Beam Area Research Articles

Effect of equalization filters on measurements with kerma-area product meter in a cardiovascular angiography system.

PurposeThis study aimed to evaluate the effect of equalization filters (EFs) on the kerma‐area product (KAPQKM) and incident air‐kerma (Ka,i,QKM) using a kerma‐area product (KAP) meter. In addition, potential underestimations of the Ka,i,QKM values by EFs were identified.Materials and methodsA portable flat‐panel detector (FPD) was placed to measure the X‐ray beam area (A) and EFs dimension at patient entrance reference point (PERP). Afterward, a 6‐cm3 external ionization chamber was placed to measure incident air‐kerma (Ka,i,Qext) at PERP instead of the portable FPD. KAP reading and Ka,i,Qext were simultaneously measured at several X‐ray beam qualities with and without EFs. The X‐ray beam quality correction factor by KAP meter (kQ,Q0KM) was calculated by A, Ka,i,Qext and KAP reading to acquire the KAPQKM and Ka,i,QKM. Upon completion of the measurements, KAPQKM, Ka,i,QKM, and Ka,i,Qext were plotted as functions of tube potential, spectral filter, and EFs dimension. Moreover, Ka,i,QKM/Ka,i,Qext values were calculated to evaluate the Ka,i,QKM underestimation.ResultsThe kQ,Q0KM values increased with an increase in the X‐ray tube potential and spectral filter, and the maximum kQ,Q0KM was 1.18. KAPQKM and Ka,i,QKM decreased as functions of EFs dimension, whereas Ka,i,Qext was almost constant. Ka,i,QKM/Ka,i,Qext decreased with an increase in EFs dimension but increased with an increase in tube potential and spectral filter, and the range was 0.55–1.01.Conclusions Ka,i,QKM value was up to approximately two times lower than the Ka,i,Qext values by EFs. When using the Ka,i,QKM value, the potential Ka,i,QKM underestimation with EFs should be considered.

Particularities of photonic and structural transformations in the polystyrene film during pulsed infrared laser irradiation

Two new kinds of the structural in-homogeneities in the polystyrene films were created by the irradiation of the film with nanosecond pulses of the infrared laser with 1064 nm wavelength. At the beginning of the irradiation dark micro-inclusions having unusual close to rectangular geometries appeared. After about 30 seconds of the irradiation one more kind structural distortions appeared having the geometries of the systems of the concentric micro-rings. Simultaneously with the creation of these concentric micro-rings the film started to emit bright blue luminescence all over its area and significant focusing of the laser beam during its propagation through the film was observed resulting in the generation of the bright white flashes at the screen installed behind the film. The creation of the dark rectangular spots as well as of the concentric micro-rings are ascribed to the non-linear interactions between the laser radiation and the structural distortions produced in the film due to photo-thermal processes excited in the film.

A rapid method for pressure-mapping ultrasound fields using a moving hydrophone

Medical ultrasound transducers are commonly characterized in well-controlled water tanks using miniature pressure-calibrated hydrophones. Spatial beam dimensions of the ultrasound field can be quantified by positioning hydrophones in a 2D plane where acoustic waveforms are acquired at closely spaced locations. However, even when using automated computer-controlled positioning, this technique is time consuming if the hydrophone is repositioned and allowed to come to rest at each location where pressure measurements are desired. Here we present a novel technique where acoustic waveforms are acquired while the hydrophone is in motion. The transducer under test is pulsed at a rate which, depending on the hydrophone speed, determines the spatial resolution of the pressure map. Applying this technique results in substantial time savings and allows larger beam areas to be more accurately mapped. Limitations, such as translation stage motor noise and pulse length, are discussed and examples are presented which demonstrate the ability to rapidly characterize a variety of ultrasound transducer types.

