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1تقرير
المؤلفون: Lee, Hang Woon, Rogers, David O. Williams, Pearl, Brycen D., Chen, Hao, Ho, Koki
مصطلحات موضوعية: Mathematics - Optimization and Control, Electrical Engineering and Systems Science - Systems and Control
الوصف: In this paper, we address the problem of reconfiguring Earth observation satellite constellation systems through multiple stages. The Multi-stage Constellation Reconfiguration Problem (MCRP) aims to maximize the total observation rewards obtained by covering a set of targets of interest through the active manipulation of the orbits and relative phasing of constituent satellites. In this paper, we consider deterministic problem settings in which the targets of interest are known a priori. We propose a novel integer linear programming formulation for MCRP, capable of obtaining provably optimal solutions. To overcome computational intractability due to the combinatorial explosion in solving large-scale instances, we introduce two computationally efficient sequential decision-making methods based on the principles of a myopic policy and a rolling horizon procedure. The computational experiments demonstrate that the devised sequential decision-making approaches yield high-quality solutions with improved computational efficiency over the baseline MCRP. Finally, a case study using Hurricane Harvey data showcases the advantages of multi-stage constellation reconfiguration over single-stage and no-reconfiguration scenarios.
Comment: 39 pages, 13 figures, submitted to the Journal of Spacecraft and Rocketsالوصول الحر: http://arxiv.org/abs/2401.11567Test
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2تقرير
المؤلفون: Patel, Malav, Shimane, Yuri, Lee, Hang Woon, Ho, Koki
مصطلحات موضوعية: Mathematics - Optimization and Control
الوصف: Cislunar space awareness is of increasing interest to the international community as Earth-Moon traffic is projected to increase. This raises the problem of placing satellites optimally in a constellation to provide satisfactory coverage for said traffic. The Circular Restricted 3 Body Problem (CR3BP) provides promising periodic orbits in the Earth-Moon rotating frame for traffic monitoring. This work converts a spatially and temporally varying traffic coverage requirement into an integer linear programming problem, attempting to minimize the number of satellites required for the requested coverage.
Comment: 18 pages, 15 figures, submitted to 2023 AAS Conferenceالوصول الحر: http://arxiv.org/abs/2311.10252Test
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3رسالة جامعية
المؤلفون: Lee, Hang Young
مرشدي الرسالة: Keister, Lisa A., Lin, Nan
مصطلحات موضوعية: Sociology, Economics, Labor, immigrant, job attainment, job search, social capital, social inequality, social networks
الوصف: Social capital has so far been suggested to enhance the career outcomes of disadvantaged immigrants by compensating for their lack of human capital. Contrastingly, by examining labor market outcomes by immigrant groups, my dissertation argues that social capital can actually serve as a source of disadvantages for immigrants in the labor market, especially for a socially disadvantaged immigrant group like Mexican immigrants. Specifically, the dissertation proposes three kinds of social capital processes through which social status and network processes interplay to disadvantage disproportionately a low-status immigrant group in the job attainment process: access, activation, and return deficit of social capital. Using data from the 2005 U.S. Social Capital-USA survey, I examine these three kinds of social capital deficit across three ethnic immigrant groups: Mexican, non-Mexican Hispanic, and non-Hispanic immigrants. The first chapter explores the inequality of social capital across immigrant groups. The result shows that among the three immigrant groups, Mexican immigrants are the only immigrant group who have smaller, less diverse networks than the native-born. This access deficit of social capital for Mexican immigrants is driven primarily by their relative lack of human capital compared with other immigrant groups. The second chapter investigates whether ethnic enclaves constrain the access to social capital of enclave immigrants. The result shows that the constraining effect of ethnic enclaves on the social capital building of enclave immigrants is found only for the ethnic enclave of Mexican immigrants. This is because the ethnic enclaves of disadvantaged immigrants facilitate social connections to other coethnic enclave immigrants with similar socioeconomic traits, while constraining them from extending their networks beyond the enclaves. The access deficit of social capital for Mexican immigrants will eventually aggravate their job prospects because they cannot mobilize social capital for their job finding as much as other immigrant groups do. The third chapter examines the activation and mobilization of social capital in the job attainment process across immigrant groups. The result shows that Mexican immigrants activate and reap the benefit from mobilizing social capital for their job finding in ways that are different from those of the native-born as well as the high-status immigrant group. Due to their access deficit of social capital and negative stereotypes about them, Mexican immigrants are obliged to use a less rewarding job search method (i.e., using information passed from job contacts) rather than use a more rewarding job search method (i.e., using invitations from job contacts). Although Mexican immigrants benefit to some degrees from using information passed from job contacts in getting low-tier occupations, their heavy reliance on such a job search method can also prevent them from attaining middle- or top-tier occupations. By illuminating these serial processes of social capital in the job attainment for disadvantaged immigrants, my dissertation, therefore, sheds light on a new role of social capital as a source of immigrant disadvantages in the labor market.
