Striation Pattern Research Articles

Numerical analysis and Schlieren visualization of gas flow dynamics inside the plasma arc cut kerf with curved cutting fronts

In plasma arc cutting (PAC), the characteristics of the gas flow exiting the nozzle significantly influence the cut quality. The high-pressure jet in PAC forms complex shockwave structures when it is incident on the metal to be cut. In this study, the flow behavior inside the kerfs of various geometries derived from an actual PAC workpiece is assessed. The shape of the cutting front in the kerf varies with the changing cutting speed. A high cutting speed yields a curved cutting front, resulting in unwanted gas flow behavior and adversely influencing the cutting performance. In this study, a computational fluid dynamics simulation model was used to analyze the effects of a curved cutting front on the gas flow behavior during the PAC process. The gas flow patterns obtained from the numerical simulations were qualitatively compared with the Schlieren experiment results. The analysis results indicated that the curvature of the cutting fronts generated oblique shockwave structures that significantly reduced the flow velocity. In particular, the weak shock structures throughout the curved cutting front gradually decreased the flow velocity. The critical flow velocity was realized in the kerf with a highly curved cutting front, beyond which the vertical penetration of the material was not possible. The shear stress lines concurred with the striation patterns on the kerf walls, thereby validating the numerical analysis results.

Analysis of the periodic variation of pellet ablation radiation intensity in ASDEX Upgrade

Abstract In a future fusion reactor, the main fuelling method will likely rely on the injection of solid hydrogen pellets. Current predictions assume that this goal can be achieved, since being based on a technology which is already largely developed. However, this belief is founded on modelling tools that are usually aligned to the observation made in existing devices and then extrapolated to reactor conditions. This approach needs a sound consideration of its intrinsic restrictions and any observed feature not reproduced by the utilised codes should be applied to check their validation and possibly contribute to their refinement. One specific feature still lacking an explanation of a reasonable and self-consistent mechanism in the current models is the appearance of a phenomenon called striations, which are high frequency variations in the radiation emitted during the pellet ablation process. In order to provide a sound and reliable database for further considerations, a dedicated analysis of this effect has been performed on the mid-size tokamak ASDEX Upgrade. Therefore, such cases have been selected with the relevant signal recorded with sufficient temporal resolution during experiments covering a wide variation of plasma and pellet parameters which are regarded to be potentially influential on the striation pattern. In addition, it was ensured that for any specific case the observed behaviour was reproducible for several individual ablation events under identical conditions. In all cases considered, the observed radiation-intensity variations appear with a typical pattern showing a broad peak of frequencies in the range 50 to 150 kHz. This characteristic unveils a notable resilience against any parameter variation. This new collection of data can now act as firm basis to corroborate future modelling code-validation efforts. In addition, the analysis method can provide a relatively simple way of reviewing future modelling predictions.

Machetes: Sharpening materials and methods – Producing different striation patterns on bone

As forensic anthropologists play a larger role in post-mortem examinations, the examination and interpretation of skeletal trauma resulting from sharp, blunt, projectile, and thermal injuries have become of critical importance and may assist in medicolegal death investigations. Although there is a plethora of research on sharp force trauma on bone, at present, there is little research regarding the striations produced by large bladed weapons on bone, whether those striations are weapon-specific, or whether they are the result of sharpening materials and methods. To test whether striations are weapon type specific, this study aimed to examine if different sharpening materials and methods produced different striations on the kerf walls of cut marks on bone produced by machetes. Or, if they do produce the previously identified ‘rolling hill’ striation pattern. Four factory machetes sharpened by the same manufacturer were re-sharpened using a wet stone, a bastard file, and a coarse and medium-grained machine grinder. The bones and casts were subjected to both macro and micro analyses, and the results identified clear differences in the shape of striation ridges and troughs, indicating that striation patterns are not weapon type-specific. The study's findings have opened up a new area of research into weapon types and the analysis of associated striation patterns and may aid in the identification of weapon types and the materials used for maintenance or sharpening, potentially offering additional evidentiary evidence.

