83 research outputs found
Pamuklu Bezayağı Kumaşlarda Aşınma Etkisi İle Sürtme Haslığı Değişimi
Sürtme haslığına lif cinsi, boyarmadde cinsi ve
boyama prosesi gibi pek çok faktör etki etmektedir. İlave olarak aşınma işlemi
de sürtme haslığına etki etmektedir. Bu deneysel çalışmada; aşınma tur sayısı
ile pamuklu bezayağı kumaşlarda yaş ve kuru sürtme haslığının değişimi
incelenmiştir. Genel olarak kuru sürtme haslıkları yaş sürtme haslıklarından
yüksektir. Sonuçlara göre aşınma tur sayısı artıkça kuru ve yaş sürtme
haslıkları düşmektedir. Aşınma tur sayısının arttığı durumlarda kuru sürtme
haslığındaki düşüş yaş sürtme haslığındaki düşüşten daha fazladır
Binali Selman’ın Mey Açışlarına Yönelik Biçim Tâhlili
20.yüzyılın önemli mey virtüozlarından biri olan Binali Selman ( 1931 -1992), Türk halk müziği nefesli çalgıları ve mey icrâcılığı alanında ayrıcalıklı bir yere sâhiptir. Binali Selman’ın mey icrâcılığındaki teknik hâkimiyeti ve nağme zenginliği, kendisinden sonraki icrâcıları etkilemiş ve ekol olmasını sağlamıştır. Türk halk mûsikîsinde bir eserin icrâsından önce hânendeyi seslendirilecek eserin makāmına hazırlamak amacıyla irticâlen yapılan “Açış” formunun önemli temsilcisidir. Duygulu, etkileyici, teknik açıdan mükemmel özelliklere sâhip açış icrâları kişisel tavır özelliklerini yansıtması bakımından ayrı bir önem arz etmektedir. Yapılan bu araştırmada, Selman’ın mey açışlarının biçim özellikleri motif, cümle ve bölüm yapılarıyla tahlîl edilmiş ve bu bağlamda, örneklem grubu olarak san’atçıya ait üç farklı makamda mey açışı seçilmiştir. Mey açışlarının tahlîlinde “Gülçin Yahya Biçim Tahlîli Yöntemi” kullanılmış, Selman’ın mey açışlarındaki Eser Kurgusu ve İcrâ Akışı gösterimleriyle, yorumculuğuna ait değerlendirmelerde bulunulmuştur
Peripheral vs. central cannulation in cardiac reoperations: Technical considerations and outcomes
Objective: To compare peripheral and central cannulation techniques in cardiac reoperation.Methods: This retrospective study included 258 patients undergoing cardiac reoperation between January 2013 and July 2018. Patients were divided into two groups according to the cannulation type. The first group included 145 (56.2%) patients operated with standard central cannulation through aorta and right atrium or bicaval cannulation. In this group, cardiopulmonary bypass was instituted after sternotomy. The second group consisted of 113 (43.8%) patients operated with peripheral cannulation through femoral artery, vein, and internal jugular vein. In this group, cardiopulmonary bypass was started before sternotomy and after systemic heparinisation. The two groups' operative complications and postoperative outcomes were compared.Results: Procedure-related injury was higher in the central cannulation group than in the peripheral cannulation group (8.3% vs. 1.8%, respectively, P=0.038). Cardiopulmonary bypass time was shorter in the central cannulation group (P=0.008) and total operation time was similar between the groups (P=0.115). Postoperative red blood cell requirement was higher with central cannulation (P=0.004). Operative mortality (2.8% vs. 0, P=0.186), hospital mortality (4.3% vs. 2.7%, P=0.523), and one-year survival rate (90.3% vs. 94.7%, P=0.202) were similar between the groups.Conclusion: Peripheral cannulation reduces cardiac injury and blood transfusion in cardiac reoperation. The cannulation type does not affect postoperative complication, mortality, and one-year survival
Ramulator 2.0: A Modern, Modular, and Extensible DRAM Simulator
We present Ramulator 2.0, a highly modular and extensible DRAM simulator that
enables rapid and agile implementation and evaluation of design changes in the
memory controller and DRAM to meet the increasing research effort in improving
the performance, security, and reliability of memory systems. Ramulator 2.0
abstracts and models key components in a DRAM-based memory system and their
interactions into shared interfaces and independent implementations. Doing so
enables easy modification and extension of the modeled functions of the memory
controller and DRAM in Ramulator 2.0. The DRAM specification syntax of
Ramulator 2.0 is concise and human-readable, facilitating easy modifications
and extensions. Ramulator 2.0 implements a library of reusable templated lambda
functions to model the functionalities of DRAM commands to simplify the
implementation of new DRAM standards, including DDR5, LPDDR5, HBM3, and GDDR6.
