Change In Geometric Configuration Research Articles

Low voltage visible light modulation for three colors (red, green, blue) by sputtered lithium niobate thin film

In this study, lithium niobate (LN) optical modulator devices were fabricated using cost-effective sputtered LN thin films. We successfully achieved a significantly small product of half-wave voltage and interaction electrode length (VπL) of 1.2, 1.0, and 0.75 V cm using red (λ = 638 nm), green (λ = 520 nm), and blue (λ = 473 nm) laser light, respectively. This small VπL is owing to the use of a low dielectric material of LaAlSiInOx for buffer insulator between LN waveguides and electrodes, and the change of geometrical configuration of the electrode. Thus, fabricating visible light modulators at low cost can be realized, and sputtered LN thin films can be adopted for visible light communications and consumer-based applications.

기하학적 위치 변화에 따른 텐덤 날개의 고레이놀즈수 공력 특성에 대한 수치적 연구

지역항공교통 (RAM) 이 장차 상용화되면 단일 날개에 비해 도심 속 돌풍에 대한 저항력이 좋은 탠덤 날개가 잘 활용될 수 있다. 탠덤 날개는 날개가 앞뒤로 배치된 형식의 날개이다. 탠덤 날개의 배치에 따라 고받음각을 포함한 고레이놀즈수 3차원 유동 조건에서 양력과 항력 등의 공력 특성을 분석하였다. 두 날개의 수평 간격과 수직 위치 인자를 바꿔 가면서 일련의 비교 분석이 이루어졌다. 수평 간격이 작을수록 앞날개는 양력계수가 높아지나 전체 날개의 효율은 줄어든다. 수직 간격에서는 뒷날개가 아래로 배치된 형태가 더 좋은 공력 성능을 지닌다. 두 파라미터를 조합하면 뒷날개를 아래로 배치한 상태에서 수평 간격을 가까이 좁혔을 때 매우 높은 실속 성능을 보일 것으로 판단된다.

Defect Engineering of Carbons for Energy Conversion and Storage Applications

Sustainable energy conversion and storage technologies are a vital prerequisite for neutral future carbon. To this end, carbon materials with attractive features, such as tunable pore architecture, good electrical conductivity, outstanding physicochemical stability, abundant resource, and low cost, have used as promising electrode materials for energy conversion and storage. Defect engineering could modulate the structures of carbon materials, thereby affecting their electronic properties. The presence of defects on carbons may lead to asymmetric charge distribution, change in geometrical configuration, and distortion of the electronic structure that may result in unexpected electrochemical performances. In this review, recent advances in defects of carbons used for energy conversion and storage were examined in terms of types, regulation strategies, and fine characterization means of defects. The applications of such carbons in supercapacitors, rechargeable batteries, and electrocatalysis were also discussed. The perspectives toward the development of defect engineering carbons were proposed. In all, novel insights related to improvement in high‐performance carbon materials for future energy conversion and storage applications were provided.

Finite element method based damage model to characterize effect of geometric configuration on fracture properties of elastomeric composites

Excellent tire wear resistance, wet grip resistance, and rolling resistance have made silica-filled green elastomeric composites suitable for an electric vehicle to lower fuel consumption. The study of damage mechanics of such materials has to be carried out in order to maximize safety during their usage. Accordingly, we aim to develop a damage model to characterize the effect of geometric configuration for such elastomeric composites. A ‘VUSDFLD’ damage subroutine is developed for the elastomeric composites, which is used in finite element analysis (FEA) and verified experimentally within 2% error. It is demonstrated that the change in geometric configuration can affect the fracture properties like J-integral and geometry factor. The J-R curve fits with a power-law equation with a correlation factor greater than 0.98. In contrast, using analytical modeling, an empirical relationship is proposed to trace CTOD-R curves of elastomeric composites with R2 greater than 0.88, which exhibits dependency of geometric configuration on fracture of elastomeric composites. We envisage that this fracture model can solve most of the fracture-related problems in elastomeric composites used in tires for EV and allied applications.

Model updating‐based automated damage detection of concrete‐encased composite column‐beam connections

