• Journal of information and communication convergence engineering
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• 제20권1호
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• pp.22-30
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• 2022

The reinforcement learning algorithm has proven its potential in solving sequential decision-making problems under uncertainties, such as finding paths to route data packets in wireless sensor networks. With reinforcement learning, the computation of the optimum path requires careful definition of the so-called reward function, which is defined as a linear function that aggregates multiple objective functions into a single objective to compute a numerical value (reward) to be maximized. In a typical defined linear reward function, the multiple objectives to be optimized are integrated in the form of a weighted sum with fixed weighting factors for all learning agents. This study proposes a reinforcement learning -based routing protocol for wireless sensor network, where different learning agents prioritize different objective goals by assigning weighting factors to the aggregated objectives of the reward function. We assign appropriate weighting factors to the objectives in the reward function of a sensor node according to its hop-count distance to the sink node. We expect this approach to enhance the effectiveness of multi-objective reinforcement learning for wireless sensor networks with a balanced trade-off among competing parameters. Furthermore, we propose SDN (Software Defined Networks) architecture with multiple controllers for constant network monitoring to allow learning agents to adapt according to the dynamics of the network conditions. Simulation results show that our proposed scheme enhances the performance of wireless sensor network under varied conditions, such as the node density and traffic intensity, with a good trade-off among competing performance metrics.

• Journal of Korean Neurosurgical Society
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• 제30권9호
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• pp.1094-1102
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• 2001

Objective : During the trans-condylar or trans-jugular approach for the lesion of cranio-cervical junction(CCJ), its necessary to identify the accurate locations of vertebral artery(VA), internal jugular vein(IJV) and its related lower cranial nerves. These neurovascular structures can also be damaged during the operation for vascular tumor or traumatic aneurysm around extra-jugular foramen, because of their changed locations. To reduce the neurovascular injury at the operation for CCJ, morphometric relationship of its surrounding neurovascular structures based on the tip of the transverse process of atlas(C1 TP), were studied. Materials & Methods : Using 10 adult formalin fixed cadavers, tip of mastoid process(MT) and TPs of atlas and axis were exposed bilaterally after removal of occipital and posterior neck muscles. Using standard caliper, the distances were measured from the C1 TP to the following structures : 1) exit point of VA from C1 transverse foramen, 2) branching point of muscular artery from VA, 3) entry point of VA into posterior atlanto-occipital membrane(AOM), 4) branching point of C-1 nerve. In addition, the distances were measured from the mid-portion of the posterior arch of atlas to the entry point of the VA into AOM and to the exit point of the VA from C1 transverse foramen. After removal of the ventrolateral neck muscles, neurovascular structures were exposed in the extra-jugular foraminal region. Distances were then measured from the C1 TP to the following structures : 1) just extra-jugular foraminal IJV and lower cranial nerves, 2) MT and branching point of facial nerve in parotid gland. In addition, distance between MT and branching point of facial nerve was measured. Results : The VA was located at the mean distance of 12mm(range, 10.5-14mm) from the C1 transverse foramen and entered into the AOM at the mean distance of 24mm(range, 22.8-24.4mm) from the C1 TP. The mean distance from the mid portion of the C1 posterior arch was 20.6mm(range, 19.1-22.3mm) to the entry point of the VA into AOM and 38.4mm(range, 34-42.4mm) to the exit point of the VA from C1 transverse foramen. Muscular artery branched away from the posterior aspect of the transverse portion of VA below the occipital condyle at the mean distance of 22.3mm(range, 15.3-27.5mm) from the C1 TP. The C-1 nerve was identified in all specimens and ran downward through the ventroinferior surface of the transverse segment of VA and branched at the mean distance of 20mm(range, 17.7-20.3mm) from the C1 TP. The IJV was located at the mean distance of 6.7mm(range, 1-13.4mm) ventromedially from the lateral surface of the C1 TP. The XI cranial nerve ran downward on the lateral surface of the IJV at the mean distance of 5mm(range, 3-7.5mm) from the C1 TP. Both IX and X cranial nerves were located in the soft tissue between the medial aspect of the internal carotid artery(ICA) and the medial aspect of the IJV at the mean distance of 15.3mm(range, 13-24mm) and 13.7mm(range, 11-15.4mm) from the C1 TP, respectively. The IX cranial nerve ran downward ventroinferiorly crossing the lateral aspect of the ICA. The X cranial nerve ran downward posteroinferior to the IX cranial nerve and descended posterior to the ICA. The XII cranial nerve was located between the posteroinferior aspect of the IX cranial nerve and the posterior aspect of the ICA at the mean distance of 13.3mm(range, 9-15mm) ventromedially from the C1 TP. The distance between MT and C1 TP was 17.4mm(range, 12.5-23.9mm). The VII cranial nerve branched at the mean distance of 10.2mm(range, 6.8-15.3mm) ventromedially from the MT and at the mean distance of 17.3mm(range, 13-21mm) anterosuperiorly from the C1 TP. Conclusion : This study facilitates an understanding of the microsurgical anatomy of CCJ and may help to reduce the neurovascular injury at the surgery around CCJ.

