Line Focus Research Articles

Systemic value creation in knowledge organizations: aspects of a theory

The phenomenon under investigation is the transition from an industrial society to a society that is based to a larger extent on knowledge resources. The question the authors are investigating is: What are the key value creation processes in a knowledge-based organization? The objective of the article is to understand and explain the social mechanisms that influence the development of knowledge-based organizations. The method used is conceptual generalization. The findings are linked to a new emphasis on information structure (infostructure), and a new way of organizing (front line focus), the modulization of work processes, and global competence clusters.

Gouy phase shift of lens-generated quasi-nondiffractive beam

Gouy phase shift (GPS) along geometrical rays of quasi-nondiffractive beam is studied by Fresnel diffraction to understand its phase behavior. Two typical quasi-nondiffractive beams, quasi-Bessel beam generated by axicon and quasi-Airy beam generated by cubic phase mask, were studied. Results show that those two beams have different kinds of GPS. While quasi-Airy beam follows general phenomenon of converging light wave where its phase change across focal line is -π, quasi-Bessel beam has phase change of -π/2 although it is two-dimensional.

Ogival Resonator Half-filled With DNG Metamaterial

A metallic cylindrical cavity with planar bases and with side walls consisting of two equal concave parabolic cylinders having the same focal line is considered. The symmetry plane through the focal line and the intersecting lines of the parabolic cylinders divides the resonator into two equal volumes, one filled with double positive material and the other with double negative antiisorefractive metamaterial. The exact electromagnetic field inside the resonator is obtained.

Virtual Solar Field - Validation of a detailed transient simulation tool for line focus STE fields with single phase heat transfer fluid

Simulation models enable designers and operators to test different settings of the real systems while avoiding the large costs associated with experimental or practical systems. However, creating models that resemble the real physical system with acceptable accuracy and computational time remains a challenge for developers of such tools. With this motivation, a new simulation tool, the Virtual Solar Field (VSF), has been developed for line-focus power plants with single-phase heat transfer fluid (HTF) to assist in plant control during transient processes. VSF is a whole-field model based on an efficient coupling of hydraulic and thermal solvers that take into account the flow distribution in the parallel loops, as well as the transient conditions in the field.In this paper, some validation cases for VSF using data from Andasol-3 power plant are shown. Five test cases are examined, which include normal operation, start-up and evening operation during clear-sky and strong transients. The results show very good agreement with the real plant and some discrepancies are discussed and studied. The main sources of discrepancies are associated with difficulties in modelling all fine details of reality using the current technologies in some commercial power plants. For example, small cloud passage are not detected by the few weather stations in the power plant, as well as knowing the exact loop valve settings is not possible in Andasol-3. In addition, an overview of the potential applications of VSF are mentioned and briefly discussed. VSF offers a suitable platform for testing novel control strategies and assessing the performance of the solar fields.

Combination of color coding and wavefront coding for extended depth of field

Color coding has been experimentally demonstrated to be able to extend the depth of field (DoF) of an imaging system in single snapshot. A numerical model is adopted in this paper to quantitatively characterize its imaging properties (strehl ratio, point spread function and modulation transfer function). To improve the system’s performance under nonuniform spectrum, we proposed to introduce wavefront coding into the system. Numerical results show that wavefront coding acts as an average filter of the spectrum, so that it is able to get an almost invariant MTF across the focal line even under nonuniform spectrum, which is desirable in many applications.

Inverted multiscale optical resolution photoacoustic microscopy.

Optical resolution photoacoustic microscopy (ORPAM) is one of the fastest evolving photoacoustic imaging modalities. It not only has a comparable spatial resolution to pure optical microscopies such as epifluorescence microscopy, confocal microscopy, and two-photon microscopy, but also owns a higher penetration depth. In this study, we report an inverted multiscale (IM)-ORPAM that utilizes a two-dimensional galvanometric scanner integrated with two microscopic imaging lenses to achieve rotary-scanning-based multiscale imaging. A 15MHz cylindrically focused ultrasonic transducer is mounted on a motorized rotator to synchronously follow the optical scanning paths. To minimize the loss of signal-to-noise ratio, the acoustic focal line is precisely adjusted confocal with the optical focal plane. Black tapes, carbon fibers, and sharp blades are imaged to evaluate the performance of the system, and in vivo multiscale imaging of vasculatures inside the ears and brains of mice is demonstrated using this system.

