- Some recent results on links, 3-manifolds, Whitney towers and amenable Cheeger-Gromov invariants, Tokyo workshop on low dimensional topology, March 20, 2012, Tokyo Institute of Technology, Tokyo, Japan.
- Hidden torsion in 3-manifold groups and homology cobordism, The 8th East Asian School of Knots and Related Topics, January 11, 2012, Daejeon, Korea.
- An introduction to $L^2$-invariants I, II, III, The 8th East Asian School of Knots and Related Topics, January 9-11, 2012, Daejeon, Korea.
- Invariants of cobordism of knots and 3-manifolds, Invited talk at 2011 Fall Meeting of Mathematical Society of Japan, September 28, 2011, Shinshu University, Matsumoto City, Nagano, Japan.

- Whitney towers, knot concordance, and amenable L2-theoretic methods, International Conference in Memory of Hyo Chul Myung, April 27, 2011, Seoul, Korea.
- Homology localization of groups, injectivity theorems, and amenable L2-homological methods, The 1st Euro-Korean Conference on Groups and Related Topics, March 30, 2011, Pohang, Korea.
- Knots in dimension 3 and topology of dimension 4, Math Colloquium, KAIST, March 24, 2011, Daejeon, Korea.
- Applications of covering link calculus, Topology Seminar, Indiana University, February 09, 2011, Bloomington, Indiana, USA.
- Signatures of manifolds and knots, 2011 Winter Workshop for Young Mathematicians in Korea, January 28, 2011, Pohang, Korea.
- Whitney towers and Amenable L2-techniques, The 7th East Asian School of Knots and Related Topics, Hiroshima University, January 13, 2011, Hiroshima, Japan.
- Amenable L2-theoretic methods for knots and 3-manifolds, Topology Seminar, Seoul National University, October 21, 2010, Seoul, Korea.
- L2-signatures: twisted invariants from duality, RIMS Seminar, Twisted topological invariants and topology of low-dimensional manifolds, September 17, 2010, Akita, Japan.
- Why is the twisted Alexander polynomial related to fiberability? RIMS Seminar, Twisted topological invariants and topology of low-dimensional manifolds, September 15, 2010, Akita, Japan.
- L2-signatures and homology cobordism of 3-manifolds, Lecture series on L2-invariants of knots and manifolds, August 11-13, 2010, KIAS, Seoul, Korea.
- Homological L2-invariants of knots and manifolds I, II, III, Lecture series on L2-invariants of knots and manifolds, August 11-13, 2010, KIAS, Seoul, Korea.
- Amenable L2-theoretic methods and applications to knots and 3-manifolds, The 2nd TAPU-KOOK Joint Seminar, July 30, 2010, Kyungpook National University, Daegu, Korea.
- Introduction to L2-invariants, Knot Concordance and Homology Cobordism Workshop, July 23, 2010, Wesleyan University, Middletown, Connecticut, USA.
- Amenable L2-theoretic methods and applications, Knot Concordance and Homology Cobordism Workshop, July 22, 2010, Wesleyan University, Middletown, Connecticut, USA.
- Homology and L2-signatures from amenable groups, The 6th East Asian School of Knots and Related Topics, January 27, 2010, Chern Institute of Mathematics, Tianjin, China.
- L2-signature defects and amenable groups, Special Session on Knot Theory and Related Topics, Joint Meeting of the Korean Mathematical Society and the American Mathematical Society, December 18, 2009, Seoul, Korea.
- L2-signatures, homology, and amenable groups, International Conference on Symplectic, Contact and Low Dimensional Topology, November 12, 2009, Seoul, Korea.
- Links in dimension 3 and their deformation in dimension 4, Chonbuk National University, September 24, 2009, Jeonju, Korea.
- Torsion in link concordance and Hirzebruch-type invariants from iterated p-covers, Canadian Mathematical Society Summer Meeting, June 7, 2009, St. John’s, Newfoundland, Canada.
- Links and intersection form defects, Mathematical Colloquium, Seoul National University, May 14, 2009, Seoul, Korea.
- The structure of the rational concordance group of knots, Excellent Research Paper Award Lecture, 2009 Spring Meeting of the Korean Mathematical Society, April 25, 2009, Suwon, Korea.
- Links in 3-space and their deformation in 4-space, Mathematical Colloquium, Yonsei University, April 9, 2009, Seoul, Korea.
- Local derived series, L2-signatures, and applications to manifolds, The 5th East Asian School of Knots and Related Topics, January 13, 2009, Gyeongju, Korea.
- Using Artin reciprocity in knot theory, Kyushu-POSTECH joint workshop on number theory and related topics, January 6, 2009, Pohang, Korea.
- Deformation of links in dimension 4, Mathematical Colloquium, Chungang University, November 21, 2008, Seoul, Korea.
- 4-dimensional deformation of links in the 3-space, Mathematical Colloquium, Sogang University, October 9, 2008, Seoul, Korea.
- Slicing and non-slicing iterated Bing doubles, Topology-Geometry Seminar, Indiana University, August 26, 2008, Bloomington, Indiana, USA.
