Analysis of Survivabilty of the Ship Propulsion System in a Severe Shock Environment, Based on the Fuzzy Theory and Analytic Hierarchy Process

Ship survivability is a critical aspect of the design of naval ships operating in weapon-induced shock environments. While most of studies have focused on the failure mechanisms of ship structures, little work has been done to assess the damage that may be inflicted on the propulsion systems of such vessels. This paper presents a novel model for evaluating the survivability of naval ship propulsion systems subjected to severe shock environments. The model accounts for the effects of weapon damage, including blast-induced structural crevasses and shock-induced equipment failures, by conducting the vulnerability analysis using empirical formulations for pressure and fragment perforation calculation. The proposed model consists of two sub-models: a crevasse damage sub-model and a shock damage severity sub-model. The former utilizes a fifth-order analytic hierarchy process structural model, while the latter utilizes the fuzzy theory. Combining the two sub-models yields the total survivability of the propulsion system of a naval ship. The model is applied to assess the survivability of three propulsion system design types (CODOG, CODAD, and CODAG) for a 3000 T class frigate. Results demonstrate the utility of the proposed model as a fast and robust method for use during iterative design cycles, enabling design changes based on the analysis results

Bulge formation from SSCs in a responding cuspy dark matter halo

We simulate the bulge formation in very late-type dwarf galaxies from circumnuclear super star clusters (SSCs) moving in a responding cuspy dark matter halo (DMH). The simulations show that (1) the response of DMH to sinking of SSCs is detectable only in the region interior to about 200 pc. The mean logarithmic slope of the responding DM density profile over that area displays two different phases: the very early descent followed by ascent till approaching to 1.2 at the age of 2 Gyrs. (2) the detectable feedbacks of the DMH response on the bulge formation turned out to be very small, in the sense that the formed bulges and their paired nuclear cusps in the fixed and the responding DMH are basically the same, both are consistent with $HST$ observations. (3) the yielded mass correlation of bulges to their nuclear (stellar) cusps and the time evolution of cusps' mass are accordance with recent findings on relevant relations. In combination with the consistent effective radii of nuclear cusps with observed quantities of nuclear clusters, we believe that the bulge formation scenario that we proposed could be a very promising mechanism to form nuclear clusters.Comment: 27 pages, 11 figures, accepted for publication in Ap

The effects of large extra dimensions on associated ttˉh0t\bar{t} h^0 production at linear colliders

In the framework of the large extra dimensions (LED) model, the effects of LED on the processes \rrtth and \eetth at future linear colliders are investigated in both polarized and unpolarized collision modes. The results show that the virtual Kaluza-Klein (KK) graviton exchange can significantly modify the standard model expectations for these processes with certain polarizations of initial states. The process \rrtth with $\sqrt{s}=3.5 TeV$ allows the effective scale $\Lambda_T$ to be probed up to 7.8 and 8.6 TeV in the unpolarized and $P_{\gamma} = 0.9$, J=2 polarized $\gamma \gamma$ collision modes, respectively. For the \eetth process with $\sqrt{s}=3.5 TeV$, the upper limits of $\Lambda_T$ to be observed can be 6.7 and 7.0 TeV in the unpolarized and $P_{e^+} = 0.6$, $P_{e^-} = 0.8$, $-+$ polarized $e^+e^-$ collision modes, respectively. We find the \rrtth channel in J=2 polarized photon collision mode provides a possibility to improve the sensitivity to the graviton tower exchange.Comment: To be appeard in Physical Review