Reference Beam Research Articles

Minimum phantom size for megavoltage photon beam reference dosimetry.

Water phantoms are required to perform reference dosimetry and beam quality measurements but there are no published studies about the size requirements for suchphantoms. To investigate, using Monte Carlo techniques, the size requirements for water phantoms used in reference dosimetry and/or to measure the beam quality specifiers and . The EGSnrc application DOSXYZnrc is used to calculate , the dose per incident fluence at 10cm depth in a water phantom irradiated by incident beams of or 6MV photons. The water phantom dimensions are varied from to and occasionally smaller. The and values are also calculated with care being taken to distinguish results when using Method A (changing depth of water in phantom) and Method B (moving entire phantom). Typical statistical uncertainties are 0.03%. Phantom dimensions have only minor effects for phantoms larger than . A table of corrections to the dose at 10cm depth in beams of or 6MV photons are provided and range from no correction to 0.75% for a beam incident on a phantom. There can be distinct differences in the values measured using Method A or Method B, especially for smaller phantoms. It is explicitly demonstrated that, within 0.15%, values for a phantom measured using Method A or B are independent of source detector distance between 40 and200cm. The phantom sizes recommended in the TG-51 and IAEA TRS-398 reference dosimetry protocols are adequate for accurate reference dosimetry and in some cases are even conservative. Correction factors are necessary for accurate measurement of the dose at 10cm depth in smaller phantoms and these factors are provided. Very accurate beam quality specifiers are not required for reference dosimetry itself, but for specifying beam stability and characteristics it is important to specify phantom sizes and also the method used for measurements.

A Novel Repair Technique of Pre-damaged T-Beams Failing in Shear Using Eco-Friendly Steel Fibre-Reinforced Geopolymer Concrete

Repair of reinforced concrete structures is required to preserve the adequate performance of these structures throughout their service life. One of the credible techniques is using fibrous concrete as a repair material. In this paper, the performance of steel fibre-reinforced geopolymer concrete (SFRGPC) in the repair of pre-damaged reinforced concrete T-beams (pre-loaded up to 50% of their shear capacity) failing in shear was investigated. Five T-beam series and a four-point loading test were adopted: one reference beam, three beams were repaired with different fibrous ratios of 1, 2, and 3%, and one was repaired with 2% steel fibre and additional U-steel stirrups. The key test results include crack propagation, crack width, initial stiffness, load deflection, peak loads, and strain associated with web stirrups. A clear enhancement was noticed in the performance of the repaired T-beams; their shear capacity was boosted by as much as 45% compared to the control beam. It was also deduced that the beam went from a brittle to a ductile failure mode at 3% SFRGPC and at 2% SFRGPC with U-stirrups. Finally, an analytical model prediction was proposed to predict the shear capacity of repaired T-beams with the SFRGPC. The model showed a satisfactory correlation with experimental results, with an average ratio of 0.995 and a standard deviation of 0.035.

Mechanical Properties of Fire-Damaged RC Beams Reinforced with Carbon Fiber Mesh

The bearing capacity of reinforced concrete (RC) beam will be weakened by fire. It is necessary to strengthen RC beams after fire. The carbon fiber mesh (CFM) can be used to reinforce RC beams. In this paper, RC beams were exposed to varying temperatures, followed by reinforcement with varying layers of CFM. The influence of the heating temperature and the number of CFM layers on the flexural performance of RC beams was investigated. The results indicated that the cracking loads of RC beams were 18.2, 16.4, 16.3, and 15.5 kN when the RC beams were subjected to room temperatures, 150, 350, and 550 °C. Compared to the unreinforced beams at room temperature, the cracking loads of the RC beams were reduced by 9.89%, 10.44%, and 14.84%. As the quantity of CFM reinforcement layers rises, so does the ultimate bearing capacity. For example, when the temperature was 150 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 20% and 31.76% compared to the reference beam. When the temperature was 350 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 19.51% and 28.04% compared to the RC beam without CFM. When the temperature was 550 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 20% and 26.67% compared to the RC beam without CFM. Fire-damaged RC beams can be strengthened by one layer of CFM and mortar if the temperature was below 350 °C. Fire-damaged RC beams can be strengthened by three layers of CFM and mortar if the temperature was below 550 °C. The mechanical properties can be obviously enhanced.

