1,187 research outputs found
Dominating sets and connected dominating sets in dynamic graphs
In this paper we study the dynamic versions of two basic graph problems: Minimum Dominating Set and its variant Minimum Connected Dominating Set. For those two problems, we present algorithms that maintain a solution under edge insertions and edge deletions in time O( 06\ub7polylog n) per update, where 06 is the maximum vertex degree in the graph. In both cases, we achieve an approximation ratio of O(log n), which is optimal up to a constant factor (under the assumption that P 6= NP). Although those two problems have been widely studied in the static and in the distributed settings, to the best of our knowledge we are the first to present efficient algorithms in the dynamic setting. As a further application of our approach, we also present an algorithm that maintains a Minimal Dominating Set in O(min( 06, m)) per update
Effective Edge-Fault-Tolerant Single-Source Spanners via Best (or Good) Swap Edges
Computing \emph{all best swap edges} (ABSE) of a spanning tree of a given
-vertex and -edge undirected and weighted graph means to select, for
each edge of , a corresponding non-tree edge , in such a way that the
tree obtained by replacing with enjoys some optimality criterion (which
is naturally defined according to some objective function originally addressed
by ). Solving efficiently an ABSE problem is by now a classic algorithmic
issue, since it conveys a very successful way of coping with a (transient)
\emph{edge failure} in tree-based communication networks: just replace the
failing edge with its respective swap edge, so as that the connectivity is
promptly reestablished by minimizing the rerouting and set-up costs. In this
paper, we solve the ABSE problem for the case in which is a
\emph{single-source shortest-path tree} of , and our two selected swap
criteria aim to minimize either the \emph{maximum} or the \emph{average
stretch} in the swap tree of all the paths emanating from the source. Having
these criteria in mind, the obtained structures can then be reviewed as
\emph{edge-fault-tolerant single-source spanners}. For them, we propose two
efficient algorithms running in and time, respectively, and we show that the guaranteed (either
maximum or average, respectively) stretch factor is equal to 3, and this is
tight. Moreover, for the maximum stretch, we also propose an almost linear time algorithm computing a set of \emph{good} swap edges,
each of which will guarantee a relative approximation factor on the maximum
stretch of (tight) as opposed to that provided by the corresponding BSE.
Surprisingly, no previous results were known for these two very natural swap
problems.Comment: 15 pages, 4 figures, SIROCCO 201
Kajian Sistem Drainase Patukangan-pegulon Kabupaten Kendal
Kecamatan Patukangan – Pegulon adalah kawasan indsutri dan Perumahan yang berada di pusat Kota Kendal. Permasalahan banjir menyebabkan potensi ekonomi, sosial, dan lingkungan tidak dapat berkembang. Sistem draianse yang tepat adalah salah satu alternatif untuk menanggulangi permasalahan banjir di wilayah Kecamatan Patukangan – Pegulon. Kajian sistem drainase meliputi perencanaan ulang dimensi saluran, pintu air, dan sistem pipa – pompa.Data curah hujan yang digunakan untuk Sungai Kendal adalah data curah hujan dari tahun 2000 sampai 2015 dengan menggunakan stasiun hujan Sedayu, Karangtengah, dan Kedugsari. Analisis debit banjir di Sungai Kendal menggunakan metode HSS Nakayasu dengan periode ulang 20 tahun dan diperoleh debit banjir sebesar 68,19 m3/s.. Analisis pengaruh backwater dari Laut Jawa menggunakan metode tahapan langsung. Pengaruh backwater hanya sampai pada jarak 5543,88 meter dari muara sungai. Jarak outlet saluran drainase dari muara sungai adalah 6096 meter, sehingga titik outlet tidak terpengaruh backwater.Debit banjir rencana pada saluran drainase didapatkan dengan rumus Mononobe dengan periode ulang 5 tahun dan diperoleh debit banjir rencana sebesar 4,8 m3/s. Berdasar debit banjir rencana ini, dimensi saluran drainase yang baru adalah : 1,0 x 1,0 m ; 0,9 x 0,7 m ; 0,7 x 0,7 m ; 0,8 x 0,7 m ; 1,6 x 1,5 m ; 1,0 x 0,7 m ; dan 1,3 x 1,0 m. Pintu air direncanakan pada titik outlet saluran karena elevasi muka air Sungai Kendal lebih tinggi dibandingkan elevasi muka air di saluran drainase, dengan elevasi muka air Sungai Kendal + 5,9 m dan elevasi muka air saluran drainase adalah + 4,63 m. Dimensi pintu air yang direncanakan adalah 1,6 x 1,5 m. Sistem pipa - pompa direncanakan berjumlah 3 buah dengan kapasitas tiap pompa adalah 2,0 m3/s dan diameter pipa adalah 0,5 m
Stanja Jπ = 2+ i 0+, T = 0 8Be na energijama pobuđenja oko 20 MeV
The 7Li(d, αα)n reaction induced by deuterons of an incident energy of 7 MeV has been used to excite the 8Be nucleus in the region of excitation energy Ex of about 20 MeV. Each of the obtained αα coincidence spectra was fitted by an incoherent sum of the Jπ=2+ and 0+, T=0 8Be levels at Ex=20.1 and 20.2 MeV, respectively. The results show that the experimental data are well fitted when the G values deduced for these levels are 0.90 and 0.70 MeV, respectively.Reakcija 7Li (d, αα) n inducirana deuteronima energije 7 MeV je iskorištena za proučavanje jezgre 8Be na energijama pobuđenja Ex oko 20 MeV. Koincidentni αα spektri poravnani su nekoherentnim zbrojem stanja Jπ = 2 + na Ex = 20, 1 MeV i Jπ = 0+ na Ex = 20,2 MeV. Rezultati pokazuju da su eksperimentalni podaci najbolje opisani ako se za širine navedenih stanja uzmu vrijednosti 0,90 MeV odnosno 0, 70 Me V
