• Journal of Sensor Science and Technology
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• v.8 no.1
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• pp.24-31
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• 1999

Ammonia gas sensors were fabricated with ZnO-based thin films grown by RF-magnetron sputtering method. The films which were doped with $MoO_3$ catalysts of various weight percents were grown in different sputtering gases to fabricate the sensors with a high sensitivity, low working temperature and rapid response time. To improve electrical stability, the films were aged in various conditions. The sensors doped with the catalysts and grown in oxygen sputtering gas showed the improvement of sensitivity. These exhibited the increase of surface carrier concentration and electron mobility. The sensor with 0.875wt.% $MoO_3$ catalysts showed the maximum sensitivity of 70 in ammonia gas concentration of 160 ppm at a working temperature of $300^{\circ}C$. The sensor which is aged at $330^{\circ}C$ for 72hrs in oxygen ambient exhibited tourer sensitivity of 57, but more stable properties, excellent linearity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.6
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• pp.648-654
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• 2003

Diamond MIS(Metal-Insulator-Semiconductor) diodes and MISFETs(Metal-Insulator-Semiconductor Field Effect Transistors) were fabricated by employing various fluorides as gate insulator, and their electrical properties were closely investigated by means of C-V measurements. The A1/BaF$_2$/diamond MIS structure exhibited outstanding electrical properties. The MIS diode showed a very low surface state density of ∼10$\^$10//$\textrm{cm}^2$ eV near the valence band edge, and the observed effective mobility(${\mu}$$\_$eff/) of the MISFET was 400 $\textrm{cm}^2$/Vs, which is the highest value obtained until now in the diamond FET. From the chemiphysical point of view, the above result might be explained by the reduction of adsorbed-oxygen on the diamond surface via strong chemical reaction by the constituent Ba atom in the insulator during the film deposition(Oxygen-Gettering Effect).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.9
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• pp.3502-3509
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• 2010

Streaming service in the wireless mobile network environment has been a very challenging issue due to the dynamic uncertain nature of the channels. Overhead such as congestion, latency, and jitter lead to the problem of performance degradation of an adaptive multi-streaming service. This paper proposes a AMSS (Adaptive Multi-level Streaming Service) mechanism to reduce the performance degradation due to overhead such as variable network bandwidth, mobility and limited resources of the wireless mobile network. The proposed AMSS optimizes streaming services by: 1) use of fuzzy similarity metric, 2) minimization of packet loss due to buffer overflow and resource waste, and 3) minimization of packet loss due to congestion and delay. The simulation result shows that the proposed method has better performance in congestion control and packet loss ratio than the other existing methods of TCP-based method, UDP-based method and VBM-based method. The proposed method showed improvement of 10% in congestion control ratio and 8% in packet loss ratio compared with VBM-based method which is one of the best method.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.47 no.6
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• pp.113-123
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• 2010

In this paper, an efficient network configuration method is proposed for mobile nodes in LR-WPAN (Low Rate Wireless Personal Area Network) based on the IEEE 802.15.4 standard. The proposed MSBS (mobile sensor beacon setup) method can be used to implement a joining procedure by which an improved processing rate can be achieved. This improvement is achieved by using BOP (Beacon only Period). In this method, the performance of mobile nodes is enhanced by using information on depth, traffic, and RSSI (Received Signal Strength Indication). By using the MSBS method, trusted data can be transferred and traffic overloads that occur at specific nodes can be prevented. The information obtained from the mobile nodes in wireless networks is analyzed using the proposed method, in order to study the performance of the method. Simulation results show that the MSBS method can be used to obtain an efficient network configuration according to the mobility of nodes in LR-WPAN.

• The KIPS Transactions:PartC
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• v.11C no.2
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• pp.219-228
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• 2004

Wireless LAN(wireless Local Area Network) is constructed network environment by radio in indoors or outdoors environment and that to use electric wave or light instead of wire to client such as PC(Personal Computer), notebook, PDA in hub(Hub) in technological side. Now, among IEEE 802.11 WG(Working Group), there is TGf(Task Group F) that develop standard protocol between AP's(Access Point). In this group, proposed IAPP(Inter Access Point Protocol) to secure interoperability between AP producing in different manufacturer, this offers seamless connectivity between STA by sharing Security Context information or Layer 2 forwarding information between AP without passing through re-authentication process when STAs(Station) move by protocol to secure mobility between AP that differ in equal serve network. In this paper, I wish to suggest method that change avenue of communication of message to block information leakage that can occur at security message or WEP Key transmission between above AP, and uses public key to offer wireless area security little more.

• Journal of Mechanical Science and Technology
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• v.19 no.3
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• pp.778-791
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• 2005

A novel pneumatic artificial muscle actuator (PAM actuator), which has achieved increased popularity to provide the advantages such as high strength and high power/weight ratio, low cost, compactness, ease of maintenance, cleanliness, readily available and cheap power source, inherent safety and mobility assistance to humans performing tasks, has been regarded during the recent decades as an interesting alternative to hydraulic and electric actuators. However, some limitations still exist, such as the air compressibility and the lack of damping ability of the actuator bring the dynamic delay of the pressure response and cause the oscillatory motion. Then it is not easy to realize the performance of transient response of pneumatic artificial muscle manipulator (PAM manipulator) due to the changes in the external inertia load with high speed. In order to realize satisfactory control performance, a variable damper-Magneto­Rheological Brake (MRB), is equipped to the joint of the manipulator. Superb mixture of conventional PID controller and a phase plane switching control method brings us a novel controller. This proposed controller is appropriate for a kind of plants with nonlinearity, uncertainties and disturbances. The experiments were carried out in practical PAM manipulator and the effectiveness of the proposed control algorithm was demonstrated through experiments, which had proved that the stability of the manipulator can be improved greatly in a high gain control by using MRB with phase plane switching control method and without regard for the changes of external inertia loads.

