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Bubble curtains are widely used to protect marine life from exposure to noise during offshore construction. However, operating a bubble curtain is costly. Therefore optimizing the acoustic effect of the available air is important. An interesting approach is to split the airflow rate into two separate bubble curtains, rather than one single curtain. This concept is tested experimentally and numerically. The experiments and the model show an increase in performance of the compressed air when it is split between two manifolds. An increased insertion loss of up to 11dB is measured. This increase in performance is possibly due to the fact that the reflective properties of the bubble curtains are maintained when halving the airflow rate. In effect, by splitting the airflow a second acoustic barrier is added. Additionally, the variations in the bubble curtain performance between individual measurements are shown to be largely caused by temporal variations in the air distribution. The applicability of equivalent fluid models for bubble curtains is discussed, and it is shown that accounting for a gap in the bubble curtain, close to the manifold where the bubble curtain is not fully developed, results in better agreement between the modelled and the measured insertion loss.

The ultrafast and ultracold electron source, based on laser cooling and trapping of an atomic gas and its subsequent near-threshold photoionization, is capable of generating electron bunches with a high transverse brightness at energies of roughly 10 keV. This paper investigates the possibility of increasing the range of applications of this source by accelerating the bunch using radio-frequency electromagnetic fields. Bunch energies of $\sim35$ keV are measured by analyzing the diffraction patterns generated from a mono-crystalline gold sample. Further analysis points to a largely preserved normalized transverse emittance during acceleration.

An ultracold electron source based on near-threshold photoionization of a laser-cooled and trapped atomic gas is presented in this work. Initial DC acceleration to $\sim$10 keV and subsequent acceleration of the created bunches to 100 keV by RF fields makes the design suitable to serve as injector for accelerator-based light sources, single-shot ultrafast protein crystallography, applications in dielectric laser acceleration schemes, and potentially as an injector for free electron lasers operating in the quantum regime. This paper presents the design and properties of the developed DC/RF structure. It is shown that operation at a repetition frequency of 1 kHz is achievable and detailed particle tracking simulations are presented showing the possibility of achieving a brightness that can exceed conventional RF photosources.

This paper provides language identification models for low- and under-resourced languages in the Pacific region with a focus on previously unavailable Austronesian languages. Accurate language identification is an important part of developing language resources. The approach taken in this paper combines 29 Austronesian languages with 171 non-Austronesian languages to create an evaluation set drawn from eight data sources. After evaluating six approaches to language identification, we find that a classifier based on skip-gram embeddings reaches a significantly higher performance than alternate methods. We then systematically increase the number of non-Austronesian languages in the model up to a total of 800 languages to evaluate whether an increased language inventory leads to less precise predictions for the Austronesian languages of interest. This evaluation finds that there is only a minimal impact on accuracy caused by increasing the inventory of non-Austronesian languages. Further experiments adapt these language identification models for code-switching detection, achieving high accuracy across all 29 languages.

Electromagnetic radiation in the soft x-ray spectral range ($1-100~\rm{nm}$ wavelengths or $0.01-1~\rm{keV}$ photon energies) is rapidly gaining importance in both fundamental research and industrial applications. At present the degree of coherence and the average photon flux required by advanced applications is only available at large-scale synchrotron facilities and Free Electron Lasers (FELs), severely limiting the range of applications. We propose a fully coherent soft x-ray source, based on Inverse Compton Scattering (ICS) of electron bunches created by photoionization of a laser-cooled and trapped atomic gas. By combining spatial modulation of the photoionization process with radiofrequency bunch compression techniques, micro-bunching at soft x-ray wavelengths and thus coherent amplification can be realised, resulting in a soft x-ray table-top Compton light source.

The energy distribution of an ultracold rubidium ion beam, which is intended to be used as the source for a focused ion beam instrument, is measured with a retarding field analyzer. The ions are created from a laser-cooled and compressed atomic beam by two-step photoionization in which the ionization laser power is enhanced in a build-up cavity. Particle tracing simulations are performed to ensure the analyzer is able to resolve the distribution. The lowest achieved full width 50% energy spread is $\left(0.205\pm0.006\right)$ eV. The energy spread originates from the variation in the ionization position of the ions which are created inside an extraction electric field. This extraction field is essential to limit disorder-induced heating which can decrease the ion beam brightness. The ionization position distribution is limited by a tightly focused excitation laser beam. Energy distributions are measured for various ionization and excitation laser intensities and compared with calculations based on numerical solutions of the optical Bloch equations including ionization. A good agreement is found between measurements and calculations., Comment: 10 pages, 10 figures

After a review of the literature, critical reflective work behavior (CRWB) was defined as: a set of connected, individual activities aimed at analyzing, optimizing, or innovating work practices on the individual, team, or organizational level. The combination of literature review and analysis of case studies led to the operationalization of CRWB in these dimensions: reflection, learning from mistakes, vision sharing, challenging group-think, asking for feedback, knowledge sharing, experimentation, and awareness of employability. Factors influencing CRWB were categorized into these two clusters: individual factors and work and organizational factors. Individual factors were motivation, self-efficacy, and experience concentration (the diversity of experience in one's career). Job characteristics with a supposed impact on CRWB were work pace and workload, alternation, autonomy, task obscurity, information, participation in innovation and decision-making, cooperation, communication, coaching, and organizational learning climate. A survey with 742 respondents validated the dimensions of CRWB. Important influencing factors seemed to be self-efficacy (positive), participation (positive), and experienced difficulty with change (negative). Contains 32 references.) (YLB)