This paper presents a comparative study about the numerical and experimental system identification and model updating-based automated damage detection of concrete-encased composite column-beam connections. Four different column-beam connection types named as CBC#A, CBC#B, CBC#C, and CBC#D were considered without any changes in geometrical configuration. Numerical and experimental dynamic characteristics were extracted by initial finite element analysis and nondestructive experimental measurements for undamaged condition. Enhanced frequency domain decomposition (EFDD) method was used for experimental modal extractions. A good agreement was observed between experimental natural frequencies but not enough correlation between damping ratios for all connection types. Maximum differences between initial finite element and undamaged experimental results were calculated as 34.68% for CBC#A, 40.78% for CBC#B, 33.15% for CBC#C, and 47.13% for CBC#D type connection details. The differences were reduced to 0.24%, 0.24%, 0.16%, and 0.15%, respectively, by automated model updating procedure using spring coefficient, modulus of elasticity and weight per unit volume. In the case of the damaged condition, lateral forces were applied to simulate the effect of an earthquake. Cracks strongly affected the natural frequencies. The mode shapes were not broken evidently after damaged conditions. The mode shapes definitely deviated a bit, but generally the same after damages. The natural frequencies have decreased non-monotonically due to the decrease in the rigidity of the column and beam at the cracked section. Maximum differences were calculated as 14.96% for CBC#A, 41.08% for CBC#B, 31.35% for CBC#C, and 45.93% for CBC#D type connection details. After automated model updating the above-mentioned differences were reduced to 0.35%, 0.78%, 0.73%, and 0.85% respectively. Contour diagrams of changes of updating parameters were plotted for damage identification. The regions with high difference rates indicated the location of the damage.

Experimental evaluation of damage effect on dynamic characteristics of concrete encased composite column-beam connections

Abstract A major defect in determining the structural response for concrete encased composite columns using finite element is due to the uncertainties and assumption associated with the modeling process. Therefore, experimental measurements should be performed in order to validate the numerical results as well as obtain the real structural response. This paper seeks to address an experimental study about the evaluation of damage effect on the dynamic vibration characteristics of concrete encased composite columns (CECC) considering different column-beam connection types using ambient vibration tests. In an attempt to do so, four half scale concrete encased composite column-steel beam were built and tested in the laboratory with different column-beam connection types abbreviated as CECC-A, CECC-B, CECC-C and CECC-D without any changes in geometrical configuration of specimens and test setup. Cyclic loading tests were conducted in order to assess the post damage condition, while ambient vibration test were performed to extract the experimental dynamic characteristics such as natural frequencies, mode shapes and damping ratios using Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) methods for both undamaged (intact) and damaged conditions. The natural frequencies have decreased distinctly and mode shapes were broken with damages. These tests revealed that ambient vibration tests are enough to identify the dynamic characteristics of engineering structures for different conditions. The maximum differences in natural frequencies were calculated between 21.72% and 39.96%. A good agreement was noted for undamaged condition, the mode shapes were identical and the Modal Assurance Criterion (MAC) had value of 1.0. In contrast, there was not a good agreement for post damage condition. The mode shapes were different and MAC values were close to zero. Lastly, as the experimental damping ratios were examined, the results supported the idea that there were some differences and the values did not correlate favorably. These results are the compatible with the literature, but it is thought that the differences typically indicate that higher excitation levels are required to accurately capture the damping ratios.

Development of a novel radio-frequency negative hydrogen ion source in conically converging configuration

Volume-produced negative ion source still requires enhancement of current density with lower input RF (radio-frequency) power in lower operating pressure for various applications. To confirm recent observation of efficient negative ion production with a short cylindrical chamber with smaller effective plasma size, the RF-driven transformer-coupled plasma H(-) ion source at Seoul National University is modified by adopting a newly designed quartz RF window to reduce the chamber length. Experiments with the reduced chamber length show a few times enhancement of H(-) ion beam current compared to that extracted from the previous chamber design, which is consistent with the measured H(-) ion population. Nevertheless, decrease in H(-) ion beam current observed in low pressure regime below ∼5 mTorr owing to insufficient filtering of high energy electrons in the extraction region needs to be resolved to address the usefulness of electron temperature control by the change of geometrical configuration of the discharge chamber. A new discharge chamber with conically converging configuration has been developed, in which the chamber diameter decreases as approaching to the extraction region away from the planar RF antenna such that stronger filter magnetic field can be utilized to prohibit high energy electrons from transporting to the extraction region. First experimental results for the H(-) ion beam extraction with this configuration show that higher magnetic filter field makes peak negative beam currents happen in lower operating pressure. However, overall decrease in H(-) ion beam current due to the change of chamber geometry still requires further study of geometrical effect on particle transport and optimization of magnetic field in this novel configuration.

