• Spatial Information Research
• /
• v.15 no.4
• /
• pp.363-370
• /
• 2007

This study has been carried for the development of the basic algorithm of helicopter navigation system based on TRN (Terrain Referenced Navigation) with information input from the GPS. The helicopter determines flight path due to Origination-Destination analysis on the Cartesian coordinate system of 3-D DTM. This system shows 3-D mesh map and the O-D flight path profile for the pilot's acknowledgement of the terrain, at first. The system builds TCF (terrain clearance floor) far the buffer zone upon the surface of ground relief to avid the ground collision. If the helicopter enters to the buffer zone during navigation, the real-time warning message which commands to raise the body pops up using Matlab menu. While departing or landing, control of the height of the body is possible. At present, the information (x, y, z coordinates) from the GPS is assumed to be input into the system every 92.8 m of horizontal distance while navigating along flight path. DTM of 3" interval has been adopted from that which was provided by ChumSungDae Co., Ltd..

• Transactions of the Korean Society of Automotive Engineers
• /
• v.19 no.4
• /
• pp.8-15
• /
• 2011

This paper proposes a real-time navigation algorithm which integrates the artificial potential field (APF) for an unmanned vehicle in the unknown environment. This approach uses repulsive potential function around the obstacles to force the vehicle away and an attractive potential function around the goal to attract the vehicle. In this research, laser range finder is used as range sensor. An obstacle detected by the sensor creates repulsive vector. Differential global positioning system (DGPS) and digital compass are used to measure the current vehicle position and orientation. The measured vehicle position is also used to create attractive vector. This paper proposes a new concept of potential field based navigation which controls unmanned vehicle's speed and steering. The magnitude of repulsive force based on the proposed algorithm is designed not to be over the magnitude of attractive force while the magnitude is increased linearly as being closer to obstacle. Consequently, the vehicle experiences a generalized force toward the negative gradient of the total potential. This force drives the vehicle downhill towards its goal configuration until the vehicle reaches minimum potential and it stops. The effectiveness of the proposed APF for unmanned vehicle is verified through simulation and experiment.

• The Korean Journal of Food And Nutrition
• /
• v.27 no.6
• /
• pp.979-989
• /
• 2014

The purpose of this study was to investigate the association between dietary behavior and temperament & character in preschool children, and to offer basic data that can be applied for nutrition education and counseling. A total of 211 parents of preschool children aged 3~5 years performed the Korean version of Preschool Temperament and Character Inventory (K-psTCI), a questionnaire based on Cloninger's seven-factor model of personality, along with a questionnaire about the dietary behaviors of their children. K-psTCI represented seven factors such as harm avoidance (HA), novelty seeking (NS), reward dependence (RD), persistence (P), self-directedness (SD), cooperativeness (CO), and self-transcendence (ST). The subjects were divided into either the high rank group or low rank group based on the mean score of each factor. The high rank group of HA showed significantly less physical activity and less appetite than the low rank group of HA. The children in the high rank of NS were more likely to have picky eating and a late night snack. The children in the low rank of SD or CO were more likely to have undesirable dietary behaviors, such as picky eating, too much snacking, and lower appetite than those in the high rank of SD or CO. In conclusion, individual temperament & character in preschool children may be associated with their dietary behavior, and understanding temperament & character in children may be important facts to screen and to develop an effective nutrition education program for children.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.1
• /
• pp.45-57
• /
• 2005

In this paper, we extend the performance of bidirectional TCP connection over end-to-end network that uses transfer rate-based flow and congestion control. The sharing of a common buffer by TCP packets and acknowledgement has been known to result in an effect called ack compression, where acks of a connection arrive at the source bunched together, resulting in unfairness and degraded throughput. The degradation in throughput due to bidirectional traffic can be significant. Even in the simple case of symmetrical connections with adequate window size, the connection efficiency is improved about 20% for three levels of background traffic 2.5Mbps, 5.0Mbps and 7.5Mbps. Otherwise, the throughput of jitter is reduced about 50% because round trip delay time is smaller between source node and destination node. Also, we show that throughput curve is improved with connection rate algorithm which is proposed for TCP congetion avoidance as a function of aggressiveness threshold for three levels of background traffic 2.5Mbps, 5Mbps and 7.5Mbps. By analyzing the periodic bursty behavior of the source IP queue, we derive estimated for the maximum queue size and arrive at a simple predictor for the degraded throughput, applicable for relatively general situations.

• Transactions on Electrical and Electronic Materials
• /
• v.17 no.5
• /
• pp.261-269
• /
• 2016

A high-performance transmit/receive (T/R) switch is essential for every radio-frequency (RF) device. This paper proposes a T/R switch that is designed in the CEDEC 0.13 μm complementary metal-oxide-semiconductor (CMOS) technology for 2.4 GHz ISM-band RF applications. The switch exhibits a 1 dB insertion loss, a 28.6 dB isolation, and a 35.8 dBm power-handling capacity in the transmit mode; meanwhile, for the 1.8 V/0 V control voltages, a 1.1 dB insertion loss and a 19.4 dB isolation were exhibited with an extremely-low power dissipation of 377.14 μW in the receive mode. Besides, the variations of the insertion loss and the isolation of the switch for a temperature change from - 25℃ to 125℃ are 0.019 dB and 0.095 dB, respectively. To obtain a lucrative performance, an active inductor-based resonant circuit, body floating, a transistor W/L optimization, and an isolated CMOS structure were adopted for the switch design. Further, due to the avoidance of bulky inductors and capacitors, a very small chip size of 0.0207 mm² that is the lowest-ever reported chip area for this frequency band was achieved.

