• 제목/요약/키워드: Improved operating characteristics

검색결과 335건 처리시간 0.024초

Speed-Power Performance Analysis of an Existing 8,600 TEU Container Ship using SPA(Ship Performance Analysis) Program and Discussion on Wind-Resistance Coefficients

  • Shin, Myung-Soo;Ki, Min Suk;Park, Beom Jin;Lee, Gyeong Joong;Lee, Yeong Yeon;Kim, Yeongseon;Lee, Sang Bong
    • 한국해양공학회지
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    • 제34권5호
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    • pp.294-303
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    • 2020
  • This study discusses data collection, calculation of wind and wave-induced resistance, and speed-power analysis of an 8,600 TEU container ship. Data acquisition system of the ship operator was improved to obtain the data necessary for the analysis, which was accomplished using SPA (Ship Performance Analysis, Park et al., 2019) in conformation with ISO15016:2015. From a previous operation profile of the container, the standard operating conditions of mean draft were 12.5 m and 13.6 m, which were defined with the mean stowage configuration of each condition. Model tests, including the load-variation test, were conducted to validate new ship performance and for the speed-power analysis. The major part of the added resistance of container ship is due to the wind. To check the reliability of wind-resistance calculation results, the resistance coefficients, added resistance, and speed-power analysis results using the Fujiwara regression formula (ISO15016:2015) and Computational fluid dynamics (Ryu et al., 2016; Jeon et al., 2017) analysis were compared. Wind speed and direction measured using an anemometer were used for wind-resistance calculation and the wave resistance was calculated using the wave-height and direction-data from weather information. Also, measured water temperature was used to calculate the increase in resistance owing to the deviation in water density. As a result, the SPA analysis using measured data and weather information was proved to be valid and able to identify the ship's resistance propulsion performance. Even with little difference in the air-resistance coefficient value, both methods provide sufficient accuracy for speed-power analysis. The differences were unnoticeable when the speed-power analysis results using each method were compared. Also, speed-power analysis results of the 8,600 TEU container ship in two draft conditions show acceptable trends when compared with the model test results and are also able to show power increase owing to hull fouling and aging. Thus, results of speed-power analysis of the existing 8,600 TEU container ship using the SPA program appropriately exhibit the characteristics of speed-power performance in deal conditions.

해양 초고속 통신망 시스템을 위한 WLAN(Wireless Local Area Network) / UWB(Ultra Wide Band)용 안테나 설계 및 제작 (Design and Fabrication of WLAN / UWB Antenna for Marine High Speed Communication Network System)

  • 홍용표;강성운;김갑기
    • 해양환경안전학회지
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    • 제24권4호
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    • pp.489-495
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    • 2018
  • 본 논문에서는 안테나의 소형화, 이득 및 방사패턴을 개선한 초고속 통신망 시스템을 효과적으로 사용하기 위해 3.3 [GHz], 5 [GHz] 대역에서 동작하는 WLAN/UWB 통신용 안테나를 설계 및 제작을 하였다. 대역폭의 개선을 위해 마이크로스트립 패치 안테나를 선택하였고 각 단계마다 이론적인 근거에 의한 수식을 이용하여 슬롯의 폭, 길이, 전송선로의 폭 등을 계산하였다. 설계된 안테나의 시뮬레이션 결과 반사손실이 3.3 [GHz]에서 -14.053 [dB]이고 5 [GHz]에서 -13.118 [dB]의 값을 보여주었다. 이득은 3.3 [GHz]에서 2.479 [dBi]의 값과 5[GHz]에서 3.317[dBi]의 수치를 보여주었다. 또한 3D 설계가 가능한 CST Microwave Studio 2014 프로그램을 이용하여 최적화 한 후, 이를 바탕으로 제작한 안테나의 특성을 측정하여 성능을 확인하는 방법으로 연구를 진행하였다. 최근 다양하고 발전이 계속 이루어지고 있는 무선 기술인 WLAN과 해당 기술 이용자의 수요 증가에 따른 기술의 주파수 대역도 역시 증가하고 있는 추세의 통신 기술인 UWB을 초고속 무선 통신 시스템으로 사용하는 데 있어 불편함 없도록 해당 이용자를 위한 원활한 통신이 가능할 것으로 보인다.

