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-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- Among the most stable phase relationships between economic variables is that between money, the change in money, and general economic activity. Both the change in money and money itself lead production over the business cycle. This relationship buttressed with results of the Granger/Sims test for causality, has been used to support the notion that money causes real activity. This notion, in turn, is used to argue both that monetary policy causes the business cycle and that monetary policy can ameliorate the business cycle. This paper examines a hypothesis for the phase relationships which assume that money does not cause real activity, but, rather, real activity causes money. According to the hypothesis inventory assessment, which leads business activity, induces corporate borrowing, which in turn causes a money expansion with a lead similar to that observed. This has been a working hypothesis for the phasing in money of the System Dynamics National Model project. It is concluded that the hypothesis, by itself, is insufficient to account for the observed timing relationships. However, the inventory investment hypothesis combined with additional hypotheses such as a mechanism for household portfolio adjustment, can account for the phasing. These results do not depend on a causal flow from money to real activity. As a consequence, business cycle phase relationships should not be taken to imply money causes the business cycle nor that monetary policy can influence the business cycle.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- The paper is concerned with describing an investigation of information usage in the control of colliery operations. The premise of the work is that to make the most of new information retrieval technology currently being installed in collieries research is needed to provide compatible advances in the methods of information usage. The approach adopted was to construct a continuous simulation model using system dynamics capable of providing a laboratory assessment of alternative managerial control policies based on alternative sources and levels of aggregation of information. The model developed represents a typical colliery situation composed of three working coalfaces and incorporating planning production, development and manpower sectors. The face sectors transform coal reserves to mined coal output, under manpower constraints and geological shocks, and these are all interlinked by means of allocation policies for manpower and shifts. A range of policies for for the exercise of control through these allocations are considered subject to a range of shocks. It is concluded that, although there are difficulties in designing single policies which are universally best, there are clear advantages associated with fully integrated colliery policies based on information inputs from all aspects of the operations.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- It is envisaged that although the rabies system is a special case whereby there is no recovery from the disease, the principles generated by the analysis may be applicable to epidemiology in general. Such applications providing a definition of a disease system such that effective control policies may be elucidated. The work presented here is complete in itself forming a qualitative analysis of the system. It also provides the basis for a quantitative analysis using a derived computer simulation model.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- This paper discusses an approach to model refinement which involves testing the behavior of individual pieces of a model in response to empirical input data for comparison with empirical output data. Partial-model tests should be used for selecting formulations or estimating parameters only when appropriate case-specific or logical information is not available for this purpose. The smaller the model components used for partial-model testing, the more likely it is that the model will prove useful for anticipating events outside the historical experience and the less likely it is that observed behavior will be incorrectly attributed to certain relationships or parameters. Thus, from the standpoint of structural validity, partial-model testing is an improvement over whole-model testing for the purpose of structural adjustment. The paper presents a detailed example of partial-model testing in the context of a generic model of the evolving use of a new medical technology. Specifically, the technique is used for adjusting and validating a model subsystem that can explain why the reporting of clinical information on cardiac pacemakers has been marked by regular oscillations over time.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- The most basic problem of sociology as an empirical science is the difficulty of replicating studies within reasonable time limits and in genuinely comparable conditions. Sociologists aspire to make correct predictions based on verifiable statements about causal relationships, but cannot, the nature of macro-social phenomena precluding experimental designs with adequate controls. System Dynamics promises a way out of this dilemma. Four things need to be done. (1) Formulate the sociological theory as a causal loop diagram, making all causal reasoning explicit. (2) State what variables are involved in the functioning of the system. Calibrate the model until it is internally consistent. (3) Refine and adjust the constants until the model can reproduce a known time-series of relevant data. Repeat this on number of data-sets. (4) Systematically vary each constant in turn while controlling for the others. This is, in fact, the quasi-experimental procedure for testing the conditions under which the theory will stand or fall, and why. An illustrative example of the proposed strategy is presented, with encouraging results.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- Proper data management is an essential component of system dynamic modeling. The authors have developed an approach to data management, as set forth in this article. The article first describes the modeling and data management activities from a critical path point of view. The approach to handling the data associated activities is then developed. This approach asserts the following: 1. it is appropriate to address data relates activities at each stage of the model development process, and 2. when properly linked, a synergism exists between each model development stage and its associated data handling activity. It is claimed that this approach, including sequenced data handling and synergism between data and modeling activities, can produce a more comprehensive and timely model.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- This paper presents a system dynamics model of human factors in the implementation of office automation in the Job Service. The model includes sectors representing model acceptance by managers, supervisors, professionals, and clerks with the various factors impacting on such acceptance. Since the perceived usefulness of the automated system for office performance is quite important (especially for managers), sectors representing workflow and efficiency are also included.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- The strengths of the SD approach are as follows: explicit use of causal relations, the admission of qualitative information into the model and the potential for methodological ‘merges’. The drawback of the methodology is that it is difficult for the uninitiated and considerable effort is required in the modeling of SD. The purpose of strategic planning is to find a new product/market combination which accurately reflects the company’s strengths and weaknesses. In our case the SD community is the “company’; the methodology of SD is the product and different types of models correspond to market areas.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- This paper presents the discussion and the application of system dynamic methodology to study the consequences of government regulations on small surface coal operators. In 1977 Congress promulgated the surface Mining and Reclamation Act, which brought about some critical changes such as lengthy and costly permit application procedures, lengthy local and state review of permits and lands, increased bond fees and costly reclamation requirements. Small surface coal operators appeared to be particularly vulnerable. Policies frequently considered by the surface mining industry and the government to alleviate the hardship caused by the regulations are mechanisms to offset increased bond fees. It is a purpose of this paper to demonstrate the utility of system dynamics as any effective methodology to study the long term effects of such policies.
-
- Type:
- Document
- Date Created:
- 1983
- Collection:
- System Dynamic Society Records
- Collecting Area:
- University Archives
- Collection ID:
- ua435
- Parent Record(s):
- 23d738ba88f8333bc39725f9cb5bd0b8, cf82ceba47eedd73f41b00918de16477, and b0aa2a699b54f0d19f6a9d93bdbcfa18
- Description:
- The paper concludes that the general models of business performance should greatly benefit from analysis within a dynamic framework. The work has already indicated possible relationships between existing theories and formed the basis of a simulation model which may identify the possible consequences of certain strategic actions combined with alternative organization structures.