Hollow Ones Research Articles

MATHEMATICAL MODELING OF THE HOLLOW PROFILES FORMING PROCESS

Steel alloys containing manganese and boron are increasingly being used in mechanical engineering, including automotive and agricultural sectors. Products of critical application made from such steels, including hollow ones, have a high level of mechanical properties, surface hardness, and wear resistance. These products are obtained by profiling of previously electrically welded round pipes with a hot sheet stamping or pressure treatment (drawing, cold rolling, stamping). Technological parameters of combined processing methods are determined by the results of experimental research, which, due to the complexity and cost of materials, leads to significant expenses. The application of mathematical modeling can reduce the number of experiments and forecast the quality of finished products. The research focuses on investigating the possibility of obtaining square hollow profiles by means of push-pulling through one stand of a pipe welding unit and defining the requirements for geometric parameters of the billet.

Posttraumatic Ileal Perforation in Crohn's Disease A Case Report

Introduction: Free peritoneal perforations in Crohn's disease are extremely rare. In this observation, we report the case of a patient who presented with this condition following abdominal blunt trauma. Case presentation: This is a 30-year-old patient with Crohn's disease who was being followed anarchically. She presented with peritonitis following violent abdominal blunt trauma, which was operated on with some diagnostic delay. Discussion: Abdominal blunt trauma could lead to small bowel perforation in patients with Crohn's disease. Especially when the small bowel is weakened by non-adherence to therapy, as in our case. Diagnosis is often delayed, as the clinical signs are discreet. On the other hand, trauma surgeons focus more on solid organs than hollow ones. Conclusion: Abdominal blunt trauma in Crohn's disease increase the risk of occurrence of perforated bowel, especially when the therapeutic follow-up of these patients is not rigorous or in the event of non-adherence to therapy. Delayed diagnosis of these perforations may increase their morbidity.

A comprehensive multi-objective optimization study for the aerodynamic noise mitigation of a small wind turbine

The noise emitted by small wind turbines is one of the main reasons for their poor public perception for use in urban areas. An optimization study was performed to mitigate the aerodynamic noise of a 750 W turbine through altering the geometry of solid and more importantly hollow blades for the first time. A validated in-house code simultaneously minimizes the aerodynamic noise and maximizes the output power. The inertia of the blades is another important design parameter for small turbines as it influences the starting performance. The minimization of starting time was added to the above-mentioned goals and another optimization was done. The outcomes highlight the great significance of two ends of the blade; the tip section has a key role in alleviation of the noise as well as the improvement of the power coefficient while the root part could speed up the starting. Quantitatively, the optimization of solid blades shows that a 1.9 dB reduction in aerodynamic noise is attainable at the expense of a 1.6% loss in the power coefficient. Compared to solid blades, the aerodynamic noise and the starting time were reduced for hollow ones by 1 dB and 30% respectively. The latter is very attractive for use of small turbines in low-wind areas.

HOARD OF JEWELLERY AND HORSE GEAR OF THE 5th–4th CENTURIES BC FROM BRYANSK REGION

The paper discusses a hoard of the Early Iron Age from the territory of Bryansk Region. The hoard includes iron cheek-pieces, a brow band, bronze bridle plaques, as well as bracelets – smooth cast and hollow cast ones made using the technique of lost wax investment casting. Objects were placed in a crude handmade pot. The unique complex dating back to the 5th–4th centuries BC was found in the area of the Yukhnovo archaeological culture. The completeness of the analyzed hoard and the circumstances of its finding have direct analogies among the hoards originating from the southern coast of the Baltic Sea. It is possible that the hollow bracelets from the hoard are an imitation of samples found on the territory of Polish Pomerania and adjacent regions.

Wetting and complex remodeling of membranes by biomolecular condensates

Cells compartmentalize parts of their interiors into liquid-like condensates, which can be reconstituted in vitro. Although these condensates interact with membrane-bound organelles, their potential for membrane remodeling and the underlying mechanisms of such interactions are not well-understood. Here, we demonstrate that interactions between protein condensates - including hollow ones, and membranes can lead to remarkable morphological transformations and provide a theoretical framework to describe them. Modulation of solution salinity or membrane composition drives the condensate-membrane system through two wetting transitions, from dewetting, through a broad regime of partial wetting, to complete wetting. When sufficient membrane area is available, fingering or ruffling of the condensate-membrane interface is observed, an intriguing phenomenon producing intricately curved structures. The observed morphologies are governed by the interplay of adhesion, membrane elasticity, and interfacial tension. Our results highlight the relevance of wetting in cell biology, and pave the way for the design of synthetic membrane-droplet based biomaterials and compartments with tunable properties.

