Original Articles : Low Limit for Effective Signal Strength in the Stratus OCT in Imperative Low Signal Strength Cases

( Man Mook Ha ),( Joon Mo Kim ),( Hyun Joong Kim ),( Ki Ho Park ),( Martha Kim ),( Chul Young Choi ) 대한안과학회 2012 Korean Journal of Ophthalmology Vol.26 No.3

Purpose: To determine the lowest limit of signal strength that is still effective for accurate analysis of optic coherence tomography (OCT) values, we investigated the reproducibility of OCT scans by signal strength (SS). Methods: A total of 668 subjects were scanned for measurements of retinal nerve fiber layer (RNFL) thickness using the Stratus OCT twice on the same day. The variability of overall RNFL thickness parameters obtained at different SS was analyzed and compared by repeated-measures of ANOVA and Spearman`s correlation coefficient. Values of the intraclass correlation coefficient (ICC) and variability (standard deviation) of RNFL thickness were obtained. The false positive ratio was analyzed. Results: When SS was 3, the variability of RNFL thickness was significantly different (low ICC, high variability) in comparison to when SS was 4 or greater. Significant negative correlations were observed between variability in RNFL thickness and signal strength. The difference of variability of average RNFL thickness between SS 4 (4.94 μm) and SS 6 (4.41 μm) was 0.53 μm. Conclusions: Clinically, the difference of variability of average RNFL thickness between SS 4 and SS 6 was quite small. High SS is important, however, when signal strength is low due to uncorrectable factors in patients in need of OCT for glaucoma and retinal disease. Our results suggest that SS 4 is the lowest acceptable limit of signal strength for obtaining reproducible scanning images.

Low Limit for Effective Signal Strength in the Stratus OCT in Imperative Low Signal Strength Cases

하만묵,김준모,김현중,박기호,김마르다,최철영 대한안과학회 2012 Korean Journal of Ophthalmology Vol.26 No.3

Purpose: To determine the lowest limit of signal strength that is still effective for accurate analysis of optic coherence tomography (OCT) values, we investigated the reproducibility of OCT scans by signal strength (SS). Methods: A total of 668 subjects were scanned for measurements of retinal nerve fiber layer (RNFL) thickness using the Stratus OCT twice on the same day. The variability of overall RNFL thickness parameters obtained at different SS was analyzed and compared by repeated-measures of ANOVA and Spearman’s correlation coefficient. Values of the intraclass correlation coefficient (ICC) and variability (standard deviation) of RNFL thickness were obtained. The false positive ratio was analyzed. Results: When SS was 3, the variability of RNFL thickness was significantly different (low ICC, high variability)in comparison to when SS was 4 or greater. Significant negative correlations were observed between variability in RNFL thickness and signal strength. The difference of variability of average RNFL thickness between SS 4 (4.94 μm) and SS 6 (4.41 μm) was 0.53 μm. Conclusions: Clinically, the difference of variability of average RNFL thickness between SS 4 and SS 6 was quite small. High SS is important, however, when signal strength is low due to uncorrectable factors in patients in need of OCT for glaucoma and retinal disease. Our results suggest that SS 4 is the lowest acceptable limit of signal strength for obtaining reproducible scanning images.

Application of impact force response signal to non-destructive evaluation of concrete compressive strength in field structures

Moorak Son,Woori Jeong 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.6

This study aimed to evaluate the feasibility and usefulness of using the signal created by the impact force after the first impact of an object and subsequent impact of rebounds to evaluate the concrete's compressive strength non-destructively. Three distinct materials (steel, concrete, and wood) were tested to compare the compressive strengths and signal response using a developed device. The test results demonstrated that the compressive strength of different materials could be effectively represented using the impact force response signals. Following the test results, field case studies were conducted on three different structures. The studies also showed a direct correlation between the impact force response signal and the compressive strength of concrete. Based on the study findings, the total impact force signal energy, which was determined by integrating the impact force response signal, could be used to non-destructively evaluate the compressive strength of concrete materials.

