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Academic literature on the topic 'Ångström Laboratory'
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Journal articles on the topic "Ångström Laboratory"
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Rudolphi, Erik, and Sten Ljunggren. "The Ångström Laboratory – A Vibration Free Building on Loose Sand." Journal of Low Frequency Noise, Vibration and Active Control 18, no. 1 (1999): 9–12. http://dx.doi.org/10.1177/026309239901800102.
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Rennie, Megan, Vera Samburova, Deep Sengupta, et al. "Emissions from the Open Laboratory Combustion of Cheatgrass (Bromus Tectorum)." Atmosphere 11, no. 4 (2020): 406. http://dx.doi.org/10.3390/atmos11040406.
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Cheatgrass (Bromus Tectorum) is a highly invasive species in the Great Basin of the Western USA that is increasing the frequency and intensity of wildland fires. Though cheatgrass plays a significant role in the fire ecology of the Great Basin, very little is known about its combustion emissions. The fresh smoke from 16 open laboratory burns of cheatgrass was analyzed using real-time measurements and filter analysis. We presented measured intensive optical properties of the emitted smoke, including absorption Ångström exponent (AAE), scattering Ångström exponent (SAE), single scattering albedo (SSA), and other combustion properties, such as modified combustion efficiency (MCE) and fuel-based emission factors (EFs). In addition, we gave a detailed chemical analysis of polar organic species in cheatgrass combustion emissions. We presented EFs that showed a large variation between fuels and demonstrated that analysis of combustion emissions for specific fuels was important for studying and modeling the chemistry of biomass-burning emissions.
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Tobias, S. M., and F. Cattaneo. "On the measurement of the turbulent diffusivity of a large-scale magnetic field." Journal of Fluid Mechanics 717 (February 1, 2013): 347–60. http://dx.doi.org/10.1017/jfm.2012.575.
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AbstractWe argue that a method developed by Ångström (Ann. Phys. Chem., vol. 114, 1861, pp. 513–530) to measure the thermal conductivity of solids can be adapted to determine the effective diffusivity of a large-scale magnetic field in a turbulent electrically conducting fluid. The method consists of applying an oscillatory source and measuring the steady-state response. We illustrate this method in a two-dimensional system. This geometry is chosen because it is possible to compare the results with independent methods that are restricted to two-dimensional flows. We describe two variants of this method: one (the ‘turbulent Ångström method’) that is better suited to laboratory experiments and a second (the ‘method of oscillatory sines’) that is effective for numerical experiments. We show that, if correctly implemented, all methods agree. Based on these results we argue that these methods can be extended to three-dimensional numerical simulations and laboratory experiments.
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Linke, Claudia, Inas Ibrahim, Nina Schleicher, et al. "A novel single-cavity three-wavelength photoacoustic spectrometer for atmospheric aerosol research." Atmospheric Measurement Techniques 9, no. 11 (2016): 5331–46. http://dx.doi.org/10.5194/amt-9-5331-2016.
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Abstract. The spectral light-absorbing behavior of carbonaceous aerosols varies depending on the chemical composition and structure of the particles. A new single-cavity three-wavelength photoacoustic spectrometer was developed and characterized for measuring absorption coefficients at three wavelengths across the visible spectral range. In laboratory studies, several types of soot with different organic content were generated by a diffusion flame burner and were investigated for changes in mass-specific absorption cross section (MAC) values, absorption and scattering Ångström exponents (αabs and αsca), and single scattering albedo (ω). By increasing the organic carbonaceous (OC) content of the aerosol from 50 to 90 % of the total carbonaceous mass, for 660 nm nearly no change of MAC was found with increasing OC content. In contrast, for 532 nm a significant increase, and for 445 nm a strong increase of MAC was found with increasing OC content of the aerosol. Depending on the OC content, the Ångström exponents of absorption and scattering as well as the single scattering albedo increased. These laboratory results were compared to a field study at a traffic-dominated urban site, which was also influenced by residential wood combustion. For this site a daily average value of αabs(445–660) of 1.9 was found.
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Liu, Chao, Chul Eddy Chung, Yan Yin, and Martin Schnaiter. "The absorption Ångström exponent of black carbon: from numerical aspects." Atmospheric Chemistry and Physics 18, no. 9 (2018): 6259–73. http://dx.doi.org/10.5194/acp-18-6259-2018.
