1,721,034 research outputs found
Detailed aerodynamic analysis of a shrouded tail rotor using an unstructured mesh flow solver
No full textThe detailed aerodynamics of a shrouded tail rotor in hover has been numerically studied using a parallel inviscid flow solver on unstructured meshes. The numerical method is based on a cell-centered finite-volume discretization and an implicit Gauss-Seidel time integration. The calculation was made for a single blade by imposing a periodic boundary condition between adjacent rotor blades. The grid periodicity was also imposed at the periodic boundary planes to avoid numerical inaccuracy resulting from solution interpolation. The results were compared with available experimental data and those from a disk vortex theory for validation. It was found that realistic three-dimensional modeling is important for the prediction of detailed aerodynamics of shrouded rotors including the tip clearance gap flow
SoftPM: a software process management system reconciling formalism with easiness
No full textVarious formal approaches to process modeling and analysis have been proposed. With the emerging importance of practicality in this held, easiness in adopting formal technology should be taken into account. In this paper, we propose a PSEE called SoftPM that is based on a high level Petri net formalism for process modeling. To overcome the difficulty in using this formalism, SoftPM exploits a multi-level modeling mechanism for the representation of software processes. SoftPM supports three different levels for process representation. They are cognitive, MAM net, and Pr/T net. Each level has different roles in SoftPM. The cognitive-level modeling provides the means of getting free from difficulties in manipulating the modeling formalism. MAM net takes the role of core modeling formalism in SoftPM. Finally, Pr/T nets support the low-level modeling formalism as an existing Petri-net class. Moreover, SoftPM offers various analysis techniques to aid managerial decision making, as well as conventional Petri-net analysis techniques. Using a Java-based thin client/server architecture, SoftPM smoothly supports execution at distributed heterogeneous platforms over the Internet. (C) 2000 Elsevier Science B.V. All rights reserved
Real-time pinch force estimation by surface electromyography using an artificial neural network
No full textThe palmar pinch force estimation is highly relevant not only in biomechanical studies, the analysis of sports activities, and ergonomic design analyses but also in clinical applications such as rehabilitation, in which information about muscle forces influences the physician's decisions on diagnosis and treatment. Force transducers have been used for such purposes, but they are restricted to grasping points and inevitably interfere with the human haptic sense because fingers cannot directly touch the environmental surface. We propose an estimation method of the palmar pinch force using surface electromyography (SEMG). Three myoelectric sites on the skin were selected on the basis of anatomical considerations and a Fisher discriminant analysis (FDA), and SEMG at these sites yields suitable information for pinch force estimation. An artificial neural network (ANN) was implemented to map the SEMG to the force, and its structure was optimized to avoid both under- and over-fitting problems. The resulting network was tested using SEMG signals recorded from the selected myoelectric sites of ten subjects in real time. The training time for each subject was short (approximately 96 s), and the estimation results were promising, with a normalized root mean squared error (NRMSE) of 0.081 +/- 0.023 and a correlation (CORR) of 0.968 +/- 0.017. (C) 2010 IPEM. Published by Elsevier Ltd. All rights reserved
Does Mechanical Bowel Preparation Ameliorate Surgical Performance in Anterior Lumbar Interbody Fusion?
Full text linkSTUDY DESIGN: Retrospective case-control study.
OBJECTIVES: To investigate whether mechanical bowel preparation (MBP) improve surgical performance and decrease operative complications in anterior lumbar interbody fusion (ALIF).
METHODS: This study involved a retrospective analysis of 48 consecutive patients who underwent ALIF with MBP and a control cohort of 50 consecutive patients who underwent the same surgeries without MBP. The quality of each surgical procedure, operative time, estimated blood loss (EBL), intraoperative complications, changes in vital signs and patient symptoms on the day of surgery, and bowel function postoperatively were also compared between the procedures.
RESULTS: Baseline demographic characteristics were similar between the 2 groups (all Ps > .05). The quality of each procedure, operative time, EBL, intraoperative complications, and changes in body temperature and heart rate were not different between the groups (all Ps > .05). The MBP group showed more headache, tiredness, thirst, and abdominal discomfort (all Ps < .001) and decrease of the systolic blood pressure (P = .041) on the day of surgery. The return of bowel movement was not different between the groups (P = .278).
