20,275 research outputs found
On a New Approach for Constructing Wormholes in Einstein-Born-Infeld Gravity
We study a new approach for the wormhole construction in Einstein-Born-Infeld
gravity, which does not require exotic matters in the Einstein equation. The
Born-Infeld field equation is not modified from "coordinate independent"
conditions of continuous metric tensor and its derivatives, even though the
Born-Infeld fields have discontinuities in their derivatives at the throat in
general. We study the relation of the newly introduced conditions with the
usual continuity equation for the energy-momentum tensor and the gravitational
Bianchi identity. We find that there is no violation of energy conditions for
the Born-Infeld fields contrary to the usual approaches. The exoticity of
energy-momentum tensor is not essential for sustaining wormholes. Some open
problems are discussed.Comment: Minor revision to improve the clarity, Corrected typos, Added
reference and footnot
implications for paleobiogeography, paleoecology, and evolution, with a taxonomic review of Mongolian armored dinosaurs
ํ์๋
ผ๋ฌธ(๋ฐ์ฌ) -- ์์ธ๋ํ๊ต๋ํ์ : ์์ฐ๊ณผํ๋ํ ์ง๊ตฌํ๊ฒฝ๊ณผํ๋ถ, 2022. 8. ์ด์ต๋จ.๊ฐ์ท๊ณต๋ฃก(Ankylosauria)์ ์ฌ์กฑ๋ณดํ์ธ ์ด์ ๊ณต๋ฃก์ ํ ๋ฌด๋ฆฌ๋ก ๊ณจํธ(้ชจ็, osteoderm)๋ค์ด ์ตํฉ๋ ๋๊ฐ๊ณจ(้ ญ่้ชจ, skull)๊ณผ ๋ชธํต์ ๋ฐฐ์ธก๋ฉด(่ๅด้ข, dorsolateral)์ ๊ณจํธ๋ค์ด ๋ถ์์(ๅฏ็ข็, parasagittal)์ผ๋ก ๋ฎ๊ณ ์๋ ๊ฒ์ด ํน์ง์ด๋ค. 2007๋
๊ณผ 2008๋
์ฌ์ด์ ํ๊ตญ-๋ชฝ๊ณจ ๊ตญ์ ๊ณต๋ฃกํ์ฌ์ ์ํด ๊ฐ์ท๊ณต๋ฃก ํ๋ณธ๋ค์ด ๊ณ ๋น์ฌ๋ง์์ ์ถ๊ฐ๋ก ๋ฐ๊ฒฌ๋๋ค. ๋ณธ ํ๋ณธ๋ค์ ์๋ถ ๋ฐฑ์
๊ธฐ CenomanianโTuronian ๋ฐ์์๋ ์ธต(Bayanshiree Formation), middleโupper Campanian ๋ฐ๋ฃฌ๊ณ ์ง์ธต(Baruungoyot Formation), ๊ทธ๋ฆฌ๊ณ upper Campanianโlower Maastrichtian ๋ค๋ฉ๊ฒ์ธต(Nemegt Formation)์์ ๋ฐ๊ฒฌ๋๋ค. ๋ฐ์์๋ (Bayan Shiree)์ ๋ฐ์์๋ ์ธต์์ ์ฐ์ถ๋ ์๋ก์ด ๋๊ฐ๊ณจ ํ๋ณธ ์ธ ๊ฐ๋ฅผ ํตํด Talarurus plicatospineus์ ์ ์๋ฅผ ์ฌ์ ๋ฆฝํ ์ ์์๋ค. ํ๋ฉ์ํ(Hermiin Tsav)์ ๋ค๋ฉ๊ฒ์ธต์์ ์ฐ์ถ๋ ๋๊ฐ๊ณจ์ ํฌํจํ ๋ถ๋ถ์ ์ธ ๋ํ๊ณจ๊ฒฉ(้ ญๅพ้ชจๆ ผ, postcranial)์ ์๋ก์ด ๋ถ๋ฅ๊ตฐ์ผ๋ก ํ์ธ๋ผ Tarchia tumanovae๋ก ๋ช
๋ช
๋๋ค. ํ๋ฉ์ํ์ ๋ฐ๋ฃฌ๊ณ ์ง์ธต์์ ์ฐ์ถ๋ ์๋ก์ด ๋ํ๊ณจ๊ฒฉ ํ๋ณธ์ ๋ถ๋ถ๋ช
ํ ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ(Ankylosauridae)๋ก ๋ถ๋ฅ๋๋ค. ๊ณํต๋ฐ์ ๋ถ์(phylogenetic analysis) ๊ฒฐ๊ณผ๋ Talarurus์์ด Saichania chulsanensis, Tarchia kielanae, ๊ทธ๋ฆฌ๊ณ Zaraapelta nomadis๋ฅผ ํฌํจํ ์์์์ ํ์๋ ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค์๊ณผ(Ankylosaurinae)์ ์๋งค ๋ถ๋ฅ๊ตฐ(sister taxon)์์ ๋ณด์ฌ์ค๋ค. ๋ํ ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค์๊ณผ์ ์์์์์ ๋ถ์๋ฉ๋ฆฌ์นด ๋๋ฅ์ผ๋ก์ ์ด์ฃผ(็งปไฝ, migration)๊ฐ Cenomanian ์ด์ ์ ์์์์ ๋ณด์ฌ์ค๋ค. Talarurus์๊ณผ ๋ฐ์์๋ ์ธต์ ๋ ๋ค๋ฅธ ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ์ธ Tsagantegia์ ์ฌ์ด์ ์ฃผ๋ฅ์ด ํํ ์ฐจ์ด๋ ์ด๋ค์ ์ํ์ง์ ๋ถํ (niche partitioning)์ ์์ฌํ๋ค. Tar. tumanovae์ ์ธ๊ณจ๋ฟ(้ฑ้ชจโ, squamosal horn)์ ์ธํผ์ธต(ๅค็ฎๅฑค, external dermal layer)๊ณผ ๊ทธ ๋ฐ์ ์๋ ์ง์ ์ธ๊ณจ๋ฟ(็ๆ
้ฑ้ชจโ, squamosal horn proper)๋ก ๋๋๋ค. ์ธํผ์ธต์ ๋ถ๊ท์นํ ๋ณต๋ฉด(่
น้ข, ventral) ๊ฐ์ฅ์๋ฆฌ๋ ํก์๋ ํ๋ฉด์ ๋ํ๋ผ ์ ์์ผ๋ฉฐ, ์ด๋ ์ผ๋ถ ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค์๊ณผ์ ์ธ๊ณจ๋ฟ์ด ๊ทน๋จ์ ์ธ ๊ฐ์ฒด๋ฐ์์ (ontogenetic) ๋ณํ๋ฅผ ๊ฒช์์์ ์์ฌํ๋ค. ๋ํ ๋ฐฐ์ฒ์ถ(่่ฆๆค, dorsosacral vertebra)์ ๋๊ณจ(๏ฅ้ชจ, rib) ๋ถ์์ ๊ผฌ๋ฆฌ์ ๊ตญ์์ ๊ณจ์ ํ์ ์ ์ด๋ค์ ์ธ๋ ฅํฌ์ํ์(agonistic behavior)์ ์ฆ๊ฑฐ๋ฅผ ์ ๊ณตํ๋ค. Tar. tumanovae์ ๋น๋์นญ์ธ ๊ผฌ๋ฆฌ๊ณค๋ด(tail club)์ ์ด๋ฐ ํ์๋ก ์ธํ ๋ผ์ ๋น์ ์์ ์ธ ์ฑ์ฅ ๋๋ฌธ์ธ ๊ฒ์ผ๋ก ๋ณด์ธ๋ค. ๋ ๋์๊ฐ, ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ(Ankylosauridae)์ ์ญ์๋ฐฉ๋ฒ์ ์๋ถ ๋ฐฑ์
๊ธฐ middle Campanianโearly Maastrichtian ์ค์ ๋๋์ญ์(bulk-feeding)์์ ์ ํ์ ์ญ์(selective feeding)์ผ๋ก ๋ฐ๋ ๊ฒ์ผ๋ก ๋ณด์ธ๋ค. ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ์ ์ด๋ฐ ์ํ์ง์ ๋ณํ๋ ์์์ง ๋ณํ์ ๋ค๋ฅธ ๋๋์ญ์ ์ด์ ๊ณต๋ฃก๊ณผ์ ๊ฒฝ์ ๋๋ฌธ์ธ ๊ฒ์ผ๋ก ์ฌ๊ฒจ์ง๋ค. ์์์์ ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ๋ ํ๋๊ณจ๊ฒฉ์ด ๋ปฃ๋ปฃํด์ง๊ณ ๋ท๋ฐ์ ์ง๊ณจ(่ถพ้ชจ, pedal phalanges) ์๊ฐ ์ค์ด๋๋ ๋ฐฉํฅ์ผ๋ก ์งํํ๋ค. ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ์๋ ๋ ๊ฐ์ง ํํ์ ์ธก๋ฉด(ๅด้ข, flank) ๊ฐ์ท, ํ๋๋ ๊ฐ์ํ(spine-like)์ ๊ณจํธ, ๊ทธ๋ฆฌ๊ณ ๋ค๋ฅธ ํ๋๋ ์ฉ๊ณจ(๏ง้ชจ, keel)์ด ๋ฐ๋ฌํ ๋ฅํ(่ฑๅฝข, rhomboid)์ ๊ณจํธ์ด ์์์ด ํ์ธ๋๋ค. ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ์์๋ ๋
ํ๊ธฐ์ ๊ด๋ จ๋ ๋
ํนํ ํด๋ถํ์ ํน์ง๋ค๋ ํ์ธ๋๋ค. ๋
ํ๊ธฐ์ ๊ด๋ จ๋ ํน์ง๋ค๋ก๋ ๋ฐฐ๋ณต(่่
น, dorsoventral) ๋ฐฉํฅ์ผ๋ก ๋ฉ์ํ ๋ฐฉ์ถํ(็ดก้ๅฝข, fusiform)์ ๋ชธํต, ๊ด๋ฒ์ํ๊ฒ ์ตํฉ๋ ์ฒ์ถ, ์ ํ(ๅๅพ, anteroposteriorly) ๋ฐฉํฅ์ผ๋ก ๋์ ๋๊ณจ, ์ ๋ฐ๋ฌ๋ ์ผ๊ฐํ๊ทผ๋ฅ์ (ไธ่ง่ธ็ญ๏ฅ็ท, deltopectoral crest)์ ๊ฐ์ง ๊ฐ๊ฑดํ ์์๊ณจ(ไธ่
้ชจ, humerus), ์ ๋ฐ๋ฌ๋ ์ฃผ๋๋๊ธฐ(่้ ญ็ช่ตท, olecranon process)๋ฅผ ๊ฐ์ง ์งง์ ์ฒ๊ณจ(ๅฐบ้ชจ, ulna), ๋ชจ์ข
์ฝํ(trowel-like) ์๋ฐ, ๊ทธ๋ฆฌ๊ณ ์ง๊ณจ ์๊ฐ ์ค์ด๋ ๋ท๋ฐ์ด ์๋ค. ๋น๋ก ๊ตด์ฐฉํ(fossorial) ๋๋ฌผ์ ์๋์์ง๋ง, ์ํฌ๋ก์ฌ์ฐ๋ฃจ์ค๊ณผ๋ ์๊ธฐ ๋ฐฉ์ด์ ์์กด์ ์ํด ๋
์ ์ ํํค์ณค์ ๊ฒ์ผ๋ก ๋ณด์ธ๋ค. ๋ ๋์๊ฐ, ๋ณธ ํ์๋
ผ๋ฌธ์์๋ ๋ชฝ๊ณจ์์ ์๋ ค์ง 10์ข
