysian fly ash identified by using XRF was class F. Density of geopolymer concrete close to density of OPC which is approximately 2400 kg/m3 and the density was increase gradually with the additions of steel fiber. However, the inclusions of steel fibers also shows some reduction to the workability of geopolymer concrete. Besides, the compressive strength was increased with the increasing of fibers addition until maximum of 18.6 % improvement at 3 % of steel fibers.

Redox flow batteries with serpentine flow fields: Distributions of electrolyte flow reactant penetration into the porous carbon electrodes and effects on performance

NASA Astrophysics Data System (ADS)

Ke, Xinyou; Prahl, Joseph M.; Alexander, J. Iwan D.; Savinell, Robert F.

2018-04-01

Redox flow batteries with flow field designs have been demonstrated to boost their capacities to deliver high current density and power density in medium and large-scale energy storage applications. Nevertheless, the fundamental mechanisms involved with improved current density in flow batteries with serpentine flow field designs have been not fully understood. Here we report a three-dimensional model of a serpentine flow field over a porous carbon electrode to examine the distributions of pressure driven electrolyte flow penetrations into the porous carbon electrodes. We also estimate the maximum current densities associated with stoichiometric availability of electrolyte reactant flow penetrations through the porous carbon electrodes. The results predict reasonably well observed experimental data without using any adjustable parameters. This fundamental work on electrolyte flow distributions of limiting reactant availability will contribute to a better understanding of limits on electrochemical performance in flow batteries with serpentine flow field designs and should be helpful to optimizing flow batteries.

Effects of feedstock availability on the negative ion behavior in a C{sub 4}F{sub 8} inductively coupled plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, Shu-Xia; Research group PLASMANT, Dept. Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp; Gao, Fei

2015-07-21

In this paper, the negative ion behavior in a C{sub 4}F{sub 8} inductively coupled plasma (ICP) is investigated using a hybrid model. The model predicts a non-monotonic variation of the total negative ion density with power at low pressure (10–30 mTorr), and this trend agrees well with experiments that were carried out in many fluorocarbon (fc) ICP sources, like C{sub 2}F{sub 6}, CHF{sub 3}, and C{sub 4}F{sub 8}. This behavior is explained by the availability of feedstock C{sub 4}F{sub 8} gas as a source of the negative ions, as well as by the presence of low energy electrons due tomore » vibrational excitation at low power. The maximum of the negative ion density shifts to low power values upon decreasing pressure, because of the more pronounced depletion of C{sub 4}F{sub 8} molecules, and at high pressure (∼50 mTorr), the anion density continuously increases with power, which is similar to fc CCP sources. Furthermore, the negative ion composition is identified in this paper. Our work demonstrates that for a clear understanding of the negative ion behavior in radio frequency C{sub 4}F{sub 8} plasma sources, one needs to take into account many factors, like the attachment characteristics, the anion composition, the spatial profiles, and the reactor configuration. Finally, a detailed comparison of our simulation results with experiments is conducted.« less

Design rules and reality check for carbon-based ultracapacitors

NASA Astrophysics Data System (ADS)

Eisenmann, Erhard T.

1995-04-01

Design criteria for carbon-based Ultracapacitors have been determined for specified energy and power requirements, using the geometry of the components and such material properties as density, porosity and conductivity as parameters, while also considering chemical compatibility. This analysis shows that the weights of active and inactive components of the capacitor structure must be carefully balanced for maximum energy and power density. When applied to nonaqueous electrolytes, the design rules for a 5 Wh/kg device call for porous carbon with a specific capacitance of about 30 F/cu cm. This performance is not achievable with pure, electrostatic double layer capacitance. Double layer capacitance is only 5 to 30% of that observed in aqueous electrolyte. Tests also showed that nonaqueous electrolytes have a diminished capability to access micropores in activated carbon, in one case yielding a capacitance of less than 1 F/cu cm for carbon that had 100 F/cu cm in aqueous electrolyte. With negative results on nonaqueous electrolytes dominating the present study, the obvious conclusion is to concentrate on aqueous systems. Only aqueous double layer capacitors offer adequate electrostatic charging characteristics which is the basis for high power performance. There arc many opportunities for further advancing aqueous double layer capacitors, one being the use of highly activated carbon films, as opposed to powders, fibers and foams. While the manufacture of carbon films is still costly, and while the energy and power density of the resulting devices may not meet the optimistic goals that have been proposed, this technology could produce true double layer capacitors with significantly improved performance and large commercial potential.

Influences of current collector foils with different opening ratios in passive polymer electrolyte membrane fuel cells

NASA Astrophysics Data System (ADS)

Krumbholz, S.; Kaiser, J.; Weiland, M.; Hahn, R.; Reichl, H.

