Diffraction Analysis and Tactical Applications of Signal Propagation over Rough Terrain

The free space propagation model is inadequate to predict the mean path-loss in ground wireless communication. Also, many existing propagation channel models do not adequately predict path-loss in rough terrain because most of them were based on measurements in urban areas. Hence, a channel model that estimates mean path-loss over many different kinds of terrain conditions is desired. In this thesis, two new propagation channel models, Real Terrain Diffraction Model (RTDMOD) and Universal Terrain Channel Model (UTCMOD), were developed. Other geometric theory of diffraction (GTD) methods (Epstein-Peterson (EP) and Deygout (DG)) agree within 5 % from 3 MHz to 3GHz with RTDMOD. However, unlike these other methods, RTDMOD can account for an almost unlimited number of obstacles and has the advantage of predicting the significant diffraction point locations as well as the total path-loss for a given set of real terrain data. The computationally efficient stochastic channel model, UTCMOD, was developed from numerous Monte Carlo simulations using RTDMOD. UTCMOD agrees within 1 dB/km over a broad carrier frequency range and a large terrain height variance range with the popular Hata model. Furthermore, UTCMOD is applicable to many different kinds of terrain conditions whereas the Hata model is most relevant for terrain conditions characteristic of large cities or medium-small cities. Unlike previous models, UTCMOD considers communication link conditions (i.e the relative heights of transmitter, receiver, and terrain peaks along the path) and provides the correct perspective for analyzing the propagation effects. Also UTCMOD can be used to optimize many tactical communication (TAC COMM) and electronic warfare (EW) scenarios for Low Probability of Interception (LPI) performance

Determinants of Family Ownership: The Choice between Control and Performance

This paper analyzes what determines ownership structure of family firms in Korea. Our analysis shows that control is as important a factor as performance in the determination of whether a family in Korea chooses to own a firm. The controlling family prefers to own shares of de facto holding companies because they provide control over affiliated companies and firms that perform well. The family, however, allows its affiliated companies to own more shares of firms that perform poorly and of firms that do not provide the family with power to control the firm. In addition, controlling families own fewer shares of firms that make bond investments in affiliated companies because bond holding does not provide control. We carry out logit regressions for firms without family ownership and for firms with a positive family ownership. The family chooses not to own shares regardless of a firm's performance if the firm does not provide significant control over affiliated companies. We also show that the family values its control more for closely held firms.

The Choice of Group Structure: Divide and Rule

This paper concerns the structure of Korean business groups. We investigate the factors that affect a controlling shareholder's decision regarding the structure of his business group and the location of its member firms, using financial and ownership data on conglomerate groups in Korea. We define new measures that represent the levels of vertical and circuitous structures of a group, and the location of member firms in the group. We empirically confirm that controlling shareholders strategically choose the structure of their business groups to secure control over the groups and to seek private benefit of control. The risk diversification and propping incentive of controlling shareholders is also found to affect the decisions.

Hazard analysis of typhoon-related external events using extreme value theory

AbstractBackgroundAfter the Fukushima accident, the importance of hazard analysis for extreme external events was raised.MethodsTo analyze typhoon-induced hazards, which are one of the significant disasters of East Asian countries, a statistical analysis using the extreme value theory, which is a method for estimating the annual exceedance frequency of a rare event, was conducted for an estimation of the occurrence intervals or hazard levels. For the four meteorological variables, maximum wind speed, instantaneous wind speed, hourly precipitation, and daily precipitation, the parameters of the predictive extreme value theory models were estimated.ResultsThe 100-year return levels for each variable were predicted using the developed models and compared with previously reported values. It was also found that there exist significant long-term climate changes of wind speed and precipitation.ConclusionA fragility analysis should be conducted to ensure the safety levels of a nuclear power plant for high levels of wind speed and precipitation, which exceed the results of a previous analysis

Teachers’ beliefs and practices of ICT use in Secondary schools in Addis Ababa, Ethiopia.

