194 research outputs found
Optimization Models for islanded micro-grids: A comparative analysis between linear programming and mixed integer programming
This paper presents a comparison of optimization methods applied to islanded micro-grids including renewable energy sources, diesel generators and battery energy storage systems. In particular, a comparative analysis between an optimization model based on linear programming and a model based on mixed integer programming has been carried out. The general formulation of these models has been presented and applied to a real case study micro-grid installed in Somalia. The case study is an islanded micro-grid supplying the city of Garowe by means of a hybrid power plant, consisting of diesel generators, photovoltaic systems and batteries. In both models the optimization is based on load demand and renewable energy production forecast. The optimized control of the battery state of charge, of the spinning reserve and diesel generators allows harvesting as much renewable power as possible or to minimize the use of fossil fuels in energy production
Puzzling large-scale polarization in the galaxy cluster Abell 523
Large-scale magnetic fields reveal themselves through diffuse synchrotron
sources observed in galaxy clusters such as radio halos. Total intensity
filaments of these sources have been observed in polarization as well, but only
in three radio halos out of about one hundred currently known. In this paper we
analyze new polarimetric Very Large Array data of the diffuse emission in the
galaxy cluster Abell 523 in the frequency range 1-2 GHz. We find for the first
time evidence of polarized emission on scales of ~ 2.5 Mpc. Total intensity
emission is observed only in the central part of the source, likely due to
observational limitations. To look for total intensity emission beyond the
central region, we combine these data with single-dish observations from the
Sardinia Radio Telescope and we compare them with multi-frequency total
intensity observations obtained with different instruments, including the LOw
Frequency ARray and the Murchison Widefield Array. By analysing the rotation
measure properties of the system and utilizing numerical simulations, we infer
that this polarized emission is associated with filaments of the radio halo
located in the outskirts of the system, in the peripheral region closest to the
observer.Comment: 14 pages, 12 figures, accepted for publication on MNRA
Minimally invasive vs. open segmental resection of the splenic flexure for cancer: a nationwide study of the Italian Society of Surgical Oncology-Colorectal Cancer Network (SICO-CNN)
Background Evidence on the efficacy of minimally invasive (MI) segmental resection of splenic flexure cancer (SFC) is not available, mostly due to the rarity of this tumor. This study aimed to determine the survival outcomes of MI and open treatment, and to investigate whether MI is noninferior to open procedure regarding short-term outcomes. Methods This nationwide retrospective cohort study included all consecutive SFC segmental resections performed in 30 referral centers between 2006 and 2016. The primary endpoint assessing efficacy was the overall survival (OS). The secondary endpoints included cancer-specific mortality (CSM), recurrence rate (RR), short-term clinical outcomes (a composite of Clavien-Dindo > 2 complications and 30-day mortality), and pathological outcomes (a composite of lymph nodes removed >= 12, and proximal and distal free resection margins length >= 5 cm). For these composites, a 6% noninferiority margin was chosen based on clinical relevance estimate. Results A total of 606 patients underwent either an open (208, 34.3%) or a MI (398, 65.7%) SFC segmental resection. At univariable analysis, OS and CSM were improved in the MI group (log-rank test p = 0.004 and Gray's tests p = 0.004, respectively), while recurrences were comparable (Gray's tests p = 0.434). Cox multivariable analysis did not support that OS and CSM were better in the MI group (p = 0.109 and p = 0.163, respectively). Successful pathological outcome, observed in 53.2% of open and 58.3% of MI resections, supported noninferiority (difference 5.1%; 1-sided 95%CI - 4.7% to infinity). Successful short-term clinical outcome was documented in 93.3% of Open and 93.0% of MI procedures, and supported noninferiority as well (difference - 0.3%; 1-sided 95%CI - 5.0% to infinity). Conclusions Among patients with SFC, the minimally invasive approach met the criterion for noninferiority for postoperative complications and pathological outcomes, and was found to provide results of OS, CSM, and RR comparable to those of open resection
Colorectal Cancer Stage at Diagnosis Before vs During the COVID-19 Pandemic in Italy
IMPORTANCE Delays in screening programs and the reluctance of patients to seek medical
attention because of the outbreak of SARS-CoV-2 could be associated with the risk of more advanced
colorectal cancers at diagnosis.
OBJECTIVE To evaluate whether the SARS-CoV-2 pandemic was associated with more advanced
oncologic stage and change in clinical presentation for patients with colorectal cancer.
DESIGN, SETTING, AND PARTICIPANTS This retrospective, multicenter cohort study included all
17 938 adult patients who underwent surgery for colorectal cancer from March 1, 2020, to December
31, 2021 (pandemic period), and from January 1, 2018, to February 29, 2020 (prepandemic period),
in 81 participating centers in Italy, including tertiary centers and community hospitals. Follow-up was
30 days from surgery.
EXPOSURES Any type of surgical procedure for colorectal cancer, including explorative surgery,
palliative procedures, and atypical or segmental resections.
