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2. Diameters of Graphs on Reduced Words of 12 and 21-Inflations

Author

Dahlberg, Samantha and Kim, Younghwan

Subjects
Mathematics - Combinatorics, 05A05, 05C12
Abstract

It is a classical result that any permutation in the symmetric group can be generated by a sequence of adjacent transpositions. The sequences of minimal length are called reduced words, and in this paper we study the graphs of these reduced words, with edges determined by relations in the underlying Coxeter group. Recently, the diameter has been calculated for the longest permutation $n\ldots 21$ by Reiner and Roichman as well as Assaf. In this paper we find inductive formulas for the diameter of the graphs of 12-inflations and many 21-inflations. These results extend to the associated graphs on commutation and long braid classes. Also, these results give a recursive formula for the diameter of the longest permutation, which matches that of Reiner, Roichman and Assaf. Lastly, We make progress on conjectured bounds of the diameter by Reiner and Roichman, which are based on the underlying hyperplane arrangement, and find families of permutations that achieve the upper bound and lower bound of the conjecture. In particular permutations that avoid 312 or 231 have graphs that achieve the upper bound.

Published
2020

3. Identifiability of Gaussian Structural Equation Models with Homogeneous and Heterogeneous Error Variances

Author

Park, Gunwoong and Kim, Younghwan

Subjects
Statistics - Machine Learning, Computer Science - Machine Learning
Abstract

In this work, we consider the identifiability assumption of Gaussian linear structural equation models (SEMs) in which each variable is determined by a linear function of its parents plus normally distributed error. It has been shown that linear Gaussian structural equation models are fully identifiable if all error variances are the same or known. Hence, this work proves the identifiability of Gaussian SEMs with both homogeneous and heterogeneous unknown error variances. Our new identifiability assumption exploits not only error variances, but edge weights; hence, it is strictly milder than prior work on the identifiability result. We further provide a structure learning algorithm that is statistically consistent and computationally feasible, based on our new assumption. The proposed algorithm assumes that all relevant variables are observed, while it does not assume causal minimality and faithfulness. We verify our theoretical findings through simulations and real multivariate data, and compare our algorithm to state-of-the-art PC, GES and GDS algorithms., Comment: 18 pages, 7 figures, 1 table

Published
2019

8. An Educational Tool for Browsing the Semantic Web

Author

Yoo, Sujin, Kim, Younghwan, and Park, Seongbin

Abstract

The Semantic Web is an extension of the current Web where information is represented in a machine processable way. It is not separate from the current Web and one of the confusions that novice users might have is where the Semantic Web is. In fact, users can easily encounter RDF documents that are components of the Semantic Web while they navigate among Web pages. In addition, the number of RDF documents on the Web is ever-increasing and a lot of educational materials in RDF format become available on the Web. In this paper, we propose a simple Semantic Web browser by which non-expert users such as secondary school students who do not know technical details about the Semantic Web can browse through HTML documents and RDF documents.

Published
2013

10. Descriptive Study of Electromagnetic Wave Distribution for Various Seating Positions

Author

Seomun, GyeongAe, Kim, YoungHwan, Lee, Jung-Ah, Jeong, KwangHoon, Park, Seon-A, Kim, Miran, and Noh, Wonjung

Subjects
Child, Computers, Electromagnetic Radiation, Environmental Exposure, Humans, Posture, Schools, Students, Surveys and Questionnaires, digital textbook, environmental, school, electromagnetic field, elementary students, Nursing, Specialist Studies in Education
Abstract

To better understand environmental electromagnetic wave exposure during the use of digital textbooks by elementary school students, we measured numeric values of the electromagnetic fields produced by tablet personal computers (TPCs). Specifically, we examined the distribution of the electromagnetic waves for various students' seating positions in an elementary school that uses digital textbooks. Electric and magnetic fields from TPCs were measured using the HI-3603 Visual Display Terminal/ Very Low Frequency (VDT/VLF) radiation measurement system. Electromagnetic field values from TPCs measured at a student's seat and at a teacher's computer were deemed not harmful to health. However, electromagnetic field values varied based on the distance between students, other electronic devices such as a desktop computers, and student posture while using a TPC. Based on these results, it is necessary to guide students to observe proper posture and to arrange seats at an appropriate distance in the classroom.

Published
2014

12. Formative Research on the Simplifying Conditions Method (SCM) for Task Analysis and Sequencing.

Author

Kim, YoungHwan and Reigluth, Charles M.

