On a property of orthogonal arrays and optimal blocking of fractional factorial plans

It is shown that fractional factorial plans represented by orthogonal arrays of strength three are universally optimal under a model that includes the mean, all main effects and all two-factor interactions between a specified factor and each of the other factors. Thus, such plans exhibit a kind of model robustness in being universally optimal under two different models. Procedures for obtaining universally optimal block designs for fractional factorial plans represented by orthogonal arrays are also discussed. Acknowledgements. The authors wish to thank the referees for making several useful comments on a previous version.     

A note on the projection properties of Hadamard matrices obtained by the first Payley construction

We show that the projections on four factors of an arbitrary orthogonal array of strength 2 allow the estimation of main effects and two-factor interactions when all other effects are assumed to be zero, if those projections satisfy the bounds given by Weils theorem. The only exceptions are the Hadamard matrices of orders 16 and 24. A consequence is again the estimability of main effects and two-factor interactions for the projections on four factors of the first Payley construction for arbitrary run size.     

D-optimal two-level orthogonal arrays for estimating main effects and some specified two-factor interactions

Theoretical results are derived for finding D-optimal two-level orthogonal arrays for estimating main effects and some specified two-factor interactions. The upper bounds of the determinant of the related matrix for D-optimality are obtained. For run sizes 12 and 20, D-optimal orthogonal arrays are found for all requirement sets with three or less two-factor interactions, and all the D-optimal orthogonal arrays except one can be constructed by sequentially collecting columns. Examples are also given for run sizes 36 and 52 to discuss the guidelines to construct D-optimal orthogonal arrays.     

U-type and column-orthogonal designs for computer experiments

U-type designs and orthogonal Latin hypercube designs (OLHDs) have been used extensively for performing computer experiments. Both have good spaced filling properties in one-dimension. U-type designs may not have low correlations among the main effects, quadratic effects and two-factor interactions. On the other hand, OLHDs are hard to be found due to their large number of levels for each factor. Recently, alternative classes of U-type designs with zero or low correlations among the effects of interest appear in the literature. In this paper, we present new classes of U-type or quantitative \(3\) -orthogonal designs for computer experiments. The proposed designs are constructed by combining known combinatorial structures and they have their main effects pairwise orthogonal, orthogonal to the mean effect, and orthogonal to both quadratic effects and two-factor interactions.     

Orthogonal main effect plans for two and three factors in small blocks

Orthogonal main-effect plans for two and three factors in small blocks are obtained from the dual of adjusted orthogonal row-column designs. The method for constructing efficient plans is presented, and a relationship between the average efficiency factors of the row-column design and the corresponding main effects is given for the two-factor case. Orthogonal Main Effect.     

Two ge neral classes of search designs for factor screening experiments with factors at three levels

In this paper, we are presenting general classes of factor screening designs for identifying a few important factors from a list of m (≥ 3) factors each at three levels. A design is a subset of 3^m possible runs. The problem of finding designs with small number of runs is considered here. A main effect plan requires at least (2m + 1) runs for estimating the general mean, linear and quadratic effects of m factors. An orthogonal main effect plan requires, in addition, the number of runs as a multiple of 9. For example, when m=5, a main effect plan requires at least 11 runs and an orthogonal main effect plan requires 18 runs. Two general factor screening designs presented here are nonorthogonal designs with (2m− 1) runs. These designs, called search designs permit us to search for and identify at most two important factors out of m factors under the search linear model introduced in Srivastava (1975). For example, when m=5, the two new plans given in this paper have 9 runs, which is a significant improvement over an orthogonal main effect plan with 18 runs in terms of the number of runs and an improvement over a main effect plan with at least 11 runs. We compare these designs, for 4≤m≤ 10, using arithmetic and geometric means of the determinants, traces, and maximum characteristic roots of certain matrices. Two designs D1 and D2 are identical for m=3 and this design is an optimal design in the class of all search designs under the six criteria discussed above. Designs D1 and D2 are also identical for m=4 under some row and column permutations. Consequently, D1 and D2 are equally good for searching and identifying one important factor out of m factors when m=4. The design D1 is marginally better than the design D2 for searching and identifying one important factor out of m factors when m=5, … , 10. The design D1 is marginally better than the D2 for searching and identifying two important factors out of m factors when m=5, 7, 9. The design D2 is somewhat better than the design D1 for m=6, 8. For m=10, D1 is marginally better than D2 w.r.t. the geometric mean and D2 is marginally better than D1 w.r.t. the arithmetic mean of the maximum characteristic roots.     

