Understanding the Properties of the BitTorrent Overlay

In this paper, we conduct extensive simulations to understand the properties of the overlay generated by BitTorrent. We start by analyzing how the overlay properties impact the efficiency of BitTorrent. We focus on the average peer set size (i.e., average number of neighbors), the time for a peer to reach its maximum peer set size, and the diameter of the overlay. In particular, we show that the later a peer arrives in a torrent, the longer it takes to reach its maximum peer set size. Then, we evaluate the impact of the maximum peer set size, the maximum number of outgoing connections per peer, and the number of NATed peers on the overlay properties. We show that BitTorrent generates a robust overlay, but that this overlay is not a random graph. In particular, the connectivity of a peer to its neighbors depends on its arriving order in the torrent. We also show that a large number of NATed peers significantly compromise the robustness of the overlay to attacks. Finally, we evaluate the impact of peer exchange on the overlay properties, and we show that it generates a chain-like overlay with a large diameter, which will adversely impact the efficiency of large torrents

Swarming Overlay Construction Strategies

Swarming peer-to-peer systems play an increasingly instrumental role in Internet content distribution. It is therefore important to better understand how these systems behave in practice. Recent research efforts have looked at various protocol parameters and have measured how they affect system performance and robustness. However, the importance of the strategy based on which peers establish connections has been largely overlooked. This work utilizes extensive simulations to examine the default overlay construction strategy in BitTorrent systems. Based on the results, we identify a critical parameter, the maximum allowable number of outgoing connections at each peer, and evaluate its impact on the robustness of the generated overlay. We find that there is no single optimal value for this parameter using the default strategy. We then propose an alternative strategy that allows certain new peer connection requests to replace existing connections. Further experiments with the new strategy demonstrate that it outperforms the default one for all considered metrics by creating an overlay more robust to churn. Additionally, our proposed strategy exhibits optimal behavior for a well-defined value of the maximum number of outgoing connections, thereby removing the need to set this parameter in an ad-hoc manner

Studi Eksperimen dan Analisis Reduksi Respon Getaran Transversal pada Sistem Utama(Pipa Elbow 90o ) oleh Mekanisme Dynamic Vibration Absorber (DVA) tipe Beam Akibat Pengaruh Posisi Peletakan DVA

