• Title/Summary/Keyword: (Types of) Errors

Search Result 823, Processing Time 0.025 seconds

An Experimental Study on Establishing Criteria of Gripping Work in Construction Site (건설 현장 악력 작업안전 기준 설정에 관한 실험적 연구)

  • 손기상;이인홍;최만진;안병준
    • Journal of the Korean Society of Safety
    • /
    • v.10 no.3
    • /
    • pp.81-95
    • /
    • 1995
  • Now, safety assurance in construction sites should be accomplished by its own organization rather than control of the code or government. It is believed that the safety assurance can be considerably improved by a lecture or an education using the existing theories or literatures up to now, but it is thought that fundamental safety assurance we not able to be accomplished without developing safety devices '||'&'||' equipment or taking fundamental measures, based on the result analyzed from workers behaviors. There are various behaviors of the workers showed in construction site, but only tests for hammerusing works such as form, re-bar, stone workers directly related to the grip strength are mainly performed, investigated and measured here for the study. The above works are similar to power grip, 7th picture on seven items which are categorized for hand grip types(Ammermin 1956 ; Jones ; Kobrick 1958). Measurements of grip strength are commonly taken in anthropometric surveys. They are easy to administer but unfortunately it is rather dubious whether they yield any data that are of interest to the engineer. Very fewer controls of tools are grasped and squeesed studies showed very little overall correlation between grip strength and other measures of bodily strength (Laubach, Kromer, and Thordsen 1972), but hammer-using work which is practically progressed in construction site are mainly influenced with grip strength. According to the investigation on work measurement, it is shown that 77% of form worker are using hammer to be related to grip strength. In this study, it is particularly noticed that wearing safety gloves in construction site is required for workers safety but 20% difference between grip strength with safety gloves and without ones are commonly neglected in the site(Fig. 1). Nevertheless, safety operation with consideration of the above 20% difference is not considered in the construction site. Factors of age, kinds of work, working time, with or without safety gloves are in vestigated '||'&'||' collected at the sites for this study. Test, not at each working hour but at 14 : 00 when the almost all of the workers think the most tired, resulting from the questionaires, also when it is shown on the research report has been performed and compared for main kinds of works : form '||'&'||' re-bar work. Tests were performed with both left SE rightand of the workers simultaneously in construction site using Rand Dynamometer(Model 78010, Lafayette Instrument Co., Indiana, U.S.A) by reading grip strength on the gauge while they are pulling, and then by interviewing on their ages, works, experiences and etc., directly. The above tests have been performed for the dates of 15th march-26th May '95 with consideration of site condition. And even if various factors of ambient temperature on the testing date, working condition, individual worker's habit and worker's condition of the previous ate are concerned with the study. Those are considered as constants in this study. Samples are formwork 53, rebar 62, electrician 5, plumber 4, welding 1 from D construction Co., Ltd, ; formwork 12, re-bar 5, electrician 2, from S construction Co., Ltd, , formwork 78, re-bar 18, plumber 31, electrician 13, labor 48, plumber 31, plasterer 15, concrete placer 6, water proof worker 3, maisony 5 from B construction Co., Ltd. As In the previously mentioned, main aspect to be investigated in this study will be from '||'&'||' re-bar work because grip strength will be directly applied to these two kinds of works ; form '||'&'||' re-bar work, eventhough there are total 405 samples taken. It is thought that a frequency of accident occurrence will be mainly two work postures "looking up '||'&'||' looking down" to be mainly sorted, but this factor is not clarified in this study because It will be needed a lot of work more. Tests has been done at possible large scale of horizontally work-extended sites within one hour in order to prevent or decrease errors '||'&'||' discrepancies from time lag of the test. Additionally, the statistical package computer program SPSS PC+has been used for the study.

  • PDF

User Centered Interface Design of Web-based Attention Testing Tools: Inhibition of Return(IOR) and Graphic UI (웹 기반 주의력 검사의 사용자 인터페이스 설계: 회귀억제 과제와 그래픽 UI를 중심으로)

