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Sacubitril/valsartan is superior to enalapril in reducing the risks of cardiovascular death and preventing hospitalization in patients with heart failure and reduced ejection fraction (HFrEF). However, patients often do not receive sacubitril/valsartan because of concerns about hypotension. We examined the feasibility of initiating sacubitril/valsartan at a very low dose (VLD) in potentially intolerant patients with HFrEF and subsequent dose up-titration, treatment persistence and outcomes. We analyzed 206 patients with HFrEF grouped according to starting sacubitril/valsartan dose. The VLD group (n = 106) commenced 25 mg twice daily, and the standard-dose (SD) group (n = 100) started on ≥ 50 mg twice daily. Baseline systolic blood pressure was 103 ± 12 mmHg vs. 119 ± 14 mmHg in the SD group (P

To identify the agreement on Lung CT Screening Reporting and Data System 4X categorization between radiologists and an expert-adjudicated reference standard and to investigate whether training led to improvement of the agreement measures and diagnostic potential for lung cancer. Category 4 nodules in the Korean Lung Cancer Screening Project were identified retrospectively, and each 4X nodule was matched with one 4A or 4B nodule. An expert panel re-evaluated the categories and determined the reference standard. Nineteen radiologists were asked to determine the presence of CT features of malignancy and 4X categorization for each nodule. A review was performed in two sessions, and training material was given after session 1. Agreement on 4X categorization between radiologists and the expert-adjudicated reference standard and agreement between radiologist-assessed 4X categorization and lung cancer diagnosis were evaluated. The 48 expert-adjudicated 4X nodules and 64 non-4X nodules were evenly distributed in each session. The proportion of category 4X decreased after training (56.4% ± 16.9% vs. 33.4% ± 8.0%; p 0.05). All agreement measures between radiologist-assessed 4X categorization and lung cancer diagnosis increased in session 2 (p < 0.05). Radiologist training can improve reader agreement on 4X categorization, leading to enhanced diagnostic performance for lung cancer. • Agreement on 4X categorization between radiologists and an expert-adjudicated reference standard was initially poor, but improved significantly after training. • The mean proportion of 4X categorization by 19 radiologists decreased from 56.4% ± 16.9% in session 1 to 33.4% ± 8.0% in session 2. • All agreement measures between the 4X categorization and lung cancer diagnosis increased significantly in session 2, implying that appropriate training and guidance increased the diagnostic potential of category 4X.

The efficient and accurate interpretation of radiologic images is paramount.To evaluate whether a deep learning-based artificial intelligence (AI) engine used concurrently can improve reader performance and efficiency in interpreting chest radiograph abnormalities.This multicenter cohort study was conducted from April to November 2021 and involved radiologists, including attending radiologists, thoracic radiology fellows, and residents, who independently participated in 2 observer performance test sessions. The sessions included a reading session with AI and a session without AI, in a randomized crossover manner with a 4-week washout period in between. The AI produced a heat map and the image-level probability of the presence of the referrable lesion. The data used were collected at 2 quaternary academic hospitals in Boston, Massachusetts: Beth Israel Deaconess Medical Center (The Medical Information Mart for Intensive Care Chest X-Ray [MIMIC-CXR]) and Massachusetts General Hospital (MGH).The ground truths for the labels were created via consensual reading by 2 thoracic radiologists. Each reader documented their findings in a customized report template, in which the 4 target chest radiograph findings and the reader confidence of the presence of each finding was recorded. The time taken for reporting each chest radiograph was also recorded. Sensitivity, specificity, and area under the receiver operating characteristic curve (AUROC) were calculated for each target finding.A total of 6 radiologists (2 attending radiologists, 2 thoracic radiology fellows, and 2 residents) participated in the study. The study involved a total of 497 frontal chest radiographs-247 from the MIMIC-CXR data set (demographic data for patients were not available) and 250 chest radiographs from MGH (mean [SD] age, 63 [16] years; 133 men [53.2%])-from adult patients with and without 4 target findings (pneumonia, nodule, pneumothorax, and pleural effusion). The target findings were found in 351 of 497 chest radiographs. The AI was associated with higher sensitivity for all findings compared with the readers (nodule, 0.816 [95% CI, 0.732-0.882] vs 0.567 [95% CI, 0.524-0.611]; pneumonia, 0.887 [95% CI, 0.834-0.928] vs 0.673 [95% CI, 0.632-0.714]; pleural effusion, 0.872 [95% CI, 0.808-0.921] vs 0.889 [95% CI, 0.862-0.917]; pneumothorax, 0.988 [95% CI, 0.932-1.000] vs 0.792 [95% CI, 0.756-0.827]). AI-aided interpretation was associated with significantly improved reader sensitivities for all target findings, without negative impacts on the specificity. Overall, the AUROCs of readers improved for all 4 target findings, with significant improvements in detection of pneumothorax and nodule. The reporting time with AI was 10% lower than without AI (40.8 vs 36.9 seconds; difference, 3.9 seconds; 95% CI, 2.9-5.2 seconds; P .001).These findings suggest that AI-aided interpretation was associated with improved reader performance and efficiency for identifying major thoracic findings on a chest radiograph.

