Shape Of String Research Articles

Simulating Research on Rod String’s Gyro Effect Caused by Eccentric Rotation in Circular Tube

Based on the influences of eccentrical rotating inertial centrifugal force and axial force on the rod string’s lateral bending deformation, the finite beam element model of rod string’s bending deformation is established. The constraint to rod string’s bending deflection exerted by inwall of circular tube and the distinction of the constraint to rod string’s deflection because of the different gaps between rod string to circular tube and coupling to circular tube are both taken into account. Meanwhile, removable spring elements with two directions are adopted, by which the non-linear contact problem between the rod string and circular tube is well resolved. Combining space beam element and spring elements with two directions, the corresponding finite element simulating program is also developed. Several simulating results can be shown as follows: eccentric rotation of rod string is able to produce gyro effect in vertical circular tube; The shape of the rod string’s deformation is a spiral which is thin on the upper-part and dense on the under-part; Gyro wave numbers are affected obviously by rotating speed, eccentricity, axial concentrated force, axial distributed force and length of the rod string.

Violin string shape functions for finite element analysis of rotating Timoshenko beams

Violin strings are relatively short and stiff and are well modeled by Timoshenko beam theory. We use the static part of the homogeneous differential equation of violin strings to obtain new shape functions for the finite element analysis of rotating Timoshenko beams. For deriving the shape functions, the rotating beam is considered as a sequence of violin strings. The violin string shape functions depend on rotation speed and element position along the beam length and account for centrifugal stiffening effects as well as rotary inertia and shear deformation on dynamic characteristics of rotating Timoshenko beams. Numerical results show that the violin string basis functions perform much better than the conventional polynomials at high rotation speeds and are thus useful for turbo machine applications.

The preparation of calcium carbonate crystals regulated by mixed cationic/cationic surfactants

Cationic surfactants, didodecyldimethylammonium bromide (DDAB), 1-dodecyl-3-methylimidazolium bromide ([C 12mim]Br) and DDAB/[C 12mim]Br mixture were used to induce the formation of calcium carbonate (CaCO 3) crystals at ambient temperature. The obtained CaCO 3 particles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphologies of CaCO 3 crystals changed from laminated cube to sphericity and string shape with the increase of DDAB and [C 12mim]Br concentration, respectively. Flower-shaped CaCO 3 crystals were synthesized in the mixed DDAB/[C 12mim]Br system. More importantly, it was found that the complete conversion from calcite to vaterite was achieved at room temperature only through changing DDAB concentration. The regulations of DDAB and [C 12mim]Br to CaCO 3 crystals have been compared with that of dodecyltrimethylammonium bromide (DTAB) in our previous work and possible mechanisms have been proposed. It is shown that the cationic surfactants can control the crystallization of CaCO 3 and the number of hydrophobic alkyl chains of cationic surfactants might be more effective in modulating the crystallization of vaterite than the head groups.

개선된 발현악기의 루프 필터 설계 방법

본 논문에서는 발현악기 물리적 모델링에서의 개선된 루프필터 설계 방법을 제안한다. V<TEX>$\"{a}$</TEX>lim<TEX>$\"{a}$</TEX>ki가 제안한 기존의 루프필터 설계 방법은 악기의 음이 오래 지속되는 경우에는 타당하지만, 그렇지 못한 경우에는 악기 음의 주파수 의존 감쇠를 표현하지 못하는 문제점이 있다. 이를 해결하기 위해 녹음된 악기의 단위음에 대해 감쇠구간을 선택, 배음의 개수를 최소 5개부터 20개까지 변경하며 루프필터의 파라미터를 추정하고 이를 이용한 합성음과 원 신호 간 주파수 영역에서의 신호 대 잡음비가 가장 좋은 파라미터를 선택한다. 제안한 방법의 성능 검증을 위해 몸통의 구조와 현의 재질이 각각 다른 기타, 가야금, 거문고를 대상악기로 선정하였다. 제안한 방법은 배음의 지속시간에 상관없이 악기 음의 주파수 의존 감쇠를 잘 표현하는 루프필터 파라미터를 추정해 낼 수 있었다. This paper describes a development of a loop filter design in a physical modeling of the plucked string instrument. The conventional method proposed by V<TEX>$\"{a}$</TEX>lim<TEX>$\"{a}$</TEX>ki cannot estimate right parameters if a sound has either very short sustain or no sustain. In order to overcome this drawback, we propose the use of the decay region and 5 to 20 harmonics of the sound in the estimation of loop filter parameters. The most appropriate filter coefficient is chosen by frequency signal to noise ratio. To verify the performance of the proposed method, the guitar, gayageum and geomungo were selected as the target because they have different shape, structure, and material of strings. Regardless of the duration of harmonics, the proposed method was able to estimate the loop filter parameters representing frequency-dependent damping of harmonics.

