• Title/Summary/Keyword: A1B scenario

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Evolutionary Models for Helium Giant Stars as Type Ibn Supernova Progenitors.

  • Kim, Jihoon;Yoon, Sung-Chul
    • The Bulletin of The Korean Astronomical Society
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    • v.43 no.2
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    • pp.40.1-40.1
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    • 2018
  • Among Type I supernovae, which show no evidence for hydrogen lines in spectra, Type Ib/c supernovae lack of strong Si absorption lines and are involved with massive progenitors. While strong helium absorption lines are present in Type Ib supernovae, narrow helium emission lines also can appear in some Type Ib that are often called Type Ibn supernovae (SNe Ibn). We consider helium giant stars as a promising progenitor candidate for SN Ibn and suggest the evolutionary scenario through binary systems using MESA code. In our models the range of primary mass is 11 - 20 solar mass, mass ratio is 0.5 - 0.9, and initial period is 1.5 / 1.7 / 2.0 / 2.5 / 3.0 day. In particular, we find that the evolution of the secondary star can overtake the primary through mass transfer from the secondary to the primary, which is so-called 'reverse case B' mass transfer. In such systems the secondary star may undergo a supernova explosion earlier than the primary star. In this case, the primary star evolves towards a single helium giant to become a SN Ibn progenitor. These cases are more frequent in relatively low initial primary mass.

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Analysis of Impact Climate Change on Extreme Rainfall Using B2 Climate Change Scenario and Extreme Indices (B2 기후변화시나리오와 극한지수를 이용한 기후변화가 극한 강우 발생에 미치는 영향분석)

  • Kim, Bo Kyung;Kim, Byung Sik
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.1B
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    • pp.23-33
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    • 2009
  • Climate change, abnormal weather, and unprecedented extreme weather events have appeared globally. Interest in their size, frequency, and changes in spatial distribution has been heightened. However, the events do not display regional or regular patterns or cycles. Therefore, it is difficult to carry out quantified evaluation of their frequency and tendency. For more objective evaluation of extreme weather events, this study proposed a rainfall extreme weather index (STARDEX, 2005). To compare the present and future spatio-temporal distribution of extreme weather events, each index was calculated from the past data collected from 66 observation points nationwide operated by Korea Meteorological Administration (KMA). Tendencies up to now have been analyzed. Then, using SRES B2 scenario and 2045s (2031-2050) data from YONU CGCM simulation were used to compute differences among each of future extreme weather event indices and their tendencies were spatially expressed.The results shows increased rainfall tendency in the East-West inland direction during the summer. In autumn, rainfall tendency increased in some parts of Gangwon-do and the south coast. In the meanwhile, the analysis of the duration of prolonged dry period, which can be contrasted with the occurrence of rainfall or its concentration, showed that the dryness tendency was more pronounced in autumn rather than summer. Geographically, the tendency was more remarkable in Jeju-do and areas near coastal areas.

Study on D2D Relay based Interconnection Network of HAM Radio and Wi-Fi for Securing Communication Performance in Satellite Wireless Package Systems (이동단말용 위성 통신 무선 패키지 시스템을 위한 D2D Relay 기반 HAM Radio와 Wi-Fi Network 결합망의 통신 성능 확보 연구)

  • Hwang, Yu Min;Cha, Jae Sang;Kim, Jin Young
    • Journal of Satellite, Information and Communications
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    • v.10 no.1
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    • pp.12-16
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    • 2015
  • In this paper, we introduce a wireless package system based on the amateur radio HR(HAM Radio) and satellite communication as a novel wireless disaster communication system and have configured a interference scenario receiving interference from adjacent base stations and D2D groups in the disaster network. In such interference scenarios, we propose a frequency re-allocation method to avoid interference and communicate with disaster networks by securing the channel capacity required between D2D terminals. As a result of computer simulation, we can find the proposed method has improved BED performance of a gain of 1.5dB and overall system throughput than conventional methods.

An Appropriate Utilization of Agricultural Water Resources of Jeju Island with Climate Change (I) (기후변화와 관련한 제주지역 농업용수의 효율적 활용 방안(I))

  • Song, Sung-Ho;Choi, Kwang-Jun
    • Journal of Soil and Groundwater Environment
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    • v.17 no.2
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    • pp.62-70
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    • 2012
  • Rainfall, on Jeju Island varies regionally in relation to Mt. Halla with higher rainfall within southern area and lower in western area, and its variability is expected to expand according to the climate change scenario. Non-parametric trend analysis for rainfall, using both historic (1971-2010) and simulated (2011-2100) data assuming the A1B emissions scenario, shows regionally increasing trends with time. In perspective of agricultural land use, area for market garden including various crop types with high water demand is increasing over the Island, especially in the western area with lower rainfall compared to southern area. On the other hand, area for fruit including mandarin and kiwi with low water demand is widely distributed over southern and northern part having higher rainfall. These regional disparity of water demand/supply may be more affected by extreme events such as drought and heavy rainfall that has not yet been considered. Therefore, it is necessary to make policies for water resource management considering both demand and supply in different regions with climate change impacts over Jeju Island.

