3,298 research outputs found
Proto-type installation of a double-station system for the optical-video-detection and orbital characterisation of a meteor/fireball in South Korea
We give a detailed description of the installation and operation of a
double-station meteor detection system which formed part of a research &
education project between Korea Astronomy Space Science Institute and Daejeon
Science Highschool. A total of six light-sensitive CCD cameras were installed
with three cameras at SOAO and three cameras at BOAO observatory. A
double-station observation of a meteor event enables the determination of the
three-dimensional orbit in space. This project was initiated in response to the
Jinju fireball event in March 2014. The cameras were installed in
October/November 2014. The two stations are identical in hardware as well as
software. Each station employes sensitive Watec-902H2 cameras in combination
with relatively fast f/1.2 lenses. Various fields of views were used for
measuring differences in detection rates of meteor events. We employed the
SonotaCo UFO software suite for meteor detection and their subsequent analysis.
The system setup as well as installation/operation experience is described and
first results are presented. We also give a brief overview of historic as well
as recent meteor (fall) detections in South Korea. For more information please
consult http://meteor.kasi.re.kr .Comment: Technical/instrumentation description of a professional meteor
detection system, 23 pages, 20 figures (color/monochrome), 5 tables,
submitted to the Journal of Korean Astronomical Society (JKAS,
http://jkas.kas.org/, http://jkas.kas.org/history.html
Technical Efficiency in the Iron and Steel Industry: A Stochastic Frontier Approach
In this paper we examine the technical efficiency of firms in the iron and steel industry and try to identify the factors contributing to the industry's efficiency growth, using a time-varying stochastic frontier model. Based on our findings, which pertain to 52 iron and steel firms over the period of 1978-1997, POSCO and Nippon Steel were the most efficient firms, with their production, on average, exceeding 95 percent of their potential output. Our findings also shed light on possible sources of efficiency growth in the industry. If a firm is government-owned, its privatization is likely to improve its technical efficiency to a great extent. A firm's technical efficiency also tends to be positively related to its production level as measured by a share of the total world production of crude steel. Another important source of efficiency growth identified by our empirical findings is adoption of new technologies and equipment. Our findings clearly indicate that continued efforts to update technologies and equipment are critical in pursuit of efficiency in the iron and steel industry.
Quantitative and empirical demonstration of the Matthew effect in a study of career longevity
The Matthew effect refers to the adage written some two-thousand years ago in
the Gospel of St. Matthew: "For to all those who have, more will be given."
Even two millennia later, this idiom is used by sociologists to qualitatively
describe the dynamics of individual progress and the interplay between status
and reward. Quantitative studies of professional careers are traditionally
limited by the difficulty in measuring progress and the lack of data on
individual careers. However, in some professions, there are well-defined
metrics that quantify career longevity, success, and prowess, which together
contribute to the overall success rating for an individual employee. Here we
demonstrate testable evidence of the age-old Matthew "rich get richer" effect,
wherein the longevity and past success of an individual lead to a cumulative
advantage in further developing his/her career. We develop an exactly solvable
stochastic career progress model that quantitatively incorporates the Matthew
effect, and validate our model predictions for several competitive professions.
We test our model on the careers of 400,000 scientists using data from six
high-impact journals, and further confirm our findings by testing the model on
the careers of more than 20,000 athletes in four sports leagues. Our model
highlights the importance of early career development, showing that many
careers are stunted by the relative disadvantage associated with inexperience.Comment: 13 pages, 7 figures, 4 Tables; Revisions in response to critique and
suggestions of referee
Point Mutation of Hoxd12 in Mice
Purpose: Genes of the HoxD cluster play a major role in vertebrate limb development, and changes that modify the Hoxd12 locus affect other genes also, suggesting that HoxD function is coordinated by a control mechanism involving multiple genes during limb morphogenesis. In this study, mutant phenotypes were produced by treatment of mice with chemical mutagen, N-ethyl-N-nitrosourea (ENU). We analyzed mutant mice exhibiting the specific microdactyly phenotype and examined the genes affected. Materials and Methods: We focused on phenotype characteristics including size, bone formation, and digit morphology of ENU-induced microdactyly mice. The expressions of several molecules were analyzed by genome-wide screening and quantitative real-time PCR to define the affected genes. Results: We report on limb phenotypes of an ENU-induced A-to-C mutation in the Hoxd12 gene, resulting in alanine-to-serine conversion. Microdactyly mice exhibited growth defects in the zeugopod and autopod, shortening of digits, a missing tip of digit I, limb growth affected, and dramatic increases in the expressions of Fgf4 and Lmx1b. However, the expression level of Shh was not changed Hoxd12 point mutated mice. Conclusion: These results suggest that point mutation rather than the entire deletion of Hoxd12, such as in knockout and transgenic mice, causes the abnormal limb phenotype in microdactyly mice. The precise nature of the spectrum of differences requires further investigation.link_to_subscribed_fulltex
MuNES: Multifloor Navigation Including Elevators and Stairs
We propose a scheme called MuNES for single mapping and trajectory planning
including elevators and stairs. Optimized multifloor trajectories are important
for optimal interfloor movements of robots. However, given two or more options
of moving between floors, it is difficult to select the best trajectory because
there are no suitable indoor multifloor maps in the existing methods. To solve
this problem, MuNES creates a single multifloor map including elevators and
stairs by estimating altitude changes based on pressure data. In addition, the
proposed method performs floor-based loop detection for faster and more
accurate loop closure. The single multifloor map is then voxelized leaving only
the parts needed for trajectory planning. An optimal and realistic multifloor
trajectory is generated by exploring the voxels using an A* algorithm based on
the proposed cost function, which affects realistic factors. We tested this
algorithm using data acquired from around a campus and note that a single
accurate multifloor map could be created. Furthermore, optimal and realistic
multifloor trajectory could be found by selecting the means of motion between
floors between elevators and stairs according to factors such as the starting
point, ending point, and elevator waiting time. The code and data used in this
work are available at https://github.com/donghwijung/MuNES
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