Kinds Of Specimens Research Articles

A panurgine bee from the middle Miocene of Öhningen, Germany (Hymenoptera: Andrenidae)

The bee subfamily Panurginae is reported for the first time from the middle Miocene crater lake of Öhningen, southwestern Germany (Baden-Württemberg: Konstanz). A single specimen, likely a male, is preserved as a rather faint compression in limestone and was labelled more than 75 years ago as possibly Osmia Panzer. The fossil is certainly one of the less-well preserved bees from the Öhningen locality and is the kind of specimen that might quickly be relegated to incertae sedis and passed over for better material. However, close inspection with sufficient lighting reveals subtle characters divulging the fossil’s identity. In fact, the bee is of the tribe Panurgini and is here described as a new subgenus and species therein. Panurgus (Chronopanurgus) tribacus subgen. & sp. n. is distinguished from other panurgines, thereby representing not only the first panurgine fossil from Öhningen but from all Eurasia.

Experimental Study on Mechanical Properties of Thermally Conductive High-Strength Concrete.

Ultra-high-performance concrete (UHPC) is considered one of the future building materials due to its excellent performance. UHPC with good thermal conductivity has potential high-value applications in large-scale bridges and nuclear facilities. As a by-product of the coal gasification process, coal gasification slag (CGS) can replace sand in traditional UHPC. In this paper, based on the preparation of UHPC by CGS, silicon carbide (SiC) was added to improve the thermal conductivity of specimens. The application of CGS and SiC as alternatives to quartz sand with varying mix ratios in UHPC was studied. The impact of the substitution ratios of CGS and SiC on fluidity, mechanical properties, and thermal performance was analyzed. The compressive strength and splitting tensile strength of five different kinds of specimens were tested at 7 d, 14 d, and 28 d. The compressive strength and mass loss rate of specimens with five different ratios were also determined under five different temperature conditions (110 °C, 200 °C, 300 °C, 400 °C, and 500 °C). The results show that the maximum compressive strength of 28 d can reach 159.5 MPa and the splitting strength is 15.30 MPa. The addition of SiC can improve the thermal conductivity and thermal stability of concrete. The compressive strength of all specimens is improved after high-temperature treatment. When substitution rate of SiC reaches 100%, the compressive strength of the specimens is up to 182.2 MPa. With the increase in temperature, the concrete burst phenomenon occurs above 300 °C. It is observed that the high-temperature burst resistance of the specimens with low strength is better than that of the specimens with high strength. Two specimens were scanned with Industrial Computerized Tomography (ICT) and the microstructures of the specimens were compared. It was found that the samples with higher SiC substitution rates had more minor total pore defects and larger pores.

Through a Controlled Quenching to Achieve a Good Combination of Mechanical Properties in Low‐Yield Ratio 900 MPa High‐Strength Low‐Alloy Steels

Two distinct heat treatments, that is, intercritical quenching combined with low‐temperature tempering (QT) to control the initial quenching temperature, and salt‐bath quenching combined with partitioning (Q&P) to regulate the final quenching temperature, were employed on high‐strength low‐alloy (HSLA) steels to achieve multiphase microstructures characterized by high strength, low yield ratio, and good impact toughness. Comprehensive experiments involving tension test, low‐temperature impact, microstructural observation, and in situ tension have been conducted to compare the microstructures and mechanical properties. It is found that both kinds of specimens can achieve a good match between high strength‐toughness and low yield ratio. The microstructures are composed of lath martensite with ferrite for QT specimen and tempered martensite with bainite for the Q&P specimen, a combination of “soft” and “hard” phases thus resulting in a yield ratio lower than 0.85 for 900 MPa low‐alloy steels. Notably, the Q&P specimen exhibited a markedly superior uniform elongation of 6.1% compared to the QT counterpart of 3.2%, a phenomenon attributed to the work hardening rate during deformation. A combination of strong and weak lath structures in tempered martensite and bainite can induce dislocation propagation and the carbides can act as obstacles to dislocation motion, jointly enhancing work hardening.

Cross-sectional Hospital-based Investigation on Clinical Characteristics of Pediatric Staphylococcus aureus Isolates in a Beijing Hospital from 2013 to 2022.

