• Title/Summary/Keyword: Acceleration

검색결과 7,308건 처리시간 0.047초

가상 현실 기반의 교육 목적 콘텐츠에 대한 연구 - VR 키오스크 시뮬레이션 (A Study on Educational Content Based on Virtual Reality)

  • 이준섭;임병일;한지영;이택희
    • 한국컴퓨터그래픽스학회논문지
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    • 제30권3호
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    • pp.179-188
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    • 2024
  • 최근 무인 단말기(키오스크)는 기존의 인력을 대체하면서도 효율적으로 주문이나 결제가 이루어질 수 있도록 해주어 그 활용 범위가 크게 증가하고 있다. 결과로 디지털 전환이 가속화되면서 키오스크 설치 비율이 급증하여 모든 연령층이 손쉽게 키오스크를 사용할 수 있도록 돕는 것이 중요한 과제가 되고 있다. 본 연구에서는 게임엔진의 기능과 Hand Tracking 기술을 기반으로 가상의 세계에서 키오스크 교육이 진행될 수 있는 콘텐츠를 개발하였다. 키오스크에 익숙하지 않은 사용자가 가상 현실에서 대기 손님으로 인한 시각적, 청각적 스트레스를 미리 체험함으로써 실제 상황에서 자신감 있게 대처할 수 있도록 돕는 것이다. 이를 위해 두 가지 VR 콘텐츠를 개발하였다. 하나는 단순 키오스크 체험 콘텐츠이고, 다른 하나는 시각적, 청각적 스트레스를 유발하는 특화 콘텐츠이다. 실험은 두 그룹으로 나뉘어 진행되었으며, 한 그룹은 일반 VR 콘텐츠를, 다른 그룹은 특화 VR 콘텐츠를 체험하였다. 체험 후, 두 그룹 모두 실제 매장에서 주문을 진행하였고, 설문조사 결과 실험군의 85%, 대조군의 95%가 교육에 만족한다고 응답하였다. 이를 통해 본 논문의 특화된 체험이 키오스크 교육에 효과적임을 확인할 수 있었다.

지진 진앙지에서 지진 진동의 거리별 실측치와 발파 진동과의 비교분석에 관한 연구 (A Study on the Comparative Analysis of Seismic Waves and Blast Vibration Measurements by Distance from the Earthquake Epicenter)

  • 이승훈;신영철;강동현;임대규;김기묵;김동연;이진옥;이천식
    • 화약ㆍ발파
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    • 제42권3호
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    • pp.23-37
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    • 2024
  • 최근 국내에서 발생하는 지진으로 인해 건물, 구조물 등에 피해를 입는 경우가 자주 발생하고 있다. 그러나 지진은 언제 발생할지 알 수 없기 때문에, 지진 발생 시 자동화 계측기를 사전에 설치하지 않으면 진동 특성 값을 알기가 힘든 것이 사실이다. 다행히 6개 발파 현장에 자동화 계측기를 설치하고 있어서 이번에 지진 진동과 발파 진동 특성을 비교하고자 한다. 최근 2024년 6월 12일(수) 08시 26분에 전북 부안군 남남서쪽 4km 지역에서 발생한 규모 4.8의 지진에 대한 지진 진동 특성과 국내 발파 현장에서의 지진 진동과 발파 진동 실측값 등을 비교해 보았다. 또한, 이번 기회에 지진에 대한 발생 원인 및 피해 규모도 파악해 보고, 지진 진앙지로부터 여러 지역에 설치된 자동화 계측기로부터 나오는 특성값을 분석하여 감쇠 정도가 어느 정도 되는지도 알아보았다. 이를 통해 향후 발파 시 진동으로 인한 보호 물건 피해 등을 비교하여 현장에서 발생하는 민원을 사전에 대처하는 데 도움을 주고자 한다.