Optimal design for interacting blocks with OAVS incidence

Optimal design is studied for multiway cross classifications in which the blocking factors exhibit interaction and in which the incidence structure of the blocking factors describes an orthogonal array. Assuming the orthogonal array to be of sufficient strength (enough to allow orthogonal estimation of all of the interaction terms), easily used forms of the information matrix for treatment estimation are derived, and optimality conditions are stated. Some illustrative construction examples are given.     

Mixed-level fractional factorial split-plot designs containing clear effects

Mixed-level designs are widely used in the practical experiments. When the levels of some factors are difficult to be changed or controlled, fractional factorial split-plot (FFSP) designs are often used. This paper investigates the sufficient and necessary conditions for a ${2^{(n_{1}+n_{2})-(k_1+k_2)}4_s^{1}}$ FFSP design with resolution III or IV to have various clear factorial effects, including two types of main effects and three types of two-factor interaction components. The structures of such designs are shown and illustrated with examples.     

Lower bounds of various discrepancies on combined designs

The foldover is a useful technique in construction of two-level factorial designs. A foldover design is the follow-up experiment generated by reversing the sign(s) of one or more factors in the initial design. The full design obtained by joining the runs in the foldover design to those of the initial design is called the combined design. In this paper, some lower bounds of various discrepancies of combined designs, such as centered L ₂-discrepancy, symmetric L ₂-discrepancy and wrap-around L ₂-discrepancy, under a general foldover plan are obtained, which can be used as a benchmark for searching optimal foldover plans. Our results provide a theoretical justification for optimal foldover plans in terms of uniformity criterion.     

ON THE ANALYSIS OF VARIANCE FOR BETA – BINOMIA

The beta–binomial distribution is reported in literature as a useful generalization of the binomial in case of heterogeneous binomial sampling. An extra model parameter is introduced to accommodate for extra–binomial variation. Some additions to results already available will be given by presenting approximate F–tests for factorial designs, where the response variable is of 0–1 type and sampling is heterogeneous binomial. These tests can be used when sample sizes are large and equal and some degrees of freedom are left from replicates or negligible interactions to estimate the extra model parameter.     

Procedures to determine optimum two-stage sampling plans by attributes

Summary In order to compare two sampling plans we use the minimax regret principle, i.e. the minimax principle applied to regret functions. It is shown that among all two-stage sampling plans there exists an optimum sampling plan which can be computed with the aid of a procedure presented in this paper; furthermore another procedure is described how to obtain an approximately optimum two-stage sampling plan in a more direct way. Finally only those two-stage sampling plans are regarded which satisfy an additional condition; among these sampling plans an optimum one exists and is to be determined, too.     

Two-level search design for main-effect plus two plan

One important class of screening designs is the search design first proposed by Srivastava (1975). A new class of two-level factorial search designs which are capable of estimating all main-effect plus two interactions is provided. We first give a necessary and sufficient condition for the main-effect plus two plan and then show that the proposed search design always satisfies such a condition. Received October 2000     

In Pursuit of Time: Business Plan Sequencing,Duration and Intraentrainment Effects on New Venture Viability

In this study, we examine three under‐explored dimensions of the temporal relationship between formal written business plans and the achievement of new venture viability. First, we theorize and investigate the effects of plan sequencing; arguing that a business plan written early on in new venture development increases the prospects of venture viability. Second, we examine plan duration effects, and argue that there is a curvilinear relationship between spending time on a plan and achieving venture viability. Finally, we investigate plan intraentrainment effects (synchronization with other gestation activities). We theorize that if plans are synchronized with other gestation activities, venture viability is more likely. Using longitudinal data and controlling for truncation and endogeneity issues, we find that it is beneficial to plan early but that this is contingent on how long a founder spent on a plan and whether or not a plan is intraentrained with other gestation activities.     

The simulation of planning decisions

An approach to the simulation of planning decisions is presented in which techniques based on control systems analysis are used. Planning decisions are defined to be those taken by officially instituted bodies subsequent to the adoption of an official plan and in order to implement it. These decisions are in response to applications for action from the public. These decisions are assumed to be adequately represented by the mean and standard deviations of the distribution of time delays involved. These two parameters are in turn posited to be influenced by feedback, feedforward and comparison with a standard plan effects. These influences are subsumed in a Monitoring functional block, which is modelled by a set of multiple linear regression equations. The decision-making or Regulation functional block is represented by Laplace functions which makes it convenient for computer simulation. Input functions are derived from the hypothesis to be tested or theoretical considerations. The advantages of the method appear to lie in its concise form and ease of manipulation even though the system simulated is an adaptive control system. Computer simulation models are notorious for their unwieldy size (number of equations) which in turn makes intervention and manipulation of parameters impractical. The proposed model attempts to alleviate this problem by simplifying the procedure involved.     

