• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.7
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• pp.805-811
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• 2010

When we design a product, we spend a considerable amount of time in designing fasteners and their mating parts. Fasteners have special features because of which they are widely used and well standardized. Although we use some equations to design the fasteners, we should select these fasteners from the standardized table. In order to design them quickly using the CAD system, we proceeded as follows. First, we prepared some standardized shapes of fasteners to design them automatically. Next, we built a database of some fasteners such as a tension bolt, lock wire, thread, pin, and snap ring. Then, we used the design equations to quickly and precisely calculate the various parameters. Finally, we used a configuration design method to generate the shapes automatically using the results of the calculation and the values retrieved from the database. We applied this approach to the design of a propulsion structure, and demonstrated that this approach worked well and saved considerable time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.899-905
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• 2017

This paper presents a reference-less dual loop clock and data recovery (CDR) circuit that supports a data rate of 2.496 Gb/s for the mobile industry processor interface (MIPI) M-PHY. An adaptive loop bandwidth scheme is used to implement the fast lock time maintaining a low time jitter. To this scheme, the proposed CDR consists of two loops for a frequency locked loop and a phase locked loop. The proposed 2.496 Gb/s reference-less dual loop CDR is designed using a 65 nm CMOS process with 1.2 V supply voltage. The simulated peak-to-peak jitter of output clock is 9.26 ps for the input data of 2.496 Gb/s pseudo-random binary sequence (PRBS) 15. The active area and power consumption of the implemented CDR are $470{\times}400{\mu}m^2$ and 6.49 mW, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.360-361
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• 2005

Rapid progress in IC fabrication technology has strong demand in polishing of silicon wafer to meet the tight specification of nanotopography and surface roughness. One of the important issues in Si CMP is the stabilization of polishing pad. If a polishing pad is not stabilized before main Si wafer polishing process, good polishing result can not be expected. Therefore, new pad must be subjected into break-in process using dummy wafers for a certain period of time to enhance its performance. After the break-in process, the main Si wafer polishing process must be performed. In this study, the characteristics of break-in process were investigated in Si wafer polishing. Viscoelastic behavior, temperature variation of pad and friction were measured to evaluate the break-in phenomenon. Also, it is found that the characteristic of the break-in seems to be related to viscoelastic behavior of pad.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.161-166
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• 1999

The global trends of mobile communication system is moving toward digitizing, high-speed and large-capacity. Also, to utilize the limited frequency-resource efficiently, spread spectrum system is a mainstream. In this study we are concerning with the fast frequency-hopping system. Instead of the PLL with many problems such as phase-noise, we used the DDS is popular in these days minimizes the disadvantage of PLL. In the case the FFH system is designed using the PLL, it is difficult to be satisfied of the design conditions such as RF badwidth and the settling time of PLL, and it has limitation because of complex circuit by using the balanced modulator. In this study, we evaluated the performance in order to design the FFH system using the DDS. The system that has the improvement of error rate, 1Mhps hopping rate and 5MHz RF bandwidth is designed and evaluated.

• Journal of Ocean Engineering and Technology
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• v.35 no.4
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• pp.287-295
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• 2021

This paper describes a recurrent neural network (RNN) for the fault classification of a blade pitch system of a spar-type floating wind turbine. An artificial neural network (ANN) can effectively recognize multiple faults of a system and build a training model with training data for decision-making. The ANN comprises an encoder and a decoder. The encoder uses a gated recurrent unit, which is a recurrent neural network, for dimensionality reduction of the input data. The decoder uses a multilayer perceptron (MLP) for diagnosis decision-making. To create data, we use a wind turbine simulator that enables fully coupled nonlinear time-domain numerical simulations of offshore wind turbines considering six fault types including biases and fixed outputs in pitch sensors and excessive friction, slit lock, incorrect voltage, and short circuits in actuators. The input data are time-series data collected by two sensors and two control inputs under the condition that of one fault of the six types occurs. A gated recurrent unit (GRU) that is one of the RNNs classifies the suggested faults of the blade pitch system. The performance of fault classification based on the gate recurrent unit is evaluated by a test procedure, and the results indicate that the proposed scheme works effectively. The proposed ANN shows a 1.4% improvement in its performance compared to an MLP-based approach.

