Resonances in forward π+π− photoproduction on hydrogen

We show that the cross section of the Δ(1230) production in the γp → pπ+ π− reaction at forward angles and with unpolarized photons can be described in terms of gauge invariant one pion t-channel exchange amplitudes. Proper description of the polarized cross sections requires, however, the inclusion of contributions from the baryon exchanges.

Optimal depth of the computational pipeline for a given amount of input data

Рассмотрен вычислительный конвейер, ступени которого могут иметь различные временные задержки, а время обмена с каналами одинаково. При заданной вероятности того, что входной элемент данных вызывает рестарт, построена аналитическая модель для расчета вероятнейшего и среднего значений времени обработки заданного числа входных элементов данных. На основании этой модели показано, что при заданных числе ступеней и тотальной логической задержке конвейер будет иметь максимальную производительность тогда и только тогда, когда задержки ступеней равны между собой. Для конвейера с одинаковыми задержками ступеней получена поправка известной формулы Доби—Флинна для оптимальной глубины вычислительного конвейера при заданной вероятности рестарта с учетом числа обрабатываемых элементов. Приведен пример, показывающий, что эта поправка может быть существенной. Показано, что эта формула дает оптимальную глубину на множестве всех конвейеров, включая конвейеры с различными задержками ступеней. A computational pipeline is considered, the stages of which can have different logic delays, and the overhead clock of the channels is the same. Given the probability that the data element calls a restart, an analytical model is constructed to calculate the most probable and expected times for processing input data elements for a given amount of input data. Based on this model, it is shown that for a given number of stages and total logical delay, the pipeline has maximum performance if and only if the delays of the stages are equal to each other. For the pipeline with the same delays of stages, a correction is made for the well-known Duby—Flynn formula for the optimum depth of the computational pipeline with a given probability of restart, taking into account the number of elements being processed. The criterion of optimality can be the minimum most probable data processing time or the minimum value of the mathematical expectation the data processing time. An example is given showing that this correction can be significant. It is shown that for given restart probability, total logical delay, channel exchange time and data volume, this formula gives the optimum depth on the set of all pipelines, including pipelines with different stage delays.

Lateral Circulation Generates Flood Tide Stratification and Estuarine Exchange Flow in a Curved Tidal Inlet

Cross-channel transect measurements of microstructure and velocity in a well-mixed and curved tidal inlet in the German Wadden Sea show the occurrence of significant late flood stratification. This stratification is found to be a result of lateral straining. This study observes a strong single-cell lateral circulation, which is strongly pronounced at late flood and absent during most of ebb. This tidal asymmetry is caused by a systematic interplay between centrifugal forcing and the lateral baroclinic pressure gradient. During flood a positive feedback between the terms generates strong lateral circulation, whereas during ebb a negative feedback leads to a suppression of the cross-channel exchange. A theoretical framework based on vorticity is developed, which allows lateral and longitudinal circulation to be studied in a consistent way. With this framework it is possible to show that the tidal asymmetry of the lateral flow is a major driver of residual longitudinal estuarine circulation, here identified with the tidally averaged across-channel vorticity component.

Review of Robust Data Exchange Using Optical Nonlinearities

Data exchange, namely bidirectional information swapping, provides enhanced flexibility compared to the unidirectional information transfer. To fulfill the rapid development of high-speed large-capacity optical communications with emerging multiplexing/demultiplexing techniques and advanced modulation formats, a laudable goal would be to achieve data exchange in different degrees of freedom (wavelength, time, polarization), for different modulation formats (OOK, DPSK, DQPSK, pol-muxed), and at different granularities (entire data, groups of bits, tributary channels). Optical nonlinearities are potentially suitable candidates to enable data exchange in the wavelength, time, and polarization domains. In this paper, we will review our recent works towards robust data exchange by exploiting miscellaneous optical nonlinearities, including the use of cSFG/DFG in a PPLN waveguide for time- (groups of bits) and channel-selective data exchange and tributary channel exchange between two WDM+OTDM signals, nondegenerate FWM in an HNLF for phase-transparent data exchange (DPSK, DQPSK), bidirectional degenerate FWM in an HNLF for multi-channel data exchange, and Kerr-induced nonlinear polarization rotation in an HNLF for tributary channel exchange of a pol-muxed DPSK OTDM signal. The demonstrated data exchanges in different degrees of freedom, for different modulation formats, and at different granularities, open the door for alternative approaches to achieve superior network performance.