• 재활복지공학회논문지
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• 제5권1호
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• pp.41-46
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• 2011

감각신경성 난청의 원인 중 하나는 내이에 존재하는 와우(cochlea)의 기능적 이상 때문이다. 와우에서 내유모세포(inner hair cell, IHC)나 신경의 기능적 이상이 있는 곳을 'dead region'이라고 한다. 보청기에서 dead region에 속하는 주파수 영역의 증폭은 효과가 미약한 것으로 알려져 있다. 본 논문에서는 dead region의 위치에 따른 음성신호의 인지 능력 비교와 dead region이 존재할 때 보청기의 효과적인 이득값을 알아보기 위해 WRS 검사와 선호도 조사를 실시하였다. WRS(Word Recognition Score)검사와 선호도 조사를 위해 정상 청력 능력을 지닌 성인 남녀 8명을 대상으로, white noise와 babble noise를 이용하여 신호 대 잡음비(SNR) 0dB의 조건으로 검사음과 혼합하였으며, dead region의 영역을 세 가지로 분류하였다. 주파수 영역에 따라 low-frequency, mid-frequency, high-frequency dead region으로 나누고, 각 dead region에 따라 14.5 dB, 11.5 dB, 6 dB의 증폭 이득을 다르게 하여 결과를 비교하였다. dead region의 위치에 따른 검사 결과는 각 영역별로 차이가 있었다. WRS 검사결과 low-frequency dead region일 때 보다, mid-frequency dead region나 high-frequency dead region일 때의 WRS점수와 선호도 평가가 높게 나왔으며, 증폭 이득값의 차이를 비교해 보았을 때, 14.5 dB의 이득에 비해 낮은 이득을 주었을 때 WRS 검사 결과값이 더 높게 나왔으며, 높은 이득일수록 선호도 조사에서 낮은 점수를 받았다.

• Journal of Mechanical Science and Technology
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• 제16권4호
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• pp.485-491
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• 2002

The gyroscopes have been used as a suitable inertial instrument for the navigation guidance and attitude controls. The accuracy as very sensitive sensor is limited by the lock-in region (dead band) by the frequency coupling between two counter-propagating waves at low rotation rates. This frequency coupling gives no phase difference and an angular increment is not detected. This problem can be overcome by the mechanical dithering. The purpose of the mechanical dithering is to suppress the dead band, oscillate the monoblock about the rotation axis and add an external rotation rate. This paper presents the theoretical considerations of the mechanical performances of dither on the basis of the loading condition and angular characteristics due to the piezoelement deformation and the validity of theoretical equations are compared through FEM (Finite Element Method) simulations.

• Journal of Power Electronics
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• 제16권5호
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• pp.1661-1668
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• 2016

A fixed off-time controlled high power factor ac-dc LED driver is proposed in this paper, which employs a novel zero-crossing-compensation (ZCC) circuit based on a fixed off-time controlled scheme. Due to the parasitic parameters of the system, the practical waveforms have a dead region. By detecting the zero-crossing boundary, the proposed ZCC circuit compensates the control signal VCOMP within the dead region, and is invalid above this region. With further optimization of the parameters KR and Kτ of the ZCC circuit, the dead zone can be eliminated and lower THD is achieved. Finally, the chip is implemented in HHNEC 0.5μm 5V/40V HVCMOS process, and a prototype circuit, delivering 7~12W of power to several 3-W LED loads, is tested under AC input voltage ranging from 85V to 265V. The test results indicate that the average total harmonic distortion (THD) of the entire system is approximately 10%, with a minimum of 5.5%, and that the power factor is above 0.955, with a maximum of 0.999.

• 상하수도학회지
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• 제21권2호
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• pp.177-185
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• 2007

Hydraulic efficiency($T_{10}/T$) in clearwell is often estimated by L/W ratio. However, this estimation is not accurate because other factors which give an effect on hydraulic efficiency such as shape of basin, diffuser wall and intra-basin is ignored. Therefore, in this research, hydraulic efficiency is predicted by the quantitative analysis of dead zone using CFD simulation in a pilot scale clearwell. The results show that the reason why higher L/W ratio increase the hydraulic efficiency is to decrease the dead zone of linear region which is located between baffles. Diffuser wall or intra-basin also affects on hydraulic efficiency with this process. Also, we conclude that hydraulic efficiency can not be reached to 0.8 or higher.

