세균의 정족수 감지 기작을 활용한 고도 수처리용 막결합형 생물반응기에서의 막오염 제어 연구

Bacteria perceive their population density using small signal molecules called autoinducer and regulate specific group behaviors such as biofilm formation on the surface in cell density dependent way (Quorum sensing, QS). In this study, the concept of bacterial QS was applied to membrane bioreactor (MBR) for advanced wastewater treatment as a new biofouling control paradigm. The overall research was conducted in the following phases: (1) Evidence of autoinducer signal in MBR (2) Correlation between QS and membrane biofouling (3) Control of membrane biofouling by quorum quenching (4) Preparation of magnetic enzyme carrier (MEC) (5) Application of MEC to the MBR in continuous operation A bioassay with Agrobacterium tumefaciens A136 reporter strain proved that N-acyl homoserine lactone (AHL) autoinducers of gram-negative bacteria were produced in the MBR. Furthermore, thin-layer chromatographic analysis identified at least three different AHLs in the biocake, of which N-octanoyl-homoserine lactone was the most abundant. During continuous MBR operation, the membrane-biocake showed strong AHL activity simultaneously with the abrupt increase in the transmembrane pressure (TMP). Furthermore, both autoinducer level per unit biomass and filtration resistance in the biocake increased under very similar tendency, which implies that QS was closely associated with the membrane biofouling. Porcine kidney acylase I (EC-number 3.5.1.14), which can inactivate the AHL molecule by amide bond cleavage, was confirmed to prevent membrane biofouling by quenching AHL autoinducers, which suggested that quorum quenching, enzymatic destruction of QS autoinducer, could be a novel biofouling control approach in MBR. Despite of its high potential as a novel biofouling control approach, the short catalytic lifetime and difficulty in recovering free enzyme hamper the successful application of the quorum quenching technique in the MBR under a long-term continuous operation. A magnetic enzyme carrier (MEC) was prepared by immobilizing the quorum quenching enzyme (acylase) on magnetic particles to overcome the technical limitations of free enzyme. The MEC showed no activity decrease under both continuous shaking for 14 days and 29 iterative cycles of reuse. Furthermore, the comparison of the MEC with free enzyme in a batch-type MBR showed that the MEC efficiently alleviated the membrane biofouling and showed a great advantage over free enzyme in terms of recycled use and stability in mixed liquor. When the MEC was applied to the lab scale MBR in a continuous operation, it also enhanced the membrane permeability to a large extent compared with a conventional MBR with no enzyme

A Passivity-based Nonlinear Admittance Control with Application to Powered Upper-limb Control under Unknown Environmental Interactions

This paper presents an admittance controller based on the passivity theory for a powered upper-limb exoskeleton robot which is governed by the nonlinear equation of motion. Passivity allows us to include a human operator and environmental interaction in the control loop. The robot interacts with the human operator via F/T sensor and interacts with the environment mainly via end-effectors. Although the environmental interaction cannot be detected by any sensors (hence unknown), passivity allows us to have natural interaction. An analysis shows that the behavior of the actual system mimics that of a nominal model as the control gain goes to infinity, which implies that the proposed approach is an admittance controller. However, because the control gain cannot grow infinitely in practice, the performance limitation according to the achievable control gain is also analyzed. The result of this analysis indicates that the performance in the sense of infinite norm increases linearly with the control gain. In the experiments, the proposed properties were verified using 1 degree-of-freedom testbench, and an actual powered upper-limb exoskeleton was used to lift and maneuver the unknown payload.Comment: Accepted in IEEE/ASME Transactions on Mechatronics (T-MECH

Community-dwelling older adults needs and acceptance regarding the use of robot technology to assist with daily living performance

Background The rate of aging in Korea is extremely fast compared to major countries. We examined the key demands of community-dwelling older adults with regard to Connected Active Space technology, which provides tailored assistance with daily living performance through robotic services. Methods This study is based on a mixed-method design, through a quantitative survey (n = 234) first phase, followed by a qualitative study with focus group interviews (n = 23) to explore the needs and acceptance of community-dwelling aged people concerning the application of robot technology in their daily lives. Results The scores concerning the need for and acceptance of robot services to assist daily living performance were high, at 7.2 and 7.9 out of 10 points, respectively. Further, for both needs and acceptance, timely reaction to emergency situations, early detection of emergency situations, help to locate objects, assistance with mobility, and assistance in memory recall were prioritized (in that order). In a thematic analysis of qualitative data from three focus-group interviews, a mismatch between desires and functional capacity was the core characteristic of living as an older person and being a friend and helper was the most desired trait of a robot service. Conclusion Although most of the participants lived independently, they regularly experienced difficulties regarding buying products, transportation, using phones, and preparing meals. If appropriate assistance technology is developed, this population can maintain its independence. Thus, it is necessary to address main needs, including detecting and addressing emergency situations, locating objects, assisting mobility and memory recall, and assisting with daily living performance. New robot services that can be tailored to the functions or abilities of the elderly must be developed based on individually collected information.This work was funded by the Korea Institute of Science & Technology [grant Number: 2E26470–16-099]. The funding body had no role in the design of this study, in collection, analysis and interpretation of data, and in writing the manuscript