Soonkyu Hwang

Draft Genome Sequence of Clostridium aceticum DSM 1496, a Potential Butanol Producer through Syngas Fermentation

ABSTRACT Clostridium aceticum DSM 1496 is a Gram-negative anaerobic chemolithoautotrophic acetogenic bacterium that is capable of producing commodity chemicals from syngas fermentation. In this study, we report the draft genome sequence of the C. aceticum DSM 1496 strain (4.16 Mb) to elucidate the syngas fermentation metabolic pathway.

A reference-free micro defect visualization using pulse laser scanning thermography and image processing

As quality control of micro devices and early detection of micro defects in these devices are becoming increasingly important, the demand for a fast and automated online inspection technique to detect micro defects with high spatial resolution is increasing. In this study, a reference-free micro defect visualization algorithm is developed based on laser scanning thermography to detect micro defects in devices instantaneously and automatically with high spatial resolution. A pulse modulated continuous wave laser generates thermal waves in a target device, and the corresponding thermal responses are recorded by an infrared (IR) camera. When the thermal wave encounters a micro defect, the propagation of the thermal wave is blocked at the interface of the micro defect. The blockage of the thermal wave is detected by the proposed reference-free micro defect visualization algorithm. First, an edge detection algorithm is applied to a raw thermal image obtained at a specific time point to extract the thermal discontinuities formed at the boundaries of the defect. The edge images obtained from all time sequences are then assembled into a single accumulated edge image to accentuate defect-induced thermal disturbances in the form of edge features. Finally, the accumulated edge image is automatically processed using a binary imaging algorithm to visualize the micro defect in the target device. The performance of the proposed reference-free micro defect visualization algorithm is examined using two types of specimens, semiconductor chips and ceramic-epoxy composites. The proposed algorithm successfully diagnoses micro defects ranging from 4 μm to 40 μm in width.

Draft Genome Sequence of Acetobacterium bakii DSM 8239, a Potential Psychrophilic Chemical Producer through Syngas Fermentation.

ABSTRACT Acetobacterium bakii DSM 8239 is an anaerobic, psychrophilic, and chemolithoautotrophic bacterium that is a potential platform for producing commodity chemicals from syngas fermentation. We report here the draft genome sequence of A. bakii DSM 8239 (4.14 Mb) to elucidate its physiological and metabolic properties related to syngas fermentation.

Continuous-wave line laser thermography for monitoring of rotating wind turbine blades

This article presents a continuous-wave line laser thermography system for monitoring of rotating wind turbine blades. The proposed continuous-wave line laser thermography system non-destructively inspects rotating blades by generating thermal waves on the target blades using a continuous-wave line laser beam and simultaneously recording the corresponding thermal wave propagation using an infrared camera. The continuous-wave line laser thermography system is positioned at a fixed point, and the blades are automatically scanned using the continuous-wave line laser thermography system as the blades rotate under normal operational conditions. A coordinate transform algorithm named “time–space-integrated coordination transform” is developed for precise damage evaluation in rotating blades. Time–space-integrated coordination transform transforms spatially and temporally varying thermal images taken by the infrared camera to only temporally varying thermal images viewed from the perspective of the fixed blade positions. The effectiveness of the proposed continuous-wave line laser thermography system is experimentally validated by detecting hidden delamination on lab-scale rotating blades. In the experiments, artificial delaminations with diameters of 15 and 30 mm are successfully visualized with no false alarms while the blades are rotating at 10 r/min.