CONCLUSIONS: Given the similar surgical result with the substantial patient discomfort, MBP can be omitted in ALIF
Vascular anatomy and surgical approach in oblique lateral interbody fusion at lumbosacral transitional vertebrae
No full textBackground: Oblique lateral interbody fusion (OLIF) at lumbosacral junction is typically performed on the central window between the bifurcations of iliac vessels. However, the central window of lumbosacral transitional vertebrae (LSTVs) is usually obstructed by the iliocaval venous structures. We aimed to describe the vascular anatomy and surgical approach in OLIF at LSTVs compared with those in OLIF at typical L5-S1 junction. Methods: Sixty-eight consecutive patients who underwent OLIF at lumbosacral junction were included. Of these, 31 patients had LSTVs and 37 patients had typical L5-S1 junction. The position of the iliocaval junction and the configuration of the left common iliac vein were compared using the preoperative CT and MR images of the lumbar spine. The surgical approach and intraoperative vascular findings were analyzed. Results: Almost 70% of LSTVs had the iliocaval junction at low or very low position. Mobilization of left common iliac vein for central window was potentially difficult in almost 74% of OLIF at LSTVs while it was not required or was potentially easy in almost 80% of OLIF at typical L5-S1. Vascular injury was identified in 2 (6.5%) patients with OLIF at LSTVs and in 3 (8.1%) patients with OLIF at typical L5-S1 junction (P = 0.904). Conclusions: In our series, OLIF at LSTVs was performed through lateral window in 93.5% of the cases. Preoperative evaluation of the iliocaval junction using CT/MR of lumbar spine was reliable and valid in the determination of OLIF approach at lumbosacral junction
Differences in lumbar segment angle among Roussouly types of global sagittal alignment in asymptomatic adult subjects
No full textSTUDY DESIGN: A radiological study. OBJECTIVES: To examine lumbar segment angle according to the Roussouly type of global sagittal alignment and to determine the reference disc angles in minimally invasive surgery (MIS) for adult spinal deformity. Optimal restoration of lumbar lordosis (LL) in adult spinal deformity surgery includes achieving the ideal shape of LL as well as the amount of LL. However, the distribution of lumbar segment angles by the Roussouly type has yet to be elucidated. METHODS: Forty sets of whole spine lateral radiographs covering the four Roussouly types (N = 160) were obtained from a database of asymptomatic adult subjects. Global and spinopelvic parameters were measured. Disc and vertebral angles at each lumbar level were compared among the Roussouly types. RESULTS: There were 75 (46.9%) men with a mean age of 32.8 +/- 8.9 years among the total of 160 study subjects. A significant difference was found in spino-sacral angle, sacral slope, pelvic incidence, LL, and lower arc of LL (L4S1) among the Roussouly types (all P < 0.001). The ratio of the lower arc of LL (L4S1) to LL was 83.4% in Roussouly type 1, 65.2% in type 2, 64.7% in type 3, and 61.5% in type 4. The disc angles at the L1-2 and L2-3 levels in Roussouly type 1 were significantly smaller than in the other types. The disc angle at the L5-S1 level in Roussouly type 1 was significantly larger than that in type 2. Roussouly type 4 had a larger disc angle at the L2-3 and L4-5 levels than types 1 and 2. CONCLUSIONS: The results of this study showed that the disc angle distribution differs among Roussouly types. The configuration of LL as well as the amount of LL should be considered in adult spinal deformity surgery. LEVEL OF EVIDENCE: Level IV
The Impact of Vertebral End Plate Lesions on the Radiological Outcome in Oblique Lateral Interbody Fusion
