Kwansun Choi

A combined virtual and remote laboratory for microcontroller

This paper describes a web-based combined laboratory for a 8051 microcontroller-related experiment which is composed of a virtual lab and a real time remote laboratory. Authorized users are allowed to have access to both labs using a web browser. The virtual laboratory cooperates with the remote laboratory to help learners easily understand the principal concepts and the process of complex experimental operations about the 8051 microcontroller. The former is implemented by Java applets and Flash animations, and the latter network technologies such as web-based compilation and socket communication, which enables remote experimental devices to be controlled by local learners, compensating for the lack of reality in the virtual experiment. The proposed laboratory provides learners with almost all the same advantages as a real lab environment.

Implementation of a web-based hybrid educational system for enhancing learning efficiency of engineering experiments

To enhance the excellence, effectiveness, and economical efficiency in the learning process, we implement a creative hybrid educational system for engineering experiments where web-based virtual laboratory systems and distance education systems are properly integrated. In the first stage, we designed client/server distributed environment and developed web-based virtual laboratory system for electrical/electronic circuit experiments. The proposed virtual laboratory system is composed of three important sessions and their management system: concept-learning session, virtual experiment session, assessment session. With the aid of the management system every session is organically tied up together to achieve maximum learning efficiency. In addition, every activity done during the virtual laboratory session are recorded on database and will be provided to the learners as the printout report included their own experimental information and results. With this new system structure, the learners can compare theoretical and experimental data; develop their capability in designing and analyzing the circuits; and make use of auxiliary educational tools for understanding complicated concepts. In the second stage, we have implemented efficient and cost-effective distance laboratory systems for practicing electrical/ electronic circuits, which can be used to eliminate the lack of reality occurred during virtual laboratory session. The use of simple and user-friendly design allows a large number of people to access our distance laboratory systems easily. Thus, self-guided advanced training is available even if many expensive types of equipment will not be provided in the on-campus laboratories. During distance laboratory session, the learners change the settings of the input signal and the values of circuit elements, observe the output waveform from the web camera, and obtain image information regarding their experimental results. The proposed virtual/distance laboratory systems can be used in stand-alone fashion, but to enhance learning efficiency we integrated them and developed a creative hybrid education system for engineering experiments. Our hybrid education system provides interactive learning environment and a new approach for the delivery of engineering experiments.

A web-based virtual laboratory system for electronic and digital circuits experiments

To achieve an integrated environment for measurement and instrumentation, we designed and implemented a client/server distributed environment and developed a web-based virtual laboratory system for electronic and digital circuit experiments. Since our virtual laboratory system is implemented to describe the on-campus laboratory, virtual experimental data similar to real experimental data can be obtained through the system. In addition, our web-based virtual laboratory is designed to enhance the efficiency of both the learners and the educators. The learners will be able to achieve high learning standard and the educators save time and labor. The proposed virtual laboratory system is composed of three important sessions: Principle Study Session to explain the concepts and to simulate digital circuit operations, Virtual Experiment Session to provide interactive multimedia contents about the syllabus of off-line laboratory class, Assessment Session and Management System. With the aid of the Management System every session is organically tied up together to achieve maximum learning efficiency. Through our virtual laboratory, the learners will be capable of learning the theories related to electronic circuit experiments and the operation method of the experimental equipments such as multimeters, function generators, digital oscilloscopes and DC power supplies. Also, every activity occurred in our virtual laboratory will be recorded on the database and will be printed out on the preliminary report form. Finally, we have obtained several affirmative effects such as reducing the total experimental hours and the damage rate for experimental equipments.

A new extraction method for the characteristic impedance and effective dielectric constant of transmission line with DGS

In this paper, we propose a new extraction method for the characteristic impedance and effective dielectric constant of a microstrip line. It extracts the characteristic impedance and effective dielectric constant of a microstrip line that uses the results of S-Parameters through the EM - Simulation. And it also extracts the characteristic impedance and effective dielectric constant of microstrip line with DGS and compare the variation of frequency response. We simulate a microstrip line which has a dumbbell type DGS, and extract the electrical length, characteristic impedance and effective dielectric constant according to the DGSs size and the number of DGS. From these results, we analyze how DGS influence the variation of the transmission line characteristics such as the characteristic impedance and effective dielectric constant of a microstrip line.

New Performance Evaluation Method of Focused Ultrasonic Transducers By Using Virtual 3D Graphic

The performance of ultrasonic testing systems for industrial or medical purpose largely depends on the performance of ultrasonic transducers. Generally, the information about an ultrasonic transducer performance characteristics are expressed by the ultrasonic R/F signal back from a reflector and its frequency characteristics in the data sheet provided by manufacturers. In case of focused ultrasonic transducers, the two pieces of information can, however, hardly assure that the focused ultrasonic transducer would produce well-focused C-scan images. Therefore, we propose the measured size of focal spot and the reconstructed shape of effective focal zone in the focused sound field as novel measures for the performance evaluation of the focused ultrasonic transducers. The process of getting the both measures of the transducers is conducted by the implemented software including sound field scanning and virtual 3D reconstruction functions which requires the echo of a point reflector. The proposed method could, otherwise impossible in the existing method, effectively and simply distinguish superior ones among many transducers made in the same specification and be also used to detect the performance degradation due to the aging of the transducers. Eventually, the quality of performance of the ultrasonic testing systems for industrial or medical purpose is secured.

