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Volumn 41, Issue SUPPL.1, 2012, Pages 2527-2534

Motor variability - An important issue in occupational life

Author keywords

exposure variability; kinematics; motor variability; occupational health; performance; Work related musculo skeletal disorders

Indexed keywords

BIOMECHANICS; BODY POSTURE; CUMULATIVE TRAUMA DISORDERS; HUMAN; MOVEMENT (PHYSIOLOGY); MUSCLE FATIGUE; MUSCULOSKELETAL PAIN; OCCUPATIONAL DISEASES; OCCUPATIONAL HEALTH; ORGANIZATION AND MANAGEMENT; PRODUCTIVITY; WORKPLACE;

EID: 84859880535     PISSN: 10519815     EISSN: None     Source Type: Journal    
DOI: 10.3233/WOR-2012-0493-2527     Document Type: Conference Paper
Times cited : (12)

References (52)
  • 1
    • 84859817646 scopus 로고    scopus 로고
    • Arbetsorsakade besvär 2010: www.av.se/statistik/officiellt/ arbetsorsakade-besvar-2010.aspx
    • (2010) Arbetsorsakade Besvär
  • 2
    • 44349107782 scopus 로고    scopus 로고
    • Effect of physical fatigue on motor control at different skill levels
    • Aune, T. K., R. P. Ingvaldsen, et al. (2008). "Effect of physical fatigue on motor control at different skill levels." Percept Mot Skills 106(2): 371-86.
    • (2008) Percept Mot Skills , vol.106 , Issue.2 , pp. 371-386
    • Aune, T.K.1    Ingvaldsen, R.P.2
  • 3
    • 35848968469 scopus 로고    scopus 로고
    • Is movement variability important for sports biomechanists?
    • Bartlett, R., J. Wheat, et al. (2007). "Is movement variability important for sports biomechanists?" Sports Biomech 6(2): 224-43.
    • (2007) Sports Biomech , vol.6 , Issue.2 , pp. 224-243
    • Bartlett, R.1    Wheat, J.2
  • 4
    • 79551622173 scopus 로고    scopus 로고
    • The effect of work pace on workload, motor variability and fatigue during simulated light assembly work
    • Bosch, T., S. E. Mathiassen, et al. (2011). "The effect of work pace on workload, motor variability and fatigue during simulated light assembly work." Ergonomics 54(2): 154-168.
    • (2011) Ergonomics , vol.54 , Issue.2 , pp. 154-168
    • Bosch, T.1    Mathiassen, S.E.2
  • 5
    • 0000213967 scopus 로고    scopus 로고
    • Interacting intrinsic dynamics and intentionality requires coordination profiling of movement systems
    • Button, C. and K. Davids (1999). "Interacting intrinsic dynamics and intentionality requires coordination profiling of movement systems." Studies in Perception and Action V 5: 314-318.
    • (1999) Studies in Perception and Action , vol.5 , pp. 314-318
    • Button, C.1    Davids, K.2
  • 6
    • 24944448318 scopus 로고    scopus 로고
    • Managing variability in the summary and comparison of gait data
    • Chau, T., S. Young, et al. (2005). "Managing variability in the summary and comparison of gait data." J Neuroeng Rehabil 2: 22.
    • (2005) J Neuroeng Rehabil , vol.2 , pp. 22
    • Chau, T.1    Young, S.2
  • 7
    • 67649506229 scopus 로고    scopus 로고
    • Effects of fatigue on inter-cycle variability in cross-country skiing
    • Cignetti, F., F. Schena, et al. (2009). "Effects of fatigue on inter-cycle variability in cross-country skiing." Journal of Biomechanics 42(10): 1452-1459.
    • (2009) Journal of Biomechanics , vol.42 , Issue.10 , pp. 1452-1459
    • Cignetti, F.1    Schena, F.2
  • 8
    • 45549110256 scopus 로고    scopus 로고
    • Effects of fatigue on intermuscular coordination during repetitive hammering
    • Cote, J. N., A. G. Feldman, et al. (2008). "Effects of fatigue on intermuscular coordination during repetitive hammering." Motor Control 12(2): 79-92.