Ethiopian government policy is committed to integrating Information and Communication Technology (ICT) into education to improve educational quality and equity. As teachers are the fundamental element for the success of this objective, the government has included an ICT module within teacher training to realise ICT practices inside the classroom. However, the actual ICT implementation in education lags behind government expectations. This research investigates how Ethiopian secondary school teachers’ beliefs and practices in Addis Ababa about the use of ICT are constructed. With a symmetrical perspective of Sociomateriality and Actor-Network Theory, the research explores the human and nonhuman factors which facilitate or inhibit teachers’ ICT implementation from teacher training to secondary school classrooms. It also investigates teachers’ beliefs that shape individuals’ perspectives and attitudes to ICT. The analysis of Technological Pedagogical and Content Knowledge is employed to ascertain other potential factors that affect teachers’ ICT practices such as the pedagogical design of using technology and contextual characteristics. The findings show that secondary school teachers possess positive general and pedagogical beliefs with regards to ICT implementation. However, those beliefs face strong barriers when it comes to their translation into pedagogical practices inside of the classroom. In teacher training institutes, trainees are not satisfied with their instructors’ pedagogical practices. Trainees argue that the assessment and practicum as a part of teacher training are not designed to encourage ICT practices. In relation to ICT materials, trainees are held back by the institutes in terms of their ICT material access. In secondary schools in the Addis Ababa area, although ICT implementation is compulsory, the level of ICT practices is very limited. There are multiple reasons for this. Some teachers perceive that ICT itself infringes on teachers’ autonomy of pedagogical design – despite them stating that they are in favour of using ICT. Others lack confidence with the use of ICT and are afraid of making mistakes in front of the students. When it comes to ICT materials, frequent system failure makes teachers lose their motivation to use ICT in the classroom. In addition, ICT is found to be associated with being intellectual and upper class. This research also investigates the perspectives of the development stakeholders involved in Ethiopia’s ICT and education. They identify three fields that affect low level of ICT practices in the country: 1) teacher training; 2) teachers’ beliefs; 3) materiality, fields which align with the focus of my research. In addition to those commonalities, this research also documents the heterogeneity in stakeholders’ objectives and the inequitable character of the school selection process for the distribution of materials - which could jeopardise the ICT implementation at national level. This is the first study that examines and represents the voice of Ethiopian teachers in their adoption and use of ICT in teaching. This thesis contributes to synthesise theories and concepts on the adoption and use of ICT in teaching. In particular, it draws attention to the role of materiality, and how it affects teachers’ ICT beliefs and practices. Therefore, this study serves as a reference or a first step that will hopefully encourage similar research in other Ethiopian contexts or similar countries, where ICT adoption is promoted within education policy but faces crucial challenges

Anti-lipoapoptotic effect of Artemisia capillaris extract on free fatty acids-induced HepG2 cells

BACKGROUND: Artemisia capillaris (AC) has been recognized as one of the promising candidates for hepatoprotective, hypoglycemic, hypolipidemic, antiobesitic and anti-inflammatory therapeutic effectiveness. This study evaluated the inherent mechanism and anti-apoptotic activity of 30% ethanol extract of AC (AC extract) 100 μg/ml on free fatty acids (FFAs)-induced HepG2 cellular steatosis and lipoapoptosis. METHODS: Hepatic steatosis was induced by culturing HepG2 cells with a FFAs mixture (oleic and palmitic acid at the proportion of 2:1) for 24 h, thus ultimately giving rise to lipoapoptosis. Cell viability and lipid accumulation were detected by MTT assay and Oil Red O staining method respectively and Caspase-3, −9, Bax, Bcl-2, p-JNK and PUMA were measured for lipoapoptosis after 24 hours. RESULTS: AC extract significantly improved the FFAs-induced steatosis without cytotoxicity and Caspase-3, −9, Bax and Bcl-2 were modulated profitably to HepG2 cells after AC treatment. In addition, AC extract inhibited the activation of c-Jun NH(2) terminal kinase (JNK) and PUMA, which mechanism is related to non-alcoholic steatohepatitis (NASH). CONCLUSIONS: Combined together, AC extract exerted an obvious hypolipidemic and anti-apoptotic effect, indicating that AC extract might have potential therapeutic herb against NASH

