• Journal of Positioning, Navigation, and Timing
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• v.2 no.2
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• pp.115-121
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• 2013

For the auto-landing operation of an air vehicle, the possibility of auto-landing operation should be first evaluated by testing the navigation performance through a flight test. In general, navigation performance is tested by analyzing north/east/down (NED) errors relative to reference equipment whose precision is about 8~10 times higher than that of a navigation system. However, to evaluate the auto-landing operation of an air vehicle, whether the air vehicle approaches a glide path aligned with the runway, within a specific error, needs to be examined rather than examining the north/east errors of the navigation system. Therefore, the longitudinal/lateral errors of air vehicle heading need to be analyzed. In this study, a method for analyzing the longitudinal/lateral errors of a navigation system was proposed as the navigation performance test method for evaluating the safety during the auto-landing of an air vehicle. Also, flight tests were performed six times, and the safety of auto-landing was examined by analyzing the performance using the proposed method.

• International Journal of Automotive Technology
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• v.1 no.1
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• pp.17-25
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• 2000

The electromechanical valve train (EMV) technology allows for a reduction in fuel consumption while operating under a stoichiometric air-fuel-ratio and preserves the ability to use conventional exhaust gas aftertreatment technology with a 3-way-catalyst. Compared with an engine with a camshaft-driven valve train, the variable valve timing concept makes possible an additional optimization of cold start, warm-up and transient operation. In contrast with the conventionally throttled engine, optimized control of load and in-cylinder gas movement can be used for each individual cylinder and engine cycle. A load control strategy using a "Late Intake Valve Open" (LIO) provides a reduction in start-up HC emissions of approximately 60%. Due to reduced wall-wetting, the LIO control strategy improves the transition from start to idle. "Late Exhaust Valve Open" (LEO) timing during the exhaust stroke leads to exhaust gas afterburning and, thereby, results in high exhaust gas temperatures and low HC emissions. Vehicle investigations have demonstrated an improved accuracy of the air-fuel-ratio during transient operation. Results in the New European Driving Cycle have confirmed a reduction in fuel consumption of more than 15％ while meeting EURO IV emission limits.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.9-16
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• 2006

Variable valve timing is one of the attractive ways to control homogeneous charge compression ignition (HCCI) engine. Hot internal residual gas which can be controlled by variable valve timing(VVT) device, makes fuel evaporated easily, and ignition timing advanced. Regular gasoline was used as main fuel and di-methyl ether(DME) was used as ignition promoter in this research. HCCI engine operating range is limited by high combustion peak pressure and engine noise. High combustion pressure can damage the engine during operation. To avoid engine damage, the rich limits have to define using various methods. Peak combustion pressure, rate of cylinder pressure rise was considered to determine rich limit of engine operating range. Knock probability was correlated with the rate of cylinder pressure rise as well as the peak combustion pressure.

• Transactions of the Korean hydrogen and new energy society
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• v.27 no.1
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• pp.106-113
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• 2016

Lean burn engine, classified into port injection and direct injection, is recognized as a promising way to meet better fuel economy. Especially, LPG direct injection engine is becoming increasingly popular due to their potential for improved fuel economy and emissions. Also, LPDi engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. However, LPDi engine has many difficulties to be solved, such as complexity of injection control mode (fuel injection timing, injection rate), fuel injection pressure, spark timing, unburned hydrocarbon and restricted power. This study is investigated to the influence of spark timing, fuel injection position and fuel injection rate on the combustion stability of LPDi engine. Piston shape is constituted the bowl type piston. The characteristics of combustion is analyzed with the variations of spark timing, fuel injection position and fuel injection rate (early injection, late injection) in a LPDi engine.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.4
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• pp.561-571
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• 1993

In this paper, a new discrete Symbol Timing Recovery (STR) algorithm, is proposed. This algorithm is derived from the optimum estimation theory. The algorithm combines the advantages of Mueller and $M\"{u}ller$ algorithm and Gardner algorithm, and avoids some of their shortcomings. The implementation of the new timing detector is simple and the combined operations of Carrier Recovery (CR) -STR is possible because the operation of the new STR is independent of the carrier phase. On the other hand, the behavior of nonlinear characteristics in the new algorithm is analyzed and explained. The performance evaluation is accomplished in detail by numerical calculations and Monte-Carlo simulations. In these respects, this algorithm is similar to Gardner's algorithm, but in tracking performance due to pattern jitter at small rolloff, the proposed algorithm is superior to Gardner's algorithm.

