• Title, Summary, Keyword: Work Efficiency

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Collection Characteristics of a MOUDI Cascade Impactor for Coarse Particles (다단 임팩터(MOUDI)의 조대 입자 채취 특성)

  • 배귀남;지준호;문길주
    • Journal of Korean Society for Atmospheric Environment
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    • v.15 no.6
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    • pp.799-804
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    • 1999
  • Particle collection characteristics of the MOUDI cascade impactor has been studied for coarse particles in the range of 2 to 20$mu extrm{m}$ in aerodynamic diameter. A vibrating orifice aerosol generator was empolyed to generate monodisperse test aerosols. The oleic acid and sodium chloride(NaCl) particles were used as test aerosols. Aluminum foil and Teflon filter were selected as impaction media. The sampling flow rate was changed from 25 to 35L/min. Particle collection efficiency for single stage was examined for liquid particles. The stage response was obtained experimentally for the cascade impactor composed of three stages and a backup filter. The results showed that most of particle collection efficiencies measured in this work are similar to the efficiency curves obtained by Marple et al.(1991). For particles less than cut-off size of the stage, the collection efficiencies of solid particles are similar to those of loquid particles. However, the collection efficiency of solid particles decreases with mereasing particle diameter for the particles greater than the actual cut-off size of the impactor. The particle collection efficiency increases with increasing sampling flow rate at the same particel size. However, the collection efficiency curves seem not to be greatly shifted with the flow rate. The stage responses obtained by direct measurements in this work are in good agreement with those derived from the collection efficiency curves for single stage.

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New mathematical approach to calculate the geometrical efficiency using different radioactive sources with gamma-ray cylindrical shape detectors

  • Thabet, Abouzeid A.;Hamzawy, A.;Badawi, Mohamed S.
    • Nuclear Engineering and Technology
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    • v.52 no.6
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    • pp.1271-1276
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    • 2020
  • The geometrical efficiency of a source-to-detector configuration is considered to be necessary in the calculation of the full energy peak efficiency, especially for NaI(Tl) and HPGe gamma-ray spectroscopy detectors. The geometrical efficiency depends on the solid angle subtended by the radioactive sources and the detector surfaces. The present work is basically concerned to establish a new mathematical approach for calculating the solid angle and geometrical efficiency, based on conversion of the geometrical solid angle of a non-axial radioactive point source with respect to a circular surface of the detector to a new equivalent geometry. The equivalent geometry consists of an axial radioactive point source with respect to an arbitrary elliptical surface that lies between the radioactive point source and the circular surface of the detector. This expression was extended to include coaxial radioactive circular disk source. The results were compared with a number of published data to explain how significant this work is in the efficiency calibration procedure for the γ-ray detection systems, especially in case of using isotropic radiating γ-ray sources in the form of point and disk shapes.

A Preparation of Copper Phthalocyanine Photoreceptor by an Aqueous Coating Method and Study of Dark Decay and Photoinjection Efficiency (신규 제작법을 이용한 Copper Phthalocyanine 전자사진 감광체의 개발과 Dark Decay와 Photoinjection Efficiency에 관한 연구)

  • 이상남
    • Journal of the Korean Printing Society
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    • v.11 no.1
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    • pp.103-122
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    • 1993
  • A cause and counterplan of the increase in dark decay rate of$\varepsilon$-CuPc/PVCz photoreceptor which is consist of the carrier generation layer (CGL) of$\varepsilon$type copper phthalocyanine ($\varepsilon$-CuPc) thin film by an aqueous coating method and the carrier transport layer (CTL) of polyvinylcarbazol (PVCz) by spin coating, are studied in this paper. Electrochemical deposition of CGL was accompanied by an increase in work function of the aluminium substrate during the processes and the enhanced work function 5.3 eV rose above the ionization potential 5.16 eV of $\varepsilon$-CuPc. This resulted in the increased injection of holes from substrate into CGL and a fast dark decay rate. Improved photoreceptor, an electron-transport $\varepsilon$-CuPc/TNF photoreceptor, led to lowing of dark decay rate and increasing of photosensitivity. The carrier generation efficiency (ηg), carrier injection efficiency (ηi) and xerographic gain (G) of the $\varepsilon$-CuPc/TNF photoreceptor were obtained by XTOF method and PIDC.

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A Novel Two-party Scheme against Off-line Password Guessing Attacks using New Theorem of Chaotic maps

  • Zhu, Hongfeng
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.11 no.12
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    • pp.6188-6204
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    • 2017
  • Over the years, more password-based authentication key agreement schemes using chaotic maps were susceptible to attack by off-line password guess attack. This work approaches this problem by a new method--new theorem of chaotic maps: $T_{a+b}(X)+T_{a-b}(X)=2T_a(X)T_b(X)$,(a>b). In fact, this method can be used to design two-party, three-party, even in N-party intelligently. For the sake of brevity and readability, only a two-party instance: a novel Two-party Password-Authenticated Key Agreement Protocol is proposed for resisting password guess attack in this work. Compared with the related literatures recently, our proposed scheme can be not only own high efficiency and unique functionality, but is also robust to various attacks and achieves perfect forward secrecy. For capturing improved ratio of security and efficiency intuitively, the paper firstly proposes a new parameter called security/efficiency ratio(S/E Ratio). The higher the value of the S/E Ratio, the better it is. Finally, we give the security proof and the efficiency analysis of our proposed scheme.

