Uniform Cavity Research Articles

A Compact V-Band Transit Time Oscillator with Reflective Modulation Cavity

Improving compactness is essential for high-power microwave (HPM) sources. In this paper, a novel reflective modulation cavity is proposed and investigated in a V-band relativistic coaxial transit-time oscillator (RCTTO). The cold cavity analyses and particle-in-cell simulations show that the reflective modulation cavity has larger reflection coefficients of TEM mode and stronger electron beam modulation capability when compared with a uniform modulation cavity. When the input diode voltage is 391 kV, the beam current is 4.91 kA, and when the guiding magnetic field is 0.6 T, the compact V-band RCTTO produces an output microwave power of 518 MW (conversion efficiency of 27.0%). Compared with the original RCTTO, the compact V-band RCTTO featuring a reflective modulation cavity exhibits a 24.8% increase in output power and a 5.4% improvement in efficiency, and the axial length of the magnetic field uniform region is reduced by 24.2%. The compact V-band RCTTO also demonstrates a broad operation voltage range, indicating potential for stable operation with voltage fluctuations in experiments. Furthermore, the reflective modulation cavity can be integrated into other high-frequency O-type HPM devices to enhance compactness, thereby diminishing the demands on the magnetic field region, which is advantageous for the future permanent packaging of HPM sources.

Development of 1 Month Sustained-Release Microspheres Containing Liraglutide for Type 2 Diabetes Treatment.

Liraglutide has been extensively applied in the treatment of type 2 diabetes mellitus (T2DM), but its 11-15 h half-life resulted in daily administration, which led to poor patient compliance. This study aimed to solve this problem by developing liraglutide-loaded microspheres with a 1 month sustained release prepared by the W1/O/W2 method combined with the premix membrane emulsification technique to improve therapeutic efficacy. Remarkably, we found that the amphiphilic properties of liraglutide successfully reduced the oil-water interfacial tension, resulting in a stable primary emulsion and decreasing the level of drug leakage into the external water phase. As a result, exceptional drug loading (>8%) and encapsulation efficiency (>85%) of microspheres were achieved. Furthermore, the uniformity in microsphere size facilitated an in-depth exploration of the structural characteristics of liraglutide-loaded microspheres. The results indicated that the dimensions of the internal cavities of the microspheres were significantly influenced by the size of the inner water droplets in the primary emulsion. A denser and more uniform cavity structure decreased the initial burst release, improving the release process of liraglutide from the microspheres. To evaluate the release behavior of liraglutide from microspheres, a set of in vitro release assays and in vivo pharmacodynamics were performed. The liraglutide-loaded microspheres effectively decreased fasting blood glucose (FBG) levels and hemoglobin A1c (HbA1c) levels while enhancing the pancreatic and hepatic functions in db/db mice. In conclusion, liraglutide sustained-release microspheres showed the potential for future clinical applications in the management of T2DM and provided an effective therapeutic approach to overcoming patient compliance issues.

Evaluation and characterization of polyethylene composites with β-cyclodextrin andβ-cyclodextrin-based derivatives as foaming nucleating agent

In this study, we prepared nanosponges (NS) by crosslinking the hydroxyl group of β-cyclodextrin (CD) molecular. Furthermore, we modified the CD molecular by 1, 2-cyclohexanediamine (TRK) through simple chemical method. CD, NS and CD-TRK were used as nucleating agent in the injection foaming process of polyethylene (PE) with 4, 4'-oxydibenzenesulfonyl hydrazide as blowing agent. With addition of CD-TRK, the crystallinity increased from 39.17% for pure PE to 46.02% for PE/CD-TRK-1.0 composites. Results showed that PE/CD-TRK-1.0 composites presented the best foam morphology. The cell density increased by about 10 times, while the cell diameter reduced by about 56% compared with that of pure PE. Scanning electron microscopy analysis showed that CD-TRK exhibited more compact and dense network structure with uniform cavity distribution, which may reduce the cell nucleation barrier and provide proper nucleation site for cells. The dynamic mechanical analysis showed that PE/CD-TRK-1.0 composites displayed proper modulus and viscoelasticity, which were favor for cell nucleation, growth and stabilization, resulting in the best cell morphology of PE/CD-TRK composites. Tensile and impact strength of foaming PE composites were systematically analyzed. The maximum impact strength reached 27.4 KJ·m−2, and the maximum tensile strength reached 27.5 MPa.

