Large Deformation Behavior of Long Shallow Cylindrical Composite Panels

An exact solution is presented for the large deformation response of a simply supported orthotropic cylindrical panel subjected to a uniform line load along a cylinder generator. The cross section of the cylinder is circular and deformations up to the fully snapped through position are investigated. The orthotropic axes are parallel to the generator and circumferential directions. The governing equations are derived using laminated plate theory, nonlinear strain-displacement relations, and applying variational principles. The response is investigated for the case of a panel loaded exactly at midspan and for a panel with the load offset from midspan. The mathematical formulation is one dimensional in the circumferential coordinate. Solutions are obtained in closed-form. An experimental apparatus was designed to load the panels. Experimental results of displacement controlled tests performed on graphite-epoxy curved panels are compared with analytical predictions

The khmer software package: enabling efficient nucleotide sequence analysis [version 1; referees: 2 approved, 1 approved with reservations]

The khmer package is a freely available software library for working efficiently with fixed length DNA words, or k-mers. khmer provides implementations of a probabilistic k-mer counting data structure, a compressible De Bruijn graph representation, De Bruijn graph partitioning, and digital normalization. khmer is implemented in C++ and Python, and is freely available under the BSD license at https://github.com/dib-lab/khmer/

Haunted by History: China and its Northwestern Neighbors

China?s current relations with its northwestern neighbors, Russia, Mongolia, and the newly independent states of Central Asia are influenced by the shadow of the past that is cast over the present. To what degree does this checkered past fundamentally determine the possibility of close, strategic cooperation now and in the future? China?s important and complex relationship with Russia will be considered first, followed by an analysis of China-Mongolian relations and finally China?s relationship with the Central Asian states with which it shares a common border. The important America factor is also considered. The article concludes that despite the closer relations that are developing between China and it northwestern neighbors, the historical legacy of domination, unequal treaties, and ethnic conflict will haunt the significant improvement in relations. China?s current relations with its northwestern neighbors, Russia, Mongolia, and the newly independent states of Central Asia are influenced by the shadow of the past that is cast over the present. To what degree does this checkered past fundamentally determine the possibility of close, strategic cooperation now and in the future? China?s important and complex relationship with Russia will be considered first, followed by an analysis of China-Mongolian relations and finally China?s relationship with the Central Asian states with which it shares a common border. The important America factor is also considered. The article concludes that despite the closer relations that are developing between China and it northwestern neighbors, the historical legacy of domination, unequal treaties, and ethnic conflict will haunt the significant improvement in relations

Structures at Risk from an Intermetatarsal Screw for Lapidus Bunionectomy

Category: Midfoot/Forefoot Introduction/Purpose: The Lapidus procedure is a common procedure for the treatment of hallux abducto valgus. Traditional fixation consists of two crossing screws in the sagittal plane. Despite arthrodesis of the first tarsometatarsal joint, recurrence of the hallux abducto valgus deformity remains a concern. A transverse screw spanning the base of the first metatarsal to the base of the second metatarsal has been advocated to provide transverse plane stability. However, the neurovascular bundle is located within the proximity of this screw. The literature is sparse with a standard technique to safely provide appropriate fixation. An anatomic cadaver study was undertaken to assess the risk of injury to the neurovascular bundle. Methods: Ten unmatched cadaveric limbs that had been disarticulated at the knee were used. Under fluoroscopic guidance, the guide wire to a 4.0-mm screw was driven across the base of the first metatarsal and into the second metatarsal. A 4.0-mm screw was inserted, taking care to obtain osseous purchase into the second metatarsal. A longitudinal incision was made and careful dissection was carried to identify the neurovascular bundle and screw. The neurovascular bundle was inspected for trauma and the proximity of the screws was measured using a digital caliper. Results: There were three left-sided and seven right-sided specimens. Five of the specimens were male and five were female. The mean age of the specimens at date of death was 71.4 years. The mean body mass index was 20.5. The mean distance from the 4.0-mm screw to the first metatarsal base 11.24 mm distal to the first tarsometatarsal joint. The deep plantar artery and deep peroneal nerve was free from injury in 10/10 (100%) specimens. However, the screw was measured to be less than 5 mm in three specimens. In these instances, the average distance of the screw distal to the first tarsometatarsal joint was 12.1 mm. Conclusion: The addition of the intermetatarsal screw for Lapidus bunionectomy is widely accepted clinical practice. Descriptions of the operative technique for the placement of hardware into the second metatarsal have not included specific recommendations to avoid potential risk to the neurovascular bundle as it courses between the bases of the first and second metatarsals. According to this cadaveric study, the neurovascular bundle was avoided with placement of the intermetatarsal screw, if placed approximately 11.24 mm distal to the first tarsometatarsal joint. Further study is warranted to evaluate the optimal distance distal to the first tarsometatarsal joint