Pabrik industri mempunyai banyak sistem perpipaan terutama pada industri minyak , gas dan pengilangan minyak, industri air minum, pabrik yang memproduksi bahan kimia serta obat-obatan, dan juga industri pembangkit yang menyediakan sumber listrik untuk masyarakat. Sistem perpipaan adalah suatu sistem yang digunakan untuk transportasi fluida antar equipment dari suatu tempat ke tempat yang lain sehingga proses produksi dapat berlangsung. Aliran fluida pada pipa dapat memberi tekanan yang kemudian timbul getaran pada sistem perpipaan. Getaran berlebih adalah suatu hal yang tidak diharapkan muncul dalam sebuah sistem perpipaan. Getaran yang berlebih dapat terjadi karena frekuensi operasional suatu benda sama dengan frekuensi natural sistem tentunya berpengaruh terhadap performa maupun umur kekuatan dari sistem perpipaan. Getaran yang berlebih harus diredam dengan DVA (Dynamic vibration absorber). DVA (Dynamic vibration absorber) yang terpasang pada sistem perpipaan tersusun dari massa dan beam untuk mereduksi respon getaran transversal. Dalam penelitian tugas akhir ini menguji ulang mekanisme DVA (Dynamic vibration absorber) tipe beam dengan melihat pengaruh posisi peletakan DVA terhadap respon getaran pada sistem utama. Variasi yang digunakan adalah posisi peletakkan DVA pada 3 titik, variasi kecepatan aliran fluida yang melewati sistem utama sebesar 0,3 m/s; 0,5 m/s; 0,7 m/s, dan variasi rasio massa DVA 1/30,1/20,1/10 dari massa sistem utama. DVA tersebut dipasang pada sistem utama berupa fitting perpipaan jenis elbow 90º. Sistem utama diatur agar bergerak dalam 2 DOF, yaitu Translasi ke arah horizontal(x) dan vertikal(y) dengan ditumpu clamp fixed sebelum dan setelah pipa elbow 90º. Eksperimen ini dilakukan dengan dua kondisi, yaitu sistem utama tanpa penambahan DVA dan sistem utama dengan penambahan DVA. Didapatkan hasil berupa respon percepatan getaran, persentase reduksi. Berdasarkan hasil eksperimen dapat disimpulkan bahwa penambahan massa peredam 1/10 dari massa pipa elbow 90º yang direpresentasikan dengan koin mampu meredam secara efektif sebesar 55,97% getaran ke arah vertikal dan 31,73% getaran ke arah horizontal pada kecepatan aliran 0,3 m/s. Selain itu, posisi peletakan DVA mempengaruhi besarnya respon percepatan getaran yang dihasilkan, dibuktikan bahwa peletakan posisi DVA pada posisi Bend sangat meredam respon getaran. Semakin besar rasio massa DVA dari massa sistem utama maka semakin meredam untuk respon getaran dari sistem utama. ================================================================================================================================= Industrial plants have many piping systems, especially in the oil, gas and oil refining industries, the drinking water industry, factories that produce chemicals and medicines, and also the power industry that provides electricity to the community. Piping system is a system used to transport fluid between equipment from one place to another so that the production process can take place. Fluid flow in the pipe can put pressure which then emits a vibration in the piping system. Over vibration is something that is not expected to appear in a piping system. Excess vibrations can occur because the operational frequency of an object is the same as the natural frequency of the system, which certainly affects the performance and strength of the piping system. Excessive vibration must be damped with DVA (Dynamic vibration absorber). DVA (Dynamic vibration absorber) mounted on a piping system is composed of mass and beam to reduce the transverse vibration response. In this final project, retest the beam type dynamic vibration absorber DVA mechanism by looking at the influence of the positioning of the DVA on the vibration response in the main system. The variation used is the position of the placement of DVA at 3 points, variations in the speed of fluid flow through the main system of 0.3 m / s; 0.5 m / s; 0.7 m / s, and variations in the mass ratio of DVA 1 / 30.1 / 20.1 / 10 of the mass of the main system. The DVA is installed in the main system in the form of a 90º elbow piping type. The main system is set to move in 2 DOF, namely horizontal (x) and vertical (y) translation with a fixed clamp supported before and after the 90º elbow pipe. This experiment was carried out with two conditions, namely the main system without the addition of DVA and the main system with the addition of DVA. The results obtained in the form of the response of the acceleration of vibration, the percentage reduction. Based on the experimental results it can be concluded that the addition of 1/10 dampening mass of 90º elbow pipe mass represented by coins can effectively reduce 55.97% of vibrations in the vertical direction and 31.73% of vibrations in the horizontal direction at a flow velocity of 0.3 m / s. In addition, the positioning of the DVA affects the magnitude of the resulting acceleration of vibration response, it is proven that the placement of the DVA position at the Bend position greatly dampens the vibration response. The greater the ratio of the mass of the DVA from the mass of the main system, the more damping for the vibration response of the main system

Tindak Pidana Penggelapan dalam Hukum Positif Ditinjau menurut Hukum Islam

Tindak pidana penggelapan adalah salah satu kejahatan terhadap harta kekayaan manusia yang diatur dalam Kitab Undang-Undang Pidana (KUHP). Mengenai tindak pidana penggelapan itu sendiri diatur di dalam buku kedua tentang kejahatan di dalam Pasal 373 – Pasal 377 KUHP, yang merupakan kejahatan yang sering kali terjadi dan dapat terjadi di segala bidang bahkan pelakunya di berbagai lapisan masyarakat, baik dari lapisan bawah sampai masyarakat lapisan atas. Tindak pidana penggelapan merupakan kejahatan yang berawal dari adanya suatu kepercayaan pada orang lain, dan kepercayaan tersebut hilang karena lemahnya suatu kejujuran. Ancaman pidana bagi pelaku tindak pidana penggelapan juga telah diatur dalam Pasal yang sama. Sedangkan hukum Islam tidak mengatur secara khusus bagi pelaku tindak pidana ini, namun bisa dianalogikan menjadi ghulul, ghasab, sariqah, khianat. Adapun rumusan masalah dari penelitian ini adalah bagaimana tinjauan hukum Islam terhadap tindak pidana penggelapan yang terdapat dalam hukum positif dan bagaimana ketentuan ancaman hukuman tindak pidana penggelapan dalam hukum Islam. Tujuan penelitian ini yaitu: untuk mengetahui hukum Islam yang mengatur tentang penggelapan dan untuk mengetahui ketentuan ancaman hukuman tindak pidana penggelapan dalam hukum Islam. Dalam penulisan ini menggunakan metode hukum normatif yaitu penelitian hukum yang dilakukan dengan cara meneliti bahan pustaka atau data sekunder. Sedangkan teknik pengumpulan data diperoleh dengan cara penelitian pustaka. Berdasarkan hasil penelitian dapat dipahami bahwa dalam hukum Islam bagi tindak pidana penggelapan maka dikenakan hukuman ta’zir. Hukuman ta’zir diberlakukan dari yang ringan hingga terberat sesuai dengan tindak pidana yang dilakukan oleh pelaku. Ghulul, ghasab, sariqah, khianat. Hukuman ta’zir yang terberat bisa dijatuhi pada khianat,dalam beberapa kasus tertentu. Hukum Islam memandang dari segala tindakan yang dapat merugikan atau membahayakan dan juga dilihat dari perbuatan yang dilakukan baik secara sengaja maupun tidak disengaja demi kemaslahatan umat manusia