Staphylococcus aureus (S. aureus) was a prevalent pathogenic bacterium among children. Due to the extensive use of antibiotics, the sensitivity of S. aureus to these drugs has gradually declined. Since the 1960s, methicillin-resistant Staphylococcus aureus (MRSA) has emerged and spread worldwide, becoming a primary cause of both healthcare-associated (HA) and community-acquired (CA) infections. This retrospective study aimed to highlight the significance of S. aureus among bacteria isolated from children in Beijing, China, and to elucidate its antimicrobial resistance patterns. Data on all S. aureus infections from 2013 to 2022 were collected from the microbiology department of Beijing Children's Hospital. Only the first isolate from the same kind of specimen was analyzed. Antimicrobial susceptibility tests were carried out by Vitek 2 automated system (bio Mérieux, France) or Kirby-Bauer disc diffusion method, according to the guidelines recommended by the Clinical and Laboratory Standards Institute (CLSI). During the decade-long research period, a total of 47,062 bacterial isolates were isolated from 433,081 submitted specimens, with 6477 of these isolates identified as S. aureus. The majority of patients with S. aureus infections belonged to the age group of infants under one-year-old, accounting for 37.9% of cases. S. aureus isolates were predominantly found in the Pneumology Department, and the most common source of these isolates was lower respiratory tract specimens, comprising 34.3% of the total. The resistance rates of S. aureus to penicillin and erythromycin were notably high, at 89.5% and 73.8%, respectively. In contrast, the resistance rates to linezolid, vancomycin, rifampicin, and moxifloxacin were remarkably low, at 0.0%, 0.0%, 1.3%, and 3.9%, respectively. The detection rate of MRSA was 27.8%. MRSA isolates were predominantly found in the newborn group, ICU, and sterile body fluids. In our study, the most prevalent specimen type was derived from the lower respiratory tract, whereas the highest positive rate was observed in ear secretions. These findings underscored the pressing necessity for ongoing antimicrobial resistance (AMR) surveillance and the revision of treatment guidelines, particularly given the elevated detection of MRSA in ICU wards, sterile body fluids, and the neonatal age group. MRSA exhibited significant resistance to all β-lactam antibiotics, erythromycin, and ciprofloxacin. Therefore, future research endeavors should prioritize examining specific antimicrobial resistance populations and potential intervention strategies, as these were vital in mitigating the dissemination of antimicrobial-resistant isolates.

Experimental study on mechanical properties and breakage of high temperature carbon fiber-bar reinforced concrete under impact load

To investigate the effects of high temperature and carbon fiber-bar reinforcement on the dynamic mechanical properties of concrete materials, a muffle furnace was used to treat two kinds of specimens, plain and carbon fiber-bar reinforced concrete, at high temperatures of 25, 200, 400 and 600 °C. Impact compression tests were carried out on two specimens after high-temperature exposure using a Hopkinson pressure bar (SHPB) test setup combined with a high-speed camera device to observe the crack extension process of the specimens. The effects of high temperature and carbon fiber-bar reinforcement on the peak stress, energy dissipation density, crack propagation and fractal dimension of the concrete were analyzed. The results showed that the corresponding peak strengths of the plain concrete specimens at 25, 200, 400, and 600 °C were 88.37, 93.21, 68.85, and 54.90 MPa, respectively, and the peak strengths after the high-temperature exposure first increased slightly and then decreased rapidly. The mean peak strengths corresponding to the carbon fiber-bar reinforced concrete specimens after high-temperature action at 25, 200, 400, and 600 °C are 1.13, 1.13, 1.21, and 1.19 times that of plain concrete, respectively, and the mean crushing energy consumption densities are 1.27, 1.31, 1.73, and 1.59 times that of plain concrete, respectively. The addition of carbon fiber-bar reinforcement significantly enhanced the impact resistance and energy dissipation of the concrete structure, and the higher the temperature was, the more significant the increase. An increase in temperature increases the number of crack extensions and width, and the high tensile strength of the carbon fiber-bar reinforcement and the synergistic effect with the concrete material reduce the degree of crack extension in the specimen. The fractal dimension of the concrete ranged from 1.92 to 2.68, that of the carbon fiber-bar reinforced concrete specimens ranged from 1.61 to 2.42, and the mean values of the corresponding fractal dimensions of the plain concrete specimens after high-temperature effects at 25, 200, 400, and 600 °C were 1.19, 1.21, 1.10, and 1.11 times those of the fiber-reinforced concrete specimens, respectively. The incorporation of carbon fiber-bar reinforcement reduces the degree of rupture and fragmentation of concrete under impact loading and improves the safety and stability of concrete structures.

Experimental Study on Fracture Behavior of Adhesive-Bonded Structure with V-notch Based on Digital Gradient Sensing Method.