Thermal Analysis and Experimental Validation of Parabolic Trough Collector for Solar Adsorption Refrigerator

This work presents an algorithm able to simulate the heating of a solar collector throughout the day. The discussed collector is part of a solar adsorption refrigerator, and is used to regenerate the activated carbon contained inside a cylindrical recipient (absorber), which is located in the focal line of a parabolic trough concentrator. The developed algorithm takes into account all the transfer mechanisms when analyzing the heat transfers taking place between the collector’s components and the environment, as well as the transfer mechanisms towards the absorber’s interior. The temperature evolution for the collector’s elements is obtained, and the model is validated by comparing the experimentally measured surface temperature of the absorber with the one determined by the algorithm. The experimental data were gathered from similar collectors in two different scenarios: Santo Domingo (Dominican Republic) and Buenos Aires (Argentina). The model is satisfactorily validated with experimental data.

Homology Parameters for Large Axisymmetric Shaped Dual-reflector Antennas

We extend the concept of best-fitting paraboloids for large single and dual reflectors with conic-section surfaces to best-fit shaped surface for large dual reflectors shaped for uniform amplitude distribution. The point focus of the paraboloidal main reflector is replaced by focal lines for the main reflector and the primary subreflector focus, whereas the secondary subreflector point focus at the feed is kept. The reflector surfaces are shaped, and all rays from the main-reflector aperture to the feed meet an equal-path-length condition. This condition may be represented by a set of “homology parameters” determined by a least-squares method. Finally, we calculate the homology parameters and the root mean square of surface errors for an 8-m dual-reflector system including gravity effects for the antenna pointed toward zenith and the horizon.

Optical Tests on a Curve Fresnel Lens as Secondary Optics for Solar Troughs

A curve Fresnel lens is developed as secondary concentrator for solar parabolic troughs to reduce the number of photovoltaic cells. Specific measurements and optical tests are used to evaluate the optical features of manufactured samples. The cylindrical Fresnel lens transforms the focal line, produced by the primary mirror, into a series of focal points. The execution of special laboratory tests on some secondary concentrator samples is discussed in detail, illustrating the methodologies tailored to the specific case. Focusing tests are performed, illuminating different areas of the lens with solar divergence light and acquiring images on the plane of the photocell using a CMOS camera. Concentration measurements are carried out to select the best performing samples of curve Fresnel lens. The insertion of the secondary optics within the concentrating photovoltaic (CPV) trough doubles the solar concentration of the system. The mean concentration ratio is 1.73, 2.13, and 2.09 for the three tested lenses. The concentration ratio of the solar trough is 140 and approaches 300 after the introduction of the secondary lens.

Linking planning strategies with supply chain in an extended environment: a theoretical framework

Literature shows that to control production operations, to achieve optimum inventory level and to schedule the requirements according to the forecasted demand, implementation of material requirement planning (MRP) on the manufacturing system is necessary. It helps in establishing specifications of a production system and optimizes analysis of the process line focusing on establishing all the necessary data for the specification regarding the nature of production system and the inventories issues. To put MRP in to a process, the purpose of this paper is to develop a framework to integrate the work process flow that gives a simple image of the process flow for any general production system, concerning the operations and their management. Flow of data can be followed from forecasting of the demand to the delivery order, as well as tracking of material and customer order is made possible.

Linking planning strategies with supply chain in an extended environment: a theoretical framework

Literature shows that to control production operations, to achieve optimum inventory level and to schedule the requirements according to the forecasted demand, implementation of material requirement planning (MRP) on the manufacturing system is necessary. It helps in establishing specifications of a production system and optimizes analysis of the process line focusing on establishing all the necessary data for the specification regarding the nature of production system and the inventories issues. To put MRP in to a process, the purpose of this paper is to develop a framework to integrate the work process flow that gives a simple image of the process flow for any general production system, concerning the operations and their management. Flow of data can be followed from forecasting of the demand to the delivery order, as well as tracking of material and customer order is made possible.

