• BMB Reports
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• 제51권1호
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• pp.3-4
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• 2018

Parkinson's disease (PD) is a debilitating disorder resulting from loss of dopamine neurons. In dopamine deficient state, the basal ganglia increases inhibitory synaptic outputs to the thalamus. This increased inhibition by the basal ganglia output is known to reduce firing rate of thalamic neurons that relay motor signals to the motor cortex. This 'rate model' suggests that the reduced excitability of thalamic neurons is the key for inducing motor abnormalities in PD patients. We reveal that in response to inhibition, thalamic neurons generate rebound firing at the end of inhibition. This rebound firing increases motor cortical activity and induces muscular responses that triggers Parkinsonian motor dysfunction. Genetic and optogenetic intervention of the rebound firing prevent motor dysfunction in a mouse model of PD. Our results suggest that inhibitory synaptic mechanism mediates motor dysfunction by generating rebound excitability in the thalamocortical pathway.

• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.193-202
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• 2008

본 논문은 분사식 FRP의 압축 구속효과와 휨 보강 효과 및 분사식 FRP의 반발률에 대한 실험적 연구이다. 분사식 FRP란 레진과 짧게 잘려진 섬유를 고압의 공기에 의해 적용면에 분사하여 보강하는 기법이다. 분사식 FRP의 구속 및 휨 보강 효과를 알아보기 위하여 원주형 공시체와 휨 공시체를 제작하여 FRP를 분사하여 보강하였고, 보강 재료로 유리섬유와 폴리에스테르 수지를 사용하였다. 최적의 보강 조건을 알기 위해 섬유 길이, 보강 두께, 섬유 혼입비, 콘크리트 강도에 따른 실험을 실시하였고, 분사식 FRP 보강법을 섬유 매트에 의한 보강법과 비교하였다. 또한, 분사식 FRP의 반발률 역시 평가하였다. 실험을 통하여 분사식 FRP의 최적 조건을 결정하였다. 본 연구의 분사식 FRP 보강은 유리 섬유 매트에 의한 보강법 이상의 성능을 발휘하였다.

• Elastomers and Composites
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• 제53권2호
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• pp.80-85
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• 2018

Chloro isobutylene isoprene rubber (CIIR) and ethylene propylene diene monomer (EPDM) compounded with other formulation chemicals, depending on the polymer blend, were prepared by mechanical mixing. After manufacturing the rubber vulcanizate by compression molding with a hot press, the mechanical and thermal properties including thermal conductivity, rebound resilience of the CIIR/EPDM blends were measured. As the EPDM rubber content increased, hardness and tension set showed a tendency to increase. Pure CIIR exhibited the lowest tensile strength; however, tensile strength increased with loading of EPDM rubber. On the other hand, in CIIR rubber, which is usually a low-rebound elastomer owing to a high damping effect, rebound resilience exhibited an increasing trend as the content of EPDM rubber increased. As the EPDM rubber content increased, thermal stability was improved due to reduction of decomposition rate in the rubber region of the blend vulcanizate.

• Computers and Concrete
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• 제24권6호
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• pp.555-560
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• 2019

During the application of shotcrete, a part of the concrete bounces back after hitting to the surface, the reinforcement or previously sprayed concrete. This rebound material is definitely not added to the mixture and considered as waste. In this study, a deep neural network model was developed to predict the rebound material during shotcrete application. The factors affecting rebound and the datasets of these parameters were obtained from previous experiments. The Long Short-Term Memory (LSTM) architecture of the proposed deep neural network model was used in accordance with this data set. In the development of the proposed four-tier prediction model, the dataset was divided into 90% training and 10% test. The deep neural network was modeled with 11 dependents 1 independent data by determining the most appropriate hyper parameter values for prediction. Accuracy and error performance in success performance of LSTM model were evaluated over MSE and RMSE. A success of 93.2% was achieved at the end of training of the model and a success of 85.6% in the test. There was a difference of 7.6% between training and test. In the following stage, it is aimed to increase the success rate of the model by increasing the number of data in the data set with synthetic and experimental data. In addition, it is thought that prediction of the amount of rebound during dry-mix shotcrete application will provide economic gain as well as contributing to environmental protection.

• 콘크리트학회논문집
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• 제17권3호
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• pp.427-434
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• 2005

본 연구에서는 실리케이트계 급결제, 알루미네이트계 급결제, 시멘트 광물계 급결제를 사용하여 모르타르의 응결시간과 압축 강도를 실내시험하고, 현장에서 제작된 공시체로 숏크리트의 압축강도, 휨 강도, 휨 인성 및 리바운드율 시험을 시행하여, 급결제가 숏크리트에 미치는 응결, 강도, 시공성을 비교 검토하고, 특히 시멘트광물계 급결제의 성능을 평가하였다 급결제 종류별로 비교한 압축강도의 값은 각 재령별로 숏크리트의 강도 기준에는 적합하였으나 재령 28일의 강도비 $75\%$ 이상의 규정에는 시멘트광물계만이 $87\%$로 규격에 적합하였다. 휨강도시험 결과는 강섬유 숏크리트에 대한 기준에 시멘트광물계는 모든 적합하였으나 알루미네이트계는 재령 28일에서만 기준치에 적합하였으며, 실리케이트계는 모든 기준에 미흡하였으며, 휨 인성 실험결과 한국도로공사 기준에 시멘트광물계와 알루미네이트계는 규정값에 적합하였으나, 실리케이트계는 이기준에 미흡하였다 리바운드율 시험결과는 대체로 $11{\~}19\%$사이였으며, 시멘트광물계 급결제를 사용한 쪽이 알루미네이트계와 실리케이트계 급결제를 사용한 것보다 $2{\~}3\%$ 정도 작게 나타났다. 시멘트광물계 급결제는 초기의 높은 강도와 함께 종래의 급결제가 가지는 장기강도 저감을 극복하고 고강도화 됨으로써 고성능 숏크리트의 품질확보 가능성을 확인할 수 있었다.