Chitosan conduits enriched with fibrin-collagen hydrogel with or without adipose-derived mesenchymal stem cells for the repair of 15-mm-long sciatic nerve defect.

Hollow conduits of natural or synthetic origins have shown acceptable regeneration results in short nerve gap repair; however, results are still not comparable with the current gold standard technique "autografts". Hollow conduits do not provide a successful regeneration outcome when it comes to critical nerve gap repair. Enriching the lumen of conduits with different extracellular materials and cells could provide a better biomimicry of the natural nerve regenerating environment and is expected to ameliorate the conduit performance. In this study, we evaluated nerve regeneration in vivo using hollow chitosan conduits or conduits enriched with fibrin-collagen hydrogels alone or with the further addition of adipose-derived mesenchymal stem cells in a 15 mm rat sciatic nerve transection model. Unexpected changes in the hydrogel consistency and structural stability in vivo led to a failure of nerve regeneration after 15 weeks. Nevertheless, the molecular assessment in the early regeneration phase (7, 14, and 28 days) has shown an upregulation of useful regenerative genes in hydrogel enriched conduits compared with the hollow ones. Hydrogels composed of fibrin-collagen were able to upregulate the expression of soluble NRG1, a growth factor that plays an important role in Schwann cell transdifferentiation. The further enrichment with adipose-derived mesenchymal stem cells has led to the upregulation of other important genes such as ErbB2, VEGF-A, BDNF, c-Jun, and ATF3.

Synergy of yolk-shelled structure and tunable oxygen defect over CdS/CdCO3-CoS2: Wide band-gap semiconductors assist in efficient visible-light-driven H2 production and CO2 reduction

Yolk-shelled CoS2 nanospheres are designed through Kirkendall Effect and subsequently converted into defect-rich CdS/CdCO3-CoS2 photocatalysts via in-situ growth method. The optimal CdS/CdCO3-CoS2 exhibits a significant hydrogen evolution rate of 64867.88 μmol h−1 gcat−1 that is 3.23 and 49.45 folds higher than CoS2-CdS and pure CdS. CO2 reduction rate of CdS/CdCO3-CoS2 is detected additionally (654.7 μmol h−1 gcat−1). Yolk-shelled CdS/CdCO3-CoS2 induces the multi-scattering of incident light, possessing 1.52-fold H2 production rate than that of full hollow ones. Enhanced photoexcited-carriers migration efficiency is attributed to the synergistic effect between possible Mie resonance at about λ = 450 nm in yolk-shelled architecture based on Mie’s theory and monochromatic light HER test, and the formation of defect energy level within the wide-band gap of CdCO3 in Schottky-type/type II heterojunction. Electron paramagnetic resonance, positron annihilation spectroscopy and density functional theory calculation etc. are employed to validate the presence of oxygen vacancies and the photocatalytic mechanism.

Comparison of the EMWA Performance of Nickel Cored and Hollow Carbon Onions

Carbon onions (CNOs) are highly desirable in the field of electromagnetic wave absorption (EMWA) due to their onion-like structure, low density and excellent conductivity. Herein nickel encapsulated CNOs were fabricated by arc discharge and then transformed into hollow ones via annealing at 900∘C. The structure and EMWA performance of the hollow and nickel encapsulated CNOs were analyzed in detail to investigate the relationship of their EMWA properties and structure. The better EMWA properties of nickel encapsulated CNOs showed that the core–shell interface contributed more EMMA in comparison to the onion-like configuration.

An Experimental Study on Kerosene Spray Combustion Under Conventional and Hot-Diluted Conditions

