CIVIL WAR SETTLEMENTS AND COMBATANTS’ BEHAVIORS: STRATEGY, PERCEPTION, AND REPUTATION

Three projects in my dissertation focus on the termination of internal conflicts based on three critical factors: a combatant’s bargaining strategy, perceptions of relative capabilities, and reputation for toughness. My dissertation aims to provide the relevant theoretical framework to understand war termination beyond the simple two-party bargaining context. The first project focuses on the government’s strategic use of peace agreements. The first project suggests that peace can also be designed strategically to create a better bargain in the near future by changing the current power balance, and thus the timing and nature of peace is not solely a function of overcoming current barriers to successful bargaining. As long as the government has no overwhelming capability to defeat all rebel groups simultaneously, it needs to keep multiple rebel groups as divided as possible. This strategic partial peace helps to deter multiple rebel groups from collaborating in the battlefield and increases the chances of victory against non-signatories. The second project deals with combatants’ perceptions of relative capabilities. While bargaining theories of war suggest that war ends when combatants share a similar perception about their relative capabilities, combatants’ perceptions about relative capabilities are not often homogeneous. While focusing on information problems, this paper examines when a rebel group underestimates the government’s supremacy in relative capabilities and how this heterogeneous perception about the power gap influences negotiated settlements. The third project deals with the tension between different types of reputations in the context of civil wars: 1) a reputation for resolve and 2) a reputation for keeping human rights standards. In the context of civil wars, the use of indiscriminate violence by the government is costly, and as such, it signals the government’s toughness (or resolve) to rebel groups. I argue that the rebels are more likely to accept the government’s offer when the government recently engaged in indiscriminate violence against civilians during the conflict. This effect, however, is conditional on the government’s international human rights reputation; suggesting that rebel groups interpret this violence as a signal particularly when the government does not have a penchant for attacking civilians in general.

Computational evaluation of flexural toughness of FRC and fracture properties of plain concrete

In this paper, a computational tool concerning the computation of flexural and fracture toughness of cement based composites is presented. Firstly, RILEM`s (Reunion Internationale des Laboratoires d`Essais de Materiaux) recommendations related to the analysis of FRC in three-point bend tests are discussed in their relevant aspects regarding the computational implementations. The determination of other mechanical properties such as the Young modulus has been added to the program. Taking this into account, a new formulation based on displacements is used. In the second part of the paper, the determination of fracture properties of concrete, such as the fracture energy, G(F) , and the fracture toughness, K-IC(S), is discussed regarding the computational strategies used in the implementations. Several features whereby anterior data can be reanalyzed, obtained from other standards and recommendations, have been incorporated into the program, therefore allowing comparative studies and back analysis activities.

High temperature flexural strength and fracture toughness of AlN with Y(2)O(3) ceramic

The effects of temperature on the fast fracture behavior of aluminum nitride with 5 wt% Y(2)O(3) ceramic were investigated. Four-point flexural strength and fracture toughness were measured in air at several temperatures (30-1,300 A degrees C). The flexural strength gradually decreased with the increase of temperature up to 1,000 A degrees C due to the change in the fracture mode from transgranular to intergranular, and then became almost constant up to 1,300 A degrees C. Two main flaw types as fracture origin were identified: small surface flaw and large pores. The volume fraction of the large pores was only 0.01%; however, they limited the strength on about 50% of the specimens. The fracture toughness decreased slightly up to 800 A degrees C controlled by the elastic modulus change, and then decreased significantly at 1,000 A degrees C due to the decrease in the grain-boundary toughness. Above 1,000 A degrees C, the fracture toughness increased significantly, and at 1,300 A degrees C, its value was close to that measured at room temperature.

An engineering methodology to assess effects of weld strength mismatch on cleavage fracture toughness using the Weibull stress approach

This work describes the development of an engineering approach based upon a toughness scaling methodology incorporating the effects of weld strength mismatch on crack-tip driving forces. The approach adopts a nondimensional Weibull stress, (sigma) over bar (w), as a the near-tip driving force to correlate cleavage fracture across cracked weld configurations with different mismatch conditions even though the loading parameter (measured by J) may vary widely due to mismatch and constraint variations. Application of the procedure to predict the failure strain for an overmatch girth weld made of an API X80 pipeline steel demonstrates the effectiveness of the micromechanics approach. Overall, the results lend strong support to use a Weibull stress based procedure in defect assessments of structural welds.