Dissertation -
4دورية أكاديمية
المؤلفون: Lee, Hang yong, Kim, Hyeon-Wook
المصدر: KDI Journal of Economic Policy, Vol 31, Iss 2, Pp 235-266 (2009)
مصطلحات موضوعية: 환율전가(exchange rate passthrough), 수출가격(export price), 비대칭성(asymmetry), Social Sciences, Industries. Land use. Labor, HD28-9999, Economic theory. Demography, HB1-3840
الوصف: This paper investigates changes in the extent of exchange rate pass-through to export price in Korea. First, empirical results show that export prices have become less responsive to the exchange rate since the financial crisis in 1997. The decline of exchange rate pass-through to export prices suggests that Korean exporters are more likely to use profit margins to absorb part of the impact of exchange rate changes, consistent with pricing to market phenomenon. Second, this paper finds asymmetries in the response of export prices to exchange rate changes. In the post-crisis period. appreciations are more likely to be offset by markup adjustment than depreciations. Third, this paper documents that a significant portion of the decline of exchange rate pass-through is a result of both increased volatility of exchange rate and increased competition with China in the world market.
وصف الملف: electronic resource
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5تقرير
المؤلفون: Lee, Hang Woon, Ho, Koki
مصطلحات موضوعية: Mathematics - Optimization and Control, Electrical Engineering and Systems Science - Systems and Control
الوصف: A group of satellites, with either homogeneous or heterogeneous orbital characteristics and/or hardware specifications, can undertake a reconfiguration process due to variations in operations pertaining to Earth observation missions. This paper investigates the problem of optimizing a satellite constellation reconfiguration process against two competing mission objectives: (i) the maximization of the total coverage reward and (ii) the minimization of the total cost of the transfer. The decision variables for the reconfiguration process include the design of the new configuration and the assignment of satellites from one configuration to another. We present a novel bi-objective integer linear programming formulation that combines constellation design and transfer problems. The formulation lends itself to the use of generic mixed-integer linear programming (MILP) methods such as the branch-and-bound algorithm for the computation of provably-optimal solutions; however, these approaches become computationally prohibitive even for moderately-sized instances. In response to this challenge, this paper proposes a Lagrangian relaxation-based heuristic method that leverages the assignment problem structure embedded in the problem. The results from the computational experiments attest to the near-optimality of the Lagrangian heuristic solutions and a significant improvement in the computational runtime compared to a commercial MILP solver.
Comment: 41 pages, 10 figures, accepted for publication at Journal of Spacecraft and Rockets; pre-printالوصول الحر: http://arxiv.org/abs/2206.02910Test
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6دورية أكاديمية
المؤلفون: Kim, Jang ryoul, Lee, Hang yong
المصدر: KDI Journal of Economic Policy, Vol 30, Iss 2, Pp 1-25 (2008)
مصطلحات موضوعية: Consumption(소비), Housing wealth effect(주택 부 효과), Home ownership(주택보유), Social Sciences, Industries. Land use. Labor, HD28-9999, Economic theory. Demography, HB1-3840
الوصف: This paper attempts to re-evaluate the size of housing wealth effect in Korea. Our focus is on the size of ‘genuine’ housing wealth effect, i.e., the response of consumption spending by home-owners to the changes in housing wealth. Two issues show up while we estimate the ‘genuine’ wealth effects using aggregate time series data: the issues around home ownership and proper measure of consumption. We first argue that it is more appropriate to use non-housing consumption, because housing consumption is in large part not of the choice of home owners but the imputed rents they do not actually choose to pay. We then proceed to address the issue of home ownership, by examining how much to revise the estimates of housing wealth effect obtained from aggregate non-housing consumption data. We construct two structural models and estimate the share of home-owners' consumption in those models' context. It is found that, if properly revised in light of the estimated consumption shares of home-owners, the magnitude of resulting housing wealth effects are larger than what simple time series regressions imply.
وصف الملف: electronic resource
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7دورية أكاديمية
المؤلفون: Lee, Hang yong
المصدر: KDI Journal of Economic Policy, Vol 29, Iss 1, Pp 180-199 (2007)
مصطلحات موضوعية: Basel II(신바젤협약), Regulatory Capital(규제자본), Buffer Capital(잉여자본), Business Cycle(경기순환), Procyclicality(경기순응성), Social Sciences, Industries. Land use. Labor, HD28-9999, Economic theory. Demography, HB1-3840
الوصف: This paper investigates the cyclical patterns of buffer capital using an unbalanced panel data for the banks in 30 OECD countries and 7 non-OECD Asian countries. We test whether the relationships between buffer capital and business cycle are systematically different across country groups controlling for other potential determinants of bank capital. We find that the correlation is positive for developed countries while it is negative for Asian developing countries. These findings suggest that, once Basel II is implemented, developing countries are more likely to observe an increase in output volatility. We then review the policy recommendations to mitigate the procyclicality problem of Basel II.
