Phase Transitions and Thermoelectric Properties of Charge-Compensated ZnxCu12-xSb4Se13.

In this study, we investigated the phase transitions and thermoelectric properties of charge-compensated hakite (ZnxCu12-xSb4Se13) as a function of Zn content. Based on X-ray diffraction and a differential scanning calorimetric phase analysis, secondary phases (permingeatite and bytizite) transformed into hakite depending on the Zn content, while Zn2Cu10Sb4Se13 existed solely as hakite. Nondegenerate semiconductor behavior was observed, exhibiting increasing electrical conductivity with a rising temperature. With an increase in Zn content, the presence of mixed phases of hakite and permingeatite led to enhanced electrical conductivity. However, Zn2Cu10Sb4Se13 with a single hakite phase exhibited the lowest electrical conductivity. The Seebeck coefficient exhibited positive values, indicating that even after charge compensation (electron supply) by Zn, p-type semiconductor characteristics were maintained. With the occurrence of an intrinsic transition within the measured temperature range, the Seebeck coefficient decreased as the temperature increased; at a certain temperature, Zn2Cu10Sb4Se13 exhibited the highest value. Thermal conductivity showed a low temperature dependence, obtaining low values below 0.65 Wm-1K-1. A power factor of 0.22 mWm-1K-2 and dimensionless figure of merit of 0.31 were achieved at 623 K for ZnCu11Sb4Se13.

Comparison of adsorption-extraction (AE) workflows for improved measurements of viral and bacterial nucleic acid in untreated wastewater.

The lack of standardized methods and large differences in virus concentration and extraction workflows have hampered Severe Acute Respiratory Syndrome (SARS-CoV-2) wastewater surveillance and data reporting practices. Numerous studies have shown that adsorption-extraction (AE) method holds promise, yet several uncertainties remain regarding the optimal AE workflow. Several procedural components may influence the recovered concentrations of target nucleic acid, including membrane types, homogenization instruments, speed and duration, and lysis buffer. In this study, 42 different AE workflows that varied these components were compared to determine the optimal workflow by quantifying endogenous SARS-CoV-2, human adenovirus 40/41 (HAdV 40/41), and a bacterial marker gene of fecal contamination (Bacteroides HF183). Our findings suggest that the workflow chosen had a significant impact on SARS-CoV-2 concentrations, whereas it had minimal impact on HF183 and no effect on HAdV 40/41 concentrations. When comparing individual components in a workflow, such as membrane type (MF-Millipore™ 0.45 µm MCE vs. Isopore™ 0.40 µm), we found that they had no impact on SARS-CoV-2, HAdV 40/41, and HF183 concentrations. This suggests that at least some consumables and equipment are interchangeable. Buffer PM1 + TRIzol-based workflows yielded higher concentrations of SARS-CoV-2 than other workflows. HF183 concentrations were higher in workflows without chloroform. Similarly, higher homogenization speeds (5000-10,000 rpm) led to increased concentrations of SARS-CoV-2 and HF183 but had no effect on HAdV 40/41. Our findings indicate that minor enhancements to the AE workflow can improve the recovery of viruses and bacteria from the wastewater, leading to improved outcomes from wastewater surveillance efforts.

Determinants of microbial colonization on microplastics through wastewater treatment processes: The role of polymer type and sequential treatment.

