• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.11A
• /
• pp.831-843
• /
• 2009

In this paper, we propose a new adaptive cooperation scheme with multi-relay nodes which achieves higher performance and spectral efficiency than that of some conventional cooperative schemes. The relay-selection is applied to choose the most potential relay among K ones. Afterward, the instantaneous signal-to-noise ratio (SNR) differences between S-D, S-R and R-D channels are considered for adaptive selection between the direct and the cooperation transmission strategy. In the proposed adaptive protocol, if the direct link is of high quality, the source will transmit to destination directly with all power consumption. Otherwise, the source broadcasts the signal with a lower power and requires the help of the chosen relay if it decodes correctly, else the source will transmit again with remaining power. Firstly, the spectral efficiency is derived by calculating the probability of each mode. Subsequently, the BER performance for the adaptive cooperation scheme is analyzed by considering each event that one of K relays is selected and then making the summation of all. Finally, the numerical results are presented to confirm the performance enhancement offered by the proposed schemes.

• Journal of Microbiology and Biotechnology
• /
• v.8 no.3
• /
• pp.203-207
• /
• 1998

Fed-batch fermentations with different feeding media were carried out in order to increase the productivity of invertase expression using a recombinant Saccharomyces cerevisiae containing plasmid pRB58. Two batch cultures showed the expression of the SUC2 gene at a low concentration of glucose, suggesting that glucose concentration could be used as a control variable in a fed-batch operation mode. In the fed-batch culture by feeding the basal medium, cell mass and specific invertase activity did not increase much as compared with the simple batch culture. A series of fed-batch cultures revealed that the sucrose-supplemented medium increased cell mass whereas the enriched medium did specific invertase activity. To capitalize on the synergism of the sucrose-supplemented medium and the enriched medium, the sucrose-supplemented enriched medium was used as a feeding medium. The fed-batch culture using this medium resulted in a 2.4-fold increase in cell mass and a 1.9-fold enhancement in specific invertase activity compared with those of the batch culture. The increase in cell mass and specific invertase activity led to a marked increase in total invertase activity, 250U/ml, which was 6.3 times higher than that of the batch culture.

• Journal of Microbiology and Biotechnology
• /
• v.18 no.5
• /
• pp.897-900
• /
• 2008

Various sequences of pH change were applied in a batch bioreactor to investigate pH shock effects on geldanamycin production by Streptomyces hygroscopicus subsp. duamyceticus JCM4427. In the control culture where the pH was not controlled, the maximum geldanamycin concentration was 414 mg/l. With the pHS1 mode of pH shock, that is, an abrupt pH change from pH 6.5 to pH 5.0 and then being maintained at around pH 5.0 afterward, 768 mg/l of geldanamycin was produced. With pHS2, in which the pH was changed sequentially from pH 6.7 to pH 5.0 and then back to pH 6.0, 429 mg/l of geldanamycin was produced. With pHS3 having a sequential pH change from pH 6.0 to pH 4.0 and then back to pH 6.5 followed by the third pH shock to pH 5.5, no geldanamycin production was observed. Considering that the productivity with pHS1 was about two-fold of that of the control culture with no pH control, we concluded that a more sophisticated manipulation of pH would further promote geldanamycin production.

• Analytical Science and Technology
• /
• v.24 no.1
• /
• pp.15-23
• /
• 2011

An accurate mass and isotope ratio were determined using a gas chromatography/time of flight mass spectrometer in CI positive mode for the identification of unknown metabolites. High mass tune was used to improve the ion intensity of $[M+H]^+$. Chromatographic resolution and dynamic range enhancement were performed to obtain more reliable accurate masses and correct isotope abundance ratios. Average absolute errors of mass and isotope ratios for 24 reference metabolite -TMS (trimethylsilyl) derivatives were 6.8 ppm, 1.5% of (M+1/M ratio) and 1.7% of (M+2/M ratio), respectively. The correct formulas of twenty one compound were retrieved within top-2 hit from the heuristic algorithm for elemental composition using each accurate mass and isotope abundance ratio.

