Effectiveness of a Rigid Grate for Excluding Pacific Halibut, Hippoglossus stenolepis, From Groundfish Trawl Catches

A rigid grate was installed in a groundfish trawl to test its effectiveness in excluding Pacific halibut, Hippoglossus stenolepis, from commercial flatfish catches in the Gulf of Alaska. The grate was located ahead of the trawl codend to direct halibut toward an escape opening while allowing target species to pass through toward the codend. In an experimental fishery, the escape rate of halibut was estimated at 94%, while 72% of the Dover sole, Microstomas pacificus, 67% of the rex sole, Glyptocephalus zachirus, and 79% of the flathead sole, Hippoglossoides elassodon, were retained

Optimal Sequential Selection Based on Relative Ranks with Renewable Call Options

Sequential sampling problems may be affected significantly by the presence of sampling costs and the ability to recall historical observations. In the context of the classical secretary problem, we incorporate these two notions into the decision maker\u27s action set, thereby creating a stopped decision process. Whenever a desirable applicant appears, we may consider purchasing an option to recall it subsequently. The problem is solved for the best-choice criterion, reduced or discounted by the option costs incurred

The Secretary Problem with a Call Option

In addition to accepting or rejecting a candidate arrive at time r, we may consider purchasing an option at a cost cx to recall the candidate at time r+x, but this privilege may be invoked only once. For large sample size, using the best-choice criterion and deducting option costs, the optimal strategy and return are obtained

Contributions to the theory of groups

A 1. The influence on a finite group of its proper abnormal structure. J. London Math. Soc. 40 (1965). 348-61; MR30#4838. • B 2. Abnormal depth and hypereccentric length in finite soluble groups, Math. Z. 90 (1965). 29-40; MR32#141. • C 3. On a splitting theorem of Gaschiitz. Proc. Edinburgh Math. Soc. (20 15 (1966). 57-60; MR33#5708. • A 4. Finite groups with prescribed Sylow tower subgroups. Proc. London Math. Soc. (3) 16 (1966). 577-89; MR33#5734. • B 5. Remarks on system normalizers and Carter subgroups. Proc. Intemat. Conf. Theory of Groups (Canberra I965) (1967). 303-5. • B 6. Finite soluble groups with pronormal system normalizers. Proc. London Math. Soc. (3) 17 (1967). 447-69; MR35#2967. • C 7. A natural setting for the extensions of a group with trivial centre by an arbitrary group. Enseignement Math. 13 (1967). 167-73; MR3871179. • B 8. Nilpotent subgroups of finite soluble groups. Math. Z. 106 (1968). 97-112; MR40#5736. • B 9. Absolutely faithful group actions. Proc. Cambridge Philos. Soc. 66 (1969). 231-7; MR40#1465. • CIO. On the splitting of extensions by a group of prime order. Math. Z. 117 (1970). 239-48; MR43#356. • Cll. Splitting properties of group extensions. Proc. London Math. Soc. (3) 22 (1971). 1-23; MR43#7515. • C12. Extensions by a free abelian group of rank 2. Proc. Roy. Irish Acad. 71A (1971). 19-26. MR44#4097 • BI3. A subnormal embedding theorem for finite groups. J. London Math. Soc. (2) 5 (1972) 253-9; MR47#326. • C14. Universal finite group extensions and a non-splitting theorem. Israel J. Math. 15 (1973) 375-83. • A15. Sufficient conditions for the existence of ordered Sylow towers in finite groups. J. Algebra 28 (1974) 116-26. • Cl6. Automorphism groups of groups with trivial centre. Proc. London Math. Soc. • C17. Frattini normal subgroups of finite groups. unpublished. • A18. On finite insoluble groups with nilpotent maximal subgroups. unpublished

Optimal Selection with Holding

The arrival times of what we shall call offers constitute a Poisson process. The value of any offer is a nonnegative random variable with known distribution. At an arrival epoch, we may select, reject, or hold the offer. Rejected offers may not be recalled, but an offer on hold is available for future consideration. However, cost accrues during the holding period. We seek a holding and selection strategy that maximizes the expected value of the offer selected less holding costs. The discrete time version of the problem is also considered

Optimal Selection with Holding

The arrival times of what we shall call offers constitute a Poisson process. The value of any offer is a nonnegative random variable with known distribution. At an arrival epoch, we may select, reject, or hold the offer. Rejected offers may not be recalled, but an offer on hold is available for future consideration. However, cost accrues during the holding period. We seek a holding and selection strategy that maximizes the expected value of the offer selected less holding costs. The discrete time version of the problem is also considered

Continuous Review Billing Decision Systems

The subject of this paper is the recurring set of retail billing decisions: the activities whereby the firm initiates the collection of receivables from its charge account customers. A model for this decision making activity is proposed in order to enhance the profitability of the firm\u27s billing information system

Selection of the Best Pair from a Random Sequence

The model analyzed in this paper extends the clas­sical secretary problem to the situation in which the decision maker wants to select the two best objects. Exactly two selections are permitted, and a selection strategy is defined by a pair of stopping times. Characterization of the optimal strategy is cumbersome, but useful asymptotic representations are obtained for long sequences

The Newsboy with Known Demand and Uncertain Replenishment: Applications to Quality Control and Container Fill

Consider a newsboy problem with known demand and random replenishment. The distribution of the replenishment quantity is determined by a location-scale parameter, (μ, σ), which can be controlled. The usual expected cost function includes a separate term associated with the choice of σ. The asymptotic behavior of the optimal parameter values, as functions of the holding and shortage costs, is examined

A New Approach for the Analysis of Impact-Echo Data

The recently developed impact-echo (IE) method, which utilizes an impact and subsequent displacement monitoring of the concrete surface, appears promising for the inspection of concrete structures. IE has been shown to be particularly suitable for void, delamination, and cracking detection in hardened concrete structures including bridge decks since deep penetration into the structure and one-sided accessibility are obtained. For this method to be reliable, however, accurate measurements of peak frequencies in the magnitude spectrum of the frequency domain must be made. In addition, the interpretation of confusing spectrums may be required. The first part of this paper reviews the existing impact echo technique, including typical signal generation and capture possibilities as well as the accepted signal processing. Next, an alternative approach to signal processing is developed; this approach is based on a brief literature review and laboratory experiments. It is proposed that this approach, based on the spacing of peaks in the magnitude spectrum may reduce the uncertainty of impact echo signal analysis