In this review work, energy harvesting methods for waste heat with small temperature differences between heat source and sink are discussed. At present, many methods are tried and employed to utilize this type of waste heat. A typical example is found in a conventional power generation system. By utilizing this type of waste heat, additional energy can be produced in regular power generation systems. Up to this point, two energy harvesting methods have been introduced and applied for the use with this type of waste heat. One is a method using an organic Rankine cycle (ORC) while the other is a method using a thermoelectric generation (TEG). An ORC is a Rankine cycle that can be applied to this type of waste heat using organic fluids such as refrigerants as working fluids instead of water used in a typical Ranking cycle. On the other hand, a TEG utilizes Peltier, Seebeck, and Thomson effects caused by the temperature difference between the heat source and sink for energy harvesting. In this work, various aspects associated with the use ORC and TEG for waste heat harvesting with small temperature differences between the heat source and sink.

Recently, there have been many abnormal natural phenomena caused by climate change. Anthropogenic factors associated with insufficient water resource management can be another cause. Among natural causes, rainfall intensity and volume often induce flooding. Therefore, accurate rainfall estimation and prediction can prevent and mitigate damage caused by these hazards. Sadly, uncertainties often hinder accurate rainfall forecasting. This study investigates the uncertainty of the Korean rainfall ensemble prediction data and runoff analysis model in order to enhance reliability and improve prediction. The objectives of this study include: (i) evaluating the spatial characteristics and applicability of limited area ensemble prediction system (LENS) data; (ii) understanding uncertainty using parameter correction and generalized likelihood uncertainty estimation (GLUE) and grid-based rainfall-runoff model (GRM); (iii) evaluating models before and after LENS-GRM correction. In this study, data from the Wicheon Basin was used. The informal likelihood (R2, NSE, PBIAS) and formal likelihood (log-normal) were used to evaluate model applicability. The results confirmed that uncertainty of the behavioral model exists using the likelihood threshold when applying the runoff model to rainfall forecasting data. Accordingly, this method is expected to enable more reliable flood prediction by reducing the uncertainties of the rainfall ensemble data and the runoff model when selecting the behavioral model for the user’s uncertainty analysis. It also provides a basis for flood prediction studies that apply rainfall and geographical characteristics for rainfall-runoff uncertainty analysis.

Background Evaluation of the glymphatic system with intrathecal contrast material injection has limited clinical use. Purpose To investigate the feasibility of using serial intravenous contrast-enhanced T1 mapping in the quantitative evaluation of putative dynamic glymphatic activity in various brain regions and to demonstrate the effect of sleep on glymphatic activity in humans. Materials and Methods In this prospective study from May 2019 to February 2020, 25 healthy participants (mean age, 25 years ± 2 [standard deviation]; 15 men) underwent two cycles of MRI (day and night cycles). For each cycle, T1 maps were acquired at baseline and 0.5, 1, 1.5, 2, and 12 hours after intravenous contrast material injection. For the night cycle, participants had a normal night of sleep between 2 and 12 hours. The time (tmin) to reach the minimum T1 value (T1min), the absolute difference between baseline T1 and T1min (peak ΔT1), and the slope between two measurements at 2 and 12 hours (slope[2h-12h]) were determined from T1 value-time curves in cerebral gray matter (GM), cerebral white matter (WM), cerebellar GM, cerebellar WM, and putamen. Mixed-model analysis of variance (ANOVA), Friedman test, and repeated-measures ANOVA were used to assess the effect of sleep on slope(2h-12h) and to compare tmin and peak ΔT1 among different regions. Results The slope(2h-12h) increased from the day to night cycles in cerebral GM, cerebellar GM, and putamen (geometric mean ratio [night/day] = 1.4 [95% CI: 1.2, 1.7], 1.3 [95% CI: 1.1, 1.4], and 2.4 [95% CI: 1.6, 3.6], respectively; P = .001, P < .001, and P < .001, respectively). Median tmin values were 0.5 hour in cerebral and cerebellar GM and putamen for both cycles. Cerebellar GM had the highest mean peak ΔT1, followed by cerebral GM and putamen in both day (159 msec ± 6, 99 msec ± 4, and 62 msec ± 5, respectively) and night (152 msec ± 6, 104 msec ± 6, and 58 msec ± 4, respectively) cycles. Conclusion Clearance of a gadolinium-based contrast agent was greater after sleep compared with daytime wakefulness. These results suggest that sleep was associated with greater glymphatic clearance compared with wakefulness. © RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Anzai and Minoshima in this issue.

AimsSacubitril/valsartan is superior to enalapril in reducing the risks of cardiovascular death and preventing hospitalization in patients with heart failure and reduced ejection fraction (HFrEF). However, patients often do not receive sacubitril/valsartan because of concerns about hypotension. We examined the feasibility of initiating sacubitril/valsartan at a very low dose (VLD) in potentially intolerant patients with HFrEF and subsequent dose up-titration, treatment persistence and outcomes.Methods and ResultsWe analyzed 206 patients with HFrEF grouped according to starting sacubitril/valsartan dose. The VLD group (n=106) commenced 25 mg twice daily, and the standard-dose (SD) group (n=100) started on ≥50 mg twice daily. Baseline systolic blood pressure was 103±12 mmHg vs. 119±14 mmHg in the SD group (PConclusionsIn patients considered by the treating physician likely to be intolerant of sacubitril/valsartan, initiation with 25 mg twice daily was generally possible and patients remained in therapy, with similar decreases in NT-proBNP and increases in left ventricular ejection fraction to those observed in patients receiving SD sacubitril/valsartan.

