Fabrication and design of multi-layered radar absorbing structures of MWNT-filled glass/epoxy plain-weave composites

The object of this study is to design radar absorbing structures (RAS) with load-bearing ability in the X-band. Glass/epoxy plain-weave composites of excellent specific stiffness and strength, containing multi-walled carbon nanotubes (MWNT) to induce dielectric loss, were fabricated. Observations of the microstructure and the permittivity of the composites confirmed that the fabrics are suitable for use as RASs. A genetic algorithm and a theory of the reflection/transmission of electromagnetic waves in a multi-layered RAS were applied to design an optimal RAS composed of MWNT-filled composites. The thickness per ply was observed to vary, depending on the number of plies and the MWNT contents. A fabrication process was proposed that considered the variation. The proposed process was in the fabrication of a designed RAS, and the theoretical and measured reflection losses of the RAS were found to be in good agreement.     

A formula for the crack opening level under random loading in 2024-T351 aluminum alloy

Based on the fatigue crack growth results of the previous work for 2024-T351 aluminum alloy, the crack closure behavior under random loading was analyzed, and the correlation between the crack opening ratio and the stress ratio under random loading was discussed. The crack opening ratio under random loading can be expressed as a function of the stress ratio for the largest load cycle in a random load history. The correlation obtained is found to provide good predictions for crack growth under random loading.     

Equivalent multi-phase similitude law for pseudodynamic test on small scale reinforced concrete models

Small scale models have been frequently used to experimentally investigate the seismic performance of structures because capacities of testing facilities are limited and because they are more economically viable. However, not enough studies have been carried out on the development of similitude laws for accurately analogizing prototype structures with small scale models. Furthermore, conventional similitude requirements based on geometry may not be suitable in the inelastic range. When a small scale model of a prototype reinforced concrete structure is fabricated from a similar material to the prototype, an added mass would generally be required due to the volumetric variation, while the scale factor, as a ratio of the scale model to the prototype, cannot be sufficiently reduced due to the limitation of aggregate size. As an alternative, for small scale models it is desirable to use materials that are dissimilar to those of the prototype. Thus, a modified similitude law can be derived that depends on the geometric scale factor, equivalent modulus ratio and peak strain ratio. In this study, compressive strength tests were carried out to analyze the equivalent modulus ratio of micro-concrete to normal-concrete. The equivalent modulus ratios could then be divided into multi phases of strain level, which are basically dependent on the peak strain level at ultimate strength. An algorithm adaptable to the pseudodynamic test was therefore developed that considers an equivalent multi-phase similitude law based entirely on strain levels. Prior to carrying out the physical experiments, a numerical simulation was performed by idealizing the designed specimens to a single degree of freedom system with a bilinear model, and the pseudodynamic testing algorithm was numerically verified from seismic responses. A prototype and a 1/5 scale model of reinforced concrete columns as a test specimen was designed and fabricated based on the equivalent modulus ratios already defined. As a preliminary test, quasi-static tests on test specimens were carried out and their experimental results were compared using the constant and variable modulus ratios. Furthermore, in the pseudodynamic test on small scale models, it was verified that the modified pseudodynamic testing algorithm that considers the developed equivalent multi-phase similitude law may offer better simulation of the prototype structures than the conventional pseudodynamic testing algorithm. Therefore, it is found that the equivalent multi-phase similitude law would be applicable to the pseudodynamic test on small scale models.     

3D human modeling from a single depth image dealing with self-occlusion

This paper presents a 2D to 3D conversion scheme to generate a 3D human model using a single depth image with several color images. In building a complete 3D model, no prior knowledge such as a pre-computed scene structure and photometric and geometric calibrations is required since the depth camera can directly acquire the calibrated geometric and color information in real time. The proposed method deals with a self-occlusion problem which often occurs in images captured by a monocular camera. When an image is obtained from a fixed view, it may not have data for a certain part of an object due to occlusion. The proposed method consists of following steps to resolve this problem. First, the noise in a depth image is reduced by using a series of image processing techniques. Second, a 3D mesh surface is constructed using the proposed depth image-based modeling method. Third, the occlusion problem is resolved by removing the unwanted triangles in the occlusion region and filling the corresponding hole. Finally, textures are extracted and mapped to the 3D surface of the model to provide photo-realistic appearance. Comparison results with the related work demonstrate the efficiency of our method in terms of visual quality and computation time. It can be utilized in creating 3D human models in many 3D applications.     