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Abstract. The absorption Ångström exponent (AAE) is an important aerosol optical parameter used for aerosol characterization and apportionment studies. The AAE of black carbon (BC) particles is widely accepted to be 1.0, although observational estimates give quite a wide range of 0.6–1.3. With considerable uncertainties related to observations, a numerical study is a powerful method, if not the only one, to provide a better and more accurate understanding on BC AAE. This study calculates BC AAE using realistic particle geometries based on fractal aggregate and an accurate numerical optical model (namely the multiple-sphere T-matrix method), and considers bulk properties of an ensemble of BC particles following lognormal size distributions. At odds with the expectations, BC AAE is not 1.0, even when BC is assumed to have small sizes and a wavelength-independent refractive index. With a wavelength-independent refractive index, the AAE of fresh BC is approximately 1.05 and relatively insensitive to particle size. For BC with geometric mean diameters larger than 0.12 µm, BC AAE becomes smaller when BC particles are aged (compact structures or coated by other non-absorptive materials). For coated BC, we prescribe the coating fraction variation based on a laboratory study, where smaller BC cores are shown to develop larger coating fractions than those of bigger BC cores. For both compact and coated BC, the AAE is highly sensitive to particle size distribution, ranging from approximately 0.8 to even over 1.4 with wavelength-independent refractive index. When the refractive index is allowed to vary with wavelength, a feature with observational backing, the BC AAE may show an even wider range. For different BC morphologies, we derive simple empirical equations on BC AAE based on our numerical results, which can serve as a guide for the response of BC AAE to BC size and refractive index. Due to its complex influences, the effects of BC geometry is better to be discussed at certain BC properties, i.e., known size and refractive index.
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Gyawali, M., W. P. Arnott, R. A. Zaveri, et al. "Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols." Atmospheric Chemistry and Physics 12, no. 5 (2012): 2587–601. http://dx.doi.org/10.5194/acp-12-2587-2012.
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Abstract. We present the laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet wavelength (i.e., 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory-generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009 and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 μm and 10 μm, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Ångström exponent of absorption (AEA), and Ångström exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.
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Gyawali, M., W. P. Arnott, R. A. Zaveri, et al. "Photoacoustic optical properties at UV, VIS, and near IR wavelengths for laboratory generated and winter time ambient urban aerosols." Atmospheric Chemistry and Physics Discussions 11, no. 9 (2011): 25063–98. http://dx.doi.org/10.5194/acpd-11-25063-2011.
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Abstract. We present the first laboratory and ambient photoacoustic (PA) measurement of aerosol light absorption coefficients at ultraviolet (UV) wavelength (i.e. 355 nm) and compare with measurements at 405, 532, 870, and 1047 nm. Simultaneous measurements of aerosol light scattering coefficients were achieved by the integrating reciprocal nephelometer within the PA's acoustic resonator. Absorption and scattering measurements were carried out for various laboratory-generated aerosols, including salt, incense, and kerosene soot to evaluate the instrument calibration and gain insight on the spectral dependence of aerosol light absorption and scattering. Exact T-matrix method calculations were used to model the absorption and scattering characteristics of fractal-like agglomerates of different compactness and varying number of monomers. With these calculations, we attempted to estimate the number of monomers and fractal dimension of laboratory generated kerosene soot. Ambient measurements were obtained in Reno, Nevada, between 18 December 2009, and 18 January 2010. The measurement period included days with and without strong ground level temperature inversions, corresponding to highly polluted (freshly emitted aerosols) and relatively clean (aged aerosols) conditions. Particulate matter (PM) concentrations were measured and analyzed with other tracers of traffic emissions. The temperature inversion episodes caused very high concentration of PM2.5 and PM10 (particulate matter with aerodynamic diameters less than 2.5 μm and 10 μm, respectively) and gaseous pollutants: carbon monoxide (CO), nitric oxide (NO), and nitrogen dioxide (NO2). The diurnal change of absorption and scattering coefficients during the polluted (inversion) days increased approximately by a factor of two for all wavelengths compared to the clean days. The spectral variation in aerosol absorption coefficients indicated a significant amount of absorbing aerosol from traffic emissions and residential wood burning. The analysis of single scattering albedo (SSA), Ångström exponent of absorption (AEA), and Ångström exponent of scattering (AES) for clean and polluted days provides evidences that the aerosol aging and coating process is suppressed by strong temperature inversion under cloudy conditions. In general, measured UV absorption coefficients were found to be much larger for biomass burning aerosol than for typical ambient aerosols.