Comparison of full fiber coupled interferometer systems under vacuum conditions

Abstract The PTB built a comparator setup for testing length measuring systems under vacuum conditions. The setup is equipped with a linear stage which is operated in a closed loop using the feedback of a 1.5D encoder system with three encoder heads for length and vertical rotation angle and exhibits a movement range of 150 mm. The main measurement system is a heterodyne interferometer with periodic nonlinearities with amplitudes below 10 pm. The comparator setup was characterized using a mirror mounted on the stage reflecting the measurement as well as the reference beams. By these means, the resolution, the stability of the setup as well as the influence of guiding errors on position-dependent measurement deviations of the fully fiber coupled interferometer were investigated. A position-depending error was observed which was resulting from the variation of the performance of the coupling into the multi-mode fibers used to transfer the superposed beams to the photoreceivers. The measured deviations were 1.5 nm or 0.2 nm over 70 mm travel range depending on the core diameter of the multi-mode fibers of 50 µm and 200 µm, respectively. Three different commercial fiber interferometer systems were analysed under vacuum conditions with the comparator setup. All tested systems are working with light sources with a wavelength of approximately 1535 nm but differ in the amplitude of their periodic nonlinearities in the range between 10 pm and 29 nm. The tests of their resolution and stability were limited by vibrations in the comparator setup and the lack of adequate synchronization capabilities of the data acquisition of these systems.

Coupling Michelson-like lateral shear interferometric microscopy with self-referencing numerical phase calibration for quantitative measurement of 3D surface morphology of biological cells

A Michelson interferometer is commonly used for evaluating the morphology of a cell. However, the interference imaging with reference and object beams is easily affected by external vibrations and environmental disturbances, leading to unstable interference patterns. In this paper, the three-dimensional surface morphology of the biological cell is evaluated by a new quantitative phase imaging method, which couples Michelson-like lateral shear interferometric microscopy with self-referencing numerical phase calibration. The Michelson-like lateral shear interferometric microscopy is constructed by replacing the two plane mirrors of the traditional Michelson interferometer with two common right-angle prisms and generates interference fringe patterns. The lateral shear is created and freely adjustable by simply translating/or rotating one right-angle prism. To calculate the phase information of the biological cells quantitatively, the classical Fourier transform method is used to process the recorded interferogram, and then the self-referencing numerical phase calibration method is utilized for acquiring accurate phase information. Successfully achieving quantitative phase imaging of a cell verifies the feasibility and practicability of the proposed method.

Balanced-detection interferometric cavity-assisted photothermal spectroscopy via collimating fiber-array integration

This work reports on the implementation of a fiber-array with attached microlenses in the balanced-detection Interferometric Cavity-Assisted Photothermal Spectroscopy (ICAPS) scheme, enabling a highly compact probe laser beam path. The sample probe and the reference beam were coupled into a 1-mm spaced Fabry-Perot interferometer with a parallel beam separation of only 1.25 mm. A quantum cascade laser was used to induce photothermal waves, which were detected via a sample probe beam. A reference probe beam was used to realize balanced detection, allowing for significant noise reduction. The sensor’s metrological figures of merit were evaluated by detection of nitric oxide. For the targeted absorption band centered at 1900.08 cm−1 a 1 σ minimum detection limit of 64 ppbv was achieved with a 1-second integration time. This performance corresponds to a normalized noise equivalent absorption of 5.7 ×10−8 cm−1 W Hz−1/2.

A Comparative Study of the Structural Behavior of Concrete Beams Reinforced with Different Configurations of GFRP and Steel Bars

This study examined experimentally and numerically the performance of five concrete beams reinforced with longitudinal and transverse bars made of Glass Fiber Reinforced Polymer (GFRP) or steel. All beams had the same dimensions of 2700 mm in length, 180 mm in width, and 260 mm in depth. The beams were classified into two groups with different variables and compared with a reference beam reinforced with longitudinal and transverse steel bars. The first group consisted of two beams with longitudinal GFRP bars and no stirrups, varying the main reinforcement ratio. The second group comprised two beams with longitudinal GFRP bars and transverse GFRP or steel stirrups, varying the stirrup type. The results indicated that the beams with GFRP bars improved their flexural strength for different ratios but had limited shear resistance when using GFRP stirrups because increased deflection causes the number and width of cracks to grow, reducing the shear strength. All the tested beams exhibited linear elastic behavior until failure, with GFRP being more brittle than steel due to no yield point or plastic behavior in GFRP. The numerical simulation of the five beams using ABAQUS software showed good agreement with the experimental data obtained in the laboratory.

