Haut PDF Low fouling membranes for water and bio tech applications

Low fouling membranes for water and bio tech applications

Low fouling membranes for water and bio tech applications

Several techniques are widely used to assess the presence of the modifying agent, hydrophilicity of the membrane, and adsorption of the foulant. The most direct method to determine the hydrophilicity of the membrane is the water contact angle analysis. It is a quite simple method, with an easy sample preparation and results do not require a big expertise for their processing. However, results can be affected by changes in pore size, roughness, porosity and pore size distribution. Fourier-transform infrared spectroscopy FTIR has been used to qualitatively assess the modification process and sometimes of the foulants. The peaks that can be measured on these spectra correspond to a particular bond stretching, allowing the identification of the chemical species on the sample [10, 11]. Sample preparation and data analysis is quite simple, although the technique is limited to the analysis of the surface of the membrane. Atomic force microscopy AFM can be used to measure surface roughness. When used in force spectroscopy mode specific particles are attached to the probe, and it is possible to measure surface-particle interaction forces [9]. These particles can be very varied depending on which kind of system researchers want to study and their experience the team has with attaching them to the probe. A drawback of AFM is that it is a very local measurement. If the surface of membrane is not perfectly homogeneous, as it is generally assumed when membranes are produced, it might not be possible to get a realistic view of the coating homogeneity. The adsorption of foulant species can be determined by UV spectrophotometry (proteins) [2], confocal microscopy (blood cells and bacteria), X-ray photoelectron spectroscopy (XPS) [12] or sometimes with Scanning electron microscopy (SEM) [13]. The determination of fouling by most of these techniques can be regarded as static, foulants reach the surface by diffusion and adsorb, and then its presence and concentration is determined. It is an indication of the behaviour and properties of the system but they have not to be regarded as the absolute truth. These membranes are supposed to be used for filtration set-ups or in systems that there will be a flow, thus final fouling behaviour can be different.
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Impact of PAC Fines in Fouling of Polymeric and Ceramic Low-Pressure Membranes for Drinking Water Treatment

Impact of PAC Fines in Fouling of Polymeric and Ceramic Low-Pressure Membranes for Drinking Water Treatment

2.2. Pilot-Scale Membrane Set-up The pilot system included two parallel treatment trains, each one feeding two pressurized membranes: ceramic microfiltration (CeraMem TM ) and polymeric ultrafiltration (Pentair X-Flow, Minneapolis, MN, USA). One treatment train included a pretreatment consisting of a high concentration PAC contactor while the second train had no pretreatment before the membranes and served as a control. Table 2 provides information on the pilot design/operating conditions, while Figure 1 illustrates the treatment train configuration that included the PAC pretreatment. First, settled water was pumped into a stirred activated carbon contactor (CC) in which water was put in contact with a 5 g/L suspension of d 50 = 243 μm PAC (d 10 = 165 μm) (Aquasorb5000, PICA). A fraction of the PAC was purged daily in order to achieve a TOC concentration of less than 2.0 mg C/L in the PAC contactor effluent. Over the course of this project, an average equivalent PAC dosage of 18 mg/L was needed to achieve this objective. TOC concentrations were measured at the influent/effluent of the PAC contactor using an on-line TOC analyzer (Sievers 900, GE Water, Boulder, CO, USA). PAC was maintained inside the contactor and separated from the effluent by an 80-μm micro-strainer (cf. Figure 1). Approximately 0.6% of the PAC particles were below this value. The effluent water was then fed to the membranes. As discussed earlier, an identical treatment train to the one in Figure 1 was operated in parallel without a PAC suspension inside the contactor.
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Ion track grafting: A way of producing low-cost and highly proton conductive membranes for fuel cell applications

Ion track grafting: A way of producing low-cost and highly proton conductive membranes for fuel cell applications