복합에너지시스템의 성능개선에 관한 연구 (A Study on System Retrofit of Complex Energy System)

  • 최정훈;문채주;장영학
    • 한국전자통신학회논문지
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    • 제16권1호
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    • pp.61-68
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    • 2021
  • 풍력이나 태양광 같은 재생에너지의 활용은 온실가스 감축과 경제성 확보를 얻기 위해서 많은 나라에서 피할 수 없는 선택이 되고 있다. 그러나 재생에너지의 간헐성 때문에 계통으로 연계되는 재생에너지의 비중이 커지게 되어 얻어지는 문제가 더욱 크게 부각되고 있다. 복합에너지시스템은 일반적으로 2개 이상의 재생에너지원이 서로 함께 사용되면서 시스템 효율을 증가시킬 뿐만 아니라 에너지 공급에서 더욱 안정적이다. 전력시스템을 비교해 보면 복합에너지시스템의 제어 및 최적화는 모델링, 운전 및 운영계획의 요소가 더욱 어려워진다. 마이크로그리드시스템을 갖는 삼마도에 대한 복합에너지시스템 성능개선의 주 목적은 다양한 분산전원, 에너지저장장치, 전력계통의 신뢰성을 확보하기 위해서 상호 조화롭게 조정하는 것으로 운전비용을 줄이고 최상의 경제적인 이득을 얻기 위한 것이다. 본 논문은 최적의 마이크로그리드시스템을 갖는 개선된 삼마도 복합에너지시스템을 제안한다. 시험운전결과 ESS의 SOC 변동폭이 약 12%로 낮아졌으며, 태양광 발전제약이 제거되었고, 디젤발전기의 운전시간이 감소함을 확인할 수 있었다.

전이 학습을 이용한 선박 기관실 기기의 분류에 관한 연구 (Machine Classification in Ship Engine Rooms Using Transfer Learning)

  • 박경민
    • 해양환경안전학회지
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    • 제27권2호
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    • pp.363-368
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    • 2021
  • 선박 기관실은 기술의 발전으로 인해 자동화 시스템이 향상되었지만, 해상에서는 바람, 파도, 진동, 기기 노후화 등의 다양한 변수가 많아 자동화 시스템에서 계측되지 않는 풀림, 절단, 누유, 누수 등이 발생하므로 기관사는 주기적으로 순찰을 한다. 순찰 시에는 1명의 기관사만 순찰하는 경우도 있으며, 이는 고온고압 및 회전기기가 운전 중인 기관실에서 많은 위험요소를 가지고 있다. 기관사가 순찰 시에는 오감을 활용하며, 특히 시각에 의존한다. 본 논문에서는 로봇이 기관실을 순찰하며 기기의 특이사항을 검출하고 알려주는 기관실 순찰 로봇을 구현하기 위한 선행연구로서 선박 기관실 기기의 이미지를 합성곱 신경망을 이용하여 분류하였다. 선박 기관실의 이미지 데이터 셋을 구성한 후 사전 훈련된 합성곱 신경망 모델로 학습하였다. 학습한 모델의 분류 성능은 높은 재현율을 보였으며, 클래스 활성화 맵으로 이미지를 시각화 하였다. 데이터의 양이 제한적이어서 일반화할 수는 없지만, 각 선박의 데이터를 전이학습으로 학습시키면 적은 시간과 비용으로 각 선박의 특성에 맞는 모델을 구축할 수 있을 것으로 사료된다.