Even if many fuel cell applications are ready to start into the market, more research needs to be done to improve the currently achieved power density further. In the power range of about 10-20 W micro-PEM fuel cells have a high improvement potential concerning the current collector design and the design of the passive air supply. These two points have a high impact on the water management of a PEM fuel cell and allow a significant decrease of the fuel cell system in size and weight. The current work shows calculations for the fuel cell impedance based on a mathematical resistance model which was already presented for similarly constructed direct methanol fuel cells (DMFCs) [4]. Selected publications on water uptake and membrane humidification for the used Gore MEAs [6,7] are taken into account. The model is evaluated with realized versions of cathode side current collector designs, which influence the maximum power density and the self-heating of the fuel cell stack. Several measurement results are presented, which can confirm the validity of the used model. A very low opening ratio of less than 0.1 induces a very high concentration gradient of the generated water in relation to the net water outtake. From this it follows that the cell impedance is very low and the membrane has a very high ionic conductivity. Additionally it can be shown that the power density of these fuel cells is twice as high as for the cells with an opening ratio greater than 0.45.

Engineering of beam direct conversion for a 120-kV, 1-MW ion beam

NASA Technical Reports Server (NTRS)

Barr, W. L.; Doggett, J. N.; Hamilton, G. W.; Kinney, J. D.; Moir, R. W.

1977-01-01

Practical systems for beam direct conversion are required to recover the energy from ion beams at high efficiency and at very high beam power densities in the environment of a high-power neutral-injection system. Such an experiment is now in progress using a 120-kV beam with a maximum total current of 20 A. After neutralization, the H(+) component to be recovered will have a power of approximately 1 MW. A system testing these concepts has been designed and tested at 15 kV, 2 kW in preparation for the full-power tests. The engineering problems involved in the full-power tests affect electron suppression, gas pumping, voltage holding, diagnostics, and measurement conditions. Planning for future experiments at higher power includes the use of cryopumping and electron suppression by a magnetic field rather than by an electrostatic field. Beam direct conversion for large fusion experiments and reactors will save millions of dollars in the cost of power supplies and electricity and will dispose of the charged beam under conditions that may not be possible by other techniques.

A long-term stable power supply µDMFC stack for wireless sensor node applications

NASA Astrophysics Data System (ADS)

Wu, Zonglin; Wang, Xiaohong; Li, Xiaozhao; Xu, Manqi; Liu, Litian

2014-10-01

In this paper, a passive, air-breathing four-cell micro direct methanol fuel cell (µDMFC) stack featuring a fuel delivery structure for long-term and stable power supply is designed, fabricated and tested. The fuel is reserved in a T-shaped tank and diffuses through the porous diffusion layer to the catalyst at the anode. A peak power density of 25.7 mW cm-2 and a maximum power output of 113 mW are achieved with 3 M methanol at room temperature, and the stack can produce 60 mW of power, even though only 5% fuel remains in the reservoir. Combined with a low-input dc-dc convertor, the stack can realize a stable and optional constant voltage output from 1 V-6 V. The stack successfully powered a heavy metal sensor node for water environment monitoring 12 d continuously, with consumption of 10 mL 5 M methanol solution. As such, it is believed to be applicable for powering wireless sensor nodes.

[The application of stem together with visible and infrared light in regenerative medicine (Part 2)].

PubMed

Emel'yanov, A N; Kir'yanova, V V

2015-01-01

The objective of the present study was to review the experimental studies concerned with in vitro and in vivo visible and infrared light irradiation of human and animal stem cells (SC) to assess the possibilities of using its photobiomodulatory effects for the purpose of regenerative medicine (RM). Despite the long history of photochromotherapy there is thus far no reliable theoretical basis for the choice of such irradiation parameters as power density, radiation dose and exposure time. Nor is there a generally accepted opinion on the light application for the purpose of regenerative medicine. Therefore, the clinical application of light irradiation remains a matter of controversy, in the first place due to the difficulty of the rational choice of irradiation parameters. In laboratory research, the theoretical basis for the choice of irradiation parameters remains a stumbling block too. A relationship between the increased radiation power density and the cell differentiation rate was documented. SC exposure to light in the absence of the factors causing their differentiation failed to induce it. On the contrary, it increased the features characteristic of undifferentiated cells. The maximum differentiation rate of the same cells was achieved by using irradiation parameters different from those needed to achieve the maxi- mum proliferation rate. The increase of SC differentiation rate upon a rise in radiation power density was induced by increasing ir- radiation energy density. The increase of power density and the reduction of either energy density or exposure time were needed to enhance the SC responsiveness to irradiation in the form of either proliferation or differentiation. The effectiveness of phototherapy at all stages of SC treatment was documented especially when it was applied to stimulate the reservoirs of bone marrow lying far from the site of the pathogenic process together with simultaneous light irradiation of the affected site and pre-treatment of stem cells prior to their administration. Based on the results of this analysis we have proposed "a plot showing the dependence of cell response on the generalized photostimulus" and coined two new terms "photostress" and "photoshock".