- Link concordance, homology cobordism, and iterated p-covers, Fifty years since Fox and Milnor: a conference on knot concordance in honor of the memory of Jerry Levine, Brandeis University, June 3, 2008, Waltham, Massachusetts, USA.
- Link concordance and Hirzebruch-type invariants from iterated covers, Pusan Nation University, April 18, 2008, Pusan, Korea.
- Slicing iterated Bing doubles, a plenary talk at The 4th East Asian School of Knots and Related Topics, January 21, 2008, Tokyo, Japan.
- Non-slice iterated Bing doubles, Topology Seminar, UC Berkeley, November 14, 2007, Berkeley, California, USA.
- Homology, injectivity theorems, and algebraic closures with coefficients, East Asian Conference of Algebraic Topology, November 3, 2007, Seoul, Korea.
- New Hirzebruch-type invariants from iterated p-covers, The 7th KAIST Geometric Topology Fair, July 9, 2007, Gyeongju, Korea.
- An elementary tutorial on provable security, KIAS-KMS Summer workshop on Cryptography, June 29, 2007, Seoul, Korea.
- Invariants of homology cobordism and link concordance from towers of itrated abelian p-covers, Geometric Topology Conference, Peking University, June 19, 2007, Beijing, China.
- The structure of the rational knot concordance group, Department of Mathematics, POSTECH, May 23, 2007, Pohang, Korea.
- Introduction to Geometric Topology and Knot Theory, Departmental Colloquium, Department of Mathematics, Konkuk University, April 13, 2007, Seoul, Korea.
- Hirzebruch-Atiyah-Singer type invariants of manifolds and applications to knot theory, Department of Mathematics, Ewha Womans University, March 30, 2007, Seoul, Korea.
- Witt class defect invariants, homology cobordism, and link concordance, a talk at The Third East Asian School of Knots and Related Topics in Geometric Topology, February 6, 2007, Osaka, Japan.
- Classifications of manifold embeddings, Mathematical Colloquium, Korea Institute for Advanced Study, November 22, Seoul, Korea.
- Invariants from Atiyah-type theorems and applications to links, an invited talk at 2006 Geometry & Topology Day at Konkuk University, November 18, 2006, Seoul, Korea.
- Homology equivalences, injectivity theorems, and algebraic closures of groups, an invited talk at NIMS Workshop on Geometry and Topology, November 16, 2006, Daejeon, Korea.
- The structure of the concordance group of knots in rational homology spheres, an invited talk at 2005 fall meeting of the Korean Mathematical Society, 21 October, 2005, Seoul, Korea.
- Algebraic closures with coefficients and torsion-free derived series, a plenary talk at The Second East Asian School of Knots and Related Topics in Geometric Topology, August 4, 2005, Dalian, China.
- Algebraic closures with coefficients and applications to homology cobordism, January 31, 2005, Department of Mathematics, Rice University, Houston, Texas, U.S.A.
- Homology equivalences and algebraic closures, January 24, 2005, Department of Mathematics, Indiana University, Bloomington, Indiana, U.S.A.
- Classification of knots from the viewpoint of manifold theory, November 25, 2004, Department of Mathematics, Konkuk University, Seoul, Korea.
- Classification of knots from the viewpoint of manifold theory, November 4, 2004, Department of Mathematics, Ewha Womans University, Seoul, Korea.
- Torsion-free derived series, algebraic closures, and link concordance, The First KAIST Geometric Topology Fair, August 25, 2004, Chungju, Korea.
- Randomized computation and provable security I, II, Korea Institute for Advanced Study, August 6-7, 2004, Seoul, Korea.
- Rational homology concordance of knots, BIRS Workshop on Knots and Their Manifold Stories, May 11, 2004, Banff, Alberta, Canada.
- Provable security of ID-based cryptosystems, National Security Research Institute, March 11, 2004, Daejeon, Korea.
- Concordance of knots in rational homology spheres, The First East Asian School of Knots, Links, and Related Topics, February 17, 2004, Seoul, Korea.
- Localization, surgery and placement problems of manifolds, Departmental Colloquium, Department of Mathematics, Korea Advanced Institute of Science and Technology, December 4, 2003, Daejeon, Korea.
- Concordance and rational knots, Korea Advanced Institute of Science and Technology, March 27-28, 2003, Daejeon, Korea.
- The structure of the rational knot concordance group, AMS special session, March 14, 2003, Baton Rouge, Louisiana, U.S.A.
- The effect of mutation on link concordance, 3-manifolds, and the Milnor invariants, AMS special session, January 17, 2003, Baltimore, Maryland, U.S.A.
- Concordance and rational knots, Knots in Washington XV, January 10, 2003, Washington, DC, U.S.A.
- Computation of rational knot concordance, October 8, 2002, Brandeis University, Waltham, Massachusetts, U.S.A.
- A survey on link concordance, January 15, 2002, Nara Women’s University, Nara, Japan.
- Implementations of braid cryptosystems, An invited tutorial in International Workshop on Practice and Theory in Public Key Cryptography, February 13, 2001, Cheju, Korea
- Link concordance theory in rational homology spheres and its application to concordance of homology boundary links, KNOTS 2000, August 2, 2000, YoungPyong, Kangwon, Korea.