| 1. |
- A, Lavanya, et al.
(författare)
-
Smart energy monitoring and power quality performance based evaluation of 100-kW grid tied PV system
- 2023
-
Ingår i: Heliyon. - 2405-8440. ; 9:6
-
Tidskriftsartikel (refereegranskat)abstract
- Globally, the demand for energy from renewable sources is growing due to the increasing electricity consumption and the pollution of fossil fuels. The government has framed various policies to facilitate green energy generation, encouraging renewable energy source usage through PV installations in multiple sectors, including educational institutions. The primary objective of this paper is to propose a methodological approach for analysing the performance of the installed PV system on the rooftop of a university building in Tamil Nadu, India. The site selected is favourable for electricity generation from PV systems with an average global solar radiation of 5.82 kWh/m2day. Solar energy changes periodically with annual and daily variations and is not steady due to seasonal changes. The step-by-step performance assessment and the annual performance of the 100-kW solar PV system, which was instituted in 2019, with the forecasted parameters, are presented in this paper. Therefore, the assessment analysis is carried out in four phases: feasibility assessment, Energy yield assessment, Life cycle assessment, and Power quality assessment. To improve the solar PV output and efficiency, considering the solar irradiation, temperature, wind velocity, etc., PV yield is measured to evaluate the PV system's energy metrics. This paper also considers the carbon credits earned, solar power generated in the location, and the payback period. The power quality assessment is carried out in this paper to test the PV plant's compliance with effective grid integration.
|
|
| 2. |
- Aabel, Lise, et al.
(författare)
-
A TDD Distributed MIMO Testbed Using a 1-bit Radio-Over-Fiber Fronthaul Architecture
- 2024
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; In Press
-
Tidskriftsartikel (refereegranskat)abstract
- We present the uplink and downlink of a time-division duplex distributed multiple-input multiple-output (D-MIMO) testbed, based on a 1-bit radio-over-fiber architecture, which is low cost and scalable. The proposed architecture involves a central unit (CU) that is equipped with 1-bit digital-to-analog and analog-to-digital converters, operating at 10 GS/s. The CU is connected to multiple single-antenna remote radio heads (RRHs) via optical fibers, over which a binary radio frequency (RF) waveform is transmitted. In the uplink, a binary RF waveform is generated at the RRHs by a comparator, whose inputs are the received RF signal and a suitably designed dither signal. In the downlink, a binary RF waveform is generated at the CU via bandpass sigma-delta modulation. Our measurement results show that low error-vector magnitude (EVM) can be achieved in both the uplink and the downlink, despite 1-bit sampling at the CU. Specifically, for point-to-point over-cable transmission between a single user equipment (UE) and a CU equipped with a single RRH, we report, for a 10-MBd signal using single-carrier (SC) 16 quadratic-amplitude modulation (QAM) modulation, an EVM of 3.3% in the downlink, and of 4.5% in the uplink. We then consider a CU connected to three RRHs serving over the air two UEs, and show that, after over-the-air reciprocity calibration, a downlink zero-forcing precoder designed on the basis of uplink channel estimates at the CU achieves an EVM of 6.4% and 10.9% at UE 1 and UE 2, respectively. Finally, we investigate the ability of the proposed architecture to support orthogonal frequency-division multiplexing (OFDM) waveforms, and its robustness against both in-band and out-of-band interference.
|
|
| 3. |
- Aabel, Lise, 1992, et al.
(författare)
-
Distributed Massive MIMO via all-Digital Radio Over Fiber
- 2020
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2020-November, s. 319-323
-
Konferensbidrag (refereegranskat)abstract
- A crucial challenge in the implementation of distributed massive multiple-input multiple-output (MIMO) architectures is to provide phase coherence while, at the same time, limit the complexity of the remote-radio heads (RRHs), which is important for cost-efficient scalability. To address this challenge, we present in this paper a phase-coherent distributed MIMO architecture, based on off-the-shelf, low-cost components. In the proposed architecture, up- and down-conversion are carried out at the central unit (CU). The RRHs are connected to the CU by means of optical fibers carrying oversampled radio-frequency (RF) 1-bit signals. In the downlink, the 1-bit signal is generated via sigma-delta modulation. At the RRH, the RF signal is recovered from the 1-bit signal through a bandpass filter and a power amplifier, and then fed to an antenna. In the uplink, the 1-bit signal is generated by a comparator whose inputs are the low-noise-amplified received RF signal and a suitably designed dither signal. The performance of the proposed architecture is evaluated with satisfactory results both via simulation and measurements from a testbed.
|
|
| 4. |
- Aadland, Torgeir, et al.