• 한국안광학회지
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• 제19권1호
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• pp.17-22
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• 2014

목적: 시력검사거리에 따른 원거리 시력검사의 신뢰성을 평가하고자 하였다. 방법: 5 m 거리에서 교정시력이 1.0 이상이 되었던 성인 39명(78안)을 대상으로 하였다. 각각의 검사거리(5 m, 4 m, 그리고 3 m)에서 대상자의 교정굴절력을 측정하였다. 시시력표는 자동 챠트(LCD-700, Hyeseong Optic. Co., Korea)를, 타각적 굴절검사는 검영기(Beta 200, Heine, Germany)와 자동굴절검사기(RK-5, Canon, Japan)를 사용하였다. 조절력검사는 (-)렌즈 부가법으로, 조절래그 검사는 근거리 격자시표를 사용하였다. 결과: 구면교정굴절력은 5 m에 비하여 3 m에서 평균 $0.10{\pm}0.38$ D 감소하였고 난시도는 $0.05{\pm}0.10$ D 감소하였으며, 난시축은 우좌안이 귀방향으로 각각 $2.64{\pm}18.75$ 도, $11.43{\pm}48.55$ 도 회전하였다. 교정굴절력의 변동과 난시도의 변동은 최대교정굴절력과의 약한 음의 상관관계를 보였다(r=-0.31, r=-0.29). 결론: 검사거리에 따라 구면교정굴절력과 난시도는 5 m에 비하여 3 m에서 감소하며, 난시축은 귀방향으로 회전하는 경향이 있기 때문에, 안경원에서 원거리 시력검사를 위한 검사거리는 5 m로 개선되어져야 할 것이다.

• 대한소아치과학회지
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• 제48권1호
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• pp.105-114
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• 2021

이 연구의 목적은 광중합기의 조사단에 광섬유를 적용하였을 때, 조사단과 교정용 버튼의 베이스 사이의 거리와 광섬유 직경에 따른 교정용 버튼의 전단결합강도를 평가하는 것이다. 발치된 소구치 315개를 I, II, III군으로 나누어 광섬유를 사용하지 않거나 3.0, 5.0 mm 직경의 광섬유를 사용하였고 각 군을 A, B, C의 하위군으로 분리하여 5.0, 10.0, 15.0 mm 깊이로 조사단과의 거리를 설정하여 전단결합강도를 측정하였다. 거리 증가에 따라 I군의 전단결합강도가 유의하게 감소하였다. 광섬유 직경에 따른 전단결합강도를 평가했을 때 거리가 5.0 mm인 경우 군 간에 유의성이 관찰되지 않았고 10.0 mm인 경우 IB군에 비해 IIIB군에서 유의하게 높은 전단결합강도를 보였고 15.0 mm인 경우 IC군에 비해 IIC, IIIC군 모두 유의하게 높은 전단결합강도를 보였다. 고로 광중합기의 접근성이 떨어질 때, 광섬유 사용이 추천되며 직경이 큰 광섬유가 성공적인 버튼 부착에 도움이 될 것으로 사료된다.

