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Room-Temperature Strong Coupling of Hexane-Dispersed Colloidal CdSe Nanoplatelets in a Microcavity Composed of Two Bragg Reflectors
Get PDFCdSe nanoplatelets (NPLs) are suitable for exploring strong light–matter coupling in semiconductor nanocrystal systems due to their giant oscillator strength and large exciton binding energy. Here, we report the facile fabrication and optical characterization of a λ/2 planar microcavity, which consists of two distributed Bragg reflectors with a hexane layer containing concentrated colloidal CdSe NPLs. Using a hexane solution layer instead of the typically used dried active layers results in a thin and flat layer, even under dense NPL conditions, almost without stressing or charging the surface of the NPLs. Reflectance spectra showed that strong light-matter coupling can be realized at room temperature and that the vacuum Rabi splitting energy is 53.5 meV. Intense photoluminescence (PL) emerges at the lower polariton branch, 25.1 meV (=ELO: longitudinal optical (LO) phonon energy) below the energy of the dark states, i.e., the exciton reservoir, indicating that relaxation from the exciton reservoir occurs efficiently in this microcavity due to LO-phonon-assisted relaxation. We describe the reflectance and PL properties using a model in which a cavity photon couples to a one-exciton state delocalized over nonuniformly oriented NPLs. This model contributes to an intuitive, quantitative understanding of the microcavity containing colloidal NPLs.journal articl
Study on Performance Improvement of Concrete by Highly Concentrated NaCl Solution Used as Mixing Water
Get PDF練混ぜ水として用いる高濃度NaCl水溶液がコンクリートの性能向上に及ぼす影響を実験的に検討した．実験結果より，練混ぜ水のNaCl濃度が20%以上になると，練混ぜ水が水道水のものより断熱温度上昇量および発熱速度が小さくなるだけでなく，乾燥の抑制に伴い乾燥収縮量も抑制できることが明らかになった．圧縮強度は28日強度が2割程度低下するが，屋外気中養生でも封かん養生と同程度の強度発現をすること明らかになった．数値計算の結果より，練混ぜ水としてNaCl濃度が20%以上のNaCl水溶液を用いることで乾燥および温度応力による初期ひび割れの対策として効果があることが明らかになった．そして，コンクリートの飽和度が大幅に上昇することと溶質の存在により溶存酸素量が減少することにより鋼材腐食の抑制効果が示唆された．The effect of a highly concentrated NaCl solution used as mixing water on the performance of concrete was experimentally investigated. The experimental results showed that when the NaCl concentration in the mixing water was 20% or higher, the adiabatic temperature rise and heat generation rate were smaller than those of tap water, and drying shrinkage was also suppressed as a result of the suppression of drying. The compressive strength of the material was found to be about the same in outdoor air curing as in sealed curing, although the 28-day strength was reduced by about 20%. Numerical results indicate that the use of NaCl solution of more than 20% as mixing water is effective in preventing initial cracking due to drying and thermal stress. The results also suggest that the use of aqueous NaCl solution is effective in preventing steel corrosion due to the significant increase in concrete saturation and the decrease in dissolved oxygen content caused by the presence of solute.journal articl
Effects of various parameters on guidewire and catheter behavior during catheter introduction
Get PDFMany guidewire penetration accidents occur during catheter introduction. Therefore, we have evaluated the behavior of medical devices such as guidewires and catheters during catheter introduction using numerical simulations. In our previous study, we evaluated the effects of the insertion velocity of the guidewire and the catheter and confirmed that during catheter introduction, the guidewire imparted a greater load on the vessel wall than that exerted by the guidewire alone. However, it was unclear whether the above phenomenon could also occur under other conditions. In the present study, in addition to these effects, we evaluate the effects of the blood vessel elastic modulus, device insertion length, blood vessel centerline curvature, and their interactions. Furthermore, we evaluate the behavior of the medical devices during guidewire removal after catheter introduction, which was not evaluated in our previous study. We determine the simulation conditions based on the design of experiments and investigate the dominant parameters that affect the contact force between the medical devices and the blood vessel wall using two methods (one that considers parameter interactions and one that does not). We confirm that during guidewire insertion and removal, the device velocity and the vessel centerline curvature have the largest effects, respectively. For the guidewire and the catheter during catheter introduction, the vessel elastic modulus and the insertion velocity have the largest effects, respectively, and the parameter interactions have large effects. These findings are clinically important because they are counterintuitive. During catheter introduction, the average contact forces are larger than those during both guidewire insertion and removal. Furthermore, during guidewire removal, the catheter tip moves in the distal direction.journal articl
Comparative Study of Reinforcement Effects of Different Herbaceous Plant Roots on Fine-Grained Soil
