Length Of Spot Research Articles

Femtogram heavy metal element detection by simultaneous spatial and temporal focusing laser induced breakdown spectroscopy.

Laser-induced breakdown spectroscopy is a simple and fast element detection method which is applicable for liquid samples. In order to reduce the quenching effect and hydrodynamic instability of the liquid sample, the liquid-to-solid phase conversion is often performed. After phase conversion, it is difficult to confine the solute to a micrometer-scale region on the substrate, so the excited laser beam with large beam spot and small longitudinal focal length is preferred. Therefore, the simultaneous spatial and temporal focusing laser is expected to be more suitable for liquid sample detection. To evaluate the effect of the spatiotemporal focusing, a silicon wafer coated with 400-nm-thick Cr film is used as the sample. Experimental results show that the spatiotemporal focusing laser can excite only Cr film, which cannot be achieved by the spatial focusing laser. Using the spatiotemporal focusing laser, the limit of detection of Pb in water is down to 12.5 fg. Contrastingly, using the spatial focusing laser, the elements in the substrate are excited which makes the detection of the trace Pb element in liquid samples become impossible. The method presented in this study may find important applications in water pollution control, urine and blood tests.

Ice-Ice Disease Prevalence and Intensity in Eucheumatoid Seaweed Farms: Seasonal Variability and Relationship with the Physicochemical and Meteorological Parameters.

Since its initial report in the Philippines in 1981, ice-ice disease (IID) remains a substantial threat to the sustainability of eucheumatoid seaweed production. However, comprehensive investigations into the prevalence, intensity, and potential relationships with physicochemical and meteorological parameters are limited, particularly in open-sea farms. This is the first study to conduct a 12-month monitoring of IID prevalence and intensity in eucheumatoid seaweed farms in Tawi-Tawi, Philippines. The research aimed to elucidate seasonal variations and potential associations with physicochemical and meteorological parameters. The findings revealed significant seasonal variations in IID prevalence, with a higher incidence observed during the dry season compared to the wet season. Additionally, deep-water farms exhibited significantly higher prevalence and ice-ice spot numbers per bundle compared to shallow-water farms. Furthermore, Kappaphycus striatus displayed a significantly greater ice-ice spot length per bundle compared to K. alvarezii. Notably, no interaction effects were observed among season, species, and depth. Interestingly, while no correlations were found between ice-ice disease and most measured physicochemical and meteorological parameters (temperature, salinity, pH, water current velocity, wind speed) or nutrient concentrations (phosphate, nitrate, nitrite), an inverse correlation (p < 0.05) emerged between ammonium levels and IID intensity parameters (number and length of ice-ice spot per bundle). Moreover, a positive correlation was observed between monthly rainfall and IID intensity. These findings offer valuable insights into the dynamics of IID in open-sea eucheumatoid seaweed (Kappaphycus) farming, highlighting the influence of seasonality, depth, and species susceptibility, as well as the relationship between IID severity and ammonium levels and rainfall.

Effects of spot size on the operation mode of GaAs photoconductive semiconductor switch employing extrinsic photoconductivity

To guide the illuminating design to improve the on-state performances of gallium arsenide (GaAs) photoconductive semiconductor switch (PCSS), the effect of spot size on the operation mode of GaAs PCSS based on a semi-insulating wafer with a thickness of 1 mm, triggered by a 1064-nm extrinsic laser beam with the rectangular spot, has been investigated experimentally. It is found that the variation of the spot size in length and width can act on the different parts of the output waveform integrating the characteristics of the linear and nonlinear modes, and then significantly boosts the PCSS toward different operation modes. On this basis, a two-channel model containing the active and passive parts is introduced to interpret the relevant influencing mechanisms. Results indicate that the increased spot length can peak the amplitude of static domains in the active part to enhance the development of the nonlinear switching, while the extended spot width can change the distribution of photogenerated carriers on both parts to facilitate the linear switching and weaken the nonlinear switching, which have been proved by comparing the domain evolutions under different spot sizes.