Evaluation of the efficacy of gallium-aluminum-arsenide laser acupuncture in the management of knee osteoarthritis

Background/aim Knee osteoarthritis is a common degenerative disease affecting the joint, causing progressive loss of cartilage and inflammation. Its main symptoms are pain and stiffness. Medications such as NSAIDs have little benefit and are usually accompanied by serious adverse effects. The aim of this study was to evaluate the efficiency of laser acupuncture in the management of stage 2 or 3 knee osteoarthritis. Patients and methods The study was carried out on 30 patients (24 females and six males) diagnosed as having stage 2 or 3 knee osteoarthritis. The patients were recruited from the Complementary and Alternative Medicine Clinic at the Medical Centre of Excellence, National Research Centre, Cairo, Egypt. The patients were subjected to low-power laser (gallium-aluminum-arsenide 905 nm) with touch sensor guide light, power output of 100 mill watts, beam area of 1 cm2, 1-min irradiation time, frequency 10 000 Hz, duty cycle 100%, total energy per point 6 J, energy density 6 J/cm2, and irradiance 0.1 W/cm2, for 3 days/week for a duration of 4 weeks (12 session), directed at various acupuncture points (ST 35, ST 36, Sp 9, Sp 10, GB 34, Sp 6, and liv3). Clinical and laboratory parameters were assessed before and after laser therapy. Results Pain on visual analog scale, number of tender points, tenderness score, angle of knee flexion, heel to hip distance, Western Ontario McMaster Universities Osteoarthritis Index scale score, and Lequesne Index showed significant improvement after treatment (P<0.05). Timed up and go test result was decreased after laser sessions, but its improvement was insignificant statistically. Significant improvement and increase of enkephalin and immunoglobulin (IL-4) were recorded after treatment. Conclusion Laser acupuncture showed efficacy in the management of stage 2 or 3 knee osteoarthritis.

Quantifications of Intensity-Modulated Radiation Therapy Plan Complexities in Magnetic Resonance Image Guided Radiotherapy Systems

Background: In this study, the complexities of step-and-shoot intensity-modulated radiation therapy (IMRT) plans in magnetic resonance-guided radiation therapy systems were evaluated.Materials and Methods: Overall, 194 verification plans from the abdomen, prostate, and breast sites were collected using a <sup>60</sup>Co-based ViewRay radiotherapy system (ViewRay Inc., Cleveland, OH, USA). Various plan complexity metrics (PCMs) were calculated for each verification plan, including the modulation complexity score (MCS), plan-averaged beam area (PA), plan-averaged beam irregularity, plan-averaged edge (PE), plan-averaged beam modulation, number of segments, average area among all segments (AA/Seg), and total beam-on time (TBT). The plan deliverability was quantified in terms of gamma passing rates (GPRs) with a 1 mm/2% criterion, and the Pearson correlation coefficients between GPRs and various PCMs were analyzed.Results and Discussion: For the abdomen, prostate, and breast groups, the average GPRs with the 1 mm/2% criterion were 77.8 ± 6.0%, 79.8 ± 4.9%, and 84.7 ± 7.3%; PCMs were 0.263, 0.271, and 0.386; PAs were 15.001, 18.779, and 35.683; PEs were 1.575, 1.444, and 1.028; AA/Segs were 15.37, 19.89, and 36.64; and TBTs were 18.86, 19.33, and 5.91 minutes, respectively. The various PCMs, i.e., MCS, PA, PE, AA/Seg, and TBT, showed statistically significant Pearson correlation coefficients of 0.416, 0.627, −0.541, 0.635, and −0.397, respectively, with GPRs.Conclusion: The area-related metrics exhibited strong correlations with GPRs. Moreover, the AA/Seg metric can be used to estimate the IMRT plan accuracy without beam delivery in the <sup>60</sup>Co-based ViewRay radiotherapy system.

Effect of Photobiomodulation on the Incidence of Alveolar Osteitis and Postoperative Pain following Mandibular Third Molar Surgery: A Double-Blind Randomized Clinical Trial.

