On-line detection system of the abnormal states in a machining process needs to be developed to implement the IMS(Intelligent Manufacturing System). High productivity and efficient quality control can be achieved through the on-condition maintenance for normal tool condition. Generally it is difficult to determine the exact point of time for a tool change because a tool wear grows gradually on the contrary to other abnormal states such as tool fracture, chattering etc. In this article, the shape variation of cutting force signal generated by a insert during face milling was investigated along with a tool wear. The variance, skewness and kurtosis were used as the shape parameters to describe the shape variation and, consequently, utilized as the features to monitor a tool wear. Experimental results showed that the shape parameters could discriminate the tool condition reliably between a fresh tool and a worn tool. As a result, we proposed the method to diagnose a tool wear by combining these parameters with a neural network algorithm.

The specific genetic modification in porcine somatic cells by gene targeting has been very difficult because of low efficiency of homologous recombination. To improve gene targeting, we designed three kinds of knock-out vectors with α1,3-galactosyltransferase gene (α1,3-GT gene), DT-A/pGT5’/neo/pGT3’, DT-A/NLS/pGT5’/neo/pGT3’ and pGT5’/neo/ pGT3’/NLS. The knock-out vectors consisted of a 4.8-kb fragment as the 5’ recombination arm (pGT5’) and a 1.9-kb fragment as the 3’ recombination arm (pGT3’). We used the neomycin resistance gene (neo) as a positive selectable marker and the diphtheria toxin A (DT-A) gene as a negative selectable marker. These vectors have a neo gene insertion in exon 9 for inactivation of α1,3-GT locus. DT-A/pGT5’/neo/pGT3’ vector contain only positive-nega-tive selection marker with conventional targeting vector. DT-A/NLS/pGT5’/neo/pGT3’ vector contain positive-negative selection marker and NLS sequences in upstream of 5’ recombination arm which enhances nuclear transport of foreign DNA into bovine somatic cells. pGT5’/neo/pGT3’/NLS vector contain only positive selection marker and NLS sequence in downstream of 3’ recombination arm, not contain negative selectable marker. For transfection, linearzed vectors were introduced into porcine ear fibroblasts by electroporation. After 48 hours, the transfected cells were selected with 300 μg/ml G418 during 12 day. The G418-resistant colonies were picked, of which 5 colonies were positive for α1,3-GT gene disruption in 3´ PCR and southern blot screening. Three knock-out somatic cells were obtained from DT-A/NLS/ pGT5’/neo/pGT3’ knock-out vector. Thus, these data indicate that gene targeting vector using nuclear localization signal and negative selection marker improve targeting efficiency in porcine somatic cells.

A fiber-optic reference signal transmission system, which transmits the 1.4 GHz reference signal from H-maser to receiver cabin in radio telescopes, was adopted for compensating the phase changes due to temperature variation and antenna movement. At the first experiment, the remote signal’s phase changed more than 15 degrees at 1.4 GHz. We found unstable components in sub-system experiments and replaced them. The main cause of unstable phase stability was the unaligned polarization axis between Laser Diode and Mach-Zehnder Modulator (MZM). The improved system stability showed 1 × 10-16 allan standard deviation at 1,000 sec integration time with the antenna fixed. When the antenna moves in the azimuth axis, the 1.4 GHz remote signal showed the phase change smaller than 0.2 degrees.

Lamb waves are extensively used in plate-like structure inspection because of their guided nature. However, their dispersive properties often limit their use in flaw detection and other applications. Dispersion weakens and defocuses interrogating Lamb waves and makes it difficult to accurately interpret signals reflected from defects or boundaries. Time reversal (TR) processing can be applied to compensate for the effect of dispersive Lamb waves. Thus, the TR operation will enable the amplification of dispersive Lamb wave signals by signal compression in time. In this study, experiments are performed in order to examine the refocusing and recovering the initial input waveform in the long range propagation of dispersive Lamb waves in a plate. Two different time reversal processes (regular TR and reciprocal TR or inverse filtering) are tested and the experimental results are compared

