SCOPUS 정보 검색 플랫폼

Physical Review B - Condensed Matter and Materials Physics

Volumn 66, Issue 14, 2002, Pages 1442011-14420116

Hidden degree of freedom and critical phase in a two-dimensional electron gas in the presence of a random magnetic field

(1) Nguyen, Hoang K a

a UNIVERSITY OF CALIFORNIA (United States)

Author keywords

[No Author keywords available]

Indexed keywords

ARTICLE; CYCLOTRON; ELECTRIC CONDUCTIVITY; ELECTRON TRANSPORT; GAS; MAGNETIC FIELD; MATHEMATICAL ANALYSIS; MOLECULAR DYNAMICS; MOLECULAR INTERACTION; MOLECULAR MODEL; PHASE TRANSITION; QUANTUM THEORY; RADIATION SCATTERING; VORTEX MOTION;

EID: 0036812647 PISSN: 01631829 EISSN: None Source Type: Journal
DOI: 10.1103/PhysRevB.66.144201 Document Type: Article

Times cited : (9)

References (64)

1
- 0001229786
- P.A. Lee and D.S. Fisher, Phys. Rev. Lett. 47, 882 (1981).
- (1981) Phys. Rev. Lett. , vol.47 , pp. 882
- Lee, P.A.¹ Fisher, D.S.²

2
- 0001453456
- L.B. Ioffe and A.I. Larkin, Phys. Rev. B 39, 8988 (1989); N. Nagaosa and P.A. Lee, Phys. Rev. Lett. 64, 2450 (1990); Phys. Rev. B 45, 966 (1992).
- (1989) Phys. Rev. B , vol.39 , pp. 8988
- Ioffe, L.B.¹ Larkin, A.I.²

3
- 0347940353
- L.B. Ioffe and A.I. Larkin, Phys. Rev. B 39, 8988 (1989); N. Nagaosa and P.A. Lee, Phys. Rev. Lett. 64, 2450 (1990); Phys. Rev. B 45, 966 (1992).
- (1990) Phys. Rev. Lett. , vol.64 , pp. 2450
- Nagaosa, N.¹ Lee, P.A.²

4
- 12344294966
- L.B. Ioffe and A.I. Larkin, Phys. Rev. B 39, 8988 (1989); N. Nagaosa and P.A. Lee, Phys. Rev. Lett. 64, 2450 (1990); Phys. Rev. B 45, 966 (1992).
- (1992) Phys. Rev. B , vol.45 , pp. 966

5
- 0000215807
- V. Kalmeyer and S.C. Zhang, Phys. Rev. B 46, 9889 (1992); B.I. Halperin, P.A. Lee, and N. Read, ibid. 47, 7312 (1993).
- (1992) Phys. Rev. B , vol.46 , pp. 9889
- Kalmeyer, V.¹ Zhang, S.C.²

6
- 0001561066
- V. Kalmeyer and S.C. Zhang, Phys. Rev. B 46, 9889 (1992); B.I. Halperin, P.A. Lee, and N. Read, ibid. 47, 7312 (1993).
- (1993) Phys. Rev. B , vol.47 , pp. 7312
- Halperin, B.I.¹ Lee, P.A.² Read, N.³

7
- 26144433204
- E. Abrahams, P.W. Anderson, D.C. Licciardello, and T.V. Ramakrishnan, Phys. Rev. Lett. 42, 673 (1979).
- (1979) Phys. Rev. Lett. , vol.42 , pp. 673
- Abrahams, E.¹ Anderson, P.W.² Licciardello, D.C.³ Ramakrishnan, T.V.⁴

8
- 33847755141
- S. Hikami, Phys. Rev. B 24, 2671 (1981).
- (1981) Phys. Rev. B , vol.24 , pp. 2671
- Hikami, S.¹

9
- 0000540334
- H. Levine, S.B. Libby, and A.M.M. Pruisken, Phys. Rev. Lett. 51, 1915 (1983).
- (1983) Phys. Rev. Lett. , vol.51 , pp. 1915
- Levine, H.¹ Libby, S.B.² Pruisken, A.M.M.³

10
- 0001337043
- C. Pryor and A. Zee, Phys. Rev. B 46, 3116 (1992).
- (1992) Phys. Rev. B , vol.46 , pp. 3116
- Pryor, C.¹ Zee, A.²

