A review of longitudinal study in developmental psychology

The purpose of this library research thesis is to review the longitudinal study in terms of problems and present use. A preliminary search of the literature on longitudinal method revealed problems centering around two areas: (1) definition of longitudinal study and (2) practical problems of method itself. The purpose of this thesis then is to explore through a search of books and journals the following questions: 1. How can “longitudinal study” be defined? 2. What problems are inherent in the study of the same individuals over time and how can these problems be solved? A third question which emerges from these two is: 3. How is “longitudinal study” being used today? This thesis differentiates traditional longitudinal study from other methods of study: the cross-sectional study, the time-lag study, the experimental study, the retrospective study, and the study from records. Each of these methods of study is reviewed according to its unique problems and best uses and compared with the longitudinal study. Finally, the traditional longitudinal study is defined as the study: (1) of individual change under natural conditions not controlled by the experimenter, (2) which proceeds over time from the present to the future by measuring the same individuals repeatedly, and (3) which retains individuality of data in analyses. Some problem areas of longitudinal study are delineated which are either unique to this method or especially difficult. The following problems related to planning the study are reviewed: definition of study objectives, selection of method of study, statistical methods, cost, post hoc analysis and replication of the study, time factor in longitudinal study, and the problem of allowing variables to operate freely. Cultural shift and attrition are especially emphasized. The dilemma is examined which is posed by sample selection with its related problems of randomization and generalizability of the study, together with the problems of repeated measurements and selection of control groups. These problems are illustrated with studies from the literature. Not only are these problems delineated cut considerable evidence is shown that we have already started to accumulate data that will permit their solution. This paper presents a number of studies which have considered these problems separately or as a side issue of a study on some other topic. Some recommendations for further research in problem areas are suggested. At the same time that this thesis notes differentiation of the longitudinal study from other studies, it also notes integration of results of longitudinal studies with results of other studies. The tenet adopted here is: scientific knowledge is cumulative and not dependent on one crucial experiment. Trends in recent longitudinal studies are found to be toward more strict observance of scientific protocols and toward limitation of time and objectives of the study. When objectives of the study are well defined and time is limited to only enough for specified change to take place, many of the problems of longitudinal study are reduced to manageable proportions. Although modern studies are of improved quality, longitudinal method is not being sufficiently used today to supply the demand for this type of data. Longitudinal study is necessary to answer some of the questions in developmental psychology. We have no alternative but to continue to develop this important research tool

Characterization of SLM Printed 316L Stainless Steel and Investigation of Microlattice Geometry

The goal of this project was firstly to characterize Cal Poly’s SLM printed 316L stainless steel. SEM analysis showed Cal Poly’s as-printed 316L material to have a cellular dendritic microstructure containing mostly austenite and a small amount of δ-ferrite. After being heat treated to eliminate warp, its yeild and ultimate tensile strength were on par with the literature, however higher modulus and lower elongation were observed. XRD analysis confirmed residual stresses in the material, and that grains are preferentially oriented in both heat treated and non heat treated samples. The amount of porosity in the material was found to be about 0.93%, and the material experiences ductile fracture. The second part of the project was to test four different microlattice geometries in uniaxial compression, the octet truss was the most efficient geometry having the highest specific stiffness

Interfacial adhesion: Theory and experiment

Adhesion, the binding of different materials at an interface, is of general interest to many branches of technology, e.g., microelectronics, tribology, manufacturing, construction, etc. However, there is a lack of fundamental understanding of such diverse interfaces. In addition, experimental techniques generally have practical objectives, such as the achievement of sufficient strength to sustain mechanical or thermal effects and/or have the proper electronic properties. In addition, the theoretical description of binding at interfaces is quite limited, and a proper data base for such theoretical analysis does not exist. This presentation will review both experimental and theoretical aspects of adhesion in nonpolymer materials. The objective will be to delineate the critical parameters needed, governing adhesion testing along with an outline of testing objectives. A distinction will be made between practical and fundamental objectives. Examples are given where interfacial bonding may govern experimental consideration. The present status of theory is presented along wiith recommendations for future progress and needs

A Feasibility Study for Mapping Abandoned Coal Mining Areas in Young County, Texas

A total of 276 sites of possible bituminous coal mining were located within Young County, Texas, using black-and-white aerial photography at a scale of 1:20,000. More than 80 percent of these sites are less than 10 acres in size; 14 sites are 40 acres or more in size. Lack of vegetation, disturbed land surfaces, and evidence of active erosion characterize these sites. Forty-five sites are either directly adjacent to natural streams or show distinct runoff channels entering natural streams. Historical mining records were utilized where available, but no field confirmation of sites was included as part of this feasibility study.Bureau of Economic Geolog

Preliminary evaluation of a reaction control system for the space station

The challenge, ground rules and criteria, some of the Reaction Control System (RCS) concepts, classical and modern design analysis, and simulation results which are applicable to the space station are presented

Analysis of Low-Permability Gas Sands Suitable for Future Research Programs

Research on tight gas sands has traditionally focused on lenticular sands, but blanket-geometry sands, deposited by different processes, present distinct external and internal reservoir geometries requiring unique exploration and production techniques. To ensure the applicability of research findings across various reservoirs, a survey was conducted with a focus on elastic depositional systems and the potential transferability of results between different stratigraphic units. Based on the survey results, five stratigraphic units were selected for further study, and data collection efforts were initiated during the contract period. A comprehensive work plan was developed for the analysis of these units, which includes the preparation of geologic cross sections and maps, review of productive areas, resource analysis, and documentation of findings. The five selected units for study are the Travis Peak Formation, the Corcoran and Cozzette Sandstones, the Mancos "B" interval of the Mancos Shale, the upper Almond Formation, and the Frontier Formation. Data collection efforts have yielded a significant number of well logs from Colorado and Wyoming, with additional logs identified from Bureau files for the Travis Peak Formation. Wells suitable for cross-sectional analysis have been identified for the Travis Peak and Corcoran/Cozzette trends, and initial cross sections have been prepared for the latter trend. These efforts aim to enhance understanding and exploration potential of blanket-geometry tight gas sand reservoirs.Bureau of Economic Geolog

Optically Probing Spin and Charge Interactions in an Tunable Artificial Molecule

We optically probe and electrically control a single artificial molecule containing a well defined number of electrons. Charge and spin dependent inter-dot quantum couplings are probed optically by adding a single electron-hole pair and detecting the emission from negatively charged exciton states. Coulomb and Pauli blockade effects are directly observed and hybridization and electrostatic charging energies are independently measured. The inter-dot quantum coupling is confirmed to be mediated predominantly by electron tunneling. Our results are in excellent accord with calculations that provide a complete picture of negative excitons and few electron states in quantum dot molecules.Comment: shortened version: 6 pages, 3 figures, 1 table, to appear in Phys. Rev. Let