Al-Cr-Si ternary quench ribbons are fabricated using a single roll method and investigated for their structural and thermal properties. In particular, the sinterability is examined by pulse current sintering to obtain the following results. The Al74Cr20Si6 composition becomes a quasicrystalline single phase; by reducing the amount of Cr, it becomes a twophase mixed structure of Al phase and quasicrystalline phase. As a result of sintering of Al74Cr20Si6, Al77Cr13Si10 and Al90Cr6Si4 compositions, the sintering density is increased with the large amount of Al phase; the sintering density is the highest in Al90Cr6Si4 composition. In addition, as a result of investigating the effects of sintering temperature and pressurization on the sintered density of Al90Cr6Si4, a sintered compact of 99% or more at 513 K and 500 MPa is produced. In particular, since the Al-Cr-Si ternary crystal is more thermally stable than the Al-Cr binary quaternary crystal, it is possible to increase the sintering temperature by about 100 K. Therefore, using an alloy of Al90Cr6Si4 composition, a sintered compact having a sintered density of 99 % or more at 613 K and 250 MPa can be manufactured. It is possible to increase the sintering temperature by using the alloy system as a ternary system. As a result, it is possible to produce a sintered body with higher density than that possible using the binary system, and at half the pressure compared with the conventional Al-Cr binary system.

This study attempts to find optimal conditions of the friction coefficient using a discrete element method (DEM) simulation with various friction coefficient conditions and three different grinding media with various ball sizes in a traditional ball mill (TBM). Using ball motion of the DEM simulation are obtained using the optimal friction coefficient compared with actual motion; photographs are taken by the digital camera and the snapshot images are analyzed. In the simulation, the rotation speed of the mill, the materials and velocity of the grinding media, and the friction coefficient between the balls and the wall of the pot are fixed as the actual experimental conditions. We observe the velocity according to the friction coefficient from the DEM simulation. The friction coefficient is found to increase with the velocity. Milling experiments using a traditional ball mill with the same experimental conditions as those of the DEM simulation are conducted to verify the simulated results. In addition, particle morphology change of copper powder is investigated and analyzed using scanning electron microscopy (SEM) for the milling experiment.

This study produces electroconductive polycaprolactone (PCL)-based film with different amounts of graphene (G) through electrospinning, and the characteristics of the produced G/PCL composites are investigated. The G/PCL results are analyzed by comparing them with those obtained using pure PCL electrospun film as a control. The morphology of electrospun material is analyzed through scanning electron microscopy and transmission electron microscopy. Mechanical and electrical properties are also evaluated. Composites containing 1% graphene have the highest elongation rate, and 5% samples have the highest strength and elasticity. Graphene contents > 25% show electro-conductivity, which level improves with increase of graphene content. Biological characteristics of G/PCL composites are assessed through behavioral analysis of neural cell attachment and proliferation. Cell experiments reveal that compositions < 50% show slightly reduced cell viability. Moreover, graphene combinations facilitated cell proliferation compared to pure PCL. These results confirm that a 25 % G/PCL composition is best for application to systems that introduce external stimuli such as electric fields and electrodes to lead to synergistic efficiency of tissue regeneration.

Owing to its low cost, easy fabrication process, and good ionic properties, aqueous supercapacitors are under strong consideration as next-generation energy storage devices. However, the limitation of the current collector is its poor electrochemical stability, leading to low energy storage performance. Therefore, a reasonable design of the current collector and the acidic electrolyte is a necessary, as well as interfacial engineering to enhance the electrochemical performance. In the present study, graphite foil, with excellent electrochemical stability and good electrical properties, is suggested as a current collector of aqueous supercapacitors. This strategy results in excellent electrochemical performance, including a high specific capacitance of 215 F g−1 at a current density of 0.1 A g−1, a superior high-rate performance (104 F g−1 at a current density of 20.0 A g−1), and a remarkable cycling stability of 98 % at a current density of 10.0 A g−1 after 9,000 cycles. The superior energy storage performance is mainly ascribed to the improved ionic diffusion ability during cycling.