We showcase Ramulator 2.0's modularity and extensibility by implementing and
evaluating a wide variety of RowHammer mitigation techniques that require
different memory controller design changes. These techniques are added
modularly as separate implementations without changing any code in the baseline
memory controller implementation. Ramulator 2.0 is rigorously validated and
maintains a fast simulation speed compared to existing cycle-accurate DRAM
simulators. Ramulator 2.0 is open-sourced under the permissive MIT license at
https://github.com/CMU-SAFARI/ramulator
DRAM Bender: An Extensible and Versatile FPGA-based Infrastructure to Easily Test State-of-the-art DRAM Chips
To understand and improve DRAM performance, reliability, security and energy
efficiency, prior works study characteristics of commodity DRAM chips.
Unfortunately, state-of-the-art open source infrastructures capable of
conducting such studies are obsolete, poorly supported, or difficult to use, or
their inflexibility limit the types of studies they can conduct.
We propose DRAM Bender, a new FPGA-based infrastructure that enables
experimental studies on state-of-the-art DRAM chips. DRAM Bender offers three
key features at the same time. First, DRAM Bender enables directly interfacing
with a DRAM chip through its low-level interface. This allows users to issue
DRAM commands in arbitrary order and with finer-grained time intervals compared
to other open source infrastructures. Second, DRAM Bender exposes easy-to-use
C++ and Python programming interfaces, allowing users to quickly and easily
develop different types of DRAM experiments. Third, DRAM Bender is easily
extensible. The modular design of DRAM Bender allows extending it to (i)
support existing and emerging DRAM interfaces, and (ii) run on new commercial
or custom FPGA boards with little effort.
To demonstrate that DRAM Bender is a versatile infrastructure, we conduct
three case studies, two of which lead to new observations about the DRAM
RowHammer vulnerability. In particular, we show that data patterns supported by
DRAM Bender uncovers a larger set of bit-flips on a victim row compared to the
data patterns commonly used by prior work. We demonstrate the extensibility of
DRAM Bender by implementing it on five different FPGAs with DDR4 and DDR3
support. DRAM Bender is freely and openly available at
https://github.com/CMU-SAFARI/DRAM-Bender.Comment: To appear in TCAD 202
RowPress: Amplifying Read Disturbance in Modern DRAM Chips
Memory isolation is critical for system reliability, security, and safety.
Unfortunately, read disturbance can break memory isolation in modern DRAM
chips. For example, RowHammer is a well-studied read-disturb phenomenon where
repeatedly opening and closing (i.e., hammering) a DRAM row many times causes
bitflips in physically nearby rows.
This paper experimentally demonstrates and analyzes another widespread
read-disturb phenomenon, RowPress, in real DDR4 DRAM chips. RowPress breaks
memory isolation by keeping a DRAM row open for a long period of time, which
disturbs physically nearby rows enough to cause bitflips. We show that RowPress
amplifies DRAM's vulnerability to read-disturb attacks by significantly
reducing the number of row activations needed to induce a bitflip by one to two
orders of magnitude under realistic conditions. In extreme cases, RowPress
induces bitflips in a DRAM row when an adjacent row is activated only once. Our
detailed characterization of 164 real DDR4 DRAM chips shows that RowPress 1)
affects chips from all three major DRAM manufacturers, 2) gets worse as DRAM
technology scales down to smaller node sizes, and 3) affects a different set of
DRAM cells from RowHammer and behaves differently from RowHammer as temperature
and access pattern changes.