11
- 3343010090
- B.L. Altshuler and L.B. Ioffe, Phys. Rev. Lett. 69, 2979 (1992); D.V. Khveshchenko and S.V. Meshkov, Phys. Rev. B 47, 12 051 (1993); G. Gavazzi, J.M. Wheatley, and A.J. Schofield, ibid. 47, 15 170 (1993).
- (1992) Phys. Rev. Lett. , vol.69 , pp. 2979
- Altshuler, B.L.¹ Ioffe, L.B.²

12
- 0001739719
- B.L. Altshuler and L.B. Ioffe, Phys. Rev. Lett. 69, 2979 (1992); D.V. Khveshchenko and S.V. Meshkov, Phys. Rev. B 47, 12 051 (1993); G. Gavazzi, J.M. Wheatley, and A.J. Schofield, ibid. 47, 15 170 (1993).
- (1993) Phys. Rev. B , vol.47 , pp. 12051
- Khveshchenko, D.V.¹ Meshkov, S.V.²

13
- 0000936954
- B.L. Altshuler and L.B. Ioffe, Phys. Rev. Lett. 69, 2979 (1992); D.V. Khveshchenko and S.V. Meshkov, Phys. Rev. B 47, 12 051 (1993); G. Gavazzi, J.M. Wheatley, and A.J. Schofield, ibid. 47, 15 170 (1993).
- (1993) Phys. Rev. B , vol.47 , pp. 15170
- Gavazzi, G.¹ Wheatley, J.M.² Schofield, A.J.³

14
- 0000882740
- Y. Avishai, Y. Hatsugai, and M. Kohmoto, Phys. Rev. B 47, 9561 (1993); T. Kawarabayashi and T. Ohtsuki, ibid. 51, 10 897 (1995); D.Z. Liu, X.C. Xie, S. Das Sarma, and S.C. Zhang, ibid. 52, 5858 (1995).
- (1993) Phys. Rev. B , vol.47 , pp. 9561
- Avishai, Y.¹ Hatsugai, Y.² Kohmoto, M.³

15
- 0001214498
- Y. Avishai, Y. Hatsugai, and M. Kohmoto, Phys. Rev. B 47, 9561 (1993); T. Kawarabayashi and T. Ohtsuki, ibid. 51, 10 897 (1995); D.Z. Liu, X.C. Xie, S. Das Sarma, and S.C. Zhang, ibid. 52, 5858 (1995).
- (1995) Phys. Rev. B , vol.51 , pp. 10897
- Kawarabayashi, T.¹ Ohtsuki, T.²

16
- 0000886680
- Y. Avishai, Y. Hatsugai, and M. Kohmoto, Phys. Rev. B 47, 9561 (1993); T. Kawarabayashi and T. Ohtsuki, ibid. 51, 10 897 (1995); D.Z. Liu, X.C. Xie, S. Das Sarma, and S.C. Zhang, ibid. 52, 5858 (1995).
- (1995) Phys. Rev. B , vol.52 , pp. 5858
- Liu, D.Z.¹ Xie, X.C.² Das Sarma, S.³ Zhang, S.C.⁴

17
- 0000988587
- V. Kalmeyer, D. Wei, D.P. Arovas, and S. Zhang, Phys. Rev. B 48, 11 095 (1993).
- (1993) Phys. Rev. B , vol.48 , pp. 11095
- Kalmeyer, V.¹ Wei, D.² Arovas, D.P.³ Zhang, S.⁴

18
- 3342946423
- S.C. Zhang and D.P. Arovas, Phys. Rev. Lett. 72, 1886 (1994).
- (1994) Phys. Rev. Lett. , vol.72 , pp. 1886
- Zhang, S.C.¹ Arovas, D.P.²

19
- 4243481793
- D.N. Sheng and Z.Y. Weng, Phys. Rev. Lett. 75, 2388 (1995); K. Yang and R.N. Bhatt, Phys. Rev. B 55, R1922 (1997).
- (1995) Phys. Rev. Lett. , vol.75 , pp. 2388
- Sheng, D.N.¹ Weng, Z.Y.²