汽车排气消声器设计应用

文章根据消声器的消声原理,将消声器典型结构组合应用到CN100排气消声器的设计中,分别设计了2个前消声器方案和2个后消声器方案。经过对消声量的模拟计算,初步优选了前消声器方案2。而因为2个后消声器方案模拟计算结果接近,故通过制造前消声器和后消声器的样件,并将前消声器方案与2个后消声嚣方案组合进行对比试验,以确定后消声器方案。试验结果表明,后消声器方案1优于后消声器方案2,因此CN100排气消声器确定为前消声器方案2和后消声器方案1。同时试验结果表明,CN100排气消声器的排气背压、尾管口噪声达到了设计目标,有效地解决了发动机排气噪声,为整车加速行驶通过噪声提供了良好的贡献值。     

A heuristic analysis of highly fractionated 2n factorial experiments

Fractional factorial experiments are very useful in identifying active factors and the conventional method of analysis may not always detect these active factors. Box and Meyer (1993) provided a Bayesian method to compute the posterior probability that a factor is active. Their method does not indicate whether main effects or interactions are active. Following their approach in a non-Bayesian way, we will present a heuristic analysis which determines the active main effects and small order interactions in any 2ⁿ fractional factorial design. It may be noted that the method given by Box and Meyer has greater flexibility and wider applicability over the method given in this paper; however, our method is a simpler alternative for 2ⁿ experiments that determines active main effects and small order interactions. No SimplePara     

Security: The Virtual Quest

ABSTRACT

Security and related contingency recovery plans ensure a business' survival when it is faced with potential information systems breakdowns. Its primary objective is to prevent a calamity from occurring and to limit the impact of destructive events related to computer-based information systems. Most disaster recovery plans, when put into effect, fail to serve the intended purpose. The value of a properly implemented security is to prevent external intrusions before they start, and have an internal recovery plan to restore service so that assets are not adversely affected.

This paper provides some insight regarding security as well as identifying some of the pitfalls or weakness in this part of an organization's communication network. Emerging technologies such as the use of biometrics, authentications, steganography, and data encryption used for security will be the focus of the paper.     

城市总体规划中的三维空间观——浅析城市设计空间理念介入总体规划的动力及方法

有机的三维空间规划是城市规划的重要特色,也是与其他"规划"最大的区别.目前规划设计人员在从事城市总体规划过程中三维空间观缺乏,同时总规过高的法定地位导致的三维空间规划在规划体系中缺少足够的调整空间,这些原因都使得规划在三维空问领域缺乏足够的效用.本文在分析以上问题的基础上提供了一些基本的解决思路,核心就是如何将城市设计的空间理念融入城市总体规划当中.例如:提高规划人员的素质,选择合适的切入点.     

Inventory auditing: a manufacturing perspective

Despite the mystery that usually surrounds the annual audit program, its plan is easy to understand if you learn the basic concerns of the auditor. A five-step inventory audit plan usually consists of proving that the inventory exists, is completely represented, belongs to the firm, is properly valued, and is properly classified. To develop the inventory audit plan, an auditor must verify a firm's system of internal controls, in addition to verifying management's financial assertions by obtaining evidence about them. The time, cost, and frequency of the inventory audit with even the best plans may vary because of changing factors.     

Mutual fund selection and performance persistence in 401(k) Plans

We examine how plan sponsors/providers select mutual funds for 401(k) plans and whether performance persistence exists for mutual funds listed in 401(k) plans. Using a hand-collected data set of 401(k) investment options, we find that plan sponsors are likely to choose actively managed growth funds, including aggressive growth funds and long-term growth funds. Furthermore, more than 50% of the mutual funds in our sample of 401(k) plans are selected from the top 10 fund families in terms of total net assets. On average, plan sponsors select funds that outperform the funds with the same investment objective and that have low expense ratios. The performance of mutual funds in 401(k) plans only persists in a short horizon. Our analysis indicates that the menus of 401(k) investment options do not exhibit a signaling effect, indicating that investment options in 401(k) plans do not supply useful information about the future performance of mutual funds for investors in selecting mutual funds.