It can be seen on impedance spectra in the Niquist plot 2 contributions (Figure 6). The first one with a characteristic frequency of 1 kHz does not depend of the current density and corresponds probably to the loading of the electrochemical double layer. This contribution does not appear on the spectra recorded after 45 minutes in these conditions. Indeed, at the beginning of the test, the ionomer in the active layer maybe at the cathode side but most probably at the anode side is not well hydrated and, as a consequence, the electroactive surface area is very low. This could explain the low OCV measured at the beginning of the test whereas the membrane showed no significant cross-over. The second contribution with a characteristic frequency of a few Hz which decreases as the current density increases is ascribed to the charge transfer at the cathode side. The semi-circle with a characteristic frequency of about 200 Hz does not appear after 17 hours, probably because of a better hydration the anode side thanks to the back-diffusion of water from the cathode to the anode. The specific resistance of the MEA was about 110 mOhm.cm² after 17 hours and is lower than at the very beginning of the test (Figure 7). It could be due either to the increase of membrane conductivity, either to a decrease of the contact resistance between the membrane and the electrodes. The corresponding proton conductivity of the membrane of 5x10 -2 S/cm, assuming the hypotheses described above.
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Nanofiltration and tight ultrafiltration membranes for natural organic matter removal-contribution of fouling and concentration polarization to filtration resistance

Nanofiltration and tight ultrafiltration membranes for natural organic matter removal-contribution of fouling and concentration polarization to filtration resistance

filtered, and the back-diffusion of retained solutes [ 45 ]. If CP effects become extensive, solutes at the membrane surface can reach a critical concentration (i.e., solubility limit), beyond which they form a cake/gel layer which fouls the membrane surface [ 26 , 46 – 48 ]. In literature, this critical concentration is also referred to as the “gel concentration” [ 46 , 47 ]. If a material reaches the critical concentration, the back-diffusion of material is limited by the formation of a cake/gel layer. Under such conditions, the convective transport towards the membrane becomes greater than the diffusive transport away from the membrane, and fouling occurs, which increases the resistance to permeate flow throughout the filtration phase. According to the Stokes–Einstein equation, the diffusivity and the diffusive transport of material depends on its size. NOM ranges in size from a few hundred Daltons (low molecular weight acids and neutrals) to over 20,000 Da (biopolymers) [ 39 , 49 – 51 ]. The size of NOM also generally increases with ionic strength, and decreases with pH of a solution, due to changes in the shape of NOM from uncoiled to coiled [ 52 ]. CP due to the retention of salts in Reverse Osmosis (RO) and NF systems has been extensively investigated [ 19 , 53 – 56 ]. However, only a few studies have investigated CP due to the retention of NOM in NF membranes. These studies have indicated that NOM can result in CP, and therefore, affect system performance [ 26 , 57 ]. Also, comprehensive knowledge on the effect of (i) the type of NOM (e.g., polysaccharides and humic substances), and (ii) the membrane MWCO on the contribution of CP to the total increase in filtration resistance, is not currently available. This is a knowledge gap that limits the ability to develop recommendations for the optimal design and operation of NF and tight membrane systems for drinking water treatment.
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Design and function of biomimetic multilayer water purification membranes

Design and function of biomimetic multilayer water purification membranes

DISCUSSION In summary, we report a new and optimized biomimetic route to fab- ricate biomaterial-based multilayer membranes for water purification, which consists of well-organized multilayer structures through silk self-assembly and in situ HAP biomineralization. These low-cost SNF/HAP membranes exhibit universal water purification capability for dyes, proteins, and nanocolloids. Moreover, the membranes can be formed from SNF/HAP dispersions under a short processing time, enabling the fabrication of multitype purification membranes, such as pressure-derived filtration membranes and syringe ultrafilters. More remarkably, SNF/HAP membranes can be used to remove metal ions, a unique feature in comparison to the capabilities of other nanofiltra- tion membranes. The metal ion contaminants that are removed can also be reused by simple green routes to avoid secondary pollutants. These outcomes demonstrate the strong potential for this study for use of these new systems in a wide range of applications, such as wastewater treatment, nanotechnology, food industry, and the life sciences. Initially, we selected SNFs as starting materials. On the basis of our simulation results, different protein-based fibrils (that is, amyloid and collagen fibril) and their corresponding biomineral systems (that is, calcification and silicification) may be suitable for building multilayer structures in a similar fashion as demonstrated here for the SNF and HAP. In addition, engineered peptides and pro- teins, such as silk-, silk-elastin –, silaffin-, and apatite-binding peptide– based peptides and proteins, are also useful starting materials because the interaction between these peptides and proteins with minerals can be evaluated and predicted by computational simulation. We can choose the optimized protein/mineral combination according to the in silico predictions to design and fabricate the desired multilayer (or uniform) constructions. This interaction between simulation and experiment not only allows larger design space for the materials but also improves the efficiency in the design of new materials with definable structures and properties.
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Study of separation and fouling of reverse osmosis membranes during model hydrolysate solution filtration

