Compensation Of Thermal Effects Research Articles

Compensation of Thermal Effects on Tiltmeter Measurements With Moving Least Squares

Compensation of Thermal Effects on Tiltmeter Measurements With Moving Least Squares

Investigating focal spot position drift in a mobile imaging system equipped with a monobloc-based x-ray generator.

Misalignment or double-contouring artifacts can appear in high-resolution 3D cone beam computed tomography (CBCT) images, potentially indicating geometric accuracy issues in the projection data. Such artifacts may go unnoticed in low-resolution images and could be associated with changes in the focal spot (FS)position. High-resolution 3D-CBCT imaging by a mobile imaging device with a large gantry clearance offers more versatility for clinical workflows in image-guided brachytherapy (IGBT), intraoperative radiation therapy (IORT), and spinal, as well as maxillofacial surgery. However, misalignment or double-contouring artifacts hinder workflow advancements in these domains. This paper introduces intrinsic calibration and geometrical correction methods as extensions to a well-established technique for addressing geometrical deviations resulting from factors such as gravity or mechanical inconsistencies. These extensions cover shifts and drifts of the FS depending on FS size selection, temperature, tube current, and tube potential. The proposed methods effectively mitigate artifacts in high-resolution CBCT images stemming from geometrical inaccuracies in projection data, without requiring additional equipment like a pinholedevice. Geometrical offsets and drifts of the x-ray tube FS were characterized on a mobile multi-purpose imaging system, the ImagingRing-m. A pinhole-like experiment was simulated by adjusting the movable collimation unit to a small rectangular aperture within the FS size range. The influence of filament selection, that is, FS size, temperature, the relatively low tube currents, as well as tube potential settings have been studied on two different monobloc types sharing the same x-ray tube insert. The Catphan 504 and an Alderson head phantom were used to assess resulting imageartifacts. Switching the FS size to one different from what was used for geometrical (gravitation, mechanical variations) calibration induced the most notable position changes of the x-ray FS, resulting in double-contouring artifacts and blurring of high-resolution 3D-CBCT images. Incorporating these shifts into a geometrical correction method effectively minimized these artifacts. Thermal drifts exhibited the second largest geometrical changes, comparable to FS size shifts across the thermal operating conditions of the x-ray system. The proposed thermal drift compensation markedly reduced thermal drift effects. Tube current and potential had little impact within the range of available tube currents, eliminating the need for compensation in currentapplications. Augmenting the geometrical calibration pipeline with proposed FS drift compensations yielded significant enhancements in image quality for high-resolution reconstructions. While compensation for thermal effects posed challenges, it proved achievable. The roles of tube current and potential were found to benegligible.

Study on thermal effect and electro-optically Q-switching of Cr, Tm, Ho: YAG laser

The thermal effect and Q-switching of flashlamp-pumped Cr, Tm, Ho: YAG (CTH: YAG) laser were investigated systematically. The fraction of pump power dissipated as heat in flashlamp-pumped CTH: YAG laser system was evaluated for the first time by measurements and calculations on thermal lens effect. The quasi-steady state and transient temperature distributions of laser rod were numerical simulated. In addition, Electro-optically Q-switching was studied by design of thermal effect compensation resonator. An unusual phenomenon that the optimal delay time of Q-switch in CTH: YAG was shorter than the pump duration was reported for the first time as far as we know. According to the experimental and theoretical calculation results, the main cause of the phenomenon is the long lifetime of lower laser level, followed by up-conversion and fluorescence quenching at high temperature. The mechanism proposed in this paper is of great significance for the design of highly efficient Q-switched CTH: YAG lasers.

Variable Capacity for Acute and Chronic Thermal Compensation of Physiological Rates Contributes to Inter-Individual Differences in Growth Rate in Mussels (Mytilus galloprovincialis)

The aim of this study was to ascertain if the capacity for acute and chronic compensation of thermal effects on physiological rates represents a trait contributing to inter-individual growth rate differences in the mussel Mytilus galloprovincialis. Juvenile mussels (10-11 mm shell length) were collected, transported to the laboratory, and divided into two groups: one group was maintained at 20oC (warm treatment), and the other at 10oC (cold treatment). The mussels were reared at these two temperatures (continuously fed), until clear size differences allowed us to select fast- (F) and slow (S)-growing individuals from both groups (F20/S20 at 20oC and F10/S10 at 10oC). Selected F and S mussels were then exposed to three experimental temperatures (10, 15, and 20oC), and the time-course of their response, in terms of clearance rate (CR: L/h) and routine oxygen consumption (VO2: mLO2/h), was monitored. The overall growth rate of mussels in the warm treatment group was significantly higher than in the cold treatment group. For both treatments, significant differences were found in key physiological parameters between F and S mussels: F mussels had a higher CR and a larger gill surface area than their S counterparts. Although no significant differences in the thermal sensitivity of the clearance or metabolic rates were observed between F20 and S20 mussels reared at 20oC, when exposed to acute temperature changes, experiments with mussels reared at 10oC revealed a different outcome: in response to acute warming (from 10oC to 15 and 20oC), F10 were capable of compensating for the thermal effect on CR and VO2; however, no such compensatory response was observed in S10. We conclude that two significant factors contribute to endogenous differences in the growth rate of mussels: (i) the capacity to exhibit intense filtering activity, which appears to be functionally correlated with the gill surface area and ii) the capacity to compensate for the effects of temperature on filtration and metabolic rate. The second trait does not appear to make a significant contribution to the inter-individual size-differentiation observed in mussels maintained in warm environments, but explains a significant proportion of inter-individual growth rate differences in cold environments.

