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Semitransparent organic solar cells (ST-OSCs) are considered to be an influential tool for aesthetic and economic building-integrated photovoltaics, which can be fabricated by the printing technology. A poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) and ionic liquid (IL) composite has been considered as an electrode for ST-OSCs because of its high electrical conductivity, high transparency, and printability. However, we found that the introduction of IL into the PEDOT:PSS solution for enhancing its electrical conductivity results in (1) nonreliable printing of PEDOT:PSS/IL composite films because of gradual gelation of the mixture solution and (2) the production of chemically reactive ion pairs during ion exchange between PSS and IL, which induces the oxidation of the underlying organic semiconductors during printing. To solve these problems, we developed a sequential printing method using pristine PEDOT:PSS and IL solutions to retard ion exchange, thus preventing chemical doping of organic semiconductors by newly generated ion pairs. Finally, by using only solution processes, we demonstrate efficient ST-OSCs with a printed PEDOT:PSS/IL composite as the top electrode, exhibiting a power conversion efficiency of 6.32% at an average visible transmittance of 35.4%.

Iminosemiquinone-linker-based conductive metal-organic frameworks (c-MOFs) have attracted much attention as next-generation electronic materials due to their high electrical conductivity combined with high porosity. However, the utility of such c-MOFs in high-performance devices has been limited to date by the lack of high-quality MOF thin-film processing. Herein, a technique known as the microfluidic-assisted solution shearing combined with post-synthetic rapid crystallization (MASS-PRC) process is introduced to generate a high-quality, flexible, and transparent thin-film of Ni

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We have generated high-power deep ultraviolet laser pulses from a Yb-doped rod-type fiber laser through sum-frequency generation (SFG) based on lithium triborate (LBO) crystals. The 1030 nm nanosecond laser pulses from the fiber laser are frequency-tripled to 343 nm pulses with two LBO crystals, and the residual 1030 nm fundamental laser pulses are mixed with the 343 nm pulses in an LBO crystal for the generation of 257 nm pulses. The maximum 257 nm radiation power is 12 W with a repetition rate of 500 kHz, and the conversion efficiency from 1030 nm to 257 nm is 12%. It is observed that the power of 257 nm radiation is limited by the temperature increase in the LBO crystal used for the SFG.

We developed a high-power dual-wavelength green pulsed laser that generates 528-nm and 535-nm laser pulses which overlap completely in time and space. Two single-frequency seed lasers of 1056 nm and 1070 nm are combined and amplified to 140 W through a series of ytterbium-doped fiber amplifiers including a rod-type fiber amplifier, and the amplified laser pulses of two wavelengths are frequency-doubled, respectively, by two consecutive lithium triborate crystals. The total green power is more than 80 W at a 400-kHz repetition rate, and the power ratio between the two green wavelengths can be adjusted.

Underwater cutting of 50 and 60 mm thick stainless steel plates with a 6-kW fiber laser was performed as a fundamental study for application to dismantling nuclear facilities. For this purpose, an underwater cutting head was developed by upgrading our previously developed in-air cutting head. A waterproof function was added while the optical design of the in-air cutting head was maintained. In the developed head, a single supersonic minimum length nozzle was applied without any complicated nozzle features because it was enough to make a local-dry-zone. With this head, cutting tests were performed for pierced and non-pierced specimens. The pierced specimen showed a slightly better cutting performance than the non-pierced specimen. However, the cuttings were adequate for both types of specimens with thicknesses of 50 and 60 mm. In the cutting results for the non-pierced specimens, the maximum cutting speeds were 80 mm/min for the 50 mm thickness and 40 mm/min for the 60 mm thickness. To the best of our knowledge, the results from this study show the best cutting performance in terms of speed and thickness for the same laser power among the reported results of underwater laser cutting. The kerf width was also measured for each cutting. As in ordinary laser cutting, the kerf widths were narrow. For the cutting at each maximum speed, the kerf widths for the 50 mm thickness were 1.6 mm for the front surface and 0.7 mm for the rear surface, and the kerf widths for the 60 mm thickness were 1.5 mm for the front surface and 1.2 mm for the rear surface. It is expected that the results of this study will contribute to the continued development of underwater cutting research for dismantling nuclear facilities.

