Taper Configuration Research Articles

Inverse-designed taper configuration for the enhancement of integrated 1 × 4 silicon photonic power splitters

Abstract Once light is coupled to a photonic chip, its efficient distribution in terms of power splitting throughout silicon photonic circuits is very crucial. We present two types of 1 × 4 power splitters with different splitting ratios of 1:1:1:1 and 2:1:1:2. Various taper configurations were compared and analyzed to find the suitable configuration for the power splitter, and among them, parabolic tapers were chosen. The design parameters of the power splitter were determined by means of solving inverse design problems via incorporating particle swarm optimization that allows for overcoming the limitation of the intuition-based brute-force approach. The front and rear portions of the power splitters were optimized sequentially to alleviate local minima issues. The proposed power splitters have a compact footprint of 12.32 × 5 μm2 and can be fabricated through a CMOS-compatible fabrication process. Two-stage power splitter trees were measured to enhance reliability in an experiment. As a result, the power splitter with a splitting ratio of 1:1:1:1 exhibited an experimentally measured insertion loss below 0.61 dB and an imbalance below 1.01 dB within the bandwidth of 1,518–1,565 nm. Also, the power splitter with a splitting ratio of 2:1:1:2 showed an insertion loss below 0.52 dB and a targeted imbalance below 1.15 dB within the bandwidth of 1,526–1,570 nm. Such inverse-designed power splitters can be an essential part of many large-scale photonic circuits including optical phased arrays, programmable photonics, and photonic computing chips.

A novel finite element for the vibration analysis of tapered laminated plates

AbstractIn the present study, a new tapered finite element is developed by incorporating the in‐plane effect in our recently introduced element for the vibration analysis of internally tapered laminated plates. Stress and strain fields for a laminated plate with varying thickness along two orthogonal directions are expressed through extending classical laminated plate theory. Shape functions regarding bending and membrane behavior are extracted from the bending and axial basic displacement functions of the Euler‐Bernoulli beam, respectively. Several laminated plates with different taper configurations have been studied, and the results obtained from vibration analysis are compared with those of the literature. Since the element can capture the exact form of variation in thickness, the solution has shown to be competitively accurate with considerably fewer total degrees of freedom and elements in comparison with conventional finite elements.Highlight A new finite element for thin, tapered, laminated plates is introduced. Laminates' stiffness matrix is obtained for arbitrary thickness variation. A novel method is adopted to derive in‐plane shape functions. C1 continuity is guaranteed along the edges of elements. Calculation cost is considerably reduced.

Improving fatigue characteristics of ply drop-off in composite laminate with ply curving termination

Ply drop-off is a weak point of a tapered composite laminate, where stress concentration occurs and delamination initiates. By suppressing delamination from the ply drop-off, more optimized structural design and further weight reduction are possible. Ply Curving Termination (PCT), which locally changes the fiber direction at the edge of the dropped ply, is one of the promising delamination suppression mechanisms. To improve the technical maturity of PCT, this study conducted tensile fatigue tests using asymmetric taper configuration. Damage initiation, delamination propagation, and final failure were evaluated in detail by changing the PCT fiber angle and loading level, confirming that large PCT angles are effective in improving the fatigue properties of tapered laminates and that controlling the location of initial damage is necessary to maximize the effectiveness of PCT. Based on the findings, an effective design guideline for tapered laminates with PCT was presented.

Effect of customized abutment taper configuration on bone remodeling and peri-implant tissue around implant-supported single crown: A 3D nonlinear finite element study.