A CMOS MEMS-based Membrane-Bridge Nanomechanical Sensor for Small Molecule Detection

Small molecule compounds are necessary to detect with high sensitivity since they may cause a strong effect on the human body even in small concentrations. But existing methods used to evaluate small molecules in blood are inconvenient, costly, time-consuming, and do not allow for portable usage. In response to these shortcomings, we introduce a complementary metal-oxide-semiconductor bio-microelectromechanical system (CMOS BioMEMS) based piezoresistive membrane-bridge (MB) sensor for detecting small molecule (phenytoin) concentrations as the demonstration. Phenytoin is one of anticonvulsant drugs licensed for the management of seizures, which has a narrow therapeutic window hence a level of concentration monitoring was needed. The MB sensor was designed to enhance the structural stability and increase the sensitivity, which its signal response increased 2-fold higher than that of the microcantilever-based sensor. The MB sensor was used to detect phenytoin in different concentrations from 5 to 100 μg/mL. The limit of detection of the sensor was 4.06 ± 0.15 μg/mL and the linear detection range was 5–100 μg/mL, which was within the therapeutic range of phenytoin concentration (10–20 μg/mL). Furthermore, the MB sensor was integrated with an on-chip thermal effect eliminating modus and a reaction tank on a compact chip carrier for disposable utilization. The required amount of sample solution was only 10 μL and the response time of the sensor was about 25 minutes. The nano-mechanical MB sensing method with thermal effect compensation is specific, sensitive, robust, affordable and well reproducible; it is, therefore, an appropriate candidate for detecting small molecules.

E-Clutch Torque Control Including Compensation of Thermal Expansion Effects

The E-clutch considered is a dry clutch automated by means of a hydrostatic actuator, whose master cylinder is driven by an electric servomotor through a spindle drive. The paper deals with design of E-clutch open-loop torque control strategy which includes compensation of clutch thermal expansion effects. A series of experiments have been conducted by using a custom-designed E-clutch test rig, in order to characterize influence of thermal effects on clutch control performance. A comprehensive analysis of test data reveal a strong correlation of clutch torque reduction and E-clutch slave cylinder (CSC) position increase caused by clutch pack thermal expansion. The determined dependence, where CSC position measurement serves for quantification of thermal effects, is incorporated within the clutch torque control strategy for the sake of thermal effects compensation. Furthermore, it is found out that the CSC position can be effectively estimated based on clutch temperature inputs, thus implying that the CSC position sensor can be omitted, while still keeping the possibility of effective thermal expansion compensation. The proposed clutch control strategy is examined based on experimental data acquired for two clutch friction plates/materials.

Thermal effects compensation and associated uncertainty for large magnet assembly precision alignment

Big science and ambitious industrial projects continually push technical requirements forward beyond the grasp of conventional engineering techniques. An example of these are the extremely tight micrometric assembly and alignment tolerances required in the field of celestial telescopes, particle accelerators, and the aerospace industry. Achieving such extreme requirements for large assemblies is limited, largely by the capability of the metrology used, namely, its uncertainty in relation to the alignment tolerance required. The current work described here was done as part of Maria Curie European research project held at CERN, Geneva. This related to future accelerators requiring the spatial alignment of several thousand, metre-plus large assemblies to a common datum within a targeted combined standard uncertainty (uctg(y)) of 12 μm. The current work has found several gaps in knowledge limiting such a capability. Among these was the lack of uncertainty statements for the thermal error compensation applied to correct for the assembly's dimensional instability, post metrology and during assembly and alignment. A novel methodology was developed by which a mixture of probabilistic modelling and high precision traceable reference measurements were used to quantify the uncertainty of the various thermal expansion models used namely: Empirical, Finite Element Method (FEM) models and FEM metamodels. Results have shown that the suggested methodology can accurately predict the uncertainty of the thermal deformation predictions made and thus compensations. The analysis of the results further showed how using this method a ‘digital twin’ of the engineering structure can be calibrated with known uncertainty of the thermal deformation behaviour predictions in the micrometric range. Namely, the Empirical, FEM and FEM metamodels combined standard uncertainties ( uc(y) ) of prediction were validated to be of maximum: 8.7 μm, 11.28 μm and 12.24 μm for the studied magnet assemblies.