Analysis of Deep-Water Low-Frequency Sound Multipath Arrivals and Interference Striation Patterns

The deep-water sound multipath arrivals and interference striation patterns not only vary with range and depth but also with frequency. The first two cases can be solved using a ray-mode method in the high-frequency limit. However, this method may cause unsatisfactory results in treating low-frequency sounds (as low as tens of Hertz) because of the Wentzel-Kramers-Brillouin (WKB) high-frequency approximation assumption. To overcome this problem, the authors exploited phase information to modify the ray parameters, such as the propagation range, the time delay, and the group velocity. Following that, a waveguide invariant (WI) expression was derived to address low-frequency sound interference problems. Numerical investigations demonstrated that the physical mechanism of the frequency dependence of the multipath arrivals and interference striation patterns could be better understood using this modified ray-mode method. In addition, the influence of bottom sound speed on multipath interference structures is also considered.

The parabasal filaments of Trichomonas vaginalis: A new filament and observations using 0.8 nm-resolution scanning electron microscopy

Trichomonas vaginalis is the etiologic agent of trichomoniasis, the most common nonviral sexually transmitted infection worldwide, with an estimated 260 million new cases annually. T. vaginalis contains organelles common to all eukaryotic cells, uncommon cell structures such as hydrogenosomes, and a complex and elaborate cytoskeleton constituting the mastigont system. The mastigont system is mainly formed by several proteinaceous structures associated with basal bodies, the pelta-axostylar complex made of microtubules, and striated filaments named the costa and the parabasal filaments (PFs). Although the structural organization of trichomonad cytoskeletons has been analyzed using several techniques, observation using a new generation of scanning electron microscopes with a resolution exceeding 1 nm has allowed more detailed visualization of the three-dimensional organization of the mastigont system. In this study, we have investigated the cytoskeleton of T. vaginalis using a diverse range of scanning probe microscopy techniques, which were complemented by electron tomography and Fast-Fourier methods. This multi-modal approach has allowed us to characterize an unknown parabasal filament and reveal the ultrastructure of other striated fibers that have not been published before. Here, we show the differences in origin, striation pattern, size, localization, and additional details of the PFs, thus improving the knowledge of the cell biology of this parasite.

Mechanical Resistance of the Largest Denticle on the Movable Claw of the Mud Crab.

Decapod crustaceans have tooth-like white denticles that are present only on the pinching side of the claws. In the mud crab, Scylla serrata, a huge denticle exists on the movable finger of the dominant claw. This is mainly used to crush the shells of the crab's staple food. The local mechanical properties, hardness (HIT) and elastic modulus (Er), of the peak and valley areas of the largest denticle were examined via a nanoindentation test. The microstructure and elemental composition were characterized using a scanning electron microscope and energy-dispersive X-ray spectroscopy. The striation patterns originating from a twisted plywood structure parallel to the surface were visible over the entire denticle. Most of the largest denticle was occupied by a hard area without phosphorus, and there was a soft layer corresponding to the endocuticle with phosphorus in the innermost part. The HIT of the denticle valley was about 40% lower than that of the denticle peak, and the thickness of the soft endocuticle of the denticle valley was five times thicker than that of the denticle peak. The HIT-Er map showed that the abrasion resistance of the denticle surface was vastly superior and was in the top class among organisms. The claw denticles were designed with the necessary characteristics in the necessary places, as related to the ecology of the mud crab.