• Journal of The Korean Association For Science Education
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• v.21 no.1
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• pp.76-88
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• 2001

This study explored people's accuracy and methods of estimating some base physical quantities, i.e. length, mass, time and temperature. A total of 40 members, ranging from freshmen to professors, of a physics education department of a local university were asked to make two different kinds of estimations, intuitive and operational, on two sets of objects. For intuitive estimation, they were asked to make estimations on four given objects (length - wood chopsticks, mass - rubber eraser, time electric fan, temperature - water in a cup) as soon as they faced with the objects, usually within a few seconds of seeing. For operational estimation, they were allowed to make estimations on a different set of objects (length - plastic rod, mass - lock, time - simple pendulum, temperature - water in a cup) with enough time and they could apply various available methods (e.g. using pencil to estimate the object's length, counting their own pulse rate to estimate time) for the estimation. The findings of this study can be summarized as follows: (1) for length, mass and temperature the intuitive estimations were better performed while for the time estimation the result was the reverse; (2) there was no positive relationship between the amount of physics experience and the accuracy of the estimation; (3) in general, people's accuracy of the length estimation was best performed while their mass estimation was worst performed; (4) people used their own various methods for estimation, esp. using nearby objects around them and applying mental units which have convenient values (e.g. 30cm, 50cm, 1kg, 1 Keun, 1 second).

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.8 s.338
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• pp.33-40
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• 2005

This paper presents a structure of the searcher using a diversity in array antenna systems operating in the cdma2000 1x signal environments. The new technique exploits the fact that the In-phase and quadrature components of interferers can respectively be viewed as an independent gaussian noise at each antnna element in most practical cdma signal environments. The proposed PN acquisition scheme is a singles-dwell PN acquisition system consisting of two stages, that is, the searching stage and the verification stage. The searching stage independently correlates the receiver multiple signals with PN generator of each antenna element for obtaining the synchronous energy at the entire region. Then, the searching results of each antenna element are non-coherently combinind. The verification stage compares the searching energy with the optimal threshold, which is predesigned in the lock detector, and decides whether the acquisition is successful or fail. In this paper, we analyzed the effect of tile diversity order to determine the mean acquisition time. In general, it is known that the mean acquisition time significantly decrease as the number of antenna elements increases. But, as the diversity order goes up, the enhancement of the performance is saturated. Therefore, to decrease the mean acquisition time of the searcher, we must design the optimal array antenna systems by considering the operating SNR range of the receiver, the probability of detection $P_D$ and that of false alarm $P_{FA}$ . The Performance of the proposed PN acquisition scheme is analyzed in frequency selective Rayleigh fading channels. In this paper, the effect of the number of antenna elements on PN acquisition scheme is shown according to the probability of detection $P_D$ and that of false alarm $P_{FA}$.

• Journal of Korean society of Dental Hygiene
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• v.9 no.2
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• pp.111-124
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• 2009