Review of laser-plasma physics research and applications in Korea

  • W. Bang;B. I. Cho;M. H. Cho;M. S. Cho;M. Chung;M. S. Hur;G. Kang;K. Kang;T. Kang;C. Kim;H. N. Kim;J. Kim;K.B. Kim;K. N. Kim;M. Kim;M. S. Kim;M. Kumar;H. Lee;H. W. Lee;K. Lee;I. Nam;S. H. Park;V. Phung;W. J. Ryu;S. Y. Shin;H. S. Song;J. Song;J. Won;H. Suk
    • Journal of the Korean Physical Society
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    • 제80권
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    • pp.698-716
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    • 2022
  • Laser plasmas can be produced when high-power laser beams are focused in matter. A focused laser beam of TW(terawatt)-level high power has an extremely strong electric field, so neutral atoms are immediately ionized by the laser electric field, leading to a laser-produced plasma. The laser plasma can be produced by small table-top TW lasers based on the CPA (chirped-pulse amplification) technique, and now they are rather easily available even in university laboratories. In Korea, there are several CPA-based TW (or even petawatt) lasers in a few institutions, and they have been used for diverse laser plasma physics research and applications, including the laser acceleration for electrons and ions, high-power THz (tera-hertz) generation, advanced light sources, high-energy-density plasmas, plasma optics, etc. This paper reviews some of the laser plasma physics research and applications that have been performed in several universities and research institutes.

Horizontal only and horizontal-vertical combined earthquake effects on three R/C frame building structures through linear time-history analysis (LTHA): An implementation to Turkey

  • Selcuk Bas;Mustafa A. Bilgin
    • Computers and Concrete
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    • 제34권3호
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    • pp.329-346
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    • 2024
  • In this study, it is aimed to investigate the vertical seismic performance of reinforced concrete (R/C) frame buildings in two different building stocks, one of which consists of those designed as per the previous Turkish Seismic Code (TSC-2007) that does not consider the vertical earthquake load, and the other of which consists of those designed as per the new Turkish Seismic Code (TSCB-2018) that considers the vertical earthquake load. For this aim, three R/C buildings with heights of 15 m, 24 m and 33 m are designed separately as per TSC-2007 and TSCB-2018 based on some limitations in terms of seismic zone, soil class and structural behavior factor (Rx/Ry) etc. The vertical earthquake motion effects are identified according to the linear time-history analyses (LTHA) that are performed separately for only horizontal (H) and combined horizontal+vertical (H+V) earthquake motions. LTHA is performed to predict how vertical earthquake motion affects the response of the designed buildings by comparing the linear response parameters of the base shear force, the base overturning, the base axial force, top-story vertical displacement. Nonlinear time-history analysis (NLTHA) is generally required for energy dissipative buildings, not required for design of buildings. In this study, the earthquake records are scaled to force the buildings in the linear range. Since nonlinear behavior is not expected from the buildings herein, the nonlinear time-history analysis (NLTHA) is not considered. Eleven earthquake acceleration records are considered by scaling them to the design spectrum given in TSCB-2018. The base shear force is obtained not to be affected from the combined H+V earthquake load for the buildings. The base overturning moment outcomes underline that the rigidity of the frame system in terms of the dimensions of the columns can be a critical parameter for the influence of the vertical earthquake motion on the buildings. In addition, the building stock from TSC-2007 is estimated to show better vertical earthquake performance than that of TSCB-2018. The vertical earthquake motion is found out to be highly effective on the base axial force of 33 m building rather than 15 m and 24 m buildings. Thus, the building height is a particularly important parameter for the base axial force. The percentage changes in the top-story vertical displacement of the buildings designed for both codes show an increase parallel to that in the base axial force results. To extrapolate more general results, it is clear to state that many buildings should be analyzed.