Andersen과 Newman의 행동모델을 적용한 경로당 이용 영향요인에 관한 연구: 이용자 만족도 매개효과 분석 (A Study on the Factors Affecting the Use of Senior Center Applying Andersen and Newman's Behavior Model: Analysis of Mediating Effect of User Satisfaction)

  • 김정근
    • 한국노년학
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    • 제40권2호
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    • pp.291-309
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    • 2020
  • 본 연구는 Andersen과 Newman(1973)의 행동모델을 적용하여 지역사회 노인들의 경로당 이용에 영향을 미치는 요인을 규명하고, 이용자 만족도의 매개효과를 검증하여 경로당 이용 노인의 만족도 향상 및 경로당 운영 활성화를 위한 정책적·실천적 대안을 제시하고자 하였다. 연구대상자는 부산지역 2,283개소 경로당 이용 노인 578명이다. 연구결과, 경로당 총 이용기간에 영향을 미치는 요인은 선행요인 중 연령, 가능성 요인 중 경로당 유형으로 분석되었으며, 1주일간 경로당 총 이용일 수에 영향을 미치는 요인은 선행요인 중 성별, 연령, 교육수준으로 나타났다. 매개변수인 이용자 만족도에 영향을 미치는 요인은 선행요인 중 성별, 연령, 욕구요인 중 주관적 건강상태로 분석되었다. 이용자 만족도 매개효과 검증 결과, 연령과 경로당 총 이용기간 사이에는 부분 매개효과, 성별과 1주일간 경로당 이용일 수 사이에는 완전 매개효과, 연령과 1주일간 경로당 이용일 수 사이에는 부분 매개효과가 있는 것으로 분석되었다. 연구의 목적과 주요 결과에 따라 경로당 이용자 만족도 및 이용 활성화를 위한 정책적·실천적 제언은 다음과 같다. 첫째, 경로당 이용자 특성에 따른 프로그램 개발과 지원이 요구된다. 둘째, 경로당 유형 및 지역적 환경에 따라 경로당을 특성화 할 필요성이 있다. 셋째, 경로당 운영비 지원 기준 개선과 인상이 필요하다.

T1 Map-Based Radiomics for Prediction of Left Ventricular Reverse Remodeling in Patients With Nonischemic Dilated Cardiomyopathy

  • Suyon Chang;Kyunghwa Han;Yonghan Kwon;Lina Kim;Seunghyun Hwang;Hwiyoung Kim;Byoung Wook Choi
    • Korean Journal of Radiology
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    • 제24권5호
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    • pp.395-405
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    • 2023
  • Objective: This study aimed to develop and validate models using radiomics features on a native T1 map from cardiac magnetic resonance (CMR) to predict left ventricular reverse remodeling (LVRR) in patients with nonischemic dilated cardiomyopathy (NIDCM). Materials and Methods: Data from 274 patients with NIDCM who underwent CMR imaging with T1 mapping at Severance Hospital between April 2012 and December 2018 were retrospectively reviewed. Radiomic features were extracted from the native T1 maps. LVRR was determined using echocardiography performed ≥ 180 days after the CMR. The radiomics score was generated using the least absolute shrinkage and selection operator logistic regression models. Clinical, clinical + late gadolinium enhancement (LGE), clinical + radiomics, and clinical + LGE + radiomics models were built using a logistic regression method to predict LVRR. For internal validation of the result, bootstrap validation with 1000 resampling iterations was performed, and the optimism-corrected area under the receiver operating characteristic curve (AUC) with 95% confidence interval (CI) was computed. Model performance was compared using AUC with the DeLong test and bootstrap. Results: Among 274 patients, 123 (44.9%) were classified as LVRR-positive and 151 (55.1%) as LVRR-negative. The optimism-corrected AUC of the radiomics model in internal validation with bootstrapping was 0.753 (95% CI, 0.698-0.813). The clinical + radiomics model revealed a higher optimism-corrected AUC than that of the clinical + LGE model (0.794 vs. 0.716; difference, 0.078 [99% CI, 0.003-0.151]). The clinical + LGE + radiomics model significantly improved the prediction of LVRR compared with the clinical + LGE model (optimism-corrected AUC of 0.811 vs. 0.716; difference, 0.095 [99% CI, 0.022-0.139]). Conclusion: The radiomic characteristics extracted from a non-enhanced T1 map may improve the prediction of LVRR and offer added value over traditional LGE in patients with NIDCM. Additional external validation research is required.

