scholarly journals Gear Shape Parameter Measurement Using a Model-Based Scanning Multi-Distance Measurement Approach

Sensors ◽  
2020 ◽  
Vol 20 (14) ◽  
pp. 3910
Author(s):  
Marc Pillarz ◽  
Axel von Freyberg ◽  
Andreas Fischer
Keyword(s):  
Shape Parameter ◽  
Spur Gear ◽  
Distance Measurement ◽  
Measuring Instruments ◽  
Single Digit ◽  
Promising Alternative ◽  
Model Based ◽  
Base Circle ◽  
The Mean ◽  
Measurement Approach

To reduce wind turbine failures by defective drive trains, deviations in the geometry of large gears (diameter ≳ 1 m) must be extensively determined with single-digit micrometer uncertainties. Fixed measuring volumes limit standard measuring methods like coordinate and gear measuring instruments for large gear measurements. Therefore, a model-based scanning multi-distance measurement approach for gear shape parameters is presented. The measurement approach has a scalable design and consists of a confocal-chromatic sensor, rotary table as a scanning unit and model-based signal processing. A preliminary study on a midsize spur gear demonstrates the general feasibility of the model-based scanning multi-distance measurement approach. As a result, the mean base circle radius as the fundamental gear shape parameter is determined with an uncertainty of <5 μm. The calibration and adjustment of the sensor arrangement were performed with a known calibration gear. Scalability is not experimentally validated in this article. However, simulations verify the scalability of the measurement approach in a first step. For gears with 1 m in diameter and varying tooth flank geometries, the estimated achievable uncertainty of the mean base circle radius is still <5 μm. Therefore, the model-based scanning multi-distance measurement approach is a promising alternative for gear inspection.

scholarly journals Determination of the mean base circle radius of gears by optical multi-distance measurements

2020 ◽  
Vol 9 (2) ◽  
pp. 273-282
Author(s):  
Marc Pillarz ◽  
Axel von Freyberg ◽  
Andreas Fischer
Keyword(s):  
Measurement Uncertainty ◽  
Random Errors ◽  
Shape Parameters ◽  
Distance Measurements ◽  
Total Uncertainty ◽  
Large Gear ◽  
Base Circle ◽  
Single Sensor ◽  
The Mean ◽  
Measurement Approach

Abstract. The required reliability of wind turbine gearboxes increases the requirements for large gear measurements. Extensive measurements to reliably assess the geometry of large gears in the single micrometer range are necessary. Due to an individually fixed measuring volume, standard methods like coordinate and gear measuring instruments reach their limits for large gears with diameters > 1 m. Therefore, a scalable optical measurement approach consisting of a single sensor in combination with a rotary table for multi-distance measurements with subsequent model-based evaluation of shape parameters of gears is presented. The scalable measurement approach is to be extended to a multisensory system in further work. As a fundamental shape parameter the mean base circle radius using the example of spur gears is determined. The base circle radius is used due to the geometric relationship to further shape parameters for example to the profile slope deviation. The theoretically achievable measurement uncertainty of the mean base circle radius due to sensor noise is estimated to less than 5 µm (k=2) for a small and a large gear, which verifies the scalability of the sensor system. In order to show a general proof of principle, two series of optical measurements on a gear with a diameter of 0.105 m are performed and referenced with a tactile measurement. As a result, random errors of 1.2 µm for k=2 are determined. The remaining systematic deviations to the reference value amount to 4.3 and 1.6 µm, respectively. Hence, the total measurement uncertainty is currently limited by systematic effects, and the defined aim of a total uncertainty of less than 5 µm (k=2) is narrowly missed by 1.5 µm. The random errors of 1.2 µm (k=2) show, however, that an adequate measurement precision is achieved and that the multi-distance measurement approach has the potential to reach the aimed measurement uncertainty with appropriate strategies to compensate for the systematic influences. The experimental and theoretical results prove the principle applicability of the proposed single sensor multi-distance approach for the precise inspection of gears.

