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Mechanotransduction of cardiomyocytes interacting with a thin membrane transducer
Park, Jungyul,Kim, Il Chaek,Cha, Jaemin,Park, Sukho,Lee, Junghoon,Kim, Byungkyu IOP 2007 JOURNAL OF MICROMECHANICS AND MICROENGINEERING - Vol.17 No.6
<P>A novel platform is developed to study the mechanotransduction of cardiomyocytes. After the cardiomyocytes are seeded on 10 ?m thin, dome-shaped membranes with different sizes, their morphology and beating frequency are monitored. While the cells seeded on a larger membrane (800 ?m ? 800 ?m) grow normally, cells on a smaller membrane (200 ?m ? 200 ?m) grow in isolated groups, showing a lumped morphology. The beating frequency of the cells on the smaller membrane was faster than on the larger membrane. This intriguing phenomenon may be explained by the mechanical stress determined by the area of the membrane that affects the opening of ion channels.</P>
Online Implementation of DynaMIT: A Prototype Traffic Examination and Prediction Program
Byungkyu(Brian) Park,이조영,Devi M. Pampati,Brian L. Smith 대한토목학회 2008 KSCE JOURNAL OF CIVIL ENGINEERING Vol.12 No.2
This paper presents a pilot study of conducting an online implementation of DynaMIT, one of traffic estimation and prediction(TrEP) programs developed by an MIT research team with the support from the U.S. Federal Highway Administration, in HamptonRoads, VA, U.S.A. As a first step, a test-bed network was cbefore evaluating the performance of the online implementation of DynaMIT. Based on the online implementation of DynaMIT forthree days, it was found that DynaMIT showed fairly good performance on the estimation and prediction of the sensor counts withthe root mean square normalized (RMSN) error ranges betwen 0.15 and 0.25 for estimations, and 0.25 and 0.4 for predictions. Eventhough speed and travel times showed some discrepancies, further investigations indicated that the performance of DynaMIT can besignificantly improved with adequately calibrated supply parameters.
An ontology-based search engine for protein-protein interactions
Park, Byungkyu,Han, Kyungsook BioMed Central 2010 BMC bioinformatics Vol.11 No.suppl1
<P><B>Background</B></P><P>Keyword matching or ID matching is the most common searching method in a large database of protein-protein interactions. They are purely syntactic methods, and retrieve the records in the database that contain a keyword or ID specified in a query. Such syntactic search methods often retrieve too few search results or no results despite many potential matches present in the database.</P><P><B>Results</B></P><P>We have developed a new method for representing protein-protein interactions and the Gene Ontology (GO) using modified Gödel numbers. This representation is hidden from users but enables a search engine using the representation to efficiently search protein-protein interactions in a biologically meaningful way. Given a query protein with optional search conditions expressed in one or more GO terms, the search engine finds all the interaction partners of the query protein by unique prime factorization of the modified Gödel numbers representing the query protein and the search conditions.</P><P><B>Conclusion</B></P><P>Representing the biological relations of proteins and their GO annotations by modified Gödel numbers makes a search engine efficiently find all protein-protein interactions by prime factorization of the numbers. Keyword matching or ID matching search methods often miss the interactions involving a protein that has no explicit annotations matching the search condition, but our search engine retrieves such interactions as well if they satisfy the search condition with a more specific term in the ontology.</P>
Byungkyu "Brian" Park,Kangyuan Zhu 대한토목학회 2007 KSCE journal of civil engineering Vol.11 No.4
An estimation of origin-destination (OD) demand matrix is one of key elements to ensure the success in traffic modeling analysis. Even with widely deployed traffic sensors and advanced computational technologies, an estimation of time-dependent OD matrices is still a key barrier for the implementation of dynamic traffic assignment as well as simulation-based traffic modeling analysis. This paper proposes an improvement of existing time-dependent OD estimation method by updating assignment matrix at each step of OD estimation process and quantifies benefits and costs of doing so. The results from a case study with Florian network showed that the estimated OD flows from the proposed GA-based method with updated assignment matrix reduced the sum of square errors by 40% when compared with the OD flows from the DynaMIT OD estimation method with fixed assignment matrix, one of the most commonly used OD estimation methods. However, the proposed method would require significantly higher computational time than the traditional DyanMlT OD estimation method.