Coherent feedback enhanced quantum-dense metrology in a lossy environment.

Quantum dense metrology (QDM) performs high-precision measurements by a two-mode entangled state created by an optical parametric amplifier (PA), where one mode is a meter beam and the other is a reference beam. In practical applications, the photon losses of meter beam are unavoidable, resulting in a degradation of the sensitivity. Here, we employ coherent feedback that feeds the reference beam back into the PA by a beam splitter to enhance the sensitivity in a lossy environment. The results show that the sensitivity is enhanced significantly by adjusting the splitting ratio of the beam splitter. This method may find its potential applications in QDM. Furthermore, such a strategy that two non-commuting observables are simultaneous measurements could provide a new way to individually control the noise-induced random drift in phase or amplitude of the light field, which would be significant for stabilizing the system and long-term precision measurement.

Focal length measurement based on vortex beam interference

This paper proposes a new method to measure the focal lengths of both convex and concave lenses based on vortex beam interference. Theoretical analysis illustrates that the maximum intensity distribution of the interferogram is in accordance with the Fermat's spiral, and the spiral coefficient is proportional to the difference between the focal length of the test lens and the distance from the test lens to the camera. In order to calculate the precise focal length, we separately block the light paths to obtain the reference and test beam spots, and get the ratio of these two spot sizes. Then, the ratio and the spiral coefficient are used to determine the focal length. For a biconvex lens with a focal length of 200 mm and a biconcave lens with a focal length of −100 mm, the relative measurement errors are 0.0892 % and 0.0800 %, respectively. This research provides a novel and convenient method for measuring the focal length, and no-sophisticated displacement devices and moving the lens to be measured are required in the measurement.

Analysis of Polarization Angle on Holographic Recording Based on PQ/PMMA.

The polarization state of light waves significantly affects the quality of holographic recordings. This paper quantitatively analyzes the impact of different polarization states of signal and reference beams on the quality of holographic recordings in PQ/PMMA photopolymer systems during the holography process. By deriving the light field distribution of the interference between two light waves of different polarization states and introducing the interference fringe contrast and the modulation of the refractive index of the photopolymer, we established the relationship between the diffraction efficiency of PQ/PMMA photopolymer holographic gratings and the angle between polarization directions. Based on this relationship, simulations and experiments were conducted. The experimental results demonstrated that as the angle between the polarization directions increased, the diffraction efficiency of the material decreased, with the efficiency dropping to 24.69% of its original value when the angle increased from 0° to 50°. When the angle increased to 60°, the influence of polarization characteristics became gradually significant, and at 90°, it was entirely dominated by polarization characteristics. The photoinduced birefringence properties of the PQ/PMMA prepared in the measurement experiment were studied, and the polarization characteristics of the reconstructed light under polarization direction angles of 0°, 60°, and 90° were investigated. The results indicated that at a polarization direction angle of 60 degrees, the material exhibited a significant response to the polarization information of the signal light. Finally, holographic recordings of objects at different polarization direction angles were conducted, and the reconstructed images were used to visually reflect the impact of the polarization direction angle on the quality of holographic recordings.