Pointed bone tools from the Hamangia culture on the Lower Danube: Manufacture and function

This study focuses on the pointed bone tools from the Hamangia culture (Chalcolithic period, late 6th millennium BC - early 5th millennium BC), obtained from the long bones of caprines by quadri-partition with double grooving. The pointed bone tool assemblage from the Hamangia settlement at Cheia-Vatra Satului (Romania) was selected as a case study for analysing technological manufacturing sequences of these specific typological tools. Our study was two-fold: 1. identifying the sequence of the procedures in the chaîne opératoire from the original bone to the finished pointed tool; 2. determining the functionality of these tools (as multipurpose items or designed for a single activity only). For the purposes of this research, we focused on the diagnostic pieces such as preforms, blanks, and manufacturing waste, rather than the finished pieces, in an attempt to reconstruct the entire sequence of the manufacturing procedures, to visualize their transformation from the bone to the finished object. This experimental approach resulted in detailed records of the raw material used, the time necessary for each type of procedure, the tools used, and the results obtained during each operation. Next, the experimental tools were tested in various scenarios, such as hide perforation, bone breaking, shell perforation, wood processing, vegetable fiber production, etc. The active ends of these items were then observed, with variables such as frequency and distribution of polish, micro-topography, pattern of functional striations, presence of microfractures, and use-wear areas. The observations made on the archaeological specimens were compared to those on the experimental replicas in order to test the hypotheses regarding the ways the pointed tools were manufactured and used by the prehistoric communities.

Responses of diatom composition and teratological forms to environmental pollution in a post-mining lake (SW Poland)

Various types of environmental stressors, such as heavy metals, lignite residues, or extremely low water pH, cause the formation of teratological forms of diatoms during the reproductive cycle. The damage mainly includes an abnormal diatom valve outline, changes in the striation pattern, anomalies in the raphe line/sternum, reduction in the cell size, metabolism alterations, or combined deformities. Diatom remains with such morphological deformities occur in the sediments of post-mining lake ŁK-46 (SW Poland). This lake was formed by excavation after the end of lignite exploitation in the mid-1960s. The percentage of teratological valves in the studied lake ranged from 12 to 33% of the relative abundance. The majority of abnormal diatoms have been observed in species of Eunotia. The reconstruction of the diatom-inferred pH (DI-pH), together with the concentration of heavy metals in the sediments and contemporary measurements of the water pH, indicates that the lake was contaminated to varying degrees and was acidic from the beginning of lake creation until today. The lake is located in an area of acid mine drainage (AMD), and in its vicinity, there are overburden heaps containing lignite residues, which are eroded and supplied to the lake, constantly acidifying the water. In the youngest sediments, the concentration of heavy metals increased, while the percentage of abnormal diatoms decreased. Determining which factor, i.e., extremely low water pH and the presence of lignite or heavy metals, was responsible for the formation or reduction of teratogenic forms of diatoms is very difficult.

Enhancement of Green's functions based on striation pattern

Enhancement of Green's function is accomplished from the striation pattern obtained from data. The waveguide invariant theory allows a Green's function observed at one location to be extrapolated into adjacent ranges [Song and Byun, J. Acoust. Soc. Am. 147, 2150–2158 (2020)]. Conversely, Green's functions observed at adjacent ranges can converge towards a central location for coherent combination to improve the signal-to-noise ratio (SNR). This can be accomplished from the frequency shift in the striation pattern without prior range information of each Green's functions. We demonstrate a significant improvement of SNR in the broadband Green's function from a moving ship in shallow water.

Mooring Measurements of Full-Depth Zonal Currents along the 143°E Meridian in the Northwestern Pacific Ocean