    • (2008) Motor Control , vol.12 , Issue.2 , pp. 79-92
    • Cote, J.N.1    Feldman, A.G.2
  • 9
    • 20144385995 scopus 로고    scopus 로고
    • Differences in multi-joint kinematic patterns of repetitive hammering in healthy, fatigued and shoulder-injured individuals
    • Cote, J. N., D. Raymond, et al. (2005). "Differences in multi-joint kinematic patterns of repetitive hammering in healthy, fatigued and shoulder-injured individuals." Clinical Biomechanics 20(6): 581-590.
    • (2005) Clinical Biomechanics , vol.20 , Issue.6 , pp. 581-590
    • Cote, J.N.1    Raymond, D.2
  • 10
    • 33646004308 scopus 로고    scopus 로고
    • Body-goal variability mapping in an aiming task
    • Cusumano, J. P. and P. Cesari (2006). "Body-goal variability mapping in an aiming task." Biol Cybern 94(5): 367-79.
    • (2006) Biol Cybern , vol.94 , Issue.5 , pp. 367-379
    • Cusumano, J.P.1    Cesari, P.2
  • 11
    • 0037255777 scopus 로고    scopus 로고
    • Movement systems as dynamical systems: The functional role of variability and its implications for sports medicine
    • Davids, K., P. Glazier, et al. (2003). "Movement systems as dynamical systems: the functional role of variability and its implications for sports medicine." Sports Med 33(4): 245-60.
    • (2003) Sports Med , vol.33 , Issue.4 , pp. 245-260
    • Davids, K.1    Glazier, P.2
  • 12
    • 77958533643 scopus 로고    scopus 로고
    • Influence of three principles of pacing on the temporal organisation of work during cyclic assembly and disassembly tasks
    • Dempsey, P. G., S. E. Mathiassen, et al. (2010). "Influence of three principles of pacing on the temporal organisation of work during cyclic assembly and disassembly tasks." Ergonomics 53(11): 1347-1358.
    • (2010) Ergonomics , vol.53 , Issue.11 , pp. 1347-1358
    • Dempsey, P.G.1    Mathiassen, S.E.2
  • 13
    • 29744461452 scopus 로고    scopus 로고
    • Kinematic variability and local dynamic stability of upper body motions when walking at different speeds
    • Dingwell, J. B. and L. C. Marin (2006). "Kinematic variability and local dynamic stability of upper body motions when walking at different speeds." Journal of Biomechanics 39(3): 444-452.
    • (2006) Journal of Biomechanics , vol.39 , Issue.3 , pp. 444-452
    • Dingwell, J.B.1    Marin, L.C.2
  • 14
    • 34548216774 scopus 로고    scopus 로고
    • Periodic increases in force during sustained contraction reduce fatigue and facilitate spatial redistribution of trapezius muscle activity
    • Falla, D. and D. Farina (2007). "Periodic increases in force during sustained contraction reduce fatigue and facilitate spatial redistribution of trapezius muscle activity." Experimental Brain Research 182(1): 99-107.
    • (2007) Experimental Brain Research , vol.182 , Issue.1 , pp. 99-107
    • Falla, D.1    Farina, D.2
  • 15
    • 37849000563 scopus 로고    scopus 로고
    • The change in spatial distribution of upper trapezius muscle activity is correlated to contraction duration
    • Farina, D., F. Leclerc, et al. (2008). "The change in spatial distribution of upper trapezius muscle activity is correlated to contraction duration." J Electromyogr Kinesiol 18(1): 16-25.
    • (2008) J Electromyogr Kinesiol , vol.18 , Issue.1 , pp. 16-25
    • Farina, D.1    Leclerc, F.2
  • 16
    • 0032555403 scopus 로고    scopus 로고
    • The effects of muscular fatigue on the coordination of a multijoint movement in human
    • Forestier, N. and V. Nougier (1998). "The effects of muscular fatigue on the coordination of a multijoint movement in human." Neuroscience Letters 252(3): 187-190.
    • (1998) Neuroscience Letters , vol.252 , Issue.3 , pp. 187-190
    • Forestier, N.1    Nougier, V.2
  • 17
    • 44349187559 scopus 로고    scopus 로고
    • The effects of neuromuscular fatigue on task performance during repetitive goal-directed movements
    • Gates, D. H. and J. B. Dingwell (2008). "The effects of neuromuscular fatigue on task performance during repetitive goal-directed movements." Exp Brain Res 187(4): 573-85.