Experimental study on flexural performance of prestressed concrete beams strengthened by Fe-SMA plates

Shape memory alloy (SMA) is an innovative intelligent material, capable of restoring its shape before deformation upon reaching the critical activation temperature. This property promotes its promising applications in civil engineering. This paper proposes a novel reinforcement method and aims to investigate the reinforcing effect of iron-based shape memory alloy (Fe-SMA) plates on prestressed concrete (PC) beams through four-point bending tests on one reference beam without reinforcement and three Fe-SMA reinforced beams, as well as with three beams reinforced by carbon fiber-reinforced polymer (CFRP). The results show that Fe-SMA can effectively reduce concrete cracks, and improve stiffness and characteristic loads of beams without negative effects. Under the same loading conditions, new cracks of Fe-SMA reinforced beams were relatively fewer than those of CFRP reinforced beams. Besides, Fe-SMA exhibited superior performance when utilizing the same cross-sectional reinforcement material to enhance the bending capacity of beam, and proved more advantageous for improving stiffness and characteristic loads of beam under the identical initial tensile force. Furthermore, the reinforcing effectiveness of Fe-SMA positively correlates with the cross-sectional area (thickness) and recovery stress (pre-stretch level and activation temperature) of Fe-SMA. Increasing the thickness of Fe-SMA plates by 100%, while maintaining other parameters constant, resulted in a 33% increase in cracking load. Similarly, elevating the recovery stress from 314 MPa to 340 MPa led to a 12.5% rise in cracking load. This paper investigates the reinforcement effect of Fe-SMA plates on PC beams, and provides a reference for the application of Fe-SMA in PC beam reinforcement, laying a foundation for promoting the utilization of Fe-SMA in civil engineering.

Needle artifact reduction during interventional CT procedures using a silver filter

BackgroundMAR algorithms have not been productized in interventional imaging because they are too time-consuming. Application of a beam hardening filter can mitigate metal artifacts and doesn’t increase computational burden. We evaluate the ability to reduce metal artifacts of a 0.5 mm silver (Ag) additional filter in a Multidetector Computed Tomography (MDCT) scanner during CT-guided biopsy procedures.MethodsA biopsy needle was positioned inside the lung field of an anthropomorphic phantom (Lungman, Kyoto Kagaku, Kyoto, Japan). CT acquisitions were performed with beam energies of 100 kV, 120 kV, 135 kV, and 120 kV with the Ag filter and reconstructed using a filtered back projection algorithm. For each measurement, the CTDIvol was kept constant at 1 mGy. Quantitative profiles placed in three regions of the artifact (needle, needle tip, and trajectory artifacts) were used to obtain metrics (FWHM, FWTM, width at − 100 HU, and absolute error in HU) to evaluate the blooming artifact, artifact width, change in CT number, and artifact range. An image quality analysis was carried out through image noise measurement. A one-way analysis of variance (ANOVA) test was used to find significant differences between the conventional CT beam energies and the Ag filtered 120 kV beam.ResultsThe 120 kV-Ag is shown to have the shortest range of artifacts compared to the other beam energies. For needle tip and trajectory artifacts, a significant reduction of − 53.6% (p < 0.001) and − 48.7% (p < 0.001) in the drop of the CT number was found, respectively, in comparison with the reference beam of 120 kV as well as a significant decrease of up to − 34.7% in the artifact width (width at − 100 HU, p < 0.001). Also, a significant reduction in the blooming artifact of − 14.2% (FWHM, p < 0.001) and − 53.3% (FWTM, p < 0.001) was found in the needle artifact. No significant changes (p > 0.05) in image noise between the conventional energies and the 120 kV-Ag were found.ConclusionsA 0.5 mm Ag additional MDCT filter demonstrated consistent metal artifact reduction generated by the biopsy needle. This reduction may lead to a better depiction of the target and surrounding structures while maintaining image quality.

An experimental investigation and cost analysis of flexural or shear strengthening pre-damaged RC beams