상시 계측 데이터를 이용한 단경간 교량의 온도에 따른 진동 특성 변화 분석 (Analysis of Vibration Characteristics Changes in a Single-Span Bridge Due to Temperature Using Continuous Measurement Data)

  • 권태호;김병철;박기태;전치호
    • 한국구조물진단유지관리공학회 논문집
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    • 제28권5호
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    • pp.62-68
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    • 2024
  • 우리나라는 사계절이 뚜렷하고 여름과 겨울의 온도차가 커서 교량들은 1년 중 큰 폭의 온도 변화를 겪고 있다. 교량 구조계는 온도가 변할 경우 동적 특성도 변하게 되지만 국내 교량 유지관리에서 내하력 평가 수행 시에는 이 영향을 고려하지 않고 단기간에 측정된 고유진동수만 평가에 사용된다. 이 논문에서는 이론적으로 고유진동수의 변화가 교량에 미치는 영향을 분석하고 1년 이상 연직가속도가 상시 계측된 교량에 대해 매일 고유진동수 추정 데이터를 추출하여 온도에 따른 변화를 확인하였다. 그 결과 고유진동수가 1% 감소하면 교량의 공용내하력은 약 2% 감소하는 것을 확인하였으며 계측 데이터로부터 온도가 10℃ 증가하는 경우 고유진동수는 RC슬래브교 및 라멘교에서는 영향이 없었으나 PSCI형교 및 강상자형 교에서는 1.04~2.48% 감소하는 경향을 확인하였다.

1993-2018년 한반도 연안 상대해수면 수지 분석 (A Process-based Relative Sea-level Budget Along the Coast of Korean Peninsula Over 1993-2018)

  • 차현수;조성배;문재홍
    • Ocean and Polar Research
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    • 제46권1호
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    • pp.31-42
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    • 2024
  • Due to physical processes varying in space and time, regional sea-level rise (SLR) significantly deviates from the global mean. Thus, understanding and quantifying the contribution of each process to regional sea-level change is crucial to prevent low-lying inundation in preparation for future ocean conditions. In this study, we assessed to what degree sterodynamic (SD) effects (i.e., density-driven steric expansion and mass redistribution due to ocean circulation), contemporary mass redistribution (CMR), and glacial isostatic adjustment (GIA) contribute relative sea-level rise around the Korean coast from 1993 to 2018, with independent observations and reanalysis datasets. The assessment showed that the tide gauge-observed SLR trend can be explained by the sum of each component at 16 of 19 locations. The major contributors to relative SLR are SD effects of 2.03±0.27 mm/yr and CMR components of 1.31±0.05 mm/yr, while GIA drives sea-level decreasing of -0.27±0.15 mm/yr on the Korean coast. It was also found that the spatial deviations of SLR are primarily caused by the SD effects. In addition, the evaluation of vertical land motion (VLM) based on altimetry and tide gauge indicates that most tide gauge locations have experienced uplift during at least altimetry period, whereas Wido station has experienced particularly high rate of subsidence that contributed to the SLR acceleration. Further examination of the impact of earth deformation due to CMR, GIA, and local process on the VLM trends demonstrated that the GIA and CMR contribute to land uplift with the average of 0.35±0.15 mm/yr and 0.17±0.05 mm/yr, respectively. On the other hand, the local processes like groundwater depletion and sediment compaction showed a wide range of variability, from -1.61 to 0.58 mm/yr, indicating a significant contribution to regional differences in vertical land motion.

한국수산업의 해외진출전략에 관한 연구 (Foreign Entry Strategies for Korean Fishery Firms)

