Conversion Efficiency Of Radiation Research Articles

Parameters affecting the life cycle performance of PV technologies and systems

This paper assesses modeling parameters that affect the environmental performance of two state-of-the-art photovoltaic (PV) electricity generation technologies: the PVL136 thin film laminates and the KC120 multi-crystalline modules. We selected three metrics to assess the modules’ environmental performance, which are part of an actual 33 kW installation in Ann Arbor, MI. The net energy ratio (NER), the energy pay back time (E-PBT), and the CO 2 emissions are calculated using process based LCA methods. The results reveal some of the parameters, such as the level of solar radiation, the position of the modules, the modules’ manufacturing energy intensity and its corresponding fuel mix, and the solar radiation conversion efficiency of the modules, which affect the final analytical results. A sensitivity analysis shows the effect of selected parameters on the final results. For the baseline scenario, the E-PBT for the PVL136 and KC120 are 3.2 and 7.5 years, respectively. When expected future conversion efficiencies are tested, the E-PBT is 1.6 and 5.7 years for the PVL136 and the KC120, respectively. Based on the US fuel mix, the CO 2 emissions for the PVL136 and the KC120 are 34.3 and 72.4 g of CO 2/kW h, respectively. The most effective way to improve the modules’ environmental performance is to reduce the energy input in the manufacturing phase of the modules, provided that other parameters remain constant. Consequently, the use of PV as an electricity source during PV manufacturing is also assessed. The NER of the supplier PV is key for the performance of this scheme. The results show that the NER based on a PV system can be 3.7 times higher than the NER based on electricity supplied by the traditional grid mix, and the CO 2 emissions can be reduced by 80%.

Analytic modeling of the P-doped cascaded Raman fiber lasers

An approximate analytic model of the P-doped cascaded Raman fiber lasers had been developed. The threshold pump powers for the first and the second Stokes radiation, output power, slope efficiency, and energy conversion efficiency had been solved and thus the optimization of the lasers could be discussed analytically. A fast numerical simulation of the laser based on the analytic model had also been carried out. Moreover, the comparison between the analytic and numerical solution was made.

Conversion efficiency of extreme ultraviolet radiation in laser-produced plasmas

A simple analytical model is presented for the conversion of laser beam energy into extreme ultraviolet radiation. The model is compared with experimental results to show good agreements under different conditions of the laser wavelength λL, the laser intensity SL, the pulse duration tL, and the target atomic number Z0. It turns out that relatively high conversion efficiencies are obtained when the Planck optical thickness of the plasma is τ≈0.3–0.5, which is attained under an optimized combination of SL and tL once λL is fixed. The λL scaling on the conversion efficiency is derived.

Improved Estimates Of Net Primary Productivity From MODIS Satellite Data At Regional And Local Scales

We compared estimates of net primary production (NPP) from the MODIS satellite with estimates from a forest ecosystem process model (PnET-CN) and forest inventory and analysis (FIA) data for forest types of the mid-Atlantic region of the United States. The regional means were similar for the three methods and for the dominant oak-hickory forests in the region. However, MODIS underestimated NPP for less-dominant northern hardwood forests and overestimated NPP for coniferous forests. Causes of inaccurate estimates of NPP by MODIS were (1) an aggregated classification and parameterization of diverse deciduous forests in different climatic environments into a single class that averages different radiation conversion efficiencies; and (2) lack of soil water constraints on NPP for forests or areas that occur on thin or sandy, coarse-grained soil. We developed the "available soil water index" for adjusting the MODIS NPP estimates, which significantly improved NPP estimates for coniferous forests. The MODIS NPP estimates have many advantages such as globally continuous monitoring and remarkable accuracy for large scales. However, at regional or local scales, our study indicates that it is necessary to adjust estimates to specific vegetation types and soil water conditions.

Compact neodymium phosphate glass laser emitting 100-J, 100-GW pulses for pumping a parametric amplifier of chirped pulses

A five-stage neodymium phosphate glass amplifier producing 1–1.5-ns radiation pulses of energy up to 110 J is described. The use of a multistage spatial filter based on an aperture line provides efficient extraction of the stored energy. The exit aperture filling factor is 0.65 and the output radiation divergence is equal to three times the diffraction-limited divergence. The energy efficiency of radiation conversion to the second harmonic is 60%. The amplifier is intended for pumping a chirped-pulse optical parametric amplifier.