Get PDFThis study investigates the reinforcement effects of the roots of three herbaceous plants—Kentucky bluegrass, Red fescue, and Hard fescue—on the shear strength of fine-grained soil. A series of direct shear tests were conducted to evaluate how root penetration influences the shear behavior and structural stability of root-soil composites. Results indicated that root-reinforced specimens demonstrated greater ductility, with shear stress increasing in later stages of shearing, thereby contributing to soil stability. Quantitative analysis revealed that Kentucky bluegrass roots increased cohesion by 2.29 kPa and the internal friction angle by 2.6°, while Red fescue roots increased cohesion by 2.84 kPa with a slight reduction in the internal friction angle by 0.35°. For Hard fescue, cohesion increased by 3.03 kPa, with the internal friction angle decreasing by 1.54°. These findings showed that root reinforcement varied significantly under different vertical stress conditions, emphasizing the importance of environmental factors in soil behavior assessment. Comparative analysis demonstrated that each plant species exhibited unique reinforcement effects under both low and high vertical stress, providing valuable insights for designing ecological slope stabilization solutions aimed at enhancing soil stability and promoting environmental sustainability.journal articl
Projection Formula and The Brauer Groups for Arithmetic Fields of Positive Characteristic
Get PDFFor a field k of characteristic p > 0, in [5], it has been given that a group representation of the pr-torsion subgroup of the Brauer group of k arising from the projection formula. This note provides an alternative proof of this group representation using classical class field theory for local or global fields, based on Tate’s methods.departmental bulletin pape
Detection of Diffusion-Generated Images Using Sparse Coding
Get PDFThis paper proposes a method for detecting images generated by diffusion models using sparse coding. In the diffusion model, an image can be generated by removing noise from a noisy image. This different generation process from real images leads us to believe that there may be a statistical difference in pixels between the real and the generated images. Specifically, the image is divided into small patch regions, and all patch images are reconstructed using the basis image. In this process, sparse coefficients that contain many zeros are obtained using sparse coding, and features are calculated from the obtained coefficients. Then, a simple discriminator using the features as input is trained with a small number of data to discriminate the diffusion-generated images. In our experiments, we evaluated the proposed method on six datasets created using three diffusion models and two real image datasets. Experiments were also conducted to evaluate the robustness of the proposed method against JPEG compression. Experimental results show that our proposed method is sufficiently robust against JPEG compression with as few as 1800 training data.journal articl
Automatic Identification of CTC in Fluorescence Microscopy Images Based on A Lightweight Hybrid Network Model
Get PDFCirculating Tumor Cells (CTC) are expected to be a useful biomarker for cancer metastasis. CTC analysis can be used to assess cancer status and the therapeutic effects of anticancer drugs. Pathologists analyze blood samples from images taken with a fluorescence microscope. However, the number of CTCs in blood is very small, which is a time-consuming task. In this paper, we propose an automatic CTC identification method from fluorescence microscopy images. In the proposed method, we detect cell regions using a selective enhancement filter and blob analysis. Then, we identify the CTC using a SqueezeNet-based Convolutional Neural Network (CNN) model with Spatial Pyramid Pooling (SPP). We apply the proposed method to 5040 microscopy images and evaluate its effectiveness. The experimental results show that the proposed method has a true positive rate of 97.30%, a false positive rate of 2.069%, and an Area Under the Curve (AUC) of 0.991.journal articl
Unsupervised Meta-Modeling of a Set of Dynamical Systems: Latent Variable Estimation in State and Observation Spaces
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A parametric analysis of streamwise vortices on a compression ramp at Mach 4
Get PDFLarge-eddy simulations are conducted to investigate supersonic flow over a compression ramp at a free stream Mach number of 4.0 and a unit Reynolds number of 4.56×106 per meter. Two ramp angles of 15◦ and 18◦ are considered along with three different ramp positions (P1, P2, and P3) from the plate leading edge, with the plate length increasing progressively from P1 to P3. Simulations reveal that with an increase in the plate length and ramp angle, the separation point shifts downstream, accompanied by an extended separation length. Furthermore, with an increase in the ramp angle and plate length, a higher Görtler number is observed upstream of the reattachment indicating a greater likelihood of Görtler instability. In particular, no streamwise vortices were observed for the 15P1 and 15P2 cases, while for the 18P3 case, increased instability resulted in the breakdown of streamwise vortices, driving the transition to turbulence. The wavelength of streamwise streaks decreased by approximately 15% as the plate length increased by ≈ 80% from 18P1 to 18P3. Unsteady analysis revealed the role of spanwise secondary instabilities over these vortices, that trigger turbulent spots that propagate at a speed of ≈ 0.6U∞. The peak value of the Stanton number is found to be ≈ 15–27% higher than the time and span-averaged value for the 15P3 and 18P3 cases, highlighting a strong effect of downwash due to streamwise vortices on the wall heating rate distribution. The unsteady data also reveal a negative correlation between the flow reattachment location and the Stanton number close to the reattachment point. An earlier reattachment is shown to increase the Stanton number and vice versa resulting in a ≈ 40% variation compared to the time-averaged value. The results from this study underscore the critical influence of plate length on the formation of streamwise vortices, with significant implications for wall heating rate distribution and flow transition dynamics.journal articl