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"Seesaw."
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Simple machine experiments using seesaws, wheels, pulleys, and more : one hour or less science experiments
Describes experiments involving simple machines that follow the scientific method, and can be completed in an hour or less. Explore using levers to control motion and lift, and how the steepness of inclined planes affects the force needed to move something. Most experiments also include ideas for science fair projects.
Book
Design and development of children's seesaw for energy harvesting
Renewable energy systems have gained a vital impact in the following years which has the direct and important factor to decrease the carbon emission and solving the problem of global warming. Renewable energy can be produced by capturing different types of energy from several sources through various methods. A part of these sources of renewable energy relies on capturing and utilizing kinetic energy as a reliable and environmentally friendly source of power. This article introduces a novel design for a seesaw playground game that seeks to generate energy while also improving the efficiency and ease of system installation in the playground area. The overall system comprised using mechanical design, Electrical design and controller which are integrated together for the purpose of energy production. Development in the structure of mechanical parts that combined together to formulate the standard design of seesaw playground has attained in which Two- side seats are linked through a shaft in the dual-sided from the free ends of the central axis and below each seat, a column of a certain length extends vertically and downwards, and connected to a rotating disc. Two revolve rings on both sides, molded together through a shaft and gear box with a rotation ratio one to ten turns of the final rings, in which it’s finally connected into a DC generator. A booster circuit is utilized and connected with the DC generator to maintain the same level of output voltage in which a controller circuit is involved to overcome the problem of output voltage variations. The produced electricity is varying between (1.8-5) W/h that it considered an important for power generation in the activity park. Despite the relatively low gathered power, such systems are considered important and applicable by supporting the green zone area with the power demands for the small devices and lightening.
Journal Article
The seesaw path to leptonic CP violation
Future experiments such as SHiP and high-intensity
e
+
e
-
colliders will have a superb sensitivity to heavy Majorana neutrinos with masses below
M
Z
. We show that the measurement of the mixing to electrons and muons of one such state could establish the existence of CP violating phases in the neutrino mixing matrix, in the context of low-scale seesaw models. We quantify in the minimal model the CP reach of these future experiments, and demonstrate that CP violating phases in the mixing matrix could be established at 5
σ
CL in a very significant fraction of parameter space.
Journal Article
The Exceptional 2018 European Water Seesaw Calls for Action on Adaptation
Temperature and precipitation are the most important factors responsible for agricultural productivity variations. In 2018 spring/summer growing season, Europe experienced concurrent anomalies of both. Drought conditions in central and northern Europe caused yield reductions up to 50% for the main crops, yet wet conditions in southern Europe saw yield gains up to 34%, both with respect to the previous 5-year mean. Based on the analysis of documentary and natural proxy-based seasonal paleoclimate reconstructions for the past half millennium, we show that the 2018 combination of climatic anomalies in Europe was unique. The water seesaw, a marked dipole of negative water anomalies in central Europe and positive ones in southern Europe, distinguished 2018 from the five previous similar droughts since 1976. Model simulations reproduce the 2018 European water seesaw in only 4 years out of 875 years in historical runs and projections. Future projections under the RCP8.5 scenario show that 2018-like temperature and rainfall conditions, favorable to crop growth, will occur less frequent in southern Europe. In contrast, in central Europe high-end emission scenario climate projections show that droughts as intense as 2018 could become a common occurrence as early as 2043. While integrated European and global agricultural markets limited agro-economic shocks caused by 2018's extremes, there is an urgent need for adaptation strategies for European agriculture to consider futures without the benefits of any water seesaw.