Comparative Study of the Co-Occurring Alternaria and Colletotrichum Species in the Production of Citrus Leaf Spot.

Both of the two citrus diseases, Alternaria brown spot (ABS) and Anthracnose, caused by Alternaria and Colletotrichum spp., respectively, can produce leaf lesions which are hard to differentiate. These two diseases have been confused as causal agents of brown spot for over a decade in China. In this study, citrus leaves with or without brown spot were collected from Zhaoqing, Guangdong and Wanzhou, Chongqing, and were further used for the taxonomic and functional comparisons between the co-occurring Alternaria and Colletotrichum species. In the amplicon sequencing, the average relative abundance and the composition of Alternaria, but not Colletotrichum, increased (from 0.1 to 9.9, p = 0.059; and to 0.7, p < 0.05) and significantly altered (p < 0.01) with the brown spot in Zhaoqing and Wanzhou, respectively. Two representative isolates Alternaria sp. F12A and Colletotrichum sp. F12C, from the same brown spot, were proved with different virulence and host response activation to citrus leaves. F12A caused typical symptoms of brown spot with the average spot length expanded to 5 and 6.1 cm, and also altered the citrus global gene expression 48 and 72 h after inoculation. In addition, F12A enriched the expression of genes that were most frequently involved in plant defense. In comparison, F12C caused leaf spot limited to the wounded site, and its milder activation of host response recovered 72 h after inoculation. Our study indicates that the incidence of brown spot in China is caused by Alternaria species, and the ABS should be a fungal disease of major concern on citrus.

Thermal and hydraulic optimization of supercritical CO2 pillow plate heat exchanger with ellipse weld spots in CSP system

Pillow plate heat exchangers (PPHE) with compactness and high thermal performance are applying widely. In present article, PPHE with ellipse weld spots is first proposed, and turbulent flow and heat transfer of supercritical carbon dioxide (S-CO2) in PPHE channel is analyzed and optimized. The channel is made of many periodically overlapped metal plates, and the plate is a flat plate with many staggered convex-concave spots. Compared with channel section with concave spot, channel section with convex spot has higher flow velocity, lower flow fraction and higher heat transfer coefficient, so it dominates heat transfer process. Along flow direction, heat transfer coefficient in channel section with convex spot gradually increases to maximum in flat region, and then it drops to minimum in downstream region of convex spot, while friction factor has opposite tendency. A meaningful phenomenon is found that higher heat transfer coefficient (h) and lower friction factor (f) appear simultaneously in the same region. The flow and heat transfer behavior are significantly affected by weld spot geometries, and elliptic weld spot with larger ratio of spot length and width Ψ results in weaker vortices and fluid impingement, which remarkably reduces friction factor. The elliptic weld spot with Ψ = 1.4 is optimum geometry for maximum index of Nu/f1/3. In addition, correlations of f and Nusselt number (Nu) for Ψ = 0.6–1.4 and Re = 4132–6650 are developed.

Process Parameters Analysis of Laser Phase Transformation Hardening on the Raceway Surface of Shield Main Bearing

The main bearing of the shield machine has a huge structure and severe service conditions, which are prone to wear and fatigue damage. To improve the anti-wear and anti-fatigue ability of the raceway surface of the shield main bearing, laser transformation hardening under different parameters of the shield main bearing raceway material 42CrMo steel was researched. The effects of laser power and scanning speed on the phase transformation of 42CrMo steel and the depth of the hardened layer were studied. The numerical model was verified using the theoretical and experimental results. Orthogonal tables of laser processing parameters are established. The results show that the depth of the hardened raceway layer increases with increased laser power and decreased laser scanning speed. According to the results of orthogonal primary and secondary analyses and fuzzy comprehensive evaluation, the depth of the hardened layer of the raceway can reach 1.08 mm, and the hardened layer is relatively uniform (laser power, 2250 W; scanning speed, 20 mm/s; spot length, 5 mm). The research in this paper provides a theoretical basis and technological innovation for the processing methods and engineering applications of high-reliability and long-life shield main bearings, which is of great engineering significance.

