1,720,966 research outputs found
Current status of the CXI beamline at the PAL-XFEL
No full textThe Pohang Accelerator Laboratory's X-ray free electron laser (PAL-XFEL) is a research facility currently under construction. It will provide ultra-bright (1 x 10(12) photons/pulse at 12.4 keV) and ultra-short (10 - 60 femtosecond) X-ray pulses. The CXI (coherent X-ray imaging) hard X-ray experimental station is designed to deliver brilliant hard X-rays (2 - 20.4 keV) and to measure diffraction signals with a forward scattering geometry. It will not only offer imaging studies of biological, chemical and physical samples with the "diffraction-before-destruction" scheme, but also be helpful in high-field hard X-ray physics and material science. The scientific programs are currently aimed at serial femtosecond crystallography (SFX) and coherent diffraction imaging (CDI) for bio specimens, nano materials, etc. In this paper, we describe the beamline layout, beam diagnostics, X-ray focusing optics, sample environments and detector system at the CXI experimental hutch.11Nsciescopuskc
Measurement of isomeric-yield ratios for the Au-197(gamma,n)Au-196m,Au-g reactions induced by bremsstrahlung
No full textWe measured isomeric-yield ratios for the Au-197(gamma,n)Au-196m,Au-g reactions with bremsstrahlung energies of 50-, 60-, 70- MeV, and 2.5-GeV at the two different electron linac of the Pohang accelerator laboratory by using the activation method. The photons were produced when a pulsed electron beam hit a thin tungsten target. The well-known photoactivation method was used and hence the induced activities in the irradiated foils were measured with the high-resolution gamma-ray spectrometric system consisting of lithium drifted high-purity Germanium detector and a multichannel analyzer. The measured isomeric-yield ratios for the Au-197(gamma,n)Au-196m,Au-g reactions were (4.95 +/- A 0.51) x 10(-4), (5.72 +/- A 0.72) x 10(-4), (6.03 +/- A 0.50) x 10(-4), and (9.27 +/- A 0.83) x 10(-4) for 50-, 60-, 70-MeV, and 2.5-GeV bremsstrahlung energies, respectively. The present results measured with the bremsstrahlung energy higher than 60-MeV are the first measurement.X1177sciescopu
Development of PAL-XFEL undulator system
No full textPohang Accelerator Laboratory (PAL) have developed a 0.1 nm SASE based FEL based on 10 GeV S-band linear accelerator named PAL-XFEL. At the first stage, PAL-XFEL needs two undulator lines for photon source. The hard X-ray undulator line requires 20 units of 5 m long hybrid-type conventional planar undulator and soft X-ray line requires 7 units of 5 m long hybrid type planar undulators. PAL have developed undulator magnetic structure based on EU-XFEL concepts. In this report, the impact of the background field, alignment issues, the results of pole height tuning, and final magnetic measurement results are summarized.111sciescopuskc
Mass-yield distributions of fission products from photo-fission of Pb-nat induced by 50-70 MeV bremsstrahlung
No full textThe mass-yield distributions of various fission products have been determined in the 50-, 60- and 70-MeV end point bremsstrahlung induced fission of Pb-nat using off-line gamma-ray spectrometric technique in the electron linac at Pohang Accelerator Laboratory, Korea. The mass-yield distributions are symmetric with average mass of 102.34, 102.25 and 102.03 and FWHM of 21, 22 and 23 mass unit, respectively. From the present data and literature data in the 50-85 MeV bremsstrahlung induced fission of Bi-209 the following observations were obtained: (i) The average masses of the yield distributions in the 50-85 MeV bremsstrahlung induced fission of Pb-nat and Bi-209 are around 102.25 +/- A 0.25 and 103 +/- A 0.5, respectively. (ii) The FWHM of the mass-yield distributions increases from about 21 mass units at 50 MeV to 23 mass units at 70-85 MeV, which is explained from the point of increase in multi-chance fission probability with increasing excitation energy. (iii) Within the bremsstrahlung energy range of 50-85 MeV, the role of nuclear structure effect in the mass-yield distribution was observed in the photo-fission of Bi-209, whereas it was not seen in case of Pb-nat. This may be due to the presence of so many isotopes in Pb-nat unlike mono-isotopic Bi-209.X1145sciescopu