The Construction of Remote Microcontroller Laboratory Using Open Software

A microcontroller can be considered a self-contained system with a processor, memory and peripherals. It is used in automatically controlled products and devices by programming. Therefore it is adopting with the essential subject in our department. We implemented a remote laboratory for 80196KC microcontroller. The remote laboratory provides functions with which learners can perform experiments by remote-controlling circuits and equipment related to experiments and practices on the Web and gets data and image information, so through it learners can make realistic experiments at any time and in any place. Although student can not physically touch any equipment, they can confirm the operation process of the 80196KC microcontroller by observing the result of experiment transferred through the web camera. The remote laboratory module based on Internet open sources such as JAVA Web start technology, FTP technology and Telnet technology in server-client environment can be implemented at low cost. It has the object of introducing remote experimentation, offering to students the opportunity to run a C code for 80196 KC microcontroller. Our remote Lab, therefore, is a useful tool that allows students to make real experiments with 80196 KC microcontroller. It will be used an auxiliary lab for teaching and learning microcontroller.

A new extraction method of characteristic parameters of a coupled transmission line

This paper suggests a new extraction method of the characteristic parameters of a coupled transmission line, which is structured like a microstrip line. A coupled line coupler that has −20dB coupling at the center frequency 1.5GHz is used for the extraction of the characteristic parameters. First, it extracts the characteristic parameters using the simulation results of the coupler. The paper shows the accuracy of this extraction method by comparing the results of EM simulation with the results of circuit simulation using the extracted characteristic parameters.

Design and Implementation of an Effective LED Lighting Control System

본 논문에서는 빌딩이나 공장과 같은 대규모 조명 설치뿐만 아니라 정형적이지 않은 소규모 공간으로의 조명 추가 설치 및 확장을 수월하게 수용할 수 있는 효과적인 LED 조명 제어 시스템을 설계 및 구현하였다. 지그비(Zigbee) 통신 기능과 LED 조명 On/Off, 디밍 제어, 소비전력량 측정, 누전 감지 등의 기본 기능을 갖는 조명 제어장치들은 Mesh 네트워크로 연결되어 설치가 용이하다. 본 논문의 시스템은 교체 설치 시에 기존의 조명 설비의 활용률을 높일 수 있는 구조로 제어장치를 설계하여 설치비용을 절감하였다. 사용자는 관리 서버를 통해 다양한 공간 환경에 설치된 다수의 조명을 효과적으로 중앙 집중 관리할 수 있을 뿐만 아니라, 함께 구현하는 모바일 관리 어플리케이션을 이용하여 현장에서 전체 조명의 상태 정보를 확인할 수 있어 조명의 유지보수 및 제어를 수월히 수행할 수 있다.

A new de-embedding technique for arbitrary N-port networks using ideal 1:J transformers

In this paper, a new de-embedding technique that using ideal 1:j transformers is proposed. The proposed method uses cascade connection between an N-port network whose all ports are linked with 1:j transformers and the same N-port network. The ABCD matrices are fully derived in terms of the ideal 1:j transformers and the N-port network with transformers on all ports. To verify the proposed method, sample de-embedding process is performed and compared using Ansys HFSS simulation and the proposed method for a 4-port network. It is found that the magnitude (|S21|) of transmission is 0 dB, the phase difference between the through-port is 0o, and the magnitude between the input and near-/far-end ports is below −300 dB, which prove the validity of the proposed method.

Development of a Web-Based Educational Java Applet for Understanding Concepts and Principles of Digital Logic Circuits

This paper presents web-based Java applet for understanding the concepts of digital logic circuits. Through our educational Java applet, the learners will be capable of learning the concepts and theories related to circuit experiments and how to operate the virtual experimental equipments such as multimeters, function generators, digital oscilloscopes, DC power suppliers and bread board etc. The proposed our educational Java applet is composed of five important components: Principle Classroom to explain the concepts and theories of electronic and digital circuit operations, Simulation Classroom to provide a web-based simulator to the learners, Virtual Experiment Classroom to provide interactive Java applets about the syllabus of off-line laboratory class, Assessment Classroom, and Management System. With the aid of the Management System every classroom is organically tied together collaborating to achieve maximum learning efficiency. We have obtained several affirmative effects such as high learning standard, reducing the total experimental hours and the damage rate for experimental equipments.