وصف الملف: electronic resource
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8دورية أكاديمية
المؤلفون: Lee, Hang yong
المصدر: KDI Journal of Economic Policy, Vol 27, Iss 2, Pp 89-121 (2005)
مصطلحات موضوعية: 불확실성(uncertainty), 투자(investment), q모형(q model), Social Sciences, Industries. Land use. Labor, HD28-9999, Economic theory. Demography, HB1-3840
الوصف: This paper investigates the empirical relationship between investment and uncertainty using the firm level data of Korean manufacturing sector. Empirical results show that uncertainty is negatively correlated with investment only for the post-crisis sample period. In particular, the negative effect of uncertainty on investment is more significant for low interest coverage ratio firms, high debt-asset ratio firms and small firms. The results are consistent with the claim that firms act in a more risk-averse manner after the financial crisis. This paper also finds a significant sensitivity of investment to cash flows only for the pre-crisis sample period, suggesting that financial constraint is not relatively important in explaining low investment after the financial crisis.
وصف الملف: electronic resource
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9دورية أكاديمية
المؤلفون: Lee, Donghyuck, Lee, Hang-Shim (ORCID
0000-0002-1460-3852 ), Na, Wooyoul, Hwang, Mae Hyangالمصدر: Journal of Career Development. Aug 2022 49(4):875-889.
تمت مراجعته من قبل الزملاء: Y
Page Count: 15
الواصفات: Gender Differences, Foreign Countries, Vocational Interests, Personality Measures, Interest Inventories, Personality Traits, Models, Correlation, College Freshmen, Cultural Differences
مصطلحات جغرافية: South Korea
معرفات التقييم و الدراسة: Self Directed Search
مستخلص: This study examined the structure of Holland's personality model (HPM) among male and female South Korean college students using the Korean version of the Self-Directed Search (K-SDS) and investigated gender differences in the circular structure of HPM and circular plots of the K-SDS subscales (i.e., activities, competences, vocations, and self-estimates). The study outcomes were as follows: Our findings supported the validity of HPM among Korean college freshmen. However, there were gender differences in the fit between the data and the circular ordering model. Also, the differences in the realistic, investigative, artistic, social, enterprising, and conventional (RIASEC) circular plots and the magnitude of the correlations among the RIASEC types across the four subscales and gender were found. These results suggest that practitioners should cautiously interpret and communicate the results of the SDS to college students considering cultural and gender specificity. Implications and limitations of the present research are discussed.
Abstractor: As Provided
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10دورية أكاديمية
المؤلفون: Elves‑Powell, Joshua, Dolan, Jai, Durant, Sarah M., Lee, Hang, Linnell, John Durrus, Turvey, Samuel T., Axmacher, Jan C.
المصدر: 24 ; Regional Environmental Change ; 97
مصطلحات موضوعية: Democratic People’s Republic of Korea (DPRK), Northeast Asia, Normalized Difference Vegetation Index (NDVI), Deforestation, Cropland expansion, Mixed methods research, VDP::Matematikk og Naturvitenskap: 400::Zoologiske og botaniske fag: 480
جغرافية الموضوع: Democratic People’s Republic of Korea (DPRK), Northeast Asia
الوصف: Satellite-based remote sensing approaches provide a cost-efficient means to collect information on the world’s forests and to repeatedly survey large, or inaccessible, forest areas. However, it may not always be possible to ground truth–associated findings using direct ecological field surveys conducted by trained forest scientists. Local ecological knowledge (LEK) is an alternative form of data which could be used to complement, interpret and verify information from satellite data. Using a case study on the Democratic People’s Republic of Korea (North Korea), we evaluate the potential for integrating remote sensing and LEK data, gathered with non-specialist former residents, to understand patterns and drivers of forest cover change. LEK reports often concurred with, or provided key information to enable interpretation of, satellite data. This revealed that between 1986 and 2021, North Korea experienced high, but uneven, rates of deforestation. There was a pronounced northwards deforestation shift in the mid-1990s, coinciding with a period of extreme hardship and famine (the “Arduous March”), and associated with clearance of trees in more forested northern provinces as an economic and fuel resource, and conversion of forest to agricultural cropland. Loss of forest cover in North Korea has continued and recently accelerated, to a rate of > 200 km2 per annum between 2019 and 2021. This increases the vulnerability of North Korean socio-ecological systems to future environmental change and is an obstacle to the recovery of threatened species across the Korean Peninsula. We recommend that LEK- and remote sensing–based approaches are considered within a suite of complementary techniques to analyse forest changes where ecological field surveys cannot be conducted. Democratic People’s Republic of Korea (DPRK) · Northeast Asia · Normalized Difference Vegetation Index (NDVI) · Deforestation · Cropland expansion · Mixed methods research ; publishedVersion
وصف الملف: application/pdf
العلاقة: Andre: Research England; urn:issn:1436-3798; https://hdl.handle.net/11250/3135041Test; https://doi.org/10.1007/s10113-024-02254-zTest; cristin:2276987
