Internal Reflectors Research Articles

Enhancing the stepped solar still performance using internal and external reflectors

The performance of stepped solar still with internal and external reflectors have been investigated in the current study. The reflectors are used to enhance energy input to the stepped still. The influence of internal and external (top and bottom) reflectors on the performance of the stepped solar still is investigated. A comparison between modified stepped solar still and conventional solar still is carried out to evaluate the developed desalination system performance under the same climate conditions. The results indicated that, during experimentation the productivity of the modified stepped solar still with internal and external (top and bottom) reflectors is higher than that for conventional still approximately by 125%. In this case the estimated cost of 1l of distillate for stepped still with reflectors and conventional solar stills is approximately 0.031$ and 0.049$, respectively.

Subaqueous deltaic formation of the Old Yellow River (AD 1128–1855) on the western South Yellow Sea

Abstract The Yellow River presently flows into the Bohai Sea, but during the period AD 1128–1855, the river (called the Old Yellow River, OYR) flowed into the western South Yellow Sea (SYS), where the dispersal of its sediment load was controlled by the interactions among alongshore currents, waves and tides, and shelf morphology. In this study, high-resolution shallow seismic profiles, vibrocores, boreholes, and water depth data, which were obtained during geological surveys in the western SYS in recent years, are used to examine the depositional pattern and stratigraphic record related to the OYR entering the sea. Our data reveal compound clinoform morphologies (double clinoforms) – a subaerial/subaqueous delta couplet – sourced by the OYR in the western SYS. The subaerial delta comprises the currently onshore delta plain and deltafront extending to ~ 17 m in water depth, while the subaqueous delta is composed of a wide, gently inclined topset and a relatively narrow, steeply sloping foreset, stretching seaward about 160-km away from the shoreline and showing a morphological asymmetry with a generally southward deflection relative to the OYR mouth. The topset is 25–100-km wide in a shore-normal direction at water depths of 10–25 m, but is generally less than 4-m thick. The foreset is much narrower and thicker than the topset, is generally 5–30-km wide at 10–45 m water depth and is mostly 4–16-m thick with a maximum thickness of 20 m; it shows seaward-dipping internal reflectors (generally 0.3–0.5°). The rollover points (topset–foreset transition) of the subaqueous clinoform range mostly between 10 and 25 m water depth. Results of 210Pb and 137Cs geochronology indicate that maximum sediment accumulation rates (1.06 to 2.16 cm/yr) correspond to the foreset region, with much lower rates in the topset and surrounding shallow-sea regions ( 97%) in AD 1128–1855 has accumulated on the subaerial delta, and that about 10–16% of the total load on the subaqueous delta. Our data also reveal that the subaqueous delta related to the OYR is underlain by a large-scale clinoform (broadly confined to ~ 2.5–9.8 cal kyr BP in age) as thick as 4–13 m with seaward-dipping lower angled (

Integral freeform illumination lens design of LED based pico-projector

In this paper, an illumination lens design for a LED-based pico-projector is presented. Different from the traditional illumination systems composed by lens group, the integral illumination lens consists of a total internal reflector (TIR) and a freeform surface. TIR acts as collimation lens and its top surface formed by a freeform surface reshapes the nonuniform circular light pattern generated by TIR to be rectangular and uniform. Diameter and height of the lens are 16 and 10mm, respectively. An optimization method to deal with the problem of extended light source is also presented in detail in this paper. According to the simulation results of the final optimized lens, 77% (neglecting the effect of polarization) of the power of light source is collected on liquid crystal on silicon panel with a 16∶9 ratio and illumination uniformity achieves 92%.

Estudio numérico de eficiencias en estufas solares tipo caja con reflectores internos

In this work, results of efficiencies for first and second law of thermodynamics applied to four box-type solar cookers with internal reflectors are shown. The solar cooker has two glasses on its cover to diminish the losses of heat for radiation and convection, besides creating the effect hothouse inside the cooker. The interior of the cooker has flat mirrors placed at different angles to reflect the solar radiation toward a recipient with water inside the cooker. The obtained results are based on heating water temperatures which were obtained by means of numeric simulation, allowing comparison under identical conditions of four solar cookers. The treatment of the results revealed that the quantity of energy that impacts on the solar cookers is not used in right way for the heating water ends. Most of the profitable energy is stored in the glasses of the cover, what evidences the necessity to work in the development of better materials to diminish such situation.

