Processability of high-strength aluminum 6182 series alloy via laser powder bed fusion (LPBF)

The growing demand for more materials available for the LPBF-process, in particular high-strength aluminum alloys, is evident in the market. In the present work, a systematic investigation of the processability of aluminum 6182 series alloys, using LPBF, was carried out. For this purpose, the influence of process parameters, especially of enhanced preheating by heating the substrate plate during the LPBF process, on the microstructure of EN AW 6182 specimens was studied.Experiments were conducted at different preheating temperatures always using the same d-optimal design-of-experiments, the laser power, scanning speed, hatch distance, and laser focus position being varied over a wide range.It was found that the preheating temperature has the strongest impact on hot cracking. Higher temperatures result in a significantly reduced number of hot cracks in the microstructure. Moreover, an equiaxed microstructure of the specimens manufactured can be observed at preheating temperatures of 500 °C. In addition to the preheating temperature, the achievable part density is most strongly affected by the laser focus position and the laser power, whereas the hatch distance shows no discernible impact on the part density. Furthermore, neither the hatch distance nor the laser focus position shows any significant effect on hot cracking.In combination with the optimal scanning parameters, crack-free parts with a fully equiaxed grain structure and densities > 99.0% can be manufactured via LPBF at a preheating temperature of 500 °C.

Assignment of Focus Position with Convolutional Neural Networks in Adaptive Lens Based Axial Scanning for Confocal Microscopy

Adaptive lenses offer axial scanning without mechanical translation and thus are promising to replace mechanical-movement-based axial scanning in microscopy. The scan is accomplished by sweeping the applied voltage. However, the relation between the applied voltage and the resulting axial focus position is not unambiguous. Adaptive lenses suffer from hysteresis effects, and their behaviour depends on environmental conditions. This is especially a hurdle when complex adaptive lenses are used that offer additional functionalities and are controlled with more degrees of freedom. In such case, a common approach is to iterate the voltage and monitor the adaptive lens. Here, we introduce an alternative approach which provides a single shot estimation of the current axial focus position by a convolutional neural network. We use the experimental data of our custom confocal microscope for training and validation. This leads to fast scanning without photo bleaching of the sample and opens the door to automatized and aberration-free smart microscopy. Applications in different types of laser-scanning microscopes are possible. However, maybe the training procedure of the neural network must be adapted for some use cases.

The prosody of focus projection: word stress and F0 patterns in Georgian

Based on experimental evidence, this paper shows that focus projection/percolation – the phenomenon by way of which prosodic prominence on a sub-constituent signals focus on the whole constituent – has a consistent prosodic realization in Georgian. The novelty of these findings lies in two properties of Georgian that have not been explored from the perspective of focus projection: it is a language with a dedicated focus position (linearly immediately preverbal) and one that does not rely on pitch accents in the expression of phrasal prosody (Skopeteas & Féry 2010; 2016). According to focus projection accounts (Selkirk 1984; Cinque 1993; Ladd 1996; Zubizarreta 1998, a. o.), utterances with narrow focus on the direct object are realized in the same way as broad focus utterances, since in all three cases prosodic prominence is realized on the direct object. In contrast, in utterances with narrow focus on the subject, the subject is the most prosodically prominent element, which means that the whole utterance has a different prosodic realization from that of broad focus contexts. This paper shows that the distribution of prosodic prominence in object- and subject-focus contexts in Georgian fits with this generalization. Specifically, the realization of utterances with narrowly focused objects does not differ from broad focus contexts in their F0 patterns and prominence of the stressed syllable, while narrowly focused subjects differ from subjects in broad focus utterances in both of these parameters.

Laser process parameter optimization of dimple created on oriented carbon fiber reinforced epoxy composites

It was mainly aimed at the study to make the optimization of laser parameters to obtain dimples with the desired shape and size. Carbon Fiber EPOXY composite (CF-EPOXY) surfaces were ablated by Nd:YAG laser which has a 1064 nm wavelength. Some important laser process parameters such as focus position, pulse energy, duration and number were optimized to achieve maximum aspect ratio, circular shape and minimum thermal defect. In addition, it has been determined that which laser parameters are more effective to obtain the desired quality surface. These different shapes and geometry of dimples could be used to improve some properties such as wettability, friction, etc. The pulse energy with an effective rate of 55.97 % is the most effective parameter to achieve the larger aspect ratio. The focus position is the most effective parameter with the rates of 66.18 % and 47.94 % to obtain both perfect circularity and minimum thermal defects respectively. Confirmation experiments were performed and the highest aspect ratio was found as 1.14, the best circular dimple and the minimum thermal effects outside the spot area were found with the rates of 1.021. These are the optimum results of 9 experiment sets in this study for each output. The results were supported by confirmation experiments and regression analysis. It can be concluded that the Taguchi method is reliable and saves time and materials.

