• Journal of Energy Engineering
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• v.13 no.1
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• pp.75-81
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• 2004

ZZFCa sorbents for hot gas desulfurization in IGCC were prepared by adding calcium oxide to ZZF sorbent in order to improve its attrition resistance in this study. ASTM attrition test for the sorbent was performed at several different weight percentages of CaO to investigate the attrition characteristics of ZBFCa sorbents as a function of CaO content. Attrition index of ZZF without CaO was 28.3% and its collected attrition index was 10.8％. ZZFCa-3 containing 3 wt% CaO showed the lowest attrition index (AI=17.3％, CAI=8.8％) in the test. From the results of SEM morphologies and particle size distribution measurements, ZZFCa-3 maintained a fine shape and a desirable average particle size even after attrition test. In the experiments of sulfidation/regeneration for ZZFCa-3 sorbent concentration of hydrogen sulfide in coal gas was lowered from 10000 ppm to below 1 ppm. Sulfur removing capacity was about 28.8 g S/100 g sorbent. Neither formation of CaSO$_4$ was observed in XRD measurement nor SO$_2$ slippage was observed during sulfidation process.

• Applied Chemistry for Engineering
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• v.16 no.5
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• pp.603-608
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• 2005

This study was conducted to investigate particle attrition characteristics in a gas desulfurization using zinc titanate sorbent in a 0.035 m i.d. by 1.34 m height gas fluidized bed reactor. Gas jetting from the distributor and bubbling in the gas fluidized bed were found to be the main causes of particle attrition. The experiment was carried out under a slow attrition rate condition to compare the performance of the batch reactor to that of a continuous reactor. The attrition index (AI) and corrected attrition index (CAI) were measured at various the gas velocity, temperature, pressure, and bed weight, in the gas fluidized bed, during the dexulfurization process. The AI (5) and CAI (5) decreased as the bed weight increased. Particle destruction occurred when the particles started to experience physical fatigue under specific impacts over several iterations. AI (5) and CAI (5) also increased as relative humidity, gas velocity and pressure increased, and as temperature decreased. Particle attrition was mainly affected by gas jetting from the distributor, and abrasion resulted in smaller particles than fragmentation did.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.547-551
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• 2006

In the reactor following the American standard test method (ASTM) D5757-95 and lab-scale fluidized bed combustor, the attrition characteristics of sand and ash of Korean anthracite were investigated. The attrition characteristics, such as particle size distribution of fly ash, attrition rate, and attrition ratio etc, were studied with variation of gas velocities. The particle attrition of ash was more active than sand which was generally used as a fluidized material and also the attrition index of ash taken by ASTM D5757-95 was 5 times higher than that of sand. The formation of fine particles continuously occurred due to particle attrition with increasing gas velocities. The following equation has been suggested for attrition rate of ash. $$\frac{dW}{dt}=-3.18{\times}10^{-7}(U-U_{mf})W$$.

• Journal of the military operations research society of Korea
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• v.26 no.1
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• pp.1-14
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• 2000

This research studies an attrition rate considering terrain feature in a battlefield. Lanchester-type combat models for heterogeneous forces and the Weapon Effectiveness Index are used in this study. The various environments of the battlefield can be explained by the terrain feature. Attrition rates of heterogeneous model are estimated by applying the battle of Baek-Sek mountain during the Korean War. Estimated attrition rates are checked by the paired samples T-Test. Specific cases are shown in this paper as an example. If we study out the relative influence of the terrain feature upon the performance of individual weapons, these will be a possible alternative to analyze the military operations.

• Journal of the military operations research society of Korea
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• v.28 no.2
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• pp.70-84
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• 2002

This paper deals with the attrition rate of major facility such as a particular building that is one of the most important target in the war time. In order to estimate the attrition rate, we use JAWS, WinJMEM which are programed by JTCG/ME of AMSAA and spreadsheet package which is able to assist the limitation of those programs and calculate all the procedure of this computation. This method uses the effectiveness index(El) which indicates the numerical measure of the effectiveness of a given weapon of a given target. The range error probable(REP) and the deflection error probable(DEP) in the ground plane also should be used. Those mean the measure of delivery accuracy of the weapon system. In this paper, it is improved that the El can be obtained from the regression analysis using the weight of the warhead explosive as the independent variable. It implies that we are able to obtain the El and the conditional probability of damage of the enemy weapon. After that, the single-sortie probability of damage can be computed using WinJMEM or another assistant program such as the spreadsheet package which shows the result immediately.

• Clean Technology
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• v.24 no.1
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• pp.63-69
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• 2018

The reduction reaction characteristics and physicochemical properties were studied for the selection of oxygen carrier, which is the core of the chemical looping combustion (CLC) technology. Fuel conversion and $CO_2$ selectivity of oxygen carrier according to the concentration of reducing gas and the reduction temperature using three kinds of oxygen carrier (SDN70, N018-R2, N016-R4) were measured and compared. In addition, Attrition Index (AI) and BET surface area were measured to analyze the attrition resistance and the surface characteristics of the oxygen carrier. As a result, it was confirmed that all three kinds of oxygen carrier were suitable for use in chemical roofing combustion system, and the best particle was determined to be N016-R4.