Stabilization of radiation intensity at an electron-based THz radiation facility
No full textThe femtosecond (fs) terahertz (THz) beamline of Pohang Accelerator Laboratory (PAL) is providing a THz radiation with the pulse energy of 7 mu J by means of coherent transition radiation (CTR) from a 65-MeV electron beam. The fs-THz beamline is dedicated to the user service operation for which we need to provide a stable radiation for beamline experiments. For this purpose, we have improved electron bunch length measurement and an RF phase feedback system for stabilizing the THz radiation intensity.11Nsciescopuskc
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Remarks on Exceptional Case-marking in English(II)
No full textChomsky(1981)의 격이론에서 ?-Deltion이란 규칙을 통한 예외적 격표시 현상으로 다루어진 자료들을 고찰하여 보았으며, 또한 이에 대한 ?-Deletion의 특별성(ad hocness)을 지적한 제 연구들을 비판적으로 고찰하였다. 이들이 내포하고 있는 문제점들을 ?범주의 COMP에의 격표시 가능성을 제시한 고인수(1983)을 바탕으로 삼투지배라는 구조적 개념을 도입하여 설명하고자 하였다. 또한 이와같은주장을 통하여 PRO의 비지배특성을 버림으로써 일반성을 띈 설명을 할 수 있다고 보여지며, 이와 같은 공범주 PRO에 대한 재평가는 결국 Chomsky(1981)가 제시한 결속이론과 통제이론의 적용범주를 재확립할 필요성이 있음을 시사하는것이며, 이는 최근의 Manzini(1983), Sportiche(1983), Bouchard(1983)등의 접근방법과 그 맥을 같이 하는 것으로 볼 수 있다.This paper discusses some problems in connection with Chomsky's ?-Deletion approach to the analysis of Exceptional Case-marking and some alternatives proposed by Kayne(1981), Lee(1984) and Ko(1983). And it proposes a new approach with an attempt to establish the notion of percolating government without ?-Deletion.
The new solution can capture more generalization and provide a real explanation to the theory of grammar in GB theory, And this notion of percolating government suggests the dependency of Control Theory on Binding Theory which goes with the current approaches by Manzini(1983), Sportiche(1983) and Bouchard(1983).~This paper discusses some problems in connection with Chomsky's ?-Deletion approach to the analysis of Exceptional Case-marking and some alternatives proposed by Kayne(1981), Lee(1984) and Ko(1983). And it proposes a new approach with an attempt to establish the notion of percolating government without ?-Deletion.
The new solution can capture more generalization and provide a real explanation to the theory of grammar in GB theory, And this notion of percolating government suggests the dependency of Control Theory on Binding Theory which goes with the current approaches by Manzini(1983), Sportiche(1983) and Bouchard(1983).
A Pragmatic Approach to LD and TOP
No full text본고는 영어에서 유사한 통사구조를 갖는 LD와 TOP 구문을 중심으로 이들 유표적 통사구문들이 갖는 화용적 기능을 화자와 청자의 상호 관계 및 담화맥락의 관점에서 비교 검토하여 보고자 한다.
1장에서는 LD와 TOP구문이 갖는 담화상의 분포가 다름을 보이고 있으며, 2장에서 는 LD가 갖는 담화상의 기능 및 LD구문이 포함된 담화의 특성 등을 살펴보고 있다. 3장에서 TOP구문이 갖는 담화상의 기능 및 LD와의 기능상의 차이점을 살펴본다. 4장은 LD와 TOP의 담화상의 기능상 공통점과 차이점에 관한 요약과 더불어, 차후 더 보완되어야 할 점들을 살펴본다.The objective of the present paper is to define the discourse-pragmatic functions of English LD and TOP constructions. It is hypothesized that certain formally marked classes of syntactic constructions in English have certain marked classes of discourse-pragmatic functions. It is argued that English LD and TOP constructions have some differentiated pragmatic functions on the basis of interaction of interlocutors and the characteristics of discourse entities involving these constructions.The objective of the present paper is to define the discourse-pragmatic functions of English LD and TOP constructions. It is hypothesized that certain formally marked classes of syntactic constructions in English have certain marked classes of discourse-pragmatic functions. It is argued that English LD and TOP constructions have some differentiated pragmatic functions on the basis of interaction of interlocutors and the characteristics of discourse entities involving these constructions
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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