• Title, Summary, Keyword: masking effects

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Effects of Port Masking on Part Load Performance: Part I - Lean Misfire Limit (포트 마스킹이 엔진의 부분부하 성능에 미치는 영향: Part I - 희박연소 한계)

  • 이원근;엄인용
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.17-22
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    • 2001
  • This paper is the first of companion papers, which investigate port-masking effects on lean misfire limit. Port-masking was applied to commercial SOHC 3-valve and DOHC 4-valve engine by inserting masking plates between manifold and port. To induce various conditions of stratification, six types of masking plates were applied. The masking plates were placed in the upstream of injector to prevent wall wetting and two ports were not separated to permit both fuel and air entering through masked port. The results were compared with those by conventional port throttling. The results show that lean misfire limit mainly depends on masking direction, that is, high lean misfire limit is achieved when the port near the spark plug is masked. The mechanism of stratification by masking is different from axial stratification by port throttling. In this case, the rich mixture entering through masked port plays a very important role in the stratification process.

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The Masking Effects of Introducing Sounds about Road Traffic Noise (도로교통소음에 대한 도입 연출음의 마스킹 효과)

  • Shin, Hoon;Park, Sa-Keun;Kook, Chan;Jang, Gil-Soo
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.599-602
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    • 2005
  • This paper describes a experimental study determining the effects of the type and loudness of introducing sounds on the amenity and the masking degree of background noise. 132 relative test sounds with 11 types of introducing sounds and 3 steps of road traffic noise were presented to 29 subjects through headphone in the laboratory experiment. Seven scale of polar adjective such as 'Strong Weak', 'Pleasant Unpleasant', 'Clear Unclear', 'Suitable Unsuitable', 'Comfortable-Discomfortable' was employed for the evaluation of amenity. And Seven scale of mono polar adjective such as 'Very-Not at all' was employed for the evaluation of masking degree against road traffic noise. The results are as follows; Green music was evaluated the highest amenity among test sounds and murmurs of a stream, signal music, song of a bird, crying of insect was showed the amenity rank of order. The softer and weaker introducing sound was evaluated more suitable and comfortable under the road traffic noise. So adequate level of introducing sounds was considered for the desirable urban soundscape. Also the louder sounds compared to background noises had greater masking effects. But similar levels of introducing sounds were recommended considering both good amenity and masking effects.

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Multiple Deletions in Logistic Regression Models

  • Jung, Kang-Mo
    • Communications for Statistical Applications and Methods
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    • v.16 no.2
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    • pp.309-315
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    • 2009
  • We extended the results of Roy and Guria (2008) to multiple deletions in logistic regression models. Since single deletions may not exactly detect outliers or influential observations due to swamping effects and masking effects, it needs multiple deletions. We developed conditional deletion diagnostics which are designed to overcome problems of masking effects. We derived the closed forms for several statistics in logistic regression models. They give useful diagnostics on the statistics.

Effects of sound-masking on the soundscape of urban public spaces with multiple noises (복합소음 공간의 Soundscape에 대한 사운드 마스킹의 효과)

  • Jeong, Choong-Il;You, Jin;Lee, Pyoung-Jik;Jeon, Jin-Yong
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.268-271
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    • 2008
  • A sound-masking technique was applied to the urban public spaces with multiple noises in order to reduce the annoyance of the construction and traffic noise. In addition, the effects of masking system were investigated in order to improve the soundscape. In several urban spaces, building construction and nearby road traffic noise were recorded using a head and torso simulator and sound quality (SQ) system which specifies the spectral and temporal aspects of the noises. The sound-masking system which consists of the distributed speakers and control devices was applied to the boundaries of the construction sites. Synthesized masking sounds were produced with consideration of SQ characteristics of the multiple noise. Subjective evaluations on the soundscape were conducted to verify effectiveness of the system under the conditions with and without the masker sounds.

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Effects of Port Masking on fart Load Performance: Part II - Emission and Fuel Economy (포트 마스킹이 엔진의 부분부하 성능에 미치는 영향: Part II - 배기 및 연비특성)

  • 이원근;엄인용
    • Transactions of the Korean Society of Automotive Engineers
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    • v.9 no.5
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    • pp.23-29
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    • 2001
  • This paper is the second of companion papers, which investigate port-masking effects on emission and fuel economy. Port-masking was applied to commercial SOHC 3-valve engine by inserting masking plates between manifold and port. To induce various conditions of stratification, six types of masking plates were applied. In this paper, main interest is focused on the influence of injection timing on emission and fuel economy. Various injection timing was applied to the six cases, under the stoichiometric and lean-limit air-fuel ratio. Under the stoichiometric condition, an explanation about the reason of the change in emission level due to injection timing change is given. It is observed that NOx emission under the LML condition varies significantly when the injection timing changes.

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Part Load Performance Characteristics according to Port Masking (포트 마스킹에 따른 엔진 부분부하 성능 특성)

  • Kim, Hyeong-Sig;Kim, In-Ok;Park, Chan-Jun;Ohm, In-Yong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.2
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    • pp.42-49
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    • 2011
  • To expand lean misfire limit and improve combustion stability, the effects of port masking were estimated to secure basic data for applying the mechanism to SI engine instead of asymmetrical port and port throttling devises. For this purpose, various shapes and ratios of masking plates were mounted between port and manifold. The masking effects were evaluated by mixture response test under various load and speed conditions. The results showed that lean misfire limits were expended and fast combustion was observed for all masking shapes and ratios, especially, the effect of diagonal 1/4 masking was remarkable. In conclusion, the port masking method could be easily applied to engine without redesign of port for improving part load performance.