Redescription of Astyanax brevoortii (Gill, 1858) (Characiformes, Characidae) and description of three new species of Astyanax subgenus Poecilurichthys, from Caribbean Sea basins, Venezuela

In Astyanax (Poecilurichthys), we recognize six species-groups defined by the distribution of melanophores on the body: 1. bimaculatus; 2. rupununi; 3. abramis: 4. orthodus; 5. asuncionensis; and 6. anterior, which are named for a representative species. Astyanax brevoortii1 is redescribed using specimens from Trinidad (including types). This species, as a member of the bimaculatus species-group, is distinguished by lacking a concentration of melanophores outlining the scale margins on the sides of body. Three new species of the bimaculatus species-group are described: A. caroni n. sp. from the Caroni River drainage, which differs in having all of the teeth of the internal premaxillary series pentacuspid (vs. heptacuspid), and the length of the caudal-peduncle spot which is less than two times the eye diameter (vs. at least twice eye diameter). A. garuttii n. sp. from the San Juan River and Gulf of Cariaco drainages is distinguished by osteological characters and by morphological characters identified by principal component analysis. A. cuyuni n. sp. from the Cuyuni River (Essequibo River Basin), is distinguished by having a foramen in the pterotic and sphenotic bones (vs. absent), and the shape of the last two neural spines that form a posteriorly directed arc, that covers the epineurals.

Redescription of Astyanax brevoortii (Gill, 1858) (Characiformes, Characidae) and description of three new species of Astyanax subgenus Poecilurichthys, Caribbean Sea, Venezuela

In Astyanax (Poecilurichthys), we recognize six species-groups defined by the distribution of melanophores on the body: 1. bimaculatus; 2. rupununi; 3. abramis: 4. orthodus; 5. asuncionensis; and 6. anterior, which are named for a representative species. Astyanax brevoortii1 is redescribed using specimens from Trinidad (including types). This species, as a member of the bimaculatus species-group, is distinguished by lacking a concentration of melanophores outlining the scale margins on the sides of body. Three new species of the bimaculatus species-group are described: A. caroni n. sp. from the Caroni River drainage, which differs in having all of the teeth of the internal premaxillary series pentacuspid (vs. heptacuspid), and the length of the caudal-peduncle spot which is less than two times the eye diameter (vs. at least twice eye diameter). A. garuttii n. sp. from the San Juan River and Gulf of Cariaco drainages is distinguished by osteological characters and by morphological characters identified by principal component analysis. A. cuyuni n. sp. from the Cuyuni River (Essequibo River Basin), is distinguished by having a foramen in the pterotic and sphenotic bones (vs. absent), and the shape of the last two neural spines that form a posteriorly directed arc, that covers the epineurals.

Ultrabright Electron Bunch Injection in a Plasma Wakefield Driven by a Superluminal Flying Focus Electron Beam

We propose a new method for self-injection of high-quality electron bunches in the plasma wakefield structure in the blowout regime utilizing a "flying focus" produced by a drive beam with an energy chirp. In a flying focus the speed of the density centroid of the drive bunch can be superluminal or subluminal by utilizing the chromatic dependence of the focusing optics. We first derive the focal velocity and the characteristic length of the focal spot in terms of the focal length and an energy chirp. We then demonstrate using multidimensional particle-in-cell simulations that a wake driven by a superluminally propagating flying focus of an electron beam can generate GeV-level electron bunches with ultralow normalized slice emittance (∼30 nm rad), high current (∼17 kA), low slice energy spread (∼0.1%), and therefore high normalized brightness (>10^{19} A/m^{2}/rad^{2}) in a plasma of density ∼10^{19} cm^{-3}. The injection process is highly controllable and tunable by changing the focal velocity and shaping the drive beam current. Near-term experiments at FACET II where the capabilities to generate tens of kA, <10 fs drivers are planned, could potentially produce beams with brightness near 10^{20} A/m^{2}/rad^{2}.