This study examines the microbial colonization characteristics of microplastics (MPs) in wastewater treatment plants (WWTPs), focusing on polymer types (High-Density Polyethylene (HDPE) and Polyethylene Terephthalate (PET)) and various stages of wastewater treatments. Through individual and sequential deployment approaches, the research aimed to identify the determinants of bacterial colonization on MPs, whether they were introduced at each stage of treatment individually or in sequence from primary to tertiary stages. The study revealed that the stage of wastewater treatment profoundly influenced bacterial colonization on the polymer types MPs, with bacterial attachment being largely niche-specific. HDPE showed increased sensitivity to wastewater composition, leading to selective biofilm formation. For instance, in HDPE, Firmicutes accounted for 25.1 ± 0.04 % during primary treatment, while Alphaproteobacteria increased significantly in the tertiary treatment to 19.8 ± 0.1 %. Conversely, PET exhibited a stochastic pattern of bacterial colonization due to differences in surface hydrophilicity. Additionally, in sequential deployments, a notable shift towards stochastic bacterial attachment on MPs, particularly with HDPE was observed. The Shannon diversity values for MP biofilms were consistently higher than those for wastewater across all stages, with PET showing an increase in diversity in sequential deployments (Shannon diversity: 5.01 ± 0.03 for tertiary stage). These findings highlight the critical role of MPs as carriers of diverse bacteria, emphasizing the necessity for strategies to mitigate their impact in WWTPs. This study presents a significant advancement in our understanding of the interactions between MPs and microbial populations in WWTP environments.

Real-time organic compound monitoring in advanced oxidation process (AOP) of anaerobic digestion effluent: introduction of UV-VIS spectrum representative index by discrete Fourier transform.

Anaerobic digestion effluent from sewage treatment plants (STP) poses a challenge to the operator because of its high organic matter and inorganic nitrogen concentrations, which require an effective process for biological treatment. This study aimed to introduce a UV-VIS spectrum representative index by discrete Fourier transform (DFT) and apply UV-Vis spectrophotometric techniques for real-time organic compound monitoring in the AOP process using anaerobic digestion tank effluent wastewater. The effect of advanced oxidation on the organic compounds of effluent using ozonation was examined. In this research, after treating secondary treated water with the UV-AOP process and anaerobic digestion effluent with ozone microbubble systems, changes in organic substances were expressed by the UV-Vis spectrum and compared with conventional water quality parameters. The anaerobic digestion process effluent was treated through ozone oxidation, had a high curve, and fell gently from 230 to 667 nm. Discrete Fourier transform (DFT) was applied to obtain representative values from the obtained spectrum. From among the coefficients obtained by analyzing the UV-Vis spectrum through DFT, an expected value was selected, and the correlation between CODMn and a3 was the highest (correlation function = 0.694, RSQ = 0.482). Therefore, a linear regression analysis was performed to determine which water quality factor it was related to.

The Trajectory of Depressive Symptoms Across Years of Community Care Utilization Among Older Adults: A 14-Year Follow-up Study Using the 'Korean Welfare Panel Survey'.

OBJECTIVES: While older adults using community care services are known to be vulnerable for depression, community care utilization (CCU) may help to improve the mental health of these elderly. To date, however, it is much less clear how CCU affects depressive symptoms in the elderly population. This study focuses on the trajectory of depressive symptoms across years of CCU among older adults in Korea. METHODS: Using the 2006-2019 Korean Welfare Panel Survey, this study is focused on elderly born in 1940 or earlier and selected 3281 persons for baseline interviews in 2006. This consisted of 35 800 person-year observations during a period of 14 years. Panel data analysis were employed to construct years of CCU. RESULTS: After controlling for covariates, linear term of years using community care was negatively associated with depressive symptoms, but a quadratic term was positively significant. The trajectory of depressive symptoms across the years of CCU follows a U-shaped curve. Older adults in the first year of using community care reported the highest level of depressive symptoms. However, a significant and steady decrease in depressive symptoms was observed during the following 9 years of CCU, which then gradually increased. The level of depressive symptoms at the 14th year of using community care remains significantly lower than the level at the outset of its utilization. CONCLUSIONS: This finding implies that CCU could be beneficial for improving mental health among older adults.

Exploring the vertical transport of microplastics in subsurface environments: Lab-scale experiments and field evidence.