• Physical Therapy Rehabilitation Science
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• v.4 no.1
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• pp.22-27
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• 2015

Objective: Jump training helps increase the muscle power by improving the muscle strength and reaction time of the muscle in operation. The purpose of this study was to identify the effects of strengthening, stretching exercise and meditation on electromyographic (EMG) onset timing of rectus femoris and gastrocnemius muscle during vertical jump performance. Design: Cross-sectional study. Methods: Ten healthy adults (5 male and 5 female) who were familiar with the vertical jumping task and had no lower extremity injuries or any bone or joint disorders, were recruited for this study. Muscle onset timing was measured by surface EMG. After EMG onset timing were measured during performing three baseline vertical jump trials, strengthening and stretching exercises of the rectus femoris and gastrocnemius, and meditation were performed in random order. EMG onset timing was measured during vertical jump after intervention, respectively. EMG value was averaged for the three trials and analyzed using one-way repeated ANOVA. Results: During vertical jump, EMG onset timing of gastrocnemius was a significant difference after intervention (p<0.05), and then there was significantly faster in strengthening exercise than meditation (p<0.05). Conclusions: These results indicate the potential positive effect of performing strengthening exercise of the gastrocnemius before a jumping event. Future research is required to identify the effects of intervention over a long period.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.14 no.1
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• pp.74-80
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• 2011

Purpose: Based on previous research findings, it is well-known that the timing of surgery is generally considered the most important prognostic factor for a Kasai portoenterostomy, the primary treatment for biliary atresia. This research aimed to identify the optimal timing of a Kasai portoenterostomy and to verify if the proposed optimal timing corresponds to previous studies. All patients were classified by the timing of surgery, and pre- and post-operative fibrotic changes of the liver were measured with the elasticity value from fibroscans. Methods: The stiffness scores of the pre- and post-operative fibroscans in 34 patients who were treated by Kasai portoenterostomy from October 2007 to September 2010 in Severance children's hospital were reviewed. Results: The earlier the patients were treated by Kasai portoenterostomy, the lower the fibroscan scores. When the patients were treated prior to the 8th week, the post-operative scores of the fibroscans were significantly better than those patients who were treated after the 8th week, and some even recovered partially. Moreover, when operated before the 8th week, the differences between each pre- and postoperative fibroscan score also showed statistical relevance (p=0.0002). Conclusion: The earlier the patient was treated by Kasai portoenterostomy, the less liver fibrosis that developed, the lower the level of post-operative fibrosis, and the less the degree of fibrotic progress before and after the operation. Thus, this research proposal reconfirms once more that the 8th week is the optimal timing for a Kasai portoenterostomy.

• Journal of Chest Surgery
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• v.45 no.4
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• pp.213-224
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• 2012

Tetralogy of Fallot (TOF) is an index lesion for all paediatric and congenital heart surgeons. In designing an appropriate operation for children with TOF, the predicted postoperative physiology must be taken into account, both for the short and long term. A favourable balance between pulmonary stenosis (PS) and pulmonary insufficiency (PI) may be critical for preservation of biventricular function. A unified repair strategy to limit both residual PS and PI is presented, along with supportive experimental evidence. A strategy for dealing with coronary anomalies and some comments regarding best timing of operation are also included.

• ETRI Journal
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• v.29 no.6
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• pp.835-837
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• 2007

A multi-bit sigma-delta modulator architecture is described for low-distortion performance and a high-speed operation. The proposed architecture uses both a delayed code and a delayed differential code of analog-to-digital converter in the feedback path, thereby suppressing signal components in the integrators and relaxing the timing requirement of the analog-to-digital converter and the scrambler logic. Implemented by a 0.13 ${\mu}m$ CMOS process, the sigma-delta modulator achieves high linearity. The measured spurious-free dynamic range is 89.1 dB for -6 dBFS input signal.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1345-1359
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• 1996

This paper presents a floating point arithmetic unit (FPAU) for supescalar microprocessor that executes fifteen operations such as addition, subtraction, data format converting, and compare operation using two pipelined arithmetic paths and new rounding and normalization scheme. By using two pipelined arithmetic paths, each aritchmetic operation can be assigned into appropriate arithmetic path which high speed operation is possible. The proposed normalization an rouding scheme enables the FPAU to execute roundig operation in parallel with normalization and to reduce timing delay of post-normalization. And by predicting leading one position of results using input operands, leading one detection(LOD) operation to normalize results in the conventional arithmetic unit can be eliminated. Because the FPAU can execuate fifteen single-precision or double-precision floating-point arithmetic operations through three-stage pipelined datapath and support IEEE standard 754, it has appropriate structure which can be ingegrated into superscalar microprocessor.