Single-frequency operation of a Cr:YAG laser from 1332 to 1554 nm

We report the first demonstration to our knowledge of broadly tunable, single-frequency operation of a cw Cr:YAG laser. Single-frequency operation was obtained from 1332 to 1554 nm with a maximum output power of 680 mW generated at 1457 nm with 10% conversion efficiency of 1047-nm pump laser radiation. A traveling-wave ring resonator was forced to operate unidirectionally by use of Faraday rotation in the Cr:YAG gain medium with a nonplanar resonator alignment, providing the required compensating polarization rotation. Tuning was accomplished with a single-plate birefringent tuning element, and single-longitudinal-mode operation was obtained by the addition of a 9.5-mm-thick uncoated CaF2 etalon. An instrument-limited single-frequency linewidth of 2.3 MHz was measured.

Characteristics of Extreme Ultraviolet Radiation Conversion Efficiency of Xenon Plasma

The characteristics of the plasma conversion efficiency of 4d75p→4d8 transitions of xenon have been theoretically investigated using the quasi-steady-state collisional radiative model. Results indicate that a large conversion efficiency is achieved for electron densities between 1018 and 1019 cm-3. In relation to rapid plasma heating in capillary discharges, the influence of nonequilibrium ionization on the conversion efficiency has been investigated. The study clearly shows that the ionization state distribution is a function of the history of plasma evolution, and a rapid heating process under appropriate plasma conditions allows us to obtain higher conversion efficiency values compared with the steady-state calculations.

The Broom's Barn sugar beet growth model and its adaptation to soils with varied available water content

The important environmental variables that determine sugar beet growth and yield are: temperature, radiation, rainfall, potential evapotranspiration and soil available water capacity (AWC). It is important to understand the integrated effects of these variables on the production of crop dry matter and sugar yield if reliable mathematical models are required to accurately predict sugar beet growth and yield between years and across different soil conditions. The original Broom's Barn sugar beet growth model is process-based, weather-driven and uses a daily time-step simulation. It was developed from observations on beet crops grown at Broom's Barn to take into account the integrated effects of these variables, assuming that the crop has a plant population density of ≥75,000/ha, is supplied adequately with nutrients and is free of weeds, pests and diseases. Soil at Broom's Barn is generally sandy loam and has AWC of about 14%. Initial testing of the model against sequential harvest data from commercial fields at different sites in the UK and Germany showed that the original model simulated total dry matter and sugar yields with good agreement to the field observations from soils which had AWC <18%. However, three of the original parameters in the model had to be adjusted to accurately simulate the total dry matter and sugar yields with the field observations from soils which had AWC >18%. The three parameters are: the rate of foliage cover decay – μ min0, the rate of decay in intercepted radiation conversion efficiency – γ and the sugar partitioning coefficient – κ. The choice of these three parameters was based on the following observations made where water is plentiful: crop foliage cover declines at a slower rate after it reaches a maximum value; crop canopy intercepted radiation use efficiency declines at a slower rate late in the growing season as less of the canopy is composed of old leaves; the proportion of total dry matter apportioned to sugar is reduced.

Functional approach to lead tungstate (PWO) scintillators in development of their fabrication technology

The problem of fabrication of lead tungstate (PWO) scintillation crystals with reproducible characteristics is approached by distinguishing two main functions of the scintillator: (i) conversion of the high-energy irradiation to light photons, and (ii) guiding of the light through the crystal to the detector. Optical transmittivity and, thus, the lightguiding capability of the crystal are mainly influenced by inclusions of W1−yLyO3−x. Variation of tungsten valency in the inclusions under irradiation or thermal treatment influences the transmittivity and, thus, the external light yield. The efficiency of radiation conversion into light is mainly governed by crystal structure. Radiative recombination in scheelite-type PbWO4 results in emission in the blue region. The green luminescence component is shown to be caused by tungstenite-type regions, which occur in the surface layer under certain conditions of thermal treatment. The influence of the surface modification on the lightguiding properties of PWO scintillators is also discussed.