Suspension Grafting Copolymerization of EPM-g-MAN and Its Toughening Effect on SAN Resin

EPM-graft-methyl methacrylate and acrylonitrile (EPM-g-MAN) was synthesized by graft copolymerization of methyl methacrylate (MMA) and acrylonitrile (AN) onto ethylene—propylene bipolymer (EPM) using the method of suspension polymerization. A novel engineering plastic with high impact strength, AEMS, which shows excellent resistance to weatherability and yellow discoloration and aging properties, were prepared by blending EPM-g-MAN with styrene—acrylonitrile (SAN) resin. The influence of the suspension grafting copolymerization technologies, including monomer ratios, EPM ratios, initiator content on monomer conversion ratio, grafting ratio, grafting efficiency, and the impact strength of AEMS, were investigated. The result showed that the optimized reaction conditions were obtained when the mass ratio of AN/MMAAN(fAN) was 15 wt%, the mass ratio of EPM/(EPM + MMA-AN) was 60 wt%, and the mass ratio of BPO/(EPM + MMA-AN) was 0.6 wt%. When the EPM/ AEMS mass ratio was 25 wt%, the notched Izod impact strength of AEMS reached 55.9 kJ/m2. DSC and DMA analysis showed that the compatibility of EPM-g-MAN and SAN resin improved when the grafting chain polarity was appropriate. Transmission electron microscopy analysis showed that EPM phase was the near continuous phase in the shape of bead string with diameter of about 0.15 μm and had good compatibility with SAN resin. Scanning electron microscopy analysis indicated that AEMS fracture surface appeared ‘root beard’ morphology. These phenomena indicated that the toughening mechanism was shear yielding of matrix, which endowed AEMS with remarkable toughness.

Positioning system of the ANTARES neutrino telescope

The ANTARES neutrino telescope consists of 12 string lines housing the optical detectors. Sea water currents may result in drifts for these strings by several metres from the vertical. However, muon track reconstruction is based on precise arrival time measurement of Cherenkov photons to the Optical Modules (∼1 ns) and knowledge of the Optical Module positions with respect to a fixed reference system with a corresponding resolution of ∼20 cm. The relative positioning of the detector is monitored combining two systems: an acoustic system giving the 3D position of five hydrophones along the line and a set of tiltmetre–compasses giving the local tilt and orientation of each Optical Module storey. With this information, a global fit of the string shape leads to the 3D positioning of the detector within the requirements. In this paper, the positioning system is described, and the performance and results for the first years of operation in ANTARES are shown.

Shape of Elastic Strings in Euclidean Space

We construct a 1-parameter family of geodesic shape metrics on a space of closed parametric curves in Euclidean space of any dimension. The curves are modeled on homogeneous elastic strings whose elasticity properties are described in terms of their tension and rigidity coefficients. As we change the elasticity properties, we obtain the various elastic models. The metrics are invariant under reparametrizations of the curves and induce metrics on shape space. Analysis of the geometry of the space of elastic strings and path spaces of elastic curves enables us to develop a computational model and algorithms for the estimation of geodesics and geodesic distances based on energy minimization. We also investigate a curve registration procedure that is employed in the estimation of shape distances and can be used as a general method for matching the geometric features of a family of curves. Several examples of geodesics are given and experiments are carried out to demonstrate the discriminative quality of the elastic metrics.