Microplastics (MPs) defined as smaller 5 mm plastic particles have received increasing attention due to their global occurrence and potential toxicity. This study investigated the effects of environmental factors (rainfall intensity, 13 and 29 mm/h) and MP characteristics (morphology (fiber, flake, and film), polymer type (polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS)) and size (100-300, 300-500, and 500-1000 µm)) on the vertical transport of MP in unsaturated soil conditions using lab-scale column experiments. Additionally, the occurrence and characteristics of MP detected in soil/sediment (total 13 samples) and groundwater samples (total 6 samples) were explored in the field study. Laboratory-scale column experiments revealed that heavy rainfall intensity (29 mm/h) increased the degree of MP vertical transport in unsaturated soil conditions and MP fibers showed the greatest vertical mobility among the various morphologies of MPs assessed. For the polymer type and size, the lighter PP polymer or the larger size of MP (500-1000 µm) showed higher mobility. In the field study, a statistical difference in MP abundance was observed depending on the population density and degree of urban development in both soil and groundwater samples. Comparing to the two different types of environmental media samples obtained from the same site, there was a significant difference in the composition of polymer types present while statistically no difference in MP abundance was observed between the two media samples (i.e., soil or sediment and groundwater). In addition, MP fibers and polyethylene (PE) were predominantly detected in our two study areas. These results suggest that various types of MP can pass through the unsaturated zone by water infiltration, even if it takes a long time to reach groundwater. Overall, we found that the degree of vertical transport of the MPs was highly sensitive to environmental conditions and MP characteristics.

"Leisure Life Satisfaction:" Will It Have a Beneficial Impact on Depression Among Older Adults in Community Care Settings in Korea?

OBJECTIVES: While the risk of depression is expected to substantially increase among older adults receiving community care, leisure life satisfaction can be regarded as a key component in enhancing the mental health of those receiving community care. However, it is not yet known whether community care utilization increases the risk of depression, or what role is played by leisure life satisfaction in these settings. This study investigated the relationship between community care utilization and depression, as well as the main effect and the moderating role of leisure life satisfaction on the link between community care utilization and depression among older adults. METHODS: This study, using the 2019 Korean Welfare Panel Survey, conducted multiple regression analysis on data from 4494 elderly people aged 65 years or older. RESULTS: After controlling for potential covariates, older community care recipients were more likely to report symptoms of depression than those who did not receive community care. Meanwhile, leisure life satisfaction was negatively associated with depression in older adults. The test for interaction between community care utilization and leisure life satisfaction revealed that leisure life satisfaction significantly attenuated the link between depression and community care utilization. CONCLUSIONS: The findings of this study imply that leisure life satisfaction could play a meaningful role in improving the mental health of older adults receiving community care. Welfare policies affecting older adults should consider leisure life satisfaction as an important resource for reducing depression in community care settings.

Analysis of the 2012 Canadian Community Health Survey-Mental Health demonstrates employment insecurity to be associated with mental illness.

ABSTRACT: A growing number of people depend on flexible employment, characterized by outsider employment and lower levels of job security. This study investigated whether there was a synergistic effect of employment status and job insecurity on mental disorders.This study used data from the 2012 Canadian Community Health Survey-Mental Health (CCHS) of 13,722 Canada's labor force population aged 20 to 70. Data were collected from January to December, 2012, using computer-assisted personal interviewing. As combining employment status with perceived job insecurity, we formed five job categories: secure full-time, full-time insecure, part-time secure, part-time insecure employment, and unemployment.Results showed that, regardless of employment status (full-time vs part-time), insecure employment was significantly associated with high risk of mental disorders. Furthermore, the odds ratios for insecure employment were similar to those for unemployment. Male workers who are full-time, but with insecure jobs, were more likely to experience mental disorders than female workers.This study's findings imply that while perceived job insecurity may be a critical factor for developing mental health problems among workers, providing effective health care services can mitigate an excessive health risk for the most vulnerable employment, especially for insecure part-time employment and unemployment.

Is Job Insecurity Worse for Mental Health Than Having a Part-time Job in Canada?