Ultrasound Measurements of Temperature Profile Across Gasifier Refractories: Method and Initial Validation

A gasifier’s performance and the longevity of its refractory are directly affected by the temperature of its reaction zone. One of the key technological challenges impacting the reliability and economics of coal and biomass gasification is the lack of temperature sensors capable of reliably performing in a harsh gasification environment over extended periods of operation. In this paper, we describe and experimentally validate a novel approach that uses noninvasive ultrasound to measure the temperature distribution across the refractory or other containments, including the temperature of the hot side of the refractory. This method uses an ultrasound propagation path across a refractory that has been engineered to contain multiple internal partial reflectors. Beginning with an ultrasound excitation pulse introduced on the cold side of the refectory, a train of echoes created by partial reflectors is acquired and used to determine the speed of sound in the corresponding segments of the refractory. By using an experimentally established relationship between the speed of sound in the refractory material and the temperature, the temperature distribution across the refectory is obtained. The initial validation of the proposed approach is reported for a model cementitious refractory heated up to 100 °C. The options for incorporating partial ultrasound refractors into the refractory, the achievable accuracy, and the spatial resolution of the measured temperature profile are discussed.

Enhancing the stepped solar still performance using internal reflectors

This paper presents a modification of stepped solar still through internal reflectors. A comparison study between modified stepped solar still with trays (5mm depth×120mm width) and conventional solar still was carried out to evaluate the developed desalination system performance under the same climate conditions. The effect of installing a reflecting mirror on the vertical sides of the steps of stepped still on the distillate productivity was investigated. An experimental as well as theoretical investigation is carried out. The results indicate that, during experimentation the productivity of the modified stepped solar still with and without internal reflectors is higher than that for conventional still approximately by 75% and 57%, respectively. Also the daily efficiency for modified stepped still with and without internal reflectors and conventional solar still is approximately 56%, 53% and 34%, respectively.

An Experimental Study on a New Design of Double Slope Solar Still with External Flatted and Internal Parabolic Reflectors

The world demand for potable water is increasing steadily with growing population. Desalination using solar energy is suitable for potable water production from brackish and seawater. In this paper, we presents design, fabrication and testing of double slope solar still with external flatted and internal parabolic reflectors and also optimization of external flat reflector tilt angle for Egyptian climatic conditions. The external flat reflector tilted at (30°, 45°, 60° and 75°) on the horizontal plane. The depth of water inside basin still is 1cm. Experimental results were compared with conventional double slope solar still. Optimum tilt angle is found to be 60° with a maximum daily productivity of 9.89 lit/m 2 . Clean water is essential for good health which influences the social and economic development of any nation. People who use contaminated water are prone to waterborne diseases and they cannot effectively engage themselves in economic activities. Moreover, financial resources that could have been allocated to developmental projects are channelled to disease-curing efforts. Consequently, ill health contributes to the retardation of economic growth. The shortage of drinking water is expected to be the biggest problem of the world in this century due to unsustainable consumption rates and population growth. Pollution of fresh water resources (rivers, lakes and underground water) by industrial wastes has heightened the problem. Water is one of the most abundant resources on earth, covering three fourths of the planet's surface. About 97% of the earth's water is salt water in the oceans covering three fourths of the planet's surface covering three fourths of the planet's surface. About 97% of the earth's water is salt water in the oceans and 3% (about 36 million km 3 ) is fresh water contained in the poles (in the form of ice), ground water, lakes and rivers, which supply most of human and animal needs. Nearly, 70% from this tiny 3% of the world's fresh water is frozen in glaciers, permanent snow cover, ice and permafrost. Thirty percent of all fresh water is underground, most of it in deep, hard-to-reach aquifers. Lakes and rivers together contain just a little more than 0.25% of all fresh water; lakes contain most of it (1). Water is a basic necessity for sustaining life on the earth. With the passage of time due to technological usage and their waste disposal along with ignorance of human being caused water pollution which led the world to water scarcity. Due to water pollution the surface and under ground water reservoirs are now highly contaminated. The demand of fresh water is increasing with growth in human population. To meet the demand of potable water, scientists have developed various technologies such as reverse osmosis (RO), vapour compression (VC) and electro dialysis (ED) (2). These water purification methods are highly energy and cost intensive. It is well known that desalination plants use electrical energy which have both economical and environmental drawbacks and rely on conventional fuels (3). Therefore a method is required to use renewable energy, low input cost and less effort for the production of potable water. Solar distillation is a thermal desalination method where solar energy is used to distill fresh water from saline and brackish water. A distillation is one of many processes available for water purification, and sunlight is one of several forms of heat energy that can be used to power that process. Sunlight has the advantage of zero fuel cost but it requires more space for its collection. It is a great practical alternative, which offers life to those regions where the lack of fresh water hinders development (4). Solar water distillation is a solar technology with a very long history, and installations were found to be built over 2000 years ago, to produce salt rather than drinking water. An early large-scale solar still was built in 1874 to supply drinking water to mining community in Chile. Mass production occurred for the first time during the Second World War (5).