To investigate clinical and CT factors associated with local resectability in patients with nonmetastatic pancreatic cancers after neoadjuvant chemotherapy ± radiation therapy (CRT). This retrospective study included consecutive patients with nonmetastatic pancreatic cancers who underwent neoadjuvant CRT between June 2009 and June 2019. Tumor size, tumor-vascular contact with artery/vein, and local resectability categories (resectable, borderline resectable, or locally advanced) were assessed at baseline and post-CRT CT. Baseline and post-CRT carbohydrate antigen (CA) 19-9 levels were also assessed. Clinical or imaging features related to R0 resection were determined using logistic regression analysis. A total of 179 patients (mean age, 62.4 ± 9.3 years; 92 men) were included. After neoadjuvant CRT, 105 (58.7%) patients received R0 resection, while 74 (41.3%) did not. R0 resection rates were significantly different according to post-CRT CT resectability categories (p < 0.001): 82.8% (48/58), 70.1% (47/67), and 18.5% (10/54) for resectable, borderline resectable, and locally advanced disease, respectively. For post-CRT borderline resectable disease, ≥ 50% decrease in CA 19-9 was significantly associated with R0 resection (odds ratio (OR), 3.160; p = 0.02). For post-CRT locally advanced disease, small post-CRT tumor size ≤ 2 cm (OR, 9.668; p = 0.026) and decreased tumor-arterial contact (OR, 24.213; p = 0.022) were significantly associated with R0 resection. Post-CRT CT resectability categorization may be useful for the assessment of R0 resectability in patients with pancreatic cancer following neoadjuvant CRT. Additionally, ≥ 50% decrease in CA 19-9 was associated with R0 resection in post-CRT borderline resectable disease, while small post-CRT tumor size and decreased tumor-arterial contact were with locally advanced disease. • R0 resection rates following neoadjuvant chemotherapy ± radiation therapy (CRT) were 82.8%, 70.1%, and 18.5% in resectable, borderline resectable, and locally advanced disease, respectively, at post-CRT CT (p < 0.001). • For post-CRT borderline resectable disease, ≥ 50% decrease in carbohydrate antigen (CA) 19-9 was significantly associated with R0 resection. • For post-CRT locally advanced disease, small post-CRT tumor size ≤ 2 cm and decreased tumor-arterial contact were significantly associated with R0 resection.

To identify the agreement on Lung CT Screening Reporting and Data System 4X categorization between radiologists and an expert-adjudicated reference standard and to investigate whether training led to improvement of the agreement measures and diagnostic potential for lung cancer.Category 4 nodules in the Korean Lung Cancer Screening Project were identified retrospectively, and each 4X nodule was matched with one 4A or 4B nodule. An expert panel re-evaluated the categories and determined the reference standard. Nineteen radiologists were asked to determine the presence of CT features of malignancy and 4X categorization for each nodule. A review was performed in two sessions, and training material was given after session 1. Agreement on 4X categorization between radiologists and the expert-adjudicated reference standard and agreement between radiologist-assessed 4X categorization and lung cancer diagnosis were evaluated.The 48 expert-adjudicated 4X nodules and 64 non-4X nodules were evenly distributed in each session. The proportion of category 4X decreased after training (56.4% ± 16.9% vs. 33.4% ± 8.0%; p0.001). Cohen's κ indicated poor agreement (0.39 ± 0.16) in session 1, but agreement improved in session 2 (0.47 ± 0.09; p = 0.03). The increase in agreement in session 2 was observed among inexperienced radiologists (p0.05), and experienced and inexperienced reviewers exhibited comparable agreement performance in session 2 (p0.05). All agreement measures between radiologist-assessed 4X categorization and lung cancer diagnosis increased in session 2 (p0.05).Radiologist training can improve reader agreement on 4X categorization, leading to enhanced diagnostic performance for lung cancer.• Agreement on 4X categorization between radiologists and an expert-adjudicated reference standard was initially poor, but improved significantly after training. • The mean proportion of 4X categorization by 19 radiologists decreased from 56.4% ± 16.9% in session 1 to 33.4% ± 8.0% in session 2. • All agreement measures between the 4X categorization and lung cancer diagnosis increased significantly in session 2, implying that appropriate training and guidance increased the diagnostic potential of category 4X.