The optimal configuration of a customized implant abutment plays a crucial role in promoting bone remodeling and maintaining the peri-implant gingival contour. However, the biomechanical effects of abutment configuration on bone remodeling and peri-implant tissue remain unclear. This study aimed to evaluate the influence of abutment taper configurations on bone remodeling and peri-implant tissue. Five models with different abutment taper configurations (10°, 20°, 30°, 40°, and 50°) were analyzed using finite element analysis (FEA) to evaluate the biomechanical responses in peri-implant bone and the hydrostatic pressure in peri-implant tissue. The results demonstrated that the rate of increase in bone density was similar in all models. On the other hand, the hydrostatic pressure in peri-implant gingiva revealed significantly different results. Model 10° showed the highest maximum and volume-averaged hydrostatic pressures (69.31 and 4.5mmHg), whereas Model 30° demonstrated the lowest values (57.83 and 3.88mmHg) with the lowest excessive pressure area. The area of excessive hydrostatic pressure decreased in all models as the degree of abutment taper increased from 10° to 30°. In contrast, Models 40° and 50° exhibited greater hydrostatic pressure concentration at the cervical region. In conclusion, the abutment taper configuration had a slight effect on bone remodeling but exerted a significant effect on the peri-implant gingiva above the implant platform via hydrostatic pressure. Significant decreases in greatest and average hydrostatic pressures were observed in the peri-implant tissues of Model 30°. However, the results indicate that implant abutment tapering wider than 40° could result in a larger area of excessive hydrostatic pressure in peri-implant tissue, which could induce gingival recession.

“Aortic Balloon Molding” during Ovation Endograft Implantation Expands Graft Use for Hostile Neck Anatomy

Challenging aortoiliac anatomy such as short neck and narrow access vessels is responsible for endovascular repair of abdominal aortic aneurysm (EVAR) ineligibility in up to 50% of cases. The Ovation stent graft helped widen the range of abdominal aortic aneurysms (AAAs) suitable for EVAR thanks to its low-profile delivery system and polymer-filled sealing rings. However, its advantages are offset by a tight sizing chart that can lead to increased risk of type Ia endoleak or endograft infolding from under- or oversizing, respectively. We sought to assess the safety and efficacy of a novel endovascular technique developed to expand the use of the Ovation endograft while avoiding these issues. We conducted a retrospective review of all patients who underwent EVAR with the Ovation endograft at our institution between March 2019 and December 2020. "Aortic Balloon Molding" or ABM is a novel endovascular technique in which the graft is pre-cannulated and a compliant aortic balloon is inflated at the site of the graft's sealing rings during polymer administration. The technique was preferentially performed in patients with hostile neck anatomy (HNA) defined as any or all of angulation >60°, reverse taper configuration, ≥50% circumferential thrombus, or calcification. Patients undergoing traditional deployment were compared to those in whom ABM was performed. End points included neck-related adjunctive procedures, technical success, type Ia endoleak at completion angiogram, and 1-year freedom from type Ia endoleak and migration. A total of 43 patients were included in the study, of which 26 (60.5%) were treated with the ABM technique. Mean follow-up was 7.9±6months. Patients in the ABM group were more likely to have a reverse taper neck (61.5% vs. 41.2%, P=0.1), have significant circumferential thrombus or calcium (23.1% vs. 5.9%, P=0.1), and be treated outside of the Ovation indications for use regarding anatomic characteristics (65.4% vs. 41.2%, P=0.1). Technical success was achieved in 100% of cases. However, patients in the ABM group were less likely to require a neck-related adjunctive procedure (7.7% vs. 23.5%, P=0.1). Only 1 type Ia endoleak was observed at completion angiogram in a patient treated without ABM. At 1 year, freedom from type Ia endoleak or migration was 100% for both groups. ABM proves to be a safe and effective adjunctive technique for the treatment of AAAs with HNA using the Ovation stent graft. This may allow optimal endograft sizing to achieve adequate seal in complex aortic anatomies. Further research is warranted to evaluate the long-term outcomes of this technique.

