496 research outputs found
PV System Design in Different Climates: A BIM-Based Methodology
Get PDFOne of the goals of Agenda 2030 is to increase the share of renewable energy in the global energy mix. In this context, photovoltaic systems play a key role in the transition to clean energy. According to the International Energy Agency, in 2023, solar photovoltaic alone accounted for three-quarters of renewable capacity additions worldwide. Designing a performing photovoltaic system requires careful planning that takes into account various factors, both internal and external, in order to maximize energy production and optimize costs. In addition to the technical characteristics of the system (internal factors), the positionsand the shapes of external buildings and surrounding obstacles (external factors) have a significant impact on the output of photovoltaic systems. However, given the complexity of these environmental factors, they cannot be treated accurately in manual design practice. For this reason, this paper proposes a Building Information Modeling-based workflow for the design of a photovoltaic system that can guide the professional step-by-step throughout the design process, starting from the embryonic phase to the definitive, and therefore more detailed, one. The developed methodology allows for an in-depth analysis of the shading,the photovoltaic potential of the building, the performance of the photovoltaic system, and the costs for its construction in order to evaluate the appropriateness of the investment. The main aim of the paper is to create a standardized procedure applicable on a large scale for photovoltaic integration within Building Information Modeling workflows. The methodology is tested on two case studies, characterized by different architectural features and geographical positions
Performance analysis of optical code division multiple access (Ocdma) technique for metropolitan area network / Go Yun Ii
Get PDFOptical code division multiple access (OCDMA) allows signal to be transmitted in an
asynchronous manner, and promises high flexibility and simplicity with considerable
security. OCDMA harnesses an enormous bandwidth that provides high spectral
utilization and efficiency to support multiple, simultaneous active users. However, this
multiple access technique also has impairments such as multiple user interference (MUI)
and signal dispersion over distance. Thus, traditional metropolitan area network (MAN)
must be developed by considering system performance optimization.
Optimization is typically achieved by increasing code length and system complexity, or by
applying a high level of medium access control (MAC) supervision. Numerous code set
developments have been proposed to overcome the aforementioned impairments.
However, the proposed code sets have not been demonstrated in an actual optical system
that supports multiple users, particularly in a MAN, which has various noise sources and
MUI effects. Thus, the feasibility of these code sets cannot be verified with absolute
certainty. Conventional OCDMA architecture and encoding stage also exhibit various
deficiencies, including rigid synchronization, fiber delay line (FDL) accuracy issues,
stability resulting from environmental fluctuations, high costs, difficulty in fabrication,
lack of compactness, and spectral resolution issues. In this work, an optimized model is
presented as an enhanced solution to the limitations of the existing approach to be applied
in a MAN.
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This work proposes an integrated formulation that can be realized by three key aspects:
differential modulation, optimal optical code design, and the MUI reduction. This work
also addresses the development of an optimized OCDMA architecture that includes a
transmitter and a receiver, designed for a MAN. This thesis presents new grating
configurations for fiber Bragg grating (FBG) and investigates the possibility of achieving
system performance optimization in a MAN while considering the effects of various noise
sources, non-linearity, and dispersion. The encoding and decoding schemes are designed
based on the bipolar phase shift by using FBG. This work presents optimal grating
configurations that embodies the orthogonality aspect and demonstrates consistent
performance in different scenarios: intensity modulation-direct detection, external
modulation, non-return-to-zero (NRZ)-differential phase shift keying and NRZ-differential
quadrature phase shift keying, thus obtaining satisfactory agreement with the theoretical
analysis. This work requires minimum MAC supervision and eliminates the need for FDL
for queuing, which is in line with the requirement of real-time delivery.
System optimization is achieved by using an integrated formulation that embodies the
differential modulation approach, optimal grating configurations, and the MUI reduction.
This optimization approach is verified by the design parameters, and enhancement is
demonstrated by the performance parameters, which are over 2, 4, 8, and 12 users at bit
rates of 1.25 Gbps, 2.5 Gbps, 10 Gbps, and 40 Gbps, respectively, spanning from 5 km to
100 km. This integrated optimization formulation extends the maximum allowable singlemode
fiber span, which offers error-free transmission for BER ≤ 10-9 and accommodates
higher aggregated traffic capacity than the conventional approach
Optical Packet Switching Contention Resolution Based On A Hybrid Wavelength Conversion-Fiber Delay Line Scheme
Get PDFDue to the convergence of computer communication and telecommunication technology,
data traffic exceeds the telephony traffic. Thus, existing connection oriented and circuit
switched network will need to be upgraded toward optical packet switched network.