Effect of Synthesis Procedure on Thermoelectric Property of SiGe Alloy

NASA Astrophysics Data System (ADS)

Li, Jing; Han, Jun; Jiang, Tao; Luo, Lili; Xiang, Yongchun

2018-05-01

SiGe thermoelectric material has been synthesized by ball milling combined with hot pressing (HP) or spark plasma sintering (SPS). Effects of ball milling time, powder to ball weight ratio and sintering method on microstructure and thermoelectric properties of SiGe are studied. The results show that longer ball milling time leads to decreased density and worse electrical properties. In the sintering process, SPS results in much larger density and better electrical properties than HP. The Si0.795Ge0.2B0.005 sample prepared by 2 h ball milling combined with SPS obtains a maximum power factor of 3.0 mW m-1 K-2 at 860 K and ZT of 0.95 at 1000 K.

Highly Flexible and Planar Supercapacitors Using Graphite Flakes/Polypyrrole in Polymer Lapping Film.

PubMed

Raj, C Justin; Kim, Byung Chul; Cho, Won-Je; Lee, Won-gil; Jung, Sang-Don; Kim, Yong Hee; Park, Sang Yeop; Yu, Kook Hyun

2015-06-24

Flexible supercapacitor electrodes have been fabricated by simple fabrication technique using graphite nanoflakes on polymer lapping films as flexible substrate. An additional thin layer of conducting polymer polypyrrole over the electrode improved the surface conductivity and exhibited excellent electrochemical performances. Such capacitor films showed better energy density and power density with a maximum capacitance value of 37 mF cm(-2) in a half cell configuration using 1 M H2SO4 electrolyte, 23 mF cm(-2) in full cell, and 6 mF cm(-2) as planar cell configuration using poly(vinyl alcohol) (PVA)/phosphoric acid (H3PO4) solid state electrolyte. Moreover, the graphite nanoflakes/polypyrrole over polymer lapping film demonstrated good flexibility and cyclic stability.

Determination of potential solar power sites in the United States based upon satellite cloud observations

NASA Technical Reports Server (NTRS)

Hiser, H. W.; Senn, H. V.; Bukkapatnam, S. T.; Akyuzlu, K.

1977-01-01

The use of cloud images in the visual spectrum from the SMS/GOES geostationary satellites to determine the hourly distribution of sunshine on a mesoscale in the continental United States excluding Alaska is presented. Cloud coverage and density as a function of time of day and season are evaluated through the use of digital data processing techniques. Low density cirrus clouds are less detrimental to solar energy collection than other types; and clouds in the morning and evening are less detrimental than those during midday hours of maximum insolation. Seasonal geographic distributions of cloud cover/sunshine are converted to langleys of solar radiation received at the earth's surface through relationships developed from long term measurements at six widely distributed stations.

SCB thermite igniter studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bickes, R.W. Jr.; Wackerbarth, D.E.; Mohler, J.H.

1996-12-31

The authors report on recent studies comparing the ignition threshold of temperature cycled, SCB thermite devices with units that were not submitted to temperature cycling. Aluminum/copper-oxide thermite was pressed into units at two densities, 45% of theoretical maximum density (TMD) or 47% of TMD. Half of each of the density sets underwent three thermal cycles; each cycle consisted of 2 hours at 74 C and 2 hours at {minus}54 C, with a 5 minute maximum transfer time between temperatures. The temperature cycled units were brought to ambient temperature before the threshold testing. Both the density and the thermal cycling affectedmore » the all-fire voltage. Using a 5.34 {micro}F CDU (capacitor discharge unit) firing set, the all-fire voltage for the units that were not temperature cycled increased with density from 32.99 V (45% TMD) to 39.32 V (47% TMD). The all-fire voltages for the thermally cycled units were 34.42 V (45% TMD) and 58.1 V (47% TMD). They also report on no-fire levels at ambient temperature for two component designs; the 5 minute no-fire levels were greater than 1.2 A. Units were also subjected to tests in which 1 W of RF power was injected into the bridges at 10 MHz for 5 minutes. The units survived and fired normally afterwards. Finally, units were subjected to pin-to-pin electrostatic discharge (ESD) tests. None of the units fired upon application of the ESD pulse, and all of the tested units fired normally afterwards.« less

77 FR 4014 - Takes of Marine Mammals Incidental to Specified Activities; Physical Oceanographic Studies in the...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-26

... chambers for a total discharge volume of 210 in\\3\\) with a 1,200 m long hydrophone streamer. GI guns will... require the Navy to use species-specific mean maximum densities, rather than the mean average densities... use mean maximum densities, rather than mean average densities. Marine mammal population density...

Facile synthesis of ultrathin manganese dioxide nanosheets arrays on nickel foam as advanced binder-free supercapacitor electrodes

NASA Astrophysics Data System (ADS)

Huang, Ming; Zhao, Xiao Li; Li, Fei; Zhang, Li Li; Zhang, Yu Xin

2015-03-01

Ultrathin MnO2 nanosheets arrays on Ni foam have been fabricated by a facile hydrothermal approach and further investigated as the binder-free electrode for high-performance supercapacitors. This unique well-designed binder-free electrode exhibits a high specific capacitance (595.2 F g-1 at a current density of 0.5 A g-1), good rate capability (64.1% retention), and excellent cycling stability (89% capacitance retention after 3000 cycles). Moreover, an asymmetric supercapacitor is constructed using the as-prepared MnO2 nanosheets arrays as the positive electrode and activated microwave exfoliated graphite oxide (MEGO) as the negative electrode. The optimized asymmetric supercapacitor displays excellent electrochemical performance with an energy density of 25.8 Wh kg-1 and a maximum power density of 223.2 kW kg-1. These impressive performances suggest that the MnO2 nanosheet array is a promising electrode material for supercapacitors.

