Torsional Measurements Research Articles

Simultaneous Measurement of Torsion and Temperature Based on π-Phase-Shifted Long-Period Fiber Grating Inscribed on Double-Clad Fiber.

In this work, we experimentally demonstrated an optical fiber sensor capable of performing simultaneous measurement of torsion and temperature using a π-phase-shifted long-period fiber grating (LPFG) inscribed on double-clad fiber (DCF), referred to as a PS-DC-LPFG. The fabricated PSDC- LPFG showed split attenuation bands near its resonance wavelength, and the two dips in these bands were selected as sensor indicators, denoted as Dips A and B, for the simultaneous measurement of torsion and temperature. The torsion and temperature responses of the two indicators were investigated in a twist angle range from -360° to 360° and a temperature range from 30 to 120 °C, respectively. When the twist angle increased from 0° to 360° (clockwise) at room temperature, both Dips A and B showed redshifts. On the contrary, when the twist angle decreased from 0° to -360° (counterclockwise), the two dips showed blueshifts. In terms of temperature responses, both dips showed redshifts with increasing ambient temperature while the sensor head (i.e., the PS-DC-LPFG) remained straight without any applied torsion. Owing to their linear and independent responses to torsion and temperature, the changes in torsion and temperature applied to the PSDC- LPFG could be simultaneously estimated from the measured wavelength shifts and calculated sensitivities of the two indicator dips.

High sensitivity directional torsion sensor based on double-helix long-period grating in tapered polarization-maintaining fiber

We propose a fiber torsion sensor based on double-helix long-period grating (DH-LPG) written in a tapered polarization-maintaining fiber (PMF). A series of DH-LPGs were fabricated in the tapered PMFs with waist diameters of 85 to 67 μm by a CO2-laser heating and twisting system. The torsion, temperature and surrounding refractive index sensing characteristics were investigated experimentally. Thanks to the special structures combined DH-LPGs with tapered PMFs, the proposed sensor can realize directional torsion measurement. The maximum torsion sensitivity of the proposed grating could be up to -2.28 nm/(rad/m) when the tapered waist diameter was 67 μm. The DH-LPGs have potential application in field of all-fiber high sensitivity directional torsion sensing.

Biomechanical evaluation of an intramedullary clavicle screw in simple oblique and butterfly wedge fractures.

This biomechanical study evaluates the performance of a solid titanium-alloy intra-medullary (IM) clavicular screw in torsion and cantilever bending in cadaveric clavicle specimens with simulated simple oblique and butterfly wedge midshaft fractures. Thirty-two fresh-frozen male clavicles were sorted into six experimental groups: Torsion Control, Torsion Simple Oblique Fracture, Torsion Butterfly Wedge Fracture, Bending Control, Bending Simple Oblique Fracture, and Bending Butterfly Wedge Fracture. The experimental groups were controlled for density, length, diameter, and laterality. All other samples were osteotomy-induced and implanted with a single 90 mm × 3 mm clavicle screw. All groups were tested to physiologically relevant cutoff points in torsion or bending. There were no statistically significant differences in the performance of the oblique and butterfly wedge fracture models for any torsion or bend testing measures, including maximum torsional resistance (p = 0.66), torsional stiffness (p = 0.51), maximum bending moment (p = 0.43), or bending stiffness (p = 0.73). Torsional testing of samples in the direction of thread tightening tended to be stronger than samples tested in loosening, with all groups either approaching or achieving statistical significance. There were no significant differences between the simple oblique or the butterfly-wedge fracture groups for any of the tested parameters, suggesting that there is no difference in the gross biomechanical properties of the bone-implant construct when the IM clavicle screw is used in either a simple midshaft fracture pattern or a more complex butterfly wedge fracture pattern.

Radiation Dose Reduction in CT Torsion Measurement of the Lower Limb: Introduction of a New Ultra-Low Dose Protocol.