РАБОТА КОЛЕСНОГО ДИФФЕРЕНЦИАЛА В ПРОЦЕССЕ РАЗГОНА ПАХОТНОГО АГРЕГАТА

The use of ballast on wheeled tractors leads to over-compaction of the soil, including sub-arable horizons. When overclocking arable units with buried working bodies at operating speed, the engine will inevitably enter the overload mode. This leads to a decrease in productivity, fuel overspending, and deterioration of environmental indicators. The authors proposed for the first time to equip the driving wheels with built-in differentials. The basis of the wheel differential development concept is the eccentric application of external loads and the driving torque to the wheel. The purpose of the research is to identify structural and operational factors affecting the efficiency of the wheel differential, to establish the nature of the relationships between them. The operation of the driving wheel tire occurs under conditions of a deformed support surface. Acceleration of a mobile power vehicle with a built-in differential in the wheels is presented as a two-stage process. The first stage of acceleration corresponds to the operation of the gearbox in the planetary gearbox mode, the second stage - in the differential gearbox mode. The translational movement of the wheel, its rotation along the bearing surface is possible if the torque on the wheel rim is provided by the moment of friction force in the contact spot. The rotation of the bearing gear along the epicyclical gear, the formation of the tilting and lever moments in the wheel reducer contribute to the advancement of the pressure center along the length of the contact spot in the oncoming sector of the wheel, an increase in the friction force and tangential force, ensuring smooth starting of the tractor unit. After overcoming the moment of inertia of the rotating and translationally moving masses of the unit, the value of the required moment decreases. The driving bearing gear, remaining in the lower position, rotates the wheel. The gearbox has switched to differential operation. At the same time, the driver performs angular oscillations, the magnitude of which depends on the conditions of movement of the wheel and the traction resistance of the unit. The amount of torque required depends on the design parameters of the built-in differential, operating conditions, and gravity applied to the bearing drive gear of the planetary gearbox

Tightly focusing properties of chirped phase modulate Bessel-Gaussian beam

This research is to explore the focusing characteristics of chirped phase modulating the Bessel-Gaussian (BG) beam. It can be observed that the focal spot of mixed chirped phase of BG beam will split along the optical axis under different beam parameters β. Simultaneously, the spot length, the spot position and the peak intensity is tunable by modulating the light distribution factor b and chirped factor c1 and c2. In addition, the evolution of longitudinal field and transverse field is also explored in detail. With the introduction of the special chirped phase, the focusing pattern obtains a series of observable evolution characteristics. These results will be potentially applied to many optical frontier areas, such as optical information transmission, optical capture and modern medical treatment.

Identifying risk factors of intracerebral hemorrhage stability using explainable attention model.

Segmentation of intracerebral hemorrhage (ICH) helps improve the quality of diagnosis, draft the desired treatment methods, and clinically observe the variations with healthy patients. The clinical utilization of various ICH progression scoring systems has limitations due to the systems' modest predictive value. This paper proposes a single pipeline of a multi-task model for end-to-end hemorrhage segmentation and risk estimation. We introduce a 3D spatial attention unit and integrate it into the state-of-the-art segmentation architecture, UNet, to enhance the accuracy by bootstrapping the global spatial representation. We further extract the geometric features from the segmented hemorrhage volume and fuse them with clinical features such as CT angiography (CTA) spot, Glasgow Coma Scale (GCS), and age to predict the ICH stability. Several state-of-the-art machine learning techniques such as multilayer perceptron (MLP), support vector machine (SVM), gradient boosting, and random forests are applied to train stability estimation and to compare the performances. To align clinical intuition with model learning, we determine the shapely values (SHAP) and explain the most significant features for the ICH risk scoring system. A total of 79 patients are included, of which 20 are found in critical condition. Our proposed single pipeline model achieves a segmentation accuracy of 86.3%, stability prediction accuracy of 78.3%, and precision of 82.9%; the mean square error of exact expansion rate regression is observed to be 0.46. The SHAP analysis reveals that CTA spot sign, age, solidity, location, and length of the first axis of the ICH volume are the most critical characteristics that help define the stability of the stroke lesion. We also show that integrating significant geometric features with clinical features can improve the ICH progression scoring by predicting long-term outcomes. Graphical abstract Overview of our proposed method comprising of spatial attention and feature extraction mechanisms. The architecture is trained on the input CT images, and the first step output is the predicted segmentation of the hemorrhagic region. The output is fed into a geometric feature extractor and is fused with clinical features to estimate ICH stability using a multilayer perceptron (MLP).

