Hollow Cones Research Articles

A Planar Darkfield Illuminator for Wide‐Field High‐Contrast Imaging of Specimens in Microfluidic Chips

AbstractDarkfield microscopy is an effective technique and well suited for use involving live and unstained biological samples, where a bulky condenser should be precisely aligned in the optical path to produce a cone of illumination light. Here, a compact darkfield illuminator is invented that has a planar shape and can work at broadband wavelengths. It can be easily incorporated into a conventional microscope as a substrate to produce hollow cones of light for large‐area darkfield illumination, resulting in a high‐contrast high‐sensitivity widefield microscopy images. Taking advantages of its planar and compact structure, this darkfield illuminator is successfully integrated with a microfluidic chip; thus, the actions and reactions of biological and chemical specimens flowing inside micrometer‐sized channels, can be real‐time imaged with high contrast and sensitivity in a large field‐of‐view (FoV). For the first time, the work integrates a compact darkfield illuminator with microfluidic chips, which produces a new platform for applications in biology, chemistry, and biomedical engineering.

Performance evaluation of a solar thermal storage system proposed for concentrated solar power plants

This study aims to assess the performance of the Hybrid Solar Thermal Storage (HSTS) system, the storage system proposed for concentrated solar power (CSP) plants. The heat storage hybridisation concept is based on coupling latent phase change material (PCM) and thermochemical storage system containing paired metal hydride (MH) beds. One base design which uses only thermochemical heat storage mode and two designs of the HSTS system with two distinct PCM heat exchanger designs (i.e., shell-and-tube and cylinder with truncated hollow cones) are proposed and numerically investigated. To predict the dynamic behavior of the three storage systems, a bidimensional mathematical model is established and a numerical code written in Fortran-90 is developed. Key performance indicators used to evaluate the performance of the three storage systems include volumetric storage capacity, specific power, state of hydrogen charge, and energy storage efficiency. Comparing the performance of the three systems reveals that the HSTS system's energy storage efficiency increased by 36% due to the integration of a reaction heat recovery internal system based on Na3Al as PCM. The use of the PCM in truncated hollow cones resulted in a 36.4% reduction of the heat charging and discharging time, an 18.5% increase storage capacity, and a 54.1% increase in specific power. In addition, this study proves that the third design can be imlpemented as a HSTS system in a solar power plant with the following performance indexes: 128 W/kg- Mg2FeH6, 160 MJ/m3 and 88% for specific power, volumetric storage capacity and energy storage efficiency, respectively.

Rotating Translating Cones

A first attempt has been made to confirm experimentally a theoretical concept, recently published, involving a rigid cone rotating about its long axis under still water: it should tend to translate along that axis blunt end leading and apex trailing. Two identical hollow cones, neutrally buoyant, with equal weights attached to the apexes, were released simultaneously at the surface of a swimming pool. One cone had a thin light weight spiral vane vertically attached to the cone’s outside surface in order to cause it to rotate as it sank. Several trial runs were made in the shallow and deep ends of the pool, and in every case, the non-rotating cone without a vane hit the bottom of the pool first. These comparisons qualitatively and indirectly validate the prediction.

4D Printing of shape-memory polymeric scaffolds for adaptive biomedical implantation

4D printing has shown great potential in a variety of biomedical applications due to the adaptability and minimal invasiveness of fabricated devices. However, commonly employed shape memory polymers (SMPs) possess undesirable transition temperatures (Ttranss), leading to complications in implantation operations. Herein, we demonstrate 4D printing of a new SMP named poly(glycerol dodecanoate) acrylate (PGDA) with a Ttrans in a range of 20 °C - 37 °C making it appropriate for shape programming at room temperature and then shape deployment within the human body. In addition, the material possesses suitable rheological properties to allow for the fabrication of a variety of delicate 3D structures such as “triangular star”, “six-petal flower”, “honeycomb”, “tube”, tilted “truncated hollow cones”, as well as overhanging “bridge”, “cage”, and “mesh”. The printed 3D structures show shape memory properties including a large fixity ratio of 100% at 20 °C, a large recovery ratio of 98% at 37 °C, a stable cyclability of > 100 times, and a fast recovery speed of 0.4 s at 37 °C. Moreover, the Young's moduli of the printed structures can be decreased by 5 times due to the phase transition of PGDA, which is compatible with biological tissues. Finally, in vitro stenting and in vivo vascular grafting demonstrated the geometrical and mechanical adaptivity of the printed constructs for biomedical implantation. This newly developed PGDA SMP based 4D printing technology has the potential to pave a new route to the fabrication of shape memory scaffolds for personalized biomedical applications.

