• 한국군사과학기술학회지
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• 제16권3호
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• pp.277-284
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• 2013

In this paper, the ventilating and heating system of T-103 trainer aircraft were investigated and redesigned to improve its poor performance. The ventilation system of the trainer was designed to increase the mass flow rate of fresh air by using air intake valves. The flow-in air through the air intake valve is supplied to the cabin by the ram effect of aircraft and the propeller. And the additional heating system was installed to improve the temperature of the cabin inside. The wasted heat from the exhaust gas of the engines was used as heat source of the additional heating system by installing an heat exchanger around the exhaust nozzle. The additional fresh air and the heated air enter the cabin via two ducts mounted under the instrument panel and behind the pedal in the cabin. The additional ventilating and heating system can be controlled by the first pilot and the secondary pilot individually using the control knob equipped separately. After mounting the additional ventilating and heating system, evaluations such as inspection of parts and component, ground run-up test, in-flight test, user test, etc. were conducted. The result of the tests was sufficient to meet the requirements of the manuals, and the pilots were satisfied with the additionally mounted systems.

• 대기
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• 제20권4호
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• pp.495-503
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• 2010

Satellite data have an intrinsic problem due to a number of various physical parameters, which can have a similar effect on measured radiance. Most evaluations of satellite performance have relied on comparisons with limited spatial and temporal resolution of ground-based measurements such as soundings and in-situ measurements. In order to overcome this problem, a new way of satellite data evaluation is suggested with statistical tools such as empirical orthogonal function(EOF), and singular value decomposition(SVD). The EOF analyses with OMI and OMI HCHO over northeast Asia show that the spatial pattern show high correlation with population density. This suggests that human activity is a major source of as well as HCHO over this region. However, this analysis is contradictory to the previous finding with GOME HCHO that biogenic activity is the main driving mechanism(Fu et al., 2007). To verify the source of HCHO over this region, we performed the EOF analyses with vegetation and HCHO distribution. The results showed no coherence in the spatial and temporal pattern between two factors. Rather, the additional SVD analysis between $NO_2$ and HCHO shows consistency in spatial and temporal coherence. This outcome suggests that the anthropogenic emission is the main source of HCHO over the region. We speculate that the previous study appears to be due to low temporal and spatial resolution of GOME measurements or uncertainty in model input data.

• International Journal of Contents
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• 제10권1호
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• pp.47-53
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• 2014

The paper considers the challenges involved in measuring the similarities between time series, such as time shifts and the mixture of frequencies. To improve recognition accuracy, we investigate an improved linear dynamical system for discovering prominent features by exploiting the evolving dynamics and correlations in a time series, as the quality of unsupervised pattern recognition relies strongly on the extracted features. The proposed approach yields a set of compact extracted features that boosts the accuracy and reliability of clustering for time series data. Experimental evaluations are carried out on time series applications from the scientific, socio-economic, and business domains. The results show that our method exhibits improved clustering performance compared to conventional methods. In addition, the computation time of the proposed approach increases linearly with the length of the time series.

• 전기학회논문지
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• 제64권6호
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• pp.872-877
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• 2015

The Permanent Magnet (PM) machine used at speed control using field-weakening control method. But the field-weakening current, which reduces the field flux for high speeds, causes significant copper and core losses. Therefore, this paper deals with the PM performance evaluations in a pole changing memory motor (PCMM). The PCMM can change the number of magnetic poles and produce two types of torque. When the motor operates with eight poles, it produces a magnetic torque at low rotational speeds. When the motor changes to four poles, it produces both magnetic torque and reluctance torque at high speeds. The paper explain the principle and basic characteristics of the motor by using a finite element method magnetic-field analysis, which consists of a PM magnetized by a pulse d-axis current of the armature winding. The results of our experiment show that the proposed motor reduces core loss by 10% and 55% under no-load and load conditions, and doubles the speed range of the motor.

• 센서학회지
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• 제23권5호
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• pp.326-331
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• 2014

In this study, a MEMS microphone that uses $Si_3N_4$ as the vibration membrane was produced for application as an auditory device using a sound visualization technique (sound visualization) for the hearing impaired. Two sheets of 6-inch silicon wafer were each fabricated into a vibration membrane and back plate, after which, wafer bonding was performed. A certain amount of charge was created between the bonded vibration membrane and the back plate electrodes, and a MEMS microphone that functioned through the capacitive method that uses change in such charge was fabricated. In order to evaluate the characteristics of the prepared MEMS microphone, the frequency flatness, frequency response, properties of phase between samples, and directivity according to the direction of sound source were analyzed. The MEMS microphone showed excellent flatness per frequency in the audio frequency (100 Hz-10 kHz) and a high response of at least -42 dB (sound pressure level). Further, a stable differential phase between the samples of within -3 dB was observed between 100 Hz-6 kHz. In particular, excellent omnidirectional properties were demonstrated in the frequency range of 125 Hz-4 kHz.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1789-1794
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• 2014