Optimization of Norbornadiene Compounds for Solar Thermal Storage by First-Principles Calculations.

PubMed

Kuisma, Mikael; Lundin, Angelica; Moth-Poulsen, Kasper; Hyldgaard, Per; Erhart, Paul

2016-07-21

Molecular photoswitches capable of storing solar energy are interesting candidates for future renewable energy applications. Here, using quantum mechanical calculations, we carry out a systematic screening of crucial optical (solar spectrum match) and thermal (storage energy density) properties of 64 such compounds based on the norbornadiene-quadricyclane system. Whereas a substantial number of these molecules reach the theoretical maximum solar power conversion efficiency, this requires a strong red-shift of the absorption spectrum, which causes undesirable absorption by the photoisomer as well as reduced thermal stability. These compounds typically also have a large molecular mass, leading to low storage densities. By contrast, single-substituted systems achieve a good compromise between efficiency and storage density, while avoiding competing absorption by the photo-isomer. This establishes guiding principles for the future development of molecular solar thermal storage systems. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development and characterization of direct ethanol fuel cells using alkaline anion-exchange membranes

NASA Astrophysics Data System (ADS)

Lim, Peck Cheng

2009-08-01

Alkaline membrane fuel cell (AMFC) is a relatively new fuel cell technology that is generating considerable interests. It offers the electrocatalytic advantages of conventional alkaline fuel cells, and the manufacturing and cost advantages of solid polymer electrolyte fuel cells. This project was carried out to develop and characterize high performance membrane electrode assemblies (MEAs) for all-solid-state AMFCs. The primary fuel of interests is ethanol, but hydrogen was used in the development stages to facilitate the diagnostic and evaluation of the fuel cell performance. In the preliminary investigation, AMFC was assembled using off-the-shelf electrodes and anion-exchange membrane (AEM). It was found that the performance of AMFC operating on ethanol fuel was limited by a large high-frequency resistance (HFR) value. The advantage of using non-toxic ethanol fuel was also compromised by the need to add hydrazine and potassium hydroxide to the fuel blend. Subsequently, a high performance MEA was developed for an all-solid-state AMFC, in which liquid electrolyte or other additives were not required during the operation of the fuel cell. Ionomer was incorporated in the formulation of catalyst ink, and the catalyst ink was directly coated on the anion-exchange membrane (AEM). An ionomer content of 20 wt.% was found to be the optimum amount required in the catalyst layers. It was demonstrated that the AMFC generated a maximum power density of 365 mW/cm2 and 213 mW/cm 2 with the use of hydrogen/oxygen and hydrogen/pure air, respectively. The performance of the AMFC was also found to be influenced by exposure to carbon dioxide in the air. Hence, the CCMs were pre-treated in potassium hydroxide solution and pure oxygen was used to condition the fuel cell to maximize the power output from the AMFCs. Although satisfactory performance was demonstrated in the AMFC, its stability during cell operation remains a major issue. The poor stability was attributed to degradation of ionomer in the catalyst layers, especially at the catalyst/ionomer interfaces. Ethanol was also used as a fuel in the AMFC with newly developed MEAs. Wetproof gas diffusion layers (GDLs) was found to enhance mass transport in liquid-fed AMFC. With the use of 1M ethanol, the AMFC exhibited a maximum power density of 6.482 mW/cm2 and 3.380 mW/cm2 with pure oxygen and ambient air as oxidant, respectively. These maximum power density values are the highest reported to-date. However, significant work is still necessary in advancing the AMFC technology for direct alcohol fuel cell applications.

40 CFR 1054.140 - What is my engine's maximum engine power and displacement?

Code of Federal Regulations, 2010 CFR

2010-07-01

... power and displacement? 1054.140 Section 1054.140 Protection of Environment ENVIRONMENTAL PROTECTION... engine power and displacement? This section describes how to quantify your engine's maximum engine power and displacement for the purposes of this part. (a) An engine configuration's maximum engine power is...

40 CFR 1054.140 - What is my engine's maximum engine power and displacement?

Code of Federal Regulations, 2011 CFR

2011-07-01

... power and displacement? 1054.140 Section 1054.140 Protection of Environment ENVIRONMENTAL PROTECTION... engine power and displacement? This section describes how to quantify your engine's maximum engine power and displacement for the purposes of this part. (a) An engine configuration's maximum engine power is...

40 CFR 1054.140 - What is my engine's maximum engine power and displacement?

Code of Federal Regulations, 2012 CFR

2012-07-01

... power and displacement? 1054.140 Section 1054.140 Protection of Environment ENVIRONMENTAL PROTECTION... engine power and displacement? This section describes how to quantify your engine's maximum engine power and displacement for the purposes of this part. (a) An engine configuration's maximum engine power is...