Abstract

The Simplifying Conditions Method (SCM) is a set of guidelines for task analysis and sequencing of instructional content under the Elaboration Theory (ET). This article introduces the fundamentals of SCM and presents the findings from a formative research study on SCM. It was conducted in two distinct phases: design and instruction. In the first phase, the SCM process was used to design a course in order to determine the weaknesses of the SCM process. In the second phase, the course was taught using the SCM sequence in order to determine the weaknesses of SCM principles. Results suggest that the current SCM process is workable; however, three recommendations were offered: (1) the need to stress the holistic rather than the step-by-step approach; (2) the need to add more detailed prescriptions; and (3) the need for formative evaluation. Second, the study yielded no critical weaknesses that might lead to possible improvements in the SCM principles, since most of the learners were very satisfied with the sequence of the instruction. Three figures present results. (Contains 34 references.) (AEF)

Published
1996

23. Experience of augmenting critical care capacity in Daegu during COVID-19 incident in South Korea

Author

Kim, Je Hyeong, Hong, Suk-Kyung, Kim, Younghwan, Ryu, Ho Geol, Park, Chi-Min, Lee, Young Seok, and Hong, Sung Jin

Subjects
2019-20 coronavirus outbreak, Coronavirus disease 2019 (COVID-19), business.industry, Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), Intensivist, lcsh:Medical emergencies. Critical care. Intensive care. First aid, MEDLINE, lcsh:RC86-88.9, Brief Communication, Critical Care and Intensive Care Medicine, Critical Care Nursing, medicine.disease, Care capacity, Policy, Medicine, Medical emergency, business
Published
2020

24. Additional file 1 of Patient and hospital characteristics predict prolonged emergency department length of stay and in-hospital mortality: a nationwide analysis in Korea

Author

Lee, Kyung-Shin, Min, Hye Sook, Moon, Jae Young, Lim, Daesung, Kim, Younghwan, Ko, Eunsil, Kim, You Sun, Kim, Joohae, Lee, Jeehye, and Sung, Ho Kyung

Abstract

Additional file 1: Table S1. Characteristics of critically ill patients directly admitted to the intensive care unit from the emergency department by hospital staffed-bed category. Table S2. Characteristics of critically ill patients directly admitted to the intensive care unit by type of emergency department. Table S3. Sensitivity analysis for prolonged EDLOS. Table S4. Sensitivity analysis for in-hospital mortality.

Published
2022
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29. Association Between β-Blockers and Outcome of Coronary Artery Bypass Grafting: Before and After 1 Year

Author

Park, Jungchan, primary, Lee, Seung-Hwa, additional, Jeong, Dong Seop, additional, Lee, Young Tak, additional, Kim, Younghwan, additional, Lee, Sang On, additional, Lee, Sangmin Maria, additional, Lee, Jong-Hwan, additional, Min, Jeong Jin, additional, Choi, Jin-ho, additional, Gwon, Hyeon-Cheol, additional, Carriere, Keumhee, additional, Ahn, Joonghyun, additional, and Kim, Wook Sung, additional

Published
2021
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37. Ischemic Infarcion Model by Middle Cerebral Artery Occlusion using Allogenic Blood Clot in Beagle Dogs

Author

Choi SooYoung, Lee， Young-Won, Kim YoungHwan, Lee KiJa, Han WooSok, and Choi HoJung

Subjects
medicine.medical_specialty, General Veterinary, medicine.diagnostic_test, business.industry, Infarction, Magnetic resonance imaging, medicine.disease, Beagle, Brain infarction, Internal medicine, Anesthesia, Parenchyma, medicine, Cardiology, Histopathology, Middle cerebral artery occlusion, business, Stroke
Published
2016

41. An error-controlled detection method for PR-IV magnetic recording systems

Author

Kim, Younghwan, You, Cheolwoo, Ong, Sunghwan, Bang, Keukjoon, and Hong, Daesik

Subjects
Detector circuits (Telecommunications) -- Design and construction, Magnetic recorders and recording -- Equipment and supplies, Communications circuits -- Models, Business, Electronics, Electronics and electrical industries
Abstract

The major advantage of PR-IV channel modeling on high-density magnetic recording systems is that the maximum-likelihood sequence detector (MLSD) with optimal performance can be used. However, the MLSD has a complex structure and a high cost. Another detection method is the three-level detector (TLD). Its structure is simpler than the MLSD's, but its performance is extremely poor. Sometimes it is necessary to use a detection method that has a simpler structure than the MLSD, yet performs competitively. In this paper, a new detection scheme called an error-controlled detection (ECD), is proposed for PR-IV systems. Its hardware complexity is greatly reduced and the performance is competitive with the MLSD.

Published
1997

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