  • 김회천
    • 수산경영론집
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    • 제15권1호
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    • pp.131-153
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    • 1984
  • Fishery resources are still abundant compared with other resources and the possibility of exploitation is probably great. The Korean fishery industry has grown remarkably since 1957, and Korea is ranked as one of the major fishery countries. Its of fishery products reached the 9th in the world and the value of exports was 5th in 1982. But recently a growth rate has slowed down, due to the enlargement of territorial seas by the declaration of the 200 mile, Exclusive Economic Zone, the tendency to develop fishery resources strate-gically in international bargaining, the change in function of the international organizations, the expansion of regulated waters, the illegal arrest of our fishing boats, the rapid rise in oil prices, and the fall in fish prices, the development of fishery resources as a symbol of nationalism, the fishing boats decreptitude, the rise of crew wages, regulations on fishing methods, fish species, fishing season, size of fish, and mesh size, fishing quotas and the demand of excessive fishing royalties. Besides the the obligation of coastal countries, employing crews of their host countries is also an example of the change in the international environment which causes the aggravation of foreign profit of fishing firms. To ameliorate the situation, our Korean fishery firms must prepare efficient plans and study systematically to internationalize themselves because such existing methods as conventional fishing entry and licence fishing entry are likely to be unable to cope with international environmental change. Thus, after the systematic analysis of the problem, some new combined alternatives might be proposed. These are some of the new schemes to support this plan showing the orientation of our national policy: 1. Most of the coastal states, to cope with rapid international environmental change and to survive in the new era of ocean order, have rationalized their higher governmental structure concerning the fishery industries. And the coastal countries which are the objectives of our expecting entry, demand excessive economic and technical aid, limit the number of fishing boats’entry and the use of our foreign fishing bases, and regulate the membership of the international fishery commissions. Especially, most of the coastal or island countries are recently independent states, which are poorer in national budget, depend largely on fishing royalties and licence entry fees as their main resources of national finance. 2. Alternatives to our entry to deep sea fishing, as internationalization strategies, are by direct foreign investment method. About 30 firms have already invested approximately US $ 8 million in 9 coastal countries. Areas of investment comprise the southern part of the Atlantic Ocean, the Moroccan sea and five other sea areas. Trawling, tuna purse seining and five other fields are covered by the investment. Joint-venture is the most prominent method of this direct investment. If we consider the number of entry firms, the host countries, the number of seas available and the size of investment, this method of cooperation is perhaps insufficient so far. Our fishery firms suffer from a weakness in international competitive ability, an insufficiency of information, of short funds, incompetency in the market, the unfriendliness of host coastal countries, the incapability of partners in joint-ventures and the political instability of the host countries. To enlarge our foreign fishing grounds, we are to actively adopt the direct investment entry method and to diversity our collaboraboration with partner countries. Consequently, besides proper fishing, we might utilize forward integration strategies, including the processing fied. a. The enterprise emigration method is likely to be successful in Argentina. It includes the development of Argentinian fishing grounds which are still not exploited in spite of abundant resources. Besides, Arentina could also be developed as a base for the exploitation of the krill resources and for further entries into collaboration with other Latin American countries. b. The co-business contract fishing method works in American territorial seas where American fishermen sell their fishery products to our factory ships at sea. This method contributes greatly to obtaining more fishing quotas and in innovation bottom fishing operation. Therefore we may apply this method to other countres to diffuse our foreign fishing entry. c. The new fishing ground development method was begun in 1957 by tuna long-line experimental fishing in the Indian Ocean. It has five fields, trawling, skipjack pole fishing and shrimp trawling, and so on. Recently, Korean fisheries were successful in the development of the Antarctic Ocean krill and tuna purse seining. 3. The acceleration of the internationalization of deep sea fishing; a. Intense information exchange activities and commission participation are likely to be continues as our contributions to the international fishery organizations. We should try to enter international fishery commissions in which we are not so far participating. And we have to reform adequately to meet the changes of the function of the international commissions. With our partner countries, we ought to conclude bilateral fishery agreements, thus enlarging our collaboration. b. Our government should offer economic and technical aids to host countries to facilitate our firms’fishery entry and activities. c. To accelerate technical innovation, our fishery firms must invest greater amount in technical innovation, at the same time be more discriminatory in importing exogeneous fishery technologies. As for fishing methods; expanded use of multi-purpose fishing boats and introduction of automation should be encuraged to prevent seasonal fluctuations in fishery outputs. d. The government should increases financial and tax aid to Korean firms in order to elevate already weak financial structure of Korean fishery firms. e. Finally, the government ought to revise foreign exchange regulations being applied to deep sea fishery firms. Furthermore, dutes levied on foreign purchaed equipments and supplies used by our deep sea fishing boats thould be reduced or exempted. when the fish caught by Korean partner of joint-venture firms is sold at the home port, pusan, import duty should be exempted.