Optical packet switching has characteristics like high speed, data rate/data format
transparency and configurable. Wavelength Division Multiplexing is the technology of
combining a number of wavelengths in a single fiber. It is a tremendous trend to harness
larger bandwidth for enormous delivery. WDM optical devices for multiplexing and
switching in simple configuration are now available at a reasonable cost. It is a very
appealing solution for development of optical packet switching.
The issue of contention arises when two or more packets contend for the same output
port in a switch with the same wavelength, which results to packet loss. The packet loss
probability is addressed as the most inevitable and significant measurable performance
parameter with QoS provisioning that is dominated by wavelength contention in optical packet switches. In electronic domain packet switched network, the contention is
resolved by store and forward technique using the available electronic random access
memory (RAM). Due to the immaturity of optical memory storage technology, there is
no available ready-to-use optical random access memory.
In order to overcome this bottleneck, several approaches have been adopted to resolve
the contention problem from three domains: time, space and wavelength as stated: fiber
delay line (time), deflection routing (space) and wavelength conversion (wavelength).
Consequently, contention resolution in wavelength domain has attracted considerable
interest among the optical communications community instead of implementing optical
buffering and deflection routing that have been studied previously.
This thesis proposes a bufferless, single stage, non-blocking fully connected optical
packet switch for synchronous optical packet switching network, followed by a
prioritized scheduling algorithm in association with hybrid contention resolution
schemes. This iterative prioritized scheduling comprises of a set of preemptive selective
policies for contention resolution. It is a hybrid technique that integrates wavelength
conversion with feedback mechanism realized by fiber delay lines (FDL).
By means of simulation, the proposed scheme has been investigated and compared with
the conventional baseline scheme. A sensitive description of the satisfied packet loss
probability and average packet delay as a function of main design parameters such as
switch size, number of wavelengths, traffic load, degree of conversion and number of
fiber delay lines have been carried out with significant improvement.Simulation results proved that the proposed scheme is an efficient approach in resolving
packet contention with less complexity in execution. Relatively, number of wavelength,
traffic load and degree of conversion has significant impact to packet loss ratio. The
implementation of fiber delay lines results on average packet delay. Simulation results
demonstrated that the switch size mildly affect the performance parameter.
Respectively, packet loss ratio below 10-10 is obtained via simulation by the means of
wavelength conversion without conventional buffering delay. The packet loss ratio is
further reduced with the method as aforementioned with the insertion of fiber delay lines
where PLR below 10-13 is achieved, which is much lower than the benchmark value.
Furthermore, the obtained simulation results show that by classifying packet priority, the
proposed scheduling scheme and architecture are able to offer differentiated class of
service
Prognostic Value of Non-Invasive Global Myocardial Work in Asymptomatic Aortic Stenosis.