Echelle grating silicon multi/demultiplexers with single-reflection total internal reflectors

We present a silicon-on-insulator Echelle grating 8-channel demutiplexer showing characteristic features, average insertion loss 2.4 dB measured at 1520~1570 nm, adjacent channel crosstalk 15-18 dB, and channel spacing 11.9 nm. Our Echelle grating is remarked by a total internal reflector (TIR) which reflects incident light by a single reflection in contrast to the double reflections of retro-reflector TIR Echelle gratings.

Quasi-Distributed IFPI Sensing System Demultiplexed With FFT-Based Wavelength Tracking Method

In this paper, we fabricated a quasi-distributed intrinsic Fabry-Perot interferometric (IFPI) sensing array with the femtosecond laser. Each IFPI sensor is constituted by a pair of laser-induced internal reflectors and has a different cavity length. After multiplexing, IFPI sensors can be distinguished in the frequency domain for their different free spectral ranges. Next, a fast-Fourier-transform-based wavelength tracking method was proposed to demodulate the sensing signal. With a specially designed digital filter, frequency components corresponding to each sensor are extracted from the transmission spectra and are transformed back to the wavelength domain. Then the wavelength tracking method is utilized to demodulate the temperature information applied on the individual sensors. Experimental results show that the multiplexed sensors have good consistency and the temperature sensitivity is 11.24 pm/°C.

Testing for flow in the north polar layered deposits of Mars using radar stratigraphy and a simple 3D ice-flow model

[1] The water-ice-rich north polar layered deposits (NPLD) of Mars play a key role in the Martian climate through an active exchange of water vapor with the atmosphere. Conditions are not currently amenable for flow of the NPLD; however, gross morphological evidence for past flow suggests the possibility of a warmer climate in the past. Here we present the first comparison of internal stratigraphy predicted by a flow model with that observed by an orbital radar sounder. We have analyzed radar data from Gemina Lingula, the southernmost tongue of the NPLD, acquired by the Shallow Radar on board NASA’s Mars Reconnaissance Orbiter. The data shows extensive internal reflections and several radar reflectors were mapped to create gridded surfaces of this part of the NPLD. All the mapped radar reflectors were smooth with no sudden dips towards the surface or the bedrock. The internal radar reflectors were then compared with modeled isochrones in two different areas of Gemina Lingula under the assumption of flow occurring. Results indicate that flow of ice is unlikely to have occurred between the main dome and Gemina Lingula. Furthermore, we found no evidence for the existence of a prior ablation zone in Gemina Lingula as predicted in another study.

Wavelet-based 2D fusing of ultrasonic pulse-echo traces measured from two arrays radiating orthogonal beams

Ultrasonic measurements using orthogonal collimated beams provide both complementary and redundant information about internal parts of pieces or structures being tested, which must be fused. In this paper, a new wavelet-based digital-processing technique which fuses ultrasonic pulse-echo traces obtained from several transducers located in two perpendicularly coupled arrays is proposed. This is applied to accurately visualize the location of a small internal reflector by means of two-dimensional (2D) displays. A-scans are processed in a wavelet domain and fused in a common 2D pattern. A mathematical expression of the resulting 2D signal-to-noise ratio (SNR) is derived, and its accuracy is confirmed using benchmark tests performed with simulated registers and real measurements acquired using a multi-channel laboratory prototype. The measurement system consists of two properly coupled perpendicular arrays comprising four square pulsed transducers and electronic driving circuitry. This technique improves the 2D-SNR by a factor of twice the number of bands. In addition, good reflector location is obtained, since submillimeter 2D resolution is achieved, despite only requiring eight ultrasonic channels. This good performance is confirmed by comparing the new wavelet fusing method with the two previously described techniques.

A theoretical analysis of basin type solar still with flat plate external bottom reflector

A basin type solar still with a flat plate external bottom reflector extending from the front wall of the still in addition to the internal (two sides and back walls) reflector is presented and analyzed theoretically on three days (the spring equinox and summer and winter solstices) at 30°N latitude. We proposed a geometrical model to calculate the direct solar radiation reflected by the external bottom reflector and then absorbed onto the basin liner. We also performed a numerical analysis of heat and mass transfer in the still. We found that the external reflector can reflect the sunrays to the basin liner and increase distillate productivity. The daily amount of distillate of the still with internal and external bottom reflector is predicted to be 41%, 25% and 62% greater than that of a conventional basin type still on the spring equinox and summer and winter solstices, respectively, by setting the external reflector's inclination to the proper values according to the seasons when the glass cover's inclination angle is fixed at 20° from horizontal and the length of the external reflector is the same as the length of the basin liner.