Birth and Death of One-dimensional Domains in Cylindrically Confined Liquid Crystals

Nematic liquid crystal (LC) is a partially ordered matter that has been a popular model system for studying a variety of topological behaviors in condensed matter. In this work, utilizing a spontaneously twisting achiral LC, we introduce a one-dimensional (1D) model system to investigate how domains and topological defects arise and annihilate, reminiscing the Kibble-Zurek mechanism. Because of the unusual elastic properties, lyotropic chromonic LCs form a double-twist structure in a cylindrical capillary with degenerate planar anchoring, exhibiting chiral symmetry breaking despite the absence of intrinsic chirality. Consequently, the domains of different handedness coexist with equal probabilities, forming the topological defects between them. We experimentally measure the domain-length distribution and its time evolution, best fitted by a three-parameter log-normal distribution. We propose that the coalescence within a train of 1D domains having the normal length distribution and randomly assigned handedness, may lead to the domains of the log-normal-like length distribution. Our cylindrically confined LC provides a practical model system to study the formation and annihilation of domains and defects in 1D

Association between thyroid hormones and the components of metabolic syndrome

BACKGROUND: Thyroid hormones are known to have direct and indirect effects on metabolism. Individuals with metabolic syndrome, a disease that is growing in incidence at a rapid rate, are at higher risk for cardiovascular disease, diabetes, and cancer. The aim of this study was to identify whether significant correlations exist between thyroid hormone levels and components of the metabolic syndrome in the general population of Korea. METHODS: The data were collected from the sixth Korea National Health and Nutrition Examination Surveys from 2013 to 2015. A total of 1423 participants were tested for thyroid function. The analysis of variance and multiple linear regression were performed to analyze the relationship between thyroid hormone level and components of the metabolic syndrome. RESULTS: A positive association between free thyroxine and fasting glucose level was observed in patients with high free thyroxine levels (≥1.70 ng/dL, β = 15.992, p = < 0.0001), when compared with patients with normal-middle free thyroxine levels. Moreover, a negative association was observed between free thyroxine and triglyceride levels in patients with normal-high free thyroxine levels (β = - 21.145, p = 0.0054) and those with high free thyroxine levels (β = - 49.713, p = 0.0404). CONCLUSION: Free thyroxine shows a partially positive association with fasting glucose and a partially negative association with triglycerides in the Korean population. In patients with abnormal thyroid function, follow up tests for glucose levels and lipid profiling during treatment for thyroid dysfunction would be beneficial in terms of overlooking metabolic syndrome and to prevent related diseases

Analysis of speech and tongue motion in normal and post-glossectomy speaker using cine MRI

Objective Since the tongue is the oral structure responsible for mastication, pronunciation, and swallowing functions, patients who undergo glossectomy can be affected in various aspects of these functions. The vowel /i/ uses the tongue shape, whereas /u/ uses tongue and lip shapes. The purpose of this study is to investigate the morphological changes of the tongue and the adaptation of pronunciation using cine MRI for speech of patients who undergo glossectomy. Material and Methods Twenty-three controls (11 males and 12 females) and 13 patients (eight males and five females) volunteered to participate in the experiment. The patients underwent glossectomy surgery for T1 or T2 lateral lingual tumors. The speech tasks “a souk” and “a geese” were spoken by all subjects providing data for the vowels /u/ and /i/. Cine MRI and speech acoustics were recorded and measured to compare the changes in the tongue with vowel acoustics after surgery. 2D measurements were made of the interlip distance, tongue-palate distance, tongue position (anterior-posterior and superior-inferior), tongue height on the left and right sides, and pharynx size. Vowel formants Fl, F2, and F3 were measured. Results The patients had significantly lower F2/Fl ratios (F=5.911, p=0.018), and lower F3/F1 ratios that approached significance. This was seen primarily in the /u/ data. Patients had flatter tongue shapes than controls with a greater effect seen in /u/ than /i/. Conclusion The patients showed complex adaptation motion in order to preserve the acoustic integrity of the vowels, and the tongue modified cavity size relationships to maintain the value of the formant frequencies