ABSTRACT The combustion of kerosene spray under hot-diluted conditions and conventional conditions was experimentally investigated. By examining flame photographs, chemiluminescence images, and in-field temperature measurements, the separate effect of different variables including oxygen concentration, temperature and velocity of the co-flowing air, fuel flow rate and injection pressure, and eventually the type of spray nozzle on multiple parameters such as flame stability, structure, luminosity, temperature field, and qualitative CH radical distribution, as well as HCO and NO2 with lower precision, in the reaction region, have been studied. It was observed that an increment in injection pressure and co-flow temperature enhances the spray flame stability, while dilution exacerbates it. Also, a solid cone spray pattern with a lower spray angle has better stability than hollow cone ones with a higher spray angle. Moreover, it was noted that liquid fuels, compared to gaseous fuels, require higher preheating temperatures, for the same dilution level, to engender a stable flame. For combustion of spray in conventional conditions, a double-flame structure was observed consisting of a bluish section at the leading edge emerging into a yellowish sooting trail. An increase in co-flow velocity, as well as injection pressure, strengthens the inner flame front, whereas raising the co-flow temperature or diluting the oxidant, deteriorates the inner flame front. In the case of highly preheated air (without dilution), the flame liftoff height is reduced to as close to the atomizer as a few millimeters, forming a single flame structure similar to gaseous flames. In this case, the peak temperature was considerably higher than the conventional combustion, yet the gain was much lower than the preheating level. Combined effects of preheating and dilution alter the spray flame structure in a way that the flame volume is reduced, the temperature field has become more homogeneous, the peak temperature is limited to less than 1500 K, and temperature fluctuations have significantly decreased, seemingly approaching MILD combustion regime conditions.

Theoretical inspection of the spin-crossover [Fe(tzpy)2(NCS)2] complex on Au(100) surface.

We explore the deposition of the spin-crossover [Fe(tzpy)2(NCS)2] complex on the Au(100) surface by means of density functional theory (DFT) based calculations. Two different routes have been employed: low-cost finite cluster-based calculations, where both the Fe complex and the surface are maintained fixed while the molecule approaches the surface; and periodic DFT plane-wave calculations, where the surface is represented by a four-layer slab and both the molecule and surface are relaxed. Our results show that the bridge adsorption site is preferred over the on-top and fourfold hollow ones for both spin states, although they are energetically close. The LS molecule is stabilized by the surface, and the HS-LS energy difference is enhanced by about 15%-25% once deposited. The different Fe ligand field for LS and HS molecules manifests on the composition and energy of the low-lying bands. Our simulated STM images indicate that it is possible to distinguish the spin state of the deposited molecules by tuning the bias voltage of the STM tip. Finally, it should be noted that the use of a reduced size cluster to simulate the Au(100) surface proves to be a low-cost and reliable strategy, providing results in good agreement with those resulting from state-of-the-art periodic calculations for this system.

Natural Convection Heat Transfer from a Heat Sink with Hollow/ perforated circular Pin Fins (Dept.M)

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Seismic performance of railway rounded rectangular hollow tall piers using the shaking table test

The seismic performance of rounded rectangular hollow tall piers, applied popularly in railway bridges in high-intensity areas in China, has rarely been investigated till now. The current seismic design approaches mostly stem from short-to-medium solid columns whose seismic behavior is different from those of hollow members. According to cyclic tests in publications, there are also obvious differences in the seismic performance between the rounded rectangular hollow piers and the common hollow ones. To clarify the differences among them and update the existing design approach, the damage modes and dynamic responses of rounded rectangular hollow columns under different-level earthquakes should be studied comprehensively. Therefore, three 1/6-scale models from a 40 m prototype pier were tested using a 10.1 m × 8.1 m 6DOFs shaking table. The experimental outcomes were analyzed and compared with those previous semistatic tests. The results showed that the three specimens underwent flexural damage with horizontal cracks distributing along the whole body. Moreover, a second plastic hinge region, evidenced by the denser flexural cracks around the middle part, appeared in addition to the lengthened plastic hinge close to the pier footing. These findings are mainly attributed to the combined influence of the variable hollow section and higher-order effects, which differs greatly from the damage behaviors of specimens under cyclic loads. As expected, the increased stirrup ratio produced great improvement in the seismic performance of rounded rectangular hollow tall piers (DB1 and DB2), while fewer stirrups corresponded to a decrease in ductility (DB3).

Hybrid and hollow Poly(N,N-dimethylaminoethyl methacrylate) nanogels as stimuli-responsive carriers for controlled release of doxorubicin