고해상도 탄성파 자료를 이용한 부산 수영만의 퇴적층서 연구

부산 수영만의 퇴적환경을 파악하기 위해 고해상도 탄성파 자료(chirp and sparker system)를 활용한 해석을 실시하였다. 연구해역의 퇴적단위는 음향기반을 피복하는 세 개의 퇴적단위(SU1a, SU1b, SU2)로 구성되며 각각의 퇴적단위는 침식 부정합면에 의해 구분된다. 최하부의 SU1a는 음향학적으로 평행하고 연속적인 내부 반사면의 특징을 가지며, 상부의 SU1b는 불규칙한 내부 반사면을 보인다. 최상부 퇴적단위인 SU2는 탄성파 단면상에서 투명 음향상 특징을 가진다. 음향기반 상부경계면은 침식 부정합면의 특징을 보이며 동쪽으로 향하면서 깊어지는데, 이는 인접한 수영강의 영향에 의한 것으로 생각된다. 이 침식면 상부에 퇴적된 SU1a와 SU1b는 저지대를 충진하는 형태로 분포한다. SU2는 연구해역 전반에 걸쳐 광역적으로 나타난다. 본 연구에 활용된 고해상도 탄성파 자료는 수영만의 퇴적환경 및 역사에 대한 중요한 정보를 제공하였으며, 그 결과 해수면 변동, 염하구 환경 및 인접 하천에서의 육상기원 퇴적물 유입 등이 연구해역의 주요 퇴적기작에 해당하는 것으로 해석된다.

Experimental study on the effect of internal and external refl ectors on the performance of basin type solar stills at various seasons

This paper presents an experimental investigation on the effect of internal and external reflectors on the output of simple-basin solar stills in summer, autumn and winter. A simple still that equipped with internal reflectors and an external reflector is investigated at a latitude angle of 33.3o N. It was found that the internal and the external reflectors increase the daily output throughout the different seasons except for summer where the reflector(s) effect was insignificant. The increase in the daily output averaged over the seven months test period by adding both internal and external reflectors was 35.5%, and that by adding the internal reflector only was 19.9% compared to a still with no reflectors. The percentage increase in output by adding the internal and/or external reflector(s) is higher in winter than in summer. The results of this study agree with the trend of the theoretical predictions and with the winter experimental results cited in the literature at 30o N and 32.2o N latitude angles,...

Computation of solar radiation distribution in a solar still with internal and external reflectors

A model that calculates the distribution of solar radiation inside a basin-type solar still with plane reflectors has been proposed. In this model, both surface finish and optical view factors are taken into consideration in the computation of solar radiation that effectively reaches the surface of saline water in the distillation system. The model was applied to a conventional solar still and an advanced solar still with separate condenser. The conventional solar still was tested at New Delhi (28°35′N, 77°12′E) in previous work while the advanced distillation system was developed in this investigation and it comprised three basins with saline water. Basin 1 was fitted horizontally in the evaporator chamber, with the condenser chamber housing basins 2 and 3. The top part of the evaporator unit was covered with glass to allow solar radiation to reach water in basin 1. In addition, the internal surfaces of the walls of the evaporator and external surface of the front wall of the condenser unit reflected part of the incoming solar radiation onto the surface of saline water in basin 1. The distillation system was tested outdoors at the Malawi Polytechnic (15°48′S, 35°02′E). Under the prevailing meteorological conditions, it is found that the computed solar load on the surface of saline water in the evaporator basin is lower than that observed on a horizontal plane outside each energy system. The new model exhibited a higher degree of accuracy than the previous one. Other results are presented and discussed in this paper.

Yield of an improved solar still: numerical approach

Abstract In this work we propose to improve the production of active solar still by the use on the one hand, of external and internal reflectors in order to increase the rate of received overall solar radiation and on the other hand by using a thermal storage tank of in order to feed the still of the hot water for the night period. The input parameters of the computer program include the climatic conditions concerning Constantine town, Algeria (36 0 70’ N, 6 0 37’ E) for typical winter, spring and summer days. The results obtained show without ambiguity that the effect of the reflectors on the increase in the daily productivity of distillate is very significant for the winter period compared to the summer and spring. This increase is about 72.8% in the winter. In addition it appears clearly that the night production of the still increases when this last is coupled with a storage tank out of the sunshine hours. This increase is about 27.54%, 21% and 23.28% respectively for winter, spring and summer.

