• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.464-473
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• 2006

This paper summarises theoretical and experimental work on the feedback control of sound radiation from honeycomb panels using piezoceramic actuators. It is motivated by the problem of sound transmission in aircraft, specifically the active control of trim panels. Trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. Local coupling of the closely-spaced sensor and actuator was observed experimentally and modelled using a single degree of freedom system. The effect of the local coupling was to roll-off the response between the actuator and sensor at high frequencies, so that a feedback control system can have high gain margins. Unfortunately, only relatively poor global performance is then achieved because of localisation of reduction around the actuator. This localisation prompts the investigation of a multichannel active control system. Globalised reduction was predicted using a model of 12 channel direct velocity feedback control. The multichannel system, however, does not appear to yield a significant improvement in the performance because of decreased gain margin.

• 한국소음진동공학회논문집
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• 제16권12호
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• pp.1252-1261
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• 2006

This paper summarizes theoretical work on the multichannel decentralized feedback control of sound radiation from aircraft trim panels using piezoceramic actuators. The aircraft trim panels are generally honeycomb structures designed to meet the design requirement of low weight and high stiffness. They are resiliently-mounted to the fuselage for the passive reduction of noise transmission. It is motivated by the localization of reduction in vibration of single channel active trim panels. 12-channel decentralized feedback control systems are investigated in terms of the reduction of noise and vibration for three configurations of sensor actuator pairs. Local coupling of the closely-spaced sensor and actuator pairs was modeled using single degree of freedom systems. The multichannel control system is characterized using the state-space model. For the stability point of view, the relative stability or robustness is evaluated by comparing the real part of eigenvalues of the system matrix for the three configurations. The control performance is also evaluated and compared for the three configurations. It is found that the multichannel system can lead to the globalization of the reduction in vibration and radiated noise. It does not appear to yield a significant improvement in the vibration because of decreased gain margin. However, the reduction in the radiated noise is remarkably improved due to the variation of the vibration pattern with the actuation configurations.

• 제어로봇시스템학회논문지
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• 제12권7호
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• pp.621-630
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• 2006

The T-50 advanced trainer aircraft combines advanced aerodynamic features and a fly-by-wire flight control system in order to produce a stability and highly maneuverability. The flight control system both longitudinal and lateral-directional axes to achieve performance enhancements and improve stability. The T-50 employs the RSS concept in order to improve the aerodynamic performance in longitudinal axis and the longitudinal control laws employ the dynamic inversion with proportional-plus-integral control method. And, lateral-directional control laws employ the blended roll system both beta-betadot feedback and simple roll rate feedback with proportional control method in order to guarantee aircraft stability. This paper details the design process of developing lateral-directional control laws, utilizing the requirement of MIL-F-8785C and MIL-F-9490D. And, this paper propose the analysis of aircraft characteristics such as dutch-roll mode, roll mode, spiral mode, gain and phase margin about gains for lateral-directional inner loop feedback.

• Asian-Australasian Journal of Animal Sciences
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• 제13권9호
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• pp.1235-1238
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• 2000

Thirty-six Holstein dairy cows were used to evaluate the effect of a rumen protected methionine supplement (RPMet). The cows were divided into two groups of 18 each (control/experimental). The experimental group was given 15 g/d of RPMet (Mepron $^{(R)}$M85, Degussa) from the 4th to the 26th week postpartum. All cows were fed a similar amount of forage including alfalfa silage, corn silage and timothy silage. Concentrate mixture was offered in proportion to the milk yield of each cow. Sufficiency of major metabolizable AAs was checked. Milk yield and milk composition was monitored for each individual cow. A metabolic profile test (MPT) was carried out at the 7th, 11th and 21st week postpartum. Without supplement, both methionine and leucine fell short of the daily requirement. Supplementation with 15 g/d RPMet was calculated to be within a sufficient margin of safety. Milk yield tended to remain higher in the supplemented group than in the controls during supplementation with RPMet. The differences in weekly milk production at the 17th, 18th, 19th and 22nd weeks postpartum were significantly high in the RPMet group (p<0.05). The average 305-d milk yield and the percentages of milk fat, milk protein and solids-not-fat were not affected by the treatment. No differences were observed in either the somatic cell count in the milk or the reproductive status. Judging from MPT, all the cows were in good health during lactation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권5호
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• pp.691-708
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• 2010

An important issue of supporting multi-users with diverse quality-of-service (QoS) requirements over wireless networks is how to optimize the systematic scheduling by intelligently utilizing the available network resource while, at the same time, to meet each communication service QoS requirement. In this work, we study the problem of a variety of communication services over multi-media heterogeneous cognitive OFDM system. We first divide the communication services into two parts. Multimedia applications such as broadband voice transmission and real-time video streaming are very delay-sensitive (DS) and need guaranteed throughput. On the other side, services like file transmission and email service are relatively delay tolerant (DT) so varying-rate transmission is acceptable. Then, we formulate the scheduling as a convex optimization problem, and propose low complexity distributed solutions by jointly considering channel assignment, bit allocation, and power allocation. Unlike prior works that do not care computational complexity. Furthermore, we propose the FAASA (Fairness Assured Adaptive Sub-carrier Allocation) algorithm for both DS and DT users, which is a dynamic sub-carrier allocation algorithm in order to maximize throughput while taking into account fairness. We provide extensive simulation results which demonstrate the effectiveness of our proposed schemes.