Added Value of Chemical Exchange-Dependent Saturation Transfer MRI for the Diagnosis of Dementia

  • Jang-Hoon Oh;Bo Guem Choi;Hak Young Rhee;Jin San Lee;Kyung Mi Lee;Soonchan Park;Ah Rang Cho;Chang-Woo Ryu;Key Chung Park;Eui Jong Kim;Geon-Ho Jahng
    • Korean Journal of Radiology
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    • 제22권5호
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    • pp.770-781
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    • 2021
  • Objective: Chemical exchange-dependent saturation transfer (CEST) MRI is sensitive for detecting solid-like proteins and may detect changes in the levels of mobile proteins and peptides in tissues. The objective of this study was to evaluate the characteristics of chemical exchange proton pools using the CEST MRI technique in patients with dementia. Materials and Methods: Our institutional review board approved this cross-sectional prospective study and informed consent was obtained from all participants. This study included 41 subjects (19 with dementia and 22 without dementia). Complete CEST data of the brain were obtained using a three-dimensional gradient and spin-echo sequence to map CEST indices, such as amide, amine, hydroxyl, and magnetization transfer ratio asymmetry (MTRasym) values, using six-pool Lorentzian fitting. Statistical analyses of CEST indices were performed to evaluate group comparisons, their correlations with gray matter volume (GMV) and Mini-Mental State Examination (MMSE) scores, and receiver operating characteristic (ROC) curves. Results: Amine signals (0.029 for non-dementia, 0.046 for dementia, p = 0.011 at hippocampus) and MTRasym values at 3 ppm (0.748 for non-dementia, 1.138 for dementia, p = 0.022 at hippocampus), and 3.5 ppm (0.463 for non-dementia, 0.875 for dementia, p = 0.029 at hippocampus) were significantly higher in the dementia group than in the non-dementia group. Most CEST indices were not significantly correlated with GMV; however, except amide, most indices were significantly correlated with the MMSE scores. The classification power of most CEST indices was lower than that of GMV but adding one of the CEST indices in GMV improved the classification between the subject groups. The largest improvement was seen in the MTRasym values at 2 ppm in the anterior cingulate (area under the ROC curve = 0.981), with a sensitivity of 100 and a specificity of 90.91. Conclusion: CEST MRI potentially allows noninvasive image alterations in the Alzheimer's disease brain without injecting isotopes for monitoring different disease states and may provide a new imaging biomarker in the future.

A Prospective Study on the Value of Ultrasound Microflow Assessment to Distinguish Malignant from Benign Solid Breast Masses: Association between Ultrasound Parameters and Histologic Microvessel Densities