์ ๊ฐ์ท๊ณต๋ฃก์ ๋ํ ๋ถ๋ฅํ์ ๋ฆฌ๋ทฐ๋ฅผ ์ค์ํ์๋ค.Ankylosaurs are a group of dinosaurs that are quadrupedal, herbivorous, and have a heavily ornamented skull and parasagittal rows of osteoderms covering the dorsolateral surfaces of the body. Additional ankylosaur specimens were discovered in the Gobi Desert of Mongolia by the Korea-Mongolia International Dinosaur Expedition between 2007 and 2008. They were excavated from the Upper Cretaceous Bayanshiree (CenomanianโTuronian), Baruungoyot (middleโupper Campanian), and Nemegt (upper Campanianโlower Maastrichtian) formations. Based on the three new skulls from the Bayanshiree Formation of Bayan Shiree cliffs, the diagnosis of Talarurus plicatospineus is revised. A new skull with a partial postcranial skeleton collected from the Nemegt Formation in Hermiin Tsav turned out to be a new taxon, Tarchia tumanovae sp. nov. A new articulated postcranial specimen from the Baruungoyot Formation in Hermiin Tsav is classified as an indeterminate ankylosaurid dinosaur. The phylogenetic analysis showed that Talarurus is sister to the clade that includes the derived Asian ankylosaurines (Saichania chulsanensis, Tarchia kielanae, and Zaraapelta nomadis). It also showed that there was the dispersal of ankylosaurines from Asia to western North America before the Cenomanian. The rostral differences between Talarurus and Tsagantegia, another ankylosaurine from the Bayanshiree Formation, suggest possible niche partitioning among these taxa. The squamosal horns of Tar. tumanovae are divided into the external dermal layer and the underlying squamosal horn proper. The irregular ventral margin of the base of the upper dermal layer may represent a resorption surface, suggesting that the squamosal horns of some ankylosaurines underwent extreme ontogenetic remodeling. Localized pathologies on the dorsosacral ribs and the tail provide evidence of agonistic behavior. The tail club knob asymmetry of Tar. tumanovae resulted from restricted bone growth due to tail club strikes. Furthermore, ankylosaurid diets shifted from low-level bulk feeding to selective feeding during the Baruungoyot and the Nemegt โageโ (middle Campanianโlower Maastrichtian). This ankylosaurid niche shifting might have responded to habitat change and competition with other bulk-feeding herbivores. Asian ankylosaurids evolved rigid bodies with a decreased number of pedal phalanges. There were also at least two forms of flank armor within Ankylosauridae, one with spine-like osteoderms and the other with keeled rhomboidal osteoderms. Unique anatomical features related to digging are present in Ankylosauridae, such