A Study on the Development of Masking Models for the Improvement of Amenity at Urban Small Green Spaces (도시 소녹지공간 어메니티 증진을 위한 교통소음 Masking Models 개발에 관한 연구)

  • 안득수;정태섭;박영민
    • Journal of the Korean Institute of Landscape Architecture
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    • v.26 no.3
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    • pp.19-33
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    • 1998
  • The primary objective of this research was to develop optimal models for masking the road traffic noise with the sound of a waterfall at urban small green spaces. Noise levels were measured at 8 roadside green spaces in SEOUL and questionnaires were randomly distributed to 40 users for evaluating the noise at each site at the same time. College students participated in the experiment for the development of masking models and the developed models were tested by users at 2 green spaces. The major results are as follows ; 1. Traffic noises ranged from 65dBto 70 dB. Users' satisfaction with the noise became considerably low on the basis of 60 dB and it was highly related to noise level. 2. Noise was a main factor to depreciate the amenity of green spaces where its level was more than 60 dB and so it neds to be excluded or reduced the traffic noise at the process of design. 3. Masking effects kept constant independent of the spatial location of masker on condition that masker levels were equal. It was effective when masker was 5-10dB greater than noise level which was masked. 4. As noise level went up, satisfaction ratings about the masked noise became low but masking effects increased in proportion to its level. 5. It was proved that the models were valid through the field experiment.

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Effects of Port Masking on Emission (포트 마스킹이 엔진의 배기에 미치는 영향)

  • Kim, Hyeong-Sig;Park, Chan-Jun;Ohm, In-Yong
    • Transactions of the Korean Society of Automotive Engineers
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    • v.19 no.3
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    • pp.23-28
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    • 2011
  • To secure basic data for intake port design, effects of a port masking on the part load performance were investigated in a 4 valve SI engine. For this purpose, 9 kinds of masking, which have different shapes and masking ratio, are applied to the engine intake system. The characteristics of the performance were estimated through mixture response test at various engine load and speed. The results show that NOx emission, one of indexes for stratification, increases considerably in spite of retarded spark timing due to the stratification which is caused by unequal flow distribution between the two intake ports. The mechanism of stratification by masking is different from axial stratification and the fuel entering through masked port plays a very important role in this stratification process. In conclusion, the port masking method could be easily applied to engine intake system and be very effective for inducing the stratified charging without the change of port design.

Visibility Evaluation for Agricultural Tractor Operators According to ISO 5006 and 5721-1 Standards

  • Kabir, Md. Shaha Nur;Song, Mingzhang;Chung, Sun-Ok;Kim, Yong-Joo;Kim, Su-Chul;Ha, Jong-Kyou
    • Journal of Biosystems Engineering
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    • v.40 no.1
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    • pp.19-27
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    • 2015
  • Purpose: A system to measure the visibility of agricultural tractor operators was designed and evaluated according to ISO standards, and a blind area diagram around the tested tractor was created based on the manual method recommended by the National Institute for Occupational Safety and Health (NIOSH). Methods: A visibility measurement system was designed and evaluated based on the ISO 5006 and ISO 5721-1 standards. Two bulbs used to simulate the operator's eyes were mounted on a bar with a supporting frame. A wooden frame was used to determine the seat index point position. The 12-m visibility test circle was divided into six sectors of vision, and the test tractor was placed at the center of the circle. Artificial light was supplied in the darkened environment, and shadow or masking effects were measured manually around the 12-m circle. Results: When the bulbs were placed at the operator's eye level, front visibility was good; no masking was found in the "A" vision sector, but larger masking widths were found in the "B" and "C" vision sectors. Since the masking width exceeded 700 mm, additional tests, such as movement of the light sources to both sides of the operator's eye level, were performed. Less than six masking effects were found in the semi-circle of vision to the front, and more than one masking was found in the "B" and "C" visual fields. The minimum distance between the centers of two masking effects exceeded 2500 mm when measured as a chord on the semi-circle of vision. A blind area diagram was created to define the exact nature of the blind spots and mirror visibility. Conclusions: Visibility evaluation is an effective way to enable proper and safe operation for agricultural tractor operators. Inclusion of this visibility evaluation test in the general testing process might aid tractor manufacturers.

A Video Watermarking Method using Global Masking (전역 마스킹을 이용한 비디오 워터마킹 방법)

  • 문지영;호요성
    • Journal of Broadcast Engineering
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    • v.8 no.3
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    • pp.268-277
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    • 2003
  • In this paper, we propose a new video watermarking method exploiting the human visual system (HVS) to find effective locations. in the video frames which make the watermark robust and imperceptible simultaneously. In particular, we propose a new HVS-optimized weighting map for hiding the watermark by considering HVS in three different aspects : frequency, spatial, and motion masking effects. The global masking map is modeled by combining the frequency masking, the spatial masking, and the motion masking. In this paper, we use a watermark which is generated by the bitwise exclusive-OR operation between a logo image and a random sequence. The amount of watermarks is weighted by a control parameter. Furthermore, we embed the watermark in the uncompressed video sequence for the general watermarking method available to various coding schemes. Simulation results show that the watermark is imperceptible and the proposed method is good for watermark capacity. It is also demonstrated that the proposed method is robust against various attacks, such as MPEG coding, MPEG re-encoding, and frame attacks.