• Steel and Composite Structures
• /
• 제6권6호
• /
• pp.531-555
• /
• 2006

H-shaped welded steel column members are fabricated by welding together pre-cut flanges and the web. Modern fabricators are increasingly using plasma-cutting technique instead of traditional flame cutting. Different fabrication techniques result in different degrees of geometric imperfections and residual stresses, which can have considerable influence on the strength of steel columns. This paper presents the experimental investigation based temperature profiles, geometric imperfections, and built-in residual stresses in plasma cut-welded H-shaped steel column members and in similar flame cut-welded H-shaped steel columns. Temperature measurements were taken during and immediately after the cutting operations and the welding operations. The geometric imperfections were established at closely spaced grid locations on the original plates, after cutting plates into plate strips, and after welding plate strips into columns. Geometric imperfections associated with plasma cut element and members were found to be less than those of the corresponding elements and members made by flame cutting. The "Method of Section" technique was used to establish the residual stresses in the plate, plate strip, and in the welded columns. Higher residual stress values were observed in flame cut-welded columns. Models for idealized residual stress distributions for plasma cut and flame cut welded sections have been proposed.

• Journal of Communications and Networks
• /
• 제4권4호
• /
• pp.266-281
• /
• 2002

The General Packet Radio Service (GPRS) is being deployed by GSM network operators world-wide, and promises to provide users with “always-on” data access at bandwidths comparable to that of conventional fixed-wire telephone modems. However, many users have found the reality to be rather different, experiencing very disappointing performance when, for example, browsing the web over GPRS. In this paper, we examine the causes, and show how unfortunate interactions between the GPRS link characteristics and TCP/IP protocols lead to poor performance. A performance characterization of the GPRS link-layer is presented, determined through extensive measurements taken over production networks. We present measurements of packet loss rates, bandwidth availability, link stability, and round-trip time. The effect these characteristics have on TCP behavior are examined, demonstrating how they can result in poor link utilization, excessive packet queueing, and slow recovery from packet losses. Further, we show that the HTTP protocol can compound these issues, leading to dire WWW performance. We go on to show how the use of a transparent proxy interposed near the wired-wireless border can be used to alleviate many of these performance issues without requiring changes to either client or server end systems.

• 한국건설관리학회:학술대회논문집
• /
• 한국건설관리학회 2006년도 정기학술발표대회 논문집
• /
• pp.92-97
• /
• 2006

지금까지 건설산업은 재무 중심의 성과측정에 주로 의존하여 왔다. 또한 성과측정시스템에 관한 연구는 대부분 프로젝트 레벨에서 이루어졌다. 그러나 최근 들어 산업 또는 기업 레벨의 성과측정 및 관리에 대한 요구가 높아지고 있다. 최근의 몇몇 선행연구들은 기업 레벨의 성과측정을 위한 지표, 측정방법, 개념적 모델 등을 제시한 바 있다. 본 연구는 이러한 연구 결과들을 활용하여 건설산업 참여기업들(발주기업, 건설회사, 설계 ${\cdot}$ 엔지니어링회사)을 위한 web 기반의 성과 및 정보화수준 측정 시스템을 개발하였다. 또한 국내의 78개 기업들로부터 수집한 성과 데이터를 이용한 시스템 테스트 및 성과분석을 수행하였으며, 마지막으로 시스템의 개선 및 효과적 활용을 위한 이슈들을 제시하였다.

