Power and Bandwidth Efficient Coded Modulation for Linear Gaussian Channels

A scheme for power- and bandwidth-efficient communication on the linear Gaussian channel is proposed. A scenario is assumed in which the channel is stationary in time and the channel characteristics are known at the transmitter. Using interleaving, the linear Gaussian channel with its intersymbol interference is decomposed into a set of memoryless subchannels. Each subchannel is further decomposed into parallel binary memoryless channels, to enable the use of binary codes. Code bits from these parallel binary channels are mapped to higher-order near-Gaussian distributed constellation symbols. At the receiver, the code bits are detected and decoded in a multistage fashion. The scheme is demonstrated on a simple instance of the linear Gaussian channel. Simulations show that the scheme achieves reliable communication at 1.2 dB away from the Shannon capacity using a moderate number of subchannels

Queues with random back-offs

We consider a broad class of queueing models with random state-dependent vacation periods, which arise in the analysis of queue-based back-off algorithms in wireless random-access networks. In contrast to conventional models, the vacation periods may be initiated after each service completion, and can be randomly terminated with certain probabilities that depend on the queue length. We examine the scaled queue length and delay in a heavy-traffic regime, and demonstrate a sharp trichotomy, depending on how the activation rate and vacation probability behave as function of the queue length. In particular, the effect of the vacation periods may either (i) completely vanish in heavy-traffic conditions, (ii) contribute an additional term to the queue lengths and delays of similar magnitude, or even (iii) give rise to an order-of-magnitude increase. The heavy-traffic asymptotics are obtained by combining stochastic lower and upper bounds with exact results for some specific cases. The heavy-traffic trichotomy provides valuable insight in the impact of the back-off algorithms on the delay performance in wireless random-access networks

Water-wise Rice Production

Rice is a profligate user of water. It takes 3,000–5,000 liters to produce 1 kilogram of rice, which is about 2 to 3 times more than to produce 1 kilogram of other cereals such as wheat or maize. Until recently, this amount of water has been taken for granted. Now, however, the water crisis threatens the sustainability of the irrigated rice ecosystem. In Asia, 17 million ha of irrigated rice areas may experience ‘physical water scarcity’ and 22 million ha ‘economic water scarcity’ by 2025. To safeguard food security and preserve precious water resources, ways must be explored to grow rice using less water. IRRI, together with Plant Research International of Wageningen University and Research Centre, organized a thematic workshop on Water-Wise Rice Production held 8-11 April 2002 at IRRI, Los Baños, Philippines. The objectives were to present and discuss the state-of-the-art in the development, dissemination, and adoption of water-saving technologies at spatial scales ranging from the field to irrigation system. This book contains the papers presented at the workshop

Effects of fallow replacement green manuring with annual legumes on soil water reserves

Non-Peer ReviewedLegume green manures are used in crop rotations to add organic matter, enhance N availability and to provide ground cover for soil conservation. In drought-prone regions like the Palliser Triangle, annual rather than perennial legumes could be used for fallow replacement green manuring in short rotations to avoid excessive depletion of soil water reserves. Results from a 6-year study of green manuring with 4 annual legumes in combination with snow trapping on a Brown loam at Swift Current were used to assess water use during legume growth, water use efficiency (WOE) of green manure production and amounts of soil water remaining for subsequent spring wheat. Each spring Black lentil, Tangier flatpea, Chickling vetch and Feedpea were seeded into wheat stubble with tall stubble trap strips along with continuous wheat and wheat-fallow plots. Legumes were incorporated in some and chemically desiccated in other plots as soon as they reached full bloom. Water use by the 4 legumes was generally related to DM production and did not differ from the amount used by wheat during the same vegetative growth period. Most of the water used was extracted from the 0- to 60-cm soil depth. On average, inoculated legumes used only 12% more water but produced much more DM than uninoculated legumes. Thus rhizobial seed inoculation and the enhanced N2-fixation elicited a doubling of the WUE by these green manures. Chickling vetch and feedpea were able to use water at a 20% greater efficiency than well fertilized spring wheat. Contrary to expectations, levels of soil water recharge between legume bloom and the following spring were always as high for incorporated as for desiccated green manures. At seeding time there was generally 20% less water under continuous wheat than in the fallow soil. In green manured soils, water reserves in spring did not differ between legume species and were usually 15% lower than in fallow plots with wheat trap strips. Wheat yields after green manures were affected primarily by weather and legume management but not by legume species. After incorporated green manures grain production was, on average, 12% and 17% greater than after conventional fallow or desiccated green manure, respectively. The presence of wheat strips in the fallow phase increased subsequent grain yields by an average 20%. We concluded that green manuring with annual legumes, when combined with snow trapping, offers a more bio-resource efficient and soil conserving alternative to conventional summer fallowing for wheat production within the Palliser Triangle