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Hallar, A. G., R. Petersen, E. Andrews, J. Michalsky, I. B. McCubbin, and J. A. Ogren. "Contributions of dust and biomass-burning to aerosols at a Colorado mountain-top site." Atmospheric Chemistry and Physics Discussions 15, no. 15 (2015): 21299–334. http://dx.doi.org/10.5194/acpd-15-21299-2015.
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Abstract. Visible Multifilter Rotating Shadowband Radiometer (MFRSR) data were collected at Storm Peak Laboratory (SPL), a mountain top facility in northwest Colorado, from 1999–2011 and in 2013. From 2011–2014, in situ measurements of aerosol light scattering were also obtained. Using these datasets together, the seasonal impact of dust and biomass burning is considered for the western United States. Analysis indicates that the median contributions to spring and summer aerosol optical depth (AOD) from dust and biomass-burning aerosols across the dataset are comparable. The mean AOD is slightly greater in the summer, with significantly more frequent and short duration high AOD measurements due to biomass-burning episodes, than in the spring. The Ångström exponent showed a significant increase in the summer for both the in situ and MFRSR data, indicating an increase in combustion aerosols. Spring dust events are less distinguishable in the in situ data than the column measurement, suggesting that a significant amount of dust may be found above the elevation of SPL, 3220 m a.s.l. Twenty-two known case studies of intercontinental dust, regional dust, and biomass burning events were investigated. These events were found to follow a similar pattern, in both aerosol loading and Ångström exponent, as the seasonal mean signal in both the MFRSR and ground-based nephelometer. This dataset highlights the wide scale implications of a warmer, drier climate on visibility in the western United States.
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Hallar, A. G., R. Petersen, E. Andrews, J. Michalsky, I. B. McCubbin, and J. A. Ogren. "Contributions of dust and biomass burning to aerosols at a Colorado mountain-top site." Atmospheric Chemistry and Physics 15, no. 23 (2015): 13665–79. http://dx.doi.org/10.5194/acp-15-13665-2015.
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Abstract. Visible Multifilter Rotating Shadowband Radiometer (vis-MFRSR) data were collected at Storm Peak Laboratory (SPL), a mountain-top facility in northwest Colorado, from 1999 to 2011 and in 2013. From 2011 to 2014, in situ measurements of aerosol light scattering were also obtained. Using these data sets together, the seasonal impact of dust and biomass burning is considered for the western USA. Analysis indicates that the median contributions to spring and summer aerosol optical depth (AOD) from dust and biomass-burning aerosols across the data set are comparable. The mean AOD is slightly greater in the summer, with significantly more frequent and short-duration high AOD measurements due to biomass-burning episodes than in the spring. The Ångström exponent showed a significant increase in the summer for both the in situ and vis-MFRSR data, suggesting an increase in combustion aerosols. Spring dust events are less distinguishable in the in situ data than the column measurement, suggesting that a significant amount of dust may be found above the elevation of SPL, 3220 m a.s.l. Twenty-two known case studies of intercontinental dust, regional dust, and biomass-burning events were investigated. These events were found to follow a similar pattern, in both aerosol loading and Ångström exponent, as the seasonal mean signal in both the vis-MFRSR and ground-based nephelometer. This data set highlights the wide-scale implications of a warmer, drier climate on visibility in the western USA.
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Hoffer, A., A. Tóth, I. Nyirő-Kósa, M. Pósfai, and A. Gelencsér. "Light absorption properties of laboratory generated tar ball particles." Atmospheric Chemistry and Physics Discussions 15, no. 12 (2015): 16215–34. http://dx.doi.org/10.5194/acpd-15-16215-2015.