  • Ah Young Park;Myoungae Kwon;Ok Hee Woo;Kyu Ran Cho;Eun Kyung Park;Sang Hoon Cha;Sung Eun Song;Ju-Han Lee;JaeHyung Cha;Gil Soo Son;Bo Kyoung Seo
    • Korean Journal of Radiology
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    • 제20권5호
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    • pp.759-772
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    • 2019
  • Objective: To investigate the value of ultrasound (US) microflow assessment in distinguishing malignant from benign solid breast masses as well as the association between US parameters and histologic microvessel density (MVD). Materials and Methods: Ninety-eight breast masses (57 benign and 41 malignant) were examined using Superb Microvascular Imaging (SMI) and contrast-enhanced US (CEUS) before biopsy. Two radiologists evaluated the quantitative and qualitative vascular parameters on SMI (vascular index, morphology, distribution, and penetration) and CEUS (time-intensity curve analysis and enhancement characteristics). US parameters were compared between benign and malignant masses and the diagnostic performance was compared between SMI and CEUS. Subgroup analysis was performed according to lesion size. The effect of vascular parameters on downgrading Breast Imaging Reporting and Data System (BI-RADS) category 4A masses was evaluated. The association between histologic MVD and US parameters was analyzed. Results: Malignant masses were associated with a higher vascular index (15.1 ± 7.3 vs. 5.9 ± 5.6), complex vessel morphology (82.9% vs. 42.1%), central vascularity (95.1% vs. 59.6%), penetrating vessels (80.5% vs. 31.6%) on SMI (all, p < 0.001), as well as higher peak intensity (37.1 ± 25.7 vs. 17.0 ± 15.8, p < 0.001), slope (10.6 ± 11.2 vs. 3.9 ± 4.2, p = 0.001), area (1035.7 ± 726.9 vs. 458.2 ± 410.2, p < 0.001), hyperenhancement (95.1% vs. 70.2%, p = 0.005), centripetal enhancement (70.7% vs. 45.6%, p = 0.023), penetrating vessels (65.9% vs. 22.8%, p < 0.001), and perfusion defects (31.7% vs. 3.5%, p < 0.001) on CEUS (p ≤ 0.023). The areas under the receiver operating characteristic curve (AUCs) of SMI and CEUS were 0.853 and 0.841, respectively (p = 0.803). In 19 masses measuring < 10 mm, central vascularity on SMI was associated with malignancy (100% vs. 38.5%, p = 0.018). Considering all benign SMI parameters on the BI-RADS assessment, unnecessary biopsies could be avoided in 12 category 4A masses with improved AUCs (0.500 vs. 0.605, p < 0.001). US vascular parameters associated with malignancy showed higher MVD (p ≤ 0.016). MVD was higher in malignant masses than in benign masses, and malignant masses negative for estrogen receptor or positive for Ki67 had higher MVD (p < 0.05). Conclusion: US microflow assessment using SMI and CEUS is valuable in distinguishing malignant from benign solid breast masses, and US vascular parameters are associated with histologic MVD.

네트워크 구조와 조직학습문화, 지식경영참여가 개인창의성 및 성과에 미치는 영향에 관한 실증분석: SI제안팀과 R&D팀의 비교연구 (Exploring Influence of Network Structure, Organizational Learning Culture, and Knowledge Management Participation on Individual Creativity and Performance: Comparison of SI Proposal Team and R&D Team)