• Journal of Power Electronics
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• 제16권1호
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• pp.1-8
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• 2016

Dead time is typically incorporated in voltage source inverter systems to prevent short circuit cases. However, dead time causes an error between the output voltage and reference voltage. Hence, voltage equation-based algorithms, such as motor parameter estimation and back electromotive force (EMF)-based sensorless algorithms, are prone to estimation errors. Several dead-time compensation methods have been developed to reduce output voltage errors. However, voltage errors are still common in zero current crossing areas, and an effect of the error is much worse in a low speed region. Therefore, employing voltage equation-based algorithms in low speed regions is difficult. This study analyzes the conventional dead-time compensation method and output voltage errors in low speed operation areas. A current shaping method that can reduce output voltage errors is also proposed. Experimental results prove that the proposed method reduces voltage errors and improves the accuracy of the parameter estimation method and the performance of the back EMF-based sensorless algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.698-700
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• 1993

This paper describes characteristic analysis of VVVf type high-frequency considering dead time. Static power conversion are now used in a great variety of application including induction heating, high-frequency generation, DC/DC power converter, etc. In the circuit analysis, an offer circuit was compared with safety operating region and steady state characteristics considering dead time.

• 대한한방내과학회지
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• 제25권4호
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• pp.227-241
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• 2004

Objective : This study was performed to investigate neuroprotective effects of Bupleuri Radix against oxidative and ischemic damages. Method : To observe the neuroprotective effects against ischemic damage, ischemic insult was induced by oxygen/glucose deprivation (OGD) on organotypic hippocampal slice cultures (OHSC) from 1 week-old Sprague-Dawley rats. Propidium iodide (PI) fluorescence-stained neuronal dead-cell areas, area percentages and TUNEL-positive apoptotic cells in CA1 and dentate gyrus, and LDH levels in culture media of the OHSC were measured following Bupleuri Radix extract treatment. Result : The following results were obtained: (1) The $5\;{\mu}g/ml$ of Bupleuri Radix treatment demonstrated a significant decrease in PI fluorescence-stained neuronal dead-cell areas and area percentage in CA1 region of the OHSC from 18 hrs to 48 hrs following the OGD. The $50\;{\mu}g/ml$ of Bupleuri Radix treatment was also significant from 6 hrs to 48 hrs following the OGD and was more effective. (2) The 5 and $50\;{\mu}g/ml$ of Bupleuri Radix treatment demonstrated a significant decrease in PI fluorescence-stained neuronal dead-cell areas and area percentage in DG region of the OHSC from 6 hrs to 48 hrs following the OGD. The $50\;{\mu}g/ml$ treatment was more effective than the $5\;{\mu}g/ml$ treatment. (3) Bupleuri Radix treatment demonstrated a significant decrease in TUNEL-positive apoptotic cells in CA1 region (with 5 and $50\;{\mu}g/ml$) and in DG region (with $50\;{\mu}g/ml$) of the OHSC damaged by the OGD. (4) Bupleuri Radix treatment demonstrated a significant decrease in LDH concentrations in culture media of the OHSC damaged by the OGD. Conclusion : These results suggest that Bupleuri Radix has neuroprotective and control effects on inflammatory and immune responses where there has been ischemic damage to the central nervous system.

• Journal of international Conference on Electrical Machines and Systems
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• 제2권1호
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• pp.40-44
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• 2013

This paper presents a design and characteristics analysis of novel 2-phase 4/3 switched reluctance motor (SRM) with short flux path for an air-blower application. The desired air-blower is unidirectional application, and requires a wide positive torque region without torque dead-zone. In order to get a wide positive torque region without torque dead-zone during phase commutation, asymmetric inductance characteristic with non-uniform air-gap is considered. The proposed motor could be started at any rotor position with high efficiency drive. The proposed 2-phase 4/3 SRM is verified by finite element method analysis.

• 한국멀티미디어학회논문지
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• 제17권4호
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• pp.458-465
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• 2014

In this paper, we propose a strategy to distribute the energy consumption over the network. The proposed strategy is based on geographic routing. We use a smart base station that maintains the residual energy and location information of sensor nodes and selects a head node and an anchor node using this information. A head node gathers and aggregates data from the sensor nodes in a target region that interests the user. An anchor node then transmits the data that was forwarded from the head node back to the smart base station. The smart base station extends network lifetime by selecting an optimal head node and an optimal anchor node. We simulate the proposed protocol and compare it with the LEACH protocol in terms of energy consumption, the number of dead nodes, and a distribution map of dead node locations.

• 정보처리학회논문지A
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• 제17A권2호
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• pp.53-62
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• 2010

모바일 센서 네트워크(Mobile Sensor Network)의 노드(Node)인 모바일 센서 차량(Mobile Sensor Vehicles)들은 특정 지역에 관해 획득한 정보를 서로 교환하고 통합하는 과정을 거쳐 자신의 위치를 파악하게 되는데 이를 지역화(localization)라 한다. 이때 모바일 센서 차량은 탑재된 각종 센서를 이용하여 자신의 위치 정보를 파악한다. 본 연구에서는 데드-레코닝(Dead-Reckoning), 컴퓨터 비전 기법, 그리고 RSSI(Received Signal Strength Identification)를 사용한 모바일 센서 차량(MSV)의 지역화 정밀도를 향상시키는 방안을 제시하고, 각각의 방식들이 가진 장점을 융합하여 보다 정밀한 지역화를 할 수 있는지 살펴본다.