In this paper, a comparative study of the mode-I fracture behaviors of two types of specimens with a V-notch defect under plane stress conditions was performed using the digital gradient sensing (DGS) method. First, two types of specimens (namely one-piece specimen and bonded specimen) with the same V-notch defect were both made of polymethyl methacrylate (PMMA), and three different V-notch angles' defect were considered for each type of specimen. Then, three-point bending tests were performed on both types of specimens. The angular deflection field of light near the V-notch region was recorded using a CCD during the experiments. Finally, by utilizing the relationship between the stress gradient and angular deflection as established by the elasto-optic effect, in conjunction with the principles of linear elastic fracture mechanics theory, the stress intensity factors (SIFs) of two types of specimens under different stress conditions were calculated using the least square method. According to the experimental results, the influence of V-notch angle on fracture load and fracture toughness of two kinds of specimens was discussed. Meanwhile, the experimental results show the significant differences in the fracture behaviors of the two types of specimens under mode-I loading conditions.

Experimental Investigation of Damping Properties of Selected Polymer Materials.

This paper presents the results of an experimental modal analysis of a beam covered by polymer materials used as a passive vibration isolation. The main aim of this study was to determine the damping properties of selected viscoelastic materials. In order to check the damping properties of tested materials, an experimental modal analysis, with the use of an electrodynamic vibration system, was performed. In this study, four kinds of specimens were considered. In the first step of the work, the beam made out of aluminum alloy was investigated. Afterwards, a cantilever beam was covered with a layer of bitumen-based material acting as a damper. This method is commonly known as a free layer damping treatment (FLD). In order to increase the damping capabilities, the previous configuration was improved by fixing a thin aluminum layer directly to the viscoelastic core. Such a treatment is called constrained layer damping (CLD). Subsequently, another polymer (butyl rubber) in the CLD configuration was tested for its damping properties. As a result of the performed experimental modal analysis, the frequencies of resonant vibrations and their corresponding amplitudes were obtained. The experimental results were used to quantitatively evaluate the damping properties of tested materials.

Interpretation of Frequency Effect for High-Strength Steels with Three Different Strength Levels via Crystal Plasticity Finite Element Method.

The fatigue behavior of a high-strength bearing steel tempered under three different temperatures was investigated with ultrasonic frequency and conventional frequency loading. Three kinds of specimens with various yield strengths exhibited obvious higher fatigue strengths under ultrasonic frequency loading. Then, a 2D crystal plasticity finite element method was adopted to simulate the local stress distribution under different applied loads and loading frequencies. Simulations showed that the maximum residual local stress was much smaller under ultrasonic frequency loading in contrast to that under conventional frequency at the same applied load. It was also revealed that the maximum local stress increases with the applied load under both loading frequencies. The accumulated plastic strain was adopted as a fatigue indicator parameter to characterize the frequency effect, which was several orders smaller than that obtained under conventional loading frequencies when the applied load was fixed. The increment of accumulated plastic strain and the load stress amplitude exhibited a linear relationship in the double logarithmic coordinate system, and an improved fatigue life prediction model was established.

Study of activation parameters in Fe-SMA reinforced concrete structures using multiphysics modelling

Study of activation parameters in Fe-SMA reinforced concrete structures using multiphysics modelling

Influence of different long and short ageing protocols on the mechanical behaviour and damage mechanisms of a hemp fibre reinforced polypropylene

This paper deals with the study of the evolution of the durability of short hemp fibres reinforced composites subjected to long-term ageing. The compounds were stored for ten years in atmospheric conditions (natural ageing) prior to the study. Therefore, two kinds of specimen are studied. First, the aged compounds were used to moulded tensile specimens. The residual mechanical behaviour of natural aged hemp/PP composites (natural aged specimens) were compared to properties obtained 10 years ago. This storage showed that the hemp is more sensitive to time degradation than PP and was confirmed by the initial degradation of compounds pointed out by ATG. Then, injected natural aged polypropylene reinforced with several hemp fibre weight fractions compounds were subjected to two different protocols in order to characterize their durability (aged specimens). The specimens were subjected to water immersion at ambient temperature and storage in a climatic chamber maintained at 40 °C with a relative humidity of 98%. The fracture surfaces were observed with SEM to identify the physical phenomena leading to the observed loss of mechanical properties. A weight water sorption of 14% with respect to hemp weight fraction was, for the first time, determined as a critical water sorption for which the reinforcement effect becomes negligible. The physical phenomenon responsible for this critical absorption was finally investigated with Infrared Spectroscopy, showing the occurring of a dissolution of the fibres.