    • (2008) Exp Brain Res , vol.187 , Issue.4 , pp. 573-585
    • Gates, D.H.1    Dingwell, J.B.2
  • 18
    • 0019595754 scopus 로고
    • Work load and fatigue in repetitive arm elevations
    • Hagberg, M. (1981). "Work load and fatigue in repetitive arm elevations." Ergonomics 24(7): 543-55.
    • (1981) Ergonomics , vol.24 , Issue.7 , pp. 543-555
    • Hagberg, M.1
  • 19
    • 0026570746 scopus 로고
    • Exposure variables in ergonomic epidemiology
    • Hagberg, M. (1992). "Exposure variables in ergonomic epidemiology." Am J Ind Med 21(1): 91-100.
    • (1992) Am J Ind Med , vol.21 , Issue.1 , pp. 91-100
    • Hagberg, M.1
  • 20
    • 0025435142 scopus 로고
    • Shoulder arm muscular-activity and reproducibility in carpenters work
    • Hammarskjold, E., K. Harmsringdahl, et al. (1990). "Shoulder Arm Muscular-Activity and Reproducibility in Carpenters Work." Clinical Biomechanics 5(2): 81-87.
    • (1990) Clinical Biomechanics , vol.5 , Issue.2 , pp. 81-87
    • Hammarskjold, E.1    Harmsringdahl, K.2
  • 21
    • 0026953964 scopus 로고
    • Electromyographic fatigue in neck/shoulder muscles and endurance in women with repetitive work
    • Hansson, G. A., U. Stromberg, et al. (1992). "Electromyographic fatigue in neck/shoulder muscles and endurance in women with repetitive work." Ergonomics 35(11): 1341-52.
    • (1992) Ergonomics , vol.35 , Issue.11 , pp. 1341-1352
    • Hansson, G.A.1    Stromberg, U.2
  • 22
    • 33645726542 scopus 로고    scopus 로고
    • Effects of distal and proximal arm muscles fatigue on multi-joint movement organization
    • Huffenus, A. F., N. Forestier, et al. (2006). "Effects of distal and proximal arm muscles fatigue on multi-joint movement organization." Experimental Brain Research 170(4): 438-447.
    • (2006) Experimental Brain Research , vol.170 , Issue.4 , pp. 438-447
    • Huffenus, A.F.1    Forestier, N.2
  • 23
    • 0028148777 scopus 로고
    • Assessment of physical exposure in relation to work-related musculoskeletal disorders-what information can be obtained from systematic observations?
    • Kilbom, A. (1994). "Assessment of physical exposure in relation to work-related musculoskeletal disorders-what information can be obtained from systematic observations?" Scand J Work Environ Health 20 Spec No: 30-45.
    • (1994) Scand J Work Environ Health , vol.20 , Issue.30
    • Kilbom, A.1
  • 24
    • 0023284961 scopus 로고
    • Work technique and its consequences for musculoskeletal disorders
    • Kilbom, A. and J. Persson (1987). "Work technique and its consequences for musculoskeletal disorders." Ergonomics 30(2): 273-9.
    • (1987) Ergonomics , vol.30 , Issue.2 , pp. 273-279
    • Kilbom, A.1    Persson, J.2
  • 25
    • 77957666567 scopus 로고    scopus 로고
    • Movement timing and reach to reach variability during a repetitive reaching task in persons with chronic neck/shoulder pain and healthy subjects
    • Lomond, K. V. and J. N. Cote (2010). "Movement timing and reach to reach variability during a repetitive reaching task in persons with chronic neck/shoulder pain and healthy subjects." Experimental Brain Research 206(3): 271-282.
    • (2010) Experimental Brain Research , vol.206 , Issue.3 , pp. 271-282
    • Lomond, K.V.1    Cote, J.N.2
  • 26
    • 84859830037 scopus 로고    scopus 로고
    • On functional motor adaptations: From the quantification of motor strategies to the prevention of musculoskeletal disorders in the neck-shoulder region (vol 199, pg 1, 2010)
    • Madeleine, P. (2010). "On functional motor adaptations: from the quantification of motor strategies to the prevention of musculoskeletal disorders in the neck-shoulder region (vol 199, pg 1, 2010)." Acta Physiologica 200(3): 289-289.
