• KSBB Journal
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• v.24 no.3
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• pp.259-266
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• 2009

AfsR2 in Streptomyces lividans, a 63-amino acid protein with limited sequence homology to Streptomyces sigma factors, has been known for a global regulatory protein stimulating multiple antibiotic biosynthetic pathways. Although the detailed regulatory mechanism of AfsK-AfsR-AfsR2 system has been well characterized, very little information about the AfsR2-dependent down-stream regulatory genes were characterized. Recently, the null mutant of afsS in S. coelicolor (the identical ortholog of afsR2) has been characterized through DNA microarray system, revealing that afsS deletion regulated several genes involved in antibiotic biosynthesis as well as phosphate-starvation. Through comparative DNA microarray analysis of afsR2-overexpressed S. lividans, here we also identify several afsR2-dependent genes involved in phosphate starvation, morphological differentiation, and antibiotic regulation in S. lividans, confirming that the AfsR2 plays an important pleiotrophic regulatory role in Streptomyces species.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.6
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• pp.59-67
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• 2014

A numerical model and a controller of Active Front wheel Steer (AFS) system are designed in this study. The AFS model consists of four sub models, and the AFS controller uses sliding mode control and PID control methods. To test this model and controller an Integrated Dynamics Control with Steering (IDCS) system is also designed. The IDCS system integrates an AFS system and an ARS (Active Rear wheel Steering) system. The AFS controller and IDCS controller are compared under several driving and road conditions. An 8 degree of freedom vehicle model is also employed to test the controllers. The results show that the model of AFS system shows good kinematic steering assistance function. Steering ratio varies depends on vehicle velocity between 12 and 24. Kinematic stabilization function also shows good performance because yaw rate of AFS vehicle tracks the reference yaw rate. IDCS shows improved responses compared to AFS because body side slip angle is also reduced. This result also proves that AFS system shows satisfactory result when it is integrated with another chassis system. On a split-m road, two controllers forced the vehicle to proceed straight ahead.

• Biotechnology and Bioprocess Engineering:BBE
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• v.10 no.3
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• pp.248-253
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• 2005

AfsR2, originally identified from Streptomyces lividans, is a global regulatory protein which stimulates antibiotic biosynthesis. Through its stable chromosomal integration, the high level of gene expression of afsR2 significantly induced antibiotic production as well as the sporulation of S. lividans, implying the presence of yet-uncharacterized AfsR2-target proteins. To identify and evaluate the putative AfsR2-target proteins involved in antibiotic regulation, the proteomics-driven approach was applied to the wild-type S. lividans and the afsR2-integrated actinorhodin overproducing strain. The 20 gel-electrophoresis gave approximately 340 protein spots showing different protein expression patterns between these two S. lividans strains. Further MALDI-TOF analysis revealed several AfsR2-target proteins, including glyceraldehyde-3-phosphate dehydrogenase, putative phosphate transport system regulator, guanosine penta phosphate synthetase/polyribonucleotide nucleotidyltransferase, and superoxide dismutase, which suggests that the AfsR2 should be a pleiotropic regulatory protein which controls differential expressions of various kinds of genes in Streptomyces species.

• Journal of Microbiology and Biotechnology
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• v.16 no.9
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• pp.1477-1480
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• 2006

The 63-amino-acid-encoding afsR2 is a global antibiotics-stimulating regulatory gene identified from the chromosome of Streptomyces lividans. To dissect a putative functional domain in afsR2, several afsR2-derivative deletion constructs were generated and screened for the loss of actinorhodin-stimulating capability. The afsR2-derivative construct missing a 50-bp C-terminal region significantly lost its actinorhodin-stimulating capability in S. lividans. In addition, site-directed mutagenesis on amino acid positions of #57-#61 in a 50-bp C-terminal region, some of which are conserved among known Sigma 70 family proteins, significantly changed the AfsR2's activity. These results imply that the C-terminal region of AfsR2 is functionally important for antibiotics-stimulating capability and the regulatory mechanism might be somehow related to the sigma-like domain present in the C-terminal of AfsR2.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.2
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• pp.72-80
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• 2013

This study is to develop and evaluate an AFS and an ARS controllers to enhance lateral stability of a vehicle. A sliding mode control (SMC) and a fuzzy logic control (FLC) methods are applied to calculate the desired additional steering angle of AFS equipped vehicle or desired rear steer angle of ARS equipped vehicle. To validate AFS and ARS systems, an eight degree of freedom, nonlinear vehicle model and an ABS controllers are also used. Several road conditions are used to test the performances. The results showed that the yaw rate of the AFS and the ARS vehicle followed the reference yaw rate very well within the adhesion limit. However, the AFS improves the lateral stability near the limit compared with the ARS. Because the SMC and the FLC show similar vehicle responses, performance discrimination is small. On split-${\mu}$ road, the AFS and the ARS vehicle had enhanced the lateral stability.

