27 research outputs found
Global Mortality Benefits of COVID-19 Action
No full textThe rapid spread of COVID-19 motivated countries worldwide to mitigate mortality through actions including social distancing, home quarantine, school closures, and case isolation. We estimate the global mortality benefits of these actions. We use county-level data on COVID-19 from January 2020, project the number of mortalities until September 2020, and calculate the global mortality benefits using the age- and country-specific value of a statistical life (VSL). Implementing all four types of actions above would save approximately 40.76 trillion USD globally, with social distancing accounting for 55% of the benefits. The monetary benefit would be the largest in the US, Japan and China. Our findings indicate that global actions during COVID-19 have substantial economic benefits and must be implemented in response to COVID-19
Analytical regularization of hypersingular integral for Helmholtz equation in boundary element method
No full textThis paper presents a gradient field representation using an analytical regularization of a hypersingular boundary integral equation for a 2-dimensional time harmonic wave equation called the Helmholtz equation. The regularization is based on cancelation of the hyper-singularity by considering properties of hypersingular elements that are adjacent to a singular node. Advantages to this regularization include applicability to evaluate cornet nodes, no limitation for element size, and reduced computational cost compared to other methods. To demonstrate capability and accuracy, regularization is estimated for a problem about plane wave propagation. As a result, it is found that even at a corner node the most significant error in the proposed method is due to truncation error of non-singular elements in discretization, and error from hypersingular elements is negligibly small
Stark spectroscopy at Balmer-αline of atomic hydrogen for measuring sheath electric field in a hydrogen plasma
No full textThis paper reports a diode laser based system which is applicable to the measurement of electric field in the sheath region of a hydrogen plasma. The electric field is deduced from the Stark spectrum of the Balmer-α line of atomic hydrogen. Saturation spectroscopy with a Doppler-free spectral resolution is adopted to detect the Stark effects of the low energy states. We have demonstrated a detection limit of 10 V cm−1, which is a sufficient sensitivity for investigating the structures of the sheath electric fields in low-temperature plasmas. We have discussed the detection limit, the measurement ambiguity, the spatial resolution, and the limitation of the developed method
plasma jet
No full textWe observed green optical emission from an atmospheric-pressureN(2)/O(2)plasma jet. The green optical emission was composed of a line emission at lambda = 557.71 +/- 0.03 nmand a broadband component at530 <= lambda <= 560 nm. The line emission was assigned to the(1)D-(1)Sforbidden transition of atomic oxygen, whereas the broadband emission was due to the formation ofO(S-1)N(2)excimer. We measured the absolute densities ofO(S-1)andO(S-1)N(2)using a spectrograph with the absolute sensitivity calibration, and we discussed the kinetics in the green plasma jet on the basis of the absoluteO(S-1)andO(S-1)N(2)densities. According to the rate coefficients and the transition probabilities reported in literature, the present experimental results are explained if the densities ofN2(A3 n-ary sumation u+)andO(P-3)are9 x 10(13)and3 x 10(13)cm(-3), respectively
Comparison among translational temperatures of He(P-1(1)o), He(S-3(1)), and Ar(4s [3/2](2)(o)) in inductively coupled plasmas
No full textWe compared the translational temperatures of He(P-1(1)o), He(S-3(1)), and Ar(4s [3/2](2)(o)) in low-pressure inductively coupled plasmas. We employed laser absorption spectroscopy for measuring the Doppler broadening widths of the transition lines, and they told us the translational temperatures of the three electronic excited states. From the comparison between the temperatures of He(P-1(1)o) and He(S-3(1)), we confirmed that the metastable S-3(1) state can work as the probe for the temperature measurement of the ground state helium atoms. We observed higher temperatures for Ar(4s [3/2](2)(o)) than He(S-3(1)) in helium-argon mixture plasmas with total pressures less than 80 mTorr. The higher Ar(4s [3/2](2)(o)) temperature is considered to be due to the selective heating of argon by the charge exchange collision with Ar+
Estimation of sheath electric field in inductively coupled hydrogen plasma on the basis of Doppler-broadened absorption spectrum of hydrogen Balmer-alpha line