Young children, adolescents and alcohol - Part II: Reputation enhancement and self-concept

The research reported builds on our earlier work (Houghton, Carroll, & Odgers, 1998) which explored young children's and adolescents' views pertaining to knowledge and awareness of alcohol and alcohol-related issues. In this second study 640 (286 male and 354 female) school students randomly selected from five primary schools and five high schools in Perth, Western Australia participated. Data were obtained using The Which Group picture booklet questionnaire which comprises five parts and utilises illustrations (drawn by a professional children's artist) to gather information about children's and adolescents' orientations towards alcohol risk social situations, reputation enhancement, self-concept, and other related issues. Of the sample, 73% of males and 70.6% of females had tried alcohol, with beer being consumed most often. Significantly more participants in higher Year levels had tried alcohol. Over 90% said they drank at a party. Multivariate analysis revealed that nine of the 11 dependent variables contributed to the significant main effect of alcohol risk group, of which three were self-concept variables and six were reputation enhancement variables. It appears that individuals with the highest levels of orientation to alcohol risk believe that they are liked by their families, are physically attractive and have greater confidence in themselves. They also have higher levels of Admiration of Alcohol Related Activities and also of prosocial activities. While striving to attain a non-conforming reputation these individuals also wish to be ideally perceived by others as conforming. Gender and Age differences are investigated.

Adolescent reputation enhancement: Differentiating delinquent, nondelinquent, and at-risk youths

This research reports the findings of two studies conducted to measure and then investigate differences between delinquent, nondelinquent, and at-risk youths' orientations towards reputation enhancement. In the first study, concerning item selection and scale development, the factor structure and content validity of a potential Reputation Enhancement Scale were tested by examining the item responses of the scale completed by 230 high-school students. In the second study, the scale was validated by comparing the item responses of 80 delinquent, 90 at-risk, and 90 nondelinquent adolescents with the responses of the original students. The instrument was found to be reliable (alphas from .64 to .92), indicating that the factors are dependable across different samples, and the coefficients of congruence were sufficiently high to investigate meaningful group differences. Three second-order factors (Conforming Reputation, Nonconforming Reputation, Self-presentation) were derived from the 15 first-order factors. Although multivariate analyses revealed significant differences between the reputational orientations of delinquent, at-risk, and nondelinquent participants, the self-presentation second-order factor did not differentiate the three groups.

Goals and reputations amongst young children - The validation of the importance of goals and reputation enhancement scales

The aim of the present research was to provide school psychologists with valid instruments with which to assess the goals and reputations of young children. This was achieved by ascertaining whether the factor structures and the second-order factor models of the high school versions of the Importance of Goals (Carroll, et al., 1997) and Reputation Enhancement Scales (Carroll, et al., 1999) could be replicated with a primary school sample. Eight hundred and eighty-six 10 to 12 year old children were administered modified versions of the two scales, which were combined and renamed the Children's Activity Questionnaire. For the two scales, the factor structure proved replicable and reliable with the primary school sample. A comparison between the factor loadings of the primary school and the high school samples using the coefficient of congruence procedure demonstrated similarity indicating that the scales are replicable and able to be used with a younger primary school sample. Structural equation modelling indicated that the second-order factor structure of the Importance of Goals Scale was acceptable but this was not the case for the second-order factor structure of the Reputation Enhancement Scale.

Effect of processing induced particle alignment on the fracture toughness and fracture behavior of multiphase dental ceramics

Objective. To investigate the processing induced particle alignment on fracture behavior of four multiphase dental ceramics (one porcelain, two glass-ceramics and a glass-infiltrated-alumina composite). Methods. Disks (empty set12mm x 1.1 mm-thick) and bars (3 mm x 4 mm x 20 mm) of each material were processed according to manufacturer instructions, machined and polished. Fracture toughness (K(IC)) was determined by the indentation strength method using 3-point bending and biaxial flexure fixtures for the fracture of bars and disks, respectively. Microstructural and fractographic analyses were performed with scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Results. The isotropic microstructure of the porcelain and the leucite-based glass-ceramic resulted in similar fracture toughness values regardless of the specimen geometry. On the other hand, materials containing second-phase particles with high aspect ratio (lithium disilicate glass-ceramic and glass-infiltrated-alumina composite) showed lower fracture toughness for disk specimens compared to bars. For the lithium disilicate glass-ceramic disks, it was demonstrated that the occurrence of particle alignment during the heat-pressing procedure resulted in an unfavorable pattern that created weak microstructural paths during the biaxial test. For the glass-infiltrated-alumina composite, the microstructural analysis showed that the large alumina platelets tended to align their large surfaces perpendicularly to the direction of particle deposition during slip casting of green preforms. Significance. The fracture toughness of dental ceramics with anisotropic microstructure should be determined by means of biaxial testing, since it results in lower values. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Bis-GMA co-polymerizations: Influence on conversion, flexural properties, fracture toughness and susceptibility to ethanol degradation of experimental composites