Focus Attracts Attachment

There is growing evidence that pitch accents as well as prosodic boundaries can affect syntactic attachment. But is this an effect of their perceptual salience (the Salience Hypothesis), or is it because accents mark the position of focus (the Focus Attraction Hypothesis)? A pair of auditory comprehension experiments shows that focus position, as indicated by preceding wh-questions instead of by pitch accents, affects attachment by drawing the ambiguous phrase to the focus. This supports the Focus Attraction Hypothesis (or a pragmatic version of salience) for both these results and previous results of accents on attachment. These experiments show that information structure, as indicated with prosody or other means, influences sentence interpretation, and suggests a view on which modifiers are drawn to the most important information in a sentence.

The Intervention Effect in Late Archaic Chinese and Modern Mandarin

I investigate the Intervention Effect in Late Archaic Chinese (LAC) and modern Mandarin. In LAC, negation displays the Intervention Effect on wh-phrases. There are two types of wh-items that are subject to the Intervention Effect triggered by negation, namely, wh-arguments and wh-adverbials that are supposed to move to a lower focus position below the negation; and those that have the option to stay in situ. Due to the intervening negative barrier, these c-commanded wh-phrases have to rise to a higher focus position above the negation so as to circumvent the Intervention Effect. I propose that the Intervention Effect in LAC is a consequence of Q-binding as a feature movement of [wh], interacting with movement into the hierarchy of clause-internal positions driven by [Topic] or [Focus] features. By contrast, focus or quantificational phrases do not display the Intervention Effect in LAC. In modern Mandarin, focus phrases, but not negation or quantified structures, impose the Intervention Effect on wh-items; negation, but not focus phrases or quantified structures, imposes the Intervention Effect on temporal wh-adverbials. I also propound three obligatory requirements for the Intervention Effect to take place in LAC, namely, interrogativity of wh-items, the possibility of feature wh-movement, and a hierarchy of clausal positions. Although the Intervention Effect in LAC and modern Mandarin are triggered by different barriers, it always needs to meet the three requirements. Data from both LAC and Mandarin justify previous analyses regarding feature movement.

An Auto-Focus Method of Microscope for the Surface Structure of Transparent Materials under Transmission Illumination

This paper is concerned with auto-focus of microscopes for the surface structure of transparent materials under transmission illumination, where two distinct focus states appear in the focusing process and the focus position is located between the two states with the local minimum of sharpness. Please note that most existing results are derived for one focus state with the global maximum value of sharpness, they cannot provide a feasible solution to this particular problem. In this paper, an auto-focus method is developed for such a specific situation with two focus states. Firstly, a focus state recognition model, which is essentially an image classification model based on a deep convolution neural network, is established to identify the focus states of the microscopy system. Then, an endpoint search algorithm which is an evolutionary algorithm based on differential evolution is designed to obtain the positions of the two endpoints of the region where the real focus position is located, by updating the parameters according to the focus states. At last, a region search algorithm is devised to locate the focus position. The experimental results show that our method can achieve auto-focus rapidly and accurately for such a specific situation with two focus states.

SAR distribution of non-invasive hyperthermia with microstrip applicators on different breast cancer stages

<span>This paper presents the microstrip antenna with different applied frequencies used as a non-invasive hyperthermia applicator. This non-invasive hyperthermia applicator is introduced to clarify the sufficient heat distribution on the treated tissue for different breast cancer stages. 57 mammogram breast cancer images from early-stage to stage-3 are analyzed to obtain the required penetration depth and focus position distance. Then, the simulation-based experiment is carried out to observe the heating distribution on different stages of cancer with two different operating frequencies; 915MHz and 2450MHz. Also included in this paper is the prediction on the period for hyperthermia treatment planning execution. Based on the results, various penetration depths are obtained when different operating frequencies are applied. 915MHz antenna showed better results when compared to 2450MHz, where microstrip applicator with 915MHz is able to heat cancer at stage-1, stage-2, and stage-3 with good penetration depth and focus position distance, while 2450MHz only performed well in early-stage cancer. Meanwhile, different stages require various periods of time. From the results, the shortest period for hyperthermia execution simulated in the early-stage and then followed by stage-3, stage-2, and the longest period is in stage-1.</span>

Wh-P and the Intervention Effect of negation

Following the Government and Binding theory mainly developed by Chomsky (1981, 1982, 1986), I explore wh-P and the Intervention Effect of negation in Late Archaic Chinese (LAC). I propose that the inverted order of wh-P in LAC is generated via PP inversion followed by the separate preposing of wh and P. The wh-complement raises to [Spec, PP] and further moves to the specifier position of a functional projection. If the wh-PP is base-generated preverbally, the preposition moves to the head position of the functional projection directly; if the wh-PP is base-generated postverbally, the preposition must first incorporate to a V0 and then move to the head position of the functional projection through excorporation. In terms of the Intervention Effect, wh-arguments and adverbials that usually move to the Low focus position below negation are subject to a blocking effect caused by negation, so these wh-phrases have to land in the High focus position above negation which is expected to accommodate ‘high’ adverbials exclusively. I argue that the Intervention Effect in LAC is a consequence of Q-binding as feature movement of [wh], interacting with fronting into the hierarchy of clause-internal positions driven by [Focus] feature.