On reducing the number of states in a PDA

A transformation is presented which converts any pushdown automaton (PDA)M ₀ withn ₀ states andp ₀ stack symbols into an equivalent PDAM withn states and n ₀ /n² p ₀ stack symbols into an equivalent ofn, 1n ₀. This transformation preserves realtime behavior but not derterminism. The transformation is proved to be the best possible one in the following sense: for each choice of the parametersn ₀ + 1 stack symbols for any desired value realtime PDAM ₀ such that any equivalent PDAM (whether realtime or not) havingn states must have at least (n ₀ /n)² p₀ stack symbols. Furthermore, the loss of deterministic behavior cannot be avoided, since for each choice ofn ₀ andp ₀, there is a deterministic PDAM ₀ such that no equivalent PDAM with fewer states can be deterministic.This research was supported in part by the National Science Foundation under Grants MCS76-10076 and MCS76-10076A01.     

Chemical doping of single-wall carbon nanotubes

Single-wall carbon nanotubes can be doped, or intercalated, with electron donors or acceptors, similar to graphite and some conjugated polymers. The resulting materials show many of the same features: enhanced electrical conductivity, conduction electron paramagnetism, partial or complete reversibility, and cyclability. Reactions may be carried out in vapor or liquid phase, or electrochemically. Structural information is sketchy at best, due to the limited quality of currently available materials and solvent-related effects. Recent developments in coagulation-based fiber extrusion and partially aligned materials offer new opportunities for novel material modifications by chemical doping.     

The aging effect of the thermoelectric power of thin copper films

The thermoelectricpower, referenced to bulk copper, of thin films of copper about 150 Å thick was measured by preparing a thin film bridge between two copper wires which served as leads. This arrangement produces two junctions between the thin film copper and the bulk copper. The two junctions were maintained at a temperature difference which was measured using a calibrated copper-constantan thermocouple. It was found that the thin film-to-bulk thermoelectric power varies with time and can be fitted to an equation of the form

$\text{S = S}{}_{\mathrm{<mtext>F</mtext>}}\text{(1?}\text{e}{}^{\mathrm{-\lambda t}}\text{)}$

where λ depends on temperature. The constant λ in the equation has values very close to those found from thin film resistance aging measurements, suggesting that the same mechanism is responsible for both aging phenomena. The heated junctions is negative, in agreement with a simple electron diffusion model of thermoelectric power.     

Whatever happened to neurosis? An overview.

Discusses the decision to eliminate the term "neurosis" from the DSM-III. The history of the term is traced; weaknesses of DSM-II pertaining to neurosis are presented; theoretical and political processes in the deletion procedure are described; and an overview is given of the current resolution as presented in DSM-III. Instead of neurosis, "neurotic disorder" and "neurotic process" were distinguished to reduce potential theoretical bias. The process may or may not be seen by the clinician as causal in the disorder, but those of all theoretical persuasions should be able to agree on what the disorder is. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Space-time tradeoffs for linear recursion

A linear recursive procedure is one each of whose executions activates at most one invocation of itself. When linear recursion cannot be replaced by iteration, it is usually implemented with a stack of size proportional to the depth of recursion. In this paper we analyze implementations of linear recursion which permit large reductions in storage space at the expense of a small increase in computation time. For example, if the depth of recursion isn, storage space can be reduced to \(\sqrt n \) at the cost of a constant factor increase in running time. The problem is treated by abstracting any implementation of linear recursion as the pebbling of a simple graph, and for this abstraction we exhibit the optimal space-time tradeoffs.     

复合材料层板+θ/-θ层间断裂韧性研究

本文讨论了纤维增强复合材料层板沿+θ/-θ层间断裂韧性的研究方法;提出在满足一定力学条件时,可沿用机械载荷实验方法测得G_C中“纯机械部分”G_m;结合数值方法计算得出“纯温度部分”G_T,从而得到G_C.给出一个针对DCB试验的充分条件,据此设计铺层并对T300/648和T300/QY8911进行试验和分析(θ=0～30°)、讨论了大变形的影响并提出一个新的修正系数.结合θ对G_C的影响及断口微观形貌作了进一步讨论.     