BGP Add-Paths: The Scaling/Performance Tradeoffs

Internet Service Providers design their network with resiliency in mind, having multiple paths towards external IP subnets available at the borders of their network. However, with the current internal Border Gateway Protocol, BGP routers and route reflectors only propagate their (unique) best path over their iBGP sessions. As a result, at the BGP router level, path diversity tends to be poor. Such lack of path diversity can lead to MED oscillations, prevents an efficient use of multipath BGP and does not allow for a fast and local recovery upon nexthop failure. Advertising multiple paths over iBGP sessions with BGP Add-Paths solves those issues, depending on the way the additional paths are selected. In this paper, we analyze the various options for the selection mode of the paths to be advertised. We show that these modes differently fulfill the needs of Add-Paths applications such as fast recovery upon failure and MED oscillation avoidance. We also show in our analysis that the costs and benefits bound with these modes depend on the connectivity of the AS where it is deployed. To support the analysis, we developed a tool allowing to measure the scaling of these modes in a given network. We illustrate the utilization of this tool on synthetic Internet topologies, and provide some recommendations for the choice of an Add-Paths selection mode.

Monthly optimum inclination of glass cover and external reflector of a basin type solar still with internal and external reflector

In this report, we present a theoretical analysis of a basin type solar still with internal and external reflectors. The external reflector is a flat plate that extends from the back wall of the still, and can presumably be inclined forwards or backwards according to the month. We have theoretically predicted the daily amount of distillate produced by the still throughout the year, which varies according to the inclination angle of both the glass cover and the external reflector, at 30°N latitude. We found the optimum external reflector inclination for each month for a still with a glass cover inclination of 10–50°. The increase in the average daily amount of distillate throughout the year of a still with inclined external reflector with optimum inclination in addition to an internal reflector, compared to a conventional basin type still was predicted to be 29%, 43% or 67% when the glass cover inclination is 10°, 30° or 50° and the length of external reflector is half the still’s length.

Effect of inclination of the external reflector of simple solar still in winter: An experimental investigation for different cover angles

This paper presents an experimental investigation on the productivity of a basin type solar still with internal and external reflector tilted at angles of 0° (vertical), 10°, 20° and 30° for still cover angles of 20°, 30° and 40°. A simple still equipped with internal and external reflectors is investigated in winter at latitude angle of 33.3° N. It was found that the daily productivity is greater for a still with a larger cover angle at any reflector angle. The daily productivity of the still with no reflectors would remain almost the same at any glass cover angle. The benefit of the vertical external reflector in winter is decreased as the cover angle exceeds 40°. The most productive solar still in winter is a still that has a cover angle of 20° and an internal and external reflector inclined at 20°; its productivity will be around 2.45 times that of simple still with no reflectors. The conclusions of this study validated the trend of some of the theoretical results cited in the literature at 30° N latitude.

High-resolution geophysical observations of the Yermak Plateau and northern Svalbard margin: implications for ice-sheet grounding and deep-keeled icebergs

High-resolution geophysical evidence on the seafloor morphology and acoustic stratigraphy of the Yermak Plateau and northern Svalbard margin between 79°20′ and 81°30′N and 5° and 22°E is presented. Geophysical datasets are derived from swath bathymetry and sub-bottom acoustic profiling and are combined with existing cores to derive chronological control. Seafloor landforms, in the form of ice-produced lineations, iceberg ploughmarks of various dimensions (including features over 80 m deep and down to about 1000 m), and a moat indicating strong currents are found. The shallow stratigraphy of the Yermak Plateau shows three acoustic units: the first with well-developed stratification produced by hemipelagic sedimentation, often draped over a strong and undulating internal reflector; a second with an undulating upper surface and little acoustic penetration, indicative of the action of ice; a third unit of an acoustically transparent facies, resulting from debris flows. Core chronology suggests a MIS 6 age for the undulating seafloor above about 580 m. There are several possible explanations, including: (a) the flow of a major grounded ice sheet across the plateau crest from Svalbard (least likely given the consolidation state of the underlying sediments); (b) the more transient encroachment of relatively thin ice from Svalbard; or (c) the drift across the plateau of an ice-shelf remnant or megaberg from the Arctic Basin. The latter is our favoured explanation given the evidence currently at our disposal.