Porous carbons have been widely used as electrode material for supercapacitors. However, commercial porous carbons, such as activated carbons, have low electrochemical performance. Nitrogen-doping is one of the most promising strategies to improve electrochemical performance of porous carbons. In this study, nitrogen self-doped porous carbon (NPC) is prepared from melamine foam by carbonization to improve the supercapacitive performance. The prepared NPC is characterized in terms of the chemical structures and elements, morphology, pore structures, and electrochemical performance. The results of the N2 physisorption measurement, X-ray diffraction, and Raman analyses reveal that the prepared NPC has bimodal pore structures and pseudo-graphite structures with nitrogen functionality. The NPC-based electrode exhibits a gravimetric capacitance of 153 F g−1 at 1 A g−1, a rate capability of 73.2 % at 10 A g−1, and an outstanding cycling ability of 97.85% after 10,000 cycles at 10 A g−1. Thus, the NPC prepared in this study can be applied as electrode material for high-performance supercapacitors.

P91 steel has been a highly researched material because of its applicability for high-temperature applications. Considerable efforts have been made to produce experimental creep data and develop models for creep life prediction. As creep tests are expensive and difficult to conduct, it is vital to develop authenticated empirical methods from experimental results that can be utilized for better understanding of creep behavior and can be incorporated into computational models for reliable prediction of creep life. In this research, a series of creep rupture tests are performed on the P91 specimens within a stress range of 155 MPa to 200 MPa and temperature range of 640 oC (913 K) to 675 oC (948 K). The microstructure, hardness, and fracture surfaces of the specimens are investigated. To analyze the results of the creep rupture tests at a macro level, a parameter called creep work density is derived. Then, the relationships between various creep parameters such as strain, strain rate, time to rupture, creep damage tolerance factor, and creep work density are investigated, and various empirical equations are obtained.

Wire arc additive manufacturing (WAAM) is being considered as a technology to replace the conventional manufacturing process of titanium alloys. However, coarse β grains, which can extend through several deposited materials, result in strong textures and anisotropy. As a solution, we study the plastic deformation effects of ultrasonic needle peening (UNP) on the microstructure. UNP treated materials deform plastically and the dislocation density increases. Fine α+α' grains with low aspect ratio are observed in the UNP treated specimens. UNP treated WAAM Ti-6Al-4V alloys have higher strength and lower elongation than those characteristics of WAAM Ti-6Al-4V alloys. Due to UNP treatment, the z-axis directional specimens exhibit a greater effect of reducing elongation than do the x-axis directional specimens. The UNP treatment produces fine grains in proportion to the number of times UNP is performed, thereby increasing strength. UNP processes produce a large number of dislocations in the WAAM Ti-6Al-4V alloys, with the most dislocations being formed at the surface.

Purpose: This study was aimed to examine the background of the emergence of qualitative research and the purpose pursued by qualitative research. Based on this, it was to derive ethical principles and considerations that the researcher should reflect and practice in the process of conducting qualitative research. Methods: A review article was constructed by collecting and analyzing extensive literature related to the research ethics topics. Results: In a human subject research, both positivistic and qualitative researchers should most sensitively consider the protection of the research subjects, especially those in vulnerable situations. Ethical principles for human subject research can be suggested as follows. The first is to respect and protect the subject's autonomy, which is linked to the principle of informed consent and subject protection. Second, the researcher should conduct research according to the best interests of the study participants. This is linked to the selection of research topics and the reciprocity of the research results. Third, it is necessary to maintain an open attitude to the study participants. To this end, it is also linked to the researcher's open and sympathetic attitude to respect the emotions and experiences of the study participants, and to treat them truthfully without hiding or deceived during the data collection process. Conclusion: The core purpose of qualitative research is to restore humanity. Qualitative research needs to go deeper into the lives of others. Researchers who are conducting qualitative research must reflect on ethics and consider ethical guidelines.

Purpose: This study was aimed to analyze the research trends by investigating the nursing theories used in research articles in Journal of Korean Academy of Nursing for the last 10 years. Methods: Among the research articles published in the Journal of Korean Academy of Nursing for the past 10 years from 2010 to 2019, the research trends was analyzed by investigating the nursing theories used in the studies. Results: As the results of a survey of 847 papers published in the Journal of Korean Academy of Nursing from 2010 to 2019, 139 studies applied to the theory were extracted. As for the theory, one Grand Theory, Roy’s adaptation model, and 6 Middle Range Theories including Kolcaba’s comfort theory, Pender's health promotion model, King's goal attainment theory, Watson's human caring theory, Reed's self-transcendence theory, Mishel's uncertainty in illness theory. Conclusion: In nursing, more use of nursing theories in research is necessary in the future, not only in quantitative research methods but also in qualitative research.