Energy and exergy studies on the receiver models with materials and heat transfer fluids.

This work focuses on meeting the growing demand in solar energy conversion for small-scale applications. In this regard, experimental and CFD research has been done to examine the thermal performance (energy and exergy efficiencies) of a dish collector (reflector and receiver) system with different receiver models. In this work, receivers with uniform absorber cavity areas having cylindrical and hemispherical shapes were modeled for length-to-diameter ratios (L/D) of 1.5, 1, and 0.75. The modeled receivers having coil tube configurations concerning the geometrical shape of the models were tested with two different materials of aluminum and copper. The performance of the receiver models was compared by experimental and CFD methods for the average solar direct normal irradiations of 860 W/m2 by the dish reflector area of almost 12 m2. The supplied average heat flux by the dish reflector was 7kW/m2 at the absorbing area of the cavity receivers. The energy and exergy efficiencies from the experimental and CFD analyses on the models were determined based on the cavity surface temperature distribution of receiver walls, and heat gain for different mass flow rates by the heat transfer fluid water. The receiver with copper material and L/D ratio of 0.75 has been found as the optimized one among all other models with the maximum obtained energy and exergy efficiencies of 73.64 and 7.31% when water is used as the heat transfer fluid. The performance of the optimized receiver model was also validated with a few other heat transfer fluids such as SiC + water nanofluid and therminol VP1.

Modeling analysis of combustion instability in an annular combustor equipped with circumferentially segmented perforated liner

Hazardous azimuthal thermoacoustic modes often occur in lean-premixed annular combustors. One practical control method is the application of perforated liners with bias flow. However, circumferentially uniform perforated liners are not competent to control them, because the perforated plate covered by a single azimuthally uniform backing cavity cannot provide sufficient acoustic pressure difference across the perforated plate to bring in adequate acoustic damping. In this work, we developed a three-dimensional thermoacoustic model to consider the effects of a novel passive control damper of the circumferentially segmented perforated liner. Emphasis is placed on the effects of the segmented liner on controlling the azimuthal modes. It is found that the azimuthal mode in the premixed annular combustor can be either plenum-dominant or combustor-dominant, with the frequency of the latter one larger than the former. The stabilities of the two kinds of modes behave differently with the change of time delay. The results of the lined combustor cases indicate that the circumferentially segmented perforated liner generally improves the control effectiveness compared with the circumferentially uniform perforated liner thanks to the rigid plates inserted in the backing cavity. At the locally inserted position, the rigid plate enforces a rigid boundary condition that changes the azimuthal pressure mode shape in the backing cavity. As a result, more acoustic damping through the pressure difference across the plate is produced. Symmetry-breaking effects are found if the segmentation is asymmetric or two-fold symmetric. The behavior of the splitting frequencies caused by the segmented liner is also studied, and the symmetric segmented liner turns out to be a better choice because the resulting azimuthal mode is degenerate with two equivalent suppressed growth rates. In order to further enhance the control effect, one significant effective measure is to increase the depth of the backing cavity.

Enhancing the Photocatalytic Degradation Efficiency of Dyes of Copper-Based Metal-Organic Frameworks through a Dimension-Induced Structural Strategy.