Journal Article
Ocean circulation, ice shelf, and sea ice interactions explain Dansgaard–Oeschger cycles
The last glacial interval experienced abrupt climatic changes called Dansgaard–Oeschger (DO) events. These events manifest themselves as rapid increases followed by slow decreases of oxygen isotope ratios in Greenland ice core records. Despite promising advances, a comprehensive theory of the DO cycles, with their repeated ups and downs of isotope ratios, is still lacking. Here, based on earlier hypotheses, we introduce a dynamical model that explains the DO variability by rapid retreat and slow regrowth of thick ice shelves and thin sea ice in conjunction with changing subsurface water temperatures due to insulation by the ice cover. Our model successfully reproduces observed features of the records, such as the sawtooth shape of the DO cycles, waiting times between DO events across the last glacial, and the shifted antiphase relationship between Greenland and Antarctic ice cores. Our results show that these features can be obtained via internal feedbacks alone. Warming subsurface waters could have also contributed to the triggering of Heinrich events. Our model thus offers a unified framework for explaining major features of multimillennial climate variability during glacial intervals.
Journal Article
Precipitation seesaw phenomenon and its formation mechanism in the eastern and western parts of Northwest China during the flood season
Extending across three major plateaus, namely the Qinghai-Tibetan Plateau, the Inner Mongolia-Xinjiang Plateau and the Loess Plateau, Northwest China has the complex terrain and spatio-temporal climate variations, and is affected by the interactions among different circulation systems, such as the summer monsoon, the westerlies and the plateau monsoon. The understanding of the climate variability, as well as its characteristics and evolution mechanisms in this area has been limited so far. In this paper, the precipitation characteristics and mechanisms in the eastern and western parts of Northwest China during the flood season are compared and analyzed based on the data from 192 national meteorological observational sites in Northwest China in 1961–2016. The results show that, divided by the northern boundary of the East Asian summer monsoon, there are huge differences in the precipitation variation characteristics between the eastern and western parts. The inter-annual variations, inter-decadal variations and total trends in the two parts all show a significant seesaw phenomenon. Moreover, it is found that the seesaw phenomenon of precipitation variation is closely related to the opposite variation between the East Asian summer monsoon index (MI) and the westerly circulation index (WI). In addition, the inverse variations on different time scales are only related to the contributions of precipitation at specific grades. Besides, in the two matching patterns of precipitation in the seesaw phenomenon, the middle and high latitudes are occupied by the “high-low-high” wave trains in the precipitation increases in the east of Northwest China (ENWC) and decreases in the west of Northwest China (WNWC) pattern, meaning precipitation increases in ENWC and decreases in WNWC. Whereas the opposite “low-high-low” wave trains at 500 hPa height are observed in the middle and high latitudes in the WH-EA pattern at 500 hPa height, meaning precipitation increases in WNWC and decreases in ENWC. Thus, the atmosphere circulation situation with two wave train types can support both the precipitation seesaw phenomenon and the opposite variation between MI and WI. Moreover, the seesaw phenomenon is shown to be related to the separate or joint effects of the South Asian High, ENSO and the plateau heating on the common but opposite effect on the summer monsoon and the westerlies, in which the South Asian High probably plays a more critical role. This study could deepen the scientific understanding of precipitation mechanisms and improve the weather forecast technology in Northwest China during the flood season.
Journal Article
LEPTOGENESIS AS THE ORIGIN OF MATTER
▪ Abstract We explore in some detail the hypothesis that the generation of a primordial lepton-antilepton asymmetry (Leptogenesis) early on in the history of the Universe is the root cause for the origin of matter. After explaining the theoretical conditions for producing a matter-antimatter asymmetry in the Universe we detail how, through sphaleron processes, it is possible to transmute a lepton asymmetry—or, more precisely, a (B – L)-asymmetry—into a baryon asymmetry. Because Leptogenesis depends in detail on properties of the neutrino spectrum, we review briefly existing experimental information on neutrinos as well as the seesaw mechanism, which offers a theoretical understanding of why neutrinos are so light. The bulk of the review is devoted to a discussion of thermal Leptogenesis, and we show that for the neutrino spectrum suggested by oscillation experiments, one obtains the observed value for the baryon to photon density ratio in the Universe, independently of any initial boundary conditions. In the latter part of the review we consider how well Leptogenesis fits with particle physics models of dark matter. Although axionic dark matter and Leptogenesis can be very naturally linked, there is a potential clash between Leptogenesis and models of supersymmetric dark matter because the high temperature needed for Leptogenesis leads to an overproduction of gravitinos, which alter the standard predictions of Big Bang Nucleosynthesis. This problem can be resolved, but it constrains the supersymmetric spectrum at low energies and the nature of the lightest supersymmetric particle (LSP). Finally, as an illustration of possible other options for the origin of matter, we discuss the possibility that Leptogenesis may occur as a result of non-thermal processes.
