99 research outputs found
Main restrictions in the synthesis of new superheavy elements: quasifission or/and fusion-fission
The synthesis of superheavy elements stimulates the effort to study the
peculiarities of the complete fusion with massive nuclei and to improve
theoretical models in order to extract knowledge about reaction mechanism in
heavy ion collisions at low energies. We compare the theoretical results of the
compound nucleus (CN) formation and evaporation residue (ER) cross sections
obtained for the Ca+Cm and Fe+Th reactions
leading to the formation of the isotopes A=296 and A=290, respectively, of the
new superheavy element Lv (Z=116). The ER cross sections, which can be measured
directly, are determined by the complete fusion and survival probabilities of
the heated and rotating compound nucleus. That probabilities can not be
measured unambiguously but the knowledge about them is important to study the
formation mechanism of the observed products. For this aim, the
Ca+Cf and Ni+Th reactions have been considered
too. The use of the mass values of superheavy nuclei calculated in the
framework of the macroscopic-microscopic model by Warsaw group leads to smaller
ER cross section for all of the reactions (excluding the Ni+Th
reaction) in comparison with the case of using the masses calculated by Peter
M\"oller {\it et al}.Comment: 26 pages and 15 figures. arXiv admin note: text overlap with
arXiv:1109.201
Diquarks: a QCD sum rule perspective
We propose a phenomenological QCD sum rule with an explicit diquark field to
investigate the essential ingredients inside the hadrons. Introducing the mass
(m_\phi) and the condensate (\phi^2) for the diquark field as parameters in the
model, we find that the sum rule works well for Lambda, Lambda_c and Lambda_b.
This implies that these Lambda baryons can be represented by a diquark and a
quark configuration. We also find that there is a duality relation among the
parameters (m_\phi, \phi^2), for which the sum rule is equally good. In the
limit when \phi^2 =0 we find m_\phi=0.4 GeV, which can be thought as the
constituent diquark mass.Comment: 4 pages, 4 figures, revised version published in Phys. Rev.
Assessment of weather events impacts on forage production trend of sorghum-sudangrass hybrid
This study aimed to assess the impact of weather events on the sorghum-sudangrass hybrid (Sorghum bicolor L.) cultivar production trend in the central inland region of Korea during the monsoon season, using time series analysis. The sorghum-sudangrass production data collected between 1988 and 2013 were compiled along with the production year’s weather data. The growing degree days (GDD), accumulated rainfall, and sunshine duration were used to assess their impacts on forage production (kg/ha) trend. Conversely, GDD and accumulated rainfall had positive and negative effects on the trend of forage production, respectively. Meanwhile, weather events such as heavy rainfall and typhoon were also collected based on weather warnings as weather events in the Korean monsoon season. The impact of weather events did not affect forage production, even with the increasing frequency and intensity of heavy rainfall. Therefore, the trend of forage production for the sorghum-sudangrass hybrid was forecasted to slightly increase until 2045. The predicted forage production in 2045 will be 14,926 ± 6,657 kg/ha. It is likely that the damage by heavy rainfall and typhoons can be reduced through more frequent harvest against short-term single damage and a deeper extension of the root system against soil erosion and lodging. Therefore, in an environment that is rapidly changing due to climate change and extreme/abnormal weather, the cultivation of the sorghum-sudangrass hybrid would be advantageous in securing stable and robust forage production. Through this study, we propose the cultivation of sorghum-sudangrass hybrid as one of the alternative summer forage options to achieve stable forage production during the dynamically changing monsoon, in spite of rather lower nutrient value than that of maize (Zea mays L.)
Parameter Calibration Method Based On GA Technique For Multi-Event
Accurate parameter estimation based catchment modeling systems requires considerable work to establish credibility. In this paper, a methodology for parameter estimation of hydrologic simulation model is proposed to simultaneously include several rainfall events using Shannon entropy. The proposed methodology uses Genetic Algorithm(GA) optimization techniques for the Storm Water Management Model (SWMM). Shannon entropy theory was applied to calculate weights according to each rainfall event in study area. A case study application was undertaken using the Milyang-dam basin, in Korea. Three events are applied to calculate Shannon entropy weights. Then, Nash-Sutcliffe Efficiency(NSE) & Root Mean Square Error(RMSE) are compared with those from single event. This study suggests that the proposed methodology is capable of providing effective parameter estimation method
Characteristics of Korean Suicide: A Case-control Psychological Autopsy Study
Translated from the article published in Korean Journal of Psychology: General, Vol.31, No. 2 (2012), with permission from the Korean Psychological Association.The pattern of psychological and clinical risk factors for suicide among Korean population is an important issue. This study aimed to identify the risk factor characteristics for Korean suicides. This case-control psychological autopsy (PA) study compared 56 suicide deceased with 36 living controls matched by age and gender. Semi-structured interviews were conducted with family members, cohabitants, and the next of kin of the subjects. Data were collected on a wide range of potential risk and protective factors, including demographic, life event, clinical and psychological variables. The relative contribution of these factors to suicide was examined using a binary logistic regression model. As a result, several factors were found to significantly and independently contribute to suicide: adjustment to work and school, trusting people, problem with cohabitants, unhappiness in childhood, history of past suicide attempts, psychiatric illness, psychological stress from life events, and difficulties with life in the aspect of object and duration. Though both case group and control group have life events and difficulties such as financial problem, relationship conflicts, and so on over the ratio of 90%, the level of stress in the case groups was significantly much more severe. Besides, psychological strain was found to play an important role in suicide. Risk factors for suicide in Korea are definitely similar to those in the West, China, and Japan
Observation of surface layering in a nonmetallic liquid
Oscillatory density profiles (layers) have previously been observed at the
free surfaces of liquid metals, but not in other isotropic liquids. We have
used x-ray reflectivity to study a molecular liquid,
tetrakis(2-ethylhexoxy)silane. When cooled to T/Tc~0.25 (well above the
freezing point for this liquid), density oscillations appear at the surface.
Lateral order within the layers is liquid-like. Our results confirm theoretical
predictions that a surface-layered state will appear even in dielectric liquids
at sufficiently low temperatures, if not preempted by freezing.Comment: accepted for publication in Phys. Rev. Lett. 15 pages 4 figure
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