This study analyzed the radiation exposure of a new ultra-low dose (ULD) protocol compared to a high-quality (HQ) protocol for CT-torsion measurement of the lower limb. The analyzed patients (n = 60) were examined in the period March to October 2019. In total, 30 consecutive patients were examined with the HQ and 30 consecutive patients with the new ULD protocol comprising automatic tube voltage selection, automatic exposure control, and iterative image reconstruction algorithms. Radiation dose parameters as well as the contrast-to-noise ratio (CNR) and diagnostic confidence (DC; rated by two radiologists) were analyzed and potential predictor variables, such as body mass index and body volume, were assessed. The new ULD protocol resulted in significantly lower radiation dose parameters, with a reduction of the median total dose equivalent to 0.17 mSv in the ULD protocol compared to 4.37 mSv in the HQ protocol (p < 0.001). Both groups showed no significant differences in regard to other parameters (p = 0.344–0.923). CNR was 12.2% lower using the new ULD protocol (p = 0.033). DC was rated best by both readers in every HQ CT and in every ULD CT. The new ULD protocol for CT-torsion measurement of the lower limb resulted in a 96% decrease of radiation exposure down to the level of a single pelvic radiograph while maintaining good image quality.

Development and implementation on torsional vibration measurement of rotational machinery’s shaft

The measurement and analysis on torsional vibration is an important aspect to research the performance state of rotating machinery’s shaft. This paper introduces the basic procedure of torsional vibration measurement, deduces the manifestation of torsional vibration signal, focuses on the hardware design and software implementation of torsional vibration measurement system, and applies the measurement system to a certain type of ship and steam turbine generator shaft in actual testing. The measurement results verify the practicability and accuracy of the system.

Non-invasive recognition of eye torsion through optical imaging of the iris pattern in ocular proton therapy

The introduction of non-invasive imaging techniques such as MRI imaging for treatment planning and optical eye tracking for in-room eye localization would obviate the requirement of clips implantation for many patients undergoing ocular proton therapy. This study specifically addresses the issue of torsional eye movement detection during patient positioning. Non-invasive detection of eye torsion is performed by measuring the iris pattern rotations using a beams eye view optical camera. When handling images of patients to be treated using proton therapy, a number of additional challenges are encountered, such as changing eye position, pupil dilatation and illumination. A method is proposed to address these extra challenges while also compensating for the effect of cornea distortion in eye torsion computation. The accuracy of the proposed algorithm was evaluated against corresponding measurement of eye torsion using the clips configuration measured on x-ray images. This study involves twenty patients who received ocular proton therapy at Paul Scherrer Institute and it is covered by ethical approval (EKNZ 2019-01987).

Torsional vibration test and analysis of an internal combustion engine power assembly by RLV-5500

The vibration characteristics of marine power plant and propulsion system shafting directly affect the navigation safety of the ship. Shafting torsional vibration is an important parameter to evaluate the stability and reliability of shafting. The demand of ship shafting torsional vibration measurement is gradually developing towards high resolution and high accuracy. According to the characteristics of ship shafting installation and operation, this paper selects an internal combustion engine powertrain as the test object, and uses rlv-5500 rotary laser vibration measurement system to test the shafting torsional vibration. The time-frequency analysis of the test results is carried out to calculate the comprehensive angular displacement and the angular displacement amplitude of each harmonic order. The maximum comprehensive amplitude of crankshaft free end torsional vibration is 0.33 °. The crankshaft will not be damaged by torsional vibration.

Multifunctional fiber-optic sensor, based on helix structure and fiber Bragg gratings, for shape sensing

In order to realize the simultaneous measurement of directional torsion and vector bending, a multifunctional fiber-optic sensor, based on helical-twisted-structure-assisted fiber Bragg gratings (HTSA-FBGs) on a triangular four-core fiber (TFCF), is proposed. The helical-twisted region (HTR) was fabricated using CO2 laser beam. FBGs were prepared in the HTR of the TFCF cores through the defocusing phase mask method. The sensing mechanism of directional torsion and vector bending was analyzed. The influence of temperature and strain can be eliminated by subtracting the wavelength change of the central core HTSA-FBG from the wavelength change of the side core HTSA-FBGs, so shape accuracy can be improved. The torsion sensitivity can be changed by adjusting the pitch of the HTR.