Since aluminum responds to various oxidizers and has a high energy density, there are high expectations for its usefulness as a fuel. However, it is covered with an aluminum oxide film, which has a high melting point, and thus, its ignition is difficult. One method suggested to solve this problem is nickel coating; however, in contrast to the extensive amount of research conducted on the overall phenomenon of aluminum combustion, research regarding Ni-coated aluminum is still in nascent stages. This study was carried out to further elucidate the ignition mechanism; thus, millimeter-sized (∼2.38 mm) aluminum particles were used to observe the surface where ignition occurs in air. The spatial and temporal resolutions were heightened by prolonging the heating period. The aluminum particles were nickel coated using electro/electroless methods, and surface analysis by SEM, thermal analysis by TGA/DSC, and species analysis by XRD and EDS were carried out. In addition, two-wavelength pyrometry was used to measure the ignition temperature. The results show that regardless of the nickel content in the coating of the aluminum particles, the ignition temperature was approximately 2400 K, similar to the melting point of aluminum oxide. The thermodynamic and thermophysical characteristics of nickel, aluminum, aluminum oxide, and nickel (II) oxide, and the surface/cross-sectional analysis, thermal and species analysis, and high-speed cinematography of the quenched samples provided a detailed explanation of the ignition process. Through this ignition mechanism, the emitted spectrum of AlO (as an intermediate combustion material) was traced to explain the decrease in ignition delay with increase in nickel content.

Since predicting rapidly fluctuating water levels is very important in water resource engineering, Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) were used to evaluate water-level-prediction accuracy at Hangang Bridge Station in Han River, South Korea, where seasonal fluctuations were large and rapidly changing water levels were observed. The hydrological data input to each model were collected from the Water Resources Management Information System (WAMIS) at the Hangang Bridge Station, and the meteorological data were provided by the Seoul Observatory of the Meteorological Administration. For high-accuracy high-water-level prediction, the correlation between water level and collected hydrological and meteorological data was analyzed and input into the models to determine the priority of the data to be trained. Multivariate input data were created by combining daily flow rate (DFR), daily vapor pressure (DVP), daily dew-point temperature (DDPT), and 1-hour-max precipitation (1HP) data, which are highly correlated with the water level. It was possible to predict improved high water levels through the training of multivariate input data of LSTM and GRU. In the prediction of water-level data with rapid temporal fluctuations in the Hangang Bridge Station, the accuracy of GRU’s predicted water-level data was much better in most multivariate training than that of LSTM. When multivariate training data with a large correlation with the water level were used by the GRU, the prediction results with higher accuracy (R2=0.7480–0.8318; NSE=0.7524–0.7965; MRPE=0.0807–0.0895) were obtained than those of water-level prediction results by univariate training.

Aluminum particles 15–25 μm in size are widely used in fuel propellants and underwater propulsion systems in national defense research. However, these particles are covered with an aluminum oxide film, which has a high melting point, so ignition is difficult. To improve the ignitability of high-energy aluminum powder and to understand the reaction phenomenon as a function of particle size(15–25 μm, 74–105 μm, and 2.38 mm) and oxidizer(air, CO2, and argon), the natural oxide films are chemically removed. The particles are then coated with nickel using an electro-less method. The degree of nickel deposition is confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, elemental analysis is also conducted by using X-ray diffraction. Thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) enable comparisons between the uncoated and coated aluminum, and the reaction process are investigated through fine structural analysis of the particle surfaces and cross sections. There are little difference in reactivity as a function of oxidant type. However, a strong exothermic reaction in the smaller nickel-coated aluminum particles near the melting point of aluminum accelerates the reaction of the smaller particles. Explanation of the reactivity of the nickel-coated aluminum depending on the particle sizes is attempted.

The upsurges in population, internal migration, and various development works have caused significant land use and land cover (LULC) changes in the Bagmati Basin of Nepal. The effects of climate change such as increased precipitation and temperature are affecting the provision of ecosystem services (ES). In this regard, this study particularly treated water yield (WY), soil loss, nitrogen export, and carbon fluctuation in the basin. Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) tools were used to carry out a comparative analysis of ES based on LULC data for 2000 and 2010 and corresponding climate data. To analyze the future period (2010&ndash, 2099), we have used climate data from the multi-model ensemble (MME) of statistically downscaled and bias-corrected 12 best global climate models (GCMs). A raw GCM analysis (based on historical observational data) from 29 GCMs was done first. The results shows with a subsequent degradation of ES providers like forests and an increment in agricultural and urban areas, ES are on a verge of degradation. Furthermore, a projection of future climate patterns depicts increased precipitation and temperature. Thus, urgent measures are required for the sustainable provision of ES. Outcomes of the study are expected to help in the incorporation of ES in development policies promoting low-impact development along with maintaining ecological and economic goals. The study closes by presenting a recommendation for model application and future study needs.

Geographical characteristics give the island of Heuksando no choice but to use diesel power generation. This option is not economical, and more than half of the generated energy is released through exhaust gas, cooling water, and other sources of energy loss. In order to reduce these losses and improve power generation efficiency, this research studied Organic Rankine Cycle systems that use waste heat from diesel power plants as a heat source. Unlike previous Rankine cycles, electric power generation and operation are possible because of low heat source and capacity. Cycle design and demonstration-operation logic are required to set the range of waste heat temperature and capacity. In addition, as the overall efficiency may change substantially depending on the efficiency of each component, the operating conditions of various BOPs should be optimized. It is necessary to obtain the optimization and operating conditions of each element of the system through modeling and numerical study of the whole system. In this research, heat source analysis and BOP design were conducted in order to apply the 20kW/30kW ORC systems to the Heuksando Island 1MW diesel power plant. A heat-connecting technique that thermally connects the heat exhaust end piping and the evaporator of the ORC system was developed in this study. The demonstration experiment was conducted sharing the waste heat source with the 20kW and 30kW ORC systems. This paper presents the waste heat analysis and the demonstration operation results of the Heuksando island power plant.