Megacomplex organization of the oxidative phosphorylation system by structural analysis of respiratory supercomplexes from potato

The individual protein complexes of the oxidative phosphorylation system (OXPHOS complexes I to V) specifically interact and form defined supramolecular structures, the so-called “respiratory supercomplexes”. Some supercomplexes appear to associate into larger structures, or megacomplexes, such as a string of dimeric ATP synthase (complex V 2). A row-like organization of OXPHOS complexes I, III and IV into respiratory strings has also been proposed. These transient strings cannot be purified after detergent solubilization. Hence the shape and composition of the respiratory string was approached by an extensive structural characterization of all its possible building blocks, which are the supercomplexes. About 400,000 molecular projections of supercomplexes from potato mitochondria were processed by single particle electron microscopy. We obtained two-dimensional projection maps of at least five different supercomplexes, including the supercomplex I + III 2, III 2 + IV 1, V 2, I + III 2 + IV 1 and I 2 + III 2 in different types of position. From these maps the relative position of the individual complexes in the largest unit, the I 2 + III 2 + IV 2 supercomplex, could be determined in a coherent way. The maps also show that the I + III 2 + IV 1 supercomplex, or respirasome, differs from its counterpart in bovine mitochondria. The new structural features allow us to propose a consistent model of the respiratory string, composed of repeating I 2 + III 2 + IV 2 units, which is in agreement with dimensions observed in former freeze-fracture electron microscopy data.

Cosmic string formation by flux trapping

We study the formation of cosmic strings by confining a stochastic magnetic field into flux tubes in a numerical simulation. We use overdamped evolution in a potential that is minimized when the flux through each face in the simulation lattice is a multiple of the fundamental flux quantum. When the typical number of flux quanta through a correlation-length-sized region is initially about 1, we find a string network similar to that generated by the Kibble-Zurek mechanism. With larger initial flux, the loop distribution and the Brownian shape of the infinite strings remain unchanged, but the fraction of length in infinite strings is increased. A 2D slice of the network exhibits bundles of strings pointing in the same direction, as in earlier 2D simulations. We find, however, that strings belonging to the same bundle do not stay together in 3D for much longer than the correlation length. As the initial flux per correlation length is decreased, there is a point at which infinite strings disappear, as in the Hagedorn transition.

Ejection characteristics of micropumps for motorcycle fuel atomizer in high-temperature environment

This study applied thermal bubble micropump on motorcycle fuel atomizer which is installed on the upper end of intake manifold and 20 cm away from the engine, and used ink and Stoddard solvent as work liquid. Based on computational fluid dynamics (CFD) simulation, it discussed the ejection characteristics of a single micropump and two adjacent micropumps with time-lagged ejections in a high-temperature environment, the temperature is higher than room temperature and lower than water boiling temperature. The results showed that due to contact with high-temperature external air, the surface tension of the ejected droplet string decreases. Therefore, the volume of the main ejected droplet decreases, and the neck and tail of the droplet string are scattered. The flying velocity of ejected droplet decreases as well. As the surface tension of the work liquid inside the micropump decreases, the air trapped inside the micropump is less obvious. As a result, the work liquid replenishes more smoothly, and the starting time of replenishment is advanced. Consequently, the work liquid replenishment rate is improved. The shape and velocity of droplet strings ejected from two adjacent micropumps are approximate. Because the density of Stoddard solvent is low, as it is driven by flowing external air, the offset value of the movement track of ejected droplet is large. As a result, the particle shape of ejected droplet is irregular. If the external air is still, the starting time of the same work liquid replenishment for both single and two adjacent micropumps is approximate. The starting time for Stoddard solvent is faster than that for ink, but the replenishment rates for both are very close, with the rate for two adjacent micropumps is higher than that for a single micropump. The flowing external air has insignificant effect on the work liquid replenishment rate for two adjacent micropumps in a high-temperature environment.