40 CFR 1054.140 - What is my engine's maximum engine power and displacement?

Code of Federal Regulations, 2014 CFR

2014-07-01

... power and displacement? 1054.140 Section 1054.140 Protection of Environment ENVIRONMENTAL PROTECTION... engine power and displacement? This section describes how to quantify your engine's maximum engine power and displacement for the purposes of this part. (a) An engine configuration's maximum engine power is...

40 CFR 1054.140 - What is my engine's maximum engine power and displacement?

Code of Federal Regulations, 2013 CFR

2013-07-01

... power and displacement? 1054.140 Section 1054.140 Protection of Environment ENVIRONMENTAL PROTECTION... engine power and displacement? This section describes how to quantify your engine's maximum engine power and displacement for the purposes of this part. (a) An engine configuration's maximum engine power is...

77 FR 40092 - License Amendment To Increase the Maximum Reactor Power Level, Florida Power & Light Company, St...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-06

... Increase the Maximum Reactor Power Level, Florida Power & Light Company, St. Lucie, Units 1 and 2 AGENCY... amendment for Renewed Facility Operating License Nos. DPR-67 and NPF-16, issued to Florida Power & Light... St. Lucie County, Florida. The proposed license amendment would increase the maximum thermal power...

Hierarchical Mn₂O₃ Microspheres In-Situ Coated with Carbon for Supercapacitors with Highly Enhanced Performances.

PubMed

Gong, Feilong; Lu, Shuang; Peng, Lifang; Zhou, Jing; Kong, Jinming; Jia, Dianzeng; Li, Feng

2017-11-23

Porous Mn₂O₃ microspheres have been synthesized and in-situ coated with amorphous carbon to form hierarchical C@Mn₂O₃ microspheres by first producing MnCO₃ microspheres in solvothermal reactions, and then annealing at 500 °C. The self-assembly growth of MnCO₃ microspheres can generate hollow structures inside each of the particles, which can act as micro-reservoirs to store biomass-glycerol for generating amorphous carbon onto the surfaces of Mn₂O₃ nanorods consisting of microspheres. The C@Mn₂O₃ microspheres, prepared at 500 °C, exhibit highly enhanced pseudocapacitive performances when compared to the particles after annealed at 400 °C and 600 °C. Specifically, the C@Mn₂O₃ microspheres prepared at 500 °C show high specific capacitances of 383.87 F g -1 at current density of 0.5 A g -1 , and excellent cycling stability of 90.47% of its initial value after cycling for 5000 times. The asymmetric supercapacitors assembled with C@Mn₂O₃ microspheres after annealed at 500 °C and activated carbon (AC) show an energy density of up to 77.8 Wh kg -1 at power density of 500.00 W kg -1 , and a maximum power density of 20.14 kW kg -1 at energy density of 46.8 Wh kg -1 . We can attribute the enhanced electrochemical performances of the materials to their three-dimensional (3D) hierarchical structure in-situ coated with carbon.

Paper-based enzymatic microfluidic fuel cell: From a two-stream flow device to a single-stream lateral flow strip

NASA Astrophysics Data System (ADS)

González-Guerrero, Maria José; del Campo, F. Javier; Esquivel, Juan Pablo; Giroud, Fabien; Minteer, Shelley D.; Sabaté, Neus

2016-09-01

This work presents a first approach towards the development of a cost-effective enzymatic paper-based glucose/O2 microfluidic fuel cell in which fluid transport is based on capillary action. A first fuel cell configuration consists of a Y-shaped paper device with the fuel and the oxidant flowing in parallel over carbon paper electrodes modified with bioelectrocatalytic enzymes. The anode consists of a ferrocenium-based polyethyleneimine polymer linked to glucose oxidase (GOx/Fc-C6-LPEI), while the cathode contains a mixture of laccase, anthracene-modified multiwall carbon nanotubes, and tetrabutylammonium bromide-modified Nafion (MWCNTs/laccase/TBAB-Nafion). Subsequently, the Y-shaped configuration is improved to use a single solution containing both, the anolyte and the catholyte. Thus, the electrolytes pHs of the fuel and the oxidant solutions are adapted to an intermediate pH of 5.5. Finally, the fuel cell is run with this single solution obtaining a maximum open circuit of 0.55 ± 0.04 V and a maximum current and power density of 225 ± 17 μA cm-2 and 24 ± 5 μW cm-2, respectively. Hence, a power source closer to a commercial application (similar to conventional lateral flow test strips) is developed and successfully operated. This system can be used to supply the energy required to power microelectronics demanding low power consumption.

Unification of field theory and maximum entropy methods for learning probability densities

NASA Astrophysics Data System (ADS)

Kinney, Justin B.