Study of separation and fouling of reverse osmosis membranes during model hydrolysate solution filtration

of the product portfolio of a mill by integrating new processes for sustainable products, such as biochemicals, bioenergy, biofuels, or biomaterials. Other advantages of a biorefinery integrated into a Kraft dissolving pulping mill include: (i) the existing infrastructure on site can reduce the investment costs for the biorefinery; (ii) skilled manpower with experience in biomass handling and processing is available on site; (iii) the heating and cooling utility requirements can be provided (partially or totally) by the mill. Five Kraft pulp mills in Canada have been converted from paper grade to dissolving grade pulp processes in the past. In 2014, three other mills were under conversion, due to an increase in the price and global demand for dissolving grade pulp, which can be used for the manufacture of textile fibers [ 2 ]. Dissolving Kraft pulp mills are suitable receptors of a sugar platform biorefinery, because the prehydrolysis of the wood chips to remove the hemicellulose fraction is carried out prior to cooking, thus making hemicellulosic sugars available for new products. Presently, the hemicelluloses are typically combusted to produce energy in the chemical recovery cycle of the pulping process. Several methods exist for the prehydrolysis of wood chips. The use of hot water is advantageous, because it is a mature, cost-efficient technique, and does not require the use of chemicals. Furthermore, the hemicellulose sugars can be easily extracted and recovered. The resulting stream is dilute, and contains a mixture of pentose and hexose sugars with less than 4% w/v total sugar [ 3 ], and small quantities of organic acids and phenolics. Valorization of this stream via a biochemical pathway to produce biofuels, such as ethanol and butanol, or a chemical pathway for bioproducts, such as furfural or xylitol, is possible. In mills with a hardwood feedstock, it is advantageous to produce a platform bio-product, such as furfural, because the pentoses, which make up the highest proportion of the prehydrolysate stream, are more difficult to ferment into biofuels than hexoses. Also, the production cost of biofuels from such a stream is higher than from alternative feedstock, like sugar cane or corn [ 4 ]. Furfural is a platform chemical, which can replace several industrial organic compounds that are presently produced from crude oil. An exhaustive overview of furfural feedstock, production pathways, derivatives and applications, energy intensity, and the design of a cost-efficient process for its production, was previously presented [ 5 , 6 ]. To produce high purity furfural from prehydrolysate in an IFBR, three main steps are required: (i) concentration of the generated prehydrolysate; (ii) sugars (pentose) conversion by a dehydration reaction into furfural; and (iii) product purification by distillation as shown in Figure 1 .
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Ecodesign of ultrafiltration membranes for drinking water production : an experimental and modelling approach

Ecodesign of ultrafiltration membranes for drinking water production : an experimental and modelling approach

attention is for example given to biosourced polymers since carbon composing these polymers originates from atmos- pheric carbon dioxide and is released back into the atmo- sphere whenever the polymers are incinerated: no additional carbon dioxide is emitted in this case. 26 Since Dobry’s treat- ment of cellulose esters 27 and Loeb and Sourirajan ’s prepa- ration of asymetric membranes, 28 membranes prepared with cellulose acetate (CA) offer a bio-sourced alternative to other conventional membranes prepared with petrochemical poly- ether sulfone (PES), polysulfone or polyvinylidene difluoride. 29 CA membranes were first developed for desalination of water by reverse osmosis 28,30 and are now found in other appli- cations such as hemodialysis or drinking water treament. 31,32 As regards water treatment applications, CA membranes are cheap, easily available and highly resistant to fouling. 33 Cellulose triacetate and diacetate (CTA and CDA respectively) are synthesized from cellulose, the most abundant organic polymer on Earth and industrially extracted from wood pulp or cotton. 34 Krishna Manda et al. 35 calculated that CA has a slightly better environmental profile than PES for most impact categories (climate change, human toxicity, marine and fresh- water ecotoxicity …). Only the production and disposal of both polymers have been considered; the production and operation of the two associated membranes have been simplistically taken as equal to one another.
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Characteristics of membranes and insulations used for low-sloped roofs

