29 research outputs found
Power computation for the triboelectric nanogenerator
We consider, from a mathematical perspective, the power generated by a
contact-mode triboelectric nanogenerator, an energy harvesting device that has
been well studied recently. We encapsulate the behaviour of the device in a
differential equation, which although linear and of first order, has periodic
coefficients, leading to some interesting mathematical problems. In studying
these, we derive approximate forms for the mean power generated and the current
waveforms, and describe a procedure for computing the Fourier coefficients for
the current, enabling us to show how the power is distributed over the
harmonics. Comparisons with accurate numerics validate our analysis
Effectiveness of Early Warning Dissemination A Case Study on Tsunami Early Warning in Sri Lanka
Media & Communication technology has an important role to play in disastercommunication by educating people about natural disasters. As the whole world isentertaining the results of new communication technology, the attention of the disastermanagement experts has driven towards, using this new technology in disastercommunication. Accurate and timely information about natural disasters were needednot only for the people at risk ,but also for the government officials, community leaders,donor agencies and media, to take necessary steps to reduce risk as well as to speedrecovery. Effective risk reduction involves mitigation measures in hazards prone areas.It may also involve overcoming the socioeconomic, institutional and political barriers tothe adoption of effective risk reduction strategies and measures in developing countries.Therefore, effective disaster communication is very essential for the sustainable disasterrisk reduction. As Sri Lanka is a country accustomed to disasters, this is an importantfact. In 2004, tsunami hit Sri Lanka without any prior warning. But in April, 2012 theDisaster Management Center, official institution involved in Early Warningdissemination, was equipped with new technology. Therefore, this paper is aiming atinvestigating the effectiveness of the present Early Warning dissemination mechanismin Sri Lanka. The study, being basically quantitative, employed descriptive statistics foranalytical purpose using the primary data collected in one GN Division in Galle district.The study revealed that the strongest method of Early Warning dissemination is theSiren. The community was already aware on the way they should behave on such anevent. The trust worthiness about the Early Warning message seemed to have a linkwith the authority of the party who disseminate the message. Furthermore, the electronicmedia seems to have a good reputation among the public regarding there work in EarlyWarning dissemination.Key words: Disaster communication, Early warning, Disaster risk reduction, Naturaldisaste
Kaolin shear thickening fluid reinforced UHMWPE composites for protective clothing
This study reports the designing and reinforcing of impact resistant textile composites using kaolin based shear thickening colloidal dispersions as the filler material. The reinforced fabric is targeted for the chest protection of cricketers. A shear thickening fluid (STF) has been prepared using kaolin and glycerol, at kaolin volume fractions of 34% and 38%. A combination of mixing techniques including mechanical blending and ultra-sonication are used to prepare the colloidal dispersions. Ultra high molecular weight polyethylene (UHMWPE) woven fabric structures are reinforced with the STF. The fabric coated with STF are then measured for their flexibility, and impact resistance using Shirley stiffness tester and a series of modified drop tower tests respectively. Kaolin STF at 38% volume fraction shows best results in impregnated fabric samples. STF reinforced fabrics provide better impact resistance with improved moisture absorption and flexibility in comparison to the conventional chest guard material
The use of common bean (Phaseolus vulgaris ) traditional varieties and their mixtures with commercial varieties to manage bean fly (Ophiomyia spp .) infestations in Uganda
The bean fly (Ophiomyia spp.) is considered the most economically damaging field insect pest of common beans in Uganda. Despite the use of existing pest management approaches, reported damage has remained high. Forty-eight traditional and improved common bean varieties currently grown in farmers’ fields were evaluated for resistance against bean fly. Data on bean fly incidence, severity and root damage from bean stem maggot were collected. Generalized linear mixed model (GLMM) revealed significant resistance to bean fly in the Ugandan traditional varieties. A popular resistant traditional variety and a popular susceptible commercial variety were selected from the 48 varieties and evaluated in pure and mixed stands. The incidence of bean fly infestation on both varieties in mixtures with different arrangements (systematic random versus rows), and different proportions within each of the two arrangements, was measured and analysed using GLMMs. The proportion of resistant varieties in a
mixture and the arrangement type significantly decreased bean fly damage compared to pure stands, with the highest decrease in damage registered in the systematic random mixture with at least 50 % of resistant variety. The highest reduction in root damage, obvious 21 days after planting, was found in systematic random mixtures with at least 50 % of the resistant variety. Small holder farmers in East Africa and elsewhere in the world have local preferences for growing bean varieties in genetic mixtures. These mixtures can be enhanced by the use of resistant varieties in the mixtures to reduce bean fly damage on susceptible popular varieties
A new direct detection electron scattering experiment to search for the X17 particle