Theoretical and experimental study of wind turbine drivetrain fault diagnosis by using torsional vibrations and modal estimation

This paper provides an analytical proof and the theoretical development of the idea of using the torsional vibration measurements for a system-level condition monitoring of the drivetrain system. The method relies on modal parameter estimation of the drivetrain system by using the torsional measurements and subsequent monitoring of the variations in the system eigenfrequencies and normal modes. Angular velocity error function extracted from encoder outputs at both input and output of drivetrain is used to estimate modal parameters including natural frequencies and damping coefficients. In the proposed condition monitoring approach, it is shown that any abnormal deviation from the reference values of the drivetrain system dynamic properties can be translated into the progression of a specific fault in the system. In order to extract the condition monitoring features, local sensitivity analysis is engaged to establish a relationship between different categories of drivetrain faults with the system dynamic properties and the amplitude of torsional response, which helps with both to identify the state of the progressive faults and to localize them. Local sensitive analysis shows that abnormal deviations in stiffness and moment of inertia due to the presence of faults result in considerable changes in natural frequencies and modal responses which can be measured and used as fault detecting features by using the proposed analytical approach. Sensitivity analysis is also employed along with the estimated modal frequency for estimation of modal damping from the amplitude of response at the natural frequencies and their subsequent use for estimation of undamped natural frequencies which are later used in the proposed condition monitoring approach. The proposed approach is computationally inexpensive and can be implemented without additional instrumentation. Two test cases, using 10 MW simulated and 1.75 MW operational drivetrains have been demonstrated.

Simultaneous measurement of directional torsion and temperature by using a DC-sampled helical long-period fiber grating

A new approach based on the utilization of a DC-sampled helical long-period fiber grating (DCSHLPG), enabling the simultaneous measurement of the directional torsion and ambient temperature is proposed and demonstrated. The DCSHLPG is fabricated by specially designed CO2-Laser processing platform which supports both sapphire-tube based fiber twisting and point-by-point grating writing technique. By adopting the proposed method, the crosstalk effects between the temperature and the torsion can be well discriminated, and both the torsion amounts and the torsion direction can be measured simultaneously. Moreover, the proposed sensor has competitive sensing sensitivity and low-cost. Resolutions of the torsion and temperature obtained in this study are estimated to be 0.49°at a torsion angle ranging from −360° to + 360° and 0.08 °C in a temperature ranging from 24 °C to 100 °C, respectively.

Outcomes of the Harada–Ito Procedure

ABSTRACT Purpose Fell’s modification of the Harada–Ito (HI) procedure is often used to tackle subjective torsion usually following superior oblique palsy. There is limited published data on the longer-term outcomes and the effect on horizontal incomitance of the procedure. The purpose of this study is to report on the medium to long-term outcomes of the HI procedure. Materials and methods A retrospective review of 20 patients who had all undergone a single surgeon modified HI procedure to correct subjective torsion was undertaken. Follow-up data were analyzed in relation to stability of torsion measurements, the effect on vertical incomitance of horizontal deviation and the final treatment outcome. Results There was a significant reduction in median maximum torsion from preoperative to immediately post-op (p < .01) and there remained a significant difference in maximum torsion from preoperative measurement at both the 3-month (p = .02), and 12-twelve month (p = .01) follow-up. HI had a significant effect on associated V-pattern esotropia (p < .05). Conclusion The HI procedure is effective in eliminating subjective torsion initially and reducing incomitant horizontal deviation; however, regression toward preoperative torsion measurement occurs after time.

Polarization-insensitive Simultaneous Measurement of Torsion and Temperature Using Long-period Fiber Grating Written on Polarization-maintaining Photonic Crystal Fiber

Polarization-insensitive Simultaneous Measurement of Torsion and Temperature Using Long-period Fiber Grating Written on Polarization-maintaining Photonic Crystal Fiber

Supracondylar rotation osteotomy of the femur influences the coronal alignment of the ankle