Effects of a prepulse on laser-induced EUV radiation conversion efficiency

The influence of prepulses on the conversion efficiency (CE) of laser radiation into 13 nm extreme ultraviolet (EUV) radiation, resulting from lithium-like oxygen ions from O20 μm water droplets, was investigated. The laser pulse durations in the experiment ranged from 200 fs to 120 ps. Applying prepulses preceding the main pulse at various delays of up to 11 ns, it was shown that the CE increases differently for each measured pulse duration. The strongest dependence on the introduction of a prepulse was observed for 2 ps laser pulses with a 20 mJ laser pulse energy. The EUV CE was improved by a factor of 15 by the introduction of a prepulse. Calculations on the atomic physics of oxygen ions and simulations of the laser–plasma interaction revealed the influence of the prepulse on the EUV yield.

The effect of nitrogen supply and virus yellows infection on the growth, yield and processing quality of sugarbeet (Beta vulgaris)

The effects of supplying the fertilizer nitrogen (N) as a recommended quantity of ammonium nitrate or as a commonly used dose of poultry manure on yield of sugarbeet infected with Beet mild yellowing virus (BMYV) or Beet yellows virus (BYV) were studied in field experiments at IACR-Broom's Barn in 1990, 1991 and 1992. Three N fertilizer treatments comprising Zero (N0), standard rate of 110 kg N/ha (N1) and poultry manure equivalent to c. 300 kg/ha of available N (N2) were applied to plots which were uninoculated or were subsequently inoculated with either BMYV or BYV. Averaged over virus treatments, N1 increased sugar yields by 23% relative to N0: there was no further increase when N2 was applied. When averaged over N treatments, early virus yellows infection reduced the sugar yields by 23%. Generally there was no significant interaction between N supply and virus infection. There was no evidence that the large N supply could reduce the yield effect of virus yellows infection, as had previously been thought. Crops infected from late July produced similar yields to uninoculated controls. The main effect of virus yellows was to reduce the efficiency of radiation conversion even when account was taken of the light intercepted by yellow foliage. Whilst the N2 treatment helped to maintain a green leaf cover throughout the season on virus yellows infected crops, it had no effect on virus replication. Beet processing quality was impaired by increasing the N supply and by virus infection, but again there were generally no significant interactions between infection and N rate.

Nonlinear-optical vacuum ultraviolet generation at maximum atomic coherence controlled by a laser-induced Stark chirp of two-photon resonance

A novel scheme is analyzed for efficient generation of vacuum ultraviolet radiation through four-wave mixing processes assisted by the Stark chirp of two photon resonance. In this three-laser technique, a delayed-pulse of strong off-resonant infrared radiation sweeps the laser-induced Stark shift of a two-photon transition and facilitates maximum two-photon coherence induced by the second ultraviolet laser. A judiciously delayed third pulse beats with this coherence and generates short-wavelength radiation. A numerical simulation of transient processes, which ensure maximum coherence, including those leading to Stark-chirped rapid adiabatic passage, is presented. Potential high power and energy conversion efficiency of the weak long-wavelength radiation to the VUV range is shown for a difference-frequency scheme based on parametric amplification of this signal and strong four-wave coupling at maximum atomic coherence.

Spectrum of shock waves produced by an optical discharge at a high laser-pulse repetition rate

The acceleration of a plasma jet by an optical pulsating discharge is studied. The optical discharge generated periodic shock waves or shock waves combined in periodic trains. For a pulse repetition rate f > 50 kHz, the line at frequency f dominated in the spectrum of periodic waves. The spectrum of trains following with the frequency F0 ≪ f contained an ultrasonic component and a low-frequency component. The trains produces a strong acoustic effect. The average power of the waves amounted to 160 W, and the conversion efficiency of laser radiation to shock waves was ~10% — 25%.

Energy Dynamics of Pinus taiwanensis Community in the Wuyi Mountains, Fujian, China

Based on the measurement of biomass and productivity, the calorific values of plant samples, the total amounts of energy, annual net energy fixation and energy conversion efficiency of 29-year-old Pinus taiwanensis community in the Wuyi Mountains were determined. There were some differences in calorific values among the various components of P. taiwanensis community, in which the calorific value of trunk bark was the highest and that of dead roots was the lowest. The total amounts of energy in 29-year-old P. taiwanensis community was 379.82 MJ/m2, in which that accumulated in the aboveground biomass was 275.48 MJ/m2, accounting for 72.53% of the total; that of below-ground was 104.34 MJ/m2, 27.47% of the total. Net energy fixation for this community was 20.66 MJ/m2·yr in 1993. The energy conversion efficiency of the photosynthetic active radiation on the stand was 1.00%.