String deformations induced by retardation effects in mesons

The rotating-string model is an effective model of mesons, in which the quark and the antiquark are linked by a straight string. We previously developed a method to estimate the retardation effects in this model, but the string was still kept straight. We now go a step further and show that this kind of retardation effects cause a small deviation of the string from the straight line. We first give general arguments constraining the string shape. Then, we find analytical and numerical solutions for the string deformation induced by retardation effects. We finally discuss the influence of the curved string on the energy spectrum of the model.

Shadow resistant tracking using inertia constraints

In this paper, we present a new method for tracking objects with shadows. Traditional motion-based tracking schemes cannot usually distinguish the shadow from the object itself, and this results in a falsely captured object shape. If we want to utilize the object's shape information for a pattern recognition task, this poses a severe difficulty. In this paper we present a color processing scheme to project the image into an illumination invariant space such that the shadow's effect is greatly attenuated. The optical flow in this projected image together with the original image is used as a reference for object tracking so that we can extract the real object shape in the tracking process. We present a modified snake model for general video object tracking. Two new external forces are introduced into the snake equation based on the predictive contour and a new chordal string shape descriptor such that the active contour is attracted to a shape similar to the one in the previous video frame. The proposed method can deal with the problem of an object's ceasing movement temporarily, and can also avoid the problem of the snake tracking into the object interior. Global affine motion estimation is applied to mitigate the effect of camera motion, and hence the method can be applied in a general video environment. Experimental results show that the proposed method can track the real object even if there is strong shadow influence.

Formation of Magnetic Clusters in Perpendicular Thin Films

The formation and growing process of magnetic clusters in perpendicular thin films were investigated using micromagnetic simulation. Two estimation methods of cluster size were proposed. CS(area) was defined as the diameter of the circle which has the same area as the reversed region. CS(corr) was defined from the correlation between magnetizations of adjacent grains. These cluster sizes were calculated in the demagnetizing process. The shape of the cluster can be estimated from comparison between CS(area) and CS(corr). If CS(area) is larger than CS(corr), string shape clusters are formed. If CS(area) coincides with CS(corr), there are nonstring shape clusters. In order to make cluster size small in the demagnetizing process it is useful for the perpendicular thin film to have grain size dispersion

Meson Strings and Flavor Branes

In a QCD-like string model based on D6 flavor branes in the presence of D4 color branes wrapping one of the compactified dimension on an $S^1$, the shape of meson strings in the five dimensional curved space as well as the potential between quark and anti-quark are investigated. The flavor branes on which both ends of a meson string live are assumed to be separated in this five dimensional space, depending on the values of the constituent quark masses. It is shown in this picture that the meson string with different flavors on both ends changes its shape at a critical distance. There is, however, no critical distance for the meson with the same flavors. At this critical distance the potential between quark and anti-quark with different flavors gives a point of reflection and changes its shape around this point. Accordingly, the attractive force between quark and anti-quark seems to become stronger when the distance of flavor branes connecting meson strings becomes larger. This indicates quark systems with different flavors can form high-density states.

The template preparation and characterization of three new shapes of titania nanometer-array systems

A two-step anodization process was used to prepare highly ordered porous anodic alumina template (PAA). The template method was combined with the sol-electrophoresis deposition and sol-gel method to synthesize three types of nanometer-array systems. The titania nano-arrays have a high specific surface area. The sol-gel template method was also applied to prepare the rod-shaped titania nanowire-arrays. The diameter of titania nanometer-array is about 50 nm; the length is about 20 μm; and the distance of neighboring two nanowires is about 100 nm. Through controlling the pore depth of the template, the membrane with periodical modulating titania nanodots was prepared. The diameter of the nanodots on the membrane surface was about 75 nm and the dot distance was about 100 nm. Also a compact structure has been found on the back face of the membrane. The sol-electrophoresis template method was used to prepare the nanowire-array system with the shape of string of candied haws. The diameter of nanowires was about 75 nm and the length was about 20 μm. The periodic concave-convex structures were found in each nanowire and the shape looked like string of candied haws. The three types of nano-array systems have a high specific surface area. It can be predicted that this type of surface modulating array system will have new properties and effects that are different from those of common membranes, nanodots and nanowires.