PurposeOsteotomies represent well-established treatment-options for the redistribution of loads and forces within and around the knee-joint. Effects of these osteotomies on the remaining planes and adjacent joints are not fully understood. The aim of this study was to determine the influence of a distal-femoral-rotation-osteotomy on the coronal alignment of the ankle. It was hypothesized that supracondylar-external-rotation-osteotomy of the distal femur leads to a change in the coronal orientation of the ankle joint.MethodsLong-leg standing radiographs and CT-based torsional measurements of 27 patients undergoing supracondylar-rotational-osteotomy of the femur between 2012 and 2019 were obtained and utilized for the purpose of this study. Postoperative radiographs were obtained after union at the osteotomy-site. The hip-knee-ankle-angle (HKA), the mechanical-lateral-distal-femur-angle (mLDFA), and Tibia-Plafond-Horizontal-Orientation-Angle (TPHA) around the ankle were measured. Comparison between means was performed using the Wilcoxon-Mann–Whitney test.ResultsTwenty-seven patients with high femoral antetorsion (31.3° ± 4.0°) underwent supracondylar-external-rotation-osteotomy. The osteotomy led to a reduced antetorsion (17.4 ± 5.1; p < 0.001) and to a valgisation of the overall limb-alignment. The HKA decreased by 2.4° ± 1.4° (p < 0.001). The TPHA decreased by 2.6° (p < 0.001).ConclusionsSupracondylar external rotation osteotomy of the femur leads to lateralization of the weight bearing line at the knee and ankle due to valgisation of the coronal limb alignment. The mobile subtalar joint has to compensate (inversion) for the resulting valgus orientation of the ankle to ensure contact between the foot and the floor. When planning a rotational osteotomy of the lower limb, this should be appreciated – especially in patients with a preexisting valgus alignment of the lower extremities or restricted mobility in the subtalar joint.

A torsional thrust stand for measuring the thrust response time of micro-Newton thrusters

Drag-free technology functions as the keystone for space-based gravitational wave detection satellites moving along a geodesic path, like the Laser Interferometer Space Antenna (LISA) Pathfinder, to achieve ultra-high microgravity level. Several prerequisites for micro-thrusters operated under the drag-free technique include constantly adjustable thrust, high resolution, low noise and fast response time. Accordingly, a torsional thrust measurement system was methodically devised to measure the thrust response time of such micro-thrusters on the ground. The characteristics of the dynamic thrust change with time are inverted by the angular displacement of the torsional pendulum, established by the dynamic equation of the same, thus, measuring the rise/fall time of the thrust applied to the torsional pendulum. Calibration of the torsional pendulum thrust measurement system is carried out by the standard electrostatic force generated by the electrostatic comb-drive or microelectromechanical actuator, facilitating the suitable identification of the pendulum parameters. Afterwards, the electrostatic and electromagnetic forces generated by the actuator are applied to validate the measurable thrust response time of the torsional thrust stand. The experimental results show that the above-mentioned thrust stand can effectively measure the thrust response time up to 10 ms for a thrust step in 10 s of micronewtons, which qualifies as the thrust response time required by micro-thrusters for space-based gravitational wave detection.

Comparison of Subjective and Objective Torsion in Normal Patients.

To compare subjective and objective torsion in normal individuals. A total of 59 individuals (118 eyes) were recruited from one ophthalmology institute in New South Wales, Australia. Objective torsion was measured with optical coherence tomography (OCT) (Heidelberg Engineering) and subjective torsion measurements were obtained with the Torsionometer (INNOVA). Kendall's tau correlation coefficient when comparing the Torsionometer to combined left and right OCT measurements was 0.115 (95% CI: -0.085 to 0.322), inferring a weak correlation. Similarly, when the Torsionometer readings were compared with the OCT measurements of each eye separately, the results demonstrated a weak correlation. To the authors' knowledge, this is the first study comparing subjective and objective torsion in normal individuals. The results demonstrate that subjective and objective torsion in normal individuals should be considered as separate entities and the terms should not be used interchangeably. [J Pediatr Ophthalmol Strabismus. 2021;58(2):112-117.].