Objective To evaluate whether computed tomography (CT) reconstruction algorithms affect the CT texture features of the liver parenchyma. Materials and Methods This retrospective study comprised 58 patients (normal liver, n = 34; chronic liver disease [CLD], n = 24) who underwent liver CT scans using a single CT scanner. All CT images were reconstructed using filtered back projection (FBP), hybrid iterative reconstruction (IR) (iDOSE4), and model-based IR (IMR). On arterial phase (AP) and portal venous phase (PVP) CT imaging, quantitative texture analysis of the liver parenchyma using a single-slice region of interest was performed at the level of the hepatic hilum using a filtration-histogram statistic-based method with different filter values. Texture features were compared among the three reconstruction methods and between normal livers and those from CLD patients. Additionally, we evaluated the inter- and intra-observer reliability of the CT texture analysis by calculating intraclass correlation coefficients (ICCs). Results IR techniques affect various CT texture features of the liver parenchyma. In particular, model-based IR frequently showed significant differences compared to FBP or hybrid IR on both AP and PVP CT imaging. Significant variation in entropy was observed between the three reconstruction algorithms on PVP imaging (p < 0.05). Comparison between normal livers and those from CLD patients revealed that AP images depend more strongly on the reconstruction method used than PVP images. For both inter- and intra-observer reliability, ICCs were acceptable (> 0.75) for CT imaging without filtration. Conclusion CT texture features of the liver parenchyma evaluated using the filtration-histogram method were significantly affected by the CT reconstruction algorithm used.

High-temperature ignition is essential for the ignition and combustion of energetic metal fuels, including aluminum and magnesium particles which are protected by their high-melting-temperature oxides. A plasma torch characterized by an ultrahigh-temperature plasma plume fulfills such high-temperature ignition conditions. A new steam plasma igniter is designed and successfully validated by aluminum power ignition and combustion tests. The steam plasma rapidly stabilizes in both plasma and steam jet modes. Parametric investigation of the steam plasma jet is conducted in terms of arc strength. A high-speed camera and an oscilloscope method visualize the discharge characteristics, and optical emission spectroscopy measures the thermochemical properties of the plasma jet. The diatomic molecule OH fitting method, the Boltzmann plot method, and short exposure capturing with an intensified charge coupled device record the axial distributions of the rotational gas temperature, excitation temperature, and OH radical distribution, respectively. The excitation temperature at the nozzle tip is near 5500 K, and the gas temperature is 5400 K.

Ignition and the burning of air-born single aluminum and magnesium particles are experimentally investigated. Particles of 30 to 106 μm-diameters were electrodynamically levitated, ignited, and burnt in atmospheric air. The particle combustion evolution was recorded by high-speed cinematography. Instant temperature and thermal radiation intensity were measured using two-wavelength pyrometry and photomultiplier tube methods. Ignition of the magnesium particle is prompt and substantially advances the aluminum particle by 10 ms. Burning time of the aluminum particles is extended 3 to 5 times longer than the magnesium particles. Exponents of a power-law fit of the burning rates are 1.55 and 1.24 for aluminum and magnesium particles, respectively. Flame temperature is slightly lower than the oxide melting temperature. For the aluminum, dimensionless flame diameter is inert to the initial particle size, but for the magnesium inversely proportional to the initial diameter.

T-Burner tests of an Al/HTPB propellant in conjunction with a Pulsed DB/AB Method were conducted to find an acoustic amplification factor. Aluminum-fr ee and aluminum-heavy propellants were examined. Instant surface ignition was successfully made by the use of a supplementary propellant of fractionally higher reaction rate. With the prese nce of higher aluminum concentration in the propellants, the pressure perturbations were promptly dampe d down and the pressure fluctuations were no longer dispersive. Addition of aluminum particles into the propellant was advantageous for stabilizing pressure-coupled unstable waves.초 록 연소 시, 입자상 물질에 대한 HTPB/AP 계열 고체추진제의 음향특성을 정량화하기 위해서, Pulsed DB/AB T-burner 실험을 수행하였다. 추진제 전면에서 동시 점화를 위해, 대상 고체추진제보다 연소속도가 빠른 다른 고체추진제를 대상 추진제 앞면에 부착하였다. 다량의 알루미늄이 포함된 고체추진제에서는 T-burner 내부에서 만들어진 압력섭동에 의한 음향학적 불안정성이 매우 빠르게 감쇠되었고, 반대로 알루미늄이 포함되지 않은 고체추진제에서는 상대적으로 매우 느리게 감쇠함을 확인하였다. 본 연구에서는 음향학적 특성값들을 정량화하였고, 이를 통해 연소응답 특성을 계산하였다.Key Words: Solid Propellant(고체추진제), Combustion Response(연소응답), T-burner(T-버너), Fast Ignition Disk(점화보조제), Pulsed DB/AB Method(펄스형 DB/AB 방법)Received 2 December 2013 / Revised 1 March 2014 / Accepted 8 Ma rch 2014

