Dimensional verification and correction of five-axis numerically controlled milling tool paths

A system of algorithms is presented for material removal simulation, automatic dimensional verification and integrated error correction of numerically controlled (NC) milling tool paths. Several different approaches to these problems have been proposed including direct solid modeling, discrete vector intersection, and spatial partitioning. However, each of these methods suffer inherent restrictions that limit their practical application. This dissertation presents a discrete dexel NC verification algorithm based on a spatial partitioning technique (dexel representation) which incorporates the advantages of the discrete vector intersection approach. Hence, real-time animated five-axis milling simulation is supported by efficient regularized Boolean set operations, and dimensional milling errors are verified simultaneously with the simulation process. Based on intermediate dimensional verification results, a reduction of intersection volume algorithm is developed to eliminate detected gouges on the part surface. In addition, a technique for detection and elimination of unexpected collisions between the tool assembly and the workpiece is developed. These combined algorithms automatically correct tool paths to avoid gouges and collisions resulting in tool paths that are ready for immediate industrial application. A major disadvantage of dexel-based spatial partitioning, as originally proposed, is view dependency, i.e., dexels are constructed along a specific viewing vector so reconstruction of dexels is required for each new viewing direction. To overcome this problem, a contour display method is developed to transform dexel-based objects into a set of parallel planar contours thus enabling dynamic viewing transformations. In summary, this dissertation describes a unique hybrid approach to NC milling verification which provides for efficient, accurate and automatic assessment and correction of five-axis milling tool paths

THE REGULATION OF LEG STIFFNESS AND EMG ACTIVITIES ON PERSON WITH VISUAL IMPAIRED DURING STEP-DOWN WALKING

The purpose of present study was to evaluate leg muscular regulation and neuromuscular activation by investigating the stiffness and EMG amplitude of normal vision students and visually impaired students. 10 normal vision (age: 24.3±20 years; height: 171.5±4.6cm; mass: 65.9±8.0kg) and 10 visually impaired students (age: 23.2±2.4 years; height: 163.4±9.6cm; mass: 62.8±15.0kg) were served as subjects. AMTI force platform (1200 Hz), Peak Performance motion analysis system (60Hz) and Biovision EMG system were used synchronously to record the ground reaction force, the kinematic parameters and EMG signals of lower extremity during the subjects stepped down from height 20, 30 and 40cm. The results revealed that the regulation of neuromuscular system of the impaired is less efficient compared to the normal one because of lower muscle stiffness and EMG activity

Constrained K-means and Genetic Algorithm-based Approaches for Optimal Placement of Wireless Structural Health Monitoring Sensors

Optimal placement of wireless structural health monitoring (SHM) sensors has to consider modal identification accuracy and power efficiency. In this study, two-tier wireless sensor network (WSN)-based SHM systems with clusters of sensors are investigated to overcome this difficulty. Each cluster contains a number of sensor nodes and a cluster head (CH). The lower tier is composed of sensors communicating with their associated CHs, and the upper tier is composed of the network of CHs. The first step is the optimal placement of sensors in the lower tier via the effective independence method by considering the modal identification accuracy. The second step is the optimal placement of CHs in the upper tier by considering power efficiency. The sensors in the lower tier are partitioned into clusters before determining the optimal locations of CHs in the upper tier. Two approaches, a constrained K-means clustering approach and a genetic algorithm (GA)-based clustering approach, are proposed in this study to cluster sensors in the lower tier by considering two constraints: (1) the maximum data transmission distance of each sensor; (2) the maximum number of sensors in each cluster. Given that each CH can only manage a limited number of sensors, these constraints should be considered in practice to avoid overload of CHs. The CHs in the upper tier are located at the centers of the clusters determined after clustering sensors in the lower tier. The two proposed approaches aim to construct a balanced size of clusters by minimizing the number of clusters (or CHs) and the total sum of the squared distance between each sensor and its associated CH under the two constraints. Accordingly, the energy consumption in each cluster is decreased and balanced, and the network lifetime is extended. A numerical example is studied to demonstrate the feasibility of using the two proposed clustering approaches for sensor clustering in WSN-based SHM systems. In this example, the performances of the two proposed clustering approaches and the K-means clustering method are also compared. The two proposed clustering approaches outperform the K-means clustering method in terms of constructing balanced size of clusters for a small number of clusters. Doi: 10.28991/CEJ-2022-08-12-01 Full Text: PD

Biomechanical Characteristics and EMG Activities of Weighted Countermovement Jump