Peptide Transporter CstA Imports Pyruvate in Escherichia coli K-12

ABSTRACT Pyruvate is an important intermediate of central carbon metabolism and connects a variety of metabolic pathways in Escherichia coli. Although the intracellular pyruvate concentration is dynamically altered and tightly balanced during cell growth, the pyruvate transport system remains unclear. Here, we identified a pyruvate transporter in E. coli using high-throughput transposon sequencing. The transposon mutant library (a total of 5 × 105 mutants) was serially grown with a toxic pyruvate analog (3-fluoropyruvate [3FP]) to enrich for transposon mutants lacking pyruvate transport function. A total of 52 candidates were selected on the basis of a stringent enrichment level of transposon insertion frequency in response to 3FP treatment. Subsequently, their pyruvate transporter function was examined by conventional functional assays, such as those measuring growth inhibition by the toxic pyruvate analog and pyruvate uptake activity. The pyruvate transporter system comprises CstA and YbdD, which are known as a peptide transporter and a conserved protein, respectively, whose functions are associated with carbon starvation conditions. In addition to the presence of more than one endogenous pyruvate importer, it has been suggested that the E. coli genome encodes constitutive and inducible pyruvate transporters. Our results demonstrated that CstA and YbdD comprise the constitutive pyruvate transporter system in E. coli, which is consistent with the tentative genomic locus previously suggested and the functional relationship with the extracellular pyruvate sensing system. The identification of this pyruvate transporter system provides valuable genetic information for understanding the complex process of pyruvate metabolism in E. coli. IMPORTANCE Pyruvate is an important metabolite as a central node in bacterial metabolism, and its intracellular levels are tightly regulated to maintain its functional roles in highly interconnected metabolic pathways. However, an understanding of the mechanism of how bacterial cells excrete and transport pyruvate remains elusive. Using high-throughput transposon sequencing followed by pyruvate uptake activity testing of the selected candidate genes, we found that a pyruvate transporter system comprising CstA and YbdD, currently annotated as a peptide transporter and a conserved protein, respectively, constitutively transports pyruvate. The identification of the physiological role of the pyruvate transporter system provides valuable genetic information for understanding the complex pyruvate metabolism in Escherichia coli.

Automated Inspection System using Thermography for Uncured Damage Detection in LNG Carrier Triplex Bonding Layer

This paper describes the automated thermography system (ATS) using a halogen thermography technique for detecting the uncured damage in liquefied natural gas (LNG) carrier triplex bonding layers. The uncured damage in the triplex bonding layers weaken the shearing stress and cause the failure of triplex bonding layers which can occur the reduction of structural longevity. To detect the uncured damage, first, the thermal wave is generated on the target structure by the halogen lamp, and the corresponding thermal wave propagation is measured by an infrared (IR) camera. Next, the uncured damage part can be extracted based on the phenomena that an abnormal temperature fluctuation is observed near the uncured areas compared with the intact area. Even though there has a small temperature difference between intact and uncured part, the proposed image processing algorithm can extract the uncured part. Here, the ATS is synchronized with mobile system so that ATS can inspect the whole area of LNG carrier automatically. The effectiveness of the proposed ATS is successfully validated by validation test with quantifying the uncured area.

Laser Thermography and Image Processing for Under-Paint Corrosion Detection

In this study, a line laser thermography system (LLTS) is developed for rapid and automated detection of under-paint corrosion. First, the heat energy is generated on the target structure by line laser scanning, and the corresponding heat energy propagation is measured by an infrared (IR) camera. Then hidden corrosion areas on the painted target structure are visualized based on the phenomena that the abnormal temperature fluctuation is observed near the hidden corrosion areas after the heat energy generation, due to the differences of thermal conductivities between the intact and corrosion regions. The proposed LLTS can detect the under-paint corrosion in non-contact, non-destructive and remote manner, thus, LLTS can be applied in the various fields. Also, by using the proposed LLTS, the corrosion areas can be detected using only current-state IR data with minimizing the false alarms caused by the environmental and operational variations. The effectiveness of the proposed LLTS is validated by both lab-scale and real-scale structures with successfully detecting and quantifying the hidden corrosion areas.

Active Infrared Thermography for Visualizing Subsurface Micro Voids in an Epoxy Molding Compound

This paper presents an automated subsurface micro void detection technique based on pulsed infrared thermography for inspecting epoxy molding compounds (EMC) used in electronic device packaging. Subsurface micro voids are first detected and visualized by extracting a lock-in amplitude image from raw thermal images. Binary imaging follows to achieve better visualization of subsurface micro voids. A median filter is then applied for removing sparse noise components. The performance of the proposed technique is tested using 36 EMC samples, which have subsurface (below 150 μm ~ 300 μm from the inspection surface) micro voids (150 μm ~ 300 μm in diameter). The experimental results show that the subsurface micro voids can be successfully detected without causing any damage to the EMC samples, making it suitable for automated online inspection.