Maximum Total Point Motion of Five Points Versus All Points in Assessing Tibial Baseplate Stability

2021 ◽  
Author(s):  
Abigail Niesen ◽  
Anna L Garverick ◽  
Maury Hull
Keyword(s):  
Degrees Of Freedom ◽  
Stability Limit ◽  
3D Models ◽  
Six Degrees Of Freedom ◽  
Percent Error ◽  
Model Based ◽  
Point Motion ◽  
The Mean ◽  
The Difference ◽  
Total Point

Abstract Maximum total point motion (MTPM), the point on a baseplate that migrates the most, has been used to assess the risk of tibial baseplate loosening using radiostereometric analysis (RSA). Two methods for determining MTPM for model-based RSA are to use either 5 points distributed around the perimeter of the baseplate or to use all points on the 3D model. The objectives were to quantify the mean difference in MTPM using 5 points vs. all points, compute the percent error relative to the 6-month stability limit for groups of patients, and to determine the dependency of differences in MTPM on baseplate size and shape. A dataset of 10,000 migration values was generated using the mean and standard deviation of migration in six degrees of freedom at 6 months from an RSA study. The dataset was used to simulate migration of 3D models (two baseplate shapes and two baseplate sizes) and calculate the difference in MTPM using 5 virtual points vs. all points and the percent error (i.e. difference in MTPM/stability limit) relative to the 6-month stability limit. The difference in MTPM was about 0.02 mm, or 4% percent relative to the 6-month stability limit, which is not clinically important. Furthermore, results were not affected by baseplate shape or size. Researchers can decide whether to use 5 points or all points when computing MTPM for model-based RSA. The authors recommend using 5 points to maintain consistency with marker-based RSA.

scholarly journals On double stage minimax-shrinkage estimator for generalized Rayleigh model

2016 ◽  
Vol 5 (1) ◽  
pp. 39 ◽  
Author(s):  
Abbas Najim Salman ◽  
Maymona Ameen
Keyword(s):  
Sample Size ◽  
Shape Parameter ◽  
Mean Squared Error ◽  
Scale Parameter ◽  
Rayleigh Distribution ◽  
Shrinkage Estimator ◽  
Squared Error ◽  
Expected Sample Size ◽  
Generalized Rayleigh Distribution ◽  
The Mean

<p>This paper is concerned with minimax shrinkage estimator using double stage shrinkage technique for lowering the mean squared error, intended for estimate the shape parameter (a) of Generalized Rayleigh distribution in a region (R) around available prior knowledge (a<sub>0</sub>) about the actual value (a) as initial estimate in case when the scale parameter (l) is known .</p><p>In situation where the experimentations are time consuming or very costly, a double stage procedure can be used to reduce the expected sample size needed to obtain the estimator.</p><p>The proposed estimator is shown to have smaller mean squared error for certain choice of the shrinkage weight factor y(<strong>×</strong>) and suitable region R.</p><p>Expressions for Bias, Mean squared error (MSE), Expected sample size [E (n/a, R)], Expected sample size proportion [E(n/a,R)/n], probability for avoiding the second sample and percentage of overall sample saved  for the proposed estimator are derived.</p><p>Numerical results and conclusions for the expressions mentioned above were displayed when the consider estimator are testimator of level of significanceD.</p><p>Comparisons with the minimax estimator and with the most recent studies were made to shown the effectiveness of the proposed estimator.</p>

scholarly journals Factors Affecting Radiation Dose in Computed Tomography Angiograms for Pulmonary Embolism: A Retrospective Cohort Study

2020 ◽  
Vol 10 ◽  
pp. 74
Author(s):  
Prashant Nagpal ◽  
Sarv Priya ◽  
Ali Eskandari ◽  
Aidan Mullan ◽  
Tanya Aggarwal ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Pulmonary Embolism ◽  
Radiation Dose ◽  
Care Center ◽  
Tertiary Care ◽  
Multivariate Logistic Regression Analysis ◽  
Factors Affecting ◽  
Model Based ◽  
Pulmonary Angiogram ◽  
The Mean