The current study aimed to evaluate the effectiveness of photobiomodulation therapy for the prevention of incidence of alveolar osteitis (AO) and postoperative pain following third molar surgery. In this double-blind clinical trial, the impacted teeth of patients having bilateral impacted mandibular third molars were surgically extracted; for each participant, one socket was randomly assigned to receive photobiomodulation treatment, the other received sham treatment. 660nm 200mW CW was applied at a distance of ~1cm to 4 points onthe occlusal area of extraction socket (beam area at the tissue ~0.64 cm2 , 312.5mWcm-2 , 1J, 1.6Jcm-2 ). Also, 810nm 200mW CW was applied at tissue surface at three points on the buccal and three points on the lingual gingiva, for 15s (400mWcm-2 , 3J, 6Jcm-2 ). There was a statistically meaningful difference in AO frequency between the two groups, and the photobiomodulation group showed lower AO frequency compared with the sham PBM treatment (P-value=0.035). According to the findings of this study, photobiomodulation therapy reduced the incidence of AO following surgical removal of impacted mandibular third molars. The incidence of AO typically occurs 3-7days post-extraction, and our results suggest that PBM treatment within the 7days could help reduce the risk of AO development.

Seismic Performance of Steel Fiber Reinforced High-Strength Concrete Beam-Column Joints.

In high–strength concrete, the reinforcement concentration will cause some problems in the beam–column joints (BCJs) due to a large amount of transverse reinforcement. Hence, the main object of this paper is to prevent the reinforcement concentration and reduce the amount of transverse reinforcement in the BCJs through the ideal usage of steel fibers and reinforced high–strength concrete. Pseudo–static tests on seven specimens were carried out to investigate and evaluate the seismic performance of beam–column joints in steel fiber reinforced high–strength concrete (SFRHC). Test variables were steel fiber volume ratio, concrete strength, the stirrup ratio in the core area, and an axial compression ratio of the column end. During the test, the hysteresis curves and failure mode were recorded. The seismic indicators, such as energy dissipation, ductility, strength, and stiffness degradation, were determined. The experimental results indicated that the failure modes of SFRHC beam–column joints mainly included the core area failure and the beam end bending failure. With the increase in stirrup ratio, volume ratio of steel fiber, and axial compression ratio in the core area, both the ductility and energy consumption of beam–column joints increased, while the opposite was true for concrete strength.

Numerical investigation of temperature distribution and melt pool dimension during dissimilar laser welding of AISI 304 and pure copper

In this research, the numerical simulation of the heat transfer phenomenon in dissimilar laser welding was performed. Metals of stainless steel 304 (AISI 304) and pure copper in the moving state were exposed to laser energy, and an asymmetric thermal field was obtained. The cross-sectional area of the concentrated beam and its intensity distribution were considered circular and Gaussian, respectively. Physical properties of metals, depending on temperature and thermophysical changes in the material properties, were considered. Different temperature distributions were obtained by changing various parameters, such as focal length, welding speed, and power; the obtained results were then compared with the experimental ones. The results showed that the molten pool formation was asymmetric and deviated toward the AISI 304 sheet. The heat affected zone (HAZ) was also more toward the AISI 304 sheet. The increase of the molten pool dimensions was much more significant due to the enhancement in the average power, as compared to the other parameters, thus indicating that the average power was a key factor increasing the dimensions of the molten pool. The results of the numerical simulation were consistent with the experimental results, proving their correctness.

Analysis and sizing of RC beams reinforced by external bonding of imperfect functionally graded plate

An analytical method based on the compatibility of deformations and equilibrium of forces is investigated to predict the reinforcement plate area in concrete beams strengthened with Functionally Graded (FG) plates bonded to the tension face of the beams. The models are given for beams having rectangular and T-crosssections. The effect of porosity that can happen inside FGM materials during their manufacture is also shown. New rules of the mixture that take into account different distribution rates of porosity in FG plates have been developed in this study. A parametric study is conducted to investigate the effect of several parameters such as the ultimate moment, plate stiffness, the distribution rate of the porosity, and compressive strength of the concrete. The results obtained show a significant gain in the reinforcement plate area of the RC beam strengthened with an FG plate relative to another reinforced with FRP plate, which makes it possible to reduce the interfacial stresses and prevents detachment of the reinforcing plate.