The purpose of this study was to investigate the biomechanical characteristics and EMG activities during a weighted countermovement jump (WCMJ) with 0%, 25% and 50% of body weight. Eight male college students participated this study. An AMTI force platform, Penny&Giles goniometer and Biovision EMG system were used synchronously to record the related parameters while subjects performed WCMJs. The results indicate that by increasing load, the eccentric mean force, the maximum force and concentric impulse increases significantly. With the load increase, the EMG activities of soleus and gastrocnemius did not changed significantly, while the eccentric mean EMG amplitude of rectus femoris got greater. This reveals that WCMJ has a marked influence on the lower extremity, especially on the rectus femoris

Knowledge-Rich Approach to Automatic Grammatical Information Acquisition: Enriching Chinese Sketch Engine with a Lexical Grammar

PACLIC 20 / Wuhan, China / 1-3 November, 200

Knowledge-Rich Approach to Automatic Grammatical Information Acquisition: Enriching Chinese Sketch Engine with a Lexical Grammar

PACLIC 20 / Wuhan, China / 1-3 November, 200

Methicillin-Resistant Staphylococcus aureus Nasal Colonization among Adult Patients Visiting Emergency Department in a Medical Center in Taiwan

Within the past 10 years, methicillin-resistant Staphylococcus aureus (MRSA) has not only been a hospital pathogen but also a community pathogen. To understand the carriage rate of methicillin-resistant Staphylococcus aureus (MRSA) among the adult patients visiting emergency department (ED), we conducted this study.From May 21 to August 12, 2009, a total of 502 adult patients visiting emergency department (ED) of a tertiary care hospital in northern Taiwan were recruited in this study and surveyed for nasal carriage of MRSA. A questionnaire regarding the risk factors for MRSA acquisition was also obtained. The overall prevalence of MRSA nasal carriage among the patients was 3.8%. The carriage rate was significantly higher in patients with risk factors for MRSA acquisition (5.94%) than those without risk factors (2.12%). Patients with urinary complaints, diabetes mellitus, chronic kidney disease and current percutaneous tube usage were significantly associated with MRSA colonization. By multiple logistic regression analysis, only current usage of catheters or tubes was the independent predictor for MRSA nasal colonization. Of the 19 MRSA, most isolates belonged to one of two linages, characterized as sequence type (ST) 239 (32%) and ST 59 (58%). The latter linage, accounting for 83% of 6 isolates from patients without risk factors, is a community-associated (CA) clone in Taiwan, while the former linage is among healthcare-associated clones.A substantial proportion of patients visiting ED, particularly with current usage of percutaneous catheter or tubes, in northern Taiwan carried MRSA, mostly community strains, in nares

EBV-positive Hodgkin lymphoma is associated with suppression of p21cip1/waf1 and a worse prognosis

<p>Abstract</p> <p>Background</p> <p>About 30-50% of Hodgkin lymphomas (HLs) harbor the Epstein-Barr virus (EBV), but the impact of EBV infection on clinical outcomes has been unclear. EBV-encoded small RNAs (<it>EBER</it>s) are presented in all EBV-infected cells, but their functions are still less understood.</p> <p>Results</p> <p><it>EBER1 </it>was transfected into two HL cell lines, KMH2 and L428, and microarrays were used to screen for <it>EBER1</it>-induced changes. We found that <it>EBER1 </it>suppressed <it>p21</it>^cip1/waf1transcription in HL cell lines. In addition, positive regulators of <it>p21</it>^cip1/waf1transcription, such as p53, EGR1, and STAT1, were decreased. Suppression of <it>p21</it>^cip1/waf1in the <it>EBER1</it>⁺HL cell lines was associated with increased resistance to histone deacetylase inhibitors or proteasome inhibitors, drugs known to cause apoptosis by increasing p21^cip1/waf1levels. On biopsy specimens, EBV⁺HLs had weaker expression of both p21^cip1/waf1and active caspase 3. Clinically, suppression of p21^cip1/waf1in EBV⁺HLs was associated with a worse 2-year disease-free survival rate (45% for EBV⁺HLs <it>vs</it>. 77% for EBV^-HLs, <it>p </it>= 0.002).</p> <p>Conclusion</p> <p>Although the underlying mechanisms are still relatively unclear, <it>EBER1 </it>inhibits <it>p21</it>^cip1/waf1transcription and prevents apoptosis through down-regulation of p53, EGR1, and STAT1. The anti-apoptotic activity of <it>EBER1 </it>may be important in the rescue of Reed-Sternberg cells from drug-induced apoptosis and in the clinical behaviors of EBV⁺HLs.</p