Nord-Oriented Burial on the Muslim Burial Ground in Bulgar and the Issue of Interpretation of Iron Cones

The burial of a nomad woman with the northern orientation on a Moslem burial ground of the second half of the 14th and early 15th centuries was found in Bulgar (burial 4, excavation CXXXIV). The findings from this burial are analyzed in the paper. Four beads of multicolored pasta, a knife, a bronze mirror and eight iron hollow cones were found in the grave. 37 burials with cones are taken into account as belonged to the Golden Horde population. Most of them were buried according to the Mongolian burial tradition with the northern orientation. These objects were found in burials with orientations of the northern direction (65%), as well as western (22%) and eastern ones (13%). Usually, the cones have been revealed within the vessels, flats or near them. The cones are associated with Buddhist religion and are used for making tsatsa. Tsatsa was made in rituals during funeral rites. The vessels might contain sacred ingredients in order to add them into the clay. The flats and fragments of metal vessels were used for aromatic smoking scars or as stands in the manufacture of tsatsa. On the author’s opinion, appearance of the iron cones in the Golden Horde burial complexes may be associated with the spread of Buddhism among the Mongols.

Computational Fluid Dynamics study of a corrugated hollow cone for enhanced dew yield

Dew condensation is the result of cooling by radiative deficit between a substrate and the atmosphere. Dew yield can be enhanced in hollow structures like hollow cones where the influence of wind is lowered. Corrugation increases the local tilt angle with horizontal and makes dew drop grow faster on edges, then drops detach sooner and act as natural wipers. However, corrugation increases the heat exchange with surrounding local air, which may reduce cooling.In order to evaluate these effects on cooling and dew yield, a corrugated, W-shaped hollow cone is compared to the same, smooth structure (S-cone) by Computational Fluid Dynamics. Two softwares were used: Ansys CFX for a pre-study concerning detailed aerodynamics where the computational domain is modeled to obtain a fully developed wind profile assuming an unobstructed inlet and COMSOL Multiphysics for aerodynamics coupled with heat flux, including radiative exchange surface-to-sky and surface-to-surface. Local temperatures can be obtained, which can be related to the dew yield. Turbulence is seen at all speeds but stagnation of the flow is also observed, which limits the convective heat exchanges and facilitates dew formation. At low wind speed, convective heat exchange is similar for both smooth and corrugated surfaces, and corrugation increases cooling. At higher air flow velocities, convective heat exchange is larger for the W-cone but cooling is only slightly smaller than found on the S-cone. Corrugated W-cone should thus give larger yield than the corresponding smooth S-cone.

Combination of Reactive-Ion Etching and Chemical Etching as a Method for Optimizing the Surface Relief on AlGaInN Heterostructures

A relief on the surface of GaN previously released from the growth substrate is formed by a combined method in which reactive ion etching is used in combination with liquid etching (in KOH or hydrochloric-acid solutions). The dependence of obtained relief on the sequence of operations used is studied. It is shown that etching in a KOH solution followed by reactive ion etching provides the appearance of truncated hollow cones on the surface. In experiments, the ability of a hydrochloric-acid solution for etching exclusively GaN relief elements formed by reactive ion etching of the surface is also found. As a result, reactive ion etching of the sample followed by immersion into hydrochloric acid forms objects of cylindrical shape on its surface transforming at the base into conical or strongly distorted pyramidal structures. The appearance of this relief can be explained by the predominance of the chemical component in reactive ion etching with increasing distance from the sample surface. Further optimization of the relief parameters obtained as a result of combined etching is possible by varying the modes of operation under use.

