Proximal Diagonal Newton Methods for Composite Optimization Problems

This paper proposes new proximal Newton-type methods with a diagonal metric for solving composite optimization problems whose objective function is the sum of a twice continuously differentiable function and a proper closed directionally differentiable function. Although proximal Newton-type methods using diagonal metrics have been shown to be superior to the proximal gradient method numerically, no theoretical results have been obtained to suggest this superiority. Even though our proposed method is based on a simple idea, its convergence rate suggests an advantage over the proximal gradient method in certain situations. Numerical experiments show that our proposed algorithms are effective, especially in the nonconvex case

Exact Penalty Method for Knot Selection of B-Spline Regression

This paper presents a new approach to selecting knots at the same time as estimating the B-spline regression model. Such simultaneous selection of knots and model is not trivial, but our strategy can make it possible by employing a nonconvex regularization on the least square method that is usually applied. More specifically, motivated by the constraint that directly designates (the upper bound of) the number of knots to be used, we present an (unconstrained) regularized least square reformulation, which is later shown to be equivalent to the motivating cardinality-constrained formulation. The obtained formulation is further modified so that we can employ a proximal gradient-type algorithm, known as GIST, for a class of non-smooth non-convex optimization problems. We show that under a mild technical assumption, the algorithm is shown to reach a local minimum of the problem. Since it is shown that any local minimum of the problem satisfies the cardinality constraint, the proposed algorithm can be used to obtain a spline regression model that depends only on a designated number of knots at most. Numerical experiments demonstrate how our approach performs on synthetic and real data sets

SIC/SIC composite thruster for a non-toxic liquid propellant rocket engine

Combustion chamber and nozzle for a non-toxic liquid rocket engine made by Tyrano ZMI SiC fiber reinforced SiC matrix composite were tested under sea level combustion tests. Combustion chamber and nozzle are the key hot parts for small liquid propellant engine, since chamber wall needs to be cooled by fuel rich low temperature gas. To create fuel rich low temperature gas, excess amount of fuel is consumed. Consequently, high temperature heat resisting material is indispensable to have better performance rocket engine. Nb based alloy are commonly used in combustion chamber and nozzle for a liquid propellant rocket engine for a satellite maneuver system with the maximum operating temperature around 1300°C. In this study, SiC/SiC combustion chamber with nozzle were examined and its performance was demonstrated by sea level static combustion tests in air and under vacuum. Tyrano ZMI SiC fiber (Ube Industry) was used as reinforcing fiber and carbon interface was selected to have higher temperature resistance. Fiber preform was fabricated by tri-axial braiding technique and carbon interface and SiC matrix were formed by chemical vapor infiltration (CVI). After CVI process, further densification was conducted by polymer infiltration and pyrolysis (PIP) process until no gas leak was detected under low pressure of 0.2 MPa. Largest inner diameter of the chamber was designed as 65 mm and the smallest inner diameter of 26 mm as a nozzle throat. Nozzle was designed with opening area ratio of 25 to investigate manufacturability. The combustion chamber and nozzle attached with a core engine as shown in Figure 1. Non-toxic fuel, ethanol, and oxidizer, N2O, were supplied through the showerhead type injection into combustion chamber. Sea level static combustion tests were conducted both in air and under vacuum (1.3 kPa). The engine combustion tests were successful (30s in air and 19 s in vacuum) and no damage could be found. The performance of the engine improved to specific impulse of 290s with assumption of nozzle area ratio 100. The maximum surface temperature reached to 1250°C, where the inner wall temperature could be calculated about 1600°C. Prototype engine development program successfully completed and we are preparing to start real application project of this engine system as a final stage of solid propellant satellite launcher Please click Additional Files below to see the full abstract

Confocal Laser Scanning Microscopic Studies on Alveolar Bone Remodeling with Orthodontic Tooth Movement and Retention