A Highly Inclusive Theory of Q-Switched Lasers

A highly inclusive theory of Q-switched lasers is presented which applies to both actively and passively Q-switched lasers. The theory expands on the author’s previous publications on energy optimization to include: (1) saturable absorbers exhibiting excited state absorption and therefore a finite Figure of Merit (FOM); (2) unequal beam areas in the gain and absorbing media; and (3) both pulsed and CW pumping. Design curves for optimizing the output energy for pulse pumped lasers and CW pumped lasers at a desired pulse rate are provided. As in the author’s previous work, the optimization equation is obtained utilizing Lagrange Multipliers and yields the value of the parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho = ln(n_{i}/n_{f})$ </tex-math></inline-formula> which maximizes the single pulse energy, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{i}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{f}$ </tex-math></inline-formula> are the laser inversion population densities before and after Q-switching. Using this initial result, the associated optimum absorber transmission and mirror reflectivity, pulse energy, peak power, and pulse width can be computed sequentially via simple formulas. The aforementioned parameters can all be expressed as functions of two variables, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z_{eff}$ </tex-math></inline-formula> , which are slight modifications of the variables <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and z previously introduced by the author for passively Q-switched lasers having infinite FOM and equal beam areas The term “plane wave theory” has sometimes been used by this and other authors in prior publications to describe a uniform pump profile in the laser medium, but we will refer to this special case more accurately as the “uniform pump theory”. The theory is extended here in the final section to include non-uniform pumping. The common case of a Q-switched laser end-pumped by a quasi-Gaussian CW laser is considered in detail and the theoretical results are found to agree well with experimental data.

Towards Transabdominal Functional Photoacoustic Imaging of the Placenta: Improvement in Imaging Depth Through Optimization of Light Delivery

Functional photoacoustic imaging of the placenta could provide an innovative tool to diagnose preeclampsia, monitor fetal growth restriction, and determine the developmental impacts of gestational diabetes. However, transabdominal photoacoustic imaging is limited in imaging depth due to the tissue’s scattering and absorption of light. The aim of this paper was to investigate the impact of geometry and wavelength on transabdominal light delivery. Our methods included the development of a multilayer model of the abdominal tissue and simulation of the light propagation using Monte Carlo methods. A bifurcated light source with varying incident angle of light, distance between light beams, and beam area was simulated to analyze the effect of light delivery geometry on the fluence distribution at depth. The impact of wavelength and the effects of variable thicknesses of adipose tissue and muscle were also studied. Our results showed that the beam area plays a major role in improving the delivery of light to deep tissue, in comparison to light incidence angle or distance between the bifurcated fibers. Longer wavelengths, with incident fluence at the maximum permissible exposure limit, also increases fluence within deeper tissue. We validated our simulations using a commercially available light delivery system and ex vivo human placental tissue. Additionally, we compared our optimized light delivery to a commercially available light delivery system, and conclude that our optimized geometry could improve imaging depth more than 1.6×, bringing the imaging depth to within the needed range for transabdominal imaging of the human placenta.