Abstract Full-depth ocean zonal currents in the tropical and extratropical northwestern Pacific (TNWP) are studied using current measurements from 17 deep-ocean moorings deployed along the 143°E meridian from the equator to 22°N during January 2016–February 2017. Mean transports of the North Equatorial Current and North Equatorial Countercurrent are estimated to be 42.7 ± 7.1 Sv (1 Sv ≡ 106 m3 s−1) and 10.5 ± 5.3 Sv, respectively, both of which exhibit prominent annual cycles with opposite phases in this year. The observations suggest much larger vertical extents of several of the major subsurface currents than previously reported, including the Lower Equatorial Intermediate Current, Northern Intermediate Countercurrent, North Equatorial Subsurface Current, and North Equatorial Undercurrent (NEUC) from south to north. The Northern Subsurface Countercurrent and NEUC are found to be less steady than the other currents. Seasonal variations of these currents are also revealed in the study. In the deep ocean, the currents below 2000 m are reported for the first time. The observations confirm the striation patterns of meridionally alternating zonal currents in the intermediate and deep layers. Further analyses suggest a superposition of at least the first four and two baroclinic modes to represent the mean equatorial and off-equatorial currents, respectively. Meanwhile, seasonal variations of the currents are generally dominated by the first baroclinic mode associated with the low-mode Rossby waves. Overall, the above observational results not only enhance the knowledge of full-depth current system in the TNWP but also provide a basis for future model validation and skill improvement.

Intraspecific variation in Storchia pacifica (Summers) (Trombidiformes: Stigmaeidae), a widespread species intercepted by Australian biosecurity from seventeen countries

Storchia pacifica (Summers, 1964) is redescribed from specimens intercepted by staff of the Australian Department of Agriculture, Fisheries and Forestry from Cambodia, Fiji, India, Indonesia, Kiribati, Laos, Pakistan, Papua New Guinea, New Zealand, Nigeria, Samoa, Singapore, Solomon Islands, Tonga, Uganda, Vanuatu, and Vietnam. Most of the specimens were intercepted on products made from woven natural fibre such as mats and baskets. The specimens show variation in the form of their dorsal setae, which are slender and tapered to strongly clavate distally. Otherwise, dorsal and leg chaetotaxy is consistent, as is the characteristic pattern of body striation of this species.

Magnetic field effects on the corrosion behavior of magnetocaloric alloys LaFe13.9Si1.4 under paramagnetic states

The effect of magnetic fields on the corrosion mechanism of LaFe13.9Si1.4 alloys, which were under paramagnetic states was investigated via immersion tests under controlled magnetic field conditions, and numerous analytical techniques. The results indicate that the presence of magnetic fields have a significant effect on the corrosion rate, morphology, and products, which may be due to the magnetohydrodynamics. Immersion in magnetic fields of 1 T for 72 h resulted in a significant reduction of the corrosion rate. The corrosion morphology showed cluster-like, specific striation, and mesh-like patterns for zero and 1 T (parallel and perpendicular) magnetic fields, respectively.

Prefiltered Striation-Based Beamforming for Range Estimation of Multiple Sources

The element–frequency acoustic intensity of a horizontal line array with a sufficient aperture exhibits interference striation patterns, which can be used for source range estimation without prior environmental information. Under multisource scenarios, the interference striations of the sources overlap with each other, leading to great difficulty in utilizing the information of striations. In this paper, the wavenumber filtering method is applied to each sensor of the horizontal line array to extract the surface-reflected–bottom-reflected modes and reconstruct the recognizable interference spectrogram for each source. Then, via beamforming along the striations, the source ranges can be estimated individually with little prior environmental information and without the long-time observation of moving sources. The required sensor spacing is analyzed, and the spatial filtering capabilities for a single source from different bearings and two sources for which azimuth angles are close to each other have also been investigated. The simulation results indicate that the proposed algorithm can estimate ranges of multiple sources within 25 km, with relative errors of less than 4%.

Taxonomy of three new Neidium Pfitzer species of the Arapiuns and Tapajós Rivers Basin (Santarém, Pará, Brazil)

During our investigations on the taxonomy of diatoms of clear water habitats in the western Pará region, we found three interesting, previously undocumented Neidium species. This study was based on samples taken from different habitats (plankton and sediment) in the Arapiuns and Tapajós Rivers, as well as three lakes. Based on light and scanning electron microscope observations, three new Neidium are distinguished from one another and their congeners by differences in valve outline, stria density, striation pattern, number and position of longitudinal canals and external proximal raphe endings. Furthermore, we provide formal descriptions of these new species and compare them with others similar species. We also discuss variation in several features of taxa currently assigned to the genus Neidium.