Parametric design, simulation, fabrication, and test of an Origami-core based sandwich composite material

Sandwich panel structures are widely used for light-weight applications due to their high strength and stiffness to density ratios. They are composed of two main parts: the skins and the core. This paper investigates a Miura-ori structural sandwich core with open cells that can be used as an alternative to the existing honeycomb structures. A fully parametric design approach, starting from drawing to Finite Element Analysis (FEA), is presented to efficiently analyze the effect of different geometries on the resulting structure. The geometric model was built based on the kinematic model, which can represent the folding process of the foldcore using the Matlab script. The obtained coordinates of the vertices of the folding pattern were exported to ANSYS APDL where the surfaces were automatically created and meshed. The created mesh was imported to LS-Dyna where explicit compression analyses were performed to evaluate the compression stiffness and strength of the studied geometries. The developed parametric model aims to find the best configuration for a given application, based on three sets of geometric parameters that define the shape of the Miura Ori folding pattern. Therefore, in the range of the studied geometries, the best parameter combination for specific compression stiffness and specific compression strength was found. To evaluate the performance of the foldcore and to validate the FE model, experimental quasi-static compression tests were undertaken with two kinds of specimens (‘strip’ and “panel”), and the measured force-displacement curves were obtained. The result of the test agrees with that of the FE simulations, with an error of <6.6% in the elastic region.

Characterisation of strength and deformation characteristics of alkali-activated rice husk ash filler-assemblage perimeter rock

In this study, the strength characteristics, deformation characteristics and damage characteristics of three kinds of specimens, namely, surrounding rock, cemented paste backfill (CPB) and a surrounding rock-CPB combination, were studied by uniaxial compression testing using rice husk ash and slag as cementing materials, and the mechanical properties of the combination specimens with different height ratios were also analyzed. The results showed that the surrounding rock specimens were the strongest, followed by the composite body, and the CPB was the weakest. The relationship between different height ratios of the assemblage and the cut line modulus was found according to the fitted curves. The CPB specimens and the surrounding rock specimens showed ductile damage, while the assemblage specimens showed brittle damage.

Fabrication and Damping Property of Porous Cu–Al–Ni Shape Memory Alloys Fabricated using Different Raw Materials

Porous Cu–Al–Ni shape memory alloys (SMAs) are fabricated via powder metallurgy method using Cu, Al, Ni powders and Cu–Al–Ni alloy powder as raw materials, respectively. It is found that the two kinds of specimens have similar macroscopic morphologies: connected pores are uniformly distributed in the Cu–Al–Ni matrix, forming a 3D network structure. By comparison, the specimen fabricated using alloy powder has much finer microstructures than the specimens fabricated using Cu, Al, Ni powders. After adding Ce element to the latter, the microstructure of the Cu–Al–Ni matrix is significantly refined because of the formation of Ce‐rich particles. Damping tests show that the latter has superior damping capacity than the former. With the increase of Ce content, the damping of the latter increases first and then decreases. When the Ce content reaches 0.05 wt%, the highest damping can be achieved. Correlated mechanisms are discussed based on the microstructural observations.

Fatigue behaviour of EA4T notched specimens: experiments and predictions using the theory of critical distance

Fatigue behaviour of EA4T notched specimens: experiments and predictions using the theory of critical distance

Influence of Repeated Bending Loading on the Residual Stresses in Multilayer Coating Materials

The technology of multilayer thin films to improve performance is widely used in the fields of semiconductors and functional composite materials. However, each layer of the multilayer film generates a residual stress during deposition due to differences in Young's modulus and coefficient of thermal expansion. In addition, the residual stress of the coating material is significantly affected by the mechanical load during use. In this study, the coated materials with deposited multilayer thin films were subjected to repeated bending loads, and the effects on the residual stresses in the thin films and substrates were investigated. Carbon steel (JIS: S45C) was used as the substrate material for the specimens. The thin films were deposited by sputtering. Three kinds of specimens were used, in which Cu, TiN and SiO2 films were deposited as a single Cu layer, a Cu/TiN double layer and a SiO2/Cu/TiN multilayer. The residual stress values of the Cu layer within the thin films were evaluated by X-ray stress measurement method using 311 and 222 diffractions of Cu. As a result, the tensile residual stress values in the Cu layers within each thin film were approximately 60~70 MPa for the single layer and 110~120 MPa for the double and multi-layer films. The residual stress values in the substrate, carbon steel, were evaluated using 211 diffractions of α-Fe. As a result, a tensile residual stress of about 30 MPa is existed. When all the coated materials were subjected to repeated bending loads, the change in the residual stress values of Cu layer showed that the residual stresses relaxed rapidly after several cycles of repeated loading and saturated to a value of about 30 MPa after 100 cycles. On the other hand, the residual stress evaluation by 222 diffractions of Cu showed that for all coated materials the residual stress values increased and decreased repeatedly with increasing number of repeated loadings. For the carbon steel substrate, the residual stress values hardly changed due to repeated loading.