Objectives. The aim of this study was to evaluate the influence of monomer content on fracture toughness (K(Ic)) before and after ethanol solution storage, flexural properties and degree of conversion (DC) of bisphenol A glycidyl methacrylate (Bis-GMA) co-polymers. Methods. Five formulations were tested, containing Bis-GMA (B) combined with TEGDMA (T), UDMA (U) or Bis-EMA (E), as follows (in mol%): 30B:70T; 30B:35T:35U; 30B:70U; 30B:35T:35E; 30B:70E. Bimodal filler was introduced at 80 wt%. Single-edge notched beams for fracture toughness (FT, 25 mm x 5 mm x 2.5 mm, a/w = 0.5, n = 20) and 10 mm x 2 mm x 1 mm beams for flexural strength (FS) and modulus (FM) determination (10 mm x 2 mm x 1 mm, n = 10) were built and then stored in distilled water for 24 h at 37 degrees C. All FS/FM beams and half of the FT specimens were immediately submitted to three-point bending test. The remaining FT specimens were stored in a 75%ethanol/25%water (v/v) solution for 3 months prior to testing. DC was determined with FT-Raman spectroscopy in fragments of both FT and FS/FM specimens at 24 h. Data were submitted to one-way ANOVA/Tukey test (alpha = 5%). Results. The 30B:70T composite presented the highest K(Ic) value (in MPa m(1/2)) at 24 h (1.3 +/- 0.4), statistically similar to 30B:35T:35U and 30B:70U, while 30B:70E presented the lowest value (0.5 +/- 0.1). After ethanol storage, reductions in K(Ic) ranged from 33 to 72%. The 30B:70E material presented the lowest reduction in FT and 30B:70U, the highest. DC was similar among groups (69-73%), except for 30B:70U (52 +/- 4%, p < 0.001). 30B:70U and 30B:35T:35U presented the highest FS (125 +/- 21 and 122 +/- 14 MPa, respectively), statistically different from 30B:70T or 30B:70E (92 +/- 20 and 94 +/- 16 MPa, respectively). Composites containing UDMA or Bis-EMA associated with Bis-GMA presented similar FM, statistically lower than 30B:35T:35U. Significance. Composites formulated with Bis-GMA:TEGDMA:UDMA presented the best compromise between conversion and mechanical properties. (C) 2009 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

The effect of heat treatment on the toughness, hardness and microstructure of low carbon white cast irons

The effect of destabilisation and subcritical heat treatment on the impact toughness, hardness, and the amount and mechanical stability of retained austenite in a low carbon white cast iron have been investigated. The experimental results show that the impact energy constantly increases when the destabilisation temperature is raised from 950 degreesC to 1200 degreesC. Although the hardness decreases, the heat-treated hardness is still greater than the as-cast state. After destabilisation treatment at 1130 degreesC, tempering at 200 to 250 degreesC for 3 hours leads to the highest impact toughness, and secondary hardening was observed when tempering over 400 degreesC. The amount of retained austenite increased with the increase in the destabilisation temperature, and the treatment significantly improves the mechanical stability of the retained austenite compared with the as-cast state. Tempering below 400 degreesC does not affect the amount of retained austenite and its mechanical stability. But the amount of retained austenite is dramatically reduced when tempered above 400 degreesC. The relationship between the mechanical properties and the microstructure changes was discussed. (C) 2001 Kluwer Academic Publishers.

Relationship between stress-induced martensitic transformation and impact toughness in low carbon austenitic steels

The effect of test temperature, which controls the stability of austenite, on the impact toughness of a low carbon Fe-Ni-Mn-C austenitic steel and 304 stainless steel, has been investigated. Under impact conditions, stress-induced martensitic transformation occurred, in a region near the fracture surface, at test temperatures below 80degreesC for the Fe-Ni-Mn-C steel and below -25degreesC for 304 stainless steel. The former shows significant transformation toughening and the highest impact toughness was obtained at 10degreesC, which corresponds to the maximum amount of martensite formed by stress-induced transformation above the Ms temperature. The stress-induced martensitic transformation contributes negatively to the impact toughness in the 304 stainless steel. Increasing the amount of stress-induced transformation to martensite, lowered the impact toughness. The experimental results can be well explained by the Antolovich theory through the analysis of metallography and fractography. The different effect of stress-induced transformation on the impact toughness in Fe-Ni-Mn-C steel and 304 stainless steel has been further understood by applying the crystallographic model for stress-induced martensitic transformation to these two steels. (C) 2002 Kluwer Academic Publishers.