Photocatalytic degradation of pollutants is an effective environment purification strategy. Metal-organic frameworks (MOFs) have attracted extensive attention in the field of photocatalysis owing to their structural diversity, uniform cavity, and large specific surface area. However, poor electrical conductivity, light absorption, and water stability restrict their development. The tailorable structure of MOFs may effectively overcome these limitations. Herein, three Cu-based MOFs (complexes 1-3) with one-dimensional (1D), two-dimensional (2D), and three-dimensional (3D) structures, respectively, were successfully prepared by introducing different uncoordinated ligands and adjusting the ligand/metal salt ratio. Among them, complex 1 with a 1D chain was constructed as a typical J-type aggregation by π-π stacking interactions between adjacent naphthalene rings. This intermolecular aggregation mode enhances strong exciton coupling between conjugated rings, reduces the transition energy, expands the intrinsic light absorption edge, and provides a channel for electron transport, thus improving the charge-separation efficiency. As expected, complex 1 with a 1D chain structure exhibited excellent Fenton-like catalytic activity. The apparent reaction rates were 3.2 and 2.0 times higher than those of 2D and 3D MOFs, respectively.

Numerical study of flow and free convection of water/silver nanofluid in a circular cavity influenced by hot fluid flow

In this numerical study, the numerical simulation of laminar free convection of water/silver nanofluid in a circular cavity under the effect of hot water fluid outside the cavity is carried out. The cooling fluid is water silver nanofluid at a volume concentration of φ = 0–0.06. This study was done for Gr = 102, 103 and 104 using the finite volume method. The Reynolds numbers of Re = 1, 10 and 100 were used. The results of the study show that due to the temperature difference between the cavity and the entering fluid, heat transfer occurs between the hot fluid in the channel and the nanofluid in the cavity at the start of the channel. This temperature difference between the surface and the fluid reinforces the buoyancy force and the Grashof number, intensifying the cavity flow and creating a more uniform cavity temperature distribution. For low Gr number, higher φ results in modest temperature gradient reduction. Using a higher fluid flow, the channel-cavity heat transfer increases which elevate dimensionless temperature curves. At a higher φ, due to the higher fluid viscosity and density, a higher momentum is required for flow convection and circulation. As a result, a stronger buoyancy force aids with free convection intensity, which is effective in elevating the Nusselt number curve values. By increasing the Reynolds number, a higher cavity heat transfer occurs due to the stronger circulating fluid's momentum.

Structural acoustic controlled active micro-perforated panel absorber for improving wide-band low frequency sound absorption

This paper investigates the performance of the structural acoustic controlled active micro-perforated panel absorber (SAC-AMPPA), which can achieve wide-band perfect low frequency sound absorption (absorption coefficient is close to 1). The SAC-AMPPA applies point force-controlled backing panel to actively improve the low-frequency sound absorption of the MPPA with the purpose of saving space to suit it better for applications. The theoretical model of the SAC-AMPPA is firstly established using the modal analysis approach. Influence of structure size and point force position on sound absorption performance is explored. Then, the experimental tests were performed to validate the theoretical modeling and findings. Finally, the physical mechanisms of active control are analyzed in detail and some physical insights are summarized. Simplified error sensing strategy for small sized SAC-AMPPA is also constructed. Results obtained show that the preconditions of the point force locating at the center of the backing panel or relatively small sized SAC-AMPPA can guarantee less cavity modes being excited and achieving perfect sound absorption in a very wide controllable bandwidth. The main reason of this lies in the key findings, i.e., except for the (0,0,m) mode, other cavity modes excited by the backing panel cannot contribute to the improvement of low-frequency sound absorption below their resonant frequencies. They radiate sound energy towards the outside of SAC-AMPPA and play a negative role above their resonant frequencies. Provided a uniform cavity sound field is guaranteed in controlled condition, the sound pressure release (PR) and impedance matching (IM) strategies can be used to conveniently construct error sensing strategy of the SAC-AMPPA.