The Impacts of Climate Change on Paddy Water Demand and Unit Duty of Water using High-Resolution Climate Scenarios (고해상도 기후시나리오를 이용한 논용수 수요량 및 단위용수량의 기후변화 영향 분석)

  • Yoo, Seung-Hwan;Choi, Jin-Yong;Lee, Sang-Hyun;Oh, Yun-Gyeong;Park, Na-Young
    • Journal of The Korean Society of Agricultural Engineers
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    • v.54 no.2
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    • pp.15-26
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    • 2012
  • For stable and sustainable crop production, understanding the effects of climate changes on agricultural water resources is necessary to minimize the negative effects which might occur due to shifting weather conditions. Although various studies have been carried out in Korea concerning changes in evapotranspiration and irrigation water requirement, the findings are still difficult to utilize fordesigning the demand and unit duty of water, which are the design criteria of irrigation systems. In this study, the impact analysis of climate changes on the paddy water demand and unit duty of water was analyzed based on the high resolution climate change scenarios (specifically under the A1B scenario) provided by the Korea Meteorological Administration. The result of the study indicated that average changes in the paddy water demand in eight irrigation districts were estimated as -2.4 % (2025s), -0.2 % (2055s), and 3.2 % (2085s). The unit duty of water was estimated to increase on an average within 2 % during paddy transplanting season and within 5 % during growing season after transplanting. This result could be utilized for irrigation system design, agricultural water resource development, and rice paddy cultivation policy-making in South Korea.

Simulation of the Effects of the A1B Climate Change Scenario on the Potential Yield of Winter Naked Barley in Korea (A1B 기후변화 시나리오가 국내 가을 쌀보리의 잠재수량에 미치는 영향 모사)

  • Shim, Kyo-Moon;Min, Sung-Hyun;Lee, Deog-Bae;Kim, Gun-Yeob;Jeong, Hyun-Cheol;Lee, Seul-Bi;Kang, Ki-Keong
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.13 no.4
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    • pp.192-203
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    • 2011
  • The CERES-Barley crop simulation model was used to assess the impacts of climate change on the potential yield of winter naked barley in Korea. Fifty six sites over the southern part of the Korean Peninsula were selected to compare the climate change impacts in various climatic conditions. Based on the A1B climate change scenarios of Korea, the present climatological normal (1971-2000) and the three future ones (2011-2040, 2041-2070, and 2071-2100) were considered in this study. The three future normals were divided by three environmental conditions with changes in: (1) temperature only, (2) carbon dioxide concentration only, and (3) both temperature and carbon dioxide concentration. The agreement between the observed and simulated outcomes was reasonable with the coefficient of determination of grain yield to be 0.78. We concluded that the CERES-Barley model was suitable for predicting climate change impacts on the potential yield of winter naked barley. The effect of the increased temperature only with the climate change scenario was negative to the potential yield of winter naked barley, which ranges from -34 to -9% for the three future normals. However, the effect of the elevated carbon dioxide concentration only on the potential yield of winter naked barley was positive, ranging from 6 to 31% for the three future normals. For the elevated conditions of both temperature and carbon dioxide concentration, the potential yields increased by 8, 15, and 13% for the 2011-2040, 2041-2070, and 2071-2100 normals, respectively.

Analysis of Rainfall-Runoff Characteristics on Bias Correction Method of Climate Change Scenarios (기후변화 시나리오 편의보정 기법에 따른 강우-유출 특성 분석)