• 한국측량학회지
• /
• 제22권2호
• /
• pp.145-150
• /
• 2004

웹 기반 GPS 자료처리 시스템의 프로토콜을 개발하였다. 다양한 사용자가 획득한 GPS 자료를 웹을 통하여 전송하고 또한 결과를 전송 받을 수 있도록 하였으며, 특히 이기종(different operating system)의 클라이언트를 보유하는 다수의 사용자들의 GPS 자료를 수신 받아 사용자가 원하는 자료 처리 컴포넌트로 자료를 처리하여 결과를 사용자에게 전송하는 전형적인 ASP(Application Service Provider) 시스템으로 구성되었다. 또한 새로운 알고리즘의 업그레이드가 용이하도록 하였으며, 비동기 방식의 자료 처리로 인하여 효과적인 다중 접속의 운용과 높은 사용자의 유연성을 구현하였다. 효율적인 GPS 자료의 관리 및 운용을 위한 데이터베이스 컴포넌트도 함께 개발되어 향후 상시관측소등의 자료를 활용할 수 있도록 하였다. 현재 자료처리 모듈은 코드를 이용한 절대 및 상대측위가 완성되었으며, 향후 사용자 자료의 질적 조정, 반송파를 이용한 자료 처리 등의 다양한 자료처리 모듈이 포함될 예정이다.

• 한국수산과학회지
• /
• 제54권2호
• /
• pp.194-207
• /
• 2021

It is necessary to assess and manage the different elements of the marine ecosystem, such as climate change, habitat, primary and secondary production, energy flow, food web, potential yield, and fishing, to maintain the health of the ecosystem as well as support sustainable development of fishery. We set up an ecosystem model around the Korean peninsula to produce scientific predictions necessary for the assessment and management of marine ecosystems and presented the usability of the model with scenario experiments. We used the Atlantis ecosystem model based on the marine food web; Atlantis is a three-dimensional end-to-end model that includes the information and processes within an entire system, from an abiotic environment to human activity. We input the ecological and biological parameters, such as growth, mortality, spawning, recruitment, and migration, to the Atlantis model via functional groups using existing research and local measurements. During the simulation period (2018-2019), we confirmed that the model reproduced the observed data reasonably and reflected the actual ecosystem characteristics appropriately. We thus identified the usability of a marine ecosystem model with experiments on different environmental change scenarios.

• 한국컴퓨터산업학회논문지
• /
• 제5권3호
• /
• pp.383-392
• /
• 2004

전자게시판은 비동기적으로 생각을 교환하고 정보를 공유하는 적절한 매체로써 널리 인식되어왔다. 게시판의 의사소통 능력은 협력학습을 위한 도구로 사용하는 주된 이유이다. 최근 이 분야의 연구자들은 게시판의 교육적 활용에 대한 연구결과를 다수 보고하고 있다. 이 논문에서는 게시판에서의 의사소통 활동을 측정함으로써 토의 참여자들의 복잡한 토의 행동을 정량적으로 이해할 수 있는 분석적 방법을 제안한다 토의 집단이나 개인들의 토의 행동을 기술하기 위한 특성 벡터를 제안한다. 이 특성 벡터는 토의 집단과 개인에 대한 특성화와 비교를 편리하게 할 수 있도록 한다. 상호작용 활동을 표현하는 상호작용 모델은 토의 그룹과 개인에 대한 상호작용 정도를 시각적으로 나타낸 준다. 또한, 시간에 따른 토의 활동을 분석하기 위해 시간 종속적인 측정을 탐구한다. 전자 게시판을 사용한 웹 기반 토의 프로젝트를 통하여 제안한 측정이 어떻게 이루어지는지, 또 특성 벡터와 상호작용 모델이 어떻게 구축되고 사용되는지를 실험을 통하여 보여준다.

