Heat transfer within linear Fresnel unit using parabolic reflector

Purpose This paper scrutinizes exergy loss and hydrothermal analysis of Linear Fresnel Reflector (LFR) unit by means of FLUENT. Several mirrors were used to guide the solar radiation inside the receiver, which has parabolic shape. Radiation model was used to simulate radiation mode. Design/methodology/approach Heat losses from receiver should be minimized to reach the optimized design. Outputs were summarized as contours of incident radiation, isotherm and streamline. Outputs were classified in terms of contours and plots to depict the influence of temperature of hot wall, wind velocity and configurations on performance of Linear Fresnel Reflector (LFR) based on thermal and exergy treatment. Four arrangements for LFR units are considered and all of them have same height. Findings Greatest Nu and Ex can be obtained for case D due to the highest heat loss from hot wall. Share of radiative heat flux relative to total heat flux is about 94% for case D. In case D when Tr = 0.388, As hext rises from 5 to 20, Nutotal enhances about 11.42% when Tr = 0.388. By selecting case D instead of case A, Ex rises about 16.14% for lowest Tr. Nutotal and Ex of case D augment by 3.65 and 6.23 times with rise of Tr when hext = 5. To evaluate the thermal performance (ηth) of system, absorber pipe was inserted below the parabolic reflector and 12 mirrors were used above the ground. The outputs revealed that ηth decreases about 14.31% and 2.54% with augment of Tin and Q if other factors are minimum. Originality value This paper scrutinizes exergy loss and hydrothermal analysis of LFR unit by means of finite volume method. Several mirror used to guide the solar radiation inside the receiver, which has parabolic shape. DO model was used to simulate radiation mode. Heat losses from receiver should be minimized to reach the optimized design. Outputs were summarized as contours of incident radiation, isotherm and streamline.

Passive Measurements of the Refractive Index of Liquid Nitrogen and Free-flowing substances by the Prism Method in the Millimeter Wavelength Range

It is proposed to use the classical prism method in the millimeter wavelength range for measuring the refractive index of liquid and free-flowing substances, including mixtures with particle sizes comparable to the wavelength. The method is implemented using a hollow radio transparent rectangular prism filled with a test substance. The measurements were carried out in the thermal radiation mode using radiometers with horn-lens antennas at frequencies of 37.5 and 94 GHz. To measure the deflection of the refracted beam, a linear scanner with a black body mounted on it, cooled with liquid nitrogen, was used. The distance between the prism and the scanner was 1 m. The refractive index of liquid nitrogen, sand, gravel, marble chips and granular polyethylene were measured. Using the refractive formula and the Landau-Lifshitz-Looeng formula for calculating the dependence of the refractive index of binary mixtures on the bulk density of particles, estimates of the refractive index of the material of the particles that make up the substances under study are obtained. They are in satisfactory agreement with the known experimental data for quartz, feldspar, granite, and marble.

Effect of brain radiotherapy strategies on prognosis of patients with EGFR-mutant lung adenocarcinoma with brain metastasis

Purpose Epidermal growth factor receptor (EGFR)-mutant lung cancers have a high risk of developing brain metastases (BM). Whole brain radiotherapy (WBRT), local radiotherapy, and WBRT + Boost are frequently used for treatment of BM. This retrospective study aimed to evaluate the difference in efficacy of these radiotherapy modes in patients with EGFR-mutant lung adenocarcinoma with BMs. Further, we determined the optimal radiotherapy regimen for patients based on Lung-molGPA. Methods and materials We retrospectively enrolled 232 patients with EGFR-mutant lung adenocarcinoma with BMs. Patients were divided into three groups based on the different modes of brain radiotherapy: WBRT group, local radiotherapy group, and WBRT + Boost group. Graded prognostic assessment for lung cancer using molecular markers (Lung molGPA), overall survival (OS), and intracranial progression-free survival (iPFS) were calculated. Kaplan–Meier was used to compare iPFS and OS in different groups. Results The median OS for the WBRT (n = 84), local radiotherapy (n = 65), and WBRT + Boost (n = 83) cohorts was 32.8, 59.1, and 41.7 months, respectively (P = 0.0002). After stratification according to the Lung-molGPA score, the median OS for the WBRT (n = 56), local radiotherapy (n = 19), and WBRT + Boost (n = 28) cohorts was 32.5, 30.9, and 30.8 months, respectively, in subgroup with score 1–2 (P = 0.5097). In subgroup with score 2.5–4, the median OS for the WBRT (n = 26), local radiotherapy (n = 45), and WBRT + Boost (n = 54) cohorts was 32, 68.4, and 51 months, respectively (P = 0.0041). Conclusion The present study showed that in patients with EGFR-mutant lung adenocarcinoma with BM, local radiotherapy and WBRT + Boost perform similarly well both in the subgroups with low and high scores of Lung-molGPA. Considering the side effect caused by whole brain radiotherapy, we recommended local radiotherapy as optimal brain radiation mode for those subtype lung cancer patients.