Laser meter for hydrosphere pressure variations with a mechanical temperature compensation system

Based on modern laser interferometric methods, a laser meter has been developed, equipped with a mechanical external thermal effect compensation system designed to record hydrospheric pressure variations in the frequency range from 0 (conventionally) to 1000 Hz with an accuracy of 50 μPa.

Thermal Modelling of Drilling Steel

The modelling of machining operations aiming at the compensation of thermal effects regarding workpiece distortion requires detailed knowledge of the thermal impact of the examined process. The objective of this paper is therefore to form an empirical basis for the modelling of the heat flux into the workpiece in drilling of steel. In order to achieve this goal the temperature matching technique in combination with two dimensional thermographic measurements was utilised. The moving heat source was characterised as a primary heat source with a constant heat flux density near the cutting zone and a secondary declining heat source on the bore hole wall. With an iterative approach it was possible to match the simulated temperature fields very closely to the measured temperature fields. The evaluation of the thermal impact of the drilling process with varying machine parameters yielded additional insight into the generation and distribution of thermal energy in drilling. The lowest overall heat partition to the workpiece was observed at the higher feed rate in combination with the lower cutting speed where the heat partition in the cutting zone as well as heat transfer to the bore hole wall are minimal.

Modelling, simulation and compensation of thermal effects for complex machining processes

This special issue was initiated by the priority programme 1480 “Modelling, simulation and compensation of thermal effects for complex machining processes” and presents current investigations, new approaches and relevant results with regard to the specific topic. In addition to the contributions from the priority programme, this issue contains selected publications, which complement the substantial overview of novel developments in the area of heat source identification, modelling, simulation, minimisation and compensation of thermal effects in machining operations.

Variable Symbol-Rate DPSK Receiver Based on Silicon Photonics Coupled-Resonator Delay Line

We present a compact (<; 0.65 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) silicon photonics variable-delay receiver for DPSK optical transmission systems consisting of a Mach-Zehnder interferometer (MZI) loaded with an integrated tunable delay line. The delay line is realized by using a thermally actuated coupled-resonator optical waveguide (CROW) in reflective configuration, providing a continuous control of the MZI delay from 66 to 102 ps, thus allowing the optimization of the receiver performance for the detection of DPSK signals at any symbol rates between 9.8 and 15 Gsym/s. The tuning scheme is simple, requiring the control of only two ring resonators, and enables the active compensation of thermal effects induced by silicon nonlinearity at high input power. The scalability of the proposed scheme to 100 Gsym/s systems and the maximum achievable tunability range are also discussed.

Passive Temperature Stabilization of Silicon Photonic Devices Using Liquid Crystals.

In this work we explore the negative thermo-optic properties of liquid crystal claddings for passive temperature stabilization of silicon photonic integrated circuits. Photonic circuits are playing an increasing role in communications and computing, but they suffer from temperature dependent performance variation. Most existing techniques aimed at compensation of thermal effects rely on power hungry Joule heating. We show that integrating a liquid crystal cladding helps to minimize the effects of a temperature dependent drift. The advantage of liquid crystals lies in their high negative thermo-optic coefficients in addition to low absorption at the infrared wavelengths.

Modeling and Compensation of Thermal Effects on an Ironless Inductive Position Sensor

The ironless inductive position sensor can be the ideal candidate for linear position sensing in harsh environment and in the presence of external magnetic fields. Starting from the validated electromagnetic characteristics, this paper presents a model of thermal effects influencing the sensor's position reading and an effective algorithm to compensate them. The compensation is performed without affecting the nominal sensor's functioning and without using additional temperature probes, which would complicate the sensor's assembly. The model constitutes the basis of this algorithm, which is then validated through experimental measurements on a custom ironless position sensor prototype.