Get PDFpeer reviewedThis study aimed to evaluate the modification of non-invasive myocardial work (MW) indices related to aortic stenosis (AS) stages of cardiac damage and their prognostic value. The echocardiographic and outcome data of 170 patients, with asymptomatic moderate-to-severe AS and left ventricular ejection fraction (LVEF) ≥ 50%, and 50 age- and sex-comparable healthy controls were analysed. Primary endpoints were the occurrence of all-cause and cardiovascular death. Increased values of the global work index (GWI), global constructive work (GCW), and global wasted work (GWW) were observed in AS patients compared to controls (GWI: 2528 ± 521 vs. 2005 ± 302 mmHg%, GCW: 2948 ± 598 vs. 2360 ± 353 mmHg%, p < 0.001; GWW: 139 ± 90 vs. 90 ± 49 mmHg%, p = 0.005), with no changes in the global work efficiency. When patients were stratified according to the stages of cardiac damage, the GWI showed lower values in Stage 3-4 as compared to Stage 0 and Stage 2 (p = 0.024). During a mean follow-up of 30 months, 27 patients died. In multivariable Cox-regression analysis, adjusted for confounders, GWI (HR: 0.998, CI: 0.997-1.000; p = 0.034) and GCW (HR:0.998, CI: 0.997-0.999; p = 0.003) were significantly associated with excess mortality. When used as categorical variables, a GWI ≤ 1951 mmHg% and a GCW ≤ 2475 mmHg% accurately predicted all-cause and cardiovascular death at 4-year follow-up. In conclusion, in asymptomatic patients with moderate-to-severe AS, reduced values of GWI and GCW are associated with increased mortality. Therefore, the evaluation of MW indices may allow for a better identification of asymptomatic patients with moderate to severe AS and preserved LVEF whom are at increased risk of worse prognosis during follow-up
Evaluation of direct modulation and external modulation in temporal phase encoding system
No full text
On the association between land system architecture and land surface temperatures: Evidence from a Desert Metropolis - Phoenix, Arizona, U.S.A
No full textabstract: The relationship between the characteristics of the urban land system and land surface temperature (LST) has received increasing attention in urban heat island and sustainability research, especially for desert cities. This research generally employs medium or coarser spatial resolution data and primarily focuses on the effects of a few classes of land-cover composition and pattern at the neighborhood or larger level using regression models. This study explores the effects of land system architecture—composition and configuration, both pattern and shape, of fine-grain land-cover classes—on LST of single family residential parcels in the Phoenix, Arizona (southwestern USA) metropolitan area. A 1 m resolution land-cover map is used to calculate land architecture metrics at the parcel level, and 6.8 m resolution MODIS/ASTER data are employed to retrieve LST. Linear mixed-effects models quantify the impacts of land configuration on LST at the parcel scale, controlling for the effects of land composition and neighborhood characteristics. Results indicate that parcel-level land-cover composition has the strongest association with daytime and nighttime LST, but the configuration of this cover, foremost compactness and concentration, also affects LST, with different associations between land architecture and LST at nighttime and daytime. Given information on land system architecture at the parcel level, additional information based on geographic and socioeconomic variables does not improve the generalization capability of the statistical models. The results point the way towards parcel-level land-cover design that helps to mitigate the urban heat island effect for warm desert cities, although tradeoffs with other sustainability indicators must be considered.Corresponding Author:
Xiaoxiao Li
Arizona State University
[email protected]
Power management scheme development for large-scale solar grid integration
No full textAs solar power is an intermittent source of energy, it causes uncertainties when connected to the electrical grid. This work presents an optimised power management system for the integration of large-scale solar with improved voltage profile and power quality in compliance with the Malaysian Grid Code Requirements of 0.95–1.05 p.u. at the Point of Common Coupling. An integration of volt-var regulation using a smart inverter for solar photovoltaic system and optimised capacitor placements to attain a voltage profile close this Grid Code Requirements on all buses in the IEEE-9 bus will be carried out. The 116 MWp (peak) solar farm will be modelled to obtain the load profile of electricity injected into the grid on an annual hourly basis. This will be used to model the solar bus in the power system to test the changes in voltage profile, voltage deviations and reactive power flow. In the final results, the voltage profile improved to a range of 0.94–1.01 p.u. in the IEEE-9 bus even for the worse case scenarios of solar power penetration which happens from 12 to 1 pm
Techno-socio-economic analysis of fog-to-water solution for climate change hazard area:Sumba Island, Indonesia
No full textThe global demand for water has been growing rapidly in the last decade with a global population growth rate of 1.1% p.a., which is equivalent to 81 million people per year. Southeast Asian countries are facing severe water scarcity challenge due to their location in the tropics. In 2018, the Sumba Island experienced the highest temperature of 36°C and lesser rainfall of 911.1 mm3 per year and it was classified as a long dry island prone to drought due to dry winds from Australian desserts. This paper focuses on the perceived effect of water scarcity on livelihoods in the Mandahu Village, Indonesia, due to climate change. Sampling and survey covered rural households and the findings showed that the average household of 4 to 8 people consumed around 250 dm3 of water per day. The community relied on two main sources of clean water from two main springs. However, the prolonged dry season from May until December every year results in major challenges to access water and eventually affect the agricultural productivity. Hence, the feasibility of the fog collection technology has been investigated from technological, economic and social points of view as a reliable and cost-effective source of water. The outcome of this work will produce a feasibility statement for fog-to-water as an alternative solution counteracting water scarcity in the Sumba Island, a solution which can be replicated in other climate change stricken hot spots in Southeast Asia.</p
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