Universiẗat, Diss., 2005--Bonn.

The gun barrel is one of the most important parts of the whole artillery system. During firing, the wear leads to reduced performance and availability. Wear in gun barrels has different types of erosion mechanisms, in particular chemical-, thermal- and mechanical erosion. This takes place in the internal ballistic process when the projectile is fired from the gun barrel and it will affect the external ballistic parameters. Therefore, an equipment is needed to monitor and measure the wear inside different calibre gun barrels. Wear in gun barrels takes place under extreme conditions during firing due tohigh gas pressures and high temperatures arise as propellant burns. The present thesis aims to develop a type of measuring equipment that should be able to measure and monitor wear inside gun barrels between the diameter ranges of A-C mm. In this master thesis, the product development process has been adapted in order to reach the following goal which is to accomplish a technical solution for the problem associated with wear in gun barrels. The product development process is a systematical approach of developing new products. The different steps that have been evaluated are the product specification, generation of concepts, selection of concepts and layout- and detail design. Before these steps where performed, a project plan was done in order to organize the project. This was then followed by a literature review to obtain information about the problems in the project and to find inspiration from similar applications. The results of the product development process led to a concept of a moveable measure-head which uses a crawler to move inside the gun barrel and adapters to be able to use inside different calibre gun barrels. Then a rotating 3D-laser scanner to measure the change in diameter of the bore. A laser distance sensor and a receiver in order to measure the straightness and to be able to know the position of the moving measure-head in the gun barrel. At last, a wireless camera to monitor the wear inside the gun barrel. The selected concept has been developed and potential solutions for the problem have been described and formed. For the next phase of the project, the concept needs to be developed into a complete model. The next phase of the project is the prototype testing phase.

Gun barrels are an important component in advanced defence systems. The gun barrels are used for direct and indirect fire and the material of the gun barrel is exposed to great strains and high temperatures. This sets high demands on the material of the gun barrel. During firing the gun barrel can be damaged. The first damage in gun barrels is the wear of the rifling followed by fatigue. When fatigue occurs cracks can propagate downwards into the bore and could result in catastrophic failure. Therefore investigation regarding the wear, the mechanisms and the underlying factors causing the damage will be performed. How and where the wear in gun barrels occur and also which wear mechanisms causing the wear. Wear in gun barrels involves extreme conditions during firing such as high gas pressure and high temperature from the burning propellant. This thesis work aims to understand how and why wear and damaging mechanisms in gun barrels occurs. Moreover how other ballistic factors influences have on the wear. The wear in gun barrels is caused by erosion from the combustion gases or/and sliding wear caused by the high-speed projectile. The phenomena of wear are complicated and factors like deformation state, types of wear, environment and process are interrelated with each other. These give the rise of wear. In this thesis, samples from three gun barrels were analysed. A new unworn gun barrel, a medium worn gun barrel and a severely worn gun barrel. From the used gun barrels 4 critical positions were identified, then samples from both surface and cross-section were obtained from the gun barrels. The surface and cross-section were analysed using different methods including optical light microscopy and scanning electron microscopy to characterise the surface damage and wear mechanisms. The results from the investigation revealed the dominating wear mechanism to be thermal and chemical erosion at the positions closest to the combustion chamber with heat checks as its signature feature. The heat checks are associated with fatigue cracks developed at the surface and during thermo-mechanical loading, allows it to propagate down into the surface. For both samples at position 2, after the start of the rifling, adhesive wear was obtained too. The adhesive wear was induced by material pick-up from the driving band of the projectile during sliding. In other meaning, the material is transferred from the counter-face to the bore surface. The severely worn gun barrel had been subjected to sliding wear at the muzzle end compared to the medium worn gun barrel which hadn’t experience the same wear rate at the same position. The analysis of the cross-section examination revealed information about the structure and condition of the material. To obtain more information about mechanical properties, a hardness test was performed. The hardness test revealed a hard but brittle surface which can be sheared by the frictional force caused by the sliding projectile. The analysis of the gun barrels revealed information about wear mechanisms and damages in medium and severely worn gun barrels. The detected wear mechanism was thermal erosion, chemical erosion, mechanical erosion and sliding wear.

This diploma thesis deals with the choice of suitable VBD for longitudinal turning barrel steel OCHN3MFA. In the theoretical part, serving as a basis for the experimental part, the technology of turning, tooling and coating methods was analyzed. In the experimental part, ten VBDs were tested, eight of which were of cemented carbide and two of ceramic. The monitored parameters were force load and tool wear VB. From the evaluated load data and tool wear, a suitable VBD for turning barrel steel was selected. The most suitable VBD for turning barrel steel is VBD – G. Tools VBD – I and VBD – J from ceramics are inappropriate tools for turning barrel steel.