Numerical and experimental investigation of first ply failure response of multi-walled carbon nanotubes/epoxy/glass fiber hybrid laminated tapered curved composite panels

In this study, first ply failure (FPF) analysis of multi-walled carbon nanotubes (MWCNTs)/epoxy/glass fiber laminated curved composite panels with various taper configuration under transverse uniform pressure load distributed over the panel surface has been performed. In this regard, various failure criterion were considered, including Hoffman, Tsai–Wu, Tsai–Hill, and maximum stress, to investigate the numerical FPF load using finite element (FE) formulation with displacement fields derived from high order shear deformation theory (HSDT) with displacement field having seven degrees of freedom. The effectiveness of the proposed formulation was validated by comparing the numerically predicted FPF load with experimentally obtained FPF load using a universal testing machine from displacement/strain measurement. Finally, the effects of aspect ratio, different weight fraction of MWCNTs, taper configuration, curved geometry, and aspect ratio on the FPF load of the laminated tapered composite panels are studied. The numerical and experimental studies of the first ply failure behavior have demonstrated that the use of MWCNTs ensures a significant improvement in the FPF load of the analyzed laminated tapered curved composite panels. The taper configuration 3 (TC-3) with hyperbolic curved geometry exhibited the highest resistance to failure than taper configuration 1 (TC-1) and taper configuration 2 (TC-2). Moreover, the aforementioned parameters significantly influence the FPF load of laminated curved panels with various taper configurations. Furthermore, this study can be effectively used as a benchmark problem for researchers and as a tool to design practical laminated tapered curved composite panels with sufficient accuracy.

Nonlinear effect of Low-velocity impact on tapered laminated composite structures using spline finite strip method

In present paper, the behavior of tapered composite plate under low-velocity impact was studied. The tapered plates were used in many structures according to their stiffness to weight ratio, while, the behavior of such plates did not evaluate under impact load in the literatures. Geometrically nonlinear Von-Karman strain was taken into account with respect to large deformations. The spline finite strip method (SFSM) was used to predict the impact behavior of composite laminates. The numerical fourth-order Runge-Kutta integration technique was used to solve the governing differential equations. The displacement field was defined according to the refined plate theory. The four most common internal taper configurations were considered. Local indentation was modeled with the help of contact Hertz’s laws. The governing differential equation was written based on the principal of virtual displacement and Hamilton’s principle for dynamic systems. The obtained results on eccentric impact showed that contact force and indentation are increased when indenter contact near supports.

Bending response analysis of a laminated, tapered, curved, composite panel made from an agglomerated and wavy MWCNT–glass fiber–polymer hybrid

The work investigates the influence of multiwalled carbon nanotubes (MWCNTs) on the bending behavior of laminated, spherical, cylindrical, hyperbolic, and elliptical tapered composite panels made from a MWCNT–glass fiber–polymer hybrid and subjected to transverse loading conditions. The deflection and stress behavior of the composite panels were studied by developing a mathematical model based on high-order shear deformation theory using finite element (FE) formulation. In this context, the agglomeration and waviness of MWCNTs were modeled and characterized using the Eshelby–Mori–Tanaka approach and a continuum mechanics based 3-D representative volume element (RVE), respectively. Subsequently, glass fiber was introduced as a reinforcement phase, and the elastic properties of the three-phase hybrid composite material were obtained using the Chamis model. The developed FE formulation was validated theoretically and experimentally. Further, detailed parametric studies were performed to examine the influence of micromechanical and structural characteristics such as weight fraction of MWCNTs, weight fraction of fiber, type of load, taper configuration, curved geometry, curvature ratio, and length to thickness ratio of the panel on the bending behavior of the composite panels. The effective laminated tapered curved composite panel, TC-3, tailored with improved MWCNT characteristics, can substantially resist the stresses from a bending load.

Investigation of the bending response of carbon nanotubes reinforced laminated tapered spherical composite panels with the influence of waviness, interphase and agglomeration

In the present study, the bending analysis of multi walled carbon nanotubes (MWCNTs) reinforced laminated tapered spherical composite panels subjected to transverse loading conditions is carried out using the finite element method (FEM) with displacement fields derived from high order shear deformation theory. In this regard, the elastic properties of the polymeric nanocomposite, considering the MWCNTs agglomeration, waviness and interphase thickness between the MWCNTs and polymer matrix were computed by employing various micromechanical approaches. Subsequently, glass-fiber were introduced as a reinforcement phase, and the overall elastic properties of a three-phase MWCNT/fiber/polymer hybrid nanocomposite material were obtained using Chamis model. The accuracy of the developed FE formulation were verified using the experimental and numerical data available in the open literature. After verification, the deflection and stresses of the panel are numerically determined for various taper configurations. Further, detailed parametric analysis is carried out to explore the influence of various parameters such as CNT content, agglomeration, waviness, interphase area, thickness ratio, curvature ratio and taper configurations on the bending results of laminated tapered spherical panels. It was observed that an increase in the weight fraction of CNTs, an equal number of agglomeration parameter and the thickness of the interphase have a positive effect in minimizing the deflection and stresses. It was also observed that the TC-2 and TC-3 taper configurations results the highest and lowest deflection. Finally, it can be concluded the current work can serve as a guide for the effective design and development of CNT reinforced composite structures.