OBJECTIVES: A growing number of people depend on flexible employment, characterized by outsider employment status and perceived job insecurity. This study investigated whether there was a synergistic effect of employment status (full-time vs. part-time) and perceived job insecurity on major depressive disorder. METHODS: Data were derived from the 2012 Canadian Community Health Survey-Mental Health of 12 640 of Canada's labor force population, aged 20 to 74. By combining employment status with perceived job insecurity, we formed four employment categories: full-time secure, full-time insecure, part-time secure, and part-time insecure. RESULTS: Results showed no synergistic health effect between employment status and perceived job insecurity. Regardless of employment status (full-time vs. part-time), insecure employment was significantly associated with a high risk of major depressive disorder. Analysis of the interaction between gender and four flexible employment status showed a gender-contingent effect on this link in only full-time insecure category. Men workers with full-time insecure jobs were more likely to experience major depressive disorders than their women counterparts. CONCLUSIONS: This study's findings imply that perceived job insecurity may be a critical factor for developing major depressive disorder, in both men and women workers.

Thermoelectric and Transport Properties of Permingeatite Cu3SbSe4 Prepared Using Mechanical Alloying and Hot Pressing.

Permingeatite (Cu3SbSe4) is a promising thermoelectric material because it has a narrow band gap, large carrier effective mass, and abundant and nontoxic components. Mechanical alloying (MA), which is a high-energy ball mill process, has various advantages, e.g., segregation/evaporation is not required and homogeneous powders can be prepared in a short time. In this study, the effects of MA and hot-pressing (HP) conditions on the synthesis of the Cu3SbSe4 phase and its thermoelectric properties were evaluated. The electrical conductivity decreased with increasing HP temperature, while the Seebeck coefficient increased. The power factor (PF) was 0.38-0.50 mW m-1 K-2 and the thermal conductivity was 0.76-0.78 W m-1 K-1 at 623 K. The dimensionless figure of merit, ZT, increased with increasing temperature, and a reliable and maximum ZT value of 0.39 was obtained at 623 K for Cu3SbSe4 prepared using MA at 350 rpm for 12 h and HP at 573 K for 2 h.

Highly Flexible Graphene Derivative Hybrid Film: An Outstanding Nonflammable Thermally Conductive yet Electrically Insulating Material for Efficient Thermal Management.

In modern society, advanced technology has facilitated the emergence of multifunctional appliances, particularly, portable electronic devices, which have been growing rapidly. Therefore, flexible thermally conductive materials with the combination of properties like outstanding thermal conductivity, excellent electrical insulation, mechanical flexibility, and strong flame retardancy, which could be used to efficiently dissipate heat generated from electronic components, are the demand of the day. In this study, graphite fluoride, a derivative of graphene, was exfoliated into graphene fluoride sheets (GFS) via the ball-milling process. Then, a suspension of graphene oxide (GO) and GFSs was vacuum-filtrated to obtain a mixed mass, and subsequently, the mixed mass was subjected to reduction under the action hydrogen iodide at low temperature to transform the GO to reduced graphene oxide (rGO). Finally, a highly flexible and thermally conductive 30-µm thick GFS@rGO hybrid film was prepared, which showed an exceptional in-plane thermal conductivity (212 W·m-1·K-1) and an excellent electrical insulating property (a volume resistivity of 1.1 × 1011 Ω·cm). The extraordinary in-plane thermal conductivity of the GFS@rGO hybrid films was attributed to the high intrinsic thermal conductivity of the filler components and the highly ordered filler alignment. Additionally, the GFS@rGO films showed a tolerance to bending cycles and high-temperature flame. The tensile strength and Young's modulus of the GFS@rGO films increased with increasing the rGO content and reached a tensile strength of 69.3 MPa and a Young's modulus of 10.2 GPa at 20 wt % rGO. An experiment of exposing the films to high-temperature flame demonstrated that the GFS@rGO films could efficiently prevent fire spreading. The microcombustion calorimetry results indicated that the GFS@rGO had significantly lower heat release rate (HRR) compared to the GO film. The peak HRR of GFS@rGO10 was only 21 W·g-1 at 323 °C, while that of GO was 198 W·g-1 at 159 °C.