Alveolar bone reconstruction in growing dog during the retention period following orthodontic tooth movement was studied. Three beagle dogs (8-10 kg body weight, about one-year-old) were used and two of the animals were subjected to histological observation. The upper 2nd and lower 3rd premolars on both sides were extracted prior to the orthodontic treatments. After a healing period of one month, the upper 3rd premolar and the lower 4th premolar on the right side were moved mesially with a conventional orthodontic force for 8 weeks, and then retained in their new position for 4 weeks. The contralateral corresponding premolars were used as control. The alveolar bone was double-labeled with tetracycline (TC) during the movement and calcein (Cal) during the retention period. Alveolar bone structure and labeling patterns were examined by contact microradiography, conventional fluorescence microscopy, and confocal laser scanning microscopy (CLSM). Optimizing the separation of TC and Cal labelings in the alveolar bone was attained by the simultaneous use of ultraviolet (364 nm) and argon (488 nm) laser sources for excitation of TC and Cal, respectively. Cal labeling, indicative of new bone deposition showed two distinct patterns: lamination at the periodontal surface and rings circumscribing the vascular canal. The cementum surface also exhibited active deposition during the experimental period. Bone formation was affected by slight changes in magnitude and direction of orthodontic or occlusal forces. CLSM is valuable in deciphering the process of alveolar bone remodeling

Urban Transport Sustainability

The paper describes the possible direction of Asian EST, starting with an overview of recent trends and problems in transport systems within Asia, policy practices are also introduced. It was found that although the current situation and trend of transport in the Asian region presents a diverse picture stemming from geographical differences and levels of economic development, most Asian countries share similar concerns about transport-related problems, namely severe congestion, air and noise pollution,. Common patterns can be identified behind these problems, which include: a)large increases in traffic demand, resulting from rapid economic growth, urbanization, and motorisation, b)poor control of vehicle emissions and the absence of effective inspection and maintenance systems, c)lack of adequate and appropriate infrastructures, and d)poor coordination of transport and land-use policies. In the current situation, insufficient understanding of environmental deterioration mechanisms delay the implementation of necessary policy measures in many Asian countries. Each country should find the best way to achieve EST as fast as possible by learning from others’ experiences. Existing good examples within the region, such as intermediate public transport systems and electric road pricing, can provide a strong foundation for this purpose

The effect of eccentric exercise on injured patellar tendon healing in rats: a gene expression study

Recently, clinical studies have suggested that eccentric exercise can be beneficial for patellar tendinopathy. It is known that loading induces collagen synthesis in tendon, but the mechanisms responsible for mediating this effect are still unclear. We hypothesized that loading-induced expression of collagen depends on a specific contraction type. Eccentric exercise induces a more beneficial healing response than concentric exercise. Two longitudinal incisions were made in rat patellar tendons and the rats were then divided into three groups: eccentric exercise group (group E; n=35); concentric exercise group (group C; n=35); non-exercise group (group N; n=35). Each rat was taught to run downhill (eccentric) or uphill (concentric) for 14 days. Patellar tendons were collected at 1, 4, 7, 14, 21, 28 and 42 days following injury. Type I and III collagen, transforming growth factor-β-1 (TGF-β-1), and matrix metalloproteinase-13 (MMP-13) were measured by reverse transcription polymerase chain reaction. The gene expression level of type I collagen of group E was significantly greater than that of group N on day 4. The gene expression level of type III collagen of group E was significantly greater than that of group N on days 7 and 14. The gene expression level of TGF-β-1 of group E was significantly greater than that of group C and group N on days 4 and 7. The gene expression level of MMP-13 of group C and group N was significantly greater than that of group E on day 21. Eccentric exercise can more effectively induce TGF- β-1 expression compared to concentric exercise and subsequently cause high expression of type I and III collagen. In addition, our results showed that eccentric exercise also reduces MMP-13 gene expression. In conclusion, eccentric exercise can aid tendon repair.[Originals][原著]平成23年5月18日受付，平成23年6月17日受