CFD analysis to study the effect of design variables on the particle cut size in hydrocyclones

ABSTRACTThe modification of hydrocyclone geometry changes the dynamics of the flow, so the particle cut size is affected. Computational fluid dynamics was applied to predict particle classification according to size. Fluent code was used to perform computer simulations for five different hydrocyclone geometries using large eddy simulation and volume of fluid models. The sensitivity to computed modifications in particle classification was evaluated by changing basic design variables, such as spigot diameter, vortex finder diameter, and cone angle. The results show that the particle cut size can be predicted for changes in geometric configuration for a wide range of slurry concentration with a small degree of error using computational fluid dynamics. The error can be attributed to the absence of particle–particle and fluid–particle interaction modeling. However, this assumption is known to be valid only for diluted slurries and some regions within the hydrocyclone. As soon as the particles enter the system, most of them are located within the walls, creating diluted slurry conditions in the main core of the hydrocyclone. The computed results for more concentrated slurries were therefore close to the experimental cut‐size values. In all cases, the particle cut size was predicted successfully. Therefore, the evaluation of changes in the standard geometry to manipulate the dynamics and achieve the desired particle cut size becomes possible. © 2012 Curtin University of Technology and John Wiley & Sons, Ltd.

Cabling Arrangement Influence on Repeatability of Immunity EMC Measurements

The paper deals with the analysis of induced current of differential loops of transmission lines during immunity test against electromagnetic field measurement. The influence of geometrical configuration of cabling arrangement on induced current values is surveyed. The problem is described for the case of a short two-wire line creating differential mode loop. The current induced at both ends of the line is the characteristics observed in the performed studies. The comparison between the results of measurements on real physical line, numerical simulations and analytical solution is presented. OST ELECTRICAL devices are connected to external cabling. This ensures power supply, transmission of analogue and digital signals, etc. The cabling is connected with the surrounding environment including electromagnetic (EM) fields. Then it becomes the element of transfer path between the source of disturbance and an electrical device, which becomes subject to disturbance. Hence the present legislation requires the guarantee of immunity against electromagnetic fields of electrical devices available on the market - they have to be tested for immunity. Reproducibility of the testing plays a very important role. During this high frequency immunity test, the configuration of the test place and the testing procedure are the determining elements for the reproducibility of the measurements. This paper is focused on studying the influence of changes in geometric configuration of cabling upon the repeatability of immunity against EM field tests. It is based upon the analysis of impact of the EM field on short transmission lines. The analysis is carried out by measurements, analytical solution as well as numerical analysis. After understanding the problem by means of simple analytical solutions, we focused mainly on the comparison of the measured and simulated results of currents induced on terminating interfaces of the connection cable models. 2. THEORETICAL ANALYSIS

Analysis of flexible frames by energy search

A geometrically nonlinear finite element formulation based on a moving Eulerian coordinate system is used to predict the structural response of flexible planar frames. The total potential energy of the system is expressed in terms of the strain inducing displacements and parameters that reflect the coupling between axial (tension or compression) and bending effects. A conjugate gradient energy search procedure is employed to minimize directly the total potential energy of the structural system. The method includes the effects of prestressing and prescribing displacements in addition to abrupt changes in geometric configuration due to buckling of compression members and slackening of tension elements. Numerical examples illustrate and verify the accuracy of the technique presented.

The compound atomization by air action. The effect of a geometrical configuration of resonant chamber.

In the former report, it was described that the high-velocity air flow and the pneumoacoustic ultrasonic vibration were effective for atomization, and that the acoustic singular point was found on the compound injection nozzle with the loop convergent nozzle and the resonant chamber. A favorable size of the resonant chamber with the compound spray D-type injection nozzle (used in the former paper) is experimentally obtained. The effect on the acoustic characteristics with the change of geometrical configuration of the resonant chamber, the relation between the acoustic characteristics and the atomization, and the condition of favorable atomization are obtained. The correlations between the acoustics and the atomization characteristics are clarified on the D-type injection nozzle with the various geometrical configurations, and a favorable geometrical size of the resonant chamber is obtained.

A cis-trans isomerising activity of Escherichia coli. Isomerization from [formula omitted] acrylamide (furylfuramide) to its trans isomer

The soluble enzyme fraction derived from Escherichia coli K-12 JE2100 cells was found to exhibit, in addition to NADH- and NADPH-dependent reductase activities, NADH-dependent cis-trans isomerising activity toward 2-(2-furyl-3(5-nitro-2-furyl)acrylamide leading to a specific change in geometrical configuration of the vinyl group at the 2-position from cis to trans but not in the reverse direction. This furylfuramide-isomerising action of bacteria was dicoumarol insensitive, and did not require glutathione for full activity. The particulate enzyme fraction derived from JE2100 cells, although it showed little reductase activity toward furylfuramide in the presence of either NADH or NADPH, revealed an isomerising activity in the presence of NADH.

Finite deformation of a fully fixed beam comprised of a non-linear material

The structural behaviour at finite deformation of a mild steel beam of rectangular cross-section, fully encastré at both ends and subjected to a concentrated load at mid-span, is examined in this paper. The axial tension, induced in the beam by virtue of its change in geometric configuration, gives rise to a load-carrying capacity of the beam in excess of that predicted by first-order flexural theory. Existing methods of analysis, assuming the beam to be composed solely of a linear elastic or a pure plastic material, are reviewed and an analysis is proposed for a beam composed of an elastic-plastic material. Experimental results are compared with theoretical predictions and the proposed elastic-plastic analysis is seen to give the most realistic prediction of the overall behaviour of the beam.