The direct influence of retinal degeneration on electrical stimulation efficacy: Significant implications for retinal prostheses
Photoreceptor loss and inner retinal network remodeling severely impacts the ability of retinal prosthetic devices to create artificial vision. We developed a computational model of a degenerating retina based on rodent data and tested its response to retinal electrical stimulation. This model includes detailed network connectivity and diverse neural intrinsic properties, capable of exploring how the degenerated retina influences the performance of electrical stimulation during the degeneration process. Our model suggests the possibility of quantitatively modulating retinal ON and OFF pathways between phase II and III of retinal degeneration without requiring any differences between ON and OFF RGC intrinsic cellular properties. The model also provided insights about how remodeling events influence stage-dependent differential electrical responses of ON and OFF pathways.Clinical Relevance-This data-driven model can guide future development of retinal prostheses and stimulation strategies that may benefit patients at different stages of retinal disease progression, particularly in the early and mid-stages, thus increasing their global acceptance
Methanol synthesis: A distributed production concept based on biogas plants
Today biogas produced from anaerobic digestion is used mainly for thermic and electric energy production. Its use as raw material for syngas production and further upgrading to chemical products like methanol (MeOH), dimethyl ether (DME) or acetic acid could be an interesting option as process intensification. In this work the sustainability of a Biogas-to-MeOH (BtoMeOH) or Biogas-to-DME (BtoDME) process was studied. The biogas feedstock of the Combined Heat, Power and Chemicals (CHPC) is equivalent to the production of 1 MWe in a Combined Heat and Power Plant (CHP). Biogas is converted using a reformer into syngas to produce methanol. The plant was designed considering mild conditions for chemical production and the energy necessary to reactors was generated using a fraction of the inlet biogas. This process was studied using the Simulation Suite PRO/II\uae by Schneider-Electric Simulation Science. The reformer and the methanol reactor productivity were evaluated with the experimental data obtained through bench scale plants. An economic analysis was performed to assess the sustainability of these new processes, capital and operative costs of the plants were evaluated using the Guthrie\u2019s method. The Biogas-to-MeOH process can produce up to 297 kg h-1 of methanol with recycle. The biogas necessary to supply the energy demand of the plant is 192 kg h-1, a third of the inlet feedstock. For the Biogas-to-DME process the energy demand is similar while the DME production is 173 kg h-1. The preliminary economic evaluation shows that the main item for the capital costs are reactors and compressors and the breakeven point of both processes is 3 years. Despite the lower productivity, DME process is more convenient due to a higher market value
Evaluation of acute cardiovascular effects of immediate-release methylphenidate in children and adolescents with attention-deficit hyperactivity disorder
Attention-deficit hyperactivity disorder is a frequent condition in children and often extends into adulthood. Use of immediate-release methylphenidate (MPH) has raised concerns about potential cardiovascular adverse effects within a few hours after administration. This study was carried out to investigate acute effects of MPH on electrocardiogram (ECG) in a pediatric population. A total of 54 consecutive patients with attention-deficit hyperactivity disorder (51 males and 3 females; mean age =12.14±2.6 years, range 6–19 years), receiving a new prescription of MPH, underwent a standard ECG 2 hours before and after the administration of MPH 10 mg per os. Basal and posttreatment ECG parameters, including mean QT (QT interval when corrected for heart rate [QTc]), QTc dispersion (QTd) interval duration, T-peak to T-end (TpTe) intervals, and TpTe/QT ratio were compared. Significant modifications of both QTc and QTd values were not found after drug administration. QTd fluctuated slightly from 25.7±9.3 milliseconds to 25.1±8.4 milliseconds; QTc varied from 407.6±12.4 milliseconds to 409.8±12.7 milliseconds. A significant variation in blood pressure (systolic blood pressure 105.4±10.3 vs 109.6±11.5; P<0.05; diastolic blood pressure 59.2±7.1 vs 63.1±7.9; P<0.05) was observed, but all the data were within normal range. Heart rate moved from 80.5±15.5 bpm to 87.7±18.8 bpm. No change in TpTe values was found, but a statistically significant increase in TpTe/QTc intervals was found with respect to basal values (0.207±0.02 milliseconds vs 0.214±0.02 milliseconds; P<0.01). The findings of this study show no significant changes in ECG parameters. TpTe values can be an additional parameter to evaluate borderline cases
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