    • (2010) Acta Physiologica , vol.200 , Issue.3 , pp. 289-289
    • Madeleine, P.1
  • 27
    • 0141884302 scopus 로고    scopus 로고
    • Standardized low-load repetitive work: Evidence of different motor control strategies between experienced workers and a reference group
    • Madeleine, P., B. Lundager, et al. (2003). "Standardized low-load repetitive work: evidence of different motor control strategies between experienced workers and a reference group." Applied Ergonomics 34(6): 533-542.
    • (2003) Applied Ergonomics , vol.34 , Issue.6 , pp. 533-542
    • Madeleine, P.1    Lundager, B.2
  • 28
    • 67349221754 scopus 로고    scopus 로고
    • Changes in the amount and structure of motor variability during a deboning process are associated with work experience and neck-shoulder discomfort
    • Madeleine, P. and T. M. T. Madsen (2009). "Changes in the amount and structure of motor variability during a deboning process are associated with work experience and neck-shoulder discomfort." Applied Ergonomics 40(5): 887-894.
    • (2009) Applied Ergonomics , vol.40 , Issue.5 , pp. 887-894
    • Madeleine, P.1    Madsen, T.M.T.2
  • 29
    • 43149084132 scopus 로고    scopus 로고
    • Changes in the degree of motor variability associated with experimental and chronic neck-shoulder pain during a standardised repetitive arm movement
    • Madeleine, P., S. E. Mathiassen, et al. (2008a). "Changes in the degree of motor variability associated with experimental and chronic neck-shoulder pain during a standardised repetitive arm movement." Experimental Brain Research 185(4): 689-698.
    • (2008) Experimental Brain Research , vol.185 , Issue.4 , pp. 689-698
    • Madeleine, P.1    Mathiassen, S.E.2
  • 30
    • 46249091433 scopus 로고    scopus 로고
    • The size of cycle-to-cycle variability in biomechanical exposure among butchers performing a standardised cutting task
    • Madeleine, P., M. Voigt, et al. (2008b). "The size of cycle-to-cycle variability in biomechanical exposure among butchers performing a standardised cutting task." Ergonomics 51(7): 1078-1095.
    • (2008) Ergonomics , vol.51 , Issue.7 , pp. 1078-1095
    • Madeleine, P.1    Voigt, M.2
  • 31
    • 0027752428 scopus 로고
    • The influence of exercise/rest schedule on the physiological and psychophysical response to isometric shoulder-neck exercise
    • Mathiassen, S. E. (1993). "The Influence of Exercise/Rest Schedule on the Physiological and Psychophysical Response to Isometric Shoulder-Neck Exercise." European Journal of Applied Physiology and Occupational Physiology 67(6): 528-539.
    • (1993) European Journal of Applied Physiology and Occupational Physiology , vol.67 , Issue.6 , pp. 528-539
    • Mathiassen, S.E.1
  • 32
    • 33744939465 scopus 로고    scopus 로고
    • Diversity and variation in biomechanical exposure: What is it, and why would we like to know?
    • Mathiassen, S. E. (2006). "Diversity and variation in biomechanical exposure: What is it, and why would we like to know?" Applied Ergonomics 37(4): 419-427.
    • (2006) Applied Ergonomics , vol.37 , Issue.4 , pp. 419-427
    • Mathiassen, S.E.1
  • 33
    • 0030710598 scopus 로고    scopus 로고
    • Motor control and cardiovascular responses during isoelectric contractions of the upper trapezius muscle: Evidence for individual adaptation strategies
    • Mathiassen, S. E. and T. Aminoff (1997). "Motor control and cardiovascular responses during isoelectric contractions of the upper trapezius muscle: evidence for individual adaptation strategies." European Journal of Applied Physiology 76(5): 434-444.
    • (1997) European Journal of Applied Physiology , vol.76 , Issue.5 , pp. 434-444
    • Mathiassen, S.E.1    Aminoff, T.2
  • 34
    • 0038053146 scopus 로고    scopus 로고
    • Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task
    • Mathiassen, S. E., T. Moller, et al. (2003). "Variability in mechanical exposure within and between individuals performing a highly constrained industrial work task." Ergonomics 46(8): 800-824.