This study analyzes through the review of literature and laws the exposure time, clinical frequency, and radiation exposure of intraoral and extraoral radiography as well as of panoramic radiography performed by dental hygienists in dental clinics, compares the dental radiology curriculums of radiological science and dental hygiene departments, and proposes the expansion of dental hygienists' radiography operations. The radiology curriculums were compared between the radiological science and dental hygiene departments of colleges. For new analysis by radiography for dental diagnosis, the exposure time, radiation absorbed dose, effective dose, and number of days of natural radiation were compared by the type of oral radiation films and radiographical techniques proposed by domestic and international studies. The exposure time of panoramic radiography is 15 seconds and it takes about two minutes for completion, whereas the exposure time of the standard radiography is 0.2~0.8 seconds and it takes 10 times longer for completion of the radiography of full mouth than the panoramic radiography. The standard radiography can cause distortions of radiation at severely curved parts of dental arch and palatopharyngeal reflex. However, panoramic radiography can be performed even for lock jaw patients, causes less inconvenience to patients and is much simpler than the standard radiography. The percentage of dental clinics where radiography is performed by dental hygienists was 92.0%, and the percentage of standard film radiography by dental hygienists was 98% whereas the percentage of panoramic radiography by dental hygienists was 92%. For the absorbed dose which is an indicator of radiation exposure, the When the effective dose which is an indicator of the danger of radiation exposure was converted to the number of days of natural radiation, it was 3.3 days for panoramic radiography, but 13.9 days for the full mouth standard radiography by bisecting angle technique which was 4.2 times longer than the panoramic radiography. There were two colleges that had a dental radiology course with two credits in the departments of radiological science. The credits for dental radiology courses in the department of dental hygiene ranged varied by college, ranging from 3 to 8; on average, the theory course was 2.2 credits and the practice course was 2.02 credits. To summarize the above results, the percentage of dental clinics where panoramic radiography is performed by dental hygienists under the guidance of dentists is high. Panoramic radiography has become an essential facility for dental clinics. It is faster than standard film radiography and less dangerous due to low radiation exposure. Panoramic radiography is a simple mechanical job that does not require training of oral radiography by radiotechnologist. Because panoramic radiography is one of major operations which must be performed at all times in dental clinics, it must be designated as intraoral technique rather than extraoral technique, or legalized for inclusion in the scope of operations of dental hygienists.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.4
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• pp.433-448
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• 2012

A source-synchronous receiver based on a delay-locked loop is presented. It employs a shared global calibration control between channels, yet achieves channel expandability for high aggregate I/O bandwidth. The global calibration control accomplishes skew calibration, equalizer adaptation, and phase lock of all the channels in a calibration period, resulting in the reduced hardware overhead and area of each data lane. In addition, the weight-adjusted dual-interpolating delay cell, which is used in the multiphase DLL, guarantees sufficient phase linearity without using dummy delay cells, while offering a high-frequency operation. The proposed receiver is designed in the 90-nm CMOS technology, and achieves error-free eye openings of more than 0.5 UI across 9-28 inch Nelco4000-6 microstrips at 4-7 Gb/s and more than 0.42 UI at data rates of up to 9 Gb/s. The data lane occupies only $0.152mm^2$ and consumes 69.8 mW, while the rest of the receiver occupies $0.297mm^2$ and consumes 56.0 mW at the 7- Gb/s data-rate and supply voltage of 1.35 V.

• The Korean Journal of Community Living Science
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• v.27 no.4
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• pp.739-753
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• 2016

This study was performed to identify the tendency and benefits of outdoor recreation in rural areas. The preferences and importance of the benefits of outdoor recreation activities in rural areas were simultaneously compared and analyzed through the discussion of a four quadrants portfolio map using importance-performance analysis. The social benefits in quadrant i had the characteristics of 'sharing nice experiences with others', 'having contact/interchange with others', 'colleagueship/helping each other', 'being together with friends', and 'making new friends.' These social benefit types were perceived as very important characteristics, but the real level of achievement was rather low. Thus it seems necessary, in the process of program development, to apply the social benefit types to the characteristics of the participants. The experience of nature and relaxation benefits in quadrant ii had the characteristics of 'relaxation and recreation', 'understanding nature', 'nature experience', 'getting away from everyday life', and 'experiencing new things.' These benefits and experience of nature were regarded as very important characteristics by the participants in outdoor recreation and, at the same time, their real achievements were highly recognized, thus they seemed to be proper types for the goals involved in developing an outdoor recreation activity program in rural areas. The personal and challenge benefits in quadrant iv had the characteristics of 'training of mental ability', 'improvement of self-esteem', 'fitness', 'increase in determination', 'possible danger', 'achievement', 'excitement', and 'adventure.' These benefits had less importance to the participants, but had relatively high achievement, thus it might be important to make further suggestions for the direction of development according to the participants' tendency, seasons and facilities.