• Korean Journal of Cognitive Science
• /
• v.23 no.1
• /
• pp.25-46
• /
• 2012

When performing a monotonous task, one often experiences an urge to quit. This urge may vary depending on how long one has performed the task (a temporal factor) and on which particular component of the task one is carrying out (an event-based factor). Using the Stroop task and a working memory task, we examined changes in the urge to quit as a function of basic temporal (repetition) and event-based (cognitive conflict) factors. Consistent with the law of least work and recent theorizing, for the memory task, urges to quit were greater following difficult trials; for the Stroop task, urges to quit were greater following incongruent than congruent trials, but only during early/novice phases of performance, when responding is inefficient. This is a demonstration of an avoidance response toward cognitive conflict. Regarding temporal sources of quitting, urges to quit were greater for late task stages than early stages. These basic findings may illuminate the nature of the more 'hot' motivational struggles involving the delay of gratification.

• Journal of Advanced Navigation Technology
• /
• v.8 no.1
• /
• pp.65-72
• /
• 2004

A basic access method using for IEEE 802.11a wireless LANs is the DCF method that is based on the CSMA/CA. But, Since IEEE 802.11 MAC layer uses original backoff algorithm (Exponential backoff method), when collision occurs, the size of contention windows increases the double size. Hence, packet transmission delay time increases and efficiency is decreased by original backoff scheme. In this paper, we have analyzed TCP packet transmission time of IEEE 802.11 MAC DCF protocol for wireless LANs using a proposed enhanced backoff algorithm. From the results, in OFDM/quadrature phase shift keying channel (QPSK), we can achieve that the transmission time in wireless channel decreases as the TCP packet size increases and based on the data collected, we can infer the correlation between TCP packet size and total message transmission time, allowing for an inference of the optimal packet size in the TCP layer.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.20 no.4
• /
• pp.707-714
• /
• 2016

Active driving safety systems for vehicle, such as the front collision avoidance, lane departure warning, and lane change assistance, have been popular to be adopted to the compact car. For improving performance and competitive cost, FMCW radar has been researched to adopt a phased array or a multi-beam antenna, and to integrate the front and the side radar. In this paper we propose several efficient methods to implement the signal processing module of FMCW radar system using low cost DSP. The pulse width modulation (PWM) based analog conversion, the approximation of time-eating functions, and the adoption of vector-based computation, etc, are proposed and implemented. The implemented signal processing board shows the real-time performance of 1.4ms pulse repetition interval (PRI) with 1024pt-FFT. In real road we verify the radar performance under real-time constraints of 10Hz update time.

• Proceedings of the Korea Society for Simulation Conference
• /
• 2001.10a
• /
• pp.231-236
• /
• 2001

Virtual Reality (VR) is a new technology that enables humans to communicate with a computer, It allows the user to see, hear, fuel and interact in a three-dimensional virtual world created graphically. Virtual Reality Therapy (VRT), based on this sophisticated technology, has been recently used in the treatment of subjects diagnosed with acrophobia. Acrophobia is a disorder that is characterized by marked anxiety upon exposure to heights, avoidance of heights, and a resulting impairment in functioning. Conventional virtual reality systems for the treatment of acrophobia have limitations, such as overly expensive devices or somewhat unrealistic graphic scenes. The goal of this study is to develop an inexpensive and more realistic virtual environment in which to perform an exposure therapy fur acrophobia. It runs on a personal computer, and a virtual scene ova bunge-jump tower in the middle of a large city. The virtual scenario includes an open tin surrounded by props beside a tower, which allows the patient to feel a sense of heights. The effectiveness of the VR environment was evaluated through the clinical treatment of a subject who was suffering from the fear of heights. Based on pre- and post- questionnaires and subjective comments from the subject. This virtual reality environment proved to be an effective and realistic tool fur the treatment of acrophobia.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.4
• /
• pp.76-89
• /
• 2014

In this paper, we propose a MAC(Media Access Control) protocol based on flexible RWT(RTS Waiting Time) for underwater mobile ad-hoc networks with a three-way handshaking mechanism. This protocol can solve a problem of collision between RTS(Request-To-Send) and CTS(Clear-To-Send) packets in existing MACA(Multiple Access with Collision Avoidance) protocol. This proposed MAC protocol is also an effective protocol which can apply to underwater mobile ad-hoc networks in a real field by using implementable technologies. We set flexible RTS Waiting Time called RWT, considering various characteristics of underwater environment. It is possible to support variable network size according to node mobility. Finally, we conduct a performance evaluation between proposed MAC protocol and existing MACA based MAC protocol through practical implementation and experiment. As a result, we verify the superiority of our proposed MAC protocol in terms of throughput, packet drop rate, average transmission time, energy consumption and channel utilization.