• The Transactions of the Korea Information Processing Society
• /
• v.4 no.10
• /
• pp.2521-2532
• /
• 1997

The next generation internet protocol, IPv6, have been developed by the IETF according to the requirements of enhancement of classic IP protocols to satisfy the lack of Internet address space as well as the support of multimedia applications. This paper presents an implementation of IPv6 protocols on the Windows NT kernel environment. In this work, we developed and also tested the basic functions, required for operating as an IPv6 host, such as IPv6 header processing, IPv6 address handling, control message processing, group membership processing and neighbor discovery functions. The implemented IPv6 protocol driver module is connected to the lower network interface card through NDIS, a standard network interface. And this driver module that operates within kernel, is implemented as it is connected to upper user applications and lower NDIS using dispatch and lower-edge functions. The developed IPv6 protocol driver can provide not only enhanced performance because it is implemented in kernel mode, but also convenience of usage to the application developers because it gives user interface as a dynamic link library.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.37 no.5
• /
• pp.379-388
• /
• 2019

Recently, a technique for acquiring spatial information data using UAV (Unmanned Aerial Vehicle) has been greatly developed. It is a very crucial issue of the GIS (Geographic Information System) mapping system that passes way point in the unmanned airframe and finally measures the accurate image and stable localization to the desired destination. Though positioning using DGPS (Differential Global Navigation System) or RTK-GPS (Real Time Kinematic-GPS) guarantee highly accurate, they are more expensive than the construction of a single positioning system using a single GPS. In the case of a low-priced single GPS system, the stability of the positioning data deteriorates. Therefore, it is necessary to supplement the uncertainty of the absolute position data of the UAV and to improve the accuracy of the current position data economically in the operating state of the UAV. The aim of this study was to present an algorithm enhancing the stability of position data in a single GPS mode of UAV with multiple GPS. First, the arrangement of multiple GPS receivers through the center of gravity of the UAV were examined. Next, MD (Mahalanobis Distance) is applied to detect instantaneous errors of GPS data in advance and eliminate outliers to increase the accuracy of previously collected multiple GPS data. Processing procedure for multiple GPS reception data by applying the center of the triangular method were presented to improve the position accuracy. Second, UAV navigation systems integrated multiple GPS through configuration of the UAV specifications were implemented. Using the unmanned airframe equipped with multiple GPS receivers, GPS data is measured with the TCM (Triangular Center Method). In addition, UAV equipped with multiple GPS were operated in study area and locational accuracy of multiple GPS of UAV with VRS (Virtual Reference Station) GNSS surveying were compared. The result showed that the error factors are compensated, and the error range are reduced, resulting in the reliability of the corrected value. In conclusion, the result in this paper is expected to realize high-precision position estimation at low cost in UAV using multiple low-cost GPS receivers.

• International Journal of High-Rise Buildings
• /
• v.7 no.4
• /
• pp.375-387
• /
• 2018

This paper presents a review on progressive collapse mechanism of steel framed buildings exposed to fire. The influence of load ratios, strength of structural members (beam, column, slab, connection), fire scenarios, bracing systems, fire protections on the collapse mode and collapse time of structures is comprehensively reviewed. It is found that the key influencing factors include load ratio, fire scenario, bracing layout and fire protection. The application of strong beams, high load ratios, multi-compartment fires will lead to global downward collapse which is undesirable. The catenary action in beams and tensile membrane action in slabs contribute to the enhancement of structural collapse resistance, leading to a ductile collapse mechanism. It is recommended to increase the reinforcement ratio in the sagging and hogging region of slabs to not only enhance the tensile membrane action in the slab, but to prevent the failure of beam-to-column connections. It is also found that a frame may collapse in the cooling phase of compartment fires or under travelling fires. This is because that the steel members may experience maximum temperatures and maximum displacements under these two fire scenarios. An edge bay fire is more prone to induce the collapse of structures than a central bay fire. The progressive collapse of buildings can be effectively prevented by using bracing systems and fire protections. A combination of horizontal and vertical bracing systems as well as increasing the strength and stiffness of bracing members is recommended to enhance the collapse resistance. A protected frame dose not collapse immediately after the local failure but experiences a relatively long withstanding period of at least 60 mins. It is suggested to use three-dimensional models for accurate predictions of whether, when and how a structure collapses under various fire scenarios.