This study conducted a series of experimental works to repair and strengthen beams with different flexural and shear damage levels using various repair/strengthening techniques such as carbon fiber-reinforced polymer (CFRP), steel plate (SP), and mechanical steel stitches (MSS). Within the scope of the study, post-strengthening performances of pre-damaged shear beams and flexural beams were investigated. For this, 1/2 geometrical scaled 20 reinforced concrete rectangular cross‐section beams, with dimensions of 125/250 mm and a span of 2500 mm, were produced. Half of these beams (type-SB) were designed to meet shear damage due to insufficient shear reinforcement, while the other half (type-BB) was designed to undergo flexural damage (sufficient shear reinforcement). Subsequently, a reference beam was produced in both shear and bending test groups, the other beams were strengthened with different techniques, and four-point bending tests were performed. Reference (non-damaged) bending and shear beams were vertically loaded and comprehensive data for these specimens were obtained. Later, the flexural beams (type-BB) were vertically loaded until reaching mid-displacement/span length (δu/L) ratios of 1%, 2%, and 3% of the flexural reference beam, while the shear beams (type-SB) were loaded up to 50%, 65%, and 85% of the maximum load-carrying capacity (Pmax) of the shear reference beam to induce different damage levels. Then the specimens were strengthened with three strengthening methods (CFRP, SP, and MSS). The data obtained from the experiments were compared, considering each group specimen's strength, displacement ductility, stiffness, and energy dissipation capacity. In addition, the cost of each strengthening type was calculated, and the ratio of the strengthening costs / the production cost of the element itself was determined. According to load carrying capacity and ductility behavior, experimental studies have shown that CFRP has proven to be more effective for type-BB beams (3% pre-damaged level), whereas MSS has proven to be more effective for type-SB beams (85% pre-damaged level) than other methods. While both MSS and SP have been effective for all damage levels in BB beams, CFRP has only shown effectiveness for a damage level of 3%. In the case of shear beams, the load-carrying capacity has increased for various damage levels with CFRP, SP, and MSS. However, typical bending beam behavior was exhibited for CFRP 85%, SP 65%, and MSS 85% load levels. It was also determined that SP and MSS contributed to the ductility orientation for the 65% damage level. However, in terms of cost, CFRP was the most expensive, whereas MSS was the least expensive strengthening method. CFRP was approximately twice as costly as SP and three times more costly than MSS. Finally, due to its ease of application and low cost, MSS, which is a relatively new strengthening technique, has been found that the MSS method is a better alternative than other methods, especially for the strengthening of beams that have received shear damage.

Influence of fiber orientation on flexural‐based design of steel fiber‐reinforced concrete slabs: Experimental and numerical program

AbstractSteel fiber‐reinforced concrete (SFRC) has proven to be a suitable structural material for constructing elevated flat slabs, and several existing office and residential buildings, in which SFRC was used for these components, highlighted the positive outcomes from both technical and sustainability perspectives. However, research on the influence of fiber orientation on the flexural performance of SFRC slabs is relatively scarce despite the fact that a number of studies revealed that the use of constitutive models derived from three‐point bending tests on notched beams leads to overestimations of the bearing capacity of statically indeterminate slabs. In this context, this study aims at presenting an extensive experimental program that consisted of testing three SFRC slabs (3.0 × 3.0 × 0.1 m3) subjected to point load under a statically indeterminate test configuration. The testing procedure was followed by the extraction of 88 cores in order to analyze both fiber distribution and orientation by means of a non‐destructive inductive method. The results indicate that lower orientation numbers were observed in cylinders drilled from the slabs in comparison with those observed in the 150 × 150 × 600 mm3 notched reference beams tested to characterize the pre‐ and post‐cracking flexural performance of the SFRC produced. Based on these results, a straightforward design‐oriented approach to compute an orientation factor was proposed and considered to develop the constitutive law used to simulate the structural response of SFRC slabs by means of nonlinear finite element model. The numerical simulation results showed a good agreement with the experimental response, this evidencing that the orientation factor may permit to account for the differences caused by geometric and statistical scale‐induced factors between both the beams used for the SFRC flexural properties characterization and slabs produced with the same SFRC.

Experimental investigation of the effect of horizontal construction joints on the behavior of deep beams

Abstract Construction joints serve as interruption points in the concrete placement process, which is necessary because it is often not feasible to pour concrete continuously in many structures. The quantity of concrete that can be poured at a single instance depends on the batching and mixing capacity, as well as the strength of the formwork. An effective construction joint must ensure sufficient flexural and shear continuity across the junction. Many studies investigated the construction joints in the reinforced concrete (RC) normal beams, but there are no studies investigating the effect of construction joints on the behavior of the RC deep beams. This study was prepared to show the behavior of deep beams having horizontal construction joints (HCJs) extended through their entire length. The parameter studied in this research was the location of the HCJ within the beam height. Four simply supported RC deep beams were tested under a two-point static load up to failure. One of these beams was without a construction joint and was considered a reference beam. Each one of the other beams has only one horizontal construction. The location of these joints was below, at, or above the beam mid-height. The crack patterns, the strain distributions, the mode of failure, deflection, and failure load are discussed. It was found that the existence of construction joints below, at, or above the beam mid-height results in a decrease in load failure load by 9, 11, and 1% compared with the reference beam. It can be concluded that the best location of the HCJ in the RC deep beam is in the upper part of the beam.