Mechanical analysis of woven composites at high strain rates and its application to predicting impact behavior

The deformation behavior of woven composites at high strain rates was analyzed using a constitutive equation developed to describe the nonlinear, anisotropic/asymmetric and rate-dependent mechanical behavior of woven composites. The rate-dependent nonlinear behavior of woven composites was characterized at high strain rates (1 s⁻¹ to 100 s⁻¹) using a tensile testing method first proposed in this research. The material properties for the developed constitutive equation were determined and subsequently used in a finite element analysis of the deformation behavior of woven composites at high strain rates. Finally, the impact behavior of woven composites was predicted using the constitutive equation and the results were compared with experiments, showing that the current constitutive equation including the characterization method is adequate to describe the deformation behavior of woven composites at high strain rates up to impact level.     

Exposure to ethyl carbamate in alcohol-drinking and nondrinking adults and its reduction by simple charcoal filtration

The risk of exposure to ethyl carbamate from the consumption of kimchi, soy sauce, and alcoholic beverages was assessed in alcohol-drinking and nondrinking adults. An alcohol-drinking adult obtains 5.6–9.2 ng/kg bw/day of ethyl carbamate through the addition of kimchi and soy sauce, while a nondrinking adult receives 3.3–4.0 ng/kg bw/day via kimchi and soy sauce alone. The average excess cancer risk of an alcohol-drinking adult (3.9 × 10^?7) was also twice higher than that of an adult who does not drink (1.9 × 10^?7). We achieved a maximum of 47% and 45% removal of the ethyl carbamate present in diluted spirits and soy sauce, respectively, through a simple charcoal filtration process. This resulted in a reduction of the average daily intakes of ethyl carbamate through diluted spirits and soy sauce from 1.7 and 2.2 ng/kg bw/day to 0.9 and 1.2 ng/kg bw/day, respectively.     

Identifying and Verifying Vulnerabilities through PLC Network Protocol and Memory Structure Analysis

Cyberattacks on the Industrial Control System (ICS) have recently been increasing, made more intelligent by advancing technologies. As such, cybersecurity for such systems is attracting attention. As a core element of control devices, the Programmable Logic Controller (PLC) in an ICS carries out on-site control over the ICS. A cyberattack on the PLC will cause damages on the overall ICS, with Stuxnet and Duqu as the most representative cases. Thus, cybersecurity for PLCs is considered essential, and many researchers carry out a variety of analyses on the vulnerabilities of PLCs as part of preemptive efforts against attacks. In this study, a vulnerability analysis was conducted on the XGB PLC. Security vulnerabilities were identified by analyzing the network protocols and memory structure of PLCs and were utilized to launch replay attack, memory modulation attack, and FTP/Web service account theft for the verification of the results. Based on the results, the attacks were proven to be able to cause the PLC to malfunction and disable it, and the identified vulnerabilities were defined.     

Nanowire-based single-cell endoscopy

One-dimensional smart probes based on nanowires and nanotubes that can safely penetrate the plasma membrane and enter biological cells are potentially useful in high-resolution and high-throughput gene and drug delivery, biosensing and single-cell electrophysiology. However, using such probes for optical communication across the cellular membrane at the subwavelength level remains limited. Here, we show that a nanowire waveguide attached to the tapered tip of an optical fibre can guide visible light into intracellular compartments of a living mammalian cell, and can also detect optical signals from subcellular regions with high spatial resolution. Furthermore, we show that through light-activated mechanisms the endoscope can deliver payloads into cells with spatial and temporal specificity. Moreover, insertion of the endoscope into cells and illumination of the guided laser did not induce any significant toxicity in the cells.     

Performance evaluation of integrated gasification solid oxide fuel cell/gas turbine systems including carbon dioxide capture

In this study, system layouts for integrated gasification solid oxide fuel cell/gas turbine (IG-SOFC/GT) systems were proposed and their performance was comparatively evaluated. A baseline IGCC was simulated, and the calculation models were validated. Based on the IGCC system, two IG-SOFC/GT system layouts with different SOFC thermal management methods were established, and their performance was analyzed. The IG-SOFC/GT systems were found to produce much higher power and better efficiency than the IGCC. With regard to SOFC thermal management, the exit gas recirculation scheme showed better performance than the cathode heat exchange scheme. The impact of CO₂ capture was investigated in both the IGCC and IG-SOFC/GT systems, and the penalties in power output and efficiency due to pre-combustion CO₂ capture were found to be milder in the IG-SOFC/GT systems than in the IGCC. An IG-SOFC/GT system adopting oxy-combustion-based CO₂ capture was proposed, and its thermal efficiency was predicted to be sensibly higher than the system with pre-combustion CO₂ capture. Its net power output was predicted to be less than that of the system with pre-combustion technology, but was still much larger than that of the IGCC with pre-combustion CO₂ capture.