Purpose: This study was to identify the perception of death in nursing students. Methods: This study adopted the triangulation method. The participants was third grade nursing students. Quantitative data was analyzed using descriptive statistics. Qualitative data was analyzed using qualitative content analysis. Results: Among the participants' perception of death, the highest score was the respect for life, and the lowest was anxiety about death. The participants believed that there was a relatively happy and unfortunate death, and that well-dying was achieved through acceptance, reflection, and rigorous preparation in life. Well-dying was possible only when well-being was proceeded. Nursing students perceived death as the end stage of life that needed preparation. Conclusion: It is necessary for nursing students to have opportunities to reflect on death when they observe a patient’s death in clinical practice. Also, they need to have death-related education for them to grow as competent nurses to deal with life and death journey of their patients in future.

Purpose: The purpose of this study was to understand in-depth experiences of role conflict among infection control nurses’ (ICNs) in terms of the gaps between the role expectations and actual roles. Methods: This study was a qualitative study to explore and describe the implications of role conflict experiences of ICNs through a phenomenological approach. One-on-one in-depth interviews were conducted with ICNs who worked as full-time for more than three years in the infection control department, and the results were analyzed using Colaizzi’s (1978) phenomenological method. Results: Topics brought up by the participants were categorized into five themes. The themes included "lack of awareness of infection control", "psychological burden of professional competence", "infectious control not being accepted due to different management and operational goals", "unrelentingly overworked", "shadow labor without adequate compensation", and "The process of earning mutual trust". Conclusion: In order to resolve the role conflict of ICNs, it is necessary to establish a career management system for ICNs and to have an appropriate compensation system.

Purpose: The purpose of this study was to understand the meaning and nature of the experiences of adult patients infected with HIV (Human Immunodeficiency Virus) when they were teens. Methods: To this end, we analyzed how the experience was interpreted in their daily lives and what its meaning was through the Interpretative Phenomenological Analysis (IPA), a new method of extensive qualitative research in the UK. Among the confirmed HIV infections in teenagers, three people who agreed to participate in the study were men in their 20s and 30s. Participants were interviewed in-depth to collect data and the data was analyzed and interpreted using IPA. Results: As the results, eight themes and 18 sub-themes were derived from meaningful statements through in-depth analysis, and these were categorized into 4 categories. The four categories included ‘shock and despair’, ‘realistic difficulties’, ‘barriers in relationships’, and ‘life transitions’. Conclusion: Adolescent infected persons had support from their families or surroundings, and this positively influenced on the recovery of infected persons. We discussed the implications of the understanding of HIV infection, changes in social perception, the need for correct sex education, and the experiences of teenagers infected with HIV, and suggested follow-up studies.

Purpose: The purpose of this study was to explore and analyze the education experiences of nursing graduate students in training simulation educators. Methods: Data were collected using a focus group method with a total of 13 nursing graduate students who ever participated in simulation education for nursing college students. Results: Four theme clusters and 15 sub-themes were emerged through qualitative content analysis. The core theme was “Flapping wings as a novice simulation educator”. The four theme clusters include ‘Confronting myself where expectations and worries coexist’, ‘Experience a new world untrained in the hospital’, ‘Limitation of simulation hard to reach the reality’, ‘Way to become an expert in simulation education’. Conclusion: Nursing graduate students found that the experiences of novice learners as a simulation educator was rewarding and helpful in increasing their self-confidence prior to being placed in an educational setting. Creating a simulation experience for college students could be a daunting task for educators in nursing. Therefore, continued and sustainable efforts are mandated by developing the curriculum for training simulation educators.

Background: Theoretically, balance is affected by the height of center of mass (COM) during quiet standing. However, no one examined this in humans with variables derived from the center of pressure (COP). Objects: We have conducted balance experiment to measure COP data during quiet standing, in order to examine how the COP measures were affected by the height of COM, vision, floor conditions, and gender. Methods: Twenty individuals stood still with feet together and arms at sides for 30 seconds on a force plate. Trials were acquired with three COM heights: 1% increased or decreased, and not changed, with two vision conditions: eyes closed (EC) and eyes open (EO), and with two floor conditions: unstable (foam pad) and stable (force plate) floor. Outcome variables included the mean distance, root mean square distance, total excursion, mean velocity, and 95% confidence circle area. Results: All outcome variables were associated with the COM height (p < 0.0005), vision (p < 0.0005), and floor condition (p < 0.003). The mean velocity and 95% confidence circle area were 5.7% and 21.8% greater, respectively, in raised COM than in lowered COM (24.6 versus 23.2 mm/s; 1,013.4 versus 832.3 mm2). However, there were no interactions between the COM height and vision condition (p > 0.096), and between the COM height and floor condition (p > 0.183) for all outcome variables. Furthermore, there was no gender difference in all outcome variables (p > 0.186). Conclusion: Balance was affected by the change of COM height induced by a weight belt in human. However, the effect was not affected by vision or floor condition. Our results should inform the design of balance exercise program to improve the outcome of the balance training.