Effect of strengthening by carbon fiber reinforced polymer sheets on the flexural behavior of reinforced self-compacting concrete beams under repeated loads

This study investigates the effect of strengthening self-compacted concrete (SCC) beams using CFRP sheets on flexural behaviour subjected to repeated loads. During the experiment, six rectangular reinforced SCC beams were evaluated; two were reference beams without strengthening, while the remaining four were strengthened with CFRP sheets. The beam’s length, depth, and width are 2100 mm, 300 mm, and 200 mm, respectively. A monotonic load was applied to one of the reference beams, while repeated loads were applied to the remaining (compression cyclic loads). The main parameters studied in this experimental work were the type of loading (monotonic and repeated), the positions of strengthening and the dimensions of CFRP sheets. The flexural behaviour of these beams was investigated through experimental examination by recording the ultimate load and maximum deflection. Meanwhile, the cracks’ pattern and failure modes were observed. The findings of the present study demonstrated that the limited cycles of repeated loads have marginal effect on the flexural behaviour of the beams. This results in an ultimate load reduction of no more than 11%. It was also noted that SCC beams strengthened using CFRP sheets subjected to repeated loads significantly affected the flexural behaviour of these beams. Consequently, the ultimate load of the strengthened beams was improved by up to 18%. Besides, the maximum deflection of the strengthened SCC beams was reduced by 45% compared to those without strengthening. Using strengthening throughout the beams’ entire width and length that are subjected to repeated loads improved their ultimate load to surpass that of non-strengthened beams under monotonic loads by as much as 7%.

Flexural behavior of beams strengthened with GFRP bars and high‐performance fiber‐reinforced concrete

AbstractThe flexural behavior of beams strengthened with GFRP bars and high‐performance fiber‐reinforced concrete (HPFRC) was investigated in this paper. The four‐point flexural response of one reference beam and four beams strengthened with high‐performance fiber‐reinforced concrete was investigated by experimental research and theoretical calculation. The experimental and theoretical data (strain, load, etc.) are discussed. Parameters varied included the strengthening scheme (bottom‐side strengthening and three‐side strengthening) and the type of high‐performance fiber‐reinforced concrete (engineered cementitious composite [ECC] and ultra‐high‐performance concrete [UHPC]). The results showed that the cracking load and ultimate load of beams strengthened with UPFRC material were 31.3%–170% and 9.6%–20.7% higher, respectively, relative to the reference beam. Beams with three‐side strengthening (without interfacial debonding) had higher ultimate load, smaller crack width, and better durability relative to beams with bottom‐side strengthening. The UHPC layer was more effective in increasing the ultimate bearing capacity, and ECC strengthening layer was more effective in inhibiting cracking development of beams. Based on the experimental results, a model was proposed to predict the ultimate bearing capacity of beams strengthened with high‐performance fiber‐reinforced concrete, which could provide good agreement between the experimental and predicted results.

Flexural behavior of RC beams with multiple parallelogram openings

On account of the detrimental effects of the post-drilling holes in hardened RC beams, designing the beams with transverse openings before construction is becoming more popular in the last decades. The contribution of the transverse openings to the overall economy and efficiency of construction by reducing the unusable dead space in the floor height is a rather significant motivation behind the vast number of studies on this topic. In search for the opening geometries and reinforcement schemes with the least negative effects on the beam behavior, the present study focused on the parallelogram (diamond) opening geometry, which is thought to facilitate the transmission of diagonal compression forces in the beam web thanks to the inclination of the posts. Within this scope, a total of 12 beams, including two reference beams without openings, were tested under four-point bending. Circular, square and parallelogram (45°−60°−75°) opening geometries were adopted and the test results were evaluated based on the opening geometry and the longitudinal reinforcement ratio. In order to avoid various shear failure modes of beams with openings, different special reinforcement schemes were employed around the web openings. Two different longitudinal reinforcement ratios were used to understand if pure flexural failure can be reached in RC beams with openings without being affected by different shear failure modes (beam- and frame-type diagonal tension and diagonal compression). The inclination angle of the posts between the openings in parallelogram opening geometry was found to be the most crucial parameter in the final beam failure and beam ductility. The use of diagonal cables surrounding the openings and connecting the posts and chords was established to be obligatory in square and parallelogram opening geometries to reach a ductile beam behavior without being affected by Vierendeel panel action and different shear failure modes.

