356 research outputs found
The NATO III 5 MHz Distribution System
A high performance 5 MHz distribution system is described which has extremely low phase noise and jitter characteristics and provides multiple buffered outputs. The system is completely redundant with automatic switchover and is self-testing. Since the 5 MHz reference signals distributed by the NATO III distribution system are used for up-conversion and multiplicative functions, a high degree of phase stability and isolation between outputs is necessary. Unique circuit design and packaging concepts insure that the isolation between outputs is sufficient to quarantee a phase perturbation of less than 0.0016 deg when other outputs are open circuited, short circuited or terminated in 50 ohms. Circuit design techniques include high isolation cascode amplifiers. Negative feedback stabilizes system gain and minimizes circuit phase noise contributions. Balanced lines, in lieu of single ended coaxial transmission media, minimize pickup
The SA-2239/WLQ-4(V) Cutty Sark distribution system
A redundant frequency and time distribution system provides a multiplicity of isolated outputs, all of which are derived from three atomic frequency standards. The distribution system monitors input parameters of the signals coming from the Cesium Standards and selects one to be the primary standard, phase locks an internal oscillator which has excellent aging characteristics in the open loop mode and acts as a filter to provide phase noise improvement, and generates 1 megahertz and 100 kHz by direct synthesis. Additionally, the system distributes RF and timing signals consisting of 5 MHz, 1 MHz, 100 kHz, BCD Time-of-Day, 1 pps and 1 ppm
Resisting Action: Slow Response and Care-Full Movement in a Post-Fire Terrain
Initially I stood at a threshold peering into a place of momentous ending. I shook my head. Gundungurra country needs to burn, I imagine its people say across time, just not like this. There is a requirement for care-full in/action when living with and on a post-fire terrain while still in trauma. It is a difficult balancing act for humans who like to fix things. Beyond the domestic clean-up of burnt buildings and infrastructure, my teachers await my attention. They are not of the human kind, rather they are the critters that perch in branches or skitter under rock. They are the soil movers, the crevice crouchers and the mark makers. They are the stirring plants and the underground tendrils of fungal hyphae. They send slow signals and resist tidy aesthetics. They challenge the perception of “dead” and question short-term human economies of usefulness. Ultimately, they remind me that home is made up of many intersecting homes weaving, twisting and turning in a constant process of becoming
Role of β-Hydroxy-β-methylbutyrate (HMB) on inflammation after eccentric exercise
When exposed to resistance exercise, untrained muscle can develop micro-tears and disruptions in the sarcomeres. This is followed by swelling, pain and decreased muscle performance, which can be attenuated by taking β-hydroxy-β-methylbutyrate (HMB). The acute phase response is the inflammatory change that occurs to repair damaged tissue, and is mediated by cytokines. It is the purpose of this study to determine if HMB can influence the acute phase response. 32 untrained subjects (16 men, 16 women) completed three sets of 50 eccentric leg extensions on each leg. The subjects were group matched and randomly assigned to one of three treatment groups: placebo (CON), HMB pre exercise (PRE) or HMB pre-exercise and for 4 days following the exercise protocol (PRE-POST). We observed a drop in serum concentration of IL-1ra and TNF-α for the CON, that was attenuated by HMB at 48h and 72h post exercise (p\u3c.05). The observed reduction in acute phase response suggests that HMB may moderate inflammatory response to exercise induced muscle damage
Going dark : care-full castings and delight-full deviations for a networked fiction in an everyday world
Going dark is a technical term within the world of theatre. It has the double meaning of lights out during rehearsal and a temporary venue closure for maintenance and resetting. In this way it speaks to matters of care in the form of attending to one’s environs while resisting the excess of twenty-four hour productivity. This thesis appropriates going dark as a practice and methodology. In both instances it considers how deviation from the familiar; steady observation; and a kind of slow liveliness might reveal delight-full throughways for a less human-centric worlding. This project emerges from a confluence of driving commitments-digital media, the dark, and speculative fiction - embedded in the habitual and affective processes of everyday activities. Each concern additionally has the capacity to disturb the mundane in ordinary and extraordinary ways. How then might such an everyday landscape be harnessed to explore speculative projects embedded in the digital fabric of social media as a type of textual creative resistance? To assist me in this enquiry I travel along the submerged pathways of stinkhorn fungi, lively soil, and social media networks in conversation with the experimental online project Going DARK. Engaging a fictocritical framework I draw sustenance from the disruptive practices of feminist science fiction writers and look to the messy earth-bound provocations of Anna Tsing, Donna Haraway, and Maria Puig de la Bellacasa. Threaded below the carefully composed registers are the influential figurations of Rosi Braidotti’s nomadic subject and the processes of becoming and assemblage engaged in the work of Deleuze and Guattari. Consequently my thesis travels multiple lines of curious deviation to inform, borrow, expand or temporarily submerge a story. Viewed through a posthuman lens it seeks to find delight and direction in the inbetween dark and dirty spaces. Equally it is an endeavor to interrupt the off-world utopian dream embedded in idealistic paternal views of escape to another planet in order to make us accountable for our actions on the world we are in now