Study on Temperature-Dependent Uniaxial Tensile Tests and Constitutive Relationship of Modified Polyurethane Concrete.

Modified polyurethane concrete (MPUC) is a new material for steel deck pavements. In service, the pavement is often cracked due to excessive tensile stress caused by temperature changes. In order to study the tensile properties of MPUC in the diurnal temperature range of steel decks, uniaxial tensile tests of MPUC were carried out at five temperatures. Three kinds of specimens and a novel fixture were designed and fabricated to compare the results of four different tensile test methods. The deformation of the specimen was collected synchronously by two methods: pasting strain gauge and digital image correlation (DIC) technique. Based on the experiment, the tensile mechanical properties, failure modes, and constitutive relations of MPUC were studied under the effect of temperature. The research results show that the novel fixture can avoid stress concentration. By observing the fracture surface of the specimens, the bonding performance is great between the binder and the aggregate at different temperatures. The tensile strength and elastic modulus of MPUC decrease with increasing temperatures, while the fracture strain, and fracture energy increase with increasing temperatures. The formulas of temperature-dependent tensile strength, fracture strain, and elastic modulus of MPUC were established, and the constitutive relationship of MPUC is further constructed in the rising stage under uniaxial tension. The calculation results show good agreement with experimental ones.

Observation of the same asbestos body by both phase contrast microscope and analytical transmission electron microscope

The amount of asbestos body (AB) in the human lungs is used as an index to assess asbestos lung cancer (ALC). This study reports a new method to observe the same AB previously observed by analytical transmission electron microscope (ATEM) by phase contrast microscope (PCM) or the contrary order. Four kinds of specimens were prepared from the lung tissue of an asbestos related worker: ordinary PCM specimen (A); PCM specimen (B) of which the cover glass was stripped off and ashed at a low temperature; transmission electron microscope (TEM) specimen (C); and PCM specimen (D) covered a TEM specimen (C) with immersion liquid and cover glass. These specimens were all observed by PCM, and the specimen (C) by analytical TEM (ATEM). The results showed that the TEM specimen (C) is transparent in visible light and we can also see the particles by PCM. The image by PCM of the TEM specimen (C) showed very similar features to that of PCM specimens (A) and (B). Accordingly, we could observe various same particles by both ATEM and PCM. In conclusion, the method observing the same AB by both PCM and ATEM will contribute to standardize the recognition of AB for PCM analysts.

Language as a Specimen.

Language was never studied by linguists (or philologists) alone. The greater part of the languages of the world was first known in the West through the reports of missionaries, explorers, and colonial administrators, and what they documented reflected their specific interests. Missionaries wrote catechisms, primers, dictionaries, and Bible translations (especially Lord's Prayers); for explorers and administrators, language was one aspect among many to cover in their accounts of faraway regions. Peoples were identified by their language; toponyms served for geographic description; names of plants and animals were gathered together with specimens and images of plants and animals. In this context, linguistic materials were equally described as "specimens." This article investigates the various ways in which language material was used and conceived of as a specimen, and the global trajectories of these "specimens." Especially the role of naturalist explorers deserves closer attention in this regard. What they did, throughout the late 18th and 19th century, was gathering language material as one kind of specimen among others, Forster in the Pacific, Humboldt, Martius, and d'Orbigny in South America, and Peters in Mozambique. Two large-scale expeditions from the mid-19th century stand out as examples: the U.S. Exploring Expedition (1838-1842), whose collections later filled the Smithsonian Institution, and the Austrian-Hungarian Novara expedition (1857-1859).

Quantitative hydrogen trap states on high-angle grain boundaries and at dislocations in iron

Quantitative hydrogen trap states on high-angle grain boundaries and at dislocations in iron

Influence of induction hardening on the damage tolerance of EA4T railway axles

Influence of induction hardening on the damage tolerance of EA4T railway axles