    • (2003) Ergonomics , vol.46 , Issue.8 , pp. 800-824
    • Mathiassen, S.E.1    Moller, T.2
  • 35
    • 0030054061 scopus 로고    scopus 로고
    • Physiological comparison of three interventions in light assembly work: Reduced work pace, increased break allowance and shortened working days
    • Mathiassen, S. E. and J. Winkel (1996). "Physiological comparison of three interventions in light assembly work: Reduced work pace, increased break allowance and shortened working days." International Archives of Occupational and Environmental Health 68(2): 94-108.
    • (1996) International Archives of Occupational and Environmental Health , vol.68 , Issue.2 , pp. 94-108
    • Mathiassen, S.E.1    Winkel, J.2
  • 36
    • 38649085630 scopus 로고    scopus 로고
    • The role of cocontraction in the impairment of movement accuracy with fatigue
    • Missenard, O., D. Mottet, et al. (2008). "The role of cocontraction in the impairment of movement accuracy with fatigue." Experimental Brain Research 185(1): 151-156.
    • (2008) Experimental Brain Research , vol.185 , Issue.1 , pp. 151-156
    • Missenard, O.1    Mottet, D.2
  • 37
    • 33744492078 scopus 로고    scopus 로고
    • Reduced variability of postural strategy prevents normalization of motor changes induced by back pain: A risk factor for chronic trouble?
    • Moseley, G. L. and P. W. Hodges (2006). "Reduced variability of postural strategy prevents normalization of motor changes induced by back pain: A risk factor for chronic trouble?" Behavioral Neuroscience 120(2): 474-476.
    • (2006) Behavioral Neuroscience , vol.120 , Issue.2 , pp. 474-476
    • Moseley, G.L.1    Hodges, P.W.2
  • 38
    • 0003799618 scopus 로고    scopus 로고
    • National Research Council. Washington DC: National Academies Press
    • National Research Council (2001). Musculoskeletal Disorders and the Workplace. Washington DC: National Academies Press.
    • (2001) Musculoskeletal Disorders and the Workplace
  • 39
    • 0031870913 scopus 로고    scopus 로고
    • Consequences of trapezius relaxation on the distribution of shoulder muscle forces: An electromyographic study
    • Palmerud, G., H. Sporrong, et al. (1998). "Consequences of trapezius relaxation on the distribution of shoulder muscle forces: an electromyographic study." Journal of Electromyography and Kinesiology 8(3): 185-193.
    • (1998) Journal of Electromyography and Kinesiology , vol.8 , Issue.3 , pp. 185-193
    • Palmerud, G.1    Sporrong, H.2
  • 40
    • 84949159141 scopus 로고
    • Recent developments and problems in human movement science and their conceptual implications
    • Schoner, G. (1995). "Recent developments and problems in human movement science and their conceptual implications." Ecological Psychology 7(4): 291-314.
    • (1995) Ecological Psychology , vol.7 , Issue.4 , pp. 291-314
    • Schoner, G.1
  • 41
    • 34447095858 scopus 로고    scopus 로고
    • Fatigueinduced changes of impedance and performance in target tracking
    • Selen, L. P. J., P. J. Beek, et al. (2007). "Fatigueinduced changes of impedance and performance in target tracking." Experimental Brain Research 181(1): 99-108.
    • (2007) Experimental Brain Research , vol.181 , Issue.1 , pp. 99-108
    • Selen, L.P.J.1    Beek, P.J.2
  • 42
    • 0023615752 scopus 로고
    • Hand-wrist disorders among investment casting plant workers
    • Silverstein, B., L. Fine, et al. (1987). "Hand-wrist disorders among investment casting plant workers." J Hand Surg Am 12(5 Pt 2): 838-44.
    • (1987) J Hand Surg Am , vol.12 , Issue.5 PART 2 , pp. 838-844
    • Silverstein, B.1    Fine, L.2
  • 44
    • 0031428126 scopus 로고    scopus 로고
    • The effect of fatigue on multijoint kinematics and load sharing during a repetitive lifting test
    • Sparto, P. J., M. Parnianpour, et al. (1997). "The effect of fatigue on multijoint kinematics and load sharing during a repetitive lifting test." Spine 22(22): 2647-2654.
