Movable Ring Research Articles

Ferrofluids to improve field homogeneity in permanent magnet assemblies

• Halbach magnet adapted with magnet rings for mechanical shimming. • Novel passive magnetic field shimming method based on ferrofluid suspensions in microvolumes. • Small size light-weight magnet assembly suitable for mobile magnetic resonance applications. A novel principle of passive magnetic field shimming for permanent magnet assemblies is introduced, based on defined amounts of a ferrofluid suspension contained in a microliter volume plastic container that is accurately positioned within the magnet bore. The ferrofluid volume acts as a micromagnet that compensates inhomogeneities in the magnetic field profile. A proof of principle is shown for a permanent magnet assembly, derived from a Halbach design, with two additional movable rings of magnets. These rings result in an average magnetic field strength of 1.06 T inside the bore, 19 % higher than the Halbach alone. Two options for field shimming with ferrofluids are shown: changing the material volume or choosing a ferrofluid with different saturation magnetization value. With the tested simple single-cube ferrofluid implementation the field homogeneity is improved from 86 ppm to 8 ppm over a sampling length of 5.5 mm. Better homogeneity is expected with more sophisticated ferrofluid arrangements. The complete assembly has a size of 5 × 5 × 4.2 cm 3 and a weight of 332 g. The demonstrated concept is particularly attractive for mobile magnetic resonance systems, as it does not require electrical power during operation.

Комплекс конской узды из меотского погребения на правобережье Кубани

The paper presents an overview of a unique Maeotian horse bridle assemblage from the cemetery of Starokorsunskaya settlement No. 2 located on the right bank of the Kuban river. The horse was buried lying with its abdomen in a ventral position, its legs folded up underneath its abdomen, its face turned east-north-east. The eastern part of the burial construction was damaged and collapsed into the storage reservoir. It is possible that the person‘s burial who was accompanied by the horse, also disintegrated. Two iron socketed arrowheads dating back to the 6th – 3rd centuries BC were found between the horse ribs. In the horse’s teeth there were two-piece iron bits with rigid check-devices; more than six sets of iron single-gnawed bits lay next to the horse. Two-piece iron bits were equipped with rigid check-devices in the form of short crosses, the ends of which were forged into blades with sharp small teeth (variant B). The check-devices of this variant were recorded in the Maeotian culture of the second quarter – middle 4th century BC, and possibly existed throughout the first half of the next century. However, the latest assemblages with such check-devices from the sites on the right bank of the Kuban river dating back precisely to the beginning – the first quarter of the 3rd century BC according to the amphorae containers. A group of single-gnawed bits consisted of six sets with cheek-pieces of different types. The bits themselves (except for one set) are pseudo-twisted, with a movable ring at one end and a cheek-piece at the other. Cheek-pieces with an 8-shaped widening in the middle are of two different types. Three pairs of bits are equipped with a pseudo-twisted rod-shaped cheek-pieces, the other three blade cheek-pieces with conical and moon-shaped pendants. Cheeks of these types do not yet have close analogies either in the Maeotian or in the Scythian culture, and the singlegnawed bits were never found anywhere before. According to cross-shaped rigid check-devices on two-piece bits, the chronology of the burial is limited to the second quarter of the 4th – beginning of the 3rd century BC. The set of single-gnawed bits was most likely intended for training young horses on the lane. The presence of six sets of such bits in the burial probably indicates that a horse-breaker was buried there.

An Angular Displacement Sensor-Based Active Feedback Open Complementary Split-Ring Resonator

This letter presents an active feedback microwave sensor with a wide dynamic range and high sensitivity for detecting angular displacement. The sensor comprises two types of movable ring resonators (the rotor), split-ring resonator (SRR) and complement SRR (CSRR), and a modified convex-shaped open complementary split-ring resonator (the stator). The stator is designed with an active circuitry to enhance the quality factor over 4.7 K, and the feedback loop surrounds the sensing zone to enhance the mutual coupling for tracking a finite rotation of rotors in a wide dynamic range. The stator uses the separation between two reflection coefficients or the decibel magnitude variation at a fixed frequency, which is generated from its resonance frequency shift and whose values vary as a function of the rotation angle to be measured. After rotor loading, the average decibel sensitivity in terms of variation in reflection was calculated as 0.32 and 0.13 dB/degree for the SRR and CSRR, respectively, within a dynamic range of 0°–90°.