• 한국안광학회지
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• 제18권3호
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• pp.347-356
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• 2013

목적: 비구면 다초점 인공수정체인 ReSTOR$^{(R)}$ SN6AD3 삽입안의 시력과 시기능 변화를 분석하였다. 방법: 양안 또는 단안에 비구면 다초점 인공수정체(ReSTOR$^{(R)}$ SN6AD3)를 삽입한 백내장 환자 19명의 30안을 대상으로 하였다. 수술 전, 수술 후 1주일, 1개월 및 3개월 후에 시력과 객관적인 시기능을 측정하였고 수술 3개월 후 인공수정체 삽입안의 시기능 측정값을 동일 연령대의 정상안 20명(38안)과 비교하였다. 원거리 시력은 2 m 거리에서 LCD chart ETDRS 시력표를 이용하여 측정하였고, 중간거리(50 cm)과 근거리(30 cm) 시력은 Jaeger chart를 이용하였다. 객관적인 시기능은 OQAS 장비를 이용하여 OSI (objective scatter index, 객관적 산란지수), MTF (modulation transfer function, 변조전달함수) cut off, Strehl ratio를 4 mm 동공크기에서 측정하여 수술 후 경과기간에 따른 측정값을 비교 평가하였다. 수술 3개월 째 시력 및 시기능은 객관적 평가와 주관적인 평가를 통해 동일 연령대의 정상안과 비교하였다. 결과: 나안 원거리 시력과 OSI, MTF와 Strehl ratio는 다초점 인공수정체 삽입 1개월까지 유의하게 향상되었다(p<0.05). 수술 3개월 후 다초점 인공수정체 삽입안의 MTF와 Strehl ratio는 정상 대조군의 수준으로 회복되었지만, OSI는 대조군보다 높은 값으로 측정되었다(p<0.001). 자각적인 원거리 및 근거리 시력에 대한 만족도는 높았지만, 중간거리 시력에 대한 만족도가 낮으며 눈부심과 빛 번짐 증상이 나타났다. 결론: 비구면 다초점 인공수정체 삽입안의 시기능은 수술 1개월 후부터 안정화되며 동일 연령대의 정상안의 수준으로 개선되지만 만족스러운 중간거리 시력을 제공하지 못하며 눈부심과 빛 번짐의 시각적 불편감이 나타나는 것으로 사료된다.

• 대한인간공학회지
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• 제31권2호
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• pp.413-419
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• 2012

Objective: This study presents an observation and analysis on behavioral characteristics of old users in comparison to young users in the use of control on display interface. Background: Touch interface which allows users to control directly on display, is conceived as delight and easy way of human-computer interaction. Due to the advantage in stimulus-response ensemble, the old users, who typically experiencing difficulties in interacting with computer, would expected to have better experience in using computing machines. Method: Twenty nine participants who are over 50 years old and 14 participants who are in 20s years old were participated in this study. Three primary tasks in touch interface, which are tap, move, and flick, were delivered by the users. For the tap task, response time and point of touch response were collected and the response bias was calculated for each trial. For the move task, delivery time and the distance of finger movements were recorded for each trial. For the flick task, task completion time and flicking distance were recorded. Results: From the collected behavioral data, temporal and spatial differences between young and old users behavior were analyzed. The older users showed difficulty in completing move task requiring eye-hand coordination.