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다시기 Landsat TM 영상과 기계학습을 이용한 토지피복변화에 따른 산림탄소저장량 변화 분석 (Change Analysis of Aboveground Forest Carbon Stocks According to the Land Cover Change Using Multi-Temporal Landsat TM Images and Machine Learning Algorithms)

  • 이정희;임정호;김경민;허준
    • 한국지리정보학회지
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    • 제18권4호
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    • pp.81-99
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    • 2015
  • 가속되는 지구온난화로 인해 한반도 주변의 탄소순환에 대한 명확한 이해의 필요성이 제기되고 있다. 산림은 이산화탄소의 주요 흡수원으로 지상 탄소량의 대부분을 저장하고 있어 이에 대한 추정이 필요하다. 우리나라에서는 국가산림자원조사의 표본점에서 측정되는 헥타르당 임목축적량을 활용하여 산림 탄소저장량을 추정한다. 하지만 탄소저장량은 요약된 수치 형태로 발표하고 있어 탄소저장량의 공간적 분포를 파악하는 것이 어렵다. 본 연구에서는 토지피복변화가 빠르고 국가산림자원조사 표본점 배치가 부족한 도시지역을 대상으로 UNFCCC의 Approach 3와 Tier 3를 충족하는 격자 기반 산림탄소저장량을 추정하였다. 토지피복변화 및 산림탄소저장량은 1991, 1992, 2010, 2011년에 취득된 Landsat 5 TM 영상과 고해상도 항공사진, 제 3차 및 제 5, 6차 국가산림자원조사 자료를 이용하여 추정하였다. 토지피복변화는 기계학습을 이용하여 변화된 토지피복과 변화되지 않은 토지피복 항목을 한 번에 분류하여 추정하였으며, 산림탄소저장량은 반사도, 밴드비율, 식생지수, 지형변수를 입력변수로 하여 기계학습을 통해 추정하였다. 연구 결과, 산림이 그대로 산림으로 유지되는 지역의 경우 33.23tonC/ha의 흡수를 하였으며 비산림이 산림으로 변한 지역의 경우 이보다 큰 36.83tonC/ha의 흡수가 진행된 것으로 추정되었다. 산림이 비산림으로 바뀐 경우에는 -7.35tonC/ha로, 배출이 일어난 것으로 추정되었다. 본 연구를 통하여 토지피복변화에 따른 산림탄소저장량 변화를 정량적으로 이해할 수 있었으며, 향후 효율적인 산림관리에 기여할 수 있을 것으로 판단된다.

Optimization of the Flip Angle and Scan Timing in Hepatobiliary Phase Imaging Using T1-Weighted, CAIPIRINHA GRE Imaging