2015-09-01

The need to estimate smooth probability distributions (a.k.a. probability densities) from finite sampled data is ubiquitous in science. Many approaches to this problem have been described, but none is yet regarded as providing a definitive solution. Maximum entropy estimation and Bayesian field theory are two such approaches. Both have origins in statistical physics, but the relationship between them has remained unclear. Here I unify these two methods by showing that every maximum entropy density estimate can be recovered in the infinite smoothness limit of an appropriate Bayesian field theory. I also show that Bayesian field theory estimation can be performed without imposing any boundary conditions on candidate densities, and that the infinite smoothness limit of these theories recovers the most common types of maximum entropy estimates. Bayesian field theory thus provides a natural test of the maximum entropy null hypothesis and, furthermore, returns an alternative (lower entropy) density estimate when the maximum entropy hypothesis is falsified. The computations necessary for this approach can be performed rapidly for one-dimensional data, and software for doing this is provided.

Unification of field theory and maximum entropy methods for learning probability densities.

PubMed

Kinney, Justin B

2015-09-01

The need to estimate smooth probability distributions (a.k.a. probability densities) from finite sampled data is ubiquitous in science. Many approaches to this problem have been described, but none is yet regarded as providing a definitive solution. Maximum entropy estimation and Bayesian field theory are two such approaches. Both have origins in statistical physics, but the relationship between them has remained unclear. Here I unify these two methods by showing that every maximum entropy density estimate can be recovered in the infinite smoothness limit of an appropriate Bayesian field theory. I also show that Bayesian field theory estimation can be performed without imposing any boundary conditions on candidate densities, and that the infinite smoothness limit of these theories recovers the most common types of maximum entropy estimates. Bayesian field theory thus provides a natural test of the maximum entropy null hypothesis and, furthermore, returns an alternative (lower entropy) density estimate when the maximum entropy hypothesis is falsified. The computations necessary for this approach can be performed rapidly for one-dimensional data, and software for doing this is provided.

Porous dimanganese trioxide microflowers derived from microcoordinations for flexible solid-state asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Pang, Huan; Li, Xinran; Li, Bing; Zhang, Yizhou; Zhao, Qunxing; Lai, Wen-Yong; Huang, Wei

2016-06-01

Dimanganese trioxide microflowers are easily obtained from a Mn(ii) 8-hydroxyquinoline microcoordination after calcination in air. We also look into the possible formation mechanism of the flower-like morphology, and find that the reaction time affects the morphology of the coordination. Furthermore, the as-prepared porous Mn2O3 microflowers are made of many nanoplates which form many nanogaps and nanochannels. Interestingly, the assembled electrode based on the as-prepared porous Mn2O3 microflowers proves to be a high-performance electrode material for supercapacitors. The electrode shows a specific capacitance of 994 F g-1, which can work well even after 4000 cycles at 0.75 A g-1. More importantly, the porous Mn2O3 microflowers and activated carbons are assembled into a high-performance flexible solid-state asymmetric supercapacitor with a specific capacitance of 312.5 mF cm-2. The cycle test shows that the device can offer 95.6% capacity of the initial capacitance at 2.0 mA cm-2 after 5000 cycles with little decay. The maximum energy density of the device can achieve 6.56 mWh cm-3 and the maximum power density can also achieve 283.5 mW cm-3, which are among the best results for manganese based materials.Dimanganese trioxide microflowers are easily obtained from a Mn(ii) 8-hydroxyquinoline microcoordination after calcination in air. We also look into the possible formation mechanism of the flower-like morphology, and find that the reaction time affects the morphology of the coordination. Furthermore, the as-prepared porous Mn2O3 microflowers are made of many nanoplates which form many nanogaps and nanochannels. Interestingly, the assembled electrode based on the as-prepared porous Mn2O3 microflowers proves to be a high-performance electrode material for supercapacitors. The electrode shows a specific capacitance of 994 F g-1, which can work well even after 4000 cycles at 0.75 A g-1. More importantly, the porous Mn2O3 microflowers and activated carbons are assembled into a high-performance flexible solid-state asymmetric supercapacitor with a specific capacitance of 312.5 mF cm-2. The cycle test shows that the device can offer 95.6% capacity of the initial capacitance at 2.0 mA cm-2 after 5000 cycles with little decay. The maximum energy density of the device can achieve 6.56 mWh cm-3 and the maximum power density can also achieve 283.5 mW cm-3, which are among the best results for manganese based materials. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02267g

Fabrication of high performance bioanode based on fruitful association of dendrimer and carbon nanotube used for design O2/glucose membrane-less biofuel cell with improved bilirubine oxidase biocathode.