Microbusinesses and Occupational Stress: Emotional Demands, Job Resources, and Depression Among Korean Immigrant Microbusiness Owners in Toronto, Canada.

OBJECTIVES: While occupational stress has long been a central focus of psychological research, few studies have investigated how immigrant microbusiness owners (MBOs) respond to their unusually demanding occupation, or how their unresolved occupational stress manifests in psychological distress. Based on the job demands-resources model, this study compared MBOs to employees with regard to the relationships among emotional demands, job resources, and depressive symptoms. METHODS: Data were derived from a cross-sectional survey of 1288 Korean immigrant workers (MBOs, professionals, office workers, and manual workers) aged 30 to 70, living in Toronto and surrounding areas. Face-to-face interviews were conducted between March 2013 and November 2013. RESULTS: Among the four occupational groups, MBOs appeared to endure the greatest level of emotional demands, while reporting relatively lower levels of job satisfaction and job security; but MBOs reported the greatest job autonomy. The effect of emotional demands on depressive symptoms was greater for MBOs than for professionals. However, an inspection of stress-resource interactions indicated that though MBOs enjoyed the greatest autonomy, the protective effects of job satisfaction and security on the psychological risk of emotional demands appeared to be more pronounced for MBOs than for any of the employee groups. CONCLUSIONS: One in two Korean immigrants choose self-employment, most typically in family-owned microbusinesses that involve emotionally taxing dealings with clients and suppliers. However, the benefits of job satisfaction and security may protect MBOs from the adverse mental health effects of job stress.

Validating a single-question depression measure among older adults.

BACKGROUND: A single-item depression measure may not be adequate in capturing the complex entity of mental health, despite wide use of this indicator in community studies. This study evaluated the accuracy of a single-question depression measure in comparison to two composite indices-the Center for Epidemiologic Studies Depression Scale (CESD) and the Geriatric Depression Scale (GDS). MATERIALS AND METHODS: A total of 800 elderly participants ranging from 60 to 89 years of age and residing in Seoul were recruited using a multistage sampling scheme in 2015. The survey was conducted by trained interviewers with a constructed questionnaire. Reliability and validity measures such as the Kappa index, sensitivity, specificity, PPV, NPV, and AUC were used to evaluate the accuracy of the single question measure. Socio-demographic group differences in accuracy were compared by age, sex, marital status, education, employment, and financial status. RESULTS: The prevalence of depression by a single-question measure was much lower than those of CESD and GDS (5.5%, 12.3%, and 12.1%, respectively). The sensitivity of the single-item measure, based on CESD and GDS, was extremely low at 30.6% and 36.1%. In the subgroup analysis, however, there was a marked educational discrepancy in all accuracy measures; in sensitivity, people with a university degree or higher showed about 2.4 times higher sensitivity than those having only a primary school education. CONCLUSIONS: The results show that a single-question depression measure should be used with caution. In addition, the single-question measure could substantially underestimate depression among the risk group of older adults.

Facilitators of and Barriers to Gastric Cancer Screening Among Korean Americans.

BACKGROUND: Gastric cancer is the most highly prevalent cancer among Korean Americans, occurring at a higher rate than among other Asian Americans and non-Latino Whites. However, little is known about the culturally specific barriers to gastric cancer screening among Korean Americans. OBJECTIVE: The aim of this study was to explore facilitators of and barriers to gastric cancer screening among Korean Americans. METHODS: In this qualitative focus group study, a convenience sample of 50 Korean Americans aged 21 to 75 years was recruited from the Puget Sound area of Washington with the assistance of Korean churches. Five focus groups of 6 to 8 and 1 focus group of 13 were conducted in a church, a café, and an apartment community center. The focus group discussions lasted approximately 30 minutes to 1 hour. Directed content analysis was used to analyze the data. RESULTS: Facilitators included exposure to Korean media, history and prevalence of gastric problems, perceptions concerning positive aspects of the healthcare system in South Korea, physician recommendations, technology, and church health fair. Barriers included a lack of knowledge, finance/lack of health insurance, fear of test results, perceptions of an inconvenient American healthcare system, a lack of knowledge of American healthcare providers on culturally related health risks, a dislike of medical procedures, and no preventive measures. CONCLUSIONS: Sociocultural facilitators and barriers add new knowledge in a field with scarce information available. IMPLICATIONS FOR PRACTICE: The study findings lay the groundwork for developing culturally relevant interventions that enhance healthcare providers' awareness while empowering Korean Americans to prevent gastric cancer.