  • Kwahk, Ji-Eun;Kwak, Ho-Wan
    • Korean Journal of Cognitive Science
    • /
    • v.19 no.4
    • /
    • pp.331-367
    • /
    • 2008
  • This study aims to validate a web-based neuropsychological testing tool developed by Kwak(2007) and to suggest solutions to potential problems that can deteriorate its validity. When it targets a wider range of subjects, a web-based neuropsychological testing tool is challenged by high drop-out rates, lack of motivation, lack of interactivity with the experimenter, fear of computer, etc. As a possible solution to these threats, this study aims to redesign the user interface of a web-based attention testing tool through three phases of study. In Study 1, an extensive analysis of Kwak's(2007) attention testing tool was conducted to identify potential usability problems. The Heuristic Walkthrough(HW) method was used by three usability experts to review various design features. As a result, many problems were found throughout the tool. The findings concluded that the design of instructions, user information survey forms, task screen, results screen, etc. did not conform to the needs of users and their tasks. In Study 2, 11 guidelines for the design of web-based attention testing tools were established based on the findings from Study 1. The guidelines were used to optimize the design and organization of the tool so that it fits to the user and task needs. The resulting new design alternative was then implemented as a working prototype using the JAVA programming language. In Study 3, a comparative study was conducted to demonstrate the excellence of the new design of attention testing tool(named graphic style tool) over the existing design(named text style tool). A total of 60 subjects participated in user testing sessions where their error frequency, error patterns, and subjective satisfaction were measured through performance observation and questionnaires. Through the task performance measurement, a number of user errors in various types were observed in the existing text style tool. The questionnaire results were also in support of the new graphic style tool, users rated the new graphic style tool higher than the existing text style tool in terms of overall satisfaction, screen design, terms and system information, ease of learning, and system performance.

  • PDF

Assessment of Positioning Accuracy of UAV Photogrammetry based on RTK-GPS (RTK-GPS 무인항공사진측량의 위치결정 정확도 평가)

  • Lee, Jae-One;Sung, Sang-Min
    • Journal of the Korea Academia-Industrial cooperation Society
    • /
    • v.19 no.4
    • /
    • pp.63-68
    • /
    • 2018
  • The establishment of Ground Control Points (GCPs) in UAV-Photogrammetry is a working process that requires the most time and expenditure. Recently, the rapid developments of navigation sensors and communication technologies have enabled Unmanned Aerial Vehicles (UAVs) to conduct photogrammetric mapping without using GCP because of the availability of new methods such as RTK (Real Time Kinematic) and PPK (Post Processed Kinematic) technology. In this study, an experiment was conducted to evaluate the potential of RTK-UAV mapping with no GCPs compared to that of non RTK-UAV mapping. The positioning accuracy results produced by images obtained simultaneously from the two different types of UAVs were compared and analyzed. One was a RTK-UAV without GCPs and the other was a non RTK-UAV with different numbers of GCPs. The images were taken with a Canon IXUS 127 camera (focal length 4.3mm, pixel size $1.3{\mu}m$) at a flying height of approximately 160m, corresponding to a nominal GSD of approximately 4.7cm. As a result, the RMSE (planimetric/vertical) of positional accuracy according to the number of GCPs by the non-RTK method was 4.8cm/8.2cm with 5 GCPs, 5.4cm/10.3cm with 4 GCPs, and 6.2cm/12.0cm with 3 GCPs. In the case of non RTK-UAV photogrammetry with no GCP, the positioning accuracy was decreased greatly to approximately 112.9 cm and 204.6 cm in the horizontal and vertical coordinates, respectively. On the other hand, in the case of the RTK method with no ground control point, the errors in the planimetric and vertical position coordinates were reduced remarkably to 13.1cm and 15.7cm, respectively, compared to the non-RTK method. Overall, UAV photogrammetry supported by RTK-GPS technology, enabling precise positioning without a control point, is expected to be useful in the field of spatial information in the future.

Measurement and Quality Control of MIROS Wave Radar Data at Dokdo (독도 MIROS Wave Radar를 이용한 파랑관측 및 품질관리)

  • Jun, Hyunjung;Min, Yongchim;Jeong, Jin-Yong;Do, Kideok
    • Journal of Korean Society of Coastal and Ocean Engineers
    • /
    • v.32 no.2
    • /
    • pp.135-145
    • /
    • 2020
  • Wave observation is widely used to direct observation method for observing the water surface elevation using wave buoy or pressure gauge and remote-sensing wave observation method. The wave buoy and pressure gauge can produce high-quality wave data but have disadvantages of the high risk of damage and loss of the instrument, and high maintenance cost in the offshore area. On the other hand, remote observation method such as radar is easy to maintain by installing the equipment on the land, but the accuracy is somewhat lower than the direct observation method. This study investigates the data quality of MIROS Wave and Current Radar (MWR) installed at Dokdo and improve the data quality of remote wave observation data using the wave buoy (CWB) observation data operated by the Korea Meteorological Administration. We applied and developed the three types of wave data quality control; 1) the combined use (Optimal Filter) of the filter designed by MIROS (Reduce Noise Frequency, Phillips Check, Energy Level Check), 2) Spike Test Algorithm (Spike Test) developed by OOI (Ocean Observatories Initiative) and 3) a new filter (H-Ts QC) using the significant wave height-period relationship. As a result, the wave observation data of MWR using three quality control have some reliability about the significant wave height. On the other hand, there are still some errors in the significant wave period, so improvements are required. Also, since the wave observation data of MWR is different somewhat from the CWB data in high waves of over 3 m, further research such as collection and analysis of long-term remote wave observation data and filter development is necessary.