Control over milling of rolled non-ferrous metal products

This paper looks at some hot-rolled strips that were to be cold-rolled and that were machined in order to enhance the process performance. It was done, in particular, to reach an optimized topography of the machined surface that consisted of alternating high and low spots. The high surface roughness (especially in the case of soft non-ferrous metals) caused turn-to-turn friction defects during further rolling operation. A two-sided processing line was examined that comprises an unwinder, pinch rolls, a leveler, shears, machines for up-milling of the strip top and bottom and a folder. Both conventional (with 14 helical teeth) and custom-built (with 2 or 7 helical teeth) interlocking slabtype milling cutters with the diameter of ~250 mm were used. Copper strips and strips made of copper alloys (including double brass) were machined. The authors examined the effect of the cutting mode (a relationship between the feed per minute SМ and the cutter RPM n) on the formation and removal of chips, durability of the tool, quality of the cold-rolled and machined surface &mdash; in particular on the length of the low spot (L). It was calculated how much travel the strips do in a full revolution of the cutter (SО) and in one fourteenth of a full revolution per tooth (SZ). Comparing these values with the length of the low spot the number of teeth was determined responsible for one low spot (L/SZ or L/SZ). Depending on the machining mode (SМ/n ratio) and based on the earlier proposed model, the following equation was performed: L = SО(L/SZ = 14), L = SZ (L/ SZ = 1) or SZ &lt; L &lt; SО (1 &lt; L`/SZ &lt; 14). A number of different constant milling modes was compared with the new dynamic technique which allows to account for the tool wear and adjust the milling mode in relation to the initial mode by reducing SМ/n. An analytical technique is described that allows to precisely choose the initial milling mode. It is shown that due to the mode adjustment the length of the low spot L` and the number of backup teeth increase. This appears to be reasonable before the preset maximum allowable value L`critical is reached. Note that as the plasticity of a rolled non-ferrous metal product rises, the value L critical decreases. It was found that this process control technique helps extend the uptime and the overall service life of the tool and improve the process performance.

Location and direction dependence in the 3D MTF for a high-resolution CT system.

