NTP

O artigo faz uma descrição sucinta dos protocolos IRIG-B e NTP, ressaltando suas vantagens e desvantagens, e
apresenta o protocolo IEEE1588 Precision Time Protocol (PTP), explicando sua filosofia de funcionamento,
vantagens e perspectivas do seu uso no setor elétrico brasileiro.

For the past two decades, the design of high-performance
stratum-1 NTP servers, those with internal means of
synchronization to hardware clocks, have involved the use
of specialized bus interface cards often utilizing
proprietary device drivers. Those commercially available
bus clocks provide memory-mappable time registers
synchronized to GPS or Master Clock time code (such as
IRIG-B and, more recently, IEEE 1588). Providing an
essentially global NTP service has proven costly for
timing labs as at the U.S. Naval Observatory. In 2007 a
trio of Hewlett-Packard Unix servers, each with two bus
clocks, and fronted by a redundant pair of IP load
balancers cost over $53 thousand in 2014 dollars. A
growing number of LAN-on-Motherboard (LoM) and bus
card Ethernet adapters are now providing support for
IEEE 1588 Precise Time Protocol, perhaps obviating the
need for costly synchronized bus clocks. Open-source
development projects at ntp.org, linuxptp.org, and
kernel.org have resulted in widespread access to PPS and
PTP hosted on low-cost platforms. To investigate the
utility of inexpensive network timing a pair of Supermicro
SYS-5015A-EHF-D525 servers with Intel® Atom
processors were integrated with PTP-enabled NICs, GPS,
and NTP and Linux PTP to test network timing in a PTP
Grandmaster/Slave configuration. Results of long-term
tests show quite satisfactory timing stability, well within
the range of NTP timing requirements.

Although LRU replacement policy has been commonly used in the buffer cache management, it is well known for its inability to cope with access patterns with weak locality. Previous work, such as LRU-K and 2Q, attempts to enhance LRU capacity by making use of additional history information of previous block references other than only the recency information used in LRU. These algorithms greatly increase complexity and/or can not consistently provide performance improvement. Many recently proposed policies, such as UBM and SEQ, improve replacement performance by exploiting access regularities in references. They only address LRU problems on certain specific and well-defined cases such as access patterns like sequences and loops. Motivated by the limits of previous studies, we propose an efficient buffer cache replacement policy, called Low Inter-reference Recency Set (LIRS). LIRS effectively addresses the limits of LRU by using recency to evaluate Inter-Reference Recency (IRR) for maki...

With virtual assistants, both changes and serious conveniences are provided in human life. For this reason, the use of virtual assistants is increasing. The virtual assistant software has started to be produced as separate devices as well as working on phones, tablets, and computer systems. Google Home is one of these devices. Google Home can work integrated with smart home systems and various Internet of Things devices. The security of these systems is an important issue. As a result of attackers taking over these systems, very serious problems may occur. It is very important to take the necessary actions to detect these problems and to take the necessary measures to prevent possible attacks. The purpose of this study is to test whether an attack that attackers can make to these systems via network time protocol will be successful or not. Accordingly, it has been tried to attack the wireless connection established between Google Home and an Internet of Things device over the network time protocol. Attack results have been shared.

Bacterial biofilms were constructed in vitro with two pathogenic strains of Pseudomonas aeruginosa and Staphylococcus aureus using a modified, novel sequential bioreactor system. The structure and stability of bacterial biofilms were evaluated following exposure to non-thermal plasma (NTP) discharge. Mathematical software was used to determine structural changes as biofilms grew over the course of 7 days. Statistical modeling was also performed to assess the ability of NTP to affect the development of the biofilms over different periods of time. Several structural characteristics were significantly affected by NTP discharge whereas others were unaffected. Changes in the three-dimensional structure of the biofilm following introduction of NTP was not limited to one period of development. The mechanism for this phenomenon is not understood but is likely to be a dual, synergistic effect due to the composition of the reactive species and other plasma-associated molecules isolated previously in the NTP discharge used in this study.

We prove that in theories without the tree property of the second kind (which include dependent and simple theories) forking and dividing over models are the same, and in fact over any extension base. As an application we show that dependence is equivalent to bounded non-forking assuming NTP_2.