ПОЯС ЕПИСКОПА ЦЕЗАРИЯ АРЕЛАТСКОГО: МЕЖДУ "ВЕЩЬЮ" И "СИМВОЛОМ"

The article studies the question whether bishop Caesarius of Arles (503–542) could be the owner of a leather belt with an ivory buckle from the Museum of Antique Arles. The issue is the absence of narrative sources directly proving that idea. High price of the object did not match the bishop’s ascetic reputation. Still that did not preclude that someone from the closest circle of his associates or supporters could make that gift to Caesarius. The article studies the ornament of the movable ring of the buckle and the iconographic type of the plot of the Resurrection of Christ carved on its surface. Some parts of the belt, its decoration and manufacturing techniques find parallels with various artifacts (buckles, sarcophagi, diptychs) stored in other museums or discovered during archaeological excavations in Gaul. A review of the elements of the liturgical vestments of the clergy of Late Antiquity led to the conclusion that the belt could not have a liturgical status. On the basis of narrative sources related to the life and work of Caesarius, the author makes assumptions about the possible extra-liturgical contexts of wearing such a belt. The data presented in the study make it possible not only to attribute the belt to the period of bishop Caesarius’s life, but also to consider the latter as the most likely owner of the thing.

Elite Military Belts of the 8th – 9th Centuries from the Stavropol State Museum Reserve Funds

Introduction. The article is devoted to the typological and chronological analysis of the details of three prestigious belt sets stored in the funds of the G.N. Prozritelev and G.K. Prave Stavropol State History, Culture and Natural Landscape Reserve Museum. Methods and materials. The comparative typological method is used as a working one. It is based on the classification by material, processing method, shape, ornament, as well as on the selection and study of the types of buckles and waist plaques. The comparative analysis of the decor of belt parts from the Stavropol Museum and the like found in the Don region, Prikamye and on the territory of Hungary allows us to characterize the technology for producing a belt headset in the region in the 8th – 9th centuries. Analysis. The composition of the belt headset of the first belt found in a rich burial in Sadovoye, Arzgirsky District, Stavropol Krai, includes an iron buckle with an oval-triangular frame and a rectangular shield with a zavovanny edge, a belt tip, a clip, and a buckle. Every item is inlaid with thin gold plates. On the flap buckle and clip they are laid out in the form of a spiral. On every detail of the girdle, the gold foil is decorated with floral ornaments: five-beam rosettes, heraldic lilies (they even adorn the buckle frame), shoots with buds and leaves. Belt no. 2 found in 1969 in the rich burial 2 of Eshkakon burial ground no. 3, most likely, consisted of a belt and harness belts. The girdle set includes 10 heart-shaped patches (plaques), 4 elongated pads with rectangular slots, 9 round-triangular plaques with suspended movable rings (three rings are missing) and an oval-triangular buckle (rectangular shield is lost). Every listed item is made of white metal (silver). A floral ornament consisting of shamrocks (lotuses) is applied on the front side of all the buckles. Belt no. 3, which is also found in one of the Eshkakon burial grounds, consists of a buckle with a triangular frame and a pentagonal shield and 10 plaques of rounded triangular shape with suspended movable rings. Every item is made of bronze. Results. The rich funerary inventory of the burials in which the belts were found and their comparison with complexes that include a similar belt headset from other regions, indicate that all three belts from the Stavropol State Museum-Reserve are attributes of the military aristocracy of the second half of the 8th – 9th centuries. Chronologically, belt no. 1 is the earliest. Belt no. 2 should be considered close in time. The latest is belt no. 3.

Designing the Slide-Ring Polymer Network with both Good Mechanical and Damping Properties via Molecular Dynamics Simulation.

Through coarse-grained molecular dynamics simulation, we have successfully designed the chemically cross-linked (fixed junction) and the slide-ring (SR) systems. Firstly, we examine the dynamic properties such as the mean-square displacement, the bond, and the end-to-end autocorrelation functions as a function of the cross-linking density, consistently pointing out that the SR system exhibits much lower mobility compared with the fixed junction one at the same cross-linking density. This is further validated by a relatively higher glass transition temperature for the SR system compared with that of the fixed junction one. Then, we calculated the effect of the cross-linking density on the stretch-recovery behavior for the SR and fixed junction systems. Although the chain orientation of the SR system is higher than that of the fixed-junction system, the tensile stress is smaller than the latter. We infer that much greater chain sliding can occur during the stretch, because the movable ring structure homogeneously sustains the external force of the SR system, which, therefore, leads to much larger permanent set and higher hysteresis during the recovery process compared with the fixed-junction one. Based on the stretch-recovery behavior for various cross-linking densities, we obtain the change of the hysteresis loss, which is larger for the SR system than that of the fixed junction system. Lastly, we note that the relatively bigger compressive stress for the SR system results from the aggregation of the rigid rings compared with the fixed junction system. In general, compared with the traditionally cross-linked system, a deep molecular-level insight into the slide-ring polymer network is offered and thus is believed to provide some guidance to the design and preparation of the slide-ring polymer network with both good mechanical and damping properties.