MAIN OUTCOMES AND MEASURES The primary outcome was advanced stage of colorectal cancer
at diagnosis. Secondary outcomes were distant metastasis, T4 stage, aggressive biology (defined as
cancer with at least 1 of the following characteristics: signet ring cells, mucinous tumor, budding,
lymphovascular invasion, perineural invasion, and lymphangitis), stenotic lesion, emergency surgery,
and palliative surgery. The independent association between the pandemic period and the outcomes
was assessed using multivariate random-effects logistic regression, with hospital as the cluster
variable.
RESULTS A total of 17 938 patients (10 007 men [55.8%]; mean [SD] age, 70.6 [12.2] years)
underwent surgery for colorectal cancer: 7796 (43.5%) during the pandemic period and 10 142
(56.5%) during the prepandemic period. Logistic regression indicated that the pandemic period was
significantly associated with an increased rate of advanced-stage colorectal cancer (odds ratio [OR],
1.07; 95%CI, 1.01-1.13; P = .03), aggressive biology (OR, 1.32; 95%CI, 1.15-1.53; P < .001), and stenotic
lesions (OR, 1.15; 95%CI, 1.01-1.31; P = .03).
CONCLUSIONS AND RELEVANCE This cohort study suggests a significant association between the
SARS-CoV-2 pandemic and the risk of a more advanced oncologic stage at diagnosis among patients
undergoing surgery for colorectal cancer and might indicate a potential reduction of survival for
these patients
Modified droop control for the optimal management of the battery systems in isolated microgrids
Microgrids are often made up with Hybrid Power Plants (HPPs), which include storage batteries. To enhance system efficiency, it is important to manage the batteries so as to avoid that one gets charged at other batteries' expense. To reduce costs and increase robustness, a Microgrid Controller that communicates with all the HPPs can be avoided and the droop control is often adopted for the HPPs' interface inverters. This paper proposes a method to change the droop coefficients so as to get the described target with no communication available between the HPPs. Theoretical analysis is validated through a simulation carried out on a study case
Harmonic Analysis of Output Filters for Grid Connected Converters in Battery Energy Storage Systems
Battery Energy Storage Systems, as well as many distributed generation systems, use voltage source inverter as interface with the grid. These converters require a filtering section to reduce current harmonics injected to the grid. Usually, harmonic filter is a series inductance connected between grid and inverter. Higher order filters can provide better harmonic attenuation at lower switching frequency and reduce filter size, with potential benefits for high power applications. This paper deals with the sizing and the frequency response of three different harmonic filters suitable to reduce the ripple in the grid current waveform. Dynamic simulations of a 100 kW Battery Energy Storage System highlight the better performance of high order filters
Blue Ocean or Dry Desert? Blockchain & Bitcoin impact on Tourism Industry
The technological innovation has yielded great opportunities to expand and innovate the
scope of services offered. This is particularly true for tourism, which has always been
characterized by extensive innovativeness. The pace at which technological innovations
diffuse within a specific sector depends on a variety of factors, among which the influence of
peers and of relevant actors. The present study explores the level of interest about these new
technologies on social media with the aim to explore the dynamics of reciprocal networking
influence in technological diffusion. To capture the attitudes expressed in the industry, the
study analyzes the ongoing discussions on Twitter as a proxy for the actors\u2019 interest.
Through a social network analysis of the flow of tweets, the analysis maps the current online
discourse about new technologies diffusion. Moreover, the sentiment analysis draws the
current perceptions towards the diffusion of new technologies.
While previous research is focused on the users\u2019 perception toward the development of new
technologies in tourism, the aim of this study is to investigate the dynamics underneath the
level of diffusion of information and awareness about these new technologies, which still
represents an unexplored area of research. Thus, the paper contributes to the literature on
new technology diffusion by intercepting current social media debate and literature studies
focused on the diffusion of new technologies in tourism. The paper also highlights the role of
knowledge broker in influencing this public debate
Blue Ocean or Dry Desert? Blockchain and Bitcoin Impact on Tourism Industry
The technological innovation has yielded great opportunities to expand and innovate the scope of services offered. This is particularly true for tourism, which has always been characterized by extensive innovativeness. The pace at which technological innovations diffuse within a specific sector depends on a variety of factors, including the influence of peers and relevant actors. The present study explores the level of interest about these new technologies on social media with the aim to explore the dynamics of reciprocal networking influence in technological diffusion. To capture the attitudes expressed in the industry, the study analyzes the ongoing discussions on Twitter as a proxy for the actors\u2019 interest. Through a social network analysis of the flow of tweets, the analysis maps the current online discourse about new technologies diffusion. Moreover, the sentiment analysis draws the current perceptions toward the diffusion of new technologies. While previous research is focused on the users\u2019 perception toward the development of new technologies in tourism, the aim of this study is to investigate the dynamics underneath the level of diffusion of information and awareness about these new technologies, which still represents an unexplored area of research. Thus, the paper contributes to the literature on new technology diffusion by intercepting current social media debate and literature studies focused on the diffusion of new technologies in tourism. The paper also highlights the role of knowledge broker in influencing this public debate
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