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Abstract. Tar balls (TBs) are a specific particle type which is abundant in the global troposphere, in particular in biomass smoke plumes. These particles belong to the family of atmospheric brown carbon (BrC) which can absorb light in the visible range of the solar spectrum. Albeit TBs are typically present as individual particles in biomass smoke plumes, their absorption properties have been only indirectly inferred from field observations or calculations based on their electron energy-loss spectra. This is because in biomass smoke TBs coexist with various other particle types (e.g. organic particles with inorganic inclusions and soot, the latter is emitted mainly during flaming conditions) from which they cannot be physically separated; thus, a direct experimental determination of their absorption properties is not feasible. Very recently we have demonstrated that TBs can be generated in the laboratory from droplets of wood tar that resemble atmospheric TBs in all of their observed properties. As a follow-up study we have installed on-line instruments to our laboratory set-up generating pure TB particles to measure the absorption and scattering, as well as size distribution of the particles. In addition, samples were collected for transmission electron microscopy (TEM) and total carbon (TC) analysis. The effects of experimental parameters were also studied. The mass absorption coefficients of the laboratory generated TBs were found to be in the range of 0.8–3.0 m2 g−1 at 550 nm, with absorption Ångström exponents (AAE) between 2.7 and 3.4 (average 2.9) in the wavelength range 467–652 nm. The refractive index of TBs as derived from Mie calculations was about 1.84–0.21i at 550 nm. In the brown carbon continuum these values fall closer to those of soot than to other light-absorbing species such as humic-like substances (HULIS). Considering the abundance of TBs in biomass smoke and the global magnitude of biomass burning emissions, these findings may have substantial influence on the understanding of global radiative energy fluxes.
Dissertations / Theses on the topic "Ångström Laboratory"
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Kanestad, Linus, Gustaf Andersson, and Karl-Johan Hällgren. "Monitoring Air Quality in Ångström Cleanroom Laboratory." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-384803.
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The air quality in the Ångström cleanroom was to be measured for monitoring and control purposes, with the measurements displayed on a website. To do this several sensors, micro controllers, means of communication, and ways to host the server were investigated. In the end the chosen components were the DHT12 sensor, Arduino Nano micro controllers, 433MHz LoRa modules for communication, and a Raspberry Pi for data aggregation and website hosting. Four edge nodes with sensors were placed in locations of interest and transmitted data to the central node that hosted the website. For the website a development methodology called AJAX was used to handle data, and the HTML canvas element was used to display data. The system as a whole met its requirements.
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Svensson, Sjöbom Ludvig. "Channeling of MeV ion beams : Improving sample alignment at the tandem accelerator, Ångström laboratory." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-230962.
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At the Tandem accelerator in the Ångström laboratory, Uppsala, Rutherford backscattering spectrometry (RBS) is one of the methods used for thin film analysis, providing information on thickness and composition. The films are commonly grown on silicon substrates, whose crystal structure gives rise to channelling effects (a strong angular dependence in the intensity of the signal), which can cause faulty results. For other samples, channelling may also be used to get information on crystal structure and quality. This work demonstrates new functions to the existing software, aiming at minimizing these effects. The new methods have been tested by measurements both in channelling directions and in directions determined by the old method. In comparison with the earlier method the worst-case error is of order 80 %,commonly around 20 %, but it is possible to achieve an error which is not detectable. It is worth to note that the stated errors appear in tests oriented for maximum channelling, where effects without the new methods give an error corresponding to an apparent thin-film thickness almost 18 times that of the actual thickness.<br>Vid Tandemlabbet i Ångströmlaboratoriet, Uppsala, används bland annat Rutherford backscattering spectrometry (RBS) för att undersöka egenskaper, t.ex tjocklek och sammansättning, hos tunnfilmer som ofta är odlade på kiselsubstrat. Kiselkristallernas struktur ger upphov till kanaliseringseffekter, d.v.s starkt vinkelberoende intensitet, som i detta sammanhang kan ge felaktiga resultat. För andra prover kan kanaliseringseffekter användas för att få information om kristallstruktur och kvalitet. I det här arbetet demonstreras nyskrivna funktioner till befintlig mjukvara med syfte att minimera dessa effekter. De nya funktionerna har testats genom provtagningar i orienteringar som är gynnsamma och icke gynnsamma för kanalisering. Vid jämförelse med tidigare metoder ger de nya metoderna ett fel på i värsta fall ca. 80%, med bättre parametrar sjunker felet till ca 20 % och med rätt val av parametrar försvinner felet jämfört med tidigare metod. Värt att notera är att ovanstående maximala fel uppstår vid test orienterat för maximal kanalisering, där effekterna utan de nya metoderna ger ett fel på uppemot en faktor 18.
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Roland, Sandblad Maria, and Johannes Nilsson. "Kommunikation i byggprojektering : En studie över användandet av agila ärendehanteringsverktyg inom byggprojektering." Thesis, Uppsala universitet, Byggteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-355760.