Characteristics of membranes and insulations used for low-sloped roofs

5. Cold-applied liquid compounds This category of membrane materials consists of emulsions and solutions of (a) various resins or elastomers, such as polyurethanes, silicones and acrylics and (b) bitumens and modified bitumens. To protect membranes from solar radiation, their surface coatings may contain white pigment or aluminum flakes, or they may consist of a vinyl film. These liquids are generally applied by spraying or with rollers. The emulsions cure slowly at low temperatures and they cannot be applied at a temperature below that at which water freezes because the solution forms a film too quickly. Cutbacks (solutions) and emulsions (water dispersions) of asphalt and coal-tar pitch are also used in various types of cold applications of built-up roofing, and polyester mats are used as alternatives to conventional felts for plies. The market share of cold-applied built-up roofing is small, and because of higher costs and lesser availability, asphalt is used more often in this type of application.
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New membranes based on polyethersulfone – SlipSkin™ polymer blends with low fouling and high blood compatibility

New membranes based on polyethersulfone – SlipSkin™ polymer blends with low fouling and high blood compatibility

In this work, we investigate a simple method for preparing low fouling blood compatible membranes for dialysis by blending PES with SlipSkin™ (50:50) (indicated as PES-SS). The SlipSkin™ (50:50) (SS) is a random copolymer of 50:50 ratio of hydrophilic N-vinylpyrrolidone (NVP) and hydrophobic N-butylmethacrylate (BMA) originally devel- oped for coating of catheters and guide wires for intravascular inter- ventions (Fig. 1) [25–27]. The advantage of using SS for membrane preparation is that both hydrophilic and hydrophobic blocks contribute to the membranes’ blood compatibility and fouling resistance [2,28]. In earlier work, we developed pristine SS membranes based on various ratio of NVP and BMA. The membranes with 50:50 ratio showed ex- cellent blood compatibility, but they had high water permeance, of 100–200 L m -2 h −1 bar −1 but also very high albumin leakage (BSA sieving coefficient (SC) was 0.83). This is undesirable, since the typical membranes for dialysis therapy should have little or no albumin leakage (SC for albumin should be around 0.015) [29]. Besides, due to the rather high amounts of the hydrophilic component NVP, these SS membranes swell significantly in aqueous solutions and require delicate handling for achieving stable filtration p erformance u sing t hese solu- tions. Here, we investigate whether membranes based on PES-SS polymer blends with low amounts of SS (2–6 wt%) would combine the positive characteristics of SS (high hydrophilicity, low fouling, good blood compatibility) with the positive characteristics of PES (good membrane formation, minimal swelling).
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New membranes based on polyethersulfone – SlipSkin™ polymer blends with low fouling and high blood compatibility

New membranes based on polyethersulfone – SlipSkin™ polymer blends with low fouling and high blood compatibility

2. Materials and methods 2.1. Materials SlipSkin™ (50:50) (SS), a copolymer of N-vinylpyrrolidone (NVP) and N-butylmethacrylate (BMA) (kindly provided by Interface BIOmaterials BV, Geleen, The Netherlands), polyethersulfone (PES) (ULTRASON, E6020P, BASF, Arnhem, The Netherlands) and poly- vinylpyrrolidone (PVP) (K90, MW≈360 000) (Fluka, Sigma-Aldrich, Germany) were used to prepare the membranes. N-methyl-2-pyrroli- done (NMP) (Acros Organics, Geel, Belgium) was used as solvent. PES membranes (molecular weight cut-off, MWCO of 50 kDa), purchased from Sartorius, Göttingen, Germany, indicated PES-50 kDa) were used as reference. A Milli-Q purification unit (Merck Millipore, Czech Republic) was used to prepare ultrapure water. Ultrapure water was used as a non-solvent in the coagulation bath and for transport ex- periments. Phosphate-buffered saline (PBS) (pH 7.45, GibCo, United Kingdom), bovine serum albumin (BSA) and α-Lactalbumin (LALBA) from bovine milk both purchased from Sigma-Aldrich (Zwijndrecht, The Netherlands) were used to evaluate membranes’ transport proper- ties and fouling resistance. An Atto 647 N Protein Labeling Kit was purchased from Sigma-Aldrich (France) for the microchip fouling ex- periments on the PES-50 kDa and custom-made PES-SS membranes. Glass coverslips (VWR, Amsterdam, The Netherlands) were used as positive control. All chemicals necessary for the blood compatibility tests, such as the thrombin generation tests, lactate dehydrogenase as- says, hematology and complement tests, were the same as stated in
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Phrase-Verified Voting: Verifiable Low-Tech Remote Boardroom Voting