Full text linkSTUDY DESIGN: Retrospective case-control study. OBJECTIVES: Vertebral end plate (EP) lesions include Modic changes, Schmorl's nodes, EP erosion, EP sclerosis, and so on. While previous studies have mostly focused on the association between vertebral EP lesions and low back pain, few studies evaluated the influence of vertebral EP lesions on the radiological outcomes in lumbar interbody fusion. METHODS: This study included a total of 125 operated disc levels from 86 consecutive patients who underwent a 1- or 2-level oblique lateral interbody fusion (OLIF) and had more than 1-year regular follow-up. The presence of vertebral EP lesions, changes in disc heights/angle, cage subsidence, and fusion grade were examined. The associations between vertebral EP lesions and radiological parameters were analyzed. RESULT: The presence of Modic changes, Schmorl's node, EP cartilage erosion, and EP sclerosis were found in 72 (57.6%), 26 (20.8%), 31 (24.8%), and 44 (35.2%) disc levels, respectively. The mean anterior disc height increased from 6.9 +/- 3.8 mm to 13.1 +/- 2.7 mm (P < .001) and the mean segmental angle increased from 2.9 degrees +/- 5.8 degrees to 9.2 degrees +/- 4.8 degrees (P < .001) at the last follow-up. The overall fusion rate was 98.4% (123/125) and cage subsidence rate was 7.2% (9/125). All radiological parameters and cage subsidence rate were not different regardless of vertebral EP lesions. CONCLUSIONS: Vertebral EP lesions did not affect the overall radiological outcome in 1- or 2-level OLIF. These results come from the stable contact between lateral cage and peripheral rim of vertebral EP
Degenerative changes of sagittal alignment in patients with Roussouly type 1
No full textSTUDY DESIGN: A cross-sectional radiological study. OBJECTIVES: We aimed to examine the degenerative changes of sagittal alignment in patients with Roussouly type 1. Roussouly type 1 is unique in shape, characterized by short lumbar lordosis (LL) with the apex at L5 and thoracolumbar kyphosis (TLK). Because of the unique shape of sagittal alignment and the small pelvic incidence (PI) in Roussouly type 1, the degenerative changes of sagittal alignment may differ. METHODS: A total of 145 patients with Roussouly type 1 were recruited and distributed into three age groups; Group I (N = 40) were young patients (20-40 years of age), Group II (N = 47) were middle-aged patients (45-60 years of age), and Group III (N = 48) were elderly patients (>65 years of age). Sagittal parameters including sagittal vertical axis (SVA), PI, pelvic tilt (PT), L1S1 LL, L4S1 LL, thoracic kyphosis (TK), and TLK were measured using Surgimap((R)) software. The occurrence of lumbar retrolisthesis was also examined. RESULTS: The SVA, PI, PT, L1S1 LL, L4S1 LL, TK, and TLK in group I were - 25.9 degrees +/- 23.4 mm, 37.1 degrees +/- 5.3 degrees , 10.3 degrees +/- 5.5 degrees , 42.7 degrees +/- 8.8 degrees , 35.5 degrees +/- 6.9 degrees , 29.5 degrees +/- 23.5 degrees , and 9.7 degrees +/- 5.9 degrees , respectively. Among the Groups I, II, and III, there was a stepwise increase in the SVA, PT, TLK, and lumbar retrolisthesis (all P < 0.001). The PI, L4S1 LL, and TK were identical among the three groups. CONCLUSIONS: Degenerative changes of Roussouly type 1 include increase in the SVA, PT, TLK, and lumbar retrolisthesis, while the PI, L4S1 LL, and TK remain unchanged. LEVEL OF EVIDENCE: Level IV
Lumbar radiculopathy and fracture risk: A Korean nationwide population-based cohort study
No full textIntroduction: Lumbar radiculopathy is a common disease with a high economic burden, and fractures in adults are a significant public health problem. However, studies of the relationship between lumbar radiculopathy and fractures are scarce. We investigated the fracture risk in patients with lumbar radiculopathy. Methods: This nationwide retrospective cohort study identified 815,101 patients with lumbar radiculopathy and randomly matched individuals without lumbar radiculopathy (1:1) who were included in the Korean National Health Insurance System in 2012. Cox proportional hazards regression analyses were performed to calculate the hazard ratio (HR) for fracture risk in patients with lumbar radiculopathy. Results: The study included 301,347 patients with lumbar radiculopathy and matched 289,618 individuals without lumbar radiculopathy. Compared to individuals without lumbar radiculopathy, patients with lumbar radiculopathy had a 27 % increased fracture risk (adjusted HR = 1.27, 95 % confidence interval = 1.24–1.31). The Kaplan-Meier plot showed a significantly higher fracture incidence in patients with lumbar radiculopathy than in individuals without lumbar radiculopathy at all times. Conclusion: Lumbar radiculopathy is significantly associated with fracture risk
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