  • Kum, Donghyuk;Park, Younsik;Jung, Young Hun;Shin, Min Hwan;Ryu, Jichul;Park, Ji Hyung;Yang, Jae E;Lim, Kyoung Jae
    • Journal of Korean Society on Water Environment
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    • v.31 no.3
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    • pp.241-252
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    • 2015
  • Runoff behaviors by five bias correction methods were analyzed, which were Change Factor methods using past observed and estimated data by the estimation scenario with average annual calibration factor (CF_Y) or with average monthly calibration factor (CF_M), Quantile Mapping methods using past observed and estimated data considering cumulative distribution function for entire estimated data period (QM_E) or for dry and rainy season (QM_P), and Integrated method of CF_M+QM_E(CQ). The peak flow by CF_M and QM_P were twice as large as the measured peak flow, it was concluded that QM_P method has large uncertainty in monthly runoff estimation since the maximum precipitation by QM_P provided much difference to the other methods. The CQ method provided the precipitation amount, distribution, and frequency of the smallest differences to the observed data, compared to the other four methods. And the CQ method provided the rainfall-runoff behavior corresponding to the carbon dioxide emission scenario of SRES A1B. Climate change scenario with bias correction still contained uncertainty in accurate climate data generation. Therefore it is required to consider the trend of observed precipitation and the characteristics of bias correction methods so that the generated precipitation can be used properly in water resource management plan establishment.

Han River Basin climate forecast using multi-site artificial neural network (다지점 인공신경망을 이용한 한강수계 기후전망)

  • Kang, Boo-Sik;Moon, Su-Jin;Kim, Jung-Joong
    • Proceedings of the Korea Water Resources Association Conference
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    • 2011.05a
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    • pp.371-371
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    • 2011
  • 본 연구에서는 한강유역 내 관측기간이 충분한 기상청 지상관측소 10개소를 선정하고 CCCma(Canadian Century for Climate modeling and analysis)에서 제공하는 자료에 대한 인공신경망기법 상세화 적용을 실시하였다. 인공신경망의 학습을 위해 CGCM3.1/T63 20C3M시나리오(reference scenario)의 22개 2D변수 중 물리적으로 민감도가 높다고 판단되는 GCM_Prec, huss, ps를 입력변수로 선정하였으며 인공신경망 학습기간은 1991년~1995년, 검증기간은 1996년~2000년, 예측기간은 2011년~2100년으로 A1B, A2 B1 시나리오 등 다양한 기후변화 시나리오를 통해 예측band를 제시하고자 하였다. 하지만 공간상관을 고려하기 위하여 각 관측소에 대하여 인공신경망 학습을 하는 경우 관측소간 spatial correlation 및 spatial cluster구현이 어렵기 때문에 Spatial Rectangular Pulse모형을 이용하고자 하였으나, 강수면적에 대한 scale의 결정이 어렵다는 단점을 확인 하고 본 연구에서는 Random Cascade 모형을 이용하여 ${\beta}$를 통한 강수면적 scale(rainy area fraction)을 결정하고자 하였다. Random Cascade모형의 기법은 격자단위의 downscaling기법으로 강수대의 공간적 형상을 재현하며 스케일에 비종속적인(scale-invariant)프랙탈 특성을 이용하여 매개변수를 최소화 할 수 있는 장점을 가진 기법으로 한강유역 1Km내외 강우장을 만들어 topographic effect를 첨가하고자 한다.

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Assessing the Damage: An Exploratory Examination of Electronic Word of Mouth (손해평고(损害评估): 대전자구비행소적탐색성고찰(对电子口碑行销的探索性考察))