Objectives: Computed tomography pulmonary angiogram (CTPA) is one of the most commonly ordered and frequently overused tests. The purpose of this study was to evaluate the mean radiation dose to patients getting CTPA and to identify factors that are associated with higher dose. Material and Methods: This institutionally approved retrospective study included all patients who had a CTPA to rule out acute pulmonary embolism between 2016 and 2018 in a tertiary care center. Patient data (age, sex, body mass index [BMI], and patient location), CT scanner type, image reconstruction methodology, and radiation dose parameters (dose-length product [DLP]) were recorded. Effective dose estimates were obtained by multiplying DLP by conversion coefficient (0.014 mSv•mGy−1•cm−1). Multivariate logistic regression analysis was performed to determine the factors affecting the radiation dose. Results: There were 2342 patients (1099 men and 1243 women) with a mean age of 58.1 years (range 0.2–104.4 years) and BMI of 31.3 kg/m2 (range 12–91.5 kg/m2). The mean effective radiation dose was 5.512 mSv (median – 4.27 mSv; range 0.1–43.0 mSv). Patient factors, including BMI >25 kg/m2, male sex, age >18 years, and intensive care unit (ICU) location, were associated with significantly higher dose (P < 0.05). CT scanning using third generation dual-source scanner with model-based iterative reconstruction (IR) had significantly lower dose (mean: 4.90 mSv) versus single-source (64-slice) scanner with filtered back projection (mean: 9.29 mSv, P < 0.001). Conclusion: Patients with high BMI and ICU referrals are associated with high CT radiation dose. They are most likely to benefit by scanning on newer generation scanner using advance model-based IR techniques.

Comparison of Three Different Screw Trajectories in Osteoporotic Vertebrae: A Biomechanical Investigation

2020 ◽  
Author(s):  
Jan-Sven Jarvers ◽  
Stefan Schleifenbaum ◽  
Christian Pfeifle ◽  
Christoph Oefner ◽  
Melanie Edel ◽  
...  
Keyword(s):  
Cortical Bone ◽  
Fatigue Behavior ◽  
Fixation Strength ◽  
Patient Specific ◽  
Promising Alternative ◽  
Cortical Bone Trajectory ◽  
Pull Out ◽  
Group A ◽  
The Mean ◽  
Group B

Abstract Background: Pedicle screw insertion in osteoporotic patients is challenging. Achieving more screw-cortical bone purchase and invasiveness minimization, the cortical bone trajectory and the midline cortical techniques represent alternatives to traditional pedicle screws. This study compares the fatigue behavior and fixation strength of the cement-augmented traditional trajectory (TT), the cortical bone trajectory (CBT) and the midline cortical (MC). Methods: Ten human cadaveric spine specimens (L1 - L5) were examined. The average age was 86.3 ± 7.2 years. CT scans were provided for preoperative planning. CBT and MC were implanted by using the patient-specific 3D-printed placement guide (MySpine®, Medacta International), TT were implanted freehand. All 10 cadaveric specimens were randomized to group A (CBT vs. MC) or group B (MC vs. TT). Each screw was loaded for 10,000 cycles. The failure criterion was doubling of the initial screw displacement resulting from the compressive force (60 N) at the first cycle, the stop criterion as a doubling of the initial screw displacement. After dynamic testing, screws were pulled out axially at 5 mm/min to determine their remaining fixation strength. Results: The mean pull-out forces did not differ significantly. Concerning the fatigue performance, only one out of ten MC of group A failed prematurely due to loosening after 1,500 cycles (L3). Five CBT already loosened during the first 500 cycles. The mean displacement was always lower in the MC. In group B, all TT showed no signs of failure or loosening. Three MC failed already after 26 cycles, 1,510 cycles, and 2,144 cycles, respectively. The TT showed always a lower mean displacement. In the subsequent pull-out tests, the remaining mean fixation strength of the MC (449.6 ± 298.9 N) was slightly higher compared to the mean pull-out force of the CBT (401.2 ± 261.4 N). However, MC (714.5 ± 488.0 N) were inferior to TT (990.2 ± 451.9 N).Conclusion: The current study demonstrated that cement-augmented TT have best fatigue and pull-out characteristics in osteoporotic lumbar vertebrae, followed by the MC and CBT. MC represent a promising alternative in osteoporotic bone if cement augmentation should be avoided. Using the patient-specific guide contributes to improve screws’ biomechanical properties.