20
- 0000337381
- D.N. Sheng and Z.Y. Weng, Phys. Rev. Lett. 75, 2388 (1995); K. Yang and R.N. Bhatt, Phys. Rev. B 55, R1922 (1997).
- (1997) Phys. Rev. B , vol.55
- Yang, K.¹ Bhatt, R.N.²

21
- 3843134772
- X.C. Xie, X.R. Wang, and D.Z. Liu, Phys. Rev. Lett. 80, 3563 (1998).
- (1998) Phys. Rev. Lett. , vol.80 , pp. 3563
- Xie, X.C.¹ Wang, X.R.² Liu, D.Z.³

22
- 0034636606
- D.N. Sheng and Z.Y. Weng, Europhys. Lett. 50, 776 (2000).
- (2000) Europhys. Lett. , vol.50 , pp. 776
- Sheng, D.N.¹ Weng, Z.Y.²

23
- 0034226096
- D. Taras-Semchuk and K.B. Efetov, Phys. Rev. Lett. 85, 1060 (2000); Phys. Rev. B 64, 115301 (2001).
- (2000) Phys. Rev. Lett. , vol.85 , pp. 1060
- Taras-Semchuk, D.¹ Efetov, K.B.²

24
- 0035884112
- D. Taras-Semchuk and K.B. Efetov, Phys. Rev. Lett. 85, 1060 (2000); Phys. Rev. B 64, 115301 (2001).
- (2001) Phys. Rev. B , vol.64 , pp. 115301

25
- 0000004553
- T. Sugiyama and N. Nagaosa, Phys. Rev. Lett. 70, 1980 (1993).
- (1993) Phys. Rev. Lett. , vol.70 , pp. 1980
- Sugiyama, T.¹ Nagaosa, N.²

26
- 0000656758
- A.G. Aronov, A.D. Mirlin, and P. Wölfle, Phys. Rev. B 49, 16 609 (1994).
- (1994) Phys. Rev. B , vol.49 , pp. 16609
- Aronov, A.G.¹ Mirlin, A.D.² Wölfle, P.³

27
- 0001028396
- D.K.K. Lee and J.T. Chalker, Phys. Rev. Lett. 72, 1510 (1994); D.K.K. Lee, J.T. Chalker, and D.Y.K. Ko, Phys. Rev. B 50, 5272 (1994).
- (1994) Phys. Rev. Lett. , vol.72 , pp. 1510
- Lee, D.K.K.¹ Chalker, J.T.²

28
- 0001218753
- D.K.K. Lee and J.T. Chalker, Phys. Rev. Lett. 72, 1510 (1994); D.K.K. Lee, J.T. Chalker, and D.Y.K. Ko, Phys. Rev. B 50, 5272 (1994).
- (1994) Phys. Rev. B , vol.50 , pp. 5272
- Lee, D.K.K.¹ Chalker, J.T.² Ko, D.Y.K.³

29
- 0000472685
- Y.B. Kim, A. Furusaki, and D.K.K. Lee, Phys. Rev. B 52, 16 646 (1995).
- (1995) Phys. Rev. B , vol.52 , pp. 16646
- Kim, Y.B.¹ Furusaki, A.² Lee, D.K.K.³

30
- 0001729260
- K. Yakubo and Y. Goto, Phys. Rev. B 54, 13 432 (1996); J.A. Vergés, ibid. 57, 870 (1998); M. Batcsh, L. Schweitzer, and B. Kramer, Physica B 249, 792 (1998); H. Potempa and L. Schweitzer, Ann. Phys. (Leipzig) 8, SI-209 (1999); A. Furusaki, Phys. Rev. Lett. 82, 604 (1999).
- (1996) Phys. Rev. B , vol.54 , pp. 13432
- Yakubo, K.¹ Goto, Y.²

31
- 0000703865
- K. Yakubo and Y. Goto, Phys. Rev. B 54, 13 432 (1996); J.A. Vergés, ibid. 57, 870 (1998); M. Batcsh, L. Schweitzer, and B. Kramer, Physica B 249, 792 (1998); H. Potempa and L. Schweitzer, Ann. Phys. (Leipzig) 8, SI-209 (1999); A. Furusaki, Phys. Rev. Lett. 82, 604 (1999).
- (1998) Phys. Rev. B , vol.57 , pp. 870
- Vergés, J.A.¹

