We have observed that the collisional frequency shift in primary caesium fountain clocks varies with the clock state population composition and, in particular, is zero for a given fraction of the |F=4,mF=0) atoms, depending on the initial cloud parameters. We present a theoretical model explaining our observations. The possibility of the collisional shift cancellation implies an improvement in ...

This paper proposes a universal variable-length lossless compression algorithm based on fountain codes. The compressor concatenates the Burrows-Wheeler block sorting transform (BWT) with a fountain encoder, together with the closed-loop iterative doping algorithm. The decompressor uses a Belief Propagation algorithm in conjunction with the iterative doping algorithm and the inverse BWT. Linear-...

Atomization of liquid into the air attained through submerged ultrasound irradiation will involve formation fountain, which exhibits a sequence oscillating and/or intermittent characteristics/events: its vertical/axial growth and breakup; lateral “compound swinging”; associated dynamics mist spreading. This study attempts to provide mechanistic view ultrasonic atomization (UsA) process in terms...

Field and laboratory studies were carried out to test factors expected to be relevant for the germination of fountain grass: (1) light; (2) emergence of fountain grass seedlings from depths of 0, 2.5, and 5 cm; (3) fire passing over exposed and buried seeds; (4) laboratory heat treatment mimicking exposure to grass fire. Both fire in the field and heat applied in the laboratory killed fountain ...

Background and purpose: School, as a reliable place in educating students, has an important role in training. The aim of this study was the assessment of environmental health of primary schools in Norabad Mamasani city of Fars Province. Materials and Methods: In this analytical-descriptive and cross-sectional study, all of 26 primary schools in Norabad Mamasani city were surveyed by using cens...

In the uncertainty budget of primary atomic cesium fountain clocks, evaluations of frequency-pulling shifts of the hyperfine clock transition caused by unintentional excitation of its nearby transitions (Rabi and Ramsey pulling) have been based so far on an approach developed for cesium beam clocks. We re-evaluate this type of frequency pulling in fountain clocks and pay particular attention to...

Digital fountain codes were originally packet-level forward erasure codes, but researchers have found that they are good at correcting bit errors. Modern LDPC and turbo codes have been shown to approach the Shannon limit. However, they are fixed rate codes and cannot well satisfy the Internet services that may encounter variable loss rates or asynchronous data access. For both packet and bit le...

We describe the recent progress in our cesium atomic fountains at National Metrology Institute of Japan (NMIJ). We have developed three atomic fountains: NMIJ-F1, NMIJ-F2, and a truncated atomic beam fountain. NMIJ-F1 has been the primary frequency standard with uncertainty of 4×10 -15 since 2004. Especially in the last 4 years, we have reported the data to Bureau International des Poids et Mes...

For almost two decades, caesium fountain primary frequency standards (PFS) have represented the best realization of the definition of the second in the International System of units. Their accuracy has progressively improved with time, reaching a few parts in 1016. In this paper, we present the accuracy evaluation of ITCsF2, the new Cs fountain PFS developed at the Italian National Metrological...

The proliferation of applications that must reliably distribute large, rich content to a vast number of autonomous receivers motivates the design of new multicast and broadcast protocols. We describe an ideal, fully scalable protocol for these applications that we call a digital fountain. A digital fountain allows any number of heterogeneous receivers to acquire content with optimal efficiency ...