scholarly journals High-Precision Distance Measurement with an unmanned, Moving Target

1986 ◽  
Vol 8 ◽  
pp. 93-95
Author(s):  
H. Ito ◽  
K. Schroff ◽  
Hans-jörg Frei
Keyword(s):  
Sea Ice ◽  
High Precision ◽  
Distance Measurement ◽  
Moving Object ◽  
Measuring Instruments ◽  
Moving Target ◽  
Personnel Cost ◽  
Greenland Sea ◽  
Single Station ◽  
Set Up

A device was developed, which rotates a marker for the distance measurement in the desired direction, without an operator at the spot. This is also possible with a moving object, on which the marker is set up. The device, together with adequate distance-measuring instruments, yields a precise distance measurement by a single observer at a single station. Examples of measurements using it during sea-ice studies in the Greenland Sea are described. It is shown that the application of the instrument provides a satisfactory basis for precise glacier surveying with limited personnel, cost, and time.

scholarly journals Hybrid Operating Room System for the Treatment of Thoracic and Abdominal Aortic Aneurysms: Evaluation of the Radiation Dose Received by Patients

Diagnostics ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 846
Author(s):  
Yoshihiro Haga ◽  
Koichi Chida ◽  
Masahiro Sota ◽  
Yuji Kaga ◽  
Mitsuya Abe ◽  
...  
Keyword(s):  
Radiation Dose ◽  
Operating Room ◽  
Radiation Effects ◽  
Aortic Aneurysms ◽  
Endovascular Aortic Repair ◽  
Hybrid Operating Room ◽  
Promising Alternative ◽  
Dose Area Product ◽  
Aortic Repair ◽  
The Mean

In recent years, endovascular treatment of aortic aneurysms has attracted considerable attention as a promising alternative to traditional surgery. Hybrid operating room systems (HORSs) are increasingly being used to perform endovascular procedures. The clinical benefits of endovascular treatments using HORSs are very clear, and these procedures are increasing in number. In procedures such as thoracic endovascular aortic repair (TEVAR) and endovascular aortic repair (EVAR), wires and catheters are used to deliver and deploy the stent graft in the thoracic/abdominal aorta under fluoroscopic control, including DSA. Thus, the radiation dose to the patient is an important issue. We determined radiation dose indicators (the dose–area product (DAP) and air karma (AK) parameters) associated with endovascular treatments (EVAR and TEVAR) using a HORS. As a result, the mean ± standard deviation (SD) DAPs of TEVAR and EVAR were 323.7 ± 161.0 and 371.3 ± 186.0 Gy × cm2, respectively. The mean ± SD AKs of TEVAR and EVAR were 0.92 ± 0.44 and 1.11 ± 0.54 Gy, respectively. The mean ± SD fluoroscopy times of TEVAR and EVAR were 13.4 ± 7.1 and 23.2 ± 11.7 min, respectively. Patient radiation dose results in this study of endovascular treatments using HORSs showed no deterministic radiation effects, such as skin injuries. However, radiation exposure during TEVAR and EVAR cannot be ignored. The radiation dose should be evaluated in HORSs during endovascular treatments. Reducing/optimizing the radiation dose to the patient in HORSs is important.