In this study, DC (Direct current) type steam plasma igniter is developed for effective ignition of high-energy density metal aluminum and gas temperature is measu red by emission spectrum of OH radical. Because of the ultra-high gas temperature, the DC plas ma jet is measured by Boltzmann plot method which is the non-contact optical technique and spectrum comparison-analysis. And both methods were applied to experiment after accurate verification. As a result, we could identify that plasma jet temperature is 2900 K ~ 5800 K in the 30 mm range fr om the nozzle tip.초 록 본 연구에서 고에너지 금속 알루미늄의 효과적인 점화를 위해 개발한 직류 방식의 스팀 플라즈마 점화기 가스온도를 OH radical의 방출 스펙트럼을 사용하여 측정하였다. 플라즈마 제트온도는 초고온이므로 비접촉식 광학 계측 방법인 볼츠만 기울기법과 스펙트럼 비교 분석법을 이용하여 측정하였으며 각각의 방법은 정밀하게 검증 후 실험에 적용되었다. 플라즈마 점화기의 노즐 팁으로부터 30 mm 범위에서의 제트온도 측정결과 두 방법 모두 알루미늄의 점화온도(≈2400 K) 이상의 2900 K ~ 5800 K 를 확인할 수 있었다.Key Words: Steam Plasma Igniter(스팀 플라즈마 점화기), High Temperature Measurement(고온측정법), Emission Spectroscopy(방출분광법), Aluminum Ignition(알루미늄 점화)Received 2 June 2013 / Revised 3 January 2014 / Accepted 11 Jan uary 2014

Corresponding author. E-mail: wsyoon@yonsei.ac.krABSTRACT In this study, In order to develop the measurement method of high energy density metal aluminum dust cloud combustion, flame temperature and emission spectrum was measured using spectrometer. Because of the ultra high ㎛-sized aluminum flame temperature more than 2400 K, it was meas ured by non-contact optical technique which is the modified two wavelength pyrometry with 520, 640 nm and spectrum comparison method. These methods were applied to e xperiment after accurate verification. As a result, we could identify that flame tempera ture is more than 2400 K in bottom of combustor in both methods. And on the emission spectrum analysi s, we could measure AlO radical which is occurred dominantly in aluminum combustion.초 록 본 연구에서는 고에너지 금속 알루미늄 군입자 연소 화염 분석을 위한 측정기법 개발 연구로서 스펙트로메터를 사용하여 화염 온도와 자발광 스펙트럼을 측정하였다. 마이크로 크기의 알루미늄 군입자 연소 반응시 발생하는 화염온도는 약 2400 K 이상의 초고온이므로 비접촉식 광학 계측 방법을 사용하였으며, 측정을 위해 개발된 기법은 520 nm, 640 nm를 사용하는 이색법을 응용한 방법과 광대역 파장 비교법으로서 각각의 방법은 정밀하게 검증 후 실험에 적용되었다. 연소실 하단에서 화염온도 측정결과 두 방법 모두 2400 K 이상의 화염온도를 확인할 수 있었으며 자발광 측정 결과 알루미늄 연소 반응시 가장 지배적으로 발생하는 화학종인 AlO를 확인할 수 있었다.Key Words: High Temperature Measurement(고온측정법), Emission Spectroscopy(방출분광법)Received 14 June 2013 / Revised 11 September 2013 / Accepted 18 September 2013

Basically, in order to apply solid propellant as ignition source to high energy metal particle combustion system, we analyzed combustion characteristics of the HTPB/AP/Al, HTPE/AP/Al propellants by using a strand burner. The propellants were tested in a high-pressure windowed strand burner, which was pressurized up to 300 psia with pure argon gas. Strand burner was visualized with two quartz windows and ignition was accomplished by a 10 W laser. The burning rate of propellant was measured with high-speed camera method for frame analysis and photodiode method for combustion time analysis. Emission spectrum was measured with spectrometer at 300 nm ~ 800 nm and 1500 nm ~ 5000 nm and then we analyzed species during propellant combustion.

The purpose of this research is to solve flexible job-shop scheduling problems with ‘AND’/‘OR’ precedence constraints in the operations. We first formulate the problem as a Mixed-Integer Linear Program (MILP). The MILP can be used to compute optimal solutions for small-sized problems. We also developed a heuristic algorithm that can obtain a good solution for the problem regardless of its size. Moreover, we have developed a representation and schedule builder that always produces a legal and feasible solution for the problem, and developed genetic and tabu search algorithms based on the proposed schedule builder. The results of the computational experiments show that the developed meta-heuristics are very effective.