A Photoresponsive Polymeric Actuator Topologically Cross-Linked by Movable Rings Based on a [2]Rotaxane Structure

A photoresponsive polymeric material, in which [2]rotaxane units with α-cyclodextrin (αCD) threading onto an azobenzene (Azo) derivative is used as a topological cross-link for the main chains of the polymeric material in aqueous media, was achieved. As shown in Figure 1a, A polycondensation reaction between Lys-αCD/Am2Azo inclusion complex and Su2PEG gave polymeric material cross-linked by [2]rotaxane (αCD-Azo hydrogel). [2]Rotaxane structures in the αCD-Azo hydrogel were found to act as movable links in the polymer network, and the mechanical properties of the material were enhanced to show a rupture strain of 2800%. The materials were reversibly deformed by irradiation with UV or visible lights in aqueous media, which caused photoisomerization of the azobenzene moiety and changed the structure of the [2]rotaxane linker, leading to deformation of the polymer network (Figure 1b). Surprisingly, the dry material (αCD-Azo xerogel), which had been uniaxially extended in air, showed a faster response than the αCD-Azo hydrogel. The orientation of the polymeric network in the materials enables the efficient response. As shown in Figure 1c, the αCD-Azo xerogel quickly bent towards the light source side within 3 seconds upon irradiation with UV light. 5.6 mg of the αCD-Azo xerogel also performed 5.6 μJ of mechanical work within 10 seconds by the UV-irradiation, which is approximately 50 times higher than that achieved in our previous work1. Figure 1. The preparation of the αCD-Azo hydrogel as a topological material (a), schematic illustration of the αCD-Azo hydrogel before and afeter the irradiation with UV (b), and lateral views of the αCD-Azo xerogel showing deformations driven by UV irradiation. [1]. Iwaso, K.; Takashima, Y.; Harada, A. Nat. Chem. 2016, 8, 625-632. Figure 1

Dynamic model of pulse mechanical seal

Double mechanical shafts seals with gas lubrication constructions are widely used in modern machine engineering for sealing the centrifugal machines, pumping aggressive, cryogenic substances and the melts. These constructions mainly use creating and maintaining a stable value for gas-dynamic method and the special microgrooves to draw the barrier gas into sealing gap are shaped to draw the barrier gas into the sealing gap. This article deals with the mathematical model of the pulse gas-barrier mechanical seal dynamics that synchronically use both gas-static and gas-dynamic methods of maintaining the contactless mode of operation, and is out of the disadvantages inherent for seals with microgrooves. The aim of this work is to develop a mathematical model of pulse seal functioning dynamics. The object of the research is the workflow of the seal. Іt is necessary to complement the existing method of pulse seals parameters calculation, and propose a methodology of operation gap pressure distribution calculation for achieve the objectives of the study. This model applies the numerical boundary element method, which allows to determine the pressure distribution in the operation gap due to the Reynolds equation. The model can be used to define the response of the movable face ring for the harmonic changes of external influences as well as for the frequencies risky range identification and for selecting such parameters of the seal where the movable ring oscillation amplitude would not be exceed by the allowable limits

Large Aperture, Tip Tilt Mirror for Beam Jitter correction in High Power Lasers

This paper describes a large aperture tip-tilt mirror (TTM) assembly for correction of beam jitter in high power lasers. The design intricacies and trade-offs among various parameters of TTM to meet the desired goals are discussed. The TTM assembly uses a 180 mm diameter and 5 mm thick silicon mirror glued onto the movable ring of a solid flexure. Four stacked piezo-ceramic based actuators have been used to incorporate angular tilts of the mirror along two orthogonal directions. Simulation studies have been carried out to study the dynamics of the TTM. The performance of the TTM assembly in both static and dynamic condition is provided. An experimental set-up is described to test the TTM performance in closed loop conditions. A tilt correction of ±200 micro-radians along two orthogonal directions with a closed loop bandwidth of 20 Hz has been achieved.Defence Science Journal, 2013, 63(6), pp.606-610, DOI:http://dx.doi.org/10.14429/dsj.63.5760