The purpose of this study was to quantify location and direction-dependent variations in the 3D modulation transfer function (MTF) of a high-resolution CT scanner with selectable focal spot sizes and resolution modes. The Aquilion Precision CT scanner (Canon Medical Systems) has selectable 0.25mm or 0.5mm detectors (by binning) in both the axial (x-y) and detector array width (z) directions. For the x-y and z orientations, detectors are configured (x-y)=0.5 mm/(z)=0.5mm for normal resolution (NR), 0.25/0.5mm for high resolution (HR), and 0.25/0.25mm for super high resolution (SHR). Six focal spots (FS1-FS6) range in size from 0.4 (x-y)×0.5mm (z) for FS1 to 1.6×1.4mm for FS6. Phantoms fabricated from spherical objects were positioned at radial distances of 0, 4.0, 7.5, 11.0, 14.5, and 18.5cm. Axial and helical acquisitions were utilized and reconstructed using filtered back projection with the FC18 "Body," FC30 "Bone," and FC81 "Bone Sharp" kernels. The reconstructions were used to measure a 1D slice of the 3D MTF by oversampling the 3D ESF in the axial plane [MTF(fr ); φ=0°)], 45° out of the axial plane [MTF(fr ); φ=45°)], in the longitudinal direction [MTF(fr ); φ=80°)], and along the radial and azimuthal directions within the axial plane. The MTF(fr ); φ=45°) drops to 10% (f10 ) at 1.20, 1.45, and 2.06mm-1 for NR, HR, and SHR, respectively, for a helical acquisition with FS1, FC30, and r=4cm from the isocenter. The MTF(fr ); φ=45°) includes contributions of both the axial-plane MTF (f10 =1.10, 2.04, and 2.01mm-1 ) and the longitudinal MTF (f10 =1.17, 1.18, and 1.82mm-1 ) for the NR, HR, and SHR modes, respectively. For SHR, the axial scan mode showed a 15-25% improvement over helical mode in the longitudinal resolution. Helical pitch, ranging from 0.569 to 1.381, did not appreciably affect the 3D resolution (<2%). The radial MTFs across the axial field of view (FOV) showed dependencies on the focal spot length in z; for example, for SHR with FS2 (0.6×0.6mm), f10 at r=11cm was within 17% of the value at r=4cm, but for SHR with FS3 (0.6×1.3), the reduction in f10 was 46% from 4 to 11cm from the isocenter. The azimuthal MTF also decreased as r increased but less so for longer gantry rotation times and smaller focal spot dimensions in the axial plane. The longitudinal MTF was minimally affected (<11%) by position in the FOV and was principally affected by the focal spot length in the z-dimension. The 3D MTF was measured throughout the FOV of a high-resolution CT scanner, quantifying the advantages of different resolution modes and focal spot sizes on the axial-plane and longitudinal MTF. Reconstruction kernels were shown to impact axial-plane resolution, imparting non-isotropic 3D resolution characteristics. Focal spot size (both in x-y and in z) and gantry rotation time play important roles in preserving the high-resolution characteristics throughout the field of view for this new high-resolution CT scanner technology.

Approaching the radiating X-point in SOLPS-ITER modeling of ASDEX Upgrade H-mode discharges

In the present paper the ASDEX Upgrade (AUG) experimental trend of reaching the radiating X-point with nitrogen seeding is reproduced by SOLPS-ITER code modeling. In these experiments the whole divertor region below the X-point is cooled down by the impurity radiation if the seeding rate is large enough, and the maximal radiation is registered from the X-point region, or even from the confinement zone above the X-point. It is demonstrated that for constant seeding rate SOLPS-ITER simulations of the intensively seeded AUG discharges result in that the confined plasma goes into the radiation collapse as a certain threshold in seeding rate is exceeded. This threshold value increases with increasing discharge power. No stable regimes with the electron temperature below 5 eV in the confinement zone even above the X-point are achieved in the modeling if the seeding rate is large enough, in contrast to the experiment. However, such a regime may be achieved if the fueling, seeding and pumping rates are changing in time. Since the SOLPS-ITER code can simulate only steady state, another modeling strategy is chosen. The fueling and seeding rates are artificially reduced by 3 orders of magnitude and the impurity content is set to satisfy the condition that the ratio of electrons contribution originating from fuel atoms to ones coming from impurity atoms is about unity. It is suggested that the radial width of the cooled region in the confinement zone is of the order of the scrape-off layer width λ q , since it is driven by the same physics leading the energy flux to go from mostly radial to mostly parallel. Under these conditions, the radiative spot above the X-point behaves as the energy sink similarly to the energy sink near the divertor in the conventional regime. In extreme regimes (with large seeding rate), the width of the cold region inside the separatrix may exceed λ q , and up to 90% of discharge power can be radiated from the confined region. An estimate of the poloidal length of the radiative spot is suggested as well. Flow patterns of neutrals, deuterium ions, impurities, electric current and heat flows are analyzed for the regimes with intensive X-point radiation. The formation of an electric potential peak above the X-point is observed in the simulations, and the corresponding E × B drift flux appears to give the largest contribution to the main ion and impurity fluxes. This E × B drift flux together with the large ionization source change the parallel velocity with respect to its neoclassical profile. Consequently, the radial E field deviates from the neoclassical one, which might improve the turbulence suppression.