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.265-270
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• 2007

Polarization imaging systems have been widely used to selectively characterize skin lesions. Nevertheless, current systems are used in single-mode due to the limitations of a fixed polarization mode and a single-working distance of light source, in which uniform light distribution is achieved on target area. To address such limitations, we developed a variable polarization imaging system based on multi-working distance of light source for various clinical diagnoses. In this study, we characterize the imaging system and present experiment results demonstrating its clinical usefulness. The imaging system consists of a CCD color camera, linear polarization filters, and a single-layered LED ring light source which provides uniform light distribution at multi-working distances. The first polarizer was placed on the light source and the second polarizer placed on objective lens provides continuous linear polarization angle from $0^{\circ}\;to\;90^{\circ}$. The clinical efficacy of the imaging system was investigated by acquiring and analyzing clinical images of skin wrinkle and dental plaque. With the experiments, we verified the potential usefulness of the imaging system for other clinical applications.

• 한국의류학회지
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• 제25권3호
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• pp.629-637
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• 2001

The objective of this study was to identify the cultural characteristics affecting advertising contents of the consumer products. Hofstedes(1991) five cultural characteristics such as individualism-collectivism, power distance, masculinity-feminity, avoidance of uncertainty, confucian dynamism were used. Ten kinds of consumer products were included and data were collected from France, Japan, Korea, and U. S. during 1999∼2000. All ads were evaluated and compared their cultural characteristics in terms of country, product involvement and usage, and magazine type. ANOVA, Duncan test, and Pearson correlation-coefficient were applied to analyze data. The results were shown as follows: First, most ads tended to be individual, less power oriented, feministic, and showed high tendency of uncertainty avoidance as well as long term confucianism for all the countries. And some cultural characteristics were different among countries. Japan, France, U. S. and Korea in order showed higher individualism and lower power distance. Also Korea and Japan showed relatively short term confucian culture while U. S. and France did ling term perspectives in the ads. Second, product involvement and usage type had a significant impact on the characteristics of individualism-collectivism and feminity-masculinity. That is, product ads of lower involvement and personal use were likely to show individualistic messages and to have more feministic appeals. Third, magazine type had an impact on some cultural characteristics. Womens magazines would have more individualistic, less power oriented, and feministic appeals of ads. In conclusion, global ads should be localized and differentiated in terms of some cultural characteristics and differ depending on product characteristics.

• 한국생산제조학회지
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• 제6권2호
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• pp.34-41
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• 1997

The objective of this study is to investigate experimentally the frequency characteristics of the hole tones generated by a circular jet of low speed impinging on a plate with a round hole. The experimental results about the sound spectrum and the time wave of the hole tone are presented and discussed in relation with the hole type, the jet velocity and the distance of the nozzle-to-plate with a round hole. From the sound spectrum and time wave measurements, it is found that the hole tone is generated not only by an interaction of convected vortices with a round hole but also by a series of vortex shedding from jets passing through a hole. The hole tones generated by a feedback mechanism consist of many frequency stages and also have a hysteresis phenomenon like an edge tone. But the hole tones generated by a series of vortex shedding have nothing with the stage characteristics. The frequencies of hole tones are influenced by the jet velocity, the distance of the nozzle-to-plate with a round hole and the hole type.

• 한국공작기계학회논문집
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• 제15권5호
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• pp.104-113
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• 2006

The main objective of this study is to investigate the effect of compounded welding by using acoustic emission (AE) signals and doing a source location for weld heat affected zone (HAZ) through tensile testing. This study was carried out an SWS 490A high strength steel for electric shield metal arc welding, SMAW; $CO_2$ gas metal arc welding, GMAW($CO_2$); and gas tungsten arc welding, GTAW/TIG. Data displays are based on the measured parameters of the AE signals, along with environmental variables such as time and load. For instance, Gutenberg-Richter magnitude-frequency relationship (G-R MFR) offers useful b-value in data analysis. Namely event identification, source location gives the X- and Y-coordinates of the AE source. And K-means clustering analysis by Euclidean distance confirmed that was powerful to source location. Generally, strength of welded metal zone was stronger than strength of base metal. As the result, confirmed certainly that fracture is produced in HAZ instead of welded metal zone from source location.