Department of Industrial Engineering, Pusan National University, Busan 609-735, KoreaAt a shipyard, the efficient handling of blocks is one of the most important factors in the shipbuilding process. We consider the problem of deployment planning of blocks from storage yards. As some information of block arrangement should be considered to handle the problem, we adopt the block arrangement based on the coordinates and sizes of each block at a storage yard. Deployment planning for a block involves deciding upon its transportation route from the storage yard and searching for blocks that would obstruct its transportation along this route. A tabu search algorithm for deploying several blocks is developed to minimize the number of obstructive blocks deployed together from the storage yards at a shipyard. The results of computational experiments show that the developed algorithm is very useful in the deployment planning of multiple blocks from the storage yards.

Objective To compare the lumbar vertebral bone marrow fat-signal fractions obtained from six-echo modified Dixon sequence (6-echo m-Dixon) with those from single-voxel magnetic resonance spectroscopy (MRS) in patients with low back pain. Materials and Methods Vertebral bone marrow fat-signal fractions were quantified by 6-echo m-Dixon (repetition time [TR] = 7.2 ms, echo time (TE) = 1.21 ms, echo spacing = 1.1 ms, total imaging time = 50 seconds) and single-voxel MRS measurements in 25 targets (23 normal bone marrows, two focal lesions) from 24 patients. The point-resolved spectroscopy sequence was used for localized single-voxel MRS (TR = 3000 ms, TE = 35 ms, total scan time = 1 minute 42 seconds). A 2 × 2 × 1.5 cm3 voxel was placed within the normal L2 or L3 vertebral body, or other lesions including a compression fracture or metastasis. The bone marrow fat spectrum was characterized on the basis of the magnitude of measurable fat peaks and a priori knowledge of the chemical structure of triglycerides. The imaging-based fat-signal fraction results were then compared to the MRS-based results. Results There was a strong correlation between m-Dixon and MRS-based fat-signal fractions (slope = 0.86, R2 = 0.88, p < 0.001). In Bland-Altman analysis, 92.0% (23/25) of the data points were within the limits of agreement. Bland-Altman plots revealed a slight but systematic error in the m-Dixon based fat-signal fraction, which showed a prevailing overestimation of small fat-signal fractions (< 20%) and underestimation of high fat-signal fractions (> 20%). Conclusion Given its excellent agreement with single-voxel-MRS, 6-echo m-Dixon can be used for visual and quantitative evaluation of vertebral bone marrow fat in daily practice.

Inert/pseudoinert gases, including argon, nitrogen, and carbon dioxide, were utilized to stabilize synthesized Fe0-nanoparticles after lyophilization to prevent self-ignition. In addition, the aging effect was investigated for these stabilized Fe0-nanoparticles both in humid and dry conditions. Particles’ shapes, sizes, and structures were characterized for these fresh and aged Fe0-nanoparticles using X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Brunauer−Emmett−Teller surface area and porosity analyzer, transmission electronic microscopy, and energy dispersive X-ray spectroscopy (EDX). Even when aged Fe0-nanoparticles were exposed to the atmosphere, the Fe0 content in these aged Fe0-nanoparticles did not change significantly, which was confirmed by XRD, EDX, and HCl digestion methods. Reactivity of the fresh Fe0-nanoparticles stabilized using inert/pseudoinert gases for bromate reduction was more than 99% in 20 min, much higher than for microsized ZVI. However, for the aged Fe0-nanoparticles...

Abstract In passive RFID environment, this paper presents an efficient mobile robot localization and a pseudorandom tag arrangement for improved performance. It is assumed that a mobile robot travels along a series of linear segments, each at a constant velocity, and the number of tags sensed at once is at most one. First, using the spatio-temporal information during tag traversing, a simple but effective mobile robot localization method is developed. Second, three representative tag arrangements, including square, parallelogram, and tilted square, are examined. Special attention is given to the problem of long navigation without tag sensing, so called tag invisibility. Taking into account both tag invisibility and tag installation, a pseudorandom tag arrangement, inspired from the Sudoku puzzle, is proposed. To demonstrate the validity of the proposed mobile robot localization system, some experimental results are given.

Under passive RFID environment, this paper presents a new localization of a mobile robot traversing over the floor covered with tags, which is superior to existing methods in terms of estimation performance and cost effectiveness. Basically, it is assumed that a mobile robot is traveling along a series of straight line segments, each segment at a certain constant velocity, and that the number of tags sensed by a mobile robot at each sampling instant is at most one. First, for a given line segment with known starting point, the velocity and position of a mobile robot is estimated using the spatial and temporal information acquired from the traversed tag. Some discussions are made on the validity of the basic assumptions and the localization for the initial segment with unknown starting point. Second, for a given tag distribution density, the optimal tag arrangement is considered to reduce the position estimation error as well as to make easy the tag attachment on the floor. After reviewing typical tag arrangements, the pseudorandom tag arrangement is devised inspired from the Sudoku puzzle, a number placement puzzle. Third, through experiments using our passive RFID localization system, the validity and performance of the mobile robot localization proposed in this paper is demonstrated.