• Steel and Composite Structures
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• v.39 no.3
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• pp.229-241
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• 2021

This work focused on aluminum foam sandwich (AFS) with different foam core densities and different face-sheet thicknesses subjected to constant amplitude three-point bending cyclic loading to study its fatigue performance. The experiments were conducted out by a high frequency fatigue test machine named GPS-100. The experimental results showed that the fatigue life of AFS decreased with the increasing loading level and the structure was sensitive to cyclic loading, especially when the loading level was under 20%. S-N curves of nine groups of AFS specimens were obtained and the fatigue life of AFS followed three-parameter lognormal distribution well. AFS under low cyclic loading showed pronounced cyclic hardening and the static strength after fatigue test increased. For the same loading level, effects of foam core density and face-sheet thickness on the fatigue life of AFS structure were trade-off and for the same loading value, the fatigue life of AFS increased with aluminum foam core density or face-sheet thickness monotonously. Core shear was the main failure mode in the present study.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.10
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• pp.903-909
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• 2015

This article presents an integrated chassis control with electronic stability control (ESC) and active front steering (AFS) under saturation of front lateral tire force. Regardless of the use of AFS, the front lateral tire forces can be easily saturated. Under the saturated front lateral tire force, AFS cannot be effective to generate a control yaw moment needed for the integrated chassis control. In this paper, new integrated chassis control is proposed in order to limit the use of AFS in case the front lateral tire force is saturated. Weighed pseudo-inverse control allocation (WPCA) with variable weight is adopted to adaptively use the AFS. To check the effectiveness of the proposed scheme, simulation is performed on a vehicle simulation package, CarSim. From simulation, the proposed integrated chassis control is effective for vehicle stability control under saturated front lateral tire force.

• Steel and Composite Structures
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• v.29 no.3
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• pp.301-308
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• 2018

Properties of AFS vary with the changes in the face-sheet materials. Hence, the performance of AFS can be optimized by selecting face-sheet materials. In this work, three types of face-sheet materials representing elastic-perfectly plastic, elastic-plastic strain hardening and purely elastic materials were employed to study their effects on the flexural behavior and failure mechanism of AFS systematically. Result showed face-sheet materials affected the failure mechanism and energy absorption ability of AFS significantly. When the foam cores were sandwiched by aluminum alloy 6061, the AFS failed by face-sheet yielding and crack without collapse of the foam core, there was no clear plastic platform in the Load-Displacement curve. When the foam cores were sandwiched by stainless steel 304 and carbon fiber fabric, there were no face-sheet crack and the sandwich structure failed by core shear and collapse, plastic platform appeared. Energy absorption abilities of steel and carbon fiber reinforced AFS were much higher than aluminum alloy reinforced one. Carbon fiber was suggested as the best choice for AFS for its light weight and high performance. The versus strength ratio of face sheet to core was suggested to be a significant value for AFS structure design which may determine the failure mechanism of a certain AFS structure.

• Journal of Microbiology and Biotechnology
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• v.17 no.9
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• pp.1563-1567
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• 2007

AfsKav is a eukaryotic-type serine/threonine protein kinase, required for sporulation and avermectin production in Streptomyces avermitilis. In terms of their ability to complement SJW4001 (${\Delta}afsK$-av), afsK-av mutants T165A and T168A were not functional, whereas mutants T165D and T168D retained their ability, indicating that Thr-165 and Thr-168 are the phosphorylation sites required for the role of AfsKav. Expression of the S-adenosylmethione synthetase gene promoted avermectin production in the wild-type S. avermitilis, yet not in the mutant harboring T168D or T165D, demonstrating that tandem phosphorylation on Thr-165 and Thr-168 in AfsKav is the mechanism modulating avermectin production in response to S-adenosylmethione accumulation in S. avermitilis.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.7
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• pp.595-601
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• 2015

This paper presents an unified chassis control with electronic stability control (ESC) and active front steering (AFS) under lateral force constraint on AFS. When generating the control yaw moment, an optimization problem is formulated in order to determine the tire forces, generated by ESC and AFS. With Karush-Kuhn-Tucker optimality condition, the optimum tire forces can be algebraically calculated. On low friction road, the lateral force in front wheels is easily saturation. When saturated, AFS cannot generate the required control yaw moment. To cope with this problem, new constraint on the lateral tire force is added into the original optimization problem. To check the effectiveness of the propose method, simulation is performed on the vehicle simulation package, CarSim.