Temperature evolution, phase ratio and corrosion resistance of duplex stainless steels treated by laser surface heat treatment

• Laser surface heat treatment (LSHT) was performed on duplex stainless steels 2304, 2205, and 2507. • The effect of laser spot size and cooling time t 12/8 was investigated by numerical simulation and microstructure analysis. • LSHT obtained the peak temperature, the t 12/8 and the effective depth as 1350 °C, 8.9 s and 1.5 mm respectively. • Austenite percentage increased from 2%, 5%, and 38% to 27%, 36% and 55 % respectively for 2304, 2205, and 2507. • LSHT increased the corrosion pitting temperature from 13, 42 and 66 °C to 19, 52 and 76 °C respectively for 2304, 2205, and 2507. Duplex stainless steels (DSS) are promising materials due to excellent corrosion resistance and good mechanical properties. However, the corrosion resistance of DSS welded joints deteriorates unavoidably due to the unbalanced phase ratio, namely a low austenite percentage resulted from the welding thermal cycle. Laser surface heat treatment (LSHT) exhibits tremendous advantages to restore the corrosion resistance especially regarding efficiency and flexibility. By adjusting laser energy input, including laser power and spot size, different LSHT conditions were applied to DSS 2304, 2205 and 2507, whose austenite content were deliberately decreased to a very low percentage. The temperature evolution during the LSHT was calculated out by finite element analysis. Critical pitting temperature (CPT) was measured to evaluate the corrosion resistance. A long length of laser spot and a slow scanning speed were beneficial for increasing the austenite percentage during the LSHT. With the length of laser spot as 100 mm and the scan speed as 2 mm/s, the laser power was adjusted to obtain a target peak temperature of 1350 ℃, which provided a cooling time t 12/8 as 8.9 s and an effective action depth as 1.5 mm. For DSS 2304 and 2205, the austenite percentage increased from 2% and 5% in deteriorated samples to 28 % and 56 % after the LSHT; the CPT increased from 12.5 and 42.3 ℃ to 19.2 and 51.8 ℃ respectively. DSS 2507 remained the highest austenite percentage after the same deterioration and exhibited the best corrosion resistance under all the used conditions. The influence of LSHT processing parameters and material compositions on the phase transformation and the corrosion resistance was discussed accordingly.

Measurement of Chladni Mode Shapes with an Optical Lever Method.

Quantitatively determining the Chladni pattern of an elastic plate is of great interest in both physical science and engineering applications. In this paper, a method of measuring mode shapes of a vibrating plate based on an optical lever method is proposed. Three circular acrylic plates were employed in the measurement under different center harmonic excitations. Different from a traditional method, only an ordinary laser pen and a light screen made of ground glass are employed in this novel approach. The approach is as follows: the laser pen projects a beam to the vibrating plate perpendicularly, and then the beam is reflected to the light screen in the distance, on which a line segment made of the reflected spot is formed. Due to the principle of vision persistence, the light spot could be read as a bright straight line. The relationship between the slope of the mode shape, length of the light spot and the distance of the vibrating plate and the light screen can be obtained with algebraic operations. Then the mode shape can be determined by integrating the slope distribution with suitable boundary conditions. The full-field mode shapes of Chladni plate could also be determined further in such a simple way.