No full textWe examined the applicability of the Doppler-broadened absorption spectrum of the hydrogen Balmer-alpha line to the estimation of the sheath electric field in plasma. The Stark splitting of the fine-structure components was calculated by solving the time-independent Schrodinger equation at various electric field strengths, and the theoretical absorption spectrum was obtained by the superposition of the fine-structure components with the same Doppler broadening widths. The spectrum of the Balmer-alpha line of atomic hydrogen, which was measured by standard diode laser absorption spectroscopy, was fitted with the theoretical spectrum. We succeeded in determining the translational temperature of atomic hydrogen, which was obtained from the Doppler broadening width, and the electric field strength by the spectral fitting. We have evaluated that the minimum electric field strength that can be detected by the present method is approximately 350 V cm(-1) when the translational temperature of atomic hydrogen is 400-500 K
Performance of sheath electric field measurement by saturation spectroscopy in Balmer-α line of atomic hydrogen
No full textWe developed a diode laser-based system for measuring the sheath electric fields in low-temperature plasmas. The Stark spectrum of the Balmer-α line of atomic hydrogen was measured by saturation spectroscopy with a fine spectral resolution. The spectrum observed experimentally was consistent with the theoretical Stark spectrum, and we succeeded in evaluating the electric field strength on the basis of the experimental Stark spectrum. A sensitive detection limit of 10 V/cm was achieved by the developed system
Desingularization of matrix equations employing hypersingular integrals in boundary element methods using double nodes
No full textIn boundary element methods, using double nodes at corners is a useful approach to uniquely define the normal direction of boundary elements. However, matrix equations constructed by conventional boundary integral equations (CBIEs) become singular under certain combinations of double node boundary conditions. In this paper, we analyze the singular conditions of the CBIE formulation for cases where the boundary conditions at the double node are imposed by combinations of Dirichlet, Neumann, Robin, and interface conditions. To address this singularity, we propose the use of hypersingular integral equations (HBIEs) for wave propagation problems that obey the Helmholtz equation. To demonstrate the applicability of HBIE, we compare three types of simultaneous equations: (i) CBIE, (ii) partial-HBIE where the HBIE is only applied to the double nodes at corners while the CBIE is applied to the other nodes, and (iii) full-HBIE where the HBIE is applied to all nodes. Based on our numerical results, we observe the following results. The singularity of the matrix equations for problems with any combination of boundary conditions can be resolved by both full-HBIEs and partial-HBIEs, and the partial-HBIE exhibits better accuracy than the full-HBIE. Furthermore, the computational cost of partial-HBIEs is smaller than that of full-HBIEs
Numerical reconstruction of an infrared wavefront utilizing an optical phase modulation device
No full textWe utilize nitroanisole, that absorbs infrared(IR) radiation as heat, as an optical modulation device based on a thermal process. The nitroanisole exhibits a thermal lens effect, i.e. a temperature dependent refractive index. Hence, the nitroanisole can induce phase modulation to visible light, in direct response to intensity of the incident IR radiation. The proposed method can be used to obtain the phase modulation distribution that corresponds to the IR intensity distribution, i.e. the IR hologram itself, on the nitroanisole by examining the phase map of visible light that is modulated upon passing through the nitroanisole. The IR wavefront can be reconstructed by calculating extracted IR holograms through the Fresnel transform. It is verified that both the amplitude and the phase of the IR wavefront can be reconstructed accurately by proposed method
Application of the nitroanisole as an infrared detector used in middle infrared interferometer
No full textWe propose the application of nitroanisole as a detector for middle infrared (mid-IR) interferometry or holography. The present experiment utilizes the liquid form of nitroanisole, which has a thermal lens effect, i.e. a temperature dependent refractive index. Since the nitroanisole absorbs IR radiation as heat, it is possible to estimate the IR intensity distribution on the nitroanisole from the diffraction pattern made by visible laser light that is transmitted through the nitroanisole. In this study, the time resolution and the diffraction efficiency of the nitroanisole was measured under various conditions. The experimental results show that the nitroanisole has a time resolution as high as that of a standard video camera, as well as a high diffraction efficiency and the spatial resolution equivalent to that of a conventional IR camera. Furthermore, we confirmed that the phase shift in mid-IR region can be estimated by analyzing the change in the visible diffraction pattern