Prediction of bottom dynamic conditions in coastal waters

1995 ◽  
Vol 46 (1) ◽  
pp. 359 ◽  
Author(s):  
J Persson ◽  
L Hakanson
Keyword(s):  
Coastal Areas ◽  
Model Parameters ◽  
Direct Connection ◽  
Digital Technique ◽  
Computer Data ◽  
Dynamic Conditions ◽  
Model Based ◽  
Open Sea ◽  
The Mean ◽  
The Impact

Bottom dynamic conditions (areas of accumulation, erosion or transportation) in aquatic ecosystems influence the dispersal, sedimentation and recirculation of most substances, such as metals, organic toxins and nutrients. The aim of the present work was to establish a simple and general method to predict sediment types/bottom dynamic conditions in Baltic coastal areas. As a working hypothesis, it is proposed that the morphometry and the absence or presence of an archipelago outside a given coastal area regulate what factors determine the prevailing bottom dynamic conditions. Empirical data on the proportion of accumulation bottoms (BA) were collected from 38 relatively small (1-14 km²) and enclosed coastal areas in the Baltic Sea. Morphometric data were obtained by using a digital technique to transfer information from standard bathymetric maps into a computer. Data were processed by means of multivariate statistical methods. In the first model, based on data from all 38 areas, 55% of the variation in BA among the areas was statistically explained by five morphometric parameters. The data set was then divided into two parts: areas in direct connection with the open sea, and areas inside an archipelago. In the second model, based on data from 15 areas in direct connection with the open sea, 77% of the variation in BA was statistically explained by the mean depth of the deep water (the water mass below 10 m) and the mean slope. In the third model, based on data from 23 areas inside an archipelago, 70% of the variation in BA was statistically explained by the mean slope, the topographic form factor, the proportion of islands and the mean filter factor (which is a relative measure of the impact of winds and waves from outside the area). The model parameters describe the sediment trapping capacity of the areas investigated.

scholarly journals Relationships Between Vein Repairs, Postoperative Transfusions, and Survival in Single Digit Replantation

Hand ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 488-494
Author(s):  
Michael T. Milone ◽  
Christopher S. Klifto ◽  
Z-Hye Lee ◽  
Vishal Thanik ◽  
Jacques H. Hacquebord
Keyword(s):  
Survival Rates ◽  
Proximal Phalanx ◽  
Common Mechanism ◽  
Traditional Teaching ◽  
Venous Outflow ◽  
Single Digit ◽  
Patient Demographics ◽  
Transfusion Requirements ◽  
Arterial Anastomosis ◽  
The Mean

Background: The general teaching is that increased number of vein repairs in digit replantation leads to improved venous outflow, resulting in lower need for iatrogenic bleeding, lower postoperative transfusion requirements, and better survival rates. The purpose of this study was to determine whether the traditional teaching that emphasizes the repair of multiple veins per arterial anastomosis results in superior survival rates. Methods: A retrospective review of a single urban replant center’s single-digit replants distal to the mid-metacarpal level in adult patients from 2007 to 2017 was performed. Data on patient demographics, mechanism and level of injury, veins repaired, iatrogenic bleeding, postoperative transfusions, and replant survival were obtained. Results: There were a total of 54 single-digit replants. The most common mechanism was lacerations (N = 38), and the most common injury level was at the proximal phalanx (N = 21). All digits were replanted with a single arterial anastomosis—44% via grafting. In all, 0 to 3 veins were repaired per digit (mean = 1.5 veins). The mean transfusion requirement was 1.7 units. The survival rate was 50%. Digits with 1 or 2 veins repaired had lower transfusion requirements (1.1-1.3 units) and higher survival rates (56%-61%) compared with those replanted with 0 or 3 veins repaired (2.9-3.5 transfused units, 25%-29% survival). There were no differences between those digits replanted with either 1 or 2 veins repaired for transfusion requirements or survival. Conclusions: More veins repaired do not necessarily improve survival or possibly venous outflow, calling into question the traditional teaching that 2 veins should be repaired for every arterial anastomosis.

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