Phrase-Verified Voting: Verifiable Low-Tech Remote Boardroom Voting

computer risks compromise of that machine, which could threaten denial-of-service and to some extent erosion of ballot privacy. Furthermore, introducing software into the voting process might cause conflict with institutional policies that seek clarity and transparency of the voting process. After user feedback, we implemented a method to instantly generate the verification prompt using a second Google sheet, with the first sheet having the automatic verification table. However, the system as described is transparent. Automatically generating the verification prompt should be introduced only after voters (and other parties) are comfortable with the process, since it introduces multiple spreadsheet functions. Alternatively, one could create a remote cloud service to accept a vote table and return a verification prompt, rather than running custom scripts on the EA’s computer.
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Hybrid catalytic membranes: tunable and versatile materials for fine chemistry applications

Hybrid catalytic membranes: tunable and versatile materials for fine chemistry applications

nanocomposite catalytic membranes has notably increased in recent years. The simple incorporation of ex-situ generated MNP into a polymeric matrix is made possible by immersion of the membrane in a colloidal solution [1]. However, adsorption is sometimes not efficient enough to retain the catalyst. Alternatively, Intermatrix Synthesis (IMS) is a technique based on the immobilization of MNP precursors (metal ions or complexes) into polymeric matrices followed by their chemical or electrochemical reduction. This technique provides the production of desired hybrid metal-polymer nanocomposite materials, which have already demonstrated their catalytic and bactericidal properties [2].
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The renewal and transformation of high, medium and low tech: a comparative approach

The renewal and transformation of high, medium and low tech: a comparative approach

Analyzing strategy and competition firms in HT are faced with a remarkable fast pace of change compared to LMT (Comp_Change_H8). In HT, rivals enter markets due to their innovative products (Comp_Prod_H8). Technological advancement accelerates at a very fast pace (Tech_Speed_H3). Results for Comp_Prod_H8 and Tech_Speed_H3 enormously differentiate HT from LMT, with the highest significant difference of means across all questions answers. In HT, external factors are forcing unpredictable transformations (Strat_Trans_H1). This result is not significant in Split Half 1. However we notice that the significance level is very small. This indicates that both LMT and HT are influenced by unpredictable transformations. The turbulence of the sector and breakthrough innovations are the major characteristics of the HT sector and the results are consistent for all samples. Competition is extremely severe in both sectors but slightly higher in HT (Comp_Rival_H8). Another important result is related to low cost substitutes (Comp_CostSub_H8); all results across all samples, are non significant for that factor. However in all samples, LMT is slightly higher than HT firms. This suggests that LMT still is focusing on cost; however HT too is facing severe cost substitution attacks. Finally the results concerning the variable AbCp_H2 suggest that HT have a better knowledge search strategy than LMT, indicating a more coherent and efficient absorptive capacity.
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De la démesure à la juste mesure : le low-tech, entre confort et volonté de changer

De la démesure à la juste mesure : le low-tech, entre confort et volonté de changer

TE MESURE Le lo w -tech entr e conf ort et v olont é de changer CHAPITRE 3 Exemples de vie en basses technologies ECOLE NATIONALE SUPERIEURE D'ARCHITECTURE DE NANTES DOCUMENT SO[r]

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Hybrid Catalytic Membranes: Tunable and Versatile Materials for Fine Chemistry Applications