Study on Line CARS for Temperature Measurement in Combustion Flow Field

Some laser beams meet at a single point by a convex len in normal coherent anti-Stokes Raman scattering (CARS), and the CARS signal with temperature information of the focal piont yields under phase matching. Normal CARS can only get the temperature of one spatial piont in one measurement, which can not meet the needs of deep research on combustion flow field. In order to get more information in one test and improve the measuring capacity of CARS, line CARS (L-CARS) was presented. In L-CARS, convex lens are replaced by cylindrical convex lens to get a focal line, and nearly all the points on the line meet the phase matching. So, the CARS signal of each point on the line yield in one test. Cylindrical convex lens are also used in subsequent beam path to focus the CARS signals into spectrometer, and ICCD camera transfers the signals to computer to acquire the temperature of each point. Then, the measuring capacity of CARS is advanced from piont measuring to line measuring. Experimental results based on plain flame furnace suggest that L-CARS can acquire about 200 points’ temperatures effectively in one test, and the length of the measuring line is about 3.6mm. The spatial resolution is about 18μm and the uncertainty is less than 7%, which is as the same as the ordinary CARS’s.

On the impossibility of double focusing in combined electric and magnetic fields homogeneous in Euler’ terms

The use of Euler’s homogeneous electric and magnetic fields can be a good basis for designing static mass spectrometers capable of operating in a spectrographic mode and enabling recording of mass spectra with a wide mass range in one measurement. It is proved mathematically that, when combined Euler’s homogeneous electric and magnetic fields are used to design a single-cascade mass-spectrometer, the double focusing mode cannot be achieved practically along the entire focal line. It is demonstrated that the use of mass spectrographic schemes in which the electric stage and the magnetic stage are separated is an inevitable solution in the creating of a mass spectrograph with high analytical performance.

On the calculation of occlusal bite pressures for fossil hominins

Reconstructing the feeding behavior of fossil hominins, and especially of australopiths, is currently the focus of several lines of work (e.g., Grine et al., 2006; Sponheimer et al., 2006, 2013; Ungar et al., 2008; Strait et al., 2009; Constantino et al., 2010; Wroe et al., 2010; Cerling et al., 2011; Henry et al., 2012; Delezene et al., 2013; Zink et al., 2014; Smith et al., 2015). One of these lines of research consists of estimating bite forces from fossil skulls based on estimates of lever arm length and cross sectional area of the masticatory muscles (e.g., Demes and Creel, 1988; Eng et al., 2013). The results of such studies can be expressed as unitless values (Demes and Creel, 1988), or as estimates of the maximal vertical (i.e., perpendicular to the occlusal plane) adducting force that could be produced by a given jaw (Demes and Creel, 1988). Although this kind of analysis does not take into account other aspects, such as the differential activity of the muscles involved in mastication, or food processing modes, the results are still related to the bite force capabilities of fossil hominins. Demes and Creel (1988) proposed the existence of a nearly linear correlation between bite force produced at themesial margin of the second upper molar (M2) and M2 area for extant hominoids and fossil hominins, although early Homo (represented by the fossil specimens OH 24 and KNM-ER 1813) and Australopithecus africanus (Less).

Influence of different types of astigmatism on visual acuity

PurposeTo investigate the change in visual acuity (VA) produced by different types of astigmatism (on the basis of the refractive power and position of the principal meridians) on normal accommodating eyes. MethodsThe lens induced method was employed to simulate a set of 28 astigmatic blur conditions on different healthy emmetropic eyes. Additionally, 24 values of spherical defocus were also simulated on the same eyes for comparison. VA was measured in each case and the results, expressed in logMAR units, were represented against of the modulus of the dioptric power vector (blur strength). ResultsLogMAR VA varies in a linear fashion with increasing astigmatic blur, being the slope of the line dependent on the accommodative demand in each type of astigmatism. However, in each case, we found no statistically significant differences between the three axes investigated (0°, 45°, 90°). Non-statistically significant differences were found either for the VA achieved with spherical myopic defocus (MD) and mixed astigmatism (MA). VA with simple hyperopic astigmatism (SHA) was higher than with simple myopic astigmatism (SMA), however, in this case non conclusive results were obtained in terms of statistical significance. The VA achieved with imposed compound hyperopic astigmatism (CHA) was highly influenced by the eye's accommodative response. ConclusionsVA is correlated with the blur strength in a different way for each type of astigmatism, depending on the accommodative demand. VA is better when one of the focal lines lie on the retina irrespective of the axis orientation; accommodation favors this situation.