Characteristics of Spectra of Daily Satellite Sea Surface Temperature Composites in the Seas around the Korean Peninsula (한반도 주변해역 일별 위성 해수면온도 합성장 스펙트럼 특성)

  • Woo, Hye-Jin;Park, Kyung-Ae;Lee, Joon-Soo
    • Journal of the Korean earth science society
    • /
    • v.42 no.6
    • /
    • pp.632-645
    • /
    • 2021
  • Satellite sea surface temperature (SST) composites provide important data for numerical forecasting models and for research on global warming and climate change. In this study, six types of representative SST composite database were collected from 2007 to 2018 and the characteristics of spatial structures of SSTs were analyzed in seas around the Korean Peninsula. The SST composite data were compared with time series of in-situ measurements from ocean meteorological buoys of the Korea Meteorological Administration by analyzing the maximum value of the errors and its occurrence time at each buoy station. High differences between the SST data and in-situ measurements were detected in the western coastal stations, in particular Deokjeokdo and Chilbaldo, with a dominant annual or semi-annual cycle. In Pohang buoy, a high SST difference was observed in the summer of 2013, when cold water appeared in the surface layer due to strong upwelling. As a result of spectrum analysis of the time series SST data, daily satellite SSTs showed similar spectral energy from in-situ measurements at periods longer than one month approximately. On the other hand, the difference of spectral energy between the satellite SSTs and in-situ temperature tended to magnify as the temporal frequency increased. This suggests a possibility that satellite SST composite data may not adequately express the temporal variability of SST in the near-coastal area. The fronts from satellite SST images revealed the differences among the SST databases in terms of spatial structure and magnitude of the oceanic fronts. The spatial scale expressed by the SST composite field was investigated through spatial spectral analysis. As a result, the high-resolution SST composite images expressed the spatial structures of mesoscale ocean phenomena better than other low-resolution SST images. Therefore, in order to express the actual mesoscale ocean phenomenon in more detail, it is necessary to develop more advanced techniques for producing the SST composites.

Comparison of Multi-Satellite Sea Surface Temperatures and In-situ Temperatures from Ieodo Ocean Research Station (이어도 해양과학기지 관측 수온과 위성 해수면온도 합성장 자료와의 비교)

  • Woo, Hye-Jin;Park, Kyung-Ae;Choi, Do-Young;Byun, Do-Seung;Jeong, Kwang-Yeong;Lee, Eun-Il
    • Journal of the Korean earth science society
    • /
    • v.40 no.6
    • /
    • pp.613-623
    • /
    • 2019
  • Over the past decades, daily sea surface temperature (SST) composite data have been produced using periodically and extensively observed satellite SST data, and have been used for a variety of purposes, including climate change monitoring and oceanic and atmospheric forecasting. In this study, we evaluated the accuracy and analyzed the error characteristic of the SST composite data in the sea around the Korean Peninsula for optimal utilization in the regional seas. We evaluated the four types of multi-satellite SST composite data including OSTIA (Operational Sea Surface Temperature and Sea Ice Analysis), OISST (Optimum Interpolation Sea Surface Temperature), CMC (Canadian Meteorological Centre) SST, and MURSST (Multi-scale Ultra-high Resolution Sea Surface Temperature) collected from January 2016 to December 2016 by using in-situ temperature data measured from the Ieodo Ocean Research Station (IORS). Each SST composite data showed biases of the minimum of 0.12℃ (OISST) and the maximum of 0.55℃ (MURSST) and root mean square errors (RMSE) of the minimum of 0.77℃ (CMC SST) and the maximum of 0.96℃ (MURSST) for the in-situ temperature measurements from the IORS. Inter-comparison between the SST composite fields exhibited biases of -0.38-0.38℃ and RMSE of 0.55-0.82℃. The OSTIA and CMC SST data showed the smallest error while the OISST and MURSST data showed the most obvious error. The results of comparing time series by extracting the SST data at the closest point to the IORS showed that there was an apparent seasonal variation not only in the in-situ temperature from the IORS but also in all the SST composite data. In spring, however, SST composite data tended to be overestimated compared to the in-situ temperature observed from the IORS.