무선 센서네트워크 기반 신호강도 맵을 이용한 재택형 위치인식 및 사용자 식별 시스템

양용주,이정훈,송상하,윤영로,Yang, Yong-Ju,Lee, Jung-Hoon,Song, Sang-Ha,Yoon, Young-Ro 대한의용생체공학회 2007 의공학회지 Vol.28 No.4

Ubiquitous location based services (u-LBS) will be interested to an important services. They can easily recognize object position at anytime, anywhere. At present, many researchers are making a study of the position recognition and tracking. This paper consists of postion recognition and user identification system. The position recognition is based on location under services (LBS) using a signal strength map, a database is previously made use of empirical measured received signal strength indicator (RSSI). The user identification system automatically controls instruments which is located in home. Moreover users are able to measures body signal freely. We implemented the multi-hop routing method using the Star-Mesh networks. Also, we use the sensor devices which are satisfied with the IEEE 802.15.4 specification. The used devices are the Nano-24 modules in Octacomm Co. Ltd. A RSSI is very important factor in position recognition analysis. It makes use of the way that decides position recognition and user identification in narrow indoor space. In experiments, we can analyze properties of the RSSI, draw the parameter about position recognition. The experimental result is that RSSI value is attenuated according to increasing distances. It also derives property of the radio frequency (RF) signal. Moreover, we express the monitoring program using the Microsoft C#. Finally, the proposed methods are expected to protect a sudden death and an accident in home.

Evaluation of Fracture Behavior of SA-516 Steel Welds Using Acoustic Emission Analysis

Na, Eui-Gyun,Ono, Kanji,Lee, Dong-Whan The Korean Society of Mechanical Engineers 2006 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.20 No.2

The purpose of this study is to evaluate the AE characteristics for the basemetal, PWHT (post-weld heat treatment) and weldment specimens of SA-516 steel during fracture testing. Four-point bending and AE tests were conducted simultaneously. AE signals were emitted in the process of plastic deformation. AE signal strength and amplitude of the weldment was the strongest, followed by PWHT specimen and basemetal. More AE signals were emitted from the weldment samples because of the oxides, and discontinuous mechanical properties. AE signal strength and amplitude for the basemetal or PWHT specimen decreased remarkably compared to the weldment because of lower strength. Pre-cracked specimens emitted even lower event counts than the corresponding blunt notched specimens. Dimple fracture from void coalescence mechanism is associated with low-level AE signal strength for the basemetal or PWHT. Tearing mode and dimple formation were shown on the fracture surfaces of the weldment, but only a small fraction produced detectable AE.

A Received Signal Strength-based Primary User Localization Scheme for Cognitive Radio Sensor Networks Using Underlay Model-based Spectrum Access

( Young-doo Lee ),( Insoo Koo ) 한국인터넷정보학회 2014 KSII Transactions on Internet and Information Syst Vol.8 No.8

For cognitive radio sensor networks (CRSNs) that use underlay-based spectrum access, the location of the primary user (PU) plays an important role in the power control of the secondary users (SUs), because the SUs must keep the minimum interference level required by the PU. Received signal strength (RSS)-based localization schemes provide low-cost implementation and low complexity, thus it is suitable for the PU localization in CRSNs. However, the RSS-based localization schemes have a high localization error because they use an inexact path loss exponent (PLE). Thus, applying a RSS-based localization scheme into the PU localization would cause a high interference to the PU. In order to reduce the localization error and improve the channel reuse rate, we propose a RSS-based PU localization scheme that uses distance calibration for CRSNs using underlay model-based spectrum access. Through the simulation results, it is shown that the proposed scheme can provide less localization error as well as more spectrum utilization than the RSS-based PU localization using the mean and the maximum likelihood calibration.