Axisymmetric transient response of a cylindrical cavity in an unsaturated poroelastic medium

In this study, the transient response of an infinite unsaturated poroelastic medium with an infinitely long uniform cylindrical cavity subjected to axially symmetric transient radial tractions is investigated. Using the Laplace transform, analytical solutions are obtained for three different types of prescribed transient radial pressures (step, gradually applied step, and triangular pulse loads) acting on the surface of a permeable cavity and that of an impermeable cavity. The time histories of the radial displacement, stresses, pore pressure, and discharge are derived by inverting the Laplace domain solutions using a reliable numerical scheme. The solution can be simplified to one in which the infinite medium is assumed to be a saturated poroelastic medium. The validity of the solution was confirmed by comparison with COMSOL numerical solutions. A detailed parametric study is presented to illustrate the influence of the saturation of the unsaturated poroelastic medium on the response of the radial displacement, hoop stress, and pore fluid pressure at the cavity surface under different boundary conditions.

Optimization and application of temperature field in rapid heat cycling molding

The rapid thermal cycle molding belongs to the injection mold temperature control system which is helpful to improve moldability and enhance part quality. Despite many available literatures, rapid thermal cycle molding does not represent a well-developed area of practice. The challenge is the uneven distribution of temperature in the cavity after heating, which mostly leads to defects on the surface of the products. In order to obtain uniform cavity surface temperature distribution of rapid thermal cycle molding, the power of heating rods of the electric-heating system in an injection mold was optimized by the response surface method in this work. The proposed optimization result was applied to design a complex rapid thermal cycle molding injection mold with side core-pulling, holes, and different thickness of an automotive part to verify its effectiveness by injection molding. Compared with initial design, the mold temperature uniformity was remarkably improved by 79%. Based on the optimization and injection molding numerical simulation results, the workable molding process to weaken the weld-lines effects on the quality was suggested and the practical injection molded parts were well produced

Structural basis of constitutive c-Src kinase activity due to R175L and W118A mutations

Cellular Src (c-Src) belongs to a non-receptor membrane-associated tyrosine kinase family that plays essential roles in cellular processes. Growing evidence suggests that R175L and W118A mutations in SH2/SH3 domains of c-Src functionally inactivate these domains leading to constitutive activation of kinase domain (KD). Here we modeled c-SrcR175L, c-SrcW118A and c-SrcW118A+R175L structures by inducing phosphorylation at Y416 or Y527, respectively to characterize the comparative dynamics in the active versus inactive states through molecular dynamics simulation assay. We observed more conformational readjustments in c-Srcopen than its close variants. In particular, C-terminal tail residues of c-SrcW118A-open and c-SrcW118A+R175L-open demonstrate significantly higher transitions. The cross-correlation analysis revealed an anticorrelation behavior in the motion of KD with respect to SH2, SH3 and the linker region of SrcW118A+R175L-open, while in c-SrcWT-open, SH2 and SH3 domains were anticorrelated, while KD and C-terminal tail motions were correlated. Due to these conformational differences, c-Src open forms exhibited lower interaction between pY527 and SH2 domain. Through detailed structural analysis, we observed a uniform myristate binding cavity in c-SrcWT-open, while the myristoyl pockets of mutant forms were deformed. We propose that constitutive activation of mutant Src forms may presumably be achieved by the prolonged membrane binding due to unusual conformations of C-terminal and myristoyl switch residues that may result in a higher dephosphorylation rate at pY527 in the myristoylated c-Src. Thus, our study establishes novel clues to decipher the constitutive activation status of c-Src in response to known mutations that may help in devising novel therapeutic strategies for cancer metastasis treatment. Communicated by Ramaswamy H. Sarma

Regional temperature control in ceramic injection moulding: An approach based on cooling rate optimisation