Analysis of thermal effects in end-diode-pumped, Q-switched Nd:YVO4 laser

We present a laboratory model of a Q-switched Nd:YVO 4 laser with thermal effects compensation dedicated as a laser head for marking devices. Theoretical analysis on thermal effects were performed and resonator parameters were optimized. For 10 kHz repetition rate we obtained about 0.25 mJ of pulse energy corresponding to about 45 kW of peak power with slope efficiency 14%. M 2 parameter was 1.6. Full Text: PDF References J. E. Geusic, H. M. Marcos, L. G. Van Uitert, "Laser oscillations in nd-doped yttrium aluminum, yttrium gallium and gadolinium garnets", Applied Physics Letters 4 (10), (1964) CrossRef L. Gorajek, L. Galecki, "Tunable, gain switched Ti3+:Al2O3 laser pumped by intracavity frequency doubled Nd3+:YLF laser", Photonics Letters of Poland 1, No 3, 136-138 (2009) CrossRef W. Zendzian, J. K. Jabczynski, P. Wachulak, J. Kwiatkowski, "High-repetition-rate, intracavity-pumped KTP OPO at 1572 nm", Appl. Phys. B 80, 329-332 (2005) CrossRef J. Swiderski, A. Zajac, P. Konieczny, M. Skorczakowski, "Numerical model of a Q-switched double-clad fiber laser", Opt. Express 12, 3554-3559 (2004) CrossRef J. Swiderski, A. Zajac, P. Konieczny, M. Skorczakowski, "Q-switched Nd-doped double-clad fiber laser", Opto-Electronics Review, vol. 13, no. 3, 29-33, 2005 DirectLink

Athermalization of Long Focal Length IR Optical Systems by Hydraulics

The effects of temperature changes on the focus of IR optical system are described in this paper, and the general methods used for compensation of thermal effects are analyzed. On this basis, the feasibility of athermalization of long focal length IR optical systems by using of hydraulics is studied, and an athermalization design of an uncooled IR optical system with focal length 200mm and F-number 1 is presented. The result shows that within the temperature range from -30 to 50 °C, the defocus of this system is less than the depth of focus.

Strain induced bandgap and refractive index variation of silicon

We present a study of the influence of high strain on the bandgap and the refractive index of silicon. The results of photoluminescence show that with the strain applied, the silicon bandgap can be adjusted to 0.84 eV and the refractive index of silicon increases significantly. 1.4% change of refractive index of silicon was observed. The strain-induced bandgap shrinkage and absorption coefficient change of silicon are considered as the main cause of the significant refractive index change. The present work indicates that the application of strain is promising to control the refractive index of silicon in devices so that applications such as compensation of thermal effect in optical devices can be achieved.

Compensation of thermal effects in Faraday isolator for high average power lasers

A Faraday isolator system with external compensation of thermally induced birefringence was investigated for the case when optical components of the Faraday isolator and the compensator are made of different materials. Simultaneous reduction of thermally induced depolarization and thermal lens in the Faraday isolator based on a TGG crystal was demonstrated experimentally for the first time using an Sm:CaF2 crystal. A method of compensating thermally induced birefringence without reciprocal polarization rotator was described theoretically and demonstrated in experiments for the first time. It was used as a basis for a new scheme of Faraday isolator with external compensation of thermally induced birefringence.

High-resolution confocal fluorescence thermal imaging of tightly pumped microchip Nd:YAG laser ceramics

A modified two-path confocal microscope was used to obtain fluorescence images of a Nd:YAG microchip element in the presence of a tightly focused 808 nm pump beam. Based on the temperature-induced homogeneous line broadening, high-resolution (<1 μm, <1°C) thermal images of the pump volume and surroundings were obtained from the spatial variation of Nd3+ linewidth. Based on this direct, pure optical and non-contact method, thermal gradients as low as 0.02°C/μm were detected at focal volume, this being in agreement with theoretical predictions. The thermal imaging technique here presented opens the possibility of accurate compensation of thermal effects for the development of stable and efficient microchip lasers.

Experimental and Numerical Determination of Cutting Forces and Temperatures in Gear Hobbing

Hobbing is one of the most productive methods for manufacturing external gears. According to the requirements of green manufacturing, the lubrication in gear hobbing has to be reduced with the final aim of dry machining. Influences due to thermal aspects during machining have to be considered, especially in hobbing of large modules or ring gears, because in this case, hobbing could be the last step in the process chain. Within the priority program (SPP) “Modeling, Simulation and Compensation of Thermal Effects for Complex Machining Processes”, founded by the DFG, special emphasis is laid on the thermally caused geometrical deviation in dry cutting. To predict the heat flux, which leads to thermal expansions and geometrical deviations of the gear, a validated model for forces and temperatures is necessary. The validation of single generation positions and chips is focused in this paper.

应用于光刻领域中的固态紫外激光源的制作

An intracavity frequency-tripling of a diode-edge-pumped passively Q-switched 1 064 nm Nd∶YAG laser is presented to generate high power 355 nm UV laser.Several essential technologies are put forward to achieve the best beam quality such as a volume grating to maintain quasi phase matching with narrow linewidth,optimization and thermal effects compensation for cavity.The task first takes advantage of volume grating and two CBO crystals as SHG and THG nonlinear optical conversion material to obtain high UV laser power output more than 4 W,light quality factor M22.5,meanwhile it is the first time to realize thermal effect using 45° Faraday rotator.The achievement is expected to be the popular light source system in lithography instead of conventional excimer laser.