We demonstrate in a real DDR4-based system with RowHammer protection that 1)
a user-level program induces bitflips by leveraging RowPress while conventional
RowHammer cannot do so, and 2) a memory controller that adaptively keeps the
DRAM row open for a longer period of time based on access pattern can
facilitate RowPress-based attacks. To prevent bitflips due to RowPress, we
describe and evaluate a new methodology that adapts existing RowHammer
mitigation techniques to also mitigate RowPress with low additional performance
overhead. We open source all our code and data to facilitate future research on
RowPress.Comment: Extended version of the paper "RowPress: Amplifying Read Disturbance
in Modern DRAM Chips" at the 50th Annual International Symposium on Computer
Architecture (ISCA), 202
TuRaN: True Random Number Generation Using Supply Voltage Underscaling in SRAMs
Prior works propose SRAM-based TRNGs that extract entropy from SRAM arrays.
SRAM arrays are widely used in a majority of specialized or general-purpose
chips that perform the computation to store data inside the chip. Thus,
SRAM-based TRNGs present a low-cost alternative to dedicated hardware TRNGs.
However, existing SRAM-based TRNGs suffer from 1) low TRNG throughput, 2) high
energy consumption, 3) high TRNG latency, and 4) the inability to generate true
random numbers continuously, which limits the application space of SRAM-based
TRNGs. Our goal in this paper is to design an SRAM-based TRNG that overcomes
these four key limitations and thus, extends the application space of
SRAM-based TRNGs. To this end, we propose TuRaN, a new high-throughput,
energy-efficient, and low-latency SRAM-based TRNG that can sustain continuous
operation. TuRaN leverages the key observation that accessing SRAM cells
results in random access failures when the supply voltage is reduced below the
manufacturer-recommended supply voltage. TuRaN generates random numbers at high
throughput by repeatedly accessing SRAM cells with reduced supply voltage and
post-processing the resulting random faults using the SHA-256 hash function. To
demonstrate the feasibility of TuRaN, we conduct SPICE simulations on different
process nodes and analyze the potential of access failure for use as an entropy
source. We verify and support our simulation results by conducting real-world
experiments on two commercial off-the-shelf FPGA boards. We evaluate the
quality of the random numbers generated by TuRaN using the widely-adopted NIST
standard randomness tests and observe that TuRaN passes all tests. TuRaN
generates true random numbers with (i) an average (maximum) throughput of
1.6Gbps (1.812Gbps), (ii) 0.11nJ/bit energy consumption, and (iii) 278.46us
latency
An Experimental Analysis of RowHammer in HBM2 DRAM Chips
RowHammer (RH) is a significant and worsening security, safety, and
reliability issue of modern DRAM chips that can be exploited to break memory
isolation. Therefore, it is important to understand real DRAM chips' RH
characteristics. Unfortunately, no prior work extensively studies the RH
vulnerability of modern 3D-stacked high-bandwidth memory (HBM) chips, which are
commonly used in modern GPUs.