  • Funches, Venessa Martin;Foxx, William;Park, Eun-Joo;Kim, Eun-Young
    • Journal of Global Scholars of Marketing Science
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    • v.20 no.2
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    • pp.188-198
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    • 2010
  • This study attempts to examine the influence that negative WOM (NWOM) has in an online context. It specifically focuses on the impact of the service failure description and the perceived intention of the communication provider on consumer evaluations of firm competence, attitude toward the firm, positive word of mouth and behavioral intentions. Studies of communication persuasiveness focus on "who says what; to whom; in which channel; with what effect (Chiu 2007)." In this research study, we examine electronic web posting, particularly focusing on two aspects of "what": the level of service failure communicated and perceived intention of the individual posting. It stands to reason electronic NWOM that appears to be trying to damage a product’s or firm's reputation will be viewed as more biased and will thus be considered as less credible. According to attribution theory, people search for the causes of events especially those that are negative and unexpected (Weiner 2006). Hennig-Thurau and Walsh (2003) state "since the reader has only limited knowledge and trust of the author of an online articulation the quality of the contribution could be expected to serve as a potent moderator of the articulation-behavior relationship. We therefore posit the following hypotheses: H1. Subjects exposed to electronic NWOM describing a high level of service failure will provide lower scores on measures of (a) firm competence, (b) attitude toward the firm, (c) positive word of mouth, and (d) behavioral intention than will subjects exposed to electronic NWOM describing a low level of service failure. H2. Subjects exposed to electronic NWOM with a warning intent will provide lower scores on measures of (a) firm competence, (b) attitude toward the firm, (c) positive word of mouth, and (d) behavioral intention than will subjects exposed to electronic NWOM with a vengeful intent. H3. Level of service failure in electronic NWOM will interact with the perceived intention of the electronic NWOM, such that there will be a decrease in mean response on measures of (a) firm competence, (b) attitude toward the firm, (c) positive word of mouth, and (d) behavioral intention from electronic NWOM with a warning intent to a vengeful intent. The main study involved a2 (service failure severity) x2 (NWOM with warning versus vengeful intent) factorial experiment. Stimuli were presented to subjects online using a mock online web posting. The scenario described a service failure associated with non-acceptance of a gift card in a brick-and-mortar retail establishment. A national sample was recruited through an online research firm. A total of 113 subjects participated in the study. A total of 104 surveys were analyzed. The scenario was perceived to be realistic with 92.3% giving the scenario a greater than average response. Manipulations were satisfactory. Measures were pre-tested and validated. Items were analyzed and found reliable and valid. MANOVA results found the multivariate interaction was not significant, allowing our interpretation to proceed to the main effects. Significant main effects were found for post intent and service failure severity. The post intent main effect was attributable to attitude toward the firm, positive word of mouth and behavioral intention. The service failure severity main effect was attributable to all four dependent variables: firm competence, attitude toward the firm, positive word of mouth and behavioral intention. Specifically, firm competence for electronic NWOM describing high severity of service failure was lower than electronic NWOM describing low severity of service failure. Attitude toward the firm for electronic NWOM describing high severity of service failure was lower than electronic NWOM describing low severity of service failure. Positive word of mouth for electronic NWOM describing high severity of service failure was lower than electronic NWOM describing low severity of service failure. Behavioral intention for electronic NWOM describing high severity of service failure was lower for electronic NWOM describing low severity of service failure. Therefore, H1a, H1b, H1c and H1d were all supported. In addition, attitude toward the firm for electronic NWOM with a warning intent was lower than electronic NWOM with a vengeful intent. Positive word of mouth for electronic NWOM with a warning intent was lower than electronic NWOM with a vengeful intent. Behavioral intention for electronic NWOM with a warning intent was lower than electronic NWOM with a vengeful intent. Thus, H2b, H2c and H2d were supported. However, H2a was not supported though results were in the hypothesized direction. Otherwise, there was no significant multivariate service failure severity by post intent interaction, nor was there a significant univariate service failure severity by post intent interaction for any of the three hypothesized variables. Thus, H3 was not supported for any of the four hypothesized variables. This study has research and managerial implications. The findings of this study support prior research that service failure severity impacts consumer perceptions, attitude, positive word of mouth and behavioral intentions (Weun et al. 2004). Of further relevance, this response is evidenced in the online context, suggesting the need for firms to engage in serious focused service recovery efforts. With respect to perceived intention of electronic NWOM, the findings support prior research suggesting reader's attributions of the intentions of a source influence the strength of its impact on perceptions, attitude, positive word of mouth and behavioral intentions. The implication for managers suggests while consumers do find online communications to be credible and influential, not all communications are weighted the same. A benefit of electronic WOM, even when it may be potentially damaging, is it can be monitored for potential problems and additionally offers the possibility of redress.

Performance Analysis and Equivalent Circuit Extraction for Magnetic Resonance Type Wireless Power Transfer (자기공진방식 무선전력전송 등가회로 추출 및 특성 분석)

  • Park, Dae Kil;Kim, Young Hyun;Koo, Kyung Heon
    • Journal of Advanced Navigation Technology
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    • v.21 no.4
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    • pp.371-376
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    • 2017
  • In this paper, we propose a magnetic resonant WPT(wireless power transfer) scenario using a large coil resonating at 6.78 MHz, and compare the characteristics through a three-dimensional electromagnetic field simulation and a magnetic resonant WPT equivalent circuit. The magnetic resonant WPT equivalent circuit proposed in this paper considers the parasitic capacitance generated between the coils in addition to the conventional equivalent circuit. Based on this analysis, we fabricated the magnetic resonant WPT coil and compared it with simulation prediction. As a result of comparison, the transfer characteristics and the resonance frequency shift can be predicted. Error proposed characteristics of equivalent circuit for the magnetic resonant WPT and the measured values are estimated to be ${\Delta}{\mid}S11{\mid}=1.31dB$ and ${\Delta}{\mid}S21{\mid}=1.21dB$, respectively.