Design, Development and Testing of a Low-cost Sub-Joule μPPT for a PocketQube

Small satellites are unmanned spacecraft with small size and mass weighing less than 500kg. A small satellite called the CubeSat was created by two university professors to help students understand satellite design. The idea of small satellites caught on and they became popular due to their low cost, quick development time and easy deployment. The inexpensive nature of small satellites has helped lower the entry barrier to space and led to a movement called the “democratisation of space”. The popularity of small satellites has also caught the eye of private companies that recognise the potential of commercialising small satellite technologies. Nowadays, small satellites are being considered for more complex and challenging space missions. However for a small satellite to reach its full potential, it needs to be equipped with a proper propulsion system. Governments, space agencies, companies and universities around the world have started to research new innovative miniaturised space propulsion technologies. Nowadays, there are many newly developed miniaturised propulsion technologies available. The new propulsion systems are either sold by the companies and universities at a very high price, or research and development is closely guarded due to the potential commercial value of the propulsion system. Companies and universities have primarily focused on researching and developing top-of-the-line micro-propulsion devices to win lucrative research funds. This has resulted in a lack of research into cheap reliable micropropulsion as there have been no incentives for companies and universities to develop this area. As a result, fund-limited students and individuals have been left behind, defeating the purpose of small satellites. This dissertation focuses on designing and developing a low-cost sub-joule micro-PPT propulsion system for a PocketQube satellite. The first section covers the literature review, which looks at the different space propulsion technologies currently available. The next section covers the micro-PPT propulsion system’s mechanical and electrical design and development process. After the development process, the performance of the prototype is tested using various input parameters, as well as in vacuum conditions and over its lifetime. The test results show that the optimal performance is obtained with an input voltage supply of 5V at a pulse frequency of 0.5Hz, which achieves a minimal impulse bit v of 0.698μNs and thrust range of 0.349~1.071μN. In comparison to the STRaND-1 3U CubeSat’s PPT, performance data show that the developed μPPT propulsion system is a competitive propulsion solution, as it achieves more thrust with similar minimal impulse bit, using only one third of the power consumption. The μPPT propulsion system is able to produce 1980 shots so far, which is far lower relatively than other established PPTs due to the limitations resulting from capacitor failure.Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 202

Design, Development and Testing of a Low-cost Sub-Joule μPPT for a PocketQube

Small satellites are unmanned spacecraft with small size and mass weighing less than 500kg. A small satellite called the CubeSat was created by two university professors to help students understand satellite design. The idea of small satellites caught on and they became popular due to their low cost, quick development time and easy deployment. The inexpensive nature of small satellites has helped lower the entry barrier to space and led to a movement called the “democratisation of space”. The popularity of small satellites has also caught the eye of private companies that recognise the potential of commercialising small satellite technologies. Nowadays, small satellites are being considered for more complex and challenging space missions. However for a small satellite to reach its full potential, it needs to be equipped with a proper propulsion system. Governments, space agencies, companies and universities around the world have started to research new innovative miniaturised space propulsion technologies. Nowadays, there are many newly developed miniaturised propulsion technologies available. The new propulsion systems are either sold by the companies and universities at a very high price, or research and development is closely guarded due to the potential commercial value of the propulsion system. Companies and universities have primarily focused on researching and developing top-of-the-line micro-propulsion devices to win lucrative research funds. This has resulted in a lack of research into cheap reliable micropropulsion as there have been no incentives for companies and universities to develop this area. As a result, fund-limited students and individuals have been left behind, defeating the purpose of small satellites. This dissertation focuses on designing and developing a low-cost sub-joule micro-PPT propulsion system for a PocketQube satellite. The first section covers the literature review, which looks at the different space propulsion technologies currently available. The next section covers the micro-PPT propulsion system’s mechanical and electrical design and development process. After the development process, the performance of the prototype is tested using various input parameters, as well as in vacuum conditions and over its lifetime. The test results show that the optimal performance is obtained with an input voltage supply of 5V at a pulse frequency of 0.5Hz, which achieves a minimal impulse bit v of 0.698μNs and thrust range of 0.349~1.071μN. In comparison to the STRaND-1 3U CubeSat’s PPT, performance data show that the developed μPPT propulsion system is a competitive propulsion solution, as it achieves more thrust with similar minimal impulse bit, using only one third of the power consumption. The μPPT propulsion system is able to produce 1980 shots so far, which is far lower relatively than other established PPTs due to the limitations resulting from capacitor failure.Thesis (MA) -- Faculty of Engineering, the Built Environment, and Technology, 202