PubMed

Korani, Aazam; Salimi, Abdollah

2013-12-15

In this study, the preparation of an integrated modified electrode based on the covalent attachment of glucose dehydrogenase (GDH) enzyme and safranin O to amine-derivative multiwalled carbon nanotubes (MWCNTs-NH2) modified glassy carbon (GC) electrode using G2.5-carboxylated PAMAM dendrimer (Den) as linking agent is reported. The obtained results indicated that the proposed system has effective bioelectrocatalytic activity toward glucose oxidation at 100 mV with onset potential of -130 mV (vs. Ag/AgCl). The performance of the prepared hybrid system of GC/MWCNTs-NH2/Den/GDH/Safranin as anode in a membraneless enzyme-based glucose/O2 biofuel cell is further evaluated. The biocathode in this system was composed of bilirubin oxidase (BOX) enzyme immobilized onto a bilirubin modified carbon nanotube GC electrode. Immobilized BOX onto CNTs/bilirubin not only show direct electron transfer but also it has excellent electrocatalytic activity toward oxygen reduction at a positive potential of 610 mV. The open circuit voltage of the cell was 590 mV. The maximum current density was 0.5 mA cm(-2), while maximum power density of 108 μW cm(-2) was achieved at voltage of 330 mV. The immobilized enzymes in anode and cathode are very stable and output power of the BFC is approximately constant after 12 h continues operation. Copyright © 2013 Elsevier B.V. All rights reserved.

Macroscopic time and altitude distribution of plasma turbulence induced in ionospheric modification experiments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rose, H.; Dubois, D.; Russell, D.

1996-03-01

This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This research concentrated on the time dependence of the heater, induced-turbulence, and electron-density profiles excited in the ionosphere by a powerful radio-frequency heater wave. The macroscopic density is driven by the ponderomotive pressure and the density self-consistently determines the heater propagation. For typical parameters of the current Arecibo heater, a dramatic quasi-periodic behavior was found. For about 50 ms after turn-on of the heater wave, the turbulence is concentrated at the first standing-wave maximum of the heater near reflectionmore » altitude. From 50--100 ms the standing-wave pattern drops by about 1--2 km in altitude and the quasi-periodicity reappears at the higher altitudes with a period of roughly 50 ms. This behavior is due to the half-wavelength density depletion grating that is set up by the ponderomotive pressure at the maxima of the heater standing-wave pattern. Once the grating is established the heater can no longer propagate to higher altitudes. The grating is then unsupported by the heater at these altitudes and decays, allowing the heater to propagate again and initiate another cycle. For stronger heater powers, corresponding to the Arecibo upgrade and the HAARP heater now under construction, the effects are much more dramatic.« less

Directly Grown Nanostructured Electrodes for High Volumetric Energy Density Binder-Free Hybrid Supercapacitors: A Case Study of CNTs//Li4Ti5O12

NASA Astrophysics Data System (ADS)

Zuo, Wenhua; Wang, Chong; Li, Yuanyuan; Liu, Jinping

2015-01-01

Hybrid supercapacitor (HSC), which typically consists of a Li-ion battery electrode and an electric double-layer supercapacitor electrode, has been extensively investigated for large-scale applications such as hybrid electric vehicles, etc. Its application potential for thin-film downsized energy storage systems that always prefer high volumetric energy/power densities, however, has not yet been explored. Herein, as a case study, we develop an entirely binder-free HSC by using multiwalled carbon nanotube (MWCNT) network film as the cathode and Li4Ti5O12 (LTO) nanowire array as the anode and study the volumetric energy storage capability. Both the electrode materials are grown directly on carbon cloth current collector, ensuring robust mechanical/electrical contacts and flexibility. Our 3 V HSC device exhibits maximum volumetric energy density of ~4.38 mWh cm-3, much superior to those of previous supercapacitors based on thin-film electrodes fabricated directly on carbon cloth and even comparable to the commercial thin-film lithium battery. It also has volumetric power densities comparable to that of the commercial 5.5 V/100 mF supercapacitor (can be operated within 3 s) and has excellent cycling stability (~92% retention after 3000 cycles). The concept of utilizing binder-free electrodes to construct HSC for thin-film energy storage may be readily extended to other HSC electrode systems.

The relative density of forests in the United States

Treesearch

Christopher W. Woodall; Charles H. Perry; Patrick D. Miles

2006-01-01

A relative stand density assessment technique, using the mean specific gravity of all trees in a stand to predict its maximum stand density index (SDI) and subsequently its relative stand density (current SDI divided by maximum SDI), was used to estimate the relative density of forests across the United States using a national-scale forest inventory. Live tree biomass...

Two-Dimensional Microdischarge Jet Array in Air: Characterization and Inactivation of Virus

NASA Astrophysics Data System (ADS)

