• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.207-214
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• 2009

Purpose: In arthroscopic rotator cuff repairs there are generally weak link in tendon suture interface, arthroscopic rotator cuff repairs can have higher retear rates than open repairs. The purpose of this study was to compare the strength of UU (Ulsan University) suture than open modified MA (Mason-Allen) suture when suture anchored into bone. Materials and Methods: The human supraspinatus tendons were harvested from the shoulder of the cadaver and split in 2 times, producing four tendons per one shoulder, for a total of 24 specimens. Two suture configurations (UU, MA) were randomized and checked on each set of tendons. Specimens were cyclically loaded under force control between 5 and 30 N at 0.25 Hz for fifty cycles. Each specimen was loaded to failure under displacement control at 1 mm/sec. Cyclic elongation, peak to peak displacement, stiffness, ultimate tensile load, mode of failure were checked. Results: No significant difference was found between two suture configuration with respect to peak to peak displacement, cyclic elongation, and stiffness. With regard to ultimate failure load, there were no significant difference statistically between the UU suture and modified MA suture (109.4 N, 110.6 N). The most common mode of failure between both sutures was suture pull-out through the tendon. Conclusion: The UU suture and modified MA suture produced similar biomechanical properties.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.503-514
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• 2011

In this research, the seismic connection details for two concrete-filled U-shape steel beam-to-H columns were proposed and cyclically tested under a full-scale cruciform configuration. The key connecting components included the U-shape steel section (450 and 550 mm deep for specimens A and B, respectively), a concrete floor slab with a ribbed deck (165 mm deep for both specimens), welded couplers and rebars for negative moment transfer, and shear studs for full composite action and strengthening plates. Considering the unique constructional nature of the proposed connection, the critical limit states, such as the weld fracture, anchorage failure of the welded coupler, local buckling, concrete crushing, and rebar buckling, were carefully addressed in the specimen design. The test results showed that the connection details and design methods proposed in this study can well control the critical limit states mentioned above. Especially, the proposed connection according to the strengthening strategy successfully pushed the plastic hinge to the tip of the strengthened zone, as intended in the design, and was very effective in protecting the more vulnerable beam-to-column welded joint. The maximum story drift capacities of 6.0 and 6.8% radians were achieved in specimens A and B, respectively, thus far exceeding the minimumlimit of 4% radians required of special moment frames. Low-cycle fatigue fracture across the beam bottom flange at a 6% drift level was the final failure mode of specimen A. Specimen B failed through the fracture of the top splice plate of the bolted splice at a very high drift ratio of 8.0% radian.

• Strategy21
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• s.34
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• pp.236-261
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• 2014

The future role of nuclear extended deterrence in the security alliance between the United States and the Republic of Korea is currently a central concern. The gradually lessening role of reliance on nuclear weapons in US security policies broadly, combined with increasing North Korean nuclear capabilities and belligerence, raise fresh questions about the sufficiency of the "nuclear umbrella" as a pillar of the US-ROK defense posture. This article addresses the current and future role of nuclear extended deterrence in Korea in this dynamic context. The article reviews the longstanding trend toward reducing the overall size of the US nuclear arsenal, and assesses developments in US-ROK outlooks toward extended deterrence in response to the Obama administration's nuclear policies and North Korea's recent smaller-scale aggressions. The analysis finds that the challenges of deterrence credibility and allied reassurance are difficult and long-term. The analysis explains how these challenges emerge less from a shrinking US numerical arsenal size than from the sufficiency of specific nuclear and non-nuclear capabilities to meet emerging smaller-scale threats. The analysis also highlights the importance of broader strategic and political interaction in sustaining allied confidence in any joint security posture. The evaluation concludes that a strong US-ROK alliance relationship can be maintained while the size of the US nuclear arsenal continues to decline, in part because nuclear weapons in any deployment configuration are relatively ineffective means for deterring smaller-scale aggression. Nevertheless, continuing adjustment of the US-ROK extended deterrence posture to the evolving, complex and uncertain Korean peninsula security environment will remain an ongoing challenge. Finally, the article encourages further examination of the potential specific role ROK maritime forces might serve in enhancing deterrence of smaller-scale threats while minimizing risks of conflict escalation.