• 복식문화연구
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• 제11권5호
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• pp.721-736
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• 2003

As for the purposes of the research: First, on the wearers of snowboard wear on the market, I intend to investigate contents related with purchase, price, brand, style, etc., and grasp requirements and complaints. Second, I intend to know the evaluations of users according to itemized questions on the snowboard wear on the market. Third, I like to provide basic materials by investigating itemized requirements for the development of snowboard wear. On the male & female snowboarders on a skiing ground, I carried out a preliminary investigation in December, 2001, and a main investigation from January to February, 2002. The results are as follows: 1. Many of them purchased imported quality goods, and the rate purchase was high between 20～25 year. Loose two-piece suits of different colors were preferred. The most uncomfortable part proved to be a neck part. 2. The degree of general satisfaction with the snowboard wear on the market was 4.60. And in terms of itemized evaluation, dissatisfaction was found in Clothing construction, facility of laundry and handling, price and brand rather than in style, fiber composition and tactile sensation. 3. In the investigation of the requirements in case of snowboard wear development, the most common requirement was the facility of action. I believe this should be met by study on the choice of pertinent margin and the pattern development.

• Geomechanics and Engineering
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• 제6권3호
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• pp.235-248
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• 2014

Population increase and economic developments can lead to construction as well as demolition of infrastructures such as buildings, bridges, roads, etc resulting in used concrete as a primary waste product. Recycling of waste concrete to obtain the recycled concrete aggregates (RCA) for base and/or sub-base materials in road construction is a foremost application to be promoted to gain economical and sustainability benefits. As the mortar, bricks, glass and reclaimed asphalt pavement (RAP) present as constituents in RCA, it exhibits inconsistent properties and performance. In this study, six different types of RCA samples were subjected classification tests such as particle size distribution, plasticity, compaction test, unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. Results were compared with those of the standard road materials used in Queensland, Australia. It was found that material type 'RM1-100/RM3-0' and 'RM1-80/RM3-20' samples are in the margin of the minimum required specifications of base materials used for high volume unbound granular roads while others are lower than that the minimum requirement.

• 전기학회논문지
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• 제57권4호
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• pp.567-575
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• 2008

Transient security assessment(TSA) is becoming an essential requirement not only for security monitoring but also for stabilizing control of power systems under new electricity environments. It has already been pointed out that fast transient stability study is an important part for monitoring and controlling system security. In this paper, we discuss an energy function method for stabilizing control of transiently unstable systems by introducing generator tripping system to enhance the transient stability of power systems. The stabilization with less tripped power can be obtained by tripping the generators faster than out-of-synchronism relay. Fast transient stability assessment based on the state estimation and direct transient energy function method is an important part of the stabilizing scheme. It is possible to stabilize the transiently unstable system by tripping less generators before the action of out-of-synchronism relay, especially when a group of generator are going to be out-of-synchronism. Moreover, the amount of generator output needed for tripping can be decided by Transient Energy Function(TEF) method. The main contribution of this paper is on the stabilizing scheme which can be running in the Wide Area Control System.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2003년도 춘계 학술발표회논문집
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• pp.50-58
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• 2003

We have developed a locally variable time-step scheme matching with discontinuous grids in the flute-difference method for the efficient simulation of seismic wave propagation. The first-order velocity-stress formulations are used to obtain the spatial derivatives using finite-difference operators on a staggered grid. A three-times coarser grid in the high-velocity region compared with the grid in the low-velocity region is used to avoid spatial oversampling. Temporal steps corresponding to the spatial sampling ratio between both regions are determined based on proper stability criteria. The wavefield in the margin of the region with smaller time-step are linearly interpolated in time using the values calculated in the region with larger one. The accuracy of the proposed scheme is tested through comparisons with analytic solutions and conventional finite-difference scheme with constant grid spacing and time step. The use of the locally variable time-step scheme with discontinuous grids results in remarkable saving of the computation time and memory requirement with dependency of the efficiency on the simulation model. This implies that ground motion for a realistic velocity structures including near-surface sediments can be modeled to high frequency (several Hz) without requiring severe computer memory

• Nuclear Engineering and Technology
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• 제39권4호
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• pp.257-272
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• 2007

Supercritical water-cooled reactors (SCWRs) are recognized as a Generation IV reactor concept. The Super LWR is a pressure-vessel type thermal spectrum SCWR with downward-flow water rods and is currently under study at the University of Tokyo. This paper reviews Super LWR safety. The fundamental requirement for the Super LWR, which has a once-through coolant cycle, is the core coolant flow rate rather than the coolant inventory. Key safety characteristics of the Super LWR inhere in the design features and have been identified through a series of safety analyses. Although loss-of-flow is the most important abnormality, fuel rod heat-up is mitigated by the "heat sink" and "water source" effects of the water rods. Response of the reactor power against pressurization events is mild due to a small change in the average coolant density and flow stagnation of the once-through coolant cycle. These mild responses against transients and also reactivity feedbacks provide good inherent safety against anticipated-transient-without-scram (ATWS) events without alternative actions. Initiation of an automatic depressurization system provides effective heat removal from the fuel rods. An "in-vessel accumulator" effect of the reactor vessel top dome enhances the fuel rod cooling. This effect enlarges the safety margin for large LOCA.