as dorsoventrally flattened and fusiform body shapes, extensively fused series of vertebrae, anteroposteriorly broadened dorsal ribs, a robust humerus with a well-developed deltopectoral crest, a short and robust ulna with a well-developed olecranon process, a trowel-like manus, and decreased numbers of pedal phalanges. Although not fossorial, ankylosaurids were likely to dig the substrate, taking advantage of it for self-defense and survival. Moreover, all ten ankylosaur species known in Mongolia are reviewed in this dissertation.I. INTRODUCTION 1
II. MATERIALS AND METHODS 6
III. GEOLOGICAL SETTING 8
III-1. Bayanshiree Formation 8
III-2. Baruungoyot Formation 13
III-3. Nemegt Formation 18
IV. RESULTS 25
IV-1. Systematic paleontology 25
Talarurus plicatospineus Maleev, 1952b 25
Tarchia Maryanska, 1977 44
Tarchia tumanovae sp. nov. 45
Ankylosauridae, gen. et sp. indet. 73
V. PHYLOGENETIC ANALYSES 99
V-1. Phylogenetic placement of Talarurus plicatospineus 99
V-2. Phylogenetic placement of Tarchia tumanovae sp. nov. 103
VI. DISCUSSION 105
VI-1. Paleoecology of Talarurus and Tsagantegia 105
VI-2. Squamosal horn remodeling in ankylosaurines 110
VI-3. Evidence of agonistic behavior in ankylosaurines 111
VI-4. Niche shifting in Mongolian ankylosaurids 114
VI-5. Postcranial evolution of ankylosaurids 117
VI-6. Digging ability of ankylosaurids 121
VII. TAXONOMIC REVIEW OF MONGOLIAN ANKYLOSAURS 125
VII-1. Introduction 125
VII-2. Systematic paleontology 126
Shamosaurus scutatus Tumanova, 1983 126
Minotaurasaurus ramachandrani Miles and Miles, 2009 132
Pinacosaurus grangeri Gilmore, 1933 137
Saichania chulsanensis Maryaska, 1977 148
Talarurus plicatospineus Maleev, 1952b 155
Tarchia kielanae Maryanska, 1977 160
Tarchia teresae Penkalski and Tumanova, 2017 165
Tarchia tumanovae sp. nov. 170
Tsagantegia longicranialis Tumanova, 1993 171
Zaraapelta nomadis Arbour et al., 2014b 175
VIII. CONCLUSIONS 179
REFERENCES 182
APPENDIX 1. Institutional abbreviations 228
APPENDIX 2. Abbreviations used in figures 229
APPENDIX 3. Data matrix related to chapter V-1 231
APPENDIX 4. Character statements related to chapter V-2 238
APPENDIX 5. Data matrix related to chapter V-2 239
๊ตญ๋ฌธ์ด๋ก 240
๊ฐ์ฌ์ ๊ธ 243๋ฐ
The effect of rare-earth element additions on microstructural properties and irradiation behavior of an Fe-Ni-Cr alloy for LMFBR and fusion reactor applications