The injection moulding of ceramic components with uneven wall thickness presents challenges due to differential cooling rates developing in the injected parts, which cause premature solidification of the feedstock at thin features and lead to detrimental defects, worsening in components from green to sintered states. To cope with this, suitable mould thermal control approaches have to be selected and validated, as current control methods are based on the achievement of a uniform cavity surface temperature, which is not tailored to such complex geometries. In this work, a novel thermal control system is proposed, based on regional mould temperatures, implemented with the use of Peltier modules, which locally and independently heat and cool different cavity features according to their thickness. The regional temperature profiles are optimised over time with the use of a coupled Finite Element - Particle Swarm Optimisation (FE-PSO), to achieve uniform cooling rates throughout the moulded components. The performance of this approach is compared to both constant ambient mould temperature and Rapid Heat Cycle Moulding (RHCM) techniques, which instead aim at achieving uniform temperatures throughout the mould cavity surface. Results show that the novel proposed method, based on regional temperature control and uniform cooling rates, promotes the simultaneous solidification of features with a 10-times difference in surface-to-volume ratio. Due to this, in terms of components quality, the novel method brings the advantages of higher dimensional control and reduction of differential shrinkage compared to the other analysed approaches, thus increasing the capability to use injection moulding to manufacture ceramic components characterised by non-uniform wall thickness.

The Multi-slice Spiral Computed Tomography (MSCT) Features of Thin-Walled Cystic Lung Cancer with Ground Glass Opacity

Background: Lung cancer is the leading cause of cancer-related mortality worldwide. Thin-walled cystic lung cancer with ground glas s opacity (GGO) is a type of lung carcinoma with specific computed tomography (CT) features. Objectives: To investigate the imaging features of multi-slice spiral computed tomography (MSCT) of GGO and to improve the imaging diagnosis of this type of lung cancer. Patients and Methods: The clinical data of 24 patients with pathologically confirmed thin-walled cystic lung cancer with GGO were retrospectively analyzed in this study. The imaging features of preoperative MSCT, including vascular convergence, burr signs, pleural depression signs, lobulation signs, thickness and uniformity of the cavity wall, partitive membranes, and position of the ground-glass cavity, were examined. The relationship between the imaging features and postoperative pathological findings of lung carcinoma were also explored. Results: Most of the lesions (75.0%) were located in the upper lobe of the lungs. The size range of the cavity was 5.8 - 28.1 mm, with a mean of 13.6 ± 7.2 mm. Fifteen patients (62.5%) had a cavity wall thickness < 2 mm, 6 (25.0%) patients had a cavity wall thickness in the range of 2 - 3 mm, and 3 (12.5%) patients had a cavity wall thickness of about 3 - 4 mm. A uniform cavity wall was found in 10 (41.7%) cases, while a non-uniform cavity wall was observed in 14 (58.3%) cases. Eleven patients showed pure GGO (45.8%), while 13 patients showed mixed GGO (54.2%). Besides, nine patients (37.5%) showed lobular signs, 12 (50.0%) patients showed spicule signs, and 6 (28.6%) patients showed vascular convergence signs. Twelve patients (50.0%) had signs of pleural indentation, while 14 (66.7%) patients showed thick or thin small blood vessel opacity or fine partitive membranes. Twenty-three patients were diagnosed with lung adenocarcinoma, while one patients was diagnosed with mixed adenosquamous carcinoma. Conclusion: Thin-walled cystic lung cancer with GGO is a rare clinical phenomenon. The imaging features of this type of lung cancer on MSCT are consistent with the characteristics of lung cancers.

A robust scheme for unidirectional emission from a hybrid whispering gallery cavity system based on transformation optics.

Using the transformation cavity, a gradient index cavity designed by transformation optics, we propose a hybrid resonator system to extract unidirectional narrow-beam emission from high-Q whispering gallery modes by embedding a transformation cavity inside a deformed uniform index cavity that exhibits unidirectional narrow-beam emission. For effective mode coupling between the transformation cavity and enclosing cavity, the embedded transformation cavity is designed to have bidirectional evanescent emission, which enables most of the emission from the transformation cavity to be laterally incident on the rim of the enclosing deformed cavity. Consequently, ultrahigh-Q resonances of this system can provide a sharp free-space light output, which is difficult to achieve by embedding a homogeneous disk cavity instead of the transformation cavity.