Application of a Randomized Algorithm for Extracting a Shallow Low-Rank Structure in Low-Frequency Reverberation

The detection performance of active sonar is often hindered by the presence of seabed reverberation in shallow water. Separating the reverberations from the target echo and noise in the received signal is a crucial challenge in the field of underwater acoustic signal processing. To address this issue, an improved Go-SOR decomposition method is proposed based on the subspace-orbit-randomized singular value decomposition (SOR-SVD). This method successfully extracts the low-rank structure with a certain striation pattern. The results demonstrate that the proposed algorithm outperforms both the original Go algorithm and the current state-of-the-art (SOTA) algorithm in terms of the definition index of the low-rank structure and computational efficiency. Based on the monostatic reverberation theory of the normal mode, it is established that the low-rank structure is consistent with the low-frequency reverberation interference striation. This study examines the interference characteristics of the low-rank structure in the experimental sea area and suggests that the interferences of the fifth and seventh modes mainly control the low-rank structure. The findings of this study can be applied to seafloor exploration, reverberation waveguide invariant (RWI) extraction, and data-driven reverberation suppression methods.

Striation-Based Broadband Source Localization Using a Particle Velocity Sensor in Deep Water

Depth-related striations in the acoustic intensities due to interference between the direct and sea surface reflected arrivals have been exploited to estimate the source depth by vertical arrays deployed near the bottom of the deep sea. This article presents an efficient technique to predict the constructive and destructive interference striation patterns observed in the broadband acoustic intensities for both the pressure and particle velocity ( <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">PV</small> ) fields. The consistency of striation patterns for the pressure and PV fields provides a basis for striation matching methods extended from the pressure array to a PV sensor array or an acoustic vector sensor array. To estimate the source depth, 1- and 2-D striation pattern matching methods have been proposed, which match the measured striations with the replica over either the frequency or the source range for each hypothesized source depth. Their effectiveness and performance have been evaluated through simulations and experimental data of a PV sensor in deep water. The results demonstrate that they have a narrow main lobe width and a good performance under a low signal-to-noise ratio and are applicable for shallow and distant sources when the number of interference striations is few.

Poster 321: MENISCAL RAMP LESIONS IN ADOLESCENT PATIENTS UNDERGOING PRIMARY ACL RECONSTRUCTION

Objectives: Meniscal ramp lesions describe a specific injury to the meniscocapsular junction at the posterior horn of the medial meniscus. The lesions are strongly associated with anterior cruciate ligament (ACL) injuries and may affect the biomechanical stability of the knee if left untreated. Despite the increasing rates of ACL reconstructions performed in adolescents each year, the prevalence and risk factors for ramp lesions in this patient population is poorly understood. The purpose of this study was to determine the prevalence and risk factors for ramp lesions in children and adolescent patients undergoing primary ACL reconstruction. Methods: All patients ≤19 who underwent primary ACL reconstruction at a single institutional between 2019 and 2021 were included. All surgeries were performed by three fellowship trained orthopedic surgeons. Patients were considered to have a ramp lesion if one was identified arthroscopically at the time of ACL reconstruction. Basic demographic data, preoperative imaging, and other arthroscopic findings at the time of ACL reconstruction were reviewed. Results: 247 consecutive patients who underwent ACL reconstruction were reviewed. Patients were excluded if they had had prior ACL injury, prior knee surgery, fibular hemimelia, or incomplete documentation. A total of 230 patients met inclusion criteria. Average age at time of injury was 15.7 years (range 4.0-18.2 years). A ramp lesion was identified in 12% of patients. Posteromedial tibial bone bruise on preoperative MRI and medial femoral chondromalacia at time of ACL reconstruction were associated with the presence of a ramp lesion, Figure 1A (OR = 2.6, 95% CI [1.15, 5.93]). A striation pattern of medial femoral chondromalacia was highly specific for the presence of a ramp lesion, Figure 1B (OR = 424.3, 95% CI [50.99, 3531.3]). Sensitivity and specificity for detecting a ramp lesion was 68% and 76% with preoperative MRI and 68% and 99.5% with medial condyle striations, respectively. Conclusions: The prevalence of a ramp lesion in our cohort was 12%, mirroring historical reports in adult patients. Posteromedial bone bruising and medial femoral chondromalacia, especially in a striation pattern, should increase suspicion for the presence of a ramp lesion in patients undergoing ACL reconstruction.