Accuracy of Self-reported Hypertension, Diabetes, and Hypercholesterolemia: Analysis of a Representative Sample of Korean Older Adults.

OBJECTIVES: This study will assess the accuracy of self-reported hypertension, diabetes, and hypercholesterolemia among Korean older adults. METHODS: Using data from the fourth Korean National Health Examination and Nutrition Survey (KNHANES IV, 2007-2009), we selected 7,270 individuals aged 50 years and older who participated in both a health examination and a health interview survey. Self-reported prevalence of hypertension (HTN), diabetes mellitus (DM), and hypercholesterolemia was compared with measured data (arterial systolic/diastolic blood pressure, fasting glucose, and total cholesterol). RESULTS: An agreement between self-reported and measured data was only moderate for hypercholesterolemia (κ, 0.48), even though it was high for HTN (κ, 0.72) and DM (κ, 0. 82). Sensitivity was low in hypercholesterolemia (46.7%), but high in HTN and DM (73% and 79.3%, respectively). Multiple analysis shows that predictors for sensitivity differed by disease. People with less education were more likely to exhibit lower sensitivity to HTN and hypercholesterolemia, and people living in rural areas were less sensitive to DM and hypercholesterolemia. CONCLUSION: Caution is needed in interpreting the results of community studies using self-reported data on chronic diseases, especially hypercholesterolemia, among adults aged 50 years and older.

Mediating and Moderating Effects in Ageism and Depression among the Korean Elderly: The Roles of Emotional Reactions and Coping Reponses.

OBJECTIVES: This study evaluated the relationship between ageism and depression, exploring the stress-mediating and stress-moderating roles of emotional reactions and coping behaviors. METHODS: Data were from the 2013 Ageism and Health Study (n = 816), a cross-sectional survey of urban and rural community-dwelling seniors aged 60-89 years in South Korea. Participants with at least one experience of ageism reported on their emotional reactions and coping responses. The measure yielded two types of coping: problem-focused (taking formal action, confrontation, seeking social support) and emotion-focused (passive acceptance, emotional discharge). RESULTS: Although ageism was significantly associated with depressive symptoms (B = 0.27, p < 0.0001), the association was entirely mediated by emotional reactions such as anger, sadness, and powerlessness. Problem-focused coping, especially confrontation and social support, seemingly reduced the impact of emotional reactions on depression, whereas emotion-focused coping exacerbated the adverse effects. CONCLUSION: These findings support the cultural characterization explanation of ageism and related coping processes among Korean elderly and suggest that regulating emotional reactions may determine the efficacy of coping with ageism.

Racial/ethnic variations in the main and buffering effects of ethnic and nonethnic supports on depressive symptoms among five ethnic immigrant groups in Toronto.