Toepassing van weefselkweek en embryogenese bij vermeerdering en veredeling van tulp

In dit rapport worden de resultaten beschreven van twee projecten waarin weekfselkweekmethoden voor vermeerderding en veredeling van tulp zijn onderzocht. Vermeerdering van tulp op het veld gaat erg langzaam waardoor het lang duurt voordat nieuwe cultivars op de markt kunnen worden gebracht. Vermeerdering m.b.v. weefselkweek kan dit aanzienlijk versnellen. Het protocol dat bij aanvang van de twee projecten beschikbaar was, is aanzienlijk verbeterd. In het eerste project werd nagegaan of somatische embryogenese (vorming van embryo's uit niet-geslachtscellen) toepasbaar is voor een sneller vermeerderingssysteem van tulp. Het tweede project draaide om het verbeteren van de vermeedering van tulp in vitro, uitgaande van scheutvorming op bloemstengelplakje

Entwuerfe ueber die von der Synodalkonferenz angenommene Epistelreihe

Entwuerfe ueber die von der Synodalkonferenz angenommene Epistelreihe (Drafts on the series of epistles adopted by the Synodal Conference

Direct microwave measurement of Andreev-bound-state dynamics in a proximitized semiconducting nanowire

The modern understanding of the Josephson effect in mesosopic devices derives from the physics of Andreev bound states, fermionic modes that are localized in a superconducting weak link. Recently, Josephson junctions constructed using semiconducting nanowires have led to the realization of superconducting qubits with gate-tunable Josephson energies. We have used a microwave circuit QED architecture to detect Andreev bound states in such a gate-tunable junction based on an aluminum-proximitized InAs nanowire. We demonstrate coherent manipulation of these bound states, and track the bound-state fermion parity in real time. Individual parity-switching events due to non-equilibrium quasiparticles are observed with a characteristic timescale $T_\mathrm{parity} = 160\pm 10~\mathrm{\mu s}$. The $T_\mathrm{parity}$ of a topological nanowire junction sets a lower bound on the bandwidth required for control of Majorana bound states

Ontwerpen van weefselkweekmedia met een gewasspecifieke samenstelling aan minrale nutrienten

In dit rapport wordt een handleiding aangeboden voor het ontwerpen van soortspecifieke weefselkweekvermeerderingsmedia. De handleiding bestaat uit een methode met vijf stappen. Bij de verschillende stappen wordt achtergrondinformatie gegeven om het geheel te verduidelijken. Voor een aantal gewassen zijn de soortspecifieke media getest

Cryopreservering: een techniek met toekomst

Voor veredelaars en kwekers is langdurige bewaring van interessante genotypen essentieel. Cypropreservering (invriezen in vloeibare stikstof) kan een goed alternatief zijn voor veld- of weefselbewaring. Voor lelie wordt dit duidelijk aangetoond in dit rapport. Het is veiliger en goedkoper. Met betrekking tot de actieve collectie kan cypropreservering als zekerheidbiedende aanvulling dienen voor veredelaar