An OSCA™ architecture characterization of network functionality and data

This article demonstrates that the Bellcore OSCA architecture can serve as a basis for the metaarchitecture for software architectures that must support interoperability among functionality that traditionally has resided in operation systems and functionality that traditionally has resided in network elements (NE) (i.e., interoperability among operations functionality and network functionality). The need for this interoperability is driven by such telephone company business needs, as the need for customers to access operations capabilities spanning operations systems and NEs, the need for new service offerings to span operations systems and NEs, the need for a flexible environment for service development, and the need to manage all corporate data as a company resource. As a result, it is becoming beneficial to apply interoperability requirements to the network functionality that interfaces with operations systems. Therefore, it is reasonable to apply the OSCA architecture to network functionality. This article applies the OSCA architecture interoperability principles of separation of concerns to current and emerging network functionality. It demonstrates that this functionality can be partitioned among the three OSCA architecture layers of corporate data, processing, and user, and that there are a number of benefits to applying the OSCA interoperability principles to network functionality.     

Spatial distribution and habitat characterization of schistosomiasis host snails in lake and land habitats of western Kenya

Intermediate host snails of schistosomiasis were surveyed in this study to determine their abundance and distribution in the lake and land aquatic habitats of Lake Victoria basin of Kenya. Several sites were sampled at eight locations, both in the lake and on the land. The habitat and/or vegetation type (i.e. open water, hippo grass, hyacinth, ambatch trees, other vegetation, stream, swamp, pond, dam) of the sampled aquatic sites within the locations were also differentiated, water physicochemical parameters were determined, and the abundance of different species or taxa of phytoplankton and zooplankton were enumerated and correlated with the abundance of schistosomiasis snails in the sites. The results indicated significantly more Biomphalaria sudanica snails than Bulinus africanus snails in different physical habitats on land (Student's t‐test, P < 0.05), as well as in different locations on land (Student's t‐test, P = 0.026). Regression analyses revealed that several physicochemical parameters, including dissolved oxygen (R² = ?0.659; n = 8; P = 0.014), pH (R² = 0.728; n = 8; P = 0.007) and turbulence (R² = ?0.616; n = 8; P = 0.02), were predictive of Biomphalaria spp. abundance, while pH (R² = 0.610; n = 8; P = 0.02) and turbulence (R² = ?0.578; n = 8; P = 0.028) were predictive of Bulinus spp. abundance in different locations in the lake. Cyanobacteria (R² = 0.638; n = 8; P = 0.02) and chlorophyceae (R² = ?0.50; n = 8; P = 0.05) were shown to be predictive of both Biomphalaria spp. and Bulinus spp. abundance in different locations in the lake. Zooplankton abundance varied significantly between different locations in the lake (One‐way anova , P < 0.001). Bosmina spp. were found to be predictive of both Biomphalaria spp. (R² = ?0.627; n = 8; P = 0.01) and Bulinus spp. (R² = ?0.50; n = 8; P = 0.05) in different locations in the lake. The results from this study will help inform policy regarding control measures for schistosomias and intermediate snail hosts in Lake Victoria waters, as well as in adjacent terrestrial aquatic habitats and even beyond.     

Distribution of ground stress on Puhe Coal Mine

Puhe Coal Mine is a typical Tertiary coal in Shenbei mining area. With an increase in mining depth, tectonic stress field becomes more complex, leading to increased deformation and failure of the soft rock roadway. Stress becomes an important factor of mine safety and stability. This paper analyzes the distribution of the regional tectonic field, and determines the distribution of situ stress measurement through measuring the ground stress field in the main mining area level of Puhe Coal Mine using stress relief method. The acquired in situ stress data at different locations and depths provide a reference for the rational arrangement of the stop and mine roadway supporting design, which are of great significance for the efficient safety production of the mine.     

玻璃幕墙传热系数计算方法及工程应用

在研究玻璃幕墙热传递特点的基础上,基于一维稳态热传导理论,以中空玻璃为例建立了玻璃系统传热系数计算模型;基于二维稳态热传导理论和有限单元法,采用三节点三角形单元对二维温度场进行了离散,推导了单元热传导矩阵和温度载荷列阵,并推导了热对流、热流密度、辐射以及各种边界条件耦合作用下对单元热传导矩阵和温度载荷列阵的修正公式,建立了玻璃幕墙框及附加线传热系数计算模型。利用Visual C++和ObjectARX对AutoCAD进行了二次开发,研发了玻璃幕墙传热系数计算软件TJCW,并通过算例与LBNL系列软件计算结果进行比较,验证了所编软件的正确性和有效性。最后对某工程实例中玻璃幕墙传热系数进行了节能验算。研究结果表明:建立的传热系数计算模型能够正确的计算玻璃幕墙传热系数,基于该计算模型开发出的软件能够应用于实际工程的节能分析和计算中。