Study on the influence of tank structure and fin configuration on heat transfer performance of phase change thermal storage system

Owing to the intermittent and fluctuating nature of solar energy, thermal energy storage (TES) plays a vital role in solar energy utilization. The structural and geometric limits of the traditional heat storage systems, as well as the low thermal conductivity of phase change materials (PCMs), decrease the heat storage and exothermic efficiency of TES severely. To alleviate these shortcomings and improve the TES heat storage and release efficiency, the geometrical structure of TES and fin structure of the heat storage system need to be optimized. This study established a 2D model of the phase change TES unit with a single tank and auxiliary electric heating based on the experimental findings. The heat transfer performance of the truncated cone model with different taper configurations was also analyzed numerically. The influence of long and short fins on PCM heat transfer was analyzed under the premise of a certain fin volume. The influence of fins with different inclinations on the heat transfer process was also analyzed. The results show that the truncated cone with a taper of 0.37 performs best in the charging and discharging process. Compared with long fins, most short fins showed to have a more significant effect on accelerating the charging process. The enhancement effect of the different fin on the heat transfer process was divided into two categories, and the analysis shows that the fins with an inclination angle of −15° have the most significant enhancement effect. These findings of the study will guide the optimization design of the heat transfer structure of TES with a single tank configuration.

Free vibration response of internally-thickness-tapered laminated composite square plates based on an energy method

In the present work, the free vibration response of symmetric linearly-thickness-tapered laminated composite square plates is considered for a variety of taper configurations. Since exact and closed-form solutions for the natural frequencies and mode shapes of the plates could not be obtained from the corresponding complex partial differential equations in space and time coordinates, the Ritz method in conjunction with the Classical Laminated Plate Theory (CLPT) and then the First-order Shear Deformation Theory (FSDT) is used to obtain the system’s mass and stiffness matrices for out-of-plane bending vibrations. The free vibration analysis of the plates is conducted using these system matrices and the natural frequencies and mode shapes are determined. Different boundary conditions are considered for the free vibration response of the plates and the computational work is performed in the MATLAB® environment. The convergence of the series expansions used for the out-of-plane displacement functions and the Ritz solutions for plates with various boundary conditions are established. The demonstration of solution accuracy is performed by conducting a so-called “layer reduction test” and also by comparing the results obtained by using the Ritz method with the solution obtained based on the Finite Element Method (FEM) using ANSYS®. A parametric study is then conducted to investigate the influences of taper configurations and taper parameters on the free vibration response of the composite plates.

FEL Simulation of New Hard X-ray Undulator Line at PAL-XFEL

The Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) has been successfully operating as a remarkably-stable XFEL facility in the world. The hard X-ray beamline, however, has only one undulator line (HX1) with a 26-mm undulator period for which the maximum undulator parameter K is 1.87. The lowest photon energy that can be generated from the HX1 with a maximum electron beam energy at PAL-XFEL (10.5 GeV) is about 14.65 keV. When a lower photon energy than that is required by the beamline users, the electron beam energy has to be decreased, which results in a decreased accessible FEL pulse energy. Therefore, a new hard X-ray undulator line (HX2) with a higher undulator parameter K is needed to make full use of the PAL-XFEL performance in the lower photon energies by increasing the resonant electron beam energy. The undulator period of the HX2 is decided as 35 mm by using Ming Xie’s fitting formula to estimate the performance of the HX2. FEL simulations with the GENESIS code are carried out to evaluate the performance of the HX2, including the effect of the post-saturation region. The undulator tapering configuration is optimized by maximizing the FEL intensity for each case. We show that the radiation power at the end of the HX2 can be increased up to 2.5 times higher than that of the HX1 over the entire target photon-energy range of the HX2 (2 ∼ 10 keV) by utilizing an undulator with a longer period and a higher undulator parameter K.