How does the introduction of smart technology change school science inquiry?: Perceptions of elementary school teachers (스마트 기기 도입이 과학탐구 활동을 어떻게 변화시킬 것인가? -교육대학원 초등과학 전공 교사의 인식 사례를 중심으로-)

  • Chang, Jina;Joung, Yong Jae
    • Journal of The Korean Association For Science Education
    • /
    • v.37 no.2
    • /
    • pp.359-370
    • /
    • 2017
  • The purpose of this study is to explore the changes caused by using smart technology in school science inquiry. For this, we investigated 12 elementary school teachers' perceptions by using an open-ended questionnaire, group discussions, classroom discussions, and participant interviews. The results of this study indicate that the introduction of technology into classroom inquiry can open up the various possibilities and can cause additional burdens as well. First, teachers explained that smart technology can expand the opportunities to observe natural phenomena such as constellations and changing phases of the moon. However, some teachers insisted that, sometimes, learning how to use new devices disrupts students' concentration on the inquiry process itself. Second, teachers introduced the way of digital measurement using smart phone sensors in inquiry activities. They said that digital measurement is useful in terms of the reduction of errors and of the simplicity to measure. However, other teachers insisted that using new devices in classroom inquiry can entail additional variables and confuse the students' focus of inquiry. Communication about inquiry process can also be improved by using digital media. However, some teachers emphasized that they always talked about both the purpose of using SNS and online etiquettes with their students before using SNS. Based on these results, we discussed the necessity of additional analysis on the various ways of using digital devices depending on teachers' perceptions, the types of digital competency required in science inquiry using smart technology, and the features of norms shaped in inquiry activities using smart technology.

Repeatability and Reproducibility in Effective Porosity Measurements of Rock Samples (암석시험편 유효공극률 측정의 반복성과 재현성)

  • Lee, Tae Jong;Lee, Sang Kyu
    • Geophysics and Geophysical Exploration
    • /
    • v.15 no.4
    • /
    • pp.209-218
    • /
    • 2012
  • Repeatability and reproducibility in solid weight and effective porosity measurements have been discussed using 8 core samples with different diameters, lengths, rock types, and effective porosities. Further, the effect of temperature on the effective porosity measurement has been discussed as well. Effective porosity of each sample has been measured 7 times with vacuum saturation method with vacuum pressure of 1 torr and vacuum time of 80 minutes. Firstly, effective porosity of each sample is measured one by one, so that it can provide a reference value. Then for reproducibility check, effective porosity measurements with vacuum saturation of 2, 4, and 8 samples simultaneously have been performed. And finally, repeated measurements for 3 times for each sample are made for repeatability check. Average deviation from the reference set in solid weight showed 0.00 $g/cm^3$, which means perfect repeatability and reproducibility. For effective porosity, average deviations are less than 0.07% and 0.05% in repeatability and reproducibility test sets, respectively, which are in good agreement too. Most of porosities measured in reproducibility test lies within the deviation range in repeatability test sets. Thus, simultaneous vacuum saturation of several samples has little impact on the effective porosity measurement when high vacuum pressure of 1 torr is used. Air temperature can cause errors on submerged weight read and even effective porosity, because it is closely related to the temperature, density, and buoyancy of water. Consequently, for accurate measurement of effective porosity in a laboratory, efforts for maintaining air or water temperature constant during the experiment, or a temperature correction from other information are needed.

Methodological Comparison of the Quantification of Total Carbon and Organic Carbon in Marine Sediment (해양 퇴적물내 총탄소 및 유기탄소의 분석기법 고찰)

  • Kim, Kyeong-Hong;Son, Seung-Kyu;Son, Ju-Won;Ju, Se-Jong
    • Journal of the Korean Society for Marine Environment & Energy
    • /
    • v.9 no.4
    • /
    • pp.235-242
    • /
    • 2006
  • The precise estimation of total and organic carbon contents in sediments is fundamental to understand the benthic environment. To test the precision and accuracy of CHN analyzer and the procedure to quantify total and organic carbon contents(using in-situ acidification with sulfurous acid($H_2SO_3$)) in the sediment, the reference material s such as Acetanilide($C_8H_9NO$), Sulfanilammide($C_6H_8N_2O_2S$), and BCSS-1(standard estuary sediment) were used. The results indicate that CHN analyzer to quantify carbon and nitrogen content has high precision(percent error=3.29%) and accuracy(relative standard deviation=1.26%). Additionally, we conducted the instrumental comparison of carbon values analyzed using CHN analyzer and Coulometeric Carbon Analyzer. Total carbon contents measured from two different instruments were highly correlated($R^2=0.9993$, n=84, p<0.0001) with a linear relationship and show no significant differences(paired t-test, p=0.0003). The organic carbon contents from two instruments also showed the similar results with a significant linear relationship($R^2=0.8867$, n=84, p<0.0001) and no significant differences(paired t-test, p<0.0001). Although it is possible to overestimate organic carbon contents for some sediment types having high inorganic carbon contents(such as calcareous ooze) due to procedural and analytical errors, analysis of organic carbon contents in sediments using CHN Analyzer and current procedures seems to provide the best estimates. Therefore, we recommend that this method can be applied to measure the carbon content in normal any sediment samples and are considered to be one of the best procedure far routine analysis of total and organic carbon.