Electromechanical changes of the myocardium after anthracycline chemotherapy

Abstract Funding Acknowledgements Type of funding sources: None. Background and objectives The most common side effects of chemotherapeutics in breast cancer is on the cardiovascular system. Global longitudinal strain (GLS) is the only parameter recommended for follow-up in current guidelines with limited evidence. Other strain imaging parameters and electrical changes after chemotherapy is not well studied. It is not known whether electrical or mechanical changes occur initially. The aim of this study is to evaluate repolarization parameters on ECG and mechanical changes together after chemotherapy in breast cancer patients. Subjects and method Consecutive patients who received chemotherapy due to breast cancer were included. Strain echocardiography and ECGs were performed pre-treatment (T0) and 3rd month after chemotherapy (T2). Additionally, just in three hours of first dose of chemotherapy (T1) another ECG was performed. QT and QT correction for heart rate (QTc), QT dispersion (QT disp) and QTc dispersion (QTc disp), T wave peak to end time (Tpe) and Tpe corrected for QT-QTc measurements were performed (figüre 1 and 2). GLS, longitudinal strain for myocardial layers, circumferential strain (CS), radial strain (RS) and torsion measurements were performed. All mechanical and electrical parameters from different time intervals were compared. Results Thirty-five consecutive patients (35 females, mean age 48.9 ± 11.8 years) who received chemotherapy (mean doxorubicin cumulative dose 415 ± 32 mg/m2) due to breast cancer were included. There was no significant change in mean GLS values before and after treatment (T0 -%18.8 ± 6.82, T1 18.6 ± 3.5 p = 0,863 respectively). However, there was a significant decrease in CS, RS and torsion (T0 -%17,2 ± 3,5, T1-%13 ± 2,84 p &amp;lt;0,001, T0 %45,1 ± 8,3, T1 %35,6 ±10 p &amp;lt;0,001 and T0 %12,1 ± 3.5, T1 %7.7 ± 2.1 p &amp;lt;0,001, respectively). QT, QTc, QTc disp and Tpe, Tpe/QTc parameters were prolonged just after chemotherapy and were still prolonged 3 months after ((QTc: T1 440.01 ± 27.63, T2 468.00 ± 38.98, T3 467.86 ± 35.09), (QTc disp T1 55.48 ± 20.22, T2 78.59 ± 16.15, T3 66.16 ± 14.62), (Tpe (QTc) T1 104 ± 18.52, T2 148.62 ± 19.16, T3 139.77 ± 21.63), (Tpe/QTc T1 0.213 ± 0.05, T2 0.281 ± 0.08, T3 0.258 ± 0.06). Conclusion Electrical and mechanical functions of the heart could be impaired together acutely even three months after doxorubicin chemotherapy. Cardio toxicity should be evaluated in terms of both electrically and mechanically. Abstract Figure. ECG repolarization parameters

A Validated, Automated, 3-Dimensional Method to Reliably Measure Tibial Torsion

Background: Tibial torsion is a twist in the tibia measured as an angle between a proximal axis line and a distal axis line. Abnormal torsion has been associated with a variety of painful clinical syndromes of the lower limb. Measurements of normal tibial torsion reported by different authors vary by 100% (ranging from 20° to 42°), making it impossible to determine normal and pathological levels. Purpose: To address the problem of unreliable measurements, this study was conducted to define an automated, validated computer method to calculate tibial torsion. Reliability was compared with current clinical methods. The difference between measurements of torsion generated from computed tomography (CT) and magnetic resonance imaging (MRI) scans of the same bone, and between males and females, was assessed. Study Design: Controlled laboratory study. Methods: Previous methods of analyzing tibial torsion were reviewed, and limitations were identified. An automated measurement method to address these limitations was defined. A total of 56 cadaveric and patient tibiae (mean ± SD age, 37 ± 15 years; range, 17-71 years; 28 female) underwent CT scanning, and 3 blinded assessors made torsion measurements by applying 2 current clinical methods and the automated method defined in the present article. Intraclass correlation coefficient (ICC) values were calculated. Further, 12 cadaveric tibiae were scanned by MRI, stripped of tissue, and measured using a structured light (SL) scanner. Differences between torsion values obtained from CT, SL, and MRI scans, and between males and females, were compared using t tests. SPSS was used for all statistical analysis. Results: When the automated method was used, the tibiae had a mean external torsion of 29°± 11° (range, 9°-65). Automated torsion assessment had excellent reliability (ICC, 1), whereas current methods had good reliability (ICC, 0.78-0.81). No significant difference was found between the torsion values calculated from SL and CT (P = .802), SL and MRI (P = .708), or MRI and CT scans (P = .826). Conclusion: The use of software to automatically perform measurements ensures consistency, time efficiency, validity, and accuracy not possible with manual measurements, which are dependent on assessor experience. Clinical Relevance: We recommend that this method be adopted in clinical practice to establish databases of normal and pathological tibial torsion reference values and ultimately guide management of related conditions.