• The Journal of the Korea Contents Association
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• v.7 no.1
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• pp.131-138
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• 2007

In wired networks, packet losses mostly occur due to congestion. TCP reacts to the congestion by decreasing its congestion window, thus to reduce network utilization. In wireless networks, however, losses may occur due to the high bit-error rate of the transmission medium or due to fading and mobility. Nevertheless, TCP still reacts to packet losses according to its congestion control scheme, thus to reduce the network utilization unnecessarily. This reduction of network utilization causes the performance of TCP to decrease. In this paper, we predict packet loss by using RSS(Received Signal Strengths) on the wireless and suggest adding RSS flag bit in ACK packet of MH. By using RSS flag bit in ACK, the FH(Fixed Host) decides whether it adopt congestion control scheme or not for the maximum throughput. The result of the simulation by NS-2 shows that the proposed mechanism significantly increases sending amount and receiving amount by 40% at maximum.

• The Korean Journal of Pain
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• v.29 no.1
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• pp.12-17
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• 2016

Background: The study aimed to determine if ultrasonography of masseter can be used to evaluate the outcome of transcutaneous electrical nerve stimulation (TENS) in subjects with temporomandibular disorders (TMDs) such as myositis and myofascial pain. Methods: Fifteen TMD subjects with myofascial pain/myositis who satisfied the RDC/McNeil criteria were included in the study. All the subjects were administered TENS therapy for a period of 6 days (30 minutes per session). The mouth opening (in millimeters) and severity of pain (visual analogue scale score) and ultrasonographic thickness of the masseter (in millimeters) in the region of trigger/tender areas was assessed in all the subjects both prior and post TENS therapy. A comparison of the pre-treatment and post-treatment values of the VAS score, mouth opening and masseter thickness was done with the help of a t-test. Results: There was a significant reduction in the thickness of masseter muscle (P = 0.028) and VAS scores (P < 0.001) post TENS therapy. There was also a significant improvement in the mouth opening (P = 0.011) post TENS therapy. Conclusions: In the present study, ultrasonography was found to be an effective measuring tool in the assessment of TENS therapy in subjects with myositis and myofascial pain.

• Journal of Korean Physical Therapy Science
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• v.8 no.1
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• pp.907-915
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• 2001

The purpose of this study is to effectively treat low back pain for the out patients who have been treated at the oriental hospital. Sorting the low back pain patients into four types based on scapular and ilium tilting hyper/hypo mobility characteristics, it has used several kinds of acupuncture stimuli on the 4 motor points of limb skeletal muscles, analyzing the acupuncture treatment on the 12 acupuncture points with which oriental hospitals has given to the low back pain patients and comparing with this effect. It has been analyzed how effectively the acupuncture stimuli has been contributed to the low back pain patients who suffered from skeletal muscles of spinal limb thorax abdominal and spinal skeletal system. The results are as follows. 1. There has been changes after treatment in both the control and experimental groups for low back pain patients, but the latter has been more increased in changes than the former. 2. There were much effects on the balanced restorations for spinal skeletal muscle in both the control group and experimental one, but on terms of restoration degree, the degree of the experimental group was higher than that of the control group. 3. Both the contrastive treatment and the experimental one have been contributed to the balanced restoration for all of the limb thorax abdominal muscles, but there were a few differences in terms of the way for restoration and the effects for improvement according to body types. 4. On both the control and the experimental group, spinal skeletal system has been restored with balance, but the experimental group has been higher effective on the balanced restoration than the one of the control group. Considering these results both the control and the experimental treatments have been contributed to the balanced restorations for all of low back pain patients who were suffering from skeletal muscles of spinal limb thorax abdominal and spinal skeletal system, but the contribution degree for the experimental group has been higher than that of the control group.

• Journal of Korean Ophthalmic Optics Society
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• v.19 no.3
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• pp.407-412
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• 2014

Purpose: It is investigated whether the time division system can extend the field without diplopia for people with homonymous hemianopia. Methods: The time division system was manufactured by a modified mini fan and a black cardboard. In order to verify the effectiveness of the equipment, subjects with and without the equipment took part in the experiment to bisect the space and to recognize letters. Results: Subjects with and without the equipment showed +8.91 and +18.14 degrees in the experiment to bisect the space. In the experiment reading the letters and numbers with the equipment, there were 9 percentage point increase in $4{\times}4$ charts and 15 percentage point increase in $6{\times}6$ charts. It turned out that there was a remarkable improvement for the worst group for reading the charts. Conclusions: The time division system is effective in the mobility and orientation for people with homonymous hemianopia.