Electrode shape dependence of output microwave characteristics in reflex triode virtual cathode oscillator

A virtual cathode oscillator (vircator), which can generate a high-power microwave, has been widely studied over the last four decades. This paper describes the dependence of microwaves and electron beams generated in a reflex triode vircator on the electrode shape and material. The reflex triode vircator is driven by a Marx generator with an output voltage of 200 kV and a stored energy of 240 J. Experiments were conducted with aluminum and velvet cathodes and two types of electrode shapes: (1) circular, with a diameter of 46 mm, and (2) elliptical, with an aspect ratio of 2:3. Both shapes have the same emitting area. Experimental results revealed that the electric field strength of the microwave pulse generated with the elliptical area electrode was 1.3 times greater than that with the circular area electrode. In addition, an x-ray pinhole camera with a beryllium window was used to evaluate the cross-sectional shape of the electron beam. It was found from the x-ray images that the shape of the electron beam was nearly the same as that of the electrode and that the cross-sectional area of the elliptical electron beam was larger than that of the circular electrode although both the circular and elliptical electrodes have the same emitting area. These results show that the electrode shape is one of the important parameters for the vircator.

Mathematical Modeling of Multilayered Skin with Embedded Tumor Through Combining Laser Ablation and Nanoparticles: Effects of Laser Beam Area, Wavelength, Intensity, Tumor Absorption Coefficient and Its Position

Laser ablation is gaining acceptance as a cancer treatment technique because of its localized energy delivery to the tumorous tissue. The combination of laser ablation with nanoparticles allows for more precise targeting of the ablative area with less damage to adjacent healthy tissue. Nevertheless, heat damage to adjacent tissue is still a potential concern. Therefore, mathematical modeling of laser-tissue interactions is a necessary part of clinical treatment planning. In this study, the temperature distribution during laser-induced thermotherapy in cancer treatment investigates using a multilayered skin (epidermis, dermis, subcutaneous fat, and muscle) with an embedded tumor model. The effects of related parameters systematically investigate; wavelength, laser intensity, beam area, tumor absorption coefficient, tumor position, tumor blood perfusion rate, and irradiation time. Mathematical modeling in this study is solved by finite element method (FEM) via COMSOLTM Multiphysics Software. Laser absorption and thermal phenomena are described by Beer-Lambert’s law and Pennes’s bioheat equation.

Physical and Biological Properties of a Chitosan Hydrogel Scaffold Associated to Photobiomodulation Therapy for Dental Pulp Regeneration: An In Vitro and In Vivo Study.

Background The regeneration of dental pulp, especially in cases of pulp death of immature teeth, is the goal of the regenerative endodontic procedures (REPs) that are based on tissue engineering principles, consisting of stem cells, growth factors, and scaffolds. Photobiomodulation therapy (PBMT) showed to improve dental pulp regeneration through cell homing approaches in preclinical studies and has been proposed as the fourth element of tissue engineering. However, when a blood clot was used as a scaffold in one of these previous studies, only 30% of success was achieved. The authors pointed out the instability of the blood clot as the regeneration shortcoming. Then, to circumvent this problem, a new scaffold was developed to be applied with the blood clot. The hypothesis of the present study was that an experimental injectable chitosan hydrogel would facilitate the three-dimensional spatial organization of endogenous stem cells in dental pulp regeneration with no interference on the positive influence of PBMT. Methods For the in vitro analysis, stem cells from the apical papilla (SCAPs) were characterized by flow cytometry and applied in the chitosan scaffold for evaluating adhesion, migration, and proliferation. For the in vivo analysis, the chitosan scaffold was applied in a rodent orthotopic dental pulp regeneration model under the influence of PBMT (660 nm; power output of 20 mW, beam area of 0.028 cm2, and energy density of 5 J/cm2). Results The scaffold tested in this study allowed significantly higher viability, proliferation, and migration of SCAPs in vitro when PBMT was applied, especially with the energy density of 5 J/cm2. These results were in consonance to those of the in vivo data, where pulp-like tissue formation was observed inside the root canal. Conclusion Chitosan hydrogel when applied with a blood clot and PBMT could in the future improve previous results of dental pulp regeneration through cell homing approaches.