In this work, we experimentally characterize the RH vulnerability of a real
HBM2 DRAM chip. We show that 1) different 3D-stacked channels of HBM2 memory
exhibit significantly different levels of RH vulnerability (up to 79%
difference in bit error rate), 2) the DRAM rows at the end of a DRAM bank (rows
with the highest addresses) exhibit significantly fewer RH bitflips than other
rows, and 3) a modern HBM2 DRAM chip implements undisclosed RH defenses that
are triggered by periodic refresh operations. We describe the implications of
our observations on future RH attacks and defenses and discuss future work for
understanding RH in 3D-stacked memories.Comment: To appear at DSN Disrupt 202
Antimicrobial resistance among migrants in Europe: a systematic review and meta-analysis
BACKGROUND: Rates of antimicrobial resistance (AMR) are rising globally and there is concern that increased migration is contributing to the burden of antibiotic resistance in Europe. However, the effect of migration on the burden of AMR in Europe has not yet been comprehensively examined. Therefore, we did a systematic review and meta-analysis to identify and synthesise data for AMR carriage or infection in migrants to Europe to examine differences in patterns of AMR across migrant groups and in different settings. METHODS: For this systematic review and meta-analysis, we searched MEDLINE, Embase, PubMed, and Scopus with no language restrictions from Jan 1, 2000, to Jan 18, 2017, for primary data from observational studies reporting antibacterial resistance in common bacterial pathogens among migrants to 21 European Union-15 and European Economic Area countries. To be eligible for inclusion, studies had to report data on carriage or infection with laboratory-confirmed antibiotic-resistant organisms in migrant populations. We extracted data from eligible studies and assessed quality using piloted, standardised forms. We did not examine drug resistance in tuberculosis and excluded articles solely reporting on this parameter. We also excluded articles in which migrant status was determined by ethnicity, country of birth of participants' parents, or was not defined, and articles in which data were not disaggregated by migrant status. Outcomes were carriage of or infection with antibiotic-resistant organisms. We used random-effects models to calculate the pooled prevalence of each outcome. The study protocol is registered with PROSPERO, number CRD42016043681. FINDINGS: We identified 2274 articles, of which 23 observational studies reporting on antibiotic resistance in 2319 migrants were included. The pooled prevalence of any AMR carriage or AMR infection in migrants was 25·4% (95% CI 19·1-31·8; I2 =98%), including meticillin-resistant Staphylococcus aureus (7·8%, 4·8-10·7; I2 =92%) and antibiotic-resistant Gram-negative bacteria (27·2%, 17·6-36·8; I2 =94%). The pooled prevalence of any AMR carriage or infection was higher in refugees and asylum seekers (33·0%, 18·3-47·6; I2 =98%) than in other migrant groups (6·6%, 1·8-11·3; I2 =92%). The pooled prevalence of antibiotic-resistant organisms was slightly higher in high-migrant community settings (33·1%, 11·1-55·1; I2 =96%) than in migrants in hospitals (24·3%, 16·1-32·6; I2 =98%). We did not find evidence of high rates of transmission of AMR from migrant to host populations. INTERPRETATION: Migrants are exposed to conditions favouring the emergence of drug resistance during transit and in host countries in Europe. Increased antibiotic resistance among refugees and asylum seekers and in high-migrant community settings (such as refugee camps and detention facilities) highlights the need for improved living conditions, access to health care, and initiatives to facilitate detection of and appropriate high-quality treatment for antibiotic-resistant infections during transit and in host countries. Protocols for the prevention and control of infection and for antibiotic surveillance need to be integrated in all aspects of health care, which should be accessible for all migrant groups, and should target determinants of AMR before, during, and after migration. FUNDING: UK National Institute for Health Research Imperial Biomedical Research Centre, Imperial College Healthcare Charity, the Wellcome Trust, and UK National Institute for Health Research Health Protection Research Unit in Healthcare-associated Infections and Antimictobial Resistance at Imperial College London
Validation of the Short Version (TLS-15) of the Triangular Love Scale (TLS-45) Across 37 Languages
Love is a phenomenon that occurs across the world and affects many aspects of human life, including the choice of, and process of bonding with, a romantic partner. Thus, developing a reliable and valid measure of love experiences is crucial. One of the most popular tools to quantify love is Sternberg’s 45-item Triangular Love Scale (TLS-45), which measures three love components: intimacy, passion, and commitment. However, our literature review reveals that most studies (64%) use a broad variety of shortened versions of the TLS-45. Here, aiming to achieve scientific consensus and improve the reliability, comparability, and generalizability of results across studies, we developed a short version of the scale—the TLS-15—comprised of 15 items with 5-point, rather than 9-point, response scales. In Study 1 (N = 7,332), we re-analyzed secondary data from a large-scale multinational study that validated the original TLS-45 to establish whether the scale could be truncated. In Study 2 (N = 307), we provided evidence for the three-factor structure of the TLS-15 and its reliability. Study 3 (N = 413) confirmed convergent validity and test–retest stability of the TLS-15. Study 4 (N = 60,311) presented a large-scale validation across 37 linguistic versions of the TLS-15 on a cross-cultural sample spanning every continent of the globe. The overall results provide support for the reliability, validity, and cross-cultural invariance of the TLS-15, which can be used as a measure of love components—either separately or jointly as a three-factor measure
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