Simplified Sensorless Torque Estimation Method for Harmonic Drive Based Electro-Mechanical Actuator

Torque measurements can significantly enhance control and monitoring loops for many mechatronic and aerospace applications. A typical challenge is to justify incorporating a torque sensor in terms of cost, system complexity, and reliability. Recently, sensorless torque estimation methods have been developed for robotic joints that include harmonic drive transmissions (HDTs). The principle is based on their relatively low torsional stiffness, which allows for estimating the transmitted torque by measuring the torsional angles (via existing joint encoders) and a compliance model. However, these methods are based on nonlinear models that are difficult to identify and tune. In this study, a simplified torque estimation method is introduced based on the structural damping friction of the HDTs. The structural damping can be correlated to the HDT torque using a simplified linear dynamic model and torsional rate measurements. Experimental results have validated the proposed method, using a robotic joint setup with an external torque sensor that has been previously utilized for testing several torque estimation methods.

Laboratory testing and numerical modelling of pin-ended hot-rolled stainless steel angle section columns failing by flexural-torsional buckling

The flexural-torsional buckling behaviour and resistances of pin-ended hot-rolled stainless steel angle section columns have been studied in the present paper, based on laboratory testing and numerical modelling. The testing programme adopted four hot-rolled stainless steel angle sections and included initial global and torsional geometric imperfection measurements and twelve pin-ended column tests. The key obtained test results, including the failure loads and deformations at the failure loads, the load–mid-height lateral deflection curves and failure modes, were fully reported and discussed. Strong interaction between flexural-torsional buckling about the major principal axis and flexural buckling about the minor principal axis was observed for each pin-ended hot-rolled stainless steel angle section column specimen during and upon testing. The testing programme was followed by a numerical modelling programme; finite element models were developed and validated against the test results, and afterwards used to perform parametric studies to generate further numerical data over a wide range of cross-section dimensions and member lengths. On the basis of the experimentally and numerically obtained data, the accuracy of the codified design methods, as adopted in Europe, America and Australia/New Zealand, and a recently proposed DSM-based design approach for pin-ended hot-rolled stainless steel angle section columns susceptible to flexural-torsional buckling, were evaluated. Overall, it may be concluded that (i) all the three considered design codes result in conservative flexural-torsional buckling resistance predictions, (ii) the current European code leads to more accurate resistance predictions for pin-ended columns with non-slender hot-rolled stainless steel angle sections, but a lower degree of design accuracy for pin-ended columns with slender hot-rolled stainless steel angle sections, in comparison with the American specification and Australian/New Zealand standard, and (iii) the DSM-based design approach yields substantially improved resistance predictions, due to the rational consideration of the length-dependent characteristic of flexural-torsional buckling and the interaction of flexural-torsional buckling with minor-axis flexural buckling, but with many predictions lying on the unsafe side.

How Much Superior Rectus Underaction is Considered Normal?

Purpose:It is considered normal to have a small amount of superior rectus weakness in laevo and dextro elevation; however, there is no documented definition for these normal parameters within a healthy young adult population using ocular movement testing and the synoptophore. The aim of this study was to collect normative data on the degree of superior rectus underaction in healthy young adults.Method:Twenty-nine healthy adults (3 males and 26 females, mean age 20.30 ± 1.70 years) were recruited. Superior recti underactions and inferior oblique overactions were recorded during routine ocular movement testing and mean and median values calculated. Subjective horizontal, vertical and torsional measurements were taken in degrees on the synoptophore in primary position, laevo elevation and dextro elevation.Results:Most participants (79.31%) had some degree of observable superior rectus underaction in either eye or in both eyes on ocular movement testing (mean superior rectus underaction of –0.69 units in laevo elevation and –0.71 units in dextro elevation, range = –1.5 to –0.5 units; median –1 units, interquartile range (IQR) = –1 to –1 units). Most participants (62.07%) had some degree of superior rectus underaction in either eye or in both eyes on the synoptophore (mean left and right superior recti underactions of –0.48 degrees, range = –3 to –1 degrees; median 0 degrees, IQR = –1 to –1 degrees).Conclusion:The majority of young healthy adults in this study showed some degree of superior rectus underaction. On ocular movement testing, –0.70 units of underaction, and on the synoptophore, –0.48 degrees of underaction are the mean levels of weakness to be expected. Superior rectus underactions greater than –1 units for ocular movement testing and –1 degrees on the synoptophore in healthy young adults should be carefully evaluated, together with other important clinical signs.