Smart drug-delivery systems based on stimuli-responsive polymers are extensively studied because of their advantages in controlled release of anti-cancer drugs in response to induced stimuli. To develop a smart drug-delivery system, silica nanoparticles modified with 3-(trimethoxysilyl) propyl methacrylate (MPS) were used in inverse emulsion polymerization of N,N-dimethylaminoethyl methacrylate with N,N-methylene bisacrylamide in different amounts (MBA: 2, 4, and 8 mol%). The temperature- and pH-responsive hybrid core-shell nanoparticles were used for preparation of hollow poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA) nanogels by hydrolysis of the silica cores. Fourier-transform infrared spectroscopy was used to confirm the surface modification of silica nanoparticles with MPS. Successful synthesis of the hybrid and hollow nanogels was investigated by thermogravimetric analysis, scanning electron microscopy, and transmission electron microscopy. In addition, temperature-responsivity and phase separation behavior of the hybrid and hollow nanogels were studied by UV/Vis spectroscopy. The UV/Vis spectra showed that the absorption intensity was increased with increasing MPS and MBA contents in basic conditions. The hollow nanogels showed higher swelling/deswelling ratio compared to the hybrid nanogels in acidic media (pH 3.5) and at temperatures above the volume phase transition temperature (70 °C). Some of the hybrid and hollow nanogels with different crosslinking densities were used as smart drug carriers for doxorubicin (DOX), and their release behavior were investigated at different pH (3.5 and 7.5) by UV/Vis spectroscopy. The release profiles display that release of DOX has increased in pH of 3.5, and the hollow nanogels showed lower release contents than the hybrid nanogels because of diffusion and encapsulation of DOX molecules in the hollow space. The experimental release profiles confirmed that DOX release percentage in the hybrid nanogels was more than the hollow ones, while loading capacity of the hollow nanogels was higher. The Korsmeyer-Peppas model showed the best fitting with the experimental results of DOX release from PDMAEMA carriers.

Three-dimensional structure and formation mechanisms of Y2O3 hollow-precipitates in a Cu-based metallic glass

Recently, the high ductility of Cu-based bulk metallic glasses (BMGs) has been directly linked to the presence of Y2O3 precipitates, and surrounding crystallized areas. Nevertheless, the formation of the precipitates remains to be defined. In this work, the structure of Y2O3 precipitates and crystallized zones of the BMG are investigated at the nanoscale in three-dimensions, shining light on their spatial distribution and their origin. Two kinds of precipitates were observed: small solid ones and large hollow ones. The mechanism proposed to explain the formation of hollow-precipitates is based on the Kirkendall effect. A model was implemented to assess the feasibility of this mechanism with the experimental results. Moreover, our results suggest that micro and nano-crystallized areas within the BMG are induced by the presence of yttria precipitates, with a correspondence between the size of the precipitate and the size of the crystallized areas.

Strategies of Perception of Europe and their Reception in Lithuania

This article analyses strategies of perception of Europe that fit into a triple structure. The traditional division into philosophical, cultural, and political Europe is intersected with more fundamental European perceptions determined by different ways of thinking. In this article, these ways are referred to as the closed, the open and the hollow ones. Thus, three different conceptions of Europe arise: the closed Europe characterized by essentialism, ethnocentrism, and monologic consciousness; the open Europe based on the standpoint that protection of one’s own identity and maturity depend on a dialogic relationship with representatives of other identities; and the hollow Europe that makes absolute the imperative of moral self-criticism, as well as identity’s deconstruction and its relativism. The discussion of all three strategies of perception of Europe is followed by the analysis of how they were received in Lithuania. The conclusion highlights the necessity to further research the relationship between all three conceptions of European identity.

Compressive behavior of circular hollow and concrete-filled steel tubular stub columns under atmospheric corrosion

This paper aims to study the compressive behavior of circular hollow and concrete-filled steel tubular stub columns under simulated marine atmospheric corrosion. The specimens after salt spray corrosion were tested under axial compressive load. Steel grade and corrosion level were mainly considered in the study. The mechanical behavior of circular CFST specimens is compared with that of the corresponding hollow ones. Design methods for circular hollow and concrete-filled steel tubular stub columns are modified to consider the effect of marine atmospheric corrosion. The results show that linear fitting curves could be used to present the relationship between corrosion rate and the mechanical properties of steel after simulated marine atmospheric corrosion. The ultimate strength of hollow steel tubular and CFST columns decrease with the increase of corrosion rate while the ultimate displacement of those are hardly affected by corrosion rate. Increasing corrosion rate would change the failure of CFST stub column from ductile failure to brittle failure. Corrosion rate would decrease the ductility indexes of CFST columns, rather than those of hollow steel tubular columns. The confinement factor

Chlorine-doped α-Co(OH)2 hollow nano-dodecahedrons prepared by a ZIF-67 self-sacrificing template route and enhanced OER catalytic activity.