京都大学 / 0048 / 新制・論文博士 / 博士(医学) / 乙第13156号 / 論医博第2143号 / 新制||医||1028(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 林 康紀, 教授 渡邉 大, 教授 影山 龍一郎 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

No description available.

My thesis explores the potential manipulation of Roman brick using a Flemish bond, corner quoining, and barrel vaulting. The design uses this brick module to re-interpret the Ancient Roman domus, an urban residence embedded within the heart of the city. This classical inspiration is apparent in the tripartite plan and elevation as well as the use of the Golden Ratio, a classical proportioning system, incorporated throughout the design, revealed on both large and small scales. However, the emphasis of the project is on true brick construction, a process irrelevant to historical allusion. / Master of Architecture

Single-molecule force spectroscopy (SMFS) is a unique approach to study the mechanical unfolding of proteins. SMFS unfolding experiments yield insight into how interactions stabilize a protein and guide its unfolding and refolding pathways. In contrast to various water-soluble proteins whose unfolding and refolding patterns have been characterized, only α-helical membrane proteins have been probed by SMFS. It was shown that α-helical membrane proteins unfold via many intermediates; this differs from the two-state unfolding process usually observed in water-soluble proteins. In membrane proteins, upon mechanically pulling the peptide end of the protein, single and grouped α-helices and polypeptide loops unfold in steps until the entire protein is unfolded. Whether the α-helices and loops unfold individually or cooperatively to form an unfolding intermediate depends on the interactions established within the membrane protein and the membrane. Each unfolding event relates to an unfolding intermediate with the sequence of these intermediates defining the unfolding pathway of the protein. β-barrel-forming membrane proteins are the second major group of membrane proteins and have not yet been studied by SMFS. To fill this void this study was designed to characterize interactions, unfolding, and refolding of the β-barrel forming outermembrane protein G (OmpG).Folding of transmembrane proteins, despite the important part these proteins play in every biological process in a cell, is studied in only a few examples. Of those only a handful were β-stranded membrane proteins (Tamm et al., 2004; Kleinschmidt et al., 2006). Current models describe that transmembrane β-barrels fold into the lipid membrane via two major steps. First the unfolded polypeptide interacts with the lipid surface where it then folds and inserts into the membrane (Kleinschmidt et al., 2006; Huysmans et al., 2010). Conventionally, thermal or chemical denaturation is used to study folding of membrane proteins. In most cases membrane proteins were solubilized in detergent or exposed to urea to be studied, conditions that are not compatible with In vivo conditions. This suggests that the folding pathways described so far may not be a realistic representation of such pathways in nature. SMFS represents a unique approach to study the unfolding and refolding of membrane proteins into the lipid membrane (Kedrov et al., 2006; Kessler et al., 2006). Using SMFS makes it possible to study unfolding and refolding of membrane proteins in their nativephysiological environment with controlled pH, electrolyte, temperature, and most importantly in the absence of any chemical denaturant or detergent. In this thesis, SMFS was utilized to unfold and refold OmpG in E coli lipid extract. Bulk unfolding experiments suggested that OmpG unfolds and folds reversibly and much faster than α-helical proteins (Conlan et al., 2000). The folding process is thought to be a coupled two-state membrane partition-folding reaction. To the contrary, the mechanical unfolding of OmpG consisted of many sequential unfolding intermediates. Our SMFS refolding experiments showed that a partially unfolded OmpG molecule also refolds via several sequential steps. The predominant refolding steps are defined by individual β-hairpins that could later assemble the transmembrane β-barrel of OmpG. In conclusion, the most probable unfolding and refolding pathways of OmpG as a membrane β-barrel protein go through the β-hairpins as the structural segments or unfolding-refolding intermediates and the process is a multi step one rather than the simple two state process. We also used SMFS to study the physical interactions that switch the functional state and gating of OmpG. The structural changes that gate OmpG have been previously described by X-ray crystallography (Yildiz et al., 2006). They showed when the pH changes from neutral to acidic the flexible extracellular loop L6 folds into the pore and closes the OmpG pore. Here, SMFS was used to structurally localize and quantify the interactions that are associated with the pH-dependent closure. At an acidic pH, a pH-dependent interaction at loop L6 was detected. This interaction changed the unfolding of loop L6 and β-strands 11 and 12, which connect loop L6. All other interactions detected within OmpG were found to be unaffected by changes in pH. These results provide a quantitative and mechanistic explanation of how pHdependent interactions change the folding of a peptide loop to gate the transmembrane pore. It has also been shown how the stability of OmpG is optimized so that pH changes modify only those interactions necessary to gate the transmembrane pore and there are no global changes in protein conformation or mechanical properties. In the next step of interactions study, dynamic SMFS (DFS) was applied to quantify the parameters characterizing the energy barriers in energy landscape for unfolding of the OmpG. Some of these parameters are: free energy of activation and distance of the transition state from the folded state. The pH-dependent functional switching of OmpG directs the protein along different regions at the unfolding energy landscape. The two functional states of OmpG sequential folding take the same unfolding pathway as β-hairpins I–IV. After the initial unfolding events, the unfolding pathways diverge. In the open state, the unfolding of β-hairpin V in one step precedes the unfolding of β-hairpin VI. In the closed state, β-hairpin V and β-strand S11 with a part of extracellular loop L6 unfold cooperatively, and subsequently β-strand S12 unfolds with the remaining loop L6. These two unfolding pathways in the open and closed states join again in the last unfolding step of β-hairpin VII. Also, the conformational change from the open to the closed state witnesses a difference in Xu and κ in the energy landscape that translates to rigidified extracellular loop L6 at the gating area. Thus, a change in the conformational state of OmpG not only bifurcates its unfolding pathways but also tunes its mechanical properties for optimum function.

