PERFORMANCE ANALYSIS AND KINEMATIC DESIGN OF PURE TRANSLATIONAL PARALLEL MECHANISM WITH VERTICAL GUIDE-WAYS

Performance analysis and kinematic design of the 3-PUU pure translational parallel mechanism with vertical guide-ways are investigated. Two novel performance indices, the critical slider stroke and the main section area of workspace, are defined; The expressions of two other indices, i.e. the global dexterity and global force transfer ratio are revised based on the main section of workspace. Using these indices, performance changes versus the varieties of dimensional parameters of mechanism are investigated in detail and the graphic descriptions of change tendencies of the performance indices are illustrated. By means of these obtained graphic descriptions, kinematic parameters for the 3-PUU pure translational parallel mechanism with better characteristics can be directly acquired.

KINEMATIC DESIGN OF A RECONFIGURABLE MINIATURE PARALLEL KINEMATIC MACHINE

The kinematic design of a reconfigurable miniature parallel kinematic machineis dealt with. It shows that the reconfigurability may be realized by packaging a tripod-basedparallel mechanism with fixed length struts into a compact and rigid frame with which the differentconfigurations can be formed. Utilizing a dual parameter model, the influences of the geometricalparameters on the dexterous performance and the workspace/machine volume ratio are investigated. Anovel global performance index for the dimensional synthesis is proposed and optimized, resulting ina set of dimensionless geometrical parameters.

Mid-term outcomes of a kinematically designed cruciate retaining total knee arthroplasty

BACKGROUND Advances in implant material and design have allowed for improvements in total knee arthroplasty(TKA)outcomes.A cruciate retaining(CR)TKA provides the least constraint of TKA designs by preserving the native posterior cruciate ligament.Limited research exists that has examined clinical outcomes or patient reported outcome measures(PROMs)of a large cohort of patients undergoing a CR TKA utilizing a kinematically designed implant.It was hypothesized that the studied CR Knee System would demonstrate favorable outcomes and a clinically significant improvement in pain and functional scores.AIM To assess both short-term and mid-term clinical outcomes and PROMs of a novel CR TKA design.METHODS A retrospective,multi-surgeon study identified 255 knees undergoing a TKA utilizing a kinematically designed CR Knee System(JOURNEY™II CR;Smith and Nephew,Inc.,Memphis,TN)at an urban,academic medical institution between March 2015 and July 2021 with a minimum of two-years of clinical follow-up with an orthopedic surgeon.Patient demographics,surgical information,clinical outcomes,and PROMs data were collected via query of electronic medical records.The PROMs collected in the present study included the Knee Injury and Osteoarthritis Outcome Score for Joint Replacement(KOOS JR)and Patient-Reported Outcomes Measurement Information System(PROMIS■)scores.The significance of improvements in mean PROM scores from preoperative scores to scores collected at six months and two-years postoperatively was analyzed using Independent Samples t-tests.RESULTS Of the 255 patients,65.5%were female,43.8%were White,and patients had an average age of 60.6 years.Primary osteoarthritis(96.9%)was the most common primary diagnosis.The mean surgical time was 105.3 minutes and mean length of stay was 2.1 d with most patients discharged home(92.5%).There were 18 emergency department(ED)visits within 90 d of surgery resulting in a 90 d ED visit rate of 7.1%,including a 2.4%orthopedic-related ED visit rate and a 4.7%non-orthopedic-related ED visit rate.There were three(1.2%)hospital readmissions within 90 d postoperatively.With a mean time to latest follow-up of 3.3 years,four patients(1.6%)required revision,two for arthrofibrosis,one for aseptic femoral loosening,and one for peri-prosthetic joint infection.There were significant improvements in KOOS JR,PROMIS Pain Intensity,PROMIS Pain Interference,PROMIS Mobility,and PROMIS Physical Health from preoperative scores to six month and two-year postoperative scores.CONCLUSION The evaluated implant is an effective,novel design offering excellent outcomes and low complication rates.At a mean follow up of 3.3 years,four patients required revisions,three aseptic and one septic,resulting in an overall implant survival rate of 98.4%and an aseptic survival rate of 98.8%.The results of our study demonstrate the utility of this kinematically designed implant in the setting of primary TKA.

A New Type of Waveguide Distribution for the Accelerator Module Test Facility of the European XFEL

The European XFEL, which has been constructed at DESY in Hamburg, Germany, is an X-ray-Free Electron Laser, which provides X-ray light of unprecedented properties for different experiments in physics, chemistry, biology and technology [1]. The XFEL is based on superconducting cavity technology, which is required to accelerate an electron beam up to 17.5 GeV. The facility is installed about 20 m underground in a 3.4 km long tunnel of 5.2 m diameter. High power RF systems are required to accelerate the beam to the required energy. Each RF station provides RF power to 4 accelerator modules with 8 superconducting cavities by a waveguide RF distribution system [2, 3]. Besides electrical and RF properties, mechanical properties are of high importance, since the waveguide distribution system and its components have to be manufactured, assembled and aligned with high precision. In order to test 100 superconducting accelerator modules within two years three test benches have been created in the AMTF （accelerator module test facility） to achieve the rate of one superconducting module per week. Each RF station of the test facility consists ofa 5 MW RF station at 1.3 GHz, 1.37 ms pulse width and 10 Hz repetition rate, with a waveguide distribution system. Each waveguide distribution supplies RF power to eight cavities, four times a pair of cavities. The distribution allows for a maximum power of 1 MW per cavity when the distribution is switched to a mode supplying power to only four cavities. A new type of 1 MW isolator and a new compact 5 MW power divider have been developed to achieve that goal. We present the waveguide distribution for this test stand and describe the performance of the different elements.

Two-dimensional piston pump: Principle, design,and testing for aviation fuel pumps

Aviation fuel pumps of the future are required to be highly efficient and lightweight.As such,this work presents the designs of various mechanisms and structures of advanced twodimensional piston pumps for aero-engines,and their universal kinematic design methods are detailed herein.The efficiency of various piston pump prototypes was experimentally tested at various speeds in an open circuit.The experimental results indicate that two-dimensional piston pumps have a volumetric efficiency>91%and a higher power–mass ratio than conventional fuel pumps under all the conditions studied.Furthermore,the structural and material problems encountered during testing can provide a blueprint for further improvement of the design and processing of two-dimensional piston fuel pumps.