PURPOSES : Under the capacity conditions with balanced approach flows, roundabouts give less delay than existing signalized intersections; however, flows over 450 vehicles/hour/lane with unbalanced approach flow conditions, roundabouts efficiency drops due to the short time difference between the critical gap and the follow-up headway. The purpose of this study is developing a roundabout Signal Metering operation method by considering approach lanes degree of saturation. METHODS : A four-way-approach with one-lane roundabout is selected to compare the Signal Metering performance for the case of 16 different unbalanced flow conditions. Based on these traffic conditions, the performance is evaluated for 64 different cases of Signal Metering combinations by using SIDRA software. A degree of saturation(V/C ratio) sum for two adjoined approaches is used for the performance index of choosing Metered Approach and Controlling Approach. RESULTS : When the V/C ratio sum is 0.29~0.81 and Metered Approach flow is less than Controlling Approach flow, the average delay saving per vehicle is about 7 seconds; however, after this rage the delay saving decreases gradually until the V/C ratio sum reaches around 1.0. The range of V/C ratio sum 0.93~1.09 provides average delay saving per vehicle about 3 seconds. In case of V/C ratio sum is grater than 1.0 and the flows of Metered Approach is grater than Controlling Approach, the average delay per vehicle increases 3~11 times respectively. CONCLUSIONS : As expected, the Signal Metering provides substantial improvements in delay saving for the case of V/C ratio sum is 0.3~1.0 under the traffic flow conditions of Metered Approach is less than Controlling Approach.

Song I-Yeong (宋以頴, 1619 ~ 1692), who was an astronomy professor of Gwansanggam (觀象監, Bureau of Astronomy), created the Honcheonsigye (渾天時計, Armillary Clock) in 1669 (10th year of King Hyeonjong Era). Honcheonsigye was a unique astronomical clock which combined an armillary sphere, the traditional astronomical instrument of the Far East, with the power mechanism of western alarm clock. The clock part of this armillary clock is composed of two major parts which are the going-train, power unit used the weight, and the time signal system in a wooden case. The time signal system is composed of four parts which are the time-annunciator, the striking train, the 12 different time-announcing medallions and the sound bell. This clock has been neglected for many years and its several components have been lost. This study is to understand the structure of time signal system and suggests the restoration process.

This paper is to investigate propagation path characteristics of GPS potential jamming signal. To do this, the spherical ground diffraction model is applied to the potential jamming scenario referred to the GPS jamming events occurred in recent years. The fundamental theory on the propagation path loss is discussed and a specific model is applied to several vehicles types which have own heights of antennas in order to compare their propagation path loss values at same 2-D location. The transmitting powers are appropriately given as the ordinary GPS jamming events. And then the received powers in dBW are obtained with given transmitting powers and the estimated total loss. The result of received jamming power at various locations due to the given scenario was distinct. For example, propagation loss values were estimated as -147 ~ -142dBW and -167 ~ -162dBW in 106W and 104W, respectively. This computation result of the loss can be seriously considered with the tolerable jammer power against L1- C/A GPS receiver under any real jamming situations.

현재의 내비게이션 시스템은 대부분 미국의 GPS(Global Positioning System)로부터 전파를 수신하여 측위를 수행하고 있으며, 수신기 알고리듬과 안테나 성능의 발전으로 인해 위치정확도가 지속적으로 향상되고 있다. 그러나 도심부 빌딩숲에서는 GNSS(Global Navigation Satellite System) 전파가 고층건물에 가려져 도달하지 않거나 반사 및 회절에 의해 위치정확도가 매우 저하되기도 한다. 도심부의 GNSS 측위정확도를 현장 관측하는 데에는 많은 비용과 시간이 소요되므로, 이 연구에서는 3차원 건물지도와 전파도달모형 및 상관기모형을 이용하여 도심부 GNSS의 측위정확도를 모의하는 GPASS(GNSS Position Accuracy Simulation System)를 개발하고 그 가용성을 검증하고자 한다. 대표적 빌딩숲인 도쿄도청 부근을 대상으로 모의를 수행하고 현장 관측치와 비교한 결과, 측위율은 실측치와 4.6% 정도의 차이를 보였고 위치정확도는 실측치와 3.0% 정도의 차이를 나타냄으로써 상당히 정밀한 모의가 가능함이 확인되었다. 본 연구에서 개발한 GPASS는 3차원 건물지도를 이용하여 임의의 시공간에 대해 모의를 수행하므로, 내비게이션 서비스 품질의 시공간적 평가 및 개선을 위한 기초자료 산출에 활용될 수 있다.