Journal Article
West-warming East-cooling trend over Antarctica reversed since early 21st century driven by large-scale circulation variation
Antarctic climate changes prior to 2000 were characterized by a strong zonally asymmetric pattern. Over 90% of the land ice mass loss occurred around a limited area in West Antarctica, accompanied by a rapid surface warming rate about three times the global mean. In contrast, surface warming and glacier mass loss around East Antarctica are not significant, until the decades since 2000 when several individual stations show that the temperature trends might have reversed. The asymmetric climate changes between East- and West-Antarctica are largely attributable to the inter-decadal variabilities over the Pacific and Atlantic Oceans through tropical–polar teleconnections, leaving open the question of whether the post-2000 phase shift of the lower-latitude decadal variability causes a flip of the asymmetric Antarctic changes. Here, by synthesizing 26 in-situ observations and 6 reanalysis datasets using a statistical method and integrating the results with a series of climate model experiments, we find that the West-warming, East-cooling trend over Antarctica has systematically reversed in austral spring since the early 21st century, largely due to the atmospheric circulation anomaly over the Antarctic Peninsula–Weddell Sea region, which is associated to the teleconnection with Pacific and atmospheric internal variability. This reversal of the temperature seesaw suggests that substantial decadal-scale fluctuations of the Antarctic climate system exist, including for sea-ice and land-ice systems, superimposed on and modifying longer term changes.
Journal Article
Renormalization group running of neutrino parameters
Neutrinos are ghost-like particles that interact only very weakly with other particles. As ongoing experiments to measure their properties improve, Ohlsson and Zhou review neutrino mass models and the renormalization group running of neutrino parameters that aim to understand the origin of neutrino mass.
Neutrinos are the most elusive particles in our Universe. They have masses at least one million times smaller than the electron mass, carry no electric charge and very weakly interact with other particles, meaning that they are rarely captured in terrestrial detectors. Tremendous efforts in the past two decades have revealed that neutrinos can transform from one type to another as a consequence of neutrino oscillations—a quantum mechanical effect over macroscopic distances—yet the origin of neutrino masses remains puzzling. The physical evolution of neutrino parameters with respect to energy scale may help elucidate the mechanism for their mass generation.
Journal Article
Deviations From μ ‐ τ Symmetry Using Δ (27) Group on Neutrino Masses and Mixings
The implication of the neutrino mass model based on Δ (27) discrete flavor symmetry, on parameters of neutrino oscillations, CP violation, and effective neutrino masses is studied using the Type I seesaw mechanism. The standard model particle content is extended by adding two additional Higgs doublets, three right‐handed neutrinos, and two scalar triplets under Δ (27) symmetry predicting diagonal charged lepton mass matrix. This can generate the desired deviation from μ ‐ τ symmetry. The resulting neutrino oscillation parameters are well agreed with the latest global fit oscillation data. The sum of the three absolute neutrino mass eigenvalues, ∑ i | m i | ( i = 1, 2, 3), is found to be consistent with the value given by the latest Planck cosmological data, ∑ i | m i | < 0.12 eV. The model further predicts effective neutrino masses for neutrinoless double beta decay, 4.15 meV ≤ m e e ≤ 30.6 meV; tritium beta decay, 8.4 meV ≤ m β ≤ 30.5 meV; Jarlskog invariant, J C P = ±0.022 for CP violation; baryon asymmetry Y B = 1.15 × 10 −10 for normal hierarchical case; and also 49.5 meV ≤ m e e ≤ 51.7 meV, 49.5 meV ≤ m β ≤ 51.4 meV, J C P = ±0.022, and Y B = 1.12 × 10 −10 for inverted hierarchical case, respectively.
Journal Article