Gauge fixing for strongly correlated electrons coupled to quantum light

We discuss the problem of gauge fixing for strongly correlated electrons coupled to quantum light, described by projected low-energy models such as those obtained within tight-binding methods. Drawing from recent results in the field of quantum optics, we present a general approach to write down quantum light-matter Hamiltonian in either dipole or Coulomb gauge which are explicitly connected by a unitary transformation, thus ensuring gauge equivalence even after projection. The projected dipole gauge Hamiltonian features a linear light-matter coupling and an instantaneous self-interaction for the electrons, similar to the structure in the full continuum theory. On the other hand, in the Coulomb gauge the photon field enters in a highly non-linear way, through phase factors that dress the electronic degrees of freedom. We show that our approach generalises the well-known Peierls approximation, to which it reduces when only local, on-site orbital contributions to light-matter coupling are taken into account. As an application, we study a two-orbital model of interacting electrons coupled to a uniform cavity mode, recently studied in the context of excitonic superradiance and associated no-go theorems. Using both gauges we recover the absence of superradiant phase in the ground state and show that excitations on top of it, described by polariton modes, contain instead non-trivial light-matter entanglement. Our results highlight the importance of treating the non-linear light-matter interaction of the Coulomb gauge non-perturbatively, to obtain a well-defined ultrastrong coupling limit and to not spoil gauge equivalence.

Abstract PS1-27: A novel technology for uniform post-lumpectomy radio-frequency ablation for margin extension and local control tested in IRB-approved pilot mastectomy study

Abstract Background: Radio-frequency ablation (RfA) of post-lumpectomy breast cavities has been shown to extend the surgical margin to reduce the need for re-operations and to provide local control without radiation therapy in many Breast Conservation Surgery (BCS) patients. However, all studies to-date have had to use adapted RfA needle electrodes designed for inoperable solid liver/kidney tumor ablation as no devices had been specifically developed for breast lumpectomy application. The SIRA™ device (Innoblative Designs Inc., Chicago, IL) is a first-in-class Saline-coupled Intra-cavitary RfA device specifically designed to fit the post-lumpectomy breast cavity and deliver uniform post-lumpectomy cavity ablation for margin extension and local control. We aimed to evaluate the SIRA device’s ablation performance in human breasts of patients undergoing prophylactic mastectomy. The device settings and ablation dose (i.e., power and duration) were previously optimized within this same model to target a ~1cm ablation depth, where residual cancer cells are most likely to be located. The study was designed to evaluate the repeatability and uniformity of the optimized settings across multiple patients. Methods: This study was approved by the Northwestern University IRB. Immediately following the prophylactic mastectomy, simulated lumpectomies 3-4cm in diameter were removed from the breast specimen by a surgeon. The SIRA device was then inserted and secured in place within the cavity with suture by the surgeon. Once secured, the ablation procedure was performed using the optimized modelled ablation dose (80W for 22min). Following each procedure, 18 representative tissue blocks were taken around each ablation cavity, H&E slides were made, and the resulting ablation zones were analyzed histologically by a board-certified pathologist, including the percent fat per slide. Results: In the 10 procedures performed, a mean ablation depth across all margins of 8mm (SD = 1.3mm) was achieved. The standard deviation within each individual procedure ranges between 0.3mm and 2.8mm, indicating the ablation is relatively uniform around the cavity. 70% of the patients had calculated BIRADs scores of either Heterogeneously Dense or Extremely Dense. Conclusions: The results of this study confirmed the feasibility of the SIRA device to create consistent and effective uniform ablations to targeted depth of ~1cm around a lumpectomy cavity in fresh human breasts undergoing mastectomy. The prophylactic mastectomy model allows for analysis of the SIRA in freshly excised ex vivo tissue to provide nearly identical electrical conductivity, thermal conductive, and mechanical stress-strain properties as in vivo breast tissue. Future studies will provide more statistical clarity on the effect of breast density on ablation depth. Most patients in the study had Heterogeneously Dense or Extremely Dense breasts, which was expected due to the nature of the younger patients receiving prophylactic mastectomy; however, the performance here was consistent across densities and supplemented with a parallel study in older, fattier breasts in a cadaveric model. Ultimately, these data show proof-of-concept for the SIRA device to provide margin extension and local control, which may ultimately reduce the need for reoperations and for adjunctive radiation in select BCS patients. Citation Format: Tyler R Wanke, Thomas Kurth, Alyssa Bailey, Zach Rzeszutek, Luis Blanco, Jr., Kevin Bethke. A novel technology for uniform post-lumpectomy radio-frequency ablation for margin extension and local control tested in IRB-approved pilot mastectomy study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS1-27.