A new electron scattering experiment (E12-21-003) to verify and understand
the nature of hidden sector particles, with particular emphasis on the
so-called X17 particle, has been approved at Jefferson Lab. The search for
these particles is motivated by new hidden sector models introduced to account
for a variety of experimental and observational puzzles: excess in
pairs observed in multiple nuclear transitions, the 4.2 disagreement
between experiments and the standard model prediction for the muon anomalous
magnetic moment, and the small-scale structure puzzle in cosmological
simulations. The aforementioned X17 particle has been hypothesized to account
for the excess in pairs observed from the Be M1, He M0, and,
most recently, C E1 nuclear transitions to their ground states observed
by the ATOMKI group. This experiment will use a high resolution electromagnetic
calorimeter to search for or set new limits on the production rate of the X17
and other hidden sector particles in the MeV mass range via their
decay (or decay with limited tracking). In these
models, the MeV mass range is particularly well-motivated and the
lower part of this range still remains unexplored. Our proposed direct
detection experiment will use a magnetic-spectrometer-free setup (the PRad
apparatus) to detect all three final state particles in the visible decay of a
hidden sector particle for an effective control of the background and will
cover the proposed mass range in a single setting. The use of the
well-demonstrated PRad setup allows for an essentially ready-to-run and
uniquely cost-effective search for hidden sector particles in the MeV
mass range with a sensitivity of 8.910 - 5.810 to
, the square of the kinetic mixing interaction constant between
hidden and visible sectors.Comment: 6 pages, 7 figures. arXiv admin note: substantial text overlap with
arXiv:2108.1327
The use of common bean (Phaseolus vulgaris) traditional varieties and their mixtures with commercial varieties to manage bean fly (Ophiomyia spp.) infestations in Uganda
The potential impact on obesity of a 10% tax on sugar-sweetened beverages in Ireland, an effect assessment modelling study
Power computation for the triboelectric nanogenerator
We consider, from a mathematical perspective, the power generated by a contact-mode triboelectric nanogenerator, an energy harvesting device that has been thoroughly studied recently. We encapsulate the behaviour of the device in a differential equation, which although linear and of first order, has periodic coefficients, leading to some interesting mathematical problems. In studying these, we derive approximate forms for the mean power generated and the current waveforms, and describe a procedure for computing the Fourier coefficients for the current, enabling us to compute the power accurately and show how the power is distributed over the harmonics. Comparisons with numerics validate our analysis
Kaolin shear thickening fluid reinforced UHMWPE composites for protective clothing
241-244This study reports the designing and reinforcing of impact resistant textile composites using kaolin based shear thickening colloidal dispersions as the filler material. The reinforced fabric is targeted for the chest protection of cricketers. A shear thickening fluid (STF) has been prepared using kaolin and glycerol, at kaolin volume fractions of 34% and 38%. A combination of mixing techniques including mechanical blending and ultra-sonication are used to prepare the colloidal dispersions. Ultra high molecular weight polyethylene (UHMWPE) woven fabric structures are reinforced with the STF. The fabric coated with STF are then measured for their flexibility, and impact resistance using Shirley stiffness tester and a series of modified drop tower tests respectively. Kaolin STF at 38% volume fraction shows best results in impregnated fabric samples. STF reinforced fabrics provide better impact resistance with improved moisture absorption and flexibility in comparison to the conventional chest guard material
Direct Current Contact-Mode Triboelectric Nanogenerators via Systematic Phase Shifting
The intermittency and discontinuous nature of power generation in Triboelectric Nanogenerators (TENGs) are arguably their most significant drawback, despite the promise demonstrated in low-power electronics. Herein, we introduce a novel technology to overcome this issue, in which, built-in systematic phase shifting of multiple poles is used to design a pseudo direct-current TENG. Unlike previous attempts of constructing near direct-current TENGs that base on the segmentation of electrodes of a sliding mode TENG, this technology introduces a new method that depends on planned excitation of constituent TENG units at different time intervals to obtain the necessary phase shifts, achieved by their structural design that contains an asymmetric spatial arrangement. Therefore, the direct current generation for TENG, which was previously limited to the sliding mode TENG units, are expanded to contact-mode TENGs. The technology allows for continuous and smooth operation of the driven loads and paves the way for a new dawn in energy scavenging from mechanical sources. We use the distance-dependent electric field (DDEF) platform to design the systematic phase shifting technology, which is experimentally demonstrated via a free-standing mode TENG (FSTENG) based design, to power a number of prototype devices. The resultant power output of the TENG indicates a crest factor close to 1.1 at relatively low frequencies, the best reported values for TENGs with contact-mode basic units, to date. This work provides a highly awaited solution to overcome the intermittency and sporadic nature of TENG outputs, thus, promoting the field towards powering next generation autonomous and mobile electronics