Background: Researchers have previously commenced examining the degree of concordance between parent proxy and child self-reports on health-related quality of life (HRQOL) of many disease and impairment populations. Objects: To explore the differences between parent proxy and child self-reports on the HRQOL using Korean version of KIDSCREEN-10 questionnaires for applying to elementary school children and their parents who participated for a school-based wellness program. Methods: The focus groups were recruited for a school-based wellness program by implementing the following wellness services: 1) referring to a screening session for detecting potential posture-related musculoskeletal problems and 2) recommending home exercise programs. Before a primary field testing for the program, two focus groups were formed with a group of 9 parents and their 9 elementary school children aged 8–10 years of age. The parent proxy and child self-report versions of KIDSCREEN-10 questionnaires were administered to both groups after completion of the wellness program. Item level Rasch rating scale analysis was applied to compute logit scales of KIDSCREEN-10 questionnaire. Intraclass correlation coefficients (ICCs) and scatterplot of item difficulty between two reports were analyzed. Results: For fit statistics of parent proxy report, all items except 4 items (i.e., psychological well-being, mood/emotions, self-perception, parent relation) were found to be acceptable. For fit statistics of child self-report, all items except 3 items (i.e., psychological well-being, autonomy and home life) were acceptable. The relationship between two reports using ICCs were ranging from weak to very strong at p = 0.05 (i.e, ICCs = 0.011 to 0.905). Scatterplot analysis between two reports showed a major disparity on self-perception item at 95% confidence intervals. Conclusion: Both item level analyses and ICC comparisons provided a disparity between parent proxy and child self-reports of the HRQOL on self-perception item after competing a school-based wellness program. Therapist should consider the item as part of the HRQOL assessment.

Background: Forward head posture (FHP) causes various posture imbalances associated with the head and neck. Myofascial release is an effective treatment method used for relaxing muscles and reducing muscle hyperactivity, but no studies have been conducted on suboccipital and neck muscles related to FHP. Objects: The purpose of this study was to investigate the immediate effect of roller massages on the cranio-cervical flexion (CCF) range of motion (ROM) and CCF strength applied to suboccipital and neck muscles in subject with forward head posture. Methods: Twenty-four FHP subjects (male: 13, female: 11) were recruited for this study. All subjects were recruited with a craniovertebral angle (CVA) of 53 degrees or less and a head tilt angle (HTA) of 20.66 degrees or higher. CCF strength was measured using Pressure biofeedback unit (PBU) in the supine posture and CCF ROM was measured using smartphone-based inclinometer. Roller massage (RM) was applied to suboccipital and neck muscles for 2 minutes and CCF ROM and strength were remeasured. Results: These results of this study showed that CCF ROM was a significant difference in CCF ROM before and after RM (p < 0.05). CCF strength also showed a significant difference before and after RM (p < 0.05). Conclusion: RM method might be recommended to increase the immediate ROM and strength of CCF in subjects with forward head posture.

Background: Flat feet can be identified by assessing the collapse of the medial longitudinal arch (MLA) and these conditions can trigger epidemiological changes in the feet. Many of previous studies compared the muscle activity of lower body in terms of intervention and dynamics to treat the structural defect of flat feet. However, few studies have investigated or analyzed the muscle activity of gastrocnemius muscle in the subjects with flat feet. Objects: This study investigated the differences in changes of medial and lateral plantar flexors in subjects with flat feet during bipedal heel-rise (BHR) task and analyzed the differences in muscle activity between two groups by measuring the electromyography (EMG) of abductor hallucis (AH), tibialis anterior (TA), medial gastrocnemius (MG), lateral gastrocnemius (LG). Methods: A total of Twenty one adult females participated in this experiment. Subjects were assigned to groups according to the navicular drop test. The task was applied to the leg, where the heel lifting action prevailed. The muscle activity of the medial and lateral feet plantar flexors was evaluated, and the % maximum voluntary isometric contractions (%MVIC) of these were compared. Results: For the difference between groups the muscle activity (%MVIC) of LG muscle was statistically significantly low in flat feet group compared to healthy feet group (flat feet: 64.57, healthy feet: 90.17; p < 0.05). Conclusion: The results of this study will contribute to identifying the muscle activities of medial and lateral feet plantar flexors among subjects with flat feet, which can cause abnormal epidemiological changes in the feet.