Innovative therapeutic pants for children with genu varum and genu valgum

Background: This research is motivated by the absence of therapeutic pants in patients with genu deformity, so innovations to create latest medical products are needed to prevent the disease. One of the innovations is development of therapeutic pants for genu varum and genu valgum. Objective: It aims to research and develop therapeutic pants to improve comfort of children with genu varum and genu valgum.Methods: This study used Research and Development (R&D) approach. It consisted of 3 phases, namely phase I, II, and III or product trials.Result: From the literary study in phase I, it was obtained that materials used to make the therapeutic pants were cotton cloth fabric and foam. In the second phase of the research, it was also discovered that designs and shapes of the pants were as needed. The results of product trials or phase III of this study involved 5 respondents; it showed that the use of therapeutic pants in toddlers resulted comfort and satisfaction for them.Conclusion: The therapeutic pants are proven to increase comfort in toddlers with genu varum and genu valgum

Swarming Overlay Construction Strategies

International audienceSwarming peer-to-peer systems play an increasingly instrumental role in Internet content distribution. It is therefore important to better understand how these systems behave in practice. Recent research efforts have looked at various protocol parameters and have measured how they affect system performance and robustness. However, the importance of the strategy based on which peers establish connections has been largely overlooked. This work utilizes extensive simulations to examine the default overlay construction strategy in BitTorrent systems. Based on the results, we identify a critical parameter, the maximum allowable number of outgoing connections at each peer, and evaluate its impact on the robustness of the generated overlay. We find that there is no single optimal value for this parameter using the default strategy. We then propose an alternative strategy that allows certain new peer connection requests to replace existing connections. Further experiments with the new strategy demonstrate that it outperforms the default one for all considered metrics by creating an overlay more robust to churn. Additionally, our proposed strategy exhibits optimal behavior for a well-defined value of the maximum number of outgoing connections, thereby removing the need to set this parameter in an ad-hoc manner

Adapting BitTorrent for Wireless Ad Hoc networks

International audienceBitTorrent is one of the Internet''s most efficient content distribution protocols. It is known to perform very well over the wired Internet where end-to-end performance is almost guaranteed. However, in wireless ad hoc networks, many constraints appear as the scarcity of resources and their shared nature, which make running BitTorrent in such an environment with its default configuration not lead to best performances. To these constraints it adds the fact that peers are both routers and end-users and that TCP-performance drops seriously with the number of hops. We show in this work that the neighbor selection mechanism in BitTorrent plays an important role in determining the performance of the protocol when deployed over a wireless ad hoc network. It is no longer efficient to choose and treat with peers independently of their location. A first solution is to limit the scope of the neighborhood. In this case, TCP connections are fast but there is no more diversity of pieces in the network: pieces propagate in a unique direction from the seed to distant peers. This prohibits peers from reciprocating data and leads to low sharing ratios and suboptimal utilization of network resources. To recover from these impairments, we propose BitHoc, an enhancement to BitTorrent, which aims to minimize the time to download the content and at the same time to enforce cooperation and fairness among peers. BitHoc considers a restricted neighborhood to reduce routing overhead and to improve throughput, while establishing few connections to remote peers to improve diversity of pieces. To support this, BitHoc modifies the choking algorithm and adds a new piece selection strategy. With the help of extensive NS-2 simulations, we show that these enhancements to BitTorrent significantly improve the file completion time while fully profiting from the incentives implemented in BitTorrent to enforce fair sharing

Effect of stigma reduction intervention strategies on HIV test uptake in low- and middle-income countries: a realist review protocol