Finite Element Analysis on Seismic Performance of Tubular Web Reduced Section Connection

In order to avoid the brittle failure of the weld at the beam and column interface, a new type of prefabricated joint with tubular web reduced section connection (PTWRBS) between concrete-filled square steel tubular column and steel beam was proposed, so that move plastic hinge outward from the contact area of beam and column under earthquake action and be repaired and strengthened rapidly after earthquake. Numerical models of this new joint were established by using the finite element software ABAQUS and validated by test data. The finite element models were used to analyse the mechanical property of the joint under cyclic loading. The load-carrying capacity, hysteretic behaviour and failure mode were compared, and the influence of the thickness of cantilever beam flange, the number of high strength bolts, the widened width of cantilever beam flange and the weakening length of the tubular web beam flange on the seismic behaviour of PTWRBS. The research results showed that the energy dissipation of the joints under earthquake is mainly achieved through the plastic deformation of the tubular web beam section and the friction slip of the high-strength bolted area. The failure mode of the joint is local buckling in the plane of the tubular web beam segment, which realizes the plastic hinge outward from cantilever beam. In the design of the joint, parameters such as the thickness of cantilever beam flange, the number of connecting bolts, the widened width of cantilever beam flange and the weakening length of tubular web beam section flange should be taken into comprehensive consideration and selected reasonably, so as to the transfer of plastic hinge under earthquake action and the rehabilitation of the joint after earthquake could be achieved.

The Novel CPW 2.4 GHz Antenna with Parallel Hybrid Electromagnetic Solar for IoT Energy Harvesting and Wireless Sensors

The design and implementation's novelty simultaneously utilizes the antenna's frequency, polarization, and feed structure to maximize the harvested RF energy and become a microstrip communication circuit for wireless sensor or communication systems in IoT devices. In addition, the optimization of the parallel circuit configuration has a voltage doubler model with an integrated parallel system and thin-film solar cells. Implementation of the antenna structure has two-line feeds in one antenna. Usage both feeds have the same function as CPW circular polarization. Another advantage is that there is no miss-configuration when installing the port exchanges when using both output ports simultaneously. The 2-port antenna has an area of 1/2 per port (where accessible wavelengths work well at the 2.4 GHz frequency). It has been shown to achieve a relatively narrow bandwidth of 86.5 percent covering WiFi frequency band networks and IoT communications. It does not require additional filters and analog matching circuits that cause power loss in the transmission process in parallel voltage doubler circuits. Integrating a reflector on the CPW antenna with two ports for placement of thin-film solar cells provides antenna gain of up to 8.2 dB. It provides a wide beam range with directional radiation. Using a multi-stage parallel to increase voltage output and integrated with a thin-film solar cell converter proves efficient in the 2.4 GHz frequency band. When the transmission power density is -16.15 dBm with a tolerance of 0.023, the novel energy harvester configuration circuit can produce an output voltage of 54 mV dc without adding solar cell energy. And Integrated thin-film solar cell a light beam of 300 lux in the radiation beam area of -16.15 dBm, the energy obtained has a value of 1,74467V. It also shows that the implementation of this configuration can produce an optimal dc output voltage in the actual indoor and outdoor ambient settings. The optimization of antenna implementation and the communication process with Multiple signal classifications improves the configuration of antennas that are close to each other and have identical phase outputs. It is instrumental and efficient when applied to IoT devices.

MEVCUT BETONARME BİR TRİBÜNÜN TBDY 2019' A GÖRE PERFORMANSININ DEĞERLENDİRİLMESİ

The point to be considered in reinforced concrete building design is the purpose of use of the building. There is a significant risk in places where people spend a short time but use them heavily. Essential structures such as grandstands are designed according to the calculation and construction rules of reinforced concrete and steel structures according to TBDY 2019. However, in Turkey, this regulation has been newly added, and the previous calculation methods have changed; the new regulation has focused on the non-linear behavior through plastic hinge behavior and adopted the capacity design principle. Structures are exposed to horizontal and vertical loads over time. Most of the energy in a structure exposed to repetitive loads is consumed in the plastic hinges formed in the building elements. The distribution in the transfer of the sections forced in the structure under these loads changes. In our study, the determined building performance level of the tribune designed by the regulation, the damaged beam areas, and the axial capacity of the columns under seismic and non-earthquake conditions was determined. Then, these demand magnitudes will be compared with strain and internal force capacities, and structural performance evaluation will be made at the cross-section and building level.