32
- 33744690809
- K. Yakubo and Y. Goto, Phys. Rev. B 54, 13 432 (1996); J.A. Vergés, ibid. 57, 870 (1998); M. Batcsh, L. Schweitzer, and B. Kramer, Physica B 249, 792 (1998); H. Potempa and L. Schweitzer, Ann. Phys. (Leipzig) 8, SI-209 (1999); A. Furusaki, Phys. Rev. Lett. 82, 604 (1999).
- (1998) Physica B , vol.249 , pp. 792
- Batcsh, M.¹ Schweitzer, L.² Kramer, B.³

33
- 4243778672
- K. Yakubo and Y. Goto, Phys. Rev. B 54, 13 432 (1996); J.A. Vergés, ibid. 57, 870 (1998); M. Batcsh, L. Schweitzer, and B. Kramer, Physica B 249, 792 (1998); H. Potempa and L. Schweitzer, Ann. Phys. (Leipzig) 8, SI-209 (1999); A. Furusaki, Phys. Rev. Lett. 82, 604 (1999).
- (1999) Ann. Phys. (Leipzig) , vol.8
- Potempa, H.¹ Schweitzer, L.²

34
- 0001574666
- K. Yakubo and Y. Goto, Phys. Rev. B 54, 13 432 (1996); J.A. Vergés, ibid. 57, 870 (1998); M. Batcsh, L. Schweitzer, and B. Kramer, Physica B 249, 792 (1998); H. Potempa and L. Schweitzer, Ann. Phys. (Leipzig) 8, SI-209 (1999); A. Furusaki, Phys. Rev. Lett. 82, 604 (1999).
- (1999) Phys. Rev. Lett. , vol.82 , pp. 604
- Furusaki, A.¹

35
- 0035896793
- A.D. Mirlin and P. Woelfle, Phys. Rev. Lett. 86, 3688 (2001); I.V. Gornyi, A.D. Mirlin, and P. Wölfle, Phys. Rev. B 64, 115403 (2001).
- (2001) Phys. Rev. Lett. , vol.86 , pp. 3688
- Mirlin, A.D.¹ Woelfle, P.²

36
- 0035884525
- A.D. Mirlin and P. Woelfle, Phys. Rev. Lett. 86, 3688 (2001); I.V. Gornyi, A.D. Mirlin, and P. Wölfle, Phys. Rev. B 64, 115403 (2001).
- (2001) Phys. Rev. B , vol.64 , pp. 115403
- Gornyi, I.V.¹ Mirlin, A.D.² Wölfle, P.³

37
- 4243643447
- J. Miller and J. Wang, Phys. Rev. Lett. 76, 1461 (1996); Y. Hatsugai, X.-G. Wen, and M. Kohmoto, Phys. Rev. B 56, 1061 (1997); Y. Morita and Y. Hatsugai, Phys. Rev. Lett. 79, 3728 (1998); Phys. Rev. B 58, 6680 (1998); P.W. Brouwer, C. Mudry, B.D. Simons, and A. Altland, Phys. Rev. Lett. 81, 862 (1998).
- (1996) Phys. Rev. Lett. , vol.76 , pp. 1461
- Miller, J.¹ Wang, J.²

38
- 0000487496
- J. Miller and J. Wang, Phys. Rev. Lett. 76, 1461 (1996); Y. Hatsugai, X.-G. Wen, and M. Kohmoto, Phys. Rev. B 56, 1061 (1997); Y. Morita and Y. Hatsugai, Phys. Rev. Lett. 79, 3728 (1998); Phys. Rev. B 58, 6680 (1998); P.W. Brouwer, C. Mudry, B.D. Simons, and A. Altland, Phys. Rev. Lett. 81, 862 (1998).
- (1997) Phys. Rev. B , vol.56 , pp. 1061
- Hatsugai, Y.¹ Wen, X.-G.² Kohmoto, M.³

39
- 4243832500
- J. Miller and J. Wang, Phys. Rev. Lett. 76, 1461 (1996); Y. Hatsugai, X.-G. Wen, and M. Kohmoto, Phys. Rev. B 56, 1061 (1997); Y. Morita and Y. Hatsugai, Phys. Rev. Lett. 79, 3728 (1998); Phys. Rev. B 58, 6680 (1998); P.W. Brouwer, C. Mudry, B.D. Simons, and A. Altland, Phys. Rev. Lett. 81, 862 (1998).
- (1998) Phys. Rev. Lett. , vol.79 , pp. 3728
- Morita, Y.¹ Hatsugai, Y.²