Guidelines Aimed at Reducing the Risks of User Acceptance Delay in the Context of an IT Service Project Management Plan

Delays in the user acceptance of information technology (IT) service projects in Korea have occurred frequently due to various risk factors. User acceptance delays may hinder the achievement of the client’s project objectives and cause schedule delays or cost overruns. Furthermore, the client may impose a delay charge and claim for additional damages, causing serious disputes between buyer and supplier. The main causes of user acceptance delays are unclear user requirements, changes in user requirements, poor-quality development outputs, excessive functional and non-functional errors, lack of user involvement, unclear user roles and responsibilities, and unclear criteria of user acceptance test.We help foster the timely completion of user acceptance by proposing a method of identifying the risk factors in user acceptance delay and creating a project management plan to weed out the identified risks. We propose a guideline for an IT service management plan that weeds out or lowers the risk factors well in advance. To validate the guideline’s utility, we apply it to IT service projects. The results show that the guideline is effective in identifying and removing risk factors affecting delays in the user acceptance of IT service projects

Orphan nuclear receptor Nurr1 induces neuron differentiation from embryonic cortical precursor cells via an extrinsic paracrine mechanism

AbstractNurr1 is an orphan nuclear receptor-type transcription factor (TF) that plays critical roles in midbrain dopamine neuron development. This study demonstrated a novel role for Nurr1 in neuronal/astrocytic differentiation of neural precursor (NP) cells isolated from rat embryonic cortices: overexpression of this TF promoted NP cell differentiation towards neurons at the expense of astrocytic differentiation. Single cell-based lineage analyses and experiments using co-cultures revealed that Nurr1 elicited its neurogenic role in an extrinsic paracrine manner. We defined diffusible factors and downstream neurogenic TFs responsible for the Nurr1-mediated neuronal differentiation

Silicon improves growth and antioxidative defense system in salt-stressed Kentucky bluegrass (Poa pratensis L.), ‘Perfection’ and ‘Midnight’

After 400 mM of NaCl treatment, 0.1 and 1.0 mM of silicon (Si) were added to Kentucky bluegrass, ‘Perfection’ and ‘Midnight,’ to identify the effect of Si on the antioxidant defense mechanisms and inorganic ions as a parameter in the salt stress on grass. Compared to the control, the NaCl treatment caused a significant decrease in the shoot length and the fresh and dry weight of shoot and root of the both types of Kentucky bluegrass. Adding Si after the NaCl treatment increased the growth and dry and fresh weight of shoot and root in the grass. In both types, the Na+ concentration significantly increased after the NaCl-only treatment compared to control and decreased dramatically after 0.1 and 1.0 mM Si were added following the NaCl treatment compared to the NaCl-only treatment. K+ and Si concentrations remarkably increased in the shoot and root when Si was added after NaCl treatment. There was a significant reduction in the oxygen radical absorption capacity and the total phenolic compounds in the both types. Compared to the NaCl-only treatment, higher glutathione and lower proline concentrations were observed in the plant treated with Si after NaCl treatment. These results suggest that, even though Si is not generally classified as ‘essential element’, Si may have a significant involvement in the antioxidant defense mechanisms and inorganic ions in the salt stress on grass.Key words: diphenyl-1-picrylhydrazyl (DPPH), total phenolic concentration, proline, salt stress

Nanomechanical behavior of biodegradable metallic glass for transient electrodes

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Incidence of varicella in children in Jeju-do, Korea, 2005-2016: age-period-cohort analysis

OBJECTIVES Although the nationwide inoculation rate of varicella vaccine was approximately 95% in Korean children recently, the number of notified varicella cases is unexpectedly continuously increasing till now. To suggest some hypotheses regarding this discrepancy, an age-period-cohort (APC) analysis as a descriptive epidemiology study was conducted for children residing in Jeju-do, Korea. METHODS The raw data were obtained from the nationwide database for insurance claim of healthcare fee provided by the National Health Insurance Service, Korea. The selection criteria were children aged 2-13 years who visited any healthcare center due to varicella from 2005 to 2016 while residing in Jeju-do. After calculating the birth cohort-specific crude incidence rates by age and year, the intrinsic estimator method was used to perform the APC analysis. RESULTS As the annual crude incidence rates decreased with increasing age between 2005 and 2016, the age and period effects also decreased. The intrinsic estimator coefficients suggesting the cohort effect shifted from positive to negative in 2011, the starting year of free varicella vaccine program in Jeju-do. CONCLUSIONS The results suggested that inoculated varicella vaccines have preventive effects. However, further studies to evaluate waning immunity would be needed