Miskonsepsi Siswa pada Pemahaman Konsep Bangun Ruang

The purpose of this study is to describe 8th-grade students’ misconceptions in solving surface area and volume of beam and cube problems and their causal factors. This is qualitative descriptive research. Based on the research, students’ misconceptions in solving surface area and volume of beam and cube problems are misconceptions on the concept of a beam, misconceptions on the concept of the cube, misconceptions on the concept of prerequisite material, misconceptions on unit comprehension, misconceptions on the understanding of meaning, and misconceptions on sign and number operations. While the causal factors of misconception are students’ assumptions about the lack of importance of concepts so students only memorize formulas, students are not able to associate one concept with other concepts, lack of understanding concepts in prerequisite material, misunderstanding the meaning of words in a problem, students have difficulty understanding pictures., misunderstanding the difference in the size of area and length.

Design parameters and material‐scale damage evolution of seismic upgraded RC frames by viscoelastic haunch bracing‐dampers

AbstractTo improve the seismic design of reinforced concrete (RC) frame structures and upgrade existing RC frame structures that have insufficient seismic design, a new suitable seismic upgraded solution, the installation of viscoelastic haunch bracing‐dampers (VHBD) to increase the seismic performance of RC frames, is proposed in this paper. For a comprehensive and systematical research about this new upgraded frames system, a comparative study on the seismic performance between 15 RC frame structure specimens by adding the VHBD with different design parameters and one common RC frame structure specimen is performed under sinusoidal dynamic loading. The specific items of seismic performance mainly include hysteresis performance, load‐bearing capacity, stiffness degradation, energy dissipation capacity, and additional damping ratio, and so on. First, on the basic of this, the material‐scale damage evolution of structure specimens at each stage is qualitatively analyzed. Then, six reasonable material‐scale damage indexes that can describe the damage evolution of the structures precisely are proposed. Finally, a quantitative comparative analysis on the material‐scale damage evolution of structure specimens in the whole process is carried out under different design parameters. The research results indicate that the upgraded scheme (reasonable design parameters of and ) proposed in this study can improve the seismic performance of RC frame structures to the appropriate level required for the design, in terms of load‐bearing capacity, stiffness, energy dissipation capacity, and damping ratio. At the same time, the failure mode of the structures can be well controlled. The occurred damage at beam‐column joints is reasonably transferred to the beam area, which can guarantee the seismic design requirements of “strong joints and weak components.”

Air-Coupled Ultrasonic Probe Integrity Test Using a Focused Transducer with Similar Frequency and Limited Aperture for Contrast Enhancement.

Air-coupled ultrasonic probes require a special design approach and handling due to the significant mismatch to the air. Outer matching layers have to be soft so can be easily damaged and excitation voltages might cause the degradation of electrodes or bonding between the layers. Integrity inspection is desired during design, manufacturing, and exploitation. Spatial distribution of a transduction efficiency over piezoelement surface is proposed as a convenient means for the air-coupled probe integrity inspection. Focused transducer of similar center frequency is used to scan the surface of the inspected probe. However, such approach creates a challenge, i.e., area of the scanning beam is much smaller than the total receiving area of the inspected probe, therefore, contrast and imaging resolution are significantly degraded. Masking aperture made from cardboard and felt, placed at the focal point was proposed as solution. Far-range sidelobes were suppressed down to the noise floor (−50 dB) and the near-range sidelobes were reduced down to −17 dB. The proposed modification allows to use a similar frequency focused transducer. Probe integrity inspection can be carried out at significantly enhanced contrast and lateral resolution. Natural and artificial defects can be detected by the use of the proposed method.