This paper presents the robust localization of an omnidirectional mobile robot using a regular polygonal array of optical mice that are installed at the bottom of a mobile robot. First, the basic principle of the proposed localization scheme is explained. Second, the velocity kinematics from a mobile robot to an array of optical mice is derived as an overdetermined linear system. Third, for a given set of optical mouse readings, the least squares velocity estimation of a mobile robot is obtained as the simple average. Fourth, the robustness of the proposed least squares velocity estimation against measurement noise, partial malfunction, and imprecise installation is analyzed.

This paper presents the velocity estimation of a mobile robot using a regular polygonal array of optical mice that are installed at the bottom of a mobile robot. First, the basic principle of the proposed velocity estimation method is explained. Second, the velocity kinematics from a mobile robot to an array of optical mice is derived as an overdetermined linear system. Third, for a given set of optical mouse readings, the mobile robot velocity is estimated based on the least squares solution to the obtained system. Finally, simulation results are given to demonstrate the validity of the proposed velocity estimation method.

In this study, aluminum flame analysis was researched in order to develop a measurement method for high-energy-density metal aluminum dust cloud combustion, and the flame temperature and UV-VIS-IR emission spectra were precisely measured using a spectrometer. Because the micron-sized aluminum flame temperature was higher than 2400 K, Flame temperature was measured by a non-contact optical technique, namely, a modified two-color method using 520 and 640 nm light, as well as by a polychromatic fitting method. These methods were applied experimentally after accurate calibration. The flame temperature was identified to be higher than 2400 K using both methods. By analyzing the emission spectra, we could identify AlO radicals, which occur dominantly in aluminum combustion. This study paves the way for realization of a measurement technique for aluminum dust cloud combustion flames, and it will be applied in the aluminum combustors that are in development for military purposes.

To improve the ignitability of high energy aluminum powder, in this study, natural oxide films (alumina, Al2O3) were chemically removed and nickel coatings were deposited using an electroless method for nickel plating. The time-dependent degree of nickel deposition was confirmed qualitatively and quantitatively through surface analysis using scanning electron microscopy/energy dispersive spectroscopy. To characterize the nickel coatings, we also conducted elemental analysis by using X-ray diffraction and weight analysis by using inductively coupled plasma optical emission spectrometry. Thermophysical studies were also conducted using thermogravimetric analysis/differential scanning calorimetry in an airoxidized environment. The results of these analyses explain the ignition enhancement mechanism observed in the nickel-coated aluminum powder. A novel plating method for creating a nickel-coated aluminum powder was established and the mechanism for the enhancement of the ignition and combustion of the powder is elucidated.

In the near future, personal service robots are expected to come into human daily life as supporters in education, leisure, house care, health care, and so on. Most of them are built on an omnidirectional mobile robot so as to navigate in an environment restricted in space and cluttered with obstacles. Caster wheels have been chosen for the development of an omnidirectional mobile robot, as reported in (Holmberg, 2000), among several omnidirectional wheel mechanisms, including universal wheels, Swedish wheels, orthogonal wheels, and ball wheels. This is because caster wheels can operate without additional peripheral rollers or support structure, and maintain good performance even though payload or ground condition changes. There have been several works on the kinematics of a caster wheeled omnidirectional mobile robot (COMR), including the kinematic modeling, the design and control, the isotropy analysis, as reported in (Holmberg, 2000; Muir & Neuman, 1987; Campion et al., 1996; Kim & Kim, 2004; Park et al., 2002; Kim & Moon, 2005; Oetomo et al., 2005; Kim & Jung, 2007). Previous isotropy analysis, as reported in (Kim & Kim, 2004; Park et al., 2002; Kim & Moon, 2005; Oetomo et al., 2005), has been made only for a COMR in which the steering link offset is equal to the wheel radius, except our recent work, as reported in (Kim & Jung, 2007). It was found that such a restriction is necessary to have globally optimal isotropic characteristics of a COMR, as reported in (Park et al., 2002; Kim & Moon, 2005; Oetomo et al., 2005). Nevertheless, many practical COMR's in use take advantage of the steering link offset which is different from the wheel radius, mainly for improved tipover stability, as reported in (McGhee & Frank, 1968; Papadopoulos & Rey, 1996). The tipover stability becomes critical when a COMR makes a rapid turn or sudden external forces are applied to a COMR. The accuracy of the velocity kinematics of a robotic system depends on the condition number of the Jacobian matrix involved. Based on the Euclidean norm, the condition number of a matrix can be defined as the ratio of the largest to smallest singular values of the matrix, as reported in (Strang, 1988), whose value ranges from unity to infinity. For a given linear system b Ax = , the condition number of A represents the amplification of the

This paper presents the robust velocity estimation of an omnidirectional mobile robot using a polygonal array of optical mice that are installed at the bottom of a mobile robot. First, the velocity kinematics from a mobile robot to an array of optical mice is derived as an overdetermined linear system. Second, the velocity of a mobile robot is estimated by the least squares solution, which is shown to the same as the simple average of the velocity measurements from optical mice. Third, the redundant number of optical mice is shown to contribute to the robustness of the proposed velocity estimation method against both measurement noises and partial malfunctions. Finally, experimental results are given to demonstrate the validity and performance of the proposed mobile robot velocity estimation scheme.