가까운 거리에서 상대선과의 마주치는 상황 또는 교차된 상황에서 상호 피항동작을 취하게 되는데, 상대선박의 변침의도를 정확히 파악하지 못해 서로 같은 방향으로 피항동작을 취함으로써 충돌위험에 처하게 되기도 한다. 항해사는 피항동작을 취함에 있어 시각에 의한 판단, 레이더 또는 AIS 벡터를 이용한 판단, 또는 VHF 통신을 활용하여 피항동작을 취하고 있으나, 레이더 및 AIS를 이용한 기존의 방식은 선박이 선회 후 선수방위가 표시되기 때문에 선회를 탐지하기까지는 상당한 시간이 요구된다. 따라서 조타기 작동 신호를 상대선박에 신속하게 전달하여 상대선의 선회의도를 보다 신속히 판단할 수 있는 선회조기감지 방안을 제안하였다. 이러한 방법은 상대선의 변침의도를 보다 신속하게 파악함으로써 선박 상호간 충돌예방에 효과적이며, VTS 시스템 및 해양사고 분석에서 활용이 가능하다.

본 논문에서는 단일 센서와 공간집속 신호처리 기술로 시간 역전과 인버스 필터링을 이용하여 이방성 평판에 서 충격 위치를 결정할 수 있는 탐상법을 다루었다. 유한 평면에서 굽힘 파의 운동 방정식을 유도하여, 그 식을 통해 얻어진 데이터를 기반으로 해석적인 시뮬레이션을 통해 시간 역전과 인버스 필터링의 시간 집속 효과를 확 인하고 충격 위치와 그 주변에서 신호의 공간 집속 효과를 관찰하고 충격 위치 결정에 영향을 미칠 수 있는 인자 들(총 수신시간, 샘플링 주파수)에 대해 살펴보았다. 그리고 충격원의 위치에 따른 2차원 결과를 제시하고, 실제 충격 위치를 정확하게 결정할 수 있음을 확인하였다. 여기서 제안한 방법은 기존의 충격 위치 결정법에 비해 많은 장점을 갖고 있다. 첫 번째로 단일 센서를 사용하는 것과 시험체의 형상과 물성을 몰라도 된다는 점이다. 또한 판 에서와 같이 분산성에 의한 다중모드 파동이 발생하는 경우에도 특정 모드나 주파수에 의존할 필요가 없다.

본 논문에서는 단일 센서와 공간집속 신호처리 기술로 시간 역전과 인버스 필터링을 이용하여 등방성 평판에 서 충격 위치를 결정할 수 있는 탐상법을 다루었다. 유한 평면에서 굽힘 파의 운동 방정식을 유도하여, 그 식을 통해 얻어진 데이터를 기반으로 해석적인 시뮬레이션을 통해 시간 역전과 인버스 필터링의 시간 집속 효과를 확 인하고 충격 위치와 그 주변에서 신호의 공간 집속 효과를 관찰하고 충격 위치 결정에 영향을 미칠 수 있는 인자 들(총 수신시간, 샘플링 주파수)에 대해 살펴보았다. 그리고 충격원의 위치에 따른 2차원 결과를 제시하고, 실제 충격 위치를 정확하게 결정할 수 있음을 확인하였다. 여기서 제안한 방법은 기존의 충격 위치 결정법에 비해 많 은 장점을 갖고 있다. 첫 번째로 단일 센서를 사용하는 것과 시험체의 형상과 물성을 몰라도 된다는 점이다. 또한 판 에서와 같이 분산성에 의한 다중모드 파동이 발생하는 경우에도 특정 모드나 주파수에 의존할 필요가 없다.

One of the main problems concerning the shallow seismic survey is how to generate high frequency signals with large amplitudes using small seismic sources. If one could focus the seismic energy in the direction of the survey line, it will be much helpful in identifying the first break. In this research, we have used hammer as an impulsive source and compared the signal powers generated by different shapes of the hammer plates: circular, square, and rectangular. The experiment was conducted by calculating the power spectral density function to compare the frequency spectrum and signal power. In the direction perpendicular to the long side of the rectangular plate, the largest seismic energy with the highest frequency was achieved even with the same weights of hammer plates. Our conclusion is that it is more efficient to use a rectangular plate than a circular (or square) one when conducting a 2-D shallow seismic survey.