Gamma dose rate at an internal point on the axis of a solid radioactive spheroid source

A formula has been derived for the γ-dose rate at an internal point on the axis of a solid spheroidal source having uniform distribution of radioactivity. The spheroidal source has been compared with a cylindrical source of comparable geometry at the point of interest. The effect of change of geometrical configuration on the dose rate has been studied in detail using an IBM-1620 computer.

Gamma dose rate at an external point on the axis of a solid radioactive spheroid source

An expression has been derived for the γ-ray dose rate at an external point on the axis due to a spheroidal source with uniform distribution of radioactivity. The values for the spheroidal source have been compared with those of point, spherical and cylindrical sources. The effect of change of geometrical configuration on the dose rate has been studied in detail using an IBM-1620 computer.

Cis-Trans Isomerization in Natural Polyisoprenes

Abstract The cis and trans isomers of many simple olefins and conjugated polyolefins can be interconverted by the action of heat, light, and various catalysts, and in many such systems the changes in geometric configuration can be readily followed and the isomers separated and identified. Previous attempts to isomerize natural rubber and gutta-percha by treatment with ultraviolet light and various chemicals gave no detectable cis-trans isomerization, and in general configurational changes in unconjugated polyolefins have been unknown until recently when Golub converted the cis-1,4 units in polybutadiene into the corresponding trans units. This isomerization was achieved by irradiation of the cis-polymer with ultraviolet light in the presence of various organic bromides and sulfur compounds, but apparently this method did not isomerize natural rubber. In attempts to retard the rate of crystallization of natural rubber at moderately low temperatures—i.e., −10° to −40° C—by the attachment of side groups which would interfere with the molecular packing, it was observed that very small amounts of thiol acids were remarkably effective. This suggested that structural changes other than simply the attachment of side groups were occurring in the polyisoprene molecule. Recently it was found that thiol acids could interconvert the cis and trans forms of a simple trialkyl ethylene—e.g., 3-methylpent-2-ene—and subsequently, the isomerization of natural rubber and gutta-percha by these reagents was also observed. Following this, natural rubber, gutta-percha, squalene and cis and trans forms of 3-methylpent-2-ene have also been isomerized by treatment with sulfur dioxide and allied compounds; this work, including an investigation of the physical properties of the vulcanizates obtained from some of the isomerized polyisoprenes, is described in the present paper.

Investigation of the products of the addition of mercury salts to disubstituted acetylenes

1. On the basis of a study of their infrared absorption spectra, thea-isomer of 2-acetoxy-1-methylpropenyl-mercury chloride, which has a C=C frequency at 1667 cm−1, is assigned the trans configuration, and its stereoisomer, which has a C=C frequency of 1655 cm−1, is assigned the cis configuration. 2. Bis(2-acetoxy-1-methylpropenyl)mercury of m.p. 114, which has a C=C frequency of 1621 cm−1, has been assigned to the trans series, and its stereoisomer of m.p. 101, which is obtained from theβ-compound and has a C=C frequency of 1616 cm−1, has been assigned the cis-cis configuration. 3. Two new stereoisomeric bis(2-acetoxy-1-methylpropenyl)thallium chloride have been synthesized from the stereoisomeric bis(2-acetoxy-1-methylpropenyl)mercurys and thallium trichloride, and some of their chemical properties have been investigated. Their geometric configurations have been established by the method of even and odd cycles. 4. It has been shown that the stereoisomeric bis(2-acetoxy-1-methylpropenyl)mercurys react at different rates with thallium trichloride, the trans-trans compound reacting much more rapidly that the cis-cis isomer. 5. A new reaction has been described in which organothallium compounds of the type RTICl2 are synthezised directly from symmetrical organomercury compounds and thallium trichloride. 6. By means of a symmetrization reaction, bis(2-acetoxy-1-methylallyl)mercury has been prepared, and some of its chemical properties have been studied. It reacts with thallium trichloride with formation of bis(2-acetoxy-1-methylallyl)thallium chloride. 7. It has been shown that in the symmetrization and reverse dissymmetrization reactiions and also in the double-decomposition reactions with metal salts, the transfer of the 2-acetoxy-1-methylpropenyl group from one metal atom to another and back occur without any change in geometric configuration. This behaviour confirms the rule that we have established relating to the preservation of the configuration ogf cis and trans isomers in metathetic reactions with electrophilic reagents and in homolytic exchange reactions.