Motion-artifact-free single shot two-beam optical coherence elastography system.

The assessment of the biomechanical properties of the skin using various imaging techniques has been used as a diagnostic tool in dermatology. Optical coherence elastography (OCE) is one of the techniques that allows for the measurement of elastic properties. OCE relies on measuring tissue displacements induced by external sources. Measuring the tissue's mechanical properties in vivo using OCE is often challenging due to bulk tissue movement. This study aimed to develop an OCE system that allows for minimizing the effects of bulk tissue movements. To achieve this, we designed a two-beam OCE system that simultaneously measures the tissue displacement at two locations on the sample. This allows for cancelling the effect of the tissue bulk movement, which is common to both measurement points. We used a piezoelectric transducer to generate surface acoustic waves (SAW) in the sample. The velocity of the excited waves, which is proportional to the rigidity of the sample, was measured by calculating the phase delay of the SAW at two locations on the sample. Simultaneous measurement at two locations was achieved by dividing a single light beam into two by focusing on the sample at two different locations. The two beams travel different optical path lengths, and the reflected signals were depth encoded in a single optical coherence tomography scan using a single reference beam. The system was characterized using different tissue-mimicking phantoms and the skin of healthy volunteers at the wrist and the palm. We achieved an approximately 50-fold increase in phase sensitivity measurement. We designed a simple two-beam OCE system that effectively minimizes the effect of tissue movement. We believe that the presented system will find immediate applications in the clinic to monitor the progression of systemic sclerosis disease.

Применение термически поврежденной древесины в деревоклееных балочных конструкциях

This paper deals with the experimental research results of laminated wood beam structures made using lamellas produced from the pine trees, partially damaged in forest plantations. The purpose of the research has been to study the stress-strain state of laminated wood beam structures utilizing the wood damaged by the thermal exposure caused by a forest fire. Previously, the authors have carried out a significant amount of research into the physical, mechanical and strength properties of thermally damaged pine wood. They have established the dependence of the strength properties of the wood on the degree of fire damage and the wood sampling points according to the height of the stem. Prior to the experiment on the large-scale models in the “Lira 10.12” software complex, numerical studies of four series of single beams with a span of 6.0 m and a section of 140×500 mm produced from the 1st grade pine wood in the upper and lower parts of the section and from thermally damaged pine wood in the middle part of the section. A comparative analysis of the beams has been performed with varying percentages of replacement of the healthy pine wood with the one weakened by the fire along the height of the section: 76, 62, 51 and 36 %. As a result of the numerical calculation of the beams under study using the derived safety factor equaling 1.136, their actual load-bearing capacity has been determined. It has been established that a decrease in the load-bearing capacity of the СB-2 beams equals 12.2 kN, which is 16.05 % relative to the reference beam CB-5, made entirely of the 1st grade pine wood. For the CB-4 beams a decrease in the load-bearing capacity equals 7.4 kN, which is 9.74 % relative to the reference beam CB-5. The difference between the calculated and experimental breaking loads is 9.5 to 14.3 %. The introduction of the safety factor equaling 1.136 in the numerical calculation ensures sufficient convergence of the calculated and experimental data (the measurement error is 3 %). The load-bearing capacity of the reference beam СB-5, made entirely of the 1st grade pine wood, is 12.38 kN/m. For beams CB-1 to CB-4 it equals from 8.53 to 12.06 kN/m. The relative decrease in the load-bearing capacity did not exceed 31.1 to 32.5 %. It has been established that the CB-4 beam, made using 34 % of lamellas produced from thermally damaged pine wood, allows for the load-bearing capacity of 97.5 % relative to the beams made entirely of the 1st grade pine wood.