The cutting performance of thick steel plates and large size pipes with a 10 kW fiber laser was studied for the dismantling of nuclear facilities. First, thick steel plates of up to 100 mm were tried to be cut at a high speed. For the thickness of 100 mm, both stainless steel and carbon steel plates were cut at maximum cutting speeds of ∼30 mm/min. And narrow kerf widths of less than 5 mm were obtained for all cutting tests. Second, a 150-mm thick stainless steel plate near the cutting thickness limit was attempted to be cut. The specimen was able to be cut even with a low cutting speed of 3 mm/min. To the best of our knowledge, this thickness is the largest among the published reports with a laser power of 10 kW. And this corresponds to a cutting capability in which most thick structures in a nuclear reactor can be cut. In addition, large size stainless steel pipes were also attempted to be cut. For a 165 mm diameter pipe, it was possible to be cut at high speed by one scan at a speed of 50 mm/min and round trip scan at a speed of 100 mm/min. This result implies that high-speed cutting was also possible for most pipe-type components inside the nuclear reactor. As a result, our 10-kW laser cutting system showed very efficient cutting performance in terms of the cutting speed and thickness. Moreover, the cuttings showed narrow kerf widths of less than 5 mm even for very thick steel of up to 150 mm in thickness. In the future, it is expected that the results of this work will contribute to cutting thick metal structures as basic research data in the dismantling of nuclear facilities using a laser. In addition, it is also expected that this work will contribute to other industrial fields requiring a thick steel cutting technique.

Skin conductance is an important bio-signal and generally measured between two fingers using a commercial Galvanic Skin Response (GSR) sensor. In this study, an ultra-thin (6 μm thick) and highly flexible GSR (f-GSR) sensor was developed for application to wearable devices. The f- GSR sensor consists of a Ag-Au core-shell nanowire array embedded in polyimide matrix. Since the nanowire array is vertically aligned in the matrix, the f-GSR sensor has anisotropic electrical conductivity, i.e., electrically conducting in the thickness-direction and electrically insulating in the in-plane direction. Results show that after the nanowire tips contacted skin they did not degrade during repeated measurement for three months, indicating the mechanical and chemical stability of the f-GSR sensor. The f-GSR sensor exhibits significantly better sensitivity than a commercial sensor: the f-GSR sensor can detect an NaCl solution mimicking human sweat in the concentration range of 10−6 to 1 M. The f-GSR sensor is expected to be used in wearable or patch healthcare devices.

This paper presents an optimal digital filtering technique to enhance the resolution of incremental delta-sigma modulators (incremental DSMs, IDSMs) using a low-power passive integrator. We first describe a link between a passive integrator and its impact on the output of the IDSM. We then show that the optimal digital filter design can be cast as a convex optimization problem, which can be efficiently solved. As a test vehicle of the proposed technique, we use a behavioral 2nd-order IDSM model that captures critical non-idealities of the integrator, such as gain compression and output saturation. The effectiveness of the presented technique is verified using extensive simulations. The result shows that the presented filtering technique improves signal-to-noise and distortion ratio (SNDR) by 15 dB&ndash, 20 dB, achieving SNDR over 90 dB when the oversampling ratio (OSR) = 256, and this corresponds to best-in-class performance when compared to previously published DSM designs using passive integrators.

This paper proposes a method of using internet of things (IoT) technology and walkie-talkies to notify factory operators of information about the manufacturing system of the factory. The proposed automatic notification system consists of walkie-talkies, manufacturing IT systems, and a device called the walkie-talkie automatic notification device based on IoT. The role of the walkie-talkie automatic notification device is to act as a gateway that sends information from the manufacturing IT systems to walkie-talkies as voice automatically. It is based on Raspberry Pi 3 hardware. We designed a simple automatic notification system that does not require extra infrastructure costs by using walkie-talkies that are in widespread use at manufacturing sites. This makes it possible to convey information about the machines in a factory or give other instructions to operators easily and efficiently.