Passive source depth estimation using beam intensity striations of a horizontal linear array in deep water.

Source depth estimation is an important yet very difficult task for passive sonars, especially for horizontal linear arrays (HLAs). This paper proposes an efficient two-step depth estimation scheme using narrowband and broadband constructive and deconstructive striation patterns due to interference between the direct (D) and sea surface reflected (SR) arrivals at an HLA on the bottom of deep water. First, the horizontal source-array ranges are derived from triangulation results of solid angle estimates by subarray beamforming. The applicable areas of the method in deep water are investigated through Mento Carlo simulations, assuming different subarray partitioning ways of a given HLA aperture. Second, cost functions are built to match the measured beam intensity striations with modeled ones. To mitigate the spatial smoothing effect of the beam intensity striations during beamforming, a criterion of the largest subarray aperture is established, and a computationally efficient way is presented to model the replicas by the D-SR time delay templates at a single element of the array calculated by ray theory. The performance degradation due to limited source range spans, the distortion of the beam intensity striations, and range estimation errors has been analyzed. Two experimental datasets verify the effectiveness of the proposed method.

Waveguide invariant estimation based on correlation coefficient of tonal acoustic intensity interference fluctuation

The waveguide invariant is usually not extracted from the striation pattern of broadband continuous spectrum in the low frequency analysis and recording spectrum at low signal-to-noise ratio. In this paper, the correlation coefficient of multi-tonal acoustic intensity interference fluctuation is utilized to estimate waveguide invariant. Since the proportional relationship between the reference intensity interference fluctuation and the scaled intensity interference fluctuation is dependent on waveguide invariant, the waveguide invariant estimation can be done. Firstly, the tonal intensity interference fluctuation has been resampled in the new time domain under the radial and non-radial motion models respectively. Then, the similarity degree between the resampling reference tonal intensity interference fluctuation and the scaling tonal intensity interference fluctuation can be described by correlation coefficient, and the peak of correlation coefficient is corresponding to the true value. Finally, the numerical results and the experimental results prove the proposed method's effectiveness.

Technology or taphonomy? A study of the 2.04–1.95 Ma bone tools from Drimolen Main Quarry, South Africa

Analysis of 124 rounded fossils, potential bone tools, from the 2.04–1.95 Ma early hominin-bearing Drimolen Main Quarry palaeocave deposits in South Africa were subject to comparative analysis of fossil and bone collections with known taphonomic accumulator/s, actualistic experiments, and comparative analysis relative to published data in the taphonomic literature. From this sample, 51 specimens were identified as bone tools. The inclusion of these specimens raises the number of bone tools identified at Drimolen Main Quarry to 65. The bone tools have a rounded tip and an associated use-wear pattern that is restricted to, and radiates from, this rounded tip. Diaphyseal fragments were the most common raw material selected for tool use. We hypothesise that the raw material was collected from both carnivore kill and natural death sites. The striation patterns, identified though visual comparisons, present on the bone tools comprise parallel, subparallel and diagonal striations which suggests that the tools may have had a multi-use application. The place of bone technology within the South African Earlier Stone Age is also discussed.