    • (1997) Spine , vol.22 , Issue.22 , pp. 2647-2654
    • Sparto, P.J.1    Parnianpour, M.2
  • 45
    • 34548289802 scopus 로고    scopus 로고
    • Optimal movement variability: A new theoretical perspective for neurologic physical therapy
    • Stergiou, N., R. Harbourne, et al. (2006). "Optimal movement variability: a new theoretical perspective for neurologic physical therapy." J Neurol Phys Ther 30(3): 120-9.
    • (2006) J Neurol Phys Ther , vol.30 , Issue.3 , pp. 120-129
    • Stergiou, N.1    Harbourne, R.2
  • 46
    • 4744346535 scopus 로고    scopus 로고
    • The effect of the walking speed on the stability of the anterior cruciate ligament deficient knee
    • Stergiou, N., C. Moraiti, et al. (2004). "The effect of the walking speed on the stability of the anterior cruciate ligament deficient knee." Clinical Biomechanics 19(9): 957-963.
    • (2004) Clinical Biomechanics , vol.19 , Issue.9 , pp. 957-963
    • Stergiou, N.1    Moraiti, C.2
  • 47
    • 0027266983 scopus 로고
    • Patterns of electromyographic shoulder muscle fatigue during MTM-paced repetitive arm work with and without pauses
    • Sundelin, G. (1993). "Patterns of electromyographic shoulder muscle fatigue during MTM-paced repetitive arm work with and without pauses." Int Arch Occup Environ Health 64(7): 485-93.
    • (1993) Int Arch Occup Environ Health , vol.64 , Issue.7 , pp. 485-493
    • Sundelin, G.1
  • 48
    • 63049103166 scopus 로고    scopus 로고
    • Low-level activity of the trunk extensor muscles causes electromyographic manifestations of fatigue in absence of decreased oxygenation
    • van Dieen, J. H., E. P. Westebring-van der Putten, et al. (2009). "Low-level activity of the trunk extensor muscles causes electromyographic manifestations of fatigue in absence of decreased oxygenation." Journal of Electromyography and Kinesiology 19(3): 398-406.
    • (2009) Journal of Electromyography and Kinesiology , vol.19 , Issue.3 , pp. 398-406
    • Van Dieen, J.H.1    Westebring-Van Der Putten, E.P.2
  • 49
    • 0027526488 scopus 로고
    • An investigation into the relevance of the pattern of temporal activation with respect to erector spinae muscle endurance
    • van Dieen, J. H., H. H. E. O. Vrielink, et al. (1993). "An Investigation into the Relevance of the Pattern of Temporal Activation with Respect to Erector Spinae Muscle Endurance." European Journal of Applied Physiology and Occupational Physiology 66(1): 70-75.
    • (1993) European Journal of Applied Physiology and Occupational Physiology , vol.66 , Issue.1 , pp. 70-75
    • Van Dieen, J.H.1    Vrielink, H.H.E.O.2
  • 50
    • 0027469594 scopus 로고
    • Individual and work-related risk factors associated with symptoms of musculoskeletal complaints
    • Westgaard, R. H., C. Jensen, et al. (1993). "Individual and work-related risk factors associated with symptoms of musculoskeletal complaints." Int Arch Occup Environ Health 64(6): 405-13.
    • (1993) Int Arch Occup Environ Health , vol.64 , Issue.6 , pp. 405-413
    • Westgaard, R.H.1    Jensen, C.2
  • 51
    • 0029931853 scopus 로고    scopus 로고
    • Guidelines for occupational musculoskeletal load as a basis for intervention: A critical review
    • Westgaard, R. H. and J. Winkel (1996). "Guidelines for occupational musculoskeletal load as a basis for intervention: a critical review." Appl Ergon 27(2): 79-88.
    • (1996) Appl Ergon , vol.27 , Issue.2 , pp. 79-88
    • Westgaard, R.H.1    Winkel, J.2
  • 52
    • 42449129294 scopus 로고    scopus 로고
    • Coordination variability and skill development in expert triple jumpers
    • Wilson, C., S. E. Simpson, et al. (2008). "Coordination variability and skill development in expert triple jumpers." Sports Biomechanics 7(1): 2-9.
    • (2008) Sports Biomechanics , vol.7 , Issue.1 , pp. 2-9
    • Wilson, C.1    Simpson, S.E.2


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.