Background Several stigma reduction intervention strategies have been developed and tested for effectiveness in terms of increasing human immunodeficiency virus (HIV) test uptake. These strategies have been more effective in some contexts and less effective in others. Individual factors, such as lack of knowledge and fear of disclosure, and social-contextual factors, such as poverty and illiteracy, might influence the effect of stigma reduction intervention strategies on HIV test uptake in low- and middle-income countries. So far, it is not clearly known how the stigma reduction intervention strategies interact with these contextual factors to increase HIV test uptake. Therefore, we will conduct a review that will synthesize existing studies on stigma reduction intervention strategies to increase HIV test uptake to better understand the mechanisms underlying this process in low- and middle-income countries. Methods A realist review will be conducted to unpack context-mechanism-outcome configurations of the effect of stigma reduction intervention strategies on HIV test uptake. Based on a scoping review, we developed a preliminary theoretical framework outlining a potential mechanism of how the intervention strategies influence HIV test uptake. Our realist synthesis will be used to refine the preliminary theoretical framework to better reflect mechanisms that are supported by existing evidence. Journal articles and grey literature will be searched following a purposeful sampling strategy. Data will be extracted and tested against the preliminary theoretical framework. Data synthesis and analysis will be performed in five steps: organizing extracted data into evidence tables, theming, formulating chains of inference from the identified themes, linking the chains of inference and developing generative mechanisms, and refining the framework. Discussion This will be the first realist review that offers both a quantitative and a qualitative exploration of the available evidence to develop and propose a theoretical framework that explains why and how HIV stigma reduction intervention strategies influence HIV test uptake in low- and middle-income countries. Our theoretical framework is meant to provide guidance to program managers on identifying the most effective stigma reduction intervention strategies to increase HIV test uptake. We also include advice on how to effectively implement these strategies to reduce the rate of HIV transmission.status: publishe

Phenol Dissociation on Pristine and Defective Graphene

Phenol (C6H5O‒H) dissociation on both pristine and defective graphene sheets in terms of associated enthalpic requirements of the reaction channels was investigated. Here, we considered three common types of defective graphene, namely, Stone-Wales, monovacancy and divacancy configurations. Theoretical results demonstrate that, graphene with monovacancy creates C atoms with dangling bond (unpaired valence electron), which remains particularly useful for spontaneous dissociation of phenol into phenoxy (C6H5O) and hydrogen (H) atom. The reactions studied herein appear barrierless with reaction exothermicity as high as 2.2 eV. Our study offers fundamental insights into another potential application of defective graphene sheets

Remdesivir and three other drugs for hospitalised patients with COVID-19: final results of the WHO Solidarity randomised trial and updated meta-analyses.

BACKGROUND World Health Organization expert groups recommended mortality trials of four repurposed antiviral drugs - remdesivir, hydroxychloroquine, lopinavir, and interferon beta-1a - in patients hospitalized with coronavirus disease 2019 (Covid-19). METHODS We randomly assigned inpatients with Covid-19 equally between one of the trial drug regimens that was locally available and open control (up to five options, four active and the local standard of care). The intention-to-treat primary analyses examined in-hospital mortality in the four pairwise comparisons of each trial drug and its control (drug available but patient assigned to the same care without that drug). Rate ratios for death were calculated with stratification according to age and status regarding mechanical ventilation at trial entry. RESULTS At 405 hospitals in 30 countries, 11,330 adults underwent randomization; 2750 were assigned to receive remdesivir, 954 to hydroxychloroquine, 1411 to lopinavir (without interferon), 2063 to interferon (including 651 to interferon plus lopinavir), and 4088 to no trial drug. Adherence was 94 to 96% midway through treatment, with 2 to 6% crossover. In total, 1253 deaths were reported (median day of death, day 8; interquartile range, 4 to 14). The Kaplan-Meier 28-day mortality was 11.8% (39.0% if the patient was already receiving ventilation at randomization and 9.5% otherwise). Death occurred in 301 of 2743 patients receiving remdesivir and in 303 of 2708 receiving its control (rate ratio, 0.95; 95% confidence interval [CI], 0.81 to 1.11; P = 0.50), in 104 of 947 patients receiving hydroxychloroquine and in 84 of 906 receiving its control (rate ratio, 1.19; 95% CI, 0.89 to 1.59; P = 0.23), in 148 of 1399 patients receiving lopinavir and in 146 of 1372 receiving its control (rate ratio, 1.00; 95% CI, 0.79 to 1.25; P = 0.97), and in 243 of 2050 patients receiving interferon and in 216 of 2050 receiving its control (rate ratio, 1.16; 95% CI, 0.96 to 1.39; P = 0.11). No drug definitely reduced mortality, overall or in any subgroup, or reduced initiation of ventilation or hospitalization duration. CONCLUSIONS These remdesivir, hydroxychloroquine, lopinavir, and interferon regimens had little or no effect on hospitalized patients with Covid-19, as indicated by overall mortality, initiation of ventilation, and duration of hospital stay. (Funded by the World Health Organization; ISRCTN Registry number, ISRCTN83971151; ClinicalTrials.gov number, NCT04315948.)