Protective effect of genistein on radiation-induced intestinal injury in tumor bearing mice

BACKGROUND: Radiation therapy is the most widely used treatment for cancer, but it causes the side effect of mucositis due to intestinal damage. We examined the protective effect of genistein in tumor-bearing mice after abdominal irradiation by evaluation of apoptosis and intestinal morphological changes. METHODS: Mouse colon cancer CT26 cells were subcutaneously injected at the flank of BALB/c mice to generate tumors. The tumor-bearing mice were treated with abdominal radiation at 5 and 10 Gy, and with genistein at 200 mg/kg body weight per day for 1 d before radiation. The changes in intestinal histology were evaluated 12 h and 3.5 d after irradiation. To assess the effect of the combination treatment on the cancer growth, the tumor volume was determined at sacrifice before tumor overgrowth occurred. RESULTS: Genistein significantly decreased the number of apoptotic nuclei compared with that in the irradiation group 12 h after 5 Gy irradiation. Evaluation of histological changes showed that genistein ameliorated intestinal morphological changes such as decreased crypt survival, villus shortening, and increased length of the basal lamina 3.5 d after 10 Gy irradiation. Moreover, the genistein-treated group exhibited more Ki-67-positive proliferating cells in the jejunum than the irradiated control group, and crypt depths were greater in the genistein-treated group than in the irradiated control group. The mean weight of the CT26 tumors was reduced in the group treated with genistein and radiation compared with the control group. CONCLUSION: Genistein had a protective effect on intestinal damage induced by irradiation and delayed tumor growth. These results suggest that genistein is a useful candidate for preventing radiotherapy-induced intestinal damage in cancer patients

Unleashing the full potential of Hsp90 inhibitors as cancer therapeutics through simultaneous inactivation of Hsp90, Grp94, and TRAP1

Cancer therapeutics: Extending a drug's reach A new drug that blocks heat shock proteins (HSPs), helper proteins that are co-opted by cancer cells to promote tumor growth, shows promise for cancer treatment. Several drugs have targeted HSPs, since cancer cells are known to hijack these helper proteins to shield themselves from destruction by the body. However, the drugs have had limited success. Hye-Kyung Park and Byoung Heon Kang at Ulsan National Institutes of Science and Technology in South Korea and coworkers noticed that the drugs were not absorbed into mitochondria, a key cellular compartment, and HSPs in this compartment were therefore not being blocked. They identified a new HSP inhibitor that can reach every cellular compartment and inhibit all HSPs. Testing in mice showed that this inhibitor effectively triggered death of tumor cells, and therefore shows promise for anti-cancer therapy. The Hsp90 family proteins Hsp90, Grp94, and TRAP1 are present in the cell cytoplasm, endoplasmic reticulum, and mitochondria, respectively; all play important roles in tumorigenesis by regulating protein homeostasis in response to stress. Thus, simultaneous inhibition of all Hsp90 paralogs is a reasonable strategy for cancer therapy. However, since the existing pan-Hsp90 inhibitor does not accumulate in mitochondria, the potential anticancer activity of pan-Hsp90 inhibition has not yet been fully examined in vivo. Analysis of The Cancer Genome Atlas database revealed that all Hsp90 paralogs were upregulated in prostate cancer. Inactivation of all Hsp90 paralogs induced mitochondrial dysfunction, increased cytosolic calcium, and activated calcineurin. Active calcineurin blocked prosurvival heat shock responses upon Hsp90 inhibition by preventing nuclear translocation of HSF1. The purine scaffold derivative DN401 inhibited all Hsp90 paralogs simultaneously and showed stronger anticancer activity than other Hsp90 inhibitors. Pan-Hsp90 inhibition increased cytotoxicity and suppressed mechanisms that protect cancer cells, suggesting that it is a feasible strategy for the development of potent anticancer drugs. The mitochondria-permeable drug DN401 is a newly identified in vivo pan-Hsp90 inhibitor with potent anticancer activity