Spatially Resolved Ion Density Measurements in an Oxyfuel Cutting Flame

ABSTRACT A novel variation of the Langmuir probe for spatially resolved ion density measurements in a dense flowing plasma is presented. The technique uses a spinning disc to rapidly transit a wire probe through the flame. Spatial resolution is accomplished by post-processing data collected with many wire locations. The technique resolves ion density with a resolution of 0.5 mm in a 3000 K atmospheric pressure flame. The oxyfuel cutting torch flame under study is found to have twelve hollow cones with a 1 mm base and 4 mm height with ion density m along their surface. The base of the cones forms a ring, the inner diameter of which exhibits similarly large ion density, while the outer diameter appears to be weakened by entrained air. The ion densities decay over mm length scales from their peaks in the inner cones to form a semi-homogeneous annulus with ion density on the order m.

Low-altitude frequency-banded equatorial emissions observed below the electron cyclotron frequency

Abstract. The ICE (Instrument Champ Électrique) experiment on board the DEMETER (Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions) satellite recorded frequency-banded wave emissions below the electron cyclotron frequency, with band spacing ≳ frequency low-hybrid resonance, in the vicinity of the magnetic equatorial plane. Those radiations were observed in the beginning of the year 2010 on the night side of Earth and rarely on the day side. We distinguish two components: one appears as frequency bands continuous in time between a few kilohertz and up to 50 kHz, and the other one is from 50 to 800 kHz. The first component exhibits positive and negative frequency drift rates in the Southern Hemisphere and Northern Hemisphere, at latitudes between 40 and 20∘. The second one displays multiple spaced frequency bands. Such bands mainly occur near the magnetic equatorial plane with a particular enhancement of the power level when the satellite latitude is close to the magnetic equatorial plane. We show in this study the similarities and the discrepancies between the non-free-space DEMETER frequency-banded emissions and the well-known free-space terrestrial kilometric radiation. The hollow cones of the DEMETER frequency-banded wave emissions are oriented towards Earth's ionosphere. We suggest that the source region is localized in regions poleward of the plasmapause where the ratio of the plasma frequency to gyro-frequency is smaller than one.

A Paul trap with sectored ring electrodes for experiments with two-dimensional ion crystals.

We have developed a trapped ion system for producing two-dimensional (2D) ion crystals for applications in scalable quantum computing, quantum simulations, and 2D crystal phase transition and defect studies. The trap is a modification of a Paul trap with its ring electrode flattened and split into eight identical sectors and its two endcap electrodes shaped as truncated hollow cones for laser and imaging optics access. All ten trap electrodes can be independently DC-biased to create various aspect ratio trap geometries. We trap and Doppler cool 2D crystals of up to 30 Ba+ ions and demonstrate the tunability of the trapping potential both in the plane of the crystal and in the transverse direction.

Experimental Study on Spray Breakup in Turbulent Atomization Using a Spiral Nozzle

Spiral nozzles are widely used in wet scrubbers to form an appropriate spray pattern to capture the polluting gas/particulate matterwith the highest possible efficiency. Despite this fact, and a fact that it is a nozzle with a very atypical spray pattern (a full cone consisting of three concentric hollow cones), very limited amount of studies have been done so far on characterization of this type of nozzle. This work reports preliminary results on the spray characteristics of a spiral nozzle used for gas absorption processes. First, we experimentally measured the pressure impact footprint of the spray generated. Then effective spray angles were evaluated from the photographs of the spray and using the pressure impact footprint records via Archimedean spiral equation. Using the classical photography, areas of primary and secondary atomization were determined together with the droplet size distribution, which were further approximated using selected distribution functions. Radial and tangential spray velocity of droplets were assessed using the laser Doppler anemometry. The results show atypical behavior compared to different types of nozzles. In the investigated measurement range, the droplet-size distribution showed higher droplet diameters (about 1 mm) compared to, for example, air assisted atomizers. It was similar for the radial velocity, which was conversely lower (max velocity of about 8 m/s) compared to, for example, effervescent atomizers, which can produce droplets with a velocity of tens to hundreds m/s. On the contrary, spray angle ranged from 58° and 111° for the inner small and large cone, respectively, to 152° for the upper cone, and in the measured range was independent of the inlet pressure of liquid at the nozzle orifice.

