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이정권,문병연,조현국 대한시과학회 2012 대한시과학회지 Vol.14 No.4
Purpose : This study was designed to investigate the distribution for lengths of progressive corridor at habitual reading posture for fitting of progressive addition lenses (PALs). Methods : Measurement was performed to 5,925 subjects between 39 and 83 years of age using EMP from January 2010 to June 2012. The measured values were analyzed the distribution according to age bands. Result : The distribution of measured lengths of progressive corridor (from eyepoint to near reference point) was 34.45% of 10~11 mm, 32.66% of 12~13 mm, 16.96% of 8~9 mm, 10.13% of 14~15 mm,4.30% of 6~7 mm, 1.27% of 16~17 mm, and 0.25% of 18~19 mm. The length of 10~11 mm was accounted for the largest percentage in 39~49 age band (42.05%) and 12~13 mm was accounted for the largest percentage in all of 50~59 age band (31.84%), 60~69 age band (35.48%), and 70~83 age band (46.15%). Conclusion : The practitioners have to invent the advanced methods continuously for accurate measurement of the length of progressive corridor at habitual reading posture. 목 적 : 누진굴절력렌즈의 피팅을 위하여 습관적인 독서자세에서 측정한 누진대 길이의 분포를 알아보았다. 방 법 : 2010년 1월부터 2012년 6월까지 39~83세의 남녀 5,925명을 대상으로 Eye Move Photographing (EMP)을 이용하여 누진대 길이를 측정하였고, 연령대별 분포를 분석하였다. 결 과: 측정된 누진대 길이(아이포인트에서 근용부 측정점까지) 분포는 10~11mm(34.45%), 12~13mm (32.66), 8~9mm(16.96%), 14~15mm(10.13%), 6~7mm(4.30%), 16~17mm(1.27%), 그리고 18~19mm (0.25%)로 나타났다. 39~49세에서는 10~11mm가 42.05%로 가장 많은 비율이었고, 50~59세, 60~69세,그리고 70~83세에서는 12~13mm가 각각 31.84%, 35.48%, 그리고 46.15%로 가장 많은 비율이었다. 결 론 : 안경실무 종사자들은 습관적 독서자세에서 정확한 누진대 길이를 측정할 수 있는 진보적인 방법들을 계속적으로 고안할 필요가 있다.
OPTIMAL DESIGN OF THE EXHAUST SYSTEM LAYOUT TO SUPPRESS THE DISCHARGE NOISE FROM AN IDLING ENGINE
이정권,C.-Y. CHOI,T.-K. KIM,S.-H. JANG,H.-J. KIM 한국자동차공학회 2011 International journal of automotive technology Vol.12 No.4
At the idle engine speed, the exhaust discharge noise is influenced by resonances in the whole system, which is composed of connecting pipes and silencers. This pipe resonance radiates a high level of low frequency discharge noise, which is dominated by the low order harmonics of the engine firing frequency. This low frequency noise deteriorates the vehicle’s interior noise level and quality. The following study attempted to optimize the layout of an exhaust system to minimize low frequency noise by changing the position of silencers and the lengths of inlet and outlet pipes in each silencer. After modeling the exhaust system using four-pole parameters, the acoustical performance of the system was evaluated using the system insertion loss. In the optimization, the virtual attenuation coefficient, which corresponds to the amount of attenuation coefficient required for the silencers, was calculated to find a minimum value for the layout. The simulated annealing method, which is also known as finding an optimal, was employed in searching for the optimized exhaust layout. Test examples of two cases, for two and six design variables, were used. When the number of design variables was two, the positions of the center and rear silencers were considered. When the number of design variables was six, the positions of the two silencers and the lengths of the inlet and outlet pipes were considered. Three typical layouts for the exhaust system of each case were designed, including the given system and an optimal system. By comparing the predicted and measured discharge noise level, it was confirmed that the optimized exhaust layout has a higher noise reduction than the other layout designs.