Hybrid Catalytic Membranes: Tunable and Versatile Materials for Fine Chemistry Applications

of ionic groups was localized inside the bulk material without being accessible to the Pd 2+ solution for an anionic exchange with the counter ion. Thus, Pd 2+ (0.4 meq/m 2 ) loading, expressed in milliequivalent (meq) per surface of membrane (m 2 ), was less important than in the former case. The highest efficiency was observed with PAA swelling network attaining with incorporation 8 times superior than expected for a stoichiometric ionic exchange. Nevertheless, network pores could probably act as a pool of Pd 2+ solution, feeding the reaction. In the case of PIL, ion exchange is retarded by the poor mobility of the counter ion (NTf 2 - ).Results are summarized in Table 1.
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Functional polypyrrole core-shell particles and flexible membranes for biomedical applications

Functional polypyrrole core-shell particles and flexible membranes for biomedical applications

152 5.5 Results and discussion 5.5.1 Flexible PPy membane and P(Py-PyCOOH) core-shell particles Through the TIP method, highly flexible and free-standing PPy membranes (ϕ 15 cm) were obtained after washing and drying. An asymmetrical surface morphology of the membrane was confirmed, showing densely packed nanotubes on the water-facing side, and multiple bubbles side on the chloroform-facing side (Fig. 5.2a - 5.2c). The PPy nanotubes formed randomly oriented bundles. Under TEM, these PPy nanotubes were found about 300 nm in diameter and 30 nm in wall thickness as shown in Figure 5.1e. The other side of the membrane is formed entirely by overlapped PPy bubbles, some of which are either broken or collapsed (Fig. 5.2c). Figure 5.2b represents the cross-section of the PPy membrane, from which a nominal thickness about 0.3 mm was measured. The mechanism of how such an asymmetrical PPy membrane was formed has been discussed in our previous report 29 . Chloroform vapor produced by pyrrole reaction heat 33 was considered causing the formation of chloroform bubbles that in turn supported multiple interfacial polymerization on their surface. Noticeably, during the drying of the membrane, the PPy nanotubes became compactly stacked similar to the drying of aquatic plants, leading to a decreased membrane thickness and a microporous network as shown in the insert of Figure 5.2a. Thanks to the nano- and micro-structures, this PPy membrane can be cut, tied, folded, laminated and rolled into tubes. In addition, after drying, the PPy nanotube network cannot be rehydrated or damaged under ultrasonic treatment.
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Algorithms and low-power hardware for image processing applications

Algorithms and low-power hardware for image processing applications

The total energy required for a set of computations includes the energy for performing accumulations in the array, reading and broadcasting input activations and w[r]

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Lateral porous silicon membranes for planar microfluidic applications

Lateral porous silicon membranes for planar microfluidic applications

Classical PSi interferometric configuration PSi-based interferometric sensors and biosensors consist of vertical porous silicon layers created into a silicon wafer where the pores are or[r]

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Data Sculptures as a Playful and Low-Tech Introduction to Working with Data

Data Sculptures as a Playful and Low-Tech Introduction to Working with Data

5 Explore 2016 sketches at http://datastudio2016.datatherapy.org/ that situates our project within the urban and/or social con- text of each city" (student writing). It mixes quantitative and qualitative data. It builds on that mix to offer an invitation for readers to explore a deeper layer of reading to flesh out the significance of the data story - to perform a "physical action intending to reveal more information about refugee popula- tion in that city" (student writing). This project demonstrates how in a short period of time the students were able to ex- plore some fundamental concepts of creating data sculp- tures - the mapping of physical variables, allowing for layers of reading, and careful combination of elements to con- struct a physically interactive story. They argue that this combination serves to "bring across our message for the need of integration of refugee and native communities and to show how we are already all living side-by-side" (student writing).
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Low energy LIDARs for biomass applications

Low energy LIDARs for biomass applications

From the waveforms it was then possible to generate discrete statistically representative low flux events detected by the instrument. Indeed, operating the laser at low energy leads to work with low return flux from the scene (in photon counting regime). The arrival of the incoming photons to the instrument follows the Poisson statistical law. From these discrete pseudo-waveforms one could extract the time duration between the top of canopy echo and the ground echo and derive the tree height in consequence. It is important to note that the data processing algorithm enabling to derive canopy height from the return signal contributes to a large extent to the altimetry accuracy. If future investigations were to be led, this processing aspect should be further addressed. In this study, for the purpose of simplicity of both implementation and interpretation, canopy height was defined based on the cumulated energy of accumulated return signals, with thresholds set to 3% and 97% for canopy top and ground, respectively.
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