OBJECTIVES: This study examined variations in the main and buffering effects of ethnic and nonethnic social support on depressive symptoms associated with discrimination among five immigrant groups in Toronto. DESIGN: Data were taken from the Toronto Study of Settlement and Health, a cross-sectional survey of adult immigrants from five ethnic communities (Vietnamese, Ethiopian, Iranian, Korean, and Irish) in Toronto. A total of 900 surveys were collected through face-to-face interviews conducted between April and September 2001. RESULTS: Significant ethnic variations were observed in the effects of both ethnic and nonethnic social supports on discrimination-related depressive symptoms. Regarding the main effect, ethnic social support was significantly stronger for Iranian, Ethiopian, and Korean immigrants than for Irish immigrants. The benefits of nonethnic support were stronger for Iranian immigrants compared to the effect found in the Irish sample. With respect to stress-buffering or stress-moderating effects of social support, ethnic support was significant in all ethnic groups, except the Vietnamese group. Nonethnic support aggravated the negative impact of discrimination on depressive symptoms in the Irish group, but exerted a stress-buffering effect in the Iranian group. CONCLUSIONS: Overall, social supports received from fellow ethnic group members had significant main effects (suppressing depressive symptoms) and stress-buffering effects and were most pronounced in the minority ethnic immigrant groups of Ethiopians, Koreans, and Iranians. The effects were least evident among the Vietnamese and Irish. Evidence for the stress-suppressing and stress-buffering role of cross-ethnic group supports was unclear, and even inverted among Irish immigrants. Empirical evidence from the current study seems to support the sociocultural similarity hypothesis of social support.

Microstructure and Mechanical Properties of Ultra-Fine Grain Al-Zr Alloy Fabricated by Mechanical Alloying Process.

The ultra-fine grain Al-4Zr alloy has been successfully fabricated by a mechanical alloying process. The intermetallic Al3Zr phases strongly enhance the mechanical properties of Al-based alloy and prevent grain growth of alloy. The phase stability and transformation during mechanical alloying process have been investigated. The ultra-fine grain alloy has been successfully obtained. The thin film of Al-4Zr alloy has been observed by a transmission electron microscope. The equivalent grain size of as-milling specimen is 55 nm. After milling process, the specimens were heat treated at 350 °C to 650 °C. The equivalent grain size of heat treated specimens were 80 nm at 350 °C and 130 nm at 650 °C. Some of Zr atoms were dissolved into the Al matrix and most of them reacted with hydrogen produced by decomposition of PCA to form ZrH2 during mechanical alloying process. These ZrH2 hydrides decomposed gradually after the heat treatment. Stable A13Zr with a D023 structure was formed by heat treatment at temperature of 550 °C.

Effect of Al and Y2O3 on Mechanical Properties in Mechanically Alloyed Nanograin Ni-Based Alloys.

The effects of aluminum and Y2O3 on the mechanical properties in nano grain Ni-based alloys have been investigated. The test specimens are prepared by mechanical alloying at an Ar atmosphere. The addition of Y2O3 and Al may cause an increase in the tensile strength at room temperature, 400 °C and 600 °C. However, it was confirmed that the increase of tensile strength at room temperature and 400 °C was predominantly caused by addition of Y2O3, while that at 600 °C was mainly due to addition of Al. These results can be attributed to the dispersion strengthening of Y2O3, preventing the formation of Cr2O3 and the change of fracture mode at 600 °C by the addition of Al.

Mini-review on river eutrophication and bottom improvement techniques, with special emphasis on the Nakdong River.

Water quality in rivers is vital to humans and to maintenance of biotic and ecological integrity. During the Four Major Rivers restoration of South Korea, remarkable attempts have been made to decrease external nutrient loads and moveable weirs were designed to discharge silt that may deposit in pools. However, recently eutrophication of the Nakdong River, which was limited to the lower reaches, is seen to be spreading upstream. The reduction of external nutrient loads to rivers is a long-term goal that is unlikely to lead to reductions in algal blooms for many years because of the time required to implement effective land management strategies. It would therefore be desirable to implement complementary strategies. Regulating the amount of water released is effective at preventing algae blooms in weir pools; so, the relationship between discharge, stratification and bloom formation should be understood in this regard. However, pollutants are likely to accumulate in the riverbed upstream from release points. Thus, to control phosphorus levels, total phosphorus density should be lowered by applying in-river techniques as well. As many ecosystem properties are controlled by multiple processes, simultaneous river bottom improvement techniques, such as combined dissolved oxygen supply and nutrient inactivation, are likely to be effective. The purpose of this review is to present a series of technological approaches that can be used to improve the river bottom area and hence sediment nutrient release, and to illustrate the application of these techniques to the Nakdong River.