  • PDF

An Exploratory Study on the Competition Patterns Between Internet Sites in Korea (한국 인터넷사이트들의 산업별 경쟁유형에 대한 탐색적 연구)

  • Park, Yoonseo;Kim, Yongsik
    • Asia Marketing Journal
    • /
    • v.12 no.4
    • /
    • pp.79-111
    • /
    • 2011
  • Digital economy has grown rapidly so that the new business area called 'Internet business' has been dramatically extended as time goes on. However, in the case of Internet business, market shares of individual companies seem to fluctuate very extremely. Thus marketing managers who operate the Internet sites have seriously observed the competition structure of the Internet business market and carefully analyzed the competitors' behavior in order to achieve their own business goals in the market. The newly created Internet business might differ from the offline ones in management styles, because it has totally different business circumstances when compared with the existing offline businesses. Thus, there should be a lot of researches for finding the solutions about what the features of Internet business are and how the management style of those Internet business companies should be changed. Most marketing literatures related to the Internet business have focused on individual business markets. Specifically, many researchers have studied the Internet portal sites and the Internet shopping mall sites, which are the most general forms of Internet business. On the other hand, this study focuses on the entire Internet business industry to understand the competitive circumstance of online market. This approach makes it possible not only to have a broader view to comprehend overall e-business industry, but also to understand the differences in competition structures among Internet business markets. We used time-series data of Internet connection rates by consumers as the basic data to figure out the competition patterns in the Internet business markets. Specifically, the data for this research was obtained from one of Internet ranking sites, 'Fian'. The Internet business ranking data is obtained based on web surfing record of some pre-selected sample group where the possibility of double-count for page-views is controlled by method of same IP check. The ranking site offers several data which are very useful for comparison and analysis of competitive sites. The Fian site divides the Internet business areas into 34 area and offers market shares of big 5 sites which are on high rank in each category daily. We collected the daily market share data about Internet sites on each area from April 22, 2008 to August 5, 2008, where some errors of data was found and 30 business area data were finally used for our research after the data purification. This study performed several empirical analyses in focusing on market shares of each site to understand the competition among sites in Internet business of Korea. We tried to perform more statistically precise analysis for looking into business fields with similar competitive structures by applying the cluster analysis to the data. The research results are as follows. First, the leading sites in each area were classified into three groups based on averages and standard deviations of daily market shares. The first group includes the sites with the lowest market shares, which give more increased convenience to consumers by offering the Internet sites as complimentary services for existing offline services. The second group includes sites with medium level of market shares, where the site users are limited to specific small group. The third group includes sites with the highest market shares, which usually require online registration in advance and have difficulty in switching to another site. Second, we analyzed the second place sites in each business area because it may help us understand the competitive power of the strongest competitor against the leading site. The second place sites in each business area were classified into four groups based on averages and standard deviations of daily market shares. The four groups are the sites showing consistent inferiority compared to the leading sites, the sites with relatively high volatility and medium level of shares, the sites with relatively low volatility and medium level of shares, the sites with relatively low volatility and high level of shares whose gaps are not big compared to the leading sites. Except 'web agency' area, these second place sites show relatively stable shares below 0.1 point of standard deviation. Third, we also classified the types of relative strength between leading sites and the second place sites by applying the cluster analysis to the gap values of market shares between two sites. They were also classified into four groups, the sites with the relatively lowest gaps even though the values of standard deviation are various, the sites with under the average level of gaps, the sites with over the average level of gaps, the sites with the relatively higher gaps and lower volatility. Then we also found that while the areas with relatively bigger gap values usually have smaller standard deviation values, the areas with very small differences between the first and the second sites have a wider range of standard deviation values. The practical and theoretical implications of this study are as follows. First, the result of this study might provide the current market participants with the useful information to understand the competitive circumstance of the market and build the effective new business strategy for the market success. Also it might be useful to help new potential companies find a new business area and set up successful competitive strategies. Second, it might help Internet marketing researchers take a macro view of the overall Internet market so that make possible to begin the new studies on overall Internet market beyond individual Internet market studies.

  • PDF