A Procedure for Determining Time-of-Day Break Points for Coordinated Actuated Traffic Signal Systems
Byungkyu(Brian) Park,이조영 대한토목학회 2008 KSCE JOURNAL OF CIVIL ENGINEERING Vol.12 No.1
This paper presents the development and evaluation of a procedure for determining optimal break points for time-of-day basedcoordinated actuated traffic signal operations. The proposed procedure uses a feature vector of optimal cycle length per time intervalinstead of traffic volume itself. Initial break points determined by the proposed feature vector are used in the greedy search algorithmthe number of evaluations in the search are dramatically reducedwhen compared to an exhaustive search or other common heuristic search methods such as a genetic algorithm. The proposedprocedure was evaluated using a hypothetical network consisting of four signalized intersections and the results indicated that theproposed procedure effectively improved the performance of the coordinated actuated signal control. In addition, sensitivity analysesresults on randomly varying demand conditions up to 20% and randomly increased demand conditions up to 30% indicated that thenewly developed break points were robust for such varying demand fluctuations.
Byungkyu Kim,Sunghak Lee,Jong Heong Park,Jong-Oh Park IEEE 2005 IEEE/ASME transactions on mechatronics Vol.10 No.1
<P>Endoscopes are medical devices to diagnose various kinds of diseases throughout the whole gastrointestinal tracks. Generally, they are divided into conventional push-type endoscopes and more recently developed wireless capsule-type endoscopes. The conventional endoscopes cannot reach the small intestines and generate pain and discomfort to patients due to the stiffness of their body. Such disadvantages do not exist in wireless capsule-type endoscopes. However, commercialized capsule-type endoscopes move passively by peristaltic waves (and the gravity), which makes it impossible for doctors to diagnose the areas of his or her interest more thoroughly and actively. To address this problem of passivity, a locomotive mechanism is proposed for wireless capsule-type endoscopes. Prototypes with micro brushless dc motors, ionic polymer metal composite actuator, and shape memory alloy (SMA) wires are designed and fabricated for preliminary tests. Based on the tests, spring-type SMA actuators are selected to be microactuators for capsule endoscopes. Thus, two-way linear actuators using a pair of SMA springs are developed based on a static analysis on them. Moreover, a simple and effective clamping device is developed based on biomimetic approach. A prototype endoscope with four pairs of SMA springs and four clampers was developed. It has 13 mm in diameter and 33 mm in total length, with a hollow space of 7.6 mm in diameter to house other parts that are needed for endoscopy such as a camera, an RF module, sensors, e.g., for endoscopic ultrasound, and a battery. A sequential control of the four actuators improves the efficiency of locomotion up to four times. To validate the performance of the proposed locomotive mechanism, a series of experiments were carried out including in-vitro tests. The results of the experiments indicate that the proposed locomotion mechanism is effective to be used for micro capsule-type endoscopes.</P>
Identification and control of a sensorized microgripper for micromanipulation
Park, Jungyul,Kim, Sangmin,Kim, Deok-Ho,Kim, Byungkyu,Kwon, Sang Joo,Park, Jong-Oh,Lee, Kyo-Il IEEE 2005 IEEE/ASME transactions on mechatronics Vol.10 No.5
This paper presents the design and control of a sensorized microgripper using a voice coil motor and a flexure mechanism. To increase the gripping sensitivity, shape design and determination of sensor attachment position are performed using finite element analysis. Empirical models of the microgripper are acquired for the design of position control and gripping force control. By using the identified models, both the perfect tracking controller for position control and the adaptive zero-phase error tracking controller for force control are implemented. The effectiveness of the proposed model-based control methods is verified by experimental studies.