40
- 0000513009
- J. Miller and J. Wang, Phys. Rev. Lett. 76, 1461 (1996); Y. Hatsugai, X.-G. Wen, and M. Kohmoto, Phys. Rev. B 56, 1061 (1997); Y. Morita and Y. Hatsugai, Phys. Rev. Lett. 79, 3728 (1998); Phys. Rev. B 58, 6680 (1998); P.W. Brouwer, C. Mudry, B.D. Simons, and A. Altland, Phys. Rev. Lett. 81, 862 (1998).
- (1998) Phys. Rev. B , vol.58 , pp. 6680

41
- 0002972775
- J. Miller and J. Wang, Phys. Rev. Lett. 76, 1461 (1996); Y. Hatsugai, X.-G. Wen, and M. Kohmoto, Phys. Rev. B 56, 1061 (1997); Y. Morita and Y. Hatsugai, Phys. Rev. Lett. 79, 3728 (1998); Phys. Rev. B 58, 6680 (1998); P.W. Brouwer, C. Mudry, B.D. Simons, and A. Altland, Phys. Rev. Lett. 81, 862 (1998).
- (1998) Phys. Rev. Lett. , vol.81 , pp. 862
- Brouwer, P.W.¹ Mudry, C.² Simons, B.D.³ Altland, A.⁴

42
- 0000176164
- A. MacKinnon and B. Kramer, Phys. Rev. Lett. 47, 1546 (1981); Z. Phys. B: Condens. Matter 53, 1 (1983).
- (1981) Phys. Rev. Lett. , vol.47 , pp. 1546
- MacKinnon, A.¹ Kramer, B.²

43
- 0000176164
- A. MacKinnon and B. Kramer, Phys. Rev. Lett. 47, 1546 (1981); Z. Phys. B: Condens. Matter 53, 1 (1983).
- (1983) Z. Phys. B: Condens. Matter , vol.53 , pp. 1

44
- 0000401687
- N. Schultka and E. Manousakis, Phys. Rev. B 49, 12 071 (1994).
- (1994) Phys. Rev. B , vol.49 , pp. 12071
- Schultka, N.¹ Manousakis, E.²

45
- 0003517281
- Cambridge University Press, Cambridge, England
- P.M. Chaikin and T.C. Lubensky, Principles of Condensed Matter Physics (Cambridge University Press, Cambridge, England, 1997).
- (1997) Principles of Condensed Matter Physics
- Chaikin, P.M.¹ Lubensky, T.C.²

46
- 4243971222
- D.S. Fisher and P.A. Lee, Phys. Rev. B 23, 6851 (1981).
- (1981) Phys. Rev. B , vol.23 , pp. 6851
- Fisher, D.S.¹ Lee, P.A.²

47
- 0000382546
- S. Yoshino and M. Okazaki, J. Phys. Soc. Jpn. 43, 415 (1977).
- (1977) J. Phys. Soc. Jpn. , vol.43 , pp. 415
- Yoshino, S.¹ Okazaki, M.²

48
- 0012861668
- J.T. Chalker and P.D. Coddington, J. Phys. C 21, 2665 (1988).
- (1988) J. Phys. C , vol.21 , pp. 2665
- Chalker, J.T.¹ Coddington, P.D.²

49
- 0001416680
- H.W. Jiang, H.L. Stormer, D.C. Tsui, L.N. Pfeiffer, and K.W. West, Phys. Rev. B 40, 12 013 (1989); R.L. Willett, M.A. Paalanen, R.R. Ruel, K.W. West, L.N. Pfeiffer, and D.J. Bishop, Phys. Rev. Lett. 65, 112 (1990).
- (1989) Phys. Rev. B , vol.40 , pp. 12013
- Jiang, H.W.¹ Stormer, H.L.² Tsui, D.C.³ Pfeiffer, L.N.⁴ West, K.W.⁵