  • Kim, Jeongjae;Kim, Bong Soo;Lee, Jeong Sub;Woo, Seung Tae;Choi, Guk Myung;Kim, Seung Hyoung;Lee, Ho Kyu;Lee, Mu Sook;Lee, Kyung Ryeol;Park, Joon Hyuk
    • Investigative Magnetic Resonance Imaging
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    • 제22권1호
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    • pp.1-9
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    • 2018
  • Purpose: This study was designed to optimize the flip angle (FA) and scan timing of the hepatobiliary phase (HBP) using the 3D T1-weighted, gradient-echo (GRE) imaging with controlled aliasing in parallel imaging results in higher acceleration (CAIPIRINHA) technique on gadoxetic acid-enhanced 3T liver MR imaging. Materials and Methods: Sixty-two patients who underwent gadoxetic acid-enhanced 3T liver MR imaging were included in this study. Four 3D T1-weighted GRE imaging studies using the CAIPIRINHA technique and FAs of $9^{\circ}$ and $13^{\circ}$ were acquired during HBP at 15 and 20 min after intravenous injection of gadoxetic acid. Two abdominal radiologists, who were blinded to the FA and the timing of image acquisition, assessed the sharpness of liver edge, hepatic vessel clarity, lesion conspicuity, artifact severity, and overall image quality using a five-point scale. Quantitative analysis was performed by another radiologist to estimate the relative liver enhancement (RLE) and the signal-to-noise ratio (SNR). Statistical analyses were performed using the Wilcoxon signed rank test and one-way analysis of variance. Results: The scores of the HBP with an FA of $13^{\circ}$ during the same delayed time were significantly higher than those of the HBP with an FA of $9^{\circ}$ in all the assessment items (P < 0.01). In terms of the delay time, images at the same FA obtained with a 20-min-HBP showed better quality than those obtained with a 15-min-HBP. There was no significant difference in qualitative scores between the 20-min-HBP and the 15-min-HBP images in the non-liver cirrhosis (LC) group except for the hepatic vessel clarity score with $9^{\circ}$ FA. In the quantitative analysis, a statistically significant difference was found in the degree of RLE in the four HBP images (P = 0.012). However, in the subgroup analysis, no significant difference in RLE was found in the four HBP images in either the LC or the non-LC groups. The SNR did not differ significantly in the four HBP images. In the subgroup analysis, 20-min-HBP imaging with a $13^{\circ}$ FA showed the highest SNR value in the LC-group, whereas 15-min-HBP imaging with a $13^{\circ}$ FA showed the best value of SNR in the non-LC group. Conclusion: The use of a moderately high FA improves the image quality and lesion conspicuity on 3D, T1-weighted GRE imaging using the CAIPIRINHA technique on gadoxetic acid, 3T liver MR imaging. In patients with normal liver function, the 15-min-HBP with a $13^{\circ}$ FA represents a feasible option without a significant decrease in image quality.

진공 내 상대론적인 영역의 전자빔을 이용한 플라즈마 항적장 가속기 기반 체렌코프 방사를 통한 결맞는 고출력 전자파 발생 기술 연구 (Study of Coherent High-Power Electromagnetic Wave Generation Based on Cherenkov Radiation Using Plasma Wakefield Accelerator with Relativistic Electron Beam in Vacuum)

  • 민선홍;권오준;사토로프마틀랍;백인근;김선태;홍동표;장정민;라나조이;조일성;김병수;박차원;정원균;박승혁;박건식
    • 한국전자파학회논문지
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    • 제29권6호
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    • pp.407-410
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    • 2018
  • 일반적으로 전자파의 동작 주파수가 높아짐에 따라 최대 출력이 작아지고, 파동의 파장도 작아지기 때문에, 회로의 크기도 작아질 수밖에 없다. 특히, kW급 이상의 고출력 테라헤르츠파 주파수 대역의 회로를 제작하려면, ${\mu}m{\sim}mm$ 규모의 회로 크기 문제 때문에 제작에 한계점이 있다. 이러한 한계점을 극복하기 위해 본 논문에서는 회로의 지름이 2.4 cm 정도의 원통형으로, 0.1 THz~0.3 GW급의 발생원 설계 기술을 제안한다. 판드로모티브 힘이 생기는 플라즈마 항적장 가속원리와 인위적인 유전체 활용한 체렌코프방사 발생 기술 기반의 고출력 전자파 발생원의 최적화된 설계를 위해 모델링 및 전산모사를 수행하였다. 객관적인 검증 과정을 통해 회로의 크기에 제한을 덜 받도록 하는 대구경 형태의 고출력 테라헤르츠파 진공소자 제작이 용이하도록 효과적인 설계의 가이드라인을 제시하였다.