(författare)
-
Mitigating the lack of prior entrepreneurial experience and exposure through entrepreneurship education programs
- 2023
-
Ingår i: International Journal of Entrepreneurial Behaviour and Research. - 1355-2554. ; 30:11, s. 19-44
-
Tidskriftsartikel (refereegranskat)abstract
- Purpose : To increase the understanding of how entrepreneurship education impacts entrepreneurial careers, the purpose of the paper is to investigate the role that a venture creation program (VCP) might have in mitigating or surpassing a lack of other antecedents of entrepreneurial careers. In particular, the authors focus on entrepreneurial pedigree and prior entrepreneurial experience. Design/methodology/approach : Data from graduates of VCPs at three universities in Northern Europe were collected through an online survey. Questions addressed graduate background prior to education, yearly occupational employment subsequent to graduation and graduates' own perceptions of entrepreneurial activity in employment positions. The survey was sent to 1,326 graduates and received 692 responses (52.2% response rate). Findings : The type of VCP, either independent (Ind-VCP) or corporate venture creation (Corp-VCP), influenced the mitigation of prior entrepreneurial experience. Prior entrepreneurial experience, together with Ind-VCP, made a career as self-employed more likely. However, this was not the case for Corp-VCP in subsequently choosing intrapreneurial careers. Entrepreneurial pedigree had no significant effect on career choice other than for hybrid careers. Research limitations/implications : Entrepreneurial experience gained from VCPs seems to influence graduates toward future entrepreneurial careers. Evidence supports the conclusion that many VCP graduates who lack prior entrepreneurial experience or entrepreneurial pedigree can develop sufficient entrepreneurial competencies through the program. Originality/value : This study offers novel evidence that entrepreneurship education can compensate for a lack of prior entrepreneurial experience and exposure for students preparing for entrepreneurial careers.
|
|
| 5. |
- Aadland, Torgeir, et al.
(författare)
-
The gender gap in entrepreneurship: The role of the relative pay off from entrepreneurship
- 2022
-
Ingår i: RENT Proceedings. - 2219-5572. ; 2022
-
Konferensbidrag (refereegranskat)abstract
- Objectives Entrepreneurship education garners increasing interest, with current trends showing a greater number of women applying. However, less is known about how attendees experience the use of their education post-education in general, in regard to the relative pay-off in graduates’ subsequent careers. Similarly, the extent to which applied entrepreneurial competencies gained may differentiate in careers of women compared to men is also understudied. Research on the distinct gender populations, focusing on occupational differences have limited space in literature. The objective of this paper is to investigate the career metrics in income and work-life balance, comparing and contrasting a population of entrepreneurship education graduates, along gender lines. Literature review Literature points an underlying gender bias in entrepreneurship, where opportunity-based entrepreneurial careers and self-concept of an entrepreneur has predominantly been studied from a male perspective. For example, studies have highlighted aspects of gender bias towards women engaging in opportunity-based entrepreneurship such as difficulty in obtaining necessary funding for growth, challenges in accessing entrepreneurial networks, lower levels of self-belief and self-efficacy regarding entrepreneurial activity, differences in education, and imbalance in work expectations relative to home life. However, these studies have predominantly focused on a new firm formation definition of entrepreneurship. The utilization of entrepreneurial competencies, as developed through entrepreneurship education that focuses on experience- and reflection-based approaches to learning, have in recent studies shown to be equally important for intrapreneurs as self-employed entrepreneurs. This reflects the broader contextual spread of applied entrepreneurial competence in graduate careers. The entrepreneurial careers of the female graduates who engage in ideation and implementation of new business activity after an entrepreneurship education, may it be in firm formation or in employed roles, remains understudied. Therefore, the question is raised: What is the relative pay-off (i.e., income and work-life balance) of entrepreneurship in relation to occupational choice and gender for graduates of entrepreneurship educations? Approach/Method Alumni from three master-level venture creation programs at three universities in Northern Europe were contacted for this study. From a total population of 1103 (graduating between 1997-2018),531 graduates responded, resulting in a response rate of 48.1 percent. The gender distribution in the total population is 28.5 percent female, and within the respondent sample it is 29.5 percent female. Two dimensions of career progress: income and work-life balance, was then analyzed with a set of dependent variables and control variables in ordinal regression. These regressors include career start-up experience and to what extent ideation and implementation of new business activity in employed occupations impacts the independent variables. Models are based on separate regressions on men and women with the purpose to highlight gendered differences in career progression and what regressors contributes to this. Results/Findings The findings were divided into separate sets by the two dependent variables, income and work-life balance. For income levels, career length is shared by both men and women as being a strong predictor. Beyond that, the regression analysis gives different versions for