This study consists of a survey of the effect of yttrium, lanthanum, and cerium rare-earth additions on the microstructure and radiation swelling behavior of an Fe-25.6Ni-8.7Cr-3.3Ti-1.6Al alloy. The undoped alloy was investigated in the as-received, annealed, and arc-melted conditions, and twelve arc melted and rare-earth doped alloys were prepared (doping levels of 0.05, 0.1, 0.5, and 1.0 wt % for each of the three rare earths). The ion bombardments were carried out at 570 and 600(DEGREES)C with 4 MeV Ni or Fe ions to nominal 100 dpa and to 100 and 550 appm He. Lattice parameter, hardness, swelling, and optical and transmission electron microscopy observations were conducted;Ion bombardment at 600(DEGREES)C produced negligible swelling. For ion bombardment at 570(DEGREES)C and helium implantation to 100 appm He, the as-received, annealed, and arc-melted undoped alloy swelled 4.0, 5.1, and 3.8%, respectively. The increase in swelling upon annealing the as-received alloy is believed to be due to the removal of cold work. The subsequent decrease in swelling upon arc melting is interpreted in terms of the reduction in size of the large Ti-rich precipitate and the consequent increase in Ti in solid solution. For ion bombardment at 570(DEGREES)C and helium implantation to 550 appm He, the arc-melted undoped alloy gave 5.2% swelling (as compared to 3.8% for 100 appm He) due to the higher helium loading;The introduction of yttrium or cerium at levels between 0.1 and 1.0% gives rise to a reduction in swelling. This may be due to a decrease in the amount of G-phase precipitate and the size of the large Ti-rich particles. For concentrations above 0.5%, a rare-earth-rich precipitate appeared. At 1% concentrations, the precipitates were observed to swell themselves and to give rise to bulk matrix swelling. The optimum concentrations of Y or Ce for swelling reduction are therefore, considered to be about 0.2-0.4%. Lanthanum additions were not observed to suppress swelling;Unique surface deformations were observed as a result of ion bombardment, especially at and near grain boundaries. At low swelling, the grain boundary region was raised or ridged, probably because of the lateral extrusion-like action of the swelled grains. At higher swelling, the grain bodies were elevated above the grain boundary regions
Applications of photonic bandgap structures with arbitrary surface impedance to Luneburg lenses for automotive radar [online]
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