Spatial Beam Self-Cleaning in Tapered Yb-Doped GRIN Multimode Fiber With Decelerating Nonlinearity

We experimentally demonstrate spatial beam self-cleaning in an Yb-doped graded-index multimode fiber taper, both in passive and active configurations. The input laser beam at 1064 nm was injected for propagation from the small to the large core side of the taper, with laser diode pumping in a counterdirectional configuration. The Kerr effect permits to obtain high-beam quality amplification with no accompanying frequency conversions. As a result, our nonlinear taper amplifier may provide an important building block for multimode fiber lasers and amplifiers.

Investigation of optical fiber-tip probes for common and ultrafast SERS

In this study, we performed a three-dimensional computational experiment on ultrashort pulse propagation in an optical fiber-tip probe that is decorated with gold nanoparticles (NPs) using a constant structure for the probe’s dielectric taper and different spatial configurations of the gold nanoparticles. Interestingly, a hot spot with the highest amplitude of the electric field was found not along the same chain of the NPs but between terminal NPs of neighboring chains of NPs at the probe’s tip (the amplitude of the electric field in the hot spots between the NPs along the same chain was of the order of 101, while that between terminal NPs of neighboring chains was of the order of 103). We eventually identified a configuration with only six terminal nanoparticles (Config4) which is characterized by the highest electric field amplitude enhancement and can provide the highest spatial resolution in the SERS interrogation of an object of interest. The ultrashort temporal responses of the hot spots for all configurations exhibited relatively high pulse elongation (relative elongation was greater than 4.3%). At the same time, due to the reflection of the incident pulse and consequent interference, the temporal responses of most hot spots contained several peaks for all configurations except for the optimum Config4. Nonetheless, the ultrashort temporal responses of all hot spots for Config4 were characterized by a single peak but with a relatively large pulse elongation (relative elongation was 234.1%). The results indicate that further examination of this new structure of a nanoparticles-coated optical fiber-tip probe with only six terminal NPs may provide attractive characteristics for its practical applications.

Development of XANES nanoscopy on BL7C at PLS-II.

X-ray absorption near-edge structure (XANES) imaging is a powerful tool to visualize the chemical state distribution of transition-metal-based materials at synchrotron radiation facilities. In recent years, the electrochemical working rechargeable battery has been the most studied material in XANES imaging owing to the large increase of portable electronics and electric vehicles. This work acknowledges the importance of battery analysis and has developed the XANES imaging system on BL7C at Pohang Light Source-II (PLS-II). BL7C employs an undulator taper configuration to obtain an energy band >130 eV near the K-absorption edge of the target element with a minimum energy interval >0.2 eV. While measuring energy-dependent images, the zone plate translation maintains the best focus, and then various data processes such as background correction, image registration and clustering allow single XANES spectrum extraction and chemical distribution mapping. Here, the XANES imaging process is described, the XANES spectrum quality is identified and the chemical states of the partially charged cathode material used in lithium-ion batteries as an application example are examined.

Characterization of a dual taper thermosiphon loop for CPU cooling in data centers

The inefficient cooling processes in data centers consume a large amount of energy making them very expensive. This study is focuses on using a thermosiphon loop as an efficient replacement of currently used air cooling and water cooling techniques for dissipating large heat loads from the CPUs. A symmetric dual taper configuration is introduced in the evaporator to generate a highly efficient and stable two-phase flow in the system using HFE7000. Three different taper angles in the evaporator – 2°, 2.5°, and 3° – are studied, and the respective heat transfer performances are evaluated. The evaporator has 200 µm square microchannels machined on a 34.5 mm × 32 mm copper heat sink. Prior to CPU testing, the dual taper evaporator performance is evaluated in a benchtop thermosiphon loop in which the evaporator is heated by electric heaters. The loop is able to dissipate 280 W without reaching the critical flux point with a heat transfer coefficient of 26 kW/m2 °C. The thermosiphon loop is then tested for cooling a data center server with an i7-930 processor with thermal design power (TDP) of 130 W. The cooling performance of the thermosiphon loop is compared with commercial air based and water based coolers in both server and benchtop configurations.