Intra-Operative Correction of Taylor Spatial Frame Without a Computer

The Taylor Spatial Frame (TSF) is a circular external fixator used to treat complex fractures and skeletal deformities. The device consists of 2 rings attached to bone by wires or half pins, connected by universal hinge joints to 6 independent telescopic struts, creating a hexapod. The output piece is defined as the movable ring, which has 6 degree of freedom relative to the other ring, which is the base. With 6 degree of freedom, the movable platform is capable of moving in 3 linear directions and 3 angular directions singularly or in any combination. These hexapod devices require complex mathematical software programs to accurately control the output piece. In the case of the TSF, the deformity and positional frame parameters can be indentified on postoperative radiographs. They are then input into internet-based software to calculate strut adjustments required to achieve deformity correction. When treating fractures with the TSF, the rings can be connected using FastFx struts. These struts can be locked in position or left in a sliding mode (unlocked) allowing manual manipulation of the frame to acutely correct the position of the fracture fragments. This reduction is rarely perfect however and often requires further postoperative frame adjustments using software calculations. We describe an intra-operative method for accurately adjusting the frame in its locked mode without the need for software input.

Design and Calculation for Test Tube with the Aim of Regulation Simultaneous Crystallization Tests

A design for an air-cooled test tube, with a series of modular and movable rings (cylindrical “crystallization comb”), installed in a laboratory crucible furnace is presented. The setup allows easy regulation simultaneous crystallization tests of a series of different crystallization rates in several columns (matrix) of test tubes, enabling fast studies of obtaining crystals. This low-budget, portable device (i.e. adjustable airstream with more simple control options), can also be applied in tube and chamber furnaces. The relations between the crystallization rate and parameters of air-cooled test tube are given and numerically analyzed.

Split Ring Resonators (SRRs) Based on Micro-Electro-Mechanical Deflectable Cantilever-Type Rings: Application to Tunable Stopband Filters

A new principle for the implementation of tunable split ring resonators (SRRs) is presented. The rings forming the SRRs are partly fixed to the substrate (anchor) and partly suspended (up-curved cantilever). Through electrostatic actuation, the suspended parts are deflected down, the distributed capacitance between the pair of coupled rings is modified, and hence the resonance frequency of the SRR can be electrically tuned. To obtain electrically movable rings, a cantilever-type micro-electro-mechanical-system (MEMS) design and fabrication process is applied. The resonance frequencies at the different switching states are measured by coupling the tunable SRR to a host microstrip line, and reveal that significant tuning ranges can be achieved. This novel tuning concept is applied to the implementation of tunable stopband filters at Ku band as proof-of-concept demonstrators.

Haptic perception of objects in infancy

Four-month-old infants held two rings, one in each hand, out of the field of view. In one condition, the rings could be moved independently; in the other condition, the rings could only be moved rigidly together. After exploring the rings haptically, infants received a haptic or visual test with pairs of rings that were connected or separated. The findings of four experiments provide evidence that infants explored the rings bimanually, producing patterns of rigid or independent motion, that infants discriminated between the two motion patterns, and that this discrimination transferred from touch to vision. Most importantly, the experiments provide evidence that infants perceived the unity and boundaries of objects by detecting the motion patterns they themselves produced. Infants who explored the independently movable rings perceived two distinct objects, whereas those who explored the rigidly movable rings perceived a single object that was connected between the two hands. Since the same motion patterns specify object boundaries in the visual mode, object perception may depend on a relatively central process.

The British Association: Section A—Mathematical and Physical Science

New Electric Balances, by Sir William Thomson, F.R.S.—These balances are founded On the mutual forces, discovered by Ampère, between the fixed and movable portions of an electric circuit. The mutually-influencing portions are usually circular rings. Circular coils or rings are fixed, with their planes horizontal, to the ends of the beam of a balance, and are each acted on by two horizontal fixed rings placed one above and the other below the movable ring. Six grades of instrument are made, named centi-ampere, deci-ampere, ampere, deca-ampere, hecto-ampere, and kilo-ampere balance. The range of each balance is about 25. Thus, the centi-ampere balance will measure currents of from 2 to 50 centi-amperes, while the kilo-ampere balance will measure currents of from 100 to 2500 amperes. Since the indications of the instrument depend on the mutual forces between two parts of an electric circuit of permanent form and relative position, they are not subject to the changes with time which are so troublesome in instruments the constants of which depend on the strength of permanent magnets.