ОСНОВА МАТЕМАТИЧЕСКИХ МОДЕЛЕЙ ВЗАИМОДЕЙСТВИЯ КОЛЕСНЫХ ДВИЖИТЕЛЕЙ ЛЕСНЫХ МАШИН С ПОВЕРХНОСТЯМИ ДВИЖЕНИЯ

The purpose of the research, the results of which are presented in this article, is to analyze the scientific description of the properties of weak bearing movement surfaces of forest machines. The analysis has showed that universal mathematical models of the wheel propeller interaction with soil are based on the provisions of soil mechanics. This approach has been tested in the science of forestry production. It is successfully used by modern domestic and foreign researchers. However, with regard to the development and implementation of a mathematical description of interaction of ultra-low pressure&#x0D; wheeled mover (for example, in all-terrain wheeled vehicle) with supporting surfaces, it is necessary to take into account the ratio of the sides of the mover’s contact spot with the soil, since: mover pressure on the ground is defined as the partial load of a single mover and the area contact spots; the distribution of compressive stress over the depth of the soil mass depends on the ratio of the length and width of the contact spot; the bearing capacity characterizing the resistance to shear of the soil layers depends not only on its physical and mechanical properties, but also on the parameters of the contact spot, which is&#x0D; taken into account by special correction factors, the values of which depend on the aspect ratio of the contact spot. Soil rheology is considered to take into account the number of passes of a wheeled all-terrain vehicle along the route and its speed. One of the characteristics of the impact of the mover is exposure time. Value of the length of the contact spot is also used when determining the impact time of the mover on the soil.

Validation of the proton range accuracy and optimization of CT calibration curves utilizing range probing

Proton therapy is affected by range uncertainty, which is partly caused by an ambiguous conversion from x-ray attenuation to proton stopping power. CT calibration curves, or Hounsfield look-up tables (HLUTs), are institution-specific and may be a source of systematic errors in treatment planning. A range probing method to verify, optimize and validate HLUTs for proton treatment is proposed.An initial HLUT was determined according to the stoichiometric approach. For HLUT validation, three types of animal tissue phantoms were prepared: a pig’s head, ‘thorax’ and femur. CT scans of the phantoms were taken and a structure, simulating a water slab, was added on the scan distal to the phantoms to mimic the detector used for integral depth-dose measurements. The CT scans were imported into the TPS to calculate individual pencil beams directed through the phantoms. The phantoms were positioned at the therapy system isocenter using x-ray imaging. Shoot-through pencil beams were delivered, and depth-dose profiles were measured using a multi-layer ionization chamber. Measured depth-dose curves were compared to the calculated curves and the range error per spot was determined. Based on the water equivalent path length (WEPL) of individual spot, a range error margin was defined. Ratios between measured error and theoretical margin were calculated per spot. The HLUT optimization was performed by identifying systematic shifts of the mean range error per phantom and minimizing the ratios between range errors and uncertainty margins.After optimization, the ratios of the actual range error and the uncertainty margin over the complete data set did not exceed 0.75 (1.5 SD), indicating that the actual errors are covered by the theoretical uncertainty recipe.The feasibility of using range probing to assess range errors was demonstrated. The theoretical uncertainty margins in the institution-specific setting potentially may be reduced by ~25%.

A simple approach to determine the mode shapes of Chladni plates based on the optical lever method

This article introduces a simple approach based on the optical lever method to quantitatively determine the Chladni patterns of 2D plane standing waves on an elastic plate. Only an ordinary laser pen and a light screen made of ground glass are auxiliarily used during the measurement, which can be done quickly during classroom demonstrations in college physics courses. Three circular acrylic plates each with a thickness of 1 mm are tested under different center harmonic excitations. The beam from the laser pen is projected to the vibrating plate perpendicularly and reflected to the light screen in the distance, and the slope of the mode shape at the laser point can be determined with the length of the light spot on the light screen. Then, the observed mode shape can be obtained by integrating the slope distribution. Theoretical models and numerical simulations are also conducted to verify the accuracy of the present method, and results show that they compare very well. The present approach can be further applied to determine the full-field mode shapes of Chladni plates in a rather simple fashion.