50
- 3342910006
- H.W. Jiang, H.L. Stormer, D.C. Tsui, L.N. Pfeiffer, and K.W. West, Phys. Rev. B 40, 12 013 (1989); R.L. Willett, M.A. Paalanen, R.R. Ruel, K.W. West, L.N. Pfeiffer, and D.J. Bishop, Phys. Rev. Lett. 65, 112 (1990).
- (1990) Phys. Rev. Lett. , vol.65 , pp. 112
- Willett, R.L.¹ Paalanen, M.A.² Ruel, R.R.³ West, K.W.⁴ Pfeiffer, L.N.⁵ Bishop, D.J.⁶

51
- 0039423952
- J.E. Müller, Phys. Rev. Lett. 68, 385 (1992).
- (1992) Phys. Rev. Lett. , vol.68 , pp. 385
- Müller, J.E.¹

52
- 0001303317
- D.B. Chklovskii and P.A. Lee, Phys. Rev. B 48, 18 060 (1993).
- (1993) Phys. Rev. B , vol.48 , pp. 18060
- Chklovskii, D.B.¹ Lee, P.A.²

53
- 0000170570
- R.E. Prange and R. Joynt, Phys. Rev. B 25, 2943 (1982).
- (1982) Phys. Rev. B , vol.25 , pp. 2943
- Prange, R.E.¹ Joynt, R.²

54
- 0002060250
- P.A.M. Dirac, Proc. R. Soc. London, Ser. A 133, 60 (1931).
- (1931) Proc. R. Soc. London, Ser. A , vol.133 , pp. 60
- Dirac, P.A.M.¹

55
- 3543050845
- J.S. Langer and T. Neal, Phys. Rev. Lett. 16, 984 (1966).
- (1966) Phys. Rev. Lett. , vol.16 , pp. 984
- Langer, J.S.¹ Neal, T.²

56
- 0000184388
- H. Wu and D.W.L. Sprung, Phys. Lett. A 183, 413 (1993).
- (1993) Phys. Lett. A , vol.183 , pp. 413
- Wu, H.¹ Sprung, D.W.L.²

57
- 0008135999
- J.T. Edwards and D.J. Thouless, J. Phys. C 5, 807 (1972).
- (1972) J. Phys. C , vol.5 , pp. 807
- Edwards, J.T.¹ Thouless, D.J.²

58
- 0000415007
- D.-H. Lee, Z. Wang, and S. Kivelson, Phys. Rev. Lett. 70, 4130 (1993).
- (1993) Phys. Rev. Lett. , vol.70 , pp. 4130
- Lee, D.-H.¹ Wang, Z.² Kivelson, S.³

59
- 0000145843
- V. Kagalovsky, B. Horovitz, and Y. Avishai, Phys. Rev. B 55, 7761 (1997).
- (1997) Phys. Rev. B , vol.55 , pp. 7761
- Kagalovsky, V.¹ Horovitz, B.² Avishai, Y.³

60
- 4243790193
- Z. Wang, D.-H. Lee, and X.-G. Wen, Phys. Rev. Lett. 72, 2454 (1994).
- (1994) Phys. Rev. Lett. , vol.72 , pp. 2454
- Wang, Z.¹ Lee, D.-H.² Wen, X.-G.³

61
- 33744683643
- unpublished
- H.K. Nguyen (unpublished).
- Nguyen, H.K.¹

62
- 0035535326
- and references cited therein
- E. Abrahams, S.V. Kravchenko, and M.P. Sarachik, Rev. Mod. Phys. 73, 251 (2001), and references cited therein.
- (2001) Rev. Mod. Phys. , vol.73 , pp. 251
- Abrahams, E.¹ Kravchenko, S.V.² Sarachik, M.P.³

63
- 0034900625
- A. Kapitulnik, N. Mason, S.A. Kivelson, and S. Chakravarty, Phys. Rev. B 63, 125322 (2001); K. Voelker and S. Chakravarty, ibid. 64, 235125 (2001).
- (2001) Phys. Rev. B , vol.63 , pp. 125322
- Kapitulnik, A.¹ Mason, N.² Kivelson, S.A.³ Chakravarty, S.⁴

64
- 0035893985
- A. Kapitulnik, N. Mason, S.A. Kivelson, and S. Chakravarty, Phys. Rev. B 63, 125322 (2001); K. Voelker and S. Chakravarty, ibid. 64, 235125 (2001).
- (2001) Phys. Rev. B , vol.64 , pp. 235125
- Voelker, K.¹ Chakravarty, S.²

* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.