• 대한통합의학회지
• /
• 제9권4호
• /
• pp.149-158
• /
• 2021

Purpose : Forward head posture (FHP) is one of the most common postural malalignment of the cranio-cervical region. Previous studies have reported that FHP might affect both temporomandibular joint (TMJ) and cervical muscles, but still remains unclear. The purpose of this study was to compare the changes of craniovertebral angle (CVA) and muscle properties after smartphone use in healthy individuals with and without FHP. Methods : Fifteen healthy individuals aged 18 to 22 years were included. CVA was evaluated using Dartfish motion analysis, and the subjects were divided into two groups according to their CVA: a FHP group (n = 7, CVA less than 48 °) and a control group (n = 8, CVA more than 48 °). MyotonPro was used to measure muscle properties of masseter, digastric and sternocleidomastoid muscles (SCM). Each subject underwent 15-minutes of smartphone task (web browsing or video watching) in relaxed sitting posture. CVA and muscles properties were assessed both before and after the smartphone task. Results : There were significant changes in post measurements of CVA between the groups. Masseter muscle showed significant differences in pre and post measurements of all muscle properties, and digastric muscle showed significance only in muscle tone. Amount of changes (post-pre), however, showed no significant difference in this study. Conclusion : 15-minutes of smartphone task did not affect CVA and muscle properties of masseter, digastric and SCM in both groups, however, there were significant changes in pre and post measurements of CVA and some muscle properties of masseter and digastric muscles. Therefore, CVA, masseter and digastric muscles might be significantly changed in a heavy duration of smartphone usage more than 15-minutes. Further studies are needed regarding duration of smartphone task, assessments in other various TMJ muscle groups, and participants with pathological FHP conditions.

• International Journal of Contents
• /
• 제11권1호
• /
• pp.41-51
• /
• 2015

Management systems for electronic library have been developed on the basis of Client/Server or ASP framework in domestic market for a long time. Therefore, both service provider and user suffer from their high cost and effort in management, maintenance, and repairing of software as well as hardware. Recently in addition, mobile devices like smartphone and tablet PC are frequently used as terminal devices to access computers through the Internet or other networks, sophisticatedly customized or personalized interface for n-screen service became more important issue these days. In this paper, we propose a new scheme of integrated management system for electronic library based on SaaS and Web Standard. We design and implement the proposed scheme applying Electronic Cabinet Guidelines for Web Standard and Universal Code System. Hosted application management style and software on demand style service models based on SaaS are basically applied to develop the management system. Moreover, a newly improved concept of duplication check algorithm in a hierarchical evaluation process is presented and a personalized interface based on web standard is applied to implement the system. Algorithms of duplication check for journal, volume/number, and paper are hierarchically presented with their logic flows. Total framework of our development obeys the standard feature of Electronic Cabinet Guidelines offered by Korea government so that we can accomplish standard of application software, quality improvement of total software, and reusability extension. Scope of our development includes core services of library automation system such as acquisition, list-up, loan-and-return, and their related services. We focus on interoperation compatibility between elementary sub-systems throughout complex network and structural features. Reanalyzing and standardizing each part of the system under the concept on the cloud of service, we construct an integrated development environment for generating, test, operation, and maintenance. Finally, performance analyses are performed about resource usability of server, memory amount used, and response time of server etc. As a result of measurements fulfilled over 5 times at different test points and using different data, the average response time is about 62.9 seconds for 100 clients, which takes about 0.629 seconds per client on the average. We can expect this result makes it possible to operate the system in real-time level proof. Resource usability and memory occupation are also good and moderate comparing to the conventional systems. As total verification tests, we present a simple proof to obey Electronic Cabinet Guidelines and a record of TTA authentication test for topics about SaaS maturity, performance, and application program features.

• Safety and Health at Work
• /
• 제10권4호
• /
• pp.452-460
• /
• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• ALGAE
• /
• 제19권2호
• /
• pp.149-151
• /
• 2004

Freshwater algae make up a very important portion of the autotrophic component of the aquatic food web. Therefore, the study of freshwater algal structure and biomass is central to aquatic ecosystem studies. Due to variations in cell shape and size for each species (or taxon) and survey site, cell abundance (or cell numbers per chosen volume) often leads to misrepresentation of the true importance of some species because of the great differences in size of various algae. Thus, it is necessary to investigate the freshwater algal species of a site in order to calculate the cell volume. Although direct cell counting, species volume measurement, as well as biomass calculation are time-consuming and requiring specialists in taxonomy.