A study was conducted to improve the cutting performance of a 60-mm thick stainless steel plate using a 6-kW fiber laser. Two techniques for improving the initial cutting performance were evaluated by preheating the work piece with a waiting time and step-like cutting speed increase. Both techniques showed improved cutting results compared to constant speed cutting. Among them, the method with a step-like cutting speed increase showed the better result in terms of cutting performance. As a result, a 60-mm thick stainless steel plate was cut at a maximum cutting speed of 72 mm/min with a preheating cutting speed of 24 mm/min. In order to confirm the effect of preheating, an additional experiment was performed to measure the temperature variation during the cutting process. Through this experiment, preheating temperature conditions were found to allow the specimen to be cut. It is expected that the results of this work will contribute to improving the cutting performance of thick metal structures in various industrial fields, as well as the dismantling of nuclear facilities using lasers in the future.

A cutting study with a high-power ytterbium-doped fiber laser was conducted for the dismantling of nuclear facilities. Stainless steel and carbon steel plates of various thicknesses were cut at a laser power of 6-kW. Despite the use of a low output of 6-kW, the cutting was successful for both stainless steel and carbon steel plates of up to 100 mm in thickness. In addition, the maximum cutting speeds against the thicknesses were obtained to evaluate the cutting performance. As representative results, the maximum cutting speeds for a 60-mm thickness were 72 mm/min for the stainless steel plates and 35 mm/min for the carbon steel plates, and those for a 100-mm thickness were 7 mm/min for stainless steel and 5 mm/min for carbon steel plates. These results show an efficient cutting capability of about 16.7 mm by kW, whereas other groups have shown cutting capabilities of ∼10 mm by kW. Moreover, the maximum cutting speeds were faster for the same thicknesses than those from other groups. In addition, the kerf widths of 60-mm and 100-mm thick steels were also obtained as another important parameter determining the amount of secondary waste. The front kerf widths were ∼1.0 mm and the rear kerf widths were larger than the front kerf widths but as small as a few millimeters.

In underwater laser cutting of steel plates thicker than 40 mm, the initial cutting speed was previously limited to 5–10 mm/min, because the generated melt could not be smoothly blown near the start point. Oblique cutting was considered a way to overcome this problem and speed up the initial cut. For this reason, underwater laser cutting tests were conducted to verify the improvement in initial cutting performance of thick steel plates through oblique cutting. First, constant speed cutting tests at oblique angle of 5° were performed on stainless steel plates. Compared to straight cutting, this method allowed initial cutting speed to be significantly increased. The maximum initial cutting speeds were 50, 25, and 15 mm/min for thicknesses of 48, 57, and 67 mm, respectively. When the oblique angle further increased to 15°, the initial cutting speed reached the maximum cutting speed achievable for each thickness. Therefore, there was no longer a need for 2-step cutting with low initial cutting speed. The maximum cutting speeds at the oblique angle of 15° were 100, 50, and 15 mm/min for thicknesses of 48, 57, and 68 mm, respectively. Additional cutting tests were performed for carbon steel plates. Due to the material properties of carbon steel, its cutting speed must be lower than that of stainless steel; however, all specimens were successfully cut at the oblique angle of 15°. The maximum cutting speeds of carbon steel plates were 40, 15, and 7 mm/min for thicknesses of 48, 59, and 69 mm, respectively.

Video monitoring environment of underwater cutting objects is rapidly deteriorated due to the increasing water turbidity in proportion to cutting operation. Precise monitoring of the cutting area is one of keys to improve work efficiency. In this paper, we studied a visibility improvement technique based on an artificial neural network for monitoring objects in a turbid underwater cutting site. In order to improve visibility in turbid water, a deep learning neural network that learned two types of visibility enhancement process was adopted. The first type is to train to restore an ideal underwater image with the best visibility from a turbid underwater image, and the second type is to train to restore an image with improved visibility using the conventional visibility improvement technique. We adopted two types of training real images based on the GAN (generative adversarial networks) model for the corresponding turbid input images. The first training image is the histogram-equalized image of a clear underwater image. If the first training image does not exist, an image with improved visibility by using histogram equalization for the turbid input image itself was used as the second training image. Experiments demonstrated that the trained neural network provided significantly improved clarity in turbid images compared to that of the conventional improving technique.