Lower Bound of Partial Packet Recovery (패킷부분재전송기법의 수율 최저 한계)

  • Jeong, Choong-Kyo
    • Journal of Industrial Technology
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    • v.28 no.A
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    • pp.113-117
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    • 2008
  • Wireless carrier sense multiple access (CSMA) systems are widely used but show extremely different transmission efficiency according to the operation environment. Simulation or prototype deployment is needed to see the transmission efficiency of a wireless CSMA system with the partial packet retransmission scheme. The lower bound for the transmission efficiency of such a system is found mathematically in this work. This shows how much the partial packet retransmission scheme improves the transmission efficiency quantitatively. It also shows that the maximum throughput is obtained at higher offered load compared to the conventional CSMA system without the partial packet transmission. The result of this work can be applied to IEEE 802.11 networks or wireless mesh networks.

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Task-Visual Information Map to Develop AR Navigators of Construction Equipment (건설장비 AR 네비게이터 개발을 위한 작업-시각정보 맵 도출)

  • Song, Sujin;Kang, Hojun;Kim, Hanbeen;Moon, Taenam;Shin, Do Hyoung
    • Korean Journal of Construction Engineering and Management
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    • v.17 no.3
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    • pp.116-124
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    • 2016
  • Work efficiency of earth work which is one of the main works occurring in construction site mainly depends on the performance of individual operators of earth work equipment. Consequently, the skill of individual operators of earth work equipment can significantly affect overall construction schedules. Many invisible areas inevitably exist in construction site because of the nature of construction site where occlusions occur from structures being built, installed or moving equipment, moving workers, etc. The lack of visual information regarding tasks critically impedes the effective performance of operators of earth work equipment. AR (Augmented Reality) is a computer technology that superimposes virtual objects onto the real world scene. This characteristic of AR may address the lack of visual informations in earth work process, thus helping to improve the work efficiency of operators of earth work equipment. The purpose of this study is to present a task-visual information map that identifies visual informations required in tasks of earth work and which of the tasks are suitable for AR technology. This study focuses on visual informations in tasks of earth work with excavators. The map was created based on the investigations on the problems of each task of earth work with excavators and visual informations required to address the problems. Through the map, four visual informations were found to be suitable for AR technology to improve the work efficiency of excavator operators. Based on the findings of this study, AR systems for excavators can be developed more effectively.

Design and Development of Health Screening Data Input Mobile Application Using App-Inventor (앱인벤터를 이용한 건강검진 데이터 입력 모바일 애플리케이션 설계 및 개발)

  • Lee, Hyo-Seung;Oh, Jae-Chul
    • The Journal of the Korea institute of electronic communication sciences
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    • v.13 no.1
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    • pp.193-198
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    • 2018
  • These days, computer system has been introduced for work in most areas, including manufacturing, medical service, education, logistics, and other services. To increase work efficiency, mobile system has been more applied. However, on the basis of Android applications, it is hard for laypersons who have no enough knowledge of Android, or computer team members in general firms to develop mobile App. As a result, work efficiency comes to low. Therefore, this study designed and developed the mobile application for anthropometry data input of medical checkup with the use of App Inventor. As shown in the designed and developed mobile application, it is expected to develop a work process mobile App, it is expected to develop a work process mobile App easily and quickly with the use of App Inventor and to increase work efficiency even though there is not much knowledge of mobile application development.

Green Phosphorescent OLEDs for Low Power Displays

  • Weaver, Michael S.;Adamovich, Vadim I.;Kwong, Raymond C.;Brown, Julie J.
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.1513-1515
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    • 2008
  • High efficiency phosphorescent organic light emitting devices ($PHOLED^{TM}s$) are now widely used in commercial displays. In this paper we describe some of the work behind the development of high efficiency stable green PHOLEDs capable of fulfilling display specifications.

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High Efficiency Design Procedure of a Second Stage Phase Shifted Full Bridge Converter for Battery Charge Applications Based on Wide Output Voltage and Load Ranges

  • Cetin, Sevilay
    • Journal of Power Electronics
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    • v.18 no.4
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    • pp.975-984
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    • 2018
  • This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

The rock fragmentation mechanism and plastic energy dissipation analysis of rock indentation

  • Zhu, Xiaohua;Liu, Weiji
    • Geomechanics and Engineering
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    • v.16 no.2
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    • pp.195-204
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    • 2018
  • Based on theories of rock mechanics, rock fragmentation, mechanics of elasto-plasticity, and energy dissipation etc., a method is presented for evaluating the rock fragmentation efficiency by using plastic energy dissipation ratio as an index. Using the presented method, the fragmentation efficiency of rocks with different strengths (corresponding to soft, intermediately hard and hard ones) under indentation is analyzed and compared. The theoretical and numerical simulation analyses are then combined with experimental results to systematically reveal the fragmentation mechanism of rocks under indentation of indenter. The results indicate that the fragmentation efficiency of rocks is higher when the plastic energy dissipation ratio is lower, and hence the drilling efficiency is higher. For the rocks with higher hardness and brittleness, the plastic energy dissipation ratio of the rocks at crush is lower. For rocks with lower hardness and brittleness (such as sandstone), most of the work done by the indenter to the rocks is transferred to the elastic and plastic energy of the rocks. However, most of such work is transferred to the elastic energy when the hardness and the brittleness of the rocks are higher. The plastic deformation is small and little energy is dissipated for brittle crush, and the elastic energy is mainly transferred to the kinetic energy of the rock fragment. The plastic energy ratio is proved to produce more accurate assessment on the fragmentation efficiency of rocks, and the presented method can provide a theoretical basis for the optimization of drill bit and selection of well drilling as well as for the selection of the rock fragmentation ways.