This paper suggests an application method for a superconducting fault current limiter (SFCL) using an evaluation index to estimate the risk regarding the short-circuit capacity of the circuit breaker (CB). Recently, power distribution systems have become more complex to ensure that supply continuously keeps pace with the growth of demand. However, the mesh or loop network power systems suffer from a problem in which the fault current exceeds the short-circuit capacity of the CBs when a fault occurs. Most case studies on the application of the SFCL have focused on its development and performance in limiting fault current. In this study, an analysis of the application method of an SFCL considering the risk of the CB's short-circuit capacitor was carried out in situations when a fault occurs in a loop network power system, where each line connected with the fault point carries a different current that is above or below the short-circuit capacitor of the CB. A loop network power system using PSCAD/EMTDC was modeled to investigate the risk ratio of the CB and the effect of the SFCL on the reduction of fault current through various case studies. Through the risk evaluations of the simulation results, the estimation of the risk ratio is adequate to apply the SFCL and demonstrate the fault current limiting effect.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제5권11호
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• pp.1997-2015
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• 2011

In this paper, we propose the enhanced network-based mobility management protocol, called enhanced proxy mobile ipv6 (E-PMIPv6), which can provide mobile nodes (MNs) with a fast and efficient mobility service in PMIPv6 domain. The proposed scheme can provide a fast and efficient mobility service to MNs and also the strength of network scalability and stability to an access network by proposing the dynamic virtual hierarchical network architecture. In addition, the pre-authentication procedure for an MN, based on the information of neighbor mobile access gateway (MAG) list in the enhanced-policy server (E-PS), is proposed to support seamless handover by reducing MN's handover latency. Through performance evaluations of numerical analyses and simulations, we have confirmed and verified the superiority of the proposed scheme compared to the conventional proxy mobile ipv6 (PMIPv6).

• Earthquakes and Structures
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• 제4권2호
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• pp.157-179
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• 2013

Vulnerability studies on the existing building stock require that a large number of buildings is analyzed to obtain statistically significant evaluations of the seismic performance. Therefore, analytical evaluation methods need to be based on simplified methodologies of analysis which can afford the treatment of a large building population with a reasonable computational effort. Simplified Pushover-Based Earthquake Loss Assessment approach (SP-BELA), where a simplified methodology to identify the structural capacity of the building through the definition of a pushover curve is adopted, was developed on these bases. Main objective of the research work presented in this paper is to validate the simplified methodology implemented in SP-BELA against the results of more sophisticated nonlinear dynamic analyses (NLDAs). The comparison is performed for RC buildings designed only to vertical loads, representative of the "as built" in Italy and in Mediterranean countries with a building stock very similar to the Italian one. In NLDAs the non linear and degrading behaviour, typical of the structures under consideration when subjected to high seismic loads, is evaluated using models able to capture, with adequate accuracy, the non linear behaviour of RC structural elements taking into account stiffness degradation, strength deterioration, and pinching effect. Results show when simplified analyses are in good agreement with NLDAs. As a consequence, unsatisfactory results from simplified analysis are pointed out to address their current applicability limits.

• 한국항공우주학회지
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• 제38권2호
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• pp.200-205
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• 2010

고온고압, 장시간 연소조건하에서 일정한 추력을 유지하는 로켓 추진기관 개발을 위해 W/$Y_2O_3$ 노즐목 삽입재를 평가하였다. 연소시간 증가에 따른 내열성능 변화를 검토하였으며, 비삭마 소재로 범용되고 있는 CIT의 내열성능과 비교하였다. 연소시간이 증가함에 따라 삭마율은 감소하는 경향을 보였으며, W/$Y_2O_3$의 삭마율은 CIT의 약 55 %이었다. 노즐목 삽입재의 육안검사와 미세조직검사에서 연소시간의 증가로 인한 특이 현상은 발견되지 않았으며, 진공 열처리는 균열 방지에 효과가 있음을 확인하였다.

• Steel and Composite Structures
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• 제23권3호
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• pp.303-315
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• 2017

This paper describes the finite element model for predicting the fundamental performance of embedded steel column base connections under monotonic and cyclic loading. Geometric and material nonlinearities were included in the proposed finite element model. Bauschinger and pinching effects were considered in the simulation of embedded column base connections under cyclic loading. The degradation of steel yield strength and accumulation of plastic damage can be well simulated. The accuracy of the finite element model is examined by comparing the predicted results with independent experimental dataset. It is demonstrated that the finite element model accurately predicts the behaviour and failure models of the embedded steel column base connections. The finite element model is extended to carry out evaluations and parametric studies. The investigated parameters include column embedded length, concrete strength, axial load and base plate thickness. Moreover, analytical models for predicting the initial stiffness and bending moment strength of the embedded column base connection were developed. The comparison between results from analytical models and those from experiments and finite element analysis proved the developed analytical model was accurate and conservative for design purposes.