Antistatic performance and morphological observation of ternary blends of poly(ethylene terephthalate), poly(ether esteramide), and Na-neutralized poly(ethylene- co-methacrylic acid) copolymers

Blends of poly(ethylene terephthalate) (PET) and poly(ether esteramide) (PEEA), which is known as an ion conductive polymer, were prepared by melt mixing using a twin screw extruder. Antistatic performance of the molded plaques of the binary blends was investigated and the effects of adding sodium ionomer, Na-neutralized poly(ethylene- co-methacrylic acid) (E/MAA) Copolymers, in comparison with NaI, were also investigated. We found Na-neutralized E/MAA significantly improved static dissipation performance when blended with above PET/PEEA system whereas NaI was only effective when PEEA amount was larger than 25 wt%. Morphological study of these ternary blends system was conducted by using TEM and it was observed that PEEA domain formed platelet structure in PET matrix when PEEA content was 30%. The domain shape changed from sphere particle to platelet structure via string shape with the increase of PEEA content. And the thickness of the PEEA layers was confirmed as thin as 10 nm. Specific interaction between PEEA and Na-neutralized E/MAA was found by TEM. The Na-neutralized E/MAA domain was encapsulated by PEEA, which could increase the surface area of PEEA in PET matrix. This encapsulation effect explains the unexpected synergy for the static dissipation performance on addition of Na-neutralized E/MAA to PET/PEEA blends.

GROWTH MECHANISM OF COILED CARBON WHISKERS

The growth mechanism of coiled carbon whiskers was thoroughly studied. The carbon whiskers were prepared by chemical vapor deposition (CVD) at high temperature (500-650 °C) using acetylene as the carbon source and metal powder as the catalyst. The results show that the shape, diameter and pitch of the coiled carbon whiskers are dependent on the particle size of metal powder: when the sizes of metal powder particles are in the range of tens of microns, carbon whiskers have twisted string shape with diameters between 130 nm and 180 nm and a pitch of 100 to 350 nm. When the diameters of metal powder particles are about several hundred microns, tube shape of carbon whiskers with diameters between 280nm and 350 nm and a pitch between 150nm and 180nm are obtained. The range of temperature for the preparation of coiled carbon whiskers by the CVD method follows Quasi-VLS theory.

Infinite‐dimensional projected dynamics and the 1‐dimensional obstacle problem

In this paper we present a direct application of the theory of infinite‐dimensional projected dynamical systems (PDS) related to the well‐known obstacle problem, i.e., the problem of determining the shape of an elastic string stretched over a body (obstacle). While the obstacle problem is static in nature and is solved via variational inequalities theory, we show here that the dynamic problem of describing the vibration movement of the string around the obstacle is solved via the infinite‐dimensional theory of projected dynamical systems.

Speaking of Infinity

We study the redundancy of three approaches to compression of independent and identically distributed (i.i.d.) strings over large, possibly infinite, alphabets: standard compression of the string itself and compression of the string's shape and pattern, which describe its symbols' relative magnitude and precedence, respectively. We determine the rate at which per-symbol standard redundancy increases to infinity as the alphabet size increases, show that the maximum per-symbol shape redundancy is between 0.027 and 1, and compare these to results showing that per-symbol pattern redundancy diminishes to zero for all alphabet sizes. We relate these concepts to ordered and unordered partitions of integers and sets, and use this framework to explore relations between several combinatorial quantities, including the Bell, Fubini, and second-type Stirling numbers.

String Form Factors

We compute the cross section for scattering of light string probes by randomly excited closed strings. For high energy probes, the cross section factorizes and can be used to define effective form factors for the excited targets. These form factors are well defined without the need for infinite subtractions and contain information about the shape and size of typical strings. For highly excited strings the elastic form factor can be written in terms of the `plasma dispersion function', which describes charge screening in high temperature plasmas.