Sonochemical synthesis of flower-like ZnO assembled by hollow cones toward water vapor permeability and water resistance enhancement of waterborne film

In this study, flower-like ZnO assembled by hollow cones (F-ZnO-HCs) were synthesized via sonochemical route and the related morphology and structure of product were characterized. Then, F-ZnO-HCs nanostructures were employed to polyacrylate and the effect of F-ZnO-HCs on the properties of waterborne films was investigated. Meanwhile, the morphological evolution of F-ZnO-HCs was proposed and the superiority of F-ZnO-HCs on synchronously improving the water resistance and water vapor permeability of polyacrylate film was discussed. The results showed that F-ZnO-HCs possessed an average diameter of ∼800nm and a large specific surface area of 16.01m2g−1. Adjusting the water content and citric acid dosage, the morphology of ZnO transformed from F-ZnO-HCs to ZnO nanoparticles, F-ZnO-NSs, F-ZnO-SCs and F-ZnO-NRs. F-ZnO-HCs nanostructures as fillers not only significantly enhance the stability of polyacrylate latex but also simultaneously improve the water vapor permeability and water resistance of polyacrylate film. Moreover, compared with other morphological ZnO, F-ZnO-HCs was the best for simultaneously improving the water resistance and water vapor permeability of polyacrylate film. F-ZnO-HCs is an ideal candidate for resolving the contradiction of the water resistance and water vapor permeability of waterborne films.

Construction of Analytical Eigensolutions for Isotropic Conical Bodies and Their Application for Estimation of Stresses Singularity

A complete set of eigensolutions is constructed for different variants of circular conical bodies: homogeneous cone with one lateral surface (solid cone), homogeneous cone with two lateral surfaces (hollow cone) and composite cone for different variants of boundary conditions on the lateral surface. It has been shown that the constructed eigensolutions can be readily applied for estimation of the character of stress singularity at the vertices of conical bodies. The character of stress singularity at the vertex of the solid and hollow cones for different variants of boundary conditions on the lateral surfaces has been defined by direct numerical simulations. Numerical results obtained for solid, hollow and compose cones under different boundary conditions on the lateral surfaces are discussed.

New light trap design for stray light reduction for a polarized scanning nephelometer.

Light scattering is an important tool for gathering information about the structure and origin of atmospheric aerosols. We build a polarized scanning nephelometer to measure the properties of aerosol particles. However, the accuracy of the backward-scattered light measurements is limited by stray forward-scattered light reflected back into the collection optics. We briefly analyze this stray light. A new form of light trap with multiple hollow cones is introduced to suppress backward-scattered stray light. To evaluate the effect of the light trap on suppressing stray light for our nephelometer, a simulation model with and without the light trap was analyzed. Our results show that without the light trap, the percentage of backward-scattered stray light can be more than 50% for some kinds of particles. With the light trap with multiple hollow cones, the percentage of stray light with a backward-scattered angle can be less than 0.7%, which remains stable over different angles. Our results indicate that this structure could be particularly suitable for a light trap with a very large aperture but limited space.

On intense proton beam generation and transport in hollow cones

Proton generation, transport and interaction with hollow cone targets are investigated by means of two-dimensional PIC simulations. A scaled-down hollow cone with gold walls, a carbon tip and a curved hydrogen foil inside the cone has been considered. Proton acceleration is driven by a 1020 W·cm−2 and 1 ps laser pulse focused on the hydrogen foil. Simulations show an important surface current at the cone walls which generates a magnetic field. This magnetic field is dragged by the quasi-neutral plasma formed by fast protons and co-moving electrons when they propagate towards the cone tip. As a result, a tens of kT Bz field is set up at the cone tip, which is strong enough to deflect the protons and increase the beam divergence substantially. We propose using heavy materials at the cone tip and increasing the laser intensity in order to mitigate magnetic field generation and proton beam divergence.