Background: Only 2% of falls in older adults result in serious injuries (i.e., hip fracture). Therefore, it is important to differentiate injurious versus non-injurious falls, which is critical to develop effective interventions for injury prevention. Objects: The purpose of this study was to a. extract the best features of surface electromyography (sEMG) for classification of injurious falls, and b. find a best model provided by data mining techniques using the extracted features. Methods: Twenty young adults self-initiated falls and landed sideways. Falling trials were consisted of three initial fall directions (forward, sideways, or backward) and three knee positions at the time of hip impact (the impacting-side knee contacted the other knee (“knee together”) or the mat (“knee on mat”), or neither the other knee nor the mat was contacted by the impacting-side knee (“free knee”). Falls involved “backward initial fall direction” or “free knee” were defined as “injurious falls” as suggested from previous studies. Nine features were extracted from sEMG signals of four hip muscles during a fall, including integral of absolute value (IAV), Wilson amplitude (WAMP), zero crossing (ZC), number of turns (NT), mean of amplitude (MA), root mean square (RMS), average amplitude change (AAC), difference absolute standard deviation value (DASDV). The decision tree and support vector machine (SVM) were used to classify the injurious falls. Results: For the initial fall direction, accuracy of the best model (SVM with a DASDV) was 48%. For the knee position, accuracy of the best model (SVM with an AAC) was 49%. Furthermore, there was no model that has sensitivity and specificity of 80% or greater. Conclusion: Our results suggest that the classification model built upon the sEMG features of the four hip muscles are not effective to classify injurious falls. Future studies should consider other data mining techniques with different muscles.

Background: Flat-back posture refers to a posture in which the pelvis is tilted backward, the lumbar spine is bent, the upper thoracic spine is increasingly bent, and the lower thoracic spine is straight. Given that most of the day is spent sitting, we need to develop exercise programs and devices that are suitable for people who spend less time exercising than sitting. Objects: This study investigated the effects of resistance footrest exercise on spine posture angles in visual display terminal (VDT) workers with flat back. Methods: We measured the upper lumbar angle (ULA) and lower lumbar angle (LLA) using a flexible ruler for the ULA and LLA. Then, after 1 week of resistance footrest exercise designed to strengthen the lumbar spine musculature, we measured these angles again. We measured each angle three times and then compared measurements from before and after exercise. Results: There were no significant differences in the ULA following the strengthening exercise, but significant differences were observed in LLA. Conclusion: The resistance footrest exercise strengthened the muscles affecting the pelvic and lumbar lordotic angles, and increases in the LLA were changed. This suggests that the role of the lower lumbar spine in the lumbar lordotic curve is greater than that of the upper lumbar spine. In addition, considering the contemporary tendency to lead fairly sedentary lives, these results indicate that exercising while seated can be effective.

Background: Whole-body vibration (WBV) has been used to alleviate proprioceptive damage by musculoskeletal and neurological conditions. However, no study has determined whether wearing shoes while applying WBV can affect proprioception precision of the knee joint. Objects: This study aimed to determine the differences in the proprioceptive precision of the knee joint before and after WBV and to compare the proprioceptive precision of the knee joint between barefoot and shoe-wearing conditions. Methods: This study recruited 33 healthy participants. A passive-to-active angle reproduction test was used to measure the proprioception precision of the knee joint using an electrogoniometer, and the target angle was set to a knee flexion of 30°. Proprioception precision was calculated using the error angle (angular difference from 30°). Proprioceptive precision was measured in weight-bearing and non-weight-bearing positions before and after applying WBV for 20 minutes at 12 Hz in barefoot and shoe-wearing conditions. Mixed repeated analysis of variance was used to determine the differences in changes in the proprioceptive precision of the knee joint according to foot conditions. Results: There were significant improvements in the weight-bearing (p = 0.002) and nonweight- bearing (p < 0.001) proprioceptive precision of the knee joint after applying WBV. However, there was no significant difference in the change in proprioceptive precision of the knee joint after applying WBV between the barefoot and shoe-wearing conditions. Conclusion: WBV stimulation had an immediate effect on improving the proprioceptive precision of the knee joint. However, foot conditions (barefoot or shoe-wearing) during WBV application did not influence the proprioceptive precision of the knee joint.