스펙트럼 영역 빛간섭단층촬영 결과에 영향을 주는 다양한 인자 분석

이용준,Yong Jun Lee,MD 대한안과학회 2012 대한안과학회지 Vol.53 No.5

Purpose: To identify factors associated with variability in measures obtained by spectral domain optical coherence tomography (SD-OCT). Methods: One hundred ninety-six subjects (370 eyes) with no ophthalmic evidence of retinopathy and with corrected visual acuities better than 0.6 were included. Macular thickness and retinal nerve fiber layer (RNFL) thickness were measured using SD-OCT and were analyzed according to sex, laterality, age, spherical equivalent and signal strength. Results: The central subfield thickness was significantly lower in the female subjects (r = -0.260, p = 0.000). As age increased, average inner and outer macular thickness increased significantly (r = 0.153, p = 0.010; r = 0.193, p = 0.001). Spherical equivalent correlated negatively with central subfield thickness (r = -0.352, p = 0.000) but correlated positively with average inner macular thickness, average outer macular thickness, overall average thickness, overall macular volume, and average RNFL thickness (r = 0.181, p = 0.002; r = 0.287, p = 0.000; r = 0.346, p = 0.000; r = 0.341, p = 0.000; and r = 0.261, p = 0.000, respectively). Signal strength correlated negatively with average inner macular thickness (r = -0.136, p = 0.023). Conclusions: SD-OCT shows that retinal thickness is related to age, sex, spherical equivalent and signal strength. Analysis of retinal thickness by SD-OCT should be interpreted in the context of these findings. J Korean Ophthalmol Soc 2012;53(5):639-646

유·무선 혼합망에서 이동 호스트의 패킷 손실 예측을 통한 TCP 성능 향상

김진희,권경희 한국콘텐츠학회 2007 한국콘텐츠학회논문지 Vol.7 No.1

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. 유선망에서 패킷 손실은 대부분 혼잡에 인해 발생하며 TCP는 패킷이 손실되면 혼잡을 제어하기 위한 방법으로 윈도우 사이즈(Window Size)를 줄여서 네트워크 이용률을 감소시킨다. 반면에 무선망에서의 패킷 손실은 높은 비트 에러율과 핸드오프 그리고 노드의 이동성 등으로 인해 발생하고 TCP는 무선망에서의 패킷 손실시에도 혼잡 제어 메커니즘을 사용한다. 이는 불필요한 네트워크 이용률을 감소로 TCP 성능 저하의 원인이 된다.본 논문에서는 무선상에서의 패킷 손실을 RSS(Received Signal Strengths:수신신호세기)를 이용하여 예측하고 ACK에 RSS 관련 flag bit 추가를 제안한다. RTO(Retransmit Time Out:재전송 타임아웃) 가 발생하면 FH(Fixed Host:고정 호스트)는 수신된 RSS flag bit를 통해 혼잡 제어 메커니즘의 적용여부를 결정함으로써 처리율를 최대화하는 것이다. NS-2를 이용한 시뮬레이션 결과 송신량과 수신량이 최대 40% 증가 되었다.

An Innovative Approach to Track Moving Object based on RFID and Laser Ranging Information

( Gaoli Liang ),( Ran Liu ),( Yulu Fu ),( Hua Zhang ),( Heng Wang ),( Shafiq Ur Rehman ),( Mingming Guo ) 한국인터넷정보학회 2020 KSII Transactions on Internet and Information Syst Vol.14 No.1

RFID (Radio Frequency Identification) identifies a specific object by radio signals. As the tag provides a unique ID for the purpose of identification, RFID technology effectively solves the ambiguity and occlusion problem that challenges the laser or camera-based approach. This paper proposes an approach to track a moving object based on the integration of RFID and laser ranging information using a particle filter. To be precise, we split laser scan points into different clusters which contain the potential moving objects and calculate the radial velocity of each cluster. The velocity information is compared with the radial velocity estimated from RFID phase difference. In order to achieve the positioning of the moving object, we select a number of best matching clusters to update the weights of the particle filter. To further improve the positioning accuracy, we incorporate RFID signal strength information into the particle filter using a pre-trained sensor model. The proposed approach is tested on a SCITOS service robot under different types of tags and various human velocities. The results show that fusion of signal strength and laser ranging information has significantly increased the positioning accuracy when compared to radial velocity matching-based or signal strength-based approaches. The proposed approach provides a solution for human machine interaction and object tracking, which has potential applications in many fields for example supermarkets, libraries, shopping malls, and exhibitions.

Cramer-Rao Lower Bound for Estimating Signal Strength of a Censored Swerling Target

Won-Yong Choi(최원용),Sun-Mog Hong(홍순목) 대한전자공학회 2018 전자공학회논문지 Vol.55 No.11