  • 이건창;서영욱;채성욱;송석우
    • Asia pacific journal of information systems
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    • 제20권4호
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    • pp.101-123
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    • 2010
  • Recently, firms are operating a number of teams to accomplish organizational performance. Especially, ad hoc teams like proposal preparation team are quite different from permanent teams like R&D team in the sense of how the team forms network structure and deals with organizational learning culture and knowledge management participation efforts. Moreover, depending on the team characteristics, individual creativity will differ from each other, which will lead to organizational performance eventually. Previous studies in the field of creativity are lacking in this issue. So main objectives of this study are organized as follows. First, the issue of how to improve individual creativity and organizational performance will be analyzed empirically. This issue will be performed depending on team characteristics such as ad hoc team and permanent team. Antecedents adopted for this research objective are cultural and knowledge factors such as organizational learning culture, and knowledge management participation. Second, the network structure such as degree centrality, and structural hole is used to analyze its influence on individual creativity and organizational performance. SI (System Integration) companies are facing severely tough requirements from clients to submit very creative proposals. Also, R&D teams are widely accepted as relatively creative teams because their responsibilities are focused on suggesting innovative techniques to make their companies remain competitive in the market. SI teams are usually ad hoc, while R&D teams are permanent on an average. By taking advantage of these characteristics of the two kinds of teams, we will prove the validity of the proposed research questions. To obtain the survey data, we accessed 7 SI teams (74 members), and 6 R&D teams (63 members), collecting 137 valid questionnaires. PLS technique was applied to analyze the survey data. Results are as follows. First, in case of SI teams, organizational learning culture affects individual creativity significantly. Meanwhile, knowledge management participation has a significant influence on Individual creativity for the permanent teams. Second, degree centrality Influences individual creativity significantly in case of SI teams. This is comparable with the fact that structural hole has a significant impact on individual creativity for the R&D teams. Practical implications can be summarized as follows: First, network structure of ad hoc team should be designed differently from one of permanent team. Ad hoc team is supposed to show a high creativity in a rather short period, implying that network density among team members should be improved, and those members with high degree centrality should be encouraged to show their Individual creativity and take a leading role by allowing them to get heavily engaged in knowledge sharing and diffusion. In contrast, permanent team should be designed to take advantage of structural hole instead of focusing on network density. Since structural hole can be utilized very effectively in the permanent team, strong arbitrators' merits in the permanent team will increase and therefore helps increase both network efficiency and effectiveness too. In this way, individual creativity in the permanent team is likely to lead to organizational creativity in a seamless way. Second, way of Increasing individual creativity should be sought from the perspective of organizational culture and knowledge management. Organization is supposed to provide a cultural atmosphere in which Innovative idea suggestions and active discussion among team members are encouraged. In this way, trust builds up among team members, facilitating the formation of organizational learning culture. Third, in the ad hoc team, organizational looming culture should be built such a way that individual creativity can grow up fast in a rather short period. Since time is tight, reasonable compensation policy, leader's Initiatives, and learning culture formation should be done In a short period so that mutual trust is built among members quickly, and necessary knowledge and information can be learnt rapidly. Fourth, in the permanent team, it should be kept in mind that the degree of participation in knowledge management determines level of Individual creativity. Therefore, the team ought to facilitate knowledge circulation process such as knowledge creation, storage, sharing, utilization, and learning among team members, which will lead to team performance. In this way, firms must control knowledge networks in permanent team and ad hoc team in a way mentioned above so that individual creativity as well as team performance can be maximized.

고상법으로 합성된 리튬이온 이차전지용 음극물질로서 전이금속 피로인산화물의 전기화학적 특성 (Electrochemical Characteristics of Transition Metal Pyrophosphate as Negative Electrode Materials through Solid-state Reaction)

  • 홍민영;안상조;류지헌
    • 전기화학회지
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    • 제23권4호
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    • pp.105-112
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    • 2020
  • 리튬이온 이차전지용 음극 활물질 중 전환반응을 거치는 전이금속 산화물은 높은 용량을 지니고 있으나, 아직 해결되어야 하는 여러 문제점을 지니고 있다. 본 연구에서는 새로운 음극 활물질로써 망간 피로인산화물(Mn2P2O7) 및 니켈 피로인산화물(Ni2P2O7)과 이를 포함하는 탄소 복합물질을 고상법으로 간단하게 합성하였다. 망간 피로인산화물 및 니켈 피로인산화물의 초기 가역용량은 각각 333 및 340 mAh g-1의 용량을 나타내었으며, 탄소와 복합재료를 구성하면 각각 433 및 387 mAh g-1로 가역용량이 증가하였을 뿐만 아니라 초기효율도 약 10% 정도 향상되었다. 망간 피로인산화물과 탄소와의 복합재료로 구성된 활물질이 가장 높은 초기용량과 효율을 지니며, 사이클 성능도 가장 우수하였다. 다중 음이온을 포함하는 망간 피로인산화물은 망간 산화물인 MnO와 비교하였을 때, 음이온의 질량이 크기 때문에 무게당 용량은 낮았지만, 전압곡선이 기울기를 지니는 형태를 나타내면서 충전(lithiation)전압은 0.51에서 0.57 V (vs. Li/Li+)로 높아지고, 방전(delithiation)전압은 1.15에서 1.01 V (vs. Li/Li+)로 낮아졌다. 따라서, 충전과 방전에서의 전압차이가 0.64 에서 0.44 V로 크게 감소하므로 전지의 전압효율이 개선되며, 방전과정에서 음극전위가 낮아지게 되어 완전지의 작동전압을 높일 수 있다.