Facile construction of honeycomb-shaped porous carbon electrode materials using recyclable sodium chloride template for efficient lithium storage

Carbon materials are the preferred anode materials for Li-ion batteries. Here, we propose an easy and sustainable strategy to prepare honeycomb-shaped porous carbon (HPC) electrode materials through a process involving simple calcination and subsequent water washing by using polyvinyl-pyrrolidone (PVP) as carbon source and NaCl as pore-forming agent. A controllable cavity size and distribution of the carbon materials can be readily obtained solely by adjusting the NaCl amount. Results showed that the optimized HPC sample had a relatively uniform cavity distribution and a highly porous structure. Moreover, the special honeycomb-shaped structure was conducive to the electronic conductivity of the electrode materials, provided a short path for Li-ion transport and a wide interface with the electrolyte, and buffered the volume change of active materials. The special honeycomb-shaped structure was also maintained well after long cycles, which improved electrode stability. When used as anode materials for Li-ion batteries (LIBs), the sample demonstrated excellent cycling stability and rate performance, with a high specific capacity of 230 mA h g−1 and a reversible capacity of 197 mA h g−1, after 1200 cycles at 2 C. Overall, we introduced a simple strategy for the potential mass production of porous carbon materials for LIBs.

Etch-stop process for precisely controlling the vertical cavity length of GaN-based devices

In this study, an etch-stop process was developed using inductively coupled plasma reactive-ion etching for precisely controlling the vertical cavity length of GaN-based devices, such as vertical-cavity surface-emitting lasers (VCSELs) and VCSEL 2D arrays. An AlN layer, which was the etch-stop layer, was added to the epitaxial structure for defining the bottom of a vertical cavity. A uniform vertical cavity length was thus obtained across the entire wafer. Consequently, the flatness of the bottom-end facet was determined from the quality of epitaxial growth rather than the quality of chemical mechanical polishing. The surface morphologies of the wafer in various processing stages were also inspected and compared.

Boundary integral equation method for resonances in gradient index cavities designed by conformal transformation optics

In the case of two-dimensional gradient index cavities designed by the conformal transformation optics, we propose a boundary integral equation method for the calculation of resonant mode functions by employing a fictitious space which is reciprocally equivalent to the physical space. Using the Green’s function of the interior region of the uniform index cavity in the fictitious space, resonant mode functions and their far-field distributions in the physical space can be obtained. As a verification, resonant modes in limaçon-shaped transformation cavities were calculated and mode patterns and far-field intensity distributions were compared with those of the same modes obtained from the finite element method.

Construction of Carbon Dots Coated Magnetic Hollow Silica Spheres.

Magnetic hollow silica spheres (MHSS) with uniform cavity size and shell thickness were prepared using functionalized SiO₂ spheres as templates, on which the magnetic particles were uniformly deposited on their surface. The obtained MHSS exhibited a super-paramagnetic behavior at room temperature. Due to large hollow cavity space and super-paramagnetic characteristics, the MHSS were coated with carbon dots with assistance of (3-Aminopropyl) trimethoxysilane (APS). Thus, the preparedMHSS were mixed with citric acid and APS, followed by hydrothermal reaction at 180 °C, to generate carbon quantum dots coated MHSS (MHSS@CDs). Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder scattering (XRD), X-ray energy dispersive spectral analysis (EDS), Raman spectra and laser scattering particle analyzer were applied to characterize the MHSS and MHSS@CDs.