Ratten verwenden Schnurrhaare (Vibrissen) zur Berührungswahrnehmung, und die Leitungsbahn von den Vibrissen zum primären somatosensorischen Areal (Barrel Cortex, BC) ist gut untersucht. Ratten zeigen auch vielfältiges Sozialverhalten, u.a. Berührung von Artgenossen mit ihren Vibrissen. Es ist jedoch unbekannt, wie diese sozialen Berührungssignale im Gehirn repräsentiert sind. Deshalb hatte die vorliegende Studie zum Ziel, die neuronale Repräsentation von sozialen Berührungen im BC zu untersuchen und mit anderer somatosensorischer Stimulation zu vergleichen. Mit extrazellulären Einzelzellableitungen in sich frei bewegenden Ratten habe ich gezeigt, dass die Aktivität eines Großteils von Neuronen im BC durch soziale Berührungen moduliert wird. Antworten waren meist erregend und Feuerraten während sozialer Interaktionen unterschieden sich zwischen kortikalen Schichten. Ratten bevorzugten Interaktionen mit Artgenossen gegenüber unbelebten Stimuli. Auch die Berührungsstrategien unterschieden sich, dabei wurden Objekte mit regelmäßigeren Bewegungen abgetastet, und die Vibrissen weiter vorgestreckt. Neuronale Antworten unterschieden sich ebenso, mit leicht aber konsistent schwächeren Antworten auf Objekte. Interessanterweise habe ich geschlechtsspezifische Unterschiede in neuronalen Antworten beobachtet. Der ausgeprägteste war die stärkere Modulation regulär-feuernder (RF) Zellen in Männchen während sozialer Berührungen. Dieser Unterschied konnte nicht mit sozialem Berührungsverhalten erklärt werden, was eventuell auf eine neurale Grundlage dieser Differenz hindeutet. Zudem feuerten RF-Zellen von Weibchen deutlich seltener, wenn das Weibchen im Östrus war. Zusammenfassend ist dies die erste Studie, die soziale Signale in einem primären sensorischen Areal bei sich frei bewegenden Tieren auf zellulärer Ebene untersuchte. Sie legt nahe, dass die Repräsentationen sensorischer Hirnrinde weniger stimulusabhängig und stärker top-down-moduliert sein könnten, als zuvor angenommen. / Rats use their stiff facial hairs (whiskers) for somatosensation, and the pathway from the whiskers to the primary somatosensory cortex (barrel cortex, BC) is well known. Rats also show diverse social behaviors, including touch of conspecifics with their whiskers. The representation of these social touch signals in the brain is however unknown. Thus, the present study aimed at characterizing the neuronal representation of social touch signals in BC and comparing them with non-social somatosensory stimulation. Using extracellular single-cell recordings in freely-moving rats, I could show that the activity of a large fraction of BC neurons is modulated by social touch. Responses were typically excitatory and the pattern of firing rates during interactions differed between cortical layers. Rats preferred interactions with alive conspecifics over inanimate stimuli. Whisking strategies also differed in that inanimate stimuli were whisked at with more regular movements from more protracted set angles. Neuronal responses were also different, such that objects elicited slightly but consistently weaker responses than alive rats. Interestingly, I observed sex-specific differences in neuronal responses. Prominently, there was stronger modulation by social touch in regular-spikers (RS) recorded from males. This could not be explained by behavioral measures, possibly indicating a neural origin of this difference. Further, RS from females fired much more weakly when females were in estrus. In summary, this is the first study that investigated social signals in a primary sensory area of freely-moving animals at the cellular level. It suggests that representations in sensory cortices might be less stimulus-driven and more top-down modulated than previously thought.

No description available.