Nayak, Gaurav

Cold atmospheric pressure plasmas (CAPs) have proven to be quite effective for surface disinfection, wound healing and even cancer treatment in recent years. One of the major societal challenges faced today is related to illness caused by food-borne bacteria and viruses, particularly in minimally processed, fresh or ready-to-eat foods. Gastroenteritis outbreaks, caused, for example, by the human Norovirus (NV) is a growing concern. Current used technologies seem not to be fully effective. In this work we focus on a possible solution based on CAP technology for surface disinfection. Many discharge sources have been studied for disinfection and the two major challenges faced are the use of expensive noble gases (Ar/He) by many plasma sources and the difficulty to scale up the plasma devices. The efficacies of these devices also vary for different plasma sources, making it difficult to compare results from different research groups. Also, the interaction of plasma with the biological matter is not understood well, particularly for virus. In this work, a two-dimensional array of micro dielectric barrier discharge is used to treat Feline Calicivirus (FCV), which is a surrogate for human Norovirus. The plasma source can be operated with an air flow rate (up to 94 standard liters per minute or slm). The use of such discharge source also raises important scientific questions which are addressed in this work. These questions include the effect of gas flow rate on discharge properties and the production of reactive species responsible for virus inactivation and the underlying inactivation mechanism. The plasma source is characterized via several diagnostic techniques such as current voltage measurements for electrical characterization and power measurements, optical emission spectroscopy (OES) to determine the gas temperature, cross-correlation spectroscopy (CCS) for microdischarge evolution and timescales, UV absorption spectroscopy to measure the O3 density, absolute IR OES to measure the O2(a 1Deltag) density and spectrophotometry to estimate the NOx species density in aqueous medium. The results show that the discharge activity is strongly dependent on the gas flow rate particularly for gas residence times comparable to the applied high voltage cycle. The maximum difference in gas temperature at extreme plasma conditions do not exceed 50 K. The NO density is found to be reducing with smaller gas residence time. It is found that the reduced field E/N is dependent on the flow rate. The observed variation in the electric field is attributed to the change in the neutral gas densities. Both gas residence time and humidity have an impact on the space-charge distribution. The O 3 density is found to increase with increasing power density and saturates at higher power above 12 W, and the maximum density of 1022 m-3 is achieved at an intermediate flow rate of 20 slm. An optimal condition for O2(a 1Deltag) generation is found that is a balance between power and gas residence. Higher specific energy leads to higher increase of O2(a 1Deltag) density as compared to the O3 density. It is also observed that the O2(a 1Deltag) to O3 density ratio could be controlled by the flow rate from 0.7 to almost 0. The discharge source is used for FCV inactivation on surfaces (in the gas phase) and suspended in solution. Discharge power and treatment time have strong effect on the reduction in virus titer, while exposure distance or flow rate have negligible effect. Humidity plays a major effect on FCV inactivation on surfaces, leading to complete inactivation (>4 log10) within 3 minutes of treatment. FCV inactivation can be explained by O3 in gas phase and RNS in liquid phase. Nonetheless synergistic effects of ROS and RNS cannot be excluded, as similar production rates of O3 and NOx in discharge are determined. The O2(a 1Deltag) density at conditions used for FCV treatment is at least 2 orders of magnitude lower than the ozone density and is not a dominant factor in the inactivation.

Indirectly pumped 3.7 THz InGaAs/InAlAs quantum-cascade lasers grown by metal-organic vapor-phase epitaxy.

PubMed

Fujita, Kazuue; Yamanishi, Masamichi; Furuta, Shinichi; Tanaka, Kazunori; Edamura, Tadataka; Kubis, Tillmann; Klimeck, Gerhard

2012-08-27

Device-performances of 3.7 THz indirect-pumping quantum-cascade lasers are demonstrated in an InGaAs/InAlAs material system grown by metal-organic vapor-phase epitaxy. The lasers show a low threshold-current-density of ~420 A/cm2 and a peak output power of ~8 mW at 7 K, no sign of parasitic currents with recourse to well-designed coupled-well injectors in the indirect pump scheme, and a maximum operating temperature of Tmax ~100 K. The observed roll-over of output intensities in current ranges below maximum currents and limitation of Tmax are discussed with a model for electron-gas heating in injectors. Possible ways toward elevation of Tmax are suggested.

On Spatial Structuring of the F2 Layer Studied by the Satellite Radio Sounding of the Ionosphere Disturbed by High-Power HF Radio Waves

NASA Astrophysics Data System (ADS)

Tereshchenko, E. D.; Turyansky, V. A.; Khudukon, B. Z.; Yurik, R. Yu.; Frolov, V. L.

2018-01-01

We present the results of studying the characteristics of the artificial plasma structures excited in the ionospheric F2 region modified by high-power HF radio waves. The experiments were carried out at the Sura heating facility using satellite radio sounding of the ionosphere. The plasma density profile was reconstructed with the highest possible spatial resolution for today, about 4 km. In a direction close to the magnetic zenith of the pump wave, the following phenomena were observed: the formation of a cavity with a 15% lower plasma density at the altitudes of the F2 layer and below; the formation of an area with plasma density increased by 12% at altitudes greater than 400 km. With a long-term quasiperiodic impact of the pump wave on the ionosphere, wavy large-scale electron-density perturbations (the meridional scale λx ≈ 130 km and the vertical scale λz ≈ 440 km) are also formed above the Sura facility. These perturbations can be due to the plasma density modulation by an artificial acoustic-gravity wave with a period of 10.6 m, which was formed by the heat source inside a large-scale cavity with low plasma density; there is generation of the electron density irregularities for the electrons with ΔNe/Ne ≈ 3% in the form of layers having the sizes 10-12 km along and about 24 km across the geomagnetic field, which are found both below and above the F2-layer maximum. The mechanisms of the formation of these plasma structures are discussed.