Convergence and frequency-domain analysis of a discrete first-order model reference adaptive controller
SUMMARY We study the convergence properties of a direct model reference adaptive control system by applying techniques from numerical analysis. In particular, a first-order discrete system coupled to a minimal control synthesis algorithm discretized by the one-step one-stage zero-order-hold sampling is studied. This results in a strongly non-linear dynamic system owing to the adaptive mechanism where stability at steady state, i.e. at the operating point, equates to successful control. This paper focuses on the convergence analysis of the overall dynamical system for understanding accuracy, stability and performance at steadystate. The local stability of the steady state solution is considered by linearizing the system in the neighbourhood of an operating point when the input is a step function. This analysis allows us to specify two gain space domains which define the region of local stability. Moreover, both the accuracy and the frequency-domain analyses give insight into the range of adaptive control weightings that results in optimal performance of the minimal control synthesis algorithm and also highlights a possible approach to a priori selection of the time step and adaptive weighting values. The effectiveness of the proposed analysis is further demonstrated by simulations and experiments on a first-order plant. Copyright # 2006 John Wiley & Sons, Ltd
Radiative impact of aerosols generated from biomass burning
Atmospheric aerosol particles play a vital role in the Earth's radiative energy budget. They exert a net cooling influence on climate by directly reflecting the solar radiation to space and by modifying the shortwave reflective properties of clouds. Each year, increasing amounts of aerosol particles are released into the atmosphere due to biomass burning, dust storms, forest fires, and volcanic activity. These particles significantly perturb the radiative balance on local, regional, and global scales. While the detection of aerosols over water is a well established procedure, the detection of aerosols over land is often difficult due to the poor contrast between the aerosols and the underlying terrain. In this study, we use textural measures in order to detect aerosols generated from biomass burning over South America, using AVHRR data. The regional radiative effects are then examined using ERBE data. Preliminary results show that the net radiative forcing of aerosols is about -36 W/sq m
Regional Comparisons of Satellite (AVHRR) and Space Shuttle (MAPS) Derived Estimates of CO and Aerosol Concentrations
Biomass burning is considered to be a major source of trace gas species and aerosol particles which play a vital role in tropospheric chemistry and climate. Anthropogenic biomass burning has largely expanded in the last 15 years, due to increased deforestation practices in the Amazon Basin, as well as to clear land for shifting cultivation in South America, southern Asia, and Africa. Biomass burning produces large amounts of carbon dioxide, carbon monoxide (CO), water, hydrocarbons, nitrous oxides, and smoke particles
“My life during the lockdown”: emotional experiences of european adolescents during the COVID-19 crisis
This study investigates, using an online self-report questionnaire, adolescents' emotional reactions during the lockdown in a sample of 2105 secondary school students (aged 14-19) in Italy, Romania, and Croatia. We used a self-reported online questionnaire (answers on a 5-point scale or binary), composed of 73 questions investigating the opinions, feelings, and emotions of teenagers, along with sociodemographic information and measures of the exposure to lockdown. The survey was conducted online through a web platform in Italy (between 27 April and 15 June 2020), Romania, and Croatia (3 June and 2 July 2020). Students aged >14 years, living in a small flat, and not spending time outside were more likely to report anger, sadness, boredom/emptiness, and anxiety. Boys were significantly less likely than girls to report all measured emotional reactions. Those who lost someone from COVID-19 were more than twice as likely to experience anger compared to those who did not. Our findings may help identifying adolescents more likely to report negative emotional reactions during the COVID-19 pandemic and inform public health strategies for improving mental health among adolescents during/after the COVID-19 crisis
Correlated Strength in Nuclear Spectral Function
We have carried out an (e,e'p) experiment at high momentum transfer and in
parallel kinematics to measure the strength of the nuclear spectral function
S(k,E) at high nucleon momenta k and large removal energies E. This strength is
related to the presence of short-range and tensor correlations, and was known
hitherto only indirectly and with considerable uncertainty from the lack of
strength in the independent-particle region. This experiment confirms by direct
measurement the correlated strength predicted by theory.Comment: 4 pages, 2 figures, accepted by Phys. Rev. Let
- …