Search results for "raft"
showing 10 items of 1545 documents
Reducing False Node Failure Predictions in HPC
2019
Future HPC applications must be able to scale to thousands of compute nodes, while running for several days. The increased runtime and node count inconveniently raises the probability of hardware failures that may interrupt computations. Scientists must therefore protect their simulations against hardware failures. This is typically done using frequent checkpoint& restart, which may have significant overheads. Consequently, the frequency in which checkpoints are taken should be minimized. Predicting hardware failures ahead of time is a promising approach to address this problem, but has remaining issues like false alarms at large scales. In this paper, we introduce the probability of unnece…
Aalto-1, multi-payload CubeSat: Design, integration and launch
2021
The design, integration, testing, and launch of the first Finnish satellite Aalto-1 is briefly presented in this paper. Aalto-1, a three-unit CubeSat, launched into Sun-synchronous polar orbit at an altitude of approximately 500 km, is operational since June 2017. It carries three experimental payloads: Aalto Spectral Imager (AaSI), Radiation Monitor (RADMON), and Electrostatic Plasma Brake (EPB). AaSI is a hyperspectral imager in visible and near-infrared (NIR) wavelength bands, RADMON is an energetic particle detector and EPB is a de-orbiting technology demonstration payload. The platform was designed to accommodate multiple payloads while ensuring sufficient data, power, radio, mechanica…
Conducting Polymer with Orthogonal Catechol and Disulfide Anchor Groups for the Assembly of Inorganic Nanostructures
2017
To combine several inorganic components with organic material in a controlled special and permanent manner still remains a difficult issue. Two specifically functionalized block copolymers were synthesized separately and combined in a second step. A heterofunctional poly(ethylene glycol) (PEG) block copolymer bearing a single amino unit, a short PEG spacer, and multiple catechol functionalities was obtained via anionic ring-opening polymerization (AROP). Using the reversible addition–fragmentation chain transfer (RAFT) radical polymerization technique, a semiconducting block copolymer with carbazole side groups was obtained. The second polyacrylate block contained reactive ester groups and …
Green apparel buying behaviour : A Stimulus–Organism–Behaviour–Consequence (SOBC) perspective on sustainability-oriented consumption in Japan
2021
The green apparel literature has previously examined the disparity between consumers' positive purchase intentions and their actual purchase behaviour. This dichotomous behaviour represents the critical ‘intention–behaviour gap’, which marketers must seek to reduce to increase sales of their products. The current study thus seeks to identify the drivers of green apparel purchase behaviour that may potentially mitigate this gap. The proposed conceptual model is grounded in the Stimulus–Organism–Behaviour–Consequence (SOBC) paradigm and is tested through an analysis of cross-sectional data collected from 387 green apparel product consumers in Japan who were sourced through Macromill Inc. The …
Optimal Starting Conditions for the Rendezvous Maneuver, Part 1: Optimal Control Approach
2008
We consider the three-dimensional rendezvous between two spacecraft: a target spacecraft on a circular orbit around the Earth and a chaser spacecraft initially on some elliptical orbit yet to be determined. The chaser spacecraft has variable mass, limited thrust, and its trajectory is governed by three controls, one determining the thrust magnitude and two determining the thrust direction. We seek the time history of the controls in such a way that the propellant mass required to execute the rendezvous maneuver is minimized. Two cases are considered: (i) time-to-rendezvous free and (ii) time-to-rendezvous given, respectively equivalent to (i) free angular travel and (ii) fixed angular trave…
Guidance Trajectories for Spacecraft Rendezvous
2007
In a previous paper of Miele et al. (J. Optim. Theory Appl. 132(1), 2007), we employed the single-subarc sequential gradient-restoration algorithm to optimize the three-dimensional rendezvous between a target spacecraft in a planar circular orbit and a chaser spacecraft with an initial separation distance and separation velocity. The achieved continuous solutions are characterized by two, three, or four subarcs depending on the performance index (time, fuel) and the constraints. In this paper, based on the solutions in Miele et al. (J. Optim. Theory Appl. 132(1), 2007), we employ the multiple-subarc sequential gradient-restoration algorithm to produce pieced guidance trajectories implementa…
Optimal Trajectories for Spacecraft Rendezvous
2007
The efficient execution of a rendezvous maneuver is an essential component of various types of space missions. This work describes the formulation and numerical investigation of the thrust function required to minimize the time or fuel required for the terminal phase of the rendezvous of two spacecraft. The particular rendezvous studied concerns a target spacecraft in a circular orbit and a chaser spacecraft with an initial separation distance and separation velocity in all three dimensions. First, the time-optimal rendezvous is investigated followed by the fuel-optimal rendezvous for three values of the max-thrust acceleration via the sequential gradient-restoration algorithm. Then, the ti…
Use of Unrooted Grafted Vegetable Cuttings: I. Effects of Healing Duration and Transportation Temperature
2013
ogy to overcome soil-borne diseases and pests and to add extra vigor to the plants under various environmental stress conditions. In order to advance the use of grafting in U.S. vegetable production in open fields, key issues to address include 1) increasing the propagation capacity to meet the expected large number of seedlings necessary to supply the demands of typically large farms and 2) reducing production costs. Traditionally, vegetable grafting is a labor-intensive process involving much training and logistics. However, the seasonal nature of nursery operations due to the limitation of transportation of the grafted seedlings is problematic when nurseries are interested in introducing…
Sensitivities of Amazonian clouds to aerosols and updraft speed
2017
Abstract. The effects of aerosol particles and updraft speed on warm-phase cloud microphysical properties are studied in the Amazon region as part of the ACRIDICON-CHUVA experiment. Here we expand the sensitivity analysis usually found in the literature by concomitantly considering cloud evolution, putting the sensitivity quantifications into perspective in relation to in-cloud processing, and by considering the effects on droplet size distribution (DSD) shape. Our in situ aircraft measurements over the Amazon Basin cover a wide range of particle concentration and thermodynamic conditions, from the pristine regions over coastal and forested areas to the southern Amazon, which is highly poll…
The ACRIDICON-CHUVA campaign: Studying tropical deep convective clouds and precipitation over Amazonia using the new German research aircraft HALO
2016
Abstract Between 1 September and 4 October 2014, a combined airborne and ground-based measurement campaign was conducted to study tropical deep convective clouds over the Brazilian Amazon rain forest. The new German research aircraft, High Altitude and Long Range Research Aircraft (HALO), a modified Gulfstream G550, and extensive ground-based instrumentation were deployed in and near Manaus (State of Amazonas). The campaign was part of the German–Brazilian Aerosol, Cloud, Precipitation, and Radiation Interactions and Dynamics of Convective Cloud Systems–Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud Resolving Modeling and to the GPM (Global Precipitatio…