Preparation, Luminescence Properties, and Application of Scintillators Based on Lu 3 Al 5 O 12 :Ce Single‐Crystal Films

The possibility of obtaining scintillators with a high effective atomic number of the element Z ef based on Lu3Al5O12:Ce3+ single‐crystal films (SCF) on doping with La3+ and Sc3+ ions on Y3Al5O12 substrates has been investigated. It is established that the SCF of (LuLaY)3Al5O12:Ce3+ (Z ef = 58.9 and ρ = 6.67 g/cm2) does not rank below those of Y3Al5O12:Ce3+ (Z ef = 29 and ρ = 4.52 g/cm2) in the conversion efficiency of radiation at the band with λmax = 515 nm. This allows their use as screens of x‐ray images with a space resolution of 0.75–1.00 μm. It is suggested that in the SCF of Lu3Al5O12 the isoelectronic impurities of lanthanum and scandium form radiative recombination centers of the type LaLu, ScLu, and ScAl as well as the centers Lu as a consequence of the effect of replacement of some Lu3+ ions by the La3+ ions to octanodes of the garnet lattice. The low efficiency of Ce3+ radiation in the SCF of (LuSc)3(AlSc)5O12:Ce is explained by substantial losses due to excitation of the recombination luminescence in the UV region of the centers formed by the isoelectronic impurities of scandium and to the possible existence of the channel of energy excitation dissipation related to the transitions between extrema of the allowed energy bands and activator levels.

Production and Resource Use Efficiencies in N- and P-Limited Tropical Forests: A Comparison of Responses to Long-term Fertilization

At two sites at the extreme ends of a soil development chronosequence in Hawaii, we investigated whether forest responses to fertilization on young soils were similar to those on highly weathered soils and whether the initial responses were maintained after 6–11 years of fertilization. Aboveground net primary production (ANPP) was increased by nitrogen (N) application at the 300-year-old site and phosphorus (P) application at the 4.1-million-year-old site, thus confirming earlier results and their designations as N- and P-limited forests. Along with ANPP, application of the limiting element consistently increased leaf area index (LAI), radiation conversion efficiency (RCE), and foliar and litter nutrient concentrations. Fertilization did not consistently alter N or P retranslocation from senescent leaves at either site, but a comparison with other sites on the chronosequence and with a common-garden study suggests that there is a genetic basis for low foliar and litter nutrients and higher retranslocation at infertile sites vs more fertile sites. N limitation appears to be expressed as limitation to carbon gain, with long leaf lifespans and high leaf mass per area. P limitation results in high P-use efficiency and disproportionally large increases in P uptake after fertilization; a comparison with other studies indicates large investments in acquiring and storing P. Although the general responses of ANPP, LAI, and RCE were similar for the two sites, other aspects of nutrient use differ in relation to the physiological and biogeochemical roles of the two elements.

Physiological basis of spacing effects on tree growth and form in Eucalyptus globulus

We examine the effects of spacing and layout on the growth and form of 3- to 4-year-old Eucalyptus globulus in a farm forestry context. Four planting layouts were chosen. These represented the range commonly in use in farm forestry: block plantings (2×4 m), triple rows (2×4 m) at 10-m intervals, single rows (2×10 m) and isolated trees (10×10 m). The physiological significance of key results is interpreted in terms of changes in the parameters of a simple plantation growth model. Under conditions where levels of direct light are high, for example during summer, block-planted trees intercepted only 38% of the light intercepted by isolated trees. On a stand basis, however, the combination of incident radiation and ground coverage declined with lower stand densities. While stand leaf area index declined from around 6 to 1 with increased spacing, individual tree leaf areas rose from around 50 m2 in block plantings to 150 m2 in isolated trees. The proportion of above-ground biomass found in stems declined with increasing spacing as the mass in foliage and branches increased. Stems accounted for 65% of above-ground biomass in block-planted trees but only 35% in isolated trees. The contributions of leaves and branches correspondingly rose from 19% to 35% and from 16% to 29%, respectively. Changes in biomass distribution were accompanied by increasing branch number, branch thickness, flatter branch angles and the longer retention of lower branches with greater spacing. These changes have implications for the merchantability of the timber. The efficiency of above-ground radiation conversion was constant at 0.67 g MJ–1 irrespective of spacing. We estimated that foliar maintenance respiration (R m) accounted for about 90% of above-ground R m. On a stand basis R m costs block plantings 23.90 t DM ha–1 year–1 (50% annual above-ground photosynthetic production) compared with 6.22 t DM ha–1 year–1 (40% annual above-ground photosynthetic production) in stands of isolated trees.