• Current Optics and Photonics
• /
• v.6 no.5
• /
• pp.497-505
• /
• 2022

Topological photonic nanocavities are considered to possess outstanding optical performance, and provide new platforms for realizing strong interaction between light and matter, due to their robustness to impurities and defects. Here hybrid plasmonic topological photonic nanocavities are proposed, by embedding various plasmon nanoantennas such as gold nanospheres, cylinders, and rectangles in a topological photonic crystal corner-state nanocavity. The maximum quality factor Q and minimum effective mode volume V_eff of these hybrid nanocavities can reach the order of 10⁴ and 10^-4 (𝜆/n)³ respectively, and the high figures of merit Q/V_eff for all of these hybrid nanocavites are stable and on the order of 10⁵ (𝜆/n)^-3. The relative positions of the plasmon nanoantennas will influence the coupling strength between the plasmon structures and the topological nanocavity. The hybrid nanocavity with gold nanospheres possesses much higher Q, but relatively large V_eff. The presence of a gold rectangular structure can confine more electromagnetic energy within a smaller space, since its V_eff is smallest, although Q is lowest among these structures. This work provides an outstanding platform for cavity quantum electrodynamics and has a wide range of applications in topological quantum light sources, such as single-photon sources and nanolasers.

• Journal of Sensor Science and Technology
• /
• v.31 no.6
• /
• pp.423-427
• /
• 2022

A pressure sensor that mimics the sensing ability of human skin has emerged as high-profile technology because it shows remarkable applications in numerous fields such as robotics, human health monitoring, and artificial prosthetics. Whereas recent pressure sensors have achieved high sensitivity similar to that of human skin, they still show limited detection bandwidth. Moreover, once these e-skin are fabricated, their sensitivity and stiffness are fixed; therefore, they can be used for only limited applications. Our study proposes a new adaptive pressure sensor built with uniform gallium microdroplet-elastomer composite. Based on the phase transition of gallium microdroplets, the proposed sensor undergoes mode transformation, enabling it to have a higher sensitivity and wider detection bandwidth compared with those of human skin. In addition, we succeeded in extending a single adaptive pressure sensor to sensor arrays based on its high uniformity, reproducibility, and large-scale manufacturability. Finally, we designed an adaptive e-skin with the sensor array and demonstrated its applications on health monitoring tasks including blood pulse and body weight measurements.

• Steel and Composite Structures
• /
• v.45 no.6
• /
• pp.797-818
• /
• 2022

Steel-precast ultra-high-performance concrete (UHPC) composite beams with demountable high-strength friction-grip bolt (HSFGB) shear connectors can be used for accelerated bridge construction (ABC) and achieve excellent structural performance, which is expected to be dismantled and recycled at the end of the service life. However, no investigation focuses on the demountability and reusability of such composite beams, as well as the installation difficulties during construction. To address this issue, this study conducted twelve push-out tests to investigate the effects of assembly condition, bolt grade, bolt-hole clearance, infilling grout and pretension on the crack pattern, failure mode, load-slip/uplift relationship, and the structural performance in terms of ultimate shear strength, friction resistance, shear stiffness and slip capacity. The experimental results demonstrated that the presented composite beams exhibited favorable demountability and reusability, in which no significant reduction in strength (less than 3%) and stiffness (less than 5%), but a slight improvement in ductility was observed for the reassembled specimens. Employing oversized preformed holes could ease the fabrication and installation process, yet led to a considerable degradation in both strength and stiffness. With filling the oversized holes with grout, an effective enhancement of the strength and stiffness can be achieved, while causing a difficulty in the demounting of shear connectors. On the basis of the experimental results, more accurate formulations, which considered the effect of bolt-hole clearance, were proposed to predict the shear strength as well as the load-slip relationship of HSFGBs in steel-precast UHPC composite beams.