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Byggbranschen är en konservativ bransch som länge har setts som motsträvig och traditionell. Detta har resulterat i en långsam utveckling av kommunikationsmönster och former för ledning och samverkan i branschen. En god kommunikation är en förutsättning för lyckade byggprojekt, varför det är av stort intresse att säkerställa en sådan. Denna rapport undersöker hur projekteringsbranschens kommunikation ser ut i dag och hur denna kan förbättras med hjälp av nätverksbaserade agila projektlednings- och kommunikationssystem. Den utreder även hur de i dag tillgängliga systemen anses fungera och dessa kan utveckla kommunikationen inom byggprojektering. Detta görs genom att studera hur användare av det agila projektlednings- och kommunikationssystemet Jira upplever att det fungerar och används. För att undersöka detta användes en kvalitativ metod i form av intervjuer med projektledare, BIM-samordnare och konsulter vid projekten. Denna intervjustudie kompletterades med en kvantitativ undersökning med ett internetbaserat formulär. Båda dessa studier är baserade på en inledande litteraturstudie. Genom att jämföra och analysera de två studierna har slutsatser dragits kring dagens och framtidens kommunikation. De visar att det finns en positiv inställning hos respondenterna till att använda nätverksbaserade kommunikationssystem hos respondenterna. Man kan se att kommunikationen inom byggprojektering kan förbättras och effektiviseras med hjälp av den typ av nätverksbaserade kommunikationssystem som behandlas i rapporten. Baserat på dessa resultat samt tidigare forskning kan man dra slutsatsen att detta nya kommunikationssätt kan leda till en sänkning av både kostnad och tidsåtgång vid byggprojekt. Utöver dessa frågeställningar och slutsatser har studien resulterat i ett antal rekommendationer för det företag som arbetet har skrivits för, Plan B AB. Dessa rekommendationer bildar ett underlag för en ytterligare utveckling av den Jira som används i deras nuvarande projekt vid Ångströmlaboratoriet.<br>The construction industry is a conservative industry that has for a long time been seen as recalcitrant and traditional, which has resulted in a slow development in business communication systems. This report covers how communication in project planning looks like today. The report also sheds light on opinions this branch of industry has of agile project leading- and communication systems. The study that was performed provided information on how the users view Jira, the agile project leading and communication system, and how it operates. To examine this a qualitative investigation was done in the form of interviews with project leaders, coordinators and consultants. To achieve a somewhat wider response group a survey was conducted through an Internet based questionnaire. The purpose of the study was to identify how coworkers in a Jirabased project feel about the program’s usefulness, if it helps or hinders productivity, if there are any possible features that need improving, and what the users think about the work environment of Jira. The result of the study was a positive opinion of both Jira as a software program and the overall change in project communication opportunities. The study also provided ideas on how to adapt Jira to the project planning branch of the construction industry. In addition, the study also resulted in suggestions on how the company can improve their usage of Jira in the case study for the thesis.
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Alfateh, Muhammad, and Yasir Ali Khan. "The effects of client’s requirements on construction innovation : A case study of the new Ångström Laboratory construction project." Thesis, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-398343.
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It has often been noted that the construction sector is quite inefficient in producing innovation especially when compared with other industries (Winch,2003). Moreover, innovation is becoming more and more a key competence in competitive environment of construction. Clients were found to play a pivotal role of clients in promoting construction innovation. However, how clients contribute to innovation is less investigated. Also, the construction project consists of a network of actors who interact with each other on different levels.These interactions affect and shape the requirements of the clients which then influence the innovation process of the construction project. It is important to take into account the several aspects of these interactions into consideration (Havenvid et al., 2016).The aim of this study is to investigate the role of clients in driving construction innovation by studying how their requirements may generate change within the project network. The second question aims to capture the different project actors’ views and perspective on construction innovation. This is done by conducting a case study on the construction project of the New Ångström Laboratory; an academic building of Uppsala University in Sweden. The data were collected following a qualitative approach. The results were analysed using ARA model (Actors, Activities and resources) framework.The study concludes that partnering can lead to an increase in productivity and efficiency of carrying out construction project work. The study also found that clients requirements can trigger innovation in a construction project. Another finding is that process innovation may generate greater effects on the actor's network than product innovations and suggest focusing on process innovation to accelerate the overall innovation process.