Development of a Global/Local Approach and a Geometrically Non-linear Local Panel Analysis for Structural Design

A computationally efficient analysis capability for the geometrically non-linear response of compressively loaded prismatic plate structures was developed. Both a "full" finite strip solution procedure and a "reduced" solution procedure were implemented in a FORTRAN 90 computer code, and comparisons were made with results available in the technical literature. Both the full and reduced solution procedures were demonstrated to provide accurate results for displacement and strain quantities through moderately large post-buckling loads. The full method is a non-linear nite strip analysis of the semi-analytical, multi-term type. Individual finite strips are modeled as balanced and symmetric laminated composite materials which are assumed to behave orthotropically in bending, and the structure is loaded in uniaxial or biaxial compression. The loaded ends of the structure are assumed to be simply supported, and geometric shape imperfections may be modeled. The reduced solution method makes use of a reduced basis technique in conjunction with the full nite strip analysis. Here, the potentially large set of non-linear algebraic equations produced by the finite strip method are replaced by a small set of system equations. In the present implementation, the basis vectors consist of successive derivatives of the non-linear solution vector with respect to a loading parameter. Depending on the nature of the problem,..

Overloaded overheads: Activity-based cost analysis of material handling in cell manufacturing

Manufacturing managers today are pressed by aggressive international competitors, high input factor prices, and customers who demand better quality at lower cost. In such an environment, there is a growing need to exploit the time, cost and quality advantages of cell manufacturing (Hyer and Wemmerlov (1984)). Unfortunately, traditional cost accounting systems may be a major roadblock on the highway to future manufacturing competitiveness. These systems may stifle manufacturing initiatives to improve process design by providing inaccurate cost information. They may also send the wrong signals to managers who must evaluate the cost/benefit impact of process innovation (such as cells and group technology implementation), thereby causing companies to retain outmoded, inefficient manufacturing practices.We discuss the results of our field study which illustrates the use of activity-based costing (ABC) to quantify the benefits of cell manufacturing and synchronized process flows. Auto Light Company, a Fortune 500 automobile components manufacturer, had begun to replace its functional layout with synchronous manufacturing cells. Although dramatic progress had been made in operational measures (such as throughput time, work-in-process (WIP) inventories, and material flow distance), existing accounting systems failed to trace these savings to the source, namely the change in manufacturing practices. Overheads were being allocated to products on the basis of direct labor or machine hours, which at Auto Light are no different in cells than in traditional manufacturing.A joint Auto Light management/Carnegie Mellon University team examined the impact of cell manufacturing on major cost categories. The group identified material handling expenses (which exceed $5,000,000 per year, and comprise approximately 10% of total factory costs) as a promising area for analysis using ABC principles. We sought to identify relevant material handling cost drivers: that is, activities that (1) create costs and (2) seem reasonable to use as proxies for assigning costs to products. Interviews, plant records and time-and-effort studies pointed to "number of moves" and "distance moved" as key drivers of material handling costs. Annual production volumes, physical dimensions of products and their production routings were used to calculate the number of moves, and the distancePeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29552/1/0000640.pd

A Comparison of Complications and Reoperations Between Open Reduction and Internal Fixation Versus Primary Arthrodesis Following Lisfranc Injury.

There is a lack of consensus in the literature regarding optimal treatment methods for Lisfranc injuries, and recent literature has emphasized the need to compare open reduction and internal fixation (ORIF) with primary arthrodesis (PA). The purpose of the current study is to compare reoperation and complication rates between ORIF and PA following Lisfranc injury in a private, outpatient, orthopaedic practice. A retrospective chart review was performed on patients undergoing operative intervention for Lisfranc injury between January 2009 and September 2015. A total of 196 patients met the inclusion criteria (130 ORIF, 66 PA), with a mean follow-up of 61.3 and 81.7 weeks, respectively. The ORIF group had a higher reoperation rate than the PA group, due to hardware removal. When hardware removals were excluded, the reoperation rate was similar. Postsurgical complications were compared between the 2 groups with no significant difference. In conclusion, ORIF and PA had similar complication rates. When hardware removals were excluded, the reoperation rates were similar, although hardware removals were more common in the ORIF group compared with the PA group