A new approach for measuring corporate reputation

This study describes the concept of corporate reputation and reviews some of the major points that exist when it comes to measuring it. It thus suggests a new index for measurement and its advantages and disadvantages are pointed out. The consistency of the seven key variables for the collecting indicator is described by the results of a factor analysis and correlations. Finally, the indicator is put to test by gathering the perception of corporate reputation of 1500 individuals for 69 companies belonging to 15 different industrial sectors, in Peru. The results indicate that the proposed index variables are not necessarily of greatest interest to the study sample in which companies have a better performance. Also greater memorial companies aren't necessarily those that enjoy a greater corporate reputation. Managerial implications for the organizations in the process of managing and monitoring the dimensions involved of this key asset are also referenced.

Fracture toughness determination of adhesive and co-cured joints in natural fibre composites

Adhesive bonding has become more efficient in the last few decades due to the adhesives developments, granting higher strength and ductility. On the other hand, natural fibre composites have recently gained interest due to the low cost and density. It is therefore essential to predict the fracture behavior of joints between these materials, to assess the feasibility of joining or repairing with adhesives. In this work, the tensile fracture toughness (Gc n) of adhesive joints between natural fibre composites is studied, by bonding with a ductile adhesive and co-curing. Conventional methods to obtain Gc n are used for the co-cured specimens, while for the adhesive within the bonded joint, the J-integral is considered. For the J-integral calculation, an optical measurement method is developed for the evaluation of the crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab sub-routine for the automated extraction of these quantities. As output of this work, an optical method that allows an easier and quicker extraction of the parameters to obtain Gc n than the available methods is proposed (by the J-integral technique), and the fracture behaviour in tension of bonded and co-cured joints in jute-reinforced natural fibre composites is also provided for the subsequent strength prediction. Additionally, for the adhesively- bonded joints, the tensile cohesive law of the adhesive is derived by the direct method.

Adherend thickness effect on the tensile fracture toughness of a structural adhesive using an optical data acquisition method

Adhesive bonding is nowadays a serious candidate to replace methods such as fastening or riveting, because of attractive mechanical properties. As a result, adhesives are being increasingly used in industries such as the automotive, aerospace and construction. Thus, it is highly important to predict the strength of bonded joints to assess the feasibility of joining during the fabrication process of components (e.g. due to complex geometries) or for repairing purposes. This work studies the tensile behaviour of adhesive joints between aluminium adherends considering different values of adherend thickness (h) and the double-cantilever beam (DCB) test. The experimental work consists of the definition of the tensile fracture toughness (GIC) for the different joint configurations. A conventional fracture characterization method was used, together with a J-integral approach, that take into account the plasticity effects occurring in the adhesive layer. An optical measurement method is used for the evaluation of crack tip opening and adherends rotation at the crack tip during the test, supported by a Matlab® sub-routine for the automated extraction of these quantities. As output of this work, a comparative evaluation between bonded systems with different values of adherend thickness is carried out and complete fracture data is provided in tension for the subsequent strength prediction of joints with identical conditions.

Performance evaluation of a cooperative reputation system for vehicular delay-tolerant networks

In the last decade, both scientific community and automotive industry enabled communications among vehicles in different kinds of scenarios proposing different vehicular architectures. Vehicular delay-tolerant networks (VDTNs) were proposed as a solution to overcome some of the issues found in other vehicular architectures, namely, in dispersed regions and emergency scenarios. Most of these issues arise from the unique characteristics of vehicular networks. Contrary to delay-tolerant networks (DTNs), VDTNs place the bundle layer under the network layer in order to simplify the layered architecture and enable communications in sparse regions characterized by long propagation delays, high error rates, and short contact durations. However, such characteristics turn contacts very important in order to exchange as much information as possible between nodes at every contact opportunity. One way to accomplish this goal is to enforce cooperation between network nodes. To promote cooperation among nodes, it is important that nodes share their own resources to deliver messages from others. This can be a very difficult task, if selfish nodes affect the performance of cooperative nodes. This paper studies the performance of a cooperative reputation system that detects, identify, and avoid communications with selfish nodes. Two scenarios were considered across all the experiments enforcing three different routing protocols (First Contact, Spray and Wait, and GeoSpray). For both scenarios, it was shown that reputation mechanisms that punish aggressively selfish nodes contribute to increase the overall network performance.