Modeling Annual Carbon Uptake for the Indigenous Forests of New Zealand

Abstract A regional estimate of annual gross carbon uptake for the indigenous forests of New Zealand is presented. Carbon uptake for forest canopies occupying 59,311 sites on a 1 km grid (25% of the total land area) is estimated daily using a leaf-level photosynthesis–stomatal conductance model with appropriate scaling procedures (Leuning et al. 1995), and a model of site water balance. For each site, estimates of monthly climate data, soil physical properties, root-zone depth, and nitrogen availability were matched from maps. Forest type was distinguished into 18 classes and values for the maximum rate of carboxylation, Vcmax0, were assigned according to the ratio of conifer to broadleaved trees and nitrogen availability. Mean annual carbon uptake across all sites was 1.5 kg m-2. Variability between sites was attributable principally to the value for Vcmax0, followed by temperature. The effects of water stress integral, air saturation deficit, and solar radiation on carbon uptake were much less. Mean radiation conversion efficiency (ratio of carbon uptake to intercepted solar radiation) was low at 0.79 kg GJ-1, consistent with low nitrogen availability. The analysis highlights the sensitivity of carbon uptake to physiological characteristics and nitrogen status and thus the need to determine values for photosynthesis parameters for trees growing in field conditions. FOR. Sci. 47(1):9–20.

Radiation conversion efficiency and the regulation of photosynthetic development in tropical field grown rice

Following full expansion of rice leaves, a decline in light saturated photosynthetic rate (Pmax) can occur before shading by the subsequent expanding leaf. The duration of expression of Pmax is affected by such factors as irradiance and nitrogen nutrition. The rationale for the decline in Pmax is believed to be the breakdown and re-mobilisation of existing leaf components to expanding and rapidly growing tissue. During the expansion of the rice canopy under tropical, high irradiance conditions, this can potentially affect the radiation conversion efficiency of the crop (RCE: biomass produced per unit radiation intercepted). We have investigated the relationship between Pmax, total leaf nitrogen, protein and chlorophyll content in flag leaves and first leaves of rice plants growing in a tropical environment. Rubisco and total protein content declined before the reduction in Pmax. In flag leaves of 5 rice varieties during grain filling a sharp decline (typically over 3-6 days) in Rubisco content and chlorophyll a: b ratio occurred with no fall in Pmax or total chlorophyll content. This reduction was initiated at the same number of days after flowering in each variety although there was no consistent relationship between the timing of the rapid phase of grain filling and the decline in photosynthetic components in flag leaves. We conclude that in field-grown rice, certain photosynthetic components are produced in greater amounts than needed to maintain in situ rates of leaf photosynthesis. Results are discussed in terms of the impact upon RCE of rice crops in high irradiance conditions.

Polarisation characteristics of the harmonics and reflected radiation upon the interaction of 100-GW picosecond pulses with aluminium films

The generation of harmonics from a solid surface irradiated by 27-ps pulses (I≤1.5×1015 W cm-2) from a neodymium laser is studied. The conversion efficiency of p-polarised laser radiation was more than ten times greater than that of the s-polarised radiation for the second harmonic generation and more than one hundred times greater for the third harmonic generation. The optical rotation of the second harmonic generated by s- and p-polarised laser radiation is studied. The efficiencies of the second, third, and fourth harmonic generation were 2×10-8, 2×10-10, and 5×10-12, respectively. The intensities of the second, third, and fourth harmonics exhibit a power dependence on the laser radiation intensity with exponents equal to 1.5, 1.8, and 3.8, respectively.