• 열처리공학회지
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• 제8권4호
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• pp.318-325
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• 1995

Information of change of hardness values during applying load is needed often to control the quality of metal products efficiently, but the relation between applied stress and hardness has not been established. In this paper the theoretical relation between the rebound hardness and stress was examined briefly and the experiment was performed with some materials. Materials used in test were mild steel(SB41), 7-3 brass and copper, which were widely used in the commercial plants. Hardness was measured during stress applied using the Equo-Tip hardness tester as a kind of rebound hardness tester. Hardness values decreased as tensile stress increased, the decreasing rate was effected by the Young's modulus of each material, and the rebound hardness values showed linear relationship with the applied stress in elastic region.

• 대한기계학회논문집B
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• 제29권2호
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• pp.287-293
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• 2005

In the present study, to determine the flow rate of droplets supplied to heat transfer surface after (j-1)th rebound, $D_X[j{\ge}2]^{\ast}$, it was assumed that the rebound droplets are distributed according to the Gaussian distribution from 0 to L, in which the flight distance L is determined by maximum flight distance $L_{max}$. We also assumed that $L_{max}$ is dependent on the air flow velocity and mean size of droplets. The local heat flux of a dilute spray in high temperature region was predicted using the newly evaluated $D_X[j{\ge}2]^{\ast}$. In addition, the predicted results by the present model were compared with the existing experimental data.

• 콘크리트학회논문집
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• 제11권4호
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• pp.157-167
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• 1999

Among several non-destructive testing methods, ultrasonic pulse velocity method and rebound index method have been widely used for the evaluation of concrete strength. However, such methods might not provide accurate estimated results since factors influencing the relationship between strength and either ultrasonic pulse velocity or rebound index are not considered. In this paper, the evaluation method of concrete strength using rod-wave velocity measured by impact-resonance method is proposed. A basic equation is obtained by the linear regression of velocity vs, strength data at specific age and then, aging factor is employed in the equation to consider the difference of the increasing rate between wave velocity and strength. Strengths predicted by the proposed equation agree well with test results. Furthermore, the combined method of rod-wave velocity and rebound index is proposed.

• 대한토목학회논문집
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• 제32권6D호
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• pp.615-622
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• 2012

숏크리트는 현장에서 빠른 시공을 실시하여 굴착면을 침식으로부터 보호하고 암괴의 전단이동방지, 암괴의 붕괴방지, 개구절리의 봉합, 응력의 집중완화, 응력전달효과 등에 의하여 후속작업의 원활한 진행이 될 수 있도록 굴착면을 방지하여 지내력을 증대시키는 것이 주목적이다. 숏크리트공법으로는 건식과 습식의 두 가지방법이 있으며, 1997년 이후부터는 건식보다 습식 숏크리트가 많이 이용되고 있다. 그러나 작업 중 목적물에 부착되지 않고 반발되는 현상, 즉 리바운드가 많이 발생하며 이러한 많은 양의 리바운드는 숏크리트와 전체 공사비 원가에 중대한 영향을 미치게 된다. 특히 숏크리트는 재료비, 배합, 타설시간 증가, 재료의 취급과 계량장치에 소요되는 인력 및 버력제거를 위한 비용 증가 발생원인이 되고 있다. 이 연구에서는 국내현장에서 시행한 급결제 함유량에 따른 일반 습식 숏크리트 및 강섬유 습식 숏크리트공법의 시공실적을 분석하여 반발 양 및 강도의 실험적인 분석을 실시하였다. 또한 국내 건설공사에 실제 사용할 수 있는 효과적이고 합리적인 방법을 제시하였다.

• Journal of Electrical Engineering and Technology
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• 제10권2호
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• pp.496-503
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• 2015

In order to let a wind generator (WG) support the frequency control of a power system, a conventional inertial control algorithm using the rate of change of frequency (ROCOF) and frequency deviation loops was suggested. The ROCOF loop is prevailing at the initial stage of the disturbance, but the contribution becomes smaller as time goes on. Moreover, its contribution becomes negative after the frequency rebound. This paper proposes an inertial control algorithm of a wind power plant (WPP) using the maximum ROCOF and frequency deviation loops. The proposed algorithm replaces the ROCOF loop in the conventional inertial control algorithm with the maximum ROCOF loop to retain the maximum value of the ROCOF and eliminate the negative effect after the frequency rebound. The algorithm releases more kinetic energy both before and after the frequency rebound and increases the frequency nadir more than the conventional ROCOF and frequency loops. The performance of the algorithm was investigated under various wind conditions in a model system, which includes a doubly-fed induction generator-based WPP using an EMTP-RV simulator. The results indicate that the algorithm can improve the frequency drop for a disturbance by releasing more kinetic energy.