Hollow α-Co(OH)2 and Cl-doped α-Co(OH)2 nano-dodecahedrons were successfully synthesized via a ZIF-67-assisted template route in the absence/presence of NaCl. The reactions were carried out in a Teflon-lined stainless-steel autoclave at 40 °C for 4 h, employing dodecahedral ZIF-67 and hexamethylenetetramine (HMT) as the reactants. The as-obtained hollow nano-dodecahedrons were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared (FTIR), X-ray photoelectron energy, EDS mapping and N2 sorption-desorption technologies. Electrochemical measurements showed that both α-Co(OH)2 and Cl-doped α-Co(OH)2 hollow nano-dodecahedrons displayed excellent catalytic activities for the oxygen evolution reaction (OER) and Cl-doped α-Co(OH)2 hollow ones possessed stronger electrocatalytic performances. To deliver a current density of 10 mA cm-2, Cl-doped α-Co(OH)2 hollow nano-dodecahedrons required a low overpotential of 298 mV, which is smaller than most reported α-Co(OH)2 catalysts. Also, the as-obtained hollow catalyst still had excellent OER cycling stability and durability. After 1000 CV cycles, the overpotential merely slightly increased. Continuously catalyzing at the current density of 10 mA cm-2 for 40 h, the voltage only increased ∼2.5%.

Hierarchical MFI zeolite synthesized via regulating the kinetic of dissolution-recrystallization and their catalytic properties

Hierarchical MFI zeolites with open pores were synthesized by a temperature programmed dissolution-recrystallization post-treatment. By controlling the temperature of post-treatment using TPAOH, open macropores and mesopores were created by simply regulating the kinetics of dissolution and recrystallization. Benzyl alcohol self-etherification reaction, which only occurs in micropores, was tested on ZSM-5 to understand the effect of hierarchical pore system. The catalytic activity of hierarchical TS-1 was tested with cyclohexanone ammoximation. Hierarchical ZSM-5 and TS-1 zeolites with open pores showed higher catalytic activity compared with both hollow and conventional ones. The increased catalytic activities can be ascribed to the enhanced diffusion.

Stainless Steel Hollow Microspheres for Arterial Embolization Hyperthermia

To find a novel microscaled mediator suitable for arterial embolization hyperthermia (AEH). Stainless steel microspheres including both hollow (H1) and solid ones (S1) were produced with dispersing molten steel stream by water jet. Theoretically analyzing the power absorption of them in alternating magnetic field revealed that larger size and smaller permeability led to more heat generation. Higher field intensity and frequency also improved the heating power. Given the same condition, heating power per unit mass was greater in hollow microsphere than solid one. Microscopic observations of H1 and S1 were conducted along with particle size distribution, magnetization curve and heating power measurement. In vivo heating test, in vitro hyperthermia test and in vitro biocompatibility test were conducted for the finally selected mediator H1. The measured heating power of H1 and S1 met the theoretical values in low intensity field, but was considerably below expectation in strong field. Power density of H1 was clearly greater than that of S1 as theoretically predicted. The temperature of a rabbit ear in magnetic field injected with H1 maintained 50 °C for 10 min. In vitro hyperthermia test showed its outstanding treatment effectiveness for cancer cells. Cytotoxicity of H1 was categorized as Grade I, which is regarded as no cytotoxicity. Stainless steel hollow microsphere H1 was a promising mediator for AEH for its high efficiency in heating tumor region and killing cancer cells as well as good biocompatibility.

Phase and Composition Tuning of 1D Platinum‐Nickel Nanostructures for Highly Efficient Electrocatalysis

Among various platinum (Pt)‐based nanostructures, porous or hollow ones are of great importance because they exhibit fantastic oxygen reduction reaction (ORR) enhancements and maximize atomic utilization by exposing both exterior and interior surfaces. Here, a new class of porous Pt3Ni nanowires (NWs) with 1D architecture, an ultrathin Pt‐rich shell, high index facets, and a highly open structure is designed via a selective etching strategy by using the phase and composition segregated Pt‐Ni NWs as the starting material. The porous feature of Pt3Ni NWs can be readily fulfilled by changing the Pt/Ni atomic ratio of the starting Pt‐Ni NWs. Such porous Pt3Ni NWs show extraordinary activity and stability enhancements toward methanol oxidation reaction and ORR. The porous Pt3Ni NWs can deliver ORR mass activity of 5.60 A mg−1, which is 37.3‐fold higher than that of the Pt/C. They also show outstanding stability with negligible activity loss after 20 000 cycles. This study offers a unique approach for the design of complex nanostructures as efficient catalysts through precisely tailoring.