Static deflection and thermal stress analysis of non-uniformly heated tapered composite laminate plates with ply drop-off

The effective design of tapered laminated composite structures subject to non-uniform temperature fields requires a thorough understanding of their static behaviour. In this study, a finite element analysis of tapered laminated composite plates with ply drop-off has been carried out to study the static deflection and normal stress patterns developed under non-uniform heating. The study revealed that the nature of the taper configuration, the nature of the applied temperature field and the structural boundary conditions influence the static deflection behaviour and the normal stresses developed in the tapered composite plates. It is found that the static deflection pattern of a tapered plate subject to a particular temperature profile is not sensitive to the nature of the taper configuration. It is also observed that the static deflection pattern of a tapered plate is significantly influenced by the nature of temperature field. Normal stress variation of tapered plates subject to various temperature fields reflects the nature of the temperature profile. Maximum normal stress occurs at locations where the highest temperature exists for that particular temperature field. The stresses are also influenced by the nature of the taper - Taper D plates experience low stresses while Taper B and Taper C plates experience similar values. It was also found that large variations in stresses are observed at resin pockets.

Dynamic instability of rotating doubly-tapered laminated composite beams under periodic rotational speeds

Dynamic instability analysis of doubly-tapered cantilever composite beams rotating with periodic rotational velocity is conducted in the present work for out-of-plane bending (flap), in-plane bending (lag) and axial vibrations. Rayleigh-Ritz method and classical lamination theory are used along with an energy formulation. Bolotin’s method is applied to obtain the instability regions. To verify the dynamic instability analysis results, time responses are investigated at different locations of the instability region by using the Runge-Kutta method. A comprehensive parametric study is conducted in order to understand the effects of taper configurations and various system parameters including mean rotational velocity, hub radius, double-tapering angles and stacking sequences, on the dynamic instability characteristics of the composite beam. The composite material considered in the present work in numerical results is NCT-301 graphite-epoxy prepreg.

Buckling Behavior of Non-Uniformly Heated Tapered Laminated Composite Plates with Ply Drop-Off

The thermal buckling characteristics of non-uniformly heated tapered laminated composites plates with ply drop-off have been investigated numerically. Detailed parametric studies have been carried out for the effects of taper configuration, temperature variation, aspect ratio and structural boundary conditions on critical buckling temperatures and buckling mode shapes. It is found that the nature of taper as well as the applied temperature field have considerable effects on the critical buckling temperatures of laminated composite tapered plates. Square plates buckle at the highest temperature when subjected to the decreasing temperature profile. Additionally, it is noted that Taper B and Taper C plates show the best behavior under buckling for most structural boundary conditions. Moreover, the change in buckling mode shapes with respect to temperature profile and taper configuration is significant for rectangular plates in comparison with square plates.

A Comparison of the Vibrational Responses of Four Different Uniform and Tapered Composite Beams

A combined experimental and finite element approach was used to compare the vibrational response of the composite beams with different configurations of internal taper and uniform cross sections. Composite beams were made using the hand lay-up process. Glass fibre was used as reinforcement in the form of a bidirectional fabric and a general-purpose epoxy resin as the matrix for the composite material. Experimental dynamic tests were carried out on FFT analyzer using specimens with different taper configurations. From the results, the effect of different taper configurations on the flexural natural frequencies and mode shapes was investigated. Finite element analysis of the same problem was carried out on software package ANSYS and the results were validated using the experimental results. From the results, a thorough comparison was made between the natural frequencies, loss factors, displacements and mode shapes of the specimens with different taper configurations and uniform cross sections considered. The aerospace implications are provided.