women and men of what contributes to a high income. Men in paid employment (as conventional employees or intrapreneurs) earns more than their self-employed and hybrid (combining employment and self-employment) peers. For women, there is no significant differences among the occupations. For both genders, type of industry is also influential towards the income level. Work-life balance generated regressions that points towards small influences of the regressors for women. For men, having a partner indicates a higher work-life balance, which is not significant for women. Also, having less work related to entrepreneurial competencies (i.e., being conventional employed), results in a more positive work-life balance. Value & Implications Entrepreneurship education is shown to have many positive impacts on subsequent careers. However, entrepreneurial competencies developed through education do not appear to counteract the general gender differences seen in society, as differentiation between male and female graduates is evident through the study. Where previous research has focused on studying these differences, this study instead focuses on how income and work-life balance unfolds across gender categories of venture creation program graduates. These programs have shown to produce graduates who have developed and later utilized entrepreneurial competencies to a high degree in both employed and self-employed contexts. Though in the subsequent careers, the progression of income and work-life balance falls under different mechanisms depending on the gender of the graduate. Women seems to have more stable progression compared to men, with less variation between occupations. Though a limitation lies within that the regressors builds lesser models for women compared to men. This indicates that future research should consider an expanded set of variables or focus on designing qualitative studies target towards career progression of female entrepreneurs. In conclusion this study informs the need to consider the entrepreneurial career progression of women as different compared to their male graduates.
|
|
| 6. |
- Aalbers, J., et al.
(författare)
-
A next-generation liquid xenon observatory for dark matter and neutrino physics
- 2023
-
Ingår i: Journal of Physics G: Nuclear and Particle Physics. - : IOP Publishing. - 0954-3899 .- 1361-6471. ; 50:1
-
Forskningsöversikt (refereegranskat)abstract
- The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for weakly interacting massive particles, while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector.
|
|
| 7. |
- Aalto, Susanne, 1964, et al.
(författare)
-
ALMA resolves the remarkable molecular jet and rotating wind in the extremely radio-quiet galaxy NGC 1377
- 2020
-
Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 640
-
Tidskriftsartikel (refereegranskat)abstract
- Submillimetre and millimetre line and continuum observations are important in probing the morphology, column density, and dynamics of the molecular gas and dust around obscured active galactic nuclei (AGNs) and their mechanical feedback. With very high-resolution (0.'' 02x0.'' 03 (2x3 pc)) ALMA 345 GHz observations of CO 3-2, HCO+ 4-3, vibrationally excited HCN 4-3 nu (2)=1f, and continuum we have studied the remarkable, extremely radio-quiet, molecular jet and wind of the lenticular galaxy NGC 1377. The outflow structure is resolved, revealing a 150 pc long, clumpy, high-velocity (similar to 600 km s(-1)), collimated molecular jet where the molecular emission is emerging from the spine of the jet with an average diameter of 3-7 pc. The jet widens to 10-15 pc about 25 pc from the centre, which is possibly due to jet-wind interactions. A narrow-angle (50 degrees -70 degrees), misaligned and rotating molecular wind surrounds the jet, and both are enveloped by a larger-scale CO-emitting structure at near-systemic velocity. The jet and narrow wind have steep radial gas excitation gradients and appear turbulent with high gas dispersion (sigma> 40 km s(-1)). The jet shows velocity reversals that we propose are caused by precession, or more episodic directional changes. We discuss the mechanisms powering the outflow, and we find that an important process for the molecular jet and narrow wind is likely magneto-centrifugal driving. In contrast, the large-scale CO-envelope may be a slow wind, or cocoon that stems from jet-wind interactions. An asymmetric, nuclear r similar to 2 pc dust structure with a high inferred molecular column density N(H-2) similar or equal to 1.8x10(24) cm(-2) is detected in continuum and also shows compact emission from vibrationally excited HCN. The nuclear dust emission is hot (T-d> 180 K) and its luminosity is likely powered by a buried AGN. The lopsided structure appears to be a warped disk, which is responsible for a significant part of the nuclear obscuration and possibly formed as a result of uneven gas inflows. The dynamical mass inside r=1.4 pc is estimated to 9(-3)(+2) x 10(6)M(circle dot) 9 - 3 + 2 x 10 6 M circle dot , implying that the supermassive black hole (SMBH) has a high mass with respect to the stellar velocity dispersion of NGC 1377. We suggest that the SMBH of NGC 1377 is currently in a state of moderate growth, at the end of a more intense phase of accretion and also evolving from a state of more extreme nuclear obscuration. The nuclear growth may be fuelled by low-angular momentum gas inflowing from the gas ejected in the molecular jet and wind. Such a feedback-loop of cyclic outflows and central accretion could explain why there is still a significant reservoir of molecular gas in this ageing, lenticular galaxy. A feedback-loop would be an effective process in growing the nuclear SMBH and thus would constitute an important phase in the evolution of NGC 1377. This also invites new questions as to SMBH growth processes in obscured, dusty galaxies.
