Average-Case Competitive Analyses for Ski-Rental Problems

Let $s$ be the ratio of the cost for purchasing skis over the cost for renting them. Then the famous result for the ski-rental problem shows that skiers should buy their skis after renting them $(s-1)$ times, which gives us an optimal competitive ratio of $2-frac{1}{s}$. In practice, however, it appears that many skiers buy their skis before this optimal point of time and also many skiers keep renting them forever. In this paper we show that these behaviors of skiers are quite reasonable by using an {em average-case competitive ratio}. For an exponential input distribution $f(t) = lambda e^{-lambda t}$, optimal strategies are (i) if $frac{1}{lambda} leq s$, then skiers should rent their skis forever and (ii) otherwise should purchase them after renting approximately $s^2lambda ;;

A Study on single Crystals of Nylon 12

Single crystals of two crystatalline forms, α and γ, in nylon 12 were obtained from dilute solutions. The single crystals of γ-form from diols solutions are ribbon like lamellae in shape, and that of α-form obtained from solution in water-formic acid are parallelogramic. Electron diffraction study shows that chain packings in single crystals of two crystalline forms are very similar to those of nylon 6, respectivel

Crystallization of Polymers from Solution under ShearingStress III Polybutene-1

It was shown that the fibrous crystals of isotactic polybutene-l crystallized from solution under shearing stress are also composed of the central threads with an extended chain character and the epitaxally deposited lamellae with a folded chain character. The characteristic behaviors in this polymer exist in; (1) that the resulting crystals possess the hexagonal modification of form 1'; (2) that at low polymer concentrations the lamellar crystals with an orthorhombic modification of form Ⅲ are precipitated in similar fashion to the case in the absence of stirring; (3) that the morphology in surface replica of thick deposited film is very similar to that of melt extruded polyethylene film crystallized in a highly stressed state

Teaching English to Japanese EFL Learners Using Phonetics : A Pedagogical Application of the Vowel Triangle

English Teaching in Japan is facing a reformation and changing its “Government Course Guideline”. In the new Guideline, teaching communicative English is one of the biggest goals and teaching pronunciation is a hot topic on the agenda. This paper tries to show the effectiveness of using the knowledge of phonetics, more specifically, the knowledge of Vowel Triangle, in teaching pronunciation to Japanese elementary students, especially focusing on the [æ] sound, which is one of the most difficult sounds for Japanese to produce, and aims to contribute to the better English pedagogy.Article2017 Arts, Humanities, Social Sciences & Education PROCEEDINGS.2017:(2017)conference pape

Average-case competitive analyses for one-way trading

Consider a trader who exchanges one dollar into yen and assume that the exchange rate fluctuates within the interval [m, M]. The game ends without advance notice, then the trader is forced to exchange all the remaining dollars at the minimum rate m. El-Yaniv et al. presented the optimal worst-case threat-based strategy for this game (El-Yaniv et al. 2001). In this paper, under the assumption that the distribution of the maximum exchange rate is known, we provide average-case analyses using all the reasonable optimization measures and derive different optimal strategies for each of them. Remarkable differences in behavior are as follows: Unlike other strategies, the average-case threat-based strategy that minimizes E[OPT/ALG] exchanges little by little. The maximization of E[ALG/OPT] and the minimization of E[OPT]/E[ALG] lead to similar strategies in that both exchange all at once. However, their timing is different. We also prove minimax theorems with respect to each objective function.ArticleJOURNAL OF COMBINATORIAL OPTIMIZATION. 21(1): 83-107 (2011)journal articl

Dynamic Finite Element Analysis of Impulsive Stress Waves Propagating from Distal End of Femur

The human femur is subjected to an impulsive load at its distal end during daily life. Femoral bone fracture caused by impact loading is common in elderly women. It is important to clarify the dynamic response of the femur and to evaluate the change in its stress state during impact loading. A 3-dimensional model of the femur was prepared in the present study, and the impulsive stress waves propagating from the distal end of the femur were analyzed by the dynamic finite element method. This model showed that the von Mises equivalent stress is large on the anterior and posterior sides of the mid-diaphysis when the impact direction is different from that of the bone axis. As for the femoral neck, the absolute value of minimum principal stress initially increases on the medial side;slightly later the maximum principal stress increases on the lateral side. In this case, the absolute value of the maximum principal stress was found to be larger than that of the minimum principal stress, and the absolute value of the principal stress decreased as the impact angle increased. Further, the femoral neck and the trochanter were shown to have a higher risk of bone fracture when the impact direction is coincident with the bone axis

Coexistence of a pulmonary adenocarcinoma with a focal organizing pneumonia

We report a case of a pulmonary adenocarcinoma in coexistence with an organizing pneumonia. A 73-year-old male presented with an abnormal shadow on a chest X-ray. The pathological diagnosis, made via a partial resection, was a focal organizing pneumonia with reactive proliferation of the bronchial epithelium. Three years later, two tumors adjacent to the staple line were revealed by computed tomography. A left lower lobectomy was performed and both tumors were diagnosed as an adenocarcinoma. Because the histological findings for the atypical epithelial areas of the previous tumor were similar to the two new lesions in this patient, we regarded these tumors as a marginal recurrence.ArticleINTERACTIVE CARDIOVASCULAR AND THORACIC SURGERY. 13(4):444-446 (2011)journal articl