401 research outputs found

    Producing Scheduling that Causes Concurrent Programs to Fail

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    A noise maker is a tool that seeds a concurrent program with conditional synchronization primitives (such as yield()) for the purpose of increasing the likelihood that a bug manifest itself. This work explores the theory and practice of choosing where in the program to induce such thread switches at runtime. We introduce a novel fault model that classifies locations as .good., .neutral., or .bad,. based on the effect of a thread switch at the location. Using the model we explore the terms in which efficient search for real-life concurrent bugs can be carried out. We accordingly justify the use of probabilistic algorithms for this search and gain a deeper insight of the work done so far on noise-making. We validate our approach by experimenting with a set of programs taken from publicly available multi-threaded benchmark. Our empirical evidence demonstrates that real-life behavior is similar to what our model predicts

    Policy Constraints And Strategic Choices: MNE Subsidiaries Market Penetration In China

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    This study describes how firm level decisions and capabilities correspond to policy conditions in a host country where local market access is constrained and success is contingent on compliance with cultural hegemony. Using data from surveys gathered from multinational enterprise (MNE) subsidiaries operating in China, we describe the mode of entry the firms have used to penetrate and exploit markets in light of the constrained strategic choices open to their subsidiaries. We also expose the patterns of growth accomplished by the MNE and their underlying bases of competitive advantage. Finally, we relate the degree of centralization we observe among the respondents strategies

    Development of a force-feedback laparoscopic surgery simulator

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    Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1999.Includes bibliographical references (p. 77-78).The work presented here addressed the development of an electro-mechanical force-feedback device to provide more realistic and complete sensations to a laparoscopic surgery simulator than currently available. A survey of the issues surrounding haptic (touch) displays and training for laparoscopic or "keyhole" procedures was performed. A number of primary and secondary sources including surgeon consultation , operating room observations, and task analyses were used to accumulate a list of needs. Subsequent requirements analysis translated these into a set of specifications for the kinematics, dynamics and actuators, and configuration of the device. These suggested a design with five actuated axes (pitch and yaw about the entrance to the abdomen, insertion, rotation about the tool axis, and gripper feedback) amenable to a configuration including two actuated tools in a lifelike torso. These specifications were the basis for the generation and selection of design concepts. The PHANTOM haptic interface from Sensable Devices was chosen from among a number of existing devices and original designs to actuate the pitch, yaw, and insertion degrees of freedom. A separate end effector actuator was specified to supply feedback to the handle rotation and gripper. Mechanisms were proposed for each of these axes; a linear cable capstan was selected for the gripper and a cable capstan/drum for the rotation. The kinematics, bearings, transmissions, and user interface for both axes were designed in detail, and first- and second generation prototypes were built. The finished devices were integrated with the PHANTOM hardware, electronics, and software. Performance and design evaluations were performed, and plans for future device improvements and user studies were outlined.by Ela Ben-Ur.S.M

    A Defect-tolerant Cluster in a Mesh SRAM-based FPGA

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    International audienceIn this paper, we propose the implementation of multiple defect-tolerant techniques on an SRAM-based FPGA. These techniques include redundancy at both the logic block and intra-cluster interconnect. In the logic block, redundancy is implemented at the multiplexer level. Its efficiency is analyzed by injecting a single defect at the output of a multiplexer, considering all possible locations and input combinations. While at the interconnect level, fine grain redundancy is introduced which not only bypasses defects but also increases routability. Taking advantage of the sparse intra-cluster interconnect structures, routability is further improved by efficient distribution of feedback paths allowing more flexibility in the connections among logic blocks. Emulation results show a significant improvement of about 15% and 34% in the robustness of logic block and intra-cluster interconnect respectively. Furthermore, the impact of these hardening schemes on the testability of the FPGA cluster for manufacturing defects is also investigated in terms of maximum achievable fault coverage and the respective cost

    The Role and Limitations of 18-Fluoro-2-deoxy-d-glucose Positron Emission Tomography (FDG-PET) Scan and Computerized Tomography (CT) in Restaging Patients with Hepatic Colorectal Metastases Following Neoadjuvant Chemotherapy: Comparison with Operative and Pathological Findings

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    BACKGROUND: Recent data confirmed the importance of 18-fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) in the selection of patients with colorectal hepatic metastases for surgery. Neoadjuvant chemotherapy before hepatic resection in selected cases may improve outcome. The influence of chemotherapy on the sensitivity of FDG-PET and CT in detecting liver metastases is not known. METHODS: Patients were assigned to either neoadjuvant treatment or immediate hepatic resection according to resectability, risk of recurrence, extrahepatic disease, and patient preference. Two-thirds of them underwent FDG-PET/CT before chemotherapy; all underwent preoperative contrast-enhanced CT and FDG-PET/CT. Those without extensive extrahepatic disease underwent open exploration and resection of all the metastases according to original imaging findings. Operative and pathological findings were compared to imaging results. RESULTS: Twenty-seven patients (33 lesions) underwent immediate hepatic resection (group 1), and 48 patients (122 lesions) received preoperative neoadjuvant chemotherapy (group 2). Sensitivity of FDG-PET and CT in detecting colorectal (CR) metastases was significantly higher in group 1 than in group 2 (FDG-PET: 93.3 vs 49%, P < 0.0001; CT: 87.5 vs 65.3, P = 0.038). CT had a higher sensitivity than FDG-PET in detecting CR metastases following neoadjuvant therapy (65.3 vs 49%, P < 0.0001). Sensitivity of FDG-PET, but not of CT, was lower in group 2 patients whose chemotherapy included bevacizumab compared to patients who did not receive bevacizumab (39 vs 59%, P = 0.068). CONCLUSIONS: FDG-PET/CT sensitivity is lowered by neoadjuvant chemotherapy. CT is more sensitive than FDG-PET in detecting CR metastases following neoadjuvant therapy. Surgical decision-making requires information from multiple imaging modalities and pretreatment findings. Baseline FDG-PET and CT before neoadjuvant therapy are mandatory
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