|
|
| 8. |
- Aalto, Susanne, 1964, et al.
(författare)
-
Extragalactic Science with the Orbiting Astronomical Satellite Investigating Stellar Systems (OASIS) Observatory
- 2023
-
Ingår i: Space Science Reviews. - : Springer Science and Business Media LLC. - 0038-6308 .- 1572-9672. ; 219:1
-
Forskningsöversikt (refereegranskat)abstract
- The Orbiting Astronomical Satellite for Investigating Stellar Systems (OASIS), a proposed Astrophysics MIDEX-class mission concept, has an innovative 14-meter diameter inflatable primary mirror that will provide the sensitivity to study far-infrared continuum and line emission from galaxies at all redshifts with high spectral resolution heterodyne receivers. OASIS will have the sensitivity to follow the water trail from galaxies to the comets that create oceans. It will bring an understanding of the role of water in galaxy evolution and its part of the oxygen budget, by measuring water emission from local to intermediate redshift galaxies, observations that have not been possible from the ground. Observation of the ground-state HD line will accurately measure gas mass in a wide variety of astrophysical objects. Thanks to its exquisite spatial resolution and sensitivity, OASIS will, during its one-year baseline mission, detect water in galaxies with unprecedented statistical significance. This paper reviews the extragalactic science achievable and planned with OASIS.
|
|
| 9. |
- Aalto, Susanne, 1964, et al.
(författare)
-
OH megamaser emission in the outflow of the luminous infrared galaxy Zw049.057
- 2022
-
Ingår i: Proceedings of the International Astronomical Union. - 1743-9213 .- 1743-9221. ; 18, s. 40-44
-
Konferensbidrag (refereegranskat)abstract
- High resolution (0.”26 × 0.”13 (70 × 35 pc)) L-band (18 cm) OH megamaser (OHM) e-Merlin observations of the LIRG Zw049.057 show that the emission is emerging from a low velocity outflowing structure - which is foreground to a fast, dense and collimated molecular outflow detected by ALMA. The extremely dusty compact obscured nucleus (CON) of Zw049.057 has no (or only little) OHM emission associated with it - possibly because of too high number densities that quench the OHM. In contrast we detect 6 cm H2CO emission primarily from the CON-region. We suggest that the OHM-region of Zw049.057 is not directly associated with star formation, but instead occurs in a wide-angle, slow outflow that surrounds the fast and dense outflow. The OHM is pumped by IR emission that likely stems from activities in the nucleus. We briefly discuss how OHM emission can be used as a probe of LIRG-CON galaxies.
|
|
| 10. |
- Aarrestad, Thea, et al.
(författare)
-
Fast convolutional neural networks on FPGAs with hls4ml
- 2021
-
Ingår i: Machine Learning: Science and Technology. - : IOP Publishing. - 2632-2153. ; 2:4
-
Tidskriftsartikel (refereegranskat)abstract
- We introduce an automated tool for deploying ultra low-latency, low-power deep neural networks with convolutional layers on field-programmable gate arrays (FPGAs). By extending the hls4ml library, we demonstrate an inference latency of 5 mu s using convolutional architectures, targeting microsecond latency applications like those at the CERN Large Hadron Collider. Considering benchmark models trained on the Street View House Numbers Dataset, we demonstrate various methods for model compression in order to fit the computational constraints of a typical FPGA device used in trigger and data acquisition systems of particle detectors. In particular, we discuss pruning and quantization-aware training, and demonstrate how resource utilization can be significantly reduced with little to no loss in model accuracy. We show that the FPGA critical resource consumption can be reduced by 97% with zero loss in model accuracy, and by 99% when tolerating a 6% accuracy degradation.
|
|