The Possible Role of Peripheral Refraction in Development of Myopia.

Recent longitudinal studies do not support the current theory of relative peripheral hyperopia causing myopia. The theory is based on misunderstanding of the Hoogerheide et al. article of 1971, which actually found relative peripheral hyperopia to be present after, rather than before, myopia development. The authors present two alternative theories of the role of peripheral refraction in the development and progression of myopia. The one for which most detail is given is based on cessation of ocular growth when the periphery is at an emmetropic stage as determined by equivalent blur of the two line foci caused by oblique astigmatism. This paper is based on an invited commentary on the role of lens treatments in myopia from the 15th International Myopia Conference in Wenzhou, China in September 2015.

Performance study of an enhanced solar greenhouse combined with the phase change material using genetic algorithm optimization method

There are several common shapes for solar greenhouses structure. In a special structure, the curved glass roof is equipped with a thin remarkable cover. In this case, the cover modifies the solar light spectrally and reflects the unnecessarily wavelengths on a tubular collector installed in the focal line of the curved roof, out of the greenhouse, for greenhouse multipurpose applications. In this work, the basic idea for mentioned above special greenhouse was enhanced. As a new study, the performance effects of the collectors numbers (here, 1, 2, and 3) used for roof of the one solar greenhouse system was investigated. Also, for better saving energy process, a specific amount of phase change material (PCM) was applied in the collector. A genetic algorithm method was used to optimize the collector pipe radius versus the volume of the PCM placed inside this pipe. Simulation results indicated that the use of this enhanced system solar greenhouse leads to the remarkable results in the energy budget and the economic factors.

Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces

Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication.

Carrier Lifetime in Liquid-phase Crystallized Silicon on Glass

Liquid-phase crystallized silicon on glass (LPCSG) presents a promising material to fabricate high quality silicon thin films, e.g. for solar cells and modules. Barrier layers and a doped amorphous silicon layer are deposited on the glass substrate followed by crystallization with a line focus laser beam. In this paper we introduce injection level dependent lifetime measurements generated by the quasi steady-state photoconductance decay method (QSSPC) to characterize LPCSG absorbers. This contactless method allows a determination of the LPCSG absorber quality already at an early stage of solar cell fabrication, and provides a monitoring of the absorber quality during the solar cell fabrication steps. We found minority carrier lifetimes higher than 200ns in our layers (e.g. n-type absorber with ND=2x1015cm-3) indicating a surface recombination velocity SBL<3000cm/s at the barrier layer/Si interface.

Experimental investigations into low concentrating line axis solar concentrators for CPV applications

Solar photovoltaic conversion systems with integrated, low concentration ratio, non-imaging reflective concentrators, could be on south facing building roofs used to generate power at a lower cost than currently available proprietary systems. The experimental investigation presented by this research provides information on the optical and energy conversion characteristics of two geometrically equivalent non-imaging concentrators; a compound parabolic concentrator and a V-trough reflector. The aim was to investigate the assumption of uniform cell illumination when PV cells located on the receiver surface with their central axes are aligned parallel with the focal line of the line-axis concentrator. Solar radiation incident was measured at the aperture and the PV cell surface using respectively a pyranometer and photodiodes at six different collector tilt angles of 0°, 10°, 20°, 30°, 40° and 52°. The analysis of the collected experimental data presented demonstrated that the V-trough system had a more even distribution of solar radiation than the CPC and a higher optical concentration ratio (ratio of solar radiation incident on the aperture cover to that incident on the receiver) though the geometrical concentration ratio of the two collectors was equal to 2.2×. Also, the V-trough concentrator had an electrical power output up to 17.2% higher than the CPC system at a specific tilt angle of 30°. The V-trough had a consistently higher receiver plate temperature as it was reflecting larger quantities of solar radiation than the CPC. Over 17 consecutive typical summer days’ similar performance was observed over the range of tilt angles studied. The development of V-trough concentrators should be preferred due to higher power production, reduced complexity, increased uniformity of illumination and lower manufacturing costs compared to CPCs.