• Nutrition Research and Practice
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• v.8 no.1
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• pp.94-102
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• 2014

Diet attrition and failure of long term treatment are very frequent in obese patients. This study aimed to identify pre-treatment variables determining dropout and to customise the characteristics of those most likely to abandon the program before treatment, thus making it possible to modify the therapy to increase compliance. A total of 146 outpatients were consecutively enrolled; 73 patients followed a prescriptive diet while 73 followed a novel brief group Cognitive Behavioural Treatment (CBT) in addition to prescriptive diet. The two interventions lasted for six months. Anthropometric, demographic, psychological parameters and feeding behaviour were assessed, the last two with the Italian instrument VCAO Ansisa; than, a semi-structured interview was performed on motivation to lose weight. To identify the baseline dropout risk factors among these parameters, univariate and multivariate logistic models were used. Comparison of the results in the two different treatments showed a higher attrition rate in CBT group, despite no statistically significant difference between the two treatment arms (P = 0.127). Dropout patients did not differ significantly from those who did not dropout with regards to sex, age, Body Mass Index (BMI), history of cycling, education, work and marriage. Regardless of weight loss, the most important factor that determines the dropout appears to be a high level of stress revealed by General Health Questionnaire-28 items (GHQ-28) score within VCAO test. The identification of hindering factors during the assessment is fundamental to reduce the dropout risk. For subjects at risk, it would be useful to dedicate a stress management program before beginning a dietary restriction.

• Clinics in Shoulder and Elbow
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• v.27 no.1
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• pp.26-31
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• 2024

Background: The coracoacromial ligament (CAL) is frequently observed to be damaged during arthroscopy and it is unclear how demographic, anatomic, and radiographic factors are related to CAL degeneration in full-thickness rotator cuff tears. Methods: A prospective study was conducted of patients at a single institution undergoing shoulder arthroscopy for first-time, full-thickness rotator cuff tears. We evaluated preoperative anteroposterior radiographs to obtain critical shoulder angle, glenoid inclination, acromial index, acromiohumeral distance, lateral acromial angle, and acromial morphology. We documented CAL quality, rotator cuff tear size and pattern during arthroscopy. Multiple logistic regression was used to identify predictive factors for encountering severe CAL fraying during arthroscopy. Results: Shoulders had mild CAL degeneration in 58.1% of cases, whereas severe CAL degeneration was present in 41.9% of shoulders. Patients with severe CAL attrition were significantly older (62.0 years vs. 58.0 years, P=0.042). Shoulders with severe CAL attrition had large rotator cuff tears in 54.1% of cases (P<0.001), and tears involving the infraspinatus (63.2% vs. 29.6%, P=0.003). The severe degeneration group was more likely to have a larger critical shoulder angle measurement on preoperative radiographs than those in the mild attrition group (36.1°±3.6° [range, 30°-45°] vs. 34.1°±3.8° [range, 26°-45°], P=0.037). Conclusions: While the clinical impact of CAL degeneration remains uncertain, increased severity of CAL degeneration is associated with older age, larger rotator cuff tear size, presence of infraspinatus tearing, and increased preoperative critical shoulder angle. Level of evidence: III.

• Journal of the Korean Ceramic Society
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• v.38 no.9
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• pp.822-828
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• 2001

Bayer process is based on the extraction of aluminium trihydroxide from bauxite. The process is operated with the several criteria such as primary crystal size, particle size distribution and yield etc.. In this study basing on the previous results, an investigation on the effect of chemical grade and smelting grade aluminium trihydroxide precipitation condition were undertaken. As a result, particle size was 42∼44${\mu}$m form chemical grade product and 74∼77${\mu}$m for smelting grade product. The yield and solubility by acid of chemical grade product was higher than smelting grade product. The attrition index of smelting grade product was lower than that of other commercial product because primary crystal size of the smelting grade product was small.

• Journal of Climate Change Research
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• v.2 no.2
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• pp.107-113
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• 2011

In this research, we described the experimental results for the improvement of Potassium based sorbents. These sorbents have been actually used in the 0.5 MW $CO_2$ capture plant located in Hadong #3 Power Plant. Firstly, we had shaped two kinds of sorbents using a spray dryer. These sorbents applied magnetite & copper oxide as an additive. And the magnetite sorbent was evaluated more excellent relatively in the attrition index. Secondly, We had obtained TGA multicycle experimental results of the improved Potassium based sorbent which applied magnetite as an additive. Consequently, $CO_2$ sorption capacity had been sustained 5.5 wt% after 2nd cycle and attrition index was very excellent as 0.5%. Finally, we had investigated the characteristics of the sorbent following in properties of supporters. As a result, the sorption capacity of the KMO sorbent used base material as a supporter was appeared as 7.2 wt%.