Spectral collapse in anisotropic two-photon Rabi model

In this communication, based upon a squeezed-state trial wave function, we have performed a simple variational study of the spectral collapse in the anisotropic two-photon Rabi model. Our analysis indicates that the light-matter interaction and the spin-flipping (together with the anisotropy) effectively constitute two competing impacts upon the radiation mode. Whilst the former tries to decrease the radiation mode frequency, the latter may counteract or reinforce it. The light-matter interaction appears to dominate the frequency modulation as its coupling strengths go beyond the critical values, leading to the emergence of the spectral collapse. However, at the critical couplings the dominance of the light-matter interaction is not complete, and incomplete spectral collapse appears. Accordingly, at the critical couplings the eigenenergy spectrum comprises both a set of discrete energy levels and a continuous energy spectrum. The discrete eigenenergy spectrum can be derived via a simple one-to-one mapping to the bound state problem of a particle of variable effective mass in a finite potential well, and the number of bound states available is determined by the energy difference between the two atomic levels. Each of these eigenenergies has a twofold degeneracy corresponding to the spin degree of freedom.

Deciphering the spectral collapse in two-photon Rabi model

In this communication, based upon a squeezed-state trial wave function, we have performed a simple variational study of the spectral collapse of the two-photon Rabi model. Our analysis indicates that the light-matter interaction and the spin-flipping effectively constitute two competing impacts upon the radiation mode. Whilst the former tries to decrease the radiation mode frequency, the latter may counteract or reinforce it, contingent upon the state of the atomic system. The light–matter interaction appears to dominate the frequency modulation as its coupling strength goes beyond the critical value, leading to the emergence of the spectral collapse. However, at the critical coupling the dominance of the light–matter interaction is not complete, and incomplete spectral collapse appears. The extent of incomplete spectral collapse is found to depend upon the energy difference between the two atomic levels as well.

Nanoslot metasurface design and characterization for enhanced organic light-emitting diodes

We investigate bottom-emitting organic light-emitting diodes (B-OLEDs) integrated with metasurface (MS) to analyze the effect of the structural parameters on the output performance. The performance of the MS-integrated B-OLED (MIB-OLED) is evaluated by out-coupling efficiency (OCE) and reflection of the ambient light, while attention is paid mainly to dielectric capping and metal structure of MS that may influence excitation of surface plasmon (SP). The results suggest that layer thicknesses affect the performance by as much as 10% for the OCE and up to 32% for reflectance. The OCE is in general weakly affected by the structural parameters of MS. In contrast, the reflectance characteristics are found to be dominated by localized SP that is largely determined by the length and the width of a unit slot of MS. An optimization factor introduced to evaluate the performance based on out-coupling power to the radiation mode and reflectance of MIB-OLEDs confirms that integration with MS improves performance by 16% over conventional planar structure. In particular, MIB-OLED is found to enhance OCE by 51% with Lambertian-like pattern. Enhanced performance is experimentally confirmed. The findings provide insights on how to optimize the MS structure to produce MIB-OLEDs with enhanced out-coupled power and contrast ratio.