Holographic entanglement entropy for hollow cones and banana shaped regions

We consider banana shaped regions as examples of compact regions, whose boundary has two conical singularities. Their regularised holographic entropy is calculated with all divergent as well as finite terms. The coefficient of the squared logarithmic divergence, also in such a case with internally curved boundary, agrees with that calculated in the literature for infinite circular cones with their internally flat boundary. For the otherwise conformally invariant coefficient of the ordinary logarithmic divergence an anomaly under exceptional conformal transformations is observed. The construction of minimal submanifolds, needed for the entanglement entropy of cones, requires fine-tuning of Cauchy data. Perturbations of such fine-tuning leads to solutions relevant for hollow cones. The divergent parts for the entanglement entropy of hollow cones are calculated. Increasing the difference between the opening angles of their outer and inner boundary, one finds a transition between connected solutions for small differences to disconnected solutions for larger ones.

Submicrometer Hollow Bioglass Cones Deposited by Radio Frequency Magnetron Sputtering: Formation Mechanism, Properties, and Prospective Biomedical Applications.

This work reports on the unprecedented magnetron sputtering deposition of submicrometric hollow cones of bioactive glass at low temperature in the absence of any template or catalyst. The influence of sputtering conditions on the formation and development of bioglass cones was studied. It was shown that larger populations of well-developed cones could be achieved by increasing the argon sputtering pressure. A mechanism describing the growth of bioglass hollow cones is presented, offering the links for process control and reproducibility of the cone features. The composition, structure, and morphology of the as-synthesized hollow cones were investigated by energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), grazing incidence geometry X-ray diffraction (GIXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM)-selected area electron diffraction (SAED). The in vitro biological performance, assessed by degradation tests (ISO 10993-14) and cytocompatibility assays (ISO 10993-5) in endothelial cell cultures, was excellent. This allied with resorbability and the unique morphological features make the submicrometer hollow cones interesting candidate material devices for focal transitory permeabilization of the blood-brain barrier in the treatment of carcinoma and neurodegenerative disorders.

Integral Transform and Heat Conduction in a Hollow Cone with Radiation

A new integral transform is development whose kernal is a spherical function a solution of Legendre differential equation. This transform is used to determine the temperature at any point in a hollow finite cone whose inner angle is a and outer angle is b, with boundary conditions of radiation type on the outside and inside surface having independent radiation constants. It is evident that most of the possible problems on boundary conditions hollow cones can be solved by particularising the method described here.

Dynamic analysis of composite laminated and sandwich hollow bodies of revolution based on three-dimensional elasticity theory

This paper presents a semi-analytical procedure for solving linear vibration problems of composite laminated and sandwich hollow bodies of revolution with arbitrary combinations of boundary constraints in the framework of the three-dimensional theory of elasticity. Multilevel partitioning hierarchy, viz., multilayered body of revolution, individual layer and layer segment, is adopted in the theoretical analysis. The appropriate continuity constraints on common interfaces are imposed by means of a modified variational principle combined with the least-squares weighted residual method. The displacement field of each layer segment is characterized by a mixed series of basis functions, i.e., Fourier series and orthogonal polynomials. Numerical examples concerning the free vibrations of composite laminated and sandwich hollow cylinders, cones, and spheres, are presented to show the performance of the method, and comparisons of the present results are made with solutions available in the literature and those obtained from finite element analyses. With regard to the forced vibration problems, steady-state vibration responses of a sandwich hollow cylinder under a uniformly distributed normal harmonic pressure are analyzed, and time-domain solutions of composite laminated and sandwich hollow spheres subjected to various impulsive loads, including a rectangular pulse, a triangular pulse, a half-sine pulse and an exponential pulse, are also examined. Numerical experiments show that the present method is accurate, efficient and reliable for predicting the full spectrum of vibration behaviors of multilayered hollow bodies of revolution.

Physics of Hypercumulation: Jet Formation in Shaped Charge and Ablatively-Driven Implosion of Hollow Cones

In this letter we suggest a new approach to the physical principles for hypercumulative plasma jet formation. This new approach leads to several new results which are of fundamental importance. The simulation results of hypercumulative plasma jet are discussed. It has been shown that the increase of the plasma jet speed in the suggested configuration is 25-30% and the increase of jet pulse is more than 90 times which are not achievable in the classical cumulation.